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Sample records for advanced energetic pair

  1. Development of the Advanced Energetic Pair Telescope (AdEPT) for Medium-Energy Gamma-Ray Astronomy

    NASA Technical Reports Server (NTRS)

    Hunter, Stanley D.; Bloser, Peter F.; Dion, Michael P.; McConnell, Mark L.; deNolfo, Georgia A.; Son, Seunghee; Ryan, James M.; Stecker, Floyd W.

    2011-01-01

    Progress in high-energy gamma-ray science has been dramatic since the launch of INTEGRAL, AGILE and FERMI. These instruments, however, are not optimized for observations in the medium-energy (approx.0.3< E(sub gamma)< approx.200 MeV) regime where many astrophysical objects exhibit unique, transitory behavior, such as spectral breaks, bursts, and flares. We outline some of the major science goals of a medium-energy mission. These science goals are best achieved with a combination of two telescopes, a Compton telescope and a pair telescope, optimized to provide significant improvements in angular resolution and sensitivity. In this paper we describe the design of the Advanced Energetic Pair Telescope (AdEPT) based on the Three-Dimensional Track Imager (3-DTI) detector. This technology achieves excellent, medium-energy sensitivity, angular resolution near the kinematic limit, and gamma-ray polarization sensitivity, by high resolution 3-D electron tracking. We describe the performance of a 30x30x30 cm3 prototype of the AdEPT instrument.

  2. The Advanced Energetic Pair Telescope (AdEPT}: A Future Medium-Energy Gamma-Ray Balloon (and Explorer?) Mission

    NASA Technical Reports Server (NTRS)

    Hunter, Stanley D.

    2011-01-01

    Gamma-ray astrophysics probes the highest energy, exotic phenomena in astrophysics. In the medium-energy regime, 0.1-200 MeV, many astrophysical objects exhibit unique and transitory behavior such as the transition from electron dominated to hadron dominated processes, spectral breaks, bursts, and flares. Medium-energy gamma-ray imaging however, continues to be a major challenge particularly because of high background, low effective area, and low source intensities. The sensitivity and angular resolution required to address these challenges requires a leap in technology. The Advance Energetic Pair Telescope (AdEPT) being developed at GSFC is designed to image gamma rays above 5 MeV via pair production with angular resolution of 1-10 deg. In addition AdEPT will, for the first time, provide high polarization sensitivity in this energy range. This performance is achieved by reducing the effective area in favor of enhanced angular resolution through the use of a low-density gaseous conversion medium. AdEPT is based on the Three-Dimensional Track Imager (3-DTI) technology that combines a large volume Negative Ion Time Projection Chamber (NITPC) with 2-D Micro-Well Detector (MWD) readout. I will review the major science topics addressable with medium-energy gamma-rays and discuss the current status of the AdEPT technology, a proposed balloon instrument, and the design of a future satellite mission.

  3. MeV Science with the Advanced Energetic Pair Telescope (AdEPT), a High Sensitivity Medium-Energy Gamma-Ray Polarimeter

    NASA Astrophysics Data System (ADS)

    Venters, Tonia M.; Hunter, Stanley D.; De Nolfo, Georgia; Hanu, Andrei R.; Krizmanic, John F.; Stecker, Floyd W.; Timokhin, Andrey

    2016-04-01

    Many high-energy astrophysical phenomena exhibit unique, transitory behavior, such as spectral breaks, bursts, and flares below ~200 MeV. However, while significant progress in gamma-rays has been made by instruments such as Fermi and AGILE, a significant sensitivity gap remains in the medium-energy regime (0.75 - 200 MeV) that has been explored only by COMPTEL and EGRET on CGRO. Tapping into this unexplored regime requires development of a telescope with significant improvement in sensitivity. Our mission concept, covering ~5 to ~200 MeV, is the Advanced Energetic Pair Telescope (AdEPT). The AdEPT telescope will achieve angular resolution of ~0.6 deg at 70 MeV, similar to the angular resolution of Fermi/LAT at ~1 GeV that brought tremendous success in identifying new sources. AdEPT will also provide unprecedented polarization sensitivity, ~1% for a 1 Crab source. The enabling technology for AdEPT is the Three-Dimensional Track Imager (3-DTI) a low-density, large volume, gas time-projection chamber with a 2-dimensional readout. The 3-DTI provides high-resolution three-dimensional electron tracking with minimal Coulomb scattering that is essential to achieve high angular resolution and polarization sensitivity. We describe the design, fabrication, and performance of the 3-DTI detector, describe the development of a 50x50x100 cm3 AdEPT prototype, and highlight a few of the key science questions that AdEPT will address.

  4. Cluster pair correlation function of simple fluids: energetic connectivity criteria.

    PubMed

    Pugnaloni, Luis A; Zarragoicoechea, Guillermo J; Vericat, Fernando

    2006-11-21

    We consider the clustering of Lennard-Jones particles by using an energetic connectivity criterion proposed long ago by Hill [J. Chem. Phys. 32, 617 (1955)] for the bond between pairs of particles. The criterion establishes that two particles are bonded (directly connected) if their relative kinetic energy is less than minus their relative potential energy. Thus, in general, it depends on the direction as well as on the magnitude of the velocities and positions of the particles. An integral equation for the pair connectedness function, proposed by two of the authors [Phys. Rev. E 61, R6067 (2000)], is solved for this criterion and the results are compared with those obtained from molecular dynamics simulations and from a connectedness Percus-Yevick-type integral equation for a velocity-averaged version of Hill's energetic criterion.

  5. Regimes of Pulsar Pair Formation and Particle Energetics

    NASA Technical Reports Server (NTRS)

    Harding, Alice K.; Muslimov, Alexander G.; Zhang, Bing; White, Nicholas E. (Technical Monitor)

    2002-01-01

    We investigate the conditions required for the production of electron-positron pairs above a pulsar polar cap (PC) and the influence of pair production on the energetics of the primary particle acceleration. Assuming space-charge limited flow acceleration including the inertial frame-dragging effect, we allow both one-photon and two-photon pair production by either curvature radiation (CR) photons or photons resulting from inverse-Compton scattering of thermal photons from the PC by primary electrons. We find that,, while only the younger pulsars can produce pairs through CR, nearly all known radio pulsars are capable of producing pairs through non-resonant inverse-Compton scatterings. The effect of the neutron star equations of state on the pair death lines is explored. We show that pair production is facilitated in more compact stars and more a massive stars. Therefore accretion of mass by pulsars in binary systems may allow pair production in most of the millisecond purser population. We also find that two-photon pair production may be important in millisecond pursers if their surface temperatures are above approx. or equal to three million degrees K. Pursers that produce pairs through CRT wilt have their primary acceleration limited by the effect of screening of the electric field. In this regime, the high-energy luminosity should follow a L(sub HE) proportional to dot-E(sup 1/2, sub rot) dependence. The acceleration voltage drop in pursers that produce pairs only through inverse-Compton emission will not be limited by electric field screening. In this regime, the high-energy luminosity should follow a L(sub HE) proportional to dot-E(sub rot) dependence. Thus, older pursers will have significantly lower gamma-ray luminosity.

  6. Advanced Energetics for Aeronautical Applications. Volume II

    NASA Technical Reports Server (NTRS)

    Alexander, David S.

    2005-01-01

    NASA has identified water vapor emission into the upper atmosphere from commercial transport aircraft, particularly as it relates to the formation of persistent contrails, as a potential environmental problem. Since 1999, MSE has been working with NASA-LaRC to investigate the concept of a transport-size emissionless aircraft fueled with liquid hydrogen combined with other possible breakthrough technologies. The goal of the project is to significantly advance air transportation in the next decade and beyond. The power and propulsion (P/P) system currently being studied would be based on hydrogen fuel cells (HFCs) powering electric motors, which drive fans for propulsion. The liquid water reaction product is retained onboard the aircraft until a flight mission is completed. As of now, NASA-LaRC and MSE have identified P/P system components that, according to the high-level analysis conducted to date, are light enough to make the emissionless aircraft concept feasible. Calculated maximum aircraft ranges (within a maximum weight constraint) and other performance predictions are included in this report. This report also includes current information on advanced energy-related technologies, which are still being researched, as well as breakthrough physics concepts that may be applicable for advanced energetics and aerospace propulsion in the future.

  7. Monopole pair creation in energetic collisions: Is it possible

    SciTech Connect

    Drukier, A.K.; Nussinov, S.

    1982-07-12

    It is suggested that monopole-antimonopole pair production initiated by pointlike particles (electrons, quarks) has widely different cross sections in the two cases of ''pointlike'' and composite monopoles, respectively. Production of 't Hooft--Polyakov monopoles is expected to be suppressed by a hugh factor, > or =10/sup 30/. Furthermore, astrophysical evidence is presented suggesting that monopoles with m/sub m/roughly-equal10/sup 4/ GeV/c/sup 2/ cannot be pointlike.

  8. Energetic, electronic, and magnetic properties of Mn pairs on reconstructed (001) GaAs surfaces

    NASA Astrophysics Data System (ADS)

    Birowska, Magdalena; Śliwa, Cezary; Majewski, Jacek A.

    2017-03-01

    We study energetic, magnetic, and electronic properties of diluted substitutional Mn pairs on reconstructed (001 ) GaAs surfaces. The studies are based on first-principles calculations in the framework of density functional theory. We demonstrate that the stability of the systems strongly depends on the position, orientation, and the distance between the Mn atoms constituting the pair. Independently of the considered surface reconstruction pattern, the Mn pairs with Mn atoms being the nearest neighbors (NN) on a cationic sublattice turn out to be energetically more favorable than the pairs with the larger distance between the Mn atoms. However, the preferential buildup orientation of the Mn-NN pair depends on the surface reconstruction and is parallel to either the [110 ] or the [1 1 ¯0 ] crystallographic direction. We reveal also the mechanisms of the magnetic ordering of Mn-NN pairs. The Mn-NN pairs along the [110 ] crystallographic direction exhibit always ferromagnetic alignment of Mn spins, whereas the spins in the Mn-NN pairs along the [1 1 ¯0 ] direction are mostly antiferromagnetically aligned. In the electronic structure of the systems containing Mn pairs with ferromagnetically aligned spins, we observe the valence band hole states in the neighborhood of Fermi energy. This indicates that the surface ferromagnetism in this prototype of dilute magnetic semiconductors can be explained in terms of the p -d Zener model.

  9. Anomalous maximum and minimum for the dissociation of a geminate pair in energetically disordered media

    NASA Astrophysics Data System (ADS)

    Govatski, J. A.; da Luz, M. G. E.; Koehler, M.

    2015-01-01

    We study the geminated pair dissociation probability φ as function of applied electric field and temperature in energetically disordered nD media. Regardless nD, for certain parameters regions φ versus the disorder degree (σ) displays anomalous minimum (maximum) at low (moderate) fields. This behavior is compatible with a transport energy which reaches a maximum and then decreases to negative values as σ increases. Our results explain the temperature dependence of the persistent photoconductivity in C60 single crystals going through order-disorder transitions. They also indicate how an energetic disorder spatial variation may contribute to higher exciton dissociation in multicomponent donor/acceptor systems.

  10. Structures and Energetics of Four Adjacent G·U Pairs That Stabilize an RNA Helix

    PubMed Central

    Gu, Xiaobo; Mooers, Blaine H.M.; Thomas, Leonard M.; Malone, Joshua; Harris, Steven; Schroeder, Susan J.

    2016-01-01

    Consecutive G·U base pairs inside RNA helices can be destabilizing while those at the ends of helices are thermodynamically stabilizing. To determine if this paradox could be explained by differences in base stacking, we determined the high-resolution (1.32 Å) crystal structure of (5’-GGUGGCUGUU-3')2 and studied three sequences with four consecutive terminal G·U pairs by NMR spectroscopy. In the crystal structure of (5’-GGUGGCUGUU-3')2, the helix is overwound but retains the overall features of A-form RNA. The penultimate base steps at each end of the helix have high base overlap and contribute to the unexpectedly favorable energetic contribution for the 5’-GU-3’/3’-UG-5’ motif in this helix position. The balance of base stacking and helical twist contributes to the positional dependence of G·U pair stabilities. The energetic stabilities and similarity to A-form RNA helices suggest that consecutive G·U pairs would be recognized by RNA helix binding proteins, such as Dicer and Ago. Thus, these results will aid future searches for target sites of small RNAs in gene regulation. PMID:26425937

  11. The "Puck" energetic charged particle detector: Design, heritage, and advancements.

    PubMed

    Clark, G; Cohen, I; Westlake, J H; Andrews, G B; Brandt, P; Gold, R E; Gkioulidou, M A; Hacala, R; Haggerty, D; Hill, M E; Ho, G C; Jaskulek, S E; Kollmann, P; Mauk, B H; McNutt, R L; Mitchell, D G; Nelson, K S; Paranicas, C; Paschalidis, N; Schlemm, C E

    2016-08-01

    Energetic charged particle detectors characterize a portion of the plasma distribution function that plays critical roles in some physical processes, from carrying the currents in planetary ring currents to weathering the surfaces of planetary objects. For several low-resource missions in the past, the need was recognized for a low-resource but highly capable, mass-species-discriminating energetic particle sensor that could also obtain angular distributions without motors or mechanical articulation. This need led to the development of a compact Energetic Particle Detector (EPD), known as the "Puck" EPD (short for hockey puck), that is capable of determining the flux, angular distribution, and composition of incident ions between an energy range of ~10 keV to several MeV. This sensor makes simultaneous angular measurements of electron fluxes from the tens of keV to about 1 MeV. The same measurements can be extended down to approximately 1 keV/nucleon, with some composition ambiguity. These sensors have a proven flight heritage record that includes missions such as MErcury Surface, Space ENvironment, GEochemistry, and Ranging and New Horizons, with multiple sensors on each of Juno, Van Allen Probes, and Magnetospheric Multiscale. In this review paper we discuss the Puck EPD design, its heritage, unexpected results from these past missions and future advancements. We also discuss high-voltage anomalies that are thought to be associated with the use of curved foils, which is a new foil manufacturing processes utilized on recent Puck EPD designs. Finally, we discuss the important role Puck EPDs can potentially play in upcoming missions.

  12. The "Puck" energetic charged particle detector: Design, heritage, and advancements

    NASA Astrophysics Data System (ADS)

    Clark, G.; Cohen, I.; Westlake, J. H.; Andrews, G. B.; Brandt, P.; Gold, R. E.; Gkioulidou, M. A.; Hacala, R.; Haggerty, D.; Hill, M. E.; Ho, G. C.; Jaskulek, S. E.; Kollmann, P.; Mauk, B. H.; McNutt, R. L.; Mitchell, D. G.; Nelson, K. S.; Paranicas, C.; Paschalidis, N.; Schlemm, C. E.

    2016-08-01

    Energetic charged particle detectors characterize a portion of the plasma distribution function that plays critical roles in some physical processes, from carrying the currents in planetary ring currents to weathering the surfaces of planetary objects. For several low-resource missions in the past, the need was recognized for a low-resource but highly capable, mass-species-discriminating energetic particle sensor that could also obtain angular distributions without motors or mechanical articulation. This need led to the development of a compact Energetic Particle Detector (EPD), known as the "Puck" EPD (short for hockey puck), that is capable of determining the flux, angular distribution, and composition of incident ions between an energy range of ~10 keV to several MeV. This sensor makes simultaneous angular measurements of electron fluxes from the tens of keV to about 1 MeV. The same measurements can be extended down to approximately 1 keV/nucleon, with some composition ambiguity. These sensors have a proven flight heritage record that includes missions such as MErcury Surface, Space ENvironment, GEochemistry, and Ranging and New Horizons, with multiple sensors on each of Juno, Van Allen Probes, and Magnetospheric Multiscale. In this review paper we discuss the Puck EPD design, its heritage, unexpected results from these past missions and future advancements. We also discuss high-voltage anomalies that are thought to be associated with the use of curved foils, which is a new foil manufacturing processes utilized on recent Puck EPD designs. Finally, we discuss the important role Puck EPDs can potentially play in upcoming missions.

  13. The Effects of Dominance on Leadership and Energetic Gain: A Dynamic Game between Pairs of Social Foragers

    PubMed Central

    Rands, Sean A.

    2011-01-01

    Although social behaviour can bring many benefits to an individual, there are also costs that may be incurred whenever the members of a social group interact. The formation of dominance hierarchies could offer a means of reducing some of the costs of social interaction, but individuals within the hierarchy may end up paying differing costs dependent upon their position within the hierarchy. These differing interaction costs may therefore influence the behaviour of the group, as subordinate individuals may experience very different benefits and costs to dominants when the group is conducting a given behaviour. Here, a state-dependent dynamic game is described which considers a pair of social foragers where there is a set dominance relationship within the pair. The model considers the case where the subordinate member of the pair pays an interference cost when it and the dominant individual conduct specific pairs of behaviours together. The model demonstrates that if the subordinate individual pays these energetic costs when it interacts with the dominant individual, this has effects upon the behaviour of both subordinate and the dominant individuals. Including interaction costs increases the amount of foraging behaviour both individuals conduct, with the behaviour of the pair being driven by the subordinate individual. The subordinate will tend to be the lighter individual for longer periods of time when interaction costs are imposed. This supports earlier suggestions that lighter individuals should act as the decision-maker within the pair, giving leadership-like behaviours that are based upon energetic state. Pre-existing properties of individuals such as their dominance will be less important for determining which individual makes the decisions for the pair. This suggests that, even with strict behavioural hierarchies, identifying which individual is the dominant one is not sufficient for identifying which one is the leader. PMID:22028645

  14. Synthesis and Investigation of Advanced Energetic Materials Based on Bispyrazolylmethanes.

    PubMed

    Fischer, Dennis; Gottfried, Jennifer L; Klapötke, Thomas M; Karaghiosoff, Konstantin; Stierstorfer, Jörg; Witkowski, Tomasz G

    2016-12-23

    Herein we present the preparation and characterization of three new bispyrazolyl-based energetic compounds with great potential as explosive materials. The reaction of sodium 4-amino-3,5-dinitropyrazolate (5) with dimethyl iodide yielded bis(4-amino-3,5-dinitropyrazolyl)methane (6), which is a secondary explosive with high heat resistance (Tdec =310 °C). The oxidation of this compound afforded bis(3,4,5-trinitropyrazolyl)methane (7), which is a combined nitrogen- and oxygen-rich secondary explosive with very high theoretical and estimated experimental detonation performance (Vdet (theor)=9304 m s(-1) versus Vdet (exp)=9910 m s(-1) ) in the range of that of CL-20. Also, the thermal stability (Tdec =205 °C) and sensitivities of 7 are auspicious. The reaction of 6 with in situ generated nitrous acid yielded the primary explosive bis(4-diazo-5-nitro-3-oxopyrazolyl)methane (8), which showed superior properties to those of currently used diazodinitrophenol (DDNP).

  15. Chemical Energetics. Independent Learning Project for Advanced Chemistry (ILPAC). Unit S3.

    ERIC Educational Resources Information Center

    Inner London Education Authority (England).

    This unit on chemical energetics is one of 10 first year units produced by the Independent Learning Project for Advanced Chemistry (ILPAC). The unit, which consists of two levels, provides a clear yet detailed and thorough introduction to the topic. Level one extends ideas from previous courses, introduces and emphasizes the importance of Hess'…

  16. Dislocation kink-pair energetics and pencil glide in body-centered-cubic crystals.

    PubMed

    Ngan, A H; Wen, M

    2001-08-13

    When body-centered-cubic crystals undergo plastic deformation, the slip planes are often noncrystallographic. By performing atomistic simulation on the activation pathway of dislocation jumps in bcc iron, we show that the main reason for bcc crystals to exhibit this phenomenon is that one type of kink pair has significantly lower energy than all the other types on the same slip plane. Dislocation motion therefore cannot continue on the same slip plane, and the dislocation has to cross slip onto an intersecting slip plane after each atomic jump. Thus in the long run, the average slip plane would be zigzag and noncrystallographic.

  17. Differences in muscle fiber size and associated energetic costs in phylogenetically paired tropical and temperate birds.

    PubMed

    Jimenez, Ana Gabriela; Williams, Joseph B

    2014-01-01

    Tropical and temperate birds provide a unique system to examine mechanistic consequences of life-history trade-offs at opposing ends of the pace-of-life spectrum; tropical birds tend to have a slow pace of life whereas temperate birds the opposite. Birds in the tropics have a lower whole-animal basal metabolic rate and peak metabolic rate, lower rates of reproduction, and longer survival than birds in temperate regions. Although skeletal muscle has a relatively low tissue-specific metabolism at rest, it makes up the largest fraction of body mass and therefore contributes more to basal metabolism than any other tissue. A principal property of muscle cells that influences their rate of metabolism is fiber size. The optimal fiber size hypothesis attempts to link whole-animal basal metabolic rate to the cost of maintaining muscle mass by stating that larger fibers may be metabolically cheaper to maintain since the surface area∶volume ratio (SA∶V) is reduced compared with smaller fibers and thus the amount of area to transport ions is also reduced. Because tropical birds have a reduced whole-organism metabolism, we hypothesized that they would have larger muscle fibers than temperate birds, given that larger muscle fibers have reduced energy demand from membrane Na(+)-K(+) pumps. Alternatively, smaller muscle fibers could result in a lower capacity for shivering and exercise. To test this idea, we examined muscle fiber size and Na(+)-K(+)-ATPase activity in 16 phylogenetically paired species of tropical and temperate birds. We found that 3 of the 16 paired comparisons indicated that tropical birds had significantly larger fibers, contrary to our hypothesis. Our data show that SA∶V is proportional to Na(+)-K(+)-ATPase activity in muscles of birds.

  18. Multiconfiguration pair-density functional theory: barrier heights and main group and transition metal energetics.

    PubMed

    Carlson, Rebecca K; Li Manni, Giovanni; Sonnenberger, Andrew L; Truhlar, Donald G; Gagliardi, Laura

    2015-01-13

    Kohn-Sham density functional theory, resting on the representation of the electronic density and kinetic energy by a single Slater determinant, has revolutionized chemistry, but for open-shell systems, the Kohn-Sham Slater determinant has the wrong symmetry properties as compared to an accurate wave function. We have recently proposed a theory, called multiconfiguration pair-density functional theory (MC-PDFT), in which the electronic kinetic energy and classical Coulomb energy are calculated from a multiconfiguration wave function with the correct symmetry properties, and the rest of the energy is calculated from a density functional, called the on-top density functional, that depends on the density and the on-top pair density calculated from this wave function. We also proposed a simple way to approximate the on-top density functional by translation of Kohn-Sham exchange-correlation functionals. The method is much less expensive than other post-SCF methods for calculating the dynamical correlation energy starting with a multiconfiguration self-consistent-field wave function as the reference wave function, and initial tests of the theory were quite encouraging. Here, we provide a broader test of the theory by applying it to bond energies of main-group molecules and transition metal complexes, barrier heights and reaction energies for diverse chemical reactions, proton affinities, and the water dimerization energy. Averaged over 56 data points, the mean unsigned error is 3.2 kcal/mol for MC-PDFT, as compared to 6.9 kcal/mol for Kohn-Sham theory with a comparable density functional. MC-PDFT is more accurate on average than complete active space second-order perturbation theory (CASPT2) for main-group small-molecule bond energies, alkyl bond dissociation energies, transition-metal-ligand bond energies, proton affinities, and the water dimerization energy.

  19. Advancing Transdisciplinary Research: The Transdisciplinary Research on Energetics and Cancer Initiative.

    PubMed

    Gehlert, Sarah; Hall, Kara; Vogel, Amanda; Hohl, Sarah; Hartman, Sheri; Nebeling, Linda; Redline, Susan; Schmitz, Kathryn; Thornquist, Mark; Patterson, Ruth; Thompson, Beti

    2014-09-01

    Strategies for constructing and maintaining cross-disciplinary teams are in their infancy. We outline strategies to support one form, transdisciplinary research, in a major initiative of the National Cancer Institute, the Transdisciplinary Research in Energetics and Cancer 2 (TREC2) initiative. Discussion of the TREC2 sites' experiences with transdisciplinarity is structured around a conceptual model that identifies four iterative phases of transdisciplinary research. An active coordination center, regular face-to-face meetings, and input from external advisors were instrumental in moving TREC2 to the translation phase. The possibilities for advancements in the science of energetics and cancer increased as investigator ties became denser. TREC2 can be seen as a flagship effort in transdisciplinary science that provides lessons on moving ideas from development to translation.

  20. Research Area 3 - Mathematical Sciences: Multiscale Modeling of the Mechanics of Advanced Energetic Materials Relevant to Detonation Prediction

    DTIC Science & Technology

    2015-08-24

    new energetic materials with enhanced energy release rates and reduced sensitivity to unintentional detonation . The following results have been...Mechanics of Advanced Energetic Materials Relevant to Detonation Prediction The views, opinions and/or findings contained in this report are those of the...modeling, molecular simulations, detonation prediction REPORT DOCUMENTATION PAGE 11. SPONSOR/MONITOR’S REPORT NUMBER(S) 10. SPONSOR/MONITOR’S

  1. The “Puck” energetic charged particle detector: Design, heritage, and advancements

    PubMed Central

    Cohen, I.; Westlake, J. H.; Andrews, G. B.; Brandt, P.; Gold, R. E.; Gkioulidou, M. A.; Hacala, R.; Haggerty, D.; Hill, M. E.; Ho, G. C.; Jaskulek, S. E.; Kollmann, P.; Mauk, B. H.; McNutt, R. L.; Mitchell, D. G.; Nelson, K. S.; Paranicas, C.; Paschalidis, N.; Schlemm, C. E.

    2016-01-01

    Abstract Energetic charged particle detectors characterize a portion of the plasma distribution function that plays critical roles in some physical processes, from carrying the currents in planetary ring currents to weathering the surfaces of planetary objects. For several low‐resource missions in the past, the need was recognized for a low‐resource but highly capable, mass‐species‐discriminating energetic particle sensor that could also obtain angular distributions without motors or mechanical articulation. This need led to the development of a compact Energetic Particle Detector (EPD), known as the “Puck” EPD (short for hockey puck), that is capable of determining the flux, angular distribution, and composition of incident ions between an energy range of ~10 keV to several MeV. This sensor makes simultaneous angular measurements of electron fluxes from the tens of keV to about 1 MeV. The same measurements can be extended down to approximately 1 keV/nucleon, with some composition ambiguity. These sensors have a proven flight heritage record that includes missions such as MErcury Surface, Space ENvironment, GEochemistry, and Ranging and New Horizons, with multiple sensors on each of Juno, Van Allen Probes, and Magnetospheric Multiscale. In this review paper we discuss the Puck EPD design, its heritage, unexpected results from these past missions and future advancements. We also discuss high‐voltage anomalies that are thought to be associated with the use of curved foils, which is a new foil manufacturing processes utilized on recent Puck EPD designs. Finally, we discuss the important role Puck EPDs can potentially play in upcoming missions. PMID:27867799

  2. Advancements toward matter-antimatter pair plasmas in the laboratory

    NASA Astrophysics Data System (ADS)

    Stenson, E. V.; Hergenhahn, U.; Niemann, H.; Paschkowski, N.; Sunn Pedersen, T.; Saitoh, H.; Stanja, J.; Stoneking, M. R.; Hugenschmidt, C.; Piochacz, C.; Vohburger, S.; Schweikhard, L.; Danielson, J. R.; Surko, C. M.

    2015-11-01

    APEX/PAX (A Positron Electron Experiment/Positron Accumulation Experiment) has as its overarching goal the creation and magnetic confinement of a laboratory electron-positron pair plasma, thereby enabling experimental investigations of a topic that has already been the subject of hundreds of analytical and computational studies. This goal involves several interdependent challenges: design and construction of a suitable magnetic confinement device, access to a sufficient number of sufficiently cool positrons, and refinement of methods for the transfer of the positrons (and an equal number of electrons) into the device. The latest results of the subprojects addressing these challenges will be summarized here. Highlights include efficient (40 percent) injection of the NEPOMUC (Neutron-Inducted Positron Source Munich) positron beam into the confinement region of a dipole magnetic field, characterization of the beam at energies from 5 eV to 1 keV, and hour-long electron plasma confinement in a high-field (2.3 Telsa) Penning-Malmberg trap. on behalf of the APEX/PAX team and collaborators.

  3. Overview study of Space Power Technologies for the advanced energetics program. [spacecraft

    NASA Technical Reports Server (NTRS)

    Taussig, R.; Gross, S.; Millner, A.; Neugebauer, M.; Phillips, W.; Powell, J.; Schmidt, E.; Wolf, M.; Woodcock, G.

    1981-01-01

    Space power technologies are reviewed to determine the state-of-the-art and to identify advanced or novel concepts which promise large increases in performance. The potential for incresed performance is judged relative to benchmarks based on technologies which have been flight tested. Space power technology concepts selected for their potentially high performance are prioritized in a list of R & D topical recommendations for the NASA program on Advanced Energetics. The technology categories studied are solar collection, nuclear power sources, energy conversion, energy storage, power transmission, and power processing. The emphasis is on electric power generation in space for satellite on board electric power, for electric propulsion, or for beamed power to spacecraft. Generic mission categories such as low Earth orbit missions and geosynchronous orbit missions are used to distinguish general requirements placed on the performance of power conversion technology. Each space power technology is judged on its own merits without reference to specific missions or power systems. Recommendations include 31 space power concepts which span the entire collection of technology categories studied and represent the critical technologies needed for higher power, lighter weight, more efficient power conversion in space.

  4. Recent advances in the molten salt technology for the destruction of energetic materials

    SciTech Connect

    Upadhye, R.S.; Watkins, B.E.; Pruneda, C.O.

    1995-11-01

    The DOE has thousands of pounds of energetic materials which result from dismantlement operations at the Pantex Plant. The authors have demonstrated the Molten Salt Destruction (MSD) Process for the treatment of explosives and explosive-containing wastes on a 1.5 kilogram of explosive per hour scale and are currently building a 5 kilogram per hour unit. MSD converts the organic constituents of the waste into non-hazardous substances such as carbon dioxide, nitrogen and water. Any inorganic constituents of the waste, such as binders and metallic particles, are retained in the molten salt. The destruction of energetic material waste is accomplished by introducing it, together with air, into a crucible containing a molten salt, in this case a eutectic mixture of Na, K, and Li carbonates. The following pure component DOE and DoD explosives have been destroyed in LLNL`s experimental unit at their High Explosives Applications Facility (HEAF): ammonium picrate, HMX, K-6, NQ, NTO, PETN, RDX, TATB, and TNT. In addition, the following formulations were also destroyed: Comp B, LX-10, LX-16, LX-17, PBX-9404, and XM46, a US Army liquid gun propellant. In this 1.5 kg/hr unit, the fractions of carbon converted to CO and of chemically bound nitrogen converted to NOx were found to be well below 1T. In addition to destroying explosive powders and molding powders the authors have also destroyed materials that are typical of real world wastes. These include shavings from machined pressed parts of plastic bonded explosives and sump waste containing both explosives and non-explosive debris. Based on the information obtained on the smaller unit, the authors have constructed a 5 kg/hr MSD unit, incorporating LLNL`s advanced chimney design. This unit is currently under shakedown tests and evaluation.

  5. Advancements in the Coupling of State-of-the-Art Energetic Particle and Magnetohydrodynamic Simulations

    NASA Astrophysics Data System (ADS)

    Gorby, M.

    2015-12-01

    Recent advancements in coupling the Earth Moon Mars Radiation Environment Module (EMMREM) and two MHD models, Magnetohydrodynamics Around a Sphere (MAS) and ENLIL, have yielded promising results for predicting differential energy flux and radiation doses at 1AU. The EMMREM+MAS coupling focuses on the details of particle acceleration due to CMEs initiated low in the corona (1Rs - 20Rs). The EMMREM+ENLIL coupling gives results for CMEs initiated at ~20Rs and is part of a predictive capability being developed in conjunction with the CCMC. The challenge in forming large solar energetic particle events in both the prompt scenario lower down or for a gradual CME further out is to have enhanced scattering within the acceleration regions while also allowing for efficient escape of accelerated particles downstream. We present here details of the MHD parameters and topology of a CME around the acceleration regions in the early evolution (below 2Rs), dose and flux predictions at 1AU, and how compression regions vs. shocks affect the evolution and spectrum of an SEP event.

  6. Energetics of median and paired fin swimming, body and caudal fin swimming, and gait transition in parrotfish (Scarus schlegeli) and triggerfish (Rhinecanthus aculeatus).

    PubMed

    Korsmeyer, Keith E; Steffensen, John Fleng; Herskin, Jannik

    2002-05-01

    To determine the energetic costs of rigid-body, median or paired-fin (MPF) swimming versus undulatory, body-caudal fin (BCF) swimming, we measured oxygen consumption as a function of swimming speed in two MPF swimming specialists, Schlegel's parrotfish and Picasso triggerfish. The parrotfish swam exclusively with the pectoral fins at prolonged swimming speeds up to 3.2 total lengths per second (L s(-1); 30 min critical swimming speed, U(crit)). At higher speeds, gait transferred to a burst-and-coast BCF swimming mode that resulted in rapid fatigue. The triggerfish swam using undulations of the soft dorsal and anal fins up to 1.5 L s(-1), beyond which BCF undulations were recruited intermittently. BCF swimming was used continuously above 3.5 L s(-1), and was accompanied by synchronous undulations of the dorsal and anal fins. The triggerfish were capable of high, prolonged swimming speeds of up to 4.1 L s(-1) (30 min U(crit)). In both species, the rates of increase in oxygen consumption with swimming speed were higher during BCF swimming than during rigid-body MPF swimming. Our results indicate that, for these species, undulatory swimming is energetically more costly than rigid-body swimming, and therefore support the hypothesis that MPF swimming is more efficient. In addition, use of the BCF gait at higher swimming speed increased the cost of transport in both species beyond that predicted for MPF swimming at the same speeds. This suggests that, unlike for terrestrial locomotion, gait transition in fishes does not occur to reduce energetic costs, but to increase recruitable muscle mass and propulsive surfaces. The appropriate use of the power and exponential functions to model swimming energetics is also discussed.

  7. A review of advanced high performance, insensitive and thermally stable energetic materials emerging for military and space applications.

    PubMed

    Sikder, A K; Sikder, Nirmala

    2004-08-09

    Energetic materials used extensively both for civil and military applications. There are continuous research programmes worldwide to develop new materials with higher performance and enhanced insensitivity to thermal or shock insults than the existing ones in order to meet the requirements of future military and space applications. This review concentrates on recent advances in syntheses, potential formulations and space applications of potential compounds with respect to safety, performance and stability.

  8. Photofragmentation, state interaction, and energetics of Rydberg and ion-pair states: Resonance enhanced multiphoton ionization of HI

    SciTech Connect

    Hróðmarsson, Helgi Rafn; Wang, Huasheng; Kvaran, Ágúst

    2014-06-28

    Mass resolved resonance enhanced multiphoton ionization data for hydrogen iodide (HI), for two-photon resonance excitation to Rydberg and ion-pair states in the 69 600–72 400 cm{sup −1} region were recorded and analyzed. Spectral perturbations due to homogeneous and heterogeneous interactions between Rydberg and ion-pair states, showing as deformations in line-positions, line-intensities, and line-widths, were focused on. Parameters relevant to photodissociation processes, state interaction strengths and spectroscopic parameters for deperturbed states were derived. Overall interaction and dynamical schemes to describe the observations are proposed.

  9. [Structural and energetic properties of the four configurations of the A.T and G.C DNA base pairs].

    PubMed

    Brovarets', O O

    2013-01-01

    Using the methods of non-empirical quantum chemistry at the MP2/6-311++G(2df,pd)// B3LYP/6-311++G(d,p) level of theory it was established for the first time, that Hoogsteen, reverse Hoogsteen, Watson-Crick and reverse Watson-Crick configurations of the A.T and G.C DNA base pairs are isoelectronic and isomorphic structures with similar dynamic properties. Based on these results, non-ionisation mechanism of the Hoogsteen <"breathing" of the G*.C* DNA base pair, namely transformation of the tautomerised (Lowdin's) G-C base pair with Watson-Crick geometry into the Hoogsteen electroneutral G*.C* H base pair stabilized by the three O6H...N4, N3H...N7 and C8H...02 H-bonds, was postulated. It is suggested that such scenario activates only in those cases, when DNA is not located in aqueous solution, but works together with proteins and cytosine protonation at the N3 atom is precluded.

  10. Production and Characterization of Silicon Nanostructures for the Advancement of Novel Energetic Formulations

    DTIC Science & Technology

    2008-12-01

    the reduced sensitivity to ESD event in comparison with that of other nanothermites such as CuO-Al, Bi2O3 -Al, WO3-Al etc. 3.6 Future...Perspective of Si Nanostructures in Energetics It is expected that mixing traditional metal oxides like CuO, Bi2O3 , WO3 etc with high aspect ratio Si

  11. Modulation of primary radical pair kinetics and energetics in photosystem II by the redox state of the quinone electron acceptor Q(A).

    PubMed Central

    Gibasiewicz, K; Dobek, A; Breton, J; Leibl, W

    2001-01-01

    Time-resolved photovoltage measurements on destacked photosystem II membranes from spinach with the primary quinone electron acceptor Q(A) either singly or doubly reduced have been performed to monitor the time evolution of the primary radical pair P680(+)Pheo(-). The maximum transient concentration of the primary radical pair is about five times larger and its decay is about seven times slower with doubly reduced compared with singly reduced Q(A). The possible biological significance of these differences is discussed. On the basis of a simple reversible reaction scheme, the measured apparent rate constants and relative amplitudes allow determination of sets of molecular rate constants and energetic parameters for primary reactions in the reaction centers with doubly reduced Q(A) as well as with oxidized or singly reduced Q(A). The standard free energy difference DeltaG degrees between the charge-separated state P680(+)Pheo(-) and the equilibrated excited state (Chl(N)P680)* was found to be similar when Q(A) was oxidized or doubly reduced before the flash (approximately -50 meV). In contrast, single reduction of Q(A) led to a large change in DeltaG degrees (approximately +40 meV), demonstrating the importance of electrostatic interaction between the charge on Q(A) and the primary radical pair, and providing direct evidence that the doubly reduced Q(A) is an electrically neutral species, i.e., is doubly protonated. A comparison of the molecular rate constants shows that the rate of charge recombination is much more sensitive to the change in DeltaG degrees than the rate of primary charge separation. PMID:11259277

  12. Photofragmentations, state interactions, and energetics of Rydberg and ion-pair states: resonance enhanced multiphoton ionization via E and V (B) states of HCl and HBr.

    PubMed

    Long, Jingming; Wang, Huasheng; Kvaran, Ágúst

    2013-01-28

    (2 + n) resonance enhanced multiphoton ionization mass spectra for resonance excitations to diabatic E(1)Σ(+) (v') Rydberg and V (1)Σ(+) (v') ion-pair states (adiabatic B(1)Σ(+)(v') states) of H(i)Cl (i = 35,37) and H(i)Br (i = 79,81) were recorded as a function of excitation wavenumber (two-dimensional REMPI). Simulation analyses of ion signal intensities, deperturbation analysis of line shifts and interpretations of line-widths are used to derive qualitative and quantitative information concerning the energetics of the states, off-resonance interactions between the E states and V states, closest in energy as well as on predissociation channels. Spectroscopic parameters for the E(1)Σ(+) (v')(v' = 1) for H(35)Cl and v' = 0 for H(79)Br states, interaction strengths for E - V state interactions and parameters relevant to dissociation of the E states are derived. An overall interaction and dynamical scheme, to describe the observations for HBr, is proposed.

  13. NATO (North Atlantic Treaty Organization) Advanced Study Institute Fast Reactions in Energetic Systems

    DTIC Science & Technology

    1980-07-01

    Chief. ,i #’ - r: [" k I TABLE OF CONTEhTS Page No. ORGANIZING COHITTEE 1 A. -FAST REACTIONS AND ENERGY TRANSFER PROCESSESI ADVANCED DIAGNOSTICS. , 3...Subpicosecond Spearroscopies. Lecture II. Phocophysics of Electr - nically 9 Excited States Lecture 111. Chemical Reactivity of Electronically 9 Excited...Excitation by High 12 Energy Electrons Lecture 11. Pulse Radiolysis; Formation of 13 Organic Anions and Cations Lecture III. Fast Reactions of Organic

  14. Observation of Energetic Particle Driven Modes Relevant to Advanced Tokamak Regimes

    SciTech Connect

    R. Nazikian; B. Alper; H.L. Berk; D. Borba; C. Boswell; R.V. Budny; K.H. Burrell; C.Z. Cheng; E.J. Doyle; E. Edlund; R.J. Fonck; A. Fukuyama; N.N. Gorelenkov; C.M. Greenfield; D.J. Gupta; M. Ishikawa; R.J. Jayakumar; G.J. Kramer; Y. Kusama; R.J. La Haye; G.R. McKee; W.A. Peebles; S.D. Pinches; M. Porkolab; J. Rapp; T.L. Rhodes; S.E. Sharapov; K. Shinohara; J.A. Snipes; W.M. Solomon; E.J. Strait; M. Takechi; M.A. Van Zeeland; W.P. West; K.L. Wong; S. Wukitch; L. Zeng

    2004-10-21

    Measurements of high-frequency oscillations in JET [Joint European Torus], JT-60U, Alcator C-Mod, DIII-D, and TFTR [Tokamak Fusion Test Reactor] plasmas are contributing to a new understanding of fast ion-driven instabilities relevant to Advanced Tokamak (AT) regimes. A model based on the transition from a cylindrical-like frequency-chirping mode to the Toroidal Alfven Eigenmode (TAE) has successfully encompassed many of the characteristics seen in experiments. In a surprising development, the use of internal density fluctuation diagnostics has revealed many more modes than has been detected on edge magnetic probes. A corollary discovery is the observation of modes excited by fast particles traveling well below the Alfven velocity. These observations open up new opportunities for investigating a ''sea of Alfven Eigenmodes'' in present-scale experiments, and highlight the need for core fluctuation and fast ion measurements in a future burning-plasma experiment.

  15. Measurements and calculations of the Coulomb cross section for the production of direct electron pairs by energetic heavy nuclei in nuclear track emulsion

    NASA Technical Reports Server (NTRS)

    Derrickson, J. H.; Eby, P. B.; Fountain, W. F.; Parnell, T. A.; Dong, B. L.; Gregory, J. C.; Takahashi, Y.; King, D. T.

    1988-01-01

    Measurements and theoretical predictions of the Coulomb cross section for the production of direct electron pairs by heavy ions in emulsion have been performed. Nuclear track emulsions were exposed to the 1.8 GeV/amu Fe-56 beam at the Lawrence Berkeley Laboratory bevalac and to the 60 and 200 GeV/amu O-16 and the 200 GeV/amu S-32 beam at the European Center for Nuclear Research Super Proton Synchrotron modified to accelerate heavy ions. The calculations combine the Weizsacker-Williams virtual quanta method applicable to the low-energy transfers and the Kelner-Kotov relativistic treatment for the high-energy transfers. Comparison of the measured total electron pair yield, the energy transfer distribution, and the emission angle distribution with theoretical predictions revealed a discrepancy in the frequency of occurrence of the low-energy pairs (less than or = 10 MeV). The microscope scanning criteria used to identify the direct electron pairs is described and efforts to improve the calculation of the cross section for pair production are also discussed.

  16. Energetics and excited state dynamics of the radical pair formation in isolated CP47-reaction center complex of photosystem II at various temperatures

    SciTech Connect

    Groot, Marie-Louise; Paa lsson, Lars-Olof; Pribic, Radmila; Stokkum, Ivo H. van; Dekker, Jan P.; Grondelle, Rienk van

    1996-04-01

    The isolated CP47-reaction center complex of spinach photosystem II has been studied with time resolved picosecond fluorescence spectroscopy between 77 K and 270 K. It was observed that these particles exhibit multi-exponential fluorescence decays of the excited state at all temperatures. The major observations are an energy transfer/trapping time of {approx}40 picoseconds and a long-lived {approx}23 nanosecond component attributed to the recombination of the radical pair. These experimentally obtained parameters were used to estimate the free energy difference for the radical pair formation.

  17. Advances in understanding the genesis and evolution solar energetic particle events over the last two solar cycles

    NASA Astrophysics Data System (ADS)

    Vainio, Rami

    2016-04-01

    I will review the observational and modeling efforts related to solar energetic particle (SEP) events over the 23rd and 24th solar cycles. I will concentrate on large SEP events related to coronal mass ejections (CMEs), but discuss observations related to the possible role of flares in the acceleration of particles in those events, as well. The possible roles of various acceleration and transport processes in understanding the characteristics of the events will be discussed. This work has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 637324 (HESPERIA).

  18. Advanced seasonal reproductive development in a male urban bird is reflected in earlier plasma luteinizing hormone rise but not energetic status.

    PubMed

    Davies, Scott; Behbahaninia, Hirbod; Giraudeau, Mathieu; Meddle, Simone L; Waites, Kyle; Deviche, Pierre

    2015-12-01

    Urban animals inhabit an environment considerably different than do their non-urban conspecifics, and to persist urban animals must adjust to these novel environments. The timing of seasonal reproductive development (i.e., growth of gonads and secondary sex organs) is a fundamental determinant of the breeding period and is frequently advanced in urban bird populations. However, the underlying mechanism(s) by which birds adjust the timing of reproductive development to urban areas remain(s) largely unknown. Here, we compared the timing of vernal reproductive development in free-ranging urban and non-urban male Abert's Towhees, Melozone aberti, in Phoenix, Arizona, USA, and tested the non-mutually exclusive hypotheses that earlier reproductive development is due to improved energetic status and/or earlier increase in endocrine activity of the reproductive system. We found that urban birds initiated testicular development earlier than non-urban birds, but this disparity was not associated with differences in body condition, fat stores, or innate immune performance. These results provide no support for the hypothesis that energetic constraints are responsible for delayed reproductive development of non-urban relative to urban male Abert's Towhees. Urban birds did, however, increase their plasma luteinizing hormone, but not plasma testosterone, earlier than non-urban birds. These findings suggest that adjustment to urban areas by Abert's Towhees involves increases in the endocrine activity of the anterior pituitary gland and/or hypothalamus earlier than non-urban towhees.

  19. Energetic composites

    DOEpatents

    Danen, Wayne C.; Martin, Joe A.

    1993-01-01

    A method for providing chemical energy and energetic compositions of matter consisting of thin layers of substances which will exothermically react with one another. The layers of reactive substances are separated by thin layers of a buffer material which prevents the reactions from taking place until the desired time. The reactions are triggered by an external agent, such as mechanical stress or an electric spark. The compositions are known as metastable interstitial composites (MICs). This class of compositions includes materials which have not previously been capable of use as energetic materials. The speed and products of the reactions can be varied to suit the application.

  20. Energetic composites

    DOEpatents

    Danen, W.C.; Martin, J.A.

    1993-11-30

    A method for providing chemical energy and energetic compositions of matter consisting of thin layers of substances which will exothermically react with one another. The layers of reactive substances are separated by thin layers of a buffer material which prevents the reactions from taking place until the desired time. The reactions are triggered by an external agent, such as mechanical stress or an electric spark. The compositions are known as metastable interstitial composites (MICs). This class of compositions includes materials which have not previously been capable of use as energetic materials. The speed and products of the reactions can be varied to suit the application. 3 figures.

  1. Destruction of Energetic Materials in Supercritical Water

    DTIC Science & Technology

    2002-06-25

    THERMOCHEMISTRY OF ENERGETIC MATERIALS IN SUPERCRITICAL WATER...fringe spacing is 13.5 µm and the acoustic signal period is 28.3 ns. 138 SECTION VI THERMOCHEMISTRY OF ENERGETIC MATERIALS IN...validation calculation studied the solvation free energies of alkali–chloride ion pairs in liquid water. Such information can teach us about the

  2. Flare energetics

    NASA Technical Reports Server (NTRS)

    Wu, S. T.; Dejager, C.; Dennis, B. R.; Hudson, H. S.; Simnett, G. M.; Strong, K. T.; Bentley, R. D.; Bornmann, P. L.; Bruner, M. E.; Cargill, P. J.

    1986-01-01

    In this investigation of flare energetics, researchers sought to establish a comprehensive and self-consistent picture of the sources and transport of energy within a flare. To achieve this goal, they chose five flares in 1980 that were well observed with instruments on the Solar Maximum Mission, and with other space-borne and ground-based instruments. The events were chosen to represent various types of flares. Details of the observations available for them and the corresponding physical parameters derived from these data are presented. The flares were studied from two perspectives, the impulsive and gradual phases, and then the results were compared to obtain the overall picture of the energics of these flares. The role that modeling can play in estimating the total energy of a flare when the observationally determined parameters are used as the input to a numerical model is discussed. Finally, a critique of the current understanding of flare energetics and the methods used to determine various energetics terms is outlined, and possible future directions of research in this area are suggested.

  3. Benchtop Energetics Progress

    NASA Astrophysics Data System (ADS)

    Fajardo, Mario

    2011-06-01

    We have constructed an apparatus for investigating the reactive chemical dynamics of mg-scale energetic materials samples. We seek to advance the understanding of the reaction kinetics of energetic materials, and of the chemical influences on energetic materials sensitivity. We employ direct laser irradiation, and indirect laser-driven shock, techniques to initiate thin-film explosive samples contained in a high-vacuum chamber. Expansion of the reacting flow into vacuum quenches the chemistry and preserves reaction intermediates for interrogation via time-of-flight mass spectrometry (TOFMS). By rastering the sample coupon through the fixed laser beam focus, we generate hundreds of repetitive energetic events in a few minutes. A detonation wave passing through an organic explosive, such as pentaerythritol tetranitrate (PETN, C5H4N4O12) , is remarkably efficient in converting the solid explosive into final thermodynamically-stable gaseous products (e . g . N2, CO2, H2O...). Termination of a detonation at an explosive-to-vacuum interface produces an expanding pulse of hyperthermal molecular species, with leading-edge velocities ~10 km/s. In contrast, deflagration (subsonic combustion) of PETN in vacuum produces mostly reaction intermediates, such as NO and NO2, with much slower molecular velocities; consistent with expansion-quenched thermal decomposition of PETN. We propose to exploit these differences in product chemical identities and molecular species velocities to provide a chemically-based diagnostic for distinguishing between detonation and deflagration events. In this talk we also report recent progress towards the quantitative detection of hyperthermal neutral species produced by direct laser ablation of aluminum metal and of organic energetic materials, as a step towards demonstrating the ability to discriminate slow reaction intermediates from fast thermodynamically-stable final products. Work done in collaboration with Emily Fossum, Christopher Molek, and

  4. Energetic powder

    DOEpatents

    Jorgensen, Betty S.; Danen, Wayne C.

    2003-12-23

    Fluoroalkylsilane-coated metal particles. The particles have a central metal core, a buffer layer surrounding the core, and a fluoroalkylsilane layer attached to the buffer layer. The particles may be prepared by combining a chemically reactive fluoroalkylsilane compound with an oxide coated metal particle having a hydroxylated surface. The resulting fluoroalkylsilane layer that coats the particles provides them with excellent resistance to aging. The particles can be blended with oxidant particles to form energetic powder that releases chemical energy when the buffer layer is physically disrupted so that the reductant metal core can react with the oxidant.

  5. Observations and Modeling of Geospace Energetic Particles

    NASA Astrophysics Data System (ADS)

    Li, Xinlin

    2016-07-01

    Comprehensive measurements of energetic particles and electric and magnetic fields from state-of-art instruments onboard Van Allen Probes, in a geo-transfer-like orbit, revealed new features of the energetic particles and the fields in the inner magnetosphere and impose new challenges to any quantitative modeling of the physical processes responsible for these observations. Concurrent measurements of energetic particles by satellites in highly inclined low Earth orbits and plasma and fields by satellites in farther distances in the magnetospheres and in the up stream solar wind are the critically needed information for quantitative modeling and for leading to eventual accurate forecast of the variations of the energetic particles in the magnetosphere. In this presentation, emphasis will be on the most recent advance in our understanding of the energetic particles in the magnetosphere and the missing links for significantly advance in our modeling and forecasting capabilities.

  6. Photofragmentations, state interactions, and energetics of Rydberg and ion-pair states: two-dimensional resonance enhanced multiphoton ionization of HBr via singlet-, triplet-, Ω = 0 and 2 states.

    PubMed

    Long, Jingming; Hróðmarsson, Helgi Rafn; Wang, Huasheng; Kvaran, Ágúst

    2012-06-07

    Mass spectra were recorded for one-colour resonance enhanced multiphoton ionization (REMPI) of H(i)Br (i = 79, 81) for the two-photon resonance excitation region 79,040-80,300 cm(-1) to obtain two-dimensional REMPI data. The data were analysed in terms of rotational line positions, intensities, and line-widths. Quantitative analysis of the data relevant to near-resonance interactions between the F(1)Δ(2)(v' = 1) and V(1)Σ(+)(v' = m + 7) states gives interaction strengths, fractional state mixing, and parameters relevant to dissociation of the F state. Qualitative analysis further reveals the nature of state interactions between ion-pair states and the E(1)Σ(+) (v' = 1) and H(1)Σ(+)(v' = 0) Rydberg states in terms of relative strengths and J' dependences. Large variety in line-widths, depending on electronic states and J' quantum numbers, is indicative of number of different predissociation channels. The relationship between line-widths, line-shifts, and signal intensities reveals dissociation mechanisms involving ion-pair to Rydberg state interactions prior to direct or indirect predissociations of Rydberg states. Quantum interference effects are found to be important. Moreover, observed bromine atom (2 + 1) REMPI signals support the importance of Rydberg state predissociation channels. A band system, not previously observed in REMPI, was observed and assigned to the k(3)Π(0)(v' = 0) ←← X transition with band origin 80,038 cm(-1) and rotational parameter B(v('))=7.238 cm(-1).

  7. Pick a Pair. Pancake Pairs

    ERIC Educational Resources Information Center

    Miller, Pat

    2005-01-01

    Cold February weather and pancakes are a traditional pairing. Pancake Day began as a way to eat up the foods that were abstained from in Lent--traditionally meat, fat, eggs and dairy products. The best-known pancake event is The Pancake Day Race in Buckinghamshire, England, which has been run since 1445. This column describes pairs of books that…

  8. Solar Energetic Particles

    NASA Astrophysics Data System (ADS)

    Király, Péter

    Energetic particles recorded in the Earth environment and in interplanetary space have a multitude of origins, i.e. acceleration and propagation histories. At early days practically all sufficiently energetic particles were considered to have come either from solar flares or from interstellar space. Later on, co-rotating interplanetary shocks, the termination shock of the supersonic solar wind, planetary bow shocks and magnetospheres, and also coronal mass ejections (CME) were recognized as energetic particle sources. It was also recognized that less energetic (suprathermal) particles of solar origin and pick-up ions have also a vital role in giving rise to energetic particles in interplanetary disturbances. The meaning of the term "solar energetic particles" (SEP) is now somewhat vague, but essentially it refers to particles produced in disturbances fairly directly related to solar processes. Variation of intensity fluctuations with energy and with the phase of the solar cycle will be discussed. Particular attention will be given to extremes of time variation, i.e. to very quiet periods and to large events. While quiet-time fluxes are expected to shed light on some basic coronal processes, large events dominate the fluctuation characteristics of cumulated fluence, and the change of that fluctuation with energy and with the phase of the solar cycle may also provide important clues. Mainly ISEE-3 and long-term IMP-8 data will be invoked. Energetic and suprathermal particles that may never escape into interplanetary space may play an important part in heating the corona of the sun.

  9. A Pair Production Telescope for Medium-Energy Gamma-Ray Polarimetry

    SciTech Connect

    Hunter , Stanley D.; Bloser, Peter F.; Depaola, Gerardo O.; Dion, Michael P.; DeNolfo, Georgia A.; Hanu, Andrei; Iparraguirre, Marcos; Legere, Jason; Longo, Francesco; McConnell, Mark L.; Nowicki, Suzanne F.; Ryan, James M.; Son, Seunghee; Stecker, Floyd W.

    2014-08-01

    We describe the science motivation and development of a pair production telescope for medium-13 energy gamma-ray polarimetry. Our instrument concept, the Advanced Energetic Pair Telescope 14 (AdEPT), takes advantage of the Three-Dimensional Track Imager, a low-density gaseous time 15 projection chamber, to achieve angular resolution within a factor of two of the pair production 16 kinematics limit (~0.6° at 70 MeV), continuum sensitivity comparable with the Fermi-LAT front 17 detector (<3×10-6 MeV cm-2 s-1 at 70 MeV), and minimum detectable polarization less than 10% 18 for a 10 millicrab source in 106 seconds.

  10. A Pair Production Telescope for Medium-Energy Gamma-Ray Polarimetry

    NASA Technical Reports Server (NTRS)

    Hunter, Stanley D.; Bloser, Peter F.; Depaola, Gerardo; Dion, Michael P.; DeNolfo, Georgia A.; Hanu, Andrei; Iparraguirre, Marcos; Legere, Jason; Longo, Francesco; McConnell, Mark L.; Nowicki, Suzanne F.; Ryan, James M.; Son, Seunghee; Stecker, Floyd W.

    2014-01-01

    We describe the science motivation and development of a pair production telescope for medium-energy (approximately 5-200 Mega electron Volts) gamma-ray polarimetry. Our instrument concept, the Advanced Energetic Pair Telescope (AdEPT), takes advantage of the Three-Dimensional Track Imager, a low-density gaseous time projection chamber, to achieve angular resolution within a factor of two of the pair production kinematics limit (approximately 0.6 deg at 70 Mega electron Volts), continuum sensitivity comparable with the Fermi-LAT front detector (is less than 3 x 10(exp -6) Mega electron Volts per square centimeter per second at 70 Mega electron Volts), and minimum detectable polarization less than 10% for a 10 milliCrab source in 10(exp 6) s.

  11. Cooper Pair Insulators

    NASA Astrophysics Data System (ADS)

    Valles, James

    One of the recent advances in the field of the Superconductor to Insulator Transition (SIT) has been the discovery and characterization of the Cooper Pair Insulator phase. This bosonic insulator, which consists of localized Cooper pairs, exhibits activated transport and a giant magneto-resistance peak. These features differ markedly from the weakly localized transport that emerges as pairs break at a ``fermionic'' SIT. I will describe how our experiments on films nano-patterned with a nearly triangular array of holes have enabled us to 1) distinguish bosonic insulators from fermionic insulators, 2) show that Cooper pairs, rather than quasi-particles dominate the transport in the Cooper Pair insulator phase, 3) demonstrate that very weak, sub nano-meter thickness inhomogeneities control whether a bosonic or fermionic insulator forms at an SIT and 4) reveal that Cooper pairs disintegrate rather than becoming more tightly bound deep in the localized phase. We have also developed a method, using a magnetic field, to tune flux disorder reversibly in these films. I will present our latest results on the influence of magnetic flux disorder and random gauge fields on phenomena near bosonic SITs. This work was performed in collaboration with M. D. Stewart, Jr., Hung Q. Nguyen, Shawna M. Hollen, Jimmy Joy, Xue Zhang, Gustavo Fernandez, Jeffrey Shainline and Jimmy Xu. It was supported by NSF Grants DMR 1307290 and DMR-0907357.

  12. Environmentally compatible next generation green energetic materials (GEMs).

    PubMed

    Talawar, M B; Sivabalan, R; Mukundan, T; Muthurajan, H; Sikder, A K; Gandhe, B R; Rao, A Subhananda

    2009-01-30

    This paper briefly reviews the literature work reported on the environmentally compatible green energetic materials (GEMs) for defence and space applications. Currently, great emphasis is laid in the field of high-energy materials (HEMs) to increase the environmental stewardship along with the deliverance of improved performance. This emphasis is especially strong in the areas of energetic materials, weapon development, processing, and disposal operations. Therefore, efforts are on to develop energetic materials systems under the broad concept of green energetic materials (GEMs) in different schools all over the globe. The GEMs program initiated globally by different schools addresses these challenges and establishes the framework for advances in energetic materials processing and production that promote compliance with environmental regulations. This review also briefs the principles of green chemistry pertaining to HEMs, followed by the work carried out globally on environmentally compatible green energetic materials and allied ingredients.

  13. Advanced formulation of base pair changes in the stem regions of ribosomal RNAs; its application to mitochondrial rRNAs for resolving the phylogeny of animals.

    PubMed

    Otsuka, Jinya; Sugaya, Nobuyoshi

    2003-06-21

    The ribosomal RNAs (rRNAs) of animal mitochondria, especially those of arthropod mitochondria, have a higher content of G:U and U:G base pairs in their stem regions than the nuclear rRNAs. Thus, the theoretical formulation of base pair changes is extended to incorporate the faster base pair changes A:U<-->G:U<-->G:C and U:A<-->U:G<-->C:G into the previous formulation of the slower base pair changes between A:U, G:C, C:G and U:A. The relative base pair change probability containing the faster and slower base pair changes is theoretically derived to estimate the divergence time of rRNAs under the influence of selection for these base pairs. Using the cartilaginous fish-teleost fish divergence and the crustacean-insect divergence as calibration points, the present method successfully predicts the divergence times of the main branches of animals: Deuterostomia and Protostomia diverged 9.2 x 10(8) years ago, the divergence of Echinodermata, Hemichordata and Cephalochordata succeedingly occurred during the period from 8 x 10(8) to 6 x 10(8) years ago, while Arthropoda, Annelida and Mollusca diverged almost concomitantly about 7 x 10(8) years ago. The dating for the divergence of Platyhelminthes and Cnidaria is traced back to 1.2 x 10(9) years ago. This result is consistent with the fossil records in the Stirling Range Formation of southwestern Australia, the Ediacara and Avalon faunas and the Cambrian Burgess Shale. Thus, the present method may be useful for estimating the divergence times of animals ranging from 10(8) to 10(9) years ago, resolving the difficult problems, e.g. deviation from rate constancy and large sampling variances, in the usual methods of treating apparent change rates between individual bases and/or base pairs.

  14. Time Evolution of Elemental Ratios in Solar Energetic Particle Events

    NASA Astrophysics Data System (ADS)

    Zelina, P.; Dalla, S.; Cohen, C. M. S.; Mewaldt, R. A.

    2017-01-01

    Heavy ion ratio abundances in solar energetic particle (SEP) events, e.g., Fe/O, often exhibit decreases over time. Using particle instruments on the Advanced Composition Explorer, Solar and Heliospheric Observatory and Solar Terrestrial Relations Observatory spacecraft, we analyzed heavy ion data from 4 SEP events taking place between 2006 December and 2014 December. We constructed 36 different ionic pairs and studied their time evolution in each event. We quantified the temporal behavior of abundant SEP ratios by fitting the data to derive a decay time constant B. We also considered the ratio of ionic mass-to-charge for each pair, the S value given, e.g., for Fe/O by {S}{Fe/{{O}}}={(M/Q)}{Fe}/{(M/Q)}{{O}}. We found that the temporal behavior of SEP ratios is ordered by the value of S: ratios with S> 1 showed decreases over time (i.e., B< 0) and those with S< 1 showed increases (B> 0). We plotted B as a function of S and observed a clear monotonic dependence: ratios with a large S decayed at a higher rate. A prominent discontinuity at S = 2.0 (corresponding to He/H) was found in three of the four events, suggesting anomalous behavior of protons. The X/H ratios often show an initial increase followed by a decrease, and decay at a slower rate. We discuss possible causes of the observed B versus S trends within current understanding of SEP propagation.

  15. Cookoff of energetic materials

    SciTech Connect

    Baer, M.R.; Hobbs, M.L.; Gross, R.J.; Schmitt, R.G.

    1998-09-01

    An overview of cookoff modeling at Sandia National Laboratories is presented aimed at assessing the violence of reaction following cookoff of confined energetic materials. During cookoff, the response of energetic materials is known to involve coupled thermal/chemical/mechanical processes which induce thermal damage to the energetic material prior to the onset of ignition. These damaged states enhance shock sensitivity and lead to conditions favoring self-supported accelerated combustion. Thus, the level of violence depends on the competition between pressure buildup and stress release due to the loss of confinement. To model these complex processes, finite element-based analysis capabilities are being developed which can resolve coupled heat transfer with chemistry, quasi-static structural mechanics and dynamic response. Numerical simulations that assess the level of violence demonstrate the importance of determining material damage in pre- and post-ignition cookoff events.

  16. INTENSE ENERGETIC GAS DISCHARGE

    DOEpatents

    Luce, J.S.

    1960-03-01

    A method and apparatus for initiating and sustaining an energetic gas arc discharge are described. A hollow cathode and a hollow anode are provided. By regulating the rate of gas flow into the interior of the cathode, the arc discharge is caused to run from the inner surface of the cathode with the result that adequate space-charge neutralization is provided inside the cathode but not in the main arc volume. Thus, the gas fed to the cathode is substantially completely ionized before it leaves the cathode, with the result that an energetic arc discharge can be maintained at lower operating pressures.

  17. Nanostructured Energetic Materials

    DTIC Science & Technology

    2006-11-01

    for the nanoenergetic composites prepared using mesoporous Fe2O3 gel, nanoparticles of WO3, MoO3, Bi2O3 , and CuO mixed with Al-nanoparticles and...used in the energetic composite. For example, in the energetic reactions of the composites containing Fe2O3, WO3, MoO3, Bi2O3 , and CuO, combined...MA), WO3 (Aldrich, WI), MoO3 and Bi2O3 (Accumet Materials, NY) and nanoparticles of Al (avg. size 80 nm with 2 nm passivation layer from

  18. Nanostructured energetic composites: synthesis, ignition/combustion modeling, and applications.

    PubMed

    Zhou, Xiang; Torabi, Mohsen; Lu, Jian; Shen, Ruiqi; Zhang, Kaili

    2014-03-12

    Nanotechnology has stimulated revolutionary advances in many scientific and industrial fields, particularly in energetic materials. Powder mixing is the simplest and most traditional method to prepare nanoenergetic composites, and preliminary findings have shown that these composites perform more effectively than their micro- or macro-sized counterparts in terms of energy release, ignition, and combustion. Powder mixing technology represents only the minimum capability of nanotechnology to boost the development of energetic material research, and it has intrinsic limitations, namely, random distribution of fuel and oxidizer particles, inevitable fuel pre-oxidation, and non-intimate contact between reactants. As an alternative, nanostructured energetic composites can be prepared through a delicately designed process. These composites outperform powder-mixed nanocomposites in numerous ways; therefore, we comprehensively discuss the preparation strategies adopted for nanostructured energetic composites and the research achievements thus far in this review. The latest ignition and reaction models are briefly introduced. Finally, the broad promising applications of nanostructured energetic composites are highlighted.

  19. Pair extended coupled cluster doubles

    SciTech Connect

    Henderson, Thomas M.; Scuseria, Gustavo E.; Bulik, Ireneusz W.

    2015-06-07

    The accurate and efficient description of strongly correlated systems remains an important challenge for computational methods. Doubly occupied configuration interaction (DOCI), in which all electrons are paired and no correlations which break these pairs are permitted, can in many cases provide an accurate account of strong correlations, albeit at combinatorial computational cost. Recently, there has been significant interest in a method we refer to as pair coupled cluster doubles (pCCD), a variant of coupled cluster doubles in which the electrons are paired. This is simply because pCCD provides energies nearly identical to those of DOCI, but at mean-field computational cost (disregarding the cost of the two-electron integral transformation). Here, we introduce the more complete pair extended coupled cluster doubles (pECCD) approach which, like pCCD, has mean-field cost and reproduces DOCI energetically. We show that unlike pCCD, pECCD also reproduces the DOCI wave function with high accuracy. Moreover, pECCD yields sensible albeit inexact results even for attractive interactions where pCCD breaks down.

  20. Nano Engineered Energetic Materials (NEEM)

    DTIC Science & Technology

    2011-01-12

    REPORT Nano Engineered Energetic Materials (NEEM) 14 . ABSTRACT 16. SECURITY CLASSIFICATION OF: The ARO Nano Engineered Energetic Materials (NEEM) MURI...PROPELLANTS EXPLOSIVES PYROTECHNICS 34, 5, 385-393, 2009. 14 . Sabourin, JL; Yetter, RA; Parimi, S, Exploring the Effects of High Surface Area Metal...Energetic Materials, Aberdeen, MD, June 2010, "Fundamental Processes and Properties of Insensitive Energetic Materials". 14 . UIUC group (Dlott

  1. Cryocycling of energetic materials. Final report

    SciTech Connect

    Griffiths, S.; Nilson, R.; Handrock, J.; Revelli, V.; Weingarten, L.

