WorldWideScience

Sample records for surface neutron probe

  1. Neutrons as a probe

    International Nuclear Information System (INIS)

    Iizumi, Masashi

    1993-01-01

    As an introduction to the symposium a brief overview will be given about the features of neutrons as a probe. First it will be pointed out that the utilization of neutrons as a probe for investigating the structural and dynamical properties of condensed matters is a benign gift eventuated from the release of atomic energy initiated by Enrico Fermi exactly half century ago. Features of neutrons as a probe are discussed in accordance with the four basic physical properties of neutrons as an elementary particle; (1) no electric charge (the interaction with matter is nuclear), (2) the mass of neutron is 1 amu, (3) spin is 1/2 and (4) neutrons have magnetic dipole moment. Overview will be given on the uniqueness of neutrons as a probe and on the variety in the way they are used in the wide research area from the pure science to the industrial applications. (author)

  2. Development of Neutron Probes for Characterization of Hazardous Materials in the Sub-surface Medium

    International Nuclear Information System (INIS)

    Keegan, R.P.; McGrath, C.A.; Lopez, J.C.

    2002-01-01

    Neutron probes are being developed at the Idaho National Engineering and Environmental Laboratory (INEEL) for the detection, identification and quantification of hazardous materials in the ground. Such materials include plutonium, uranium, americium, chlorine and fluorine. Both a Neutron Gamma (NG) probe and a Prompt Fission Neutron (PFN) probe are being developed. The NG probe is used primarily for nuclide identification and quantification measurements. The PFN is used mostly for the detection and measurement of fissile material, but also for the determination of thermal neutron macroscopic absorption cross sections of the various elements comprising the ground matrix. Calibration of these probes will be carried out at the INEEL using an indoor facility that has been designed for this activity

  3. Surface and Downhole Prospecting Tools for Planetary Exploration: Tests of Neutron and Gamma Ray Probes - Research Paper

    Energy Technology Data Exchange (ETDEWEB)

    R. C. Elphic; P. Chu; S. Hahn; M. R. James; D. J. Lawrence; T. H. Prettyman; J. B. Johnson; R. K. Podgorney

    2008-06-01

    The ability to locate and characterize icy deposits and other hydrogenous materials on the Moon and Mars will help us understand the distribution of water and, therefore, possible habitats at Mars, and may help us locate primitive prebiotic compounds at the Moon’s poles. We have developed a rover-borne neutron probe that localizes a near-surface icy deposit and provides information about its burial depth and abundance. We have also developed a borehole neutron probe to determine the stratigraphy of hydrogenous subsurface layers while operating within a drill string segment. In our field tests, we have used a neutron source to “illuminate” surrounding materials and gauge the instruments’ efficacy, and we can simulate accurately the observed instrument responses using a Monte Carlo nuclear transport code (MCNPX). An active neutron source would not be needed for lunar or martian near-surface exploration: cosmic-ray interactions provide sufficient neutron flux to depths of several meters and yield better depth and abundance sensitivity than an active source. However, for deep drilling (>10 m depth), a source is required. We also present initial tests of a borehole gamma ray lithodensity tool and demonstrate its utility in determining soil or rock densities and composition.

  4. Dynamics of phenanthrenequinone on carbon nano-onion surfaces probed by quasielastic neutron scattering.

    Science.gov (United States)

    Chathoth, Suresh M; Anjos, Daniela M; Mamontov, Eugene; Brown, Gilbert M; Overbury, Steven H

    2012-06-21

    We used quasielastic neutron scattering (QENS) to study the dynamics of phenanthrenequinone (PQ) on the surface of onion-like carbon (OLC), or so-called carbon onions, as a function of surface coverage and temperature. For both the high- and low-coverage samples, we observed two diffusion processes; a faster process and nearly an order of magnitude slower process. On the high-coverage surface, the slow diffusion process is of long-range translational character, whereas the fast diffusion process is spatially localized on the length scale of ∼4.7 Å. On the low-coverage surface, both diffusion processes are spatially localized; on the same length scale of ∼4.7 Å for the fast diffusion and a somewhat larger length scale for the slow diffusion. Arrhenius temperature dependence is observed except for the long-range diffusion on the high-coverage surface. We attribute the fast diffusion process to the generic localized in-cage dynamics of PQ molecules, and the slow diffusion process to the long-range translational dynamics of PQ molecules, which, depending on the coverage, may be either spatially restricted or long-range. On the low-coverage surface, uniform surface coverage is not attained, and the PQ molecules experience the effect of spatial constraints on their long-range translational dynamics. Unexpectedly, the dynamics of PQ molecules on OLC as a function of temperature and surface coverage bears qualitative resemblance to the dynamics of water molecules on oxide surfaces, including practically temperature-independent residence times for the low-coverage surface. The dynamics features that we observed may be universal across different classes of surface adsorbates.

  5. Dynamics of Phenanthrenequinone on Carbon Nano-Onion Surfaces Probed by Quasielastic Neutron Scattering

    International Nuclear Information System (INIS)

    Mamontov, Eugene; Brown, Gilbert M.; Overbury, Steven H.; Mavila Chathoth, Suresh

    2012-01-01

    We used quasielastic neutron scattering (QENS) to study the dynamics of phenanthrenequinone (PQ) on the surface of onion-like carbon (OLC), or so called carbon onions, as a function of surface coverage and temperature. For both the high- and low-coverage samples, we observed two diffusion processes; a faster process and nearly an order of magnitude slower process. On the high-coverage surface, the slow diffusion process is of long-range translational character, whereas the fast diffusion process is spatially localized on the length scale of ∼ 4.7. On the low-coverage surface, both diffusion processes are spatially localized; on the same length scale of ∼ 4.7 for the fast diffusion and a somewhat larger length scale for the slow diffusion. Arrhenius temperature dependence is observed except for the long-range diffusion on the high-coverage surface. We attribute the fast diffusion process to the generic localized in-cage dynamics of PQ molecules, and the slow diffusion process to the long-range translational dynamics of PQ molecules, which, depending on the coverage, may be either spatially restricted, or long-range. On the low-coverage surface, uniform surface coverage is not attained, and the PQ molecules experience the effect of spatial constraints on their long-range translational dynamics. Unexpectedly, the dynamics of PQ molecules on OLC as a function of temperature and surface coverage bears qualitative resemblance to the dynamics of water molecules on oxide surfaces, including practically temperature-independent residence times for the low-coverage surface. The dynamics features that we observed may be universal across different classes of surface adsorbates.

  6. Neutrons for probing matter

    International Nuclear Information System (INIS)

    Torres, F. Ed.; Mazzucchetti, D.

    2008-01-01

    The authors tell the story of the French Orphee reactor located in Saclay from the decision to build it in the seventies, to its commissioning in 1980, to its upgrading in the nineties and to its today's operating life. As early as its feasibility studies Orphee has been designed as a dual-purpose reactor: scientific research for instance in crystallography and magnetism, and industrial uses like neutron radiography, silicon doping or radionuclide production. This book is divided into 4 parts: 1) the neutron: an explorer of the matter, 2) the Orphee reactor: a neutron source, 3) the adventurers of the matter: Leon Brillouin laboratory's staff, and 4) the perspectives for neutrons

  7. Quality of the neutron probe calibration curve

    International Nuclear Information System (INIS)

    Libardi, Paulo Leonel; Moraes, Sergio Oliveira

    1997-01-01

    An experiment of neutron probe calibration has been performed, involving various volume size samples and collected at various distances from the access tubes. The experiment aimed to give some answers to questions such as suitable sample physical volume, always use of the same volume and sample distance from the neutron probe access tube

  8. Probing neutron star physics using accreting neutron stars

    NARCIS (Netherlands)

    Patruno, A.

    2010-01-01

    We give an obervational overview of the accreting neutron stars systems as probes of neutron star physics. In particular we focus on the results obtained from the periodic timing of accreting millisecond X-ray pulsars in outburst and from the measurement of X-ray spectra of accreting neutron stars

  9. Probing fine magnetic particles with neutron scattering

    International Nuclear Information System (INIS)

    Pynn, R.

    1991-01-01

    Because thermal neutrons are scattered both by nuclei and by unpaired electrons, they provide an ideal probe for studying the atomic and magnetic structures of fine-grained magnetic materials, including nanocrystalline solids, thin epitaxial layers, and colloidal suspensions of magnetic particles, known as ferrofluids. Diffraction, surface reflection, and small angle neutron scattering (SANS) are the techniques used. With the exception of surface reflection, these methods are described in this article. The combination of SANS with refractive-index matching and neutron polarisation analysis is particularly powerful because it allows the magnetic and atomic structures to be determined independently. This technique has been used to study both dilute and concentrated ferrofluid suspensions of relatively monodisperse cobalt particles, subjected to a series of applied magnetic fields. The size of the cobalt particle core and the surrounding surfactant layer were determined. The measured interparticle structure factor agrees well with a recent theory that allows correlations in binary mixtures of magnetic particles to be calculated in the case of complete magnetic alignment. When one of the species in such a binary mixture is a nonmagnetic, cyclindrical macromolecule, application of a magnetic field leads to some degree of alignment of the nonmagnetic species. This result has been demonstrated with tobacco mosaic virus suspended in a water-based ferrofluid

  10. Neutron-based portable drug probe

    International Nuclear Information System (INIS)

    Womble, P. C.; Vourvopoulos, G.; Ball Howard, J.; Paschal, J.

    1999-01-01

    Based on previous measurements, a probe prototype for contraband detection utilizing the neutron technique of Pulsed Fast-Thermal Neutron Analysis (PFTNA) is being constructed. The prototype weighs less than 45 kg and is composed of a probe (5 cm diameter), a power pack and a data acquisition and display system. The probe is designed to be inserted in confined spaces such as the boiler of a ship or a tanker truck filled with liquid. The probe provides information on a) the elemental content, and b) the density variations of the interrogated object. By measuring elemental content, the probe can differentiate between innocuous materials and drugs. Density variations can be found through fast neutron transmission. In all cases, hidden drugs are identified through the measurement of the elemental content of the object, and the comparison of expected and measured elemental ratios

  11. Project and construction of counting system for neutron probe

    International Nuclear Information System (INIS)

    Monteiro, W.P.

    1985-01-01

    A counting system was developed for coupling neutron probe aiming to register pulses produced by slow neutron interaction in the detector. The neutron probe consists of fast neutron source, thermal neutron detector, amplifier circuit and pulse counting circuit. The counting system is composed by counting circuit, timer and signal circuit. (M.C.K.)

  12. Neutronic density perturbation by probes

    International Nuclear Information System (INIS)

    Vigon, M. A.; Diez, L.

    1956-01-01

    The introduction of absorbent materials of neutrons in diffuser media, produces local disturbances of neutronic density. The disturbance depends especially on the nature and size of the absorbent. Approximated equations which relates te disturbance and the distance to the absorbent in the case of thin disks have been drawn. The experimental comprobation has been carried out in two especial cases. In both cases the experimental results are in agreement with the calculated values from these equations. (Author)

  13. Neutron probe measurement of soil water content close to soil surface Medida de umidade do solo com sonda de nêutrons nas proximidades da superfície

    Directory of Open Access Journals (Sweden)

    M.C. Falleiros

    1993-12-01

    Full Text Available The problem of neutron probe soil water content measurements close to soil surface is analysed from the spatial variability and also from the slow neutron "loss" to the atmosphere points of view. Results obtained on a dark red latosol of the county of Piracicaba,SP, indicate the possibility of precisely measuring the neutron "sphere of influence" when different media are used on soil surface.O problema da medida da umidade nas proximidades da superfície do solo é abordado do ponto de vista de sua variabitidade espacial e da "perda" de nêutrons lentos para a atmosfera. Dados, obtidos em terra roxa estruturada do município de Piracicaba,SP, mostram a possibilidade de se avaliar, com precisão, a "esfera de influência" da medida, quando se utilizam meios diferentes na superfície do solo.

  14. Radioactive Probes on Ferromagnetic Surfaces

    CERN Multimedia

    2002-01-01

    On the (broad) basis of our studies of nonmagnetic radioactive probe atoms on magnetic surfaces and at interfaces, we propose to investigate the magnetic interaction of magnetic probe atoms with their immediate environment, in particular of rare earth (RE) elements positioned on and in ferromagnetic surfaces. The preparation and analysis of the structural properties of such samples will be performed in the UHV chamber HYDRA at the HMI/Berlin. For the investigations of the magnetic properties of RE atoms on surfaces Perturbed Angular Correlation (PAC) measurements and Mössbauer Spectroscopy (MS) in the UHV chamber ASPIC (Apparatus for Surface Physics and Interfaces at CERN) are proposed.

  15. Neutron moisture probes : the minimum error attainable

    International Nuclear Information System (INIS)

    Wilson, D.J.

    1987-04-01

    The effect of the soil parameters dry density, mass absorption and mass scattering coefficients on the neutron flux at the detector of a neutron moisture probe has been described previously by a set of polynomial equations. The partial derivatives of these equations have been used to determine the deviation introduced into water density calculation by a one per cent inaccuracy in each of the parameters. Accuracy of measurement of the soil parameters is discussed and applied to a typical soil at various water densities. The accuracy to which soil parameters can be measured is examined and found to be approximately ± 2% for the dry soil density, ± 1% for the mass absorption coefficient and ± 2% for the mass scattering coefficient. Using these data, together with a statistical accuracy of ± 1% in the probe count rate, the minimum error achievable for the water density varies between ± 3.5% at a water density of 0.06 g cm -3 and ± 1.55% at a water density of 0.41 g cm -3

  16. Magnetism and magnetic materials probed with neutron scattering

    Energy Technology Data Exchange (ETDEWEB)

    Velthuis, S.G.E. te, E-mail: tevelthuis@anl.gov [Materials Science Division, Argonne National Laboratory, 9700 S Cass Ave, Argonne, IL 60439 (United States); Pappas, C. [Faculty of Applied Sciences, Delft University of Technology, Mekelweg 15, NL-2629JB Delft (Netherlands)

    2014-01-15

    Neutron scattering techniques are becoming increasingly accessible to a broader range of scientific communities, in part due to the onset of next-generation, high-power spallation sources, high-performance, sophisticated instruments and data analysis tools. These technical advances also advantageously impact research into magnetism and magnetic materials, where neutrons play a major role. In this Current Perspective series, the achievements and future prospects of elastic and inelastic neutron scattering, polarized neutron reflectometry, small angle neutron scattering, and neutron imaging, are highlighted as they apply to research into magnetic frustration, superconductivity and magnetism at the nanoscale. - Highlights: • Introduction to Current Perspective series titled Magnetism and Magnetic Materials probed with Neutron Scattering. • Elastic and inelastic neutron scattering in systems with magnetic frustration and superconductivity. • Small angle neutron scattering and polarized neutron reflectometry in studying magnetism at the nanoscale. • Imaging of magnetic fields and domains.

  17. Magnetism and magnetic materials probed with neutron scattering

    International Nuclear Information System (INIS)

    Velthuis, S.G.E. te; Pappas, C.

    2014-01-01

    Neutron scattering techniques are becoming increasingly accessible to a broader range of scientific communities, in part due to the onset of next-generation, high-power spallation sources, high-performance, sophisticated instruments and data analysis tools. These technical advances also advantageously impact research into magnetism and magnetic materials, where neutrons play a major role. In this Current Perspective series, the achievements and future prospects of elastic and inelastic neutron scattering, polarized neutron reflectometry, small angle neutron scattering, and neutron imaging, are highlighted as they apply to research into magnetic frustration, superconductivity and magnetism at the nanoscale. - Highlights: • Introduction to Current Perspective series titled Magnetism and Magnetic Materials probed with Neutron Scattering. • Elastic and inelastic neutron scattering in systems with magnetic frustration and superconductivity. • Small angle neutron scattering and polarized neutron reflectometry in studying magnetism at the nanoscale. • Imaging of magnetic fields and domains

  18. Planetary Geochemistry Techniques: Probing In-Situ with Neutron and Gamma Rays (PING) Instrument

    Science.gov (United States)

    Parsons, A.; Bodnarik, J.; Burger, D.; Evans, L.; Floyd, S.; Lin, L.; McClanahan, T.; Nankung, M.; Nowicki, S.; Schweitzer, J.; hide

    2011-01-01

    The Probing In situ with Neutrons and Gamma rays (PING) instrument is a promising planetary science application of the active neutron-gamma ray technology so successfully used in oil field well logging and mineral exploration on Earth. The objective of our technology development program at NASA Goddard Space Flight Center's (NASA/GSFC) Astrochemistry Laboratory is to extend the application of neutron interrogation techniques to landed in situ planetary composition measurements by using a 14 MeV Pulsed Neutron Generator (PNG) combined with neutron and gamma ray detectors, to probe the surface and subsurface of planetary bodies without the need to drill. We are thus working to bring the PING instrument to the point where it can be flown on a variety of surface lander or rover missions to the Moon, Mars, Venus, asteroids, comets and the satellites of the outer planets.

  19. Influence of access hole parameters on neutron moisture probe readings

    International Nuclear Information System (INIS)

    Abeele, W.V.

    1979-10-01

    Computing soil moisture content with a neutron probe requires use of a calibration curve that considers the thermal neutron capture cross section of the hole liner, as well as the hole diameter. The influence of steel, polyvinyl chloride, and aluminum casings that fit 0.051- to 0.102-m hole diameters was determined by comparison with neutron probe readings in uncased holes of corresponding diameters. Eccentricity of probe location was considered a potentially significant variable. The experiment was run in disturbed Bandelier tuff with an average dry density of 1.35g . cm -3 and moisture content of 3.8 to 26.7% by volume. The casing material and hole diameter influenced the probe readings significantly, whereas eccentric location of the probe did not. Regression analyses showed an almost perfect inverse linear correlation between hole diameter and count rate

  20. Influence of access hole parameters on neutron moisture probe readings

    International Nuclear Information System (INIS)

    Abeele, W.V.

    1978-04-01

    Computing soil moisture content with a neutron probe requires use of a calibration curve that considers the thermal neutron capture cross section of the hole liner as well as the hole diameter. The influence of steel, polyvinyl chloride, and aluminum casings that fit 0.051 to 0.102-hole diameters was determined by comparison with neutron probe readings in uncased holes of corresponding diameters. Eccentricity of probe location was considered a potentially significant variable. The relationship between hole diameter and count rate also was investigated. The experiment was run in disturbed Bandelier tuff with an average dry density of 1.2 g . cm -3 and moisture content of 1.3 to 35.5% by volume. The casing material and hole diameter influenced the probe readings significantly, whereas eccentric location of the probe did not. Regression analyses showed an almost perfect inverse linear correlation between hole diameter and count rate

  1. Dendrimer sensors probed with neutron reflectometry

    International Nuclear Information System (INIS)

    Cavaye, Hamish; Smith, Arthur R.G.; Burn, Paul L.; Lo, Shih-Chun; Meredith, Paul; Gentle, Ian R.; James, Michael; Nelson, Andrew

    2009-01-01

    Full text: Oxidative photoluminescence (PL) quenching utilizing conjugated polymers as the sensing has proved to be one of the best of many methods for sensing explosive analytes.[1] However are a number of issues that can make polymers difficult to work with, including complex morphologies reproducibility of syntheses, and the need to include elaborate structures to reduce the packing of the polymer chains. Dendrimers, consisting of a core, dendrons, and surface groups, address these issues by being monodisperse and modular in their design. Determining how analytes are sequestered into thin films is important for solid-state sensors. We show that thin (230 ± 30 A ) and thick (750 ± 50 A) films of a first-generation dendrimer comrised of 2-ethylhexyloxy surface groups, biphenyl-based dendrons, and a 9,9,9',9'-tetra-n-propyl-2,2'-bifluorene core, can rapidly and reversibly detect p-nitrotoll oxidative luminescence quenching. For both the thin and thick films the PL is quenched by just 4 s . Combined PL and neutron reflectometry measurements on pristine and analyte-satura showed that during the adsorption process the films swelled, being on average 4% thicker for thin and thick dendrimer films. At the same time the PL was completely quenched. On removal of the analyte the films returned to their original thickness and scattering length density, and the restored, showing that the sensing process was fully reversible.

  2. Probing thermonuclear burning on accreting neutron stars

    NARCIS (Netherlands)

    Keek, L.

    2008-01-01

    Neutron stars are the most compact stars that can be directly observed, which makes them ideal laboratories to study physics at extreme densities. Neutron stars in low-mass X-ray binaries accrete hydrogen and helium from a lower-mass companion star through Roche lobe overflow. This matter undergoes

  3. Alternative technique to neutron probe calibration in situ

    International Nuclear Information System (INIS)

    Encarnacao, F.; Carneiro, C.; Dall'Olio, A.

    1990-01-01

    An alternative technique of neutron probe calibration in situ was applied for Podzolic soil. Under field condition, the neutron probe calibration was performed using a special arrangement that prevented the lateral movement of water around the access tube of the neutron probe. During the experiments, successive amounts of water were uniformly infiltrated through the soil profile. Two plots were set to study the effect of the plot dimension on the slope of the calibration curve. The results obtained shown that the amounts of water transferred to the soil profile were significantly correlated to the integrals of count ratio along the soil profile on both plots. In consequence, the slope of calibration curve in field condition was determined. (author)

  4. Neutrons: The kinder, gentler probe of condensed matter

    International Nuclear Information System (INIS)

    Axe, J.D.

    1989-01-01

    Neutrons play an increasingly important role in the characterization of advanced modern materials. They provide information that complements rather than competes with that provided by other scattering probes. Although neutrons require heroic efforts to produce, the techniques for using them are not particularly difficult, and with the advent of sufficient user friendly facilities, are becoming a routine tool in the arsenal of expanding numbers of materials scientists. 10 refs., 5 figs

  5. The neutron probe and the detection of soil moisture

    International Nuclear Information System (INIS)

    Luft, G.; Morgenschweis, G.

    1981-01-01

    The authors present a brief outline of the direct and indirect field methods used at present in soil moisture measurement; particularly the advantages and disadvantages of neutron diffusion measurement are illustrated by means of various types of instruments available. The recently developed Wellingford Neutron Moisture Probe IH II, used for hydrological and pedohydrological fieldwork respectively, is presented and the first test results concerning the handling, measuring time, measured volume and layer thickness are discussed. (orig.) [de

  6. Prospects for neutron probed magnetic resonance imaging

    International Nuclear Information System (INIS)

    Granroth, Garrett E.

    2009-01-01

    The information gained from magnetic resonance imaging has provided useful insight into many insulators. Extending this technique to conductors requires an alternative means of spin manipulation besides electromagnetic radiation. A method to use neutron measurement of the Zeeman splitting to measure the relaxation time is described. The Zeeman splitting is observed by a neutron spectrometer as an incoherent signal with an energy transfer equal to the Zeeman energy. This energy scale is so small that fields in excess of 15 T are required to sufficiently separate this line from other incoherent processes. Once the Zeeman splitting is observed, a perturbation of the system is required to enable measurement of the nuclear spin relaxation time; the physical quantity measured in a Nuclear Magnetic Resonance experiment. The proposed perturbation is a pulsed field of 10 T. The relaxation of the Zeeman splitting back to the 15 T condition is then recorded as a function of time. The resultant data is the aforementioned measure of the relaxation time. With the ability to measure the relaxation times the image map can be created by rastering the sample with respect to the beam.

  7. Probing the pairing interaction through two-neutron transfer reactions

    Directory of Open Access Journals (Sweden)

    Margueron J.

    2012-12-01

    Full Text Available The treatment of the pairing interaction in mean-field-based models is addressed. In particular, the possibility to use pair transfers as A tool to better constrain this interaction is discussed. First, pairing inter-actions with various density dependencies (surface/volume mixing are used in the microscopic Hartree-Fock-Bogoliubov + quasiparticle random-phase approximation model to generate the form factors to be used in reaction calculations. Cross sections for (p,t two-neutron transfer reactions are calculated in the one-step zero-range distorted-wave Born approximation for some Tin isotopes and for incident proton energies from 15 to 35 MeV. Three different surface/volume mixings of A zero-range density-dependent pairing interaction are employed in the microscopic calculations and the sensitivity of the cross sections to the different mixings is analyzed. Differences among the three different theoretical predictions are found espacially for the nucleus 136Sn and they are more important at the incident proton energy of 15 MeV. We thus indicate (p,t two-neutron transfer reactions with very neutron-rich Sn isotopes and at proton energies around 15 MeV as good experimental cases where the surface/volume mixing of the pairing interaction may be probed. In the second part of the manuscript, ground-state to ground-state transitions are investigated. Approximations made to estimate two-nucleon transfer probabilities in ground-state to ground-state transitions and the physical interpretation of these probabilities are discussed. Probabilities are often calculated by approximating both ground states of the initial nucleus A and of the final nucleus A±2 by the same quasiparticle vacuum. We analyze two improvements of this approach. First, the effect of using two different ground states with average numbers of particles A and A±2 is quantified. Second, by using projection techniques, the role of particle number restoration is analyzed. Our analysis

  8. Surface charge measurement using an electrostatic probe

    DEFF Research Database (Denmark)

    Crichton, George C; McAllister, Iain Wilson

    1998-01-01

    During the 1960s, the first measurements of charge on dielectric surfaces using simple electrostatic probes were reported. However it is only within the last 10 years that a proper understanding of the probe response has been developed. This situation arose as a consequence of the earlier studies...

  9. Influence of density and chemical composition of soils in the neutrons probes answer

    International Nuclear Information System (INIS)

    Crispino, Marcos Luiz; Antonino, Antonio Celso Dantas; Dall'Olio, Attilio; Oliveira Lira, Carlos Alberto Brayner de; Carneiro, Clemente J. Gusmao

    1996-08-01

    The determination of soil humidity with neutron probes is based in the measure of the thermal neutron flux intensity and its behavior with the soil depend: soil's chemical composition; soils physical parameters; neutrons' energetic spectrum and neutron-source detector geometry.The objective of this paper is to apply the multigroup function theory to calculate a neutron probe calibration curve utilizing representatives parameters and coefficients of soils horizons in a experimental station in Zona da Mata, Pernambuco, Brazil

  10. Neutron scattering as a probe of small-particle dynamics in hydroxylated amorphous silica

    International Nuclear Information System (INIS)

    Richter, D.; Passell, L.

    1980-01-01

    Incoherent, inelastic scattering of neutrons by hydrogen in surface hydroxyl groups has been used to probe the dynamics of 60--70-A-diameter spheres of amorphous silica. The high-temperature spectra indicate a pronounced ''small-particle'' enhancement of low-frequency vibrational modes as predicted by theory. At low temperatures, the scattering changes in character and shows evidence of hindered rotational transitons

  11. Probing surface magnetism with ion beams

    International Nuclear Information System (INIS)

    Winter, H.

    2007-01-01

    Ion beams can be used to probe magnetic properties of surfaces by a variety of different methods. Important features of these methods are related to trajectories of atomic projectiles scattered from the surface of a solid target and to the electronic interaction mechanisms in the surface region. Both items provide under specific conditions a high sensitivity for the detection of magnetic properties in the region at the topmost layer of surface atoms. This holds in particular for scattering under planar surface channeling conditions, where under grazing impact atoms or ions are reflected specularly from the surface without penetration into the subsurface region. Two different types of methods are employed based on the detection of the spin polarization of emitted or captured electrons and on spin blocking effects for capture into atomic terms. These techniques allow one to probe the long range and short range magnetic order in the surface region

  12. Neutron and gamma probes: Their use in agronomy. Second edition

    International Nuclear Information System (INIS)

    2003-01-01

    Water is an essential requirement for life on the planet. It is often the single most limiting factor in crop and livestock production. Water is a scarce resource in many urban and rural environments worldwide. According to the FAO, the global demand for fresh water is doubling every 21 years. The quality of the finite water supplies is also under threat from industrial, agricultural and domestic sources of pollution. The majority of crops are grown under rain-fed conditions and adequate water supply is the main factor limiting crop production in semi-arid and sub-humid regions. On the other hand, currently 20% of the world's arable land is under irrigation providing 35 to 40% of all agricultural production. Irrigation mismanagement poses a serious threat to the environment through groundwater pollution and salinization. It is therefore, essential that water resources be used efficiently by regular monitoring of soil-water status in the unsaturated zone. The neutron depth probe, a nuclear-based technique, is utilized worldwide for this purpose. The neutron moisture gauge, since its introduction some 40 years ago, can now be considered a routine method in soil water studies. Many developments have since been introduced, in particular electronic components, which have significantly improved performance and expanded applications. Although the neutron scattering method is routinely utilised in many developed countries, its use is still limited in developing countries due to several factors. Neutron depth probes contain radioactive sources, which will present health and environmental hazards if a probe is improperly used, stored or disposed of. National and international legislation and regulations must be complied with. The strategic objective of the sub-program Soil and Water Management and Crop Nutrition of the Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture is to develop and promote the adoption of nuclear-based technologies for optimising soil

  13. Evaluation of Flat Surface Temperature Probes

    Science.gov (United States)

    Beges, G.; Rudman, M.; Drnovsek, J.

    2011-01-01

    The objective of this paper is elaboration of elements related to metrological analysis in the field of surface temperature measurement. Surface temperature measurements are applicable in many fields. As examples, safety testing of electrical appliances and a pharmaceutical production line represent case studies for surface temperature measurements. In both cases correctness of the result of the surface temperature has an influence on final product safety and quality and thus conformity with specifications. This paper deals with the differences of flat surface temperature probes in measuring the surface temperature. For the purpose of safety testing of electrical appliances, surface temperature measurements are very important for safety of the user. General requirements are presented in European standards, which support requirements in European directives, e.g., European Low Voltage Directive 2006/95/EC and pharmaceutical requirements, which are introduced in official state legislation. This paper introduces a comparison of temperature measurements of an attached thermocouple on the measured surface and measurement with flat surface temperature probes. As a heat generator, a so called temperature artifact is used. It consists of an aluminum plate with an incorporated electrical heating element with very good temperature stability in the central part. The probes and thermocouple were applied with different forces to the surface in horizontal and vertical positions. The reference temperature was measured by a J-type fine-wire (0.2 mm) thermocouple. Two probes were homemade according to requirements in the European standard EN 60335-2-9/A12, one with a fine-wire (0.2 mm) thermocouple and one with 0.5mm of thermocouple wire diameter. Additional commercially available probes were compared. Differences between probes due to thermal conditions caused by application of the probe were found. Therefore, it can happen that measurements are performed with improper equipment or

  14. Surface sampling concentration and reaction probe

    Science.gov (United States)

    Van Berkel, Gary J; Elnaggar, Mariam S

    2013-07-16

    A method of analyzing a chemical composition of a specimen is described. The method can include providing a probe comprising an outer capillary tube and an inner capillary tube disposed co-axially within the outer capillary tube, where the inner and outer capillary tubes define a solvent capillary and a sampling capillary in fluid communication with one another at a distal end of the probe; contacting a target site on a surface of a specimen with a solvent in fluid communication with the probe; maintaining a plug volume proximate a solvent-specimen interface, wherein the plug volume is in fluid communication with the probe; draining plug sampling fluid from the plug volume through the sampling capillary; and analyzing a chemical composition of the plug sampling fluid with an analytical instrument. A system for performing the method is also described.

  15. Synopsis of moisture monitoring by neutron probe in the unsaturated zone at Area G

    Energy Technology Data Exchange (ETDEWEB)

    Vold, E.

    1997-12-31

    Moisture profiles from neutron probe data provide valuable information in site characterization and to supplement ground water monitoring efforts. The neutron probe precision error (reproducibility) is found to be about 0.2 vol% under in situ field conditions where the slope in moisture content with depth is varying slowly. This error is about 2 times larger near moisture spikes (e.g., at the vapor phase notch), due to the sensitivity of the probe response to vertical position errors on the order of 0.5 inches. Calibrations were performed to correct the downhole probe response to the volumetric moisture content determined on core samples. Calibration is sensitive to borehole diameter and casing type, requiring 3 separate calibration relations for the boreholes surveyed here. Power law fits were used for calibration in this study to assure moisture content results greater than zero. Findings in the boreholes reported here confirm the broad features seen previously in moisture profiles at Area G, a near-surface region with large moisture variability, a very dry region at greater depths, and a moisture spike at the vapor phase notch (VPN). This feature is located near the interface between the vitrified and vitrified stratigraphic units and near the base of the mesa. This report describes the in-field calibration methods used for the neutron moisture probe measurements and summarizes preliminary results of the monitoring program in the in-situ monitoring network at Area G. Reported results include three main areas: calibration studies, profiles from each of the vertical boreholes at Area G, and time-dependent variations in a select subset of boreholes. Results are reported here for the vertical borehole network. Results from the horizontal borehole network will be described when available.

  16. Synopsis of moisture monitoring by neutron probe in the unsaturated zone at Area G

    International Nuclear Information System (INIS)

    Vold, E.

    1997-01-01

    Moisture profiles from neutron probe data provide valuable information in site characterization and to supplement ground water monitoring efforts. The neutron probe precision error (reproducibility) is found to be about 0.2 vol% under in situ field conditions where the slope in moisture content with depth is varying slowly. This error is about 2 times larger near moisture spikes (e.g., at the vapor phase notch), due to the sensitivity of the probe response to vertical position errors on the order of 0.5 inches. Calibrations were performed to correct the downhole probe response to the volumetric moisture content determined on core samples. Calibration is sensitive to borehole diameter and casing type, requiring 3 separate calibration relations for the boreholes surveyed here. Power law fits were used for calibration in this study to assure moisture content results greater than zero. Findings in the boreholes reported here confirm the broad features seen previously in moisture profiles at Area G, a near-surface region with large moisture variability, a very dry region at greater depths, and a moisture spike at the vapor phase notch (VPN). This feature is located near the interface between the vitrified and vitrified stratigraphic units and near the base of the mesa. This report describes the in-field calibration methods used for the neutron moisture probe measurements and summarizes preliminary results of the monitoring program in the in-situ monitoring network at Area G. Reported results include three main areas: calibration studies, profiles from each of the vertical boreholes at Area G, and time-dependent variations in a select subset of boreholes. Results are reported here for the vertical borehole network. Results from the horizontal borehole network will be described when available

  17. Calibration of a neutron probe for determining the humidity in deep alluvial soils

    International Nuclear Information System (INIS)

    Ferrer, A.; Rivero, H.; Lopez, F.; Cantillo, O.

    1993-01-01

    Preliminary data for the calibration of a neutron probe in deep alluvial soils for determining the humidity are reported. Comparisons of Neutron flow behaviour with the depth of the land are established. A characteristic curve of amount of detected neutrons according to the humidity percentage (from 50 to 100 % of the field humidity) is obtained

  18. A multilayer surface detector for ultracold neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Zhehui, E-mail: zwang@lanl.gov [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Hoffbauer, M.A.; Morris, C.L. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Callahan, N.B.; Adamek, E.R. [Indiana University, Bloomington, IN 47405 (United States); Bacon, J.D. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Blatnik, M. [Cleveland State University, Cleveland, OH 44115 (United States); Brandt, A.E. [North Carolina State University, Raleigh, NC 27695 (United States); Broussard, L.J.; Clayton, S.M. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Cude-Woods, C. [North Carolina State University, Raleigh, NC 27695 (United States); Currie, S. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Dees, E.B. [North Carolina State University, Raleigh, NC 27695 (United States); Ding, X. [Virginia Polytechnic Institute and State University, Blacksburg, VA 24061 (United States); Gao, J. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Gray, F.E. [Regis University, Denver, CO 80221 (United States); Hickerson, K.P. [University of California Los Angeles, Los Angeles, CA 90095 (United States); Holley, A.T. [Tennessee Technological University, Cookeville, TN 38505 (United States); Ito, T.M. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Liu, C.-Y. [Indiana University, Bloomington, IN 47405 (United States); and others

    2015-10-21

    A multilayer surface detector for ultracold neutrons (UCNs) is described. The top {sup 10}B layer is exposed to vacuum and directly captures UCNs. The ZnS:Ag layer beneath the {sup 10}B layer is a few microns thick, which is sufficient to detect the charged particles from the {sup 10}B(n,α){sup 7}Li neutron-capture reaction, while thin enough that ample light due to α and {sup 7}Li escapes for detection by photomultiplier tubes. A 100-nm thick {sup 10}B layer gives high UCN detection efficiency, as determined by the mean UCN kinetic energy, detector materials, and other parameters. Low background, including negligible sensitivity to ambient neutrons, has also been verified through pulse-shape analysis and comparison with other existing {sup 3}He and {sup 10}B detectors. This type of detector has been configured in different ways for UCN flux monitoring, development of UCN guides and neutron lifetime research.

  19. Pulsar H(alpha) Bowshocks probe Neutron Star Physics

    Science.gov (United States)

    Romani, Roger W.

    2014-08-01

    We propose a KOALA/AAOmega study of southern pulsar bow shocks. These rare, Balmer-dominated, non-radiative shocks provide an ideal laboratory to study the interaction of the relativistic pulsar wind with the ISM. We will cover H(alpha) at high spectral resolution to measure the kinematics of the upstream ISM and the post-shock flow, while the blue channel measures the Balmer decrement and probes for a faint cooling component. These data, with MHD models, allow us to extract the 3D flow geometry and the orientation and asymmetry of the pulsar wind. These data can also measure the pulsar spindown power, thus estimating the neutron star moment of inertia and effecting a fundamental test of dense matter physics.

  20. Evaluation of the NDP (neutron diagnostic probe) system

    Energy Technology Data Exchange (ETDEWEB)

    Pentaleri, E.A.; Eisen, Y.Y.

    1990-12-01

    The neutron diagnostic probe (NDP), an explosive detection system developed by Consolidated Controls Corporation and based on the associated-alpha-particle technique, was evaluated. Although many problems were found with the prototype system that make it useless for most practical applications, the NDP system may be considered a successful proof-of-principle for the basic explosive detection system design. In addition to evaluating the design and performance of the present system, models were developed to estimate the performance that might reasonably be expected from full scale systems of different conceptual design. Specific examples involved various types of bulk and sheet explosives contained in a suitcase and a large crate. Also considered were the effects of innocuous materials surrounding explosives in different scenarios, including the deliberate use of shielding materials as a countermeasure to detection. 11 refs., 46 figs., 24 tabs.

  1. Neutron and gamma probes: Their use in agronomy

    International Nuclear Information System (INIS)

    Bacchi, O.O.; Reichart, K.; Calvache, M.

    2002-01-01

    The concept of this training manual originated during a regional training workshop on the use of neutron probe in water and nutrient balance studies, organized in 1997 in the frame of an IAEA Regional Technical Co-operation Project for Latin America entitle Plant Nutrition, Water and Soil Management, for which the integrated approach was adopted. The original version (in Spanish) was a comprehensive manual covering theoretical and practical aspects required for the proper utilization of the equipment. The contributions of the peer reviewers, editors and technical translators of the three versions in English, French and Spanish have greatly enhanced the content and quality of the manual. It is hoped that this manual will be useful for future training events and serve as a key reference to soil/water scientists in the field of sustainable management of scarce water resources in both rain-fed and irrigated agricultural production systems

  2. Tree tomato water requirements determined by neutron probe

    International Nuclear Information System (INIS)

    1994-01-01

    The dynamics of water was studied at ''La Tola'', experimental teaching center of the Central University of Ecuador, in a sandy-loan, typic durustoll soil in which trees tomato were growing. All the components of the crop water balance were determined. Real evapotranspiration (ETR) was estimated through the mass balance method, using every 5-10 days a neutron probe to access the volumetric humidity of the soil. The real evapotranspiration was in direct relation with the growth of the crop, reaching its maximum value of 3,8 mm day-1, at vegetative stage. The soil layer supplying most of the water for the consumptive use of the crop was between 0-40 cm being the root activity also greater in that layer

  3. Neutron scattering on magnetic surfaces

    International Nuclear Information System (INIS)

    Ott, F.

    2007-01-01

    During the early eighties, advanced techniques for the deposition of ultra-thin metal films were developed. The combination of different types of materials gave rise to new physical phenomena such as the magnetic exchange coupling in superlattices or the exchange bias between ferro and anti-ferro layers. New types of heterostructures combining magnetic oxides, insulating oxides or magnetic semiconductors are still being developed. Alongside the fabrication of these new meta-materials made of thin films stacking, polarized neutron reflectometry has emerged as a routine tool for the characterization of magnetic hetero-structures. In the recent years, the new developments of polarized reflectivity have been connected to the study of micro- and nano-structures, especially micro-magnetic structures in multilayers. The technique of off-specular scattering has been developed for the study of the roughness or the micro magnetism at a micro metric scale. For the study of nano-metric structures, in the range below 100 nm, grazing incidence Small Angle Scattering is being considered. In thin films, the volume of magnetic matter is very small but nevertheless, diffraction experiments can be performed owing to the good performances of modern neutron spectrometers

  4. Eddy Current Probe for Surface and Sub-Surface Inspection

    Science.gov (United States)

    Wincheski, Russell A. (Inventor); Simpson, John W. (Inventor)

    2014-01-01

    An eddy current probe includes an excitation coil for coupling to a low-frequency alternating current (AC) source. A magneto-resistive sensor is centrally disposed within and at one end of the excitation coil to thereby define a sensing end of the probe. A tubular flux-focusing lens is disposed between the excitation coil and the magneto-resistive sensor. An excitation wire is spaced apart from the magneto-resistive sensor in a plane that is perpendicular to the sensor's axis of sensitivity and such that, when the sensing end of the eddy current probe is positioned adjacent to the surface of a structure, the excitation wire is disposed between the magneto-resistive sensor and the surface of the structure. The excitation wire is coupled to a high-frequency AC source. The excitation coil and flux-focusing lens can be omitted when only surface inspection is required.

  5. Neutron scattering on magnetic surfaces

    Science.gov (United States)

    Ott, Frédéric

    2007-09-01

    During the early 1980s, advanced techniques for the deposition of ultra-thin metal films were developed. The combination of different types of materials gave rise to new physical phenomena such as the magnetic exchange coupling in superlattices or the exchange bias between ferro and anti-ferro layers. The field was very active because of the associated industrial applications in magnetic field sensors. New types of heterostructures combining magnetic oxides, insulating oxides or magnetic semiconductors are still being developed. Alongside the fabrication of these new meta-materials made of thin films stacking, polarized neutron reflectometry has emerged as a routine tool for the characterization of magnetic hetero-structures. In the recent years, the new developments of polarized reflectivity have been connected to the study of micro and nanostructures, especially micromagnetic structures in multilayers. The technique of off-specular scattering has been developed for the study of the roughness or the micromagnetism at a micrometric scale. For the study of nanometric structures, in the range below 100 nm, grazing incidence Small Angle Scattering is being considered. To cite this article: F. Ott, C. R. Physique 8 (2007).

  6. Probes for anionic cell surface detection

    Science.gov (United States)

    Smith, Bradley D.

    2013-03-05

    Embodiments of the present invention are generally directed to compositions comprising a class of molecular probes for detecting the presence of anionic cell surfaces. Embodiments include compositions that are enriched for these compositions and preparations, particularly preparations suitable for use as laboratory/clinical reagents and diagnostic indicators, either alone or as part of a kit. An embodiment of the invention provides for a highly selective agent useful in the discernment and identification of dead or dying cells, such as apoptotic cells, in a relatively calcium-free environment. An embodiment of the invention provides a selective agent for the identification of bacteria in a mixed population of bacterial cells and nonbacterial cells.

  7. Probing Anisotropic Surface Properties and Surface Forces of Fluorite Crystals.

    Science.gov (United States)

    Gao, Zhiyong; Xie, Lei; Cui, Xin; Hu, Yuehua; Sun, Wei; Zeng, Hongbo

    2018-02-20

    Fluorite is the most important mineral source for producing fluorine-based chemicals and materials in a wide range of engineering and technological applications. In this work, atomic force microscopy was employed, for the first time, to probe the surface interactions and adhesion energy of model oleic acid (a commonly used surface modification organics for fluorite) molecules on fluorite surfaces with different orientations in both air and aqueous solutions at different pH conditions. Fitted with the Derjaguin-Landau-Verwey-Overbeek theory, the force results during surface approaching demonstrate the anisotropy in the surface charge of different orientations, with the {111} surface exhibiting a higher magnitude of surface charge, which could be attributed to the difference in the atomic composition. The adhesion measured during surface retraction shows that model oleic acid molecules have a stronger adhesion with the {100} surface than with the {111} surface in both air and aqueous solutions. The anisotropic adhesion energy was analyzed in relation to the surface atom (especially calcium) activity, which was supported by the surface free energy results calculated based on a three-probe-liquid method. Each calcium atom on the {100} surface with four dangling bonds is more active than the calcium atom on the {111} surface with only one dangling bond, supported by a larger value of the Lewis acid component for the {100} surface. The model oleic acid molecules present in the ionic form at pH 9 exhibit a higher adhesion energy with fluorite surfaces as compared to their molecular form at pH 6, which was related to the surface activity of different forms. The adhesion energy measured in solution is much lower than that in air, indicating that the solvent exerts an important influence on the interactions of organic molecules with mineral surfaces. The results provide useful information on the fundamental understanding of surface interactions and adhesion energy of organic

  8. Capturing the Future: Direct and Indirect Probes of Neutron Capture

    Energy Technology Data Exchange (ETDEWEB)

    Couture, Aaron Joseph [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-08-31

    This report documents aspects of direct and indirect neutron capture. The importance of neutron capture rates and methods to determine them are presented. The following conclusions are drawn: direct neutron capture measurements remain a backbone of experimental study; work is being done to take increased advantage of indirect methods for neutron capture; both instrumentation and facilities are making new measurements possible; more work is needed on the nuclear theory side to understand what is needed furthest from stability.

  9. The orientation effect in the activities of neutronic probes

    International Nuclear Information System (INIS)

    Vigon, M. A.

    1956-01-01

    The formulae relating activity and position of a neutron irradiated Indium foil, have been verified experimentally. Measurements with both thin and thick foils for epithermal neutrons and with thick foils for thermal neutrons have been carried out. The experimental results agree qualitatively with the theoretical predictions. (Author)

  10. Neutron stars as probes of extreme energy density matter

    Indian Academy of Sciences (India)

    2015-05-07

    May 7, 2015 ... Although the focus is on the much needed information on masses and radii of several individual neutron stars, the need for additional knowledge about the many facets of neutron stars is stressed. The extent to which quark matter can be present in neutron stars is summarized with emphasis on the ...

  11. Comparative experimental and theoretical investigations of the DM neutron moisture probe

    DEFF Research Database (Denmark)

    Ølgaard, Povl Lebeck; Haahr, Vagner

    1967-01-01

    Theoretical and experimental investigations of the Danish produced DM subsurface moisture probe have been carried out at the Research Establishment Risö, and the results obtained are presented in this paper. The DM probe contains an Am-Be fast neutron source and has a glass scintillator containing...

  12. Surface emission from neutron stars and implications for the physics of their interiors

    International Nuclear Information System (INIS)

    Özel, Feryal

    2013-01-01

    Neutron stars are associated with diverse physical phenomena that take place in conditions characterized by ultrahigh densities as well as intense gravitational, magnetic and radiation fields. Understanding the properties and interactions of matter in these regimes remains one of the challenges in compact object astrophysics. Photons emitted from the surfaces of neutron stars provide direct probes of their structure, composition and magnetic fields. In this review, I discuss in detail the physics that governs the properties of emission from the surfaces of neutron stars and their various observational manifestations. I present the constraints on neutron star radii, core and crust composition, and magnetic field strength and topology obtained from studies of their broadband spectra, evolution of thermal luminosity, and the profiles of pulsations that originate on their surfaces. (review article)

  13. Surface emission from neutron stars and implications for the physics of their interiors.

    Science.gov (United States)

    Ozel, Feryal

    2013-01-01

    Neutron stars are associated with diverse physical phenomena that take place in conditions characterized by ultrahigh densities as well as intense gravitational, magnetic and radiation fields. Understanding the properties and interactions of matter in these regimes remains one of the challenges in compact object astrophysics. Photons emitted from the surfaces of neutron stars provide direct probes of their structure, composition and magnetic fields. In this review, I discuss in detail the physics that governs the properties of emission from the surfaces of neutron stars and their various observational manifestations. I present the constraints on neutron star radii, core and crust composition, and magnetic field strength and topology obtained from studies of their broadband spectra, evolution of thermal luminosity, and the profiles of pulsations that originate on their surfaces.

  14. Soft-landing deposition of radioactive probe atoms on surfaces

    NARCIS (Netherlands)

    Laurens, C.R; Rosu, M.F; Pleiter, F; Niesen, L

    1999-01-01

    We present a method to deposit a wide range of radioactive probe atoms on surfaces, without introducing lattice damage or contaminating the surface with other elements or isotopes. In this method, the probe atoms are mass-separated using an isotope separa-tor, decelerated to 5 eV, and directly

  15. Influence of density and chemical composition of soils in the neutrons probes answer; Influencia da densidade e da composicao quimica dos solos na resposta de sondas de neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Crispino, Marcos Luiz; Antonino, Antonio Celso Dantas; Dall`Olio, Attilio; Oliveira Lira, Carlos Alberto Brayner de [Pernambuco Univ., Recife, PE (Brazil). Dept. de Energia Nuclear; Carneiro, Clemente J. Gusmao [Minas Gerais Univ., Belo Horizonte, MG (Brazil). Dept. de Engenharia Nuclear

    1996-08-01

    The determination of soil humidity with neutron probes is based in the measure of the thermal neutron flux intensity and its behavior with the soil depend: soil`s chemical composition; soils physical parameters; neutrons` energetic spectrum and neutron-source detector geometry.The objective of this paper is to apply the multigroup function theory to calculate a neutron probe calibration curve utilizing representatives parameters and coefficients of soils horizons in a experimental station in Zona da Mata, Pernambuco, Brazil 2 tabs., 3 figs.

  16. The role of probe oxide in local surface conductivity measurements

    Science.gov (United States)

    Barnett, C. J.; Kryvchenkova, O.; Wilson, L. S. J.; Maffeis, T. G. G.; Kalna, K.; Cobley, R. J.

    2015-05-01

    Local probe methods can be used to measure nanoscale surface conductivity, but some techniques including nanoscale four point probe rely on at least two of the probes forming the same low resistivity non-rectifying contact to the sample. Here, the role of probe shank oxide has been examined by carrying out contact and non-contact I V measurements on GaAs when the probe oxide has been controllably reduced, both experimentally and in simulation. In contact, the barrier height is pinned but the barrier shape changes with probe shank oxide dimensions. In non-contact measurements, the oxide modifies the electrostatic interaction inducing a quantum dot that alters the tunneling behavior. For both, the contact resistance change is dependent on polarity, which violates the assumption required for four point probe to remove probe contact resistance from the measured conductivity. This has implications for all nanoscale surface probe measurements and macroscopic four point probe, both in air and vacuum, where the role of probe oxide contamination is not well understood.

  17. ZEEMANS - a new facility to probe matter at high magnetic field through neutron scattering

    International Nuclear Information System (INIS)

    Savici, A T; Granroth, G E; Broholm, C; Lee, Y S; Bird, M D

    2010-01-01

    We describe ZEEMANS, a new instrument proposed for the Spallation Neutron Source (SNS) to probe matter at extremely high magnetic fields. The complexity of the high field magnet demands a versatile neutron scattering instrument, capable of performing diffraction (powder and single crystal), SANS, reflectometry, and inelastic spectrometry, with minimal modifications between configurations. In this paper we present a conceptual design for neutron scattering instrumentation to be built around the horizontal conical high field magnet. Monte Carlo simulations and analytical calculations indicate performance on a par with other SNS instrumentation despite limited access to the sample.

  18. Nuclear Symmetry Energy Probed by Neutron Skin Thickness of Nuclei

    International Nuclear Information System (INIS)

    Centelles, M.; Roca-Maza, X.; Vinas, X.; Warda, M.

    2009-01-01

    We describe a relation between the symmetry energy coefficients c sym (ρ) of nuclear matter and a sym (A) of finite nuclei that accommodates other correlations of nuclear properties with the low-density behavior of c sym (ρ). Here, we take advantage of this relation to explore the prospects for constraining c sym (ρ) of systematic measurements of neutron skin sizes across the mass table, using as example present data from antiprotonic atoms. The found constraints from neutron skins are in harmony with the recent determinations from reactions and giant resonances

  19. Use of neutron probe and tensiometry techniques in determining ...

    African Journals Online (AJOL)

    Characterisation of soil water, in particular water flow dynamics is fundamental in assessing the environmental implications to soil management. Soil water characterisation was assessed by measuring soil water content and soil water potential in a draining profile of sandy and loamy soils. Mercury manometers and Neutron ...

  20. Neutron stars as probes of extreme energy density matter

    Indian Academy of Sciences (India)

    2015-05-07

    May 7, 2015 ... Accretion of matter induces compression of matter in the crust of a neutron star triggering pycno-nuclear reactions that ... Employing these scaling relations, the compactness ratio (GMmax/Rmaxc2) is smallest when [16,41] .... the variable h is defined through dh = dp/(p + ρ(p)). The advantages of this refor-.

  1. Probing Trace-elements in Bitumen by Neutron Activation Analysis

    NARCIS (Netherlands)

    Nahar, S.N.; Schmets, A.J.M.; Scarpas, Athanasios

    Trace elements and their concentrations play an important role in both chemical and physical properties of bitumen. Instrumental Neutron Activation Analysis (INAA) has been applied to determine the concentration of trace elements in bitumen. This method requires irradiation of the material with

  2. Neutron stars as probes of extreme energy density matter

    Indian Academy of Sciences (India)

    2015-05-07

    May 7, 2015 ... Neutron stars have long been regarded as extraterrestrial laboratories from which we can learn about extreme energy density matter at low temperatures. In this article, some of the recent advances made in astrophysical observations and related theory are highlighted. Although the focus is on the much ...

  3. Neutron skin thickness in neutron-rich nuclei: bulk and surface contributions and shell effects

    International Nuclear Information System (INIS)

    Vinas, X.; Centelles, M.; Warda, M.; Roca-Maza, X.

    2012-01-01

    We analyze theoretically the neutron skin thickness in nuclei and its correlation with the symmetry energy by using semiclassical and mean field approaches together with nuclear effective interactions. Semiclassical approaches reveal that the neutron skin thickness in nuclei is formed by a combination of bulk and surface contributions. To investigate the neutron skin thickness predicted by mean field models, we fit the corresponding densities by two-parameter Fermi distributions. Using these parametrized densities, we study the neutron skin thickness as well as its bulk and surface contributions in 208 Pb and in Zr isotopes, where the influence of shell effects along the isotopic chain is discussed. (author)

  4. Delayed neutrons as a probe of nuclear charge distribution in fission of heavy nuclei by neutrons

    International Nuclear Information System (INIS)

    Isaev, S.G.; Piksaikin, V.M.; Kazakov, L.E.; Roshchenko, V.A.

    2002-01-01

    A method of the determination of cumulative yields of delayed neutron precursors is developed. This method is based on the iterative least-square procedure applied to delayed neutron decay curves measured after irradiation of 235 U sample by thermal neutrons. Obtained cumulative yields in turns were used for deriving the values of the most probable charge in low-energy fission of the above-mentioned nucleus. (author)

  5. A new technique for the calibration of neutron probes by volumetric method

    International Nuclear Information System (INIS)

    Encarnacao, F.A.F. da.

    1988-01-01

    Laboratory and field studies were performed for the determination of a calibration curve of a neutron probe in three different kinds of soils: Red Yellow PODZOLIC, LITOLIC and ALLUVIAL, in the last one laboratory studies were done to determine local humidity on the calibration curve parameters. (A.C.A.S.) [pt

  6. Analysis of bulk and surface contributions in the neutron skin of nuclei

    International Nuclear Information System (INIS)

    Warda, M.; Vinas, X.; Roca-Maza, X.; Centelles, M.

    2010-01-01

    The neutron skin thickness of nuclei is a sensitive probe of the nuclear symmetry energy and has multiple implications for nuclear and astrophysical studies. However, precision measurements of this observable are difficult to obtain. The analysis of the experimental data may imply some assumptions about the bulk or surface nature of the formation of the neutron skin. Here we study the bulk or surface character of neutron skins of nuclei following from calculations with Gogny, Skyrme, and covariant nuclear mean-field interactions. These interactions are successful in describing nuclear charge radii and binding energies but predict different values for neutron skins. We perform the study by fitting two-parameter Fermi distributions to the calculated self-consistent neutron and proton densities. We note that the equivalent sharp radius is a more suitable reference quantity than the half-density radius parameter of the Fermi distributions to discern between the bulk and surface contributions in neutron skins. We present calculations for nuclei in the stability valley and for the isotopic chains of Sn and Pb.

  7. Surface chemical reactions probed with scanning force microscopy

    NARCIS (Netherlands)

    Werts, M.P L; van der Vegte, E.W.; Hadziioannou, G

    1997-01-01

    In this letter we report the study of surface chemical reactions with scanning force microscopy (SFM) with chemical specificity. Using chemically modified SFM probes, we can determine the local surface reaction conversion during a chemical surface modification. The adhesion forces between a

  8. Engineering related neutron diffraction measurements probing strains, texture and microstructure

    Energy Technology Data Exchange (ETDEWEB)

    Clausen, Bjorn [Los Alamos National Laboratory; Brown, Donald W [Los Alamos National Laboratory; Tome, Carlos N [Los Alamos National Laboratory; Balogh, Levente [Los Alamos National Laboratory; Vogel, Sven C [Los Alamos National Laboratory

    2010-01-01

    Neutron diffraction has been used for engineering applications for nearly three decades. The basis of the technique is powder diffraction following Bragg's Law. From the measured diffraction patterns information about internal, or residual, strain can be deduced from the peak positions, texture information can be extracted from the peak intensities, and finally the peak widths can provide information about the microstructure, e.g. dislocation densities and grain sizes. The strains are measured directly from changes in lattice parameters, however, in many cases it is non-trivial to determine macroscopic values of stress or strain from the measured data. The effects of intergranular strains must be considered, and combining the neutron diffraction measurements with polycrystal deformation modeling has proven invaluable in determining the overall stress and strain values of interest in designing and dimensioning engineering components. Furthelmore, the combined use of measurements and modeling has provided a tool for elucidating basic material properties, such as critical resolved shear stresses for the active deformation modes and their evolution as a function of applied deformation.

  9. Atomic probes of surface structure and dynamics

    International Nuclear Information System (INIS)

    Heller, E.J.; Jonsson, H.

    1992-01-01

    Progress for the period Sept. 15, 1992 to Sept. 14, 1993 is discussed. Semiclassical methods that will allow much faster and more accurate three-dimensional atom--surface scattering calculations, both elastic and inelastic, are being developed. The scattering of He atoms from buckyballs is being investigated as a test problem. Somewhat more detail is given on studies of He atom scattering from defective Pt surfaces. Molecular dynamics simulations of He + and Ar + ion sputtering of Pt surfaces are also being done. He atom scattering from Xe overlayers on metal surfaces and the thermalized dissociation of H 2 on Cu(110) are being studied. (R.W.R.) 64 refs

  10. Profiling water content in soils with TDR: Comparison with the neutron probe technique

    International Nuclear Information System (INIS)

    Laurent, J.P.

    2000-01-01

    In November 1996, at a site on the Grenoble campus a 1.2-m-long neutron access tube, a 0.8-m fibreglass Trime access tube and three sets of 1-m twin-rod TDR probes were installed. Weekly measurements were made over a 9-month period. In addition, soil samples were taken from time to time with an auger, to determine gravimetric water-contents. The soil bulk density profile was initially characterised by gammametry using a Campbell TM probe. A Troxler TM 4300 was used for the neutron-probe measurements. The TDR signals, for further processing by TDR-SSI, were logged using a Trase 2000 from Soil Moisture Equipment Corporation TM . TDR methods were employed without any special calibration of the permittivity/water-content relationship: standard internal calibrations of the devices or Topp polynomial relation were always applied. The results of all these water-content profiling methods were compared in three ways: (i) the water-content profiles were plotted directly on the same graph for different dates; (ii) all the water contents measured at all dates and all depths were plotted against a corresponding 'reference', namely neutron probe or gravimetry; (iii) water balances were calculated for each method and their respective time-profiles analysed. There was fairly good agreement among the three profiling methods, indicating that TDR is now a viable alternative to nuclear techniques for soil water-content profiling. (author)

  11. Neutron reflectometry of soft films supported on electrified surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Quirk, A.I. [Univ. of Saskatchewan, Dept. of Chemistry, Saskatoon, Saskatchewan (Canada); Vezvaie, M. [Canadian Neutron Beam Centre, Chalk River, Ontario (Canada); Burgess, I.J., E-mail: ian.burgess@usask.ca [Univ. of Saskatchewan, Dept. of Chemistry, Saskatoon, Saskatchewan (Canada)

    2014-07-01

    The specular reflection of neutrons is a non-destructive, nuclear-based technique, sensitive to low atomic number elements, has a high penetration depth, and can distinguish between isotopes of the same element. This makes neutron reflectometry (NR) especially effective for the study of biological membranes, soft films and buried interfaces. Furthermore, commonly used NR substrates such as silicon and quartz single-crystals can be modified with thin metallic layers to form conductive supports allowing for the precise control of the electrical state of the interface. The coupling of NR with in-situ electrochemical control provides a powerful tool to study the composition of soft and/or buried interfaces under conditions that mimic, for example, transmembrane potentials or corrosion potentials. Here we report our recent efforts to perform in situ electrochemical NR studies and the previous experimental framework from which they were developed. The talk will address technical and infrastructure challenges but emphasize scientific highlights from our work with biomimetic phospholipid membranes. 'Isotopic variation has been applied to quantify the electroporation and distribution of water as a function of surface charge density in lipid bilayers. These studies have more recently been extended to study the location of redox-active ubiquinone (coenzyme Q{sub 10}) in biomimetic lipid bilayers as a function of potential and temperature. To probe the location of ubiquinone, a phospholipid bilayer was prepared on a gold coated solid substrate using a combination of Langmuir-Blodgett and vesicle fusion techniques. The combination of these two methods allowed for the composition of the inner and outer membrane leaflets to be varied. Preliminary results show sensitivity to the location of a small biologically relevant molecule. (author)

  12. Effect of some soil physical properties on water holding capacity, neutron probe calibration and salt movement

    International Nuclear Information System (INIS)

    Razzouk, A.

    2010-01-01

    This study was conducted in tow areas representing in silty soil in Southern Syria (Dra'a), loamy and sandy soil in Eastern Syria (Deir Al zour) to compare the soil effect on the calibration of the neutron probe, correlation coefficient, soil characteristics curve, soil solution content of nitrates, potassium and sodium for the estimation of the optimum sampling time of soil solution by porous ceramic cups. Regression analysis results showed that the three soils curves, in which the soil contained the lowest content of clay had a high correlation coefficient and decreased with increasing the clay content. Whereas, the correlation coefficient in sandy soil was 0.96 while decreased to 0.79 in silty soil. The hydraulic head increased with decreasing the water content, which was obvious in the three soils characteristic curves. The NO 3 content decreased due to the plants roots absorption and leaching to deeper layers, while the NO 3 content in the surfaces layer significantly decreased in the sandy soil. Results showed that equilibrium between the soil solution and the NO 3 content in the solution in porous cups occurred within 8 days. (author)

  13. Development of a probe by neutron activation for chemical analysis in drillings

    International Nuclear Information System (INIS)

    Baron, J.P.; Carriou, J.; Alexandre, J.; Pinault, J.L.; Dumas, A.; Huet, D.; Collins, V.

    1983-01-01

    Laboratory studies on simulated drillings have been made and compared to calculations on mathematical models. A probe design has been developed with the Laboratory of Ponts et Chaussees. The probe has been tested in-situ on polymetallic sulfide mineralization. The study of the activation gamma allowed to log copper, iron, silicon and potassium. A very feasibility of neutronic activation has been proved during these three years. At the end of this optimization phase, the mining operators will have a device able to give them in real time informations necessary to control their operations [fr

  14. Doped organic films for OLEDs probed with neutron reflectometry

    International Nuclear Information System (INIS)

    Smith, Arthur R. G.; Lo, Shih-Chun; Gentle, Ian R.

    2009-01-01

    Full text: Conjugated organic semiconductors form an exciting class of materials that can be used in a variety of cutting edge technologies including organic light-emitting diodes, solar cells and transistors. In all these technologies the thin film morphology and interfacial interactions are key areas for their operation. In order to optimise the materials and devices it is critical to understand the structural property relationships for the organic semiconductors by relating the 'molecular' structure to the film morphology and correlating these to the photophysical and device characteristics. Organic light emitting diodes (OLEO) have gained interest for their superior performance compared to current display technologies. Optimising the active emissive layer remains a challenge which can significantly affect the final performance of the device [1]. We have investigated the layering behaviour of small molecule co-evaporated films of deuterated 4,4'-bis(9-carbazolyl)-1, 1 '-biphenyl doped with tris-phenylpyridine iridium(llI) using neutron reflectometry The behaviour of doped emissive layers is dependent on the ratio between dopant and host material. The morphology and internal structure of such films have not yet been investigated, leading to questions about the phase separation and ordering of layers within the film.

  15. Surface Plasmon Polaritons Probed with Cold Atoms

    DEFF Research Database (Denmark)

    Kawalec, Tomasz; Sierant, Aleksandra; Panas, Roman

    2017-01-01

    We report on an optical mirror for cold rubidium atoms based on a repulsive dipole potential created by means of a modified recordable digital versatile disc. Using the mirror, we have determined the absolute value of the surface plasmon polariton (SPP) intensity, reaching 90 times the intensity...

  16. Calibration and correction procedures for cosmic-ray neutron soil moisture probes located across Australia

    Science.gov (United States)

    Hawdon, Aaron; McJannet, David; Wallace, Jim

    2014-06-01

    The cosmic-ray probe (CRP) provides continuous estimates of soil moisture over an area of ˜30 ha by counting fast neutrons produced from cosmic rays which are predominantly moderated by water molecules in the soil. This paper describes the setup, measurement correction procedures, and field calibration of CRPs at nine locations across Australia with contrasting soil type, climate, and land cover. These probes form the inaugural Australian CRP network, which is known as CosmOz. CRP measurements require neutron count rates to be corrected for effects of atmospheric pressure, water vapor pressure changes, and variations in incoming neutron intensity. We assess the magnitude and importance of these corrections and present standardized approaches for network-wide analysis. In particular, we present a new approach to correct for incoming neutron intensity variations and test its performance against existing procedures used in other studies. Our field calibration results indicate that a generalized calibration function for relating neutron counts to soil moisture is suitable for all soil types, with the possible exception of very sandy soils with low water content. Using multiple calibration data sets, we demonstrate that the generalized calibration function only applies after accounting for persistent sources of hydrogen in the soil profile. Finally, we demonstrate that by following standardized correction procedures and scaling neutron counting rates of all CRPs to a single reference location, differences in calibrations between sites are related to site biomass. This observation provides a means for estimating biomass at a given location or for deriving coefficients for the calibration function in the absence of field calibration data.

  17. Isolated Neutron Stars: From the Surface to the Interior

    CERN Document Server

    Zane, Silvia; Page, Dany

    2007-01-01

    This book collects the contributions presented at the conference Isolated Neutron Stars: From the Surface to the Interior, held in London in April 2006. Forty years after the discovery of radio pulsars it presents an up-to-date description of the new vision of isolated neutron stars that has emerged in recent years with the advance of multi-wavelength observations. The great variety of isolated neutron stars, from pulsars to magnetars, some of them discovered very recently and many of them not detectable in radio wavelengths, is amply covered by descriptions of recent observational results and presentations of the latest theoretical interpretation of these data.

