Science.gov

Sample records for reflected atomic particles

  1. Why Do We Believe that an Atom Is Colourless? Reflections about the Teaching of the Particle Model.

    ERIC Educational Resources Information Center

    Albanese, Alessandro; Vicentini, Matilde

    1997-01-01

    Highlights students' ideas about the particle model of matter and its use. Discusses the atomic model in teaching and the rules of the particle modeling game. Demonstrates how a complete understanding of the rules of the model construction yields guidelines for didactic practice. Focuses on problems connected with visual communication through…

  2. Atomic Particle Detection, Understanding the Atom Series.

    ERIC Educational Resources Information Center

    Hellman, Hal

    This booklet is one of the booklets in the "Understanding the Atom Series" published by the U. S. Atomic Energy Commission for high school science teachers and their students. The instruments used to detect both particles and electromagnetic radiation that emerge from the nucleus are described. The counters reviewed include ionization chambers,…

  3. Cold atom reflection from curved magnetic mirrors

    NASA Astrophysics Data System (ADS)

    Hughes, Ifan G.; Barton, P. A.; Boshier, M. G.; Hinds, Edward A.

    1997-05-01

    Multiple bounces of cold rubidium atoms have been observed for times up to one second in a trap formed by gravity and a 2 cm-diameter spherical mirror made from a sinusoidally magnetized floppy disk. We have studied the dynamics of the atoms bouncing in this trap from several different heights up to 40.5 mm and we conclude that the atoms are reflected specularly and with reflectivity 1.01(3). Slight roughness of the mirror is caused by harmonics in the magnetization of the surface and by discontinuities at the boundaries between recorded tracks. As the next step in this atom optics program we propose using a magnetic mirror to create a 2D atomic gas. We discuss how cold atoms can be loaded into the ground state of a static magnetic potential well that exists above the surface of the mirror as a consequence of the intermediate-field Zeeman effect.

  4. Atomic Coordination Reflects Peptide Immunogenicity

    PubMed Central

    Antipas, Georgios S. E.; Germenis, Anastasios E.

    2016-01-01

    We demonstrated that the immunological identity of variant peptides may be accurately predicted on the basis of atomic coordination of both unprotonated and protonated tertiary structures, provided that the structure of the native peptide (index) is known. The metric which was discovered to account for this discrimination is the coordination difference between the variant and the index; we also showed that increasing coordination difference in respect to the index was correlated to a correspondingly weakening immunological outcome of the variant. Additionally, we established that this metric quickly seizes to operate beyond the peptide scale, e.g., within a coordination shell inclusive of atoms up to a distance of 7 Å away from the peptide or over the entire pMHC-TCR complex. Analysis of molecular orbital interactions for a range of formal charges further revealed that the N-terminus of the agonists was always able to sustain a stable ammonium (NH3+) group which was consistently absent in antagonists. We deem that the presence of NH3+ constitutes a secondary observable with a biological consequence, signifying a change in T cell activation. While our analysis of protonated structures relied on the quantum chemical relaxation of the H species, the results were consistent across a wide range of peptide charge and spin polarization conditions. PMID:26793714

  5. Influence of realistic atom wall potentials in quantum reflection traps

    NASA Astrophysics Data System (ADS)

    Madroñero, Javier; Friedrich, Harald

    2007-02-01

    We study the influence of atom-surface interactions close to the surface on the confinement properties in a recently proposed model [A. Jurisch and H. Friedrich, Phys. Lett. A 349, 230 (2006)] for quantum reflection traps and test the reliability of the sharp-step approximation used there. Accurate numerical calculations show a dependence of the surviving particle fraction on characteristic potential lengths determined by the behavior of the interaction in the limits r→0 and r→∞ of the atom-surface distance r . For interactions dominated by the retarded potential proportional to 1/r4 we find that the simplified sharp-step potential reproduces the behavior of the trapped atoms well, both qualitatively and quantitatively.

  6. The albedo of particles in reflection nebulae

    NASA Technical Reports Server (NTRS)

    Rush, W. F.

    1974-01-01

    The relation between the apparent angular extent of a reflection nebula and the apparent magnitude of its illuminating star was reconsidered under a less restrictive set of assumptions. A computational technique was developed which permits the use of fits to the observed m-log a values to determine the albedo of particles composing reflection nebulae, providing only that a phase function and average optical thickness are assumed. Multiple scattering, anisotropic phase functions, and illumination by the general star field are considered, and the albedo of reflection nebular particles appears to be the same as that for interstellar particles in general. The possibility of continuous fluorescence contributions to the surface brightness is also considered.

  7. Solid Hydrogen Particles Analyzed for Atomic Fuels

    NASA Technical Reports Server (NTRS)

    Palaszewski, Bryan A.

    2001-01-01

    Solid hydrogen particles have been selected as a means of storing atomic propellants in future launch vehicles (refs. 1 to 2). In preparation for this, hydrogen particle formation in liquid helium was tested experimentally. These experiments were conducted to visually characterize the particles and to observe their formation and molecular transformations (aging) while in liquid helium. The particle sizes, molecular transformations, and agglomeration times were estimated from video image analyses. The experiments were conducted at the NASA Glenn Research Center in the Supplemental Multilayer Insulation Research Facility (SMIRF, ref. 3). The facility has a vacuum tank, into which the experimental setup was placed. The vacuum tank prevented heat leaks and subsequent boiloff of the liquid helium, and the supporting systems maintained the temperature and pressure of the liquid helium bath where the solid particles were created. As the operation of the apparatus was developed, the hydrogen particles were easily visualized. The figures (ref. 1) show images from the experimental runs. The first image shows the initial particle freezing, and the second image shows the particles after the small particles have agglomerated. The particles finally all clump, but stick together loosely. The solid particles tended to agglomerate within a maximum of 11 min, and the agglomerate was very weak. Because the hydrogen particles are buoyant in the helium, the agglomerate tends to compact itself into a flat pancake on the surface of the helium. This pancake agglomerate is easily broken apart by reducing the pressure above the liquid. The weak agglomerate implies that the particles can be used as a gelling agent for the liquid helium, as well as a storage medium for atomic boron, carbon, or hydrogen. The smallest particle sizes that resulted from the initial freezing experiments were about 1.8 mm. About 50 percent of the particles formed were between 1.8 to 4.6 mm in diameter. These very

  8. Characteristics of flows of energetic atoms reflected from metal targets during ion bombardment

    NASA Astrophysics Data System (ADS)

    Kuzmichev, A.; Perevertaylo, V.; Tsybulsky, L.; Volpian, O.

    2016-07-01

    Particle number and energy reflection coefficients for energetic neutralized gas ions (Ar and O atoms) backscattered from metal targets during ion bombardment have been calculated using TRIM code. The energy distributions of reflected atoms are computed, too, and their dependence on the primary ion energy and the angle of ion incidence is determined. The obtained data confirm the possibility of employing energetic atoms reflection for generation of high energy neutral beams and point out to take this phenomenon into account under analysis of the ion technology for coating deposition.

  9. Reflection of cold atoms by a cobalt single crystal

    NASA Astrophysics Data System (ADS)

    Rosenbusch, P.; Retter, J. A.; Hall, B. V.; Hinds, E. A.; Lison, F.; Haubrich, D.; Meschede, D.

    2000-05-01

    We have demonstrated that a cobalt single crystal can be used to make a remarkably smooth retro-reflector for cold paramagnetic atoms. The crystal is cut so that its surface lies in the (0001) plane and the atoms are reflected by the magnetic field above the surface due to the self-organized pattern of magnetic domains in the material. We find that the reflectivity for suitably polarized atoms exceeds 90% and may well be unity. We use the angular spread of a reflected atom cloud to measure the roughness of the mirror. We find that the angular variation of the equivalent hard reflecting surface is (3.1±0.3°)rms for atoms dropped onto the mirror from a height of 2 cm.

  10. Subnanometer Palladium Particles Synthesized by Atomic Layer Deposition

    SciTech Connect

    Feng, Hao P.; Libera, Joseph A.; Stair, Peter C.; Miller, Jeffrey T.; Elam, Jeffrey W.

    2011-06-03

    Monodispersed palladium nanoparticle catalysts were synthesized by atomic layer deposition (ALD) using alternating exposures of Pd hexafluoroacetylacetonate (Pd(hfac)₂) and formalin on an alumina support. The size of the ALD Pd particles could be tuned by adjusting the preparation conditions. Conventional ALD conditions produced Pd particles with an average size of 1.4 nm. Removal of surface hydroxyls from the alumina support by a chemical treatment using trimethyl aluminum (TMA) before performing Pd ALD led to nanoparticles larger than 2 nm. Ultrasmall (subnanometer) Pd particles were synthesized using low-temperature metal precursor exposures, followed by applying protective ALD alumina overcoats. The ALD Pd particles were characterized by transmission electron microscopy, extended X-ray absorption fine structure, and diffuse reflectance infrared Fourier transform spectroscopy techniques. The Pd loadings were measured by X-ray fluorescence. The catalytic performance of ALD Pd particles of different sizes was compared in the methanol decomposition reaction. The specific activity (normalized by Pd loading) of the ultrasmall Pd particles was higher than those of the larger particles. Considering the metal dispersion factor, the turnover frequency (TOF) of the ultrasmall Pd particles is comparable to that of the medium-sized (1.4 nm, on average) Pd particles synthesized under standard ALD conditions. The large Pd particles (>2 nm) are a factor of 2 less active than the smaller Pd particles.

  11. Reflection and Non-Reflection of Particle Wavepackets

    ERIC Educational Resources Information Center

    Cox, Timothy; Lekner, John

    2008-01-01

    Exact closed-form solutions of the time-dependent Schrodinger equation are obtained, describing the propagation of wavepackets in the neighbourhood of a potential. Examples given include zero reflection, total reflection and partial reflection of the wavepacket, for the sech[superscript 2]x/a, 1/x[superscript 2] and delta(x) potentials,…

  12. Photoionization of Endohedral Atoms: Collective, Reflective and Collateral Emissions

    SciTech Connect

    Chakraborty, Himadri S.; McCune, Matthew A.; Hopper, Dale E.; Madjet, Mohamed E.; Manson, Steven T.

    2009-12-03

    The photoionization properties of a fullerene-confined atom differ dramatically from that of an isolated atom. In the low energy region, where the fullerene plasmons are active, the electrons of the confined atom emerge through a collective channel carrying a significant chunk of plasmon with it. The photoelectron angular distribution of the confined atom however shows far lesser impact of the effect. At higher energies, the interference between two single-electron ionization channels, one directly from the atom and another reflected off the fullerene cage, producuces oscillatory cross sections. But for the outermost atomic level, which transfers some electrons to the cage, oscillations are further modulated by the collateral emission from the part of the atomic charge density transferred to the cage. These various modes of emissions are studied for the photoionization of Ar endohedrally confined in C{sub 60}.

  13. Quantum reflection: Focusing of hydrogen atoms with a concave mirror

    SciTech Connect

    Berkhout, J.J.; Luiten, O.J.; Setija, I.D.; Hijmans, T.W.; Mizusaki, T.; Walraven, J.T.M. Van der Waals Laboratorium, Universiteit van Amsterdam, Valckenierstraat 65/67, 1018 XE Amsterdam, The Netherlands )

    1989-10-16

    We use a concave spherical mirror to focus at 18-mm-diam beam of H atoms down to 0.5 mm. The mirror consists of a fused-quartz substrate polished to optical precision and coated with a liquid-{sup 4}He film to obtain high reflectivity. The temperature dependence of the focused beam intensity enables us to study the influence of the dynamic surface roughness on the reflection of the H atoms. Both zero-point fluctuations and thermal excitations turn out to be of importance. A monolayer of {sup 3}He does not significantly affect the results.

  14. Particle reflection and TFTR neutral beam diagnostics

    SciTech Connect

    Kamperschroer, J.H.; Grisham, L.R.; Kugel, H.W.; O`Connor, T.E.; Newman, R.A.; Stevenson, T.N.; von Halle, A.; Williams, M.D.

    1992-04-01

    Determination of two critical neutral beam parameters, power and divergence, are affected by the reflection of a fraction of the incident energy from the surface of the measuring calorimeter. On the TFTR Neutral Beam Test Stand, greater than 30% of the incident power directed at the target chamber calorimeter was unaccounted for. Most of this loss is believed due to reflection from the surface of the flat calorimeter, which was struck at a near grazing incidence (12{degrees}). Beamline calorimeters, of a ``V``-shape design, while retaining the beam power, also suffer from reflection effects. Reflection, in this latter case, artificially peaks the power toward the apex of the ``V``, complicating the fitting technique, and increasing the power density on axis by 10 to 20%; an effect of import to future beamline designers. Agreement is found between measured and expected divergence values, even with 24% of the incident energy reflected.

  15. Particle reflection and TFTR neutral beam diagnostics

    SciTech Connect

    Kamperschroer, J.H.; Grisham, L.R.; Kugel, H.W.; O'Connor, T.E.; Newman, R.A.; Stevenson, T.N.; von Halle, A.; Williams, M.D.

    1992-04-01

    Determination of two critical neutral beam parameters, power and divergence, are affected by the reflection of a fraction of the incident energy from the surface of the measuring calorimeter. On the TFTR Neutral Beam Test Stand, greater than 30% of the incident power directed at the target chamber calorimeter was unaccounted for. Most of this loss is believed due to reflection from the surface of the flat calorimeter, which was struck at a near grazing incidence (12{degrees}). Beamline calorimeters, of a V''-shape design, while retaining the beam power, also suffer from reflection effects. Reflection, in this latter case, artificially peaks the power toward the apex of the V'', complicating the fitting technique, and increasing the power density on axis by 10 to 20%; an effect of import to future beamline designers. Agreement is found between measured and expected divergence values, even with 24% of the incident energy reflected.

  16. Reflection of hydrogen atoms from the surface of superfluid helium

    SciTech Connect

    Tiesinga, E.; Stoof, H.T.C.; Verhaar, B.J. )

    1990-05-01

    We propose a new method for studying the reflection of a hydrogen atom from a superfluid-helium film. Starting from the narrow width of the reflected angular distribution recently found experimentally, we tentatively extrapolate to the extreme limit of low ripplon wave numbers in which the adiabatic or degenerate-internal-states approximation becomes valid. We obtain simple closed expressions for single- and multiple-ripplon processes, which do not require the integration of a Schroedinger equation for their evaluation and do not depend on the specific form of the potential.

  17. Exact simulation of polarized light reflectance by particle deposits

    NASA Astrophysics Data System (ADS)

    Ramezan Pour, B.; Mackowski, D. W.

    2015-12-01

    The use of polarimetric light reflection measurements as a means of identifying the physical and chemical characteristics of particulate materials obviously relies on an accurate model of predicting the effects of particle size, shape, concentration, and refractive index on polarized reflection. The research examines two methods for prediction of reflection from plane parallel layers of wavelength—sized particles. The first method is based on an exact superposition solution to Maxwell's time harmonic wave equations for a deposit of spherical particles that are exposed to a plane incident wave. We use a FORTRAN-90 implementation of this solution (the Multiple Sphere T Matrix (MSTM) code), coupled with parallel computational platforms, to directly simulate the reflection from particle layers. The second method examined is based upon the vector radiative transport equation (RTE). Mie theory is used in our RTE model to predict the extinction coefficient, albedo, and scattering phase function of the particles, and the solution of the RTE is obtained from adding—doubling method applied to a plane—parallel configuration. Our results show that the MSTM and RTE predictions of the Mueller matrix elements converge when particle volume fraction in the particle layer decreases below around five percent. At higher volume fractions the RTE can yield results that, depending on the particle size and refractive index, significantly depart from the exact predictions. The particle regimes which lead to dependent scattering effects, and the application of methods to correct the vector RTE for particle interaction, will be discussed.

  18. Improved atomic force microscopy cantilever performance by partial reflective coating.

    PubMed

    Schumacher, Zeno; Miyahara, Yoichi; Aeschimann, Laure; Grütter, Peter

    2015-01-01

    Optical beam deflection systems are widely used in cantilever based atomic force microscopy (AFM). Most commercial cantilevers have a reflective metal coating on the detector side to increase the reflectivity in order to achieve a high signal on the photodiode. Although the reflective coating is usually much thinner than the cantilever, it can still significantly contribute to the damping of the cantilever, leading to a lower mechanical quality factor (Q-factor). In dynamic mode operation in high vacuum, a cantilever with a high Q-factor is desired in order to achieve a lower minimal detectable force. The reflective coating can also increase the low-frequency force noise. In contact mode and force spectroscopy, a cantilever with minimal low-frequency force noise is desirable. We present a study on cantilevers with a partial reflective coating on the detector side. For this study, soft (≈0.01 N/m) and stiff (≈28 N/m) rectangular cantilevers were used with a custom partial coating at the tip end of the cantilever. The Q-factor, the detection and the force noise of fully coated, partially coated and uncoated cantilevers are compared and force distance curves are shown. Our results show an improvement in low-frequency force noise and increased Q-factor for the partially coated cantilevers compared to fully coated ones while maintaining the same reflectivity, therefore making it possible to combine the best of both worlds. PMID:26199849

  19. Highly reflective polymeric substrates functionalized utilizing atomic layer deposition

    SciTech Connect

    Zuzuarregui, Ana Gregorczyk, Keith E.; Coto, Borja; Ruiz de Gopegui, Unai; Barriga, Javier; Rodríguez, Jorge; Knez, Mato

    2015-08-10

    Reflective surfaces are one of the key elements of solar plants to concentrate energy in the receivers of solar thermal electricity plants. Polymeric substrates are being considered as an alternative to the widely used glass mirrors due to their intrinsic and processing advantages, but optimizing both the reflectance and the physical stability of polymeric mirrors still poses technological difficulties. In this work, polymeric surfaces have been functionalized with ceramic thin-films by atomic layer deposition. The characterization and optimization of the parameters involved in the process resulted in surfaces with a reflection index of 97%, turning polymers into a real alternative to glass substrates. The solution we present here can be easily applied in further technological areas where seemingly incompatible combinations of polymeric substrates and ceramic coatings occur.

  20. Effect of particle nonsphericity on bidirectional reflectance of cirrus clouds

    SciTech Connect

    Mishchenko, M.I.; Rossow, W.B.; Macke, A.; Lacis, A.A.

    1996-04-01

    This paper describes the use of the fractal ice particle method to study the differences in bidirectional reflectance caused by the differences in the single scattering phase functions of spherical water droplets and nonspherical ice crystals.

  1. The Influence of Particle Size on Infrared Reflectance Spectra

    SciTech Connect

    Myers, Tanya L.; Brauer, Carolyn S.; Su, Yin-Fong; Blake, Thomas A.; Johnson, Timothy J.; Richardson, Robert L.

    2014-06-13

    Reflectance spectra of solids are influenced by the absorption coefficient as well as the particle size and morphology. In the infrared, spectral features may be observed as either maxima or minima: in general, the upward-going peaks in the reflectance spectrum result from surface scattering, which are rays that have reflected from the surface without penetration, whereas downward-going peaks result from either absorption or volume scattering, i.e. rays that have penetrated into the sample or refracted into the sample interior and are not reflected. The light signal reflected from solids usually encompasses all these effects which include dependencies on particle size, morphology and sample density. This paper measures the reflectance spectra in the 1.3 – 16 micron range for various bulk materials that have a combination of strong and weak absorption bands in order to understand the effects on the spectral features as a function of the mean grain size of the sample. The bulk materials were ground with a mortar and pestle and then sieved to separate the samples into various size fractions: 0-45, 45-90, 90-180, 180-250, 250-500, and >500 microns. The directional-hemispherical spectra were recorded using a Fourier transform infrared spectrometer equipped with an integrating sphere to measure the reflectance for all of the particle-size fractions. We have studied both organic and inorganic materials, but this paper focuses on inorganic salts, NaNO3 in particular. Our studies clearly show that particle size has an enormous influence on the measured reflectance spectra for bulk materials and that successful identification requires sufficient representative reflectance data so as to include the particle size(s) of interest. Origins of the effects are discussed.

  2. Reflection Spectrum of Two Level Atoms by an Evanescent Laser Wave

    NASA Technical Reports Server (NTRS)

    Tan, Weihan; Li, Qingning

    1996-01-01

    An exact solution and numerical calculation of the reflection of two level atoms by atomic mirror are presented. The curve of reflection coefficient against Rabi frequency calculated shows some new features, and the physical machanism underlying is analyzed.

  3. Universal diffraction of atoms and molecules from a quantum reflection grating.

    PubMed

    Zhao, Bum Suk; Zhang, Weiqing; Schöllkopf, Wieland

    2016-03-01

    Since de Broglie's work on the wave nature of particles, various optical phenomena have been observed with matter waves of atoms and molecules. However, the analogy between classical and atom/molecule optics is not exact because of different dispersion relations. In addition, according to de Broglie's formula, different combinations of particle mass and velocity can give the same de Broglie wavelength. As a result, even for identical wavelengths, different molecular properties such as electric polarizabilities, Casimir-Polder forces, and dissociation energies modify (and potentially suppress) the resulting matter-wave optical phenomena such as diffraction intensities or interference effects. We report on the universal behavior observed in matter-wave diffraction of He atoms and He2 and D2 molecules from a ruled grating. Clear evidence for emerging beam resonances is observed in the diffraction patterns, which are quantitatively the same for all three particles and only depend on the de Broglie wavelength. A model, combining secondary scattering and quantum reflection, permits us to trace the observed universal behavior back to the peculiar principles of quantum reflection. PMID:27034979

  4. Universal diffraction of atoms and molecules from a quantum reflection grating

    PubMed Central

    Zhao, Bum Suk; Zhang, Weiqing; Schöllkopf, Wieland

    2016-01-01

    Since de Broglie’s work on the wave nature of particles, various optical phenomena have been observed with matter waves of atoms and molecules. However, the analogy between classical and atom/molecule optics is not exact because of different dispersion relations. In addition, according to de Broglie’s formula, different combinations of particle mass and velocity can give the same de Broglie wavelength. As a result, even for identical wavelengths, different molecular properties such as electric polarizabilities, Casimir-Polder forces, and dissociation energies modify (and potentially suppress) the resulting matter-wave optical phenomena such as diffraction intensities or interference effects. We report on the universal behavior observed in matter-wave diffraction of He atoms and He2 and D2 molecules from a ruled grating. Clear evidence for emerging beam resonances is observed in the diffraction patterns, which are quantitatively the same for all three particles and only depend on the de Broglie wavelength. A model, combining secondary scattering and quantum reflection, permits us to trace the observed universal behavior back to the peculiar principles of quantum reflection. PMID:27034979

  5. Infrared reflectance spectra: Effects of particle size, provenance and preparation

    SciTech Connect

    Su, Yin-Fong; Myers, Tanya L.; Brauer, Carolyn S.; Blake, Thomas A.; Forland, Brenda M.; Szecsody, James E.; Johnson, Timothy J.

    2014-09-22

    We have recently developed methods for making more accurate infrared total and diffuse directional - hemispherical reflectance measurements using an integrating sphere. We have found that reflectance spectra of solids, especially powders, are influenced by a number of factors including the sample preparation method, the particle size and morphology, as well as the sample origin. On a quantitative basis we have investigated some of these parameters and the effects they have on reflectance spectra, particularly in the longwave infrared. In the IR the spectral features may be observed as either maxima or minima: In general, upward-going peaks in the reflectance spectrum result from strong surface scattering, i.e. rays that are reflected from the surface without bulk penetration, whereas downward-going peaks are due to either absorption or volume scattering, i.e. rays that have penetrated or refracted into the sample interior and are not reflected. The light signals reflected from solids usually encompass all such effects, but with strong dependencies on particle size and preparation. This paper measures the reflectance spectra in the 1.3 – 16 micron range for various bulk materials that have a combination of strong and weak absorption bands in order to observe the effects on the spectral features: Bulk materials were ground with a mortar and pestle and sieved to separate the samples into various size fractions between 5 and 500 microns. The median particle size is demonstrated to have large effects on the reflectance spectra. For certain minerals we also observe significant spectral change depending on the geologic origin of the sample. All three such effects (particle size, preparation and provenance) result in substantial change in the reflectance spectra for solid materials; successful identification algorithms will require sufficient flexibility to account for these parameters.

