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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

A Printing-Centric Approach to the Electrostatic Modification of Polymer/Clay Composites for Use in 3D Direct-Ink Writing

Polymer/clay composite inks are exceptionally useful materials for fabrication processes based on 3D direct-ink writing, however, there remains an insufficient understanding of how their physiochemical dynamics impact printability. Using a model system, N-isopropylacrylamide/Laponite, the electrostatic interactions between Laponite platelets are modified to tune critical rheological properties in order to improve printability. Rheological measurements and X-ray scattering experiments are carried out to monitor the nano/micro-structural dynamics and complex physicochemical interactions of Laponite as it impacts complex modulus in the linear region, flow behavior, thixotropy, and yield stress of the composite ink. Modification of the electrostatic interactions between platelets reduces the yield stress of the material, while maintaining a complex microstructure that allows for sufficient recovery times upon removal of stress to form stable, and thus printable, filaments. A printing-centric approach is established based on a fundamental understanding of electrostatic inter-particle interactions, harnessing the innate microstructure of Laponite in 3D direct-ink writing of composites.

Rauzan, Brittany M.↗
DOE OSTI2016

Safety and Feasibility of Transradial Access for Visceral Interventions in Patients with Thrombocytopenia

PurposeTransradial access (TRA) has shown lower morbidity and decreased bleeding complications compared to transfemoral access. This study evaluates the safety and feasibility of TRA in thrombocytopenic patients undergoing visceral interventions.Methods and MaterialsPatients who underwent visceral interventions via the radial artery with platelet count less than or equal to 50,000/µL were included in the study. Outcome variables included technical success, access site, bleeding, transfusion, and neurological complications.ResultsFrom July 1, 2012, to May 31, 2015, a total of 1353 peripheral interventions via TRA were performed, of which 85 procedures were performed in 64 patients (mean age 62.2 years) with a platelet count <50,000/µL (median 39,000/µL). Interventions included chemoembolization (n = 46), selective internal radiation therapy (n = 30), and visceral embolization (n = 9). Technical success was 97.6 % with two cases of severe vessel spasm requiring ipsilateral femoral crossover. There was no major access site, bleeding, or neurological adverse events at 30 days. Minor access site hematomas occurred in five cases (5.9 %) and were treated conservatively in all cases. Pre-procedural platelet transfusions were administered in 23 (27.1 %) cases. There was no statistically significant difference in access site or bleeding complications between the transfused and nontransfused groups.ConclusionsTransradial visceral interventions in patients with thrombocytopenia are both feasible and safe, possibly without the need for platelet transfusions.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2018

Adamts18 deficiency increases arterial thrombus formation associated with vascular defects in mice

Highlights: • We validated ADAMTS18 modulates thrombosis using Adamts18 KO mice. • We validated ADAMTS18 affects carotid remodeling in mice. • We validated ADAMTS18 exerts little effects on platelet functions. • The increased thrombosis in Adamts18 KO mice is associated with the vascular defects. ADAMTS18 is a member of a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTSs) that are known for their crucial role in development, angiogenesis, inflammation and coagulation. It was previously reported that ADAMTS18 cleaved by thrombin induced platelet fragmentation, through which thrombus were dissolved. However, it remains unclear whether this represents a dominant physiologic mechanism controlling thrombus growth in vivo. Here, we used an established Adamts18 knockout (KO) mouse model to determine its function in thrombus formation. ADAMTS18 deficiency accelerated FeCl{sub 3}-induced carotid artery thrombosis and aggravated postischemic cerebral infarction in mice. However, this accelerated thrombus phenotype in Adamts18 KO mice was not due to the lack of ADAMTS18-mediated-platelet fragmentation. Moreover, Adamts18 deficiency exerted little effects on mouse platelet functions. The underlying molecular mechanisms could be attributed in part to the abnormal vascular remodeling, including deficiency of carotid body (glomus) and aberrant carotid basal lamina. These results indicate a novel function of ADAMTS18 in vascular remodeling and associated thrombus formation.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2025

