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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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All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Length‐Independent Charge Transport in Chimeric Molecular Wires

Abstract Advanced molecular electronic components remain vital for the next generation of miniaturized integrated circuits. Thus, much research effort has been devoted to the discovery of lossless molecular wires, for which the charge transport rate or conductivity is not attenuated with length in the tunneling regime. Herein, we report the synthesis and electrochemical interrogation of DNA‐like molecular wires. We determine that the rate of electron transfer through these constructs is independent of their length and propose a plausible mechanism to explain our findings. The reported approach holds relevance for the development of high‐performance molecular electronic components and the fundamental study of charge transport phenomena in organic semiconductors.

Wardrip, Austin G.↗
DOE OSTI2025

Reductant‐ or Light‐Driven ATP‐Independent Reduction of CO 2 by Nitrogenase MoFe Protein

Nitrogenase is a versatile metalloenzyme that activates and reduces small molecules like N 2 , CO, and CO 2 into value-added chemicals at ambient conditions. Previously, it is shown that the Mo-nitrogenase could reduce CO 2 to CO, but not to hydrocarbons, in an ATP-dependent reaction. Here, it is reported that the ability of the catalytic component of Mo-nitrogenase (MoFe protein) enables ATP-independent reduction of CO 2 to up to C 4 hydrocarbons in room-temperature reactions driven by a chemical reductant (Eu II –DTPA) or visible light (via CdS@ZnS (CZS) quantum dots). Moreover, an opposite deuterium isotope effect is observed on the Eu II –DTPA driven reactions of CO 2 reduction by MoFe protein and its V-counterpart (VFe protein), in that the former displays higher activities in H 2 O, and the latter displays higher activities in D 2 O. Furthermore, these results provide an important foundation for further mechanistic exploration of the nitrogenase-enabled, atypical Fischer–Tropsch type reaction that uses CO 2 instead of CO as a substrate; moreover, they serves as a potential template for the future development of nitrogenase-based applications that effectively recycle the greenhouse gas CO 2 into valuable fuel products.

C-C coupling↗
DOE OSTI2015

Coupling of Independent Electrochemical Reactions and Fluorescence at Closed Bipolar Interdigitated Electrode Arrays

Electrochemical reactions occurring at the opposite ends of bipolar electrodes (BPEs) are necessarily coupled, enabling electron transfer events at one end to be read out optically, for example, by coupling to fluorogenic reactions at the other end. In order to explore the potential of this technique for studying multiple redox events, arrays of parallel BPE interdigitated electrode arrays (IDEAs) were fabricated and integrated with separate analytical and reporter microfluidic channels, respectively, in a closed BPE configuration. The apparatus was initially evaluated employing Fe(CN) 6 3/4- in the analytical channel coupled to weakly emissive resazurin and strongly emissive resorufin as the fluorogenic redox reporter pair. We then used the device to investigate a proton-coupled electron transfer reaction, hydroquinone (QH 2 ) oxidation, in structures with an integrated pH modulation electrode (PME). A pH-sensitive dye, fluorescein, was co-introduced into the analytical channel to monitor PME modulation of solution pH, and its coupling to QH 2 oxidation, thereby permitting changes in solution pH, and consequently QH 2 oxidation rate, to be monitored directly in the analytical channel and compared to the fluorescence in the reporter channel. Additionally, diffusion of OH - generated at the PME produced a spatial pH profile that was visualized via fluorescein emission, and, because the oxidation of QH 2 at each BPE is strongly dependent on the local pH, via the coupled fluorogenic reaction at the opposite pole of the corresponding BPE digit in the reporter channel. Thus, BPE IDEAs support the coupling of independent redox reactions and the use of fluorescence imaging to explore a diverse set of spatially varying electrochemical phenomena realized in a variety of electrochemical geometries.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Crystal Orientation Independent Strong TERS Response in Anisotropic ReS2 on Gold

Rhenium disulfide (ReS2) crystallizes in a distorted 1T' lattice with triclinic symmetry arising from Re–Re dimerization, which produces in-plane anisotropic properties and a dense set of Raman-active modes with mixed atomic displacements. Unlike far-field Raman spectroscopy, which shows strong polarization and orientation dependence, tip-enhanced Raman spectroscopy (TERS) probes out-of-plane Raman tensor components. Here we use 785 nm (1.58 eV) gap-mode TERS to investigate monolayer to four-layer thick ReS2 crystals.. TERS maps and averaged spectra reveal that all modes remain invariant under 90° rotation of the crystal, and the only thickness-dependent feature is the emergence of the multilayer breathing mode. These results demonstrate that TERS yields a crystal-orientation-independent Raman response in ReS2 and provides direct access to Raman tensor components that are not easily accessible in conventional far-field measurements.

