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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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Formation of rippled β-sheets from mixed chirality linear and cyclic peptides—new structural motifs based on the pauling-corey rippled β-sheet
Shown here is the first mixed chirality macrocycle that is intrinsically locked into a rippled sheet configuration. The rippled β-sheet is a structural motif formed by certain racemic peptides that is distinct from the commonly known pleated β-sheet.
Exploration of Neutron-Rich Isotopes around N = 50 via the In-Flight Fission of a 345 MeV/Nucleon 238 U Beam
A search for new neutron-rich isotopes beyond $Z=28$ and $N=50$ was performed using a 345 MeV/nucleon $^{238}$U beam at RI Beam Factory in RIKEN Nishina Center. The BigRIPS separator and state-of-the-art radiation detectors were used to efficiently separate and identify the produced nuclei. For the first time, we have observed and determined the production cross sections for eight neutron-rich isotopes $^{72}$Cr, $^{74,75}$Mn, $^{77}$Fe, $^{79,80}$Co, $^{85}$Cu, and $^{90}$Ga. This study broadens our understanding of nuclear existence and paves the way for investigating the properties of neutron-rich medium-mass nuclei.
Capillary Wave Dynamics of Thin Polymer Films over Submerged Nanostructures
Not Available
Formation and transfer of GaAsN nanostructure layers
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Ultra-Sharp Nanowire Arrays Natively Permeate, Record, and Stimulate Intracellular Activity in Neuronal and Cardiac Networks
Intracellular access with high spatiotemporal resolution can enhance the understanding of how neurons or cardiomyocytes regulate and orchestrate network activity and how this activity can be affected with pharmacology or other interventional modalities. Nanoscale devices often employ electroporation to transiently permeate the cell membrane and record intracellular potentials, which tend to decrease rapidly with time. Here, one reports innovative scalable, vertical, ultrasharp nanowire arrays that are individually addressable to enable long-term, native recordings of intracellular potentials. One reports electrophysiological recordings that are indicative of intracellular access from 3D tissue-like networks of neurons and cardiomyocytes across recording days and that do not decrease to extracellular amplitudes for the duration of the recording of several minutes. The findings are validated with cross-sectional microscopy, pharmacology, and electrical interventions. The experiments and simulations demonstrate that the individual electrical addressability of nanowires is necessary for high-fidelity intracellular electrophysiological recordings. This work advances the understanding of and control over high-quality multichannel intracellular recordings and paves the way toward predictive, high-throughput, and low-cost electrophysiological drug screening platforms.
Cubic Silsesquioxanes as a Green, High-Performance Mold Material for Nanoimprint Lithography
Optical lithography deep in the UV spectrum is the predominate route for high-resolution, high-volume nanoscale pattering. However, state-of-the-art optical lithography tools are exceedingly expensive and this places serious limitations on the applications, technical sectors, and markets where highresolution patterning can be implemented. To date the only substantial market for high-end optical lithography tools has been semiconductor fabrication. Nanoimprint lithography (NIL) has recently emerged as an alternative to optical lithography and combines the potential of sub-fi ve-nanometer patterning resolution with the low cost and simplicity of a stamping process. [ 1–4 ] This has led to signifi cant efforts to implement NIL methods, not only for semiconductor logic devices, but also in fi elds as diverse as the direct patterning of interlayer dielectrics (ILDs) for back-end-of-line (BEOL) interconnect structures, [ 5–7 ] bitpatterned magnetic media for data storage, [ 8 , 9 ] and high-brightness light-emitting diodes (LEDs). [ 10 ] Some of these are new areas where nanoscale patterning has previously not been considered, and are made possible here by the low cost and simplicity of the NIL stamping processes.
Improved Performance of Zinc Oxide Thin Film Transistor Pressure Sensors and a Demonstration of a Commercial Chip Compatibility with the New Force Sensing Technology
Abstract A zinc oxide thin film transistor is developed and optimized that simultaneously functions as a transistor and a force sensor, thus allowing for scalable integration of sensors into arrays without the need for additional addressing elements. Through systematic material deposition, microscopy, and piezoelectric characterization, it is determined that an O 2 rich deposition condition improves the transistor performance and pressure sensing characteristics. With these optimizations, a sensitivity of 4 nA kPa −1 and a latency of below 1 ms are achieved, exceeding the criteria for successful commercialization of arrayed pressure sensors. The functionality of 16 × 16 pressure sensor arrays on thin bendable glass substrates for integrated low weight and flexible touchscreen displays is fabricated and demonstrated and read‐out electronics to interface with the arrays and to record their response in real‐time are developed. Finally, the application of these sensors for mobile displays via their operation with an existing commercial touch integrated circuit controller is demonstrated.
