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Sample records for par neutrons rapides

  1. Rapidly rotating neutron star progenitors

    NASA Astrophysics Data System (ADS)

    Postnov, K. A.; Kuranov, A. G.; Kolesnikov, D. A.; Popov, S. B.; Porayko, N. K.

    2016-08-01

    Rotating proto-neutron stars can be important sources of gravitational waves to be searched for by present-day and future interferometric detectors. It was demonstrated by Imshennik that in extreme cases the rapid rotation of a collapsing stellar core may lead to fission and formation of a binary proto-neutron star which subsequently merges due to gravitational wave emission. In the present paper, we show that such dynamically unstable collapsing stellar cores may be the product of a former merger process of two stellar cores in a common envelope. We applied population synthesis calculations to assess the expected fraction of such rapidly rotating stellar cores which may lead to fission and formation of a pair of proto-neutron stars. We have used the BSE population synthesis code supplemented with a new treatment of stellar core rotation during the evolution via effective core-envelope coupling, characterized by the coupling time, τc. The validity of this approach is checked by direct MESA calculations of the evolution of a rotating 15 M⊙ star. From comparison of the calculated spin distribution of young neutron stars with the observed one, reported by Popov and Turolla, we infer the value τc ≃ 5 × 105 years. We show that merging of stellar cores in common envelopes can lead to collapses with dynamically unstable proto-neutron stars, with their formation rate being ˜0.1 - 1% of the total core collapses, depending on the common envelope efficiency.

  2. L'analyse par activation de neutrons de réacteur

    NASA Astrophysics Data System (ADS)

    Meyer, G.

    2003-02-01

    Quand les neutrons traversent la matière, certains sont transmis sans interaction, les autres interagissent avec le milieu traversé par diffusion et par absorption. Ce phénomène d'absorption est utilisé pour se protéger des neutrons, mais aussi pour les détecter; il peut également être utilisé pour identifier les noyaux “absorbants" et ainsi analyser le milieu traversé. En effet par différentes réactions nucléaires (n,γ), (n,p), (n,α), (n,fission), on obtient des noyaux résiduels qui sont souvent radioactifs; on dit que l'échantillon est “activé". Si l'on connaît le rendement d'activation et donc le pourcentage de noyaux ainsi “transmutés", les mesures de radioactivité induite vont permettre de déterminer la composition de l'échantillon irradié. Cette méthode dite d'analyse par activation neutronique est pratiquée depuis la découverte du neutron. Elle a permis grâce à sa sélectivité et à sa sensibilité d'avoir accès au domaine des traces et des ultra-traces dans des champs d'application très divers comme la métallurgie, l'archéologie, la biologie, la géochimie etc...

  3. NARROW ATOMIC FEATURES FROM RAPIDLY SPINNING NEUTRON STARS

    SciTech Connect

    Bauboeck, Michi; Psaltis, Dimitrios; Oezel, Feryal E-mail: dpsaltis@email.arizona.edu

    2013-04-01

    Neutron stars spinning at moderate rates ({approx}300-600 Hz) become oblate in shape and acquire a nonzero quadrupole moment. In this paper, we calculate the profiles of atomic features from such neutron stars using a ray-tracing algorithm in the Hartle-Thorne approximation. We show that line profiles acquire cores that are much narrower than the widths expected from pure Doppler effects for a large range of observer inclinations. As a result, the effects of both the oblateness and the quadrupole moments of neutron stars need to be taken into account when aiming to measure neutron-star radii from rotationally broadened lines. Moreover, the presence of these narrow cores substantially increases the likelihood of detecting atomic lines from rapidly spinning neutron stars.

  4. Some implications of neutron mirror neutron oscillation [rapid communication

    NASA Astrophysics Data System (ADS)

    Mohapatra, R. N.; Nasri, S.; Nussinov, S.

    2005-10-01

    We comment on a recently discussed possibility of oscillations between neutrons and degenerate mirror neutrons in the context of mirror models for particles and forces. It has been noted by Bento and Berezhiani that if these oscillations occurred at a rate of τNN‧-1 ∼s-1, it would help explain putative super GKZ cosmic ray events provided the temperature of the mirror radiation is ∼ 0.3- 0.4 times that of familiar cosmic microwave background radiation. We discuss how such oscillation time scales can be realized in mirror models and find that the simplest nonsupersymmetric model for this idea requires the existence of a low mass (30-3000 GeV) color triplet scalar or vector boson. A supersymmetric model, where this constraint can be avoided is severely constrained by the requirement of maintaining a cooler mirror sector. We also find that the reheat temperature after inflation in generic models that give fast n-n‧ oscillation be less than about 300 GeV in order to maintain the required relative coolness of the mirror sector.

  5. Instability windows and evolution of rapidly rotating neutron stars.

    PubMed

    Gusakov, Mikhail E; Chugunov, Andrey I; Kantor, Elena M

    2014-04-18

    We consider an instability of rapidly rotating neutron stars in low-mass x-ray binaries (LMXBs) with respect to excitation of r modes (which are analogous to Earth's Rossby waves controlled by the Coriolis force). We argue that finite temperature effects in the superfluid core of a neutron star lead to a resonance coupling and enhanced damping (and hence stability) of oscillation modes at certain stellar temperatures. Using a simple phenomenological model we demonstrate that neutron stars with high spin frequency may spend a substantial amount of time at these "resonance" temperatures. This finding allows us to explain puzzling observations of hot rapidly rotating neutron stars in LMXBs and to predict a new class of hot, nonaccreting, rapidly rotating neutron stars, some of which may have already been observed and tentatively identified as quiescent LMXB candidates. We also impose a new theoretical limit on the neutron star spin frequency, which can explain the cutoff spin frequency ∼730  Hz, following from the statistical analysis of accreting millisecond x-ray pulsars. In addition to explaining the observations, our model provides a new tool to constrain superdense matter properties by comparing measured and theoretically predicted resonance temperatures. PMID:24785021

  6. Instability windows and evolution of rapidly rotating neutron stars.

    PubMed

    Gusakov, Mikhail E; Chugunov, Andrey I; Kantor, Elena M

    2014-04-18

    We consider an instability of rapidly rotating neutron stars in low-mass x-ray binaries (LMXBs) with respect to excitation of r modes (which are analogous to Earth's Rossby waves controlled by the Coriolis force). We argue that finite temperature effects in the superfluid core of a neutron star lead to a resonance coupling and enhanced damping (and hence stability) of oscillation modes at certain stellar temperatures. Using a simple phenomenological model we demonstrate that neutron stars with high spin frequency may spend a substantial amount of time at these "resonance" temperatures. This finding allows us to explain puzzling observations of hot rapidly rotating neutron stars in LMXBs and to predict a new class of hot, nonaccreting, rapidly rotating neutron stars, some of which may have already been observed and tentatively identified as quiescent LMXB candidates. We also impose a new theoretical limit on the neutron star spin frequency, which can explain the cutoff spin frequency ∼730  Hz, following from the statistical analysis of accreting millisecond x-ray pulsars. In addition to explaining the observations, our model provides a new tool to constrain superdense matter properties by comparing measured and theoretically predicted resonance temperatures.

  7. HOW CAN NEWLY BORN RAPIDLY ROTATING NEUTRON STARS BECOME MAGNETARS?

    SciTech Connect

    Cheng, Quan; Yu, Yun-Wei

    2014-05-10

    In a newly born (high-temperature and Keplerian rotating) neutron star, r-mode instability can lead to stellar differential rotation, which winds the seed poloidal magnetic field (∼10{sup 11} G) to generate an ultra-high (∼10{sup 17} G) toroidal field component. Subsequently, by succumbing to the Tayler instability, the toroidal field could be partially transformed into a new poloidal field. Through such dynamo processes, the newly born neutron star with sufficiently rapid rotation could become a magnetar on a timescale of ∼10{sup 2} {sup –} {sup 3} s, with a surface dipolar magnetic field of ∼10{sup 15} G. Accompanying the field amplification, the star could spin down to a period of ∼5 ms through gravitational wave radiation due to the r-mode instability and, in particular, the non-axisymmetric stellar deformation caused by the toroidal field. This scenario provides a possible explanation for why the remnant neutron stars formed in gamma-ray bursts and superluminous supernovae could be millisecond magnetars.

  8. Does SN 1987A contain a rapidly vibrating neutron star

    NASA Technical Reports Server (NTRS)

    Wang, Q.; Chen, K.; Hamilton, T. T.; Ruderman, M.; Shaham, Jacob

    1989-01-01

    If the recently reported 0.5 ms-period pulsed optical signal from the direction of Supernova 1987A originated in a young neutron star, its interpretation as a rotational period has difficulties. The surface magnetic field would have to be much lower than expected, and the high rotation rate may rule out preferred nuclear equations of state. It is pointed out here that a remnant radial vibration of a neutron star, excited in the supernova event, may survive for several years with about the observed (gravitationally redshifted) period. Heavy ions at the low-density stellar surface, periodically shocked by the vibration, may efficiently produce narrow pulses of optical cyclotron radiation in a surface field of about a trillion gauss.

  9. Constraining Properties of Rapidly Rotating Neutron Stars Using Data from Heavy-Ion Collisions

    NASA Astrophysics Data System (ADS)

    Krastev, Plamen G.; Li, Bao-An; Worley, Aaron

    2008-04-01

    Properties, structure, and thermal evolution of neutron stars are determined by the equation of state of stellar matter. Recent data on isospin diffusion and isoscaling in heavy-ion collisions at intermediate energies as well as data on the size of the neutron skin in 208Pb have considerably constrained the density dependence of the nuclear symmetry energy and, in turn, the equation of state of neutron-rich nucleonic matter. These constraints could provide useful information about the global properties of rapidly rotating neutron stars. Models of rapidly rotating neutron stars are constructed by applying several nucleonic equations of state. Particular emphasis is placed on configurations rotating rigidly at 716 and 1122 Hz. The range of allowed hydrostatic equilibrium solutions is determined and tested for stability. The effect of rotation on the internal composition and thermal properties of neutron stars is also examined. At a given rotational frequency, each equation of state yields a range of possible neutron stars configurations restricted by the Keplerian (mass-shedding) limit, corresponding to the maximal circumferential radius, and the limit due to the onset of instabilities with respect to axisymmetric perturbations, corresponding to the minimal equatorial radius of a stable neutron star model. We show that the mass of a neutron star rotating uniformly at 1122 Hz is between 1.7 and 2.1 M⊙. Central stellar density and proton fraction decrease with increasing rotational frequency with respect to static models and, depending on the exact stellar mass and angular velocity, can drop below the direct Urca threshold, thus closing the fast cooling channel.

  10. Relativistic g-modes in rapidly rotating neutron stars

    SciTech Connect

    Gaertig, Erich; Kokkotas, Kostas D.

    2009-09-15

    We study the g-modes of fast rotating stratified neutron stars in the general relativistic Cowling approximation, where we neglect metric perturbations and where the background models take into account the buoyant force due to composition gradients. This is the first paper studying this problem in a general relativistic framework. In a recent paper [A. Passamonti, B. Haskell, N. Andersson, D. I. Jones, and I. Hawke, Mon. Not. R. Astron. Soc. 394, 730 (2009)], a similar study was performed within the Newtonian framework, where the authors presented results about the onset of CFS-unstable g-modes and the close connection between inertial and gravity modes for sufficiently high rotation rates and small composition gradients. This correlation arises from the interplay between the buoyant force which is the restoring force for g-modes and the Coriolis force which is responsible for the existence of inertial modes. In our relativistic treatment of the problem, we find an excellent qualitative agreement with respect to the Newtonian results.

  11. THE UBIQUITY OF THE RAPID NEUTRON-CAPTURE PROCESS

    SciTech Connect

    Roederer, Ian U.; Sneden, Christopher; Cowan, John J.; Karakas, Amanda I.; Kratz, Karl-Ludwig; Lugaro, Maria; Simmerer, Jennifer; Farouqi, Khalil

    2010-12-01

    To better characterize the abundance patterns produced by the r-process, we have derived new abundances or upper limits for the heavy elements zinc (Zn, Z= 30), yttrium (Y, Z= 39), lanthanum (La, Z= 57), europium (Eu, Z= 63), and lead (Pb, Z= 82). Our sample of 161 metal-poor stars includes new measurements from 88 high-resolution and high signal-to-noise spectra obtained with the Tull Spectrograph on the 2.7 m Smith Telescope at the McDonald Observatory, and other abundances are adopted from the literature. We use models of the s-process in asymptotic giant branch stars to characterize the high Pb/Eu ratios produced in the s-process at low metallicity, and our new observations then allow us to identify a sample of stars with no detectable s-process material. In these stars, we find no significant increase in the Pb/Eu ratios with increasing metallicity. This suggests that s-process material was not widely dispersed until the overall Galactic metallicity grew considerably, perhaps even as high as [Fe/H] =-1.4, in contrast with earlier studies that suggested a much lower mean metallicity. We identify a dispersion of at least 0.5 dex in [La/Eu] in metal-poor stars with [Eu/Fe] <+0.6 attributable to the r-process, suggesting that there is no unique 'pure' r-process elemental ratio among pairs of rare earth elements. We confirm earlier detections of an anti-correlation between Y/Eu and Eu/Fe bookended by stars strongly enriched in the r-process (e.g., CS 22892-052) and those with deficiencies of the heavy elements (e.g., HD 122563). We can reproduce the range of Y/Eu ratios using simulations of high-entropy neutrino winds of core-collapse supernovae that include charged-particle and neutron-capture components of r-process nucleosynthesis. The heavy element abundance patterns in most metal-poor stars do not resemble that of CS 22892-052, but the presence of heavy elements such as Ba in nearly all metal-poor stars without s-process enrichment suggests that the r

  12. Nano-ingenierie de bande interdite des semiconducteurs quantiques par recuit thermique rapide au laser

    NASA Astrophysics Data System (ADS)

    Stanowski, Radoslaw Wojciech

    The ability to fabricate semiconductor wafers with spatially selected regions of different bandgap material is required for the fabrication of monolithic photonic integrated circuits (PIC's). Although this subject has been studied for three decades and many semiconductor engineering approaches have been proposed, the problem of achieving reproducible results has constantly challenged scientists and engineers. This concerns not only the techniques relaying on multiple sequential epitaxial growth and selective area epitaxy, but also the conventional quantum well intermixing (QWI) technique that has been investigated as a post-growth approach for bandgap engineering. Among different QWI techniques, those based on the use of different lasers appear to be attractive in the context of high-precision and the potential for cost-effective bandgap engineering. For instance, a tightly focused beam of the infrared (IR) laser could be used for the annealing of small regions of a semiconductor wafer comprising different quantum well (QW) or quantum dot (QD) microstructures. The precision of such an approach in delivering wafers with well defined regions of different bandgap material will depend on the ability to control the laser-induced temperature, dynamics of the heating-cooling process and the ability to take advantage of the bandgap engineering diagnostics. In the frame of this thesis, I have investigated IR laser-induced QWI processes in QW wafers comprising GaAs/A1GaAs and InP/InGaAsP microstructures and in InAs QD microstructures grown on InP substrates. For that purpose, I have designed and set up a 2-laser system for selective area rapid thermal annealing (Laser-RTA) of semiconductor wafers. The advantage of such an approach is that it allows carrying out annealing with heating-cooling rates unattainable with conventional RTA techniques, while a tightly focused beam of one of the IR lasers is used for 'spot annealing'. These features have enabled me to introduce a new

  13. Galactic evolution of rapid neutron capture process abundances: the inhomogeneous approach

    NASA Astrophysics Data System (ADS)

    Wehmeyer, B.; Pignatari, M.; Thielemann, F.-K.

    2015-09-01

    For the origin of heavy rapid neutron capture process (r-process) elements, different sources have been proposed, e.g. core-collapse supernovae or neutron star mergers. Old metal-poor stars carry the signature of the astrophysical source(s). Among the elements dominantly made by the r-process, europium (Eu) is relatively easy to observe. In this work we simulate the evolution of Eu in our Galaxy with the inhomogeneous chemical evolution (ICE) model, and compare our results with spectroscopic observations. We test the most important parameters affecting the chemical evolution of Eu: (a) for neutron star mergers the coalescence time-scale of the merger (tcoal) and the probability to experience a neutron star merger event after two supernova explosions occurred and formed a double neutron star system (PNSM) and (b) for the subclass of magnetorotationally driven supernovae (`Jet-SNe'), their occurrence rate compared to standard supernovae (PJet-SN). We find that the observed [Eu/Fe] pattern in the Galaxy can be reproduced by a combination of neutron star mergers and Jet-SNe as r-process sources. While neutron star mergers alone seem to set in at too high metallicities, Jet-SNe provide a cure for this deficiency at low metallicities. Furthermore, we confirm that local inhomogeneities can explain the observed large spread in the Eu abundances at low metallicities. We also predict the evolution of [O/Fe] to test whether the spread in α-elements for inhomogeneous models agrees with observations and whether this provides constraints on supernova explosion models and their nucleosynthesis.

  14. Neutron Imaging of Rapid Water Imbibition in Fractured Sedimentary Rock Cores

    NASA Astrophysics Data System (ADS)

    Cheng, Chu-Lin; Perfect, Edmund; Donnelly, Brendan; Bilheux, Hassina; Tremsin, Anton; McKay, Larry; Distefano, Victoria; Cai, Jianchao; Santodonato, Lou

    2015-03-01

    Advances in nondestructive testing methods, such as neutron, nuclear magnetic resonance, and x-ray imaging, have significantly improved experimental capabilities to visualize fracture flow in various important fossil energy contexts, e.g. enhanced oil recovery and shale gas. We present a theoretical framework for predicting the rapid movement of water into air-filled fractures within a porous medium based on early-time capillary dynamics and spreading over rough fracture surfaces. The theory permits estimation of sorptivity values for the matrix and fracture zone, as well as a dispersion parameter which quantifies the extent of spreading of the wetting front. Dynamic neutron imaging of water imbibition in unsaturated fractured Berea sandstone cores was employed to evaluate the proposed model. The experiments were conducted at the Neutron Imaging Prototype Facility at Oak Ridge National Laboratory. Water uptake into both the matrix and fracture zone exhibited square-root-of-time behavior. Both theory and neutron imaging data indicated that fractures significantly increase imbibition in unsaturated sedimentary rock by capillary action and surface spreading on rough fracture faces. Fractures also increased the dispersion of the wetting front.

  15. Universality of the acceleration due to gravity on the surface of a rapidly rotating neutron star

    SciTech Connect

    AlGendy, Mohammad; Morsink, Sharon M.

    2014-08-20

    On the surface of a rapidly rotating neutron star, the effective centrifugal force decreases the effective acceleration due to gravity (as measured in the rotating frame) at the equator while increasing the acceleration at the poles due to the centrifugal flattening of the star into an oblate spheroid. We compute the effective gravitational acceleration for relativistic rapidly rotating neutron stars and show that for a star with mass M, equatorial radius R{sub e} , and angular velocity Ω, the deviations of the effective acceleration due to gravity from the nonrotating case take on a universal form that depends only on the compactness ratio M/R{sub e} , the dimensionless square of the angular velocity Ω{sup 2}R{sub e}{sup 3}/GM, and the latitude on the star's surface. This dependence is universal, in that it has very little dependence on the neutron star's equation of state. The effective gravity is expanded in the slow-rotation limit to show the dependence on the effective centrifugal force, oblate shape of the star, and the quadrupole moment of the gravitational field. In addition, an empirical fit and simple formula for the effective gravity is found. We find that the increase in the acceleration due to gravity at the poles is of the same order of magnitude as the decrease in the effective acceleration due to gravity at the equator for all realistic value of mass, radius, and spin. For neutron stars that spin with frequencies near 600 Hz, the difference between the effective gravity at the poles and the equator is about 20%.

  16. Rapid detection of gyrA and parC mutations in fluoroquinolone-resistant Neisseria gonorrhoeae by denaturing high-performance liquid chromatography.

    PubMed

    Shigemura, Katsumi; Shirakawa, Toshiro; Okada, Hiroshi; Tanaka, Kazushi; Udaka, Tohru; Kamidono, Sadao; Arakawa, Soichi; Gotoh, Akinobu

    2004-12-01

    The detection of DNA sequence variation is fundamental to the identification of the genomic basis of phenotypic variability. Denaturing high-performance liquid chromatography (DHPLC) is a novel technique that is used to detect mutations in human DNA. This is the first report that this technique is used as a tool to detect mutations in genes encoding fluoroquinolone resistance in Neisseria gonorrhoeae. Eighty-one strains of N. gonorrhoeae were used in this study. Genomic DNA from each strain was subjected to PCR amplification of 225 bp in gyrA and 166 bp in parC spanning the fluoroquinolone-resistance determining regions (QRDRs). After we performed DNA sequencing of these amplicons and identification of mutations in the QRDRs, DHPLC was undertaken to investigate whether its results correlate the distinctive chromatogram with their DNA mutations pattern. The profilings detected by DHPLC completely corresponded to the results of the DNA sequencing in mutation patters in gyrA and parC genes. They resulted in the following amino acid substitutions: Ser-91Phe, Asp-95Gly, and Asp-95Asn in gyrA; and Gly-85Asp, Asp-86Asn, Ser-87Arg, and Ser-88Pro in parC, respectively. These mutations existed alone or as combinations, and we identified five mutations patterns in gyrA and six in parC including wild-type. These mutations and their patterns could be rapidly and reproducibly identified from the PCR products using DHPLC, producing specific peak patterns that correlate with genotypes. This novel detection system facilitates the detection of resistance alleles, providing a rapid (5 min per sample), economic (96 sample per run), and reliable technique for characterizing fluoroquinolone resistance in N. gonorrhoeae. PMID:15488283

  17. Rapidly rotating neutron stars in general relativity: Realistic equations of state

    NASA Technical Reports Server (NTRS)

    Cook, Gregory B.; Shapiro, Stuart L.; Teukolsky, Saul A.

    1994-01-01

    We construct equilibrium sequences of rotating neutron stars in general relativity. We compare results for 14 nuclear matter equations of state. We determine a number of important physical parameters for such stars, including the maximum mass and maximum spin rate. The stability of the configurations to quasi-radial perturbations is assessed. We employ a numerical scheme particularly well suited to handle rapid rotation and large departures from spherical symmetry. We provide an extensive tabulation of models for future reference. Two classes of evolutionary sequences of fixed baryon rest mass and entropy are explored: normal sequences, which behave very much like Newtonian sequences, and supramassive sequences, which exist for neutron stars solely because of general relativistic effects. Adiabatic dissipation of energy and angular momentum causes a star to evolve in quasi-stationary fashion along an evolutionary sequence. Supramassive sequences have masses exceeding the maximum mass of a nonrotating neutron star. A supramassive star evolves toward eventual catastrophic collapse to a black hole. Prior to collapse, the star actually spins up as it loses angular momentum, an effect that may provide an observable precursor to gravitational collapse to a black hole.

  18. RAPIDLY EVOLVING AND LUMINOUS TRANSIENTS DRIVEN BY NEWLY BORN NEUTRON STARS

    SciTech Connect

    Yu, Yun-Wei; Li, Shao-Ze; Dai, Zi-Gao

    2015-06-10

    We provide a general analysis on the properties of the emitting material of some rapidly evolving and luminous transients discovered recently with the Pan-STARRS1 Medium Deep Survey. It was found that these transients are probably produced by a low-mass non-relativistic outflow that is continuously powered by a newly born, rapidly spinning, and highly magnetized neutron star (NS). Such a system could originate from an accretion-induced collapse of a white dwarf or a merger of an NS–NS binary. Therefore, observations of these transients would be helpful for constraining white dwarf and NS physics and/or for searching and identifying gravitational wave signals from the mergers.

  19. /sup 16/O(n, p)/sup 16/N: A fast neutron detector for rapid tissue inhomogeneity correction

    SciTech Connect

    Beach, J.L.; Watts, R.J.; Milavickas, L.R.

    1981-05-01

    We have devised a transit dose technique for fast neutron therapy treatment planning based on the /sup 16/O(n, p)/sup 16/N reaction in recirculating water, and have determined the effect of simulated bone and lung inhomogeneities in phantom. An effective threshold of 10.2 MeV in the /sup 16/O(n, p) reaction is exploited to detect transmitted neutrons without the need for detector collimation. This system has been demonstrated with 14 MeV (d, T) neutrons and with cyclotron produced p(42)+Be neutrons. /sup 16/N decays to the 6.13 MeV excited states of /sup 16/O in 7.14 s, allowing for easy identification by NaI(Tl) and for rapid recirculation. The transmission of fast neutrons can thus be related to an effective thickness of soft tissue, providing a rapid and direct measure of the effects of inhomogeneities under actual treatment conditions, with the 10 MeV threshold providing a useful degree of insensitivity to multiply scattered neutrons. Equivalent thicknesses of compact bone and lung relative to water were found to be 1.4 and 0.34 respectively, closely resembling the effective thicknesses for Cobalt-60 gamma rays.

  20. Explaining observations of rapidly rotating neutron stars in low-mass x-ray binaries

    NASA Astrophysics Data System (ADS)

    Gusakov, Mikhail E.; Chugunov, Andrey I.; Kantor, Elena M.

    2014-09-01

    In a previous paper [M. E. Gusakov, A. I. Chugunov, and E. M. Kantor, Phys. Rev. Lett. 112, 151101 (2014)], we introduced a new scenario that explains the existence of rapidly rotating warm neutron stars (NSs) observed in low-mass x-ray binaries (LMXBs). Here it is described in more detail. The scenario takes into account the interaction between superfluid inertial modes and the normal (quadrupole) m=2 r mode, which can be driven unstable by the Chandrasekhar-Friedman-Schutz (CFS) mechanism. This interaction can only occur at some fixed "resonance" stellar temperatures; it leads to formation of the "stability peaks" which stabilize a star in the vicinity of these temperatures. We demonstrate that a NS in LMXB spends a substantial fraction of time on the stability peak, that is, in the region of stellar temperatures and spin frequencies that has been previously thought to be CFS unstable with respect to excitation of r modes. We also find that the spin frequencies of NSs are limited by the CFS instability of normal (octupole) m=3 r mode rather than by m=2 r mode. This result agrees with the predicted value of the cutoff spin frequency ˜730 Hz in the spin distribution of accreting millisecond x-ray pulsars. In addition, we analyze evolution of a NS after the end of the accretion phase and demonstrate that millisecond pulsars can be born in LMXBs within our scenario. Besides millisecond pulsars, our scenario also predicts a new class of LMXB descendants—hot and rapidly rotating nonaccreting NSs ("hot widows"/HOFNARs). Further comparison of the proposed theory with observations of rotating NSs can impose new important constraints on the properties of superdense matter.

  1. Etude physicochimique et structurale de nitrures et d'oxynitrures de silicium très minces formés par traitement thermique rapide

    NASA Astrophysics Data System (ADS)

    Saoudi, R.; Hollinger, G.; Pitaval, M.; Molle, P.

    1995-05-01

    X-ray photoelectron spectroscopy, high resolution cross-sectional transmission electron microscopy (METHR) and spectroscopic ellipsometry have been used to investigate physico-chemical and structural properties of very thin silicon nitride layers. These layers have been formed by rapid thermal nitridation at 1000 ^{circ}C of very thin silica films or silicon substrate in an ammonia atmosphere at atmospheric pressure. in order to examine the influence of silicon substrate surface on the chemical nature of the obtained oxinitride film, three types of samples have been analysed. In addition, the oxygen and nitrogen distribution profiles have been estimated using core level angular distributions and chemical thinning. La spectroscopie de photoélectrons XPS, la Microscopie Electronique en Transmission à Haute Résolution (METHR) et l'ellipsométrie spectroscopique ont été utilisées pour étudier les propriétés physicochimiques et structurales de couches très minces de nitrures et d'oxynitrures de silicium. Ces couches ont été formées par traitement thermique rapide à 1000 ^{circ}C de films minces de silice ou d'un substrat de silicium dans une atmosphère d'ammoniac à la pression atmosphérique. Pour examiner l'influence de l'état de surface du substrat de silicium sur la nature chimique du film d'oxynitrure obtenu, trois types d'échantillons ont été analysés. De plus, les profils de répartition de l'oxygène et de l'azote ont été estimés au moyen de distributions angulaires des niveaux de coeur et d'amincissements chimiques.

  2. Formulation and experimental evaluation of closed-form control laws for the rapid maneuvering of reactor neutronic power

    SciTech Connect

    Bernard, J.A. . Nuclear Reactor Lab.)

    1989-09-01

    This report describes both the theoretical development and the experimental evaluation of a novel, robust methodology for the time-optimal adjustment of a reactor's neutronic power under conditions of closed-loop digital control. Central to the approach are the MIT-SNL Period-Generated Minimum Time Control Laws' which determine the rate at which reactivity should be changed in order to cause a reactor's neutronic power to conform to a specified trajectory. Using these laws, reactor power can be safely raised by five to seven orders of magnitude in a few seconds. The MIT-SNL laws were developed to facilitate rapid increases of neutronic power on spacecraft reactors operating in an SDI environment. However, these laws are generic and have other applications including the rapid recovery of research and test reactors subsequent to an unanticipated shutdown, power increases following the achievement of criticality on commercial reactors, power adjustments on commercial reactors so as to minimize thermal stress, and automated startups. The work reported here was performed by the Massachusetts Institute of Technology under contract to the Sandia National Laboratories. Support was also provided by the US Department of Energy's Division of University and Industry Programs. The work described in this report is significant in that a novel solution to the problem of time-optimal control of neutronic power was identified, in that a rigorous description of a reactor's dynamics was derived in that the rate of change of reactivity was recognized as the proper control signal, and in that extensive experimental trials were conducted of these newly developed concepts on actual nuclear reactors. 43 refs., 118 figs., 11 tabs.

  3. The search for the site of the r-process. [rapid neutron capture in stellar nucleosynthesis

    NASA Technical Reports Server (NTRS)

    Cowan, John J.; Cameron, A. G. W.; Truran, J. W.; Sneden, Christopher

    1986-01-01

    A number of sites have been suggested for the r-process, including neutronized cores of exploding supernovae, jets of neutronized matter ejected from the collapse of rotating magnetized stellar cores, the helium and carbon zones of stars undergoing supernova explosions, and helium core flashes in low-mass stars. Despite much work and many advances in nuclear physics, the site or sites of the r-process is still unknown. Observations of metal-poor stars in the halo of the Galaxy indicate r-process production early in the history of the Galaxy and provide important constraints on galactic nucleosynthesis. Further observations of metal-poor stars, along with advances in understanding the nuclear properties of neutron-rich nuclei and improved astrophysical models of stars in the late stages of evolution, should help to identify the site of the r-process.

  4. Optimization of neutron tomography for rapid hydrogen concentration inspection of metal castings

    SciTech Connect

    Gibbons, M. R., LLNL

    1998-02-03

    Hydrogen embrittlement describes a group of phenomena leading to the degradation of metal alloy properties. The hydrogen concentration in the alloy can be used as an indicator for the onset of embrittlement. A neutron tomography system has been optimized to perform nondestructive detection of hydrogen concentration in titanium aircraft engine compressor blades. Preprocessing of back projection images and postprocessing of tomographic reconstructions are used to achieve hydrogen concentration sensitivity below 200 ppm weight. This paper emphasizes the postprocessing techniques which allow automated reporting of hydrogen concentration.

  5. Radiographie par rayons X à haute résolution de défauts topologiques en volume de structures modulées comparée aux neutrons en faisceau blanc

    NASA Astrophysics Data System (ADS)

    Fernandez Palacio, J.; Hamelin, B.; Marmeggi, J. C.

    2004-11-01

    Une émission de rayons X par un générateur à haute tension (plage : 50 - 410 kV) a été développée pour être utilisée avec un diffractomètre à rayons X durs et caractériser en volume des monocristaux. Le fort flux issu d'une installation de radiologie à foyer fin avec un grand pouvoir de pénétration en profondeur autorise l'étude d'échantillons très absorbants. Quelques exemples de l'utilisation de ces propriétés pour des échantillons épais et très absorbants sont présentés ; principalement l'analyse de contraintes et la topographie X projetée 2D dans des matériaux en comparaison avec l'information par la diffraction des neutrons. La diffraction à haute énergie apparaît dans la direction transmise, les angles de Bragg sont petits et ainsi les différentes lignes de réflexions sont réparties autour du faisceau principal. La presse uni-axiale utilisée pour les expériences est optimisée effectivement avec l'absence d'un bruit de fond dû à l'usage de fentes. L'optique des rayons X durs et neutrons appliquée aux échantillons épais donne une information complémentaire dans les expériences sur l'analyse de la densité volumétrique par la diffusion des rayons X et neutrons. On l'applique à des problèmes concernant des cristaux aux structures modulées étudiées sous des charges mécaniques et thermiques.

  6. Optimization of microwave-induced chemical etching for rapid development of neutron-induced recoil tracks in CR-39 detectors

    NASA Astrophysics Data System (ADS)

    Sahoo, G. S.; Tripathy, S. P.; Bandyopadhyay, T.

    2014-03-01

    A systematic investigation is carried out to optimize the recently established microwave-induced chemical etching (MICE) parameters for rapid development of neutron-induced recoil tracks in CR-39 detectors. Several combinations of all available microwave powers with different etching durations were analysed to determine the most suitable etching condition. The etching duration was found to reduce with increasing microwave power and the tracks were observed at about 18, 15, 12, and 6 min for 300, 450, 600 and 900 W of microwave powers respectively compared to a few hours in chemical etching (CE) method. However, for complete development of tracks the etching duration of 30, 40, 50 and 60 min were found to be suitable for the microwave powers of 900, 600, 450 and 300 W, respectively. Temperature profiles of the etchant for all the available microwave powers at different etching durations were generated to regulate the etching process in a controlled manner. The bulk etch rates at different microwave powers were determined by 2 methods, viz., gravimetric and removed thickness methods. A logarithmic expression was used to fit the variation of bulk etch rate with microwave power. Neutron detection efficiencies were obtained for all the cases and the results on track parameters obtained with MICE technique were compared with those obtained from another detector processed with chemical etching.

  7. Impedance measurements of the extraction kicker system for the rapid cycling synchrotron of China Spallation Neutron Source

    NASA Astrophysics Data System (ADS)

    Huang, Liang-Sheng; Wang, Sheng; Liu, Yu-Dong; Li, Yong; Liu, Ren-Hong; Xiao, Ou-Zheng

    2016-04-01

    The fast extraction kicker system is one of the most important accelerator components and the main source of impedance in the Rapid Cycling Synchrotron of the China Spallation Neutron Source. It is necessary to understand the kicker impedance before its installation into the tunnel. Conventional and improved wire methods are employed in the impedance measurement. The experimental results for the kicker impedance are explained by comparison with simulation using CST PARTICLE STUDIO. The simulation and measurement results confirm that the window-frame ferrite geometry and the end plate are the important structures causing coupling impedance. It is proved in the measurements that the mismatching from the power form network to the kicker leads to a serious oscillation sideband of the longitudinal and vertical impedance and the oscillation can be reduced by ferrite absorbing material. Supported by National Natural Science Foundation of China (11175193, 11275221)

  8. The 'virtual density' principle of neutronics: Toward rapid computation of reactivity effects in practical core distortion scenarios

    SciTech Connect

    Reed, M.; Smith, K.; Forget, B.

    2013-07-01

    Fast reactor core reactivities are sensitive to geometric distortions arising from three distinct phenomena: (1) irradiation swelling of fuel throughout core lifetime, (2) thermal expansion of fuel during transients, and (3) mechanical oscillations during seismic events. Performing comprehensive reactivity analysis of these distortions requires methods for rapidly computing a multitude of minute reactivity changes. Thus, we introduce the 'virtual density' principle of neutronics as a new perturbation technique to achieve this rapid computation. This new method obviates many of the most challenging aspects of conventional geometric perturbation theory. Essentially, this 'virtual density' principle converts geometric perturbations into equivalent material density perturbations (either isotropic or anisotropic), which are highly accurate and comparatively simple to evaluate. While traditional boundary perturbation theory employs surface integrals, the 'virtual density' principle employs equivalent volume integrals. We introduce and validate this method in three subsequent stages: (1) isotropic 'virtual density', (2) anisotropic 'virtual density' for whole cores, and (3) anisotropic 'virtual density' for interior zones within cores. We numerically demonstrate its accuracy for 2-D core flowering scenarios. (authors)

  9. Asymmetric Neutrino Emissions in Relativistic Mean-Field Approach and Observables: Pulsar Kick and Rapid Spin-Deceleration of Magnetized Proto-Neutron Stars

    NASA Astrophysics Data System (ADS)

    Maruyama, T.; Kajino, T.; Yasutake, N.; Hidaka, J.; Kuroda, T.; Cheoun, M. K.; Ryu, C. Y.; Mathews, G. J.

    2015-11-01

    We calculate absorption cross-sections of neutrino in proto-neutron stars with strong magnetic field in the relativistic mean-field theory. Then, we apply this result to the neutrino transfer in the matter, and study the pulsar kick and the rapid spin down of magnetars.

  10. Molecular analysis of ciprofloxacin resistance mechanisms in Malaysian ESBL-producing Klebsiella pneumoniae isolates and development of mismatch amplification mutation assays (MAMA) for rapid detection of gyrA and parC mutations.

    PubMed

    Al-Marzooq, Farah; Mohd Yusof, Mohd Yasim; Tay, Sun Tee

    2014-01-01

    Ninety-three Malaysian extended-spectrum β-lactamase (ESBL)-producing Klebsiella pneumoniae isolates were investigated for ciprofloxacin resistance. Two mismatch amplification mutation (MAMA) assays were developed and used to facilitate rapid detection of gyrA and parC mutations. The isolates were also screened for plasmid-mediated quinolone resistance (PMQR) genes including aac(6')-Ib-cr, qepA, and qnr. Ciprofloxacin resistance (MICs 4- ≥ 32  μ g/mL) was noted in 34 (37%) isolates, of which 33 isolates had multiple mutations either in gyrA alone (n = 1) or in both gyrA and parC regions (n = 32). aac(6')-Ib-cr was the most common PMQR gene detected in this study (n = 61), followed by qnrB and qnrS (n = 55 and 1, resp.). Low-level ciprofloxacin resistance (MICs 1-2  μ g/mL) was noted in 40 (43%) isolates carrying qnrB accompanied by either aac(6')-Ib-cr (n = 34) or a single gyrA 83 mutation (n = 6). Ciprofloxacin resistance was significantly associated with the presence of multiple mutations in gyrA and parC regions. While the isolates harbouring gyrA and/or parC alteration were distributed into 11 PFGE clusters, no specific clusters were associated with isolates carrying PMQR genes. The high prevalence of ciprofloxacin resistance amongst the Malaysian ESBL-producing K. pneumoniae isolates suggests the need for more effective infection control measures to limit the spread of these resistant organisms in the hospital.

  11. Techniques for measuring intercepted and absorbed PAR in corn canopies

    NASA Technical Reports Server (NTRS)

    Gallo, K. P.; Daughtry, C. S. T.

    1984-01-01

    The quantity of radiation potentially available for photosynthesis that is captured by the crop is best described as absorbed photosynthetically active radiation (PAR). Absorbed PAR (APAR) is the difference between descending and ascending fluxes. The four components of APAR were measured above and within two planting densities of corn (Zea mays L.) and several methods of measuring and estimating APAR were examined. A line quantum sensor that spatially averages the photosynthetic photon flux density provided a rapid and portable method of measuring APAR. PAR reflectance from the soil (Typic Argiaquoll) surface decreased from 10% to less than 1% of the incoming PAR as the canopy cover increased. PAR reflectance from the canopy decreased to less than 3% at maximum vegetative cover. Intercepted PAR (1 - transmitted PAR) generally overestimated absorbed PAR by less than 4% throughout most of the growing season. Thus intercepted PAR appears to be a reasonable estimate of absorbed PAR.

  12. A Combined Global and Local Approach to Elucidate Spatial Organization of the Mycobacterial ParB-parS Partition Assembly

    SciTech Connect

    B Chaudhuri; S Gupta; V Urban; M Chance; R DMello; L Smith; K Lyons; J Gee

    2011-12-31

    Combining diverse sets of data at global (size, shape) and local (residue) scales is an emerging trend for elucidating the organization and function of the cellular assemblies. We used such a strategy, combining data from X-ray and neutron scattering with H/D-contrast variation and X-ray footprinting with mass spectrometry, to elucidate the spatial organization of the ParB-parS assembly from Mycobacterium tuberculosis. The ParB-parS participates in plasmid and chromosome segregation and condensation in predivisional bacterial cells. ParB polymerizes around the parS centromere(s) to form a higher-order assembly that serves to recruit cyto-skeletal ParA ATPases and SMC proteins for chromosome segregation. A hybrid model of the ParB-parS was built by combining and correlating computational models with experiment-derived information about size, shape, position of the symmetry axis within the shape, internal topology, DNA-protein interface, exposed surface patches, and prior knowledge. This first view of the ParB-parS leads us to propose how ParB spread on the chromosome to form a larger assembly.

  13. A combined global and local approach to elucidate spatial organization of the Mycobacterial ParB-parS partition assembly.

    PubMed

    Chaudhuri, Barnali N; Gupta, Sayan; Urban, Volker S; Chance, Mark R; D'Mello, Rhijuta; Smith, Lauren; Lyons, Kelly; Gee, Jessica

    2011-03-22

    Combining diverse sets of data at global (size, shape) and local (residue) scales is an emerging trend for elucidating the organization and function of the cellular assemblies. We used such a strategy, combining data from X-ray and neutron scattering with H/D-contrast variation and X-ray footprinting with mass spectrometry, to elucidate the spatial organization of the ParB-parS assembly from Mycobacterium tuberculosis. The ParB-parS participates in plasmid and chromosome segregation and condensation in predivisional bacterial cells. ParB polymerizes around the parS centromere(s) to form a higher-order assembly that serves to recruit cyto-skeletal ParA ATPases and SMC proteins for chromosome segregation. A hybrid model of the ParB-parS was built by combining and correlating computational models with experiment-derived information about size, shape, position of the symmetry axis within the shape, internal topology, DNA-protein interface, exposed surface patches, and prior knowledge. This first view of the ParB-parS leads us to propose how ParB spread on the chromosome to form a larger assembly.

  14. A Combined Global and Local Approach to Elucidate Spatial Organization of the Mycobacterial ParB-parS Partition

    SciTech Connect

    Chaudhuri, Barnali; Gupta, Sayan; Urban, Volker S; Chance, Mark; D'Mello, Rhijuta; Smith, Lauren; Lyons, Kelly; Gee, Jessica

    2010-01-01

    Combining diverse sets of data at global (size, shape) and local (residue) scales is an emerging trend for elucidating the organization and function of the cellular assemblies. We used such a strategy, combining data from X-ray and neutron scattering with H/D-contrast variation and X-ray footprinting with mass spectrometry, to elucidate the spatial organization of the ParB-parS assembly from Mycobacterium tuberculosis. The ParB-parS participates in plasmid and chromosome segregation and condensation in predivisional bacterial cells. ParB polymerizes around the parS centromere(s) to form a higher-order assembly that serves to recruit cyto-skeletal ParA ATPases and SMC proteins for chromosome segregation. A hybrid model of the ParB-parS was built by combining and correlating computational models with experiment-derived information about size, shape, position of the symmetry axis within the shape, internal topology, DNA-protein interface, exposed surface patches, and prior knowledge. This first view of the ParB-parS leads us to propose how ParB spread on the chromosome to form a larger assembly.

  15. De Par en Par (Wide Open), 1993.

    ERIC Educational Resources Information Center

    De Par en Par, 1993

    1993-01-01

    This document consists of the four issues of the serial "De Par en Par" published during 1993. This serial provides lessons in Spanish for elementary school children. It is written by bilingual education teachers for use in the bilingual classroom. The magazine bases itself on the K-6 curriculum and offers a variety of activities for classroom…

  16. Pars Injuries in Athletes.

    PubMed

    Oren, Jonathan H; Gallina, Jason M

    2016-03-01

    Pars injuries are common causes of low back pain in adolescent athletes. Workup traditionally has included lumbar radiographs with oblique views and single-photon emission computed tomography (SPECT). However, recent literature has demonstrated the accuracy of MRI as a diagnostic modality. Acute injuries may be amenable to bracing with the goal of a healed lesion. Most cases of spondylolysis will result in asymptomatic non-union, though pars repair is an option for symptomatic pars defects without spondylolisthesis. PMID:26977552

  17. Nonconsecutive Pars Interarticularis Defects.

    PubMed

    Elgafy, Hossein; Hart, Ryan C; Tanios, Mina

    2015-12-01

    Lumbar spondylolysis is a well-recognized condition occurring in adolescents because of repetitive overuse in sports. Nonconsecutive spondylolysis involving the lumbar spine is rare. In contrast to single-level pars defects that respond well to conservative treatment, there is no consensus about the management of multiple-level pars fractures; a few reports indicated that conservative management is successful, and the majority acknowledged that surgery is often required. The current study presents a rare case of pars fracture involving nonconsecutive segments and discusses the management options. In this case report, we review the patient's history, clinical examination, radiologic findings, and management, as well as the relevant literature. An 18-year-old man presented to the clinic with worsening lower back pain related to nonconsecutive pars fractures at L2 and L5. After 6 months of conservative management, diagnostic computed tomography-guided pars block was used to localize the symptomatic level at L2, which was treated surgically; the L5 asymptomatic pars fracture did not require surgery. At the last follow-up 2 years after surgery, the patient was playing baseball and basketball, and denied any back pain. This article reports a case of rare nonconsecutive pars fractures. Conservative management for at least 6 months is recommended. Successful management depends on the choice of appropriate treatment for each level. Single-photon emission computed tomography scan, and computed tomography-guided pars block are valuable preoperative tools to identify the symptomatic level in such a case. PMID:26665257

  18. Nonconsecutive Pars Interarticularis Defects.

    PubMed

    Elgafy, Hossein; Hart, Ryan C; Tanios, Mina

    2015-12-01

    Lumbar spondylolysis is a well-recognized condition occurring in adolescents because of repetitive overuse in sports. Nonconsecutive spondylolysis involving the lumbar spine is rare. In contrast to single-level pars defects that respond well to conservative treatment, there is no consensus about the management of multiple-level pars fractures; a few reports indicated that conservative management is successful, and the majority acknowledged that surgery is often required. The current study presents a rare case of pars fracture involving nonconsecutive segments and discusses the management options. In this case report, we review the patient's history, clinical examination, radiologic findings, and management, as well as the relevant literature. An 18-year-old man presented to the clinic with worsening lower back pain related to nonconsecutive pars fractures at L2 and L5. After 6 months of conservative management, diagnostic computed tomography-guided pars block was used to localize the symptomatic level at L2, which was treated surgically; the L5 asymptomatic pars fracture did not require surgery. At the last follow-up 2 years after surgery, the patient was playing baseball and basketball, and denied any back pain. This article reports a case of rare nonconsecutive pars fractures. Conservative management for at least 6 months is recommended. Successful management depends on the choice of appropriate treatment for each level. Single-photon emission computed tomography scan, and computed tomography-guided pars block are valuable preoperative tools to identify the symptomatic level in such a case.

  19. Rapid, non-destructive carbon analysis of forest soils using neutron-induced gamma-ray spectroscopy

    SciTech Connect

    Wielopolski, L.; Mitra, S.; Yanai, R. D.; Levine, C. R.; Vadeboncoeur, M. A.

    2010-08-01

    Forest soils are pivotal to understanding global carbon (C) cycling and evaluating policies for mitigating global change. However, they are very difficult to monitor because of the heterogeneity of soil characteristics, the difficulty of representative sampling, and the slow time scale of response to environmental change. Here we demonstrate that use of gamma-ray spectroscopy facilitates in situ non-destructive analysis of C and other elements in forest soils. In this approach the element-specific gamma-rays are induced by fast and thermal neutrons interacting with the nuclei of the elements present in the soil. Background gamma-rays emanating from naturally occurring radionuclides in the forest are recorded as well. We applied this approach in a mature northern hardwood forest on glacial till soils at the Bartlett Experimental Forest in New Hampshire, USA. The inelastic neutron scattering (INS) system yielded strong signals in gamma-ray counts/h, from C and other elements present in the soil matrix that included silicon, oxygen, hydrogen, iron, aluminum, manganese and potassium. The INS sensitivity for carbon was 20.656 counts h{sup -1} kg{sup -1} C m{sup -2} based on current net C gamma-ray counts and the data for the O horizon and mineral soil to a depth of 30 cm obtained from a nearby quantitative soil pit (7.35 kg C m{sup -2}). We estimate the minimum detectable change to be {approx}0.34 kg C m{sup -2}, which is {approx}5% of the current soil C content, and the minimum detectable limit to be {approx}0.23 kg C m{sup -1}. Eight % reproducibility from 11 measurements was limited, in part, by the large variability in the system counting geometry due to the uneven forest microtopography. The INS approach has the potential to revolutionize belowground monitoring of C and other elements, because the possibility of detecting a 5% change in forest soils has not been possible with destructive sampling methods.

  20. Rapid MCNP simulation of DNA double strand break (DSB) relative biological effectiveness (RBE) for photons, neutrons, and light ions.

    PubMed

    Stewart, Robert D; Streitmatter, Seth W; Argento, David C; Kirkby, Charles; Goorley, John T; Moffitt, Greg; Jevremovic, Tatjana; Sandison, George A

    2015-11-01

    To account for particle interactions in the extracellular (physical) environment, information from the cell-level Monte Carlo damage simulation (MCDS) for DNA double strand break (DSB) induction has been integrated into the general purpose Monte Carlo N-particle (MCNP) radiation transport code system. The effort to integrate these models is motivated by the need for a computationally efficient model to accurately predict particle relative biological effectiveness (RBE) in cell cultures and in vivo. To illustrate the approach and highlight the impact of the larger scale physical environment (e.g. establishing charged particle equilibrium), we examined the RBE for DSB induction (RBEDSB) of x-rays, (137)Cs γ-rays, neutrons and light ions relative to γ-rays from (60)Co in monolayer cell cultures at various depths in water. Under normoxic conditions, we found that (137)Cs γ-rays are about 1.7% more effective at creating DSB than γ-rays from (60)Co (RBEDSB  =  1.017) whereas 60-250 kV x-rays are 1.1 to 1.25 times more efficient at creating DSB than (60)Co. Under anoxic conditions, kV x-rays may have an RBEDSB up to 1.51 times as large as (60)Co γ-rays. Fission neutrons passing through monolayer cell cultures have an RBEDSB that ranges from 2.6 to 3.0 in normoxic cells, but may be as large as 9.93 for anoxic cells. For proton pencil beams, Monte Carlo simulations suggest an RBEDSB of about 1.2 at the tip of the Bragg peak and up to 1.6 a few mm beyond the Bragg peak. Bragg peak RBEDSB increases with decreasing oxygen concentration, which may create opportunities to apply proton dose painting to help address tumor hypoxia. Modeling of the particle RBE for DSB induction across multiple physical and biological scales has the potential to aid in the interpretation of laboratory experiments and provide useful information to advance the safety and effectiveness of hadron therapy in the treatment of cancer.

  1. Rapid MCNP simulation of DNA double strand break (DSB) relative biological effectiveness (RBE) for photons, neutrons, and light ions.

    PubMed

    Stewart, Robert D; Streitmatter, Seth W; Argento, David C; Kirkby, Charles; Goorley, John T; Moffitt, Greg; Jevremovic, Tatjana; Sandison, George A

    2015-11-01

    To account for particle interactions in the extracellular (physical) environment, information from the cell-level Monte Carlo damage simulation (MCDS) for DNA double strand break (DSB) induction has been integrated into the general purpose Monte Carlo N-particle (MCNP) radiation transport code system. The effort to integrate these models is motivated by the need for a computationally efficient model to accurately predict particle relative biological effectiveness (RBE) in cell cultures and in vivo. To illustrate the approach and highlight the impact of the larger scale physical environment (e.g. establishing charged particle equilibrium), we examined the RBE for DSB induction (RBEDSB) of x-rays, (137)Cs γ-rays, neutrons and light ions relative to γ-rays from (60)Co in monolayer cell cultures at various depths in water. Under normoxic conditions, we found that (137)Cs γ-rays are about 1.7% more effective at creating DSB than γ-rays from (60)Co (RBEDSB  =  1.017) whereas 60-250 kV x-rays are 1.1 to 1.25 times more efficient at creating DSB than (60)Co. Under anoxic conditions, kV x-rays may have an RBEDSB up to 1.51 times as large as (60)Co γ-rays. Fission neutrons passing through monolayer cell cultures have an RBEDSB that ranges from 2.6 to 3.0 in normoxic cells, but may be as large as 9.93 for anoxic cells. For proton pencil beams, Monte Carlo simulations suggest an RBEDSB of about 1.2 at the tip of the Bragg peak and up to 1.6 a few mm beyond the Bragg peak. Bragg peak RBEDSB increases with decreasing oxygen concentration, which may create opportunities to apply proton dose painting to help address tumor hypoxia. Modeling of the particle RBE for DSB induction across multiple physical and biological scales has the potential to aid in the interpretation of laboratory experiments and provide useful information to advance the safety and effectiveness of hadron therapy in the treatment of cancer. PMID:26449929

  2. Rapid MCNP simulation of DNA double strand break (DSB) relative biological effectiveness (RBE) for photons, neutrons, and light ions

    NASA Astrophysics Data System (ADS)

    Stewart, Robert D.; Streitmatter, Seth W.; Argento, David C.; Kirkby, Charles; Goorley, John T.; Moffitt, Greg; Jevremovic, Tatjana; Sandison, George A.

    2015-11-01

    To account for particle interactions in the extracellular (physical) environment, information from the cell-level Monte Carlo damage simulation (MCDS) for DNA double strand break (DSB) induction has been integrated into the general purpose Monte Carlo N-particle (MCNP) radiation transport code system. The effort to integrate these models is motivated by the need for a computationally efficient model to accurately predict particle relative biological effectiveness (RBE) in cell cultures and in vivo. To illustrate the approach and highlight the impact of the larger scale physical environment (e.g. establishing charged particle equilibrium), we examined the RBE for DSB induction (RBEDSB) of x-rays, 137Cs γ-rays, neutrons and light ions relative to γ-rays from 60Co in monolayer cell cultures at various depths in water. Under normoxic conditions, we found that 137Cs γ-rays are about 1.7% more effective at creating DSB than γ-rays from 60Co (RBEDSB  =  1.017) whereas 60-250 kV x-rays are 1.1 to 1.25 times more efficient at creating DSB than 60Co. Under anoxic conditions, kV x-rays may have an RBEDSB up to 1.51 times as large as 60Co γ-rays. Fission neutrons passing through monolayer cell cultures have an RBEDSB that ranges from 2.6 to 3.0 in normoxic cells, but may be as large as 9.93 for anoxic cells. For proton pencil beams, Monte Carlo simulations suggest an RBEDSB of about 1.2 at the tip of the Bragg peak and up to 1.6 a few mm beyond the Bragg peak. Bragg peak RBEDSB increases with decreasing oxygen concentration, which may create opportunities to apply proton dose painting to help address tumor hypoxia. Modeling of the particle RBE for DSB induction across multiple physical and biological scales has the potential to aid in the interpretation of laboratory experiments and provide useful information to advance the safety and effectiveness of hadron therapy in the treatment of cancer.

  3. Par Pond water balance

    SciTech Connect

    Hiergesell, R.A.; Dixon, K.L.

    1996-06-01

    A water budget for the Par Pond hydrologic system was established in order to estimate the rate of groundwater influx to Par Pond. This estimate will be used in modeling exercises to predict Par Pond reservoir elevation and spillway discharge in the scenario where Savannah River water is no longer pumped and discharged into Par Pond. The principal of conservation of mass was used to develop the water budget, where water inflow was set equal to water outflow. Components of the water budget were identified, and the flux associated with each was determined. The water budget was considered balanced when inflow and outflow summed to zero. The results of this study suggest that Par Pond gains water from the groundwater system in the upper reaches of the reservoir, but looses water to the groundwater system near the dam. The rate of flux of groundwater from the water table aquifer into Par Pond was determined to be 13 cfs. The rate of flux from Par Pond to the water table aquifer near the dam was determined to be 7 cfs.

  4. Protease-activated receptor 1 (PAR1) signalling desensitization is counteracted via PAR4 signalling in human platelets.

    PubMed

    Fälker, Knut; Haglund, Linda; Gunnarsson, Peter; Nylander, Martina; Lindahl, Tomas L; Grenegård, Magnus

    2011-06-01

    PARs (protease-activated receptors) 1 and 4 belong to the family of G-protein-coupled receptors which induce both G(α12/13) and G(αq) signalling. By applying the specific PAR1- and PAR4-activating hexapeptides, SFLLRN and AYPGKF respectively, we found that aggregation of isolated human platelets mediated via PAR1, but not via PAR4, is abolished upon homologous receptor activation in a concentration- and time-dependent fashion. This effect was not due to receptor internalization, but to a decrease in Ca²⁺ mobilization, PKC (protein kinase C) signalling and α-granule secretion, as well as to a complete lack of dense granule secretion. Interestingly, subthreshold PAR4 activation rapidly abrogated PAR1 signalling desensitization by differentially reconstituting these affected signalling events and functional responses, which was sufficient to re-establish aggregation. The lack of ADP release and P2Y₁₂ receptor-induced G(αi) signalling accounted for the loss of the aggregation response, as mimicking G(αi/z) signalling with 2-MeS-ADP (2-methylthioadenosine-5'-O-diphosphate) or epinephrine (adrenaline) could substitute for intermediate PAR4 activation. Finally, we found that the re-sensitization of PAR1 signalling-induced aggregation via PAR4 relied on PKC-mediated release of both ADP from dense granules and fibrinogen from α-granules. The present study elucidates further differences in human platelet PAR signalling regulation and provides evidence for a cross-talk in which PAR4 signalling counteracts mechanisms involved in PAR1 signalling down-regulation. PMID:21391917

  5. THE MEASURES PAR PROJECT

    NASA Astrophysics Data System (ADS)

    Frouin, R. J.; Franz, B.

    2009-12-01

    The solar energy available for photosynthesis, known as PAR, controls the growth of phytoplankton and, therefore, regulates the composition and evolution of marine ecosystems. Knowing the spatial and temporal distribution of PAR over the oceans is critical to understanding biogeochemical cycles of carbon, nutrients, and oxygen, and to address important climate and global change issues such as the fate of anthropogenic atmospheric carbon dioxide. In view of this, a 12-year time series of PAR at the ocean surface, starting in September 1997, is being produced by the NASA Ocean Biology Processing Group from SeaWiFS, MODIS-Terra, and MODIS-Aqua data. The product covers the global oceans, with a spatial resolution of about 9.3x9.3 km (equal area grid) and a temporal resolution of one day. PAR is computed as the difference between the 400-700 nm solar flux incident on the top of the atmosphere (known) and reflected back to space by the atmosphere and surface (derived from satellite radiance), taking into account atmospheric absorption (modeled). Knowledge of pixel composition is not required, eliminating the need for cloud screening and arbitrary assumptions about sub-pixel cloudiness. Combining data from satellite sensors with different equatorial crossing times accounts for the diurnal variability of clouds and, therefore, increases accuracy on a daily time scale. The processing system, including routine check of accuracy and control of quality, is designed to operate during the entire lifetime of SeaWiFS and MODIS, and to accommodate future sensors with ocean-color capabilities. Maps of daily, weekly, and monthly PAR obtained from individual sensors are presented, as well as merged products. Accuracy is quantified in comparisons with other satellite estimates, the National Centers for Environmental Prediction reanalysis product, and in-situ measurements from fixed buoys and platforms. The good statistical performance makes the satellite PAR product suitable for large

  6. Characterization of a Pulse Neutron Source Yield under Field Conditions

    SciTech Connect

    Barzilov, Alexander; Novikov, Ivan; Womble, Phillip C.; Hopper, Lindsay

    2009-03-10

    Technique of rapid evaluation of a pulse neutron sources such as neutron generators under field conditions has been developed. The phoswich sensor and pulse-shape discrimination techniques have been used for the simultaneous measurements of fast neutrons, thermal neutrons, and photons. The sensor has been calibrated using activation neutron detectors and a pulse deuterium-tritium fusion neutron source.

  7. Combined DSEK and Transconjunctival Pars Plana Vitrectomy

    PubMed Central

    Sane, Mona; Shaikh, Naazli

    2016-01-01

    We report here three patients who underwent combined Descemet's stripping with endothelial keratoplasty and transconjunctival pars plana vitrectomy for bullous keratopathy and posterior segment pathology. A surgical technique and case histories are described. Anatomic and visual outcomes of combined Descemet's stripping with endothelial keratoplasty and vitrectomy were excellent. Our experience provides technical guidelines and limitations. The combined minimally invasive techniques allow for rapid anatomical recovery and return of function and visual acuity in a single sitting. PMID:27413563

  8. La pelade par plaques

    PubMed Central

    Spano, Frank; Donovan, Jeff C.

    2015-01-01

    Résumé Objectif Présenter aux médecins de famille des renseignements de base pour faire comprendre l’épidémiologie, la pathogenèse, l’histologie et l’approche clinique au diagnostic de la pelade par plaques. Sources des données Une recension a été effectuée dans PubMed pour trouver des articles pertinents concernant la pathogenèse, le diagnostic et le pronostic de la pelade par plaques. Message principal La pelade par plaques est une forme de perte pileuse auto-immune dont la prévalence durant une vie est d’environ 2 %. Des antécédents personnels ou familiaux de troubles auto-immuns concomitants, comme le vitiligo ou une maladie de la thyroïde, peuvent être observés dans un petit sous-groupe de patients. Le diagnostic peut souvent être posé de manière clinique en se fondant sur la perte de cheveux non cicatricielle et circulaire caractéristique, accompagnée de cheveux en « point d’exclamation » en périphérie chez ceux dont le problème en est aux premiers stades. Le diagnostic des cas plus complexes ou des présentations inhabituelles peut être facilité par une biopsie et un examen histologique. Le pronostic varie largement et de mauvais résultats sont associés à une apparition à un âge précoce, une perte importante, la variante ophiasis, des changements aux ongles, des antécédents familiaux ou des troubles auto-immuns concomitants. Conclusion La pelade par plaques est une forme auto-immune de perte de cheveux périodiquement observée en soins primaires. Les médecins de famille sont bien placés pour identifier la pelade par plaques, déterminer la gravité de la maladie et poser le diagnostic différentiel approprié. De plus, ils sont en mesure de renseigner leurs patients à propos de l’évolution clinique de la maladie ainsi que du pronostic général selon le sous-type de patients.