  6. Laser steering of particle beams: Refraction and reflection ofparticle beams

    SciTech Connect

    Esarey, Eric; Katsouleas, T.; Mori, W.B.; Dodd, E.; Lee, S.; Hemker, R.; Clayton, C.; Joshi, C.

    1999-11-01

    The co-propagation of an intense particle beam with an ionizing laser beam in a working gas/plasma is considered. When the axes of the laser and particle beam are not aligned, then asymmetric plasma lensing results in a net dipole field acting on the particle beam. The particle beam can be steered or bent (as well as focused) by steering the laser. An analogy is made between the bending of the particle beam by collective effects at a plasma boundary and the refraction or reflection of light at an interface. This mechanism of particle steering may be of interest in applications for which permanent magnets are inconvenient of a fast turn on is required. 3-D particle-in-cell simulations and relevance to a recent experiment are discussed.

  7. Three-dimensional light trap for reflective particles

    DOEpatents

    Neal, Daniel R.

    1999-01-01

    A system for containing either a reflective particle or a particle having an index of refraction lower than that of the surrounding media in a three-dimensional light cage. A light beam from a single source illuminates an optics system and generates a set of at least three discrete focussed beams that emanate from a single exit aperture and focus on to a focal plane located close to the particle. The set of focal spots defines a ring that surrounds the particle. The set of focussed beams creates a "light cage" and circumscribes a zone of no light within which the particle lies. The surrounding beams apply constraining forces (created by radiation pressure) to the particle, thereby containing it in a three-dimensional force field trap. A diffractive element, such as an aperture multiplexed lens, or either a Dammann grating or phase element in combination with a focusing lens, may be used to generate the beams. A zoom lens may be used to adjust the size of the light cage, permitting particles of various sizes to be captured and contained.

  8. Three-dimensional light trap for reflective particles

    DOEpatents

    Neal, D.R.

    1999-08-17

    A system is disclosed for containing either a reflective particle or a particle having an index of refraction lower than that of the surrounding media in a three-dimensional light cage. A light beam from a single source illuminates an optics system and generates a set of at least three discrete focused beams that emanate from a single exit aperture and focus on to a focal plane located close to the particle. The set of focal spots defines a ring that surrounds the particle. The set of focused beams creates a ``light cage`` and circumscribes a zone of no light within which the particle lies. The surrounding beams apply constraining forces (created by radiation pressure) to the particle, thereby containing it in a three-dimensional force field trap. A diffractive element, such as an aperture multiplexed lens, or either a Dammann grating or phase element in combination with a focusing lens, may be used to generate the beams. A zoom lens may be used to adjust the size of the light cage, permitting particles of various sizes to be captured and contained. 10 figs.

  9. Multiple scattering and charged-particle - hydrogen-atom collisions

    NASA Technical Reports Server (NTRS)

    Franco, V.; Thomas, B. K.

    1979-01-01

    Glauber-approximation scattering amplitudes for charged-particle - hydrogen-atom elastic and inelastic collisions are derived directly in terms of the known particle-electron and particle-proton Coulomb scattering amplitudes and the known hydrogen-atom form factors. It is shown that the particle-hydrogen amplitude contains no single-scattering term. The double-scattering term is obtained as a two-dimensional integral in momentum space. It is demonstrated how the result can be used as the starting point for an alternative and relatively simple derivation, in closed form, of the Glauber particle-hydrogen scattering amplitude for transitions from the ground state to an arbitrary (nlm) state.

  10. SPARC: The Stored Particle Atomic Research Collaboration At FAIR

    SciTech Connect

    Stoehlker, Th.; Beyer, H. F.; Braeuning-Demian, A.; Brandau, C.; Herfurth, F.; Kozhuharov, Ch.; Kuehl, Th.; Liesen, D.; Litvinov, Yu.; Noertershaeuser, W.; Kester, O.; Quint, W.; Spillmann, U.; Winters, D.; Gumberidze, A.; Grisenti, R. E.; Petridis, N.; Hagmann, S.; Maertin, R.; Schramm, U.

    2011-06-01

    The future international accelerator Facility for Antiproton and Ion Research (FAIR) encompasses 4 scientific pillars containing at this time 14 approved technical proposals worked out by more than 2000 scientists from all over the world. They offer a wide range of new and challenging opportunities for atomic physics research in the realm of highly-charged heavy ions and exotic nuclei. As one of the backbones of the Atomic, Plasma Physics and Applications (APPA) pillar, the Stored Particle Atomic Physics Research Collaboration (SPARC) has organized tasks and activities in various working groups for which we will present a concise survey on their current status.

  11. Analog simulation of Weyl particles with cold atoms

    NASA Astrophysics Data System (ADS)

    Suchet, Daniel; Rabinovic, Mihail; Reimann, Thomas; Kretschmar, Norman; Sievers, Franz; Salomon, Christophe; Lau, Johnathan; Goulko, Olga; Lobo, Carlos; Chevy, Frédéric

    2016-04-01

    In this letter we report on a novel approach to study the dynamics of harmonically confined Weyl particles using magnetically trapped fermionic atoms. We find that after a kick of its center of mass, the system relaxes towards a steady state even in the absence of interactions, in stark contrast with massive particles which would oscillate without damping. Remarkably, the equilibrium distribution is non-Boltzmann, exhibiting a strong anisotropy which we study both numerically and experimentally.

  12. Interactions of satellite-speed helium atoms with satellite surfaces. 2: Energy distributions of reflected helium atoms

    NASA Technical Reports Server (NTRS)

    Liu, S. M.; Knuth, E. L.

    1976-01-01

    Energy transfer in collisions of satellite-speed (7,000 m/sec) helium atoms with a cleaned 6061-T6 satellite-type aluminum surface was investigated using the molecular-beam technique. The amount of energy transferred was determined from the measured energy of the molecular-beam and the measured spatial and energy distributions of the reflected atoms. Spatial distributions of helium atoms scattered from a 6061-T6 aluminum surface were measured. The scattering pattern exhibits a prominent backscattering, probably due to the gross surface roughness and/or the relative lattice softness of the aluminum surface. Energy distributions of reflected helium atoms from the same surface were measured for six different incidence angles. For each incidence angle, distributions were measured at approximately sixty scattering positions. At a given scattering position, the energy spectra of the reflected helium atoms and the background gas were obtained using the retarding-field energy analyzer.

  13. Measurement of particle speed through optical reflective sensing

    SciTech Connect

    McCardle, J.

    1993-12-31

    Two methods determine the speed of 3 m glass spheres using optical reflective sensors embedded in a micro-processor system. The first method, which will be referred to as the one pulse method, is sensitive to particle size and shape. The pulse width of a detected particle is measured and normalized by a shape correction factor resulting in a speed estimate. Three models are developed to correct for effects due to particle shape and light scattering inhomogeneities. The second method, which will be referred to as the two pulse method, measures individual particle velocity components independent of size and shape with two detectors spaced a known distance apart. This distance is divided by the delay between the two detector output pulses to determine speed. A by-product of both methods is a localized particle flux. The microprocessor subsystem automates the pulse detection, timing, velocity calculation and display which are accomplished by the micro-processor subsystem. In the laboratory, a chute is used to generate particle flows with different characteristics. The detection system is tested in the chute for two different flows. A mechanical speed measurement is used for comparison to the one pulse method. The one pulse method is used for comparison to the two pulse method. A mechanical average mass flow rate is used for comparison to the flow rate measurements. Results obtained indicate that the one pulse method estimate is within 4% of the mechanically measured speed. The two pulse method gives erroneous results, in this application, due to detector separation distance greater than 3 particle diameters. The mass flow rate measurement gives erroneous results due to detector head placement. Solutions are proposed to correct discrepancies.

  14. Big Bang Day : The Great Big Particle Adventure - 1. Atom

    SciTech Connect

    2009-10-08

    In this series, comedian and physicist Ben Miller asks the CERN scientists what they hope to find. The notion of atoms dates back to Greek philosophers who sought a natural mechanical explanation of the Universe, as opposed to a divine one. The existence what we call chemical atoms, the constituents of all we see around us, wasn't proved until a hundred years ago, but almost simultaneously it was realised these weren't the indivisible constituents the Greeks envisaged. Much of the story of physics since then has been the ever-deeper probing of matter until, at the end of the 20th century, a complete list of fundamental ingredients had been identified, apart from one, the much discussed Higgs particle. In this programme, Ben finds out why this last particle is so pivotal, not just to atomic theory, but to our very existence - and how hopeful the scientists are of proving its existence.

  15. Ionization of Atoms by Slow Heavy Particles, Including Dark Matter

    NASA Astrophysics Data System (ADS)

    Roberts, B. M.; Flambaum, V. V.; Gribakin, G. F.

    2016-01-01

    Atoms and molecules can become ionized during the scattering of a slow, heavy particle off a bound electron. Such an interaction involving leptophilic weakly interacting massive particles (WIMPs) is a promising possible explanation for the anomalous 9 σ annual modulation in the DAMA dark matter direct detection experiment [R. Bernabei et al., Eur. Phys. J. C 73, 2648 (2013)]. We demonstrate the applicability of the Born approximation for such an interaction by showing its equivalence to the semiclassical adiabatic treatment of atomic ionization by slow-moving WIMPs. Conventional wisdom has it that the ionization probability for such a process should be exponentially small. We show, however, that due to nonanalytic, cusplike behavior of Coulomb functions close to the nucleus this suppression is removed, leading to an effective atomic structure enhancement. We also show that electron relativistic effects actually give the dominant contribution to such a process, enhancing the differential cross section by up to 1000 times.

  16. Ionization of Atoms by Slow Heavy Particles, Including Dark Matter.

    PubMed

    Roberts, B M; Flambaum, V V; Gribakin, G F

    2016-01-15

    Atoms and molecules can become ionized during the scattering of a slow, heavy particle off a bound electron. Such an interaction involving leptophilic weakly interacting massive particles (WIMPs) is a promising possible explanation for the anomalous 9σ annual modulation in the DAMA dark matter direct detection experiment [R. Bernabei et al., Eur. Phys. J. C 73, 2648 (2013)]. We demonstrate the applicability of the Born approximation for such an interaction by showing its equivalence to the semiclassical adiabatic treatment of atomic ionization by slow-moving WIMPs. Conventional wisdom has it that the ionization probability for such a process should be exponentially small. We show, however, that due to nonanalytic, cusplike behavior of Coulomb functions close to the nucleus this suppression is removed, leading to an effective atomic structure enhancement. We also show that electron relativistic effects actually give the dominant contribution to such a process, enhancing the differential cross section by up to 1000 times. PMID:26824537

  17. Big Bang Day : The Great Big Particle Adventure - 1. Atom

    ScienceCinema

    None

    2011-04-25

    In this series, comedian and physicist Ben Miller asks the CERN scientists what they hope to find. The notion of atoms dates back to Greek philosophers who sought a natural mechanical explanation of the Universe, as opposed to a divine one. The existence what we call chemical atoms, the constituents of all we see around us, wasn't proved until a hundred years ago, but almost simultaneously it was realised these weren't the indivisible constituents the Greeks envisaged. Much of the story of physics since then has been the ever-deeper probing of matter until, at the end of the 20th century, a complete list of fundamental ingredients had been identified, apart from one, the much discussed Higgs particle. In this programme, Ben finds out why this last particle is so pivotal, not just to atomic theory, but to our very existence - and how hopeful the scientists are of proving its existence.

  18. Reflective particle technology for identification of critical components

    SciTech Connect

    Tolk, K M

    1992-01-01

    Reflective Particle Tags were developed for uniquely identifying individual strategic weapons that would be counted in order to verify arms control treaties. These tags were designed to be secure from copying and transfer even after being lift under the control of a very determined adversary for a number of years. This paper discusses how this technology can be applied in other applications requiring confidence that a piece of equipment, such as a seal or a component of a secure, has not been replaced with a similar item. The hardware and software needed to implement this technology is discussed, and guidelines for the sign of systems that rely on these or similar randomly formed features for security applications are presented. Substitution of identical components is one of the easiest ways to defeat security seals, secure containers, verification instrumentation, and similar equipment. This technology, when properly applied, provides a method to counter this defeat scenario. This paper presents a method for uniquely identifying critical security related equipment. Guidelines for implementing identification systems based on reflective particles or similar random features without compromising their intrinsic security are discussed.

  19. Atomic Bose-Hubbard Systems with Single-Particle Control

    NASA Astrophysics Data System (ADS)

    Preiss, Philipp Moritz

    Experiments with ultracold atoms in optical lattices provide outstanding opportunities to realize exotic quantum states due to a high degree of tunability and control. In this thesis, I present experiments that extend this control from global parameters to the level of individual particles. Using a quantum gas microscope for 87Rb, we have developed a single-site addressing scheme based on digital amplitude holograms. The system self-corrects for aberrations in the imaging setup and creates arbitrary beam profiles. We are thus able to shape optical potentials on the scale of single lattice sites and control the dynamics of individual atoms. We study the role of quantum statistics and interactions in the Bose-Hubbard model on the fundamental level of two particles. Bosonic quantum statistics are apparent in the Hong-Ou-Mandel interference of massive particles, which we observe in tailored double-well potentials. These underlying statistics, in combination with tunable repulsive interactions, dominate the dynamics in single- and two-particle quantum walks. We observe highly coherent position-space Bloch oscillations, bosonic bunching in Hanbury Brown-Twiss interference and the fermionization of strongly interacting bosons. Many-body states of indistinguishable quantum particles are characterized by large-scale spatial entanglement, which is difficult to detect in itinerant systems. Here, we extend the concept of Hong-Ou-Mandel interference from individual particles to many-body states to directly quantify entanglement entropy. We perform collective measurements on two copies of a quantum state and detect entanglement entropy through many-body interference. We measure the second order Renyi entropy in small Bose-Hubbard systems and detect the buildup of spatial entanglement across the superfluid-insulator transition. Our experiments open new opportunities for the single-particle-resolved preparation and characterization of many-body quantum states.

  20. A theoretical investigation of the origins of atoms and sub-atomic particles

    NASA Astrophysics Data System (ADS)

    Derow, Catherine

    2015-03-01

    It seems the universe was at some very early stage shortwave energy. When the universe cooled some of this became matter, perhaps best thought of as waves confined into quanta. The change into longer wavelengths, if we think of the wavelengths of the particles that make up atoms when emitted as radioactivity, with different properties was presumably brought about by this cooling. In atoms these quantized waves are further confined by electrostatic forces and perhaps other forces. It seems that the electrostatic forces caused the coalescence of neutrons and electrons into atoms, with neutrons being there to keep like charges in the nucleus from like charges i.e., protons, and maybe providing some kind of mass force in the atom. It may be the further cooling of the universe allowed larger atoms than hydrogen to form later as well as having allowed the electrostatic forces to cause the formation of the first atoms. Note the sheer explosive forces present at early stages may have also prevented atom formation and later relative stability allowed this process to take place.

  1. Reflection of a slow cesium atomic beam from a naturally magnetized Nd-Fe-B surface

    NASA Astrophysics Data System (ADS)

    Lison, F.; Haubrich, D.; Schuh, P.; Meschede, D.

    We have demonstrated the partly directed reflection of a slow cesium atomic beam by using the natural magnetic stray field above a Nd-Fe-B surface. From these experiments we determine the reflectivity and a minimum value for the magnetic stray field directly at the surface.

  2. Continuous production of nanostructured particles using spatial atomic layer deposition

    SciTech Connect

    Ommen, J. Ruud van Kooijman, Dirkjan; Niet, Mark de; Talebi, Mojgan; Goulas, Aristeidis

    2015-03-15

    In this paper, the authors demonstrate a novel spatial atomic layer deposition (ALD) process based on pneumatic transport of nanoparticle agglomerates. Nanoclusters of platinum (Pt) of ∼1 nm diameter are deposited onto titania (TiO{sub 2}) P25 nanoparticles resulting to a continuous production of an active photocatalyst (0.12–0.31 wt. % of Pt) at a rate of about 1 g min{sup −1}. Tuning the precursor injection velocity (10–40 m s{sup −1}) enhances the contact between the precursor and the pneumatically transported support flows. Decreasing the chemisorption temperature (from 250 to 100 °C) results in more uniform distribution of the Pt nanoclusters as it decreases the reaction rate as compared to the rate of diffusion into the nanoparticle agglomerates. Utilizing this photocatalyst in the oxidation reaction of Acid Blue 9 showed a factor of five increase of the photocatalytic activity compared to the native P25 nanoparticles. The use of spatial particle ALD can be further expanded to deposition of nanoclusters on porous, micron-sized particles and to the production of core–shell nanoparticles enabling the robust and scalable manufacturing of nanostructured powders for catalysis and other applications.

  3. Laser cooling and trapping of atomic particles. (Latest citations from the NTIS bibliographic database). Published Search

    SciTech Connect

    Not Available

    1994-12-01

    The bibliography contains citations concerning theory and experiments on laser cooling and laser trapping of neutral atoms and atomic ions. Atoms and ions are cooled by laser radiation pressure to very low Kelvin temperatures and confined in electromagnetic traps of very high density. Atomic particles cover sodium atoms, mercury ions, beryllium ions, magnesium ions, and hydrogen. Citations discuss applications in high performance spectroscopy, atomic clocks, microwave and optical frequency standards, relativistic neutral particle beam weapons, exotic fuels, cooling of electron beams, and space propulsion. (Contains a minimum of 204 citations and includes a subject term index and title list.)

  4. Laser cooling and trapping of atomic particles. (Latest citations from the NTIS bibliographic database). Published Search

    SciTech Connect

    1994-02-01

    The bibliography contains citations concerning theory and experiments on laser cooling and laser trapping of neutral atoms and atomic ions. Atoms and ions are cooled by laser radiation pressure to very low Kelvin temperatures and confined in electromagnetic traps of very high density. Atomic particles cover sodium atoms, mercury ions, beryllium ions, magnesium ions, and hydrogen. Citations discuss applications in high performance spectroscopy, atomic clocks, microwave and optical frequency standards, relativistic neutral particle beam weapons, exotic fuels, cooling of electron beams, and space propulsion. (Contains a minimum of 185 citations and includes a subject term index and title list.)

  5. Laser cooling and trapping of atomic particles. (Latest citations from the NTIS data base). Published Search

    SciTech Connect

    Not Available

    1992-04-01

    The bibliography contains citations concerning theory and experiments on laser cooling and laser trapping of neutral atoms and atomic ions. Atoms and ions are cooled by laser radiation pressure to very low Kelvin temperatures and confined in electromagnetic traps of very high density. Atomic particles discussed include sodium atoms, mercury ions, beryllium ions, magnesium ions, and hydrogen. Applications for high performance spectroscopy, atomic clocks, microwave and optical frequency standards, relativistic neutral particle beam weapons, exotic fuels, cooling of electron beams, and space propulsion are examined. (Contains a minimum of 151 citations and includes a subject term index and title list.)

  6. Independent-particle models for light negative atomic ions

    NASA Technical Reports Server (NTRS)

    Ganas, P. S.; Talman, J. D.; Green, A. E. S.

    1980-01-01

    For the purposes of astrophysical, aeronomical, and laboratory application, a precise independent-particle model for electrons in negative atomic ions of the second and third period is discussed. The optimum-potential model (OPM) of Talman et al. (1979) is first used to generate numerical potentials for eight of these ions. Results for total energies and electron affinities are found to be very close to Hartree-Fock solutions. However, the OPM and HF electron affinities both depart significantly from experimental affinities. For this reason, two analytic potentials are developed whose inner energy levels are very close to the OPM and HF levels but whose last electron eigenvalues are adjusted precisely with the magnitudes of experimental affinities. These models are: (1) a four-parameter analytic characterization of the OPM potential and (2) a two-parameter potential model of the Green, Sellin, Zachor type. The system O(-) or e-O, which is important in upper atmospheric physics is examined in some detail.

  7. Effects of particle size on bidirectional reflectance factor measurements from particulate surfaces.

    PubMed

    Sun, Zhongqiu; Lv, Yunfeng; Tong, Zhijun

    2016-03-21

    The bidirectional reflectance factor (BRF) is commonly used to study the structure of a particulate surface based on photometric measurements. In this paper, we describe the bidirectional reflectance factor distribution of natural particulate surfaces with particles sizes varying from 0.15 mm to 0.9 mm. Two types of natural particulate surfaces (one with low reflectance and the other with moderate reflectance) were measured at visible and near-infrared wavelengths using the Northeast Normal University Laboratory Goniospectrometer System (NENULGS). Both the BRFs and anisotropic reflectance factors (ARFs) at selected wavelengths were compared with previously published results to verify the accuracy of our measurements, and we also quantitatively analyzed the effects of particle size on the BRF. It was found that the maximum reflectance difference, which was more distinct for the low-reflectance samples, between particulate surfaces with particle sizes of 0.15 mm and 0.9 mm occurred in the forward scattering direction for all samples, and the value of this maximum difference reached 59% for the low-reflectance samples. Then, we conducted a test of a photometric model to determine which parameters could be confidently linked to the surfaces' reflectance behavior. The inverted parameters were compared with the known physical parameters of our samples, such as the particle size. We found that the single-scattering albedo could be empirically used to determine the particle sizes of our samples when measurements of particulate surfaces with different particle sizes were performed under the same incidence conditions and with wide viewing angles. The potential applications of our results appear very promising for empirically resolving the spatial distribution of particle size within a given particulate sample as well as for deepening our understanding of the scattering properties of particulate media. PMID:27136881

  8. Determination of the coefficient of reflection of metastable argon atoms from the discharge tube wall

    SciTech Connect

    Grigorian, G. M.; Dyatko, N. A.; Kochetov, I. V.

    2015-05-15

    Radial profiles of the density of metastable atoms Ar({sup 3}P{sub 2}) in the positive column of a dc glow discharge in argon were measured. Gas-discharge glass tubes with clean inner surfaces and surfaces covered with a carbonitride or carbon film were utilized. The parameters of the discharge plasma under experimental conditions were calculated in the framework of a one-dimensional (along the tube radius) discharge model. The coefficient K of reflection of Ar({sup 3}P{sub 2}) atoms from the tube wall was estimated by comparing the measured and calculated density profiles. It is found that, for a clean tube wall, the coefficient of reflection is K = 0.4 ± 0.2, whereas for a wall covered with a carbonitride or carbon film, it is K < 0.2.

  9. OBSERVATIONAL EVIDENCE ON THE PRESENCE OF AN OUTER REFLECTING BOUNDARY IN SOLAR ENERGETIC PARTICLE EVENTS

    SciTech Connect

    Tan, Lun C.; Reames, Donald V.; Ng, Chee K.; Saloniemi, Oskari; Wang Linghua

    2009-08-20

    We have focused primarily on the 2001 September 24 solar energetic particle (SEP) event to verify previous indications of the presence of an outer reflecting boundary of SEPs. By using energetic electron and ion data obtained from multi-spacecraft observations, we have identified a collimated particle beam consisting of reflected particles returning from an outer boundary. The peak of reflected particles appears before the arrival of particles at 90 deg. pitch angle. In addition, an onset time analysis is carried out in order to determine parameters characterizing the boundary. Our analysis suggests that the presence of a counter-streaming particle beam with a deep depression at {approx}90 deg. pitch angle during the onset phase is evidence for a nearby reflecting boundary. We have compared this property in the SEP events of 2002 April 21 and August 24. A reflecting boundary that blocks a flux tube is important in space weather forecasting since it can cause the 'reservoir' effect that may enhance the intensity and duration of high-energy particles.