  18. Neutron Capture Cross Sections of Zr and La: Probing Neutron Exposure and Neutron Flux in Red Giant Stars

    CERN Multimedia

    Kitis, G; Wiescher, M; Dahlfors, M; Soares, J

    2002-01-01

    We propose to measure the neutron capture cross sections of $^{139}$La, of $^{93}$Zr (t$_{1/2}$)=1.5 10$^{6}$ yr), and of all the stable Zr isotopes at n_TOF. The aim of these measurements is to improve the accuracy of existing results by at least a factor of three in order to meet the quality required for using the s-process nucleosynthesis as a diagnostic tool for neutron exposure and neutron flux during the He burning stages of stellar evolution. Combining these results with a wealth of recent information coming from high-resolution stellar spectroscopy and from the detailed analysis of presolar dust grains will shed new light on the chemical history of the universe. The investigated cross sections are also needed for technological applications, in particular since $^{93}$Zr is one of the major long-lived fission products.

  19. X-ray and neutron scattering from surface and interface

    International Nuclear Information System (INIS)

    Metoki, Naoto

    1995-01-01

    Recent X-ray and neutron surface scattering studies of magnetic metal thin films and superlattices are reviewed. The Fresnel and Master formula for the specular reflectivity of ideal and real surfaces, respectively, are explained. We show some experimental results of X-ray specular reflectivity of Si, Co thin film, and Co/Cr superlattices as well as spin-polarized neutron reflectivity of a non-colinearly coupled Fe/Cr superlattice. A recent surface scattering study of hcp-bcc structural change of Co layers in Co/Cr (001) superlattices is reviewed as an example of this method. (author)

  20. Probing droplets on superhydrophobic surfaces by synchrotron radiation scattering techniques

    KAUST Repository

    Accardo, Angelo

    2014-06-10

    Droplets on artificially structured superhydrophobic surfaces represent quasi contact-free sample environments which can be probed by X-ray microbeams and nanobeams in the absence of obstructing walls. This review will discuss basic surface wettability concepts and introduce the technology of structuring surfaces. Quasi contact-free droplets are compared with contact-free droplets; processes related to deposition and evaporation on solid surfaces are discussed. Droplet coalescence based on the electrowetting effect allows the probing of short-time mixing and reaction processes. The review will show for several materials of biological interest that structural processes related to conformational changes, nucleation and assembly during droplet evaporation can be spatially and temporally resolved by raster-scan diffraction techniques. Orientational ordering of anisotropic materials deposited during solidification at pinning sites facilitates the interpretation of structural data. 2014 International Union of Crystallography.

  1. Measuring the surface-heating of medical ultrasonic probes

    International Nuclear Information System (INIS)

    Kollmann, Chr; Vacariu, G; Fialka-Moser, V; Bergmann, H

    2004-01-01

    Due to converting losses the probe's surface itself is heated up, especially when emitting into air. Possible temperature increases in an ensemble of 15 different diagnostic and therapeutic ultrasound probes from 7 manufacturers in the frequency range between 0.05-7.5 MHz have been examined. Surface temperatures were detected by means of a calibrated IR-thermographic camera using a scheme of various power and pulse settings, as well as different imaging modalitites as used in clinical routine. Depending on the setup and the output power, the absolute surface temperatures of some of the probes emitting in air can be beyond 43 deg. C within 5-7 min.; a maximum surface temperature of 84 deg. C has been detected. Continuous mode or high pulse repetition frequencies on the therapeutic system side, small focused Doppler modes on the diagnostic system side combined with increased emitted acoustic intensities result in high surface temperatures. Within a worst case scenario a potential risk of negative skin changes (heat damage) or non-optimal therapeutic effects seems to be possible if a therapeutic system is used very often and if its emission continues unintentionally. In general the user should be aware that low emission intensities of e.g. 50 mW cm -2 could already produce hot surfaces

  2. Probing the conformation of FhaC with small-angle neutron scattering and molecular modeling.

    Science.gov (United States)

    Gabel, Frank; Lensink, Marc F; Clantin, Bernard; Jacob-Dubuisson, Françoise; Villeret, Vincent; Ebel, Christine

    2014-07-01

    Probing the solution structure of membrane proteins represents a formidable challenge, particularly when using small-angle scattering. Detergent molecules often present residual scattering contributions even at their match point in small-angle neutron scattering (SANS) measurements. Here, we studied the conformation of FhaC, the outer-membrane, β-barrel transporter of the Bordetella pertussis filamentous hemagglutinin adhesin. SANS measurements were performed on homogeneous solutions of FhaC solubilized in n-octyl-d17-βD-glucoside and on a variant devoid of the α helix H1, which critically obstructs the FhaC pore, in two solvent conditions corresponding to the match points of the protein and the detergent, respectively. Protein-bound detergent amounted to 142 ± 10 mol/mol as determined by analytical ultracentrifugation. By using molecular modeling and starting from three distinct conformations of FhaC and its variant embedded in lipid bilayers, we generated ensembles of protein-detergent arrangement models with 120-160 detergent molecules. The scattered curves were back-calculated for each model and compared with experimental data. Good fits were obtained for relatively compact, connected detergent belts, which occasionally displayed small detergent-free patches on the outer surface of the β barrel. The combination of SANS and modeling clearly enabled us to infer the solution structure of FhaC, with H1 inside the pore as in the crystal structure. We believe that our strategy of combining explicit atomic detergent modeling with SANS measurements has significant potential for structural studies of other detergent-solubilized membrane proteins. Copyright © 2014 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  3. Neutron and Gamma Probe Application to Hanford Tank 241-SY-101

    Energy Technology Data Exchange (ETDEWEB)

    CANNON, N.S.

    2000-02-01

    A neutron (moisture-sensitive) and gamma (in-situ radiation) probe technique has been utilized at a number of Hanford radioactive waste tanks for many years. This technology has been adapted for use in tank 241-SY-101's two Multifunction Instrument Trees (MITs) which have a hollow dry-well center opening two inches (51 cm) in diameter. These probes provide scans starting within a few inches of the tank bottom and traversing up through the top of the tank revealing a variety of waste features as a function of tank elevation. These features have been correlated with void fraction data obtained independently from two other devices, the Retained Gas Sampler (RGS) and the Void Fraction Instrument (VFI). The MIT probes offer the advantage of nearly continuous count-rate versus elevation scans and they can be operated significantly more often and at lower cost than temperature probes or the RGS or VFI devices while providing better depth resolution. The waste level in tank 241-SY-101 had been rising at higher rates than expected during 1998 and early 1999 indicating an increasing amount of trapped gas in the waste. The use of the MIT probes has assisted in evaluating changes in crust thickness and level and also in estimating relative changes in gas stored in the crust. This information is important in assuring that the tank remains in a safe configuration and will support safe waste transfer when those operations take place.

  4. Neutron and Gamma Probe Application to Hanford Tank 241-SY-101

    International Nuclear Information System (INIS)

    CANNON, N.S.

    2000-01-01

    A neutron (moisture-sensitive) and gamma (in-situ radiation) probe technique has been utilized at a number of Hanford radioactive waste tanks for many years. This technology has been adapted for use in tank 241-SY-101's two Multifunction Instrument Trees (MITs) which have a hollow dry-well center opening two inches (51 cm) in diameter. These probes provide scans starting within a few inches of the tank bottom and traversing up through the top of the tank revealing a variety of waste features as a function of tank elevation. These features have been correlated with void fraction data obtained independently from two other devices, the Retained Gas Sampler (RGS) and the Void Fraction Instrument (VFI). The MIT probes offer the advantage of nearly continuous count-rate versus elevation scans and they can be operated significantly more often and at lower cost than temperature probes or the RGS or VFI devices while providing better depth resolution. The waste level in tank 241-SY-101 had been rising at higher rates than expected during 1998 and early 1999 indicating an increasing amount of trapped gas in the waste. The use of the MIT probes has assisted in evaluating changes in crust thickness and level and also in estimating relative changes in gas stored in the crust. This information is important in assuring that the tank remains in a safe configuration and will support safe waste transfer when those operations take place

  5. Tendamistat surface accessibility to the TEMPOL paramagnetic probe

    Energy Technology Data Exchange (ETDEWEB)

    Scarselli, Maria; Bernini, Andrea; Segoni, Claudia [Universita di Siena, Dipartimento di Biologia Molecolare and Centro per lo Studio Strutturale di Sistemi Biomolecolari (Italy); Molinari, Henriette [Universita di Verona, Istituto Policattedra (Italy); Esposito, Gennaro [Universita di Udine, Dipartimento di Scienze e Tecnologie Biomediche (Italy); Lesk, Arthur M. [University of Cambridge, Department of Haematology (United Kingdom); Laschi, Franco [Universita di Siena, Dipartimento di Chimica (Italy); Temussi, Pierandrea [Universita di Napoli, Dipartimento di Chimica (Italy); Niccolai, Neri [Universita di Siena, Dipartimento di Biologia Molecolare and Centro per lo Studio Strutturale di Sistemi Biomolecolari (Italy)

    1999-10-15

    TEMPOL, the soluble spin-label 4-hydroxy-2,2,6,6-tetramethyl-piperidine-1-oxyl, has been used to determine the surface characteristics of tendamistat, a small protein with a well-characterised structure both in solution and in the crystal. A good correlation has been found between predicted regions of exposed protein surface and the intensity attenuations induced by the probe on 2D NMR TOCSY cross peaks of tendamistat in the paramagnetic water solution. All the high paramagnetic effects have been interpreted in terms of more efficient competition of TEMPOL with water molecules at some surface positions. The active site of tendamistat coincides with the largest surface patch accessible to the probe. A strong hydration of protein N and C termini can also be suggested by this structural approach, as these locations exhibit reduced paramagnetic perturbations. Provided that the solution structure is known, the use of this paramagnetic probe seems to be well suited to delineate the dynamic behaviour of the protein surface and, more generally, to gain relevant information about the molecular presentation processes.

  6. Measurement of steep aspheric surfaces using an anamorphic probe

    International Nuclear Information System (INIS)

    Biswas, Amiya; Coupland, Jeremy

    2008-01-01

    Synthetic aperture interferometry has been previously proposed as a possible in-process method to measure aspheric form (R. Tomlinson, Appl. Opt.42, 701, 2003.APOPAI0003-693510.1364/AO.42.000701). Preliminary demonstration utilized a scanning probe consisting of a pair of bare single mode fibers to perform source and receive functions. It was found that this probe did not have sufficient numerical aperture (NA) to measure steep surfaces and that simply increasing the NA decreases the light gathering efficiency substantially. In this paper, we introduce supplementary optics to increase the NA, and the light gathering efficiency has been increased by adopting an anamorphic design. A spherical test optic of known form is measured to demonstrate the capability of the new probe design

  7. Measurement of steep aspheric surfaces using an anamorphic probe

    Science.gov (United States)

    Biswas, Amiya; Coupland, Jeremy

    2008-04-01

    Synthetic aperture interferometry has been previously proposed as a possible in-process method to measure aspheric form (R. Tomlinson, Appl. Opt.42, 701, 2003.APOPAI0003-693510.1364/AO.42.000701). Preliminary demonstration utilized a scanning probe consisting of a pair of bare single mode fibers to perform source and receive functions. It was found that this probe did not have sufficient numerical aperture (NA) to measure steep surfaces and that simply increasing the NA decreases the light gathering efficiency substantially. In this paper, we introduce supplementary optics to increase the NA, and the light gathering efficiency has been increased by adopting an anamorphic design. A spherical test optic of known form is measured to demonstrate the capability of the new probe design.

  8. Neutron radiography of aircraft composite flight control surfaces

    International Nuclear Information System (INIS)

    Lewis, W.J.; Bennett, L.G.I.; Chalovich, T.R.; Francescone, O.

    2001-01-01

    A small (20 kWth), safe, pool-type nuclear research reactor called the SLOWPOKE-2 is located at the Royal Military College of Canada (RMC). The reactor was originally installed for teaching, training, research and semi-routine analysis, specifically, neutron activation analysis. It was envisioned that the neutrons from the SLOWPOKE-2 could also be used for neutron radiography, and so a research program was initiated to develop this technology. Over a period of approximately 15 years, and through a series of successive modifications, a neutron radiography system (NRS) was developed. Once completed, several applications of the technology have been demonstrated, including the nondestructive examination of the composite flight control surfaces from the Canadian Air Force's primary jet fighter, the CF18 Hornet aircraft. An initial trial was setup to investigate the flight control surfaces of 3 aircraft, to determine the parameters for a final licensed system, and to compare the results to other nondestructive methods. Over 500 neutron radiographs were made for these first 3 aircraft, and moisture and corrosion were discovered in the honeycomb structure and hydration was found in the composite and adhesive layers. In comparison with other NDT methods, neutron radiography was the only method that could detect the small areas of corrosion and moisture entrapment. However, before examining an additional 7 aircraft, the recommended modifications to the NRS were undertaken. These modifications were necessary to accommodate the larger flight control surfaces safely by incorporating flexible conformable shielding. As well, to expedite inspections so that all flight control surfaces from one aircraft could be completed in less than two weeks, there was a need to decrease the exposure time by both faster film/conversion screen combinations and by incorporating the capability of near realtime, digital radioscopy. Finally, as there are no inspection specific image quality

  9. Probing Extreme-density Matter with Gravitational-wave Observations of Binary Neutron Star Merger Remnants

    Energy Technology Data Exchange (ETDEWEB)

    Radice, David [Institute for Advanced Study, 1 Einstein Drive, Princeton, NJ 08540 (United States); Bernuzzi, Sebastiano [Department of Mathematical, Physical and Computer Sciences, University of Parma, I-43124 Parma (Italy); Pozzo, Walter Del [Dipartimento di Fisica “Enrico Fermi,” Università di Pisa, Pisa I-56127 (Italy); Roberts, Luke F. [NSCL/FRIB and Department of Physics and Astronomy, Michigan State University, 640 S Shaw Lane, East Lansing, MI 48824 (United States); Ott, Christian D. [TAPIR, Walter Burke Institute for Theoretical Physics, California Institute of Technology, 1200 E. California Boulevard, Pasadena, CA 91125 (United States)

    2017-06-20

    We present a proof-of-concept study, based on numerical-relativity simulations, of how gravitational waves (GWs) from neutron star merger remnants can probe the nature of matter at extreme densities. Phase transitions and extra degrees of freedom can emerge at densities beyond those reached during the inspiral, and typically result in a softening of the equation of state (EOS). We show that such physical effects change the qualitative dynamics of the remnant evolution, but they are not identifiable as a signature in the GW frequency, with the exception of possible black hole formation effects. The EOS softening is, instead, encoded in the GW luminosity and phase and is in principle detectable up to distances of the order of several megaparsecs with advanced detectors and up to hundreds of megaparsecs with third-generation detectors. Probing extreme-density matter will require going beyond the current paradigm and developing a more holistic strategy for modeling and analyzing postmerger GW signals.

  10. Molecular Tension Probes for Imaging Forces at the Cell Surface.

    Science.gov (United States)

    Liu, Yang; Galior, Kornelia; Ma, Victor Pui-Yan; Salaita, Khalid

    2017-12-19

    Mechanical forces are essential for a variety of biological processes ranging from transcription and translation to cell adhesion, migration, and differentiation. Through the activation of mechanosensitive signaling pathways, cells sense and respond to physical stimuli from the surrounding environment, a process widely known as mechanotransduction. At the cell membrane, many signaling receptors, such as integrins, cadherins and T- or B-cell receptors, bind to their ligands on the surface of adjacent cells or the extracellular matrix (ECM) to mediate mechanotransduction. Upon ligation, these receptor-ligand bonds transmit piconewton (pN) mechanical forces that are generated, in part, by the cytoskeleton. Importantly, these forces expose cryptic sites within mechanosensitive proteins and modulate the binding kinetics (on/off rate) of receptor-ligand complexes to further fine-tune mechanotransduction and the corresponding cell behavior. Over the past three decades, two categories of methods have been developed to measure cell receptor forces. The first class is traction force microscopy (TFM) and micropost array detectors (mPADs). In these methods, cells are cultured on elastic polymers or microstructures that deform under mechanical forces. The second category of techniques is single molecule force spectroscopy (SMFS) including atomic force microscopy (AFM), optical or magnetic tweezers, and biomembrane force probe (BFP). In SMFS, the experimenter applies external forces to probe the mechanics of individual cells or single receptor-ligand complexes, serially, one bond at a time. Although these techniques are powerful, the limited throughput of SMFS and the nN force sensitivity of TFM have hindered further elucidation of the molecular mechanisms of mechanotransduction. In this Account, we introduce the recent advent of molecular tension fluorescence microscopy (MTFM) as an emerging tool for molecular imaging of receptor mechanics in living cells. MTFM probes are

  11. Surface acoustic wave probe implant for predicting epileptic seizures

    Science.gov (United States)

    Gopalsami, Nachappa [Naperville, IL; Kulikov, Stanislav [Sarov, RU; Osorio, Ivan [Leawood, KS; Raptis, Apostolos C [Downers Grove, IL

    2012-04-24

    A system and method for predicting and avoiding a seizure in a patient. The system and method includes use of an implanted surface acoustic wave probe and coupled RF antenna to monitor temperature of the patient's brain, critical changes in the temperature characteristic of a precursor to the seizure. The system can activate an implanted cooling unit which can avoid or minimize a seizure in the patient.

  12. Surface potential modeling and reconstruction in Kelvin probe force microscopy.

    Science.gov (United States)

    Xu, Jie; Wu, Yangqing; Li, Wei; Xu, Jun

    2017-09-08

    Kelvin probe force microscopy (KPFM) measurement has been extensively applied in metallic, semiconductor and organic electronic or photovoltaic devices, to characterize the local contact potential difference or surface potential of the samples at the nanoscale. Here, a comprehensive modeling of surface potential in KPFM is established, from the well-known single capacitance model to a precise electrodynamic model, considering the long range property of the electrostatic force in KPFM. The limitations and relations of different models are also discussed. Besides, the feedback condition of the KPFM system is reconsidered and modified, showing that the influence of the cantilever has been overestimated by about 20% in previous reports. Afterwards, the surface potential of charged Si-nanocrystals is reconstructed based on the electrodynamic model, and the calculated surface charge density is very consistent with the macroscopic capacitance-voltage (C-V) measurement. A deep understanding and correct reconstruction of surface potential is crucial to the quantitative analysis of KPFM results.

  13. Portable gamma and thermal neutron probe using a {sup 6}LiI(Eu) crystal

    Energy Technology Data Exchange (ETDEWEB)

    Carneiro, Clemente J.G.; Araujo, Geraldo P.; Milian, Felix M.; Barbosa, Jurandir C.; Garcia, Fermin [Universidade Estadual de Santa Cruz (UESC), Ilheus, BA (Brazil). Centro de Pesquisas em Ciencias e Tecnologias das Radiacoes (CPqCTR); Oliveira, Arno H.; Silva, Mario R.S.; Penna, Rodrigo [Universidade Federal de Minas Gerais (DEN-UFMG), Belo Horizonte, MG (Brazil). Dept. de Engenharia Nuclear

    2011-07-01

    Europium-activated lithium-6 iodide is a scintillator used for gamma and neutron counting. A portable detection system was built based on this scintillator. This system has three modules: the scintillator, a 10 m liquid light guide, and a Hamamatsu photon counting head H9319 used as a light pulse digitizer. Data transfer, measurement time and other necessary adjustment can be controlled by software from the PC through the RS-232C interface. The scintillator, a crystal of {sup 6}LiI(Eu), is a small cylinder with 3 mm diameter and 40 mm length completely sealed in an aluminum tube coupled to the light guide. The small size of the scintillator increases the neutron/gamma count ratio, since 2 to 3 mm of thickness of this crystal absorbs all thermal neutrons. Intensities of X and gamma rays, and thermal neutrons can be recorded for time intervals of 10 ms to 1 s storing up to 10000 countings. The system was calibrated for measuring radiation doses for validating numerical models in dosimetry. Two characteristic reinforce this application, measurements can be done at several meters away from the radiation source and also inside of water. In addition, it was used to build nuclear probes based on Compton scattering or neutron moderation in porous media by attaching an AmBe source to the top of the aluminum tube. Tests were done to determine the reproducibility of counting rates. Background counting was measured at several temperatures to verify the influence of dark current of PMT. Sealed AmBe, low activity Am, and X rays sources were used for studies of radiation counting statistics. X rays apparatus was used to correlate counting rates measured with the {sup 6}LiI(Eu) detection system and doses measured with an ionization chamber at several distances from the X ray source. (author)

  14. Portable gamma and thermal neutron probe using a 6LiI(Eu) crystal

    International Nuclear Information System (INIS)

    Carneiro, Clemente J.G.; Araujo, Geraldo P.; Milian, Felix M.; Barbosa, Jurandir C.; Garcia, Fermin; Oliveira, Arno H.; Silva, Mario R.S.; Penna, Rodrigo

    2011-01-01

    Europium-activated lithium-6 iodide is a scintillator used for gamma and neutron counting. A portable detection system was built based on this scintillator. This system has three modules: the scintillator, a 10 m liquid light guide, and a Hamamatsu photon counting head H9319 used as a light pulse digitizer. Data transfer, measurement time and other necessary adjustment can be controlled by software from the PC through the RS-232C interface. The scintillator, a crystal of 6 LiI(Eu), is a small cylinder with 3 mm diameter and 40 mm length completely sealed in an aluminum tube coupled to the light guide. The small size of the scintillator increases the neutron/gamma count ratio, since 2 to 3 mm of thickness of this crystal absorbs all thermal neutrons. Intensities of X and gamma rays, and thermal neutrons can be recorded for time intervals of 10 ms to 1 s storing up to 10000 countings. The system was calibrated for measuring radiation doses for validating numerical models in dosimetry. Two characteristic reinforce this application, measurements can be done at several meters away from the radiation source and also inside of water. In addition, it was used to build nuclear probes based on Compton scattering or neutron moderation in porous media by attaching an AmBe source to the top of the aluminum tube. Tests were done to determine the reproducibility of counting rates. Background counting was measured at several temperatures to verify the influence of dark current of PMT. Sealed AmBe, low activity Am, and X rays sources were used for studies of radiation counting statistics. X rays apparatus was used to correlate counting rates measured with the 6 LiI(Eu) detection system and doses measured with an ionization chamber at several distances from the X ray source. (author)

  15. Use of Neutron Probe to Quantify the Soil Moisture Flux in Layers of Cultivated Soil by Chickpea

    International Nuclear Information System (INIS)

    El- Gendy, R.W.

    2008-01-01

    This work aims to use the neutron moisture meter and the soil moisture retention curve to quantify the soil moisture flux in the soil profile of Nubarria soil in Egypt at 15, 30, 45, and 60-cm depths during the growth season of Chickpea. This method depends on the use of in situ θ measurements via neutron moisture meter and soil matric suction using model of the soil moisture retention curve at different soil depths, which can be determined in situ. Total hydraulic potential values at the different soil depths were calculated as a function (θ) using the derivative model. The gradient of hydraulic potential at any soil depth can be obtained by detecting of the hydraulic potential within the soil profile. The soil water fluxes at the different soil depths were calculated using In situ measured unsaturated hydraulic conductivity and the gradient of hydraulic potential, which correlated with soil moisture contents as measured by neutron probe. Values of hydraulic potentials after and before irrigation indicate that the direction of soil moisture movement was downward after irrigation and was different before next irrigation. Collecting active roots for water absorption of chickpea were defined from direction of soil water movement from up and down to a certain soil depth was 19 cm depth from the soil surface. Active rooting depth was 53 cm depth, which separates between evapotranspiration and gravity effects The soil water fluxes after and before the next irrigation of chickpea were 1.2453, 0.8613, 0.8197 and 0.6588 cm/hr and 0.0037, - 0.0270,- 0.1341, and 0.2545 cm/hr at 15, 30, 45 and 60 cm depths, respectively. The negative values at 30 and 45 cm depth before the next irrigation indicates there were up ward movement for soil water flux, where finding collecting active roots for water absorption of chickpea at 19 cm depth. Direction of soil water movement, soil water flux, collecting active roots for water absorption and active rooting depth can be determined using

  16. Surface physics with cold and thermal neutron reflectometry

    International Nuclear Information System (INIS)

    Steyerl, A.

    1991-11-01

    Three aspects of the research project ''Surface physics with cold and ultracold neutron reflectometry'' were stressed during the present first year: (1) Setup of the reflectometer facility at the research reactor of the Rhode Island Nuclear Science Center. The installation provides a narrow ''pencil beam'' analyzed by time of flight using a chopper system. Following beam characterization and a test measurement of the total cross section of copper single crystal first reflectivity measurements are currently performed using a supermirror. (2) Design stud for the ultracold neutron imaging system, with involvement of the relevant industry. Bids are available for several components indicating that it will be very difficult to build the entire system unless further funds become available. (3) Analysis of features of neutron reflection from surfaces with special emphasis on the effect of surface roughness both on the specular beam and the diffusely reflected and refracted intensity. Previous theoretical studies were supplemented by further numerical calculations of diffuse scattering distributions using different models. Application of ultracold and cold neutron reflectometry to the study of liquid-vapor phase transition were discussed. The theoretical work also includes the development of tentative ideas for novel fundamental physics experiments

  17. Measurement of soil water content using TDR and the neutron probe in tillage experiments in semi-arid SW Spain

    International Nuclear Information System (INIS)

    Moreno, F.; Pelegrin, F.; Fernandez, J.E.; Murillo, J.M.

    2000-01-01

    Some examples of soil water content measurements using Time Domain Reflectrometry (TDR) and the neutron probe are presented in this paper. The data are from experiments on water recharge and water conservation in the soil profile under different tillage methods. TDR is a useful technique with which to follow changes of soil water content in the top soil layers. Under sunflower, measurements showed differences in soil water content within and between the plant rows. Measurements with the neutron probe showed changes of soil water content profile down to a depth of 2 m. Soil water profile recharge and water depletion by the sunflower crop were established from measurements with both techniques. The combined use of TDR and neutron probe is very appropriate to establish the soil water balance in such experiments. (author)

  18. Neutron physics

    International Nuclear Information System (INIS)

    Beckurts, K.H.; Wirtz, K.

    1974-01-01

    This textbook consists of four sections which deal with the following subjects: 1. Production of neutrons and their interactions with the nuclei; neutron sources; neutron detectors; cross-section measurements. 2. Theory of neutron interactions with macroscopic media; neutron slowing down; space distribution of moderated neutrons; neutron thermalization; neutron scattering. 3. Radioactive probe measurements of thermal neutron fluxes; activation by means of epithermal neutrons; threshold detectors of fast neutrons; neutron calibration. 4. Neutron energy; slowing down kernels; neutron age; diffusion length and absorption of neutrons

  19. Measuring surface temperature of isolated neutron stars and related problems

    Science.gov (United States)

    Teter, Marcus Alton

    New and exciting results for measuring neutron star surface temperatures began with the successful launch of the Chandra X-ray observatory. Among these results are new detections of neutron star surface temperatures which have made it possible to seriously test neutron star thermal evolution theories. The important new temperature determination of the Vela pulsar (Pavlov, et al., 2001a) requires a non-standard cooling scenario to explain it. Apart from this result, we have measured PSR B1055-52's surface temperature in this thesis, determining that it can be explained by standard cooling with heating. Our spectral fit of the combined data from ROSAT and Chandra have shown that a three component model, two thermal blackbodies and an non-thermal power-law, is required to explain the data. Furthermore, our phase resolved spectroscopy has begun to shed light on the geometry of the hot spot on PSR B1055-52's surface as well as the structure of the magnetospheric radiation. Also, there is strong evidence for a thermal distribution over its surface. Most importantly, the fact that PSR B1055-52 does not have a hydrogen atmosphere has been firmly established. To reconcile these two key observations, on the Vela pulsar and PSR B1055-52, we tested neutron star cooling with neutrino processes including the Cooper pair neutrino emission process. Overall, it has been found that a phase change associated with pions being present in the cores of more massive neutron stars explains all current of the data. A transition from neutron matter to pion condensates in the central stellar core explains the difference between standard and non-standard cooling scenarios, because the superfluid suppression of pion cooling will reduce the emissivity of the pion direct URCA process substantially. A neutron star with a mass of [Special characters omitted.] with a medium stiffness equation of state and a T72 type neutron superfluid models the standard cooling case well. A neutron star of [Special

  20. Extremal surfaces as bulk probes in AdS/CFT

    Science.gov (United States)

    Hubeny, Veronika E.

    2012-07-01

    Motivated by the need for further insight into the emergence of AdS bulk spacetime from CFT degrees of freedom, we explore the behaviour of probes represented by specific geometric quantities in the bulk. We focus on geodesics and n-dimensional extremal surfaces in a general static asymptotically AdS spacetime with spherical and planar symmetry, respectively. While our arguments do not rely on the details of the metric, we illustrate some of our findings explicitly in spacetimes of particular interest (specifically AdS, Schwarzschild-AdS and extreme Reissner-Nordstrom-AdS). In case of geodesics, we find that for a fixed spatial distance between the geodesic endpoints, spacelike geodesics at constant time can reach deepest into the bulk. We also present a simple argument for why, in the presence of a black hole, geodesics cannot probe past the horizon whilst anchored on the AdS boundary at both ends. The reach of an extremal n-dimensional surface anchored on a given region depends on its dimensionality, the shape and size of the bounding region, as well as the bulk metric. We argue that for a fixed extent or volume of the boundary region, spherical regions give rise to the deepest reach of the corresponding extremal surface. Moreover, for physically sensible spacetimes, at fixed extent of the boundary region, higher-dimensional surfaces reach deeper into the bulk. Finally, we show that in a static black hole spacetime, no extremal surface (of any dimensionality, anchored on any region in the boundary) can ever penetrate the horizon.

  1. Probing and Mapping Electrode Surfaces in Solid Oxide Fuel Cells

    Science.gov (United States)

    Blinn, Kevin S.; Li, Xiaxi; Liu, Mingfei; Bottomley, Lawrence A.; Liu, Meilin

    2012-01-01

    Solid oxide fuel cells (SOFCs) are potentially the most efficient and cost-effective solution to utilization of a wide variety of fuels beyond hydrogen 1-7. The performance of SOFCs and the rates of many chemical and energy transformation processes in energy storage and conversion devices in general are limited primarily by charge and mass transfer along electrode surfaces and across interfaces. Unfortunately, the mechanistic understanding of these processes is still lacking, due largely to the difficulty of characterizing these processes under in situ conditions. This knowledge gap is a chief obstacle to SOFC commercialization. The development of tools for probing and mapping surface chemistries relevant to electrode reactions is vital to unraveling the mechanisms of surface processes and to achieving rational design of new electrode materials for more efficient energy storage and conversion2. Among the relatively few in situ surface analysis methods, Raman spectroscopy can be performed even with high temperatures and harsh atmospheres, making it ideal for characterizing chemical processes relevant to SOFC anode performance and degradation8-12. It can also be used alongside electrochemical measurements, potentially allowing direct correlation of electrochemistry to surface chemistry in an operating cell. Proper in situ Raman mapping measurements would be useful for pin-pointing important anode reaction mechanisms because of its sensitivity to the relevant species, including anode performance degradation through carbon deposition8, 10, 13, 14 ("coking") and sulfur poisoning11, 15 and the manner in which surface modifications stave off this degradation16. The current work demonstrates significant progress towards this capability. In addition, the family of scanning probe microscopy (SPM) techniques provides a special approach to interrogate the electrode surface with nanoscale resolution. Besides the surface topography that is routinely collected by AFM and STM

  2. Cholesterol solubility limit in lipid membranes probed by small angle neutron scattering and MD simulations.

    Science.gov (United States)

    Garg, Sumit; Castro-Roman, Francisco; Porcar, Lionel; Butler, Paul; Bautista, Pedro Jesus; Krzyzanowski, Natalie; Perez-Salas, Ursula

    2014-12-14

    The solubility limits of cholesterol in small unilamellar vesicles made of POPS and POPC were probed using Small Angle Neutron Scattering (SANS) and coarse grained (CG) molecular dynamics (MD) simulations. SANS, being non-invasive, allowed the direct and quantitative measurement of cholesterol in intact vesicles. Our experimental measurements reveal a 61% mole fraction solubility limit of cholesterol in POPC, consistent with previous studies. However, in POPS the solubility limit of cholesterol is found to be 73% mole fraction. Previous work reports solubility limits of cholesterol in POPS varying significantly, ranging from 36% up to 66%. The CG MD simulations are in remarkable quantitative agreement with our experimental results showing similar solubility limits. Further, neither experiments nor simulations show evidence of stable nanodomains of cholesterol in POPS membranes as suggested in some previous reports.

  3. Diffuse reflection of ultracold neutrons from low-roughness surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Atchison, F.; Daum, M.; Henneck, R.; Horisberger, M.; Kirch, K.; Lauss, B.; Mtchedlishvili, A.; Meier, M.; Petzoldt, G.; Schelldorfer, R.; Zsigmond, G. [Paul Scherrer Institut, PSI, Villigen (Switzerland); Heule, S.; Knecht, A. [Paul Scherrer Institut, PSI, Villigen (Switzerland); University Zuerich, Zuerich (Switzerland); Kasprzak, M. [Paul Scherrer Institut, PSI, Villigen (Switzerland); Stefan Meyer Institut, Vienna (Austria); Kuzniak, M. [Paul Scherrer Institut, PSI, Villigen (Switzerland); Jagiellonian University, Smoluchowski Institute of Physics, Cracow (Poland); Plonka-Spehr, C. [Institut Laue Langevin, ILL, Grenoble (France); Straumann, U. [University Zuerich, Zuerich (Switzerland)

    2010-04-15

    We report a measurement of the reflection of ultracold neutrons from flat, large-area plates of different Fermi potential materials with low surface roughness. The results were used to test two diffuse reflection models, the well-known Lambert model and the micro-roughness model which is based on wave scattering. The Lambert model fails to reproduce the diffuse reflection data. The surface roughness b and correlation length w, obtained by fitting the micro-roughness model to the data are in the range 1{<=}b{<=}3 nm and 10{<=}w{<=}120 nm, in qualitative agreement with independent measurements using atomic force microscopy. (orig.)

  4. Diffuse reflection of ultracold neutrons from low-roughness surfaces

    International Nuclear Information System (INIS)

    Atchison, F.; Daum, M.; Henneck, R.; Horisberger, M.; Kirch, K.; Lauss, B.; Mtchedlishvili, A.; Meier, M.; Petzoldt, G.; Schelldorfer, R.; Zsigmond, G.; Heule, S.; Knecht, A.; Kasprzak, M.; Kuzniak, M.; Plonka-Spehr, C.; Straumann, U.

    2010-01-01

    We report a measurement of the reflection of ultracold neutrons from flat, large-area plates of different Fermi potential materials with low surface roughness. The results were used to test two diffuse reflection models, the well-known Lambert model and the micro-roughness model which is based on wave scattering. The Lambert model fails to reproduce the diffuse reflection data. The surface roughness b and correlation length w, obtained by fitting the micro-roughness model to the data are in the range 1≤b≤3 nm and 10≤w≤120 nm, in qualitative agreement with independent measurements using atomic force microscopy. (orig.)

  5. Structural Formation of Huntingtin Exon 1 Aggregates Probed by Small-Angle Neutron Scattering

    Science.gov (United States)

    Stanley, Christopher B.; Perevozchikova, Tatiana; Berthelier, Valerie

    2011-01-01

    In several neurodegenerative disorders, including Huntington's disease, aspects concerning the earliest of protein structures that form along the aggregation pathway have increasingly gained attention because these particular species are likely to be neurotoxic. We used time-resolved small-angle neutron scattering to probe in solution these transient structures formed by peptides having the N-terminal sequence context of mutant huntingtin exon 1. We obtained snapshots of the formed aggregates as the kinetic reaction ensued to yield quantitative information on their size and mass. At the early stage, small precursor species with an initial radius of gyration of 16.1 ± 5.9 Å and average mass of a dimer to trimer were monitored. Structural growth was treated as two modes with a transition from three-dimensional early aggregate formation to two-dimensional fibril growth and association. Our small-angle neutron scattering results on the internal structure of the mature fibrils demonstrate loose packing with ∼1 peptide per 4.75 Å β-sheet repeat distance, which is shown to be quantitatively consistent with a β-helix model. This research provides what we believe to be new insights into the structures forming along the pathway of huntingtin exon 1 aggregation and should assist in determining the role that precursors play in neuronal toxicity. PMID:21575585

  6. On the control of irrigation through soil moisture measurement using a neutron depth probe in horizontal subsurface measuring circuits

    International Nuclear Information System (INIS)

    Schaecke, B.; Schaecke, E.

    1977-01-01

    An outline is given of the advantages inherent in soil moisture measurement by means of a neutron probe in horizontal subsurface measuring circuits for irrigation control. Preliminary experience for the setting up of a field calibration curve and for practical measurement are submitted. This technique includes the following advantages: almost complete covering of the upper soil range which is of interest to irrigation control; good measuring density; suitable distribution of measuring points per unit area; possibility of continuous probe passage; optimal repeatability of measurements; exploration of a unit area with but few measuring circuits; no obstacles to tillage, drilling, intercultivation and harvest operations; and complete conservation of crop and plot which is not reached with any other soil moisture measurement technique so far available. Making use of the above advantages, the new technique allows automatic irrigation control with only one neutron depth probe. (author)

  7. Astronomers Use X-Rays To Probe Gravitational Field Of A Neutron Star

    Science.gov (United States)

    2002-06-01

    With NASA's Chandra X-ray Observatory, astronomers have detected features that may be the first direct evidence of the effect of gravity on radiation from a neutron star. This finding, if confirmed, could enable scientists to measure the gravitational field of neutron stars and determine whether they contain exotic forms of matter not seen on Earth. A team led by George Pavlov of Penn State University in University Park observed 1E 1207.4-5209, a neutron star in the center of a supernova remnant about 7,000 light years from Earth. The results were presented on June 6, 2002, at the American Astronomical Society in Albuquerque, NM. Pavlov's group found two dips, or absorption features, in the spectrum of X-rays from the star. If these dips are due to the absorption of X-rays near the star by helium ions in a strong magnetic field, they indicate that the gravitational field reduces the energies of X-rays escaping from near the surface of a neutron star. "This interpretation is consistent with the data," said Pavlov, "but the features may be a blend of many other features. More precise measurements, preferably with Chandra's grating spectrometer, are needed." "These absorption features may be the first evidence of the effect of gravity on radiation near the surface of an isolated neutron star," said Pavlov. "This is particularly important because it would allow us to set limits on the type of matter that comprises this star." Neutron stars are formed when a massive star runs out of fuel and its core collapses. A supernova explosion occurs and the collapsed core is compressed to a hot object about 12 miles in diameter, with a thin atmosphere of hydrogen and possibly heavier ions in a gravitational field 100 billion times as strong as Earth's. These objects, which have a density of more than 1 billion tons per teaspoonful, are called neutron stars because they have been thought to be composed mostly of neutrons. Although neutron stars have been studied extensively for

  8. Numerical simulation of directivity for angle probe and surface defect

    International Nuclear Information System (INIS)

    Nam, Young Hyun

    1995-01-01

    An ultrasonic testing uses the directivity of the ultrasonic wave which propagates in one direction. The directivity is expressed as the relationship between the propagate direction and i ts sound pressure. This paper studied the directivity of shear waves emitted from angle probes and scattered from surface defects by using visualization method. These experimental results were compared with the theory which was based on the continuous wave. The applicability of continuous wave theory was discussed in terms of the parameter d/λ where d is transducer or defect size and λ is the wavelength. In the case of angle probes, the experimental results show good agreement with theoretical directivity on the principal lobe. When defect size was smaller than the wavelengths, clear directivity in the reflected wave was observed. In the case of the same ratio of defect size to wavelength, the directivity of reflected waves from the defect show almost the same directivity in spite of frequency differences. When the d/λ is greater than 1.5, measured directivities almost agreed with the theoretical one.

  9. Quantitatively Probing the Means of Controlling Nanoparticle Assembly on Surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Patete, J.m.; Wong, S.; Peng, X.; Serafin, J.M.

    2011-05-17

    As a means of developing a simple, cost-effective, and reliable method for probing nanoparticle behavior, we have used atomic force microscopy to gain a quantitative 3D visual representation of the deposition patterns of citrate-capped Au nanoparticles on a substrate as a function of (a) sample preparation, (b) the choice of substrate, (c) the dispersion solvent, and (d) the number of loading steps. Specifically, we have found that all four parameters can be independently controlled and manipulated in order to alter the resulting pattern and quantity of as-deposited nanoparticles. From these data, the sample preparation technique appears to influence deposition patterns most broadly, and the dispersion solvent is the most convenient parameter to use in tuning the quantity of nanoparticles deposited onto the surface under spin-coating conditions. Indeed, we have quantitatively measured the effect of surface coverage for both mica and silicon substrates under preparation techniques associated with (i) evaporation under ambient air, (ii) heat treatment, and (iii) spin-coating preparation conditions. In addition, we have observed a decrease in nanoparticle adhesion to a substrate when the ethylene glycol content of the colloidal dispersion solvent is increased, which had the effect of decreasing interparticle-substrate interactions. Finally, we have shown that substrates prepared by these diverse techniques have potential applicability in surface-enhanced Raman spectroscopy.

  10. Quantitatively Probing the Means of Controlling Nanoparticle Assembly on Surfaces

    International Nuclear Information System (INIS)

    Patete, J.M.; Wong, S.; Peng, X.; Serafin, J.M.

    2011-01-01

    As a means of developing a simple, cost-effective, and reliable method for probing nanoparticle behavior, we have used atomic force microscopy to gain a quantitative 3D visual representation of the deposition patterns of citrate-capped Au nanoparticles on a substrate as a function of (a) sample preparation, (b) the choice of substrate, (c) the dispersion solvent, and (d) the number of loading steps. Specifically, we have found that all four parameters can be independently controlled and manipulated in order to alter the resulting pattern and quantity of as-deposited nanoparticles. From these data, the sample preparation technique appears to influence deposition patterns most broadly, and the dispersion solvent is the most convenient parameter to use in tuning the quantity of nanoparticles deposited onto the surface under spin-coating conditions. Indeed, we have quantitatively measured the effect of surface coverage for both mica and silicon substrates under preparation techniques associated with (i) evaporation under ambient air, (ii) heat treatment, and (iii) spin-coating preparation conditions. In addition, we have observed a decrease in nanoparticle adhesion to a substrate when the ethylene glycol content of the colloidal dispersion solvent is increased, which had the effect of decreasing interparticle-substrate interactions. Finally, we have shown that substrates prepared by these diverse techniques have potential applicability in surface-enhanced Raman spectroscopy.

  11. Probing the Hydrogen Sublattice of FeHx with High-Pressure Neutron Diffraction

    Science.gov (United States)

    Murphy, C. A.; Guthrie, M.; Boehler, R.; Somayazulu, M.; Fei, Y.; Molaison, J.; dos Santos, A. M.

    2013-12-01

    The combination of seismic, cosmochemical, and mineral physics observations have revealed that Earth's iron-rich core must contain some light elements, such as hydrogen, carbon, oxygen, silicon, and/or sulfur. Therefore, understanding the influence of these light elements on the structural, thermoelastic, and electronic properties of iron is important for constraining the composition of this remote layer of the Earth and, in turn, providing constraints on planetary differentiation and core formation models. The high-pressure structural and magnetic properties of iron hydride (FeHx) have previously been studied using synchrotron x-ray diffraction and Mössbauer spectroscopy. Such experiments revealed that the double hexagonal close-packed (dhcp) structure of FeHx is stable above a pressure of ~5 GPa and up to at least 80 GPa at 300 K [1]. In addition, dhcp-FeHx is ferromagnetic at low-pressures, but undergoes a magnetic collapse around 22 GPa [2]. X-ray experiments provide valuable insight into the properties of FeHx, but such techniques are largely sensitive to the iron component because it is difficult to detect the hydrogen sublattice with x-rays. Therefore, neutron diffraction has been used to investigate metastable FeHx, which is formed by quenching the high-pressure phase to liquid nitrogen temperatures and probing the sample at ambient pressure [3]. However, such neutron experiments have been limited to formation pressures below 10 GPa, and cannot be performed at ambient temperature. Here we present the first in-situ investigation of FeHx at 300 K using high-pressure neutron diffraction experiments performed at the Spallation Neutrons and Pressure Diffractometer (SNAP) instrument at the Spallation Neutron Source, Oak Ridge National Laboratory. In order to achieve pressures of ~50 GPa, we loaded iron samples with a hydrogen gas pressure medium into newly designed large-volume panoramic diamond-anvil cells (DACs) for neutron diffraction experiments [4; 5]. We

  12. Direct measurement of surface-state conductance by microscopic four-point probe method

    DEFF Research Database (Denmark)

    Hasegawa, S.; Shiraki, I.; Tanikawa, T.

    2002-01-01

    For in situ measurements of local electrical conductivity of well defined crystal surfaces in ultrahigh vacuum, we have developed microscopic four-point probes with a probe spacing of several micrometres, installed in a scanning-electron - microscope/electron-diffraction chamber. The probe...

  13. Surface roughness effect on ultracold neutron interaction with a wall and implications for computer simulations

    OpenAIRE

    Steyerl, A.; Malik, S. S.; Desai, A. M.; Kaufman, C.

    2009-01-01

    We review the diffuse scattering and the loss coefficient in ultracold neutron reflection from slightly rough surfaces, report a surprising reduction in loss coefficient due to roughness, and discuss the possibility of transition from quantum treatment to ray optics. The results are used in a computer simulation of neutron storage in a recent neutron lifetime experiment that re-ported a large discrepancy of neutron lifetime with the current particle data value. Our partial re-analysis suggest...

  14. Structural formation of huntingtin-like aggregates probed by small-angle neutron scattering

    Energy Technology Data Exchange (ETDEWEB)

    Stanley, Christopher B [ORNL; Perevozchikova, Tatiana [ORNL; Berthelier-Jung, Valerie M [ORNL

    2011-01-01

    In several neurodegenerative disorders, including Huntington s disease (HD), aspects concerning the earliest of protein structures that form along the aggregation pathway have increasingly gained attention since these particular species are likely to be neurotoxic. We used time-resolved small-angle neutron scattering (SANS) to probe in solution these transient structures formed by peptides having the N-terminal sequence context of mutant huntingtin (Htt) exon 1. We obtained snapshots of the formed aggregates as the kinetic reaction ensued to yield quantitative information on their size and mass. At the early stage, small precursor species with an initial radius of gyration (Rg) of 16.1 5.9 and average mass of a dimer to trimer were monitored. Structural growth was treated as two modes with a transition from three-dimensional early aggregate formation to two-dimensional fibril growth and association. Our SANS results on the internal structure of the mature fibrils demonstrate loose packing with about 1 peptide per 4.75 -sheet repeat distance, which is shown to be quantitatively consistent with a -helix model. This research provides new insights into the structures forming along the pathway of Htt exon 1 aggregation and should assist in determining the role that precursors play in neuronal toxicity.

  15. Probing altered hematopoietic progenitors of preleukemic dogs with JANUS fission neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Seed, T.M.; Kaspar, L.V.

    1990-01-01

    Toward the goal of developing basic insights to mechanisms of radiation leukemogenesis, the authors have developed a canine model that responds to protracted courses of low-daily-dose gamma irradiation with high incidences of myeloproliferative disease (MPD), principally myeloid leukemia. Using this model system, the authors have identified and partially characterized a four-phase preclinical sequence in the induction of MPD, including (1) suppression, (2) recovery, (3) accommodation, and (4) preleukemic transition. Further, they have identified within this sequence, a critical early hematopoietic target cell event that appears to promote progression of the initial preclinical phase to the second preclinical phase. This key target cell event is characterized by the acquisition of increased radioresistance to low-LET gamma rays by granulocyte/monocyte-committed progenitors (CFU-GM). In order to gain further insight into the basis of this critical event, the acquired survival responses of preleukemic progenitors have been probed in vitro with high-LET fission neutrons. 23 refs., 4 figs., 1 tab.

  16. Probing altered hematopoietic progenitors of preleukemic dogs with JANUS fission neutrons

    International Nuclear Information System (INIS)

    Seed, T.M.; Kaspar, L.V.

    1990-01-01

    Toward the goal of developing basic insights to mechanisms of radiation leukemogenesis, the authors have developed a canine model that responds to protracted courses of low-daily-dose gamma irradiation with high incidences of myeloproliferative disease (MPD), principally myeloid leukemia. Using this model system, the authors have identified and partially characterized a four-phase preclinical sequence in the induction of MPD, including (1) suppression, (2) recovery, (3) accommodation, and (4) preleukemic transition. Further, they have identified within this sequence, a critical early hematopoietic target cell event that appears to promote progression of the initial preclinical phase to the second preclinical phase. This key target cell event is characterized by the acquisition of increased radioresistance to low-LET gamma rays by granulocyte/monocyte-committed progenitors (CFU-GM). In order to gain further insight into the basis of this critical event, the acquired survival responses of preleukemic progenitors have been probed in vitro with high-LET fission neutrons. 23 refs., 4 figs., 1 tab

  17. Acceptance and operational test procedure for neutron and gamma probe application to tank 241-SY-101 MITs

    Energy Technology Data Exchange (ETDEWEB)

    CANNON, N.S.

    1999-06-02

    This ATP/OTP provides procedures for testing to be performed to verify that newly procured neutron and gamma probes (reduced diameter design modifications) for operation in the Tank 241-SY-101 MlTs are compatible with existing LOW van instrumentation and hardware. A set of moisture data versus elevation will be obtained from the Tank 241-SY-101 MITs, and (optionally) from the Tank 241-AX-I01 LOW as part of this testing program.

  18. Water dynamics in a lithium chloride aqueous solution probed by Brillouin neutron and x-ray scattering.

    Science.gov (United States)

    Mamontov, E; De Francesco, A; Formisano, F; Laloni, A; Sani, L; Leu, B M; Said, A H; Kolesnikov, A I

    2012-02-15

    We studied the collective excitations in an aqueous solution of lithium chloride over the temperature range of 270-205 K using neutron and x-ray Brillouin scattering. Both neutron and x-ray experiments revealed the presence of low- and high-frequency excitations, similar to the low- and high-frequency excitations in pure water. These two excitations were detectable through the entire temperature range of the experiment, at all probed values of the scattering momentum transfer (0.2 Å(-1) temperature range was investigated using elastic intensity neutron and x-ray scans. Clear evidence of the crossover in the dynamics of the water molecules in the solution was observed in the single-particle relaxational dynamics on the µeV (nanosecond) time scale, but not in the collective dynamics on the meV (picosecond) time scale.

  19. Neutron activation probe for measuring the presence of uranium in ore bodies

    International Nuclear Information System (INIS)

    Goldstein, N.P.; Smith, R.C.

    1979-01-01

    A neutron activation proble comprises a pulsed neutron source in series with a plurality of delayed neutron detectors for measuring radioactivity in a well borehole together with a NaI (Tl) counter for measuring the high energy 2.62 MeV gamma line from thorium. The neutron source emits neutrons which produce fission in uranium and thorium in the ore body and the delayed neutron detectors measure the delayed neutrons produced from such fission while the NaI (Tl) counter measures the 2.62 MeV gamma line from the undisturbed thorium in the ore body. The signal from the NaI (Tl) counter is processed and subtracted from the signal from the delayed neutron detectors with the result being indicative of the amount of uranium present in the ore body

  20. Direct measurement of surface-state conductance by microscopic four-point probe method

    DEFF Research Database (Denmark)

    Hasegawa, S.; Shiraki, I.; Tanikawa, T.

    2002-01-01

    For in situ measurements of local electrical conductivity of well defined crystal surfaces in ultrahigh vacuum, we have developed microscopic four-point probes with a probe spacing of several micrometres, installed in a scanning-electron - microscope/electron-diffraction chamber. The probe...... is precisely positioned on targeted areas of the sample surface by using piezoactuators. This apparatus enables conductivity measurement with extremely high surface sensitivity, resulting in direct access to surface-state conductivity of the surface superstructures, and clarifying the influence of atomic steps...

  1. Soft-landing ion deposition of isolated radioactive probe atoms on surfaces: A novel method

    NARCIS (Netherlands)

    Laurens, C.R; Rosu, M.F; Pleiter, F; Niesen, L

    1997-01-01

    We present a method to deposit a wide range of radioactive probe atoms on surfaces, without introducing lattice damage or contaminating the surface with other elements or isotopes. In this method, the probe atoms are mass separated using an isotope separator, decelerated to 5 eV, and directly

  2. Minimum dimensions of rock models for calibration of radiometric probes for the neutron-gamma well logging

    International Nuclear Information System (INIS)

    Czubek, J.A.; Lenda, A.

    1979-01-01

    The minimum dimensions have been calculated assuring 91, 96 and 98 % of the probe response in respect to the infinite medium. The models are of cylindrical form, the probe (source-to-detector distance equal to 60 or 90 cm) being placed on the model axis, symmetrically with respect to the two end-faces. All the models are ''embedded'' in various media, such as: air, sand of 40% porosity and completely saturated with water, sand of 30 % porosity and of moisture content equal to 10 %, and water. The models are of three types of material: sandstone, limestone and dolomite, with various porosities, ranging from 0 to 100 %. The probe response is due to gamma rays arising from the radiativecapture of thermal neutrons. The calculations were carried out for the highest energy line of gamma rays arising in given litology. Gamma-ray flux from the neutron radiative capture has been calculated versus rock porosity and model dimensions and radiation migration lengths determined for given litologies. The minimum dimensions of cylindrical models are given as functions of: porosity, probe length (source-to-detector distance) lithology of model and type of medium surrounding our model. (author)

  3. Electrical conduction through surface superstructures measured by microscopic four-point probes

    DEFF Research Database (Denmark)

    Hasegawa, S.; Shiraki, I.; Tanabe, F.

    2003-01-01

    For in-situ measurements of the local electrical conductivity of well-defined crystal surfaces in ultra-high vacuum, we have developed two kinds of microscopic four-point probe methods. One involves a "four-tip STM prober," in which four independently driven tips of a scanning tunneling microscope...... (STM) are used for measurements of four-point probe conductivity. The probe spacing can be changed from 500 nm to 1 mm. The other method involves monolithic micro-four-point probes, fabricated on silicon chips, whose probe spacing is fixed around several mum. These probes are installed in scanning...... compared with the macroscopic four-point probe method. Then the conduction through the topmost atomic layers (surface-state conductivity) and the influence of atomic steps on conductivity can be directly measured....

  4. The Fifth International Symposium on Advanced Nuclear Energy Research - neutrons as microscopic probes

    International Nuclear Information System (INIS)

    Hayter, J.B.

    1994-01-01

    New neutron sources being planned, such as the Advanced Neutron Source (ANS) or the European Spallation Source (ESS), will provide an order of magnitude flux increase over what is available today, but neutron scattering will still remain a signal-limited technique. At the same time, the development of new materials, such as polymer and ceramic composites or a variety of complex fluids, will increasingly require neutron-based research. This paper will discuss some of the new techniques which will allow us to make. better use of the available neutrons, either through improved instrumentation or through sample manipulation. Discussion will center primarily on unpolarized neutron techniques since polarized neutrons will be the subject of the next paper

  5. Boron carbide coatings for neutron detection probed by x-rays, ions, and neutrons to determine thin film quality

    Science.gov (United States)

    Nowak, G.; Störmer, M.; Becker, H.-W.; Horstmann, C.; Kampmann, R.; Höche, D.; Haese-Seiller, M.; Moulin, J.-F.; Pomm, M.; Randau, C.; Lorenz, U.; Hall-Wilton, R.; Müller, M.; Schreyer, A.

    2015-01-01

    Due to the present shortage of 3He and the associated tremendous increase of its price, the supply of large neutron detection systems with 3He becomes unaffordable. Alternative neutron detection concepts, therefore, have been invented based on solid 10B converters. These concepts require development in thin film deposition technique regarding high adhesion, thickness uniformity and chemical purity of the converter coating on large area substrates. We report on the sputter deposition of highly uniform large-area 10B4C coatings of up to 2 μm thickness with a thickness deviation below 4% using the Helmholtz-Zentrum Geesthacht large area sputtering system. The 10B4C coatings are x-ray amorphous and highly adhesive to the substrate. Material analysis by means of X-ray-Photoelectron Spectroscopy, Secondary-Ion-Mass-Spectrometry, and Rutherford-Back-Scattering (RBS) revealed low impurities concentration in the coatings. The isotope composition determined by Secondary-Ion-Mass-Spectrometry, RBS, and inelastic nuclear reaction analysis of the converter coatings evidences almost identical 10B isotope contents in the sputter target and in the deposited coating. Neutron conversion and detection test measurements with variable irradiation geometry of the converter coating demonstrate an average relative quantum efficiency ranging from 65% to 90% for cold neutrons as compared to a black 3He-monitor. Thus, these converter coatings contribute to the development of 3He-free prototype detectors based on neutron grazing incidence. Transferring the developed coating process to an industrial scale sputtering system can make alternative 3He-free converter elements available for large area neutron detection systems.

  6. Probing nanoparticle-macromolecule interaction and resultant structure by small-angle neutron scattering

    International Nuclear Information System (INIS)

    Aswal, V.K.

    2013-01-01

    Nanoparticles display unique and distinct characteristics from those of their constituent atoms and bulk materials which are being employed in numerous applications in the fields of medicine, electronics, optics, communications, energy, environment etc. Many of these applications require adjoining of nanoparticles with macromolecules such as proteins, polymers and surfactants to obtain functional objects. For example, nanoparticle-protein complexes are of great importance in controlling enzymatic behavior, targeted drug delivery and developing biocompatible materials. The nanoparticles interfaced with polymers are shown to be useful in developing protein sensor arrays. Interaction of surfactants with nanoparticles is utilized extensively for technical and industrial applications associated with colloidal stability, detergency and design of nanostructured functional interfaces. The interaction of two components, nanoparticles and macromolecule, strongly depends on the characteristics of both the nanoparticles (size, shape, surface roughness, charge density etc.) and macromolecules (type, charge, shape and solution conditions etc.) used. The interaction of macromolecule on nanoparticle surface is a cumulative effect of a number of forces such as electrostatic force, covalent bonding, hydrogen bonding, non-polar interaction, hydrophobic interactions etc. These interactions depending on the system conditions can lead to various structures. Small-angle neutron scattering (SANS) with the possibility to vary contrast is an ideal technique to study such multi-component systems. In this talk, some of our results of SANS from the complexes of nanoparticle-protein and nanoparticle surfactant systems will be discussed. (author)

  7. AFM fluid delivery/liquid extraction surface sampling/electrostatic spray cantilever probe

    Science.gov (United States)

    Van Berkel, Gary J.

    2015-06-23

    An electrospray system comprises a liquid extraction surface sampling probe. The probe comprises a probe body having a liquid inlet and a liquid outlet, and having a liquid extraction tip. A solvent delivery conduit is provided for receiving solvent liquid from the liquid inlet and delivering the solvent liquid to the liquid extraction tip. An open liquid extraction channel extends across an exterior surface of the probe body from the liquid extraction tip to the liquid outlet. An electrospray emitter tip is in liquid communication with the liquid outlet of the liquid extraction surface sampling probe. A system for analyzing samples, a liquid junction surface sampling system, and a method of analyzing samples are also disclosed.

  8. Relativistic iron emission lines in neutron star low-mass X-ray binaries as probes of neutron star radii

    NARCIS (Netherlands)

    Cackett, E.M.; Miller, J.M.; Bhattacharyya, S.; Grindlay, J.E.; Homan, J.; van der Klis, M.; Miller, M.C.; Strohmayer, T.E.; Wijnands, R.

    2008-01-01

    Using Suzaku observations of three neutron star low-mass X-ray binaries ( Ser X-1, 4U 1820-30, and GX 349+2) we have found broad, asymmetric, relativistic Fe K emission lines in all three objects. These Fe K lines can be well fit by a model for lines from a relativistic accretion disk ("diskline''),

  9. Combined use of small-angle neutron scattering and atom probe tomography for the analysis of precipitates in a Fe-15 m% Co-25 m% Mo alloy

    International Nuclear Information System (INIS)

    Eidenberger, Elisabeth; Stergar, Erich; Clemens, Helmut; Leitner, Harald; Staron, Peter; Spitaler, Juergen; Ambrosch-Draxl, Claudia

    2009-01-01

    Atom probe tomography (APT) measurements were conducted to analyze nm-sized precipitates in a Fe-25 m% Co-15 m% Mo model alloy. Calculation of isoconcentration surfaces and application of cluster-search algorithms yielded the chemical compositions of matrix and precipitates. Small-angle neutron scattering (SANS) was performed in order to calculate the ratio of magnetic to nuclear scattering. This so-called A-ratio was compared with values calculated from the chemical information derived from the atom probe data. For this, the magnetism of the precipitates has to be taken into account. Ab-initio studies have been carried out to determine the magnetic moment of the precipitate phase. The results show that the extremely fine precipitates are ferromagnetic and exhibit near-equilibrium composition. In the very early stage of decomposition, however, the composition is different from near-equilibrium. The influences of the magnetism of the precipitates as well as of artifacts from atom probe measurements on the obtained results are discussed. (orig.)

  10. Microfour-point probe for studying electronic transport through surface states

    DEFF Research Database (Denmark)

    Petersen, Christian Leth; Grey, Francois; Shiraki, I.

    2000-01-01

    Microfour-point probes integrated on silicon chips have been fabricated with probe spacings in the range 4-60 mum. They provide a simple robust device for electrical transport measurements at surfaces, bridging the gap between conventional macroscopic four-point probes and scanning tunneling...... microscopy. Measurements on Si(111) surfaces in ultrahigh vacuum reveal that the Si(111)-root 3x root3-Ag structure induced by a monolayer of Ag atoms has a four-point resistance two orders of magnitude lower than that of the Si(111)-7x7 clean surface. We attribute this remarkable difference to direct...

  11. Pressure/temperature fluid cell apparatus for the neutron powder diffractometer instrument: Probing atomic structure in situ

    International Nuclear Information System (INIS)

    Wang, Hsiu-Wen; Fanelli, Victor R.; Reiche, Helmut M.; Larson, Eric; Taylor, Mark A.; Siewenie, Joan; Xu, Hongwu; Zhu, Jinlong; Page, Katharine

    2014-01-01

    This contribution describes a new local structure compatible gas/liquid cell apparatus for probing disordered materials at high pressures and variable temperatures in the Neutron Powder Diffraction instrument at the Lujan Neutron Scattering Center, Los Alamos National Laboratory. The new sample environment offers choices for sample canister thickness and canister material type. Finite element modeling is utilized to establish maximum allowable working pressures of 414 MPa at 15 K and 121 MPa at 600 K. High quality atomic pair distribution function data extraction and modeling have been demonstrated for a calibration standard (Si powder) and for supercritical and subcritical CO 2 measurements. The new sample environment was designed to specifically target experimental studies of the local atomic structures involved in geologic CO 2 sequestration, but will be equally applicable to a wide variety of energy applications, including sorption of fluids on nano/meso-porous solids, clathrate hydrate formation, catalysis, carbon capture, and H 2 and natural gas uptake/storage

  12. Pressure/temperature fluid cell apparatus for the neutron powder diffractometer instrument: Probing atomic structure in situ

    Science.gov (United States)

    Wang, Hsiu-Wen; Fanelli, Victor R.; Reiche, Helmut M.; Larson, Eric; Taylor, Mark A.; Xu, Hongwu; Zhu, Jinlong; Siewenie, Joan; Page, Katharine

    2014-12-01

    This contribution describes a new local structure compatible gas/liquid cell apparatus for probing disordered materials at high pressures and variable temperatures in the Neutron Powder Diffraction instrument at the Lujan Neutron Scattering Center, Los Alamos National Laboratory. The new sample environment offers choices for sample canister thickness and canister material type. Finite element modeling is utilized to establish maximum allowable working pressures of 414 MPa at 15 K and 121 MPa at 600 K. High quality atomic pair distribution function data extraction and modeling have been demonstrated for a calibration standard (Si powder) and for supercritical and subcritical CO2 measurements. The new sample environment was designed to specifically target experimental studies of the local atomic structures involved in geologic CO2 sequestration, but will be equally applicable to a wide variety of energy applications, including sorption of fluids on nano/meso-porous solids, clathrate hydrate formation, catalysis, carbon capture, and H2 and natural gas uptake/storage.

  13. Pressure/temperature fluid cell apparatus for the neutron powder diffractometer instrument: probing atomic structure in situ.

    Science.gov (United States)

    Wang, Hsiu-Wen; Fanelli, Victor R; Reiche, Helmut M; Larson, Eric; Taylor, Mark A; Xu, Hongwu; Zhu, Jinlong; Siewenie, Joan; Page, Katharine

    2014-12-01

    This contribution describes a new local structure compatible gas/liquid cell apparatus for probing disordered materials at high pressures and variable temperatures in the Neutron Powder Diffraction instrument at the Lujan Neutron Scattering Center, Los Alamos National Laboratory. The new sample environment offers choices for sample canister thickness and canister material type. Finite element modeling is utilized to establish maximum allowable working pressures of 414 MPa at 15 K and 121 MPa at 600 K. High quality atomic pair distribution function data extraction and modeling have been demonstrated for a calibration standard (Si powder) and for supercritical and subcritical CO2 measurements. The new sample environment was designed to specifically target experimental studies of the local atomic structures involved in geologic CO2 sequestration, but will be equally applicable to a wide variety of energy applications, including sorption of fluids on nano/meso-porous solids, clathrate hydrate formation, catalysis, carbon capture, and H2 and natural gas uptake/storage.

  14. Neutrons probing the structure and dynamics of liquids; Les neutrons sondent la structure et la dynamique des liquides

    Energy Technology Data Exchange (ETDEWEB)

    Leclercq-Hugeux, F. [LASIR/HEI, UMR 8516 CNRS, 59 - Lille (France); Coulet, M.V. [Universite Paul-Cezanne, Lab. TECSEN - UMR 6122 CNRS, 13 - Marseille (France); Gaspard, J.P. [Liege Univ. (Belgium); Pouget, St. [CEA Grenoble, Dept. de Recherche Fondamentale sur la Matiere Condensee, Service General des rayons X (DRFMC/SP2M), 38 (France); Zanotti, J.M. [CEA Saclay, Lab. Leon Brillouin, CNRS, 91 - Gif-sur-Yvette (France)

    2007-09-15

    This article illustrates the benefits of neutron techniques to the understanding of the liquid state. As opposed to the nearly complete order of crystals or the nearly complete disorder of gas, the disorder of a liquid is partial and results from dynamical events acting on a broad range of space and time scales. Consequently, no single, simple parameter can encompass the concept of order or disorder in the liquid state. The wide variety of neutron techniques (diffraction, quasi-elastic and inelastic scattering) is a key asset to solve the issue. Selected studies ranging over typical interactions and conditions relevant to liquids (metallic, covalent, molecular, liquids near a phase transition and confined fluids) are presented. In each case, both structural and dynamical aspects, along with the connections to complementary techniques (computer simulation, X-ray absorption and/or scattering) are highlighted. (authors)

  15. Vibrational Surface Electron-Energy-Loss Spectroscopy Probes Confined Surface-Phonon Modes

    Directory of Open Access Journals (Sweden)

    Hugo Lourenço-Martins

    2017-12-01

    Full Text Available Recently, two reports [Krivanek et al. Nature (London 514, 209 (2014NATUAS0028-083610.1038/nature13870, Lagos et al. Nature (London 543, 529 (2017NATUAS0028-083610.1038/nature21699] have demonstrated the amazing possibility to probe vibrational excitations from nanoparticles with a spatial resolution much smaller than the corresponding free-space phonon wavelength using electron-energy-loss spectroscopy (EELS. While Lagos et al. evidenced a strong spatial and spectral modulation of the EELS signal over a nanoparticle, Krivanek et al. did not. Here, we show that discrepancies among different EELS experiments as well as their relation to optical near- and far-field optical experiments [Dai et al. Science 343, 1125 (2014SCIEAS0036-807510.1126/science.1246833] can be understood by introducing the concept of confined bright and dark surface phonon modes, whose density of states is probed by EELS. Such a concise formalism is the vibrational counterpart of the broadly used formalism for localized surface plasmons [Ouyang and Isaacson Philos. Mag. B 60, 481 (1989PMABDJ1364-281210.1080/13642818908205921, García de Abajo and Aizpurua Phys. Rev. B 56, 15873 (1997PRBMDO0163-182910.1103/PhysRevB.56.15873, García de Abajo and Kociak Phys. Rev. Lett. 100, 106804 (2008PRLTAO0031-900710.1103/PhysRevLett.100.106804, Boudarham and Kociak Phys. Rev. B 85, 245447 (2012PRBMDO1098-012110.1103/PhysRevB.85.245447]; it makes it straightforward to predict or interpret phenomena already known for localized surface plasmons such as environment-related energy shifts or the possibility of 3D mapping of the related surface charge densities [Collins et al. ACS Photonics 2, 1628 (2015APCHD52330-402210.1021/acsphotonics.5b00421].

