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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS2017

Effects of Chronic Hypergravity on the Dopaminergic Neuronal System in Drosophila Melanogaster

Upon atmospheric exitre-entry and during training, astronauts are subjected to temporary periods of hypergravity, which has been implicated in the activation of oxidative stress pathways contributing to mitochondrial dysfunction and neuronal degeneration. The pathogenesis of Parkinsons disease and other neurodegenerative disorders is associated with oxidative damage to neurons involved in dopamine systems of the brain. Our study aims to examine the effects of a hypergravitational developmental environment on the degeneration of dopaminergic systems in Drosophila melanogaster. Male and female flies (Gal4-UAS transgenic line) were hatched and raised to adulthood in centrifugal hypergravity (97rpm, 3g). The nuclear expression of the reporter, Green Fluorescent Protein (GFP) is driven by the dopaminergic enzyme tyrosine hydroxylase (TH) promoter, allowing for the targeted visualization of dopamine producing neurons. After being raised to adulthood and kept in hypergravity until 18 days of age, flies were dissected and the expression of TH was measured by fluorescence confocal microscopy. TH expression in the fly brains was used to obtain counts of healthy dopaminergic neurons for flies raised in chronic hypergravity and control groups. Dopaminergic neuron expression data were compared with those of previous studies that limited hypergravity exposure to late life in order to determine the flies adaptability to the gravitational environment when raised from hatching through adulthood. Overall, we observed a significant effect of chronic hypergravity exposure contributing to deficits in dopaminergic neuron expression (p 0.003). Flies raised in 3g had on average lower dopaminergic neuron counts (mean 97.7) when compared with flies raised in 1g (mean 122.8). We suspect these lower levels of TH expression are a result of oxidative dopaminergic cell loss in flies raised in hypergravity. In future studies, we hope to further elucidate the mechanism by which hypergravity-induced oxidative stress damages the dopaminergic neuronal system, as well as examining possible chemical countermeasures to the hypergravity-induced oxidative stress response in dopaminergic neurons in order to combat cell death and consequent mental and behavioral deficits.

Pelos, Andrew↗
NASA NTRSDate not supplied

Phase transitions in colloids under microgravity

Research on colloids is motivated by several factors. They can be used to answer fundamental questions related to the assembly of materials, and they have many potential applications in electronics, photonics, and life sciences. However, the rich variety of colloidal structures observed on the Earth can be influenced by the effects of gravity, which leads to particles settling and the motion of the surrounding fluid. To suppress the gravity effects, experiments on concentrated colloids of spherical and ellipsoidal fluorescent particles were carried out aboard the International Space Station. The particles were suspended in a decalin/tetralin mixture to match the particle refractive index. Confocal microscopy was used to visualize the particle behavior.

microgravity↗
NASA NTRSDate not supplied

Murine Spine Composition and Mechanics are Maintained After 30-Days of Spaceflight

As NASA prepares to send astronauts on deep space missions, understanding the detrimental effects of spaceflight on the body is imperative. Spaceflight is known to negatively affect the spine, with astronauts experiencing systemic bone loss and increased post-flight risk of intervertebral disc herniation. Space investigations with rodent models have characterized some of the effects of spaceflight on the mammalian body, but variable experimental conditions have made it difficult to cohesively interpret results. These conditions include housing, flight duration, and for the spine, anatomical location. Thus, the objective of this study was to comprehensively characterize the effects of spaceflight on the bulk properties of the murine lumbar spine. To do this, we examined the lumbar spine of mice flown on the NASA Rodent Research 10 mission and analyzed disc biochemical content, disc joint material properties, lumbar vertebral body microarchitecture, and proximal tibia microarchitecture. Finally, we qualitatively examined bone growth in the vertebral bodies using confocal microscopy and on-orbit injections of calcein. Contrary to prior results, we found little to no effect of spaceflight on lumbar spine properties. Spaceflight, however, did negatively affect both cortical and trabecular bone properties of the proximal tibia load-bearing site. We hypothesize that this may be due to loading associated with increased physical activity in the second half of the mission, observed on in-flight videos, that reload the lumbar spine as mice utilize quadruped ambulation. This increased activity occurs after an initial period of relative inactivity in microgravity. In support of this hypothesis, we observed new L5 bone formation in the last seven days of spaceflight, suggesting that current 30-day experimental flight conditions may not be as effective at lumbar spine unloading as previous shorter flights.

mouse↗
DOE OSTI2025

Controlling Oxidation of Nb in Oxygen Abundant Environments.

