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At least 973 records · Page 54

A discussion of interplanetary postshock flows with two examples

Plasma and magnetometer observations of two types of flare-associated shock flows are described and compared with present models. One type represents a class of flows in which the shock is followed by a stream and separated from it by a region in which density, temperature, and speed decrease monotonically. Neither the blast wave model nor the two-stage model, in which the stream and the shock are attributed to the same flare, can quantitatively describe this class. The other type is characterized by a complex region between the shock and the following stream, which has many discontinuities and fluctuations but in which there is no increase in helium concentration. This class of event is not describable in terms of the conventional pictures presented, for example, by Hundhausen (1972). These two types of flow can be distinguished by using ground magnetograms, since the first type shows no sudden impulses following the shock, whereas the second type shows many.

Ogilvie, K. W.↗

Temporal expression and immunogold localization of Plodia interpunctella granulosis virus structural proteins

Monospecific antisera were produced against four structural proteins (VP12, VP17, VP31, and granulin) of the Plodia interpunctella granulosis virus using polypeptides derived by sodium dodecyl sulfate-polyacrylamide gel electrophoresis or acid extraction. The antisera were shown to be specific on immunoblots of SDS-PAGE separated granulosis virus and were further used to detect structural proteins in infected fat body lysates. Immunoblots of fat body lysates from early stages of infection indicated that VP12, VP17, VP31, and granulin were expressed by 2.5 days post-infection. Immunogold labeling of the virus using the monospecific antisera and electron microscopy confirmed earlier reports that granulin is located in the protein matrix, V17 is an envelope protein, and VP31 is a capsid protein.

Non-NASA Center↗

Study on separation of minor actinides from HLLW with new extractant of TODGA-DHOA/Kerosene

The extraction behavior of U, Np, Pu, Am, rare earth elements and Sr from nitric acid solutions by TODGA/dodecan, DHOA/dodecane and TODGA-DHOA/dodecane were investigated, respectively. Based on experimental results, a separation process was proposed for minor actinide isolation from high level liquid waste (HLLW): the TODGA-DHOA/kerosene system. The multi-stage counter-current cascade experiments were carried out for the purpose by 0.1 mol/l TODGA-1.0 mol/l DHOA/kerosene with miniature mixer- settler contactor rigs (8 stages for extraction, 6 stages for scrubbing, 8 stages for first stripping, 8 stages for second stripping). The results show that the recovery efficiencies of the actinides and lanthanides are more than 99.9%, whereas less than 1% Sr was extracted by 0.1 mol/l TODGA - 1.0 mol/l DHOA/kerosene. The stripping efficiencies of U, Np and Pu are more than 95% in the first stripping step by 0.5 mol/l HNO{sub 3} + 0.5 mol/l AHA(aceto-hydroxamic acid), all of the remained actinides and lanthanides can be stripped by 0.01 mol/l HNO{sub 3} in the second stripping step. 99% Sr was extracted by 0.1 mol/l TODGA/kerosene, so Sr can be recovered efficiently directly from the raffinate by 0.1 mol/l TODGA/kerosene. (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

Generalized optimization-based synthesis of membrane systems for multicomponent gas mixture separation

Synthesizing a membrane system to separate multicomponent gas mixture is challenging due to the combinatorial number of feasible configurations and the difficulties in describing the multicomponent permeators. Here we present a mixed-integer nonlinear programming (MINLP) model for synthesizing membrane systems for multicomponent gas mixture separation. The approach employs a richly connected superstructure to represent numerous potential system configurations, and different physics-based surrogate permeator models, such as countercurrent flow or crossflow, to be used in each stage. Moreover, to describe realistic systems, pressure drop equations can be included. We also present solution methods to accelerate the solution process. Through a case study of natural gas sweetening, we demonstrate that the proposed approach is able to obtain good solutions using an off-the-shelf global optimization solver. Finally, we expand the conventional membrane system synthesis problem by introducing feed variability in our model through a case study of an integrated reactor-separation system.

