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NASA NTRS1976

Magnetostrictive ultrasonic probes

The principles underlying the design and use of magnetostrictive ultrasonic probes is illustrated by oscillograms and sketches. Attention is given to such concepts as magnetostrictive transduction, broadband pulse shaping, guided wave propagation, wave impedance, reflection, transmission, and attenuation coefficients, coupling methods, and impulse-induced resonance. A number of applications of such probes are discussed including the measurement of elastic moduli, temperature, and acoustic emission and resonance studies.

Lynnworth, L. C.↗

NASA NTRS1979

A study of the mechanism of thigmomorphogenesis in plants, with special reference to the role of ethylene and its significance to research with plants in space

Because of the paucity of data concerning thigmomorphogenesis, all aspects of the phenomenon were under study, although the role of ethylene mediation was central to the approach. Although this report must necessarily point to a specific time in ongoing research, several aspects of the study reached at least temporary stopping points and were therefore written and submitted for publication. These are identified. Other papers which are currently in preparation, but not yet submitted, are also identified. The phenomenon of thigmomorphogenesis is divided into the sensory function, transduction step(s) and the response function.

Jaffe, M. J.↗

NASA NTRS1980

Stress wave attenuation in thin structures by ultrasonic through-transmission

The steady state amplitude of the output of an ultrasonic through transmission measurement is analyzed and the result is given in closed form. Provided that the product of the input and output transduction ratios; the specimen-transducer reflection coefficient; the specimen-transducer phase shift parameter; and the material phase velocity are known, this analysis gives a means for determining the through-thickness attenuation of an individual thin sample. Multiple stress wave reflections are taken into account and so signal echoes do not represent a difficulty. An example is presented for a graphite fiber epoxy composite (Hercules AS/3501-6). A direct method for continuous or intermittent monitoring of through thickness attenuation of plate structures which may be subject to service structural degradation is provided.

Lee, S. S.↗

NASA NTRS1982

The influence of varied gravito-inertial fields on the cardiac response of orb-weaving spiders

The Gz transfer function was described for the orb weaving spider A. sericatus. The functional relationship between the heartrate and the intensity of G is linear in the form of: Y = a Log Gz-1 +k. The heartrate in unrestrained animals was recorded by a laser plethysmograph developed specifically for this purpose. Following a control, sample heartrate were taken postrotation between 1.001 and 1.5 Gz in 6 steps. The underlying distribution of heartrates does not appear significantly different from a Gaussian distribution. A method of varnishing the legs of the spider was developed. This was done in order to compromise the lyriform organs, especially those located on the patellae. The lyriform organ is hypothesized to serve the receptor role in the transduction of gravity related stimuli. In preliminary animals the Gz function, post varnishing of the patellae, appears to be changed in the direction of poorer discrimination. We also observed that the resting heartrate following the varnish procedure is substantially increased.

Finck, A.↗

NASA NTRS1980

Stress-wave attenuation in thin structures by ultrasonic through-transmission

The steady-state amplitude of the output of an ultrasonic through-transmission measurement is analyzed and the result is given in closed form. Provided that the product of the input and output transduction ratios, the specimen-transducer reflection coefficient, the specimen-transducer phase-shift parameter, and the material phase velocity are known, this analysis gives a means for determining the through-thickness attenuation of an individual thin sample. Multiple stress-wave reflections are taken into account, and so signal echoes do not represent a difficulty. An example is presented for a graphite fiber epoxy composite (Hercules AS/3501-6). Thus, the technique provides a direct method for continuous or intermittent monitoring of through-thickness attenuation of plate structures which may be subject to service structural degradation.

Lee, S. S.↗

NASA NTRS1981

Models for protocellular photophosphorylation

Several photoreactions for transducing light energy have been analyzed for their relevance as models for protocellular photophosphorylation. Inorganic ions and compounds could have played a role in protocellular photophosphorylation. Organic catalysts may have been the next significant agents used by protocells for photophosphorylation. Membranous photophosphorylation probably became the most recent type of photoenergy transduction to be acquired by protocells; it is still used by modern cells although components of the other types of phosphorylation are found in present day cells. Recorded yields of energy-rich phosphates from the model reactions discussed are small. Arguments are advanced that such yields could have been sufficient to have fueled protocellular metabolism, which was probably very slow compared to modern cellular metabolism. Future prospects for research in this area are discussed.

