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At least 181 records · Page 10

All sources NASA NTRS DOE OSTI

NASA NTRS2015

A Comparison of Three Algorithms for Orion Drogue Parachute Release

The Orion Multi-Purpose Crew Vehicle is susceptible to ipping apex forward between drogue parachute release and main parachute in ation. A smart drogue release algorithm is required to select a drogue release condition that will not result in an apex forward main parachute deployment. The baseline algorithm is simple and elegant, but does not perform as well as desired in drogue failure cases. A simple modi cation to the baseline algorithm can improve performance, but can also sometimes fail to identify a good release condition. A new algorithm employing simpli ed rotational dynamics and a numeric predictor to minimize a rotational energy metric is proposed. A Monte Carlo analysis of a drogue failure scenario is used to compare the performance of the algorithms. The numeric predictor prevents more of the cases from ipping apex forward, and also results in an improvement in the capsule attitude at main bag extraction. The sensitivity of the numeric predictor to aerodynamic dispersions, errors in the navigated state, and execution rate is investigated, showing little degradation in performance.

Matz, Daniel A.↗

NASA NTRSDate not supplied

Force Measurements to Excavate Lightly Compacted Granular Lunar Soil Simulant GRC-3B

The Advanced Planetary Excavator (APEX) was used to measure the forces to dig in lightly compacted granular lunar soil simulant GRC-3B with a 21.6-cm wide bucket which has a 30° leading edge. Long linear digs at 10-cm depth and variable rake angle were conducted to determine the reproducibility of the soil preparation. Cone penetrometer tests measured the soil condition prior to each test. Linear trajectories at 10-cm depth with rake angles of 10, 20, and 30 degrees show horizontal force increased and vertical force decreased as rake angle increased. NASA Glenn’s excavation laboratory and the APEX provide the capability of repeatable excavation trajectories and consistent soil preparation. The APEX can provide both linear and arc trajectories to measure excavation forces required for a small rover pushing a blade or a bucket on the lunar surface. To determine scaling effects, the forces to excavate with different sized implements can be measured directly

Margaret P Proctor↗

DOE OSTI2016

Pyramidal space frame and associated methods

A space frame having a high torsional strength comprising a first square bipyramid and two planar structures extending outward from an apex of the first square bipyramid to form a "V" shape is disclosed. Some embodiments comprise a plurality of edge-sharing square bipyramids configured linearly, where the two planar structures contact apexes of all the square bipyramids. A plurality of bridging struts, apex struts, corner struts and optional internal bracing struts increase the strength and rigidity of the space frame. In an embodiment, the space frame supports a solar reflector, such as a parabolic solar reflector. Methods of fabricating and using the space frames are also disclosed.

14 SOLAR ENERGY↗

DOE OSTI2017

M3 Wave DMP/APEX WEC Laboratory Testing Content Model

Laboratory Testing Content Model of Hinsdale 1:5 testing of thirteen different APEX I and APEX II configurations in the Long Wave Flume with a 0.5m deep sediment bed and under 4 different wave conditions.

16 TIDAL AND WAVE POWER↗

DOE OSTI2017

XPRESS: eXascale PRogramming Environment and System Software, Final Report

The University of Oregon (UO) was a partner in the XPRESS project together with Sandia National Laboratories (SNL), Indiana University (IU), Lawrence Berkeley National Laboratory (LBL), Louisiana State University (LSU), Oak Ridge National Laboratory (ORNL), University of Houston (UH), and University of North Carolina (RENCI). UO's objective in the project was to develop "APEX (Asynchronous Performance Environment for eXascale)": performance measurement, analysis, feedback and control infrastructure to asynchronous tasking runtimes, specifically HPX (LSU) and HPX-5 (IU). During the project period, our efforts focused on the need to measure complex tasking models where the traditional instrumentation methods would not work due to an absent/meaningless call-path context and runtime control of task pre-emption and resumption, usually on a different operating system thread. In addition to the challenges of performance measurement, we developed a framework to provide information from all levels of the stack (hardware, operating system, runtime, application) to a feedback & control mechanism for controlling concurrency, task granularity, networking parameters, and other aspects of execution in order to improve execution performance, throughput and/or efficiency. UO demonstrated these developments on leading edge HPC machines at large scale, including a 2017 Gordon Bell submission in which APEX was used to optimize key bottlenecks in an astrophysics application. The following final report summarizes our accomplishments during the XPRESS project.