  16. Vibrational Surface Electron-Energy-Loss Spectroscopy Probes Confined Surface-Phonon Modes

    Science.gov (United States)

    Lourenço-Martins, Hugo; Kociak, Mathieu

    2017-10-01

    Recently, two reports [Krivanek et al. Nature (London) 514, 209 (2014), 10.1038/nature13870, Lagos et al. Nature (London) 543, 529 (2017), 10.1038/nature21699] have demonstrated the amazing possibility to probe vibrational excitations from nanoparticles with a spatial resolution much smaller than the corresponding free-space phonon wavelength using electron-energy-loss spectroscopy (EELS). While Lagos et al. evidenced a strong spatial and spectral modulation of the EELS signal over a nanoparticle, Krivanek et al. did not. Here, we show that discrepancies among different EELS experiments as well as their relation to optical near- and far-field optical experiments [Dai et al. Science 343, 1125 (2014), 10.1126/science.1246833] can be understood by introducing the concept of confined bright and dark surface phonon modes, whose density of states is probed by EELS. Such a concise formalism is the vibrational counterpart of the broadly used formalism for localized surface plasmons [Ouyang and Isaacson Philos. Mag. B 60, 481 (1989), 10.1080/13642818908205921, García de Abajo and Aizpurua Phys. Rev. B 56, 15873 (1997), 10.1103/PhysRevB.56.15873, García de Abajo and Kociak Phys. Rev. Lett. 100, 106804 (2008), 10.1103/PhysRevLett.100.106804, Boudarham and Kociak Phys. Rev. B 85, 245447 (2012), 10.1103/PhysRevB.85.245447]; it makes it straightforward to predict or interpret phenomena already known for localized surface plasmons such as environment-related energy shifts or the possibility of 3D mapping of the related surface charge densities [Collins et al. ACS Photonics 2, 1628 (2015), 10.1021/acsphotonics.5b00421].

  17. Investigation of inelastic scattering of ultracold neutrons with small energy transfer at solid state surfaces

    International Nuclear Information System (INIS)

    Lychagin, E.V.; Muzychka, A.Yu.; Nekhaev, G.V.; Strelkov, A.V.; Shvetsov, V.N.; Nesvizhevskij, V.V.; Tal'daev, R.R.

    2001-01-01

    Inelastic scattering of neutrons with small energy transfer of ∼10 -7 eV was investigated using gravitational UCN spectrometer. The probability of such a process at stainless steel and beryllium surfaces was measured. It was also estimated at copper surface. The measurement showed that the detected flux of neutrons scattered at beryllium and copper surfaces is ∼ 2 times higher at room temperature compared to that at the liquid nitrogen temperature. (author)

  18. Using the lambda function to evaluate probe measurements of charged dielectric surfaces

    DEFF Research Database (Denmark)

    Rerup, T. O.; Crichton, George C; McAllister, Iain Wilson

    1996-01-01

    The use of Pedersen's λ function to evaluate electrostatic probe measurements of charged dielectric surfaces is demonstrated. With a knowledge of the probe λ function, the procedure by which this function is employed is developed, and thereafter applied to a set of experimental measurements avail...

  19. Water utilization of vegetables grown under plastic greenhouse conditions in Ankara using neutron probe technique

    International Nuclear Information System (INIS)

    Halitligil, M.B.; Kislal, H.; Sirin, H.; Sirin, C.; Kilicaslan, A.

    2004-01-01

    In order to find suitable varieties of tomato, pepper and cucumber for plastic greenhouse conditions in Ankara and ensure both higher yields and lower NO 3 leaching greenhouse experiments were conducted for three years. In the first year (2001) of the experiment four different varieties from each vegetable, namely, Tomato (Ecem F 1 , 9920 F 1 , 2116 F 1 and Yazg1 F 1 ), Cucumber (Hizir F 1 , Rapido, Hana, and Luna) and Pepper (1245 F 1 , 730 F 1 , Serademre 8 and 710 F 1 ) had been grown in the plastic greenhouse using drip irrigation-fertilization system. Yazg1 F 1 variety for tomato, Hizir F 1 variety for cucumber and Serademre 8 variety for pepper were chosen to be suitable varieties to grow in the plastic greenhouse conditions in Ankara. One access tube in each N 3 and N 0 treatment plots of tomato, cucumber and pepper in 2002 and 2003 experiments were installed for the soil moisture determinations at 30, 60 and 90 cm depths. Readings with the neutron probe were taken before planting and after harvest for the water consumption calculations using the water balance approach and the WUE was calculated on the basis of the ratio of dry matter weight to the amount of water consumed. Tensiometer and suction cups were installed at 15, 30, 45 and 60 cm depths only to N 1 , N 2 and N 3 treatments plots of each vegetable in 2002 and 2003. Tensiometer readings were taken just before irrigation. Also, soil solution samples from suction cups were taken at final harvest and NO 3 determinations were done with RQFLEX nitrate test strips. Significantly higher yields and WUE values were obtained when the same amount of N fertilizer is applied through fertigation compared to the treatment where N fertilizer applied to the soil then drip irrigated. The nitrate concentrations of the soil solution increased as the N rates increased and no NO 3 had been found in the soil solution taken from 75 cm soil depth, indicating that no leaching of N fertilizer occurred beyond 75 cm soil depth

  20. Water utilization of vegetables grown under plastic greenhouse conditions in Ankara using neutron probe technique

    International Nuclear Information System (INIS)

    Halitligil, M.B.; Kislal, H.; Sirin, H.; Sirin, C.; Kilicaslan, A.

    2004-01-01

    Full text: In order to find suitable varieties of tomato, pepper and cucumber for plastic greenhouse conditions in Ankara and ensure both higher yields and lower NO 3 leaching greenhouse experiments were conducted for three years. In the first year (2001) of the experiment four different varieties from each vegetable, namely, Tomato (Ecem F 1 , 9920 F 1 , 2116 F 1 and Yazg1 F 1 ), Cucumber (Hizir F 1 , Rapido, Hana, and Luna) and Pepper (1245 F 1 , 730 F 1 , Serademre 8 and 710 F 1 ) had been grown in the plastic greenhouse using drip irrigation-fertiligation system. Yazg1 F 1 variety for tomato, Hizir F 1 variety for cucumber and Serademre 8 variety for pepper were chosen to be suitable varieties to grow in the plastic greenhouse conditions in Ankara. One access tube in each N 3 and N 0 treatment plots of tomato, cucumber and pepper in 2002 and 2003 experiments were installed for the soil moisture determinations at 30, 60 and 90 cm depths. Readings with the neutron probe were taken before planting and after harvest for the water consumption calculations using the water balance approach and the WUE was calculated on the basis of the ratio of dry matter weight to the amount of water consumed. Tensiometer and suction cups were installed at 15, 30, 45 and 60 cm depths only to N 1 , N 2 and N 3 treatments plots of each vegetable in 2002 and 2003. Tensiometer readings were taken just before irrigation. Also, soil solution samples from suction cups were taken at final harvest and NO 3 determinations were done with RQFLEX nitrate test strips. Significantly higher yields and WUE values were obtained when the same amount of N fertilizer is applied through fertigation compared to the treatment where N fertilizer applied to the soil then drip irrigated. The nitrate concentrations of the soil solution increased as the N rates increased and no NO 3 had been found in the soil solution taken from 75 cm soil depth, indicating that no leaching of N fertilizer occurred beyond 75 cm

  1. Using Cosmic-Ray Neutron Probes to Monitor Landscape Scale Soil Water Content in Mixed Land Use Agricultural Systems

    International Nuclear Information System (INIS)

    Franz, Trenton E.; Wahbi, Ammar; Weltin, Georg; Heng, Lee; Dercon, Gerd; Vreugdenhi, Mariette; Oismueller, Markus; Strauss, Peter; Desilets, Darin

    2016-01-01

    With an ever-increasing demand for natural resources and the societal need to understand and predict natural disasters such as flood, soil water content (SWC) observations remain a critical variable to monitor in order to optimally allocate resources, establish early warning systems, and improve weather forecasts. However, routine agricultural production practices of soil cultivation, planting, and harvest make the operation and maintenance of direct contact point sensors for long-term monitoring a challenging task. In this work, we used Cosmic-Ray Neutron Probe (CRNP) to monitor landscape average SWC in a mixed agricultural land use system in northeast Austria since December 2013.

  2. Interpreting the probe-surface interaction of surface measuring instruments, or what is a surface?

    Science.gov (United States)

    Leach, Richard; Weckenmann, Albert; Coupland, Jeremy; Hartmann, Wito

    2014-09-01

    When using dimensional measuring instruments it is assumed that there is a property of the object, which we call surface, that is present before during and after the measurement, i.e. the surface is a fundamental property of an object that can, by appropriate means, be used to measure geometry. This paper will attempt to show that the fundamental property ‘surface’ does not exist in any simple form and that all the information we can have about a surface is the measurement data, which will include measurement uncertainty. Measurement data, or what will be referred to as the measured surface, is all that really exists. In this paper the basic physical differences between mechanically, electromagnetically and electrically measured surfaces are highlighted and discussed and accompanied by measurement results on a roughness artefact.

  3. Interpreting the probe-surface interaction of surface measuring instruments, or what is a surface?

    International Nuclear Information System (INIS)

    Leach, Richard; Weckenmann, Albert; Hartmann, Wito; Coupland, Jeremy

    2014-01-01

    When using dimensional measuring instruments it is assumed that there is a property of the object, which we call surface, that is present before during and after the measurement, i.e. the surface is a fundamental property of an object that can, by appropriate means, be used to measure geometry. This paper will attempt to show that the fundamental property ‘surface’ does not exist in any simple form and that all the information we can have about a surface is the measurement data, which will include measurement uncertainty. Measurement data, or what will be referred to as the measured surface, is all that really exists. In this paper the basic physical differences between mechanically, electromagnetically and electrically measured surfaces are highlighted and discussed and accompanied by measurement results on a roughness artefact. (paper)

  4. Simultaneous surface and depth neural activity recording with graphene transistor-based dual-modality probes.

    Science.gov (United States)

    Du, Mingde; Xu, Xianchen; Yang, Long; Guo, Yichuan; Guan, Shouliang; Shi, Jidong; Wang, Jinfen; Fang, Ying

    2018-05-15

    Subdural surface and penetrating depth probes are widely applied to record neural activities from the cortical surface and intracortical locations of the brain, respectively. Simultaneous surface and depth neural activity recording is essential to understand the linkage between the two modalities. Here, we develop flexible dual-modality neural probes based on graphene transistors. The neural probes exhibit stable electrical performance even under 90° bending because of the excellent mechanical properties of graphene, and thus allow multi-site recording from the subdural surface of rat cortex. In addition, finite element analysis was carried out to investigate the mechanical interactions between probe and cortex tissue during intracortical implantation. Based on the simulation results, a sharp tip angle of π/6 was chosen to facilitate tissue penetration of the neural probes. Accordingly, the graphene transistor-based dual-modality neural probes have been successfully applied for simultaneous surface and depth recording of epileptiform activity of rat brain in vivo. Our results show that graphene transistor-based dual-modality neural probes can serve as a facile and versatile tool to study tempo-spatial patterns of neural activities. Copyright © 2018 Elsevier B.V. All rights reserved.

  5. Advances in associated-particle sealed-tube neutron probe diagnostics for substance detection

    International Nuclear Information System (INIS)

    Rhodes, E.; Dickerman, C.E.; Frey, M.

    1995-01-01

    The development and investigation of a small associated-particle sealed-tube neutron generator (APSTNG) shows potential to allow the associated-particle diagnostic method to be moved out of the laboratory into field applications. The APSTNG interrogates the inspected object with 14-MeV neutrons generated from the deuterium-tritium reaction and detects the alpha-particle associated with each neutron inside a cone encompassing the region of interest. Gamma-ray spectra of resulting neutron reactions identify many nuclides. Flight-times determined from detection times of the gamma-rays and alpha-particles can yield a separate coarse tomographic image of each identified nuclide, from a single orientation. Chemical substances are identified by comparing relative spectral line intensities with ratios of elements in reference compounds. The high-energy neutrons and gamma-rays penetrate large objects and dense materials. Generally no collimators or radiation shielding are needed. Proof-of-concept laboratory experiments have been successfully performed for simulated nuclear, chemical warfare, and conventional munitions. Most recently, inspection applications have been investigated for radioactive waste characterization, presence of cocaine in propane tanks, and uranium and plutonium smuggling. Based on lessons learned with the present APSTNG system, an advanced APSTNG tube (along with improved high voltage supply and control units) is being designed and fabricated that will be transportable and rugged, yield a substantial neutron output increase, and provide sufficiently improved lifetime to allow operation at more than an order of magnitude increase in neutron flux

  6. Surface roughness effect on ultracold neutron interaction with a wall and implications for computer simulations

    International Nuclear Information System (INIS)

    Steyerl, A.; Malik, S. S.; Desai, A. M.; Kaufman, C.

    2010-01-01

    We review the diffuse scattering and the loss coefficient in ultracold neutron reflection from slightly rough surfaces, report a surprising reduction in loss coefficient due to roughness, and discuss the possibility of transition from quantum treatment to ray optics. The results are used in a computer simulation of neutron storage in a recent neutron lifetime experiment that reported a large discrepancy of neutron lifetime with the current particle data value. Our partial reanalysis suggests the possibility of systematic effects that were not included in this publication.

  7. Probing the nuclear equation of state by heavy-ion reactions and neutron star properties

    Energy Technology Data Exchange (ETDEWEB)

    Sahu, P.K.; Cassing, W.; Thoma, M.H. [Inst. fuer Theoretische Physik, Univ. Giessen (Germany)

    1998-06-01

    We discuss the nuclear equation of state (EOS) using a non-linear relativistic transport model. From the baryon flow for Ni + Ni as well as Au + Au systems we find that the strength of the vector potential has to be reduced at high density or at high relative momenta to describe the experimental flow data at 1-2 A GeV. We use the same dynamical model to calculate the nuclear EOS and then employ this EOS to neutron star structure calculations. We consider the core of the neutron star to be composed of neutrons with an admixture of protons, electrons, muons, sigmas and lambdas at zero temperature. We find that the nuclear equation of state is softer at high densities and hence the maximum mass and the radius of the neutron star are in the observable range of M {proportional_to} 1.7 M{sub s}un and R = 8 km, respectively. (orig.)

  8. Probing color superconducting phases and neutron superfluidity via hydrodynamic evolution at FAIR and NICA

    International Nuclear Information System (INIS)

    Dave, Shreyansh Shanker; Bagchi, Partha; Srivastava, Ajit M.; Das, Arpan; Sengupta, Srikumar

    2016-01-01

    High baryon density regions of the cores of neutron stars are expected to have exotic phases such as color superconducting phases. The symmetry breaking pattern of these phases allows for topological vortices. Even in the lower density region of neutron star, neutron superfluid and associated topological vortices play important role in the dynamics of neutron star, e.g. in pulsar timings and glitches. We consider the possibility of formation of these superfluid phases in heavy-ion collision experiments, e.g. at FAIR and NICA, by carrying out Hydrodynamic simulation. Our result shows that existence of superfluid phases can be detected by studying the effect of vortices on power spectrum of flow fluctuations. (author)

  9. Neutronic density perturbation by probes; Pertubacion de densidades neutronicas por sondas

    Energy Technology Data Exchange (ETDEWEB)

    Vigon, M. A.; Diez, L.

    1956-07-01

    The introduction of absorbent materials of neutrons in diffuser media, produces local disturbances of neutronic density. The disturbance depends especially on the nature and size of the absorbent. Approximated equations which relates te disturbance and the distance to the absorbent in the case of thin disks have been drawn. The experimental comprobation has been carried out in two especial cases. In both cases the experimental results are in agreement with the calculated values from these equations. (Author)

  10. Bio-polymer coatings on neural probe surfaces: Influence of the initial sample composition

    Energy Technology Data Exchange (ETDEWEB)

    Chow, Winnie W.Y. [Department of Physics and Astronomy, Uppsala University, Box 516, 751 20 Uppsala (Sweden); Herwik, Stanislav; Ruther, Patrick [Department of Microsystems Engineering (IMTEK), University of Freiburg (Germany); Goethelid, Emmanuelle [Department of Physics and Astronomy, Uppsala University, Box 516, 751 20 Uppsala (Sweden); Oscarsson, Sven, E-mail: sven@svenoscarsson.com [Department of Organic Chemistry, Stockholm University, Arrhenius Laboratory, SE-106 91 Stockholm (Sweden)

    2012-08-01

    This paper presents the results of the study of hyaluronic acid (HyA) coating on two structural materials, silicon oxide (dielectric) surface and platinum (Pt) surface used for fabrication of probes developed for neurological investigations in the framework of the EU-project NeuroProbes. The silicon-based neural probes consist of multiple Pt electrodes on the probe shafts for neural recording applications. HyA coatings were proposed to apply on the probe surfaces to enhance the biocompatibility. This study aims at understanding the influence of the initial composition of the probe surface on the structure and morphology of HyA coating. HyA was chemically functionalized by SS-pyridin using (N-Succinimidyl 3-[2-pyridyldithio]-propionate) (SPDP) and was immobilized on the surfaces via a covalent bond. The dielectric and Pt surfaces were derivatized by use of (3-mercaptopropyl) methyldimethoxysilane (MPMDMS). The silanol groups in MPMDMS bind to the dielectric surface, leaving the thiol groups at the uppermost surface and the thiol groups then bind covalently to the functionalized HyA. On the Pt surface, it is the thiol group which binds on the Pt surface. The coated surfaces were characterized by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). A well-defined HyA layer was observed on both dielectric and Pt surfaces. The coating of two molecular weights (340 kDa and 1.3 MDa) of HyA was examined. The influence of the silanized layer on the HyA coating was also investigated.

  11. Atom Probe Tomography Characterization of the Solute Distributions in a Neutron-Irradiated and Annealed Pressure Vessel Steel Weld

    Energy Technology Data Exchange (ETDEWEB)

    Miller, M.K.

    2001-01-30

    A combined atom probe tomography and atom probe field ion microscopy study has been performed on a submerged arc weld irradiated to high fluence in the Heavy-Section Steel irradiation (HSSI) fifth irradiation series (Weld 73W). The composition of this weld is Fe - 0.27 at. % Cu, 1.58% Mn, 0.57% Ni, 0.34% MO, 0.27% Cr, 0.58% Si, 0.003% V, 0.45% C, 0.009% P, and 0.009% S. The material was examined after five conditions: after a typical stress relief treatment of 40 h at 607 C, after neutron irradiation to a fluence of 2 x 10{sup 23} n m{sup {minus}2} (E > 1 MeV), and after irradiation and isothermal anneals of 0.5, 1, and 168 h at 454 C. This report describes the matrix composition and the size, composition, and number density of the ultrafine copper-enriched precipitates that formed under neutron irradiation and the change in these parameters with post-irradiation annealing treatments.

  12. Surface scattering efficiency of some common materials for shielding pulsed neutron scattering instruments

    International Nuclear Information System (INIS)

    Bartoli, L.; Becherini, F.; Grazzi, F.; Zoppi, M.

    2009-01-01

    We have measured the surface scattering efficiency of a new ceramic composite, based on boron carbide, that was recently proposed for use as a shielding material for pulsed neutron scattering instrumentation. The results show that, due to a relevant presence of clay material in the composite, the surface scattering efficiency is higher than other common shielding materials, which are used on pulsed neutron scattering instrumentation, and suggest revising the material composition.

  13. Associated-particle sealed-tube neutron probe: Detection of explosives, contraband, and nuclear materials

    International Nuclear Information System (INIS)

    Rhodes, E.; Dickerman, C.E.

    1996-01-01

    Continued research and development of the APSTNG shows the potential for practical field use of this technology for detection of explosives, contraband, and nuclear materials. The APSTNG (associated-particle sealed-tube generator) inspects the item to be examined using penetrating 14-MeV neutrons generated by the deuterium-tritium reaction inside a compact accelerator tube. An alpha detector built into the sealed tube detects the alpha-particle associated with each neutron emitted in a cone encompassing the volume to be inspected. Penetrating high-energy gamma-rays from the resulting neutron reactions identify specific nuclides inside the volume. Flight-times determined from the detection times of gamma-rays and alpha-particles separate the prompt and delayed gamma-ray spectra and allow a coarse 3-D image to be obtained of nuclides identified in the prompt spectrum. The generator and detectors can be on the same side of the inspected object, on opposite sides, or with intermediate orientations. Thus, spaces behind walls and other confined regions can be inspected. Signals from container walls can be discriminated against using the flight-time technique. No collimators or shielding are required, the neutron generator is relatively small, and commercial-grade electronics are employed. The use of 14-MeV neutrons yields a much higher cross-section for detecting nitrogen than that for systems based on thermal-neutron reactions alone, and the broad range of elements with significant 14-MeV neutron cross-sections extends explosives detection to other elements including low-nitrogen compounds, and allows detection of many other substances. Proof-of-concept experiments have been successfully performed for conventional explosives, chemical warfare agents, cocaine, and fissionable materials

  14. Probing photoinduced spin states in spin-crossover molecules with neutron scattering

    Science.gov (United States)

    Ridier, K.; Craig, G. A.; Damay, F.; Fennell, T.; Murrie, M.; Chaboussant, G.

    2017-03-01

    We report a neutron-scattering investigation of the spin-crossover compound [Fe (ptz) 6] (BF4)2 , which undergoes an abrupt thermal spin transition from high spin (HS), S =2 , to low spin (LS), S =0 , around 135 K. The HS magnetic state can be restored at low temperature under blue/green light irradiation. We have developed a specially designed optical setup for neutron scattering to address the magnetic properties of the light-induced HS state. By using neutron diffraction, we demonstrate that significant HS/LS ratios (of up to 60%) can be obtained with this experimental setup on a sample volume considered large (400 mg), while a complete recovery of the LS state is achieved using near-infrared light. Finally, with inelastic neutron scattering (INS) we have observed magnetic transitions arising from the photo-induced metastable HS S =2 state split by crystal-field and spin-orbit coupling. We interpret the INS data assuming a spin-only model with a zero-field splitting of the S =2 ground state. The obtained parameters are D ≈-1.28 ±0.03 meV and |E |≈0.08 ±0.03 meV. The present results show that in situ magnetic inelastic neutron-scattering investigations on a broad range of photomagnetic materials are now possible.

  15. In-situ soil composition and moisture measurement by surface neutron activation analysis

    Science.gov (United States)

    Waring, C.; Smith, C.; Marks, A.

    2009-04-01

    Neutron activation analysis is widely known as a laboratory technique dependent upon a nuclear reactor to provide the neutron flux and capable of precise elemental analysis. Less well known in-situ geochemical analysis is possible with isotopic (252Cf & 241Am) or compact accelerator (D-T, D-D fusion reaction) neutron sources. Prompt gamma neutron activation analysis (PGNAA) geophysical borehole logging has been applied to mining issues for >15 years (CSIRO) using isotopic neutron sources and more recently to environmental and hydro-geological applications by ANSTO. Similarly, sophisticated geophysical borehole logging equipment based on inelastic neutron scattering (INS) has been applied in the oil and gas industry by large oilfield services companies to measure oil saturation indices (carbon/oxygen) using accelerator neutron sources. Recent advances in scintillation detector spectral performance has enabled improved precision and detection limits for elements likely to be present in soil profiles (H, Si, Al, Fe, Cl) and possible detection of many minor to trace elements if sufficiently abundant (Na, K, Mg, Ca, S, N, + ). To measure carbon an accelerator neutron source is required to provide fast neutrons above 4.8 MeV. CSIRO and ANSTO propose building a soil geochemical analysis system based on experience gained from building and applying PGNA borehole logging equipment. A soil geochemical analysis system could effectively map the 2D geochemical composition of the top 50cm of soil by dragging the 1D logging equipment across the ground surface. Substituting an isotopic neutron source for a D-T accelerator neutron source would enable the additional measurement of elemental carbon. Many potential ambiguities with other geophysical proxies for soil moisture may be resolved by direct geochemical measurement of H. Many other applications may be possible including time series in-situ measurements of soil moisture for differential drainage, hydrology, land surface

  16. Negligible water surface charge determined using Kelvin probe and total reflection X-ray fluorescence techniques.

    Science.gov (United States)

    Shapovalov, Vladimir L; Möhwald, Helmuth; Konovalov, Oleg V; Knecht, Volker

    2013-09-07

    The water surface charge has been extensively debated in recent decades. Electrophoretic mobilities of air bubbles in water and disjoining pressures between the surfaces of aqueous films suggest that the surface of water exhibits a significant negative charge. This is commonly attributed to a strong adsorption of hydroxide ions at the interface, though spectroscopic measurements and simulation studies suggest surface depletion of hydroxide ions. Alternatively, the negative surface charge could arise from surface contamination with trace charged surfactants. We have probed the variation in the surface charge of water with pH by measuring surface potentials using the Kelvin probe technique. Independently, the abundance in the interfacial layer of "reporter ions" (Rb(+) and Br(-)), which must be affected by a charged surface, has been monitored using the total reflection X-ray fluorescence (TRXF) technique. Special care was taken to prove the high sensitivity of this technique as well as to avoid surface contaminants. The magnitude of the surface charge was found to be below 1 e per 500 nm(2) (TRXF). No evidence of variations in the surface potential between pH 2-3 and pH 9-12 was detected within the accuracies of the methods (5 mV for Kelvin probe and 2 mV for TRXF). Hence, our findings suggest that the clean water surface exhibits negligible charge in a wide pH range.

  17. Probing spin frustration in high-symmetry magnetic nanomolecules by inelastic neutron scattering

    DEFF Research Database (Denmark)

    Garlea, V.O.; Nagler, S.E.; Zarestky, J.L.

    2006-01-01

    Low temperature inelastic neutron scattering studies have been performed to characterize the low energy magnetic excitation spectrum of the magnetic nanomolecule {Mo(72)Fe(30)}. This unique highly symmetric cluster features spin frustration and is one of the largest discrete magnetic molecules...... of the temperature dependence of the observed neutron scattering are explained by a quantum model of the frustrated spin cluster. However, no satisfactory theoretical explanation is yet available for the observed magnetic field dependence....... studied to date by inelastic neutron scattering. The 30 s=5/2 Fe(III) ions, embedded in a spherical polyoxomolybdate molecule, occupy the vertices of an icosidodecahedron and are coupled via nearest-neighbor antiferromagnetic interactions. The overall energy scale of the excitation and the gross features...

  18. Using Cosmic-Ray Neutron Probes to Monitor Landscape Scale Soil Water Content in Mixed Land Use Agricultural Systems

    Directory of Open Access Journals (Sweden)

    Trenton E. Franz

    2016-01-01

    Full Text Available With an ever-increasing demand for natural resources and the societal need to understand and predict natural disasters, soil water content (SWC observations remain a critical variable to monitor in order to optimally allocate resources, establish early warning systems, and improve weather forecasts. However, routine agricultural production practices of soil cultivation, planting, and harvest make the operation and maintenance of direct contact point sensors for long-term monitoring challenging. In this work, we explore the use of the newly established Cosmic-Ray Neutron Probe (CRNP and method to monitor landscape average SWC in a mixed agricultural land use system in northeast Austria. The calibrated CRNP landscape SWC values compare well against an independent in situ SWC probe network (MAE = 0.0286 m3/m3 given the challenge of continuous in situ monitoring from probes across a heterogeneous agricultural landscape. The ability of the CRNP to provide real-time and accurate landscape SWC measurements makes it an ideal method for establishing long-term monitoring sites in agricultural ecosystems to aid in agricultural water and nutrient management decisions at the small tract of land scale as well as aiding in management decisions at larger scales.

  19. Constraints on the symmetry energy from observational probes of the neutron star crust

    International Nuclear Information System (INIS)

    Newton, William G.; Hooker, Joshua; Gearheart, Michael; Fattoyev, Farrukh J.; Li, Bao-An; Murphy, Kyleah; Wen, De-Hua

    2014-01-01

    A number of observed phenomena associated with individual neutron star systems or neutron star populations find explanations in models in which the neutron star crust plays an important role. We review recent work examining the sensitivity to the slope of the symmetry energy L of such models, and constraints extracted on L from confronting them with observations. We focus on six sets of observations and proposed explanations: (i) The cooling rate of the neutron star in Cassiopeia A, confronting cooling models which include enhanced cooling in the nuclear pasta regions of the inner crust; (ii) the upper limit of the observed periods of young X-ray pulsars, confronting models of magnetic field decay in the crust caused by the high resistivity of the nuclear pasta layer; (iii) glitches from the Vela pulsar, confronting the paradigm that they arise due to a sudden recoupling of the crustal neutron superfluid to the crustal lattice after a period during which they were decoupled due to vortex pinning; (iv) the frequencies of quasi-periodic oscillations in the X-ray tail of light curves from giant flares from soft gamma-ray repeaters, confronting models of torsional crust oscillations; (v) the upper limit on the frequency to which millisecond pulsars can be spun-up due to accretion from a binary companion, confronting models of the r-mode instability arising above a threshold frequency determined in part by the viscous dissipation timescale at the crust-core boundary; and (vi) the observations of precursor electromagnetic flares a few seconds before short gamma-ray bursts, confronting a model of crust shattering caused by resonant excitation of a crustal oscillation mode by the tidal gravitational field of a companion neutron star just before merger. (orig.)

  20. Associated-particle sealed-tube neutron probe for nonintrusive inspection

    International Nuclear Information System (INIS)

    Rhodes, E.; Dickerman, C.E.

    1996-01-01

    The development and investigation of a small associated-particle sealed-tube neutron generator (APSTNG) show potential to allow the associated-particle method to be moved out of the laboratory into field applications. Alpha particles associated with 14 MeV neutrons generated from the D-T reaction travel in the opposite direction and are detected inside the sealed tube. Gamma-ray spectra of resulting neutron reactions in the inspected volume encompassed by the alpha- detector solid angle identify many nuclides. Flight-times determined from detection times of the gamma-rays and alpha-particles not only separate the prompt and delayed gamma-rays but can also yield a separate coarse tomographic image of each identified nuclide, from a single orientation without collimation. A continuous ion beam allows data acquisition by relatively low-bandwidth commercial electronics. This efficient collection of maximum information from each detected neutron by the associated-particle method can allow a much lower source intensity than pulsed accelerator methods, provided a sufficient usable signal rate is obtained. When this method is coupled with a compact sealed-tube neutron generator, a relatively small, inexpensive, reliable, and easily maintainable inspection system can be developed, that is rugged enough to be transportable. Proof-of- concept laboratory experiments have been performed for simulated explosives, drugs, special nuclear materials, and chemical warfare agents. Based on lessons learned with the present APSTNG system, an advanced APSTNG system is being designed and built that will be transportable, yield a substantial neutron output increase, and provide a substantially improved target lifetime

  1. Magnetic and Crystalline Nanostructures in Ferrofluids as Probed by Small Angle Neutron Scattering

    Science.gov (United States)

    Wiedenmann, A.

    We present a newly developed technique of nuclear and magnetic contrast variation by using polarised neutrons in Small Angle Neutron Scattering (SANSPOL) which allows density, concentration and magnetisation fluctuations in magnetic liquids to be analysed simultaneously. Diluted Ferrofluids based on different magnetic materials (Co, Magnetite, Ba-ferrite) and stabilized by charges or surfactants in different carrier liquids have been investigated. In such polydisperse systems several constituents of similar sizes have been identified by this technique: Magnetic core-shell composites, magnetic aggregates and free surfactants. The corresponding size distributions, compositions and magnetic moments have been determined. In more concentrated Co-FF the nature of field induced particle arrangements has been determined.

  2. Quantum phase transitions and local magnetism in Mott insulators: A local probe investigation using muons, neutrons, and photons

    Science.gov (United States)

    Frandsen, Benjamin A.

    Mott insulators are materials in which strong correlations among the electrons induce an unconventional insulating state. Rich interplay between the structural, magnetic, and electronic degrees of freedom resulting from the electron correlation can lead to unusual complexity of Mott materials on the atomic scale, such as microscopically heterogeneous phases or local structural correlations that deviate significantly from the average structure. Such behavior must be studied by suitable experimental techniques, i.e. "local probes", that are sensitive to this local behavior rather than just the bulk, average properties. In this thesis, I will present results from our studies of multiple families of Mott insulators using two such local probes: muon spin relaxation (muSR), a probe of local magnetism; and pair distribution function (PDF) analysis of x-ray and neutron total scattering, a probe of local atomic structure. In addition, I will present the development of magnetic pair distribution function analysis, a novel method for studying local magnetic correlations that is highly complementary to the muSR and atomic PDF techniques. We used muSR to study the phase transition from Mott insulator to metal in two archetypal Mott insulating systems: RENiO3 (RE = rare earth element) and V2O3. In both of these systems, the Mott insulating state can be suppressed by tuning a nonthermal parameter, resulting in a "quantum" phase transition at zero temperature from the Mott insulating state to a metallic state. In RENiO3, this occurs through variation of the rare-earth element in the chemical composition; in V 2O3, through the application of hydrostatic pressure. Our results show that the metallic and Mott insulating states unexpectedly coexist in phase-separated regions across a large portion of parameter space near the Mott quantum phase transition and that the magnitude of the ordered antiferromagnetic moment remains constant across the phase diagram until it is abruptly

  3. Conformation of bovine submaxillary mucin layers on hydrophobic surface as studied by biomolecular probes

    DEFF Research Database (Denmark)

    Pakkanen, Kirsi I.; Madsen, Jan Busk; Lee, Seunghwan

    2015-01-01

    non-linear responses with increasing surface concentration. The results from this study support the conventional amphiphilic, triblock model of BSM in the adsorption onto hydrophobic surface from aqueous solution.The biomolecular probe-based approaches employed in this study, however, provided further...

  4. Surface-sensitive conductivity measurement using a micro multi-point probe approach

    DEFF Research Database (Denmark)

    Perkins, Edward; Barreto, Lucas; Wells, Justin

    2013-01-01

    measurements with an equidistant four-point probe for a wide range of contact spacings. In this way, it is possible to distinguish between bulk-like and surface-like conduction. The paper describes the design of the instrument and the approach to data and error analysis. Application examples are given......An instrument for microscale electrical transport measurements in ultra-high vacuum is presented. The setup is constructed around collinear lithographically-created multi-point probes with a contact spacing down to 500 nm. Most commonly, twelve-point probes are used. These probes are approached...... to the surface via piezoelectric positioners. Standard four-point resistance measurements can be performed using any combination of contacts out of the twelve available. Current/voltage measurements are taken semi-automatically for a variety of the possible contact configurations, effectively emulating...

  5. In situ neutron depth profiling: A powerful method to probe lithium transport in micro-batteries

    NARCIS (Netherlands)

    Oudenhoven, J.F.M.; Labohm, F.; Mulder, M.; Niessen, R.A.H.; Mulder, F.M.; Notten, P.H.L.

    2011-01-01

    In situ neutron depth profiling (NDP) offers the possibility to observe lithium transport inside micro-batteries during battery operation. It is demonstrated that NDP results are consistent with the results of electrochemical measurements, and that the use of an enriched6LiCoO2 cathode offers more

  6. Surface morphology of contact lenses probed with microscopy techniques

    Czech Academy of Sciences Publication Activity Database

    Guryča, Vilém; Hobzová, Radka; Přádný, Martin; Širc, Jakub; Michálek, Jiří

    2007-01-01

    Roč. 30, č. 4 (2007), s. 215-222 ISSN 1367-0484 R&D Projects: GA AV ČR 1QS400500558 Institutional research plan: CEZ:AV0Z40500505 Keywords : atomic force microscopy * scanning electron microscopy * surface roughness Subject RIV: CD - Macromolecular Chemistry

  7. Small angle neutron scattering in surface-active agents mixtures

    Science.gov (United States)

    Bulavin, L. A.; Garamus, V. M.; Ostanevich, Yu. M.

    The method of study of micelle structure by small angle neutron scattering is studied. The determination of maximum size, radius of gyration, average scattering density of micelles is presented. The way of study of distribution of scattering density in micelle is described. The problem of micelles interaction is discussed.

  8. Gamma-ray and neutron spectroscopy of planetary surfaces and atmospheres

    International Nuclear Information System (INIS)

    Reedy, R.C.

    1987-01-01

    The neutrons and gamma rays escaping from a planet can be used to map the concentrations of various elements in its surface. In a planet, the high-energy particles in the galactic cosmic rays induce a cascade of particles that includes many neutrons. The γ rays are made by the decay of the naturally-occurring radioelements and by nuclear excitations induced by cosmic-ray particles and their secondaries (especially neutron capture or inelastic scattering reactions). After a short history of planetary γ-ray and neutron spectroscopy, the γ-ray spectrometer and active neutron detection system planned for the Mars Observer Mission are presented. The results of laboratory experiments that simulate the cosmic-ray bombardments of planetary surfaces and the status of the theoretical calculations for the processes that make and transport neutrons and γ rays will be reviewed. Studies of Mars, including its atmosphere, are emphasized, as are new ideas, concepts, and problems that have arisen over the last decade, such as Doppler broadening and peaks from neutron scattering with germanium nuclei in a γ-ray spectrometer. 23 refs., 1 fig

  9. ANALYSIS OF SURFACE DEFECTS OF ALUMINUM AND ITS ALLOYS WITH A SCANNING KELVIN PROBE

    Directory of Open Access Journals (Sweden)

    A. K. Tyavlovsky

    2017-01-01

    Full Text Available Currently, the use of probe electrometry in non-destructive testing is constrained by the complexity of measurement results interpretation. An output signal of electrometric probe depends on a number of physical and chemical parameters of surface including chemical composition variations, stresses, dislocations, crystallographic orientation of a surface, etc. The study aims to the use of probe electrometry methods for nondestructive testing and analysis of precision metal surfaces’ defects after different treatment or processing.Control of surface defects of aluminum and its alloys was performed with a scanning Kelvin probe technique. The results of scanning were plotted in a form of contact potential difference (CPD distribution map. Additionally, a histogram of CPD values distribution and statistical characteristics including the expectation of CPD mean value and histogram half-width were calculated either for the whole distribution or for each individual mode in a case of multimodal distribution.The spatial CPD distribution of A99 aluminum and AMG-2 alloy surfaces after electrochemical polishing and diamond finishing was studied. An additional study was held for AMG-2 surface after the formation of 30 microns thick specific nanostructured alumina oxide surface layer. Higher quality surfaces have characterized as more homogeneous distribution of the physical properties (at half-width distribution histogram. Surfaces with higher mechanical strength and overall better mechanical properties found to have lower CPD values that correspond to higher electron work function and surface energy. The presence of the second mode in the CPD distribution histogram indicates the significant proportion of defect areas on the sample surface.Analysis of visualized CPD distribution maps using defined criteria allows detecting and characterizing such defects as residual stress areas, areas with reduced microhardness, surface contamination spots, corrosion

  10. Probing hydrogen positions in hydrous compounds: information from parametric neutron powder diffraction studies.

    Science.gov (United States)

    Ting, Valeska P; Henry, Paul F; Schmidtmann, Marc; Wilson, Chick C; Weller, Mark T

    2012-05-21

    We demonstrate the extent to which modern detector technology, coupled with a high flux constant wavelength neutron source, can be used to obtain high quality diffraction data from short data collections, allowing the refinement of the full structures (including hydrogen positions) of hydrous compounds from in situ neutron powder diffraction measurements. The in situ thermodiffractometry and controlled humidity studies reported here reveal that important information on the reorientations of structural water molecules with changing conditions can be easily extracted, providing insight into the effects of hydrogen bonding on bulk physical properties. Using crystalline BaCl2·2H2O as an example system, we analyse the structural changes in the compound and its dehydration intermediates with changing temperature and humidity levels to demonstrate the quality of the dynamic structural information on the hydrogen atoms and associated hydrogen bonding that can be obtained without resorting to sample deuteration.

  11. Micro reflectance difference techniques: Optical probes for surface exploration

    Energy Technology Data Exchange (ETDEWEB)

    Lastras-Martinez, L.F.; Del Pozo-Zamudio, O.; Herrera-Jasso, R.; Ulloa-Castillo, N.A.; Balderas-Navarro, R.E.; Ortega-Gallegos, J.; Lastras-Martinez, A. [Instituto de Investigacion en Comunicacion Optica, Universidad Autonoma de San Luis Potosi, Alvaro Obregon 64, 78000 San Luis Potosi, S.L.P. (Mexico)

    2012-06-15

    Micro reflectance difference spectroscopy ({mu}-RDS) is a promising tool for the in-situ and ex-situ characterization of semiconductors surfaces and interfaces. We discuss and compare two different approaches used to measure {mu}-RD spectra. One is based on a charge-coupled device (CCD) camera, while the other uses a laser and a XY translation stage. To show the performance of these systems, we have measured surface optical anisotropies of GaSb(001) sample on which anisotropic strains have been generated by preferential mechanical polishing along [110] and [1 anti 10] directions. The spectrometers are complementary and the selection of one of them depends on the sample to be investigated and on experimental conditions. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  12. Probing shape coexistence in neutron-deficient $^{72}$Se via low-energy Coulomb excitation

    CERN Multimedia

    We propose to study the evolution of nuclear structure in neutron-­deficient $^{72}$Se by performing a low-­energy Coulomb excitation measurement. Matrix elements will be determined for low-­lying excited states allowing for a full comparison with theoretical predictions. Furthermore, the intrinsic shape of the ground state, and the second 0$^{+}$ state, will be investigated using the quadrupole sum rules method.

  13. Neutron emission as a probe of fusion-fission and quasi-fission dynamics

    International Nuclear Information System (INIS)

    Hinde, D.J.

    1991-01-01

    Pre- and post scission neutron yeilds have been measured as a function of projectile mass, compound nucleus fissility, and fission mass-split and total kinetic energy (TKE) for 27 fusion-fission and quasi-fission reactions induced by beams of 16,18 O, 40 Ar and 64 Ni. A new method of interpretation of experimental pre-scission neutron multiplicities ν-pre and mean kinetic energies ε ν allows the extraction of fission time scales with much less uncertainty than previously, all fusion-fission results being consistent with a dynamical time scale of (35±15) x 10 -21 s for symmetric fission. All reactions show that ν-pre falls quite rapidly with increasing mass-asymmetry; evidence is presented that for fusion-fission reactions this is partly due to a reduction of the dynamical fission time scale with mass-asymmetry. For quasi-fission, the data indicate that the pre-scission multiplicity and mean neutron kinetic energy are very sensitive to the final mass-asymmetry, but that the time scale is virtually independent of mass-asymmetry. It is concluded that for fusion-fission there is no dependence of ν-pre on TKE, whilst for 64 Ni-induced quasi-fission reactions, a strong increase of ν-pre with decreasing TKE is observed, probably largely caused by neutron emission during the acceleration time of the fission fragments in these fast reactions. Interpretation of post-scission multiplicities in terms of fragment excitation energies leads to deduced time scales consistent with those determined from the pre-scission data. 54 refs., 17 tabs., 25 figs

  14. Probing the selectivity of a nanostructured surface by xenon adsorption.

    Science.gov (United States)

    Widmer, Roland; Passerone, Daniele; Mattle, Thomas; Sachdev, Hermann; Gröning, Oliver

    2010-04-01

    Surface-supported molecular self-assembly with the goal to produce highly ordered, functional supramolecular nanostructures are often realized using nanopatterned surfaces, which exhibit long range - ideally periodic - modulations of the molecule adsorption properties. To elucidate the physical origins of the site-specific adsorption properties of such a nanopatterned substrate, we investigated the temperature-dependent microscopic structure and the dynamics of adsorbed Xe at different temperatures on single-sheet h-BN on a Rh(111) nanomesh. In combination with molecular dynamics simulations we show that the site-specific adsorption arises from two different interactions of similar magnitude with respect to their lateral variations. The first can be attributed to a van der Waals type interaction, whereas the second originates from lateral variation of the electrostatic surface potential and is of polarization type. Both types lead to an adsorption energy minimum at the rim of the nanomesh pore and are therefore responsible for stabilizing dynamic and static Xe rings in these pores. The insight into this interplay of interactions should pave the way to gain a more general knowledge on such site-specific adsorption processes.

  15. Ultrasound surface probe as a screening method for evaluating the patients with blunt abdominal trauma

    Directory of Open Access Journals (Sweden)

    Mohammad Nasr-Esfahani

    2014-01-01

    Full Text Available Background: Blunt abdominal trauma is one of the causes of mortality in emergency department. Free fluid in the abdomen due to intra-abdominal blunt trauma can be determined by the surface probe of ultrasound. Since the importance of this free fluid in hemodynamic stable patients with blunt trauma is associated with the unknown outcome for surgeons, this study was performed to evaluate the role of ultrasound surface probe as a screening method in evaluating the patients with blunt abdominal trauma. Materials and Methods: A descriptive-analytical study was done on 45 patients with blunt abdominal trauma and hemodynamic stability. The patients were evaluated twice during the three-hours, including repeated ultrasound surface probe and clinical examinations. Computerized tomography was also performed. The patients were divided based on the amount of the free fluid in the abdomen during the evaluations into two groups: Fixed or increased, and decreased free fluid. The results of the different evaluated methods were compared using the sensitivity and specificity. Results: From 17 patients with CT abnormalities, free fluid increased in 14 patients (82.4%. Free fluid was decreased in three patients who were discharged well from the surgery service without any complication. Surface probe in prognosis detection had a sensitivity of 82.4% and specificity of 92.9%. The percentage of false positive and negative ultrasound compared with CT scan was 7.1% and 17.6%. Also, positive and negative predictive value of the ultrasound with surface probe was 87.5% and 89.7% respectively. Conclusion: The use of the ultrasound with surface probe in the diagnosis of free fluid in blunt abdominal trauma in hemodynamic stable patients can be considered as a useful screening method.

  16. Neutron star mergers as a probe of modifications of general relativity with finite-range scalar forces

    Science.gov (United States)

    Sagunski, Laura; Zhang, Jun; Johnson, Matthew C.; Lehner, Luis; Sakellariadou, Mairi; Liebling, Steven L.; Palenzuela, Carlos; Neilsen, David

    2018-03-01

    Observations of gravitational radiation from compact binary systems provide an unprecedented opportunity to test general relativity in the strong field dynamical regime. In this paper, we investigate how future observations of gravitational radiation from binary neutron star mergers might provide constraints on finite-range forces from a universally coupled massive scalar field. Such scalar degrees of freedom (d.o.f.) are a characteristic feature of many extensions of general relativity. For concreteness, we work in the context of metric f (R ) gravity, which is equivalent to general relativity and a universally coupled scalar field with a nonlinear potential whose form is fixed by the choice of f (R ). In theories where neutron stars (or other compact objects) obtain a significant scalar charge, the resulting attractive finite-range scalar force has implications for both the inspiral and merger phases of binary systems. We first present an analysis of the inspiral dynamics in Newtonian limit, and forecast the constraints on the mass of the scalar and charge of the compact objects for the Advanced LIGO gravitational wave observatory. We then perform a comparative study of binary neutron star mergers in general relativity with those of a one-parameter model of f (R ) gravity using fully relativistic hydrodynamical simulations. These simulations elucidate the effects of the scalar on the merger and postmerger dynamics. We comment on the utility of the full waveform (inspiral, merger, postmerger) to probe different regions of parameter space for both the particular model of f (R ) gravity studied here and for finite-range scalar forces more generally.

  17. Epithermal Neutron Evidence for a Diurnal Surface Hydration Process in the Moon's High Latitudes

    Science.gov (United States)

    McClanahan, T. P.; Mitrofanov, I. G.; Boynton, W. V.; Chin, G.; Parsons, A.; Starr, R. D.; Evans, L. G.; Sanin, A.; Litvak, M.; Livengood, T.

    2015-01-01

    We report evidence from epithermal neutron flux observations that show that the Moon's high latitude surfaces are being actively hydrated, dehydrated and rehydrated in a diurnal cycle. The near-surface hydration is indicated by an enhanced suppression of the lunar epithermal neutron leakage flux on the dayside of the dawn terminator on poleward-facing slopes (PFS). At 0600 to 0800 local-time, hydrogen concentrations within the upper 1 meter of PFS are observed to be maximized relative to equivalent equator-facing slopes (EFS). During the lunar day surface hydrogen concentrations diminish towards dusk and then rebuild overnight. Surface hydration is determined by differential comparison of the averaged EFS to PFS epithermal neutron count rates above +/- 75 deg latitude. At dawn the contrast bias towards PFS is consistent with at least 15 to 25 parts-per-million (ppm) hydrogen that dissipates by dusk. We review several lines of evidence derived from temperature and epithermal neutron data by a correlated analysis of observations from the Lunar Reconnaissance Orbiter's (LRO) Lunar Exploration Neutron Detector (LEND) that were mapped as a function of lunar local-time, Lunar Observing Laser Altimeter (LOLA) topography and Diviner (DLRE) surface temperature.

  18. Electronic transport at semiconductor surfaces - from point-contact transistor to micro-four-point probes

    DEFF Research Database (Denmark)

    Hasegawa, S.; Grey, Francois

    2002-01-01

    show that this type of conduction is measurable using new types of experimental probes, such as the multi-tip scanning tunnelling microscope and the micro-four-point probe. The resulting electronic transport properties are intriguing, and suggest that semiconductor surfaces should be considered...... of the first point-contact transistors, and led to the successful fabrication of field-effect transistors. However, to this day, one property of semiconductor surface states remains poorly understood, both theoretically and experimentally. That is the conduction of electrons or holes directly through...

  19. Controlled Clustering of Gold Nanoparticles using Solid-support for Surface-enhanced Raman Spectroscopic Probes

    International Nuclear Information System (INIS)

    Chang, Hyejin; Chae, Jinjoo; Jeong, Hong; Kang, Homan; Lee, Yoonsik

    2014-01-01

    We fabricated small clusters of gold nanoparticles by using solid-supported aggregation of gold nanoparticles. The fabricated Au nanoclusters consisting mainly of dimers showed homogeneous characteristics in cluster size and SERS intensity. The SERS enhancement of 4-ABT molecules in an effective area within 2-nm gap appeared to be approximately 10. Detachment process by ultrasonication was successively carried out in order to use the nanoclusters as SERS probes. The possibility of these clusters as SERS probe was proved in terms of signal and cluster size. Single molecule-level sensitivity of surface-enhanced Raman scattering (SERS) was known approximately fifteen years ago. Ever since there have been many different applications benefiting from the ultra-high sensitivity such as single molecule detection, chemical sensing and bio-molecular probes. Especially, SERS has drawn much attention in bio-multiplexing probes owing to its unique optical characteristics claiming extremely narrow bandwidth, high sensitivity of light signals, and non-bleaching feature

  20. Electronic transport at semiconductor surfaces - from point-contact transistor to micro-four-point probes

    DEFF Research Database (Denmark)

    Hasegawa, S.; Grey, Francois

    2002-01-01

    show that this type of conduction is measurable using new types of experimental probes, such as the multi-tip scanning tunnelling microscope and the micro-four-point probe. The resulting electronic transport properties are intriguing, and suggest that semiconductor surfaces should be considered......The electrical properties of semiconductor surfaces have played a decisive role in one of the most important discoveries of the last century, transistors. In the 1940s, the concept of surface states-new electron energy levels characteristic of the surface atoms-was instrumental in the fabrication...... of the first point-contact transistors, and led to the successful fabrication of field-effect transistors. However, to this day, one property of semiconductor surface states remains poorly understood, both theoretically and experimentally. That is the conduction of electrons or holes directly through...

  1. Energy dependent neutron sputtering and surface damage cross sections

    International Nuclear Information System (INIS)

    Odette, G.R.; Doiron, D.R.; Kennerley, R.J.

    1976-01-01

    The results clearly indicate that damage function analysis might be usefully applied to define both the neutron and primary recoil energy dependence of sputtering yields. Even with relatively large data errors, it appears that it is possible to both detect the existence and indicate the form of the deviation of sputtering yield from linear damage energy dependence (if such deviation exists). This information would be very useful in developing improved models of the sputtering phenomena

  2. Probing surfaces with single-polymer atomic force microscope experiments.

    Science.gov (United States)

    Friedsam, C; Gaub, H E; Netz, R R

    2006-03-01

    In the past 15 years atomic force microscope (AFM) based force spectroscopy has become a versatile tool to study inter- and intramolecular interactions of single polymer molecules. Irreversible coupling of polymer molecules between the tip of an AFM cantilever and the substrate allows one to study the stretching response up to the high force regime of several nN. For polymers that glide or slip laterally over the surface with negligible friction, on the other hand, the measured force profiles exhibit plateaus which allow one to extract the polymer adsorption energies. Long-term stable polymer coatings of the AFM tips allow for the possibility of repeating desorption experiments from solid supports with individual molecules many times, yielding good sampling statistics and thus reliable estimates for adsorption energies. In combination with recent advances in theoretical modeling, a detailed picture of the conformational statistics, backbone elasticity, and the adsorption characteristics of single polymer molecules is obtained.

  3. In vitro study of proteins surface activity by tritium probe

    International Nuclear Information System (INIS)

    Chernysheva, M.G.; Badun, G.A.

    2010-01-01

    A new technique for in vitro studies of biomacromolecules interactions, their adsorption at aqueous/organic liquid interfaces and distribution in the bulk of liquid/liquid systems was developed. The method includes (1) tritium labeling of biomolecules by tritium thermal activation method and (2) scintillation phase step with organic phase, which can be concerned as a model of cellular membrane. Two globular proteins lysozyme and human serum albumin tested. We have determined the conditions of tritium labeling when labeled by-products can be easy separated by means of dialysis and size-exclusion chromatography. Scintillation phase experiments were conducted for three types of organic liquids. Thus, the influences of the nature of organic phase on proteins adsorption and its distribution in the bulk of aqueous/organic liquid system were determined. It was found that proteins possess high surface activity at aqueous/organic liquid interface. Furthermore, values of hydrophobicity of globular proteins were found by the experiment. (author)

  4. Probing vibrational excitations in molecular crystals by inelastic scattering: From neutrons to X-rays

    International Nuclear Information System (INIS)

    Plazanet, Marie; Beraud, Alexandre; Johnson, Mark; Krisch, Michael; Trommsdorff, H. Peter

    2005-01-01

    Inelastic X-ray scattering spectra of single crystalline benzoic acid have been measured as a function of the momentum transfer vector, Q , in the frequency range of 300-1800 cm -1 . These measurements are confronted with dispersion curves that have been calculated using force constants derived from periodic DFT calculations in a (2, 2, 1) supercell. Even though limited by the signal-to-noise ratio and the resolution of the spectra, all spectral features and their Q -vector dependence are reproduced by the calculations. A comparison of this technique with inelastic neutron and light (Raman) scattering is made

  5. Probing the collectivity in neutron-rich Cd isotopes via γ-ray spectroscopy

    International Nuclear Information System (INIS)

    Naqvi, Farheen

    2011-01-01

    The spin and configurational structure of excited states of 127 Cd, 125 Cd and 129 Cd, having two proton and three, five and one neutron holes, respectively in the doubly magic 132 Sn core have been studied. The isomeric states in Cd isotopes were populated in the fragmentation of a 136 Xe beam at an energy of 750 MeV/u on a 9 Be target of 4 g/cm 2 . The experiment was performed at GSI Darmstadt. The neutron-rich Cd isotopes were selected using the Bρ - ΔE - Bρ method at the FRagment Separator (FRS). Event by event identification of fragments in terms of their A (mass) and Z (charge) was provided by the standard FRS detectors. The reaction residues were implanted in a plastic stopper surrounded by 15 Ge cluster detectors from the RISING array to detect the γ decays. In 127 Cd, an isomeric state with a half-life of 17.5(3) μs has been detected. This yrast (19/2) + isomer is proposed to have mixed proton-neutron configurations and to decay by two competing stretched M2 and E3 transitions. Experimental results are compared with the isotone 129 Sn. In 125 Cd, apart from the previously observed (19/2) + isomer, two new metastable states at 3896 keV and 2141 keV have been detected. A half-life of 13.6(2) μs was measured for the (19/2) + isomer, having a decay structure similar to the corresponding isomeric state in 127 Cd. The higher lying isomers have a half-life of 3.1(1) μs and 2.5(15) ns, respectively. Time distributions of delayed γ transitions and γγ-coincidence relations were exploited to construct decay schemes for the two nuclei. Comparison of the experimental data with shell-model calculations is also discussed. The new information provides input for the proton-neutron interaction in nuclei around the doubly magic 132 Sn core. The γ decays of the isomeric states in 129 Cd were not observed experimentally. The reasons for the non-observation of delayed γ rays for 129 Cd are either an isomeric half-life of less than 93 ns based on the experimentally

  6. Probing Ultrafast Electron Dynamics at Surfaces Using Soft X-Ray Transient Reflectivity Spectroscopy

    Science.gov (United States)

    Baker, L. Robert; Husek, Jakub; Biswas, Somnath; Cirri, Anthony

    The ability to probe electron dynamics with surface sensitivity on the ultrafast time scale is critical for understanding processes such as charge separation, injection, and surface trapping that mediate efficiency in catalytic and energy conversion materials. Toward this goal, we have developed a high harmonic generation (HHG) light source for femtosecond soft x-ray reflectivity. Using this light source we investigated the ultrafast carrier dynamics at the surface of single crystalline α-Fe2O3, polycrystalline α-Fe2O3, and the mixed metal oxide, CuFeO2. We have recently demonstrated that CuFeO2 in particular is a selective catalyst for photo-electrochemical CO2 reduction to acetate; however, the role of electronic structure and charge carrier dynamics in mediating catalytic selectivity has not been well understood. Soft x-ray reflectivity measurements probe the M2,3, edges of the 3d transition metals, which provide oxidation and spin state resolution with element specificity. In addition to chemical state specificity, these measurements are also surface sensitive, and by independently simulating the contributions of the real and imaginary components of the complex refractive index, we can differentiate between surface and sub-surface contributions to the excited state spectrum. Accordingly, this work demonstrates the ability to probe ultrafast carrier dynamics in catalytic materials with element and chemical state specificity and with surface sensitivity.

  7. Inspection of CF188 composite flight control surfaces with neutron radiography

    International Nuclear Information System (INIS)

    Lewis, W.J.; Bennett, L.G.I.; Mullin, S.K.

    1996-01-01

    At the Royal Military College of Canada's SLOWPOKE-2 Facility, a neutron radiography facility has been designed and installed using a small (20kWth), pool-type research reactor called the SLOWPOKE-2 (Safe Low Power c(K)ritical Experiment) as the neutron source. Since then, the research has continued along two fronts: developing applications and improving the quality of the neutron beam. The most interesting applications investigated to date has been the inspection of various metal ceramic composites and the inspection of the composite flight control surfaces of some of the CF188 Hornet aircraft. As part of the determination of the integrity of the aircraft, it was decided to inspect an aircraft with the highest flight house using both X- and neutron radiography. The neutron radiography and, to a lesser extent, X-radiography inspections completed at McClellan AFB revealed 93 anomalies. After returning to Canada, the component with the greatest structural significance, namely the right hand rudder from the vertical stabilizer, was removed from the aircraft and put through a rigorous program of numerous NDT inspections, including X-radiography (film and real-time), eddy current, ultrasonics (through transmission and pitch-catch), infrared thermography, and neutron radiography. Therefore, of all the techniques investigated, only through transmission ultrasonics and neutron radiography were able to identify large areas of hydration. However, only neutron radiography could identify the small areas of moisture and hydration. Given the structural significance of the flight control surfaces in modern fighter aircraft, even the smallest amounts of hydration could potentially lead to catastrophic results

  8. The use of low energy alkali ion scattering as a probe of surface structure

    International Nuclear Information System (INIS)

    Overbury, S.H.

    1987-01-01

    An overview is given of the use of low energy ion scattering as a probe of surface structure with emphasis on work done using alkali ions. Various schemes for extracting structural information from the ion energy and angle distribution are discussed in therms of advantages and disadvantages of each. The scattering potential, which is the primary nonstructural parameter needed for analysis, is discussed in terms of recent experimental results. The structures of clean and reconstructed surfaces are discussed, with examples of measurements of layer relaxations on the Mo (111) surface and missing row reconstructions on the Au (110) and Pt (110) surfaces. Studies of adsorbate covered surfaces are presented with respect to location of the adsorbate and its effect on the structure of the underlying substrate. Finally, examples are given which demonstrate the sensitivity of ion scattering to surface defects and disordering on reconstructed Au (110) and Pt (110) surfaces and reconstructed Mo (111) surfaces, and to ordering of adsorbates on Mo

  9. A precision measurement of the neutron2. Probing the color force

    Energy Technology Data Exchange (ETDEWEB)

    Posik, Matthew R. [Temple Univ., Philadelphia, PA (United States)

    2014-01-01

    The g2 nucleon spin-dependent structure function measured in electron deep inelastic scattering contains information beyond the simple parton model description of the nucleon. It provides insight into quark-gluon correlations and a path to access the confining local color force a struck quark experiences just as it is hit by the virtual photon due to the remnant di-quark. The quantity d2, a measure of this local color force, has its information encoded in an x2 weighted integral of a linear combination of spin structure functions g1 and g2 and thus is dominated by the valence-quark region at large momentum fraction x. To date, theoretical calculations and experimental measurements of the neutron d2 differ by about two standard deviations. Therefore, JLab experiment E06-014, performed in Hall A, made a precision measurement of this quantity at two mean four momentum transfers values of 3.21 and 4.32 GeV2. Double spin asymmetries and absolute cross-sections were measured in both DIS and resonance regions by scattering longitudinally polarized electrons at beam energies of 4.74 and 5.89 GeV from a longitudinally and transversely polarized 3He target. Results for the absolute cross-sections and spin structure functions on 3He will be presented in the dissertation, as well as results for the neutron d2 and extracted color forces.

  10. Micro-four-point probes in a UHV scanning electron microscope for in-situ surface-conductivity measurements

    DEFF Research Database (Denmark)

    Shiraki, I.; Nagao, T.; Hasegawa, S.

    2000-01-01

    For in-situ measurements of surface conductivity in ultrahigh vacuum (UHV), we have installed micro-four-point probes (probe spacings down to 4 mum) in a UHV scanning electron microscope (SEM) combined with scanning reflection-high-energy electron diffraction (RHEED). With the aid of piezoactuators...... for precise positioning of the probes, local conductivity of selected surface domains of well-defined superstructures could be measured during SEM and RHEED observations. It was found that the surface sensitivity of the conductivity measurements was enhanced by reducing the probe spacing, enabling...

  11. Probing the switching state of a surface-mounted azobenzene derivative using femtosecond XUV photoemission

    Science.gov (United States)

    Grunau, Jan; Heinemann, Nils; Rohwer, Timm; Zargarani, Dordaneh; Kuhn, Sonja; Jung, Ullrich; Kipp, Lutz; Magnussen, Olaf; Herges, Rainer; Bauer, Michael

    2012-03-01

    Photoemission spectroscopy using femtosecond XUV light pulses is applied to probe the isomerization state of the molecular switch 3-(4-(4-hexyl-phenylazo)-phenoxy)-propane-1-thiol deposited by liquid phase self-assembly on Au(111). Spectral shifts of valence-electronic signatures that we associate with the carbon C2s orbital enable us to distinguish the trans and the cis isomerization state of the adsorbed molecules. These preliminary results envision the potential to probe reversible switching processes of surface-mounted molecules in real time by tracking the temporal evolution of the electronic and nuclear degrees of freedom in a femtosecond XUV photoemission experiment.

  12. Research and Training of Using Neutron Scattering to Probe the Collective Phenomena in Doped Transition-Metal Oxides. Final report

    International Nuclear Information System (INIS)

    Zhang, Jiandi

    2008-01-01

    The objective of this funded research program include: explore and understand the microscopic origins of collective phenomena in doped transition-metal oxides (TMOs) using neutrons as one of the primary tools, and train new generation of neutron scatters and collaborate with Oak Ridge National Lab in both materials synthesis and characterization. The major physics issues focused on in this project consist of the microscopic correlations between lattice structure and magnetic ordering, the nature of elementary lattice and spin excitations, the origin of nanometer-scale phase separations, and the effects of dimensional confinement and broken symmetry. The main materials are doped TMOs grown as single crystals by a floating-zone technique at ORNL as well as multiplayer films grown with a laser-MBE facility at Florida International University (FIU). Our educational objective is the training of our graduate and undergraduate students, especially Hispanic and other minority students, to use neutrons as a probe for materials research by taking advantage of national neutron facilities and to grow novel materials by using the floating-zone and laser-MBE technique. The main achievements of the project include the systematic study of the spin dynamics, especially the spin wave excitations in ferromagnetic manganites; the discovery of the critical doping concentration for the magnetic phase separation of the charge-ordered state in Pr 1-x Ca x MnO 3 - ; the study of Σ 4 phonon softening associated with the lattice instability near the quantum critical point as well as the discovery of an anomalous mode in single-layered ruthenates. These results gain some important insights into the collective excitations in both spin and lattice degrees of freedom as well as their close coupling in these correlated TMO systems. Furthermore, this project also accomplished the synthesis and some characterization of the single crystals of a new material Ba 2-x Sr x CoO 4 , a compound in which

  13. Determination of planetary surfaces elemental composition by gamma and neutron spectroscopy

    International Nuclear Information System (INIS)

    Diez, B.

    2009-06-01

    Measuring the neutron and gamma ray fluxes produced by the interaction of galactic cosmic rays with planetary surfaces allow constraining the chemical composition of the upper tens of centimeters of material. Two different angles are proposed to study neutron and gamma spectroscopy: data processing and data interpretation. The present work is in line with two experiments, the Mars Odyssey Neutron Spectrometer (MONS) and the Selene Gamma Ray Spectrometer. A review of the processing operations applied to the MONS dataset is proposed. The resulting dataset is used to determine the depth of the hydrogen deposits below the Martian surface. In water depleted regions, neutron data allow constraining the concentration in elements likely to interact with neutrons. The confrontation of these results to those issued from the Gamma Ray Spectrometer onboard Mars Odyssey provides interesting insight on the geologic context of the Central Elysium Planitia region. These martian questions are followed by the study of the Selene gamma ray data. Although only preliminary processing has been done to date, qualitative lunar maps of major elements (Fe, Ca, Si, Ti, Mg, K, Th, U) have already been realized. (author)

  14. Magnetization anomalies of fine particles interpreted as surface effects by inelastic neutron scattering

    International Nuclear Information System (INIS)

    Hennion, M.; Mirebeau, I.; Bellouard, C.