Superconducting Radio Frequency (SRF) cavities, the core of modern particle accelerators, rely on high-purity niobium (Nb) to achieve high quality factors and accelerating gradients. However, native oxidation in ambient conditions introduces a complex oxide layer with increased surface defects and contamination, particularly from carbon. This research explores a controlled oxidation processes in an oxygen-abundant environment to try to control this complex oxide stack, with the goal of improving surface purity and uniformity. Using standard surface preparation techniques—including electropolishing, vacuum baking, and sonication—followed by a custom oxidation protocol, we compared structural and chemical changes through Confocal Microscopy, Scanning Electron Microscopy (SEM), and X-Ray Photoelectron Spectroscopy (XPS). Results show that iterative oxidation cycles can significantly reduce carbon-related defects, even without baking. Aditionally, baked samples with a specific oxidation technique demonstrated a measurable 25\% decrease in carbide formation.

Romero, Juan [Fermilab]↗
NASA NTRS2007

Aerogel Track Morphology: Measurement, Three Dimensional Reconstruction and Particle Location using Confocal Laser Scanning Microscopy

The Stardust spacecraft returned the first undoubted samples of cometary dust, with many grains embedded in the silica aerogel collector . Although many tracks contain one or more large terminal particles of a wide range of mineral compositions , there is also abundant material along the track walls. To help interpret the full particle size, structure and mass, both experimental simulation of impact by shots and numerical modeling of the impact process have been attempted. However, all approaches require accurate and precise measurement of impact track size parameters such as length, width and volume of specific portions. To make such measurements is not easy, especially if extensive aerogel fracturing and discoloration has occurred. In this paper we describe the application and limitations of laser confocal imagery for determination of aerogel track parameters, and for the location of particle remains.

Kearsley, A. T.↗
NASA NTRS2000

Quantitative image analysis of laminin immunoreactivity in skin basement membrane irradiated with 1 GeV/nucleon iron particles

We previously reported that laminin immunoreactivity in mouse mammary epithelium is altered shortly after whole-body irradiation with 0.8 Gy from 600 MeV/nucleon iron ions but is unaffected after exposure to sparsely ionizing radiation. This observation led us to propose that the effect could be due to protein damage from the high ionization density of the ion tracks. If so, we predicted that it would be evident soon after radiation exposure in basement membranes of other tissues and would depend on ion fluence. To test this hypothesis, we used immunofluorescence, confocal laser scanning microscopy, and image segmentation techniques to quantify changes in the basement membrane of mouse skin epidermis. At 1 h after exposure to 1 GeV/nucleon iron ions with doses from 0.03 to 1.6 Gy, neither the visual appearance nor the mean pixel intensity of laminin in the basement membrane of mouse dorsal skin epidermis was altered compared to sham-irradiated tissue. This result does not support the hypothesis that particle traversal directly affects laminin protein integrity. However, the mean pixel intensity of laminin immunoreactivity was significantly decreased in epidermal basement membrane at 48 and 96 h after exposure to 0.8 Gy 1 GeV/nucleon iron ions. We confirmed this effect with two additional antibodies raised against affinity-purified laminin 1 and the E3 fragment of the long-arm of laminin 1. In contrast, collagen type IV, another component of the basement membrane, was unaffected. Our studies demonstrate quantitatively that densely ionizing radiation elicits changes in skin microenvironments distinct from those induced by sparsely ionizing radiation. Such effects may might contribute to the carcinogenic potential of densely ionizing radiation by altering cellular signaling cascades mediated by cell-extracellular matrix interactions.

