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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 397 records · Page 22
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

INTERFERENCE AS AN ORIGIN OF THE PEAKED NOISE IN ACCRETING X-RAY BINARIES

We propose a physical model for the peaked noise in the X-ray power density spectra of accreting X-ray binaries. We interpret its appearance as an interference of two Comptonization continua: one coming from the upscattering of seed photons from the cold thin disk and the other fed by the synchrotron emission of the hot flow. Variations of both X-ray components are caused by fluctuations in mass accretion rate, but there is a delay between them corresponding to the propagation timescale from the disk Comptonization radius to the region of synchrotron Comptonization. If the disk and synchrotron Comptonization are correlated, the humps in the power spectra are harmonically related and the dips between them appear at frequencies related as odd numbers 1:3:5. If they are anti-correlated, the humps are related as 1:3:5, but the dips are harmonically related. Similar structures are expected to be observed in accreting neutron star binaries and supermassive black holes. The delay can be easily recovered from the frequency of peaked noise and further used to constrain the combination of the viscosity parameter and disk height-to-radius ratio α ( H / R ){sup 2} of the accretion flow. We model multi-peak power spectra of black hole X-ray binaries GX 339–4 and XTE J1748–288 to constrain these parameters.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2011

Interference Terms for Xenon-135

Systems to measure radioxenon concentrations are continually being improved to provide greater sensitivity and precision. As the systems become more capable, additional terms need to be added to the calculations to account for small previously insignificant effects such as minor decay branches. Recently, additional terms present in the {sup 135}Xe decay were added to the calculations to account for the small (5.2%) fraction of decays that produce cesium K-shell x-rays with an average energy of 32 keV and the Compton scatter of the dominant 250-keV gamma ray. These events overlap with the regions of interest of {sup 133}Xe, {sup 131m}Xe, and {sup 133m}Xe. In typical field applications, the amount of expected {sup 135}Xe is low due to the short half-life (9.14 hours) therefore the small fraction that could be mis-categorized as other isotopes is insignificant in most cases. However, for much more active samples, such as those recently measured in calibration and testing samples with high activity, the amount of mis-categorization can be significant. The additions to the calculations use calibration values to estimate the amount of a possible interference of {sup 135}Xe in the other regions of interest, which are then subtracted out. The calibration values, which are ratios of counts in one region of interest to another, are obtained by measuring with single isotope gases during the calibration process.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2012

Performance Study of Hybrid DS/FFH Spread-Spectrum Systems in the Presence of Frequency-Selective Fading and Multiple-Access Interference

Hybrid spread-spectrum (HSS) systems have recently received considerable interest in commercial, Smart Grid, and military communication systems because they accommodate high data rates with high link integrity, even in the presence of significant multipath effects and interfering signals. A highly useful form of this modulation scheme is the specific code-related combination of standard direct-sequence spread spectrum (DSSS) with fast frequency-hopping (FFH) spread spectrum, denoted hybrid DS/FFH, wherein multiple frequency hops occur within a single data-bit time. In this paper we perform a simulation-based study of the DS/FFH performance as compared to the existing standard DSSS and FHSS wireless networks. The performance metrics are bit-error probability and multiple-access capability. The parameter space of DS/FFH, including the DS spreading rate, frequency hopping rate, carrier frequencies, and numbers of users, is explored to show its performance under frequency-selective Rayleigh fading environments and multiuser interference. Direct digital synthesizers to achieve fast hopping speeds are also considered in our study.

99 GENERAL AND MISCELLANEOUS↗
DOE OSTI2014

Study of {sup 31}P(n,α){sup 28}Al reaction using d(d,n){sup 3}He for the possible interference with {sup 27}Al(n,γ){sup 28}Al - Paper 44

At McMaster we use neutrons from the {sup 7}Li(p,n){sup 7}Be reaction to measure aluminum in human subjects via the {sup 27}Al(n,γ){sup 28}Al reaction. We use proton energies of between 1.9 MeV and 2.3 MeV, yielding maximum neutron energy of 0.575 MeV. In principle, {sup 28}Al can also be produced via the {sup 31}P(n,α){sup 28}Al reaction, which has a neutron energy threshold of 2.008 MeV. When aluminum is measured in bone, there can be 10{sup 5} times the mass of phosphorus present as there is aluminum. However, this potential interference cannot arise using the {sup 7}Li(p,n){sup 7}Be reaction in the proton energy range specified. Collaborators at Atomic Energy of Canada Limited (AECL), Chalk River, Purdue University in the USA and Shanxi Medical University in Taiyuan, China are also interested in being able to measure aluminum in bone in living human subjects. Both AECL and Purdue have acquired D-D sets (accelerators producing neutrons via the d(d,n){sup 3}He reaction). These operate at high current (∼mA) and relatively low accelerating voltage (150 kV), relying on quantum mechanical tunneling through the Coulomb barrier. These D-D sets produce neutrons of energy 2.565 MeV. This is above the threshold for the {sup 31}P(n,α){sup 28}Al reaction, but we have not been able to find any report in which this reaction has had a cross section measurably greater than zero for neutron energies of less than 3 MeV. So, it is an open question as to whether the potential interfering reaction with phosphorus is a concern when using neutrons from a D-D set to measure aluminum in bone. (authors)

