Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “degradable”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 577 records · Page 32
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

GRIK phosphorylates and activates KIN10 which also promotes its degradation

The sensor kinase Sucrose Non-fermenting-1-Related Kinase 1 (SnRK1) plays a central role in energy and metabolic homeostasis. KIN10 is a major catalytic (a) kinase subunit of SnRK1 regulated by transcription, posttranslational modification, targeted protein degradation, and its subcellular localization. Geminivirus Rep Interacting Kinase 1 and 2 (GRIK1 and 2) are immediate upstream kinases of KIN10. In the transient protein expression assays carried out in Nicotiana benthamiana (N. benthamiana) leaves, GRIK1 not only phosphorylates KIN10 but also simultaneously initiates its degradation. Posttranslational GRIK-mediated KIN10 degradation is dependent on both GRIK kinase activity and phosphorylation of the KIN10 T-loop. KIN10 proteins are significantly enriched in the grik1-1 grik2-1 double mutant, consistent with the transient assays in N. benthamiana. Interestingly. Among the enriched KIN10 proteins from grik1-1 grik2-1, is a longer isoform, putatively derived by alternative splicing which is barely detectable in wild-type plants. The reduced stability of KIN10 upon phosphorylation and activation by GRIK represents a mechanism that enables the KIN10 activity to be rapidly reduced when the levels of intracellular sugar/energy are restored to their set point, representing an important homeostatic control that prevents a metabolic overreaction to low sugar conditions. Since GRIKs are activating kinases of KIN10, KIN10s in the grik1 grik2 double null mutant background remain un-phosphorylated, with only their basal level of activity, are more stable, and therefore increase in abundance, which also explains the longer isoform KIN10L which is a minor isoform in wild type is clearly detected in the grik1 grik2 double mutant.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2023

Phenothiazines Rapidly Induce Laccase Expression and Lignin-Degrading Properties in the White-Rot Fungus Phlebia radiata

Phlebia radiata is a widespread white-rot basidiomycete fungus with significance in diverse biotechnological applications due to its ability to degrade aromatic compounds, xenobiotics, and lignin using an assortment of oxidative enzymes including laccase. In this work, a chemical screen with 480 conditions was conducted to identify chemical inducers of laccase expression in P. radiata. Among the chemicals tested, phenothiazines were observed to induce laccase activity in P. radiata, with promethazine being the strongest laccase inducer of the phenothiazine-derived compounds examined. Secretomes produced by promethazine-treated P. radiata exhibited increased laccase protein abundance, increased enzymatic activity, and an enhanced ability to degrade phenolic model lignin compounds. Transcriptomics analyses revealed that promethazine rapidly induced the expression of genes encoding lignin-degrading enzymes, including laccase and various oxidoreductases, showing that the increased laccase activity was due to increased laccase gene expression. Finally, the generality of promethazine as an inducer of laccases in fungi was demonstrated by showing that promethazine treatment also increased laccase activity in other relevant fungal species with known lignin conversion capabilities including Trametes versicolor and Pleurotus ostreatus.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

Electrospun Nanofiber Dopped with TiO2 and Carbon Quantum Dots for the Photocatalytic Degradation of Antibiotics

Novel photocatalysts were synthesized through the association of carbon quantum dots (CQDs) with commercial (P25) titanium dioxide (TiO2) by sonication. The resulting TiO2/CQDs composite was then incorporated into the polyamide 66 (PA66) biopolymer nanofibers using the electrospinning technique, considering a composite nanoparticles-to-polymer ratio of 1:2 in the electrospinning precursor solution. The produced nanofibers presented suitable morphology and were tested for the photocatalytic degradation under simulated solar radiation of 10 mg L−1 of amoxicillin (AMX) and sulfadiazine (SDZ), in phosphate buffer solution (pH 8.06) and river water, using 1.5 g L−1 of photocatalyst. The presence of the photocatalyst increased the removal of AMX in phosphate buffer solution by 30 times, reducing the AMX degradation half-life time from 62 ± 1 h (without catalyst) to 1.98 ± 0.06 h. Moreover, SDZ degradation half-life time in phosphate buffer solution was reduced from 5.4 ± 0.1 h (without catalyst) to 1.87 ± 0.05 h in the presence of the photocatalyst. Furthermore, the PA66/TiO2/CQDs were also efficient in river water samples and maintained their performance in at least three cycles of SDZ photodegradation in river water. The presented results evidence that the produced photocatalyst can be a promising and sustainable solution for antibiotics’ efficient removal from water.