    1997-08-01

    The Cryocycling of Energetic Materials Project was executed in the period FY`94-96 as a Life Cycle Engineering activity in the Memorandum of Understanding (MOU) on advanced conventional munitions. This MOU is an agreement between the Departments of Energy and Defense (Office of Munitions) that facilitates the development of technologies of mutual interest to the two Departments. The cryocycling process is a safe, environmentally friendly, and cost effective means of rubblizing bulk energetic materials so that they can be easily reused in a variety of new products. For this reason, cryocycling of excess solid energetic materials is one of the recycle/reuse strategies under study for demilitarized munitions in the Departments of Energy and Defense. These strategies seek to minimize the environmental damage associated with disposal of decommissioned energetic materials. In addition, they encourage technologies that can be used to derive economic benefit from reuse/reapplication of materials that would otherwise be treated as hazardous wastes. 45 refs., 38 figs., 7 tabs.

  2. Pairing Learners in Pair Work Activity

    ERIC Educational Resources Information Center

    Storch, Neomy; Aldosari, Ali

    2013-01-01

    Although pair work is advocated by major theories of second language (L2) learning and research findings suggest that pair work facilitates L2 learning, what is unclear is how to best pair students in L2 classes of mixed L2 proficiency. This study investigated the nature of pair work in an English as a Foreign Language (EFL) class in a college in…

  3. Polymorphism in Energetic Materials

    DTIC Science & Technology

    2008-01-01

    2008 NRL REVIEW 71 Polymorphism in Energetic Materials J.R. Deschamps,1 D.A. Parrish,1 and R.J. Butcher2 1Laboratory for Structure of Matter...can lead to substantial alterations in stability and performance. The authors recently reported on the crystal structures of five polymorphs of picryl...cally distinct forms. Since the properties of a solid sub- stance are determined by its composition and structure , polymorphs, although chemically

  4. Energetics of tropical hibernation.

    PubMed

    Dausmann, K H; Glos, J; Heldmaier, G

    2009-04-01

    In this field study, the energetic properties of tropical hibernation were investigated by measuring oxygen consumption and body temperature of the Malagasy primate Cheirogaleus medius in their natural hibernacula. These lemurs use tree holes with extremely varying insulation capacities as hibernacula. In poorly insulated tree holes, tree hole temperature and body temperature fluctuated strongly each day (between 12.8 and 34.4 degrees C). The metabolic rate under these conditions also showed large daily fluctuations between about 29.0 ml O(2)/h and 97.9 ml O(2)/h in parallel with changes in body temperature. In well insulated tree holes in very large trees on the other hand, tree hole temperature and body temperature remained relatively constant at about 25 degrees C. Lemurs hibernating in these tree holes showed a more constant metabolic rate at an intermediate level, but hibernation was interrupted by repeated arousals with peak metabolic rates up to 350 ml O(2)/h. The occurrence of these spontaneous arousals proved that the ability for thermoregulation persists during hibernation. Arousals were energetically costly, but much less so than in temperate and arctic hibernators. Despite the decisive influence of tree hole properties on the pattern of body temperature and metabolic rate during hibernation, the choice of the hibernaculum does not seem to be of energetic importance. The overall energetic savings by tropical hibernation amounted to about 70% as compared to the active season (31.5 vs. 114.3 kJ/d). Therefore, tropical hibernation in C. medius is an effective, well-regulated adaptive response to survive unfavourable seasons.

  5. Synthesis of Energetic Materials.

    DTIC Science & Technology

    1986-03-31

    1 ) ................... 2 2 GPC of Polyformal of Decafluorodiol ( 2 ) .......................... 4 3 GPC of Polyformal of...turn: ( 1 ) synthesis of energetic monomers and polymers, and ( 2 ) synthesis of polycyclic and adamantoid nitramines. Both tasks were continuations of...preparation of 2,2,3,3,4,4-hexafluoropentane-l,lidiol polyformal (FPF- 1 ) by the 2 step sequence shown below was reported. " HOCH2 (CF2 )3CH20H + (CH20) 3

  6. Energetic component treatability study

    SciTech Connect

    Gildea, P.D.; Brandon, S.L.; Brown, B.G.

    1997-11-01

    The effectiveness of three environmentally sound processes for small energetic component disposal was examined experimentally in this study. The three destruction methods, batch reactor supercritical water oxidation, sodium hydroxide base hydrolysis and calcium carbonate cookoff were selected based on their potential for producing a clean solid residue and minimum release of toxic gases after component detonation. The explosive hazard was destroyed by all three processes. Batch supercritical water oxidation destroyed both the energetics and organics. Further development is desired to optimize process parameters. Sodium hydroxide base hydrolysis and calcium carbonate cookoff results indicated the potential for scrubbing gaseous detonation products. Further study and testing are needed to quantify the effectiveness of these later two processes for full-scale munition destruction. The preliminary experiments completed in this study have demonstrated the promise of these three processes as environmentally sound technologies for energetic component destruction. Continuation of these experimental programs is strongly recommended to optimize batch supercritical water oxidation processing, and to fully develop the sodium hydroxide base hydrolysis and calcium carbonate cookoff technologies.

  7. Protonation of base pairs in RNA: context analysis and quantum chemical investigations of their geometries and stabilities.

    PubMed

    Chawla, Mohit; Sharma, Purshotam; Halder, Sukanya; Bhattacharyya, Dhananjay; Mitra, Abhijit

    2011-02-17

    Base pairs involving protonated nucleobases play important roles in mediating global macromolecular conformational changes and in facilitation of catalysis in a variety of functional RNA molecules. Here we present our attempts at understanding the role of such base pairs by detecting possible protonated base pairs in the available RNA crystal structures using BPFind software, in their specific structural contexts, and by the characterization of their geometries, interaction energies, and stabilities using advanced quantum chemical computations. We report occurrences of 18 distinct protonated base pair combinations from a representative data set of RNA crystal structures and propose a theoretical model for one putative base pair combination. Optimization of base pair geometries was carried out at the B3LYP/cc-pVTZ level, and the BSSE corrected interaction energies were calculated at the MP2/aug-cc-pVDZ level of theory. The geometries for each of the base pairs were characterized in terms of H-bonding patterns observed, rmsd values observed on optimization, and base pair geometrical parameters. In addition, the intermolecular interaction in these complexes was also analyzed using Morokuma energy decomposition. The gas phase interaction energies of the base pairs range from -24 to -49 kcal/mol and reveal the dominance of Hartree-Fock component of interaction energy constituting 73% to 98% of the total interaction energy values. On the basis of our combined bioinformatics and quantum chemical analysis of different protonated base pairs, we suggest resolution of structural ambiguities and correlate their geometric and energetic features with their structural and functional roles. In addition, we also examine the suitability of specific base pairs as key elements in molecular switches and as nucleators for higher order structures such as base triplets and quartets.

  8. Energetics in robotic flight at small scales.

    PubMed

    Karydis, Konstantinos; Kumar, Vijay

    2017-02-06

    Recent advances in design, sensing and control have led to aerial robots that offer great promise in a range of real-world applications. However, one critical open question centres on how to improve the energetic efficiency of aerial robots so that they can be useful in practical situations. This review paper provides a survey on small-scale aerial robots (i.e. less than 1 m(2) area foot print, and less than 3 kg weight) from the point of view of energetics. The paper discusses methods to improve the efficiency of aerial vehicles, and reports on recent findings by the authors and other groups on modelling the impact of aerodynamics for the purpose of building energy-aware motion planners and controllers.

  9. Energetics of Nanomaterials

    SciTech Connect

    Alexandra Navrotsky; Brian Woodfield; Juliana Boerio-Goates; Frances Hellman

    2005-01-28

    This project, "Energetics of Nanomaterials," represents a three-year collaboration among Alexandra Navrotsky (UC Davis), Brian Woodfield and Juliana Boerio-Goates (BYU), and Frances Hellman (UC Berkeley). It's purpose has been to explore the differences between bulk materials, nanoparticles, and thin films in term of their thermodynamic properties, with an emphasis on heat capaacities and entropies, as well as enthalpies. the three groups have brought very different expertise and capabilities to the project. Navrotsky is a solid-state chemist and geochemist, with a unique Thermochemistry Facility emphasizing enthalpy of formation measurements by high temperature oxide melt and room temperatue acid solution calorimetry. Boerio-Goates and Woodfield are calorimetry. Hellman is a physicist with expertise in magnetism and heat capacity measurements using microscale "detector on a chip" calorimetric technology that she pioneered. The overarching question of our work is "How does the free energy play out in nanoparticles?", or "How do differences in free energy affect overall nanoparticle behavior?" Because the free energy represents the temperature-dependent balance between the enthalpy of a system and its entropy, there are two separate, but related, components to the experimental investigations: Solution calorimetric measurements provide the energetics and two types of heat capacity measurements the entropy. We use materials that are well characterized in other ways (structurally, magnetically, and chemically), and samples are shared across the collaboration.

  10. New energetic epoxy binders

    SciTech Connect

    Jain, S.R.; Amanulla, S.

    1996-07-01

    A new class of epoxy resins having N{single_bond}N bonds in the backbone has been synthesized with a view to explore their properties as energetic binders. The N-epoxidation of bis-dicarbonylhydrazones of adipic, azelaic and sebacic dihydrazides results in the formation of viscous resins having epoxide end groups. The resins have been characterized by the elemental and end group analyses, IR and NMR spectra. Relevant properties for their use as binders in solid propellants, such as thermal stability, heat of combustion, burn rate and performance parameters of AP-based propellant systems, have been evaluated. A significant increase in the burn rate of AP-based propellants noticed, is perhaps related to the exothermicity of the binder decomposition and the reactivity of N{single_bond}N bonds with perchloric acid formed during the combustion of AP.

  11. Energetics of Nanomaterials

    SciTech Connect

    Hellman, Frances

    2004-12-13

    This project, ''Energetics of Nanomaterials'', represents a three-year collaboration among Alexandra Navrotsky (University of California at Davis), Brian Woodfield and Juliana Boerio-Goates (Brigham Young University) and Frances Hellman (University of California at San Diego). Its purpose has been to explore the differences between bulk materials, nanoparticles, and thin films in terms of their thermodynamic properties, with an emphasis on heat capacities and entropies, as well as enthalpies. We used our combined experimental techniques to address the following questions: How does energy and entropy depend on particle size and crystal structure? Do entropic differences have their origins in changes in vibrational densities of states or configurational (including surface configuration) effects? Do material preparation and sample geometry, i.e., nanoparticles versus thin films, change these quantities? How do the thermodynamics of magnetic and structural transitions change in nanoparticles and thin films? Are different crystal structures stabilized for a given composition at the nanoscale, and are the responsible factors energetic, entropic, or both? How do adsorption energies (for water and other gases) depend on particle size and crystal structure in the nanoregime? What are the energetics of formation and strain energies in artificially layered thin films? Do the differing structures of grain boundaries in films and nanocomposites alter the energetics of nanoscale materials? Of the several directions we first proposed, we initially concentrated on a few systems: TiO(sub 2), CoO, and CoO-MgO. In these systems, we were able to clearly identify particle size-dependent effects on energy and vibrational entropy, and to separate out the effect of particle size and water content on the enthalpy of formation of the various TiO(sub 2) polymorphs. With CoO, we were able to directly compare nanoparticle films and bulk materials; this comparison is important because films can

  12. Utilization of FEP energetics

    NASA Technical Reports Server (NTRS)

    Frederking, T. H. K.; Abbassi, P.; Afifi, F.; Khandhar, P. K.; Ono, D. Y.; Chen, W. E. W.

    1987-01-01

    The research and development work on Fountain Effect Pump Systems (FEP systems) has been of interest in the competition between mechanical pumps for He II and FEP units. The latter do not have moving parts. In the course of the work, the energetics have been addressed using one part of a simple four-changes-of-state cycle. One option is the FEP ideal change of state at constant chemical potential (mu). The other option is the two-state sequence mu-P with a d mu=0 state change followed by an isobar. Questions of pump behavior, of flow rate response to temperature difference at the hot end, and related questions of thermodynamic cycle completion and heat transfer have been addressed. Porous media data obtained elucidate differences between vapor-liquid phase separation (VLPS) and Zero Net Mass Transfer (ZNMF).

  13. Compositions of energetic particle populations in interplanetary space

    NASA Technical Reports Server (NTRS)

    Gloeckler, G.

    1979-01-01

    Observations of helium and heavier particles with energies below about 10 to 20 MeV/nucleon are discussed with emphasis on the composition of solar flare particles, corotating energetic particle streams, and the anomalous cosmic ray component. Future advances expected from results obtained from ISEE -3, Voyager, and the international solar polar spacecraft are reviewed.

  14. Pair supersolid with atom-pair hopping on the state-dependent triangular lattice

    NASA Astrophysics Data System (ADS)

    Zhang, Wanzhou; Yin, Ruoxi; Wang, Yancheng

    2013-11-01

    We systematically study an extended Bose-Hubbard model with atom hopping and atom-pair hopping in the presence of a three-body constraint on the triangular lattice. By means of large-scale quantum Monte Carlo simulations, the ground-state phase diagram is studied. We find a first-order transition between the atomic superfluid phase and the pair superfluid phase when the ratio of the atomic hopping and the atom-pair hopping is adapted. The first-order transition remains unchanged under various conditions. We then focus on the interplay among the atom-pair hopping, the on-site repulsion, and the nearest-neighbor repulsion. With on-site repulsion present, we observe first-order transitions between the Mott insulators and pair superfluid driven by the pair hopping. With the nearest-neighbor repulsion turning on, three typical solid phases with 2/3, 1, and 4/3 filling emerge at small atom-pair hopping region. A stable pair supersolid phase is found at small on-site repulsion. This is due to the three-body constraint and the pair hopping, which essentially make the model a quasihardcore boson system. Thus the pair supersolid state emerges basing on the order-by-disorder mechanism, by which hardcore bosons avoid classical frustration on the triangular lattice. Without on-site repulsion, the transitions between the pair supersolid and the atom superfluid or pair superfluid are first order, except for the particle-hole symmetric point. With weak on-site repulsion and atom hopping turning on, the transition between the pair supersolid and pair superfluid phase becomes continuous. The transition between solid and pair supersolid is three-dimensional XY university, with dynamical exponent z=1 and correlation exponent ν=0.67155. The thermal melting of pair supersolid belongs to the two-dimensional Ising university. We check both energetic and mechanical balance of pair supersolid phase. Lowering the three-body constraint, no pair supersolid is found due to the absence of

  15. Electrical initiation of an energetic nanolaminate film

    DOEpatents

    Tringe, Joseph W.; Gash, Alexander E.; Barbee, Jr., Troy W.

    2010-03-30

    A heating apparatus comprising an energetic nanolaminate film that produces heat when initiated, a power source that provides an electric current, and a control that initiates the energetic nanolaminate film by directing the electric current to the energetic nanolaminate film and joule heating the energetic nanolaminate film to an initiation temperature. Also a method of heating comprising providing an energetic nanolaminate film that produces heat when initiated, and initiating the energetic nanolaminate film by directing an electric current to the energetic nanolaminate film and joule heating the energetic nanolaminate film to an initiation temperature.

  16. Stab Sensitivity of Energetic Nanolaminates

    SciTech Connect

    Gash, A; Barbee, T; Cervantes, O

    2006-05-22

    This work details the stab ignition, small-scale safety, and energy release characteristics of bimetallic Al/Ni(V) and Al/Monel energetic nanolaminate freestanding thin films. The influence of the engineered nanostructural features of the energetic multilayers is correlated with both stab initiation and small-scale energetic materials testing results. Structural parameters of the energetic thin films found to be important include the bi-layer period, total thickness of the film, and presence or absence of aluminum coating layers. In general the most sensitive nanolaminates were those that were relatively thick, possessed fine bi-layer periods, and were not coated. Energetic nanolaminates were tested for their stab sensitivity as freestanding continuous parts and as coarse powders. The stab sensitivity of mock M55 detonators loaded with energetic nanolaminate was found to depend strongly upon both the particle size of the material and the configuration of nanolaminate material, in the detonator cup. In these instances stab ignition was observed with input energies as low as 5 mJ for a coarse powder with an average particle dimension of 400 {micro}m. Selected experiments indicate that the reacting nanolaminate can be used to ignite other energetic materials such as sol-gel nanostructured thermite, and conventional thermite that was either coated onto the multilayer substrate or pressed on it. These results demonstrate that energetic nanolaminates can be tuned to have precise and controlled ignition thresholds and can initiate other energetic materials and therefore are viable candidates as lead-free impact initiated igniters or detonators.

  17. ENERGETICS, EPIGENETICS, MITOCHONDRIAL GENETICS

    PubMed Central

    Wallace, Douglas C.; Fan, Weiwei

    2011-01-01

    The epigenome has been hypothesized to provide the interface between the environment and the nuclear DNA (nDNA) genes. Key factors in the environment are the availability of calories and demands on the organism’s energetic capacity. Energy is funneled through glycolysis and mitochondrial oxidative phosphorylation (OXPHOS), the cellular bioenergetic systems. Since there are thousands of bioenergetic genes dispersed across the chromosomes and mitochondrial DNA (mtDNA), both cis and trans regulation of the nDNA genes is required. The bioenergetic systems convert environmental calories into ATP, acetyl-Coenzyme A (acetyl-CoA), S-adenosyl-methionine (SAM), and reduced NAD+. When calories are abundant, ATP and acetyl-CoA phosphorylate and acetylate chromatin, opening the nDNA for transcription and replication. When calories are limiting, chromatin phosphorylation and acetylation are lost and gene expression is suppressed. DNA methylaton via SAM can also be modulated by mitochondrial function. Phosphorylation and acetylation are also pivotal to regulating cellular signal transduction pathways. Therefore, bioenergetics provides the interface between the environment and the epigenome. Consistent with this conclusion, the clinical phenotypes of bioenergetic diseases are strikingly similar to those observed in epigenetic diseases (Angelman, Rett, Fragile X Syndromes, the laminopathies, cancer, etc.), and an increasing number of epigenetic diseases are being associated with mitochondrial dysfunction. This bioenergetic-epigenomic hypothesis has broad implications for the etiology, pathophysiology, and treatment of a wide range of common diseases. PMID:19796712

  18. "Energetics of Nanomaterials"

    SciTech Connect

    Professor Alexandra Navrotsky

    2005-01-31

    This project represents a three-year collaboration among Alexandra Navrotsky, Brian Woodfield, Juliana Bocrio-Goates and Frances Hellman. It's purpose has been to explore the differences between bulk materials, nanoparticles, and thin films in terms of their thermodynamic properties, with an emphasis on heat capacities and entropies, as well as enthalpies. The three groups have brought very different expertise and capabilities to the project. Navrotsky is a solid-state chemist and geochemist, with a unique Thermochemistry Facility emphasizing enthalpy of formation measurements by high temperature oxide melt and room temperature acid solution calorimetry. Bocrio-Goates and Woodfield are physical chemists with unique capabilities in accurate cryogenic heat capacity measurements using adiabatic calorimetry. Hellman is a physicist with expertise in magnetism and heat capacity measurements using microscale ''detector on a chip'' calorimetric technology that she pioneered. The overarching question of the work is ''How does the free energy play out in nanoparticles''? or ''How do differences in free energy affect overall nanoparticle behavior''? Because the free energy represents the temperature-dependent balance between the enthalpy of a system and its entropy, there are two separate, but related, components to the experimental investigations: Solution calorimetric measurements provide the energetics and two types of heat capacity measurements the entropy. They use materials that are well characterized in other ways (structurally, magnetically, and chemically), and samples are shared across the collaboration.

  19. Tutorial on Solar Energetic-Particle Events

    NASA Technical Reports Server (NTRS)

    vonRosenvinge, Tycho T.

    2004-01-01

    Particles from the Sun at energies above approx. 1 MeV/nucleon have been studied in space for over 35 years. There have been major advances in instrumentation for studying elemental and isotopic composition, kinetic energy, charge states, time intensity histories, and anisotropies of energetic particles. There have also been extensive improvements in the observations of solar phenomena, including radio bursts, Coronal Mass Ejections (CMEs), and solar photons from soft X-ray to gamma-ray energies. Despite these advances, there is a lack of agreement as to the acceleration processes responsible for the particles seen in space shortly after the solar event. In particular, the relative importance of solar flares and CME-driven shocks is disputed for events of moderate to larger size. The reasons for this will be reviewed, and the prospects for resolving this issue will be evaluated.

  20. Energetic Constraints on Species Coexistence in Birds

    PubMed Central

    Pigot, Alexander L.

    2016-01-01

    The association between species richness and ecosystem energy availability is one of the major geographic trends in biodiversity. It is often explained in terms of energetic constraints, such that coexistence among competing species is limited in low productivity environments. However, it has proven challenging to reject alternative views, including the null hypothesis that species richness has simply had more time to accumulate in productive regions, and thus the role of energetic constraints in limiting coexistence remains largely unknown. We use the phylogenetic relationships and geographic ranges of sister species (pairs of lineages who are each other’s closest extant relatives) to examine the association between energy availability and coexistence across an entire vertebrate class (Aves). We show that the incidence of coexistence among sister species increases with overall species richness and is elevated in more productive ecosystems, even when accounting for differences in the evolutionary time available for coexistence to occur. Our results indicate that energy availability promotes species coexistence in closely related lineages, providing a key step toward a more mechanistic understanding of the productivity–richness relationship underlying global gradients in biodiversity. PMID:26974194

  1. Energetic Supernovae from the Cosmic Dawn

    NASA Astrophysics Data System (ADS)

    Chen, Ke-Jung

    2013-04-01

    We present the results from our 3D supernova simulations by using CASTRO, a new radiation-hydrodynamics code. The first generation of stars in the universe ended the cosmic dark age by shining the first light. But what was the fate of these stars? Based on the stellar evolution models, the fate of stars depends on their masses. Modern cosmological simulations suggest that the first stars could be very massive, with a typical mass scale over 50 solar masses. We look for the possible supernovae from the death of the first stars with masses over 50 solar masses. Besides the iron-core collapse supernovae, we find energetic thermonuclear supernovae, including two types of pair-instability supernovae and one type of general-relativity instability supernovae. Our models capture all explosive burning and follow the explosion until the shock breaks out from the stellar surface. We will discuss the energetics, nucleosynthesis, and possible observational signatures for these primordial supernovae that will be the prime targets for future large telescopes such as the James Webb Space Telescope (JWST).

  2. Method for forming energetic nanopowders

    DOEpatents

    Lee, Kien-Yin; Asay, Blaine W.; Kennedy, James E.

    2013-10-15

    A method for the preparation of neat energetic powders, having nanometer dimensions, is described herein. For these neat powder, a solution of a chosen energetic material is prepared in an aprotic solvent and later combined with liquid hexane that is miscible with such solvent. The energetic material chosen is less soluble in the liquid hexane than in the aprotic solvent and the liquid hexane is cooled to a temperature that is below that of the solvent solution. In order to form a precipitate of said neat powders, the solvent solution is rapidly combined with the liquid hexane. When the resulting precipitate is collected, it may be dried and filtered to yield an energetic nanopowder material.

  3. Voyager 2 Observes Energetic Electrons

    NASA Video Gallery

    This animation shows the Voyager 2 observations of energetic electrons. Voyager 2 detected a dramatic drop of the flux of electrons as it left the sector region. The intense flux came back as soon ...

  4. Photodecomposition of energetic nitro compounds

    SciTech Connect

    Mialocq, J.C.

    1989-03-14

    The photodecomposition of energetic nitrocompounds depends on the excitation energy, the light intensity which determines the mono-, bi- or multiphotonic character of the initial process and their gaseous, liquid or solid state. The initial processes of the photodecomposition of nitromethane and nitroalcanes are reviewed and their relevance to the initiation of energetic nitrocompounds detonation is discussed. The case of nitramines (dimethylnitramine and tutorial) is also briefly introduced.

  5. Design of Energetic Ionic Liquids

    DTIC Science & Technology

    2009-05-12

    effectiveness of the FMO method in both providing accurate results and reducing computational requirements, timings were performed for the ionic liquid ...Technical Paper 3. DATES COVERED (From - To) 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER Design of Energetic Ionic Liquids 5b. GRANT NUMBER 5c...Design of Energetic Ionic Liquids challenge project is to address several key technical issues and challenges associated with the characterization

  6. Solar Energetic Particle Variations

    NASA Technical Reports Server (NTRS)

    Reames, D. V.

    2003-01-01

    In the largest solar energetic-particle (SEP) events, acceleration occurs at shock waves driven out from the Sun by coronal mass ejections (CMEs). In fact, the highest proton intensities directly measured near Earth at energies up to approximately 1 GeV occur at the time of passage of shocks, which arrive about a day after the CMEs leave the Sun. CME-driven shocks expanding across magnetic fields can fill over half of the heliosphere with SEPs. Proton-generated Alfven waves trap particles near the shock for efficient acceleration but also throttle the intensities at Earth to the streaming limit early in the events. At high energies, particles begin to leak from the shock and the spectrum rolls downward to form an energy-spectral 'knee' that can vary in energy from approximately 1 MeV to approximately 1 GeV in different events. All of these factors affect the radiation dose as a function of depth and latitude in the Earth's atmosphere and the risk to astronauts and equipment in space. SEP ionization of the polar atmosphere produces nitrates that precipitate to become trapped in the polar ice. Observations of nitrate deposits in ice cores reveal individual large SEP events and extend back approximately 400 years. Unlike sunspots, SEP events follow the approximately 80-100-year Gleissberg cycle rather faithfully and are now at a minimum in that cycle. The largest SEP event in the last 400 years appears to be related to the flare observed by Carrington in 1859, but the probability of SEP events with such large fluences falls off sharply because of the streaming limit.

  7. Kinetic Simulation and Energetic Neutral Atom Imaging of the Magnetosphere

    NASA Technical Reports Server (NTRS)

    Fok, Mei-Ching H.

    2011-01-01

    Advanced simulation tools and measurement techniques have been developed to study the dynamic magnetosphere and its response to drivers in the solar wind. The Comprehensive Ring Current Model (CRCM) is a kinetic code that solves the 3D distribution in space, energy and pitch-angle information of energetic ions and electrons. Energetic Neutral Atom (ENA) imagers have been carried in past and current satellite missions. Global morphology of energetic ions were revealed by the observed ENA images. We have combined simulation and ENA analysis techniques to study the development of ring current ions during magnetic storms and substorms. We identify the timing and location of particle injection and loss. We examine the evolution of ion energy and pitch-angle distribution during different phases of a storm. In this talk we will discuss the findings from our ring current studies and how our simulation and ENA analysis tools can be applied to the upcoming TRIO-CINAMA mission.

  8. Ion pair receptors†

    PubMed Central

    Kim, Sung Kuk

    2010-01-01

    Compared with simple ion receptors, which are able to bind either a cation or an anion, ion pair receptors bearing both a cation and an anion recognition site offer the promise of binding ion pairs or pairs of ions strongly as the result of direct or indirect cooperative interactions between co-bound ions. This critical review focuses on the recent progress in the design of ion pair receptors and summarizes the various binding modes that have been used to accommodate ion pairs (110 references). PMID:20737073

  9. Highly energetic compositions based on functionalized carbon nanomaterials.

    PubMed

    Yan, Qi-Long; Gozin, Michael; Zhao, Feng-Qi; Cohen, Adva; Pang, Si-Ping

    2016-03-07

    In recent years, research in the field of carbon nanomaterials (CNMs), such as fullerenes, expanded graphite (EG), carbon nanotubes (CNTs), graphene, and graphene oxide (GO), has been widely used in energy storage, electronics, catalysts, and biomaterials, as well as medical applications. Regarding energy storage, one of the most important research directions is the development of CNMs as carriers of energetic components by coating or encapsulation, thus forming safer advanced nanostructures with better performances. Moreover, some CNMs can also be functionalized to become energetic additives. This review article covers updated preparation methods for the aforementioned CNMs, with a more specific orientation towards the use of these nanomaterials in energetic compositions. The effects of these functionalized CNMs on thermal decomposition, ignition, combustion and the reactivity properties of energetic compositions are significant and are discussed in detail. It has been shown that the use of functionalized CNMs in energetic compositions greatly improves their combustion performances, thermal stability and sensitivity. In particular, functionalized fullerenes, CNTs and GO are the most appropriate candidate components in nanothermites, solid propellants and gas generators, due to their superior catalytic properties as well as facile preparation methods.

  10. Highly energetic compositions based on functionalized carbon nanomaterials

    NASA Astrophysics Data System (ADS)

    Yan, Qi-Long; Gozin, Michael; Zhao, Feng-Qi; Cohen, Adva; Pang, Si-Ping

    2016-02-01

    In recent years, research in the field of carbon nanomaterials (CNMs), such as fullerenes, expanded graphite (EG), carbon nanotubes (CNTs), graphene, and graphene oxide (GO), has been widely used in energy storage, electronics, catalysts, and biomaterials, as well as medical applications. Regarding energy storage, one of the most important research directions is the development of CNMs as carriers of energetic components by coating or encapsulation, thus forming safer advanced nanostructures with better performances. Moreover, some CNMs can also be functionalized to become energetic additives. This review article covers updated preparation methods for the aforementioned CNMs, with a more specific orientation towards the use of these nanomaterials in energetic compositions. The effects of these functionalized CNMs on thermal decomposition, ignition, combustion and the reactivity properties of energetic compositions are significant and are discussed in detail. It has been shown that the use of functionalized CNMs in energetic compositions greatly improves their combustion performances, thermal stability and sensitivity. In particular, functionalized fullerenes, CNTs and GO are the most appropriate candidate components in nanothermites, solid propellants and gas generators, due to their superior catalytic properties as well as facile preparation methods.

  11. Solar flares and energetic particles.

    PubMed

    Vilmer, Nicole

    2012-07-13

    Solar flares are now observed at all wavelengths from γ-rays to decametre radio waves. They are commonly associated with efficient production of energetic particles at all energies. These particles play a major role in the active Sun because they contain a large amount of the energy released during flares. Energetic electrons and ions interact with the solar atmosphere and produce high-energy X-rays and γ-rays. Energetic particles can also escape to the corona and interplanetary medium, produce radio emissions (electrons) and may eventually reach the Earth's orbit. I shall review here the available information on energetic particles provided by X-ray/γ-ray observations, with particular emphasis on the results obtained recently by the mission Reuven Ramaty High-Energy Solar Spectroscopic Imager. I shall also illustrate how radio observations contribute to our understanding of the electron acceleration sites and to our knowledge on the origin and propagation of energetic particles in the interplanetary medium. I shall finally briefly review some recent progress in the theories of particle acceleration in solar flares and comment on the still challenging issue of connecting particle acceleration processes to the topology of the complex magnetic structures present in the corona.

  12. Matched-pair classification

    SciTech Connect

    Theiler, James P

    2009-01-01

    Following an analogous distinction in statistical hypothesis testing, we investigate variants of machine learning where the training set comes in matched pairs. We demonstrate that even conventional classifiers can exhibit improved performance when the input data has a matched-pair structure. Online algorithms, in particular, converge quicker when the data is presented in pairs. In some scenarios (such as the weak signal detection problem), matched pairs can be generated from independent samples, with the effect not only doubling the nominal size of the training set, but of providing the structure that leads to better learning. A family of 'dipole' algorithms is introduced that explicitly takes advantage of matched-pair structure in the input data and leads to further performance gains. Finally, we illustrate the application of matched-pair learning to chemical plume detection in hyperspectral imagery.

  13. Vortex pairs on surfaces

    SciTech Connect

    Koiller, Jair

    2009-05-06

    A pair of infinitesimally close opposite vortices moving on a curved surface moves along a geodesic, according to a conjecture by Kimura. We outline a proof. Numerical simulations are presented for a pair of opposite vortices at a close but nonzero distance on a surface of revolution, the catenoid. We conjecture that the vortex pair system on a triaxial ellipsoid is a KAM perturbation of Jacobi's geodesic problem. We outline some preliminary calculations required for this study. Finding the surfaces for which the vortex pair system is integrable is in order.

  14. Energetic dose: Beyond fire and flint?

    USGS Publications Warehouse

    Linder, G.; Rattner, B.; Cohen, J.

    2000-01-01

    Nutritional and bioenergetic interactions influence exposure to environmental chemicals and may affect the risk realized when wildlife are exposed in the field. Here, food-chain analysis focuses on prairie voles (Microtus ochrogaster) and the evaluation of chemical risks associated with paraquat following 10-d dietary exposures. Reproductive effects were measured in 60-d trials that followed exposures to paraquat-tainted feed: control (untainted feed); 21 mg paraquat/kg feed; 63 mg paraquat/kg feed; and feed-restricted control (untainted feed restricted to 60% baseline consumption). Reproductive success was evaluated in control and treated breeding pairs, and a preliminary bioenergetics analysis was completed in parallel to derive exposure dose. Although reproductive performance differed among groups, feed-restriction appeared to be the dominant treatment effect observed in these 10-d feeding exposure/limited reproductive trials. Exposure dose ranged from 3.70-3.76 to 9.41-11.51 mg parquat/kg BW/day at 21 and 63 mg paraquat/kg feed stock exposures, respectively. Energetic doses as ug paraquat/kcal yielded preliminary estimates of energetic costs associated with paraquat exposure, and were similar within treatments for both sexes, ranging from 4.2-5.5 and 13.1-15.0 ug paraquat/kcal for voles exposed to 21 mg/kg feed stock and 63 mg/kg feed stock, respectively. Given the increasing likelihood that environmental chemicals will be found in wildlife habitat at 'acceptable levels', the critical role that wildlife nutrition plays in evaluating ecological risks should be fully integrated into the assessment process. Tools applied to the analysis of risk must gain higher resolution than the relatively crude methods we currently bring to the process.

  15. Heliospheric Observations of Energetic Particles

    NASA Technical Reports Server (NTRS)

    Summerlin, Errol J.

    2011-01-01

    Heliospheric observations of energetic particles have shown that, on long time averages, a consistent v^-5 power-law index arises even in the absence of transient events. This implies an ubiquitous acceleration process present in the solar wind that is required to generate these power-law tails and maintain them against adiabatic losses and coulomb-collisions which will cool and thermalize the plasma respectively. Though the details of this acceleration process are being debated within the community, most agree that the energy required for these tails comes from fluctuations in the magnetic field which are damped as the energy is transferred to particles. Given this source for the tail, is it then reasonable to assume that the turbulent LISM should give rise to such a power-law tail as well? IBEX observations clearly show a power-law tail of index approximately -5 in energetic neutral atoms. The simplest explanation for the origins of these ENAs are that they are energetic ions which have charge-exchanged with a neutral atom. However, this would imply that energetic ions possess a v^-5 power-law distribution at keV energies at the source of these ENAs. If the source is presumed to be the LISM, it provides additional options for explaining the, so called, IBEX ribbon. This presentation will discuss some of these options as well as potential mechanisms for the generation of a power-law spectrum in the LISM.

  16. Jet propagation through energetic materials

    SciTech Connect

    Pincosy, P; Poulsen, P

    2004-01-08

    In applications where jets propagate through energetic materials, they have been observed to become sufficiently perturbed to reduce their ability to effectively penetrate subsequent material. Analytical calculations of the jet Bernoulli flow provides an estimate of the onset and extent of such perturbations. Although two-dimensional calculations show the back-flow interaction pressure pulses, the symmetry dictates that the flow remains axial. In three dimensions the same pressure impulses can be asymmetrical if the jet is asymmetrical. The 3D calculations thus show parts of the jet having a significant component of radial velocity. On the average the downstream effects of this radial flow can be estimated and calculated by a 2D code by applying a symmetrical radial component to the jet at the appropriate position as the jet propagates through the energetic material. We have calculated the 3D propagation of a radio graphed TOW2 jet with measured variations in straightness and diameter. The resultant three-dimensional perturbations on the jet result in radial flow, which eventually tears apart the coherent jet flow. This calculated jet is compared with jet radiographs after passage through the energetic material for various material thickness and plate thicknesses. We noted that confinement due to a bounding metal plate on the energetic material extends the pressure duration and extent of the perturbation.

  17. Progress Towards a Laser Produced Relativistic Electron-Positron Pair Plasma

    NASA Astrophysics Data System (ADS)

    Chen, Hui; Bonlie, J.; Cauble, R.; Fiuza, F.; Goldstein, W.; Hazi, A.; Keane, C.; Link, A.; Marley, E.; Nagel, S. R.; Park, J.; Shepherd, R.; Williams, G. J.; Meyerhofer, D. D.; Fiksel, G.; Barnak, D.; Chang, P. Y.; Nakai, M.; Arikawa, Y.; Azechi, H.; Fujioka, S.; Kojima, S.; Miyanaga, N.; Morita, T.; Nagai, T.; Nishimura, H.; Ozaki, T.; Sakawa, Y.; Takabe, H.; Zhang, Z.; Kerr, S.; Fedosejevs, R.; Sentoku, Y.; Hill, M. P.; Hoarty, D. J.; Hobbs, L. M. R.; James, S. F.

    2016-03-01

    A set of experiments has been performed exploring unique characteristics of pair jets and plasmas at several energetic short-pulse laser facilities including Titan at Livermore and OMEGA EP in Rochester, as well as the Osaka LFEX and AWE Orion lasers. New results are summarized, including positron beam emittance, scaling of pair production vs. laser energy, and initial results on the pair jet collimation using electromagnetic fields.

  18. Progress towards a laser produced relativistic electron-positron pair plasma

    SciTech Connect

    Chen, Hui; Bonlie, J.; Cauble, R.; Fiuza, F.; Goldstein, W.; Hazi, A.; Keane, C.; Link, A.; Marley, E.; Nagel, S. R.; Park, J.; Shepherd, R.; Williams, G. J.; Meyerhofer, D. D.; Fiksel, G.; Barnak, D.; Chang, P. Y.; Nakai, M.; Arikawa, Y.; Azechi, H.; Fujioka, S.; Kojima, S.; Miyanaga, N.; Morita, T.; Nagai, T.; Nishimura, H.; Ozaki, T.; Sakawa, Y.; Takabe, H.; Zhang, Z.; Kerr, S.; Fedosejevs, R.; Sentoku, Y.; Hill, M. P.; Hoarty, D. J.; Hobbs, L. M. R.; James, S. F.

    2016-03-01

    Here, a set of experiments has been performed exploring unique characteristics of pair jets and plasmas at several energetic short-pulse laser facilities including Titan at Livermore and OMEGA EP in Rochester, as well as the Osaka LFEX and AWE Orion lasers. New results are summarized, including positron beam emittance, scaling of pair production vs. laser energy, and initial results on the pair jet collimation using electromagnetic fields.

  19. Progress towards a laser produced relativistic electron-positron pair plasma

    DOE PAGES

    Chen, Hui; Bonlie, J.; Cauble, R.; ...

    2016-04-01

    Here, a set of experiments has been performed exploring unique characteristics of pair jets and plasmas at several energetic short-pulse laser facilities including Titan at Livermore and OMEGA EP in Rochester, as well as the Osaka LFEX and AWE Orion lasers. New results are summarized, including positron beam emittance, scaling of pair production vs. laser energy, and initial results on the pair jet collimation using electromagnetic fields.

  20. Cooper pairs and bipolarons

    NASA Astrophysics Data System (ADS)

    Lakhno, Victor

    2016-11-01

    It is shown that Cooper pairs are a solution of the bipolaron problem for model Fröhlich Hamiltonian. The total energy of a pair for the initial Fröhlich Hamiltonian is found. Differences between the solutions for the model and initial two-particle problems are discussed.

  1. Cooper Pairs in Insulators?!

    ScienceCinema

    James Valles

    2016-07-12

    Nearly 50 years elapsed between the discovery of superconductivity and the emergence of the microscopic theory describing this zero resistance state. The explanation required a novel phase of matter in which conduction electrons joined in weakly bound pairs and condensed with other pairs into a single quantum state. Surprisingly, this Cooper pair formation has also been invoked to account for recently uncovered high-resistance or insulating phases of matter. To address this possibility, we have used nanotechnology to create an insulating system that we can probe directly for Cooper pairs. I will present the evidence that Cooper pairs exist and dominate the electrical transport in these insulators and I will discuss how these findings provide new insight into superconductor to insulator quantum phase transitions. 

  2. SIMULATION OF ENERGETIC NEUTRAL ATOMS FROM SOLAR ENERGETIC PARTICLES

    SciTech Connect

    Wang, Linghua; Li, Gang; Shih, Albert Y.; Lin, Robert P.; Wimmer-Schweingruber, Robert F.

    2014-10-01

    Energetic neutral atoms (ENAs) provide the only way to observe the acceleration site of coronal-mass-ejection-driven (CME-driven) shock-accelerated solar energetic particles (SEPs). In gradual SEP events, energetic protons can charge exchange with the ambient solar wind or interstellar neutrals to become ENAs. Assuming a CME-driven shock with a constant speed of 1800 km s{sup –1} and compression ratio of 3.5, propagating from 1.5 to 40 R{sub S} , we calculate the accelerated SEPs at 5-5000 keV and the resulting ENAs via various charge-exchange interactions. Taking into account the ENA losses in the interplanetary medium, we obtain the flux-time profiles of these solar ENAs reaching 1 AU. We find that the arriving ENAs at energies above ∼100 keV show a sharply peaked flux-time profile, mainly originating from the shock source below 5 R{sub S} , whereas the ENAs below ∼20 keV have a flat-top time profile, mostly originating from the source beyond 10 R{sub S} . Assuming the accelerated protons are effectively trapped downstream of the shock, we can reproduce the STEREO ENA fluence observations at ∼2-5 MeV/nucleon. We also estimate the flux of ENAs coming from the charge exchange of energetic storm protons, accelerated by the fast CME-driven shock near 1 AU, with interstellar hydrogen and helium. Our results suggest that appropriate instrumentation would be able to detect ENAs from SEPs and to even make ENA images of SEPs at energies above ∼10-20 keV.

  3. Energetic costs of cellular computation.

    PubMed

    Mehta, Pankaj; Schwab, David J

    2012-10-30

    Cells often perform computations in order to respond to environmental cues. A simple example is the classic problem, first considered by Berg and Purcell, of determining the concentration of a chemical ligand in the surrounding media. On general theoretical grounds, it is expected that such computations require cells to consume energy. In particular, Landauer's principle states that energy must be consumed in order to erase the memory of past observations. Here, we explicitly calculate the energetic cost of steady-state computation of ligand concentration for a simple two-component cellular network that implements a noisy version of the Berg-Purcell strategy. We show that learning about external concentrations necessitates the breaking of detailed balance and consumption of energy, with greater learning requiring more energy. Our calculations suggest that the energetic costs of cellular computation may be an important constraint on networks designed to function in resource poor environments, such as the spore germination networks of bacteria.

  4. Energetic costs of cellular computation

    PubMed Central

    Mehta, Pankaj; Schwab, David J.

    2012-01-01

    Cells often perform computations in order to respond to environmental cues. A simple example is the classic problem, first considered by Berg and Purcell, of determining the concentration of a chemical ligand in the surrounding media. On general theoretical grounds, it is expected that such computations require cells to consume energy. In particular, Landauer’s principle states that energy must be consumed in order to erase the memory of past observations. Here, we explicitly calculate the energetic cost of steady-state computation of ligand concentration for a simple two-component cellular network that implements a noisy version of the Berg–Purcell strategy. We show that learning about external concentrations necessitates the breaking of detailed balance and consumption of energy, with greater learning requiring more energy. Our calculations suggest that the energetic costs of cellular computation may be an important constraint on networks designed to function in resource poor environments, such as the spore germination networks of bacteria. PMID:23045633

  5. Combined effects of space charge and energetic disorder on photocurrent efficiency loss of field-dependent organic photovoltaic devices

    NASA Astrophysics Data System (ADS)

    Yoon, Sangcheol; Park, Byoungchoo; Hwang, Inchan

    2015-11-01

    The loss of photocurrent efficiency by space-charge effects in organic solar cells with energetic disorder was investigated to account for how energetic disorder incorporates space-charge effects, utilizing a drift-diffusion model with field-dependent charge-pair dissociation and suppressed bimolecular recombination. Energetic disorder, which induces the Poole-Frenkel behavior of charge carrier mobility, is known to decrease the mobility of charge carriers and thus reduces photovoltaic performance. We found that even if the mobilities are the same in the absence of space-charge effects, the degree of energetic disorder can be an additional parameter affecting photocurrent efficiency when space-charge effects occur. Introducing the field-dependence parameter that reflects the energetic disorder, the behavior of efficiency loss with energetic disorder can differ depending on which charge carrier is subject to energetic disorder. While the energetic disorder that is applied to higher-mobility charge carriers decreases photocurrent efficiency further, the efficiency loss can be suppressed when energetic disorder is applied to lower-mobility charge carriers.

  6. Cardiac energetics: sense and nonsense.

    PubMed

    Gibbs, Colin L

    2003-08-01

    1. The background to current ideas in cardiac energetics is outlined and, in the genomic era, the need is stressed for detailed knowledge of mouse heart mechanics and energetics. 2. The mouse heart is clearly different to the rat in terms of its excitation-contraction (EC) coupling and the common assumption that heart rate difference between mice and humans will account for the eightfold difference in myocardial oxygen consumption is wrong, because the energy per beat of the mouse heart is approximately one-third that of the human heart. 3. In vivo evidence suggests that there may well be an eightfold species difference in the non-beating metabolism of mice and human hearts. It is speculated that the magnitude of basal metabolism in the heart is regulatable and that, in the absence of perfusion, it falls to approximately one-quarter of its in vivo rate and that in clinical conditions, such as hibernation, it probably decreases; its magnitude may be controlled by the endothelium. 4. The active energy balance sheet is briefly discussed and it is suggested that the activation heat accounts for 20-25% of the active energy per beat and cross-bridge turnover accounts for the balance. It is argued that force, not shortening, is the major determinant of cardiac energy usage. 5. The outcome of recent cardiac modelling with variants of the Huxley and Hill/Eisenberg models is described. It has been necessary to invoke 'loose coupling' to replicate the low cardiac energy flux measured at low afterloads (medium to high velocities of shortening). 6. Lastly, some of the unexplained or 'nonsense' energetic data are outlined and eight unsolved problems in cardiac energetics are discussed.

  7. Process for preparing energetic materials

    DOEpatents

    Simpson, Randall L [Livermore, CA; Lee, Ronald S [Livermore, CA; Tillotson, Thomas M [Tracy, CA; Hrubesh, Lawrence W [Pleasanton, CA; Swansiger, Rosalind W [Livermore, CA; Fox, Glenn A [Livermore, CA

    2011-12-13

    Sol-gel chemistry is used for the preparation of energetic materials (explosives, propellants and pyrotechnics) with improved homogeneity, and/or which can be cast to near-net shape, and/or made into precision molding powders. The sol-gel method is a synthetic chemical process where reactive monomers are mixed into a solution, polymerization occurs leading to a highly cross-linked three dimensional solid network resulting in a gel. The energetic materials can be incorporated during the formation of the solution or during the gel stage of the process. The composition, pore, and primary particle sizes, gel time, surface areas, and density may be tailored and controlled by the solution chemistry. The gel is then dried using supercritical extraction to produce a highly porous low density aerogel or by controlled slow evaporation to produce a xerogel. Applying stress during the extraction phase can result in high density materials. Thus, the sol-gel method can be used for precision detonator explosive manufacturing as well as producing precision explosives, propellants, and pyrotechnics, along with high power composite energetic materials.

  8. Energetic Neutral Atom Precipitation (ENAP)

    NASA Technical Reports Server (NTRS)

    Tinsley, B. A.

    1988-01-01

    The Energetic Neutral Atom Precipitation experiment is scheduled to be flown on the Atmospheric Laboratory for Applications and Science (ATLAS 1) NASA mission. The objective of this experiment is to measure very faint emissions at nighttime arising from fluxes of energetic neutral atoms in the thermosphere. These energetic atoms have energies ranging up to about 50 keV, and arise from ions of hydrogen, helium, and oxygen trapped in the inner magnetosphere. Some of these ions become neutralized in charge exchange reactions with neutral hydrogen in the hydrogen geocorona that extends through the region. The ions are trapped on magnetic field lines which cross the equatorial plane at 2 to 6 earth radii distance, and they mirror at a range of heights on these field lines, extending down to the thermosphere at 500 km altitude. The ATLAS 1 measurements will not be of the neutral atoms themselves but of the optical emission produced by those on trajectories that intersect the thermosphere. The ENAP measurements are to be made using the Imaging Spectrometric Observatory (ISO) which is being flown on the ATLAS mission primarily for daytime spectral observations, and the ENAP measurements will all be nighttime measurements because of the faintness of the emissions and the relatively low level of magnetic activity expected.

  9. Energetic ions in ITER plasmas

    SciTech Connect

    Pinches, S. D.; Chapman, I. T.; Sharapov, S. E.; Lauber, Ph. W.; Oliver, H. J. C.; Shinohara, K.; Tani, K.

    2015-02-15

    This paper discusses the behaviour and consequences of the expected populations of energetic ions in ITER plasmas. It begins with a careful analytic and numerical consideration of the stability of Alfvén Eigenmodes in the ITER 15 MA baseline scenario. The stability threshold is determined by balancing the energetic ion drive against the dominant damping mechanisms and it is found that only in the outer half of the plasma (r/a>0.5) can the fast ions overcome the thermal ion Landau damping. This is in spite of the reduced numbers of alpha-particles and beam ions in this region but means that any Alfvén Eigenmode-induced redistribution is not expected to influence the fusion burn process. The influence of energetic ions upon the main global MHD phenomena expected in ITER's primary operating scenarios, including sawteeth, neoclassical tearing modes and Resistive Wall Modes, is also reviewed. Fast ion losses due to the non-axisymmetric fields arising from the finite number of toroidal field coils, the inclusion of ferromagnetic inserts, the presence of test blanket modules containing ferromagnetic material, and the fields created by the Edge Localised Mode (ELM) control coils in ITER are discussed. The greatest losses and associated heat loads onto the plasma facing components arise due to the use of the ELM control coils and come from neutral beam ions that are ionised in the plasma edge.

  10. Energetic Charged Particles Above Thunderclouds

    NASA Astrophysics Data System (ADS)

    Füllekrug, Martin; Diver, Declan; Pinçon, Jean-Louis; Phelps, Alan D. R.; Bourdon, Anne; Helling, Christiane; Blanc, Elisabeth; Honary, Farideh; Harrison, R. Giles; Sauvaud, Jean-André; Renard, Jean-Baptiste; Lester, Mark; Rycroft, Michael; Kosch, Mike; Horne, Richard B.; Soula, Serge; Gaffet, Stéphane

    2013-01-01

    The French government has committed to launch the satellite TARANIS to study transient coupling processes between the Earth's atmosphere and near-Earth space. The prime objective of TARANIS is to detect energetic charged particles and hard radiation emanating from thunderclouds. The British Nobel prize winner C.T.R. Wilson predicted lightning discharges from the top of thunderclouds into space almost a century ago. However, new experiments have only recently confirmed energetic discharge processes which transfer energy from the top of thunderclouds into the upper atmosphere and near-Earth space; they are now denoted as transient luminous events, terrestrial gamma-ray flashes and relativistic electron beams. This meeting report builds on the current state of scientific knowledge on the physics of plasmas in the laboratory and naturally occurring plasmas in the Earth's atmosphere to propose areas of future research. The report specifically reflects presentations delivered by the members of a novel Franco-British collaboration during a meeting at the French Embassy in London held in November 2011. The scientific subjects of the report tackle ionization processes leading to electrical discharge processes, observations of transient luminous events, electromagnetic emissions, energetic charged particles and their impact on the Earth's atmosphere. The importance of future research in this area for science and society, and towards spacecraft protection, is emphasized.

  11. Orbital-selective pairing: a τ3 B1g pairing candidate state for the alkaline iron selenides

    NASA Astrophysics Data System (ADS)

    Yu, Rong; Nica, Emilian M.; Si, Qimiao

    The iron-based unconventional superconductors are inherently multi-orbital systems and show remarkable variation in the Fermi-surfaces and pairing symmetries. In the alkaline iron selenides cases, ARPES experiments indicate fully gapped superconducting states, which suggests s-wave pairing, while neutron-scattering studies show resonances in the spin-spectrum with wave vectors across the electron Fermi pockets, suggesting d-wave pairing. We propose a novel superconducting state composed of a direct product of an s-wave form factor and a rotational symmetry-breaking orbital matrix in the dxz / yz sectors. It belongs to the B1 g representation of the D4h point group, allowing for the overall change in sign between the pairing field at the electron pockets close to the 1-Fe BZ edge. While it supports a spin resonance, it also produces a fully gapped quasiparticle spectrum, making it a candidate pairing state for the alkaline iron selenide compounds. Our results also show how such a state can become energetically competitive in the regime of quasi-degeneracy between the s and d-wave pairing states. In a broader context, this pairing provides an alternative to the s + idto reconstruct the degenerate pairing states, while preserving the time-reversal symmetry. We discuss possible analogs in other multi-band strong-coupling superconductors such as the heavy fermions. ''Emergent superconducting state from quasi-degenerate s - and d -wave pairing channels in iron-based superconductors,''.

  12. Paired Straight Hearth Furnace

    SciTech Connect

    2009-04-01

    This factsheet describes a research project whose goals are to design, develop, and evaluate the scalability and commercial feasibility of the PSH Paired Straight Hearth Furnace alternative ironmaking process.

  13. Virtual Energetic Particle Observatory (VEPO)

    NASA Technical Reports Server (NTRS)

    Cooper, John F.; Lal, Nand; McGuire, Robert E.; Szabo, Adam; Narock, Thomas W.; Armstrong, Thomas P.; Manweiler, Jerry W.; Patterson, J. Douglas; Hill, Matthew E.; Vandergriff, Jon D.; McKibben, Robert B.; Lopate, Clifford; Tranquille, Cecil

    2008-01-01

    The Virtual Energetic Particle Observatory (VEPO) focuses on improved discovery, access, and usability of heliospheric energetic particle and ancillary data products from selected spacecraft and sub-orbital instruments of the heliophysics data environment. The energy range of interest extends over the full range of particle acceleration from keV energies of suprathermal seed particles to GeV energies of galactic cosmic ray particles. Present spatial coverage is for operational and legacy spacecraft operating from the inner to the outer heliosphere, e.g. from measurements by the two Helios spacecraft to 0.3 AU to the inner heliosheath region now being traversed by the two Voyager spacecraft. This coverage will eventually be extended inward to ten solar radii by the planned NASA solar probe mission and at the same time beyond the heliopause into the outer heliosheath by continued Voyager operations. The geospace fleet of spacecraft providing near-Earth interplanetary measurements, selected magnetospheric spacecraft providing direct measurements of penetrating interplanetary energetic particles, and interplanetary cruise measurements from planetary spacecraft missions further extend VEPO resources to the domain of geospace and planetary interactions. Ground-based (e.g., neutron monitor) and high-altitude suborbital measurements can expand coverage to the highest energies of galactic cosmic rays affected by heliospheric interaction and of solar energetic particles. Science applications include investigation of solar flare and coronal mass ejection events. acceleration and transport of interplanetary particles within the inner heliosphere, cosmic ray interactions with planetary surfaces and atmospheres, sources of suprathermal and anomalous cosmic ray ions in the outer heliosphere, and solar cycle modulation of galactic cosmic rays. Robotic and human exploration, and eventual habitation, of planetary and space environments beyond the Earth require knowledge of radiation

  14. Physicochemical Properties of Ion Pairs of Biological Macromolecules

    PubMed Central

    Iwahara, Junji; Esadze, Alexandre; Zandarashvili, Levani

    2015-01-01

    Ion pairs (also known as salt bridges) of electrostatically interacting cationic and anionic moieties are important for proteins and nucleic acids to perform their function. Although numerous three-dimensional structures show ion pairs at functionally important sites of biological macromolecules and their complexes, the physicochemical properties of the ion pairs are not well understood. Crystal structures typically show a single state for each ion pair. However, recent studies have revealed the dynamic nature of the ion pairs of the biological macromolecules. Biomolecular ion pairs undergo dynamic transitions between distinct states in which the charged moieties are either in direct contact or separated by water. This dynamic behavior is reasonable in light of the fundamental concepts that were established for small ions over the last century. In this review, we introduce the physicochemical concepts relevant to the ion pairs and provide an overview of the recent advancement in biophysical research on the ion pairs of biological macromolecules. PMID:26437440

  15. [Under what conditions does G.C Watson-Crick DNA base pair acquire all four configurations characteristic for A.T Watson-Crick DNA base pair?].

    PubMed

    Brovarets', O O

    2013-01-01

    At the MP2/6-311++G(2df,pd)//B3LYP/6-311++G(d,p) level of theory it was established for the first time, that the Löwdin's G*.C* DNA base pair formed by the mutagenic tautomers can acquire, as the A-T Watson-Crick DNA base pair, four biologically important configurations, namely: Watson-Crick, reverse Watson-Crick, Hoogsteen and reverse Hoogsteen. This fact demonstrates rather unexpected role of the tautomerisation of the one of the Watson-Crick DNA base pairs, in particular, via double proton transfer: exactly the G.C-->G*.C* tautomerisation allows to overcome steric hindrances for the implementation of the above mentioned configurations. Geometric, electron-topological and energetic properties of the H-bonds that stabilise the studied pairs, as well as the energetic characteristics of the latters are presented.

  16. Diagnostics for the Analysis of Surface Chemistry Effects on Composite Energetic Material Reactions

    DTIC Science & Technology

    2015-10-30

    heat flow and phase change allowing chemical kinetic modeling of surface chemistry using an advanced DSC – TGA via simultaneous thermal analysis (STA...allowing chemical kinetic modeling of surface chemistry using an advanced DSC – TGA via simultaneous thermal analysis (STA). This diagnostic couples...2.00 4.00 Evan Vargas, Michelle L. Pantoya, Mohammed A Saed, Brandon L Weeks. Advanced Susceptors for Microwave Heating of Energetic Materials

  17. Connecting Shock Parameters to the Radiation Hazard from Energetic Particles

    NASA Technical Reports Server (NTRS)

    Berdichevsky, Daniel B.; Reames, Donald V.; Lepping, Ronald P.; Schwenn, Rainer W.

    2004-01-01

    We use data from Helios, IMP-8, and other spacecraft (e.g. ISEE) to systematically investigate solar energetic particle (SEP) events from different longitudes and distances in the heliosphere. The purpose of the project is to assess empirically the connection between the morphology of the travelling shock and strength with observed enhancements in the flow of energized particles in shock accelerated particle (SEP) events (also often identified as "gradual" solar energetic particle events). Activities during this first year centered on the organization of the SEPs events and their correlation with solar wind observations at multiple spacecraft locations. From an identified list of more than 30 SEPs events at multiple spacecraft locations, currently four single cases for detailed study were selected and are in an advance phase of preparation for publication. Preliminary results of these four cases were presented at AGU Spring and Fall 2003 meetings, and other meetings on SEPs.

  18. Energetic Particles in Saturn's Magnetotail

    NASA Astrophysics Data System (ADS)

    Mitchell, D. G.; Carbary, J. F.; Krupp, N.; Krimigis, S. M.; Hamilton, D. C.; Kane, M.

    2007-12-01

    Energetic particle measurements in Saturn's magnetotail reveal a magnetotail dominated by Saturn's rotational dynamics as far back in the tail as 60 Rs, rarely but sometimes spectacularly disrupted by tail reconnection events. Although Cassini spent little time in the tail, and even less at the location of the tail current sheet, the time spent there revealed a pattern of very regular encounters with the energetic particles that fill the current sheet, usually once every Saturn rotation. Carbary et al. 2007a, b show that energetic electrons reappear every rotation when the spacecraft is sufficiently close to the current sheet location, and further that they lie along a spiral in longitude when mapped into the SKR coordinate system (Kurth et al., 2007). Energetic ions are also observed in the same locations, with a mix of hydrogen and oxygen not very different from that observed in the magnetosphere between 10 and 20 Rs. These ions generally display velocities approximately in the corotation direction, but with magnitudes well below rigid corotation (Kane et al., 2007, manuscript in preparation). Two other classes of energetic particle events are also seen in the magnetotail. The first consists of energetic ion and electron beams, likely accelerated in the auroral zone over downward current regions. The second are those generated in tail reconnection events (e.g., Jackman et al., 2007; Hill et al. 2007). We will give examples of all of these phenomena, including both in situ measurements and ENA images/movies. Carbary, J.~F., Mitchell, D.~G., Krimigis, S.~M., Hamilton, D.~C., Krupp, N., Charged particle periodicities in Saturn's outer magnetosphere, Journal of Geophysical Research (Space Physics) 112, 6246 {2007JGRA..11206246C} 2007a Carbary, J. F., D. G. Mitchell, S. M. Krimigis, and N. Krupp (2007), Evidence for spiral pattern in Saturn's magnetosphere using the new SKR longitudes, Geophys. Res. Lett., 34, L13105, doi:10.1029/2007GL030167 2007b Kurth, W. S., A

  19. Mesoscale Modeling of Energetic Materials

    DTIC Science & Technology

    2014-10-23

    This briefing represents interim progress towards these goals. 15. SUBJECT TERMS Heterogeneous explosives , Mesoscale dynamics, Level set method...High  Explosives  Research and Development Branch (RWME) – Damage Mechanisms Branch (RWMW) • Goal: Predict survivability of energetic payload of high...the mechanical  behavior of simple  explosive – Pristine – Damaged • Performed simulations on mechanical RVE’s – From XCMT – Idealized • Developed and

  20. Method for calculating alloy energetics

    NASA Technical Reports Server (NTRS)

    Bozzolo, Guillermo; Ferrante, John; Smith, John R.

    1992-01-01

    A semiempirical method for the computation of alloy energies is introduced. It is based on the equivalent-crystal theory of defect-formation energies in elemental solids. The method is both simple and accurate. Heats of formation as a function of composition are computed for some binary alloys of Cu, Ni, Al, Ag, Pd, Pt, and Au using the heats of solution in the dilute limit as experimental input. The separation of heats into strain and chemical components helps in understanding the energetics. In addition, lattice-parameter contractions seen in solid solutions of Ag and Au are accurately predicted. Good agreement with experiment is obtained in all cases.

  1. The Effect of Correlated Energetic Disorder on Charge Transport in Organic Semiconductors

    NASA Astrophysics Data System (ADS)

    Allen, Jonathan; Röding, Sebastian; Cherqui, Charles; Dunlap, David

    2012-10-01

    In their 1995 paper describing a Monte Carlo simulation for dissociation of an electron-hole pair in the presence of Gaussian energetic disorder, Albrect and Bäassler reported a surprising result. They found that increasing the width σ of the energetic disorder increases the quantum yield φ. They attributed this behavior to the tendency for energy fluctuations to compete against the Coulombic pair attraction, driving the electron-hole pair apart at short distances where, without disorder, recombination would be almost certain. We have expanded upon this notion, and introduced spatial correlation into the energetic disorder. By correlating the energetic disorder, we have demonstrated even larger quantum yields in simulation, attributable to the tendency of correlation to drive the charges further apart spatially than merely random disorder. Our results generally support the findings of Greenham et al. in that a larger correlation radius gives a larger quantum yield. In addition to larger quantum yield, we believe that correlated disorder could be used to create pathways for charge transport within a material, allowing the charge carrier behavior to be tuned.

  2. On Adiabatic Pair Creation

    NASA Astrophysics Data System (ADS)

    Pickl, Peter; Dürr, Detlef

    2008-08-01

    We give here a rigorous proof of the well known prediction of pair creation as it arises from the Dirac equation with an external time dependent potential. Pair creation happens with probability one if the potential changes adiabatically in time and becomes overcritical, which means that an eigenvalue curve (as a function of time) bridges the gap between the negative and positive spectral continuum. The potential can be thought of as being zero at large negative and large positive times. The rigorous treatment of this effect has been lacking since the pioneering work of Beck, Steinwedel and Süßmann [1] in 1963 and Gershtein and Zeldovich [8] in 1970.

  3. Dynamic Deformation Properties of Energetic Composite Materials

    DTIC Science & Technology

    2002-12-01

    the dynamic mechanical properties and detonation of energetic materials. It also included some preliminary data on the effect of particle size on the...study of the dynamic mechanical properties and detonation of energetic materials. It also included some preliminary data on the effect of particle size...qualitative only. 33 5. DEFLAGRATION-TO- DETONATION (DDT) STUDIES As part of an on-going programme to investigate the properties of ultrafine energetic

  4. Multiphase Combustion of Metalized Nanocomposite Energetic Materials

    DTIC Science & Technology

    2014-12-19

    2013 08/21/2013 08/21/2013 12/19/2014 12/19/2014 Received Paper Shawn C. Stacy, Michelle L. Pantoya. Laser Ignition of Nano -Composite Energetic Loose...Chaudhuri. Linking Molecular Level Chemistry to Macroscopic Combustion Behavior for Nano -energetic Materials with Halogen Containing Oxides, Journal...Keerti Kappagantula, Michelle L. Pantoya, Emily M. Hunt. Impact ignition of aluminum-teflon based energetic materials impregnated with nano

  5. EFFECT OF COHERENT STRUCTURES ON ENERGETIC PARTICLE INTENSITY IN THE SOLAR WIND AT 1 AU

    SciTech Connect

    Tessein, Jeffrey A.; Matthaeus, William H.; Wan, Minping; Ruffolo, David; Giacalone, Joe; Neugebauer, Marcia

    2015-10-10

    We present results from an analysis of Advanced Composition Explorer (ACE) observations of energetic particles in the 0.047–4.78 MeV range associated with shocks and discontinuities in the solar wind. Previous work found a strong correlation between coherent structures and energetic particles measured by ACE/EPAM. Coherent structures are identified using the Partial Variance of Increments (PVI) method, which is essentially a normalized vector increment. The correlation was based on a superposed epoch analysis using over 12 years of data. Here, we examine many individual high-PVI events to better understand this association emphasizing intervals selected from data with shock neighborhoods removed. We find that in many cases the local maximum in PVI is in a region of rising or falling energetic particle intensity, which suggests that magnetic discontinuities may act as barriers inhibiting the motion of energetic particles across them.

  6. Solar Energetic Particle Spectrometer (SEPS)

    NASA Technical Reports Server (NTRS)

    Christl, Mark J.

    2009-01-01

    An outstanding problem of solar and heliospheric physics is the transport of solar energetic particles. The more energetic particles arriving early in the event can be used to probe the transport processes. The arrival direction distribution of these particles carries information about scattering during their propagation to Earth that can be used to test models of interplanetary transport. Also, of considerable importance to crewed space missions is the level of ionizing radiation in the interplanetary medium, and the dose that the crew experiences during an intense solar particle event, as well as the risk to space systems. A recent study concludes that 90% of the absorbed dose results from particles in the energy range 20-550 MeV. We will describe a new compact instrument concept, SEPS, that can cover the energy range from 50-600 MeV with a single compact detector. This energy range has been difficult to cover. There are only limited data, generally available only in broad energy bins, from a few past and present instruments outside Earth s magnetosphere. The SEPS concept can provide improved measurements for this energy range and its simple light-weight design could be easily accommodated on future missions.

  7. National Ignition Campaign Hohlraum Energetics

    SciTech Connect

    Meezan, N B; Atherton, L J; Callahan, D A; Dewald, E L; Dixit, S N; Dzenitis, E G; Edwards, M J; Haynam, C A; Hinkel, D E; Jones, O S; Landen, O; London, R A; Michel, P A; Moody, J D; Milovich, J L; Schneider, M B; Thomas, C A; Town, R J; Warrick, A L; Weber, S V; Widmann, K; Glenzer, S H; Suter, L J; MacGowan, B J; Kline, J L; Kyrala, G A; Nikroo, A

    2009-11-16

    The first series of experiments on the National Ignition Facility (NIF) [E. I. Moses, R. N. Boyd, B. A. Remington, C. J. Keane, and R. Al-Ayat, 'The National Ignition Facility: ushering in a new age for high energy density science,' Phys. Plasmas 16, 041006 (2009)] tested ignition hohlraum 'energetics,' a term described by four broad goals: (1) Measurement of laser absorption by the hohlraum; (2) Measurement of the x-ray radiation flux (T{sub RAD}{sup 4}) on the surrogate ignition capsule; (3) Quantitative understanding of the laser absorption and resultant x-ray flux; and (4) Determining whether initial hohlraum performance is consistent with requirements for ignition. This paper summarizes the status of NIF hohlraum energetics experiments. The hohlraum targets and experimental design are described, as well as the results of the initial experiments. The data demonstrate low backscattered energy (< 10%) for hohlraums filled with helium gas. A discussion of our current understanding of NIF hohlraum x-ray drive follows, including an overview of the computational tools, i.e., radiation-hydrodynamics codes, that have been used to design the hohlraums. The performance of the codes is compared to x-ray drive and capsule implosion data from the first NIF experiments. These results bode well for future NIF ignition hohlraum experiments.

