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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 721 records · Page 40
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Explicitly determined sea ice emissivity and emission temperature over the Arctic for surface–sensitive microwave channels

Data assimilation of satellite microwave measurements is one of the important keys to improving weather forecasting over the Arctic region. However, the use of surface-sensitive microwave-sounding channel measurements for data assimilation or retrieval has been limited, especially during winter, due to the poorly constrained sea ice emissivity. In this study, aiming at more use of those channel measurements in the data assimilation, we propose an explicit method for specifying the surface radiative boundary conditions (namely emissivity and emitting layer temperature of snow and ice). These were explicitly determined with a radiative transfer model for snow and ice and with snow/ice physical parameters (i.e., snow/ice depths and vertical distributions of temperature, density, salinity, and grain size) simulated from the thermodynamically-driven snow/ice growth model. Here we conducted 1-D Var experiments in order to examine whether this approach can help to use the surface-sensitive microwave temperature channel measurements over the Arctic sea ice region for data assimilation. Results show that (1) the surface-sensitive microwave channels can be used in the 1-D Var retrieval, and (2) the specification of the radiative boundary condition at the surface using the snow/sea ice emission model can significantly improve the atmospheric temperature retrieval, especially in the lower troposphere (500 hPa to surface). The successful retrieval suggests that useful information can be extracted from surface-sensitive microwave-sounding channel radiances over sea ice surfaces through the explicit determination of snow/ice emissivity and emitting layer temperature.

1-D Var retrieval↗
DOE OSTI2024

Benchmarking of X‐Ray Fluorescence Microscopy with Ion Beam Implanted Samples Showing Detection Sensitivity of Hundreds of Atoms

Abstract Single impurities in insulators are now often used for quantum sensors and single photon sources, while nanoscale semiconductor doping features are being constructed for electrical contacts in quantum technology devices, implying that new methods for sensitive, non‐destructive imaging of single‐ or few‐atom structures are needed. X‐ray fluorescence (XRF) can provide nanoscale imaging with chemical specificity, and features comprising as few as 100 000 atoms have been detected without any need for specialized or destructive sample preparation. Presently, the ultimate limits of sensitivity of XRF are unknown – here, gallium dopants in silicon are investigated using a high brilliance, synchrotron source collimated to a small spot. It is demonstrated that with a single‐pixel integration time of 1 s, the sensitivity is sufficient to identify a single isolated feature of only 3000 Ga impurities (a mass of just 350 zg). With increased integration (25 s), 650 impurities can be detected. The results are quantified using a calibration sample consisting of precisely controlled numbers of implanted atoms in nanometer‐sized structures. The results show that such features can now be mapped quantitatively when calibration samples are used, and suggest that, in the near future, planned upgrades to XRF facilities might achieve single‐atom sensitivity.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Sensitivity of the NEXT experiment to Xe-124 double electron capture

Double electron capture by proton-rich nuclei is a second-order nuclear process analogous to double beta decay. Despite their similarities, the decay signature is quite different, potentially providing a new channel to measure the hypothesized neutrinoless mode of these decays. The Standard-Model-allowed two-neutrino double electron capture (2$\nu$EC EC) has been predicted for a number of isotopes, but only observed in 78 Kr, 130 Ba and, recently, 124 Xe. The sensitivity to this decay establishes a benchmark for the ultimate experimental goal, namely the potential to discover also the lepton-number-violating neutrinoless version of this process, 0$\nu$EC EC. Here we report on the current sensitivity of the NEXT-White detector to 124 Xe 2$\nu$EC EC and on the extrapolation to NEXT-100. Using simulated data for the 2$\nu$EC EC signal and real data from NEXT-White operated with 124 Xe-depleted gas as background, we define an optimal event selection that maximizes the NEXT-White sensitivity. We estimate that, for NEXT-100 operated with xenon gas isotopically enriched with 1 kg of 124 Xe and for a 5-year run, a sensitivity to the 2$\nu$EC EC half-life of 6 × 10 22 y (at 90% confidence level) or better can be reached.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2019

{sup 68}Ga-PSMA-11 PET/CT in newly diagnosed prostate cancer: diagnostic sensitivity and interobserver agreement

