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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS2000

New Human-Computer Interface Concepts for Mission Operations

The current climate of budget cuts has forced the space mission operations community to reconsider how it does business. Gone are the days of building one-of-kind control centers with teams of controllers working in shifts 24 hours per day, 7 days per week. Increasingly, automation is used to significantly reduce staffing needs. In some cases, missions are moving towards lights-out operations where the ground system is run semi-autonomously. On-call operators are brought in only to resolve anomalies. Some operations concepts also call for smaller operations teams to manage an entire family of spacecraft. In the not too distant future, a skeleton crew of full-time general knowledge operators will oversee the operations of large constellations of small spacecraft, while geographically distributed specialists will be assigned to emergency response teams based on their expertise. As the operations paradigms change, so too must the tools to support the mission operations team's tasks. Tools need to be built not only to automate routine tasks, but also to communicate varying types of information to the part-time, generalist, or on-call operators and specialists more effectively. Thus, the proper design of a system's user-system interface (USI) becomes even more importance than before. Also, because the users will be accessing these systems from various locations (e.g., control center, home, on the road) via different devices with varying display capabilities (e.g., workstations, home PCs, PDAS, pagers) over connections with various bandwidths (e.g., dial-up 56k, wireless 9.6k), the same software must have different USIs to support the different types of users, their equipment, and their environments. In other words, the software must now adapt to the needs of the users! This paper will focus on the needs and the challenges of designing USIs for mission operations. After providing a general discussion of these challenges, the paper will focus on the current efforts of creatin(y an effective USI for one specific suite of tools, SERS (The Spacecraft Emergency Response System), which has been built to enable lights-out operations. SERS is a Web-based collaborative environment that enables secure distributed fault management.

Fox, Jeffrey A.↗
NASA NTRS1993

Identification of amino acid sequences in the polyomavirus capsid proteins that serve as nuclear localization signals

The molecular mechanism participating in the transport of newly synthesized proteins from the cytoplasm to the nucleus in mammalian cells is poorly understood. Recently, the nuclear localization signal sequences (NLS) of many nuclear proteins have been identified, and most have been found to be composed of a highly basic amino acid stretch. A genetic "subtractive" and a biochemical "additive" approach were used in our studies to identify the NLS's of the polyomavirus structural capsid proteins. An NLS was identified at the N-terminus (Ala1-Pro-Lys-Arg-Lys-Ser-Gly-Val-Ser-Lys-Cys11) of the major capsid protein VP1 and at the C-terminus (Glu307 -Glu-Asp-Gly-Pro-Glu-Lys-Lys-Lys-Arg-Arg-Leu318) of the VP2/VP3 minor capsid proteins.

NASA Discipline Number 93-10↗
NASA NTRS2000

A calcium-dependent protein kinase can inhibit a calmodulin-stimulated Ca2+ pump (ACA2) located in the endoplasmic reticulum of Arabidopsis

The magnitude and duration of a cytosolic Ca(2+) release can potentially be altered by changing the rate of Ca(2+) efflux. In plant cells, Ca(2+) efflux from the cytoplasm is mediated by H(+)/Ca(2+)-antiporters and two types of Ca(2+)-ATPases. ACA2 was recently identified as a calmodulin-regulated Ca(2+)-pump located in the endoplasmic reticulum. Here, we show that phosphorylation of its N-terminal regulatory domain by a Ca(2+)-dependent protein kinase (CDPK isoform CPK1), inhibits both basal activity ( approximately 10%) and calmodulin stimulation ( approximately 75%), as shown by Ca(2+)-transport assays with recombinant enzyme expressed in yeast. A CDPK phosphorylation site was mapped to Ser(45) near a calmodulin binding site, using a fusion protein containing the N-terminal domain as an in vitro substrate for a recombinant CPK1. In a full-length enzyme, an Ala substitution for Ser(45) (S45/A) completely blocked the observed CDPK inhibition of both basal and calmodulin-stimulated activities. An Asp substitution (S45/D) mimicked phosphoinhibition, indicating that a negative charge at this position is sufficient to account for phosphoinhibition. Interestingly, prior binding of calmodulin blocked phosphorylation. This suggests that, once ACA2 binds calmodulin, its activation state becomes resistant to phosphoinhibition. These results support the hypothesis that ACA2 activity is regulated as the balance between the initial kinetics of calmodulin stimulation and CDPK inhibition, providing an example in plants for a potential point of crosstalk between two different Ca(2+)-signaling pathways.