Surface Passivation and Carrier Collection in {110}, {100} and Circular Si Microwire Solar Cells
Surface recombination is a major bottleneck for realizing highly efficient micro/nanostructure solar cells. Parametric studies of the influence of Si microwire (SiMW) surface-facet orientation (rectangular with flat-facets, {110}, {100} and circular), with a fixed height of 10 µm, diameter (D = 1.5–9.5 µm), and sidewall spacing (S = 2.5–8.5 µm), and mesh-grid density (1–16 mm -2 ) on recombination and carrier collection in SiMW solar cells with radial p-n junctions are reported. An effective surface passivation layer composed of thin thermally grown silicon dioxide (SiO 2 ) and silicon nitride (SiN x ) layers is employed. For a fixed D of 1.5 µm, tight SiMW spacing results in improved short-circuit current density (J sc = 30.1 mA cm -2 ) and sparse arrays result in open-circuit voltages (V oc = 0.552 V) that are similar to those of control Si planar cells. For a fixed S, smaller D results in better light trapping at shorter wavelengths and higher J sc while larger D exhibits better light trapping at larger wavelengths and a higher V oc . With a mesh-grid electrode the power conversion efficiency increases to 15.3%. Finally, these results provide insights on the recombination mechanisms in SiMW solar cells and provide general design principles for optimizing their performance.
Structure and function of the lanthanide-dependent methanol dehydrogenase XoxF from the methanotroph Methylomicrobium buryatense 5GB1C
Abstract not provided
Evolution of Microstructure and Creep Behavior in an Fe-Ni-Cr-Nb-C Alloy during Service in Hydrocarbon Cracker Tubes
Heat resistant, cast austenitic Fe-Ni-Cr-Nb-C alloy tubes are used by the petrochemical industry to transport hydrocarbons at temperatures between 850 and 1050 °C. Exposure to carbon from the process stream and nitrogen from the air causes severe carburization and nitridation in the tube walls, which influences creep resistance and degrades their ductility. A better understanding of these processes would enable their service life to be extended. To this end, we report the results of an experimental and computational study of the changes in microstructure and creep behavior in a representative alloy during service. The microstructure of the fresh material is compared to that of 8- and 10-year-old tubes. The results confirm the presence of M{sub 23}C{sub 6}, M{sub 7}C{sub 3}, and M{sub 2}(CN) phases reported in prior studies, and also reveal the nucleation and growth of the carbo-nitride phase M{sub 6}(CN). We show that the spatial variations of carbide and nitride particle volume fractions in aged tubes can be predicted by a simple reaction–diffusion equation. In addition, the uniaxial compressive creep response of the fresh and aged tubes was obtained as functions of temperature and strain rate. The materials deform by power-law creep, with strain rate versus stress relation as ε-dot =Aσ{sup n}. Aging reduces the stress exponent from n = 8 in fresh tubes to n = 5 in aged tubes, and also reduces the pre-exponential coefficient A. Tests on model alloys with composition identical to that of the matrix combined with finite element simulations of creep in model microstructures reveal that Cr depletion is responsible for the change in stress exponent, while the change in A is caused by the increase in particle volume fraction. By combining the microstructure-scale simulations of creep with the predictions of the reaction–diffusion model of microstructure evolution, the creep behavior of tubes left in service beyond 10 years is estimated.
Numerical analysis of 1/28 scaled NGNP HTGR reactor building test facility response to depressurization event using GOTHIC
Not provided.
Salinomycin sensitizes antimitotic drugs-treated cancer cells by increasing apoptosis via the prevention of G2 arrest
Highlights: Black-Right-Pointing-Pointer Sal sensitizes antimitotic drugs-treated cancer cells. Black-Right-Pointing-Pointer Sal sensitizes them by prevention of G2 arrest and reduced cyclin D1 levels. Black-Right-Pointing-Pointer Sal also sensitizes them by increasing DNA damage and reducing p21 level. Black-Right-Pointing-Pointer A low concentration of Sal effectively sensitized the cancer cells to antimitotic drugs. -- Abstract: Here, we investigated whether Sal could sensitize cancer cells to antimitotic drugs. We demonstrated that Sal sensitized paclitaxcel (PAC)-, docetaxcel (DOC)-, vinblastin (VIN)-, or colchicine (COL)-treated cancer cell lines, suggesting that Sal has the ability to sensitize the cells to any form of microtubule-targeting drugs. Sensitization to the antimitotic drugs could be achieved with very low concentrations of Sal, suggesting that there is a possibility to minimize Sal toxicity associated with human cancer patient treatments. Sensitization by Sal increased apoptosis, which was observed by C-PARP production. Sal sensitized the cancer cells to antimitotic drugs by preventing G2 arrest, suggesting that Sal contributes to the induction of mitotic catastrophe. Sal generally reduced cyclin D1 levels in PAC-, DOC-, and VIN-treated cells. In addition, Sal treatment increased pH2AX levels and reduced p21 levels in antimitotic drugs-treated cells. These observations suggest that the mechanisms underlying Sal sensitization to DNA-damaging compounds, radiation, and microtubule-targeting drugs are similar. Our data demonstrated that Sal sensitizes cancer cells to antimitotic drugs by increasing apoptosis through the prevention of G2 arrest via conserved Sal-sensitization mechanisms. These results may contribute to the development of Sal-based chemotherapy for cancer patients treated with antimitotic drugs.