  8. Hosting anions. The energetic perspective.

    PubMed

    Schmidtchen, Franz P

    2010-10-01

    Hosting anions addresses the widely spread molecular recognition event of negatively charged species by dedicated organic compounds in condensed phases at equilibrium. The experimentally accessible energetic features comprise the entire system including the solvent, any buffers, background electrolytes or other components introduced for e.g. analysis. The deconvolution of all these interaction types and their dependence on subtle structural variation is required to arrive at a structure-energy correlation that may serve as a guide in receptor construction. The focus on direct host-guest interactions (lock-and-key complementarity) that have dominated the binding concepts of artificial receptors in the past must be widened in order to account for entropic contributions which constitute very significant fractions of the total free energy of interaction. Including entropy necessarily addresses the ambiguity and fuzziness of the host-guest structural ensemble and requires the appreciation of the fact that most liquid phases possess distinct structures of their own. Apparently, it is the perturbation of the intrinsic solvent structure occurring upon association that rules ion binding in polar media where ions are soluble and abundant. Rather than specifying peculiar structural elements useful in anion binding this critical review attempts an illumination of the concepts and individual energetic contributions resulting in the final observation of specific anion recognition (95 references).

  9. Minimal Pairs: Minimal Importance?

    ERIC Educational Resources Information Center

    Brown, Adam

    1995-01-01

    This article argues that minimal pairs do not merit as much attention as they receive in pronunciation instruction. There are other aspects of pronunciation that are of greater importance, and there are other ways of teaching vowel and consonant pronunciation. (13 references) (VWL)

  10. Feasibility of occurrence of different types of protonated base pairs in RNA: a quantum chemical study.

    PubMed

    Halder, Antarip; Halder, Sukanya; Bhattacharyya, Dhananjay; Mitra, Abhijit

    2014-09-14

    Protonated nucleobases have significant roles in facilitating catalytic functions of RNA, and in stabilizing different structural motifs. Reported pKa values of nucleobase protonation suggest that the population of neutral nucleobases is 10(3)-10(4) times higher than that of protonated nucleobases under physiological conditions (pH ∼ 7.4). Therefore, a molecular level understanding of various putative roles of protonated nucleobases cannot be achieved without addressing the question of how their occurrence propensities and stabilities are related to the free energy costs associated with the process of protonation under physiological conditions. With water as the proton donor, we use advanced QM methods to evaluate the site specific protonation propensities of nucleobases in terms of their associated free energy changes (ΔGprot). Quantitative follow up on the energetics of base pair formation and database search for evaluating their occurrence frequencies, reveal a lack of correlation between base pair stability and occurrence propensities on the one hand, and ease of protonation on the other. For example, although N7 protonated adenine (ΔGprot = 40.0 kcal mol(-1)) is found to participate in stable base pairing, base pairs involving N7 protonated guanine (ΔGprot = 36.8 kcal mol(-1)), on geometry optimization, converge to a minima where guanine transfers its extra proton to its partner base. Such observations, along with examples of weak base pairs involving N3 protonation of cytosine (ΔGprot = 37.0 kcal mol(-1)) are rationalized by analysing the protonation induced charge redistributions which are found to significantly influence, both positively and negatively, the hydrogen bonding potentials of different functional sites of individual nucleobases. Protonation induced charge redistribution is also found to strongly influence (i) the aromatic character of the rings of the participating bases and (ii) hydrogen bonding potential of the free edges of the

  11. Energetic Particles in the Inner Heliosphere

    NASA Astrophysics Data System (ADS)

    Malandraki, Olga

    2016-07-01

    Solar Energetic Particle (SEP) events are a key ingredient of Solar-Terrestrial Physics both for fundamental research and space weather applications. SEP events are the defining component of solar radiation storms, contribute to radio blackouts in polar regions and are related to many of the fastest Coronal Mass Ejections (CMEs) driving major geomagnetic storms. In addition to CMEs, SEPs are also related to flares. In this work, the current state of knowledge on the SEP field will be reviewed. Key issues to be covered and discussed include: the current understanding of the origin, acceleration and transport processes of SEPs at the Sun and in the inner heliosphere, lessons learned from multi-spacecraft SEP observations, statistical quantification of the comparison of solar events and SEP events of the current solar cycle 24 with previous solar cycles, causes of the solar-cycle variations in SEP fluencies and composition, theoretical work and current SEP acceleration models. Furthermore, the outstanding issues that constitute a knowledge gap in the field will be presented and discussed, as well as future directions and expected advances from the observational and modeling perspective, also in view of the unique observations provided by the upcoming Solar Orbiter and Solar Probe Plus missions. Acknowledgement: This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 637324.

  12. A novel tomographic technique for energetic materials

    NASA Astrophysics Data System (ADS)

    Stennett, C. C.; Stennett, S. E.; Rau, Christoph; McDonald, S. A.; Bourne, N. K.; Withers, P. J.; Cranfield-Manchester Collaboration

    2015-06-01

    It is a pressing matter to understand microstructural details within polymer matrix composites with energetic filler particles within. The generation of three-dimensional microstructure, using a noninvasive method of high resolution will advance knowledge in a range of fields. A range of inert composites analogous to plastic bonded explosives (PBXs) with crystalline and amorphous phases have been studied, and X-ray microtomography for microstructural investigation on the Diamond-Manchester I13 beamline. One of the compositions had crystal densities close to the binder and the other very different so that particles could be resolved easily in the one case and with great difficulty, even with phase contrast techniques in the other. Improvements int eh imaging made it possible to adequately define the bulk morphology, to determine the geometry of defects that might lead to sites for accidental ignition within the material and to demonstrate a direct linkage into the finite element predictions of mechanical response. Once demonstrated, the damage in a real loaded HE was assessed and quantified.

  13. Energetic materials and methods of tailoring electrostatic discharge sensitivity of energetic materials

    DOEpatents

    Daniels, Michael A.; Heaps, Ronald J.; Wallace, Ronald S.; Pantoya, Michelle L.; Collins, Eric S.

    2016-11-01

    An energetic material comprising an elemental fuel, an oxidizer or other element, and a carbon nanofiller or carbon fiber rods, where the carbon nanofiller or carbon fiber rods are substantially homogeneously dispersed in the energetic material. Methods of tailoring the electrostatic discharge sensitivity of an energetic material are also disclosed.

  14. ON THE POLAR CAP CASCADE PAIR MULTIPLICITY OF YOUNG PULSARS

    SciTech Connect

    Timokhin, A. N.; Harding, A. K.

    2015-09-10

    We study the efficiency of pair production in polar caps of young pulsars under a variety of conditions to estimate the maximum possible multiplicity of pair plasma in pulsar magnetospheres. We develop a semi-analytic model for calculation of cascade multiplicity which allows efficient exploration of the parameter space and corroborate it with direct numerical simulations. Pair creation processes are considered separately from particle acceleration in order to assess different factors affecting cascade efficiency, with acceleration of primary particles described by recent self-consistent non-stationary model of pair cascades. We argue that the most efficient cascades operate in the curvature radiation/synchrotron regime, the maximum multiplicity of pair plasma in pulsar magnetospheres is ∼few × 10{sup 5}. The multiplicity of pair plasma in magnetospheres of young energetic pulsars weakly depends on the strength of the magnetic field and the radius of curvature of magnetic field lines and has a stronger dependence on pulsar inclination angle. This result questions assumptions about very high pair plasma multiplicity in theories of pulsar wind nebulae.

  15. Anisotropic decomposition of energetic materials

    SciTech Connect

    Pravica, Michael; Quine, Zachary; Romano, Edward; Bajar, Sean; Yulga, Brian; Yang Wenge; Hooks, Daniel

    2007-12-12

    Using a white x-ray synchrotron beam, we have dynamically studied radiation-induced decomposition in single crystalline PETN and TATB. By monitoring the integrated intensity of selected diffraction spots via a CCD x-ray camera as a function of time, we have found that the decomposition rate varies dramatically depending upon the orientation of the crystalline axes relative to polarized x-ray beam and for differing diffracting conditions (spots) within the same crystalline orientation. We suggest that this effect is due to Compton scattering of the polarized x-rays with electron clouds that is dependent upon their relative orientation. This novel effect may yield valuable insight regarding anisotropic detonation sensitivity in energetic materials such as PETN.

  16. Extreme solar energetic particle events

    NASA Astrophysics Data System (ADS)

    Vainio, Rami; Afanasiev, Alexandr; Battarbee, Markus

    2016-04-01

    Properties of extreme solar energetic particle (SEP) events, here defined as those leading to ground level enhancements (GLEs) of cosmic rays, are reviewed. We review recent efforts on modeling SEP acceleration to relativistic energies and present simulation results on particle acceleration at shocks driven by fast coronal mass ejections (CMEs) in different types of coronal magnetic structures and turbulent downstream compression regions. Based on these modeling results, we discuss the possible role of solar and CME parameters in the lack of GLEs during the present sunspot cycle. This work has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 637324 (HESPERIA). The Academy of Finland is thanked for financial support.

  17. Nuclear gamma rays from energetic particle interactions

    NASA Technical Reports Server (NTRS)

    Ramaty, R.; Kozlovsky, B.; Lingenfelter, R. E.

    1978-01-01

    Gamma ray line emission from nuclear deexcitation following energetic particle reactions is evaluated. The compiled nuclear data and the calculated gamma ray spectra and intensities can be used for the study of astrophysical sites which contain large fluxes of energetic protons and nuclei. A detailed evaluation of gamma ray line production in the interstellar medium is made.

  18. Energetics and the immune system

    PubMed Central

    Reiches, Meredith W.; Prentice, Andrew M.; Moore, Sophie E.; Ellison, Peter T.

    2017-01-01

    Abstract Background and objectives: The human immune system is an ever-changing composition of innumerable cells and proteins, continually ready to respond to pathogens or insults. The cost of maintaining this state of immunological readiness is rarely considered. In this paper we aim to discern a cost to non-acute immune function by investigating how low levels of C-reactive protein (CRP) relate to other energetic demands and resources in adolescent Gambian girls. Methodology: Data from a longitudinal study of 66 adolescent girls was used to test hypotheses around investment in immune function. Non-acute (under 2 mg/L) CRP was used as an index of immune function. Predictor variables include linear height velocity, adiposity, leptin, and measures of energy balance. Results: Non-acute log CRP was positively associated with adiposity (β = 0.16, P < 0.001, R2 = 0.17) and levels of the adipokine leptin (β = 1.17, P = 0.006, R2 = 0.09). CRP was also negatively associated with increased investment in growth, as measured by height velocity (β = −0.58, P < 0.001, R2 = 0.13) and lean mass deposition β = −0.42, P = 0.005, R2 = 0.08). Relationships between adiposity and growth explained some, but not all, of this association. We do not find that CRP was related to energy balance. Conclusions and implications: These data support a hypothesis that investment in non-acute immune function is facultative, and sensitive to energetic resources and demands. We also find support for an adaptive association between the immune system and adipose tissue. PMID:28003312

  19. Pioneer 11 observations of energetic particles in the jovian magnetosphere.

    PubMed

    Van Allen, J A; Randall, B A; Baker, D N; Goertz, C K; Sentman, D D; Thomsen, M F; Flindt, H R

    1975-05-02

    Knowledge of the positional distributions, absolute intensities, energy spectra, and angular distributions of energetic electrons and protons in the Jovian magnetosphere has been considerably advanced by the planetary flyby of Pioneer 11 in November-December 1974 along a quite different trajectory from that of Pioneer 10 a year earlier. (i) The previously reported magnetodisc is shown to be blunted and much more extended in latitude on the sunward side than on the dawn side. (ii) Rigid corotation of the population of protons E(p) approximately 1 million electron volts in the magnetodisc is confirmed. (iii) Angular distributions of energetic electrons E(e) > 21 million electron volts in the inner magnetosphere are shown to be compatible with the Kennel-Petschek whistler-mode instability. (iv) A diverse body of magnetospheric effects by the Jovian satellites is found. (v) Observations of energetic electrons in to a radial distance of 1.59 Jovian radii provide a fresh basis for the interpretation of decimetric radio noise emission.

  20. Protected Flux Pairing Qubit

    NASA Astrophysics Data System (ADS)

    Bell, Matthew; Zhang, Wenyuan; Ioffe, Lev; Gershenson, Michael

    2014-03-01

    We have studied the coherent flux tunneling in a qubit containing two submicron Josephson junctions shunted by a superinductor (a dissipationless inductor with an impedance much greater than the resistance quantum). The two low energy quantum states of this device, 0 and 1, are represented by even and odd number of fluxes in the loop, respectively. This device is dual to the charge pairing Josephson rhombi qubit. The spectrum of the device, studied by microwave spectroscopy, reflects the interference between coherent quantum phase slips in the two junctions (the Aharonov-Casher effect). The time domain measurements demonstrate the suppression of the qubit's energy relaxation in the protected regime, which illustrates the potential of this flux pairing device as a protected quantum circuit. Templeton Foundation, NSF, and ARO.

  1. Junctionless Cooper pair transistor

    NASA Astrophysics Data System (ADS)

    Arutyunov, K. Yu.; Lehtinen, J. S.

    2017-02-01

    Quantum phase slip (QPS) is the topological singularity of the complex order parameter of a quasi-one-dimensional superconductor: momentary zeroing of the modulus and simultaneous 'slip' of the phase by ±2π. The QPS event(s) are the dynamic equivalent of tunneling through a conventional Josephson junction containing static in space and time weak link(s). Here we demonstrate the operation of a superconducting single electron transistor (Cooper pair transistor) without any tunnel junctions. Instead a pair of thin superconducting titanium wires in QPS regime was used. The current-voltage characteristics demonstrate the clear Coulomb blockade with magnitude of the Coulomb gap modulated by the gate potential. The Coulomb blockade disappears above the critical temperature, and at low temperatures can be suppressed by strong magnetic field.

  2. Femtosecond laser interaction with energetic materials

    NASA Astrophysics Data System (ADS)

    Roos, Edward V.; Benterou, Jerry J.; Lee, Ronald S.; Roseke, Frank; Stuart, Brent C.

    2002-09-01

    Femtosecond laser ablation shows promise in machining energetic materials into desired shapes with minimal thermal and mechanical effects to the remaining material. We will discuss the physical effects associated with machining energetic materials and assemblies containing energetic materials, based on experimental results. Interaction of ultra-short laser pulses with matter will produce high temperature plasma at high-pressure which results in the ablation of material. In the case of energetic material, which includes high explosives, propellants and pyrotechnics, this ablation process must be accomplished without coupling energy into the energetic material. Experiments were conducted in order to characterize and better understand the phenomena of femtosecond laser pulse ablation on a variety of explosives and propellants. Experimental data will be presented for laser fluence thresholds, machining rates, cutting depths and surface quality of the cuts.

  3. Energetic Particle Influence on the Earth's Atmosphere

    NASA Astrophysics Data System (ADS)

    Mironova, Irina A.; Aplin, Karen L.; Arnold, Frank; Bazilevskaya, Galina A.; Harrison, R. Giles; Krivolutsky, Alexei A.; Nicoll, Keri A.; Rozanov, Eugene V.; Turunen, Esa; Usoskin, Ilya G.

    2015-11-01

    This manuscript gives an up-to-date and comprehensive overview of the effects of energetic particle precipitation (EPP) onto the whole atmosphere, from the lower thermosphere/mesosphere through the stratosphere and troposphere, to the surface. The paper summarizes the different sources and energies of particles, principally galactic cosmic rays (GCRs), solar energetic particles (SEPs) and energetic electron precipitation (EEP). All the proposed mechanisms by which EPP can affect the atmosphere are discussed, including chemical changes in the upper atmosphere and lower thermosphere, chemistry-dynamics feedbacks, the global electric circuit and cloud formation. The role of energetic particles in Earth's atmosphere is a multi-disciplinary problem that requires expertise from a range of scientific backgrounds. To assist with this synergy, summary tables are provided, which are intended to evaluate the level of current knowledge of the effects of energetic particles on processes in the entire atmosphere.

  4. Femtosecond Laser Interaction with Energetic Materials

    SciTech Connect

    Roos, E; Benterou, J; Lee, R; Roeske, F; Stuart, B

    2002-03-25

    Femtosecond laser ablation shows promise in machining energetic materials into desired shapes with minimal thermal and mechanical effects to the remaining material. We will discuss the physical effects associated with machining energetic materials and assemblies containing energetic materials, based on experimental results. Interaction of ultra-short laser pulses with matter will produce high temperature plasma at high-pressure which results in the ablation of material. In the case of energetic material, which includes high explosives, propellants and pyrotechnics, this ablation process must be accomplished without coupling energy into the energetic material. Experiments were conducted in order to characterize and better understand the phenomena of femtosecond laser pulse ablation on a variety of explosives and propellants. Experimental data will be presented for laser fluence thresholds, machining rates, cutting depths and surface quality of the cuts.

  5. Interchange mode excited by trapped energetic ions

    SciTech Connect

    Nishimura, Seiya

    2015-07-15

    The kinetic energy principle describing the interaction between ideal magnetohydrodynamic (MHD) modes with trapped energetic ions is revised. A model is proposed on the basis of the reduced ideal MHD equations for background plasmas and the bounce-averaged drift-kinetic equation for trapped energetic ions. The model is applicable to large-aspect-ratio toroidal devices. Specifically, the effect of trapped energetic ions on the interchange mode in helical systems is analyzed. Results show that the interchange mode is excited by trapped energetic ions, even if the equilibrium states are stable to the ideal interchange mode. The energetic-ion-induced branch of the interchange mode might be associated with the fishbone mode in helical systems.

  6. Interchange mode excited by trapped energetic ions

    NASA Astrophysics Data System (ADS)

    Nishimura, Seiya

    2015-07-01

    The kinetic energy principle describing the interaction between ideal magnetohydrodynamic (MHD) modes with trapped energetic ions is revised. A model is proposed on the basis of the reduced ideal MHD equations for background plasmas and the bounce-averaged drift-kinetic equation for trapped energetic ions. The model is applicable to large-aspect-ratio toroidal devices. Specifically, the effect of trapped energetic ions on the interchange mode in helical systems is analyzed. Results show that the interchange mode is excited by trapped energetic ions, even if the equilibrium states are stable to the ideal interchange mode. The energetic-ion-induced branch of the interchange mode might be associated with the fishbone mode in helical systems.

  7. Methods and systems for electrophoretic deposition of energetic materials and compositions thereof

    SciTech Connect

    Sullivan, Kyle T.; Gash, Alexander E.; Kuntz, Joshua D.; Worsley, Marcus A.

    2015-06-23

    A product includes: a part including at least one component characterized as an energetic material, where the at least one component is at least partially characterized by physical characteristics of being deposited by an electrophoretic deposition process. A method includes: providing a plurality of particles of an energetic material suspended in a dispersion liquid to an EPD chamber or configuration; applying a voltage difference across a first pair of electrodes to generate a first electric field in the EPD chamber; and depositing at least some of the particles of the energetic material on at least one surface of a substrate, the substrate being one of the electrodes or being coupled to one of the electrodes.

  8. An Intelligent Model for Pairs Trading Using Genetic Algorithms.

    PubMed

    Huang, Chien-Feng; Hsu, Chi-Jen; Chen, Chi-Chung; Chang, Bao Rong; Li, Chen-An

    2015-01-01

    Pairs trading is an important and challenging research area in computational finance, in which pairs of stocks are bought and sold in pair combinations for arbitrage opportunities. Traditional methods that solve this set of problems mostly rely on statistical methods such as regression. In contrast to the statistical approaches, recent advances in computational intelligence (CI) are leading to promising opportunities for solving problems in the financial applications more effectively. In this paper, we present a novel methodology for pairs trading using genetic algorithms (GA). Our results showed that the GA-based models are able to significantly outperform the benchmark and our proposed method is capable of generating robust models to tackle the dynamic characteristics in the financial application studied. Based upon the promising results obtained, we expect this GA-based method to advance the research in computational intelligence for finance and provide an effective solution to pairs trading for investment in practice.

  9. An Intelligent Model for Pairs Trading Using Genetic Algorithms

    PubMed Central

    Huang, Chien-Feng; Hsu, Chi-Jen; Chen, Chi-Chung; Chang, Bao Rong; Li, Chen-An

    2015-01-01

    Pairs trading is an important and challenging research area in computational finance, in which pairs of stocks are bought and sold in pair combinations for arbitrage opportunities. Traditional methods that solve this set of problems mostly rely on statistical methods such as regression. In contrast to the statistical approaches, recent advances in computational intelligence (CI) are leading to promising opportunities for solving problems in the financial applications more effectively. In this paper, we present a novel methodology for pairs trading using genetic algorithms (GA). Our results showed that the GA-based models are able to significantly outperform the benchmark and our proposed method is capable of generating robust models to tackle the dynamic characteristics in the financial application studied. Based upon the promising results obtained, we expect this GA-based method to advance the research in computational intelligence for finance and provide an effective solution to pairs trading for investment in practice. PMID:26339236

  10. Research and Development of Energetic Ionic Liquids. Next Generation Energetic Materials Striking a Balance between Performance, Insensitivity, and Environmental Sustainability

    DTIC Science & Technology

    2011-12-01

    Chemical Propulsion- ILs in Advanced Monopropellants Constituents Weight % ADN 60-65 Methanol 15-20 Ammonia 3-6 H2O balance Properties LMP - 103S AF...Distribution Unlimited. 8 Much Effort Required in Small- Scale Safety/Hazard Evaluations Propellant AF-M315E* LMP - 103S ** Unconfined Burn Test 1 and 3: No...1.01 Vapor Pressure (torr) Ammonia Methanol H2O ɘ.1 (w/o H2O) 14.3 ADN (M.P. 92oC) is also an Energetic Ionic Liquid • ADN-based monopropellant ( LMP

  11. Energetic Fermi/LAT GRB 100414A: Energetic and Correlations

    NASA Astrophysics Data System (ADS)

    Urata, Yuji; Huang, Kuiyun; Yamaoka, Kazutaka; Tsai, Patrick P.; Tashiro, Makoto S.

    2012-03-01

    This study presents multi-wavelength observational results for energetic GRB 100414A with GeV photons. The prompt spectral fitting using Suzaku/WAM data yielded spectral peak energies of E src peak of 1458.7+132.6 - 106.6 keV and E iso of 34.5+2.0 - 1.8 × 1052 erg with z = 1.368. The optical afterglow light curves between 3 and 7 days were effectively fitted according to a simple power law with a temporal index of α = -2.6 ± 0.1. The joint light curve with earlier Swift/UVOT observations yields a temporal break at 2.3 ± 0.2 days. This was the first Fermi/LAT detected event that demonstrated the clear temporal break in the optical afterglow. The jet opening angle derived from this temporal break was 5fdg8, consistent with those of other well-observed long gamma-ray bursts (GRBs). The multi-wavelength analyses in this study showed that GRB 100414A follows E src peak-E iso and E src peak-E γ correlations. The late afterglow revealed a flatter evolution with significant excesses at 27.2 days. The most straightforward explanation for the excess is that GRB 100414A was accompanied by a contemporaneous supernova. The model light curve based on other GRB-SN events is marginally consistent with that of the observed light curve.

  12. Global Energetics of Solar Flares. IV. Coronal Mass Ejection Energetics

    NASA Astrophysics Data System (ADS)

    Aschwanden, Markus J.

    2016-11-01

    This study entails the fourth part of a global flare energetics project, in which the mass m cme, kinetic energy E kin, and the gravitational potential energy E grav of coronal mass ejections (CMEs) is measured in 399 M and X-class flare events observed during the first 3.5 years of the Solar Dynamics Observatory (SDO) mission, using a new method based on the EUV dimming effect. EUV dimming is modeled in terms of a radial adiabatic expansion process, which is fitted to the observed evolution of the total emission measure of the CME source region. The model derives the evolution of the mean electron density, the emission measure, the bulk plasma expansion velocity, the mass, and the energy in the CME source region. The EUV dimming method is truly complementary to the Thomson scattering method in white light, which probes the CME evolution in the heliosphere at r ≳ 2 R ⊙, while the EUV dimming method tracks the CME launch in the corona. We compare the CME parameters obtained in white light with the LASCO/C2 coronagraph with those obtained from EUV dimming with the Atmospheric Imaging Assembly onboard the SDO for all identical events in both data sets. We investigate correlations between CME parameters, the relative timing with flare parameters, frequency occurrence distributions, and the energy partition between magnetic, thermal, nonthermal, and CME energies. CME energies are found to be systematically lower than the dissipated magnetic energies, which is consistent with a magnetic origin of CMEs.

  13. "Spatial Energetics": Integrating Data From GPS, Accelerometry, and GIS to Address Obesity and Inactivity.

    PubMed

    James, Peter; Jankowska, Marta; Marx, Christine; Hart, Jaime E; Berrigan, David; Kerr, Jacqueline; Hurvitz, Philip M; Hipp, J Aaron; Laden, Francine

    2016-11-01

    To address the current obesity and inactivity epidemics, public health researchers have attempted to identify spatial factors that influence physical inactivity and obesity. Technologic and methodologic developments have led to a revolutionary ability to examine dynamic, high-resolution measures of temporally matched location and behavior data through GPS, accelerometry, and GIS. These advances allow the investigation of spatial energetics, high-spatiotemporal resolution data on location and time-matched energetics, to examine how environmental characteristics, space, and time are linked to activity-related health behaviors with far more robust and detailed data than in previous work. Although the transdisciplinary field of spatial energetics demonstrates promise to provide novel insights on how individuals and populations interact with their environment, there remain significant conceptual, technical, analytical, and ethical challenges stemming from the complex data streams that spatial energetics research generates. First, it is essential to better understand what spatial energetics data represent, the relevant spatial context of analysis for these data, and if spatial energetics can establish causality for development of spatially relevant interventions. Second, there are significant technical problems for analysis of voluminous and complex data that may require development of spatially aware scalable computational infrastructures. Third, the field must come to agreement on appropriate statistical methodologies to account for multiple observations per person. Finally, these challenges must be considered within the context of maintaining participant privacy and security. This article describes gaps in current practice and understanding and suggests solutions to move this promising area of research forward.

  14. Geometry dependence of electronic and energetic properties of one-dimensional peanut-shaped fullerene polymers.

    PubMed

    Noda, Yusuke; Ono, Shota; Ohno, Kaoru

    2015-03-26

    In the present study, we investigate different types of 1D peanut-shaped fullerene polymers (PSFPs) using density functional theory to understand the electronic states and the energetic stability of curved carbon nanomaterials. We generated 53 different models of the 1D PSFPs by means of the generalized Stone-Wales transformations and performed structural optimization for each model. Band structures of the 1D PSFPs exhibit either metallic or semiconducting property according to the geometrical structures. We find that the energetic stability of the 1D PSFPs depends on the geometry: the more octagon and pentagon-octagon pairs (heptagons and hexagon-heptagon pairs) in their geometrical structures, the more stable (unstable) the 1D PSFPs.

  15. Pair of Craters

    NASA Technical Reports Server (NTRS)

    2005-01-01

    14 July 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a 1.5 meters per pixel (5 ft/pixel) view of a pair of small meteor impact craters in the Arena Colles region of Mars, located north of Isidis Planitia.

    Location near: 22.7oN, 278.5oW Image width: width: 3 km (1.9 mi) Illumination from: lower left Season: Northern Autumn

  16. Type III burst pair

    NASA Astrophysics Data System (ADS)

    Ning, Zongjun; Fu, Qijun; Lu, Quankang

    2000-05-01

    We present a special solar radio burst detected on 5 January 1994 using the multi-channel (50) spectrometer (1.0-2.0 GHz) of the Beijing Astronomical Observatory (BAO). Sadly, the whole event could not be recorded since it had a broader bandwidth than the limit range of the instrument. The important part was obtained, however. The event is composed of a normal drift type III burst on the lower frequency side and a reverse drift type III burst appearing almost simultaneously on the high side. We call the burst type III a burst pair. It is a typical characteristic of two type III bursts that they are morphologically symmetric about some frequency from 1.64 GHz to 1.78 GHz on the dynamic spectra records, which indicates that there are two different electron beams from the same acceleration region travelling simultaneously in opposite directions (upward and downward). A magnetic reconnection mode is a nice interpretation of type III burst pair since the plasma beta β~=0.01 is much less than 1 and the beams have velocity of about 1.07×10^8 cm s^-1 after leaving the reconnection region if we assume that the ambient magnetic field strength is about 100 G.

  17. Type III burst pair.

    NASA Astrophysics Data System (ADS)

    Zongjun, Ning; Fu, Qijun; Quankang, Lu

    2000-05-01

    Presents a special solar radio burst detected on 5 January 1994 using the multi-channel (50) spectrometer (1.0 - 2.0 GHz) of the Beijing Astronomical Observatory. Sadly, the whole event could not be recorded since it had a broader bandwidth than the limit range of the instrument. The important part was obtained, however. The event is composed of a normal drift type III burst on the lower frequency side and a reverse drift type III burst appearing almost simultaneously on the high side. The authors call the burst type III a burst pair. It is a typical characteristic of two type III bursts that they are morphologically symmetric about some frequency from 1.64 GHz to 1.78 GHz on the dynamic spectra records, which indicates that there are two different electron beams from the same acceleration region travelling simultaneously in opposite directions (upward and downward). A magnetic reconnection mode is an interpretation of type III burst pair.

  18. Paleo Mars energetic particle precipitation

    NASA Astrophysics Data System (ADS)

    Alho, Markku; McKenna-Lawlor, Susan; Kallio, Esa

    2015-12-01

    A young Mars may well have possessed a global dipolar magnetic field that provided protection for the planet's atmosphere from the space weather environment. Against this background, we study in the present paper the effect of various dipole magnetic fields on particle precipitation (range 10 keV-4.5 MeV) on the upper Martian atmosphere as the magnetosphere gradually declined to become an induced magnetosphere. We utilized a hybrid plasma model to provide, in a self-consistent fashion, simulations (that included ion-kinetic effects) of the interaction between the Martian obstacle (magnetized or otherwise) and the solar wind. Besides the intrinsic dipole, with field strengths of ~100 nT and below, we assume modern solar and atmospheric parameters to examine the effect of the single variable, that is the dipole strength. We thereby investigated the precipitation of solar energetic particles on the upper atmosphere of the planet in circumstances characterized by the evolution of a diminishing Martian dynamo that initially generated an ideal dipolar field. It is demonstrated that an assumed Martian dipole would have provided, in the energy range investigated, significant shielding against proton impingement and that the interaction between the solar wind and the assumed Martian magnetic dipole would have been responsible for generating the shielding effect identified.

  19. The Galileo Energetic Particles Detector

    NASA Technical Reports Server (NTRS)

    Williams, D. J.; Mcentire, R. W.; Jaskulek, S.; Wilken, B.

    1992-01-01

    Amongst its complement of particles and fields instruments, the Galileo spacecraft carries an Energetic Particles Detector (EPD) designed to measure the characteristics of particle populations important in determining the size, shape, and dynamics of the Jovian magnetosphere. To do this the EPD provides 4pi angular coverage and spectral measurements for Z greater than or equal to 1 ions from 20 keV to 55 MeV, for electrons from 15 keV to greater than 11 MeV, and for the elemental species helium through iron from approximately 10 keV/nucl to 15 MeV/nucl. Two bidirectional telescopes, mounted on a stepping platform, employ magnetic deflection, energy loss versus energy, and time-of-flight techniques to provide 64 rate channels and pulse height analysis of priority selected events. The EPD data system provides a large number of possible operational modes from which a small number will be selected to optimize data collection during the many encounter and cruise phases of the mission. The EPD employs a number of safeing algorithms that are to be used in the event that its self-checking procedures indicate a problem. The instrument and its operation are described.

  20. Cosmic Ray Energetics And Mass

    NASA Astrophysics Data System (ADS)

    Seo, Eun-Suk

    2014-08-01

    The balloon-borne Cosmic Ray Energetics And Mass (CREAM) experiment was flown for ~161 days in six flights over Antarctica. High energy cosmic-ray data were collected over a wide energy range from ~ 10^10 to > 10^14 eV at an average altitude of ~38.5 km with ~3.9 g/cm2 atmospheric overburden. Cosmic-ray elements from protons (Z = 1) to iron nuclei (Z = 26) are separated with excellent charge resolution. Building on success of the balloon flights, the payload is being reconfigured for exposure on the International Space Station (ISS). This ISS-CREAM instrument is configured with the CREAM calorimeter for energy measurements, and four finely segmented Silicon Charge Detector layers for precise charge measurements. In addition, the Top and Bottom Counting Detectors (TCD and BCD) and Boronated Scintillator Detector (BSD) have been newly developed. The TCD and BCD are scintillator based segmented detectors to separate electrons from nuclei using the shower profile differences, while BSD distinguishes electrons from nuclei by detecting thermal neutrons that are dominant in nuclei induced showers. An order of magnitude increase in data collecting power is possible by utilizing the ISS to reach the highest energies practical with direct measurements. The project status including results from on-going analysis of existing data and future plans will be discussed.

  1. POET: POlarimeters for Energetic Transients

    NASA Technical Reports Server (NTRS)

    Hill, J. E.; McConnell, M. L.; Bloser, P.; Legere, J.; Macri, J.; Ryan, J.; Barthelmy, S.; Angelini, L.; Sakamoto, T.; Black, J. K.; Hartmann, D. H.; Kaaret, P.; Zhang, B.; Ioka, K.; Nakamura, T.; Toma, K.; Yamazaki, R.; Wu, X.

    2008-01-01

    POET (Polarimeters for Energetic Transients) is a Small Explorer mission concept proposed to NASA in January 2008. The principal scientific goal of POET is to measure GRB polarization between 2 and 500 keV. The payload consists of two wide FoV instruments: a Low Energy Polarimeter (LEP) capable of polarization measurements in the energy range from 2-15 keV and a high energy polarimeter (Gamma-Ray Polarimeter Experiment - GRAPE) that will measure polarization in the 60-500 keV energy range. Spectra will be measured from 2 keV up to 1 MeV. The POET spacecraft provides a zenith-pointed platform for maximizing the exposure to deep space. Spacecraft rotation will provide a means of effectively dealing with systematics in the polarization response. POET will provide sufficient sensitivity and sky coverage to measure statistically significant polarization for up to 100 GRBs in a two-year mission. Polarization data will also be obtained for solar flares, pulsars and other sources of astronomical interest.

  2. ENERGETIC FERMI/LAT GRB 100414A: ENERGETIC AND CORRELATIONS

    SciTech Connect

    Urata, Yuji; Tsai, Patrick P.; Huang, Kuiyun; Yamaoka, Kazutaka; Tashiro, Makoto S.

    2012-03-20

    This study presents multi-wavelength observational results for energetic GRB 100414A with GeV photons. The prompt spectral fitting using Suzaku/WAM data yielded spectral peak energies of E{sup src}{sub peak} of 1458.7{sup +132.6}{sub -106.6} keV and E{sub iso} of 34.5{sup +2.0}{sub -1.8} Multiplication-Sign 10{sup 52} erg with z = 1.368. The optical afterglow light curves between 3 and 7 days were effectively fitted according to a simple power law with a temporal index of {alpha} = -2.6 {+-} 0.1. The joint light curve with earlier Swift/UVOT observations yields a temporal break at 2.3 {+-} 0.2 days. This was the first Fermi/LAT detected event that demonstrated the clear temporal break in the optical afterglow. The jet opening angle derived from this temporal break was 5.{sup 0}8, consistent with those of other well-observed long gamma-ray bursts (GRBs). The multi-wavelength analyses in this study showed that GRB 100414A follows E{sup src}{sub peak}-E{sub iso} and E{sup src}{sub peak}-E{sub {gamma}} correlations. The late afterglow revealed a flatter evolution with significant excesses at 27.2 days. The most straightforward explanation for the excess is that GRB 100414A was accompanied by a contemporaneous supernova. The model light curve based on other GRB-SN events is marginally consistent with that of the observed light curve.

  3. Impairment of cardiac function and energetics in experimental renal failure.

    PubMed Central

    Raine, A E; Seymour, A M; Roberts, A F; Radda, G K; Ledingham, J G

    1993-01-01

    Cardiac function and energetics in experimental renal failure in the rat (5/6 nephrectomy) have been investigated by means of an isolated perfused working heart preparation and an isometric Langendorff preparation using 31P nuclear magnetic resonance (31P NMR). 4 wk after nephrectomy cardiac output of isolated hearts perfused with Krebs-Henseleit buffer was significantly lower (P < 0.0001) at all levels of preload and afterload in the renal failure groups than in the pair-fed sham operated control group. In control hearts, cardiac output increased with increases in perfusate calcium from 0.73 to 5.61 mmol/liter whereas uremic hearts failed in high calcium perfusate. Collection of 31P NMR spectra from hearts of renal failure and control animals during 30 min normoxic Langendorff perfusion showed that basal phosphocreatine was reduced by 32% to 4.7 mumol/g wet wt (P < 0.01) and the phosphocreatine to ATP ratio was reduced by 32% (P < 0.01) in uremic hearts. During low flow ischemia, there was a substantial decrease in phosphocreatine in the uremic hearts and an accompanying marked increase in release of inosine into the coronary effluent (14.9 vs 6.1 microM, P < 0.01). We conclude that cardiac function is impaired in experimental renal failure, in association with abnormal cardiac energetics and increased susceptibility to ischemic damage. Disordered myocardial calcium utilization may contribute to these derangements. PMID:8254048

  4. Energetic Extremes in Aquatic Locomotion by Coral Reef Fishes

    PubMed Central

    Fulton, Christopher J.; Johansen, Jacob L.; Steffensen, John F.

    2013-01-01

    Underwater locomotion is challenging due to the high friction and resistance imposed on a body moving through water and energy lost in the wake during undulatory propulsion. While aquatic organisms have evolved streamlined shapes to overcome such resistance, underwater locomotion has long been considered a costly exercise. Recent evidence for a range of swimming vertebrates, however, has suggested that flapping paired appendages around a rigid body may be an extremely efficient means of aquatic locomotion. Using intermittent flow-through respirometry, we found exceptional energetic performance in the Bluelined wrasse Stethojulis bandanensis, which maintains tuna-like optimum cruising speeds (up to 1 metre s−1) while using 40% less energy than expected for their body size. Displaying an exceptional aerobic scope (22-fold above resting), streamlined rigid-body posture, and wing-like fins that generate lift-based thrust, S. bandanensis literally flies underwater to efficiently maintain high optimum swimming speeds. Extreme energetic performance may be key to the colonization of highly variable environments, such as the wave-swept habitats where S. bandanensis and other wing-finned species tend to occur. Challenging preconceived notions of how best to power aquatic locomotion, biomimicry of such lift-based fin movements could yield dramatic reductions in the power needed to propel underwater vehicles at high speed. PMID:23326566

  5. Energetic extremes in aquatic locomotion by coral reef fishes.

    PubMed

    Fulton, Christopher J; Johansen, Jacob L; Steffensen, John F

    2013-01-01

    Underwater locomotion is challenging due to the high friction and resistance imposed on a body moving through water and energy lost in the wake during undulatory propulsion. While aquatic organisms have evolved streamlined shapes to overcome such resistance, underwater locomotion has long been considered a costly exercise. Recent evidence for a range of swimming vertebrates, however, has suggested that flapping paired appendages around a rigid body may be an extremely efficient means of aquatic locomotion. Using intermittent flow-through respirometry, we found exceptional energetic performance in the Bluelined wrasse Stethojulis bandanensis, which maintains tuna-like optimum cruising speeds (up to 1 metre s(-1)) while using 40% less energy than expected for their body size. Displaying an exceptional aerobic scope (22-fold above resting), streamlined rigid-body posture, and wing-like fins that generate lift-based thrust, S. bandanensis literally flies underwater to efficiently maintain high optimum swimming speeds. Extreme energetic performance may be key to the colonization of highly variable environments, such as the wave-swept habitats where S. bandanensis and other wing-finned species tend to occur. Challenging preconceived notions of how best to power aquatic locomotion, biomimicry of such lift-based fin movements could yield dramatic reductions in the power needed to propel underwater vehicles at high speed.

  6. Dynamics and energetics of emergent magnetic monopoles in chiral magnets

    NASA Astrophysics Data System (ADS)

    Schütte, Christoph; Rosch, Achim

    2014-11-01

    The formation and destruction of topologically quantized magnetic whirls, i.e., the so-called skyrmions, in chiral magnets is driven by the creation and motion of singular hedgehog defects. These Bloch points can be identified with emergent magnetic monopoles and antimonopoles. We investigate how the energetics of and forces between monopoles and antimonopoles influence their creation rate and dynamics. We study a single skyrmion line defect in the helical phase using both micromagnetic simulations and a Ginzburg-Landau analysis. Monopole-antimonopole pairs are created in a thermally activated process, largely controlled by the (core) energy of the monopole. The force between monopoles and antimonopoles is linear in distance and described by a string tension. The sign and size of the string tension determines the stability of the phases and the velocity of the monopoles.

  7. Double proton transfer in the isolated and DNA-embedded guanine-cytosine base pair

    NASA Astrophysics Data System (ADS)

    Zoete, Vincent; Meuwly, Markus

    2004-09-01

    The energetics and dynamics of double proton transfer (DPT) is investigated theoretically for the Watson-Crick conformation of the guanine-cytosine (GC) base pair. Using semiempirical density functional theory the isolated and DNA-embedded GC pair is considered. Differences in the energetics and dynamics of DPT thus addresses the question of how relevant studies of isolated base pairs are for the understanding of processes occurring in DNA. Two-dimensional potential energy surfaces involving the transferring hydrogen atoms and the proton donors and acceptors are presented for both systems. The DPT reaction is accompanied by a contraction of the distance between the two bases with virtually identical energetic barriers being 18.8 and 18.7 kcal/mol for the isolated and DNA-embedded system, respectively. However, the transition state for DPT in the DNA-embedded GC pair is offset by 0.1 Å to larger N-H separation compared to the isolated GC pair. Using activated ab initio molecular dynamics, DPT is readily observed for the isolated base pair with a minimal amount of 21.4 kcal/mol of initial average kinetic energy along the DPT normal mode vector. On a time scale of ≈100 fs DPT has occurred and the excess energy is redistributed. For the DNA-embedded GC pair considerably more kinetic energy is required (30.0 kcal/mol) for DPT and the process is completed within one hydrogen vibration. The relevance of studies of isolated base pairs and base pair analogs in regard of reactions or properties involving DNA is discussed.

  8. Applications and implications of ecological energetics.

    PubMed

    Tomlinson, Sean; Arnall, Sophie G; Munn, Adam; Bradshaw, S Don; Maloney, Shane K; Dixon, Kingsley W; Didham, Raphael K

    2014-05-01

    The ecological processes that are crucial to an animal's growth, survival, and reproductive fitness have energetic costs. The imperative for an animal to meet these costs within the energetic constraints of the environment drives many aspects of animal ecology and evolution, yet has largely been overlooked in traditional ecological paradigms. The field of 'ecological energetics' is bringing comparative physiology out of the laboratory and, for the first time, is becoming broadly accessible to field ecologists addressing real-world questions at many spatial and temporal scales. In an era of unprecedented global environmental challenges, ecological energetics opens up the tantalising prospect of a more predictive, mechanistic understanding of the drivers of threatened species decline, delivering process-based modelling approaches to natural resource management.

  9. Energetic particle characteristics of magnetotail flux ropes

    NASA Technical Reports Server (NTRS)

    Scholer, M.; Klecker, B.; Hovestadt, D.; Gloeckler, G.; Ipavich, F. M.; Galvin, A. B.

    1985-01-01

    During the recent ISEE-3 Geotail Mission three events have been identified from the magnetometer data which are consistent with a spacecraft crossing of a magnetotail flux rope. Energetic electron and proton observations obtained by the Max-Planck-Institut/University of Maryland sensor system during two of the possible flux rope events are presented. During one event remote sensing of the flux rope with energetic protons reveals that the flux rope is crossed by the spacecraft from south to north. This allows determination of the bandedness of the magnetic field twist and of the flux rope velocity relative to the spacecraft. A minimal flux rope radius of 3 earth radii is derived. Energetic proton intensity is highest just inside of the flux rope and decreases towards the core. Energetic electrons are streaming tailward near the outer boundary, indicating openness of the field lines, and are isotropic through the inner part of the flux rope.

  10. Energetic salt of trinitrophloroglucinol and melamine

    NASA Astrophysics Data System (ADS)

    Bowden, Patrick R.; Leonard, Philip W.; Lichthardt, Joseph P.; Tappan, Bryce C.; Ramos, Kyle J.

    2017-01-01

    We hope to harness the field of energetic co-crystals for development of insensitive, high-performing explosives. As demonstrated by other groups, co-crystals of energetic materials are diverse in their resultant properties versus the native materials. Herein, we discuss the synthesis, characterization, and testing of an energetic co-crystal of trinitrophloroglucinol (1,3,5-trihydroxy-2,4,6-trinitrobenzene) and melamine. Although melamine is not an energetic material, high nitrogen content and insensitivity can be of benefit in a co-crystal. Currently, trinitrophloroglucinol (TNPG) and melamine have been found to exist as a 1:1 ionic co-crystal. Characterization by NMR, IR, small-scale sensitivity, thermal stability and powder X-ray diffraction have all been used to characterize the individual compounds as well as the co-crystals developed.

  11. New Trends in Research of Energetic Materials

    DTIC Science & Technology

    2007-11-02

    material costs) recycling liquidation by combustion liquidation costs " safe " material usage safe disarming cost decreasing about 60-80...4. TITLE AND SUBTITLE New Trends in Research of Energetic Materials 5. FUNDING NUMBERS FA8655-04-1-5001 6. AUTHOR(S) Prof Zvatopluk Zeman...Affairs Office) 12b. DISTRIBUTION CODE A ABSTRACT (Maximum 200 words) The Final Proceedings for New Trends in Research of Energetic Materials , 20

  12. Size distributions of solar energetic particle events

    NASA Technical Reports Server (NTRS)

    Cliver, E.; Reames, D.; Kahler, S.; Cane, H.

    1991-01-01

    NASA particle detectors on the IMP-8 are employed to determine the size distributions of the peak fluxes of events related to solar-energetic particles including protons and electrons. The energetic proton events show a flatter size distribution which suggests that not all flares are proton flares. Both the electron and proton events are classified as either 'impulsive' or 'gradual', and the impulsive events tend to have a steeper power-law distribution.

  13. Carmustine, etoposide, cytarabine and melphalan versus a newly designed intravenous busulfan-based Busulfex, etoposide and melphalan conditioning regimen for autologous hematopoietic cell transplant: a retrospective matched-pair analysis in advanced Hodgkin and non-Hodgkin lymphomas.

    PubMed

    Sakellari, Ioanna; Mallouri, Despoina; Batsis, Ioannis; Apostolou, Chrysa; Konstantinou, Varnavas; Abela, Eleni-Maria; Douka, Vasiliki; Marvaki, Anastasia; Karypidis, Kyriakos; Iskas, Michalis; Baliakas, Panayiotis; Kaloyannidis, Panayotis; Yannaki, Evangelia; Sotiropoulos, Damianos; Kouvatseas, Giorgos; Smias, Christos; Anagnostopoulos, Achilles

    2015-01-01

    Optimal conditioning remains a challenge in lymphomas. We designed a regimen consisting of Busulfex, etoposide and melphalan (BuEM). We retrospectively analyzed the outcome of patients conditioned with carmustine, etoposide, cytarabine and melphalan (BEAM) or BuEM in matched-pair analysis on a planned 2:1 ratio. Eighty-seven patients treated with BEAM who fulfilled the matching criteria were randomly selected. Two-year progression-free survival/overall survival (PFS/OS) were 63.2%/76.7% for BEAM vs. 65.6%/79.8% for BuEM after 64.7 and 42.7 months, respectively. Furthermore, marginally better PFS and OS were noted in Hodgkin lymphoma (HL) after BuEM. In multivariate analysis, PFS was superior in HL, chemosensitive disease and complete remission post-transplant. BEAM correlated with faster engraftment, reduced infections, less mucositis and liver toxicity, and BuEM with less need for blood cell and platelet transfusions and granulocyte colony-stimulating factor administration. In conclusion, BuEM was well tolerated and equally highly efficacious as BEAM for non-Hodgkin lymphoma and offered marginally significantly improved PFS and OS in HL with acceptable toxicity and zero mortality.

  14. The energetics of Titan's ionosphere

    NASA Astrophysics Data System (ADS)

    Roboz, A.; Nagy, A. F.

    1994-02-01

    We have developed a comprehensive model to study the dynamics and energetics of the ionosphere of Titan. We solved the one-dimensional, time-dependent, coupled continuity and momentum equations for several ion species, together with single ion and electron energy equations, in order to calculate density, velocity, and temperature profiles. Calculations were carried out for several cases corresponding to different local times and configurations of the Titan-Saturn system. In our model the effects of horizontal magnetic fields were assumed to be negligible, except for their effect on reducing the electron and ion thermal conductivities and inhibiting vertical transport in the subram region. The ionospheric density peak was found to be at an altitude of about 1100 km, in accordance with earlier model calculations. The ionosphere is chemically controlled below an altitude of about 1500 km. Above this level, ion densities differ significantly from their chemical equilibrium values due to strong upward ion velocities. Heat is deposited in a narrow region around the ionospheric peak, resulting in temperature profiles increasing sharply and reaching nearly constant values of 800-1000 deg K for electrons and 300 deg K for ions in the topside, assuming conditions appropriate for the wake region. In the subram region magnetic correction factors make the electron heat conductivities negligible, resulting in electron temperatures increasing strongly with altitude and reaching values in the order of 5000 deg K at our upper boundary located at 2200 km. Ion chemical heating is found to play an important role in shaping the ion energy balance in Titan's ionosphere.

  15. The energetics of Titan's ionosphere

    NASA Technical Reports Server (NTRS)

    Roboz, A.; Nagy, A. F.

    1994-01-01

    We have developed a comprehensive model to study the dynamics and energetics of the ionosphere of Titan. We solved the one-dimensional, time-dependent, coupled continuity and momentum equations for several ion species, together with single ion and electron energy equations, in order to calculate density, velocity, and temperature profiles. Calculations were carried out for several cases corresponding to different local times and configurations of the Titan-Saturn system. In our model the effects of horizontal magnetic fields were assumed to be negligible, except for their effect on reducing the electron and ion thermal conductivities and inhibiting vertical transport in the subram region. The ionospheric density peak was found to be at an altitude of about 1100 km, in accordance with earlier model calculations. The ionosphere is chemically controlled below an altitude of about 1500 km. Above this level, ion densities differ significantly from their chemical equilibrium values due to strong upward ion velocities. Heat is deposited in a narrow region around the ionospheric peak, resulting in temperature profiles increasing sharply and reaching nearly constant values of 800-1000 deg K for electrons and 300 deg K for ions in the topside, assuming conditions appropriate for the wake region. In the subram region magnetic correction factors make the electron heat conductivities negligible, resulting in electron temperatures increasing strongly with altitude and reaching values in the order of 5000 deg K at our upper boundary located at 2200 km. Ion chemical heating is found to play an important role in shaping the ion energy balance in Titan's ionosphere.

  16. Solar Energetic Particle Spectral Breaks

    NASA Astrophysics Data System (ADS)

    Mewaldt, R.; Cohen, C.; Mason, G.; Desai, M.; Labrador, A.; Lee, M.; Li, G.

    2008-05-01

    A new generation of instruments during solar cycle 23 made it possible to measure solar energetic particle (SEP) energy spectra for many species over a broad energy interval (~0.1 to ~100 MeV/nucleon). These observations revealed that most large SEP events have power-law spectra below a few MeV/nucleon with rather hard spectral indices, followed by spectral steepening at higher energies. These spectral breaks are ordered by species - the spectra of lighter elements break at higher energy/nucleon than those for heavier species. To understand the charge-to-mass (Q/M) dependence of these spectral breaks, we have located the breaks for a range of species (e.g., H, He, C, N, O, Ne, Mg, Si, and Fe) and correlated the break locations with either measured or average Q/M ratios. As of this writing there are results for 13 large SEP events, based on data from ACE, GOES, SAMPEX, and STEREO, and charge state data from SAMPEX and ACE. We find that the location of the breaks is generally well-represented by a power-law in Q/M. This power-law fit can be related to the Q/M- dependence of the interplanetary diffusion coefficient and to the turbulence spectrum of the interplanetary magnetic field. We find that the slope of the deduced turbulence spectra are correlated with Fe/O and the proton fluence. These results support the idea that proton-amplified Alfven waves are generated in large SEP events, as expected for acceleration at parallel shocks.

  17. Theoretical studies on nitrogen rich energetic azoles.

    PubMed

    Ghule, Vikas Dasharath; Sarangapani, Radhakrishnan; Jadhav, Pandurang M; Tewari, Surya P

    2011-06-01

    Different nitro azole isomers based on five membered heterocyclics were designed and investigated using computational techniques in order to find out the comprehensive relationships between structure and performances of these high nitrogen compounds. Electronic structure of the molecules have been calculated using density functional theory (DFT) and the heat of formation has been calculated using the isodesmic reaction approach at B3LYP/6-31G* level. All designed compounds show high positive heat of formation due to the high nitrogen content and energetic nitro groups. The crystal densities of these energetic azoles have been predicted with different force fields. All the energetic azoles show densities higher than 1.87 g/cm(3). Detonation properties of energetic azoles are evaluated by using Kamlet-Jacobs equation based on the calculated densities and heat of formations. It is found that energetic azoles show detonation velocity about 9.0 km/s, and detonation pressure of 40GPa. Stability of the designed compounds has been predicted by evaluating the bond dissociation energy of the weakest C-NO(2) bond. The aromaticity using nucleus independent chemical shift (NICS) is also explored to predict the stability via delocalization of the π-electrons. Charge on the nitro group is used to assess the impact sensitivity in the present study. Overall, the study implies that all energetic azoles are found to be stable and expected to be the novel candidates of high energy density materials (HEDMs).

  18. Energetic neutral particles from Jupiter and Saturn

    NASA Technical Reports Server (NTRS)

    Cheng, A. F.

    1986-01-01

    The Voyager 1 spacecraft has detected energetic neutral particles escaping from the magnetospheres of Jupiter and Saturn. These energetic neutrals are created in charge exchange reactions between radiation belt ions and ambient atoms or molecules in the magnetosphere. If the Io torus is assumed to be the dominant Jovian source region for energetic neutrals, the Voyager observations can be used to infer upper limits to the average ion intensities there below about 200 keV. No readily interpretable in-situ measurements are available in the Io torus at these energies. The middle and outer Jovian magnetospheres may also be a significant source of energetic neutrals. At Saturn, the observed neutral particle count rates are too high to be explained by charge exchange between fast protons and H atoms of the Titan torus. Most of the energetic neutrals may be produced by charge exchanges between heavy ions and a neutral cloud containing H2O in Saturn's inner magnetosphere. If so, the Voyager measurements of energetic neutral fluxes would be the first detected emissions from this region of Saturn's magnetosphere.

  19. Multiprocessor switch with selective pairing

    DOEpatents

    Gara, Alan; Gschwind, Michael K; Salapura, Valentina

    2014-03-11

    System, method and computer program product for a multiprocessing system to offer selective pairing of processor cores for increased processing reliability. A selective pairing facility is provided that selectively connects, i.e., pairs, multiple microprocessor or processor cores to provide one highly reliable thread (or thread group). Each paired microprocessor or processor cores that provide one highly reliable thread for high-reliability connect with a system components such as a memory "nest" (or memory hierarchy), an optional system controller, and optional interrupt controller, optional I/O or peripheral devices, etc. The memory nest is attached to a selective pairing facility via a switch or a bus

  20. Stereo Pair, Pasadena, California

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This stereoscopic image pair is a perspective view that shows the western part of the city of Pasadena, California, looking north toward the San Gabriel Mountains. Portions of the cities of Altadena and La Canada Flintridge are also shown. The cluster of large buildings left of center, at the base of the mountains, is the Jet Propulsion Laboratory. This image shows the power of combining data from different sources to create planning tools to study problems that affect large urban areas. In addition to the well-known earthquake hazards, Southern California is affected by a natural cycle of fire and mudflows. Data shown in this image can be used to predict both how wildfires spread over the terrain and how mudflows are channeled down the canyons.

    The image was created from three datasets: the Shuttle Radar Topography Mission (SRTM) supplied the elevation, U. S. Geological Survey digital aerial photography provided the image detail, and the Landsat Thematic Mapper provided the color. The United States Geological Survey's Earth Resources Observations Systems (EROS) Data Center, Sioux Falls, South Dakota, provided the Landsat data and the aerial photography. The image can be viewed in 3-D by viewing the left image with the right eye and the right image with the left eye (cross-eyed viewing), or by downloading and printing the image pair, and viewing them with a stereoscope.

    The Shuttle Radar Topography Mission (SRTM), launched on February 11, 2000, used the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) that flew twice on the Space Shuttle Endeavour in 1994. The mission was designed to collect three-dimensional measurements of the Earth's surface. To collect the 3-D data, engineers added a 60-meter-long (200-foot) mast, an additional C-band imaging antenna and improved tracking and navigation devices. The mission is a cooperative project between the National Aeronautics and Space Administration

  1. African easterly wave energetics on intraseasonal timescales

    NASA Astrophysics Data System (ADS)

    Alaka, Ghassan J., Jr.

    African easterly waves (AEWs) are synoptic-scale eddies that dominate North African weather in boreal summer. AEWs propagate westward with a maximum amplitude near 700 hPa and a period of 2.5-6-days. AEWs and associated perturbation kinetic energy (PKE) exhibit significant intraseasonal variability in tropical North Africa during boreal summer, which directly impacts local agriculture and tropical cyclogenesis. This study performs a comprehensive analysis of the 30-90-day variability of AEWs and associated energetics using both reanalysis data and model output. Specifically, the PKE and perturbation available potential energy (PAPE) budgets are used to understand the factors that contribute to PKE maxima in West Africa and the extent to which these surges of AEW activity are modulated by the Madden-Julian oscillation (MJO). The role of the MJO in the intraseasonal variability of AEWs is assessed by comparing PKE sources as a function of an MJO index and a local 30-90-day West African PKE index. Since East Africa is an initiation zone for AEW activity and is modulated by the MJO, the relationship between this region and West Africa is a primary focus in this study. The intraseasonal variability of AEW energetics is first investigated in reanalysis products. While reanalysis data depicts a similar evolution of 30-90-day PKE anomalies in both the MJO and a local PKE index, the MJO index describes only a small (yet still significant) fraction of the local 30-90-day variance. In boreal summers with more significant MJO days, the correlation between the two indices is higher. Baroclinic energy conversions are important for the initiation of 30-90-day West African PKE events east of Lake Chad. In West Africa, both barotropic and baroclinic energy conversions maintain positive PKE anomalies before they propagate into the Atlantic. The primary role of diabatic heating is to destroy PAPE in a negative feedback to baroclinic energy conversions in West Africa. More frequent

  2. Pygmy stars: first pair.

    PubMed

    Zwicky, F

    1966-07-01

    The binary LP 101-15/16 having the proper motion of 1.62 seconds of arc per year has been studied with the prime-focus spectrograph of the 200-inch (508 cm) telescope. Indications are that LP 101-15/16 is the first pair of pygmy stars ever discovered. One of its components, LP 101-16, is probably a blue pygmy star which is at least four magnitudes fainter than the ordinary white dwarfs. Also, two of the Balmer lines in absorption appear to be displaced toward the red by amounts which indicate the existence of an Einstein gravitational red shift corresponding to about 1000 km sec-1. On the other hand LP 101-15 is red and shows an entirely new type of spectrum, which suggests that it may be a first representative of a type of red pygmy star which is 2.5 magnitudes fainter than the M-type dwarf stars of the main sequence.

  3. Models of charge pair generation in organic solar cells.

    PubMed

    Few, Sheridan; Frost, Jarvist M; Nelson, Jenny

    2015-01-28

    Efficient charge pair generation is observed in many organic photovoltaic (OPV) heterojunctions, despite nominal electron-hole binding energies which greatly exceed the average thermal energy. Empirically, the efficiency of this process appears to be related to the choice of donor and acceptor materials, the resulting sequence of excited state energy levels and the structure of the interface. In order to establish a suitable physical model for the process, a range of different theoretical studies have addressed the nature and energies of the interfacial states, the energetic profile close to the heterojunction and the dynamics of excited state transitions. In this paper, we review recent developments underpinning the theory of charge pair generation and phenomena, focussing on electronic structure calculations, electrostatic models and approaches to excited state dynamics. We discuss the remaining challenges in achieving a predictive approach to charge generation efficiency.

  4. Satellite observations and instrumentation for measuring energetic neutral atoms

    SciTech Connect

    Voss, H.D.; Mobilia, J.; Collin, H.L.; Imhof, W.L. . Space Sciences Lab.)

    1993-12-01

    Direct measurements of energetic neutral atoms (ENA) and ions have been obtained with the cooled solid state detectors on the low-altitude (220 km) three-axis stabilized S81-1/ stimulated emissions of energetic particles (SEEP) satellite and on the spinning 400 km [times] 5.5 R[sub e] (where R[sub e] is Earth radii) Combined Release and Radiation Effects Satellite (CRRES). During magnetic storms ENA and ion precipitation (E > 10 keV) are evident over the low-altitude equatorial region based on data from the SEEP (ONR 804) spectrometers and CRRES ion mass spectrometer (IMS-HI) (ONR 307-8-3) ion composition and ENA instrument. The IMS-HI neutral atom spectrometer covers the energy range from 20 to 1,500 keV with a geometrical factor of 10[sub [minus]3] cm[sup 2] sr and uses a 7-kG magnetic field to screen out protons less than about 50 MeV. During the strong magnetic storm of 24 March 1991 the first ENA and ion mass composition measurements were obtained of ring current particles below the inner belt and these fluxes are compared to the IMS-HI flux measurements in the ring current. Recently, an advanced spectrometer, the Source/Loss-cone Energetic Particle Spectrometer (SEPS), has been developed to image electrons, ions, and neutrals on the despun platform of the POLAR satellite ([approximately]1.8 [times] 9 R[sub e]) for launch in the mid 1990s as part of NASA's International Solar Terrestrial Physics/Global Geospace Science (ISTP/GGS) program.

  5. Energetic-ion-driven global instabilities in stellarator/helical plasmas and comparison with tokamak plasmas

    SciTech Connect

    Toi, K.; Ogawa, K.; Isobe, M.; Osakabe, M.; Spong, Donald A; Todo, Yasushi

    2011-01-01

    Comprehensive understanding of energetic-ion-driven global instabilities such as Alfven eigenmodes (AEs) and their impact on energetic ions and bulk plasma is crucially important for tokamak and stellarator/helical plasmas and in the future for deuterium-tritium (DT) burning plasma experiments. Various types of global modes and their associated enhanced energetic ion transport are commonly observed in toroidal plasmas. Toroidicity-induced AEs and ellipticity-induced AEs, whose gaps are generated through poloidal mode coupling, are observed in both tokamak and stellarator/helical plasmas. Global AEs and reversed shear AEs, where toroidal couplings are not as dominant were also observed in those plasmas. Helicity induced AEs that exist only in 3D plasmas are observed in the large helical device (LHD) and Wendelstein 7 Advanced Stellarator plasmas. In addition, the geodesic acoustic mode that comes from plasma compressibility is destabilized by energetic ions in both tokamak and LHD plasmas. Nonlinear interaction of these modes and their influence on the confinement of the bulk plasma as well as energetic ions are observed in both plasmas. In this paper, the similarities and differences in these instabilities and their consequences for tokamak and stellarator/helical plasmas are summarized through comparison with the data sets obtained in LHD. In particular, this paper focuses on the differences caused by the rotational transform profile and the 2D or 3D geometrical structure of the plasma equilibrium. Important issues left for future study are listed.

  6. Energetic particles detected by the Electron Reflectometer instrument on the Mars Global Surveyor, 1999-2006

    NASA Astrophysics Data System (ADS)

    Delory, Gregory T.; Luhmann, Janet G.; Brain, David; Lillis, Robert J.; Mitchell, David L.; Mewaldt, Richard A.; Falkenberg, Thea Vilstrup

    2012-06-01

    We report the observation of galactic cosmic rays and solar energetic particles by the Electron Reflectometer instrument aboard the Mars Global Surveyor (MGS) spacecraft from May of 1999 to the mission conclusion in November 2006. Originally designed to detect low-energy electrons, the Electron Reflectometer also measured particles with energies >30 MeV that penetrated the aluminum housing of the instrument and were detected directly by microchannel plates in the instrument interior. Using a combination of theoretical and experimental results, we show how the Electron Reflectometer microchannel plates recorded high energy galactic cosmic rays with ˜45% efficiency. Comparisons of this data to galactic cosmic ray proton fluxes obtained from the Advanced Composition Explorer yield agreement to within 10% and reveal the expected solar cycle modulation as well as shorter timescale variations. Solar energetic particles were detected by the same mechanism as galactic cosmic rays; however, their flux levels are far more uncertain due to shielding effects and the energy-dependent response of the microchannel plates. Using the solar energetic particle data, we have developed a catalog of energetic particle events at Mars associated with solar flares and coronal mass ejections, which includes the identification of interplanetary shocks. MGS observations of energetic particles at varying geometries between the Earth and Mars that include shocks produced by halo, limb, and backsided events provide a unique data set for use by the heliophysics modeling community.

  7. Energetic-ion-driven global instabilities in stellarator/helical plasmas and comparison with tokamak plasmas

    NASA Astrophysics Data System (ADS)

    Toi, K.; Ogawa, K.; Isobe, M.; Osakabe, M.; Spong, D. A.; Todo, Y.

    2011-02-01

    Comprehensive understanding of energetic-ion-driven global instabilities such as Alfvén eigenmodes (AEs) and their impact on energetic ions and bulk plasma is crucially important for tokamak and stellarator/helical plasmas and in the future for deuterium-tritium (DT) burning plasma experiments. Various types of global modes and their associated enhanced energetic ion transport are commonly observed in toroidal plasmas. Toroidicity-induced AEs and ellipticity-induced AEs, whose gaps are generated through poloidal mode coupling, are observed in both tokamak and stellarator/helical plasmas. Global AEs and reversed shear AEs, where toroidal couplings are not as dominant were also observed in those plasmas. Helicity induced AEs that exist only in 3D plasmas are observed in the large helical device (LHD) and Wendelstein 7 Advanced Stellarator plasmas. In addition, the geodesic acoustic mode that comes from plasma compressibility is destabilized by energetic ions in both tokamak and LHD plasmas. Nonlinear interaction of these modes and their influence on the confinement of the bulk plasma as well as energetic ions are observed in both plasmas. In this paper, the similarities and differences in these instabilities and their consequences for tokamak and stellarator/helical plasmas are summarized through comparison with the data sets obtained in LHD. In particular, this paper focuses on the differences caused by the rotational transform profile and the 2D or 3D geometrical structure of the plasma equilibrium. Important issues left for future study are listed.

  8. SDSS DR2 Merging pairs

    NASA Astrophysics Data System (ADS)

    Allam, S. S.; Tucker, D. L.; SDSS Collaboration

    2004-05-01

    We present and analyze a catalog of 9,000 Merging pairs candidates to g=21 from the imaging data of the Sloan Digital Sky Survey (SDSS) Second Data Release (DR2). Candidates were selected using an automated algorithm (Allam et al. 2004) that is efficient in its selection of galaxy pairs. We highlight possible science applications of such a large photometric sample of merging pais and discuss future improvements, including incorporating magnitudes and pushing to higher redshifts and fainter pairs.