Non-NASA Center↗
NASA NTRS1998

The role of biomineralization in microbiologically influenced corrosion

Synthetic iron oxides (goethite, alpha-FeO.OH; hematite, Fe2O3; and ferrihydrite, Fe(OH)3) were used as model compounds to simulate the mineralogy of surface films on carbon steel. Dissolution of these oxides exposed to pure cultures of the metal-reducing bacterium, Shewanella putrefaciens, was followed by direct atomic absorption spectroscopy measurement of ferrous iron coupled with microscopic analyses using confocal laser scanning and environmental scanning electron microscopies. During an 8-day exposure the organism colonized mineral surfaces and reduced solid ferric oxides to soluble ferrous ions. Elemental composition, as monitored by energy dispersive x-ray spectroscopy, indicated mineral replacement reactions with both ferrihydrite and goethite as iron reduction occurred. When carbon steel electrodes were exposed to S. putrefaciens, microbiologically influenced corrosion was demonstrated electrochemically and microscopically.

Non-programmatic↗
NASA NTRS1997

Bone formation by three-dimensional stromal osteoblast culture in biodegradable polymer scaffolds

Bone formation was investigated in vitro by culturing stromal osteoblasts in three-dimensional (3-D), biodegradable poly(DL-lactic-co-glycolic acid) foams. Three polymer foam pore sizes, ranging from 150-300, 300-500, and 500-710 microns, and two different cell seeding densities, 6.83 x 10(5) cells/cm2 and 22.1 x 10(5) cells/cm2, were examined over a 56-day culture period. The polymer foams supported the proliferation of seeded osteoblasts as well as their differentiated function, as demonstrated by high alkaline phosphatase activity and deposition of a mineralized matrix by the cells. Cell number, alkaline phosphatase activity, and mineral deposition increased significantly over time for all the polymer foams. Osteoblast foam constructs created by seeding 6.83 x 10(5) cells/cm2 on foams with 300-500 microns pores resulted in a cell density of 4.63 x 10(5) cells/cm2 after 1 day in culture; they had alkaline phosphatase activities of 4.28 x 10(-7) and 2.91 x 10(-6) mumol/cell/min on Days 7 and 28, respectively; and they had a cell density that increased to 18.7 x 10(5) cells/cm2 by Day 56. For the same constructs, the mineralized matrix reached a maximum penetration depth of 240 microns from the top surface of the foam and a value of 0.083 mm for mineralized tissue volume per unit of cross sectional area. Seeding density was an important parameter for the constructs, but pore size over the range tested did not affect cell proliferation or function. This study suggests the feasibility of using poly(alpha-hydroxy ester) foams as scaffolding materials for the transplantation of autogenous osteoblasts to regenerate bone tissue.

Non-NASA Center↗
DOE OSTI2025

Print-and-Plate Architected Electrodes for Electrochemical Transformations Under Flow

Flow cell electrodes are typically composed of porous carbon materials, such as papers, felts, and cloths. However, their random architecture hinders the fundamental characterization of electrode structure-performance relationships during in situ operation of porous electrochemical flow systems. This work describes a “print-and-plate” method that combines direct ink writing of micro-periodic lattices with a two-step metal plating process that converts them into highly conductive (sheet resistance 40 mΩ sq -1 ) electrodes. Their operando performance is assessed in an anthraquinone disulfonic acid half-cell using widefield electrochemical fluorescence microscopy, where output current and fluorescence intensity are in excellent agreement. The pressure drop associated with flow through three electrode designs is determined via simulations from which the most efficient design is identified and manufactured via print-and-plate. Confocal fluorescence microscopy is then used to create a 3D map of the state of charge (SOC) inside this print-and-plate electrode. The experimental state of the charge map is in good agreement with computational predictions. The rapid design, simulation, and fabrication of print-and-plate electrodes enable fundamental investigations of how architected porosity affects electrochemical performance under flow.