    1994-01-01

    Inelastic neutron scattering experiments on small Fe particles (R=12 Angstrom) reveal that some part of the magnetic intensity is paramagnetic at 300 K. As T decreases it freezes and develops short range ferromagnetic correlations. It is attributed to spins at the particle surface. (authors). 3 figs., 5 refs

  15. Neutron activation analysis to the profile surface sediments from several sites on the Havana Bay

    International Nuclear Information System (INIS)

    Diaz Riso, O.; Gelen, A.; Lopez, N.; Gonzalez, H.; Manso, M.V.; Graciano, A.M.; Nogueira, C.A.; Beltran, J.; Soto, J.

    2003-01-01

    Instrumental neutron activation analysis (INAA) technique was employed to analyze the surface sediments from several sites on the Havana Bay, Cuba. Measurements of heavy and trace elements in the sediments are reported. The results show that the concentration of the elements is site dependent. The data suggest that an anthropogenic input into the bay from domestic sewage and industries occurred

  16. Minimum activation martensitic alloys for surface disposal after exposure to neutron flux

    Science.gov (United States)

    Lechtenberg, Thomas

    1985-01-01

    Steel alloys for long-term exposure to neutron flux have a martensitic microstructure and contain chromium, carbon, tungsten, vanadium and preferably titanium. Activation of the steel is held to within acceptable limits for eventual surface disposal by stringently controlling the impurity levels of Ni, Mo, Cu, N, Co, Nb, Al and Mn.

  17. Spin excitations in 3D molecular magnets probed by neutron scattering

    International Nuclear Information System (INIS)

    Bordallo, H.N.; Goremychkin, E.; Chapon, L.C.; Manson, J.L.; Cook, J.C.; Lee, S.H.; Copley, J.R.D.; Yildirim, T.; Kern, S.

    2002-01-01

    The emerging field of molecular magnetism constitutes a new branch of materials science that deals with the magnetic properties of molecules, or assemblies of molecules, that contain magnetic centers. The growing interest in understanding the origin of the magnetic ordering in these materials is to obtain novel multiproperty molecular magnetic materials with high transition temperatures. Molecules based on the dicyanamide ion [N≡C-N-C≡N], abbreviated (dca), such as M(dca) 2 [M=Mn, Ni], have shown interesting bulk properties that prompted our inelastic neutron scattering (INS) studies. While the Mn 2+ ion is isotropic because of its L=0 configuration, the isostructural Ni analog has S=1 and demonstrates marked single-ion anisotropy. Mn(dca) 2 is a canted antiferromagnet below 16 K, while Ni(dca) 2 is a ferromagnet below 21 K. INS has been used to investigate the magnetic excitations in Mn(dca) 2 and Ni(dca) 2 . For Mn(dca) 2 , a Heisenberg model gives good correspondence with the experimental results. (orig.)

  18. Spin excitations in 3D molecular magnets probed by neutron scattering

    CERN Document Server

    Bordallo, H N; Chapon, L C; Manson, J L; Cook, J C; Lee, S H; Copley, J R D; Yildirim, T; Kern, S

    2002-01-01

    The emerging field of molecular magnetism constitutes a new branch of materials science that deals with the magnetic properties of molecules, or assemblies of molecules, that contain magnetic centers. The growing interest in understanding the origin of the magnetic ordering in these materials is to obtain novel multiproperty molecular magnetic materials with high transition temperatures. Molecules based on the dicyanamide ion [N ident to C-N-C ident to N], abbreviated (dca), such as M(dca) sub 2 [M=Mn, Ni], have shown interesting bulk properties that prompted our inelastic neutron scattering (INS) studies. While the Mn sup 2 sup + ion is isotropic because of its L=0 configuration, the isostructural Ni analog has S=1 and demonstrates marked single-ion anisotropy. Mn(dca) sub 2 is a canted antiferromagnet below 16 K, while Ni(dca) sub 2 is a ferromagnet below 21 K. INS has been used to investigate the magnetic excitations in Mn(dca) sub 2 and Ni(dca) sub 2. For Mn(dca) sub 2 , a Heisenberg model gives good corr...

  19. Low moment ferrimagnetism in Mn3Al as probed by Polarized Neutron Reflectometry

    Science.gov (United States)

    Jamer, Michelle; Wang, Yung-Jui; Borchers, Julie; Kirby, Brian; Barbiellini, Bernardo; Bansil, Arun; Heiman, Don

    For future spintronic devices, it is paramount to limit stray magnetic interactions which can negatively impact spin injection. A new class of materials called half-metallic antiferromagnets or compensated ferrimagnets have been proposed to remedy this problem. In this work, Mn3Al thin films have shown promising room temperature low-moment ferrimagnetic magnetic properties. Epitaxial Mn3Al thin films (50 nm) were grown on desorbed GaAs(001) substrates via MBE at 200 °C and annealed further to temperatures between 250 - 350 °C. The D03 Heusler-type phase was determined by X-ray diffraction with texturing in the [311] direction. Density functional theory, performed using VASP, indicated that the crystallographic structure of Mn3Al is able to form energetically with a low magnetic moment (0.017 μB/f.u.) despite some epitaxial distortion. SQUID magnetometry confirmed the low magnetic moment and high Curie temperature (610 K) of the structure. Polarized Neutron Reflectometry was used to determine the effect of epitaxy on the magnetic moment of Mn3Al, and analysis confirms a low magnetic moment (0.11 μB/f.u.) for the samples annealed at temperatures between 200-300 °C. This analysis further suggests that the relaxation of the Mn3Al at the interface. National Science Foundation ECCS-1402738.

  20. A new capacitive/resistive probe method for studying magnetic surfaces

    International Nuclear Information System (INIS)

    Kitajima, Sumio; Takayama, Masakazu; Zama, Tatsuya; Takaya, Kazuhiro; Takeuchi, Nobunao; Watanabe, Hiroshige

    1991-01-01

    A new capacitive/resistive probe method for mapping the magnetic surfaces from resistance or capacitance between a magnetic surface and a vacuum vessel was developed and tested. Those resistances and capacitances can be regarded as components of a simple electrical bridge circuit. This method exploits electrical transient response of the bridge circuit for a square pulse. From equiresistance or equicapacitance points, the magnetic surface structure can be deduced. Measurements on the Tohoku University Heliac, which is a small-size standard heliac, show good agreement with numerical calculations. This method is particularly useful for pulse-operated machines. (author)

  1. Neutron Diffraction Evaluation of Near Surface Residual Stresses at Welds in 1300 MPa Yield Strength Steel

    Directory of Open Access Journals (Sweden)

    Ebrahim Harati

    2017-05-01

    Full Text Available Evaluation of residual stress in the weld toe region is of critical importance. In this paper, the residual stress distribution both near the surface and in depth around the weld toe was investigated using neutron diffraction, complemented with X-ray diffraction. Measurements were done on a 1300 MPa yield strength steel welded using a Low Transformation Temperature (LTT consumable. Near surface residual stresses, as close as 39 µm below the surface, were measured using neutron diffraction and evaluated by applying a near surface data correction technique. Very steep surface stress gradients within 0.5 mm of the surface were found both at the weld toe and 2 mm into the heat affected zone (HAZ. Neutron results showed that the LTT consumable was capable of inducing near surface compressive residual stresses in all directions at the weld toe. It is concluded that there are very steep stress gradients both transverse to the weld toe line and in the depth direction, at the weld toe in LTT welds. Residual stress in the base material a few millimeters from the weld toe can be very different from the stress at the weld toe. Care must, therefore, be exercised when relating the residual stress to fatigue strength in LTT welds.

  2. Neutron Diffraction Evaluation of Near Surface Residual Stresses at Welds in 1300 MPa Yield Strength Steel.

    Science.gov (United States)

    Harati, Ebrahim; Karlsson, Leif; Svensson, Lars-Erik; Pirling, Thilo; Dalaei, Kamellia

    2017-05-29

    Evaluation of residual stress in the weld toe region is of critical importance. In this paper, the residual stress distribution both near the surface and in depth around the weld toe was investigated using neutron diffraction, complemented with X-ray diffraction. Measurements were done on a 1300 MPa yield strength steel welded using a Low Transformation Temperature (LTT) consumable. Near surface residual stresses, as close as 39 µm below the surface, were measured using neutron diffraction and evaluated by applying a near surface data correction technique. Very steep surface stress gradients within 0.5 mm of the surface were found both at the weld toe and 2 mm into the heat affected zone (HAZ). Neutron results showed that the LTT consumable was capable of inducing near surface compressive residual stresses in all directions at the weld toe. It is concluded that there are very steep stress gradients both transverse to the weld toe line and in the depth direction, at the weld toe in LTT welds. Residual stress in the base material a few millimeters from the weld toe can be very different from the stress at the weld toe. Care must, therefore, be exercised when relating the residual stress to fatigue strength in LTT welds.

  3. X-ray and neutron reflectivity

    International Nuclear Information System (INIS)

    Deutsch, M.

    1994-01-01

    The intensity of X-rays and neutrons reflected from an interface at near-grazing incidence depends sensitively on the refractive index profile normal to the interface. As the refractive index depends on the density, the measured reflectivity vs. incidence angle can be used to determine the Interfacial density profile with sub angstrom resolution. The density sampled is, however, different for the two probes. As neutrons interact with the atomic nuclei, they probe the scattering amplitude density profile of the nuclei. This amounts effectively to probing the average mass density profile, where the contribution of each atomic species is weighted by its nucleus-neutron interaction strength, which varies irregularly throughout the periodic table. X-rays, however, interact with the electronic charge and thus probe the total electronic density profile of the interface. The two probes provide, therefore, slightly different, though related, information on the interface structure. Since modern synchrotron X-ray sources are 5-6 orders of magnitude brighter than the best neutron sources, X-ray reflectivity measurements routinely achieve much higher resolutions and accuracies than their neutron counterparts. However, the magnetic interaction and the large variation of the neutron scattering length upon isotopic substitution renders neutron reflectivity a method-of-choice in special cases such as studies of surface magnetism and the adsorption of polymers at liquid and solid surfaces

  4. A surface plasmon resonance probe without optical fibers as a portable sensing device

    International Nuclear Information System (INIS)

    Akimoto, Takuo; Wada, Syunsuke; Karube, Isao

    2008-01-01

    A surface plasmon resonance (SPR) sensor integrating a small sensor probe, a laser emission diode, a photo detector, and a polarizer was developed as a portable sensing device. The sensor probe was made with a glass cylinder, 50 mm long and 1.5 mm in diameter, that was connected directly to a beam splitter without optical fibers. The SPR spectrum obtained with this probe system showed a 10% reflectivity minimum at 690 nm. Shifts of the SPR spectrum induced by refractive index (RI) changes in the sample were measured by detecting the reflection light intensity at 670 nm. When the sensitivity was compared using a BIAcore TM SPR instrument, the lowest sensor response of 1 mV observed with the SPR probe system coincided with 1.4 x 10 -6 of the RI changes. The RI resolution of the SPR probe was estimated with experimentally evaluated noise on the signal, and, consequently, it was concluded that the RI resolution was 1.2 x 10 -5 . Moreover, immunoreaction was demonstrated with adsorbed bovine serum albumin (BSA) and anti-BSA antibody as an analyte. As a result, 50 ng mL -1 of the lower detection limit was estimated

  5. Ferromagnetic Cu-O-Cu coupling in CaCu3Sn4O12 probed by neutron diffraction.

    Science.gov (United States)

    Kayser, P; Retuerto, M; Sánchez-Benítez, J; Martínez-Lope, M J; Fernández-Díaz, M T; Alonso, J A

    2012-12-12

    The A-site ordered perovskite oxide with the formula CaCu(3)Sn(4)O(12) has been synthesized in polycrystalline form under moderate pressure conditions (3.5 GPa) in combination with high temperature (1000 °C). This oxide crystallizes in the cubic space group [Formula: see text] (no. 204) with the unit-cell parameter a = 7.64535(6) Å at 300 K. The SnO(6) network is extremely tilted, giving rise to a square planar coordination for Cu(2+) cations. The non-magnetic character of Sn(4+) offers an excellent opportunity to probe the magnetism of Cu(2+) at the A sublattice in CaCu(3)Sn(4)O(12). Magnetic susceptibility shows that this compound is ferromagnetic below T(C) = 10 K, which is an unusual magnetic behaviour in cuprates. This peculiar aspect has been examined by neutron powder diffraction. The refinement of the magnetic structure at 4 K indeed indicates a parallel coupling between Cu(2+) spins with a magnetic moment of 0.5 μ(B)/Cu atom.

  6. Neutron-proton bremsstrahlung from intermediate energy heavy-ion reactions as a probe of the nuclear symmetry energy?

    International Nuclear Information System (INIS)

    Yong, G.-C.; Li Baoan; Chen Liewen

    2008-01-01

    Hard photons from neutron-proton bremsstrahlung in intermediate energy heavy-ion reactions are examined as a potential probe of the nuclear symmetry energy within a transport model. Effects of the symmetry energy on the yields and spectra of hard photons are found to be generally smaller than those due to the currently existing uncertainties of both the in-medium nucleon-nucleon cross sections and the photon production probability in the elementary process pn→pnγ. Very interestingly, nevertheless, the ratio of hard photon spectra R 1/2 (γ) from two reactions using isotopes of the same element is not only approximately independent of these uncertainties but also quite sensitive to the symmetry energy. For the head-on reactions of 132 Sn + 124 Sn and 112 Sn + 112 Sn at E beam /A=50 MeV, for example, the R 1/2 (γ) displays a rise up to 15% when the symmetry energy is reduced by about 20% at ρ=1.3ρ 0 which is the maximum density reached in these reactions

  7. Personal and environmental dosimetry of neutrons in a storage facility and humidity probes soil density; Dosimetria personal y ambiental de neutrones en una instalacion de almacenamiento de sondas de densidad y humedad de suelos

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Fuste, M. J.; Amgarou, K.; Dan Pedro, M. de; Garcia-Orellana, J.; Domingo, C.

    2011-07-01

    The equipment operators are professionally exposed to radiation and the premises where stored are considered controlled areas. Although control of the personal doses of gamma radiation received by the operators during the operation, maintenance and storage of the probes is required and is performed by dosimetry services officially approved, the control of personal and environmental doses due to neutrons generally omitted, since they are small in comparison to the gamma dose.

  8. Improvement to surface lagging systems in a nuclear reactor, particularly of the fast neutron type

    International Nuclear Information System (INIS)

    Lemercier, Guy.

    1979-01-01

    Improvements to surface lagging systems in a nuclear reactor, particularly of the fast neutron kind. This system is composed of an assembly of panels each formed of a stack of metal fabric or trellis held against the surface to be protected, by a double fixing system comprising (a) a tubular component passing through a hole in the panel and applying it against the surface through a bearing plate, and (b) a bolt fitted in the centre of the tubular component, also secured to the surface and holding a washer capable of preventing the fall of the tubular component and the panel should the tubular component fracture [fr

  9. Characterisation of engineered surfaces and molecular sensing by neutron and X-ray reflectometry

    International Nuclear Information System (INIS)

    James, Michael

    2010-01-01

    This presentation will give a theoretical and experimental background to the techniques of X-ray and neutron reflectometry for the study of nanoscale thin-films and processes occurring at surfaces. It will discuss the design of optimum samples; as well as the limits of X-ray and neutron reflectometry for such studies. Investigations of thin-films and surfaces in Australia has entered a 'golden age', with the combination of the Platypus time-of-flight neutron reflectometer and a modern laboratory-based X-ray reflectometer at the OPAL research reactor in Sydney. The presentation will then concentrate on studies of engineered thin-film nanostructures. These studies represent a cross-section of results from the first 18 months of operation of the Platypus neutron reflectometer in 2009 and 2010. Molecular systems that will be reported include self-assembled monolayers, diblock copolymer thin-films, bioimetic membranes and light-emitting surfaces created by polymers or fluorescent dendrimers. (author)

  10. Study of Binding between Protein A and Immunoglobulin G Using a Surface Tension Probe

    OpenAIRE

    Yang, L.; Biswas, M. E.; Chen, P.

    2003-01-01

    Molecular interactions and binding are one of the most important and fundamental properties in the study of biochemical and biomedical systems. The understanding of such interactions and binding among biomolecules forms the basis for the design and processing of many biotechnological applications, such as bioseparation and immunoadsorption. In this study, we present a novel method to probe molecular interactions and binding based on surface tension measurement. This method complements convent...

  11. Friction as a probe of surface properties of a polymer glass

    OpenAIRE

    Bureau, Lionel

    2007-01-01

    We probe the temperature dependence of friction at the interface between a glassy poly(methylmethacrylate) lens and a flat substrate coated with a methyl-terminated self-assembled monolayer. The monolayer exhibits density defects which act as pinning sites for the polymer chains. We show that the shear response of such an interface supports the existence, at the surface of the glassy polymer, of a nanometer-thick layer of mobile chains. Friction can be ascribed to the interplay between viscou...

  12. In situ surface reduction of a NiO-YSZ-alumina composite using scanning probe microscopy

    DEFF Research Database (Denmark)

    Hansen, Karin Vels; Jacobsen, Torben; Thydén, Karl Tor Sune

    2014-01-01

    In situ surface reductions of NiO-YSZ-Al2O3 composites into Ni-YSZ-Al2O3 cermets were carried out at 312–525 °C in a controlled atmosphere high-temperature scanning probe microscope (CAHT-SPM) in dry and humidified 9 % H2 in N2. The reduction of NiO was followed by contact mode scanning of topogr...

  13. Protein surface topology-probing by selective chemical modification and mass spectrometric peptide mapping.

    OpenAIRE

    Suckau, D; Mak, M; Przybylski, M

    1992-01-01

    Aminoacetylation of lysine residues and the modification of arginine by 1,2-cyclohexanedione to N7,N8-(dihydroxy-1,2-cyclohexylidene)arginine were used for probing the surface topology of hen-eggwhite lysozyme as a model protein. The molecular identification of lysine and arginine modification sites was provided by molecular weight determinations of modified and unmodified tryptic peptide mixtures (peptide mapping) using 252Cf plasma desorption mass spectrometry. At conditions of limited chem...

  14. Surfaces of colloidal PbSe nanocrystals probed by thin-film positron annihilation spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Chai, L.; Schut, H.; Schaarenburg, L. C. van; Eijt, S. W. H., E-mail: S.W.H.Eijt@tudelft.nl [Department of Radiation, Radionuclides and Reactors, Faculty of Applied Sciences, Delft University of Technology, Mekelweg 15, NL-2629 JB Delft (Netherlands); Al-Sawai, W.; Barbiellini, B.; Bansil, A. [Physics Department, Northeastern University, Boston, Massachusetts 02115 (United States); Gao, Y. [Department of Chemical Engineering, Faculty of Applied Sciences, Delft University of Technology, Julianalaan 136, NL-2628 BL Delft (Netherlands); Kavli Institute of Nanoscience, Faculty of Applied Sciences, Delft University of Technology, Lorentzweg 1, NL-2628 CJ Delft (Netherlands); Houtepen, A. J. [Department of Chemical Engineering, Faculty of Applied Sciences, Delft University of Technology, Julianalaan 136, NL-2628 BL Delft (Netherlands); Mijnarends, P. E. [Department of Radiation, Radionuclides and Reactors, Faculty of Applied Sciences, Delft University of Technology, Mekelweg 15, NL-2629 JB Delft (Netherlands); Physics Department, Northeastern University, Boston, Massachusetts 02115 (United States); Huis, M. A. van [Kavli Institute of Nanoscience, Faculty of Applied Sciences, Delft University of Technology, Lorentzweg 1, NL-2628 CJ Delft (Netherlands); Ravelli, L.; Egger, W. [Institut für Angewandte Physik und Messtechnik, Universität der Bundeswehr München, Werner-Heisenberg-Weg 39, D-85579 Neubiberg (Germany); Kaprzyk, S. [Physics Department, Northeastern University, Boston, Massachusetts 02115 (United States); Academy of Mining and Metallurgy AGH, PL-30059 Kraków (Poland)

    2013-08-01

    Positron annihilation lifetime spectroscopy and positron-electron momentum density (PEMD) studies on multilayers of PbSe nanocrystals (NCs), supported by transmission electron microscopy, show that positrons are strongly trapped at NC surfaces, where they provide insight into the surface composition and electronic structure of PbSe NCs. Our analysis indicates abundant annihilation of positrons with Se electrons at the NC surfaces and with O electrons of the oleic ligands bound to Pb ad-atoms at the NC surfaces, which demonstrates that positrons can be used as a sensitive probe to investigate the surface physics and chemistry of nanocrystals inside multilayers. Ab initio electronic structure calculations provide detailed insight in the valence and semi-core electron contributions to the positron-electron momentum density of PbSe. Both lifetime and PEMD are found to correlate with changes in the particle morphology characteristic of partial ligand removal.

  15. Surfaces of colloidal PbSe nanocrystals probed by thin-film positron annihilation spectroscopy

    Directory of Open Access Journals (Sweden)

    L. Chai

    2013-08-01

    Full Text Available Positron annihilation lifetime spectroscopy and positron-electron momentum density (PEMD studies on multilayers of PbSe nanocrystals (NCs, supported by transmission electron microscopy, show that positrons are strongly trapped at NC surfaces, where they provide insight into the surface composition and electronic structure of PbSe NCs. Our analysis indicates abundant annihilation of positrons with Se electrons at the NC surfaces and with O electrons of the oleic ligands bound to Pb ad-atoms at the NC surfaces, which demonstrates that positrons can be used as a sensitive probe to investigate the surface physics and chemistry of nanocrystals inside multilayers. Ab initio electronic structure calculations provide detailed insight in the valence and semi-core electron contributions to the positron-electron momentum density of PbSe. Both lifetime and PEMD are found to correlate with changes in the particle morphology characteristic of partial ligand removal.

  16. Developing an optical chopper-modulated capacitive probe for measuring surface charge.

    Science.gov (United States)

    Ugolini, D; McKinney, R; Harry, G M

    2007-04-01

    Gravitational-wave observatories such as Laser Interferometer Gravitational-Wave Observatory (LIGO) use suspended optics in a Michelson interferometer configuration to measure strains in space between 10 Hz and 3 kHz. One potential noise source in this frequency range is the buildup and motion of surface charge on the optics, which can generate fluctuating electric fields, interfere with position control, and reduce reflectance by attracting dust to the optical surface. We have developed a capacitive probe to measure the magnitude and relaxation time of surface charge deposited on smaller test optics in high vacuum ( approximately 10(-5) Torr). Our device modulates capacitance with a tuning-fork optical chopper between probe and sample, chosen for vacuum compatibility and minimal cost. We have found that the probe has a resolution of (3.5+/-0.5)x10(5) e(-)cm(2) in air, on the order of charging levels that could contribute noise to Advanced LIGO, and sufficient for measuring relaxation times on test optics.

  17. Methicillin-Resistant Bacteria Inhabiting Surface Waters Monitored by mecA-Targeted Oligonucleotide Probes.

    Science.gov (United States)

    Seyedmonir, Elnaz; Yilmaz, Fadime; Icgen, Bulent

    2016-08-01

    Part of a 20-60 kb staphylococcal chromosome cassette called mecA encodes low-affinity penicillin-binding protein PBP2a and causes methicillin resistance. Among all methicillin-resistant bacteria, methicillin-resistant Staphylococcus aureus is a major pathogen and main concern worldwide. Although the origin of the mecA is not very well-defined, mecA homologues are also ubiquitous in methicillin-resistant non-staphylococcal bacteria. Due to the dissemination of methicillin resistance through the transmission of mecA gene among staphylococcal and non-staphylococcal bacteria inhabiting surface waters, there is a need to monitor mecA gene in these waters for public health safety. Therefore, this study aimed at monitoring mecA harboring bacteria inhabiting surface waters by using fluorescently labelled mecA-targeted oligonucleotide probes. Under the hybridization conditions of 55 % formamide and 0.020 M NaCl at 46°C, the oligonucleotide probe used in the study showed high hybridization stringency to the mecA gene targeted. The strong linear relationships observed between the signal intensity and the target gene were used to assess the population dynamics of mecA harboring isolates over a 2-year-period. The results indicated that mecA-targeted oligonucleotide probes can be effectively used for in situ monitoring of methicillin resistant isolates inhabiting surface waters.

  18. The orientation effect in the activities of neutronic probes; Efecto de orientacion en las actividades de sondas neutronicas

    Energy Technology Data Exchange (ETDEWEB)

    Vigon, M. A.

    1956-07-01

    The formulae relating activity and position of a neutron irradiated Indium foil, have been verified experimentally. Measurements with both thin and thick foils for epithermal neutrons and with thick foils for thermal neutrons have been carried out. The experimental results agree qualitatively with the theoretical predictions. (Author)

  19. Probing surface tension additivity on chemically heterogeneous surfaces by a molecular approach.

    Science.gov (United States)

    Wang, Jihang; Bratko, Dusan; Luzar, Alenka

    2011-04-19

    Surface free energy of a chemically heterogeneous surface is often treated as an approximately additive quantity through the Cassie equation [Cassie ABD (1948) Discuss Faraday Soc 3:11-16]. However, deviations from additivity are common, and molecular interpretations are still lacking. We use molecular simulations to measure the microscopic analogue of contact angle, Θ(c), of aqueous nanodrops on heterogeneous synthetic and natural surfaces as a function of surface composition. The synthetic surfaces are layers of graphene functionalized with prototypical nonpolar and polar head group: methyl, amino, and nitrile. We demonstrate positive as well as negative deviations from the linear additivity. We show the deviations reflect the uneven exposure of mixture components to the solvent and the linear relation is recovered if fractions of solvent-accessible surface are used as the measure of composition. As the spatial variations in polarity become of larger amplitude, the linear relation can no longer be obtained. Protein surfaces represent such natural patterned surfaces, also characterized by larger patches and roughness. Our calculations reveal strong deviations from linear additivity on a prototypical surface comprising surface fragments of melittin dimer. The deviations reflect the disproportionately strong influence of isolated polar patches, preferential wetting, and changes in the position of the liquid interface above hydrophobic patches. Because solvent-induced contribution to the free energy of surface association grows as cos Θ(c), deviations of cos Θ(c) from the linear relation directly reflect nonadditive adhesive energies of biosurfaces.

  20. Probing the spectral density of the surface electromagnetic fields through scattering of waveguide photons.

    Science.gov (United States)

    Chen, Guang-Yin

    2016-02-10

    The spectral density of the metal-surface electromagnetic fields will be strongly modified in the presence of a closely-spaced quantum emitter. In this work, we propose a feasible way to probe the changes of the spectral density through the scattering of the waveguide photon incident on the quantum emitter. The variances of the lineshape in the transmission spectra indicate the coherent interaction between the emitter and the pseudomode resulting from all the surface electromagnetic modes. We further investigate the quantum coherence between the emitter and the pseudomode of the metal-dielectric interface.

  1. Probing the surface of aqueous surfactant-perfume mixed solutions during perfume evaporation

    OpenAIRE

    Penfold, J; Thomas, RK; Bradbury, R; Tucker, I; Petkov, JT; Jones, CW; Webster, JRP

    2017-01-01

    The rate of release or evaporation of perfume molecules from surfaces is a key factor in determining the impact of the perfume in a range of applications relating to home and personal care products. For mixtures of the anionic surfactant sodium dodecylsulfate and the model perfume linalool the rate of change of adsorption with time due to forced air flow over a fixed headspace was evaluated using neutron reflectivity over a period of up to ∼250 min. The measurements were made in the limit of ...

  2. Gravimetric and density profiling using the combination of surface acoustic waves and neutron reflectivity.

    Science.gov (United States)

    Toolan, Daniel T W; Barker, Robert; Gough, Tim; Topham, Paul D; Howse, Jonathan R; Glidle, Andrew

    2017-02-01

    A new approach is described herein, where neutron reflectivity measurements that probe changes in the density profile of thin films as they absorb material from the gas phase have been combined with a Love wave based gravimetric assay that measures the mass of absorbed material. This combination of techniques not only determines the spatial distribution of absorbed molecules, but also reveals the amount of void space within the thin film (a quantity that can be difficult to assess using neutron reflectivity measurements alone). The uptake of organic solvent vapours into spun cast films of polystyrene has been used as a model system with a view to this method having the potential for extension to the study of other systems. These could include, for example, humidity sensors, hydrogel swelling, biomolecule adsorption or transformations of electroactive and chemically reactive thin films. This is the first ever demonstration of combined neutron reflectivity and Love wave-based gravimetry and the experimental caveats, limitations and scope of the method are explored and discussed in detail. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

  3. Transmission X-ray scattering as a probe for complex liquid-surface structures

    Energy Technology Data Exchange (ETDEWEB)

    Fukuto, Masafumi; Yang, Lin; Nykypanchuk, Dmytro; Kuzmenko, Ivan

    2016-01-28

    The need for functional materials calls for increasing complexity in self-assembly systems. As a result, the ability to probe both local structure and heterogeneities, such as phase-coexistence and domain morphologies, has become increasingly important to controlling self-assembly processes, including those at liquid surfaces. The traditional X-ray scattering methods for liquid surfaces, such as specular reflectivity and grazing-incidence diffraction, are not well suited to spatially resolving lateral heterogeneities due to large illuminated footprint. A possible alternative approach is to use scanning transmission X-ray scattering to simultaneously probe local intermolecular structures and heterogeneous domain morphologies on liquid surfaces. To test the feasibility of this approach, transmission small- and wide-angle X-ray scattering (TSAXS/TWAXS) studies of Langmuir films formed on water meniscus against a vertically immersed hydrophilic Si substrate were recently carried out. First-order diffraction rings were observed in TSAXS patterns from a monolayer of hexagonally packed gold nanoparticles and in TWAXS patterns from a monolayer of fluorinated fatty acids, both as a Langmuir monolayer on water meniscus and as a Langmuir–Blodgett monolayer on the substrate. The patterns taken at multiple spots have been analyzed to extract the shape of the meniscus surface and the ordered-monolayer coverage as a function of spot position. These results, together with continual improvement in the brightness and spot size of X-ray beams available at synchrotron facilities, support the possibility of using scanning-probe TSAXS/TWAXS to characterize heterogeneous structures at liquid surfaces.

  4. Surface electronic transport measurements: A micro multi-point probe approach

    DEFF Research Database (Denmark)

    Barreto, Lucas

    2014-01-01

    This work is mostly focused on the study of electronic transport properties of two-dimensional materials, in particular graphene and topological insulators. To study these, we have improved a unique micro multi-point probe instrument used to perform transport measurements. Not only the experimental...... quantities are extracted, such as conductivity, carrier density and carrier mobility. • A method to insulate electrically epitaxial graphene grown on metals, based on a stepwise intercalation methodology, is developed and transport measurements are performed in order to test the insulation. • We show...... a direct measurement of the surface electronic transport on a bulk topological insulator. The surface state conductivity and mobility are obtained. Apart from transport properties, we also investigate the atomic structure of the Bi2Se3(111) surface via surface x-ray diraction and low-energy electron...

  5. The Probing Radio Signal Polarization Effect on Separation Efficiency of Surface Target Response

    Directory of Open Access Journals (Sweden)

    A. N. Pinchuk

    2015-01-01

    Full Text Available The aim of the study was a quantitative analysis of the level of interference with radar monitoring characteristics of surface targets, caused by the scattered electromagnetic field, arising due to the interaction between radio waves and sea surface, which is a study aspect a radiooceanography encompasses. Backscatter signal, arising from the interaction of radio waves and sea surface, extends in a direction opposite the probing radar signal of spread marine and coastal radar stations.With radar sounding of sea surface at high incidence angles of radio waves, a basic physical mechanism to form the received signal is resonant (Bragg scattering, and at small incidence angles of radio waves it is quasi-specular reflection. Consequently, the energy of electromagnetic radiation, backscattered by the sea surface, depends on the type of wave polarization: for horizontal polarization it is less than for vertical one.The paper presents a mathematical model, which describes dependence of interference level caused by interaction between radio waves and sea surface, on the radio wave polarization for the case when the same polarization is used to sent-out and receive a radio wave.To determine the noise reduction to be achievable with radar monitoring the surface targets by selecting the polarization of the probing radar signal, a signal/noise ratio is analyzed for its different polarizations.It is shown that in order to reduce the noise level caused by the interaction between radio waves and sea surface, it is possible to use the differences in the level of scattered radio signals of different polarization: with horizontally-polarized radar operation at incidence angles of 75°- 85° a signal/noise ratio is by 20-35 dB higher than that of vertically- polarized one.

  6. Signal Evaluation System of Flexible Array Ect Probes for Inspecting Complexly Shaped Surfaces

    Science.gov (United States)

    Endo, H.; Nishimizu, A.; Tooma, M.; Ouchi, H.; Yoshida, I.; Nonaka, Y.; Otani, K.

    2011-06-01

    We developed a signal evaluation system of flexible array eddy current testing (ECT) probes for inspecting complexly shaped metal surfaces. Our probes employ excitation and pickup coil pairs arrayed on a bendable substrate to measure curved targets. Since the developed probes produce signals due to the change in the relative position between the coil pair, an evaluation module for flaw signal identification is integrated into the system. The identification utilizes signal phase combination of the coil pairs. It is represented as a two-dimensional diagram constituting the phase values of two of the coil pairs with different positions. The phase of signals around flaws is significantly affected by their orientations. The diagram is therefore capable of separating flaw information from other information and of imaging flaw positions. We applied the system to complex geometric mock-ups. Flaw signals were successfully identified and the images obtained for identified positions could be used to efficiently measure the length of surface flaws by the 12 decibel down method.

  7. Study of plasma-material surface interaction using Langmuir probe technique during plasma treatment

    International Nuclear Information System (INIS)

    Saloum, S.; Akel, M.

    2009-06-01

    In this study, we tried to understand the plasma-surface interactions by using Langmuir probes. Two different types of plasmas were studied, the first is the electropositive plasma in Argon and the second is the electronegative plasma in Sulfur Hexafluoride. In the first type, the effects of Argon gas pressure, the injection of Helium in the remote zone and the substrate bias on the measurements of the Electron Energy Probability Function (EEPF) and on the plasma parameters (electron density (n e ), effective electron temperature (T e ff), plasma potential (V p ) and floating potential (V f )) have been investigated. The obtained EEPFs and plasma parameters have been used to control two remote plasma processes. The first is the remote Plasma Enhanced Chemical Vapor Deposition (PE-CVD) of thin films, on silicon wafers, from Hexamethyldisoloxane (HMDSO) precursor diluted in the remote Ar-He plasma. The second is the pure Argon remote plasma treatment of polymethylmethacrylate (PMMA) polymer surface. In the second type, the plasma diagnostics were performed in the remote zone as a function of SF 6 flow rate, where relative concentrations of fluorine atoms were measured using actinometry optical emission spectroscopy; electron density, electron temperature and plasma potential were determined using single cylindrical Langmuir probe, positive ion flux and negative ion fraction were determined using an planar probe. The silicon etching process in SF 6 plasma was studied. (author)

  8. Probing the hydrogen equilibrium and kinetics in zeolite imidazolate frameworks via molecular dynamics and quasi-elastic neutron scattering experiments.

    Science.gov (United States)

    Pantatosaki, Evangelia; Jobic, Hervé; Kolokolov, Daniil I; Karmakar, Shilpi; Biniwale, Rajesh; Papadopoulos, George K

    2013-01-21

    The problem of simulating processes involving equilibria and dynamics of guest sorbates within zeolitic imidazolate frameworks (ZIF) by means of molecular dynamics (MD) computer experiments is of growing importance because of the promising role of ZIFs as molecular "traps" for clean energy applications. A key issue for validating such an atomistic modeling attempt is the possibility of comparing the MD results, with real experiments being able to capture analogous space and time scales to the ones pertained to the computer experiments. In the present study, this prerequisite is fulfilled through the quasi-elastic neutron scattering technique (QENS) for measuring self-diffusivity, by elaborating the incoherent scattering signal of hydrogen nuclei. QENS and MD experiments were performed in parallel to probe the hydrogen motion, for the first time in ZIF members. The predicted and measured dynamics behaviors show considerable concentration variation of the hydrogen self-diffusion coefficient in the two topologically different ZIF pore networks of this study, the ZIF-3 and ZIF-8. Modeling options such as the flexibility of the entire matrix versus a rigid framework version, the mobility of the imidazolate ligand, and the inclusion of quantum mechanical effects in the potential functions were examined in detail for the sorption thermodynamics and kinetics of hydrogen and also of deuterium, by employing MD combined with Widom averaging towards studying phase equilibria. The latter methodology ensures a rigorous and efficient way for post-processing the dynamics trajectory, thereby avoiding stochastic moves via Monte Carlo simulation, over the large number of configurational degrees of freedom a nonrigid framework encompasses.

  9. Oxidation of clean silicon surfaces studied by four-point probe surface conductance measurements

    DEFF Research Database (Denmark)

    Petersen, Christian Leth; Grey, Francois; Aono, M.

    1997-01-01

    We have investigated how the conductance of Si(100)-(2 x 1) and Si(111)-(7 x 7) surfaces change during exposure to molecular oxygen. A monotonic decrease in conductance is seen as the (100) surfaces oxidizes. In contract to a prior study, we propose that this change is caused by a decrease in sur...

  10. Nanoscale Surface Photovoltage Mapping of 2D Materials and Heterostructures by Illuminated Kelvin Probe Force Microscopy

    KAUST Repository

    Shearer, Melinda J.

    2018-02-01

    Nanomaterials are interesting for a variety of applications, such as optoelectronics and photovoltaics. However, they often have spatial heterogeneity, i.e. composition change or physical change in the topography or structure, which can lead to varying properties that would influence their applications. New techniques must be developed to understand and correlate spatial heterogeneity with changes in electronic properties. Here we highlight the technique of surface photovoltage-Kelvin probe force microscopy (SPV-KFM), which is a modified version of non-contact atomic force microscopy capable of imaging not only the topography and surface potential, but also the surface photovoltage on the nanoscale. We demonstrate its utility in probing monolayer WSe2-MoS2 lateral heterostructures, which form an ultrathin p-n junction promising for photovoltaic and optoelectronic applications. We show surface photovoltage maps highlighting the different photoresponse of the two material regions as a result of the effective charge separation across this junction. Additionally, we study the variations between different heterostructure flakes and emphasize the importance of controlling the synthesis and transfer of these materials to obtain consistent properties and measurements.

  11. In situ X-ray probing reveals fingerprints of surface platinum oxide.

    Science.gov (United States)

    Friebel, Daniel; Miller, Daniel J; O'Grady, Christopher P; Anniyev, Toyli; Bargar, John; Bergmann, Uwe; Ogasawara, Hirohito; Wikfeldt, Kjartan Thor; Pettersson, Lars G M; Nilsson, Anders

    2011-01-07

    In situ X-ray absorption spectroscopy (XAS) at the Pt L(3) edge is a useful probe for Pt-O interactions at polymer electrolyte membrane fuel cell (PEMFC) cathodes. We show that XAS using the high energy resolution fluorescence detection (HERFD) mode, applied to a well-defined monolayer Pt/Rh(111) sample where the bulk penetrating hard X-rays probe only surface Pt atoms, provides a unique sensitivity to structure and chemical bonding at the Pt-electrolyte interface. Ab initio multiple-scattering calculations using the FEFF code and complementary extended X-ray absorption fine structure (EXAFS) results indicate that the commonly observed large increase of the white-line at high electrochemical potentials on PEMFC cathodes originates from platinum oxide formation, whereas previously proposed chemisorbed oxygen-containing species merely give rise to subtle spectral changes.

  12. In Situ X-Ray Probing Reveals Fingerprints of Surface Platinum Oxide

    Energy Technology Data Exchange (ETDEWEB)

    Friebel, Daniel

    2011-08-24

    In situ x-ray absorption spectroscopy (XAS) at the Pt L{sub 3} edge is a useful probe for Pt-O interactions at polymer electrolyte membrane fuel cell (PEMFC) cathodes. We show that XAS using the high energy resolution fluorescence detection (HERFD) mode, applied to a well-defined monolayer Pt/Rh(111) sample where the bulk penetrating hard x-rays probe only surface Pt atoms, provides a unique sensitivity to structure and chemical bonding at the Pt-electrolyte interface. Ab initio multiple-scattering calculations using the FEFF8 code and complementary extended x-ray absorption fine structure (EXAFS) results indicate that the commonly observed large increase of the white-line at high electrochemical potentials on PEMFC cathodes originates from platinum oxide formation, whereas previously proposed chemisorbed oxygen-containing species merely give rise to subtle spectral changes.

  13. Evolution of the surface magnetic field of rotating proto-neutron stars

    Science.gov (United States)

    Obergaulinger, M.; Aloy, M. Á.

    2017-12-01

    We study the evolution of the field on the surface of proto-neutron stars in the immediate aftermath of stellar core collapse by analyzing the results of self-consistent, axisymmetric simulations of the cores of rapidly rotating high-mass stars. To this end, we compare the field topology and the angular spectra of the poloidal and toroidal field components over a time of about one seconds for cores. Both components are characterized by a complex geometry with high power at intermediate angular scales. The structure is mostly the result of the accretion of magnetic flux embedded in the matter falling through the turbulent post-shock layer onto the PNS. Our results may help to guide further studies of the long-term magneto-thermal evolution of proto-neutron stars. We find that the accretion of stellar progenitor layers endowed with low or null magnetization bury the magnetic field on the PNS surface very effectively.

  14. Determination of Substances Content of Soil Surface Using Fast Neutron Activation Analysis

    International Nuclear Information System (INIS)

    Elin Nuraini; Elisabeth; Sunardi

    2002-01-01

    Determination of substances content of soil surface using neutron activation analysis has been performed. The aim of this research is to determine whether there are any dangerous, hazardous and toxic substances that released from The Research and Development Center for Advanced Technology (RDCAT) as a government institution has possibility in releasing that substances to the environment by surface water, sewage or rain water that give any dangerous the environmental. The fast neutron activation analysis was used to analyze the type and concentration of substances qualitative and quantitatively. The quantitative analysis was performed using relative method. Samples were counted using NaI(TI) detector. The result showed that there are several substances such as Mn-55, Fe-56, P-31, Al-27. Zn,65 and Mg-24. And there are found any hazardous, dangerous and toxic substances in the samples that causing any danger to human and environment. (author)

  15. Use of low energy alkali ion scattering as a probe of surface structure

    International Nuclear Information System (INIS)

    Overbury, S.H.

    1986-01-01

    An overview is given of the use of low energy ion scattering as a probe of surface structure with emphasis on work done using alkali ions. Various schemes for extracting structural information from the ion energy and angle distributions are discussed in terms of advantages and disadvantages of each. The scattering potential which is the primary non-structural parameter needed for analysis, is discussed in terms of recent experimental results. The structure of clean and reconstructed surfaces are discussed, with examples of measurements of layer relaxations on the Mo(111) surface and missing row reconstructions on the Au(110) and Pt(110) surfaces. Studies of adsorbate covered surfaces are presented with respect to location of the adsorbate and its effect on the structure of the underlying substrate. Finally, examples are given which demonstrate the sensitivity of ion scattering to surface defects and disordering on reconstructed Au(110) and Pt(110) surfaces and unreconstructed Mo(111) surfaces, and to ordering of adsorbates on Mo(001). 47 refs., 12 figs

  16. Search for low-energy upscattering of ultracold neutrons from a beryllium surface

    International Nuclear Information System (INIS)

    Muzychka, Al.Yu.; Pokotilovskij, Yu.N.; Geltenbort, P.

    1998-01-01

    The results are presented of the search for the anomalous low energy upcattering of ultracold neutrons from beryllium surface. This upscaterring is considered as one of the possible reasons of UCN 'disappearance' from very cold beryllium bottles, observed in experiments. The Indium foil activation method was used to measure a very low intensity flux of upscattered UCN. The (15-250) m/s velocity interval of upscattered UCN is excluded in these measurements with CL 90%

  17. THE INTEGRATED USE OF COMPUTATIONAL CHEMISTRY, SCANNING PROBE MICROSCOPY, AND VIRTUAL REALITY TO PREDICT THE CHEMICAL REACTIVITY OF ENVIRONMENTAL SURFACES

    Science.gov (United States)

    In the last decade three new techniques scanning probe microscopy (SPM), virtual reality (YR) and computational chemistry ave emerged with the combined capability of a priori predicting the chemically reactivity of environmental surfaces. Computational chemistry provides the cap...

  18. Probing the Surface of Platinum during the Hydrogen Evolution Reaction in Alkaline Electrolyte

    Energy Technology Data Exchange (ETDEWEB)

    Stoerzinger, Kelsey A. [Physical; Favaro, Marco [Advanced; Joint; Chemical; Ross, Philip N. [Materials; Yano, Junko [Joint; Molecular; Liu, Zhi [State; Division; Hussain, Zahid [Advanced; Crumlin, Ethan J. [Advanced; Joint Center

    2017-11-02

    Understanding the surface chemistry of electrocatalysts in operando can bring insight into the reaction mechanism, and ultimately the design of more efficient materials for sustainable energy storage and conversion. Recent progress in synchrotron based X-ray spectroscopies for in operando characterization allows us to probe the solid/liquid interface directly while applying an external potential, applied here to the model system of Pt in alkaline electrolyte for the hydrogen evolution reaction (HER). We employ ambient pressure X-ray photoelectron spectroscopy (AP-XPS) to identify the oxidation and reduction of Pt-oxides and hydroxides on the surface as a function of applied potential, and further assess the potential for hydrogen adsorption and absorption (hydride formation) during and after the HER. This new window into the surface chemistry of Pt in alkaline brings insight into the nature of the rate limiting step, the extent of H ad/absorption and it’s persistence at more anodic potentials.

  19. Probing the surface profile and friction behavior of heterogeneous polymers: a molecular dynamics study

    Science.gov (United States)

    Dai, L.; Sorkin, V.; Zhang, Y. W.

    2017-04-01

    We perform molecular dynamics simulations to investigate molecular structure alternation and friction behavior of heterogeneous polymer (perfluoropolyether) surfaces using a nanoscale probing tip (tetrahedral amorphous carbon). It is found that depending on the magnitude of the applied normal force, three regimes exist: the shallow depth-sensing (SDS), deep depth-sensing (DDS), and transitional depth-sensing (TDS) regimes; TDS is between SDS and DDS. In SDS, the tip is floating on the polymer surface and there is insignificant permanent alternation in the polymer structure due to largely recoverable atomic deformations, and the surface roughness profile can be accurately measured. In DDS, the tip is plowing through the polymer surface and there is significant permanent alternation in the molecular structure. In this regime, the lateral friction force rises sharply and fluctuates violently when overcoming surface pile-ups. In SDS, the friction can be described by a modified Amonton’s law including the adhesion effect; meanwhile, in DDS, the adhesion effect is negligible but the friction coefficient is significantly higher. The underlying reason for the difference in these regimes rests upon different contributions by the repulsion and attraction forces between the tip and polymer surfaces to the friction force. Our findings here reveal important insights into lateral depth-sensing on heterogeneous polymer surfaces and may help improve the precision of depth-sensing devices.

  20. Atomic species recognition on oxide surfaces using low temperature scanning probe microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Zong Min, E-mail: mzmncit@163.com [National Key Laboratory for Electronic Measurement Technology, North University of China, Taiyuan, 030051 (China); Key Laboratory of Instrumentation Science & Dynamic Measurement, North University of China, Ministry of Education, Taiyuan, 030051 (China); School of Instrument and Electronics, North University of China, Taiyuan, 030051 (China); Shi, Yun Bo; Mu, Ji Liang; Qu, Zhang; Zhang, Xiao Ming; Qin, Li [National Key Laboratory for Electronic Measurement Technology, North University of China, Taiyuan, 030051 (China); Key Laboratory of Instrumentation Science & Dynamic Measurement, North University of China, Ministry of Education, Taiyuan, 030051 (China); School of Instrument and Electronics, North University of China, Taiyuan, 030051 (China); Liu, Jun, E-mail: liuj@nuc.edu.cn [National Key Laboratory for Electronic Measurement Technology, North University of China, Taiyuan, 030051 (China); Key Laboratory of Instrumentation Science & Dynamic Measurement, North University of China, Ministry of Education, Taiyuan, 030051 (China); School of Instrument and Electronics, North University of China, Taiyuan, 030051 (China)

    2017-02-01

    Highlights: • The coexisted phase of p(2 × 1)and c(6 × 2) on Cu(110)-O surface using AFM under UHV at low temperature. • Two different c(6 × 2) phase depending on the status of the tip apex. • Electronic state of tip seriously effect the resolution and stability of the sample surface. - Abstract: In scanning probe microscopy (SPM), the chemical properties and sharpness of the tips of the cantilever greatly influence the scanning of a sample surface. Variation in the chemical properties of the sharp tip apex can induce transformation of the SPM images. In this research, we explore the relationship between the tip and the structure of a sample surface using dynamic atomic force microscopy (AFM) on a Cu(110)-O surface under ultra-high vacuum (UHV) at low temperature (78 K). We observed two different c(6 × 2) phase types in which super-Cu atoms show as a bright spot when the tip apex is of O atoms and O atoms show as a bright spot when the tip apex is of Cu atoms. We also found that the electronic state of the tip has a serious effect on the resolution and stability of the sample surface, and provide an explanation for these phenomena. This technique can be used to identify atom species on sample surfaces, and represents an important development in the SPM technique.

  1. Development of Cold Neutron Activation Station at HANARO Cold Neutron Source

    International Nuclear Information System (INIS)

    Sun, G. M.; Hoang, S. M. T.; Moon, J. H.; Chung, Y. S.; Cho, S. J.; Lee, K. H.; Park, B. G.; Choi, H. D.

    2012-01-01

    A new cold neutron source at the HANARO Research Reactor had been constructed in the framework of a five-year project, and ended in 2009. It has seven neutron guides, among which five guides were already allocated for a number of neutron scattering instruments. A new two-year project to develop a Cold Neutron Activation Station (CONAS) was carried out at the two neutron guides since May 2010, which was supported by the program of the Ministry of Education, Science and Technology, Korea. Fig. 1 shows the location of CONAS. CONAS is a complex facility including several radioanalytical instruments utilizing neutron capture reaction to analyze elements in a sample. It was designed to include three instruments like a CN-PGAA (Cold Neutron - Prompt Gamma Activation Analysis), a CN-NIPS (Cold Neutron - Neutron Induced Pair Spectrometer), and a CN-NDP (Cold Neutron - Neutron-induced prompt charged particle Depth Profiling). Fig. 2 shows the conceptual configuration of the CONAS concrete bioshield and the instruments. CN-PGAA and CN-NIPS measure the gamma-rays promptly emitted from the sample after neutron capture, whereas CN-NDP is a probe to measure the charged particles emitted from the sample surface after neutron capture. For this, we constructed two cold neutron guides called CG1 and CG2B guides from the CNS

  2. AFM Colloidal Probe Measurements Implicate Capillary Condensation in Punch-Particle Surface Interactions during Tableting.

    Science.gov (United States)

    Badal Tejedor, Maria; Nordgren, Niklas; Schuleit, Michael; Millqvist-Fureby, Anna; Rutland, Mark W

    2017-11-21

    Adhesion of the powders to the punches is a common issue during tableting. This phenomenon is known as sticking and affects the quality of the manufactured tablets. Defective tablets increase the cost of the manufacturing process. Thus, the ability to predict the tableting performance of the formulation blend before the process is scaled-up is important. The adhesive propensity of the powder to the tableting tools is mostly governed by the surface-surface adhesive interactions. Atomic force microscopy (AFM) colloidal probe is a surface characterization technique that allows the measurement of the adhesive interactions between two materials of interest. In this study, AFM steel colloidal probe measurements were performed on ibuprofen, MCC (microcrystalline cellulose), α-lactose monohydrate, and spray-dried lactose particles as an approach to modeling the punch-particle surface interactions during tableting. The excipients (lactose and MCC) showed constant, small, attractive, and adhesive forces toward the steel surface after a repeated number of contacts. In comparison, ibuprofen displayed a much larger attractive and adhesive interaction increasing over time both in magnitude and in jump-in/jump-out separation distance. The type of interaction acting on the excipient-steel interface can be related to a van der Waals force, which is relatively weak and short-ranged. By contrast, the ibuprofen-steel interaction is described by a capillary force profile. Even though ibuprofen is not highly hydrophilic, the relatively smooth surfaces of the crystals allow "contact flooding" upon contact with the steel probe. Capillary forces increase because of the "harvesting" of moisture-due to the fast condensation kinetics-leaving a residual condensate that contributes to increase the interaction force after each consecutive contact. Local asperity contacts on the more hydrophilic surface of the excipients prevent the flooding of the contact zone, and there is no such adhesive

  3. I. Surface properties of neutron-rich nuclei. II. Pion condensation at finite temperature

    International Nuclear Information System (INIS)

    Kolehmainen, K.A.

    1983-01-01

    In part I, the energy density formalism, the Thomas-Fermi approximation, and Skyrme-type interactions were used to describe the energy density of a semi-infinite slab of neturon-rich nuclear matter at zero temperature. The existence of a drip phase at low proton fractions is allowed in addition to the more dense nuclear phase, and various bulk properties of both phases are found when the system is in equilibrium. The usual definition of the surface energy is extended to apply to the case where drip is present. Assuming a Fermi function type density profile, a constrained variational calculation is performed to determine the neutron and proton surface diffuseness parameters, the thickness of the neutron skin, and the surface energy. Results are obtained for proton fractions reanging from 0.5 (symmetric nuclear matter) to zero (pure neutron matter) for most Skyrme-type interactions in common use. The results are in close agreement with the predictions of the droplet model, as well as with the results of more exact calculations in those cases where the more exact results exist (only for symmetric or nearly symmetric matter in most cases). Significantly different asymmetry dependences for different interactions are found. In part II, several simple but increasingly complex models are used to calculate the threshold for charged pion condensation in neutron-rich nuclear matter at finite temperature. Unlike in mean field theory descriptions of pion condensation, the effects of thermal excitations of the pion field are included. The thermal pion excitations have two important effects: first, to modify the phase diagram qualitatively from that predicted by mean field theory, and second, to make the phase transition to a spatially nonuniform condensed state at finite temperature always first, rather than second, order

  4. A new optical method for measuring surface temperature at large incident probe angles

    Science.gov (United States)

    Lee, A. S.; Norris, P. M.

    1997-02-01

    A novel thermoreflectance technique has been developed for noncontact temperature measurements using laser light incident at large angles on solid materials and devices. The method involves measuring the differential reflectance from a polarization modulated laser beam. The polarization differential reflectance technique is demonstrated on single-crystal Si wafers and on a polycrystalline carbon thin film over a temperature range of 20-60 °C. The method is shown to be an extremely sensitive temperature probe for near grazing angle measurements, which could be useful for monitoring the surface temperature of closely stacked silicon wafers used in batch processing in the microelectronics industry.

  5. Neutron Scattering

    International Nuclear Information System (INIS)

    Fayer, Michael J.; Gee, Glendon W.

    2005-01-01

    The neutron probe is a standard tool for measuring soil water content. This article provides an overview of the underlying theory, describes the methodology for its calibration and use, discusses example applications, and identifies the safety issues. Soil water makes land-based life possible by satisfying plant water requirements, serving as a medium for nutrient movement to plant roots and nutrient cycling, and controlling the fate and transport of contaminants in the soil environment. Therefore, a successful understanding of the dynamics of plant growth, nutrient cycling, and contaminant behavior in the soil requires knowledge of the soil water content as well as its spatial and temporal variability. After more than 50 years, neutron probes remain the most reliable tool available for field monitoring of soil water content. Neutron probes provide integrated measurements over relatively large volumes of soil and, with proper access, allow for repeated sampling of the subsurface at the same locations. The limitations of neutron probes include costly and time-consuming manual operation, lack of data automation, and costly regulatory requirements. As more non-radioactive systems for soil water monitoring are developed to provide automated profiling capabilities, neutron-probe usage will likely decrease. Until then, neutron probes will continue to be a standard for reliable measurements of field water contents in soils around the globe

  6. Description of a neutron field perturbed by a probe using coupled Monte Carlo and discrete ordinates radiation transport calculations

    International Nuclear Information System (INIS)

    Zazula, J.M.

    1984-01-01

    This work concerns calculation of a neutron response, caused by a neutron field perturbed by materials surrounding the source or the detector. Solution of a problem is obtained using coupling of the Monte Carlo radiation transport computation for the perturbed region and the discrete ordinates transport computation for the unperturbed system. (author). 62 refs

  7. Probing the surface properties of a polymer glass with macroscopic friction

    International Nuclear Information System (INIS)

    Bureau, Lionel

    2007-01-01

    We show how macroscopic friction can be used as a sensitive probe of chain dynamics at the surface of a glassy polymer. We present experiments in which a smooth poly(methylmethacrylate) (PMMA) solid slides on flat surfaces presenting different densities of pinning sites available for polymer/substrate bond formation. These experiments indicate that: (i) at high pinning level, frictional dissipation occurs through the sudden flips of molecular-sized bistable regions localized in a nm-thick layer of confined chains, which responds to shear as an elasto-plastic solid, and (ii) in situations of weak pinning, dissipation appears to be governed by a process akin to that proposed for rubber friction. This suggests that some 'glass-to-rubber' transition occurs at the polymer surface when its interaction with the substrate goes from strong to weak. The temperature-dependence of friction provides further support for the presence of a nm-thick layer at the polymer surface, which exhibits a rubberlike response in situation of weak interaction with the countersurface. This behavior results from the interplay between viscous flow in this surface layer, and shear induced depinning of adsorbed surface chains. Moreover, a quantitative analysis of the results indicates that the pinning dynamics of polymer chains is controlled by localized β rotational motions at the interface

  8. Rain, winds and haze during the Huygens probe's descent to Titan's surface

    Science.gov (United States)

    Tomasko, M.G.; Archinal, B.; Becker, T.; Bezard, B.; Bushroe, M.; Combes, M.; Cook, D.; Coustenis, A.; De Bergh, C.; Dafoe, L.E.; Doose, L.; Doute, S.; Eibl, A.; Engel, S.; Gliem, F.; Grieger, B.; Holso, K.; Howington-Kraus, E.; Karkoschka, E.; Keller, H.U.; Kirk, R.; Kramm, R.; Kuppers, M.; Lanagan, P.; Lellouch, E.; Lemmon, M.; Lunine, J.; McFarlane, E.; Moores, J.; Prout, G.M.; Rizk, B.; Rosiek, M.; Rueffer, P.; Schroder, S.E.; Schmitt, B.; See, C.; Smith, P.; Soderblom, L.; Thomas, N.; West, R.

    2005-01-01

    The irreversible conversion of methane into higher hydrocarbons in Titan's stratosphere implies a surface or subsurface methane reservoir. Recent measurements from the cameras aboard the Cassini orbiter fail to see a global reservoir, but the methane and smog in Titan's atmosphere impedes the search for hydrocarbons on the surface. Here we report spectra and high-resolution images obtained by the Huygens Probe Descent Imager/Spectral Radiometer instrument in Titan's atmosphere. Although these images do not show liquid hydrocarbon pools on the surface, they do reveal the traces of once flowing liquid. Surprisingly like Earth, the brighter highland regions show complex systems draining into flat, dark lowlands. Images taken after landing are of a dry riverbed. The infrared reflectance spectrum measured for the surface is unlike any other in the Solar System; there is a red slope in the optical range that is consistent with an organic material such as tholins, and absorption from water ice is seen. However, a blue slope in the near-infrared suggests another, unknown constituent. The number density of haze particles increases by a factor of just a few from an altitude of 150 km to the surface, with no clear space below the tropopause. The methane relative humidity near the surface is 50 per cent. ?? 2005 Nature Publishing Group.

  9. Studies of float glass surfaces by neutron and x-ray reflection

    International Nuclear Information System (INIS)

    Dalgliesh, R.

    2001-09-01

    The surface of glass and glass coatings have been studied using x-ray and neutron scattering techniques. In particular, the effect of aqueous solutions and humid atmospheres on both the fire polished and the tin rich side of float glass have been investigated using neutron and x-ray reflection. Isotopic substitution has enabled the number density of water molecules within the float glass surface to be monitored with respect to immersion time, temperature and impurity content. A thin gel-like water-rich layer of thickness ∼30A is observed at the surface accompanied by a more deeply penetrating layer which increases in depth with time reaching ∼500A after 6 months. The rate of water ingression is higher than predicted from previous work carried out at elevated temperatures. Small decreases in the depth of penetration have been observed for glass containing alumina and tin. Water penetration into thin films made by a sol-gel process have also been studied. The hydrophobicity of these films had been varied by the addition of fluoroalkylsilane. Neutron and X-ray reflection revealed that water entered the highly hydrophobic films readily from the vapour phase. This suggests a method of film destabilisation by which water enters the film and freezes, causing the film to crack. Changes in fluoroalkylsilane content and annealing have little effect on the penetration of water into the coatings. Etched float glass surfaces have been used as a system for testing the applicability of current off-specular scattering models. A rich surface structure has been found which results in reflection effects that cannot be explained by these models. Model systems have also been developed in an attempt to combine x-ray fluorescence techniques with reflectivity. (author)

  10. Antibody adsorption on the surface of water studied by neutron reflection.

    Science.gov (United States)

    Smith, Charles; Li, Zongyi; Holman, Robert; Pan, Fang; Campbell, Richard A; Campana, Mario; Li, Peixun; Webster, John R P; Bishop, Steven; Narwal, Rojaramani; Uddin, Shahid; van der Walle, Christopher F; Lu, Jian R

    2017-04-01

    Surface and interfacial adsorption of antibody molecules could cause structural unfolding and desorbed molecules could trigger solution aggregation, resulting in the compromise of physical stability. Although antibody adsorption is important and its relevance to many mechanistic processes has been proposed, few techniques can offer direct structural information about antibody adsorption under different conditions. The main aim of this study was to demonstrate the power of neutron reflection to unravel the amount and structural conformation of the adsorbed antibody layers at the air/water interface with and without surfactant, using a monoclonal antibody 'COE-3' as the model. By selecting isotopic contrasts from different ratios of H 2 O and D 2 O, the adsorbed amount, thickness and extent of the immersion of the antibody layer could be determined unambiguously. Upon mixing with the commonly-used non-ionic surfactant Polysorbate 80 (Tween 80), the surfactant in the mixed layer could be distinguished from antibody by using both hydrogenated and deuterated surfactants. Neutron reflection measurements from the co-adsorbed layers in null reflecting water revealed that, although the surfactant started to remove antibody from the surface at 1/100 critical micelle concentration (CMC) of the surfactant, complete removal was not achieved until above 1/10 CMC. The neutron study also revealed that antibody molecules retained their globular structure when either adsorbed by themselves or co-adsorbed with the surfactant under the conditions studied.

  11. Crystallographic analysis of thin film surfaces using micro-probe reflexion high-energy electron diffraction

    International Nuclear Information System (INIS)

    Ichikawa, Masakazu; Doi, Takahisa; Hayakawa, Kazunobu

    1984-01-01

    Micro-probe reflexion high-energy electron diffraction using an electron beam having a 20nm beam diameter at a beam current of 8 nA, has been developed for performing crystallographic analyses of thin film and bulk crystal surfaces. High spatial resolution and high brightness have made it possible to perform analyses of thin films on substrates having fine structures without such sample preparation as thinning. A dark field imaging method using part of the diffraction spot intensity has also been developed. Using this method, it was found that atomic steps and dislocations on bulk and material-deposited Si surfaces can be observed. This shows the usefulness of the technique for studying crystal growth of thin films with mono-layer depth resolution. (author)

  12. Nanoscale surface photovoltage of organic semiconductors with two pass Kelvin probe microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Escasain, E; Colchero, J; Palacios-Lidon, E [Departamento Fisica, Facultad de Quimica (Campus Espinardo), Universidad de Murcia, E-30100 Murcia (Spain); Lopez-Elvira, E; Baro, A M, E-mail: elisapl@um.es [Instituto de Ciencia de Materiales de Madrid-CSIC, Campus de Cantoblanco, E-28049, Madrid (Spain)

    2011-09-16

    Kelvin probe microscopy implemented with controlled sample illumination is used to study nanoscale surface photovoltage effects. With this objective a two trace method, where each scanning line is measured with and without external illumination, is proposed. This methodology allows a direct comparison of the contact potential images acquired in darkness and under illumination and, therefore, the surface photovoltage is simply inferred. Combined with an appropriate data analysis, the temporal and spatial evolution of reversible and irreversible photo-induced processes can be obtained. The potential and versatility of this technique is applied to MEH-PPV thin films. Photo-physical phenomena such as the mesoscale polymer electronic light-induced response as well as the local nanoscale electro-optical properties are studied.

  13. Multiparametric Kelvin Probe Force Microscopy for the Simultaneous Mapping of Surface Potential and Nanomechanical Properties.

    Science.gov (United States)

    Xie, Hui; Zhang, Hao; Hussain, Danish; Meng, Xianghe; Song, Jianmin; Sun, Lining

    2017-03-21

    We report high-resolution multiparametric kelvin probe force microscopy (MP-KPFM) measurements for the simultaneous quantitative mapping of the contact potential difference (CPD) and nanomechanical properties of the sample in single-pass mode. This method combines functionalities of the force-distance-based atomic force microscopy and amplitude-modulation (AM) KPFM to perform measurements in single-pass mode. During the tip-sample approach-and-retract cycle, nanomechanical measurements are performed for the retract part of nanoindentation, and the CPD is measured by the lifted probe with a constant tip-sample distance. We compare the performance of the proposed method with the conventional KPFMs by mapping the CPD of multilayer graphene deposited on n-doped silicon, and the results demonstrate that MP-KPFM has comparable performance to AM-KPFM. In addition, the experimental results of a custom-fabricated polymer grating with heterogeneous surfaces validate the multiparametric imaging capability of the MP-KPFM. This method can have potential applications in finding the inherent link between nanomechanical properties and the surface potential of the materials, such as the quantification of the electromechanical response of the deformed piezoelectric materials.

  14. Probing electronic phase transitions with phonons via inelastic neutron scattering: superconductivity in borocarbides, charge and magnetic order in manganites

    International Nuclear Information System (INIS)

    Weber, F.

    2007-01-01

    The present thesis concentrates on the signatures of strong electron-phonon coupling in phonon properties measured by inelastic neutron scattering. The inelastic neutron scattering experiments were performed on the triple-axis spectrometers 1T and DAS PUMA at the research reactors in Saclay (France) and Munich (Germany), respectively. The work is subdivided into two separate chapters: In the first part, we report measurements of the lattice dynamical properties, i.e. phonon frequency, linewidth and intensity, of the conventional, i.e. phonon-mediated, superconductor YNi 2 B 2 C of the rare-earth-borocarbide family. The detailed check of theoretical predictions for these properties, which were calculated in the theory group of our institute, was one major goal of this work. We measured phonons in the normal state, i.e. T>T c , for several high symmetry directions up to 70 meV. We were able to extract the full temperature dependence of the superconducting energy gap 2Δ(T) from our phonon scans with such accuracy that even deviations from the weak coupling BCS behaviour could be clearly observed. By measuring phonons at different wave vectors we demonstrated that phonons are sensitive to the gap anisotropy under the precondition, that different phonons get their coupling strength from different parts of the Fermi surface. In the second part, we investigated the properties of Mn-O bond-stretching phonons in the bilayer manganite La 2-2x Sr 1+2x Mn 2 O 7 . At the doping level x=0.38 this compound has an ferromagnetic groundstate and exhibits the so-called colossal magnetoresistance effect in the vicinity of the Curie temperature T C . The atomic displacement patterns of the investigated phonons closely resemble possible Jahn-Teller distortions of the MnO 6 octahedra, which are introduced in this compound by the Jahn-Teller active Mn 3+ ions. We observed strong renormalizations of the phonon frequencies and clear peaks of the intrinsic phonon linewidth near the order

  15. Probing electronic phase transitions with phonons via inelastic neutron scattering: superconductivity in borocarbides, charge and magnetic order in manganites

    Energy Technology Data Exchange (ETDEWEB)

    Weber, F.