  9. Coronal Dimmings and Energetic CMEs

    NASA Technical Reports Server (NTRS)

    Thompson, B. J.; Cliver, E. W.; Nitta, N.; Delannee, C.; Delaboudiniere, J.-P.

    1999-01-01

    We have analyzed the coronal dimmings for seven fast (> 600 km/s) coronal mass ejections (CMEs) occurring between 23 April and 9 May which were associated with flares from NOAA active region (AR) 8210. These dimming regions were identified by their strong depletion in coronal emission within a half hour of the estimated time of CME lift-off. They included areas which were as dark as quiescent coronal holes as well as other regions with weaker brightness depletions. We found that the extended dimming areas in these events generally mapped out the apparent "footprint" of the CME. In two of the seven cases, a pair of dimmings were more or less symmetrically positioned north and south of the flare site. In the five remaining cases, the dimmings were most prominent to the north of AR 8210 (approximately S15 latitude) and extended well north of the solar equator, consistent with the locations of the CMEs. We discuss the implications of these results for the sigmoid/double dimming/flux rope model of CMEs.

  10. Controversies in kidney paired donation.

    PubMed

    Gentry, Sommer E; Montgomery, Robert A; Segev, Dorry L

    2012-07-01

    Kidney paired donation represented 10% of living kidney donation in the United States in 2011. National registries around the world and several separate registries in the United States arrange paired donations, although with significant variations in their practices. Concerns about ethical considerations, clinical advisability, and the quantitative effectiveness of these approaches in paired donation result in these variations. For instance, although donor travel can be burdensome and might discourage paired donation, it was nearly universal until convincing analysis showed that living donor kidneys can sustain many hours of cold ischemia time without adverse consequences. Opinions also differ about whether the last donor in a chain of paired donation transplants initiated by a nondirected donor should donate immediately to someone on the deceased donor wait-list (a domino or closed chain) or should be asked to wait some length of time and donate to start another sequence of paired donations later (an open chain); some argue that asking the donor to donate later may be coercive, and others focus on balancing the probability that the waiting donor withdraws versus the number of additional transplants if the chain can be continued. Other controversies in paired donation include simultaneous versus nonsimultaneous donor operations, whether to enroll compatible pairs, and interactions with desensitization protocols. Efforts to expand public awareness of and participation in paired donation are needed to generate more transplant opportunities.

  11. Cryocycling of energetic materials: Status report for FY94

    SciTech Connect

    Lipkin, J.; Kasberg, D.; Whinnery, L.; Handrock, J.; Revelli, V.; Weingarten, L.; Griffiths, S.; Nilson, R.

    1995-07-01

    The Cryocycling of Energetic Materials Project is sponsored by the Memorandum of Understanding (MOU) on advanced munition technologies. This MOU is an agreement between the Department of Energy and the Department of Defense (Office of Munitions) that facilitates the development of technologies of mutual interest to the two Departments. The cryocycling project is one of several that focus on demilitarization aspects of conventional weapons and weapon systems. During FY94 the project pursued the development of analytical and numerical models that can be used to describe and optimize the cryocycling process for preparing energetic materials for recycle and reuse. In addition, the demilitarization stockpile of the Department of Defense was analyzed to identify candidate munitions for the process, and pilot scale cryocycling operations were begun at an industrial contractor. When a material is cryocycled, it is repeatedly subjected to cycles of rapid cooling in a liquid nitrogen bath at 77 K followed by warming to ambient temperature. In laboratory and pilot scale demonstrations, the authors have shown that cryocycling can dramatically reduce the size of a variety of propellant grains and a number of cast and plastic bonded explosives.

  12. The composition of heavy ions in solar energetic particle events

    NASA Technical Reports Server (NTRS)

    Fan, C. Y.; Gloeckler, G.; Hovestadt, D.

    1983-01-01

    Recent advances in determining the elemental, charge state, and isotopic composition of or approximate to 1 to or approximate to 20 MeV per nucleon ions in solar energetic particle (SEP) events and outline our current understanding of the nature of solar and interplanetary processes which may explain the observations. Average values of relative abundances measured in a large number of SEP events were found to be roughly energy independent in the approx. 1 to approx. 20 MeV per nucleon range, and showed a systematic deviation from photospheric abundances which seems to be organized in terms of the first ionization potential of the ion. Direct measurements of the charge states of SEPs revealed the surprisingly common presence of energetic He(+) along with heavy ion with typically coronal ionization states. High resolution measurements of isotopic abundance ratios in a small number of SEP events showed these to be consistent with the universal composition except for the puzzling overabundance of the SEP(22)Ne/(20)Ne relative to this isotopes ratio in the solar wind. The broad spectrum of observed elemental abundance variations, which in their extreme result in composition anomalies characteristic of (3)He rich, heavy ion rich and carbon poor SEP events, along with direct measurements of the ionization states of SEPs provided essential information on the physical characteristics of, and conditions in the source regions, as well as important constraints to possible models for SEP production.

  13. Laser Ignition of Energetic Materials Workshop

    NASA Astrophysics Data System (ADS)

    Devries, Nora M.; Oreilly, John J.; Forch, Brad E.

    1993-11-01

    Lasers inherently possess many desirable attributes making them excellent igniters for a wide range of energetic materials such as pyrotechnics, explosives, and gun propellants. Lasers can be made very small, have modest powereD requirements, are invulnerable to external stimuli, are very reliable, and can deliver radiative energy to remote locations through optical fibers. Although the concept of using lasers for the initiation of energetic materials is not new, successful integration of laser technology into military systems has the potential to provide significant benefits. In order to efficiently expedite the evolution of the laser ignition technology for military applications, it was desirable to coordinate the effort with the JANNAF combustion community. The laser ignition of Energetic Materials Workshop was originated by Brad Forch, Austin Barrows, Richard Beyer and Arthur Cohen of the Army Research Laboratory (ARL).

  14. Sol-gel processing of energetic materials

    SciTech Connect

    Tillotson, T.M.; Hrubesh, L.H.; Fox, G.L.; Simpson, R.L.; Lee, R.W.; Swansiger, R.W.; Simpson, L.R.

    1997-08-18

    As part of a new materials effort, we are exploring the use of sol- gel chemistry to manufacture energetic materials. Traditional manufacturing of energetic materials involves processing of granular solids. One application is the production of detonators where powders of energetic material and a binder are typically mixed and compacted at high pressure to make pellets. Performance properties are strongly dependent on particle size distribution, surface area of its constituents, homogeneity of the mix, and void volume. The goal is to produce detonators with fast energy release rate the are insensitive to unintended initiation. In this paper, we report results of our early work in this field of research, including the preparation of detonators from xerogel molding powders and aerogels, comparing the material properties with present state-of-the-art technology.

  15. Viewing perspective in energetic neutral atom intensity

    NASA Astrophysics Data System (ADS)

    Zheng, Yihua; Lui, Anthony T. Y.; Fok, Mei-Ching

    2008-09-01

    Through interspacecraft comparison of energetic neutral oxygen (ENO) intensity from two different vantage points provided by IMAGE and Geotail, Lui et al. (2005) showed that viewing perspective plays a very important role in the observed ENO intensity level during a magnetic storm period. Motivated by the findings of Lui et al. (2005), we investigate how viewing perspective influences energetic neutral atom emissions from a modeling perspective. The main results of this paper are that (1) our simulation results, based upon O+ ion fluxes from the Comprehensive Ring Current Model and the subsequent ENO calculation, reproduce the total differential ENO intensity obtained from two spacecraft to a reasonable degree and (2) further analysis of our results indicates that pitch angle anisotropy in ring current ion flux, a crucial physical quantity in ring current dynamics, is one major contributor to the difference in energetic neutral atom intensity from different viewing perspectives.

  16. Binaries and triples among asteroid pairs

    NASA Astrophysics Data System (ADS)

    Pravec, Petr; Scheirich, Peter; Kušnirák, Peter; Hornoch, Kamil; Galád, Adrián

    2015-08-01

    Despite major achievements obtained during the past two decades, our knowledge of the population and properties of small binary and multiple asteroid systems is still far from advanced. There is a numerous indirect evidence for that most small asteroid systems were formed by rotational fission of cohesionless parent asteroids that were spun up to the critical frequency presumably by YORP, but details of the process are lacking. Furthermore, as we proceed with observations of more and more binary and paired asteroids, we reveal new facts that substantially refine and sometimes change our understanding of the asteroid systems. One significant new finding we have recently obtained is that primaries of many asteroid pairs are actually binary or triple systems. The first such case found is (3749) Balam (Vokrouhlický, ApJL 706, L37, 2009). We have found 9 more binary systems among asteroid pairs within our ongoing NEOSource photometric project since October 2012. They are (6369) 1983 UC, (8306) Shoko, (9783) Tensho-kan, (10123) Fideoja, (21436) Chaoyichi, (43008) 1999 UD31, (44620) 1999 RS43, (46829) 1998 OS14 and (80218) 1999 VO123. We will review their characteristics. These paired binaries as we call them are mostly similar to binaries in the general ("background") population (of unpaired asteroids), but there are a few trends. The paired binaries tend to have larger secondaries with D_2/D_1 = 0.3 to 0.5 and they also tend to be wider systems with 8 of the 10 having orbital periods between 30 and 81 hours, than average among binaries in the general population. There may be also a larger fraction of triples; (3749) Balam is a confirmed triple, having a larger close and a smaller distant satellite, and (8306) Shoko and (10123) Fideoja are suspect triples as they show additional rotational lightcurve components with periods of 61 and 38.8 h that differ from the orbital period of 36.2 and 56.5 h, respectively. The unbound secondaries tend to be of the same size or

  17. Evaluation of water displacement energetics in protein binding sites with grid cell theory.

    PubMed

    Gerogiokas, G; Southey, M W Y; Mazanetz, M P; Heifetz, A; Hefeitz, A; Bodkin, M; Law, R J; Michel, J

    2015-04-07

    Excess free energies, enthalpies and entropies of water in protein binding sites were computed via classical simulations and Grid Cell Theory (GCT) analyses for three pairs of congeneric ligands in complex with the proteins scytalone dehydratase, p38α MAP kinase and EGFR kinase respectively. Comparative analysis is of interest since the binding modes for each ligand pair differ in the displacement of one binding site water molecule, but significant variations in relative binding affinities are observed. Protocols that vary in their use of restraints on protein and ligand atoms were compared to determine the influence of protein-ligand flexibility on computed water structure and energetics, and to assess protocols for routine analyses of protein-ligand complexes. The GCT-derived binding affinities correctly reproduce experimental trends, but the magnitude of the predicted changes in binding affinities is exaggerated with respect to results from a previous Monte Carlo Free Energy Perturbation study. Breakdown of the GCT water free energies into enthalpic and entropic components indicates that enthalpy changes dominate the observed variations in energetics. In EGFR kinase GCT analyses revealed that replacement of a pyrimidine by a cyanopyridine perturbs water energetics up three hydration shells away from the ligand.

  18. Spectral and temporal changes to speech produced in the presence of energetic and informational maskers.

    PubMed

    Cooke, Martin; Lu, Youyi

    2010-10-01

    Talkers change the way they speak in noisy conditions. For energetic maskers, speech production changes are relatively well-understood, but less is known about how informational maskers such as competing speech affect speech production. The current study examines the effect of energetic and informational maskers on speech production by talkers speaking alone or in pairs. Talkers produced speech in quiet and in backgrounds of speech-shaped noise, speech-modulated noise, and competing speech. Relative to quiet, speech output level and fundamental frequency increased and spectral tilt flattened in proportion to the energetic masking capacity of the background. In response to modulated backgrounds, talkers were able to reduce substantially the degree of temporal overlap with the noise, with greater reduction for the competing speech background. Reduction in foreground-background overlap can be expected to lead to a release from both energetic and informational masking for listeners. Passive changes in speech rate, mean pause length or pause distribution cannot explain the overlap reduction, which appears instead to result from a purposeful process of listening while speaking. Talkers appear to monitor the background and exploit upcoming pauses, a strategy which is particularly effective for backgrounds containing intelligible speech.

  19. The energetic costs of stereotyped behavior in the paper wasp, Polistes dominulus

    NASA Astrophysics Data System (ADS)

    Weiner, Susan A.; Woods, William A.; Starks, Philip T.

    2009-02-01

    Polistes wasps engage in many behavioral interactions. Although there has been debate over the meaning of these interactions, these stereotypical behaviors can be used to determine a colony’s linear dominance hierarchy. Due to the implicit relationship between behavioral and reproductive dominance, behavioral interactions are commonly used to distinguish the reproductively dominant alpha foundress from the beta foundress. It has been suggested that in order to maintain reproductive control, the alpha foundress is forced to remain at a physiologically constrained activity limit. This, in turn, may allow aggressive interactions to be used as determinants influencing reproductive partitioning between cooperating individuals. Energetic costs can place important limitations on behavior, but the energetic cost of the interactions has not previously been measured. To address this, we measured the CO2 production of 19 non-nestmate pairs displaying interactive and noninteractive behavior. The rate of energy used during interaction behavior was positively associated with published rankings of aggression. However, our results indicate that interactions are not very energetically costly in Polistes, particularly when compared to the likely cost of foraging. These data suggest that maintaining reproductive dominance is not very energetically expensive for the dominant and that the dominant foundress expends energy at a lower rate than the subordinate foundress.

  20. Novel Energetic Materials for Counter WMD Applications

    DTIC Science & Technology

    2011-09-01

    derivatives Dense high nitrogen molecular and ionic materials A. Structure and synthesis of energetic salts ofN, N’ -dinitrourea (DNU) B. Impact...Engineering Data, 2008, 53(2), 520-524. Ye, C.; Gao, H.; Twamley, B.; Shreeve, J. M. " Structure and Synthesis of Energetic Salts ofN, N’ -dinitrourea...N Y (~+ ~SFs 2a-c NH2 N y ~ " N-N~ \\-sFs 4a-c Q y- N ~SFs 6a Structure and Properties ofSFs-containing Salts Cation Anion No. Td d 6

  1. Electronic pairing in exotic superconductors

    SciTech Connect

    Cox, D.L. ); Maple, M.B. )

    1995-02-01

    Superconductivity in heavy-fermion materials and high T[sub c] cuprates may involve electronic pairing with unconventional symmetries and mechanisms. Although there has been no smoking-gun proof, numerous pieces of circumstantial evidence combined with heuristic theoretical arguments make a compelling case that these materials have pairs with exotic symmetry bound by nonphonon glue. 20 refs., 5 figs.

  2. Finite-Time Shock Acceleration of Energetic Storm Particles

    NASA Astrophysics Data System (ADS)

    Channok, Chanruangrit; Ruffolo, David; Desai, Mihir I.; Mason, Glenn M.

    2005-11-01

    Energetic storm particles (ESPs) of various ion species have been shown to arise from suprathermal seed ions accelerated by traveling interplanetary (IP) shocks. The observed spectral rollovers at ~0.1-10 MeV nucleon-1 can be attributed to the finite time available for shock acceleration. Using the locally measured shock strength parameters as inputs, the finite-time shock acceleration model can successfully fit the energy spectra of carbon, oxygen, and iron ions measured by the Ultra Low Energy Isotope Spectrometer (ULEIS) on board the Advanced Composition Explorer (ACE) during three ESP events. The inferred scattering mean free path in the acceleration region ranges from a typical IP value for the weakest ESP event down to 3.0×10-3 AU for the strongest event. This is consistent with the idea that proton-amplified waves result from the very intense particle fluxes in major events.

  3. Study on Solar Energetic proton (SEP) Prediction using Regression Technique

    NASA Astrophysics Data System (ADS)

    Yoon, KiChang; Kim, Jae-Hun; Kim, Young Yun; Kwon, Yongki; Wi, Gwan-sik

    2016-07-01

    It is well known that Solar Energetic Proton (SEP) can cause significant effects on electric devices in satellite such as displacement damage and single event effect. It can be dangerous to flight crew/passenger flying high altitude with polar route, and therefore, it is essential that it should be predicted in advance to mitigate radiation exposure risk. However, SEP has been hard to predict, because it is not well-connected solar activities such as solar flare, coronal mass ejection (CME). In this study, we analyzed the variation pattern of proton event from 2000 to 2015, and suggested optimum Gaussian function which can well describe the maximum value of previous event, after then, we finally adopted the regression technique to predict SEP value repetitively. This paper shows that the maximum value and duration of ongoing SEP events can be well predicted, but this model typically has large errors in case of predicting starting point and occurrence of SEP events.

  4. Chemical Dynamics, Molecular Energetics, and Kinetics at the Synchrotron

    SciTech Connect

    Leone, Stephen R.; Ahmed, Musahid; Wilson, Kevin R.

    2010-03-14

    Scientists at the Chemical Dynamics Beamline of the Advanced Light Source in Berkeley are continuously reinventing synchrotron investigations of physical chemistry and chemical physics with vacuum ultraviolet light. One of the unique aspects of a synchrotron for chemical physics research is the widely tunable vacuum ultraviolet light that permits threshold ionization of large molecules with minimal fragmentation. This provides novel opportunities to assess molecular energetics and reaction mechanisms, even beyond simple gas phase molecules. In this perspective, significant new directions utilizing the capabilities at the Chemical Dynamics Beamline are presented, along with an outlook for future synchrotron and free electron laser science in chemical dynamics. Among the established and emerging fields of investigations are cluster and biological molecule spectroscopy and structure, combustion flame chemistry mechanisms, radical kinetics and product isomer dynamics, aerosol heterogeneous chemistry, planetary and interstellar chemistry, and secondary neutral ion-beam desorption imaging of biological matter and materials chemistry.

  5. Homologous pairing and the role of pairing centers in meiosis.

    PubMed

    Tsai, Jui-He; McKee, Bruce D

    2011-06-15

    Homologous pairing establishes the foundation for accurate reductional segregation during meiosis I in sexual organisms. This Commentary summarizes recent progress in our understanding of homologous pairing in meiosis, and will focus on the characteristics and mechanisms of specialized chromosome sites, called pairing centers (PCs), in Caenorhabditis elegans and Drosophila melanogaster. In C. elegans, each chromosome contains a single PC that stabilizes chromosome pairing and initiates synapsis of homologous chromosomes. Specific zinc-finger proteins recruited to PCs link chromosomes to nuclear envelope proteins--and through them to the microtubule cytoskeleton--thereby stimulating chromosome movements in early prophase, which are thought to be important for homolog sorting. This mechanism appears to be a variant of the 'telomere bouquet' process, in which telomeres cluster on the nuclear envelope, connect chromosomes through nuclear envelope proteins to the cytoskeleton and lead chromosome movements that promote homologous synapsis. In Drosophila males, which undergo meiosis without recombination, pairing of the largely non-homologous X and Y chromosomes occurs at specific repetitive sequences in the ribosomal DNA. Although no other clear examples of PC-based pairing mechanisms have been described, there is evidence for special roles of telomeres and centromeres in aspects of chromosome pairing, synapsis and segregation; these roles are in some cases similar to those of PCs.

  6. Towards laboratory produced relativistic electron–positron pair plasmas

    SciTech Connect

    Chen, Hui; Meyerhofer, D. D.; Wilks, S. C.; Cauble, R.; Dollar, F.; Falk, K.; Gregori, G.; Hazi, A.; Moses, E. I.; Murphy, C. D.; Myatt, J.; Park, J.; Seely, J.; Shepherd, R.; Spitkovsky, A.; Stoeckl, C.; Szabo, C. I.; Tommasini, R.; Zulick, C.; Beiersdorfer, P.

    2011-12-01

    We review recent experimental results on the path to producing electron–positron pair plasmas using lasers. Relativistic pair-plasmas and jets are believed to exist in many astrophysical objects and are often invoked to explain energetic phenomena related to Gamma Ray Bursts and Black Holes. On earth, positrons from radioactive isotopes or accelerators are used extensively at low energies (sub-MeV) in areas related to surface science positron emission tomography and basic antimatter science. Experimental platforms capable of producing the high-temperature pair-plasma and high-flux jets required to simulate astrophysical positron conditions have so far been absent. In the past few years, we performed extensive experiments generating positrons with intense lasers where we found that relativistic electron and positron jets are produced by irradiating a solid gold target with an intense picosecond laser pulse. The positron temperatures in directions parallel and transverse to the beam both exceeded 0.5 MeV, and the density of electrons and positrons in these jets are of order 1016 cm-3 and 1013 cm-3, respectively. With the increasing performance of high-energy ultra-short laser pulses, we expect that a high-density, up to 1018 cm-3, relativistic pair-plasma is achievable, a novel regime of laboratory-produced hot dense matter.

  7. Base pairing and base mis-pairing in nucleic acids

    NASA Technical Reports Server (NTRS)

    Wang, A. H. J.; Rich, A.

    1986-01-01

    In recent years we have learned that DNA is conformationally active. It can exist in a number of different stable conformations including both right-handed and left-handed forms. Using single crystal X-ray diffraction analysis we are able to discover not only additional conformations of the nucleic acids but also different types of hydrogen bonded base-base interactions. Although Watson-Crick base pairings are the predominant type of interaction in double helical DNA, they are not the only types. Recently, we have been able to examine mismatching of guanine-thymine base pairs in left-handed Z-DNA at atomic resolution (1A). A minimum amount of distortion of the sugar phosphate backbone is found in the G x T pairing in which the bases are held together by two hydrogen bonds in the wobble pairing interaction. Because of the high resolution of the analysis we can visualize water molecules which fill in to accommodate the other hydrogen bonding positions in the bases which are not used in the base-base interactions. Studies on other DNA oligomers have revealed that other types of non-Watson-Crick hydrogen bonding interactions can occur. In the structure of a DNA octamer with the sequence d(GCGTACGC) complexed to an antibiotic triostin A, it was found that the two central AT base pairs are held together by Hoogsteen rather than Watson-Crick base pairs. Similarly, the G x C base pairs at the ends are also Hoogsteen rather than Watson-Crick pairing. Hoogsteen base pairs make a modified helix which is distinct from the Watson-Crick double helix.

  8. Stereo Pair, Patagonia, Argentina

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This view of northern Patagonia, at Los Menucos, Argentina shows remnants of relatively young volcanoes built upon an eroded plain of much older and contorted volcanic, granitic, and sedimentary rocks. The large purple, brown, and green 'butterfly' pattern is a single volcano that has been deeply eroded. Large holes on the volcano's flanks indicate that they may have collapsed soon after eruption, as fluid molten rock drained out from under its cooled and solidified outer shell. At the upper left, a more recent eruption occurred and produced a small volcanic cone and a long stream of lava, which flowed down a gully. At the top of the image, volcanic intrusions permeated the older rocks resulting in a chain of small dark volcanic peaks. At the top center of the image, two halves of a tan ellipse pattern are offset from each other. This feature is an old igneous intrusion that has been split by a right-lateral fault. The apparent offset is about 6.6 kilometers (4 miles). Color, tonal, and topographic discontinuities reveal the fault trace as it extends across the image to the lower left. However, young unbroken basalt flows show that the fault has not been active recently.

    This cross-eyed stereoscopic image pair was generated using topographic data from the Shuttle Radar Topography Mission, combined with an enhanced Landsat 7satellite color image. The topography data are used to create two differing perspectives of a single image, one perspective for each eye. In doing so, each point in the image is shifted slightly, depending on its elevation. When stereoscopically merged, the result is a vertically exaggerated view of the Earth's surface in its full three dimensions.

    Landsat satellites have provided visible light and infrared images of the Earth continuously since 1972. SRTM topographic data match the 30-meter (99-foot) spatial resolution of most Landsat images and provide a valuable complement for studying the historic and growing Landsat data archive

  9. Stereo Pair: Patagonia, Argentina

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This view of northern Patagonia, near El Cain, Argentina shows complexly eroded volcanic terrain, with basalt mesas, sinkholes, landslide debris, playas, and relatively few integrated drainage channels. Surrounding this site (but also extending far to the east) is a broad plateau capped by basalt, the Meseta de Somuncura. Here, near the western edge of the plateau, erosion has broken through the basalt cap in a variety of ways. On the mesas, water-filled sinkholes (lower left) are most likely the result of the collapse of old lava tubes. Along the edges of the mesas (several locations) the basalt seems to be sliding away from the plateau in a series of slices. Water erosion by overland flow is also evident, particularly in canyons where vegetation blankets the drainage channels (green patterns, bottom of image). However, overland water flow does not extend very far at any location. This entire site drains to local playas, some of which are seen here (blue). While the water can reach the playas and then evaporate, what becomes of the eroded rock debris? Wind might excavate some of the finer eroded debris, but the fate of much of the missing bedrock remains mysterious.

    This cross-eyed stereoscopic image pair was generated using topographic data from the Shuttle Radar Topography Mission, combined with an enhanced Landsat 7 satellite color image. The topography data are used to create two differing perspectives of a single image, one perspective for each eye. In doing so, each point in the image is shifted slightly, depending on its elevation. When stereoscopically merged, the result is a vertically exaggerated view of the Earth's surface in its full three dimensions.

    Landsat satellites have provided visible light and infrared images of the Earth continuously since 1972. SRTM topographic data match the 30-meter (99-foot) spatial resolution of most Landsat images and provide a valuable complement for studying the historic and growing Landsat data archive. The

  10. Pair fireball precursors of neutron star mergers

    NASA Astrophysics Data System (ADS)

    Metzger, Brian D.; Zivancev, Charles

    2016-10-01

    If at least one neutron star (NS) is magnetized in a binary NS merger, then the orbital motion of the conducting companion during the final inspiral induces a strong voltage and current along the magnetic field lines connecting the NSs. If a modest fraction η of the extracted electromagnetic power extracted accelerates relativistic particles, the resulting gamma-ray emission a compact volume will result in the formation of an electron-positron pair fireball. Applying a steady-state pair wind model, we quantify the detectability of the precursor fireball with gamma-ray satellites. For η ˜ 1 the gamma-ray detection horizon of Dmax ≈ 10(Bd/1014 G)3/4 Mpc is much closer than the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO)/Virgo horizon of 200 Mpc, unless the NS surface magnetic field strength is very large, B_d ≲ 10^{15} G. Given the quasi-isotropic nature of the emission, mergers with weaker NS fields could contribute a nearby population of short gamma-ray bursts. Power not dissipated close to the binary is carried to infinity along the open field lines by a large-scale Poynting flux. Reconnection within this outflow, well outside of the pair photosphere, provides a potential site for non-thermal emission, such as a coherent millisecond radio burst.

  11. Energetics of the Semiconductor-Electrolyte Interface.

    ERIC Educational Resources Information Center

    Turner, John A.

    1983-01-01

    The use of semiconductors as electrodes for electrochemistry requires an understanding of both solid-state physics and electrochemistry, since phenomena associated with both disciplines are seen in semiconductor/electrolyte systems. The interfacial energetics of these systems are discussed. (JN)

  12. Energetics of geostrophic adjustment in rotating flow

    NASA Astrophysics Data System (ADS)

    Fang, J.; Wu, R. S.

    2002-09-01

    Energetics of geostrophic adjustment in rotating how is examined in detail with a linear shallow water model. The Initial Unbalanced flow considered first falls under two classes. The first is similar to that adopted by Gill and is here referred to as it mass imbalance model, for the flow is initially motionless but with a sea surface displacement. The other is the same as that considered by Rossby and is referred to as I momentum imbalance model since there is only a velocity perturbation in the initial field. The significant feature of the energetics of geostrophic adjustment for the above two extreme models is that althongh the energy conversion ratio has a large case-to-case variability for different initial conditions, Its value is bounded below by 0 and above by 1 / 2. Based on the discussion of the above extreme models, the energetics of adjustment for an arbitrary initial condition is investigated. It is found that the characteristics of the energetics of geostrophic adjustment mentioned above are also applicable to adjustment of the general unbalanced flow under the condition that the energy conversion ratio is redefined as the conversion ratio between the change of kinetic energy and potential energy of the deviational fields.

  13. Pulsed source of energetic atomic oxygen

    NASA Technical Reports Server (NTRS)

    Caledonia, George E.; Krech, Robert H.

    1989-01-01

    A large area, high flux beam of energetic oxygen atoms, E about 5 eV, has been developed to study the interaction of atomic oxygen with materials appropriate for spacecraft in low earth orbit. A description of the operating conditions and characteristics of the beam along with typical sample irradiation results are provided.

  14. Chapter 4: Measuring Energetics of Biological Processes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Measurement of the energetics of biological processes is the key component in understanding the thermodynamic responses of homoeothermic animals to the environment. For these animals to achieve body temperature control, they must adapt to thermal-environmental conditions and variations caused by wea...

  15. Estimating Instantaneous Energetic Cost During Gait Adaptation

    DTIC Science & Technology

    2014-08-31

    Energetic cost, in this context, refers to the input energy required to 23   power the cellular processes underlying the body’s movement. This energy is...entering the body is allowed to reach equilibrium with the rate at which cellular 57   processes are consuming it. By averaging over minutes of data

  16. The Energetic Brain: Understanding and Managing ADHD

    ERIC Educational Resources Information Center

    Reynolds, Cecil R.; Vannest, Kimberly J.; Harrison, Judith R.

    2012-01-01

    ADHD affects millions of people-some 3 to 5% of the general population. Written by a neuroscientist who has studied ADHD, a clinician who has diagnosed and treated it for 30 years, and a special educator who sees it daily, "The Energetic Brain" provides the latest information from neuroscience on how the ADHD brain works and shows how to harness…

  17. The energetics of low browsing in sauropods

    PubMed Central

    Ruxton, Graeme D.; Wilkinson, David M.

    2011-01-01

    It has recently been argued that the probable high cost of travel for sauropod dinosaurs would have made exploiting high forage energetically attractive, if this reduced the need to travel between food patches. This argument was supported by simple calculations. Here, we take a similar approach to evaluate the energetics of foraging close to the ground. We predict that small extensions of the neck beyond the minimum required for the mouth to reach the ground bring substantial energetic savings. Each increment of length brings a further saving, but the sizes of such benefits decrease with increasing neck length. However, the observed neck length of around 9 m for Brachiosaurus (for example) is predicted to reduce the overall cost of foraging by 80 per cent, compared with a minimally necked individual. We argue that the long neck of the sauropods may have been under positive selection for low foraging (instead of, or as well as, exploitation of high foraging), if this long neck allowed a greater area of food to be exploited from a given position and thus reduced the energetically expensive movement of the whole animal. PMID:21429913

  18. Energy Harvesting from Energetic Porous Silicon

    DTIC Science & Technology

    2016-07-01

    ARL-TR-7719 ● JULY 2016 US Army Research Laboratory Energy Harvesting from Energetic Porous Silicon by Louis B Levine, Matthew...it is no longer needed. Do not return it to the originator. ARL-TR-7719 ● JULY 2016 US Army Research Laboratory Energy ...

  19. Error propagation in energetic carrying capacity models

    USGS Publications Warehouse

    Pearse, Aaron T.; Stafford, Joshua D.

    2014-01-01

    Conservation objectives derived from carrying capacity models have been used to inform management of landscapes for wildlife populations. Energetic carrying capacity models are particularly useful in conservation planning for wildlife; these models use estimates of food abundance and energetic requirements of wildlife to target conservation actions. We provide a general method for incorporating a foraging threshold (i.e., density of food at which foraging becomes unprofitable) when estimating food availability with energetic carrying capacity models. We use a hypothetical example to describe how past methods for adjustment of foraging thresholds biased results of energetic carrying capacity models in certain instances. Adjusting foraging thresholds at the patch level of the species of interest provides results consistent with ecological foraging theory. Presentation of two case studies suggest variation in bias which, in certain instances, created large errors in conservation objectives and may have led to inefficient allocation of limited resources. Our results also illustrate how small errors or biases in application of input parameters, when extrapolated to large spatial extents, propagate errors in conservation planning and can have negative implications for target populations.

  20. Energetic electrons generated during solar flares

    NASA Astrophysics Data System (ADS)

    Mann, Gottfried

    2015-12-01

    > electrons are accelerated up to energies beyond 30 keV is one of the open questions in solar physics. A flare is considered as the manifestation of magnetic reconnection in the solar corona. Which mechanisms lead to the production of energetic electrons in the magnetic reconnection region is discussed in this paper. Two of them are described in more detail.

  1. Hedgehog excitations in double-exchange magnetism: Energetics and electronic structure

    NASA Astrophysics Data System (ADS)

    Pekker, David; Goldbart, Paul; Salamon, Myron; Abanov, Alexander

    2004-03-01

    Topological hedgehog excitations of the magnetic state are believed to play an important role in the three-dimensional ferromagnet-to-paramagnet phase transition. This is true not only in Heisenberg magnets but also in double-exchange magnets, for which the transition is accompanied by a metal-insulator transition. The energetics and electronic structure of hedgehog excitations in double-exchange systems are investigated using a model in which the electrons move through a lattice of classical spins, to which they are coupled via Hund's Rule interactions. The core energy of hedgehog excitations is determined, as is the extent to which charge is expelled from the hedgehog cores. In settings involving pairs of hedgehogs, the manner in which the electronic energetics determines the magnetic structure is explored variationally, especially in the region between the hedgehogs.

  2. Development of Metal Cluster-Based Energetic Materials at NSWC-IHD

    DTIC Science & Technology

    2011-01-01

    oxidation is observed [9]. However, the observed decomposition behavior is similar to perfluoroalkyl coated nano-aluminum produced by Dr. Jason Jouet...under the Advanced Energetics Program. REFERENCES 1. Jouet, R. J., et al., “Preparation and Reactivity Analysis of Novel Perfluoroalkyl Coated...Using Perfluoroalkyl Carboxylic Acids.” Chem. Mater., 17, 2987 (2005). 4. Lightstone, J. M.; Patterson, M. J.; Liu, P.; White, M. G., “Reactivity

  3. Energetic particle physics issues for ITER

    SciTech Connect

    Cheng, C.Z.; Budny, R.; Fu, G.Y.

    1996-12-31

    This paper summarizes our present understanding of the following energetic/alpha particle physics issues for the 21 MA, 20 TF coil ITER Interim Design configuration and operational scenarios: (a) toroidal field ripple effects on alpha particle confinement, (b) energetic particle interaction with low frequency MHD modes, (c) energetic particle excitation of toroidal Alfven eigenmodes, and (d) energetic particle transport due to MHD modes. TF ripple effects on alpha loss in ITER under a number of different operating conditions are found to be small with a maximum loss of 1%. With careful plasma control in ITER reversed-shear operation, TF ripple induced alpha loss can be reduced to below the nominal ITER design limit of 5%. Fishbone modes are expected to be unstable for {beta}{sub {alpha}} > 1%, and sawtooth stabilization is lost if the ideal kink growth rate exceeds 10% of the deeply trapped alpha precessional drift frequency evaluated at the q = 1 surface. However, it is expected that the fishbone modes will lead only to a local flattening of the alpha profile due to small banana size. MHD modes observed during slow decrease of stored energy after fast partial electron temperature collapse in JT-60U reversed-shear experiments may be resonant type instabilities; they may have implications on the energetic particle confinement in ITER reversed-shear operation. From the results of various TAE stability code calculations, ITER equilibria appear to lie close to TAE linear stability thresholds. However, the prognosis depends strongly on q profile and profiles of alpha and other high energy particles species. If TAE modes are unstable in ITER, the stochastic diffusion is the main loss mechanism, which scales with ({delta}B{sub r}/B){sup 2}, because of the relatively small alpha particle banana orbit size. For isolated TAE modes the particle loss is very small, and TAE modes saturate via the resonant wave-particle trapping process at very small amplitude.

  4. Pairing Correlations at High Spins

    NASA Astrophysics Data System (ADS)

    Ma, Hai-Liang; Dong, Bao-Guo; Zhang, Yan; Fan, Ping; Yuan, Da-Qing; Zhu, Shen-Yun; Zhang, Huan-Qiao; Petrache, C. M.; Ragnarsson, I.; Carlsson, B. G.

    The pairing correcting energies at high spins in 161Lu and 138Nd are studied by comparing the results of the cranked-Nilsson-Strutinsky (CNS) and cranked-Nilsson-Strutinsky-Bogoliubov (CNSB) models. It is concluded that the Coriolis effect rather than the rotational alignment effect plays a major role in the reduction of the pairing correlations in the high spin region. Then we proposed an average pairing correction method which not only better reproduces the experimental data comparing with the CNS model but also enables a clean-cut tracing of the configurations thus the full-spin-range discussion on the various rotating bands.

  5. Micro-initiators as the fundamental building blocks of micro-energetic systems

    NASA Astrophysics Data System (ADS)

    Desai, Amish; Fuchs, Brian

    2007-04-01

    The need for smaller and less expensive MIL-STD 1901A compliant safe and arm-fire (S&A/A-F) devices to safely initiate rocket motors requires a better understanding of energetic initiation and firing train functionality. Applications broadly include NLOS artillery rocket-assist motors, high I sp miniature thrusters for UAVs, composite molded thrusters for hypersonic flow temperatures, and smart munitions. Every energetic system needs an initiation mechanism. For the past decade, many groups have worked on reducing the footprint of these systems through batch processing and miniaturization. However, the typical miniaturization and semiconductor-style benefits such as "faster, smaller, cheaper" are only now being investigated for micro-energetics. Advancement of this field requires key breakthroughs in the following areas: 1) a SAFE and batch micro-energetics deposition and patterning step, 2) The compatibility of subsequent (post or pre) MEMS processing steps, 3) better understanding of the micro-initiation energetic train, and 4) special environmental standards for the manufacturer and specialized product qualification/testing. This body of work spotlights 'low-cost' MEMS-based initiators, typical chemical compounds used today in the industry and the associated sensitivities and dangers to be encountered. The micro-scale firing trains required for smart munitions, including warhead and propellant applications, can be made multifunctional for use with legacy and IM-compliant energetics. Methods of focusing industry on reliability and the importance of characterizing formulation, composition, and performance will also be discussed. Most importantly, however, is the need to focus industry on implementing a low-cost micro initiator methodology.

  6. Stability and proton transfer in DNA base pairs of AMD473-DNA adduct

    NASA Astrophysics Data System (ADS)

    Sarmah, Pubalee; Deka, Ramesh C.

    2011-05-01

    We investigate the energetics of four different adducts of cisplatin analogue cis-[PtCl 2(NH 3)(2-picoline)] (AMD473) with a duplex DNA using DFT/ONIOM methods to probe their stabilities. Further, we study the possibilities of proton transfer between DNA base pairs of the most stable drug-DNA adduct. The adduct b(2-picoline trans to 3'-G and 2-methyl group directs to the DNA major groove) is found to be the most stable configuration among all the possible adducts. From the proton transfer analysis we found that the single proton transfer between N1 position of guanine (G) and N3 position of cytosine (C) of each GC pair gives a structure energetically as stable as the original one.

  7. Exploring Ultrafast Structural Dynamics for Energetic Enhancement or Disruption

    DTIC Science & Technology

    2016-03-01

    indirect laser heating and on-resonant optical pumping, to excite/perturb the energetic material to observe changes in the electronic and molecular...time scales necessary to monitor early times of energetic events. 15. SUBJECT TERMS ultrafast, energetic, femtosecond, TATB, flash heating , transient...absorption spectra of RDX after flash heating (left) Raman spectra of RDX after flash heating (right) .............................................7

  8. Excessive production of electron pairs by soft photons in low multiplicity ion interactions

    NASA Technical Reports Server (NTRS)

    Burnett, T. H.; Dake, S.; Fuki, M.; Gregory, J. C.; Hayashi, T.; Holynski, R.; Iwai, J.; Jones, W. V.; Jurak, A.; Lord, J. J.

    1985-01-01

    Three multiply charged primary cosmic ray interactions with carbon nuclei are reported, in which the number of materialized electron pairs within a distance of about 0.3 conversion length is larger than predicted from isospin considerations. These are the most energetic (sigma E gamma 4 TeV) of the low multiplicity ( 15 tracks) events observed in the Japanese-American Cooperative Experiment (JACEE-2) emulsion chamber.

  9. Laser-induced reactions in energetic materials

    NASA Astrophysics Data System (ADS)

    Ling, Ping

    1999-07-01

    Several energetic materials have been investigated under shock wave loading, heating, and photodissociation. This dissertation highlights some efforts to understand energetic material from an angle of basic physical processes and elementary chemical reactions. The first series of experiments was performed to study laser-generated shock waves in energetic materials. Shock waves are generated by pulsed laser vaporization of thin aluminum films. The rapidly expanding aluminum plasma launches a shock wave into the adjacent layer of energetic material, initiating chemical reactions. The shock velocity has been measured by a velocity interferometer. Shock pressures as high as 8 GPa have been generated in this manner. A simple model is proposed to predict laser-generated shock pressure. Several energetic materials have been studied under laser- generated shock wave. The second series of experiments was conducted to study thermal decomposition and photodissociation of energetic materials. Glycidyl azide polymer (GAP) and poly(glycidyl nitrate) (PGN) have been investigated by pulsed infrared laser pyrolysis and ultraviolet laser photolysis of thin films at 17-77 K. Reactions are monitored by transmission infrared spectroscopy. Photolysis of GAP at 266 nm shows that the initial reaction steps are elimination of molecular nitrogen with subsequent formation of imines. Thermal decomposition of GAP by infrared laser pyrolysis reveals products similar to the UV experiments after warming. Laser pyrolysis of PGN indicated that the main steps of decomposition are elimination of NO2 and CH2O from the nitrate ester functional group. It seems that the initial thermal decomposition mechanism of GAP and PGN are the same from heating rate of several degrees per second to 107 oC/s. The third series of experiments is about detailed study of photodissociation mechanism of methyl nitrate. Photodissociation of methyl nitrate isolated in an argon matrix at 17 K has been investigated by 266 nm

  10. Studying dissociative electron attachment through formation of heavy-Rydberg ion-pair states

    NASA Astrophysics Data System (ADS)

    Kelley, Michael; Buathong, Sitti; Dunning, F. Barry

    2016-05-01

    Following dissociative electron transfer in collisions between Rydberg atoms and electron-attaching targets, it is possible for the resulting pair of ions to remain electrostatically bound, forming heavy-Rydberg ion-pair states. Precise measurement of the velocity distributions of such ion-pair states provides information concerning the dissociation dynamics of the excited intermediates initially created by electron transfer. Here, electric-field-induced dissociation is used to detect the product ion pairs and observe their velocity distributions. These distributions are analyzed with the aid of a Monte Carlo collision code that models the electron transfer. Measurements with a number of different target species show that through this analysis, dissociation energetics, the branching ratios into different dissociation products, and the lifetimes of the excited intermediates can be examined. Research supported by the Robert A. Welch Foundation.

  11. Molecular Beam Studies of Hot Atom Chemical Reactions: Reactive Scattering of Energetic Deuterium Atoms

    DOE R&D Accomplishments Database

    Continetti, R. E.; Balko, B. A.; Lee, Y. T.

    1989-02-01

    A brief review of the application of the crossed molecular beams technique to the study of hot atom chemical reactions in the last twenty years is given. Specific emphasis is placed on recent advances in the use of photolytically produced energetic deuterium atoms in the study of the fundamental elementary reactions D + H{sub 2} -> DH + H and the substitution reaction D + C{sub 2}H{sub 2} -> C{sub 2}HD + H. Recent advances in uv laser and pulsed molecular beam techniques have made the detailed study of hydrogen atom reactions under single collision conditions possible.

  12. A Density Functional Theory Examination of the Local Conformational Energetics of Normal and Epigenetically Modified Duplex DNA

    NASA Astrophysics Data System (ADS)

    Yusufaly, Tahir; Olson, Wilma

    2013-03-01

    We report density functional theory calculations of various local regions of duplex DNA, including hydrogen bonded base pairs, stacked nearest-neighbor bases, and sugar-phosphate backbones. Special attention is given to the methylation of 5-cytosine, an epigenetic modification believed to play a key role in eukaryotic gene regulation. Energetically stable molecular conformations are identified and their elastic properties analyzed. Our results are compared with previous ab initio studies and high-resolution crystalline structural data.

  13. Constitution and energetics of photosystem I and photosystem II in the chlorophyll d-dominated cyanobacterium Acaryochloris marina.

    PubMed

    Tomo, Tatsuya; Allakhverdiev, Suleyman I; Mimuro, Mamoru

    2011-01-01

    This mini review presents current topics of discussion about photosystem (PS) I and PS II of photosynthesis in the Acaryochloris marina. A. marina is a photosynthetic cyanobacterium in which chlorophyll (Chl) d is the major antenna pigment (>95%). However, Chl a is always present in a few percent. Chl d absorbs light with a wavelength up to 30 nm red-shifted from Chl a. Therefore, the chlorophyll species of the special pair in PS II has been a matter of debate because if Chl d was the special pair component, the overall energetics must be different in A. marina. The history of this field indicates that a purified sample is necessary for the reliable identification and characterization of the special pair. In view of the spectroscopic data and the redox potential of pheophytin, we discuss the nature of special pair constituents and the localization of the enigmatic Chl a.

  14. Superconductivity: The persistence of pairs

    SciTech Connect

    Edelman, Alex; Littlewood, Peter

    2015-05-20

    Superconductivity stems from a weak attraction between electrons that causes them to form bound pairs and behave much like bosons. These so-called Cooper pairs are phase coherent, which leads to the astonishing properties of zero electrical resistance and magnetic flux expulsion typical of superconducting materials. This coherent state may be qualitatively understood within the Bose–Einstein condensate (BEC) model, which predicts that a gas of interacting bosons will become unstable below a critical temperature and condense into a phase of matter with a macroscopic, coherent population in the lowest energy state, as happens in 4He or cold atomic gases. The successful theory proposed by Bardeen, Cooper and Schrieffer (BCS) predicts that at the superconducting transition temperature Tc, electrons simultaneously form pairs and condense, with no sign of pairing above Tc. Theorists have long surmised that the BCS and BEC models are opposite limits of a single theory and that strong interactions or low density can, in principle, drive the system to a paired state at a temperature Tpair higher than Tc, making the transition to the superconducting state BEC-like (Fig. 1). Yet most superconductors to date are reasonably well described by BCS theory or its extensions, and there has been scant evidence in electronic materials for the existence of pairing independent of the full superconducting state (though an active debate rages over the cuprate superconductors). Writing in Nature, Jeremy Levy and colleagues have now used ingenious nanostructured devices to provide evidence for electron pairing1. Perhaps surprisingly, the material they have studied is a venerable, yet enigmatic, low-temperature superconductor, SrTiO3.

  15. The role of kinetic effects, including plasma rotation and energetic particles, in resistive wall mode stability

    SciTech Connect

    Berkery, J. W.; Sabbagh, S. A.; Reimerdes, H.; Betti, R.; Hu, B.; Bell, R. E.; Gerhardt, S. P.; Manickam, J.; Podesta, M.

    2010-08-15

    The resistive wall mode (RWM) instability in high-beta tokamaks is stabilized by energy dissipation mechanisms that depend on plasma rotation and kinetic effects. Kinetic modification of ideal stability calculated with the 'MISK' code [B. Hu et al., Phys. Plasmas 12, 057301 (2005)] is outlined. For an advanced scenario ITER [R. Aymar et al., Nucl. Fusion 41, 1301 (2001)] plasma, the present calculation finds that alpha particles are required for RWM stability at presently expected levels of plasma rotation. Kinetic stabilization theory is tested in an experiment in the National Spherical Torus Experiment (NSTX) [M. Ono et al., Nucl. Fusion 40, 557 (2000)] that produced marginally stable plasmas with various energetic particle contents. Plasmas with the highest and lowest energetic particle content agree with calculations predicting that increased energetic particle pressure is stabilizing but does not alter the nonmonotonic dependence of stability on plasma rotation due to thermal particle resonances. Presently, the full MISK model, including thermal particles and an isotropic slowing-down distribution function for energetic particles, overpredicts stability in NSTX experiments. Minor alteration of either effect in the theory may yield agreement; several possibilities are discussed.

  16. Molten salt destruction of energetic waste materials

    DOEpatents

    Brummond, William A.; Upadhye, Ravindra S.; Pruneda, Cesar O.

    1995-01-01

    A molten salt destruction process is used to treat and destroy energetic waste materials such as high explosives, propellants, and rocket fuels. The energetic material is pre-blended with a solid or fluid diluent in safe proportions to form a fluid fuel mixture. The fuel mixture is rapidly introduced into a high temperature molten salt bath. A stream of molten salt is removed from the vessel and may be recycled as diluent. Additionally, the molten salt stream may be pumped from the reactor, circulated outside the reactor for further processing, and delivered back into the reactor or cooled and circulated to the feed delivery system to further dilute the fuel mixture entering the reactor.

  17. Molten salt destruction of energetic waste materials

    DOEpatents

    Brummond, W.A.; Upadhye, R.S.; Pruneda, C.O.

    1995-07-18

    A molten salt destruction process is used to treat and destroy energetic waste materials such as high explosives, propellants, and rocket fuels. The energetic material is pre-blended with a solid or fluid diluent in safe proportions to form a fluid fuel mixture. The fuel mixture is rapidly introduced into a high temperature molten salt bath. A stream of molten salt is removed from the vessel and may be recycled as diluent. Additionally, the molten salt stream may be pumped from the reactor, circulated outside the reactor for further processing, and delivered back into the reactor or cooled and circulated to the feed delivery system to further dilute the fuel mixture entering the reactor. 4 figs.

  18. Probing the heliosphere with energetic hydrogen atoms

    NASA Technical Reports Server (NTRS)

    Hsieh, K. C.; Shih, K. L.; Jokipii, J. R.; Grzedzielski, S.

    1992-01-01

    The idea of using energetic neutral atoms (ENAs), produced by charge exchange between energetic ions and ambient neutral atoms, as a diagnostic tool to investigate planetary magnetospheres from a distance has been extended to the investigation of the heliosphere. The paper explores what one can reasonably expect of the heliospheric ENA (HSENA) and what criteria would be imposed on HSENA instruments by concentrating on 10-10 exp 3 keV protons in quiet-time interplanetary space, solar-flare events, corotating interaction regions, and populations have distinctive signatures and that the detection of these particles can reveal energy spatial and propagation of ions in 3D interplanetary space, including the solar-wind termination shock. Such breadth of information could not be gained by in situ means.

  19. Kinetic versus Energetic Discrimination in Biological Copying

    NASA Astrophysics Data System (ADS)

    Sartori, Pablo; Pigolotti, Simone

    2013-05-01

    We study stochastic copying schemes in which discrimination between a right and a wrong match is achieved via different kinetic barriers or different binding energies of the two matches. We demonstrate that, in single-step reactions, the two discrimination mechanisms are strictly alternative and cannot be mixed to further reduce the error fraction. Close to the lowest error limit, kinetic discrimination results in a diverging copying velocity and dissipation per copied bit. On the other hand, energetic discrimination reaches its lowest error limit in an adiabatic regime where dissipation and velocity vanish. By analyzing experimentally measured kinetic rates of two DNA polymerases, T7 and Polγ, we argue that one of them operates in the kinetic and the other in the energetic regime. Finally, we show how the two mechanisms can be combined in copying schemes implementing error correction through a proofreading pathway.

  20. Energetics of compost production and utilization

    SciTech Connect

    Diaz, L.F.; Golueke, C.G.; Savage, G.M.

    1986-09-01

    Developments during the past decade have led to a fairly clear delineation of the role of composting in municipal solid waste (MSW) management. However, before that role can be accepted and implemented on a practical scale, certain important environmental and economic factors must be resolved. Of the economic factors, the energetics of composting in waste management is in urgent need of further elaboration and exploration. This need prompted an attempt on the part of the authors of this paper to resolve basic questions regarding the energetics involved in the production and utilization of compost from urban solid waste and municipal sludges, and peripherally, the applicability of these findings to the management of other wastes (e.g., agricultural). Progress made in pursuing this attempt is described in the present paper.

  1. Exploratory analysis of Spanish energetic mining accidents.

    PubMed

    Sanmiquel, Lluís; Freijo, Modesto; Rossell, Josep M

    2012-01-01

    Using data on work accidents and annual mining statistics, the paper studies work-related accidents in the Spanish energetic mining sector in 1999-2008. The following 3 parameters are considered: age, experience and size of the mine (in number of workers) where the accident took place. The main objective of this paper is to show the relationship between different accident indicators: risk index (as an expression of the incidence), average duration index for the age and size of the mine variables (as a measure of the seriousness of an accident), and the gravity index for the various sizes of mines (which measures the seriousness of an accident, too). The conclusions of this study could be useful to develop suitable prevention policies that would contribute towards a decrease in work-related accidents in the Spanish energetic mining industry.

  2. Energetic protons from a disappearing solar filament

    NASA Technical Reports Server (NTRS)

    Kahler, S. W.; Cliver, E. W.; Cane, H. V.; Mcguire, R. E.; Stone, R. G.; Sheeley, N. R., Jr.

    1985-01-01

    A solar energetic (E 50 MeV) particle (SEP) event observed at 1 AU began about 15000 UT on 1981 December 5. This event was associated with a fast coronal mass ejection observed with the Solwind coronagraph on the P78-1 satellite. No metric type 2 or type 4 burst was observed, but a weak interplanetary type 2 burst was observed with the low frequency radio experiment on the International Sun-Earth Explorer-3 satellite. The mass ejection was associated with the eruption of a large solar quiescent filament which lay well away from any active regions. The eruption resulted in an H alpha double ribbon structure which straddled the magnetic inversion line. No impulsive phase was obvious in either the H alpha or the microwave observations. This event indicates that neither a detectable impulsive phase nor a strong or complex magnetic field is necessary for the production of energetic ions.

  3. Assessment of CRBR core disruptive accident energetics

    SciTech Connect

    Theofanous, T.G.; Bell, C.R.

    1984-03-01

    The results of an independent assessment of core disruptive accident energetics for the Clinch River Breeder Reactor are presented in this document. This assessment was performed for the Nuclear Regulatory Commission under the direction of the CRBR Program Office within the Office of Nuclear Reactor Regulation. It considered in detail the accident behavior for three accident initiators that are representative of three different classes of events; unprotected loss of flow, unprotected reactivity insertion, and protected loss of heat sink. The primary system's energetics accommodation capability was realistically, yet conservatively, determined in terms of core events. This accommodation capability was found to be equivalent to an isentropic work potential for expansion to one atmosphere of 2550 MJ or a ramp rate of about 200 $/s applied to a classical two-phase disassembly.

  4. Mitochondrial network energetics in the heart.

    PubMed

    Aon, Miguel A; Cortassa, Sonia

    2012-01-01

    At the core of eukaryotic aerobic life, mitochondrial function like 'hubs' in the web of energetic and redox processes in cells. In the heart, these networks-extending beyond the complex connectivity of biochemical circuit diagrams and apparent morphology-exhibit collective dynamics spanning several spatiotemporal levels of organization, from the cell, to the tissue, and the organ. The network function of mitochondria, i.e., mitochondrial network energetics, represents an advantageous behavior. Its coordinated action, under normal physiology, provides robustness despite failure in a few nodes, and improves energy supply toward a swiftly changing demand. Extensive diffuse loops, encompassing mitochondrial-cytoplasmic reaction/transport networks, control and regulate energy supply and demand in the heart. Under severe energy crises, the network behavior of mitochondria and associated glycolytic and other metabolic networks collapse, thereby triggering fatal arrhythmias.

  5. The energetic basis of acoustic communication.

    PubMed

    Gillooly, James F; Ophir, Alexander G

    2010-05-07

    Animals produce a tremendous diversity of sounds for communication to perform life's basic functions, from courtship and parental care to defence and foraging. Explaining this diversity in sound production is important for understanding the ecology, evolution and behaviour of species. Here, we present a theory of acoustic communication that shows that much of the heterogeneity in animal vocal signals can be explained based on the energetic constraints of sound production. The models presented here yield quantitative predictions on key features of acoustic signals, including the frequency, power and duration of signals. Predictions are supported with data from nearly 500 diverse species (e.g. insects, fishes, reptiles, amphibians, birds and mammals). These results indicate that, for all species, acoustic communication is primarily controlled by individual metabolism such that call features vary predictably with body size and temperature. These results also provide insights regarding the common energetic and neuromuscular constraints on sound production, and the ecological and evolutionary consequences of producing these sounds.

  6. Streaming energetic electrons in reconnection events

    NASA Astrophysics Data System (ADS)

    Bieber, John W.

    Energetic electrons can be used to probe the large-scale topology of magnetic fields in Earth's magnetotail. In the plasma sheet region near the tail's midplane, these particles normally exhibit the trapped or isotropic angular distributions characteristic of closed magnetic field lines, but brief intervals of intense tailward streaming, indicative of open field lines, are occasionally observed. Such streaming events occur preferentially near the time of substorm onset as the observing spacecraft exits the thinning plasma sheet, and they are usually preceded by a 5-10 minute interval of fast tailward plasma flow and southward magnetic field. These correlated phenomena have been interpreted as evidence for magnetic reconnection at a transient magnetic X-line located ˜15 RE tailward of Earth. Recent studies of energetic electron streaming events report novel reconnection-related phenomena, including heating of plasma electrons, bump-in-tail electron velocity distributions, and possible rotational and tangential magnetic discontinuities.

  7. Streaming energetic electrons in reconnection events

    NASA Astrophysics Data System (ADS)

    Bieber, J. W.

    Energetic electrons can be used to probe the large-scale topology of magnetic fields in earth's magnetotail. In the plasma sheet region near the tail's midplane, these particles normally exhibit the trapped or isotropic angular distributions characteristic of closed magnetic field lines, but brief intervals of intense tailward streaming, indicative of open field lines, are occasionally observed. Such streaming events occur preferentially near the time of substorm onset as the observing spacecraft exits the thinning plasma sheet, and they are usually preceded by a 5-10 minute interval of fast tailward plasma flow and southward magnetic field. These correlated phenomena have been interpreted as evidence for magnetic reconnection at a transient magnetic X-line located at 15 earth radii tailward of earth. Recent studies of energetic electron streaming events report novel reconnection-related phenomena, including heating of plasma electrons, bump-in-tail electron velocity distributions, and possible rotational and tangential magnetic discontinuities.

  8. HAWC and Solar Energetic Transient Events

    NASA Astrophysics Data System (ADS)

    Lara, A.; Ryan, J. M.

    2013-12-01

    The High Altitude Water Cherenkov (HAWC) observatory is being constructed at the volcano Sierra Negra (4100 m a.s.l.) in Mexico. HAWC's primary purpose is the study of both galactic and extra-galactic sources of high energy gamma rays. The HAWC instrument will consist of 300 large water Cherenkov detectors whose counting rate will be sensitive to cosmic rays with energies above the geomagnetic cutoff of the site ( ˜ 8 GV). In particular, HAWC will detect solar energetic particles known as Ground Level Enhancements (GLEs), and the effect of Coronal Mass Ejections on the galactic cosmic rays, known as Forbush Decreases (FDs). The Milagro experiment, the HAWC predecessor, successfully observed GLEs and the HAWC engineering array "VAMOS" already observed a FD. HAWC will be sensitive to γ rays and neutrons produced during large solar flares. In this work, we present the instrument and discuss its capability to observe solar energetic events. i. e., flares and CMEs.

  9. Mitochondrial network energetics in the heart

    PubMed Central

    Aon, Miguel A.; Cortassa, Sonia

    2012-01-01

    At the core of eukaryotic aerobic life, mitochondria function like “hubs” in the web of energetic and redox processes in cells. In the heart, these networks - extending beyond the complex connectivity of biochemical circuit diagrams and apparent morphology - exhibit collective dynamics spanning several spatio-temporal levels of organization, from the cell, to the tissue, and the organ. The network function of mitochondria, i.e. mitochondrial network energetics, represents an advantageous behaviour. Its coordinated action, under normal physiology, provides robustness despite failure in a few nodes, and improves energy supply toward a swiftly changing demand. Extensive diffuse loops, encompassing mitochondrialcytoplasmic reaction/transport networks, control and regulate energy supply and demand in the heart. Under severe energy crises, the network behaviour of mitochondria and associated glycolytic and other metabolic networks collapse, thereby triggering fatal arrhythmias. PMID:22899654

  10. Supernova 2007bi as a pair-instability explosion.

    PubMed

    Gal-Yam, A; Mazzali, P; Ofek, E O; Nugent, P E; Kulkarni, S R; Kasliwal, M M; Quimby, R M; Filippenko, A V; Cenko, S B; Chornock, R; Waldman, R; Kasen, D; Sullivan, M; Beshore, E C; Drake, A J; Thomas, R C; Bloom, J S; Poznanski, D; Miller, A A; Foley, R J; Silverman, J M; Arcavi, I; Ellis, R S; Deng, J

    2009-12-03

    Stars with initial masses such that 10M[symbol: see text] or= 140M[symbol: see text] (if such exist) develop oxygen cores with masses, M(core), that exceed 50M[symbol: see text], where high temperatures are reached at relatively low densities. Conversion of energetic, pressure-supporting photons into electron-positron pairs occurs before oxygen ignition and leads to a violent contraction which triggers a nuclear explosion that unbinds the star in a pair-instability supernova. Transitional objects with 100M[symbol: see text] < M(initial) < 140M[symbol: see text] may end up as iron-core-collapse supernovae following violent mass ejections, perhaps as a result of brief episodes of pair instability, and may already have been identified. Here we report observations of supernova SN 2007bi, a luminous, slowly evolving object located within a dwarf galaxy. We estimate the exploding core mass to be M(core) approximately 100M[symbol: see text], in which case theory unambiguously predicts a pair-instability supernova. We show that >3M[symbol: see text] of radioactive (56)Ni was synthesized during the explosion and that our observations are well fitted by models of pair-instability supernovae. This indicates that nearby dwarf galaxies probably host extremely massive stars, above the apparent Galactic stellar mass limit, which perhaps result from processes similar to those that created the first stars in the Universe.

  11. Energetic additive manufacturing process with feed wire

    DOEpatents

    Harwell, Lane D.; Griffith, Michelle L.; Greene, Donald L.; Pressly, Gary A.

    2000-11-07

    A process for additive manufacture by energetic wire deposition is described. A source wire is fed into a energy beam generated melt-pool on a growth surface as the melt-pool moves over the growth surface. This process enables the rapid prototyping and manufacture of fully dense, near-net shape components, as well as cladding and welding processes. Alloys, graded materials, and other inhomogeneous materials can be grown using this process.

  12. Measurement System for Energetic Materials Decomposition

    DTIC Science & Technology

    2015-01-05

    Measurement System for Energetic Materials Decomposition This DURIP grant was used to purchase: 1. Q600 SDT Simultaneous DSC-TGA 2... Decomposition Report Title This DURIP grant was used to purchase: 1. Q600 SDT Simultaneous DSC-TGA 2. Pfeiffer Vacuum Benchtop Thermostar Mass...Spectrometer 3. Vision Research Phantom V12.1-8G-M high speed camera These instruments have been used to evaluate and study decomposition and

  13. Energetic and Structural Study of Diphenylpyridine Isomers

    NASA Astrophysics Data System (ADS)

    Rocha, Marisa A. A.; Gomes, Lígia R.; Low, John N.; Santos, Luís M. N. B. F.

    2009-09-01

    The energetic and structural study of three diphenylpyridine isomers is presented in detail. The three isomers, 2,6-, 2,5-, and 3,5-diphenylpyridines, were synthesized via Suzuki-Miyaura methodology based on palladium catalysis, and the crystal structures of the isomers were obtained by X-ray diffraction. The relative energetic stabilities in the condensed and gaseous phases as well as volatilities and structures of the three studied isomers were evaluated, regarding the position of the phenyl groups relative to the nitrogen atom of the pyridine ring. The temperature, standard molar enthalpies, and entropies of fusion were measured and derived by differential scanning calorimetry. The vapor pressures of the considered isomers were determined by a static apparatus based on a MKS capacitance diaphragm manometer. The standard molar enthalpies, entropies, and Gibbs energies of sublimation, at T = 298.15 K, were derived, and the phase diagram near the triple point coordinates were determined for all isomers. The standard (p° = 0.1 MPa) molar enthalpies of combustion of all crystalline isomers were determined, at T = 298.15 K, by static bomb combustion calorimetry. The standard molar enthalpies of formation, in the crystalline and gaseous phases, at T = 298.15 K, were derived. The experimental results for the energetics in the gaseous phase of the three compounds were compared and assessed with the values obtained by ab initio calculations at different levels of theory (DFT and MP2) showing that, at this level of theory, the computational methods underestimate the energetic stability, in the gaseous phase, for these molecules. In order to understand the aromaticity in the central ring of each isomer, calculations of NICS (B3LYP/6-311G++(d,p) level of theory) values on the pyridine ring were also performed.

  14. Composition of energetic particles from solar flares.

    PubMed

    Garrard, T L; Stone, E C

    1994-10-01

    We present a model for composition of heavy ions in the solar energetic particles (SEP). The SEP composition in a typical large solar particle event reflects the composition of the Sun, with adjustments due to fractionation effects which depend on the first ionization potential (FIP) of the ion and on the ratio of ionic charge to mass (Q/M). Flare-to-flare variations in composition are represented by parameters describing these fractionation effects and the distributions of these parameters are presented.

  15. The energetic alpha particle transport method EATM

    SciTech Connect

    Kirkpatrick, R.C.

    1998-02-01

    The EATM method is an evolving attempt to find an efficient method of treating the transport of energetic charged particles in a dynamic magnetized (MHD) plasma for which the mean free path of the particles and the Larmor radius may be long compared to the gradient lengths in the plasma. The intent is to span the range of parameter space with the efficiency and accuracy thought necessary for experimental analysis and design of magnetized fusion targets.

  16. Energetic ion composition of the plasma sheet

    SciTech Connect

    Peterson, W.K.; Sharp, R.D.; Shelley, E.G.; Johnson, R.G.; Balsiger, H.

    1981-02-01

    Data obtained from the energetic ion mass spectrometer experiment on Isee 1 in the distant plasma sheet are presented. These data show that (1) the plasma sheet has a significant and variable ionospheric component (H/sup +/ and O/sup +/) representing from 10% to more than 50% of the total number density and (2) there is more than one process responsible for the energization of solar wind plasma (H/sup +/ and He/sup + +/) to plasma sheet energies.

  17. Energetic ion composition of the plasma sheet

    NASA Technical Reports Server (NTRS)

    Peterson, W. K.; Sharp, R. D.; Shelley, E. G.; Johnson, R. G.; Balsiger, H.

    1981-01-01

    Data obtained from the energetic ion mass spectrometer experiment on Isee 1 in the distant plasma sheet are presented. These data show that (1) the plasma sheet has a significant and variable ionospheric component (H(+) and O(+)) representing from 10% to more than 50% of the total number density and (2) there is more than one process responsible for the energization of solar wind plasma (H(+) and He(++)) to plasma sheet energies.

  18. Radiation Hydrodynamics Modeling of Hohlraum Energetics

    NASA Astrophysics Data System (ADS)

    Patel, Mehul V.; Mauche, Christopher W.; Jones, Ogden S.; Scott, Howard A.

    2015-11-01

    Attempts to model the energetics in NIF Hohlraums have been made with varying degrees of success, with discrepancies of 0-25% being reported for the X-ray flux (10-25% for the NIC ignition platform hohlraums). To better understand the cause(s) of these discrepancies, the effects of uncertainties in modeling thermal conduction, laser-plasma interactions, atomic mixing at interfaces, and NLTE kinetics of the high-Z wall plasma must be quantified. In this work we begin by focusing on the NLTE kinetics component. We detail a simulation framework for developing an integrated HYDRA hohlraum model with predefined tolerances for energetics errors due to numerical discretization errors or statistical fluctuations. Within this framework we obtain a model for a converged 1D spherical hohlraum which is then extended to 2D. The new model is used to reexamine physics sensitivities and improve estimates of the energetics discrepancy. Prepared by LLNL under Contract DE-AC52-07NA27344.

  19. Nonadditive Compositional Curvature Energetics of Lipid Bilayers

    NASA Astrophysics Data System (ADS)

    Sodt, A. J.; Venable, R. M.; Lyman, E.; Pastor, R. W.