Purpose: To determine the diagnostic sensitivity and interobserver agreement of Gallium 68-prostate-specific membrane antigen positron emission tomography/computed tomography ({sup 68}Ga-PSMA-11 PET/CT) imaging for diagnosis and staging of patients with newly diagnosed prostate cancer (PC). Materials and methods: One hundred and seventy-three men (mean age, 68 ± 7.7 years; range 46–84 years) with newly diagnosed, untreated PC were enrolled in this prospective study between January 2017 and August 2018. All patients underwent a {sup 68}Ga-PSMA-11 PET/CT examination. For each patient, we determined the disease stage, the Gleason score, and the maximum standardized uptake value (SUVmax) for primary prostatic tumor and extraprostatic metastases. The diagnostic sensitivity and interobserver agreement of {sup 68}Ga-PSMA-11 PET/CT for diagnosis and staging of PC were established by histopathology as the reference standard. Results: {sup 68}Ga-PSMA-11 PET/CT examinations were interpreted as positive for PC in 166 of 173 patients (101 patients had primary prostatic tumor only, two patients had extraprostatic metastases only and 63 patients had combined lesions). The sensitivity of {sup 68}Ga-PSMA-11 PET/CT examination in the diagnosis of PC was 96%. {sup 68}Ga-PSMA-11 PET/CT produced a significant change of stage in 28.6% patients with an upstage in 17.9% patients and a downstage in 10.7% patients. The interobserver agreements were almost good to perfect (k = 0.63–0.89) for visual image interpretation, SUVmax measurement, and tumor staging. Conclusion: {sup 68}Ga-PSMA-11 PET/CT is a valuable tool with high diagnostic sensitivity (96%) and high reproducibility for diagnosis and staging of patients with newly diagnosed PC.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2019

Hierarchical sensitivity analysis for simulating barrier island geomorphologic responses to future storms and sea-level rise

This paper presents a new application of an advanced hierarchical sensitivity analysis of a new climate model of barrier island geomorphological evolution. The implemented sensitivity analysis in this study integrates a hierarchical uncertainty framework with a variance-based global sensitivity analysis to decompose the different model input uncertainties. The analysis can provide quantitative and accurate measurements for the relative importance of uncertain model input factors while considering their dependence relationships. The climate model used in this research was the barrier island profile (BIP) model, which is a new computer code developed to simulate barrier island morphological evolution over periods ranging from years to decades under the impacts of accelerated future sea-level rise and long-term changes in the storm climate. In the application of the model, the BIP model was used to evaluate the responses of a series of barrier island cross-sections derived for Santa Rosa Island, Florida, to random storm events and five potential accelerated rates of sea-level rise projected over the next century. The uncertain model input factors thus include the scenario uncertainty caused by alternative future sea-level rise scenarios and the parametric uncertainties of random storm parameters and dune characteristics. The study results reveal that the occurrence of storms is the most important factor for the evolution of sand dunes on the barrier island and the impact of sea-level rise is essential to the morphological change of the island backshore environment. The analysis can provide helpful insights for coastal management and planning. This hierarchical sensitivity analysis is mathematically general and rigorous and can be applied to a wide range of climate models.

Dai, Heng↗
DOE OSTI2018

Magnetic Sensitivity of AlMn TESes and Shielding Considerations for Next-Generation CMB Surveys

In the next decade, new ground-based cosmic microwave background (CMB) experiments such as Simons Observatory, CCAT-prime, and CMB-S4 will increase the number of detectors observing the CMB by an order of magnitude or more, dramatically improving our understanding of cosmology and astrophysics. These projects will deploy receivers with as many as hundreds of thousands of transition edge sensor (TES) bolometers coupled to superconducting quantum interference device (SQUID)-based readout systems. It is well known that superconducting devices such as TESes and SQUIDs are sensitive to magnetic fields. However, the effects of magnetic fields on TESes are not easily predicted due to the complex behavior of the superconducting transition, which motivates direct measurements of the magnetic sensitivity of these devices. We present comparative four-lead measurements of the critical temperature versus applied magnetic field of AlMn TESes varying in geometry, doping, and leg length, including Advanced ACT and POLARBEAR-2/Simons Array bolometers. MoCu ACTPol TESes are also tested and are found to be more sensitive to magnetic fields than the AlMn devices. We present an observation of weak-link-like behavior in AlMn TESes at low critical currents. We also compare measurements of magnetic sensitivity for time division multiplexing SQUIDs and frequency division multiplexing microwave (mMUX) rf-SQUIDs. We discuss the implications of our measurements on the magnetic shielding required for future experiments that aim to map the CMB to near-fundamental limits.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2022