Silva, Valentina (ORCID:0000000285394787)↗
DOE OSTI2024

Optimization of Solid Oxide Electrolysis Cell Systems Accounting for Long-Term Performance and Health Degradation

This study focuses on optimizing solid oxide electrolysis cell (SOEC) systems for efficient and durable long-term hydrogen (H2) production. While the elevated operating temperatures of SOECs offer advantages in terms of efficiency, they also lead to chemical degradation, which shortens cell lifespan. To address this challenge, dynamic degradation models are coupled with a steady-state, two-dimensional, non-isothermal SOEC model and steady-state auxiliary balance of plant equipment models, within the IDAES modeling and optimization framework. A quasi-steady state approach is presented to reduce model size and computational complexity. Long-term dynamic simulations at constant H2 production rate illustrate the thermal effects of chemical degradation. Dynamic optimization is used to minimize the lifetime cost of H2 production, accounting for SOEC replacement, operating, and energy expenses. Several optimized operating profiles are compared by calculating the Levelized Cost of Hydrogen (LCOH).

Giridhar, Nishant↗
DOE OSTI2022

Nanoscale resolution of microbial fiber degradation in action

The lives of microbes unfold at the micron scale, and their molecular machineries operate at the nanoscale. Their study at these resolutions is key toward achieving a better understanding of their ecology. We focus on cellulose degradation of the canonical Clostridium thermocellum system to comprehend how microbes build and use their cellulosomal machinery at these nanometer scales. Degradation of cellulose, the most abundant organic polymer on Earth, is instrumental to the global carbon cycle. We reveal that bacterial cells form ‘cellulosome capsules’ driven by catalytic product-dependent dynamics, which can increase the rate of hydrolysis. Biosynthesis of this energetically costly machinery and cell growth are decoupled at the single-cell level, hinting at a division-of-labor strategy through phenotypic heterogeneity. This novel observation highlights intrapopulation interactions as key to understanding rates of fiber degradation.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

Targeted protein degradation systems to enhance Wnt signaling

Molecules that facilitate targeted protein degradation (TPD) offer great promise as novel therapeutics. The human hepatic lectin asialoglycoprotein receptor (ASGR) is selectively expressed on hepatocytes. We have previously engineered an anti-ASGR1 antibody-mutant RSPO2 (RSPO2RA) fusion protein (called SWEETS) to drive tissue-specific degradation of ZNRF3/RNF43 E3 ubiquitin ligases, which achieved hepatocyte-specific enhanced Wnt signaling, proliferation, and restored liver function in mouse models, and an antibody–RSPO2RA fusion molecule is currently in human clinical trials. In the current study, we identified two new ASGR1- and ASGR1/2-specific antibodies, 8M24 and 8G8. High-resolution crystal structures of ASGR1:8M24 and ASGR2:8G8 complexes revealed that these antibodies bind to distinct epitopes on opposing sides of ASGR, away from the substrate-binding site. Both antibodies enhanced Wnt activity when assembled as SWEETS molecules with RSPO2RA through specific effects sequestering E3 ligases. In addition, 8M24-RSPO2RA and 8G8-RSPO2RA efficiently downregulate ASGR1 through TPD mechanisms. These results demonstrate the possibility of combining different therapeutic effects and degradation mechanisms in a single molecule.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1972

Degradation of learned skills. Effectiveness of practice methods on simulated space flight skill retention

Manual flight control and emergency procedure task skill degradation was evaluated after time intervals of from 1 to 6 months. The tasks were associated with a simulated launch through the orbit insertion flight phase of a space vehicle. The results showed that acceptable flight control performance was retained for 2 months, rapidly deteriorating thereafter by a factor of 1.7 to 3.1 depending on the performance measure used. Procedural task performance showed unacceptable degradation after only 1 month, and exceeded an order of magnitude after 4 months. The effectiveness of static rehearsal (checklists and briefings) and dynamic warmup (simulator practice) retraining methods were compared for the two tasks. Static rehearsal effectively countered procedural skill degradation, while some combination of dynamic warmup appeared necessary for flight control skill retention. It was apparent that these differences between methods were not solely a function of task type or retraining method, but were a function of the performance measures used for each task.

Sitterley, T. E.↗
NASA NTRS1972

Diffusional creep and creep degradation in the dispersion-strengthened alloy TD-NiCr

Dispersoid-free regions were observed in TD-NiCr (Ni-20Cr-2ThO2) after slow strain rate testing in air from 1145 to 1590 K. Formation of the dispersoid-free regions appears to be the result of diffusional creep. The net effect of this creep is the degradation of TD-NiCr to a duplex microstructure. Degradation is further enhanced by the formation of voids and integranular oxidation in the thoria-free regions. These regions apparently provided sites for void formation and oxide growth since the strength and oxidation resistance of Ni-20Cr is much less than Ni-20Cr-2ThO2. This localized oxidation does not appear to reduce the static load bearing capacity of TD-NiCr since long stress rupture lives were observed even with heavily oxidized microstructures. But this oxidation does significantly reduce the ductility and impact resistance of the material. Dispersoid-free bands and voids were also observed for two other dispersion strengthened alloys, TD-NiCrAl and IN-853. Thus, it appears that diffusional creep is charactertistic of dispersion-strengthened alloys and can play a major role in the creep degradation of these materials.

