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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS2001

Nitrate concentration effects on NO3-N uptake and reduction, growth, and fruit yield in strawberry

Strawberries (Fragaria xananassa Duch. 'Osogrande') were grown hydroponically with three NO3-N concentrations (3.75, 7.5, or 15.0 mM) to determine effects of varying concentration on NO3-N uptake and reduction rates, and to relate these processes to growth and fruit yield. Plants were grown for 32 weeks, and NO3-N uptake and nitrate reductase (NR) activities in roots and shoots were measured during vegetative and reproductive growth. In general, NO3-N uptake rates increased as NO3-N concentration in the hydroponics system increased. Tissue NO3- concentration also increased as external NO3-N concentration increased, reflecting the differences in uptake rates. There was no effect of external NO3-N concentration on NR activities in leaves or roots during either stage of development. Leaf NR activity averaged approximately 360 nmol NO2 formed/g fresh weight (FW)/h over both developmental stages, while NR activity in roots was much lower, averaging approximately 115 nmol NO2 formed/g FW/h. Vegetative organ FW, dry weight (DW), and total fruit yield were unaffected by NO3-N concentration. These data suggest that the inability of strawberry to increase growth and fruit yield in response to increasing NO3-N concentrations is not due to limitations in NO3-N uptake rates, but rather to limitations in NO3- reduction and/or assimilation in both roots and leaves.

NASA Center KSC↗
NASA NTRS1984

Crack tip field and fatigue crack growth in general yielding and low cycle fatigue

Fatigue life consists of crack nucleation and crack propagation periods. Fatigue crack nucleation period is shorter relative to the propagation period at higher stresses. Crack nucleation period of low cycle fatigue might even be shortened by material and fabrication defects and by environmental attack. In these cases, fatigue life is largely crack propagation period. The characteristic crack tip field was studied by the finite element method, and the crack tip field is related to the far field parameters: the deformation work density, and the product of applied stress and applied strain. The cyclic carck growth rates in specimens in general yielding as measured by Solomon are analyzed in terms of J-integral. A generalized crack behavior in terms of delta is developed. The relations between J and the far field parameters and the relation for the general cyclic crack growth behavior are used to analyze fatigue lives of specimens under general-yielding cyclic-load. Fatigue life is related to the applied stress and strain ranges, the deformation work density, crack nucleus size, fracture toughness, fatigue crack growth threshold, Young's modulus, and the cyclic yield stress and strain. The fatigue lives of two aluminum alloys correlate well with the deformation work density as depicted by the derived theory. The general relation is reduced to Coffin-Manson low cycle fatigue law in the high strain region.

Minzhong, Z.↗
NASA NTRS1989

Effects of incandescent radiation on photosynthesis, growth rate and yield of 'Waldmann's Green' leaf lettuce

Effects of different ratios incandescent (ln) to fluorescent (Fl) radiation were tested on growth of 'Waldmann's Green' leaf lettuce (Lactuca sativa L.) in a controlled environment. After 4 days of treatment, dry weight, leaf area, relative growth rate (RGR), net assimilation rate (NAR), leaf area ratio (LAR) and photosynthetic rate (Pn) were greater for plants grown at 84 rather than 16% of total irradiance (82 W m-2) from ln lamps. Although leaf dry weight and area were 12-17% greater at 84% ln after the first 8 days of treatment, there were no differences in RGR or Pn between treatments during the last 4 days. If 84% ln was compared with 50% ln, all cumulative growth parameters, RGR, NAR and Pn were greater for 84% ln during the first 4 days of treatment. However, during the second 4 days, RGR was greater for the 50% ln treatment, resulting in no net difference in leaf dry weight or area between treatments. Shifting from 84 to 50% ln radiation between the first and second 4 days of treatment increased plant dry weight, leaf area, RGR and NAR relative to those under 84% ln for 8 days continuously.