NASA Discipline Plant Biology↗
NASA NTRS1998

Site-specific regulatory interaction between spinach leaf sucrose-phosphate synthase and 14-3-3 proteins

We report an Mg2+-dependent interaction between spinach leaf sucrose-phosphate synthase (SPS) and endogenous 14-3-3 proteins, as evidenced by co-elution during gel filtration and co-immunoprecipitation. The content of 14-3-3s associated with an SPS immunoprecipitate was inversely related to activity, and was specifically reduced when tissue was pretreated with 5-aminoimidazole-4-carboxamide riboside, suggesting metabolite control in vivo. A synthetic phosphopeptide based on Ser-229 was shown by surface plasmon resonance to bind a recombinant plant 14-3-3, and addition of the phosphorylated SPS-229 peptide was found to stimulate the SPS activity of an SPS:14-3-3 complex. Taken together, the results suggest a regulatory interaction of 14-3-3 proteins with Ser-229 of SPS.

Non-NASA Center↗
NASA NTRS1995

EDTA-insoluble, calcium-binding proteoglycan in bovine bone

A calcium ion precipitable, trypsin-generated proteoglycan fragment has been isolated from the demineralized, EDTA-insoluble matrices of bone. The demineralized matrix was completely digested with trypsin, increasing concentrations of CaCl2 were added to the supernatant, and the resulting precipitates were analyzed. The amount of precipitate gradually increased with higher concentrations of calcium and was reversibly solubilized by EDTA. After molecular sieve and anion exchange chromatography, a proteoglycan-containing peak was obtained. Immunochemical analysis showed that this peak contained chondroitin 4-sulfate and possibly keratan sulfate. Amino acid analysis showed that this proteoglycan contained high amounts of aspartic acid/asparagine (Asx), serine (Ser), glutamic acid/glutamine (Glx), proline (Pro), and glycine (Gly); however, it contained little leucine (Leu) which suggests that it is not a member of the leucine-rich small proteoglycan family. In addition, significant amounts of phosphoserine (P-Ser) and hydroxyproline (Hyp) were identified in hydrolysates of this fraction. A single band (M(r) 59 kDa) was obtained on SDS-PAGE that stained with Stains-all but not with Coomassie Brilliant Blue R-250. If bone powder was trypsinized prior to demineralization, this proteoglycan-containing fraction was not liberated. Collectively, these results indicate that a proteoglycan occurs in the demineralized matrix that is precipitated with CaCl2 and is closely associated with both mineral and collagen matrices. Such a molecule might facilitate the structural network for the induction of mineralization in bone.

NASA Program Space Physiology and Countermeasures↗
NASA NTRS1992

The use of additive and subtractive approaches to examine the nuclear localization sequence of the polyomavirus major capsid protein VP1

A nuclear localization signal (NLS) has been identified in the N-terminal (Ala1-Pro-Lys-Arg-Lys-Ser-Gly-Val-Ser-Lys-Cys11) amino acid sequence of the polyomavirus major capsid protein VP1. The importance of this amino acid sequence for nuclear transport of VP1 protein was demonstrated by a genetic "subtractive" study using the constructs pSG5VP1 (full-length VP1) and pSG5 delta 5'VP1 (truncated VP1, lacking amino acids Ala1-Cys11). These constructs were used to transfect COS-7 cells, and expression and intracellular localization of the VP1 protein was visualized by indirect immunofluorescence. These studies revealed that the full-length VP1 was expressed and localized in the nucleus, while the truncated VP1 protein was localized in the cytoplasm and not transported to the nucleus. These findings were substantiated by an "additive" approach using FITC-labeled conjugates of synthetic peptides homologous to the NLS of VP1 cross-linked to bovine serum albumin or immunoglobulin G. Both conjugates localized in the nucleus after microinjection into the cytoplasm of 3T6 cells. The importance of individual amino acids found in the basic sequence (Lys3-Arg-Lys5) of the NLS was also investigated. This was accomplished by synthesizing three additional peptides in which lysine-3 was substituted with threonine, arginine-4 was substituted with threonine, or lysine-5 was substituted with threonine. It was found that lysine-3 was crucial for nuclear transport, since substitution of this amino acid with threonine prevented nuclear localization of the microinjected, FITC-labeled conjugate.