3D-printing↗
NASA NTRS2022

The Dark Annulus of a Drop in a Hele-Shaw Cell Is Caused by the Refraction of Light through Its Meniscus

Knowing the meniscus shape of confined drops is important for understanding how they make first contact and then coalesce. When imaged from the top view by brightfield microscopy, a liquid drop (e.g., corn syrup) confined in a Hele-Shaw cell, surrounded by immiscible liquid (e.g., mineral oil), had a dark annulus, and the width of the annulus decreased with increasing concentration of corn syrup. Since the difference in the annulus width was presumed to be related to the meniscus shape of the drops, three-dimensional images of the drops with different concentrations were obtained using confocal fluorescence microscopy, and their cross-sectional meniscus profile was determined by image processing. The meniscus of the drops remained circular despite varying concentration. Since the refractive index of corn syrup increased with concentration, while the surface tension coefficient between corn syrup and mineral oil remained unchanged, the observed change in the annulus width was then attributed to the refraction of light passing through the drop’s meniscus. As such, a ray optics model was developed, which predicted that the annulus width of the drop would decrease as the refractive index of the drop approached that of the surrounding liquid. Therefore, the dark annulus of the drops in the Hele-Shaw cell was caused by the refraction of light passing through the circular meniscus of the drop.

Sangjin Ryu↗
NASA NTRS2002

A microarray immunoassay for simultaneous detection of proteins and bacteria

We report the development and characterization of an antibody microarray biosensor for the rapid detection of both protein and bacterial analytes under flow conditions. Using a noncontact microarray printer, biotinylated capture antibodies were immobilized at discrete locations on the surface of an avidin-coated glass microscope slide. Preservation of capture antibody function during the deposition process was accomplished with the use of a low-salt buffer containing sucrose and bovine serum albumin. The slide was fitted with a six-channel flow module that conducted analyte-containing solutions over the array of capture antibody microspots. Detection of bound analyte was subsequently achieved using fluorescent tracer antibodies. The pattern of fluorescent complexes was interrogated using a scanning confocal microscope equipped with a 635-nm laser. This microarray system was employed to detect protein and bacterial analytes both individually and in samples containing mixtures of analytes. Assays were completed in 15 min, and detection of cholera toxin, staphylococcal enterotoxin B, ricin, and Bacillus globigii was demonstrated at levels as low as 8 ng/mL, 4 ng/mL, 10 ng/mL, and 6.2 x 10(4) cfu/mL, respectively. The assays presented here are very fast, as compared to previously published methods for measuring antibody-antigen interactions using microarrays (minutes versus hours).

Non-NASA Center↗
NASA NTRS2001

Cytoplasmic pH dynamics in maize pulvinal cells induced by gravity vector changes

In maize (Zea mays) and other grasses, changes in orientation of stems are perceived by pulvinal tissue, which responds to the stimulus by differential growth resulting in upward bending of the stem. The amyloplast-containing bundle sheath cells are the sites of gravity perception, although the initial steps of gravity perception and transmission remain unclear. In columella cells of Arabidopsis roots, we previously found that cytoplasmic pH (pH(c)) is a mediator in early gravitropic signaling (A.C. Scott, N.S. Allen [1999] Plant Physiol 121: 1291-1298). The question arises whether pH(c) has a more general role in signaling gravity vector changes. Using confocal ratiometric imaging and the fluorescent pH indicator carboxy seminaphtorhodafluor acetoxymethyl ester acetate, we measured pH(c) in the cells composing the maize pulvinus. When stem slices were gravistimulated and imaged on a horizontally mounted confocal microscope, pH(c) changes were only apparent within the bundle sheath cells, and not in the parenchyma cells. After turning, cytoplasmic acidification was observed at the sides of the cells, whereas the cytoplasm at the base of the cells where plastids slowly accumulated became more basic. These changes were most apparent in cells exhibiting net amyloplast sedimentation. Parenchyma cells and isolated bundle sheath cells did not show any gravity-induced pH(c) changes although all cell types responded to external stimuli in the predicted way: Propionic acid and auxin treatments induced acidification, whereas raising the external pH caused alkalinization. The results suggest that pH(c) has an important role in the early signaling pathways of maize stem gravitropism.

