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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Highly interactive, steered scientific workflows on HPC systems: optimizing design solutions

Scientific workflows are becoming increasingly important in high performance computing (HPC) settings, as the feasibility and appeal of many simultaneous heterogeneous tasks increases with increasing hardware capabilities. Currently no HPC-based workflow platform supports a dynamically adaptable workflow with interactive steering and analysis at run-time. Furthermore, for most workflow programs, compute resources are fixed for a given instance, resulting in a possible waste of expensive allocation resources when tasks are spawned and killed. Here we describe the design and testing of a run-time-interactive, adaptable, steered workflow tool capable of executing thousands of parallel tasks without an MPI programming model, using a database management system to facilitate task management through multiple live connections. We find that on the Oak Ridge Leadership Computing Facility pre-exascale Summit supercomputer it is possible to launch and interactively steer workflows with thousands of simultaneous tasks with negligible latency. For the case of particle simulation and analysis tasks that run for minutes to hours, this paradigm offers the prospect of a robust and efficient means to perform simulation-space exploration with on-the-fly analysis and adaptation.

Ossyra, John R↗
DOE OSTI2016

Witten diagrams revisited: the AdS geometry of conformal blocks

Here, we develop a new method for decomposing blocks. The steps involved are elementary, requiring no explicit integration, and operate directly in position space. Central to this construction is an appealingly simple answer to the question: what object in AdS computes a conformal block? The answer is a "geodesic Witten diagram", which is essentially an ordinary exchange Witten diagram, except that the cubic vertices are not integrated over all of AdS, but only over bulk geodesics connecting the boundary operators. In particular, we also consider the case of four-point functions of scalar operators, and show how to easily reproduce existing results for the relevant conformal blocks in arbitrary dimension.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Entanglement wedge reconstruction using the Petz map

At the heart of recent progress in AdS/CFT is the question of subregion duality, or entanglement wedge reconstruction: which part(s) of the boundary CFT are dual to a given subregion of the bulk? This question can be answered by appealing to the quantum error correcting properties of holography, and it was recently shown that robust bulk (entanglement wedge) reconstruction can be achieved using a universal recovery channel known as the twirled Petz map. In short, one can use the twirled Petz map to recover bulk data from a subset of the boundary. However, this map involves an averaging procedure over bulk and boundary modular time, and hence it can be somewhat intractable to evaluate in practice. We show that a much simpler channel, the Petz map, is sufficient for entanglement wedge reconstruction for any code space of fixed finite dimension – no twirling is required. Moreover, the error in the reconstruction will always be non-perturbatively small. From a quantum information perspective, we prove a general theorem extending the use of the Petz map as a general-purpose recovery channel to subsystem and operator algebra quantum error correction.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2021

Functional prescription for EFT matching

We simplify the one-loop functional matching formalism to develop a streamlined prescription. The functional approach is conceptually appealing: all calculations are performed within the UV theory at the matching scale, and no prior determination of an Effective Field Theory (EFT) operator basis is required. Our prescription accommodates any relativistic UV theory that contains generic interactions (including derivative couplings) among scalar, fermion, and vector fields. As an example application, we match the singlet scalar extended Standard Model (SM) onto SMEFT.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Tadpole-induced electroweak symmetry breaking and pNGB Higgs models

We investigate induced electroweak symmetry breaking (EWSB) in models in which the Higgs is a pseudo-Nambu-Goldstone boson (pNGB). In pNGB Higgs models, Higgs properties and precision electroweak measurements imply a hierarchy between the EWSB and global symmetry-breaking scales, $v_H \ll f_H$. When the pNGB potential is generated radiatively, this hierarchy requires fine-tuning to a degree of at least $\sim v_H^2/f_H^2$. We show that if Higgs EWSB is induced by a tadpole arising from an auxiliary sector at scale $f_\Sigma \ll v_H$, this tuning is significantly ameliorated or can even be removed. We present explicit examples both in Twin Higgs models and in Composite Higgs models based on $SO(5)/SO(4)$. For the Twin case, the result is a fully natural model with $f_H \sim 1$ TeV and the lightest colored top partners at 2 TeV. These models also have an appealing mechanism to generate the scales of the auxiliary sector and Higgs EWSB directly from the scale $f_H$, with a natural hierarchy $f_\Sigma \ll v_H \ll f_H \sim{\rm TeV}$. Finally, the framework predicts modified Higgs coupling as well as new Higgs and vector states at LHC13.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Freeze-in, glaciation, and UV sensitivity from light mediators

