Search NASA⌕ Search

SEARCH · Search NASA

Results for “growth”

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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Biostimulation of Salicornia europaea L. crops with plant growth-promoting bacteria in laboratory and field conditions: effects on growth and metabolite profile

Abstract Aim The objective of the work was to assess the effect of biostimulation with selected plant growth-promoting bacteria on growth and metabolite profile of Salicornia europaea. Methods and results Salicornia europaea seeds were inoculated with different combinations of plant growth-promoting bacteria Brevibacterium casei EB3, Pseudomonas oryzihabitans RL18, and Bacillus aryabhattai SP20. Plants germinated from inoculated seeds were grown either in laboratory conditions or in a saline crop field. Fresh and dry weight were determined at the end of the experiment, for biomass quantification. The microbiological quality of fresh shoots for human consumption as salad greens was assessed, and the persistence of the inoculated strains in the plant rhizosphere was confirmed by next-generation sequencing (Illumina) of the 16S rDNA gene. The primary metabolite profile of biostimulated plants was characterized by GC–TOF-MS. In laboratory conditions, inoculation with the two strains Br. casei EB3 and Ps. oryzihabitans RL18 caused the most significant increase in biomass production (fresh and dry weight), and caused a shift in the central metabolic pathways of inoculated plants toward amino acid biosynthesis. In the field experiment, no significant biostimulation effect was detected with any of the tested inoculants. Seed inoculation had no significant effect on the microbiological quality of the edible parts. The persistence of inoculants was confirmed in both experiments. Conclusions Manipulation of the plant microbiome can trigger primary metabolic reconfiguration and modulate the plant metabolism while promoting plant growth.

Ferreira, Maria J.↗
NASA NTRS1978

Laser-zone growth in a Ribbon-To-Ribbon (RTR) process. Silicon sheet growth development for the large area sheet task of the low-cost solar array project

A new calculation of the effects of thermal stresses during growth on silicon ribbon quality is reported. Thermal stress distributions are computed for ribbon growth under a variety of temperature profiles. A growth rate of 55 cu cm/min with a single ribbon was achieved. The growth of RTR ribbon with a fairly uniform parallel dendritic structure was demonstrated. Results with two approaches were obtained for reducing the Mo impurity level in polycrystalline feedstock. Coating the Mo substrate with Si3N4 does not effect thermal shear separation of the polyribbon; this process shows promise of improving cell efficiency and also increasing the useful life of the molybdenum substrate. A number of solar cells were fabricated on RTR silicon grown from CVD feedstock.

Baghdadi, A.↗
NASA NTRS1980

The effect of growth rate, diameter and impurity concentration on structure in Czochralski silicon crystal growth

It is demonstrated that maximum growth rates of up to 80% of the theoretical limit can be attained in Czochralski-grown silicon crystals while maintaining single crystal structure. Attaining the other 20% increase is dependent on design changes in the grower, to reduce the temperature gradient in the liquid while increasing the gradient in the solid. The conclusions of Hopkins et al. (1977) on the effect of diameter on the breakdown of structure at fast growth rates are substantiated. Copper was utilized as the test impurity. At large diameters (greater than 7.5 cm), concentrations of greater than 1 ppm copper were attained in the solid (45,000 ppm in the liquid) without breakdown at maximum growth speeds. For smaller diameter crystals, the sensitivity of impurities is much more apparent. For solar cell applications, impurities will limit cell performance before they cause crystal breakdown for fast growth rates of large diameter crystals.

Digges, T. G., Jr.↗
NASA NTRS1981

Stimulation of body weight increase and epiphyseal cartilage growth by insulin like growth factor

The ability of insulin-like growth factor (IGF) to induce growth in hypophysectomized immature rats was tested by continuous infusion of the partially purified factor at daily doses of 6, 21, and 46 mU for an 8-day period. A dose-dependent growth of the proximal epiphyseal cartilage of the tibia and an associated stimulation of the primary spongiosa were produced by these amounts of IGF. The two highest doses of IGF also resulted in dose-dependent increases of body weight. Gel permeation of the sera at neutrality showed that the large-molecular-weight IGF binding protein was not induced by the infusion of IGF, whereas it ws generated in the sera of hypophysectomized rats that were infused with daily doses of 86 mU of human growth hormone.

Ellis, S.↗
NASA NTRS1987

Growth factor involvement in tension-induced skeletal muscle growth

Muscle tissue culture techniques were developed to grow skeletal myofibers which differentiate into more adult-like myofibers. Mechanical simulation studies of these muscle cells in a newly developed mechanical cell simulator can now be performed to study growth processes in skeletal muscle. Conditions in the mechanical cell simulator were defined where mechanical activity can either prevent muscle wasting or stimulate muscle growth. The role of endogenous and exogenous growth factors in tension-induced muscle growth is being investigated under the defined conditions of tissue culture.