Non-NASA Center↗
NASA NTRS2005

Local Intensity Enhancements in Spherical Microcavities: Implications for Photonic Chemical and Biological Sensors

In this report, we summarize recent findings regarding the use spherical microcavities in the amplification of light that is inelastically scattered by either fluorescent or Raman-active molecules. This discussion will focus on Raman scattering, with the understanding that analogous processes apply to fluorescence. Raman spectra can be generated through the use of a very strong light source that stimulates inelastic light scattering by molecules, with the scattering occurring at wavelengths shifted from that of the source and being most prominent at shifts associated with the molecules natural vibrational frequencies. The Raman signal can be greatly enhanced by exposing a molecule to the intense electric fields that arise near surfaces (typically of gold or silver) exhibiting nanoscale roughness. This is known as surface-enhanced Raman scattering (SERS). SERS typically produces gain factors of 103 - 106, but under special conditions, factors of 1010 - 1014 have been achieved.

Fuller, Kirk A.↗
NASA NTRS2005

Comparison of Grammar-Based and Statistical Language Models Trained on the Same Data

This paper presents a methodologically sound comparison of the performance of grammar-based (GLM) and statistical-based (SLM) recognizer architectures using data from the Clarissa procedure navigator domain. The Regulus open source packages make this possible with a method for constructing a grammar-based language model by training on a corpus. We construct grammar-based and statistical language models from the same corpus for comparison, and find that the grammar-based language models provide better performance in this domain. The best SLM version has a semantic error rate of 9.6%, while the best GLM version has an error rate of 6.0%. Part of this advantage is accounted for by the superior WER and Sentence Error Rate (SER) of the GLM (WER 7.42% versus 6.27%, and SER 12.41% versus 9.79%). The rest is most likely accounted for by the fact that the GLM architecture is able to use logical-form-based features, which permit tighter integration of recognition and semantic interpretation.

Hockey, Beth Ann↗
NASA NTRS2008

Near-Field Spectroscopy with Nanoparticles Deposited by AFM

An alternative approach to apertureless near-field optical spectroscopy involving an atomic-force microscope (AFM) entails less complexity of equipment than does a prior approach. The alternative approach has been demonstrated to be applicable to apertureless near-field optical spectroscopy of the type using an AFM and surface enhanced Raman scattering (SERS), and is expected to be equally applicable in cases in which infrared or fluorescence spectroscopy is used. Apertureless near-field optical spectroscopy is a means of performing spatially resolved analyses of chemical compositions of surface regions of nanostructured materials. In apertureless near-field spectroscopy, it is common practice to utilize nanostructured probe tips or nanoparticles (usually of gold) having shapes and dimensions chosen to exploit plasmon resonances so as to increase spectroscopic-signal strengths. To implement the particular prior approach to which the present approach is an alternative, it is necessary to integrate a Raman spectrometer with an AFM and to utilize a special SERS-active probe tip. The resulting instrumentation system is complex, and the tasks of designing and constructing the system and using the system to acquire spectro-chemical information from nanometer-scale regions on a surface are correspondingly demanding.

Anderson, Mark S.↗
NASA NTRS2008

Microfluidics, Chromatography, and Atomic-Force Microscopy

A Raman-and-atomic-force microscope (RAFM) has been shown to be capable of performing several liquid-transfer and sensory functions essential for the operation of a microfluidic laboratory on a chip that would be used to perform rapid, sensitive chromatographic and spectro-chemical analyses of unprecedentedly small quantities of liquids. The most novel aspect of this development lies in the exploitation of capillary and shear effects at the atomic-force-microscope (AFM) tip to produce shear-driven flow of liquids along open microchannels of a microfluidic device. The RAFM can also be used to perform such functions as imaging liquids in microchannels; removing liquid samples from channels for very sensitive, tip-localized spectrochemical analyses; measuring a quantity of liquid adhering to the tip; and dip-pen deposition from a chromatographic device. A commercial Raman-spectroscopy system and a commercial AFM were integrated to make the RAFM so as to be able to perform simultaneous topographical AFM imaging and surface-enhanced Raman spectroscopy (SERS) at the AFM tip. The Raman-spectroscopy system includes a Raman microprobe attached to an optical microscope, the translation stage of which is modified to accommodate the AFM head. The Raman laser excitation beam, which is aimed at the AFM tip, has a wavelength of 785 nm and a diameter of about 5 m, and its power is adjustable up to 10 mW. The AFM is coated with gold to enable tip-localized SERS.

Anderson, Mark↗
NASA NTRS2010

On-Demand Urine Analyzer

A lab-on-a-chip was developed that is capable of extracting biochemical indicators from urine samples and generating their surface-enhanced Raman spectra (SERS) so that the indicators can be quantified and identified. The development was motivated by the need to monitor and assess the effects of extended weightlessness, which include space motion sickness and loss of bone and muscle mass. The results may lead to developments of effective exercise programs and drug regimes that would maintain astronaut health. The analyzer containing the lab-on-a- chip includes materials to extract 3- methylhistidine (a muscle-loss indicator) and Risedronate (a bone-loss indicator) from the urine sample and detect them at the required concentrations using a Raman analyzer. The lab-on- a-chip has both an extractive material and a SERS-active material. The analyzer could be used to monitor the onset of diseases, such as osteoporosis.