Valencia Acuna, Pavel A.↗
DOE OSTI2017

Evaluation of energy balance closure adjustment methods by independent evapotranspiration estimates from lysimeters and hydrological simulations

Here, we report non-closure of the surface energy balance is a frequently observed phenomenon of hydrometeorological field measurements, when using the eddy-covariance method, which can be ascribed to an underestimation of the turbulent fluxes. Several approaches have been proposed in order to adjust the measured fluxes for this apparent systematic error. However, there are uncertainties about partitioning of the energy balance residual between the sensible and latent heat flux and whether such a correction should be applied on 30-minute data or longer time scales. The data for this study originate from two grassland sites in southern Germany, where measurements from weighable lysimeters are available as reference. The adjusted evapotranspiration rates are also compared with joint energy and water balance simulations using a physically-based distributed hydrological model. We evaluate two adjustment methods: the first one preserves the Bowen ratio and the correction factor is determined on a daily basis. The second one attributes a smaller portion of the residual energy to the latent heat flux than to the sensible heat flux for closing the energy balance for every 30-minute flux integration interval. Both methods lead to an improved agreement of the eddy-covariance based fluxes with the independent lysimeter estimates and the physically-based model simulations. The first method results in a better comparability of evapotranspiration rates, and the second method leads to a smaller overall bias. These results are similar between both sites despite considerable differences in terrain complexity and grassland management. Moreover, we found that a daily adjustment factor leads to less scatter than a complete partitioning of the residual for every half-hour time interval. Lastly, the vertical temperature gradient in the surface layer and friction velocity were identified as important predictors for a potential future parameterization of the energy balance residual.

58 GEOSCIENCES↗
DOE OSTI2016

Model-independent measurement of mixing parameters in D 0 → K$^{0}_{S}$ π+π– decays

The first model-independent measurement of the charm mixing parameters in the decay D 0 → K$^{0}_{S}$ π+π– is reported, using a sample of pp collision data recorded by the LHCb experiment, corresponding to an integrated luminosity of 1.0 fb –1 at a centre-of-mass energy of 7 TeV. The measured values are x = (–0.86 ± 0.53 ± 0.17) x 10 –2 , y = (+0.03 ± 0.46 ± 0.13) x 10 –2 , where the first uncertainties are statistical and include small contributions due to the external input for the strong phase measured by the CLEO collaboration, and the second uncertainties are systematic.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Model-independent measurement of the CKM angle γ using B 0 → DK* 0 decays with D→K S 0 π + π – and K S 0 K + K –

A binned Dalitz plot analysis of the decays B 0 → DK* 0 , with D → K S 0 π + π – and D → K S 0 K + K – , is performed to measure the observables x ± and y ± , which are related to the CKM angle γ and the hadronic parameters of the decays. The D decay strong phase variation over the Dalitz plot is taken from measurements performed at the CLEO-c experiment, making the analysis independent of the D decay model. With a sample of proton-proton collision data, corresponding to an integrated luminosity of 3.0 fb –1 , collected by the LHCb experiment, the values of the CP violation parameters are found to be x + = 0.05 ± 0.35 ± 0.02, x – = –0.31 ± 0.20 ± 0.04, y + = –0.81 ± 0.28 ± 0.06 and y – = 0.31 ± 0.21 ± 0.05, where the first uncertainties are statistical and the second systematic. These observables correspond to values γ = (71 ± 20)°, $r_{B^{0}}$= 0.56 ± 0.17 and δ$_{B^{0}}$ = ($204^{+21}_{–20}$)°. The parameters $r_{B^{0}}$ and δ$_{B^{0}}$ are the magnitude ratio and strong phase difference between the suppressed and favoured B 0 decay amplitudes, and have been measured in a region of ±50 MeV/c 2 around the K*(892) 0 mass and with the magnitude of the cosine of the K*(892) 0 helicity angle larger than 0.4.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Model-independent search for the presence of new physics in events including H → γγ with $\sqrt{s}$ = 13 TeV pp data recorded by the ATLAS detector at the LHC