Non-NASA Center↗
NASA NTRS1997

The organization of the actin cytoskeleton in vertical and graviresponding primary roots of maize

To determine whether actin microfilament (MF) organization is correlated with differential elongation, primary roots of Zea mays cv Merit maintained vertically or reoriented horizontally for 15 to 120 min were stained with rhodamine phalloidin and examined with a confocal microscope. Root curvature was measured with a computer-controlled video digitizer. In vertical roots bundles of MFs in the elongation and maturation zone were oriented parallel to the longitudinal axis of cells. MFs in the vascular parenchyma cells were more abundant than in the cortex and epidermis. Epidermal and proendodermal cells in the meristematic region contained transverse cortical MFs. The organization of MFs of graviresponding roots was similar to that of vertical roots. Application of cytochalasin B or cytochalasin D resulted in extensive disruption of MFs in the cortex and epidermis, but only partially affected MFs in the stele. Despite the cytochalasin B-induced depolymerization of MFs, gravicurvature exceeded that of controls. In contrast, the auxin transport inhibitor N-1 naphthylphthalamic acid suppressed root curvature but had no observable effect on the integrity of the MFs. The data indicate that MFs may not be involved in the graviresponse of maize roots.

NASA Discipline Plant Biology↗
DOE OSTI2025

Performance improvement of proton exchange membrane water electrolysis by surface modification of porous transport layers

Proton exchange membrane water electrolysis (PEMWE) is a promising option for hydrogen production from a variety of energy sources. Cost-effective production of hydrogen with PEMWE requires reduction of costly precious metals as well as optimization of the components and interfaces in the cell. The interface between the platinum-coated titanium porous transport layer (PTL) and catalyst layer (CL) significantly impacts the performance of the electrolyzer cell. Here, we report on two PTL modification methods, mechanical abrasion and chemical etching, which we find improve PEMWE performance by lowering the resistance of the PTL/CL interface. The PTL surface modifications enabled performance improvements up to 77 mV at 4 A cm −2 and reduction of the high frequency resistance, demonstrating that the resistance of the PTL/CL interface is a significant factor in the cell performance. The PTL surface roughness was varied using abrasive materials ranging from 0.1 to 140 μm in grain sizes and chemical etching was found to also increase the surface roughness. The surface roughness was quantified using confocal laser microscopy and the surface oxidation was measured using X-ray photoemission spectroscopy. These results demonstrate that both increasing surface roughness and oxide removal contribute to lowering the PTL/CL interfacial resistance and increasing cell performance.

08 HYDROGEN↗
DOE OSTI2025

Autocorrelation and Multifractal Detrended Fluctuation Analyses Reveal Superdiffusive Mass Transport in Solvent-Filled Nanoporous Media

Fluorescence fluctuation spectroscopy experiments were conducted to better understand the complex mass transport dynamics of organic molecules in liquid-filled nanoporous media. Anodic aluminum oxide (AAO) membranes incorporating 10 and 20 nm diameter cylindrical pores were employed as model materials. Nile red (NR) dye was used as a fluorescent tracer. The dye was dissolved separately in ethanol and toluene at a concentration of 20 nM and used to fill the membrane nanopores. Confocal fluorescence microscopy was employed to capture photon intensity time series data reflecting apparent diffusion of the dye within the pores. Autocorrelation of these data revealed that NR diffusion within the membranes occurred over a broad range of time scales. The autocorrelation decays were fit to a model for one-dimensional diffusion incorporating both fast and slow components having apparent diffusion coefficients, D f and D s , differing by a factor of ∼100. The fast mechanism was attributed to hindered bulk-like diffusion in the central pore cavity, while slow diffusion likely involved absorption of the dye to the pore surfaces. Unfortunately, important evidence of diffusion anomalies is lost in the broad autocorrelation decays obtained. The method of multifractal detrended fluctuation analysis (MF-DFA) was applied to the same data as a means to overcome this limitation. MF-DFA revealed that time series acquired from within the nanopores were multifractal and exhibited evidence of anomalous superdiffusion, likely resulting from the participation of a desorption-mediated diffusion mechanism. Monte Carlo simulations of time series modeling desorption-mediated diffusion in cylindrical nanopores provided support for this assignment. Here, the new knowledge gained affords an improved understanding of hydrocarbon dynamics within nanoporous oil and gas shales.