99 GENERAL AND MISCELLANEOUS↗

DOE OSTI2021

Preserved and variable spatial‐chemical changes of lipids across tomato leaves in response to central vein wounding reveals potential origin of linolenic acid in signal transduction cascade

Abstract Membrane lipids serve as substrates for the generation of numerous signaling lipids when plants are exposed to environmental stresses, and jasmonic acid, an oxidized product of 18‐carbon unsaturated fatty acids (e.g., linolenic acid), has been recognized as the essential signal in wound‐induced gene expression. Yet, the contribution of individual membrane lipids in linolenic acid generation is ill‐defined. In this work, we performed spatial lipidomic experiments to track lipid changes that occur locally at the sight of leaf injury to better understand the potential origin of linolenic and linoleic acids from individual membrane lipids. The central veins of tomato leaflets were crushed using surgical forceps, leaves were cryosectioned and analyzed by two orthogonal matrix‐assisted laser desorption/ionization mass spectrometry imaging platforms for insight into lipid spatial distribution. Significant changes in lipid composition are only observed 30 min after wounding, while after 60 min lipidome homeostasis has been re‐established. Phosphatidylcholines exhibit a variable pattern of spatial behavior in individual plants. Among lysolipids, lysophosphatidylcholines strongly co‐localize with the injured zone of wounded leaflets, while, for example, lysophosphatidylglycerol (LPG) (16:1) accumulated preferentially toward the apex in the injured zone of wounded leaflets. In contrast, two other LPGs (LPG [18:3] and LPG [18:2]) are depleted in the injured zone. Our high‐resolution co‐localization imaging analyses suggest that linolenic acids are predominantly released from PCs with 16_18 fatty acid composition along the entire leaf, while it seems that in the apex zone PG (16:1_18:3) significantly contributes to the linolenic acid pool. These results also indicate distinct localization and/or substrate preferences of phospholipase isoforms in leaf tissue.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2013

Endovascular Treatment of Two Pseudoaneurysms Originating From the Left Ventricle

A 67-year-old woman resented with an acute type A aortic dissection, which was treated surgically with aortic valve replacement as a composite graft with reimplantation of the coronary arteries. At the end of surgery, a left-ventricular venting catheter was placed through the apex and closed with a buffered suture. Consecutive computed tomography (CT) examinations verified a growing apex pseudoaneurysm. Communication between the ventricle and the pseudoaneurysm was successfully closed with an Amplatz septal plug by the transfemoral route. Follow-up CT showed an additional pseudoaneurysm, which also was successfully closed using the same method.

62 RADIOLOGY AND NUCLEAR MEDICINE↗

DOE OSTI2018

Apical sparing pattern of left ventricular myocardial {sup 99m}Tc-HMDP uptake in patients with transthyretin cardiac amyloidosis