Dark matter (DM) freeze-in through a light mediator is an appealing model with excellent detection prospects at current and future experiments. Light mediator freeze-in is UV-insensitive insofar as most DM is produced at late times, and thus the DM abundance does not depend on the unknown early evolution of our universe. However the final DM yield retains a dependence on the initial DM population, which is usually assumed to be exactly zero. We point out that in models with light mediators, the final DM yield will also depend on the initial conditions assumed for the light mediator population. We describe a class of scenarios we call “glaciation” where DM freezing in from the SM encounters a pre-existing thermal bath of mediators, and study the dependence of the final DM yield on the initial temperature of this dark radiation bath. To compute DM scattering rates in this cosmology, we derive for the first time an exact integral expression for the Boltzmann collision term describing interactions between two species at different temperatures. We quantify the dependence of the DM yield on the initial dark temperature and find that it can be sizeable in regions near the traditional (zero initial abundance) freeze-in curve. We generalize the freeze-in curve to a glaciation band, which can extend as much as an order of magnitude below the traditional freeze-in direct detection target, and point out that the DM phase space distribution as well as the yield can be strongly dependent on initial conditions.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2021

Revisiting the multi-monopole point of SU( N ) $\mathcal{N}$ = 2 gauge theory in four dimensions

Motivated by applications to soft supersymmetry breaking, we revisit the expansion of the Seiberg-Witten solution around the multi-monopole point on the Coulomb branch of pure SU(N) $\mathcal{N}$ = 2 gauge theory in four dimensions. At this point N - 1 mutually local magnetic monopoles become massless simultaneously, and in a suitable duality frame the gauge couplings logarithmically run to zero. We explicitly calculate the leading threshold corrections to this logarithmic running from the Seiberg-Witten solution by adapting a method previously introduced by D’Hoker and Phong. We compare our computation to existing results in the literature; this includes results specific to SU(2) and SU(3) gauge theories, the large-N results of Douglas and Shenker, as well as results obtained by appealing to integrable systems or topological strings. We find broad agreement, while also clarifying some lingering inconsistencies. Finally, we explicitly extend the results of Douglas and Shenker to finite N, finding exact agreement with our first calculation.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2012

A Surgeon's View on Endarterectomy and Stenting in 2011: Lest We Forget, It's All About Preventing Stroke

It has been nearly 60 years since Felix Eastcott published his seminal paper on carotid reconstruction, which paved the way for carotid endarterectomy (CEA) and then carotid artery stenting (CAS) to assume prominent roles in the prevention of stroke. Yet the ensuing 60 years has witnessed repeated cycles of challenges to practice, professional mistrust, conflicts of interest, dogmatic retention of traditional management strategies, inappropriate corporate interventions, and a general failure to adapt to new evidence. Even the performance of large-scale randomised trials has been associated with rancour and a lack of consensus. This article reviews the history of invasive interventions in the treatment of carotid disease and makes a plea to both the surgical and interventional communities that the fundamental priority must always be the prevention of stroke. It concludes with an appeal for colleagues to collaborate to determine how best to treat patients during the hyperacute period after the onset of symptoms and to identify a smaller cohort of asymptomatic patients who are truly at high risk for stroke in whom to target CAS or CEA.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2012

Chemosaturation with Percutaneous Hepatic Perfusion for Unresectable Isolated Hepatic Metastases from Sarcoma

