SEARCH · Search NASA
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.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
A Detector Response Matrix (DRM) is a discrete representation of an instrument’s Detector Response Function (DRF), which quantifies how many discrete energy depositions occur in a detector volume for a given distribution of particles incident on the detector.
High dose rate radiation has gained considerable interest recently as a possible avenue for increasing the therapeutic window in cancer radiation treatment. The sparing of healthy tissue at high dose rates relative to conventional dose rates, while maintaining tumor control, has been termed the FLASH effect. Although the effect has been validated in animal models using multiple radiation sources, it is not yet well understood. Here, in this work, we demonstrate a new experimental platform for quantifying oxidative damage to protein sidechains in solution as a function of radiation dose rate and oxygen availability using liquid chromatography mass spectrometry. Using this reductionist approach, we show that for both X-ray and electron sources, isolated peptides in solution are oxidatively modified to different extents as a function of both dose rate and oxygen availability. Our method provides an experimental platform for exploring the parameter space of the dose rate effect on oxidative changes to proteins in solution.
Ultrahigh dose rate (FLASH) radiation therapy is reported to reduce normal tissue toxicity while maintaining tumor control; however, mechanism(s) remain obscure. To study FLASH mechanisms in brain tissue, we developed a novel experimental platform featuring a specialized high-energy electron linear accelerator, High Intensity Gamma Ray Source (HIGS), paired with an organotypic ex vivo brain metastasis model. We varied interpulse spacing to modulate the mean dose rate (MDR) of our unique 35 MeV electron beam, while maintaining extremely high instantaneous dose rate (IDR). We characterized dosimetry and targeting accuracy of the FLASH beam with film dosimetry. We combined this FLASH beam with an organotypic rat brain slice/breast carcinoma coculture model of brain metastasis to assess effects on normal and neoplastic tissues. Live-cell and bioluminescence imaging demonstrated cancer cell growth effects, whereas normal tissue responses and immune activation were assessed using live-cell imaging, cytokine profiles, and confocal microscopy. Here, we performed comparison experiments with 20 MeV electrons from a Varian clinical linear accelerator (VCLA) using conventional dose rates. The highest IDR of the FLASH beam to date was 20.7 ± 0.6 MGy/s, with maximum MDR of 20.7 MGy/s delivered in 1 pulse of 1 µs duration. Beam targeting was accurate to <1 mm and reproducible. HIGS-FLASH and VCLA dose rates equivalently decreased cancer cell growth. HIGS-FLASH irradiation significantly increased tumor necrosis factor α and fractalkine levels and confocal microscopy revealed distinct changes in microglial morphology slices suggesting microglia activation. Our novel experimental platform produces extremely high dose rates and rapid normal/neoplastic tissue readouts for mechanistic research into the effects of FLASH radiation in the brain. HIGS-FLASH irradiation induces comparable cancer cell growth inhibition but differential effects on cytokines and microglial morphology, suggesting that acute innate immune responses may be involved in FLASH normal tissue effects in the brain.
Explore the source record for details and available documents.
Features of flash memories: Flash memories are non-volatile; that is they do not require power to retain the information in its memory. They can be erased and written to while the device is still in the circuit.
Explore the source record for details and available documents.
This paper presents the results of measurements performed on two different flash memory types, NOR and NAND technologies.
Flash sintering (FS) is a potentially rapid and low-cost manufacturing technique for advanced ceramics. There are still many unknowns about ceramic FS, especially for highly conductive high-temperature ceramics (HTC), which often display decreased bulk conductivity with increasing temperature. This study qualitatively characterizes the flash behavior of highly conductive HTC materials using zirconium nitride (ZrN) as an example. The effects of processing parameters (e.g., DC voltage/electrical field strength, voltage ramp rate, post-flash holding time, mechanical pressure, sample milling, and choice of electrode materials) on ZrN flash behavior are also qualitatively studied and linked to samples microstructure and hardness. It is observed that best densification was achieved using 5 min Spex-milled ZrN powder under 25 MPa of applied pressure and constant 8 V DC. The potential mechanism for ZrN FS and the similarity and difference from FS of conventional oxides like YSZ have been proposed based on experimental observations, and the directions for future research are also pointed out.
