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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1998

Acid-growth response and alpha-expansins in suspension cultures of bright yellow 2 tobacco

The possibility that Bright Yellow 2 (BY2) tobacco (Nicotiana tabacum L.) suspension-cultured cells possess an expansin-mediated acid-growth mechanism was examined by multiple approaches. BY2 cells grew three times faster upon treatment with fusicoccin, which induces an acidification of the cell wall. Exogenous expansins likewise stimulated BY2 cell growth 3-fold. Protein extracted from BY2 cell walls possessed the expansin-like ability to induce extension of isolated walls. In western-blot analysis of BY2 wall protein, one band of 29 kD was recognized by anti-expansin antibody. Six different classes of alpha-expansin mRNA were identified in a BY2 cDNA library. Northern-blot analysis indicated moderate to low abundance of multiple alpha-expansin mRNAs in BY2 cells. From these results we conclude that BY2 suspension-cultured cells have the necessary components for expansin-mediated cell wall enlargement.

Non-NASA Center↗
NASA NTRS2003

The Effect of Spaceflight on the Ultrastructure of the Cerebellum

In weightlessness, astronauts and cosmonauts may experience postural illusions as well as motion sickness symptoms known as the space adaptation syndrome. Upon return to Earth, they have irregularities in posture and balance. The adaptation to microgravity and subsequent re-adaptation to Earth occurs over several days. At the cellular level, a process called neuronal plasticity may mediate this adaptation. The term plasticity refers to the flexibility and modifiability in the architecture and functions of the nervous system. In fact, plastic changes are thought to underlie not just behavioral adaptation, but also the more generalized phenomena of learning and memory. The goal of this experiment was to identify some of the structural alterations that occur in the rat brain during the sensory and motor adaptation to microgravity. One brain region where plasticity has been studied extensively is the cerebellar cortex-a structure thought to be critical for motor control, coordination, the timing of movements, and, most relevant to the present experiment, motor learning. Also, there are direct as well as indirect connections between projections from the gravity-sensing otolith organs and several subregions of the cerebellum. We tested the hypothesis that alterations in the ultrastructural (the structure within the cell) architecture of rat cerebellar cortex occur during the early period of adaptation to microgravity, as the cerebellum adapts to the absence of the usual gravitational inputs. The results show ultrastructural evidence for neuronal plasticity in the central nervous system of adult rats after 24 hours of spaceflight. Qualitative studies conducted on tissue from the cerebellar cortex (specifically, the nodulus of the cerebellum) indicate that ultrastructural signs of plasticity are present in the cerebellar zones that receive input from the gravity-sensing organs in the inner ear (the otoliths). These changes are not observed in this region in cagematched ground control animals. The specific changes include the formation of lamellar bodies, profoundly enlarged Purkinje cell mitochondria, the presence of inter-neuronal cellular protrusions in the molecular layer, and signs of degeneration in the distal dendrites of the Purkinje cells. Since these morphologic signs are not apparent in the control animals, they are not likely to be due to caging or tissue processing effects. The particular nature of the structural alterations in the nodulus, most notably the formation of lamellar bodies and the presence of degeneration, further suggests that excitotoxicity (damaging overstimulation of neurons) may play a role in the short-term neural response to spaceflight. These findings suggest a structural basis for the neuronal and synaptic plasticity accompanying the central nervous system response to altered gravity and help identify the cellular bases underlying the vestibular abnormalities experienced by astronauts during periods of adaptation and re-adaptation to different gravitational forces. Also, since the short- and long-term changes in neural structure occurring during such periods of adaptation resemble the neuronal alterations that occur in some neurologic disorders such as stroke, these findings may offer guidance in the development of strategies for rehabilitation and treatment of such disorders.

Holstein, Gay R.↗
NASA NTRS1992

Ventral horn cell responses to spaceflight and hindlimb suspension

Ventral horn cells of the lumbosacral enlargement of the spinal cord were studied focusing on the succinate dehydrogenase (SDH) activity and cross-sectional area of the soma of ventral horn cells which were measured using a computer-aided image-processing system. The relationships between the soma size and SDH activities of lumber ventral horn cells after 14 days of spaceflight (Cosmos 2044) or of hindlimb suspension are considered. Three groups of rats under consideration include control, 14-day spaceflight, and 14-day hindlimb suspension. Data obtained indicate that, compared to the control group, the population distribution of SDH activities in the flight rats shifted toward higher activities, whereas in the suspended rats the distribution shifted toward lower activities. The interactive effects within individual cells showed that there was a higher percentage of small cells with high SDH activities in the flight than in the control or suspended rats. It is suggested that changes in ventral horn cells were due to factors other than simply the absence of weight support.

