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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 NTRS1986

Determination of cosmogenic Ca-41 in a meteorite with tandem accelerator mass spectrometry

The first use of tandem accelerator mass spectrometry (TAMS) to measure the content of Ca-41 in a natural sample, the iron Bogou meteorite, is reported. Ca in the samples was extracted by hydroxide precipitation and purified by means of a caution exchange resin (AG 50W-X8). After adding 4 percent ammonium oxide, the precipitate was ignited to CaO in a quartz vial at about 1100 C. The Ca-41/Ca ratios were determined following acceleration by alternate measurements of the Ca-40 beam current in an image Faraday cup. Ca-41 particles were also measured using a gas counter. The measured Ca-41/Ca ratio was 3.8 + or -0.6 x 10 to the 12th, which corresponds to a Ca-41 activity of 6.9 + or -1.1 d.p.m. per kg. Calculation of the half-life of Ca-41 in the Bogou meteorite yielded an age of 103,000 years.

Kubik, P. W.↗
NASA NTRS1989

The 3-(bromoacetamido)-propylamine hydrochloride: A novel sulfhydryl reagent and its future potential in the configurational study of S1-myosin

Configurational study of S1-Myosin is an important step towards understanding force generation in muscle contraction. Previously reported NMR studies were corroborated. A new compound was synthesized, 3-(Bromoacetamido)-propylamine hydrochloride. Its potential as a sulfhydryl reagent provides an indirect but elegant approach towards future structural elucidation of S1-Myosin. The preliminary investigation has shown that this compound, BAAP, reacted with S1 in the absence of MgADP. The modified enzyme had a 2-fold increase in CaATPase activity and no detectable K-EDTA ATPase activity. Reaction of BAAP with S1 in the presence of MgADP resulted in a modified enzyme which retained a Ca-ATPase activity that was about 60 percent of the unmodified S1 and had essentially zero K-EDTA ATPase activity. Sulfhydryl titration indicated that about 1.5 and 3.5 SH groups per S1 molecule were blocked by BAAP in the absence and presence of MgADP, respectively. When coupled to a carboxyl group of EDTA, the resulting reagent could become a useful SH reagent in which chelated paramagnetic or luminescent lanthanide ions can be exploited to probe S1 conformation.

Sharma, Prasanta↗
NASA NTRS2005

Modeling regulation of cardiac KATP and L-type Ca2+ currents by ATP, ADP, and Mg2+

Changes in cytosolic free Mg(2+) and adenosine nucleotide phosphates affect cardiac excitability and contractility. To investigate how modulation by Mg(2+), ATP, and ADP of K(ATP) and L-type Ca(2+) channels influences excitation-contraction coupling, we incorporated equations for intracellular ATP and MgADP regulation of the K(ATP) current and MgATP regulation of the L-type Ca(2+) current in an ionic-metabolic model of the canine ventricular myocyte. The new model: 1), quantitatively reproduces a dose-response relationship for the effects of changes in ATP on K(ATP) current, 2), simulates effects of ADP in modulating ATP sensitivity of K(ATP) channel, 3), predicts activation of Ca(2+) current during rapid increase in MgATP, and 4), demonstrates that decreased ATP/ADP ratio with normal total Mg(2+) or increased free Mg(2+) with normal ATP and ADP activate K(ATP) current, shorten action potential, and alter ionic currents and intracellular Ca(2+) signals. The model predictions are in agreement with experimental data measured under normal and a variety of pathological conditions.

Validation Studies↗
NASA NTRS2000

Extracellular calcium-sensing-receptor (CaR)-mediated opening of an outward K(+) channel in murine MC3T3-E1 osteoblastic cells: evidence for expression of a functional CaR