  9. suPAR and Team Nephrology

    PubMed Central

    2014-01-01

    Primary focal segmental glomerulosclerosis (FSGS) accounts for nearly 10 % of patients who require renal replacement therapy. Elevated circulating levels of soluble urokinase receptor (suPAR) have been identified as a biomarker to discriminate primary FSGS from other glomerulopathies. Subsequent reports have questioned the diagnostic utility of this test. In a study in BMC Medicine, Huang et al. demonstrate that urinary soluble urokinase receptor (suPAR) excretion assists in distinguishing primary FSGS from other glomerular diseases, and that high plasma suPAR concentrations are not directly linked to a decline in glomerular filtration rate (GFR). This observation suggests that further investigation of suPAR is warranted in patients with FSGS. It should be interpreted in light of a recent report that B7-1 is expressed in the podocytes of a subset of patients with FSGS, and that blocking this molecule may represent the first successful targeted intervention for this disease. These advances highlight the rapid pace of scientific progress in the field of nephrology. Nephrologists should work together, share resources, and expedite the design of protocols to evaluate these novel biomarkers in a comprehensive and scientifically valid manner. Please see related article http://www.biomedcentral.com/1741-7015/12/81. PMID:24885021

  10. La pelade par plaques

    PubMed Central

    Spano, Frank; Donovan, Jeff C.

    2015-01-01

    Résumé Objectif Présenter aux médecins de famille des renseignements de base pour faire comprendre les schémas thérapeutiques et les résultats des traitements pour la pelade par plaques, de même que les aider à identifier les patients pour qui une demande de consultation en dermatologie pourrait s’imposer. Sources des données Une recension a été effectuée dans PubMed pour trouver des articles pertinents concernant le traitement de la pelade par plaques. Message principal La pelade par plaques est une forme auto-immune de perte pileuse qui touche à la fois les enfants et les adultes. Même s’il n’y a pas de mortalité associée à la maladie, la morbidité découlant des effets psychologiques de la perte des cheveux peut être dévastatrice. Lorsque la pelade par plaques et le sous-type de la maladie sont identifiés, un schéma thérapeutique approprié peut être amorcé pour aider à arrêter la chute des cheveux et possiblement faire commencer la repousse. Les traitements de première intention sont la triamcinolone intralésionnelle avec des corticostéroïdes topiques ou du minoxidil ou les 2. Les médecins de famille peuvent prescrire ces traitements en toute sécurité et amorcer ces thérapies. Les cas plus avancés ou réfractaires pourraient avoir besoin de diphénylcyclopropénone topique ou d’anthraline topique. On peut traiter la perte de cils avec des analogues de la prostaglandine. Les personnes ayant subi une perte de cheveux abondante peuvent recourir à des options de camouflage ou à des prothèses capillaires. Il est important de surveiller les troubles psychiatriques en raison des effets psychologiques profonds de la perte de cheveux. Conclusion Les médecins de famille verront de nombreux patients qui perdent leurs cheveux. La reconnaissance de la pelade par plaques et la compréhension du processus pathologique sous-jacent permettent d’amorcer un schéma thérapeutique approprié. Les cas plus graves ou r

  11. Heavy and Superheavy Elements Production in High Intensive Neutron Fluxes of Explosive Process

    NASA Astrophysics Data System (ADS)

    Lutostansky, Yu. S.; Lyashuk, V. I.; Panov, I. V.

    2015-06-01

    Mathematical model of heavy and superheavy nuclei production in intensive pulsed neutron fluxes of explosive process is developed. The pulse character of the process allows dividing it in time into two stages: very short rapid process of multiple neutron captures with higher temperature and very intensive neutron fluxes, and relatively slower process with lesser temperature and neutron fluxes. The model was also extended for calculation of the transuranium yields in nuclear explosions takes into account the adiabatic character of the process, the probabilities of delayed fission, and the emission of delayed neutrons. Also the binary starting target isotopes compositions were included. Calculations of heavy transuranium and transfermium nuclei production were made for "Mike", "Par" and "Barbel" experiments, performed in USA. It is shown that the production of transfermium neutron-rich nuclei and superheavy elements with A ~ 295 is only possible when using binary mixture of starting isotopes with the significant addition of heavy components, such as long-lived isotopes of curium, or californium.

  12. Compact neutron generator

    DOEpatents

    Leung, Ka-Ngo; Lou, Tak Pui

    2005-03-22

    A compact neutron generator has at its outer circumference a toroidal shaped plasma chamber in which a tritium (or other) plasma is generated. A RF antenna is wrapped around the plasma chamber. A plurality of tritium ion beamlets are extracted through spaced extraction apertures of a plasma electrode on the inner surface of the toroidal plasma chamber and directed inwardly toward the center of neutron generator. The beamlets pass through spaced acceleration and focusing electrodes to a neutron generating target at the center of neutron generator. The target is typically made of titanium tubing. Water is flowed through the tubing for cooling. The beam can be pulsed rapidly to achieve ultrashort neutron bursts. The target may be moved rapidly up and down so that the average power deposited on the surface of the target may be kept at a reasonable level. The neutron generator can produce fast neutrons from a T-T reaction which can be used for luggage and cargo interrogation applications. A luggage or cargo inspection system has a pulsed T-T neutron generator or source at the center, surrounded by associated gamma detectors and other components for identifying explosives or other contraband.

  13. APPARATUS FOR CONTROLLING NEUTRONIC REACTORS

    DOEpatents

    Dietrich, J.R.; Harrer, J.M.

    1958-09-16

    A device is described for rapidly cortrolling the reactivity of an active portion of a reactor. The inveniion consists of coaxially disposed members each having circumferenital sections of material having dlfferent neutron absorbing characteristics and means fur moving the members rotatably and translatably relative to each other within the active portion to vary the neutron flux therein. The angular and translational movements of any member change the neutron flux shadowing effect of that member upon the other member.

  14. Megestrol acetate NCD oral suspension--Par Pharmaceutical: megestrol acetate nanocrystal dispersion oral suspension, PAR 100.2, PAR-100.2.

    PubMed

    2007-01-01

    Par Pharmaceutical has developed megestrol acetate (Megace ES) oral suspension for the treatment of anorexia, cachexia and a significant weight loss associated with AIDS. Par Pharmaceutical used Elan Corporation's NanoCrystal Dispersion (NCD) technology to develop an advanced, concentrated formulation of megestrol acetate with improved bioavailability, more rapid onset of action, more convenient dosing and a lower dosing regimen compared with the original marketed formulation of megestrol acetate oral suspension. Patients are administered a teaspoon (5mL) of the new NCD formulation once daily, compared with a daily 20mL dosage cup of the original formulation. The new megestrol acetate NCD formulation represents a line-extension of Par's megestrol acetate oral suspension (800mg/20mL, Megace O/S) that has been marketed for anorexia, cachexia and AIDS-related weight loss since July 2001. Par's megestrol acetate is the generic version of Bristol-Myers Squibb's Megace Oral Suspension. NanoCrystal Dispersion (NCD) is a trademark of Elan Corporation. Par Pharmaceutical will market megestol acetate NCD oral suspension under the Megace brand name. The company licensed the Megace name from Bristol-Myers Squib in August 2003. The US FDA approved megestrol acetate oral suspension (625 mg/mL) in July 2005 for the treatment of anorexia, cachexia or a significant, unexplained weight loss in patients with AIDS. The NDA for the product was accepted for review by the agency in September 2004, following its submission in June of that year.Par Pharmaceutical commenced the first of two phase III clinical trials of megestrol acetate oral suspension (PAR 100.2) in cancer-induced anorexia in the first quarter of 2006. However, this trial was discontinued in September 2006 because of slow patient enrolment. The company intends to discuss future development options in this indication with the FDA.New formulations or dosage forms of megestrol acetate concentrated suspension are also in

  15. Megestrol acetate NCD oral suspension -- Par Pharmaceutical: megestrol acetate nanocrystal dispersion oral suspension, PAR 100.2, PAR-100.2.

    PubMed

    2007-01-01

    Par Pharmaceutical has developed megestrol acetate (Megace ES) oral suspension for the treatment of anorexia, cachexia and a significant weight loss associated with AIDS. Par Pharmaceutical used Elan Corporation's NanoCrystal Dispersion (NCD) technology to develop an advanced, concentrated formulation of megestrol acetate with improved bioavailability, more rapid onset of action, more convenient dosing and a lower dosing regimen compared with the original marketed formulation of megestrol acetate oral suspension. Patients are administered a teaspoon (5mL) of the new NCD formulation once daily, compared with a daily 20mL dosage cup of the original formulation. The new megestrol acetate NCD formulation represents a line-extension of Par's megestrol acetate oral suspension (800mg/20mL, Megace O/S) that has been marketed for anorexia, cachexia and AIDS-related weight loss since July 2001. Par's megestrol acetate is the generic version of Bristol-Myers Squibb's Megace Oral Suspension. NanoCrystal Dispersion (NCD) is a trademark of Elan Corporation. Par Pharmaceutical will market megestol acetate NCD oral suspension under the Megace brand name. The company licensed the Megace name from Bristol-Myers Squib in August 2003. The US FDA approved megestrol acetate oral suspension (625 mg/mL) in July 2005 for the treatment of anorexia, cachexia or a significant, unexplained weight loss in patients with AIDS. The NDA for the product was accepted for review by the agency in September 2004, following its submission in June of that year.Par Pharmaceutical commenced the first of two phase III clinical trials of megestrol acetate oral suspension (PAR 100.2) in cancer-induced anorexia in the first quarter of 2006. However, this trial was discontinued in September 2006 because of slow patient enrolment. The company intends to discuss future development options in this indication with the FDA.New formulations or dosage forms of megestrol acetate concentrated suspension are also in

  16. Par Pond vegetation status 1996

    SciTech Connect

    Mackey, H.E. Jr.; Riley, R.S.

    1996-12-01

    The water level of Par Pond was lowered approximately 20 feet in mid-1991 in order to protect downstream residents from possible dam failure suggested by subsidence on the downstream slope of the dam and to repair the dam. This lowering exposed both emergent and nonemergent macrophyte beds to drying conditions resulting in extensive losses. A survey of the newly emergent, shoreline aquatic plant communities of Par Pond began in June 1995, three months after the refilling of Par Pond to approximately 200 feet above mean sea level. These surveys continued in July, September, and late October, 1995, and into the early spring and late summer of 1996. Communities similar to the pre-drawdown, Par Pond aquatic plant communities continue to become re-established. Emergent beds of maidencane, lotus, waterlily, watershield, and Pontederia are extensive and well developed. Measures of percent cover, width of beds, and estimates of area of coverage with satellite data indicate regrowth within two years of from 40 to 60% of levels prior to the draw down. Cattail occurrence continued to increase during the summer of 1996, especially in the former warm arm of Par Pond, but large beds common to Par Pond prior to the draw down still have not formed. Lotus has invaded and occupies many of the areas formerly dominated by cattail beds. To track the continued development of macrophytes in Par Pond, future surveys through the summer and early fall of 1997, along with the evaluation of satellite data to map the extent of the macrophyte beds of Par Pond, are planned.

  17. Chandra Captures Neutron Star Action

    NASA Video Gallery

    This movie from NASA's Chandra X-ray Observatory shows a fast moving jet of particles produced by a rapidly rotating neutron star, and may provide new insight into the nature of some of the densest...

  18. Neutron Activation Analysis of Water - A Review

    NASA Technical Reports Server (NTRS)

    Buchanan, John D.

    1971-01-01

    Recent developments in this field are emphasized. After a brief review of basic principles, topics discussed include sources of neutrons, pre-irradiation physical and chemical treatment of samples, neutron capture and gamma-ray analysis, and selected applications. Applications of neutron activation analysis of water have increased rapidly within the last few years and may be expected to increase in the future.

  19. Cooling of neutron stars

    NASA Technical Reports Server (NTRS)

    Pethick, C. J.

    1992-01-01

    It is at present impossible to predict the interior constitution of neutron stars based on theory and results from laboratory studies. It has been proposed that it is possible to obtain information on neutron star interiors by studying thermal radiation from their surfaces, because neutrino emission rates, and hence the temperature of the central part of a neutron star, depend on the properties of dense matter. The theory predicts that neutron stars cool relatively slowly if their cores are made up of nucleons, and cool faster if the matter is in an exotic state, such as a pion condensate, a kaon condensate, or quark matter. This view has recently been questioned by the discovery of a number of other processes that could lead to copious neutrino emission and rapid cooling.

  20. Operational Principles for the Dynamics of the In Vitro ParA-ParB System

    PubMed Central

    Jindal, Lavisha; Emberly, Eldon

    2015-01-01

    In many bacteria the ParA-ParB protein system is responsible for actively segregating DNA during replication. ParB proteins move by interacting with DNA bound ParA-ATP, stimulating their unbinding by catalyzing hydrolysis, that leads to rectified motion due to the creation of a wake of depleted ParA. Recent in vitro experiments have shown that a ParB covered magnetic bead can move with constant speed over a DNA covered substrate that is bound by ParA. It has been suggested that the formation of a gradient in ParA leads to diffusion-ratchet like motion of the ParB bead but how it forms and generates a force is still a matter of exploration. Here we develop a deterministic model for the in vitro ParA-ParB system and show that a ParA gradient can spontaneously form due to any amount of initial spatial noise in bound ParA. The speed of the bead is independent of this noise but depends on the ratio of the range of ParA-ParB force on the bead to that of removal of surface bound ParA by ParB. We find that at a particular ratio the speed attains a maximal value. We also consider ParA rebinding (including cooperativity) and ParA surface diffusion independently as mechanisms for ParA recovery on the surface. Depending on whether the DNA covered surface is undersaturated or saturated with ParA, we find that the bead can accelerate persistently or potentially stall. Our model highlights key requirements of the ParA-ParB driving force that are necessary for directed motion in the in vitro system that may provide insight into the in vivo dynamics of the ParA-ParB system. PMID:26670738

  1. Atmospheric neutrons

    NASA Technical Reports Server (NTRS)

    Korff, S. A.; Mendell, R. B.; Merker, M.; Light, E. S.; Verschell, H. J.; Sandie, W. S.

    1979-01-01

    Contributions to fast neutron measurements in the atmosphere are outlined. The results of a calculation to determine the production, distribution and final disappearance of atmospheric neutrons over the entire spectrum are presented. An attempt is made to answer questions that relate to processes such as neutron escape from the atmosphere and C-14 production. In addition, since variations of secondary neutrons can be related to variations in the primary radiation, comment on the modulation of both radiation components is made.

  2. Neutron guide

    DOEpatents

    Greene, Geoffrey L.

    1999-01-01

    A neutron guide in which lengths of cylindrical glass tubing have rectangular glass plates properly dimensioned to allow insertion into the cylindrical glass tubing so that a sealed geometrically precise polygonal cross-section is formed in the cylindrical glass tubing. The neutron guide provides easier alignment between adjacent sections than do the neutron guides of the prior art.

  3. Neutron dosimetry

    DOEpatents

    Quinby, Thomas C.

    1976-07-27

    A method of measuring neutron radiation within a nuclear reactor is provided. A sintered oxide wire is disposed within the reactor and exposed to neutron radiation. The induced radioactivity is measured to provide an indication of the neutron energy and flux within the reactor.

  4. Par Pond Fish, Water, and Sediment Chemistry

    SciTech Connect

    Paller, M.H.; Wike, L.D.

    1996-06-01

    The objectives of this report are to describe the Par Pond fish community and the impact of the drawdown and refill on the community, describe contaminant levels in Par Pond fish, sediments, and water and indicate how contaminant concentrations and distributions were affected by the drawdown and refill, and predict possible effects of future water level fluctuations in Par Pond.

  5. Directed and persistent movement arises from mechanochemistry of the ParA/ParB system

    NASA Astrophysics Data System (ADS)

    Hu, Longhua; Vecchiarelli, Anthony G.; Mizuuchi, Kiyoshi; Neuman, Keir C.; Liu, Jian

    The segregation of DNA prior to cell division is essential for faithful genetic inheritance. In many bacteria, segregation of the low-copy-number plasmids involves an active partition system composed of ParA ATPase and its stimulator protein ParB. Recent experiments suggest that ParA/ParB system motility is driven by a diffusion-ratchet mechanism in which ParB-coated plasmid both creates and follows a ParA gradient on the nucleoid surface. However, the detailed mechanism of ParA/ParB-mediated directed and persistent movement remains unknown. We develop a theoretical model describing ParA/ParB-mediated motility. We show that the ParA/ParB system can work as a Brownian ratchet, which effectively couples the ATPase-dependent cycling of ParA-nucleoid affinity to the motion of the ParB bound cargo. Paradoxically, the resulting processive motion relies on quenching diffusive plasmid motion through a large number of transient ParA/ParB-mediated tethers to the nucleoid surface. Our work sheds light on a new emergent phenomenon in which non-motor proteins work collectively via mechanochemical coupling to propel cargos -- an ingenious solution shaped by evolution to cope with the lack of processive motor proteins in bacteria.

  6. Neutron detector

    DOEpatents

    Stephan, Andrew C.; Jardret; Vincent D.

    2011-04-05

    A neutron detector has a volume of neutron moderating material and a plurality of individual neutron sensing elements dispersed at selected locations throughout the moderator, and particularly arranged so that some of the detecting elements are closer to the surface of the moderator assembly and others are more deeply embedded. The arrangement captures some thermalized neutrons that might otherwise be scattered away from a single, centrally located detector element. Different geometrical arrangements may be used while preserving its fundamental characteristics. Different types of neutron sensing elements may be used, which may operate on any of a number of physical principles to perform the function of sensing a neutron, either by a capture or a scattering reaction, and converting that reaction to a detectable signal. High detection efficiency, an ability to acquire spectral information, and directional sensitivity may be obtained.

  7. Neutron detector

    SciTech Connect

    Stephan, Andrew C; Jardret, Vincent D

    2009-04-07

    A neutron detector has a volume of neutron moderating material and a plurality of individual neutron sensing elements dispersed at selected locations throughout the moderator, and particularly arranged so that some of the detecting elements are closer to the surface of the moderator assembly and others are more deeply embedded. The arrangement captures some thermalized neutrons that might otherwise be scattered away from a single, centrally located detector element. Different geometrical arrangements may be used while preserving its fundamental characteristics. Different types of neutron sensing elements may be used, which may operate on any of a number of physical principles to perform the function of sensing a neutron, either by a capture or a scattering reaction, and converting that reaction to a detectable signal. High detection efficiency, an ability to acquire spectral information, and directional sensitivity may be obtained.

  8. Atmospheric neutrons

    NASA Technical Reports Server (NTRS)

    Preszler, A. M.; Moon, S.; White, R. S.

    1976-01-01

    Additional calibrations of the University of California double-scatter neutron detector and additional analysis corrections lead to slightly changed neutron fluxes. The theoretical angular distributions of Merker (1975) are in general agreement with the reported experimental fluxes but do not give the peaks for vertical upward and downward moving neutrons. The theoretical neutron escape current is in agreement with the experimental values from 10 to 100 MeV. The experimental fluxes obtained agree with those of Kanbach et al. (1974) in the overlap region from 70 to 100 MeV.

  9. Parallel Climate Analysis Toolkit (ParCAT)

    SciTech Connect

    Smith, Brian Edward

    2013-06-30

    The parallel analysis toolkit (ParCAT) provides parallel statistical processing of large climate model simulation datasets. ParCAT provides parallel point-wise average calculations, frequency distributions, sum/differences of two datasets, and difference-of-average and average-of-difference for two datasets for arbitrary subsets of simulation time. ParCAT is a command-line utility that can be easily integrated in scripts or embedded in other application. ParCAT supports CMIP5 post-processed datasets as well as non-CMIP5 post-processed datasets. ParCAT reads and writes standard netCDF files.

  10. suPAR: The Molecular Crystal Ball

    PubMed Central

    Thunø, Maria; Macho, Betina; Eugen-Olsen, Jesper

    2009-01-01

    soluble urokinase Plasminogen Activator Receptor (suPAR) levels reflect inflammation and elevated suPAR levels are found in several infectious diseases and cancer. suPAR exists in three forms; suPARI-III, suPARII-III and suPARI which show different properties due to structural differences. Studies suggest that full-length suPAR is a regulator of uPAR/uPA by acting as uPA-scavenger, whereas the cleaved suPARII-III act as a chemotactic agent promoting the immune response via the SRSRY sequence in the linker-region. This review focus on the various suPAR fragments and their involvement in inflammation and pathogenic processes. We focus on the molecular mechanisms of the suPAR fragments and the link to the inflammatory process, as this could lead to medical applications in infectious and pathological conditions. PMID:19893210

  11. Directed and persistent movement arises from mechanochemistry of the ParA/ParB system.

    PubMed

    Hu, Longhua; Vecchiarelli, Anthony G; Mizuuchi, Kiyoshi; Neuman, Keir C; Liu, Jian

    2015-12-22

    The segregation of DNA before cell division is essential for faithful genetic inheritance. In many bacteria, segregation of low-copy number plasmids involves an active partition system composed of a nonspecific DNA-binding ATPase, ParA, and its stimulator protein ParB. The ParA/ParB system drives directed and persistent movement of DNA cargo both in vivo and in vitro. Filament-based models akin to actin/microtubule-driven motility were proposed for plasmid segregation mediated by ParA. Recent experiments challenge this view and suggest that ParA/ParB system motility is driven by a diffusion ratchet mechanism in which ParB-coated plasmid both creates and follows a ParA gradient on the nucleoid surface. However, the detailed mechanism of ParA/ParB-mediated directed and persistent movement remains unknown. Here, we develop a theoretical model describing ParA/ParB-mediated motility. We show that the ParA/ParB system can work as a Brownian ratchet, which effectively couples the ATPase-dependent cycling of ParA-nucleoid affinity to the motion of the ParB-bound cargo. Paradoxically, this resulting processive motion relies on quenching diffusive plasmid motion through a large number of transient ParA/ParB-mediated tethers to the nucleoid surface. Our work thus sheds light on an emergent phenomenon in which nonmotor proteins work collectively via mechanochemical coupling to propel cargos-an ingenious solution shaped by evolution to cope with the lack of processive motor proteins in bacteria.

  12. Directed and persistent movement arises from mechanochemistry of the ParA/ParB system

    PubMed Central

    Hu, Longhua; Vecchiarelli, Anthony G.; Mizuuchi, Kiyoshi; Neuman, Keir C.; Liu, Jian

    2015-01-01

    The segregation of DNA before cell division is essential for faithful genetic inheritance. In many bacteria, segregation of low-copy number plasmids involves an active partition system composed of a nonspecific DNA-binding ATPase, ParA, and its stimulator protein ParB. The ParA/ParB system drives directed and persistent movement of DNA cargo both in vivo and in vitro. Filament-based models akin to actin/microtubule-driven motility were proposed for plasmid segregation mediated by ParA. Recent experiments challenge this view and suggest that ParA/ParB system motility is driven by a diffusion ratchet mechanism in which ParB-coated plasmid both creates and follows a ParA gradient on the nucleoid surface. However, the detailed mechanism of ParA/ParB-mediated directed and persistent movement remains unknown. Here, we develop a theoretical model describing ParA/ParB-mediated motility. We show that the ParA/ParB system can work as a Brownian ratchet, which effectively couples the ATPase-dependent cycling of ParA–nucleoid affinity to the motion of the ParB-bound cargo. Paradoxically, this resulting processive motion relies on quenching diffusive plasmid motion through a large number of transient ParA/ParB-mediated tethers to the nucleoid surface. Our work thus sheds light on an emergent phenomenon in which nonmotor proteins work collectively via mechanochemical coupling to propel cargos—an ingenious solution shaped by evolution to cope with the lack of processive motor proteins in bacteria. PMID:26647183

  13. Neutronic reactor

    DOEpatents

    Wende, Charles W. J.

    1976-08-17

    A safety rod for a nuclear reactor has an inner end portion having a gamma absorption coefficient and neutron capture cross section approximately equal to those of the adjacent shield, a central portion containing materials of high neutron capture cross section and an outer end portion having a gamma absorption coefficient at least equal to that of the adjacent shield.

  14. NEUTRONIC REACTOR

    DOEpatents

    Fermi, E.; Zinn, W.H.; Anderson, H.L.

    1958-09-16

    Means are presenied for increasing the reproduction ratio of a gaphite- moderated neutronic reactor by diminishing the neutron loss due to absorption or capture by gaseous impurities within the reactor. This means comprised of a fluid-tight casing or envelope completely enclosing the reactor and provided with a valve through which the casing, and thereby the reactor, may be evacuated of atmospheric air.

  15. Neutron tubes

    DOEpatents

    Leung, Ka-Ngo; Lou, Tak Pui; Reijonen, Jani

    2008-03-11

    A neutron tube or generator is based on a RF driven plasma ion source having a quartz or other chamber surrounded by an external RF antenna. A deuterium or mixed deuterium/tritium (or even just a tritium) plasma is generated in the chamber and D or D/T (or T) ions are extracted from the plasma. A neutron generating target is positioned so that the ion beam is incident thereon and loads the target. Incident ions cause D-D or D-T (or T-T) reactions which generate neutrons. Various embodiments differ primarily in size of the chamber and position and shape of the neutron generating target. Some neutron generators are small enough for implantation in the body. The target may be at the end of a catheter-like drift tube. The target may have a tapered or conical surface to increase target surface area.

  16. Neutron source

    DOEpatents

    Cason, J.L. Jr.; Shaw, C.B.

    1975-10-21

    A neutron source which is particularly useful for neutron radiography consists of a vessel containing a moderating media of relatively low moderating ratio, a flux trap including a moderating media of relatively high moderating ratio at the center of the vessel, a shell of depleted uranium dioxide surrounding the moderating media of relatively high moderating ratio, a plurality of guide tubes each containing a movable source of neutrons surrounding the flux trap, a neutron shield surrounding one part of each guide tube, and at least one collimator extending from the flux trap to the exterior of the neutron source. The shell of depleted uranium dioxide has a window provided with depleted uranium dioxide shutters for each collimator. Reflectors are provided above and below the flux trap and on the guide tubes away from the flux trap.

  17. Protease-activated receptor-1 (PAR1) and PAR2 but not PAR4 mediate relaxations in lower esophageal sphincter.

    PubMed

    Huang, Shih-Che

    2007-07-01

    Protease-activated receptor-1 (PAR1), PAR2 and PAR4 activation can alter the gastrointestinal motility. To investigate effects mediated by PARs in the lower esophageal sphincter, we measured contraction or relaxation of transverse strips from the guinea-pig lower esophageal sphincter caused by PAR1 (TFLLR-NH2 and SFLLRN-NH2), PAR2 (SLIGKV-NH2 and SLIGRL-NH2) and PAR4 peptide agonists (GYPGKF-NH2, GYPGQV-NH2 and AYPGKF-NH2) as well as PAR protease activators (thrombin and trypsin). In resting lower esophageal sphincter strips, TFLLR-NH2 and SFLLRN-NH2 caused moderate concentration-dependent relaxation whereas thrombin did not cause any relaxation or contraction. Furthermore, in carbachol-contracted strips, TFLLR-NH2 and SFLLRN-NH2 caused marked whereas thrombin caused mild concentration-dependent relaxation. These indicate the existence of PAR1 mediating relaxation. Similarly, in resting lower esophageal sphincter strips, trypsin caused moderate concentration-dependent relaxation whereas SLIGRL-NH2 and SLIGKV-NH2 did not cause any relaxation or contraction. In addition, in carbachol-contracted strips, trypsin caused marked whereas SLIGRL-NH2 and SLIGKV-NH2 caused mild concentration-dependent relaxation. These indicate the existence of PAR2 mediating relaxation. The relaxant response of thrombin, TFLLR-NH2, trypsin and SLIGKV-NH2 was insensitive to atropine or tetrodotoxin, suggesting a direct effect. The relaxant response of trypsin was not affected by apamin, charybdotoxin, indomethacin and capsaicin but was attenuated by NG-nitro-L-arginine methyl ester, indicating involvement of NO. FSLLR-NH2, a PAR1 control peptide, and VKGILS-NH2, a PAR2 control peptide, as well as all three PAR4 peptide agonists, GYPGKF-NH2, GYPGQV-NH2 and AYPGKF-NH2, did not cause any relaxation or contraction. Taken together, these results demonstrate that PAR1 and PAR2 but not PAR4 mediate relaxations in the guinea-pig lower esophageal sphincter. PMID:17335921

  18. Argonne potential and multi-neutron systems

    SciTech Connect

    Gridnev, D. K.; Gridnev, K. A.; Schramm, S.; Greiner, Walter

    2009-01-01

    Recently it was proved that the neutron matter interacting through Argonne V18 pair-potential plus modern variants of Urbana or Illinois three-body forces is unstable. For the energy of N neutrons E(N), which interact through these forces one has E(N) = −cN³⁺+O(N{sup 8/3}), where c > 0 is a constant. This means that: (i) the energy per particle and neutron density diverge rapidly for large neutron numbers; (ii) bound states of N neutrons exist for N large enough. The neutron matter collapse is possible due to the form of the repulsive core in three-body forces, which vanishes when three nucleons occupy the same site in space. The obtained results partly change the paradigm, in which the stability of neutron stars is attained through the Pauli principle; the strong repulsive core in the nucleon interactions is by no means less important.

  19. NEUTRON SOURCE

    DOEpatents

    Bernander, N.K. et al.

    1960-10-18

    An apparatus is described for producing neutrons through target bombardment with deuterons. Deuterium gas is ionized by electron bombardment and the deuteron ions are accelerated through a magnetic field to collimate them into a continuous high intensity beam. The ion beam is directed against a deuteron pervious metal target of substantially the same nnaterial throughout to embed the deuterous therein and react them to produce neutrons. A large quantity of neutrons is produced in this manner due to the increased energy and quantity of ions bombarding the target.

  20. Atmospheres around Neutron Stars

    NASA Astrophysics Data System (ADS)

    Fryer, Chris L.; Benz, Willy

    1994-12-01

    Interest in the behavior of atmospheres around neutron stars has grown astronomically in the past few years. Some of this interest arrived in the wake of the explosion of Supernova 1987A and its elusive remnant; spawning renewed interest in a method to insure material ``fall-back'' onto the adolescent neutron star in an effort to transform it into a silent black hole. However, the bulk of the activity with atmospheres around neutron stars is concentrated in stellar models with neutron star, rather than white dwarf, cores; otherwise known as Thorne-Zytkow objects. First a mere seed in the imagination of theorists, Thorne-Zytkow objects have grown into an observational reality with an ever-increasing list of formation scenarios and observational prospects. Unfortunately, the analytic work of Chevalier on supernova fall-back implies that, except for a few cases, the stellar simulations of Thorne-Zytkow objects are missing an important aspect of physics: neutrinos. Neutrino cooling removes the pressure support of these atmospheres, allowing accretion beyond the canonical Eddington rate for these objects. We present here the results of detailed hydrodynamical simulations in one and two dimensions with the additional physical effects of neutrinos, advanced equations of state, and relativity over a range of parameters for our atmosphere including entropy and chemical composition as well as a range in the neutron star size. In agreement with Chevalier, we find, under the current list of formation scenarios, that the creature envisioned by Thorne and Zytkow will not survive the enormous appetite of a neutron star. However, neutrino heating (a physical effect not considered in Chevalier's analysis) can play an important role in creating instabilities in some formation schemes, leading to an expulsion of matter rather than rapid accretion. By placing scrutiny upon the formation methods, we can determine the observational prospects for each.

  1. Thermal neutron detection system

    DOEpatents

    Peurrung, Anthony J.; Stromswold, David C.

    2000-01-01

    According to the present invention, a system for measuring a thermal neutron emission from a neutron source, has a reflector/moderator proximate the neutron source that reflects and moderates neutrons from the neutron source. The reflector/moderator further directs thermal neutrons toward an unmoderated thermal neutron detector.

  2. NEUTRONIC REACTOR

    DOEpatents

    Wade, E.J.

    1958-09-16

    This patent relates to a reflector means for a neutronic reactor. A reflector comprised of a plurality of vertically movable beryllium control members is provided surrounding the sides of the reactor core. An absorber of fast neutrons comprised of natural uramum surrounds the reflector. An absorber of slow neutrons surrounds the absorber of fast neutrons and is formed of a plurality of beryllium blocks having natural uranium members distributcd therethrough. in addition, a movable body is positioned directly below the core and is comprised of a beryllium reflector and an absorbing member attached to the botiom thereof, the absorbing member containing a substance selected from the goup consisting of natural urantum and Th/sup 232/.

  3. NEUTRONIC REACTOR

    DOEpatents

    Fraas, A.P.; Mills, C.B.

    1961-11-21

    A neutronic reactor in which neutron moderation is achieved primarily in its reflector is described. The reactor structure consists of a cylindrical central "island" of moderator and a spherical moderating reflector spaced therefrom, thereby providing an annular space. An essentially unmoderated liquid fuel is continuously passed through the annular space and undergoes fission while contained therein. The reactor, because of its small size, is particularly adapted for propulsion uses, including the propulsion of aircraft. (AEC)

  4. NEUTRON SOURCES

    DOEpatents

    Richmond, J.L.; Wells, C.E.

    1963-01-15

    A neutron source is obtained without employing any separate beryllia receptacle, as was formerly required. The new method is safer and faster, and affords a source with both improved yield and symmetry of neutron emission. A Be container is used to hold and react with Pu. This container has a thin isolating layer that does not obstruct the desired Pu--Be reaction and obviates procedures previously employed to disassemble and remove a beryllia receptacle. (AEC)

  5. NEUTRONIC REACTOR

    DOEpatents

    Wigner, E.P.

    1958-04-22

    A nuclear reactor for isotope production is described. This reactor is designed to provide a maximum thermal neutron flux in a region adjacent to the periphery of the reactor rather than in the center of the reactor. The core of the reactor is generally centrally located with respect tn a surrounding first reflector, constructed of beryllium. The beryllium reflector is surrounded by a second reflector, constructed of graphite, which, in tune, is surrounded by a conventional thermal shield. Water is circulated through the core and the reflector and functions both as a moderator and a coolant. In order to produce a greatsr maximum thermal neutron flux adjacent to the periphery of the reactor rather than in the core, the reactor is designed so tbat the ratio of neutron scattering cross section to neutron absorption cross section averaged over all of the materials in the reflector is approximately twice the ratio of neutron scattering cross section to neutron absorption cross section averaged over all of the material of the core of the reactor.

  6. FOREWORD: Neutron metrology Neutron metrology

    NASA Astrophysics Data System (ADS)

    Thomas, David J.; Nolte, Ralf; Gressier, Vincent

    2011-12-01

    The International Committee for Weights and Measures (CIPM) has consultative committees covering various areas of metrology. The Consultative Committee for Ionizing Radiation (CCRI) differs from the others in having three sections: Section (I) deals with radiation dosimetry, Section (II) with radionuclide metrology and Section (III) with neutron metrology. In 2003 a proposal was made to publish special issues of Metrologia covering the work of the three Sections. Section (II) was the first to complete their task, and their special issue was published in 2007, volume 44(4). This was followed in 2009 by the special issue on radiation dosimetry, volume 46(2). The present issue, volume 48(6), completes the trilogy and attempts to explain neutron metrology, the youngest of the three disciplines, the neutron only having been discovered in 1932, to a wider audience and to highlight the relevance and importance of this field. When originally approached with the idea of this special issue, Section (III) immediately saw the value of a publication specifically on neutron metrology. It is a topic area where papers tend to be scattered throughout the literature in journals covering, for example, nuclear instrumentation, radiation protection or radiation measurements in general. Review articles tend to be few. People new to the field often ask for an introduction to the various topics. There are some excellent older textbooks, but these are now becoming obsolete. More experienced workers in specific areas of neutron metrology can find it difficult to know the latest position in related areas. The papers in this issue attempt, without presenting a purely historical outline, to describe the field in a sufficiently logical way to provide the novice with a clear introduction, while being sufficiently up-to-date to provide the more experienced reader with the latest scientific developments in the different topic areas. Neutron radiation fields obviously occur throughout the nuclear

  7. PAR for the Course: A Congruent Pedagogical Approach for a PAR Methods Class

    ERIC Educational Resources Information Center

    Hammond, Joyce D.; Hicks, Maria; Kalman, Rowenn; Miller, Jason

    2005-01-01

    In the past two years, three graduate students and a senior faculty member have co-taught a participatory action research (PAR) course to undergraduate and graduate students. In this article the co-teachers advocate a set of pedagogical principles and practices in a PAR-oriented classroom that establishes congruency with community PAR projects in…

  8. FOREWORD: Neutron metrology Neutron metrology

    NASA Astrophysics Data System (ADS)

    Thomas, David J.; Nolte, Ralf; Gressier, Vincent

    2011-12-01

    The International Committee for Weights and Measures (CIPM) has consultative committees covering various areas of metrology. The Consultative Committee for Ionizing Radiation (CCRI) differs from the others in having three sections: Section (I) deals with radiation dosimetry, Section (II) with radionuclide metrology and Section (III) with neutron metrology. In 2003 a proposal was made to publish special issues of Metrologia covering the work of the three Sections. Section (II) was the first to complete their task, and their special issue was published in 2007, volume 44(4). This was followed in 2009 by the special issue on radiation dosimetry, volume 46(2). The present issue, volume 48(6), completes the trilogy and attempts to explain neutron metrology, the youngest of the three disciplines, the neutron only having been discovered in 1932, to a wider audience and to highlight the relevance and importance of this field. When originally approached with the idea of this special issue, Section (III) immediately saw the value of a publication specifically on neutron metrology. It is a topic area where papers tend to be scattered throughout the literature in journals covering, for example, nuclear instrumentation, radiation protection or radiation measurements in general. Review articles tend to be few. People new to the field often ask for an introduction to the various topics. There are some excellent older textbooks, but these are now becoming obsolete. More experienced workers in specific areas of neutron metrology can find it difficult to know the latest position in related areas. The papers in this issue attempt, without presenting a purely historical outline, to describe the field in a sufficiently logical way to provide the novice with a clear introduction, while being sufficiently up-to-date to provide the more experienced reader with the latest scientific developments in the different topic areas. Neutron radiation fields obviously occur throughout the nuclear

  9. DETERMINATION OF SPECIFIC NEUTRONIC REACTIVITY

    DOEpatents

    Dessauer, G.

    1960-05-10

    A method is given for production-line determination of the specific neutronic reactivity of such objects as individual nuclear fuel or neutron absorber elements and is notable for rapidity and apparatus simplicity. The object is incorporated in a slightly sub-critical chain fission reactive assembly having a discrete neutron source, thereby establishing a K/sub eff/ within the crucial range of 0.95 to 0.995. The range was found to afford, uniquely, flux- transient damped response in a niatter of seconds simultaneously with acceptable analytical sensitivity. The resulting neutron flux measured at a situs spaced from both object and source within the assembly serves as a calibrable indication of said reactivity.

  10. Par Pond vegetation status Summer 1995 -- Summary

    SciTech Connect

    Mackey, H.E. Jr.; Riley, R.S.

    1996-01-01

    The water level of Par Pond was lowered approximately 20 feet in mid-1991 in order to protect downstream residents from possible dam failure suggested by subsidence on the downstream slope of the dam and to repair the dam. This lowering exposed both emergent and nonemergent macrophyte beds to drying conditions resulting in extensive losses. A survey of the newly emergent, shoreline aquatic plant communities of Par Pond began in June 1995, three months after the refilling of Par Pond to approximately 200 feet above mean sea level. These surveys continued in July, September, and late October, 1995. Communities similar to the pre-drawdown, Par Pond aquatic plant communities are becoming re-established. Emergent beds of maidencane, lotus, waterlily, and watershield are extensive and well developed. Cattail occurrence continued to increase during the summer, but large beds common to Par Pond prior to the drawdown have not formed. Estimates from SPOT HRV, remote sensing satellite data indicated that as much as 120 hectares of emergent wetlands vegetation may have been present along the Par Pond shoreline by early October, 1995. To track the continued development of macrophytes in Par Pond, future surveys throughout 1996 and 1997, along with the continued evaluation of satellite data to map the areal extent of the macrophyte beds of Par Pond, are planned.

  11. Physical basis for prompt-neutron activation analysis

    SciTech Connect

    Chrien, R.E.

    1982-01-01

    The technique called prompt ..gamma..-ray neutron activation analysis has been applied to rapid materials analysis. The radiation following the neutron radiation capture is prompt in the sense that the nuclear decay time is on the order of 10/sup -15/ second, and thus the technique is not strictly activation, but should be called radiation neutron capture spectroscopy or neutron capture ..gamma..-ray spectroscopy. This paper reviews the following: sources and detectors, theory of radiative capture, nonstatistical capture, giant dipole resonance, fast neutron capture, and thermal neutron capture ..gamma..-ray spectra. 14 figures.

  12. Planets Around Neutron Stars

    NASA Technical Reports Server (NTRS)

    Wolszczan, Alexander; Kulkarni, Shrinivas R; Anderson, Stuart B.

    2003-01-01

    The objective of this proposal was to continue investigations of neutron star planetary systems in an effort to describe and understand their origin, orbital dynamics, basic physical properties and their relationship to planets around normal stars. This research represents an important element of the process of constraining the physics of planet formation around various types of stars. The research goals of this project included long-term timing measurements of the planets pulsar, PSR B1257+12, to search for more planets around it and to study the dynamics of the whole system, and sensitive searches for millisecond pulsars to detect further examples of old, rapidly spinning neutron stars with planetary systems. The instrumentation used in our project included the 305-m Arecibo antenna with the Penn State Pulsar Machine (PSPM), the 100-m Green Bank Telescope with the Berkeley- Caltech Pulsar Machine (BCPM), and the 100-m Effelsberg and 64-m Parkes telescopes equipped with the observatory supplied backend hardware.

  13. ParAB Partition Dynamics in Firmicutes: Nucleoid Bound ParA Captures and Tethers ParB-Plasmid Complexes

    PubMed Central

    Lioy, Virginia S.; Volante, Andrea; Soberón, Nora E.; Lurz, Rudi; Ayora, Silvia; Alonso, Juan C.

    2015-01-01

    In Firmicutes, small homodimeric ParA-like (δ2) and ParB-like (ω2) proteins, in concert with cis-acting plasmid-borne parS and the host chromosome, secure stable plasmid inheritance in a growing bacterial population. This study shows that (ω:YFP)2 binding to parS facilitates plasmid clustering in the cytosol. (δ:GFP)2 requires ATP binding but not hydrolysis to localize onto the cell’s nucleoid as a fluorescent cloud. The interaction of (δ:CFP)2 or δ2 bound to the nucleoid with (ω:YFP)2 foci facilitates plasmid capture, from a very broad distribution, towards the nucleoid and plasmid pairing. parS-bound ω2 promotes redistribution of (δ:GFP)2, leading to the dynamic release of (δ:GFP)2 from the nucleoid, in a process favored by ATP hydrolysis and protein-protein interaction. (δD60A:GFP)2, which binds but cannot hydrolyze ATP, also forms unstable complexes on the nucleoid. In the presence of ω2, (δD60A:GFP)2 accumulates foci or patched structures on the nucleoid. We propose that (δ:GFP)2 binding to different nucleoid regions and to ω2-parS might generate (δ:GFP)2 gradients that could direct plasmid movement. The iterative pairing and unpairing cycles may tether plasmids equidistantly on the nucleoid to ensure faithful plasmid segregation by a mechanism compatible with the diffusion-ratchet mechanism as proposed from in vitro reconstituted systems. PMID:26161642

  14. Neutron therapy of cancer

    NASA Technical Reports Server (NTRS)

    Frigerio, N. A.; Nellans, H. N.; Shaw, M. J.

    1969-01-01

    Reports relate applications of neutrons to the problem of cancer therapy. The biochemical and biophysical aspects of fast-neutron therapy, neutron-capture and neutron-conversion therapy with intermediate-range neutrons are presented. Also included is a computer program for neutron-gamma radiobiology.

  15. NEUTRONIC REACTOR

    DOEpatents

    Hurwitz, H. Jr.; Brooks, H.; Mannal, C.; Payne, J.H.; Luebke, E.A.

    1959-03-24

    A reactor of the heterogeneous, liquid cooled type is described. This reactor is comprised of a central region of a plurality of vertically disposed elongated tubes surrounded by a region of moderator material. The central region is comprised of a central core surrounded by a reflector region which is surrounded by a fast neutron absorber region, which in turn is surrounded by a slow neutron absorber region. Liquid sodium is used as the primary coolant and circulates through the core which contains the fuel elements. Control of the reactor is accomplished by varying the ability of the reflector region to reflect neutrons back into the core of the reactor. For this purpose the reflector is comprised of moderator and control elements having varying effects on reactivity, the control elements being arranged and actuated by groups to give regulation, shim, and safety control.

  16. Neutron multiplicity analysis tool

    SciTech Connect

    Stewart, Scott L

    2010-01-01

    I describe the capabilities of the EXCOM (EXcel based COincidence and Multiplicity) calculation tool which is used to analyze experimental data or simulated neutron multiplicity data. The input to the program is the count-rate data (including the multiplicity distribution) for a measurement, the isotopic composition of the sample and relevant dates. The program carries out deadtime correction and background subtraction and then performs a number of analyses. These are: passive calibration curve, known alpha and multiplicity analysis. The latter is done with both the point model and with the weighted point model. In the current application EXCOM carries out the rapid analysis of Monte Carlo calculated quantities and allows the user to determine the magnitude of sample perturbations that lead to systematic errors. Neutron multiplicity counting is an assay method used in the analysis of plutonium for safeguards applications. It is widely used in nuclear material accountancy by international (IAEA) and national inspectors. The method uses the measurement of the correlations in a pulse train to extract information on the spontaneous fission rate in the presence of neutrons from ({alpha},n) reactions and induced fission. The measurement is relatively simple to perform and gives results very quickly ({le} 1 hour). By contrast, destructive analysis techniques are extremely costly and time consuming (several days). By improving the achievable accuracy of neutron multiplicity counting, a nondestructive analysis technique, it could be possible to reduce the use of destructive analysis measurements required in safeguards applications. The accuracy of a neutron multiplicity measurement can be affected by a number of variables such as density, isotopic composition, chemical composition and moisture in the material. In order to determine the magnitude of these effects on the measured plutonium mass a calculational tool, EXCOM, has been produced using VBA within Excel. This

  17. NEUTRONIC REACTOR

    DOEpatents

    Fermi, E.; Szilard, L.

    1957-09-24

    Reactors of the type employing plates of natural uranium in a moderator are discussed wherein the plates are um-formly disposed in parallel relationship to each other thereby separating the moderator material into distinct and individual layers. Each plate has an uninterrupted sunface area substantially equal to the cross-sectional area of the active portion of the reactor, the particular size of the plates and the volume ratio of moderator to uranium required to sustain a chain reaction being determinable from the known purity of these materials and other characteristics such as the predictable neutron losses due to the formation of radioactive elements of extremely high neutron capture cross section.

  18. NEUTRONIC REACTOR

    DOEpatents

    Wigner, E.P.; Weinberg, A.W.; Young, G.J.

    1958-04-15

    A nuclear reactor which uses uranium in the form of elongated tubes as fuel elements and liquid as a coolant is described. Elongated tubular uranium bodies are vertically disposed in an efficient neutron slowing agent, such as graphite, for example, to form a lattice structure which is disposed between upper and lower coolant tanks. Fluid coolant tubes extend through the uranium bodies and communicate with the upper and lower tanks and serve to convey the coolant through the uranium body. The reactor is also provided with means for circulating the cooling fluid through the coolant tanks and coolant tubes, suitable neutron and gnmma ray shields, and control means.

  19. Old and new neutron stars

    SciTech Connect

    Ruderman, M.

    1984-09-01

    The youngest known radiopulsar in the rapidly spinning magnetized neutron star which powers the Crab Nebula, the remnant of the historical supernova explosion of 1054 AD. Similar neutron stars are probably born at least every few hundred years, but are less frequent than Galactic supernova explosions. They are initially sources of extreme relativistic electron and/or positron winds (approx.10/sup 38/s/sup -1/ of 10/sup 12/ eV leptons) which greatly decrease as the neutron stars spin down to become mature pulsars. After several million years these neutron stars are no longer observed as radiopulsars, perhaps because of large magnetic field decay. However, a substantial fraction of the 10/sup 8/ old dead pulsars in the Galaxy are the most probable source for the isotropically distributed ..gamma..-ray burst detected several times per week at the earth. Some old neutron stars are spun-up by accretion from companions to be resurrected as rapidly spinning low magnetic field radiopulsars. 52 references, 6 figures, 3 tables.

  20. Neutronic reactor

    DOEpatents

    Carleton, John T.

    1977-01-25

    A graphite-moderated nuclear reactor includes channels between blocks of graphite and also includes spacer blocks between adjacent channeled blocks with an axis of extension normal to that of the axis of elongation of the channeled blocks to minimize changes in the physical properties of the graphite as a result of prolonged neutron bombardment.

  1. NEUTRONIC REACTORS

    DOEpatents

    Anderson, H.L.

    1958-10-01

    The design of control rods for nuclear reactors are described. In this design the control rod consists essentially of an elongated member constructed in part of a neutron absorbing material and having tube means extending therethrough for conducting a liquid to cool the rod when in use.

  2. NEUTRONIC REACTOR

    DOEpatents

    Wigner, E.P.

    1960-09-27

    A unit assembly is described for a neutronic reactor comprising a tube and plurality of spaced parallel sandwiches in the tube extending lengthwise thereof, each sandwich including a middle plate having a central opening for plutonium and other openings for fertile material at opposite ends of the plate.

  3. Methods for absorbing neutrons

    DOEpatents

    Guillen, Donna P.; Longhurst, Glen R.; Porter, Douglas L.; Parry, James R.

    2012-07-24

    A conduction cooled neutron absorber may include a metal matrix composite that comprises a metal having a thermal neutron cross-section of at least about 50 barns and a metal having a thermal conductivity of at least about 1 W/cmK. Apparatus for providing a neutron flux having a high fast-to-thermal neutron ratio may include a source of neutrons that produces fast neutrons and thermal neutrons. A neutron absorber positioned adjacent the neutron source absorbs at least some of the thermal neutrons so that a region adjacent the neutron absorber has a fast-to-thermal neutron ratio of at least about 15. A coolant in thermal contact with the neutron absorber removes heat from the neutron absorber.

  4. Recent Advances in Neutron Physics

    ERIC Educational Resources Information Center

    Feshbach, Herman; Sheldon, Eric

    1977-01-01

    Discusses new studies in neutron physics within the last decade, such as ultracold neutrons, neutron bottles, resonance behavior, subthreshold fission, doubly radiative capture, and neutron stars. (MLH)

  5. Neutron reflecting supermirror structure

    DOEpatents

    Wood, J.L.

    1992-12-01

    An improved neutron reflecting supermirror structure comprising a plurality of stacked sets of bilayers of neutron reflecting materials. The improved neutron reflecting supermirror structure is adapted to provide extremely good performance at high incidence angles, i.e. up to four time the critical angle of standard neutron mirror structures. The reflection of neutrons striking the supermirror structure at a high critical angle provides enhanced neutron throughput, and hence more efficient and economical use of neutron sources. 2 figs.

  6. Neutron reflecting supermirror structure

    DOEpatents

    Wood, James L.

    1992-01-01

    An improved neutron reflecting supermirror structure comprising a plurality of stacked sets of bilayers of neutron reflecting materials. The improved neutron reflecting supermirror structure is adapted to provide extremely good performance at high incidence angles, i.e. up to four time the critical angle of standard neutron mirror structures. The reflection of neutrons striking the supermirror structure at a high critical angle provides enhanced neutron throughput, and hence more efficient and economical use of neutron sources.

  7. Comparative cactus architecture and par interception

    SciTech Connect

    Geller, G.N.; Nobel, P.S. )

    1987-07-01

    Because CO{sup 2} uptake by cacti can be limited by low levels of photosynthetically active radiation (PAR) and because plant form affects PAR interception, various cactus forms were studied using a computer model, field measurements, and laboratory phototropic studies. Model predictions indicated that CO{sub 2} uptake by individual stems at an equinox was greatest when the stem were vertical, but at the summer and the winter solstice CO{sub 2} uptake was greatest for stems titled 30{degree} away from the equator. Stem tilting depended on form and taxonomic group. Not only can the shape of cacti be affected by PAR, but also shape influences PAR interception and hence CO{sub 2} uptake.

  8. Proteinase-activated receptor-1 (PAR(1)) and PAR(2) but not PAR(4) mediate contraction in human and guinea-pig gallbladders.

    PubMed

    Lee, M-C; Huang, S-C

    2008-04-01

    Proteinase-activated receptor-1 (PAR(1)) and PAR(2) mediate contraction in the guinea-pig gallbladder. To investigate and compare the effects mediated by PARs in the human gallbladder with those in the guinea-pig gallbladder, we measured contractions of isolated human and guinea-pig gallbladder strips caused by PAR agonists. Results in human were similar to those in guinea-pig gallbladder. The PAR(1) agonists, thrombin, TFLLR-NH2 and SFLLRN-NH2, as well as the PAR(2) agonists, trypsin, SLIGKV-NH2 and SLIGRL-NH2, caused contraction in both human and guinea-pig gallbladders. These indicate the existence of PAR(1) and PAR(2) mediating gallbladder contraction. Furthermore, the existence of PAR(1) and PAR(2) in the human gallbladder was confirmed by reverse transcription-polymerase chain reaction. In contrast, FSLLR-NH2, a PAR(1) control peptide, and VKGILS-NH2, a PAR(2) control peptide, as well as three PAR(4) agonists, GYPGKF-NH2, GYPGQV-NH2 and AYPGKF-NH2, did not cause any contraction or relaxation. The contractile responses to TFLLR-NH2, SFLLRN-NH2 and trypsin in both human and guinea-pig gallbladders were insensitive to atropine and tetrodotoxin, suggesting direct effects. These results demonstrate that, similar to the guinea-pig gallbladder, both PAR(1) and PAR(2) but not PAR(4) mediate muscle contraction in the human gallbladder. PAR(1) and PAR(2) may play important roles in the control of both human and guinea-pig gallbladder motility. PMID:18179608

  9. Proteinase-activated receptor-1 (PAR1) and PAR2 mediate relaxation of guinea pig internal anal sphincter.

    PubMed

    Huang, Shih-Che

    2014-02-10

    Activation of proteinase-activated receptor-1 (PAR1) and PAR2 stimulates contraction of the rat but relaxation of the guinea pig colon. The aim of the present study was to investigate PAR effects on internal anal sphincter (IAS) motility. We measured relaxation of isolated muscle strips from the guinea pig IAS caused by PAR agonists using isometric transducers. Reverse transcription polymerase chain reaction (RT-PCR) was performed to determine the existence of PAR. In the IAS, thrombin and PAR1 peptide agonists TFLLR-NH2 and SFLLRN-NH2 evoked moderate to marked relaxation in a concentration-dependent manner. In addition, trypsin and PAR2 peptide agonists 2-furoyl-LIGRLO-NH2, SLIGRL-NH2 and SLIGKV-NH2 produced relaxation. In contrast, both PAR1 and PAR2 inactive control peptides did not elicit relaxation. Furthermore, the selective PAR1 antagonist vorapaxar and PAR2 antagonist GB 83 specifically inhibited thrombin and trypsin-induced relaxations, respectively. RT-PCR revealed the presence of PAR1 and PAR2 in the IAS. This indicates that PAR1 and PAR2 mediate the IAS relaxation. The relaxant responses of TFLLR-NH2 and trypsin were attenuated by N(omega)-Nitro-L-arginine (L-NNA), indicating involvement of NO. These responses were not affected by tetrodotoxin, implying that the PAR effects are not neurally mediated. On the other hand, PAR4 agonists GYPGKF-NH2, GYPGQV-NH2 and AYPGKF-NH2 did not cause relaxation or contraction, suggesting that PAR4 is not involved in the sphincter motility. Taken together, these results demonstrate that both PAR1 and PAR2 mediate relaxation of the guinea pig IAS through the NO pathway. PAR1 and PAR2 may regulate IAS tone and might be potential therapeutic targets for anal motility disorders. PMID:24631471

  10. NEUTRONIC REACTORS

    DOEpatents

    Vernon, H.C.

    1959-01-13

    A neutronic reactor of the heterogeneous, fluid cooled tvpe is described. The reactor is comprised of a pressure vessel containing the moderator and a plurality of vertically disposed channels extending in spaced relationship through the moderator. Fissionable fuel material is placed within the channels in spaced relationship thereto to permit circulation of the coolant fluid. Separate means are provided for cooling the moderator and for circulating a fluid coolant thru the channel elements to cool the fuel material.

  11. NEUTRON COUNTER

    DOEpatents

    Curtis, C.D.; Carlson, R.L.; Tubinis, M.P.

    1958-07-29

    An ionization chamber instrument is described for cylindrical electrodes with an ionizing gag filling the channber. The inner electrode is held in place by a hermetic insulating seal at one end of the outer electrode, the other end of the outer electrode being closed by a gas filling tube. The outer surface of the inner electrode is coated with an active material which is responsive to neutron bombardment, such as uranium235 or boron-10, to produce ionizing radiations in the gas. The transverse cross sectional area of the inner electrode is small in relation to that of the channber whereby substantially all of the radiations are directed toward the outer electrode.

  12. NEUTRON SOURCE

    DOEpatents

    Reardon, W.A.; Lennox, D.H.; Nobles, R.G.

    1959-01-13

    A neutron source of the antimony--beryllium type is presented. The source is comprised of a solid mass of beryllium having a cylindrical recess extending therein and a cylinder containing antimony-124 slidably disposed within the cylindrical recess. The antimony cylinder is encased in aluminum. A berylliunn plug is removably inserted in the open end of the cylindrical recess to completely enclose the antimony cylinder in bsryllium. The plug and antimony cylinder are each provided with a stud on their upper ends to facilitate handling remotely.

  13. PAR polarity: from complexity to design principles.

    PubMed

    Goehring, Nathan W

    2014-11-01

    The par-titioning-defective or PAR proteins comprise the core of an essential cell polarity network that underlies polarization in a wide variety of cell types and developmental contexts. The output of this network in nearly every case is the establishment of opposing and complementary membrane domains that define a cell׳s polarity axis. Yet, behind this simple pattern is a complex system of interactions, regulation and dynamic behaviors. How these various parts combine to generate polarized patterns of protein localization in cells is only beginning to become clear. This review, part of the Special Issue on Cell Polarity, aims to highlight several emerging themes and design principles that underlie the process of cell polarization by components of the PAR network. PMID:25128809

  14. Experimental search for neutron mirror neutron oscillations using storage of ultracold neutrons

    NASA Astrophysics Data System (ADS)

    Serebrov, A. P.; Aleksandrov, E. B.; Dovator, N. A.; Dmitriev, S. P.; Fomin, A. K.; Geltenbort, P.; Kharitonov, A. G.; Krasnoschekova, I. A.; Lasakov, M. S.; Murashkin, A. N.; Shmelev, G. E.; Varlamov, V. E.; Vassiljev, A. V.; Zherebtsov, O. M.; Zimmer, O.

    2008-05-01

    The idea of a hidden sector of mirror partners of elementary particles has attracted considerable interest as a possible candidate for dark matter. Recently it was pointed out by Berezhiani and Bento that the present experimental data cannot exclude the possibility of a rapid oscillation of the neutron n to a mirror neutron n‧ with oscillation time much smaller than the neutron lifetime. A dedicated search for vacuum transitions n →n‧ has to be performed at weak magnetic field, where both states are degenerate. We report the result of our experiment, which compares rates of ultracold neutrons after storage at a weak magnetic field well below 20 nT and at a magnetic field strong enough to suppress the seeked transitions. We obtain a new limit for the oscillation time of n-n‧ transitions, τosc (90 % C.L.) > 414 s. The corresponding limit for the mixing energy of the normal and mirror neutron states is δm (90 % C.L.) < 1.5 ×10-18 eV.

  15. Humanizing the Protease-Activated Receptor (PAR) Expression Profile in Mouse Platelets by Knocking PAR1 into the Par3 Locus Reveals PAR1 Expression Is Not Tolerated in Mouse Platelets

    PubMed Central

    French, Shauna L.; Paramitha, Antonia C.; Moon, Mitchell J.; Dickins, Ross A.; Hamilton, Justin R.

    2016-01-01

    Anti-platelet drugs are the mainstay of pharmacotherapy for heart attack and stroke prevention, yet improvements are continually sought. Thrombin is the most potent activator of platelets and targeting platelet thrombin receptors (protease-activated receptors; PARs) is an emerging anti-thrombotic approach. Humans express two PARs on their platelets–PAR1 and PAR4. The first PAR1 antagonist was recently approved for clinical use and PAR4 antagonists are in early clinical development. However, pre-clinical studies examining platelet PAR function are challenging because the platelets of non-primates do not accurately reflect the PAR expression profile of human platelets. Mice, for example, express Par3 and Par4. To address this limitation, we aimed to develop a genetically modified mouse that would express the same repertoire of platelet PARs as humans. Here, human PAR1 preceded by a lox-stop-lox was knocked into the mouse Par3 locus, and then expressed in a platelet-specific manner (hPAR1-KI mice). Despite correct targeting and the predicted loss of Par3 expression and function in platelets from hPAR1-KI mice, no PAR1 expression or function was detected. Specifically, PAR1 was not detected on the platelet surface nor internally by flow cytometry nor in whole cell lysates by Western blot, while a PAR1-activating peptide failed to induce platelet activation assessed by either aggregation or surface P-selectin expression. Platelets from hPAR1-KI mice did display significantly diminished responsiveness to thrombin stimulation in both assays, consistent with a Par3-/- phenotype. In contrast to the observations in hPAR1-KI mouse platelets, the PAR1 construct used here was successfully expressed in HEK293T cells. Together, these data suggest ectopic PAR1 expression is not tolerated in mouse platelets and indicate a different approach is required to develop a small animal model for the purpose of any future preclinical testing of PAR antagonists as anti-platelet drugs. PMID

  16. ParA and ParB coordinate chromosome segregation with cell elongation and division during Streptomyces sporulation

    PubMed Central

    Donczew, Magdalena; Mackiewicz, Paweł; Wróbel, Agnieszka; Flärdh, Klas; Zakrzewska-Czerwińska, Jolanta

    2016-01-01

    In unicellular bacteria, the ParA and ParB proteins segregate chromosomes and coordinate this process with cell division and chromosome replication. During sporulation of mycelial Streptomyces, ParA and ParB uniformly distribute multiple chromosomes along the filamentous sporogenic hyphal compartment, which then differentiates into a chain of unigenomic spores. However, chromosome segregation must be coordinated with cell elongation and multiple divisions. Here, we addressed the question of whether ParA and ParB are involved in the synchronization of cell-cycle processes during sporulation in Streptomyces. To answer this question, we used time-lapse microscopy, which allows the monitoring of growth and division of single sporogenic hyphae. We showed that sporogenic hyphae stop extending at the time of ParA accumulation and Z-ring formation. We demonstrated that both ParA and ParB affect the rate of hyphal extension. Additionally, we showed that ParA promotes the formation of massive nucleoprotein complexes by ParB. We also showed that FtsZ ring assembly is affected by the ParB protein and/or unsegregated DNA. Our results indicate the existence of a checkpoint between the extension and septation of sporogenic hyphae that involves the ParA and ParB proteins. PMID:27248800

  17. Recent advances in fast neutron radiography for cargo inspection

    NASA Astrophysics Data System (ADS)

    Sowerby, B. D.; Tickner, J. R.