    2016-09-01

    The unique properties of the individual lipids that compose biological membranes together determine the energetics of the surface. The energetics of the surface, in turn, govern the formation of membrane structures and membrane reshaping processes, and thus they will underlie cellular-scale models of viral fusion, vesicle-dependent transport, and lateral organization relevant to signaling. The spontaneous curvature, to the best of our knowledge, is always assumed to be additive. We describe observations from simulations of unexpected nonadditive compositional curvature energetics of two lipids essential to the plasma membrane: sphingomyelin and cholesterol. A model is developed that connects molecular interactions to curvature stress, and which explains the role of local composition. Cholesterol is shown to lower the number of effective Kuhn segments of saturated acyl chains, reducing lateral pressure below the neutral surface of bending and favoring positive curvature. The effect is not observed for unsaturated (flexible) acyl chains. Likewise, hydrogen bonding between sphingomyelin lipids leads to positive curvature, but only at sufficient concentration, below which the lipid prefers negative curvature.

  20. Sol-Gel Manufactured Energetic Materials

    DOEpatents

    Simpson, Randall L.; Lee, Ronald S.; Tillotson, Thomas M.; Hrubesh, Lawrence W.; Swansiger, Rosalind W.; Fox, Glenn A.

    2005-05-17

    Sol-gel chemistry is used for the preparation of energetic materials (explosives, propellants and pyrotechnics) with improved homogeneity, and/or which can be cast to near-net shape, and/or made into precision molding powders. The sol-gel method is a synthetic chemical process where reactive monomers are mixed into a solution, polymerization occurs leading to a highly cross-linked three dimensional solid network resulting in a gel. The energetic materials can be incorporated during the formation of the solution or during the gel stage of the process. The composition, pore, and primary particle sizes, gel time, surface areas, and density may be tailored and controlled by the solution chemistry. The gel is then dried using supercritical extraction to produce a highly porous low density aerogel or by controlled slow evaporation to produce a xerogel. Applying stress during the extraction phase can result in high density materials. Thus, the sol-gel method can be used for precision detonator explosive manufacturing as well as producing precision explosives, propellants, and pyrotechnics, along with high power composite energetic materials.

  1. Sol-gel manufactured energetic materials

    DOEpatents

    Simpson, Randall L.; Lee, Ronald S.; Tillotson, Thomas M.; Hrubesh, Lawrence W.; Swansiger, Rosalind W.; Fox, Glenn A.

    2003-12-23

    Sol-gel chemistry is used for the preparation of energetic materials (explosives, propellants and pyrotechnics) with improved homogeneity, and/or which can be cast to near-net shape, and/or made into precision molding powders. The sol-gel method is a synthetic chemical process where reactive monomers are mixed into a solution, polymerization occurs leading to a highly cross-linked three dimensional solid network resulting in a gel. The energetic materials can be incorporated during the formation of the solution or during the gel stage of the process. The composition, pore, and primary particle sizes, gel time, surface areas, and density may be tailored and controlled by the solution chemistry. The gel is then dried using supercritical extraction to produce a highly porous low density aerogel or by controlled slow evaporation to produce a xerogel. Applying stress during the extraction phase can result in high density materials. Thus, the sol-gel method can be used for precision detonator explosive manufacturing as well as producing precision explosives, propellants, and pyrotechnics, along with high power composite energetic materials.

  2. Fundamental energetic limits of radio communication systems

    NASA Astrophysics Data System (ADS)

    Baudais, Jean-Yves

    2017-02-01

    The evaluation of the energy consumption of a radiocommunication requires to analyse the life cycle of the elements used. However, this analysis does not specify the energetic limits. Theoretical approaches allow one to draw these limits, which are known in multiple cases of information transmission. However, the answers are not always satisfactory, in particular in the case of time-varying channels. After a brief presentation of the notion of energetic limits of a radiocommunication, and beginning with a global approach, we show that, contrary to the published results, the energetic limits always differ from zero if the physical constraints are correctly expressed. xml:lang="fr" Cependant, les réponses ne sont pas toujours satisfaisantes, particulièrement dans le cas de canaux variants dans le temps. Après une rapide présentation des notions d'énergie limite d'une radiocommunication, et en commençant par une approche globale du problème, nous montrons que, contrairement aux résultats publiés, les limites énergétiques sont toujours différentes de zéro si les contraintes physiques sont correctement exprimées.

  3. Energetic Particles Dynamics in Mercury's Magnetosphere

    NASA Technical Reports Server (NTRS)

    Walsh, Brian M.; Ryou, A.S.; Sibeck, D. G.; Alexeev, I. I.

    2013-01-01

    We investigate the drift paths of energetic particles in Mercury's magnetosphere by tracing their motion through a model magnetic field. Test particle simulations solving the full Lorentz force show a quasi-trapped energetic particle population that gradient and curvature drift around the planet via "Shabansky" orbits, passing though high latitudes in the compressed dayside by equatorial latitudes on the nightside. Due to their large gyroradii, energetic H+ and Na+ ions will typically collide with the planet or the magnetopause and will not be able to complete a full drift orbit. These simulations provide direct comparison for recent spacecraft measurements from MESSENGER. Mercury's offset dipole results in an asymmetric loss cone and therefore an asymmetry in particle precipitation with more particles precipitating in the southern hemisphere. Since the planet lacks an atmosphere, precipitating particles will collide directly with the surface of the planet. The incident charged particles can kick up neutrals from the surface and have implications for the formation of the exosphere and weathering of the surface

  4. Energetic neutral atoms: Imaging the magnetospheric ring current

    NASA Technical Reports Server (NTRS)

    Roelof, Edmond C.

    1990-01-01

    Magnetospheric imaging is a new discipline whose goal is to make pictures of the energetic particle populations trapped in the magnetic field of Earth (or any other planet). This project demonstrated the technical feasibility and scientific validity of magnetospheric imaging using energetic neutral atoms (ENA) with the publication and quantitative analysis of the first ENA images ever obtained from space. ENA's are produced when singly-charged energetic (approximately 100 keV) trapped ions make an atomic collision with the neutral hydrogen atoms which boil of the top of the Earth's atmosphere. These hydrogen atoms suffuse the entire trapping volume of the magnetosphere. The energetic ion steals the electron from the atmospheric hydrogen, so the energetic ion is transformed into an energetic neutral atom with a velocity of several thousands of kilometers/second. Moreover, the new-born ENA preserves the velocity that the trapped ion had at the time of the collision. Consequently, any population of energetic ions emits ENA's.

  5. Energetics and Defect Interactions of Complex Oxides for Energy Applications

    NASA Astrophysics Data System (ADS)

    Solomon, Jonathan Michael

    The goal of this dissertation is to employ computational methods to gain greater insights into the energetics and defect interactions of complex oxides that are relevant for today's energy challenges. To achieve this goal, the development of novel computational methodologies are required to handle complex systems, including systems containing nearly 650 ions and systems with tens of thousands of possible atomic configurations. The systems that are investigated in this dissertation are aliovalently doped lanthanum orthophosphate (LaPO4) due to its potential application as a proton conducting electrolyte for intermediate temperature fuel cells, and aliovalently doped uranium dioxide (UO2) due to its importance in nuclear fuel performance and disposal. First we undertake density-functional-theory (DFT) calculations on the relative energetics of pyrophosphate defects and protons in LaPO4, including their binding with divalent dopant cations. In particular, for supercell calculations with 1.85 mol% Sr doping, we investigate the dopant-binding energies for pyrophosphate defects to be 0.37 eV, which is comparable to the value of 0.34 eV calculated for proton-dopant binding energies in the same system. These results establish that dopant-defect interactions further stabilize proton incorporation, with the hydration enthalpies when the dopants are nearest and furthest from the protons and pyrophosphate defects being -1.66 eV and -1.37 eV, respectively. Even though our calculations show that dopant binding enhances the enthalpic favorability of proton incorporation, they also suggest that such binding is likely to substantially lower the kinetic rate of hydrolysis of pyrophosphate defects. We then shift our focus to solid solutions of fluorite-structured UO 2 with trivalent rare earth fission product cations (M3+=Y, La) using a combination of ionic pair potential and DFT based methods. Calculated enthalpies of formation with respect to constituent oxides show higher

  6. RNA-PAIRS: RNA probabilistic assignment of imino resonance shifts

    PubMed Central

    Bahrami, Arash; Clos, Lawrence J.; Markley, John L.; Butcher, Samuel E.

    2012-01-01

    The significant biological role of RNA has further highlighted the need for improving the accuracy, efficiency and the reach of methods for investigating RNA structure and function. Nuclear magnetic resonance (NMR) spectroscopy is vital to furthering the goals of RNA structural biology because of its distinctive capabilities. However, the dispersion pattern in the NMR spectra of RNA makes automated resonance assignment, a key step in NMR investigation of biomolecules, remarkably challenging. Herein we present RNA Probabilistic Assignment of Imino Resonance Shifts (RNA-PAIRS), a method for the automated assignment of RNA imino resonances with synchronized verification and correction of predicted secondary structure. RNA-PAIRS represents an advance in modeling the assignment paradigm because it seeds the probabilistic network for assignment with experimental NMR data, and predicted RNA secondary structure, simultaneously and from the start. Subsequently, RNA-PAIRS sets in motion a dynamic network that reverberates between predictions and experimental evidence in order to reconcile and rectify resonance assignments and secondary structure information. The procedure is halted when assignments and base-parings are deemed to be most consistent with observed crosspeaks. The current implementation of RNA-PAIRS uses an initial peak list derived from proton-nitrogen heteronuclear multiple quantum correlation (1H–15N 2D HMQC) and proton–proton nuclear Overhauser enhancement spectroscopy (1H–1H 2D NOESY) experiments. We have evaluated the performance of RNA-PAIRS by using it to analyze NMR datasets from 26 previously studied RNAs, including a 111-nucleotide complex. For moderately sized RNA molecules, and over a range of comparatively complex structural motifs, the average assignment accuracy exceeds 90%, while the average base pair prediction accuracy exceeded 93%. RNA-PAIRS yielded accurate assignments and base pairings consistent with imino resonances for a majority

  7. Pair-Starved Pulsar Magnetospheres

    NASA Technical Reports Server (NTRS)

    Muslimov, Alex G.; Harding, Alice K.

    2009-01-01

    We propose a simple analytic model for the innermost (within the light cylinder of canonical radius, approx. c/Omega) structure of open-magnetic-field lines of a rotating neutron star (NS) with relativistic outflow of charged particles (electrons/positrons) and arbitrary angle between the NS spin and magnetic axes. We present the self-consistent solution of Maxwell's equations for the magnetic field and electric current in the pair-starved regime where the density of electron-positron plasma generated above the pulsar polar cap is not sufficient to completely screen the accelerating electric field and thus establish thee E . B = 0 condition above the pair-formation front up to the very high altitudes within the light cylinder. The proposed mode1 may provide a theoretical framework for developing the refined model of the global pair-starved pulsar magnetosphere.

  8. Invisibly Sanitizable Signature without Pairings

    NASA Astrophysics Data System (ADS)

    Yum, Dae Hyun; Lee, Pil Joong

    Sanitizable signatures allow sanitizers to delete some pre-determined parts of a signed document without invalidating the signature. While ordinary sanitizable signatures allow verifiers to know how many subdocuments have been sanitized, invisibly sanitizable signatures do not leave any clue to the sanitized subdocuments; verifiers do not know whether or not sanitizing has been performed. Previous invisibly sanitizable signature scheme was constructed based on aggregate signature with pairings. In this article, we present the first invisibly sanitizable signature without using pairings. Our proposed scheme is secure under the RSA assumption.

  9. MULTI-DIMENSIONAL SIMULATIONS OF ROTATING PAIR-INSTABILITY SUPERNOVAE

    SciTech Connect

    Chatzopoulos, E.; Wheeler, J. Craig; Couch, Sean M.

    2013-10-20

    We study the effects of rotation on the dynamics, energetics, and {sup 56}Ni production of pair instability supernova (PISN) explosions by performing rotating two-dimensional ({sup 2}.5D{sup )} hydrodynamics simulations. We calculate the evolution of eight low-metallicity (Z = 10{sup –3}, 10{sup –4} Z{sub ☉}) massive (135-245 M{sub ☉}) PISN progenitors with initial surface rotational velocities of 50% of the critical Keplerian value using the stellar evolution code MESA. We allow for both the inclusion and the omission of the effects of magnetic fields in the angular momentum transport and in chemical mixing, resulting in slowly rotating and rapidly rotating final carbon-oxygen cores, respectively. Increased rotation for carbon-oxygen cores of the same mass and chemical stratification leads to less energetic PISN explosions that produce smaller amounts of {sup 56}Ni due to the effect of the angular momentum barrier that develops and slows the dynamical collapse. We find a non-monotonic dependence of {sup 56}Ni production on rotational velocity in situations when smoother composition gradients form at the outer edge of the rotating cores. In these cases, the PISN energetics are determined by the competition of two factors: the extent of chemical mixing in the outer layers of the core due to the effects of rotation in the progenitor evolution and the development of angular momentum support against collapse. Our 2.5D PISN simulations with rotation are the first presented in the literature. They reveal hydrodynamic instabilities in several regions of the exploding star and increased explosion asymmetries with higher core rotational velocity.

  10. [The pairing, synapsis and recombination of meiosis in plant].

    PubMed

    Liu, Chun-Xia; He, Qun-Yan; Jin, Wei-Wei

    2010-12-01

    Meiosis is the crucial step for sexual reproduction, while the pairing, synapsis and recombination are the key events in this process and have become the hotspots in meiosis studies. In recent years, with the development of the molecular biology and cell biology, associated with the mutant screened from mutant libraries, much advances were achieved in pairing, synapsis and recombination of meiosis in plant. In this review, we have gave an overview of the genes identification in this field and further studies of its molecular mechanism in plant.

  11. Mammalian energetics. Flexible energetics of cheetah hunting strategies provide resistance against kleptoparasitism.

    PubMed

    Scantlebury, David M; Mills, Michael G L; Wilson, Rory P; Wilson, John W; Mills, Margaret E J; Durant, Sarah M; Bennett, Nigel C; Bradford, Peter; Marks, Nikki J; Speakman, John R

    2014-10-03

    Population viability is driven by individual survival, which in turn depends on individuals balancing energy budgets. As carnivores may function close to maximum sustained power outputs, decreased food availability or increased activity may render some populations energetically vulnerable. Prey theft may compromise energetic budgets of mesopredators, such as cheetahs and wild dogs, which are susceptible to competition from larger carnivores. We show that daily energy expenditure (DEE) of cheetahs was similar to size-based predictions and positively related to distance traveled. Theft at 25% only requires cheetahs to hunt for an extra 1.1 hour per day, increasing DEE by just 12%. Therefore, not all mesopredators are energetically constrained by direct competition. Other factors that increase DEE, such as those that increase travel, may be more important for population viability.

  12. Mammalian energetics. Instantaneous energetics of puma kills reveal advantage of felid sneak attacks.

    PubMed

    Williams, Terrie M; Wolfe, Lisa; Davis, Tracy; Kendall, Traci; Richter, Beau; Wang, Yiwei; Bryce, Caleb; Elkaim, Gabriel Hugh; Wilmers, Christopher C

    2014-10-03

    Pumas (Puma concolor) live in diverse, often rugged, complex habitats. The energy they expend for hunting must account for this complexity but is difficult to measure for this and other large, cryptic carnivores. We developed and deployed a physiological SMART (species movement, acceleration, and radio tracking) collar that used accelerometry to continuously monitor energetics, movements, and behavior of free-ranging pumas. This felid species displayed marked individuality in predatory activities, ranging from low-cost sit-and-wait behaviors to constant movements with energetic costs averaging 2.3 times those predicted for running mammals. Pumas reduce these costs by remaining cryptic and precisely matching maximum pouncing force (overall dynamic body acceleration = 5.3 to 16.1g) to prey size. Such instantaneous energetics help to explain why most felids stalk and pounce, and their analysis represents a powerful approach for accurately forecasting resource demands required for survival by large, mobile predators.

  13. Correlations in laser-induced electron-positron pair creation

    SciTech Connect

    Krajewska, K.; Kaminski, J. Z.

    2011-09-15

    Probability rates of electron-positron pair creation in head-on laser-beam-proton collisions are investigated, using an exact treatment of the colliding proton as a finite-mass particle. We observe that the recoil effects become more important when passing from the perturbative multiphoton regime to the nonperturbative above-threshold regime of laser-matter coupling. Thus we concentrate on the latter case. In this regime, our detailed analysis shows that energy supplied by the colliding proton makes the process more effective, and that the electrons and positrons that are created during the collision are more energetic than in the case when the momentum transfer from the proton is neglected. A number of similarities to above-threshold atomic ionization are also illustrated.

  14. Solar flares, coronal mass ejections and solar energetic particle event characteristics

    NASA Astrophysics Data System (ADS)

    Papaioannou, Athanasios; Sandberg, Ingmar; Anastasiadis, Anastasios; Kouloumvakos, Athanasios; Georgoulis, Manolis K.; Tziotziou, Kostas; Tsiropoula, Georgia; Jiggens, Piers; Hilgers, Alain

    2016-12-01

    A new catalogue of 314 solar energetic particle (SEP) events extending over a large time span from 1984 to 2013 has been compiled. The properties as well as the associations of these SEP events with their parent solar sources have been thoroughly examined. The properties of the events include the proton peak integral flux and the fluence for energies above 10, 30, 60 and 100 MeV. The associated solar events were parametrized by solar flare (SF) and coronal mass ejection (CME) characteristics, as well as related radio emissions. In particular, for SFs: the soft X-ray (SXR) peak flux, the SXR fluence, the heliographic location, the rise time and the duration were exploited; for CMEs the plane-of-sky velocity as well as the angular width were utilized. For radio emissions, type III, II and IV radio bursts were identified. Furthermore, we utilized element abundances of Fe and O. We found evidence that most of the SEP events in our catalogue do not conform to a simple two-class paradigm, with the 73% of them exhibiting both type III and type II radio bursts, and that a continuum of event properties is present. Although, the so-called hybrid or mixed events are found to be present in our catalogue, it was not possible to attribute each SEP event to a mixed/hybrid sub-category. Moreover, it appears that the start of the type III burst most often precedes the maximum of the SF and thus falls within the impulsive phase of the associated SF. At the same time, type III bursts take place within ≈5.22 min, on average, in advance from the time of maximum of the derivative of the SXR flux (Neupert effect). We further performed a statistical analysis and a mapping of the logarithm of the proton peak flux at E > 10 MeV, on different pairs of the parent solar source characteristics. This revealed correlations in 3-D space and demonstrated that the gradual SEP events that stem from the central part of the visible solar disk constitute a significant radiation risk. The velocity of

  15. Missing energies at pair creation

    NASA Technical Reports Server (NTRS)

    El-Ela, A. A.; Hassan, S.; Bagge, E. R.

    1985-01-01

    Wilson cloud chamber measurements of the separated spectra of positrons and electrons produced by gamma quanta of 6.14 MeV differ considerably from the theoretically predicted spectra by BETHE and HEITLER, but are in good agreement with those of a modified theory of pair creation.

  16. Pairing Linguistic and Music Intelligences

    ERIC Educational Resources Information Center

    DiEdwardo, MaryAnn Pasda

    2005-01-01

    This article describes how music in the language classroom setting can be a catalyst for developing reading, writing, and understanding skills. Studies suggest that pairing music and linguistic intelligences in the college classroom improves students' grades and abilities to compose theses statements for research papers in courses that emphasize…

  17. Pick a Pair. Being Bony

    ERIC Educational Resources Information Center

    Miller, Pat

    2004-01-01

    This column suggests pairings of fiction and nonfiction books to meet curricular needs and help students to compare/contrast the texts as they may be asked on state tests. The author of this paper focuses on activities surrounding Halloween. Since many schools are discouraged from teaching about Halloween, this can be a great time to investigate…

  18. Solar energetic particle arrival at Mars due to the 27 January 2012 solar storm

    NASA Astrophysics Data System (ADS)

    Frahm, R. A.; Sharber, J. R.; Winningham, J. D.; Elliott, H. A.; Howard, T. A.; DeForest, C. E.; Odstrĉil, D.; Kallio, E.; McKenna-Lawlor, S.; Barabash, S.

    2013-06-01

    On January 27, 2012, an X-class flare brightened on the Sun at 18:15 UT. This event was associated with the generation of a high-energy stream of Solar Energetic Particles (SEPs) advancing along the Interplanetary Magnetic Field (IMF) which arrived at Mars in about 39 minutes. A Coronal Mass Ejection (CME) arrived at Mars several days later. The Electron Spectrometer (ELS), a part of the Analyzer of Space Plasmas and Energetic Atoms (ASPERA-3) experiment on the European Mars Express (MEx) Spacecraft, associatively detected elevated background levels of penetrating particle radiation which abruptly increased above the baseline level by two orders of magnitude within several hours after first arrival, allowing the particle arrival time to be accurately determined from this gradual SEP. As Mars reacted to the SEP, the atmosphere heated driving expansion of the ionosphere.

  19. The MAVEN Solar Energetic Particle instrument

    NASA Astrophysics Data System (ADS)

    Dunn, P.; Lillis, R. J.; Larson, D. E.; Lin, R. P.; Jakosky, B. M.

    2012-12-01

    The Solar Energetic Particle (SEP) instrument will travel to Mars onboard the Mars Atmosphere and Volatile EvolutioN (MAVEN) Mission, launching in November 2013. In order for MAVEN to determine the role that loss of volatiles to space has played through time, solar energy input to the Martian system must be characterized. An important (if infrequent and episodic) portion of this input is in the form of solar energetic particle (SEP) events. Understanding the relationship between SEP events and atmospheric escape is crucial to understanding the climate history of Mars. The SEP instrument will characterize such events at Mars by measuring energetic protons and electrons in the energy range absorbed by the upper atmosphere. SEP takes much of its heritage from the Solid State Telescope (SST) on the THEMIS mission, consisting of 2 orthogonal dual double-ended solid-state telescopes. Proton spectra from 25 keV to 6 MeV and electron spectra from 25 keV to 1 MeV will be collected in 4 look directions at 3 measurement cadences over MAVEN's 4.5-hour elliptical orbit: 32s far from the planet, 8s between 300 and 800 km altitude and 2s below 300 km. SEP will measure particle fluxes from ~20 to ~107 cm-2s-1sr-1. Here we present a full description of the instrument, as well as GEANT4 simulations of the detailed detector response.; Cross-section view of SEP sensor. Collimators are shown in yellow, baffles are in black. The sweep magnet (blue and brown) prevents electrons < 350 keV from reaching the detector stack (mounted on circuit board shown in green) from the left. A Kapton foil (not visible) prevent ions < 250 keV from reaching the stack from the right.

  20. Solar Energetic Particle Studies with PAMELA

    NASA Technical Reports Server (NTRS)

    Bravar, U.; Christian, E. R.; deNolfo, Georgia; Ryan, J. M.; Stochaj, S.

    2011-01-01

    The origin of the high-energy solar energetic particles (SEPs) may conceivably be found in composition signatures that reflect the elemental abundances of the low corona and chromosphere vs. the high corona and solar wind. The presence of secondaries, such as neutrons and positrons, could indicate a low coronal origin of these particles. Velocity dispersion of different species and over a wide energy range can be used to determine energetic particle release times at the Sun. Together with multi-wavelength imaging, in- situ observations of a variety of species, and coverage over a wide energy range provide a critical tool in identifying the origin of SEPs, understanding the evolution of these events within the context of solar active regions, and constraining the acceleration mechanisms at play. The Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA)instrument, successfully launched in 2006 and expected to remain operational until at least the beginning of 2012, measures energetic particles in the same energy range as ground-based neutron monitors, and lower energies as well. It thus bridges the gap between low energy in-situ observations and ground-based Ground Level Enhancements (GLE) observations. It can measure the charge (up to Z=6) and atomic number of the detected particles, and it can identify and measure positrons and detect neutrons-an unprecedented array of data channels that we can bring to bear on the origin of high-energy SEPs. We present prelimiary results on the for the 2006 December 13 solar flare and GLE and the 2011 March 21 solar flare, both registering proton and helium enhancements in PAMELA. Together with multi- spacecraft contextual data and modeling, we discuss the PAMELA results in the context of the different acceleration mechanisms at play.

  1. Energetic constraints on monsoonal Hadley circulations

    NASA Astrophysics Data System (ADS)

    Merlis, T. M.; Schneider, T.; Bordoni, S.; Eisenman, I.

    2011-12-01

    The strength of monsoons is believed to have varied in the past in response to changes in the seasonal shortwave radiation distribution associated with orbital precession and is expected to vary during the coming century due to increases in greenhouse gas concentrations. Here, we examine the constraint that the moist static energy budget imposes on the response to radiative perturbations of the cross-equatorial, or monsoonal, Hadley circulations. Changes in the strength of the mass transport can occur in response to radiative perturbations, which has been frequently discussed in the past. An additional factor in the energetic balance, however, is the atmosphere's energy stratification, which is commonly known as the gross moist stability in tropical meteorology. Therefore, changes in the atmosphere's gross moist stability can play a fundamental role in determining changes in the mass transport of mean circulations. Also, the influence of spatial variations in surface heat capacity on the top-of-the-atmosphere energy balance, rather than its widely discussed role in determining surface temperature, is important in determining how radiative perturbations are energetically balanced by monsoonal Hadley circulations. We examine the importance of energetic constraints on monsoonal Hadley circulations in idealized general circulation model simulations that have either an aquaplanet slab-ocean boundary condition or a zonally symmetric subtropical continent. The radiative balance in the simulations is perturbed first by insolation variations associated with orbital precession and then by increased carbon dioxide concentration. The simulation results demonstrate that summertime changes in gross moist stability are important for understanding past and future monsoon variations.

  2. Energetic Ion Interactions with the Galilean Satellites

    NASA Technical Reports Server (NTRS)

    Cooper, John F.

    2000-01-01

    The principal research tasks of this investigation are: (1) specification of the energetic (keV to MeV) ion environments upstream of the four Galilean satellites and (2) data analysis and numerical modeling of observed ion interactions with the satellites. Differential flux spectra are being compiled for the most abundant ions (protons, oxygen, and sulfur) from measurements at 20 keV to 100 MeV total energy by the Energetic Particle Detector (EPD) experiment and at higher ion energies by the Heavy Ion Counter (HIC) experiment. Runge-Kutta and other numerical techniques are used to propagate test particles sampled from the measured upstream spectra to the satellite surface or spacecraft through the local magnetic and corotational electric field environment of each satellite. Modeling of spatial variations in directional flux anisotropies measured during each close flyby provides limits on atomic charge states for heavy (O, S) magnetospheric ions and on internal or induced magnetic fields of the satellites. Validation of models for magnetic and electric field configurations then allows computation of rates for ion implantation, sputtering, and energy deposition into the satellite surfaces for further modeling of observable chemical changes induced by irradiation. Our ongoing work on production of oxidants and other secondary species by ice irradiation on Europa's surface has significant applications, already acknowledged in current literature, to astrobiological evolution. Finally, the work will improve understanding of energetic ion sources and sinks at the satellite orbits for improved modeling of magnetospheric transport processes. The scope of the research effort mainly includes data from the primary Galileo mission (1995-1997) but may also include some later data where directly relevant (e.g., comparison of J0 and I27 data for Io) to the primary mission objectives. Funding for this contract also includes partial support for our related education and public

  3. Synthesis of a new energetic nitrate ester

    SciTech Connect

    Chavez, David E

    2008-01-01

    Nitrate esters have been known as useful energetic materials since the discovery of nitroglycerin by Ascanio Sobrero in 1846. The development of methods to increase the safety and utility of nitroglycerin by Alfred Nobel led to the revolutionary improvement in the utility of nitroglycerin in explosive applications in the form of dynamite. Since then, many nitrate esters have been prepared and incorporated into military applications such as double-based propellants, detonators and as energetic plasticizers. Nitrate esters have also been shown to have vasodilatory effects in humans and thus have been studied and used for treatments of ailments such as angina. The mechanism of the biological response towards nitrate esters has been elucidated recently. Interestingly, many of the nitrate esters used for military purposes are liquids (ethylene glycol dinitrate, propylene glycol dinitrate, etc). Pentaerythritol tetranitrate (PETN) is one of the only solid nitrate esters, besides nitrocellulose, that is used in any application. Unfortunately, PETN melting point is above 100 {sup o}C, and thus must be pressed as a solid for detonator applications. A more practical material would be a melt-castable explosive, for potential simplification of manufacturing processes. Herein we describe the synthesis of a new energetic nitrate ester (1) that is a solid at ambient temperatures, has a melting point of 85-86 {sup o}C and has the highest density of any known nitrate ester composed only of carbon, hydrogen, nitrogen and oxygen. We also describe the chemical, thermal and sensitivity properties of 1 as well as some preliminary explosive performance data.

  4. Preferred and Energetically Optimal Transition Speeds During Backward Human Locomotion

    PubMed Central

    Hreljac, Alan; Imamura, Rodney; Escamilla, Rafael F.; Casebolt, Jeffrey; Sison, Mitell

    2005-01-01

    Some aspects of backward locomotion are similar to forward locomotion, while other aspects are not related to their forward counterpart. The backward preferred transition speed (BPTS) has never been directly compared to the energetically optimal transition speed (EOTS), nor has it been compared to the preferred transition speed (PTS) during forward locomotion. The purpose of this study was to determine whether the BPTS occurs at the EOTS, and to examine the relationship between the backward and forward preferred gait transition speeds. The preferred backward and forward transition speeds of 12 healthy, young subjects (7 males, 5 females) were determined after subjects were familiarized with forward and backward treadmill locomotion. On a subsequent day, subjects walked backward at speeds of 70, 80, 90, 100, and 110% of the BPTS and ran backward at speeds of 60, 75, 90, 100, and 120% of the BPTS while VO2 and RPE data were collected. After subtracting standing VO2, exercise VO2 was normalized to body mass and speed. For each subject, energy-speed curves for walking and running were fit to the normalized data points. The intersection of these curves was defined as the EOTS which was compared to the BPTS using a paired t-test (p < 0.05). RPE and VO2 at the BPTS were also compared between walking and running conditions, and the correlation between BPTS and PTS was calculated. The EOTS (1.85 ± 0.09 m·s-1) was significantly greater than the BPTS (1.63 ± 0.11 m·s-1). Even though RPE was equal for walking and running at the BPTS, VO2 was significantly greater when running. There was a strong correlation (r = 0.82) between the BPTS and the PTS. Similar to forward locomotion, the determinants of the BPTS must include factors other than metabolic energy. The gait transition during backward locomotion exhibits several similarities to its forward counterpart. Key Points The backward preferred transition speed (1.63 ± 0.11 m·s-1) was significantly less than the

  5. Recombination, dissociation, and transport of ion pairs across the liquid/liquid interface. implications for phase transfer catalysis.

    PubMed

    Benjamin, Ilan

    2013-04-25

    Molecular dynamics simulations are used to calculate several free energy profiles relevant to the recombination/dissociation and transport of individual ions and ion pairs across the water/chloroform interface. Tetra methyl ammonium (TMA(+)) and tetra butyl ammonium (TBA(+)) (typically used as phase transfer catalysts) and a chloride ion (as an example of a transferred nucleophile) are considered. The free-energy profiles for the transfer of the three ions and the two ion pairs (TMA(+)Cl(-) and TBA(+)Cl(-)) across the interface, as well as the potential of mean force for the dissociation of these two ion pairs at different interface locations, are calculated and correlated with structural and energetic changes at the interface. These equilibrium calculations, together with nonequilibrium trajectory calculations, provide molecular insight into the mechanism of phase transfer catalysis. In particular, water surface fluctuations are strongly coupled to the ion-pair location along the interface normal and the ion-pair bond length.

  6. Energetics of hydrogen storage in organolithium nanostructures

    SciTech Connect

    Namilae, Sirish; Fuentes-Cabrera, Miguel A; Radhakrishnan, Balasubramaniam; Gorti, Sarma B; Nicholson, Don M

    2007-01-01

    Ab-initio calculations based on the second order Moller-Plesset perturbation theory (MP2) were used to investigate the interaction of molecular hydrogen with alkyl lithium organometallic compounds. It is found that lithium in organolithium structures attracts two hydrogen molecules with a binding energy of about 0.14 eV. The calculations also show that organolithium compounds bind strongly with graphitic nanostructures. Therefore, these carbon based nanostructures functionalized with organolithium compounds can be effectively used for storage of molecular hydrogen. Energetics and mechanisms for achieving high weight percent hydrogen storage in organolithium based nanostructures are discussed.

  7. Nonlinear electromagnetic interactions in energetic materials

    DOE PAGES

    Wood, Mitchell Anthony; Dalvit, Diego Alejandro; Moore, David Steven

    2016-01-12

    We study the scattering of electromagnetic waves in anisotropic energetic materials. Nonlinear light-matter interactions in molecular crystals result in frequency-conversion and polarization changes. Applied electromagnetic fields of moderate intensity can induce these nonlinear effects without triggering chemical decomposition, offering a mechanism for the nonionizing identification of explosives. We use molecular-dynamics simulations to compute such two-dimensional THz spectra for planar slabs made of pentaerythritol tetranitrate and ammonium nitrate. Finally, we discuss third-harmonic generation and polarization-conversion processes in such materials. These observed far-field spectral features of the reflected or transmitted light may serve as an alternative tool for standoff explosive detection.

  8. A chondrule - Evidence of energetic impact unlikely

    NASA Technical Reports Server (NTRS)

    Vedder, J. F.; Gault, D. E.

    1974-01-01

    It had been concluded by Lange and Larimer (1973) that the morphology and mineralogy of an unusual chondrule from the Ngawi meteorite are the results of a highly energetic impact within the solar nebula. The evidence for this conclusion is examined. It is found that the chondrule does not show evidence of high relative velocities in the solar nebula. It is pointed out that arguments against chondrule production by impact on planetary surfaces on the basis of ejection velocities are not supported by laboratory experiments.

  9. Stimulated Emission of Energetic Particles (SEEP).

    DTIC Science & Technology

    1987-11-30

    a.... W W w w w w w I I li IJr Ir % i "f J2 I l AD-A 188 724 MLMSCD068456 For Period Ending 30 September 1987 CD Contract N00014-79-C4824 0 IC FILE...CLASSIFICATION 0 -UNCLASSIFIED/UNLIMITED [ SAME AS RPT C:" DTIC USERS UNCLASSIFIED 22a NAME OF RESPONSIBLE INDIVIDUAL 22b TELEPHONE (Include Area Code) 22c O...34---" ,. LMSC/D068456 . 0 SEEP FINAL REPORT I. OBJECTIVES OF THE SEEP PROGRAM The SEEP (Stimulated Emission of Energetic Particles) program had important

  10. Solar Energetic Particles: Acceleration and Observations

    NASA Astrophysics Data System (ADS)

    Sako, Takashi

    Research of solar energetic particles (SEPs) is important in understanding particle acceleration, transport and interactions taking place in the universe. The importance of space weather to modern human life is also increasing. In this lecture, I introduce a selected subset of SEP observations together with observation techniques and future plans. The aim is to connect these SEP observations with associated particle acceleration mechanisms and the subsequent transport and interaction processes. Because the observational properties are determined by different processes, a wide range of observations is necessary in order to fully understand the phenomena taking place. I will also give an overview of the role of the SEP studies in general astrophysics.

  11. Semiconductor bridge, SCB, ignition of energetic materials

    SciTech Connect

    Bickes, R.W.; Grubelich, M.D.; Harris, S.M.; Merson, J.A.; Tarbell, W.W.

    1997-04-01

    Sandia National Laboratories` semiconductor bridge, SCB, is now being used for the ignition or initiation of a wide variety of exeoergic materials. Applications of this new technology arose because of a need at the system level to provide light weight, small volume and low energy explosive assemblies. Conventional bridgewire devices could not meet the stringent size, weight and energy requirements of our customers. We present an overview of SCB technology and the ignition characteristics for a number of energetic materials including primary and secondary explosives, pyrotechnics, thermites and intermetallics. We provide examples of systems designed to meet the modern requirements that sophisticated systems must satisfy in today`s market environments.

  12. Synthesis and Characterization of Energetic Plasticizer AMDNNM

    NASA Astrophysics Data System (ADS)

    Schulze, Maxwell C.; Chavez, David E.

    2016-04-01

    The synthesis of room temperature liquid azidomethyl-dinitroxydimethyl-nitromethane (AMDNNM, 5) in 57% overall yield and its formulation with nitrocellulose (AMDNNM/NC) are described. The small-scale explosive sensitivity of neat AMDNNM was determined to be slightly more sensitive than PETN, whereas AMDNNM/NC is significantly less sensitive. Both neat AMDNNM and AMDNNM/NC have thermal stabilities similar to that of pentaerythritol tetranitrate (PETN). The explosive and chemical properties of this novel material make it a good candidate for an energetic plasticizer.

  13. Simmer analysis of prompt burst energetics experiments

    SciTech Connect

    Hitchcock, J.T.

    1982-03-01

    The Prompt Burst Energetics experiments are designed to measure the pressure behavior of fuel and coolant as working fluids during a hypothetical prompt burst disassembly in an LMFBR. The work presented in this report consists of a parametric study of PBE-5S, a fresh oxide fuel experiment, using SIMMER-II. The various pressure sources in the experiment are examined, and the dominant source identified as incondensable contaminant gasses in the fuel. The important modeling uncertainties and limitations of SIMMER-II as applied to these experiments are discussed.

  14. R&D of Energetic Ionic Liquids

    DTIC Science & Technology

    2011-11-01

    Ammonia 3-6 H2O balance Properties LMP - 103S AF-M315E Hydrazine Ispvac,lbf sec/lbm (e = 50:1 Pc = 300 psi) 252 (theor.) 235 (del) 266...92oC) is also an Energetic Ionic Liquid • ADN-based monopropellant ( LMP - 103S ) from ECAPS, Swedish Space Corporation • High performance „green...Much Effort Required in Small- Scale Safety/Hazard Evaluations Propellant AF-M315E* LMP - 103S ** Unconfined Burn Test 1 and 3: No reaction Test 2

  15. Studies of yeast cell oxygenation and energetics by laser fluorometry of reduced nicotinamide adenine dinucleotide

    NASA Astrophysics Data System (ADS)

    Pan, Fu-shih; Chen, Stephen; Mintzer, Robert A.; Chen, Chin-Tu; Schumacker, Paul

    1991-03-01

    It is of fundamental importance for biological scientists to assess cellular energetics. Under aerobic conditions, the tricarboxylic acid cycle (TCA cycle) is coupled with the mitochondrial electron cascade pathway to provide the cell with energy. The nicotinamide adenine dinucleotide-conjugated pair (NAD and NADH) is the coenzyme in numerous important biomedical reactions which include several important dehydrogenase reactions in the TCA cycle. Based on Le Chatelier's principle, NADH will accumulate when this energy production mechanism is impaired. The relative amounts of NAD and NADH in a cell are defined as the redox state of the cell (Williamson et.al. 1967) which provides a valuable index of cellular energetics. The sum of the amounts of NAD and NADH in a cell may be assumed to be constant during a finite time; therefore, a reliable means of measuring the NADH concentration would provide us with a useful indicator of tissue viability. Traditionally, the quantities of NADH and NAD may be measured by chemical assay methods. We can avoid these tediois analyses by exploiting the significant difference between the ultraviolet absorption spectra of this redox pair. However, because of the opacity of biological samples and the interference of other biochemicals that also absorb ultraviolet radiation, measurement of NADH and NAD+ concentrations in vivo by absorption spectroscopy is not feasible.

  16. Trapped energetic ion dynamics affected by localized electric field perturbations

    NASA Astrophysics Data System (ADS)

    Nishimura, Seiya

    2016-01-01

    Trapped energetic ion orbits in helical systems are numerically simulated using the Lorentz model. Simulation results of precession drift frequencies of trapped energetic ions are benchmarked by those of analytic solutions. The effects of the electric field perturbation localized at the rational surface on trapped energetic ions are examined, where the perturbation has an arbitrary rotation frequency and an amplitude fixed in time. It is found that the trapped energetic ions resonantly interact with the perturbation, when the rotation frequency of the perturbation is comparable to the precession drift frequencies of trapped energetic ions. The simulation results are suggestive to a mechanism of the energetic-ion-induced interchange mode, which might be associated with the fishbone mode observed in helical systems.

  17. Nonlocal continuum electrostatic theory predicts surprisingly small energetic penalties for charge burial in proteins

    NASA Astrophysics Data System (ADS)

    Bardhan, Jaydeep P.

    2011-09-01

    We study the energetics of burying charges, ion pairs, and ionizable groups in a simple protein model using nonlocal continuum electrostatics. Our primary finding is that the nonlocal response leads to markedly reduced solvent screening, comparable to the use of application-specific protein dielectric constants. Employing the same parameters as used in other nonlocal studies, we find that for a sphere of radius 13.4 Å containing a single +1e charge, the nonlocal solvation free energy varies less than 18 kcal/mol as the charge moves from the surface to the center, whereas the difference in the local Poisson model is ˜35 kcal/mol. Because an ion pair (salt bridge) generates a comparatively more rapidly varying Coulomb potential, energetics for salt bridges are even more significantly reduced in the nonlocal model. By varying the central parameter in nonlocal theory, which is an effective length scale associated with correlations between solvent molecules, nonlocal-model energetics can be varied from the standard local results to essentially zero; however, the existence of the reduction in charge-burial penalties is quite robust to variations in the protein dielectric constant and the correlation length. Finally, as a simple exploratory test of the implications of nonlocal response, we calculate glutamate pKa shifts and find that using standard protein parameters (ɛprotein = 2-4), nonlocal results match local-model predictions with much higher dielectric constants. Nonlocality may, therefore, be one factor in resolving discrepancies between measured protein dielectric constants and the model parameters often used to match titration experiments. Nonlocal models may hold significant promise to deepen our understanding of macromolecular electrostatics without substantially increasing computational complexity.

  18. Nonlocal continuum electrostatic theory predicts surprisingly small energetic penalties for charge burial in proteins.

    PubMed

    Bardhan, Jaydeep P

    2011-09-14

    We study the energetics of burying charges, ion pairs, and ionizable groups in a simple protein model using nonlocal continuum electrostatics. Our primary finding is that the nonlocal response leads to markedly reduced solvent screening, comparable to the use of application-specific protein dielectric constants. Employing the same parameters as used in other nonlocal studies, we find that for a sphere of radius 13.4 Å containing a single +1e charge, the nonlocal solvation free energy varies less than 18 kcal/mol as the charge moves from the surface to the center, whereas the difference in the local Poisson model is ∼35 kcal/mol. Because an ion pair (salt bridge) generates a comparatively more rapidly varying Coulomb potential, energetics for salt bridges are even more significantly reduced in the nonlocal model. By varying the central parameter in nonlocal theory, which is an effective length scale associated with correlations between solvent molecules, nonlocal-model energetics can be varied from the standard local results to essentially zero; however, the existence of the reduction in charge-burial penalties is quite robust to variations in the protein dielectric constant and the correlation length. Finally, as a simple exploratory test of the implications of nonlocal response, we calculate glutamate pK(a) shifts and find that using standard protein parameters (ε(protein) = 2-4), nonlocal results match local-model predictions with much higher dielectric constants. Nonlocality may, therefore, be one factor in resolving discrepancies between measured protein dielectric constants and the model parameters often used to match titration experiments. Nonlocal models may hold significant promise to deepen our understanding of macromolecular electrostatics without substantially increasing computational complexity.

  19. Ultrafast dynamics in DNA base pairs following ultraviolet excitation.

    NASA Astrophysics Data System (ADS)

    Orr-Ewing, Andrew

    2015-03-01

    Photo-protective mechanisms in DNA are essential to maintain the integrity of the genetic code by preventing damage from absorption of solar ultraviolet (UV) radiation. We have used time-resolved infra-red (TRIR) spectroscopy to observe the dynamics of Watson-Crick nucleobase pairs following absorption of femtosecond UV laser pulses. The base pairs are prepared as nucleosides in solution, and photo-induced dynamics are probed in the carbonyl and N-H bond stretching regions using broadband IR pulses with picosecond time resolution. Results will be presented for the guanine-cytosine (G-C) base pair, contrasting the rapid recovery of ground-state products (the photo-protection pathway) with formation of other photoproducts which might represent photo-damage mechanisms. This work is a collaboration with the group of Prof F. Temps (Christian-Albrechts-Universitat zu Kiel). This research is supported by ERC Advanced Grant 290966 CAPRI.

  20. Energetic Ion Loss Diagnostic for the Wendelstein 7-AS Stellarator

    SciTech Connect

    D. S. Darrow; A. Werner; A. Weller

    2000-12-07

    A diagnostic to measure the loss of energetic ions from the Wendelstein 7-AS (W7-AS) stellarator has been built. It is capable of measuring losses of both neutral beam ions and energetic ions arising from ion cyclotron resonant heating. The probe can measure losses of both clockwise and counterclockwise-going energetic ions simultaneously, and accepts a wide range of pitch angles in both directions. Initial measurements by the diagnostic are reported.

  1. Field Demonstration/Validation of Electrolytic Barriers for Energetic Compounds at Pueblo Chemical Depot

    DTIC Science & Technology

    2010-01-01

    demonstration showed improvement over those previously employed. Specific advances included: • Use of four active electrodes (i.e., two sequential pairs...reactive barrier via the natural flow of groundwater. Within the barrier, contaminants are degraded as they pass through titanium screen electrodes ...Department of Defense (DoD) facilities. This included the goal of employing promising design improvements that were advanced from the 2002-2005 iii

  2. Segregation and redistribution of end-of-process energetic materials

    SciTech Connect

    McCabe, R.A.; Cummins, B.; Gonzalez, M.A.

    1993-03-01

    A system recovering then recycling or reusing end-of-process energetic materials has been developed at the Lawrence Livermore National Laboratory (LLNL). The system promotes separating energetic materials with high potential for reuse or recycling from those that have no further value. A feature of the system is a computerized electronic bulletin board for advertising the availability of surplus and recovered energetic materials and process chemicals to LLNL researchers, and for posting energetic materials, ``want ads.`` The system was developed and implemented to promote waste minimization and pollution prevention at LLNL.

  3. Collisions of Vortex Filament Pairs

    NASA Astrophysics Data System (ADS)

    Banica, Valeria; Faou, Erwan; Miot, Evelyne

    2014-12-01

    We consider the problem of collisions of vortex filaments for a model introduced by Klein et al. (J Fluid Mech 288:201-248, 1995) and Zakharov (Sov Phys Usp 31(7):672-674, 1988, Lect. Notes Phys 536:369-385, 1999) to describe the interaction of almost parallel vortex filaments in three-dimensional fluids. Since the results of Crow (AIAA J 8:2172-2179, 1970) examples of collisions are searched as perturbations of antiparallel translating pairs of filaments, with initial perturbations related to the unstable mode of the linearized problem; most results are numerical calculations. In this article, we first consider a related model for the evolution of pairs of filaments, and we display another type of initial perturbation leading to collision in finite time. Moreover, we give numerical evidence that it also leads to collision through the initial model. We finally study the self-similar solutions of the model.

  4. Multidimensional DDT modeling of energetic materials

    SciTech Connect

    Baer, M.R.; Hertel, E.S.; Bell, R.L.

    1995-07-01

    To model the shock-induced behavior of porous or damaged energetic materials, a nonequilibrium mixture theory has been developed and incorporated into the shock physics code, CTH. The foundation for this multiphase model is based on a continuum mixture formulation given by Baer and Nunziato. This multiphase mixture model provides a thermodynamic and mathematically-consistent description of the self-accelerated combustion processes associated with deflagration-to-detonation and delayed detonation behavior which are key modeling issues in safety assessment of energetic systems. An operator-splitting method is used in the implementation of this model, whereby phase diffusion effects are incorporated using a high resolution transport method. Internal state variables, forming the basis for phase interaction quantities, are resolved during the Lagrangian step requiring the use of a stiff matrix-free solver. Benchmark calculations are presented which simulate low-velocity piston impact on a propellant porous bed and experimentally-measured wave features are well replicated with this model. This mixture model introduces micromechanical models for the initiation and growth of reactive multicomponent flow that are key features to describe shock initiation and self-accelerated deflagration-to-detonation combustion behavior. To complement one-dimensional simulation, two-dimensional numerical calculations are presented which indicate wave curvature effects due to the loss of wall confinement. This study is pertinent for safety analysis of weapon systems.

  5. How do energetic ions damage metallic surfaces?

    DOE PAGES

    Osetskiy, Yury N.; Calder, Andrew F.; Stoller, Roger E.

    2015-02-20

    Surface modification under bombardment by energetic ions observed under different conditions in structural and functional materials and can be either unavoidable effect of the conditions or targeted modification to enhance materials properties. Understanding basic mechanisms is necessary for predicting properties changes. The mechanisms activated during ion irradiation are of atomic scale and atomic scale modeling is the most suitable tool to study these processes. In this paper we present results of an extensive simulation program aimed at developing an understanding of primary surface damage in iron by energetic particles. We simulated 25 keV self-ion bombardment of Fe thin films withmore » (100) and (110) surfaces at room temperature. A large number of simulations, ~400, were carried out allow a statistically significant treatment of the results. The particular mechanism of surface damage depends on how the destructive supersonic shock wave generated by the displacement cascade interacts with the free surface. Three basic scenarios were observed, with the limiting cases being damage created far below the surface with little or no impact on the surface itself, and extensive direct surface damage on the timescale of a few picoseconds. In some instances, formation of large <100> vacancy loops beneath the free surface was observed, which may explain some earlier experimental observations.« less

  6. Energetic photoelectrons and the polar rain

    NASA Technical Reports Server (NTRS)

    Decker, Dwight T.; Jasperse, J. R.; Winningham, J. D.

    1990-01-01

    In the daytime midlatitudes, the Low Altitude Plasma Instrument (LAPI) on board the Dynamics Explorer 2 satellite has observed photoelectrons with energies as high as 850 eV. These energetic photoelectrons are an extension of the 'classical' photoelectrons (less than 60 eV) and result from photoionization of neutrals by soft solar X-rays. Since these photoelectrons are produced wherever the solar flux is incident on the earth's atmosphere, they should be present in sunlit polar cap. But in the polar cap, over these same energies, there is a well-known electron population: the polar rain, a low intensity electron flux of magnetospheric origin. Thus, in the sunlit polar cap, an energetic population of electrons should consist of both an ionospheric (photoelectron) and a magnetospheric (polar rain) component. Using numerical solutions of an electron transport equation with appropriate boundary conditions and sunlit polar cap LAPI data, it is shown that the two populations (photoelectron and polar rain) are indeed present and are both needed to explain polar cap observations.

  7. Solar filament eruptions and energetic particle events

    NASA Technical Reports Server (NTRS)

    Kahler, S. W.; Cliver, E. W.; Cane, H. V.; Mcguire, R. E.; Stone, R. G.

    1986-01-01

    The 1981 December 5 solar filament eruption that is associated with an energetic (E greater than 50 MeV) particle event observed at 1 AU. The eruption was photographed in H-alpha and was observed by the Solwind whitelight coronagraph on P78-1. It occurred well away from any solar active region and was not associated with an impulsive microwave burst, indicating that magnetic complexity and a detectable impulsive phase are not required for the production of a solar energetic particle (SEP) event. No metric type II or IV emission was observed, but an associated interplanetary type II burst was detected by the low-frequency radio experiment on ISEE 3. The December 5 and two other SEP events lacking evidence for low coronal shocks had unusually steep energy spectra (gamma greater than 3.5). In terms of shock acceleration, this suggests that shocks formed relatively high in the corona may produce steeper energy spectra than those formed at lower altitudes. It is noted that the filament itself maybe one source of the ions accelerated to high energies, since it is the only plausible coronal source of the He(+) ions observed in SEP events.

  8. Energetic particle effects on global magnetohydrodynamic modes

    NASA Astrophysics Data System (ADS)

    Cheng, C. Z.

    1990-06-01

    The effects of energetic particles on magnetohydrodynamic (MHD) type modes are studied using analytical theories and the nonvariational kinetic-MHD stability code (nova-k) [Workshop on Theory of Fusion Plasmas, (Societa Italiana di Fisica, Bologna, 1987), p. 185]. In particular, the problems of (1) the stabilization of ideal MHD internal kink modes and the excitation of resonant ``fishbone'' internal modes and (2) the alpha particle destabilization of toroidicity-induced Alfvén eigenmodes (TAE) via transit resonances are addressed. Analytical theories are presented to help explain the nova-k results. For energetic trapped particles generated by neutral beam injection or ion cyclotron resonant heating, a stability window for the n=1 internal kink mode in the hot particle beta space exists even in the absence of core ion finite Larmor radius effect. On the other hand, the trapped alpha particles are found to resonantly excite instability of the n=1 internal mode and can lower the critical beta threshold. The circulating alpha particles can strongly destabilize TAE modes via inverse Landau damping associated with the spatial gradient of the alpha-particle pressure.

  9. Energetic solar electrons in the interplanetary medium

    NASA Technical Reports Server (NTRS)

    Lin, R. P.

    1985-01-01

    Results are given of ISEE-3 measurements of energetic solar electrons extending down to 2 keV energy. Such measurements have provided a new perspective on energetic solar electrons in the interplanetary medium. Impulsive solar electron events are observed, on the average, several times a day near solar maximum, with about 40 percent detected only below about 15 keV. The electron energy spectra have a nearly power-law shape extending smoothly down to 2 keV, indicating that the origin of these events is high in the corona. In large solar flares which accelerate electrons and ions to relativistic energies, the electron spectrum appears to be modified by a second acceleration which results in a double power-law shape above about 10 keV with a break near 100 keV and flattening from about 10-100 keV. Solar type-III radio bursts are produced by the escaping 2-100 keV electrons through a beam-plasma instability.

  10. Energetics and mechanics for partial gravity locomotion.

    PubMed

    Newman, D J; Alexander, H L; Webbon, B W

    1994-09-01

    The role of gravitational acceleration on human locomotion is not clearly understood. It is hypothesized that the mechanics and energetics of locomotion depend upon the prevailing gravity level. A unique human-rated underwater treadmill and an adjustable ballasting harness were used to stimulate partial gravity environments. This study has two research aspects, biomechanics and energetics. Vertical forces which are exerted by subjects on the treadmill-mounted, split-plate force platform show that peak vertical force and stride frequency significantly decrease (p < 0.05) as the gravity level is reduced, while ground contact time is independent of gravity level. A loping gait is employed over a wide range of speeds (approximately 1.5 m/s to approximately 2.3 m/s) suggesting a change in the mechanics for lunar (1/6 G) and Martian (3/8 G) locomotion. As theory predicts, locomotion energy requirements for partial gravity levels are significantly less than at 1 G (p < 0.05).

  11. Synthesis and evaluation of energetic materials

    NASA Astrophysics Data System (ADS)

    Santhosh, G.

    Over the years new generations of propellants and explosives are being developed. High performance and pollution prevention issues have become the subject of interest in recent years. Desired properties of these materials are a halogen-free, nitrogen and oxygen rich molecular composition with high density and a positive heat of formation. The dinitramide anion is a new oxy anion of nitrogen and forms salts with variety of metal, organic and inorganic cations. Particular interest is in ammonium dinitramide (ADN, NH4N(NO 2)2) which is a potentially useful energetic oxidizer. ADN is considered as one of the most promising substitutes for ammonium perchlorate (AP, NH4ClO4) in currently used composite propellants. It is unique among energetic materials in that it has no carbon or chlorine; its combustion products are not detrimental to the atmosphere. Unquestionable advantage of ADN over AP is the significant improvement in the performance of solid rocket motors by 5-15%. The present thesis is centered on the experimental results along with discussion of some of the most pertinent aspects related to the synthesis and characterization of few dinitramide salts. The chemistry, mechanism and kinetics of the formation of dinitramide salts by nitration of deactivated amines are investigated. The evaluation of the thermal and spectral properties along with the adsorption and thermal decomposition characteristics of the dinitramide salts are also explored in this thesis.

  12. Temperature dependent terahertz properties of energetic materials

    NASA Astrophysics Data System (ADS)

    Azad, Abul K.; Whitley, Von H.; Brown, Kathryn E.; Ahmed, Towfiq; Sorensen, Christian J.; Moore, David S.

    2016-04-01

    Reliable detection of energetic materials is still a formidable challenge which requires further investigation. The remote standoff detection of explosives using molecular fingerprints in the terahertz spectral range has been an evolving research area for the past two decades. Despite many efforts, identification of a particular explosive remains difficult as the spectral fingerprints often shift due to the working conditions of the sample such as temperature, crystal orientation, presence of binders, etc. In this work, we investigate the vibrational spectrum of energetic materials including RDX, PETN, AN, and 1,3-DNB diluted in a low loss PTFE host medium using terahertz time domain spectroscopy (THz-TDS) at cryogenic temperatures. The measured absorptions of these materials show spectral shifts of their characteristic peaks while changing their operating temperature from 300 to 7.5 K. We have developed a theoretical model based on first principles methods, which is able to predict most of the measured modes in 1, 3-DNB between 0.3 to 2.50 THz. These findings may further improve the security screening of explosives.

  13. How do energetic ions damage metallic surfaces?

    SciTech Connect

    Osetskiy, Yury N.; Calder, Andrew F.; Stoller, Roger E.

    2015-02-20

    Surface modification under bombardment by energetic ions observed under different conditions in structural and functional materials and can be either unavoidable effect of the conditions or targeted modification to enhance materials properties. Understanding basic mechanisms is necessary for predicting properties changes. The mechanisms activated during ion irradiation are of atomic scale and atomic scale modeling is the most suitable tool to study these processes. In this paper we present results of an extensive simulation program aimed at developing an understanding of primary surface damage in iron by energetic particles. We simulated 25 keV self-ion bombardment of Fe thin films with (100) and (110) surfaces at room temperature. A large number of simulations, ~400, were carried out allow a statistically significant treatment of the results. The particular mechanism of surface damage depends on how the destructive supersonic shock wave generated by the displacement cascade interacts with the free surface. Three basic scenarios were observed, with the limiting cases being damage created far below the surface with little or no impact on the surface itself, and extensive direct surface damage on the timescale of a few picoseconds. In some instances, formation of large <100> vacancy loops beneath the free surface was observed, which may explain some earlier experimental observations.

  14. Synthesis of dense energetic materials. Annual report

    SciTech Connect

    Coon, C.

    1982-07-01

    The objective of the research described in the report is to synthesize new, dense, stable, highly energetic materials which will ultimately be a candidates for improved explosive and propellant formulations. Following strict guidelines pertaining to energy, density, stability, etc. Specific target molecules were chosen that appear to possess the improved properties desired for new energetic materials. This report summarizes research on the synthesis of these target materials from February 1981 to January 1982. The following compounds were synthesized: 5,5'-diamino-3,3'-bioxadiazole(1,2,4); 5,5'-bis(trichloromethyl)-3,3'-di(1,2,4-oxadiazole); 3,3'-bi(1,2,4-oxadiazole); ethylene tetranitramine (ETNA); N,N-bis(methoxymethyl)acetamide; N,N-bis(chloromethyl)acetamide; 7,8-dimethylglycoluril; Synthesis of 3,9-Di(t-butyl)-13,14-dimethyl-tetracyclo-(5,5,2,0/sup 5/ /sup 13/ 0/sup 11/ /sup 14/)-1,3,5,7,9,11-hexaaza-6,12-dioxotetradecane.

  15. Energetics of water permeation through fullerene membrane

    PubMed Central

    Isobe, Hiroyuki; Homma, Tatsuya; Nakamura, Eiichi

    2007-01-01

    Lipid bilayer membranes are important as fundamental structures in biology and possess characteristic water-permeability, stability, and mechanical properties. Water permeation through a lipid bilayer membrane occurs readily, and more readily at higher temperature, which is largely due to an enthalpy cost of the liquid-to-gas phase transition of water. A fullerene bilayer membrane formed by dissolution of a water-soluble fullerene, Ph5C60K, has now been shown to possess properties entirely different from those of the lipid membranes. The fullerene membrane is several orders of magnitude less permeable to water than a lipid membrane, and the permeability decreases at higher temperature. Water permeation is burdened by a very large entropy loss and may be favored slightly by an enthalpy gain, which is contrary to the energetics observed for the lipid membrane. We ascribe this energetics to favorable interactions of water molecules to the surface of the fullerene molecules as they pass through the clefts of the rigid fullerene bilayer. The findings provide possibilities of membrane design in science and technology. PMID:17846427

  16. Solar Energetic Particle Events Observed by MAVEN

    NASA Astrophysics Data System (ADS)

    Lee, C. O.; Larson, D. E.; Lillis, R. J.; Luhmann, J. G.; Halekas, J. S.; Brain, D.; Connerney, J. E. P.; Espley, J. R.; Epavier, F.; Thiemann, E.; Zeitlin, C.; Jakosky, B. M.

    2015-12-01

    We present observations of solar energetic particle (SEP) events made by the Mars Atmosphere and Volatile EvolutioN (MAVEN) SEP instrument, which measures energetic ions and electrons impacting the upper Martian atmosphere. Since the arrival of the MAVEN spacecraft at Mars, a large number of solar flares and a few major coronal mass ejections (CMEs) erupted from the Sun. The SEPs are accelerated by the related shock in the solar corona or by the propagating interplanetary shock ahead of the CME ejecta. Mixed in with these SEPs are particles accelerated by the shocks of corotating streams, some of which have recurred for several solar cycles due to the persistent coronal hole sources. The SEP events are analyzed together with the upstream solar wind observations from the MAVEN Solar Wind Ion Analyzer (SWIA) and magnetometer (MAG). The sources of the SEP events are determined from Earth-based solar imagery and the MAVEN Extreme Ultra-violet Monitor (EUVM) together with numerical simulations of the inner heliospheric conditions. A comparison with the radiation dose rate measurements from the Mars Science Laboratory (MSL) Radiation Assessment Detector (RAD) reveals a lack of ground signatures during the onset of the highest energy SEPs for the events observed by MAVEN, indicating that the SEPs fully deposit their energies into the Martian atmosphere. Using measurements made from the ensemble of instruments onboard MAVEN, we investigate the consequences of SEPs at Mars for a number of events observed during the primary science mapping phase of the MAVEN mission.

  17. Energetic particle effects on global magnetohydrodynamic modes

    SciTech Connect

    Cheng, C.Z. )

    1990-06-01

    The effects of energetic particles on magnetohydrodynamic (MHD) type modes are studied using analytical theories and the nonvariational kinetic-MHD stability code (NOVA-K) ({ital Workshop} {ital on} {ital Theory} {ital of} {ital Fusion} {ital Plasmas}, (Societa Italiana di Fisica, Bologna, 1987), p. 185). In particular, the problems of (1) the stabilization of ideal MHD internal kink modes and the excitation of resonant fishbone'' internal modes and (2) the alpha particle destabilization of toroidicity-induced Alfven eigenmodes (TAE) via transit resonances are addressed. Analytical theories are presented to help explain the NOVAresults. For energetic trapped particles generated by neutral beam injection or ion cyclotron resonant heating, a stability window for the {ital n}=1 internal kink mode in the hot particle beta space exists even in the absence of core ion finite Larmor radius effect. On the other hand, the trapped alpha particles are found to resonantly excite instability of the {ital n}=1 internal mode and can lower the critical beta threshold. The circulating alpha particles can strongly destabilize TAE modes via inverse Landau damping associated with the spatial gradient of the alpha-particle pressure.

  18. Energetics of calcium-rich dolomite

    SciTech Connect

    Chai, L.; Navrotsky, A.; Reeder, R.J.

    1995-03-01

    The enthalpy of formation of sedimentary Ca-rich dolomite has been determined by oxide melt calorimetry. The results show that Ca-rich dolomite is energetically different from well-ordered stoichiometric dolomite. The enthalpy of formation from calcite and magnesite becomes strongly more endothermic with increasing excess Ca content. This supports the idea that the substitution of Ca in the Mg layer of dolomite is energetically unfavorable. Ca-rich dolomite is unstable relative to well-ordered stoichiometric dolomite and calcite. The enthalpy behavior for excess Ca substitution in dolomite is different from that of Mg substitution in calcite; the enthalpy change is much larger in magnitude in dolomite and is more strongly dependent on composition. Differences in cation order as well as the presence of a modulated structure and low-symmetry domains in Ca-rich dolomite cannot be discerned from the enthalpy data. The findings confirm that the growth and occurrence of Ca-rich dolomite in sedimentary environments must be attributed to kinetic factors rather than to equilibrium. 47 refs., 2 figs., 1 tab.

  19. Asymmetric Ion-Pairing Catalysis

    PubMed Central

    Brak, Katrien

    2014-01-01

    Charged intermediates and reagents are ubiquitous in organic transformations. The interaction of these ionic species with chiral neutral, anionic, or cationic small molecules has emerged as a powerful strategy for catalytic, enantioselective synthesis. This review describes developments in the burgeoning field of asymmetric ion-pairing catalysis with an emphasis on the insights that have been gleaned into the structural and mechanistic features that contribute to high asymmetric induction. PMID:23192886

  20. Septin pairs, a complex choreography.

    PubMed

    Ewers, Helge

    2011-06-13

    Septins form a filamentous collar at the mother-bud neck in budding yeast. In cytokinesis, this collar splits into two rings and the septin complexes undergo a dramatic reorientation. Using fluorescence polarization microscopy, DeMay et al. (2011. J. Cell Biol. doi:10.1083/jcb.201012143) now demonstrate that septin complexes assemble as paired filaments in vivo and reveal new insights into septin organization during cytokinesis.

  1. Lowering of Boson-Fermion System Energy with a Gapped Cooper Resonant-Pair Dispersion Relation

    NASA Astrophysics Data System (ADS)

    Mamedov, T. A.; de Llano, M.

    2007-09-01

    Applying two-time Green-function techniques to the Friedberg-T.D. Lee phenomenological Hamiltonian of a many-fermion system, it is shown that positive-energy resonant bosonic pairs associated with four-fermion excitations above the Fermi sea are energetically lower in a ground-state that is a mixture of two coexisting and dynamically interacting many-particle subsystems: a) unpaired fermions and b) composite bosons. It is argued that an interaction between free fermions and bosons excited above the Fermi sea in the mixture, namely, the continuous processes of pair-formation from, and disintegration into, two unpaired electrons, results in a substantially lowering the total system energy. The positive-energy composite bosons begin to appear incoherently below a de-pairing temperature T* as their coupling- and temperature-dependent number density gradually increases from zero. This leads quite naturally to the pseudogap phenomenon observed in high-Tc cuprates

  2. Implications of RHESSI Observations for Solar Flare Models and Energetics

    NASA Technical Reports Server (NTRS)

    Holman, Gordon D.

    2006-01-01

    Observations of solar flares in X-rays and gamma-rays provide the most direct information about the hottest plasma and energetic electrons and ions accelerated in flares. The Ramaty High Energy Solar Spectroscopic Imager (RHESSI) has observed over 18000 solar flares in X-rays and gamma-rays since its launch in February of 2002. RHESSI observes the full Sun at photon energies from as low as 3 keV to as high as 17 MeV with a spectral resolution on the order of 1 keV. It also provides images in arbitrary bands within this energy range with spatial resolution as good as 3 seconds of arc. Full images are typically produced every 4 seconds, although higher time resolution is possible. This unprecedented combination of spatial, spectral, and temporal resolution, spectral range and flexibility has led to fundamental advances in our understanding of flares. I will show RHESSI and coordinated observations that confirm coronal magnetic reconnection models for eruptive flares and coronal mass ejections, but also present new puzzles for these models. I will demonstrate how the analysis of RHESSI spectra has led to a better determination of the energy flux and total energy in accelerated electrons, and of the energy in the hot, thermal flare plasma. I will discuss how these energies compare with each other and with the energy contained in other flare-related phenomena such as interplanetary particles and coronal mass ejections.

  3. Laser System for Livermore's Mono Energetic Gamma-Ray Source

    SciTech Connect

    Gibson, D; Albert, F; Bayramian, A; Marsh, R; Messerly, M; Ebbers, C; Hartemann, F

    2011-03-14

    A Mono-energetic Gamma-ray (MEGa-ray) source, based on Compton scattering of a high-intensity laser beam off a highly relativistic electron beam, requires highly specialized laser systems. To minimize the bandwidth of the {gamma}-ray beam, the scattering laser must have minimal bandwidth, but also match the electron beam depth of focus in length. This requires a {approx}1 J, 10 ps, fourier-transform-limited laser system. Also required is a high-brightness electron beam, best provided by a photoinjector. This electron source requires a second laser system with stringent requirements on the beam including flat transverse and longitudinal profiles and fast rise times. Furthermore, these systems must be synchronized to each other with ps-scale accuracy. Using a novel hyper-dispersion compressor configuration and advanced fiber amplifiers and diode-pumped Nd:YAG amplifiers, we have designed laser systems that meet these challenges for the X-band photoinjector and Compton-scattering source being built at Lawrence Livermore National Laboratory.