The recently baselined Space Shuttle lightning effects flash model is discussed. The discussion is limited to the current rate(s) of rise. A review of some of the recent data is presented, as well as a discussion of how interaction processes affect the induced voltages and currents which arise from a lightning strike. It is concluded that the multiple pulse components of the new flash model present a more severe threat to complex avionic systems, than is presented by a single pulse having an extremely fast rate of rise.
This paper discusses the space radiation effects in advanced flash memories.
Finite laser pulse time effects on temperature wave retardation in flash diffusivity techniques
Flash memories have evolved very rapidly in recent years.
Accurate predictions of fuel spray behavior and mixture formation in simulations of direct-injection spark-ignition (DISI) engines are fundamental to ensure proper description of all subsequent processes including ignition, combustion, and emissions. In this work, the spray evolution in a single-cylinder optical DISI engine was studied experimentally and numerically with the goal of enabling predictive computational fluid dynamics (CFD) modeling of in-cylinder sprays. The authors explored a wide range of operating conditions characterized by several fuel injection temperatures and engine speeds, using a well-characterized nine-component gasoline surrogate known as PACE-20. The effect of flash boiling and intake crossflow on the spray is discussed, with a focus on evaluating the ability of the spray models to capture highly transient spray behavior. In the experiments, the fuel temperature was varied between 20°C and 80°C, allowing for non-flash- to flash-boiling transition to emerge with enhanced flashing intensity at the highest temperatures. Spray collapse resulted in vapor-rich regions, owing to the locally lower inertia of the fluid. Varying the engine speed from 650 to 1950 rpm promoted increasingly more turbulent in-cylinder crossflow which interacted with the spray during the injection event and resulted in enhanced spray dispersion. The CFD model was able to capture the spray morphology transition at different fuel temperatures and engine speeds adequately. Further, it is shown that the spray breakup model could capture the transitional spray behavior induced by flash boiling atomization and intake flow via proper initialization of the spray cone angle and calibration of the spray models’ constants.
Memory storage requirements in space systems have steadily increased, much like storage requirements in terrestrial systems. Large arrays of dynamic memories (DRAMs) have been used in solid-state recorders, relying on a combination of shielding and error-detection-and correction (EDAC) to overcome the extreme sensitivity of DRAMs to space radiation. For example, a 2-Gbit memory (with 4-Mb DRAMs) used on the Clementine mission functioned perfectly during its moon mapping mission, in spite of an average of 71 memory bit flips per day from heavy ions. Although EDAC worked well with older types of memory circuits, newer DRAMs use extremely complex internal architectures which has made it increasingly difficult to implement EDAC. Some newer DRAMs have also exhibited catastrophic latchup. Flash memories are an intriguing alternative to DRAMs because of their nonvolatile storage and extremely high storage density, particularly for applications where writing is done relatively infrequently. This paper discusses radiation effects in advanced flash memories, including general observations on scaling and architecture as well as the specific experience obtained at the Jet Propulsion Laboratory in evaluating high-density flash memories for use on the NASA mission to Europa, one of Jupiter's moons. This particular mission must pass through the Jovian radiation belts, which imposes a very demanding radiation requirement.
Flash memories have evolved very rapidly in recent ears. New design techniques such as multilevel storage have been proposed to increase storage density, and are now available commercially. Threshold voltage distributions for single- and three-level technologies are compared. In order to implement this technology special circuitry must be added to allow the amount of charge stored in the floating gate to be controlled within narrow limits during the writing and also to detect the different amounts of charge during reading.
The purpose of this testing is to characterize the Single-Event Effect (SEE) response of the Micron MT29F1T08CMHBBJ4 3D NAND Flash memory. The MT29F1T08CMHBBJ4 is a 1Tb NAND Flash memory, consisting of a four-die stack of 256Gb MLC dice packaged in a 132-ball VBGA package. All data presented is the result of testing only the top die (256Gb) of the package. Testing was performed at two heavy-ion cyclotron facilities with an identical test setup, over the course of four test trips from 2017-2019.