    2007-11-02

    The present thesis concentrates on the signatures of strong electron-phonon coupling in phonon properties measured by inelastic neutron scattering. The inelastic neutron scattering experiments were performed on the triple-axis spectrometers 1T and DAS PUMA at the research reactors in Saclay (France) and Munich (Germany), respectively. The work is subdivided into two separate chapters: In the first part, we report measurements of the lattice dynamical properties, i.e. phonon frequency, linewidth and intensity, of the conventional, i.e. phonon-mediated, superconductor YNi{sub 2}B{sub 2}C of the rare-earth-borocarbide family. The detailed check of theoretical predictions for these properties, which were calculated in the theory group of our institute, was one major goal of this work. We measured phonons in the normal state, i.e. T>T{sub c}, for several high symmetry directions up to 70 meV. We were able to extract the full temperature dependence of the superconducting energy gap 2{delta}(T) from our phonon scans with such accuracy that even deviations from the weak coupling BCS behaviour could be clearly observed. By measuring phonons at different wave vectors we demonstrated that phonons are sensitive to the gap anisotropy under the precondition, that different phonons get their coupling strength from different parts of the Fermi surface. In the second part, we investigated the properties of Mn-O bond-stretching phonons in the bilayer manganite La{sub 2-2x}Sr{sub 1+2x}Mn{sub 2}O{sub 7}. At the doping level x=0.38 this compound has an ferromagnetic groundstate and exhibits the so-called colossal magnetoresistance effect in the vicinity of the Curie temperature T{sub C}. The atomic displacement patterns of the investigated phonons closely resemble possible Jahn-Teller distortions of the MnO{sub 6} octahedra, which are introduced in this compound by the Jahn-Teller active Mn{sup 3+} ions. We observed strong renormalizations of the phonon frequencies and clear peaks of

  16. Virus-based surface patterning of biological molecules, probes, and inorganic materials.

    Science.gov (United States)

    Ahn, Suji; Jeon, Seongho; Kwak, Eun-A; Kim, Jong-Man; Jaworski, Justyn

    2014-10-01

    An essential requirement for continued technological advancement in many areas of biology, physics, chemistry, and materials science is the growing need to generate custom patterned materials. Building from recent achievements in the site-specific modification of virus for covalent surface tethering, we show in this work that stable 2D virus patterns can be generated in custom geometries over large area glass surfaces to yield templates of biological, biochemical, and inorganic materials in high density. As a nanomaterial building block, filamentous viruses have been extensively used in recent years to produce materials with interesting properties, owing to their ease of genetic and chemical modification. By utilizing un-natural amino acids generated at specific locations on the filamentous fd bacteriophage protein coat, surface immobilization is carried out on APTES patterned glass resulting in precise geometries of covalently linked virus material. This technique facilitated the surface display of a high density of virus that were labeled with biomolecules, fluorescent probes, and gold nanoparticles, thereby opening the possibility of integrating virus as functional components for surface engineering. Copyright © 2014 Elsevier B.V. All rights reserved.

  17. Approximate method for measurement of phase-distribution in multiphase materials with small neutron-attenuation using a neutron beam as a probe

    International Nuclear Information System (INIS)

    Hibiki, T.; Mishima, K.

    1996-01-01

    An approximate method for the quantification of a neutron radiography image was proposed for measuring the phase-distribution of multiphase materials with small neutron-attenuation. Since it is not necessary for this method to put a standard calibration sample in a field of a view, this method has an advantage of measuring the phase-distribution of multiphase materials with unknown internal-structure and neutron-attenuation in the object in an enlarged field of view. Although its application is limited to an object with small neutron-attenuation, it was revealed from a numerical analysis that the approximate method can be applicable to heavy water, liquid sodium and liquid potassium, which are important materials in relation to research on the thermalhydraulics of the nuclear reactor. The validity of the approximate method was also confirmed experimentally by comparing the void fraction of air-water flows in round tubes measured by the approximate method with those by the other more-accurate method. (orig.)

  18. Adhesion and friction of polymer surfaces studied using scanning probe microscopy

    Science.gov (United States)

    Moon, Seung-Ho

    2003-10-01

    Scanning Probe Microscopy has been utilized to investigate the nanomechanical and nanorheological properties at the surface of polymers and polymer blends. To study the surface behavior in detail, it is critical that the SPM instrument have sufficient flexibility. A temperature stage and environmental chamber have been implemented and measurement automation has been achieved using a high-speed data acquisition system controlled by LabView(TM). Finally, new measurement protocols, "X-modulation" and "Force-Distance with X-modulation", have been developed. First measurements using those techniques have been performed for the study of aged model pressure sensitive adhesives. It has been found that the magnitude of the lateral force is so sensitive to adhesion force that X-modulation can identify qualitative differences in the strength of surface stickiness. Variations in surface adhesiveness with humidity are more obvious when the tackifier is present. A large lateral force and strongly reduced stiffness, measured using F-d with X-modulation, have been observed at high humidity for the homogeneous, hydrophilic surface of the adhesive loaded with 60wt% tackifier. These observations are consistent with a model that envisions a tackifier-enriched region near the surface. A large creep effect has also been observed for this sample, and the creep effect is magnified with temperature. These results are consistent with the hypothesis that at a hydrophilic adhesive surface water molecules may strongly alter the surface-tip interactions or modify the mechanical properties of the material nearest the surface. By changing the Z-loading velocity, dynamic adhesion behavior has been investigated. The mechanism of adhesive failure have been elucidated by comparing the velocity dependence of pull-off force and lateral force. Since this dynamic measurement is sensitive to the material composition at the surface, it has been utilized to study the surface segregation of one component at

  19. Laser spectroscopy of cadmium isotopes: probing the nuclear structure between the neutron 50 and 82 shell closures

    CERN Multimedia

    Blaum, K; Stroke, H H; Krieger, A R

    We propose to study the isotopic chain of cadmium with high-resolution laser spectroscopy for the first time. Our goal is to determine nuclear spins, moments and root-mean-square charge radii of ground and isomeric states between the neutron 50 and 82 shell closures, contributing decisively to a better understanding of the nuclear structure in the vicinity of the doubly-magic $^{100}$Sn and $^{132}$Sn. On the neutron-rich side this is expected to shed light on a shell-quenching hypothesis and consequently on the duration of the r-process along the waiting-point nuclei below $^{130}$Cd. On the neutron-deficient side it may elucidate the role of the cadmium isotopes in the rp-process for rapidly accreting neutron stars.

  20. Large area window on vacuum chamber surface for neutron scattering instruments

    International Nuclear Information System (INIS)

    Itoh, Shinichi; Yokoo, Tetsuya; Ueno, Kenji; Suzuki, Junichi; Teraoku, Takuji; Tsuchiya, Masao

    2012-01-01

    The feasibility of a large area window using a thin aluminum plate on the surface of the vacuum chamber for neutron scattering instruments at a pulsed neutron source was investigated. In the prototype investigation for a window with an area of 1m×1.4m and a thickness of 1 mm, the measured pressure dependence of the displacement agreed well with a calculation using a nonlinear strain–stress curve up to the plastic deformation region. In addition, we confirmed the repetition test up to 2000 pressurization-and-release cycles, which is sufficient for the lifetime of the vacuum chamber for neutron scattering instruments. Based on these investigations, an actual model of the window to be mounted on the vacuum chamber of the High Resolution Chopper Spectrometer (HRC) at J-PARC was designed. By using a calculated stress distribution on the window, the clamping structure capable of balancing the tension in the window was determined. In a model with a structure identical to the actual window, we confirmed the repetition test over more than 7000 pressurization-and-release cycles, which shows a lifetime long enough for the actual usage of the vacuum chamber on the HRC.

  1. Probing surface plasmons in individual Ag nanoparticles in the ultra-violet spectral regime.

    Science.gov (United States)

    Chu, Ming-Wen; Sharma, Pradeep; Chang, Ching-Pin; Liou, Sz Chian; Tsai, Kun-Tong; Wang, Juen-Kai; Wang, Yuh-Lin; Chen, Cheng Hsuan

    2009-06-10

    Previous investigations of surface plasmons in Ag largely focused on their excitations in the visible spectral regime. Using scanning transmission electron microscopy with an electron beam of 0.2 nm in conjunction with electron energy-loss spectroscopy, we spectrally and spatially probe the surface plasmons in individual Ag nanoparticles (approximately 30 nm), grown on Si, in the ultra-violet spectral regime. The nanomaterials show respective sharp and broad surface-plasmon resonances at approximately 3.5 eV (approximately 355 nm) and approximately 7.0 eV (approximately 177 nm), and the correlated spectral calculations established their multipolar characteristics. The near-field distributions of the surface plasmons on the nanoparticles were also mapped out, revealing the predominant dipolar nature of the 3.5 eV excitation with obvious near-field enhancements at one end of the nano-object. The unveiled near-field enhancements have potential applications in plasmonics and molecular sensing.

  2. Probing surface plasmons in individual Ag nanoparticles in the ultra-violet spectral regime

    International Nuclear Information System (INIS)

    Chu, M-W; Chang, C-P; Liou, S C; Wang, J-K; Chen, C H; Sharma, Pradeep; Tsai, K-T; Wang, Y-L

    2009-01-01

    Previous investigations of surface plasmons in Ag largely focused on their excitations in the visible spectral regime. Using scanning transmission electron microscopy with an electron beam of 0.2 nm in conjunction with electron energy-loss spectroscopy, we spectrally and spatially probe the surface plasmons in individual Ag nanoparticles (∼30 nm), grown on Si, in the ultra-violet spectral regime. The nanomaterials show respective sharp and broad surface-plasmon resonances at ∼3.5 eV (∼355 nm) and ∼7.0 eV (∼177 nm), and the correlated spectral calculations established their multipolar characteristics. The near-field distributions of the surface plasmons on the nanoparticles were also mapped out, revealing the predominant dipolar nature of the 3.5 eV excitation with obvious near-field enhancements at one end of the nano-object. The unveiled near-field enhancements have potential applications in plasmonics and molecular sensing.

  3. Interactions between protein coated particles and polymer surfaces studied with the rotating particles probe.

    Science.gov (United States)

    Kemper, M; Spridon, D; van IJzendoorn, L J; Prins, M W J

    2012-05-29

    Nonspecific interactions between proteins and polymer surfaces have to be minimized in order to control the performance of biosensors based on immunoassays with particle labels. In this paper we investigate these nonspecific interactions by analyzing the response of protein coated magnetic particles to a rotating magnetic field while the particles are in nanometer vicinity to a polymer surface. We use the fraction of nonrotating (bound) particles as a probe for the interaction between the particles and the surface. As a model system, we study the interaction of myoglobin coated particles with oxidized polystyrene surfaces. We measure the interaction as a function of the ionic strength of the solution, varying the oxidation time of the polystyrene and the pH of the solution. To describe the data we propose a model in which particles bind to the polymer by crossing an energy barrier. The height of this barrier depends on the ionic strength of the solution and two interaction parameters. The fraction of nonrotating particles as a function of ionic strength shows a characteristic shape that can be explained with a normal distribution of energy barrier heights. This method to determine interaction parameters paves the way for further studies to quantify the roles of protein coated particles and polymers in their mutual nonspecific interactions in different matrixes.

  4. MAGNETIC NEUTRON SCATTERING

    International Nuclear Information System (INIS)

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

    2004-01-01

    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. MAGNETIC NEUTRON SCATTERING

    Energy Technology Data Exchange (ETDEWEB)

    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

  6. Footprint radius of a cosmic-ray neutron probe for measuring soil-water content and its spatiotemporal variability in an alpine meadow ecosystem

    Science.gov (United States)

    Zhu, Xuchao; Cao, Ruixue; Shao, Mingan; Liang, Yin

    2018-03-01

    Cosmic-ray neutron probes (CRNPs) have footprint radii for measuring soil-water content (SWC). The theoretical radius is much larger at high altitude, such as the northern Tibetan Plateau, than the radius at sea level. The most probable practical radius of CRNPs for the northern Tibetan Plateau, however, is not known due to the lack of SWC data in this hostile environment. We calculated the theoretical footprint of the CRNP based on a recent simulation and analyzed the practical radius of a CRNP for the northern Tibetan Plateau by measuring SWC at 113 sampling locations on 21 measuring occasions to a depth of 30 cm in a 33.5 ha plot in an alpine meadow at 4600 m a.s.l. The temporal variability and spatial heterogeneity of SWC within the footprint were then analyzed. The theoretical footprint radius was between 360 and 420 m after accounting for the influences of air humidity, soil moisture, vegetation and air pressure. A comparison of SWCs measured by the CRNP and a neutron probe from access tubes in circles with different radii conservatively indicated that the most probable experimental footprint radius was >200 m. SWC within the CRNP footprint was moderately variable over both time and space, but the temporal variability was higher. Spatial heterogeneity was weak, but should be considered in future CRNP calibrations. This study provided theoretical and practical bases for the application and promotion of CRNPs in alpine meadows on the Tibetan Plateau.

  7. Hydraulic conductivity obtained by instantaneous profile method using retention curve and neutron probes and Genuchten model; Condutividade hidraulica obtida pelo metodo do perfil instantaneo utilizando curva de retencao e sonda de neutrons e pelo modelo de Genuchten

    Energy Technology Data Exchange (ETDEWEB)

    Berretta, Ana Lucia Olmedo

    1999-07-01

    The hydraulic conductivity is one of the most important parameters to understand the movement of water in the unsaturated zone. Reliable estimations are difficult to obtain, once the hydraulic conductivity is highly variable. This study was carried out at 'Escola Superior de Agricultura Luiz de Queiroz', Universidade de Sao Paulo, in a Kandiudalfic Eutrudox soil. The hydraulic conductivity was determined by a direct and an indirect method. The instantaneous profile method was described and the hydraulic conductivity as a function of soil water content was determined by solving the Richards equation. Tensiometers were used to estimate the total soil water potential, and the neutron probe and the soil retention curve were used to estimate soil water content in the direct method. The neutron probe showed to be not adequately sensible to the changes of soil water content in this soil. Despite of the soil retention curve provides best correlation values to soil water content as a function of water redistribution time, the soil water content in this soil did not vary too much till the depth of 50 cm, reflecting the influence of the presence of a Bt horizon. The soil retention curve was well fitted by the van Genuchten model used as an indirect method. The values of the van Genuchten and the experimental relative hydraulic conductivity obtained by the instantaneous profile method provided a good correlation. However, the values estimated by the model were always lower than that ones obtained experimentally. (author)

  8. Surface topography acquisition method for double-sided near-right-angle structured surfaces based on dual-probe wavelength scanning interferometry.

    Science.gov (United States)

    Zhang, Tao; Gao, Feng; Jiang, Xiangqian

    2017-10-02

    This paper proposes an approach to measure double-sided near-right-angle structured surfaces based on dual-probe wavelength scanning interferometry (DPWSI). The principle and mathematical model is discussed and the measurement system is calibrated with a combination of standard step-height samples for both probes vertical calibrations and a specially designed calibration artefact for building up the space coordinate relationship of the dual-probe measurement system. The topography of the specially designed artefact is acquired by combining the measurement results with white light scanning interferometer (WLSI) and scanning electron microscope (SEM) for reference. The relative location of the two probes is then determined with 3D registration algorithm. Experimental validation of the approach is provided and the results show that the method is able to measure double-sided near-right-angle structured surfaces with nanometer vertical resolution and micrometer lateral resolution.

  9. Epitaxial growth of pentacene on alkali halide surfaces studied by Kelvin probe force microscopy.

    Science.gov (United States)

    Neff, Julia L; Milde, Peter; León, Carmen Pérez; Kundrat, Matthew D; Eng, Lukas M; Jacob, Christoph R; Hoffmann-Vogel, Regina

    2014-04-22

    In the field of molecular electronics, thin films of molecules adsorbed on insulating surfaces are used as the functional building blocks of electronic devices. Control of the structural and electronic properties of the thin films is required for reliably operating devices. Here, noncontact atomic force and Kelvin probe force microscopies have been used to investigate the growth and electrostatic landscape of pentacene on KBr(001) and KCl(001) surfaces. We have found that, together with molecular islands of upright standing pentacene, a new phase of tilted molecules appears near step edges on KBr. Local contact potential differences (LCPD) have been studied with both Kelvin experiments and density functional theory calculations. Our images reveal that differently oriented molecules display different LCPD and that their value is independent of the number of molecular layers. These results point to the formation of an interface dipole, which may be explained by a partial charge transfer from the pentacene to the surface. Moreover, the monitoring of the evolution of the pentacene islands shows that they are strongly affected by dewetting: Multilayers build up at the expense of monolayers, and in the Kelvin images, previously unknown line defects appear, which reveal the epitaxial growth of pentacene crystals.

  10. Probing protein: DNA interactions using a uniform monolayer of DNA and surface plasmon resonance

    Science.gov (United States)

    Shumaker-Parry, Jennifer S.; Campbell, Charles T.; Stormo, Gary D.; Silbaq, Fauzi S.; Aebersold, Rudolf H.

    2000-04-01

    A method is described for immobilizing double-stranded DNAs to a planar gold surface with high density and uniform spacing. This is accomplished by adsorbing biotinylated DNAs onto a nearly close-packed monolayer of the protein streptavidin. This streptavidin monolayer, which offers approximately 5 X 1012 biotin sites per cm2, is prepared first by adsorbing it onto a mixed self-assembled monolayer on gold which contains biotin-terminated and oligo-terminated alkylthiolates in a 3/7 ratio. This DNA- functionalized surface resists non-specific protein adsorption and is useful for probing the kinetics and equilibrium binding of proteins to DNA with surface plasmon resonance. This is demonstrated with the Mnt protein, which is found to bind in 3.8:1 ratio to its immobilized DNA operator sequence. This is consistent with its behavior in homogeneous solution, where it binds as a tetramer to its DNA. A sequence with a single base-pair mutation shows nearly as much Mnt binding, but a completely random DNA sequence shows only 5 percent of this binding. This proves that DNA-binding proteins bind sequence-specifically to double-stranded DNAs which are immobilized to gold with this streptavidin linker layer.

  11. Characterization of local hydrophobicity on sapphire (0001) surfaces in aqueous environment by colloidal probe atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Wada, Tomoya; Yamazaki, Kenji; Isono, Toshinari; Ogino, Toshio, E-mail: ogino-toshio-rx@ynu.ac.jp

    2017-02-28

    Highlights: • Local hydrophobicity of phase-separated sapphire (0001) surfaces was investigated. • These surfaces are featured by coexistence of hydrophilic and hydrophobic domains. • Each domain was characterized by colloidal probe atomic force microscopy in water. • Both domains can be distinguished by adhesive forces of the probe to the surfaces. • Characterization in aqueous environment is important in bio-applications of sapphire. - Abstract: Sapphire (0001) surfaces exhibit a phase-separation into hydrophobic and hydrophilic domains upon high-temperature annealing, which were previously distinguished by the thickness of adsorbed water layers in air using atomic force microscopy (AFM). To characterize their local surface hydrophobicity in aqueous environment, we used AFM equipped with a colloidal probe and measured the local adhesive force between each sapphire domain and a hydrophilic SiO{sub 2} probe surface, or a hydrophobic polystyrene one. Two data acquisition modes for statistical analyses were used: one is force measurements at different positions of the surface and the other repeated measurement at a fixed position. We found that adhesive force measurements using the polystyrene probe allow us to distinctly separate the hydrophilic and hydrophobic domains. The dispersion in the force measurement data at different positions of the surface is larger than that in the repeated measurements at a fixed position. It indicates that the adhesive force measurement is repeatable although their data dispersion for the measurement positions is relatively large. From these results, we can conclude that the hydrophilic and hydrophobic domains on the sapphire (0001) surfaces are distinguished by a difference in their hydration degrees.

  12. Probing Nuclear Symmetry Energy and its Imprints on Properties of Nuclei, Nuclear Reactions, Neutron Stars and Gravitational Waves

    International Nuclear Information System (INIS)

    Li Baoan; Chen Liewen; Fattoyev, Farrukh J; Newton, William G; Xu Chang

    2013-01-01

    Significant progress has been made in recent years in constraining nuclear symmetry energy at and below the saturation density of nuclear matter using data from both terrestrial nuclear experiments and astrophysical observations. However, many interesting questions remain to be studied especially at supra-saturation densities. In this lecture note, after a brief summary of the currently available constraints on nuclear symmetry energy near the saturation density we first discuss the relationship between the symmetry energy and the isopin and momentum dependence of the single-nucleon potential in isospin-asymmetric nuclear medium. We then discuss several open issues regarding effects of the tensor force induced neutron-proton short-range correlation (SRC) on nuclear symmetry energy. Finally, as an example of the impacts of nuclear symmetry energy on properties of neutron stars and gravitational waves, we illustrate effects of the high-density symmetry energy on the tidal polarizability of neutron stars in coalescing binaries.

  13. Neutron emission as a clock and thermometer to probe the dynamics of fusion-fission and quasi-fission

    Science.gov (United States)

    Hinde, D. J.

    1993-03-01

    A compilation of currently available data on pre-scission neutron multiplicities shows clearly that the excitation energy in the fission fragments hardly increases with bombarding energy. This can be explained if fission is always a slow process, whilst evaporation becomes more and more rapid. The neutron clock-thermometer is introduced as a tool to deduce the dynamical timescale for fusion-fission, giving (35±15)×10-21 s. Quasi-fission is faster than fusion-fission because the equilibrium deformation is never reached (the mononucleus is thought to be always very deformed) thus fragment temperatures are higher, and the strong variation of vpre with TKE shows that a significant number of neutrons are emitted while the fragments are accelerating after scission. This appears not to be the case for fusion-fission. The fall in vpre for asymmetric mass-splits suggests that the dynamical time scale is shorter: this will influence fission mass-distributions.

  14. Modelling and experimental verification of tip-induced polarization in Kelvin probe force microscopy measurements on dielectric surfaces

    DEFF Research Database (Denmark)

    Nielsen, Dennis Achton; Popok, Vladimir; Pedersen, Kjeld

    2015-01-01

    Kelvin probe force microscopy is a widely used technique for measuring surface potential distributions on the micro- and nanometer scale. The data are, however, often analyzed qualitatively, especially for dielectrics. In many cases, the phenomenon of polarization and its influence on the measured...... signals is disregarded leading to misinterpretation of the results. In this work, we present a model that allows prediction of the surface potential on a metal/polymer heterostructure as measured by Kelvin probe force microscopy by including the tip-induced polarization of the dielectric that arises...

  15. A Small Angle Neutron Scattering Study of Cylindrical nanoparticle with Controlled Surface Charge Density

    International Nuclear Information System (INIS)

    Kim, Tae-Hwan; Choi, Sung-Min; Kline, Steven R.

    2007-01-01

    Surfactant molecules in aqueous solution self assemble into various micellar structures such as sphere, rod, vesicle, and lamellar, above critical micelle concentration (CMC). Self-assembled surfactants systems, therefore, have been very popular as templates for preparing various nanostructured materials. Due to their dynamic nature, however, micellar structures are very susceptible to solution conditions such as temperature, concentration, pH and pressure, limiting their applications. In this study, we have developed rigid rod-like nanoparticles with controlled surface charge density by the free radical polymerization of cationic surfactants with polymerizable counterions, cetyltrimethylammonium 4- vinylbenzoate (CTVB), with varying concentration of sodium styrenesulfonate (NaSS). The structure and surface charge density of the nanoparticles were characterized by small angle neutron scattering (SANS) and zeta potential measurements

  16. Study on characteristics of eddy current array coil operated in transmit-receive mode and surface inspection using this probe

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Tae Hun; Jee, Dong Hyun; Cho, Chan Hee; Kim, In Chul [KHNP Central Research Institute, Daejeon (Korea, Republic of)

    2017-02-15

    Eddy current array (ECA) technology provides the ability to electronically scan without mechanical scanning for a footprint of probe that consists of several eddy current coils arranged side-by-side and two dimensionally. Compared to single-coil eddy current technology, the ECA technology has a higher inspection speed and reliability because a large area can be covered in a single-probe pass and the obtained images can facilitate data interpretation. In this study, we developed an eddy current array probe with 2×16 coil arrays and a multiplexer that can select transmit-receive coils sequentially and operate in transmit-receive mode. Surface inspection was performed using this probe for specimens that had various flaws and the characteristics of transmit-receive mode ECA technology was studied through an analysis of the obtained eddy current signals and C-scan images.

  17. Structural study, by surface differential diffraction of neutrons, of the surface of a nickel powder covered with deuterium

    Science.gov (United States)

    Beaufils, J. P.

    1993-01-01

    The analysis of the data of a neutron surface differential diffraction experiment, using H positions determined in the literature whenever available, supports the following model: Grains of the studied nickel powder are limited by (20 ± 10)% of (111) faces and 80% of (110) faces. The (110) faces expose (111) and (1¯11) facets because of anisotropic roughening. A new interpretation of the streaks observed in LEED patterns and a discussion of the coverage provides additional arguments in favour of the roughening. On the facets of the rough faces, the D atoms are displaced from the position they would have on a genuine (111) face. They are no longer on a C3 axis. The Ni atoms of the rough faces suffer an average displacement of 0.015 ± 0.015 nm in the [110] outward direction. The shortest NiD distance on the rough face is equal to 0.19 ± 0.015 nm.

  18. A study of Venus surface elemental composition from 14 MeV neutron induced gamma ray spectroscopy: Activation analysis

    International Nuclear Information System (INIS)

    Jun, I.; Kim, W.; Smith, M.; Mitrofanov, I.; Litvak, M.

    2011-01-01

    The surface elemental composition of Venus can be determined using an artificially pulsed 14 MeV neutron generator (PNG) combined with a gamma ray spectrometer (GRS). The 14 MeV neutrons will interact with the surface materials and generate gamma rays, characteristic of specific elements, whose energy spectrum will be measured by GRS. These characteristic gamma rays are produced mainly through 3 different neutron interaction mechanisms: capture, inelastic, and activation reactions. Each reaction type has a different neutron energy dependency and different time scale for gamma ray production and transport. Certain elements are more easily identified through one reaction type over the others. Thus, careful analysis of the gamma ray spectra during and after the neutron pulse provides a comprehensive understanding of the surface elemental composition. In this paper, we use a well-tested neutron/gamma transport code, called Monte Carlo N-Particles (MCNP), to investigate the measurement capability of a PNG-GRS detection system through the neutron activation reactions. An activation analysis was performed for a representative soil composition of Venus with a notional operational scenario of PNG and GRS. The analysis shows that the proposed instrument concept can identify most of the modeled surface elements at Venus with sufficient accuracy through the activation mode. Specifically, U, Th, K, Si can be measured to within 1%, Fe within 2%, Al within 10%, Ca within 5%, Mg with 15%, Mn with 20%, and Cl within 6%. Although modeled in the analysis, it is shown that the activation mode alone cannot distinguish the S and Ti peaks.

  19. Probing the neutron star interior and the Equation of State of cold dense matter with the SKA

    NARCIS (Netherlands)

    Watts, A.; Xu, R.; Espinoza, C.; Andersson, N.; Antoniadis, J.; Antonopoulou, D.; Buchner, S.; Dai, S.; Demorest, P.; Freire, P.; Hessels, J.; Margueron, J.; Oertel, M.; Patruno, A.; Possenti, A.; Ransom, S.; Stairs, I.; Stappers, B.

    2015-01-01

    With an average density higher than the nuclear density, neutron stars (NS) provide a unique testground for nuclear physics, quantum chromodynamics (QCD), and nuclear superfluidity. Determination of the fundamental interactions that govern matter under such extreme conditions is one of the major

  20. Spectroscopic, imaging, and probe diagnostics of laser plasma plumes expanding between confining surfaces

    International Nuclear Information System (INIS)

    Yeates, P.; Kennedy, E. T.

    2010-01-01

    Laser plasma plumes were generated in aluminum rectangular cavities of fixed depth (6 mm) and varying height (2.0, 1.5, and 1.0 mm). Space and time resolved visible emission spectroscopy, gated intensified visible imaging, and Langmuir probe diagnostics were utilized to diagnose the evolution of the confined plasma plumes in comparison to freely expanding plasma plume generated from ablation of a planar target. The constrained plasma behavior displayed a multiphase history. Early stage interactions (t 160 ns) resulted in sustained 'decay', i.e., a rapid termination of continuum emission, in concert with decreases in peak electron density (N e ) and plasma temperature (T). This later phase originates from loss mechanisms which bleed the plasma plume of thermal energy and charged particles. These loss mechanisms increase in magnitude as the duration of the plasma-surface interaction increases. The transition from enhancement phase, originating from hydrodynamic containment, and plasma-surface collisions, to decay phase is described and occurs for each cavity at a different point in the space time history.

  1. Lavoisier: A Low Altitude Balloon Network for Probing the Deep Atmosphere and Surface of Venus

    Science.gov (United States)

    Chaasefiere, E.; Berthelier, J. J.; Bertaux, J.-L.; Quemerais, E.; Pommereau, J.-P.; Rannou, P.; Raulin, F.; Coll, P.; Coscia, D.; Jambon, A.; hide

    2005-01-01

    The in-situ exploration of the low atmosphere and surface of Venus is clearly the next step of Venus exploration. Understanding the geochemistry of the low atmosphere, interacting with rocks, and the way the integrated Venus system evolved, under the combined effects of inner planet cooling and intense atmospheric greenhouse, is a major challenge of modern planetology. Due to the dense atmosphere (95 bars at the surface), balloon platforms offer an interesting means to transport and land in-situ measurement instruments. Due to the large Archimede force, a 2 cubic meter He-pressurized balloon floating at 10 km altitude may carry up to 60 kg of payload. LAVOISIER is a project submitted to ESA in 2000, in the follow up and spirit of the balloon deployed at cloud level by the Russian Vega mission in 1986. It is composed of a descent probe, for detailed noble gas and atmosphere composition analysis, and of a network of 3 balloons for geochemical and geophysical investigations at local, regional and global scales.

  2. Measurement of neutron diffraction with compact neutron source RANS

    Science.gov (United States)

    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.

  3. Depth distribution studies of carbon, oxygen and nitrogen in metal surfaces by means of neutron spectrometry

    International Nuclear Information System (INIS)

    Lorenzen, J.

    1975-03-01

    A method has been developed to reveal the depth distributions of the light elements carbon, nitrogen and oxygen in heavy matrices. For this purpose steel and zircaloy samples have been irradiated with deuterons and the neutron groups emitted in (d,n)-reactions with the different light nuclei have been measured using time-of-flight technique. The method has been applied to the study of steel samples that feature inhomogeneous carbon and nitrogen distributions and also to the measurement of diffusion profiles of oxygen in zirconium. With the present technique depth ranges of 10 to 15 μm can be analysed if the deuteron energy is chosen between 2.5 MeV and 3.5 MeV. The depth resolution improves with penetration from being of the order of 1 - 2 μm at the surface to 0.5 μm at greater depths under optimum conditions. The detection limit of the light element increases with the atomic number of the matrix and the analysed depth. For oxygen in zirconium and carbon in steel the limit of detection is of the order of 100 ppm at a depth of 10 μm. Limitations in the analysable range of the different profiles due to interfering neutron groups are discussed. The method is particularly useful for the study of oxygen profiles. It is less adequate for reactions with positive Q-values above 5 MeV. (author)

  4. Investigation of benzene and toluene layers on 0001 surface of graphite by means of neutron scattering

    International Nuclear Information System (INIS)

    Monkenbusch, M.

    1981-01-01

    The structures of benzene (C 6 H 6 , C 6 D 6 ) and toluene (C 6 H 5 -CH 3 , C 6 D 5 -CD 3 ) monolayers on the basal planes of graphite have been investigated by neutron diffraction. The dynamics of the benzene layer has been studied by observing the incoherently, inelastically scattered neutrons using the time-of-flight method. The main results are: Above a phase transition temperature Tsub(c)approx.=145 K benzene on the basal planes of graphite forms a quasi 2D-fluid with high compressibility. For toluene a fluid phase exists above 140 K, between 70 K and 140 K it forms an incommensurate layer and below 70 K a 3x3 structure has been observed. The fluid phase of adsorbed benzene shows a broad quasielastic scattering indicating an effective surface diffusion coefficient of 10 -4 cm 2 /s at 200 K. The inelastic spectrum has been compared with an appropriate lattice dynamical model. The comparison with the data reveals, can be considered as a fairly anharmonic 2D-solid with a static external potential due to the substrate. (orig./HK)

  5. Probing potential energy surfaces with high-resolution spectroscopy : From the Universe's carbon locker to molecular machines

    NARCIS (Netherlands)

    Maltseva, E.O.

    2017-01-01

    Light is a powerful tool that, on the one hand, can alter the molecular state and, on the other hand, can be used to probe molecular properties without changing the state. Fundamentals of these interactions are potential energy surfaces (PESs) of molecular ground and electronically excited states.

  6. A new temperature profiling probe for investigating groundwater-surface water interaction

    Science.gov (United States)

    Naranjo, Ramon C.; Robert Turcotte,

    2015-01-01

    Measuring vertically nested temperatures at the streambed interface poses practical challenges that are addressed here with a new discrete subsurface temperature profiling probe. We describe a new temperature probe and its application for heat as a tracer investigations to demonstrate the probe's utility. Accuracy and response time of temperature measurements made at 6 discrete depths in the probe were analyzed in the laboratory using temperature bath experiments. We find the temperature probe to be an accurate and robust instrument that allows for easily installation and long-term monitoring in highly variable environments. Because the probe is inexpensive and versatile, it is useful for many environmental applications that require temperature data collection for periods of several months in environments that are difficult to access or require minimal disturbance.

  7. Direct Surface and Droplet Microsampling for Electrospray Ionization Mass Spectrometry Analysis with an Integrated Dual-Probe Microfluidic Chip

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Cong-Min [Institute of Microanalytical; Zhu, Ying [Institute of Microanalytical; Jin, Di-Qiong [Institute of Microanalytical; Kelly, Ryan T. [Environmental; Fang, Qun [Institute of Microanalytical

    2017-08-15

    Ambient mass spectrometry (MS) has revolutionized the way of MS analysis and broadened its application in various fields. This paper describes the use of microfluidic techniques to simplify the setup and improve the functions of ambient MS by integrating the sampling probe, electrospray emitter probe, and online mixer on a single glass microchip. Two types of sampling probes, including a parallel-channel probe and a U-shaped channel probe, were designed for dryspot and liquid-phase droplet samples, respectively. We demonstrated that the microfabrication techniques not only enhanced the capability of ambient MS methods in analysis of dry-spot samples on various surfaces, but also enabled new applications in the analysis of nanoliter-scale chemical reactions in an array of droplets. The versatility of the microchip-based ambient MS method was demonstrated in multiple different applications including evaluation of residual pesticide on fruit surfaces, sensitive analysis of low-ionizable analytes using postsampling derivatization, and high-throughput screening of Ugi-type multicomponent reactions.

  8. Global Distribution of Shallow Water on Mars: Neutron Mapping of Summer-Time Surface by HEND/Odyssey

    Science.gov (United States)

    Mitrofanov, I. G.; Litvak, M. L.; Kozyrev, A. S.; Sanin, A. B.; Tretyakov, V. I.; Boynton, W.; Hamara, D.; Shinohara, C.; Saunders, R. S.; Drake, D.

    2003-01-01

    Orbital mapping of induced neutrons and gamma-rays by Odyssey has recently successfully proven the applicability of nuclear methods for studying of the elementary composition of Martian upper-most subsurface. In particular, the suite of Gamma-Ray Spectrometer (GRS) has discovered the presence of large water-ice rich regions southward and northward on Mars. The data of neutron mapping of summer-time surface are presented below from the Russian High Energy Neutron Spectrometer (HEND), which is a part of GRS suite. These maps represent the content of water in the soil for summer season at Southern and Northern hemispheres, when the winter deposit of CO2 is absent on the surface. The seasonal evolution of CO2 coverage on Mars is the subject of the complementary paper.

  9. Real-time small-angle neutron scattering techniques probing sub-millisecond dynamics in magnetic nanomaterials

    International Nuclear Information System (INIS)

    Wiedenmann, A.; Gaehler, R.; Dewhurst, C.; Keiderling, U.; Prevost, S.; Kohlbrecher, J.

    2010-01-01

    Stroboscopic Small Angle Neutron Scattering (SANS) techniques have recently been developed which allow ordering and relaxation processes of magnetic moments in nano-particles to be monitored. By applying a periodic external magnetic field the time-resolved SANS response to a forced oscillation could be analyzed. Here we present results from stroboscopic measurements on nanoscaled materials such as Cobalt ferrofluids and solid alloys by using polarised neutrons. SANS scattering response in an oscillating magnetic field was measured as a function of temperature, frequency and amplitude of the applied field. The fraction of superparamagnetic moments that can follow the oscillating field produces scattering patterns alternating between fully isotropic and strongly anisotropic. When the relaxation time of the ferrofluid to get in thermal equilibrium wit an applied magnetic field becomes similar to the period of the oscillating magnetic field one expects a phase shift and a damping in the magnetic response of the ferrofluid particles. To measure these polarized neutrons with polarisation analysis (POLARIS) are of great advantage

  10. Probing the properties of the pulsar wind via studying the dispersive effects in the pulses from the pulsar companion in a double neutron-star binary system

    Science.gov (United States)

    Yi, Shu-Xu; Cheng, K.-S.

    2017-12-01

    The velocity and density distribution of e± in the pulsar wind are crucial distinction among magnetosphere models, and contain key parameters determining the high-energy emission of pulsar binaries. In this work, a direct method is proposed, which might probe the properties of the wind from one pulsar in a double-pulsar binary. When the radio signals from the first-formed pulsar travel through the relativistic e± flow in the pulsar wind from the younger companion, the components of different radio frequencies will be dispersed. It will introduce an additional frequency-dependent time-of-arrival delay of pulses, which is function of the orbital phase. In this paper, we formulate the above-mentioned dispersive delay with the properties of the pulsar wind. As examples, we apply the formula to the double-pulsar system PSR J0737-3039A/B and the pulsar-neutron star binary PSR B1913+16. For PSR J0737-3039A/B, the time delay in 300 MHz is ≲ 10 μ s-1 near the superior conjunction, under the optimal pulsar wind parameters, which is approximately half of the current timing accuracy. For PSR B1913+16, with the assumption that the neutron-star companion has a typical spin-down luminosity of 1033 erg s-1, the time delay is as large as 10 - 20 μ s-1 in 300 MHz. The best timing precision of this pulsar is ∼ 5 μ s-1 in 1400 MHz. Therefore, it is possible that we can find this signal in archival data. Otherwise, we can set an upper limit on the spin-down luminosity. Similar analysis can be applied to other 11 known pulsar-neutron star binaries.

  11. Neutron scattering: Revealing the structure of matter

    International Nuclear Information System (INIS)

    Zeyher, A.

    1996-01-01

    Neutrons are being used to explore materials and biological molecules in a growing number of applications, such as advanced steels and other materials, polymer films, complex molecular structures, and magnetic behavior. open-quotes Virtually all we know about the structure of the new high-transition temperature superconductors was determined using neutron scattering,close quotes said Bill Appleton, associate director for advanced materials, physical, and neutron sciences at Oak Ridge National Laboratory, in Oak Ridge, Tennessee. Neutrons are the only way to see what happens inside superconductors because of the neutron's penetrating power and its magnetic moment. Penetrating power means that neutrons can look up to several centimetres below the surface of a material without damaging it; the neutron's magnetic moment means that it is sensitive to the magnetic fields inside a material. Research in high-temperature superconductivity is only one example of the power of neutrons to illuminate, without disturbing, the structure and behavior of matter at the atomic or molecular scale. In many applications, neutron scattering serves as a complement to X-ray diffraction. In others, neutrons are the only nondestructive probe for looking inside materials or processes

  12. Research on the best measurement situation between optical probe and tissue surfaces in non-invasive detection

    Science.gov (United States)

    Yu, Xuyao; Liu, Rong; Yu, Hui; Wang, Jiao; Wang, Jun; Xu, Kexin

    2016-11-01

    Near-infrared spectroscopy is often used for the non-invasive detection of composition in the human body, such as that of blood glucose and haemoglobin, due to its high penetration depth into tissues. Although it is feasible to position the optical probe precisely, contact situation between probe and human tissues is a difficult problem to determine because of physiological tremor and mechanical performance of bio-soft tissue. Here, we proposed a novel estimation method for the situation between the optical probe and tissue surfaces based on the dynamic auto-correlation matrix of two-dimensional correlation spectroscopy (2DCOS) and radar chart. The diffuse reflectance spectra from the left palm of 4 healthy volunteers were collected while the optical probe gradually approached and pressed bio-tissues with a custom-design controlling device. 2DCOS in the wavelength with lower absorption (1000-1400 nm) was calculated under the perturbation of relative-distance and contact pressure between the optical probe and tissue surface. The synchronous 2DCOS showed that the surface reflection and diffuse reflectance were greatly affected by the contact conditions in 1100 nm, 1220 nm, and 1300 nm. Then the dynamic auto-correlation matrix of 2DCOS was established for the adjacent spectra, and the significant difference wavelengths were used to build radar charts to determine the critical contact situation visually. Results showed that the maximum variations of dynamic auto-correlation matrix appeared at near 1300 nm, and the relative distance between the probe and tissue corresponding to the critical contact state can be easily observed with radar charts with 0.25 mm uncertainty, which was consistent with the self-feeling of each volunteer. So this method can be applied to exactly determine the optimal measurement status for the non-invasive body composition detection in vivo. It is important for the design of human-machine interface and the accuracy improvement of body

  13. Hotspot detection and spatial distribution of methane emissions from landfills by a surface probe method.

    Science.gov (United States)

    Gonzalez-Valencia, Rodrigo; Magana-Rodriguez, Felipe; Cristóbal, Jordi; Thalasso, Frederic

    2016-09-01

    A surface probe method previously developed was used to detect hotspots and to determine spatial variation of methane (CH4) emissions from three landfills located in Mexico, with an intermediate or a final cover, as well as with or without a landfill gas collection system. The method was effective in the three landfills and allowed mapping of CH4 emissions with a resolution of 24-64 measurements per hectare, as well as the detection and quantification of hotspots, with a moderate experimental effort. In the three selected landfills, CH4 emissions were quantified to 10, 72, and 575gm(-2)d(-1). Two straightforward parameters describing the spatial distribution of CH4 emissions were also developed. The first parameter provides the percentage of area responsible for a given percentage of total emissions, while the second parameter assigns a numerical value to flux homogeneity. Together, the emissions map and the spatial distribution parameters offer an appropriate tool to landfill operators willing to begin recovering CH4 emissions or to improve the effectiveness of an existing recovery system. This method may therefore help to reduce the greenhouse gas footprint of landfills, which are still the primary option for waste management in developing countries. Copyright © 2016 Elsevier Ltd. All rights reserved.

  14. Direct protein quantification in complex sample solutions by surface-engineered nanorod probes

    KAUST Repository

    Schrittwieser, Stefan

    2017-06-30

    Detecting biomarkers from complex sample solutions is the key objective of molecular diagnostics. Being able to do so in a simple approach that does not require laborious sample preparation, sophisticated equipment and trained staff is vital for point-of-care applications. Here, we report on the specific detection of the breast cancer biomarker sHER2 directly from serum and saliva samples by a nanorod-based homogeneous biosensing approach, which is easy to operate as it only requires mixing of the samples with the nanorod probes. By careful nanorod surface engineering and homogeneous assay design, we demonstrate that the formation of a protein corona around the nanoparticles does not limit the applicability of our detection method, but on the contrary enables us to conduct in-situ reference measurements, thus further strengthening the point-of-care applicability of our method. Making use of sandwich assays on top of the nanorods, we obtain a limit of detection of 110 pM and 470 pM in 10-fold diluted spiked saliva and serum samples, respectively. In conclusion, our results open up numerous applications in direct protein biomarker quantification, specifically in point-of-care settings where resources are limited and ease-of-use is of essence.

  15. Curling probe measurement of a large-volume pulsed plasma with surface magnetic confinement

    Science.gov (United States)

    Pandey, A.; Tashiro, H.; Sakakibara, W.; Nakamura, K.; Sugai, H.

    2016-12-01

    A curling probe (CP) based on microwave resonance is applied to the measurement of electron density in a pulsed DC glow discharge under surface magnetic confinement (SMC) provided by a number of permanent magnets on a chamber wall. Owing to the SMC effects, a 1 m scale large-volume plasma is generated by a relatively low voltage (~1 kV) at low pressure (~1 Pa) in various gases (Ar, CH4, and C2H2). Temporal variation of the electron density is measured for pulse frequency f  =  0.5-25 kHz for various discharge-on times (T ON) with a high resolution time (~0.2 µs), using the on-point mode. In general, the electron density starts to increase at time t  =  0 after turn-on of the discharge voltage, reaches peak density at t  =  T ON, and then decreases after turn-off. The peak electron density is observed to increase with the pulse frequency f for constant T ON owing to the residual plasma. This dependence is successfully formulated using a semi-empirical model. The spatio-temporal evolution of the cathode sheath in the pulsed discharge is revealed by a 1 m long movable CP. The measured thickness of the high-voltage cathode fall in a steady state coincides with the value of the so-called Child-Langmuir sheath.

  16. Surface Photochemistry: Benzophenone as a Probe for the Study of Modified Cellulose Fibres

    Directory of Open Access Journals (Sweden)

    L. F. Vieira Ferreira

    2007-01-01

    Full Text Available This work reports the use of benzophenone, a very well characterized probe, to study new hosts (i.e., modified celluloses grafted with alkyl chains bearing 12 carbon atoms by surface esterification. Laser-induced room temperature luminescence of air-equilibrated or argon-purged solid powdered samples of benzophenone adsorbed onto the two modified celluloses, which will be named C12-1500 and C12-1700, revealed the existence of a vibrationally structured phosphorescence emission of benzophenone in the case where ethanol was used for sample preparation, while a nonstructured emission of benzophenone exists when water was used instead of ethanol. The decay times of the benzophenone emission vary greatly with the solvent used for sample preparation and do not change with the alkylation degree in the range of 1500–1700 micromoles of alkyl chains per gram of cellulose. When water was used as a solvent for sample preparation, the shortest lifetime for the benzophenone emission was observed; this result is similar to the case of benzophenone adsorbed onto the “normal” microcrystalline cellulose surface, with this latter case previously reported by Vieira Ferreira et al. in 1995. This is due to the more efficient hydrogen abstraction reaction from the glycoside rings of cellulose when compared with hydrogen abstraction from the alkyl chains of the modified celluloses. Triplet-triplet transient absorption of benzophenone was obtained in both cases and is the predominant absorption immediately after laser pulse, while benzophenone ketyl radical formation occurs in a microsecond time scale both for normal and modified celluloses.

  17. Neutron reflectivity study of substrate surface chemistry effects on supported phospholipid bilayer formation on (1120) sapphire.

    Energy Technology Data Exchange (ETDEWEB)

    Oleson, Timothy A. [University of Wisconsin, Madison; Sahai, Nita [University of Akron; Wesolowski, David J [ORNL; Dura, Joseph A [ORNL; Majkrzak, Charles F [ORNL; Giuffre, Anthony J. [University of Wisconsin, Madison

    2012-01-01

    Oxide-supported phospholipid bilayers (SPBs) used as biomimetric membranes are significant for a broad range of applications including improvement of biomedical devices and biosensors, and in understanding biomineralization processes and the possible role of mineral surfaces in the evolution of pre-biotic membranes. Continuous-coverage and/or stacjed SPBs retain properties (e.,g. fluidity) more similar to native biological membranes, which is desirable for most applications. Using neutron reflectivity, we examined face coverage and potential stacking of dipalmitoylphosphatidylcholine (DPPC) bilayers on the (1120) face of sapphire (a-Al2O3). Nearly full bilayers were formed at low to neutral pH, when the sapphire surface is positively charged, and at low ionic strength (l=15 mM NaCl). Coverage decreased at higher pH, close to the isoelectric point of sapphire, and also at high I>210mM, or with addition of 2mM Ca2+. The latter two effects are additive, suggesting that Ca2+ mitigates the effect of higher I. These trends agree with previous results for phospholipid adsorption on a-Al2O3 particles determined by adsorption isotherms and on single-crystal (1010) sapphire by atomic force microscopy, suggesting consistency of oxide surface chemistry-dependent effects across experimental techniques.

  18. Probing astrophysically important states in the 26Mg nucleus to study neutron sources for the s process

    Science.gov (United States)

    Talwar, R.; Adachi, T.; Berg, G. P. A.; Bin, L.; Bisterzo, S.; Couder, M.; deBoer, R. J.; Fang, X.; Fujita, H.; Fujita, Y.; Görres, J.; Hatanaka, K.; Itoh, T.; Kadoya, T.; Long, A.; Miki, K.; Patel, D.; Pignatari, M.; Shimbara, Y.; Tamii, A.; Wiescher, M.; Yamamoto, T.; Yosoi, M.

    2016-05-01

    Background: The 22Ne(α ,n )25Mg reaction is the dominant neutron source for the slow neutron capture process (s process) in massive stars, and contributes, together with 13C (α ,n )16O, to the production of neutrons for the s process in asymptotic giant branch (AGB) stars. However, the reaction is endothermic and competes directly with 22Ne(α ,γ )26Mg radiative capture. The uncertainties for both reactions are large owing to the uncertainty in the level structure of 26Mg near the α and neutron separation energies. These uncertainties affect the s -process nucleosynthesis calculations in theoretical stellar models. Purpose: Indirect studies in the past have been successful in determining the energies and the γ -ray and neutron widths of the 26Mg states in the energy region of interest. But, the high Coulomb barrier hinders a direct measurement of the resonance strengths, which are determined by the α widths for these states. The goal of the present experiments is to identify the critical resonance states and to precisely measure the α widths by α -transfer techniques. Methods: The α -inelastic scattering and α -transfer measurements were performed on a solid 26Mg target and a 22Ne gas target, respectively, using the Grand Raiden Spectrometer at the Research Center for Nuclear Physics in Osaka, Japan. The (α ,α') measurements were performed at 0 .45∘ , 4 .1∘ , 8 .6∘ , and 11 .1∘ and the (6Li,d ) measurements at 0∘ and 10∘. The scattered α particles and deuterons were detected by the focal plane detection system consisting of multiwire drift chambers and plastic scintillators. The focal plane energy calibration allowed the study of 26Mg levels from Ex = 7.69-12.06 MeV in the (α ,α') measurement and Ex = 7.36-11.32 MeV in the (6Li,d ) measurement. Results: Six levels (Ex = 10717, 10822, 10951, 11085, 11167, and 11317 keV) were observed above the α threshold in the region of interest (10.61-11.32 MeV). The α widths were calculated for these

  19. Neutron moisture gaging of agricultural soil

    International Nuclear Information System (INIS)

    Pospisil, S.; Janout, Z.; Kovacik, M.

    1987-01-01

    The design is described of a neutron moisture gage which consists of a measuring probe, neutron detector, small electronic recording device and a 241 Am-Be radionuclide source. The neutron detector consists of a surface barrier semiconductor silicon detector and a conversion layer of lithium fluoride. The detection of triton which is the reaction product of lithium with neutrons by the silicon detector is manifested as a voltage pulse. The detector has low sensitivity for fast neutrons and for gamma radiation and is suitable for determining moisture values in large volume samples. Verification and calibration measurements were carried out of chernozem, brown soil and podzolic soils in four series. The results are tabulated. Errors of measurement range between 0.8 to 1.0%. The precision of measurement could be improved by the calibration of the device for any type of soil. (E.S.). 4 tabs., 6 refs., 5 figs

  20. Circular mode: a new scanning probe microscopy method for investigating surface properties at constant and continuous scanning velocities.

    Science.gov (United States)

    Nasrallah, Hussein; Mazeran, Pierre-Emmanuel; Noël, Olivier

    2011-11-01

    In this paper, we introduce a novel scanning probe microscopy mode, called the circular mode, which offers expanded capabilities for surface investigations especially for measuring physical properties that require high scanning velocities and/or continuous displacement with no rest periods. To achieve these specific conditions, we have implemented a circular horizontal displacement of the probe relative to the sample plane. Thus the relative probe displacement follows a circular path rather than the conventional back and forth linear one. The circular mode offers advantages such as high and constant scanning velocities, the possibility to be combined with other classical operating modes, and a simpler calibration method of the actuators generating the relative displacement. As application examples of this mode, we report its ability to (1) investigate the influence of scanning velocity on adhesion forces, (2) measure easily and instantly the friction coefficient, and (3) generate wear tracks very rapidly for tribological investigations. © 2011 American Institute of Physics

  1. Field and laboratory calibration of neutron probes for soil moisture measurements on a deep loess chernozem soil

    International Nuclear Information System (INIS)

    Schaecke, B.; Schaecke, E.

    1979-01-01

    In the case of a varying profile structure it is necessary to use different calibration curves and adequate correction factors, respectively. The bulk density of the soil had the greatest influence on the calibration. An increase in bulk density by 0.2 g/cm 3 at a clay content of 18% resulted in an apparent increase in the values of moisture measurements by 1.5 to 2.0% of the volume of water. In naturally stratified soil the humus content of the chernozem horizon, being 3% higher than that of the underlying loess horizon, was found to influence the measuring results obtained by the probe. The calibration curves determined for chernozem and loess horizons in the laboratory agreed well with those obtained in the field. The measured values read from the probe and the gravimetrically determined values of the soil moisture were of great significance in all measured depths of the profile. (author)

  2. Magnetic and chemical nonuniformity in Ga1-xMnxAs films as probed by polarized neutron and x-ray reflectometry

    International Nuclear Information System (INIS)

    Kirby, B. J.; Borchers, J. A.; Rhyne, J. J.; O'Donovan, K. V.; Velthuis, S. G. E. te; Roy, S.; Sanchez-Hanke, Cecilia; Wojtowicz, T.; Liu, X.; Lim, W. L.; Dobrowolska, M.; Furdyna, J. K.

    2006-01-01

    We have used complementary neutron and x-ray reflectivity techniques to examine the depth profiles of a series of as-grown and annealed Ga 1-x Mn x As thin films. A magnetization gradient is observed for two as-grown films and originates from a nonuniformity of Mn at interstitial sites, and not from local variations in Mn at Ga sites. Furthermore, we see that the depth-dependent magnetization can vary drastically among as-grown Ga 1-x Mn x As films despite being deposited under seemingly similar conditions. These results imply that the depth profile of interstitial Mn is dependent not only on annealing, but is also extremely sensitive to initial growth conditions. We observe that annealing improves the magnetization by producing a surface layer that is rich in Mn and O, indicating that the interstitial Mn migrates to the surface. Finally, we expand upon our previous neutron reflectivity study of Ga 1-x Mn x As, by showing how the depth profile of the chemical composition at the surface and through the film thickness is directly responsible for the complex magnetization profiles observed in both as-grown and annealed films

  3. Probing surface distributions of α clusters in 20Ne via α -transfer reaction

    Science.gov (United States)

    Fukui, Tokuro; Taniguchi, Yasutaka; Suhara, Tadahiro; Kanada-En'yo, Yoshiko; Ogata, Kazuyuki

    2016-03-01

    Background: Direct evidence of the α -cluster manifestation in bound states has not been obtained yet, although a number of experimental studies were carried out to extract the information of the clustering. In particular in conventional analyses of α -transfer reactions, there exist a few significant problems on reaction models, which are insufficient to qualitatively discuss the cluster structure. Purpose: We aim to verify the manifestation of the α -cluster structure from observables. As the first application, we plan to extract the spatial information of the cluster structure of the 20Ne nucleus in its ground state through the cross section of the α -transfer reaction 16O(6Li,d )20Ne. Methods: For the analysis of the transfer reaction, we work with the coupled-channel Born approximation (CCBA) approach, in which the breakup effect of 6Li is explicitly taken into account by means of the continuum-discretized coupled-channel method based on the three-body α +d +16O model. The two methods are adopted to calculate the overlap function between 20Ne and α +16O ; one is the microscopic cluster model (MCM) with the generator coordinate method, and the other is the phenomenological two-body potential model (PM). Results: We show that the CCBA calculation with the MCM wave function gives a significant improvement of the theoretical result on the angular distribution of the transfer cross section, which is consistent with the experimental data. Employing the PM, it is discussed which region of the cluster wave function is probed on the transfer cross section. Conclusions: It is found that the surface region of the cluster wave function is sensitive to the cross section. The present work is situated as the first step in obtaining important information to systematically investigate the cluster structure.

  4. Production of a faithful realistic phantom to human head and thermal neutron flux measurement on the brain surface. Cooperative research

    Energy Technology Data Exchange (ETDEWEB)

    Yamamoto, Kazuyoshi; Kumada, Hiroaki; Kishi, Toshiaki; Torii, Yoshiya; Uchiyama, Junzo [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Endo, Kiyoshi; Yamamoto, Tetsuya; Matsumura, Akira; Nose, Tadao [Tsukuba Univ., Tsukuba, Ibaraki (Japan)

    2002-12-01

    Thermal neutron flux is determined using the gold wires in current BNCT irradiation, so evaluation of arbitrary points after the irradiation is limited in the quantity of these detectors. In order to make up for the weakness, dose estimation of a patient is simulated by a computational dose calculation supporting system. In another way without computer simulation, a medical irradiation condition can be replicate experimentally using of realistic phantom which was produced from CT images by rapid prototyping technique. This phantom was irradiated at a same JRR-4 neutron beam as clinical irradiation condition of the patient and the thermal neutron distribution on the brain surface was measured in detail. This experimental evaluation technique using a realistic phantom is applicable to in vitro cell irradiation experiments for radiation biological effects as well as in-phantom experiments for dosimetry under the nearly medical irradiation condition of patient. (author)

  5. Note: Proton irradiation at kilowatt-power and neutron production from a free-surface liquid-lithium target

    Energy Technology Data Exchange (ETDEWEB)

    Halfon, S.; Feinberg, G. [Soreq NRC, Yavne 81800 (Israel); Racah Institute of Physics, Hebrew University, Jerusalem 91904 (Israel); Arenshtam, A.; Kijel, D.; Weissman, L.; Aviv, O.; Berkovits, D.; Dudovitch, O.; Eisen, Y.; Eliyahu, I.; Haquin, G.; Hazenshprung, N.; Kreisel, A.; Mardor, I.; Shimel, G.; Shor, A.; Silverman, I.; Yungrais, Z. [Soreq NRC, Yavne 81800 (Israel); Paul, M., E-mail: paul@vms.huji.ac.il; Tessler, M. [Racah Institute of Physics, Hebrew University, Jerusalem 91904 (Israel)

    2014-05-15

    The free-surface Liquid-Lithium Target, recently developed at Soreq Applied Research Accelerator Facility (SARAF), was successfully used with a 1.9 MeV, 1.2 mA (2.3 kW) continuous-wave proton beam. Neutrons (∼2 × 10{sup 10} n/s having a peak energy of ∼27 keV) from the {sup 7}Li(p,n){sup 7}Be reaction were detected with a fission-chamber detector and by gold activation targets positioned in the forward direction. The setup is being used for nuclear astrophysics experiments to study neutron-induced reactions at stellar energies and to demonstrate the feasibility of accelerator-based boron neutron capture therapy.

  6. Production of a faithful realistic phantom to human head and thermal neutron flux measurement on the brain surface. Cooperative research

    CERN Document Server

    Yamamoto, K; Kishi, T; Kumada, H; Matsumura, A; Nose, T; Torii, Y; Uchiyama, J; Yamamoto, T

    2002-01-01

    Thermal neutron flux is determined using the gold wires in current BNCT irradiation, so evaluation of arbitrary points after the irradiation is limited in the quantity of these detectors. In order to make up for the weakness, dose estimation of a patient is simulated by a computational dose calculation supporting system. In another way without computer simulation, a medical irradiation condition can be replicate experimentally using of realistic phantom which was produced from CT images by rapid prototyping technique. This phantom was irradiated at a same JRR-4 neutron beam as clinical irradiation condition of the patient and the thermal neutron distribution on the brain surface was measured in detail. This experimental evaluation technique using a realistic phantom is applicable to in vitro cell irradiation experiments for radiation biological effects as well as in-phantom experiments for dosimetry under the nearly medical irradiation condition of patient.

  7. Lunar prospector epithermal neutrons from impact craters and landing sites: Implications for surface maturity and hydrogen distribution

    Science.gov (United States)

    Johnson, J. R.; Feldman, W.C.; Lawrence, D.J.; Maurice, S.; Swindle, T.D.; Lucey, P.G.

    2002-01-01

    Initial studies of neutron spectrometer data returned by Lunar Prospector concentrated on the discovery of enhanced hydrogen abundances near both lunar poles. However, the nonpolar data exhibit intriguing patterns that appear spatially correlated with surface features such as young impact craters (e.g., Tycho). Such immature crater materials may have low hydrogen contents because of their relative lack of exposure to solar wind-implanted volatiles. We tested this hypothesis by comparing epithermal* neutron counts (i.e., epithermal -0.057 ?? thermal neutrons) for Copernican-age craters classified as relatively young, intermediate, and old (as determined by previous studies of Clementine optical maturity variations). The epithermal* counts of the crater and continuous ejecta regions suggest that the youngest impact materials are relatively devoid of hydrogen in the upper 1 m of regolith. We also show that the mean hydrogen contents measured in Apollo and Luna landing site samples are only moderately well correlated to the epithermal* neutron counts at the landing sites, likely owing to the effects of rare earth elements. These results suggest that further work is required to define better how hydrogen distribution can be revealed by epithermal neutrons in order to understand more fully the nature and sources (e.g., solar wind, meteorite impacts) of volatiles in the lunar regolith.

  8. Effect of surfactant excess on the stability of low-polarity ferrofluids probed by small-angle neutron scattering

    Energy Technology Data Exchange (ETDEWEB)

    Petrenko, V. I., E-mail: vip@nf.jinr.ru; Avdeev, M. V. [Joint Institute for Nuclear Research (Russian Federation); Bulavin, L. A. [Taras Shevchenko National University of Kyiv (Ukraine); Almasy, L. [Hungarian Academy of Science, Wigner Research Centre for Physics (Hungary); Grigoryeva, N. A. [St. Petersburg State University (Russian Federation); Aksenov, V. L. [National Research Centre “Kurchatov Institute”, Konstantinov Petersburg Nuclear Physics Institute (Russian Federation)

    2016-01-15

    The structures of ferrofluids (FFs) based on nonpolar solvent decahydronaphthalene, stabilized by saturated monocarboxylic acids with hydrocarbon chains of different lengths, C16 (palmitic acid) and ?12 (lauric acid), with an excess of acid molecules, have been studied by small-angle neutron scattering. It is found that the addition of acid to an initially stable system with optimal composition leads to more significant structural changes (related to aggregation) than those observed previously for this class of FFs. A comparison of the influence of monocarboxylic acids on the stability of nonpolar FFs suggests that the enhancement of aggregation is much more pronounced in the case of palmitic acid excess. This fact confirms the conclusion of previous studies, according to which an increase in the hydrocarbon chain length in a saturated acid reduces the efficiency of the corresponding FF stabilization.

  9. Magnetic structure of Ba (TiO ) Cu4(PO4)4 probed using spherical neutron polarimetry

    Science.gov (United States)

    Babkevich, P.; Testa, L.; Kimura, K.; Kimura, T.; Tucker, G. S.; Roessli, B.; Rønnow, H. M.

    2017-12-01

    The antiferromagnetic compound Ba (TiO ) Cu4(PO4)4 contains square cupola of corner-sharing CuO4 plaquettes, which were proposed to form effective quadrupolar order. To identify the magnetic structure, we have performed spherical neutron polarimetry measurements. Based on symmetry analysis and careful measurements, we conclude that the orientation of the Cu2 + spins form a noncollinear in-out structure with spins approximately perpendicular to the CuO4 motif. Strong Dzyaloshinskii-Moriya interaction naturally lends itself to explain this phenomenon. The identification of the ground-state magnetic structure should serve well for future theoretical and experimental studies into this and closely related compounds.

  10. Nanopatterning on silicon surface using atomic force microscopy with diamond-like carbon (DLC-coated Si probe

    Directory of Open Access Journals (Sweden)

    Zhou Jingfang

    2011-01-01

    Full Text Available Abstract Atomic force microscope (AFM equipped with diamond-like carbon (DLC-coated Si probe has been used for scratch nanolithography on Si surfaces. The effect of scratch direction, applied tip force, scratch speed, and number of scratches on the size of the scratched geometry has been investigated. The size of the groove differs with scratch direction, which increases with the applied tip force and number of scratches but decreases slightly with scratch speed. Complex nanostructures of arrays of parallel lines and square arrays are further fabricated uniformly and precisely on Si substrates at relatively high scratch speed. DLC-coated Si probe has the potential to be an alternative in AFM-based scratch nanofabrication on hard surfaces.

  11. Probing the density content of the nuclear symmetry energy

    Indian Academy of Sciences (India)

    Abstract. The nature of equation of state for the neutron star matter is crucially governed by the density dependence of the nuclear symmetry energy. We attempt to probe the behaviour of the nuclear symmetry energy around the saturation density by exploiting the empirical values for volume and surface symmetry energy ...

  12. Probing the density content of the nuclear symmetry energy

    Indian Academy of Sciences (India)

    2014-04-30

    Apr 30, 2014 ... The nature of equation of state for the neutron star matter is crucially governed by the density dependence of the nuclear symmetry energy. We attempt to probe the behaviour of the nuclear symmetry energy around the saturation density by exploiting the empirical values for volume and surface symmetry ...

  13. A Tailorable Structural Composite for GCR and Albedo Neutron Protection on the Lunar Surface, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — A tailorable structural composite that will provide protection from the lunar radiation environment, including GCR and albedo neutrons will be developed. This...

  14. In-situ determining the unsaturated hydraulic conductivity ksub(u) in ground- and backwater soils by the evaporation method with the neutron-gamma probe and with tensiometers

    International Nuclear Information System (INIS)

    Krahmer, U.

    1973-01-01

    The unsaturated hydraulic conductivity ksub(u) is determined in this work as soil parameter under free land, weather and vegetation conditions using the evaporation method. In the applied method with in-situ measurements one assumes that water rises in the root fringes as a capillary from the ground or moisture-retaining soil layers or from the water unsaturated soil zone by means of evapotranspiration effects; i.e. the water is evaporated at the surface or consumed by the plants. The hence resulting moisture and unavoidable changes in potential over a certain period of time are the basis for the measuring principle. Moisture-retaining soils from the saale ice-age ground moraine deposits of the western Muensterland were mainly used as samples from which a few essential soil-physical and chemical analyses could be performed. The tensiometer and the neutron gamma depth probe were provided by the firm Berthold to measure and determine the unsaturated hydraulic conductivity Ksub(u) in the suction tension region of 0 to 900 cm WS. (orig./HK) [de

  15. Neutron scattering. Lectures

    Energy Technology Data Exchange (ETDEWEB)

    Brueckel, Thomas; Heger, Gernot; Richter, Dieter; Roth, Georg; Zorn, Reiner (eds.)