    2007-09-01

    Fast neutron radiography techniques are attractive for screening cargo for contraband such as narcotics and explosives. Neutrons have the required penetration, they interact with matter in a manner complementary to X-rays and they can be used to determine elemental composition. Compared to neutron interrogation techniques that measure secondary radiation (neutron or gamma-rays), neutron radiography systems are much more efficient and rapid and they are much more amenable to imaging. However, for neutron techniques to be successfully applied to cargo screening, they must demonstrate significant advantages over well-established X-ray techniques. This paper reviews recent developments and applications of fast neutron radiography for cargo inspection. These developments include a fast neutron and gamma-ray radiography system that utilizes a 14 MeV neutron generator as well as fast neutron resonance radiography systems that use variable energy quasi-monoenergetic neutrons and pulsed broad energy neutron beams. These systems will be discussed and compared with particular emphasis on user requirements, sources, detector systems, imaging ability and performance.

  18. Neutron matter, symmetry energy and neutron stars

    SciTech Connect

    Stefano, Gandolfi; Steiner, Andrew W

    2016-01-01

    Recent progress in quantum Monte Carlo with modern nucleon-nucleon interactions have enabled the successful description of properties of light nuclei and neutron-rich matter. Of particular interest is the nuclear symmetry energy, the energy cost of creating an isospin asymmetry, and its connection to the structure of neutron stars. Combining these advances with recent observations of neutron star masses and radii gives insight into the equation of state of neutron-rich matter near and above the saturation density. In particular, neutron star radius measurements constrain the derivative of the symmetry energy.

  19. Fast neutron environments.

    SciTech Connect

    Buchheit, Thomas Edward; Kotula, Paul Gabriel; Lu, Ping; Brewer, Luke N.; Goods, Steven Howard; Foiles, Stephen Martin; Puskar, Joseph David; Hattar, Khalid Mikhiel; Doyle, Barney Lee; Boyce, Brad Lee; Clark, Blythe G.

    2011-10-01

    The goal of this LDRD project is to develop a rapid first-order experimental procedure for the testing of advanced cladding materials that may be considered for generation IV nuclear reactors. In order to investigate this, a technique was developed to expose the coupons of potential materials to high displacement damage at elevated temperatures to simulate the neutron environment expected in Generation IV reactors. This was completed through a high temperature high-energy heavy-ion implantation. The mechanical properties of the ion irradiated region were tested by either micropillar compression or nanoindentation to determine the local properties, as a function of the implantation dose and exposure temperature. In order to directly compare the microstructural evolution and property degradation from the accelerated testing and classical neutron testing, 316L, 409, and 420 stainless steels were tested. In addition, two sets of diffusion couples from 316L and HT9 stainless steels with various refractory metals. This study has shown that if the ion irradiation size scale is taken into consideration when developing and analyzing the mechanical property data, significant insight into the structural properties of the potential cladding materials can be gained in about a week.

  20. Neutron reflecting supermirror structure

    DOEpatents

    Wood, James L.

    1992-01-01

    An improved neutron reflecting supermirror structure comprising a plurality of stacked sets of bilayers of neutron reflecting materials. The improved neutron reflecting supermirror structure is adapted to provide extremely good performance at high incidence angles, i.e. up to four time the critical angle of standard neutron mirror structures. The reflection of neutrons striking the supermirror structure at a high critical angle provides enhanced neutron throughput, and hence more efficient and economical use of neutron sources. One layer of each set of bilayers consist of titanium, and the second layer of each set of bilayers consist of an alloy of nickel with carbon interstitially present in the nickel alloy.

  1. NEUTRONIC REACTOR

    DOEpatents

    Stewart, H.B.

    1958-12-23

    A nuclear reactor of the type speclfically designed for the irradiation of materials is discussed. In this design a central cyllndrical core of moderating material ls surrounded by an active portlon comprlsed of an annular tank contalning fissionable material immersed ln a liquid moderator. The active portion ls ln turn surrounded by a reflector, and a well ls provided in the center of the core to accommodate the materlals to be irradiated. The over-all dimensions of the core ln at least one plane are equal to or greater than twice the effective slowing down length and equal to or less than twlce the effective diffuslon length for neutrons in the core materials.

  2. NEUTRONIC REACTORS

    DOEpatents

    Wigner, E.P.; Young, G.J.

    1958-10-14

    A method is presented for loading and unloading rod type fuel elements of a neutronic reactor of the heterogeneous, solld moderator, liquid cooled type. In the embodiment illustrated, the fuel rods are disposed in vertical coolant channels in the reactor core. The fuel rods are loaded and unloaded through the upper openings of the channels which are immersed in the coolant liquid, such as water. Unloading is accomplished by means of a coffer dam assembly having an outer sleeve which is placed in sealing relation around the upper opening. A radiation shield sleeve is disposed in and reciprocable through the coffer dam sleeve. A fuel rod engaging member operates through the axial bore in the radiation shield sleeve to withdraw the fuel rod from its position in the reactor coolant channel into the shield, the shield snd rod then being removed. Loading is accomplished in the reverse procedure.

  3. Direct Measurement of Neutron-Neutron Scattering

    SciTech Connect

    Sharapov, E.I.; Furman, W.I.; Lychagin, W.I.; Muzichka, G.V.; Nekhaev, G.V.; Safronov, Yu.V.; Shvetsov, V.N.; Strelkov, A.V.; Bowman, C.D.; Crawford, B.E.; Stephenson, S.L.; Howell, C.R.; Tornow, W.; Levakov, B.G.; Litvin, V.I.; Lyzhin, A.E.; Magda, E.P.; Mitchell, G.E.

    2003-08-26

    In order to resolve long-standing discrepancies in indirect measurements of the neutron-neutron scattering length ann and contribute to solving the problem of the charge symmetry of the nuclear force, the collaboration DIANNA (Direct Investigation of ann Association) plans to measure the neutron-neutron scattering cross section {sigma}nn. The key issue of our approach is the use of the through-channel in the Russia reactor YAGUAR with a peak neutron flux of 10{sup 18} /cm2/s. The proposed experimental setup is described. Results of calculations are presented to connect {sigma}nn with the nn-collision detector count rate and the neutron flux density in the reactor channel. Measurements of the thermal neutron fields inside polyethylene converters show excellent prospects for the realization of the direct nn-experiment.

  4. Solar neutron emissivity during the large flare on 1982 June 3

    NASA Technical Reports Server (NTRS)

    Chupp, E. L.; Forrest, D. J.; Kanbach, G.; Flueckiger, E.; Golliez, F.

    1987-01-01

    For the solar neutron event on June 3, 1982, it is shown here that the combined SMM Gamma Ray Spectrometer and Jungfraujoch neutron monitor data require a time-extended emission of neutrons at the sun with energies of 100 MeV to about 2 GeV. The solar neutron emissivity spectrum is shown to have a strong downward curvature or truncation between 2 and 4 GeV. A Bessel function and truncated power law give acceptable fits to the observational data, but only the power law can explain the rapid rise of the neutron monitor count rate. The integrated emissivity of neutrons above E(n) of 100 MeV is strongly constrained at 8 x 10 to the 28th neutrons/sr and is essentially independent of neutron spectral shape. At neutron energies of about 100 MeV, good agreement is found for both spectral forms with observations of neutron decay protons.

  5. View from east to west of PAR site storage building; ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    View from east to west of PAR site storage building; formerly PAR dispensary - Stanley R. Mickelsen Safeguard Complex, Storage Building, Across street from Family Housing Units 110 & 111, Nekoma, Cavalier County, ND

  6. View from west to east of PAR site resident engineer's ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    View from west to east of PAR site resident engineer's office building (REOB) - Stanley R. Mickelsen Safeguard Complex, Resident Engineers Office Building, Southeast of intersection of PAR Access Road & Fourth Avenue, Nekoma, Cavalier County, ND

  7. Host response biomarker in sepsis: suPAR detection.

    PubMed

    Giamarellos-Bourboulis, Evangelos J; Georgitsi, Marianna

    2015-01-01

    Recent studies of our group have shown that suPAR may complement APACHE II score for risk assessment in sepsis. suPAR may be measured in serum of patients by an enzyme immunosorbent assay developed by Virogates (suPARnostic™). Production of suPAR from circulating neutrophils and monocytes may be assessed after isolation of neutrophils and monocytes and ex vivo culture. This is followed by measurement of suPAR in culture supernatants.

  8. The breaking strain of neutron star crust

    SciTech Connect

    Kadau, Kai; Horowitz, C J

    2009-01-01

    Mountains on rapidly rotating neutron stars efficiently radiate gravitational waves. The maximum possible size of these mountains depends on the breaking strain of neutron star crust. With multimillion ion molecular dynamics simulations of Coulomb solids representing the crust, we show that the breaking strain of pure single crystals is very large and that impurities, defects, and grain boundaries only modestly reduce the breaking strain to around 0.1. Due to the collective behavior of the ions during failure found in our simulations, the neutron star crust is likely very strong and can support mountains large enough so that their gTavitational wave radiation could limit the spin periods of some stars and might be detectable in large scale interferometers. Furthermore, our microscopic modeling of neutron star crust material can help analyze mechanisms relevant in Magnetar Giant and Micro Flares.

  9. Neutron range spectrometer

    DOEpatents

    Manglos, Stephen H.

    1989-06-06

    A neutron range spectrometer and method for determining the neutron energy spectrum of a neutron emitting source are disclosed. Neutrons from the source are collimnated along a collimation axis and a position sensitive neutron counter is disposed in the path of the collimated neutron beam. The counter determines positions along the collimation axis of interactions between the neutrons in the neutron beam and a neutron-absorbing material in the counter. From the interaction positions, a computer analyzes the data and determines the neutron energy spectrum of the neutron beam. The counter is preferably shielded and a suitable neutron-absorbing material is He-3. The computer solves the following equation in the analysis: ##EQU1## where: N(x).DELTA.x=the number of neutron interactions measured between a position x and x+.DELTA.x, A.sub.i (E.sub.i).DELTA.E.sub.i =the number of incident neutrons with energy between E.sub.i and E.sub.i +.DELTA.E.sub.i, and C=C(E.sub.i)=N .sigma.(E.sub.i) where N=the number density of absorbing atoms in the position sensitive counter means and .sigma. (E.sub.i)=the average cross section of the absorbing interaction between E.sub.i and E.sub.i +.DELTA.E.sub.i.

  10. NEUTRONIC REACTOR

    DOEpatents

    Ohlinger, L.A.; Wigner, E.P.; Weinberg, A.M.; Young, G.J.

    1958-09-01

    This patent relates to neutronic reactors of the heterogeneous water cooled type, and in particular to a fuel element charging and discharging means therefor. In the embodiment illustrated the reactor contains horizontal, parallel coolant tubes in which the fuel elements are disposed. A loading cart containing a magnzine for holding a plurality of fuel elements operates along the face of the reactor at the inlet ends of the coolant tubes. The loading cart is equipped with a ram device for feeding fuel elements from the magazine through the inlot ends of the coolant tubes. Operating along the face adjacent the discharge ends of the tubes there is provided another cart means adapted to receive irradiated fuel elements as they are forced out of the discharge ends of the coolant tubes by the incoming new fuel elements. This cart is equipped with a tank coataining a coolant, such as water, into which the fuel elements fall, and a hydraulically operated plunger to hold the end of the fuel element being discharged. This inveation provides an apparatus whereby the fuel elements may be loaded into the reactor, irradiated therein, and unloaded from the reactor without stopping the fiow of the coolant and without danger to the operating personnel.

  11. Proteinase-activated receptors (PARs) as targets for antiplatelet therapy.

    PubMed

    Cunningham, Margaret; McIntosh, Kathryn; Bushell, Trevor; Sloan, Graeme; Plevin, Robin

    2016-04-15

    Since the identification of the proteinase-activated receptor (PAR) family as mediators of serine protease activity in the 1990s, there has been tremendous progress in the elucidation of their pathophysiological roles. The development of drugs that target PARs has been the focus of many laboratories for the potential treatment of thrombosis, cancer and other inflammatory diseases. Understanding the mechanisms of PAR activation and G protein signalling pathways evoked in response to the growing list of endogenous proteases has yielded great insight into receptor regulation at the molecular level. This has led to the development of new selective modulators of PAR activity, particularly PAR1. The mixed success of targeting PARs has been best exemplified in the context of inhibiting PAR1 as a new antiplatelet therapy. The development of the competitive PAR1 antagonist, vorapaxar (Zontivity), has clearly shown the value in targeting PAR1 in acute coronary syndrome (ACS); however the severity of associated bleeding with this drug has limited its use in the clinic. Due to the efficacy of thrombin acting via PAR1, strategies to selectively inhibit specific PAR1-mediated G protein signalling pathways or to target the second thrombin platelet receptor, PAR4, are being devised. The rationale behind these alternative approaches is to bias downstream thrombin activity via PARs to allow for inhibition of pro-thrombotic pathways but maintain other pathways that may preserve haemostatic balance and improve bleeding profiles for widespread clinical use. This review summarizes the structural determinants that regulate PARs and the modulators of PAR activity developed to date.

  12. Les Brulures Chimiques Par Le Laurier Rose

    PubMed Central

    Bakkali, H.; Ababou, M.; Nassim Sabah, T.; Moussaoui, A.; Ennouhi, A.; Fouadi, F.Z.; Siah, S.; Ihrai, H.

    2010-01-01

    Summary Le laurier rose ou Nerium oleander est un arbuste qui pousse naturellement dans les régions méditerranéennes. Au Maroc on le trouve dans les lieux humides. Il est réputé par ses risques de toxicité systémique en cas d'empoisonnement à cause de la présence de deux alcaloïdes, surtout l'oléandrine. La littérature illustre des cas d'utilisation locale des feuilles de cette plante contre la gale, les hémorroïdes et les furoncles. Nous rapportons deux cas de brûlures chimiques par le laurier rose de gravité différente. Cela doit aboutir à une information élargie de la population, ainsi qu'une réglementation stricte de sa commercialisation. PMID:21991211

  13. Discovery of Octahydroindenes as PAR1 Antagonists

    PubMed Central

    2013-01-01

    Octahydroindene was identified as a novel scaffold for protease activated receptor 1 (PAR1) antagonists. Herein, the 2-position (C2) was explored for structure–activity relationship (SAR) studies. Compounds 14, 19, and 23b showed IC50 values of 1.3, 8.6, and 2.7 nM in a PAR1 radioligand binding assay, respectively, and their inhibitory activities on platelet activation were comparable to that of vorapaxar in a platelet rich plasma (PRP) aggregation assay. This series of compounds showed high potency and no significant cytotoxicity; however, the compounds were metabolically unstable in both human and rat liver microsomes. Current research efforts are focused on optimizing the compounds to improve metabolic stability and physicochemical properties as well as potency. PMID:24900604

  14. Monte Carlo code for neutron scattering instrumentation design and analysis

    SciTech Connect

    Daemen, L.; Fitzsimmons, M.; Hjelm, R.; Olah, G.; Roberts, J.; Seeger, P.; Smith, G.; Thelliez, T.

    1996-09-01

    This is the final report of a one-year, Laboratory-Directed Research and Development (LDRD) at the Los Alamos National Laboratory (LANL). The development of next generation, accelerator based neutron sources calls for the design of new instruments for neutron scattering studies of materials. It will be necessary, in the near future, to evaluate accurately and rapidly the performance of new and traditional neutron instruments at short- and long-pulse spallation neutron sources, as well as continuous sources. We have developed a code that is a design tool to assist the instrument designer model new or existing instruments, test their performance, and optimize their most important features.

  15. Neutron streak camera

    DOEpatents

    Wang, Ching L.

    1983-09-13

    Apparatus for improved sensitivity and time resolution of a neutron measurement. The detector is provided with an electrode assembly having a neutron sensitive cathode which emits relatively low energy secondary electrons. The neutron sensitive cathode has a large surface area which provides increased sensitivity by intercepting a greater number of neutrons. The cathode is also curved to compensate for differences in transit time of the neutrons emanating from the point source. The slower speeds of the secondary electrons emitted from a certain portion of the cathode are matched to the transit times of the neutrons impinging thereupon.

  16. Layered semiconductor neutron detectors

    DOEpatents

    Mao, Samuel S; Perry, Dale L

    2013-12-10

    Room temperature operating solid state hand held neutron detectors integrate one or more relatively thin layers of a high neutron interaction cross-section element or materials with semiconductor detectors. The high neutron interaction cross-section element (e.g., Gd, B or Li) or materials comprising at least one high neutron interaction cross-section element can be in the form of unstructured layers or micro- or nano-structured arrays. Such architecture provides high efficiency neutron detector devices by capturing substantially more carriers produced from high energy .alpha.-particles or .gamma.-photons generated by neutron interaction.

  17. Neutron streak camera

    DOEpatents

    Wang, C.L.

    1981-05-14

    Apparatus for improved sensitivity and time resolution of a neutron measurement. The detector is provided with an electrode assembly having a neutron sensitive cathode which emits relatively low energy secondary electrons. The neutron sensitive cathode has a large surface area which provides increased sensitivity by intercepting a greater number of neutrons. The cathode is also curved to compensate for differences in transit time of the neutrons emanating from the point source. The slower speeds of the secondary electrons emitted from a certain portion of the cathode are matched to the transit times of the neutrons impinging thereupon.

  18. Neutron streak camera

    DOEpatents

    Wang, C.L.

    1983-09-13

    Disclosed is an apparatus for improved sensitivity and time resolution of a neutron measurement. The detector is provided with an electrode assembly having a neutron sensitive cathode which emits relatively low energy secondary electrons. The neutron sensitive cathode has a large surface area which provides increased sensitivity by intercepting a greater number of neutrons. The cathode is also curved to compensate for differences in transit time of the neutrons emanating from the point source. The slower speeds of the secondary electrons emitted from a certain portion of the cathode are matched to the transit times of the neutrons impinging thereupon. 4 figs.

  19. Organic metal neutron detector

    DOEpatents

    Butler, M.A.; Ginley, D.S.

    1984-11-21

    A device for detection of neutrons comprises: as an active neutron sensing element, a conductive organic polymer having an electrical conductivity and a cross-section for said neutrons whereby a detectable change in said conductivity is caused by impingement of said neutrons on the conductive organic polymer which is responsive to a property of said polymer which is altered by impingement of said neutrons on the polymer; and means for associating a change in said alterable property with the presence of neutrons at the location of said device.

  20. Par Pond refill water quality sampling

    SciTech Connect

    Koch, J.W. II; Martin, F.D.; Westbury, H.M.

    1996-08-01

    This study was designed to document anoxia and its cause in the event that the anoxia caused a fish kill. However, no fish kill was observed during this study, and dissolved oxygen and nutrient concentrations generally remained within the range expected for southeastern reservoirs. Par Pond water quality monitoring will continue during the second summer after refill as the aquatic macrophytes become reestablished and nutrients in the sediments are released to the water column.

  1. Neutronic Reactor Design to Reduce Neutron Loss

    DOEpatents

    Miles, F. T.

    1961-05-01

    A nuclear reactor construction is described in which an unmoderated layer of the fissionable material is inserted between the moderated portion of the reactor core and the core container steel wall. The wall is surrounded by successive layers of pure fertile material and moderator containing fertile material. The unmoderated layer of the fissionable material will insure that a greater portion of fast neutrons will pass through the steel wall than would thermal neutrons. Since the steel has a smaller capture cross section for the fast neutrons, greater nunnbers of neutrons will pass into the blanket, thereby increasing the over-all efficiency of the reactor. (AEC)

  2. NEUTRONIC REACTOR DESIGN TO REDUCE NEUTRON LOSS

    DOEpatents

    Mills, F.T.

    1961-05-01

    A nuclear reactor construction is described in which an unmoderated layer of the fissionable material is inserted between the moderated portion of the reactor core and the core container steel wall which is surrounded by successive layers of pure fertile material and fertile material having moderator. The unmoderated layer of the fissionable material will insure that a greater portion of fast neutrons will pass through the steel wall than would thermal neutrons. As the steel has a smaller capture cross-section for the fast neutrons, then greater numbers of the neutrons will pass into the blanket thereby increasing the over-all efficiency of the reactor.

  3. Mixed field dosimetry of epithermal neutron beams for boron neutron capture therapy at the MITR-II research reactor.

    PubMed

    Rogus, R D; Harling, O K; Yanch, J C

    1994-10-01

    During the past several years, there has been growing interest in Boron Neutron Capture Therapy (BNCT) using epithermal neutron beams. The dosimetry of these beams is challenging. The incident beam is comprised mostly of epithermal neutrons, but there is some contamination from photons and fast neutrons. Within the patient, the neutron spectrum changes rapidly as the incident epithermal neutrons scatter and thermalize, and a photon field is generated from neutron capture in hydrogen. In this paper, a method to determine the doses from thermal and fast neutrons, photons, and the B-10(n, alpha)Li-7 reaction is presented. The photon and fast neutron doses are measured with ionization chambers, in realistic phantoms, using the dual chamber technique. The thermal neutron flux is measured with gold foils using the cadmium difference technique, the thermal neutron and B-10 doses are determined by the kerma factor method. Representative results are presented for a unilateral irradiation of the head. Sources of error in the method as applied to BNCT dosimetry, and the uncertainties in the calculated doses are discussed.

  4. Neutron Stars are Follicly Challenged

    NASA Astrophysics Data System (ADS)

    Yunes, Nicolas; Yagi, Kent; Stein, Leo; Pappas, George; Apostolatos, Theocharis; Kyutoku, Koutarou

    2015-04-01

    Black holes satisfy certain no-hair relations through which all multipole moments of the spacetime can be specified in terms of just a few quantities, like their mass and spin angular momentum. I will describe how neutron stars and quark stars also satisfy similar no-hair relations that are approximately independent of their equation of state. I will show how these results hold for both slowly- and rapidly-rotating stars in full General Relativity, provided the stars are uniformly rotating and uncharged. I will then explain why such relations may be relevant to observations of the pulse profile of hot spots on rotating neutron stars with NICER, as well as how they could be used to test General Relativity with binary pulsar and gravitational wave observations. I acknowledge support from the NSF CAREER Award PHY-1250636.

  5. High energy radiation from neutron stars

    SciTech Connect

    Ruderman, M.

    1985-04-01

    Topics covered include young rapidly spinning pulsars; static gaps in outer magnetospheres; dynamic gaps in pulsar outer magnetospheres; pulse structure of energetic radiation sustained by outer gap pair production; outer gap radiation, Crab pulsar; outer gap radiation, the Vela pulsar; radioemission; and high energy radiation during the accretion spin-up of older neutron stars. 26 refs., 10 figs. (GHT)

  6. Neutron anatomy

    SciTech Connect

    Bacon, G.E.

    1994-12-31

    The familiar extremes of crystalline material are single-crystals and random powders. In between these two extremes are polycrystalline aggregates, not randomly arranged but possessing some preferred orientation and this is the form taken by constructional materials, be they steel girders or the bones of a human or animal skeleton. The details of the preferred orientation determine the ability of the material to withstand stress in any direction. In the case of bone the crucial factor is the orientation of the c-axes of the mineral content - the crystals of the hexagonal hydroxyapatite - and this can readily be determined by neutron diffraction. In particular it can be measured over the volume of a piece of bone, utilizing distances ranging from 1mm to 10mm. The major practical problem is to avoid the intense incoherent scattering from the hydrogen in the accompanying collagen; this can best be achieved by heat-treatment and it is demonstrated that this does not affect the underlying apatite. These studies of bone give leading anatomical information on the life and activities of humans and animals - including, for example, the life history of the human femur, the locomotion of sheep, the fracture of the legs of racehorses and the life-styles of Neolithic tribes. We conclude that the material is placed economically in the bone to withstand the expected stresses of life and the environment. The experimental results are presented in terms of the magnitude of the 0002 apatite reflection. It so happens that for a random powder the 0002, 1121 reflections, which are neighboring lines in the powder pattern, are approximately equal in intensity. The latter reflection, being of manifold multiplicity, is scarcely affected by preferred orientation so that the numerical value of the 0002/1121 ratio serves quite accurately as a quantitative measure of the degree of orientation of the c-axes in any chosen direction for a sample of bone.

  7. Dose equivalent neutron dosimeter

    DOEpatents

    Griffith, Richard V.; Hankins, Dale E.; Tomasino, Luigi; Gomaa, Mohamed A. M.

    1983-01-01

    A neutron dosimeter is disclosed which provides a single measurements indicating the amount of potential biological damage resulting from the neutron exposure of the wearer, for a wide range of neutron energies. The dosimeter includes a detecting sheet of track etch detecting material such as a carbonate plastic, for detecting higher energy neutrons, and a radiator layer containing conversion material such as .sup.6 Li and .sup.10 B lying adjacent to the detecting sheet for converting moderate energy neutrons to alpha particles that produce tracks in the adjacent detecting sheet. The density of conversion material in the radiator layer is of an amount which is chosen so that the density of tracks produced in the detecting sheet is proportional to the biological damage done by neutrons, regardless of whether the tracks are produced as the result of moderate energy neutrons striking the radiator layer or as the result of higher energy neutrons striking the sheet of track etch material.

  8. Ultrafast neutron detector

    DOEpatents

    Wang, C.L.

    1985-06-19

    A neutron detector of very high temporal resolution is described. It may be used to measure distributions of neutrons produced by fusion reactions that persist for times as short as about 50 picoseconds.

  9. On neutron surface waves

    SciTech Connect

    Ignatovich, V. K.

    2009-01-15

    It is shown that neutron surface waves do not exist. The difference between the neutron wave mechanics and the wave physics of electromagnetic and acoustic processes, which allows the existence of surface waves, is analyzed.

  10. Neutron dose equivalent meter

    DOEpatents

    Olsher, Richard H.; Hsu, Hsiao-Hua; Casson, William H.; Vasilik, Dennis G.; Kleck, Jeffrey H.; Beverding, Anthony

    1996-01-01

    A neutron dose equivalent detector for measuring neutron dose capable of accurately responding to neutron energies according to published fluence to dose curves. The neutron dose equivalent meter has an inner sphere of polyethylene, with a middle shell overlying the inner sphere, the middle shell comprising RTV.RTM. silicone (organosiloxane) loaded with boron. An outer shell overlies the middle shell and comprises polyethylene loaded with tungsten. The neutron dose equivalent meter defines a channel through the outer shell, the middle shell, and the inner sphere for accepting a neutron counter tube. The outer shell is loaded with tungsten to provide neutron generation, increasing the neutron dose equivalent meter's response sensitivity above 8 MeV.

  11. Pulsed-neutron monochromator

    DOEpatents

    Mook, H.A. Jr.

    1984-01-01

    In one aspect, the invention is an improved pulsed-neutron monochromator of the vibrated-crystal type. The monochromator is designed to provide neutron pulses which are characterized both by short duration and high density. A row of neutron-reflecting crystals is disposed in a neutron beam to reflect neutrons onto a common target. The crystals in the row define progressively larger neutron-scattering angles and are vibrated sequentially in descending order with respect to the size of their scattering angles, thus generating neutron pulses which arrive simultaneously at the target. Transducers are coupled to one end of the crystals to vibrate them in an essentially non-resonant mode. The transducers propagate transverse waves in the crystal which progress longitudinally therein. The waves are absorbed at the undriven ends of the crystals by damping material mounted thereon. In another aspect, the invention is a method for generating neutron pulses characterized by high intensity and short duration.

  12. Pulsed-neutron monochromator

    DOEpatents

    Mook, Jr., Herbert A.

    1985-01-01

    In one aspect, the invention is an improved pulsed-neutron monochromator of the vibrated-crystal type. The monochromator is designed to provide neutron pulses which are characterized both by short duration and high density. A row of neutron-reflecting crystals is disposed in a neutron beam to reflect neutrons onto a common target. The crystals in the row define progressively larger neutron-scattering angles and are vibrated sequentially in descending order with respect to the size of their scattering angles, thus generating neutron pulses which arrive simultaneously at the target. Transducers are coupled to one end of the crystals to vibrate them in an essentially non-resonant mode. The transducers propagate transverse waves in the crystal which progress longitudinally therein. The wave are absorbed at the undriven ends of the crystals by damping material mounted thereon. In another aspect, the invention is a method for generating neutron pulses characterized by high intensity and short duration.

  13. ULTRASONIC NEUTRON DOSIMETER

    DOEpatents

    Truell, R.; de Klerk, J.; Levy, P.W.

    1960-02-23

    A neutron dosimeter is described which utilizes ultrasonic waves in the megacycle region for determination of the extent of neutron damage in a borosilicate glass through ultrasonic wave velocity and attenuation measurements before and after damage.

  14. Intense fusion neutron sources

    NASA Astrophysics Data System (ADS)

    Kuteev, B. V.; Goncharov, P. R.; Sergeev, V. Yu.; Khripunov, V. I.

    2010-04-01

    The review describes physical principles underlying efficient production of free neutrons, up-to-date possibilities and prospects of creating fission and fusion neutron sources with intensities of 1015-1021 neutrons/s, and schemes of production and application of neutrons in fusion-fission hybrid systems. The physical processes and parameters of high-temperature plasmas are considered at which optimal conditions for producing the largest number of fusion neutrons in systems with magnetic and inertial plasma confinement are achieved. The proposed plasma methods for neutron production are compared with other methods based on fusion reactions in nonplasma media, fission reactions, spallation, and muon catalysis. At present, intense neutron fluxes are mainly used in nanotechnology, biotechnology, material science, and military and fundamental research. In the near future (10-20 years), it will be possible to apply high-power neutron sources in fusion-fission hybrid systems for producing hydrogen, electric power, and technological heat, as well as for manufacturing synthetic nuclear fuel and closing the nuclear fuel cycle. Neutron sources with intensities approaching 1020 neutrons/s may radically change the structure of power industry and considerably influence the fundamental and applied science and innovation technologies. Along with utilizing the energy produced in fusion reactions, the achievement of such high neutron intensities may stimulate wide application of subcritical fast nuclear reactors controlled by neutron sources. Superpower neutron sources will allow one to solve many problems of neutron diagnostics, monitor nano-and biological objects, and carry out radiation testing and modification of volumetric properties of materials at the industrial level. Such sources will considerably (up to 100 times) improve the accuracy of neutron physics experiments and will provide a better understanding of the structure of matter, including that of the neutron itself.

  15. Dibaryons in neutron stars

    NASA Technical Reports Server (NTRS)

    Olinto, Angela V.; Haensel, Pawel; Frieman, Joshua A.

    1991-01-01

    The effects are studied of H-dibaryons on the structure of neutron stars. It was found that H particles could be present in neutron stars for a wide range of dibaryon masses. The appearance of dibaryons softens the equations of state, lowers the maximum neutron star mass, and affects the transport properties of dense matter. The parameter space is constrained for dibaryons by requiring that a 1.44 solar mass neutron star be gravitationally stable.

  16. Neutrino Processes in Neutron Stars

    NASA Astrophysics Data System (ADS)

    Kolomeitsev, E. E.; Voskresensky, D. N.

    2010-10-01

    The aim of these lectures is to introduce basic processes responsible for cooling of neutron stars and to show how to calculate the neutrino production rate in dense strongly interacting nuclear medium. The formalism is presented that treats on equal footing one-nucleon and multiple-nucleon processes and reactions with virtual bosonic modes and condensates. We demonstrate that neutrino emission from dense hadronic component in neutron stars is subject of strong modifications due to collective effects in the nuclear matter. With the most important in-medium processes incorporated in the cooling code an overall agreement with available soft X ray data can be easily achieved. With these findings the so-called “standard” and “non-standard” cooling scenarios are replaced by one general “nuclear medium cooling scenario” which relates slow and rapid neutron star coolings to the star masses (interior densities). The lectures are split in four parts. Part I: After short introduction to the neutron star cooling problem we show how to calculate neutrino reaction rates of the most efficient one-nucleon and two-nucleon processes. No medium effects are taken into account in this instance. The effects of a possible nucleon pairing are discussed. We demonstrate that the data on neutron star cooling cannot be described without inclusion of medium effects. It motivates an assumption that masses of the neutron stars are different and that neutrino reaction rates should be strongly density dependent. Part II: We introduce the Green’s function diagram technique for systems in and out of equilibrium and the optical theorem formalism. The latter allows to perform calculations of production rates with full Green’s functions including all off-mass-shell effects. We demonstrate how this formalism works within the quasiparticle approximation. Part III: The basic concepts of the nuclear Fermi liquid approach are introduced. We show how strong interaction effects can be

  17. Arsenic activation neutron detector

    DOEpatents

    Jacobs, E.L.

    1980-01-28

    A detector of bursts of neutrons from a deuterium-deuteron reaction includes a quantity of arsenic adjacent a gamma detector such as a scintillator and photomultiplier tube. The arsenic is activated by the 2.5-MeV neutrons to release gamma radiation which is detected to give a quantitative representation of detected neutrons.

  18. Arsenic activation neutron detector

    DOEpatents

    Jacobs, Eddy L.

    1981-01-01

    A detector of bursts of neutrons from a deuterium-deuteron reaction includes a quantity of arsenic adjacent a gamma detector such as a scintillator and photomultiplier tube. The arsenic is activated by the 2.5 Mev neutrons to release gamma radiation which is detected to give a quantitative representation of detected neutrons.

  19. Perforated diode neutron sensors

    NASA Astrophysics Data System (ADS)

    McNeil, Walter J.

    A novel design of neutron sensor was investigated and developed. The perforated, or micro-structured, diode neutron sensor is a concept that has the potential to enhance neutron sensitivity of a common solid-state sensor configuration. The common thin-film coated diode neutron sensor is the only semiconductor-based neutron sensor that has proven feasible for commercial use. However, the thin-film coating restricts neutron counting efficiency and severely limits the usefulness of the sensor. This research has shown that the perforated design, when properly implemented, can increase the neutron counting efficiency by greater than a factor of 4. Methods developed in this work enable detectors to be fabricated to meet needs such as miniaturization, portability, ruggedness, and adaptability. The new detectors may be used for unique applications such as neutron imaging or the search for special nuclear materials. The research and developments described in the work include the successful fabrication of variant perforated diode neutron detector designs, general explanations of fundamental radiation detector design (with added focus on neutron detection and compactness), as well as descriptive theory and sensor design modeling useful in predicting performance of these unique solid-state radiation sensors. Several aspects in design, fabrication, and operational performance have been considered and tested including neutron counting efficiency, gamma-ray response, perforation shapes and depths, and silicon processing variations. Finally, the successfully proven technology was applied to a 1-dimensional neutron sensor array system.

  20. Advanced neutron absorber materials

    DOEpatents

    Branagan, Daniel J.; Smolik, Galen R.

    2000-01-01

    A neutron absorbing material and method utilizing rare earth elements such as gadolinium, europium and samarium to form metallic glasses and/or noble base nano/microcrystalline materials, the neutron absorbing material having a combination of superior neutron capture cross sections coupled with enhanced resistance to corrosion, oxidation and leaching.

  1. LGB neutron detector

    NASA Astrophysics Data System (ADS)

    Quist, Nicole

    2012-10-01

    The double pulse signature of the Gadolinium Lithium Borate Cerium doped plastic detector suggests its effectiveness for analyzing neutrons while providing gamma ray insensitivity. To better understand this detector, a californium gamma/neutron time of flight facility was constructed in our lab. Reported here are efforts to understand the properties and applications of the LGB detector with regards to neutron spectroscopy.

  2. Continuum quasiparticle random-phase approximation for astrophysical direct neutron capture reactions on neutron-rich nuclei

    NASA Astrophysics Data System (ADS)

    Matsuo, Masayuki

    2015-03-01

    I formulate a many-body theory to calculate the cross section of direct radiative neutron capture reaction by means of the Hartree-Fock-Bogoliubov mean-field model and the continuum quasiparticle random-phase approximation (QRPA). A focus is put on very-neutron-rich nuclei and low-energy neutron kinetic energy in the range from 1 keV to several MeV, which is relevant to the rapid neutron capture process of nucleosynthesis. I begin with the photoabsorption cross section and the E 1 strength function. Next, in order to apply the reciprocity theorem, I decompose the cross section into partial cross sections corresponding to different channels of one- and two-neutron emission decays of photo-excited states. A numerical example is shown for the photo-absorption of 142Sn and the neutron capture of 141Sn .

  3. Modelisation par elements finis du muscle strie

    NASA Astrophysics Data System (ADS)

    Leonard, Mathieu

    Ce present projet de recherche a permis. de creer un modele par elements finis du muscle strie humain dans le but d'etudier les mecanismes engendrant les lesions musculaires traumatiques. Ce modele constitue une plate-forme numerique capable de discerner l'influence des proprietes mecaniques des fascias et de la cellule musculaire sur le comportement dynamique du muscle lors d'une contraction excentrique, notamment le module de Young et le module de cisaillement de la couche de tissu conjonctif, l'orientation des fibres de collagene de cette membrane et le coefficient de poisson du muscle. La caracterisation experimentale in vitro de ces parametres pour des vitesses de deformation elevees a partir de muscles stries humains actifs est essentielle pour l'etude de lesions musculaires traumatiques. Le modele numerique developpe est capable de modeliser la contraction musculaire comme une transition de phase de la cellule musculaire par un changement de raideur et de volume a l'aide des lois de comportement de materiau predefinies dans le logiciel LS-DYNA (v971, Livermore Software Technology Corporation, Livermore, CA, USA). Le present projet de recherche introduit donc un phenomene physiologique qui pourrait expliquer des blessures musculaires courantes (crampes, courbatures, claquages, etc.), mais aussi des maladies ou desordres touchant le tissu conjonctif comme les collagenoses et la dystrophie musculaire. La predominance de blessures musculaires lors de contractions excentriques est egalement exposee. Le modele developpe dans ce projet de recherche met ainsi a l'avant-scene le concept de transition de phase ouvrant la porte au developpement de nouvelles technologies pour l'activation musculaire chez les personnes atteintes de paraplegie ou de muscles artificiels compacts pour l'elaboration de protheses ou d'exosquelettes. Mots-cles Muscle strie, lesion musculaire, fascia, contraction excentrique, modele par elements finis, transition de phase

  4. A magneto-gravitational neutron trap for the measurement of the neutron lifetime

    NASA Astrophysics Data System (ADS)

    Salvat, Daniel J.

    Neutron decay is the simplest example of nuclear beta-decay. The mean decay lifetime is a key input for predicting the abundance of light elements in the early universe. A precise measurement of the neutron lifetime, when combined with other neutron decay observables, can test for physics beyond the standard model in a way that is complimentary to, and potentially competitive with, results from high energy collider experiments. Many previous measurements of the neutron lifetime used ultracold neutrons (UCN) confined in material bottles. In a material bottle experiment, UCN are loaded into the apparatus, stored for varying times, and the surviving UCN are emptied and counted. These measurements are in poor agreement with experiments that use neutron beams, and new experiments are needed to resolve the discrepancy and precisely determine the lifetime. Here we present an experiment that uses a bowl-shaped array of NdFeB magnets to confine neutrons without material wall interactions. The trap shape is designed to rapidly remove higher energy UCN that might slowly leak from the top of the trap, and can facilitate new techniques to count surviving UCN within the trap. We review the scientific motivation for a precise measurement of the neutron lifetime, and present the commissioning of the trap. Data are presented using a vanadium activation technique to count UCN within the trap, providing an alternative method to emptying neutrons from the trap and into a counter. Potential systematic effects in the experiment are then discussed and estimated using analytical and numerical techniques. We also investigate solid nitrogen-15 as a source of UCN using neutron time-of-flight spectroscopy. We conclude with a discussion of forthcoming research and development for UCN detection and UCN sources.

  5. Neutron scatter camera

    DOEpatents

    Mascarenhas, Nicholas; Marleau, Peter; Brennan, James S.; Krenz, Kevin D.

    2010-06-22

    An instrument that will directly image the fast fission neutrons from a special nuclear material source has been described. This instrument can improve the signal to background compared to non imaging neutron detection techniques by a factor given by ratio of the angular resolution window to 4.pi.. In addition to being a neutron imager, this instrument will also be an excellent neutron spectrometer, and will be able to differentiate between different types of neutron sources (e.g. fission, alpha-n, cosmic ray, and D-D or D-T fusion). Moreover, the instrument is able to pinpoint the source location.

  6. PERSONNEL NEUTRON DOSIMETER

    DOEpatents

    Fitzgerald, J.J.; Detwiler, C.G. Jr.

    1960-05-24

    A description is given of a personnel neutron dosimeter capable of indicating the complete spectrum of the neutron dose received as well as the dose for each neutron energy range therein. The device consists of three sets of indium foils supported in an aluminum case. The first set consists of three foils of indium, the second set consists of a similar set of indium foils sandwiched between layers of cadmium, whereas the third set is similar to the second set but is sandwiched between layers of polyethylene. By analysis of all the foils the neutron spectrum and the total dose from neutrons of all energy levels can be ascertained.

  7. Organic metal neutron detector

    DOEpatents

    Butler, Michael A.; Ginley, David S.

    1987-01-01

    A device for detecting neutrons comprises a layer of conductive polymer sandwiched between electrodes, which may be covered on each face with a neutron transmissive insulating material layer. Conventional electrodes are used for a non-imaging integrating total neutron fluence-measuring embodiment, while wire grids are used in an imaging version of the device. The change in conductivity of the polymer after exposure to a neutron flux is determined in either case to provide the desired data. Alternatively, the exposed conductive polymer layer may be treated with a chemical reagent which selectively binds to the sites altered by neutrons to produce an image of the flux detected.

  8. Grazing incidence neutron optics

    NASA Technical Reports Server (NTRS)

    Gubarev, Mikhail V. (Inventor); Ramsey, Brian D. (Inventor); Engelhaupt, Darell E. (Inventor)

    2012-01-01

    Neutron optics based on the two-reflection geometries are capable of controlling beams of long wavelength neutrons with low angular divergence. The preferred mirror fabrication technique is a replication process with electroform nickel replication process being preferable. In the preliminary demonstration test an electroform nickel optics gave the neutron current density gain at the focal spot of the mirror at least 8 for neutron wavelengths in the range from 6 to 20 .ANG.. The replication techniques can be also be used to fabricate neutron beam controlling guides.

  9. Grazing Incidence Neutron Optics

    NASA Technical Reports Server (NTRS)

    Gubarev, Mikhail V. (Inventor); Ramsey, Brian D. (Inventor); Engelhaupt, Darell E. (Inventor)

    2013-01-01

    Neutron optics based on the two-reflection geometries are capable of controlling beams of long wavelength neutrons with low angular divergence. The preferred mirror fabrication technique is a replication process with electroform nickel replication process being preferable. In the preliminary demonstration test an electroform nickel optics gave the neutron current density gain at the focal spot of the mirror at least 8 for neutron wavelengths in the range from 6 to 20.ANG.. The replication techniques can be also be used to fabricate neutron beam controlling guides.

  10. Neutron activation analysis system

    DOEpatents

    Taylor, M.C.; Rhodes, J.R.

    1973-12-25

    A neutron activation analysis system for monitoring a generally fluid media, such as slurries, solutions, and fluidized powders, including two separate conduit loops for circulating fluid samples within the range of radiation sources and detectors is described. Associated with the first loop is a neutron source that emits s high flux of slow and thermal neutrons. The second loop employs a fast neutron source, the flux from which is substantially free of thermal neutrons. Adjacent to both loops are gamma counters for spectrographic determination of the fluid constituents. Other gsmma sources and detectors are arranged across a portion of each loop for deterMining the fluid density. (Official Gazette)

  11. A Conserved Mode of Protein Recognition and Binding in a ParD−ParE Toxin−Antitoxin Complex

    SciTech Connect

    Dalton, Kevin M.; Crosson, Sean

    2010-05-06

    Toxin-antitoxin (TA) systems form a ubiquitous class of prokaryotic proteins with functional roles in plasmid inheritance, environmental stress response, and cell development. ParDE family TA systems are broadly conserved on plasmids and bacterial chromosomes and have been well characterized as genetic elements that promote stable plasmid inheritance. We present a crystal structure of a chromosomally encoded ParD-ParE complex from Caulobacter crescentus at 2.6 {angstrom} resolution. This TA system forms an {alpha}{sub 2}{beta}{sub 2} heterotetramer in the crystal and in solution. The toxin-antitoxin binding interface reveals extensive polar and hydrophobic contacts of ParD antitoxin helices with a conserved recognition and binding groove on the ParE toxin. A cross-species comparison of this complex structure with related toxin structures identified an antitoxin recognition and binding subdomain that is conserved between distantly related members of the RelE/ParE toxin superfamily despite a low level of overall primary sequence identity. We further demonstrate that ParD antitoxin is dimeric, stably folded, and largely helical when not bound to ParE toxin. Thus, the paradigmatic model in which antitoxin undergoes a disorder-to-order transition upon toxin binding does not apply to this chromosomal ParD-ParE TA system.

  12. Rabies in humans and non-human in the state of Pará, Brazilian Amazon.

    PubMed

    Fernandes, Marcus Emanuel Barroncas; Costa, Lanna Jamile Corrêa da; Andrade, Fernanda Atanaena Gonçalves de; Silva, Lucila Pereira

    2013-01-01

    We evaluate the relationship of positive cases of rabies with the continuing expansion of livestock production, and analyse the trends of this zoonosis in human population in the state of Pará, Brazilian Amazon. The distribution of rabies cases was recorded between 1999 and 2004. Of 148 cases of rabies, 21% were in humans and 79% in non-human mammals. The rapid growth in livestock numbers seems to be associated with the increase of positive cases in bovine livestock transmitted by vampire bats. This idea is supported by positive and significant relationship of both events in time (p<0.01), but failed when spatial distribution among regions of the state was considered. However, rabies cases tend to occur toward the northeastern of the state of Pará, where rabies cases are proportionally five times greater than other mesoregions, suggesting that increased livestock production may influence the increase of this zoonosis. PMID:23477765

  13. Apoptosis and Tumor Resistance Conferred by Par-4

    PubMed Central

    Zhao, Yanming; Rangnekar, Vivek M.

    2009-01-01

    Par-4 is a tumor suppressor protein with a pro-apoptotic function. Epigenetic silencing of Par-4 is seen in diverse tumors, and Par-4 knockout mice develop spontaneous tumors in various tissues. Endogenous Par-4 is essential for sensitization of cells to diverse apoptotic stimuli, whereas ectopic expression of Par-4 can selectively induce apoptosis in cancer cells. The cancer-specific pro-apoptotic action of Par-4 resides in its centrally located SAC domain. This chapter reviews a novel mouse model with ubiquitous expression of the SAC domain. These SAC transgenic mice display normal development and life span, and, most importantly, are resistant to spontaneous, as well as oncogene-induced, autochthonous tumors. The tumor resistant phenotype and undetectable toxicity of SAC in vivo suggests the SAC domain possesses tremendous therapeutic potential. PMID:18836307

  14. NEUTRON DENSITY CONTROL IN A NEUTRONIC REACTOR

    DOEpatents

    Young, G.J.

    1959-06-30

    The method and means for controlling the neutron density in a nuclear reactor is described. It describes the method and means for flattening the neutron density distribution curve across the reactor by spacing the absorbing control members to varying depths in the central region closer to the center than to the periphery of the active portion of the reactor to provide a smaller neutron reproduction ratio in the region wherein the members are inserted, than in the remainder of the reactor thereby increasing the over-all potential power output.

  15. A new model for estimating boreal forest fPAR

    NASA Astrophysics Data System (ADS)

    Majasalmi, Titta; Rautiainen, Miina; Stenberg, Pauline

    2014-05-01

    Life on Earth is continuously sustained by the extraterrestrial flux of photosynthetically active radiation (PAR, 400-700 nm) from the sun. This flux is converted to biomass by chloroplasts in green vegetation. Thus, the fraction of absorbed PAR (fPAR) is a key parameter used in carbon balance studies, and is listed as one of the Essential Climate Variables (ECV). Temporal courses of fPAR for boreal forests are difficult to measure, because of the complex 3D structures. Thus, they are most often estimated based on models which quantify the dependency of absorbed radiation on canopy structure. In this study, we adapted a physically-based canopy radiation model into a fPAR model, and compared modeled and measured fPAR in structurally different boreal forest stands. The model is based on the spectral invariants theory, and uses leaf area index (LAI), canopy gap fractions and spectra of foliage and understory as input data. The model differs from previously developed more detailed fPAR models in that the complex 3D structure of coniferous forests is described using an aggregated canopy parameter - photon recollision probability p. The strength of the model is that all model inputs are measurable or available through other simple models. First, the model was validated with measurements of instantaneous fPAR obtained with the TRAC instrument in nine Scots pine, Norway spruce and Silver birch stands in a boreal forest in southern Finland. Good agreement was found between modeled and measured fPAR. Next, we applied the model to predict temporal courses of fPAR using data on incoming radiation from a nearby flux tower and sky irradiance models. Application of the model to simulate diurnal and seasonal values of fPAR indicated that the ratio of direct-to-total incident radiation and leaf area index are the key factors behind the magnitude and variation of stand-level fPAR values.

  16. 2. HI PAR (ACQUISITION RADAR) TOWER AND ENLISTED MEN (EM) ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    2. HI PAR (ACQUISITION RADAR) TOWER AND ENLISTED MEN (EM) BARRACKS WITH RADAR ATTACHED. - Nike Hercules Missile Battery Summit Site, Battery Control Administration & Barracks Building, Anchorage, Anchorage, AK

  17. Neutron chopper development at LANSCE

    SciTech Connect

    Nutter, M.; Lewis, L.; Tepper, S.; Silver, R.N.; Heffner, R.H.

    1985-01-01

    Progress is reported on neutron chopper systems for the Los Alamos Neutron Scattering Center pulsed spallation neutron source. This includes the development of 600+ Hz active magnetic bearing neutron chopper and a high speed control system designed to operate with the Proton Storage Ring to phase the chopper to the neutron source. 5 refs., 3 figs.

  18. Neutron metrology laboratory facility simulation.

    PubMed

    Pereira, Mariana; Salgado, Ana P; Filho, Aidano S; Pereira, Walsan W; Patrão, Karla C S; Fonseca, Evaldo S

    2014-10-01

    The Neutron Low Scattering Laboratory in Brazil has been completely rebuilt. Evaluation of air attenuation parameters and neutron component scattering in the room was done using Monte Carlo simulation code. Neutron fields produced by referenced neutron source were used to calculate neutron scattering and air attenuation.

  19. Neutron metrology laboratory facility simulation.

    PubMed

    Pereira, Mariana; Salgado, Ana P; Filho, Aidano S; Pereira, Walsan W; Patrão, Karla C S; Fonseca, Evaldo S

    2014-10-01

    The Neutron Low Scattering Laboratory in Brazil has been completely rebuilt. Evaluation of air attenuation parameters and neutron component scattering in the room was done using Monte Carlo simulation code. Neutron fields produced by referenced neutron source were used to calculate neutron scattering and air attenuation. PMID:24864318

  20. Binary Neutron Star Mergers with Initial Spin

    NASA Astrophysics Data System (ADS)

    Kastaun, Wolfgang; Galeazzi, Filippo

    2015-04-01

    Recently, we performed simulations of binary neutron star mergers which included both nuclear physics equations of state and stars with initial spin for the first time. The focus was on systems resulting in hyper-massive neutron stars. I will discuss the influence of realistic amounts of spin on the outcome, in particular regarding the gravitational wave signal. We also investigated the structure and dynamics of the remnant in detail, revealing some interesting new aspects. For example, we observe rotational profiles not fitting the standard notion of a rapidly rotating core, and show that strong quasi-radial oscillations in the post merger phase have an impact on the gravitational wave spectrum via a modulation of the m=2 mode frequency, offering an alternative to recent interpretations of high frequency side-peaks as non-linear combination frequencies. Finally, we discuss a possible mechanism in which the initial neutron star spins can influence the amount of ejected matter in some cases.

  1. Intrinsic and integrative properties of substantia nigra pars reticulata neurons

    PubMed Central

    Zhou, Fu-Ming; Lee, Christian R.

    2011-01-01

    The GABA projection neurons of the substantia nigra pars reticulata (SNr) are output neurons for the basal ganglia and thus critical for movement control. Their most striking neurophysiological feature is sustained, spontaneous high frequency spike firing. A fundamental question is: what are the key ion channels supporting the remarkable firing capability in these neurons? Recent studies indicate that these neurons express tonically active TRPC3 channels that conduct a Na-dependent inward current even at hyperpolarized membrane potentials. When the membrane potential reaches −60 mV, a voltage-gated persistent sodium current (INaP) starts to activate, further depolarizing the membrane potential. At or slightly below −50 mV, the large transient voltage-activated sodium current (INaT) starts to activate and eventually triggers the rapid rising phase of action potentials. SNr GABA neurons have a higher density of (INaT), contributing to the faster rise and larger amplitude of action potentials, compared with the slow-spiking dopamine neurons. INaT also recovers from inactivation more quickly in SNr GABA neurons than in nigral dopamine neurons. In SNr GABA neurons, the rising phase of the action potential triggers the activation of high-threshold, inactivation-resistant Kv3-like channels that can rapidly repolarize the membrane. These intrinsic ion channels provide SNr GABA neurons with the ability to fire spontaneous and sustained high frequency spikes. Additionally, robust GABA inputs from direct pathway medium spiny neurons in the striatum and GABA neurons in the globus pallidus may inhibit and silence SNr GABA neurons, whereas glutamate synaptic input from the subthalamic nucleus may induce burst firing in SNr GABA neurons. Thus, afferent GABA and glutamate synaptic inputs sculpt the tonic high frequency firing of SNr GABA neurons and the consequent inhibition of their targets into an integrated motor control signal that is further fine-tuned by neuromodulators

  2. Neutron sources and applications

    SciTech Connect

    Price, D.L.; Rush, J.J.

    1994-01-01

    Review of Neutron Sources and Applications was held at Oak Brook, Illinois, during September 8--10, 1992. This review involved some 70 national and international experts in different areas of neutron research, sources, and applications. Separate working groups were asked to (1) review the current status of advanced research reactors and spallation sources; and (2) provide an update on scientific, technological, and medical applications, including neutron scattering research in a number of disciplines, isotope production, materials irradiation, and other important uses of neutron sources such as materials analysis and fundamental neutron physics. This report summarizes the findings and conclusions of the different working groups involved in the review, and contains some of the best current expertise on neutron sources and applications.

  3. Transcriptome profiling reveals links between ParS/ParR, MexEF-OprN, and quorum sensing in the regulation of adaptation and virulence in Pseudomonas aeruginosa

    PubMed Central

    2013-01-01

    Background The ParS/ParR two component regulatory system plays critical roles for multidrug resistance in Pseudomonas aeruginosa. It was demonstrated that in the presence of antimicrobials, ParR enhances bacterial survival by distinct mechanisms including activation of the mexXY efflux genes, enhancement of lipopolysaccharide modification through the arn operon, and reduction of the expression of oprD porin. Results In this study, we report on transcriptomic analyses of P. aeruginosa PAO1 wild type and parS and parR mutants growing in a defined minimal medium. Our transcriptomic analysis provides the first estimates of transcript abundance for the 5570 coding genes in P. aeruginosa PAO1. Comparative transcriptomics of P. aeruginosa PAO1 and par mutants identified a total of 464 genes regulated by ParS and ParR. Results also showed that mutations in the parS/parR system abolished expression of the mexEF-oprN operon by down-regulating the regulatory gene mexS. In addition to the known effects on drug resistance genes, transcript abundances of the quorum sensing genes (rhlIR and pqsABCDE-phnAB) were higher in both parS and parR mutants. In accordance with these results, a significant portion of the ParS/ParR regulated genes belonged to the MexEF-OprN and quorum sensing regulons. Deletion of the par genes also led to increased phenazine production and swarming motility, consistent with the up-regulation of the phenazine and rhamnolipid biosynthetic genes, respectively. Conclusion Our results link the ParS/ParR two component signal transduction system to MexEF-OprN and quorum sensing systems in P. aeruginosa. These results expand our understanding of the roles of the ParS/ParR system in the regulation of gene expression in P. aeruginosa, especially in the absence of antimicrobials. PMID:24034668

  4. ATR neutron spectral characterization

    SciTech Connect

    Rogers, J.W.; Anderl, R.A.

    1995-11-01

    The Advanced Test Reactor (ATR) at INEL provides intense neutron fields for irradiation-effects testing of reactor material samples, for production of radionuclides used in industrial and medical applications, and for scientific research. Characterization of the neutron environments in the irradiation locations of the ATR has been done by means of neutronics calculations and by means of neutron dosimetry based on the use of neutron activation monitors that are placed in the various irradiation locations. The primary purpose of this report is to present the results of an extensive characterization of several ATR irradiation locations based on neutron dosimetry measurements and on least-squares-adjustment analyses that utilize both neutron dosimetry measurements and neutronics calculations. This report builds upon the previous publications, especially the reference 4 paper. Section 2 provides a brief description of the ATR and it tabulates neutron spectral information for typical irradiation locations, as derived from the more historical neutron dosimetry measurements. Relevant details that pertain to the multigroup neutron spectral characterization are covered in section 3. This discussion includes a presentation on the dosimeter irradiation and analyses and a development of the least-squares adjustment methodology, along with a summary of the results of these analyses. Spectrum-averaged cross sections for neutron monitoring and for displacement-damage prediction in Fe, Cr, and Ni are given in section 4. In addition, section4 includes estimates of damage generation rates for these materials in selected ATR irradiation locations. In section 5, the authors present a brief discussion of the most significant conclusions of this work and comment on its relevance to the present ATR core configuration. Finally, detailed numerical and graphical results for the spectrum-characterization analyses in each irradiation location are provided in the Appendix.

  5. Mechanism of DNA Segregation in Prokaryotes: Replicon Pairing by parC of Plasmid R1

    NASA Astrophysics Data System (ADS)

    Jensen, Rasmus Bugge; Lurz, Rudi; Gerdes, Kenn

    1998-07-01

    Prokaryotic chromosomes and plasmids encode partitioning systems that are required for DNA segregation at cell division. The systems are thought to be functionally analogous to eukaryotic centromeres and to play a general role in DNA segregation. The parA system of plasmid R1 encodes two proteins ParM and ParR, and a cis-acting centromere-like site denoted parC. The ParR protein binds to parC in vivo and in vitro. The ParM protein is an ATPase that interacts with ParR specifically bound to parC. Using electron microscopy, we show here that parC mediates efficient pairing of plasmid molecules. The pairing requires binding of ParR to parC and is stimulated by the ParM ATPase. The ParM mediated stimulation of plasmid pairing is dependent on ATP hydrolysis by ParM. Using a ligation kinetics assay, we find that ParR stimulates ligation of parC-containing DNA fragments. The rate-of-ligation was increased by wild type ParM protein but not by mutant ParM protein deficient in the ATPase activity. Thus, two independent assays show that parC mediates pairing of plasmid molecules in vitro. These results are consistent with the proposal that replicon pairing is part of the mechanism of DNA segregation in prokaryotes.

  6. Introduction to neutron stars

    SciTech Connect

    Lattimer, James M.

    2015-02-24

    Neutron stars contain the densest form of matter in the present universe. General relativity and causality set important constraints to their compactness. In addition, analytic GR solutions are useful in understanding the relationships that exist among the maximum mass, radii, moments of inertia, and tidal Love numbers of neutron stars, all of which are accessible to observation. Some of these relations are independent of the underlying dense matter equation of state, while others are very sensitive to the equation of state. Recent observations of neutron stars from pulsar timing, quiescent X-ray emission from binaries, and Type I X-ray bursts can set important constraints on the structure of neutron stars and the underlying equation of state. In addition, measurements of thermal radiation from neutron stars has uncovered the possible existence of neutron and proton superfluidity/superconductivity in the core of a neutron star, as well as offering powerful evidence that typical neutron stars have significant crusts. These observations impose constraints on the existence of strange quark matter stars, and limit the possibility that abundant deconfined quark matter or hyperons exist in the cores of neutron stars.

  7. Neutron and gamma irradiation effects on power semiconductor switches

    NASA Technical Reports Server (NTRS)

    Schwarze, G. E.; Frasca, A. J.

    1990-01-01

    The performance characteristics of high-power semiconductor switches subjected to high levels of neutron fluence and gamma dose must be known by the designer of the power conditioning, control and transmission subsystem of space nuclear power systems. Location and the allowable shielding mass budget will determine the level of radiation tolerance required by the switches to meet performance and reliability requirements. Neutron and gamma ray interactions with semiconductor materials and how these interactions affect the electrical and switching characteristics of solid state power switches is discussed. The experimental measurement system and radiation facilities are described. Experimental data showing the effects of neutron and gamma irradiation on the performance characteristics are given for power-type NPN Bipolar Junction Transistors (BJTs), and Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs). BJTs show a rapid decrease in gain, blocking voltage, and storage time for neutron irradiation, and MOSFETs show a rapid decrease in the gate threshold voltage for gamma irradiation.

  8. Neutron and gamma irradiation effects on power semiconductor switches

    NASA Technical Reports Server (NTRS)

    Schwarze, G. E.; Frasca, A. J.

    1990-01-01

    The performance characteristics of high power semiconductor switches subjected to high levels of neutron fluence and gamma dose must be known by the designer of the power conditioning, control and transmission subsystem of space nuclear power systems. Location and the allowable shielding mass budget will determine the level of radiation tolerance required by the switches to meet performance and reliability requirements. Neutron and gamma ray interactions with semiconductor materials and how these interactions affect the electrical and switching characteristics of solid state power switches is discussed. The experimental measurement system and radiation facilities are described. Experimental data showing the effects of neutron and gamma irradiation on the performance characteristics are given for power-type NPN Bipolar Junction Transistors (BJTs), and Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs). BJTs show a rapid decrease in gain, blocking voltage, and storage time for neutron irradiation, and MOSFETs show a rapid decrease in the gate threshold voltage for gamma irradiation.