Coarse-grained simulation of colloidal self-assembly, cation exchange, and rheology in Na/Ca smectite clay gels

Knowledge Gap: The aggregation of clay minerals—layered silicate nanoparticles—strongly impacts fluid flow, solute migration, and solid mechanics in soils, sediments, and sedimentary rocks. Experimental and computational characterization of clay aggregation is inhibited by the delicate water-mediated nature of clay colloidal interactions and by the range of spatial scales involved, from 1 nm thick platelets to flocs with dimensions up to micrometers or more. Simulations: Using a new coarse-grained molecular dynamics (CGMD) approach, we predicted the microstructure, dynamics, and rheology of hydrated smectite (more precisely, montmorillonite) clay gels containing up to 2,000 clay platelets on length scales up to 0.1 μm. Further, simulations investigated the impact of simulation time, platelet diameters (6 to 25nm), and the ratio of Na to Ca exchangeable cations on the assembly of tactoids (i.e., stacks of parallel clay platelets) and larger aggregates (i.e., assemblages of tactoids). We analyzed structural features including tactoid size and size distribution, basal spacing, counterion distribution in the electrical double layer, clay association modes, and the rheological properties of smectite gels. Findings: Our results demonstrate new potential to characterize and understand clay aggregation in dilute suspensions and gels on a scale of thousands of particles with explicit representation of counterion clouds and with accuracy approaching that of all-atom molecular dynamics (MD) simulations. For example, our simulations predict the strong impact of Na/Ca ratio on clay tactoid formation and the shear-thinning rheology of clay gels.

42 ENGINEERING↗
DOE OSTI2016

“Non-hydrolytic” sol–gel synthesis of molybdenum sulfides

Non-hydrolytic sol–gel reactions provide a low temperature solution based synthetic approach to solid-state materials. In this paper, reactions between molybdenum chloride and hexamethyldisilthiane in chloroform were explored, which gave access to both MoS{sub 2} and Mo{sub 2}S{sub 3} after heat treatment of as-recovered amorphous samples to 600–1000 °C. Interesting morphologies were obtained for MoS{sub 2}, ranging from fused spherical particles to well-defined nanoplatelets and nanoflakes. Both 2H- and 3R-MoS{sub 2} were observed, which formed thin hexagonal and triangular platelets, respectively. The platelets exhibited thicknesses of 10–30 nm, which corresponds to 15–50 MoS{sub 2} layers. No attempts to prevent agglomeration were made, however, well separated platelets were observed for many samples. Heating at 1000 °C led to formation of Mo{sub 2}S{sub 3} for samples that showed well-defined MoS{sub 2} at lower temperatures, while less crystalline samples had a tendency to retain the MoS{sub 2} structure. - Graphical abstract: Overlay of variable pressure X-ray diffraction data of Al{sub 2}Mo{sub 3}O{sub 12} collected in a diamond anvil cell. Both subtle and discontinuous phase transitions are clearly observed. - Highlights: • Molybdenum sulfides were prepared by non-hydrolytic sol–gel chemistry. • Nanocrystalline 3R-MoS{sub 2} and 2H-MoS{sub 2}, and microcrystalline Mo{sub 2}S{sub 3} were obtained. • Particle morphology correlated strongly with crystalline phases. • Ultrathin platelets with limited tendency to agglomerate were recovered.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Influence of Clay size on corrosion protection by Clay nanocomposite thin films