61 RADIATION PROTECTION AND DOSIMETRY↗
DOE OSTI2016

A mechanism-denial study on the Madden-Julian Oscillation with reduced interference from mean state changes

In this paper, mechanism-denial experiments using Superparameterized Community Atmosphere Model are conducted to investigate the importance of extratropical and circumnavigating waves, wind-evaporation feedback, and radiative-convective feedback to the Madden-Julian Oscillation (MJO). A common issue with mechanism-denial studies is the interference from mean state changes when processes are turned off in the model. Here time-invariant forcing and nudging on effective timescales longer than the intraseasonal timescale are implemented to maintain the mean state. The MJO activity remains largely unchanged with suppressed extratropical and circumnavigating waves when the mean state is maintained to be close to that of the control run, suggesting that excitation of MJO by extratropical and circumnavigating waves is not necessary for the existence of MJO in this model. Finally, it is also shown that the wind-evaporation feedback slows down eastward propagation of the MJO, and the radiative-convective feedback amplifies the MJO.

58 GEOSCIENCES↗
DOE OSTI2024

Infrared-Transparent Semiconductor Membranes for Electromagnetic Interference Shielding of Millimeter Waves

Here, it is demonstrated that single-crystalline and highly doped GaAs membranes are excellent candidates for realizing infrared-transparent shields of electromagnetic interference at millimeter frequencies. Measured optical transmittance spectra for the semiconductor membranes show resonant features between 750 and 2500 nm, with a 100% maximum transmittance. The shielding effectiveness of the membranes is extracted from measured scattering parameters between 65 and 85 GHz. Selected GaAs membranes and membranes/polyamide films exhibit shielding effectiveness ranging from 22 to 40 dB, which are suitable values to ensure the safe operation of infrared devices for commercial applications. Theoretical calculations based on a plane wave model show that the interplay of primary reflection and multiple internal reflections of the radio-frequency waves results in broadband shielding capabilities of the membrane between 10 and 300 GHz.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2012

Determining Full Three-Dimensional Orientation of Single Anisotropic Nanoparticles by Differential Interference Contrast Microscopy

Keeping track: By combining differential interference contrast (DIC) image pattern recognition with DIC polarization anisotropy, the exact full three-dimensional angular information of individual tilted gold nanorods positioned in the focal plane of the objective lens can be readily determined. The angular rotational modes and kinetics of individual in-focus gold nanorods can thus be resolved dynamically.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Intrinsic Chirality and Prochirality at Air/R-(+)- and S-(-)-Limonene Interfaces: Spectral Signatures with Interference Chiral Sum-Frequency Generation Vibrational Spectroscopy

We report in this work detailed measurements on the chiral and achiral sum-frequency vibrational spectra in the C-H stretching vibration region (2800-3050cm-1) of the air/liquid interfaces of R-limonene and S-limonene, using the recently developed high-resolution broadband sum-frequency generation vibrational spectroscopy (HR-BB-SFG-VS). The achiral SFG spectra of R-limonene and S-limonene, as well as the equal amount (50/50) racemic mixture show that the enantiomers are with the same interfacial orientations. The interference chiral SFG spectra of the limonene enantiomers exhibit spectral signature from chiral response of the Cα-H stretching mode, and spectral signature from prochiral response of the CH2 asymmetric stretching mode, respectively. The chiral spectral feature of the Cα-H stretching mode changes sign from R-limonene to S-limonene, and disappears for the 50/50 racemic mixture. While the prochiral spectral feature of the CH2 asymmetric stretching mode is the same for R-limonene and S-limonene, and also surprisingly remains the same for the 50/50 racemic mixture. These results provided detail information in understanding the structure and chirality of molecular interfaces, and demonstrated the sensitivity and potential of SFG-VS as unique spectroscopic tool for chirality characterization and chiral recognition at the molecular interface.

