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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 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

A Data Base of Crop Nutrient Use, Water Use, and Carbon Dioxide Exchange in a 20 Square Meter Growth Chamber: Wheat as a Case Study - Part 1

A data set is given describing the daily nutrient uptake, gas exchange, environmental conditions, and carbon (C), and nutrient partitioning at harvest for the entire canopy and root system of a wheat crop (Triticum aestivum, cv. Yecora Rojo). The data were obtained from a 20 sq m stand of wheat plants grown from planting to maturity in a closed, controlled environment, and include daily nutrient uptake [macronutrients, nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and sulfur (S); and micronutrients, iron (Fe), boron (B), manganese (Mn), zinc (Zn), copper (Cu), and molybdenum (Mo)], canopy carbon dioxide (CO2) exchange rates, and transpiration. Environmental factors such as relative humidity, air temperature, nutrient solution temperature, pH and electrical conductivity, and photoperiod were controlled in the chamber to specific set points. A detailed description of biomass yield for each of the 64 plant growth trays comprising the 20 sq m of growth area is also provided, and includes dry weights of grain, straw, chaff, and roots, along with the concentration of nutrients in different plant tissues and the percent carbohydrate, fat, and protein. To our knowledge, this information represents one of the most extensive data sets available for a canopy of wheat grown from seed to maturity under controlled environmental and nutritional conditions, and thus may provide useful information for model development and validation. A methods section is included to qualify any assumptions that might he required for the use of the data in plant growth models, along with a daily event calendar indicating when adjustments in set points and occasional equipment or sensor failures occurred.

Wheeler, Raymond M.↗
NASA NTRS1982

Pole placement by static and dynamic output feedback

This paper gives new results concerning pole-assignability by static and dynamic output feedback, based on the interpretation of transfer functions, feedback laws, poles and zeroes in terms of the incidence geometry of m-planes and p-planes in (m+p)-space. As an illustration of the most basic ideas, a short proof of the Brasch-Pearson theorem is given. A more careful analysis of this proof yields a significant extension of this theorem, which is considerably sharpened in the case of pole-assignment by constant gain output feedback. As a final application, a root-locus design technique for non-square systems is introduced: zero placement by pre- or post-compensation. This zero placement problem is then analyzed by methods similar to those developed for pole placement by output feedback.

Byrnes, C. I.↗
DOE OSTI2023

Numerical Modeling of Air-Blast Suppression as a Function of Explosive-Charge Burial Depth

As a chemical explosion is buried, the mechanism for acoustic wave generation transitions from fully gas-generated at the surface to completely spall-induced at full containment depth. The fully gas-generated and completely spall-induced signals in the acoustic waveform are well described; however, the transition between these two end-members eludes numerical modeling because of the complex phenomena that are involved. The phenomena of crater formation and explosive cloud evolution are simulated using an Eulerian hydrocode that incorporates geomaterials with strength and porosity. Having accurately modeled these phenomena, we can confidently predict the propagation and relative strength of the gas-generated and spall-induced pulses in the recorded acoustic waveform. The numerical predictions agree with observations from the historical Stagecoach experiment as well as modern recordings from the Source Physics Experiment. In particular, the peak pressure p generated by an explosion is initially due to the gas-generated mechanism and decays with scaled depth of burial d s (depth d scaled by the cube-root of explosive yield w 1/3 ) as exp(-d s ) but then transitions near a scaled depth of 6 m/ton 1/3 to the spall-generated mechanism in which the decay is d$_{s}^{-7/4}$. This decay form is related to the strong ground-motion attenuation relationship that affects spall strength. So these results can improve seismoacoustic inverse models for the explosive source that need to account for the gas-generated and spall-induced signals and their effect on peak pressures and other acoustic signal features.

58 GEOSCIENCES↗
NASA NTRS1972

Discrete square root smoothing.

The basic techniques applied in the square root least squares and square root filtering solutions are applied to the smoothing problem. Both conventional and square root solutions are obtained by computing the filtered solutions, then modifying the results to include the effect of all measurements. A comparison of computation requirements indicates that the square root information smoother (SRIS) is more efficient than conventional solutions in a large class of fixed interval smoothing problems.

Kaminski, P. G.↗
NASA NTRS1978

Large eddy simulation of incompressible turbulent channel flow

The three-dimensional, time-dependent primitive equations of motion were numerically integrated for the case of turbulent channel flow. A partially implicit numerical method was developed. An important feature of this scheme is that the equation of continuity is solved directly. The residual field motions were simulated through an eddy viscosity model, while the large-scale field was obtained directly from the solution of the governing equations. An important portion of the initial velocity field was obtained from the solution of the linearized Navier-Stokes equations. The pseudospectral method was used for numerical differentiation in the horizontal directions, and second-order finite-difference schemes were used in the direction normal to the walls. The large eddy simulation technique is capable of reproducing some of the important features of wall-bounded turbulent flows. The resolvable portions of the root-mean square wall pressure fluctuations, pressure velocity-gradient correlations, and velocity pressure-gradient correlations are documented.