Sensitivity Analysis of an Electrospray Dehumidification System

Electrically enhanced condensation achieved by an electrospray system can enhance dehumidification in HVAC applications if successfully scaled up. The first step towards scale-up is identifying critical design and operating parameters that significantly impact dehumidification for the electrospray system. Sensitivity analysis is one approach for identifying critical parameters. This paper presents a methodology that can efficiently perform quantitative sensitivity analysis on a computationally expensive high fidelity simulation model, which is a computational fluid dynamics (CFD) model of the electrospray system. The methodology employs surrogate modeling and Sobol sensitivity analysis. We estimate the main and total effect Sobol sensitivity indices of four operating parameters of the electrospray system. The results reveal that the most important parameter is the size of the sprayed droplets, followed by the volumetric flow rate of the bulk air and injected water in the system. The water injection velocity of the spray was found to have little to no impact on dehumidification.

Young, David↗
DOE OSTI2020

Assessing the sensitivity of land-atmosphere coupling strength to boundary and surface layer parameters in the WRF model over Amazon

Modeling tools can be used to diagnose regional land-atmosphere (L-A) coupling strength in the absence of sufficient observations, but subject to uncertainties associated with parameters in model physical parameterizations. Different sensitivity analysis (SA) approaches may lead to different conclusions about the underlying sensitivities. In this study, we quantify simulation uncertainties related to parameter perturbations, and use different approaches to conduct parameter SA on the WRF model pertaining to L-A coupling strength for simulations over the Amazon region. A total of twenty parameters from the Yonsei University (YSU) planetary boundary layer (PBL) and the revised MM5 surface layer (SL) schemes were selected in this analysis. Three different SA methods, the Morris One-at-A-Time (MOAT) method, the Multivariate Adaptive Regression Splines (MARS) method, and the Sobol’ method, were employed to analyze seven WRF-simulated variables and five L-A coupling metrics. Results show that 1) parameter perturbations cause large simulation uncertainties which are comparable to those in the observations; 2) three different SA methods give consistent L-A coupling strength outcomes; 3) six out of the twenty parameters contribute 80%–95% of the total variance in the metrics analyzed, and first-order effects dominate over interaction effects; 4) the twelve variables/metrics of interest show similar sensitivity patterns to the selected parameters, which is consistent across all the methods used. Physical mechanisms for how the sensitive parameters act in determining the L-A coupling strength and associated variables also are illustrated. Our results will help quantifying L-A coupling strength and establishing a basis for parameter calibration over the Amazon region.

Wang, Chen↗
DOE OSTI2016

Heme oxygenase-1-mediated apoptosis under cadmium-induced oxidative stress is regulated by autophagy, which is sensitized by tumor suppressor p53

Heme oxygenase-1 (HO-1) is a stress-inducible cytoprotective enzyme. It is often overexpressed in different types of cancers and promotes cell survival. However, the role of HO-1 and the underlying molecular mechanism of cadmium (Cd)-induced oxidative stress in cancer cells remain undefined. Here we show that the role of HO-1 under Cd-induced oxidative stress is dependent upon autophagy, which is sensitized by the tumor suppressor p53. The sensitivity to Cd was 3.5- and 14-fold higher in p53-expressing YD8 and H460 cells than in p53-null YD10B and H1299 cells, respectively. The levels of p53 in YD8 and H460 cells decreased in a Cd concentration-dependent manner, which was inhibited by pretreatment with N-acetylcysteine. In both cell lines, Cd exposure resulted in caspase-3-mediated PARP-1 cleavage and the induction of CHOP, LC3-II, and HO-1, which were limited in YD10B and H1299 cells exposed to high concentrations of Cd. Cd exposure to p53-overexpressing YD10B cells enhanced Cd-induced HO-1 and LC3-II levels, whereas genetic knockdown of p53 in YD8 cells resulted in the suppression of Cd-induced levels of HO-1 and LC3-II, indicating that p53 is required in the sensing of HO-1 and induction of autophagy. The inhibition of autophagy using small interfering RNA (siRNA) for the autophagy-related gene atg5 enhanced HO-1, CHOP, and PARP-1 cleavage induced by Cd. However, transfection with HO-1 siRNA increased Cd-induced LC3-II, and suppressed the expression of CHOP and cleavage of PARP-1. Collectively, the role of HO-1 in apoptosis could be modulated by autophagy, which is sensitized by p53 expression in human cancer cell lines. - Highlights: • Cadmium exposure decreased p53 level, and induced HO-1, apoptosis, and autophagy. • p53 sensitized Cadmium-induced HO-1 and autophagy induction. • Cadmium induced HO-1 under autophagy impairment and increased apoptosis. • Cadmium-induced autophagy was enhanced under HO-1 impaired conditions. • The role of HO-1 in Cadmium-induced apoptosis is modulated by autophagy.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Biomarker identification for statin sensitivity of cancer cell lines