  9. Neutron-emission measurements at a white neutron source

    SciTech Connect

    Haight, Robert C

    2010-01-01

    Data on the spectrum of neutrons emittcd from neutron-induced reactions are important in basic nuclear physics and in applications. Our program studies neutron emission from inelastic scattering as well as fission neutron spectra. A ''white'' neutron source (continuous in energy) allows measurements over a wide range of neutron energies all in one experiment. We use the tast neutron source at the Los Alamos Neutron Science Center for incident neutron energies from 0.5 MeV to 200 MeV These experiments are based on double time-of-flight techniques to determine the energies of the incident and emitted neutrons. For the fission neutron measurements, parallel-plate ionization or avalanche detectors identify fission in actinide samples and give the required fast timing pulse. For inelastic scattering, gamma-ray detectors provide the timing and energy spectroscopy. A large neutron-detector array detects the emitted neutrons. Time-of-flight techniques are used to measure the energies of both the incident and emitted neutrons. Design considerations for the array include neutron-gamma discrimination, neutron energy resolution, angular coverage, segmentation, detector efficiency calibration and data acquisition. We have made preliminary measurements of the fission neutron spectra from {sup 235}U, {sup 238}U, {sup 237}Np and {sup 239}Pu. Neutron emission spectra from inelastic scattering on iron and nickel have also been investigated. The results obtained will be compared with evaluated data.

  10. Proteases in agricultural dust induce lung inflammation through PAR-1 and PAR-2 activation.

    PubMed

    Romberger, Debra J; Heires, Art J; Nordgren, Tara M; Souder, Chelsea P; West, William; Liu, Xiang-de; Poole, Jill A; Toews, Myron L; Wyatt, Todd A

    2015-08-15

    Workers exposed to aerosolized dust present in concentrated animal feeding operations (CAFOs) are susceptible to inflammatory lung diseases, such as chronic obstructive pulmonary disease. Extracts of dust collected from hog CAFOs [hog dust extract (HDE)] are potent stimulators of lung inflammatory responses in several model systems. The observation that HDE contains active proteases prompted the present study, which evaluated the role of CAFO dust proteases in lung inflammatory processes and tested whether protease-activated receptors (PARs) are involved in the signaling pathway for these events. We hypothesized that the damaging proinflammatory effect of HDE is due, in part, to the proteolytic activation of PARs, and inhibiting the proteases in HDE or disrupting PAR activation would attenuate HDE-mediated inflammatory indexes in bronchial epithelial cells (BECs), in mouse lung slices in vitro, and in a murine in vivo exposure model. Human BECs and mouse lung slice cultures stimulated with 5% HDE released significantly more of each of the cytokines measured (IL-6, IL-8, TNF-α, keratinocyte-derived chemokine/CXC chemokine ligand 1, and macrophage inflammatory protein-2/CXC chemokine ligand 2) than controls, and these effects were markedly diminished by protease inhibition. Inhibition of PARs also blunted the HDE-induced cytokine release from BECs. In addition, protease depletion inhibited HDE-induced BEC intracellular PKCα and PKCε activation. C57BL/6J mice administered 12.5% HDE intranasally, either once or daily for 3 wk, exhibited increased total cellular and neutrophil influx, bronchial alveolar fluid inflammatory cytokines, lung histopathology, and inflammatory scores compared with mice receiving protease-depleted HDE. These data suggest that proteases in dust from CAFOs are important mediators of lung inflammation, and these proteases and their receptors may provide novel targets for therapeutic intervention in CAFO dust-induced airways disease.

  11. Proteases in agricultural dust induce lung inflammation through PAR-1 and PAR-2 activation.

    PubMed

    Romberger, Debra J; Heires, Art J; Nordgren, Tara M; Souder, Chelsea P; West, William; Liu, Xiang-de; Poole, Jill A; Toews, Myron L; Wyatt, Todd A

    2015-08-15

    Workers exposed to aerosolized dust present in concentrated animal feeding operations (CAFOs) are susceptible to inflammatory lung diseases, such as chronic obstructive pulmonary disease. Extracts of dust collected from hog CAFOs [hog dust extract (HDE)] are potent stimulators of lung inflammatory responses in several model systems. The observation that HDE contains active proteases prompted the present study, which evaluated the role of CAFO dust proteases in lung inflammatory processes and tested whether protease-activated receptors (PARs) are involved in the signaling pathway for these events. We hypothesized that the damaging proinflammatory effect of HDE is due, in part, to the proteolytic activation of PARs, and inhibiting the proteases in HDE or disrupting PAR activation would attenuate HDE-mediated inflammatory indexes in bronchial epithelial cells (BECs), in mouse lung slices in vitro, and in a murine in vivo exposure model. Human BECs and mouse lung slice cultures stimulated with 5% HDE released significantly more of each of the cytokines measured (IL-6, IL-8, TNF-α, keratinocyte-derived chemokine/CXC chemokine ligand 1, and macrophage inflammatory protein-2/CXC chemokine ligand 2) than controls, and these effects were markedly diminished by protease inhibition. Inhibition of PARs also blunted the HDE-induced cytokine release from BECs. In addition, protease depletion inhibited HDE-induced BEC intracellular PKCα and PKCε activation. C57BL/6J mice administered 12.5% HDE intranasally, either once or daily for 3 wk, exhibited increased total cellular and neutrophil influx, bronchial alveolar fluid inflammatory cytokines, lung histopathology, and inflammatory scores compared with mice receiving protease-depleted HDE. These data suggest that proteases in dust from CAFOs are important mediators of lung inflammation, and these proteases and their receptors may provide novel targets for therapeutic intervention in CAFO dust-induced airways disease. PMID

  12. Proteases in agricultural dust induce lung inflammation through PAR-1 and PAR-2 activation

    PubMed Central

    Heires, Art J.; Nordgren, Tara M.; Souder, Chelsea P.; West, William; Liu, Xiang-de; Poole, Jill A.; Toews, Myron L.; Wyatt, Todd A.

    2015-01-01

    Workers exposed to aerosolized dust present in concentrated animal feeding operations (CAFOs) are susceptible to inflammatory lung diseases, such as chronic obstructive pulmonary disease. Extracts of dust collected from hog CAFOs [hog dust extract (HDE)] are potent stimulators of lung inflammatory responses in several model systems. The observation that HDE contains active proteases prompted the present study, which evaluated the role of CAFO dust proteases in lung inflammatory processes and tested whether protease-activated receptors (PARs) are involved in the signaling pathway for these events. We hypothesized that the damaging proinflammatory effect of HDE is due, in part, to the proteolytic activation of PARs, and inhibiting the proteases in HDE or disrupting PAR activation would attenuate HDE-mediated inflammatory indexes in bronchial epithelial cells (BECs), in mouse lung slices in vitro, and in a murine in vivo exposure model. Human BECs and mouse lung slice cultures stimulated with 5% HDE released significantly more of each of the cytokines measured (IL-6, IL-8, TNF-α, keratinocyte-derived chemokine/CXC chemokine ligand 1, and macrophage inflammatory protein-2/CXC chemokine ligand 2) than controls, and these effects were markedly diminished by protease inhibition. Inhibition of PARs also blunted the HDE-induced cytokine release from BECs. In addition, protease depletion inhibited HDE-induced BEC intracellular PKCα and PKCε activation. C57BL/6J mice administered 12.5% HDE intranasally, either once or daily for 3 wk, exhibited increased total cellular and neutrophil influx, bronchial alveolar fluid inflammatory cytokines, lung histopathology, and inflammatory scores compared with mice receiving protease-depleted HDE. These data suggest that proteases in dust from CAFOs are important mediators of lung inflammation, and these proteases and their receptors may provide novel targets for therapeutic intervention in CAFO dust-induced airways disease. PMID

  13. Neutron elastic backscattering with resonance enhancement

    SciTech Connect

    Gomberg, H.J.; McEllistrem, M.T.

    1993-12-31

    Reliable detection of explosives and narcotics depends on generating signatures of compounds which characterize them. Major explosives and also alkaloid narcotics contain unique concentrations of Carbon, Oxygen, and Nitrogen which provide specific elemental ratios and chemical signatures. Neutron-induced reaction methods are rapid and non-invasive means of probing container interiors for special element-ratio signatures which signal the presence of significant amounts of contraband. Among these reactions the highest probabilities occur for neutron from different light elements, allowing determination of relative abundance of these elements. The authors have already demonstrated signature for simulated explosives and simulated narcotics in experimental tests at 1-4 MeV at the University of Kentucky accelerator labs. Intensities of neutron scatter at angles near 150{degrees} from three different elements, C, N, and O, were determined. Fast neutron time-of-flight detection methods enabled measurement of neutron energies, and thus separation of scattering from the different elements. Making measurements on and off strong resonances for specific elements, increases PFD and reduces PFA. Measurements illustrating this resonance enhancement technique will be presented.

  14. Neutrons on a surface of liquid helium

    NASA Astrophysics Data System (ADS)

    Grigoriev, P. D.; Zimmer, O.; Grigoriev, A. D.; Ziman, T.

    2016-08-01

    We investigate the possibility of ultracold neutron (UCN) storage in quantum states defined by the combined potentials of the Earth's gravity and the neutron optical repulsion by a horizontal surface of liquid helium. We analyze the stability of the lowest quantum state, which is most susceptible to perturbations due to surface excitations, against scattering by helium atoms in the vapor and by excitations of the liquid, comprised of ripplons, phonons, and surfons. This is an unusual scattering problem since the kinetic energy of the neutron parallel to the surface may be much greater than the binding energies perpendicular. The total scattering time of these UCNs at 0.7 K is found to exceed 1 h, and rapidly increases with decreasing temperature. Such low scattering rates should enable high-precision measurements of the sequence of discrete energy levels, thus providing improved tests of short-range gravity. The system might also be useful for neutron β -decay experiments. We also sketch new experimental propositions for level population and trapping of ultracold neutrons above a flat horizontal mirror.

  15. The Neutron Star Zoo

    NASA Technical Reports Server (NTRS)

    Harding, Alice K.

    2014-01-01

    Neutron stars are a very diverse population, both in their observational and their physical properties. They prefer to radiate most of their energy at X-ray and gamma-ray wavelengths. But whether their emission is powered by rotation, accretion, heat, magnetic fields or nuclear reactions, they are all different species of the same animal whose magnetic field evolution and interior composition remain a mystery. This article will broadly review the properties of inhabitants of the neutron star zoo, with emphasis on their high-energy emission. XXX Neutron stars are found in a wide variety of sources, displaying an amazing array of behavior. They can be isolated or in binary systems, accreting, heating, cooling, spinning down, spinning up, pulsing, flaring and bursting. The one property that seems to determine their behavior most strongly is their magnetic field strength, structure and evolution. The hot polar caps, bursts and flares of magnetars are likely due to the rapid decay and twisting of their superstrong magnetic fields, whose very existence requires some kind of early dynamo activity. The intermediate-strength magnetic fields of RPPs determines their spin-down behavior and radiation properties. However, the overlap of the magnetar and RPP populations is not understood at present. Why don't high-field RPPs burst or flare? Why don't lower-field magnetars sometimes behave more like RPPs? INS may be old magnetars whose high fields have decayed, but they do not account for the existence of younger RPPs with magnetar-strength fields. Not only the strength of the magnetic field but also its configuration may be important in making a NS a magnetar or a RPP. Magnetic field decay is a critical link between other NS populations as well. "Decay" of the magnetic field is necessary for normal RPPs to evolve into MSPs through accretion and spin up in LMXBs. Some kind of accretion-driven field reduction is the most likely mechanism, but it is controversial since it is not

  16. Neutron spin echo study of the dynamics of undercooled selenium

    NASA Astrophysics Data System (ADS)

    Simon, Ch.; Faivre, G.; Zorn, R.; Batallan, F.; Legrand, J. F.

    1992-03-01

    We present neutron spin echo measurements on the structural relaxation of undercooled liquid selenium above glass transition. We find a two-stage relaxation process essentially similar to that generally observed in liquids, except for the fact that the slow-stage characteristic time tau_1 varies with the temperature T more slowly than η(T)/T, where η(T) is the macroscopic viscosity. We interpret this apparent discrepancy with respect to the usually found scaling law as the manifestation of the equilibrium-polymer nature of liquid selenium. On the other hand, the data suggest that the Kohlrausch exponent of the slow stage is temperature dependent. Concerning the rapid stage of the relaxation, we show that a possible alternative to the mode-coupling interpretation is to attribute it to the existence of local inhomogeneities of the density close to the glass transition. Nous présentons des résultats de mesures au spectromètre à écho de spin sur la relaxation structurale du sélenium en surfusion près de la transition vitreuse. Nous trouvons une relaxation en deux étapes, essentiellement conforme à celle trouvée antérieurement dans d'autres liquides, à ceci près que le temps caractéristique tau_1 du stade lent varie avec la température T plus lentement que η(T)/T, où η(T) est la viscosité macroscopique. Nous interprétons cet écart apparent à la loi d'échelle généralement observée comme la manifestation du fait que le sélénium liquide est un polymère d'équilibre. L'analyse des données suggège d'autre part que l'exposant de Kohlrausch du stade lent dépend de la température. Quant au stade rapide de la relaxation, nous montrons qu'il peut être interprété, sans recourir à la théorie du couplage de modes, par l'existance d'hétérogénéités locales de la densité au voisinage de la transition vitreuse.

  17. SPRY1 promotes the degradation of uPAR and inhibits uPAR-mediated cell adhesion and proliferation

    PubMed Central

    Liu, Xiufeng; Lan, Yan; Zhang, Di; Wang, Kai; Wang, Yao; Hua, Zi-Chun

    2014-01-01

    Urokinase plasminogen activator receptor (uPAR) is a GPI anchored cell surface protein that is closely associated with invasion, migration, and metastasis of cancer cells. Many functional extracellular proteins and transmembrane receptors interact with uPAR. However, few studies have examined the association of uPAR with cytoplasm proteins. We previously used yeast two-hybrid screening to isolate several novel uPAR-interacting cytoplasmic proteins, including Sprouty1 (SPRY1), an inhibitor of the (Ras-mitogen-activated protein kinase) MAPK pathway. In this study, we show that SPRY1 interacts with uPAR and directs it toward lysosomal-mediated degradation. Overexpression of SPRY1 decreased the cell surface and cytoplasmic uPAR protein level. Moreover, SPRY1 overexpression augmented uPAR-induced cell adhesion to vitronectin as well as proliferation of cancer cells. Our results also further support the critical role of SPRY1 contribution to tumor growth. In a subcutaneous tumor model, overexpression of SPRY1 in HCT116 or A549 xenograft in athymic nude mice led to great suppression of tumor growth. These results show that SPRY1 may affect tumor cell function through direct interaction with uPAR and promote its lysosomal degradation. PMID:25520860

  18. Influence of thermal and resonance neutron on fast neutron flux measurement by 239Pu fission chamber

    NASA Astrophysics Data System (ADS)

    Zeng, Li-Na; Wang, Qiang; Song, Ling-Li; Zheng, Chun

    2015-01-01

    The 239Pu fission chambers are widely used to measure fission spectrum neutron flux due to a flat response to fast neutrons. However, in the meantime the resonance and thermal neutrons can cause a significant influence on the measurement if they are moderated, which could be eliminated by using 10B and Cd covers. At a column enriched uranium fast neutron critical assembly, the fission reaction rates of 239Pu are measured as 1.791×10-16, 2.350×10-16 and 1.385×10-15 per second for 15 mm thick 10B cover, 0.5 mm thick Cd cover, and no cover respectively, while the fission reaction rate of 239Pu is rapidly increased to 2.569×10-14 for a 20 mm thick polythene covering fission chamber. The average 239Pu fission cross-section of thermal and resonance neutrons is calculated to be 500 b and 24.95 b with the assumption of 1/v and 1/E spectra respectively, then thermal, resonance and fast neutron flux are achieved to be 2.30×106, 2.24×106 and 1.04×108 cm-2·s-1.

  19. Understanding Neutron Stars using Thermonuclear X-ray Bursts

    NASA Technical Reports Server (NTRS)

    Bhattacharyya, S.

    2007-01-01

    Studies of thermonuclear X-ray bursts can be very useful to constrain the spin rate, mass and radius of a neutron star = EOS model of high density cold matter in the neutron star cores. Extensive observation and analysis of the data from the rising portions of the bursts = modeling of burst oscillations and thermonuclear flame spreading. Theoretical study of thermonuclear flame spreading on the rapidly spinning neutron stars should be done considering all the main physical effects (including magnetic field, nuclear energy generation, Coriolis effect, strong gravity, etc.).

  20. Neutron Stars and Thermonuclear X-ray Bursts

    NASA Technical Reports Server (NTRS)

    Bhattacharyya, Sudip

    2007-01-01

    Studies of thermonuclear X-ray bursts can be very useful to constrain the spin rate, mass and radius of a neutron star approaching EOS model of high density cold matter in the neutron star cores. +k Extensive observation and analysis of the data from the rising portions of the bursts - modeling of burst oscillations and thermonuclear flame spreading. +k Theoretical study of thermonuclear flame spreading on the rapidly spinning neutron stars should be done considering all the main physical effects (including magnetic field, nuclear energy generation, Coriolis effect, strong gravity, etc.).

  1. INJECTION CHOICE FOR SPALLATION NEUTRON SOURCE RING.

    SciTech Connect

    WEI,J.; BEEBE-WANG,J.; BLASKIEWICZ,M.; BRODOWSKI,J.; FEDOTOV,A.; GARDNER,C.; LEE,Y.Y.; RAPARIA,D.; DANILOV,V.; HOLMES,J.; PRIOR,C.; REES,G.; MACHIDA,S.

    2001-06-18

    Injection is key in the low-loss design of high-intensity proton facilities like the Spallation Neutron Source (SNS). During the design of both the accumulator and the rapid-cycling-synchrotron version of the SNS, extensive comparison has been made to select injection scenarios that satisfy SNS's low-loss design criteria. This paper presents issues and considerations pertaining to the final choice of the SNS injection systems.

  2. Neutron capture therapies

    SciTech Connect

    Yanch, J.C.; Shefer, R.E.; Klinkowstein, R.E.

    1999-11-02

    In one embodiment there is provided an application of the {sup 10}B(n,{alpha}){sup 7}Li nuclear reaction or other neutron capture reactions for the treatment of rheumatoid arthritis. This application, called Boron Neutron Capture Synovectomy (BNCS), requires substantially altered demands on neutron beam design than for instance treatment of deep seated tumors. Considerations for neutron beam design for the treatment of arthritic joints via BNCS are provided for, and comparisons with the design requirements for Boron Neutron Capture Therapy (BNCT) of tumors are made. In addition, exemplary moderator/reflector assemblies are provided which produce intense, high-quality neutron beams based on (p,n) accelerator-based reactions. In another embodiment there is provided the use of deuteron-based charged particle reactions to be used as sources for epithermal or thermal neutron beams for neutron capture therapies. Many d,n reactions (e.g. using deuterium, tritium or beryllium targets) are very prolific at relatively low deuteron energies.

  3. Fundamental Neutron Physics

    NASA Astrophysics Data System (ADS)

    Marciano, William J.

    A precise connection between Vud, gA ≡ GA/GV and rn is reviewed. Implications for CKM unitarity and muon capture are discussed. The neutron electric dipole moment and CP violation in H → yy are related. ΔB = 2 n oscillations are shown to probe the neutron's Majorana nature and provide a possible paradigm for dark matter behavior.

  4. NEUTRONIC REACTOR CONTROL

    DOEpatents

    Untermyer, S.; Hutter, E.

    1959-08-01

    This patent relates to "shadow" control of a nuclear reactor. The control means comprises a plurality ot elongated rods disposed adjacent and parallel to each other, The morphology and effects of gases generated within sections of neutron absorbing materials and equal length sections of neutron permeable materials together with means for longitudinally pcsitioning the rcds relative to each other.

  5. Neutron capture therapies

    DOEpatents

    Yanch, Jacquelyn C.; Shefer, Ruth E.; Klinkowstein, Robert E.

    1999-01-01

    In one embodiment there is provided an application of the .sup.10 B(n,.alpha.).sup.7 Li nuclear reaction or other neutron capture reactions for the treatment of rheumatoid arthritis. This application, called Boron Neutron Capture Synovectomy (BNCS), requires substantially altered demands on neutron beam design than for instance treatment of deep seated tumors. Considerations for neutron beam design for the treatment of arthritic joints via BNCS are provided for, and comparisons with the design requirements for Boron Neutron Capture Therapy (BNCT) of tumors are made. In addition, exemplary moderator/reflector assemblies are provided which produce intense, high-quality neutron beams based on (p,n) accelerator-based reactions. In another embodiment there is provided the use of deuteron-based charged particle reactions to be used as sources for epithermal or thermal neutron beams for neutron capture therapies. Many d,n reactions (e.g. using deuterium, tritium or beryllium targets) are very prolific at relatively low deuteron energies.

  6. Control of cleavage spindle orientation in Caenorhabditis elegans: The role of the genes par-2 and par-3

    SciTech Connect

    Cheng, N.N.; Kirby, C.M.; Kemphues, K.J.

    1995-02-01

    Polarized asymmetric divisions play important roles in the development of plants and animals. The first two embryonic cleavages of Caenorhabditis elegans provide an opportunity to study the mechanisms controlling polarized asymmetric divisions. The first cleavage is unequal, producing daughters with different sizes and fates. The daughter blastomeres divide with different orientations at the second cleavage; the anterior blastomere divides equally across the long axis of the egg, whereas the posterior blastomere divides unequally along the long axis. We report here the results of our analysis of the genes par-2 and par-3 with respect to their contribution to the polarity of these divisions. Strong loss-of-function mutations in both genes lead to an equal first cleavage and an altered second cleavage. Interestingly, the mutations exhibit striking gene-specific differences at the second cleavage. The par-2 mutations lead to transverse spindle orientations in both blastomeres, whereas par-3 mutations lead to longitudinal spindle orientations in both blastomeres. The spindle orientation defects correlate with defects in centrosome movements during both the first and the second cell cycle. Temperature shift experiments with par-2 (it5ts) indicate that the par-2(+) activity is not required after the two-cell stage. Analysis of double mutants shows that par-3 is epistatic to par-2. We propose a model wherein par-2(+) and par-3(+) act in concert during the first cell cycle to affect asymmetric modification of the cytoskeleton. This polar modification leads to different behaviors of centrosomes in the anterior and posterior and leads ultimately to blastomere-specific spindle orientations at the second cleavage. 44 refs., 5 figs., 5 tabs.

  7. Pocked surface neutron detector

    DOEpatents

    McGregor, Douglas; Klann, Raymond

    2003-04-08

    The detection efficiency, or sensitivity, of a neutron detector material such as of Si, SiC, amorphous Si, GaAs, or diamond is substantially increased by forming one or more cavities, or holes, in its surface. A neutron reactive material such as of elemental, or any compound of, .sup.10 B, .sup.6 Li, .sup.6 LiF, U, or Gd is deposited on the surface of the detector material so as to be disposed within the cavities therein. The portions of the neutron reactive material extending into the detector material substantially increase the probability of an energetic neutron reaction product in the form of a charged particle being directed into and detected by the neutron detector material.

  8. Neutrons against cancer

    NASA Astrophysics Data System (ADS)

    Dovbnya, A. N.; Kuplennikov, E. L.; Kandybey, S. S.; Krasiljnikov, V. V.

    2014-09-01

    The review is devoted to the analysis and generalization of the research carried out during recent years in industrially advanced countries on the use of fast, epithermal, and thermal neutrons for therapy of malignant tumors. Basic facilities for neutron production used for cancer treatment are presented. Optimal parameters of therapeutic beams are described. Techniques using neutrons of different energy regions are discussed. Results and medical treatment efficiency are given. Comparison of the current state of neutron therapy of tumors and alternative treatments with beams of protons and carbon ions has been conducted. Main attention is given to the possibility of the practical use of accumulated experience of application of neutron beams for cancer therapy.

  9. THERMAL NEUTRON BACKSCATTER IMAGING.

    SciTech Connect

    VANIER,P.; FORMAN,L.; HUNTER,S.; HARRIS,E.; SMITH,G.

    2004-10-16

    Objects of various shapes, with some appreciable hydrogen content, were exposed to fast neutrons from a pulsed D-T generator, resulting in a partially-moderated spectrum of backscattered neutrons. The thermal component of the backscatter was used to form images of the objects by means of a coded aperture thermal neutron imaging system. Timing signals from the neutron generator were used to gate the detection system so as to record only events consistent with thermal neutrons traveling the distance between the target and the detector. It was shown that this time-of-flight method provided a significant improvement in image contrast compared to counting all events detected by the position-sensitive {sup 3}He proportional chamber used in the imager. The technique may have application in the detection and shape-determination of land mines, particularly non-metallic types.

  10. Pulsed neutron detector

    DOEpatents

    Robertson, deceased, J. Craig; Rowland, Mark S.

    1989-03-21

    A pulsed neutron detector and system for detecting low intensity fast neutron pulses has a body of beryllium adjacent a body of hydrogenous material the latter of which acts as a beta particle detector, scintillator, and moderator. The fast neutrons (defined as having En>1.5 MeV) react in the beryllium and the hydrogenous material to produce larger numbers of slow neutrons than would be generated in the beryllium itself and which in the beryllium generate hellium-6 which decays and yields beta particles. The beta particles reach the hydrogenous material which scintillates to yield light of intensity related to the number of fast neutrons. A photomultiplier adjacent the hydrogenous material (scintillator) senses the light emission from the scintillator. Utilization means, such as a summing device, sums the pulses from the photo-multiplier for monitoring or other purposes.

  11. NEUTRON SHIELDING STRUCTURE

    DOEpatents

    Mattingly, J.T.

    1962-09-25

    A lightweight neutron shielding structure comprises a honeycomb core which is filled with a neutron absorbing powder. The honeycomb core is faced with parallel planar facing sheets to form a lightweight rigid unit. Suitable absorber powders are selected from among the following: B, B/sub 4/C, B/sub 2/O/ sub 3/, CaB/sub 6/, Li/sub 2/CO3, LiOH, LiBO/sub 2/, Li/s ub 2/O. The facing sheets are constructed of a neutron moderating material, so that fast neutrons will be moderated while traversing the facing sheets, and ultimately be absorbed by the absorber powder in the honeycomb. Beryllium is a preferred moderator material for use in the facing sheets. The advantage of the structure is that it combines the rigidity and light weight of a honeycomb construction with the neutron absorption properties of boron and lithium. (AEC)

  12. Simulated workplace neutron fields

    NASA Astrophysics Data System (ADS)

    Lacoste, V.; Taylor, G.; Röttger, S.

    2011-12-01

    The use of simulated workplace neutron fields, which aim at replicating radiation fields at practical workplaces, is an alternative solution for the calibration of neutron dosemeters. They offer more appropriate calibration coefficients when the mean fluence-to-dose equivalent conversion coefficients of the simulated and practical fields are comparable. Intensive Monte Carlo modelling work has become quite indispensable for the design and/or the characterization of the produced mixed neutron/photon fields, and the use of Bonner sphere systems and proton recoil spectrometers is also mandatory for a reliable experimental determination of the neutron fluence energy distribution over the whole energy range. The establishment of a calibration capability with a simulated workplace neutron field is not an easy task; to date only few facilities are available as standard calibration fields.

  13. Measurement of the scattering cross section of slow neutrons on liquid parahydrogen from neutron transmission

    DOE PAGESBeta

    Grammer, K. B.; Alarcon, R.; Barrón-Palos, L.; Blyth, D.; Bowman, J. D.; Calarco, J.; Crawford, C.; Craycraft, K.; Evans, D.; Fomin, N.; et al

    2015-05-08

    Liquid hydrogen is a dense Bose fluid whose equilibrium properties are both calculable from first principles using various theoretical approaches and of interest for the understanding of a wide range of questions in many-body physics. Unfortunately, the pair correlation function g(r) inferred from neutron scattering measurements of the differential cross section dσ/dΩ from different measurements reported in the literature are inconsistent. We have measured the energy dependence of the total cross section and the scattering cross section for slow neutrons with energies between 0.43 and 16.1 meV on liquid hydrogen at 15.6 K (which is dominated by the parahydrogen component)more » using neutron transmission measurements on the hydrogen target of the NPDGamma collaboration at the Spallation Neutron Source at Oak Ridge National Laboratory. The relationship between the neutron transmission measurement we perform and the total cross section is unambiguous, and the energy range accesses length scales where the pair correlation function is rapidly varying. At 1 meV our measurement is a factor of 3 below the data from previous work. We present evidence that these previous measurements of the hydrogen cross section, which assumed that the equilibrium value for the ratio of orthohydrogen and parahydrogen has been reached in the target liquid, were in fact contaminated with an extra nonequilibrium component of orthohydrogen. Liquid parahydrogen is also a widely used neutron moderator medium, and an accurate knowledge of its slow neutron cross section is essential for the design and optimization of intense slow neutron sources. Furthermore, we describe our measurements and compare them with previous work.« less

  14. Measurement of the scattering cross section of slow neutrons on liquid parahydrogen from neutron transmission

    SciTech Connect

    Grammer, K. B.; Alarcon, R.; Barrón-Palos, L.; Blyth, D.; Bowman, J. D.; Calarco, J.; Crawford, C.; Craycraft, K.; Evans, D.; Fomin, N.; Fry, J.; Gericke, M.; Gillis, R. C.; Greene, G. L.; Hamblen, J.; Hayes, C.; Kucuker, S.; Mahurin, R.; Maldonado-Velázquez, M.; Martin, E.; McCrea, M.; Mueller, P. E.; Musgrave, M.; Nann, H.; Penttilä, S. I.; Snow, W. M.; Tang, Z.; Wilburn, W. S.

    2015-05-08

    Liquid hydrogen is a dense Bose fluid whose equilibrium properties are both calculable from first principles using various theoretical approaches and of interest for the understanding of a wide range of questions in many-body physics. Unfortunately, the pair correlation function g(r) inferred from neutron scattering measurements of the differential cross section dσ/dΩ from different measurements reported in the literature are inconsistent. We have measured the energy dependence of the total cross section and the scattering cross section for slow neutrons with energies between 0.43 and 16.1 meV on liquid hydrogen at 15.6 K (which is dominated by the parahydrogen component) using neutron transmission measurements on the hydrogen target of the NPDGamma collaboration at the Spallation Neutron Source at Oak Ridge National Laboratory. The relationship between the neutron transmission measurement we perform and the total cross section is unambiguous, and the energy range accesses length scales where the pair correlation function is rapidly varying. At 1 meV our measurement is a factor of 3 below the data from previous work. We present evidence that these previous measurements of the hydrogen cross section, which assumed that the equilibrium value for the ratio of orthohydrogen and parahydrogen has been reached in the target liquid, were in fact contaminated with an extra nonequilibrium component of orthohydrogen. Liquid parahydrogen is also a widely used neutron moderator medium, and an accurate knowledge of its slow neutron cross section is essential for the design and optimization of intense slow neutron sources. Furthermore, we describe our measurements and compare them with previous work.

  15. SINGLE CRYSTAL NEUTRON DIFFRACTION.

    SciTech Connect

    KOETZLE,T.F.

    2001-03-13

    Single-crystal neutron diffraction measures the elastic Bragg reflection intensities from crystals of a material, the structure of which is the subject of investigation. A single crystal is placed in a beam of neutrons produced at a nuclear reactor or at a proton accelerator-based spallation source. Single-crystal diffraction measurements are commonly made at thermal neutron beam energies, which correspond to neutron wavelengths in the neighborhood of 1 Angstrom. For high-resolution studies requiring shorter wavelengths (ca. 0.3-0.8 Angstroms), a pulsed spallation source or a high-temperature moderator (a ''hot source'') at a reactor may be used. When complex structures with large unit-cell repeats are under investigation, as is the case in structural biology, a cryogenic-temperature moderator (a ''cold source'') may be employed to obtain longer neutron wavelengths (ca. 4-10 Angstroms). A single-crystal neutron diffraction analysis will determine the crystal structure of the material, typically including its unit cell and space group, the positions of the atomic nuclei and their mean-square displacements, and relevant site occupancies. Because the neutron possesses a magnetic moment, the magnetic structure of the material can be determined as well, from the magnetic contribution to the Bragg intensities. This latter aspect falls beyond the scope of the present unit; for information on magnetic scattering of neutrons see Unit 14.3. Instruments for single-crystal diffraction (single-crystal diffractometers or SCDs) are generally available at the major neutron scattering center facilities. Beam time on many of these instruments is available through a proposal mechanism. A listing of neutron SCD instruments and their corresponding facility contacts is included in an appendix accompanying this unit.

  16. Scleral Buckling for Rhegmatogenous Retinal Detachment Associated with Pars Planitis

    PubMed Central

    Ahn, Jae Kyoun

    2016-01-01

    Purpose. To evaluate the surgical outcome of scleral buckling (SB) in rhegmatogenous retinal detachment (RRD) patients associated with pars planitis. Methods. Retrospective review of RRD patients (32 eyes of pars planitis RRD and 180 eyes of primary RRD) who underwent SB. We compared primary and final anatomical success rates and visual outcomes between two groups. Results. Primary and final anatomical success were achieved in 25 (78.1%) and 31 (96.8%) eyes in the pars planitis RRD group and in 167 eyes (92.7%) and 176 eyes (97.7%) in primary RRD group, respectively. Both groups showed significant visual improvement (p < 0.001) and there were no significant differences in final visual acuity. Pars planitis RRD group was associated with higher rate of postoperative proliferative vitreoretinopathy (PVR) development (12.5% versus 2.8%, p = 0.031). Pars planitis and high myopia were significant preoperative risk factors and pseudophakia was borderline risk for primary anatomical failure after adjusting for various clinical factors. Conclusions. Pars planitis associated RRD showed inferior primary anatomical outcome after SB due to postoperative PVR development. However, final anatomical and visual outcomes were favorable. RRD cases associated with pars planitis, high myopia, and pseudophakia might benefit from different surgical approaches, such as combined vitrectomy and SB. PMID:27688907

  17. Scleral Buckling for Rhegmatogenous Retinal Detachment Associated with Pars Planitis.

    PubMed

    Kim, Yong-Kyu; Yoon, Wontae; Ahn, Jae Kyoun; Park, Sung Pyo

    2016-01-01

    Purpose. To evaluate the surgical outcome of scleral buckling (SB) in rhegmatogenous retinal detachment (RRD) patients associated with pars planitis. Methods. Retrospective review of RRD patients (32 eyes of pars planitis RRD and 180 eyes of primary RRD) who underwent SB. We compared primary and final anatomical success rates and visual outcomes between two groups. Results. Primary and final anatomical success were achieved in 25 (78.1%) and 31 (96.8%) eyes in the pars planitis RRD group and in 167 eyes (92.7%) and 176 eyes (97.7%) in primary RRD group, respectively. Both groups showed significant visual improvement (p < 0.001) and there were no significant differences in final visual acuity. Pars planitis RRD group was associated with higher rate of postoperative proliferative vitreoretinopathy (PVR) development (12.5% versus 2.8%, p = 0.031). Pars planitis and high myopia were significant preoperative risk factors and pseudophakia was borderline risk for primary anatomical failure after adjusting for various clinical factors. Conclusions. Pars planitis associated RRD showed inferior primary anatomical outcome after SB due to postoperative PVR development. However, final anatomical and visual outcomes were favorable. RRD cases associated with pars planitis, high myopia, and pseudophakia might benefit from different surgical approaches, such as combined vitrectomy and SB. PMID:27688907

  18. Scleral Buckling for Rhegmatogenous Retinal Detachment Associated with Pars Planitis

    PubMed Central

    Ahn, Jae Kyoun

    2016-01-01

    Purpose. To evaluate the surgical outcome of scleral buckling (SB) in rhegmatogenous retinal detachment (RRD) patients associated with pars planitis. Methods. Retrospective review of RRD patients (32 eyes of pars planitis RRD and 180 eyes of primary RRD) who underwent SB. We compared primary and final anatomical success rates and visual outcomes between two groups. Results. Primary and final anatomical success were achieved in 25 (78.1%) and 31 (96.8%) eyes in the pars planitis RRD group and in 167 eyes (92.7%) and 176 eyes (97.7%) in primary RRD group, respectively. Both groups showed significant visual improvement (p < 0.001) and there were no significant differences in final visual acuity. Pars planitis RRD group was associated with higher rate of postoperative proliferative vitreoretinopathy (PVR) development (12.5% versus 2.8%, p = 0.031). Pars planitis and high myopia were significant preoperative risk factors and pseudophakia was borderline risk for primary anatomical failure after adjusting for various clinical factors. Conclusions. Pars planitis associated RRD showed inferior primary anatomical outcome after SB due to postoperative PVR development. However, final anatomical and visual outcomes were favorable. RRD cases associated with pars planitis, high myopia, and pseudophakia might benefit from different surgical approaches, such as combined vitrectomy and SB.

  19. Optical polarizing neutron devices designed for pulsed neutron sources

    SciTech Connect

    Takeda, M.; Kurahashi, K.; Endoh, Y.; Itoh, S.

    1997-09-01

    We have designed two polarizing neutron devices for pulsed cold neutrons. The devices have been tested at the pulsed neutron source at the Booster Synchrotron Utilization Facility of the National Laboratory for High Energy Physics. These two devices proved to have a practical use for experiments to investigate condensed matter physics using pulsed cold polarized neutrons.

  20. Multi-scale photoacoustic remote sensing (PARS) (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Haji Reza, Parsin; Bell, Kevan; Shi, W.; Zemp, Roger J.

    2016-03-01

    We introduce a novel multi-scale photoacoustic remote sensing (PARS) imaging system. Our system can provide optical resolution details for superficial structures as well as acoustic resolution for deep-tissue imaging down to 5 cm, in a non-contact setting. PARS system does not require any contact with the sample or ultrasound coupling medium. The optical resolution PARS (OR-OARS) system uses optically focused pulsed excitation with optical detection of photoacoustic signatures using a long-coherence interrogation beam co-focused and co-scanned with the excitation spot. In the OR-PARS initial pressures are sampled right at their subsurface origin where acoustic pressures are largest. The Acoustic resolution PARS (AR-PARS) picks up the surface oscillation of the tissue caused by generated photoacoustic signal using a modified version of Michelson interferometry. By taking advantage of 4-meters polarization maintaining single-mode fiber and a green fiber laser we have generated a multi-wavelength source using stimulated Raman scattering. Remote functional imaging using this multi-wavelength excitation source and PARS detection mechanism has been demonstrated. The oxygen saturation estimations are shown for both phantom and in vivo studies. Images of blood vessel structures for an In vivo chicken embryo model is demonstrated. The Phantom studies indicates ~3µm and ~300µm lateral resolution for OR-PARS and AR-PARS respectively. To the best of our knowledge this is the first dual modality non-contact optical and acoustic resolution system used for in vivo imaging.

  1. Precision neutron flux measurement with a neutron beam monitor

    NASA Astrophysics Data System (ADS)

    Ino, T.; Otono, H.; Mishima, K.; Yamada, T.

    2014-07-01

    Neutron beam monitors are regularly used in various neutron beam experiments to compare two or more sets of data taken in different experimental conditions. A neutron lifetime experiment at BL05, the NOP beamline, in J-PARC requires to monitor the initial neutron intensity with an precision of 0.1% to measure the neutron lifetime with the same accuracy. The performance of a thin 3He gas neutron beam monitor used for the experiment was studied to estimate the systematic uncertainties in the neutron lifetime measurement.

  2. Limnological database for Par Pond: 1959 to 1980

    SciTech Connect

    Tilly, L.J.

    1981-03-01

    A limnological database for Par Pond, a cooling reservoir for hot reactor effluent water at the Savannah River Plant, is described. The data are derived from a combination of research and monitoring efforts on Par Pond since 1959. The approximately 24,000-byte database provides water quality, primary productivity, and flow data from a number of different stations, depths, and times during the 22-year history of the Par Pond impoundment. The data have been organized to permit an interpretation of the effects of twenty years of cooling system operations on the structure and function of an aquatic ecosystem.

  3. Predicted PAR1 inhibitors from multiple computational methods

    NASA Astrophysics Data System (ADS)

    Wang, Ying; Liu, Jinfeng; Zhu, Tong; Zhang, Lujia; He, Xiao; Zhang, John Z. H.

    2016-08-01

    Multiple computational approaches are employed in order to find potentially strong binders of PAR1 from the two molecular databases: the Specs database containing more than 200,000 commercially available molecules and the traditional Chinese medicine (TCM) database. By combining the use of popular docking scoring functions together with detailed molecular dynamics simulation and protein-ligand free energy calculations, a total of fourteen molecules are found to be potentially strong binders of PAR1. The atomic details in protein-ligand interactions of these molecules with PAR1 are analyzed to help understand the binding mechanism which should be very useful in design of new drugs.

  4. An electromagnetic PIC code on the MasPar

    SciTech Connect

    MacNeice, P.

    1993-12-31

    A 3D electromagnetic particle-in-cell code has been rewritten to run on the MasPar. The original code; known as TRISTAN which was written by Oscar Buneman was rewritten in MPL and its data structure altered to suit the MasPar architecture and exploit the fully local property of the algorithm. We discuss the significant issues associated with porting the code and present a comparative analysis of the code run times on the MasPar and on the CRAY YMP and C90. Results of a simulation of the interaction of the solar wind with the earth`s magnetosphere are shown.

  5. Protease-Activated Receptor (PAR)2, but Not PAR1, Is Involved in Collateral Formation and Anti-Inflammatory Monocyte Polarization in a Mouse Hind Limb Ischemia Model

    PubMed Central

    Nossent, Anne Yael; van Oeveren-Rietdijk, Annemarie M.; de Vries, Margreet R.; Spek, C. Arnold; van Zonneveld, Anton Jan; Reitsma, Pieter H.; Hamming, Jaap F.; de Boer, Hetty C.; Versteeg, Henri H.; Quax, Paul H. A.

    2013-01-01

    Aims In collateral development (i.e. arteriogenesis), mononuclear cells are important and exist as a heterogeneous population consisting of pro-inflammatory and anti-inflammatory/repair-associated cells. Protease-activated receptor (PAR)1 and PAR2 are G-protein-coupled receptors that are both expressed by mononuclear cells and are involved in pro-inflammatory reactions, while PAR2 also plays a role in repair-associated responses. Here, we investigated the physiological role of PAR1 and PAR2 in arteriogenesis in a murine hind limb ischemia model. Methods and Results PAR1-deficient (PAR1-/-), PAR2-deficient (PAR2-/-) and wild-type (WT) mice underwent femoral artery ligation. Laser Doppler measurements revealed reduced post-ischemic blood flow recovery in PAR2-/- hind limbs when compared to WT, while PAR1-/- mice were not affected. Upon ischemia, reduced numbers of smooth muscle actin (SMA)-positive collaterals and CD31-positive capillaries were found in PAR2-/- mice when compared to WT mice, whereas these parameters in PAR1-/- mice did not differ from WT mice. The pool of circulating repair-associated (Ly6C-low) monocytes and the number of repair-associated (CD206-positive) macrophages surrounding collaterals in the hind limbs were increased in WT and PAR1-/- mice, but unaffected in PAR2-/- mice. The number of repair-associated macrophages in PAR2-/- hind limbs correlated with CD11b- and CD115-expression on the circulating monocytes in these animals, suggesting that monocyte extravasation and M-CSF-dependent differentiation into repair-associated cells are hampered. Conclusion PAR2, but not PAR1, is involved in arteriogenesis and promotes the repair-associated response in ischemic tissues. Therefore, PAR2 potentially forms a new pro-arteriogenic target in coronary artery disease (CAD) patients. PMID:23637930

  6. Inhibition of diacylglycerol lipase (DAGL) in the lateral hypothalamus of rats prevents the increase in REMS and food ingestion induced by PAR1 stimulation.

    PubMed

    Pérez-Morales, Marcel; López-Colomé, Ana María; Méndez-Díaz, Mónica; Ruiz-Contreras, Alejandra E; Prospéro-García, Oscar

    2014-08-22

    Stimulation of the protease-activated receptor 1 (PAR1) in vitro, was shown to induce synaptic retrograde signaling through the endocannabinoid 2-arachidonoylglycerol (2-AG) synthesis and activation of the cannabinoid receptor type 1 (CB1R). The activation of PAR1 by the agonist S1820 in the lateral hypothalamus (LH) increases rapid eye movement sleep (REMS) and food intake in rats, and both effects are prevented by the CB1R inverse agonist AM251. In the present study, we implanted rats with electrodes and with cannulae aimed bilaterally to the LH. We administered tetrahydrolipstatin (THL), an inhibitor of the diacylglycerol lipase (DAGL), the enzyme responsible for 2-AG synthesis, to evaluate the sleep-wake cycle and food ingestion. THL in the LH readily prevented the increase in REMS and food intake induced by PAR1 stimulation, further supporting 2-AG as an upstream activator of PAR1. Our results demonstrate that the effect of PAR1 on REMS and food intake is blocked by the inhibition of DAGL, further suggesting that PAR1 stimulation in the lateral hypothalamus of rats induces an increase in sleep and food intake through 2-AG.

  7. Nucleosynthesis, neutrino bursts and gamma-rays from coalescing neutron stars

    NASA Technical Reports Server (NTRS)

    Eichler, David; Livio, Mario; Piran, Tsvi; Schramm, David N.

    1989-01-01

    It is pointed out here that neutron-star collisions should synthesize neutron-rich heavy elements, thought to be formed by rapid neutron capture (the r-process). Furthermore, these collisions should produce neutrino bursts and resultant bursts of gamma rays; the latter should comprise a subclass of observable gamma-ray bursts. It is argued that observed r-process abundances and gamma-ray burst rates predict rates for these collisions that are both significant and consistent with other estimates.

  8. Thermally driven neutron star glitches

    SciTech Connect

    Link, B. |; Epstein, R.I.

    1996-02-01

    We examine the thermal and dynamical response of a neutron star to a sudden perturbation of the inner crust temperature. During the star{close_quote}s evolution, starquakes and other processes may deposit {approx_gt}10{sup 42} ergs, causing significant internal heating and increased frictional coupling between the crust and the more rapidly rotating neutron superfluid the star is expected to contain. Through numerical simulation we study the propagation of the thermal wave created by the energy deposition, the induced motion of the interior superfluid, and the resulting spin evolution of the crust. We find that energy depositions of {approximately}10{sup 40} ergs produce gradual spin-ups above the timing noise level, while larger energy depositions produce sudden spin jumps resembling pulsar glitches. For a star with a temperature in the observed range of the Vela pulsar, an energy deposition of {approximately}10{sup 42} ergs produces a large spin-up taking place over minutes, similar to the Vela {open_quote}{open_quote}Christmas{close_quote}{close_quote} glitch. Comparable energy deposition in a younger and hotter {open_quote}{open_quote}Crab-like{close_quote}{close_quote} star produces a smaller spin-up taking place over {approximately}1{sup d}, similar to that seen during the partially time-resolved Crab glitch of 1989. {copyright} {ital 1996 The American Astronomical Society.}

  9. 2010 Neutron Review: ORNL Neutron Sciences Progress Report

    SciTech Connect

    Bardoel, Agatha A; Counce, Deborah M; Ekkebus, Allen E; Horak, Charlie M; Nagler, Stephen E; Kszos, Lynn A

    2011-06-01

    . This method of data collection provides a much more efficient way for users to gather data and get the most from their beam time. (7) New Laboratories for Users - The HFIR and SNS user communities continue to grow dramatically. In 2010, HFIR hosted 862 users and SNS 796, outpacing projections for both facilities. To meet the needs of those users, a new complex of 13 laboratories is now open for users at SNS. (8) Innovative Detectors Provide Relief from Helium-3 Shortage - Helium-3 ({sup 3}He) has been the gas of choice for gaseous detectors since the early days of neutron science. About two years ago, detector scientists worldwide faced the reality that stockpiles of {sup 3}He are dwindling rapidly, while demand for it has risen by a factor of five. The Neutron Sciences Detectors Group has developed two new types of detectors that don't rely on {sup 3}He: the Anger camera and the wavelength shifting fiber neutron detector, both of which use lithium ({sup 6}Li).

  10. FABRICATION OF NEUTRON SOURCES

    DOEpatents

    Birden, J.H.

    1959-04-21

    A method is presented for preparing a neutron source from polonium-210 and substances, such as beryllium and boron, characterized by emission of neutrons upon exposure to alpha particles from the polonium. According to the invention, a source is prepared by placing powdered beryllium and a platinum foil electroplated with polonium-2;.0 in a beryllium container. The container is sealed and then heated by induction to a temperature of 450 to 1100 deg C to volatilize the polonium off the foil into the powder. The heating step is terminated upon detection of a maximum in the neutron flux level.

  11. METHOD OF PRODUCING NEUTRONS

    DOEpatents

    Imhoff, D.H.; Harker, W.H.

    1964-01-14

    This patent relates to a method of producing neutrons in which there is produced a heated plasma containing heavy hydrogen isotope ions wherein heated ions are injected and confined in an elongated axially symmetric magnetic field having at least one magnetic field gradient region. In accordance with the method herein, the amplitude of the field and gradients are varied at an oscillatory periodic frequency to effect confinement by providing proper ratios of rotational to axial velocity components in the motion of said particles. The energetic neutrons may then be used as in a blanket zone containing a moderator and a source fissionable material to produce heat and thermal neutron fissionable materials. (AEC)

  12. Coupled moderator neutronics

    SciTech Connect

    Russell, G.J.; Pitcher, E.J.; Ferguson, P.D.

    1995-12-01

    Optimizing the neutronic performance of a coupled-moderator system for a Long-Pulse Spallation Source is a new and challenging area for the spallation target-system designer. For optimal performance of a neutron source, it is essential to have good communication with instrument scientists to obtain proper design criteria and continued interaction with mechanical, thermal-hydraulic, and materials engineers to attain a practical design. A good comprehension of the basics of coupled-moderator neutronics will aid in the proper design of a target system for a Long-Pulse Spallation Source.

  13. Fruits of neutron research

    SciTech Connect

    Krause, C.

    1994-12-31

    Car windshields that don`t break during accidents and jets that fly longer without making a refueling stop. Compact discs, credit cards, and pocket calculators. Refrigerator magnets and automatic car window openers. Beach shoes, food packaging, and bulletproof vests made of tough plastics. The quality and range of consumer products have improved steadily since the 1970s. One of the reasons: neutron research. Industries, employing neutron scattering techniques, to study materials properties, to act as diagnostics in tracing system performance, or as sources for radioactive isotopes used in medical fields for diagnostics or treatment, have all benefited from the fruits of advanced work with neutron sources.

  14. NEUTRONIC REACTOR CONTROL

    DOEpatents

    Metcalf, H.E.

    1958-10-14

    Methods of controlling reactors are presented. Specifically, a plurality of neutron absorber members are adjustably disposed in the reactor core at different distances from the center thereof. The absorber members extend into the core from opposite faces thereof and are operated by motive means coupled in a manner to simultaneously withdraw at least one of the absorber members while inserting one of the other absorber members. This feature effects fine control of the neutron reproduction ratio by varying the total volume of the reactor effective in developing the neutronic reaction.

  15. Rapid Risk Assessment: FY05 Annual Summary Report

    SciTech Connect

    Whelan, Gene; Millard, W. David; Gelston, Gariann M.; Pelton, Mitch A.; Yang, Zhaoqing; Strenge, Dennis L.; Lee, Cheegwan; Sivaraman, Chitra; Simpson, Mary J.; Young, Joan K.; Khangaonkar, Tarang P.; Downing, Timothy R.; Hoopes, Bonnie L.; Hachmeister, Lon E.

    2006-03-06

    The Pacific Northwest National Laboratory (PNNL) is developing decision support tools that will assist in the transition of incident information into Protective Action Recommendations (PARs) that are understandable and can be executed in a real-world, operational environment. During emergencies, responders must rapidly assess risks and decide on the best course of action—all within minutes to hours. PNNL is blending existing modeling and decision support technology to develop new methods for transitioning science-based threat assessment to PARs. The rapid risk assessment tool will be both understandable and applicable to the emergency management community and would be a valuable tool during any water security-related incident. In 2005, PNNL demonstrated the integration of the multi-thematic modeling with emergency management decision support tools to create a Rapid Risk Assessment (RRA) tool that will transition risk to PARs that assist in responding to or mitigating the direct and indirect impacts of the incident(s). The RRA tool does this by aligning multi-thematic modeling capabilities with real-world response zones established by emergency and site operations managers. The RRA tool uses the risk assessment tool to drive prognostic models that use the type of incident, time of impact, severity of impact, and duration of impact to select the most appropriate PAR. Because PARs (and the thresholds by which they are selected) are jointly established by the technologists and the emergency management and operations decision makers, the science-based risk assessment can transition into a recommendation that can be understood and executed by people in the field.

  16. PAR1 signaling regulates the retention and recruitment of EPCR-expressing bone marrow hematopoietic stem cells

    PubMed Central

    Gur-Cohen, Shiri; Itkin, Tomer; Chakrabarty, Sagarika; Graf, Claudine; Kollet, Orit; Ludin, Aya; Golan, Karin; Kalinkovich, Alexander; Ledergor, Guy; Wong, Eitan; Niemeyer, Elisabeth; Porat, Ziv; Erez, Ayelet; Sagi, Irit; Esmon, Charles T; Ruf, Wolfram; Lapidot, Tsvee

    2016-01-01

    Retention of long-term repopulating hematopoietic stem cells (LT-HSCs) in the bone marrow is essential for hematopoiesis and for protection from myelotoxic injury. We report that signaling cascades that are traditionally viewed as coagulation-related also control retention of EPCR+ LT-HSCs in the bone marrow and their recruitment to the blood via two different protease activated receptor 1 (PAR1)-mediated pathways. Thrombin-PAR1 signaling induces nitric oxide (NO) production, leading to TACE-mediated EPCR shedding, enhanced CXCL12-CXCR4-induced motility, and rapid stem and progenitor cell mobilization. Conversely, bone marrow blood vessels provide a microenvironment enriched with protein C that retain EPCR+ LT-HSCs by limiting NO generation, reducing Cdc42 activity and enhancing VLA4 affinity and adhesion. Inhibition of NO production by activated protein C (aPC)-EPCR-PAR1 signaling reduces progenitor cell egress, increases NOlow bone marrow EPCR+ LT-HSCs retention and protects mice from chemotherapy-induced hematological failure and death. Our study reveals new roles for PAR1 and EPCR that control NO production to balance maintenance and recruitment of bone marrow EPCR+ LT-HSCs with clinical relevance. PMID:26457757

  17. Isotope-Identifying neutron reflectometry

    SciTech Connect

    Nikitenko, Yu. V. Petrenko, A. V.; Gundorin, N. A.; Gledenov, Yu. M.; Aksenov, V. L.

    2015-07-15

    The possibilities of an isotope-indentifying study of layered structures in different regimes of a neutron wave field are considered. The detection of specularly reflected neutrons and secondary radiation (caused by neutron capture) in the form of charged particles, γ quanta, and nuclear fission fragments, as well as neutrons spin-flipped in a noncollinear magnetic field and on nuclei of elements with spin, makes it possible to implement isotope-indentifying neutron reflectometry.

  18. Switchable radioactive neutron source device

    DOEpatents

    Boyar, Robert E.; DeVolpi, Alexander; Stanford, George S.; Rhodes, Edgar A.

    1989-01-01

    This invention is a switchable neutron generating apparatus comprised of a pair of plates, the first plate having an alpha emitter section on it and the second plate having a target material portion on it which generates neutrons when its nuclei absorb an alpha particle. In operation, the alpha portion of the first plate is aligned with the neutron portion of the second plate to produce neutrons and brought out of alignment to cease production of neutrons.

  19. Switchable radioactive neutron source device

    DOEpatents

    Stanford, G.S.; Rhodes, E.A.; Devolpi, A.; Boyar, R.E.

    1987-11-06

    This invention is a switchable neutron generating apparatus comprised of a pair of plates, the first plate having an alpha emitter section on it and the second plate having a target material portion on it which generates neutrons when its nuclei absorb an alpha particle. In operation, the alpha portion of the first plate is aligned with the neutron portion of the second plate to produce neutrons and brought out of alignment to cease production of neutrons. 3 figs.

  20. Croissance epitaxiale de GaAs sur substrats de Ge par epitaxie par faisceaux chimiques

    NASA Astrophysics Data System (ADS)

    Belanger, Simon

    La situation energetique et les enjeux environnementaux auxquels la societe est confrontee entrainent un interet grandissant pour la production d'electricite a partir de l'energie solaire. Parmi les technologies actuellement disponibles, la filiere du photovoltaique a concentrateur solaire (CPV pour concentrator photovoltaics) possede un rendement superieur et mi potentiel interessant a condition que ses couts de production soient competitifs. La methode d'epitaxie par faisceaux chimiques (CBE pour chemical beam epitaxy) possede plusieurs caracteristiques qui la rendent interessante pour la production a grande echelle de cellules photovoltaiques a jonctions multiples a base de semi-conducteurs III-V. Ce type de cellule possede la meilleure efficacite atteinte a ce jour et est utilise sur les satellites et les systemes photovoltaiques a concentrateur solaire (CPV) les plus efficaces. Une des principales forces de la technique CBE se trouve dans son potentiel d'efficacite d'utilisation des materiaux source qui est superieur a celui de la technique d'epitaxie qui est couramment utilisee pour la production a grande echelle de ces cellules. Ce memoire de maitrise presente les travaux effectues dans le but d'evaluer le potentiel de la technique CBE pour realiser la croissance de couches de GaAs sur des substrats de Ge. Cette croissance constitue la premiere etape de fabrication de nombreux modeles de cellules solaires a haute performance decrites plus haut. La realisation de ce projet a necessite le developpement d'un procede de preparation de surface pour les substrats de germanium, la realisation de nombreuses sceances de croissance epitaxiale et la caracterisation des materiaux obtenus par microscopie optique, microscopie a force atomique (AFM), diffraction des rayons-X a haute resolution (HRXRD), microscopie electronique a transmission (TEM), photoluminescence a basse temperature (LTPL) et spectrometrie de masse des ions secondaires (SIMS). Les experiences ont permis

  1. Neutron Characterization for Additive Manufacturing

    NASA Technical Reports Server (NTRS)

    Watkins, Thomas; Bilheux, Hassina; An, Ke; Payzant, Andrew; DeHoff, Ryan; Duty, Chad; Peter, William; Blue, Craig; Brice, Craig A.

    2013-01-01

    Oak Ridge National Laboratory (ORNL) is leveraging decades of experience in neutron characterization of advanced materials together with resources such as the Spallation Neutron Source (SNS) and the High Flux Isotope Reactor (HFIR) shown in Fig. 1 to solve challenging problems in additive manufacturing (AM). Additive manufacturing, or three-dimensional (3-D) printing, is a rapidly maturing technology wherein components are built by selectively adding feedstock material at locations specified by a computer model. The majority of these technologies use thermally driven phase change mechanisms to convert the feedstock into functioning material. As the molten material cools and solidifies, the component is subjected to significant thermal gradients, generating significant internal stresses throughout the part (Fig. 2). As layers are added, inherent residual stresses cause warping and distortions that lead to geometrical differences between the final part and the original computer generated design. This effect also limits geometries that can be fabricated using AM, such as thin-walled, high-aspect- ratio, and overhanging structures. Distortion may be minimized by intelligent toolpath planning or strategic placement of support structures, but these approaches are not well understood and often "Edisonian" in nature. Residual stresses can also impact component performance during operation. For example, in a thermally cycled environment such as a high-pressure turbine engine, residual stresses can cause components to distort unpredictably. Different thermal treatments on as-fabricated AM components have been used to minimize residual stress, but components still retain a nonhomogeneous stress state and/or demonstrate a relaxation-derived geometric distortion. Industry, federal laboratory, and university collaboration is needed to address these challenges and enable the U.S. to compete in the global market. Work is currently being conducted on AM technologies at the ORNL

  2. Par-4 secretion: stoichiometry of 3-arylquinoline binding to vimentin.

    PubMed

    Sviripa, Vitaliy M; Burikhanov, Ravshan; Obiero, Josiah M; Yuan, Yaxia; Nickell, Justin R; Dwoskin, Linda P; Zhan, Chang-Guo; Liu, Chunming; Tsodikov, Oleg V; Rangnekar, Vivek M; Watt, David S

    2016-01-01

    Advanced prostate tumors usually metastasize to the lung, bone, and other vital tissues and are resistant to conventional therapy. Prostate apoptosis response-4 protein (Par-4) is a tumor suppressor that causes apoptosis in therapy-resistant prostate cancer cells by binding specifically to a receptor, Glucose-regulated protein-78 (GRP78), found only on the surface of cancer cells. 3-Arylquinolines or "arylquins" induce normal cells to release Par-4 from the intermediate filament protein, vimentin and promote Par-4 secretion that targets cancer cells in a paracrine manner. A structure-activity study identified arylquins that promote Par-4 secretion, and an evaluation of arylquin binding to the hERG potassium ion channel using a [(3)H]-dofetilide binding assay permitted the identification of structural features that separated this undesired activity from the desired Par-4 secretory activity. A binding study that relied on the natural fluorescence of arylquins and that used the purified rod domain of vimentin (residues 99-411) suggested that the mechanism behind Par-4 release involved arylquin binding to multiple sites in the rod domain.

  3. Neutron personnel dosimetry

    SciTech Connect

    Griffith, R.V.

    1981-06-16

    The current state-of-the-art in neutron personnel dosimetry is reviewed. Topics covered include dosimetry needs and alternatives, current dosimetry approaches, personnel monitoring devices, calibration strategies, and future developments. (ACR)

  4. NEUTRON-COUNTER

    DOEpatents

    Gunst, S.B.; Bayard, R.T.

    1960-12-20

    A heat- aud pressure-resistant radiation counter adaptable to the counting of thermal neutrons comprising a spheroidal chamber electrode having a coating of fissionable material and containing a spherical electrode is described.

  5. Shifting scintillator neutron detector

    SciTech Connect

    Clonts, Lloyd G; Cooper, Ronald G; Crow, Jr., Morris Lowell; Hannah, Bruce W; Hodges, Jason P; Richards, John D; Riedel, Richard A

    2014-03-04

    Provided are sensors and methods for detecting thermal neutrons. Provided is an apparatus having a scintillator for absorbing a neutron, the scintillator having a back side for discharging a scintillation light of a first wavelength in response to the absorbed neutron, an array of wavelength-shifting fibers proximate to the back side of the scintillator for shifting the scintillation light of the first wavelength to light of a second wavelength, the wavelength-shifting fibers being disposed in a two-dimensional pattern and defining a plurality of scattering plane pixels where the wavelength-shifting fibers overlap, a plurality of photomultiplier tubes, in coded optical communication with the wavelength-shifting fibers, for converting the light of the second wavelength to an electronic signal, and a processor for processing the electronic signal to identify one of the plurality of scattering plane pixels as indicative of a position within the scintillator where the neutron was absorbed.

