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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 OSTI2011

Bound-state properties of four-body muonic quasiatoms

Total energies and various bound-state properties are determined for the ground states in all six four-body muonic a{sup +}b{sup +}{mu}{sup -}e{sup -} quasiatoms. These quasiatoms contain two nuclei of the hydrogen isotopes p{sup +},d{sup +},t{sup +}, one negatively charged muon {mu}{sup -}, and one electron e{sup -}. In general, each of the four-body muonic a{sup +}b{sup +}{mu}{sup -}e{sup -} quasiatoms, where (a,b)=(p,d,t), can be considered as the regular one-electron (hydrogen) atom with the complex nucleus a{sup +}b{sup +}{mu}{sup -} that has a finite number of bound states. Furthermore, all properties of such quasinuclei a{sup +}b{sup +}{mu}{sup -} are determined from highly accurate computations performed for the three-body muonic ions a{sup +}b{sup +}{mu}{sup -} with the use of pure Coulomb interaction potentials between particles. It is shown that the bound-state spectra of such quasiatoms are similar to the spectrum of the regular hydrogen atom, but there are a few important differences. Such differences can be used in future experiments to improve the overall accuracy of current evaluations of various properties of hydrogenlike systems, including the lowest-order relativistic and quantum electrodynamics corrections to the total energies.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2011

Numerical study of three-body recombination for systems with many bound states

Three-body recombination processes are treated numerically for a system of three identical bosons. The two-body model potentials utilized support many bound states, a major leap in complexity that produces an intricate structure of sharp nonadiabatic avoided crossings in the three-body hyperradial adiabatic potentials at short distances. This model thus displays the usual difficulties of more realistic systems. To overcome the numerical challenges associated with sharp avoided crossings, the slow variable discretization approach is adopted in the region of small hyperradii. At larger hyperradii, where the adiabatic potentials and couplings are smooth, the traditional adiabatic method suffices. Despite the high degree of complexity, recombination into deeply bound states behaves regularly due to the dominance of one decay pathway, resulting from the strong coupling between different recombination channels. Moreover, the usual Wigner threshold law must be modified for excited incident recombination channels.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2011

First Mott lobe of bosons with local two- and three-body interactions

Using the density matrix renormalization group method, we determine the phase diagram of the Bose-Hubbard model with local two- and three-body interactions, describing polar molecules in one-dimensional optical lattices. The difference in the block von Neumann entropy with different system sizes was used to establish the critical points. We found that the quantum critical point position increases with the three-body interaction. We show that the model studied is in the same universality class as the model with pure two-body interactions.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2021

Exact representations of many-body interactions with restricted-Boltzmann-machine neural networks

Restricted Boltzmann machines (RBMs) are simple statistical models defined on a bipartite graph which have been successfully used in studying more complicated many-body systems, both classical and quantum. In this work, we exploit the representation power of RBMs to provide an exact decomposition of many-body contact interactions into one-body operators coupled to discrete auxiliary fields. This construction generalizes the well known Hirsch's transform used for the Hubbard model to more complicated theories such as pionless effective field theory in nuclear physics, which we analyze in detail. Finally, we also discuss possible applications of our mapping for quantum annealing applications and conclude with some implications for RBM parameter optimization through machine learning.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

Three-Body Correlation Functions and Recombination Rates for Bosons in Three Dimensions and One Dimension

We investigate local three-body correlations for bosonic particles in three dimensions and one dimension as a function of the interaction strength. The three-body correlation function g{sup (3)} is determined by measuring the three-body recombination rate in an ultracold gas of Cs atoms. In three dimensions, we measure the dependence of g{sup (3)} on the gas parameter in a BEC, finding good agreement with the theoretical prediction accounting for beyond-mean-field effects. In one dimension, we observe a reduction of g{sup (3)} by several orders of magnitude upon increasing interactions from the weakly interacting BEC to the strongly interacting Tonks-Girardeau regime, in good agreement with predictions from the Lieb-Liniger model for all strengths of interaction.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Technical Note: Partial body irradiation of mice using a customized PMMA apparatus and a clinical 3D planning/LINAC radiotherapy system

