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Results for “Granulation”

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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Balloon-borne imagery of the solar granulation. II - The lifetime of solar granulation

Phenomenological aspects of the temporal evolution of photospheric granulation are reported as derived from time series of granulation photographs obtained during a flight of a balloon-borne telescope. The distribution of granule lifetime probabilities is determined, and it is found that the data can be represented by an exponential decrease with a 'decay constant' of 5.9 min. The general properties of granular evolution are described along with the way individual granules evolve with time. The most common type of granule is shown to be a medium-sized or small fragment, and it is suggested that all granules are produced by fragmentation of preexisting granules. The relative frequencies of granule destruction by fragmentation, fading, and merging are determined to be 51%, 21%, and 28%, respectively. An average radial velocity of 0.8 km/s is computed for conglomerates with an average diameter of 2.25 arcsec.

Mehltretter, J. P.↗
NASA NTRS2002

Ca2+-dependent dephosphorylation of kinesin heavy chain on beta-granules in pancreatic beta-cells. Implications for regulated beta-granule transport and insulin exocytosis

The specific biochemical steps required for glucose-regulated insulin exocytosis from beta-cells are not well defined. Elevation of glucose leads to increases in cytosolic [Ca2+]i and biphasic release of insulin from both a readily releasable and a storage pool of beta-granules. The effect of elevated [Ca2+]i on phosphorylation of isolated beta-granule membrane proteins was evaluated, and the phosphorylation of four proteins was found to be altered by [Ca2+]i. One (a 18/20-kDa doublet) was a Ca2+-dependent increase in phosphorylation, and, surprisingly, three others (138, 42, and 36 kDa) were Ca2+-dependent dephosphorylations. The 138-kDa beta-granule phosphoprotein was found to be kinesin heavy chain (KHC). At low levels of [Ca2+]i KHC was phosphorylated by casein kinase 2, but KHC was rapidly dephosphorylated by protein phosphatase 2B beta (PP2Bbeta) as [Ca2+]i increased. Inhibitors of PP2B specifically reduced the second, microtubule-dependent, phase of insulin secretion, suggesting that dephosphorylation of KHC was required for transport of beta-granules from the storage pool to replenish the readily releasable pool of beta-granules. This is distinct from synaptic vesicle exocytosis, because neurotransmitter release from synaptosomes did not require a Ca2+-dependent KHC dephosphorylation. These results suggest a novel mechanism for regulating KHC function and beta-granule transport in beta-cells that is mediated by casein kinase 2 and PP2B. They also implicate a novel regulatory role for PP2B/calcineurin in the control of insulin secretion downstream of a rise in [Ca2+]i.

NASA Discipline Neuroscience↗
NASA NTRS1985

A comparison of artificial solar granules with real solar granules

The properties of computer-generated images of solar granules were compared with data from the literature and with observations of granules from 1975 and 1979. The lifetimes, shapes, and dimensions of the granules were estimated, and the results are discussed. No significant differences were found between the artificial images and the observed granules. The ratios of width to length among the artificial granules are given in a table.

Woehl, H.↗
DOE OSTI2024

Investigating the Effects of Mixing Dynamics on Twin-Screw Granule Quality Attributes via the Development of a Physics-Based Process Map

Twin-screw granulation (TSG) is an emerging continuous wet granulation technique that has not been widely applied in the industry due to a poor mechanistic understanding of the process. This study focuses on improving this mechanistic understanding by analyzing the effects of the mixing dynamics on the granule quality attributes (PSD, content uniformity, and microstructure). Mixing is an important dynamic process that simultaneously occurs along with the granulation rate mechanisms during the wet granulation process. An improved mechanistic understanding was achieved by identifying and quantifying the physically relevant intermediate parameters that affect the mixing dynamics in TSG, and then their effects on the granule attributes were analyzed by investigating their effects on the granulation rate mechanisms. The fill level, granule liquid saturation, extent of nucleation, and powder wettability were found to be the key physically relevant intermediate parameters that affect the mixing inside the twin-screw granulator. An improved geometrical model for the fill level was developed and validated against existing experimental data. Finally, a process map was developed to depict the effects of mixing on the temporal and spatial evolution of the materials inside the twin-screw granulator. This process map illustrates the mechanism of nucleation and the growth of the granules based on the fundamental material properties of the primary powders (solubility and wettability), liquid binders (viscosity), and mixing dynamics present in the system. Furthermore, it was shown that the process map can be used to predict the granule product quality based on the granule growth mechanism.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1988