In this work, the influence of clay platelet size on the corrosion barrier performance of highly-aligned polymer clay nanocomposite (PCN) thin films was examined. Layer-by-layer (LbL) deposition of alternating branched polyethylenimine (PEI) and either laponite (LAP), montromorillonite (MMT) or vermiculite (VMT) clay platelets were assembled on mild steel plates to obtain 20 bilayer (BL) films and cross-linked using glutaraldehyde after deposition. The clay platelets were chosen based on their aspect ratio, approximately 30:1, 400:1, and 2000:1, respectively. Electrochemical impedance spectroscopy of the coated steel plates during immersion showed corrosion rates and coating permeability followed LAP > MMT > VMT for up to 7 days of exposure in 0.6 M NaCl. The PEI/VMT films, ~250 nm thick, slowed corrosion by a factor of >1000 compared to bare steel. The results support the premise that high aspect ratio clay platelets can improve the corrosion barrier efficacy of LbL PCN films by decreasing film permeability and provide exceptional protection to steel in saline environments compared to other thin multilayer coatings and pretreatments.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Pathways of Growth of CdSe Nanocrystals from Nucleant (CdSe) 34 Clusters

The first steps in the growth of quantum platelets from the wurtzite-type (CdSe) 34 clusters are simulated using density functional theory with the generalized gradient approximation. The nucleant (CdSe) 34 cluster has been chosen for simulations because it has experimentally been discovered to be a magic-size nucleant for the low-temperature growth of CdSe quantum platelets. According to the results of our calculations, the growth is anisotropic and favors the (0001) direction, which is consistent with the experimental findings. We discover that growth in other directions lowers the symmetry of the resulting clusters and that the asymmetrical positioning of rhombic defects causes the growing platelet to bend due to the surface strain, which appears to be the limiting factor of growth. An alternative pathway to quantum platelet growth could proceed via the decomposition of (CdSe) 34 to (CdSe) 13 in electron-donating media, which was found to be thermodynamically favorable. Side product (CdSe) 21 generated in this process is capable of growing via hexagonal stacking as well as propagating as a nanotube.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Laponite-Incorporated UiO-66-NH2-Polyethylene Oxide Composite Membranes for Protection against Chemical Warfare Agent Simulants

A strategy is developed to enhance the barrier protection of polyethylene oxide (PEO)-metal–organic framework (MOF) composite films against chemical warfare agent simulants. To achieve enhanced protection, an impermeable high-aspect-ratio filler in the form of Laponite RD (LRD) clay platelets was incorporated into a composite PEO film containing MOF UiO-66-NH 2 . The inclusion of the platelets aids in mitigating permeation of inert hydrocarbons (octane) and toxic chemicals (2-chloroethyl ethyl sulfide, 2-CEES) of dimensions/chemistry similar to prominent vesicant threats while still maintaining high water vapor transport rates (WVTR). By utilizing small-angle neutron scattering, small-angle X-ray scattering, and wide-angle X-ray scattering, the LRD platelet alignment of the films was determined, and the structure of the films was correlated with performance as a barrier material. Performance of the membranes against toxic chemical threats was assessed using permeation testing of octane and 2-CEES, a common simulant for the vesicant mustard gas, and breathability of the membranes was assessed using WVTR measurements. To assess their robustness, chemical exposure (in situ diffuse reflectance infrared Fourier transform spectroscopy) and mechanical (tensile strength) measurements were also performed. It was demonstrated that the barrier performance of the film upon inclusion of the LRD platelets exceeds that of other MOF-polymer composites found in the literature and that this approach establishes a new path for improving permselective materials for chemical protection applications.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Mutational Constraints on Local Unfolding Inhibit the Rheological Adaptation of von Willebrand Factor