The existence in osteoblasts of the G-protein-coupled extracellular calcium (Ca(o)(2+))-sensing receptor (CaR) that was originally cloned from parathyroid and kidney remains controversial. In our recent studies, we utilized multiple detection methods to demonstrate the expression of CaR transcripts and protein in several osteoblastic cell lines, including murine MC3T3-E1 cells. Although we and others have shown that high Ca(o)(2+) and other polycationic CaR agonists modulate the function of MC3T3-E1 cells, none of these actions has been unequivocally shown to be mediated by the CaR. Previous investigations using neurons and lens epithelial cells have shown that activation of the CaR stimulates Ca(2+)-activated K(+) channels. Because osteoblastic cells express a similar type of channel, we have examined the effects of specific "calcimimetic" CaR activators on the activity of a Ca(2+)-activated K(+) channel in MC3T3-E1 cells as a way of showing that the CaR is not only expressed in those cells but is functionally active. Patch-clamp analysis in the cell-attached mode showed that raising Ca(o)(2+) from 0.75 to 2.75 mmol/L elicited about a fourfold increase in the open state probability (P(o)) of an outward K(+) channel with a conductance of approximately 92 pS. The selective calcimimetic CaR activator, NPS R-467 (0.5 micromol/L), evoked a similar activation of the channel, while its less active stereoisomer, NPSS-467 (0.5 micromol/L), did not. Thus, the CaR is not only expressed in MC3T3-E1 cells, but is also functionally coupled to the activity of a Ca(2+)-activated K(+) channel. This receptor, therefore, could transduce local or systemic changes in Ca(o)(2+) into changes in the activity of this ion channel and related physiological processes in these and perhaps other osteoblastic cells.

NASA Discipline Musculoskeletal↗
NASA NTRS1981

A comparison of rat myosin from fast and slow skeletal muscle and the effect of disuse

Certain enzymatic and structural features of myosin, purified from rat skeletal muscles representative of the fast twitch glycolytic (type IIb), the fast twitch oxidative (type IIa), and the slow twitch oxidative (type I) fiber, were determined and the results were compared with the measured contractile properties. Good correlation was found between the shortening velocities and Ca(2+)-activated ATPase activity for each fiber type. Short term hind limb immobilization caused prolongation of contraction time and one-half relaxation time in the fast twitch muscles and a reduction of these contractile properties in slow twitch soleus. Furthermore, the increased maximum shortening velocity in the immobilized soleus could be correlated with increased Ca(2+)-ATPase, but no change was observed in the enzymatic activity of the fast twitch muscles. No alteration in light chain distribution with disuse was observed in any of the fiber types. The myosin from slow twitch soleus could be distinguished from fast twitch myosins on the basis of the pattern of peptides generated by proteolysis of the heavy chains. Six weeks of hind limb immobilization resulted in both an increased ATPase activity and an altered heavy chain primary structure in the slow twitch soleus muscle.

Unsworth, B. R.↗
NASA NTRS2002

Recovery of resources for advanced life support space applications: effect of retention time on biodegradation of two crop residues in a fed-batch, continuous stirred tank reactor

Bioreactor retention time is a key process variable that will influence costs that are relevant to long distance space travel or long duration space habitation. However. little is known about the effects of this parameter on the microbiological treatment options that are being proposed for Advanced Life Support (ALS) systems. Two bioreactor studies were designed to examine this variable. In the first one, six retention times ranging from 1.3 to 21.3 days--were run in duplicate, 81 working-volume continuous stirred tank reactors (CSTR) that were fed ALS wheat residues. Ash-free dry weight loss, carbon mineralization, soluble TOC reduction, changes in fiber content (cellulose, hemicellulose, and lignin), bacterial numbers, and mineral recoveries were monitored. At short retention times--1.33 days--biodegradation was poor (total: 16-20%, cellulose - 12%, hemicellulose - 28%) but soluble TOC was decreased by 75-80% and recovery of major crop inorganic nutrients was adequate, except for phosphorus. A high proportion of the total bacteria (ca. 83%) was actively respiring. At the longest retention time tested, 21.3 days, biodegradation was good (total: 55-60%, cellulose ca. 70%, hemicellulose - ca. 55%) and soluble TOC was decreased by 80%. Recovery of major nutrients, except phosphorus, remained adequate. A very low proportion of total bacteria was actively respiring (ca. 16%). The second bioreactor study used potato residue to determine if even shorter retention times could be used (range 0.25-2.0 days). Although overall biodegradation deteriorated, the degradation of soluble TOC continued to be ca. 75%. We conclude that if the goal of ALS bioprocessing is maximal degradation of crop residues, including cellulose, then retention times of 10 days or longer will be needed. If the goal is to provide inorganic nutrients with the smallest volume/weight bioreactor possible, then a retention time of 1 day (or less) is sufficient.

