KeyW (United States)

View Video Presentation: https://doi.org/10.2514/6.2022-1172.vid An approach for dynamically adapting body-fitted overset Strand meshes in HPCMP CREATETM-AV Helios is demonstrated. The approach couples the Strand-Cartesian near-body/off-body meshing paradigm with the HPCMP CREATETM-FT Capstone software to generate and refine surface meshes. Helios then constructs the dual volume mesh and interpolates data to the adapted mesh. The approach is parallel and fully automated, requiring no intervention on the part of the user during the adaptation process. Tests are conducted for RANS calculations on the ONERA M6 wing configuration, both static and pitching. With the pitching wing, the adaptive process completes 192 time-dependent adapt cycles, maintaining good quality and good solution accuracy. On 440 processors, the adaptive process incurred less than 8% computation overhead.

Heavy-ion, focused X-ray, and pulsed laser single-event transient (SET) experiments are performed on a silicon epitaxial diode. Collected charge, transient rise times, and transient fall times are calculated and compared between different sources. The transient shape characteristics depend on the source (ion, X-ray, or laser), even when similar amounts of charge are generated. The observed differences are examined and explained in terms of basic charge collection mechanisms.

The zebrafish is an important vertebrate model for disease, drug discovery, toxicity, embryogenesis, and neuroscience. In vivo fluorescence microscopy can reveal cellular and subcellular details down to the molecular level with fluorescent proteins (FPs) currently the main tool for zebrafish imaging. However, long maturation times, low brightness, photobleaching, broad emission spectra, and sample autofluorescence are disadvantages that cannot be easily overcome by FPs. Here, a bright and photostable terbium-to-quantum dot (QD) Förster resonance energy transfer (FRET) nanoprobe with narrow and tunable emission bands for intracellular in vivo imaging is presented. The long photoluminescence (PL) lifetime enables time-gated (TG) detection without autofluorescence background. Intracellular four-color multiplexing with a single excitation wavelength and in situ assembly and FRET to mCherry demonstrate the versatility of the TG-FRET nanoprobes and the possibility of in vivo bioconjugation to FPs and combined nanoprobe-FP FRET sensing. Upon injection at the one-cell stage, FRET nanoprobes can be imaged in developing zebrafish embryos over seven days with toxicity similar to injected RNA and strongly improved signal-to-background ratios compared to non-TG imaging. This work provides a strategy for advancing in vivo fluorescence imaging applications beyond the capabilities of FPs.

We demonstrate efficient pulse-energy extraction from a partly quenched erbium-doped aluminosilicate fiber amplifier. This has a high erbium concentration that allows for short devices with reduced nonlinear distortions but also results in partial quenching and thus significant unsaturable absorption, even though the fiber is still able to amplify. Although the quenching degrades the average-power efficiency, the pulse energy remains high, and our results point to an increasingly promising outcome for short pulses. Furthermore, unlike unquenched fibers, the conversion efficiency improves at low repetition rates, which we attribute to smaller relative energy loss to quenched ions at higher pulse energy. A short (2.6 m) cladding-pumped partly quenched Er-doped fiber with 95-dB/m 1530-nm peak absorption and saturation energy estimated to 85 µJ reached 0.8 mJ of output energy when seeded by 0.2-µs, 23-µJ pulses. Thus, according to our results, pulses can be amplified to high energy in short highly Er-doped fibers designed to reduce nonlinear distortions at the expense of average-power efficiency.

The interaction of quantum systems with mechanical resonators is of practical interest for applications in quantum information and sensing and also of fundamental interest as hybrid quantum systems. Achieving a large and tunable interaction strength is of great importance in this field as it enables controlled access to the quantum limit of motion and coherent interactions between different quantum systems. This has been challenging with solid state spins, where typically the coupling is weak and cannot be tuned. Here we use pairs of coupled quantum dots embedded within cantilevers to achieve a high coupling strength of the singlet-triplet spin system to mechanical motion through strain. Two methods of achieving strong, tunable coupling are demonstrated. The first is through different strain-induced energy shifts for the two QDs when the cantilever vibrates, resulting in changes to the exchange interaction. The second is through a laser-driven AC Stark shift that is sensitive to strain-induced shifts of the optical transitions. Both of these mechanisms can be tuned to zero with electrical bias or laser power, respectively, and give large spin-mechanical coupling strengths.