Jiang, Bian↗
NASA NTRS1995

Method for characterizing the upset response of CMOS circuits using alpha-particle sensitive test circuits

A method for predicting the SEU susceptibility of a standard-cell D-latch using an alpha-particle sensitive SRAM, SPICE critical charge simulation results, and alpha-particle interaction physics. A technique utilizing test structures to quickly and inexpensively characterize the SEU sensitivity of standard cell latches intended for use in a space environment. This bench-level approach utilizes alpha particles to induce upsets in a low LET sensitive 4-k bit test SRAM. This SRAM consists of cells that employ an offset voltage to adjust their upset sensitivity and an enlarged sensitive drain junction to enhance the cell's upset rate.

Buehler, Martin G.↗
NASA NTRS1993

Wall extensibility: its nature, measurement and relationship to plant cell growth

Expansive growth of plant cells is controlled principally by processes that loosen the wall and enable it to expand irreversibly. The central role of wall relaxation for cell expansion is reviewed. The most common methods for assessing the extension properties of plant cell walls ( wall extensibility') are described, categorized and assessed critically. What emerges are three fundamentally different approaches which test growing cells for their ability (a) to enlarge at different values of turgor, (b) to induce wall relaxation, and (c) to deform elastically or plastically in response to an applied tensile force. Analogous methods with isolated walls are similarly reviewed. The results of these different assays are related to the nature of plant cell growth and pertinent biophysical theory. I argue that the extensibilities' measured by these assays are fundamentally different from one another and that some are more pertinent to growth than others.

Review, Academic↗
NASA NTRS1994

Experiment K-7-29: Connective Tissue Studies: Rodent Tissue Repair: Skeletal Muscle - Part 3

Myofiber injury-repair was studied in the rat gastrocnemius following a crush injury to the lower leg prior to flight in order to understand if the regenerative responses of muscles are altered by the lack of gravitational forces during Cosmos 2044 flight. After 14 days of flight, the gastrocnemius muscle was removed from the 5 injured flight rodents and various Earth-based treatment groups for comparison. The Earth-based animals consisted of three groups of five rats with injured muscles from a simulated, tail-suspended, and vivarium as well as an uninjured basal group. The gastrocnemius muscle from each was evaluated by histochemical and immunohistochemical techniques to document myofiber, vascular, and connective tissue alterations following injury. In general the repair process was somewhat similar in all injured muscle samples with regard to extracellular matrix organization and myofiber regeneration. Small and large myofibers were present with a newly organized extracellular matrix indicative of myogenesis and muscle regeneration. In the tail-suspended animals, a more complete repair was observed with no enlarged area of non-muscle cells or matrix material visible. In contrast, the muscle samples from the flight animals were less well differentiated with more macrophages and blood vessels in the repair region but small myofibers and proteoglycans, nevertheless, were in their usual configuration. Thus, myofiber repair did vary in muscles from the different groups, but for the most part, resulted in functional muscle tissue.

Stauber, W.↗
NASA NTRS1995

3-D Reconstruction of Macular Type II Cell Innervation Patterns in Space-Flight and Control Rats

A semiautomated method for reconstructing objects from serial thin sections has been developed in the Biocomputation Center. The method is being used to completely, for the first time, type II hair cells and their innervations. The purposes are to learn more about the fundamental circuitry of the macula on Earth and to determine whether changes in connectivities occur under space flight conditions. Data captured directly from a transmission electron microscope via a video camera are sent to a graphics workstation. There, the digitized micrographs are mosaicked into sections and contours are traced, registered and displayed by semiautomated methods. Current reconstructions are of type II cells from the medial part of rat maculas collected in-flight on the Space Life Sciences-2 mission, 4.5 hrs post-flight, and from a ground control. Results show that typical type II cells receive processes from tip to six nearby calyces or afferents. Nearly all processes are elongated and have bouton-like enlargements; some have numerous vesicles. Multiple (2 to 4) processes from a single calyx to a type II cell are common, and approximately 1/3 of the processes innervale 2 or 3 type II cells or a neighboring cluster. From 2% to 6% of the cells resemble type I cells morphologically but have demi-calyces. Thus far, increments in synaptic number in type II cells of flight rats are prominent along processes that supply two hair cells. It is clear that reconstruction methods provide insights into details of macular circuitry not obtainable by other techniques. The results demonstrate a morphological basis for interactions between adjacent receptive fields through feed back-feed forward connections, and for dynamic alterations in receptive field range and activity during preprocessing of linear acceleratory information by the maculas. The reconstruction method we have developed will find further applications in the study of the details of neuronal architecture of more complex systems, to seek out shared organizational properties or neuronal networks and to understand better localization of synaptic changes in altered environments.