Whittenberger, J. D.↗
NASA NTRS1972

Degradation of learned skills: Effectiveness of practice methods on visual approach and landing skill retention

Flight control and procedural task skill degradation, and the effectiveness of retraining methods were evaluated for a simulated space vehicle approach and landing under instrument and visual flight conditions. Fifteen experienced pilots were trained and then tested after 4 months either without the benefits of practice or with static rehearsal, dynamic rehearsal or with dynamic warmup practice. Performance on both the flight control and procedure tasks degraded significantly after 4 months. The rehearsal methods effectively countered procedure task skill degradation, while dynamic rehearsal or a combination of static rehearsal and dynamic warmup practice was required for the flight control tasks. The quality of the retraining methods appeared to be primarily dependent on the efficiency of visual cue reinforcement.

Sitterley, T. E.↗
NASA NTRS1973

Effects of diffusion on aluminum depletion and degradation of NiAl coatings

Experiments were performed to critically demonstrate the effects of diffusion on the aluminum depletion and degradation of NiAl coatings on superalloys. Pack aluminized IN 100 and Mar-M200 were diffusion annealed in 0.0005 torr vacuum at 1100 C for 300 hours. Aluminum losses due to oxidation and vaporization were minimal. Metallographic and electron microprobe analyses showed considerable interdiffusion of the coating with the substrate, which caused a large decrease in the original aluminum level of the coating. Subsequent cyclic furnace oxidation tests were performed at 1100 C using 1 hour cycles on pre-diffused and as-coated specimens. The pre-diffusion treatment decreased the oxidation protection for both alloys, but more dramatically for IN 100. Identical oxidation tests of bulk NiAl, where such diffusion effects are precluded, showed no signs of degradation at twice the time needed to degrade the coated superalloys.

Smialek, J. L.↗
NASA NTRS1974

Partial performance degradation of a remote sensor in a space environment, and some probable causes

The Multispectral Scanner (MSS) was launched on the Earth Resources Technology Satellite (ERTS-1) on July 23, 1972. The MSS has two calibration systems, one internal and one external. Both calibration systems have shown strong, spectrally dependent performance degradation since launch. This paper presents details on the optical system of the MSS and data on the performance degradation as a function of both spectral interval and time in orbit. The history of the MSS during tests is traced, and it is shown that hydrocarbons from an external source may have been deposited on optical surfaces in the instrument. It is postulated that these contaminant coatings may have polymerized as a result of the exposure to UV light from the sun, increasing their blue absorbtion and accounting for the observed performance degradation.

Horan, J. J.↗
NASA NTRS1974

Effects of diffusion on aluminum depletion and degradation of NiAl coatings

Experiments were performed to critically demonstrate the effects of diffusion on the aluminum depletion and degradation of NiAl coatings on superalloys. Pack aluminized IN 100 and Mar-M200 were diffusion annealed in 5 mtorr vacuum at 1100 C for 300 hr. Aluminum losses due to oxidation and vaporization were minimal. Metallographic and electron microprobe analyses showed considerable interdiffusion of the coating with the substrate, which caused a large decrease in the original aluminum level of the coating. Subsequent cyclic furnace oxidation tests were performed at 1100 C using 1 hr cycles on prediffused and as-coated specimens. The prediffusion treatment decreased the oxidation and as-coated specimens. The prediffusion treatment decreased the oxidation protection for both alloys, but more dramatically for IN 100. Identical oxidation tests of bulk NiAl, where such diffusion effects are precluded, showed no signs of degradation at twice the time needed to degrade the coated superalloys.

Smialek, J. L.↗
NASA NTRS1975

Study of the thermal degradation mechanism of a composite propellant

The current experimental program was designed to systematically investigate the role of the oxidizer in the thermal degradation process of composite propellants. The scanning electron microscope (SEM) was used to examine the failure sites in thermally degraded propellant samples. The formulation variables tested were oxidizer purity, oxidizer particle size, and oxidizer to binder bonding agent. The binder, a saturated hydrocarbon, was kept constant throughout the experiments. The oxidizers were: AP, chlorate-doped AP, arsenate-doped AP, and phosphate-doped AP. The oxidizer particle size distribution was 60% of the large fraction and 40% of the small fraction. The bonding agent, when present, was used at the 0.15% level. The data showed that both the oxidizer purity and particle size had an important affect on the thermal degradation process. The affect of the oxidizer particle size was more noticeable at the higher temperature and stress levels. An examination of the failure site, by SEM, of propellants subject to these latter conditions indicated that the fracturing of the large oxidizer particles led to the propellant cracking.