Background: A decreased longitudinal strain in basal segments with a base-to-apex gradient has been described in patients with cardiac amyloidosis (CA). Objectives: Aim was to investigate the left ventricular (LV) regional distribution of early-phase {sup 99m}Tc-Hydroxymethylene diphosphonate ({sup 99m}Tc-HMDP) uptake in patients with transthyretin-related cardiac amyloidosis (TTR-CA). Methods: All patients underwent a whole-body planar {sup 99m}Tc-HMDP scintigraphy acquired at 10-min post-injection (early-phase) followed by a thorax SPECT/CT. The segmental uptake (expressed as % of maximal myocardial HMDP uptake) was investigated on the AHA 17-segment model and 3-segment model (basal, mid-cavity, apical). Results: Sixty-one TTR-CA patients were included of whom 29 were wild-type (wt-TTR-CA) and 32 had hereditary TTR-CA (m-TTR-CA). Early myocardial {sup 99m}Tc-HMDP uptake occurred in all TTR-CA. In all patients, segmental analysis of the LV myocardial distribution of {sup 99m}Tc-HMDP uptake showed an increased median uptake (interquartile range) in basal/mid-cavity segments compared to the lowest median uptake of apical segments (respectively, 79% [72%-86%] vs. 72% [64%-81%]; P < 10{sup −6}). This pattern was similar in wt-TTR-CA group (78% [70%-84%] vs. 70% [61%-81%]; P < 10{sup −6}), in m-TTR-CA group (80% [74%-86%] vs. 73 [66%-82%]; P < 10{sup −7}) and remained constant independently of the TTR mutation subtype with P ranging 10{sup −5} to 0.03. Conclusions: Early-phase myocardial scintigraphy identified regional distribution of {sup 99m}Tc-HMDP uptake characterized by a base-to-apex gradient, corroborating echocardiographic, and cardiac magnetic resonance findings. This apical sparing pattern was similar across TTR-CA and TTR mutation subtypes.

62 RADIOLOGY AND NUCLEAR MEDICINE↗

DOE OSTI2024

Effect of micro-fin tube geometry parameters on evaporator material savings

A Performance Evaluation Criteria (PEC) analysis is presented that explores the influence of the micro-fin tube geometry on the required material volume. The analysis was done using a local flow boiling model, which can quantify the effect of fin parameters and the tube diameter. The PEC was done while requiring that the compared surfaces satisfy the same heat duty and pressure drop. The following tube parameters and ranges were explored: tube diameter (3 mm ≤ D o ≤ 6 mm), fin base thickness (0.12 mm ≤ t bf ≤ 0.29 mm), helix angle (6° ≤ α ≤ 30°), fin apex angle (11° ≤ β ≤ 22°), total number of fins (43 ≤ n f ≤ 70), and the fin height (0.11 mm ≤ e ≤ 0.3 mm). The tube that provided the smallest material requirements within the examined parameter ranges had: D o = 3 mm, t bf = 0.12 mm, α = 6°, β = 11°, n f = 43, and e = 0.3 mm. In general, small D o and t bf and large n f and e provided the best performance and work to minimize the required material volume to provide a given heat duty and pressure drop. The helix and the fin-tip apex angles were found to have very little influence on the performance for the examined range of parameters and angles associated with the lowest production cost should be chosen.

Evaporation↗

DOE OSTI2016

MRI-Based Evaluation of the Vaginal Cuff in Brachytherapy Planning: Are We Missing the Target?

Purpose: Although recurrences and toxicity occur after vaginal cuff (VC) brachytherapy, little is known about dosimetry due to the inability to clearly visualize the VC on computed tomography (CT). T2-weighted (T2W) magnetic resonance imaging (MRI) is superior to CT in this setting, and we hypothesized that it could provide previously unascertainable dosimetric information. Methods and Materials: In a cohort of 32 patients who underwent cylinder-based brachytherapy for endometrial cancer with available MR simulation images, the VC was retrospectively contoured on T2W images, and cases were replanned to treat the upper VC to a dose of 7 Gy/fraction prescribed to 5 mm. Relevant dose-volume parameters for the VC were calculated. Results: T2W MRI identified significant underdosing not observed on CT or T1-weighted imaging. Over two-thirds (69%) of patients had at least 1 cm{sup 3} of VC that received less than 75% of the prescription dose and half (50%) of patients had a least 1 cm{sup 3} of VC that received less than 50% of the prescription dose. The mean minimum point dose to the VC was 2.4 Gy, or 34% of the intended prescription dose (range: 0.53-6.4 Gy). Conclusions: We identified previously unreported VC underdosing in over two-thirds of our patients, with most of these patients having volumes of undistended VC that received less than half of the prescription dose. The maximum dimension was along the craniocaudal axis in some patients or left-right/anterior-posterior axis in others, suggesting that suture material may be restricting access to the vaginal apex and that alternative applicators may be needed when the diameter of the apex is larger than the introitus. Additional follow-up will be needed to determine whether underdosing is associated with isolated VC failure or whether low failure rates across the cohort suggest that some patients are being exposed to excessive dose and unnecessary risk of toxicity.