  10. SIMULATION OF ENERGETIC NEUTRAL ATOMS FROM SOLAR ENERGETIC PARTICLES

    SciTech Connect

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

    2014-10-01

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

  11. Quantitative reflectance spectra of solid powders as a function of particle size.

    PubMed

    Myers, Tanya L; Brauer, Carolyn S; Su, Yin-Fong; Blake, Thomas A; Tonkyn, Russell G; Ertel, Alyssa B; Johnson, Timothy J; Richardson, Robert L

    2015-05-20

    We have recently developed vetted methods for obtaining quantitative infrared directional-hemispherical reflectance spectra using a commercial integrating sphere. In this paper, the effects of particle size on the spectral properties are analyzed for several samples such as ammonium sulfate, calcium carbonate, and sodium sulfate as well as one organic compound, lactose. We prepared multiple size fractions for each sample and confirmed the mean sizes using optical microscopy. Most species displayed a wide range of spectral behavior depending on the mean particle size. General trends of reflectance versus particle size are observed such as increased albedo for smaller particles: for most wavelengths, the reflectivity drops with increased size, sometimes displaying a factor of 4 or more drop in reflectivity along with a loss of spectral contrast. In the longwave infrared, several species with symmetric anions or cations exhibited reststrahlen features whose amplitude was nearly invariant with particle size, at least for intermediate and large size sample fractions: that is, ≳150  μm. Trends of other types of bands (Christiansen minima, transparency features) are also investigated as well as quantitative analysis of the observed relationship between reflectance versus particle diameter. PMID:26192525

  12. Ion-acoustic shocks with reflected ions: modelling and particle-in-cell simulations

    NASA Astrophysics Data System (ADS)

    Liseykina, T. V.; Dudnikova, G. I.; Vshivkov, V. A.; Malkov, M. A.

    2015-10-01

    > Non-relativistic collisionless shock waves are widespread in space and astrophysical plasmas and are known as efficient particle accelerators. However, our understanding of collisionless shocks, including their structure and the mechanisms whereby they accelerate particles, remains incomplete. We present here the results of numerical modelling of an ion-acoustic collisionless shock based on the one-dimensional kinetic approximation for both electrons and ions with a real mass ratio. Special emphasis is paid to the shock-reflected ions as the main driver of shock dissipation. The reflection efficiency, the velocity distribution of reflected particles and the shock electrostatic structure are studied in terms of the shock parameters. Applications to particle acceleration in geophysical and astrophysical shocks are discussed.

  13. Model solution for volume reflection of relativistic particles in a bent crystal

    SciTech Connect

    Bondarenco, M. V.

    2010-10-15

    For volume reflection process in a bent crystal, exact analytic expressions for positively- and negatively-charged particle trajectories are obtained within a model of parabolic continuous potential in each interplanar interval, with the neglect of incoherent multiple scattering. In the limit of the crystal bending radius greatly exceeding the critical value, asymptotic formulas are obtained for the particle mean deflection angle in units of Lindhard's critical angle, and for the final beam profile. Volume reflection of negatively charged particles is shown to contain effects of rainbow scattering and orbiting, whereas with positively charged particles none of these effects arise within the given model. The model predictions are compared with experimental results and numerical simulations. Estimates of the volume reflection mean angle and the final beam profile robustness under multiple scattering are performed.

  14. Agglomeration rate and action forces between atomized particles of agglomerator and inhaled-particles from coal combustion.

    PubMed

    Wei, Feng; Zhang, Jun-ying; Zheng, Chu-guang

    2005-01-01

    In order to remove efficiently haled-particles emissions from coal combustions, a new way was used to put forward the process of agglomeration and the atomization was produced by the nozzle and then sprayed into the flue before precipitation devices of power station boiler in order to make inhaled-particles agglomerate into bigger particles, which can be easily removed but not change existing running conditions of boiler. According to this idea, a model is set up to study agglomeration rate and effect forces between fly ash inhaled-particles and atomized agglomerator particles. The developed agglomeration rate was expressed by relative particle number decreasing speed per unit volume. The result showed that viscosity force and flow resistance force give main influences on agglomeration effect of inhaled-particles, while springiness force and gravity have little effect on agglomeration effect of theirs. Factors influencing the agglomeration rate and effect forces are studied, including agglomerator concentration, agglomerator flux and agglomerator density, atomized-particles diameters and inhaled-particles diameter and so on. PMID:16295917

  15. Fresnel reflectance in refractive index estimation of light scattering solid particles in immersion liquid

    NASA Astrophysics Data System (ADS)

    Räty, J.; Niskanen, I.; Peiponen, K.-E.

    2010-06-01

    The refractive index of homogenous particle population can be determined by the so-called immersion liquid method. The idea is to find a known liquid whose refractive index matches the index of the particles. We report on a method that simultaneously obtains the refractive index of particles and that of the immersion liquid. It is based on a system using internal light reflection and Fresnel's theory. The method includes a series of straightforward reflection measurements and a fitting procedure. The validity of the method was tested with CaF2 particles. The method has applications within scientific studies of microparticles and nanoparticles or micro-organism in suspensions. It can be also be utilized in industry for the detection of the refractive index of products involving particles for the purpose of improvement of product quality.

  16. Layered periodic disperse structures of spherical alumina particles: Coherent transmittance and reflectance spectra

    NASA Astrophysics Data System (ADS)

    Miskevich, Alexander A.; Loiko, Valery A.

    2014-03-01

    Coherent transmittance and reflectance spectra of multilayers consisting of plane-parallel monolayers of spherical monodisperse alumina particles are investigated. In the quasicrystalline approximation (QCA) of the statistical theory of multiple scattering of waves the coherent transmission and reflection coefficients of constituent monolayers are computed. Using the coefficients obtained, the transmittance and reflectance of the multilayers are calculated using the transfer matrix method (TMM) within the wavelength range of 0.3-2.0 μm. Multilayers consisting of close-to-regularly-packed monolayers (planar photonic crystals with nonideal lattice) and partially-ordered monolayers of particles are investigated. Three types of coherent transmittance minima caused by the wave interference are singled out. The spectral positions and values of these minima are determined by optical constants, size, concentration, and the arrangement of particles in a monolayer, as well as by the spacing between the monolayer and their thicknesses. The results are in good agreement with the known theoretical and experimental data. They can be used to solve the problem of a lattice quality control in photonic crystals. Coherent transmittance and reflectance spectra of a system consisting of a glass plate coated with monolayers of spherical alumina particles are analyzed. Monolayer parameters for creating antireflection coatings, diffuse light scattering structures, and filters of transmitted and reflected light are considered. The approach developed can be applied to disperse structures of isotropic particles of other materials.

  17. Hydrodynamics of shock waves with reflected particles. I. Rankine-Hugoniot relations and stationary solutions

    SciTech Connect

    Dasgupta, B.; Burrows, R.; Zank, G. P.; Webb, G. M.

    2006-08-15

    In this work we investigate how reflected particles modify the Rankine-Hugoniot (RH) relations in a simple hydrodynamical framework. It is assumed that the ions are specularly reflected by the cross-shock potential. For simplicity, an exactly perpendicular shock is assumed, thus other reflection mechanisms, such as magnetic mirroring, can be neglected. Momentum and energy terms are introduced to model reflected particles at the shock and the RH conditions are examined using a geometrical entropy condition to distinguish the physically relevant states. Although such shocks have some common features with combustion shocks within a narrow range of reflection parameters, for a wide range of reflection parameters, particularly for highly oblique shocks, Chapman-Jouguet solutions do not exist. It is conjectured that these shocks comprise a distinct class. Decelerated solutions of the RH conditions are shown to exist only under specific conditions for shocks with reflected particles. Velocity flows both parallel and oblique to the perpendicular shock (with respect to an upstream magnetic field) are considered and found to be strongly sheared.

  18. Launch Vehicle Performance with Solid Particle Feed Systems for Atomic Propellants

    NASA Technical Reports Server (NTRS)

    Palaszewski, Bryan

    1998-01-01

    An analysis of launch vehicle Gross Liftoff Weight (GLOW) using high energy density atomic propellants with solid particle feed systems was conducted. The analyses covered several propellant combinations, including atoms of aluminum (Al), boron (B). carbon (C), and hydrogen (H) stored in a solid cryogenic particle, with a cryogenic liquid as the carrier fluid. Several different weight percents (wt%) for the liquid carrier were investigated and the gross lift off weight (GLOW) of the vehicles using the solid particle feed systems were compared with a conventional 02/H2 propellant vehicle. The potential benefits and effects of feed systems using solid particles in a liquid cryogenic fluid are discussed.

  19. A High-Reflectivity, Ambient-Stable Graphene Mirror for Neutral Atomic and Molecular Beams

    SciTech Connect

    Sutter, P.; Minniti, M.; Albrecht, P.; Farias, D.; Miranda, R.; Sutter, E.

    2011-11-21

    We report a He and H{sub 2} diffraction study of graphene-terminated Ru(0001) thin films grown epitaxially on c-axis sapphire. Even for samples exposed for several weeks to ambient conditions, brief annealing in ultrahigh vacuum restored extraordinarily high specular reflectivities for He and H{sub 2} beams (23% and 7% of the incident beam, respectively). The quality of the angular distributions recorded with both probes exceeds the one obtained from in-situ prepared graphene on Ru(0001) single crystals. Our results for graphene-terminated Ru thin films represent a significant step toward ambient tolerant, high-reflectivity curved surface mirrors for He-atom microscopy.

  20. Diffuse reflectance infrared spectroscopic identification of dispersant/particle bonding mechanisms in functional inks.

    PubMed

    Deiner, L Jay; Farjami, Elaheh

    2015-01-01

    In additive manufacturing, or 3D printing, material is deposited drop by drop, to create micron to macroscale layers. A typical inkjet ink is a colloidal dispersion containing approximately ten components including solvent, the nano to micron scale particles which will comprise the printed layer, polymeric dispersants to stabilize the particles, and polymers to tune layer strength, surface tension and viscosity. To rationally and efficiently formulate such an ink, it is crucial to know how the components interact. Specifically, which polymers bond to the particle surfaces and how are they attached? Answering this question requires an experimental procedure that discriminates between polymer adsorbed on the particles and free polymer. Further, the method must provide details about how the functional groups of the polymer interact with the particle. In this protocol, we show how to employ centrifugation to separate particles with adsorbed polymer from the rest of the ink, prepare the separated samples for spectroscopic measurement, and use Diffuse Reflectance Fourier Transform Infrared Spectroscopy (DRIFTS) for accurate determination of dispersant/particle bonding mechanisms. A significant advantage of this methodology is that it provides high level mechanistic detail using only simple, commonly available laboratory equipment. This makes crucial data available to almost any formulation laboratory. The method is most useful for inks composed of metal, ceramic, and metal oxide particles in the range of 100 nm or greater. Because of the density and particle size of these inks, they are readily separable with centrifugation. Further, the spectroscopic signatures of such particles are easy to distinguish from absorbed polymer. The primary limitation of this technique is that the spectroscopy is performed ex-situ on the separated and dried particles as opposed to the particles in dispersion. However, results from attenuated total reflectance spectra of the wet separated

  1. Solid Hydrogen Experiments for Atomic Propellants: Particle Formation, Imaging, Observations, and Analyses

    NASA Technical Reports Server (NTRS)

    Palaszewski, Bryan

    2005-01-01

    This report presents particle formation observations and detailed analyses of the images from experiments that were conducted on the formation of solid hydrogen particles in liquid helium. Hydrogen was frozen into particles in liquid helium, and observed with a video camera. The solid hydrogen particle sizes and the total mass of hydrogen particles were estimated. These newly analyzed data are from the test series held on February 28, 2001. Particle sizes from previous testing in 1999 and the testing in 2001 were similar. Though the 2001 testing created similar particles sizes, many new particle formation phenomena were observed: microparticles and delayed particle formation. These experiment image analyses are some of the first steps toward visually characterizing these particles, and they allow designers to understand what issues must be addressed in atomic propellant feed system designs for future aerospace vehicles.

  2. Solid Hydrogen Experiments for Atomic Propellants: Particle Formation Energy and Imaging Analyses

    NASA Technical Reports Server (NTRS)

    Palaszewski, Bryan

    2002-01-01

    This paper presents particle formation energy balances and detailed analyses of the images from experiments that were conducted on the formation of solid hydrogen particles in liquid helium during the Phase II testing in 2001. Solid particles of hydrogen were frozen in liquid helium and observed with a video camera. The solid hydrogen particle sizes and the total mass of hydrogen particles were estimated. The particle formation efficiency is also estimated. Particle sizes from the Phase I testing in 1999 and the Phase II testing in 2001 were similar. Though the 2001 testing created similar particles sizes, many new particle formation phenomena were observed. These experiment image analyses are one of the first steps toward visually characterizing these particles and it allows designers to understand what issues must be addressed in atomic propellant feed system designs for future aerospace vehicles.

  3. Simple algorithms for remote determination of mineral abundances and particle sizes from reflectance spectra

    NASA Technical Reports Server (NTRS)

    Johnson, Paul E.; Smith, Milton O.; Adams, John B.

    1992-01-01

    Algorithms were developed, based on Hapke's (1981) equations, for remote determinations of mineral abundances and particle sizes from reflectance spectra. In this method, spectra are modeled as a function of end-member abundances and illumination/viewing geometry. The method was tested on a laboratory data set. It is emphasized that, although there exist more sophisticated models, the present algorithms are particularly suited for remotely sensed data, where little opportunity exists to independently measure reflectance versus article size and phase function.

  4. Plasma injection and atomic physics models for use in particle simulation codes

    SciTech Connect

    Procassini, R.J. California Univ., Berkeley, CA . Electronics Research Lab.)

    1991-06-12

    Models of plasma injection (creation) and charged/neutral atomic physics which are suitable for incorporation into particle simulation codes are described. Both planar and distributed source injection models are considered. Results obtained from planar injection into a collisionless plasma-sheath region are presented. The atomic physics package simulates the charge exchange and impact ionization interactions which occur between charged particles and neutral atoms in a partially-ionized plasma. These models are applicable to a wide range of problems, from plasma processing of materials to transport in the edge region of a tokamak plasma. 18 refs., 6 figs.

  5. Vacuum fluctuations and Brownian motion of a charged test particle near a reflecting boundary

    SciTech Connect

    Yu Hongwei; Ford, L. H.

    2004-09-15

    We study the Brownian motion of a charged test particle coupled to electromagnetic vacuum fluctuations near a perfectly reflecting plane boundary. The presence of the boundary modifies the quantum fluctuations of the electric field, which in turn modifies the motion of the test particle. We calculate the resulting mean squared fluctuations in the velocity and position of the test particle. In the case of directions transverse to the boundary, the results are negative. This can be interpreted as reducing the quantum uncertainty which would otherwise be present.

  6. Analog simulation of Weyl particles with cold atoms

    NASA Astrophysics Data System (ADS)

    Rabinovic, Mihail; Suchet, Daniel; Reimann, Thomas; Kretzschmar, Norman; Sievers, Franz; Salomon, Christophe; Lau, Jonathan; Lobo, Carlos; Goulko, Olga; Chevy, Frederic

    2016-05-01

    The high degree of control of the properties of ultracold gases offers the possibility to study experimentally unconventional many-body systems. An example is given by massless relativistic Weyl fermions, which are of particular interest in high energy and condensed matter physics, where they emerge in the form of low energy excitations of exotic compounds like TaAs. The particular case of harmonically trapped Weyl particles can be mimicked by a laser-cooled cloud of 6Li trapped in a magnetic quadrupole potential. The non-separability of this particular potential enables a quasi-thermalization of the single particle distribution function even in the absence of interactions. Surprisingly, the dynamics features an effective decoupling between the strong trapping axis and the weak trapping plane. We studied both, numerically and experimentally, the relaxation of the excited cloud towards its equilibrium distribution, mapping this dynamics directly to the case of non-interaction massless particles in a harmonic potential.

  7. Inelastic transitions in slow heavy-particle atomic collisions

    SciTech Connect

    Krstic, P. S.; Reinhold, C. O.; Burgdo''rfer, J.

    2001-05-01

    It is a generally held belief that inelastic transition probabilities and cross sections in slow, nearly adiabatic atomic collisions decrease exponentially with the inverse of the collision velocity v [i.e., {sigma}{proportional_to}exp(-const/v)]. This notion is supported by the Landau-Zener approximation and the hidden crossings approximation. We revisit the adiabatic limit of ion-atom collisions and show that for very slow collisions radial transitions are dominated by the topology of the branch points of the radial velocity rather than the branch points of the energy eigensurface. This can lead to a dominant power-law dependence of inelastic cross sections, {sigma}{proportional_to}v{sup n}. We illustrate the interplay between different contributions to the transition probabilities in a one-dimensional collision system for which the exact probabilities can be obtained from a direct numerical solution of the time-dependent Scho''dinger equation.

  8. Landau Zener scenario in a trapped atomic gas: multi-level multi-particle model

    NASA Astrophysics Data System (ADS)

    Fai, Lukong Cornelius; Tchoffo, Martin; Jipdi, Michael Nana

    2015-07-01

    The paper investigates multi-level and multi-particle Landau-Zener problem applying the dynamic matrix approach. The Landau Zener transitions are observed to depend sensitively on the frequency, phase of interaction and number of levels and particles. The dynamic behaviour of atomic trapped gas is solved for one particle model that permits to deduce different probabilities for particular initial conditions. The generalization of the probabilities permits to solve any multi-level system with an arbitrary number of particles and controlled particle transitions.

  9. Monte Carlo simulation of light reflection from cosmetic powder particles near the human skin surface

    NASA Astrophysics Data System (ADS)

    Okamoto, Takashi; Kumagawa, Tatsuya; Motoda, Masafumi; Igarashi, Takanori; Nakao, Keisuke

    2013-06-01

    The reflection and scattering properties of light incident on human skin covered with powder particles have been investigated. A three-layer skin structure with a pigmented area is modeled, and the propagation of light in the skin's layers and in a layer of particles near the skin's surface is simulated using the Monte Carlo method. Assuming that only single scattering of light occurs in the powder layer, the simulation results show that the reflection spectra of light from the skin change with the size of powder particles. The color difference between normal and discolored skin is found to decrease considerably when powder particles with a diameter of approximately 0.25 μm are present near the skin's surface. The effects of the medium surrounding the particles, and the influence of the distribution of particle size (polydispersity), are also examined. It is shown that a surrounding medium with a refractive index close to that of the skin substantially suppresses the extreme spectral changes caused by the powder particles covering the skin surface.

  10. Why Do Marbles Become Paler on Grinding? Reflectance, Spectroscopy, Color, and Particle Size

    ERIC Educational Resources Information Center

    Lagorio, Maria Gabriela

    2004-01-01

    A qualitative description of the color-change problem, which will assist in rationalizing the change in color of marbles after grinding them using a simple physical picture and the qualitative dependence of diffuse reflectance on particle size is presented. Different approaches are discussed but it is seen that the interpretation of nanoparticles…

  11. Phase-sensitive measurements of order parameters for ultracold atoms through two-particle interferometry.

    PubMed

    Kitagawa, Takuya; Aspect, Alain; Greiner, Markus; Demler, Eugene

    2011-03-18

    Nontrivial symmetry of order parameters is crucial in some of the most interesting quantum many-body states of ultracold atoms as well as condensed matter systems. Examples in cold atoms include p-wave Feshbach molecules and d-wave paired states of fermions that could be realized in optical lattices in the Hubbard regime. Identifying these states in experiments requires measurements of the relative phase of different components of the entangled pair wave function. We propose and discuss two schemes for such phase-sensitive measurements, based on two-particle interference revealed in atom-atom or atomic density correlations. Our schemes can also be used for relative phase measurements for nontrivial particle-hole order parameters, such as d-density wave order. PMID:21469872

  12. Geometric phase of an accelerated two-level atom in the presence of a perfectly reflecting plane boundary

    NASA Astrophysics Data System (ADS)

    Zhai, Hua; Zhang, Jialin; Yu, Hongwei

    2016-08-01

    We study the geometric phase of a uniformly accelerated two-level atom coupled with vacuum fluctuations of electromagnetic fields in the presence of a perfectly reflecting plane. We find that the geometric phase difference between the accelerated and inertial atoms which can be observed by atom interferometry crucially depends on the polarizability of the atom and the distance to the boundary and it can be dramatically manipulated with anisotropically polarizable atoms. In particular, extremely close to the boundary, the phase difference can be increased by two times as compared to the case without any boundary. So, the detectability of the effects associated with acceleration using an atom interferometer can be significantly increased by the presence of a boundary using atoms with anisotropic polarizability.

  13. Bidirectional reflectance spectroscopy 7. The single particle phase function hockey stick relation

    NASA Astrophysics Data System (ADS)

    Hapke, Bruce

    2012-11-01

    The measured volume-average single particle angular scattering functions of a large number of types of particle of interest for planetary regoliths in the visible-near-IR wavelength region can be represented to a reasonable approximation by two-parameter, double Henyey-Greenstein functions. When the two parameters of this function are plotted against one another they are found to be inversely correlated and lie within a restricted zone shaped like a hockey stick within the parameter space. The centroid of the zone is a curve that can be represented by a simple empirical equation. The wide variety of types of particles used to construct the plot implies that this equation may represent most of the particles found in regoliths. This means that when modeling the bidirectional reflectance of a regolith it may be possible to reduce the number of parameters necessary to specify the reflectance, and also to characterize the entire single particle phase function from observations at phase angles less than 90°. Even if the hockey stick relation has a finite width, rather than being a line, it restricts the parameter space that must be searched when fitting data. The curve should also be useful for forward modeling particle phase functions.

  14. Composite material reinforced with atomized quasicrystalline particles and method of making same

    DOEpatents

    Biner, Suleyman B.; Sordelet, Daniel J.; Lograsso, Barbara K.; Anderson, Iver E.

    1998-12-22

    A composite material comprises an aluminum or aluminum alloy matrix having generally spherical, atomized quasicrystalline aluminum-transition metal alloy reinforcement particles disposed in the matrix to improve mechanical properties. A composite article can be made by consolidating generally spherical, atomized quaiscrystalline aluminum-transition metal alloy particles and aluminum or aluminum alloy particles to form a body that is cold and/or hot reduced to form composite products, such as composite plate or sheet, with interfacial bonding between the quasicrystalline particles and the aluminum or aluminum alloy matrix without damage (e.g. cracking or shape change) of the reinforcement particles. The cold and/or hot worked compositehibits substantially improved yield strength, tensile strength, Young's modulus (stiffness).

  15. Composite material reinforced with atomized quasicrystalline particles and method of making same

    DOEpatents

    Biner, S.B.; Sordelet, D.J.; Lograsso, B.K.; Anderson, I.E.

    1998-12-22

    A composite material comprises an aluminum or aluminum alloy matrix having generally spherical, atomized quasicrystalline aluminum-transition metal alloy reinforcement particles disposed in the matrix to improve mechanical properties. A composite article can be made by consolidating generally spherical, atomized quasicrystalline aluminum-transition metal alloy particles and aluminum or aluminum alloy particles to form a body that is cold and/or hot reduced to form composite products, such as composite plate or sheet, with interfacial bonding between the quasicrystalline particles and the aluminum or aluminum alloy matrix without damage (e.g. cracking or shape change) of the reinforcement particles. The cold and/or hot worked composite exhibits substantially improved yield strength, tensile strength, Young`s modulus (stiffness). 3 figs.

  16. Measurement of Few Body Interactions in Tri-Atomic Molecular Dissociation into Three Charged Particles

    NASA Astrophysics Data System (ADS)

    Mueller, Dennis; Jordon-Thaden, Brandon; Weise, Lisa; Jaecks, Duane

    2010-03-01

    Threshold ionization of atoms by electron impact remains an area of interest. Near threshold, where the total energy of the system is approximately zero, the motion of charged particles is highly correlated. Similarly, near threshold dissociation into three or more charges particles is involve highly correlated motion as the particles slowly move apart under the influence of the long-range Coulomb interaction. We will present a novel approach to gain insight into these interactions, where no simplifying approximations such as placing one of the particles near the center-of-mass, is theoretically viable. In these triple coincidence experiments, the final state momenta of all particles are measured with sub-meV resolution sufficient to resolve rovibrational levels. This allows us to determine the initial state of the tri-atomic molecular ion.

  17. Determination of diffusion, reflection and deexcitation coefficients of metastable excited Ne(3P2) atom

    NASA Astrophysics Data System (ADS)

    Suzuki, S.; Itoh, H.