Highlights: • Graphical modeling is used to find a biomarker signature for statin sensitivity. • Predictions from the model were experimentally validated in four human cell lines. • Enrichment analysis and predicted combination therapies show relevance of signature. Statins are potent cholesterol reducing drugs that have been shown to reduce tumor cell proliferation in vitro and tumor growth in animal models. Moreover, retrospective human cohort studies demonstrated decreased cancer-specific mortality in patients taking statins. We previously implicated membrane E-cadherin expression as both a marker and mechanism for resistance to atorvastatin-mediated growth suppression of cancer cells; however, a transcriptome-profile-based biomarker signature for statin sensitivity has not yet been reported. Here, we utilized transcriptome data from fourteen NCI-60 cancer cell lines and their statin dose-response data to produce gene expression signatures that identify statin sensitive and resistant cell lines. We experimentally confirmed the validity of the identified biomarker signature in an independent set of cell lines and extended this signature to generate a proposed statin-sensitive subset of tumors listed in the TCGA database. Finally, we predicted drugs that would synergize with statins and found several predicted combination therapies to be experimentally confirmed. The combined bioinformatics-experimental approach described here can be used to generate an initial biomarker signature for anticancer drug therapy.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Inhibition of MALAT1 sensitizes liver cancer cells to 5-flurouracil by regulating apoptosis through IKKα/NF-κB pathway

Highlights: • MALAT1 knockdown inhibits liver cancer cell proliferation. • MALAT1 silence enhances apoptosis and liver cancer cells sensibility to 5-FU incubation. • MALAT1 deficiency related increase in sensitivity of liver cancer cells was associated with regulation of NF-κB. • MALAT1 knockdown reduces tumor growth in vivo. Metastasis associated lung adenocarcinoma transcript 1 (MALAT1) is involved in tumor cell growth process. However, its role and molecular mechanism in liver cancer is still not fully understood. In this study, we found that MALAT1 was significantly expressed in liver cancer cell lines. And knockdown of MALAT1 suppressed proliferation, migration and invasion of HepG2 cells, accompanied with decrease of Rho-associated coiled-coil-forming protein kinase 1 (ROCK1), α-smooth muscle actin (α-SMA), N-cadherin, Vimentin and TWIST. Significantly, MALAT1 deletion sensitized HepG2 cells to 5-FU-induced cell cycle arrest in G1 phase, as evidenced by the significant reduction in Cyclin D1 and CDK4 and increase in p53, p21 and p27 protein levels. In addition, MALAT1 knockdown triggered 5-FU induced apoptosis in HepG2 cells by inducing intrinsic apoptosis-related signals, including Cyto-c, Apaf-1, cleaved Caspase-9/-7/-3 and poly (ADP-ribose) polymerase (PARP). Furthermore, phosphorylated nuclear factor-κB (p-NF-κB) was also down-regulated by MALAT1 silence. Importantly, suppression of IKKα/NF-κB significantly elevated apoptosis and reduced liver cancer cell viability in MALAT1-knockdown cells with 5-FU incubation. The nude mice transplantation model also confirmed the promoted sensitivity of MALAT1-silenced HepG2 cells to 5-FU by blocking tumor cell proliferation and inducing apoptosis. Therefore, our data supplied a potential mechanism by which knockdown of MALAT1 might play an important role in augmenting sensitivity of HepG2 cells to 5-FU in therapeutic approaches, demonstrating suppressing of MALAT1 may serve as a combination with chemotherapeutic agents in liver cancer treatment.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

