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.
Ni( ii ) ions have been deposited on the Zr 6 nodes of a metal–organic framework (MOF), UiO-66, via an ALD-like process (ALD = atomic layer deposition).
The tetrairidium carbonyl cluster Ir 4 L 3 (CO) 9 (L = tert-butyl-calix[4]arene(OPr) 3 (OCH 2 PPh 2 ) (Ph = phenyl; Pr = propyl)) on a partially dehydroxylated silica support undergoes hydrogen activation at a rate and with a mechanism different from those pertaining to the cluster in alkane solution. These results are unobvious in view of the sterically bulky ligands protecting the cluster and the nearly identical CO band frequencies in the infrared spectra characterizing the supported and dissolved Ir 4 L 3 (CO) 9 , both before reaction and during reaction involving decarbonylation in the presence of either helium or H 2 (and H 2 reacted with the clusters to form hydrides with the same Ir–H band frequencies for clusters in alkane solvent and supported on silica). The initial rates of CO loss from the supported clusters in the presence of helium were the same as those in the presence of H 2 . In this work, the comparison demonstrates that the rate-determining step for hydride formation on the silica-supported cluster is CO dissociation. In contrast, the comparable dissociation of CO from the cluster in n-decane solution requires a higher temperature, 343 K, and is at least an order of magnitude slower than when the clusters were supported on silica. CO dissociation is not the rate-determining step for hydrogen activation on the cluster in n-decane, as the rate is influenced by reactant H 2 as well.
This work studied how in-cylinder flow structure is affected in a light-duty, swirl-supported diesel engine when equipped with three different piston geometries: the first two featuring a conventional re-entrant bowl, either with or without valve cut-outs on the piston surface and the third featuring a stepped-lip bowl. Particle image velocimetry experiments were conducted inside an optical engine to measure swirl vortex intensity and structure during the intake and compression strokes. A full computational model of the optical diesel engine was built using the FRESCO code, a recently developed object-oriented parallel computational fluid dynamics platform for engine simulations. The model was first validated against the measured swirl-plane velocity fields, and the simulation convergence for multiple cycles was assessed. Flow topology was studied by addressing bulk flow and turbulence quantities, including swirl structure, squish flux, plus geometric and operating parameters, such as the presence of valve cut-outs on the piston surface, compression ratio and engine speed. The results demonstrated that conventional re-entrant bowls have stronger flow separation at intake, hampering bowl swirl, but higher global swirl than for stepped-lip bowls thanks to a stronger and more axisymmetric squish mechanism and less tilted swirl. Stepped-lip bowls have larger inhomogeneities (tilt and axisymmetry) and higher turbulence levels, but also faster turbulence dissipation toward top dead center. They have weaker squish flux but larger squish inversion momentum as a result of the smaller inertia.
Microwave (MW)-assisted methane dehydroaromatization (MDHA) using an Mo-supported HZSM-5 catalyst (Mo/HZ5) can convert methane into value-added aromatic products in modular microwave reactor systems, enabling producers to generate revenue from an otherwise wasted resource. Modifying the local environments of active Mo species with metal promoters potentially regulates the reaction/deactivation pathways and improves the heating properties of the Mo/HZ5 under microwaves. Herein, metal promoters (M), including monovalent K+ and bivalent Co2+ and Ni2+, were incorporated to form M-Mo/HZ5 and their MDHA performance was investigated.
Explore the source record for details and available documents.
The goal of this review is to summarize the evidence for non-targeted and delayed effects of exposure to ionizing radiation in vivo. Currently, human health risks associated with radiation exposures are based primarily on the assumption that the detrimental effects of radiation occur in irradiated cells. Over the years a number of non-targeted effects of radiation exposure in vivo have been described that challenge this concept. These include radiation-induced genomic instability, bystander effects, clastogenic factors produced in plasma from irradiated individuals that can cause chromosomal damage when cultured with nonirradiated cells, and transgenerational effects of parental irradiation that can manifest in the progeny. These effects pose new challenges to evaluating the risk(s) associated with radiation exposure and understanding radiation-induced carcinogenesis.
