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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 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Evidence for lack of direct causality between pain and affective disturbances in a rat peripheral neuropathy model

Chronic pain is frequently accompanied by the manifestation of emotional disturbances and cognitive deficits. While a causality relation between pain and emotional/cognitive disturbances is generally assumed, several observations suggest a temporal dissociation and independent mechanisms. We therefore studied Sprague‐Dawley rats that presented a natural resistance to pain manifestation in a neuropathy model (spared nerve injury [SNI]) and compared their performance in a battery of behavioral paradigms—anxiety, depression and fear memory—with animals that presented a pain phenotype. Afterward, we performed an extensive volumetric analysis across prefrontal, orbitofrontal and insular cortical areas. The majority of SNI animals manifested mechanical allodynia (low threshold [LT]), but 13% were similar to Sham controls (high threshold [HT]). Readouts of spontaneous hypersensivity (paw flinches) were also significantly reduced in HT and correlated with allodynia. To increase the specificity of our findings, we segregated the SNI animals in those with left (SNI‐L) and right (SNI‐R) lesions and the lack of association between pain and behavior still remains. Left‐lesioned animals, independent of the LT or HT phenotype, presented increased anxiety‐like behaviors and decreased well‐being. In contrast, we found that the insular cortex (agranular division) was significantly smaller in HT than in LT. To conclude, pain and emotional disturbances observed following nerve injury are to some extent segregated phenomena. Also, HT and LT SNI presented differences in insular volumes, an area vastly implicated in pain perception, suggesting a supraspinal involvement in the manifestation of these phenotypes.

Guimarães, Marco R.↗
DOE OSTI2017

Gaseous swelling of U 3 Si 2 during steady-state LWR operation: A rate theory investigation

Rate theory simulations of fission gas behavior in U 3 Si 2 are reported for light water reactor (LWR) steady-state operation scenarios. We developed a model of U 3 Si 2 and implemented into the GRASS-SST code based on available research reactor post-irradiation examination (PIE) data, and density functional theory (DFT) calculations of key material properties. Simplified peripheral models were also introduced to capture the fuel-cladding interaction. The simulations identified three regimes of U 3 Si 2 swelling behavior between 390 K and 1190 K. Under typical steady-state LWR operating conditions where U 3 Si 2 temperature is expected to be below 1000 K, intragranular bubbles are dominant and fission gas is retained in those bubbles. The consequent gaseous swelling is low and associated degradation in the fuel thermal conductivity is also limited. Those predictions of U 3 Si 2 performance during steady-state operations in LWRs suggest that this fuel material is an appropriate LWR candidate fuel material. Fission gas behavior models established based on this work are being coupled to the thermo-mechanical simulation of the fuel behavior using the BISON fuel performance multi-dimensional finite element code.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2011

Superscaling predictions for NC and CC quasi-elastic neutrino-nucleus scattering

Quasielastic double differential neutrino cross sections can be obtained in a phenomenological model based on the superscaling behavior of electron scattering data. In this talk the superscaling approach (SuSA) is reviewed and its validity is tested in a relativistic shell model. Results including meson exchange currents for the kinematics of the MiniBoone experiment are presented.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Tetraquark states from lattice QCD

Recently there have been considerable interests in studying hadronic states beyond the usual two and three quark configurations. With the renewed experimental interests in {sigma}(600) and the inability of quark model to incorporate too many light scalar mesons, it is quite appropriate to study hadronic states with four quark configurations. Moreover, some of the newly observed charmed hadrons may well be described by four quark configurations. Lattice QCD is perhaps the most desirable tool to adjudicate the theoretical controversy of the scalar mesons and to interpret the structures of the newly observed charmed states. Here we briefly reviewed the lattice studies of four-quark hadrons.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

NN*(1440) quasi-bound states

Inspired by a recent observation of a narrow resonance-like structure around 2360 MeV in the pn {yields} d{pi}{sup 0}{pi}{sup 0} cross section, we investigate the possibility of forming NN*(1440) quasi-bound state by meson exchange potential. With parameters of the t-channel {pi}, {sigma}, {rho} and {omega} exchanges determined by relevant NN scattering and N*(1440) decay processes, it is found that a NN*(1440) quasi-bound state with the same quantum numbers as the deuteron can be formed with binding energy about 20 MeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Possible molecular bound state of two charmed baryons