NASA Program CELSS↗
NASA NTRS1988

Effects of incandescent radiation on photosynthesis, growth rate and yield of 'Waldmann's Green' leaf lettuce

Effects of different ratios of incandescent (ln) to fluorescent (Fl) radiation were tested on growth of 'Waldmann's Green' leaf lettuce in a controlled environment. After 4 days of treatment, dry weight, leaf area, relative growth rate (RGR), net assimilation rate (NAR), leaf area ratio (LAR) and photosynthetic rate (Pn) were greater for plants grown at 84 rather than 16 percent of total irradiance (82 W/sq m) from ln lamps. Although leaf dry weight and area were 12-17 percent greater at 84 percent ln after the first 8 days of treatment, there were no differences in RGR or Pn between treatments during the last 4 days. If 84 percent ln was compared with 50 percent ln, all cumulative growth parameters, RGR, NAR and Pn were greater for 84 percent ln during the first 4 days of treatment. However, during the second 4 days, RGR was greater for the 50 percent ln treatment, resulting in no net difference in leaf dry weight or area between treatments. Shifting from 84 to 50 percent ln radiation between the first and second 4 days of treatment increased plant dry weight, leaf area, RGR and NAR relative to those under 84 percent ln for 8 days continuously.

Knight, Sharon L.↗
DOE OSTI2021

Understanding Growth Dynamics and Yield Prediction of Sorghum Using High Temporal Resolution UAV Imagery Time Series and Machine Learning

Unmanned aerial vehicles (UAV) carrying multispectral cameras are increasingly being used for high-throughput phenotyping (HTP) of above-ground traits of crops to study genetic diversity, resource use efficiency and responses to abiotic or biotic stresses. There is significant unexplored potential for repeated data collection through a field season to reveal information on the rates of growth and provide predictions of the final yield. Generating such information early in the season would create opportunities for more efficient in-depth phenotyping and germplasm selection. This study tested the use of high-resolution time-series imagery (5 or 10 sampling dates) to understand the relationships between growth dynamics, temporal resolution and end-of-season above-ground biomass (AGB) in 869 diverse accessions of highly productive (mean AGB = 23.4 Mg/Ha), photoperiod sensitive sorghum. Canopy surface height (CSM), ground cover (GC), and five common spectral indices were considered as features of the crop phenotype. Spline curve fitting was used to integrate data from single flights into continuous time courses. Random Forest was used to predict end-of-season AGB from aerial imagery, and to identify the most informative variables driving predictions. Improved prediction of end-of-season AGB (RMSE reduction of 0.24 Mg/Ha) was achieved earlier in the growing season (10 to 20 days) by leveraging early- and mid-season measurement of the rate of change of geometric and spectral features. Early in the season, dynamic traits describing the rates of change of CSM and GC predicted end-of-season AGB best. Late in the season, CSM on a given date was the most influential predictor of end-of-season AGB. The power to predict end-of-season AGB was greatest at 50 days after planting, accounting for 63% of variance across this very diverse germplasm collection with modest error (RMSE 1.8 Mg/ha). End-of-season AGB could be predicted equally well when spline fitting was performed on data collected from five flights versus 10 flights over the growing season. This demonstrates a more valuable and efficient approach to using UAVs for HTP, while also proposing strategies to add further value.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1977

Estimated winter wheat yield from crop growth predicted by LANDSAT

An evapotranspiration and growth model for winter wheat is reported. The inputs are daily solar radiation, maximum temperature, minimum temperature, precipitation/irrigation and leaf area index. The meteorological data were obtained from National Weather Service while LAI was obtained from LANDSAT multispectral scanner. The output provides daily estimates of potential evapotranspiration, transpiration, evaporation, soil moisture (50 cm depth), percentage depletion, net photosynthesis and dry matter production. Winter wheat yields are correlated with transpiration and dry matter accumulation.