Unusually large von Willebrand factor (VWF), the first responder to vascular injury in primary hemostasis, is designed to capture platelets under the high shear stress of rheological blood flow. In type 2M von Willebrand disease, two rare mutations (G1324A and G1324S) within the platelet GPIbα binding interface of the VWF A1 domain impair the hemostatic function of VWF. We investigate structural and conformational effects of these mutations on the A1 domain's efficacy to bind collagen and adhere platelets under shear flow. These mutations enhance the thermodynamic stability, reduce the rate of unfolding, and enhance the A1 domain's resistance to limited proteolysis. Collagen binding affinity is not significantly affected indicating that the primary stabilizing effect of these mutations is to diminish the platelet binding efficiency under shear flow. The better stability stems from the steric consequences of adding a side chain (G1324A) and additionally a hydrogen bond (G1324S) to His 1322 across the β2-β3 hairpin in the GPIbα binding interface, which restrains the conformational degrees of freedom and the overall flexibility of the native state. These studies reveal a novel rheological strategy in which the incorporation of a single glycine within the GPIbα binding interface of normal VWF enhances the probability of local unfolding that enables the A1 domain to conformationally adapt to shear flow while maintaining its overall native structure.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1992

Thermal/structural analysis of a transpiration cooled nozzle

The 8-foot High Temperature Tunnel (HTT) at LaRC is a combustion driven, high enthalpy blow down wind tunnel. In Mar. 1991, during check out of the transpiration cooled nozzle, pieces of platelets were found in the tunnel test section. It was determined that incorrect tolerancing between the platelets and the housing was the primary cause of the platelet failure. An analysis was performed to determine the tolerance layout between the platelets and the housing to meet the structural and performance criteria under a range of thermal, pressure, and bolt preload conditions. Three recommendations resulted as a product of this analysis.

Gregory, Peyton B.↗
NASA NTRS2003

Alumina-Reinforced Zirconia Composites

Alumina-reinforced zirconia composites, used as electrolyte materials for solid oxide fuel cells, were fabricated by hot pressing 10 mol percent yttria-stabilized zirconia (10-YSZ) reinforced with two different forms of alumina particulates and platelets each containing 0 to 30 mol percent alumina. Major mechanical and physical properties of both particulate and platelet composites including flexure strength, fracture toughness, slow crack growth, elastic modulus, density, Vickers microhardness, thermal conductivity, and microstructures were determined as a function of alumina content either at 25 C or at both 25 and 1000 C. Flexure strength and fracture toughness at 1000 C were maximized with 30 particulate and 30 mol percent platelet composites, respectively, while resistance to slow crack growth at 1000 C in air was greater for 30 mol percent platelet composite than for 30 mol percent particulate composites.

Choi, Sung R.↗
NASA NTRS1988

Serotonin, atherosclerosis, and collateral vessel spasm

Studies on animal models demonstrate that platelet products contribute to vascular spasm in ischemic syndromes and that this is reversible with administration of ketanserin and thromboxane synthesis inhibitors. Laboratory animals (dogs, rabbits, and rats) that had femoral artery ligations exhibited supersensitivity to serotonin within days in their collateral blood vessels. This supersensitivity lasted at least 6 months. The response to serotonin was reversed by ketanserin, but not by 5HT-1 antagonists. Supersensitivity does not extend to norepinephrine, and alpha blockers do not influence the response to serotonin. It appears that platelet activation by endothelial injury contributes to ischemia through blood vessel occlusion and vascular spasm. When platelet activation occurs in vivo, blood vessel occlusion and vascular spasm are reversible in part by using ketanserin or agents that block thromboxane synthesis or its action. Combining both classes of agents reverses spasm completely. These findings support existing evidence that platelet products contribute to vascular disease, and provide an approach to improved management with currently available pharmacologic agents.

Review, Tutorial↗
DOE OSTI2021

Enabling AI-Accelerated Multiscale Modeling of Thrombogenesis at Millisecond and Molecular Resolutions on Supercomputers

We report the first congruent integration of HPC, AI, and multiscale modeling (MSM) for solving a mainstream biomechanical problem of thrombogenesis involving 6 million particles at record molecular-scale resolutions in space and at simulation rates of milliseconds per day. The two supercomputers, the IBM Summit-like AiMOS and our University’s SeaWulf, are used for scalability analysis of, and production runs with, the LAMMPS with our customization and AI augmentation and they attained optimal simulation speeds of 3,077 µs/day and 266 µs/day respectively. The long-time and large scales simulations enable the first study of the integrated platelet flowing, flipping, aggregating dynamics in one dynamically-coupled production run. The platelets’ angular and translational speeds, membrane particles’ speeds, and the membrane stress distributions are presented for the analysis of platelets’ aggregations.