Chirality↗
DOE OSTI2016

Stable isotope analyses of oxygen ( 18 O: 17 O: 16 O) and chlorine ( 37 Cl: 35 Cl) in perchlorate: reference materials, calibrations, methods, and interferences

Perchlorate (ClO 4 - ) is a common trace constituent of water, soils, and plants; it has both natural and synthetic sources and is subject to biodegradation. The stable isotope ratios of Cl and O provide three independent quantities for ClO 4 - source attribution and natural attenuation studies: δ 37 Cl, δ 18 O, and δ 17 O (or Δ 17 O or 17 Δ) values. Finally, documented reference materials, calibration schemes, methods, and interferences will improve the reliability of such studies.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Winding θ and destructive interference of instantons

While the θ dependence of field theories is 2π periodic, the ground-state wavefunctions at θ and θ + 2π often belong to different classes of symmetry-protected topological states. When this is the case, a continuous change of the θ parameter can introduce an interface that supports a nontrivial field theory localized on the wall. We consider the 2d CP N-1 sigma model as an example and construct a weak-coupling setup of this interface theory by considering the small S1 compactification with nonzero winding θ parameter and a suitable symmetry-twisted boundary condition. This system has N classical vacua connected by fractional instantons, but the anomaly constraint tells us that the fractional-instanton amplitudes should vanish completely to have N-fold degeneracy at the quantum level. We show how this happens in this purely bosonic system, uncovering that the integration over the zero modes annihilates the fractional instanton amplitudes, in sharp contrast to what happens when the θ angle is constant. Moreover, we provide another explanation of this selection rule by showing that the N perturbative vacua acquire different charges under the global symmetry with the activation of the winding θ angle. We also demonstrate a similar destructive interference between instanton effects in the CP N-1 quantum mechanics with the Berry phase.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

A Limit to Accelerated Free-Sintering: Nano-Phase Separation Interferes With Organic Debinding

Nano-phase separating Ni–12 at. pct Ag powders are processed via high-energy ball milling and brought into a supersaturated state with a reduction of the grain size to the nanocrystalline scale, a combination that is designed to encourage rapid densification by phase separation upon heating. This unstable powder is then characterized by dilatometry, in-situ x-ray diffraction, thermogravimetry and microstructure analysis for sintering cycles up to 940 °C. However, these powder compacts exhibit excessive pore evolution and significant macroscopic swelling caused by removal of the organic process additives. This competition of organic removal with densification is known in nanocrystalline metals, but the present study adds an additional dimension of phase separation, which shifts the dominant swelling mechanism as the formation of the second phase traps the volatilizing organics and hinders the debinding process. The creep swelling and overall loss in relative density is then dominated by the creep deformation of the second Ag phase. The interference between organic removal and low-temperature onset of consolidation represents a new challenge to efforts aimed at rapid free sintering and should guide the design of rapidly sintering alloys; specifically, the present work emphasizes the need to select alloys that have their sintering-accelerating phase separation temperature above the range where gases are evolved.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Surface characterization of carbon fiber polymer composites and aluminum alloys after laser interference structuring

Here, the increasing use of Carbon Fiber-reinforced Polymer matrix Composites (CFPC) and aluminum alloys as lightweight materials in the automotive and aerospace industries demands enhanced surface preparation and control of surface morphology prior to joining. In this study, surfaces of both composite and aluminum were prepared for joining using an Nd:YAG laser in a two-beam interference setup, enabling the (a) structuring of the AL 5182 surface, (b) removal of the resin layer on top of carbon fibers, and (c) structuring of the carbon fibers. CFPC specimens of T700S carbon fiber, Prepreg - T8 3 epoxy, 5 ply thick, 0/90o plaques were used. The effect of laser fluence, scanning speed, and number of shots-per-spot was investigated on the removal rate of the resin without an excessive damage of the fibers. Optical micrographs, 3D imaging, and scanning electron microscope (SEM) imaging were used to study the effect of the laser processing on surface morphology.