Non-NASA Center↗
NASA NTRS1996

Soleus Fiber Force and Maximal Shortening Velocity After Non-Weight Bearing with Intermittent Activity

This study examined the effectiveness of intermittent weight bearing (IWB) as a countermeasure to non-weight-bearing (NWB)-induced alterations in soleus type 1 fiber force (in mN), tension (P(sub o); force per fiber cross-sectional area in kN/sq m), and maximal unloaded shortening velocity (V(sub o), in fiber lengths/s). Adult rats were assigned to one of the following groups: normal weight bearing (WB), 14 days of hindlimb NWB (NWB group), and 14 days of hindlimb NWB with IWB treatments (IWB group). The IWB treatment consisted of four 10-min periods of standing WB each day. Single, chemically permeabilized soleus fiber segments were mounted between a force transducer and position motor and were studied at maximal Ca(2+) activation, after which type 1 fiber myosin heavy-chain composition was confirmed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. NWB resulted in a loss in relative soleus mass (-45%), with type 1 fibers displaying reductions in diameter (-28%) and peak isometric force (-55%) and an increase in V(sub o) (+33%). In addition, NWB induced a 16% reduction in type 1 fiber P., a 41% reduction in type 1 fiber peak elastic modulus [E(sub o), defined as ((delta)force/(delta)length x (fiber length/fiber cross-sectional area] and a significant increase in the P(sub o)/E(sub o) ratio. In contrast to NWB, IWB reduced the loss of relative soleus mass (by 22%) and attenuated alterations in type 1 fiber diameter (by 36%), peak force (by 29%), and V(sub o)(by 48%) but had no significant effect on P(sub o), E(sub o) or P(sub o)/E(sub o). These results indicate that a modest restoration of WB activity during 14 days of NWB is sufficient to attenuate type 1 fiber atrophy and to partially restore type 1 peak isometric force and V(sub o) to WB levels. However, the NWB-induced reductions in P(sub o) and E(sub o) which we hypothesize to be due to a decline in the number and stiffness of cross bridges, respectively, are considerably less responsive to this countermeasure treatment.

Widrick, Jeffrey J.↗
NASA NTRS1993

Exposure history of the lunar meteorite, Elephant Moraine 87521

We report the noble gas concentrations and the Al-26, Be-10, Cl-36, and Ca-41 activities of the Antarctic lunar meteorite Elephant Moraine 87521. Although the actual exposure history of the meteorite may have been more complex, the following model history accounts satisfactorily for the cosmogenic nuclide data: A first stage of lunar irradiation for about 1 Ma at a depth of 1-5 g/sq cm followed, not necessarily directly, by a second one for 26 Ma at about 565 g/sq cm; launch from the moon less than 0.1 Ma ago; and arrival on earth 15-50 ka ago. The small concentration of trapped gases shows that except for some material that may have been introduced at the moment of launch, EET 87521 spent less than 1 Ma at a lunar depth less than 1 g/sq cm. EET 87521 has a K/Ar age in the range 3.0-3.4 Ga, which is typical for lunar mare basalts.

Vogt, S.↗
NASA NTRS1997

Effect of 17 days of bed rest on peak isometric force and unloaded shortening velocity of human soleus fibers

