SEARCH · Engineering Papers
Results for “NUCLEATION”
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.
Nanoparticle Nucleation Is Termolecular in Metal and Involves Hydrogen: Evidence for a Kinetically Effective Nucleus of Three {Ir 3 H 2 x ·P 2 W 15 Nb 3 O 62 } 6– in Ir(0) n Nanoparticle Formation From [(1,5-COD)Ir I ·P 2 W 15 Nb 3 O 62 ] 8– Plus Dihydrogen
Not Available
Cooperative Reorganization of Mineral and Template during Directed Nucleation of Calcium Carbonate
Self-assembled monolayers (SAMs) prepared from organic thiol molecules on metal substrates are known to exert substantial influence over mineralization and, as such, provide model systems for investigating the mechanisms of templated crystallization by organic matrices. Characterizing the structural evolution at the organic/inorganic interface in SAM/crystal systems is of paramount importance in understanding these mechanisms. In this study, X-ray absorption spectroscopy is used to characterize the structural evolution of SAMs prepared from purpose-synthesized organic thiols, with similar yet subtly different structures and compositions, during the course of mineralization at their surfaces. The studies reveal that the structure of the thiol molecules strongly affects their ability to reorient within the SAM. Complementary scanning electron microscopy measurements demonstrate that the feature of the SAMs is strongly correlated with the capability of the monolayers to induce preferential ordering among the organic crystals. Consistent with recent modeling studies of SAM/crystal systems, these findings provide experimental evidence that structural flexibility within the SAMs is crucial for achieving templated crystallization and that templating is inherently a cooperative process that selects the most favorable combination of SAM and crystal orientations.
Graphene Nucleation Density on Copper: Fundamental Role of Background Pressure
Explore the source record for details and available documents.
Nucleation-Suppressed Phase Stabilization in Fe–Au Nanoparticles
Four nanoparticle compositions, Fe–21, 35, 47, and 67 at. % Au, have been prepared to study the phase stability and solid-state transformation in confined Fe–Au nanoalloys. The formation of two phases, predicted from bulk thermodynamics, has been suppressed in all compositions. Instead, a single phase solid solution forms after heat treatment at 600 °C and slow cooling. However, bulk phase relationships, signified by the precipitation of α-Fe upon cooling, was observed in larger particles (>20 nm) with composition Fe–35 at. % Au. The suppression of the phase transformation/precipitation in small particles is explained thermodynamically, as the free energy decrease associated with the phase transformation does not exceed the increase in energy due to the introduction of an interphase interface (grain boundary) within the cluster. A general equation has been derived to predict the critical cluster size below which transformations are inhibited, which agrees well with the observed experimental results.
Charge, Stereochemistry, or Epitaxy? Toward Controlled Biomimetic Nucleation at Mixed Monolayer Templates
Abstract not provided
High Supersaturation in the Wake of Falling Hydrometeors: Implications for Cloud Invigoration and Ice Nucleation
Aerosol particles, cloud droplets, and ice crystals, coupled through the supersaturation field, play an important role in the buoyancy and life cycle of convective clouds. This letter reports laboratory observations of copious cloud droplets and ice crystals formed in the wake of a warm, falling water drop, which is a laboratory surrogate for a relatively warm hydrometeor in atmospheric clouds, such as a graupel particle in the wet growth regime. Aerosols were activated in the regions of very high supersaturation due to mixing in the wake. A mechanism is explored for attaining very high supersaturations capable of activating significant fractions of the interstitial aerosols within the lifetime of a convective cloud. The latent heat released from the activation of interstitial aerosols and subsequent growth may provide an additional source of buoyancy for cloud invigoration and may lead to larger concentrations of ice crystals.
Refining the Simulation of Mixed‐Phase Clouds Over Coastal Antarctica With a Tailored Ice Nucleating Particle Parameterization
Explore the source record for details and available documents.
A stable transcription factor complex nucleated by oligomeric AML1–ETO controls leukaemogenesis
Transcription factors are frequently altered in leukaemia through chromosomal translocation, mutation or aberrant expression. AML1–ETO, a fusion protein generated by the t(8;21) translocation in acute myeloid leukaemia, is a transcription factor implicated in both gene repression and activation. AML1–ETO oligomerization, mediated by the NHR2 domain, is critical for leukaemogenesis, making it important to identify co-regulatory factors that ‘read’ the NHR2 oligomerization and contribute to leukaemogenesis. Here we show that, in human leukaemic cells, AML1–ETO resides in and functions through a stable AML1–ETO-containing transcription factor complex (AETFC) that contains several haematopoietic transcription (co)factors. These AETFC components stabilize the complex through multivalent interactions, provide multiple DNA-binding domains for diverse target genes, co-localize genome wide, cooperatively regulate gene expression, and contribute to leukaemogenesis. Within the AETFC complex, AML1–ETO oligomerization is required for a specific interaction between the oligomerized NHR2 domain and a novel NHR2-binding (N2B) motif in E proteins. Crystallographic analysis of the NHR2–N2B complex reveals a unique interaction pattern in which an N2B peptide makes direct contact with side chains of two NHR2 domains as a dimer, providing a novel model of how dimeric/oligomeric transcription factors create a new protein-binding interface through dimerization/oligomerization. Intriguingly, disruption of this interaction by point mutations abrogates AML1–ETO-induced haematopoietic stem/progenitor cell self-renewal and leukaemogenesis. These results reveal new mechanisms of action of AML1–ETO, and provide a potential therapeutic target in t(8;21)-positive acute myeloid leukaemia.
Nucleation effects of high molecular weight polymer additives on low molecular weight gels
Explore the source record for details and available documents.
Weathering influences the ice nucleation activity of microplastics
Not Available
Pre-ceramic polymer-assisted nucleation and growth of copper sulfide nanoplates
Abstract Polymer-derived ceramics derived from pre-ceramic polymers (PCPs), have access to several form factors and are highly tunable systems. Tunability can be further expanded with the incorporation of functional nanoparticle fillers throughout the matrix for advanced nanocomposite polymer-derived ceramic development. However, capping ligands used in nanoparticle syntheses mix unfavorably with PCPs, giving aggregated filler material and diminished properties. To control dispersion, secondary nanoparticle processing is performed by adhering PCP-miscible caps to the surface after synthesis. This often sacrifices size control established for small nanoparticles (<10 nm). Herein, we successfully eliminate the need for extra nanoparticle processing through the development of a one-pot, copper sulfide synthesis in which a PCP assists the stable formation of nanoparticles and serves as the final graft molecule. We monitor the success of this methodology and the PCP’s role in the reaction through several characterization methods probing both the nanoparticle core and polymer graft.
Insights into carbon nanotube nucleation: Cap formation governed by catalyst interfacial step flow
Explore the source record for details and available documents.
Solvent Quality-Induced Nucleation and Growth of Parallelepiped Nanorods in Dilute Poly(3-Hexylthiophene) (P3HT) Solution and the Impact on the Crystalline Morphology of Solution-Cast Thin Film
Explore the source record for details and available documents.
Structural evolution, formation pathways and energetic controls during template-directed nucleation of CaCO3
Explore the source record for details and available documents.