Bahn, P. R.↗

NASA NTRS1984

Integrated Tactile Sensor for Robots

Proposed large-scale integrated (LSI) circuit gives robots, partshandling machines, and remote-control devices sense of touch. LSI circuits, placed on contact surfaces of manipulators combine functions of transduction, computing and communicating. Beneath layer of pressure sensitive rubber, resistivity of which changes with pressure, electrodes furnish pressuredependent signal to computation elements. Electrodes and computation elements contained in silicon integrated-circuit wafer.

Raibert, M. H.↗

NASA NTRS1982

Optimal preparation of the ECC ozonesonde

The ECC background current was identified as the removal of residual tri-iodide (iodine) as the cell approaches equilibrium. The altitude dependence of this source of the background current is expected to be only slowly changed in the troposphere with a more rapid decrease in the stratosphere. Oxygen does not play a role in the background current except in the unlikely situation where the electrodes have had all forms of iodine removed from them and the electrodes have not re-equilibrated with the sonde solutions before use. A solution mass transport parameter in the ECC was identified and its altitude dependence determined. The mass transport of tri-iodide dominates in the chemical transduction of ozone to electrical signal. The effect of the mass transport on the ECC background current is predicted. An electrochemical model of the ECC has been developed to predict the response of the ECC to various ozone vertical profiles. The model corresponds very closely to the performance of the ECC in the laboratory. Based on this model, an ECC with no background current is predicted to give total ozone values within 1% of the correct value, although the vertical profile may be in error by as much as + or - 15%.

Thornton, D. C.↗

NASA NTRS1983

Interrelated striated elements in vestibular hair cells of the rat

A series of interrelated striated organelles in types I and II vestibular hair cells of the rat which appear to be less developed in cochlear hair cells have been revealed by unusual fixation procedures, suggesting that contractile elements may play a role in sensory transduction in the inner ear, especially in the vestibular system. Included in the series of interrelated striated elements are the cuticular plate and its basal attachments to the hair cell margins, the connections of the strut array of the kinociliary basal body to the cuticular plate, and striated organelles associated with the plasma membrane and extending below the apical junctional complexes.

Ross, M. D.↗

NASA NTRS1983

Calcium movements and the cellular basis of gravitropism

Evidence that calcium is a significant factor in gravitropism of plants is examined, together with the regulatory mechanism that controls calcium efflux in plant cells. Calcium has been found to accumulate on the upper surface of a plant placed in a horizontal attitude, which is followed by growth to the vertical within a half-hour. It has also been determined that the upper surface of the plant simultaneously experiences a reduced growth rate, compared to the lower surface. The substance calmodulin has been identified as the calcium-binding regulatory protein most influential in the transduction process leading to gravitropism, while chlorpromazine can inhibit its effects. The calcium is transported by ATPase located in the cell membrane. A possibility that the calcium pump is regulated by a feedback mechanism involving the presence of calmodulin is discussed.

Roux, S. J.↗

NASA NTRS1984

Inhibition of gravitropism in oat coleoptiles by calcium chelation

Some cellular event necessary for gravitropism is inhibited by EGTA without interferring with the overall growth. Calcium relieves this inhibition and demonstrates both that inhibition is reversible and was probably due to a reduction in the ability to free calcium required for one or more at the transduction steps of gravitropism. At the near neutral pH used, EGTA is charged and would not be expected to readily cross the membrane. One of its primary effects, then, is probably the bringing of free calcium in the apoplastic space exterior to the cell membranes.

Roux, S. J.↗

NASA NTRS1985

NASA Space Biology Program: 9th Annual Symposium

Topics covered include plant and animal gravity receptors and transduction; the role of gravity in growth and development of plants and animals; biological support structures and the role of calcium; mechanisms and responses of gravity sensitive systems; and mechanisms of plant responses to gravity.