Zhu, Yicong↗
DOE OSTI2019

Hemobilia after CT-guided radiofrequency ablation of liver tumors: frequency, risk factors, and clinical significance

Purpose: The purpose of the study is to evaluate the frequency, risk factors, and clinical significance of hemobilia after percutaneous computed tomography (CT)-guided radiofrequency ablation (RFA) of liver tumors. Materials and methods: From January 2013 to September 2016, 195 patients received 267 sessions of CT-guided RFA for liver tumors at our institution. The CT images during and immediately after the RFA were retrospectively reviewed. The frequency of hemobilia development and clinical outcome of patients with hemobilia were studied. Risk factors were identified by comparison between the hemobilia and non-hemobilia groups using univariate and multivariate analysis. The clinical courses of patients with hemobilia were also reviewed. Results: The frequency of CT detected hemobilia after RFA was 8.2% (22/267). The majority of the clinical courses were self-limited. Univariate analysis showed that the tumor numbers (p = 0.015), the central type puncture track (p < 0.001), the length of the puncture track (p = 0.033), and the platelet count (p = 0.026) were significantly associated with the development of hemobilia. Multivariate analysis demonstrated that the central type puncture track (p < 0.024) and the platelet count (p = 0.023) were significant independent risk factors. Conclusion: Detection of hemobilia on CT images immediately after percutaneous RFA for liver tumors was not rare. Low platelet count and central type puncture track are independent risk factors. In most cases, hemobilia presented as a minor complication with favorable prognosis.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2018

Investigation of the Tribological Properties of AlxSi-1.2Fe(Mn) (x = 5-13 wt.%) Alloys

The effect of Fe-impurity and Mn modification on the sliding wear behavior of Al-xSi-1.2Fe(Mn) (x = 5-13 wt.%) alloys was investigated in dry sliding against AISI 52100 steel. According to the results, in the Si range of 5-9 wt.%, Fe-impurity promotes the formation of finely distributed β-Al{sub 5}FeSi intermetallics in the matrix increasing its hardness and potential to support the tribolayer leading to the improved wear characteristics. The presence of Fe in the composition of Al-(9-13)Si alloys, however, leads to the formation of primary β-platelets that their sizes and volume fractions increase with Si concentration. The formation of primary compounds increases the hardness, but makes the alloys less ductile and more vulnerable to microcracking and wear. Manganese modification converts the β-Fe platelets to the α-Al{sub 15}(Fe,Mn){sub 3}Si{sub 2} compounds with different morphologies. The substitution of fine β-platelets by α-Chinese scripts in Al-(5-9)Si-1.2FeMn alloys reduces the wear resistance, but the formation of primary α-compounds with star-like or polyhedral morphologies in Al-(9-13)Si-1.2FeMn alloys improves their wear characteristics. Moreover, it was found that the formation of Fe(Mn)-rich compounds affects the friction coefficient which is likely due to the fracture of particles in the subsurface region, their interaction with contacting surfaces, and their effect on the stability of the tribolayer.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Effect of TGFβ on calcium signaling in megakaryocytes

