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At least 361 records · Page 20

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DOE OSTI2024

Exploring the Impact of Copper Oxide Substitution on Structure, Morphology, Bioactivity, and Electrical Properties of 45S5 Bioglass®

In recent decades, the requirements for implantable medical devices have increased, but the risks of implant rejection still exist. These issues are primarily associated with poor osseointegration, leading to biofilm formation on the implant surface. This study focuses on addressing these issues by developing a biomaterial for implant coatings. 45S5 bioglass® has been widely used in tissue engineering due to its ability to form a hydroxyapatite layer, ensuring a strong bond between the hard tissue and the bioglass. In this context, 45S5 bioglasses®, modified by the incorporation of different amounts of copper oxide, from 0 to 8 mol%, were synthesized by the melt–quenching technique. The incorporation of Cu ions did not show a significant change in the glass structure. Since the bioglass exhibited the capacity for being polarized, thereby promoting the osseointegration effectiveness, the electrical properties of the prepared samples were studied using the impedance spectroscopy method, in the frequency range of 102–106 Hz and temperature range of 200–400 K. The effects of CuO on charge transport mobility were investigated. Additionally, the bioactivity of the modified bioglasses was evaluated through immersion tests in simulated body fluid. The results revealed the initiation of a Ca–P-rich layer formation on the surface within 24 h, indicating the potential of the bioglasses to enhance the bone regeneration process.

Hammami, Imen (ORCID:0000000290072221)↗

DOE OSTI2023

Structural Similarities and Overlapping Activities among Dihydroflavonol 4-Reductase, Flavanone 4-Reductase, and Anthocyanidin Reductase Offer Metabolic Flexibility in the Flavonoid Pathway

Flavonoids are potent antioxidants that play a role in defense against pathogens, UV-radiation, and the detoxification of reactive oxygen species. Dihydroflavonol 4-reductase (DFR) and flavanone 4-reductase (FNR) reduce dihydroflavonols and flavanones, respectively, using NAD(P)H to produce flavan-(3)-4-(di)ols in flavonoid biosynthesis. Anthocyanidin reductase (ANR) reduces anthocyanidins to flavan-3-ols. In addition to their sequences, the 3D structures of recombinant DFR, FNR and ANR from sorghum and switchgrass showed a high level of similarity. The catalytic mechanism, substrate-specificity and key residues of three reductases were deduced from crystal structures, site-directed mutagenesis, molecular docking, kinetics, and thermodynamic ana-lyses. Although DFR displayed its highest activity against dihydroflavonols, it also showed activity against flavanones and anthocyanidins. It was inhibited by the flavonol quercetin and high concentrations of dihydroflavonols/flavonones. SbFNR1 and SbFNR2 did not show any activity against dihydroflavonols. However, SbFNR1 displayed activity against flavanones and ANR activity against two anthocyanidins, cyanidin and pelargonidin. Therefore, SbFNR1 and SbFNR2 could be specific ANR isozymes without delphinidin activity. Sorghum has high concentrations of 3-deoxyanthocyanidins in vivo, supporting the observed high activity of SbDFR against flavonols. Mining of expression data indicated substantial induction of these three reductase genes in both switchgrass and sorghum in response to biotic stress. Key signature sequences for proper DFR/ANR classification are proposed and could form the basis for future metabolic engineering of flavonoid metabolism.

3-deoxyanthocyanidin↗

NASA NTRS1972

The synthesis of starch from carbon dioxide using isolubilized stabilized enzymes

Systems for artificial manufacture of starch and for delineation of technological areas, and the rationale for studying them are considered. A discussion of the enzyme-catalyzed routes of synthesis available and a choice as to the most promising route are presented. A discussion of the enzymes involved, of enzyme insolubilization technology, and of possible engineering approaches, with examples in the form of model calculations for both reactors and separators, are also presented.

Bassham, J. A.↗

NASA NTRS1972

Computer calculation of device, circuit, equipment, and system reliability.

A grouping into four classes is proposed for all reliability computations that are related to electronic equipment. Examples are presented of reliability computations in three of these four classes. Each of the three specific reliability tasks described was originally undertaken to satisfy an engineering need for reliability data. The form and interpretation of the print-out of the specific reliability computations is presented. The justification for the costs of these computations is indicated. The skills of the personnel used to conduct the analysis, the interfaces between the personnel, and the timing of the projects is discussed.