    2016-05-01

    The diffusion coefficient of the metastable excited Ne(3P2) atom in neon, the reflection coefficient of Ne(3P2) at the surface of an electrode and the rate coefficient of Ne(3P2) for collisional quenching by Ne(1S0) were determined from the gas pressure dependence of the effective lifetime of Ne(3P2). The effective lifetime of Ne(3P2) was measured from the transient current after turning off the Ultraviolet (UV) light in a Townsend discharge. The observed transient current waveform was analysed by solving the diffusion equation for the metastable excited Ne(3P2) atom using the third kind of boundary condition. The rate coefficient of Ne(3P2) for collisional quenching by Ne(1S0) and the reflection coefficient were determined by a nonspectroscopic method for the first time in neon to the best of our knowledge and were (3.2  ±  0.4)  ×  10‑16 cm3 s‑1 and 0.10  ±  0.04, respectively. The obtained diffusion coefficient at 1 Torr was 177  ±  17 cm2 s‑1, which is consistent with the value reported by Dixon and Grant. Moreover, the present results are compared with the results of Phelps and were found to be in good agreement. We also discuss the deexcitation rate of Ne(3P2) at pressures of up to 60 Torr in comparison with previously reported values.

  18. Digital atom interferometer with single particle control on a discretized space-time geometry

    PubMed Central

    Steffen, Andreas; Alberti, Andrea; Alt, Wolfgang; Belmechri, Noomen; Hild, Sebastian; Karski, Michał; Widera, Artur; Meschede, Dieter

    2012-01-01

    Engineering quantum particle systems, such as quantum simulators and quantum cellular automata, relies on full coherent control of quantum paths at the single particle level. Here we present an atom interferometer operating with single trapped atoms, where single particle wave packets are controlled through spin-dependent potentials. The interferometer is constructed from a sequence of discrete operations based on a set of elementary building blocks, which permit composing arbitrary interferometer geometries in a digital manner. We use this modularity to devise a space-time analogue of the well-known spin echo technique, yielding insight into decoherence mechanisms. We also demonstrate mesoscopic delocalization of single atoms with a separation-to-localization ratio exceeding 500; this result suggests their utilization beyond quantum logic applications as nano-resolution quantum probes in precision measurements, being able to measure potential gradients with precision 5 × 10-4 in units of gravitational acceleration g. PMID:22665771

  19. Laser-Induced Particle Adsorption on Atomically Thin MoS2.

    PubMed

    Tran Khac, Bien Cuong; Jeon, Ki-Joon; Choi, Seung Tae; Kim, Yong Soo; DelRio, Frank W; Chung, Koo-Hyun

    2016-02-10

    Atomically thin molybdenum disulfide (MoS2) shows great potential for use in nanodevices because of its remarkable electronic, optoelectronic, and mechanical properties. These material properties are often dependent on the thickness or the number of layers, and hence Raman spectroscopy is widely used to characterize the thickness of atomically thin MoS2 due to the sensitivity of the vibrational spectrum to thickness. However, the lasers used in Raman spectroscopy can increase the local surface temperature and eventually damage the upper layers of the MoS2, thereby changing the aforementioned material properties. In this work, the effects of lasers on the topography and material properties of atomically thin MoS2 were systematically investigated using Raman spectroscopy and atomic force microscopy. In detail, friction force microscopy was used to study the friction characteristics of atomically thin MoS2 as a function of laser powers from 0.5 to 20 mW and number of layers from 1 to 3. It was found that particles formed on the top surface of the atomically thin MoS2 due to laser-induced thermal effects. The degree of particle formation increased as the laser power increased, prior to the thinning of the atomically thin MoS2. In addition, the degree of particle formation increased as the number of MoS2 layers increased, which suggests that the thermal behavior of the supported MoS2 may differ depending on the number of layers. The particles likely originated from the atmosphere due to laser-induced heating, but could be eliminated via appropriate laser powers and exposure times, which were determined experimentally. The outcomes of this work indicate that thermal management is crucial in the design of reliable nanoscale devices based on atomically thin MoS2. PMID:26795729

  20. Spectroscopy, Manipulation and Trapping of Neutral Atoms, Molecules, and Other Particles Using Optical Nanofibers: A Review

    PubMed Central

    Morrissey, Michael J.; Deasy, Kieran; Frawley, Mary; Kumar, Ravi; Prel, Eugen; Russell, Laura; Truong, Viet Giang; Chormaic, Síle Nic

    2013-01-01

    The use of tapered optical fibers, i.e., optical nanofibers, for spectroscopy and the detection of small numbers of particles, such as neutral atoms or molecules, has been gaining interest in recent years. In this review, we briefly introduce the optical nanofiber, its fabrication, and optical mode propagation within. We discuss recent progress on the integration of optical nanofibers into laser-cooled atom and vapor systems, paying particular attention to spectroscopy, cold atom cloud characterization, and optical trapping schemes. Next, a natural extension of this work to molecules is introduced. Finally, we consider several alternatives to optical nanofibers that display some advantages for specific applications. PMID:23945738

  1. New atomic probes for dark matter detection: Axions, axion-like particles and topological defects

    NASA Astrophysics Data System (ADS)

    Stadnik, Yevgeny V.; Flambaum, Victor V.

    2014-11-01

    We present a brief overview of recently proposed detection schemes for axion, axion-like pseudoscalar particle and topological defect dark matter. We focus mainly on the possibility of using atomic and molecular systems for dark matter detection. For axions and axion-like particles, these methods are complementary probes to ongoing photon-axion interconversion experiments and astrophysical observations. For topological defects, these methods are complementary to conventional astrophysical search schemes based on gravitational signatures.

  2. Methodology for the Elimination of Reflection and System Vibration Effects in Particle Image Velocimetry Data Processing

    NASA Technical Reports Server (NTRS)

    Bremmer, David M.; Hutcheson, Florence V.; Stead, Daniel J.

    2005-01-01

    A methodology to eliminate model reflection and system vibration effects from post processed particle image velocimetry data is presented. Reflection and vibration lead to loss of data, and biased velocity calculations in PIV processing. A series of algorithms were developed to alleviate these problems. Reflections emanating from the model surface caused by the laser light sheet are removed from the PIV images by subtracting an image in which only the reflections are visible from all of the images within a data acquisition set. The result is a set of PIV images where only the seeded particles are apparent. Fiduciary marks painted on the surface of the test model were used as reference points in the images. By locating the centroids of these marks it was possible to shift all of the images to a common reference frame. This image alignment procedure as well as the subtraction of model reflection are performed in a first algorithm. Once the images have been shifted, they are compared with a background image that was recorded under no flow conditions. The second and third algorithms find the coordinates of fiduciary marks in the acquisition set images and the background image and calculate the displacement between these images. The final algorithm shifts all of the images so that fiduciary mark centroids lie in the same location as the background image centroids. This methodology effectively eliminated the effects of vibration so that unbiased data could be used for PIV processing. The PIV data used for this work was generated at the NASA Langley Research Center Quiet Flow Facility. The experiment entailed flow visualization near the flap side edge region of an airfoil model. Commercial PIV software was used for data acquisition and processing. In this paper, the experiment and the PIV acquisition of the data are described. The methodology used to develop the algorithms for reflection and system vibration removal is stated, and the implementation, testing and

  3. Use of Incident and Reflected Solar Particle Beams to Trace the Topology of Magnetic Clouds

    NASA Astrophysics Data System (ADS)

    Tan, Lun C.; Malandraki, Olga E.; Reames, Donald V.; Ng, Chee K.; Wang, Linghua; Dorrian, Gareth

    2012-05-01

    Occasionally, large solar energetic particle (SEP) events occur inside magnetic clouds (MCs). In this work, the onset time analysis, the peak intensity analysis, and the decay phase analysis of SEPs are used to investigate two large SEP events inside MCs: the 1998 May 2 and 2002 April 21 events. The onset time analysis of non-relativistic electrons and ~MeV nucleon-1 heavy ions shows the stability of the magnetic loop structure during a period of a few hours in the events examined. The joint analysis of pitch-angle distributions and peak intensities of electrons exhibits that, depending on the particle pitch angle observed at 1 AU, in the April event the reflection point of particles may be distributed along a wide spatial range, implying that the magnetic loop is a magnetic bottle connected to the Sun with both legs. In contrast, in the May event particle reflection occurs abruptly at the magnetic mirror formed by a compressed field enhancement behind the interplanetary shock, consistent with its open field line topology.

  4. USE OF INCIDENT AND REFLECTED SOLAR PARTICLE BEAMS TO TRACE THE TOPOLOGY OF MAGNETIC CLOUDS

    SciTech Connect

    Tan, Lun C.; Malandraki, Olga E.; Dorrian, Gareth; Reames, Donald V.; Ng, Chee K.; Wang Linghua

    2012-05-10

    Occasionally, large solar energetic particle (SEP) events occur inside magnetic clouds (MCs). In this work, the onset time analysis, the peak intensity analysis, and the decay phase analysis of SEPs are used to investigate two large SEP events inside MCs: the 1998 May 2 and 2002 April 21 events. The onset time analysis of non-relativistic electrons and {approx}MeV nucleon{sup -1} heavy ions shows the stability of the magnetic loop structure during a period of a few hours in the events examined. The joint analysis of pitch-angle distributions and peak intensities of electrons exhibits that, depending on the particle pitch angle observed at 1 AU, in the April event the reflection point of particles may be distributed along a wide spatial range, implying that the magnetic loop is a magnetic bottle connected to the Sun with both legs. In contrast, in the May event particle reflection occurs abruptly at the magnetic mirror formed by a compressed field enhancement behind the interplanetary shock, consistent with its open field line topology.

  5. Determining the band gap and mean kinetic energy of atoms from reflection electron energy loss spectra

    SciTech Connect

    Vos, M.; Marmitt, G. G.; Finkelstein, Y.; Moreh, R.

    2015-09-14

    Reflection electron energy loss spectra from some insulating materials (CaCO{sub 3}, Li{sub 2}CO{sub 3}, and SiO{sub 2}) taken at relatively high incoming electron energies (5–40 keV) are analyzed. Here, one is bulk sensitive and a well-defined onset of inelastic excitations is observed from which one can infer the value of the band gap. An estimate of the band gap was obtained by fitting the spectra with a procedure that includes the recoil shift and recoil broadening affecting these measurements. The width of the elastic peak is directly connected to the mean kinetic energy of the atom in the material (Doppler broadening). The experimentally obtained mean kinetic energies of the O, C, Li, Ca, and Si atoms are compared with the calculated ones, and good agreement is found, especially if the effect of multiple scattering is taken into account. It is demonstrated experimentally that the onset of the inelastic excitation is also affected by Doppler broadening. Aided by this understanding, we can obtain a good fit of the elastic peak and the onset of inelastic excitations. For SiO{sub 2}, good agreement is obtained with the well-established value of the band gap (8.9 eV) only if it is assumed that the intensity near the edge scales as (E − E{sub gap}){sup 1.5}. For CaCO{sub 3}, the band gap obtained here (7 eV) is about 1 eV larger than the previous experimental value, whereas the value for Li{sub 2}CO{sub 3} (7.5 eV) is the first experimental estimate.

  6. Atomic-scale modeling of particle size effects for the oxygen reduction reaction on Pt.

    SciTech Connect

    Tritsaris, G. A.; Greeley, J.; Rossmeisl, J.; Norskov, J. K.

    2011-07-01

    We estimate the activity of the oxygen reduction reaction on platinum nanoparticles of sizes of practical importance. The proposed model explicitly accounts for surface irregularities and their effect on the activity of neighboring sites. The model reproduces the experimentally observed trends in both the specific and mass activities for particle sizes in the range between 2 and 30 nm. The mass activity is calculated to be maximized for particles of a diameter between 2 and 4 nm. Our study demonstrates how an atomic-scale description of the surface microstructure is a key component in understanding particle size effects on the activity of catalytic nanoparticles.

  7. Heterogeneous reactivity of chlorine atoms with ammonium sulfate and ammonium nitrate particles.

    PubMed

    Ciuraru, Raluca; Gosselin, Sylvie; Visez, Nicolas; Petitprez, Denis

    2012-04-01

    In this laboratory study, model particles of ammonium sulfate (AS) and ammonium nitrate (AN) were exposed to chlorine atoms and uptake experiments were performed in a coated wall flow tube reactor coupled to a molecular beam mass spectrometer. The reactive surfaces were prepared by coating the inner surface of the reactor using two different methods: either by depositing size-selected particles on the halocarbon wax or by spray depositing thin films using a constant output atomizer. The observed uptake coefficients vary for (NH(4))(2)SO(4), ranging from γ(Cl)(AS)≈ 1 × 10(-3) for size-selected particles to γ(Cl)(AS)≈ 6 × 10(-2) for thin films prepared by spray. An uptake coefficient of γ(Cl)(AN)≈ 2.5 × 10(-3) of Cl˙ on size-selected NH(4)NO(3) particles was measured. A heterogeneous recombination of Cl atoms to from Cl(2) molecules was observed for the two surfaces. Furthermore, an ageing process was observed for AS particles, this phenomenon leading to the formation of new chlorine species on the solid substrate. PMID:22374517

  8. Microstructure simulation of rapidly solidified ASP30 high-speed steel particles by gas atomization

    NASA Astrophysics Data System (ADS)

    Ma, Jie; Wang, Bo; Yang, Zhi-liang; Wu, Guang-xin; Zhang, Jie-yu; Zhao, Shun-li

    2016-03-01

    In this study, the microstructure evolution of rapidly solidified ASP30 high-speed steel particles was predicted using a simulation method based on the cellular automaton-finite element (CAFE) model. The dendritic growth kinetics, in view of the characteristics of ASP30 steel, were calculated and combined with macro heat transfer calculations by user-defined functions (UDFs) to simulate the microstructure of gas-atomized particles. The relationship among particle diameter, undercooling, and the convection heat transfer coefficient was also investigated to provide cooling conditions for simulations. The simulated results indicated that a columnar grain microstructure was observed in small particles, whereas an equiaxed microstructure was observed in large particles. In addition, the morphologies and microstructures of gas-atomized ASP30 steel particles were also investigated experimentally using scanning electron microscopy (SEM). The experimental results showed that four major types of microstructures were formed: dendritic, equiaxed, mixed, and multi-droplet microstructures. The simulated results and the available experimental data are in good agreement.

  9. Surface roughtness and its influence on particle adhesion using atomic force microscope techniques

    SciTech Connect

    Gady, B.; Schaefer, D.; Reifenberger, R.; Rimai, D.; DeMejo, L.P.

    1996-12-31

    The surface force interactions between individual 8 {mu}m diameter spheres and atomically flat substrates have been systematically investigated using atomic force techniques. The lift-off force of glass, polystyrene and tin particles from atomically smooth mica and highly oriented pyrolytic graphite substrates was determined as a function of the applied loading force in an inert nitrogen environment. While the relative magnitudes of the measured lift-off force was found to scale as expected between the various systems studied, the absolute values were a factor of {approximately}50 smaller than expected from the Johnson, Kendall, and Roberts theory. The surface topography of representative spheres was characterized with atomic force microscopy, allowing a quantitative assessment of the role that surface roughness plays in the adhesion of micrometer-size particles to substrates. Taking into account the radius of curvature of the asperities measured from the atomic force scans, agreement between the measured and theoretical estimates for the lift-off forces was improved, with the corrected experimental forces about a factor of 3 smaller than theoretical expectations.

  10. Total reflection X-ray fluorescence (TXRF) for direct analysis of aerosol particle samples.

    PubMed

    Bontempi, E; Zacco, A; Benedetti, D; Borgese, L; Colombi, P; Stosnach, H; Finzi, G; Apostoli, P; Buttini, P; Depero, L E

    2010-04-14

    Atmospheric aerosol particles have a great impact on the environment and on human health. Routine analysis of the particles usually involves only the mass determination. However, chemical composition and phases provide fundamental information about the particles' origins and can help to prevent health risks. For example, these particles may contain heavy metals such as Pb, Ni and Cd, which can adversely affect human health. In this work, filter samples were collected in Brescia, an industrial town located in Northern Italy. In order to identify the chemical composition and the phases of the atmospheric aerosols, the samples were analysed by means of total reflection X-ray fluorescence (TXRF) spectrometry with a laboratory instrument and X-ray microdiffraction at Synchrotron Daresbury Laboratories, Warrington (Cheshire, UK). The results are discussed and correlated to identify possible pollution sources. The novelty of this analytical approach is that filter samples for TXRF were analysed directly and did not require chemical pretreatment to leach elements from the aerosol particulates. The results of this study clearly show that TXRF is a powerful technique for the analysis of atmospheric aerosols on 'as-received' filters, thereby leaving samples intact and unaltered for possible subsequent analyses by other methods. In addition, the low detection limits for many elements (low ng/cm2) indicate that this method may hold promise in various application fields, such as nanotechnology. PMID:20480822

  11. Asymptotics of a Discrete-Time Particle System Near a Reflecting Boundary

    NASA Astrophysics Data System (ADS)

    Kuan, Jeffrey

    2013-01-01

    We examine a discrete-time Markovian particle system on ℕ×ℤ+ introduced in Defosseux (arXiv: 1012.0117v1 ). The boundary {0}×ℤ+ acts as a reflecting wall. The particle system lies in the Anisotropic Kardar-Parisi-Zhang with a wall universality class. After projecting to a single horizontal level, we take the long-time asymptotics and obtain the discrete Jacobi and symmetric Pearcey kernels. This is achieved by showing that the particle system is identical to a Markov chain arising from representations of O(∞) (introduced in Borodin and Kuan (Commun. Pure. Appl. Math. 63(7):831-894, 2010, arXiv: 0904.2607 )). The fixed-time marginals of this Markov chain are known to be determinantal point processes, allowing us to take the limit of the correlation kernel. We also give a simple example which shows that in the multi-level case, the particle system and the Markov chain evolve differently.

  12. Analysis of environmental particles by atomic force microscopy, scanning and transmission electron microscopy.

    PubMed

    Mavrocordatos, D; Pronk, W; Boiler, M

    2004-01-01

    Due to their large specific surface and their abundance, micro and nano particles play an important role in the transport of micropollutants in the environment. Natural particles are usually composed of a mixture of inorganic amorphous or crystalline material (mainly FeOOH, Fe(x)Oy, Mn(x)Oy and clays) and organic material (humics and polysaccharides). They all tend to occur as very small particles (1-1,000 nm in diameter). Most natural amorphous particles are unstable and tend to transform with time towards more crystalline forms, either by aging or possibly, by dissolution and re-crystallization. Such transformations affect the fate of sorbed micropollutants and the scavenging properties are therefore changed. As these entities are sensitive to dehydration (aggregation, changes in the morphology), it is highly important to observe their morphology in their natural environment and understand their composition at the scale of the individual particles. Also for the understanding and optimization of water treatment technologies, the knowledge of the occurrence and behavior of nano-particles is of high importance. Some of the possible particle analysis methods are presented: aggregation processes, biomineralization, bacterial adhesion, biofilms in freshwaters, ferrihydrite as heavy metals remover from storm water. These examples demonstrate the capabilities and focus of the microscopes. Atomic Force Microscopy (AFM) allows to analyze the particles in their own environment, meaning in air or in the water. Thus, native aspects of particles can be observed. As well, forces of interactions between particles or between particles and other surfaces such as membranes will be highly valuable data. Scanning Electron Microscopy (SEM) and for higher lateral resolution, Transmission Electron Microscopy (TEM) allow measurement of the morphology and composition. Especially, TEM coupled with Electron Energy Loss Spectroscopy (TEM-EELS) is a powerful technique for elemental analysis

  13. Fast Pyrolysis of Wood for Biofuels: Spatiotemporally Resolved Diffuse Reflectance In situ Spectroscopy of Particles.

    PubMed

    Paulsen, Alex D; Hough, Blake R; Williams, C Luke; Teixeira, Andrew R; Schwartz, Daniel T; Pfaendtner, Jim; Dauenhauer, Paul J

    2014-02-20

    Fast pyrolysis of woody biomass is a promising process capable of producing renewable transportation fuels to replace gasoline, diesel, and chemicals currently derived from nonrenewable sources. However, biomass pyrolysis is not yet economically viable and requires significant optimization before it can contribute to the existing oil-based transportation system. One method of optimization uses detailed kinetic models for predicting the products of biomass fast pyrolysis, which serve as the basis for the design of pyrolysis reactors capable of producing the highest value products. The goal of this work is to improve upon current pyrolysis models, usually derived from experiments with low heating rates and temperatures, by developing models that account for both transport and pyrolysis decomposition kinetics at high heating rates and high temperatures (>400 °C). A new experimental technique is proposed herein: spatiotemporally resolved diffuse reflectance in situ spectroscopy of particles (STR-DRiSP), which is capable of measuring biomass composition during fast pyrolysis with high spatial (10 μm) and temporal (1 ms) resolution. Compositional data were compared with a comprehensive 2D single-particle model, which incorporated a multistep, semiglobal reaction mechanism, prescribed particle shrinkage, and thermophysical properties that varied with temperature, composition, and orientation. The STR-DRiSP technique can be used to determine the transport-limited kinetic parameters of biomass decomposition for a wide variety of biomass feedstocks. PMID:24678023

  14. Probing Membrane Order and Topography in Supported Lipid Bilayers by Combined Polarized Total Internal Reflection Fluorescence-Atomic Force Microscopy

    PubMed Central

    Oreopoulos, John; Yip, Christopher M.

    2009-01-01

    Determining the local structure, dynamics, and conformational requirements for protein-protein and protein-lipid interactions in membranes is critical to understanding biological processes ranging from signaling to the translocating and membranolytic action of antimicrobial peptides. We report here the application of a combined polarized total internal reflection fluorescence microscopy-in situ atomic force microscopy platform. This platform's ability to image membrane orientational order was demonstrated on DOPC/DSPC/cholesterol model membranes containing the fluorescent membrane probe, DiI-C20 or BODIPY-PC. Spatially resolved order parameters and fluorophore tilt angles extracted from the polarized total internal reflection fluorescence microscopy images were in good agreement with the topographical details resolved by in situ atomic force microscopy, portending use of this technique for high-resolution characterization of membrane domain structures and peptide-membrane interactions. PMID:19254557

  15. Localization and force analysis at the single virus particle level using atomic force microscopy

    SciTech Connect

    Liu, Chih-Hao; Horng, Jim-Tong; Chang, Jeng-Shian; Hsieh, Chung-Fan; Tseng, You-Chen; Lin, Shiming

    2012-01-06

    Highlights: Black-Right-Pointing-Pointer Localization of single virus particle. Black-Right-Pointing-Pointer Force measurements. Black-Right-Pointing-Pointer Force mapping. -- Abstract: Atomic force microscopy (AFM) is a vital instrument in nanobiotechnology. In this study, we developed a method that enables AFM to simultaneously measure specific unbinding force and map the viral glycoprotein at the single virus particle level. The average diameter of virus particles from AFM images and the specificity between the viral surface antigen and antibody probe were integrated to design a three-stage method that sets the measuring area to a single virus particle before obtaining the force measurements, where the influenza virus was used as the object of measurements. Based on the purposed method and performed analysis, several findings can be derived from the results. The mean unbinding force of a single virus particle can be quantified, and no significant difference exists in this value among virus particles. Furthermore, the repeatability of the proposed method is demonstrated. The force mapping images reveal that the distributions of surface viral antigens recognized by antibody probe were dispersed on the whole surface of individual virus particles under the proposed method and experimental criteria; meanwhile, the binding probabilities are similar among particles. This approach can be easily applied to most AFM systems without specific components or configurations. These results help understand the force-based analysis at the single virus particle level, and therefore, can reinforce the capability of AFM to investigate a specific type of viral surface protein and its distributions.