62 RADIOLOGY AND NUCLEAR MEDICINE↗

DOE OSTI2013

The synthesis and characterisation of LaCa{sub 2}Fe{sub 2}GaO{sub 8}

The synthesis and characterisation of LaCa{sub 2}Fe{sub 2}GaO{sub 8} is described. Neutron powder diffraction data reveal LaCa{sub 2}Fe{sub 2}GaO{sub 8} adopts an anion-vacancy ordered, 'triple layer' structure consisting of an OOT{sub L}OOT{sub R} stacking sequence of layers of (Fe/Ga)O{sub 6} octahedra (O) and (Fe/Ga)O{sub 4} tetrahedra (T), related to that of the 4-layer brownmillerite structures (a=5.4784(1) A, b=22.6780(4) A, c=5.6007(1) A, space group Pbma). The apex-linked chains of tetrahedra within structure of LaCa{sub 2}Fe{sub 2}GaO{sub 8} exhibit a cooperative twisting distortion which alternates in direction between adjacent layers of tetrahedra, the first time such an arrangement has been seen in a triple-layer phase. Magnetisation and neutron diffraction data reveal that LaCa{sub 2}Fe{sub 2}GaO{sub 8} exhibits two magnetic ordering transitions. On cooling below 550 K the phase adopts a state with short range antiferromagnetic coupling within each double layer of (Fe/Ga)O{sub 6} octahedra, but only weak coupling between layers. On cooling below 470 K full three-dimensional, G-type antiferromagnetic order is observed. - Graphical abstract: LaCa{sub 2}Fe{sub 2}GaO{sub 8} adopts an anion-vacancy ordered, 'triple layer' structure consisting of an OOT{sub L}OOT{sub R} stacking sequence of layers of FeO{sub 6} octahedra (O) and GaO{sub 4} tetrahedra (T), in which the chains of apex-linked tetrahedra exhibit a cooperative twisting distortion which alternates in direction between adjacent layers of tetrahedra. On cooling below 550 K, LaCa{sub 2}Fe{sub 2}GaO{sub 8} adopts a state with strong two-dimensional antiferromagnetic order within each double layer of FeO{sub 6} octahedra, but only weak coupling between layers. On cooling below 470 K full three-dimensional antiferromagnetic order is observed. Highlights: Black-Right-Pointing-Pointer LaCa{sub 2}Fe{sub 2}GaO{sub 8} exhibits a novel anion-vacancy ordered triple-layer structure type. Black-Right-Pointing-Pointer New structure variant rationalised on the basis of strucutral parameters. Black-Right-Pointing-Pointer Multiple magnetic transitions: paramagnetic-two-dimensional-three-dimensional.

36 MATERIALS SCIENCE↗

DOE OSTI2014

Dosimetric differences between intraoperative and postoperative plans using Cs-131 in transrectal ultrasound–guided brachytherapy for prostatic carcinoma

The aim of the study was to investigate the differences between intraoperative and postoperative dosimetry for transrectal ultrasound–guided transperineal prostate implants using cesium-131 ({sup 131}Cs). Between 2006 and 2010, 166 patients implanted with {sup 131}Cs had both intraoperative and postoperative dosimetry studies. All cases were monotherapy and doses of 115 were prescribed to the prostate. The dosimetric properties (D{sub 90}, V{sub 150}, and V{sub 100} for the prostate) of the studies were compared. Two conformity indices were also calculated and compared. Finally, the prostate was automatically sectioned into 6 sectors (anterior and posterior sectors at the base, midgland, and apex) and the intraoperative and postoperative dosimetry was compared in each individual sector. Postoperative dosimetry showed statistically significant changes (p < 0.01) in every dosimetric value except V{sub 150}. In each significant case, the postoperative plans showed lower dose coverage. The conformity indexes also showed a bimodal frequency distribution with the index indicating poorer dose conformity in the postoperative plans. Sector analysis revealed less dose coverage postoperatively in the base and apex sectors with an increase in dose to the posterior midgland sector. Postoperative dosimetry overall and in specific sectors of the prostate differs significantly from intraoperative planning. Care must be taken during the intraoperative planning stage to ensure complete dose coverage of the prostate with the understanding that the final postoperative dosimetry will show less dose coverage.