Crosby, D. R.↗

NASA NTRS1972

Rocket ascent G-limited moment-balanced optimization program (RAGMOP)

This document describes the RAGMOP (Rocket Ascent G-limited Momentbalanced Optimization Program) computer program for parametric ascent trajectory optimization. RAGMOP computes optimum polynomial-form attitude control histories, launch azimuth, engine burn-time, and gross liftoff weight for space shuttle type vehicles using a search-accelerated, gradient projection parameter optimization technique. The trajectory model available in RAGMOP includes a rotating oblate earth model, the option of input wind tables, discrete and/or continuous throttling for the purposes of limiting the thrust acceleration and/or the maximum dynamic pressure, limitation of the structural load indicators (the product of dynamic pressure with angle-of-attack and sideslip angle), and a wide selection of intermediate and terminal equality constraints.

Lyons, J. T.↗

NASA NTRS1973

Shuttle cryogenic supply system optimization study. Volume 2: Technical report, sections 4 through 9

The design and development of cryogenic supply systems for space shuttle vehicles are discussed. The weights, component counts, and statements of advantages and disadvantages of the systems considered are presented. Performance characteristics of the systems are analyzed in the form of graphs. Block diagrams and engineering drawings of the candidate systems are provided. Special consideration is given to flow rates and thermodynamic properties of the cryogenic systems.

Source record↗

NASA NTRS1973

The Earth Resources Program of the Corps of Engineers

The mission of the Corps of Engineers of the U.S. Army and the contributions made by the ERTS-1 data system are discussed. The use of satellite-borne sensors and aerial photography for projects involving engineering geology, flood control, master planning, and fluid dynamics and interations is reported. Examples of engineering projects are provided in the form of aerial photographs and multispectral band scanner imagery.

Jarman, J. W.↗

NASA NTRS1974

Space shuttle orbit maneuvering engine reusable thrust chamber. Task 13: Subscale helium ingestion and two dimensional heating test report

Descriptions are given of the test hardware, facility, procedures, and results of electrically heated tube, channel and panel tests conducted to determine effects of helium ingestion, two dimensional conduction, and plugged coolant channels on operating limits of convectively cooled chambers typical of space shuttle orbit maneuvering engine designs. Helium ingestion in froth form, was studied in tubular and rectangular single channel test sections. Plugged channel simulation was investigated in a three channel panel. Burn-out limits (transition of film boiling) were studied in both single channel and panel test sections to determine 2-D conduction effects as compared to tubular test results.

Tobin, R. D.↗

NASA NTRS1976

Ion beam thruster shield

An ion thruster beam shield is provided that comprises a cylindrical housing that extends downstream from the ion thruster and a plurality of annular vanes which are spaced along the length of the housing, and extend inwardly from the interior wall of the housing. The shield intercepts and stops all charge exchange and beam ions, neutral propellant, and sputter products formed due to the interaction of beam and shield emanating from the ion thruster outside of a fixed conical angle from the thruster axis. Further, the shield prevents the sputter products formed during the operation of the engine from escaping the interior volume of the shield.

Power, J. L.↗

NASA NTRS1980

Modular instrumentation system for real-time measurements and control on reciprocating engines

An instrumentation system was developed for reciprocating engines. Among the parameters measured are the indicated mean effective pressure, or theoretical work per cycle, and the mass fraction burn rate, a measure of the combustion rate in the cylinder. These computations are performed from measured cylinder pressure and crankshaft angle and are available in real time for the experimenter. A 100 or 200 consecutive-cycle sample is analyzed to reduce the effect of cyclic variations in the engine. Data are displayed in bargraph form, and the mean and standard deviation are computed. Other instruments are also described.

Rice, W. J.↗

NASA NTRS1981

Combustion system processes leading to corrosive deposits

Degradation of turbine engine hot gas path components by high temperature corrosion can usually be associated with deposits even though other factors may also play a significant role. The origins of the corrosive deposits are traceable to chemical reactions which take place during the combustion process. In the case of hot corrosion/sulfidation, sodium sulfate was established as the deposited corrosive agent even when none of this salt enters the engine directly. The sodium sulfate is formed during the combustion and deposition processes from compounds of sulfur contained in the fuel as low level impurities and sodium compounds, such as sodium chloride, ingested with intake air. In other turbine and power generation situations, corrosive and/or fouling deposits can result from such metals as potassium, iron, calcium, vanadium, magnesium, and silicon.

Stearns, C. A.↗

NASA NTRS1981

Cost effective flat plate photovoltaic modules using light trapping

Work in optical trapping in 'thick films' is described to form a design guide for photovoltaic engineers. A thick optical film can trap light by diffusive reflection and total internal reflection. Light can be propagated reasonably long distances compared with layer thicknesses by this technique. This makes it possible to conduct light from inter-cell and intra-cell areas now not used in photovoltaic modules onto active cell areas.