A model-independent search for new physics leading to final states containing a Higgs boson, with a mass of 125.09 GeV, decaying to a pair of photons is performed with 139 fb -1 of $\sqrt{s}$ = 13 TeV $pp$ collision data recorded by the ATLAS detector at the Large Hadron Collider at CERN. This search examines 22 final states categorized by the objects that are produced in association with the Higgs boson. These objects include isolated electrons or muons, hadronically decaying $τ$-leptons, additional photons, missing transverse momentum, and hadronic jets, as well as jets that are tagged as containing a $b$-hadron. No significant excesses above Standard Model expectations are observed and limits on the production cross section at 95% confidence level are set. Detector efficiencies are reported for all 22 signal regions, which can be used to convert detector-level cross-section limits reported in this paper to particle-level cross-section constraints.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Model-independent bounds on R(J/ψ)

We present a model-independent bound on R(J/ψ)≡BR(B+C→J/ψτ+ντ)/BR(B+C→J/ψμ+νμ) . This bound is constructed by constraining the form factors through a combination of dispersive relations, heavy-quark relations at zero-recoil, and the limited existing determinations from lattice QCD. The resulting 95% confidence-level bound, 0.20 ≤ R(J/ψ) ≤ 0.39, agrees with the recent LHCb result at 1.3σ, and rules out some previously suggested model form factors.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Model-independent prediction of R(η c )

We present a model-independent prediction for R(η c )≡$\mathscr{BR}$(B$^+_c$ → η c τ+ν τ )/$\mathscr{BR}$(B +c → η c µ + ν µ ). This prediction is obtained from the form factors through a combination of dispersive relations, heavy-quark relations at zero-recoil, and the limited existing determinations from lattice QCD. The resulting prediction, R(η c ) = 0.29(5), agrees with previous model predictions, but without uncontrolled systematic uncertainties.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2012

Obesity: An Independent Risk Factor for Insufficient Hemostasis Using the AngioSeal Vascular Closure Device After Antegrade Puncture

Purpose: This study was designed to investigate the efficacy of the AngioSeal vascular closure device after antegrade puncture of the femoral artery. Methods: In a prospective study, 120 consecutive patients underwent lower limb vascular intervention by an antegrade access to the common femoral artery (CFA). After intervention, a 6F (n = 88) or an 8F (n = 32) AngioSeal vascular closure device was used to achieve hemostasis. The technical success or the cause of failure was documented. In addition, the coagulation status (platelets, INR, prothrombin time, atrial thromboplastin time (PTT)), hypertonus, locoregional habitus of the groin, body mass index (BMI), presence of calcifications, and history of previous surgical interventions of the CFA were evaluated. Results: Hemostasis was achieved in 97 patients (81%). In 12 patients (10%), persistent bleeding of the puncture site required manual compression. In another nine patients (8%) a kink of the sheath obviated the passage of the collagen plug toward the vessel, and in two patients the anchor dislodged out of the vessel, requiring manual compression. There were no significant differences between the groups of successful and unsuccessful sealing regarding the mean platelets (241 vs. 254 * 10{sup 9}/l; P = 0.86), INR (1.06 vs. 1.02; P = 0.52), prothrombin time (90% vs. 90%; P = 0.86), and PTT (30 vs. 31 s; P = 0.82). However, unsuccessful sealing was more likely in obese patients with an increased BMI (26.6 vs. 28.8 kg/m{sup 2}; P = 0.04). Conclusions: Obesity seems to be an independent risk factor for insufficient sealing using the AngioSeal vascular closure device after antegrade puncture of the CFA. In 8% of our patients, hemostasis could not be achieved due to kink of the flexible sheath.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2013

Margin Size is an Independent Predictor of Local Tumor Progression After Ablation of Colon Cancer Liver Metastases