  16. Multi-Scale Simulation of Atomization with small drops represented by Lagrangian Point-Particle Model

    NASA Astrophysics Data System (ADS)

    Ling, Yue; Zaleski, Stéphane; Institut Jean Le Rond d'Alembert Team

    2014-11-01

    Numerical simulation is conducted to investigate the drop formation and evolution in gas-assisted atomization. The atomizer consists of two parallel planar jets: the fast gas jet and the slow liquid jet. Due to the shear between gas and liquid streams, the liquid-gas interface is unstable, and this eventually leads to full atomization. A fundamental challenge in atomization simulations is the existence of multiple length scales involved. In order to accurately capture both the gas-liquid interface instability and the drop dynamics, a multi-scale multiphase flow simulation strategy is proposed. In the present model, the gas-liquid interface is resolved by the Volume-of-Fluid (VOF) method, while the small drops are represented by Lagrangian point-particle (LPP) models. Particular attention is paid on validating the coupling and conversion between LPP and VOF. The present model is validated by comparing with direct numerical simulation (DNS) results and also experimental data. The simulation results show complex coupling between the interface instability and the turbulent gas jet, which in turn influence the formation and evolution of the drops formed in atomization. ANR-11-MONU-0011.

  17. DFT studies of oxygen dissociation on the 116-atom platinum truncated octahedron particle.

    PubMed

    Jennings, Paul C; Aleksandrov, Hristiyan A; Neyman, Konstantin M; Johnston, Roy L

    2014-12-28

    Density functional theory calculations are performed to investigate oxygen dissociation on 116-atom truncated octahedron platinum particles. This work builds on results presented previously [Jennings et al., Nanoscale, 2014, 6, 1153], where it was shown that shell flexibility played an important role in facilitating fast oxygen dissociation. In this study, through investigation of the larger particle size, it is shown that oxygen dissociation on the (111) facet of pure platinum species is still aided by shell flexibility at larger sizes. Only the hollow sites close to the edges of the (111) facet mediate oxygen dissociation; oxygen is bound too weakly at other hollow sites for dissociation to occur. Further studies are performed on the (100) facet, which is larger for the Pt116 particle than for either the Pt38 or Pt79 ones. Much higher dissociation barriers are found on the (100) facet compared to the (111) facet, where the bridge sites are favourable for oxygen dissociation. PMID:25070716

  18. Analysis of Atomic Force Microscopy Images of Crystal Originated "Particles" on (100) Silicon Wafer through its Side Wall Angle Measurement

    NASA Astrophysics Data System (ADS)

    Lee, W. P.; Yow, H. K.; Tou, T. Y.

    2001-04-01

    Crystal originated "particle" (COP) on (100) silicon wafer surface was analyzed by Atomic Force Microscopy (AFM). The AFM analyzed COP was pyramidal pit mostly originated from twin octahedral voids surrounded by side walls in {111} planes. The appearance of COP on the (100) polished silicon wafer surface could be either single, separated or joined twin type and square in shape depends which portion of octahedral voids had been cut across during watering processes. As a result, the measured COP image by AFM might not reflect the shape of the COP or in the worst case, the AFM tip shape is misinterpreted as the COP shape. Hence, the side wall angle of COP image obtained by AFM is used to differentiate between actual COP or tip shape. If the side wall angle is comparable to the maximum measurable slope angle of tip, the tip shape is obtained instead of true COP shape. However, if the side wall angle is 55° or below with respect to (100) plane, the AFM image reflect the true COP shape.

  19. Automated Reflectance Measurement System Designed and Fabricated to Determine the Limits of Atomic Oxygen Treatment of Art Through Contrast Optimization

    NASA Technical Reports Server (NTRS)

    Sechkar, Edward A.; Stueber, Thomas J.; Rutledge, Sharon K.

    2000-01-01

    Atomic oxygen generated in ground-based research facilities has been used to not only test erosion of candidate spacecraft materials but as a noncontact technique for removing organic deposits from the surfaces of artwork. NASA has patented the use of atomic oxygen to remove carbon-based soot contamination from fire-damaged artwork. The process of cleaning soot-damaged paintings with atomic oxygen requires exposures for variable lengths of time, dependent on the condition of a painting. Care must be exercised while cleaning to prevent the removal of pigment. The cleaning process must be stopped as soon as visual inspection or surface reflectance measurements indicate that cleaning is complete. Both techniques rely on optical comparisons of known bright locations against known dark locations on the artwork being cleaned. Difficulties arise with these techniques when either a known bright or dark location cannot be determined readily. Furthermore, dark locations will lighten with excessive exposure to atomic oxygen. Therefore, an automated test instrument to quantitatively characterize cleaning progression was designed and developed at the NASA Glenn Research Center at Lewis Field to determine when atomic oxygen cleaning is complete.

  20. Use of incident and reflected solar particle beams to trace the topology of magnetic clouds

    NASA Astrophysics Data System (ADS)

    Malandraki, O.; Tan, L.; Reames, D.; Ng, C.; Wang, L.; Dorrian, G.

    2012-04-01

    Occasionally, large solar energetic particle (SEP) events occur inside magnetic clouds (MCs). In this work the onset time analysis, the peak intensity analysis, and the decay phase analysis of SEPs are used to investigate two large SEP events inside MCs: the 1998 May 2 and 2002 April 21 events. The onset time analysis of non-relativistic electrons and ~MeVnucleon-1 heavy ions exhibits the stability of the magnetic loop structure during a period of a few hours in the events examined. The joint analysis of pitch-angle distributions (PADs) and peak intensities of electrons indicates that in the April event the reflected particles with nearly zero pitch-angle at 1 AU could reach the vicinity of the Sun, implying that the magnetic loop was a magnetic bottle connected to the Sun with both legs. In contrast, in the May event the magnetic mirror was formed by a compressed field enhancement behind the interplanetary shock driven by a preceding coronal mass ejection, being consistent with its open field line topology. We have also measured the anisotropy characteristic of SEPs in the solar wind frame. At the MC boundary the PADs of both non-relativistic electrons and ~MeVnucleon-1 heavy ions are nearly isotropic, suggesting a diffusive transport environment of SEPs there. This work has received funding from the European Commission FP7 Project COMESEP (263252)

  1. Effective three-particle interactions in atoms with partly filled f-shell

    NASA Astrophysics Data System (ADS)

    Kozlov, Mikhail; Konovalova, Elena; Viatkina, Anna; Safronova, Marianna

    2016-05-01

    Three particle forces are known to be very important in nuclear physics. In atoms such forces appear between valence electrons in the second order of many-body perturbation theory due to the exchange interaction with the core. Usually their contribution to the valence energy is very small, of the order of few inverse centimeters. However, for atoms and ions with partly filled d and f shells the overlap between valence and core electrons may be large. This leads to significant enhancement of the effective three particle interactions. In Ti II (ground configuration (GC) 3 d2 4s) these interactions change binding energy by few hundred inverse centimeters. In Ce I (GC 4f5d 6 s2) these interactions contribute few thousand inverse centimeters. Three particle forces are also important for highly charged ions with low-lying f shell, such as Pr9 + , 10 +, Nd10 + , 11 +, and Sm13+. These ions may have narrow optical transitions and are now considered for the new generation of optical clocks. This work was supported in part by RFBR Grant No. 14-02-00241.

  2. Investigating the particle to fibre transition threshold during electrohydrodynamic atomization of a polymer solution.

    PubMed

    Husain, O; Lau, W; Edirisinghe, M; Parhizkar, M

    2016-08-01

    Electrohydrodynamic atomization (EHDA) is a key research area for producing micro and nano-sized structures. This process can be categorized into two main operating regimes: electrospraying for particle generation and electrospinning for fibre production. Producing particles/fibres of the desired size or morphology depends on two main factors; properties of the polymeric solution used and the processing conditions including flow rate, applied voltage and collection distance. In this work the particle-fibre transition region was analyzed by changing the polymer concentration of PLGA poly (lactic-co-glycolic acid) in acetone between 2 and 25wt%. Subsequently the processing conditions were adjusted to study the optimum transition parameters. Additionally the EHDA configuration was also modified by adding a metallic plate to observe the deposition area. The diameter and the distance of the plate from the capillary tip were adjusted to investigate variations in particle and fibre morphologies as well. It was found that complete transition from particles to fibres occurs at 20wt% indicating concentration to be the dominant criterion. Low flow rates yielded fibres without beads. However the applied voltage and distance between the tip of the nozzle jetting the polymer solution and collector (working distance) did not yield definitive results. Reducing the collector distance and increasing applied voltages produces smooth as well as beaded fibres. Addition of a metal plate reduces particle size by ~1μm; the fibre size increases especially with increasing plate diameter while bead density and size reduces when the disc is fixed closer to the capillary tip. Additionally, the deposition area is reduced by 70% and 57% with the addition of metal plates of 30mm and 60mm, respectively. The results indicate that a metal plate can be utilized further to tune the particle/fibre size and morphology and this also significantly increases the yield of EHDA process which is currently a

  3. The effective potential in the scattering of a charged particle by an atom in the presence of weak screening

    NASA Astrophysics Data System (ADS)

    Au, C. K.; Baird, W. H.

    1996-09-01

    We use perturbation theory to derive an expression for the effective potential in the scattering between a charged particle and a coulombic complex (an atom) in the presence of weak screening in terms of the screening length and the atomic structure sum rules. Contact-type terms are neglected.

  4. Ultra-narrow spectroscopic cells in atomic spectroscopy: reflection, transmission, fluorescence, and nonadiabatic transitions at the walls

    NASA Astrophysics Data System (ADS)

    Pazgalev, A.; Sarkisyan, D.; Cartaleva, S.; Przhibelskii, S.; Vartanyan, T.

    2014-11-01

    Ultra-narrow cells with the thicknesses in the range from several wavelengths to the small fractions of the wavelength brought a number of new opportunities for atomic spectroscopy. Depending on the cell thickness, spectral lines recorded in ultra-narrow cells are either Doppler-free or Doppler-broadened. With careful selection of the cell thickness hyperfine structure may be easily resolved without resorting on the multibeam nonlinear optical techniques. Moreover, frequent collisions with the walls leads to the important modifications of velocity selective optical pumping resonances. Finally, ultra-narrow cells provide with the unique opportunity to study collisions of the excited atoms with the solid surfaces. In this contribution several examples of the use of the ultra-narrow spectroscopic cells filled with the alkali atomic vapour is presented. First, we discuss general aspects of the transient polarisation that defines all peculiarities of an ultra-narrow cell as a spectroscopic tool. Second, we demonstrate the resolution of the magnetic sublevels in the transition from Zeeman to Paschen-Back regime in the Cs hyperfine structure. Third, new aspects of velocity selective optical pumping resonances in reflection and transmission of resonant radiation by the 6 wavelengths thick cell filled with Cs are discussed. Forth, the experimental evidences of the nonadiabatic transitions between excited states of Rb atoms in the course of collisions with the sapphire surface are presented.

  5. Analysis of beam interference reflected from atomic force microscope tip and periodic silicon surface under various humidity conditions

    NASA Astrophysics Data System (ADS)

    Banerjee, Hans P.; Weerasinghe, Asanka T.; Lyuksyutov, Sergei F.

    2012-10-01

    Dynamical sensing based on combination of classical optical effects and atomic force microscopy (AFM) presents challenge for analysis of the forces at the nanoscale and beyond. An interference effect between light reflected from an AFM cantilever and highly reflective silicon surface of the calibration grating was studied for relative humidity (RH) varied between 9 and 60%. Force-distance analysis indicates on separation of capillary, van der Waals, adhesion, and electrostatic forces. The measurements performed in contact AFM mode suggest that the period of interference pattern observed in displacement curves is a function of humidity and varies between 293 nm at RH = 9% and 335 nm at RH > 50% with standard deviation less than 8 nm. Clear change of the interference period suggests that other than hardwarerelated factors may be involved in the formation of the interference in force-distance curves.

  6. Optimization of Electric Power Leveling Systems by using Taper-Off-Reflectance Particle Swarm Optimization

    NASA Astrophysics Data System (ADS)

    Makino, Yohei; Fujii, Toshinori; Imai, Jun; Funabiki, Shigeyuki

    Recently, it is desired to develop energy control technologies for environmental issues such as global warming and exhaustion of fossil fuel. Power fluctuations in large power consumers may cause the instability of electric power systems and increase the cost of the electric power facility and electricity charges. Developing the electric power-leveling systems (EPLS) to compensate the power fluctuations is necessary for future electric power systems. Now, EPLS with an SMES have been proposed as one of the countermeasures for the electric power quality improvement. The SMES is superior to other energy storage devices in response and storage efficiency. The authors proposed the EPLS based on fussy control with the SMES. For this practical implementation, optimizing control gain and SMES capacity is an important issue. This paper proposes a new optimization method of the EPLS. The proposed algorithm is novel particle swarm optimization based on taper-off reflectance (TRPSO). The proposed TRPSO optimizes the design variables of the EPLS efficiently and effectively.

  7. Electronic excitation of ground state atoms by collision with heavy gas particles

    NASA Technical Reports Server (NTRS)

    Hansen, C. Frederick

    1993-01-01

    point where the initial and final potentials cross, or at least come very close. Therefore, this mechanism would be applicable to the case where a gas is initially at very low temperature suddenly subjected to high energy heavy particle bombardment. This situation would model the measurement of excitation cross section by molecular beam techniques, for example. The purpose is to report values of cross sections and rate coefficients for collision excitation of ground state atoms estimated with the Landau-Zener transition theory and to compare results with measurement of excitation cross sections for a beam of Hydrogen atoms impacting Argon atom targets. Some very dubious approximations are used, and the comparison with measurement is found less than ideal, but results are at least consistent within order of magnitude. The same model is then applied to the case of N-N atom collisions, even though the approximations then become even more doubtful. Still the rate coefficients obtained are at least plausible in both magnitude and functional form, and as far as I am aware these are the only estimates available for such rate coefficients.

  8. Infrared reflectance spectra and formalism of precipitation of acicular magnetic particles in network glasses

    NASA Astrophysics Data System (ADS)

    Ram, S.; Ram, K.

    1996-06-01

    discussed using the BO stretching or bending vibrations in the thin glass-platelets and the platelets milled (removing the rather long range atomic ordering) into powder of particle size of 1 μm or lower.

  9. Atomic Scale Flatness of Chemically Cleaned Silicon Surfaces Studied by Infrared Attenuated-Total-Reflection Spectroscopy

    NASA Astrophysics Data System (ADS)

    Sawara, Kenichi; Yasaka, Tatsuhiro; Miyazaki, Seiichi; Hirose, Masataka

    1992-07-01

    Hydrogen-terminated Si(111) and Si(100) surfaces obtained by aqueous HF or pH-modified (pH{=}5.3) buffered-HF (BHF) treatments have been characterized by a Fourier transform infrared (FT-IR) attenuated-total-reflection (ATR) technique. The BHF treatment provides better surface flatness than the HF treatment. Pure water rinse is effective for improving the Si(111) surface flatness, while this is not the case for Si(100) because the pure water acts as an alkaline etchant and promotes the formation of (111) microfacets or microdefects on the (100) surface.

  10. Andreev reflection in graphene

    NASA Astrophysics Data System (ADS)

    Beenakker, Carlo

    2007-03-01

    Relativity and superconductivity have no common ground in ordinary matter, because the velocity of electrons is only a small fraction of the velocity of light. The unusual band structure of a single layer of carbon atoms (graphene) contains negatively and positively charged particles that move as relativistic electrons and positrons. The electron-like particles in the conduction band can be converted into positron-like particles in the valence band when they are reflected by a superconductor. (The missing charge of 2e enters the superconductor as a Cooper pair.) This interband reflection process can be distinguished from the usual intraband Andreev reflection, because the reflection angle has the opposite sign. A new phenomenology of graphene--superconductor junctions is predicted, including an anomalous scaling of the supercurrent with the length of the junction and the existence of charge-neutral modes propagating along the interface.

  11. Backscattered energetic neutral atoms from the Moon in the Earth's plasma sheet observed by Chandarayaan-1/Sub-keV Atom Reflecting Analyzer instrument

    NASA Astrophysics Data System (ADS)

    Harada, Yuki; Futaana, Yoshifumi; Barabash, Stas; Wieser, Martin; Wurz, Peter; Bhardwaj, Anil; Asamura, Kazushi; Saito, Yoshifumi; Yokota, Shoichiro; Tsunakawa, Hideo; Machida, Shinobu

    2014-05-01

    We present the observations of energetic neutral atoms (ENAs) produced at the lunar surface in the Earth's magnetotail. When the Moon was located in the terrestrial plasma sheet, Chandrayaan-1 Energetic Neutrals Analyzer (CENA) detected hydrogen ENAs from the Moon. Analysis of the data from CENA together with the Solar Wind Monitor (SWIM) onboard Chandrayaan-1 reveals the characteristic energy of the observed ENA energy spectrum (the e-folding energy of the distribution function) ˜100 eV and the ENA backscattering ratio (defined as the ratio of upward ENA flux to downward proton flux) <˜0.1. These characteristics are similar to those of the backscattered ENAs in the solar wind, suggesting that CENA detected plasma sheet particles backscattered as ENAs from the lunar surface. The observed ENA backscattering ratio in the plasma sheet exhibits no significant difference in the Southern Hemisphere, where a large and strong magnetized region exists, compared with that in the Northern Hemisphere. This is contrary to the CENA observations in the solar wind, when the backscattering ratio drops by ˜50% in the Southern Hemisphere. Our analysis and test particle simulations suggest that magnetic shielding of the lunar surface in the plasma sheet is less effective than in the solar wind due to the broad velocity distributions of the plasma sheet protons.

  12. Development of Spectral and Atomic Models for Diagnosing Energetic Particle Characteristics in Fast Ignition Experiments

    SciTech Connect

    MacFarlane, Joseph J

    2009-08-07

    This Final Report summarizes work performed under DOE STTR Phase II Grant No. DE-FG02-05ER86258 during the project period from August 2006 to August 2009. The project, “Development of Spectral and Atomic Models for Diagnosing Energetic Particle Characteristics in Fast Ignition Experiments,” was led by Prism Computational Sciences (Madison, WI), and involved collaboration with subcontractors University of Nevada-Reno and Voss Scientific (Albuquerque, NM). In this project, we have: Developed and implemented a multi-dimensional, multi-frequency radiation transport model in the LSP hybrid fluid-PIC (particle-in-cell) code [1,2]. Updated the LSP code to support the use of accurate equation-of-state (EOS) tables generated by Prism’s PROPACEOS [3] code to compute more accurate temperatures in high energy density physics (HEDP) plasmas. Updated LSP to support the use of Prism’s multi-frequency opacity tables. Generated equation of state and opacity data for LSP simulations for several materials being used in plasma jet experimental studies. Developed and implemented parallel processing techniques for the radiation physics algorithms in LSP. Benchmarked the new radiation transport and radiation physics algorithms in LSP and compared simulation results with analytic solutions and results from numerical radiation-hydrodynamics calculations. Performed simulations using Prism radiation physics codes to address issues related to radiative cooling and ionization dynamics in plasma jet experiments. Performed simulations to study the effects of radiation transport and radiation losses due to electrode contaminants in plasma jet experiments. Updated the LSP code to generate output using NetCDF to provide a better, more flexible interface to SPECT3D [4] in order to post-process LSP output. Updated the SPECT3D code to better support the post-processing of large-scale 2-D and 3-D datasets generated by simulation codes such as LSP. Updated atomic physics modeling to provide for

  13. Characterization of virus-like particles by atomic force microscopy in ambient conditions

    NASA Astrophysics Data System (ADS)

    Oropesa, Reinier; Ramos, Jorge R.; Falcón, Viviana; Felipe, Ariel

    2013-06-01

    Recombinant virus-like particles (VLPs) are attractive candidates for vaccine design since they resemble native viroids in size and morphology, but they are non-infectious due to the absence of a viral genome. The visualization of surface morphologies and structures can be used to deepen the understanding of physical, chemical, and biological phenomena. Atomic force microscopy (AFM) is a useful tool for the visualization of soft biological samples in a nanoscale resolution. In this work we have investigated the morphology of recombinant surface antigens of hepatitis B (rHBsAg) VLPs from Cuban vaccine against hepatitis B. The rHBsAg VLPs sizes estimated by AFM between 15 and 30 nm are similar to those reported on previous transmission electron microscopy (TEM) studies.

  14. Control of degreening in postharvest green sour citrus fruit by electrostatic atomized water particles.

    PubMed

    Yamauchi, Naoki; Takamura, Kohtaro; Shigyo, Masayoshi; Migita, Catharina Taiko; Masuda, Yukihiro; Maekawa, Tetsuya

    2014-08-01

    The effect of electrostatic atomized water particles (EAWP) on degreening of green sour citrus fruit during storage was determined. Superoxide anion and hydroxyl radicals included in EAWP were present on the surface of the fruit peel after the treatment. Hydrogen peroxide was formed from EAWP in an aqueous solution, which could indicate that a hydroxyl radical of EAWP turns to hydrogen peroxide in the fruit flavedo as well as in the aqueous solution. EAWP treatment effectively suppressed the degreening of green yuzu and Nagato-yuzukichi fruits during storage at 20°C. The enhancement in K+ ion leakage of both EAWP-treated fruits reduced in comparison with the control. In spite of EAWP treatment, total peroxide level in both fruits showed almost no changes during storage, suggesting that hydrogen peroxide formed by EAWP treatment could stimulate the activation of hydrogen peroxide scavenging system and control degreening of these fruits during storage. PMID:24629952

  15. Photoluminescence of atomic gold and silver particles in soda-lime silicate glasses.

    PubMed

    Eichelbaum, Maik; Rademann, Klaus; Hoell, Armin; Tatchev, Dragomir M; Weigel, Wilfried; Stößer, Reinhard; Pacchioni, Gianfranco

    2008-04-01

    We report the chemistry and photophysics of atomic gold and silver particles in inorganic glasses. By synchrotron irradiation of gold-doped soda-lime silicate glasses we could create and identify unambiguously the gold dimer as a stable and bright luminescing particle embedded in the glassy matrix. The gold dimer spectra coincide perfectly with rare gas matrix spectra of Au(2). The glass matrix is, however, stable for years, and is hence perfectly suited for various applications. If the irradiated gold-doped sample is annealed at 550 degrees C a bright green luminescence can be recognized. Intense 337 nm excitation induces a decrease of the green luminescence and the reappearance of the 753 nm Au(2) emission, indicating a strong interrelationship between both luminescence centers. Time-dependent density functional theory (TD-DFT) calculations indicate that the green luminescence can be assigned to noble metal dimers bound to silanolate centers. These complexes are recognized as the first stages in the further cluster growth process, which has been investigated with small-angle x-ray scattering (SAXS). In silver-doped glasses, Ag(0) atoms can be identified with electron paramagnetic resonance (EPR) spectroscopy after synchrotron activation. Annealing at 300 degrees C decreases the concentration of Ag(1), but induces an intense white light emission with 337 nm excitation. The white luminescence can be decomposed into bands that are attributed to small silver clusters such as Ag(2), Ag(3) and Ag(4), and an additional band matching the green emission of gold-doped glasses. PMID:19636156

  16. Photoluminescence of atomic gold and silver particles in soda-lime silicate glasses

    NASA Astrophysics Data System (ADS)

    Eichelbaum, Maik; Rademann, Klaus; Hoell, Armin; Tatchev, Dragomir M.; Weigel, Wilfried; Stößer, Reinhard; Pacchioni, Gianfranco

    2008-04-01

    We report the chemistry and photophysics of atomic gold and silver particles in inorganic glasses. By synchrotron irradiation of gold-doped soda-lime silicate glasses we could create and identify unambiguously the gold dimer as a stable and bright luminescing particle embedded in the glassy matrix. The gold dimer spectra coincide perfectly with rare gas matrix spectra of Au2. The glass matrix is, however, stable for years, and is hence perfectly suited for various applications. If the irradiated gold-doped sample is annealed at 550 °C a bright green luminescence can be recognized. Intense 337 nm excitation induces a decrease of the green luminescence and the reappearance of the 753 nm Au2 emission, indicating a strong interrelationship between both luminescence centers. Time-dependent density functional theory (TD-DFT) calculations indicate that the green luminescence can be assigned to noble metal dimers bound to silanolate centers. These complexes are recognized as the first stages in the further cluster growth process, which has been investigated with small-angle x-ray scattering (SAXS). In silver-doped glasses, Ag0 atoms can be identified with electron paramagnetic resonance (EPR) spectroscopy after synchrotron activation. Annealing at 300 °C decreases the concentration of Ag1, but induces an intense white light emission with 337 nm excitation. The white luminescence can be decomposed into bands that are attributed to small silver clusters such as Ag2, Ag3 and Ag4, and an additional band matching the green emission of gold-doped glasses.

