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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 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

Spatial and temporal variations of new particle formation in East Asia using an NPF-explicit WRF-chem model: North-south contrast in new particle formation frequency

The new particle formation (NPF)-explicit version of the WRF-chem model, which we developed recently, can calculate the growth and sink of nucleated clusters explicitly with 20 aerosol size bins from 1 nm to 10 μm. In this study, the model is used to understand spatial and temporal variations of the frequency of NPF events and the concentrations of aerosols (condensation nuclei, CN) and cloud condensation nuclei (CCN) within the boundary layer in East Asia in spring 2009. Model simulations show distinct north-south contrast in the frequency and mechanism of NPF in East Asia. NPF mostly occurred over limited periods and regions between 30° and 45°N, such as northeast China, Korea, and Japan, including regions around active volcanoes (Miyakejima and Sakurajima). At these latitudes, NPF was considerably suppressed by high concentrations of preexisting particles under stagnant air conditions associated with high-pressure systems, while nucleation occurred more extensively on most days during the simulation period. Conversely, neither nucleation nor NPF occurred frequently south of 30°N because of lower SO2 emissions and H2SO4 concentrations. The period-averaged NPF frequency was 3 times higher at latitudes of 30° - 45°N than at latitudes of 20° - 30°N. The north-south contrast of NPF frequency is validated by surface measurements in outflow regions in East Asia. The period- and domain-averaged contribution of secondary particles is estimated to be 44% for CN (> 10 nm) and 26% for CCN at a supersaturation of 1.0% in our simulation, though the contribution is highly sensitive to the magnitudes and size distributions of primary aerosol emissions and the coefficients in the nucleation parameterizations.

Matsui, H.↗
DOE OSTI2014

Search for new particles in events with one lepton and missing transverse momentum in pp collisions at $ \sqrt{s} $ = 8 TeV with the ATLAS detector

This paper presents a search for new particles in events with one lepton (electron or muon) and missing transverse momentum using 20.3 fb -1 of proton-proton collision data at $ \sqrt{s} $ = 8 TeV recorded by the ATLAS experiment at the Large Hadron Collider. No significant excess beyond Standard Model expectations is observed. A W' with Sequential Standard Model couplings is excluded at the 95% confidence level for masses up to 3.24 TeV. Excited chiral bosons (W*) with equivalent coupling strengths are excluded for masses up to 3.21 TeV. In the framework of an effective field theory limits are also set on the dark matter-nucleon scattering cross-section as well as the mass scale M* of the unknown mediating interaction for dark matter pair production in association with a leptonically decaying W.[Figure not available: see fulltext.]

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Search for new phenomena in events with same-charge leptons and b-jets in pp collisions at $ \sqrt{s}=13 $ TeV with the ATLAS detector

A search for new phenomena in events with two same-charge leptons or three leptons and jets identified as originating from b-quarks in a data sample of 36.1 fb -1 of pp collisions at √s=13 TeV recorded by the ATLAS detector at the Large Hadron Collider is reported. No significant excess is found and limits are set on vector-like quark, four-top-quark, and same-sign top-quark pair production. The observed (expected) 95% CL mass limits for a vector-like T- and B-quark singlet are m T > 0.98 (0.99) TeV and m B > 1.00 (1.01) TeV respectively. Limits on the production of the vector-like T 5/3 -quark are also derived considering both pair and single production; in the former case the lower limit on the mass of the T 5/3 -quark is (expected to be) 1.19 (1.21) TeV. The Standard Model four-top-quark production cross-section upper limit is (expected to be) 69 (29) fb. Constraints are also set on exotic four-top-quark production models. Finally, limits are set on same-sign top-quark pair production. The upper limit on uu → tt production is (expected to be) 89 (59) fb for a mediator mass of 1 TeV, and a dark-matter interpretation is also derived, excluding a mediator of 3 TeV with a dark-sector coupling of 1.0 and a coupling to ordinary matter above 0.31.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Design, synthesis, and antihypertensive activity of new pyrimidine derivatives endowing new pharmacophores