Purpose: Treatment of patients with unresectable liver metastases is challenging. Regional therapies to the liver have been developed that maximize treatment of the localized disease process without systemic toxic adverse effects. We discuss the procedural aspects of liver chemosaturation with percutaneous hepatic perfusion (CS-PHP). Methods: We present as an illustration of this technique a case report of the treatment of unresectable metastatic leiomyosarcoma of the liver. Results: A randomized phase III trial for unresectable liver metastases from melanoma was recently completed comparing CS-PHP with melphalan vs. best alternative care (BAC). When compared with BAC, CS-PHP was associated with a significant improvement in hepatic progression-free survival (8.0 months CS-PHP vs. 1.6 months BAC, p < 0.0001) and overall progression-free survival (6.7 months CS-PHP vs. 1.6 months BAC, p < 0.0001), respectively. On the basis of these results, and given our experience as one of the treating institutions for this phase III trial, we appealed for compassionate use of CS-PHP in a patient with isolated bilobar unresectable hepatic metastases from leiomyosarcoma. Four target lesions were identified and monitored to assess treatment response. A total of 4 CS-PHP procedures were performed, with a 25 % reduction in size of the largest lesion observed and 16 month hepatic progression-free survival. Toxicity was mild (neutropenia) and manageable on an outpatient basis. Conclusion: CS-PHP offers several advantages for unresectable hepatic sarcoma metastases. CS-PHP is minimally invasive and repeatable, and it has a predictable and manageable systemic toxicity profile. For appropriately selected patients, CS-PHP can delay tumor progression and could potentially improve survival.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2015

Removing chiral contamination of lactate solutions by selective metabolism of the D-enantiomer

A bio-based process is appealing for purification of L-lactic acid, the major enantiomer of polylactic acid syrup, generated by thermochemical processes at the end of life of PLA-based plastics, from its chiral impurity, d-lactic acid, before reuse. Polylactic acid (PLA), a renewable alternative to petroleum-derived plastics, contains a mixture of l- and d-lactic acid (LA) isomers with the l-isomer dominating (up to 95 %). A novel bio-based process was developed to produce chirally pure l-LA from syrup produced during recycling of PLA-plastics. This process utilizes an engineered Escherichia coli (strain DC1001) containing novel gene deletions (lld, ykg) that eliminated the oxidative metabolism of L-lactate, leaving the membrane-bound d-lactate dehydrogenases to selectively metabolize the d-isomer. Strain DC1001 removed 8.7 g d-lactate l –1 from a PLA-syrup containing 135 g total lactic acid l –1 in 24 h. Average rates of removal of D-lactic acid were 0.25 g D-lactate h –1 (g cell dry weight) –1 and 0.36 g D-lactate l –1 h –1 . Bio-based purification of PLA-syrup utilizing E. coli strain DC1001 is an attractive process step during recycling of PLA-plastics. Here, this selective oxidation process can also be used to remove chiral contamination of L-lactate in medical applications.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2018

Naturalness, Extra-Empirical Theory Assessments, and the Implications of Skepticism

Naturalness is an extra-empirical quality that aims to assess plausibility of a theory. Finetuning measures are often deputized to quantify the task. However, knowing statistical distributions on parameters appears necessary. Such meta-theories are not known yet. A critical discussion of these issues is presented, including their possible resolutions in fixed points. Both agreement to and skepticism of naturalness's utility remains credible, as is skepticism to any extra-empirical theory assessment (SEETA) that claims to identify "more correct" theories that are equally empirically adequate. The severe implications of SEETA are set forward in some detail. Here, we conclude with a summary and discussion of the viability of three main viewpoints toward naturalness and fine-tuning, where the "moderate naturalness position" is suggested to be most appealing, not suffering from the disquietudes of the extreme pro- and anti-naturalness positions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Biomass Derived Antimicrobial Hybrid Cellulose Hydrogel with Green ZnO Nanoparticles for Curcumin Delivery and its Kinetic Modelling

