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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 649 records · Page 36
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Solid-state NMR of unlabeled plant cell walls: high-resolution structural analysis without isotopic enrichment

Abstract Background Multidimensional solid-state nuclear magnetic resonance (ssNMR) spectroscopy has emerged as an indispensable technique for resolving polymer structure and intermolecular packing in primary and secondary plant cell walls. Isotope ( 13 C) enrichment provides feasible sensitivity for measuring 2D/3D correlation spectra, but this time-consuming procedure and its associated expenses have restricted the application of ssNMR in lignocellulose analysis. Results Here, we present a method that relies on the sensitivity-enhancing technique Dynamic Nuclear Polarization (DNP) to eliminate the need for 13 C-labeling. With a 26-fold sensitivity enhancement, a series of 2D 13 C– 13 C correlation spectra were successfully collected using the unlabeled stems of wild-type Oryza sativa (rice). The atomic resolution allows us to observe a large number of intramolecular cross peaks for fully revealing the polymorphic structure of cellulose and xylan. NMR relaxation and dipolar order parameters further suggest a sophisticated change of molecular motions in a ctl1 ctl2 double mutant: both cellulose and xylan have become more dynamic on the nanosecond and microsecond timescale, but the motional amplitudes are uniformly small for both polysaccharides. Conclusions By skipping isotopic labeling, the DNP strategy demonstrated here is universally extendable to all lignocellulose materials. This time-efficient method has landed the technical foundation for understanding polysaccharide structure and cell wall assembly in a large variety of plant tissues and species.

09 BIOMASS FUELS↗
NASA NTRS1970

Vacuum leak detector features higher sensitivity

Technique for measuring partial pressures utilizes extremely large resonance scattering cross section of xenon at 1471 angstroms to scatter light in a vacuum cell. Output signal of ultraviolet-sensitive photodetector is proportional to the partial pressure and to the rate of inleakage of xenon probe gas.

Barrington, A. E.↗
NASA NTRS1973

Ultrasonic calibration device

Device is an instrument for producing known changes in both acoustic absorption and phase velocity. Calibration signal arises from actual change of acoustic parameters, not from electrical simulation. Instrument is able to simulate changes in sensitivity enhancement achieved by use of ultrasonic resonators, which cannot be achieved using electrical calibration techniques.

Heyman, J. S.↗
NASA NTRS1977

Calibration of marginal oscillator sensitivity for use in ICR spectrometry

A constant-reference load is utilized as Q-spoiler in calibrations of relative sensitivity variations of a marginal oscillator with frequency. Frequency-dependent effects troublesome in earlier Q-spoilers are compensated by employing a pure resistive calibration load with compensation for the small distributed capacitance of large resistors. The validity of the approach is demonstrated for a 2:1 mass ratio range, and validity for a mass ratio range greater than 10:1 is claimed. The circuit and technique were developed for use in ion cyclotron resonance (ICR) spectrometric practice.

Anicich, V. G.↗
NASA NTRS1985

Energy transfer mechanisms between molecules

Reliable rate coefficients for energy transfer and relaxation phenomena are needed in order to do the theoretical modeling which is necessary for accomplishing the following objectives: understanding and justifying proposed laser systems, determining limitations, identifying control parameters, and scaling to space-power requirements. Modeling also establishes the criteria to be followed for lasant selection. Lack of knowledge of rate coefficients is invariably the biggest obstacle to successful modeling. Existing theoretical methods are discussed, sources of error are identified, and transfer laser criteria suggested by the theory are listed. The emphasis is on vibrational-vibrational (V-V) energy transfer caused by both short range and long range interactions between molecules. Special attention is given to the importance of near-resonant collisional and dipole-dipole transfer. A technique is proposed for significantly improving the theoretical predictions of rate coefficients.