Moin, P.↗
NASA NTRS1979

Linear state feedback, quadratic weights, and closed loop eigenstructures

Results are given on the relationships between closed loop eigenstructures, state feedback gain matrices of the linear state feedback problem, and quadratic weights of the linear quadratic regulator. Equations are derived for the angles of general multivariable root loci and linear quadratic optimal root loci, including angles of departure and approach. The generalized eigenvalue problem is used for the first time to compute angles of approach. Equations are also derived to find the sensitivity of closed loop eigenvalues and the directional derivatives of closed loop eigenvectors (with respect to a scalar multiplying the feedback gain matrix or the quadratic control weight). An equivalence class of quadratic weights that produce the same asymptotic eigenstructure is defined, sufficient conditions to be in it are given, a canonical element is defined, and an algorithm to find it is given. The behavior of the optimal root locus in the nonasymptotic region is shown to be different for quadratic weights with the same asymptotic properties.

Thompson, P. M.↗
NASA NTRS1986

A brief description of the simple biosphere model (SiB)

A biosphere model for calculating the transfer of energy, mass, and momentum between the atmosphere and the vegetated surface of the Earth was designed for atmospheric general circulation models. An upper vegetation layer represents the perennial canopy of trees or shrubs, a lower layer represents the annual ground cover of grasses and other herbacious species. The local coverage of each vegetation layer may be fractional or complete but as the individual vegetation elements are considered to be evenly spaced, their root systems are assumed to extend uniformly throughout the entire grid-area. The biosphere has seven prognostic physical-state variables: two temperatures (one for the canopy and one for the ground cover and soil surface); two interception water stores (one for the canopy and one for the ground cover); and three soil moisture stores (two of which can be reached by the vegetation root systems and one underlying recharge layer into and out of which moisture is transferred only by hydraulic diffusion).

Sellers, P. J.↗
NASA NTRS1993

Organization of cortical microtubules in graviresponding maize roots

Immunofluorescence labeling of cortical microtubules (MTs) was used to investigate the relationship between MT arrangement and changes in growth rate of the upper and lower sides of horizontally placed roots of maize (Zea mays L. cv. Merit). Cap cells and cells of the elongation zone of roots grown vertically in light or darkness showed MT arrangements that were transverse (perpendicular) to the growth direction. Microtubules of cells basal to the elongation zone typically showed oblique orientation. Two hours after horizontal reorientation, cap cells of gravicompetent, light-grown and curving roots contained MTs parallel to the gravity vector. The MT arrangement on the upper side of the elongation zone remained transverse but the MTs of the outer four to five layers of cortical cells along the lower side of the elongation zone showed reorientation parallel to the axis of the root. The MTs of the lower epidermis retained their transverse orientation. Dark-grown roots did not curve and did not show reorientation of MTs in cells of the root cap or elongation zone. The data indicate that MT depolymerization and reorientation is correlated with reduction in growth rate, and that MT reorientation is one of the steps of growth control of graviresponding roots.

NASA Discipline Plant Biology↗
NASA NTRS1990

Defective secretion of mucilage is the cellular basis for agravitropism in primary roots of Zea mays cv. Ageotropic

Root caps of primary, secondary, and seminal roots of Z. mays cv. Kys secrete large amounts of mucilage and are in close contact with the root all along the root apex. These roots are strongly graviresponsive. Secondary and seminal roots of Z. mays cv. Ageotropic are also strongly graviresponsive. Similarly, their caps secrete mucilage and closely appress the root all along the root apex. However, primary roots of Z. mays cv. Ageotropic are non-responsive to gravity. Their caps secrete negligible amounts of mucilage and contact the root only at the extreme apex of the root along the calyptrogen. These roots become graviresponsive when their tips are coated with mucilage or mucilage-like materials. Peripheral cells of root caps of roots of Z. mays cv. Kys contain many dictyosomes associated with vesicles that migrate to and fuse with the plasmalemma. Root-cap cells of secondary and seminal (i.e. graviresponsive) roots of Z. mays cv. Ageotropic are similar to those of primary roots of Z. mays cv. Kys. However, root-cap cells of primary (i.e. non-graviresponsive) roots of Z. mays cv. Ageotropic have distended dictyosomal cisternae filled with an electron-dense, granular material. Large vesicles full of this material populate the cells and apparently do not fuse with the plasmalemma. Taken together, these results suggest that non-graviresponsiveness of primary roots of Z. mays cv. Ageotropic results from the lack of apoplastic continuity between the root and the periphery of the root cap. This is a result of negligible secretion of mucilage by cells along the edge of the root cap which, in turn, appears to be due to the malfunctioning of dictyosomes in these cells.