  6. Temperature of neutron stars

    NASA Astrophysics Data System (ADS)

    Tsuruta, Sachiko

    2016-07-01

    We start with a brief introduction to the historical background in the early pioneering days when the first neutron star thermal evolution calculations predicted the presence of neutron stars hot enough to be observable. We then report on the first detection of neutron star temperatures by ROSAT X-ray satellite, which vindicated the earlier prediction of hot neutron stars. We proceed to present subsequent developments, both in theory and observation, up to today. We then discuss the current status and the future prospect, which will offer useful insight to the understanding of basic properties of ultra-high density matter beyond the nuclear density, such as the possible presence of such exotic particles as pion condensates.

  7. Neutron resonance averaging

    SciTech Connect

    Chrien, R.E.

    1986-10-01

    The principles of resonance averaging as applied to neutron capture reactions are described. Several illustrations of resonance averaging to problems of nuclear structure and the distribution of radiative strength in nuclei are provided. 30 refs., 12 figs.

  8. NEUTRONIC REACTOR FUEL COMPOSITION

    DOEpatents

    Thurber, W.C.

    1961-01-10

    Uranium-aluminum alloys in which boron is homogeneously dispersed by adding it as a nickel boride are described. These compositions have particular utility as fuels for neutronic reactors, boron being present as a burnable poison.

  9. Cylindrical neutron generator

    DOEpatents

    Leung, Ka-Ngo

    2008-04-22

    A cylindrical neutron generator is formed with a coaxial RF-driven plasma ion source and target. A deuterium (or deuterium and tritium) plasma is produced by RF excitation in a cylindrical plasma ion generator using an RF antenna. A cylindrical neutron generating target is coaxial with the ion generator, separated by plasma and extraction electrodes which contain many slots. The plasma generator emanates ions radially over 360.degree. and the cylindrical target is thus irradiated by ions over its entire circumference. The plasma generator and target may be as long as desired. The plasma generator may be in the center and the neutron target on the outside, or the plasma generator may be on the outside and the target on the inside. In a nested configuration, several concentric targets and plasma generating regions are nested to increase the neutron flux.

  10. Cylindrical neutron generator

    DOEpatents

    Leung, Ka-Ngo

    2005-06-14

    A cylindrical neutron generator is formed with a coaxial RF-driven plasma ion source and target. A deuterium (or deuterium and tritium) plasma is produced by RF excitation in a cylindrical plasma ion generator using an RF antenna. A cylindrical neutron generating target is coaxial with the ion generator, separated by plasma and extraction electrodes which contain many slots. The plasma generator emanates ions radially over 360.degree. and the cylindrical target is thus irradiated by ions over its entire circumference. The plasma generator and target may be as long as desired. The plasma generator may be in the center and the neutron target on the outside, or the plasma generator may be on the outside and the target on the inside. In a nested configuration, several concentric targets and plasma generating regions are nested to increase the neutron flux.

  11. Cylindrical neutron generator

    DOEpatents

    Leung, Ka-Ngo

    2009-12-29

    A cylindrical neutron generator is formed with a coaxial RF-driven plasma ion source and target. A deuterium (or deuterium and tritium) plasma is produced by RF excitation in a cylindrical plasma ion generator using an RF antenna. A cylindrical neutron generating target is coaxial with the ion generator, separated by plasma and extraction electrodes which contain many slots. The plasma generator emanates ions radially over 360.degree. and the cylindrical target is thus irradiated by ions over its entire circumference. The plasma generator and target may be as long as desired. The plasma generator may be in the center and the neutron target on the outside, or the plasma generator may be on the outside and the target on the inside. In a nested configuration, several concentric targets and plasma generating regions are nested to increase the neutron flux.

  12. FABRICATION OF NEUTRON SOURCES

    DOEpatents

    Birden, J.H.

    1959-01-20

    A method is presented for preparing a more efficient neutron source comprising inserting in a container a quantity of Po-210, inserting B powder coated with either Ag, Pt, or Ni. The container is sealed and then slowly heated to about 450 C to volatilize the Po and effect combination of the coated powder with the Po. The neutron flux emitted by the unit is moritored and the heating step is terminated when the flux reaches a maximum or selected level.

  13. NEUTRON FLUX INTENSITY DETECTION

    DOEpatents

    Russell, J.T.

    1964-04-21

    A method of measuring the instantaneous intensity of neutron flux in the core of a nuclear reactor is described. A target gas capable of being transmuted by neutron bombardment to a product having a resonance absorption line nt a particular microwave frequency is passed through the core of the reactor. Frequency-modulated microwave energy is passed through the target gas and the attenuation of the energy due to the formation of the transmuted product is measured. (AEC)

  14. Pulsed spallation neutron sources

    SciTech Connect

    Carpenter, J.M.

    1996-05-01

    This paper reviews the early history of pulsed spallation neutron source development ar Argonne and provides an overview of existing sources world wide. A number of proposals for machines more powerful than currently exist are under development, which are briefly described. The author reviews the status of the Intense Pulsed Neutron Source, its instrumentation, and its user program, and provide a few examples of applications in fundamental condensed matter physics, materials science and technology.

  15. Neutron ion temperature measurement

    SciTech Connect

    Strachan, J.D.; Hendel, H.W.; Lovberg, J.; Nieschmidt, E.B.

    1986-11-01

    One important use of fusion product diagnostics is in the determination of the deuterium ion temperature from the magnitude of the 2.5 MeV d(d,n)/sup 3/He neutron emission. The detectors, calibration methods, and limitations of this technique are reviewed here with emphasis on procedures used at PPPL. In most tokamaks, the ion temperature deduced from neutrons is in reasonable agreement with the ion temperature deduced by other techniques.

  16. Pulsed spallation Neutron Sources

    SciTech Connect

    Carpenter, J.M.

    1994-12-31

    This paper reviews the early history of pulsed spallation neutron source development at Argonne and provides an overview of existing sources world wide. A number of proposals for machines more powerful than currently exist are under development, which are briefly described. The author reviews the status of the Intense Pulsed Neutron Source, its instrumentation, and its user program, and provides a few examples of applications in fundamental condensed matter physics, materials science and technology.

  17. Boron neutron capture therapy (BNCT): implications of neutron beam and boron compound characteristics.

    PubMed

    Wheeler, F J; Nigg, D W; Capala, J; Watkins, P R; Vroegindeweij, C; Auterinen, I; Seppälä, T; Bleuel, D

    1999-07-01

    The potential efficacy of boron neutron capture therapy (BNCT) for malignant glioma is a significant function of epithermal-neutron beam biophysical characteristics as well as boron compound biodistribution characteristics. Monte Carlo analyses were performed to evaluate the relative significance of these factors on theoretical tumor control using a standard model. The existing, well-characterized epithermal-neutron sources at the Brookhaven Medical Research Reactor (BMRR), the Petten High Flux Reactor (HFR), and the Finnish Research Reactor (FiR-1) were compared. Results for a realistic accelerator design by the E. O. Lawrence Berkeley National Laboratory (LBL) are also compared. Also the characteristics of the compound p-Boronophenylaline Fructose (BPA-F) and a hypothetical next-generation compound were used in a comparison of the BMRR and a hypothetical improved reactor. All components of dose induced by an external epithermal-neutron beam fall off quite rapidly with depth in tissue. Delivery of dose to greater depths is limited by the healthy-tissue tolerance and a reduction in the hydrogen-recoil and incident gamma dose allow for longer irradiation and greater dose at a depth. Dose at depth can also be increased with a beam that has higher neutron energy (without too high a recoil dose) and a more forward peaked angular distribution. Of the existing facilities, the FiR-1 beam has the better quality (lower hydrogen-recoil and incident gamma dose) and a penetrating neutron spectrum and was found to deliver a higher value of Tumor Control Probability (TCP) than other existing beams at shallow depth. The greater forwardness and penetration of the HFR the FiR-1 at greater depths. The hypothetical reactor and accelerator beams outperform at both shallow and greater depths. In all cases, the hypothetical compound provides a significant improvement in efficacy but it is shown that the full benefit of improved compound is not realized until the neutron beam is fully

  18. Macromolecular structure phasing by neutron anomalous diffraction

    PubMed Central

    Cuypers, Maxime G.; Mason, Sax A.; Mossou, Estelle; Haertlein, Michael; Forsyth, V. Trevor; Mitchell, Edward P.

    2016-01-01

    In this report we show for the first time that neutron anomalous dispersion can be used in a practical manner to determine experimental phases of a protein crystal structure, providing a new tool for structural biologists. The approach is demonstrated through the use of a state-of-the-art monochromatic neutron diffractometer at the Institut Laue-Langevin (ILL) in combination with crystals of perdeuterated protein that minimise the level of hydrogen incoherent scattering and enhance the visibility of the anomalous signal. The protein used was rubredoxin in which cadmium replaced the iron at the iron-sulphur site. While this study was carried out using a steady-state neutron beam source, the results will be of major interest for capabilities at existing and emerging spallation neutron sources where time-of-flight instruments provide inherent energy discrimination. In particular this capability may be expected to offer unique opportunities to a rapidly developing structural biology community where there is increasing interest in the identification of protonation states, protein/water interactions and protein-ligand interactions – all of which are of central importance to a wide range of fundamental and applied areas in the biosciences. PMID:27511806

  19. Synchrotron based spallation neutron source concepts

    SciTech Connect

    Cho, Y.

    1998-07-01

    During the past 20 years, rapid-cycling synchrotrons (RCS) have been used very productively to generate short-pulse thermal neutron beams for neutron scattering research by materials science communities in Japan (KENS), the UK (ISIS) and the US (IPNS). The most powerful source in existence, ISIS in the UK, delivers a 160-kW proton beam to a neutron-generating target. Several recently proposed facilities require proton beams in the MW range to produce intense short-pulse neutron beams. In some proposals, a linear accelerator provides the beam power and an accumulator ring compresses the pulse length to the required {approx} 1 {micro}s. In others, RCS technology provides the bulk of the beam power and compresses the pulse length. Some synchrotron-based proposals achieve the desired beam power by combining two or more synchrotrons of the same energy, and others propose a combination of lower and higher energy synchrotrons. This paper presents the rationale for using RCS technology, and a discussion of the advantages and disadvantages of synchrotron-based spallation sources.

  20. Neutron scattering in Australia

    SciTech Connect

    Knott, R.B.

    1994-12-31

    Neutron scattering techniques have been part of the Australian scientific research community for the past three decades. The High Flux Australian Reactor (HIFAR) is a multi-use facility of modest performance that provides the only neutron source in the country suitable for neutron scattering. The limitations of HIFAR have been recognized and recently a Government initiated inquiry sought to evaluate the future needs of a neutron source. In essence, the inquiry suggested that a delay of several years would enable a number of key issues to be resolved, and therefore a more appropriate decision made. In the meantime, use of the present source is being optimized, and where necessary research is being undertaken at major overseas neutron facilities either on a formal or informal basis. Australia has, at present, a formal agreement with the Rutherford Appleton Laboratory (UK) for access to the spallation source ISIS. Various aspects of neutron scattering have been implemented on HIFAR, including investigations of the structure of biological relevant molecules. One aspect of these investigations will be presented. Preliminary results from a study of the interaction of the immunosuppressant drug, cyclosporin-A, with reconstituted membranes suggest that the hydrophobic drug interdigitated with lipid chains.

  1. Neutron Nucleic Acid Crystallography.

    PubMed

    Chatake, Toshiyuki

    2016-01-01

    The hydration shells surrounding nucleic acids and hydrogen-bonding networks involving water molecules and nucleic acids are essential interactions for the structural stability and function of nucleic acids. Water molecules in the hydration shells influence various conformations of DNA and RNA by specific hydrogen-bonding networks, which often contribute to the chemical reactivity and molecular recognition of nucleic acids. However, X-ray crystallography could not provide a complete description of structural information with respect to hydrogen bonds. Indeed, X-ray crystallography is a powerful tool for determining the locations of water molecules, i.e., the location of the oxygen atom of H2O; however, it is very difficult to determine the orientation of the water molecules, i.e., the orientation of the two hydrogen atoms of H2O, because X-ray scattering from the hydrogen atom is very small.Neutron crystallography is a specialized tool for determining the positions of hydrogen atoms. Neutrons are not diffracted by electrons, but are diffracted by atomic nuclei; accordingly, neutron scattering lengths of hydrogen and its isotopes are comparable to those of non-hydrogen atoms. Therefore, neutron crystallography can determine both of the locations and orientations of water molecules. This chapter describes the current status of neutron nucleic acid crystallographic research as well as the basic principles of neutron diffraction experiments performed on nucleic acid crystals: materials, crystallization, diffraction experiments, and structure determination. PMID:26227050

  2. Neutron Nucleic Acid Crystallography.

    PubMed

    Chatake, Toshiyuki

    2016-01-01

    The hydration shells surrounding nucleic acids and hydrogen-bonding networks involving water molecules and nucleic acids are essential interactions for the structural stability and function of nucleic acids. Water molecules in the hydration shells influence various conformations of DNA and RNA by specific hydrogen-bonding networks, which often contribute to the chemical reactivity and molecular recognition of nucleic acids. However, X-ray crystallography could not provide a complete description of structural information with respect to hydrogen bonds. Indeed, X-ray crystallography is a powerful tool for determining the locations of water molecules, i.e., the location of the oxygen atom of H2O; however, it is very difficult to determine the orientation of the water molecules, i.e., the orientation of the two hydrogen atoms of H2O, because X-ray scattering from the hydrogen atom is very small.Neutron crystallography is a specialized tool for determining the positions of hydrogen atoms. Neutrons are not diffracted by electrons, but are diffracted by atomic nuclei; accordingly, neutron scattering lengths of hydrogen and its isotopes are comparable to those of non-hydrogen atoms. Therefore, neutron crystallography can determine both of the locations and orientations of water molecules. This chapter describes the current status of neutron nucleic acid crystallographic research as well as the basic principles of neutron diffraction experiments performed on nucleic acid crystals: materials, crystallization, diffraction experiments, and structure determination.

  3. Coded source neutron imaging

    SciTech Connect

    Bingham, Philip R; Santos-Villalobos, Hector J

    2011-01-01

    Coded aperture techniques have been applied to neutron radiography to address limitations in neutron flux and resolution of neutron detectors in a system labeled coded source imaging (CSI). By coding the neutron source, a magnified imaging system is designed with small spot size aperture holes (10 and 100 m) for improved resolution beyond the detector limits and with many holes in the aperture (50% open) to account for flux losses due to the small pinhole size. An introduction to neutron radiography and coded aperture imaging is presented. A system design is developed for a CSI system with a development of equations for limitations on the system based on the coded image requirements and the neutron source characteristics of size and divergence. Simulation has been applied to the design using McStas to provide qualitative measures of performance with simulations of pinhole array objects followed by a quantitative measure through simulation of a tilted edge and calculation of the modulation transfer function (MTF) from the line spread function. MTF results for both 100um and 10um aperture hole diameters show resolutions matching the hole diameters.

  4. MAGNETIC NEUTRON SCATTERING

    SciTech Connect

    ZALIZNYAK,I.A.; LEE,S.H.

    2004-07-30

    Much of our understanding of the atomic-scale magnetic structure and the dynamical properties of solids and liquids was gained from neutron-scattering studies. Elastic and inelastic neutron spectroscopy provided physicists with an unprecedented, detailed access to spin structures, magnetic-excitation spectra, soft-modes and critical dynamics at magnetic-phase transitions, which is unrivaled by other experimental techniques. Because the neutron has no electric charge, it is an ideal weakly interacting and highly penetrating probe of matter's inner structure and dynamics. Unlike techniques using photon electric fields or charged particles (e.g., electrons, muons) that significantly modify the local electronic environment, neutron spectroscopy allows determination of a material's intrinsic, unperturbed physical properties. The method is not sensitive to extraneous charges, electric fields, and the imperfection of surface layers. Because the neutron is a highly penetrating and non-destructive probe, neutron spectroscopy can probe the microscopic properties of bulk materials (not just their surface layers) and study samples embedded in complex environments, such as cryostats, magnets, and pressure cells, which are essential for understanding the physical origins of magnetic phenomena. Neutron scattering is arguably the most powerful and versatile experimental tool for studying the microscopic properties of the magnetic materials. The magnitude of the cross-section of the neutron magnetic scattering is similar to the cross-section of nuclear scattering by short-range nuclear forces, and is large enough to provide measurable scattering by the ordered magnetic structures and electron spin fluctuations. In the half-a-century or so that has passed since neutron beams with sufficient intensity for scattering applications became available with the advent of the nuclear reactors, they have became indispensable tools for studying a variety of important areas of modern science

  5. Neutron dosimetry in boron neutron capture therapy

    SciTech Connect

    Fairchild, R.G.; Miola, U.J.; Ettinger, K.V.

    1981-01-01

    The recent development of various borated compounds and the utilization of one of these (Na/sub 2/B/sub 12/H/sub 11/SH) to treat brain tumors in clinical studies in Japan has renewed interest in neutron capture therapy. In these procedures thermal neutrons interact with /sup 10/B in boron containing cells through the /sup 10/B(n,..cap alpha..)/sup 7/Li reaction producing charged particles with a maximum range of approx. 10..mu..m in tissue. Borated analogs of chlorpromazine, porphyrin, thiouracil and deoxyuridine promise improved tumor uptake and blood clearance. The therapy beam from the Medical Research Reactor in Brookhaven contains neutrons from a modified and filtered fission spectrum and dosimetric consequences of the use of the above mentioned compounds in conjunction with thermal and epithermal fluxes are discussed in the paper. One of the important problems of radiation dosimetry in capture therapy is determination of the flux profile and, hence, the dose profile in the brain. This has been achieved by constructing a brain phantom made of TE plastic. The lyoluminescence technique provides a convenient way of monitoring the neutron flux distributions; the detectors for this purpose utilize /sup 6/Li and /sup 10/B compounds. Such compounds have been synthesized specially for the purpose of dosimetry of thermal and epithermal beams. In addition, standard lyoluminescent phosphors, like glutamine, could be used to determine the collisional component of the dose as well as the contribution of the /sup 14/N(n,p)/sup 14/C reaction. Measurements of thermal flux were compared with calculations and with measurements done with activation foils.

  6. Fundamental neutron physics at LANSCE

    SciTech Connect

    Greene, G.

    1995-10-01

    Modern neutron sources and science share a common origin in mid-20th-century scientific investigations concerned with the study of the fundamental interactions between elementary particles. Since the time of that common origin, neutron science and the study of elementary particles have evolved into quite disparate disciplines. The neutron became recognized as a powerful tool for studying condensed matter with modern neutron sources being primarily used (and justified) as tools for neutron scattering and materials science research. The study of elementary particles has, of course, led to the development of rather different tools and is now dominated by activities performed at extremely high energies. Notwithstanding this trend, the study of fundamental interactions using neutrons has continued and remains a vigorous activity at many contemporary neutron sources. This research, like neutron scattering research, has benefited enormously by the development of modern high-flux neutron facilities. Future sources, particularly high-power spallation sources, offer exciting possibilities for continuing this research.

  7. Sensitivity studies for the weak r process: neutron capture rates

    SciTech Connect

    Surman, R.; Mumpower, M.; Sinclair, R.; Jones, K. L.; Hix, W. R.; McLaughlin, G. C.

    2014-04-15

    Rapid neutron capture nucleosynthesis involves thousands of nuclear species far from stability, whose nuclear properties need to be understood in order to accurately predict nucleosynthetic outcomes. Recently sensitivity studies have provided a deeper understanding of how the r process proceeds and have identified pieces of nuclear data of interest for further experimental or theoretical study. A key result of these studies has been to point out the importance of individual neutron capture rates in setting the final r-process abundance pattern for a ‘main’ (A ∼ 130 peak and above) r process. Here we examine neutron capture in the context of a ‘weak’ r process that forms primarily the A ∼ 80 r-process abundance peak. We identify the astrophysical conditions required to produce this peak region through weak r-processing and point out the neutron capture rates that most strongly influence the final abundance pattern.

  8. On neutron star structure and the millisecond pulsar

    NASA Technical Reports Server (NTRS)

    Harding, A. K.

    1983-01-01

    The millisecond pulsar is the first observed example of a neutron star spinning rapidly enough to approach the Jacobi bifurcation point and thus affords the possibility of constraining neutron star physics. The pulsar must be rotating below the critical frequency at which its equilibrium configuration would become nonaxisymmetric, since the lifetime of this configuration against decay by gravitational radiation is very short. This critical frequency may be used to set a lower limit of 2 x 10 to the 14th g/cu cm on the density of the star. If the mass is 0.5-1.5 solar mass, several of the stiffer neutron star equations of state may be ruled out, and the radius should be less than 16 km. The condition for axisymmetry also imposes an upper limit on the rotation rate to which neutron stars may be spun up by accretion disks in binary systems.

  9. Breaking strain of neutron star crust and gravitational waves.

    PubMed

    Horowitz, C J; Kadau, Kai

    2009-05-15

    Mountains on rapidly rotating neutron stars efficiently radiate gravitational waves. The maximum possible size of these mountains depends on the breaking strain of the neutron star crust. With multimillion ion molecular dynamics simulations of Coulomb solids representing the crust, we show that the breaking strain of pure single crystals is very large and that impurities, defects, and grain boundaries only modestly reduce the breaking strain to around 0.1. Because of the collective behavior of the ions during failure found in our simulations, the neutron star crust is likely very strong and can support mountains large enough so that their gravitational wave radiation could limit the spin periods of some stars and might be detectable in large-scale interferometers. Furthermore, our microscopic modeling of neutron star crust material can help analyze mechanisms relevant in magnetar giant flares and microflares.

  10. Neutron-scattering characterization of nanostructured materials relevant to biotechnology

    NASA Astrophysics Data System (ADS)

    Loong, C.-K.; Thiyagarajan, P.; Kolesnikov, A. I.

    2004-10-01

    Biomedical nanotechnology is a rapidly emerging field that encompasses many disciplines including medicine, molecular biology, materials physics and chemistry, engineering, etc. The complexity of the targeted systems demands cross-disciplinary research and international collaboration. In the materials front, understanding the fundamental properties at molecular level is important to the realization of the full potential of substances and the fruition of eventual technological applications. Neutron-scattering characterization of biomolecular systems can in principle provide unique information pertinent to nanotechnological applications. But the method is not widely utilized because neutron facilities are not normally located at industrial laboratories and university campuses. We introduce the techniques of neutron scattering for studying the organization of nanoscale structural units and their dynamic response to physical-chemical conditions. Examples are given to illustrate neutron characterization of nanostructured biomaterials and the implications for biotechnology.

  11. Efficiency and Gamma Sensitivity of a Lithium Glass Neutron Detector

    NASA Astrophysics Data System (ADS)

    Wallace, Adam; Rees, Lawrence; Czirr, Bart; Hoggan, Margarita

    2010-10-01

    Neutron detectors are used in national security applications for detecting potential radioactive material entering the country. Due to the shortage of Helium-3 for neutron detectors, Lithium-6 glass scintillators could be a good material for a replacement detector. Lithium-6 has a large neutron capture cross section, which gives high neutron detection rates. Our detector is based on the fact that neutrons are captured by Lithium-6 which rapidly decays into an alpha particle and triton. Those particles induce scintillation in the glass scintillator and are detected in a photomultiplier tube. The orientation of the plastic and Lithium-6 glass changes the efficiency of the detector. Monte Carlo for Neutral Particles (MCNP) calculations have shown that increasing amounts of plastic provide more efficient neutron detection and that placing a layer of glass in the front of the detector is the ideal configuration. Homeland Security requires that a replacement for Helium-3 detectors must have low gamma sensitivity and high neutron detection efficiency. We are measuring the absolute gamma sensitivity of various arrangements of glass and plastic scintillator. Our goal is to meet the Department of Homeland Security requirement for gamma sensitivity of one part in 10,000.

  12. Target studies for accelerator-based boron neutron capture therapy

    SciTech Connect

    Powell, J.R.; Ludewig, H.; Todosow, M.; Reich, M.

    1996-03-01

    Two new concepts, NIFTI and DISCOS, are described. These concepts enable the efficient production of epithermal neutrons for BNCT (Boron Neutron Capture Therapy) medical treatment, utilizing a low current, low energy proton beam impacting on a lithium target. The NIFTI concept uses an iron layer that strongly impedes the transmission of neutrons with energies above 24 KeV. Lower energy neutrons readily pass through this iron ``filter``, which has a deep ``window`` in its scattering cross section at 24 KeV. The DISCOS concept uses a rapidly rotating, high g disc to create a series of thin ({approximately} 1 micron thickness) liquid lithium targets in the form of continuous films through which the proton beam passes. The average energy lost by a proton as it passes through a single target is small, approximately 10 KeV. Between the targets, the proton beam is reaccelerated by an applied DC electric field. The DISCOS approach enables the accelerator -- target facility to operate with a beam energy only slightly above the threshold value for neutron production -- resulting in an output beam of low-energy epithermal neutrons -- while achieving a high yield of neutrons per milliamp of proton beam current.

  13. Par Pond vegetation status Summer 1995 -- June survey descriptive summary

    SciTech Connect

    Mackey, H.E. Jr.; Riley, R.S.

    1995-06-01

    The water level of Par Pond was lowered approximately 20 feet in mid-1991 in order to protect downstream residents from possible dam failure suggested by subsidence on the downstream slope of the dam and to repair the dam. This lowering exposed both emergent and nonemergent macrophyte beds to drying conditions resulting in extensive losses. A survey of the shoreline aquatic plant communities in June 1995, three months after the refilling of Par Pond to approximately 200 feet above mean sea level, indicated that much of the original plant communities and the intermediate shoreline communities present on the exposed sediments have been lost. The extensive old-field and emergent marsh communities that were present on the exposed shoreline during the drawdown have been flooded and much of the pre-drawdown Par Pond aquatic plant communities have not had sufficient time for re-establishment. The shoreline does, however, have extensive beds of maidencane which extend from the shoreline margin to areas as deep as 2 and perhaps 3 meters. Scattered individual plants of lotus and watershield are common and may indicate likely directions of future wetland development in Par Pond. In addition, within isolated coves, which apparently received ground water seepage and/or stream surface flows during the period of the Par Pond draw down, extensive beds of waterlilies and spike rush are common. Invasion of willow and red maple occurred along the lake shoreline as well. Although not absent from this survey, evidence of the extensive redevelopment of the large cattail and eel grass beds was not observed in this first survey of Par Pond. Future surveys during the growing seasons of 1995, 1996, and 1997 along with the evaluation of satellite date to map the areal extent of the macrophyte beds of Par Pond are planned.

  14. Pars Planitis: Epidemiology, Clinical Characteristics, Management and Visual Prognosis.

    PubMed

    Ozdal, Pinar Cakar; Berker, Nilufer; Tugal-Tutkun, Ilknur

    2015-01-01

    Pars planitis is an idiopathic chronic intermediate uveitis which predominantly affects children and adolescents, and accounts for 5-26.7% of pediatric uveitis. Although an autoimmune process with a genetic predisposition has been suggested, its etiology still remains unknown. The most common presenting symptoms are floaters and blurred vision. Diffuse vitreous cells, haze, snowballs and snowbanks are typical findings of pars planitis. Peripheral retinal vasculitis, optic disc edema and anterior segment inflammation are other well-known findings. Although pars planitis is known to be a benign form of uveitis in most cases, it may become a potentially blinding disease due to complications including cataract, cystoid macular edema, vitreous opacities and optic disc edema. Cystoid macular edema is the most common cause of visual morbidity. Band keratopathy, epiretinal membrane formation, vitreous condensation, neovascularizations, vitreous hemorrhage, retinal detachment, cyclitic membranes, glaucoma and amblyopia may develop as a consequence of the chronic course of the disease. Exclusion of infectious and non-infectious causes which may present with intermediate uveitis is of utmost importance before starting treatment. Treatment of pars planitis has been a controversial issue. There is no consensus specifically for treatment of cases with minimal inflammation and relatively good visual acuity. However, current experience shows that pars planitis may cause severe inflammation and needs an aggressive treatment. A stepladder approach including corticosteroids, immunosupressive agents, anti-tumor necrosis factor-alpha and pars plana vitrectomy and/or laser photocoagulation is the most commonly used method for treatment of pars planitis. Adequate control of inflammation and prompt detection of associated complications are crucial in order to improve the overall prognosis of the disease. PMID:27051493

  15. Pars Planitis: Epidemiology, Clinical Characteristics, Management and Visual Prognosis

    PubMed Central

    Ozdal, Pinar Cakar; Berker, Nilufer; Tugal-Tutkun, Ilknur

    2015-01-01

    Pars planitis is an idiopathic chronic intermediate uveitis which predominantly affects children and adolescents, and accounts for 5-26.7% of pediatric uveitis. Although an autoimmune process with a genetic predisposition has been suggested, its etiology still remains unknown. The most common presenting symptoms are floaters and blurred vision. Diffuse vitreous cells, haze, snowballs and snowbanks are typical findings of pars planitis. Peripheral retinal vasculitis, optic disc edema and anterior segment inflammation are other well-known findings. Although pars planitis is known to be a benign form of uveitis in most cases, it may become a potentially blinding disease due to complications including cataract, cystoid macular edema, vitreous opacities and optic disc edema. Cystoid macular edema is the most common cause of visual morbidity. Band keratopathy, epiretinal membrane formation, vitreous condensation, neovascularizations, vitreous hemorrhage, retinal detachment, cyclitic membranes, glaucoma and amblyopia may develop as a consequence of the chronic course of the disease. Exclusion of infectious and non-infectious causes which may present with intermediate uveitis is of utmost importance before starting treatment. Treatment of pars planitis has been a controversial issue. There is no consensus specifically for treatment of cases with minimal inflammation and relatively good visual acuity. However, current experience shows that pars planitis may cause severe inflammation and needs an aggressive treatment. A stepladder approach including corticosteroids, immunosupressive agents, anti-tumor necrosis factor-alpha and pars plana vitrectomy and/or laser photocoagulation is the most commonly used method for treatment of pars planitis. Adequate control of inflammation and prompt detection of associated complications are crucial in order to improve the overall prognosis of the disease. PMID:27051493

  16. Comparison of the effects of PAR1 antagonists, PAR4 antagonists, and their combinations on thrombin-induced human platelet activation.

    PubMed

    Wu, Chin-Chung; Teng, Che-Ming

    2006-09-28

    Thrombin activates human platelets through proteolytic activation of two protease-activated receptors (PARs), PAR1 and PAR4. In the present study, we show that, RWJ-56110, a potent synthetic PAR1 antagonist, inhibited platelet aggregation caused by a low concentration (0.05 U/ml) of thrombin, but lost its effectiveness when higher concentrations of thrombin were used as stimulators. YD-3, a non-peptide PAR4 antagonist, alone had little or no effect on thrombin-induced platelet aggregation, significantly enhanced the anti-aggregatory activity of PAR1 antagonist. In addition, we demonstrate for the first time that P-selectin expression in thrombin-stimulated platelets can be synergistically prevented by combined treatment of PAR1 antagonist and PAR4 antagonist. These results indicate that thrombin-induced platelet activation cannot be effectively inhibited by just blocking either single thrombin receptor pathway, and suggest a rationale for potential combination therapy in arterial thrombosis. PMID:16890935

  17. Determining cleanliness levels along the neutron tube manufacturing line

    SciTech Connect

    Lopez, E.P.; Montoya, M.G.

    1997-02-01

    A study is underway to identify a rapid, easy method for determining cleanliness levels during the manufacture of neutron tubes. Due to high reliability concerns associated with neutron tubes, cleanliness levels of metal and ceramic piece parts are critical. Sandia has traditionally used quantitative surface analytical methods, such as Auger Electron Spectroscopy and X-ray Photoelectron Spectroscopy for determining cleanliness levels. A critical disadvantage of these techniques is the time required to perform them. More rapid, reliable methods are needed for in-line testing of neutron tube assemblies. Several methods including contact angle, MESERAN, Fourier Transform Infrared Spectroscopy, and Optically Stimulated Electron Emission measurements are being evaluated as potential candidates. Cleanliness levels for each of these methods have been compared to Auger Electron Spectroscopy results, after processing samples through similar test conditions. An attempt was made to correlate the results from the alternative methods to those of Auger Electron Spectroscopy. Test results are presented.

  18. Fast neutron spectroscopy with tensioned metastable fluid detectors

    NASA Astrophysics Data System (ADS)

    Grimes, T. F.; Taleyarkhan, R. P.

    2016-09-01

    This paper describes research into development of a rapid-turnaround, neutron-spectroscopy capable (gamma-beta blind), high intrinsic efficiency sensor system utilizing the tensioned metastable fluid detector (TMFD) architecture. The inability of prevailing theoretical models (developed successfully for the classical bubble chamber) to adequately predict detection thresholds for tensioned metastable fluid conditions is described. Techniques are presented to overcome these inherent shortcomings, leading thereafter, to allow successful neutron spectroscopy using TMFDs - via the newly developed Single Atom Spectroscopy (SAS) approach. SAS also allows for a unique means for rapidly determining neutron energy thresholds with TMFDs. This is accomplished by simplifying the problem of determining Cavitation Detection Events (CDEs) arising from neutron interactions with one in which several recoiling atom species contribute to CDEs, to one in which only one dominant recoil atom need be considered. The chosen fluid is Heptane (C7H16) for which only recoiling C atoms contribute to CDEs. Using the SAS approach, the threshold curve for Heptane was derived using isotope neutron source data, and then validated against experiments with mono-energetic (2.45/14 MeV) neutrons from D-D and D-T accelerators. Thereafter the threshold curves were used to produce the response matrix for various geometries. The response matrices were in turn combined with experimental data to recover the continuous spectra of fission (Cf-252) and (α,n) Pu-Be isotopic neutron sources via an unfolding algorithm. A generalized algorithm is also presented for performing neutron spectroscopy using any other TMFD fluid that meets the SAS approach assumptions.

  19. Neutron reflectometry on highly absorbing films and its application to 10B4C-based neutron detectors

    PubMed Central

    Piscitelli, F.; Khaplanov, A.; Devishvili, A.; Schmidt, S.; Höglund, C.; Birch, J.; Dennison, A. J. C.; Gutfreund, P.; Hall-Wilton, R.; Van Esch, P.

    2016-01-01

    Neutron reflectometry is a powerful tool used for studies of surfaces and interfaces. The absorption in the typical studied materials is neglected and this technique is limited only to the reflectivity measurement. For strongly absorbing nuclei, the absorption can be directly measured by using the neutron-induced fluorescence technique which exploits the prompt particle emission of absorbing isotopes. This technique is emerging from soft matter and biology where highly absorbing nuclei, in very small quantities, are used as a label for buried layers. Nowadays, the importance of absorbing layers is rapidly increasing, partially because of their application in neutron detection; a field that has become more active also due to the 3He-shortage. We extend the neutron-induced fluorescence technique to the study of layers of highly absorbing materials, in particular 10B4C. The theory of neutron reflectometry is a commonly studied topic; however, when a strong absorption is present the subtle relationship between the reflection and the absorption of neutrons is not widely known. The theory for a general stack of absorbing layers has been developed and compared to measurements. We also report on the requirements that a 10B4C layer must fulfil in order to be employed as a converter in neutron detection. PMID:26997902

  20. Regulation of protease-activated receptor (PAR) 1 and PAR4 signaling in human platelets by compartmentalized cyclic nucleotide actions.

    PubMed

    Bilodeau, Matthew L; Hamm, Heidi E

    2007-08-01

    Thrombin potently regulates human platelets by the G protein-coupled receptors protease-activated receptor (PAR) 1 and PAR4. Platelet activation by thrombin and other agonists is broadly inhibited by prostacyclin and nitric oxide acting through adenylyl and guanylyl cyclases to elevate cAMP and cGMP levels, respectively. Using forskolin and YC-1 [3-(5'-hydroxymethyl-2'-furyl)-1-benzylindazole] to selectively activate the adenylyl and guanylyl cyclases, respectively, and the membrane-permeable analogs N(6),2'-O-dibutyryladenosine-3'-5'-cAMP (dibutyryl-cAMP) and 8-(4-parachlorophenylthoi)-cGMP (8-pCPT-cGMP), we sought to identify key antiplatelet steps for cyclic nucleotide actions in blocking platelet activation by PAR1 versus PAR4. Platelet aggregation by PAR1 or PAR4 was inhibited with similar EC(50) of 1.2 to 2.1 microM forskolin, 31 to 33 microM YC-1, 57 to 150 microM dibutyryl-cAMP, and 220 to 410 microM 8-pCPT-cGMP. There was a marked left shift in the inhibitory potencies of forskolin and YC-1 for alpha-granule release and glycoprotein IIbIIIa/integrin alphaIIbbeta3 activation (i.e., EC(50) of 1-60 and 40-1300 nM, respectively) that was not observed for dibutyryl-cAMP and 8-pCPT-cGMP (i.e., EC(50) of 200-600 and 40-140 microM, respectively). This inhibition was essentially instantaneous, and measurements of cyclic nucleotide levels and kinase activities support a model of compartmentation involving the cyclic nucleotide effectors and regulators and the key molecular targets for this platelet inhibition. The different sensitivities of PAR1 and PAR4 to inhibition of calcium mobilization and dense granule release identify key antiplatelet steps for cyclic nucleotide actions and are consistent with the signaling models for these receptors. Specifically, PAR4 inhibition depends on the regulation of both calcium mobilization and dense granule release, and PAR1 inhibition depends predominantly on the regulation of dense granule release. PMID:17525299

  1. Rapid response sensor for analyzing Special Nuclear Material

    SciTech Connect

    Mitra, S. S.; Doron, O.; Chen, A. X.; Antolak, A. J.

    2015-06-18

    Rapid in-situ analytical techniques are attractive for characterizing Special Nuclear Material (SNM). Present techniques are time consuming, and require sample dissolution. Proof-of-principal studies are performed to demonstrate the utility of employing low energy neutrons from a portable pulsed neutron generator for non-destructive isotopic analysis of nuclear material. In particular, time-sequenced data acquisition, operating synchronously with the pulsing of a neutron generator, partitions the characteristic elemental prompt gamma-rays according to the type of the reaction; inelastic neutron scattering reactions during the ON state and thermal neutron capture reactions during the OFF state of the generator. Thus, the key challenge is isolating these signature gamma- rays from the prompt fission and β-delayed gamma-rays that are also produced during the neutron interrogation. A commercial digital multi-channel analyzer has been specially customized to enable time-resolved gamma-ray spectral data to be acquired in multiple user-defined time bins within each of the ON/OFF gate periods of the neutron generator. Preliminary results on new signatures from depleted uranium as well as modeling and benchmarking of the concept are presented, however this approach should should be applicable for virtually all forms of SNM.

  2. Rapid Response Sensor for Analyzing Special Nuclear Material

    NASA Astrophysics Data System (ADS)

    Mitra, S. S.; Doron, O.; Chen, A. X.; Antolak, A. J.

    Rapid in-situ analytical techniques are attractive for characterizing Special Nuclear Material (SNM). Present techniques are time consuming, and require sample dissolution. Proof-of-principal studies are performed to demonstrate the utility of employing low energy neutrons from a portable pulsed neutron generator for non-destructive isotopic analysis of nuclear material. In particular, time-sequenced data acquisition, operating synchronously with the pulsing of a neutron generator, partitions the characteristic elemental prompt gamma-rays according to the type of the reaction; inelastic neutron scattering reactions during the ON state and thermal neutron capture reactions during the OFF state of the generator. The key challenge is isolating these signature gamma- rays from the prompt fission and β-delayed gamma-rays that are also produced during the neutron interrogation. A commercial digital multi-channel analyzer has been specially customized to enable time-resolved gamma-ray spectral data to be acquired in multiple user-defined time bins within each of the ON/OFF gate periods of the neutron generator. Preliminary results on new signatures from depleted uranium as well as modeling and benchmarking of the concept are presented, but this approach should should be applicable for virtually all forms of SNM

  3. Rapid response sensor for analyzing Special Nuclear Material

    DOE PAGESBeta

    Mitra, S. S.; Doron, O.; Chen, A. X.; Antolak, A. J.

    2015-06-18

    Rapid in-situ analytical techniques are attractive for characterizing Special Nuclear Material (SNM). Present techniques are time consuming, and require sample dissolution. Proof-of-principal studies are performed to demonstrate the utility of employing low energy neutrons from a portable pulsed neutron generator for non-destructive isotopic analysis of nuclear material. In particular, time-sequenced data acquisition, operating synchronously with the pulsing of a neutron generator, partitions the characteristic elemental prompt gamma-rays according to the type of the reaction; inelastic neutron scattering reactions during the ON state and thermal neutron capture reactions during the OFF state of the generator. Thus, the key challenge is isolatingmore » these signature gamma- rays from the prompt fission and β-delayed gamma-rays that are also produced during the neutron interrogation. A commercial digital multi-channel analyzer has been specially customized to enable time-resolved gamma-ray spectral data to be acquired in multiple user-defined time bins within each of the ON/OFF gate periods of the neutron generator. Preliminary results on new signatures from depleted uranium as well as modeling and benchmarking of the concept are presented, however this approach should should be applicable for virtually all forms of SNM.« less

  4. IMPROVEMENTS IN CODED APERTURE THERMAL NEUTRON IMAGING.

    SciTech Connect

    VANIER,P.E.

    2003-08-03

    A new thermal neutron imaging system has been constructed, based on a 20-cm x 17-cm He-3 position-sensitive detector with spatial resolution better than 1 mm. New compact custom-designed position-decoding electronics are employed, as well as high-precision cadmium masks with Modified Uniformly Redundant Array patterns. Fast Fourier Transform algorithms are incorporated into the deconvolution software to provide rapid conversion of shadowgrams into real images. The system demonstrates the principles for locating sources of thermal neutrons by a stand-off technique, as well as visualizing the shapes of nearby sources. The data acquisition time could potentially be reduced two orders of magnitude by building larger detectors.

  5. A multitask neutron beam line for spallation neutron sources

    NASA Astrophysics Data System (ADS)

    Pietropaolo, A.; Festa, G.; Grazzi, F.; Barzagli, E.; Scherillo, A.; Schooneveld, E. M.; Civita, F.

    2011-08-01

    Here we present a new concept for a time-of-flight neutron scattering instrument allowing for simultaneous application of three different techniques: time-of-flight neutron diffraction, neutron resonance capture analysis and Bragg edge transmission analysis. The instrument can provide average resolution neutron radiography too. The potential of the proposed concept was explored by implementing the necessary equipment on INES (Italian Neutron Experimental Station) at the ISIS spallation neutron source (UK). The results obtained show the effectiveness of the proposed instrument to acquire relevant quantitative information in a non-invasive way on a historical metallurgical sample, namely a Japanese hand guard (tsuba). The aforementioned neutron techniques simultaneously exploited the extended neutron energy range available from 10 meV to 1 keV. This allowed a fully satisfactory characterization of the sample in terms of metal components and their combination in different phases, and forging and assembling methods.

  6. Stochastic Self-Assembly of ParB Proteins Builds the Bacterial DNA Segregation Apparatus.

    PubMed

    Sanchez, Aurore; Cattoni, Diego I; Walter, Jean-Charles; Rech, Jérôme; Parmeggiani, Andrea; Nollmann, Marcelo; Bouet, Jean-Yves

    2015-08-26

    Many canonical processes in molecular biology rely on the dynamic assembly of higher-order nucleoprotein complexes. In bacteria, the assembly mechanism of ParABS, the nucleoprotein super-complex that actively segregates the bacterial chromosome and many plasmids, remains elusive. We combined super-resolution microscopy, quantitative genome-wide surveys, biochemistry, and mathematical modeling to investigate the assembly of ParB at the centromere-like sequences parS. We found that nearly all ParB molecules are actively confined around parS by a network of synergistic protein-protein and protein-DNA interactions. Interrogation of the empirically determined, high-resolution ParB genomic distribution with modeling suggests that instead of binding only to specific sequences and subsequently spreading, ParB binds stochastically around parS over long distances. We propose a new model for the formation of the ParABS partition complex based on nucleation and caging: ParB forms a dynamic lattice with the DNA around parS. This assembly model and approach to characterizing large-scale, dynamic interactions between macromolecules may be generalizable to many unrelated machineries that self-assemble in superstructures. PMID:27135801

  7. Rapidity-dependent chemical potentials in a statistical approach

    NASA Astrophysics Data System (ADS)

    Broniowski, Wojciech; Biedroń, Bartłomiej

    2008-04-01

    We present a single-freeze-out model with thermal and geometric parameters dependent on the position within the fireball and use it to describe the rapidity distribution and transverse-momentum spectra of pions, kaons, protons and antiprotons measured at RHIC at \\sqrt{s_NN}=200\\,\\, GeV by BRAHMS. THERMINATOR is used to perform the necessary simulation, which includes all resonance decays. The result of the fit to the data is the expected growth of the baryon and strange chemical potentials with the spatial rapidity αpar. The value of the baryon chemical potential at αpar ~ 3 is about 200 MeV, i.e. it lies in the range of the highest SPS energies. The chosen geometry of the fireball has a decreasing transverse size as the magnitude of αpar is increased, which also corresponds to decreasing transverse flow. The strange chemical potential obtained from the fit to the K+/K- ratio is such that the local strangeness density in the fireball is compatible with zero. The resulting rapidity distribution of net protons are described qualitatively within the statistical approach. As a result of our study, the knowledge of the 'topography' of the fireball is acquired, allowing for other analyses and predictions. Research supported by the Polish Ministry of Education and Science, grants N202 034 32/0918 and 2 P03B 02828.

  8. Par Pond vegetation status Summer 1995 -- September survey descriptive summary

    SciTech Connect

    Mackey, H.E. Jr.; Riley, R.S.

    1995-09-01

    The water level of Par Pond was lowered approximately 20 feet in mid-1991 in order to protect downstream residents from possible dam failure suggested by subsidence on the downstream slope of the dam and to repair the dam. This lowering exposed both emergent and nonemergent macrophyte beds to drying conditions resulting in extensive losses. A survey of the emergent shoreline aquatic plant communities began in June 1995, three months after the refilling of Par Pond to approximately 200 feet above mean sea level and continued with this mid-September survey. Communities similar to the pre-drawdown Par Pond aquatic plant communities are becoming re-established; especially, beds of maidencane, lotus, waterlily, and watershield are now extensive and well established. Cattail occurrence continues to increase, but large beds common to Par Pond prior to the drawdown have not formed. Future surveys during the late growing seasons of 1995, and throughout 1996 and 1997, along with the evaluation of satellite data to map the areal extent of the macrophyte beds of Par Pond, are planned.

  9. Par Pond vegetation status Summer 1995 -- October survey descriptive summary

    SciTech Connect

    Mackey, H.E. Jr.; Riley, R.S.

    1995-11-01

    The water level of Par Pond was lowered approximately 20 feet in mid-1991 in order to protect downstream residents from possible dam failure suggested by subsidence on the downstream slope of the dam and to repair the dam. This lowering exposed both emergent and nonemergent macrophyte beds to drying conditions resulting in extensive losses. A survey of the emergent shoreline aquatic plant communities began in June 1995, three months after the refilling of Par Pond to approximately 200 feet above mean sea level and continued with this late October survey. Communities similar to the pre-drawdown Par Pond aquatic plant communities are becoming re-established; especially, beds of maiden cane, lotus, waterlily, and watershield are now extensive and well established. Cattail occurrence continues to increase, but large beds common to Par Pond prior to the drawdown have not formed. Future surveys throughout 1996 and 1997, along with the continued evaluation of satellite data to map the areal extent of the macrophyte beds of Par Pond, are planned.

  10. Conception et caracterisation d'un magnetoplasma produit par une onde de surface pour la pulverisation d'echantillons solides

    NASA Astrophysics Data System (ADS)

    Masse, Louis Philippe

    Suite a l'extraordinaire explosion de l'informatique de la derniere decennie, la science et la technologie des materiaux ont pris un essor extraordinaire. Par exemple, il est devenu crucial de concevoir des materiaux a haut degre de purete. Ce besoin a fortement motive le developpement de methodes d'analyse de solides. Traditionnellement, la methode adoptee est l'analyse par torche ICP, mais pour de nombreuses raisons, dont la lenteur de cette methode, la communaute scientifique oeuvrant en chimie analytique recherche des techniques d'analyse de solides directes, rapides et plus sensibles. Parmi les voies possibles, on trouve les methodes basees sur la pulverisation par plasma. Dans ce contexte, nous avons etudie la possibilite et la pertinence d'utiliser un magnetoplasma entretenu par une onde de surface pour pulveriser des solides dans le but de les analyser. Nos travaux portent principalement sur l'etude du comportement du plasma lors de la pulverisation. Nous avons montre que la pulverisation affecte la decharge de diverses facons. En premier lieu, la concentration d'especes provenant du materiau pulverise dans le plasma augmente avec la tension de polarisation. De plus, la concentration d'especes pulverisees diminue lorsque la pression croit, possiblement a cause du redepot. Nous avons aussi montre qu'il etait possible de pulveriser des solides isolants en exploitant le phenomene d'autopolarisation du a l'application d'une tension RF. Nous avons aussi etudie l'effet de la pulverisation sur la temperature et la densite electronique. Ainsi, lors de la pulverisation de metaux tels que le cuivre, la temperature electronique diminue lorsque la tension de polarisation augmente. Ceci est attribuable a l'augmentation de la densite d'especes metalliques neutres facilement ionisables par impact electronique. Nous avons aussi note que la densite electronique augmente avec la concentration d'especes metalliques dans le plasma, ce qui resulte d'un meilleur bilan de

  11. Superconducting thermal neutron detectors

    NASA Astrophysics Data System (ADS)

    Merlo, V.; Pietropaolo, A.; Celentano, G.; Cirillo, M.; Lucci, M.; Ottaviani, I.; Salvato, M.; Scherillo, A.; Schooneveld, E. M.; Vannozzi, A.

    2016-09-01

    A neutron detection concept is presented that is based on superconductive niobium nitride (NbN) strips coated by a boron (B) layer. The working principle is well described by a hot spot mechanism: upon the occurrence of the nuclear reactions n + 10B → α + 7Li + 2.8 MeV, the energy released by the secondary particles into the strip induces a superconducting-normal state transition. The latter is recognized as a voltage signal which is the evidence of the incident neutron. The above described detection principle has been experimentally assessed and verified by irradiating the samples with a pulsed neutron beam at the ISIS spallation neutron source (UK). It is found that the boron coated superconducting strips, kept at a temperature T below 11K and current-biased below the critical current IC, are driven into the normal state upon thermal neutron irradiation. Measurements on the counting rate of the device are presented and the basic physical features of the detector are discussed and compared to those of a borated Nb superconducting strip.

  12. Neutron whispering gallery

    NASA Astrophysics Data System (ADS)

    Nesvizhevsky, Valery V.; Voronin, Alexei Yu.; Cubitt, Robert; Protasov, Konstantin V.

    2010-02-01

    The `whispering gallery' effect has been known since ancient times for sound waves in air, later in water and more recently for a broad range of electromagnetic waves: radio, optics, Roentgen and so on. It consists of wave localization near a curved reflecting surface and is expected for waves of various natures, for instance, for atoms and neutrons. For matter waves, it would include a new feature: a massive particle would be settled in quantum states, with parameters depending on its mass. Here, we present for the first time the quantum whispering-gallery effect for cold neutrons. This phenomenon provides an example of an exactly solvable problem analogous to the `quantum bouncer'; it is complementary to the recently discovered gravitationally bound quantum states of neutrons . These two phenomena provide a direct demonstration of the weak equivalence principle for a massive particle in a pure quantum state. Deeply bound whispering-gallery states are long-living and weakly sensitive to surface potential; highly excited states are short-living and very sensitive to the wall potential shape. Therefore, they are a promising tool for studying fundamental neutron-matter interactions, quantum neutron optics and surface physics effects.

  13. Twisting Neutron Waves

    NASA Astrophysics Data System (ADS)

    Pushin, Dmitry

    Most waves encountered in nature can be given a ``twist'', so that their phase winds around an axis parallel to the direction of wave propagation. Such waves are said to possess orbital angular momentum (OAM). For quantum particles such as photons, atoms, and electrons, this corresponds to the particle wavefunction having angular momentum of Lℏ along its propagation axis. Controlled generation and detection of OAM states of photons began in the 1990s, sparking considerable interest in applications of OAM in light and matter waves. OAM states of photons have found diverse applications such as broadband data multiplexing, massive quantum entanglement, optical trapping, microscopy, quantum state determination and teleportation, and interferometry. OAM states of electron beams have been used to rotate nanoparticles, determine the chirality of crystals and for magnetic microscopy. Here I discuss the first demonstration of OAM control of neutrons. Using neutron interferometry with a spatially incoherent input beam, we show the addition and conservation of quantum angular momenta, entanglement between quantum path and OAM degrees of freedom. Neutron-based quantum information science heretofore limited to spin, path, and energy degrees of freedom, now has access to another quantized variable, and OAM modalities of light, x-ray, and electron beams are extended to a massive, penetrating neutral particle. The methods of neutron phase imprinting demonstrated here expand the toolbox available for development of phase-sensitive techniques of neutron imaging. Financial support provided by the NSERC Create and Discovery programs, CERC and the NIST Quantum Information Program is acknowledged.

  14. Apollo 16 neutron stratigraphy.

    NASA Technical Reports Server (NTRS)

    Russ, G. P., III

    1973-01-01

    The Apollo 16 soils have the largest low-energy neutron fluences yet observed in lunar samples. Variations in the isotopic ratios Gd-158/Gd-157 and Sm-150/Sm-149 (up to 1.9 and 2.0%, respectively) indicate that the low-energy neutron fluence in the Apollo 16 drill stem increases with depth throughout the section sampled. Such a variation implies that accretion has been the dominant regolith 'gardening' process at this location. The data may be fit by a model of continuous accretion of pre-irradiated material or by models involving as few as two slabs of material in which the first slab could have been deposited as long as 1 b.y. ago. The ratio of the number of neutrons captured per atom by Sm to the number captured per atom by Gd is lower than in previously measured lunar samples, which implies a lower energy neutron spectrum at this site. The variation of this ratio with chemical composition is qualitatively similar to that predicted by Lingenfelter et al. (1972). Variations are observed in the ratio Gd-152/Gd-160 which are fluence-correlated and probably result from neutron capture by Eu-151.

  15. Origin of Neutron Stars

    NASA Astrophysics Data System (ADS)

    Brecher, K.

    1999-12-01

    The origin of the concept of neutron stars can be traced to two brief, incredibly insightful publications. Work on the earlier paper by Lev Landau (Phys. Z. Sowjetunion, 1, 285, 1932) actually predated the discovery of neutrons. Nonetheless, Landau arrived at the notion of a collapsed star with the density of a nucleus (really a "nucleus star") and demonstrated (at about the same time as, and independent of, Chandrasekhar) that there is an upper mass limit for dense stellar objects of about 1.5 solar masses. Perhaps even more remarkable is the abstract of a talk presented at the December 1933 meeting of the American Physical Society published by Walter Baade and Fritz Zwicky in 1934 (Phys. Rev. 45, 138). It followed the discovery of the neutron by just over a year. Their report, which was about the same length as the present abstract: (1) invented the concept and word supernova; (2) suggested that cosmic rays are produced by supernovae; and (3) in the authors own words, proposed "with all reserve ... the view that supernovae represent the transitions from ordinary stars to neutron stars (italics), which in their final stages consist of extremely closely packed neutrons." The abstract by Baade and Zwicky probably contains the highest density of new, important (and correct) ideas in high energy astrophysics ever published in a single paper. In this talk, we will discuss some of the facts and myths surrounding these two publications.

  16. Hybrid superconducting neutron detectors

    SciTech Connect

    Merlo, V.; Lucci, M.; Ottaviani, I.; Salvato, M.; Cirillo, M.; Scherillo, A.; Celentano, G.; Pietropaolo, A.

    2015-03-16

    A neutron detection concept is presented that is based on superconductive niobium (Nb) strips coated by a boron (B) layer. The working principle of the detector relies on the nuclear reaction, {sup 10}B + n → α + {sup 7}Li, with α and Li ions generating a hot spot on the current-biased Nb strip which in turn induces a superconducting-normal state transition. The latter is recognized as a voltage signal which is the evidence of the incident neutron. The above described detection principle has been experimentally assessed and verified by irradiating the samples with a pulsed neutron beam at the ISIS spallation neutron source (UK). It is found that the boron coated superconducting strips, kept at a temperature T = 8 K and current-biased below the critical current I{sub c}, are driven into the normal state upon thermal neutron irradiation. As a result of the transition, voltage pulses in excess of 40 mV are measured while the bias current can be properly modulated to bring the strip back to the superconducting state, thus resetting the detector. Measurements on the counting rate of the device are presented and the basic physical features of the detector are discussed.

  17. The ambiguous neutron

    NASA Astrophysics Data System (ADS)

    Hawes, Joan L.

    1980-09-01

    The ways in which a neutron may be described suggest that it is a particle; is a wave; has no electric charge; has a spin magnetic moment similar to that of an electron and a proton; is a stable fundamental unit of matter; and has a halflife of approximately 12 min. These are only some of the seemingly ambiguous properties of a very remarkable entity. Mostly-the machinations of wave mechanics notwithstanding-there seems little doubt that the neutron is imagined to be a particle. It is probably regarded as a very small, round, invisible object which has no electric charge and resides in the atomic nucleus. Indeed, the fact that without it stable nuclei cannot exist seems paradoxically allied to the statement that neither can radioactive ones. Again, a certain ambiguity is evident in the notion that any electrically neutral entity can show magnetic properties. And, if it is the force effects of the neutron that underline its role as a fundamental building brick of matter, how does it exert these forces and remain uncharged? Many of the solutions to these and other questions and propositions about the neutron are of relatively recent history; some still remain hidden-the precise nature of the neutron's forces of interaction for example. But the search to understanding lies in the same realm of patient experimental and theoretical enquiry that embodied its initial discovery by James Chadwick in 1932.

  18. Hybrid superconducting neutron detectors

    NASA Astrophysics Data System (ADS)

    Merlo, V.; Salvato, M.; Cirillo, M.; Lucci, M.; Ottaviani, I.; Scherillo, A.; Celentano, G.; Pietropaolo, A.

    2015-03-01

    A neutron detection concept is presented that is based on superconductive niobium (Nb) strips coated by a boron (B) layer. The working principle of the detector relies on the nuclear reaction, 10B + n → α + 7Li, with α and Li ions generating a hot spot on the current-biased Nb strip which in turn induces a superconducting-normal state transition. The latter is recognized as a voltage signal which is the evidence of the incident neutron. The above described detection principle has been experimentally assessed and verified by irradiating the samples with a pulsed neutron beam at the ISIS spallation neutron source (UK). It is found that the boron coated superconducting strips, kept at a temperature T = 8 K and current-biased below the critical current Ic, are driven into the normal state upon thermal neutron irradiation. As a result of the transition, voltage pulses in excess of 40 mV are measured while the bias current can be properly modulated to bring the strip back to the superconducting state, thus resetting the detector. Measurements on the counting rate of the device are presented and the basic physical features of the detector are discussed.

  19. Neutron Star Compared to Manhattan

    NASA Video Gallery

    A pulsar is a neutron star, the crushed core of a star that has exploded. Neutron stars crush half a million times more mass than Earth into a sphere no larger than Manhattan, as animated in this s...

  20. Neutron star crusts

    NASA Technical Reports Server (NTRS)

    Lorenz, C. P.; Ravenhall, D. G.; Pethick, C. J.

    1993-01-01

    We calculate properties of neutron star matter at subnuclear densities using an improved nuclear Hamiltonian. Nuclei disappear and the matter becomes uniform at a density of about 0.6n(s), where n(s) of about 0.16/cu fm is the saturation density of nuclear matter. As a consequence, the mass of matter in the crusts of neutron stars is only about half as large as previously estimated. In about half of that crustal mass, nuclear matter occurs in shapes very different from the roughly spherical nuclei familiar at lower densities. The thinner crust and the unusual nuclear shape have important consequences for theories of the rotational and thermal evolution of neutron stars, especialy theories of glitches.

  1. Personnel electronic neutron dosimeter

    DOEpatents

    Falk, R.B.; Tyree, W.H.

    1982-03-03

    A personnel electronic dosimeter includes a neutron-proton and neutron-alpha converter for providing an electrical signal having a magnitude proportional to the energy of a detected proton or alpha particle produced from the converter, a pulse generator circuit for generating a pulse having a duration controlled by the weighed effect of the amplitude of the electrical signal, an oscillator enabled by the pulse for generating a train of clock pulses for a time dependent upon the pulse length, a counter for counting the clock pulses, and an indicator for providing a direct reading and aural alarm when the count indicates that the wearer has been exposed to a selected level of neutron dose equivalent.

  2. Personnel electronic neutron dosimeter

    DOEpatents

    Falk, Roger B.; Tyree, William H.

    1984-12-18

    A personnel electronic dosimeter includes a neutron-proton and neutron-alpha converter for providing an electrical signal having a magnitude proportional to the energy of a detected proton or alpha particle produced from the converter, a pulse generator circuit for generating a pulse having a duration controlled by the weighed effect of the amplitude of the electrical signal, an oscillator enabled by the pulse for generating a train of clock pulses for a time dependent upon the pulse length, a counter for counting the clock pulses, and an indicator for providing a direct reading and aural alarm when the count indicates that the wearer has been exposed to a selected level of neutron dose equivalent.

  3. Ultrafast neutron detector

    DOEpatents

    Wang, Ching L.

    1987-01-01

    The invention comprises a neutron detector (50) of very high temporal resolution that is particularly well suited for measuring the fusion reaction neutrons produced by laser-driven inertial confinement fusion targets. The detector comprises a biased two-conductor traveling-wave transmission line (54, 56, 58, 68) having a uranium cathode (60) and a phosphor anode (62) as respective parts of the two conductors. A charge line and Auston switch assembly (70, 72, 74) launch an electric field pulse along the transmission line. Neutrons striking the uranium cathode at a location where the field pulse is passing, are enabled to strike the phosphor anode and produce light that is recorded on photographic film (64). The transmission line may be variously configured to achieve specific experimental goals.

  4. METHOD OF PRODUCING NEUTRONS

    DOEpatents

    Imhoff, D.H.; Harker, W.H.