Thora W Halstead↗

NASA NTRS1985

Gravity Perception and Response in Shoots of Cereal Grasses

Two components of the gravitropic curvature response in cereal grass pulvini are studied. These two components are gravity perception and mechanism of response following the transduction phase. The effects of gravity, time lag, protein synthesis and enzyme production are included.

Kaufman, P. B.↗

NASA NTRS1984

Mechanism of colour discrimination by a bacterial sensory rhodopsin

A photosensitive protein resembling the visual pigments of invertebrates enables phototactic archaebacteria to distinguish color. This protein exists in two spectrally-distinct forms, one of which is a transient photoproduct of the other and each of which undergoes photochemical reactions controlling the cell's swimming behaviour. Activation of a single pigment molecule in the cell is sufficient to signal the flagellar motor. This signal-transduction mechanism makes evident a color-sensing capability inherent in the retinal/protein chromophore.

Spudich, J. L.↗

NASA NTRS1988

Sulfur as a surface passivation for InP

The use of liquid and gas phase sulfur pretreatment of the surface of InP as a way to form a near-ideal passivated surface prior to chemical vapor deposition of SiO2 was investigated. Results of high-frequency and quasi-static capacitance-voltage measurements, as well as enhancement mode insulated gate field-effect transistor (FET) transductance and drain current stability studies, all support the efficacy of this approach for metal-insulator-semiconductor application of this semiconductor. In particular, surface state values in the range of 10 to the 10th to a few 10 to the 11th/sq cm per eV and enhancement mode FET drain current drifts of less than 5 percent over a 12 h test period were measured.

Iyer, R.↗

NASA NTRS1989

OTVE combustor wall condition monitoring

Conventional ultrasonics, eddy current, and electromagnetic acoustic transduction (EMAT) technologies were evaluated to determine their capability of measuring wall thickness/wear of individual cooling channels in test specimens simulating conditions in the throat region of an OTVE combustion chamber liner. Quantitative results are presented for the eddy current technology, which was shown to measure up to the optimum 20-mil wall thickness with near single channel resolution. Additional results demonstrate the capability of the conventional ultrasonics and EMAT technologies to detect a thinning or cracked wall. Recommendations for additional eddy current and EMAT development tests are presented.

Szemenyei, Brian↗

NASA NTRS1990

Localize and identify the gravity sensing mechanism of plants

The machinery by which a plant transduces the gravity stimulus into a growth response is localized and identified at the cellular level. The fact that a plant grows unequally on the lower side of a horizontally placed stem implies that there must be an asymmetric distribution of some of the chemical substances involved in the growth response. The three most likely chemicals to cause this growth were determined to be potassium, calcium, or the growth hormone, indole-3-acetic acid (IAA). IAA was chosen for this study and the results present a fairly complete understanding of the transduction of the gravity stimulus.

Bandurski, Robert S.↗

NASA NTRS1991

Photosynthetic reaction center complexes from heliobacteria

Photosynthetic reaction centers are pigment-protein complexes that are responsible for the transduction of light energy into chemical energy. Considerable evidence indicates that photosynthetic organisms were present very early in the evolution of life on Earth. The goal of this project is to understand the early evolutionary development of photosynthesis by examining the properties of reaction centers isolated from certain contemporary organisms that appear to contain the simplest photosynthetic reaction centers. The major focus is on the family of newly discovered strictly anaerobic photosynthetic organisms that are grouped with the gram-positive phylum of bacteria. The properties of these reactions centers suggest that they may be the descendants of an ancestor that also gave rise to Photosystem 1 found in oxygen-evolving photosynthetic organisms. Photoactive reaction center-core antenna complexes were isolated from the photosynthetic bacteria, Heliobacillus mobilis and Heliobacterium gestii, by extraction of membranes with Deriphat 160C followed by differential centrifugation and sucrose density gradient centrifugation. Other aspects of this investigation are briefly discussed.

Trost, J. T.↗