36 MATERIALS SCIENCE↗
DOE OSTI2011

Inhibition of hepatitis B virus (HBV) by LNA-mediated nuclear interference with HBV DNA transcription

Highlights: {yields} LNA-modified oligonucleotides can pass through the plasma membrane of cultured cells even without using transfection machinery. {yields} LNA-modified oligonucleotides passed efficiently across the cell membrane, and lipid-coating facilitated translocation from the cytoplasm to the nucleus. {yields} LNA-oligonucleotide designed to target nuclear HBV DNA efficiently suppresses HBV replication and transcription in cultured hepatic cells. -- Abstract: Silencing target genes with small regulatory RNAs is widely used to investigate gene function and therapeutic drug development. Recently, triplex-based approaches have provided another attractive means to achieve targeted gene regulation and gene manipulation at the molecular and cellular levels. Nuclear entry of oligonucleotides and enhancement of their affinity to the DNA targets are key points of such approaches. In this study, we developed lipid-based transport of a locked-nucleic-acid (LNA)-modified oligonucleotide for hepatitis B virus (HBV) DNA interference in human hepatocytes expressing HBV genomic DNA. In these cells, the LNA-modified oligonucleotides passed efficiently across the cell membrane, and lipid-coating facilitated translocation from the cytoplasm to the nucleus. The oligonucleotide specifically targeting HBV DNA clearly interfered with HBV DNA transcription as shown by a block in pregenomic RNA (pgRNA) production. The HBV DNA-targeted oligonucleotide suppressed HBV DNA replication and HBV protein production more efficiently than small interfering RNAs directed to the pgRNA. These results demonstrate that fusion with lipid can carry LNA-modified oligonucleotides to the nucleus where they regulate gene expression. Interfering with HBV DNA transcription by LNA-modified oligonucleotides has strong potential as a new strategy for HBV inhibition.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2011

The NDUFB6 subunit of the mitochondrial respiratory chain complex I is required for electron transfer activity: A proof of principle study on stable and controlled RNA interference in human cell lines

Highlights: {yields} NDUFB6 is required for activity of mitochondrial complex I in human cell lines. {yields} Lentivirus based RNA interference results in frequent off target insertions. {yields} Flp-In recombinase mediated miRNA insertion allows gene-specific extinction. -- Abstract: Molecular bases of inherited deficiencies of mitochondrial respiratory chain complex I are still unknown in a high proportion of patients. Among 45 subunits making up this large complex, more than half has unknown function(s). Understanding the function of these subunits would contribute to our knowledge on mitochondrial physiology but might also reveal that some of these subunits are not required for the catalytic activity of the complex. A direct consequence of this finding would be the reduction of the number of candidate genes to be sequenced in patients with decreased complex I activity. In this study, we tested two different methods to stably extinct complex I subunits in cultured cells. We first found that lentivirus-mediated shRNA expression frequently resulted in the unpredicted extinction of additional gene(s) beside targeted ones. This can be ascribed to uncontrolled genetic material insertions in the genome of the host cell. This approach thus appeared inappropriate to study unknown functions of a gene. Next, we found it possible to specifically extinct a CI subunit gene by direct insertion of a miR targeting CI subunits in a Flp site (HEK293 Flp-In cells). By using this strategy we unambiguously demonstrated that the NDUFB6 subunit is required for complex I activity, and defined conditions suitable to undertake a systematic and stable extinction of the different supernumerary subunits in human cells.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2012

RNA interference regulates the cell cycle checkpoint through the RNA export factor, Ptr1, in fission yeast

Highlights: Black-Right-Pointing-Pointer RNAi is linked to the cell cycle checkpoint in fission yeast. Black-Right-Pointing-Pointer Ptr1 co-purifies with Ago1. Black-Right-Pointing-Pointer The ptr1-1 mutation impairs the checkpoint but does not affect gene silencing. Black-Right-Pointing-Pointer ago1{sup +} and ptr1{sup +} regulate the cell cycle checkpoint via the same pathway. Black-Right-Pointing-Pointer Mutations in ago1{sup +} and ptr1{sup +} lead to the nuclear accumulation of poly(A){sup +} RNAs. -- Abstract: Ago1, an effector protein of RNA interference (RNAi), regulates heterochromatin silencing and cell cycle arrest in fission yeast. However, the mechanism by which Ago1 controls cell cycle checkpoint following hydroxyurea (HU) treatment has not been elucidated. In this study, we show that Ago1 and other RNAi factors control cell cycle checkpoint following HU treatment via a mechanism independent of silencing. While silencing requires dcr1{sup +}, the overexpression of ago1{sup +} alleviated the cell cycle defect in dcr1{Delta}. Ago1 interacted with the mRNA export factor, Ptr1. The ptr1-1 mutation impaired cell cycle checkpoint but gene silencing was unaffected. Genetic analysis revealed that the regulation of cell cycle checkpoint by ago1{sup +} is dependent on ptr1{sup +}. Nuclear accumulation of poly(A){sup +} RNAs was detected in mutants of ago1{sup +} and ptr1{sup +}, suggesting there is a functional link between the cell cycle checkpoint and RNAi-mediated RNA quality control.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