  4. Pair instability supernovae of very massive population III stars

    SciTech Connect

    Chen, Ke-Jung; Woosley, Stan; Heger, Alexander; Almgren, Ann; Whalen, Daniel J.

    2014-09-01

    Numerical studies of primordial star formation suggest that the first stars in the universe may have been very massive. Stellar models indicate that non-rotating Population III stars with initial masses of 140-260 M {sub ☉} die as highly energetic pair-instability supernovae. We present new two-dimensional simulations of primordial pair-instability supernovae done with the CASTRO code. Our simulations begin at earlier times than previous multidimensional models, at the onset of core contraction, to capture any dynamical instabilities that may be seeded by core contraction and explosive burning. Such instabilities could enhance explosive yields by mixing hot ash with fuel, thereby accelerating nuclear burning, and affect the spectra of the supernova by dredging up heavy elements from greater depths in the star at early times. Our grid of models includes both blue supergiants and red supergiants over the range in progenitor mass expected for these events. We find that fluid instabilities driven by oxygen and helium burning arise at the upper and lower boundaries of the oxygen shell ∼20-100 s after core bounce. Instabilities driven by burning freeze out after the SN shock exits the helium core. As the shock later propagates through the hydrogen envelope, a strong reverse shock forms that drives the growth of Rayleigh-Taylor instabilities. In red supergiant progenitors, the amplitudes of these instabilities are sufficient to mix the supernova ejecta.

  5. PAIR INSTABILITY SUPERNOVAE: LIGHT CURVES, SPECTRA, AND SHOCK BREAKOUT

    SciTech Connect

    Kasen, Daniel; Woosley, S. E.; Heger, Alexander

    2011-06-20

    For the initial mass range (140 M{sub sun} < M < 260 M{sub sun}) stars die in a thermonuclear runaway triggered by the pair-production instability. The supernovae they make can be remarkably energetic (up to {approx}10{sup 53} erg) and synthesize considerable amounts of radioactive isotopes. Here we model the evolution, explosion, and observational signatures of representative pair instability supernovae (PI SNe) spanning a range of initial masses and envelope structures. The predicted light curves last for hundreds of days and range in luminosity from very dim to extremely bright (L {approx} 10{sup 44} erg s{sup -1}). The most massive events are bright enough to be seen at high redshift, but the extended light curve duration ({approx}1 yr)-prolonged by cosmological time-dilation-may make it difficult to detect them as transients. A more promising approach may be to search for the brief and luminous outbreak occurring when the explosion shock wave first reaches the stellar surface. Using a multi-wavelength radiation-hydrodynamics code we calculate that, in the rest frame, the shock breakout transients of PI SNe reach luminosities of 10{sup 45}-10{sup 46} erg s{sup -1}, peak at wavelengths {approx}30-170 A, and last for several hours. We discuss how observations of the light curves, spectra, and breakout emission can be used to constrain the mass, radius, and metallicity of the progenitor.

  6. Pair Instability Supernovae of Very Massive Population III Stars

    NASA Astrophysics Data System (ADS)

    Chen, Ke-Jung; Heger, Alexander; Woosley, Stan; Almgren, Ann; Whalen, Daniel J.

    2014-09-01

    Numerical studies of primordial star formation suggest that the first stars in the universe may have been very massive. Stellar models indicate that non-rotating Population III stars with initial masses of 140-260 M ⊙ die as highly energetic pair-instability supernovae. We present new two-dimensional simulations of primordial pair-instability supernovae done with the CASTRO code. Our simulations begin at earlier times than previous multidimensional models, at the onset of core contraction, to capture any dynamical instabilities that may be seeded by core contraction and explosive burning. Such instabilities could enhance explosive yields by mixing hot ash with fuel, thereby accelerating nuclear burning, and affect the spectra of the supernova by dredging up heavy elements from greater depths in the star at early times. Our grid of models includes both blue supergiants and red supergiants over the range in progenitor mass expected for these events. We find that fluid instabilities driven by oxygen and helium burning arise at the upper and lower boundaries of the oxygen shell ~20-100 s after core bounce. Instabilities driven by burning freeze out after the SN shock exits the helium core. As the shock later propagates through the hydrogen envelope, a strong reverse shock forms that drives the growth of Rayleigh-Taylor instabilities. In red supergiant progenitors, the amplitudes of these instabilities are sufficient to mix the supernova ejecta.

  7. Near intron pairs and the metazoan tree.

    PubMed

    Lehmann, Jörg; Stadler, Peter F; Krauss, Veiko

    2013-03-01

    Gene structure data can substantially advance our understanding of metazoan evolution and deliver an independent approach to resolve conflicts among existing hypotheses. Here, we used changes of spliceosomal intron positions as novel phylogenetic marker to reconstruct the animal tree. This kind of data is inferred from orthologous genes containing mutually exclusive introns at pairs of sequence positions in close proximity, so-called near intron pairs (NIPs). NIP data were collected for 48 species and utilized as binary genome-level characters in maximum parsimony (MP) analyses to reconstruct deep metazoan phylogeny. All groupings that were obtained with more than 80% bootstrap support are consistent with currently supported phylogenetic hypotheses. This includes monophyletic Chordata, Vertebrata, Nematoda, Platyhelminthes and Trochozoa. Several other clades such as Deuterostomia, Protostomia, Arthropoda, Ecdysozoa, Spiralia, and Eumetazoa, however, failed to be recovered due to a few problematic taxa such as the mite Ixodesand the warty comb jelly Mnemiopsis. The corresponding unexpected branchings can be explained by the paucity of synapomorphic changes of intron positions shared between some genomes, by the sensitivity of MP analyses to long-branch attraction (LBA), and by the very unequal evolutionary rates of intron loss and intron gain during evolution of the different subclades of metazoans. In addition, we obtained an assemblage of Cnidaria, Porifera, and Placozoa as sister group of Bilateria+Ctenophora with medium support, a disputable, but remarkable result. We conclude that NIPs can be used as phylogenetic characters also within a broader phylogenetic context, given that they have emerged regularly during evolution irrespective of the large variation of intron density across metazoan genomes.

  8. The Energetics of Gravity Driven Faulting

    NASA Astrophysics Data System (ADS)

    Barrows, L.

    2007-12-01

    Faulting can result from either of two different mechanisms. These involve fundamentally different energetics. In displacement-bounded faulting, locked-in elastic strain energy is transformed into seismic waves plus work done in the fault zone. Elastic rebound is an example of displacement-bounded faulting. In force-driven faulting, the forces that create the stress on the fault supply work or energy to the faulting process. Half of this energy is transformed into seismic waves plus work done in the fault zone and half goes into an increase in locked-in elastic strain. In displacement-bounded faulting the locked-in elastic strain drives slip on the fault. In force-driven faulting it stops slip on the fault. Tectonic stress is reasonably attributed to gravity acting on topography and the Earth's lateral density variations. This includes the thermal convection that ultimately drives plate tectonics. The gravity collapse seismic mechanism assumes the fault fails and slips in direct response to the gravitational tectonic stress. Gravity collapse is an example of force-driven faulting. In the simplest case, energy that is released from the gravitational potential of the topography and internal stress-causing density variations is equally split between the seismic waves plus work done in the fault zone and the increase in locked-in elastic strain. The release of gravitational potential energy requires a change in the Earth's density distribution. Gravitational body forces are solely dependent on density so a change in the density distribution requires a change in the body forces. This implies the existence of volumetric body-force displacements. The volumetric body-force displacements are in addition to displacements generated by slip on the fault. They must exist if gravity participates in the energetics of the faulting process. From the perspective of gravitational tectonics, the gravity collapse mechanism is direct and simple. The related mechanics are a little more

  9. Solar Energetic Particle Trapping During Geomagnetic Storms

    NASA Astrophysics Data System (ADS)

    Hudson, M.; Kress, B.; Blake, J. B.; Mazur, J.

    2007-12-01

    The prompt trapping of Solar Energetic Particles (SEPs) in the inner magnetosphere inside of L = 4 has been reported, including protons and heavier ions, in association with high speed interplanetary shocks and Storm Sudden Commencements (SSCs). These observations include the Bastille Day 2000 CME-driven storm as well as two in November 2001, which produced a long-lived new proton belt, as well as trapping of heavy ions up to Fe in all three cases. A survey of such events around the most recent solar maximum, including high altitude measurements from Polar, HEO and ICO satellites along with low altitude measurements from SAMPEX, indicates similarities to the well-studied March 24, 1991 SSC event. In this event, electrons and protons in drift resonance with a magnetosonic impulse were transported radially inward, requiring a source population which is multi-MeV at geosynchronous. A requirement for such shock-induced acceleration is a high-speed CME- shock at 1 AU, which launches a perturbation with comparable velocity inside the magnetosphere. Secondly, there must be a source population which is drift-resonant with the impulse. The CME-shock itself is a source of solar energetic particles, both protons and heavy ions, with higher fluxes and harder spectra associated with faster moving CMEs. A 3D Lorentz integration of SEP trajectories in electric and magnetic fields taken from the Lyon-Fedder-Mobarry (LFM) global MHD model, using solar wind input parameters from spacecraft measurements upstream from the bow shock, has been carried out for two November, 2001 SEP trapping events, and a CME-shock associated with the Halloween 2003 storm period, 29 October, which transported outer zone electrons and trapped solar energetic electrons into around L = 2.5, with little effect on SEPs. These results indicate that an enhancement in solar wind dynamic pressure for these events plays a role in the observed injection of ions (and electrons) to low L-values, as does the extent of

  10. Huddling behaviour and energetics of Sminthopsis spp. (Marsupialia, Dasyruidae) in response to environmental challenge.

    PubMed

    Tomlinson, Sean; Withers, Philip C; Maloney, Shane K

    2014-04-10

    We describe how behavioural responses are an important adjunct to physiological responses for two dunnart marsupials that live in arid environments. Behavioural responses of the stripe-faced dunnart Sminthopsis macroura and the Ooldea dunnart Sminthopsis ooldea differed with acclimation to four ambient temperature (T(a)) regimes, 12 h:12 h of 5-15 °C, 12-22 °C, 18-28 °C and 25-35 °C. Aggression levels were low at regimes 5-15 °C and 12-22 °C, and high at regimes 18-28 °C and 25-35 °C. The proportion of S. macroura huddled in groups increased significantly with decreasing T(a) regime, but there was no aggregation by S. ooldea at low T(a) regimes. The energetic benefit of huddling by S. macroura was highest for pairs of dunnarts (27% saving compared with singles) and only 3% for triplets at T(a)=10 °C. Thermal conductance decreased for pairs but not triplets compared to singles. There were no energetic savings for S. ooldea with increased numbers, and thermal conductance was the same per individual for single, pairs and triplets, reflecting their lack of huddling behaviour. The flexible behavioural (huddling) responses of S. macroura may facilitate their capacity to occupy a broad geographical distribution, unlike S. ooldea, which had inflexible behavioural responses (no huddling) and has a more restricted geographical range. The phylogenetic relationships of the dunnarts suggest that social behaviours may have arisen only once in the most adaptable subgroup of the Sminthopsini.

  11. Rare-earth defect pairs in GaN: LDA+U calculations

    NASA Astrophysics Data System (ADS)

    Sanna, Simone; Schmidt, W. G.; Frauenheim, Th.; Gerstmann, U.

    2009-09-01

    The structural and electronic properties of rare-earth (RE) (Eu, Er, and Tm) related defect pairs in GaN have been investigated theoretically. Based on LDA+U total-energy calculations, their possible role in the luminescence process is discussed. In all charge states, the lanthanides show a strong preference for the Ga-lattice site, either as isolated substitutional or complexed with intrinsic defects. With respect to the electronic valence, a proper description of correlation effects of the strongly localized 4f electrons is shown to be crucial, especially if the REGa is paired with donors like the Ga interstitial or the N vacancy. The pairs formed by REGa substitutionals and vacancies or interstitials lower the symmetry and are found to locally distort the environment. By this, they are quite effective in relaxing the selection rules for the luminescent intra- 4f -shell transitions. While for n -type GaN, the next-nearest-neighbor pair REGaVGa pair is energetically favored, for p -type GaN, the REGaVN pair provides the most stable configuration and introduces shallow levels close to the conduction band, which can act as assistant levels in the luminescence process.

  12. Phenomenology of transionospheric pulse pairs

    NASA Astrophysics Data System (ADS)

    Massey, R. S.; Holden, D. N.

    1995-09-01

    Recent observations of transient radio impulses by an Earth-orbiting satellite appear to be quite unlike any previously reported. They appear as pairs of brief (a few microseconds), noiselike bursts, separated by a few tens of microseconds, and are dispersed in a way that implies subionospheric origin. Over 300 of these events have now been observed. These "transionospheric pulse pairs" (TIPPs) have not yet been associated with any known source, although thunderstorms are suspected. The observations, made by the Blackbeard instrument on the ALEXIS satellite, are digitized records of the electric field in a passband from about 25 to 100 MHz. Ground-based observations of lightning in this band appear quite different, even accounting for ionospheric dispersion: bursts of short pulses last hundreds of microseconds and have much lower power (when propagated to the satellite) than TIPP events. Signals that resemble the ground-based data have been observed by Blackbeard but, being much weaker, are much less likely to trigger the instrument than are the strong pulse pair events. In this paper we analyze 97 of the early TIPP observations. We compute several parameters that describe the events: the location of the satellite at the time of reception, the energy in each pulse, the separation between pulses, the duration of each pulse, and the dispersion of each pulse. The statistical distributions of these parameters provide clues to and constraints on possible source mechanisms. The possibility that the pulses might be the direct and reflected signals from a high-altitude source is considered and cannot be rejected by the data.

  13. Nutrition and energetics in rodent longevity research.

    PubMed

    Gibbs, Victoria K; Smith, Daniel L

    2016-12-15

    The impact of calorie amount on aging has been extensively described; however, variation over time and among laboratories in animal diet, housing condition, and strains complicates discerning the true influence of calories (energy) versus nutrients on lifespan. Within the dietary restriction field, single macronutrient manipulations have historically been researched as a means to reduce calories while maintaining adequate levels of essential nutrients. Recent reports of nutritional geometry, including rodent models, highlight the impact macronutrients have on whole organismal aging outcomes. However, other environmental factors (e.g., ambient temperature) may alter nutrient preferences and requirements revealing context specific outcomes. Herein we highlight factors that influence the energetic and nutrient demands of organisms which oftentimes have underappreciated impacts on clarifying interventional effects on health and longevity in aging studies and subsequent translation to improve the human condition.

  14. Energetics and stochastic dynamics of intraneuron transport

    NASA Astrophysics Data System (ADS)

    Romanovsky, Yu M.; Trifonenkov, V. P.

    2016-02-01

    Walking molecular motors performing various functions in living cells are reviewed, including kinesin, myosin V, and dynein. These motors ensure the transport of neuromediators in neurons and are therefore crucial for interaction among the hundred billion brain cells. Functional schemes based on these motors are presented, and corresponding mathematical models are constructed as systems of two coupled FitzHugh-Nagumo equations. However, polynomials describing the moments of force are of high order and nearly N-shaped. Model parameters are determined from motor functional schemes that are based on observed data from X-ray structural analysis, cryogenic electron microscopy, laser tweezer measurements, and fast point marker-based videomicroscopy. Basic data on neuron energetics are summarized.

  15. Very energetic protons in Saturn's radiation belt

    NASA Technical Reports Server (NTRS)

    Fillius, W.; Mcilwain, C.

    1980-01-01

    Very energetic protons are trapped in the inner Saturnian radiation belt. The University of California at San Diego instrument on Pioneer 11 has definitely identified protons of energy greater than 80 MeV on channel M3 and has tentatively detected protons of energy greater than 600 MeV on channel C3. The spatial distribution of the protons is distinct from that of the trapped electrons, the main difference being that the protons are strongly absorbed by the innermost moons and that the electrons are not. The source strength for injecting protons by the decay of cosmic ray albedo neutrons generated in the rings of Saturn has been estimated. The required proton lifetime is approximately 20 years.

  16. Steering the potential barriers: entropic to energetic.

    PubMed

    Burada, P S; Schmid, G

    2010-11-01

    We propose a mechanism to alter the nature of the potential barriers when a biased brownian particle undergoes a constrained motion in narrow periodic channel. By changing the angle of the external bias, the nature of the potential barriers changes from purely entropic to energetic, which in turn affects the diffusion process in the system. At an optimum angle of the bias, the nonlinear mobility exhibits a striking bell-shaped behavior. Moreover, the enhancement of the scaled effective diffusion coefficient can be efficiently controlled by the angle of the bias. This mechanism enables the proper design of channel structures for transport of molecules and small particles. The approximate analytical predictions have been verified by precise brownian dynamics simulations.

  17. Terahertz absorption spectra of highly energetic chemicals

    NASA Astrophysics Data System (ADS)

    Slingerland, E. J.; Vallon, M. K.; Jahngen, E. G. E.; Giles, R. H.; Goyette, T. M.

    2010-04-01

    Research into absorption spectra is useful for detecting chemicals in the field. Each molecule absorbs a set of specific frequencies, which are dependent on the molecule's structure. While theoretical models are available for predicting the absorption frequencies of a particular molecule, experimental measurements are a more reliable method of determining a molecule's actual absorption behavior. The goal of this research is to explore chemical markers (absorption frequencies) that can be used to identify highly energetic molecules of interest to the remote sensing community. Particular attention was paid to the frequency ranges located within the terahertz transmission windows of the atmosphere. In addition, theoretical derivations, with the purpose of calculating the detection limits of such chemicals, will also be presented.

  18. Effect of Sawtooth Oscillations on Energetic Ions

    SciTech Connect

    R.B. White; V.V. Lutsenko; Ya. I. Kolesnichenko; Yu. V. Yakovenko

    1999-12-10

    The work summarizes results of the authors' studies on the energetic ion transport induced by sawtooth oscillations in tokamaks. The main attention is paid to description of physical mechanisms responsible for the transport. In addition to overview, the work contains new material. The new results concern the resonant interaction of the particles and the electromagnetic field of the sawtooth crash. In particular, it is discovered that the dominant harmonic of the crash (m = n = 1) can lead to stochastic motion of particles having large orbit width (potatoes). Regular motion of potatoes and quasi-stagnation particles in the presence of an n = 1 mode is studied, and their characteristic displacements associated with quick switching on/off the mode are found.

  19. Sodium Pentazolate: a Nitrogen Rich Energetic Material

    NASA Astrophysics Data System (ADS)

    Oleynik, Ivan; Steele, Brad

    Sodium pentazolates NaN5 and Na2N5, new energetic materials, are discovered using first principles crystal structure search for the compounds of varying amounts of elemental sodium and nitrogen. The pentazole anion (N5-s)i stabilized in the condensed phase by sodium Na+ cations at pressures exceeding 20 GPa, and becomes metastable upon release of pressure, i.e. at ambient conditions. The sodium azide (NaN3) precursor for the new compounds is predicted to undergo a chemical transformation above 50 GPa into sodium pentazolates NaN5 and Na2N5. The calculated Raman spectrum of NaN5 is in agreement with the experimental Raman spectrum of a previously unidentified substance appearing upon compression and heating of NaN3 precursor, thus confirming the appearance of the new compound.

  20. Energetic Compounds for Future Space Applications

    NASA Astrophysics Data System (ADS)

    Davenas, A.; Jacob, G.; Longevialle, Y.; Pérut, C.

    2004-10-01

    The need for new rocket propellants to improve or replace those in use today has led during the past ten years to studies of various, ancient or relatively new, energetic ingredients. The most often mentioned compounds for solid propellants are ADN (ammonium dinitramide), the nitramines RDX and HMX, HNIW (hexanitro hexaaza isowurtzitane), HNF (hydrazinum nitroformate), GAP (glycidyl azide polymer), and high nitrogen compounds. ADN, HNF, HAN (hydroxylammonium nitrate) are mentioned as possible ingredients in liquid mono and bi propellants for the future. A review of the work being conducted in the development and testing of the candidate propellants as well as an analysis of the general constraints of the industrial use and handling of these propellants and of their basic ingredients allows for a first tentative selection of the most promising ingredients. The possible synthesis routes, main characteristics, production and cost perspectives of these compounds are summarized and discussed.

  1. Access of energetic particles to Titan's exobase

    NASA Astrophysics Data System (ADS)

    Regoli, L.; Roussos, E.; Feyerabend, M.; Jones, G.; Krupp, N.; Coates, A.; Simon, S.; Motschmann, U.

    2015-10-01

    In this contribution we use a particle tracing code to trace energetic particles close to Titan in the specific magnetospheric conditions of the Cassini T9 flyby. The particles simulated are H+and O+ions with energies ranging from 1 keV to 1 MeV and the background electromagnetic field is represented by the output of the A.I.K.E.F. hybrid code for that specific flyby. These tools are used to generate 2D maps showing the access of the particles to the moon's exobase and those maps are subsequently used to normalize the fluxes measured by the Cassini MIMI/CHEMS instrument and estimate the energy deposition at specific positions around the moon.With this, we are able to estimate the importance that the asymmetries in the access of particles to the exobase has in the dynamics of Titan's ionosphere.

  2. Fast magnetospheric echoes of energetic electron beams

    NASA Technical Reports Server (NTRS)

    Wilhelm, K.; Bernstein, W.; Kellogg, P. J.; Whalen, B. A.

    1983-01-01

    Electron beam experiments using rocket-borne instrumentation confirmed earlier observations of fast magnetospheric echoes of artificially injected energetic electrons. A total of 234 echoes were observed in a pitch angle range from 9 to 110 deg at energies of 1.87 and 3.90 keV. Of these, 102 echoes could unambiguously be identified with known accelerator operations at 2, 4 or 8 keV energy and highest current levels resulting in the determination of transit times of typically 300 to 400 ms. In most cases, when echoes were present in both energy channels, the higher energy electrons led the lower energy ones by 50 to 70 ms. Adiabatic theory applied to these observations yields a reflection height of 3000 to 4000 km. The injection process is discussed as the strong beam-plasma interaction that occurred near the electron accelerator appears to be instrumental in generating the source of heated electrons required for successful echo detection.

  3. Energetic materials destruction using molten salt

    SciTech Connect

    Upadhye, R.S.; Watkins, B.E.; Pruneda, C.O.; Brummond, W.A.

    1994-04-29

    The Lawrence Livermore National Laboratory in conjunction with the Energetic Materials Center is developing methods for the safe and environmentally sound destruction of explosives and propellants as a part of the Laboratory`s ancillary demilitarization mission. LLNL has built a small-scale unit to test the destruction of HE using the Molten Salt Destruction (MSD) Process. In addition to the high explosive HMX, destruction has been carried out on RDX, PETN, ammonium picrate, TNT, nitroguanadine, and TATB. Also destroyed was a liquid gun propellant comprising hydroxyammonium nitrate, triethanolammonium nitrate and water. In addition to these pure components, destruction has been carried out on a number of commonly used formulations, such as LX-10, LX-16, LX-17, and PBX-9404.

  4. Tackling radio polarization of energetic pulsars

    SciTech Connect

    Craig, H. A.

    2014-08-01

    The traditional, geometrical rotating vector model (RVM) has proved particularly poor at capturing the polarization sweeps of the young energetic and millisecond pulsars detected by Fermi. We augment this model by including finite altitude effects using a swept back vacuum dipole geometry. By further including the effects of orthogonal mode jumps, multiple emission altitudes, open zone growth via y-point lowering, and interstellar scattering, we show that a wide range of departures from RVM can be modeled well while retaining a geometrical picture. We illustrate these effects by fitting six Fermi-detected pulsars (J0023+0923, J1024–0719, J1744–1134, J1057–5226, J1420–6048, and J2124–3358) and we describe how such modeling can improve our understanding of their emission geometry.

  5. Towards coherent control of energetic material initiation

    SciTech Connect

    Greenfield, Margo T; Mcgrane, Shawn D; Scharff, R Jason; Moore, David S

    2009-01-01

    Direct optical initiation (DOI) of energetic materials using coherent control of localized energy deposition requires depositing energy into the material to produce a critical size hot spot, which allows propagation of the reaction and thereby initiation, The hot spot characteristics needed for growth to initiation can be studied using quantum controlled initiation (QCI). Achieving direct quantum controlled initiation (QCI) in condensed phase systems requires optimally shaped ultrafast laser pulses to coherently guide the energy flow along the desired paths. As a test of our quantum control capabilities we have successfully demonstrated our ability to control the reaction pathway of the chemical system stilbene. An acousto-optical modulator based pulse shaper was used at 266 nm, in a shaped pump/supercontinuum probe technique, to enhance and suppress th relative yields of the cis- to trans-stilbene isomerization. The quantum control techniques tested in the stilbene experiments are currently being used to investigate QCI of the explosive hexanitroazobenzene (HNAB).

  6. STEREO Observations of Solar Energetic Particles

    NASA Technical Reports Server (NTRS)

    vonRosenvinge, Tycho; Christian, Eric; Cohen, Christina; Leske, Richard; Mewaldt, Richard; Stone, Edward; Wiedenbeck, Mark

    2011-01-01

    We report on observations of Solar Energetic Particle (SEP) events as observed by instruments on the STEREO Ahead and Behind spacecraft and on the ACE spacecraft. We will show observations of an electron event observed by the STEREO Ahead spacecraft on June 12, 2010 located at W74 essentially simultaneously with electrons seen at STEREO Behind at E70. Some similar events observed by Helios were ascribed to fast electron propagation in longitude close to the sun. We will look for independent verification of this possibility. We will also show observations of what appears to be a single proton event with very similar time-history profiles at both of the STEREO spacecraft at a similar wide separation. This is unexpected. We will attempt to understand all of these events in terms of corresponding CME and radio burst observations.

  7. Energetic particle physics with applications in fusion and space plasmas

    SciTech Connect

    Cheng, C.Z.

    1997-05-01

    Energetic particle physics is the study of the effects of energetic particles on collective electromagnetic (EM) instabilities and energetic particle transport in plasmas. Anomalously large energetic particle transport is often caused by low frequency MHD instabilities, which are driven by these energetic particles in the presence of a much denser background of thermal particles. The theory of collective energetic particle phenomena studies complex wave-particle interactions in which particle kinetic physics involving small spatial and fast temporal scales can strongly affect the MHD structure and long-time behavior of plasmas. The difficulty of modeling kinetic-MHD multiscale coupling processes stems from the disparate scales which are traditionally analyzed separately: the macroscale MHD phenomena are studied using the fluid MHD framework, while microscale kinetic phenomena are best described by complicated kinetic theories. The authors have developed a kinetic-MHD model that properly incorporates major particle kinetic effects into the MHD fluid description. For tokamak plasmas a nonvariational kinetic-MHD stability code, the NOVA-K code, has been successfully developed and applied to study problems such as the excitation of fishbone and Toroidal Alfven Eigenmodes (TAE) and the sawtooth stabilization by energetic ions in tokamaks. In space plasmas the authors have employed the kinetic-MHD model to study the energetic particle effects on the ballooning-mirror instability which explains the multisatellite observation of the stability and field-aligned structure of compressional Pc 5 waves in the magnetospheric ring current plasma.

  8. Synthesis and Characterization of Mixed Metal Oxide Nanocomposite Energetic Materials

    SciTech Connect

    Gash, A; Pantoya, M; Jr., J S; Zhao, L; Shea, K; Simpson, R; Clapsaddle, B

    2003-11-18

    In the field of composite energetic materials, properties such as ingredient distribution, particle size, and morphology, affect both sensitivity and performance. Since the reaction kinetics of composite energetic materials are typically controlled by the mass transport rates between reactants, one would anticipate new and potentially exceptional performance from energetic nanocomposites. We have developed a new method of making nanostructured energetic materials, specifically explosives, propellants, and pyrotechnics, using sol-gel chemistry. A novel sol-gel approach has proven successful in preparing metal oxide/silicon oxide nanocomposites in which the metal oxide is the major component. Two of the metal oxides are tungsten trioxide and iron(III) oxide, both of which are of interest in the field of energetic materials. Furthermore, due to the large availability of organically functionalized silanes, the silicon oxide phase can be used as a unique way of introducing organic additives into the bulk metal oxide materials. As a result, the desired organic functionality is well dispersed throughout the composite material on the nanoscale. By introducing a fuel metal into the metal oxide/silicon oxide matrix, energetic materials based on thermite reactions can be fabricated. The resulting nanoscale distribution of all the ingredients displays energetic properties not seen in its microscale counterparts due to the expected increase of mass transport rates between the reactants. The synthesis and characterization of these metal oxide/silicon oxide nanocomposites and their performance as energetic materials will be discussed.

  9. Energetic adaptations persist after bariatric surgery in severely obese adolescents

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Energetic adaptations induced by bariatric surgery have not been studied in adolescents or for extended periods postsurgery. Energetic, metabolic, and neuroendocrine responses to Roux-en-Y gastric bypass (RYGB) surgery were investigated in extremely obese adolescents. At baseline and at 1.5, 6, and...

  10. Novel Theory of Energetic-Ion-Induced Interchange Mode

    NASA Astrophysics Data System (ADS)

    Nishimura, Seiya

    2015-06-01

    On the basis of a kinetic energy principle, it is shown that the interchange mode in helical systems is excited by trapped energetic ions, where the ideal interchange mode is stable. The mode has a rotation frequency comparable to precession drift frequencies of trapped energetic ions. The theory explains how to apply the fishbone mode theory originally developed in tokamaks to helical systems.

  11. Paired circularly polarized heterodyne ellipsometer

    SciTech Connect

    Yu, C.-J.; Lin, C.-E.; Yu, L.-P.; Chou, C

    2009-02-01

    We develop a paired circularly polarized heterodyne ellipsometer (PCPHE), in which a heterodyne interferometer based on a two-frequency circularly polarized laser beam is set up. It belongs to an amplitude-sensitive ellipsometer that is able to provide not only a wider dynamic range of polarization modulation frequency but also a higher detection sensitivity than that of a conventional photometric ellipsometer. A real-time and precise measurement of ellipsometric parameters, which demonstrated an accuracy of less than 1 nm on thickness measurement of SiO2 thin film deposited on silicon substrate, can be applied with the PCPHE.

  12. Lightweight Target Generates Bright, Energetic X-Rays

    SciTech Connect

    Hazi, A

    2006-01-25

    Radiography with x rays is a long-established method to see inside objects, from human limbs to weapon parts. Livermore scientists have a continuing need for powerful x rays for such applications as backlighting, or illuminating, inertial confinement fusion (ICF) experiments and imaging still or exploding materials for the nation's Stockpile Stewardship Program. X-radiography is one of the prime diagnostics for ICF experiments because it captures the fine detail needed to determine what happens to nearly microscopic targets when they are compressed by laser light. For example, Livermore scientists participating in the National Ignition Facility's (NIF's) 18-month-long Early Light experimental campaign, which ended in 2004, used x rays to examine hydrodynamic instabilities in jets of plasma. In these experiments, one laser beam irradiated a solid target of titanium, causing it to form a high-temperature plasma that generated x rays of about 4.65 kiloelectronvolts (keV). These x rays backlit a jet of plasma formed when two other laser beams hit a plastic ablator and sent a shock to an aluminum washer. Livermore physicist Kevin Fournier of the Physics and Advanced Technologies Directorate leads a team that is working to increase the efficiency of converting laser energy into x rays so the resulting images provide more information about the object being illuminated. The main characteristics of x-ray sources are energy and brightness. ''As experimental targets get larger and as compression of the targets increases, the backlighter sources must be brighter and more energetic'', says Fournier. The more energetic the x rays, the further they penetrate an object. The brighter the source--that is, the more photons it has--the clearer the image. historically, researchers have used solid targets such as thin metal foils to generate x rays. however, when photon energies are greater than a few kiloelectronvolts, the conversion efficiency of solid targets is only a fraction of 1

  13. Catalytic reaction energetics by single crystal adsorption calorimetry: hydrocarbons on Pt(111).

    PubMed

    Lytken, Ole; Lew, Wanda; Campbell, Charles T

    2008-10-01

    Single crystal adsorption calorimetry provides essential information about the energetics of surface reactions on well-defined surfaces where the adsorbed reaction products can be clearly identified. In this tutorial review, we cover the essentials of that technique, with emphasis on our lab's recent advances in sensitivity and temperature range, and demonstrate what can be achieved through a review of selected example studies concerning adsorption and dehydrogenation of hydrocarbons on Pt(111). A fairly complete reaction enthalpy diagram is presented for the dehydrogenation of cyclohexane to benzene on Pt(111).

  14. Energetics of RHESSI X-Class Flares

    NASA Technical Reports Server (NTRS)

    Dennis, Brian R.; Haga, Leah; Holman, Gordon D.; Hudson, Hugh

    2005-01-01

    The thermal and nonthermal energies of several X-class flares seen with the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) will be presented. The same techniques described by Emslie et al. (JGR, 109, A10104, 2004) are used to take the RHESSI imaging spectroscopic observations and compute the energies in the thermal plasma and in the nonthermal electrons as a function of time throughout the flares. Radiative and conductive cooling rates are estimated and total thermal and nonthermal energies are computed for each flare. Typically, the energy in nonthermal electrons integrated up to the time of peak soft X-ray emission is equal to or exceeds the energy in the thermal plasma at that time. This suggests that energy must have been converted into a form not visible with RHESSI and that the total energy released by the flares may be significantly greater than the sum of energies calculated from the RHESSI observations alone. This conclusion is supported by the high radiative energy seen with SORCE during the impulsive phase of the 28 October 2003 flare. The peak increase in total solar irradiance of 270 mW per square meters measured with SORCE was over two orders of magnitude higher than the peak soft X-ray flux seen with GOES or RHESSI. The implications of this new observation as compared to the energetics derived from the X-ray observations of that flare will be discussed along with the energetics analysis of most of the other X- class flares in October/November 2003.

  15. Energetics of vacancy segregation to [100] symmetric tilt grain boundaries in bcc tungsten

    PubMed Central

    Chen, Nanjun; Niu, Liang-Liang; Zhang, Ying; Shu, Xiaolin; Zhou, Hong-Bo; Jin, Shuo; Ran, Guang; Lu, Guang-Hong; Gao, Fei

    2016-01-01

    The harsh irradiation environment poses serious threat to the structural integrity of leading candidate for plasma-facing materials, tungsten (W), in future nuclear fusion reactors. It is thus essential to understand the radiation-induced segregation of native defects and impurities to defect sinks, such as grain boundaries (GBs), by quantifying the segregation energetics. In this work, molecular statics simulations of a range of equilibrium and metastable [100] symmetric tilt GBs are carried out to explore the energetics of vacancy segregation. We show that the low-angle GBs have larger absorption length scales over their high-angle counterparts. Vacancy sites that are energetically unfavorable for segregation are found in all GBs. The magnitudes of minimum segregation energies for the equilibrium GBs vary from −2.61 eV to −0.76 eV depending on the GB character, while those for the metastable GB states tend to be much lower. The significance of vacancy delocalization in decreasing the vacancy segregation energies and facilitating GB migration has been discussed. Metrics such as GB energy and local stress are used to interpret the simulation results, and correlations between them have been established. This study contributes to the possible application of polycrystalline W under irradiation in advanced nuclear fusion reactors. PMID:27874047

  16. Energetics of vacancy segregation to [100] symmetric tilt grain boundaries in bcc tungsten.

    PubMed

    Chen, Nanjun; Niu, Liang-Liang; Zhang, Ying; Shu, Xiaolin; Zhou, Hong-Bo; Jin, Shuo; Ran, Guang; Lu, Guang-Hong; Gao, Fei

    2016-11-22

    The harsh irradiation environment poses serious threat to the structural integrity of leading candidate for plasma-facing materials, tungsten (W), in future nuclear fusion reactors. It is thus essential to understand the radiation-induced segregation of native defects and impurities to defect sinks, such as grain boundaries (GBs), by quantifying the segregation energetics. In this work, molecular statics simulations of a range of equilibrium and metastable [100] symmetric tilt GBs are carried out to explore the energetics of vacancy segregation. We show that the low-angle GBs have larger absorption length scales over their high-angle counterparts. Vacancy sites that are energetically unfavorable for segregation are found in all GBs. The magnitudes of minimum segregation energies for the equilibrium GBs vary from -2.61 eV to -0.76 eV depending on the GB character, while those for the metastable GB states tend to be much lower. The significance of vacancy delocalization in decreasing the vacancy segregation energies and facilitating GB migration has been discussed. Metrics such as GB energy and local stress are used to interpret the simulation results, and correlations between them have been established. This study contributes to the possible application of polycrystalline W under irradiation in advanced nuclear fusion reactors.

  17. Energetics of vacancy segregation to [100] symmetric tilt grain boundaries in bcc tungsten

    NASA Astrophysics Data System (ADS)

    Chen, Nanjun; Niu, Liang-Liang; Zhang, Ying; Shu, Xiaolin; Zhou, Hong-Bo; Jin, Shuo; Ran, Guang; Lu, Guang-Hong; Gao, Fei

    2016-11-01

    The harsh irradiation environment poses serious threat to the structural integrity of leading candidate for plasma-facing materials, tungsten (W), in future nuclear fusion reactors. It is thus essential to understand the radiation-induced segregation of native defects and impurities to defect sinks, such as grain boundaries (GBs), by quantifying the segregation energetics. In this work, molecular statics simulations of a range of equilibrium and metastable [100] symmetric tilt GBs are carried out to explore the energetics of vacancy segregation. We show that the low-angle GBs have larger absorption length scales over their high-angle counterparts. Vacancy sites that are energetically unfavorable for segregation are found in all GBs. The magnitudes of minimum segregation energies for the equilibrium GBs vary from ‑2.61 eV to ‑0.76 eV depending on the GB character, while those for the metastable GB states tend to be much lower. The significance of vacancy delocalization in decreasing the vacancy segregation energies and facilitating GB migration has been discussed. Metrics such as GB energy and local stress are used to interpret the simulation results, and correlations between them have been established. This study contributes to the possible application of polycrystalline W under irradiation in advanced nuclear fusion reactors.

  18. Rashba Splitting of Cooper Pairs

    NASA Astrophysics Data System (ADS)

    Shekhter, R. I.; Entin-Wohlman, O.; Jonson, M.; Aharony, A.

    2016-05-01

    We investigate theoretically the properties of a weak link between two superconducting leads, which has the form of a nonsuperconducting nanowire with a strong Rashba spin-orbit coupling caused by an electric field. In the Coulomb-blockade regime of single-electron tunneling, we find that such a weak link acts as a "spin splitter" of the spin states of Cooper pairs tunneling through the link, to an extent that depends on the direction of the electric field. We show that the Josephson current is sensitive to interference between the resulting two transmission channels, one where the spins of both members of a Cooper pair are preserved and one where they are both flipped. As a result, the current is a periodic function of the strength of the spin-orbit interaction and of the bending angle of the nanowire (when mechanically bent); an identical effect appears due to strain-induced spin-orbit coupling. In contrast, no spin-orbit induced interference effect can influence the current through a single weak link connecting two normal metals.

  19. Optical conductivity from pair density waves

    NASA Astrophysics Data System (ADS)

    Dai, Zhehao; Lee, Patrick A.

    2017-01-01

    We present a theory of optical conductivity in systems with finite-momentum Cooper pairs. In contrast to the BCS pairing where ac conductivity is purely imaginary in the clean limit, there is nonzero ac absorption across the superconducting gap for finite-momentum pairing if we break the Galilean symmetry explicitly in the electronic Hamiltonian. Vertex correction is crucial for maintaining the gauge invariance in the mean-field formalism and dramatically changes the optical conductivity in the direction of the pairing momentum. We carried out a self-consistent calculation and gave an explicit formula for optical conductivity in a simple case. This result applies to the Fulde-Ferrell-Larkin-Ovchinnikov state and candidates with pair density waves proposed for high-Tc cuprates. It may help detect pair density waves and determine the pairing gap as well as the direction of the pairing momentum in experiments.

  20. A Study of Charge Transport: Correlated Energetic Disorder in Organic Semiconductors, and the Fragment Hamiltonian

    NASA Astrophysics Data System (ADS)

    Allen, Jonathan Robert

    This dissertation details work done on two different descriptions of charge transport. The first topic is energetic disorder in organic semiconductors, and its effect on charge transport. This is motivated primarily by solar cells, which can be broadly classified as either inorganic or organic. The inorganic class of solar cells is older, and more well-developed, with the most common type being constructed from crystalline silicon. The large silicon crystals required for these cells are expensive to manufacture, which gave rise to interest in photovoltaic cells made from much less costly organic polymers. These organic materials are also less efficient than their silicon counterparts, due to a large degree of spatial and energetic disorder. In this document, the sources and structure of energetic disorder in organic semiconductors are explored, with an emphasis on spatial correlations in energetic disorder. In order for an organic photovoltaic device to function, there must be photogeneration of an exciton (a bound electron-hole pair), exciton transport, exciton dissociation, and transport of the individual charges to their respective terminals. In the case of this thesis, the main focus is exciton dissociation. The effects of correlation on exciton dissociation are examined through computer simulation, and compared to the theory and simulations of previous researchers. We conclude that energetic disorder in organic semiconductors is spatially correlated, and that this correlation improves the ability of excitons to dissociate. The second topic of this dissertation is the Fragment Hamiltonian model. This is a model currently in development as a means of describing charge transport across a range of systems. Currently there are many different systems which exhibit various charge transport behaviors, which are described by several different models. The overarching goal of the Fragment Hamiltonian model is to construct a description of charge transport which

  1. Roles of the amino group of purine bases in the thermodynamic stability of DNA base pairing.

    PubMed

    Nakano, Shu-ichi; Sugimoto, Naoki

    2014-08-05

    The energetic aspects of hydrogen-bonded base-pair interactions are important for the design of functional nucleotide analogs and for practical applications of oligonucleotides. The present study investigated the contribution of the 2-amino group of DNA purine bases to the thermodynamic stability of oligonucleotide duplexes under different salt and solvent conditions, using 2'-deoxyriboinosine (I) and 2'-deoxyribo-2,6-diaminopurine (D) as non-canonical nucleotides. The stability of DNA duplexes was changed by substitution of a single base pair in the following order: G • C > D • T ≈ I • C > A • T > G • T > I • T. The apparent stabilization energy due to the presence of the 2-amino group of G and D varied depending on the salt concentration, and decreased in the water-ethanol mixed solvent. The effects of salt concentration on the thermodynamics of DNA duplexes were found to be partially sequence-dependent, and the 2-amino group of the purine bases might have an influence on the binding of ions to DNA through the formation of a stable base-paired structure. Our results also showed that physiological salt conditions were energetically favorable for complementary base recognition, and conversely, low salt concentration media and ethanol-containing solvents were effective for low stringency oligonucleotide hybridization, in the context of conditions employed in this study.

  2. Magnetic pair creation transparency in gamma-ray pulsars

    SciTech Connect

    Story, Sarah A.; Baring, Matthew G. E-mail: baring@rice.edu

    2014-07-20

    Magnetic pair creation, γ → e {sup +} e {sup –}, has been at the core of radio pulsar paradigms and central to polar cap models of gamma-ray pulsars for over three decades. The Fermi gamma-ray pulsar population now exceeds 140 sources and has defined an important part of Fermi's science legacy, providing rich information for the interpretation of young energetic pulsars and old millisecond pulsars. Among the population characteristics well established is the common occurrence of exponential turnovers in their spectra in the 1-10 GeV range. These turnovers are too gradual to arise from magnetic pair creation in the strong magnetic fields of pulsar inner magnetospheres. By demanding insignificant photon attenuation precipitated by such single-photon pair creation, the energies of these turnovers for Fermi pulsars can be used to compute lower bounds for the typical altitude of GeV band emission. This paper explores such pair transparency constraints below the turnover energy and updates earlier altitude bound determinations that have been deployed in various Fermi pulsar papers. For low altitude emission locales, general relativistic influences are found to be important, increasing cumulative opacity, shortening the photon attenuation lengths, and also reducing the maximum energy that permits escape of photons from a neutron star magnetosphere. Rotational aberration influences are also explored, and are found to be small at low altitudes, except near the magnetic pole. The analysis presented in this paper clearly demonstrates that including near-threshold physics in the pair creation rate is essential to deriving accurate attenuation lengths and escape energies. The altitude bounds are typically in the range of 2-7 stellar radii for the young Fermi pulsar population, and provide key information on the emission altitude in radio quiet pulsars that do not possess double-peaked pulse profiles. The bound for the Crab pulsar is at a much higher altitude, with the

  3. Rainbow trout consume less oxygen in turbulence: the energetics of swimming behaviors at different speeds.

    PubMed

    Taguchi, Masashige; Liao, James C

    2011-05-01

    Measuring the rate of consumption of oxygen ( ) during swimming reveals the energetics of fish locomotion. We show that rainbow trout have substantially different oxygen requirements for station holding depending on which hydrodynamic microhabitats they choose to occupy around a cylinder. We used intermittent flow respirometry to show that an energetics hierarchy, whereby certain behaviors are more energetically costly than others, exists both across behaviors at a fixed flow velocity and across speeds for a single behavior. At 3.5 L s(-1) (L is total body length) entraining has the lowest , followed by Kármán gaiting, bow waking and then free stream swimming. As flow speed increases the costs associated with a particular behavior around the cylinder changes in unexpected ways compared with free stream swimming. At times, actually decreases as flow velocity increases. Entraining demands the least oxygen at 1.8 L s(-1) and 3.5 L s(-1), whereas bow waking requires the least oxygen at 5.0 L s(-1). Consequently, a behavior at one speed may have a similar cost to another behavior at another speed. We directly confirm that fish Kármán gaiting in a vortex street gain an energetic advantage from vortices beyond the benefit of swimming in a velocity deficit. We propose that the ability to exploit velocity gradients as well as stabilization costs shape the complex patterns of oxygen consumption for behaviors around cylinders. Measuring for station holding in turbulent flows advances our attempts to develop ecologically relevant approaches to evaluating fish swimming performance.

  4. Computational Studies of Energetic Organic Molecules

    DTIC Science & Technology

    1993-12-27

    with greater delocalization of the amine lone pair into the bond with increasing planarity, as shown in eq. (13). For instance, the calculated HF/3-21G...Kirschenheuter and Alster, 20 1987; Politzer and Murray, 1988; Politzer and Seminario, 1989]. Our " bond deviation index " was introduced as a numerical measure of...this index is given elsewhere [Politzer and Murray, 1988]. In Table 5 are listed our bond deviation indices for a variety of strained hydrocarbons

  5. Homolog pairing and segregation in Drosophila meiosis.

    PubMed

    McKee, B D

    2009-01-01

    Pairing of homologous chromosomes is fundamental to their reliable segregation during meiosis I and thus underlies sexual reproduction. In most eukaryotes homolog pairing is confined to prophase of meiosis I and is accompanied by frequent exchanges, known as crossovers, between homologous chromatids. Crossovers give rise to chiasmata, stable interhomolog connectors that are required for bipolar orientation (orientation to opposite poles) of homologs during meiosis I. Drosophila is unique among model eukaryotes in exhibiting regular homolog pairing in mitotic as well as meiotic cells. I review the results of recent molecular studies of pairing in both mitosis and meiosis in Drosophila. These studies show that homolog pairing is continuous between pre-meiotic mitosis and meiosis but that pairing frequencies and patterns are altered during the mitotic-meiotic transition. They also show that, with the exception of X-Y pairing in male meiosis, which is mediated specifically by the 240-bp rDNA spacer repeats, chromosome pairing is not restricted to specific sites in either mitosis or meiosis. Instead, virtually all chromosome regions, both heterochromatic and euchromatic, exhibit autonomous pairing capacity. Mutations that reduce the frequencies of both mitotic and meiotic pairing have been recently described, but no mutations that abolish pairing completely have been discovered, and the genetic control of pairing in Drosophila remains to be elucidated.

  6. The energetic implications of curtailing versus storing wind- and solar-generated electricity

    NASA Astrophysics Data System (ADS)

    Barnhart, C. J.; Dale, M.; Brandt, A. R.; Benson, S. M.

    2013-12-01

    Rapid deployment of power generation technologies harnessing wind and solar resources continues to reduce the carbon intensity of the power grid. But as these technologies comprise a larger fraction of power supply, their variable, weather-dependent nature poses challenges to power grid operation. Today, during times of power oversupply or unfavorable market conditions, power grid operators curtail these resources. Rates of curtailment are expected to increase with increased renewable electricity production. That is unless technologies are implemented that can provide grid flexibility to balance power supply with power demand. Curtailment is an obvious forfeiture of energy and it decreases the profitability of electricity from curtailed generators. What are less obvious are the energetic costs for technologies that provide grid flexibility. We present a theoretical framework to calculate how storage affects the energy return on energy investment (EROI) ratios of wind and solar resources. Our methods identify conditions under which it is more energetically favorable to store energy than it is to simply curtail electricity production. Electrochemically based storage technologies result in much smaller EROI ratios than large-scale geologically based storage technologies like compressed air energy storage (CAES) and pumped hydroelectric storage (PHS). All storage technologies paired with solar photovoltaic (PV) generation yield EROI ratios that are greater than curtailment. Due to their low energy stored on electrical energy invested (ESOIe) ratios, conventional battery technologies reduce the EROI ratios of wind generation below curtailment EROI ratios. To yield a greater net energy return than curtailment, battery storage technologies paired with wind generation need an ESOIe>80. We identify improvements in cycle life as the most feasible way to increase battery ESOIe. Depending upon the battery's embodied energy requirement, an increase of cycle life to 10

  7. Chain folding and A:T pairing in human telomeric DNA: a model-building and molecular dynamics study.

    PubMed Central

    Mohanty, D; Bansal, M

    1995-01-01

    The various types of chain folding and possible intraloop as well as interloop base pairing in human telomeric DNA containing d(TTAG3) repeats have been investigated by model-building, molecular mechanics, and molecular dynamics techniques. Model-building and molecular mechanics studies indicate that it is possible to build a variety of energetically favorable folded-back structures with the two TTA loops on same side and the 5' end thymines in the two loops forming TATA tetrads involving a number of different intraloop as well as interloop A:T pairing schemes. In these folded-back structures, although both intraloop and interloop Watson-Crick pairing is feasible, no structure is possible with interloop Hoogsteen pairing. MD studies of representative structures indicate that the guanine-tetraplex stem is very rigid and, while the loop regions are relatively much more flexible, most of the hydrogen bonds remain intact throughout the 350-ps in vacuo simulation. The various possible TTA loop structures, although they are energetically similar, have characteristic inter proton distances, which could give rise to unique cross-peaks in two-dimensional nuclear Overhauser effect spectroscopy (NOESY) experiments. These folded-back structures with A:T pairings in the loop region help in rationalizing the data from chemical probing and other biochemical studies on human telomeric DNA. PMID:8519959

  8. Paired Pulse Voltammetry for differentiating complex analytes

    PubMed Central

    Jang, Dong Pyo; Kim, Inyong; Chang, Su-Youne; Min, Hoon Ki; Arora, Kanika; Marsh, Michale P.; Hwang, Sun-Chul; Kimble, Christopher J.; Bennet, Kevin E.

    2012-01-01

    Although fast-scan cyclic voltammetry (FSCV) has contributed to important advances in neuroscience research, the technique is encumbered by significant analytical challenges. Confounding factors such as pH change and transient effects at the microelectrode surface make it difficult to discern the analytes represented by complex voltammograms. Here we introduce paired-pulse voltammetry (PPV), that mitigates the confounding factors and simplifies the analytical task. PPV consists of a selected binary waveform with a specific time gap between each of its two comprising pulses, such that each binary wave is repeated, while holding the electrode at a negative potential between the waves. This allows two simultaneous yet very different voltammograms (primary and secondary) to be obtained, each corresponding to the two pulses in the binary waveform. PPV was evaluated in the flow cell to characterize three different analytes, (dopamine, adenosine, and pH changes). The peak oxidation current decreased by approximately 50%, 80%, and 4% for dopamine, adenosine, and pH, in the secondary voltammogram compared with primary voltammogram, respectively. Thus, the influence of pH changes could be virtually eliminated using the difference between the primary and secondary voltammograms in the PPV technique, which discriminates analytes on the basis of their adsorption characteristics to the carbon fiber electrode. These results demonstrate that PPV can be effectively used for differentiating complex analytes. PMID:22299131

  9. Environmentally Responsible Energetic Materials: Another Look at the Styphnates

    NASA Astrophysics Data System (ADS)

    Collins, Adam; Angliss, Timothy; Proud, William

    2009-06-01

    Lead Styphnate (lead 2,4,6-trinitroresorcinate) has many applications as a primary explosive, most notably in priming compositions. Its largest drawback, however, is the toxicity of lead. Heavy metals often feature in primary explosives, providing favourable density, bonding, and reaction products; but, the toxic nature of heavy metals makes these explosives of limited use. Current research efforts are being made to design new energetic materials (such as those based around the 5-nitrotetrazole molecule), but familiar energetics can still be of use. The styphnate anion provides many favourable energetic qualities (such as a ring structure and nitro groups), and while the lead salt has proven its usefulness, other metallic styphnates also provide a range of energetic qualities. This paper reports on ignition thresholds, energetic output, and thermal properties of the following salts of trinitroresorcinol: Barium, Bismuth, Calcium, Copper, Lithium, and Lead. Such information provides a list of characterized energetic materials, but also insight into how metal cations can control measurable energetic effects at the molecular and crystal level.

  10. The energetics of lanthanum tantalate materials

    SciTech Connect

    Forbes, Tori Z.; Nyman, May; Rodriguez, Mark A.; Navrotsky, Alexandra

    2010-11-15

    Lanthanum tantalates are important refractory materials with application in photocatalysis, solid oxide fuel cells, and phosphors. Soft-chemical synthesis utilizing the Lindqvist ion, [Ta{sub 6}O{sub 19}]{sup 8-}, has yielded a new phase, La{sub 2}Ta{sub 2}O{sub 7}(OH){sub 2}. Using the hydrated phase as a starting material, a new lanthanum orthotantalate polymorph was formed by heating to 850 {sup o}C, which converts to a previously reported LaTaO{sub 4} polymorph at 1200 {sup o}C. The stabilities of La{sub 2}Ta{sub 2}O{sub 7}(OH){sub 2} (LaTa-OH), the intermediate LaTaO{sub 4} polymorph (LaTa-850), and the high temperature phase (LaTa-1200) were investigated using high-temperature oxide melt solution calorimetry. The enthalpy of formation from the oxides were calculated from the enthalpies of drop solution to be -87.1{+-}9.6, -94.9{+-}8.8, and -93.1{+-}8.7 kJ/mol for LaTa-OH, LaTa-850, and LaTa-1200, respectively. These results indicate that the intermediate phase, LaTa-850, is the most stable. This pattern of energetics may be related to cation-cation repulsion of the tantalate cations. We also investigated possible LnTaO{sub 4} and Ln{sub 2}Ta{sub 2}O{sub 7}(OH){sub 2} analogues of Ln=Pr, Nd to examine the relationship between cation size and the resulting phases. - Graphical abstract: The energetics of three lanthanum tantalates were investigated by the high-temperature oxide melt solution calorimetry. The enthalpies of formation from the oxides were calculated from the enthalpies of drop solution to be -87.1{+-}9.6, -94.9{+-}8.8, and -93.1{+-}8.7 kJ/mol for La{sub 2}Ta{sub 2}O{sub 7}(OH){sub 2}, LaTaO{sub 4} (850 {sup o}C), and LaTaO{sub 4} (1200 {sup o}C), respectively. These results indicate that the intermediate phase, LaTaO{sub 4} (850 {sup o}C), is the most stable in energy. Display Omitted

  11. Energetics of the Ocean's Infrasonic Sound Field.

    NASA Astrophysics Data System (ADS)

    D'Spain, Gerald Lynden

    1990-01-01

    Simultaneous measurements of infrasonic (0.5-20 Hz) particle velocity and pressure made by the Marine Physical Laboratory's freely drifting, independent, and neutrally buoyant Swallow floats are analyzed in terms of the energetics of acoustic fields. The theory of acoustic field energetics is presented and compared to standard data analysis techniques. The properties of the potential and kinetic energy density spectra, and the active and reactive intensity spectra from two deep ocean deployments are discussed. Results indicate that for most of the background sound field data in the midwater column above 1.7 Hz, the potential and kinetic energy density spectra are approximately equal. In one experiment, this is a consequence of the fact that, away from the ocean boundaries, the sound field is locally spatially homogeneous. Spatial homogeneity also implies that the particle velocity cross spectral density matrix is purely real. Near the ocean bottom, the vertical spatial inhomogeneity is statistically significant between 0.6 Hz to 1.4 Hz and 7 Hz to 20 Hz. In the lower band, the pressure autospectrum decreases with increasing distance from the ocean bottom, whereas in the upper band, it increases due to the deep sound channel's ability to trap acoustic energy at the higher infrasonic frequencies. For ship signals, the signal-to-noise ratio in the active intensity magnitude spectrum is 3 to 6 dB greater than in either of the two energy density spectra due to the vector nature of acoustic intensity. Although smaller than the net horizontal flux density above a few hertz, a statistically significant net vertical flux density of energy occurs across the whole frequency band, from the ocean surface into the bottom. The net horizontal flux density for various discrete sources, e.g., a magnitude 4.1 earthquake, a blue whale, and ship -generated harmonic line sets, is discussed. The net horizontal flux density of the background sound field between 5 and 12 Hz may have been

  12. Energetics of Al13 Keggin cluster compounds

    PubMed Central

    Armstrong, Christopher R.; Casey, William H.; Navrotsky, Alexandra

    2011-01-01

    The ϵ-Al13 Keggin aluminum hydroxide clusters are essential models in establishing molecular pathways for geochemical reactions. Enthalpies of formation are reported for two salts of aluminum centered ϵ-Keggin clusters, Al13 selenate, (Na(AlO4)Al12(OH)24(SeO4)4•12H2O) and Al13 sulfate, (NaAlO4Al12(OH)24(SO4)4•12H2O). The measured enthalpies of solution, ΔHsol, at 28 °C in 5 N HCl for the ε-Al13 selenate and sulfate are −924.57 (± 3.83) and −944.30 ( ± 5.66) kJ·mol-1, respectively. The enthalpies of formation from the elements, ΔHf,el, for Al13 selenate and sulfate are −19,656.35 ( ± 67.30) kJ·mol-1, and −20,892.39 ( ± 70.01) kJ·mol-1, respectively. In addition, ΔHf,el for sodium selenate decahydrate was calculated using data from high temperature oxide melt solution calorimetry measurements: −4,006.39 ( ± 11.91) kJ·mol-1. The formation of both ε-Al13 Keggin cluster compounds is exothermic from oxide-based components but energetically unfavorable with respect to a gibbsite-based assemblage. To understand the relative affinity of the ϵ-Keggin clusters for selenate and sulfate, the enthalpy associated with two S-Se exchange reactions was calculated. In the solid state, selenium is favored in the Al13 compound relative to the binary chalcogenate, while in 5 N HCl, sulfur is energetically favored in the cluster compound compared to the aqueous solution. This contribution represents the first thermodynamic study of ε-Al13 cluster compounds and establishes a method for other such molecules, including the substituted versions that have been created for kinetic studies. Underscoring the importance of ε-Al13 clusters in natural and anthropogenic systems, these data provide conclusive thermodynamic evidence that the Al13 Keggin cluster is a crucial intermediate species in the formation pathway from aqueous aluminum monomers to aluminum hydroxide precipitates. PMID:21852572

  13. CUSP Energetic Particles: Confinement, Acceleration and Implications

    NASA Technical Reports Server (NTRS)

    Chen, Jiasheng

    1999-01-01

    The cusp energetic particle (CEP) event is a new magnetospheric phenomenon. The events were detected in the dayside cusp for hours, in which the measured helium ions had energies up to 8 MeV. All of these events were associated with a dramatic decrease and large fluctuations in the local magnetic field strength. During January 1999 - December 1999 covered by this report, I have studied the CEP events by analyzing the POLAR, GEOTAIL, and WIND particle and magnetic field data measured during the geomagnetic quiet periods in 1996 and one geomagnetic storm period in 1998. The simultaneous observations indicated that the ion fluxes in the CEP events were higher than that in both the upstream and the downstream from the bow shock. The pitch angle distribution of the helium ions in the CEP events was found to peak around 90 deg. It was found that the mirror parameter, defined as the ratio of the square root of the integration of the parallel turbulent power spectral component over the ultra-low frequency (ULF) ranges to the mean field in the cusp, is correlated with the intensity of the cusp MeV helium flux, which is a measure of the influence of mirroring interactions and an indication of local effect. It was also found that the turbulent power of the local magnetic field in the ultra-low frequency (ULF) ranges is correlated with the intensity of the cusp energetic helium ions. Such ULF ranges correspond to periods of about 0.33-500 seconds that cover the gyroperiods, the bounce periods, and the drift periods of the tens keV to MeV charged particles when they are temporarily confined in the high-altitude dayside cusp. These observations represent a discovery that the high-altitude dayside cusp is a new acceleration and dynamic trapping region of the magnetosphere. The cusp geometry is connected via gradient and curvature drift of these energized ions to the equatorial plasma sheet as close as the geostationary orbit at local midnight. It implies that the dayside cusp is

  14. Magnetic Reconnection-Powered Relativistic Particle Acceleration, High-Energy Gamma-Ray Emission, and Pair Production in Coronae of Accreting Black Holes

    NASA Astrophysics Data System (ADS)

    Uzdensky, Dmitri

    2015-11-01

    Magnetic reconnection is a fundamental plasma process believed to play an important role in energetics of magnetically-dominated coronae of various astrophysical objects including accreting black holes. Building up on recent advances in kinetic simulations of relativistic collisionless reconnection, we investigate nonthermal particle acceleration and its key observational consequences for these systems. We argue that reconnection can efficiently accelerate coronal electrons (as well as ions) up to hundreds of MeV or even GeV energies. In brightest systems, radiation back-reaction due to inverse-Compton (and/or synchrotron) emission becomes important at these energies and limits any further electron acceleration, thereby turning reconnection layers into powerful and efficient radiators of γ-rays. We then evaluate the rate of absorption of the resulting γ-ray photons by the ambient soft (X-ray) photon fields and show that it can be a significant source of pair production, with important implications for the composition of black-hole coronae and jets. Finally, we assess the prospects of laboratory studies of magnetic reconnection in the physical regimes relevant to black-hole accretion flows using modern and future laser-plasma facilities. This work is supported by DOE, NSF, and NASA.

  15. Catching the First Cosmic Explosions: Explosion and Mixing of Pair-Instability Supernovae

    NASA Astrophysics Data System (ADS)

    Chen, Ke-Jung; Heger, Alexander; Woosley, Stan

    2014-03-01

    We present multidimensional simulations of the thermonuclear supernovae from massive primordial stars. Numerical and theoretical study of the primordial star formation in the early Universe suggest that these stars could have been very massive. Primordial stars with initial masses of 150-260 solar masses may have died as energetic thermonuclear supernovae, so-called pair-instability supernovae (PSNe). We model the explosion of PSNe by using a new radiation-hydro code, CASTRO and find the fluid instabilities driven by nuclear burning and hydrodynamics during the explosion. For red supergiant models, amplitudes of these instabilities are sufficient to break down the spherical symmetry of the supernova ejecta.

  16. Conformational analysis of a covalently cross-linked Watson-Crick base pair model.

    PubMed

    Jensen, Erik A; Allen, Benjamin D; Kishi, Yoshito; O'Leary, Daniel J

    2008-11-15

    Low-temperature NMR experiments and molecular modeling have been used to characterize the conformational behavior of a covalently cross-linked DNA base pair model. The data suggest that Watson-Crick or reverse Watson-Crick hydrogen bonding geometries have similar energies and can interconvert at low temperatures. This low-temperature process involves rotation about the crosslink CH(2)C(5') (psi) carbon-carbon bond, which is energetically preferred over the alternate CH(2)N(3) (phi) carbon-nitrogen bond rotation.

  17. Internal Transport Barrier Driven by Redistribution of Energetic Ions

    SciTech Connect

    K.L. Wong; W.W. Heidbrink; E. Ruskov; C.C. Petty; C.M. Greenfield; R. Nazikian; R. Budny

    2004-11-12

    Alfven instabilities excited by energetic ions are used as a means to reduce the central magnetic shear in a tokamak via redistribution of energetic ions. When the central magnetic shear is low enough, ballooning modes become stable for any plasma pressure gradient and an internal transport barrier (ITB) with a steep pressure gradient can exist. This mechanism can sustain a steady-state ITB as demonstrated by experimental data from the DIII-D tokamak. It can also produce a shear in toroidal and poloidal plasma rotation. Possible application of this technique to use the energetic alpha particles for improvement of burning plasma performance is discussed.

  18. Elemental composition of solar energetic particles in 1977 and 1978

    NASA Technical Reports Server (NTRS)

    Cook, W. R.; Stone, E. C.; Vogt, R. E.; Trainor, J. H.; Webber, W. R.

    1979-01-01

    The elemental composition of energetic nuclei from seven major solar flare events were measured wit the cosmic ray detector systems aboard the Voyager 1 and 2 spacecraft. The energetic nuclei abundances differ significantly from those of photospheric material. They are enhanced relative to the photonsphere by a factor which is the ratio of abundance of an energetic nuclei species (relative to oxygen) over the corresponding abundance of photospheric material. This factor is common to all events and has a nonmonochromatic characteristic dependence on nuclear charge. This factor is roughly ordered by first ionization potential into two groups of elements, metallics and volatiles.

  19. Chemical Conversion of Energetic Materials to Higher Value Products

    SciTech Connect

    Mitchell, A R; Hsu, P C; Coburn, M D; Schmidt, R D; Pagoria, P F; Lee, G S

    2005-04-19

    The objective of this program is to develop new processes for the disposal of surplus energetic materials. Disposal through open burning/open detonation (OB/OD) is considered less attractive today due to environmental, cost and safety concerns. The use of energetic materials as chemical feedstocks for higher value products can provide environmentally sound and cost-effective alternatives to OB/OD. Our recent studies on the conversion of surplus energetic materials (Explosive D, TNT) to higher value products will be described.

  20. Energetics diagnosis of numerical simulation of atmospheric blocking

    NASA Technical Reports Server (NTRS)

    Kung, Ernest C.

    1990-01-01

    A series of systematic comprehensive diagnoses of Goddard Laboratory for Atmospheres (GLA) General Circulation Model (GCM) simulation experiments was performed in reference to predictability and energetics of the Northern Hemisphere blocking circulation. The simulation experiments were performed. The following subject areas are also covered: an analysis of simulated summer blocking episodes; energetics examination of winter blocking simulations in the Northern Hemisphere; normal mode energetic and error analysis of GLA GCM simulations with the different horizontal resolutions during a winter month; and simulations of winter blocking episodes using observed sea surface temperatures.

  1. Galactic substructure and energetic neutrinos from the sun and earth.

    PubMed

    Koushiappas, Savvas M; Kamionkowski, Marc

    2009-09-18

    We consider the effects of Galactic substructure on energetic neutrinos from annihilation of weakly interacting massive particles that have been captured by the Sun and Earth. Substructure gives rise to a time-varying capture rate and thus to time variation in the annihilation rate and resulting energetic-neutrino flux. However, there may be a time lag between the capture and annihilation rates. The energetic-neutrino flux may then be determined by the density of dark matter in the Solar System's past trajectory, rather than the local density. The signature of such an effect may be sought in the ratio of the direct- to indirect-detection rates.