    2010-07-01

    The following topics are dealt with: Neutron sources, neutron properties and elastic scattering, correlation functions measured by scattering experiments, symmetry of crystals, applications of neutron scattering, polarized-neutron scattering and polarization analysis, structural analysis, magnetic and lattice excitation studied by inelastic neutron scattering, macromolecules and self-assembly, dynamics of macromolecules, correlated electrons in complex transition-metal oxides, surfaces, interfaces, and thin films investigated by neutron reflectometry, nanomagnetism. (HSI)

  16. Neutron scattering. Lectures

    International Nuclear Information System (INIS)

    Brueckel, Thomas; Heger, Gernot; Richter, Dieter; Roth, Georg; Zorn, Reiner

    2010-01-01

    The following topics are dealt with: Neutron sources, neutron properties and elastic scattering, correlation functions measured by scattering experiments, symmetry of crystals, applications of neutron scattering, polarized-neutron scattering and polarization analysis, structural analysis, magnetic and lattice excitation studied by inelastic neutron scattering, macromolecules and self-assembly, dynamics of macromolecules, correlated electrons in complex transition-metal oxides, surfaces, interfaces, and thin films investigated by neutron reflectometry, nanomagnetism. (HSI)

  17. Surface Crack Detection for Carbon Fiber Reinforced Plastic Materials Using Pulsed Eddy Current Based on Rectangular Differential Probe

    Directory of Open Access Journals (Sweden)

    Jialong Wu

    2014-01-01

    Full Text Available Aiming at the surface defect inspection of carbon fiber reinforced composite, the differential and the direct measurement finite element simulation models of pulsed eddy current flaw detection were built. The principle of differential pulsed eddy current detection was analyzed and the sensitivity of defect detection was compared through two kinds of measurements. The validity of simulation results was demonstrated by experiments. The simulation and experimental results show that the pulsed eddy current detection method based on rectangular differential probe can effectively improve the sensitivity of surface defect detection of carbon fiber reinforced composite material.

  18. Neutron holography

    International Nuclear Information System (INIS)

    Beynon, T.D.

    1986-01-01

    the paper concerns neutron holography, which allows an image to be constructed of the surfaces, as well as the interiors, of objects. The technique of neutron holography and its applications are described. Present and future use of the method is briefly outlined. (U.K.)

  19. The effect of surface texture on total reflection of neutrons and X-rays from modified interfaces

    DEFF Research Database (Denmark)

    Goldar, A.; Roser, S.J.; Hughes, A.

    2002-01-01

    X-ray and neutron scattering from macroscopically rough surfaces and interfaces is considered and a new method of analysis based on the variation of the shape of the total reflection edge in the reflectivity profile is proposed. It was shown that in the limit that the correlation length...... and the height of the surface roughness are larger than the wavelength (at least 100 times bigger) of the incoming beam, the total reflection edge in the reflection profile becomes rounded. This technique allows direct analysis of the variation of the reflectivity pro le in terms of the structure of the surface...

  20. Methodical comparison of neutron depth probes and long-term soil moisture measurements on loess, sandy loess, and boulder clay

    International Nuclear Information System (INIS)

    Neue, H.U.

    1980-01-01

    Three measuring instruments were tested: 0.05 mCi Cf-252, 100 mCi Am-241/Be, 500 mCi Am-241/Be. The advantages - measurement in undisturbed soil profiles, large depths of measurement, reproducibility of measurements in the same place over several years - and the disadvantages - radiation protection, resolution, variations of measured volume in dependence of moisture, background influences etc. - have been critically checked by experiment. In addition, annual soil moisture curves have been measured over two years by parallel use of the free probes on a loess, sandy loess, and boulder clay site. The results were compared and discussed with a view to the soil water dynamics of these sites. (orig./HP) [de

  1. Effect of surface free energy on PDMS transfer in microcontact printing and its application to ToF-SIMS to probe surface energies.

    Science.gov (United States)

    Yang, Li; Shirahata, Naoto; Saini, Gaurav; Zhang, Feng; Pei, Lei; Asplund, Matthew C; Kurth, Dirk G; Ariga, Katsuhiko; Sautter, Ken; Nakanishi, Takashi; Smentkowski, Vincent; Linford, Matthew R

    2009-05-19

    Although polydimethylsiloxane (PDMS) transfer during microcontact printing (microCP) has been observed in previous reports, which generally focused on only one or a few different substrates, in this work we investigate the extent of PDMS transfer onto a series of surfaces with a wide range of hydrophobicities using an uninked, unpatterned PDMS stamp. These surfaces include clean silicon, clean titanium, clean gold, "dirty" silicon, polystyrene, Teflon, surfaces modified with PEG, amino, dodecyl, and hexadecyl monolayers, and also two loose molecular materials. The PDMS transferred onto planar surfaces is, in general, easily detected by wetting and spectroscopic ellipsometry. More importantly, it is detected by time-of-flight secondary ion mass spectrometry (ToF-SIMS) because of the sensitivity of this technique to PDMS. The effect of surface free energy on PDMS transfer in microcontact printing is investigated, and the relationship between the amount of PDMS in ToF-SIMS spectra and the surface tensions of initial surfaces is revealed. We show that PDMS transfer can be applied as a probe of surface free energies using ToF-SIMS, where PDMS preferentially transfers onto more hydrophilic surface features during stamping, with little being transferred onto very hydrophobic surface features. Multivariate curve resolution (MCR) analysis of the ToF-SIMS image data further confirms and clarifies these results. Our data lend themselves to the hypothesis that it is the free energy of the surface that plays a major role in determining the degree of PDMS transfer during microCP.

  2. Anisotropy of the structure factor of magnetic fluids under a field probed by small-angle neutron scattering

    International Nuclear Information System (INIS)

    Gazeau, F.; Bacri, J.-C.; Perzynski, R.; Dubois, E.; Boue, F.; Cebers, A.

    2002-01-01

    Small-angle neutron scattering is used to measure the two-dimensional diffraction pattern of a monophasic magnetic colloid, under an applied magnetic field. This dipolar system presents in zero field a fluidlike structure. It is well characterized by an interaction parameter K T 0 proportional to the second virial coefficient, which is here positive, expressing a repulsion of characteristic length κ 0 -1 . Under the field a strong anisotropy is observed at the lowest q vectors. The length κ 0 -1 remains isotropic, but the interaction parameter K T becomes anisotropic due to the long-range dipolar interaction. However, the system remains stable, the interaction being repulsive in all directions. Thus No.No.we do not observe any chaining of the nanoparticles under magnetic field. On the contrary, the revealed structure of our anisotropic colloid is a lowering of the concentration fluctuations along the field while the fluidlike structure, observed without field, is roughly preserved perpendicularly to the field. It expresses a strong anisotropy of the Brownian motion of the nanoparticles in the solution under applied field

  3. Anisotropy of the structure factor of magnetic fluids under a field probed by small-angle neutron scattering.

    Science.gov (United States)

    Gazeau, F; Dubois, E; Bacri, J C; Boué, F; Cebers, A; Perzynski, R

    2002-03-01

    Small-angle neutron scattering is used to measure the two-dimensional diffraction pattern of a monophasic magnetic colloid, under an applied magnetic field. This dipolar system presents in zero field a fluidlike structure. It is well characterized by an interaction parameter K(0)(T) proportional to the second virial coefficient, which is here positive, expressing a repulsion of characteristic length kappa-10. Under the field a strong anisotropy is observed at the lowest q vectors. The length kappa-10 remains isotropic, but the interaction parameter K(T) becomes anisotropic due to the long-range dipolar interaction. However, the system remains stable, the interaction being repulsive in all directions. Thus we do not observe any chaining of the nanoparticles under magnetic field. On the contrary, the revealed structure of our anisotropic colloid is a lowering of the concentration fluctuations along the field while the fluidlike structure, observed without field, is roughly preserved perpendicularly to the field. It expresses a strong anisotropy of the Brownian motion of the nanoparticles in the solution under applied field.

  4. Inhomogeneity and relaxation phenomena in the graphite anode of a lithium-ion battery probed by in situ neutron diffraction

    Science.gov (United States)

    Zinth, Veronika; von Lüders, Christian; Wilhelm, Jörn; Erhard, Simon V.; Hofmann, Michael; Seidlmayer, Stefan; Rebelo-Kornmeier, Joana; Gan, Weimin; Jossen, Andreas; Gilles, Ralph

    2017-09-01

    In this study, lithium gradients forming in the graphite anode of a commercial 18650-type lithium-ion battery during discharge and the associated relaxation processes after discharge were monitored by neutron diffraction. The experiments reveal the coexistence of several Li1-xC6 phases with different lithium contents during discharge, which can be explained by the formation of an inhomogeneity or lithium gradient in the graphite anode. The observed inhomogeneity is more pronounced at higher discharging rates, but at low temperatures it appears at a rate as low as C/10. After discharge, the inhomogeneity gradually disappears and the coexisting phases diminish in favor of one or several Li1-xC6 phases with close to mean lithium content. At room temperature these relaxation processes take 20-40 min with the main changes in the first 10 min. In contrast, at -20 °C changes are still observed after 11 h. The observed phenomena can be explained by a faster delithiation of the graphite particles than the equilibration of the resulting lithium gradient by lithium diffusion in the solid phase during discharge.

  5. Probing highly selective H/D exchange processes with a ruthenium complex through neutron diffraction and multinuclear NMR studies.

    Science.gov (United States)

    Grellier, Mary; Mason, Sax A; Albinati, Alberto; Capelli, Silvia C; Rizzato, Silvia; Bijani, Christian; Coppel, Yannick; Sabo-Etienne, Sylviane

    2013-07-01

    Deuterium labeling is a powerful way to gain mechanistic information in biology and chemistry. However, selectivity is hard to control experimentally, and labeled sites can be difficult to assign both in solution and in the solid state. Here we show that very selective high-deuterium contents can be achieved for the polyhydride ruthenium phosphine complex [RuH2(H2)2(PCyp3)2] (1) (PCyp3 = P(C5H9)3). The selectivity of the H/D exchange process is demonstrated by multinuclear NMR and neutron diffraction analyses. It has also been investigated through density functional theory (DFT) calculations. The reactions are performed under mild conditions at room temperature, and the extent of deuterium incorporation, involving selective C-H bond activation within the cyclopentyl rings of the phosphine ligands, can easily be tuned (solvent effects, D2 pressure). It is shown that D2 gas can inhibit the C-H/C-D exchange process.

  6. Using Force to Probe Single-Molecule Receptor-Cytoskeletal Anchoring Beneath the Surface of a Living Cell

    DEFF Research Database (Denmark)

    Evans, Evan; Kinoshita, Koji

    2007-01-01

    , K. (2005). Nano-to-micro scale dynamics of P-selectin detachment from leukocyte interfaces: I. Separation of PSGL-1 from the cell cytoskeleton. Biophys. J. 88, 2288-2298]. Retracting cells from receptor-surface attachments at many different speeds revealed that the kinetic rate for receptor......The ligation of cell surface receptors often communicates a signal that initiates a cytoplasmic chemical cascade to implement an important cell function. Less well understood is how physical stress applied to a cell surface adhesive bond propagates throughout the cytostructure to catalyze...... or trigger important steps in these chemical processes. Probing the nanoscale impact of pulling on cell surface bonds, we discovered that receptors frequently detach prematurely from the interior cytostructure prior to failure of the exterior adhesive bond [Evans, E., Heinrich, V., Leung, A., and Kinoshita...

  7. Neutron detector

    Science.gov (United States)

    Stephan, Andrew C [Knoxville, TN; Jardret,; Vincent, D [Powell, TN

    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.

  8. Kinetics of ultraviolet and plasma surface modification of poly(dimethylsiloxane) probed by sum frequency vibrational spectroscopy.

    Science.gov (United States)

    Ye, Hongke; Gu, Zhiyong; Gracias, David H

    2006-02-14

    In numerous applications in microfluidics, cell growth, soft lithography, and molecular imprinting, the surface of poly(dimethylsiloxane) (PDMS) is modified from a hydrophobic methyl-terminated surface to a hydrophilic hydroxyl-terminated surface. In this study, we investigated molecular structural and orientational changes at the PDMS-air interface in response to three commonly used surface modification processes: exposure to long-wavelength ultraviolet light (UV), exposure to short-wavelength UV that generates ozone (UVO), and exposure to oxygen plasma (OP). The surfaces of two PDMS compositions (10:1 and 4:1 of base polymer/curing agent) were probed during modification, using monolayer-sensitive IR + visible sum frequency generation (SFG) vibrational spectroscopy, with two different polarization combinations. During PDMS surface modification, the peak intensities of CH3 side groups and CH2 cross-link groups decreased, while peak intensities of Si-OH groups increased. There was no significant change in the average orientation of the CH3 groups on the PDMS surface during modification. The concentration of CH3 groups on the surface decreased exponentially with time, for all three UV, UVO, and OP modification processes, with first order kinetics and time constants of approximately 160, 66, and 0.3 min, respectively. At steady state, residual CH3 groups were detected at the PDMS surface for UV and UVO treatments; however, there were negligible CH3 groups detected after OP modification.

  9. Investigation of the surface potential of TiO2 (110) by frequency-modulation Kelvin probe force microscopy.

    Science.gov (United States)

    Kou, Lili; Li, Yan Jun; Kamijyo, Takeshi; Naitoh, Yoshitaka; Sugawara, Yasuhiro

    2016-12-16

    We investigate the surface potential distribution on a TiO 2 (110)-1 × 1 surface by Kelvin probe force microscopy (KPFM) and atom-dependent bias-distance spectroscopic mapping. The experimental results demonstrate that the local contact potential difference increases on twofold-coordinated oxygen sites, and decreases on OH defects and fivefold-coordinated Ti sites. We propose a qualitative model to explain the origin of the surface potential of TiO 2 (110). We qualitatively calculate the surface potential induced by chemical potential and permanent surface dipole. The calculated results agree with our experimental ones. Therefore, we suggest that the surface potential of TiO 2 (110) is dominated not only by the permanent surface dipole between the tip apex atom and surface, but also by the dipoles induced by the chemical interaction between the tip and sample. The KPFM technique demonstrate the possibility of investigation of the charge transfer phenomenon on TiO 2 surface under gas conditions. It is useful for the elucidation of the mechanism of the catalytic reactions.

  10. Liquid Microjunction Surface Sampling Probe Electrospray Mass Spectrometry for Detection of Drugs and Metabolites in Thin Tissue Sections

    Energy Technology Data Exchange (ETDEWEB)

    Van Berkel, Gary J [ORNL; Kertesz, Vilmos [ORNL; Koeplinger, Kenneth A. [Merck Research Laboratories; Vavek, Marissa [Merck Research Laboratories; Kong, Ah-Ng Tony [Rutgers University

    2008-01-01

    A self-aspirating, liquid micro-junction surface sampling probe/electrospray emitter mass spectrometry system was demonstrated for use in the direct analysis of spotted and dosed drugs and their metabolites in thin tissue sections. Proof-of-principle sampling and analysis directly from tissue without the need for sample preparation was demonstrated first by raster scanning a region on a section of rat liver onto which reserpine was spotted. The mass spectral signal from selected reaction monitoring was used to develop a chemical image of the spotted drug on the tissue. The probe was also used to selectively spot sample areas of sagittal whole mouse body tissue sections that had been dosed orally (90 mg/kg) with R,S-sulforaphane 3 hrs prior to sacrifice. Sulforaphane and its glutathione and N-acetyl cysteine conjugates were monitored with selected reaction monitoring and detected in the stomach and various other tissues from the dosed mouse. No signal for these species was observed in the tissue from a control mouse. The same dosed tissue section was used to illustrate the possibility of obtaining a line scan across the whole body section. In total these results illustrate the potential for rapid screening of the distribution of drugs and metabolites in tissue sections with the micro-liquid junction surface sampling probe/electrospray mass spectrometry approach.

  11. Existence of quasi-stationary neutron and x-ray states near the surface of a deformed single crystal

    CERN Document Server

    Iolin, E

    1999-01-01

    The problem of x-ray or neutron multiply internally reflected inside a bent single crystal plate (Bragg geometry) is considered. It is found that such multiple reflections lead to the existence of quasi-stationary (QS) states. QS states are discrete and correspond to the resonance of motion of the tie point between the front surface and a 'turning place' inside a single crystal. (author)

  12. Oxidation of hydrogen-passivated silicon surfaces by scanning near-field optical lithography using uncoated and aluminum-coated fiber probes

    DEFF Research Database (Denmark)

    Madsen, Steen; Bozhevolnyi, Sergey I.; Birkelund, Karen

    1997-01-01

    Optically induced oxidation of hydrogen-passivated silicon surfaces using a scanning near-field optical microscope was achieved with both uncoated and aluminum-coated fiber probes. Line scans on amorphous silicon using uncoated fiber probes display a three-peak profile after etching in potassium...

  13. On the mechanism of triclinic distortion in Chevrel Phase as probed by in-situ neutron diffraction.

    Science.gov (United States)

    Levi, E; Mitelman, A; Aurbach, D; Isnard, O

    2007-09-03

    This work presents, for the first time, a general mechanism of a rhombohedral (R)-triclinic (T) phase transition in Chevrel Phases (CPs) with small cations (radiusT transition in some CPs as cation ordering, T-distortion is regarded here as a particular case of general adaptation of the framework to cation insertion, which includes the deformations of the coordination polyhedra and their tilting. The research is based on a combination of experimental studies (in-situ neutron diffraction at different temperatures) for one model compound, MgMo6Se8, and structural analysis for a variety of known CPs. This analysis shows that the structure flexibility is fundamentally different for the R and T forms. As a result of the lower flexibility, in the R form, a strict correlation exists between the compression of the framework along the -3 symmetry axis and the cation position in the structure (the so-called 'delocalization'). The decreasing delocalization in the R-CPs, which occurs on cooling, leads to excessive repulsion within the cations pairs (R-Cu1.8Mo6S8 case) or undesirable asymmetry in the cation polyhedra (R-MgMo6Se8 case). The higher flexibility of the T framework allows for relaxation of these structural strains by increasing the cation-cation distances and forming a more symmetric cation environment, sometimes with higher coordination number (CN), like CN=5 in the T-Fe2Mo6S8 type. Thus, this work also proposes possible driving forces for T-distortion in CPs.

  14. Near-field optical microscopy of localized excitations on rough surfaces: influence of a probe

    DEFF Research Database (Denmark)

    Bozhevolnyi, Sergey I.

    1999-01-01

    Starting from the general principles of near-field optical microscopy. I consider the influence of a probe when being used to image localized dipolar excitations and suggest a way of evaluating the perturbation thus introduced. Using the rigorous microscopic (electric) point-dipole description, I...

  15. Fiber optic probe enabled by surface-enhanced Raman scattering for early diagnosis of potential acute rejection of kidney transplant

    Science.gov (United States)

    Chi, Jingmao; Chen, Hui; Tolias, Peter; Du, Henry

    2014-06-01

    We have explored the use of a fiber-optic probe with surface-enhanced Raman scattering (SERS) sensing modality for early, noninvasive and, rapid diagnosis of potential renal acute rejection (AR) and other renal graft dysfunction of kidney transplant patients. Multimode silica optical fiber immobilized with colloidal Ag nanoparticles at the distal end was used for SERS measurements of as-collected urine samples at 632.8 nm excitation wavelength. All patients with abnormal renal graft function (3 AR episodes and 2 graft failure episodes) who were clinically diagnosed independently show common unique SERS spectral features in the urines collected just one day after transplant. SERS-based fiber-optic probe has excellent potential to be a bedside tool for early diagnosis of kidney transplant patients for timely medical intervention of patients at high risk of transplant dysfunction.

  16. Neutron tubes

    Science.gov (United States)

    Leung, Ka-Ngo [Hercules, CA; Lou, Tak Pui [Berkeley, CA; Reijonen, Jani [Oakland, CA

    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.

  17. Neutron reflectometry

    DEFF Research Database (Denmark)

    Klösgen-Buchkremer, Beate Maria

    2014-01-01

    Neutron (and X-ray) reflectometry constitute complementary interfacially sensitive techniques that open access to studying the structure within thin films of both soft and hard condensed matter. Film thickness starts oxide surfaces on bulk substrates, proceeding to (pauci-)molecular layers and up...... to hundreds of nanometers. Thickness resolution for flat surfaces is in the range of few Ǻngstrøm, and as a peculiar benefit, the presence and properties of buried interfaces are accessible. Focus here will be on neutron reflectometry, a technique that is unique in applications involving composite organic...... films or films with magnetic properties. The reason is the peculiar property of neutron light since the mass of a neutron is close to the one of a proton, and since it bears a magnetic moment. The optical properties of matter, when interacting with neutrons, are described by a refractive index...

  18. Role of lactobacillus cell surface hydrophobicity as probed by AFM in adhesion to surfaces at low and high ionic strength

    NARCIS (Netherlands)

    Vadillo Rodriguez, Virginia; Busscher, Hendrik; van der Mei, Henderina; Norde, Willem; de Vries, Jacob

    2005-01-01

    The S-layer present at the outermost cell surface of some lactobacillus species is known to convey hydrophobicity to the lactobacillus cell surface. Yet, it is commonly found that adhesion of lactobacilli to solid substrata does not proceed according to expectations based on cell surface

  19. Role of lactobacillus cell surface hydrophobicity as probed by AMF in adhesion to surfaces at low and high ionic strength

    NARCIS (Netherlands)

    Vadillo-Rodriguez, V.; Busscher, H.J.; Meij, van der H.C.; Vries, de J.; Norde, W.

    2005-01-01

    The S-layer present at the outermost cell surface of some lactobacillus species is known to convey hydrophobicity to the lactobacillus cell surface. Yet, it is commonly found that adhesion of lactobacilli to solid substrata does not proceed according to expectations based on cell surface

  20. PREFACE: Exploring surfaces and buried interfaces of functional materials by advanced x-ray and neutron techniques Exploring surfaces and buried interfaces of functional materials by advanced x-ray and neutron techniques

    Science.gov (United States)

    Sakurai, Kenji

    2010-12-01

    This special issue is devoted to describing recent applications of x-ray and neutron scattering techniques to the exploration of surfaces and buried interfaces of various functional materials. Unlike many other surface-sensitive methods, these techniques do not require ultra high vacuum, and therefore, a variety of real and complicated surfaces fall within the scope of analysis. It must be particularly emphasized that the techniques are capable of seeing even buried function interfaces as well as the surface. Furthermore, the information, which ranges from the atomic to mesoscopic scale, is highly quantitative and reproducible. The non-destructive nature of the techniques is another important advantage of using x-rays and neutrons, when compared with other atomic-scale analyses. This ensures that the same specimen can be measured by other techniques. Such features are fairly attractive when exploring multilayered materials with nanostructures (dots, tubes, wires, etc), which are finding applications in electronic, magnetic, optical and other devices. The Japan Applied Physics Society has established a group to develop the research field of studying buried function interfaces with x-rays and neutrons. As the methods can be applied to almost all types of materials, from semiconductor and electronic devices to soft materials, participants have fairly different backgrounds but share a common interest in state-of-the-art x-ray and neutron techniques and sophisticated applications. A series of workshops has been organized almost every year since 2001. Some international interactions have been continued intensively, although the community is part of a Japanese society. This special issue does not report the proceedings of the recent workshop, although all the authors are in some way involved in the activities of the above society. Initially, we intended to collect quite long overview papers, including the authors' latest and most important original results, as well as

  1. Reciprocal space XRD mapping with varied incident angle as a probe of structure variation within surface depth

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Qiguang [Norfolk State University; Williams, Frances [Norfolk State University; Zhao, Xin [JLAB; Reece, Charles E. [JLAB; Krishnan, Mahadevan [AASC, San Leandro, California

    2013-09-01

    In this study, we used a differential-depth X-Ray diffraction Reciprocal Spacing Mapping (XRD RSM) technique to investigate the crystal quality of a variety of SRF-relevant Nb film and bulk materials. By choosing different X-ray probing depths, the RSM study successfully revealed evolution the of materials microstructure after different materials processes, such as energetic condensation or surface polishing. The RSM data clearly measured the materials crystal quality at different thickness. Through a novel differential-depth RSM technique, this study found: I. for a heteroepitaxy Nb film Nb(100)/MgO(100), the film thickening process, via a cathodic arc-discharge Nb ion deposition, created a near-perfect single crystal Nb on the surfaces top-layer; II. for a mechanically polished single-crystal bulk Nb material, the microstructure on the top surface layer is more disordered than that in-grain.

  2. Abnormal changes in the density of thermal neutron flux in biocenoses near the earth surface.

    Science.gov (United States)

    Plotnikova, N V; Smirnov, A N; Kolesnikov, M V; Semenov, D S; Frolov, V A; Lapshin, V B; Syroeshkin, A V

    2007-04-01

    We revealed an increase in the density of thermal neutron flux in forest biocenoses, which was not associated with astrogeophysical events. The maximum spike of this parameter in the biocenosis reached 10,000 n/(sec x m2). Diurnal pattern of the density of thermal neutron flux depended only on the type of biocenosis. The effects of biomodulation of corpuscular radiation for balneology are discussed.

  3. Symmetry energy and surface properties of neutron-rich exotic nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Gaidarov, M. K.; Antonov, A. N. [Institute for Nuclear Research and Nuclear Energy, Bulgarian Academy of Sciences, Sofia 1784 (Bulgaria); Sarriguren, P. [Instituto de Estructura de la Materia, IEM-CSIC, Serrano 123, E-28006 Madrid (Spain); Moya de Guerra, E. [Departamento de Fisica Atomica, Molecular y Nuclear, Facultad de Ciencias Fisicas, Universidad Complutense de Madrid, E-28040 Madrid (Spain)

    2014-07-23

    The symmetry energy, the neutron pressure and the asymmetric compressibility of spherical Ni, Sn, and Pb and deformed Kr and Sm neutron-rich even-even nuclei are calculated within the coherent density fluctuation model using the symmetry energy as a function of density within the Brueckner energy-density functional. The correlation between the thickness of the neutron skin and the characteristics related with the density dependence of the nuclear symmetry energy is investigated for isotopic chains of these nuclei in the framework of the deformed self-consistent mean-field Skyrme HF+BCS method. The mass dependence of the nuclear symmetry energy and the neutron skin thickness are also studied together with the role of the neutron-proton asymmetry. The studied correlations reveal a smoother behavior in the case of spherical nuclei than for deformed ones. We also notice that the neutron skin thickness obtained for {sup 208}Pb with SLy4 force is found to be in a good agreement with the recent data. In addition to the interest that this study may have by itself, we give some numerical arguments in proof of the existence of peculiarities of the studied quantities in Ni and Sn isotopic chains that are not present in the Pb chain.

  4. In situ real-time gravimetric and viscoelastic probing of surface films formation on lithium batteries electrodes.

    Science.gov (United States)

    Dargel, Vadim; Shpigel, Netanel; Sigalov, Sergey; Nayak, Prasant; Levi, Mikhael D; Daikhin, Leonid; Aurbach, Doron

    2017-11-09

    It is generally accepted that solid-electrolyte interphase formed on the surface of lithium-battery electrodes play a key role in controlling their cycling performance. Although a large variety of surface-sensitive spectroscopies and microscopies were used for their characterization, the focus was on surface species nature rather than on the mechanical properties of the surface films. Here we report a highly sensitive method of gravimetric and viscoelastic probing of the formation of surface films on composite Li 4 Ti 5 O 12 electrode coupled with lithium ions intercalation into this electrode. Electrochemical quartz-crystal microbalance with dissipation monitoring measurements were performed with LiTFSI, LiPF 6 , and LiPF 6  + 2% vinylene carbonate solutions from which structural parameters of the surface films were returned by fitting to a multilayer viscoelastic model. Only a few fast cycles are required to qualify surface films on Li 4 Ti 5 O 12 anode improving in the sequence LiPF 6  < LiPF 6  + 2% vinylene carbonate < LiTFSI.

  5. Comparison of neutron scattering and DFM capacitance instruments ...

    African Journals Online (AJOL)

    Soil water evaporation is an important parameter that needs to be accurately measured for the design of water-efficient agricultural systems. With this study, the abilities of the DFM capacitance probes and a neutron water meter (NWM) to measure evaporation from the soil surface were compared. Measured evaporation was ...

  6. Local Environment and Interactions of Liquid and Solid Interfaces Revealed by Spectral Line Shape of Surface Selective Nonlinear Vibrational Probe

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Shun-Li; Fu, Li; Chase, Zizwe A.; Gan, Wei; Wang, Hong-Fei

    2016-11-10

    Vibrational spectral lineshape contains important detailed information of molecular vibration and reports its specific interactions and couplings to its local environment. In this work, recently developed sub-1 cm-1 high-resolution broadband sum frequency generation vibrational spectroscopy (HR-BB-SFG-VS) was used to measure the -C≡N stretch vibration in the 4-n-octyl-4’-cyanobiphenyl (8CB) Langmuir or Langmuir-Blodgett (LB) monolayer as a unique vibrational probe, and the spectral lineshape analysis revealed the local environment and interactions at the air/water, air/glass, air/calcium fluoride and air/-quartz interfaces for the first time. The 8CB Langmuir or LB film is uniform and the vibrational spectral lineshape of its -C≡N group has been well characterized, making it a good choice as the surface vibrational probe. Lineshape analysis of the 8CB -C≡N stretch SFG vibrational spectra suggests the coherent vibrational dynamics and the structural and dynamic inhomogeneity of the -C≡N group at each interface are uniquely different. In addition, it is also found that there are significantly different roles for water molecules in the LB films on different substrate surfaces. These results demonstrated the novel capabilities of the surface nonlinear spectroscopy in characterization and in understanding the specific structures and chemical interactions at the liquid and solid interfaces in general.

  7. Workshop on Probing Frontiers in Matter with Neutron Scattering, Wrap-up Session Chaired by John C. Browne on December 14, 1997, at Fuller Lodge, Los Alamos, New Mexico

    International Nuclear Information System (INIS)

    Mezei, F.; Thompson, J.

    1998-01-01

    The Workshop on Probing Frontiers in Matter with Neutron Scattering consisted of a series of lectures and discussions about recent highlights in neutron scattering. In this report, we present the transcript of the concluding discussion session (wrap-up session) chaired by John C. Browne, Director of Los Alamos National Laboratory. The workshop had covered a spectrum of topics ranging from high T c superconductivity to polymer science, from glasses to molecular biology, a broad review aimed at identifying trends and future needs in condensed matter research. The focus of the wrap-up session was to summarize the workshop participants' views on developments to come. Most of the highlights presented during the workshop were the result of experiments performed at the leading reactor-based neutron scattering facilities. However, recent advances with very high power accelerators open up opportunities to develop new approaches to spallation technique that could decisively advance neutron scattering research in areas for which reactor sources are today by far the best choice. The powerful combination of neutron scattering and increasingly accurate computer modeling emerged as another area of opportunity for research in the coming decades

  8. Probing droplets with biological colloidal suspensions on smart surfaces by synchrotron radiation micro- and nano-beams

    KAUST Repository

    Marinaro, Giovanni

    2015-03-01

    Droplets with colloidal biological suspensions evaporating on substrates with defined wetting properties generate confined environments for initiating aggregation and self-assembly processes. We describe smart micro- and nanostructured surfaces, optimized for probing single droplets and residues by synchrotron radiation micro- and nanobeam diffraction techniques. Applications are presented for Ac-IVD and β-amyloid (1-42) peptides capable of forming cross-β sheet structures. Complementary synchrotron radiation FTIR microspectroscopy addresses secondary structure formation. The high synchrotron radiation source brilliance enables fast raster-scan experiments. © 2015 Elsevier Ltd.

  9. HI observations of low surface brightness galaxies : Probing low-density galaxies

    NARCIS (Netherlands)

    deBlok, WJG; McGaugh, SS; vanderHulst, JM

    1996-01-01

    We present Very Large Array (VLA) and Westerbork Synthesis Radio Telescope (WSRT) 21-cm HI observations of 19 late-type low surface brightness (LSB) galaxies. Our main findings are that these galaxies, as well as having low surface brightnesses, have low HI surface densities, about a factor of

  10. X-ray free electron laser as a real-time probe of chemistry on surfaces

    International Nuclear Information System (INIS)

    Katayama, Tetsuo; Ogasawara, Hirohito

    2015-01-01

    X-ray free electron laser has opened up new possibilities for the study of surface chemical reactions on ultrafast time scale. This article reviews the recent work on the desorption of a molecule from a surface, which is one of the most fundamental surface chemical process. (author)

  11. Probing adsorption phenomena on a single crystal Pt-alloy surface under oxygen reduction reaction conditions

    DEFF Research Database (Denmark)

    Bondarenko, Alexander S.; Stephens, Ifan E.L.; Bech, Lone

    2012-01-01

    The adsorption dynamics of *OH and *O species at Pt(111) and Cu/Pt(111) near-surface alloy (NSA) surfaces in oxygen-free and O2-saturated 0.1M HClO4 was investigated. Subsurface Cu modifies the electronic structure at the Pt(111) surface resulting in weaker bonding to adsorbates like *OH, *H or *...

  12. In situ probing of surface hydrides on hydrogenated amorphous silicon using attenuated total reflection infrared spectroscopy

    CERN Document Server

    Kessels, W M M; Sanden, M C M; Aydil, E S

    2002-01-01

    An in situ method based on attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) is presented for detecting surface silicon hydrides on plasma deposited hydrogenated amorphous silicon (a-Si:H) films and for determining their surface concentrations. Surface silicon hydrides are desorbed by exposing the a-Si:H films to low energy ions from a low density Ar plasma and by comparing the infrared spectrum before and after this low energy ion bombardment, the absorptions by surface hydrides can sensitively be separated from absorptions by bulk hydrides incorporated into the film. An experimental comparison with other methods that utilize isotope exchange of the surface hydrogen with deuterium showed good agreement and the advantages and disadvantages of the different methods are discussed. Furthermore, the determination of the composition of the surface hydrogen bondings on the basis of the literature data on hydrogenated crystalline silicon surfaces is presented, and quantification of the h...

  13. Directional neutronometric probe; Kierunkowa sonda neutronometryczna

    Energy Technology Data Exchange (ETDEWEB)

    Strzelecki, M.; Owczarczyk, A.; Wieclaw, B.; Szpilowwski, S.

    1991-11-04

    The neutronometric probe for direction and rate of groundwater flow measurements has been designed. The probe consists in collimated proportional neutron counter and also collimated and shielded neutron source. The neutron source can be disconnected from the detection part of the probe and transported separately in especially designed container. In the place of measurement the source can be easily joined to the detection part. 1 fig.

  14. Probing the intrinsically oil-wet surfaces of pores in North Sea chalk at subpore resolution

    DEFF Research Database (Denmark)

    Hassenkam, Tue; Skovbjerg, Lone Lindbæk; Stipp, Susan Louise Svane

    2009-01-01

    Ultimate Oil recovery from chalk reservoirs is limited by many factors - including the grain size and the surface properties of the small mainly biogenic calcite particles that chalk is made off . Wettability, the tendency for water or oil to spread over a surface, of the particle surfaces is one......, not a product of later migration of oil into the reservoir, which is known to alter the wettability of the surfaces. The data indicated distinct patches, with diameters ranging from 500 to 50 nm, which appears to have different wettability The size of the patches is significantly less than the size of the chalk...

  15. Atom probe study on microstructure change in severely deformed pearlitic steels: application to rail surfaces and drawn wires

    Science.gov (United States)

    Takahashi, Jun

    2017-07-01

    Pearlitic steel is used as the material for high tensile steel wires, rails and wheels due to its high work hardening and wear resistance. These properties arise from a layered structure comprising deformable lamellar ferrite and hard lamellar cementite. This paper reviews the microstructural change in heavily drawn pearlitic steels wires and worn surfaces of pearlitic rails using atom probe tomography analysis. The cementite decomposition mechanism was elucidated for heavily drawn pearlitic steel wires. For pearlitic rail steels, atomic scale characterization of worn surfaces and of the white etching layer (WEL) were performed, and a mechanism for the formation of the WEL was proposed. The differences and similarities in microstructure and in the state of the cementite in these severely deformed pearlitic steels are discussed.

  16. Device for positioning ultrasonic probes and/or television cameras on the outer surface of reactor pressure vessels

    International Nuclear Information System (INIS)

    Zipser, R.; Dose, G.F.

    1977-01-01

    The device makes possible periodical in-service inspections of welding seams and material of a reactor pressure vessel without local human presence. A 'support ring' encloses the pressure vessel in a horizontal plane with free space. It is vertically moved up and down in the space between pressure vessel and thermal shield by means of tackles. At a control desk placed in a protected area its movement is controlled and its vertical position is indicated. A 'rotating track' with its own drive is rotating remote-controlled on the 'support ring'. By a combination of the vertical with the rotating movement, an ultrasonic probe placed removably on the 'rotating hack', or a television camera will be brought to any position on the cylindrical circumference of the pressure vessel. Special devices extend the radius of action, in upward direction for inspecting the welding seams of the coolant nozzles, and in downward direction for the inspection of welds on the hemispherical bottom of the pressure vessel or on the outlet pipe nozzle placed there. The device remains installed during reactor operation, but is moved down to the lower horizontal surface of the thermal shield. Parts which are sensible to radiation like probes or television cameras and special devices will then be removed respectively mounted before beginning an inspection compaign. This position may be reached by the lower access in the biological shield and through an opening in the horizontal surface of the thermal shield. (HP) [de

  17. Water adsorption on TiO2 surfaces probed by soft X-ray spectroscopies: bulk materials vs. isolated nanoparticles

    Science.gov (United States)

    Benkoula, Safia; Sublemontier, Olivier; Patanen, Minna; Nicolas, Christophe; Sirotti, Fausto; Naitabdi, Ahmed; Gaie-Levrel, François; Antonsson, Egill; Aureau, Damien; Ouf, François-Xavier; Wada, Shin-Ichi; Etcheberry, Arnaud; Ueda, Kiyoshi; Miron, Catalin

    2015-01-01

    We describe an experimental method to probe the adsorption of water at the surface of isolated, substrate-free TiO2 nanoparticles (NPs) based on soft X-ray spectroscopy in the gas phase using synchrotron radiation. To understand the interfacial properties between water and TiO2 surface, a water shell was adsorbed at the surface of TiO2 NPs. We used two different ways to control the hydration level of the NPs: in the first scheme, initially solvated NPs were dried and in the second one, dry NPs generated thanks to a commercial aerosol generator were exposed to water vapor. XPS was used to identify the signature of the water layer shell on the surface of the free TiO2 NPs and made it possible to follow the evolution of their hydration state. The results obtained allow the establishment of a qualitative determination of isolated NPs’ surface states, as well as to unravel water adsorption mechanisms. This method appears to be a unique approach to investigate the interface between an isolated nano-object and a solvent over-layer, paving the way towards new investigation methods in heterogeneous catalysis on nanomaterials. PMID:26462615

  18. Investigation of simultaneously existed Raman scattering enhancement and inhibiting fluorescence using surface modified gold nanostars as SERS probes.

    Science.gov (United States)

    Shan, Feng; Zhang, Xiao-Yang; Fu, Xing-Chang; Zhang, Li-Jiang; Su, Dan; Wang, Shan-Jiang; Wu, Jing-Yuan; Zhang, Tong

    2017-07-28

    One of the main challenges for highly sensitive surface-enhanced Raman scattering (SERS) detection is the noise interference of fluorescence signals arising from the analyte molecules. Here we used three types of gold nanostars (GNSs) SERS probes treated by different surface modification methods to reveal the simultaneously existed Raman scattering enhancement and inhibiting fluorescence behaviors during the SERS detection process. As the distance between the metal nanostructures and the analyte molecules can be well controlled by these three surface modification methods, we demonstrated that the fluorescence signals can be either quenched or enhanced during the detection. We found that fluorescence quenching will occur when analyte molecules are closely contacted to the surface of GNSs, leading to a ~100 fold enhancement of the SERS sensitivity. An optimized Raman signal detection limit, as low as the level of 10 -11  M, were achieved when Rhodamine 6 G were used as the analyte. The presented fluorescence-free GNSs SERS substrates with plentiful hot spots and controllable surface plasmon resonance wavelengths, fabricated using a cost-effective self-assembling method, can be very competitive candidates for high-sensitive SERS applications.

  19. An improved thin-layer chromatography/mass spectrometry coupling using a surface sampling probe electrospray ion trap system

    Energy Technology Data Exchange (ETDEWEB)

    Ford, Michael J [ORNL; Van Berkel, Gary J [ORNL

    2004-01-01

    A combined surface sampling probe/electrospray emitter coupled with an ion trap mass spectrometer was used for the direct read out of unmodified reversed-phase C18 thin-layer chromatography (TLC) plates. The operation of the surface sampling electrospray ionization interface in positive and negative ionization modes was demonstrated through the direct analysis of TLC plates on which a commercial test mix comprised of four dye compounds viz., rhodamine B, fluorescein, naphthol blue black, and fast green FCF, and an extract of the caffeine-containing plant Ilex vomitoria, were spotted and developed. Acquisition of full-scan mass spectra and automated collection of MS/MS product ion spectra while scanning a development lane along the surface of a TLC plate demonstrated the advantages of using an ion trap in this combination. Details of the sampling system, benefits of analyzing a developed lane in both positive ion and negative ion modes, levels of detection while surface scanning, surface scan speed effects, and the utility of three-dimensional data display, are also discussed.

  20. Ag coated microneedle based surface enhanced Raman scattering probe for intradermal measurements

    Science.gov (United States)

    Yuen, Clement; Liu, Quan

    2013-06-01

    We propose a silver coated microneedle to detect test molecules, including R6G and glucose, positioned at a depth of more than 700 μm below a skin phantom surface for mimicking intradermal surface-enhanced Raman scattering measurements.

  1. Uncertainty analysis of point by point sampling complex surfaces using touch probe CMMs

    DEFF Research Database (Denmark)

    Barini, Emanuele; Tosello, Guido; De Chiffre, Leonardo

    2007-01-01

    The paper describes a study concerning point by point scanning of complex surfaces using tactile CMMs. A four factors-two level full factorial experiment was carried out, involving measurements on a complex surface configuration item comprising a sphere, a cylinder and a cone, combined in a singl...

  2. Liquid-solid contact measurements using a surface thermocouple temperature probe in atmospheric pool boiling water

    International Nuclear Information System (INIS)

    Lee, L.Y.W.; Chen, J.C.; Nelson, R.A.

    1984-01-01

    Objective was to apply the technique of using a microthermocouple flush-mounted at the boiling surface for the measurement of the local-surface-temperature history in film and transition boiling on high temperature surfaces. From this measurement direct liquid-solid contact in film and transition boiling regimes was observed. In pool boiling of saturated, distilled, deionized water on an aluminum-coated copper surface, the time-averaged, local-liquid-contact fraction increased with decreasing surface superheat. Average contact duration increased monotonically with decreasing surface superheat, while frequency of liquid contact reached a maximum of approx. 50 contacts/s at a surface superheat of approx. 100 K and decreased gradually to 30 contacts/s near the critical heat flux. The liquid-solid contact duration distribution was dominated by short contacts 4 ms at low surface superheats, passing through a relatively flat contact duration distribution at about 80 0 K. Results of this paper indicate that liquid-solid contacts may be the dominant mechanism for energy transfer in the transition boiling process

  3. An inexpensive and simple method for thermally stable immobilization of DNA on an unmodified glass surface: UV linking of poly(T)10-poly(C)10-tagged DNA probes

    DEFF Research Database (Denmark)

    Guðnason, Haukur; Dufva, Hans Martin; Bang, Dang Duong

    2008-01-01

    the hybridization performance of the immobilized probes on the amino-silane surface, indicating a general benefit of adding a TC tag to DNA probes. In conclusion, our results show that using TC-tagged DNA probes immobilized on an unmodified glass surface is a robust, heat-stable, very simple, and inexpensive method...

  4. Probing cluster surface morphology by cryo spectroscopy of N2 on cationic nickel clusters

    Science.gov (United States)

    Dillinger, Sebastian; Mohrbach, Jennifer; Niedner-Schatteburg, Gereon

    2017-11-01

    We present the cryogenic (26 K) IR spectra of selected [Nin(N2)m]+ (n = 5-20, m = 1 - mmax), which strongly reveal n- and m-dependent features in the N2 stretching region, in conjunction with density functional theory modeling of some of these findings. The observed spectral features allow us to refine the kinetic classification [cf. J. Mohrbach, S. Dillinger, and G. Niedner-Schatteburg, J. Chem. Phys. 147, 184304 (2017)] and to define four classes of structure related surface adsorption behavior: Class (1) of Ni6+, Ni13+, and Ni19+ are highly symmetrical clusters with all smooth surfaces of equally coordinated Ni atoms that entertain stepwise N2 adsorption up to stoichiometric N2:Nisurface saturation. Class (2) of Ni12+ and Ni18+ are highly symmetrical clusters minus one. Their relaxed smooth surfaces reorganize by enhanced N2 uptake toward some low coordinated Ni surface atoms with double N2 occupation. Class (3) of Ni5+ and Ni7+ through Ni11+ are small clusters of rough surfaces with low coordinated Ni surface atoms, and some reveal semi-internal Ni atoms of high next-neighbor coordination. Surface reorganization upon N2 uptake turns rough into rough surface by Ni atom migration and turns octahedral based structures into pentagonal bipyramidal structures. Class (4) of Ni14+ through Ni17+ and Ni20+ are large clusters with rough and smooth surface areas. They possess smooth icosahedral surfaces with some proximate capping atom(s) on one hemisphere of the icosahedron with the other one largely unaffected.

  5. Enhanced Dynamics of Hydrated tRNA on Nanodiamond Surfaces: A Combined Neutron Scattering and MD Simulation Study.

    Science.gov (United States)

    Dhindsa, Gurpreet K; Bhowmik, Debsindhu; Goswami, Monojoy; O'Neill, Hugh; Mamontov, Eugene; Sumpter, Bobby G; Hong, Liang; Ganesh, Panchapakesan; Chu, Xiang-Qiang

    2016-09-14

    Nontoxic, biocompatible nanodiamonds (ND) have recently been implemented in rational, systematic design of optimal therapeutic use in nanomedicines. However, hydrophilicity of the ND surface strongly influences structure and dynamics of biomolecules that restrict in situ applications of ND. Therefore, fundamental understanding of the impact of hydrophilic ND surface on biomolecules at the molecular level is essential. For tRNA, we observe an enhancement of dynamical behavior in the presence of ND contrary to generally observed slow motion at strongly interacting interfaces. We took advantage of neutron scattering experiments and computer simulations to demonstrate this atypical faster dynamics of tRNA on ND surface. The strong attractive interactions between ND, tRNA, and water give rise to unlike dynamical behavior and structural changes of tRNA in front of ND compared to without ND. Our new findings may provide new design principles for safer, improved drug delivery platforms.

  6. Analytical model for neutron diffraction peak shifts due to the surface effect

    Czech Academy of Sciences Publication Activity Database

    Šaroun, Jan; Kornmeier, J. R.; Hofmann, M.; Mikula, Pavol; Vrána, Miroslav

    2013-01-01

    Roč. 46, č. 6 (2013), s. 628-638 ISSN 0021-8898 R&D Projects: GA ČR GAP204/10/0654 Institutional support: RVO:61389005 Keywords : residual-stress * neutron diffraction * Monte Carlo simulation Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.950, year: 2013

  7. Monte Carlo simulation of an in-situ search of water on the Martian surface by using neutron spectroscopy

    CERN Document Server

    Vincke, H H; Müller, H; Bruckner, J

    2003-01-01

    In this paper the concept for in-situ search of water in the Martian soil by applying neutron spectroscopy is examined. Monte-Carlo simulations were carried out to determine homogeneous water concentrations in the Martian surface. In addition, the effect of an ice layer with a thickness of 10 cm, buried in the soil, was investigated. Furthermore, a method is presented that provides the ability to distinguish between the effects caused by a homogeneous water distribution and an ice layer located at different depths.

  8. Precision Hopping/Rolling Robotic Surface Probe Based on Tensegrity Structures

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose to overcome the limitations of wheeled surface rovers by combining recent advances in ball-shaped soft-robots based on tensegrity structures (a tension...

  9. Probing the electronic transport on the reconstructed Au/Ge(001 surface

    Directory of Open Access Journals (Sweden)

    Franciszek Krok

    2014-09-01

    Full Text Available By using scanning tunnelling potentiometry we characterized the lateral variation of the electrochemical potential µec on the gold-induced Ge(001-c(8 × 2-Au surface reconstruction while a lateral current flows through the sample. On the reconstruction and across domain boundaries we find that µec shows a constant gradient as a function of the position between the contacts. In addition, nanoscale Au clusters on the surface do not show an electronic coupling to the gold-induced surface reconstruction. In combination with high resolution scanning electron microscopy and transmission electron microscopy, we conclude that an additional transport channel buried about 2 nm underneath the surface represents a major transport channel for electrons.

  10. Probing the molecular structures of plasma-damaged and surface-repaired low-k dielectrics.

    Science.gov (United States)

    Zhang, Xiaoxian; Myers, John N; Lin, Qinghuang; Bielefeld, Jeffery D; Chen, Zhan

    2015-10-21

    Fully understanding the effect and the molecular mechanisms of plasma damage and silylation repair on low dielectric constant (low-k) materials is essential to the design of low-k dielectrics with defined properties and the integration of low-k dielectrics into advanced interconnects of modern electronics. Here, analytical techniques including sum frequency generation vibrational spectroscopy (SFG), Fourier transform infrared spectroscopy (FTIR), contact angle goniometry (CA) and X-ray photoelectron spectroscopy (XPS) have been employed to provide a comprehensive characterization of the surface and bulk structure changes of poly(methyl)silsesquioxane (PMSQ) low-k thin films before and after O2 plasma treatment and silylation repair. O2 plasma treatment altered drastically both the molecular structures and water structures at the surfaces of the PMSQ film while no bulk structural change was detected. For example, ∼34% Si-CH3 groups were removed from the PMSQ surface, and the Si-CH3 groups at the film surface tilted toward the surface after the O2 plasma treatment. The oxidation by the O2 plasma made the PMSQ film surface more hydrophilic and thus enhanced the water adsorption at the film surface. Both strongly and weakly hydrogen bonded water were detected at the plasma-damaged film surface during exposure to water with the former being the dominate component. It is postulated that this enhancement of both chemisorbed and physisorbed water after the O2 plasma treatment leads to the degradation of low-k properties and reliability. The degradation of the PMSQ low-k film can be recovered by repairing the plasma-damaged surface using a silylation reaction. The silylation method, however, cannot fully recover the plasma induced damage at the PMSQ film surface as evidenced by the existence of hydrophilic groups, including C-O/C[double bond, length as m-dash]O and residual Si-OH groups. This work provides a molecular level picture on the surface structural changes of low

  11. Nitrate as a probe of cytochrome c surface: crystallographic identification of crucial "hot spots" for protein-protein recognition.

    Science.gov (United States)

    De March, Matteo; Demitri, Nicola; De Zorzi, Rita; Casini, Angela; Gabbiani, Chiara; Guerri, Annalisa; Messori, Luigi; Geremia, Silvano

    2014-06-01

    The electrostatic surface of cytochrome c and its changes with the iron oxidation state are involved in the docking and undocking processes of this protein to its biological partners in the mitochondrial respiratory pathway. To investigate the subtle mechanisms of formation of productive macromolecular complexes and of their breakage following the electron transfer process, the X-ray structures of horse heart ferri-cytochrome c (trigonal form) and ferro-cytochrome c (monoclinic form) were obtained using nitrate ions both as a crystallizing agent and an anionic probe for mapping the electrostatic surface changes. Both crystal forms contain three protein molecules in the asymmetric unit. In addition, a total of 21.5 and 18 crystallographically independent nitrate ions were identified for the trigonal and monoclinic forms, respectively. By matching all the six crystallographically independent protein molecules, 26 different anion-protein interaction sites were identified on the surfaces of cytochrome c, 10 of which were found in both forms, 8 present only in the oxidized and 8 only in the reduced form. The structural analysis of the electron transfer complexes, based on this new information, suggests a specific exit strategy for cytochrome c after formation of productive protein-protein complexes: a directional sliding mechanism for the electron shuttle on the surface of the redox partner is proposed to take place after the electron transfer process has occurred. Copyright © 2014 Elsevier Inc. All rights reserved.

  12. Probing and mapping the binding sites on streptavidin imprinted polymer surface

    International Nuclear Information System (INIS)

    Duman, Memed

    2014-01-01

    Molecular imprinting is an effective technique for preparing recognition sites which act as synthetic receptors on polymeric surfaces. Herein, we synthesized MIP surfaces with specific binding sites for streptavidin and characterized them at nanoscale by using two different atomic force microscopy (AFM) techniques. While the single molecule force spectroscopy (SMFS) reveals the unbinding kinetics between streptavidin molecule and binding sites, simultaneous topography and recognition imaging (TREC) was employed, for the first time, to directly map the binding sites on streptavidin imprinted polymers. Streptavidin modified AFM cantilever showed specific unbinding events with an unbinding force around 300 pN and the binding probability was calculated as 35.2% at a given loading rate. In order to prove the specificity of the interaction, free streptavidin molecules were added to AFM liquid cell and the binding probability was significantly decreased to 7.6%. Moreover, the recognition maps show that the smallest recognition site with a diameter of around ∼ 21 nm which corresponds to a single streptavidin molecule binding site. We believe that the potential of combining SMFS and TREC opens new possibilities for the characterization of MIP surfaces with single molecule resolution under physiological conditions. - Graphical abstract: Simultaneous Topography and RECognition (TREC) imaging is a novel characterization technique to reveal binding sites on molecularly imprinted polymer surfaces with single molecule resolution under physiological conditions. - Highlights: • Highly specific streptavidin printed polymer surfaces were synthesized. • Unbinding kinetic rate of single streptavidin molecule was studied by SMFS. • The distribution of binding pockets was revealed for the first time by TREC imaging. • TREC showed that the binding pockets formed nano-domains on MIP surface. • SMFS and TREC are powerful AFM techniques for characterization of MIP surfaces

  13. Multi Function Heat Pulse Probes (MFHPP) to Estimate Ground Heat Flux and Reduce Surface Energy Budget Errors

    Science.gov (United States)

    Ciocca, Francesco; Sharma, Varun; Lunati, Ivan; Parlange, Marc B.

    2013-04-01

    Ground heat flux plays a crucial role in surface energy budget: an incorrect estimation of energy storage and heat fluxes in soils occur when probes such as heat flux plates are adopted, and these mistakes can account for up to 90% of the residual variance (Higgins, GRL, 2012). A promising alternative to heat flux plates is represented by Multi Function Heat Pulse Probes (MFHPP). They have proven to be accurate in thermal properties and heat fluxes estimation (e.g. Cobos, VZJ, 2003) and can be used to monitor and quantify subsurface evaporation in field experiments (Xiao et al., VZJ, 2011). We perform a laboratory experiment with controlled temperature in a small Plexiglas column (20cm diameter and 40cm height). The column is packed with homogeneously saturated sandy soil and equipped with three MFHPPs in the upper 4cm and thermocouples and dielectric soil moisture probes deeper. This configuration allows for accurate and simultaneous ground heat flux, soil moisture and subsurface evaporation measurements. Total evaporation is monitored using a precision scale, while an infrared gun and a long wave radiometer measure the soil skin temperature and the outgoing long-short wave radiation, respectively. A fan and a heat lamp placed above the column allow to mimick on a smaller and more controlled scale the field conditions induced by the diurnal cycle. At a reference height above the column relative humidity, wind speed and air temperature are collected. Results are interpreted by means of numerical simulations performed with an ad-hoc-developed numerical model that simulates coupled heat and moisture transfer in soils and is used to match and interpolate the temperature and soil moisture values got at finite depths within the column. Ground heat fluxes are then estimated by integrating over almost continuous, numerically simulated temperature profiles, which avoids errors due to use of discrete data (Lunati et al., WRR, 2012) and leads to a more reliable estimate of

  14. Probing spin helical surface states in topological HgTe nanowires

    Science.gov (United States)

    Ziegler, J.; Kozlovsky, R.; Gorini, C.; Liu, M.-H.; Weishäupl, S.; Maier, H.; Fischer, R.; Kozlov, D. A.; Kvon, Z. D.; Mikhailov, N.; Dvoretsky, S. A.; Richter, K.; Weiss, D.

    2018-01-01

    Nanowires with helical surface states represent key prerequisites for observing and exploiting phase-coherent topological conductance phenomena, such as spin-momentum locked quantum transport or topological superconductivity. We demonstrate in a joint experimental and theoretical study that gated nanowires fabricated from high-mobility strained HgTe, known as a bulk topological insulator, indeed preserve the topological nature of the surface states, that moreover extend phase-coherently across the entire wire geometry. The phase-coherence lengths are enhanced up to 5 μ m when tuning the wires into the bulk gap, so as to single out topological transport. The nanowires exhibit distinct conductance oscillations, both as a function of the flux due to an axial magnetic field and of a gate voltage. The observed h /e -periodic Aharonov-Bohm-type modulations indicate surface-mediated quasiballistic transport. Furthermore, an in-depth analysis of the scaling of the observed gate-dependent conductance oscillations reveals the topological nature of these surface states. To this end we combined numerical tight-binding calculations of the quantum magnetoconductance with simulations of the electrostatics, accounting for the gate-induced inhomogeneous charge carrier densities around the wires. We find that helical transport prevails even for strongly inhomogeneous gating and is governed by flux-sensitive high-angular momentum surface states that extend around the entire wire circumference.

  15. Neutrons and materials

    International Nuclear Information System (INIS)

    Paulus, W.; Meinnel, J.

    2003-01-01

    The neutron is the only probe that gives information simultaneously on structure issues through interference phenomena and on dynamics issues through spectroscopy. The neutron carries a s=1/2 spin value which allows it to be polarizable and to interact with any magnetic field through the magnetic momentum associated to its spin. The great interest of neutron in research relies on 3 facts: -) the neutron fluxes used to study matter are supplied by nuclear reactors and spallation sources with wave lengths and energy range that directly correspond to interatomic distances and thermal-motion energies of matter, -) the possibility of setting or changing the contrast of an element by using its different isotopes, and -) the neutron does not carry an electrical charge so it can enter the bulk of matter easily and gives an image of stress and patterns of large pieces of metal through a non-destructive examination. This course reviews all the aspects of the use of neutron in physics and is made up of 16 chapters: 1) properties of neutrons, 2) neutron production, 3) complementarity between X-ray and neutrons, 4) neutron diffraction, 5) neutron diffusion, 6) neutron spectroscopy, 7) crystallography, 8) imaging techniques with neutrons, 9) neutron activation analysis, 10) low-angle diffusion, 11) neutron reflectivity, 12) non-destructive testing, 13) microstructure and diffraction rays of X-radiation, 14) access to neutron source facilities, 15) composites materials and neutron diffusion, and 16) studies of liquids and glasses through neutron and X-ray diffraction. (A.C.)

  16. Probing anisotropic surface properties and interaction forces of chrysotile rods by atomic force microscopy and rheology.

    Science.gov (United States)

    Yang, Dingzheng; Xie, Lei; Bobicki, Erin; Xu, Zhenghe; Liu, Qingxia; Zeng, Hongbo

    2014-09-16

    Understanding the surface properties and interactions of nonspherical particles is of both fundamental and practical importance in the rheology of complex fluids in various engineering applications. In this work, natural chrysotile, a phyllosilicate composed of 1:1 stacked silica and brucite layers which coil into cylindrical structure, was chosen as a model rod-shaped particle. The interactions of chrysotile brucite-like basal or bilayered edge planes and a silicon nitride tip were measured using an atomic force microscope (AFM). The force-distance profiles were fitted using the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, which demonstrates anisotropic and pH-dependent surface charge properties of brucite-like basal plane and bilayered edge surface. The points of zero charge (PZC) of the basal and edge planes were estimated to be around pH 10-11 and 6-7, respectively. Rheology measurements of 7 vol % chrysotile (with an aspect ratio of 14.5) in 10 mM NaCl solution showed pH-dependent yield stress with a local maximum around pH 7-9, which falls between the two PZC values of the edge and basal planes of the rod particles. On the basis of the surface potentials of the edge and basal planes obtained from AFM measurements, theoretical analysis of the surface interactions of edge-edge, basal-edge, and basal-basal planes of the chrysotile rods suggests the yield stress maximum observed could be mainly attributed to the basal-edge attractions. Our results indicate that the anisotropic surface properties (e.g., charges) of chrysotile rods play an important role in the particle-particle interaction and rheological behavior, which also provides insight into the basic understanding of the colloidal interactions and rheology of nonspherical particles.

  17. Probing the intrinsically oil-wet surfaces of pores in North Sea chalk at subpore resolution

    DEFF Research Database (Denmark)

    Hassenkam, Tue; Skovbjerg, Lone Lindbæk; Stipp, Susan Louise Svane

    2009-01-01

    atomic force microscopy-mediated adhesion and elasticity mapping derived from maps of force curves, to examine 5 x 5 µm2 areas of internal pore surfaces, using a tip functionalised to make it hydrophobic.  We investigated chalk samples from inside a drill core sample from the Danish North Sea that had...... been drilled in a water-bearing formation. At this site, the chalk has never seen oil, though at other locations, the same stratigraphic horizon with the same rock properties is known to be a productive oil reservoir. Thus the properties of the investigated particle surfaces are inherent to the chalk...

  18. Topological surface states of strained Mercury-Telluride probed by ARPES

    OpenAIRE

    Crauste, Olivier; Ohtsubo, Yoshiyuki; Ballet, Philippe; Delplace, Pierre André Louis; Carpentier, David; Bouvier, Clément; Meunier, Tristan; Taleb-Ibrahimi, Amina; Lévy, Laurent

    2013-01-01

    with supplementary material; The topological surface states of strained HgTe have been measured using high-resolution ARPES measurements. The dispersion of surface states form a Dirac cone, which origin is close to the top of the \\ghh band: the top half of the Dirac cone is inside the stress-gap while the bottom half lies within the heavy hole bands and keeps a linear dispersion all the way to the X-point. The circular dichroism of the photo-emitted electron intensity has also been measured f...

  19. CO2 sorption on surface-modified carbonaceous support: Probing the influence of the carbon black microporosity and surface polarity

    International Nuclear Information System (INIS)

    Gargiulo, Valentina; Alfè, Michela; Ammendola, Paola; Raganati, Federica; Chirone, Riccardo

    2016-01-01

    Graphical abstract: - Highlights: • CO 2 -sorbent materials preparation by surface modification of CB. • CB functionalization (amino-groups), CB coating (Fe 3 O 4 ), CB impregnation (ionic liquid). • Sorbents bearing basic functionalities exhibit the higher CO 2 sorption capacity. • Microporous supporting material limits the CO 2 accessibility toward the adsorbing material. - Abstract: The use of solid sorbents is a convenient option in post-combustion CO 2 capture strategies. Sorbents selection is a key point because the materials are required to be both low-cost and versatile in typical post-combustion conditions in order to guarantee an economically advantageous overall process. This work compares strategies to tailor the chemico-physical features of carbon black (CB) by surface-modification and/or coating with a CO 2 -sorbent phase. The influence of the CB microporosity, enhanced by chemical/thermal treatments, is also taken into account. Three CB surface modifications are performed and compared: (i) oxidation and functionalization with amino-groups, (ii) coating with iron oxides and (iii) impregnation with an ionic liquid (IL). The CO 2 capture performance is evaluated on the basis of the breakthrough curves measured at atmospheric pressure and room temperature in a lab-scale fixed bed micro-reactor. Most of tested solids adsorb a CO 2 amount significantly higher than a 13X zeolite and DARCO FGD (Norit) activated carbon (up to 4 times more in the best case). The sorbents bearing basic functionalities (amino-groups and IL) exhibit the highest CO 2 sorption capacity. The use of a microporous carbonaceous support limits the accessibility of CO 2 toward the adsorbing phase (IL or FM) lowering the number of accessible binding sites for CO 2 .

  20. Neutron diffraction

    International Nuclear Information System (INIS)

    Elcomb, M.M.

    2002-01-01

    Full text: Thermal neutrons have a particular combination of properties, which make them the probe of choice for a wide range of scattering applications. They penetrate most materials easily, the wavelength matches interatomic spacings, the energy matches the atomic vibrational energies and the magnetic moment allows them to uniquely interact with magnetic structures. Their widely varying scattering length is also used to advantage. It enables the determination of light atoms in the presence of heavy ones: hydrogen in organic molecules, and oxygen in the high Tc superconductors for example, or solving problems in alloy systems where distinction of atoms, which are neighbours in the periodic table, is required. In the 50 years since thermal neutron beams have been used for research there has been a steady increase in applications as technology has advanced. This also applies to the environments in which the materials are studied. In-situ studies at other than ambient temperatures, pressures and magnetic fields are now routine. By using multiple detector channels in powder instruments the data collection rate has increased by an order of magnitude to some extent compensating for the diffuse nature of the neutron source. The applications of neutron scattering are becoming more industrially oriented. The talk will highlight the complementarity of neutrons to other more readily available techniques, and give examples of recent research and applications. Copyright (2002) Australian X-ray Analytical Association Inc

  1. Probing the Active Surface Sites for CO Reduction on Oxide-Derived Copper Electrocatalysts

    DEFF Research Database (Denmark)

    Verdaguer Casadevall, Arnau; Li, Christina W.; Johansson, Tobias Peter

    2015-01-01

    CO electroreduction activity on oxide-derived Cu (OD-Cu) was found to correlate with metastable surface features that bind CO strongly. OD-Cu electrodes prepared by H-2 reduction of Cu2O precursors reduce CO to acetate and ethanol with nearly 50% Faradaic efficiency at moderate overpotential. Tem...

  2. Probing Earth’s conductivity structure beneath oceans by scalar geomagnetic data: autonomous surface vehicle solution

    DEFF Research Database (Denmark)

    Kuvshinov, Alexey; Matzka, Jürgen; Poedjono, Benny

    2016-01-01

    to the conductivity structure beneath the ocean. We conclude that the sensitivity, depending on the bathymetry gradient, is typically largest near the coast offshore. We show that such sea-surface marine induction surveys can be performed with the Wave Glider, an easy-to-deploy, autonomous, energy-harvesting floating...

  3. CO2 sorption on surface-modified carbonaceous support: Probing the influence of the carbon black microporosity and surface polarity

    Science.gov (United States)

    Gargiulo, Valentina; Alfè, Michela; Ammendola, Paola; Raganati, Federica; Chirone, Riccardo

    2016-01-01

    The use of solid sorbents is a convenient option in post-combustion CO2 capture strategies. Sorbents selection is a key point because the materials are required to be both low-cost and versatile in typical post-combustion conditions in order to guarantee an economically advantageous overall process. This work compares strategies to tailor the chemico-physical features of carbon black (CB) by surface-modification and/or coating with a CO2-sorbent phase. The influence of the CB microporosity, enhanced by chemical/thermal treatments, is also taken into account. Three CB surface modifications are performed and compared: (i) oxidation and functionalization with amino-groups, (ii) coating with iron oxides and (iii) impregnation with an ionic liquid (IL). The CO2 capture performance is evaluated on the basis of the breakthrough curves measured at atmospheric pressure and room temperature in a lab-scale fixed bed micro-reactor. Most of tested solids adsorb a CO2 amount significantly higher than a 13X zeolite and DARCO FGD (Norit) activated carbon (up to 4 times more in the best case). The sorbents bearing basic functionalities (amino-groups and IL) exhibit the highest CO2 sorption capacity. The use of a microporous carbonaceous support limits the accessibility of CO2 toward the adsorbing phase (IL or FM) lowering the number of accessible binding sites for CO2.

  4. Quartz Crystal Microbalance Model for Quantitatively Probing the Deformation of Adsorbed Particles at Low Surface Coverage.