Meador, W. E.↗
NASA NTRS1988

Detection of bondline delaminations in multilayer structures with lossy components

The detection of bondline delaminations in multilayer structures using ultrasonic reflection techniques is a generic problem in adhesively bonded composite structures such as the Space Shuttles's Solid Rocket Motors (SRM). Standard pulse echo ultrasonic techniques do not perform well for a composite resonator composed of a resonant layer combined with attenuating layers. Excessive ringing in the resonant layer tends to mask internal echoes emanating from the attenuating layers. The SRM is made up of a resonant steel layer backed by layers of adhesive, rubber, liner and fuel, which are ultrasonically attenuating. The structure's response is modeled as a lossy ultrasonic transmission line. The model predicts that the acoustic response of the system is sensitive to delaminations at the interior bondlines in a few narrow frequency bands. These predictions are verified by measurements on a fabricated system. Successful imaging of internal delaminations is sensitive to proper selection of the interrogating frequency. Images of fabricated bondline delaminations are presented based on these studies.

Madaras, Eric I.↗
NASA NTRS1996

Reactions of CH3(+) with C2N2, CH2CHCN, and HC3N: A Low-Pressure/High-Pressure Study

The association of CH3(+) with the three molecules C2N2, CH2CHCN, and HCCCN has been examined using ion cyclotron resonance (ICR) and selected ion flow tube (SIFT) techniques at room temperature. In each reaction, the mean lifetime of the complex (CH3 x N-=C-R(+))(sup *) formed in the association has a major influence on the outcome of the reaction and the product channels that are observed using ICR and SIFT. Termolecular rate coefficients are reported for the association of CH3(+) + C2N2 for the bath gases M = He, Ar, N2, and C2N2. k(sub 3) = 8.2 x 10(exp-24) cm(sup 6)/s (M = C2N2). In each system the association product channel occurs in competition with exothermic bimolecular channels. The complex lifetimes in all three systems are in the range 30-70 microsec. Very rapid ion-molecule association reactions have been observed in several systems of hydrocarbons and nitriles, and the implications for Titan ion chemistry are discussed briefly.

McEwan, M. J.↗
NASA NTRS2002

Advances in space technology: the NSBRI Technology Development Team

As evidenced from Mir and other long-duration space missions, the space environment can cause significant alterations in the human physiology that could prove dangerous for astronauts. The NASA programme to develop countermeasures for these deleterious human health effects is being carried out by the National Space Biomedical Research Institute (NSBRI). The NSBRI has 12 research teams, ten of which are primarily physiology based, one addresses on-board medical care, and the twelfth focuses on technology development in support of the other research teams. This Technology Development (TD) Team initially supported four instrumentation developments: (1) an advanced, multiple projection, dual energy X ray absorptiometry (AMPDXA) scanning system: (2) a portable neutron spectrometer; (3) a miniature time-of-flight mass spectrometer: and (4) a cardiovascular identification system. Technical highlights of the original projects are presented along with an introduction to the five new TD Team projects being funded by the NSBRI.

Non-NASA Center↗
NASA NTRS1996

Ion-Molecule Association in Acrylonitrile

The association reaction of the ions CH(sub 2)CHCN+ and CH(sub 2)CHCN have been examined using ion cyclotron resonance (ICR) and selected ion flow tube (SIFT) techniques at room temperature.

Ion- molecule acrylonitrile↗
NASA NTRS2008

Miniature Mass Spectrometers on Space and Planetary Missions

Space flight mass spectrometers contribute our understanding of the origin and evolution of our solar system and even of life itself. This fundamental role has motivated increasing interest in miniature mass spectrometry for planetary missions. Several remarkable new instruments are en route or under development to investigate the composition of planetary bodies such as Mars and comets. For instance, the Sample Analysis at Mars (SAM) suite on the 2009 Mars Science Laboratory (MSL) mission includes a quadrupole mass spectrometer with a sophisticated gas processing system as well as pyrolysis and chemical derivatization protocols for solid samples. Future missions will require even lighter, lower power, and yet more capable mass spectrometers, particularly to analyze samples in situ on planetary surfaces. We have been developing laser-based mass spectrometers for elemental and organic/molecular analysis of rock, ice, or fine particle samples. These typically use time-of-flight (TOF) mass analyzers, which are readily miniaturized and can detect both atomic species and complex organics that occur in a variety of planetary materials. For example, nonvolatile polycyclic aromatic hydrocarbons and kerogen-like macromolecular carbon are found in some carbonaceous meteorites, which derived from asteroid parent bodies. A single focused laser pulse is able to volatilize and ionize some of these compounds for direct TOF analysis. While this is possible without any sample preparation or contact, sensitivity and quantitative performance can improve significantly with some sample handling. As such we have also been examining robotic mechanisms and protocols to accompany space flight mass spectrometers. In addition, sensors in early development may significantly improve these capabilities, via use of techniques such as switchable polarity, ambient pressure, or resonant ionization; tandem mass spectrometry (TOF or ion trap); and chemical imaging.