Farquharson, Stuart↗
NASA NTRS2012

Blocking Losses With a Photon Counter

It was not known how to assess accurately losses in a communications link due to photodetector blocking, a phenomenon wherein a detector is rendered inactive for a short time after the detection of a photon. When used to detect a communications signal, blocking leads to losses relative to an ideal detector, which may be measured as a reduction in the communications rate for a given received signal power, or an increase in the signal power required to support the same communications rate. This work involved characterizing blocking losses for single detectors and arrays of detectors. Blocking may be mitigated by spreading the signal intensity over an array of detectors, reducing the count rate on any one detector. A simple approximation was made to the blocking loss as a function of the probability that a detector is unblocked at a given time, essentially treating the blocking probability as a scaling of the detection efficiency. An exact statistical characterization was derived for a single detector, and an approximation for multiple detectors. This allowed derivation of several accurate approximations to the loss. Methods were also derived to account for a rise time in recovery, and non-uniform illumination due to diffraction and atmospheric distortion of the phase front. It was assumed that the communications signal is intensity modulated and received by an array of photon-counting photodetectors. For the purpose of this analysis, it was assumed that the detectors are ideal, in that they produce a signal that allows one to reproduce the arrival times of electrons, produced either as photoelectrons or from dark noise, exactly. For single detectors, the performance of the maximum-likelihood (ML) receiver in blocking is illustrated, as well as a maximum-count (MC) receiver, that, when receiving a pulse-position-modulated (PPM) signal, selects the symbol corresponding to the slot with the largest electron count. Whereas the MC receiver saturates at high count rates, the ML receiver may not. The loss in capacity, symbol-error-rate (SER), and count-rate were numerically computed. It was shown that the capacity and symbol-error-rate losses track, whereas the count-rate loss does not generally reflect the SER or capacity loss, as the slot-statistics at the detector output are no longer Poisson. It is also shown that the MC receiver loss may be accurately predicted for dead times on the order of a slot.

Moision, Burce E.↗
DOE OSTI2020

Methods and materials for determination of distribution coefficients for separation materials

Methods and materials for determining the affinity of separation materials for targeted species are described. A composite separation medium is described that combines a separation material such as an ion exchange material or a sorbent with an SERS substrate. Methods and materials can be utilized to determine the distribution coefficient of a species for a separation material after running a single separation protocol followed by examination of the separation material of the protocol according to SERS. Disclosed methods can be utilized to determine the affinity of existing separation materials for targeted species as well as to determine the affinity of newly engineered separation materials to characterize species.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2021

Modulating the Electron Affinity of Small Bipyridyl Molecules on Single Gold Nanoparticles for Plasmon-Driven Electron Transfer

Developing controlled platforms for plasmon-driven chemistry is of great importance in catalytic reactions at the nanoscale. We report anion radical formation for five bipyridyl complexes of varying degrees of electron affinity utilizing optically fo-cused intraband (594 nm) and interband (532 nm) pump excitation of single gold nanoparticles. The surface-enhanced Raman scattering (SERS) of anion radicals for the five non-resonant adsorbed molecules 2,2’-bipyridine (22BPY), 4,4’-bipyridine (44BPY), trans-1,2-bis(4-pyridyl)ethylene (BPE), 1,2-bis(4-pyridyl)acetylene (BPA), and 1,2-bis(4-pyridyl)ethane (BPEt) were detected using localized surface-plasmon resonance (LSPR) excitation with 785 nm. The electron affinity of the five bipyridyl complexes were determined using electrochemistry. Molecules with low electron affinity experienced high-er instances of radical anion formation under a plasmon-coupled intraband electron transfer excitation (594 nm) whereas molecules with high electron affinity showed a preference for anion radical formation under direct interband electron trans-fer excitation (532 nm). The lowest unoccupied molecular orbital (LUMO) energy levels for low electron affinity surface-bound molecules (22BPY, BPEt) are on average ~0.43 eV higher for high electron affinity surface-bound molecules (BPA, BPE, 44BPY) as calculated using time-dependent density functional theory, elucidating the importance of plasmon coupling to energy levels that facilitate charge transfer pathways. We also show the ability to ‘activate’ high vs low electron affinity single nanoparticles with the choice of pump excitation wavelength. The findings show the complex interplay between molecular electron affinity, orbital overlap with the density of states of the plasmonic metal, and excitation energetics of the pump laser wavelength. Potential applications of this work include enhanced control over molecular scale catalysis, biosensor design, and solar energy capture.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Probing the Evolution of Surface Chemistry at the Silicon–Electrolyte Interphase via In Situ Surface-Enhanced Raman Spectroscopy