One-boson-exchange approach is widely used in the study of baryon-baryon interactions. Because of the higher masses, charmed baryons are likely to form molecular bound states. We here investigate this possibility in the {Lambda}{sub c{Lambda}c}(J{sup P} = 0{sup +}, I = 0) system, which may be the lowest mass state composed of two charmed baryons. Since the long-range interactions must play an important role for the formation of possible molecular bound states, we consider the one-pion-exchange potential explicitly and embed the short-range effects into a phenomenological cutoff parameter. As single pion exchange does not occur between two {Lambda}{sub c}'s, couplings to the nearby {Sigma}{sub c{Sigma}c}, {Sigma}{sub c{Sigma}c}* and {Sigma}{sub c}*{Sigma}{sub c}{sup *} channels may be crucial in binding two {Lambda}{sub c}'s. We find that it is possible to have a molecular bound state of two {Lambda}{sub c}'s, where the tensor force plays a crucial role, although the predicted binding energies are sensitive to the cutoff parameter.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Classical and quantum aspects of brane-world cosmology

We give a brief overview of several models in brane-world cosmology. In particular, we focus on the asymmetric DGP and Regge-Teiltelboim models. We present the associated equations of motion governing the dynamics of the brane and their corresponding Friedmann-like equations. In order to develop the quantum Regge-Teiltelboim type cosmology we construct its Ostrogradski Hamiltonian formalism which naturally leads to the corresponding Wheeler-DeWitt equation. In addition, we comment on possible generalizations for these models including second order derivative geometrical terms.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Unstable particles in non-relativistic quantum mechanics?

The Schroedinger equation is up-to-a-phase invariant under the Galilei group. This phase leads to the Bargmann's superselection rule, which forbids the existence of the superposition of states with different mass and implies that unstable particles cannot be described consistently in non-relativistic quantum mechanics (NRQM). In this paper we claim that Bargmann's rule neglects physical effects and that a proper description of non-relativistic quantum mechanics requires to take into account this phase through the Extended Galilei group and the definition of its action on spacetime coordinates.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Retroactive Event Determination and Its Relativistic Roots

Quantum theory limits what we are allowed to say about the 'true' state of a quantum system if that system is unobserved. But special relativity relies fundamentally on a universal assumption about what a light particle is doing at ALL times, regardless of being observed (namely, traveling at speed c relative to any inertial observer). This constitutes a fundamental conceptual gap between the theories. In resolving this impasse we show that the state of a light particle (and hence space and time) is not objective or continuous. Time dilation and length contraction become infinite for a photon, so light has no 'experience' of event separation in space or time ({Delta}t' = 0, {Delta}x' = 0). The principle of simultaneity is applied between an inertial observer and a light particle, such that the relative speed of the two systems is c, and gamma = infinite/undefined. Although light experiences no separation between events, the Lorentz transform {Delta}t' = {gamma} ({Delta}t-{Delta}Lv/c{sup 2}) implies that the inertial observer experiences a separation between those same events of exactly {Delta}t = {Delta}L/c, a light-like separation. In other words, although light does not 'register' time or space itself, light will always be measured by an inertial observer at a position and time exactly as if it had travelled at speed c continuously through the intervening medium. This fits nicely within the limitations set by quantum mechanics. This result is connected with previous work on retroactive event determination, suggesting the ubiquitous existence of ''synchronicity''.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Causality Is Inconsistent With Quantum Field Theory

Causality in quantum field theory means the vanishing of commutators for spacelike separated fields (VCSSF). I will show that VCSSF is not tenable. For VCSSF to be tenable, and therefore, to have both retarded and advanced propagators vanish in the elsewhere, a superposition of negative energy antiparticle and positive energy particle propagators, traveling forward in time, and a superposition of negative energy particle and positive energy antiparticle propagators, traveling backward in time, are required. Hence VCSSF predicts non-vanishing probabilities for both negative energy particles in the forward-through-time direction and positive energy antiparticles in the backwards-through-time direction. Therefore, since VCSSF is unrealizable in a stable universe, tachyonic propagation must occur in denial of causality.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Constraints on effective field theory parameters for the {Lambda}N{yields}NN transition

The relation between the low-energy constants appearing in the effective field theory description of the {Lambda}N{yields}NN transition potential and the parameters of the one-meson-exchange model previously developed is obtained. We extract the relative importance of the different exchange mechanisms included in the meson picture by means of a comparison to the corresponding operational structures appearing in the effective approach. The ability of this procedure to obtain the weak baryon-baryon-meson couplings for a possible scalar exchange is also discussed.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2011

Proton-proton bremsstrahlung: Consequences of different on-shell-point conditions