Purpose: In vivo radiobiology experiments involving partial body irradiation (PBI) of mice are of major importance because they allow for the evaluation of individual organ tolerance; overcoming current limitations of experiments using lower dose, whole body irradiation. In the current study, the authors characterize and validate an effective and efficient apparatus for multiple animal PBI, directed to the head, thorax, or abdomen of mice. Methods: The apparatus is made of polymethylmethacrylate and consists of a rectangular parallelepiped prism (40 cm × 16 cm × 8 cm), in which five holes were drilled to accomodate standard 60 ml syringes, each housing an unanesthetized, fully immobilized mouse. Following CT-scanning and radiotherapy treatment planning, radiation fields were designed to irradiate the head, thorax, or abdomen of the animal. Thermoluminescent dosimeters (TLDs) were used to confirm the treatment planning dosimetry for primary beam and scattered radiation. Results: Mice are efficiently placed into 60 ml syringes and immobilized, without the use of anesthetics. Although partial rotational movement around the longitudinal axis and a minor 2 mm forward/backward movement are permitted, this does not compromise the irradiation of the chosen body area. TLDs confirmed the dose values predicted by the treatment planning dosimetry, both for primary beam and scattered radiation. Conclusions: The customized PMMA apparatus described and validated is cost-effective, convenient to use, and efficient in performing PBI without the use of anesthesia. The developed apparatus permits the isolated irradiation of the mouse head, thorax, and abdomen. Importantly, the apparatus allows the delivery of PBI to five mice, simultaneously, representing an efficient way to effectively expose a large number of animals to PBI through multiple daily fractions, simulating clinical radiotherapy treatment schedules.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

Four-body calculation of {sup 12}C(α, γ){sup 16}O radiative capture reaction at stellar energies

On the basis of the four-alphamodel, the {sup 12}C(α, γ){sup 16}Oradiative capture process is investigated by using the four-body Faddeev–Yakubovsky equations as well as the two- and three-body electromagnetic currents. The present calculation is an application of our current conservation realistic potentials method for the {sup 12}C(α, γ){sup 16}Oradiative capture process. This work clears the way formore refinedmodels of radiative capture based on two- and three-body realistic potentials and current conservation. The calculation is carried out by considering the {sup 4}He + {sup 12}C (1 + 3) and the {sup 8}Be + {sup 8}Be (2 + 2) subamplitudes, respectively. Radiative capture {sup 12}C(α, γ){sup 16}Oreaction is one of the most important reactions in nuclear astrophysics. For this reaction, the electric dipole transitions between states with the same isospin are forbidden in the first order. Because the state 1{sup +} and 0{sup +} ground state nuclei {sup 16}O have zero isospin, thus the electric dipole radiations are not at the first order between two levels and electric dipole radiation will be the second order and electric dipole radiation is the same order as the electric quadrupole radiation. Therefore, we must consider the effects of both radiations. In comparison with other theoretical methods and available experimental data, good agreement is achieved for the E{sub 1} and E{sub 2} contribution to the cross section and the astrophysical S factor for this process.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2016

( N N)-body dynamics of intermediate mass-ratio inspirals in star clusters

The intermediate mass-ratio inspiral of a stellar compact remnant into an intermediate-mass black hole (IMBH) can produce a gravitational wave (GW) signal that is potentially detectable by current ground-based GW detectors (e.g., Advanced LIGO) as well as by planned space-based interferometers (e.g., eLISA). Here, we present results from a direct integration of the post-Newtonian N-body equations of motion describing stellar clusters containing an IMBH and a population of stellar-mass black holes (BHs) and solar-mass stars. We take particular care to simulate the dynamics closest to the IMBH, including post-Newtonian effects up to an order of 2.5. Our simulations show that the IMBH readily forms a binary with a BH companion. This binary is gradually hardened by transient three-body or four-body encounters, leading to frequent substitutions of the BH companion, while the binary’s eccentricity experiences large-amplitude oscillations due to the Lidov–Kozai resonance. We also demonstrate suppression of these resonances by the relativistic precession of the binary orbit. We find an intermediate mass-ratio inspiral in 1 of the 12 cluster models we evolved for ∼100 Myr. This cluster hosts a 100M{sub ⊙} IMBH embedded in a population of 32 10M{sub ⊙} BH and 32,000 1M{sub ⊙} stars. At the end of the simulation, after ∼100 Myr of evolution, the IMBH merges with a BH companion. The IMBH–BH binary inspiral starts in the eLISA frequency window (≳1 mHz) when the binary reaches an eccentricity 1−e≃10{sup −3}. After ≃10{sup 5} yr the binary moves into the LIGO frequency band with a negligible eccentricity. We comment on the implications for GW searches, with a possible detection within the next decade.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1956

Drag Interference Between a Pointed Cylindrical Body and Triangular Wings of Various Aspect Ratios at Mach Numbers of 1.50 and 2.02

The drag of a body alone, six triangular wings of various aspect ratios, and the combinations were measured at Mach numbers of 1.50 and 2.02 at a Reynolds number of 5.5 million (based on the body length). The experimental drag-interference results were in accordance with calculations based on NACA RM A9E19, 1949, with skin-friction effects taken into account, the interference effect being principally the result of fixing transition on the body by adding a wing.