    1964-02-01

    A method for producing neutrons is described in which there is employed a confinement zone defined between longitudinally spaced localized gradient regions of an elongated magnetic field. Changed particles and neutralizing electrons, more specifically deuterons and tritons and neutralizng electrons, are injected into the confinement field from ion sources located outside the field. The rotational energy of the parrticles is increased at the gradients by imposing an oscillating transverse electrical field thereacross. The imposition of such oscillating transverse electrical fields improves the reflection capability of such gradient fielda so that the reactive particles are retained more effectively within the zone. With the attainment of appropriate densities of plasma particles and provided that such particles are at a sufficiently high temperature, neutron-producing reactions ensue and large quantities of neutrons emerge from the containment zone. (AEC)

  5. Hyperons and neutron stars

    SciTech Connect

    Vidaña, Isaac

    2015-02-24

    In this lecture I will briefly review some of the effects of hyperons on the properties of neutron and proto-neutron stars. In particular, I will revise the problem of the strong softening of the EoS, and the consequent reduction of the maximum mass, induced by the presence of hyperons, a puzzle which has become more intringuing and difficult to solve due the recent measurements of the unusually high masses of the millisecond pulsars PSR J1903+0327 (1.667±0.021M{sub ⊙}), PSR J1614–2230 (1.97±0.04M{sub ⊙}), and PSR J0348+0432 (2.01±0.04M{sub ⊙}). Finally, I will also examine the role of hyperons on the cooling properties of newly born neutron stars and on the so-called r-mode instability.

  6. Spherical neutron generator

    DOEpatents

    Leung, Ka-Ngo

    2006-11-21

    A spherical neutron generator is formed with a small spherical target and a spherical shell RF-driven plasma ion source surrounding the target. A deuterium (or deuterium and tritium) ion plasma is produced by RF excitation in the plasma ion source using an RF antenna. The plasma generation region is a spherical shell between an outer chamber and an inner extraction electrode. A spherical neutron generating target is at the center of the chamber and is biased negatively with respect to the extraction electrode which contains many holes. Ions passing through the holes in the extraction electrode are focused onto the target which produces neutrons by D-D or D-T reactions.

  7. Hyperons in Neutron Stars

    NASA Astrophysics Data System (ADS)

    Vidaña, Isaac

    2016-01-01

    In this work I briefly review some of the effects of hyperons on the properties of neutron and proto-neutron stars. In particular, I revise the problem of the strong softening of the EoS, and the consequent reduction of the maximum mass, induced by the presence of hyperons, a puzzle which has become more intringuing and difficult to solve because of the recent measurements of the unusually high masses of the millisecond pulsars PSR J1903+0327 (1.667 ± 0.021M⊙), PSR J1614-2230 (1.97 ± 0.04M⊙), and PSR J0348+0432 (2.01 ± 0.04M⊙). Some of the solutions proposed to tackle this problem are discussed. Finally, I re-examine also the role of hyperons on the cooling properties of newly born neutron stars and on the so-called r-mode instability.

  8. NEUTRONIC REACTOR CORE INSTRUMENT

    DOEpatents

    Mims, L.S.

    1961-08-22

    A multi-purpose instrument for measuring neutron flux, coolant flow rate, and coolant temperature in a nuclear reactor is described. The device consists essentially of a hollow thimble containing a heat conducting element protruding from the inner wall, the element containing on its innermost end an amount of fissionsble materinl to function as a heat source when subjected to neutron flux irradiation. Thermocouple type temperature sensing means are placed on the heat conducting element adjacent the fissionable material and at a point spaced therefrom, and at a point on the thimble which is in contact with the coolant fluid. The temperature differentials measured between the thermocouples are determinative of the neutron flux, coolant flow, and temperature being measured. The device may be utilized as a probe or may be incorporated in a reactor core. (AE C)

  9. Neutronic reactor construction

    DOEpatents

    Huston, Norman E.

    1976-07-06

    1. A neutronic reactor comprising a moderator including horizontal layers formed of horizontal rows of graphite blocks, alternate layers of blocks having the rows extending in one direction, the remaining alternate layers having the rows extending transversely to the said one direction, alternate rows of blocks in one set of alternate layers having longitudinal ducts, the moderator further including slotted graphite tubes positioned in the ducts, the reactor further comprising an aluminum coolant tube positioned within the slotted tube in spaced relation thereto, bodies of thermal-neutron-fissionable material, and jackets enclosing the bodies and being formed of a corrosion-resistant material having a low neutron-capture cross section, the bodies and jackets being positioned within the coolant tube so that the jackets are spaced from the coolant tube.

  10. Realistic fission model and the r-process in neutron star mergers

    SciTech Connect

    Shibagaki, S.; Kajino, T.; Chiba, S.; Mathews, G. J.

    2014-05-09

    About half of heavy elements are considered to be produced by the rapid neutron-capture process, r-process. The neutron star merger is one of the viable candidates for the astrophysical site of r-process nucleosynthesis. Nuclear fission reactions play an important role in the r-process of neutron star mergers. However theoretical predictions about fission properties of neutron-rich nuclei have some uncertainties. Especially, their fission fragment distributions are totally unknown and the phenomenologically extrapolated distribution was often applied to nucleosynthesis calculations. In this study, we have carried out r-process nucleosynthesis calculations based upon new theoretical estimates of fission fragment distributions. We discuss the effects on the r-process in neutron star mergers from the nuclear fission of heavy neutron-rich actinide elements. We also discuss how variations in the fission fragment distributions affect the abundance pattern.

  11. PAR-1 phosphorylates Mind bomb to promote vertebrate neurogenesis

    PubMed Central

    Ossipova, Olga; Ezan, Jerome; Sokol, Sergei Y.

    2010-01-01

    Summary Generation of neurons in the vertebrate central nervous system requires complex transcriptional regulatory network and signaling processes in polarized neuroepithelial progenitor cells. Here we demonstrate that neurogenesis in the Xenopus neural plate in vivo and mammalian neural progenitors in vitro involves intrinsic antagonistic activities of the polarity proteins PAR-1 and aPKC. Furthermore, we show that Mind bomb (Mib), a ubiquitin ligase that promotes Notch ligand trafficking and activity, is a crucial molecular substrate for PAR-1. The phosphorylation of Mib by PAR-1 results in Mib degradation, repression of Notch signaling and stimulation of neuronal differentiation. These observations suggest a conserved mechanism for neuronal fate determination that might operate during asymmetric divisions of polarized neural progenitor cells. PMID:19686683

  12. Mesure du taux de la capture radiative du muon par l'hydrogene liquide

    NASA Astrophysics Data System (ADS)

    Jonkmans, Guy

    À basse énergie, l'interaction faible entre leptons et quarks est décrite par une interaction de la forme courant × courant de type V - A. La présence de l'interaction forte induit des couplages additionnels qui doivent être déterminés expérimentalement. De ceux-ci, le couplage pseudoscalaire induit, gp , est mesuré avec la plus grande incertitude et fait l'objet de la présente recherche. L'hypothèse du Courant Axial Partiellement Conservé (CAPC) et l'usage de la relation de Goldberger-Treiman relie gp au couplage axial ga . Cette relation a été vérifiée traditionnellement par la Capture Ordinaire du Muon (COM) à une valeur fixe du moment de transfert q. La Capture Radiative du Muon (CRM), m- p-->nnmg , est un meilleur outil pour l'étude de gp à cause de sa dépendance variable en q2 qui offre une plus grande sensibilité dans la partie à haute énergie du spectre des photons. Toutefois, le petit rapport d'embranchement (~10-8) de la CRM par rapport à la désintégration du muon a retardé cette mesure jusqu'à ce jour. La théorie et les difficultés expérimentales associées à la détection des photons de CRM sont présentées au deuxième chapitre. On décrit ensuite, au troisième chapitre, les composantes du système de détection. Ce détecteur est un spectromètre à paires de grand angle solide (~3p) et qui permet l'observation des photons par l'analyse des électrons et des positrons de photo-conversion. Ainsi, le bruit de fond important des neutrons de la COM ne constitue pas un problème pour cette mesure. Nous décrivons, au quatrième chapitre, toutes les étapes de l'analyse, nécessaires pour la réduction des multiples bruits de fond. Le cinquième chapitre présente le calcul des efficacités ainsi que l'estimation des erreurs systématiques. Le sixième chapitre démontre comment l'on extrait le rapport d'embranchement pour la CRM ainsi que la valeur ae gp . On insiste sur la dépendance de gp en fonction de la valeur de

  13. POLARIZED NEUTRONS IN RHIC

    SciTech Connect

    COURANT,E.D.

    1998-04-27

    There does not appear to be any obvious way to accelerate neutrons, polarized or otherwise, to high energies by themselves. To investigate the behavior of polarized neutrons the authors therefore have to obtain them by accelerating them as components of heavier nuclei, and then sorting out the contribution of the neutrons in the analysis of the reactions produced by the heavy ion beams. The best neutron carriers for this purpose are probably {sup 3}He nuclei and deuterons. A polarized deuteron is primarily a combination of a proton and a neutron with their spins pointing in the same direction; in the {sup 3}He nucleus the spins of the two protons are opposite and the net spin (and magnetic moment) is almost the same as that of a free neutron. Polarized ions other than protons may be accelerated, stored and collided in a ring such as RHIC provided the techniques proposed for polarized proton operation can be adapted (or replaced by other strategies) for these ions. To accelerate polarized particles in a ring, one must make provisions for overcoming the depolarizing resonances that occur at certain energies. These resonances arise when the spin tune (ratio of spin precession frequency to orbit frequency) resonates with a component present in the horizontal field. The horizontal field oscillates with the vertical motion of the particles (due to vertical focusing); its frequency spectrum is dominated by the vertical oscillation frequency and its modulation by the periodic structure of the accelerator ring. In addition, the magnet imperfections that distort the closed orbit vertically contain all integral Fourier harmonics of the orbit frequency.

  14. Corrosion resistant neutron absorbing coatings

    DOEpatents

    Choi, Jor-Shan; Farmer, Joseph C; Lee, Chuck K; Walker, Jeffrey; Russell, Paige; Kirkwood, Jon; Yang, Nancy; Champagne, Victor

    2013-11-12

    A method of forming a corrosion resistant neutron absorbing coating comprising the steps of spray or deposition or sputtering or welding processing to form a composite material made of a spray or deposition or sputtering or welding material, and a neutron absorbing material. Also a corrosion resistant neutron absorbing coating comprising a composite material made of a spray or deposition or sputtering or welding material, and a neutron absorbing material.

  15. Corrosion resistant neutron absorbing coatings

    DOEpatents

    Choi, Jor-Shan; Farmer, Joseph C.; Lee, Chuck K.; Walker, Jeffrey; Russell, Paige; Kirkwood, Jon; Yang, Nancy; Champagne, Victor

    2012-05-29

    A method of forming a corrosion resistant neutron absorbing coating comprising the steps of spray or deposition or sputtering or welding processing to form a composite material made of a spray or deposition or sputtering or welding material, and a neutron absorbing material. Also a corrosion resistant neutron absorbing coating comprising a composite material made of a spray or deposition or sputtering or welding material, and a neutron absorbing material.

  16. Passive Neutron Detection at Borders

    SciTech Connect

    Kouzes, Richard T.; Siciliano, Edward R.; Ely, James H.; Keller, Paul E.; McConn, Ronald J.

    2008-03-01

    Radiation portal monitor systems have been deployed to screen for illicit trafficking of radioactive materials at international border crossings. This report reviews some of the neutron detection requirements and capabilities of passive detection systems used for such applications. Simulations show the effects of cargo materials on neutron spectra, different detector geometries, using a large-array of neutron detectors, and the effects of backgrounds including “ship effect” neutrons.

  17. NIFTI and DISCOS: New concepts for a compact accelerator neutron source for boron neutron capture therapy applications

    SciTech Connect

    Powell, J.; Ludewig, H.; Todosow, M.; Reich, M.

    1995-06-01

    Two new concepts, NIFTI and DISCOS, are described. These concepts enable the efficient production of epithermal neutrons for BNCT (Boron Neutron Capture Therapy) medical treatment, utilizing a low current, low energy proton beam impacting on a lithium target. The NIFTI concept uses fluoride compounds, such as lead or beryllium fluoride, to efficiently degrade high energy neutrons from the lithium target to the lower energies required for BNCT. The fluoride compounds are in turn encased in an iron layer that strongly impedes the transmission of neutrons with energies above 24 KeV. Lower energy neutrons readily pass through this iron filter, which has a deep window in its scattering cross section at 24 KeV. The DISCOS concept uses a rapidly rotating, high g disc to create a series of thin ({approximately} 1 micron thickness) liquid lithium targets in the form of continuous films or sheets of discrete droplets--through which the proton beam passes. The average energy lost by a proton as it passes through a single target is small, approximately 10 KeV. Between the targets, the proton beam is re-accelerated by an applied DC electric field. The DISCOS approach enables the accelerator--target facility to operate with a beam energy only slightly above the threshold value for neutron production--resulting in an output beam of low-energy epithermal neutrons--while achieving a high yield of neutrons per milliamp of proton beam current. Parametric trade studies of the NIFTI and DISCOS concepts are described. These include analyses of a broad range of NIFTI designs using the Monte carlo MCNP neutronics code, as well as mechanical and thermal-hydraulic analyses of various DISCOS designs.

  18. Neutron imaging camera

    NASA Astrophysics Data System (ADS)

    Hunter, S. D.; de Nolfo, G. A.; Barbier, L. M.; Link, J. T.; Son, S.; Floyd, S. R.; Guardala, N.; Skopec, M.; Stark, B.

    2008-04-01

    The Neutron Imaging Camera (NIC) is based on the Three-dimensional Track Imager (3_DTI) technology developed at GSFC for gamma-ray astrophysics applications. The 3-DTI, a large volume time-projection chamber, provides accurate, ~0.4 mm resolution, 3-D tracking of charged particles. The incident direction of fast neutrons, En > 0.5 MeV, are reconstructed from the momenta and energies of the proton and triton fragments resulting from 3He(n,p)3H interactions in the 3-DTI volume. The performance of the NIC from laboratory is presented.

  19. Neutron Imaging Camera

    NASA Technical Reports Server (NTRS)

    Hunter, Stanley; deNolfo, G. A.; Barbier, L. M.; Link, J. T.; Son, S.; Floyd, S. R.; Guardala, N.; Skopec, M.; Stark, B.

    2008-01-01

    The Neutron Imaging Camera (NIC) is based on the Three-dimensional Track Imager (3DTI) technology developed at GSFC for gamma-ray astrophysics applications. The 3-DTI, a large volume time-projection chamber, provides accurate, approximately 0.4 mm resolution, 3-D tracking of charged particles. The incident direction of fast neutrons, En > 0.5 MeV, are reconstructed from the momenta and energies of the proton and triton fragments resulting from (sup 3)He(n,p) (sup 3)H interactions in the 3-DTI volume. The performance of the NIC from laboratory and accelerator tests is presented.

  20. Neutrinos from neutron stars

    NASA Technical Reports Server (NTRS)

    Helfand, D. J.

    1979-01-01

    A calculation of the flux of ultra-high energy neutrinos from galactic neutron stars is presented. The calculation is used to determine the number of point sources detectable at the sensitivity threshold of a proposed deep underwater muon and neutrino detector array. The detector array would have a point source detection threshold of about 100 eV/sq cm-sec. Analysis of neutrino luminosities and the number of detectable sources suggests that the deep underwater detector may make a few discoveries. In particular, a suspected neutron star in the Cyg X-3 source seems a promising target for the deep underwater array.

  1. MCNP: Neutron benchmark problems

    SciTech Connect

    Whalen, D.J.; Cardon, D.A.; Uhle, J.L.; Hendricks, J.S.

    1991-11-01

    The recent widespread and increased use of radiation transport codes has produced greater user and institutional demand for assurances that such codes give correct results. Responding to these requirements for code validation, the general purpose Monte Carlo transport code MCNP has been tested on criticality, pulsed sphere, and shielding neutron problem families. Results for each were compared to experimental data. MCNP successfully predicted the experimental results of all three families within the expected data and statistical uncertainties. These successful predictions demonstrate that MCNP can successfully model a broad spectrum of neutron transport problems. 18 refs., 27 figs., 4 tabs.

  2. NEUTRONIC REACTOR CONTROL ELEMENT

    DOEpatents

    Newson, H.W.

    1960-09-13

    A novel composite neutronic reactor control element is offered. The element comprises a multiplicity of sections arranged in end-to-end relationship, each of the sections having a markedly different neutron-reactive characteristic. For example, a three-section control element could contain absorber, moderator, and fuel sections. By moving such an element longitudinally through a reactor core, reactivity is decreased by the absorber, increased slightly by the moderator, or increased substantially by the fuel. Thus, control over a wide reactivity range is provided.

  3. Neutron activated switch

    DOEpatents

    Barton, David M.

    1991-01-01

    A switch for reacting quickly to a neutron emission. A rod consisting of fissionable material is located inside a vacuum tight body. An adjustable contact is located coaxially at an adjustable distance from one end of the rod. Electrical leads are connected to the rod and to the adjustable contact. With a vacuum drawn inside the body, a neutron bombardment striking the rod causes it to heat and expand longitudinally until it comes into contact with the adjustable contact. This circuit closing occurs within a period of a few microseconds.

  4. GUIDE FOR POLARIZED NEUTRONS

    DOEpatents

    Sailor, V.L.; Aichroth, R.W.

    1962-12-01

    The plane of polarization of a beam of polarized neutrons is changed by this invention, and the plane can be flipped back and forth quicitly in two directions in a trouble-free manner. The invention comprises a guide having a plurality of oppositely directed magnets forming a gap for the neutron beam and the gaps are spaced longitudinally in a spiral along the beam at small stepped angles. When it is desired to flip the plane of polarization the magnets are suitably rotated to change the direction of the spiral of the gaps. (AEC)

  5. Simplified fast neutron dosimeter

    DOEpatents

    Sohrabi, Mehdi

    1979-01-01

    Direct fast-neutron-induced recoil and alpha particle tracks in polycarbonate films may be enlarged for direct visual observation and automated counting procedures employing electrochemical etching techniques. Electrochemical etching is, for example, carried out in a 28% KOH solution at room temperature by applying a 2000 V peak-to-peak voltage at 1 kHz frequency. Such recoil particle amplification can be used for the detection of wide neutron dose ranges from 1 mrad. to 1000 rads. or higher, if desired.

  6. Fast neutron dosimetry

    SciTech Connect

    DeLuca, P.M. Jr.; Pearson, D.W.

    1992-01-01

    This progress report concentrates on two major areas of dosimetry research: measurement of fast neutron kerma factors for several elements for monochromatic and white spectrum neutron fields and determination of the response of thermoluminescent phosphors to various ultra-soft X-ray energies and beta-rays. Dr. Zhixin Zhou from the Shanghai Institute of Radiation Medicine, People's Republic of China brought with him special expertise in the fabrication and use of ultra-thin TLD materials. Such materials are not available in the USA. The rather unique properties of these materials were investigated during this grant period.

  7. Lunar neutron stratigraphy.

    NASA Technical Reports Server (NTRS)

    Russ, G. P., III; Burnett, D. S.; Wasserburg, G. J.

    1972-01-01

    Study of the isotopic composition of gadolinium and samarium in four soil and seven drill stem samples returned by the Apollo 15 mission. The results show the possibility to date sedimentary processes on the lunar surface for time scales of around 100 million years because of the particular dependence of neutron capture reactions on depth. The neutron flux has a distinct peak as a function of depth. This peak appears to lie below the level of shallow cratering for time scales of less than one billion years and consequently forms a readily identified marker layer of both depth and time.

  8. The neutron star zoo

    NASA Astrophysics Data System (ADS)

    Harding, Alice K.

    2013-12-01

    Neutron stars are a very diverse population, both in their observational and their physical properties. They prefer to radiate most of their energy at X-ray and gamma-ray wavelengths. But whether their emission is powered by rotation, accretion, heat, magnetic fields or nuclear reactions, they are all different species of the same animal whose magnetic field evolution and interior composition remain a mystery. This article will broadly review the properties of inhabitants of the neutron star zoo, with emphasis on their high-energy emission.

  9. FAST NEUTRONIC REACTOR

    DOEpatents

    Snell, A.H.

    1957-12-01

    This patent relates to a reactor and process for carrying out a controlled fast neutron chain reaction. A cubical reactive mass, weighing at least 920 metric tons, of uranium metal containing predominantly U/sup 238/ and having a U/sup 235/ content of at least 7.63% is assembled and the maximum neutron reproduction ratio is limited to not substantially over 1.01 by insertion and removal of a varying amount of boron, the reactive mass being substantially freed of moderator.

  10. Par-baked Bread Technology: Formulation and Process Studies to Improve Quality.

    PubMed

    Almeida, Eveline Lopes; Steel, Caroline Joy; Chang, Yoon Kil

    2016-01-01

    Extending the shelf-life of bakery products has been an important requirement resulting from the mechanization of this industry and the need to increase the distance for the distribution of final products, caused by the increase in production and consumer demand. Technologies based on the interruption of the breadmaking process represent an alternative to overcome product staling and microbiological deterioration. The production of par-baked breads is one of these technologies. It consists of baking the bread in two stages, and due to the possibility of retarding the second stage, it can be said that the bread can always be offered fresh to the consumer. The technology inserts logistics as part of the production process and creates the "hot point" concept, these being the locations where the bread is finalized, such as in the consumers' homes or sales locations. In this work, a review of the papers published on this subject was carried out, and aspects related to both the formulation and the process were considered. This technology still faces a few challenges, such as solving bread quality problems that appear due to process modifications, and these will also be considered. The market for these breads has grown rapidly and the bakery industry searches innovations related to par-baked bread technology. PMID:25000472

  11. Par-baked Bread Technology: Formulation and Process Studies to Improve Quality.

    PubMed

    Almeida, Eveline Lopes; Steel, Caroline Joy; Chang, Yoon Kil

    2016-01-01

    Extending the shelf-life of bakery products has been an important requirement resulting from the mechanization of this industry and the need to increase the distance for the distribution of final products, caused by the increase in production and consumer demand. Technologies based on the interruption of the breadmaking process represent an alternative to overcome product staling and microbiological deterioration. The production of par-baked breads is one of these technologies. It consists of baking the bread in two stages, and due to the possibility of retarding the second stage, it can be said that the bread can always be offered fresh to the consumer. The technology inserts logistics as part of the production process and creates the "hot point" concept, these being the locations where the bread is finalized, such as in the consumers' homes or sales locations. In this work, a review of the papers published on this subject was carried out, and aspects related to both the formulation and the process were considered. This technology still faces a few challenges, such as solving bread quality problems that appear due to process modifications, and these will also be considered. The market for these breads has grown rapidly and the bakery industry searches innovations related to par-baked bread technology.

  12. NEUTRON AND NON-NEUTRON NUCLEAR DATA FOR RADIATION DOSIMETRY

    SciTech Connect

    HOLDEN,N.E.

    1999-09-10

    NEUTRON NUCLEAR DATA THAT IS USED IN REACTOR DOSIMETRY INCLUDE THERMAL NEUTRON CROSS SECTIONS AND NEUTRON RESONANCE INTEGRALS, FISSION SPECTRUM AVERAGED CROSS SECTIONS FOR REACTIONS ON A TARGET NUCLEUS. NON-NEUTRON NUCLEAR DATA USED IN REACTOR DOSIMETRY INCLUDE ISOTOPIC COMPOSITIONS OF TARGET NUCLIDES AND RADIOACTIVE HALF-LIVES, GAMMA-RAY ENERGIES AND INTENSITIES OF REACTION PRODUCT NUCLIDES. ALL OF THESE DATA ARE PERIODICALLY EVALUATED AND RECOMMENDED VALUES ARE PROVIDED IN THE HANDBOOK OF CHEMISTRY AND PHYSICS. THE LATEST RECOMMENDED VALUES ARE DISCUSSED AND THEY ARE CONTRASTED WITH SOME EARLIER NUCLEAR DATA, WHICH WAS PROVIDED WITH NEUTRON DETECTOR FOILS.

  13. Neutron reflectometry: Filling Δq with neutrons

    NASA Astrophysics Data System (ADS)

    Pleshanov, N. K.

    2016-06-01

    Luminosity of the reflectometer is defined as the neutron flux incident onto the sample surface for measurements made with a given momentum transfer resolution Δq. The filling of Δq with neutrons near a certain q depends not only on the source luminance and the source-sample tract transmittance, but also on the neutron beam tailoring. The correct choice of the working wavelength and measurements with optimum neutron beam parameters increase luminosity in several times. New optimization criteria for neutron reflectometers are suggested. Standard schemes of the reflectivity measurement with monochromatic and white beams are re-examined. Optimization of reflectivity measurements generally requires numerical calculations. Analytically, its potential is demonstrated by considering thermalized neutron beams. Such innovations as velocity selector on the basis of aperiodic multilayers, small angle Soller collimator with traps for neutrons reflected from the channel walls and fan beam time-of-flight technique are proposed to further increase the luminosity of reflectometers.

  14. Leading neutrons from polarized pp collisions

    SciTech Connect

    Kopeliovich, B. Z.; Potashnikova, I. K.; Schmidt, Ivan; Soffer, J.

    2008-10-13

    We calculate the cross section and single-spin azimuthal asymmetry, A{sub n}(t) for inclusive neutron production in pp collisions at forward rapidities relative to the polarized proton. Absorptive corrections to the pion pole generate a relative phase between the spin-flip and non-flip amplitudes, which leads to an appreciable spin asymmetry. However, the asymmetry observed recently in the PHENIX experiment at RHIC at very small |t|{approx}0.01 GeV{sup 2} cannot be explained by this mechanism.

  15. Neutronic reactor thermal shield

    DOEpatents

    Wende, Charles W. J.

    1976-06-15

    1. The method of operating a water-cooled neutronic reactor having a graphite moderator which comprises flowing a gaseous mixture of carbon dioxide and helium, in which the helium comprises 40-60 volume percent of the mixture, in contact with the graphite moderator.

  16. Surface Mounted Neutron Generators

    NASA Astrophysics Data System (ADS)

    Elizondo-Decanini, Juan M.

    2012-10-01

    A deuterium-tritium (DT) base reaction pulsed neutron generator packaged in a flat computer chip shape of 1.54 cm (0.600 in) wide by 3.175 cm (1.25 in) length and 0.3 cm (0.120 in) thick has been successfully demonstrated to produce 14 MeV neutrons at a rate of 10^9 neutrons per second. The neutron generator is based on a deuterium ion beam accelerated to impact a tritium loaded target. The accelerating voltage is in the 15 to 20 kV in a 3 mm (0.120 in) gap, the ion beam is shaped by using a lens design to produce a flat ion beam that conforms to the flat rectangular target. The ion source is a simple surface mounted deuterium filled titanium film with a fused gap that operates at a current-voltage design to release the deuterium during a pulse length of about 1 μs. We present the general description of the working prototypes, which we have labeled the ``NEUTRISTOR.''[4pt] Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration. Work funded by the LDRD office.

  17. Optical neutron polarizers

    SciTech Connect

    Hayter, J.B.

    1990-01-01

    A neutron wave will be refracted by an appropriately varying potential. Optical neutron polarizers use spatially varying, spin- dependent potentials to refract neutrons of opposite spin states into different directions, so that an unpolarized beam will be split into two beams of complementary polarization by such a device. This paper will concentrate on two methods of producing spin-dependent potentials which are particularly well-suited to polarizing cold neutron beams, namely thin-film structures and field-gradient techniques. Thin-film optical devices, such as supermirror multilayer structures, are usually designed to deviate only one spin-state, so that they offer the possibility of making insertion (transmission) polarizers. Very good supermirrors may now be designed and fabricated, but it is not always straightforward to design mirror-based devices which are useful in real (divergent beam) applications, and some practical configurations will be discussed. Field-gradient devices, which are usually based on multipolar magnets, have tended to be too expensive for general use, but this may change with new developments in superconductivity. Dipolar and hexapolar configurations will be considered, with emphasis on the focusing characteristics of the latter. 21 refs., 7 figs.

  18. NEUTRONIC REACTOR FUEL ELEMENT

    DOEpatents

    Picklesimer, M.L.; Thurber, W.C.

    1961-01-01

    A chemically nonreactive fuel composition for incorporation in aluminum- clad, plate type fuel elements for neutronic reactors is described. The composition comprises a mixture of aluminum and uranium carbide particles, the uranium carbide particles containing at least 80 wt.% UC/sub 2/.

  19. The DAMPE Neutron Detector

    NASA Astrophysics Data System (ADS)

    Yan, Zhang; Tao, Ma; Yongyi, Huang

    2016-07-01

    The first Chinese space observatory DAMPE (DArk Matter Particle Explorer) was successfully launched on Dec. 17th, 2015. One major scientific object of DAMPE is to measure electrons between 5GeV to 10TeV with excellent energy resolution (1.5% at 800GeV) to search for possible dark matter signatures. The detector consists of four subsystems: a plastic scintillator detector (PSD), a silicon-tungsten tracker (STK), a BGO calorimeter (BGO), and a neutron detector (NUD). The NUD on board DAMPE is designed to detect moderated neutrons via the boron capture of thermal neutrons in boron-doped plastics. Given the fact that hadron showers initiated in the BGO calorimeter by incident nuclei tend to be followed by significantly more neutron activities comparing to electromagnetic cascades triggered by electrons, the NUD provides an additional order of magnitude hadron rejection capability to improve the overall e/p discrimination of DAMPE up to 10 ^{5}. Preliminary analysis of the in-orbit data is given, together with comparisons to the results obtained by a detailed GEANT4 simulation of the NUD instrument.

  20. Neutron Absorbing Alloys

    DOEpatents

    Mizia, Ronald E.; Shaber, Eric L.; DuPont, John N.; Robino, Charles V.; Williams, David B.

    2004-05-04

    The present invention is drawn to new classes of advanced neutron absorbing structural materials for use in spent nuclear fuel applications requiring structural strength, weldability, and long term corrosion resistance. Particularly, an austenitic stainless steel alloy containing gadolinium and less than 5% of a ferrite content is disclosed. Additionally, a nickel-based alloy containing gadolinium and greater than 50% nickel is also disclosed.

  1. Neutron Star Mysteries

    NASA Astrophysics Data System (ADS)

    Mathews, G. J.; Fragile, P. C.; Suh, I.; Wilson, J. R.

    2003-04-01

    Neutron stars provide a unique laboratory in which to explore the nuclear equation of state at high densities. Nevertheless, their interior structure and equation of state have remained a mystery. Recently, a number of advances have been made toward unraveling this mystery. The first direct optical images of a nearby neutron star have been obtained from HST. High quality data for X-ray emission from low-mass X-ray binaries, including observations of nearly coherent oscillations (NCO's) and quasi-periodic oscillations (QPOs) now exist. The existence of a possible absorption feature as well as pulsar light curves and glitches, and studies of soft-gamma repeaters, have all led to significant new constraints on the mass-radius relation and maximum mass of neutron stars. We also discuss how models of supernova explosion dynamics and the associated r-process nucleosynthesis also constrain the nuclear equation of state, along with heavy-ion and monopole resonance data. Recent work on the search for the Friedman-Chandrasekhar-Schutz instability and the effects of internal magnetic fields are also discussed. The overall constraints on the neutron star equation of state are summarized.

  2. Neutron Star Phenomena

    NASA Technical Reports Server (NTRS)

    Ruderman, Malvin

    1998-01-01

    Various phenomena involving neutron stars are addressed. Electron-positron production in the near magnetosphere of gamma-ray pulsars is discussed along with magnetic field evolution in spun-up and spinning-down pulsars. Glitches and gamma-ray central engines are also discussed.

  3. Neutron-image intensifier

    NASA Technical Reports Server (NTRS)

    Berger, H.

    1970-01-01

    Electronic intensifier tube with a demagnification ratio of 9-1 enhances the usefulness of neutron-radiographic techniques. A television signal can be obtained by optical coupling of a small-output phosphor-light image to a television camera.

  4. Neutronic Reactor Structure

    DOEpatents

    Vernon, H. C.; Weinberg, A. M.

    1961-05-30

    The neutronic reactor is comprised of a core consisting of natural uranium and heavy water with a K-factor greater than unity. The core is surrounded by a reflector consisting of natural uranium and ordinary water with a Kfactor less than unity. (AEC)

  5. NEUTRONIC REACTOR STRUCTURE

    DOEpatents

    Weinberg, A.M.; Vernon, H.C.

    1961-05-30

    A neutronic reactor is described. It has a core consisting of natural uranium and heavy water and having a K-factor greater than unity which is surrounded by a reflector consisting of natural uranium and ordinary water having a Kfactor less than unity.

  6. NEUTRONIC REACTOR SHIELDING

    DOEpatents

    Borst, L.B.

    1961-07-11

    A special hydrogenous concrete shielding for reactors is described. In addition to Portland cement and water, the concrete essentially comprises 30 to 60% by weight barytes aggregate for enhanced attenuation of fast neutrons. The biological shields of AEC's Oak Ridge Graphite Reactor and Materials Testing Reactor are particular embodiments.

  7. Dose-equivalent neutron dosimeter

    DOEpatents

    Griffith, R.V.; Hankins, D.E.; Tomasino, L.; Gomaa, M.A.M.

    1981-01-07

    A neutron dosimeter is disclosed which provides a single measurement indicating the amount of potential biological damage resulting from the neutron exposure of the wearer, for a wide range of neutron energies. The dosimeter includes a detecting sheet of track etch detecting material such as a carbonate plastic, for detecting higher energy neutrons, and a radiator layer contaning conversion material such as /sup 6/Li and /sup 10/B lying adjacent to the detecting sheet for converting moderate energy neutrons to alpha particles that produce tracks in the adjacent detecting sheet.

  8. Neutron proton crystallography station (PCS)

    SciTech Connect

    Fisher, Zoe; Kovalevsky, Andrey; Johnson, Hannah; Mustyakimov, Marat

    2009-01-01

    The PCS (Protein Crystallography Station) at Los Alamos Neutron Science Center (LANSCE) is a unique facility in the USA that is designed and optimized for detecting and collecting neutron diffraction data from macromolecular crystals. PCS utilizes the 20 Hz spallation neutron source at LANSCE to enable time-of-flight measurements using 0.6-7.0 {angstrom} neutrons. This increases the neutron flux on the sample by using a wavelength range that is optimal for studying macromolecular crystal structures. The diagram below show a schematic of PCS and photos of the detector and instrument cave.

  9. Solid state neutron detector array

    DOEpatents

    Seidel, John G.; Ruddy, Frank H.; Brandt, Charles D.; Dulloo, Abdul R.; Lott, Randy G.; Sirianni, Ernest; Wilson, Randall O.

    1999-01-01

    A neutron detector array is capable of measuring a wide range of neutron fluxes. The array includes multiple semiconductor neutron detectors. Each detector has a semiconductor active region that is resistant to radiation damage. In one embodiment, the array preferably has a relatively small size, making it possible to place the array in confined locations. The ability of the array to detect a wide range of neutron fluxes is highly advantageous for many applications such as detecting neutron flux during start up, ramp up and full power of nuclear reactors.

  10. Solid state neutron detector array

    DOEpatents

    Seidel, J.G.; Ruddy, F.H.; Brandt, C.D.; Dulloo, A.R.; Lott, R.G.; Sirianni, E.; Wilson, R.O.

    1999-08-17

    A neutron detector array is capable of measuring a wide range of neutron fluxes. The array includes multiple semiconductor neutron detectors. Each detector has a semiconductor active region that is resistant to radiation damage. In one embodiment, the array preferably has a relatively small size, making it possible to place the array in confined locations. The ability of the array to detect a wide range of neutron fluxes is highly advantageous for many applications such as detecting neutron flux during start up, ramp up and full power of nuclear reactors. 7 figs.

  11. LiF/ZnS Neutron Multiplicity Counter

    SciTech Connect

    Stave, Sean C.; Bliss, Mary; Kouzes, Richard T.; Lintereur, Azaree T.; Robinson, Sean M.; Siciliano, Edward R.; Wood, Lynn S.

    2015-06-01

    Abstract: Alternatives to the use of 3He for the detection of thermal neutrons are being investigated. One of the most challenging applications for 3He alternatives is in neutron multiplicity counters. Neutron multiplicity counters are used to provide rapid assay of samples which contain an unknown amount of plutonium in a potentially unknown configuration. With appropriate detector design, the neutron single, double, and triple coincidence events can be used to extract information of three unknown parameters such as the 240Pu-effective mass, the sample self-multiplication, and the (α,n) rate. A project at PNNL has investigated replacing 3He-based tubes with LiF/ZnS neutron-scintillator sheets and wavelength shifting plastic for light pipes. A four-panel demonstrator module has been constructed, tested, and compared with detailed modeling results. The findings indicate that a full-scale system can be constructed with the same overall size as the most efficient 3He-based system and with improved performance. Remaining design challenges include electronics and robust neutron/gamma-ray discrimination based on pulse shape analysis at high rates. A review of the current effort and the most recent findings will be presented.

  12. Present and Future Activities on Neutron Imaging in Argentina

    NASA Astrophysics Data System (ADS)

    Tartaglione, Aureliano; Blostein, Jerónimo; Cantargi, Florencia; Marín, Julio; Baruj, Alberto; Meyer, Gabriel; Santisteban, Javier; Sánchez, Fernando

    We present here a short review of the main work which has been done in the latest years in neutron imaging in Argentina, and the future plans for the development of this technique in the country, mainly focused in the design of a new neutron imaging instrument to be installed in the future research reactor RA10. We present here the results of the implementation of the technique in samples belonging to the Argentinean cultural heritage and experiments related with hydrogen storage. At the same time, the Argentinean RA10 project for the design and construction of a 30 MW multipurpose research reactor is rapidly progressing. It started to be designed by the National Atomic Energy Commission (CNEA) and the technology company INVAP SE, both from Argentina, in June 2010. The construction will start in the beginning of 2015 in the Ezeiza Atomic Center, at 36 km from Buenos Aires City, and is expected to be finished by 2020. One of the main aims of the project is to offer to the Argentinean scientific and technology system new capabilities based on neutron techniques. We present here the conceptual design of a neutron imaging facility which will use one of the cold neutron beams, and will be installed in the reactor hall. Preliminary simulation results show that at the farthest detection position, at about 17 m from the cold source, a uniform neutron beam on a detection screen with an intensity of about 108 n/cm2/s is expected.

  13. Neutron spin-reorientation experiments

    NASA Astrophysics Data System (ADS)

    Ramsey, Norman F.

    Neutron spin-reorientation experiments which give fundamental physics information are described. The magnetic moment of the neutron has been measured to be 1.91304275(45) nuclear magnetons by separated oscillatory fields resonant reorientation's of the spins of neutrons in a beam passing through a magnetic field. In similar resonance experiments with ultracold neutrons trapped in a bottle, the neutron electric dipole moment has been shown to be less than 9 × 10 -26e cm. Neutrons “dressed” with many radio frequency quanta have been studied. The Berry phases of neutrons that have passed through a helical magnetic field or an oscillatory magnetic field have been observed. In neutron interactions experiments with condensed matter, small changes in neutron velocities have been measured by changes in the neutron precessions in magnetic fields before and after the interaction. Parity non-conserving spin rotations of neutrons passing through various materials have been observed and measured and new experiments with H 2 and He are in progress.

  14. Nanostructure Neutron Converter Layer Development

    NASA Technical Reports Server (NTRS)

    Park, Cheol (Inventor); Sauti, Godfrey (Inventor); Kang, Jin Ho (Inventor); Lowther, Sharon E. (Inventor); Thibeault, Sheila A. (Inventor); Bryant, Robert G. (Inventor)

    2016-01-01

    Methods for making a neutron converter layer are provided. The various embodiment methods enable the formation of a single layer neutron converter material. The single layer neutron converter material formed according to the various embodiments may have a high neutron absorption cross section, tailored resistivity providing a good electric field penetration with submicron particles, and a high secondary electron emission coefficient. In an embodiment method a neutron converter layer may be formed by sequential supercritical fluid metallization of a porous nanostructure aerogel or polyimide film. In another embodiment method a neutron converter layer may be formed by simultaneous supercritical fluid metallization of a porous nanostructure aerogel or polyimide film. In a further embodiment method a neutron converter layer may be formed by in-situ metalized aerogel nanostructure development.

  15. Par Pond vegetation status summer 1995 - July survey descriptive summary

    SciTech Connect

    Mackey, H.E. Jr.; Riley, R.S.

    1995-07-01

    A survey of the emergent shoreline aquatic plant, communities began in June 1995, three months after the refilling of Par Pond to approximately 200 feet (61 meters) above mean sea level, and continued with this July survey. Aquatic plant communities, similar to the pre-drawdown Par Pond communities, are becoming reestablished. Beds of maidencane (Panicum hemitomon), lotus (Nelumbo lutea), water lily (Nymphaea odorata), and watershield (Brasenia schreberi) are now extensive and well established. In addition, within isolated coves, extensive beds of water lilies and spike-rush (Eleocharis sp.) are common. Cattail occurrence has increased since refill, but large beds common to Par Pond prior to the drawdown have not formed. Invasion of willow (Salix sp.) and red maple (Acer rubrum) occurred along the lake shoreline during drawdown. The red maples along the present shoreline are beginning to show evidence of stress and mortality from flooding over the past four months. Some of the willows appear to be stressed as well. The loblolly pines (Pinus taeda), which were flooded in all but the shallow shoreline areas, are now dead. Future surveys are planned for the growing seasons of 1995, 1996, and 1997, along with the evaluation of satellite data for mapping the areal extent of the macrophyte beds of Par Pond.

  16. The Pars Triangularis in Dyslexia and ADHD: A Comprehensive Approach

    ERIC Educational Resources Information Center

    Kibby, Michelle Y.; Kroese, Judith M.; Krebbs, Hillery; Hill, Crystal E.; Hynd, George W.

    2009-01-01

    Limited research has been conducted on the structure of the pars triangularis (PT) in dyslexia despite functional neuroimaging research finding it may play a role in phonological processing. Furthermore, research to date has not examined PT size in ADHD even though the right inferior frontal region has been implicated in the disorder. Hence, one…

  17. Aqueous misdirection following pars plana vitrectomy and silicone oil injection

    PubMed Central

    Ghoraba, Hammouda H; Ghali, Ali Ahmed; Mansour, Hosam Othman

    2015-01-01

    Purpose To report a retrospective series of seven phakic eyes of seven patients suffering from a malignant glaucoma-like syndrome following pars plana vitrectomy and silicone oil (SO) injection. Materials and methods Seven eyes with retinal detachment treated with pars plana vitrectomy with or without scleral buckling with SO tamponade. This was followed by cataract extraction to manage the elevated intraocular pressure (IOP). Results This was a retrospective review of seven cases that received pars plana vitrectomy and SO with or without scleral buckling for different causes of retinal detachment (three were rhegmatogenous and four were tractional). After a period ranging from 1 week to 1 month, they presented with malignant glaucoma-like manifestations; high IOP, shallow axial anterior chamber, and remarkable decrease of visual acuity. Atropine eye drops and anti-glaucoma medical treatment (topical and systemic) had been tried but failed to improve the condition. Dramatic decrease of IOP and deepening of the axial anterior chamber was observed in all cases in the first postoperative day after phacoemulsification and posterior chamber foldable intraocular lens implantation with posterior capsulotomy. Conclusion Aqueous misdirection syndrome may be observed following pars plana vitrectomy and SO tamponade. This must be differentiated from other causes of post vitrectomy glaucoma. Cataract extraction with posterior capsulotomy controls the condition. PMID:26056429

  18. Radiological impact of Par Pond drawdown from liquid effluent pathways

    SciTech Connect

    Carlton, W.H.; Hamby, D.M.

    1991-10-25

    The water level of Par Pond has been lowered over the past several months to reduce the effects in the event of catastrophic dam failure while assessing the condition of the dam and determining if repairs are necessary. In lowering the level of Par Pond, 60 billion liters of water containing low levels of tritium and cesium-137 were discharged to several onsite streams. SRS surface streams flow to the Savannah River. An assessment made to determine the total amount of tritium and Cs-137 discharged and to estimate the consequences to downstream Savannah River users. It is estimated that a total of 160 curies of tritium were displaced from Par Pond to the Savannah River between June 28, 1991 and September 19, 1991. This release could hypothetically result in a maximum individual dose of 3. 2{times}10{sup {minus}4} mrem and a total (80-km and drinking water populations) population dose of 1.4{times}10{sup {minus}2} person-rem. Likewise, a maximum individual dose of 5.0{times}10{sup {minus}2} mrem and a total population dose of 1.7{times}10{sup {minus}1} person- rem are predicted as a result of an estimated 0.21 curies of Cs-137 being discharged from Par Pond to the Savannah River.

  19. BOREAS RSS-10 TOMS Circumpolar One-Degree PAR Images

    NASA Technical Reports Server (NTRS)

    Dye, Dennis G.; Holben, Brent; Nickeson, Jaime (Editor); Hall, Forrest G. (Editor); Smith, David E. (Technical Monitor)

    2000-01-01

    The Boreal Ecosystem-Atmosphere Study (BOREAS) Remote Sensing Science (RSS)-10 team investigated the magnitude of daily, seasonal, and yearly variations of Photosynthetically Active Radiation (PAR) from ground and satellite observations. This data set contains satellite estimates of surface-incident PAR (400-700 nm, MJ/sq m) at one-degree spatial resolution. The spatial coverage is circumpolar from latitudes of 41 to 66 degrees north. The temporal coverage is from May through September for years 1979 through 1989. Eleven-year statistics are also provided: (1) mean, (2) standard deviation, and (3) coefficient of variation for 1979-89. The PAR estimates were derived from the global gridded ultraviolet reflectivity data product (average of 360, 380 nm) from the Nimbus-7 Total Ozone Mapping Spectrometer (TOMS). Image mask data are provided for identifying the boreal forest zone, and ocean/land and snow/ice-covered areas. The data are available as binary image format data files. The PAR data are available from the Earth Observing System Data and Information System (EOSDIS) Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC). The data files are available on a CD-ROM (see document number 20010000884).

  20. Competing ParA structures space bacterial plasmids equally over the nucleoid.

    PubMed

    Ietswaart, Robert; Szardenings, Florian; Gerdes, Kenn; Howard, Martin

    2014-12-01

    Low copy number plasmids in bacteria require segregation for stable inheritance through cell division. This is often achieved by a parABC locus, comprising an ATPase ParA, DNA-binding protein ParB and a parC region, encoding ParB-binding sites. These minimal components space plasmids equally over the nucleoid, yet the underlying mechanism is not understood. Here we investigate a model where ParA-ATP can dynamically associate to the nucleoid and is hydrolyzed by plasmid-associated ParB, thereby creating nucleoid-bound, self-organizing ParA concentration gradients. We show mathematically that differences between competing ParA concentrations on either side of a plasmid can specify regular plasmid positioning. Such positioning can be achieved regardless of the exact mechanism of plasmid movement, including plasmid diffusion with ParA-mediated immobilization or directed plasmid motion induced by ParB/parC-stimulated ParA structure disassembly. However, we find experimentally that parABC from Escherichia coli plasmid pB171 increases plasmid mobility, inconsistent with diffusion/immobilization. Instead our observations favor directed plasmid motion. Our model predicts less oscillatory ParA dynamics than previously believed, a prediction we verify experimentally. We also show that ParA localization and plasmid positioning depend on the underlying nucleoid morphology, indicating that the chromosomal architecture constrains ParA structure formation. Our directed motion model unifies previously contradictory models for plasmid segregation and provides a robust mechanistic basis for self-organized plasmid spacing that may be widely applicable.

  1. ParA-mediated plasmid partition driven by protein pattern self-organization

    PubMed Central

    Hwang, Ling Chin; Vecchiarelli, Anthony G; Han, Yong-Woon; Mizuuchi, Michiyo; Harada, Yoshie; Funnell, Barbara E; Mizuuchi, Kiyoshi

    2013-01-01

    DNA segregation ensures the stable inheritance of genetic material prior to cell division. Many bacterial chromosomes and low-copy plasmids, such as the plasmids P1 and F, employ a three-component system to partition replicated genomes: a partition site on the DNA target, typically called parS, a partition site binding protein, typically called ParB, and a Walker-type ATPase, typically called ParA, which also binds non-specific DNA. In vivo, the ParA family of ATPases forms dynamic patterns over the nucleoid, but how ATP-driven patterning is involved in partition is unknown. We reconstituted and visualized ParA-mediated plasmid partition inside a DNA-carpeted flowcell, which acts as an artificial nucleoid. ParA and ParB transiently bridged plasmid to the DNA carpet. ParB-stimulated ATP hydrolysis by ParA resulted in ParA disassembly from the bridging complex and from the surrounding DNA carpet, which led to plasmid detachment. Our results support a diffusion-ratchet model, where ParB on the plasmid chases and redistributes the ParA gradient on the nucleoid, which in turn mobilizes the plasmid. PMID:23443047

  2. PH motifs in PAR1&2 endow breast cancer growth.

    PubMed

    Kancharla, A; Maoz, M; Jaber, M; Agranovich, D; Peretz, T; Grisaru-Granovsky, S; Uziely, B; Bar-Shavit, R

    2015-01-01

    Although emerging roles of protease-activated receptor1&2 (PAR1&2) in cancer are recognized, their underlying signalling events are poorly understood. Here we show signal-binding motifs in PAR1&2 that are critical for breast cancer growth. This occurs via the association of the pleckstrin homology (PH) domain with Akt/PKB as a key signalling event of PARs. Other PH-domain signal-proteins such as Etk/Bmx and Vav3 also associate with PAR1 and PAR2 through their PH domains. PAR1 and PAR2 bind with priority to Etk/Bmx. A point mutation in PAR2, H349A, but not in R352A, abrogates PH-protein association and is sufficient to markedly reduce PAR2-instigated breast tumour growth in vivo and placental extravillous trophoblast (EVT) invasion in vitro. Similarly, the PAR1 mutant hPar1-7A, which is unable to bind the PH domain, reduces mammary tumours and EVT invasion, endowing these motifs with physiological significance and underscoring the importance of these previously unknown PAR1 and PAR2 PH-domain-binding motifs in both pathological and physiological invasion processes. PMID:26600192

  3. PH motifs in PAR1&2 endow breast cancer growth

    PubMed Central

    Kancharla, A.; Maoz, M.; Jaber, M.; Agranovich, D.; Peretz, T.; Grisaru-Granovsky, S.; Uziely, B.; Bar-Shavit, R.

    2015-01-01

    Although emerging roles of protease-activated receptor1&2 (PAR1&2) in cancer are recognized, their underlying signalling events are poorly understood. Here we show signal-binding motifs in PAR1&2 that are critical for breast cancer growth. This occurs via the association of the pleckstrin homology (PH) domain with Akt/PKB as a key signalling event of PARs. Other PH-domain signal-proteins such as Etk/Bmx and Vav3 also associate with PAR1 and PAR2 through their PH domains. PAR1 and PAR2 bind with priority to Etk/Bmx. A point mutation in PAR2, H349A, but not in R352A, abrogates PH-protein association and is sufficient to markedly reduce PAR2-instigated breast tumour growth in vivo and placental extravillous trophoblast (EVT) invasion in vitro. Similarly, the PAR1 mutant hPar1-7A, which is unable to bind the PH domain, reduces mammary tumours and EVT invasion, endowing these motifs with physiological significance and underscoring the importance of these previously unknown PAR1 and PAR2 PH-domain-binding motifs in both pathological and physiological invasion processes. PMID:26600192

  4. Producing ultrastrong magnetic fields in neutron star mergers.

    PubMed

    Price, D J; Rosswog, S

    2006-05-01

    We report an extremely rapid mechanism for magnetic field amplification during the merger of a binary neutron star system. This has implications for the production of the short class of gamma-ray bursts, which recent observations suggest may originate in such mergers. In detailed magnetohydrodynamic simulations of the merger process, the fields are amplified by Kelvin-Helmholtz instabilities beyond magnetar field strength and may therefore represent the strongest magnetic fields in the universe. The amplification occurs in the shear layer that forms between the neutron stars and on a time scale of only 1 millisecond, that is, long before the remnant can collapse into a black hole.

  5. Magnetorotational instability in proto-neutron stars

    NASA Astrophysics Data System (ADS)

    Urpin, V.

    2010-01-01

    Context. Magneto-rotational instability (MRI) has been suggested to lead to a rapid growth of the magnetic field in core collapse supernovae and produce departures from spherical symmetry that are important in determining the explosion mechanism. Aims: We address the problem of stability in differentially rotating magnetized proto-neutron stars at the beginning of their evolution. Methods: To do this, we consider a linear stability taking into account non-linear effects of the magnetic field and strong gravity. Results: Criteria for MRI are derived without simplifying assumptions about a weak magnetic field. In proto-neutron stars, these criteria differ qualitatively from the standard condition dΩ/d s <0 where Ω is the angular velocity and s the cylindrical radius. If the magnetic field is strong, the MRI can occur only in the neighbourhood of the regions where the spherical radial component of the magnetic field vanishes. The growth rate of the MRI is relatively low except for perturbations with very small scales which usually are not detected in numerical simulations. We find that MRI in proto-neutron stars grows more slowly than the double diffusive instability analogous the Goldreich-Schubert-Fricke instability in ordinary stars.

  6. Que peut-on voir avec des neutrons? Une introduction pour des non spécialistes

    NASA Astrophysics Data System (ADS)

    Schweizer, J.

    2005-11-01

    Le neutron est une particule élémentaire qui a été découverte en 1932 par James Chadwick. Ses caractéristiques principales sont résumées dans le tableau I. Il a été utilisé pour la première fois par Clifford Shull en 1946 comme outil pour des expériences de diffusion. Cette technique s'est depuis constamment développée pour concerner tous les aspects de la matière condensée: physique, chimie, matériaux, biologie. Il s'agit d'un outil tout à fait exceptionnel car le neutron possède des propriétés uniques et particulièrement adaptées pour ces études.

  7. Observation of Neutron Skyshine from an Accelerator Based Neutron Source

    SciTech Connect

    Franklyn, C. B.

    2011-12-13

    A key feature of neutron based interrogation systems is the need for adequate provision of shielding around the facility. Accelerator facilities adapted for fast neutron generation are not necessarily suitably equipped to ensure complete containment of the vast quantity of neutrons generated, typically >10{sup 11} n{center_dot}s{sup -1}. Simulating the neutron leakage from a facility is not a simple exercise since the energy and directional distribution can only be approximated. Although adequate horizontal, planar shielding provision is made for a neutron generator facility, it is sometimes the case that vertical shielding is minimized, due to structural and economic constraints. It is further justified by assuming the atmosphere above a facility functions as an adequate radiation shield. It has become apparent that multiple neutron scattering within the atmosphere can result in a measurable dose of neutrons reaching ground level some distance from a facility, an effect commonly known as skyshine. This paper describes a neutron detection system developed to monitor neutrons detected several hundred metres from a neutron source due to the effect of skyshine.

  8. Beta-delayed neutron emission measurements for r-process nuclei

    NASA Astrophysics Data System (ADS)

    Dillmann, Iris

    2014-09-01

    Beta-delayed neutron- (bn-) emitters play an important, two-fold role in the stellar nucleosynthesis of heavy elements in the ``rapid neutron-capture process'' (r process). On one hand they lead to a detour of the material beta-decaying back to stability. On the other hand, the released neutrons increase the neutron-to-seed ratio, and are re-captured during the freeze-out phase and thus influence the final solar r-abundance curve. A large fraction of the isotopes for r-process nucleosynthesis are not yet experimentally accessible and are located in the ``terra incognita.'' With the next generation of fragmentation and ISOL facilities presently being built or already in operation, one of the main motivation of all projects is the investigation of very neutron-rich isotopes at and beyond the border of presently known nuclei. However, reaching more neutron-rich isotopes means also that multiple neutron-emission becomes the dominant decay mechanism. The investigation of bn-emitters has recently experienced a renaissance. I will show some recent results from a GSI campaign with the BELEN detector, and introduce the program planned for 2015/16 at RIKEN with the ``BRIKEN'' detector. ``BRIKEN'' (``Beta-delayed neutron measurements at RIKEN for nuclear structure, astrophysics, and applications'') is a worldwide effort which combines 3He-neutron counters from groups in Germany, Japan, Russia, Spain, and the USA and the implantation detector AIDA from the UK to the presently largest and most efficient neutron detection setup. Planned first experiments comprise the first-time measurements of 48 b-delayed one-neutron and 24 b-delayed two-neutron emitters in the regions around doubly-magic 78Ni and 132Sn. Even some b-delayed three-neutron emitters in the heavier mass region will be tackled for the first time.

  9. Rapid Reading, Yes

    ERIC Educational Resources Information Center

    Frommer, Harvey

    1971-01-01

    Recommends instruction in rapid reading fo high school and college students and asserts that flexibility of speed and reasoning provide the foundation for effective rapid reading. Describes the components of rapid reading as orientation, selection, clarification, arrangement, review, and study. (RW)

  10. Results of peripheral laser photocoagulation in pars planitis.

    PubMed Central

    Pulido, J S; Mieler, W F; Walton, D; Kuhn, E; Postel, E; Hartz, A; Jampol, L M; Weinberg, D V; Logani, S

    1998-01-01

    PURPOSE: To determine the effect of peripheral retinal laser photocoagulation (PLP) on visual acuity, intraocular inflammation, and other ocular findings, including retinal neovascularization in eyes with pars planitis. METHODS: A retrospective chart review of eyes with pars planitis that had undergone PLP. RESULTS: Twenty-two eyes in 17 patients with pars planitis had undergone treatment with PLP at 2 centers. The mean age at the time of treatment was 19.3 years. Following treatment, mean follow-up was 16.3 months (range, 6 to 37 months). Mean visual acuity was 20/60 preoperatively and 20/50 postoperatively. This level of improvement was not statistically significant (P > .10), but there was a statistically significant decrease in the use of corticosteroids between the preoperative examination and the last postoperative examination (86% versus 27%, P < .05). There was also a statistically significant decrease in vitritis at the last follow-up (P = .0008) and a decrease in neovascularization of the vitreous base (P = .03) and in clinically apparent cystoid macular edema (P = .02). Epiretinal membranes were noted in 23% of eyes preoperatively and in 45% of eyes postoperatively. Only one of these epiretinal membranes was considered to be visually significant. One eye developed a tonic dilated pupil, which slowly improved. CONCLUSIONS: Although the long-term natural history of clinical findings in pars planitis is not well documented, PLP appears to decrease the need for corticosteroids while stabilizing visual acuity. It also appears to decrease vitreous inflammation. PLP has few complications and should be considered in patients with pars planitis who are unresponsive or have adverse reactions to corticosteroids. PMID:10360286

  11. Thermal conductivity changes upon neutron transmutation of {sup 10}B doped diamond

    SciTech Connect

    Jagannadham, K.; Verghese, K.; Butler, J. E.

    2014-08-28

    {sup 10}B doped p-type diamond samples were subjected to neutron transmutation reaction using thermal neutron flux of 0.9 × 10{sup 13} cm{sup −2} s{sup −1} and fast neutron flux of 0.09 × 10{sup 13} cm{sup −2} s{sup −1}. Another sample of epilayer grown on type IIa (110) single crystal diamond substrate was subjected to equal thermal and fast neutron flux of 10{sup 14} cm{sup −2} s{sup −1}. The defects in the diamond samples were previously characterized by different methods. In the present work, thermal conductivity of these diamond samples was determined at room temperature by transient thermoreflectance method. The thermal conductivity change in the samples as a function of neutron fluence is explained by the phonon scattering from the point defects and disordered regions. The thermal conductivity of the diamond samples decreased more rapidly initially and less rapidly for larger neutron fluence. In addition, the thermal conductivity in type IIb diamond decreased less rapidly with thermal neutron fluence compared to the decrease in type IIa diamond subjected to fast neutron fluence. It is concluded that the rate of production of defects during transmutation reaction is slower when thermal neutrons are used. The thermal conductivity of epilayer of diamond subjected to high thermal and fast neutron fluence is associated with the covalent carbon network in the composite structure consisting of disordered carbon and sp{sup 2} bonded nanocrystalline regions.

  12. The role of pars flaccida in human middle ear sound transmission.

    PubMed

    Aritomo, H; Goode, R L; Gonzalez, J

    1988-04-01

    The role of the pars flaccida in middle ear sound transmission was studied with the use of twelve otoscopically normal, fresh, human temporal bones. Peak-to-peak umbo displacement in response to a constant sound pressure level at the tympanic membrane was measured with a noncontacting video measuring system capable of repeatable measurements down to 0.2 micron. Measurements were made before and after pars flaccida modifications at 18 frequencies between 100 and 4000 Hz. Four pars flaccida modifications were studied: (1) acoustic insulation of the pars flaccida to the ear canal with a silicone rubber baffle, (2) stiffening the pars flaccida with cyanoacrylate cement, (3) decreasing the tension of the pars flaccida with a nonperforating incision, and (4) perforation of the pars flaccida. All of the modifications (except the perforation) had a minimal effect on umbo displacement; this seems to imply that the pars flaccida has a minor acoustic role in human beings. PMID:3132684

  13. SELF-REACTIVATING NEUTRON SOURCE FOR A NEUTRONIC REACTOR

    DOEpatents

    Newson, H.W.

    1959-02-01

    Reactors of the type employing beryllium in a reflector region around the active portion and to a neutron source for use therewith are discussed. The neutron source is comprised or a quantity of antimony permanently incorporated in, and as an integral part of, the reactor in or near the beryllium reflector region. During operation of the reactor the natural occurring antimony isotope of atomic weight 123 absorbs neutrons and is thereby transformed to the antimony isotope of atomic weight 124, which is radioactive and emits gamma rays. The gamma rays react with the beryllium to produce neutrons. The beryllium and antimony thus cooperate to produce a built in neutron source which is automatically reactivated by the operation of the reactor itself and which is of sufficient strength to maintain the slow neutron flux at a sufficiently high level to be reliably measured during periods when the reactor is shut down.

  14. NASA'S Chandra Finds Superfluid in Neutron Star's Core

    NASA Astrophysics Data System (ADS)

    2011-02-01

    NASA's Chandra X-ray Observatory has discovered the first direct evidence for a superfluid, a bizarre, friction-free state of matter, at the core of a neutron star. Superfluids created in laboratories on Earth exhibit remarkable properties, such as the ability to climb upward and escape airtight containers. The finding has important implications for understanding nuclear interactions in matter at the highest known densities. Neutron stars contain the densest known matter that is directly observable. One teaspoon of neutron star material weighs six billion tons. The pressure in the star's core is so high that most of the charged particles, electrons and protons, merge resulting in a star composed mostly of uncharged particles called neutrons. Two independent research teams studied the supernova remnant Cassiopeia A, or Cas A for short, the remains of a massive star 11,000 light years away that would have appeared to explode about 330 years ago as observed from Earth. Chandra data found a rapid decline in the temperature of the ultra-dense neutron star that remained after the supernova, showing that it had cooled by about four percent over a 10-year period. "This drop in temperature, although it sounds small, was really dramatic and surprising to see," said Dany Page of the National Autonomous University in Mexico, leader of a team with a paper published in the February 25, 2011 issue of the journal Physical Review Letters. "This means that something unusual is happening within this neutron star." Superfluids containing charged particles are also superconductors, meaning they act as perfect electrical conductors and never lose energy. The new results strongly suggest that the remaining protons in the star's core are in a superfluid state and, because they carry a charge, also form a superconductor. "The rapid cooling in Cas A's neutron star, seen with Chandra, is the first direct evidence that the cores of these neutron stars are, in fact, made of superfluid and

  15. High intensity, pulsed thermal neutron source

    DOEpatents

    Carpenter, J.M.