Diffusion↗
DOE OSTI2025

Multimodal characterization of Te inclusions in Cd 1−x Zn x Te and Cd 1−x Zn x Te 1−y Se y for gamma and X-ray detectors

While CdZnTe (CZT) and CdZnTeSe (CZTS) semiconductors have emerged as compounds for room-temperature gamma and X-ray detection materials, they continue to be constrained by the formation of Te-inclusion defects generated during the growth and post-growth phases of the material, which adversely affect the detector performance. We demonstrate the utility of multimodal microscopic imaging and analysis for the characterization of the optical and electronic properties of Te inclusions in CZT and CZTS crystals at both micron and nanometer length scales. Having first identified regions with micron-scale Te inclusions using confocal Raman microscopy techniques, optically coupled infrared scattering near-field optical microscopic mapping was performed to map the distribution of these inclusions with nanometer spatial resolution and correlate the presence of Te inclusions in the matrix with other properties. Kelvin probe force microscopy was then utilized to characterize the variations of the work function associated with the presence of Te inclusions. Here, we observe an increase of ~ 240 mV in the work function associated with Te inclusions compared to the bulk CZT/CZTS crystals. Additionally, we observe that individual bulk grains in CZT can exhibit slight potential variations. Our findings develop a portrait of the charge trapping mechanisms in CZT and CZTS that act to degrade detector performance, while the demonstration of these combined microscopy techniques provides a new analytical tool that can be utilized for further optimization of the detector performance for these semiconducting compounds.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Three-dimensional characterization of modifications in sapphire exposed to laser-induced damage using multimodal spectral microimaging

Sapphire (Al 2 O 3 ) is a commonly used dielectric material with many applications in lasers and optical systems. Owing to its high resistivity to laser induced damage, it is particularly suitable for use in high power laser systems. This work focuses on developing techniques to characterize material modifications in sapphire. These techniques were applied following localized laser induced ablation, commonly referred to as laser-damage, resulting from exposure to single 100-ps and 6-ns pulses. Measurements of fluorescence-based piezospectroscopy and confocal Raman microscopy were performed with spatial resolution on the order of 1 μ m. Raman microscopy reveals that the relaxation of material exposed to the rapid laser heating, elastic and viscoplastic deformation, melting, and solidification leads to the formation of a polycrystalline material phase. In addition, narrowband fluorescence lines, referred to as R 1 and R 2 , exhibit pressure-sensitive changes to their spectral profiles, allowing 3D internal stresses to be recorded with spatial resolution of the order of a few micrometers.

Laser-damage↗
NASA NTRS1992

Dielectric breakdown studies of Teflon perfluoroalkoxy at high temperature

Teflon perfluoroalkoxy (PFA) was evaluated for use as a dielectric material in high-temperature high-voltage capacitors for space applications. The properties that were characterized included the dc dielectric strength at temperatures up to 250 C and the permittivity and dielectric loss as a function of frequency, temperature and voltage. To understand the breakdown mechanism taking place at high temperatures, the pre-breakdown discharge and conduction currents, and the dependence of dielectric strength on thickness of the film were determined. Confocal laser microscopy was performed to diagnose for microimperfections within the film structure. The results obtained show a significant decrease in the dielectric strength and an increase in dielectric loss with an increase in temperature, suggesting that impulse thermal breakdown could be a responsible mechanism in PFA film at temperatures above 150 C.

Suthar, J. L.↗