Brinckerhoff, William↗
NASA NTRS2003

Improved Interactive Medical-Imaging System

An improved computational-simulation system for interactive medical imaging has been invented. The system displays high-resolution, three-dimensional-appearing images of anatomical objects based on data acquired by such techniques as computed tomography (CT) and magnetic-resonance imaging (MRI). The system enables users to manipulate the data to obtain a variety of views for example, to display cross sections in specified planes or to rotate images about specified axes. Relative to prior such systems, this system offers enhanced capabilities for synthesizing images of surgical cuts and for collaboration by users at multiple, remote computing sites.

Ross, Muriel D.↗
NASA NTRS2021

Identifying Molecules as Biosignatures with Assembly Theory and Mass Spectrometry

The search for evidence of life elsewhere in the universe is hard because it is not obvious what signatures are unique to life. Here we postulate that complex molecules found in high abundance are universal biosignatures as they cannot form by chance. To explore this, we developed the first intrinsic measure of molecular complexity that can be experimentally determined, and this is based upon a new approach called assembly theory which gives the molecular assembly number (MA) of a given molecule. MA allows us to compare the intrinsic complexity of molecules using the minimum number of steps required to construct the molecular graph starting from basic objects, and a probabilistic model shows how the probability of any given molecule forming randomly drops dramatically as its MA increases. To map chemical space, we calculated the MA of ca. 2.5 million compounds, and collected data which showed the complexity of a molecule can be experimentally determined by using three independent techniques including infra-red spectroscopy, nuclear magnetic resonance, and by fragmentation in a mass spectrometer, and this data has an excellent corelation with the values predicted from our assembly theory. We then set out to see if this approach could allow us to identify molecular biosignatures with a set of diverse samples from around the world, outer space, and the laboratory including prebiotic soups. The results show that there is a non-living to living threshold in MA complexity and the higher the MA for a given molecule, the more likely that it had to be produced by a biological process. This work demonstrates it is possible to use this approach to build a life detection instrument that could be deployed on missions to extra-terrestrial locations to detect biosignatures, map the extent of life on Earth, and be used as a molecular complexity scale to quantify the constraints needed to direct prebiotically plausible processes in the laboratory. Such an approach is vital if we are going to find new life elsewhere in the universe or create de-novo life in the lab.

Stuart M Marshall↗
NASA NTRS2011

Reconfigurable Microwave Phase Delay Element for Frequency Reference and Phase-Shifter Applications

A technique was developed to provide a reconfigurable high-precision micro - wave electrical phase delay for resonators and phase shifters. The invention employs multiple branches of transmission lines with open-ended or ground-ended terminations as configurable bits or digits. This technique minimizes the errors due to limited precision of switching devices. In addition, the proposed linear analytical approach significantly produces a much simpler design than that of other prior inventions at the time of this reporting. Microwave components such as filters, phase delay elements, or resonators require a method that can accurately adjust their frequency responses. Most tuning techniques offer very wide frequency tuning range; however, it is often difficult and expensive to tune their response in a very narrow operating frequency, especially when the tuning element reaches its minimum discrete step due to fabrication tolerances. The problem becomes worse as the operating frequency is in mm-wave frequency range (>26 GHz). The electrical tuning sensitivity of a microwave line is dependent on the position of the tuning element with respect to the reference termination. By placing this tuning element away from this reference with the main transmission line connecting the two elements together the sensitivity of the tuning element can change significantly. This concept can be used in the system that requires multiple tuning sensitivities. In this case, multiple tuning branches are superimposed in the main transmission line. The proposed invention allows the transmission-line electrical length to be accurately programmed using switching elements that have limited accuracy. The invention consists of multiple branches of transmission lines connected to discrete switching devices with open-ended terminations. They are used as discrete tuning elements. These elements are connected to the main microwave transmission line and are separated by a well-defined electrical degree spacing. Each branch is programmed to have different electrical degree sensitivity, such as a combination of discrete steps in each branch, which results in a reflective line with a unique effective phase response. To reduce the number of switching devices, it is desirable to program the devices in binary configuration where each branch represents one bit in the base-2 number system. This invention allows the transmission line electrical length to be tuned precisely with customizable sensitivity based on the known sensitivity of the base tuning circuit. The tuning resolution is dependent on the distance among tuning branches.