TGFβ is a powerful regulator of megakaryocyte maturation and platelet formation. As previously shown for other cell types, TGFβ may up-regulate the expression of the serum & glucocorticoid inducible kinase SGK1, an effect requiring p38 kinase. SGK1 has in turn recently been shown to participate in the regulation of cytosolic Ca{sup 2+} activity ([Ca{sup 2+}]{sub i}) in megakaryocytes and platelets. SGK1 phosphorylates the IκB kinase (IKKα/β), which in turn phosphorylates the inhibitor protein IκBα resulting in nuclear translocation of nuclear factor NFκB. Genes up-regulated by NFκB include Orai1, the pore forming ion channel subunit accomplishing store operated Ca{sup 2+} entry (SOCE). The present study explored whether TGFβ influences Ca{sup 2+} signaling in megakaryocytes. [Ca{sup 2+}]{sub i} was determined by Fura-2 fluorescence and SOCE from the increase of [Ca{sup 2+}]{sub i} following re-addition of extracellular Ca{sup 2+} after store depletion by removal of extracellular Ca{sup 2+} and inhibition of the sarcoendoplasmatic Ca{sup 2+} ATPase (SERCA) with thapsigargin (1 μM). As a result, TGFβ (60 ng, 24 h) increased SOCE, an effect significantly blunted by p38 kinase inhibitor Skepinone-L (1 μM), SGK1 inhibitor EMD638683 (50 μM) and NFκB inhibitor wogonin (100 μM). In conclusion, TGFβ is a powerful regulator of store operated Ca{sup 2+} entry into megakaryocytes, an effect mediated by a signaling cascade involving p38 kinase, SGK1 and NFκB. - Highlights: • TGFβ up-regulates store operated Ca{sup 2+} entry (SOCE) in megakaryocytes. • The effect of TGFβ on SOCE is blunted by p38 kinase inhibitor Skepinone-L. • The effect of TGFβ on SOCE is virtually abrogated by SGK1 inhibitor EMD638683. • The effect of TGFβ on SOCE is almost abolished by NFκB inhibitor wogonin. • The effect of TGFβ is expected to enhance sensitivity of platelets to activation.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

Macrophage infiltration regulates the adipose ECM reconstruction and the fibrosis process after fat grafting

Background: Fat grafting experiences a regeneration process from free lipoaspirate to intact adipose tissue. The adipose extracellular matrixes (ECM) provide the structure and biochemical support for surrounding cells; inflammatory cells, like macrophages, regulate the process. Our hypothesis states that transferred fat undergoes ECM remodeling after fat grafting and this process is regulated by macrophage infiltration. Methods: Lipoaspirate was injected subcutaneously into the back of nude mice. The micro-structure of the fat grafts was observed and evaluated using scanning electron microscope (SEM) and collagen I immunohistostaining. The gene transcription level of collagen proteins and the matrix metalloproteinases (MMPs) were assessed by qRT-PCR. Local injection of clodronate-encapsulated liposome was used to evaluate the role of macrophages of fat grafts at different stages in ECM remodeling, depletion of macrophages, at different time points (Week 1 and Week 4). Results: Results from the SEM analysis showed that liposuction caused severe damage to the ECM structure in freshly aspirated adipose tissue. On Day 1 post-transplantation, the surface of adipocytes was covered with platelets and this secreted fibrin network on the fat grafts. An integral adipose structure was already established with an intact ECM at the end of Week 1. The early depletion of macrophages remarkably hindered ECM reconstruction process by down-regulating the expression of collagen proteins and MMPs. Expression of Collagen I was significantly decreased after depletion of macrophages in both gene and protein levels. Results also showed that the depletion of macrophages at the later stage of fat grafting resulted in less fibrosis and capsule formation. Conclusion: Free fat aspirates undergo a prompt ECM reconstruction process and completed in the first week; this process can be initiated with platelets and mainly modulated by inflammatory cells such as macrophages. It was also observed that prolonged macrophage infiltration contributes to fibrosis and capsule formation in fat grafts. - Highlights: • Free fat aspirates undergo a prompt ECM reconstruction process in the first week. • The ECM reconstruction process is initiated with platelets and modulated by macrophages. • Depletion of macrophage in transferred fat resulted in delayed ECM reconstruction.

60 APPLIED LIFE SCIENCES↗