Kanemasu, E. T.↗
NASA NTRS2004

Lateral Movement of Screw Dislocations During Homoepitaxial Growth and Devices Yielded Therefrom Free of the Detrimental Effects of Screw Dislocations

The present invention is related to a method that enables and improves wide bandgap homoepitaxial layers to be grown on axis single crystal substrates, particularly SiC. The lateral positions of the screw dislocations in epitaxial layers are predetermined instead of random, which allows devices to be reproducibly patterned to avoid performance degrading crystal defects normally created by screw dislocations.

Philip G Neudeck↗
NASA NTRS2000

Growth, pod, and seed yield, and gas exchange of hydroponically grown peanut in response to CO2 enrichment

The effects of elevated CO2 on growth, pod, and seed yield, and gas exchange of 'Georgia Red' peanut (Arachis hypogaea L.) were evaluated under controlled environmental conditions. Plants were exposed to concentrations of 400 (ambient), 800, and 1200 micromoles mol-1 CO2 in reach-in growth chambers. Foliage fresh and dry weights increased with increased CO2 up to 800 micromoles mol-1, but declined at 1200 micromoles mol-1. The number and the fresh and dry weights of pods also increased with increasing CO2 concentration. However, the yield of immature pods was not significantly influenced by increased CO2. Total seed yield increased 33% from ambient to 800 micromoles mol-1 CO2, and 4% from 800 to 1200 micromoles mol-1 CO2. Harvest index increased with increasing CO2. Branch length increased while specific leaf area decreased linearly as CO2 increased from ambient to 1200 micromoles mol-1. Net photosynthetic rate was highest among plants grown at 800 micromoles mol-1. Stomatal conductance decreased with increased CO2. Carboxylation efficiency was similar among plants grown at 400 and 800 micromoles mol-1 and decreased at 1200 micromoles mol-1 CO2. These results suggest that CO2 enrichment from 400 to 800 micromoles mol-1 had positive effects on peanut growth and yield, but above 800 micromoles mol-1 enrichment seed yield increased only marginally.

NASA Discipline Life Support Systems↗
DOE OSTI2023

The algal microbiome protects Desmodesmus intermedius from high light and temperature stress

The mutualistic impacts of bacterial communities on algal growth and biomass accumulation are well documented, but it is unknown how temperature and light stress influence these mutualistic interactions. Here, we generated a bacteria-free (axenic) culture of the green alga Desmodesmus intermedius C046 and compared its growth and yield in the laboratory to its native xenic counterpart - featuring a microbiome that has been maintained with its algal host for at least 5 years – under unstressed and high light, high temperature stress conditions. We then added exogenous microbiomes from high light marine environments to the axenic culture to quantify the contribution of these newly generated microbial consortia in improving D. intermedius growth, yield, and resilience to high light and heat. The native microbiome increased growth and biomass accumulation, under both unstressed and stressed conditions. Three of the five newly derived microbiomes had increased growth compared to the axenic and negligible, decreased, or increased growth impacts compared to the xenic culture. Stress conditions led to decreased algal exudation, larger algal cells when grown alone, but smaller algal cells with an associated microbiome. In conclusion, our results suggest that the algal microbiome plays a role in microalgal response to heat and light stress, and efforts for screening new algal strains for high biomass productivity under those stress conditions should include a strategy for microbiome optimization.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1986

Fatigue crack growth under general-yielding cyclic-loading

In low cycle fatigue, cracks are initiated and propagated under general yielding cyclic loading. For general yielding cyclic loading, Dowling and Begley have shown that fatigue crack growth rate correlates well with the measured delta J. The correlation of da/dN with delta J was also studied by a number of other investigators. However, none of thse studies have correlated da/dN with delta J calculated specifically for the test specimens. Solomon measured fatigue crack growth in specimens in general yielding cyclic loading. The crack tips fields for Solomon's specimens are calculated using the finite element method and the J values of Solomon's tests are evaluated. The measured crack growth rate in Solomon's specimens correlates very well with the calculated delta J.