Ross, Muriel Dorothy↗
NASA NTRS1988

Anatomical evidence for red nucleus projections to motoneuronal cell groups in the spinal cord of the monkey

In four rhesus monkeys wheat germ agglutinin-horseradish peroxidase (WGA-HRP) injections were made in the mesencephalic tegmentum. In three cases with injections involving the red nucleus (RN), rubrospinal fibers descended mainly contralaterally to terminate in laminae V, VI and dorsal VII of the spinal cord and in the lateral motoneuronal cell groups at the level of the cervical and lumbosacral enlargements. In all four cases the area of the interstitial nucleus of Cajal (INC) was injected, which resulted in labeled interstitiospinal fibers in the medial part of the ipsilateral ventral funiculus of the spinal cord. The results indicate that there is no major qualitative difference between the mesencephalic (RN and INC) and motor cortical projections to the spinal cord.

Holstege, Gert↗
NASA NTRS1983

Fine-structural changes in the midgut of old Drosophila melanogaster

Senescent fine-structural changes in the midgut of Drosophila melanogaster are investigated. A large number of midgut mitochondria in old flies exhibit nodular cristae and a tubular system located perpendicular to the normal cristae orientation. Anterior intestinal cells show a senescent accumulation of age pigment, either with a surrounding two-unit membrane or without any membrane. The predominant localization of enlarged mitochondria and pigment in the luminal gut region may be related to the polarized metabolism of the intestinal cells. Findings concur with previous observations of dense-body accumulations and support the theory that mitochondria are involved in the aging of fixed post-mitotic cells. Demonstrated by statistical analyses is that mitochondrial size increase is related to mitochondrial variation increase.

Anton-Erxleben, F.↗
NASA NTRS1992

Li/BCX (thionyl chloride) battery for the NASA AN/PRC-112 survival radio

As part of the NASA contingency planning related to aborting a launch after liftoff, an emergency radio is required for use by the crew when they return to Earth at some unplanned location. The power source for the radio must be able to satisfy the performance requirements for the radio's mission as well as be compatible with in-cabin storage in the space shuttle. The radio needs a base load power of about 1 W with capability to handle power spikes greater then 6.5 W. A slightly enlarged battery pack using the Li/BCX chemistry in C-size cells was developed that meets these power levels and extends the operational life of the radio by over a factor of four compared to its operation using a Li/SO2 cell battery pack. In addition, the cells meet the requirements for the Li/BCX cells used for extra-vehicular activities by the crew of the shuttle. One of the major qualifying tests is the ability of the cells to withstand exposure to high temperature (149 C) without leaking. Electrical performance and thermal abuse test data will be presented for the cells.

Ebel, Steven J.↗
NASA NTRS1996

Novel Afferent Terminal Structure in the Crista Ampullaris of the Goldfish, Carassius auratus

Using transmission electron microscopy, we have identified a new type of afferent terminal structure in the crista ampullaris of the goldfish Carassius auratus. In addition to the bouton-type afferent terminals previously described in the ear of this species, the crista also contained enlarged afferent terminals that enveloped a portion of the basolateral hair cell membrane. The hair cell membrane was evaginated and protruded into the afferent terminal in a glove-and-finger configuration. The membranes of the two cells were regularly aligned in the protruded region of the contact and had a distinct symmetrical electron density. The electron-dense profiles of these contacts were easily identified and were present in every crista sampled. In some cases, efferent terminals synapsed onto the afferents at a point where the hair cell protruded into the terminal. The ultrastructural similarities of the goldfish crista afferents to calyx afferents found in amniotes (birds, reptiles, and mammals) are discussed. The results of the study support the hypothesis that structural variation in the vertebrate inner ear may have evolved much earlier in evolution than previously supposed.