Bain, C. N.↗

NASA NTRS1982

Evaluation of fuel injection configurations to control carbon and soot formation in small GT combustors

An experimental program to investigate hardware configurations which attempt to minimize carbon formation and soot production without sacrificing performance in small gas turbine combustors has been conducted at the United Technologies Research Center. Four fuel injectors, embodying either airblast atomization, pressure atomization, or fuel vaporization techniques, were combined with nozzle air swirlers and injector sheaths, and evaluated at test conditions which included and extended beyond standard small gas turbine combustor operation. Extensive testing was accomplished with configurations embodying either a spill return or a T-vaporizer injector. Minimal carbon deposits were observed on the spill return nozzle for tests using either Jet A or ERBS test fuel. A more extensive film of soft carbon was observed on the vaporizer after operation at standard engine conditions, with large carbonaceous growths forming on the device during off-design operation at low combustor inlet temperature. Test results indicated that smoke emission levels depended on the combustor fluid mechanics (especially the mixing rates near the injector), the atomization quality of the injector and the fuel hydrogen content.

Rosfjord, T. J.↗

NASA NTRS1983

Combustion system processes leading to corrosive deposits

Stearns, C. A.↗

NASA NTRS1985

Optimization of mass placement in Space Station applications

A methodology is presented by means of which the projected NASA Space Station's structural elements, primarily involving externally attached masses reresenting payloads, can be prearranged to meet all constraints imposed on Station design by mission type, safety, and physical criteria. Five different configurations are considered. The methodology has been automated in the form of a computer-aided engineering tool for the optimization of masses with respect to the products of inertia. By minimizing the induced gravity-gradient torques, the momentum buildup over an orbital period is also minimized.

Ferebee, M. J., Jr.↗

NASA NTRS1988

The characteristics of the ground vortex and its effect on the aerodynamics of the STOL configuration

The interaction of the free stream velocity on the wall jet formed by the impingement of deflected engine thrust results in a rolled up vortex which exerts sizable forces on a short takeoff (STOL) airplane configuration. Some data suggest that the boundary layer under the free stream ahead of the configuration may be important in determining the extent of the travel of the wall jet into the oncoming stream. Here, early studies of the ground vortex are examined, and those results are compared to some later data obtained with moving a model over a fixed ground board. The effect of the ground vortex on the aerodynamic characteristics are discussed.

Stewart, Vearle R.↗

NASA NTRS1989

Microgravity combustion science: A program overview

The promise of microgravity combustion research is introduced by way of a brief survey of results, the available set of reduced gravity facilities, and plans for experimental capabilities in the Space Station era. The study of fundamental combustion processes in a microgravity environment is a relatively new scientific endeavor. A few simple, precursor experiments were conducted in the early 1970's. Today the advent of the U.S. space shuttle and the anticipation of the Space Station Freedom provide for scientists and engineers a special opportunity, in the form of long duration microgravity laboratories, and need, in the form of spacecraft fire safety and a variety of terrestrial applications, to pursue fresh insight into the basic physics of combustion. The microgravity environment enables a new range of experiments to be performed since buoyancy-induced flows are nearly eliminated, normally obscured forces and flows may be isolated, gravitational settling or sedimentation is nearly eliminated, and larger time or length scales in experiments become permissible. The range of experiments completed to date was not broad, but is growing. Unexpected phenomena have been observed often in microgravity combustion experiments, raising questions about the degree of accuracy and completion of our classical understanding and our ability to estimate spacecraft fire hazards. Because of the field's relative immaturity, instrumentation has been restricted primarily to high-speed photography. To better explain these findings, more sophisticated diagnostic instrumentation, similar to that evolving in terrestrial laboratories, is being developed for use on Space Station Freedom and, along the way, in existing microgravity facilities.

Source record↗

NASA NTRS1990

Proposed definition of the term en route in en route aircraft noise

The problem of en route aircraft noise was examined in a formal, dedicated, setting. Whereas the general meaning of the term en route might be intuitively understood, it is suggested that a precise formal definition of the term en route would be opportune from the outset, especially since the scientific and technical investigation of the problem of noise immissions on the ground from aircraft in flight away from the airspace of an airport may conceivably lead to administrative, regulatory, and legal consequences that would mandatorily require a precise definition of the term en route. Five flight segments, with their differing airframe configurations, engine thrusts, and airspeed management, should form the basis for the differential consideration of the noise immissions perceived on the ground underneath or near the defined segments of the flightpath in en route flight, from the end of the initial climb from an airport after takeoff until the final approach to an airport.

Garbell, Maurice A.↗