Schmidt, W. G.↗
NASA NTRS1977

Creep degradation in oxide-dispersion-strengthened alloys

Oxide dispersion strengthened Ni-base alloys in wrought bar form are studied for creep degradation effects similar to those found in thin gage sheet. The bar products evaluated included ODS-Ni, ODS-NiCr, and three types of advanced ODS-NiCrAl alloys. Tensile test specimens were exposed to creep at various stress levels at 1365 K and then tensile tested at room temperature. Low residual tensile properties, change in fracture mode, the appearance of dispersoid-free bands, grain boundary cavitation, and internal oxidation in the microstructure were interpreted as creep degradation effects. This work showed that many ODS alloys are subject to creep damage. Degradation of tensile properties occurred after very small amounts of creep strain, ductility being the most sensitive property. All the ODS alloys which were creep damaged possessed a large grain size. Creep damage appears to have been due to diffusional creep which produced dispersoid-free bands around boundaries acting as vacancy sources. Low angle and possibly twin boundaries acted as vacancy sources.

Whittenberger, J. D.↗
NASA NTRS1976

The long-term performance degradation of a radioisotope thermoelectric generator using silicon germanium

The successful utilization of a radioisotope thermoelectric generator (RTG) as the power source for spaceflight missions requires that the performance of such an RTG be predictable throughout the mission. Several mechanisms occur within the generator which tend to degrade the performance as a function of operating time. The impact which these mechanisms have on the available output power of an RTG depends primarily on such factors as time, temperature and self-limiting effects. The relative magnitudes, rates and temperature dependency of these various degradation mechanisms have been investigated separately by coupon experiments as well as 4-couple and 18-couple module experiments. This paper discusses the different individual mechanisms and summarizes their combined influence on the performance of an RTG. Also presented as part of the RTG long-term performance characteristics is the sensitivity of the available RTG output power to variations of the individual degradation mechanisms thus identifying the areas of greatest concern for a successful long-term mission.

Stapfer, G.↗
NASA NTRS1977

A study of the chemical degradation of ClONO2 in the stratosphere

The flash photolysis-resonance fluorescence system described by Davis et al. (1974) is used to measure the rate constants for the reactions of chlorine nitrate (ClONO2) with stratospheric O(3-P) and OH. Both reactions are examined in a pyrex cell with an internal volume of about 150 cu cm, where the reaction mixture was maintained at 245 K by circulating methanol from a thermostated circulation bath through the outer jacket of the reaction cell. The relative chemical degradation rates as a function of altitude for both reactions are tabulated, which shows that the chemical degradation pathways contribute less than 10% to the total rate of ClONO2 destruction at altitudes less than 30 km. Since the concentration of ClONO2 is calculated to be near its maximum around 25 km and drops off very significantly at higher altitudes, it is concluded that the photochemical decomposition of ClONO2 in the stratosphere is by far the most important degradation path for this molecule.

Ravishankara, A. R.↗
NASA NTRS1977

Isothermal degradation of poly-2,2'-/m-phenylene/-5,5'-bibenzimidazole

The isothermal degradation of poly-2,2'-(m-phenylene)-5,5'-bibenzimidazole in vacuo has been studied. Measurement of the increase in pressure with time, coupled with infrared analysis, was used to determine the distribution of the degradation products. Processes A and B with different second-order rate laws were determined to be significant in the temperature range of 550-700 C. Process A leads to the formation of equimolar quantities of hydrogen and ammonia and has an activation energy of 68 kcal/mole. Process B leads to the production of HCN, NH3, and H2 in the ratio of 1:1:2.5 and has an activation energy of 77 kcal/mole. The activation energies and the rate laws are consistent with a mechanism in which the initial degradation step is the bimolecular reaction of two aromatic rings.

Lerner, N. R.↗
NASA NTRS1978

Techniques used for limiting degradation products of polymeric materials for use in the space environment

Techniques are discussed for limiting or controlling the degradation products (outgassing) of polymeric materials in the space environment. One technique, now ASTM E-595-77, is used to screen out those materials which lose greater than 1% Total Mass Loss when in vacuum for 24 hours at 125 C and which have more than 0.10% Collected Volatile Condensable Materials condensing on a collector surface at 25 C. Examples of silicone materials which are high and low in outgassing are given. The numerous mechanical motions in spacecraft experiments require liquid lubricants which also might degrade in space. Labyrinth seals and barrier films are utilized to limit the degradation of or from these lubricants. A recoverable in-flight experiment has been proposed for making definitive measurements of how effective these techniques are in limiting the amounts and escape paths of outgassed molecules.

Vest, C. E.↗