The reason for the low Ca2+-sensitivity of thin filaments associated with the Glu41Lys mutation in the TPM2 gene is “freezing” of tropomyosin near the outer domain of actin and inhibition of actin monomer switching off during the ATPase cycle

Highlights: • E41K mutation inhibits the “off”/”on” transition of the thin filaments. • Myosin heads lose ability to shift E41K-Tpm in the open position at high Ca{sup 2+}. • E41K-Tpm is shifted towards the blocked position during the ATPase cycle. • Switching on and off of actin monomers at high and low Ca{sup 2+} is inhibited. • Mutation inhibits the growth of the fraction of strongly bound S1 at high Ca{sup 2+}. The E41K mutation in TPM2 gene encoding muscle regulatory protein beta-tropomyosin is associated with nemaline myopathy and cap disease. The mutation results in a reduced Ca{sup 2+}-sensitivity of the thin filaments and in muscle weakness. To elucidate the structural basis of the reduced Ca{sup 2+}-sensitivity of the thin filaments, we studied multistep changes in spatial arrangement of tropomyosin (Tpm), actin and myosin heads during the ATPase cycle in reconstituted fibers, using the polarized fluorescence microscopy. The E41K mutation inhibits troponin's ability to shift Tpm to the closed position at high Ca{sup 2+}, thus restraining the transition of the thin filaments from the “off” to the “on” state. The mutation also inhibits the ability of S1 to shift Tpm to the open position, decreases the amount of the myosin heads bound strongly to actin at high Ca{sup 2+}, but increases the number of such heads at low Ca{sup 2+}. These changes may contribute to the low Ca{sup 2+}-sensitivity and muscle weakness. As the mutation has no effect on troponin's ability to switch actin monomers on at high Ca{sup 2+} and inhibits their switching off at low Ca{sup 2+}, the use of reagents that increase the Ca{sup 2+}-sensitivity of the troponin complex may not be appropriate to restore muscle function in patients with this mutation.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Mutant cytoskeletal and ECM peptides sensitive to the ST14 protease are associated with a worse outcome for glioblastoma multiforme

Highlights: • In GBM, mutant ECM proteins appear largely resistant to the ST14 protease. • Patients with resistant proteins have a better survival. • The few patients with sensitive mutants have T-cell infiltrates. We previously identified a set of the most frequently mutated cytoskeleton- and extracellular matrix-related proteins (CECMPs) in numerous cancer datasets. In this report, we used a bioinformatics approach to assess the impact of amino acid (AA) substitutions on the sensitivity of CECMPs to the ST14 protease (matriptase I), a transmembrane serine protease previously implicated in cancer development. Results indicated that AA substitutions in glioblastoma multiforme (GBM) CECMPs are skewed toward increased resistance to the ST14 protease, in comparison to the wild-type peptide sequence. Furthermore, the protease resistant AA substitutions represent relatively high binding affinities to HLA class I proteins, when assessing the binding specificities using HLA class I alleles matched to the source of the mutant AA. Moreover, samples representing AA substitutions that increased protease sensitivity also represented reduced overall and disease-free survival periods for patients with glioblastoma. To assess tumor specimen immunogenicity, we identified T-cell receptor (TCR) V(D)J recombinations in GBM exome files. The overlap between ST14 protease sensitive mutant barcodes and the TCR V(D)J recombination read positive barcodes represented significantly reduced survival.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

PnpB involvement in the regulation of temperature-sensitive para-nitrophenol degradation in Pseudomonas putida MT54 via PnpA