NASA Discipline Number 29-20↗
NASA NTRS1994

Comparative assessment of the polypeptide profiles from lateral and primary roots of Phaseolus vulgaris L

In Phaseolus vulgaris, primary roots show gravitational sensitivity soon after emerging from the seed. In contrast, lateral roots are agravitropic during early development, and become gravitropic after several cm growth. Primary and lateral root tissues were examined by polyacrylamide gel electrophoresis, coupled with western blotting techniques, to compare proteins which may contribute to the acquisition of gravitational sensitivity. Root tips and zones of cell elongation were compared for each root type, using immunological probes for calmodulin, alpha-actin, alpha-tubulin, and proteins of the plastid envelope. Lateral roots contained qualitatively less calmodulin, and showed a slightly different pattern of actin-related epitope proteins, than did primary root tissues, suggesting that polypeptide differences may contribute to the gravitational sensitivity which these root types express.

Non-NASA Center↗
DOE OSTI2023

Trichoderma harzianum transcriptome in response to the nematode Pratylenchus brachyurus

The root-lesion nematode Pratylenchus brachyurus causes extensive damage in several crops of economic importance. Fungi of Trichoderma genus have been highlighted as biopesticide agents in the control of several plant diseases. Although it is already widely used in agriculture, there are few studies, especially at the molecular level, that evaluate T. harzianum in the control of P. brachyurus . The aim of the present study was to investigate how interaction with the nematode P. brachyurus influences gene expression of T. harzianum , by using RNA-Seq analysis. Of the 13,932 predicted genes in the T. harzianum genome, 2,922 (21%) were differentially expressed in the presence of P. brachyurus , in relation to the absence of the nematode. Among the differentially expressed genes, we found genes encoding Carbohydrate Active EnZymes (CAZy), MEROPS peptidases, and proteins related to secondary metabolite synthesis. 118 pathways were identified as related to the biosynthesis of secondary metabolites. Additionally, the analysis identified 136 metabolic pathways related to these differentially expressed genes, among which we highlight: aminobenzoate degradation, xenobiotic metabolism by cytochrome P450, and sesquiterpenoid and triterpenoid biosynthesis. Our results contribute to a better understanding of the response of T. harzianum to the nematode P. bracyurus , the potential for biocontrol by this fungus.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2023

Changes in soil pore structure generated by the root systems of maize , sorghum and switchgrass affect in situ N 2 O emissions and bacterial denitrification

Due to the heterogeneous nature of soil pore structure, processes such as nitrification and denitrification can occur simultaneously at microscopic levels, making prediction of small-scale nitrous oxide (N 2 O) emissions in the field notoriously difficult. We assessed N 2 O+N 2 emissions from soils under maize (Zea mays L.), switchgrass (Panicum virgatum L.), and energy sorghum (Sorghum bicolor L.), three potential bioenergy crops in order to identify the importance of different N 2 O sources to microsite production, and relate N 2 O source differences to crop-associated differences in pore structure formation. The combination of isotopic surveys of N 2 O in the field during one growing season and X-ray computed tomography (CT) enabled us to link results from isotopic mappings to soil structural properties. Further, our methodology allowed us to evaluate the potential for in situ N 2 O suppression by biological nitrification inhibition (BNI) in energy sorghum. Our results demonstrated that the fraction of N 2 O originating from bacterial denitrification and reduction of N 2 O to N 2 is largely determined by the volume of particulate organic matter occluded within the soil matrix and the anaerobic soil volume. Bacterial denitrification was greater in switchgrass than in the annual crops, related to changes in pore structure caused by the coarse root system. This led to high N-loses through N 2 emissions in the switchgrass system throughout the season a novel finding given the lack of data in the literature for total denitrification. Isotopic mapping indicated no differences in N 2 O-fluxes or their source processes between maize and energy sorghum that could be associated with the release of BNI by the investigated sorghum variety. The results of this research show how differences in soil pore structures among cropping systems can determine both N 2 O production via denitrification and total denitrification N losses in situ.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2026

Soil nutrients affect biomass allocation at the individual tree level in Populus_deltoides