  17. Particles of the soul. The medical and Lutheran context of Daniel Sennert's atomism.

    PubMed

    Stolberg, Michael

    2003-01-01

    Daniel Sennert was a well-known and influential representative of early 17th-century atomism. He used Aristolelian hylomorphic terminology to put forward medical new ideas on the relationship between matter and soul. His belief in a mere multiplication of preexistent forms/souls since the Creation and in a coexistence of dominant and subordinate forms in natural things led him to the notion of atoms of the soul which via seman could transfer the human soul form one generation to the next. Focussing on the professional and cultural context of Sennert's theory rather than on its retrospective importance in the history of chemistry, this paper argues that it was a largely medical framework from which Sennert developed these ideas, and it stresses Sennert's strong Lutheran allegiances as a major driving force, especially behind his atomist traducianism, i.e. his claim that the human soul was propagated per traducem in tiny particles of matter rather than merely being infused days or weeks after conception, as Catholics and Calvinists alike asserted. PMID:15311431

  18. Effect of projection velocity and temperature on the reflection of ultracold atoms from a periodic one-dimensional corrugated magnetic potential

    SciTech Connect

    Singh, Mandip; Hannaford, Peter

    2010-07-15

    The spatial profile of ultracold atoms reflecting from an exponentially decaying magnetic potential depends on parameters such as the corrugation in the magnetic potential and the temperature of the atomic cloud. We report on experimental investigations of the effect of projection velocity which determines the strength of the interaction of the atom cloud with the magnetic potential and the effect of temperature of ultracold {sup 87}Rb atoms reflecting from a periodic one-dimensional corrugated magnetic potential. The magnetic potential is generated on an atom chip by a periodic permanent magnetic structure of period 10 {mu}m. The amplitude of the corrugation is controlled by applying a uniform external-bias magnetic field.

  19. Liquid atomization induced by pulse laser reflection at and beneath the liquid surface

    NASA Astrophysics Data System (ADS)

    Utsunomiya, Y.; Kajiwara, T.; Nishiyama, T.; Nagayama, K.; Kubota, S.; Nakahara, M.

    2008-11-01

    In this paper, precision high speed imaging of the pulse laser ablation of liquid surface has been described. This study is based on our previous findings that appreciable reduction of pulse laser ablation threshold of transparent material in case the pulse laser beam is incident from the water side on the interface of the transparent material and air or water. We have performed a series of experiments to observe the ablation process for laser incidence on the interface of water and air. Whole processes were observed by shadowgraphy optics by using a ns pulse laser and a high-resolution film. Within the tested experimental conditions, minimum laser fluence for laser ablation at water-air interface is shown to be around 12-16 J/cm2. We have confirmed that laser ablation phenomena will take place only when laser beam is incident on the water-air interface from inside the water medium. Many slender liquid ligaments extend like milk crown and seem to be atomized at the tip of them. Jet tip is moving at supersonic velocity but is decelerated very rapidly. By changing the laser energy with keeping laser fluence at the interface, temporal evolution changes appreciably at least in the early stage of the process. These detailed structures can be resolved only by pulse laser photography by using high-resolution film.

  20. Characterization of Langmuir-Blodgett Organclay Films using X-ray Reflectivity and Atomic Fore Microscopy

    SciTech Connect

    Koo,J.; Park, S.; Satija, S.; Tikhonov, A.; Sokolov, J.; Rafailovich, M.; Koga, T.

    2008-01-01

    Monolayers of organoclay platelets were formed at the air/water interface using the Langmuir technique and were then investigated either by in situ or lifted onto Si wafers and studied ex situ, using X-ray reflectivity (XR) methods. The XR data showed that the surfactant molecules on the clay platelets formed a dense, self-assembled monolayer where the molecules were tilted at an angle of 35 {+-}6 from the normal to the dry clay surface. The surfactant layers only covered a fraction of the clay platelet surface area, where the fractional surface coverage for the three clays studied (C6A, C15A, and C20A) was found to be 0.90, 0.86, and 0.73, respectively. These values were significantly higher than those estimated from the cation exchange capacity (CEC) values. Rather than being uniformly distributed, the surfactant was clustered in patchy regions, indicating that the surface of the clay platelets had both polar and non-polar segments. This heterogeneity confirmed the hypothesis which was previously invoked to explain the distribution of the clay platelets in melt mixed homopolymer and polymer blend nanocomposites.

  1. A quantitative study of particle size effects in the magnetorelaxometry of magnetic nanoparticles using atomic magnetometry

    NASA Astrophysics Data System (ADS)

    Dolgovskiy, V.; Lebedev, V.; Colombo, S.; Weis, A.; Michen, B.; Ackermann-Hirschi, L.; Petri-Fink, A.

    2015-04-01

    The discrimination of immobilised superparamagnetic iron oxide nanoparticles (SPIONs) against SPIONs in fluid environments via their magnetic relaxation behaviour is a powerful tool for bio-medical imaging. Here we demonstrate that a gradiometer of laser-pumped atomic magnetometers can be used to record accurate time series of the relaxing magnetic field produced by pre-polarised SPIONs. We have investigated dry in vitro maghemite nanoparticle samples with different size distributions (average radii ranging from 14 to 21 nm) and analysed their relaxation using the Néel-Brown formalism. Fitting our model function to the magnetorelaxation (MRX) data allows us to extract the anisotropy constant K and the saturation magnetisation MS of each sample. While the latter was found not to depend on the particle size, we observe that K is inversely proportional to the (time- and size-) averaged volume of the magnetised particle fraction. We have identified the range of SPION sizes that are best suited for MRX detection considering our specific experimental conditions and sample preparation technique.

  2. Barrier performance optimization of atomic layer deposited diffusion barriers for organic light emitting diodes using x-ray reflectivity investigations

    SciTech Connect

    Singh, Aarti Schröder, Uwe; Klumbies, Hannes; Müller-Meskamp, Lars; Leo, Karl; Geidel, Marion; Knaut, Martin; Hoßbach, Christoph; Albert, Matthias; Mikolajick, Thomas

    2013-12-02

    The importance of O{sub 3} pulse duration for encapsulation of organic light emitting diodes (OLEDs) with ultra thin inorganic atomic layer deposited Al{sub 2}O{sub 3} layers is demonstrated for deposition temperatures of 50 °C. X-ray reflectivity (XRR) measurements show that O{sub 3} pulse durations longer than 15 s produce dense and thin Al{sub 2}O{sub 3} layers. Correspondingly, black spot growth is not observed in OLEDs encapsulated with such layers during 91 days of aging under ambient conditions. This implies that XRR can be used as a tool for process optimization of OLED encapsulation layers leading to devices with long lifetimes.

  3. Effect of Particle Size on Microstructure and Cold Compaction of Gas-Atomized Hypereutectic Al-Si Alloy Powder

    NASA Astrophysics Data System (ADS)

    Cai, Zhiyong; Wang, Richu; Peng, Chaoqun; Zhang, Chun

    2015-04-01

    The effect of particle size on the cold compaction behavior of rapidly solidified hypereutectic Al-27 wt pct Si alloy powder was studied by double action axial pressing at room temperature. The geometrical characteristics (morphology, size, shape, and distribution of Si reinforcing phase) and hardness of the powder as a function of the particle size were investigated. The result shows that finer powder particle size showed smaller primary Si particles and achieved a lower density at a given pressure. Whereas, the microhardness of Al matrix increases while the particle size decreases, which indicates that the supersaturation due to the high solidification rate increases the deformation resistance of the alloy powder. Furthermore, the geometrical characteristics of Si phases strongly depend on the particle size due to the suppressed growth of Si phases during atomization. This microstructural characteristic evidently affects the powder compactibility at high applied pressures.

  4. Ring particle sizes and composition derived from eclipse cooling curves and reflection spectra

    NASA Technical Reports Server (NTRS)

    Kieffer, H. H.

    1974-01-01

    The probable chemistry of the Saturn rings is reviewed. Reflectance spectra for H20 and NH3 frosts and Saturn's rings are compared, along with temperature dependence of 1.6 microns water frost feature. The reflection spectra of Galilean satellite J2 and water frost are also reviewed.

  5. Determination of the optical thickness and effective particle radius of clouds from reflected solar radiation measurements. I - Theory

    NASA Technical Reports Server (NTRS)

    Nakajima, Teruyuki; King, Michael D.

    1990-01-01

    A method is presented for determining the optical thickness and effective particle radius of stratiform cloud layers from reflected solar radiation measurements. A detailed study is presented which shows that the cloud optical thickness (tau c) and effective particle radius (r/e/) of water clouds can be determined solely from reflection function measurements at 0.75 micron and 2.16 microns, provided tau c is not less than 4 and r(e) is not less than 6 microns. For optically thin clouds, the retrieval becomes ambiguous, resulting in two possible solutions for the effective radius and optical thickness. Adding a third channel near 1.65 micron does not improve the situation noticeably, whereas the addition of a channel near 3.70 microns reduces the ambiguity in deriving the effective radius. The effective radius determined by the above procedure corresponds to the droplet radius at some optical depth within the cloud layer.

  6. Combination of transmission electron and atomic force microscopy techniques to determine volume equivalent diameter of submicrometer particles.

    PubMed

    Tumolva, Laarnie; Park, Ji-Yeon; Park, Kihong

    2012-04-01

    Morphological properties of atmospheric particles are directly related to their residence time and transport behaviors, and their deposition patterns in human respiratory systems. The projected properties of particles measured by transmission electron microscopy (TEM) were combined with the particle height measured by atomic force microscopy (AFM) to determine volume equivalent diameter of submicrometer particles. For nonvolatile (refractory) laboratory-generated spherical polystyrene latex and cubic NaCl particles, the measured volume equivalent diameters agreed well with the true values (within 4%). However, for nonrefractory (NH(4))(2)SO(4) particles, the measured volume equivalent diameter was much smaller than the true value due to evaporation of volatile species at low vacuum pressure and high electron-beam intensity conditions in TEM, and deformation of particles in AFM. We observed that the volume equivalent diameter of 100 nm mobility-classified atmospheric particles was 35 ± 5 nm, suggesting that these particles contain nonrefractory species, whereas that of 20 nm mobility-classified atmospheric particles was found to be 19 ± 6 nm, suggesting that these particles were refractory and spherical. PMID:21919129

  7. Laser cooling and trapping of atomic particles. January 1970-September 1989 (Citations from the NTIS data base). Report for Jan 70-Sep 89

    SciTech Connect

    Not Available

    1989-11-01

    This bibliography contains citations concerning theory and experiments on laser cooling and laser trapping of neutral atoms and atomic ions. Atoms and ions are cooled by laser radiation pressure to very low Kelvin temperatures and confined in electromagnetic traps with very high density. Atomic particles discussed include sodium atoms, mercury ions, beryllium ions, magnesium ions, and hydrogen. Applications include high performance spectroscopy, atomic clocks, microwave and optical frequency standards, relativistic neutral particle beam weapons, exotic fuels, cooling of electron beams, and space propulsion. (Contains 97 citations fully indexed and including a title list.)

  8. Effect of hard particle impacts on the atomic oxygen survivability of reflector surfaces with transparent protective overcoats

    NASA Technical Reports Server (NTRS)

    Gulino, Daniel A.

    1987-01-01

    Silver mirror samples with protective coatings were subjected to a stream of 27 microns alumina particles to induce pinhole defects. The protective coating consisted of a layer of aluminum dioxide over silver followed by a layer of silicon dioxide over the alumina. Samples were prepared on both graphite-epoxy composite and fused quartz substrates. After exposure to the hard particle stream, the samples were exposed to an oxygen plasma environment in a laboratory plasma asher. The effects of both the hard particles and the oxygen plasma were documented by both reflectance measurements and scanning electron microscopy. The results indicated that oxidative damage to the silver reflecting layer continues beyond that of the erosively exposed silver. Oxidative undercutting of the silver layer and graphite-epoxy substrate continues in undamaged areas through adjacent, particle damaged defect sites. This may have implications for the use of such mirrors in a space station solar dynamic power system.

  9. Effect of hard particle impacts on the atomic oxygen survivability of reflector surfaces with transparent protective overcoats

    NASA Technical Reports Server (NTRS)

    Gulino, D. A.

    1986-01-01

    Silver mirror samples with protective coatings were subjected to a stream of 27 microns alumina particles to induce pinhole defects. The protective coating consisted of a layer of aluminum dioxide over silver followed by a layer of silicon dioxide over the alumina. Samples were prepared on both graphite-epoxy composite and fused quartz substrates. After exposure to the hard particle stream, the samples were exposed to an oxygen plasma environment in a laboratory plasma asher. The effects of both the hard particles and the oxygen plasma were documented by both reflectance measurements and scanning electron microscopy. The results indicated that oxidative damage to the silver reflecting layer continues beyond that of the erosively exposed silver. Oxidative undercutting of the silver layer and graphite-epoxy substrate continues in undamaged areas through adjacent, particle damaged defect sites. This may have implications for the use of such mirrors in a space station solar dynamic power system.

  10. PREFACE: International Conference on Many Particle Spectroscopy of Atoms, Molecules, Clusters and Surfaces (MPS2014)

    NASA Astrophysics Data System (ADS)

    Ancarani, Lorenzo Ugo

    2015-04-01

    This volume contains a collection of contributions from the invited speakers at the 2014 edition of the International Conference on Many Particle Spectroscopy of Atoms, Molecules, Clusters and Surfaces held in Metz, France, from 15th to 18th July 2014. This biennial conference alternates with the ICPEAC satellite International Symposium on (e,2e), Double Photoionization and Related Topics, and is concerned with experimental and theoretical studies of radiation interactions with matter. These include many-body and electron-electron correlation effects in excitation, and in single and multiple ionization of atoms, molecules, clusters and surfaces with various projectiles: electrons, photons and ions. More than 80 scientists, from 19 different countries around the world, came together to discuss the most recent progress on these topics. The scientific programme included 28 invited talks and a poster session extending over the three days of the meeting. Amongst the 51 posters, 11 have been selected and were advertised through short talks. Besides, Professor Nora Berrah gave a talk in memory of Professor Uwe Becker who sadly passed away shortly after co-chairing the previous edition of this conference. Financial support from the Institut Jean Barriol, Laboratoire SRSMC, Groupement de Recherche THEMS (CNRS), Ville de Metz, Metz Métropole, Conseil Général de la Moselle and Région Lorraine is gratefully acknowledged. Finally, I would like to thank the members of the local committee and the staff of the Université de Lorraine for making the conference run smoothly, the International Advisory Board for building up the scientific programme, the sessions chairpersons, those who gave their valuable time in carefully refereeing the articles of this volume and last, but not least, all participants for contributing to lively and fruitful discussions throughout the meeting.

  11. Electron counting and beam-induced motion correction enable near atomic resolution single particle cryoEM

    PubMed Central

    Li, Xueming; Mooney, Paul; Zheng, Shawn; Booth, Chris; Braunfeld, Michael B.; Gubbens, Sander; Agard, David A.; Cheng, Yifan

    2013-01-01

    In recent work with large high symmetry viruses, single particle electron cryomicroscopy (cryoEM) has reached the milestone of determining near atomic resolution structures by allowing direct fitting of atomic models into experimental density maps. However, achieving this goal with smaller particles of lower symmetry remains extraordinarily challenging. Using a newly developed single electron counting detector, we confirm that electron beam induced motion significantly degrades resolution and, importantly, show how the combination of rapid readout and nearly noiseless electron counting allow image blurring to be corrected to subpixel accuracy. Thus, intrinsic image information can be restored to high resolution (Thon rings visible to ~3 Å). Using this approach we determined a 3.3 Å resolution structure of a ~700 kDa protein with D7 symmetry showing clear side chain density. Our method greatly enhances image quality and data acquisition efficiency - key bottlenecks in applying near atomic resolution cryoEM to a broad range of protein samples. PMID:23644547

  12. Aluminum Matrix Composites Strengthened with CuZrAgAl Amorphous Atomized Powder Particles

    NASA Astrophysics Data System (ADS)

    Dutkiewicz, Jan; Rogal, Łukasz; Wajda, Wojciech; Kukuła-Kurzyniec, Agata; Coddet, Christian; Dembinski, Lucas

    2015-06-01

    The Al-matrix composites were prepared by hot pressing in vacuum of an aluminum powder with 20 and 40 wt.% addition of the amorphous Cu43Zr43Ag7Al7 alloy (numbers indicate at.%) obtained using gas atomization method. The amorphous structure of the powder was confirmed using x-ray diffraction, DSC, and TEM. The average size of mostly spherical particles was 100 μm, so the powder was sieved to obtain maximum size of 60 μm. The composites were prepared using uniaxial cold pressing in vacuum and at a temperature of 400 °C. The composites of hardness from 43 to 53 HV were obtained for both additions of the amorphous phase. They reached compression strength of 150 MPa for 20% of amorphous phase and 250 MPa for the higher content. The modest hardening effect was caused by crack initiation at Al/amorphous interfaces. The amorphous phase was only partially crystallized in the hot-pressed composites, what did not cause hardness decrease. The application of nanocrystalline aluminum powders obtained by high-energy ball milling for the matrix of composites allowed obtaining nanocrystalline aluminum matrix composites of size near 150 nm, strengthened with the amorphous powders, whose compression strength was near 550 MPa for the composite containing 40% of the amorphous phase and slightly lower for the composite containing 20% of the phase. They showed much higher ductility of 23% in comparison with 7% for the composite containing 40% amorphous phase. The distribution of the strengthening phase in the nanocrystalline matrix was not homogeneous; the amorphous particles formed bands, where majority of cracks nucleated during compression test.

  13. Dissipative particle dynamics simulation of a liquid meniscus confined between atomic force microscope tip and substrate

    NASA Astrophysics Data System (ADS)

    Li, Zhen; Lan, Chuanjin; Ma, Yanbao

    2012-11-01

    Liquid meniscus forms between the atomic force microscope (AFM) tip and the substrate under ambient humidity. The liquid meniscus affects the AFM measurements and plays an important role in dip-pen nanolithography. To understand the behaviors of the meniscus, a mesoscopic methodology called dissipative particle dynamics (DPD) is utilized to investigate the liquid meniscus confined between AFM tip and a solid surface. Results show that the structure of the liquid meniscus is highly dependent on the wettability properties of the tip and the substrate as well as the tip-to-surface distance. The area of liquid-solid interface increases as the wetting properties of the tip and substrate change from hydrophilic to hydrophobic, which results in a transition of the meniscus shape from convex to concave. The wetting properties of solid surface affect the process of the liquid meniscus breakup as the tip-to-surface distance increase. This nonlinear process is also affected by the surface tension of the liquid, thermal fluctuation and the speed of tip.

  14. Impurity precipitation in atomized particles evidenced by nano x-ray diffraction computed tomography

    SciTech Connect

    Bonnin, Anne; Wright, Jonathan P.; Tucoulou, Rémi; Palancher, Hervé

    2014-08-25

    Performances and physical properties of high technology materials are influenced or even determined by their initial microstructure and by the behavior of impurity phases. Characterizing these impurities and their relations with the surrounding matrix is therefore of primary importance but it unfortunately often requires a destructive approach, with the risk of misinterpreting the observations. The improvement we have done in high resolution X-ray diffraction computed tomography combined with the use of an X-ray nanoprobe allows non-destructive crystallographic description of materials with microscopic heterogeneous microstructure (with a grain size between 10 nm and 10 μm). In this study, the grain localization in a 2D slice of a 20 μm solidified atomized γU-Mo particle is shown and a minority U(C,O) phase (1 wt. %) with sub-micrometer sized grains was characterized inside. Evidence is presented showing that the onset of U(C,O) grain crystallization can be described by a precipitation mechanism since one single U-Mo grain has direct orientation relationship with more than one surrounding U(C,O) grains.

  15. Precision determination of electroweak coupling from atomic parity violation and implications for particle physics.

    PubMed

    Porsev, S G; Beloy, K; Derevianko, A

    2009-05-01

    We carry out high-precision calculation of parity violation in a cesium atom, reducing theoretical uncertainty by a factor of 2 compared to previous evaluations. We combine previous measurements with calculations and extract the weak charge of the 133Cs nucleus, QW=-73.16(29)expt(20)theor. The result is in agreement with the standard model (SM) of elementary particles. This is the most accurate to-date test of the low-energy electroweak sector of the SM. In combination with the results of high-energy collider experiments, we confirm the energy dependence (or "running") of the electroweak force over an energy range spanning 4 orders of magnitude (from approximately 10 MeV to approximately 100 GeV). Additionally, our result places constraints on a variety of new physics scenarios beyond the SM. In particular, we increase the lower limit on the masses of extra Z bosons predicted by models of grand unification and string theories. PMID:19518856

  16. Development of atomic layer deposition-activated microchannel plates for single particle detection at cryogenic temperatures

    SciTech Connect

    Gorelikov, Dmitry Sullivan, Neal; Rouffignac, Philippe de; Li, Huazhi; Narayanamoorthy, Jayasri; Tremsin, Anton S.

    2014-03-15

    Atomic layer deposition (ALD) technology is used to nanoengineer functional films inside the pores of microchannel plate (MCP) electron multipliers, enabling a novel MCP manufacturing technology that substantially improves performance and opens novel applications. The authors have developed custom tools and recipes for the growth of conformal films, with optimized conductance and secondary electron emission inside very long channels (∼6–20 μm diameter and >600 μm length, with tens of millions of channels per single MCP) by ALD. The unique ability to tune the characteristics of these ALD films enables their optimization to applications where time-resolved single particle imaging can be performed in extreme conditions, such as high counting rates at cryogenic temperatures. Adhesion of the conductive and emissive nanofilms to the 20 μm pore MCP glass substrates and their mechanical stability over a very wide range of temperatures (10–700 K) were confirmed experimentally. Resistance of ALD MCPs was reproducible during multiple cool-down cycles with no film degradation observed. Optimizing resistance of novel MCPs for operation at cryogenic temperature should enable high count rate event detection at temperatures below 20 K.

  17. Low temperature hydrogen plasma-assisted atomic layer deposition of copper studied using in situ infrared reflection absorption spectroscopy

    SciTech Connect

    Chaukulkar, Rohan P.; Rai, Vikrant R.; Agarwal, Sumit; Thissen, Nick F. W.

    2014-01-15

    Atomic layer deposition (ALD) is an ideal technique to deposit ultrathin, conformal, and continuous metal thin films. However, compared to the ALD of binary materials such as metal oxides and metal nitrides, the surface reaction mechanisms during metal ALD are not well understood. In this study, the authors have designed and implemented an in situ reflection-absorption infrared spectroscopy (IRAS) setup to study the surface reactions during the ALD of Cu on Al{sub 2}O{sub 3} using Cu hexafluoroacetylacetonate [Cu(hfac){sub 2}] and a remote H{sub 2} plasma. Our infrared data show that complete ligand-exchange reactions occur at a substrate temperature of 80 °C in the absence of surface hydroxyl groups. Based on infrared data and previous studies, the authors propose that Cu(hfac){sub 2} dissociatively chemisorbs on the Al{sub 2}O{sub 3} surface, where the Al-O-Al bridge acts as the surface reactive site, leading to surface O-Cu-hfac and O-Al-hfac species. Surface saturation during the Cu(hfac){sub 2} half-cycle occurs through blocking of the available chemisorption sites. In the next half-reaction cycle, H radicals from an H{sub 2} plasma completely remove these surface hfac ligands. Through this study, the authors have demonstrated the capability of in situ IRAS as a tool to study surface reactions during ALD of metals. While transmission and internal reflection infrared spectroscopy are limited to the first few ALD cycles, IRAS can be used to probe all stages of metal ALD starting from initial nucleation to the formation of a continuous film.