The purpose of this study was to examine the effect of prolonged bed rest (BR) on the peak isometric force (P0) and unloaded shortening velocity (V0) of single Ca(2+)-activated muscle fibers. Soleus muscle biopsies were obtained from eight adult males before and after 17 days of 6 degrees head-down BR. Chemically permeabilized single fiber segments were mounted between a force transducer and position motor, activated with saturating levels of Ca2+, and subjected to slack length steps. V0 was determined by plotting the time for force redevelopment vs. the slack step distance. Gel electrophoresis revealed that 96% of the pre- and 87% of the post-BR fibers studied expressed only the slow type I myosin heavy chain isoform. Fibers with diameter > 100 microns made up only 14% of this post-BR type I population compared with 33% of the pre-BR type I population. Consequently, the post-BR type I fibers (n = 147) were, on average, 5% smaller in diameter than the pre-BR type I fibers (n = 218) and produced 13% less absolute P0. BR had no overall effect on P0 per fiber cross-sectional area (P0/CSA), even though half of the subjects displayed a decline of 9-12% in P0/CSA after BR. Type I fiber V0 increased by an average of 34% with BR. Although the ratio of myosin light chain 3 to myosin light chain 2 also rose with BR, there was no correlation between this ratio and V0 for either the pre- or post-BR fibers. In separate fibers obtained from the original biopsies, quantitative electron microscopy revealed a 20-24% decrease in thin filament density, with no change in thick filament density. These results raise the possibility that alterations in the geometric relationships between thin and thick filaments may be at least partially responsible for the elevated V0 of the post-BR type I fibers.

STS-78 Shuttle Project↗
NASA NTRS2010

Comparisons of Supergranule Properties from SDO/HMI with Other Datasets

While supergranules, a component of solar convection, have been well studied through the use of Dopplergrams, other datasets also exhibit these features. Quiet Sun magnetograms show local magnetic field elements distributed around the boundaries of supergranule cells, notably clustering at the common apex points of adjacent cells, while more solid cellular features are seen near active regions. Ca II K images are notable for exhibiting the chromospheric network representing a cellular distribution of local magnetic field lines across the solar disk that coincides with supergranulation boundaries. Measurements at 304 A further above the solar surface also show a similar pattern to the chromospheric network, but the boundaries are more nebulous in nature. While previous observations of these different solar features were obtained with a variety of instruments, SDO provides a single platform, from which the relevant data products at a high cadence and high-definition image quality are delivered. The images may also be cross-referenced due to their coincidental time of observation. We present images of these different solar features from HMI & AIA and use them to make composite images of supergranules at different atmospheric layers in which they manifest. We also compare each data product to equivalent data from previous observations, for example HMI magnetograms with those from MDI.

Pesnell, William Dean↗
NASA NTRS1988

Identifying motor and sensory myelinated axons in rabbit peripheral nerves by histochemical staining for carbonic anhydrase and cholinesterase activities

Carbonic anhydrase (CA) and cholinesterase (CE) histochemical staining of rabbit spinal nerve roots and dorsal root ganglia demonstrated that among the reactive myeliated axons, with minor exceptions, sensory axons were CA positive and CE negative whereas motor axons were CA negative and CE positive. The high specificity was achieved by adjusting reaction conditions to stain subpopulations of myelinated axons selectively while leaving 50 percent or so unstained. Fixation with glutaraldehyde appeared necessary for achieving selectivity. Following sciatic nerve transection, the reciprocal staining pattern persisted in damaged axons and their regenerating processes which formed neuromas within the proximal nerve stump. Within the neuromas, CA-stained sensory processes were elaborated earlier and in greater numbers than CE-stained regenerating motor processes. The present results indicate that histochemical axon typing can be exploited to reveal heterogeneous responses of motor and sensory axons to injury.

Riley, Danny A.↗
NASA NTRS1986

Fourier transform spectrometer observations of solar carbon monoxide. II - Simultaneous cospatial measurements of the fundamental and first-overtone bands, and Ca II K, in quiet and active regions

Fourier transform spectrometry has yielded simultaneous cospatial measurements of important diagnostics of thermal structure in the high solar photosphere and low chromosphere. It is noted that the anomalous behavior of the fundamental bands of CO in quiet areas near the limb is accentuated in an active region plage observed close to the limb. The difference between the core temperatures of the CO fundamental bands in a plage and a nearby quiet region at the limb is larger than the corresponding brightness temperature differences in the inner wings of the Ca II line measured in a quiet region and several plages closer to the disk center. Numerical simulations indicate that the disparate behavior of the CO bands with respect to Ca II K cannot be reconciled with existing single component thermal structure models; a two-component atmosphere is required.