Inhibition of the acetyl lysine-binding pocket of bromodomain and extraterminal domain proteins interferes with adipogenesis

The bromodomain and extraterminal (BET) domain family proteins are epigenetic modulators involved in the reading of acetylated lysine residues. The first BET protein inhibitor to be identified, (+)-JQ1, a thienotriazolo-1, 4-diazapine, binds selectively to the acetyl lysine-binding pocket of BET proteins. We evaluated the impact on adipogenesis of this druggable targeting of chromatin epigenetic readers, by investigating the physiological consequences of epigenetic modifications through targeting proteins binding to chromatin. JQ1 significantly inhibited the differentiation of 3T3-L1 preadipocytes into white and brown adipocytes by down-regulating the expression of genes involved in adipogenesis, particularly those encoding the peroxisome proliferator-activated receptor (PPAR-γ), the CCAAT/enhancer-binding protein (C/EBPα) and, STAT5A and B. The expression of a constitutively activated STAT5B mutant did not prevent inhibition by JQ1. Thus, the association of BET/STAT5 is required for adipogenesis but STAT5 transcription activity is not the only target of JQ1. Treatment with JQ1 did not lead to the conversion of white adipose tissue into brown adipose tissue (BAT). BET protein inhibition thus interferes with generation of adipose tissue from progenitors, confirming the importance of the connections between epigenetic mechanisms and specific adipogenic transcription factors. - Highlights: • JQ1 prevented the differentiation of 3T3-L1 preadipocytes into white adipocytes. • JQ1 affected clonal cell expansion and abolished lipid accumulation. • JQ1 prevented the differentiation of 3T3-L1 preadipocytes into brown adipocytes. • JQ1 treatment did not lead to the conversion of white adipose tissue into brown adipose tissue. • JQ1 decreased STAT5 expression, but STAT5B{sup ca} expression did not restore adipogenesis.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

shRNA interference of NLRP3 inflammasome alleviate ischemia reperfusion-induced myocardial damage through autophagy activation

Myocardial ischemia-reperfusion (I/R) injury always occur during the recovery of myocardial blood supply with high morbidity and mortality. Although, various therapeutic schedules were applied in clinic, there are real problems that have to be resolved on curative effect. Nod-like receptor protein 3 (NLRP3) inflammasome has moderation effects on cellular damage and inflammatory reaction after I/R injury. Our research aims to investigate a more effective approach to restrain the activation of NLRP3 inflammasome in treating myocardial I/R injury. Results indicated that cell viability, Bax/Bcl-2 expression were affected hardly by sh-NLRP3 transfection in normal cells. However, the decreased cell viability and increased Bax/Bcl-2 expression level caused by I/R were remarkably suppressed through sh-NLRP3 transfection. Besides that, the reduced levels of pro-autophagy proteins (Beclin1, Agt7, LC3II/LC3I) while enhanced level of anti-autophagy protein (p62) and apoptosis-related proteins (Bax/Bcl-2) were significantly repressed via sh-NLRP3 transfection. Nevertheless, the autophagy inhibitor 3 MA could reverse the results. Moreover, in vivo experiment suggested that NLRP3 was up-regulated in wild type (WT) rats with I/R injury. The expansion of infarct size induced by ischemia was tremendously constricted in NLRP3 knockout (KO) rats. NLRP3 silence had nearly no impact on myocardial enzymes (AST, LDH and CK) expressions, inflammatory factors (TNF-α and IL-1β) expressions and cell apoptosis in rats without I/R injury. Nonetheless, the elevated levels of myocardial enzymes, inflammatory factors and cell apoptosis caused by I/R injury were vastly inhibited in NLRP3 KO rats. Furthermore, NLRP3 KO itself would lead to higher level of pro-autophagy proteins (Beclin1, Agt7, LC3II/LC3I) while lower level of anti-autophagy protein (p62) in vivo. The decreased expressions of pro-autophagy proteins while increased expressions of anti-autophagy protein induced by I/R injury were remarkably suppressed by NLRP3 KO. Taken together, our study indicated that shRNA interference of NLRP3 inflammasome attenuated myocardial I/R injury via autophagy activation. These findings demonstrated that NLRP3 KO may a promising therapy in myocardial I/R injury.

60 APPLIED LIFE SCIENCES↗