  18. Atomic-scale identification of Pd leaching in nanoparticle catalyzed C–C coupling: Effects of particle surface disorder

    DOE PAGESBeta

    Briggs, Beverly D.; Bedford, Nicholas M.; Seifert, Soenke; Koerner, Hilmar; Ramezani-Dakhel, Hadi; Heinz, Hendrik; Naik, Rajesh R.; Frenkel, Anatoly I.; Knecht, Marc R.

    2015-07-23

    C–C coupling reactions are of great importance in the synthesis of numerous organic compounds, where Pd nanoparticle catalyzed systems represent new materials to efficiently drive these reactions. Despite their pervasive utility, the catalytic mechanism of these particle-based reactions remains highly contested. Herein we present evidence of an atom leaching mechanism for Stille coupling under aqueous conditions using peptide-capped Pd nanoparticles. EXAFS analysis revealed Pd coordination changes in the nanoparticle consistent with Pd atom abstraction, where sizing analysis by SAXS confirmed particle size changes associated with a leaching process. It is likely that recently discovered highly disordered surface Pd atoms aremore » the favored catalytic active sites and are leached during oxidative addition, resulting in smaller particles. Thus, probing the mechanism of nanoparticle-driven C–C coupling reactions through structural analyses provides fundamental information concerning these active sites and their reactivity at the atomic-scale, which can be used to improve catalytic performance to meet important sustainability goals.« less

  19. Atomic-scale identification of Pd leaching in nanoparticle catalyzed C–C coupling: Effects of particle surface disorder

    SciTech Connect

    Briggs, Beverly D.; Bedford, Nicholas M.; Seifert, Soenke; Koerner, Hilmar; Ramezani-Dakhel, Hadi; Heinz, Hendrik; Naik, Rajesh R.; Frenkel, Anatoly I.; Knecht, Marc R.

    2015-07-23

    C–C coupling reactions are of great importance in the synthesis of numerous organic compounds, where Pd nanoparticle catalyzed systems represent new materials to efficiently drive these reactions. Despite their pervasive utility, the catalytic mechanism of these particle-based reactions remains highly contested. Herein we present evidence of an atom leaching mechanism for Stille coupling under aqueous conditions using peptide-capped Pd nanoparticles. EXAFS analysis revealed Pd coordination changes in the nanoparticle consistent with Pd atom abstraction, where sizing analysis by SAXS confirmed particle size changes associated with a leaching process. It is likely that recently discovered highly disordered surface Pd atoms are the favored catalytic active sites and are leached during oxidative addition, resulting in smaller particles. Thus, probing the mechanism of nanoparticle-driven C–C coupling reactions through structural analyses provides fundamental information concerning these active sites and their reactivity at the atomic-scale, which can be used to improve catalytic performance to meet important sustainability goals.

  20. Stratospheric Injection of Reflective Aerosols or Particles by Means of Aviation Fuel Additives.

    NASA Astrophysics Data System (ADS)

    Gorman, J.

    2007-12-01

    Various suggestions have been made for stratospheric aerosols or particles to simulate the observed cooling effect of major volcanic eruptions. The best known is the detailed proposal of Paul Crutzen for sulphur dioxide. Also extensively discussed is diatomous earth, injected as individual diatoms. (Silica particles originating as marine shells.) This paper describes the selection and preliminary testing of chemicals that might be used as aviation fuel additives to distribute these two products, sulphur dioxide and micron sized silica particles, from a high flying commercial or military aircraft. The two chemicals tested are dimethyl sulphide to produce sulphur dioxide and tetra ethyl silicate to produce silica particles. In a closed glass jar both of these chemicals are indistinguishable from jet aviation fuel. Both are clear, colourless, oily liquids. Both dissolve in aviation fuel in any proportion. Solutions of each of these chemicals have been burned in a paraffin blowlamp as a simple simulation of a jet engine combustion chamber. Observation of the combustion suggests that the desired chemicals are produced and that the silica particles are of smoke or mist (micron) size. It is suggested that the solutions would probably have no detrimental effects on the fuel tanks, pipes, pumps or combustion chambers of the jet engine. This paper includes general facts about jet engines, aviation fuel, aircraft fuel systems and flight plans which may not be known to climate scientists. Also briefly considered are the health consequences of silica particles in the stratosphere. No tests have been done on a jet engine. Suggestions are made on the type of tests that would be needed by an organization having engine static test facilities.

  1. A total internal reflection ellipsometry and atomic force microscopy study of interactions between Proteus mirabilis lipopolysaccharides and antibodies.

    PubMed

    Gleńska-Olender, J; Sęk, S; Dworecki, K; Kaca, W

    2015-07-01

    Specific antigen-antibody interactions play a central role in the human immune system. The objective of this paper is to detect immune complexes using label-free detection techniques, that is, total internal reflection ellipsometry (TIRE) and atomic force microscopy (AFM)-based topography and recognition imaging. Interactions of purified rabbit immunoglobulin G (IgG) antibodies with bacterial endotoxins (Proteus mirabilis S1959 O3 lipopolysaccharides) were studied. Lipopolysaccharide was adsorbed on gold surface for TIRE. In the AFM imaging experiments, LPS was attachment to the PEG linker (AFM tip modification). The mica surface was covered by IgG. In TIRE, the optical parameters Ψ and Δ change when a complex is formed. It was found that even highly structured molecules, such as IgG antibodies (anti-O3 LPS rabbit serum), preserve their specific affinity to their antigens (LPS O3). LPS P. mirabilis O3 response of rabbit serum anti-O3 was also tested by topography and recognition imaging. Both TIRE and AFM techniques were recruited to check for possible detection of antigen-antibody recognition event. The presented data allow for determination of interactions between a variety of biomolecules. In future research, this technique has considerable potential for studying a wide range of antigen-antibody interactions and its use may be extended to other biomacromolecular systems. PMID:25854960

  2. Experiment and theory in particle physics: Reflections on the discovery of the tau lepton

    SciTech Connect

    Perl, M.L.

    1996-08-01

    This article is thoughts from the author on particle physics work from his perspective. It is not a summary of his work on the tau lepton, but rather a look at what makes good science, experimental and theoretical, from his experiences in the field. The section titles give a good summary on the topics the author chooses to touch upon. They are: the state of elementary particle physics; getting good ideas in experimental science; a difficult field; experiments and experimenting; 10% of the money and 30% of the time; the dictatorship of theory; technological dreams; last words.

  3. Atomic-resolution spectroscopic imaging of ensembles of nanocatalyst particles across the life of a fuel cell.

    PubMed

    Xin, Huolin L; Mundy, Julia A; Liu, Zhongyi; Cabezas, Randi; Hovden, Robert; Kourkoutis, Lena Fitting; Zhang, Junliang; Subramanian, Nalini P; Makharia, Rohit; Wagner, Frederick T; Muller, David A

    2012-01-11

    The thousand-fold increase in data-collection speed enabled by aberration-corrected optics allows us to overcome an electron microscopy paradox: how to obtain atomic-resolution chemical structure in individual nanoparticles yet record a statistically significant sample from an inhomogeneous population. This allowed us to map hundreds of Pt-Co nanoparticles to show atomic-scale elemental distributions across different stages of the catalyst aging in a proton-exchange-membrane fuel cell, and relate Pt-shell thickness to treatment, particle size, surface orientation, and ordering. PMID:22122715

  4. Effect of the particle-hole channel on BCS–Bose-Einstein condensation crossover in atomic Fermi gases

    PubMed Central

    Chen, Qijin

    2016-01-01

    BCS–Bose-Einstein condensation (BEC) crossover is effected by increasing pairing strength between fermions from weak to strong in the particle-particle channel, and has attracted a lot of attention since the experimental realization of quantum degenerate atomic Fermi gases. Here we study the effect of the (often dropped) particle-hole channel on the zero T gap Δ(0), superfluid transition temperature Tc, the pseudogap at Tc, and the mean-field ratio 2Δ(0)/, from BCS through BEC regimes, using a pairing fluctuation theory which includes self-consistently the contributions of finite-momentum pairs and features a pseudogap in single particle excitation spectrum. Summing over the infinite particle-hole ladder diagrams, we find a complex dynamical structure for the particle-hole susceptibility χph, and conclude that neglecting the self-energy feedback causes a serious over-estimate of χph. While our result in the BCS limit agrees with Gor’kov et al., the particle-hole channel effect becomes more complex and pronounced in the crossover regime, where χph is reduced by both a smaller Fermi surface and a big (pseudo)gap. Deep in the BEC regime, the particle-hole channel contributions drop to zero. We predict a density dependence of the magnetic field at the Feshbach resonance, which can be used to quantify χph and test different theories. PMID:27183875

  5. Effect of the particle-hole channel on BCS-Bose-Einstein condensation crossover in atomic Fermi gases.

    PubMed

    Chen, Qijin

    2016-01-01

    BCS-Bose-Einstein condensation (BEC) crossover is effected by increasing pairing strength between fermions from weak to strong in the particle-particle channel, and has attracted a lot of attention since the experimental realization of quantum degenerate atomic Fermi gases. Here we study the effect of the (often dropped) particle-hole channel on the zero T gap Δ(0), superfluid transition temperature Tc, the pseudogap at Tc, and the mean-field ratio 2Δ(0)/, from BCS through BEC regimes, using a pairing fluctuation theory which includes self-consistently the contributions of finite-momentum pairs and features a pseudogap in single particle excitation spectrum. Summing over the infinite particle-hole ladder diagrams, we find a complex dynamical structure for the particle-hole susceptibility χph, and conclude that neglecting the self-energy feedback causes a serious over-estimate of χph. While our result in the BCS limit agrees with Gor'kov et al., the particle-hole channel effect becomes more complex and pronounced in the crossover regime, where χph is reduced by both a smaller Fermi surface and a big (pseudo)gap. Deep in the BEC regime, the particle-hole channel contributions drop to zero. We predict a density dependence of the magnetic field at the Feshbach resonance, which can be used to quantify χph and test different theories. PMID:27183875

  6. Effect of the particle-hole channel on BCS–Bose-Einstein condensation crossover in atomic Fermi gases

    NASA Astrophysics Data System (ADS)

    Chen, Qijin

    2016-05-01

    BCS–Bose-Einstein condensation (BEC) crossover is effected by increasing pairing strength between fermions from weak to strong in the particle-particle channel, and has attracted a lot of attention since the experimental realization of quantum degenerate atomic Fermi gases. Here we study the effect of the (often dropped) particle-hole channel on the zero T gap Δ(0), superfluid transition temperature Tc, the pseudogap at Tc, and the mean-field ratio 2Δ(0)/, from BCS through BEC regimes, using a pairing fluctuation theory which includes self-consistently the contributions of finite-momentum pairs and features a pseudogap in single particle excitation spectrum. Summing over the infinite particle-hole ladder diagrams, we find a complex dynamical structure for the particle-hole susceptibility χph, and conclude that neglecting the self-energy feedback causes a serious over-estimate of χph. While our result in the BCS limit agrees with Gor’kov et al., the particle-hole channel effect becomes more complex and pronounced in the crossover regime, where χph is reduced by both a smaller Fermi surface and a big (pseudo)gap. Deep in the BEC regime, the particle-hole channel contributions drop to zero. We predict a density dependence of the magnetic field at the Feshbach resonance, which can be used to quantify χph and test different theories.

  7. Experimental impact features in Stardust aerogel: How track morphology reflects particle structure, composition, and density

    NASA Astrophysics Data System (ADS)

    Kearsley, Anton T.; Burchell, Mark J.; Price, Mark C.; Cole, Michael J.; Wozniakiewicz, Penelope J.; Ishii, Hope A.; Bradley, John P.; Fries, Marc; Foster, Nicholas J.

    2012-04-01

    The Stardust collector shows diverse aerogel track shapes created by impacts of cometary dust. Tracks have been classified into three broad types (A, B, and C), based on relative dimensions of the elongate "stylus" (in Type A "carrots") and broad "bulb" regions (Types B and C), with occurrence of smaller "styli" in Type B. From our experiments, using a diverse suite of projectile particles shot under Stardust cometary encounter conditions onto similar aerogel targets, we describe differences in impactor behavior and aerogel response resulting in the observed range of Stardust track shapes. We compare tracks made by mineral grains, natural and artificial aggregates of differing subgrain sizes, and diverse organic materials. Impacts of glasses and robust mineral grains generate elongate, narrow Type A tracks (as expected), but with differing levels of abrasion and lateral branch creation. Aggregate particles, both natural and artificial, of a wide range of compositions and volatile contents produce diverse Type B or C shapes. Creation of bulbous tracks is dependent upon impactor internal structure, grain size distribution, and strength, rather than overall grain density or content of volatile components. Nevertheless, pure organic particles do create Type C, or squat Type A* tracks, with length to width ratios dependent upon both specific organic composition and impactor grain size. From comparison with the published shape data for Stardust aerogel tracks, we conclude that the abundant larger Type B tracks on the Stardust collector represent impacts by particles similar to our carbonaceous chondrite meteorite powders.

  8. Collisions of 5 keV H+, H0, H- with Copper: Secondary Electron-Reflected Particle Coincidence Studies

    NASA Astrophysics Data System (ADS)

    Szilagyi, Zoltan; McGrath, Caith; Shah, Mansukh; McCullough, Robert; Woolsey, Jack

    2000-06-01

    The emission of secondary electrons during ion impact on a metal surface may be characterised by the secondary electron emission statistics (ES) and the mean yield g. The ES due to 5 keV H+, H0 and H- projectiles incident at 10 degrees on clean polycrystalline Copper, have been measured. Coincidence counting of electrons with reflected positive ions, neutrals and negative ions allow the ES due to specific scattering events to be recorded. The dependence of g on the incident and scattered projectile charge states has been determined. New information on the formation of negative ions from incident positive ions has been collected from this study. A time of flight technique has been employed to determine the energies of the reflected particles.

  9. Photoacoustic determination of optical properties of aerosol particles collected on filters: development of a method taking into account substrate reflectivity.

    PubMed

    Röhl, R; McClenny, W A; Palmer, R A

    1982-02-01

    The absorptivity of soot and methylene blue particles collected on Teflon filters is derived from photoacoustic measurements by least squares fitting a simple expression based on Beer's law to the experimental data. Refinements of the expression take into account the diffuse reflection of light by the filter substrate, yielding a base 10 absorptivity at 600 nm for soot of 3.00 +/- 0.37 m(2)/g. This value is in close agreement with the result of transmission measurements performed on the same samples (3.08 +/- 0.05 m(2)/g). PMID:20372465

  10. PREFACE: International Conference on Many Particle Spectroscopy of Atoms, Molecules, Clusters and Surfaces

    NASA Astrophysics Data System (ADS)

    Dowek, Danielle; Bennani, Azzedine; Lablanquie, Pascal; Maquet, Alfred

    2008-12-01

    The 2008 edition of the International Conference on Many Particle Spectroscopy of Atoms, Molecules, Clusters and Surfaces was held in Paris from 30 June to 2 July 2008. This biennial conference alternates with the International Symposium on (e,2e), Double Photoionization and Related Topics which is a satellite of the International Conference on Photonic, Electronic and Atomic Collisions (ICPEAC) conference. Over 110 participants from 20 countries gathered to examine the latest developments in the field of radiation interactions with matter. These include electron-electron correlation effects in excitation and in single and multiple ionization of atoms, molecules, clusters and surfaces with various projectiles: electrons, photons and ions. The present proceedings gathers the contributions of invited speakers and is intended to provide a detailed state-of-the-art account of the various facets of the field. Special thanks are due to Université Paris Sud XI, CNRS, and the laboratories LCAM, LIXAM and LCPMR which provided financial support for the organization of the conference. We are also grateful to the contribution of the companies Varian and RoentDek Handels GmbH. Guest Editors: Danielle Dowek and Azzedine Bennani LCAM, Université Paris Sud XI, France Pascal Lablanquie and Alfred Maquet LCPMR, Université Pierre et Marie Curie, Paris, France INTERNATIONAL SCIENTIFIC COMMITTEE Lorenzo Avaldi, (Italy) Alexei Grum Grzhimailo, (Russia) Klaus Bartschat, (USA) Nikolai Kabachnik, (Russia) Jamal Berakdar, (Germany) Birgit Lohmann, (Australia) Nora Berrah, (USA) Don H Madison, (USA) Michael Brunger, (Australia) Francis Penent, (France) Albert Crowe, (UK) Bernard Piraux, (Belgium) Claude Dal Cappello, (France) Roberto Rivarola, (Argentina) JingKang Deng, (China) Emma Sokkel, (Ireland) Alexander Dorn, (Germany) Giovanni Stefani, (Italy) Reinhardt Dorner, (Germany) Noboru Watanabe, (Japan) François Frémont, (France) LOCAL ORGANIZING COMMITTEE Azzedine BENNANI (Chair

  11. A method for the direct measurement of surface tension of collected atmospherically relevant aerosol particles using atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Hritz, Andrew D.; Raymond, Timothy M.; Dutcher, Dabrina D.

    2016-08-01

    Accurate estimates of particle surface tension are required for models concerning atmospheric aerosol nucleation and activation. However, it is difficult to collect the volumes of atmospheric aerosol required by typical instruments that measure surface tension, such as goniometers or Wilhelmy plates. In this work, a method that measures, ex situ, the surface tension of collected liquid nanoparticles using atomic force microscopy is presented. A film of particles is collected via impaction and is probed using nanoneedle tips with the atomic force microscope. This micro-Wilhelmy method allows for direct measurements of the surface tension of small amounts of sample. This method was verified using liquids, whose surface tensions were known. Particles of ozone oxidized α-pinene, a well-characterized system, were then produced, collected, and analyzed using this method to demonstrate its applicability for liquid aerosol samples. It was determined that oxidized α-pinene particles formed in dry conditions have a surface tension similar to that of pure α-pinene, and oxidized α-pinene particles formed in more humid conditions have a surface tension that is significantly higher.

  12. Some reflections on the role of semi-classical atomic models in the teaching and learning of introductory quantum mechanics

    NASA Astrophysics Data System (ADS)

    O'Sullivan, Colm

    2016-03-01

    The role of "semi-classical" (Bohr-Sommerfeld) and "semi-quantum-mechanical" (atomic orbital) models in the context of the teaching of atomic theory is considered. It is suggested that an appropriate treatment of such models can serve as a useful adjunct to quantum mechanical study of atomic systems.

  13. An atomic model AAA-ATPase/20S core particle sub-complex of the 26S proteasome

    SciTech Connect

    Foerster, Friedrich; Lasker, Keren; Beck, Florian; Nickell, Stephan; Sali, Andrej; Baumeister, Wolfgang

    2009-10-16

    The 26S proteasome is the most downstream element of the ubiquitin-proteasome pathway of protein degradation. It is composed of the 20S core particle (CP) and the 19S regulatory particle (RP). The RP consists of 6 AAA-ATPases and at least 13 non-ATPase subunits. Based on a cryo-EM map of the 26S proteasome, structures of homologs, and physical protein-protein interactions we derive an atomic model of the AAA-ATPase-CP sub-complex. The ATPase order in our model (Rpt1/Rpt2/Rpt6/Rpt3/Rpt4/Rpt5) is in excellent agreement with the recently identified base-precursor complexes formed during the assembly of the RP. Furthermore, the atomic CP-AAA-ATPase model suggests that the assembly chaperone Nas6 facilitates CP-RP association by enhancing the shape complementarity between Rpt3 and its binding CP alpha subunits partners.

  14. An atomic model AAA-ATPase/20S core particle sub-complex of the 26S proteasome.

    PubMed

    Förster, Friedrich; Lasker, Keren; Beck, Florian; Nickell, Stephan; Sali, Andrej; Baumeister, Wolfgang

    2009-10-16

    The 26S proteasome is the most downstream element of the ubiquitin-proteasome pathway of protein degradation. It is composed of the 20S core particle (CP) and the 19S regulatory particle (RP). The RP consists of 6 AAA-ATPases and at least 13 non-ATPase subunits. Based on a cryo-EM map of the 26S proteasome, structures of homologs, and physical protein-protein interactions we derive an atomic model of the AAA-ATPase-CP sub-complex. The ATPase order in our model (Rpt1/Rpt2/Rpt6/Rpt3/Rpt4/Rpt5) is in excellent agreement with the recently identified base-precursor complexes formed during the assembly of the RP. Furthermore, the atomic CP-AAA-ATPase model suggests that the assembly chaperone Nas6 facilitates CP-RP association by enhancing the shape complementarity between Rpt3 and its binding CP alpha subunits partners. PMID:19653995

  15. Infrared, spectral, directional-hemispherical reflectance of fused silica, Teflon polytetrafluoroethylene polymer, chrome oxide ceramic particle surface, Pyromark 2500 paint, Krylon 1602 paint, and Duraflect coating.

    PubMed

    Persky, Merle J; Szczesniak, Martin

    2008-04-01

    Infrared, spectral, directional-hemispherical reflectivity measurements of polished fused silica, Teflon polytetrafluoroethylene polymer, chrome oxide ceramic particle surface, Pyromark 2500 paint, Krylon 1602 paint, and Duraflect coating are provided. The reflectance was measured with an estimated accuracy of 0.01 to 0.02 units and a precision of 0.005 units. All the surfaces were measured at ambient temperatures. Additionally, the chrome oxide ceramic particle surface was measured at 486 K and the Pyromark 2500 at four temperatures to 877 K. Polarization measurements are also provided for fused silica, Duraflect, chrome oxide ceramic particle surface, and Pyromark 2500 paint. Separate diffuse and specular reflectance components for the Duraflect and chrome oxide ceramic surfaces are included. Fresnel-based predictions for fused silica parallel and perpendicular polarized reflections are compared to measurements. It is notable that the Pyromark 2500 and chrome oxide ceramic particle surfaces exhibit a significant lack of manufacturing repeatability. PMID:18382562

  16. Modeling of reflection-type laser-driven white lighting considering phosphor particles and surface topography.

    PubMed

    Lee, Dong-Ho; Joo, Jae-Young; Lee, Sun-Kyu

    2015-07-27

    This paper presents a model of blue laser diode (LD)-based white lighting coupled with a yellow YAG phosphor, for use in the proper design and fabrication of phosphor in automotive headlamps. First, the sample consisted of an LD, collecting lens, and phosphor was prepared that matches the model. The light distribution of the LD and the phosphor were modeled to investigate an effect of the surface topography and phosphor particle properties on the laser-driven white lighting systems by using the commercially available optical design software. Based on the proposed model, the integral spectrum distribution and the color coordinates were discussed. PMID:26367551

  17. Particle-in-cell charged-particle simulations, plus Monte Carlo collisions with neutral atoms, PIC-MCC

    SciTech Connect

    Birdsall, C.K. . Dept. of Electrical Engineering and Computer Sciences)

    1991-04-01

    Many-particle (meaning 100's) charged-particle plasma simulations using spatial meshes for the electromagnetic field solutions, particle-in-cell (PIC) merged with Monte Carlo collision (MCC) calculations, are coming into wide use for application to partially ionized gases. This paper emphasizes the development of PIC computer experiments since the 1950's starting with one-dimensional (1-D) charged-sheet models, the addition of the mesh, and fast direct Poisson equation solvers for 2-D and 3-D. The finite-size particle-in-mesh (finite {Delta}{chi}, {Delta}t) theory of Langdon is presented in part to display the effects of too small {lambda}{sub D}/{Delta}{chi}, even for Maxwellian velocity distributions, as a caution, for example, when some ions are cooled to background gas temperatures by charge exchange. Early work on adding collisions to 1-D charge-sheet models by Burger and Shanny et al. are presented, with many of the elements of current Monte Carlo codes. Bounded plasma modeling is presented with electrode charges and external R, L, C, and V(t), I(t) sources now in use on fast desktop computers as real-time computer experiments, complementing analytic modeling and laboratory experiments. This paper reports that the addition of Monte Carlo collisions (usually done with irregular timesteps) to PIC (usually done with uniform {Delta}t's) is displayed as a developing art, relying on experimental total cross sections and approximate analytical differential cross sections to produce changes in charged-particle speed and direction due to collisions with neutrals, so far including elastic, excitation, ionization, charge exchange, and attachment processes.