Blue light significantly increased tillering in wheat (Triticum aestivum L.) plants grown at the same photosynthetic photon flux (PPF). Plants were grown under two levels of blue light (400-500 nm) in a controlled environment with continuous irradiation. Plants received either 50 micromoles m-2 s-1 of blue light or 2 micromoles m-2 s-1 blue light from filtered metal halide lamps at a total irradiance of 200 micromoles m-2 s-1 PPF (400-700 nm). Plants tillered an average of 25% more under the higher level of blue light. Blue light also caused a small, but consistent, increase in main culm development, measured as Haun stage. Leaf length was reduced by higher levels of blue light, while plant dry-mass was not significantly affected by blue light. Applying the principle of equivalent light action, the results suggest that tillering and leaf elongation are mediated by the blue-UV light receptor(s) because phytochrome photoequilibrium for each treatment were nearly identical.
The effect of varying the amounts of metals Fe, Cu, K, and Mo was studied on a catalyst supported on activated carbon (AC), which is an item of novelty of this paper. The base-case catalyst contains 16% Fe, 0.9% K, 6% Mo, and 0.8% Cu relative to the AC support. For all of the catalysts used, alcohol production is small. The production of hydrocarbons depends upon the amount of Fe and other promoters used. The amount of Fe was increased from 0% to 32% on the catalyst containing base-case amounts of the other materials. While 0% Fe shows no activity towards Fischer–Tropsch synthesis (FTS), 32% Fe shows a marginal increase in FTS activity when compared with 16% Fe. Furthermore, the amount of K was increased from 0% to 1.8%, with the other metals in their base-case amounts. The selectivity of C1–C4 decreases with the addition of K, while the selectivity of C5+ increases. Analogously, the amount of Mo was increased from 0% to 12%. A small amount of Mo results in an increase in FTS activity but decreases with the addition of more Mo. Cu on the catalyst was increased from 0% to 1.6%, with 0.8% Cu proving optimum for FTS.
Transonic pressure tunnel tests to determine effects of sting-support interference on longitudinal aerodynamic characteristics of transport aircraft models with upswept aft ends
The Midwest Tribal Energy Resources Association (MTERA) embarked on a 5-year (extended to 7-year) initiative aimed at advancing Tribal energy resilience and sustainability through intertribal collaboration. By bringing together Tribes in Minnesota, Wisconsin, and Michigan (EPA Region 5 Tribes), the project's scope encompassed organizational growth, governance and management formalization and enhancement, and the planning and deployment of energy-related services to Member Tribes. MTERA strategically pursued four key objectives to fulfill its mission: 1. Clearinghouse Development: Creation of a centralized hub offering valuable information, education, and outreach for Tribal communities and their neighbors. 2. Policy Liaison: Serving as a vital link between federal and state agencies to contribute to the formulation of inclusive energy policies that ensure both Tribal and regional energy success. 3. Energy Planning and Research: Providing essential support for energy planning, researching financing opportunities, and exploring effective procurement strategies. 4. Training Support: Facilitating training and apprenticeship initiatives to empower the Tribal workforce and enhance community capabilities.
The objectives of the study were to examine the nature of currently planned and new evolutionary geosynchronous programs, to analyze alternative ways of conducting missions, to establish concepts for new systems to support geosynchronous programs in an effective and economical manner, and to define the logistic support to carry out these programs. In order to meet these objectives, it was necessary to define and examine general geosynchronous mission characteristics and the potentially applicable electromagnetic spectrum characteristics. An organized compilation of these data is given with emphasis on the development and use of the data. Fundamental geosynchronous orbit time histories, mission profile characteristics, and delivery system characteristics are presented. In addition, electromagnetic spectrum utilization is discussed in terms of the usable frequency spectrum, the spectrum potentially available considering established frequency allocations, and the technology status as it affects the ability to operate within specific frequency bands.
The total ozone column content (TOZ) measured from the Nimbus 4 BUV experiment is analyzed in geomagnetic coordinates to study a possible link between the solar corpuscular radiation and the lower stratosphere. Using planetary magnetic index Ap as a measure of the solar corpuscular radiation, it is shown that the correlation between TOZ and Ap, if any, occurs predominantly at high latitudes during winter seasons. This is typical of most of the claimed correlations between sun and weather and may be the result of the winter increase of planetary wave activity which by coincidence have periods comparable to magnetic activity. The fact that even major magnetic storms have no detectable effect on the stratospheric ozone during summer does not support a direct cause and effect relation between solar and stratospheric perturbations.