Statistical properties of solar granulation from the SOUP instrument on Spacelab 2

The Solar Optical Universal Polarimeter (SOUP) on Spacelab 2 collected movies of solar granulation completely free from atmospheric blurring, and are not degraded by pointint jitter (the pointing stability was 0.003 sec root mean square). The movies illustrate that the solar five minute oscillation has a major role in the appearance of solar granulation and that exploding granules are a common feature of the granule evolution. Using 3-D Fourier filtering techniques the oscillations were removed and it was demonstrated that the autocorrelation lifetime of granulation is a factor of two greater in magnetic field regions than in field-free quiet sun. Horizontal velocities were measured and flow patterns were observed on the scale of meso- and super granulation. In quiet regions the mean flow velocity is 370 m/s while in the magnetic regions it is about 125 m/s. It was also found that the root mean square (RMS) fluctuating horizonal velocity field is substantially greater in quiet sun than in strong magnetic field regions. By superimposing the location of exploding granules on the average flow maps it was found that they appear almost exclusively in the center of mesogranulation size flow cells. Because of the nonuniformity of the distribution of exploding granules, the evolution of the granulation pattern in mesogranule cell centers and boundaries differs fundamentally. It is clear from this study there is neither a typical granule nor a typical granule evolution.

Topka, K.↗
NASA NTRS1989

Video image selection studies of granules, pores, and penumbral flows near a large sunspot

The results of applying modern ground-based optical techniques using data obtained from high-resolution videotapes to the study of solar granulation are addressed. The average lifetime of granules is found to be 16 min, with larger granules having longer lifetimes. Two percent of granules explode, and the probability of a granule being hit by exploding granules at least once is 10 percent. A big exploding event covers about 10 granules. Many small pores change their size and darkness in less than a time scale of 60 min. The integrated darkness of one pore appears to be oscillating with a period of about 30 min. There are clear inflows of both bright and dark penumbra fibrils toward the umbra, from the outer edge of the penumbra. Outflow from the outer edge of penumbra is confirmed. This flow pattern may be related to the moving magnetic features and the moat structure surrounding the sunspots.

Zirin, Harold↗
NASA NTRS2001

Neuronal RNA granules: a link between RNA localization and stimulation-dependent translation

RNA granules are a macromolecular structure observed in neurons, where they serve as motile units that translocate mRNAs. Isolated RNA granules are highly enriched in Staufen protein and ultrastructurally contain densely packed clusters of ribosomes. With depolarization, many mRNAs, including those involved in plasticity, rapidly shift from the RNA granule fraction to polysomes. Depolarization reorganizes granules and induces a less compact organization of their ribosomes. RNA granules are not translationally competent, as indicated by the failure to incorporate radioactive amino acids and the absence of eIF4E, 4G, and tRNAs. We concluded that RNA granules are a local storage compartment for mRNAs under translational arrest but are poised for release to actively translated pools. Local release of mRNAs and ribosomes from granules may serve as a macromolecular mechanism linking RNA localization to translation and synaptic plasticity.

NASA Discipline Neuroscience↗
NASA NTRS1997

Composition of the carbohydrate granules of the cyanobacterium, Cyanothece sp. strain ATCC 51142

Cyanothece sp. strain ATCC 51142 is an aerobic, unicellular, diazotrophic cyanobacterium that temporally separates O2-sensitive N2 fixation from oxygenic photosynthesis. The energy and reducing power needed for N2 fixation appears to be generated by an active respiratory apparatus that utilizes the contents of large interthylakoidal carbohydrate granules. We report here on the carbohydrate and protein composition of the granules of Cyanothece sp. strain ATCC 51142. The carbohydrate component is a glucose homopolymer with branches every nine residues and is chemically identical to glycogen. Granule-associated protein fractions showed temporal changes in the number of proteins and their abundance during the metabolic oscillations observed under diazotrophic conditions. There also were temporal changes in the protein pattern of the granule-depleted supernatant fractions from diazotrophic cultures. None of the granule-associated proteins crossreacted with antisera directed against several glycogen-metabolizing enzymes or nitrogenase, although these proteins were tentatively identified in supernatant fractions. It is suggested that the granule-associated proteins are structural proteins required to maintain a complex granule architecture.