Minzhong, Z.↗
NASA NTRS1986

Fatigue crack growth under general-yielding cyclic-loading

In low cycle fatigue, cracks are initiated, and propagated under general-yielding cyclic loading. For general-yielding cyclic loading, Dowling and Begley (1976) have shown that fatigue crack growth rate correlates well with the measured Delta J. The correlation of da/dN with Delta J has also been studied by a number of other investigators. However, none of these studies has correlated da/dN with Delta J calculated specifically for the test specimens. Solomon measured fatigue crack growth in specimens in general-yielding cyclic loading. The crack tip fields for Solomon's specimens are calculated, using the finite element method, and the J-values of Solomon's tests are evaluated. The measured crack growth rate in Solomon's specimens correlates very well with the calculated Delta J.

Minzhong, Z.↗
NASA NTRS1984

Oscillating-Crucible Technique for Silicon Growth

Technique yields better mixing of impurities and superior qualiity crystals. Accellerated motion stirs melt which reduces temperature gradients and decreases boundary layer for diffusion of impurities near growing surface. Results better mixing of impurities into melt, decrease in tendency for dendritic growth or cellular growth and crystals with low dislocation density. Applied with success to solution growth and Czochralski growth, resulting in large crystals of superior quality.

Daud, T.↗
NASA NTRS1994

Effects of radiation quality, intensity, and duration on photosynthesis and growth

Differences in radiation quality from the six most common electric lamps have little effect on photosynthetic rate. Radiation quality primarily alters growth because of changes in branching or internode elongation, which change radiation absorption. Growth and yield in wheat appear to be insensitive to radiation quality. Growth and yield in soybeans can be slightly increased under high pressure sodium (HPS) lamps compared to metal halide lamps, in spite of greatly reduced chlorophyll concentrations under HPS lamps. Daily integrated photosynthetic photon flux (mol m(exp -2)d(exp -1)) most directly determines leaf anatomy and growth. Photosynthetic photon flux (PPF) levels of 800 (mu)mol m(exp -2)s(exp -1) are adequate to simulate field daily-integrated PPF levels for both short and long day plants, but plant canopies can benefit from much higher PPF levels.

Bugbee, Bruce↗
NASA NTRS1997

Super-optimal CO2 reduces seed yield but not vegetative growth in wheat

Although terrestrial atmospheric CO2 levels will not reach 1000 micromoles mol-1 (0.1%) for decades, CO2 levels in growth chambers and greenhouses routinely exceed that concentration. CO2 levels in life support systems in space can exceed 10000 micromoles mol-1(1%). Numerous studies have examined CO2 effects up to 1000 micromoles mol-1, but biochemical measurements indicate that the beneficial effects of CO2 can continue beyond this concentration. We studied the effects of near-optimal (approximately 1200 micromoles mol-1) and super-optimal CO2 levels (2400 micromoles mol-1) on yield of two cultivars of hydroponically grown wheat (Triticum aestivum L.) in 12 trials in growth chambers. Increasing CO2 from sub-optimal to near-optimal (350-1200 micromoles mol-1) increased vegetative growth by 25% and seed yield by 15% in both cultivars. Yield increases were primarily the result of an increased number of heads per square meter. Further elevation of CO2 to 2500 micromoles mol-1 reduced seed yield by 22% (P < 0.001) in cv. Veery-10 and by 15% (P < 0.001) in cv. USU-Apogee. Super-optimal CO2 did not decrease the number of heads per square meter, but reduced seeds per head by 10% and mass per seed by 11%. The toxic effect of CO2 was similar over a range of light levels from half to full sunlight. Subsequent trials revealed that super-optimal CO2 during the interval between 2 wk before and after anthesis mimicked the effect of constant super-optimal CO2. Furthermore, near-optimal CO2 during the same interval mimicked the effect of constant near-optimal CO2. Nutrient concentration of leaves and heads was not affected by CO2. These results suggest that super-optimal CO2 inhibits some process that occurs near the time of seed set resulting in decreased seed set, seed mass, and yield.