BODIES↗
NASA NTRS1953

Wind-tunnel investigation of the effects of various dorsal-fin and vertical-tail configurations on the directional stability of a streamlined body at transonic speeds : transonic-bump method

Yawing-moment coefficients were obtained for several dorsal-fin and vertical-tail configurations in combination with a streamlined body through a large angle-of-sideslip range and a Mach number range of 0.59 to 1.11. The results indicated that dorsal fins improved the directional stability characteristics of the body alone and the body-vertical-tail configuration. A ring tail was more effective at small angles of sideslip and less effective at large angles of sideslip than a tapered low-aspect-ratio vertical tail.

TAIL-BODY COMBINATIONS - MISSILES↗
NASA NTRS1999

Light masking of circadian rhythms of heat production, heat loss, and body temperature in squirrel monkeys

Whole body heat production (HP) and heat loss (HL) were examined to determine their relative contributions to light masking of the circadian rhythm in body temperature (Tb). Squirrel monkey metabolism (n = 6) was monitored by both indirect and direct calorimetry, with telemetered measurement of body temperature and activity. Feeding was also measured. Responses to an entraining light-dark (LD) cycle (LD 12:12) and a masking LD cycle (LD 2:2) were compared. HP and HL contributed to both the daily rhythm and the masking changes in Tb. All variables showed phase-dependent masking responses. Masking transients at L or D transitions were generally greater during subjective day; however, L masking resulted in sustained elevation of Tb, HP, and HL during subjective night. Parallel, apparently compensatory, changes of HL and HP suggest action by both the circadian timing system and light masking on Tb set point. Furthermore, transient HL increases during subjective night suggest that gain change may supplement set point regulation of Tb.

Non-NASA Center↗
DOE OSTI2021

Late-time small body disruptions for planetary defense

Here, diverting hazardous small bodies on impact trajectories with the Earth can in some circumstances be impossible without risking disrupting them. Disruption is a much more difficult planetary defense scenario to assess, being linked both to the response of the body to shock loading and the much more complicated gravitational dynamics of the fragments in the solar system relative to pure deflection scenarios. In this work we present a new simulation suite built on N-body gravitational methods that solves fragment orbits in the full gravitational system without recourse to more approximate methods. We assess the accuracy of our simulations and the simplifying assumptions we adopt to make the system tractable, and then discuss in more detail several specific, plausible planetary defense scenarios based on real close encounters. We find that disruption can be a very effective planetary defense strategy even for very late (sub-year) interventions, and should be considered an effective backup strategy should preferred methods, which require long warning times, fail.

42 ENGINEERING↗
DOE OSTI2014

Probing many-body interactions in an optical lattice clock

We present a unifying theoretical framework that describes recently observed many-body effects during the interrogation of an optical lattice clock operated with thousands of fermionic alkaline earth atoms. The framework is based on a many-body master equation that accounts for the interplay between elastic and inelastic p-wave and s-wave interactions, finite temperature effects and excitation inhomogeneity during the quantum dynamics of the interrogated atoms. Solutions of the master equation in different parameter regimes are presented and compared. It is shown that a general solution can be obtained by using the so called Truncated Wigner Approximation which is applied in our case in the context of an open quantum system. We use the developed framework to model the density shift and decay of the fringes observed during Ramsey spectroscopy in the JILA {sup 87}Sr and NIST {sup 171}Yb optical lattice clocks. The developed framework opens a suitable path for dealing with a variety of strongly-correlated and driven open-quantum spin systems. -- Highlights: •Derived a theoretical framework that describes many-body effects in a lattice clock. •Validated the analysis with recent experimental measurements. •Demonstrated the importance of beyond mean field corrections in the dynamics.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2017

Hyperspherical Slater determinant approach to few-body fractional quantum Hall states

In a recent study (Daily et al., 2015), a hyperspherical approach has been developed to study few-body fractional quantum Hall states. This method has been successfully applied to the exploration of few boson and fermion problems in the quantum Hall region, as well as the study of inter-Landau level collective excitations (Rittenhouse et al., 2016; Wooten et al., 2016). However, the hyperspherical method as it is normally implemented requires a subsidiary (anti-)symmetrization process, which limits its computational effectiveness. The present work overcomes these difficulties and extends the power of this method by implementing a representation of the hyperspherical many-body basis space in terms of Slater determinants of single particle eigenfunctions. A clear connection between the hyperspherical representation and the conventional single particle picture is presented, along with a compact operator representation of the theoretical framework. - Highlights: • A hyperspherical method has been implemented to study the quantum Hall effect. • The hyperspherical many-body basis space is represented with Slater determinants. • Example numerical studies of the 4- and 8-electron systems are presented.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2021