42 ENGINEERING↗

Exposure History of Separated Phases from the Kapoeta Meteorite

Cosmogenic Be-10, Al-26, Cl-36, and Mn-53 were measured in clasts and matrix samples from Kapoeta. The radionuclide data are consistent with a single stage exposure lasting approximately 3 Ma. These results are not consistent with exposure ages based on cosmogenic Ne-21.

Caffee, M. W.↗

Polysialylated N-Glycans Identified in Human Serum Through Combined Developments in Sample Preparation, Separations and Electrospray ionization-mass spectrometry

The N-glycan diversity of human serum glycoproteins, i.e. the human blood serum N-glycome, is complex due to the range of glycan structures potentially synthesizable by human glycosylation enzymes. The reported glycome, however, is limited by methods of sample preparation, available analytical platforms, e.g., based upon electrospray ionization-mass spectrometry (ESI-MS), and software tools for data analysis. In this report, several improvements have been implemented in sample preparation and analysis to extend ESI-MS glycan characterization and to provide an improved view of glycan diversity. Sample preparation improvements include acidified, microwave-accelerated, PNGase F N-glycan release, and sodium borohydride reduction were optimized to improve quantitative yields and conserve the number of glycoforms detected. Two-stage desalting (during solid phase extraction and on the analytical column) increased the sensitivity by reducing analyte signal division between multiple reducing-end-forms or cation adducts. On-line separations were improved by using extended length graphitized carbon columns and adding TFA as an acid modifier to a formic acid/reversed phase gradient which provides additional resolving power and significantly improved desorption of both large and heavily sialylated glycans. To improve MS sensitivity and provide gentler ionization conditions at the source-MS interface, subambient pressure ionization with nanoelectrospray (SPIN) has been utilized. When method improvements are combined together with the Glycomics Quintavariate Informed Quantification (GlyQ-IQ) recently described1 these technologies demonstrate the ability to significantly extend glycan detection sensitivity and provide expanded glycan coverage. We demonstrate application of these advances in the context of the human serum glycome, and for which our initial observations include detection of a new class of heavily sialylated N-glycans, including polysialylated N-glycans.

Environmental Molecular Sciences Laboratory↗

A two-stage (turbulent-drainage) mechanism for the emplacement of impact crater outflows on Venus

Several emplacement mechanisms were proposed for the unique flow features associated with 402 of the 912 impact craters found on Venus to date. Studies based on rheological models and laboratory results have suggested two separate depositional flow mechanisms: a turbulent emplacement and a lava like emplacement. Schultz proposed a progressive transition from the turbulent to the lava like mechanism during deceleration of some turbulent flows. He suggested that these composite flows were emplaced prior to the deposition of the normal ejecta. After an examination of the geomorphologic, stratigraphic, and topographic relations of the flows associated with the 402 craters, it is suggested that most of the outflows result from a two-stage emplacement process. In the first stage, a turbulent, proximal part is usually emplaced downrange of the impact site after the other ejecta materials. In the second stage, a distal part, composed of low-viscosity melt, slowly drains via dendritic channels from the proximal deposit and flows like lava. A few flows were identified that appear to have been emplaced prior to the ejecta; these flows likely result from a different mechanism.

Chadwick, D. J.↗

Augmentation of blood circulation to the fingers by warming distant body areas

Future activities in space will require greater periods of time in extreme environments in which the body periphery will be vulnerable to chilling. Maintaining the hands and fingers in comfortable conditions enhances finger flexibility and dexterity, and thus effects better work performance. We have evaluated the efficacy of promoting heat transfer and release by the extremities by increasing the blood flow to the periphery from more distant parts of the body. The experimental garment paradigm developed by the investigators was used to manipulate the temperature of different body areas. Six subjects, two females and four males, were evaluated in a stage-1 baseline condition, with the inlet temperature of the circulating water in the liquid cooling/warming garment (LCWG) at 33 degrees C. At stage 2 the total LCWG water inlet temperature was cooled to 8 degrees C, and at stage 3 the inlet water temperature in specific segments of the LCWG was warmed (according to protocol) to 45 degrees C, while the inlet temperature in the rest of the LCWG was maintained at 8 degrees C. The following four body-area-warming conditions were studied in separate sessions: (1) head, (2) upper torso/arm, (3) upper torso/arm/head, and (4) legs/feet. Skin temperature, heat flux and blood perfusion of the fingers, and subjective perception of thermal sensations and overall physical comfort were assessed. Finger temperature (T(fing)) analyses showed a statistically significant condition x stage interaction. Post-hoc comparisons (T(fing)) indicated that at stage 3, the upper torso/arm/head warming condition was significantly different from the head, upper torso/arm and legs/feet conditions, showing an increase in T(fing). There was a significant increase in blood perfusion in the fingers at stage 3 in all conditions. Subjective perception of hand warmth, and overall physical comfort level significantly increased in the stage 3 upper torso/arm/head condition. The findings indicate that physiological methods to enhance heat transfer by the blood to the periphery within protective clothing provide an additional tool for increasing total and local human comfort in extreme environments.