NASA Discipline Cell Biology↗
NASA NTRS1977

Evolution pattern of the exploding granules

Observational features of exploding granules that may be of some importance for the theory of unsteady convection are discussed on the basis of a time sequence of high-definition photographs of the solar granulation obtained during a Stratoscope flight. The evolutionary pattern of exploding granules is summarized schematically, and several characteristic features are derived from a study of seven such granules. The exploding-granule phenomenon is interpreted qualitatively in terms of cooling at the photospheric level and the subsequent sinking of cold matter at the center of a granule due to loss of buoyancy

Namba, O.↗
NASA NTRS1994

Oscillating behavior of carbohydrate granule formation and dinitrogen fixation in the cyanobacterium Cyanothece sp. strain ATCC 51142

It has been shown that some aerobic, unicellular, diazotrophic cyanobacteria temporally separate photosynthetic O2 evolution and oxygen-sensitive N2 fixation. Cyanothece sp. ATCC strain 51142 is an aerobic, unicellular, diazotrophic cyanobacterium that fixes N2 during discrete periods of its cell cycle. When the bacteria are maintained under diurnal light-dark cycles, N2 fixation occurs in the dark. Similar cycling is observed in continuous light, implicating a circadian rhythm. Under N2-fixing conditions, large inclusion granules form between the thylakoid membranes. Maximum granulation, as observed by electron microscopy, occurs before the onset of N2 fixation, and the granules decrease in number during the period of N2 fixation. The granules can be purified from cell homogenates by differential centrifugation. Biochemical analyses of the granules indicate that these structures are primarily carbohydrate, with some protein. Further analyses of the carbohydrate have shown that it is a glucose polymer with some characteristics of glycogen. It is proposed that N2 fixation is driven by energy and reducing power stored in these inclusion granules. Cyanothece sp. strain ATCC 51142 represents an excellent experimental organism for the study of the protective mechanisms of nitrogenase, metabolic events in cyanobacteria under normal and stress conditions, the partitioning of resources between growth and storage, and biological rhythms.

Non-NASA Center↗
NASA NTRS1987

Incorporation of a circulating protein into megakaryocyte and platelet granules

To determine whether or not proteins circulating in plasma can be incorporated into megakaryocytes and platelets, horseradish peroxidase (HRP) was injected intravenously into guinea pigs and these cells were examined for its uptake by electron microscopy and cytochemistry. Enriched samples of megakaryocytes enabled ultrastructural analysis of large numbers of these rare cells. In megakaryocytes, 50% of alpha granules contained HRP between 75 min and 7 hr after injection. At 24 hr, 25% of the megakaryocyte granules were peroxidase-positive, less were positive by 48 hr, and there were none at 4 days. Thus, the findings demonstrate that a circulating protein can be endocytosed by megakaryocytes and rapidly packaged into alpha granules. Platelet granules also contain HRP by 7 hr after injection, and they can secrete it in response to thrombin. Unfortunately, our present studies do not allow us to distinguish between direct endocytosis by the platelet and/or shedding of new platelets from recently labeled megakaryocytes. It is concluded that while some alpha granule proteins are synthesized by megakaryocytes, others may be acquired from plasma by endocytosis. In addition to providing evidence that some of the proteins of alpha granules may be of exogenous origin, this study has allowed the definition of a pathway whereby plasma proteins may be temporarily sequestered in megakaryocytes before reentering the circulation in platelets.

Megakaryocytes/metabolism/ultrastructure↗
NASA NTRS1989

Statistical properties of solar granulation derived from the SOUP instrument on Spacelab 2

Computer algorithms and statistical techniques were used to identify, measure, and quantify the properties of solar granulation derived from movies collected by the Solar Optical Universal Polarimeter on Spacelab 2. The results show that there is neither a typical solar granule nor a typical granule evolution. A granule's evolution is dependent on local magnetic flux density, its position with respect to the active region plage, its position in the mesogranulation pattern, and the evolution of granules in its immediate neighborhood.