Vandenburgh, H. H.↗
NASA NTRS1993

Growth of new materials for solid state laser applications. The growth of ZnGeP2 by the vertical Bridgman method

This is the final technical report on the cooperative NASA program 'Growth of New Materials for Solid State Laser Applications,' covering the period from 9-1-86 through 3-31-91. The first two and one half years of the program, from 9-1-86 through 3-31-89, was devoted to the development of new eye-safe laser sources. Single crystal fibers of rare earth doped and co-doped YAG were grown by the laser-heated pedestal growth method, characterized for their structural properties and supplied to NASA/Langley for spectroscopic evaluation. From 4-1-89 though 3-31-91, research focused on the growth of zinc germanium phosphide for nonlinear optical applications in the IR. The vertical Bridgman growth process was evaluated as a means to achieve better control over the short wavelength optical absorption in this material that adversely affects 2 micron-pumped optical parametric oscillators.

Feigelson, R. S.↗
NASA NTRS1999

Growth of Compound Semiconductors in a Low Gravity Environment: Microgravity Growth of PbSnTe

The growth of the alloy compound semiconductor lead tin telluride (PbSnTe) was chosen for a microgravity flight experiment in the Advanced Automated Directional Solidification Furnace (AADSF), on the United States Microgravity Payload-3 (USMP-3) and on USMP-4 Space Shuttle flights in February, 1996, and November, 1997. The objective of these experiments was to determine the effect of the reduction in convection, during the growth process, brought about by the microgravity environment. The properties of devices made from PbSnTe are dependent on the ratio of the elemental components in the starting crystal. Compositional uniformity in the crystal is only obtained if there is no significant mixing in the liquid during growth. Lead tin telluride is an alloy of PbTe and SnTe. The technological importance of PbSnTe lies in its band gap versus composition diagram which has a zero energy crossing at approximately 40% SnTe. This facilitates the construction of long wavelength (>6 micron) infrared detectors and lasers. Observations and experimental methods of crystal growth of PbSnTe on both Space Shuttle Flights are presented.

Fripp, Archibald L.↗
NASA NTRS2002

Transport and Growth Kinetics in Microgravity Protein Crystal Growth

The dynamic coupling between mass transport and incorporation of growth units into the surface of a crystal growing from solution in microgravity is used to derive quantitative information on the crystal growth kinetics. To this end, new procedures for experiment preparation, interferometric data processing and model fitting have been developed. The use of experimental data from the bulk diffusive maw transport together with a model for steady state stagnant crystal growth allows the detailed quantitative understanding of the kinetics of both the concentration depletion zone around the crystal and the growth of the crystal interface. The protein crystal used in the experiment is shown to be growing in the mixed kinetic regime (0.2 x 10(exp -6) centimeters per second less than beta R/D less than 0.9 x 10(exp -6) centimeters per second).

Otalora, F.↗
NASA NTRS2003

Fatigue Crack Growth Rate and Stress-Intensity Factor Corrections for Out-of-Plane Crack Growth

Fatigue crack growth rate testing is performed by automated data collection systems that assume straight crack growth in the plane of symmetry and use standard polynomial solutions to compute crack length and stress-intensity factors from compliance or potential drop measurements. Visual measurements used to correct the collected data typically include only the horizontal crack length, which for cracks that propagate out-of-plane, under-estimates the crack growth rates and over-estimates the stress-intensity factors. The authors have devised an approach for correcting both the crack growth rates and stress-intensity factors based on two-dimensional mixed mode-I/II finite element analysis (FEA). The approach is used to correct out-of-plane data for 7050-T7451 and 2025-T6 aluminum alloys. Results indicate the correction process works well for high DeltaK levels but fails to capture the mixed-mode effects at DeltaK levels approaching threshold (da/dN approximately 10(exp -10) meter/cycle).

Forth, Scott C.↗
NASA NTRS2003

Catecholamines and in vitro growth of pathogenic bacteria: enhancement of growth varies greatly among bacterial species

The purpose of this study was to examine the effects of catecholamines on in vitro growth of a range of bacterial species, including anaerobes. Bacteria tested included: Porphyromonas gingivalis, Bacteriodes fragilis, Shigella boydii, Shigella sonnie, Enterobacter Sp, and Salmonella choleraesuis. The results of the current study indicated that supplementation of bacterial cultures in minimal medium with norepinephrine or epinephrine did not result in increased growth of bacteria. Positive controls involving treatment of Escherichia coli with catecholamines did result in increased growth of that bacterial species. The results of the present study extend previous observations that showed differential capability of catecholamines to enhance bacterial growth in vitro.

Non-NASA Center↗
NASA NTRS2012

Estimation of alga growth stage and lipid content growth rate

Method and system for estimating a growth stage of an alga in an ambient fluid. Measured light beam absorption or reflection values through or from the alga and through an ambient fluid, in each of two or more wavelength sub-ranges, are compared with reference light beam absorption values for corresponding wavelength sub-ranges for in each alga growth stage to determine (1) which alga growth stage, if any, is more likely and (2) whether estimated lipid content of the alga is increasing or has peaked. Alga growth is preferably terminated when lipid content has approximately reached a maximum value.