Highlights: • P. putida MT54 is a temperature-sensitive p-nitrophenol degradation mutant strain of P. putida DLL-E4. • PnpB is essential for P. putida MT54 to degrade PNP at 37 °C. • PnpA is a psychrophilic enzyme that responsible for the temperature-sensitive degradation in P. putida MT54. Pseudomonas putida DLL-E4 can efficiently degrade para-nitrophenol and its intermediate metabolite hydroquinone at 37 °C and 30 °C. However, mutant strain Pseudomonas putida MT54, obtained by transposon mutagenesis from P. putida DLL-E4, could not degrade para-nitrophenol at 37 °C. The mutant genes including DW66{sub 0}143, DW66{sub 0}153 and pnpB were discovered in strain MT54 by whole genome resequencing. Gene knockout and complementation confirmed the necessity of PnpB in PNP degradation by temperature-sensitive strain MT54. PnpA catalyzes the first step in complete degradation of PNP, and we found its activity was significantly enhanced by PnpB. The measurement of bacterial two-hybrid system indicated that the effect was not mediated by the direct interaction between PnpA and PnpB, but caused by the elimination of product inhibition of PnpA. Furthermore, PnpA was characterized as a psychrophilic enzyme with optimum temperature of 20 °C. We concluded that the lowered activity of PnpA resulted from inactivation of PnpB at the restrictive temperature induced the temperature-sensitive characteristic of P. putida MT54.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2021

An experimental and kinetic modeling study of NO x sensitization on methane autoignition and oxidation

An experimental and kinetic modeling study of the influence of NO x (i.e. NO 2 , NO and N 2 O) addition on the ignition behavior of methane/‘air’ mixtures is performed. Ignition delay time measurements are taken in a rapid compression machine (RCM) and in a shock tube (ST) at temperatures and pressures ranging from 900–1500 K and 1.5–3.0 MPa, respectively for equivalence ratios of 0.5–2.0 in ‘air’. The conditions chosen are relevant to spark ignition and homogeneous charge compression ignition engine operating conditions where exhaust gas recirculation can potentially add NO x to the premixed charge. The RCM measurements show that the addition of 200 ppm NO 2 to the stoichiometric CH 4 /oxidizer mixture results in a factor of three increase in reactivity compared to the baseline case without NOx for temperatures in the range 600–1000 K. However, adding up to 1000 ppm N 2 O does not show any appreciable effect on the measurements. The promoting effect of NO 2 was found to increase with temperature in the range 950–1150 K, while the sensitization effect decreases at higher pressures. The experimental results measured are simulated using NUIGMech1.2 comprising an updated NO x sub-chemistry in this work. A kinetic analysis indicates that the competition between the reactions ĊH 3 + NO 2 ↔ CH 3 Ȯ + NO and ĊH 3 + NO 2 (+M) ↔ CH 3 NO 2 (+M), the former being a propagation reaction and the latter being a termination reaction governs NO x sensitization on CH 4 ignition. Recent calculations by Matsugi and Shiina (A. Matsugi, H. Shiina, J. Phys. Chem. A. 121 (2017) 4218–4224) for the nitromethane formation reaction CH 3 + NO 2 (+M) ↔ CH 3 NO 2 (+M), together with the recently calculated rate constants for HONO/HNO 2 reactions significantly improve ignition delay time predictions in the temperature range 600–1000 K. Furthermore, the experiments with NO addition reveal a non-monotonous sensitization impact on CH 4 ignition at lower temperatures with NO initially acting as an inhibitor at low NO concentrations and then as a promoter as NO concentrations increase in the mixture. This non-monotonous trend is attributed to the role of the chain-termination reaction ĊH 3 + NO 2 (+M) ↔ CH 3 NO 2 (+M) and the impact of NO on the transition to the chain-branching steps CH 2 O + HȮ 2 ↔ HĊO + H 2 O 2 , H 2 O 2 (+M) ↔ ȮH + ȮH (+M), HĊO ↔ CO + Ḣ followed by CO + O 2 ↔ CO 2 + Ö and Ḣ + O 2 ↔ Ö + ȮH. NUIGMech1.2 is systematically validated against the new ignition delay measurements taken here together with species measurements and high temperature ignition delay time data available in the literature for CH 4 /oxidizer mixtures diluted with NO 2 /N 2 O/NO and is observed to accurately capture the sensitization trends.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Chemical kinetic interactions and sensitivity analyses for 2-ethylhexyl nitrate-doped PRF91 using a reduced mechanism