Background: Proton-proton bremsstrahlung (pp{gamma}) is investigated both theoretically and experimentally. The pp{gamma} amplitudes can be classified according to the number and location of on-shell points at which they are evaluated. Quantitative understanding of the effect on the pp{gamma} cross section of using different on-shell-point conditions is lacking, but it is essential to identifying the photon emission mechanism governing the pp{gamma} process. Method: Four different pp{gamma} amplitudes, which include four-on-shell-point amplitudes and one-on-shell-point amplitude, are generated from a realistic one-boson-exchange (ROBE) model for pp scattering. These ROBE amplitudes are used to investigate the consequence of using different on-shell-point conditions in calculating the pp{gamma} cross sections. Purpose: We verify the validity of the ROBE pp{gamma} amplitudes. We explore similarities between the four-on-shell-point ROBE and two-u-two-t special (TuTts) soft-photon pp{gamma} amplitudes and important differences with the one-on-shell-point ROBE and Low pp{gamma} amplitudes. We demonstrate that the precision Kernfysisch Versneller Instituut (KVI) data can only be described by the four-on-shell-point (ROBE or TuTts) amplitude. We use the ROBE four-on-shell-point amplitude and one-on-shell-point amplitude to investigate systematically the effect of using different on-shell-point conditions to calculate the pp{gamma} cross section. Furthermore, we identify a general principle that governs the process. This general principle is also applicable to other bremsstrahlung processes involving the scattering of two identical nucleons. Results: (i) The four-on-shell-point ROBE (or TuTts) amplitude describes the high-precision KVI data much better than does the one-on-shell-point ROBE (or Low) amplitude. Although the contribution from the anomalous magnetic moment of the proton is very significant, it does not completely dominate the KVI pp{gamma} cross sections. (ii) The four-on-shell-point ROBE (or TuTts) amplitude describes the TRIUMF data better than does the one-on-shell-point ROBE (or Low) amplitude. (iii) The effect on the pp{gamma} cross section of using different on-shell-point conditions is significant in the hard-photon region, i.e., for small proton scattering angles {theta} (={theta}{sub 3}={theta}{sub 4}, symmetric scattering angles) far from the elastic limit ({theta}{yields}45 deg.); in contrast, the effect becomes insignificant in the vicinity of the elastic limit. Near the limit as {theta} tends to 45 deg. (or as the photon energy K approaches zero), the four-on-shell-point and one-on-shell-point amplitudes approach one another, a general principle applicable to all bremsstrahlung processes because only kinematics is involved. Conclusion: The four-on-shell-point ROBE amplitude provides a quantitative description of pp{gamma} cross sections. The anomalous magnetic moment is an important component of the photon emission mechanism. The four-on-shell-point property of the full ROBE amplitude is essential to properly describing the complete range of the precision KVI data and the TRIUMF data, although the one-on-shell-point ROBE amplitude is adequate in the region near the elastic limit.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

SPOC Benchmark Case: SNRE Model

The Small Nuclear Rocket Engine (SNRE) was modeled in the Center for Space Nuclear Research’s (CSNR) Space Propulsion Optimization Code (SPOC). SPOC aims to create nuclear thermal propulsion (NTP) geometries quickly to perform parametric studies on design spaces of historic and new NTP designs. The SNRE geometry was modeled in SPOC and a critical core with a reasonable amount of criticality margin was found. The fuel, tie-tubes, reflector, and control drum masses were predicted rather well. These are all very important for neutronics calculations so the active reactor geometries created with SPOC can continue to be trusted. Thermal calculations of the average and hot fuel channels agreed very well. The specific impulse calculations used historically and in SPOC disagree so mass flow rates and impulses differed. Modeling peripheral and power balance components that do not affect nuclear characteristics of the core is not a feature of SPOC and as such, these components should continue to be designed using other tools. A full paper detailing the available SNRE data and comparisons with SPOC outputs will be submitted as a follow-up to this abstract.

MCNP↗
DOE OSTI2014

SU-E-T-43: Analytical Model for Photon Peripheral Dose in Radiotherapy Treatments

Purpose: The higher survival rate of radiotherapy patients entails a growing concern on second cancers associated to peripheral doses. Currently, dosimetry of out-of field doses is still under development. Our group has developed a methodology to estimate neutron equivalent dose in organs (1,2). We aimed to propose a model to estimate out-of-field photon doses in isocentric treatments from basic clinical data. Methods: The proposed function models the dose as the sum of leakage and scatter terms. The latter is modeled as a virtual source at the collimator, which suffers from attenuation in air and tissue, corrected by the inverse-square-law. The model was parameterized using experimental measurements with TLD700 chips placed inside an anthropomorphic phantom (6–18MV) irradiated with conformal and modulated techniques in Elekta, Siemens and Varian linacs. This model provides photon dose at a point as a function of clinical parameters as prescription dose/UM, PTV volume, distance to the field edge, height of the MLC leaves and distance from the the MLC to the isocenter. Model was tested against independent measurements (TLD100) for a VMAT treatment on a Elekta. Dose to organs is modeled from dose to points along the head-to-feet axis of the organ of a “standard man” escalated by patient height. Results: Our semi-empirical model depends on 3 given parameters (leakage parameter can be individualized). A novelty of our model, over other models (e.g., PERIDOSE), arises from its applicability to any technique (independently of the number of MU needed to deliver a dose). Differences between predictions and measurements were < 0.005mSv/UM. Conclusion: We have proposed a unique model which successfully account for photon peripheral organ dose. This model can be applied in the day-to-day clinic as it only needs a few basic parameters which are readily accessible.1. Radiother. Oncol. 107:234–243, 2013. 2. Phys. Med. Biol. 57:6167–6191, 2012.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2023