This study was designed to evaluate the relationship between the minimal margin size and local tumor progression (LTP) following CT-guided radiofrequency ablation (RFA) of colorectal cancer liver metastases (CLM). An institutional review board-approved, HIPPA-compliant review identified 73 patients with 94 previously untreated CLM that underwent RFA between March 2003 and May 2010, resulting in an ablation zone completely covering the tumor 4-8 weeks after RFA dynamic CT. Comparing the pre- with the post-RFA CT, the minimal margin size was categorized to 0, 1-5, 6-10, and 11-15 mm. Follow-up included CT every 2-4 months. Kaplan-Meier methodology and Cox regression analysis were used to evaluate the effect of the minimal margin size, tumor location, size, and proximity to a vessel on LTP. Forty-five of 94 (47.9 %) CLM progressed locally. Median LTP-free survival (LPFS) was 16 months. Two-year LPFS rates for ablated CLM with minimal margin of 0, 1-5 mm, 6-10 mm, 11-15 mm were 26, 46, 74, and 80 % (p < 0.011). Minimal margin (p = 0.002) and tumor size (p = 0.028) were independent risk factors for LTP. The risk for LTP decreased by 46 % for each 5-mm increase in minimal margin size, whereas each additional 5-mm increase in tumor size increased the risk of LTP by 22 %. An ablation zone with a minimal margin uniformly larger than 5 mm 4-8 weeks postablation CT is associated with the best local tumor control.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2018

Process-Independent Effective Coupling from QCD Green's Functions to Phenomenology

This article reports on a very recent proposal for a new type of process-independent QCD effective charge (Binosi et al. in Phys Rev D 96(5):054026, 2017. https://doi.org/10.1103/PhysRevD.96.054026) defined, as an anologue of the Gell-Mann-Low effective charge in QCD, on the ground of nothing but the knowledge of the gauge-field two-point Green's function, albeit modified within a particular computational framework; namely, the combination of pinch technique and background field method which makes possible a systematic rearranging of classes of diagrams in order to redefine the Green's function and have them obey linear QED-like Slavnov-Taylor identities. We have here calculated that effective charge, shown how strikingly well it compares to a process-dependent effective charge based on the Bjorken sum rule; and, finally, employed it in an exploratory calculation of the proton electromagnetic form factor in the hard scattering regime.

confinement↗
DOE OSTI2015

An empirical study of redundant array of independent solid-state drives (RAIS)

Solid-state drives (SSD) are popular storage media devices alongside magnetic hard disk drives (HDD). SSD flash chips are packaged in HDD form factors and SSDs are compatible with regular HDD device drivers and I/O buses. This compatibility allows easy replacement of individual HDDs with SSDs in existing storage systems. However, under certain circumstances, SSD write performance can be significantly slowed by garbage collection (GC) processes. The frequency of GC activity is directly correlated with the frequency of inside-SSD write operations and the amount of data written to it. GC scheduling is locally controlled by an internal SSD logic. Here, this paper studies the feasibility of Redundant Arrays of Independent Flash-based Solid-state drives (RAIS). We empirically analyze the RAIS performance using commercially-off-the-shelf (COTS) SSDs. We investigate the performance of various RAIS configurations under a variety of I/O access patterns. Finally, we present our performance and cost comparisons of RAIS with a fast, PCIe-based COTS SSD, in terms of performance and cost.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2018

Characteristic Functions and Compactness of Distributions of Sums of Independent Random Variables

The sequences of distributions of centered sums of independent random variables are considered within the framework of the series scheme, without assuming the classical conditions for uniform asymptotic smallness and uniform limit constancy. Necessary and sufficient conditions are obtained for relative and stochastic compactness of such sequences in terms of the characteristic functions of summable random variables and with using their τ-centers.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2019

Polarization-based plug-and-play measurement-device-independent quantum key distribution

Measurement-device-independent quantum key distribution (MDI-QKD) has received much attention, with the goal of overcoming all of the security loopholes caused by an imperfect detection system. We here propose a plug-and-play MDI-QKD (P&P MDI-QKD) scheme whereby an untrusted relay node, Charlie, owns a laser and sends photons to Alice and Bob. Alice (Bob) modulates the polarization of the incident photons and returns them to Charlie. Charlie uses a modified Bell state analyzer (BSA) to perform Bell state measurements (BSM). In comparison with the original version of MDI-QKD, our scheme exploits a single untrusted laser as the photon source. This makes the signal photons identical and enhances the Hong-Ou-Mandel effect. Second, because of the P&P structure, the setup can automatically eliminate the birefringence influence of the fibers, which makes the setup highly stable. Finally, our modified BSA can identify |Φ〉{sup +} and |Φ〉{sup −} of four Bell states with polarization encoding but not |Ψ〉{sup +} and |Ψ〉{sup −}. Based on practical experimental parameters, a simulation showed that the maximum theoretical secure transmission distance could reach more 280 km.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