Enhancements in enzymatic catalytic activity are frequently observed when an enzyme is displayed on a nanoparticle (NP) surface. The exact mechanisms of how this unique interfacial environment gives rise to this phenomenon are still not understood, although evidence suggests that it can help alleviate some of the enzyme's rate-limiting mechanistic steps. The physicochemical limitations that govern when this process arises are also not known including, in particular, the range of NP size and curvature that are associated with it. To investigate the latter, we undertook a case study using the enzyme phosphotriesterase (PTE) and a series of differentially sized gold NPs (AuNPs). PTE, expressed with a terminal hexahistidine sequence, was ratiometrically coordinated to a series of increasing size AuNPs (diameter ≃ 1.5, 5, 10, 20, 55, 100 nm) surface-functionalized with Ni2+-nitrilotriacetic acid ligands and its activity assayed in a comparative format versus that of equivalent amounts of free enzyme controls. PTE-AuNP samples were prepared where the total PTE concentration and NP surface density were kept fixed by varying AuNP concentration along with the converse format. Assembly to the AuNPs increased PTE kcat ca. 3-10-fold depending upon NP size, with the smaller-sized particles showing the highest increase, while enzyme efficiency only increased 2-fold. Further kinetic testing suggested that the PTE enhancement again arose from alleviating its rate limiting step of enzyme-product release and not from a change in the activation energy. Comparison of kcat and enzyme specificity with AuNP diameter revealed that enhancement was directly correlated to AuNP size and curvature with the smaller NPs showing the largest kinetic enhancements. Kinetic simulations showed that almost all of the PTE enhancement variation across AuNP sizes could be reproduced by adjusting only the rate of enzyme-product dissociation. Understanding how NP size directly affects the enhancement of an attached enzyme can provide a rational basis for designing hybrid enzyme-NP materials that specifically exploit this emergent property.

A web-based resource for meta-analysis of nanomaterials toxicity is developed whereby the utility of Bayesian networks (BNs) is illustrated for exploring the cellular toxicity of Cd-containing quantum dots (QDs). BN models are developed based on a dataset compiled from 517 publications comprising 3028 cell viability data samples and 837 IC50 values. BN QD toxicity (BN-QDTox) models are developed using both continuous (i.e., numerical) and categorical attributes. Using these models, the most relevant attributes identified for correlating IC50 are: QD diameter, exposure time, surface ligand, shell, assay type, surface modification, and surface charge, with the addition of QD concentration for the cell viability analysis. Data exploration via BN models further enables identification of possible association rules for QDs cellular toxicity. The BN models as web-based applications can be used for rapid intelligent query of the available body of evidence for a given nanomaterial and can be readily updated as the body of knowledge expands.

The design of nanoparticles is critical for their efficient use in many applications ranging from biomedicine to sensing and energy. While shape and size are responsible for the properties of the inorganic nanoparticle core, the choice of ligands is of utmost importance for the colloidal stability and function of the nanoparticles. Moreover, the selection of ligands employed in nanoparticle synthesis can determine their final size and shape. Ligands added after nanoparticle synthesis infer both new properties as well as provide enhanced colloidal stability. In this article, we provide a comprehensive review on the role of the ligands with respect to the nanoparticle morphology, stability, and function. We analyze the interaction of nanoparticle surface and ligands with different chemical groups, the types of bonding, the final dispersibility of ligand-coated nanoparticles in complex media, their reactivity, and their performance in biomedicine, photodetectors, photovoltaic devices, light-emitting devices, sensors, memory devices, thermoelectric applications, and catalysis.

Nanoparticle (NP) bioconjugates have an important role in the development of photothermal (PT) therapy, a promising noninvasive approach wherein the NP acts as a light harvesting antenna to convert light into thermal energy to control cellular function. NP-mediated PT control of cellular membrane potential has gained significant interest in recent years as membrane potential regulates proliferation, migration, action potentials (in neurons), and contraction (in muscle cells). Recently gold nanoparticles (AuNPs) and Au nanorods have been demonstrated to induce action potentials via light-induced thermal activation of membrane tethered NPs. Spherical AuNPs have an efficient plasmonic output and are easily modified to interface with the cell surface. We demonstrate here that 20 nm diameter spherical AuNPs (tethered to the plasma membrane by a cholesterol moiety) transduce incident 532 nm light into proximal membrane heating that induces depolarization of membrane potential. Using these NP bioconjugates, we show the ability to controllably induce action potentials in dorsal root ganglion neurons and to control the membrane potential of rat pheochromocytoma cells. The ability to use light-actuated NP conjugates to control cellular behavior is an emerging research field with implications for neuronal and muscle cell modulation as well as in cancer therapeutics.