NASA Discipline Life Sciences Technologies↗

Performance of the Modified V-1710-93 Engine-Stage Supercharger with a Constant-Area Vaneless Diffuser

As part of an investigation to increase the power output of the V-1710-93 engine at altitude, the engine-stage supercharger was combined with a constant-area vaneless diffuser designed to improve the performance of the engine-stage supercharger at the rated engine operating point. The performance of the modified supercharger was investigated in a variable-component supercharger test rig and compared with that of the standard supercharger with an 8-vaned diffuser. A separate evaluation of the component efficiencies and a study of the flow characteristics of the modified supercharger was made possible by internal diffuser instrumentation. At the volume flow required by the engine for rated operating conditions, the modified supercharger increased the over-all adiabatic efficiency 0.05 and the over-all pressure coefficient 0.035. Furthermore, the capacity of the engine-stage supercharger was increased by replacing the standard 8-vaned diffuser with the vaneless diffuser. The peak over-all adiabatic efficiency for the modified supercharger, however, was 0.05 to 0.07 lower than that of the standard unit over the range of tip speeds investigated. The improved performance of the modified supercharger at rated engine operating conditions resulted from a shift of the point of peak adiabatic efficiency and pressure coefficient of the standard supercharger to a higher flow. The energy loss through the vaneless diffuser was found to be small. Because of the restricted diffuser diameter, however, diffusion was inadequate, which resulted in a relatively small static-pressure rise through the diffuser, high diffuser-exit velocities, and excessive collector-case losses.

Douglas, John E.↗

A Geometric Analysis to Protect Manned Assets from Newly Launched Objects - COLA Gap Analysis

A safety risk was identified for the International Space Station (ISS) by The Aerospace Corporation following the launch of GPS IIR-20 (March 24, 2009), when the spent upper stage of the launch vehicle unexpectedly crossed inside the ISS notification box shortly after launch. This event highlighted a 56-hour vulnerability period following the end of the launch Collision Avoidance (COLA) process where the ISS would be unable to react to a conjunction with a newly launched object. Current launch COLA processes screen each launched object across the launch window to determine if an object's nominal trajectory is predicted to pass within 200 km of the ISS (or any other manned/mannable object), resulting in a launch time closure. These launch COLA screens are performed from launch through separation plus I 00 minutes. Once the objects are in orbit, they are cataloged and evaluated as part of routine on-orbit conjunction assessment processes. However, as the GPS IIR-20 scenario illustrated, there is a vulnerability period in the time line between the end of launch COLA coverage and the beginning of standard on-orbit COLA assessment activities. The gap between existing launch and on-orbit COLA processes is driven by the time it takes to track and catalog a launched object, identify a conjunction, and plan and execute a collision avoidance maneuver. For the ISS, the total time required to accomplish an of these steps is 56 hours. To protect human lives, NASA/JSC has requested that an US launches take additional steps to protect the ISS during this "COLA gap" period. The uncertainty in the state of a spent upper stage can be quite large after all bums are complete and all remaining propellants are expelled to safe the stage. Simply extending the launch COLA process an additional 56 hours is not a viable option as the 3-sigma position uncertainty will far exceed the 200 km miss-distance criterion. Additionally, performing a probability of collision (Pc) analysis over this period is also not practical due to the limiting effects of these large orbit state uncertainties. An estimated upper bound for Pc for a typical spent upper stage if nominally aligned for a direct broadside collision with the ISS is only on the order of 10-6. For a smaller manned object such as a Soyuz capsule, the risk level decreases to an order of 10'8 . In comparison, the Air Force Range policy (AFI 91-217) for launch COLAs would only eliminate launch opportunities when conjunctions with objects exceed a Pc of 10'5 This paper demonstrates a conservative geometry-based methodology that may be used to determine if launch opportunities pose a threat to the ISS during the COLA gap period. The NASA Launch Services Program at Kennedy Space Center has developed this COLA gap analysis method and employed it fQr three NASA missions to identify potential ISS conjunctions and corresponding launch window closures during the 56-hour at-risk period. In the analysis, for each launch opportunity, the nominal trajectory of the spent upper stage and the orbit state of the ISS are propagated over the 56 hour period. Each time the upper stage crosses the orbit plane of the ISS, the relative radial and argument of latitude separations are calculated. A window cutout is identified if these separation differences fall within a mission-specific violation box, which is determined from the evaluation of a Monte Carlo dispersions analysis that quantifies the potential variation in the upper stage radial and argument of latitude differences. This paper details the results of these analyses and their impacts to each mission.