Ayres, T. R.↗
NASA NTRS1983

Bone resorption and mineral excretion in rats during spaceflight

Bone resorption was measured directly in flight and synchronous control rats during COSMOS 1129. Continuous tracer administration techniques were used, with replacement of dietary calcium with isotopically enriched Ca-40 and measurement by neutron activation analysis of the Ca-48 released by the skeleton. There is no large change in bone resorption in rats at the end of 20 days of spaceflight as has been found for bone formation. Based on the time course of changes, the measured 20-25 percent decrease in resorption is probably secondary to a decrease in total body calcium turnover. The excretion of sodium, potassium, and zinc all increase during flight, sodium and potassium to a level four to five times control values.

Cann, C. E.↗
NASA NTRS2009

NiF2/NaF:CaF2/Ca Solid-State High-Temperature Battery Cells

Experiments and theoretical study have demonstrated the promise of all-solid-state, high-temperature electrochemical battery cells based on NiF2 as the active cathode material, CaF2 doped with NaF as the electrolyte material, and Ca as the active anode material. These and other all-solid-state cells have been investigated in a continuing effort to develop batteries for instruments that must operate in environments much hotter than can be withstood by ordinary commercially available batteries. Batteries of this type are needed for exploration of Venus (where the mean surface temperature is about 450 C), and could be used on Earth for such applications as measuring physical and chemical conditions in geothermal wells and oil wells. All-solid-state high-temperature power cells are sought as alternatives to other high-temperature power cells based, variously, on molten anodes and cathodes or molten eutectic salt electrolytes. Among the all-solid-state predecessors of the present NiF2/NaF:CaF2/Ca cells are those described in "Solid-State High-Temperature Power Cells" (NPO-44396), NASA Tech Briefs, Vol. 32, No. 5 (May 2008), page 40. In those cells, the active cathode material is FeS2, the electrolyte material is a crystalline solid solution of equimolar amounts of Li3PO4 and LiSiO4, and the active anode material is Li contained within an alloy that remains solid in the intended high operational temperature range.

West, William↗
NASA NTRS1982

The solar corona - A testing ground for plasma astrophysics

The extension of solar surface activity models to the domain of stellar activity, and the possibility of testing such extensions, are discussed. The extrapolation of three canonical solar activity indicators, sunspots, Ca II emission, and solar flares, to other stars is considered. The use of satellites to study stellar activity at wavelengths at which surface activity is most prominent is briefly reviewed. The correlation of stellar activity with intrinsic stellar parameters, especially those relating to rotation, is briefly considered, and the use of phenomenological models of stellar coronal X-ray emission to deduce the magnetic flux production rate for observed stars as a function of rotation rate is discussed.

Rosner, R.↗
NASA NTRS1991

Ca-41 in iron falls, Grant and Estherville - Production rates and related exposure age calculations

Results are presented of the first phase of a Ca-41 cosmogenic studies program aimed at establishing baseline concentrations and trends in selected meteorites and the use of Ca-41 in estimating exposure ages and preatmospheric meteorite radii. The average Ca-41 saturation activity recorded in four small iron falls is 24 +/-1 dpm/kg. This finding, together with measurements at the center and surface of the large iron Grant, indicates that production of Ca-41 from spallation on iron is weakly dependent on shielding to depths as large as 250 g/sq cm. The (K-41)-Ca-41 exposure age of Grant is estimated at 330 +/-50 My, and an upper limit to its terrestrial age of 43 +/-15 ky. A comparison of the Ca-41 contents of stony and metallic material separated from the mesosiderite Estherville identifies low-energy neutron capture on native Ca as a second important channel of production. It is found that the Ca-41 signal in the stone phase from three meteorites correlates with their size, and that the inferred low-energy neutron fluxes vary by a factor of at least 20.