From Anderson localization on random regular graphs to many-body localization

Highlights: • Anderson transition from ergodicity to localization on random regular graphs (RRG). • Analytical, pool method, and exact-diagonalization study of correlations on RRG. • Many-body localization (MBL) to ergodicity transition: quantum dots and spin chains. • Dynamical eigenstate correlation functions in RRG and MBL problems. • Anderson localization on RRG as a toy model for MBL. The article reviews the physics of Anderson localization on random regular graphs (RRG) and its connections to many-body localization (MBL) in disordered interacting systems. Properties of eigenstate and energy level correlations in delocalized and localized phases, as well at criticality, are discussed. In the many-body part, models with short-range and power-law interactions are considered, as well as the quantum-dot model representing the limit of the “most long-range” interaction. Central themes – which are common to the RRG and MBL problems – include ergodicity of the delocalized phase, localized character of the critical point, strong finite-size effects, and fractal scaling of eigenstate correlations in the localized phase.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Paradeisos: A perfect hashing algorithm for many-body eigenvalue problems

Here, we describe an essentially perfect hashing algorithm for calculating the position of an element in an ordered list, appropriate for the construction and manipulation of many-body Hamiltonian, sparse matrices. Each element of the list corresponds to an integer value whose binary representation reflects the occupation of single-particle basis states for each element in the many-body Hilbert space. The algorithm replaces conventional methods, such as binary search, for locating the elements of the ordered list, eliminating the need to store the integer representation for each element, without increasing the computational complexity. Combined with the “checkerboard” decomposition of the Hamiltonian matrix for distribution over parallel computing environments, this leads to a substantial savings in aggregate memory. While the algorithm can be applied broadly to many-body, correlated problems, we demonstrate its utility in reducing total memory consumption for a series of fermionic single-band Hubbard model calculations on small clusters with progressively larger Hilbert space dimension.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

Modulation and splitting of three-body radiative heat flux via graphene/SiC core-shell nanoparticles

Here, we theoretically demonstrate the modulation and splitting of radiative heat flux in a three-body system consisting of graphene/SiC core-shell (GSCS) nanoparticles on the basis of their highly tunable polarizabilities, which play a dominant role in the coupling of localized surface resonance. The excitation of multiple photon tunneling modes enables the radiative heat transfer to be controlled in different scenarios. Using the dependence of photon tunneling on the Fermi level and radius of the intermediate GSCS nanoparticle, such a many-body system not only holds the potential to be a near-field thermal modulator with a thermal modulation ratio greater than 40, but also allows the heat splitting effect with the ratio over 99 when the intermediate particle becomes the hot source. This work may facilitate dynamical thermal management in a many-body system, and can also benefit the plasmonics community in the near future.

42 ENGINEERING↗
DOE OSTI2011

Salvage Reirradiaton With Stereotactic Body Radiotherapy for Locally Recurrent Head-and-Neck Tumors

Purpose: In this study, we present our results of reirradiation of locally recurrent head-and-neck cancer with image-guided, fractionated, frameless stereotactic body radiotherapy technique. Methods and Materials: From July 2007 to February 2009, 46 patients were treated using the CyberKnife (Accuray, Sunnyvale, CA) at the Department of Radiation Oncology, Hacettepe University, Ankara, Turkey. All patients had recurrent, unresectable, and previously irradiated head-and-neck cancer. The most prominent site was the nasopharynx (32.6%), and the most common histopathology was epidermoid carcinoma. The planning target volume was defined as the gross tumor volume identified on magnetic resonance imaging and computed tomography. There were 22 female and 24 male patients. Median age was 53 years (range, 19-87 years). The median tumor dose with stereotactic body radiotherapy was 30 Gy (range, 18-35 Gy) in a median of five (range, one to five) fractions. Results: Of 37 patients whose response to therapy was evaluated, 10 patients (27%) had complete tumor regression, 11 (29.8%) had partial response, and 10 (27%) had stable disease. Ultimate local disease control was achieved in 31 patients (83.8%). The overall survival was 11.93 months in median (ranged, 11.4 - 17.4 months), and the median progression free survival was 10.5 months. One-year progression-free survival and overall survival were 41% and 46%, respectively. Grade II or greater long-term complications were observed in 6 (13.3%) patients. On follow-up, 8 (17.3%) patients had carotid blow-out syndrome, and 7 (15.2%) patients died of bleeding from carotid arteries. We discovered that this fatal syndrome occurred only in patients with tumor surrounding carotid arteries and carotid arteries receiving all prescribed dose. Conclusions: Stereotactic body radiotherapy is an appealing treatment option for patients with recurrent head-and-neck cancer previously treated with radiation to high doses. Good local control with considerable 1-year survival is achieved with a relatively high rate of morbidity and related mortality.

62 RADIOLOGY AND NUCLEAR MEDICINE↗