Regenerated cellulose obtained from sugarcane bagasse was used for hydrogel preparation using epichlorohydrin (crosslinker) and green zinc oxide nanoparticles (ZNPs) which were phytosynthesised from musk melon seed extract. The synthesised ZNPs were characterised using FESEM and EDAX. The swelling capacity of the hydrogel was determined by swelling measurements. For drug delivery studies from hydrogel, curcumin was selected as the model drug for its appealing anticancer and antimicrobial activity. The presence of ZNPs and curcumin in the hybrid hydrogel was analysed using FTIR, XRD, TGA and SEM analysis. The drug loading efficiency was optimised by Taguchi method. The drug release studies were performed under varying pH and initial drug loading concentration. The kinetic studies showed the best fit with case II type of transport with polymer swelling as the drug release mechanism. Antimicrobial activity for curcumin loaded hybrid hydrogel and pure cellulose hydrogel was performed using Staphylococcus aureus (bacteria) and Trichophyton rubrum (fungi). Thus, the developed curcumin loaded biomass derived hybrid hydrogel could find potential application towards skin infective applications.

36 MATERIALS SCIENCE↗
DOE OSTI2016

On the Role of Fermi Energy in Determining Properties of Superconductors: a Detailed Comparative Study of Two Elemental Superconductors (Sn and Pb), a Non-cuprate (MgB{sub 2}) and Three Cuprates (YBCO, Bi-2212 and Tl-2212)

Fermi energies (E{sub F}s) of high- T{sub c} superconductors (SCs) have of late been evincing considerable interest because they are believed to be the cause of their high T{sub c}s and gap structures. Since Bardeen-Cooper-Schrieffer (BCS) equations for elemental and generalized-BCS equations for non-elemental SCs are derived under the blanket of the assumption E{sub F}/ kθ > > 1 (k = Boltzmann constant, θ = Debye temperature), they cannot shed light on the E{sub F}s of these SCs. This fact leads us to address the gaps (Δ{sub 0}s) and T{sub c}s of both types of SCs via recently derived equations which incorporate E{sub F} as a variable. For the specification of the E{sub F} of any SC, we now need another of its properties. Choosing j{sub 0}, the critical current density of the SC at T = 0, and following an idea due to Pines, we present for both types of SCs new equations for j{sub 0} that depend solely on the following properties of the SC: E{sub F}, θ, gram-atomic volume, electronic specific heat constant and a dimensionless construct y=kθ√(2m∗)/P{sub 0}√(E{sub F}), where m* is the effective mass of superconducting electrons and P{sub 0} their critical momentum. Appeal to the experimental values of Δ{sub 0}, T{sub c} and j{sub 0} of any SC then not only leads to values of E{sub F}, m* and P{sub 0} but also provides plausible clues about how its j{sub 0}—and therefore T{sub c}—may be increased.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Compressed H{sub 3}S, Superfluid Density and the Quest for Room-Temperature Superconductivity

The discovery of superconductivity at 203 K in highly compressed sulphur hydride validates the ideas put forward by Ashcroft 50 years ago and galvanises the quest for room-temperature superconductivity. But at such temperatures, thermal fluctuations might be expected to break up Cooper pairs. For example, in the cuprates, fluctuations reduce T{sub c} by 30% or more below the mean-field value. Similar effects are found in iron pnictides. Here, we ask: how does superconductivity survive in sulphur hydride at such high temperatures? To answer this, we examine the superfluid density which is the key parameter for quantifying fluctuations in both amplitude and phase. We show that dimensionality plays a key role in suppressing or enhancing thermal fluctuations to the benefit of hydrogen sulphide and the detriment of its more layered 2D competitors. We find that the temperature scale for phase fluctuations, T{sub φ}, in superconducting H{sub 3}S exceeds 1200 K, and therefore, these are irrelevant at 200 K. But the amplitude fluctuation temperature scale, T{sub amp}, at around 300 K is much lower and this has important implications for the ongoing quest for room temperature superconductivity. Appealing to the way in which superfluid density, T{sub φ}, T{sub amp} and T{sub c} scale with each other it seems that room temperature superconductivity is nearly ruled out, but perhaps not quite. It will require 3D systems with a large Fermi velocity to achieve this goal.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

The Theoretical Investigation of Electronic, Magnetic, and Thermoelectric Behavior of LiZ{sub 2}O{sub 4} (Z = Mn, Fe, Co, and Ni) by Modified Becke and Johnson Approach