Embaye, Tsegereda N.↗
DOE OSTI2020

A Potts Model parameter study of particle size, Monte Carlo temperature, and “Particle-Assisted Abnormal Grain Growth”

A Potts Model was proposed to account for temperature and particle heterogeneity-dependent Zener Pinning. This was accomplished by relating the random fluctuations of grain boundary position allowed by the Potts Model switching probability at finite simulation temperature to experimentally observed grain growth stagnation behavior. We assume that these fluctuations arise from random fluctuations in the thermodynamic and kinetic properties of the grain boundaries and/or interfaces as they change with temperature. As an application of this model, the grain growth kinetics of U-10 wt. % Mo nuclear fuels were simulated with the input of microstructural images during different heat treatment processes. Simulated average grain growth behavior is in good agreement with experiments.

Frazier, William E.↗
DOE OSTI2020

Defect cluster and nonequilibrium gas bubble associated growth in irradiated UMo fuels – a cluster dynamics and phase field model

Irradiation examination shows that gas bubble swelling kinetics is much faster after irradiation-induced recrystallization than that prior recrystallization in UMo fuels. It implies that gas bubbles in coarse grains and small recrystallized grains have different growth behavior. In this work, a phase-field model of gas bubble evolution integrating microstructure dependent cluster dynamics has been developed, for the first time, to study the gas bubble swelling behavior in the recrystallization zone of UMo fuels. Generation, diffusion, reaction, sink, emission and clustering of vacancies and interstitials are described by the cluster dynamics model while a phase-field model is used to describe the evolution of non-equilibrium gas bubbles including nucleation and growth. With the coupled model, the effect of defect generation rate, clustering rate, interstitial emission and sink rates on grain boundaries on the gas bubble evolution are systematically simulated. A set of model parameters (defect generation rate, clustering rate, interstitial emission and sink rates) is determined by comparing measured and simulated gas bubble swelling kinetics. The results demonstrate that interstitial clustering is one of the important physical mechanisms which results in a fast gas bubble swelling kinetics in the recrystallization zone. The developed model can also be extended to study the associated growth of defect and second phase precipitates often observed in irradiated materials.

Hu, Shenyang↗
DOE OSTI2020

Semi-adsorption-controlled growth window for half-Heusler FeVSb epitaxial films

The electronic, magnetic, thermoelectric, and topological properties of Heusler compounds (composition XYZ or X 2 YZ) are highly sensitive to stoichiometry and defects. Here we establish the existence and experimentally map the bounds of a semi-adsorption-controlled growth window for semiconducting half-Heusler FeVSb films, grown by molecular beam epitaxy (MBE). We show that due to the high volatility of Sb, the Sb stoichiometry is self-limiting for a finite range of growth temperatures and Sb fluxes, similar to the growth of III-V semiconductors such as GaSb and GaAs. Films grown within this window are nearly structurally indistinguishable by x-ray diffraction (XRD) and reflection high energy electron diffraction (RHEED). Here, the highest electron mobility and lowest background carrier density are obtained towards the Sb-rich bound of the window, suggesting that Sb vacancies may be a common defect. Similar semi-adsorption-controlled bounds are expected for other ternary intermetallics that contain a volatile species Z = {Sb, As, Bi}, e.g., CoTiSb, LuPtSb, GdPtBi, and NiMnSb. However, outstanding challenges remain in controlling the remaining Fe/V (X/Y) transition metal stoichiometry.

36 MATERIALS SCIENCE↗
NASA NTRS1986

A thermal-capillary mechanism for a growth rate limit in edge-defined film-fed growth of silicon sheets

Capillarity, acting to set the shape of the melt/gas interfaces, and heat transfer can interact to cause limits to steady-state growth of thin silicon sheets by the Edge-Defined Film-Fed Growth (EFG) method. A finite-element/Newton solution method for a two-dimensional thermal-capillary model of EFG is used to show that limiting values of pull rate exist beyond which steady-state growth is impossible. The pull rate limit is also predicted by a one-dimensional heat transfer model valid when the die sides and menisci are almost parallel and when the thermal conductivities of melt, crystal, and die are all equal. Both the one- and two-dimensional heat transfer models show that heat loss from the melt is dominated by conduction into the crystal and slow heat release to the ambient along the length of the ribbon. The limiting pull rate results from the reduced efficiency of conduction through the melt caused by the curvature of the meniscus which increases height of the die top above the level of the melt. Thermal-capillary limits are predicted for both positive and negative pressure differences across the meniscus.

Thomas, P. D.↗
NASA NTRS1988

Control of nucleation and growth in protein crystal growth

The potential advantages of nucleation and growth control through temperature, rather than the addition of precipitants or removal of solvent, are discussed. A simple light scattering arrangement for the characterization of nucleation and growth conditions in solutions is described. The temperature dependence of the solubility of low ionic strength lysozyme solutions is applied in preliminary nucleation and growth experiments.

Rosenberger, Franz↗
NASA NTRS1992

Growth of III-V films by control of MBE growth front stoichiometry

For the growth of strain-layer materials and high quality single and multiple quantum wells, the instantaneous control of growth front stoichiometry is critical. The process of the invention adjusts the offset or phase of molecular beam epitaxy (MBE) control shutters to program the instantaneous arrival or flux rate of In and As4 reactants to grow InAs. The interrupted growth of first In, then As4, is also a key feature.

Grunthaner, Frank J.↗