Lanford, Pamela J.↗
NASA NTRS2001

Otx1 null mutant mice show partial segregation of sensory epithelia comparable to lamprey ears

We investigated the development of inner ear innervation in Otx1 null mutants, which lack a horizontal canal, between embryonic day 12 (E12) and postnatal day 7 (P7) with DiI and immunostaining for acetylated tubulin. Comparable to control animals, horizontal crista-like fibers were found to cross over the utricle in Otx1 null mice. In mutants these fibers extend toward an area near the endolymphatic duct, not to a horizontal crista. Most Otx1 null mutants had a small patch of sensory hair cells at this position. Measurement of the area of the utricular macula suggested it to be enlarged in Otx1 null mutants. We suggest that parts of the horizontal canal crista remain incorporated in the utricular sensory epithelium in Otx1 null mutants. Other parts of the horizontal crista appear to be variably segregated to form the isolated patch of hair cells identifiable by the unique fiber trajectory as representing the horizontal canal crista. Comparison with lamprey ear innervation reveals similarities in the pattern of innervation with the dorsal macula, a sensory patch of unknown function. SEM data confirm that all foramina are less constricted in Otx1 null mutants. We propose that Otx1 is not directly involved in sensory hair cell formation of the horizontal canal but affects the segregation of the horizontal canal crista from the utricle. It also affects constriction of the two main foramina in the ear, but not their initial formation. Otx1 is thus causally related to horizontal canal morphogenesis as well as morphogenesis of these foramina.

NASA Discipline Developmental Biology↗
NASA NTRS1995

Performance of PEM Liquid-Feed Direct Methanol-Air Fuel Cells

A direct methanol-air fuel cell operating at near atmospheric pressure, low-flow rate air, and at temperatures close to 60oC would tremendously enlarge the scope of potential applications. While earlier studies have reported performance with oxygen, the present study focuses on characterizing the performance of a PEM liquid feed direct methanol-air cell consisting of components developed in house. These cells employ Pt-Ru catalyst in the anode, Pt at the cathode and Nafion 117 as the PEM. The effect of pressure, flow rate of air and temperature on cell performance has been studied. With air, the performance level is as high as 0.437 V at 300 mA/cm2 (90oC, 20 psig, and excess air flow) has been attained. Even more significant is the performance level at 60oC, 1 atm and low flow rates of air (3-5 times stoichiometric), which is 0.4 V at 150 mA/cm2. Individual electrode potentials for the methanol and air electrode have been separated and analyzed. Fuel crossover rates and the impact of fuel crossover on the performance of the air electrode have also been measured. The study identifies issues specific to the methanol-air fuel cell and provides a basis for improvement strategies.

Methanol-Air Fuel↗
NASA NTRS1992

Capacity loss on storage and possible capacity recovery for HST nickel-hydrogen cells

Negatively precharged nickel hydrogen cells will experience a useable capacity loss during extended open circuit storage periods. Some of the lost capacity can be recovered through cycling. Capacity recovery through cycling can be enhanced by cycling at high depths of discharge (DOD). The most timely procedure for recovering the faded capacity is to charge the cell fully and allow the cell to sit open-circuit at room temperature. This procedure seems to be effective in part because of the enlarged structure of the active materials. The compounds that formed during storage at the low electrode potentials can more easily dissolve and redistribute. All of the original capacity cannot be recovered because the lattice structure of the active material is irreversibly altered during storage. The recommendation is to use positively precharged cells activated with 26 percent KOH if possible. In aerospace applications, the benefits of negative precharge are offset by the possibility of delays and storage periods.

Lowery, John E.↗
NASA NTRS1995

Preliminary chaotic model of snapover on high voltage solar cells

High voltage power systems in space will interact with the space plasma in a variety of ways. One of these, snapover, is characterized by sudden enlargement of the current collection area across normally insulating surfaces generating enhanced electron current collection. Power drain on solar array power systems results from this enhanced current collection. Optical observations of the snapover phenomena in the laboratory indicates a functional relation between glow area and bia potential as a consequence of the fold/cusp bifurcation in chaos theory. Successful characterizations of snapover as a chaotic phenomena may provide a means of snapover prevention and control through chaotic synchronization.