    1973-12-11

    This invention relates to a high intensity, pulsed thermal neutron source comprising a neutron-producing source which emits pulses of fast neutrons, a moderator block adjacent to the last neutron source, a reflector block which encases the fast neutron source and the moderator block and has a thermal neutron exit port extending therethrough from the moderator block, and a neutron energy- dependent decoupling reflector liner covering the interior surfaces of the thermal neutron exit port and surrounding all surfaces of the moderator block except the surface viewed by the thermal neutron exit port. (Official Gazette)

  16. Introduction to Neutron Techniques

    NASA Astrophysics Data System (ADS)

    Eckold, Götz; Schober, Helmut

    Neutron scattering is one of the most powerful methods for the detailed investigation of condensed matter. Not only are structures from atomic to mesoscopic scales accessible, but also can dynamical properties of atoms, molecules, magnetic moments etc. be investigated. The prominent properties of neutrons with wavelengths of the order of atomic dimensions and, at the same time, frequencies of the order of characteristic vibrational frequencies allow us to investigate the space-time behavior of condensed matter on a microscopic scale over many decades. A good number of different and most efficient experimental techniques have been developed for different fields of application. Within this introductory chapter, we would like to provide the reader with a brief review about the main achievements in instrumentation without going into specific details, that may be found in the specialized literature.

  17. Neutron Imaging Camera

    NASA Technical Reports Server (NTRS)

    Hunter, Stanley D.; DeNolfo, Georgia; Floyd, Sam; Krizmanic, John; Link, Jason; Son, Seunghee; Guardala, Noel; Skopec, Marlene; Stark, Robert

    2008-01-01

    We describe the Neutron Imaging Camera (NIC) being developed for DTRA applications by NASA/GSFC and NSWC/Carderock. The NIC is based on the Three-dimensional Track Imager (3-DTI) technology developed at GSFC for gamma-ray astrophysics applications. The 3-DTI, a large volume time-projection chamber, provides accurate, approximately 0.4 mm resolution. 3-D tracking of charged particles. The incident direction of fast neutrons, E(sub N) > 0.5 MeV. arc reconstructed from the momenta and energies of the proton and triton fragments resulting from 3He(n,p)3H interactions in the 3-DTI volume. We present angular and energy resolution performance of the NIC derived from accelerator tests.

  18. Superdense neutron matter

    NASA Technical Reports Server (NTRS)

    Canuto, V.; Datta, B.; Kalman, G.

    1978-01-01

    A relativistic theory of high-density matter is presented which takes into account the short-range interaction due to the exchange of spin-2 mesons. An equation of state is derived and used to compute neutron-star properties. The prediction of the theory for the values of maximum mass and moment of inertia for a stable neutron star are 1.75 solar masses and 1.68 by 10 to the 45th power g-sq cm, in very good agreement with the presently known observational bounds. The corresponding radius is found to be 10.7 km. It is found that the inclusion of the spin-2 interaction reduces the disagreement between the relativistic and nonrelativistic theories in their predictions of masses and moments of inertia.

  19. FAST NEUTRON SPECTROMETER

    DOEpatents

    Davis, F.J.; Hurst, G.S.; Reinhardt, P.W.

    1959-08-18

    An improved proton recoil spectrometer for determining the energy spectrum of a fast neutron beam is described. Instead of discriminating against and thereby"throwing away" the many recoil protons other than those traveling parallel to the neutron beam axis as do conventional spectrometers, this device utilizes protons scattered over a very wide solid angle. An ovoidal gas-filled recoil chamber is coated on the inside with a scintillator. The ovoidal shape of the sensitive portion of the wall defining the chamber conforms to the envelope of the range of the proton recoils from the radiator disposed within the chamber. A photomultiplier monitors the output of the scintillator, and a counter counts the pulses caused by protons of energy just sufficient to reach the scintillator.

  20. Imaging with polarized neutrons

    NASA Astrophysics Data System (ADS)

    Dawson, Martin; Manke, Ingo; Kardjilov, Nikolay; Hilger, André; Strobl, Markus; Banhart, John

    2009-04-01

    Neutrons have zero net electrical charge and can thus penetrate deeply into matter, but their intrinsic magnetic moment makes them highly sensitive to magnetic fields. These properties have been combined with radiographic (2D) and tomographic (3D) imaging methods to provide a unique technique to probe macroscopic magnetic phenomena both within and around bulk matter. Based on the spin-rotation of a polarized neutron beam as it passes through a magnetic field, this method allows the direct, real-space visualization of magnetic field distributions. It has been used to investigate the Meissner effect in a type I (Pb) and a type II (YBCO) superconductor, flux trapping in a type I (Pb) superconductor, and the electromagnetic field associated with a direct current flowing in a solenoid. The latter results have been compared to predictions calculated using the Biot-Savart law and have been found to agree well.

  1. Neutron beam measurement dosimetry

    SciTech Connect

    Amaro, C.R.

    1995-11-01

    This report describes animal dosimetry studies and phantom measurements. During 1994, 12 dogs were irradiated at BMRR as part of a 4 fraction dose tolerance study. The animals were first infused with BSH and irradiated daily for 4 consecutive days. BNL irradiated 2 beagles as part of their dose tolerance study using BPA fructose. In addition, a dog at WSU was irradiated at BMRR after an infusion of BPA fructose. During 1994, the INEL BNCT dosimetry team measured neutron flux and gamma dose profiles in two phantoms exposed to the epithermal neutron beam at the BMRR. These measurements were performed as a preparatory step to the commencement of human clinical trials in progress at the BMRR.

  2. COMPOSITE NEUTRONIC REACTOR

    DOEpatents

    Menke, J.R.

    1963-06-11

    This patent relates to a reactor having a core which comprises an inner active region and an outer active region, each region separately having a k effective less than one and a k infinity greater than one. The inner and outer regions in combination have a k effective at least equal to one and each region contributes substantially to the k effective of the reactor core. The inner region has a low moderator to fuel ratio such that the majority of fissions occurring therein are induced by neutrons having energies greater than thermal. The outer region has a high moderator to fuel ratio such that the majority of fissions occurring therein are induced by thermal neutrons. (AEC)

  3. Short pulse neutron generator

    DOEpatents

    Elizondo-Decanini, Juan M.

    2016-08-02

    Short pulse neutron generators are described herein. In a general embodiment, the short pulse neutron generator includes a Blumlein structure. The Blumlein structure includes a first conductive plate, a second conductive plate, a third conductive plate, at least one of an inductor or a resistor, a switch, and a dielectric material. The first conductive plate is positioned relative to the second conductive plate such that a gap separates these plates. A vacuum chamber is positioned in the gap, and an ion source is positioned to emit ions in the vacuum chamber. The third conductive plate is electrically grounded, and the switch is operable to electrically connect and disconnect the second conductive plate and the third conductive plate. The at least one of the resistor or the inductor is coupled to the first conductive plate and the second conductive plate.

  4. Porous material neutron detector

    DOEpatents

    Diawara, Yacouba; Kocsis, Menyhert

    2012-04-10

    A neutron detector employs a porous material layer including pores between nanoparticles. The composition of the nanoparticles is selected to cause emission of electrons upon detection of a neutron. The nanoparticles have a maximum dimension that is in the range from 0.1 micron to 1 millimeter, and can be sintered with pores thereamongst. A passing radiation generates electrons at one or more nanoparticles, some of which are scattered into a pore and directed toward a direction opposite to the applied electrical field. These electrons travel through the pore and collide with additional nanoparticles, which generate more electrons. The electrons are amplified in a cascade reaction that occurs along the pores behind the initial detection point. An electron amplification device may be placed behind the porous material layer to further amplify the electrons exiting the porous material layer.

  5. Neutron Scattering Stiudies

    SciTech Connect

    Kegel, Gunter H.R.; Egan, James J

    2007-04-18

    This project covers four principal areas of research: Elastic and inelastic neutron scattering studies in odd-A terbium, thulium and other highly deformed nuclei near A=160 with special regard to interband transitions and to the investigation of the direct-interaction versus the compound-nucleus excitation process in these nuclei. Examination of new, fast photomultiplier tubes suitable for use in a miniaturized neutron-time-of-flight spectrometer. Measurement of certain inelastic cross sections of 238U. Determination of the multiplicity of prompt fission gamma rays in even-A fissile actinides. Energies and mean lives of fission isomers produced by fast fission of even-Z, even-A actinides. Study of the mean life of 7Be in different host matrices and its possible astro-physical significance.

  6. Fast neutron imaging device and method

    DOEpatents

    Popov, Vladimir; Degtiarenko, Pavel; Musatov, Igor V.

    2014-02-11

    A fast neutron imaging apparatus and method of constructing fast neutron radiography images, the apparatus including a neutron source and a detector that provides event-by-event acquisition of position and energy deposition, and optionally timing and pulse shape for each individual neutron event detected by the detector. The method for constructing fast neutron radiography images utilizes the apparatus of the invention.

  7. Neutron Activation Analysis: Techniques and Applications

    NASA Astrophysics Data System (ADS)

    MacLellan, Ryan

    2011-04-01

    The role of neutron activation analysis in low-energy low-background experimentsis discussed in terms of comparible methods. Radiochemical neutron activation analysis is introduce. The procedure of instrumental neutron activation analysis is detailed especially with respect to the measurement of trace amounts of natural radioactivity. The determination of reactor neutron spectrum parameters required for neutron activation analysis is also presented.

  8. Neutron Activation Analysis: Techniques and Applications

    SciTech Connect

    MacLellan, Ryan

    2011-04-27

    The role of neutron activation analysis in low-energy low-background experimentsis discussed in terms of comparible methods. Radiochemical neutron activation analysis is introduce. The procedure of instrumental neutron activation analysis is detailed especially with respect to the measurement of trace amounts of natural radioactivity. The determination of reactor neutron spectrum parameters required for neutron activation analysis is also presented.

  9. Proton recoil scintillator neutron rem meter

    DOEpatents

    Olsher, Richard H.; Seagraves, David T.

    2003-01-01

    A neutron rem meter utilizing proton recoil and thermal neutron scintillators to provide neutron detection and dose measurement. In using both fast scintillators and a thermal neutron scintillator the meter provides a wide range of sensitivity, uniform directional response, and uniform dose response. The scintillators output light to a photomultiplier tube that produces an electrical signal to an external neutron counter.

  10. NEUTRONIC REACTOR CONTROL

    DOEpatents

    Dreffin, R.S.

    1959-12-15

    A control means for a nuclear reactor is described. Particularly a device extending into the active portion of the reactor consisting of two hollow elements coaxially disposed and forming a channel therebetween, the cross sectional area of the channel increasing from each extremity of the device towards the center thereof. An element of neutron absorbing material is slidably positionable within the inner hollow element and a fluid reactor poison is introduced into the channel defined by the two hollow elements.

  11. European Neutron Activation System.

    2013-01-11

    Version 03 EASY-2010 (European Activation System) consists of a wide range of codes, data and documentation all aimed at satisfying the objective of calculating the response of materials irradiated in a neutron flux. The main difference from the previous version is the upper energy limit, which has increased from 20 to 60 MeV. It is designed to investigate both fusion devices and accelerator based materials test facilities that will act as intense sources of high-energymore » neutrons causing significant activation of the surrounding materials. The very general nature of the calculational method and the data libraries means that it is applicable (with some reservations) to all situations (e.g. fission reactors or neutron sources) where materials are exposed to neutrons below 60 MeV. EASY can be divided into two parts: data and code development tools and user tools and data. The former are required to develop the latter, but EASY users only need to be able to use the inventory code FISPACT and be aware of the contents of the EAF library (the data source). The complete EASY package contains the FISPACT-2007 inventory code, the EAF-2003, EAF-2005, EAF-2007 and EAF-2010 libraries, and the EASY User Interface for the Window version. The activation package EASY-2010 is the result of significant development to extend the upper energy range from 20 to 60 MeV so that it is capable of being used for IFMIF calculations. The EAF-2010 library contains 66,256 reactions, almost five times more than in EAF-2003 (12,617). Deuteron-induced and proton-induced cross section libraries are also included, and can be used with EASY to enable calculations of the activation due to deuterons and proton [2].« less

  12. NEUTRONIC REACTOR SYSTEM

    DOEpatents

    Goett, J.J.

    1961-01-24

    A system is described which includes a neutronic reactor containing a dispersion of fissionable material in a liquid moderator as fuel and a conveyor to which a portion of the dispersion may be passed and wherein the self heat of the slurry evaporates the moderator. Means are provided for condensing the liquid moderator and returning it to the reactor and for conveying the dried fissionable material away from the reactor.

  13. MONDE: MOmentum Neutron DEtector

    NASA Astrophysics Data System (ADS)

    Santa Rita, P.; Acosta, L.; Favela, F.; Huerta, A.; Ortiz, M. E.; Policroniades, R.; Chávez, E.

    2016-07-01

    MONDE is a large area neutron momentum detector, consisting of a 70x160x5 cm3 plastic scintillator slab surrounded by 16 photomultiplier tubes, standard NIM signal processing electronics and a CAMAC data acquisition system. In this work we present data from a characterization run using an external trigger. For that purpose, coincident gamma rays from a 60Co radioactive source were used together with a NaI external detector. First results with an "external" trigger are presented.

  14. THERMAL NEUTRONIC REACTOR

    DOEpatents

    Spinrad, B.I.

    1960-01-12

    A novel thermal reactor was designed in which a first reflector formed from a high atomic weight, nonmoderating material is disposed immediately adjacent to the reactor core. A second reflector composed of a moderating material is disposed outwardly of the first reflector. The advantage of this novel reflector arrangement is that the first reflector provides a high slow neutron flux in the second reflector, where irradiation experiments may be conducted with a small effect on reactor reactivity.

  15. Is There an "F" in Your PAR? Understanding, Teaching and Doing Action Research

    ERIC Educational Resources Information Center

    Lorenzetti, Liza; Walsh, Christine Ann

    2014-01-01

    Participatory Action Research (PAR) is increasingly recognized within academic research and pedagogy. What are the benefits of including feminism within participatory action research and teaching? In responding to this question, we discuss the similarities and salient differences between PAR and feminist informed PAR (FPAR). There are eight themes…

  16. ParA resolvase catalyzes site-specific excision of DNA from the Arabidopsis genome

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The small serine resolvase ParA from bacterial plasmids RK2 and RP4 catalyzes the recombination of two identical 133 bp recombination sites known as MRS. Previously, we reported that ParA is active in the fission yeast Schizosaccharomyces pombe. In this work, the parA recombinase gene was placed un...

  17. The Role of Prostate Apoptosis Response-4 (Par-4) in Mycobacterium tuberculosis Infected Macrophages

    PubMed Central

    Han, Ji-Ye; Lim, Yun-Ji; Choi, Ji-Ae; Lee, Jung-hwan; Jo, Sung-Hee; Oh, Sung-Man; Song, Chang-Hwa

    2016-01-01

    Prostate apoptosis response-4 (Par-4) is a tumor suppressor protein that forms a complex with glucose-regulated protein 78 (GRP78) to induce apoptosis. Previously, we reported that ER stress-induced apoptosis is a critical host defense mechanism against Mycobacterium tuberculosis (Mtb). We sought to understand the role of Par-4 during ER stress-induced apoptosis in response to mycobacterial infection. Par-4 and GRP78 protein levels increased in response Mtb (strain: H37Ra) infection. Furthermore, Par-4 and GRP78 translocate to the surface of Mtb H37Ra-infected macrophages and induce apoptosis via caspase activation. NF-κB activation, Mtb-mediated ER stress, and Par-4 production were significantly diminished in macrophages with inhibited ROS production. To test Par-4 function during mycobacterial infection, we analyzed intracellular survival of Mtb H37Ra in macrophages with Par-4 overexpression or knockdown. Mtb H37Ra growth was significantly reduced in Par-4 overexpressing macrophages and increased in knockdown macrophages. We also observed increased Par-4, GRP78, and caspases activation in Bacillus Calmette-Guérin (BCG)-infected prostate cancer cells. Our data demonstrate that Par-4 is associated with ER stress-induced apoptosis resulting in reduced intracellular survival of mycobacteria. BCG treatment increases Par-4-dependent caspase activation in prostate cancer cells. These results suggest ER stress-induced Par-4 acts as an important defense mechanism against mycobacterial infection and regulates cancer. PMID:27552917

  18. Alternative 3' UTR selection controls PAR-5 homeostasis and cell polarity in C. elegans embryos.

    PubMed

    Mikl, Martin; Cowan, Carrie R

    2014-09-11

    Cell polarity in one-cell C. elegans embryos guides asymmetric cell division and cell-fate specification. Shortly after fertilization, embryos establish two antagonistic cortical domains of PAR proteins. Here, we find that the conserved polarity factor PAR-5 regulates PAR domain size in a dose-dependent manner. Using quantitative imaging and controlled genetic manipulation, we find that PAR-5 protein levels reflect the cumulative output of three mRNA isoforms with different translational efficiencies mediated by their 3' UTRs. 3' UTR selection is regulated, influencing PAR-5 protein abundance. Alternative splicing underlies the selection of par-5 3' UTR isoforms. 3' UTR splicing is enhanced by the SR protein kinase SPK-1, and accordingly, SPK-1 is required for wild-type PAR-5 levels and PAR domain size. Precise regulation of par-5 isoform selection is essential for polarization when the posterior PAR network is compromised. Together, strict control of PAR-5 protein levels and feedback from polarity to par-5 3' UTR selection confer robustness to embryo polarization. PMID:25199833

  19. Biased signalling and proteinase-activated receptors (PARs): targeting inflammatory disease.

    PubMed

    Hollenberg, M D; Mihara, K; Polley, D; Suen, J Y; Han, A; Fairlie, D P; Ramachandran, R

    2014-03-01

    Although it has been known since the 1960s that trypsin and chymotrypsin can mimic hormone action in tissues, it took until the 1990s to discover that serine proteinases can regulate cells by cleaving and activating a unique four-member family of GPCRs known as proteinase-activated receptors (PARs). PAR activation involves the proteolytic exposure of its N-terminal receptor sequence that folds back to function as a 'tethered' receptor-activating ligand (TL). A key N-terminal arginine in each of PARs 1 to 4 has been singled out as a target for cleavage by thrombin (PARs 1, 3 and 4), trypsin (PARs 2 and 4) or other proteases to unmask the TL that activates signalling via Gq , Gi or G12 /13 . Similarly, synthetic receptor-activating peptides, corresponding to the exposed 'TL sequences' (e.g. SFLLRN-, for PAR1 or SLIGRL- for PAR2) can, like proteinase activation, also drive signalling via Gq , Gi and G12 /13 , without requiring receptor cleavage. Recent data show, however, that distinct proteinase-revealed 'non-canonical' PAR tethered-ligand sequences and PAR-activating agonist and antagonist peptide analogues can induce 'biased' PAR signalling, for example, via G12 /13 -MAPKinase instead of Gq -calcium. This overview summarizes implications of this 'biased' signalling by PAR agonists and antagonists for the recognized roles the PARs play in inflammatory settings. PMID:24354792

  20. Rapid scanning system for fuel drawers

    DOEpatents

    Caldwell, J.T.; Fehlau, P.E.; France, S.W.

    A nondestructive method for uniquely distinguishing among and quantifying the mass of individual fuel plates in situ in fuel drawers utilized in nuclear reactors is described. The method is both rapid and passive, eliminating the personnel hazard of the commonly used irradiation techniques which require that the analysis be performed in proximity to an intense neutron source such as a reactor. In the present technique, only normally decaying nuclei are observed. This allows the analysis to be performed anywhere. This feature, combined with rapid scanning of a given fuel drawer (in approximately 30 s), and the computer data analysis allows the processing of large numbers of fuel drawers efficiently in the event of a loss alert.

  1. Rapid scanning system for fuel drawers

    DOEpatents

    Caldwell, John T.; Fehlau, Paul E.; France, Stephen W.

    1981-01-01

    A nondestructive method for uniqely distinguishing among and quantifying the mass of individual fuel plates in situ in fuel drawers utilized in nuclear reactors is described. The method is both rapid and passive, eliminating the personnel hazard of the commonly used irradiation techniques which require that the analysis be performed in proximity to an intense neutron source such as a reactor. In the present technique, only normally decaying nuclei are observed. This allows the analysis to be performed anywhere. This feature, combined with rapid scanning of a given fuel drawer (in approximately 30 s), and the computer data analysis allows the processing of large numbers of fuel drawers efficiently in the event of a loss alert.

  2. Neutrons in the moon. [neutron flux and production rate calculations

    NASA Technical Reports Server (NTRS)

    Kornblum, J. J.; Fireman, E. L.; Levine, M.; Aronson, A.

    1973-01-01

    Neutron fluxes for energies between 15 MeV and thermal at depths of 0 to 300 g/sq cm in the moon are calculated by the discrete ordinate mathod with the ANISN code. With the energy spectrum of Lingenfelter et al. (1972). A total neutron-production rate for the moon of 26 plus or minus neutrons/sq cm sec is determined from the Ar-37 activity measurements in the Apollo 16 drill string, which are found to have a depth dependence in accordance with a neutron source function that decreases exponentially with an attenuation length of 155 g/sq cm.

  3. Review of Non-Neutron and Neutron Nuclear Data, 2004

    SciTech Connect

    Holden, Norman E.

    2005-05-24

    Review articles are in preparation for the 2004 edition of the CRC Handbook of Chemistry and Physics dealing with the evaluation of both non-neutron and neutron nuclear data. Data on the discovery of element 110, Darmstadtium, and element 111 have been officially accepted, while data on element 118 have been withdrawn. Data to be presented include revised values for very short-lived nuclides, long-lived nuclides, and beta-beta decay measurements. There has been a reassessment of the spontaneous fission (sf) half-lives, which distinguishes between sf decay half-lives and cluster decay half-lives, and with cluster-fission decay. New measurements of isotopic abundance values for many elements will be discussed with an emphasis on the minor isotopes of interest for use in neutron activation analysis measurements. Neutron resonance integrals will be discussed emphasizing the differences between the calculated values obtained from the analytical integration over neutron resonances and the measured values in a neutron reactor-spectrum, which does not quite conform to the assumed 1/E neutron energy spectrum. The method used to determine the neutron resonance integral from measurement, using neutron activation analysis, will be discussed.

  4. REVIEW OF NON-NEUTRON AND NEUTRON NUCLEAR DATA, 2004.

    SciTech Connect

    HOLDEN, N.E.

    2004-09-26

    Review articles are in preparation for the 2004 edition of the CRC Handbook of Chemistry and Physics dealing with the evaluation of both non-neutron and neutron nuclear data. Data on the discovery of element 110, Darmstadtium, and element 111 have been officially accepted, while data on element 11 8 have been withdrawn. Data to be presented include revised values for very short-lived nuclides, long-lived nuclides and beta-beta decay measurements. There has been a reassessment of the spontaneous fission (sf) half-lives, which distinguishes between sf decay half-lives and cluster decay half-lives and with cluster-fission decay. New measurements of isotopic abundance values for many elements will be discussed with an emphasis on the minor isotopes of interest for use in neutron activation analysis measurements. Neutron resonance integrals will be discussed emphasizing the differences between the calculated values obtained from the analytical integration over neutron resonances and the measured values in a neutron reactor-spectrum, which does not quite conform to the assumed 1/E neutron energy spectrum. The method used to determine the neutron resonance integral from measurement, using neutron activation analysis, will be discussed.

  5. Scattered and (n,2n) neutrons as a measure of areal density in ICF capsules

    NASA Astrophysics Data System (ADS)

    Wilson, D. C.; Murphy, T. J.; Mead, W. C.; Disdier, L.; Houry, M.; Bayer, C.; Bourgade, J.-L.

    2001-10-01

    The fraction of low energy neutrons created from 14 MeV neutrons by elastic scattering and (n,2n) reactions on D and T can measure the areal density ρ r ( radial integral of density) of ICF targets. This may be crucial since for ignition capsules the fraction of reaction-in-flight neutrons is proportional to ρ r T and not simply ρ r^2 In simple situations the fraction of neutrons between 9.4 (the upper energy of T+T neutrons) and 13 MeV (below the Doppler broadened 14.1 MeV peak) is proportional to the ρ r at the time of neutron production. The ratio of neutrons at a specific energy (e.g. 13 MeV) to the their integral over all energies can be measured along different lines of sight. Because scattering is forward peaked, comparing these ratios provides a nearly linear measure of implosion asymmetry. Gamma rays can be a negligible background if the detector is placed inside the target chamber close enough to the target that measurements are made before the 14 MeV neutrons reach the chamber wall. Calculated gamma ray and scattered neutron backgrounds from a cryogenic target support or a diagnostic instrument do not pose a problem. A GaAs detector 2.5m from the target in the NIF chamber appears to have enough sensitivity and sufficiently rapid time response to make this measurement.

  6. Neutron instrumentation for biology

    SciTech Connect

    Mason, S.A.

    1994-12-31

    In the October 1994 round of proposals at the ILL, the external biology review sub- committee was asked to allocate neutron beam time to a wide range of experiments, on almost half the total number of scheduled neutron instruments: on 3 diffractometers, on 3 small angle scattering instruments, and on some 6 inelastic scattering spectrometers. In the 3.5 years since the temporary reactor shutdown, the ILL`s management structure has been optimized, budgets and staff have been trimmed, the ILL reactor has been re-built, and many of the instruments up-graded, many powerful (mainly Unix) workstations have been introduced, and the neighboring European Synchrotron Radiation Facility has established itself as the leading synchrotron radiation source and has started its official user program. The ILL reactor remains the world`s most intense dedicated neutron source. In this challenging context, it is of interest to review briefly the park of ILL instruments used to study the structure and energetics of small and large biological systems. A brief summary will be made of each class of experiments actually proposed in the latest ILL proposal round.

  7. Neutron Diagnostics for NIF

    NASA Astrophysics Data System (ADS)

    Barnes, Cris W.; Berggren, R.; Caldwell, S.; Chrien, R. C.; Cverna, F.; Faulkner, J.; Mack, J. M.; Morgan, G. L.; Murphy, T. J.; Oertel, J. A.; Tegtmeier, J.; Walton, R.; Wilke, M.; Wilson, D. C.; Young, C. S.

    1999-11-01

    The National Ignition Facility (NIF) will be a pre-emminent facility for research on burning plasmas. Los Alamos National Laboratory is developing a focus area of coordinating fusion reaction product diagnostics on NIF and studying fusion burn. We will be developing ``core'' diagnostics for NIF including neutron time-of-flight and single-hit systems for ion temperature and neutron spectra, measurements of ``bang-time'' (time of fusion burn relative to start of laser pulse), and support for activation measurements for high-yield and radiochemical analysis. We are also developing advanced Phase 2 diagnostics including a gas Cerenkov burn history diagnostic and work on apertures and detectors for neutron imaging. This will include tests of these diagnostic systems on the OMEGA laser in the coming years. The measurement requirements and system descriptions of these NIF diagnostics will be described. This work was performed under the auspices of the U. S. Department of Energy by the Los Alamos National Laboratory under contract No. W-7405-Eng-36.

  8. NEUTRONIC REACTOR CORE

    DOEpatents

    Thomson, W.B.; Corbin, A. Jr.

    1961-07-18

    An improved core for a gas-cooled power reactor which admits gas coolant at high temperatures while affording strong integral supporting structure and efficient moderation of neutrons is described. The multiplicities of fuel elements constituting the critical amassment of fissionable material are supported and confined by a matrix of metallic structure which is interspersed therebetween. Thermal insulation is interposed between substantially all of the metallic matrix and the fuel elements; the insulation then defines the principal conduit system for conducting the coolant gas in heat-transfer relationship with the fuel elements. The metallic matrix itseif comprises a system of ducts through which an externally-cooled hydrogeneous liquid, such as water, is circulated to serve as the principal neutron moderant for the core and conjointly as the principal coolant for the insulated metallic structure. In this way, use of substantially neutron transparent metals, such as aluminum, becomes possible for the supporting structure, despite the high temperatures of the proximate gas. The Aircraft Nuclear Propulsion program's "R-1" reactor design is a preferred embodiment.

  9. Independent Confirmation of the MODIS LAI/fPAR Algorithm

    NASA Astrophysics Data System (ADS)

    Ganapol, B. D.; Dungan, J. L.

    2001-12-01

    The Leaf Canopy Model (LCM)-2 is a nested model that combines leaf radiative transfer with a full canopy reflectance model through the phase function (Ganapol et al. 1999). The basic components of the model include inversion for a leaf scattering coefficient, construction of a representative absorption coefficient and the determination of canopy reflectance given leaf area index (LAI) values and information on canopy type and structure. It can also be used to calculate the fraction of absorbed photosynthetically active radiation (fPAR) for the canopy. It therefore serves as an independent means of confirming the results of the MOD15 algorithm (Knyazikhin et al. 1998) that produces LAI and fPAR fields from reflectance measured by the Moderate Resolution Imaging Spectrometer (MODIS). In LCM2, relatively simple first principles of radiative transfer are used whereas in the MOD15 algorithm, scene variability is accounted for by specifying distributions and a response surface in a table-lookup procedure. The distributions are generated by various radiative transfer models with a host of underlying assumptions. The attempt to compare results from these two models is a useful means of addressing the structural uncertainty in the Earth Observing System prediction problem. We compared LCM2 results with those from the MOD15 algorithm for fPAR calculation. 100 pixels for an EOS Core Validation Site where there were coincident reflectance, vegetation index, fPAR and LAI products were chosen. The 8-day 500 m reflectance product was spatially degraded to coincide with 8-day 1 km LAI and fPAR products and LAI and land cover products were used to parameterize LCM2. Most fPAR results agreed to within 10 percent, though a bias was observed. Poor agreement was seen with vegetation index products. Ganapol, B.D., L.F. Johnson, C.A. Hlavka, D.L. Peterson, and B. Bond, LCM2: A coupled leaf/canopy radiative transfer model, Remote Sensing of Environment, 70:153-166, 1999. Knyazikhin, Y., J

  10. ParCAT: A Parallel Climate Analysis Toolkit

    NASA Astrophysics Data System (ADS)

    Haugen, B.; Smith, B.; Steed, C.; Ricciuto, D. M.; Thornton, P. E.; Shipman, G.

    2012-12-01

    Climate science has employed increasingly complex models and simulations to analyze the past and predict the future of our climate. The size and dimensionality of climate simulation data has been growing with the complexity of the models. This growth in data is creating a widening gap between the data being produced and the tools necessary to analyze large, high dimensional data sets. With single run data sets increasing into 10's, 100's and even 1000's of gigabytes, parallel computing tools are becoming a necessity in order to analyze and compare climate simulation data. The Parallel Climate Analysis Toolkit (ParCAT) provides basic tools that efficiently use parallel computing techniques to narrow the gap between data set size and analysis tools. ParCAT was created as a collaborative effort between climate scientists and computer scientists in order to provide efficient parallel implementations of the computing tools that are of use to climate scientists. Some of the basic functionalities included in the toolkit are the ability to compute spatio-temporal means and variances, differences between two runs and histograms of the values in a data set. ParCAT is designed to facilitate the "heavy lifting" that is required for large, multidimensional data sets. The toolkit does not focus on performing the final visualizations and presentation of results but rather, reducing large data sets to smaller, more manageable summaries. The output from ParCAT is provided in commonly used file formats (NetCDF, CSV, ASCII) to allow for simple integration with other tools. The toolkit is currently implemented as a command line utility, but will likely also provide a C library for developers interested in tighter software integration. Elements of the toolkit are already being incorporated into projects such as UV-CDAT and CMDX. There is also an effort underway to implement portions of the CCSM Land Model Diagnostics package using ParCAT in conjunction with Python and gnuplot. Par

  11. Scoping studies - photon and low energy neutron interrogation

    SciTech Connect

    Becker, G.; Harker, Y.; Jones, J.; Harmon, F.

    1997-11-01

    High energy photon interrogation of waste containers, with the aim of producing photo nuclear reactions, in specific materials, holds the potential of good penetration and rapid analysis. Compact high energy ({le} 10 MeV) photon sources in the form of electron linacs producing bremstrahlung radiation are readily available. Work with the Varitron variable energy accelerator at ISU will be described. Advantages and limitations of the technique will be discussed. Using positive ion induced neutron producing reactions, it is possible to generate neutrons in a specific energy range. By this means, variable penetration and specific reactions can be excited in the assayed material. Examples using the {sup 3}H(p,n) and {sup 7}Li(p,n) reactions as neutron sources will be discussed. 4 refs., 7 figs.

  12. Lunar Elemental Abundances from Gamma-Ray and Neutron Measurements

    NASA Astrophysics Data System (ADS)

    Reedy, R. C.; Vaniman, D. T.

    1999-01-01

    % , with Ti and Fe emitting more fast neutrons than light elements like O and Si. Most elements moderate neutrons to thermal energies at similar rates. The main exception is when neutrons scatter from H, in which case neutrons can be rapidly thermalized. The cross sections for the absorption of thermal neutrons can vary widely among elements, with major elements like Ti and Fe having high-capture cross sections. Some trace elements, such as Sm and Gd, have such large neutron-absorption cross sections that, despite their low abundances, can absorb significant amounts of thermal neutrons in the Moon. Because the processes affecting neutrons are complicated, good modeling is needed to properly extract elemental information from measured neutron fluxes. The LAHET Code System (LCS) can be use to calculate neutron fluxes from GCR interactions in the Moon. Lunar Gamma-Ray Spectroscopy: The main sources of planetary gamma-rays are the decay of the naturally occurring radioactive isotopes of K, Th, and U and the interactions of GCRs with atomic nuclei in the planet's surface. Most "cosmogenic" gamma-rays are produced by fast and thermal neutrons made in the planet's surface by GCRs, and their production rates can vary with time. Over 300 gamma-ray lines have been identified that can be emitted from planetary surfaces by a variety of production mechanisms. There exist nuclear databases that can be used to identify and quantify other gamma-ray lines. Use will be made of gamma-rays from major elements, particularly those from Si and O, that have not been routinely used in the past. The fluxes of gamma-rays from a given element can vary depending on many factors besides the concentration of that element. For example, the fluxes of neutron-capture gamma-rays in the planetary region of interest depend on (1) the total cross section for elements to absorb thermalized neutrons and (2) the H content of the top meter of the surface. The fluxes of the fast neutrons that induce inelastic

  13. Epithermal neutron instrumentation at ISIS

    NASA Astrophysics Data System (ADS)

    Gorini, G.; Festa, G.; Andreani, C.

    2014-12-01

    The advent of pulsed neutron sources makes available high epithermal neutron fluxes (in the energy range between 500 meV and 100 eV). New dedicated instrumentation, such as Resonance Detectors, was developed at ISIS spallation neutron source in the last years to apply the specific properties of this kind of neutron beam to the study of condensed matter. New detection strategies like Filter Difference method and Foil Cycling Technique were also developed in parallel to the detector improvement at the VESUVIO beamline. Recently, epithermal neutron beams were also used at the INES beamline to study elemental and isotopic composition of materials, with special application to cultural heritage studies. In this paper we review a series of epithermal neutron instrumentation developed at ISIS, their evolution over time and main results obtained.

  14. NEUTRON MEASURING METHOD AND APPARATUS

    DOEpatents

    Seaborg, G.T.; Friedlander, G.; Gofman, J.W.

    1958-07-29

    A fast neutron fission detecting apparatus is described consisting of a source of fast neutrons, an ion chamber containing air, two electrodes within the ion chamber in confronting spaced relationship, a high voltage potential placed across the electrodes, a shield placed about the source, and a suitable pulse annplifier and recording system in the electrode circuit to record the impulse due to fissions in a sannple material. The sample material is coated onto the active surface of the disc electrode and shielding means of a material having high neutron capture capabilities for thermal neutrons are provided in the vicinity of the electrodes and about the ion chamber so as to absorb slow neutrons of thermal energy to effectively prevent their diffusing back to the sample and causing an error in the measurement of fast neutron fissions.

  15. Neutron scattering and absorption properties

    SciTech Connect

    Holden, N.E.

    1993-12-01

    The Table in this report presents an evaluated set of values for the experimental quantities, which characterize the properties for scattering and absorption of neutrons. The neutron cross section is given for room temperature neutrons, 20.43{degree}C, corresponds to a thermal neutron energy of 0.0253 electron volts (eV) or a neutron velocity of 2200 meters/second. The neutron resonance integral is defined over the energy range from 0.5 eV to 0.1 {times} 10{sup 6} eV, or 0.1 MeV. A list of the major references used is given below. The literature cutoff data is October 1993. Uncertainties are given in parentheses. Parentheses with two or more numbers indicate values to the excited states(s) and to the ground state of the product nucleus.

  16. Cross ambiguity functions on the MasPar MP-2

    SciTech Connect

    Carlson, D.A.; Pryor, D.V.; Frock, C.K.

    1995-12-01

    In a signal processing environment, cross ambiguity functions are often used to detect when one signal is a time and/or frequency shift of another. They consist of multiple cross-correlations, which can be computed efficiently using complex valued FFTs. This paper discusses the implementation of cross ambiguity functions on the MasPar MP-2, a SIMD processor array. Two different implementations are developed. The first computes each cross ambiguity function serially, using FFT code that parallelizes across the complete set of processors. The second uses the MasPar IORAM to realign the data so that the cross ambiguity functions can be computed in parallel. In this case, multiple FFTs are executed in parallel on subsets of the processors, which lowers the overall amount of communication required.

  17. Design, construction, and wire calibration of PAR BPM striplines

    NASA Astrophysics Data System (ADS)

    Sellyey, W.; Barr, D.; Erwin, L.

    1995-05-01

    The Positron Accumulator Ring (PAR) is part of the APS injection system. It received 24 30-ns FWHM bursts of 450-meV positrons, and compresses them into 6-nC, 290-ps rms bunches. Striplines were selected as beam position monitors (BPMs) to assure that good position sensitivity is achieved. This paper will describe the design, construction, and wire calibration of the 16 PAR BPMs. It will be demonstrated that all relevant stripline parameters can be determined by solving the two-dimensional LaPlace equation. This was done numerically using the electrostatic part of the PE2D computer program. The construction of the units will be briefly discussed. Wire calibration data on one of the final units will be compared with theory at four frequencies.

  18. Centrifugal quantum states of neutrons

    NASA Astrophysics Data System (ADS)

    Nesvizhevsky, V. V.; Petukhov, A. K.; Protasov, K. V.; Voronin, A. Yu.

    2008-09-01

    We propose a method for observation of the quasistationary states of neutrons localized near a curved mirror surface. The bounding effective well is formed by the centrifugal potential and the mirror Fermi potential. This phenomenon is an example of an exactly solvable “quantum bouncer” problem that can be studied experimentally. It could provide a promising tool for studying fundamental neutron-matter interactions, as well as quantum neutron optics and surface physics effects. We develop a formalism that describes quantitatively the neutron motion near the mirror surface. The effects of mirror roughness are taken into account.

  19. Portable neutron spectrometer and dosimeter

    DOEpatents

    Waechter, David A.; Erkkila, Bruce H.; Vasilik, Dennis G.

    1985-01-01

    The disclosure relates to a battery operated neutron spectrometer/dosimeter utilizing a microprocessor, a built-in tissue equivalent LET neutron detector, and a 128-channel pulse height analyzer with integral liquid crystal display. The apparatus calculates doses and dose rates from neutrons incident on the detector and displays a spectrum of rad or rem as a function of keV per micron of equivalent tissue and also calculates and displays accumulated dose in millirads and millirem as well as neutron dose rates in millirads per hour and millirem per hour.

  20. Portable neutron spectrometer and dosimeter

    DOEpatents

    Waechter, D.A.; Erkkila, B.H.; Vasilik, D.G.

    The disclosure relates to a battery operated neutron spectrometer/dosimeter utilizing a microprocessor, a built-in tissue equivalent LET neutron detector, and a 128-channel pulse height analyzer with integral liquid crystal display. The apparatus calculates doses and dose rates from neutrons incident on the detector and displays a spectrum of rad or rem as a function of keV per micron of equivalent tissue and also calculates and displays accumulated dose in millirads and millirem as well as neutron dose rates in millirads per hour and millirem per hour.

  1. ACCELERATOR BASED CONTINUOUS NEUTRON SOURCE.

    SciTech Connect

    SHAPIRO,S.M.; RUGGIERO,A.G.; LUDEWIG,H.

    2003-03-25

    Until the last decade, most neutron experiments have been performed at steady-state, reactor-based sources. Recently, however, pulsed spallation sources have been shown to be very useful in a wide range of neutron studies. A major review of neutron sources in the US was conducted by a committee chaired by Nobel laureate Prof. W. Kohn: ''Neutron Sources for America's Future-BESAC Panel on Neutron Sources 1/93''. This distinguished panel concluded that steady state and pulsed sources are complementary and that the nation has need for both to maintain a balanced neutron research program. The report recommended that both a new reactor and a spallation source be built. This complementarity is recognized worldwide. The conclusion of this report is that a new continuous neutron source is needed for the second decade of the 20 year plan to replace aging US research reactors and close the US neutron gap. it is based on spallation production of neutrons using a high power continuous superconducting linac to generate protons impinging on a heavy metal target. There do not appear to be any major technical challenges to the building of such a facility since a continuous spallation source has been operating in Switzerland for several years.

  2. NEUTRON ABSORPTION AND SHIELDING DEVICE

    DOEpatents

    Axelrad, I.R.

    1960-06-21

    A neutron absorption and shielding device is described which is adapted for mounting in a radiation shielding wall surrounding a radioactive area through which instrumentation leads and the like may safely pass without permitting gamma or neutron radiation to pass to the exterior. The shielding device comprises a container having at least one nonrectilinear tube or passageway means extending therethrough, which is adapted to contain instrumentation leads or the like, a layer of a substance capable of absorbing gamma rays, and a solid resinous composition adapted to attenuate fast-moving neutrons and capture slow- moving or thermal neutrons.

  3. NEUTRON IMAGING, RADIOGRAPHY AND TOMOGRAPHY.

    SciTech Connect

    SMITH,G.C.

    2002-03-01

    Neutrons are an invaluable probe in a wide range of scientific, medical and commercial endeavors. Many of these applications require the recording of an image of the neutron signal, either in one-dimension or in two-dimensions. We summarize the reactions of neutrons with the most important elements that are used for their detection. A description is then given of the major techniques used in neutron imaging, with emphasis on the detection media and position readout principle. Important characteristics such as position resolution, linearity, counting rate capability and sensitivity to gamma-background are discussed. Finally, the application of a subset of these instruments in radiology and tomography is described.

  4. Measurement of neutron diffraction with compact neutron source RANS

    NASA Astrophysics Data System (ADS)

    Ikeda, Y.; Takamura, M.; Taketani, A.; Sunaga, H.; Otake, Y.; Suzuki, H.; Kumagai, M.; Oba, Y.; Hama, T.

    2016-11-01

    Diffraction is used as a measurement technique for crystal structure. X-rays or electron beam with wavelength that is close to the lattice constant of the crystal is often used for the measurement. They have sensitivity in surface (0.01mm) of heavy metals due to the mean free path for heavy ions. Neutron diffraction has the probe of the internal structure of the heavy metals because it has a longer mean free path than that of the X-rays or the electrons. However, the neutron diffraction measurement is not widely used because large facilities are required in the many neutron sources. RANS (Riken Accelerator-driven Compact Neutron Source) is developed as a neutron source which is usable easily in laboratories and factories. In RANS, fast neutrons are generated by 7MeV protons colliding on a Be target. Some fast neutrons are moderated with polyethylene to thermal neutrons. The thermal neutrons of 10meV which have wavelength of 10nm can be used for the diffraction measurement. In this study, the texture evolution in steels was measured with RANS and the validity of the compact neutron source was proved. The texture of IF steel sheets with the thickness of 1.0mm was measured with 10minutes run. The resolution is 2% and is enough to analyze a evolution in texture due to compression/tensile deformation or a volume fraction of two phases in the steel sample. These results have proven the possibility to use compact neutron source for the analysis of mesoscopic structure of metallic materials.

  5. The Sensitivity of r-PROCESS Nucleosynthesis to the Properties of Neutron-Rich Nuclei

    NASA Astrophysics Data System (ADS)

    Surman, R.; Mumpower, M. R.; Cass, J.; Aprahamian, A.

    2014-09-01

    About half of the heavy elements in the Solar System were created by rapid neutron capture, or r-process, nucleosynthesis. In the r-process, heavy elements are built up via a sequence of neutron captures and beta decays in which an intense neutron flux pushes material out towards the neutron drip line. The nuclear network simulations used to test potential astrophysical scenarios for the r-process therefore require nuclear physics data (masses, beta decay lifetimes, neutron capture rates, fission probabilities) for thousands of nuclei far from stability. Only a small fraction of this data has been experimentally measured. Here we discuss recent sensitivity studies that aim to determine the nuclei whose properties are most crucial for r-process calculations.

  6. Macroinvertebrates of Par Pond and Pond B: Final report, January 1984-June 1985

    SciTech Connect

    Kondratieff, B.C.; Chimney, M.J.; Painter, W.B.

    1985-08-01

    This document reports on the Par Pond and Pond B macroinvertebrate sampling program from January 1984 through June 1985. It includes data on quantitative and qualitative benthic sampling, quantitative meroplankton sampling and quarterly diel sample. The basic objectives were to: (1) characterize the benthic and meroplankton macroinvertebrate communities of Par Pond and Pond B, with respect to taxonomic composition and diversity, density and relative abundance of functional feeding groups; (2) assess the impact of thermal discharges on the macroinvertebrate community of Par Pond; (3) assess the impact and significance of entrainment losses of macroinvertebrate meroplankton from Par Pond; and (4) compare Par Pond macroninvertebrate communities with those in Pond B.

  7. The Pars Interarticularis Stress Reaction, Spondylolysis, and Spondylolisthesis Progression

    PubMed Central

    Motley, Gina; Nyland, John; Jacobs, Jake; Caborn, David N. M.

    1998-01-01

    Objective: To review the classification, etiology, clinical and radiologic evaluation, and management of the pars interarticularis stress reaction, spondylolysis, and spondylolisthesis progression. Data Sources: Grateful Med was searched from 1980 to 1998 using the terms “spondylolysis,” “spondylolisthesis,” “female athlete” “spondylogenic,” and “pars interarticularis.” Data Synthesis: The progression from pars interarticularis stress reaction through spondylolysis to spondylolisthesis is common in adolescent athletes, and, because of hormonal influences and cheerleading and gymnastic maneuvers, females are particularly at risk. Proper diagnosis and management include a thorough evaluation, radiographs (possibly with technetium bone scan or single-photon emission computed tomography), activity modification, dietary counseling, a therapeutic exercise program focusing on proper trunk and hip muscle strength and extensibility balances, and education regarding proper back postures, positioning, lifting mechanics, and jump landings. Conclusions/Recommendations: The athletic trainer plays an integral part in managing this injury progression, particularly with identifying at-risk individuals and intervening appropriately. ImagesFigure 4. PMID:16558534

  8. Enrico Fermi's Discovery of Neutron-Induced Artificial Radioactivity: Neutrons and Neutron Sources

    NASA Astrophysics Data System (ADS)

    Guerra, Francesco; Leone, Matteo; Robotti, Nadia

    2006-09-01

    We reconstruct and analyze the path leading from James Chadwick’s discovery of the neutron in February 1932 through Frédéric Joliot and Irène Curie’s discovery of artificial radioactivity in January 1934 to Enrico Fermi’s discovery of neutron-induced artificial radioactivity in March 1934. We show, in particular, that Fermi’s innovative construction and use of radon-beryllium neutron sources permitted him to make his discovery.

  9. Slow neutron leakage spectra from spallation neutron sources

    SciTech Connect

    Das, S G; Carpenter, J M; Prael, R E

    1980-02-01

    An efficient technique is described for Monte Carlo simulation of neutron beam spectra from target-moderator-reflector assemblies typical of pulsed spallation neutron sources. The technique involves the scoring of the transport-theoretical probability that a neutron will emerge from the moderator surface in the direction of interest, at each collision. An angle-biasing probability is also introduced which further enhances efficiency in simple problems. These modifications were introduced into the VIM low energy neutron transport code, representing the spatial and energy distributions of the source neutrons approximately as those of evaporation neutrons generated through the spallation process by protons of various energies. The intensity of slow neutrons leaking from various reflected moderators was studied for various neutron source arrangements. These include computations relating to early measurements on a mockup-assembly, a brief survey of moderator materials and sizes, and a survey of the effects of varying source and moderator configurations with a practical, liquid metal cooled uranium source Wing and slab, i.e., tangential and radial moderator arrangements, and Be vs CH/sub 2/ reflectors are compared. Results are also presented for several complicated geometries which more closely represent realistic arrangements for a practical source, and for a subcritical fission multiplier such as might be driven by an electron linac. An adaptation of the code was developed to enable time dependent calculations, and investigated the effects of the reflector, decoupling and void liner materials on the pulse shape.

  10. Neutron sources for a neutron capture therapy facility

    SciTech Connect

    Lennox, A.J.

    1993-04-01

    Recent advances in the development of boron pharmaceuticals have reopened the possibility of using epithermal neutrons to treat brain tumors containing boron-10. This paper summarizes the approaches being used to generate the neutron sources and identifies specific areas where more research and development are needed.

  11. LiF/ZnS neutron multiplicity counter

    NASA Astrophysics Data System (ADS)

    Stave, Sean; Bliss, Mary; Kouzes, Richard; Lintereur, Azaree; Robinson, Sean; Siciliano, Edward; Wood, Lynn

    2015-06-01

    The availability of 3He in recent years is becoming restricted with an order of magnitude price increase for this material. Alternatives to the use of 3He for the detection of thermal neutrons are under investigation. One of the most challenging applications for 3He alternatives is in neutron multiplicity counters that provide rapid assay of samples which contain an unknown amount of plutonium in a potentially unknown configuration. With appropriate detector design that has minimal gamma-ray sensitivity and a high detection efficiency even for triple coincidence events, the neutron single, double, and triple coincidence events can be used to extract three unknown parameters such as the 240Pu-effective mass, the sample self-multiplication, and the (α,n) rate. This project is aimed at determining if commercially available 3He alternatives can satisfy this challenging application. Using MCNP modeling the best alternative identified used LiF/ZnS neutron-scintillator sheets and wavelength shifting plastic for light pipes. A four-panel demonstrator module has been constructed, tested, and compared with detailed modeling results. However, to attain that desired high-level of performance two primary design challenges must be addressed. They include building a fast electronics system and robust neutron/gamma-ray discrimination based on pulse shape analysis at high rates. A review of the current effort and the most recent findings will be presented.

  12. SPINDOWN OF ISOLATED NEUTRON STARS: GRAVITATIONAL WAVES OR MAGNETIC BRAKING?

    SciTech Connect

    Staff, Jan E.; Jaikumar, Prashanth; Chan, Vincent; Ouyed, Rachid

    2012-05-20

    We study the spindown of isolated neutron stars from initially rapid rotation rates, driven by two factors: (1) gravitational wave emission due to r-modes and (2) magnetic braking. In the context of isolated neutron stars, we present the first study including self-consistently the magnetic damping of r-modes in the spin evolution. We track the spin evolution employing the RNS code, which accounts for the rotating structure of neutron stars for various equations of state. We find that, despite the strong damping due to the magnetic field, r-modes alter the braking rate from pure magnetic braking for B {<=} 10{sup 13} G. For realistic values of the saturation amplitude {alpha}{sub sat}, the r-mode can also decrease the time to reach the threshold central density for quark deconfinement. Within a phenomenological model, we assess the gravitational waveform that would result from r-mode-driven spindown of a magnetized neutron star. To contrast with the persistent signal during the spindown phase, we also present a preliminary estimate of the transient gravitational wave signal from an explosive quark-hadron phase transition, which can be a signal for the deconfinement of quarks inside neutron stars.

  13. NASA'S Chandra Finds Superfluid in Neutron Star's Core

    NASA Astrophysics Data System (ADS)

    2011-02-01

    NASA's Chandra X-ray Observatory has discovered the first direct evidence for a superfluid, a bizarre, friction-free state of matter, at the core of a neutron star. Superfluids created in laboratories on Earth exhibit remarkable properties, such as the ability to climb upward and escape airtight containers. The finding has important implications for understanding nuclear interactions in matter at the highest known densities. Neutron stars contain the densest known matter that is directly observable. One teaspoon of neutron star material weighs six billion tons. The pressure in the star's core is so high that most of the charged particles, electrons and protons, merge resulting in a star composed mostly of uncharged particles called neutrons. Two independent research teams studied the supernova remnant Cassiopeia A, or Cas A for short, the remains of a massive star 11,000 light years away that would have appeared to explode about 330 years ago as observed from Earth. Chandra data found a rapid decline in the temperature of the ultra-dense neutron star that remained after the supernova, showing that it had cooled by about four percent over a 10-year period. "This drop in temperature, although it sounds small, was really dramatic and surprising to see," said Dany Page of the National Autonomous University in Mexico, leader of a team with a paper published in the February 25, 2011 issue of the journal Physical Review Letters. "This means that something unusual is happening within this neutron star." Superfluids containing charged particles are also superconductors, meaning they act as perfect electrical conductors and never lose energy. The new results strongly suggest that the remaining protons in the star's core are in a superfluid state and, because they carry a charge, also form a superconductor. "The rapid cooling in Cas A's neutron star, seen with Chandra, is the first direct evidence that the cores of these neutron stars are, in fact, made of superfluid and

  14. ParB Partition Proteins: Complex Formation and Spreading at Bacterial and Plasmid Centromeres

    PubMed Central

    Funnell, Barbara E.

    2016-01-01

    In bacteria, active partition systems contribute to the faithful segregation of both chromosomes and low-copy-number plasmids. Each system depends on a site-specific DNA binding protein to recognize and assemble a partition complex at a centromere-like site, commonly called parS. Many plasmid, and all chromosomal centromere-binding proteins are dimeric helix-turn-helix DNA binding proteins, which are commonly named ParB. Although the overall sequence conservation among ParBs is not high, the proteins share similar domain and functional organization, and they assemble into similar higher-order complexes. In vivo, ParBs “spread,” that is, DNA binding extends away from the parS site into the surrounding non-specific DNA, a feature that reflects higher-order complex assembly. ParBs bridge and pair DNA at parS and non-specific DNA sites. ParB dimers interact with each other via flexible conformations of an N-terminal region. This review will focus on the properties of the HTH centromere-binding protein, in light of recent experimental evidence and models that are adding to our understanding of how these proteins assemble into large and dynamic partition complexes at and around their specific DNA sites. PMID:27622187

  15. ParB Partition Proteins: Complex Formation and Spreading at Bacterial and Plasmid Centromeres

    PubMed Central

    Funnell, Barbara E.

    2016-01-01

    In bacteria, active partition systems contribute to the faithful segregation of both chromosomes and low-copy-number plasmids. Each system depends on a site-specific DNA binding protein to recognize and assemble a partition complex at a centromere-like site, commonly called parS. Many plasmid, and all chromosomal centromere-binding proteins are dimeric helix-turn-helix DNA binding proteins, which are commonly named ParB. Although the overall sequence conservation among ParBs is not high, the proteins share similar domain and functional organization, and they assemble into similar higher-order complexes. In vivo, ParBs “spread,” that is, DNA binding extends away from the parS site into the surrounding non-specific DNA, a feature that reflects higher-order complex assembly. ParBs bridge and pair DNA at parS and non-specific DNA sites. ParB dimers interact with each other via flexible conformations of an N-terminal region. This review will focus on the properties of the HTH centromere-binding protein, in light of recent experimental evidence and models that are adding to our understanding of how these proteins assemble into large and dynamic partition complexes at and around their specific DNA sites.

  16. Proteinase-Activated Receptor 1 (PAR1) Regulates Leukemic Stem Cell Functions

    PubMed Central

    Bäumer, Nicole; Krause, Annika; Köhler, Gabriele; Lettermann, Stephanie; Evers, Georg; Hascher, Antje; Bäumer, Sebastian; Berdel, Wolfgang E.

    2014-01-01

    External signals that are mediated by specific receptors determine stem cell fate. The thrombin receptor PAR1 plays an important role in haemostasis, thrombosis and vascular biology, but also in tumor biology and angiogenesis. Its expression and function in hematopoietic stem cells is largely unknown. Here, we analyzed expression and function of PAR1 in primary hematopoietic cells and their leukemic counterparts. AML patients' blast cells expressed much lower levels of PAR1 mRNA and protein than CD34+ progenitor cells. Constitutive Par1-deficiency in adult mice did not affect engraftment or stem cell potential of hematopoietic cells. To model an AML with Par1-deficiency, we retrovirally introduced the oncogene MLL-AF9 in wild type and Par1−/− hematopoietic progenitor cells. Par1-deficiency did not alter initial leukemia development. However, the loss of Par1 enhanced leukemic stem cell function in vitro and in vivo. Re-expression of PAR1 in Par1−/− leukemic stem cells delayed leukemogenesis in vivo. These data indicate that Par1 contributes to leukemic stem cell maintenance. PMID:24740120

  17. ParB Partition Proteins: Complex Formation and Spreading at Bacterial and Plasmid Centromeres.

    PubMed

    Funnell, Barbara E

    2016-01-01

    In bacteria, active partition systems contribute to the faithful segregation of both chromosomes and low-copy-number plasmids. Each system depends on a site-specific DNA binding protein to recognize and assemble a partition complex at a centromere-like site, commonly called parS. Many plasmid, and all chromosomal centromere-binding proteins are dimeric helix-turn-helix DNA binding proteins, which are commonly named ParB. Although the overall sequence conservation among ParBs is not high, the proteins share similar domain and functional organization, and they assemble into similar higher-order complexes. In vivo, ParBs "spread," that is, DNA binding extends away from the parS site into the surrounding non-specific DNA, a feature that reflects higher-order complex assembly. ParBs bridge and pair DNA at parS and non-specific DNA sites. ParB dimers interact with each other via flexible conformations of an N-terminal region. This review will focus on the properties of the HTH centromere-binding protein, in light of recent experimental evidence and models that are adding to our understanding of how these proteins assemble into large and dynamic partition complexes at and around their specific DNA sites. PMID:27622187

  18. Dynamic Filament Formation by a Divergent Bacterial Actin-Like ParM Protein

    PubMed Central

    Brzoska, Anthony J.; Jensen, Slade O.; Barton, Deborah A.; Davies, Danielle S.; Overall, Robyn L.; Skurray, Ronald A.; Firth, Neville

    2016-01-01

    Actin-like proteins (Alps) are a diverse family of proteins whose genes are abundant in the chromosomes and mobile genetic elements of many bacteria. The low-copy-number staphylococcal multiresistance plasmid pSK41 encodes ParM, an Alp involved in efficient plasmid partitioning. pSK41 ParM has previously been shown to form filaments in vitro that are structurally dissimilar to those formed by other bacterial Alps. The mechanistic implications of these differences are not known. In order to gain insights into the properties and behavior of the pSK41 ParM Alp in vivo, we reconstituted the parMRC system in the ectopic rod-shaped host, E. coli, which is larger and more genetically amenable than the native host, Staphylococcus aureus. Fluorescence microscopy showed a functional fusion protein, ParM-YFP, formed straight filaments in vivo when expressed in isolation. Strikingly, however, in the presence of ParR and parC, ParM-YFP adopted a dramatically different structure, instead forming axial curved filaments. Time-lapse imaging and selective photobleaching experiments revealed that, in the presence of all components of the parMRC system, ParM-YFP filaments were dynamic in nature. Finally, molecular dissection of the parMRC operon revealed that all components of the system are essential for the generation of dynamic filaments. PMID:27310470

  19. Neutron multiplicity ,easurements With 3He alternative: Straw neutron detectors

    DOE PAGESBeta

    Mukhopadhyay, Sanjoy; Wolff, Ronald S.; Meade, John A.; Detweiler, Ryan; Maurer, Richard J.; Mitchell, Stephen E.; Guss, Paul P.; Lacy, Jeffrey L.; Sun, Liang; Athanasiades, Athanasios

    2015-01-27

    Counting neutrons emitted by special nuclear material (SNM) and differentiating them from the background neutrons of various origins is the most effective passive means of detecting SNM. Unfortunately, neutron detection, counting, and partitioning in a maritime environment are complex due to the presence of high-multiplicity spallation neutrons (commonly known as “ship effect”) and to the complicated nature of the neutron scattering in that environment. In this study, a prototype neutron detector was built using 10B as the converter in a special form factor called “straws” that would address the above problems by looking into the details of multiplicity distributions ofmore » neutrons originating from a fissioning source. This paper describes the straw neutron multiplicity counter (NMC) and assesses the performance with those of a commercially available fission meter. The prototype straw neutron detector provides a large-area, efficient, lightweight, more granular (than fission meter) neutron-responsive detection surface (to facilitate imaging) to enhance the ease of application of fission meters. Presented here are the results of preliminary investigations, modeling, and engineering considerations leading to the construction of this prototype. This design is capable of multiplicity and Feynman variance measurements. This prototype may lead to a near-term solution to the crisis that has arisen from the global scarcity of 3He by offering a viable alternative to fission meters. This paper describes the work performed during a 2-year site-directed research and development (SDRD) project that incorporated straw detectors for neutron multiplicity counting. The NMC is a two-panel detector system. We used 10B (in the form of enriched boron carbide: 10B4C) for neutron detection instead of 3He. In the first year, the project worked with a panel of straw neutron detectors, investigated its characteristics, and developed a data acquisition (DAQ) system to collect

  20. Fast Neutron Sensitivity with HPGe

    SciTech Connect

    Seifert, Allen; Hensley, Walter K.; Siciliano, Edward R.; Pitts, W. K.

    2008-01-22

    In addition to being excellent gamma-ray detectors, germanium detectors are also sensitive to fast neutrons. Incident neutrons undergo inelastic scattering {Ge(n,n')Ge*} off germanium nuclei and the resulting excited states emit gamma rays or conversion electrons. The response of a standard 140% high-purity germanium (HPGe) detector with a bismuth germanate (BGO) anti-coincidence shield was measured for several neutron sources to characterize the ability of the HPGe detector to detect fast neutrons. For a sensitivity calculation performed using the characteristic fast neutron response peak that occurs at 692 keV, the 140% germanium detector system exhibited a sensitivity of ~175 counts / kg of WGPumetal in 1000 seconds at a source-detector distance of 1 meter with 4 in. of lead shielding between source and detector. Theoretical work also indicates that it might be possible to use the shape of the fast-neutron inelastic scattering signatures (specifically, the end-point energy of the long high energy tail of the resulting asymmetric peak) to gain additional information about the energy distribution of the incident neutron spectrum. However, the experimentally observed end-point energies appear to be almost identical for each of the fast neutron sources counted. Detailed MCNP calculations show that the neutron energy distributions impingent on the detector for these sources are very similar in this experimental configuration, due to neutron scattering in a lead shield (placed between the neutron source and HPGe detector to reduce the gamma ray flux), the BGO anti-coincidence detector, and the concrete floor.