We present a novel spectroscopic technique for in situ Raman microscopy studies of battery electrodes. By creating nanostructures on a copper mesh current collector, we were able to utilize surface-enhanced Raman spectroscopy (SERS) to monitor the evolution of the silicon anode-electrolyte interphase. We report the spectra show reversible Si peak intensity changes upon lithiation and delithiation. Moreover, an alkyl carboxylate species, lithium propionate, was detected as a significant SiEI component. Our experimental setup showed reproducible and stable performance over multiple cycles in terms of both electrochemistry and spectroscopy.

25 ENERGY STORAGE↗
DOE OSTI2021

Controlling the Aspect Ratios of Au Nanocrystals with Ag+ Addition Time in Seed-Mediated Synthesis: Implications for Surface-Enhanced Raman Scattering

Among various factors playing pivotal roles in the typical seed-mediated growth of Au nanocrystals (NCs), the role of Ag (AgNO3) has remained debatable over time and seminal research efforts have helped us in reaching a consensus, albeit from the standpoint of [Ag+] concentration. This study aims to provide an understanding of the role of Ag+ from the perspective of time. Here, we show that different Au NCs with tunable aspect ratios (ARs) can be generated in one system in high yield simply by varying the time of addition of Ag+ in the growth solution. The generality of the method has been demonstrated in tuning the ARs of anisotropic Au NCs like concave cuboid (CCB, AR = 2) and elongated tetrahexahedra (AR = 2.5), where the delayed addition of Ag+ leads to the formation of their isotropic counterpart concave cube (CC, AR = 1) and tetrahexahedra (AR = 1), respectively. This work, apart from establishing timed addition of Ag+ as a crucial parameter in controlling the AR, may also help in the realization of a universal growth mechanism of Au NCs. The Au NCs with varying ARs (CCB, AR = 2 and CC, AR = 1) have been further explored as potential substrates for surface-enhanced Raman scattering (SERS) due to the presence of their high-index facets and sharp tips.

KEYWORDS:Au nanoparticles seed-mediated growth hig↗
DOE OSTI2023

USAID Colombia Young Leaders Workforce Training Program Action Plans: Forecasting Distributed Photovoltaic Adoption in Barranquilla, Colombia

As part of the U.S. Agency for International Development (USAID)-National Renewable Energy Laboratory (NREL) Young Leaders Workforce Training Program in Colombia, the Association of Renewable Energies Colombia (SER) participants leveraged their training and professional experience to develop an action plan for modeling the projected adoption of distributed solar photovoltaics (PV) out to 2050 for the city of Barranquilla, Colombia. This case study provides an overview of the key activities and outcomes of the Distributed Generation Market Demand Model (dGen™) Colombia project.

14 SOLAR ENERGY↗
DOE OSTI2023

Tailoring Electrochemical CO 2 Reduction on Copper by Reactive Ionic Liquid and Native Hydrogen Bond Donors

Abstract Electrochemical CO 2 reduction (CO 2 RR) on copper (Cu) shows promise for higher‐value products beyond CO. However, challenges such as the limited CO 2 solubility, high overpotentials, and the competing hydrogen evolution reaction (HER) in aqueous electrolytes hinder the practical realization. We propose a functionalized ionic liquid (IL) which generates ion‐CO 2 adducts and a hydrogen bond donor (HBD) upon CO 2 absorption to modulate CO 2 RR on Cu in a non‐aqueous electrolyte. As revealed by transient voltammetry, electrochemical impedance spectroscopy (EIS), and in situ surface‐enhanced Raman spectroscopy (SERS) complemented with image charge augmented quantum‐mechanical/molecular mechanics (IC‐QM/MM) computations, a unique microenvironment is constructed. In this microenvironment, the catalytic activity is primarily governed by the IL and HBD concentrations; former controlling the double layer thickness and the latter modulating the local proton availability. This translates to ample CO 2 availability, reduced overpotential, and suppressed HER where C 4 products are obtained. This study deepens the understanding of electrolyte effects in CO 2 RR and the role of IL ions towards electrocatalytic microenvironment design.

Coskun, Oguz Kagan↗