The Space Radiation Health Program intends to establish the scientific basis for the radiation protection of humans engaged in the exploration of space, with particular emphasis on the establishment of a firm knowledge base to support cancer risk assessment for future planetary exploration. This document sets forth the technical and management components involved in the implementation of the Space Radiation Health Program, which is a major part of the Life Sciences Division (LSD) effort in the Office of Space Science and Applications (OSSA) at the National Aeronautics and Space Administration (NASA). For the purpose of implementing this program, the Life Sciences Division supports scientific research into the fundamental mechanisms of radiation effects on living systems and the interaction of radiation with cells, tissues, and organs, and the development of instruments and processes for measuring radiation and its effects. The Life Sciences Division supports researchers at universities, NASA field centers, non-profit research institutes and national laboratories; establishes interagency agreements for cooperative use and development of facilities; and conducts a space-based research program using available and future spaceflight vehicles.
Two educational uses of models and simulations: 1) Students create models and use simulations ; and 2) Researchers create models of learners to guide development of reliably effective materials. Cognitive tutors simulate and support tutoring - data is crucial to create effective model. Pittsburgh Science of Learning Center: Resources for modeling, authoring, experimentation. Repository of data and theory. Examples of advanced modeling efforts: SimStudent learns rule-based model. Help-seeking model: Tutors metacognition. Scooter uses machine learning detectors of student engagement.
We examined the respiratory behaviours and swimming kinematics of Xenopus laevis tadpoles hatched in microgravity (Space Shuttle), simulated microgravity (clinostat) and hypergravity (3 g centrifuge). All observations were made in the normal 1 g environment. Previous research has shown that X. laevis raised in microgravity exhibit abnormalities in their lungs and vestibular system upon return to 1 g. The tadpoles raised in true microgravity exhibited a significantly lower tailbeat frequency than onboard 1 g centrifuge controls on the day of landing (day0), but this behaviour normalized within 9 days. The two groups did not differ significantly in buccal pumping rates. Altered buoyancy in the space-flight microgravity tadpoles was indicated by an increased swimming angle on the day after landing (day1). Tadpoles raised in simulated microgravity differed to a greater extent in swimming behaviours from their 1 g controls. The tadpoles raised in hypergravity showed no substantive effects on the development of swimming or respiratory behaviours, except swimming angle. Together, these results show that microgravity has a transient effect on the development of locomotion in X. laevis tadpoles, most notably on swimming angle, indicative of stunted lung development. On the basis of the behaviours we studied, there is no indication of neuromuscular retardation in amphibians associated with embryogenesis in microgravity.
Increasing evidence suggests that disease-associated microglia play a protective role in neurodegenerative diseases. Microglia are known to polarize into two reciprocate forms in response to external cues - inflammatory M1 state and anti-inflammatory M2 state. These cells perform key functions in the development of the brain, such as circuit refinement, neurogenesis, and neuronal growth. In this study, we analyzed the secretion effect of microglia on neural stem/progenitor cell (NSPC) proliferation and differentiation. We cultured adult mouse-derived NSPCs in a conditioned medium from BV2 immortalized microglia without growth factors and evaluated their differentiation. When cultivated with BV2-derived soluble factors in the presence of basic fibroblast growth factor (bFGF) and epidermal growth factor (EGF), NSPCs were able to maintain Nestin expression and showed increased proliferation compared with those cells cultivated with bFGF and EGF only. Moreover, conditioned media from M2-polarized primary microglia, stimulated by IL-10/IL-13, showed supportive effect on NSPC proliferation. These data suggest that microglia support neural stem cell proliferation through secreting neuro-nutritious soluble factors.
The success of physico-chemical waste processing and resource recovery technologies for life support application depends partly on the ability of gas clean-up systems to efficiently remove trace contaminants generated during the process with minimal use of expendables. Carbon nanotubes promise superior performance over conventional approaches to gas clean-up due to their ability to direct the selective uptake of gaseous species based on their controlled pore size, high surface area, ordered chemical structure that allows functionalization and their effectiveness also as catalyst support materials for toxic gas conversion. We present results and findings from a preliminary study on the effectiveness of metal impregnated single walled nanotubes as catalyst/catalyst support materials for toxic gas contaminate control. The study included the purification of single walled nanotubes, the catalyst impregnation of the purified nanotubes, the experimental characterization of the surface properties of purified single walled nanotubes and the characterization of physisorption and chemisorption of uptake molecules.
The objective of this project is to elucidate the effects of the chemical composition and microstructure of the electrocatalyst support on the activity, stability and utilization of supported Pt clusters.