Hametz, Mark E.↗

In-situ observation of an unusual phase transformation pathway with Guinier-Preston zone-like precipitates in Zr-based bulk metallic glasses

The pathway of amorphous-to-crystalline phase transformation in Zr 52.5 Cu 17.9 Ni 14.6 Al 10 Ti 5 bulk metallic glasses was studied using a suite of in-situ techniques. Multi-scale structure evidence reveals a five-stage pathway, analogous to the non-equilibrium transformation process with Guinier-Preston zones during aging in precipitation-hardened alloys, by the following sequence upon isothermal annealing the alloy in the supercooled liquid region: polyamorphous phase transition, chemical phase separation, the formation of a poorly-ordered metastable phase, and the formation of a final crystalline product. The changeable incubation periods at different annealing temperatures, and the abrupt multi-scale structure changes, as well as a latent heat release in the calorimetric measurements, support the first-order nature of the phase transformation at early stages. The structure evolution in real-space indicates that the enhancement of cluster connectivity on the medium-range scale plays essential roles in the early stages of the phase transformation, while the interface-limited ordering dominates the later stages. The experimental results suggest the phase transformation pathway with "Guinier-Preston zone-like" precipitates accompanied by the kinematic development of core-shell structures of diffuse interfaces with order parameters gradients, enabling the step-by-step decrease of free energy of the alloy system during phase transformation, which might be a universal behavior for alloys with excellent glass-forming ability.

36 MATERIALS SCIENCE↗

POPULATIONS OF YOUNG STELLAR OBJECTS IN NEARBY MOLECULAR CLOUDS

We develop a new method for identifying young stellar objects (YSOs) from star-forming regions using the photometry data from Spitzer's c2d Legacy Project. The aim is to obtain YSO lists as complete as possible for studying statistical properties such as the star formation rate (SFR) and lifetimes of YSOs in different evolutionary stages. The largest obstacle in identifying YSOs comes from background galaxies with similar spectral energy distributions to YSOs. Traditionally, selected color-color and color-magnitude criteria are used to separate YSOs and galaxies. However, since there is no obvious boundary between YSOs and galaxies in color-color diagrams and color-magnitude diagrams (CMDs), those criteria may exclude faint YSOs near the boundary. In this paper, we separate the YSOs and galaxies in a multi-dimensional (multi-D) magnitude space, which is equivalent to using all variations of CMDs simultaneously. Comparing sources from molecular clouds to Spitzer's SWIRE data, which have a negligible amount of YSOs, we can naturally identify YSO candidates (YSOc) located outside of the galaxy-populated regions in the multi-D space. In the five c2d surveyed clouds, we select 322 new YSOc and miss/exclude 33 YSOc compared to Evans et al., and this results in 1313 YSOc in total. As a result, SFR increases 28% correspondingly, but the lifetimes of YSOs in different evolutionary stages remain unchanged. Compared to theories by Krumholz and McKee, our derived SFR suggests that star formation at a large scale is dominated by supersonic turbulence rather than magnetic fields. Furthermore, we identify seven new very low luminosity objects.