  1. The physical association of the P2Y12 receptor with PAR4 regulates arrestin-mediated Akt activation.

    PubMed

    Khan, Aasma; Li, Dongjun; Ibrahim, Salam; Smyth, Emer; Woulfe, Donna S

    2014-07-01

    It is now well accepted that protease activated receptor (PAR) 1 and PAR4 have differential roles in platelet activation. PAR4, a low-affinity thrombin receptor in human platelets, participates in sustained platelet activation in a P2Y12-dependent manner; however, the mechanisms are not defined. Our previous studies demonstrated that thrombin induces the association of PAR4 with P2Y12, together with arrestin recruitment to the complex. Here we show that PAR4 and P2Y12 directly interact to coregulate Akt signaling after PAR4 activation. We observed direct and specific interaction of P2Y12 with PAR4 but not PAR1 by bioluminescent resonance energy transfer when the receptors were coexpressed in human embryonic kidney 293T cells. PAR4-P2Y12 dimerization was promoted by PAR4-AP and inhibited by P2Y12 antagonist. By using sequence comparison of the transmembrane domains of PAR1 and PAR4, we designed a mutant form of PAR4, "PAR4SFT," by replacing LGL194-196 at the base of transmembrane domain 4 with the corresponding aligned PAR1 residues SFT 220-222. PAR4SFT supported only 8.74% of PAR4-P2Y12 interaction, abolishing P2Y12-dependent arrestin recruitment to PAR4 and Akt activation. Nonetheless, PAR4SFT still supported homodimerization with PAR4. PAR4SFT failed to induce a calcium flux when expressed independently; however, coexpression of increasing concentrations of PAR4SFT, together with PAR4 potentiated PAR4-mediated calcium flux, suggested that PAR4 act as homodimers to signal to Gq-coupled calcium responses. In conclusion, PAR4 LGL (194-196) governs agonist-dependent association of PAR4 with P2Y12 and contributes to Gq-coupled calcium responses. PAR4-P2Y12 association supports arrestin-mediated sustained signaling to Akt. Hence, PAR4-P2Y12 dimerization is likely to be important for the PAR4-P2Y12 dependent stabilization of platelet thrombi.

  2. The physical association of the P2Y12 receptor with PAR4 regulates arrestin-mediated Akt activation.

    PubMed

    Khan, Aasma; Li, Dongjun; Ibrahim, Salam; Smyth, Emer; Woulfe, Donna S

    2014-07-01

    It is now well accepted that protease activated receptor (PAR) 1 and PAR4 have differential roles in platelet activation. PAR4, a low-affinity thrombin receptor in human platelets, participates in sustained platelet activation in a P2Y12-dependent manner; however, the mechanisms are not defined. Our previous studies demonstrated that thrombin induces the association of PAR4 with P2Y12, together with arrestin recruitment to the complex. Here we show that PAR4 and P2Y12 directly interact to coregulate Akt signaling after PAR4 activation. We observed direct and specific interaction of P2Y12 with PAR4 but not PAR1 by bioluminescent resonance energy transfer when the receptors were coexpressed in human embryonic kidney 293T cells. PAR4-P2Y12 dimerization was promoted by PAR4-AP and inhibited by P2Y12 antagonist. By using sequence comparison of the transmembrane domains of PAR1 and PAR4, we designed a mutant form of PAR4, "PAR4SFT," by replacing LGL194-196 at the base of transmembrane domain 4 with the corresponding aligned PAR1 residues SFT 220-222. PAR4SFT supported only 8.74% of PAR4-P2Y12 interaction, abolishing P2Y12-dependent arrestin recruitment to PAR4 and Akt activation. Nonetheless, PAR4SFT still supported homodimerization with PAR4. PAR4SFT failed to induce a calcium flux when expressed independently; however, coexpression of increasing concentrations of PAR4SFT, together with PAR4 potentiated PAR4-mediated calcium flux, suggested that PAR4 act as homodimers to signal to Gq-coupled calcium responses. In conclusion, PAR4 LGL (194-196) governs agonist-dependent association of PAR4 with P2Y12 and contributes to Gq-coupled calcium responses. PAR4-P2Y12 association supports arrestin-mediated sustained signaling to Akt. Hence, PAR4-P2Y12 dimerization is likely to be important for the PAR4-P2Y12 dependent stabilization of platelet thrombi. PMID:24723492

  3. Electroweak bremsstrahlung from neutron-neutron scattering

    SciTech Connect

    Li Yi; Liou, M. K.; Schreiber, W. M.

    2009-09-15

    Background: Nucleon-nucleon (NN) bremsstrahlung processes NN{gamma} (nn{gamma}, np{gamma}, and pp{gamma}) have been extensively investigated. Neutrino-pair bremsstrahlung processes from nucleon-nucleon scattering NN{nu}{nu} (nn{nu}{nu}, np{nu}{nu}, and pp{nu}{nu}) have recently attracted attention in studies of neutrino emission in neutron stars. The calculated NN{nu}{nu} cross sections (or emissivities) are found to be sensitive to the two-nucleon dynamical model used in the calculations. Purpose and Method: A realistic one-boson-exchange (ROBE) model for NN interactions is used to construct the electroweak bremsstrahlung amplitudes using the well-known nucleon electromagnetic and weak interaction vertices. The constructed nn{gamma} and nn{nu}{nu} amplitudes are investigated by applying them to calculate nn{gamma} and nn{nu}{nu} cross sections, respectively. Results: (i) The 190-MeV ROBE nn{gamma} cross sections agree well with those calculated using the TuTts amplitude, but they are in disagreement with those calculated using the Low amplitude. (ii) The calculated nn{nu}{nu} cross sections using the ROBE amplitude at the neutrino-pair energy {omega} = 1 MeV are in quantitative agreement with those calculated by Timmermans et al.[Phys. Rev. C 65, 064007 (2002)], who used the leading-order term of the soft neutrino-pair bremsstrahlung amplitude. Conclusions: The nn{gamma} amplitude in the ROBE approach, which obeys the soft-photon theorem, has a predictive power similar to that of the TuTts amplitude. The nn{nu}{nu} amplitude in the ROBE approach, which is consistent with the soft neutrino-pair bremsstrahlung theorem, has a predictive power similar to that of the soft neutrino-pair bremsstrahlung amplitude of Timmermans et al. in the low neutrino-pair energy region.

  4. Neutron beam imaging at neutron spectrometers at Dhruva

    SciTech Connect

    Desai, Shraddha S.; Rao, Mala N.

    2012-06-05

    A low efficiency, 2-Dimensional Position Sensitive Neutron Detector based on delay line position encoding is developed. It is designed to handle beam flux of 10{sup 6}-10{sup 7} n/cm{sup 2}/s and for monitoring intensity profiles of neutron beams. The present detector can be mounted in transmission mode, as the hardware allows maximum neutron transmission in sensitive region. Position resolution of 1.2 mm in X and Y directions, is obtained. Online monitoring of beam images and intensity profile of various neutron scattering spectrometers at Dhruva are presented. It shows better dynamic range of intensity over commercial neutron camera and is also time effective over the traditionally used photographic method.

  5. Application of imaging plate neutron detector to neutron radiography

    NASA Astrophysics Data System (ADS)

    Fujine, Shigenori; Yoneda, Kenji; Kamata, Masahiro; Etoh, Masahiro

    1999-11-01

    As an imaging plate neutron detector (IP-ND) has been available for thermal neutron radiography (TNR) which has high resolution, high sensitivity and wide range, some basic characteristics of the IP-ND system were measured at the E-2 facility of the KUR. After basic performances of the IP were studied, images with high quality were obtained at a neutron fluence of 2 to 7×10 8 n cm -2. It was found that the IP-ND system with Gd 2O 3 as a neutron converter material has a higher sensitivity to γ-ray than that of a conventional film method. As a successful example, clear radiographs of the flat view for the fuel side plates with boron burnable poison were obtained. An application of the IP-ND system to neutron radiography (NR) is presented in this paper.

  6. Accelerator based epithermal neutron source for neutron capture therapy

    SciTech Connect

    Brugger, R.; Kunze, J.

    1991-05-01

    Several investigators have suggested that a charged particle accelerator with light element reactions might be able to produce enough epithermal neutrons to be useful in Neutron Capture Therapy. The reaction choice so far has been the Li(p,n) reaction with protons up to 2.5 MeV. A moderator around the target would reduce the faster neutrons down to the epithermal energy region. The goals of the present research are: identify better reactions; improve the moderators; and find better combinations of 1 and 2. The target is to achieve, at the patient location, an epithermal neutron current of greater than 10{sup 9}n/cm{sup 2}sec, with a dose to tissue from the neutrons alone of less than 10{sup {minus}10} rads/n and a dose from the gamma rays in the beam of less than 10{sup {minus}10} rads/n.

  7. Small angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Cousin, Fabrice

    2015-10-01

    Small Angle Neutron Scattering (SANS) is a technique that enables to probe the 3-D structure of materials on a typical size range lying from ˜ 1 nm up to ˜ a few 100 nm, the obtained information being statistically averaged on a sample whose volume is ˜ 1 cm3. This very rich technique enables to make a full structural characterization of a given object of nanometric dimensions (radius of gyration, shape, volume or mass, fractal dimension, specific area…) through the determination of the form factor as well as the determination of the way objects are organized within in a continuous media, and therefore to describe interactions between them, through the determination of the structure factor. The specific properties of neutrons (possibility of tuning the scattering intensity by using the isotopic substitution, sensitivity to magnetism, negligible absorption, low energy of the incident neutrons) make it particularly interesting in the fields of soft matter, biophysics, magnetic materials and metallurgy. In particular, the contrast variation methods allow to extract some informations that cannot be obtained by any other experimental techniques. This course is divided in two parts. The first one is devoted to the description of the principle of SANS: basics (formalism, coherent scattering/incoherent scattering, notion of elementary scatterer), form factor analysis (I(q→0), Guinier regime, intermediate regime, Porod regime, polydisperse system), structure factor analysis (2nd Virial coefficient, integral equations, characterization of aggregates), and contrast variation methods (how to create contrast in an homogeneous system, matching in ternary systems, extrapolation to zero concentration, Zero Averaged Contrast). It is illustrated by some representative examples. The second one describes the experimental aspects of SANS to guide user in its future experiments: description of SANS spectrometer, resolution of the spectrometer, optimization of spectrometer

  8. Neutron quality factor

    SciTech Connect

    1995-06-01

    Both the International Commission on Radiological Protection (ICRP) and the National Council on Radiation Protection and Measurements (NCRP) have recommended that the radiation quality weighting factor for neutrons (Q{sub n}, or the corresponding new modifying factor, w{sub R}) be increased by a value of two for most radiation protection practices. This means an increase in the recommended value for Q{sub n} from a nominal value of 10 to a nominal value of 20. This increase may be interpreted to mean that the biological effectiveness of neutrons is two times greater than previously thought. A decision to increase the value of Q{sub n} will have a major impact on the regulations and radiation protection programs of Federal agencies responsible for the protection of radiation workers. Therefore, the purposes of this report are: (1) to examine the general concept of {open_quotes}quality factor{close_quotes} (Q) in radiation protection and the rationale for the selection of specific values of Q{sub n}; and (2) to make such recommendations to the Federal agencies, as appropriate. This report is not intended to be an exhaustive review of the scientific literature on the biological effects of neutrons, with the aim of defending a particular value for Q{sub n}. Rather, the working group examined the technical issues surrounding the current recommendations of scientific advisory bodies on this matter, with the aim of determining if these recommendations should be adopted by the Federal agencies. Ultimately, the group concluded that there was no compelling basis for a change in Q{sub n}. The report was prepared by Federal scientists working under the auspices of the Science Panel of the Committee on Interagency Radiation Research and Policy Coordination (CIRRPC).

  9. Modeling rapidly rotating stars

    NASA Astrophysics Data System (ADS)

    Rieutord, M.

    2006-06-01

    We review the quest of modeling rapidly rotating stars during the past 40 years and detail the challenges to be taken up by models facing new data from interferometry, seismology, spectroscopy... We then present the progress of the ESTER project aimed at giving a physically self-consistent model for the structure and evolution of rapidly rotating stars.

  10. NEUTRONIC REACTOR CONSTRUCTION

    DOEpatents

    Vernon, H.C.; Goett, J.J.

    1958-09-01

    A cover device is described for the fuel element receiving tube of a neutronic reactor of the heterogeneous, water cooled type wherein said tubes are arranged in a moderator with their longitudinal axes vertical. The cover is provided with means to support a rod-type fuel element from the bottom thereof and means to lock the cover in place, the latter being adapted for remote operation. This cover device is easily removable and seals the opening in the upper end of the fuel tube against leakage of coolant.

  11. Advanced Neutron Spectrometer

    NASA Technical Reports Server (NTRS)

    Christl, Mark; Dobson, Chris; Norwood, Joseph; Kayatin, Matthew; Apple, Jeff; Gibson, Brian; Dietz, Kurt; Benson, Carl; Smith, Dennis; Howard, David; Rodriquez, Miguel; Watts, John; Sabra, Mohammed; Kuznetsov, Evgeny

    2013-01-01

    Energetic neutron measurements remain a challenge for space science investigations and radiation monitoring for human exploration beyond LEO. We are investigating a new composite scintillator design that uses Li6 glass scintillator embedded in a PVT block. A comparison between Li6 and Boron 10 loaded scintillators are being studied to assess the advantages and shortcomings of these two techniques. We present the details of the new Li6 design and results from the comparison of the B10 and Li6 techniques during exposures in a mixed radiation field produced by high energy protons interacting in a target material.

  12. Influence of neutrinos on r-process nucleosynthesis in black hole-neutron star mergers

    NASA Astrophysics Data System (ADS)

    Lippuner, Jonas; Roberts, Luke F.; Duez, Matthew D.; Faber, Joshua A.; Foucart, Francois; Lombardi, James C.; Ott, Christian D.; Ponce, Marcelo

    2016-03-01

    During a black hole-neutron star merger, baryonic material can be dynamically ejected. Because this ejecta is extremely neutron-rich, the r-process rapidly synthesizes heavy nuclides as the material expands and cools. This can contribute to galactic chemical evolution of the r-process elements and lead to a short-lived optical transient, called a kilonova, powered by the radioactive decay of the heavy nuclides. We use the nuclear reaction network SkyNet to model r-process nucleosynthesis under varying levels of neutrino irradiation by post-processing tracer particles in the ejecta of a full numerical relativity simulation of a black hole-neutron star merger. We find the ejected material robustly produces the second and third r-process peaks, whose abundances remain unchanged even for very high neutrino luminosities, due to the rapid velocities of the outflow. Nonetheless, we find that neutrinos can have an impact on the detailed abundance pattern by significantly enhancing the amount of material produced in the first peak around A ~ 78 . Electron neutrinos are captured by neutrons to produce protons while neutron capture is occurring. These protons rapidly form low-mass seed nuclei, a fraction of which eventually ends up in the first peak after neutron capture ceases. Partially supported by NASA and NSF under AST-1205732, AST-1313091, AST-1333520, PF3-140114, PF4-150122, and PHY-1151197.

  13. Determination of indium in standard rocks by neutron activation analysis.

    PubMed

    Johansen, O; Steinnes, E

    1966-08-01

    A rapid neutron activation method for the determination of indium in rocks, based on 54 min (116m)In, is described. The method has been applied to a series of geochemical standards including granite G-1 and diabase W-1. The precision is better than +/- 5% for samples containing more than 5 x 10(-10)g indium. Good agreement with previously published values for G-1 and W-1 has been obtained.

  14. Determination of indium in standard rocks by neutron activation analysis.

    PubMed

    Johansen, O; Steinnes, E

    1966-08-01

    A rapid neutron activation method for the determination of indium in rocks, based on 54 min (116m)In, is described. The method has been applied to a series of geochemical standards including granite G-1 and diabase W-1. The precision is better than +/- 5% for samples containing more than 5 x 10(-10)g indium. Good agreement with previously published values for G-1 and W-1 has been obtained. PMID:18959988

  15. Neutrons for technology and science

    SciTech Connect

    Aeppli, G.

    1995-10-01

    We reviewed recent work using neutrons generated at nuclear reactors an accelerator-based spallation sources. Provided that large new sources become available, neutron beams will continue to have as great an impact on technology and science as in the past.

  16. Fission fragment driven neutron source

    DOEpatents

    Miller, Lowell G.; Young, Robert C.; Brugger, Robert M.

    1976-01-01

    Fissionable uranium formed into a foil is bombarded with thermal neutrons in the presence of deuterium-tritium gas. The resulting fission fragments impart energy to accelerate deuterium and tritium particles which in turn provide approximately 14 MeV neutrons by the reactions t(d,n).sup.4 He and d(t,n).sup.4 He.

  17. High power neutron production targets

    SciTech Connect

    Wender, S.

    1996-06-01

    The author describes issues of concern in the design of targets and associated systems for high power neutron production facilities. The facilities include uses for neutron scattering, accelerator driven transmutation, accelerator production of tritium, short pulse spallation sources, and long pulse spallation sources. Each of these applications requires a source with different design needs and consequently different implementation in practise.

  18. Personnel neutron monitoring in space

    NASA Technical Reports Server (NTRS)

    Schaefer, H. J.

    1978-01-01

    A brief review is presented of available information on the galactic neutron spectrum. An examination is made of the difficulties encountered in the determination of the dose equivalent of neutron recoil protons in the presence of a substantially larger background of trapped and star-produced protons as well as other ionizing particles in space.

  19. A Review of Significant Advances in Neutron Imaging from Conception to the Present

    NASA Astrophysics Data System (ADS)

    Brenizer, J. S.

    This review summarizes the history of neutron imaging with a focus on the significant events and technical advancements in neutron imaging methods, from the first radiograph to more recent imaging methods. A timeline is presented to illustrate the key accomplishments that advanced the neutron imaging technique. Only three years after the discovery of the neutron by English physicist James Chadwick in 1932, neutron imaging began with the work of Hartmut Kallmann and Ernst Kuhn in Berlin, Germany, from 1935-1944. Kallmann and Kuhn were awarded a joint US Patent issued in January 1940. Little progress was made until the mid-1950's when Thewlis utilized a neutron beam from the BEPO reactor at Harwell, marking the beginning of the application of neutron imaging to practical applications. As the film method was improved, imaging moved from a qualitative to a quantitative technique, with applications in industry and in nuclear fuels. Standards were developed to aid in the quantification of the neutron images and the facility's capabilities. The introduction of dynamic neutron imaging (initially called real-time neutron radiography and neutron television) in the late 1970's opened the door to new opportunities and new challenges. As the electronic imaging matured, the introduction of the CCD imaging devices and solid-state light intensifiers helped address some of these challenges. Development of improved imaging devices for the medical community has had a major impact on neutron imaging. Additionally, amorphous silicon sensors provided improvements in temporal resolution, while providing a reasonably large imaging area. The development of new neutron imaging sensors and the development of new neutron imaging techniques in the past decade has advanced the technique's ability to provide insight and understanding of problems that other non-destructive techniques could not provide. This rapid increase in capability and application would not have been possible without the

  20. Measuring neutron spectra in radiotherapy using the nested neutron spectrometer

    SciTech Connect

    Maglieri, Robert Evans, Michael; Seuntjens, Jan; Kildea, John; Licea, Angel

    2015-11-15

    Purpose: Out-of-field neutron doses resulting from photonuclear interactions in the head of a linear accelerator pose an iatrogenic risk to patients and an occupational risk to personnel during radiotherapy. To quantify neutron production, in-room measurements have traditionally been carried out using Bonner sphere systems (BSS) with activation foils and TLDs. In this work, a recently developed active detector, the nested neutron spectrometer (NNS), was tested in radiotherapy bunkers. Methods: The NNS is designed for easy handling and is more practical than the traditional BSS. Operated in current-mode, the problem of pulse pileup due to high dose-rates is overcome by measuring current, similar to an ionization chamber. In a bunker housing a Varian Clinac 21EX, the performance of the NNS was evaluated in terms of reproducibility, linearity, and dose-rate effects. Using a custom maximum-likelihood expectation–maximization algorithm, measured neutron spectra at various locations inside the bunker were then compared to Monte Carlo simulations of an identical setup. In terms of dose, neutron ambient dose equivalents were calculated from the measured spectra and compared to bubble detector neutron dose equivalent measurements. Results: The NNS-measured spectra for neutrons at various locations in a treatment room were found to be consistent with expectations for both relative shape and absolute magnitude. Neutron fluence-rate decreased with distance from the source and the shape of the spectrum changed from a dominant fast neutron peak near the Linac head to a dominant thermal neutron peak in the moderating conditions of the maze. Monte Carlo data and NNS-measured spectra agreed within 30% at all locations except in the maze where the deviation was a maximum of 40%. Neutron ambient dose equivalents calculated from the authors’ measured spectra were consistent (one standard deviation) with bubble detector measurements in the treatment room. Conclusions: The NNS may

  1. RPC for thermal neutron detection

    NASA Astrophysics Data System (ADS)

    Arnaldi, R.; Chiavassa, E.; Colla, A.; Cortese, P.; Dellacasa, G.; DeMarco, N.; Ferretti, A.; Gagliardi, M.; Gallio, M.; Gemme, R.; Musso, A.; Oppedisano, C.; Piccotti, A.; Poggio, F.; Scomparin, E.; Vercellin, E.

    2006-05-01

    The possibility to detect thermal neutrons with single gap Resistive Plate Chambers has been investigated. To detect neutrons a 10B4C thin coating on the inner surface of one RPC electrode is used as thermal neutron converter. The RPC detects the charged particles generated by neutrons via the (n, α) reaction on Boron. Tests on converter samples have been performed with a thermalized 252Cf source in order to evaluate the conversion efficiency: a good agreement between experimental results and simulation has been achieved. A detector prototype has been developed and tested on a low energy neutron beam at the European laboratories JRC in Belgium. A detailed description of the detector and the experimental test results are presented.

  2. Grand unification of neutron stars

    PubMed Central

    Kaspi, Victoria M.

    2010-01-01

    The last decade has shown us that the observational properties of neutron stars are remarkably diverse. From magnetars to rotating radio transients, from radio pulsars to isolated neutron stars, from central compact objects to millisecond pulsars, observational manifestations of neutron stars are surprisingly varied, with most properties totally unpredicted. The challenge is to establish an overarching physical theory of neutron stars and their birth properties that can explain this great diversity. Here I survey the disparate neutron stars classes, describe their properties, and highlight results made possible by the Chandra X-Ray Observatory, in celebration of its 10th anniversary. Finally, I describe the current status of efforts at physical “grand unification” of this wealth of observational phenomena, and comment on possibilities for Chandra’s next decade in this field. PMID:20404205

  3. Collective cell migration requires suppression of actomyosin at cell-cell contacts mediated by DDR1 and the cell polarity regulators Par3 and Par6.

    PubMed

    Hidalgo-Carcedo, Cristina; Hooper, Steven; Chaudhry, Shahid I; Williamson, Peter; Harrington, Kevin; Leitinger, Birgit; Sahai, Erik

    2011-01-01

    Collective cell migration occurs in a range of contexts: cancer cells frequently invade in cohorts while retaining cell-cell junctions. Here we show that collective invasion by cancer cells depends on decreasing actomyosin contractility at sites of cell-cell contact. When actomyosin is not downregulated at cell-cell contacts, migrating cells lose cohesion. We provide a molecular mechanism for this downregulation. Depletion of discoidin domain receptor 1 (DDR1) blocks collective cancer-cell invasion in a range of two-dimensional, three-dimensional and 'organotypic' models. DDR1 coordinates the Par3/Par6 cell-polarity complex through its carboxy terminus, binding PDZ domains in Par3 and Par6. The DDR1-Par3/Par6 complex controls the localization of RhoE to cell-cell contacts, where it antagonizes ROCK-driven actomyosin contractility. Depletion of DDR1, Par3, Par6 or RhoE leads to increased actomyosin contactility at cell-cell contacts, a loss of cell-cell cohesion and defective collective cell invasion.

  4. Characterisation of neutron fields at Cernavoda NPP.

    PubMed

    Cauwels, Vanessa; Vanhavere, Filip; Dumitrescu, Dorin; Chirosca, Alecsandru; Hager, Luke; Million, Marc; Bartz, James

    2013-04-01

    Near a nuclear reactor or a fuel container, mixed neutron/gamma fields are very common, necessitating routine neutron dosimetry. Accurate neutron dosimetry is complicated by the fact that the neutron effective dose is strongly dependent on the neutron energy and the direction distribution of the neutron fluence. Neutron field characterisation is indispensable if one wants to obtain a reliable estimate for the neutron dose. A measurement campaign at CANDU nuclear power plant located in Cernavoda, Romania, was set up to characterise the neutron fields in four different locations and to investigate the behaviour of different neutron personal dosemeters. This investigation intends to assist in choosing a suitable neutron dosimetry system at this nuclear power plant.

  5. Neutron activation for ITER

    SciTech Connect

    Barnes, C.W.; Loughlin, M.J.; Nishitani, Takeo

    1996-04-29

    There are three primary goals for the Neutron Activation system for ITER: maintain a robust relative measure of fusion power with stability and high dynamic range (7 orders of magnitude); allow an absolute calibration of fusion power (energy); and provide a flexible and reliable system for materials testing. The nature of the activation technique is such that stability and high dynamic range can be intrinsic properties of the system. It has also been the technique that demonstrated (on JET and TFTR) the highest accuracy neutron measurements in DT operation. Since the gamma-ray detectors are not located on the tokamak and are therefore amenable to accurate characterization, and if material foils are placed very close to the ITER plasma with minimum scattering or attenuation, high overall accuracy in the fusion energy production (7--10%) should be achievable on ITER. In the paper, a conceptual design is presented. A system is shown to be capable of meeting these three goals, also detailed design issues remain to be solved.

  6. Modeling Binary Neutron Stars

    NASA Astrophysics Data System (ADS)

    Park, Conner; Read, Jocelyn; Flynn, Eric; Lockett-Ruiz, Veronica

    2016-03-01

    Gravitational waves, predicted by Einstein's Theory of Relativity, are a new frontier in astronomical observation we can use to observe phenomena in the universe. Laser Interferometer Gravitational wave Observatory (LIGO) is currently searching for gravitational wave signals, and requires accurate predictions in order to best extract astronomical signals from all other sources of fluctuations. The focus of my research is in increasing the accuracy of Post-Newtonian models of binary neutron star coalescence to match the computationally expensive Numerical models. Numerical simulations can take months to compute a couple of milliseconds of signal whereas the Post-Newtonian can generate similar signals in seconds. However the Post-Newtonian model is an approximation, e.g. the Taylor T4 Post-Newtonian model assumes that the two bodies in the binary neutron star system are point charges. To increase the effectiveness of the approximation, I added in tidal effects, resonance frequencies, and a windowing function. Using these observed effects from simulations significantly increases the Post-Newtonian model's similarity to the Numerical signal.

  7. Methods for Neutron Spectrometry

    DOE R&D Accomplishments Database

    Brockhouse, Bertram N.

    1961-01-09

    The appropriate theories and the general philosophy of methods of measurement and treatment of data neutron spectrometry are discussed. Methods of analysis of results for liquids using the Van Hove formulation, and for crystals using the Born-von Karman theory, are reviewed. The most useful of the available methods of measurement are considered to be the crystal spectrometer methods and the pulsed monoenergetic beam/time-of-flight method. Pulsed-beam spectrometers have the advantage of higher counting rates than crystal spectrometers, especially in view of the fact that simultaneous measurements in several counters at different angles of scattering are possible in pulsed-beam spectrometers. The crystal spectrometer permits several valuable new types of specialized experiments to be performed, especially energy distribution measurements at constant momentum transfer. The Chalk River triple-axis crystal-spectrometer is discussed, with reference to its use in making the specialized experiments. The Chalk River rotating crystal (pulsed-beam) spectrometer is described, and a comparison of this type instrument with other pulsed-beam spectrometers is made. A partial outline of the theory of operation of rotating-crystal spectrometers is presented. The use of quartz-crystal filters for fast neutron elimination and for order elimination is discussed. (auth)

  8. ParABS Systems of the Four Replicons of Burkholderia cenocepacia: New Chromosome Centromeres Confer Partition Specificity†

    PubMed Central

    Dubarry, Nelly; Pasta, Franck; Lane, David

    2006-01-01

    Most bacterial chromosomes carry an analogue of the parABS systems that govern plasmid partition, but their role in chromosome partition is ambiguous. parABS systems might be particularly important for orderly segregation of multipartite genomes, where their role may thus be easier to evaluate. We have characterized parABS systems in Burkholderia cenocepacia, whose genome comprises three chromosomes and one low-copy-number plasmid. A single parAB locus and a set of ParB-binding (parS) centromere sites are located near the origin of each replicon. ParA and ParB of the longest chromosome are phylogenetically similar to analogues in other multichromosome and monochromosome bacteria but are distinct from those of smaller chromosomes. The latter form subgroups that correspond to the taxa of their hosts, indicating evolution from plasmids. The parS sites on the smaller chromosomes and the plasmid are similar to the “universal” parS of the main chromosome but with a sequence specific to their replicon. In an Escherichia coli plasmid stabilization test, each parAB exhibits partition activity only with the parS of its own replicon. Hence, parABS function is based on the independent partition of individual chromosomes rather than on a single communal system or network of interacting systems. Stabilization by the smaller chromosome and plasmid systems was enhanced by mutation of parS sites and a promoter internal to their parAB operons, suggesting autoregulatory mechanisms. The small chromosome ParBs were found to silence transcription, a property relevant to autoregulation. PMID:16452432

  9. Transcriptional Profiling of ParA and ParB Mutants in Actively Dividing Cells of an Opportunistic Human Pathogen Pseudomonas aeruginosa

    PubMed Central

    Bartosik, Aneta A.; Glabski, Krzysztof; Jecz, Paulina; Mikulska, Sylwia; Fogtman, Anna; Koblowska, Marta; Jagura-Burdzy, Grazyna

    2014-01-01

    Accurate chromosome segregation to progeny cells is a fundamental process ensuring proper inheritance of genetic material. In bacteria with simple cell cycle, chromosome segregation follows replication initiation since duplicated oriC domains start segregating to opposite halves of the cell soon after they are made. ParA and ParB proteins together with specific DNA sequences are parts of the segregation machinery. ParA and ParB proteins in Pseudomonas aeruginosa are important for optimal growth, nucleoid segregation, cell division and motility. Comparative transcriptome analysis of parAnull and parBnull mutants versus parental P. aeruginosa PAO1161 strain demonstrated global changes in gene expression pattern in logarithmically growing planktonic cultures. The set of genes similarly affected in both mutant strains is designated Par regulon and comprises 536 genes. The Par regulon includes genes controlled by two sigma factors (RpoN and PvdS) as well as known and putative transcriptional regulators. In the absence of Par proteins, a large number of genes from RpoS regulon is induced, reflecting the need for slowing down the cell growth rate and decelerating the metabolic processes. Changes in the expression profiles of genes involved in c-di-GMP turnover point out the role of this effector in such signal transmission. Microarray data for chosen genes were confirmed by RT-qPCR analysis. The promoter regions of selected genes were cloned upstream of the promoter-less lacZ gene and analyzed in the heterologous host E. coliΔlac. Regulation by ParA and ParB of P. aeruginosa was confirmed for some of the tested promoters. Our data demonstrate that ParA and ParB besides their role in accurate chromosome segregation may act as modulators of genes expression. Directly or indirectly, Par proteins are part of the wider regulatory network in P. aeruginosa linking the process of chromosome segregation with the cell growth, division and motility. PMID:24498062

  10. Is PAR a Good Investment? Understanding the Costs and Benefits of Teacher Peer Assistance and Review Programs

    ERIC Educational Resources Information Center

    Papay, John P.; Johnson, Susan Moore

    2012-01-01

    Peer Assistance and Review (PAR) is a local labor-management initiative designed to improve teacher quality. In PAR, expert "consulting teachers" mentor, support, and evaluate novice and underperforming veteran teachers. Evaluations under PAR can lead to dismissals. The authors examine the costs and benefits of PAR, both financial and…

  11. Rapid Airplane Parametric Input Design (RAPID)

    NASA Technical Reports Server (NTRS)

    Smith, Robert E.

    1995-01-01

    RAPID is a methodology and software system to define a class of airplane configurations and directly evaluate surface grids, volume grids, and grid sensitivity on and about the configurations. A distinguishing characteristic which separates RAPID from other airplane surface modellers is that the output grids and grid sensitivity are directly applicable in CFD analysis. A small set of design parameters and grid control parameters govern the process which is incorporated into interactive software for 'real time' visual analysis and into batch software for the application of optimization technology. The computed surface grids and volume grids are suitable for a wide range of Computational Fluid Dynamics (CFD) simulation. The general airplane configuration has wing, fuselage, horizontal tail, and vertical tail components. The double-delta wing and tail components are manifested by solving a fourth order partial differential equation (PDE) subject to Dirichlet and Neumann boundary conditions. The design parameters are incorporated into the boundary conditions and therefore govern the shapes of the surfaces. The PDE solution yields a smooth transition between boundaries. Surface grids suitable for CFD calculation are created by establishing an H-type topology about the configuration and incorporating grid spacing functions in the PDE equation for the lifting components and the fuselage definition equations. User specified grid parameters govern the location and degree of grid concentration. A two-block volume grid about a configuration is calculated using the Control Point Form (CPF) technique. The interactive software, which runs on Silicon Graphics IRIS workstations, allows design parameters to be continuously varied and the resulting surface grid to be observed in real time. The batch software computes both the surface and volume grids and also computes the sensitivity of the output grid with respect to the input design parameters by applying the precompiler tool

  12. Recent activities for β-decay half-lives and β-delayed neutron emission of very neutron-rich isotopes

    SciTech Connect

    Dillmann, Iris; Abriola, Daniel; Singh, Balraj

    2014-05-02

    Beta-delayed neutron (βn) emitters play an important, two-fold role in the stellar nucleosynthesis of heavy elements in the 'rapid neutron-capture process' (r process). On one hand they lead to a detour of the material β-decaying back to stability. On the other hand, the released neutrons increase the neutron-to-seed ratio, and are re-captured during the freeze-out phase and thus influence the final solar r-abundance curve. A large fraction of the isotopes inside the r-process reaction path are not yet experimentally accessible and are located in the (experimental) 'Terra Incognita'. With the next generation of fragmentation and ISOL facilities presently being built or already in operation, one of the main motivation of all projects is the investigation of these very neutron-rich isotopes. A short overview of one of the planned programs to measure βn-emitters at the limits of the presently know isotopes, the BRIKEN campaign (Beta delayed neutron emission measurements at RIKEN) will be given. Presently, about 600 β-delayed one-neutron emitters are accessible, but only for a third of them experimental data are available. Reaching more neutron-rich isotopes means also that multiple neutron-emission becomes the dominant decay mechanism. About 460 β-delayed two-, three-or four-neutron emitters are identified up to now but for only 30 of them experimental data about the neutron branching ratios are available, most of them in the light mass region below A=30. The International Atomic and Energy Agency (IAEA) has identified the urgency and picked up this topic recently in a 'Coordinated Research Project' on a 'Reference Database for Beta-Delayed Neutron Emission Data'. This project will review, compile, and evaluate the existing data for neutron-branching ratios and half-lives of β-delayed neutron emitters and help to ensure a reliable database for the future discoveries of new isotopes and help to constrain astrophysical and theoretical models.

  13. Neutron tube design study for boron neutron capture therapy application

    SciTech Connect

    Verbeke, J.M.; Lee, Y.; Leung, K.N.; Vujic, J.; Williams, M.D.; Wu, L.K.; Zahir, N.

    1999-05-06

    Radio-frequency (RF) driven ion sources are being developed in Lawrence Berkeley National Laboratory (LBNL) for sealed-accelerator-tube neutron generator application. By using a 5-cm-diameter RF-driven multicusp source H{sup +} yields over 95% have been achieved. These experimental findings will enable one to develop compact neutron generators based on the D-D or D-T fusion reactions. In this new neutron generator, the ion source, the accelerator and the target are all housed in a sealed metal container without external pumping. Recent moderator design simulation studies have shown that 14 MeV neutrons could be moderated to therapeutically useful energy ranges for boron neutron capture therapy (BNCT). The dose near the center of the brain with optimized moderators is about 65% higher than the dose obtained from a typical neutron spectrum produced by the Brookhaven Medical Research Reactor (BMRR), and is comparable to the dose obtained by other accelerator-based neutron sources. With a 120 keV and 1 A deuteron beam, a treatment time of {approx}35 minutes is estimated for BNCT.

  14. Accreting neutron stars by QFT

    NASA Astrophysics Data System (ADS)

    Chen, Shao-Guang

    layer with thickness of 1 km then q = 1 (N1S1), the gravity from N1S1 inside and exterior will be completely shielded. Because of net nuν _{0} flux is the medium to produce and transmit gravity, q obstructed by the shielding layer lie on the density of layer matter and the section of single nucleon to electronic neutrino obtained by nuclear physics experiments is about 1.1*10 ({-) 43} cm (2) . The mass inside N1S1 for exterior has not gravity interaction, it equivalent to has not inertia as the mass vanish. The neutron star is as a empty shell thereby may rapidly rotating and has not upper limit of mass and radii by the gravity accretion of N1S1, which will influence the mechanisms of pulsars, quasars and X-rays generated. At N1S1 interior the mass for exterior has not gravity which is just we searching dark matter. The mass each part will each other shielding and gravity decrease to less than the pressure of the degenerate neutron gas. The neutron star cannot collapse into a singular point with infinite density, i.e., the black hole with infinite gravity cannot be formed or the neutron star is jest the black hole in observational meaning. By the gravity accrete of N1S1 the neutron star may enlarge its shell radii but thickness keep. Only a shell gravity may be not less than any a observed value which to be deemed as black hole. The neutron star has powerful gravity certainly accompany with great surface negative charge and it may rapidly to rotate, so that there is a powerful magnetic field surround it. The accreting neutron star is as a slowly expand empty shell with fixed thickness of 1 km, its spin period depend on its radii or total accretion mass.

  15. Rapidly Progressive Dementia

    PubMed Central

    Geschwind, Michael D.; Shu, Huidy; Haman, Aissa; Sejvar, James J.; Miller, Bruce L.

    2009-01-01

    In contrast with more common dementing conditions that typically develop over years, rapidly progressive dementias can develop subacutely over months, weeks, or even days and be quickly fatal. Because many rapidly progressive dementias are treatable, it is paramount to evaluate and diagnose these patients quickly. This review summarizes recent advances in the understanding of the major categories of RPD and outlines efficient approaches to the diagnosis of the various neurodegenerative, toxic-metabolic, infectious, autoimmune, neoplastic, and other conditions that may progress rapidly. PMID:18668637

  16. A model for the condensation of the bacterial chromosome by the partitioning protein ParB

    NASA Astrophysics Data System (ADS)

    Broedersz, Chase; Wingreen, Ned

    2013-03-01

    The molecular machinery responsible for faithful segregation of the chromosome in bacteria such as Caulobacter crescentus and Bacillus subtilis includes the ParABS a.k.a. Spo0J/Soj partitioning system. In Caulobacter, prior to division, hundreds of ParB proteins bind to the DNA near the origin of replication, and localize to one pole of the cell. Subsequently, the ParB-DNA complex is translocated to the far pole by the binding and retraction of the ParA spindle-like apparatus. Remarkably, the localization of ParB proteins to specific regions of the chromosome appears to be controlled by only a few centromeric parS binding sites. Although lateral interactions between DNA-bound ParB are likely to be important for their localization, the long-range order of ParB domains on the chromosome appears to be inconsistent with a picture in which protein-protein interactions are limited to neighboring DNA-bound proteins. We developed a coarse-grained Brownian dynamics model that allows for lateral and 3D protein-protein interactions among bound ParB proteins. Our model shows how such interactions can condense and organize the DNA spatially, and can control the localization and the long-range order of the DNA-bound proteins.

  17. An ELISA method detecting the active form of suPAR.

    PubMed

    Zhou, Xiaolei; Xu, Mingming; Huang, Hailong; Mazar, Andrew; Iqbal, Zafar; Yuan, Cai; Huang, Mingdong

    2016-11-01

    Urokinase plasminogen activator receptor (uPAR) exists in a number of formats in human plasma, including soluble uPAR (suPAR) and uPAR fragments. We developed an ELISA method to detect specifically the active form suPAR, which binds to its natural ligand uPA. The intra CV and inter CV of this ELISA assay is 8.5% and 9.6% respectively, and the assay can recover 99.74% of added recombinant suPAR from 10% plasma. This assay is quite sensitive, capable of detecting down to 15pg/ml of suPAR, and can measure suPAR concentrations in the range of 0.031-8ng/ml with high linear relationship. Plasma samples from pregnant women were also measured for the active form of suPAR with this assay, giving an averaged level of 1.39ng/ml, slightly higher than the level of pooled plasma from healthy donors (0.96ng/ml). This study demonstrates the feasibility to measure the active form of suPAR, which will likely have value in clinical applications. PMID:27591605

  18. Serum suPAR in patients with FSGS: trash or treasure?

    PubMed

    Maas, Rutger J H; Deegens, Jeroen K J; Wetzels, Jack F M

    2013-07-01

    The urokinase-type plasminogen activator receptor (uPAR) has important functions in cell migration. uPAR can be shed from the cell membrane resulting in soluble uPAR (suPAR). Further cleavage gives rise to shorter fragments with largely unknown functions. Recent studies have demonstrated that both overexpression of uPAR on podocytes and the administration of suPAR cause proteinuria in mice. The common pathogenic mechanism involves the activation of podocyte β3-integrin. Increased activation of β3-integrin is also observed in patients with focal and segmental glomerulosclerosis (FSGS). These observations form the basis for the hypothesis that suPAR may be the circulating factor causing FSGS. A recent study fosters this idea by demonstrating increased suPAR levels in the serum of patients with FSGS and reporting an association with recurrence after transplantation and response to plasmapheresis. However, this study was heavily biased, and subsequent studies have given conflicting results. Although the experimental work is very suggestive, at present there is no proof that any known human suPAR fragment causes FSGS in humans. We therefore suggest that the measurement of suPAR using currently available assays has absolutely no value at the present time in decision-making in routine clinical practice.

  19. Design of multidirectional neutron beams for boron neutron capture synovectomy

    SciTech Connect

    Gierga, D.P.; Yanch, J.C.; Shefer, R.E.

    1997-12-01

    Boron neutron capture synovectomy (BNCS) is a potential application of the {sup 10}B(n, a) {sup 7}Li reaction for the treatment of rheumatoid arthritis. The target of therapy is the synovial membrane. Rheumatoid synovium is greatly inflamed and is the source of the discomfort and disability associated with the disease. The BNCS proposes to destroy the synovium by first injecting a boron-labeled compound into the joint space and then irradiating the joint with a neutron beam. This study discusses the design of a multidirectional neutron beam for BNCS.

  20. Neutron producing reactions in PuBe neutron sources

    NASA Astrophysics Data System (ADS)

    Bagi, János; Lakosi, László; Nguyen, Cong Tam

    2016-01-01

    There are a plenty of out-of-use plutonium-beryllium neutron sources in Eastern Europe presenting both nuclear safeguards and security issues. Typically, their actual Pu content is not known. In the last couple of years different non-destructive methods were developed for their characterization. For such methods detailed knowledge of the nuclear reactions taking place within the source is necessary. In this paper we investigate the role of the neutron producing reactions, their contribution to the neutron yield and their dependence on the properties of the source.

  1. Neutron density distribution and neutron skin thickness of Pb208

    NASA Astrophysics Data System (ADS)

    Meucci, Andrea; Vorabbi, Matteo; Giusti, Carlotta; Finelli, Paolo

    2014-08-01

    We present and discuss numerical predictions for the neutron density distribution of Pb208 using various nonrelativistic and relativistic mean-field models for the nuclear structure. Our results are compared with the very recent pion photoproduction data from Mainz. The parity-violating asymmetry parameter for elastic electron scattering at the kinematics of the PREX experiment at JLab and the neutron skin thickness are compared with the available data. We consider also the dependence between the neutron skin and the parameters of the expansion of the symmetry energy.

  2. Décontamination nucléaire par laser UV

    NASA Astrophysics Data System (ADS)

    Delaporte, Ph.; Gastaud, M.; Marine, W.; Sentis, M.; Uteza, O.; Thouvenot, P.; Alcaraz, J. L.; Le Samedy, J. M.; Blin, D.

    2003-06-01

    Le développement et l'utilisation de procédés propres pour le nettoyage ou la préparation de surfaces est l'une des priorités du milieu industriel. Cet intérêt est d'autant plus grand dans le domaine du nucléaire pour lequel la réduction des déchets est un axe de recherche important. Un dispositif de décontamination nucléaire par laser UV impulsionnel a été développé et testé. Il est composé. d'un laser à excimères de 1kW, d'un faisceau de fibres optiques et d'un dispositif de récupération des particules. Les essais réalisés en milieu actif ont démontré sa capacité à nettoyer des surfaces métalliques polluées par différents radioéléments avec des facteurs de décontamination généralement supérieurs à 10. Ce dispositif permet de décontaminer de grandes surfaces de géométrie simple en réduisant fortement la génération de déchets secondaires. Il est, à ce jour et dans ces conditions d'utilisations, le procédé de décontamination par voie sèche le plus efficace.

  3. RAPID and DDS

    NASA Technical Reports Server (NTRS)

    Utz, Hans Heinrich

    2011-01-01

    This talk gives an overview of the the Robot Applications Programmers Interface Delegate (RAPID) as well as the distributed systems middleware Data Distribution Service (DDS). DDS is an open software standard, RAPID is cleared for open-source release under NOSA. RAPID specifies data-structures and semantics for high-level telemetry published by NASA robotic software. These data-structures are supported by multiple robotic platforms at Johnson Space Center (JSC), Jet Propulsion Laboratory (JPL) and Ames Research Center (ARC), providing high-level interoperability between those platforms. DDS is used as the middleware for data transfer. The feature set of the middleware heavily influences the design decision made in the RAPID specification. So it is appropriate to discuss both in this introductory talk.

  4. Inflammation and Macular Oedema after Pars Plana Vitrectomy

    PubMed Central

    Romano, Vito; Angi, Martina; del Grosso, Renata; Romano, Davide; Vinciguerra, Paolo; Romano, Mario R.

    2013-01-01

    Cystoid macular oedema (CMO) is a major cause of reduced vision following intraocular surgery. Although the aetiology of CMO is not completely clarified, intraocular inflammation is known to play a major role in its development. The macula may develop cytotoxic oedema when the primary lesion and fluid accumulation occur in the parenchymatous cells (intracellular oedema) or vasogenic oedema when the primary defect occurs in the blood-retinal barrier and leads to extracellular fluid accumulation (extracellular oedema). We report on the mechanisms of CMO formation after pars plana vitrectomy and associated surgical procedures and discuss possible therapeutic approaches. PMID:24288446

  5. David Kasner, MD, and the Road to Pars Plana Vitrectomy.

    PubMed

    Blodi, Christopher F

    2016-01-01

    David Kasner, MD (1927-2001), used his extensive dissections of eye bank eyes and experiences in teaching cataract surgery to resident physicians to realize that excision of vitreous when present in the anterior chamber of eyes undergoing cataract surgery was preferable to prior intraoperative procedures. Noting that eyes tolerated his maneuvers, he then performed planned subtotal open-sky vitrectomies; first on a traumatized eye in 1961, then on two eyes of patients with amyloidosis (1966-1967). The success of these operations was noted by others, most particularly Robert Machemer, MD. Kasner's work directly led to further surgical developments, including closed pars plana vitrectomy. PMID:27660504

  6. BOREAS TE-12 Incoming PAR Through the Forest Canopy Data

    NASA Technical Reports Server (NTRS)

    Hall, Forrest G. (Editor); Papagno, Andrea (Editor); Walter-Shea, Elizabeth A.; Mesarch, Mark A.

    2000-01-01

    The Boreal Ecosystem-Atmospheric Study (BOREAS) TE-12 (Terrestrial Ecology) team collected photosynthetically active radiation (PAR) data sets in support of its efforts to characterize and interpret information on shoot geometry, leaf optical properties, leaf water potential, and leaf gas exchange. The data were collected at the Southern Study Area-Old Black Spruce (SSA-OBS) site from 04-Jul-1996 to 25-Jul-1996. The data are stored in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

  7. David Kasner, MD, and the Road to Pars Plana Vitrectomy

    PubMed Central

    Blodi, Christopher F.

    2016-01-01

    David Kasner, MD (1927–2001), used his extensive dissections of eye bank eyes and experiences in teaching cataract surgery to resident physicians to realize that excision of vitreous when present in the anterior chamber of eyes undergoing cataract surgery was preferable to prior intraoperative procedures. Noting that eyes tolerated his maneuvers, he then performed planned subtotal open-sky vitrectomies; first on a traumatized eye in 1961, then on two eyes of patients with amyloidosis (1966–1967). The success of these operations was noted by others, most particularly Robert Machemer, MD. Kasner’s work directly led to further surgical developments, including closed pars plana vitrectomy. PMID:27660504

  8. David Kasner, MD, and the Road to Pars Plana Vitrectomy

    PubMed Central

    Blodi, Christopher F.

    2016-01-01

    David Kasner, MD (1927–2001), used his extensive dissections of eye bank eyes and experiences in teaching cataract surgery to resident physicians to realize that excision of vitreous when present in the anterior chamber of eyes undergoing cataract surgery was preferable to prior intraoperative procedures. Noting that eyes tolerated his maneuvers, he then performed planned subtotal open-sky vitrectomies; first on a traumatized eye in 1961, then on two eyes of patients with amyloidosis (1966–1967). The success of these operations was noted by others, most particularly Robert Machemer, MD. Kasner’s work directly led to further surgical developments, including closed pars plana vitrectomy.

  9. Least-Squares Neutron Spectral Adjustment with STAYSL PNNL

    NASA Astrophysics Data System (ADS)

    Greenwood, L. R.; Johnson, C. D.

    2016-02-01

    The STAYSL PNNL computer code, a descendant of the STAY'SL code [1], performs neutron spectral adjustment of a starting neutron spectrum, applying a least squares method to determine adjustments based on saturated activation rates, neutron cross sections from evaluated nuclear data libraries, and all associated covariances. STAYSL PNNL is provided as part of a comprehensive suite of programs [2], where additional tools in the suite are used for assembling a set of nuclear data libraries and determining all required corrections to the measured data to determine saturated activation rates. Neutron cross section and covariance data are taken from the International Reactor Dosimetry File (IRDF-2002) [3], which was sponsored by the International Atomic Energy Agency (IAEA), though work is planned to update to data from the IAEA's International Reactor Dosimetry and Fusion File (IRDFF) [4]. The nuclear data and associated covariances are extracted from IRDF-2002 using the third-party NJOY99 computer code [5]. The NJpp translation code converts the extracted data into a library data array format suitable for use as input to STAYSL PNNL. The software suite also includes three utilities to calculate corrections to measured activation rates. Neutron self-shielding corrections are calculated as a function of neutron energy with the SHIELD code and are applied to the group cross sections prior to spectral adjustment, thus making the corrections independent of the neutron spectrum. The SigPhi Calculator is a Microsoft Excel spreadsheet used for calculating saturated activation rates from raw gamma activities by applying corrections for gamma self-absorption, neutron burn-up, and the irradiation history. Gamma self-absorption and neutron burn-up corrections are calculated (iteratively in the case of the burn-up) within the SigPhi Calculator spreadsheet. The irradiation history corrections are calculated using the BCF computer code and are inserted into the SigPhi Calculator

  10. Iodine neutron capture therapy

    NASA Astrophysics Data System (ADS)

    Ahmed, Kazi Fariduddin

    A new technique, Iodine Neutron Capture Therapy (INCT) is proposed to treat hyperthyroidism in people. Present thyroid therapies, surgical removal and 131I treatment, result in hypothyroidism and, for 131I, involve protracted treatment times and excessive whole-body radiation doses. The new technique involves using a low energy neutron beam to convert a fraction of the natural iodine stored in the thyroid to radioactive 128I, which has a 24-minute half-life and decays by emitting 2.12-MeV beta particles. The beta particles are absorbed in and damage some thyroid tissue cells and consequently reduce the production and release of thyroid hormones to the blood stream. Treatment times and whole-body radiation doses are thus reduced substantially. This dissertation addresses the first of the several steps needed to obtain medical profession acceptance and regulatory approval to implement this therapy. As with other such programs, initial feasibility is established by performing experiments on suitable small mammals. Laboratory rats were used and their thyroids were exposed to the beta particles coming from small encapsulated amounts of 128I. Masses of 89.0 mg reagent-grade elemental iodine crystals have been activated in the ISU AGN-201 reactor to provide 0.033 mBq of 128I. This activity delivers 0.2 Gy to the thyroid gland of 300-g male rats having fresh thyroid tissue masses of ˜20 mg. Larger iodine masses are used to provide greater doses. The activated iodine is encapsulated to form a thin (0.16 cm 2/mg) patch that is then applied directly to the surgically exposed thyroid of an anesthetized rat. Direct neutron irradiation of a rat's thyroid was not possible due to its small size. Direct in-vivo exposure of the thyroid of the rat to the emitted radiation from 128I is allowed to continue for 2.5 hours (6 half-lives). Pre- and post-exposure blood samples are taken to quantify thyroid hormone levels. The serum T4 concentration is measured by radioimmunoassay at

  11. THERMAL NEUTRON INTENSITIES IN SOILS IRRADIATED BY FAST NEUTRONS FROM POINT SOURCES. (R825549C054)

    EPA Science Inventory

    Thermal-neutron fluences in soil are reported for selected fast-neutron sources, selected soil types, and selected irradiation geometries. Sources include 14 MeV neutrons from accelerators, neutrons from spontaneously fissioning 252Cf, and neutrons produced from alp...

  12. Neutron capture therapy with deep tissue penetration using capillary neutron focusing

    DOEpatents

    Peurrung, Anthony J.

    1997-01-01

    An improved method for delivering thermal neutrons to a subsurface cancer or tumor which has been first doped with a dopant having a high cross section for neutron capture. The improvement is the use of a guide tube in cooperation with a capillary neutron focusing apparatus, or neutron focusing lens, for directing neutrons to the tumor, and thereby avoiding damage to surrounding tissue.

  13. Controlling neutron orbital angular momentum.

    PubMed

    Clark, Charles W; Barankov, Roman; Huber, Michael G; Arif, Muhammad; Cory, David G; Pushin, Dmitry A

    2015-09-24

    The quantized orbital angular momentum (OAM) of photons offers an additional degree of freedom and topological protection from noise. Photonic OAM states have therefore been exploited in various applications ranging from studies of quantum entanglement and quantum information science to imaging. The OAM states of electron beams have been shown to be similarly useful, for example in rotating nanoparticles and determining the chirality of crystals. However, although neutrons--as massive, penetrating and neutral particles--are important in materials characterization, quantum information and studies of the foundations of quantum mechanics, OAM control of neutrons has yet to be achieved. Here, we demonstrate OAM control of neutrons using macroscopic spiral phase plates that apply a 'twist' to an input neutron beam. The twisted neutron beams are analysed with neutron interferometry. Our techniques, applied to spatially incoherent beams, demonstrate both the addition of quantum angular momenta along the direction of propagation, effected by multiple spiral phase plates, and the conservation of topological charge with respect to uniform phase fluctuations. Neutron-based studies of quantum information science, the foundations of quantum mechanics, and scattering and imaging of magnetic, superconducting and chiral materials have until now been limited to three degrees of freedom: spin, path and energy. The optimization of OAM control, leading to well defined values of OAM, would provide an additional quantized degree of freedom for such studies.

  14. Neutron capture reactions at DANCE

    NASA Astrophysics Data System (ADS)

    Bredeweg, T. A.

    2008-05-01

    The Detector for Advanced Neutron Capture Experiments (DANCE) is a 4π BaF2 array consisting of 160 active detector elements. The primary purpose of the array is to perform neutron capture cross section measurements on small (>~100 μg) and/or radioactive (<~100 mCi) species. The measurements made possible with this array will be useful in answering outstanding questions in the areas of national security, threat reduction, nuclear astrophysics, advanced reactor design and accelerator transmutation of waste. Since the commissioning of DANCE we have performed neutron capture cross section measurements on a wide array of medium to heavy mass nuclides. Measurements to date include neutron capture cross sections on 241,243Am, neutron capture and neutron-induced fission cross sections and capture-to-fission ratio (α = σγ/σf) for 235U using a new fission-tagging detector as well as neutron capture cross sections for several astrophysics branch-point nuclei. Results from several of these measurements will be presented along with a discussion of additional physics information that can be extracted from the DANCE data.

  15. Fission-fusion neutron source

    NASA Astrophysics Data System (ADS)

    Yu, Jinnan; Yu, Gang

    2009-04-01

    In order to meet the requirements of fusion power reactors and nuclear waste treatment, a concept of fission-fusion neutron source is proposed, which consists of a LiD assembly located in the heavy water region of the China Advanced Research Reactor. This assembly of LiD fuel rods will be irradiated with slow neutrons and will produce fusion neutrons in the central hole via the reaction 6Li(n, α). More precisely, tritium ions with a high energy of 2.739 MeV will be produced in LiD by the impinging slow neutrons. The tritium ions will in turn bombard the deuterium ions present in the LiD assembly, which will induce fusion reaction and then the production of 14 MeV neutrons. The fusion reaction rate will increase with the accumulation of tritium in LiD by the reaction between tritium and deuteron recoils produced by the 14 MeV neutrons. When the concentration of tritium reaches 0.5 · 10 22 and the fraction of fusion reactions between tritium and deuteron recoils approaches 1, the 14 MeV neutron flux is doubled and redoubled, an so forth, approaching saturation in which the tritium produced at a time t is exhausted by the fusion reactions to keep constant the tritium concentration in LiD.

  16. Gravitational Waves from Neutron Stars

    NASA Astrophysics Data System (ADS)

    Kokkotas, Konstantinos

    2016-03-01

    Neutron stars are the densest objects in the present Universe, attaining physical conditions of matter that cannot be replicated on Earth. These unique and irreproducible laboratories allow us to study physics in some of its most extreme regimes. More importantly, however, neutron stars allow us to formulate a number of fundamental questions that explore, in an intricate manner, the boundaries of our understanding of physics and of the Universe. The multifaceted nature of neutron stars involves a delicate interplay among astrophysics, gravitational physics, and nuclear physics. The research in the physics and astrophysics of neutron stars is expected to flourish and thrive in the next decade. The imminent direct detection of gravitational waves will turn gravitational physics into an observational science, and will provide us with a unique opportunity to make major breakthroughs in gravitational physics, in particle and high-energy astrophysics. These waves, which represent a basic prediction of Einstein's theory of general relativity but have yet to be detected directly, are produced in copious amounts, for instance, by tight binary neutron star and black hole systems, supernovae explosions, non-axisymmetric or unstable spinning neutron stars. The focus of the talk will be on the neutron star instabilities induced by rotation and the magnetic field. The conditions for the onset of these instabilities and their efficiency in gravitational waves will be presented. Finally, the dependence of the results and their impact on astrophysics and especially nuclear physics will be discussed.

  17. Neutron capture reactions at DANCE

    SciTech Connect

    Bredeweg, T. A.

    2008-05-12

    The Detector for Advanced Neutron Capture Experiments (DANCE) is a 4{pi} BaF{sub 2} array consisting of 160 active detector elements. The primary purpose of the array is to perform neutron capture cross section measurements on small (> or approx.100 {mu}g) and/or radioactive (< or approx. 100 mCi) species. The measurements made possible with this array will be useful in answering outstanding questions in the areas of national security, threat reduction, nuclear astrophysics, advanced reactor design and accelerator transmutation of waste. Since the commissioning of DANCE we have performed neutron capture cross section measurements on a wide array of medium to heavy mass nuclides. Measurements to date include neutron capture cross sections on {sup 241,243}Am, neutron capture and neutron-induced fission cross sections and capture-to-fission ratio ({alpha} = {sigma}{sub {gamma}}/{sigma}{sub f}) for {sup 235}U using a new fission-tagging detector as well as neutron capture cross sections for several astrophysics branch-point nuclei. Results from several of these measurements will be presented along with a discussion of additional physics information that can be extracted from the DANCE data.

  18. Neutron detector and fabrication method thereof

    DOEpatents

    Bhandari, Harish B.; Nagarkar, Vivek V.; Ovechkina, Olena E.

    2016-08-16

    A neutron detector and a method for fabricating a neutron detector. The neutron detector includes a photodetector, and a solid-state scintillator operatively coupled to the photodetector. In one aspect, the method for fabricating a neutron detector includes providing a photodetector, and depositing a solid-state scintillator on the photodetector to form a detector structure.

  19. Boron nitride solid state neutron detector

    DOEpatents

    Doty, F. Patrick

    2004-04-27

    The present invention describes an apparatus useful for detecting neutrons, and particularly for detecting thermal neutrons, while remaining insensitive to gamma radiation. Neutrons are detected by direct measurement of current pulses produced by an interaction of the neutrons with hexagonal pyrolytic boron nitride.

  20. Shear modulus of neutron star crust

    NASA Astrophysics Data System (ADS)

    Baiko, D. A.

    2011-09-01

    The shear modulus of solid neutron star crust is calculated by the thermodynamic perturbation theory, taking into account ion motion. At a given density, the crust is modelled as a body-centred cubic Coulomb crystal of fully ionized atomic nuclei of one type with a uniform charge-compensating electron background. Classic and quantum regimes of ion motion are considered. The calculations in the classic temperature range agree well with previous Monte Carlo simulations. At these temperatures, the shear modulus is given by the sum of a positive contribution due to the static lattice and a negative ∝ T contribution due to the ion motion. The quantum calculations are performed for the first time. The main result is that at low temperatures the contribution to the shear modulus due to the ion motion saturates at a constant value, associated with zero-point ion vibrations. Such behaviour is qualitatively similar to the zero-point ion motion contribution to the crystal energy. The quantum effects may be important for lighter elements at higher densities, where the ion plasma temperature is not entirely negligible compared to the typical Coulomb ion interaction energy. The results of numerical calculations are approximated by convenient fitting formulae. They should be used for precise neutron star oscillation modelling, a rapidly developing branch of stellar seismology.