A numerical and experimental investigation about the chemical kinetic interactions between 2-ethylhexylnitrate (EHN) and PRF91 was performed in this study. Rapid compression machine experiments were conducted to investigate the effect of EHN on the autoignition reactivity of the fuel, and a reduced chemical kinetic mechanism was developed including an EHN sub-model. Experiments showed that the ignition delay decreases as the fuel is doped with EHN, but the effect of the doping level of EHN on the ignition is highly non-linear. Moreover, experiments showed that the EHN effectiveness is lowest during the transition between the low-temperature regime and the negative temperature coefficient (NTC) regime, and it rapidly increases as the temperature increases. Both detailed and (developed) reduced mechanisms were validated against the experimental results, allowing a more in-depth EHN-fuel chemistry study. Additionally, ignition delay sensitivity and EHN effectiveness sensitivity analyses were performed with the reduced mechanism to identify the reactions that control the interaction between EHN and the fuel. As the result, EHN thermal decomposition is only relevant for very low temperatures. The chemistry of EHN-doped fuel is more sensitive to intermediate temperature reactions than that of straight fuel, especially at lower temperatures, due to the effect of EHN on the NTC behavior of the fuel. Finally, the chemistry of EHN-doped fuel is very sensitive to NO 2 -to-NO reactions, especially at high temperatures, because these reactions transform the NO 2 generated by EHN into NO, which is a very effective fuel reactivity enhancer.

2-ethylhexyl nitrate↗
DOE OSTI2014

Preparation and surface modification of hierarchical nanosheets-based ZnO microstructures for dye-sensitized solar cells

This paper reports a simple one-step hydrothermal route for the preparation of hierarchical nanosheets-based ZnO microstructures and their application to dye-sensitized solar cells. The morphologies of the products were controlled by the dosage of the reactants. Their physical characteristics were detected by X-ray diffraction, a field-emission scanning electron microscope and a surface analyzer. It is proved that the sample of ZnO microspheres with larger surface area and stronger light-trapping capacity since the superiority of their entirely spherical structures exhibits better photoelectrochemical properties than the mixtures of ZnO microspheres and ZnO microflowers. A dye-sensitized solar cell assembled by the ZnO microspheres as photoanode shows an energy conversion efficiency of 2.94% after surface modification by tetrabutyl titanate solution at 90 {sup °}C. This result is over 1.6 times higher than the non-modified cell fabricated by the ZnO microspheres on the basis of the external improvement and the stability enhancement for the dye-sensitized ZnO photoanode. - Graphical abstract: Influences on energy conversion efficiency of the dye-sensitized solar cells assembled by decorating hierarchical nanosheets-based ZnO microstructures with tetrabutyl titanate solution at different temperatures. Display Omitted - Highlights: • Hierarchical nanosheets-based ZnO microstructures were controllably synthesized. • The ZnO microspheres show good optical and electrochemical properties. • The ZnO microspheres were modified by C{sub 16}H{sub 36}O{sub 4}Ti solution. • Remarkable increase of conversion efficiency is observed after surface modification.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Compressive deformation behavior and strain rate sensitivity of Al-cenosphere hybrid foam with mono-modal, bi-modal and tri-modal cenosphere size distribution

Highlights: • Cenospheres of different size ranges and distributions are used in hybrid aluminium foam. • Microstructure and deformation response of hybrid foam cenosphere size distribution. • Hybrid foam with bi or tri-modal cenosphere distribution exhibits higher strength and energy absorption. • The plateau stresses and energy absorption increased marginally with strain rate. • In case of bi- or tri-modal size distribution, strain rate sensitivity and strain rate sensitivity parameter is marginally lower. - Abstract: AlSi12Cu1Mg1 aluminium alloy-cenosphere closed cell hybrid foams with different kinds of cenosphere size distribution (mono-modal, bi-modal and tri-modal) are used to see the effect of cenosphere size distribution on their deformation behavior under quasi static compressive loading conditions at different strain rates. The stress strain curves are almost similar type irrespective of the cenosphere size distribution and strain rate. However, the plateau stress and energy absorption increased significantly when one used bi-modal and or tri-modal cenosphere size distribution instead of mono-modal cenosphere size distribution. These plateau stresses and energy absorption also increased marginally with strain rate. The densification strain remained almost invariant with strain rate and cenosphere size distribution. The strain rate sensitivity and strain rate sensitivity parameter is relatively lower in case of bi-modal and tri-modal cenosphere size distribution particularly at higher relative density.

36 MATERIALS SCIENCE↗