Discovery of germacrene A synthases in Barnadesia spinosa: The first committed step in sesquiterpene lactone biosynthesis in the basal member of the Asteraceae
The Andes-endemic Barnadesioideae lineage is the oldest surviving and phylogenetically basal subfamily of the Asteraceae (Compositae), a prolific group of flowering plants with world-wide distribution (∼24,000 species) marked by a rich diversity of sesquiterpene lactones (STLs). Intriguingly, there is no evidence that members of the Barnadesioideae produce STLs, specialized metabolites thought to have contributed to the adaptive success of the Asteraceae family outside South America. The biosynthesis of STLs requires the intimate expression and functional integration of germacrene A synthase (GAS) and germacrene A oxidase (GAO) to sequentially cyclize and oxidize farnesyl diphosphate into the advanced intermediate germacrene A acid leading to diverse STLs. Our previous discovery of GAO activity conserved across all major subfamilies of Asteraceae, including the phylogenetically basal lineage of Barnadesioideae, prompted further investigation of the presence of the gateway GAS in Barnadesioideae. Herein we isolated two terpene synthases (BsGAS1/BsGAS2) from the basal Barnadesia spinosa (Barnadesioideae) that displayed robust GAS activity when reconstituted in yeast and characterized in vitro. Despite the apparent lack of STLs in the Barnadesioideae, this work unambiguously confirms the presence of GAS in the basal genera of the Asteraceae. Phylogenetic analysis reveals that the two BsGASs fall into two distinct clades of the Asteraceae's GASs, and BsGAS1 clade is only retained in the evolutionary closer Cichorioideae subfamily, implicating BsGAS2 is likely the ancestral base of most GASs found in the lineages outside the Barnadesioideae. Taken together, these results show the enzymatic capacities of GAS and GAO emerged prior to the subsequent radiation of STL-producing Asteraceae subfamilies. - Highlights: • Sesquiterpene lactones are characteristic metabolites in Asteraceae family. • Barnadesioideae is the basal lineage of all Asteraceae plants, producing sesquiterpene lactones. • Two germacrene A synthases (GASs) were identified and characterized from Barnadesia spinosa. • A phylogenetic analysis showed two sub-clades of GASs have evolved in Asteraceae. • GAS enzymes evolved prior to the divergence and global dispersal of the modern Asteraceae.
Structure-based protein engineering of bacterial β-xylosidase to increase the production yield of xylobiose from xylose
Highlights: • The crystal structures of β-xylosidase from Bacillus pumilus in complex with xylobiose were determined. • β-xylosidase was engineered to increase the yield of xylobiose based on the determined structures. • The protein engineering strategy used in this study could be applied within the same family of enzymes. Xylobiose consists of two molecules of xylose and has been highly recognized as a food supplement because it possesses high prebiotic functions. β-xylosidase exhibits enzymatic activity to hydrolyze xylobiose, and the enzyme can also catalyze the reverse reaction in the presence of high concentrations of xylose. Previously, β-xylosidase from Bacillus pumilus IPO (BpXynB), belonging to GH family 43, was employed to produce xylobiose from xylose. To improve the enzymatic efficiency, this study determined the high-resolution structure of BpXynB in a complex with xylobiose and engineered BpXynB based on the structures. The structure of BpXynB deciphered the residues involved in the recognition of the xylobiose. A site-directed mutation at the residue for xylobiose recognition increased the yield of xylobiose by 20% compared to a similar activity of the wild type enzyme. The complex structure of the mutant enzyme and xylobiose provided the structural basis for a higher yield of the engineered protein. This engineered enzyme would enable a higher economic production of xylobiose, and a similar engineering strategy could be applied within the same family of enzymes.