    Science.gov (United States)

    Gillissen, Jurriaan J J; Jackman, Joshua A; Tabaei, Seyed R; Yoon, Bo Kyeong; Cho, Nam-Joon

    2017-11-07

    Characterizing the deformation of nanoscale, soft-matter particulates at solid-liquid interfaces is a demanding task, and there are limited experimental options to perform quantitative measurements in a nonperturbative manner. Previous attempts, based on the quartz crystal microbalance (QCM) technique, focused on the high surface coverage regime and modeled the adsorbed particles as a homogeneous film, while not considering the coupling between particles and surrounding fluid and hence resulting in an underestimation of the known particle height. In this work, we develop a model for the hydrodynamic coupling between adsorbed particles and surrounding fluid in the limit of a low surface coverage, which can be used to extract shape information from QCM measurement data. We tackle this problem by using hydrodynamic simulations of an ellipsoidal particle on an oscillating surface. From the simulation results, we derived a phenomenological relation between the aspect ratio r of the absorbed particles and the slope and intercept of the line that fits instantaneous, overtone-dependent QCM data on (δ/a, -Δf/n) coordinates where δ is the viscous penetration depth, a is the particle radius, Δf is the QCM frequency shift, and n is the overtone number. The model was applied to QCM measurement data pertaining to the adsorption of 34 nm radius, fluid-phase and gel-phase liposomes onto a titanium oxide-coated surface. The osmotic pressure across the liposomal bilayer was varied to induce shape deformation. By combining these results with a membrane bending model, we determined the membrane bending energy for the gel-phase liposomes, and the results are consistent with literature values. In summary, a phenomenological model is presented and validated in order to show for the first time that QCM experiments can quantitatively measure the deformation of adsorbed particles at low surface coverage.

  5. Surface plasmon resonator using high sensitive resonance telecommunication wavelengths for DNA sensors of Mycobacterium tuberculosis with thiol-modified probes.

    Science.gov (United States)

    Hsu, Shih-Hsiang; Hung, Shao-Chiang; Chen, Yu-Kun; Jian, Zhi-Hao

    2014-12-25

    Various analytes can be verified by surface plasmon resonance, thus continuous improvement of this sensing technology is crucial for better sensing selection and higher sensitivity. The SPR sensitivity on the wavelength modulation is enhanced with increasing wavelengths. The telecommunication wavelength range was then utilized to detect Mycobacterium tuberculosis (MTB) deoxyribonucleic acid (DNA) under two situations, without immobilization and with 5'-thiol end labeled IS6100 DNA probes, for SPR sensitivity comparison. The experimental data demonstrated that the SPR sensitivity increased more than 13 times with the wavelength modulation after immobilization. Since the operating wavelength accuracy of a tunable laser source can be controlled within 0.001 nm, the sensitivity and resolution on immobilized MTB DNA were determined as 1.04 nm/(μg/mL) and 0.9 ng/mL, respectively.

  6. High-resolution neutron-scattering study of slow dynamics of surface water molecules in zirconium oxide.

    Science.gov (United States)

    Mamontov, E

    2005-07-08

    We have performed a quasielastic neutron-scattering experiment on backscattering spectrometer with sub-mueV resolution to investigate the slow dynamics of surface water in zirconium oxide using the sample studied previously with a time-of-flight neutron spectrometer [E. Mamontov, J. Chem. Phys. 121, 9087 (2004)]. The backscattering measurements in the temperature range of 240-300 K have revealed a translational dynamics slower by another order of magnitude compared to the translational dynamics of the outer hydration layer observed in the time-of-flight experiment. The relaxation function of this slow motion is described by a stretched exponential with the stretch factors between 0.8 and 0.9, indicating a distribution of the relaxation times. The temperature dependence of the average residence time is non-Arrhenius, suggesting that the translational motion studied in this work is more complex than surface jump diffusion previously observed for the molecules of the outer hydration layer. The observed slow dynamics is ascribed to the molecules of the inner hydration layer that form more hydrogen bonds compared to the molecules of the outer hydration layer. Despite being slower by two orders of magnitude, the translational motion of the molecules of the inner hydration layer may have more in common with bulk water compared to the outer hydration layer, the dynamics of which is slower than that of bulk water by just one order of magnitude.

  7. Scaling of the Surface Plasmon Resonance in Gold and Silver Dimers Probed by EELS

    DEFF Research Database (Denmark)

    Kadkhodazadeh, Shima; de Lasson, Jakob Rosenkrantz; Beleggia, Marco

    2014-01-01

    The dependence of surface plasmon coupling on the distance between two nanoparticles (dimer) is the basis of nanometrology tools such as plasmon rulers. Application of these nanometric rulers requires an accurate description of the scaling of the surface plasmon resonance (SPR) wavelength...... with distance. Here, we have applied electron energy-loss spectroscopy (EELS) and scanning transmission electron microscopy (STEM) imaging to investigate the relationship between the SPR wavelength of gold and silver nanosphere dimers (radius R) and interparticle distance (d) in the range 0.1R .... Instead, within the range 0.1R gold and silver dimers. Despite this common power dependence, consistently larger SPR wavelength shifts are registered for silver for a given change in d, implying...

  8. I-cored Coil Probe Located Above a Conductive Plate with a Surface Hole

    Directory of Open Access Journals (Sweden)

    Tytko Grzegorz

    2018-02-01

    Full Text Available This work presents an axially symmetric mathematical model of an I-cored coil placed over a two-layered conductive material with a cylindrical surface hole. The problem was divided into regions for which the magnetic vector potential of a filamentary coil was established applying the truncated region eigenfunction expansion method. Then the final formula was developed to calculate impedance changes for a cylindrical coil with reference to both the air and to a material with no hole. The influence of a surface flaw in the conductive material on the components of coil impedance was examined. Calculations were made in Matlab for a hole with various radii and the results thereof were verified with the finite element method in COMSOL Multiphysics package. Very good consistency was achieved in all cases.

  9. Ultrasensitive probing of the protein resistance of PEG surfaces by secondary ion mass spectrometry

    DEFF Research Database (Denmark)

    Kingshott, P.; McArthur, S.; Thissen, H.

    2002-01-01

    The highly sensitive surface analytical techniques X-ray photoelectron spectroscopy (XPS) and time-of-flight static secondary ion mass spectrometry (ToF-SIMS) were used to test the resistance of poly(ethylene glycol) (PEG) coatings towards adsorption of lysozyme (LYS) and fibronectin (FN). PEG...... temperature to maximise the graft density of the PEG chains. XPS showed that the grafted density of PEG chains was slightly higher on the allylamine surface. XPS detected no adsorption of either protein on either PEG coating. ToF-SIMS analysis, on the other hand, found, in the positive ion spectra, minute...... but statistically significant signals assignable to amino acid fragment ions from both proteins adsorbed to the lower density PEG coating and from LYS but not FN on the higher density PEG coating. Negative ion spectra contained relatively more intense protein fragment ion signals for the lower density PEG coating...

  10. Endoscopic add-on stiffness probe for real-time soft surface characterisation in MIS.

    Science.gov (United States)

    Faragasso, A; Stilli, A; Bimbo, J; Noh, Y; Liu, H; Nanayakkara, T; Dasgupta, P; Wurdemann, H A; Althoefer, K

    2014-01-01

    This paper explores a novel stiffness sensor which is mounted on the tip of a laparoscopic camera. The proposed device is able to compute stiffness when interacting with soft surfaces. The sensor can be used in Minimally Invasive Surgery, for instance, to localise tumor tissue which commonly has a higher stiffness when compared to healthy tissue. The purely mechanical sensor structure utilizes the functionality of an endoscopic camera to the maximum by visually analyzing the behavior of trackers within the field of view. Two pairs of spheres (used as easily identifiable features in the camera images) are connected to two springs with known but different spring constants. Four individual indenters attached to the spheres are used to palpate the surface. During palpation, the spheres move linearly towards the objective lens (i.e. the distance between lens and spheres is changing) resulting in variations of their diameters in the camera images. Relating the measured diameters to the different spring constants, a developed mathematical model is able to determine the surface stiffness in real-time. Tests were performed using a surgical endoscope to palpate silicon phantoms presenting different stiffness. Results show that the accuracy of the sensing system developed increases with the softness of the examined tissue.

  11. Electronic excited states as a probe of surface adsorbate structure and dynamics in liquid xenon

    Energy Technology Data Exchange (ETDEWEB)

    Peterson, E.S.

    1992-08-01

    A combination of second harmonic generation (SHG) and a simple dipole-dipole interaction model is presented as a new technique for determining adsorbate geometries on surfaces. The polarization dependence of SHG is used to define possible geometries of the adsorbate about the surface normal. Absorption band shifts using geometry constraints imposed by SHG data are derived for a dimer constructed from two arbitrarily placed monomers on the surface using the dipole-dipole interaction potential. These formulae can be used to determine the orientation of the two monomers relative to each other. A simplified version of this formalism is used to interpret absorption band shifts for rhodamine B adsorbed on fused silica. A brief history of the exciton is given with particular detail to Xe. Data are presented for transient absorption at RT in liquid xenon on the picosecond time scale. These are observations of both tunneling through the barrier that separates the free and trapped exciton states and the subsequent trapping of the exciton. In high densities both of these processes are found to occur within 2 to 6 picoseconds in agreement with theories of Kmiecik and Schreiber and of Martin. A threshold density is observed that separates relaxation via single binary collisions and relaxation that proceeds via Martin's resonant energy transfer hopping mechanism.

  12. Electronic excited states as a probe of surface adsorbate structure and dynamics in liquid xenon

    Energy Technology Data Exchange (ETDEWEB)

    Peterson, Eric Scott [Univ. of California, Berkeley, CA (United States)

    1992-08-01

    A combination of second harmonic generation (SHG) and a simple dipole-dipole interaction model is presented as a new technique for determining adsorbate geometries on surfaces. The polarization dependence of SHG is used to define possible geometries of the adsorbate about the surface normal. Absorption band shifts using geometry constraints imposed by SHG data are derived for a dimer constructed from two arbitrarily placed monomers on the surface using the dipole-dipole interaction potential. These formulae can be used to determine the orientation of the two monomers relative to each other. A simplified version of this formalism is used to interpret absorption band shifts for rhodamine B adsorbed on fused silica. A brief history of the exciton is given with particular detail to Xe. Data are presented for transient absorption at RT in liquid xenon on the picosecond time scale. These are observations of both tunneling through the barrier that separates the free and trapped exciton states and the subsequent trapping of the exciton. In high densities both of these processes are found to occur within 2 to 6 picoseconds in agreement with theories of Kmiecik and Schreiber and of Martin. A threshold density is observed that separates relaxation via single binary collisions and relaxation that proceeds via Martin`s resonant energy transfer hopping mechanism.

  13. Temperature-dependent electronic decay profiles in CZT: probe of bulk and surface properties

    Science.gov (United States)

    Kessick, Royal; Maupin, Hugh; Tepper, Gary C.; Szeles, Csaba

    2003-01-01

    The electronic performance of CZT-based gamma radiation spectrometers is governed by a synergism of bulk and surface properties. Compensation is used to increase the bulk resistivity of Cd1-xZnxTe (x~0.1), but the same electronic states that are introduced to increase the material resistivity can also trap charge and reduce the carrier lifetime. Electrical and mechanical surface defects introduced during or subsequent to crystal harvesting are also known to interfere with device performance. Using a contactless, pulsed laser microwave cavity perturbation technique, electronic decay profiles were studied in high pressure Bridgman CZT as a function of temperature. The electronic decay profile was found to depend very strongly on temperature and was modeled using a function consisting of two exponential terms with temperature-dependent amplitudes and time constants. The model was used to relate the observed temperature dependent decay kinetics in CZT to specific trap energies. It was found that, at low temperatures, the electronic decay process is dominated by a deep trap with an energy of approximately 0.69 +/- 0.1 eV from the band edge. As the temperature is increased, the charge trapping becomes dominated by a second trap with an energy of approximately 0.60 +/- 0.1 eV from the band edge. Surface damage introduces additional charge traps that significantly alter the decay kinetics particularly at low temperatures.

  14. Investigations of the Reconstructed Gold Surface with Electrochemical Scanning Probe Microscopy.

    Science.gov (United States)

    Oden, Patrick Ian

    1993-03-01

    Scanning Tunneling and Atomic Force Microscopies (STM, AFM) have been used in conjunction with an electrochemical potentiostat for studying the properties of the reconstructed phase of the Au(111) surface in dilute solutions of perchloric acid (50mM) as well as comparing the STM and AFM results for the underpotential deposition (UPD) of lead on Au(111). With the STM, a variation of the out-of-plane corrugation amplitude of the reconstructed phase has been observed as a function of electrochemical potential (from -100mV to +400mV vs. a silver quasi-reference electrode). The variation in amplitude appears to be insensitive to both the sign and magnitude of the tunneling tip bias (in the range of -100mV to +100mV). From the slope of the corrugation amplitude versus electrochemical potential, an STM-tip induced modification of the corrugation amplitude of the (23 x surd3) surface near the phase transition to a (1 x 1) surface is believed to occur. For UPD of lead studies, both the STM and AFM showed similar coverages of lead as a function of electrochemical potential, but a slight variation in the two techniques results was observed at the denuted zone boundaries.

  15. Probing Water and CO2 Interactions at the Surface of Collapsed Titania Nanotubes Using IR Spectroscopy

    Directory of Open Access Journals (Sweden)

    Kaustava Bhattacharyya

    2015-08-01

    Full Text Available Collapsed titania nanotubes (cTiNT were synthesized by the calcination of titania nanotubes (TiNT at 650 °C, which leads to a collapse of their tubular morphology, a substantial reduction in surface area, and a partial transformation of anatase to the rutile phase. There are no significant changes in the position of the XPS responses for Ti and O on oxidation or reduction of the cTiNTs, but the responses are more symmetric than those observed for TiNTs, indicating fewer surface defects and no change in the oxidation state of titanium on oxidative and/or reductive pretreatment. The interaction of H2O and CO2 with the cTiNT surface was studied. The region corresponding to OH stretching absorptions extends below 3000 cm−1, and thus is broader than is typically observed for absorptions of the OH stretches of water. The exchange of protons for deuterons on exposure to D2O leads to a depletion of this extended absorption and the appearance of new absorptions, which are compatible with deuterium exchange. We discuss the source of this extended low frequency OH stretching region and conclude that it is likely due to the hydrogen-bonded OH stretches. Interaction of the reduced cTiNTs with CO2 leads to a similar but smaller set of adsorbed carbonates and bicarbonates as reported for reduced TiNTs before collapse. Implications of these observations and the presence of proton sources leading to hydrogen bonding are discussed relative to potential chemical and photochemical activity of the TiNTs. These results point to the critical influence of defect structure on CO2 photoconversion.

  16. Quantitative Caffeine Analysis Using a Surface Sampling Probe Electrospray Ionization Tandem Mass Spectrometry System

    Energy Technology Data Exchange (ETDEWEB)

    Ford, Michael J [ORNL; Deibel, Michael A. [Earlham College; Tomkins, Bruce A [ORNL; Van Berkel, Gary J [ORNL

    2005-01-01

    Quantitative determination of caffeine on reversed-phase C8 thin-layer chromatography plates using a surface sampling electrospray ionization system with tandem mass spectrometry detection is reported. The thin-layer chromatography/electrospray tandem mass spectrometry method employed a deuterium-labeled caffeine internal standard and selected reaction monitoring detection. Up to nine parallel caffeine bands on a single plate were sampled in a single surface scanning experiment requiring 35 min at a surface scan rate of 44 {mu}m/s. A reversed-phase HPLC/UV caffeine assay was developed in parallel to assess the mass spectrometry method performance. Limits of detection for the HPLC/UV and thin-layer chromatography/electrospray tandem mass spectrometry methods determined from the calibration curve statistics were 0.20 ng injected (0.50 {mu}L) and 1.0 ng spotted on the plate, respectively. Spike recoveries with standards and real samples ranged between 97 and 106% for both methods. The caffeine content of three diet soft drinks (Diet Coke, Diet Cherry Coke, Diet Pepsi) and three diet sport drinks (Diet Turbo Tea, Speed Stack Grape, Speed Stack Fruit Punch) was measured. The HPLC/UV and mass spectrometry determinations were in general agreement, and these values were consistent with the quoted values for two of the three diet colas. In the case of Diet Cherry Coke and the diet sports drinks, the determined caffeine amounts using both methods were consistently higher (by 8% or more) than the literature values.

  17. Reversal of atomic contrast in scanning probe microscopy on (111) metal surfaces

    Czech Academy of Sciences Publication Activity Database

    Ondráček, Martin; González, C.; Jelínek, Pavel

    2012-01-01

    Roč. 24, 08 (2012), 084003/1-084003/7 ISSN 0953-8984 R&D Projects: GA ČR(CZ) GPP204/11/P578; GA ČR GAP204/10/0952; GA ČR GA202/09/0545; GA MŠk(CZ) ME10076 Grant - others:AVČR(CZ) M100100904 Institutional research plan: CEZ:AV0Z10100521 Keywords : atomic force microscopy * metallic surfaces * atomic contrast * scanning tunneling microscopy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.355, year: 2012 http://iopscience.iop.org/0953-8984/24/8/084003

  18. Comparative surface electrochemistry of Co and Co3O4 nanoparticles: nitrite as an analytical probe

    CSIR Research Space (South Africa)

    Adekunle, AS

    2010-12-01

    Full Text Available color fixative and preservation in meats, manufacturing diazo dyes, in the textile industry, photography, manufacture of rubber chemicals, fertilizers in agriculture [18] and medicinal agents (used as a vasodilator [19]. It can be formed as a result... and then to a mirror finish on a Buehler felt pad. The electrode was then subjected to ultrasonic vibration in absolute ethanol to remove residual alumina particles that might have been trapped at the surface. EPPGE was modified by drop-dry method. Different...

  19. Probing cytochrome c in living mitochondria with surface-enhanced Raman spectroscopy

    DEFF Research Database (Denmark)

    Brazhe, Nadezda A.; Evlyukhin, Andrey B.; Goodilin, Eugene A.

    2015-01-01

    due to the lack of non-invasive techniques. Here we suggest a novel label-free approach based on the surface-enhanced Raman spectroscopy (SERS) to monitor the redox state and conformation of cytochrome c in the electron transport chain in living mitochondria. We demonstrate that SERS spectra of living...... mitochondria placed on hierarchically structured silver-ring substrates provide exclusive information about cytochrome c behavior under modulation of inner mitochondrial membrane potential, proton gradient and the activity of ATP-synthetase. Mathematical simulation explains the observed enhancement of Raman...

  20. sp Carbon chain interaction with silver nanoparticles probed by Surface Enhanced Raman Scattering

    Science.gov (United States)

    Lucotti, A.; Casari, C. S.; Tommasini, M.; Li Bassi, A.; Fazzi, D.; Russo, V.; Del Zoppo, M.; Castiglioni, C.; Cataldo, F.; Bottani, C. E.; Zerbi, G.

    2009-08-01

    Surface Enhanced Raman Spectroscopy (SERS) is exploited here to investigate the interaction of isolated sp carbon chains (polyynes) in a methanol solution with silver nanoparticles. Hydrogen-terminated polyynes show a strong interaction with silver colloids used as the SERS active medium revealing a chemical SERS effect. SERS spectra after mixing polyynes with silver colloids show a noticeable time evolution. Experimental results, supported by density functional theory (DFT) calculations of the Raman modes, allow us to investigate the behavior and stability of polyynes of different lengths and the overall sp conversion towards sp 2 phase.

  1. Application and outlook of the pulsed neutron beam at J-PARC (3). Introduction of high-pressure science and surface/interface analysis at J-PARC

    International Nuclear Information System (INIS)

    Hattori, Takanori; Akutsu, Kazuhiro; Suzuki, Junichi

    2015-01-01

    At the MLF (Materials and Life Science Experimental Facility) of J-PARC (Japan Proton Accelerator Research Complex), eighteen neutron beam lines equipped with experimental apparatus are in operation and deliver the world highest intensity pulsed neutron beam for fundamental sciences such as solid state physics, materials science, life science, elementary particle physics, nuclear science, and for industrial applications. We introduce studies using an ultra-high pressure neutron diffractometer 'PLANET' for the structure analysis under high-pressure surroundings and a polarized neutron reflectometer 'SHARAKU' for the analysis of surface/interface structure with scales ranging from nano- to submicron-meter. We also introduce briefly all the apparatus for neuron experiments at the MLF. (J.P.N.)

  2. Controlled-Resonant Surface Tapping-Mode Scanning Probe Electrospray Ionization Mass Spectrometry Imaging

    Energy Technology Data Exchange (ETDEWEB)

    Lorenz, Matthias [ORNL; Ovchinnikova, Olga S [ORNL; Kertesz, Vilmos [ORNL; Van Berkel, Gary J [ORNL

    2014-01-01

    This paper reports on the advancement of a controlled-resonance surface tapping-mode single capillary liquid junction extraction/ESI emitter for mass spectrometry imaging. The basic instrumental setup and the general operation of the system were discussed and optimized performance metrics were presented. The ability to spot sample, lane scan and chemically image in an automated and controlled fashion were demonstrated. Rapid, automated spot sampling was demonstrated for a variety of compound types including the cationic dye basic blue 7, the oligosaccharide cellopentaose, and the protein equine heart cytochrome c. The system was used for lane scanning and chemical imaging of the cationic dye crystal violet in inked lines on glass and for lipid distributions in mouse brain thin tissue sections. Imaging of the lipids in mouse brain tissue under optimized conditions provided a spatial resolution of approximately 35 m based on the ability to distinguish between features observed both in the optical and mass spectral chemical images. The sampling spatial resolution of this system was comparable to the best resolution that has been reported for other types of atmospheric pressure liquid extraction-based surface sampling/ionization techniques used for mass spectrometry imaging.

  3. Optical properties of single semiconductor nanowires and nanowire ensembles. Probing surface physics by photoluminescence spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Pfueller, Carsten

    2011-06-27

    This thesis presents a detailed investigation of the optical properties of semiconductor nanowires (NWs) in general and single GaN NWs and GaN NW ensembles in particular by photoluminescence (PL) spectroscopy. NWs are often considered as potential building blocks for future nanometer-scaled devices. This vision is based on several attractive features that are generally ascribed to NWs. For instance, they are expected to grow virtually free of strain and defects even on substrates with a large structural mismatch. In the first part of the thesis, some of these expectations are examined using semiconductor NWs of different materials. On the basis of the temperature-dependent PL of Au- and selfassisted GaAs/(Al,Ga)As core-shell NWs, the influence of foreign catalyst particles on the optical properties of NWs is investigated. For the Au-assisted NWs, we find a thermally activated, nonradiative recombination channel, possibly related to Auatoms incorporated from the catalyst. These results indicate the limited suitability of catalyst-assisted NWs for optoelectronic applications. The effect of the substrate choice is studied by comparing the PL of ZnO NWs grown on Si, Al{sub 2}O{sub 3}, and ZnO substrates. Their virtually identical optical characteristics indicate that the synthesis of NWs may indeed overcome the constraints that limit the heteroepitaxial deposition of thin films. The major part of this thesis discusses the optical properties of GaN NWs grown on Si substrates. The investigation of the PL of single GaN NWs and GaN NW ensembles reveals the significance of their large surface-to-volume ratio. Differences in the recombination behavior of GaNNW ensembles and GaN layers are observed. First, the large surface-to-volume ratio is discussed to be responsible for the different recombination mechanisms apparent in NWs. Second, certain optical features are only found in the PL of GaN NWs, but not in that of GaN layers. An unexpected broadening of the donor

  4. Cold-neutron depth profiling as a research tool for the study of surface oxides on metals

    International Nuclear Information System (INIS)

    Tun, Z.; Bohdanowicz, T.

    2009-01-01

    Full text: The shiny surface of most metals, with the exceptions of gold and platinum, is actually coated with a thin layer of oxide. Although typically only a few nanometres (nm) thick, the oxide layer is key for the metal's survival in our 02-containing atmosphere. Consequently, there is a continuing need to develop experimental techniques to study oxide layers on metals. The need for a technique that could track the movement of an oxygen-containing layer first came to our attention when we studied the growth of anodic oxide on Ti with neutron reflectometry. As new oxide grew with oxygen ions derived from an aqueous solution, a small amount of hydrogen was found to be incorporated into the oxide layer, and remained adjacent to the oxide/water interface. Whether the H remains attached to its companion 0, i.e., as an OH ion, or if the ion dissociates once inside the oxide layer is unknown. Whether the original air-grown oxide acts as a passive screen during anodization, or if it plays an active in the hopping of ions from site to site is also unknown. These questions could be answered unambiguously only if we can somehow label the original 0 atoms. Isotopic labeling combined with neutron scattering is not an option since the coherent scattering lengths of all three 0 isotopes are very similar. Fortunately, one of the isotopes, 170, is sensitive to neutron depth-profiling via the (n,a) reaction (1). We hereby report encouraging results obtained by a preliminary experiment carried out to assess the potential of this technique.

  5. Experimental study of angular neutron flux spectra on a slab surface to assess nuclear data and calculational methods for a fusion reactor design

    International Nuclear Information System (INIS)

    Oyama, Yukio

    1988-06-01

    This paper presents an experimental approach to interpret the results of integral experiments for fusion neutronics research. The measurement is described of the angular neutron flux on a restricted area of slab assemblies with D-T neutron bombardment by using the time-of-flight (TOF) method with an NE213 neutron detector over an energy range from 0.05 to 15 MeV. A two bias scheme was developed to obtain an accurate detection efficiency over a wide energy range. The detector-collimator response function was introduced to define the restricted surface area and to determine the effective measured area. A series of measurements of the angular neutron flux on slabs of fusion blanket materials, i.e., Be, C, and Li 2 O, as functions of neutron leaking angle and slab thickness have been performed to examine neutron transport characteristics in bulk materials. The calculational analyses of the experimental results have been also carried out by using Monte Carlo neutron transport codes, i.e., MORSE-DD and MCNP. The existing nuclear data files, i.e., JENDL-3PR1, -3PR2, ENDF/B-IV and -V were tested by comparing with the experimental results. From the comparisons, the data on C and 7 Li in the present files are fairly sufficient. Those on beryllium, however, is insufficient for the estimation of high threshold reactions such as tritium production in a fusion reactor blanket design. It is also found that the total and elastic cross sections are more important for accurate predictions of neutronic parameters at deep position. The comparisons between the measured and calculated results provide information to understand the results of the previous integral experiments for confirmation of accuracy of fusion reactor designs. (author)

  6. Characterization of ion-irradiation-induced nanodot structures on InP surfaces by atom probe tomography.

    Science.gov (United States)

    Gnaser, Hubert; Radny, Tobias

    2015-12-01

    Surfaces of InP were bombarded by 1.9 keV Ar(+) ions under normal incidence. The total accumulated ion fluence the samples were exposed to was varied from 1 × 10(17) cm(-2) to 3 × 10(18)cm(-2) and ion flux densities f of (0.4-2) × 10(14) cm(-2) s(-1) were used. Nanodot structures were found to evolve on the surface from these ion irradiations, their dimensions however, depend on the specific bombardment conditions. The resulting surface morphology was examined by atomic force microscopy (AFM). As a function of ion fluence, the mean radius, height, and spacing of the dots can be fitted by power-law dependences. In order to determine possible local compositional changes in these nanostructures induced by ion impact, selected samples were prepared for atom probe tomography (APT). The results indicate that by APT the composition of individual InP nanodots evolving under ion bombardment could be examined with atomic spatial resolution. At the InP surface, the values of the In/P concentration ratio are distinctly higher over a distance of ~1 nm and amount to 1.3-1.8. However, several aspects critical for the analyses were identified: (i) because of the small dimensions of these nanostructures a successful tip preparation proved very challenging. (ii) The elemental compositions obtained from APT were found to be influenced pronouncedly by the laser pulse energy; typically, low energies result in the correct stoichiometry whereas high ones lead to an inhomogeneous evaporation from the tips and deviations from the nominal composition. (iii) Depending again on the laser energy, a prolific emission of Pn cluster ions was observed, with n ≤ 11. Copyright © 2015. Published by Elsevier B.V.

  7. Immobilization of oligonucleotide probes on silicon surfaces using biotin–streptavidin system examined with microscopic and spectroscopic techniques

    Energy Technology Data Exchange (ETDEWEB)

    Awsiuk, K., E-mail: kamil.awsiuk@uj.edu.pl [M. Smoluchowski Institute of Physics, Jagiellonian University, Reymonta 4, Kraków 30-059 (Poland); Rysz, J. [M. Smoluchowski Institute of Physics, Jagiellonian University, Reymonta 4, Kraków 30-059 (Poland); Petrou, P. [Institute of Nuclear and Radiological Sciences and Technology, Energy and Safety, NCSR “Demokritos”, End Patriarchou Gregoriou Str., Aghia Paraskevi 15310 (Greece); Budkowski, A. [M. Smoluchowski Institute of Physics, Jagiellonian University, Reymonta 4, Kraków 30-059 (Poland); Bernasik, A. [Faculty of Physics and Applied Computer Science, AGH-University of Science and Technology, Al. Mickiewicza 30, Kraków 30-059 (Poland); Kakabakos, S. [Institute of Nuclear and Radiological Sciences and Technology, Energy and Safety, NCSR “Demokritos”, End Patriarchou Gregoriou Str., Aghia Paraskevi 15310 (Greece); Marzec, M.M. [Faculty of Physics and Applied Computer Science, AGH-University of Science and Technology, Al. Mickiewicza 30, Kraków 30-059 (Poland); Raptis, I. [Institute for Advanced Materials, Physicochemical Processes, Nanotechnology and Microsystems, NCSR “Demokritos”, End Patriarchou Gregoriou Str., Aghia Paraskevi 15310 (Greece)

    2014-01-30

    To immobilize effectively oligonucleotide probes on SiO{sub 2} modified with (3-aminopropyl)triethoxysilane, four procedures based on streptavidin–biotin system are compared with Atomic Force Microscopy, Angle-Resolved X-ray Photoelectron Spectroscopy and Time-of-Flight Secondary Ion Mass Spectrometry. The first approach involves: adsorption of biotinylated Bovine Serum Albumin, blocking free surface sites with BSA, binding of streptavidin and biotinylated oligonucleotide (b-oligo). Final steps are exchanged in the second procedure with immobilization of preformed streptavidin–b-oligo conjugate. The third approach consists of streptavidin adsorption, blocking with BSA and b-oligo binding. Finally, streptavidin–b-oligo conjugate is immobilized directly within the fourth method. Surface coverage with biomolecules, determined from ARXPS, accords with average AFM height, and is anti-correlated with the intensity of Si+ ions. Higher biomolecular coverage was achieved during the last steps of the first (2.45(±0.38) mg/m{sup 2}) and second (1.31(±0.22) mg/m{sup 2}) approach, as compared to lower surface density resulting from the third (0.58(±0.20) mg/m{sup 2}) and fourth (0.41(±0.11) mg/m{sup 2}) method. Phosphorus atomic concentration indicates effectiveness of oligonucleotide immobilization. Secondary ions intensities, characteristic for oligonucleotides, streptavidin, BSA, and proteins, allow additional insight into overlayer composition. These measurements verify the ARXPS results and show the superiority of the first two immobilization approaches in terms of streptavidin and oligonucleotide density achieved onto the surface.

  8. Structural and magnetic properties probed using neutron diffraction technique in Ni50-xCoxMn38Sb12 (x=0 and 5) Heusler system

    Science.gov (United States)

    Sahoo, Roshnee; Suresh, K. G.; Das, A.

    2014-12-01

    Magnetization and neutron diffraction studies have been carried out in Ni50-xCoxMn38Sb12 (x=0 and 5) to investigate the effect of Co on the structural and magnetic properties. A comparison of the neutron diffraction data of Ni45Co5Mn38Sb12 and Ni50Mn38Sb12 alloys shows that Co substitution leads to an increase in the Mn moments. Considerably large magnetization difference associate with martensitic transition has also been observed on Co substitution. The analysis of the neutron diffraction data has revealed that the martensitic transition is accompanied by about 70% decrease in the moment and about 0.3% decrease in the cell volume. Enhanced magneto-structural coupling resulting from the Co doping has been evidenced by the magnetization as well as the neutron data. The variations in the individual site moments on Co substitution and their temperature dependencies account for the observed bulk magnetization data.

  9. Junction formation of Cu3BiS3 investigated by Kelvin probe force microscopy and surface photovoltage measurements

    Science.gov (United States)

    Mesa, Fredy; Chamorro, William; Vallejo, William; Baier, Robert; Dittrich, Thomas; Grimm, Alexander; Lux-Steiner, Martha C

    2012-01-01

    Summary Recently, the compound semiconductor Cu3BiS3 has been demonstrated to have a band gap of ~1.4 eV, well suited for photovoltaic energy harvesting. The preparation of polycrystalline thin films was successfully realized and now the junction formation to the n-type window needs to be developed. We present an investigation of the Cu3BiS3 absorber layer and the junction formation with CdS, ZnS and In2S3 buffer layers. Kelvin probe force microscopy shows the granular structure of the buffer layers with small grains of 20–100 nm, and a considerably smaller work-function distribution for In2S3 compared to that of CdS and ZnS. For In2S3 and CdS buffer layers the KPFM experiments indicate negatively charged Cu3BiS3 grain boundaries resulting from the deposition of the buffer layer. Macroscopic measurements of the surface photovoltage at variable excitation wavelength indicate the influence of defect states below the band gap on charge separation and a surface-defect passivation by the In2S3 buffer layer. Our findings indicate that Cu3BiS3 may become an interesting absorber material for thin-film solar cells; however, for photovoltaic application the band bending at the charge-selective contact has to be increased. PMID:22497001

  10. Probing the interactions of organic molecules, nanomaterials, and microbes with solid surfaces using quartz crystal microbalances: methodology, advantages, and limitations.

    Science.gov (United States)

    Huang, Rixiang; Yi, Peng; Tang, Yuanzhi

    2017-06-21

    Quartz crystal microbalances (QCMs) provide a new analytical opportunity and prospect to characterize many environmental processes at solid/liquid interfaces, thanks to their almost real-time measurement of physicochemical changes on their quartz sensor. This work reviews the applications of QCMs in probing the interactions of organic molecules, nanomaterials (NMs) and microbes with solid surfaces. These interfacial interactions are relevant to critical environmental processes such as biofilm formation, fate and transport of NMs, fouling in engineering systems and antifouling practices. The high sensitivity, real-time monitoring, and simultaneous frequency and dissipation measurements make QCM-D a unique technique that helps reveal the interaction mechanisms for the abovementioned processes (e.g., driving forces, affinity, kinetics, and the interplay between surface chemistry and solution chemistry). On the other hand, QCM measurement is nonselective and spatially-dependent. Thus, caution should be taken during data analysis and interpretation, and it is necessary to cross-validate the results using complementary information from other techniques for more quantitative and accurate interpretation. This review summarizes the general methodologies for collecting and analyzing raw QCM data, as well as for evaluating the associated uncertainties. It serves to help researchers gain deeper insights into the fundamentals and applications of QCMs, and provides new perspectives on future research directions.

  11. Scanning compound surfaces with no existing CAD model by using laser probe of a coordinate measuring machine

    Science.gov (United States)

    Che, Chenggang

    1992-09-01

    In recent years, the manufacturing of parts with compound surfaces relies more and more on computer integrated manufacturing (CIM) because of the ever increasing complexity of surface features. For a standard CIM cycle, it starts from a computer aided design (CAD) model which was designed previously be experienced mechanical drafters. The CAD model is then interpreted as numerical controlled (NC) machining codes according to which the part is finally manufactured, this is usually referred to as the normal manufacturing process in Figure 1. However, in many cases, a CAD model of a part is not always readily available to begin the CIM cycle. For instance, in automobile industry, the development of new car models takes a long time from concept to model because of the tedious manual digitization process. Also, in some other cases, the mechanical design of a product may need frequent modification, such as ship hulls, aeroplane fuselages, wings and turbine blades, etc. This was traditionally done by copymilling of a master model. In a computer aided manufacturing (CAM) environment, a mathematical model or representation of a part is required to begin a CIM cycle. The automation of the whole manufacturing system requires a rapid part modeling tool. Fortunately, this becomes possible with the advent of recent development in optical sensing devices and many non-contact sensing techniques. Before a part model is established, surface digitization should first be implemented so that enough measurement points can be fitted later, and this is the most important step of the reverse engineering process as in Figure 1. And also, it is obvious that the efficiency and accuracy of the surface modeling relies heavily on the efficiency and accuracy of the surface digitization. The present paper aims at achieving surface digitization accurately and rapidly with a coordinate measurement machine (CMM) and an inexpensive laser range-finding probe. By making full use of the control system of

  12. Optical luminescence spectroscopy as a probe of the surface mineralogy of Mars

    Science.gov (United States)

    Treiman, A. H.

    1992-01-01

    Optical luminescence (OpL) spectroscopy is an attractive use of a visible-near-IR spectrometer on a Mars lander because mineral products of atmosphere-surface interactions on Mars will probably have characteristic OpL spectra. Optical luminescence spectra would be taken at night, when a spectrometer might otherwise sit idle. Also needed would be a source of exciting radiation, which could be shared with other experiments. Optical luminescence is emission of nonthermal optical photons (near-UV through near-IR) as a response to energy input. On absorption of energy, an atom (or ion) will enter an excited state. The favored decay of many such excited states involving valence-band electrons is emission of an optical photon. Optical luminescence spectra can be useful in determining mineralogy and mineral composition. Optical luminescence in crystals can arise from essential elements (or ions), trace-element substituents (activators), or defects. Common activators in salts of alkali and alkaline earth elements include Mn(2+)(VI), other transition metals, the rare earths, and the actinides. Trace substituents of other species can enhance or quench OpL (e.g., Pb(2+) vs. Fe(3+)). Optical luminescence can also arise from defects in crystal structures, including those caused by radiation and shock.

  13. Cooling of Accretion-Heated Neutron Stars

    Science.gov (United States)

    Wijnands, Rudy; Degenaar, Nathalie; Page, Dany

    2017-09-01

    We present a brief, observational review about the study of the cooling behaviour of accretion-heated neutron stars and the inferences about the neutron-star crust and core that have been obtained from these studies. Accretion of matter during outbursts can heat the crust out of thermal equilibrium with the core and after the accretion episodes are over, the crust will cool down until crust-core equilibrium is restored. We discuss the observed properties of the crust cooling sources and what has been learned about the physics of neutron-star crusts. We also briefly discuss those systems that have been observed long after their outbursts were over, i.e, during times when the crust and core are expected to be in thermal equilibrium. The surface temperature is then a direct probe for the core temperature. By comparing the expected temperatures based on estimates of the accretion history of the targets with the observed ones, the physics of neutron-star cores can be investigated. Finally, we discuss similar studies performed for strongly magnetized neutron stars in which the magnetic field might play an important role in the heating and cooling of the neutron stars.

  14. Direct observation of the near-surface layer in Pb(Mg1/3Nb2/3)O3 using neutron diffraction

    International Nuclear Information System (INIS)

    Conlon, K.H.; Whan, T.; Fox, J.H.; Luo, H.; Viehland, D.; Li, J.F.; Stock, C.; Shirane, G.

    2004-01-01

    Spatially resolved neutron diffraction as a function of crystal depth in Pb(Mg 1/3 Nb 2/3 )O 3 reveals the presence of a distinct near-surface region where a strong distortion in the lattice exists. A dramatic change in both the lattice constant and the Bragg peak intensity as a function of crystal depth is observed to occur in this region over a length scale ∼100 μm. This confirms a previous assertion, based on a comparison between high-energy x rays and neutrons, that such a near surface region exists in the relaxors. Consequences to both single crystal and powder diffraction measurements and previous bulk neutron diffraction measurements on large single crystals are discussed

  15. The use of a laser-assisted Local Electrode Atom Probe and TEM to examine the microstructure of Zircaloy and precipitate structure following low dose neutron irradiation at nominally 358 °C

    Science.gov (United States)

    Cockeram, B. V.; Leonard, K. J.; Snead, L. L.; Miller, M. K.

    2013-02-01

    Previous research has shown that the irradiation of Zircaloy at very low fluences (⩽7 × 1022 n/m2 (E > 1 MeV)) results in measurable irradiation hardening, but the defects or solute clusters responsible for such hardening are generally below the resolution limit of electron microscopy. Efforts to analyze Zr-based alloys using conventional atom probe have been largely unsuccessful due to the poor electrical conductivity of Zirconium at cryogenic temperatures. Laser-assisted atom probe methods were introduced in the 1980s as a means for enabling low electrical conductivity specimens to be analyzed. Some recent examples have been reported in the literature where a Local Electrode Atom Probe (LEAP)® was used to successfully analyze non-irradiated Zirconium based alloys, such as Zircaloy-4 and ZIRLO. In this work, the use of a LEAP to examine the microstructure of non-irradiated Zircaloy alloys is evaluated. Optimum conditions for applying the LEAP to non-irradiated Zircaloy-2 and Zircaloy-4 are investigated. Changes in the local composition of precipitates and grain boundaries following neutron irradiation at nominally 358 °C to a fluence of 2.9 × 1025 n/m2 in the High Flux Isotope Reactor (HFIR) are determined using Transmission Electron Microscopy. These results are provided as an example of the local changes in microstructure that can influence the evolution of the defect structure.

  16. Determination of cmc of imidazolium based surface active ionic liquids through probe-less UV-vis spectrophotometry.

    Science.gov (United States)

    Rather, Mudasir Ahmad; Rather, Ghulam Mohammad; Pandit, Sarwar Ahmad; Bhat, Sajad Ahmad; Bhat, Mohsin Ahmad

    2015-01-01

    In the first of its kind we herein report the results of our studies undertaken on the micellization behaviour of imidazolium based surface active ionic liquids (SAILs) to prove that their critical micelle concentration (cmc) can be estimated through ultraviolet-visible (UV-vis) spectroscopy without using any external probe. Tensiometric and spectrophotometric investigations of a series of freshly prepared SAILs viz. 1-octyl-3-methylimidazolium chloride ([OMIM][Cl]), 1-octyl-3-methylimidazolium dodecylsulphate ([OMIM][DS]), 1-octyl-3-methylimidazolium benzoate ([OMIM][Bz]), 1-octyl-3-methylimidazolium salicylate ([OMIM][Sc]), 1-octyl-3-methylimidazolium acetate ([OMIM][Ac]) are presented as a case study in support of the said claim. The cmcs estimated through spectrophotometric method were found to be close to the values estimated through tensiometry for the said SAILs. The cmcs for the investigated SAILS were found to vary in order of [OMIM][Cl]>[OMIM][Ac]>[OMIM][Bz]>[OMIM][Sc]>[OMIM][DS]. To the best of our knowledge the present communication will be the first report about the synthesis, characterization and micellization behaviour of [OMIM][Bz] and [OMIM][Sc]. Copyright © 2014 Elsevier B.V. All rights reserved.

  17. Chemically stable Au nanorods as probes for sensitive surface enhanced scattering (SERS) analysis of blue BIC ballpoint pens

    Science.gov (United States)

    Alyami, Abeer; Saviello, Daniela; McAuliffe, Micheal A. P.; Cucciniello, Raffaele; Mirabile, Antonio; Proto, Antonio; Lewis, Liam; Iacopino, Daniela

    2017-08-01

    Au nanorods were used as an alternative to commonly used Ag nanoparticles as Surface Enhanced Raman Scattering (SERS) probes for identification of dye composition of blue BIC ballpoint pens. When used in combination with Thin Layer Chromatography (TLC), Au nanorod colloids allowed identification of the major dye components of the BIC pen ink, otherwise not identifiable by normal Raman spectroscopy. Thanks to their enhanced chemical stability compared to Ag colloids, Au nanorods provided stable and reproducible SERS signals and allowed easy identification of phthalocyanine and triarylene dyes in the pen ink mixture. These findings were supported by FTIR and MALDI analyses, also performed on the pen ink. Furthermore, the self-assembly of Au nanorods into large area ordered superstructures allowed identification of BIC pen traces. SERS spectra of good intensity and high reproducibility were obtained using Au nanorod vertical arrays, due to the high density of hot spots and morphological reproducibility of these superstructures. These results open the way to the employment of SERS for fast screening analysis and for quantitative analysis of pens and faded pens which are relevant for the fields of forensic and art conservation sciences.

  18. Measurement of planetary surface composition by gamma-ray and neutron spectrometry - Preparatory studies for Mars and for the Moon by numerical simulations

    International Nuclear Information System (INIS)

    Gasnault, O.

    1999-01-01

    Gamma-ray and neutron spectrometry sets up a powerful tool of geological and geochemical characterization of planetary surfaces. This method allows to tackle some critical planet science questions: crustal and mantle compositions; ices; volcanism; alteration processes... Most of the neutrons and gamma photons result from the interactions of galactic cosmic rays with matter. The first chapter introduces the physics of these nuclear interactions in planetary soils and in detectors. Our work aims at optimizing the observations by specifying instrumental performances, and by highlighting relations between soil composition and neutron fluxes. Numerical simulations using the GEANT code from CERN support our analysis. The second chapter estimates the performances of the Germanium gamma-ray spectrometer for MARS SURVEYOR 2001. The result of simulations is compared to calibration measurements; then performances are calculated in flight configuration. The background at Mars is estimated to about 160 c/s. The instrument offers a fine sensitivity to: Fe, Mg, K, Si, Th, Cl and O. It will also be possible to measure U, Ti, H, C, S, Ca and Al. The emission lobes at the surface are calculated too. These measurements shall permit a better understanding of the Martian surface. The last chapter deals with fast neutrons [500 keV; 10 MeV] emitted by the Moon. The strong influence of oxygen is underlined. As observed by LUNAR PROSPECTOR, the integrated flux shows a pronounced dependence with regolith content in iron and titanium, allowing the mapping. The influence of the other chemical elements is quantified. A simple mathematical formula is suggested to estimate the integrated neutron flux according to soil composition. At last, a study of hydrogen effects on fast neutron flux is carried out; we examine the possibilities to quantify its abundance in the soil by this method. (author)

  19. Anisotropic excitation of surface plasmon polaritons on a metal film by a scattering-type scanning near-field microscope with a non-rotationally-symmetric probe tip

    Directory of Open Access Journals (Sweden)

    Walla Frederik

    2018-01-01

    Full Text Available We investigated the excitation of surface plasmon polaritons on gold films with the metallized probe tip of a scattering-type scanning near-field optical microscope (s-SNOM. The emission of the polaritons from the tip, illuminated by near-infrared laser radiation, was found to be anisotropic and not circularly symmetric as expected on the basis of literature data. We furthermore identified an additional excitation channel via light that was reflected off the tip and excited the plasmon polaritons at the edge of the metal film. Our results, while obtained for a non-rotationally-symmetric type of probe tip and thus specific for this situation, indicate that when an s-SNOM is employed for the investigation of plasmonic structures, the unintentional excitation of surface waves and anisotropic surface wave propagation must be considered in order to correctly interpret the signatures of plasmon polariton generation and propagation.

  20. Probing the semi-magicity of $^{68}$Ni via the $^{3}$H($^{66}$Ni,$^{68}$Ni)p two-neutron transfer reaction in inverse kinematics

    CERN Multimedia

    Reiter, P; Blazhev, A A; Kruecken, R; Franchoo, S; Mertzimekis, T; Darby, I G; Van de walle, J; Raabe, R; Elseviers, J; Gernhaeuser, R A; Sorlin, O H; Georgiev, G P; Bree, N C F; Habs, D; Chapman, R; Gaudefroy, L; Diriken, J V J; Jenkins, D G; Kroell, T; Axiotis, M; Huyse, M L; Patronis, N

    We propose to perform the two-neutron transfer reaction $^{3}$H($^{66}$Ni, $^{68}$Ni)$p$ using the ISOLDE radioactive ion beam at 2.7 $A$ MeV and the MINIBALL + T-REX setup to characterize the 0$^{+}$ and 2$^{+}$ states in $^{68}$Ni.

  1. Magnetic properties of UNi.sub. 2/3./sub. Rh.sub.13./sub. Al single crystal probed by polarized neutron diffraction

    Czech Academy of Sciences Publication Activity Database

    Prokeš, K.; Gukasov, A.; Sechovský, V.; Andreev, Alexander V.

    272-276, - (2004), e67-e69 ISSN 0304-8853 Institutional research plan: CEZ:AV0Z1010914 Keywords : magnetic structure determination * neutron diffraction * fied induced ferromagnetic order * UNi 2/3 Rh 1/3 Al * magnetic frustration Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.031, year: 2004

  2. Magnetic properties of LaCo.sub.12./sub. B.sub.6./sub. compound as probed by neutron diffraction and by magnetization study under high pressures

    Czech Academy of Sciences Publication Activity Database

    Diop, L.V.B.; Arnold, Zdeněk; Isnard, O.; Kamarád, Jiří

    2014-01-01

    Roč. 593, APR (2014), s. 163-168 ISSN 0925-8388 R&D Projects: GA ČR GA202/09/1027 Institutional support: RVO:68378271 Keywords : pressure effect * borides * magnetic properties * neutron diffraction Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.999, year: 2014

  3. Study of effect of aging on martensitic transformation and tribological properties of TiNi alloy using DSC, neutron diffraction, and micromechanical probing techniques

    Czech Academy of Sciences Publication Activity Database

    Li, DY.; Ma, X.; Mikula, Pavol; Vrána, Miroslav

    2002-01-01

    Roč. 18, č. 9 (2002), s. 995-1000 ISSN 0267-0836 R&D Projects: GA ČR GV202/97/K038 Institutional research plan: CEZ:AV0Z1048901 Keywords : phase transformation ,TiNi alloy * agingeffect * neutron diffraction Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.686, year: 2002

  4. Pulsed neutron uranium borehole logging with prompt fission neutrons

    International Nuclear Information System (INIS)

    Bivens, H.M.; Smith, G.W.; Jensen, D.H.

    1976-01-01

    The gross count natural gamma log normally used for uranium borehole logging is seriously affected by disequilibrium. Methods for the direct measurement of uranium, such as neutron logging, which are not affected by disequilibrium have been the object of considerable effort in recent years. This paper describes a logging system for uranium which uses a small accelerator to generate pulses of 14 MeV neutrons to detect and assay uranium by the measurement of prompt fission neutrons in the epithermal energy range. After an initial feasibility study, a prototype logging probe was built for field evaluation which began in January 1976. Physical and operational characteristics of the prototype probe, the neutron tube-transformer assembly, and the neutron tube are described. In logging operations, only the epithermal prompt fission neutrons detected between 250 microseconds to 2500 microseconds following the excitation neutron pulse are counted. Comparison of corrected neutron logs with the conventional gross count natural gamma logs and the chemical assays of cores from boreholes are shown. The results obtained with this neutron probe clearly demonstrate its advantages over the gross count natural gamma log, although at this time the accuracy of the neutron log assay is not satisfactory under some conditions. The necessary correction factors for various borehole and formation parameters are being determined and, when applied, should improve the assay accuracy

  5. Focused study of thermonuclear bursts on neutron stars

    DEFF Research Database (Denmark)

    Chenevez, Jérôme

    X-ray bursters are a class of Low Mass X-Ray Binaries where accreted material from a donor star undergoes rapid thermonuclear burning in the surface layers of a neutron star. The flux released can temporarily exceed the Eddington limit and drive the photosphere to large radii. Such photospheric...... detection would thus probe the nuclear burning as well as the gravitational redshift from the neutron star. Moreover, likely observations of atomic X-ray spectral components reflected from the inner accretion disk have been reported. The high spectral resolution capabilities of Simbol X may therefore make...

  6. Mobile Probing and Probes

    DEFF Research Database (Denmark)

    Duvaa, Uffe; Ørngreen, Rikke; Weinkouff, Anne-Gitte

    2012-01-01

    Mobile probing is a method, which has been developed for learning about digital work situations, as an approach to discover new grounds. The method can be used when there is a need to know more about users and their work with certain tasks, but where users at the same time are distributed (in time...... and space). Mobile probing was inspired by the cultural probe method, and was influenced by qualitative interview and inquiry approaches. The method has been used in two subsequent projects, involving school children (young adults at 15-17 years old) and employees (adults) in a consultancy company. Findings...... point to mobile probing being a flexible method for uncovering the unknowns, as a way of getting rich data to the analysis and design phases. On the other hand it is difficult to engage users to give in depth explanations, which seem easier in synchronous dialogs (whether online or face2face...

  7. Mobile Probing and Probes

    DEFF Research Database (Denmark)

    Duvaa, Uffe; Ørngreen, Rikke; Weinkouff Mathiasen, Anne-Gitte

    2013-01-01

    Mobile probing is a method, developed for learning about digital work situations, as an approach to discover new grounds. The method can be used when there is a need to know more about users and their work with certain tasks, but where users at the same time are distributed (in time and space......). Mobile probing was inspired by the cultural probe method, and was influenced by qualitative interview and inquiry approaches. The method has been used in two subsequent projects, involving school children (young adults at 15-17 years old) and employees (adults) in a consultancy company. Findings point...... to mobile probing being a flexible method for uncovering the unknowns, as a way of getting rich data to the analysis and design phases. On the other hand it is difficult to engage users to give in depth explanations, which seem easier in synchronous dialogs (whether online or face2face). The development...

  8. Monte Carlo simulations of the secondary neutron ambient and effective dose equivalent rates from surface to suborbital altitudes and low Earth orbit.

    Science.gov (United States)

    El-Jaby, Samy; Richardson, Richard B

    2015-07-01

    Occupational exposures from ionizing radiation are currently regulated for airline travel (Earth orbit (∼300-400 km). Aircrew typically receive between 1 and 6 mSv of occupational dose annually, while aboard the International Space Station, the area radiation dose equivalent measured over just 168 days was 106 mSv at solar minimum conditions. It is anticipated that space tourism vehicles will reach suborbital altitudes of approximately 100 km and, therefore, the annual occupational dose to flight crew during repeated transits is expected to fall somewhere between those observed for aircrew and astronauts. Unfortunately, measurements of the radiation environment at the high altitudes reached by suborbital vehicles are sparse, and modelling efforts have been similarly limited. In this paper, preliminary MCNPX radiation transport code simulations are developed of the secondary neutron flux profile in air from surface altitudes up to low Earth orbit at solar minimum conditions and excluding the effects of spacecraft shielding. These secondary neutrons are produced by galactic cosmic radiation interacting with Earth's atmosphere and are among the sources of radiation that can pose a health risk. Associated estimates of the operational neutron ambient dose equivalent, used for radiation protection purposes, and the neutron effective dose equivalent that is typically used for estimates of stochastic health risks, are provided in air. Simulations show that the neutron radiation dose rates received at suborbital altitudes are comparable to those experienced by aircrew flying at 7 to 14 km. We also show that the total neutron dose rate tails off beyond the Pfotzer maximum on ascension from surface up to low Earth orbit. Crown Copyright © 2015. Published by Elsevier Ltd. All rights reserved.

  9. Using neutron reflectometry and reflection geometry 'near-surface' SANS to investigate surfactant micelle organization at a solid-solution interface

    International Nuclear Information System (INIS)

    Hamilton, W.A.; Porcar, L.; Magid, L.J.

    2005-01-01

    We have used simultaneous neutron reflectometry (NR) and reflection geometry 'near-surface' small angle neutron scattering (NS-SANS) to investigate the ordering of cetyltrimethylammonium bromide (CTAB) micelles in aqueous (D2O) solution in the proximity of a quartz surface as a function of concentration and temperature. The NR measurements allow us to determine coherent micellar organization within a few thousand angstroms of the interface while NS-SANS allows simultaneous monitoring of 'bulk' states to the greater depth of grazing incidence penetration into the solution, typically 10-100μm. We illustrate the utility of this monitoring using the example of an apparent Poiseuille surface shear-induced change in micellar organization which is more probably the result of slight temperature increase

  10. Exploring the potential of the cosmic-ray neutron method to measure interception storage dynamics

    Science.gov (United States)

    Jakobi, Jannis; Bogena, Heye; Huisman, Johan Alexander; Diekkrüger, Bernd; Vereecken, Harry

    2017-04-01

    Cosmic-ray neutron soil moisture probes are an emerging technology that relies on the negative correlation between near-surface fast neutron counts and soil moisture content. Hydrogen atoms in the soil, which are mainly present as water, moderate the secondary neutrons on the way back to the surface. Any application of this method needs to consider the sensitivity of the neutron counts to additional sources of hydrogen (e.g. above- and below-ground biomass, humidity of the lower atmosphere, lattice water of the soil minerals, organic matter and water in the litter layer, intercepted water in the canopy, and soil organic matter). In this study, we analyzed the effects of canopy-intercepted water on the cosmic-ray neutron counts. For this, an arable field cropped with sugar beet was instrumented with several cosmic-ray neutron probes and a wireless sensor network with more than 140 in-situ soil moisture sensors. Additionally rainfall interception was estimated using a new approach coupling throughfall measurements and leaf wetness sensors. The derived interception storage was used to correct for interception effects on cosmic ray neutrons to enhance soil water content prediction. Furthermore, the potential for a simultaneous prediction of above- and below-ground biomass, soil moisture and interception was tested.

  11. Neutron and X-ray reflection from surface monolayers of a lipopolyoxazoline

    DEFF Research Database (Denmark)

    Wurlitzer, A.; Politsch, E.; Cevc, G.

    2000-01-01

    were investigated as a function of surface pressure. The data are consistent with a fraction of the polyoxazoline moieties in brush-like conformations coexisting with a smaller fraction that is closely associated with the interface. Across the phase transition that is detected in the isotherm...

  12. Neutron scattering—The key characterization tool for nanostructured magnetic materials

    International Nuclear Information System (INIS)

    Fitzsimmons, M.R.; Schuller, Ivan K.

    2014-01-01

    The novel properties of materials produced using nanoscale manufacturing processes often arise from interactions across interfaces between dissimilar materials. Thus, to characterize the structure and magnetism of nanoscale materials demands tools with interface specificity. Neutron scattering has long been known to provide unique and quantitative information about nuclear and magnetic structures of bulk materials. Moreover, the specialty techniques of polarized neutron reflectometry and small angle neutron scattering (SANS) with polarized neutron beams and polarization analysis, are ideally and often uniquely suited to studies of nanostructured magnetic materials. Since neutron scattering is a weakly interacting probe, it gives quantifiable and easily-interpreted information on properties of statistically representative quantities of bulk, thin film and interfacial materials. In addition, neutron scattering can provide information to complement that obtained with bulk probes (magnetization, Kerr effect) or surface measurements obtained with scanning probe microscopy or resonant soft x-ray scattering. The straightforward interpretation and the simultaneous availability of structural information, make neutron scattering the technique of choice for the structural and physical characterization of many novel materials, especially those with buried interfaces, ones allowing for isotopic substitutions to decorate buried interfaces, or cases where the magnetic response to an external stimulus can be measured. We describe recent applications of neutron scattering to important thin film materials systems and future opportunities. Unquestionably, neutron scattering has played a decisive role in the development and study of new emergent phenomena. We argue with the advent of new techniques in neutron scattering and sample environment, neutron scattering's role in such studies will become even more dominant. In particular, neutron scattering will clarify and distinguish

  13. Neutron scattering—The key characterization tool for nanostructured magnetic materials

    Energy Technology Data Exchange (ETDEWEB)

    Fitzsimmons, M.R., E-mail: fitz@lanl.gov [Los Alamos National Laboratory (United States); Schuller, Ivan K. [University of California, San Diego (United States)

    2014-01-15

    The novel properties of materials produced using nanoscale manufacturing processes often arise from interactions across interfaces between dissimilar materials. Thus, to characterize the structure and magnetism of nanoscale materials demands tools with interface specificity. Neutron scattering has long been known to provide unique and quantitative information about nuclear and magnetic structures of bulk materials. Moreover, the specialty techniques of polarized neutron reflectometry and small angle neutron scattering (SANS) with polarized neutron beams and polarization analysis, are ideally and often uniquely suited to studies of nanostructured magnetic materials. Since neutron scattering is a weakly interacting probe, it gives quantifiable and easily-interpreted information on properties of statistically representative quantities of bulk, thin film and interfacial materials. In addition, neutron scattering can provide information to complement that obtained with bulk probes (magnetization, Kerr effect) or surface measurements obtained with scanning probe microscopy or resonant soft x-ray scattering. The straightforward interpretation and the simultaneous availability of structural information, make neutron scattering the technique of choice for the structural and physical characterization of many novel materials, especially those with buried interfaces, ones allowing for isotopic substitutions to decorate buried interfaces, or cases where the magnetic response to an external stimulus can be measured. We describe recent applications of neutron scattering to important thin film materials systems and future opportunities. Unquestionably, neutron scattering has played a decisive role in the development and study of new emergent phenomena. We argue with the advent of new techniques in neutron scattering and sample environment, neutron scattering's role in such studies will become even more dominant. In particular, neutron scattering will clarify and distinguish

  14. Neutron and synchrotron probes in the development of Co-Re-based alloys for next generation gas turbines with an emphasis on the influence of boron additives

    Czech Academy of Sciences Publication Activity Database

    Mukherji, D.; Gilles, R.; Karge, L.; Strunz, Pavel; Beran, Přemysl; Eckerlebe, H.; Stark, A.; Szentmiklosi, L.; Macsik, Z.; Schumacher, G.; Zizak, I.; Hofmann, M.; Hoelzel, M.; Rösler, J.

    2014-01-01

    Roč. 47, č. 4 (2014), s. 1417-1430 ISSN 0021-8898 R&D Projects: GA ČR GB14-36566G EU Projects: European Commission(XE) 283883 - NMI3-II Institutional support: RVO:61389005 Keywords : high-temperature alloys * In-situ neutron * FRM-II Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.720, year: 2014

  15. Neutron scattering for materials science. Materials Research Society proceedings

    International Nuclear Information System (INIS)

    Shapiro, S.M.; Moss, S.C.; Jorgensen, J.D.

    1990-01-01

    Neutron Scattering is by now a well-established technique which has been used by condensed matter scientists to probe both the structure and the dynamical interactions in solids and liquids. The use of neutron scattering methods in materials science research has in turn increased dramatically in recent years. The symposium presented in this book was assembled to bring together scientists with a wide range of interest, including high-T c superconducting materials, phase transformations, neutron depth profiling, structure and dynamics of glasses and liquids, surfaces and interfaces, porous media, intercalation compounds and lower dimensional systems, structure and dynamics of polymers, residual stress analysis, ordering and phase separation in alloys, and magnetism in alloys and multilayers. The symposium included talks covering the latest advances in broad areas of interest such as Rietveld structure refinement, triple axis spectrometry, quasi elastic scattering and diffusion, small angle scattering and surface scattering

  16. Neutron scattering in liquids

    Energy Technology Data Exchange (ETDEWEB)

    Barocchi, F. [Florence Univ. (Italy). Ist. di Fisica

    1996-12-31

    Together with X-rays, thermal neutrons are the ideal probe to study the microscopic structure of condensed matter, however the precision attainable usually with neutrons for the measurement of atomic position correlation functions in liquids is, at least, one order of magnitude better than for X-rays. In order to measure properly the microscopic dynamics a wide range of momentum transfer with corresponding energy transfer must be available in the range of liquid state excitations. This again is only attainable, with good resolution, with neutrons. (author) 7 figs., 3 refs.

  17. Neutrons in soft matter

    CERN Document Server

    Imae, Toyoko; Furusaka, Michihiro; Torikai, Naoya

    2011-01-01

    Neutron and synchrotron facilities, which are beyond the scale of the laboratory, and supported on a national level in countries throughout the world.  These tools for probing micro- and nano-structure research and on fast dynamics research of atomic location in materials have been key in the development of new polymer-based materials. Different from several existing professional books on neutron science, this book focuses on theory, instrumentation, an applications. The book is divided into five parts: Part 1 describes the underlying theory of neutron scattering. Part 2 desc

  18. Preliminary estimations of color inhomogeneities on the Venus surface according to the data of TV survey by the 'Venera-13' and 'Venera-14' space probes

    International Nuclear Information System (INIS)

    Shkuratov, Yu.G.; Kreslavskij, M.A.; Bazilevskij, A.T.; AN SSSR, Moscow. Inst. Geokhimii i Analiticheskoj Khimii)

    1986-01-01

    Digital processing of images obtained by ''Venera-13'' and ''Venera-14'' space probes led to discovery of faint (≤10%) color differences of some areas of the observed surface. Maximum color differences (0.63 μm/0.53 μm) were observed in the right part of 14-1 panorama. Color anomaly is associated with the rock formations having slightly higher albedo than the surrounding. Possible causes of the discovered color differences are discused

  19. Pulsed neutron generator for logging

    International Nuclear Information System (INIS)

    Thibideau, F.D.

    1977-01-01

    A pulsed neutron generator for uranium logging is described. This generator is one component of a prototype uranium logging probe which is being developed by SLA to detect, and assay, uranium by borehole logging. The logging method is based on the measurement of epithermal neutrons resulting from the prompt fissioning of uranium from a pulsed source of 17.6 MeV neutrons. An objective of the prototype probe was that its diameter not exceed 2.75 inches, which would allow its use in conventional rotary drill holes of 4.75-inch diameter. This restriction limited the generator to a maximum 2.375-inch diameter. The performance requirements for the neutron generator specified that it operate with a nominal output of 5 x 10 6 neutrons/pulse at up to 100 pulses/second for a one-hour period. The development of a neutron generator meeting the preliminary design goals was completed and two prototype models were delivered to SLA. These two generators have been used by SLA to log a number of boreholes in field evaluation of the probe. The results of the field evaluations have led to the recommendation of several changes to improve the probe's operation. Some of these changes will require additional development effort on the neutron generator. It is expected that this work will be performed during 1977. The design and operation of the first prototype neutron generators is described

  20. Surface oxygen effects in 14 MeV neutron activation analysis of oxygen in metals

    International Nuclear Information System (INIS)

    Janczyszyn, J.; Sztwiertnia, K.; Tarczanowski, S.

    1976-01-01

    To examine possible ways of reduction of the signal originating from the sample surface, the etching before and after activation and/or nitrogen transport were applied. The efficiency of post activation etching was confirmed. This procedure removes quantity of oxygen equivalent to 45μg/g for aluminium and 6μg/g for copper samples. The nitrogen transport without etching removes as much as 4μg/g in case of copper, however it turned out to be inefficient for aluminium samples. (author)

  1. Development of neutron detector using sensor type surface barrier with (n,p) and (n,α) converters

    International Nuclear Information System (INIS)

    Madi Filho, Tufic

    1999-01-01

    A Si semiconductor detector, surface barrier type, with a slim film of a converter material capable to produce charged particles was used as a sensor of neutrons in an environment of a zero power reactor. Two types of converters were used to improve the detection efficiency: (1) the polyethylene, n(CH 2 ), which produces recoil protons from the (n,p) interaction and, (2) the 10 B which generates a particle from the (n,alpha) reaction. The optimal thickness of those converters was determined experimentally and specifically for the polyethylene a mathematical model R(ips) = ε p · N 0 ·(1-e -Σ·Χ ) ·e -μ ·Χ + ε n · N 0 · -Σ · Χ was used to fit to the experimental data. For the polyethylene converter the thickness was of 0.058 cm (62.64 mg.cm -2 ) while for the 10 B it was equal to 6.55 [μm (1.54 mg.cm -2 ). The converter of polyethylene or 10 B improved the detection efficiency to a factor of 4.7 and 3.0 respectively. The comparison of the spectrum of the background radiation with the spectra of the recoil protons and the a radiation from the 10 B it was concluded that the polyethylene presented better performance than the 10 B converter. (author)

  2. Combining low-energy electron microscopy and scanning probe microscopy techniques for surface science: development of a novel sample-holder.