Fink, D.↗
NASA NTRS2001

Calcium-stimulated autophosphorylation site of plant chimeric calcium/calmodulin-dependent protein kinase

The existence of two molecular switches regulating plant chimeric Ca(2+)/calmodulin-dependent protein kinase (CCaMK), namely the C-terminal visinin-like domain acting as Ca(2+)-sensitive molecular switch and calmodulin binding domain acting as Ca(2+)-stimulated autophosphorylation-sensitive molecular switch, has been described (Sathyanarayanan, P. V., Cremo, C. R., and Poovaiah, B. W. (2000) J. Biol. Chem. 275, 30417-30422). Here we report the identification of Ca(2+)-stimulated autophosphorylation site of CCaMK by matrix-assisted laser desorption ionization time of flight-mass spectrometry. Thr(267) was confirmed as the Ca(2+)-stimulated autophosphorylation site by post-source decay experiments and by site-directed mutagenesis. The purified T267A mutant form of CCaMK did not show Ca(2+)-stimulated autophosphorylation, autophosphorylation-dependent variable calmodulin affinity, or Ca(2+)/calmodulin stimulation of kinase activity. Sequence comparison of CCaMK from monocotyledonous plant (lily) and dicotyledonous plant (tobacco) suggests that the autophosphorylation site is conserved. This is the first identification of a phosphorylation site specifically responding to activation by second messenger system (Ca(2+) messenger system) in plants. Homology modeling of the kinase and calmodulin binding domain of CCaMK with the crystal structure of calcium/calmodulin-dependent protein kinase 1 suggests that the Ca(2+)-stimulated autophosphorylation site is located on the surface of the kinase and far from the catalytic site. Analysis of Ca(2+)-stimulated autophosphorylation with increasing concentration of CCaMK indicates the possibility that the Ca(2+)-stimulated phosphorylation occurs by an intermolecular mechanism.

Non-NASA Center↗
NASA NTRS1999

The Role of Calcium in the Response of Osteoblasts to Mechanical Stimulation

A major biomedical concern in the exploration and development of space is the rapid loss of bone associated with extended periods of spaceflight. Mineral content, bone formation, matrix protein production and total body calcium are all reduced during long-term periods of weightlessness. These effects of weightlessness appears to be due to decreases in the anabolic function of osteoblasts and osteocytes rather than changes in the resorptive activity of osteoclasts. Conversely, subjecting the skeleton to exogenous mechanical loading increases matrix protein synthesis and bone formation rate, a process which also appears mediated through osteogenic cells. Osteoblasts have been shown to respond to a number of types of mechanical stimulation. However recently we have demonstrated that osteoblasts respond to fluid shear, but not physiologic levels of mechanical strain, with increases in expression of the matrix protein, osteopontin. We have also shown similar responses in other markers for the anabolic response in bone. The expression of the early response gene, c-fos, and the inducible-isoform of the prostaglandin synthetic enzyme, cyclooygenase-2 (COX-2), both increase rapidly in response to fluid shear, but not strain. How osteoblasts and osteocytes perceive mechanical stimuli and convert this stimulus into a biochemical event within the cell is still unknown. However, examination of the cellular events following mechanical stimulation indicate that two of the earliest responses are a rapid increase in intracellular calcium ([Ca(2+)](sub i)) and a reorganization of the actin cytoskeleton. The increase in [Ca(2+)](sub i) is dependent on the presence of extracellular Ca(2+), suggesting the activation of membrane Ca(2+) channel. We have previously characterized a mechanosensitive, cation-selective channel (MSCC) in osteoblast-like clonal cells, which we postulate is important in this early response to mechanical loading. Using an antisense oligodeoxynucleotide strategy, we have tentatively identified this channel as an isoform of the alc subunit of the dihydropyridine-sensitive, voltage sensitive Ca(2+) channel (VSCC). However, a major component in this mechanically induced rise in [Ca(2+)](sub i) is the release of Ca(2+) from intracellular stores. The actin cytoskeleton also rapidly responds to fluid shear with an increase in stress fiber formation and a realignment of the cell parallel to the direction of flow. To ascertain whether these two observations are related and how they effect shear-induced gene expression, we examined the role of Ca(2+) channels and intracellular Ca(2+) release on cytoskeletal reorganization and the resultant increases in the expression and production of c-fos and COX-2 in response to fluid shear.

Duncan, R. L.↗