NASA Discipline Life Support Systems↗
DOE OSTI2023

Expression of V-nitrogenase and Fe-nitrogenase in Methanosarcina acetivorans is controlled by molybdenum, fixed nitrogen, and the expression of Mo-nitrogenase

ABSTRACT All nitrogen-fixing bacteria and archaea (diazotrophs) use molybdenum (Mo) nitrogenase to reduce dinitrogen (N 2 ) to ammonia, with some also containing vanadium (V) and iron-only (Fe) nitrogenases that lack Mo. Among diazotrophs, the regulation and usage of the alternative V-nitrogenase and Fe-nitrogenase in methanogens are largely unknown. Methanosarcina acetivorans contains nif , vnf , and anf gene clusters encoding putative Mo-nitrogenase, V-nitrogenase, and Fe-nitrogenase, respectively. This study investigated nitrogenase expression and growth by M. acetivorans in response to fixed nitrogen, Mo/V availability, and CRISPRi repression of the nif , vnf , and/or anf gene clusters. The availability of Mo and V significantly affected growth of M. acetivorans with N 2 but not with NH 4 Cl. M. acetivorans exhibited the fastest growth rate and highest cell yield during growth with N 2 in medium containing Mo, and the slowest growth in medium lacking Mo and V. qPCR analysis revealed the transcription of the nif operon is only moderately affected by depletion of fixed nitrogen and Mo, whereas vnf and anf transcription increased significantly when fixed nitrogen and Mo were depleted, with removal of Mo being key. Immunoblot analysis revealed Mo-nitrogenase is detected when fixed nitrogen is depleted regardless of Mo availability, while V-nitrogenase and Fe-nitrogenase are detected only in the absence of fixed nitrogen and Mo. CRISPRi repression studies revealed that V-nitrogenase and/or Fe-nitrogenase are required for Mo-independent diazotrophy, and unexpectedly that the expression of Mo-nitrogenase is also required. These results reveal that alternative nitrogenase production in M. acetivorans is tightly controlled and dependent on Mo-nitrogenase expression. IMPORTANCE Methanogens and closely related methanotrophs are the only archaea known or predicted to possess nitrogenase. Methanogens play critical roles in both the global biological nitrogen and carbon cycles. Moreover, methanogens are an ancient microbial lineage and nitrogenase likely originated in methanogens. An understanding of the usage and properties of nitrogenases in methanogens can provide new insight into the evolution of nitrogen fixation and aid in the development nitrogenase-based biotechnology. This study provides the first evidence that a methanogen can produce all three forms of nitrogenases, including simultaneously. The results reveal components of Mo-nitrogenase regulate or are needed to produce V-nitrogenase and Fe-nitrogenase in methanogens, a result not seen in bacteria. Overall, this study provides a foundation to understand the assembly, regulation, and activity of the alternative nitrogenases in methanogens.

Biotechnology & Applied Microbiology↗
NASA NTRS2018

Can Egypt Become Self-Sufficient in Wheat?

Egypt produces half of the 20 million tons of wheat that it consumes with irrigation and imports the other half. Egypt is also the world's largest importer of wheat. The population of Egypt is currently growing at 2.2% annually, and projections indicate that the demand for wheat will triple by the end of the century. Combining multi-crop and -climate models for different climate change scenarios with recent trends in technology, we estimated that future wheat yield will decline mostly from climate change, despite some yield improvements from new technologies. The growth stimulus from elevated atmospheric CO2 will be overtaken by the negative impact of rising temperatures on crop growth and yield. An ongoing program to double the irrigated land area by 2035 in parallel with crop intensification could increase wheat production and make Egypt self-sufficient in the near future, but would be insufficient after 2040s, even with modest population growth. Additionally, the demand for irrigation will increase from 6 to 20 billion m3 for the expanded wheat production, but even more water is needed to account for irrigation efficiency and salt leaching (to a total of up to 29 billion m3). Supplying water for future irrigation and producing sufficient grain will remain challenges for Egypt.

Asseng, Senthold↗