61 RADIATION PROTECTION AND DOSIMETRY↗

DOE OSTI2019

RF design of APEX2 two-cell continuous-wave normal conducting photoelectron gun cavity based on multi-objective genetic algorithm

High brightness, high repetition rate electron beams are key components for optimizing the performance of next generation scientific instruments, such as MHz-class X-ray Free Electron Laser (XFEL) and Ultra-fast Electron Diffraction/Microscopy (UED/UEM). In the Advanced Photo-injector EXperiment (APEX)at Berkeley Lab, a photoelectron gun based on a 185.7 MHz normal conducting re-entrant RF cavity, has been proven to be a feasible solution to provide high brightness, high repetition rate electron beam for both XFEL and UED/UEM. Based on the success of APEX, a new electron gun system, named APEX2, has been under development to further improve the electron beam brightness. For APEX2, we have designed a new 162.5 MHz two-cell photoelectron gun and achieved a significant increase on the cathode launching field and the beam exit energy. For a fixed charge per bunch, these improvements will allow for the emittance reduction and hence to an increased beam brightness. The design of APEX2 gun cavity is a complex problem with multiple design goals and restrictions, some even competing each other. In conclusion, for a systematic and comprehensive search for the optimized cavity geometry, we have developed and implemented a novel optimization method based on the Multi-Objective Genetic Algorithm (MOGA).

47 OTHER INSTRUMENTATION↗

DOE OSTI2015

Bioinformatic analysis of neurotropic HIV envelope sequences identifies polymorphisms in the gp120 bridging sheet that increase macrophage-tropism through enhanced interactions with CCR5

Macrophages express low levels of the CD4 receptor compared to T-cells. Macrophage-tropic HIV strains replicating in brain of untreated patients with HIV-associated dementia (HAD) express Envs that are adapted to overcome this restriction through mechanisms that are poorly understood. Here, bioinformatic analysis of env sequence datasets together with functional studies identified polymorphisms in the β3 strand of the HIV gp120 bridging sheet that increase M-tropism. D197, which results in loss of an N-glycan located near the HIV Env trimer apex, was detected in brain in some HAD patients, while position 200 was estimated to be under positive selection. D197 and T/V200 increased fusion and infection of cells expressing low CD4 by enhancing gp120 binding to CCR5. These results identify polymorphisms in the HIV gp120 bridging sheet that overcome the restriction to macrophage infection imposed by low CD4 through enhanced gp120–CCR5 interactions, thereby promoting infection of brain and other macrophage-rich tissues. - Highlights: • We analyze HIV Env sequences and identify amino acids in beta 3 of the gp120 bridging sheet that enhance macrophage tropism. • These amino acids at positions 197 and 200 are present in brain of some patients with HIV-associated dementia. • D197 results in loss of a glycan near the HIV Env trimer apex, which may increase exposure of V3. • These variants may promote infection of macrophages in the brain by enhancing gp120–CCR5 interactions.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2017

Effect of Single-Layer MoS 2 on the Geometry, Electronic Structure, and Reactivity of Transition Metal Nanoparticles