Ex vivo to in vivo model of malignant peripheral nerve sheath tumors for precision oncology

Malignant peripheral nerve sheath tumors (MPNST) are aggressive soft tissue sarcomas that often develop in patients with neurofibromatosis type 1 (NF1). To address the critical need for novel therapeutics in MPNST, we aimed to establish an ex vivo 3D platform that accurately captured the genomic diversity of MPNST and could be utilized in a medium-throughput manner for drug screening studies to be validated in vivo using patient-derived xenografts (PDX). Genomic analysis was performed on all PDX-tumor pairs. Selected PDX were harvested for assembly into 3D microtissues. Based on prior work in our labs, we evaluated drugs (trabectedin, olaparib, and mirdametinib) ex vivo and in vivo. For 3D microtissue studies, cell viability was the endpoint as assessed by Zeiss Axio Observer. For PDX drug studies, tumor volume was measured twice weekly. Bulk RNA sequencing was performed to identify pathways enriched in cells. We developed 13 NF1-associated MPNST-PDX and identified mutations or structural abnormalities in NF1 (100%), SUZ12 (85%), EED (15%), TP53 (15%), CDKN2A (85%), and chromosome 8 gain (77%). We successfully assembled PDX into 3D microtissues, categorized as robust (>90% viability at 48 h), good (>50%), or unusable (<50%). We evaluated drug response to “robust” or “good” microtissues, namely MN-2, JH-2-002, JH-2-079-c, and WU-225. Drug response ex vivo predicted drug response in vivo, and enhanced drug effects were observed in select models. These data support the successful establishment of a novel 3D platform for drug discovery and MPNST biology exploration in a system representative of the human condition.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2011

Diffractive Dissociation into {pi}{sup -{pi}-{pi}+} Final States at COMPASS

QCD predicts gluonic excitations like hybrids to contribute to the meson spectrum in addition to qq-bar pair configurations. The most promising way to identify such states is the search for J{sup PC} quantum number combinations which are forbidden in the constituent quark model. The fixed target COMPASS experiment at CERN offers the opportunity to search for such states in the light quark sector with an unprecedented statistics.Diffractive reactions of 190 GeV/c pions on a lead target were studied by COMPASS during a pilot run in 2004. A Partial Wave Analysis (PWA) of the {pi}{sup -{pi}-{pi}+} final state with 42 waves including acceptance corrections through a phase-space Monte Carlo simulation of the spectrometer was performed. The exotic {pi}{sup 1}(1600) meson with quantum numbers J{sup PC} = 1{sup -+} has been clearly established in the rho-pi decay channel with a mass of 1660{+-}10(stat) MeV/c{sup 2} and a width of 269{+-}21(stat) MeV/c{sup 2}. The improved detector performance in 2008 allows us to study this channel with significantly higher statistics. First results of the ongoing analysis of the 2008 data taking period, using a 190 GeV/c pion beam on a liquid hydrogen target are presented in this paper.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Renormalization of one meson exchange potentials and their currents

The Nucleon-Nucleon One Meson Exchange Potential, its wave functions and related Meson Exchange Currents are analyzed for point-like nucleons. The leading N{sub c} contributions generate a local and energy independent potential which presents 1/r{sup 3} singularities, requiring renormalization. We show how invoking suitable boundary conditions, neutron-proton phase shifts and deuteron properties become largely insensitive to the nucleon substructure and to the vector mesons. Actually, reasonable agreement with low energy data for realistic values of the coupling constants (e.g. SU(3) values) is found. The analysis along similar lines for the Meson Exchange Currents suggests that this renormalization scheme implies tremendous simplifications while complying with exact gauge invariance at any stage of the calculation.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Meson-baryon interaction in the meson exchange picture

Elastic {pi}N scattering and the reaction {pi}{sup +}p{yields}K{sup +}{Sigma}{sup +} are described simultaneously in a unitary coupled-channels approach which respects analyticity. SU(3) flavor symmetry is used to relate the t- and u- channel exchanges that drive the meson-baryon interaction in the different channels. Angular distributions, polarizations, and spin-rotation parameters are compared with available experimental data. The pole structure of the amplitudes is extracted from the analytic continuation.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