Title, A. M.↗
NASA NTRS1994

Vortex rings and the solar granulation

Observations indicate that solar granules have the flow topology of updraft vortex loops. We interpret granule behavior in terms of the mutual and self-interactions of such loops. In particular, the expansion phase that granules commonly undergo is explained by the self-expansion of a vortex ring in a stratified fluid. For a range of granular parameters, we find that the expansion velocity of a vortex ring varies from 0.7 to 1.5 times the maximum surface flow velocity, in agreement with granule observations. We also present speculation on the nature of granule fragmentation.

Arendt, Steve↗
DOE OSTI2025

Aqueous-Based Granulation Method Towards Syngas Production

An aqueous-based granulation method is developed to combat the structural changes associated with binder-based granulation techniques. Microwave-assisted methane reforming studies showed an improved catalyst efficiency for these aqueous-based granules compared to the powder catalysts. This granulation method has been extended to other practical applications (chemical looping gasification and air separations).

aqueous-based granulation↗
NASA NTRS1985

Carbon granule probe microphone for leak detection

A microphone which is not subject to corrosion is provided by employing carbon granules to sense sound waves. The granules are packed into a ceramic tube and no diaphragm is used. A pair of electrodes is located in the tube adjacent the carbon granules and are coupled to a sensing circuit. Sound waves cause pressure changes on the carbon granules which results in a change in resistance in the electrical path between the electrodes. This change in resistance is detected by the sensing circuit. The microphone is suitable for use as a leak detection probe in recovery boilers, where it provides reliable operation without corrosion problems associated with conventional microphones.

Parthasarathy, S. P.↗
NASA NTRS1994

Solar granulation and statistical crystallography: A modeling approach using size-shape relations

The irregular polygonal pattern of solar granulation is analyzed for size-shape relations using statistical crystallography. In contrast to previous work which has assumed perfectly hexagonal patterns for granulation, more realistic accounting of cell (granule) shapes reveals a broader basis for quantitative analysis. Several features emerge as noteworthy: (1) a linear correlation between number of cell-sides and neighboring shapes (called Aboav-Weaire's law); (2) a linear correlation between both average cell area and perimeter and the number of cell-sides (called Lewis's law and a perimeter law, respectively) and (3) a linear correlation between cell area and squared perimeter (called convolution index). This statistical picture of granulation is consistent with a finding of no correlation in cell shapes beyond nearest neighbors. A comparative calculation between existing model predictions taken from luminosity data and the present analysis shows substantial agreements for cell-size distributions. A model for understanding grain lifetimes is proposed which links convective times to cell shape using crystallographic results.

Noever, D. A.↗
NASA NTRS1987

First results on quiet and magnetic granulation from SOUP

The flight of Solar Optical Universal Polarimeter (SOUP) on Spacelab 2 allowed the collection of time sequences of diffraction limited (0.5 arc sec) granulation images with excellent pointing (0.003 arc sec) and completely free of the distortion that plagues groundbased images. The p-mode oscillations are clearly seen in the data. Using Fourier transforms in the temporal and spatial domain, it was shown that the p-modes dominate the autocorrelation lifetime in magnetic regions. When these oscillations are removed the autocorrelation lifetime is found to be 500 sec in quiet and 950 sec in magnetic regions. In quiet areas exploding granules are seen to be common. It is speculated that a significant fraction of granule lifetimes are terminated by nearby explosions. Using local correlation tracking techniques it was able to measure horizontal displacements, and thus transverse velocities, in the magnetic field. In quiet sun it is possible to detect both super and mesogranulation. Horizontal velocities are as great as 1000 m/s and the average velocity is 400 m/s. In magnetic regions horizontal velocities are much less, about 100 m/s.

Title, A. M.↗
NASA NTRS1991

High-resolution observations of the solar granulation

Digitally-enhanced high-resolution images from space and ground observatories have yielded data on the solar granulation which show it to be a more complex combination of phenomena than previously suspected. These new data have been used to detect large-scale horizontal flows over the solar surface through direct measurements of granule proper motions. The results thus obtained may have important implications for the heating of the solar chromosphere and corona. The observed intensity pattern on the surface of the sun is noted to be due not only to granulation, but the superposition of different types of waves as well. All such phenomena are modified in the presence of magnetic fields, becoming smaller and of reduced contrast.

Topka, K. P.↗