Mackey, Willie R.↗
NASA NTRS1995

Preliminary Chaotic Model of Snapover on High Voltage Solar Cells

High voltage power systems in space will interact with the space plasma in a variety of ways. One of these, Snapover, is characterized by a sudden enlargement of the electron current collection area across normally insulating surfaces. A power drain on solar array power systems will results from this enhanced current collection. Optical observations of the snapover phenomena in the laboratory indicates a functional relation between bia potential and surface glow area. This paper shall explore the potential benefits of modeling the relation between current and bia potential as an aspect of bifurcation analysis in chaos theory. Successful characterizations of snapover as a chaotic phenomena may provide a means of snapover prevention and control through chaotic synchronization.

Mackey, Willie R.↗
NASA NTRS1994

Embryonic development of the cornea in the eye of the clearnose skate, Raja eglanteria: I. Stromal development in the absence of an endothelium

Embryos of the clearnose skate, Raja eglanteria, develop in sea water at 20-22 degrees C, hatching after 82 +/- 4 days (Luer and Gilbert, Environ. Biol. Fishes, 13:161-171, 1985). Eyes develop as steadily enlarging spheres whose corneas have the same radius of curvature as the sclera. The cornea begins development as a 2-cell thick epithelium beneath which by Day 12 there is only a basal lamina and a wispy matrix separating it from the underlying lens. This matrix, modified by Day 16, is displaced on Day 22 by a few orthogonal plies of fibrillar primary stroma. Ply number increases to at least 13 by Day 30, reaching the final number of 20 +/- 2 by Day 42. Stromal fibroblasts (keratocytes) appear at the corneal periphery by Day 22, and in increased numbers by Day 30, a time at which no keratocytes are seen in the central stroma. However, by Day 40, many fibroblasts are present at the corneal periphery, invading the primary stroma between plies, occasionally reaching even the central cornea. By Day 53, keratocytes are present between all plies, from corneal periphery to center. Thickness of each ply in this secondary stroma increases, but the number of plies remains the same as in the primary stroma. Bowman's layer, non-invaded matrix beneath the epithelial basal lamina, is not evident until Day 53. Sutural fibers, first seen on Day 22, originate in the corneal epithelial basal lamina, traversing perpendicularly the plies of the primary stroma. Sutural fibers persist throughout development of the secondary stroma and into adulthood. In contrast to chicks, skate corneas remain transparent throughout development, and never form an endothelium.

Non-NASA Center↗
NASA NTRS2017

The Role of Nuclear Cytoskeleton in the Osteocytic Response to Simulated Weightlessness

While in space, astronauts exercise frequently to combat bone and muscle loss due to weightlessness. This loss in bone can lead to serious health problems, such as increased fracture risk. Osteocytes are known to play a vital role in bone resorption and formation. It is also theorized that osteocytes act as the mechanosensors of bone, detecting mechanical stimulus and relaying these signals to surrounding cells. Previous research suggests that, during space flight, osteocytes exhibit matrix remodeling and resorption capabilities (osteocytic osteolysis) leading to an enlargement of the lacunae and contributing to overall bone degradation. The intercellular causes of these changes has not yet been determined. LINC or Linker of Nucleoskeleton and Cytoskeleton is a protein complex that forms a connection between the nucleus and cytoskeleton. LINC serves as a way to transmit mechanical signals to the nucleus and is also involved in the regulation of Wnt signaling via KASH proteins (Nesprin -1 and Nesprin -2). Wnt signaling in osteocytes assists with bone homeostasis and perturbed Wnt signaling can lead to bone loss. This suggests that LINC may contribute to the bone diminishing effects of microgravity. Therefore, we hypothesize that the disruption of LINC or LINC components by simulated microgravity (using the hindlimb unloading model, HU) affects Wnt signaling in osteocytes affecting bone formation and leading to increased osteocyte lacunar size. To test these hypotheses, we plan to conduct an animal study using 16 week old male mice (n6group). The mice will undergo HU for up to 7 days. After the desired time point, we will utilize quantitative real-time PCR techniques to determine the changes in gene expression of seven LINC complex genes (Sun -1, Sun -2, Nesprin -1, Nesprin -2, Lamin AC, Lamin B, and Emerin) and genes related to bone formation and osteocyte signaling. To determine changes osteocytic remodeling activity we will immunostain for osteocyte markers (Dmp-1 and Sost) and osteolysis markers (TRAP, MMPs) and measure lacunar size.

Touchstone, Hallie↗