A new series of achiral pyrimidine derivatives based on nifedipine-like structure was designed and synthesized. These pyrimidyl derivatives contained hydrazine, hydrazones, acetohydrazide, differently substituted benzylidene functionalities, benzosulfohydrazine, various heterocycles such as pyrazole, pyrazolidinedione, thiazoline, and thiazolidinone rings, and fused ring systems such as triazolopyrimidine and pyrimidotriazine rings. Compounds 5a, 5b, 11b, 8b, 9b–d, and 15b showed a decrease in mean arterial rabbit blood pressure (MABP) ranging from 51.4 to 78.2 mmHg in rabbits in comparison with nifedipine-treated rabbits. Among these derivatives, compounds 5a, 5b, 9b, and 9c were found to exhibit calcium channel blockade activity on preparations of rabbit aortae. They exhibited relaxation in the range of 89.2% to 74.4% in comparison to nifedipine (57.6%) as well as a decrease in heart rate. Histopathological effect of compounds 5a,b on the expression of endothelial nitric oxide synthase (eNOS) was also examined on rat aorta. An intense expression of eNOS immune staining in aortic endothelium was seen for compound 5b indicating that it lowered blood pressure via activation of eNOS expression in aorta.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

A new multi-scale structure finding algorithm to identify cosmological structure

We introduce a new structure finding algorithm that self-consistently parses large scale cosmological structure into clusters, filaments and voids. This structure finding algorithm probes the structure at multiple scales and classifies the appropriate regions with the most probable structure type and size. We show that it can identify the baryon fraction of intercluster medium and cosmological voids.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

A new strategy to mitigate the initial capacity loss of lithium ion batteries

Hard carbon (non-graphitizable) and related materials, like tin, tin oxide, silicon, and silicon oxide, have a high theoretical lithium delivery capacity (>550 mAh/g depending on their structural and chemical properties) but unfortunately they also exhibit a large initial capacity loss (ICL) that overrides the true reversible capacity in a full cell. Overcoming the large ICL of hard carbon in a full-cell lithium-ion battery (LIB) necessitates a new strategy wherein a sacrificial lithium source additive, such as, Li5FeO4 (LFO), is inserted on the cathode side. Full batteries using hard carbon coupled with LFO-LiCoO2 (LCO) are currently under development at our laboratory. We find that the reversible capacity of a cathode containing LFO can be increased by 14%. Furthermore, the cycle performance of full cells with LFO additive is improved from <90% to >95%. We show that the LFO additive not only can address the irreversible capacity loss of the anode, but can also provide the additional lithium ion source required to mitigate the lithium loss caused by side reactions. In addition, we have explored the possibility to achieve higher capacity with hard carbon, whereby the energy density of full cells can be increased from ca. 300 Wh/kg to >400 Wh/kg.

hard carbon↗
DOE OSTI2013

Crystals, magnetic and electronic properties of a new ThCr{sub 2}Si{sub 2}-type BaMn{sub 2}Bi{sub 2} and K-doped compositions

This is a report on the new 122 ternary transition-metal pnictide of BaMn{sub 2}Bi{sub 2}, which is crystallized from bismuth flux. BaMn{sub 2}Bi{sub 2} adopts ThCr{sub 2}Si{sub 2}-type structure (I4/mmm) with a=4.4902(3) Å and c=14.687(1) Å; it is antiferromagnetic with anisotropic magnetic susceptibility and semiconducting with a band gap of E{sub g}=6 meV. Heat capacity result confirms the insulating ground state in BaMn{sub 2}Bi{sub 2} with the electronic residual Sommerfeld coefficient of γ=0. The high temperature magnetization results show that magnetic ordering temperature is T{sub N} ∼400 K. Hole-doping in BaMn{sub 2}Bi{sub 2} via potassium in Ba{sub 1−x}K{sub x}Mn{sub 2}Bi{sub 2} results in metallic behavior for x=0.10(1), 0.32(1) and 0.36(1). With K-doping, more magnetically anisotropic behavior is observed. Although there is a downturn in electrical resistivity and low-field magnetization data below 4 K in>30%-doped crystals, there is no sign of zero resistance or diamagnetism. - Graphical abstract: Local moment antiferromagnet BaMn{sub 2}Bi{sub 2}, the first bismuthide with ThCr{sub 2}Si{sub 2} structure, turns metallic upon K-doping. Highlights: • BaMn{sub 2}Bi{sub 2} and Ba{sub 1−x}K{sub x}Mn{sub 2}Bi{sub 2} (0≤x<0.4) measuring up to 1 cm in length have been synthesized from Bi flux reactions. • BaMn{sub 2}Bi{sub 2} is the first bismuthide with ThCr{sub 2}Si{sub 2}-type structure. • BaMn{sub 2}Bi{sub 2} is a small gap semiconductor but, upon hole-doping, turns metallic with a downturn in resistivity below 4 K. • BaMn{sub 2}Bi{sub 2} is a local moment antiferromagnet with T{sub N} ∼400 K.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Self-assembly of designed precursors: A route to crystallographically aligned new materials with controlled nanoarchitecture