79 ASTRONOMY AND ASTROPHYSICS↗

Encapsulation of large dye molecules in hierarchically superstructured metal–organic frameworks

Microporous metal–organic frameworks (MOFs) represent a new family of microporous materials, offering potential applications in gas separation and storage, catalysis, and membranes. We expect that the engineering of hierarchical superstructured MOFs, i.e., fabricating mesopores in microporous frameworks during the crystallization stage will serve a myriad of applications for molecular adsorption, drug delivery, and catalysis. But, MOFs with mesopores are rarely studied because of the lack of a simple, effective way to construct mesoscale cavities in the structures. We report the use of a perturbation-assisted nanofusion technique to construct hierarchically superstructured MOFs. In particular, the mesopores in the MOF structure enabled the confinement of large dye species, resulting in fluorescent MOF materials, which can serve as a new type of ratiometric luminescent sensors for typical volatile organic compounds.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Electrochemical strain microscopy time spectroscopy: Model and experiment on LiMn{sub 2}O{sub 4}

Electrochemical Strain Microscopy (ESM) can provide useful information on ionic diffusion in solids at the local scale. In this work, a finite element model of ESM measurements was developed and applied to commercial lithium manganese (III,IV) oxide (LiMn{sub 2}O{sub 4}) particles. ESM time spectroscopy was used, where a direct current (DC) voltage pulse locally disturbs the spatial distribution of mobile ions. After the pulse is off, the ions return to equilibrium at a rate which depends on the Li diffusivity in the material. At each stage, Li diffusivity is monitored by measuring the ESM response to a small alternative current (AC) voltage simultaneously applied to the tip. The model separates two different mechanisms, one linked to the response to DC bias and another one related to the AC excitation. It is argued that the second one is not diffusion-driven but is rather a contribution of the sum of several mechanisms with at least one depending on the lithium ion concentration explaining the relaxation process. With proper fitting of this decay, diffusion coefficients of lithium hosts could be extracted. Additionally, the effect of phase transition in LiMn{sub 2}O{sub 4} is taken into account, explaining some experimental observations.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

Tests of a full-scale ITER toroidal interferometer and polarimeter (TIP) prototype on the DIII-D tokamak (invited)

A full-scale ITER toroidal interferometer and polarimeter (TIP) prototype, including an active feedback alignment system, has been installed and tested on the DIII-D tokamak. In the TIP prototype, a two-color interferometry measurement of line-integrated density is carried out at 10.59 μm and 5.22 μm using a CO 2 and quantum cascade laser, respectively, while a separate polarimetry measurement of the plasma-induced Faraday effect is made at 10.59 μm. The TIP prototype is equipped with a piezo tip/tilt stage active feedback alignment system that minimizes noise in the measurement and keeps the diagnostic aligned throughout DIII-D discharges. The measured phase resolution for the polarimeter and interferometer is 0.05° (100 Hz bandwidth) and 1.9° (1 kHz bandwidth), respectively. Here, the corresponding line-integrated density resolution for the vibration-compensated interferometer is δnL = 1.5 × 10 18 m -2 , and the magnetic field-weighted line-integrated density from the polarimeter is δnBL = 1.5 × 10 19 Tm -2 . Both interferometer and polarimeter measurements during DIII-D discharges compare well with the expectations based on calculations using Thomson scattering measured density profiles and magnetic equilibrium reconstructions. Additionally, larger bandwidth interferometer measurements show that the diagnostic is a sensitive monitor of core density fluctuations with demonstrated measurements of Alfvén eigenmodes and tearing modes.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

Cell dynamics simulations of coupled charge and magnetic phase transformation in correlated oxides