  2. Voyager 1: energetic ions and electrons in the jovian magnetosphere.

    PubMed

    Vogt, R E; Cook, W R; Cummings, A C; Garrard, T L; Gehrels, N; Stone, E C; Trainor, J H; Schardt, A W; Conlon, T; Lal, N; McDonald, F B

    1979-06-01

    The observations of the cosmic-ray subsystem have added significantly to our knowledge of Jupiter's magnetosphere. The most surprising result is the existence of energetic sulfur, sodium, and oxygen nuclei with energies above 7 megaelectron volts per nucleon which were found inside of Io's orbit. Also, significant fluxes of similarly energetic ions reflecting solar cosmic-ray composition were observed throughout the magnetosphere beyond 11 times the radius of Jupiter. It was also found that energetic protons are enhanced by 30 to 70 percent in the active hemisphere. Finally, the first observations were made of the magnetospheric tail in the dawn direction out to 160 Jupiter radii.

  3. Large gradual solar energetic particle events

    NASA Astrophysics Data System (ADS)

    Desai, Mihir; Giacalone, Joe

    2016-12-01

    Solar energetic particles, or SEPs, from suprathermal (few keV) up to relativistic (˜ few GeV) energies are accelerated near the Sun in at least two ways: (1) by magnetic reconnection-driven processes during solar flares resulting in impulsive SEPs, and (2) at fast coronal-mass-ejection-driven shock waves that produce large gradual SEP events. Large gradual SEP events are of particular interest because the accompanying high-energy ({>}10s MeV) protons pose serious radiation threats to human explorers living and working beyond low-Earth orbit and to technological assets such as communications and scientific satellites in space. However, a complete understanding of these large SEP events has eluded us primarily because their properties, as observed in Earth orbit, are smeared due to mixing and contributions from many important physical effects. This paper provides a comprehensive review of the current state of knowledge of these important phenomena, and summarizes some of the key questions that will be addressed by two upcoming missions—NASA’s Solar Probe Plus and ESA’s Solar Orbiter. Both of these missions are designed to directly and repeatedly sample the near-Sun environments where interplanetary scattering and transport effects are significantly reduced, allowing us to discriminate between different acceleration sites and mechanisms and to isolate the contributions of numerous physical processes occurring during large SEP events.

  4. Energetic characteristics of transition metal complexes.

    PubMed

    Wojewódka, Andrzej; Bełzowski, Janusz; Wilk, Zenon; Staś, Justyna

    2009-11-15

    Ten transition metal nitrate and perchlorate complexes of hydrazine and ethylenediamine were synthesized, namely [Cu(EN)(2)](ClO(4))(2), [Co(EN)(3)](ClO(4))(3), [Ni(EN)(3)](ClO(4))(2), [Hg(EN)(2)](ClO(4))(2), [Cr(N(2)H(4))(3)](ClO(4))(3), [Cd(N(2)H(4))(3)](ClO(4))(2), [Ni(N(2)H(4))(3)](NO(3))(2), [Co(N(2)H(4))(3)](NO(3))(3), [Zn(N(2)H(4))(3)](NO(3))(2), and [Cd(N(2)H(4))(3)](NO(3))(2) based on the lines of the literature reported methods. All of them were tested with applying underwater detonation test and further compared to the typical blasting explosives: RDX, HMX, TNT and PETN. From the above presented complexes [Ni(N(2)H(4))(3)](NO(3))(2) (called NHN) and [Co(N(2)H(4))(3)](NO(3))(3) (called CoHN) are known as primary explosives and can be used as the standard explosives. Explosion parameters, such as shock wave overpressure, shock wave energy equivalent and bubble energy equivalent, were determined. Evaluated energetic characteristics of the tested compounds are comparable to those of the classic high explosives and are even enhanced in some cases.

  5. Linking energetics and overwintering in temperate insects.

    PubMed

    Sinclair, Brent J

    2015-12-01

    Overwintering insects cannot feed, and energy they take into winter must therefore fuel energy demands during autumn, overwintering, warm periods prior to resumption of development in spring, and subsequent activity. Insects primarily consume lipids during winter, but may also use carbohydrate and proteins as fuel. Because they are ectotherms, the metabolic rate of insects is temperature-dependent, and the curvilinear nature of the metabolic rate-temperature relationship means that warm temperatures are disproportionately important to overwinter energy use. This energy use may be reduced physiologically, by reducing the slope or elevation of the metabolic rate-temperature relationship, or because of threshold changes, such as metabolic suppression upon freezing. Insects may also choose microhabitats or life history stages that reduce the impact of overwinter energy drain. There is considerable capacity for overwinter energy drain to affect insect survival and performance both directly (via starvation) or indirectly (for example, through a trade-off with cryoprotection), but this has not been well-explored. Likewise, the impact of overwinter energy drain on growing-season performance is not well understood. I conclude that overwinter energetics provides a useful lens through which to link physiology and ecology and winter and summer in studies of insect responses to their environment.

  6. Update on Saturn's energetic electron periodicities

    NASA Astrophysics Data System (ADS)

    Carbary, James F.

    2017-01-01

    The periodicities in fluxes of energetic electrons (110-365 keV) in Saturn's magnetosphere were determined from late 2004 to mid-2016. The electron periods were calculated using Lomb periodogram analyses within windows of 200 days at sliding intervals of 10 days, which tracked changes in the periodicity. Sometimes the periodicity showed a clear duality, as in 2007-2008, while at other times the two periods came together so closely as to be indistinguishable, as after equinox in 2010 and in 2015. At still other times, the periodicity apparently vanished altogether, as in 2014. These periodicities generally agreed with those of other phenomena such as the magnetic field and radio emissions. Whether dual or mono, the periods generally remained between 10.58 h and 10.84 h, with two statistical peaks at 10.68 h and 10.81 h. This observation suggests that magnetospheric periodicities at Saturn lie within a limited range of values, which places constraints on the generative mechanism for the phenomena.

  7. Energetic molding of chiral magnetic bubbles

    NASA Astrophysics Data System (ADS)

    Lau, Derek; Sundar, Vignesh; Zhu, Jian-Gang; Sokalski, Vincent

    2016-08-01

    Topologically protected magnetic structures such as skyrmions and domain walls (DWs) have drawn a great deal of attention recently due to their thermal stability and potential for manipulation by spin current, which is the result of chiral magnetic configurations induced by the interfacial Dzyaloshinskii-Moriya interaction (DMI). Designing devices that incorporate DMI necessitates a thorough understanding of how the interaction presents and can be measured. One approach is to measure growth asymmetry of chiral bubble domains in perpendicularly magnetized thin films, which has been described elsewhere by thermally activated DW motion. Here, we demonstrate that the anisotropic angular dependence of DW energy originating from the DMI is critical to understanding this behavior. Domains in Co/Ni multilayers are observed to preferentially grow into nonelliptical teardrop shapes, which vary with the magnitude of an applied in-plane field. We model the domain profile using energetic calculations of equilibrium shape via the Wulff construction, which serves as a new paradigm for describing chiral domains that explains both the teardrop shape and the reversal of growth symmetry at large fields.

  8. Energetics of solar coronal mass ejections

    NASA Astrophysics Data System (ADS)

    Subramanian, P.; Vourlidas, A.

    2007-05-01

    Aims:We investigate whether solar coronal mass ejections are driven mainly by coupling to the ambient solar wind or through the release of internal magnetic energy. Methods: We examine the energetics of 39 flux-rope like coronal mass ejections (CMEs) from the Sun using data in the distance range ~2-20 R⊙ from the Large Angle Spectroscopic Coronograph (LASCO) aboard the Solar and Heliospheric Observatory (SOHO). This comprises a complete sample of the best examples of flux-rope CMEs observed by LASCO in 1996-2001. Results: We find that 69% of the CMEs in our sample experience a clearly identifiable driving power in the LASCO field of view. For those CMEs that are driven, we examine if they might be deriving most of their driving power by coupling to the solar wind. We do not find conclusive evidence in favor of this hypothesis. On the other hand, we find that their internal magnetic energy is a viable source of the required driving power. We have estimated upper and lower limits on the power that can possibly be provided by the internal magnetic field of a CME. We find that, on average, the lower limit to the available magnetic power is around 74% of what is required to drive the CMEs, while the upper limit can be as much as an order of magnitude larger.

  9. PLASMA ENERGETIC PARTICLES SIMULATION CENTER (PEPSC)

    SciTech Connect

    Berk, Herbert L.

    2014-05-23

    The main effort of the Texas group was to develop theoretical and simplified numerical models to understand chirping phenomena often seen for Alfven and geodesic acoustic waves in experimental plasmas such as D-III-D, NSTX and JET. Its main numerical effort was to modify the AEGIS code, which was originally developed as an eigenvalue solver. To apply to the chirping problem this code has to be able to treat the linear response to the continuum and the response of the plasma to external drive or to an internal drive that comes from the formation of phase space chirping structures. The theoretical underpinning of this investigation still needed to be more fully developed to understand how to best formulate the theoretical problem. Considerable progress was made on this front by B.N. Breizman and his collaborators and a new reduced model was developed by H. L. Berk and his PhD student, G. Wang which can be uses as simplified model to describe chirping in a large aspect ratio tokamak. This final report will concentrate on these two directions that were developed as well as results that were found in the work with the AEGIS code and in the progress in developing a novel quasi-linear formulation for a description of Alfvenic modes destabilized by energetic particles, such as alpha particles in a burning plasma.

  10. Excitation-contraction coupling and mitochondrial energetics

    PubMed Central

    O’Rourke, Brian

    2009-01-01

    Cardiac excitation-contraction (EC) coupling consumes vast amounts of cellular energy, most of which is produced in mitochondria by oxidative phosphorylation. In order to adapt the constantly varying workload of the heart to energy supply, tight coupling mechanisms are essential to maintain cellular pools of ATP, phosphocreatine and NADH. To our current knowledge, the most important regulators of oxidative phosphorylation are ADP, Pi, and Ca2+. However, the kinetics of mitochondrial Ca2+-uptake during EC coupling are currently a matter of intense debate. Recent experimental findings suggest the existence of a mitochondrial Ca2+ microdomain in cardiac myocytes, justified by the close proximity of mitochondria to the sites of cellular Ca2+ release, i. e., the ryanodine receptors of the sarcoplasmic reticulum. Such a Ca2+ microdomain could explain seemingly controversial results on mitochondrial Ca2+ uptake kinetics in isolated mitochondria versus whole cardiac myocytes. Another important consideration is that rapid mitochondrial Ca2+ uptake facilitated by microdomains may shape cytosolic Ca2+ signals in cardiac myocytes and have an impact on energy supply and demand matching. Defects in EC coupling in chronic heart failure may adversely affect mitochondrial Ca2+ uptake and energetics, initiating a vicious cycle of contractile dysfunction and energy depletion. Future therapeutic approaches in the treatment of heart failure could be aimed at interrupting this vicious cycle. PMID:17657400

  11. Observed deep energetic eddies by seamount wake.

    PubMed

    Chen, Gengxin; Wang, Dongxiao; Dong, Changming; Zu, Tingting; Xue, Huijie; Shu, Yeqiang; Chu, Xiaoqing; Qi, Yiquan; Chen, Hui

    2015-11-30

    Despite numerous surface eddies are observed in the ocean, deep eddies (a type of eddies which have no footprints at the sea surface) are much less reported in the literature due to the scarcity of their observation. In this letter, from recently collected current and temperature data by mooring arrays, a deep energetic and baroclinic eddy is detected in the northwestern South China Sea (SCS) with its intensity, size, polarity and structure being characterized. It remarkably deepens isotherm at deep layers by the amplitude of ~120 m and induces a maximal velocity amplitude about 0.18 m/s, which is far larger than the median velocity (0.02 m/s). The deep eddy is generated in a wake when a steering flow in the upper layer passes a seamount, induced by a surface cyclonic eddy. More observations suggest that the deep eddy should not be an episode in the area. Deep eddies significantly increase the velocity intensity and enhance the mixing in the deep ocean, also have potential implication for deep-sea sediments transport.

  12. Energetics of syntrophic cooperation in methanogenic degradation.

    PubMed Central

    Schink, B

    1997-01-01

    Fatty acids and alcohols are key intermediates in the methanogenic degradation of organic matter, e.g., in anaerobic sewage sludge digestors or freshwater lake sediments. They are produced by classical fermenting bacteria for disposal of electrons derived in simultaneous substrate oxidations. Methanogenic bacteria can degrade primarily only one-carbon compounds. Therefore, acetate, propionate, ethanol, and their higher homologs have to be fermented further to one-carbon compounds. These fermentations are called secondary or syntrophic fermentations. They are endergonic processes under standard conditions and depend on intimate coupling with methanogenesis. The energetic situation of the prokaryotes cooperating in these processes is problematic: the free energy available in the reactions for total conversion of substrate to methane attributes to each partner amounts of energy in the range of the minimum biochemically convertible energy, i.e., 20 to 25 kJ per mol per reaction. This amount corresponds to one-third of an ATP unit and is equivalent to the energy required for a monovalent ion to cross the charged cytoplasmic membrane. Recent studies have revealed that syntrophically fermenting bacteria synthesize ATP by substrate-level phosphorylation and reinvest part of the ATP-bound energy into reversed electron transport processes, to release the electrons at a redox level accessible by the partner bacteria and to balance their energy budget. These findings allow us to understand the energy economy of these bacteria on the basis of concepts derived from the bioenergetics of other microorganisms. PMID:9184013

  13. Intense and energetic radiation from crystalline undulators

    NASA Astrophysics Data System (ADS)

    Uggerhøj, U. I.; Wistisen, T. N.

    2015-07-01

    With the recent experimental confirmation of the existence of energetic radiation from a Small Amplitude, Small Period (SASP) crystalline undulator (Wistisen et al., 2014), the field of specially manufactured crystals, from which specific radiation characteristics can be obtained, has evolved substantially. In the present paper we show how the radiation spectra can be tuned, using electrons and positrons of energies from 100 MeV up to 20 GeV. The latter energy is relevant for possible experiments at the FACET facility at Stanford Linear Accelerator Center (SLAC), whereas 100 MeV has been chosen to show the potentialities connected to using crystalline undulators as radiation targets for Nuclear Waste Transmutation (NWT). Energies in the few hundred MeV range are relevant for the facilities at the MAinzer MIcrotron (MAMI). For the 20 GeV case we show explicitly that quantum corrections to the emission spectrum become very significant, an effect that may be observed in the near future using the FACET beam at SLAC.

  14. Kinetic transport simulation of energetic particles

    NASA Astrophysics Data System (ADS)

    Sheng, He; Waltz, R. E.

    2016-05-01

    A kinetic transport code (EPtran) is developed for the transport of the energetic particles (EPs). The EPtran code evolves the EP distribution function in radius, energy, and pitch angle phase space (r, E, λ) to steady state with classical slowing down, pitch angle scattering, as well as radial and energy transport of the injected EPs (neutral beam injection (NBI) or fusion alpha). The EPtran code is illustrated by treating the transport of NBI fast ions from high-n ITG/TEM micro-turbulence and EP driven unstable low-n Alfvén eigenmodes (AEs) in a well-studied DIII-D NBI heated discharge with significant AE central core loss. The kinetic transport code results for this discharge are compared with previous study using a simple EP density moment transport code ALPHA (R.E. Waltz and E.M. Bass 2014 Nucl. Fusion 54 104006). The dominant EP-AE transport is treated with a local stiff critical EP density (or equivalent pressure) gradient radial transport model modified to include energy-dependence and the nonlocal effects EP drift orbits. All previous EP transport models assume that the EP velocity space distribution function is not significantly distorted from the classical ‘no transport’ slowing down distribution. Important transport distortions away from the slowing down EP spectrum are illustrated by a focus on the coefficient of convection: EP energy flux divided by the product of EP average energy and EP particle flux.

  15. Ion energetics in the Venus nightside ionosphere

    NASA Technical Reports Server (NTRS)

    Knudsen, W. C.; Miller, K. L.; Spenner, K.; Whitten, R. C.

    1980-01-01

    Consideration is given to the energetics of the ion gas flowing across the terminator into the Venus nightside ionosphere. Expressions are derived for the transport time of the ion gas (through 1 radian in solar zenith angle), the heat transfer time from the hot electron gas to the ions of an amount equal to the ion thermal energy), and the time required for vertical heat conduction to remove the internal energy of the ion column above a reference altitude, and it is shown that the time constant for transport is an order of magnitude smaller than the electron heat transfer time and comparable to the conduction time, and thus the ion gas is not a vertical conductive steady state. The conversion of bulk flow ion kinetic energy into heat is suggested as the mechanism responsible for the maintenance of the nightside ion temperatures at their observed values. It is thus concluded that the flow of the ion gas is quasi-adiabatic, and that steady-state, vertical, one dimensional energy balance models must be used with caution in the Venus ionosphere.

  16. PoET: Polarimeters for Energetic Transients

    NASA Technical Reports Server (NTRS)

    McConnell, Mark; Barthelmy, Scott; Hill, Joanne

    2008-01-01

    This presentation focuses on PoET (Polarimeters for Energetic Transients): a Small Explorer mission concept proposed to NASA in January 2008. The principal scientific goal of POET is to measure GRB polarization between 2 and 500 keV. The payload consists of two wide FoV instruments: a Low Energy Polarimeter (LEP) capable of polarization measurements in the energy range from 2-15 keV and a high energy polarimeter (Gamma-Ray Polarimeter Experiment - GRAPE) that will measure polarization in the 60-500 keV energy range. Spectra will be measured from 2 keV up to 1 MeV. The PoET spacecraft provides a zenith-pointed platform for maximizing the exposure to deep space. Spacecraft rotation will provide a means of effectively dealing with systematics in the polarization response. PoET will provide sufficient sensitivity and sky coverage to measure statistically significant polarization for up to 100 GRBs in a two-year mission. Polarization data will also be obtained for solar flares, pulsars and other sources of astronomical interest.

  17. Shock Initiation Thresholds of Various Energetic Materials

    NASA Astrophysics Data System (ADS)

    Damm, David; Welle, Eric; Yarrington, Cole

    2013-06-01

    Shock initiation threshold data for several energetic materials has been analyzed for both short-pulses and long, sustained shocks. In the limit of long duration shocks, the critical pressure for initiation is governed by the balance between chemical energy release in the vicinity of hotspots and thermal dissipation which cools the hotspot and can quench reactions. The observed trends in critical pressure from one material to the next are related to the thermophysical properties and chemical reaction kinetics of each material. Scaling analysis, combined with hydrocode simulations of collapsing pores has confirmed these trends; however large uncertainty in the reaction kinetics under shock loading prevents an accurate quantitative description of hotspot ignition. For a given pore diameter, scaling analysis allows a quick estimate of the temperature at which the reaction rate will exceed the rate of thermal dissipation. Using published thermophysical property data and reaction kinetics we found that the trend in critical hotspot temperatures for several common materials (e.g. PETN, HMX, HNS, and TATB) matches the observed trend in initiation sensitivity. The hydrocode simulations of pore collapse provide a link between the critical temperature and the initial shock pressure. For these simulations we have used recently published QMD-based equations of state for the fully-dense, crystalline phase and have included the effects of variable specific heat, viscous dissipation, and plastic work. These results will be presented and the need for physically-meaningful reaction rates will be emphasized.

  18. Fast magnetospheric echoes of energetic electron beams

    NASA Technical Reports Server (NTRS)

    Wilhelm, K.; Bernstein, W.; Kellogg, P. J.; Whalen, B. A.

    1985-01-01

    Electron beam experiments using rocketborne instrumentation have confirmed earlier observations of fast magnetospheric echoes of artificially injected energetic electrons. A total of 234 echoes have been observed in a pitch angle range from 9 to 110 deg at energies of 1.87 and 3.90 keV. Out of this number, 95 echoes could unambiguously be identified with known accelerator operations at 2-, 4-, or 8-keV energy and highest current levels resulting in the determination of transit times of typically 300 to 400 ms. In most cases, when echoes were present in both energy channels, the higher-energy electrons led the lower-energy ones by 50 to 70 ms. Adiabatic theory applied to these observations yields a reflection height of 3000 to 4000 km. An alternative interpretation is briefly examined, and its relative merit in describing the observations is evaluated. The injection process is discussed in some detail as the strong beam-plasma interaction that occurred near the electron accelerator appears to be instrumental in generating the source of heated electrons required for successful echo detection for both processes.

  19. Energetics of Boron Doping of Carbon Pores

    NASA Astrophysics Data System (ADS)

    Wexler, Carlos; St. John, Alexander; Connolly, Matthew

    2014-03-01

    Carbon-based materials show promise, given their light weight, large surface areas and low cost for storage of hydrogen and other gases, e.g., for energy applications. Alas, the interaction of H2 and carbon, 4-5kJ/mol, is insufficient for room-temperature operation. Boron doping of carbon materials could raise the binding energy of H2 to 12-15kJ/mol. The nature of the incorporation of boron into a carbon structure has not been studied so far. In this talk we will address the energetics of boron incorporation into a carbon matrix via adsorption and decomposition of decaborane by first principles calculations. These demonstrate: (a) A strong adsorption of decaborane to carbon (70-80kJ/mol) resulting in easy incorporation of decaborane, sufficient for up to 10-20% B:C at low decaborane vapour pressures. (b) Identification that boron acts as an electron acceptor when incorporated substitutionally into a graphene-like material, as expected due to its valence. (c) The electrostatic field near the molecule is responsible for ca. 2/3 of the enhancement of the H2-adsorbent interaction in aromatic compounds such as pyrene, coronene and ovalene. Supported by DOE DE-FG36-08GO18142, ACS-PRF 52696-ND5, and NSF 1069091.

  20. Observed deep energetic eddies by seamount wake

    NASA Astrophysics Data System (ADS)

    Chen, Gengxin; Wang, Dongxiao; Dong, Changming; Zu, Tingting; Xue, Huijie; Shu, Yeqiang; Chu, Xiaoqing; Qi, Yiquan; Chen, Hui

    2015-11-01

    Despite numerous surface eddies are observed in the ocean, deep eddies (a type of eddies which have no footprints at the sea surface) are much less reported in the literature due to the scarcity of their observation. In this letter, from recently collected current and temperature data by mooring arrays, a deep energetic and baroclinic eddy is detected in the northwestern South China Sea (SCS) with its intensity, size, polarity and structure being characterized. It remarkably deepens isotherm at deep layers by the amplitude of ~120 m and induces a maximal velocity amplitude about 0.18 m/s, which is far larger than the median velocity (0.02 m/s). The deep eddy is generated in a wake when a steering flow in the upper layer passes a seamount, induced by a surface cyclonic eddy. More observations suggest that the deep eddy should not be an episode in the area. Deep eddies significantly increase the velocity intensity and enhance the mixing in the deep ocean, also have potential implication for deep-sea sediments transport.

  1. The energetic characterization of pineapple crown leaves.

    PubMed

    Braga, R M; Queiroga, T S; Calixto, G Q; Almeida, H N; Melo, D M A; Melo, M A F; Freitas, J C O; Curbelo, F D S

    2015-12-01

    Energetic characterization of biomass allows for assessing its energy potential for application in different conversion processes into energy. The objective of this study is to physicochemically characterize pineapple crown leaves (PC) for their application in energy conversion processes. PC was characterized according to ASTM E871-82, E1755-01, and E873-82 for determination of moisture, ash, and volatile matter, respectively; the fixed carbon was calculated by difference. Higher heating value was determined by ASTM E711-87 and ash chemical composition was determined by XRF. The thermogravimetric and FTIR analyses were performed to evaluate the thermal decomposition and identify the main functional groups of biomass. PC has potential for application in thermochemical processes, showing high volatile matter (89.5%), bulk density (420.8 kg/m(3)), and higher heating value (18.9 MJ/kg). The results show its energy potential justifying application of this agricultural waste into energy conversion processes, implementing sustainability in the production, and reducing the environmental liabilities caused by its disposal.

  2. MEMEX: Mechanisms of Energetic Mass Ejection Explorer

    NASA Astrophysics Data System (ADS)

    Moore, T. E.; Chappell, C. R.; Clemmons, J. H.; Cully, C. M.; Donovan, E.; Earle, G. D.; Heelis, R. A.; Kistler, L. M.; Kepko, L.; Khazanov, G. V.; Knudsen, D. J.; Lessard, M.; McFadden, J. P.; Nicolls, M. J.; Pollock, C. J.; Pfaff, R. F.; Rankin, R.; Rowland, D. E.; Semeter, J. L.; Thayer, J. P.; Winglee, R.

    2013-12-01

    MEMEX is designed to find out how gravitationally-trapped volatile matter is being lost from atmospheres by energetic processes, depleting them of key constituents, as has occurred most dramatically at Mars. This process is exemplified in geospace by the dissipation of solar energy to produce ionospheric outflows that feed back on dynamics of the solar wind interaction with Earth's magnetosphere. Kinetic and electromagnetic energy flow from the Sun into the coupled (auroral) ionosphere, where resultant electron, ion, and gas heating give rise to upwelling, ionization, and mass ejection. Proposed mechanisms involve wave-particle heating interactions, upward ambipolar electric fields, or ponderomotive forces. A large number of free energy sources have been identified, but empirical guidance remains weak concerning their relative importance. Moreover, it is unclear if the waves interact with particles primarily in a cyclotron resonant mode, or in a lower hybrid exchange of electron (parallel) and ion (perpendicular) energy, or in a bulk ponderomotive mode. MEMEX will answer the questions raised by these issues: Where do the waves that produce mass ejection grow? How do they propagate and transport energy? How can wave amplitudes, heating, and escape rates be derived from solar wind conditions? Is the heating a cyclotron resonant process or a bulk ponderomotive forcing process? To obtain answers, MEMEX will for the first time simultaneously observe the magnetospheric and atmospheric boundary conditions applied to the topside or exobase layer, and the response of ions and electrons to the ensuing battle between electrodynamic forcing and collisional damping.

  3. Energetic electrons in the magnetosphere of jupiter.

    PubMed

    Van Allen, J A; Baker, D N; Randall, B A; Thomsen, M F; Sentman, D D; Flindt, H R

    1974-01-25

    Observations of energetic electrons ( greater, similar 0.07 million electron volts) show that the outer magnetosphere of Jupiter consists of a thin disklike, quasitrapping region extending from about 20 to 100 planetary radii (R(J)). This magnetodisk is confined to the vicinity of the magnetic equatorial plane and appears to be an approximate figure of revolution about the magnetic axis of the planet. Hard trapping is observed within a radial distance of about 20 R(J). The omnidirectional intensity J(0) of electrons with energy greater, similar 21 million electron volts within the region 3 r 20 R(J) is given by the following provisional expression in terms of radial distance r and magnetic latitude theta: J(0) = 2.1 x 10(8) exp[-(r/a) - (theta/b)(2)]. In this expression J(0) is particles per square centimeter per second; a = 1.52 R(J) for 3

  4. Energetic charged particles in the uranian magnetosphere.

    PubMed

    Stone, E C; Cooper, J F; Cummings, A C; McDonald, F B; Trainor, J H; Lal, N; McGuire, R; Chenette, D L

    1986-07-04

    During the encounter with Uranus, the cosmic ray system on Voyager 2 measured significant fluxes of energetic electrons and protons in the regions of the planets magnetosphere where these particles could be stably trapped. The radial distribution of electrons with energies of megaelectron volts is strongly modulated by the sweeping effects ofthe three major inner satellites Miranda, Ariel, and Umbriel. The phase space density gradient of these electrons indicates that they are diffusing radially inward from a source in the outer magnetosphere or magnetotail. Differences in the energy spectra of protons having energies of approximately 1 to 8 megaelectron volts from two different directions indicate a strong dependence on pitch angle. From the locations of the absorption signatures observed in the electron flux, a centered dipole model for the magnetic field of Uranus with a tilt of 60.1 degrees has been derived, and a rotation period of the planet of 17.4 hours has also been calculated. This model provides independent confirmaton of more precise determinations made by other Voyager experiments.

  5. Intensity Variation of Solar Energetic Particle Events

    NASA Technical Reports Server (NTRS)

    Gopalswamy, Nat

    2011-01-01

    This paper updates the influence of environmental and source factors of shocks driven by corona) mass ejections (CMEs) that are likely to influence the intensity of solar energetic particle (SEP) events. The intensity variation due to CME interaction reported in Gopalswamy et al. (2004, JGR 109, Al2105) is confirmed by expanding the investigation to all the large SEP events of solar cycle 23. The large SEP events are separated into two groups, one associated with CMEs running into other CMEs, and the other with CMEs running into the ambient solar wind. SEP events with CME interaction generally have a higher intensity. New possibilities such as the influence of corona) holes on the SEP intensity are also discussed. For example, the presence of a large coronal hole between a well-connected eruption and the solar disk center may render the shock poorly connected because of the interaction between the CME and the coronal hole. This point is illustrated using the 2004 December 3 SEP event delayed by about 12 hours from the onset of the associated CME. There is no other event at the Sun that can be associated with the SEP onset. This event is consistent with the possibility that the coronal hole interaction influences the connectivity of the CMEs that produce SEPs, and hence the intensity of the SEP event.

  6. ENERGETIC PARTICLE DIFFUSION IN CRITICALLY BALANCED TURBULENCE

    SciTech Connect

    Laitinen, T.; Dalla, S.; Kelly, J.; Marsh, M.

    2013-02-20

    Observations and modeling suggest that the fluctuations in magnetized plasmas exhibit scale-dependent anisotropy, with more energy in the fluctuations perpendicular to the mean magnetic field than in the parallel fluctuations and the anisotropy increasing at smaller scales. The scale dependence of the anisotropy has not been studied in full-orbit simulations of particle transport in turbulent plasmas so far. In this paper, we construct a model of critically balanced turbulence, as suggested by Goldreich and Sridhar, and calculate energetic particle spatial diffusion coefficients using full-orbit simulations. The model uses an enveloped turbulence approach, where each two-dimensional wave mode with wavenumber k is packed into envelopes of length L following the critical balance condition, L{proportional_to}k {sup -2/3} , with the wave mode parameters changing between envelopes. Using full-orbit particle simulations, we find that both the parallel and perpendicular diffusion coefficients increase by a factor of two, compared to previous models with scale-independent anisotropy.

  7. Temporal Evolution of Solar Energetic Particle Spectra

    NASA Astrophysics Data System (ADS)

    Doran, Donald J.; Dalla, Silvia

    2016-08-01

    During solar flares and coronal mass ejections, Solar Energetic Particles (SEPs) may be released into the interplanetary medium and near-Earth locations. The energy spectra of SEP events at 1 AU are typically averaged over the entire event or studied in a few snapshots. In this article we analyze the time evolution of the energy spectra of four large selected SEP events using a large number of snapshots. We use a multi-spacecraft and multi-instrument approach for the observations, obtained over a wide SEP energy range. We find large differences in the spectra at the beginning of the events as measured by different instruments. We show that over time, a wave-like structure is observed traveling through the spectra from the highest energies to the lowest energies, creating an "arch" shape that then straightens into a power law later in the event, after times on the order of 10 hours. We discuss the processes that determine SEP intensities and their role in shaping the spectral time evolution.

  8. Efficient laser production of energetic neutral beams

    NASA Astrophysics Data System (ADS)

    Mollica, F.; Antonelli, L.; Flacco, A.; Braenzel, J.; Vauzour, B.; Folpini, G.; Birindelli, G.; Schnuerer, M.; Batani, D.; Malka, V.

    2016-03-01

    Laser-driven ion acceleration by intense, ultra-short, laser pulse has received increasing attention in recent years, and the availability of much compact and versatile ions sources motivates the study of laser-driven sources of energetic neutral atoms. We demonstrate the production of a neutral and directional beam of hydrogen and carbon atoms up to 200 keV per nucleon, with a peak flow of 2.7× {{10}13} atom s-1. Laser accelerated ions are neutralized in a pulsed, supersonic argon jet with tunable density between 1.5× {{10}17} cm-3and 6× {{10}18} cm-3. The neutralization efficiency has been measured by a time-of-flight detector for different argon densities. An optimum is found, for which complete neutralization occurs. The neutralization rate can be explained only at high areal densities (>1× {{10}17} cm-2) by single electron charge transfer processes. These results suggest a new perspective for the study of neutral production by laser and open discussion of neutralization at a lower density.

  9. Observed deep energetic eddies by seamount wake

    PubMed Central

    Chen, Gengxin; Wang, Dongxiao; Dong, Changming; Zu, Tingting; Xue, Huijie; Shu, Yeqiang; Chu, Xiaoqing; Qi, Yiquan; Chen, Hui

    2015-01-01

    Despite numerous surface eddies are observed in the ocean, deep eddies (a type of eddies which have no footprints at the sea surface) are much less reported in the literature due to the scarcity of their observation. In this letter, from recently collected current and temperature data by mooring arrays, a deep energetic and baroclinic eddy is detected in the northwestern South China Sea (SCS) with its intensity, size, polarity and structure being characterized. It remarkably deepens isotherm at deep layers by the amplitude of ~120 m and induces a maximal velocity amplitude about 0.18 m/s, which is far larger than the median velocity (0.02 m/s). The deep eddy is generated in a wake when a steering flow in the upper layer passes a seamount, induced by a surface cyclonic eddy. More observations suggest that the deep eddy should not be an episode in the area. Deep eddies significantly increase the velocity intensity and enhance the mixing in the deep ocean, also have potential implication for deep-sea sediments transport. PMID:26617343

  10. Dense pair plasma generation by two laser pulses colliding in a cylinder channel

    NASA Astrophysics Data System (ADS)

    Liu, Jian-Xun; Ma, Yan-Yun; Yu, Tong-Pu; Zhao, Jun; Yang, Xiao-Hu; Zou, De-Bin; Zhang, Guo-Bo; Zhao, Yuan; Yang, Jing-Kang; Li, Han-Zhen; Zhuo, Hong-Bin; Shao, Fu-Qiu; Kawata, Shigeo

    2017-03-01

    An all-optical scheme for high-density pair plasmas generation is proposed by two laser pulses colliding in a cylinder channel. Two dimensional particle-in-cell simulations show that, when the first laser pulse propagates in the cylinder, electrons are extracted out of the cylinder inner wall and accelerated to high energies. These energetic electrons later run into the second counter-propagating laser pulse, radiating a large amount of high-energy gamma photons via the Compton back-scattering process. The emitted gamma photons then collide with the second laser pulse to initiate the Breit–Wheeler process for pairs production. Due to the strong self-generated fields in the cylinder, positrons are confined in the channel to form dense pair plasmas. Totally, the maximum density of pair plasmas can be 4.60× {10}27 {{{m}}}-3, for lasers with an intensity of 4× {10}22 {{W}}\\cdot {{cm}}-2. Both the positron yield and density are tunable by changing the cylinder radius and the laser parameters. The generated dense pair plasmas can further facilitate investigations related to astrophysics and particle physics. Project supported by the National Natural Science Foundation (Grant Nos. 11475260, 11305264, 11622547, 11375265, and 11474360), the National Basic Research Program of China (Grant No. 2013CBA01504), the Research Project of National University of Defense Technology, China (Contract No. JC14-02-02), and the Science Challenge Program, China (Grant No. JCKY2016212A505).

  11. Nitrogen-14 NQR Study of Energetic Materials

    DTIC Science & Technology

    1982-09-01

    Army Research Office Research Triangle Park North Carolina 27709 Contract No. DAAG-29-79-0025 I Submitted by: BLOCK ENGINEERING Division of Bio-Rad...NQR Lines C-i F APPENDIX D Princeton Applied Research Interface D-1 References R-1 BLOCK 󈨑 7T - %. LIST OF TABLES Tables Page 2.2-I Lorentzian FID and...as can be seen by the seemingly incongruous pairing of v and v + lines in Figure 3.1-1. In fact, it will be shown that the chemical inequivalence of "o

  12. Mechanism and Energetics of Charybdotoxin Unbinding from a Potassium Channel from Molecular Dynamics Simulations

    PubMed Central

    Chen, Po-chia; Kuyucak, Serdar

    2009-01-01

    Ion channel-toxin complexes are ideal systems for computational studies of protein-ligand interactions, because, in most cases, the channel axis provides a natural reaction coordinate for unbinding of a ligand and a wealth of physiological data is available to check the computational results. We use a recently determined structure of a potassium channel-charybdotoxin complex in molecular dynamics simulations to investigate the mechanism and energetics of unbinding. Pairs of residues on the channel protein and charybdotoxin that are involved in the binding are identified, and their behavior is traced during umbrella-sampling simulations as charybdotoxin is moved away from the binding site. The potential of mean force for the unbinding of charybdotoxin is constructed from the umbrella sampling simulations using the weighted histogram analysis method, and barriers observed are correlated with specific breaking of interactions and influx of water molecules into the binding site. Charybdotoxin is found to undergo conformational changes as a result of the reaction coordinate choice—a nontrivial decision for larger ligands—which we explore in detail, and for which we propose solutions. Agreement between the calculated and the experimental binding energies is obtained once the energetic consequences of these conformational changes are included in the calculations. PMID:19348743

  13. Surface energetics and protein-protein interactions: analysis and mechanistic implications

    NASA Astrophysics Data System (ADS)

    Peri, Claudio; Morra, Giulia; Colombo, Giorgio

    2016-04-01

    Understanding protein-protein interactions (PPI) at the molecular level is a fundamental task in the design of new drugs, the prediction of protein function and the clarification of the mechanisms of (dis)regulation of biochemical pathways. In this study, we use a novel computational approach to investigate the energetics of aminoacid networks located on the surface of proteins, isolated and in complex with their respective partners. Interestingly, the analysis of individual proteins identifies patches of surface residues that, when mapped on the structure of their respective complexes, reveal regions of residue-pair couplings that extend across the binding interfaces, forming continuous motifs. An enhanced effect is visible across the proteins of the dataset forming larger quaternary assemblies. The method indicates the presence of energetic signatures in the isolated proteins that are retained in the bound form, which we hypothesize to determine binding orientation upon complex formation. We propose our method, BLUEPRINT, as a complement to different approaches ranging from the ab-initio characterization of PPIs, to protein-protein docking algorithms, for the physico-chemical and functional investigation of protein-protein interactions.

  14. A Market-Basket Approach to Predict the Acute Aquatic Toxicity of Munitions and Energetic Materials.

    PubMed

    Burgoon, Lyle D

    2016-06-01

    An ongoing challenge in chemical production, including the production of insensitive munitions and energetics, is the ability to make predictions about potential environmental hazards early in the process. To address this challenge, a quantitative structure activity relationship model was developed to predict acute fathead minnow toxicity of insensitive munitions and energetic materials. Computational predictive toxicology models like this one may be used to identify and prioritize environmentally safer materials early in their development. The developed model is based on the Apriori market-basket/frequent itemset mining approach to identify probabilistic prediction rules using chemical atom-pairs and the lethality data for 57 compounds from a fathead minnow acute toxicity assay. Lethality data were discretized into four categories based on the Globally Harmonized System of Classification and Labelling of Chemicals. Apriori identified toxicophores for categories two and three. The model classified 32 of the 57 compounds correctly, with a fivefold cross-validation classification rate of 74 %. A structure-based surrogate approach classified the remaining 25 chemicals correctly at 48 %. This result is unsurprising as these 25 chemicals were fairly unique within the larger set.

  15. Structure and energetics of Cr(CO)6 and Cr(CO)5

    NASA Technical Reports Server (NTRS)

    Barnes, Leslie A.; Liu, Bowen; Lindh, Roland

    1993-01-01

    The geometric structures and energetics of Cr(CO)6 and Cr(CO)5 are determined at the modified coupled-pair functional, single and double excitation coupled-cluster (CCSD), and CCSD(T) levels of theory. For Cr(CO)6, the structure and force constants for the totally symmetric representation are in good agreement with experimental data once basis set constants are taken into account. In the largest basis set at the CCSD(T) level of theory, the total binding energy of CR(CO)6 is estimated at around 140 kcal/mol, or about 86 percent of the experimental value. In contrast, the first bond energy of Cr(CO)6 is very well described at the CCSD(T) level of theory, with the best estimated value of 38 kcal/mol being within the experimental uncertainty.

  16. Optimum laser intensity for the production of energetic deuterium ions from laser-cluster interaction

    SciTech Connect

    Bang, W.; Dyer, G.; Quevedo, H. J.; Bernstein, A. C.; Gaul, E.; Rougk, J.; Aymond, F.; Donovan, M. E.; Ditmire, T.

    2013-09-15

    We measured, using Petawatt-level pulses, the average ion energy and neutron yield in high-intensity laser interactions with molecular clusters as a function of laser intensity. The interaction volume over which fusion occurred (1–10 mm{sup 3}) was larger than previous investigations, owing to the high laser power. Possible effects of prepulses were examined by implementing a pair of plasma mirrors. Our results show an optimum laser intensity for the production of energetic deuterium ions both with and without the use of the plasma mirrors. We measured deuterium plasmas with 14 keV average ion energies, which produced 7.2 × 10{sup 6} and 1.6 × 10{sup 7} neutrons in a single shot with and without plasma mirrors, respectively. The measured neutron yields qualitatively matched the expected yields calculated using a cylindrical plasma model.

  17. Energetic 2,2-Dimethyltriazanium Salts: A New Family of Nitrogen-Rich Hydrazine Derivatives.

    PubMed

    Forquet, Valérian; Sabaté, Carlos Miró; Jacob, Guy; Guelou, Yann; Delalu, Henri; Darwich, Chaza

    2015-08-01

    Amination of 1,1-dimethylhydrazine with NH2 Cl or hydroxylamine-O-sulfonic acid yields 2,2-dimethyltriazanium (DMTZ) chloride (3) and sulphate (4), respectively. The DMTZ cation was paired with the nitrogen-rich anions 5-aminotetrazolate (5), 5-nitrotetrazolate (6), 5,5'-azobistetrazolate (7), and azide (8), yielding a new family of energetic salts. The synthesis was carried out by metathesis reactions of salts 3 or 4 and a suitable silver or barium salt. To minimize the risks involved when using heavy metal salts, we used electrodialysis for the synthesis of azide 8, which avoids the use of highly sensitive species. The DMTZ derivatives were characterized by IR and multinuclear NMR spectroscopy, elemental analysis, and X-ray diffraction. Thermal stabilities were measured using DSC analysis and their sensitivities towards classical stimuli were determined using standard tests. Lastly, the relationship between hydrogen bonding in the solid state and sensitivity is discussed.

  18. Report on Pairing-based Cryptography

    PubMed Central

    Moody, Dustin; Peralta, Rene; Perlner, Ray; Regenscheid, Andrew; Roginsky, Allen; Chen, Lily

    2015-01-01

    This report summarizes study results on pairing-based cryptography. The main purpose of the study is to form NIST’s position on standardizing and recommending pairing-based cryptography schemes currently published in research literature and standardized in other standard bodies. The report reviews the mathematical background of pairings. This includes topics such as pairing-friendly elliptic curves and how to compute various pairings. It includes a brief introduction to existing identity-based encryption (IBE) schemes and other cryptographic schemes using pairing technology. The report provides a complete study of the current status of standard activities on pairing-based cryptographic schemes. It explores different application scenarios for pairing-based cryptography schemes. As an important aspect of adopting pairing-based schemes, the report also considers the challenges inherent in validation testing of cryptographic algorithms and modules. Based on the study, the report suggests an approach for including pairing-based cryptography schemes in the NIST cryptographic toolkit. The report also outlines several questions that will require further study if this approach is followed. PMID:26958435

  19. FIR statistics of paired galaxies

    NASA Technical Reports Server (NTRS)

    Sulentic, Jack W.

    1990-01-01

    Much progress has been made in understanding the effects of interaction on galaxies (see reviews in this volume by Heckman and Kennicutt). Evidence for enhanced emission from galaxies in pairs first emerged in the radio (Sulentic 1976) and optical (Larson and Tinsley 1978) domains. Results in the far infrared (FIR) lagged behind until the advent of the Infrared Astronomy Satellite (IRAS). The last five years have seen numerous FIR studies of optical and IR selected samples of interacting galaxies (e.g., Cutri and McAlary 1985; Joseph and Wright 1985; Kennicutt et al. 1987; Haynes and Herter 1988). Despite all of this work, there are still contradictory ideas about the level and, even, the reality of an FIR enhancement in interacting galaxies. Much of the confusion originates in differences between the galaxy samples that were studied (i.e., optical morphology and redshift coverage). Here, the authors report on a study of the FIR detection properties for a large sample of interacting galaxies and a matching control sample. They focus on the distance independent detection fraction (DF) statistics of the sample. The results prove useful in interpreting the previously published work. A clarification of the phenomenology provides valuable clues about the physics of the FIR enhancement in galaxies.

  20. Pulsational Pair-instability Supernovae

    NASA Astrophysics Data System (ADS)

    Woosley, S. E.

    2017-02-01

    The final evolution of stars in the mass range 70–140 {\\text{}}{M}ȯ is explored. Depending upon their mass loss history and rotation rates, these stars will end their lives as pulsational pair-instability supernovae (PPISN) producing a great variety of observational transients with total durations ranging from weeks to millennia and luminosities from 1041 to over 1044 erg s‑1. No nonrotating model radiates more than 5× {10}50 erg of light or has a kinetic energy exceeding 5× {10}51 erg, but greater energies are possible, in principle, in magnetar-powered explosions, which are explored. Many events resemble SNe Ibn, SNe Icn, and SNe IIn, and some potential observational counterparts are mentioned. Some PPISN can exist in a dormant state for extended periods, producing explosions millennia after their first violent pulse. These dormant supernovae contain bright Wolf–Rayet stars, possibly embedded in bright X-ray and radio sources. The relevance of PPISN to supernova impostors like Eta Carinae, to superluminous supernovae, and to sources of gravitational radiation is discussed. No black holes between 52 and 133 {\\text{}}{M}ȯ are expected from stellar evolution in close binaries.

  1. Inverse Energy Dispersion of Energetic Ions Observed in the Magnetosheath

    NASA Technical Reports Server (NTRS)

    Lee, S. H.; Sibeck, D. G.; Hwang, K.-J.; Wang, Y.; Silveira, M. V. D.; Fok, M.-C.; Mauk, B. H.; Cohen, I. J.; Ruohoniemi, J. M.; Kitamura, N.; Burch, J. L.; Giles, B. L.; Torbert, R. B.; Russell, C. T.; Lester, M.

    2016-01-01

    We present a case study of energetic ions observed by the Energetic Particle Detector (EPD) on the Magnetospheric Multiscale spacecraft in the magnetosheath just outside the subsolar magnetopause that occurred at 1000 UT on 8 December 2015. As the magnetopause receded inward, the EPD observed a burst of energetic (approximately 50-1000 keV) proton, helium, and oxygen ions that exhibited an inverse dispersion, with the lowest energy ions appearing first. The prolonged interval of fast antisunward flow observed in the magnetosheath and transient increases in the H components of global ground magnetograms demonstrate that the burst appeared at a time when the magnetosphere was rapidly compressed. We attribute the inverse energy dispersion to the leakage along reconnected magnetic field lines of betatron-accelerated energetic ions in the magnetosheath, and a burst of reconnection has an extent of about 1.5 R(sub E) using combined Super Dual Auroral Radar Network radar and EPD observations.

  2. The effect of solar energetic particles on the Martian ionosphere

    NASA Astrophysics Data System (ADS)

    Darwish, Omar Hussain Al; Lillis, Robert; Fillingim, Matthew; Lee, Christina

    2016-10-01

    The precipitation of Solar Energetic Particles (SEP) into the Martian atmosphere causes several effects, one of the most important of which is ionization. However, the importance of this process to the global structure and dynamics for the Martian ionosphere is currently not well understood. The MAVEN spacecraft carries instrumentation which allow us to examine this process. The Neutral Gas and Ion Mass Spectrometer (NGIMS) measures the densities of planetary ions in the Mars ionosphere (O+,CO2+ and O2+). The Solar Energetic Particle (SEP) detector measures the fluxes of energetic protons and electrons. In this project, we examine the degree to which the density of ions in the Martian ionosphere is affected by the precipitation of energetic particles, under conditions of different SEP ion and electron fluxes and at various solar zenith angles. We will present statistical as well as case studies.

  3. Use of energetic ion beams in materials synthesis and processing

    SciTech Connect

    Appleton, B R

    1991-01-01

    A brief review of the use energetic ion beams and related techniques for the synthesis, processing, and characterization of materials is presented. Selected opportunity areas are emphasized with examples, and references are provided for more extensive coverage.

  4. Energetic ion transport by microturbulence is insignificant in tokamaks

    SciTech Connect

    Pace, D. C.; Petty, C. C.; Staebler, G. M.; Van Zeeland, M. A.; Waltz, R. E.; Austin, M. E.; Bass, E. M.; Budny, R. V.; Gorelenkova, M.; Grierson, B. A.; McCune, D. C.; Yuan, X.; Heidbrink, W. W.; Muscatello, C. M.; Zhu, Y. B.; Hillesheim, J. C.; Rhodes, T. L.; Wang, G.; Holcomb, C. T.; McKee, G. R.; and others

    2013-05-15

    Energetic ion transport due to microturbulence is investigated in magnetohydrodynamic-quiescent plasmas by way of neutral beam injection in the DIII-D tokamak [J. L. Luxon, Nucl. Fusion 42, 614 (2002)]. A range of on-axis and off-axis beam injection scenarios are employed to vary relevant parameters such as the character of the background microturbulence and the value of E{sub b}/T{sub e}, where E{sub b} is the energetic ion energy and T{sub e} the electron temperature. In all cases, it is found that any transport enhancement due to microturbulence is too small to observe experimentally. These transport effects are modeled using numerical and analytic expectations that calculate the energetic ion diffusivity due to microturbulence. It is determined that energetic ion transport due to coherent fluctuations (e.g., Alfvén eigenmodes) is a considerably larger effect and should therefore be considered more important for ITER.

  5. Optimal workloop energetics of muscle-actuated systems: an impedance matching view.

    PubMed

    Farahat, Waleed A; Herr, Hugh M

    2010-06-03

    Integrative approaches to studying the coupled dynamics of skeletal muscles with their loads while under neural control have focused largely on questions pertaining to the postural and dynamical stability of animals and humans. Prior studies have focused on how the central nervous system actively modulates muscle mechanical impedance to generate and stabilize motion and posture. However, the question of whether muscle impedance properties can be neurally modulated to create favorable mechanical energetics, particularly in the context of periodic tasks, remains open. Through muscle stiffness tuning, we hypothesize that a pair of antagonist muscles acting against a common load may produce significantly more power synergistically than individually when impedance matching conditions are met between muscle and load. Since neurally modulated muscle stiffness contributes to the coupled muscle-load stiffness, we further anticipate that power-optimal oscillation frequencies will occur at frequencies greater than the natural frequency of the load. These hypotheses were evaluated computationally by applying optimal control methods to a bilinear muscle model, and also evaluated through in vitro measurements on frog Plantaris longus muscles acting individually and in pairs upon a mass-spring-damper load. We find a 7-fold increase in mechanical power when antagonist muscles act synergistically compared to individually at a frequency higher than the load natural frequency. These observed behaviors are interpreted in the context of resonance tuning and the engineering notion of impedance matching. These findings suggest that the central nervous system can adopt strategies to harness inherent muscle impedance in relation to external loads to attain favorable mechanical energetics.

  6. Optimal Workloop Energetics of Muscle-Actuated Systems: An Impedance Matching View

    PubMed Central

    Farahat, Waleed A.; Herr, Hugh M.

    2010-01-01

    Integrative approaches to studying the coupled dynamics of skeletal muscles with their loads while under neural control have focused largely on questions pertaining to the postural and dynamical stability of animals and humans. Prior studies have focused on how the central nervous system actively modulates muscle mechanical impedance to generate and stabilize motion and posture. However, the question of whether muscle impedance properties can be neurally modulated to create favorable mechanical energetics, particularly in the context of periodic tasks, remains open. Through muscle stiffness tuning, we hypothesize that a pair of antagonist muscles acting against a common load may produce significantly more power synergistically than individually when impedance matching conditions are met between muscle and load. Since neurally modulated muscle stiffness contributes to the coupled muscle-load stiffness, we further anticipate that power-optimal oscillation frequencies will occur at frequencies greater than the natural frequency of the load. These hypotheses were evaluated computationally by applying optimal control methods to a bilinear muscle model, and also evaluated through in vitro measurements on frog Plantaris longus muscles acting individually and in pairs upon a mass-spring-damper load. We find a 7-fold increase in mechanical power when antagonist muscles act synergistically compared to individually at a frequency higher than the load natural frequency. These observed behaviors are interpreted in the context of resonance tuning and the engineering notion of impedance matching. These findings suggest that the central nervous system can adopt strategies to harness inherent muscle impedance in relation to external loads to attain favorable mechanical energetics. PMID:20532203

  7. Critical Next Steps in Understanding Solar Energetic Particle Events (Invited)

    NASA Astrophysics Data System (ADS)

    Mason, G. M.

    2010-12-01

    Solar energetic particle (SEP) events are the most powerful explosions in the solar system, capable of accelerating charged particles to relativistic energies. In the space age they are being intensely studied not only due to their impact on space systems and advanced technologies, but also because modern observations have revealed that particle acceleration is a nearly universal phenomenon at sites through the solar system and galaxy. At the Sun, where multiple remote and in-situ features of SEPs can be obtained, we have the opportunity to develop an understanding the physics of these events which in other astrophysical site can be observed only remotely. Although large SEP events are clearly associated with flare events and associated Coronal Mass Ejections (CMEs), magnetic fields in the corona and interplanetary space confine and scatter the particles so that by the time they reach Earth orbit, many features have become thoroughly mixed. Basic questions about SEP acceleration thus remain open, such as: what are the roles of flares and CMEs in SEP acceleration? How do SEPs reach the interplanetary medium? What is the actual material (seed population) that is accelerated? During the past solar cycle, progress in understanding SEPs has resulted from greatly improved particle observations combined with remote sensing of flares, CMEs, and coronal and interplanetary shocks. This has led to new insights into both large, shock associated SEP events, and smaller 3He-rich events which may occur in the low corona. In the next few years, progress in SEP studies can be expected from multipoint measurements using STEREO and advanced imaging from SDO. Critical new insights will then emerge from the ESA Solar Orbiter and NASA Solar Probe Plus missions that will travel to the inner heliosphere where the signatures of SEPs will be nearly free of the interplanetary mixing, allowing accurate and decisive comparisons of observations with remote observations and theoretical models

  8. Effect of Energetic Ion on Spatial Distribution of Recombining Plasma

    NASA Astrophysics Data System (ADS)

    Okamoto, A.; Daibo, A.; Kitajima, S.; Kumagai, T.; Takahashi, H.; Takahashi, T.; Tsubota, S.

    Spatial distribution of electron density is considered. By using a one-dimensional recombining plasma model, effects of transient energetic ion flux are investigated. The time response of the system against the transient flux is dominated by the recombination frequency. The magnitude of modification of the spatial distribution is determined by the ratio between the ionization due to the energetic ion and the recombination of the bulk plasma.

  9. Stability of AN Axisymmetric Mirror with AN Energetic Ion Component.

    NASA Astrophysics Data System (ADS)

    Krall, Jonathan Francis

    We examine the stability of an axisymmetric mirror with an energetic ion component to finite azimuthal mode number (m) interchange modes, using a dispersion functional in which the energetic ions are described by the Vlasov equation and the background plasma is described by the magnetohydrodynamic (MHD) equations. A separate analysis is presented for the Vlasov- fluid case Freidberg, 1972 , where the background consists of fluid electrons. Stability is addressed first for an elongated equilibrium with a specific class of energetic ion orbits in the Vlasov-MHD case and then for both cases with more general equilibria and orbits. With the elongated mirror, we suppose that the axis-encircling ions have orbits that reside on flux surfaces, obtaining a sufficient condition for stability on each flux surface. Numerical evaluation of the stability condition indicates that the energetic ion component is highly stabilizing in regions where the energetic ion density increases outward and highly destabilizing where the density decreases outward. The more general problem is considered by representing the displacement in terms of a complete set of global basis functions, giving a necessary and sufficient condition for stability for each case. In each of the two cases, kinetic effects enter into the analysis through phase-space autocorrelation functions Lewis et al., 1985 . We find that in the Vlasov-MHD case, where we use a rigid-rotor distribution for the energetic ions, the net rotation of the energetic ions is destabilizing and dominates the stabilizing influence of the energetic ion current. In the Vlasov-fluid case, finite Larmor radius (FLR) effects were recovered, with growth rates reduced when ((rho)(,i)/L)('2) >(, )(gamma)(,MHD)/(OMEGA)(,i), where (rho)(,i) is the Larmor radius of the Vlasov ions, L is the plasma radius, (gamma)(,MHD) is the growth rate with FLR effects excluded and (OMEGA)(,i) is the ion gyrofrequency. These effects are discussed in terms of phase

  10. Global Energetics of Thirty-Eight Large Solar Eruptive Events

    DTIC Science & Technology

    2012-10-17

    ejection (CME), (7) the energy in solar energetic particles (SEPs) observed in interplanetary space, and ( 8 ) the amount of free (non-potential) magnetic ...the energy in solar energetic particles (SEPs) observed in interplanetary space, and ( 8 ) the amount of free (non-potential) magnetic energy estimated...as they scatter on the diverging interplanetary magnetic field . For this work, we corrected for both multiple 1 AU crossings and energy loss using

  11. SRAM As An Array Of Energetic-Ion Detectors

    NASA Technical Reports Server (NTRS)

    Buehler, Martin G.; Blaes, Brent R.; Lieneweg, Udo; Nixon, Robert H.

    1993-01-01

    Static random-access memory (SRAM) designed for use as array of energetic-ion detectors. Exploits well-known tendency of incident energetic ions to cause bit flips in cells of electronic memories. Design of ion-detector SRAM involves modifications of standard SRAM design to increase sensitivity to ions. Device fabricated by use of conventional complementary metal oxide/semiconductor (CMOS) processes. Potential uses include gas densimetry, position sensing, and measurement of cosmic-ray spectrum.

  12. Synthesis and Characterization of Mixed Metal Oxide Nanocomposite Energetic Materials

    SciTech Connect

    Clapsaddle, B; Gash, A; Plantier, K; Pantoya, M; Jr., J S; Simpson, R

    2004-04-27

    In the field of composite energetic materials, properties such as ingredient distribution, particle size, and morphology affect both sensitivity and performance. Since the reaction kinetics of composite energetic materials are typically controlled by the mass transport rates between reactants, one would anticipate new and potentially exceptional performance from energetic nanocomposites. We have developed a new method of making nanostructured energetic materials, specifically explosives, propellants, and pyrotechnics, using sol-gel chemistry. A novel sol-gel approach has proven successful in preparing metal oxide/silicon oxide nanocomposites in which the metal oxide is the major component. By introducing a fuel metal, such as aluminum, into the metal oxide/silicon oxide matrix, energetic materials based on thermite reactions can be fabricated. Two of the metal oxides are tungsten trioxide and iron(III) oxide, both of which are of interest in the field of energetic materials. In addition, due to the large availability of organically functionalized silanes, the silicon oxide phase can be used as a unique way of introducing organic additives into the bulk metal oxide materials. These organic additives can cause the generation of gas upon ignition of the materials, therefore resulting in a composite material that can perform pressure/volume work. Furthermore, the desired organic functionality is well dispersed throughout the composite material on the nanoscale with the other components, and is therefore subject to the same increased reaction kinetics. The resulting nanoscale distribution of all the ingredients displays energetic properties not seen in its microscale counterparts due to the expected increase of mass transport rates between the reactants. The synthesis and characterization of iron(III) oxide/organosilicon oxide nanocomposites and their performance as energetic materials will be discussed.

  13. LEEM investigations of clean surfaces driven by energetic ion beams

    SciTech Connect

    Abbamonte, Peter M.

    2013-04-24

    The original purpose of this award was to use low‐energy electron microscopy (LEEM) to explore the dynamics of surfaces of clean single crystal surfaces when driven by a beam of energetic ions. The goal was to understand the nanoscience of hyperthermal growth, surface erosion by sublimation and irradiation, operation of surface sinks in irradiated materials, diffusion on driven surfaces, and the creation of structural patterns. This project was based on a novel LEEM system constructed by C. P. Flynn, which provided real‐time imaging of surface dynamics by scattering low energy electrons. With the passing of Prof. Flynn in late 2011, this project was completed under a slightly different scope by constructing a low‐energy, inelastic electron scattering (EELS) instrument. Consistent with Flynn's original objectives for his LEEM system, this device probes the dynamics of crystal surfaces. However the measurements are not carried out in real time, but instead are done in the frequency domain, through the energy lost from the probe electrons. The purpose of this device is to study the collective bosonic excitations in a variety of materials, including high temperature superconductors, topological insulators, carbon allotropes including (but not limited to) graphene, etc. The ultimate goal here is to identify the bosons that mediate interactions in these and other materials, with hopes of shedding light on the origin of many exotic phenomena including high temperature superconductivity. We completed the construction of a low‐energy EELS system that operates with an electron kinetic energy of 7 - 10 eV. With this instrument now running, we hope to identify, among other things, the bosons that mediate pairing in high temperature superconductors. Using this instrument, we have already made our first discovery. Studying freshly cleaved single crystals of Bi{sub 2}Se{sub 3}, which is a topological insulator, we have observed a surface excitation at an energy loss of

  14. On the energetics of tensile and shear void coalescences

    NASA Astrophysics Data System (ADS)

    Wong, W. H.; Guo, T. F.

    2015-09-01

    This paper investigates the mechanisms of tensile and shear void coalescences in ductile materials from energetics perspective. By examining and comparing the elastic and plastic energies of a voided cell throughout its deformation history, the onset of and final coalescence can be distinctly established. This energy-based approach offers a single unified method and criterion for determining the occurrences of both mechanisms. This paper also reports a novel micromechanics model that considers general stress states described by three macroscopic normal stresses and one macroscopic shear stress. Detailed formulation of the model is presented that includes the homogenization-based derivation and implementation of a 4×4 orthogonal transformation matrix, which relates the macroscopic deformation rate of the cell to displacement rates of non-physical degrees-of-freedom (DOFs), and the polar decomposition of the macroscopic deformation gradient tensor which admits the explicit determination of the logarithmic strain measures and rotation angle. In terms of stress ratios, ρ1 (=Σ11 /Σ22) ,ρ2 (=Σ12 /Σ22) ,ρ3 (=Σ33 /Σ22), it is analytically shown that multiple macroscopic stress states {ρ1 ,ρ2 ,ρ3 } can exist that result in the same stress triaxiality T and Lode parameter L. Specifically, it is shown that for a prescribed pair of T and L and in the absence of shear stress, at most six stress states {ρ1 , 0 ,ρ3 } are possible. On the other extreme in the presence of shear stress, an infinite number of stress states is possible, due to the existence of Mohr's circle for this stress state. This model, together with the proposed energy-based criteria, is used to examine void coalescence under multiple stress-state conditions for any given T and L. Numerical results have shown that the presence of shear stress has a significant effect of reducing the effective strains for the onset of and final void coalescences. In addition, a relationship has also been

  15. Energetics and Cooling in Urban Parks

    NASA Astrophysics Data System (ADS)

    Spronken-Smith, Rachel Anne

    While there has been a long tradition for the integration of architecture and landscape to improve the urban environment, little is known about the effect of urban parks on local climate. In this study the park effect is determined through an integrated research approach incorporating field measurements of the thermal regime and energetics of urban parks, together with scale modelling of nocturnal cooling in urban parks. The research is limited to consideration of the park effect in two cities with different summer climates: Sacramento, California (hot summer Mediterranean) and Vancoucer, British Columbia (cool summer Mediterranean). In both these cities, surveys of summer-time air temperature patterns associated with urban parks confirm and extend previous findings. In temperate Vancouver, the park effect is typically 1-2^circC, rarely more than 3^circC, although it can be higher under ideal conditions. However, in a hot, dry city, the effect is considerably enhanced with parks as much as 5-7^circC cooler than their urban surrounds. A comparison of the surface energy balance of small open, grassed parks in these two cities demonstrated the importance of evapotranspiration in park energetics. In hot, dry Sacramento, evaporation in the park was advectively -assisted and exceeded that at an irrigated rural site. Strong advective edge effects on evaporation were observed in this wet park. These decayed approximately exponentially with distance into the park. The urban park in Vancouver was moist, but unirrigated. While evaporation dominated the surface energy balance, the sensible heat flux was positive through most of the day, and evaporation was not strongly influenced by advection. The evaporation trend in the park probably reflected the turbulence and soil moisture regimes. However, an irrigated lawn in Vancouver did exhibit edge-type advection. This suggests the soil moisture regime may be critical in determining whether evaporation exceeds the potential rate

  16. The effect of direct electron-positron pair production on relativistic feedback rates

    NASA Astrophysics Data System (ADS)

    Vodopiyanov, I. B.; Dwyer, J. R.; Cramer, E. S.; Lucia, R. J.; Rassoul, H. K.

    2015-01-01

    Runaway electron avalanches developing in thunderclouds in high electric field become self-sustaining due to relativistic feedback via the production of backward propagating positrons and backscattered X-rays. To date, only positrons created from pair production by gamma rays interacting with the air have been considered. In contrast, direct electron-positron pair production, also known as "trident process," occurs from the interaction of energetic runaway electrons with atomic nuclei, and so it does not require the generation of a gamma ray mediator. The positrons produced in this process contribute to relativistic feedback and become especially important when the feedback factor value approaches unity. Then the steady state flux of runaway electrons increases significantly. In certain cases, when the strong electrostatic field forms in a narrow area, the direct positrons become one of processes dominating relativistic feedback. Calculations of the direct positron production contribution to relativistic feedback are presented for different electric field configurations.

  17. Finding the first cosmic explosions. III. Pulsational pair-instability supernovae

    SciTech Connect

    Whalen, Daniel J.; Smidt, Joseph; Even, Wesley; Fryer, Chris L.; Woosley, S. E.; Heger, Alexander; Stiavelli, Massimo

    2014-02-01

    Population III supernovae have been the focus of growing attention because of their potential to directly probe the properties of the first stars, particularly the most energetic events that can be seen at the edge of the observable universe. But until now pulsational pair-instability supernovae, in which explosive thermonuclear burning in massive stars fails to unbind them but can eject their outer layers into space, have been overlooked as cosmic beacons at the earliest redshifts. These shells can later collide and, like Type IIn supernovae, produce superluminous events in the UV at high redshifts that could be detected in the near infrared today. We present numerical simulations of a 110 M {sub ☉} pulsational pair-instability explosion done with the Los Alamos radiation hydrodynamics code Radiation Adaptive Grid Eulerian. We find that collisions between consecutive pulsations are visible in the near infrared out to z ∼ 15-20 and can probe the earliest stellar populations at cosmic dawn.

  18. An Electrochemical Study of Frustrated Lewis Pairs: A Metal-Free Route to Hydrogen Oxidation

    PubMed Central

    2014-01-01

    Frustrated Lewis pairs have found many applications in the heterolytic activation of H2 and subsequent hydrogenation of small molecules through delivery of the resulting proton and hydride equivalents. Herein, we describe how H2 can be preactivated using classical frustrated Lewis pair chemistry and combined with in situ nonaqueous electrochemical oxidation of the resulting borohydride. Our approach allows hydrogen to be cleanly converted into two protons and two electrons in situ, and reduces the potential (the required energetic driving force) for nonaqueous H2 oxidation by 610 mV (117.7 kJ mol–1). This significant energy reduction opens routes to the development of nonaqueous hydrogen energy technology. PMID:24720359

  19. Lowering of Boson-Fermion System Energy with a Gapped Cooper Resonant-Pair Dispersion Relation

    NASA Astrophysics Data System (ADS)

    Mamedov, T. A.; de Llano, M.

    Applying two-time Green-function techniques to the Friedberg-T.D. Lee phenomenological Hamiltonian of a many-fermion system, it is shown that positive-energy resonant bosonic pairs associated with four-fermion excitations above the Fermi sea are energetically lower in a ground-state that is a mixture of two coexisting and dynamically interacting many-particle subsystems: a) unpaired fermions and b) composite bosons. It is argued that an interaction between free fermions and bosons excited above the Fermi sea in the mixture, namely, the continuous processes of pair-formation from, and disintegration into, two unpaired electrons, results in a substantially lowering the total system energy. The positive-energy composite bosons begin to appear incoherently below a depairing temperature T* as their coupling- and temperature-dependent number density gradually increases from zero. This leads quite naturally to the pseudogap phenomenon observed in high-Tc cuprates.