Hsieh, Wen-Ting↗
NASA NTRS2004

Measuring Radiation Patterns of Reconfigurable Patch Antennas on Wafers

An apparatus and technique have been devised for measuring the radiation pattern of a microwave patch antenna that is one of a number of identical units that have been fabricated in a planar array on a high-resistivity silicon wafer. The apparatus and technique are intended, more specifically, for application to such an antenna that includes a DC-controlled microelectromechanical system (MEMS) actuator for switching the antenna between two polarization states or between two resonance frequencies. Prior to the development of the present apparatus and technique, patch antennas on wafers were tested by techniques and equipment that are more suited to testing of conventional printed-circuit antennas. The techniques included sawing of the wafers to isolate individual antennas for testing. The equipment included custom-built test fixtures that included special signal launchers and transmission-line transitions. The present apparatus and technique eliminate the need for sawing wafers and for custom-built test fixtures, thereby making it possible to test antennas in less time and at less cost. Moreover, in a production setting, elimination of the premature sawing of wafers for testing reduces loss from breakage, thereby enhancing yield.

Simons, Rainee N.↗
NASA NTRS2008

A Resonant Damping Study Using Piezoelectric Materials

Excessive vibration of turbomachinery blades causes high cycle fatigue (HCF) problems requiring damping treatments to mitigate vibration levels. Based on the technical challenges and requirements learned from previous turbomachinery blade research, a feasibility study of resonant damping control using shunted piezoelectric patches with passive and active control techniques has been conducted on cantilever beam specimens. Test results for the passive damping circuit show that the optimum resistive shunt circuit reduces the third bending resonant vibration by almost 50%, and the optimum inductive circuit reduces the vibration by 90%. In a separate test, active control reduced vibration by approximately 98%.

Min, J. B.↗
NASA NTRS1995

Josephson frequency meter for millimeter and submillimeter wavelengths

Frequency measurements of electromagnetic oscillations of millimeter and submillimeter wavebands with frequency growth due to a number of reasons become more and more difficult. First, these frequencies are considered to be cutoffs for semiconductor converting devices and one has to use optical measurement methods instead of traditional ones with frequency transfer. Second, resonance measurement methods are characterized by using relatively narrow bands and optical ones are limited in frequency and time resolution due to the limited range and velocity of movement of their mechanical elements as well as the efficiency of these optical techniques decrease with the increase of wavelength due to diffraction losses. That requires a priori information on the radiation frequency band of the source involved. Method of measuring frequency of harmonic microwave signals in millimeter and submillimeter wavebands based on the ac Josephson effect in superconducting contacts is devoid of all the above drawbacks. This approach offers a number of major advantages over the more traditional measurement methods, that is one based on frequency conversion, resonance and interferometric techniques. It can be characterized by high potential accuracy, wide range of frequencies measured, prompt measurement and the opportunity to obtain a panoramic display of the results as well as full automation of the measuring process.

Anischenko, S. E.↗
DOE OSTI2022

Resonant ultrasound spectroscopy for crystalline samples containing initial strain

Resonant ultrasound spectroscopy (RUS) is a mature and robust technique for the nondestructive characterization of the elastic properties of solids capable of providing the elastic constants of anisotropic crystalline solids. The traditional method is based on assuming that the solid is linear elastic and, therefore, obeys a linearized Hookean constitutive relationship (Hooke’s law). In this work, an alternative constitutive law is provided that allows for an initial strain or prestrain to be present stemming from residual stress. Then, the constitutive relationship is integrated into the RUS framework. The model is demonstrated using a realistic prestrain field obtained by simulating shot-peening processing of a polycrystalline Cu sample. The sensitivity of the resonances to the developed prestrain is established and discussed. This work allows researchers to consider the influence of initial strain or residual stress in their samples and the potential influence on accurate elastic constant estimates. The model also supports the potential of RUS for the nondestructive characterization of prestrain in materials.

42 ENGINEERING↗