We present results of ab initio density functional theory (DFT) based calculations of the geometry, electronic structure, and reactivity of subnanometer-sized (29-atom) transition metal nanoparticles (NPs) (Cu 29 , Ag 29 , and Au 29 ) supported on single-layer MoS 2 . As compared to its pristine form, defect-laden MoS 2 (with a S vacancy row) has relatively larger effect on the above properties of the NPs. The NPs bind more strongly on defect-laden than on pristine MoS 2 (in the order Cu 29 > Ag 29 > Au 29 ), confirming the important role of vacancies in stabilizing the NPs on the support. The presence of vacancies also leads to an increase in charge transfer from the NPs to MoS 2 (with the same elemental trend as for their binding energy) and to a shift of the d-band center of the NPs further toward the Fermi level, in turn influencing their propensity toward chemical activity. We examine the adsorption and dissociation of O 2 as the prototype reactions and find that there is no barrier for O 2 to adsorb on top of an atom at the NP apex, where the frontier orbitals are localized, and that the dissociation channel proceeds through a chemisorbed state. The presence of the support leads to increase in the number of sites at which O 2 can adsorb with similar binding energy (<0.1 eV difference). Interestingly, energy barriers for both dissociation and recombination of O 2 , when adsorbing at the NP apex, increase in the presence of the MoS 2 support. However, since the increase in the barrier for recombination is much larger than for dissociation, the latter should be more favored. Lastly, in particular, for defect-laden MoS 2 supported Au 29 the recombination faces a barrier of 1.36 eV whereas the dissociation does 0.5 eV, implying that the defect-laden support may significantly improve the catalytic performance of Au29 toward oxidation reaction.

36 MATERIALS SCIENCE↗

DOE OSTI2021

Imaging Plasmons with Sub-2 nm Spatial Resolution via Tip-Enhanced Four-Wave Mixing

Four-wave mixing at plasmonic tip-sample nanojunctions may be used to visualize plasmonic fields with sub-2nm spatial resolution under ambient laboratory conditions. We illustrate the latter using a gold-coated atomic force microscopy probe irradiated with a pair of near-IR femtosecond laser pulses and used to interrogate plasmonic gold nanoplates and silver nanocubes. Through diagnostic polarization-dependent tip-only measurements, we illustrate that the 4-wave mixing signal is localized to the tip apex. The apex-bound signal is further enhanced when the tip is located near plasmonic nanoparticles. Overall, this work paves the way for visualizing coherent electronic and vibrational dynamics with joint femtosecond temporal and few-nanometer spatial resolution under ambient conditions.

Wang, Chih-Feng↗

DOE OSTI2018

Correlated High-Pressure Phase Sequence of VO 2 under Strong Compression

Understanding how the structures of a crystal behave under compression is a fundamental issue both for condensed matter physics and for geoscience. Traditional description of a crystal as the stacking of a unit cell with special symmetry has gained much success on the analysis of physical properties. Unfortunately, it is hard to reveal the relationship between the compressed phases. Taking the family of metal dioxides (MO 2 ) as an example, the structural evolution, subject to fixed chemical formula and highly confined space, often appears as a set of random and uncorrelated events. In this work, we provide an alternative way to treat the crystal as the stacking of the coordination polyhedron and then discover a unified structure transition pattern, in our case VO 2 . X-ray diffraction (XRD) experiments and first-principles calculations show that the coordination increase happens only at one apex of the V-centered octahedron in an orderly fashion, leaving the base plane and the other apex topologically intact. The polyhedron evolves toward increasing their sharing, indicating a general rule for the chemical bonds of MO 2 to give away the ionicity in exchange for covalency under pressure.

36 MATERIALS SCIENCE↗

DOE OSTI2013

Microelectrode for energy and current control of nanotip field electron emitters

Emerging experiments and applications in electron microscopy, holography, and diffraction benefit from miniaturized electron guns for compact experimental setups. We present a highly compact microelectrode integrated field emitter that consists of a tungsten nanotip coated with a few micrometers thick polyimide film followed by a several nanometers thick gold film, both positioned behind the exposed emitter apex by approximately 10–30 μm. The control of the electric field strength at the nanometer scale tip apex allows suppression, extraction, and energy tuning of field-emitted electrons. The performance of the microelectrode is demonstrated experimentally and supported by numerical simulations.

77 NANOSCIENCE AND NANOTECHNOLOGY↗