In this work, we present a comprehensive numerical study on the kinetics of phase transition that is characterized by two nonconserved scalar order parameters coupled by a special linear-quadratic interaction. This particular Ginzburg-Landau theory has been proposed to describe the coupled charge and magnetic transition in nickelates and the collinear stripe phase in cuprates. The inhomogeneous state of such systems at low temperatures consists of magnetic domains separated by quasimetallic domain walls where the charge order is reduced. By performing large-scale cell dynamics simulations, we find a two-stage phase-ordering process in which a short period of independent evolution of the two order parameters is followed by a correlated coarsening process. The long-time growth and coarsening of magnetic domains is shown to follow the Allen-Cahn power law. We further show that the nucleation-and-growth dynamics during phase transformation to the ordered states is well described by the Kolmogorov-Johnson-Mehl-Avrami theory in two dimensions. On the other hand, the presence of quasimetallic magnetic domain walls in the ordered states gives rise to a very different kinetics for transformation to the high-temperature paramagnetic phase. In this scenario, the phase transformation is initiated by the decay of magnetic domain walls into two insulator-metal boundaries, which subsequently move away from each other. Implications of our findings to recent nano-imaging experiments on nickelates are also discussed.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

A Self-Biasing Pulsed Depressed Collector

Depressed collectors have been utilized successfully for many years to improve the electrical efficiency of vacuum electron devices. Increasingly, pulsed, high-peak power accelerator applications are placing a premium on electrical efficiency. As RF systems are responsible for a large percentage of the overall energy usage at accelerator laboratories, methods to improve upon the state-of-the-art in pulsed high-power sources are desired. This paper presents a technique for self-biasing the stages in a multistage depressed collector. With this technique, the energy lost during the rise and fall times of the pulse can be recovered, separate power supplies are not needed, and existing modulators can be retrofitted. Calculations show that significant cost savings can be realized with the implementation of this device in high-power systems. In this paper, the technique is described along with experimental demonstration. (auth)

43 PARTICLE ACCELERATORS↗

Evaluation of Concentrated Piperazine for CO 2 Capture from Coal-Fired Flue Gas (Final Report, REV0)

Concentrated piperazine (PZ) is a novel solvent being developed by the University of Texas at Austin (UT) for CO 2 capture from coal-fired power plants. The high thermal stability of PZ permits solvent regeneration at higher temperature (150 °C) and pressure, reducing compression capital and operating costs. The purpose of Cooperative Agreement DE-FE0005654, Evaluation of Concentrated Piperazine for CO 2 Capture from Coal-Fired Flue Gas , was to gain operational experience using PZ solvent to absorb CO 2 and explore novel, high-temperature processes for solvent regeneration. The pilot-scale test campaigns funded under this project have resulted in the continual improvement in the heat duty of the regeneration systems and solvent and equipment optimization. This document summarizes the results from the Phase 1 (2011, 2013 and 2015) and Phase 2 (2018) test campaigns. In Phase 1, the campaign was conducted on synthetic flue gas at the University of Texas’ Separations Research Program (SRP) facility to investigate CO 2 capture with 5 and 8 molal (5$m$ and 8$m$) PZ and two-stage flash (2SF) and advanced flash stripper (AFS) regeneration designs. Phase 1 testing also investigated techniques for measuring amine aerosol that can be generated during operation, and the effect of absorber operating conditions and sulfur containing compounds in the flue gas on aerosol generation. This testing showed that the AFS represents an optimized amine regeneration system with superior energy performance and simple operability over the 2SF or a simple stripper (SS), that 5$m$ PZ provides an economic and operability advantage over 8$m$ PZ, and that phase doppler interferometry (PDI) can provide useful particle size information on amine aerosol. In Phase 2, the campaign was conducted on coal-fired flue gas at the National Carbon Capture Center (NCCC) to investigate CO 2 capture with 5$m$ PZ and the AFS. The PZ solvent was also used with an existing SS at the NCCC to provide comparison with the AFS performance. Additionally, the campaign investigated the effect of flue gas SO 3 on amine aerosol from the CO 2 absorber. The NCCC pilot plant testing demonstrated the robustness of the PZ solvent and the high energy performance of the AFS provided significant improvements in energy performance over the conventional SS for PZ and other solvents, and approached the DOE’s economic targets for second generation carbon capture technologies. Extended testing allowed the project team to demonstrate reliable long-term operation of this novel regeneration technology and solvent combination. EPRI, Luminant, B&W, LG&E, Chevron, Southern Company, and UT are project co-funders. UT and Trimeric were project team members. URS Group was the prime contractor.

20 FOSSIL-FUELED POWER PLANTS↗