Modulated elemental reactants is a method by which new and complex intergrowth compounds can be synthesized by the self-assembly of designed precursors prepared by physical vapor deposition. Careful calibration of the composition and thickness of the precursors ensures the formation of the desired product by precise control of local composition and diffusion lengths. Superstructures of increasing complexity can be realized using binary and ternary systems as starting points. The synthesis of systems based on three different binary compounds, either alloyed together or separated into distinct layers, expands the number of possible superstructures that can be formed using this technique, but provides analytical challenges. The synthesis of [(SnSe){sub 1.15}]{sub 1}([Ta{sub x}V{sub 1−x}]Se{sub 2}){sub 1}[(SnSe){sub 1.15}]{sub 1}([V{sub y}Ta{sub 1−y}]Se{sub 2}){sub 1} compound is used to illustrate the preparation of precursors and the challenges in both measuring and limiting the interdiffusion of layers during self-assembly. Systematic changes in the electrical properties of (SnSe){sub 1+δ}(Ta{sub x}V{sub 1−x})Se{sub 2} alloys are observed as x is varied. The electrical resistivity of [(SnSe){sub 1.15}]{sub 1}([Ta{sub x}V{sub 1−x}]Se{sub 2}){sub 1}[(SnSe){sub 1.15}]{sub 1}([V{sub y}Ta{sub 1−y}]Se{sub 2}){sub 1} can be modeled as the two constituent layers in parallel.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Self-activation of cellulose: A new preparation methodology for activated carbon electrodes in electrochemical capacitors

Current synthetic methods of biomass-derived activated carbon call for a costly chemical or physical activation process. Herein, we report a simple one-step annealing synthesis yielding a high surface area cellulose-derived activated carbon. We discover that simply varying the flow rate of Argon during pyrolysis enables ‘self-activation’ reactions that can tune the specific surface areas of the resulting carbon, ranging from 98 m2/g to values as high as 2600 m2/g. Furthermore, we, for the first time, observe a direct evolution of H2 from the pyrolysis, which gives strong evidence towards an in situ self-activation mechanism. Surprisingly, the obtained activated carbon is a crumbled graphene nanostructure composed of interconnected sheets, making it ideal for use in an electrochemical capacitor. The cellulose-derived nanoporous carbon exhibits a capacitance of 132 F g-1 at 1 A g-1, a performance comparable to the state-of-the-art activated carbons. This work presents a fundamentally new angle to look at the synthesis of activated carbon, and highlights the importance of a controlled inert gas flow rate during synthesis in general, as its contributions can have a very large impact on the final material properties.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2014

A New Approach to Estimating the Probability for β-delayed Neutron Emission

The probability for neutron emission following β decay, Pn, is a crucial property for a wide range of physics and applications including nuclear structure, r-process nucleosynthesis, the control of nuclear reactors, and the post-processing of nuclear fuel. Despite much experimental effort, knowledge of Pn values is still lacking in very neutron-rich nuclei, requiring predictions from either systematics or theoretical models. Traditionally, systematic predictions were made by investigating the Pn value as a function of the decay Q value and the neutron separation energy in the daughter nucleus. A new approach to Pn systematics is presented which incorporates the half-life of the decay and the Q value for β-delayed neutron emission. This prescription correlates the known data better, and thus improves the estimation of Pn values for neutron-rich nuclei. Such an approach can be applied to generate input values for r-process network calculations or in the modeling of advanced fuel cycles.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