  20. Modelling the locomotor energetics of extinct hominids.

    PubMed

    Kramer, P A

    1999-10-01

    Bipedality is the defining characteristic of Hominidae and, as such, an understanding of the adaptive significance and functional implications of bipedality is imperative to any study of human evolution. Hominid bipedality is, presumably, a solution to some problem for the early hominids, one that has much to do with energy expenditure. Until recently, however, little attention could be focused on the quantifiable energetic aspects of bipedality as a unique locomotor form within Primates because of the inability to measure empirically the energy expenditure of non-modern hominids. A recently published method provides a way of circumventing the empirical measurement dilemma by calculating energy expenditure directly from anatomical variables and movement profiles. Although the origins of bipedality remain clouded, two discernible forms of locomotor anatomy are present in the hominid fossil record: the australopithecine and modern configurations. The australopithecine form is best represented by AL 288-1, a partial skeleton of Australopithecus afarensis, and is characterized as having short legs and a wide pelvis. The modern form is represented by modern humans and has long legs and a narrow pelvis. Human walking is optimized to take advantage of the changing levels of potential and kinetic energy that occur as the body and limbs move through the stride cycle. Although this optimization minimizes energy expenditure, some energy is required to maintain motion. I quantify this energy by developing a dynamic model that uses kinematic equations to determine energy expenditure. By representing both configurations with such a model, I can compare their rates of energy expenditure. I find that the australopithecine configuration uses less energy than that of a modern human. Despite arguments presented in the anthropological literature, the shortness of the legs of AL 288-1 provides no evidence that she was burdened with a compromised or transitional locomotor anatomy

  1. Telemetered cephalopod energetics: swimming, soaring, and blimping.

    PubMed

    O'Dor, Ron

    2002-11-01

    Cephalopods are uniquely suited to field energetic studies. Their hollow mantles that pump water for respiration and jetting also can accommodate differential transducer-transmitters. These transmitters indicate pressure-flow power output, which can be calibrated against oxygen consumption by swim-tunnel respirometry. Radio-acoustic positioning telemetry (RAPT) records pressure-flow power and animal movements with meter accuracy in nature. Despite inherent inefficiencies, jetting is the primary mode of locomotion for both primitive nautilus and powerful, migratory oceanic squids. In between, large-finned squid and cuttlefish mix jetting with fin undulation in complex gaits that increase locomotor efficiency. Our studies show that the complex nervous systems cephalopods evolved to control mixed gaits are also sensitive to flow and density fields in nature and that they use these to further reduce locomotion costs. Buoyed up by evacuated shells, nautilus and cuttlefish live in boundary layers and navigate cheaply through them like balloonists. Large-finned, negatively buoyant squid soar like eagles in rising currents, but lose control in currents above one body length per second. Many muscular squids have life histories linked to current systems. Neutrally buoyant ammoniacal cephalopods in the mesopelagic are a limiting case in need of study. The small density differential between seawater and isotonic ammonium chloride trebles their volume, making them blimp-like with very low power densities. Some species live entirely in this restricted habitat, but most become ammoniacal late in ontogeny, as they approach semelparous reproduction. Ammonium retained for buoyancy as carbon is terminally mobilized from muscle protein for gametes and energy, compensates for lost muscle power.

  2. The Cosmic Ray Energetics And Mass Project

    NASA Astrophysics Data System (ADS)

    Seo, Eun-Suk; Iss-Cream Collaboration

    2017-01-01

    The balloon-borne Cosmic Ray Energetics And Mass (CREAM) experiment was flown for 161 days in six flights over Antarctica, the longest known exposure for a single balloon project. Elemental spectra were measured for Z = 1- 26 nuclei over a wide energy range from 1010 to >1014 eV. Building on the success of those balloon flights, one of the two balloon payloads was transformed for exposure on the International Space Station (ISS) Japanese Experiment Module Exposed Facility (JEM-EF). This ISS-CREAM instrument is configured with redundant and complementary particle detectors. The four layers of its finely segmented Silicon Charge Detector provide precise charge measurements, and its ionization calorimeter provides energy measurements. In addition, scintillator-based Top and Bottom Counting Detectors and the Boronated Scintillator Detector distinguish electrons from nuclei. An order of magnitude increase in data collecting power is expected to reach the highest energies practical with direct measurements. Following completion of its qualification tests at NASA Goddard Space Flight Center, the ISS-CREAM payload was delivered to NASA Kennedy Space Center in August 2015 to await its launch to the ISS. While waiting for ISS-CREAM to launch, the other balloon payload including a Transition Radiation Detector, which is too large for the JEM-EF envelope, has been prepared for another Antarctic balloon flight in 2016. This so-called Boron And Carbon Cosmic rays in the Upper Stratosphere (BACCUS) payload will investigate cosmic ray propagation history. The overall project status and future plans will be presented.

  3. Solar Energetic Particles and Space Weather

    NASA Technical Reports Server (NTRS)

    Reames, Donald V.; Tylka, Allan J.; Ng, Chee K.

    2001-01-01

    The solar energetic particles (SEPs) of consequence to space weather are accelerated at shock waves driven out from the Sun by fast coronal mass ejections (CMEs). In the large events, these great shocks fill half of the heliosphere. SEP intensity profiles change appearance with longitude. Events with significant intensities of greater than ten MeV protons occur at an average rate of approx. 13 per year near solar maximum and several events with high intensities of > 100 McV protons occur each decade. As particles stream out along magnetic field lines from a shock near the Sun, they generate waves that scatter subsequent particles. At high intensities, wave growth throttles the flow below the 'streaming limit.' However, if the shock maintains its strength, particle intensities can rise above this limit to a peak when the shock itself passes over the observer creating a 'delayed' radiation hazard, even for protons with energies up to approx. one GeV. The streaming limit makes us blind to the intensities at the oncoming shock, however, heavier elements such as He, O, and Fe probe the shape of the wave spectrum, and variation in abundances of these elements allow us to evade the limit and probe conditions at the shock, with the aid of detailed modeling. At high energies, spectra steepen to form a spectral 'knee'. The location of the proton spectral knee can vary from approx. ten MeV to approx. one GeV, depending on shock conditions, greatly affecting the radiation hazard. Hard spectra are a serious threat to astronauts, placing challenging requirements for shielding, especially on long-duration missions to the moon or Mars.

  4. Comparative primate energetics and hominid evolution.

    PubMed

    Leonard, W R; Robertson, M L

    1997-02-01

    There is currently great interest in developing ecological models for investigating human evolution. Yet little attention has been given to energetics, one of the cornerstones of modern ecosystem ecology. This paper examines the ecological correlates of variation in metabolic requirements among extant primate species, and uses this information to draw inferences about the changes in energy demands over the course of human evolution. Data on body size, resting metabolism, and activity budgets for selected anthropoid species and human hunter-gatherers are used to estimate total energy expenditure (TEE). Analyses indicate that relative energy expenditure levels and day ranges are positively correlated with diet quality; that is, more active species tend to consume more energy-rich diets. Human foragers fall at the positive extremes for modern primates in having high expenditure levels, large ranges, and very high quality diets. During hominid evolution, it appears that TEE increased substantially with the emergence of Homo erectus. This increase is partly attributable to larger body size as well as likely increases in day range and activity level. Assuming similar activity budgets for all early hominid species, estimated TEE for H. erectus is 40-45% greater than for the australopithecines. If, however, it is assumed that the evolution of early Homo was also associated with a shift to a more "human-like" foraging strategy, estimated expenditure levels for H. erectus are 80-85% greater than in the australopithecines. Changing patterns of resource distribution associated with the expansion of African savannas between 2.5 and 1.5 mya may been the impetus for a shift in foraging behavior among early members of the genus Homo. Such ecological changes likely would have made animal foods a more attractive resource. Moreover, greater use of animal foods and the resulting higher quality diet would have been important for supporting the larger day ranges and greater energy

  5. Cavitation Bubble Nucleation by Energetic Particles

    SciTech Connect

    West, C.D.

    1998-12-01

    In the early sixties, experimental measurements using a bubble chamber confirmed quantitatively the thermal spike theory of bubble nucleation by energetic particles: the energy of the slow, heavy alpha decay recoils used in those experiments matched the calculated bubble nucleation energy to within a few percent. It was a triumph, but was soon to be followed by a puzzle. Within a couple of years, experiments on similar liquids, but well below their normal boiling points, placed under tensile stress showed that the calculated bubble nucleation energy was an order of magnitude less than the recoil energy. Why should the theory work so well in the one case and so badly in the other? How did the liquid, or the recoil particle, "know" the difference between the two experiments? Another mathematical model of the same physical process, introduced in 1967, showed qualitatively why different analyses would be needed for liquids with high and low vapor pressures under positive or negative pressures. But, the quantitative agreement between the calculated nucleation energy and the recoil energy was still poor--the former being smaller by a factor of two to three. In this report, the 1967 analysis is extended and refined: the qualitative understanding of the difference between positive and negative pressure nucleation, "boiling" and "cavitation" respectively, is retained, and agreement between the negative pressure calculated to be needed for nucleation and the energy calculated to be available is much improved. A plot of the calculated negative pressure needed to induce bubble formation against the measured value now has a slope of 1.0, although there is still considerable scatter in the individual points.

  6. Green primaries: Environmentally friendly energetic complexes

    PubMed Central

    Huynh, My Hang V.; Hiskey, Michael A.; Meyer, Thomas J.; Wetzler, Modi

    2006-01-01

    Primary explosives are used in small quantities to generate a detonation wave when subjected to a flame, heat, impact, electric spark, or friction. Detonation of the primary explosive initiates the secondary booster or main-charge explosive or propellant. Long-term use of lead azide and lead styphnate as primary explosives has resulted in lead contamination at artillery and firing ranges and become a major health hazard and environmental problem for both military and civilian personnel. Devices using lead primary explosives are manufactured by the tens of millions every year in the United States from primers for bullets to detonators for mining. Although substantial synthetic efforts have long been focused on the search for greener primary explosives, this unresolved problem has become a “holy grail” of energetic materials research. Existing candidates suffer from instability or excessive sensitivity, or they possess toxic metals or perchlorate. We report here four previously undescribed green primary explosives based on complex metal dianions and environmentally benign cations, (cat)2[MII(NT)4(H2O)2] (where cat is NH4+ or Na+, M is Fe2+ or Cu2+, and NT− is 5-nitrotetrazolato-N2). They are safer to prepare, handle, and transport than lead compounds, have comparable initiation efficiencies to lead azide, and offer rapid reliable detonation comparable with lead styphnate. Remarkably, they possess all current requirements for green primary explosives and are suitable to replace lead primary explosives in detonators. More importantly, they can be synthesized more safely, do not pose health risks to personnel, and cause much less pollution to the environment. PMID:16567623

  7. Spectral energetics of the lower thermosphere

    SciTech Connect

    Raskin, R.G.

    1992-01-01

    A spectral energetics analysis of the lower thermosphere is carried out using simulated data from the NCAR Thermosphere-Ionosphere General Circulation Model (TIGCM). The results clarify the physical processes through which upwardly propagating semidiurnal tides dissipate and release their energy into the lower thermosphere. Energy residing within the study region is partitioned into reservoirs of available potential energy, irrotational kinetic energy, and nondivergent kinetic energy at four vertical levels. A definition of available potential energy is used that is appropriate for regions of variable mean molecular weight. The reservoirs are further subdivided by vector spherical harmonic wave numbers, and an energy budget is computed for each mode. The source, sink, and transformation terms are obtained using a post-processor that reproduces the contribution of each term in the momentum and thermodynamic equations. The loss terms for the zonal wave number two modes represent the dissipating forces for the semidiurnal tides. Viscosity, heat conduction, and ion drag represent the primary dissipative forces. Numerical smoothing within the TIGCM, representing the subgrid-scale diffusion, is found to have a non-negligible contribution to the tidal dissipation. A small terdiurnal tide that is excited by ion drag is also observed in the model. A sensitivity analysis is carried out to ascertain the effects of the seasonal cycle, solar cycle, UT, and geomagnetic activity. At solar maximum, solar heating at the trough of the tide is an important dissipative force; the altitude of tidal dissipation is correspondingly lower. At high values of geomagnetic forcing, the propagating semidiurnal tide is completely dissipated within the study region.

  8. The adolescent transition under energetic stress

    PubMed Central

    Reiches, Meredith W.; Moore, Sophie E.; Prentice, Andrew M.; Prentice, Ann; Sawo, Yankuba; Ellison, Peter T.

    2013-01-01

    Background and objectives: Life history theory predicts a shift in energy allocation from growth to reproductive function as a consequence of puberty. During adolescence, linear growth tapers off and, in females, ovarian steroid production increases. In this model, acquisition of lean mass is associated with growth while investment in adiposity is associated with reproduction. This study examines the chronological and developmental predictors of energy allocation patterns among adolescent women under conditions of energy constraint. Methodology: Fifty post-menarcheal adolescent women between 14 and 20 years old were sampled for weight and body composition at the beginning and end of 1 month in an energy-adequate season and 1 month in the subsequent energy-constrained season in a rural province of The Gambia. Results: Chronologically and developmentally younger adolescent girls gain weight in the form of lean mass in both energy-adequate and energy-constrained seasons, whereas older adolescents lose lean mass under conditions of energetic stress (generalized estimating equation (GEE) Wald chi-square comparing youngest tertile with older two tertiles 9.750, P = 0.002; GEE Wald chi-square comparing fast- with slow-growing individuals for growth rate 19.806, P < 0.001). When energy is limited, younger adolescents lose and older adolescents maintain fat (GEE Wald chi-square for interaction of age and season 6.568, P = 0.010; GEE Wald chi-square comparing fast- with slow-growing individuals for interaction of growth rate and season 7.807, P = 0.005). Conclusions and implications: When energy is constrained, the physiology of younger adolescents invests in growth while that of older adolescent females privileges reproductively valuable adipose tissue. PMID:24481188

  9. Mitochondria and Energetic Depression in Cell Pathophysiology

    PubMed Central

    Seppet, Enn; Gruno, Marju; Peetsalu, Ants; Gizatullina, Zemfira; Nguyen, Huu Phuc; Vielhaber, Stefan; Wussling, Manfred H.P.; Trumbeckaite, Sonata; Arandarcikaite, Odeta; Jerzembeck, Doreen; Sonnabend, Maria; Jegorov, Katharina; Zierz, Stephan; Striggow, Frank; Gellerich, Frank N.

    2009-01-01

    Mitochondrial dysfunction is a hallmark of almost all diseases. Acquired or inherited mutations of the mitochondrial genome DNA may give rise to mitochondrial diseases. Another class of disorders, in which mitochondrial impairments are initiated by extramitochondrial factors, includes neurodegenerative diseases and syndromes resulting from typical pathological processes, such as hypoxia/ischemia, inflammation, intoxications, and carcinogenesis. Both classes of diseases lead to cellular energetic depression (CED), which is characterized by decreased cytosolic phosphorylation potential that suppresses the cell’s ability to do work and control the intracellular Ca2+ homeostasis and its redox state. If progressing, CED leads to cell death, whose type is linked to the functional status of the mitochondria. In the case of limited deterioration, when some amounts of ATP can still be generated due to oxidative phosphorylation (OXPHOS), mitochondria launch the apoptotic cell death program by release of cytochrome c. Following pronounced CED, cytoplasmic ATP levels fall below the thresholds required for processing the ATP-dependent apoptotic cascade and the cell dies from necrosis. Both types of death can be grouped together as a mitochondrial cell death (MCD). However, there exist multiple adaptive reactions aimed at protecting cells against CED. In this context, a metabolic shift characterized by suppression of OXPHOS combined with activation of aerobic glycolysis as the main pathway for ATP synthesis (Warburg effect) is of central importance. Whereas this type of adaptation is sufficiently effective to avoid CED and to control the cellular redox state, thereby ensuring the cell survival, it also favors the avoidance of apoptotic cell death. This scenario may underlie uncontrolled cellular proliferation and growth, eventually resulting in carcinogenesis. PMID:19564950

  10. The Modeling of Pickup Ion or Energetic Particle Mediated Plasmas

    NASA Astrophysics Data System (ADS)

    Zank, G. P.; Mostafavi, P.; Hunana, P.

    2016-05-01

    Suprathermal energetic particles, such as solar energetic particles (SEPs) in the inner heliosphere and pickup ions (PUIs) in the outer heliosphere and the very local interstellar medium, often form a thermodynamically dominant component in their various environments. In the supersonic solar wind beyond > 10 AU, in the inner heliosheath (IHS), and in the very local interstellar medium (VLISM), PUIs do not equilibrate collisionally with the background plasma. Similarly, SEPs do not equilibrate collisionally with the background solar wind in the inner heliosphere. In the absence of equilibration between plasma components, a separate coupled plasma description for the energetic particles is necessary. Using a collisionless Chapman-Enskog expansion, we derive a closed system of multi-component equations for a plasma comprised of thermal protons and electrons, and suprathermal particles (SEPs, PUIs). The energetic particles contribute an isotropic scalar pressure to leading order, a collisionless heat flux at the next order, and a collisionless stress tensor at the second-order. The collisionless heat conduction and viscosity in the multi-fluid description results from a nonisotropic energetic particle distribution. A simpler single-fluid MHD-like system of equations with distinct equations of state for both the background plasma and the suprathermal particles is derived. We note briefly potential pitfalls that can emerge in the numerical modeling of collisionless plasma flows that contain a dynamically important energetic particle component.

  11. METHOD OF PRODUCING ENERGETIC PLASMA FOR NEUTRON PRODUCTION

    DOEpatents

    Bell, P.R.; Simon, A.; Mackin, R.J. Jr.

    1961-01-24

    A method is given for producing an energetic plasma for neutron production. An energetic plasma is produced in a small magnetically confined subvolume of the device by providing a selected current of energetic molecular ions at least greater than that required for producing a current of atomic ions sufficient to achieve "burnout" of neutral particles in the subvolume. The atomic ions are provided by dissociation of the molecular ions by an energetic arc discharge within the subvolume. After burnout, the arc discharge is terminated, the magnetic fields increased, and cold fuel feed is substituted for the molecular ions. After the subvolume is filled with an energetic plasma, the size of the magnetically confined subvolume is gradually increased until the entire device is filled with an energetic neutron producing plasma. The reactions which take place in the device to produce neutrons will generate a certain amount of heat energy which may be converted by the use of a conventional heat cycle to produce electrical energy.

  12. Modeling thermally driven energetic response of high explosives

    SciTech Connect

    Couch, R; McCallen, R C; Nichols III, A L; Otero, I; Sharp, R

    1998-08-17

    We have improved our ability to model the response of energetic materials to thermal stimuli and the processes involved in the energetic response. Traditionally, the analyses of energetic materials have involved coupled thermal transport/chemical reaction codes. This provides only a reasonable estimate of the time and location of ensuing rapid reaction. To predict the violence of the reaction, the mechanical motion must be included in the wide range of time scales associated with the thermal hazard. The ALE3D code has been modified to assess the hazards associated with heating energetic materials in weapons by coupling to thermal transport model and chemistry models. We have developed an implicit time step option to efficiently and accurately compute the hours of heating to reaction of the energetic material. Since, on these longer time scales materials can be expected to have significant motion, it is even more important to provide high-order advection for all components, including the chemical species. We show two examples of coupled thermal/mechanical/chemical models of energetic materials in thermal environments.

  13. Modeling thermally driven energetic response of high explosives

    SciTech Connect

    Sharp, R; Couch, R; McCallen, R C; Nichols III, A L; Otero, I

    1998-02-01

    We have improved our ability to model the response of energetic materials to thermal stimuli and the processes involved in the energetic response. Traditionally, the analyses of energetic materials have involved coupled thermal transport/chemical reaction codes. This provides only a reasonable estimate of the time and location of ensuing rapid reaction. To predict the violence of the reaction, the mechanical motion must be included in the wide range of time scales associated with the thermal hazard. The ALE3D code has been modified to assess the hazards associated with heating energetic materials in weapons by coupling to thermal transport model and chemistry models. We have developed an implicit time step option to efficiently and accurately compute the hours of heating to reaction of the energetic material. Since, on these longer time scales materials can be expected to have significant motion, it is even more important to provide high-order advection for all components, including the chemical species. We show two examples of coupled thermal/mechanical/chemical models of energetic materials in thermal environments.

  14. Helicon wave excitation to produce energetic electrons for manufacturing semiconductors

    DOEpatents

    Molvik, A.W.; Ellingboe, A.R.

    1998-10-20

    A helicon plasma source is controlled by varying the axial magnetic field or rf power controlling the formation of the helicon wave. An energetic electron current is carried on the wave when the magnetic field is 90 G; but there is minimal energetic electron current when the magnetic field is 100 G in one particular plasma source. Similar performance can be expected from other helicon sources by properly adjusting the magnetic field and power to the particular geometry. This control for adjusting the production of energetic electrons can be used in the semiconductor and thin-film manufacture process. By applying energetic electrons to the insulator layer, such as silicon oxide, etching ions are attracted to the insulator layer and bombard the insulator layer at higher energy than areas that have not accumulated the energetic electrons. Thus, silicon and metal layers, which can neutralize the energetic electron currents will etch at a slower or non-existent rate. This procedure is especially advantageous in the multilayer semiconductor manufacturing because trenches can be formed that are in the range of 0.18--0.35 mm or less. 16 figs.

  15. Helicon wave excitation to produce energetic electrons for manufacturing semiconductors

    DOEpatents

    Molvik, Arthur W.; Ellingboe, Albert R.

    1998-01-01

    A helicon plasma source is controlled by varying the axial magnetic field or rf power controlling the formation of the helicon wave. An energetic electron current is carried on the wave when the magnetic field is 90 G; but there is minimal energetic electron current when the magnetic field is 100 G in one particular plasma source. Similar performance can be expected from other helicon sources by properly adjusting the magnetic field and power to the particular geometry. This control for adjusting the production of energetic electrons can be used in the semiconductor and thin-film manufacture process. By applying energetic electrons to the insulator layer, such as silicon oxide, etching ions are attracted to the insulator layer and bombard the insulator layer at higher energy than areas that have not accumulated the energetic electrons. Thus, silicon and metal layers, which can neutralize the energetic electron currents will etch at a slower or non-existent rate. This procedure is especially advantageous in the multilayer semiconductor manufacturing because trenches can be formed that are in the range of 0.18-0.35 mm or less.

  16. MESSENGER observations of energetic electron acceleration in Mercury's magnetotail

    NASA Astrophysics Data System (ADS)

    Dewey, Ryan; Slavin, James A.; Baker, Daniel; Raines, Jim; Lawrence, David

    2016-10-01

    Energetic particle bursts within Mercury's magnetosphere have been a source of curiosity and controversy since Mariner 10's flybys. Unfortunately, instrumental effects prevent an unambiguous determination of species, flux, and energy spectrum for the Mariner 10 events. MESSENGER data taken by the Energetic Particle Spectrometer (EPS) have now shown that these energetic particle bursts are composed entirely of electrons. EPS made directional measurements of these electrons from ~30 to 300 keV at 3 s resolution, and while the energy of these electrons sometimes exceeded 200 keV, the energy distributions usually exhibited a cutoff near 100 keV. The Gamma Ray Spectrometer (GRS) has also provided measurements of these electron events, at higher time resolution (10 ms) and energetic threshold (> 50 keV) compared to EPS. We focus on GRS electron events near the plasma sheet in Mercury's magnetotail to identify reconnection-associated acceleration mechanisms. We present observations of acceleration associated with dipolarization events (betratron acceleration), flux ropes (Fermi acceleration), and tail loading/unloading (X-line acceleration). We find that the most common source of energetic electron events in Mercury's magnetosphere are dipolarization events similar to those first observed by Mariner 10. Further, a significant dawn-dusk asymmetry is found with dipolarization-associated energetic particle bursts being more common on the dawn side of the magnetotail.

  17. A Study of Energetic Neutral Oxygen Emissions and its Implications

    NASA Astrophysics Data System (ADS)

    Zheng, Y.; Lui, A. T.; Fok, M.

    2008-05-01

    Energetic Neutral Atom (ENA) emission detection serves as an innovative diagnostic tool for detailed investigations of energetic particles and has contributed greatly in addressing key issues of storm and substorm dynamics. ENAs, which are products of charge exchange between singly charged energetic ions and neutrals of the geocorona, carry not only spectral information but also composition of source plasma and therefore enable global imaging of ring current ions. An inter-spacecraft comparison of energetic neutral oxygen (ENO) intensity from two different vantage points, provided by IMAGE and Geotail, showed that viewing perspective plays a very important role in the observed ENO intensity level during a magnetic storm period [Lui et al., 2005]. Motivated by the findings, we investigate how viewing perspective influences energetic neutral atom emissions from a modeling perspective. Our simulation results, based upon O+ ion fluxes from the Comprehensive Ring Current Model (CRCM) and the subsequent ENO calculation, reproduce the total differential ENO intensity obtained from two spacecraft to a reasonable degree. Further analysis of our results indicates that pitch angle anisotropy in ring current ion flux, a crucial physical quantity in ring current and radiation belt dynamics, is one major contributor to the difference in energetic neutral atom intensity from different viewing perspectives. Using the CRCM, we will also examine the role of O+ in the storm-time ring current dynamics. Lui, A. T. Y. et al., Geophys. Res. Lett., 32, L13104, doi:10.1029/2005GL022851 (2005).

  18. Ordered pairing in liquid metallic hydrogen

    NASA Technical Reports Server (NTRS)

    Carlsson, A. E.; Ashcroft, N. W.

    1983-01-01

    We study two possible types of pairing involving the protons of a proposed low-temperature liquid phase metallic hydrogen. Electron-proton pairing, which can result in an insulating phase, is investigated by using an approximate solution of an Eliashberg-type equation for the anomalous self-energy. A very low estimate of the transition temperature is obtained by including proton correlations in the effective interaction. For proton-proton pairing, we derive a new proton pair potential based on the Abrikosov wave function. This potential includes the electron-proton interaction to all orders and has a much larger well depth than is obtained with linear screening methods. This suggests the possibility of either a superfluid paired phase analogous to that in He-3, or alternatively a phase with true molecular pairing.

  19. Ensemble treatments of thermal pairing in nuclei

    NASA Astrophysics Data System (ADS)

    Hung, Nguyen Quang; Dang, Nguyen Dinh

    2009-10-01

    A systematic comparison is conducted for pairing properties of finite systems at nonzero temperature as predicted by the exact solutions of the pairing problem embedded in three principal statistical ensembles, namely the grandcanonical ensemble, canonical ensemble and microcanonical ensemble, as well as the unprojected (FTBCS1+SCQRPA) and Lipkin-Nogami projected (FTLN1+SCQRPA) theories that include the quasiparticle number fluctuation and coupling to pair vibrations within the self-consistent quasiparticle random-phase approximation. The numerical calculations are performed for the pairing gap, total energy, heat capacity, entropy, and microcanonical temperature within the doubly-folded equidistant multilevel pairing model. The FTLN1+SCQRPA predictions are found to agree best with the exact grand-canonical results. In general, all approaches clearly show that the superfluid-normal phase transition is smoothed out in finite systems. A novel formula is suggested for extracting the empirical pairing gap in reasonable agreement with the exact canonical results.

  20. Dynamical evolution of comet pairs

    NASA Astrophysics Data System (ADS)

    Sosa, Andrea; Fernández, Julio A.

    2016-10-01

    Some Jupiter family comets in near-Earth orbits (thereafter NEJFCs) show a remarkable similarity in their present orbits, like for instance 169P/NEAT and P/2003 T12 (SOHO), or 252P/LINEAR and P/2016 BA14 (PANSTARRS). By means of numerical integrations we studied the dynamical evolution of these objects. In particular, for each pair of presumably related objects, we are interested in assessing the stability of the orbital parameters for several thousand years, and to find a minimum of their relative spatial distance, coincident with a low value of their relative velocity. For those cases for which we find a well defined minimum of their relative orbital separation, we are trying to reproduce the actual orbit of the hypothetical fragment by modeling a fragmentation of the parent body. Some model parameters are the relative ejection velocity (a few m/s), the orbital point at which the fragmentation could have happened (e.g. perihelion), and the elapsed time since fragmentation. In addition, some possible fragmentation mechanisms, like thermal stress, rotational instability, or collisions, could be explored. According to Fernández J.A and Sosa A. 2015 (Planetary and Space Science 118,pp.14-24), some NEJFCs might come from the outer asteroid belt, and then they would have a more consolidated structure and a higher mineral content than that of comets coming from the trans-Neptunian belt or the Oort cloud. Therefore, such objects would have a much longer physical lifetime in the near-Earth region, and could become potential candidates to produce visible meteor showers (as for example 169P/NEAT which has been identified as the parent body of the alpha-Capricornid meteoroid stream, according to Jenniskens, P., Vaubaillon, J., 2010 (Astron. J. 139), and Kasuga, T., Balam, D.D., Wiegert, P.A., 2010 (Astron. J. 139).

  1. Structural, electronic, and optical properties of metallo base pairs in duplex DNA: a theoretical insight.

    PubMed

    Samanta, Pralok K; Manna, Arun K; Pati, Swapan K

    2012-11-01

    Using density functional theory calculations, we investigated the structural, energetic, electronic, and optical properties of recently synthesized duplex DNA containing metal-mediated base pairs. The studied duplex DNA consists of three imidazole (Im) units linked through metal (Im-M-Im, M = metal) and four flanking A:T base pairs (two on each side). We examined the role of artificial base pairing in the presence of two distinctive metal ions, diamagnetic Ag(+) and magnetic Cu(2+) ions, on the stability of duplex DNA. We found that metal-mediated base pairs form stable duplex DNA by direct metal ion coordination to the Im bases. Our results suggest a higher binding stability of base pairing mediated by Cu(2+) ions than by Ag(+) ions, which is attributed to a larger extent of orbital hybridization. We furthermore found that DNA modified with Im-Ag(+)-Im shows the low-energy optical absorption characteristic of π-π*orbital transition of WC A:T base pairs. On the other hand, we found that the low-energy optical absorption peaks for DNA modified with Im-Cu(2+)-Im originate from spin-spin interactions. Additionally, this complex exhibits weak ferromagnetic coupling between Cu(2+) ions and strong spin polarization, which could be used for memory devices. Moreover, analyzing the role of counter ions (Na(+)) and the presence of explicit water molecules on the structural stability and electronic properties of the DNA duplex modified with Im-Ag(+)-Im, we found that the impact of these two factors is negligible. Our results are fruitful for understanding the experimental data and suggest a potential route for constructing effective metal-mediated base pairs in duplex DNA for optoelectronic applications.

  2. Lax pairs for deformed Minkowski spacetimes

    NASA Astrophysics Data System (ADS)

    Kyono, Hideki; Sakamoto, Jun-ichi; Yoshida, Kentaroh

    2016-01-01

    We proceed to study Yang-Baxter deformations of 4D Minkowski spacetime based on a conformal embedding. We first revisit a Melvin background and argue a Lax pair by adopting a simple replacement law invented in 1509.00173. This argument enables us to deduce a general expression of Lax pair. Then the anticipated Lax pair is shown to work for arbitrary classical r-matrices with Poincaré generators. As other examples, we present Lax pairs for pp-wave backgrounds, the Hashimoto-Sethi background, the Spradlin-Takayanagi-Volovich background.

  3. Dual origin of pairing in nuclei

    NASA Astrophysics Data System (ADS)

    Idini, A.; Potel, G.; Barranco, F.; Vigezzi, E.; Broglia, R. A.

    2016-11-01

    The pairing correlations of the nucleus 120Sn are calculated by solving the Nambu-Gor'kov equations, including medium polarization effects resulting from the interweaving of quasiparticles, spin and density vibrations, taking into account, within the framework of nuclear field theory (NFT), processes leading to self-energy and vertex corrections and to the induced pairing interaction. From these results one can not only demonstrate the inevitability of the dual origin of pairing in nuclei, but also extract information which can be used at profit to quantitatively disentangle the contributions to the pairing gap Δ arising from the bare and from the induced pairing interaction. The first is the strong 1 S 0 short-range NN potential resulting from meson exchange between nucleons moving in time reversal states within an energy range of hundreds of MeV from the Fermi energy. The second results from the exchange of vibrational modes between nucleons moving within few MeV from the Fermi energy. Short- ( v p bare) and long-range ( v p ind) pairing interactions contribute essentially equally to nuclear Cooper pair stability. That is to the breaking of gauge invariance in open-shell superfluid nuclei and thus to the order parameter, namely to the ground state expectation value of the pair creation operator. In other words, to the emergent property of generalized rigidity in gauge space, and associated rotational bands and Cooper pair tunneling between members of these bands.

  4. Higher order structural effects stabilizing the reverse Watson-Crick Guanine-Cytosine base pair in functional RNAs.

    PubMed

    Chawla, Mohit; Abdel-Azeim, Safwat; Oliva, Romina; Cavallo, Luigi

    2014-01-01

    The G:C reverse Watson-Crick (W:W trans) base pair, also known as Levitt base pair in the context of tRNAs, is a structurally and functionally important base pair that contributes to tertiary interactions joining distant domains in functional RNA molecules and also participates in metabolite binding in riboswitches. We previously indicated that the isolated G:C W:W trans base pair is a rather unstable geometry, and that dicationic metal binding to the Guanine base or posttranscriptional modification of the Guanine can increase its stability. Herein, we extend our survey and report on other H-bonding interactions that can increase the stability of this base pair. To this aim, we performed a bioinformatics search of the PDB to locate all the occurencies of G:C trans base pairs. Interestingly, 66% of the G:C trans base pairs in the PDB are engaged in additional H-bonding interactions with other bases, the RNA backbone or structured water molecules. High level quantum mechanical calculations on a data set of representative crystal structures were performed to shed light on the structural stability and energetics of the various crystallographic motifs. This analysis was extended to the binding of the preQ1 metabolite to a preQ1-II riboswitch.

  5. Incubation energetics of the Laysan Albatross.

    PubMed

    Pettit, T N; Nagy, K A; Ellis, H I; Whittow, G C

    1988-01-01

    The energy expenditure of incubating and foraging Laysan Albatross (Diomedea immutabilis, mean body weight 3.07 kg) was estimated by means of the doubly-labelled water technique. During incubation, the energy expenditure was similar to that of resting birds that were not incubating an egg. The energy expenditure of foraging albatross (2072 kJ/day) was 2.6 times that of resting birds. It was concluded that the energy expenditure of the tropical Laysan Albatross was not less than that of species foraging over cold, high-latitude oceans. An energy budget compiled for an incubating pair of albatross revealed that the energy expenditure of the female was greater than that of the male bird, during the incubation period.

  6. Energetic Supernovae of Very Massive Primordial Stars

    NASA Astrophysics Data System (ADS)

    Chen, Ke-Jung; Woosley, Stan

    2015-08-01

    Current models of the formation of the first stars in the universe suggest that these stars were very massive, having a typical mass scale of hundreds of solar masses. Some of them would die as pair instability supernovae (PSNe) which might be the biggest explosions of the universe. We present the results from multidimensional numerical studies of PSNe with a new radiation-hydrodynamics code, CASTRO and with realistic nuclear reaction networks. We simulate the fluid instabilities that occur in multiple spatial dimensions and discuss how the resulting mixing affects the explosion, mixing, and nucleosynthesis of these supernovae. Our simulations provide useful predictions for the observational signatures of PSNe, which might soon be examined by the James Webb Space Telescope.

  7. Energetic ion losses caused by magnetohydrodynamic activity resonant and non-resonant with energetic ions in Large Helical Device

    NASA Astrophysics Data System (ADS)

    Ogawa, Kunihiro; Isobe, Mitsutaka; Toi, Kazuo; Shimizu, Akihiro; Spong, Donald A.; Osakabe, Masaki; Yamamoto, Satoshi; the LHD Experiment Group

    2014-09-01

    Experiments to reveal energetic ion dynamics associated with magnetohydrodynamic activity are ongoing in the Large Helical Device (LHD). Interactions between beam-driven toroidal Alfvén eigenmodes (TAEs) and energetic ions have been investigated. Energetic ion losses induced by beam-driven burst TAEs have been observed using a scintillator-based lost fast-ion probe (SLIP) in neutral beam-heated high β plasmas. The loss flux of co-going beam ions increases as the TAE amplitude increases. In addition to this, the expulsion of beam ions associated with edge-localized modes (ELMs) has been also recognized in LHD. The SLIP has indicated that beam ions having co-going and barely co-going orbits are affected by ELMs. The relation between ELM amplitude and ELM-induced loss has a dispersed structure. To understand the energetic ion loss process, a numerical simulation based on an orbit-following model, DELTA5D, that incorporates magnetic fluctuations is performed. The calculation result shows that energetic ions confined in the interior region are lost due to TAE instability, with a diffusive process characterizing their loss. For the ELM, energetic ions existing near the confinement/loss boundary are lost through a convective process. We found that the ELM-induced loss flux measured by SLIP changes with the ELM phase. This relation between the ELM amplitude and measured ELM-induced loss results in a more dispersed loss structure.

  8. The Observational Signatures of Primordial Pair-Instability Supernovae

    NASA Astrophysics Data System (ADS)

    Whalen, Daniel J.; Fryer, Chris

    2010-10-01

    Massive Population III stars from 140-260 Msolar ended their lives as pair-instability supernovae (PISNe), the most energetic thermonuclear explosions in the universe. Detection of these explosions could directly constrain the primordial IMF for the first time, which is key to the formation of the first galaxies, early cosmological reionization, and the chemical enrichment of the primeval IGM. We present radiation hydrodynamical calculations of Pop III PISN light curves and spectra performed with the RAGE code. We find that the initial radiation pulse due to shock breakout from the surface of the star, although attenuated by the Lyman-alpha forest, will still be visible by JWST at z~10-15, and possibly out to z~20 with strong gravitational lensing. We have also studied metal mixing at early stages of the explosion prior to breakout from the surface of the star with the CASTRO AMR code and find vigorous mixing in primordial core-collapse explosions but very little in PISNe. This implies that the key to determining progenitor masses of the first cosmic explosions is early spectroscopy just after shock breakout, and that multidimensional mixing is crucial to accurate low-mass Pop III SNe light curves and spectra.

  9. Energetic Trend in Explosive Activity of Stromboli

    NASA Astrophysics Data System (ADS)

    Coltelli, M.; Cristaldi, A.; Mangiagli, S.; Nunnari, G.; Pecora, E.

    2003-12-01

    increasing its activity and when it declined the paroxysmal explosion occurred suddenly at the former site. From September 2001 an on-line image analyzer called VAMOS (Volcanic Activity MOnitoring System) operates detection and classification of explosive events in real-time. The system has automatically recorded and analyzed the change in the energetic trend that preceded the 20 October 2001 paroxysmal explosion that killed a woman and the strong explosive activity that preceded the onset of 28 December 2002 lava flow eruption.

  10. Molecular Theory of Detonation Initiation: Insight from First Principles Modeling of the Decomposition Mechanisms of Organic Nitro Energetic Materials.

    PubMed

    Tsyshevsky, Roman V; Sharia, Onise; Kuklja, Maija M

    2016-02-19

    This review presents a concept, which assumes that thermal decomposition processes play a major role in defining the sensitivity of organic energetic materials to detonation initiation. As a science and engineering community we are still far away from having a comprehensive molecular detonation initiation theory in a widely agreed upon form. However, recent advances in experimental and theoretical methods allow for a constructive and rigorous approach to design and test the theory or at least some of its fundamental building blocks. In this review, we analyzed a set of select experimental and theoretical articles, which were augmented by our own first principles modeling and simulations, to reveal new trends in energetic materials and to refine known existing correlations between their structures, properties, and functions. Our consideration is intentionally limited to the processes of thermally stimulated chemical reactions at the earliest stage of decomposition of molecules and materials containing defects.

  11. Molecular Theory of Detonation Initiation: Insight from First Principles Modeling of the Decomposition Mechanisms of Organic Nitro Energetic Materials

    SciTech Connect

    Tsyshevsky, Roman; Sharia, Onise; Kuklja, Maija

    2016-02-19

    Our review presents a concept, which assumes that thermal decomposition processes play a major role in defining the sensitivity of organic energetic materials to detonation initiation. As a science and engineering community we are still far away from having a comprehensive molecular detonation initiation theory in a widely agreed upon form. However, recent advances in experimental and theoretical methods allow for a constructive and rigorous approach to design and test the theory or at least some of its fundamental building blocks. In this review, we analyzed a set of select experimental and theoretical articles, which were augmented by our own first principles modeling and simulations, to reveal new trends in energetic materials and to refine known existing correlations between their structures, properties, and functions. Lastly, our consideration is intentionally limited to the processes of thermally stimulated chemical reactions at the earliest stage of decomposition of molecules and materials containing defects.

  12. Molecular Theory of Detonation Initiation: Insight from First Principles Modeling of the Decomposition Mechanisms of Organic Nitro Energetic Materials

    DOE PAGES

    Tsyshevsky, Roman; Sharia, Onise; Kuklja, Maija

    2016-02-19

    Our review presents a concept, which assumes that thermal decomposition processes play a major role in defining the sensitivity of organic energetic materials to detonation initiation. As a science and engineering community we are still far away from having a comprehensive molecular detonation initiation theory in a widely agreed upon form. However, recent advances in experimental and theoretical methods allow for a constructive and rigorous approach to design and test the theory or at least some of its fundamental building blocks. In this review, we analyzed a set of select experimental and theoretical articles, which were augmented by our ownmore » first principles modeling and simulations, to reveal new trends in energetic materials and to refine known existing correlations between their structures, properties, and functions. Lastly, our consideration is intentionally limited to the processes of thermally stimulated chemical reactions at the earliest stage of decomposition of molecules and materials containing defects.« less

  13. A rocket-borne microprocessor-based experiment for investigation of energetic particles in the D and E regions

    NASA Technical Reports Server (NTRS)

    Braswell, F. M.

    1981-01-01

    An energetic experiment using the Z80 family of microcomputer components is described. Data collected from the experiment allowed fast and efficient postprocessing, yielding both energy-spectrum and pitch-angle distribution of energetic particles in the D and E regions. Advanced microprocessor system architecture and software concepts were used in the design to cope with the large amount of data being processed. This required the Z80 system to operate at over 80% of its total capacity. The microprocessor system was included in the payloads of three rockets launched during the Energy Budget Campaign at ESRANGE, Kiruna, Sweden in November 1980. Based on preliminary examination of the data, the performance of the experiment was satisfactory and good data were obtained on the energy spectrum and pitch-angle distribution of the particles.

  14. Pairing, pseudogap and Fermi arcs in cuprates

    SciTech Connect

    Kaminski, Adam; Kondo, Takeshi; Takeuchi, Tsunehiro; Gu, Genda

    2014-04-29

    We use Angle Resolved Photoemission Spectroscopy (ARPES) to study the relationship between the pseudogap, pairing and Fermi arcs in cuprates. High quality data measured over a wide range of dopings reveals a consistent picture of Fermiology and pairing in these materials. The pseudogap is due to an ordered state that competes with superconductivity rather than preformed pairs. Pairing does occur below Tpair ~ 150K and significantly above Tc, but well below T* and the doping dependence of this temperature scale is distinct from that of the pseudogap. The d-wave gap is present below Tpair, and its interplay with strong scattering creates “artificial” Fermi arcs for Tc ≤ T ≤ Tpair. However, above Tpair, the pseudogap exists only at the antipodal region. This leads to presence of real, gapless Fermi arcs close to the node. The length of these arcs remains constant up to T*, where the full Fermi surface is recovered. As a result, we demonstrate that these findings resolve a number of seemingly contradictory scenarios.

  15. Pair condensation in a finite Fermi system

    SciTech Connect

    Sambataro, M.

    2007-05-15

    The lowest seniority-zero eigenstates of an exactly solvable multilevel pairing Hamiltonian for a finite Fermi system are examined at different pairing regimes. After briefly reviewing the form of the eigenstates in the Richardson formalism, we discuss a different representation of these states in terms of the collective pairs resulting from the diagonalization of the Hamiltonian in a space of two degenerate time-reversed fermions. We perform a two-fold analysis by working both in the fermionic space of these collective pairs and in a space of corresponding elementary bosons. On the fermionic side, we monitor the variations which occur, with increasing the pairing strength, in the structure of both these collective pairs and the lowest eigenstates. On the bosonic side, after reviewing a fermion-boson mapping procedure, we construct exact images of the fermion eigenstates and study their wave function. The analysis allows a close examination of the phenomenon of pair condensation in a finite Fermi system and gives new insights into the evolution of the lowest (seniority-zero) excited states of a pairing Hamiltonian from the unperturbed regime up to a strongly interacting one.

  16. Exploring Pair Programming Benefits for MIS Majors

    ERIC Educational Resources Information Center

    Dongo, Tendai; Reed, April H.; O'Hara, Margaret

    2016-01-01

    Pair programming is a collaborative programming practice that places participants in dyads, working in tandem at one computer to complete programming assignments. Pair programming studies with Computer Science (CS) and Software Engineering (SE) majors have identified benefits such as technical productivity, program/design quality, academic…

  17. 22 CFR 62.31 - Au pairs.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... pair participant with child development and child safety instruction, as follows: (1) Prior to... development instruction of which no less than 4 shall be devoted to specific training for children under the... and participate directly in the home life of the host family. All au pair participants provide...

  18. 22 CFR 62.31 - Au pairs.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... pair participant with child development and child safety instruction, as follows: (1) Prior to... development instruction of which no less than 4 shall be devoted to specific training for children under the... and participate directly in the home life of the host family. All au pair participants provide...

  19. 22 CFR 62.31 - Au pairs.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... pair participant with child development and child safety instruction, as follows: (1) Prior to... development instruction of which no less than 4 shall be devoted to specific training for children under the... and participate directly in the home life of the host family. All au pair participants provide...

  20. 22 CFR 62.31 - Au pairs.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... pair participant with child development and child safety instruction, as follows: (1) Prior to... development instruction of which no less than 4 shall be devoted to specific training for children under the... and participate directly in the home life of the host family. All au pair participants provide...

  1. 22 CFR 62.31 - Au pairs.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... pair participant with child development and child safety instruction, as follows: (1) Prior to... development instruction of which no less than 4 shall be devoted to specific training for children under the... and participate directly in the home life of the host family. All au pair participants provide...

  2. Top Quark Pair Production at the Tevatron

    SciTech Connect

    Nielsen, Jason

    2005-05-17

    The measurement of the top quark pair production crosssection inproton-antiproton collisions at 1.96 TeV is a test ofquantumchromodynamics and could potentially be sensitive to newphysics beyondthe standard model. I report on the latest t-tbarcross section resultsfrom the CDF and DZero experiments in various finalstate topologies whicharise from decays of top quark pairs.

  3. Synthesis of Energetic Nitrocarbamates from Polynitro Alcohols and Their Potential as High Energetic Oxidizers.

    PubMed

    Axthammer, Quirin J; Krumm, Burkhard; Klapötke, Thomas M

    2015-06-19

    A new synthesis strategy for the preparation of energetic carbamates and nitrocarbamates starting from readily available polynitro alcohols is introduced. The efficient synthesis of mainly new carbamates was performed with the reactive chlorosulfonyl isocyanate (CSI) reagent. The carbamates were nitrated using mixed acid to form the corresponding primary nitrocarbamates. The thermal stability of all synthesized compounds was studied using differential scanning calorimetry, and the energies of formation were calculated on the CBS-4 M level of theory. Detonation parameters and propulsion properties were determined with the software package EXPLO5 V6.02. Furthermore, for all new substances single-crystal X-ray diffraction studies were performed and are presented and discussed as Supporting Information.

  4. Circadian Integration of Metabolism and Energetics

    PubMed Central

    Bass, Joseph; Takahashi, Joseph S.

    2013-01-01

    Circadian clocks align behavioral and biochemical processes with the day/night cycle. Nearly all vertebrate cells possess self-sustained clocks that couple endogenous rhythms with changes in cellular environment. Genetic disruption of clock genes in mice perturbs metabolic functions of specific tissues at distinct phases of the sleep/wake cycle. Circadian desynchrony, a characteristic of shift work and sleep disruption in humans, also leads to metabolic pathologies. Here we review advances in understanding the interrelationship among circadian disruption, sleep deprivation, obesity and diabetes, and implications for rational therapeutics for these conditions. PMID:21127246

  5. Pairing in a dry Fermi sea

    NASA Astrophysics Data System (ADS)

    Maier, T. A.; Staar, P.; Mishra, V.; Chatterjee, U.; Campuzano, J. C.; Scalapino, D. J.

    2016-06-01

    In the traditional Bardeen-Cooper-Schrieffer theory of superconductivity, the amplitude for the propagation of a pair of electrons with momentum k and -k has a log singularity as the temperature decreases. This so-called Cooper instability arises from the presence of an electron Fermi sea. It means that an attractive interaction, no matter how weak, will eventually lead to a pairing instability. However, in the pseudogap regime of the cuprate superconductors, where parts of the Fermi surface are destroyed, this log singularity is suppressed, raising the question of how pairing occurs in the absence of a Fermi sea. Here we report Hubbard model numerical results and the analysis of angular-resolved photoemission experiments on a cuprate superconductor. In contrast to the traditional theory, we find that in the pseudogap regime the pairing instability arises from an increase in the strength of the spin-fluctuation pairing interaction as the temperature decreases rather than the Cooper log instability.

  6. PAIR: the predicted Arabidopsis interactome resource.

    PubMed

    Lin, Mingzhi; Shen, Xueling; Chen, Xin

    2011-01-01

    The predicted Arabidopsis interactome resource (PAIR, http://www.cls.zju.edu.cn/pair/), comprised of 5990 experimentally reported molecular interactions in Arabidopsis thaliana together with 145,494 predicted interactions, is currently the most comprehensive data set of the Arabidopsis interactome with high reliability. PAIR predicts interactions by a fine-tuned support vector machine model that integrates indirect evidences for interaction, such as gene co-expressions, domain interactions, shared GO annotations, co-localizations, phylogenetic profile similarities and homologous interactions in other organisms (interologs). These predictions were expected to cover 24% of the entire Arabidopsis interactome, and their reliability was estimated to be 44%. Two independent example data sets were used to rigorously validate the prediction accuracy. PAIR features a user-friendly query interface, providing rich annotation on the relationships between two proteins. A graphical interaction network browser has also been integrated into the PAIR web interface to facilitate mining of specific pathways.

  7. Capturing the energetics of water insertion in biological systems: the water flooding approach.

    PubMed

    Chakrabarty, Suman; Warshel, Arieh

    2013-01-01

    Consistent description of the effect of internal water in proteins has been a major challenge for both simulation and experimental studies. Describing this effect has been particularly important and elusive in cases of charges in protein interiors. Here, we present a new microscopic method that provides an efficient way for simulating the energetics of water insertion. Instead of performing explicit Monte Carlo (MC) moves on the insertion process, which generally involves an enormous number of rejected attempts, our method is based on generating trial configurations with excess amount of internal water, estimating the relevant free energy by the linear response approximation, and then using a postprocessing MC treatment to filter out a limited number of configurations from a large possible set. Our approach is validated on particularly challenging test cases including the pK(a) of the V66D mutation in Staphylococcal nuclease, Glu286 in cytochrome c oxidase (CcO) and the energetics of a protonated water molecule in the D channel of CcO. The new postprocessing method allows us to reproduce the relevant energetics of highly unstable charges in protein interiors using fully microscopic calculations and provides a substantial improvement over regular microscopic free energy estimates. This advance established the effectiveness of our water insertion strategy in challenging cases that have not been addressed successfully by other microscopic methods. Furthermore, our study provides a new exciting view on the crucial effect of water penetration in key biological systems as well as a new view on the nature of the dielectric in protein interiors.

  8. Structure and dynamics of hydrated ion pairs in a hydrophobic environment.

    PubMed

    Benjamin, Ilan

    2010-10-28

    The structure, energetics, and dynamics of different alkali halide ion pairs hydrated in a hydrophobic medium are studied using molecular dynamics computer simulations. One or two water molecules hydrating NaCl, NaI, KCl, KI, and KF in bulk carbon tetrachloride are considered. The ion pairs remain in contact throughout the simulations, so the structure of the hydration complex is well characterized. The ions' interaction energy and hydration structure are examined and correlated with the ion sizes and charges. For the first four salts, the stronger interaction of the water molecules with the cation than with the anion of the ion pair is in agreement with recent experiments. However, when the anion is significantly smaller than the cation (as in the case of KF, which was not studied experimentally), the opposite behavior is found. The asymmetry of interaction with the cation and the anion are further elucidated by examining hypothetical ion pairs made from equal-sized cations and anions and by defining an asymmetry hydration parameter, which is found to correlate well with the structural characteristics, as well as with the water molecules' reorientation dynamics.

  9. Migration of point defects and a defect pair in zinc oxide using the dimer method

    SciTech Connect

    Chen, Dong; Gao, Fei; Dong, Mingdong; Liu, Bo

    2012-09-24

    The migration mechanism and the minimum energy path of vacancies, interstitials and an interstitial-vacancy pair in zinc oxide have been studied by the dimer method. The in-plane and out-of-plane migrations of zinc and oxygen vacancies are found to be anisotropic. The kick-out mechanism is energetically preferred to zinc and oxygen interstitials that can easily migrate through the ZnO crystal lattice. In addition, the migration process of an interstitial-vacancy pair as a complex of an octahedral oxygen interstitial and a zinc vacancy is dominated by an oxygen interstitial/zinc vacancy successive migration. The energy barriers indicate that the existence of oxygen interstitial in the defect pair can promote the mobility of zinc vacancy, whereas the migration of oxygen interstitial is slowed down due to the presence of zinc vacancy. In the end, we show a possible migration path of the interstitial-vacancy pair that can be dissociated through a set of displacement movements.

  10. SRTM Stereo Pair: Fiji Islands

    NASA Technical Reports Server (NTRS)

    2000-01-01

    image pair and viewing them with a stereoscope. When stereoscopically merged, the result is a vertically exaggerated view of the Earth's surface in its full three dimensions.

    This image was acquired by SRTM aboard the Space Shuttle Endeavour, launched on February 11, 2000. SRTM used the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) that flew twice on the Space Shuttle Endeavour in 1994. SRTM was designed to collect three-dimensional measurements of the Earth's surface. To collect the 3-D data, engineers added a 60-meter-long (about 200 feet) mast, installed additional C-band and X-band antennas, and improved tracking and navigation devices. The mission is a cooperative project between the National Aeronautics and Space Administration (NASA), the National Imagery and Mapping Agency (NIMA) of the U.S. Department of Defense (DoD), and the German and Italian space agencies. It is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Earth Science Enterprise, Washington, DC.

    Size: 192 km (119 miles) x 142 km (88 miles) Location: 17.8 deg. South lat., 178.0 deg. East lon. Orientation: North at top Date Acquired: February 19, 2000 Image: NASA/JPL/NIMA

  11. Solubilization and fractionation of paired helical filaments.

    PubMed

    González, P J; Correas, I; Avila, J

    1992-09-01

    Paired helical filaments isolated from brains of two different patients with Alzheimer's disease were extensively treated with the ionic detergent, sodium dodecyl sulphate. Filaments were solubilized at different extents, depending on the brain examined, thus suggesting the existence of two types of paired helical filaments: sodium dodecyl sulphate-soluble and insoluble filaments. In the first case, the number of structures resembling paired helical filaments greatly decreased after the detergent treatment, as observed by electron microscopy. Simultaneously, a decrease in the amount of sedimentable protein was also observed upon centrifugation of the sodium dodecyl sulfate-treated paired helical filaments. A sodium dodecyl sulphate-soluble fraction was isolated as a supernatant after low-speed centrifugation of the sodium dodecyl sulphate-treated paired helical filaments. The addition of the non-ionic detergent Nonidet-P40 to this fraction resulted in the formation of paired helical filament-like structures. When the sodium dodecyl sulphate-soluble fraction was further fractionated by high-speed centrifugation, three subfractions were observed: a supernatant, a pellet and a thin layer between these two subfractions. No paired helical filaments were observed in any of these subfractions, even after addition of Nonidet P-40. However, when they were mixed back together, the treatment with Nonidet P-40 resulted in the visualization of paired helical filament-like structures. These results suggest that at least two different components are needed for the reconstitution of paired helical filaments as determined by electron microscopy. The method described here may allow the study of the components involved in the formation of paired helical filaments and the identification of possible factors capable of blocking this process.

  12. Crystallographic Structure, Intermolecular Packing Energetics, Crystal Morphology and Surface Chemistry of Salmeterol Xinafoate (Form I).

    PubMed

    Moldovan, Alexandru A; Rosbottom, Ian; Ramachandran, Vasuki; Pask, Christopher M; Olomukhoro, Oboroghene; Roberts, Kevin J

    2017-03-01

    Single crystals of salmeterol xinafoate (form I), prepared from slow cooled supersaturated propan-2-ol solutions, crystallize in a triclinic P1¯ symmetry with 2 closely related independent salt pairs within the asymmetric unit, with an approximately double-unit cell volume compared with the previously published crystal structure. Synthonic analysis of the bulk intermolecular packing confirms the similarity in packing energetics between the 2 salt pairs. The strongest synthons, as expected, are dominated by coulombic interactions. Morphologic prediction reveals a plate-like morphology, dominated by the {001}, {010}, and {100} surfaces, consistent with experimentally grown crystals. Although surface chemistry of the slow-growing {001} face comprises large sterically hindering phenyl groups, although weaker coulombic interactions still prevail from the alcohol group present on the phenyl and hydroxymethyl groups. The surface chemistry of the faster growing {010} and {100} faces are dominated by the significantly stronger cation/anion interactions occurring between the carboxylate and protonated secondary ammonium ion groups. The importance of understanding the cohesive and adhesive nature of the crystal surfaces of an active pharmaceutical ingredient, with respect to their interaction with other active pharmaceutical ingredient crystals and how that may affect formulation design, is highlighted.

  13. Automatically Pairing Measured Findings across Narrative Abdomen CT Reports

    PubMed Central

    Sevenster, Merlijn; Bozeman, Jeffrey; Cowhy, Andrea; Trost, William

    2013-01-01

    Radiological measurements are one of the key variables in widely adopted guidelines (WHO, RECIST) that standardize and objectivize response assessment in oncology care. Measurements are typically described in free-text, narrative radiology reports. We present a natural language processing pipeline that extracts measurements from radiology reports and pairs them with extracted measurements from prior reports of the same clinical finding, e.g., lymph node or mass. A ground truth was created by manually pairing measurements in the abdomen CT reports of 50 patients. A Random Forest classifier trained on 15 features achieved superior results in an end-to-end evaluation of the pipeline on the extraction and pairing task: precision 0.910, recall 0.878, F-measure 0.894, AUC 0.988. Representing the narrative content in terms of UMLS concepts did not improve results. Applications of the proposed technology include data mining, advanced search and workflow support for healthcare professionals managing radiological measurements. PMID:24551406

  14. The kinetics of energetic O‑ ions in oxygen discharge plasmas

    NASA Astrophysics Data System (ADS)

    Ponomarev, A. A.; Aleksandrov, N. L.

    2017-04-01

    Monte Carlo simulation was used to study the translational relaxation of energetic O‑ ions produced by dissociative electron attachment to O2 molecules in oxygen plasmas in a strong electric field. Initial O‑ ions have rather high energies and are more reactive than the ions reaching equilibrium with the electric field. Therefore, there is a noticeable probability that the energetic O‑ ions participate in endothermic reactions prior to energy relaxation of these ions. The probabilities of charge exchange, electron detachment and ion impact vibrational excitation of O2 molecules were calculated versus the reduced electric field. It was shown that up to 6% of energetic O‑ ions produced in oxygen by dissociative electron attachment to O2 molecules are rapidly transformed to {{{{O}}}2}- ions due to charge exchange collisions. The probability of electron detachment from energetic O‑ ions and the probability of vibrational excitation were smaller that the probability of charge exchange. Estimates showed that the increase in the effective rates of the ion–molecule reactions due to high reactivity of energetic O‑ ions can be important in oxygen plasmas for reduced electric fields of 50–100 Td.

  15. Thermal safety characterization and explosion violence of energetic materials

    NASA Astrophysics Data System (ADS)

    Hsu, Peter; Hust, Gary; Pagoria, Philip; Fried, Larry

    2015-06-01

    Some energetic materials could thermally explode at fairly low temperatures (<100 C) and the violence from thermal explosion may cause a significant damage. Thus understanding the response of energetic material to thermal events is very important for the storage and handling of energetic materials. Over the last few decades, there has been considerable research effort on the thermal decomposition and thermal explosion violence of energetic materials at elevated temperatures in different sample geometries and confinements. Among them, the ODTX system is an interesting option due to its sample requirement and easiness for data modeling. It has been used since 1970s for cook-off study at LLNL. It generates 3 technical data: (1) lowest temperature at which thermal explosion would occur (threshold temperature, Til) , (2) times to thermal explosion at temperature above Til, for the calculation of activation energy and frequency factor; and (3) thermal explosion violence. In this paper, we will present some recent ODTX experimental data of several new energetic materials as well as gas pressure data at elevated temperature.

  16. Energetic consequences of being a Homo erectus female.

    PubMed

    Aiello, Leslie C; Key, Cathy

    2002-01-01

    Body size is one of the most important characteristics of any animal because it affects a range of behavioral, ecological, and physiological traits including energy requirements, choice of food, reproductive strategies, predation risk, range size, and locomotor style. This article focuses on the implications of being large bodied for Homo erectus females, estimated to have been over 50% heavier than average australopithecine females. The energy requirements of these hominins are modeled using data on activity patterns, body mass, and life history from living primates. Particular attention is given to the inferred energetic costs of reproduction for Homo erectus females based on chimpanzee and human reproductive scheduling. Daily energy requirements during gestation and lactation would have been significantly higher for Homo erectus females, as would total energetic cost per offspring if the australopithecines and Homo erectus had similar reproductive schedules (gestation and lactation lengths and interbirth intervals). Shortening the interbirth interval could considerably reduce the costs per offspring to Homo erectus and have the added advantage of increasing reproductive output. The mother would, however, incur additional daily costs of caring for the dependent offspring. If Homo erectus females adopted this reproductive strategy, it would necessarily imply a revolution in the way in which females obtained and utilized energy to support their increased energetic requirements. This transformation is likely to have occurred on several levels involving cooperative economic division of labor, locomotor energetics, menopause, organ size, and other physiological mechanisms for reducing the energetic load on females.

  17. Cationic Noncovalent Interactions: Energetics and Periodic Trends.

    PubMed

    Rodgers, M T; Armentrout, P B

    2016-05-11

    In this review, noncovalent interactions of ions with neutral molecules are discussed. After defining the scope of the article, which excludes anionic and most protonated systems, methods associated with measuring thermodynamic information for such systems are briefly recounted. An extensive set of tables detailing available thermodynamic information for the noncovalent interactions of metal cations with a host of ligands is provided. Ligands include small molecules (H2, NH3, CO, CS, H2O, CH3CN, and others), organic ligands (O- and N-donors, crown ethers and related molecules, MALDI matrix molecules), π-ligands (alkenes, alkynes, benzene, and substituted benzenes), miscellaneous inorganic ligands, and biological systems (amino acids, peptides, sugars, nucleobases, nucleosides, and nucleotides). Hydration of metalated biological systems is also included along with selected proton-based systems: 18-crown-6 polyether with protonated peptides and base-pairing energies of nucleobases. In all cases, the literature thermochemistry is evaluated and, in many cases, reanchored or adjusted to 0 K bond dissociation energies. Trends in these values are discussed and related to a variety of simple molecular concepts.

  18. Detecting a preformed pair phase: Response to a pairing forcing field

    NASA Astrophysics Data System (ADS)

    Tagliavini, A.; Capone, M.; Toschi, A.

    2016-10-01

    The normal state of strongly coupled superconductors is characterized by the presence of "preformed" Cooper pairs well above the superconducting critical temperature. In this regime, the electrons are paired, but they lack the phase coherence necessary for superconductivity. The existence of preformed pairs implies the existence of a characteristic energy scale associated with a pseudogap. Preformed pairs are often invoked to interpret systems where some signatures of pairing are present without actual superconductivity, but an unambiguous theoretical characterization of a preformed-pair system is still lacking. To fill this gap, we consider the response to an external pairing field of an attractive Hubbard model, which hosts one of the cleanest realizations of a preformed pair phase, and a repulsive model where s -wave superconductivity cannot be realized. Using dynamical mean-field theory to study this response, we identify the characteristic features which distinguish the reaction of a preformed pair state from a normal metal without any precursor of pairing. The theoretical detection of preformed pairs is associated with the behavior of the second derivative of the order parameter with respect to the external field, as confirmed by analytic calculations in limiting cases. Our findings provide a solid test bed for the interpretation of state-of-the-art calculations for the normal state of the doped Hubbard model in terms of d -wave preformed pairs and, in perspective, of nonequilibrium experiments in high-temperature superconductors.

  19. NANOSTRUCTURE PATTERNING UNDER ENERGETIC PARTICLE BEAM IRRADIATION

    SciTech Connect

    Wang, Lumin; Lu, Wei

    2013-01-31

    Energetic ion bombardment can lead to the development of complex and diverse nanostructures on or beneath the material surface through induced self-organization processes. These self-organized structures have received particular interest recently as promising candidates as simple, inexpensive, and large area patterns, whose optical, electronic and magnetic properties are different from those in the bulk materials [1-5]. Compared to the low mass efficiency production rate of lithographic methods, these self-organized approaches display new routes for the fabrication of nanostructures over large areas in a short processing time at the nanoscale, beyond the limits of lithography [1,4]. Although it is believed that surface nanostructure formation is based on the morphological instability of the sputtered surface, driven by a kinetic balance between roughening and smoothing actions [6,7], the fundamental mechanisms and experimental conditions for the formation of these nanostructures has still not been well established, the formation of the 3-D naopatterns beneath the irradiated surface especially needs more exploration. During the last funding period, we have focused our efforts on irradiation-induced nanostructures in a broad range of materials. These structures have been studied primarily through in situ electron microscopy during electron or ion irradiation. In particular, we have performed studies on 3-D void/bubble lattices (in metals and CaF2), embedded sponge-like porous structure with uniform nanofibers in irradiated semiconductors (Ge, GaSb, and InSb), 2-D highly ordered pattern of nanodroplets (on the surface of GaAs), hexagonally ordered nanoholes (on the surface of Ge), and 1-D highly ordered ripple and periodic arrays (of Cu nanoparticles) [3,8-11]. The amazing common feature in those nanopatterns is the uniformity of the size of nanoelements (nanoripples, nanodots, nanovoids or nanofibers) and the distance separating them. Our research focuses on the

  20. Cosmic Ray Energetics And Mass (CREAM) Launch and Operations

    NASA Astrophysics Data System (ADS)

    Seo, Eun-Suk

    We request continued NASA support for the on-going Cosmic Ray Energetics And Mass (CREAM) project. The balloon-borne CREAM instrument was flown for 161 days in six flights over Antarctica, the longest known exposure for a single balloon project. Building on the success of those balloon missions, one of the two balloon payloads was successfully transformed for exposure on the International Space Station (ISS) Japanese Experiment Module Exposed Facility (JEM EF). Following completion of its systemlevel qualification and verification, this ISS-CREAM payload was delivered to the NASA Kennedy Space Center in August 2015 to await its launch to the ISS. The ISS-CREAM mission would achieve the primary science objectives of the Advanced Cosmic-ray Composition Experiment for the Space Station (ACCESS), which was given high priority in the 2001 NRC Decadal Study Report. Its nuclei composition data between 10^12 and 10^15 eV would enable detailed study of the spectral hardening first reported by the CREAM balloon project and recently confirmed for protons and helium by the PAMELA and AMS-02 space missions using permanent magnet spectrometers. In addition, multiTeV energy electron data allow searches for local sources and the signature of darkmatter, etc. The ISS-CREAM instrument is configured with redundant and complementary particle detectors capable of precise measurements of elemental spectra for Z = 1 - 26 nuclei, as well as electrons. The four layers of its finely segmented Silicon Charge Detector provide charge measurements, and its ionization calorimeter provides energy measurements. Its segmented scintillator-based Top and Bottom Counting Detectors separate electrons from nuclei using shower profile differences. Its Boronated Scintillator Detector distinguishes electrons from nuclei by detecting thermal neutrons that are dominant in nuclei induced showers. An order of magnitude increase in data collecting power is possible by utilizing the ISS to reach the highest