The allocation of carbon (C) to tree roots has implication for forest productivity and soil C storage. Here, we elucidated the factors affecting absolute and relative production of resource-acquiring absorptive fine roots (AFR) and other tree organs. We assessed soil properties, leaf (Leaves), stem and branch (Stem-Br), coarse root (CR), transport fine root (TFR), and AFR biomass, production, and allocation and leaf litterfall and AFR and TFR turnover for 12 trees in a youngPopulus deltoides plantation. On a biomass basis, standing crop of AFRs was significantly related to that of TFRs, but both were independent of biomass of leaves, CRs and Stem-Brs. Production (standing crop + turnover) as a proportion of total biomass (allocation) highlighted significant relationships between AFR%, TFR%, and tree and soil characteristics. AFR% and TFR% were negatively correlated with Stem-Br%, Leaf%, and total tree production. Spatial variation in soil nutrient gradients altered allocation withinP. deltoides.AFR% and TFR% were negatively correlated with CEC, N, and Ca but positively correlated with soil P, Fe, and Na. Stem-Br% was positively correlated with CEC and soil N but negatively correlated with P. AFR and TFR growth and death are tightly coupled at the individual tree level. AFR allocation, but not standing biomass, is highly correlated with allocation to leaves, suggesting tight regulation of the growth of these two resource-acquiring organs. Lower soil N and Ca increased allocation to AFRs at the cost of leaves, whereas allocation to AFRs and leaves increased with soil P. Such changes in response to soil P may control whole-tree production in the current study.

Biomass allocation↗
DOE OSTI2022

Root angle is controlled by EGT1 in cereal crops employing an antigravitropic mechanism

Root angle in crops represents a key trait for efficient capture of soil resources. Root angle is determined by competing gravitropic versus antigravitropic offset (AGO) mechanisms. Here we report a root angle regulatory gene termed ENHANCED GRAVITROPISM1 ( EGT1 ) that encodes a putative AGO component, whose loss-of-function enhances root gravitropism. Mutations in barley and wheat EGT1 genes confer a striking root phenotype, where every root class adopts a steeper growth angle. EGT1 encodes an F-box and Tubby domain-containing protein that is highly conserved across plant species. Haplotype analysis found that natural allelic variation at the barley EGT1 locus impacts root angle. Gravitropic assays indicated that Hvegt1 roots bend more rapidly than wild-type. Transcript profiling revealed Hvegt1 roots deregulate reactive oxygen species (ROS) homeostasis and cell wall-loosening enzymes and cofactors. ROS imaging shows that Hvegt1 root basal meristem and elongation zone tissues have reduced levels. Atomic force microscopy measurements detected elongating Hvegt1 root cortical cell walls are significantly less stiff than wild-type. In situ analysis identified HvEGT1 is expressed in elongating cortical and stele tissues, which are distinct from known root gravitropic perception and response tissues in the columella and epidermis, respectively. We propose that EGT1 controls root angle by regulating cell wall stiffness in elongating root cortical tissue, counteracting the gravitropic machinery’s known ability to bend the root via its outermost tissues. We conclude that root angle is controlled by EGT1 in cereal crops employing an antigravitropic mechanism.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1997

Cytochalasin D does not inhibit gravitropism in roots

It is generally thought that sedimenting plastids are responsible for gravity sensing in higher plants. We directly tested the model generated by the current statolith hypothesis that the gravity sensing that leads to gravitropism results from an interaction between the plastids and actin microfilaments. We find that the primary roots of rice, corn, and cress undergo normal gravitropism and growth even when exposed to cytochalasin D, a disruptor of actin microfilaments. These results indicate that an interaction between amyloplasts and the actin cytoskeleton is not critical for gravity sensing in higher plants and weaken the current statolith hypothesis.

NASA Discipline Plant Biology↗
DOE OSTI2022

A Decentralized Approach for Modeling Organized Convection Based on Thermal Populations on Microgrids

Abstract In this study, a spectral model for convective transport is coupled to a thermal population model on a two‐dimensional horizontal “microgrid,” covering the typical gridbox size of general circulation models. The goal is to explore new ways of representing impacts of spatial organization in cumulus cloud fields. The thermals are considered the smallest building block of convection, with thermal life cycle and movement represented through binomial functions. Thermals interact through two simple rules, reflecting pulsating growth and environmental deformation. Long‐lived thermal clusters thus form on the microgrid, exhibiting scale growth and spacing that represent simple forms of spatial organization and memory. Size distributions of cluster number are diagnosed from the microgrid through an online clustering algorithm, and provided as input to a spectral multiplume eddy‐diffusivity mass flux scheme. This yields a decentralized transport system, in that the thermal clusters acting as independent but interacting nodes that carry information about spatial structure. The main objectives of this study are (a) to seek proof of concept of this approach, and (b) to gain insight into impacts of spatial organization on convective transport. Single‐column model experiments demonstrate satisfactory skill in reproducing two observed cases of continental shallow convection. Metrics expressing self‐organization and spatial organization match well with large‐eddy simulation results. We find that in this coupled system, spatial organization impacts convective transport primarily through the scale break in the size distribution of cluster number. The rooting of saturated plumes in the subcloud mixed layer plays a key role in this process.

54 ENVIRONMENTAL SCIENCES↗