Magnetic spinel oxides LiZ{sub 2}O{sub 4} (Z = Mn, Fe, Co, and Ni) have recently appealed the scientific community due to their interesting magnetic and thermoelectric applications. In the current article, the electronic, magnetic, and thermoelectric properties of LZO have been elaborated using density functional theory-based Wien2k code. The band structures and total density of states ensure the half metallic ferromagnetic (HMF) nature of the studied compounds. Furthermore, the magnetism is discussed in detail using crystal field, John-Teller, and exchange energies involved in the system and spin density. Finally, electrical conductivity, thermal conductivity, power factor, Seebeck coefficient, and thermal efficiency computed by using BoltztraP code suggest these compounds for thermoelectric device fabrications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Multi-segment Winding Application for Axial Short Circuit Force Reduction Under Tap Changer Operation in HTS Transformers

High-temperature superconducting (HTS) transformers have remarkable appealing advantages over conventional ones. But higher brittleness of HTS windings with respect to copper windings makes HTS transformers more vulnerable in short circuit and inrush current situations. During tap changer operation, appreciable asymmetry and non-uniform distribution of ampere-turn along the windings causes high axial component of short circuit forces and makes the situation more severe. In this paper, multi-segment winding method is employed for reduction of axial short circuit forces. An analytical method is presented for calculation of axial component of short circuit forces under tap changer operation. Analytical method shows that with utilizing HLHLHLH asymmetrical multi-segment windings, during tap changer operation, the axial component of short circuit forces reduces significantly. The results of the analytical method are compared with the results of finite element method (FEM) model simulations, and the consistency is demonstrated.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Synthesis and characterization of intrinsically radiolabeled lanthanide phosphate nanoparticles toward biomedical and environmental applications

Lanthanide phosphate nanomaterials are appealing as multifunctional platforms for biomedical applications because of their low toxicity, radiation resistance, and unique luminescence and magnetic properties. Lanthanide phosphate nanoparticles (NPs) radiolabeled with 156 Eu were synthesized by an aqueous route using sodium tripolyphosphate as a phosphate source and complexing agent. GdPO 4 was used as a host matrix, while synthetic concentrations of Ce 3+ /Tb 3+ and Eu 3+ were varied between 5–40% and 10–30%, respectively, and yielded spherical NPs with hexagonal crystal system and particle size < 5 nm. Luminescence emission and magnetic susceptibility were influenced by lanthanide concentrations where characteristic 5 D 0 - 7 F J and 5 D 4 - 7 F J transitions were observed for Eu 3+ - and Tb 3+ -doped NPs, respectively. Chemical yield of > 90% was achieved for GdPO 4 and Gd 0.6 Ce 0.3 Tb 0.1 PO 4 NPs intrinsically radiolabeled with 156 Eu. Lastly, in vitro retention of 156 Eu within LnPO 4 NPs was > 97% over 3 weeks. Intrinsically radiolabeled LnPO 4 NPs have the potential to combine the luminescence and magnetic properties of Ln 3+ ions with lanthanide radioisotopes for biomedical and environmental applications.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Exploring the interoperability of remote GPGPU virtualization using rCUDA and directive-based programming models

Directive-based programming models, such as OpenMP, OpenACC, and OmpSs, enable users to accelerate applications by using coprocessors with little effort. These devices offer significant computing power, but their use can introduce two problems: an increase in the total cost of ownership and their underutilization because not all codes match their architecture. Remote accelerator virtualization frameworks address those problems. In particular, rCUDA provides transparent access to any graphic processor unit installed in a cluster, reducing the number of accelerators and increasing their utilization ratio. Joining these two technologies, directive-based programming models and rCUDA, is thus highly appealing. In this work, we study the integration of OmpSs and OpenACC with rCUDA, describing and analyzing several applications over three different hardware configurations that include two InfiniBand interconnections and three NVIDIA accelerators. Our evaluation reveals favorable performance results, showing low overhead and similar scaling factors when using remote accelerators instead of local devices.

97 MATHEMATICS AND COMPUTING↗