    Science.gov (United States)

    Cheynis, F; Leroy, F; Ranguis, A; Detailleur, B; Bindzi, P; Veit, C; Bon, W; Müller, P

    2014-04-01

    We introduce an experimental facility dedicated to surface science that combines Low-Energy Electron Microscopy/Photo-Electron Emission Microscopy (LEEM/PEEM) and variable-temperature Scanning Probe Microscopy techniques. A technical challenge has been to design a sample-holder that allows to exploit the complementary specifications of both microscopes and to preserve their optimal functionality. Experimental demonstration is reported by characterizing under ultrahigh vacuum with both techniques: Au(111) surface reconstruction and a two-layer thick graphene on 6H-SiC(0001). A set of macros to analyze LEEM/PEEM data extends the capabilities of the setup.

  3. Electrical resistivity probes

    Science.gov (United States)

    Lee, Ki Ha; Becker, Alex; Faybishenko, Boris A.; Solbau, Ray D.

    2003-10-21

    A miniaturized electrical resistivity (ER) probe based on a known current-voltage (I-V) electrode structure, the Wenner array, is designed for local (point) measurement. A pair of voltage measuring electrodes are positioned between a pair of current carrying electrodes. The electrodes are typically about 1 cm long, separated by 1 cm, so the probe is only about 1 inch long. The electrodes are mounted to a rigid tube with electrical wires in the tube and a sand bag may be placed around the electrodes to protect the electrodes. The probes can be positioned in a borehole or on the surface. The electrodes make contact with the surrounding medium. In a dual mode system, individual probes of a plurality of spaced probes can be used to measure local resistance, i.e. point measurements, but the system can select different probes to make interval measurements between probes and between boreholes.

  4. A Precise Distance to the Host Galaxy of the Binary Neutron Star Merger GW170817 Using Surface Brightness Fluctuations

    Science.gov (United States)

    Cantiello, Michele; Jensen, J. B.; Blakeslee, J. P.; Berger, E.; Levan, A. J.; Tanvir, N. R.; Raimondo, G.; Brocato, E.; Alexander, K. D.; Blanchard, P. K.; Branchesi, M.; Cano, Z.; Chornock, R.; Covino, S.; Cowperthwaite, P. S.; D’Avanzo, P.; Eftekhari, T.; Fong, W.; Fruchter, A. S.; Grado, A.; Hjorth, J.; Holz, D. E.; Lyman, J. D.; Mandel, I.; Margutti, R.; Nicholl, M.; Villar, V. A.; Williams, P. K. G.

    2018-02-01

    The joint detection of gravitational waves (GWs) and electromagnetic radiation from the binary neutron star (BNS) merger GW170817 has provided unprecedented insight into a wide range of physical processes: heavy element synthesis via the r-process; the production of relativistic ejecta; the equation of state of neutron stars and the nature of the merger remnant; the binary coalescence timescale; and a measurement of the Hubble constant via the “standard siren” technique. In detail, all of these results depend on the distance to the host galaxy of the merger event, NGC 4993. In this Letter we measure the surface brightness fluctuation (SBF) distance to NGC 4993 in the F110W and F160W passbands of the Wide Field Camera 3 Infrared Channel (WFC3/IR) on the Hubble Space Telescope (HST). For the preferred F110W passband we derive a distance modulus of (m-M) =33.05+/- 0.08+/- 0.10 mag, or a linear distance d = 40.7 ± 1.4 ± 1.9 Mpc (random and systematic errors, respectively); a virtually identical result is obtained from the F160W data. This is the most precise distance to NGC 4993 available to date. Combining our distance measurement with the corrected recession velocity of NGC 4993 implies a Hubble constant H 0 = 71.9 ± 7.1 km s‑1 Mpc‑1. A comparison of our result to the GW-inferred value of H 0 indicates a binary orbital inclination of i ≳ 137°. The SBF technique can be applied to early-type host galaxies of BNS mergers to ∼100 Mpc with HST and possibly as far as ∼300 Mpc with the James Webb Space Telescope, thereby helping to break the inherent distance-inclination degeneracy of the GW data at distances where many future BNS mergers are likely to be detected. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with Program #15329 (PI: E

  5. Change in the magnetic structure of (Bi,SmFeO3 thin films at the morphotropic phase boundary probed by neutron diffraction

    Directory of Open Access Journals (Sweden)

    Shingo Maruyama

    2014-11-01

    Full Text Available We report on the evolution of the magnetic structure of BiFeO3 thin films grown on SrTiO3 substrates as a function of Sm doping. We determined the magnetic structure using neutron diffraction. We found that as Sm increases, the magnetic structure evolves from a cycloid to a G-type antiferromagnet at the morphotropic phase boundary, where there is a large piezoelectric response due to an electric-field induced structural transition. The occurrence of the magnetic structural transition at the morphotropic phase boundary offers another route towards room temperature multiferroic devices.

  6. Change in the magnetic structure of (Bi,Sm)FeO3 thin films at the morphotropic phase boundary probed by neutron diffraction

    Science.gov (United States)

    Maruyama, Shingo; Anbusathaiah, Varatharajan; Fennell, Amy; Enderle, Mechthild; Takeuchi, Ichiro; Ratcliff, William D.

    2014-11-01

    We report on the evolution of the magnetic structure of BiFeO3 thin films grown on SrTiO3 substrates as a function of Sm doping. We determined the magnetic structure using neutron diffraction. We found that as Sm increases, the magnetic structure evolves from a cycloid to a G-type antiferromagnet at the morphotropic phase boundary, where there is a large piezoelectric response due to an electric-field induced structural transition. The occurrence of the magnetic structural transition at the morphotropic phase boundary offers another route towards room temperature multiferroic devices.

  7. The Mars Hopper: Development, Simulation and Experimental Validation of a Radioisotope Exploration Probe for the Martian Surface

    Energy Technology Data Exchange (ETDEWEB)

    Nathan D. Jerred; Spencer Cooley; Robert C. O' Brien; Steven D. Howe; James E. O' Brien

    2012-09-01

    An advanced exploration probe has been proposed by the Center for Space Nuclear Research (CSNR) to acquire detailed data from the Martian surface and subsurface, ‘hop’ large distances to multiple sites in short periods of time and perform this task repeatedly. Although several similar flying vehicles have been proposed utilizing various power sources and complex designs, e.g. solar-electric and chemical-based, the CSNR’s Mars Hopper is based on a radioisotope thermal rocket (RTR) concept. The Mars Hopper’s design relies on the high specific energies [J/kg] of radioisotopes and enhances their low specific power [W/kg] through the use of a thermal capacitance material to store thermal energy over time. During operation, the RTR transfers the stored thermal energy to a flowing gas, which is then expanded through a converging-diverging nozzle, producing thrust. Between flights, the platform will have ample time to perform in-depth science at each location while the propellant tanks and thermal capacitor recharge. Recharging the propellant tanks is accomplished by sublimation freezing of the ambient CO2 atmosphere with a cryocooler, followed by heating and pressurization to yield a liquid storage state. The proposed Mars Hopper will undergo a ballistic flight, consuming the propellant in both ascent and descent, and by using multiple hopper platforms, information can be gathered on a global scale, enabling better resource resolution and providing valuable information for a possible Mars sample-return mission. The CSNR, collaborating with the Idaho National Laboratory (INL) and three universities (University of Idaho, Utah State University and Oregon State University), has identified key components and sub-systems necessary for the proposed hopper. Current project activities include the development of a lab-scale prototypic Mars Hopper and test facility, along with computational fluid dynamics (CFD)/thermal-hydraulic models to yield a better understanding of the

  8. Structure-dependent vibrational dynamics of Mg(BH 4 ) 2 polymorphs probed with neutron vibrational spectroscopy and first-principles calculations

    Energy Technology Data Exchange (ETDEWEB)

    Dimitrievska, Mirjana; White, James L.; Zhou, Wei; Stavila, Vitalie; Klebanoff, Leonard E.; Udovic, Terrence J.

    2016-01-01

    The structure-dependent vibrational properties of different Mg(BH4)2 polymorphs (..alpha.., ..beta.., ..gamma.., and ..delta.. phases) were investigated with a combination of neutron vibrational spectroscopy (NVS) measurements and density functional theory (DFT) calculations, with emphasis placed on the effects of the local structure and orientation of the BH4- anions. DFT simulations closely match the neutron vibrational spectra. The main bands in the low-energy region (20-80 meV) are associated with the BH4- librational modes. The features in the intermediate energy region (80-120 meV) are attributed to overtones and combination bands arising from the lower-energy modes. The features in the high-energy region (120-200 meV) correspond to the BH4- symmetric and asymmetric bending vibrations, of which four peaks located at 140, 142, 160, and 172 meV are especially intense. There are noticeable intensity distribution variations in the vibrational bands for different polymorphs. This is explained by the differences in the spatial distribution of BH4- anions within various structures. An example of the possible identification of products after the hydrogenation of MgB2, using NVS measurements, is presented. These results provide fundamental insights of benefit to researchers currently studying these promising hydrogen-storage materials.

  9. Probing the semi-magicity of $^{68}$Ni via the $^{66}$Ni(t,p)$^{68}$Ni two-neutron transfer reaction in inverse kinematics

    CERN Document Server

    AUTHOR|(CDS)2079390; Van Duppen, Piet

    The region around the nucleus $^{68}$Ni, with a shell closure for its protons at Z=28 and a harmonic oscillator shell gap for its neutrons at N=40, has drawn considerable interest over the past decades. $^{68}$Ni has properties that are typical for a doubly-magic nucleus, such as a high excitation energy and low B($E2:2^{+} \\rightarrow 0^{+}$) transition probability for the first excited 2$^{+}$ level and a 0$^{+}$ level as the first excited state. However, it has been suggested that the magic properties of $^{68}$Ni arise due to the fact that the N=40 separates the negative parity $pf$-shell from the positive parity 1$g_{9/2}$ orbital, and indeed, recent mass measurements have not revealed a clear N = 40 energy gap. Despite all additional information that was acquired over the last decade the specific role of the N=40 is not yet understood and a new experimental approach to study $^{68}$Ni was proposed. Namely, a two-neutron transfer reaction on $^{66}$Ni to characterize and disentangle the structure of the ...

  10. Geochemistry at 4 Vesta: Observations Using Fast Neutrons

    Science.gov (United States)

    Lawrence, David J.; Prettyman, Thomas H.; Feldman, William C.; Bazell, David; Mittlefehldt, David W.; Peplowski, Patrick N.; Reedy, Robert C.

    2012-01-01

    Dawn is currently in orbit around the asteroid 4 Vesta, and one of the major objectives of the mission is to probe the relationship of Vesta to the Howardite, Eucrite, and Diogenite (HED) meteorites. As Vesta is an example of a differentiated planetary embryo, Dawn will also provide fundamental information about planetary evolution in the early solar system [1]. To help accomplish this overall goal, the Dawn spacecraft carries the Gamma-Ray and Neutron Detector (GRaND). GRaND uses planetary gamma-ray and neutron spectroscopy to measure the surface elemental composition of Vesta and will provide information that is unique and complementary to that provided by the other Dawn instruments and investigations. Gamma-ray and neutron spectroscopy is a standard technique for measuring planetary compositions [2], having successfully made measurements at near-Earth asteroids, the Moon, Mars, Mercury and now Vesta. GRaND has made the first measurements of the neutron spectrum from any asteroid (previous asteroid measurements were only made with gamma-rays). Dawn has been collecting data at Vesta since July 2011. The prime data collection period for GRaND is the Low-Altitude Mapping Orbit (LAMO), which started on 12 December 2011 and will last through spring 2012. During LAMO, the Dawn spacecraft orbits at an average altitude of 210 km above the surface of Vesta, which allows good neutron and gamma-ray signals to be detected from Vesta. A description of the overall goals of GRaND and a summary of the initial findings are given elsewhere [3,4]. The subject of this study is to present the information that will be returned from GRaND using fast neutron measurements. Here, we discuss what fast neutrons can reveal about Vesta s surface composition, how such data can address Dawn science goals, and describe fast neutron measurements made in the early portion of the Vesta LAMO phase.

  11. An attempt to correlate surface physics with chemical properties: molecular beam and Kelvin probe investigations of Ce1-xZrxO2 thin films.

    Science.gov (United States)

    Kolekar, Sadhu K; Dubey, Anjani; Date, Kalyani S; Datar, Suwarna; Gopinath, Chinnakonda S

    2016-10-05

    What is the correlation between physical properties of the surfaces (such as surface potential, electronic nature of the surface), and chemical and catalysis properties (such as chemisorption, sticking probability of surface)? An attempt has been made to explore any correlation that might exist between the physical and chemical properties of thin film surfaces. Kelvin probe microscopy (KPM) and the molecular beam (MB) methods were employed to carry out the surface potential, and oxygen adsorption and oxygen storage capacity (OSC) measurements on Ce 1-x Zr x O 2 thin films. A sol-gel synthesis procedure and spin-coating deposition method have been applied to make continuous nanocrystalline Ce 1-x Zr x O 2 (x = 0-1) (CZ) thin films with uniform thickness (35-50 nm); however, surface roughness and porosity inherently changes with CZ composition. MB studies of O 2 adsorption on CZ reveal high OSC for Ce 0.9 Zr 0.1 O 2 , which also exhibits highly porous and significantly rough surface characteristics. The surface potential observed from KPM studies varied between 30 and 80 mV, with Ce-rich compositions exhibiting the highest surface potential. Surface potential shows large changes after reduction or oxidation of the CZ film demonstrating the influence of Ce 3+ /Ce 4+ on surface potential, which is also a key to catalytic activity for ceria-based catalysts. The surface potential measured from KPM and the OSC measured from MB vary linearly and they depend on the Ce 3+ /Ce 4+ ratio. More and detailed studies are suggested to arrive at a correlation between the physical and chemical properties of the surfaces.

  12. Formation of Merocyanine Self-Assembled Monolayer and Its Nonlinear Optical Properties Probed by Second-Harmonic Generation and Surface Plasmon Resonance

    Science.gov (United States)

    Tsuboi, Kazuma; Seki, Kazuhiko; Ouchi, Yukio; Fujita, Katsuhiko; Kajikawa, Kotaro

    2003-02-01

    Nonlinear optical responses of a self-assembled monolayer (SAM) containing merocyanine chromophore, 1-alkyl-4-(4-hydroxystyryl) pyridinium bromide (HSP), on gold in water and in ethanol were studied by second-harmonic generation (SHG). The pH dependence of the SHG response clearly showed a solvatochromic characteristic of the merocyanine from a protonated form to a zwitterionic form. A large second-order susceptibility χzzz=5.0× 10-7 esu (2.1× 102 pm/V) was found in a basic solution of ethanol where the merocyanine is in the zwitterionic form. Combination of the SHG and surface plasmon resonance (SPR) spectroscopy measurements also provides us with details of the formation process of the merocyanine SAMs in the ethanol solution of the HSP-terminated-alkyldisulfide, ω,ω\\prime-dithiodi[1-undecyl-4-(4-hydroxystyryl)pyridinium bromide](HSPC11SS). A considerable difference was found in the kinetics between SPR and SHG, because SHG probes the molecules in a noncentrosymmetric fashion on the gold surface while SPR probes the optical thickness of the film. The difference enabled us to separate the chemisorption from the physisorption in the adsorption process. Interestingly, both probes showed slower kinetics in the solution of higher concentration, suggesting association of the disulfide molecules in the solution of high concentration.

  13. Analysis of surface structure and hydrogen/deuterium exchange of colloidal silica suspension by contrast-variation small-angle neutron scattering.

    Science.gov (United States)

    Suzuki, Takuya; Endo, Hitoshi; Shibayama, Mitsuhiro

    2008-05-06

    The microscopic surface structure and hydrogen/deuterium exchange effect were investigated by contrast-variation small-angle neutron scattering (CV-SANS) for three different-sized amorphous colloidal silica aqueous suspensions. The results show that the fraction of hydrogen/deuterium exchange per nanoparticle, phiH/D, strongly depends on the size of silica nanoparticles. This finding supports that the hydrogen/deuterium exchange occurs exclusively within a finite surface layer of silica nanoparticles, while the inner component remained unchanged. Detailed analyses of the scattering intensity functions led to the estimation of (1) phiH/D and (2) the thickness of the surface layer as functions of the particle radius. The surface layer thickness was found to increase from 18 to 35 A with decreasing the particle radius from 165 to 71.2 A. The surface area per unit weight of silica estimated with the CV-SANS results are comparable to those reported in the literature.

  14. Interplay of disorder and antiferromagnetism in TlFe(1.6+δ)(Se(1-x)S(x))2 probed by neutron scattering.

    Science.gov (United States)

    Carlsson, S J E; Santos-Cottin, D; Lepoittevin, Ch; Strobel, P; Nassif, V; Suard, E; Toulemonde, P

    2014-07-09

    The effect of selenium substitution by sulphur on the structural and physical properties of antiferromagnetic TlFe1.6+δSe2 has been investigated via neutron, x-ray and electron diffraction, and transport measurements. The √5a×√5a×c super-cell related to the iron vacancy ordering found in the pure TlFe1.6Se2 selenide is also present in the S-doped TlFe1.6+δ(Se1-xSx)2 compounds. Neutron scattering experiments show the occurrence of the same long range magnetic ordering in the whole series i.e. the 'block checkerboard' antiferromagnetic structure. In particular, this is the first detailed study where the crystal structure and the √5a×√5a antiferromagnetic structure is characterized by neutron powder diffraction for the pure TlFe1.6+δS2 sulphide over a large temperature range. We demonstrate the strong correlation between occupancies of the crystallographic iron sites, the level of iron vacancy ordering and the occurrence of block antiferromagnetism in the sulphur series. Introducing S into the Se sites also increases the Fe content in TlFe1.6+δ(Se1-xSx)2 which in turn leads to the disappearance of the Fe vacancy ordering at x = 0.5 ± 0.15. However, by reducing the nominal Fe content, the same √5a×√5a×c vacancy ordering and antiferromagnetic order can be recovered also in the pure TlFe1.6+δS2 sulphide with a simultaneous reduction in the Néel temperature from 435 K in the selenide TlFe1.75Se2 to 330 K in the sulphide TlFe1.5S2. The magnetic moment remains high at low temperature throughout the full substitution range, which contributes to the absence of superconductivity in these compounds.

  15. Visualization and measurement of gas-liquid metal two-phase flow with large density difference using thermal neutrons as microscopic probes

    International Nuclear Information System (INIS)

    Saito, Y.; Hibiki, T.; Mishima, K.; Nishihara, H.; Yamamoto, A.; Kanda, K.; Tobita, Y.; Konishi, K.; Matsubayashi, M.

    1998-01-01

    In a core melt accident of a fast breeder reactor there is a possibility of boiling of fuel-steel mixture in the containment pool. In relation to safety evaluation on severe accident, it is indispensable to evaluate the recriticality of melted core. Gas-liquid two-phase flow with a large density difference is formed due to the boiling of fuel-steel mixture. Although the large density difference may affect the basic characteristics of two-phase flow, little work has been performed so far on two-phase flow with large density difference has not been performed well. In this study, visualization and void fraction measurement of gas-liquid metal two-phase flow were performed by using neutron radiography. The effect of the large density difference between gas and liquid phases on the basic flow characteristics of two-phase flow was clarified. (author)

  16. Penning-trap mass spectrometry of neutron-rich copper isotopes for probing the Z = 28 and N = 50 shell closures

    CERN Multimedia

    Manea, V

    We propose to perform a Penning-trap mass measurement of $^{79}$Cu. This exotic N = 50 isotone is the last frontier before the doubly-magic $^{78}$Ni and will greatly improve our knowledge of shell evolution. In the same run, we propose $^{77-78}$Cu mass measurements, as well as the search for a possible isomer in $^{76m}$Cu. The data will help to clarify the structure of the odd proton in the Cu isotopes, the influence on the Z = 28 proton core of the νg$_{9/2}$ orbital filling and the impact of the proton-neutron residual interaction on the strength of the N = 50 shell closure.

  17. Neutron is a marvelous probe to see the living things as it is alive. Real time and in-situ observation on living polymerization

    International Nuclear Information System (INIS)

    Koizumi, Satoshi

    2011-01-01

    Small-angle neutron scattering was employed in order to perform a real time and in-situ observation on a polymerization-induced self-assembly process in in-vivo or in-vitro systems; precise living anionic polymerization of poly-styrene-b-polyisoprene, pre-irradiation radical polymerization of polystyrene onto a polytetrafluoroethylene film, and microbial or enzymatic polymerization of cellulose. The aim of these studies is to clarify self-organizations of macro-molecular assemblies appeared in open non-equilibrium systems, which are exposed to external energy and mass flows induced by chemical reactions. The open non-equilibrium systems are believed to be important for understanding pattern formations not only in materials processing in industry but also in living things. Small-angle scattering observed for the systems was investigated according to the methods established for condensed matter physics (fractal and computational analyses), bridging with synthetic chemistry and molecular biology. (author)

  18. Proton hopping and long-range transport in the protic ionic liquid [Im][TFSI], probed by pulsed-field gradient NMR and quasi-elastic neutron scattering.

    Science.gov (United States)

    Hoarfrost, Megan L; Tyagi, Madhusudan; Segalman, Rachel A; Reimer, Jeffrey A

    2012-07-19

    The management of proton conductivity in the protic ionic liquid imidazolium bis(trifluoromethylsulfonyl)imide ([Im][TFSI]) is investigated via the use of quasi-elastic neutron scattering (QENS) and pulsed-field gradient NMR. The introduction of excess neutral imidazole to [Im][TFSI] leads to enhanced conductivity. We find that proton dynamics in [Im][TFSI] with excess imidazole are characterized by proton hopping that is encompassed in the slower of two translational processes, as identified by QENS. This relatively slow process contributes to long-range diffusion more than the faster process. NMR diffusion measurements show that proton hopping decreases with increasing temperature, but significant proton hopping persists even at the maximum experimental temperature of 120 °C. This, in combination with minimal ion aggregation, leads to high proton conductivity and a high proton transference number over a wide temperature range.

  19. Excimer emission properties on pyrene-labeled protein surface: correlation between emission spectra, ring stacking modes, and flexibilities of pyrene probes.

    Science.gov (United States)

    Fujii, Akira; Sekiguchi, Yutaka; Matsumura, Hiroyoshi; Inoue, Tsuyoshi; Chung, Wen-Sheng; Hirota, Shun; Matsuo, Takashi

    2015-03-18

    The excimer emission of pyrene is popularly employed for investigating the association between pyrene-labeled biomolecules or between pyrene-labeled places in a biomolecule. The property of pyrene excimer emission is affected by the fluctuation in ring stacking modes, which originates from the structural flexibilities of pyrene probes and/or of labeled places. Investigations of the excimer emission in terms of dynamics of pyrene stacking modes provide the detailed spatial information between pyrene-labeled places. In order to evaluate the effects of probe structures and fluctuation in pyrene-pyrene association modes on their emission properties on protein surface, three types of pyrene probe with different linker lengths were synthesized and conjugated to two cysteine residues in the A55C/C77S/V169C mutant of adenylate kinase (Adk), an enzyme that shows a structural transition between OPEN and CLOSED forms. In the CLOSED form of Adk labeled by a pyrene probe with a short linker, excimer emission was found to be predominated by the ground-state association of pyrenes. The pyrene stacking structure on the protein surface was successfully determined by an X-ray crystallographic analysis. However, the emission decay in the protein suggested the existence of several stacking orientations in solution. With the increase in the linker length, the effect of fluctuation in pyrene association modes on the spectral properties distinctly emerged at both ground and excited states. The combination of steady-state and time-resolved spectroscopic analyses is useful for differentiation in the origin of the excimer emission, which is essential for precisely understanding the interaction fashions between pyrene-labeled biomolecules.

  20. Radial Flux Distribution of Low-Energy Neutrons.

    Science.gov (United States)

    Higinbotham, J.

    1979-01-01

    Describes an experiment designed to illustrate the basic principle involved in the process of moderation of fast neutrons by water, and the monitoring of the low-energy neutron flux using indium as a probe. (GA)

  1. Physical methods for studying minerals and solid materials: X-ray, electron and neutron diffraction; scanning and transmission electron microscopy; X-ray, electron and ion spectrometry

    International Nuclear Information System (INIS)

    Eberhart, J.-P.

    1976-01-01

    The following topics are discussed: theoretical aspects of radiation-matter interactions; production and measurement of radiations (X rays, electrons, neutrons); applications of radiation interactions to the study of crystalline materials. The following techniques are presented: X-ray and neutron diffraction, electron microscopy, electron diffraction, X-ray fluorescence analysis, electron probe microanalysis, surface analysis by electron emission spectrometry (ESCA and Auger electrons), scanning electron microscopy, secondary ion emission analysis [fr

  2. Condutividade hidráulica de um Latossolo Vermelho Amarelo, não-saturado, utilizando-se sonda de nêutrons = Unsaturated hydraulic conductivity of an Oxisol, using a neutron probe

    Directory of Open Access Journals (Sweden)

    Laércio Alves Carvalho

    2010-01-01

    Full Text Available O objetivo deste estudo foi determinar a condutividade hidráulica não-saturada, utilizando-se sonda de nêutrons, em um Latossolo Vermelho distrófico argissólico A moderado textura média. O estudo foi desenvolvido no campo experimental da Escola Superior deAgricultura ‘Luiz de Queiroz’, Universidade de São Paulo, município de Piracicaba, Estado de São Paulo, Brasil. A parcela experimental apresentava comprimento de 45 m e largura de 15 m, na qual foram instalados 40 tubos de alumínio para acesso de uma sonda de nêutrons para medida do conteúdo da água no solo nas profundidades 0,20; 0,40; 0,60; 0,80 e 1,00 m e cálculo da armazenagem no perfil 0 - 1,00 m. Os tubos foram distribuídos na forma de grade de quatro colunas por dez linhas, com cada tubo distando 5 m de seu vizinho. As funções K(θ nos 40 pontos foram determinadas a partir das análises de regressão de θ em função de lnt e hZ em função de lnt, durante o processo de redistribuição da água no solo. A sonda de nêutrons mostrou-se um equipamento eficiente na determinação do conteúdo de água no solo, no método do perfil instantâneo para determinação da função K(θ em solo homogêneo. The objective of this study was to determine the unsaturated hydraulic conductivity, using a neutron probe, of a clay sandy Oxisol. The study was carried out in the city of Piracicaba, State ofSão Paulo, Brazil (22º42’ 43.3’’ S, 47o 37’ 10.4’’ W, 546 m. The dimensions of the experimental plot were 45 m x 15 m, in which 40 aluminum tubes were installed in order to access a neutron probe to measure the soil water content at the depths of 0.2, 0.4, 0.6, 0.8 and 1.0 m and, then, calculate the soil water storage of the 0 - 1.0 m soil layer. The distribution of these tubes was made in grids of four columns by ten rows, in spacing of 5 x 5 m. The K(θ functions were determined in the 40 points from regression analyses of θ as function lnt and hz as a function of

  3. Technological advances in cosmogenic neutron detectors for measuring soil water content

    Science.gov (United States)

    Zreda, M. G.; Schrön, M.; Köhli, M.

    2017-12-01

    The cosmic-ray neutron probe is used for measuring area-average soil water content at the hectometer scale. Early work showed a simple exponential decrease with distance of the instrument's sensitivity and a footprint 300 m in radius. Recent research suggested a much higher sensitivity to local neutrons and reduced footprint. We show results confirming the high sensitivity to local neutrons, describe two ways to reduce local and increase far-field effects, and propose ways of measuring neutrons at different spatial scales. Measurements with moderated detectors across a 10-m-wide creek and a 2-m-wide water tank show a decrease by 30% and 20%, respectively, of neutron intensity over water compared to that over land nearby. These results mean that the detector is sensitive to meter-scale heterogeneities of water content. This sensitivity can be reduced by rising the detector or by shielding it from local neutrons. The effect of local water distributions on the measured neutron intensity decreases with height. In the water tank experiment it disappeared almost completely at the height of 2 m, leading to the conjecture that the height roughly equal to the horizontal scale of heterogeneity would eliminate the sensitivity. This may or may not be practical. Shielding the detector below by a hydrogenous material removes a substantial fraction of the local neutrons. The shielded detector has a reduced count rate, reduced sensitivity to local neutrons and increased sensitivity to neutrons farther afield, and a larger footprint. Such a detector could be preferable to the current cosmogenic-neutron probe under heterogeneous soil water conditions. The shielding experiments also inspired the development of a local-area neutron detector. It has hydrogenous neutron shields on all sides except the bottom, substantially blocking the neutrons coming from afar, while allowing the neutrons coming directly from below. Its footprint is equal to its physical dimension when the detector is

  4. Commercial applications of neutron scattering

    International Nuclear Information System (INIS)

    Hutchings, M.T.

    1993-01-01

    The fact that industry is now willing to pay the full commercial cost for certain neutron scattering experiments aimed at solving its urgent materials - related problems is a true testimony to the usefulness of neutrons as microscopic probes. This paper gives examples of such use of three techniques drawn mainly from our experience at AEA Technology Harwell Laboratory. These are diffraction to measure residual stress, small angle neutron scattering to examine hardening precipitates in ferritic steels brought about by irradiation, and reflectivity to study amorphous diamond layers deposited on silicon. In most cases it is the penetrative power of the neutron which proves to be its best asset for commercial industrial applicaitons. (author)

  5. NEUTRON IMAGING, RADIOGRAPHY AND TOMOGRAPHY.

    Energy Technology Data Exchange (ETDEWEB)

    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.

  6. Introductory theory of neutron scattering

    International Nuclear Information System (INIS)

    Gunn, J.M.F.

    1986-12-01

    The paper comprises a set of six lecture notes which were delivered to the summer school on 'Neutron Scattering at a pulsed source', Rutherford Laboratory, United Kingdom, 1986. The lectures concern the physical principles of neutron scattering. The topics of the lectures include: diffraction, incoherent inelastic scattering, connection with the Schroedinger equation, magnetic scattering, coherent inelastic scattering, and surfaces and neutron optics. (UK)

  7. Residual stress measurements by means of neutron diffraction

    International Nuclear Information System (INIS)

    Pintschovius, L.; Jung, V.; Macherauch, E.; Voehringer, O.

    1983-01-01

    A new method for the analysis of multiaxial residual stress states is presented, which is based on high resolution neutron diffraction. It is analogous to X-ray stress analysis, but the use of neutrons instead of X-rays allows the analysis of the stress distributions also in the interior of technical components in a non-destructive way. To prove the feasibility of the method, investigations of the loading stress distributions of an aluminium bar subjected to purely elastic bending were performed. Limiting factors due to the volume of the internal probe region and the sample thickness are discussed. Complete neutron residual stress analyses were carried out for a plastically deformed bending bar and a transformation-free water-quenched steel cylinder. The results are in fairly good agreement with theoretical expectations and with X-ray control measurements at the surface of the objects. (Auth.)

  8. Development of probes for bioanalytic applications of the surface-enhanced Raman scattering; Entwicklung neuer Sonden fuer bioanalytische Anwendungen der oberflaechenverstaerkten Raman-Streuung

    Energy Technology Data Exchange (ETDEWEB)

    Matschulat, Andrea Isabel

    2011-07-01

    Surface-enhanced Raman scattering (SERS) has been established as a versatile tool for probing and labeling in analytical applications, based on the vibrational spectra of samples as well as label molecules in the proximity of noble metal nanostructures. The aim of this work was the construction of novel SERS hybrid probes. The hybrid probes consisted of Au and Ag nanoparticles and reporter molecules, as well as a targeting unit. The concept for the SERS hybrid probe design was followed by experiments comprising characterization techniques such as UV/Vis-spectroscopy (UV/Vis), Transmission electron microscopy (TEM) and Dynamic Light Scattering (DLS), respectively. SERS experiments were performed for studying and optimizing the plasmonic properties of nanoparticles with respect to their enhancement capabilities. The SERS-probes had to meet following requirements: biocompatibility, stability in physiological media, and enhancement of Raman-signals from Raman reporter molecules enabling the identification of different probes even in a complex biological environment. Au and Ag nanoaggregates were found to be the most appropriate SERS substrates for the hybrid probe design. The utilization of Raman reporters enabled the identification of different SERS probes in multiplexing experiments. In particular, the multiplexing capability of ten various reporter molecules para-aminobenzenethiol, 2-naphthalenethiol, crystal violet, rhodamine (B) isothiocyanate, fluorescein isothiocyanate, 5,5'dithiobis(2-nitrobenzoic acid), para-mercaptobenzoic acid, acridine orange, safranine O und nile blue was studied using NIR-SERS excitation. As demonstrated by the results the reporters could be identified through their specific Raman signature even in the case of high structural similarity. Chemical separation analysis of the reporter signatures was performed in a trivariate approach, enabling the discrimination through an automated calculation of specific band ratios. The trivariate

  9. Observation by conductive-probe atomic force microscopy of strongly inverted surface layers at the hydrogenated amorphous silicon/crystalline silicon heterojunctions

    Science.gov (United States)

    Maslova, O. A.; Alvarez, J.; Gushina, E. V.; Favre, W.; Gueunier-Farret, M. E.; Gudovskikh, A. S.; Ankudinov, A. V.; Terukov, E. I.; Kleider, J. P.

    2010-12-01

    Heterojunctions made of hydrogenated amorphous silicon (a-Si:H) and crystalline silicon (c-Si) are examined by conducting probe atomic force microscopy. Conductive channels at both (n )a-Si:H/(p)c-Si and (p)a-Si:H/(n)c-Si interfaces are clearly revealed. These are attributed to two-dimension electron and hole gases due to strong inversion layers at the c-Si surface in agreement with previous planar conductance measurements. The presence of a hole gas in (p )a-Si:H/(n)c-Si structures implies a quite large valence band offset (EVc-Si-EVa-Si:H>0.25 eV).

  10. Structural and phase transition changes of sodium dodecyl sulfate micellar solution in alcohols probed by small-angle neutron scattering (SANS)

    International Nuclear Information System (INIS)

    Putra, Edy Giri Rachman; Patriati, Arum

    2015-01-01

    Small-angle neutron scattering (SANS) measurements on 0.3M sodium dodecyl sulfate (SDS) micellar solutions have been performed in the presence of n-alcohols, from ethanol to decanol at different alcohol concentrations, 2–10 wt%. The ellipsoid micellar structure which occurred in the 0.3M SDS in aqueous solution with the size range of 30–50 Å has different behavior at various hydrocarbon chain length and concentration of alcohols. At low concentration and short chain-length of alcohols, such as ethanol, propanol, and butanol, the size of micelles reduced and had a spherical-like structure. The opposite effect occurred as medium to long chain alcohols, such as hexanol, octanol and decanol was added into the 0.3M SDS micellar solutions. The micelles structure changed to be more elongated in major axis and then crossed the critical phase transition from micellar solution into liquid crystal phase as lamellar structure emerged by further addition of alcohols. The inter-lamellar distances were also depending on the hydrocarbon chain length and concentration of alcohols. In the meantime, the persistent micellar structures occurred in addition of medium chain of n-alcohol, pentanol at all concentrations

  11. Visualization and measurement of gas-liquid metal two-phase flow with large density difference using thermal neutrons as microscopic probes

    International Nuclear Information System (INIS)

    Mishima, K.; Hibiki, T.; Saito, Y.; Nishihara, H.; Tobita, Y.; Konishi, K.; Matsubayashi, M.

    1999-01-01

    In a core melt accident of a fast breeder reactor, there is a possibility of boiling of the fuel-steel mixture in the containment pool. In relation to safety evaluation on severe accident, it is indispensable to evaluate the possibility of re-criticality of melted core. Gas-liquid two-phase flow with a large liquid-to-gas density ratio is formed due to the boiling of fuel-steel mixture. Although it is anticipated that the large density ratio may affect the basic characteristics of two-phase flow, little work has been performed so far on two-phase flow with a large liquid-to-gas density ratio. In this study, visualization and void fraction measurement of gas-liquid metal two-phase flow were performed by using neutron radiography and image processing techniques. Then, the effect of large density difference between gas and liquid phases on the basic flow characteristics of two-phase flow was clarified

  12. Structural and phase transition changes of sodium dodecyl sulfate micellar solution in alcohols probed by small-angle neutron scattering (SANS)

    Energy Technology Data Exchange (ETDEWEB)

    Putra, Edy Giri Rachman [Neutron Scattering Laboratory, National Nuclear Energy Agency of Indonesia (BATAN), Gedung 40 BATAN, Kawasan Puspiptek Serpong, Tangerang 15314 (Indonesia); Patriati, Arum [Neutron Scattering Laboratory, National Nuclear Energy Agency of Indonesia (BATAN), Gedung 40 BATAN, Kawasan Puspiptek Serpong, Tangerang 15314 (Indonesia); Department of Chemistry, Faculty of Mathematics and Natural Sciences, University of Gadjah Mada, Bulaksumur, Yogyakarta 55281, Indonesia giri@batan.go.id (Indonesia)

    2015-04-16

    Small-angle neutron scattering (SANS) measurements on 0.3M sodium dodecyl sulfate (SDS) micellar solutions have been performed in the presence of n-alcohols, from ethanol to decanol at different alcohol concentrations, 2–10 wt%. The ellipsoid micellar structure which occurred in the 0.3M SDS in aqueous solution with the size range of 30–50 Å has different behavior at various hydrocarbon chain length and concentration of alcohols. At low concentration and short chain-length of alcohols, such as ethanol, propanol, and butanol, the size of micelles reduced and had a spherical-like structure. The opposite effect occurred as medium to long chain alcohols, such as hexanol, octanol and decanol was added into the 0.3M SDS micellar solutions. The micelles structure changed to be more elongated in major axis and then crossed the critical phase transition from micellar solution into liquid crystal phase as lamellar structure emerged by further addition of alcohols. The inter-lamellar distances were also depending on the hydrocarbon chain length and concentration of alcohols. In the meantime, the persistent micellar structures occurred in addition of medium chain of n-alcohol, pentanol at all concentrations.

  13. Minimization of spurious strains by using a Si bent-perfect-crystal monochromator: neutron surface strain scanning of a shot-peened sample

    International Nuclear Information System (INIS)

    Rebelo Kornmeier, Joana; Hofmann, Michael; Gibmeier, Jens

    2011-01-01

    Neutron strain measurements are critical at the surface. When scanning close to a sample surface, aberration peak shifts arise due to geometrical and divergence effects. These aberration peak shifts can be of the same order as the peak shifts related to residual strains. In this study it will be demonstrated that by optimizing the horizontal bending radius of a Si (4 0 0) monochromator, the aberration peak shifts from surface effects can be strongly reduced. A stress-free sample of fine-grained construction steel, S690QL, was used to find the optimal instrumental conditions to minimize aberration peak shifts. The optimized Si (4 0 0) monochromator and instrument settings were then applied to measure the residual stress depth gradient of a shot-peened SAE 4140 steel sample to validate the effectiveness of the approach. The residual stress depth profile is in good agreement with results obtained by x-ray diffraction measurements from an international round robin test (BRITE-EURAM-project ENSPED). The results open very promising possibilities to bridge the gap between x-ray diffraction and conventional neutron diffraction for non-destructive residual stress analysis close to surfaces

  14. Effect of SP-C on surface potential distribution in pulmonary surfactant: Atomic force microscopy and Kelvin probe force microscopy study

    International Nuclear Information System (INIS)

    Hane, Francis; Moores, Brad; Amrein, Matthias; Leonenko, Zoya

    2009-01-01

    The air-lung interface is covered by a molecular film of pulmonary surfactant (PS). The major function of the film is to reduce the surface tension of the lung's air-liquid interface, providing stability to the alveolar structure and reducing the work of breathing. Earlier we have shown that function of bovine lipid extract surfactant (BLES) is related to the specific molecular architecture of surfactant films. Defined molecular arrangement of the lipids and proteins of the surfactant film also give rise to a local highly variable electrical surface potential of the interface. In this work we investigated a simple model of artificial lung surfactant consisting of DPPC, eggPG, and surfactant protein C (SP-C). Effects of surface compression and the presence of SP-C on the monolayer structure and surface potential distribution were investigated using atomic force microscopy (AFM) and Kelvin probe force microscopy (KPFM). We show that topography and locally variable surface potential of DPPC-eggPG lipid mixture are similar to those of pulmonary surfactant BLES in the presence of SP-C and differ in surface potential when SP-C is absent.

  15. ;Study of secondary hydriding at high temperature in zirconium based nuclear fuel cladding tubes by coupling information from neutron radiography/tomography, electron probe micro analysis, micro elastic recoil detection analysis and laser induced breakdown spectroscopy microprobe

    Science.gov (United States)

    Brachet, Jean-Christophe; Hamon, Didier; Le Saux, Matthieu; Vandenberghe, Valérie; Toffolon-Masclet, Caroline; Rouesne, Elodie; Urvoy, Stéphane; Béchade, Jean-Luc; Raepsaet, Caroline; Lacour, Jean-Luc; Bayon, Guy; Ott, Frédéric

    2017-05-01

    This paper gives an overview of a multi-scale experimental study of the secondary hydriding phenomena that can occur in nuclear fuel cladding materials exposed to steam at high temperature (HT) after having burst (loss-of-coolant accident conditions). By coupling information from several facilities, including neutron radiography/tomography, electron probe micro analysis, micro elastic recoil detection analysis and micro laser induced breakdown spectroscopy, it was possible to map quantitatively, at different scales, the distribution of oxygen and hydrogen within M5™ clad segments having experienced ballooning and burst at HT followed by steam oxidation at 1100 and 1200 °C and final direct water quenching down to room temperature. The results were very reproducible and it was confirmed that internal oxidation and secondary hydriding at HT of a cladding after burst can lead to strong axial and azimuthal gradients of hydrogen and oxygen concentrations, reaching 3000-4000 wt ppm and 1.0-1.2 wt% respectively within the β phase layer for the investigated conditions. Consistent with thermodynamic and kinetics considerations, oxygen diffusion into the prior-β layer was enhanced in the regions highly enriched in hydrogen, where the α(O) phase layer is thinner and the prior-β layer thicker. Finally the induced post-quenching hardening of the prior-β layer was mainly related to the local oxygen enrichment. Hardening directly induced by hydrogen was much less significant.

  16. Surface studies of plasma processed Nb samples

    International Nuclear Information System (INIS)

    Tyagi, Puneet V.; Doleans, Marc; Hannah, Brian S.; Afanador, Ralph; Stewart, Stephen; Mammosser, John; Howell, Matthew P; Saunders, Jeffrey W; Degraff, Brian D; Kim, Sang-Ho

    2015-01-01

    Contaminants present at top surface of superconducting radio frequency (SRF) cavities can act as field emitters and restrict the cavity accelerating gradient. A room temperature in-situ plasma processing technology for SRF cavities aiming to clean hydrocarbons from inner surface of cavities has been recently developed at the Spallation Neutron Source (SNS). Surface studies of the plasma-processed Nb samples by Secondary ion mass spectrometry (SIMS) and Scanning Kelvin Probe (SKP) showed that the NeO 2 plasma processing is very effective to remove carbonaceous contaminants from top surface and improves the surface work function by 0.5 to 1.0 eV.

  17. Surface studies of plasma processed Nb samples

    Energy Technology Data Exchange (ETDEWEB)

    Tyagi, Puneet V. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source (SNS); Doleans, Marc [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source (SNS); Hannah, Brian S. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source (SNS); Afanador, Ralph [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source (SNS); Stewart, Stephen [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source (SNS); Mammosser, John [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source (SNS); Howell, Matthew P [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source (SNS); Saunders, Jeffrey W [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source (SNS); Degraff, Brian D [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source (SNS); Kim, Sang-Ho [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source (SNS)

    2015-01-01

    Contaminants present at top surface of superconducting radio frequency (SRF) cavities can act as field emitters and restrict the cavity accelerating gradient. A room temperature in-situ plasma processing technology for SRF cavities aiming to clean hydrocarbons from inner surface of cavities has been recently developed at the Spallation Neutron Source (SNS). Surface studies of the plasma-processed Nb samples by Secondary ion mass spectrometry (SIMS) and Scanning Kelvin Probe (SKP) showed that the NeO2 plasma processing is very effective to remove carbonaceous contaminants from top surface and improves the surface work function by 0.5 to 1.0 eV.

  18. Small angle neutron scattering on an absolute intensity scale and the internal surface of diatom frustules from three species of differing morphologies.

    Science.gov (United States)

    Garvey, C J; Strobl, M; Percot, A; Saroun, J; Haug, J; Vyverman, W; Chepurnov, V A; Ferris, J M

    2013-05-01

    The internal nanostructure of the diatoms Cyclotella meneghiniana, Seminavis robusta and Achnanthes subsessilis was investigated using small angle neutron scattering (SANS) to examine thin biosilica samples, consisting of isotropic (powder) from their isolated cell walls. The interpretation of SANS data was assisted by several other measurements. The N2 adsorption, interpreted within the Branuer-Emmet-Teller isotherm, yielded the specific surface area of the material. Fourier transform infrared (FTIR) and Raman spectroscopy indicates that the isolated material is amorphous silica with small amounts of organic cell wall materials acting as a filling material between the silica particles. A two-phase (air and amorphous silica) model was used to interpret small angle neutron scattering data. After correction for instrumental resolution, the measurements on two SANS instruments covered an extended range of scattering vectors 0.0011 nm(-1) scattering vectors, q, on an absolute scale of intensity for each sample. Each of the samples gave a characteristic scattering curve where log (intensity) versus log (q) has a -4 dependence, with other features superimposed. In the high-q regime, departure from this behaviour was observed at a length-scales equivalent to the proposed unitary silica particle. The limiting Porod scattering law was used to determine the specific area per unit of volume of each sample illuminated by the neutron beam. The Porod behaviour, and divergence from this behaviour, is discussed in terms of various structural features and the proposed mechanisms for the bio-assembly of unitary silica particles in frustules.

  19. Analysis and modification of defective surface aggregates on PCDTBT:PCBM solar cell blends using combined Kelvin probe, conductive and bimodal atomic force microscopy.

    Science.gov (United States)

    Noh, Hanaul; Diaz, Alfredo J; Solares, Santiago D

    2017-01-01

    Organic photovoltaic systems comprising donor polymers and acceptor fullerene derivatives are attractive for inexpensive energy harvesting. Extensive research on polymer solar cells has provided insight into the factors governing device-level efficiency and stability. However, the detailed investigation of nanoscale structures is still challenging. Here we demonstrate the analysis and modification of unidentified surface aggregates. The aggregates are characterized electrically by Kelvin probe force microscopy and conductive atomic force microscopy (C-AFM), whereby the correlation between local electrical potential and current confirms a defective charge transport. Bimodal AFM modification confirms that the aggregates exist on top of the solar cell structure, and is used to remove them and to reveal the underlying active layer. The systematic analysis of the surface aggregates suggests that the structure consists of PCBM molecules.

  20. Gold-decorated highly ordered self-organized grating-like nanostructures on Ge surface: Kelvin probe force microscopy and conductive atomic force microscopy studies.

    Science.gov (United States)

    Mollick, Safiul Alam; Kumar, Mohit; Singh, Ranveer; Satpati, Biswarup; Ghose, Debabrata; Som, Tapobrata

    2016-10-28

    Nanoarchitecture by atomic manipulation is considered to be one of the emerging trends in advanced functional materials. It has a gamut of applications to offer in nanoelectronics, chemical sensing, and nanobiological science. In particular, highly ordered one-dimensional semiconductor nanostructures fabricated by self-organization methods are in high demand for their high aspect ratios and large number of applications. An efficient way of fabricating semiconductor nanostructures is by molecular beam epitaxy, where atoms are added to a crystalline surface at an elevated temperature during growth, yielding the desired structures in a self-assembled manner. In this article, we offer a room temperature process, in which atoms are sputtered away by ion impacts. Using gold ion implantation, the present study reports on the formation of highly ordered self-organized long grating-like nanostructures, with grooves between them, on a germanium surface. The ridges of the patterns are shown to have flower-like protruding nanostructures, which are mostly decorated by gold atoms. By employing local probe microscopic techniques like Kelvin probe force microscopy and conductive atomic force microscopy, we observe a spatial variation in the work function and different nanoscale electrical conductivity on the ridges of the patterns and the grooves between them, which can be attributed to gold atom decorated ridges. Thus, the architecture  presented offers the advantage of using the patterned germanium substrates as periodic arrays of conducting ridges and poorly conducting grooves between them.

  1. Measurement of the high-energy neutron flux on the surface of the natural uranium target assembly QUINTA irradiated by deuterons of 4- and 8-GeV energy

    International Nuclear Information System (INIS)

    Adam, J.; Baldin, A.A.; Chilap, V.

    2014-01-01

    Experiments with a natural uranium target assembly QUINTA exposed to 4- and 8 GeV deuteron beams of the Nuclotron accelerator at the Joint Institute for Nuclear Research (Dubna) are analyzed. The 129 I, 232 Th, 233 U, 235 U, nat U, 237 Np, 238 Pu, 239 Pu and 241 Am radioactive samples were installed on the surface of the QUINTA set-up and irradiated with secondary neutrons. The neutron flux through the RA samples was monitored by Al foils. The reaction rates of 27 Al(n, y 1 ) 24 Na, 27 Al(n, y 2 ) 22 Na and 27 Al(n, y 3 ) 7 Be reactions with the effective threshold energies of 5, 27 and 119 MeV were measured at both 4- and 8-GeV deuteron beam energies. The average neutron fluxes between the effective threshold energies and the effective ends of the neutron spectra (which are 800 or 1000 MeV for energy of 4- or 8-GeV deuterons) were determined. The evidence for the intensity shift of the neutron spectra to higher neutron energies with the increase of the deuteron energy from 4 to 8 GeV was found from the ratios of the average neutron fluxes. The reaction rates and the average neutron fluxes were calculated with MCNPX2.7 and MARS15 codes.

  2. Studying the effect of the curvature of a polymer-grafted nanoparticle surface on equilibrium brush dimensions via small-angle neutron scattering (SANS) and polymer field theory

    Science.gov (United States)

    Hore, Michael J. A.; Hammouda, Boualem

    2013-03-01

    For polymer-grafted nanoparticles with a size that is on the order of the radius of gyration of the polymer chains, the curvature of the nanoparticle surface has a role in determining the equilibrium brush structure. The curvature can cause an increase in the conformational entropy of the brush chains relative to that of a flat surface, and hence has large implications for dispersion of nanoparticles within a polymer matrix. Here, small-angle neutron scattering (SANS) is performed to measure the radius of gyration of a poly(ethylene glycol) (PEG) brush that is grafted to the surface of gold nanorods (diameter x length: 10 x 30 nm) and nanospheres (diameter: 10 nm) in both solution and a within a polymer melt. To help interpret the SANS measurements, field theoretic simulations are employed to calculate density profiles for the brush polymer in solution and a polymer melt as a function of nanoparticle shape, radius, and brush grafting density.

  3. Flame propagation on the surfaces of rapidly rotating neutron stars during Type I X-ray bursts

    NARCIS (Netherlands)

    Cavecchi, Y.; Watts, A.; Braithwaite, J.; Levin, Y.

    2013-01-01

    We present the first vertically resolved hydrodynamic simulations of a laterally propagating, deflagrating flame in the thin helium ocean of a rotating accreting neutron star. We use a new hydrodynamics solver tailored to deal with the large discrepancy in horizontal and vertical length-scales

  4. Nuclear mass formula with a neutron skin degree of freedom and finite-range model for the surface energy

    International Nuclear Information System (INIS)

    Moeller, P.; Myers, W.D.

    1984-03-01

    We study the possibility of extending the model used by Moeller and Nix in 1980 to calculate nuclear masses and fission barriers for nuclei throughout the periodic system, to describe compressibility effects and the existence of a neutron skin. 9 references

  5. X-Ray Polarimetery of Neutron Stars from a CubeSat

    Science.gov (United States)

    Kaaret, Philip

    2013-04-01

    The propagation of radiation in the intense magnetic fields surrounding neutron stars is strongly affected by the fundamental quantum mechanical properties of photons and electrons as described by the theory of quantum electrodynamics (QED). Measurement of the polarization of X-rays emitted from the surface of a highly magnetized neutron star will unambiguously verify (or reject) a unique signature of strong-field QED and probe the neutron star magnetic field and X-ray emission geometry. We describe an instrument capable of measuring the polarization of soft X-rays from thermally-emitting isolated neutron stars that can be accomplished at modest cost by exploiting CubeSats as novel vehicles for high energy astrophysics.

  6. Probing the surface charge on the basal planes of Kaolinite particles with high resolution Atomic Force Microscopy

    NARCIS (Netherlands)

    Kumar, Naveen; Andersson, M.P.; van den Ende, Henricus T.M.; Mugele, Friedrich Gunther; Sîretanu, Igor

    2017-01-01

    High-resolution atomic force microscopy is used to map the surface charge on the basal planes of kaolinite nanoparticles in an ambient solution of variable pH and NaCl or CaCl2 concentration. Using DLVO theory with charge regulation, we determine from the measured force–distance curves the surface

  7. Investigation of Surface Sulfurization in CuIn1-x Gax S2-y Sey Thin Films by Using Kelvin Probe Force Microscopy.

    Science.gov (United States)

    Kim, Haeri; Park, Se Jin; Kim, Byungwoo; Hwang, Yun Jeong; Min, Byoung Koun

    2018-02-05

    CuIn 1-x Ga x S 2-y Se y (CIGSSe) thin films have attracted a great deal of attention as promising absorbing materials for solar cell applications, owing to their favorable optical properties (e.g. a direct band gap and high absorption coefficients) and stable structure. Many studies have sought to improve the efficiency of solar cells using these films, and it has been found that surface modification through post-heat treatment can lead to surface passivation of surface defects and a subsequent increase in efficiency. The surface properties of solution-processed CIGSSe films are considered to be particularly important in this respect, owing to the fact that they are more prone to defects. In this work, CIGSSe thin films with differing S/Se ratios at their surface were synthesized by using a precursor solution and post-sulfurization heat treatment. These CIGSSe thin films were investigated with current-voltage and Kelvin probe force microscope (KPFM) analyses. Surface photovoltage (SPV), which is the difference in the work function in the dark and under illumination, was measured by using KPFM, which can examine the screening and the modification of surface charge through carrier trapping. As the concentration of S increases on the CIGSSe film surface, higher work functions and more positive SPV values were observed. Based on these measurements, we inferred the band-bending behavior of CIGSSe absorber films and proposed reasons for the improvement in solar cell performance. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Polycapillary neutron lenses

    International Nuclear Information System (INIS)

    Mildner, D.F.R.

    1997-01-01

    The principle of multiple mirror reflection from smooth surfaces at small grazing angles enables the transport and guiding of high intensity slow neutron beams to locations of low background for neutron scattering and absorption experiments and to provide facilities for multiple instruments. Curved guides have been widely used at cold neutron facilities to remove the unwanted radiation (fast neutrons and gamma rays) from the beam without the use of filters. A typical guide has transverse dimensions of 50 mm and, with a radius of curvature of 1 km, transmits wavelengths longer than 5 A. Much tighter curves requires narrower transverse dimensions, otherwise there is little transmission. Typical neutron benders have a number of slots with transverse dimensions of ∼5 mm. Based on the same principle but using a different technology, recent developments in glass polycapillary fibers have produced miniature versions of neutron guides. Fibers with many thousands of channels having sizes of ∼ 10 μm enable beams of long wavelength neutrons (λ > 4 A) to be transmitted efficiently in a radius of curvature as small as a fraction of 1 m. A large collection of these miniature versions of neutron guides can be used to bend the neutron trajectories such that the incident beam can be focused. (author)

  9. Compact neutron generator

    Science.gov (United States)

    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.

  10. Probing the structure and nano-scale mechanical properties of polymer surfaces with scanning force microscopy and sum frequency vibrational spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Gracias, David Hugo [Univ. of California, Berkeley, CA (United States)

    1999-05-01

    Scanning Force Microscopy (SFM) has been used to quantitatively measure the elastic modulus, friction and hardness of polymer surfaces with special emphasis on polyethylene and polypropylene. In the experiments, tips of different radii of curvature ranging from 20 nm to 1000 nm have been used and the high pressure applied by the SFM have been observed to affect the values obtained in the measurements. The contact of the SFM tip with the polymer surface is explained by fitting the experimental curves to theoretical predictions of contact mechanics. Sum Frequency Generation (SFG) Vibrational Spectroscopy has been used to measure vibrational spectra of polymer surfaces in the vibrational range of 2700 to 3100 cm-1. Strong correlations are established between surface chemistry and surface structure as probed by SFG and mechanical properties measured by SFM on the surfaces. In these studies segregation of low surface energy moieties, from the bulk of the polymer to the surface have been studied. It was found that surface segregation occurs in miscible polymer blends and a small concentration of surface active polymer can be used to totally modify the surface properties of the blend. A novel high vacuum SFM was built to do temperature dependent measurements of mechanical changes occurring at the surface of polypropylene during the glass transition of the polymer. Using this instrument the modulus and friction of polypropylene was measured in the range of room temperature to ˜-60°C. An increase in the ordering of the backbone of the polymer chains below the glass transition measured by SFG correlates well with the increase in modulus measured on the same surface with SFM. Friction measurements have been done on polyethylene with three different instruments by applying loads ranging from nN to sub newton i.e. over eight orders of magnitude. Pressure and contact area effects were observed to play a significant role in determining the frictional response of the polymer

  11. Hardness and stability of a carburized surface layer on AISI 316L stainless steel after irradiation in a spallation neutron environment

    International Nuclear Information System (INIS)

    McClintock, David A.; Hyres, James W.; Vevera, Bradley J.

    2014-01-01

    The inner surfaces of mercury target vessels at the Spallation Neutron Source (SNS) experience material erosion caused by proton-beam induced cavitation of the liquid mercury. One approach developed and deployed to inhibit erosion of the target vessel material was surface hardening via a proprietary low-temperature carburization treatment, called Kolsterising®, to the target surfaces most susceptible to cavitation-induced erosion. Previous testing has shown that the hardened surface produced by the Kolsterising® treatment can delay the onset of erosion and inhibit erosion once initiated. But the stability of the carbon atmosphere in the treated surface layer after radiation to doses prototypic to the SNS target was unknown. Therefore, as part of the target Post Irradiation Examination program at the SNS, optical microscopy and microhardness testing were performed on material sampled from the first and second operational SNS target vessels. Optical micrographs contained no noticeable precipitation in the super-saturated carbon layer extending into the base material and several micrographs contained evidence of a proposed mechanism for mass wastage from the vessel surface. The hardened layer was characterized using Vickers microhardness testing and results show that the shape of hardness profile of the treated layer corresponded well with known pre-irradiation hardness values, though the microhardness results show some hardening occurred during irradiation. The results suggest that the hardened surface layer produced by the Kolsterising® treatment is stable at the operational temperatures and dose levels experienced by the first and second operational SNS target modules

  12. The polarized platypus polarized neutron reflectometry made possible

    International Nuclear Information System (INIS)

    Saerbeck, Thomas

    2009-01-01

    Full text: The magnetic moment of the neutron, together with it's highly penetrating non destructive manner, make polarized neutron reflectometry an excellent tool to study magnetic phenomena across surfaces and interfaces of thin films. Unlike other magnetometry techniques which ordinarily yield only average magnetization values or, in case of probes with higher spatial resolution (e.g. electron microscopy or scanning tunnelling microscopy), show a high surface sensitivity, PNR together with magnetic x-ray scattering provides the ability to spatially resolve vector magnetization well beneath the surface [1] The ability to obtain vector magnetization profiles across interfaces and surfaces of thin films and multilayers offers the intriguing possibility to study systematically magnetic configurations and magnetic exchange interactions through intervening layers. In this paper we present the performance of the new polarization system installed on the time of flight neutron reflectometer PLATYPUS at ANSTO's Bragg Institute. The spin state of the neutrons is polarized and analysed by spatial separation of different neutron spin states using polarizing Fe/Si supermirrors before, and after the sample stage. The supermirrors have a large wavelength acceptance bandwidth of 3 A to 12 A. To control the desired spin direction of the incoming and reflected beam from the sample, two sets of RF spin flippers are installed. In the free space between the spin flippers and the sample stage the neutron spin direction is maintained by two sets of magnetic guide field coils. The new sample environment for studies of magnetic samples includes a 1 T electromagnet and a closed cycle refrigerator which gives access to a temperature range from 4K to 3 50 K .

  13. Imaging of human vertebral surface using ultrasound RF data received at each element of probe for thoracic anesthesia

    Science.gov (United States)

    Takahashi, Kazuki; Taki, Hirofumi; Onishi, Eiko; Yamauchi, Masanori; Kanai, Hiroshi

    2017-07-01

    Epidural anesthesia is a common technique for perioperative analgesia and chronic pain treatment. Since ultrasonography is insufficient for depicting the human vertebral surface, most examiners apply epidural puncture by body surface landmarks on the back such as the spinous process and scapulae without any imaging, including ultrasonography. The puncture route to the epidural space at thoracic vertebrae is much narrower than that at lumber vertebrae, and therefore, epidural anesthesia at thoracic vertebrae is difficult, especially for a beginner. Herein, a novel imaging method is proposed based on a bi-static imaging technique by making use of the transmit beam width and direction. In an in vivo experimental study on human thoracic vertebrae, the proposed method succeeded in depicting the vertebral surface clearly as compared with conventional B-mode imaging and the conventional envelope method. This indicates the potential of the proposed method in visualizing the vertebral surface for the proper and safe execution of epidural anesthesia.

  14. Uncertainty analysis of point-by-point sampling complex surfaces using touch probe CMMs DOE for complex surfaces verification with CMM

    DEFF Research Database (Denmark)

    Barini, Emanuele Modesto; Tosello, Guido; De Chiffre, Leonardo

    2010-01-01

    The paper describes a study concerning point-by-point sampling of complex surfaces using tactile CMMs. A four factor, two level completely randomized factorial experiment was carried out, involving measurements on a complex surface configuration item comprising a sphere, a cylinder and a cone, co...

  15. Polymer dynamics near the surface and in the bulk of poly(tetrafluoroethylene) probed by zero-field muon-spin-relaxation spectroscopy.

    Science.gov (United States)

    McKenzie, Iain; Salman, Zaher; Giblin, Sean R; Han, Yun Yu; Leach, Gary W; Morenzoni, Elvezio; Prokscha, Thomas; Suter, Andreas

    2014-02-01

    The results of many experiments on polymers such as polystyrene indicate that the polymer chains near a free surface exhibit enhanced dynamics when compared with the bulk. We have investigated whether this is the case for poly(tetrafluoroethylene) (PTFE) by using zero-field muon-spin-relaxation spectroscopy to characterize a local probe, the F-Mu(+)-F state, which forms when spin-polarized positive muons are implanted in PTFE. Low-energy muons (implantation energies from 2.0 to 23.0 keV) were used to study the F-Mu(+)-F state between ∼ 23 and 191 nm from the free surface of PTFE. Measurements were also made with surface muons (4.1 MeV) where the mean implantation depth is on the order of ∼ 0.6 mm. The relaxation rate of the F-Mu(+)-F state up to ∼ 150 K was found to be significantly higher for muons implanted at 2.0 keV than for higher implantation energies, which suggests that the polymer chains in a region on the order of a few tens of nanometers from the free surface are more mobile than those in the bulk.

  16. Neutron study of in-plane skyrmions in MnSi thin films

    Science.gov (United States)

    Meynell, S. A.; Wilson, M. N.; Krycka, K. L.; Kirby, B. J.; Fritzsche, H.; Monchesky, T. L.

    2017-08-01

    The magnetic structure of the in-plane skyrmions in epitaxial MnSi/Si(111) thin films is probed in three dimensions by the combination of polarized neutron reflectometry (PNR) and small-angle neutron scattering (SANS). We demonstrate that skyrmions exist in a region of the phase diagram above a temperature of 10 K. PNR shows the skyrmions are confined to the middle of the film due to the potential well formed by the surface twists. However, SANS shows that there is considerable disorder within the plane indicating that the magnetic structure is a two-dimensional skyrmion glass.

  17. Probing the Surface Charge on the Basal Planes of Kaolinite Particles with High-Resolution Atomic Force Microscopy

    Science.gov (United States)

    2017-01-01

    High-resolution atomic force microscopy is used to map the surface charge on the basal planes of kaolinite nanoparticles in an ambient solution of variable pH and NaCl or CaCl2 concentration. Using DLVO theory with charge regulation, we determine from the measured force–distance curves the surface charge distribution on both the silica-like and the gibbsite-like basal plane of the kaolinite particles. We observe that both basal planes do carry charge that varies with pH and salt concentration. The silica facet was found to be negatively charged at pH 4 and above, whereas the gibbsite facet is positively charged at pH below 7 and negatively charged at pH above 7. Investigations in CaCl2 at pH 6 show that the surface charge on the gibbsite facet increases for concentration up to 10 mM CaCl2 and starts to decrease upon further increasing the salt concentration to 50 mM. The increase of surface charge at low concentration is explained by Ca2+ ion adsorption, while Cl– adsorption at higher CaCl2 concentrations partially neutralizes the surface charge. Atomic resolution imaging and density functional theory calculations corroborate these observations. They show that hydrated Ca2+ ions can spontaneously adsorb on the gibbsite facet of the kaolinite particle and form ordered surface structures, while at higher concentrations Cl– ions will co-adsorb, thereby changing the observed ordered surface structure. PMID:29140711

  18. Probing adsorption of DSPE-PEG2000 and DSPE-PEG5000 to the surface of felodipine and griseofulvin nanocrystals.

    Science.gov (United States)

    Rydberg, Hanna A; Yanez Arteta, Marianna; Berg, Staffan; Lindfors, Lennart; Sigfridsson, Kalle

    2016-08-20

    Nanosized formulations of poorly water-soluble drugs show great potential due to improved bioavailability. In order to retain colloidal stability, the nanocrystals need to be stabilized. Here we explore the use of the poly(ethylene glycol) (PEG) conjugated phospholipids DSPE-PEG2000 and DSPE-PEG5000 as stabilizers of felodipine and griseofulvin nanocrystals. Nanocrystal stability and physicochemical properties were examined and the interaction between the PEGylated lipids and the nanocrystal surface as well as a macroscopic model surface was investigated. Using quartz crystal microbalance with dissipation monitoring both mass adsorption and the thickness of the adsorbed layer were estimated. The results indicate that the PEGylated lipids are adsorbed as flat layers of around 1-3nm, and that DSPE-PEG5000 forms a thicker layer compared with DSPE-PEG2000. In addition, the mass adsorption to the drug crystals and the model surface are seemingly comparable. Furthermore, both DSPE-PEG2000 and DSPE-PEG5000 rendered stable drug nanocrystals, with a somewhat higher surface binding and stability seen for DSPE-PEG2000. These results suggest DSPE-PEG2000 and DSPE-PEG5000 as efficient nanocrystal stabilizers, with DSPE-PEG2000 giving a somewhat higher surface coverage and superior colloidal stability, whereas DSPE-PEG5000 shows a more extended structure that may have advantages for prolongation of circulation time in vivo and facilitation for targeting modifications. Copyright © 2016 Elsevier B.V. All rights reserved.

  19. Industrial applications of neutron diffraction

    International Nuclear Information System (INIS)

    Felcher, G.P.

    1989-01-01

    Neutron diffraction (or, to be more general, neutron scattering) is a most versatile and universal tool, which has been widely employed to probe the structure, the dynamics and the magnetism of condensed matter. Traditionally used for fundamental research in solid state physics, this technique more recently has been applied to problems of immediate industrial interest, as illustrated in examples covering the main fields of endeavour. 14 refs., 14 figs

  20. Site Averaged Neutron Soil Moisture: 1988 (Betts)

    Data.gov (United States)

    National Aeronautics and Space Administration — ABSTRACT: Site averaged product of the neutron probe soil moisture collected during the 1987-1989 FIFE experiment. Samples were averaged for each site, then averaged...