  18. The role of particle size in the laboratory reflectance spectra of pyroxenes: The case of the 670-nm minor feature

    NASA Astrophysics Data System (ADS)

    Mancarella, Francesca; Orofino, Vincenzo; Blanco, Armando; D'Elia, Marcella; Fonti, Sergio

    2015-11-01

    Reflectance spectroscopy is a very helpful tool for remote sensing investigations and has been widely used in terrestrial as well as planetary observations to study the surface composition. From this perspective, the visible (Vis) and near-infrared (NIR) regions of the spectrum, where several diagnostic absorption features of minerals are located, are well suited for the identification of such materials, in particular of rock-forming silicates. Among them, pyroxenes, which have been discovered on the surface of a number of different solar system bodies, play an important role. Up to now, both laboratory and remote sensing spectroscopic studies have been focused mainly on the two major bands at about 1 and 2 μm (the so-called Band I and Band II, respectively), while little attention has been paid to the minor bands falling in the visible range. One of the most important of them, present in many pyroxenes as well as in olivines, is the weak feature (reflectance minimum) near 670 nm, generally characterized by its variable wings (reflectance maxima) at about 570 nm and 720 nm. The intensity and the exact position of this feature depend on the type of pyroxene as well as on the grain size of the particles under consideration. In this work we present the Vis/NIR experimental reflectance spectra concerning enstatite and diopside, which are excellent representative of Low Calcium Pyroxenes (typically orthopyroxenes), and High Calcium Pyroxenes (typically clinopyroxenes) respectively. The results are very interesting and show a good correlation between the grain size of our samples and the relative intensities of the reflectance maxima occurring on both sides of the 670 nm feature. A similar study performed on Acfer 353, a pyroxene-rich eucritic meteorite of the Howardite-Eucrite-Diogenite family, of putative Vestan origin, shows that also in this case the variability in the Vis region of the spectra is linked to the grain size of the meteoritic particles. The connection

  19. Optimal experimental design for nano-particle atom-counting from high-resolution STEM images.

    PubMed

    De Backer, A; De Wael, A; Gonnissen, J; Van Aert, S

    2015-04-01

    In the present paper, the principles of detection theory are used to quantify the probability of error for atom-counting from high resolution scanning transmission electron microscopy (HR STEM) images. Binary and multiple hypothesis testing have been investigated in order to determine the limits to the precision with which the number of atoms in a projected atomic column can be estimated. The probability of error has been calculated when using STEM images, scattering cross-sections or peak intensities as a criterion to count atoms. Based on this analysis, we conclude that scattering cross-sections perform almost equally well as images and perform better than peak intensities. Furthermore, the optimal STEM detector design can be derived for atom-counting using the expression for the probability of error. We show that for very thin objects LAADF is optimal and that for thicker objects the optimal inner detector angle increases. PMID:25499018

  20. On reflecting boundary behind the Earth's orbit at propagation of fast particles from solar flares

    NASA Technical Reports Server (NTRS)

    Nishkovskikh, A. S.; Filippov, A. T.

    1985-01-01

    The flares of solar cosmic rays (SCR) associated with the presence of shocks in interplanetary magnetic field and with their propagation at significant heliocentric distances were always of great interest. Some events and problems concerning the peculiarities of propagation of flare CR in the interplanetary medium are considered. The distinguishing feature of such events is the presence of shock front behind the Earth's orbit having formed either directly in the process of shock generation on the Sun or at large heliocentric distances as a result of the interaction of fast and slow quasistationary recurrent solar wind (SW) streams. Based on the experimental material it is shown that the significant nonlinear disturbances in IMF behind the Earth's orbit can yield the occurrence of the additional SCR flux from shock front region as a result of the interaction of flare flux with shock and a partial reflection from it.

  1. Heavy particle atomic collisions in astrophysics: Beyond H and He targets

    SciTech Connect

    Stancil, P.C.; Krstic, P.S.; Schultz, D.R.

    1998-06-01

    The physical conditions relating to the emission of x-rays from Jovian and cometary atmospheres and to supernova ejecta are briefly described. Emphasis is placed on elucidating the relevance and importance of atomic collision processes, the availability of data, and the outstanding data needs for modeling these environments. Some preliminary theoretical studies of electron capture for important collisions systems, involving molecular and atomic metal targets, are presented.

  2. Calculation of the ground-state energy and average distance between particles for the nonsymmetric muonic {sup 3}He atom

    SciTech Connect

    Eskandari, M.R.; Rezaie, B.

    2005-07-15

    A calculation of the ground-state energy and average distance between particles in the nonsymmetric muonic {sup 3}He atom is given. We have used a wave function with one free parameter, which satisfies boundary conditions such as the behavior of the wave function when two particles are close to each other or far away. In the proposed wave function, the electron-muon correlation function is also considered. It has a correct behavior for r{sub 12} tending to zero and infinity. The calculated values for the energy and expectation values of r{sup 2n} are compared with the multibox variational approach and the correlation function hyperspherical harmonic method. In addition, to show the importance and accuracy of approach used, the method is applied to evaluate the ground-state energy and average distance between the particles of nonsymmetric muonic {sup 4}He atom. Our obtained results are very close to the values calculated by the mentioned methods and giving strong indications that the proposed wave functions, in addition to being very simple, provide relatively accurate values for the energy and expectation values of r{sup 2n}, emphasizing the importance of the local properties of the wave function.

  3. Analytic expressions for atomic layer deposition: Coverage, throughput, and materials utilization in cross-flow, particle coating, and spatial atomic layer deposition

    SciTech Connect

    Yanguas-Gil, Angel; Elam, Jeffrey W.

    2014-05-15

    In this work, the authors present analytic models for atomic layer deposition (ALD) in three common experimental configurations: cross-flow, particle coating, and spatial ALD. These models, based on the plug-flow and well-mixed approximations, allow us to determine the minimum dose times and materials utilization for all three configurations. A comparison between the three models shows that throughput and precursor utilization can each be expressed by universal equations, in which the particularity of the experimental system is contained in a single parameter related to the residence time of the precursor in the reactor. For the case of cross-flow reactors, the authors show how simple analytic expressions for the reactor saturation profiles agree well with experimental results. Consequently, the analytic model can be used to extract information about the ALD surface chemistry (e.g., the reaction probability) by comparing the analytic and experimental saturation profiles, providing a useful tool for characterizing new and existing ALD processes.

  4. Mechanism of Cluster DNA Damage Repair in Response to High-Atomic Number and Energy Particles Radiation

    PubMed Central

    Asaithamby, Aroumougame; Chen, David J.

    2012-01-01

    Low-linear energy transfer (LET) radiation (i.e., γ- and X-rays) induces DNA double-strand breaks (DSBs) that are rapidly repaired (rejoined). In contrast, DNA damage induced by the dense ionizing track of high-atomic number and energy (HZE) particles are slowly repaired or are irreparable. These unrepaired and/or misrepaired DNA lesions may contribute to the observed higher relative biological effectiveness for cell killing, chromosomal aberrations, mutagenesis, and carcinogenesis in HZE particle irradiated cells compared to those treated with low-LET radiation. The types of DNA lesions induced by HZE particles have been characterized in vitro and usually consist of two or more closely spaced strand breaks, abasic sites, or oxidized bases on opposing strands. It is unclear why these lesions are difficult to repair. In this review, we highlight the potential of a new technology allowing direct visualization of different types of DNA lesions in human cells and document the emerging significance of live-cell imaging for elucidation of the spatio-temporal characterization of complex DNA damage. We focus on the recent insights into the molecular pathways that participate in the repair of HZE particle-induced DSBs. We also discuss recent advances in our understanding of how different end-processing nucleases aid in repair of DSBs with complicated ends generated by HZE particles. Understanding the mechanism underlying the repair of DNA damage induced by HZE particles will have important implications for estimating the risks to human health associated with HZE particle exposure. PMID:21126526

  5. Broken particle-hole symmetry at atomically flat a-axis YBa2Cu3O7-delta interfaces.

    PubMed

    Davidson, Bruce A; Ramazashvili, Revaz; Kos, Simon; Eckstein, James N

    2004-09-01

    We have studied quasiparticle tunneling into atomically flat a-axis films of YBa(2)Cu(3)O(7-delta) and DyBa(2)Cu(3)O(7-delta) through epitaxial CaTiO3 barriers. The junction heterostructures were grown by oxide molecular beam epitaxy and were carefully optimized using in situ monitoring techniques, resulting in unprecedented crystalline perfection of the superconductor-insulator interface. Below T(c), the tunneling conductance shows the evolution of a large unexpected asymmetrical feature near zero-bias. This is evidence that superconducting YBCO crystals, atomically truncated along the lobe direction with a titanate layer, have intrinsically broken particle-hole symmetry over macroscopically large areas. PMID:15447441

  6. Atomic force microscopy investigation of Mason-Pfizer monkey virus and human immunodeficiency virus type 1 reassembled particles

    SciTech Connect

    Kuznetsov, Yu. G.; Ulbrich, P.; Haubova, S.; Ruml, T.; McPherson, A. . E-mail: amcphers@uci.edu

    2007-04-10

    Particles of {delta}ProCANC, a fusion of capsid (Canada) and nucleocapsid (NC) protein of Mason-Pfizer monkey virus (M-PMV), which lacks the amino terminal proline, were reassembled in vitro and visualized by atomic force microscopy (AFM). The particles, of 83-84 nm diameter, exhibited ordered domains based on trigonal arrays of prominent rings with center to center distances of 8.7 nm. Imperfect closure of the lattice on the spherical surface was affected by formation of discontinuities. The lattice is consistent only with plane group p3 where one molecule is shared between contiguous rings. There are no pentameric clusters nor evidence that the particles are icosahedral. Tubular structures were also reassembled, in vitro, from two HIV fusion proteins, {delta}ProCANC and CANC. The tubes were uniform in diameter, 40 nm, but varied in length to a maximum of 600 nm. They exhibited left handed helical symmetry based on a p6 hexagonal net. The organization of HIV fusion proteins in the tubes is significantly different than for the protein units in the particles of M-PMV {delta}ProCANC.

  7. Atomic force microscopy surface analysis of layered perovskite La2Ti2O7 particles grown by molten flux method

    NASA Astrophysics Data System (ADS)

    Orum, Aslihan; Takatori, Kazumasa; Hori, Shigeo; Ikeda, Tomiko; Yoshimura, Masamichi; Tani, Toshihiko

    2016-08-01

    Rectangular platelike particles of La2Ti2O7, a layered perovskite, were synthesized in KCl, NaCl, and LiCl by the molten flux method. The formation mechanism of the equilibrium shape in these alkali chloride fluxes was discussed in terms of the surface and interfacial energies of crystallographic planes. The atomic force microscopy (AFM) observations revealed that the developed plane of the platelike particles is along the interlayers in the {110}-type layered crystal structure, and is considered to represent the lowest surface energy plane in which strong, periodic Ti–O bond chains terminate. Herein, for the first time, a growth mechanism for La2Ti2O7 particles is proposed and discussed. Triangular prism structures along the c-axis were observed on the developed planes of KCl-grown particles whereas no such structures were found on those of LiCl-grown ones. AFM measurements suggest that the prism facets are {210}-La2Ti2O7, which results in lower interfacial energy within KCl.

  8. In situ atomic force microscopy analysis of morphology and particle size changes in lithium iron phosphate cathode during discharge.

    PubMed

    Demirocak, Dervis Emre; Bhushan, Bharat

    2014-06-01

    Li-ion batteries offer great promise for future plug-in hybrid electric vehicles (PHEVs) and pure electric vehicles (EVs). One of the challenges is to improve the cycle life of Li-ion batteries which requires detailed understanding of the aging phenomenon. In situ techniques are especially valuable to understand aging since it allows monitoring the physical and chemical changes in real time. In this study, in situ atomic force microscopy (AFM) is utilized to study the changes in morphology and particle size of LiFePO4 cathode during discharge. The guidelines for in situ AFM cell design for accurate and reliable measurements based on different designs are presented. The effect of working electrode to counter electrode surface area ratio on cycling data of an in situ cell is also discussed. Analysis of the surface area change in LiFePO4 particles when the cell was cycled between 100% and 70% state of charge is presented. Among four particles analyzed, surface area increase of particles during Li intercalation of LiFePO4 spanned from 1.8% to 14.3% indicating the inhomogeneous nature of the cathode surface. PMID:24703680

  9. Density and glass forming ability in amorphous atomic alloys: The role of the particle softness.

    PubMed

    Douglass, Ian; Hudson, Toby; Harrowell, Peter

    2016-04-14

    A key property of glass forming alloys, the anomalously small volume difference with respect to the crystal, is shown to arise as a direct consequence of the soft repulsive potentials between metals. This feature of the inter-atomic potential is demonstrated to be responsible for a significant component of the glass forming ability of alloys due to the decrease in the enthalpy of fusion and the associated depression of the freezing point. PMID:27083733

  10. Density and glass forming ability in amorphous atomic alloys: The role of the particle softness

    NASA Astrophysics Data System (ADS)

    Douglass, Ian; Hudson, Toby; Harrowell, Peter

    2016-04-01

    A key property of glass forming alloys, the anomalously small volume difference with respect to the crystal, is shown to arise as a direct consequence of the soft repulsive potentials between metals. This feature of the inter-atomic potential is demonstrated to be responsible for a significant component of the glass forming ability of alloys due to the decrease in the enthalpy of fusion and the associated depression of the freezing point.

  11. Characterization of the surface charge distribution on kaolinite particles using high resolution atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Kumar, Naveen; Zhao, Cunlu; Klaassen, Aram; van den Ende, Dirk; Mugele, Frieder; Siretanu, Igor

    2016-02-01

    Most solid surfaces, in particular clay minerals and rock surfaces, acquire a surface charge upon exposure to an aqueous environment due to adsorption and/or desorption of ionic species. Macroscopic techniques such as titration and electrokinetic measurements are commonly used to determine the surface charge and ζ -potential of these surfaces. However, because of the macroscopic averaging character these techniques cannot do justice to the role of local heterogeneities on the surfaces. In this work, we use dynamic atomic force microscopy (AFM) to determine the distribution of surface charge on the two (gibbsite-like and silica-like) basal planes of kaolinite nanoparticles immersed in aqueous electrolyte with a lateral resolution of approximately 30 nm. The surface charge density is extracted from force-distance curves using DLVO theory in combination with surface complexation modeling. While the gibbsite-like and the silica-like facet display on average positive and negative surface charge values as expected, our measurements reveal lateral variations of more than a factor of two on seemingly atomically smooth terraces, even if high resolution AFM images clearly reveal the atomic lattice on the surface. These results suggest that simple surface complexation models of clays that attribute a unique surface chemistry and hence homogeneous surface charge densities to basal planes may miss important aspects of real clay surfaces.

  12. Interplay of particle, nuclear and atomic physics in rare weak decays

    NASA Astrophysics Data System (ADS)

    Suhonen, Jouni

    2010-11-01

    The neutrinoless double beta decays of atomic nuclei are considered at the present the most viable way to access the fundamenntal nature and absolute mass scale of the neutrino. Recently one sub-class of these decays, the neutrinoless double electron capture (0νECEC), has attracted a lot of attention due to its potential of detection. In particular, the resonant 0νECEC is of interest owing to the possible huge enhancement of the corresponding decay rate by a resonance condition. At present the mass differences of the involved atom pairs are being measured by the Penning trap technique for several potential resonant 0νECEC decays. By evaluating the associated nuclear matrix elements using nuclear-structure models one can access the half-lives of these decays and thus predict their detection potential in underground experiments in the future. The absolute mass scale of the neutrino can also be accessed through beta decays of small decay energy. In these cases the effects of atomic origin may introduce non-negligible, even dramatic effects for Q values in the regime of few hundreds of eV and below.

  13. Influence of particle and surface quality on the vitrinite reflectance of dispersed organic matter: Comparative exercise using data from the qualifying system for reflectance analysis working group of ICCP

    USGS Publications Warehouse

    Borrego, A.G.; Araujo, C.V.; Balke, A.; Cardott, B.; Cook, A.C.; David, P.; Flores, D.; Hamor-Vido, M.; Hiltmann, W.; Kalkreuth, W.; Koch, J.; Kommeren, C.J.; Kus, J.; Ligouis, B.; Marques, M.; Mendonca, Filho J.G.; Misz, M.; Oliveira, L.; Pickel, W.; Reimer, K.; Ranasinghe, P.; Suarez-Ruiz, I.; Vieth, A.

    2006-01-01

    The development of a qualifying system for reflectance analysis has been the scope of a working group within the International Committee for Coal and Organic Petrology (ICCP) since 1999, when J. Koch presented a system to qualify vitrinite particles according to their size, proximity to bright components and homogeneity of the surface. After some years of work aimed at improving the classification system using photomicrographs, it was decided to run a round robin exercise on microscopy samples. The classification system tested consists of three qualifiers ranging from excellent to low quality vitrinites with an additional option for unsuitable vitrinites. This paper reports on the results obtained by 22 analysts who were asked to measure random reflectance readings on vitrinite particles assigning to each reading a qualifier. Four samples containing different organic matter types and a variety of vitrinite occurrences have been analysed. Results indicated that the reflectance of particles classified as excellent, good or poor compared to the total average reflectance did not show trends to be systematically lower or higher for the four samples analysed. The differences in reflectance between the qualifiers for any given sample were lower than the scatter of vitrinite reflectance among participants. Overall, satisfactory results were obtained in determining the reflectance of vitrinite in the four samples analysed. This was so for samples having abundant and easy to identify vitrinites (higher plant-derived organic matter) as well as for samples with scarce and difficult to identify particles (samples with dominant marine-derived organic matter). The highest discrepancies were found for the organic-rich oil shales where the selection of the vitrinite population to measure proved to be particularly difficult. Special instructions should be provided for the analysis of this sort of samples. The certainty of identification of the vitrinite associated with the vitrinite

  14. Characteristics of hypervelocity impact craters on LDEF experiment S1003 and implications of small particle impacts on reflective surfaces

    NASA Technical Reports Server (NTRS)

    Mirtich, Michael J.; Rutledge, Sharon K.; Banks, Bruce A.; Devries, Christopher; Merrow, James E.

    1993-01-01

    The Ion Beam textured and coated surfaces EXperiment (IBEX), designated S1003, was flown on LDEF at a location 98 deg in a north facing direction relative to the ram direction. Thirty-six diverse materials were exposed to the micrometeoroid (and some debris) environment for 5.8 years. Optical property measurements indicated no changes for almost all of the materials except S-13G, Kapton, and Kapton-coated surfaces, and these changes can be explained by other environmental effects. From the predicted micrometeoroid flux of NASA SP-8013, no significant changes in optical properties of the surfaces due to micrometeoroids were expected. There were hypervelocity impacts on the various diverse materials flown on IBEX, and the characteristics of these craters were documented using scanning electron microscopy (SEM). The S1003 alumigold-coated aluminum cover tray was sectioned into 2 cm x 2 cm pieces for crater documentation. The flux curve generated from this crater data fits well between the 1969 micrometeoroid model and the Kessler debris model for particles less than 10(exp -9) gm which were corrected for the S1003 positions (98 deg to ram). As the particle mass increases, the S1003 impact data is greater than that predicted by even the debris model. This, however, is consistent with data taken on intercostal F07 by the Micrometeoroid/Debris Special Investigating Group (M/D SIG). The mirrored surface micrometeoroid detector flown on IBEX showed no change in solar reflectance and corroborated the S1003 flux curve, as well as results of this surface flown on SERT 2 and OSO 3 for as long as 21 years.

  15. Characteristics of hypervelocity impact craters on LDEF experiment S1003 and implications of small particle impacts on reflective surfaces

    NASA Astrophysics Data System (ADS)

    Mirtich, Michael J.; Rutledge, Sharon K.; Banks, Bruce A.; Devries, Christopher; Merrow, James E.

    1993-04-01

    The Ion Beam textured and coated surfaces EXperiment (IBEX), designated S1003, was flown on LDEF at a location 98 deg in a north facing direction relative to the ram direction. Thirty-six diverse materials were exposed to the micrometeoroid (and some debris) environment for 5.8 years. Optical property measurements indicated no changes for almost all of the materials except S-13G, Kapton, and Kapton-coated surfaces, and these changes can be explained by other environmental effects. From the predicted micrometeoroid flux of NASA SP-8013, no significant changes in optical properties of the surfaces due to micrometeoroids were expected. There were hypervelocity impacts on the various diverse materials flown on IBEX, and the characteristics of these craters were documented using scanning electron microscopy (SEM). The S1003 alumigold-coated aluminum cover tray was sectioned into 2 cm x 2 cm pieces for crater documentation. The flux curve generated from this crater data fits well between the 1969 micrometeoroid model and the Kessler debris model for particles less than 10(exp -9) gm which were corrected for the S1003 positions (98 deg to ram). As the particle mass increases, the S1003 impact data is greater than that predicted by even the debris model. This, however, is consistent with data taken on intercostal F07 by the Micrometeoroid/Debris Special Investigating Group (M/D SIG). The mirrored surface micrometeoroid detector flown on IBEX showed no change in solar reflectance and corroborated the S1003 flux curve, as well as results of this surface flown on SERT 2 and OSO 3 for as long as 21 years.

  16. Echoing with the Voices of Victims: Reflection on Vietnamese Lessons on the Japanese Experiences of Atomic Bombs

    ERIC Educational Resources Information Center

    Saito, Eisuke; Hien, Do Thi; Hang, Khong Thi Diem

    2010-01-01

    This article explores the case of a Vietnamese teacher whose conception of teaching changed greatly following a short but intensive series of lessons based on the Japanese experiences with atomic bombs. The following three issues are considered: 1) what types of efforts teachers should make to increase the depth of their lessons, on the basis of…

  17. Particle size distribution of river-suspended sediments determined by in situ measured remote-sensing reflectance.

    PubMed

    Zhang, Yuanzhi; Huang, Zhaojun; Chen, Chuqun; He, Yijun; Jiang, Tingchen

    2015-07-10

    Suspended sediments in water bodies are classified into organic and inorganic matter and have been investigated by remote-sensing technology for years. Focusing on inorganic matter, however, detailed information such as the grain size of this matter has not been provided yet. In this study, we present a new solution for estimating inorganic suspended sediments' size distribution in highly complex Case 2 waters by using a simple spectrometer sensor rather than a backscattering sensor. An experiment was carried out in the Pearl River Estuary (PRE) in the dry season to collect the remote-sensing reflectance (Rrs) and particle size distribution (PSD) of inorganic suspended sediments. Based on Mie theory, PSDs in the PRE waters were retrieved by Rrs, colored dissolved organic matter, and phytoplankton. The retrieved median diameters in 12 stations show good agreement with those of laboratory analysis at root mean square error of 2.604 μm (27.63%), bias of 1.924 μm (20.42%), and mean absolute error of 2.298 μm (24.37%). The retrieved PSDs and previous PSDs were compared, and the features of PSDs in the PRE waters were concluded. PMID:26193416

  18. Measurements of dispersion forces between colloidal latex particles with the atomic force microscope and comparison with Lifshitz theory

    SciTech Connect

    Elzbieciak-Wodka, Magdalena; Ruiz-Cabello, F. Javier Montes; Trefalt, Gregor; Maroni, Plinio; Borkovec, Michal; Popescu, Mihail N.

    2014-03-14

    Interaction forces between carboxylate colloidal latex particles of about 2 μm in diameter immersed in aqueous solutions of monovalent salts were measured with the colloidal probe technique, which is based on the atomic force microscope. We have systematically varied the ionic strength, the type of salt, and also the surface charge densities of the particles through changes in the solution pH. Based on these measurements, we have accurately measured the dispersion forces acting between the particles and estimated the apparent Hamaker constant to be (2.0 ± 0.5) × 10{sup −21} J at a separation distance of about 10 nm. This value is basically independent of the salt concentration and the type of salt. Good agreement with Lifshitz theory is found when roughness effects are taken into account. The combination of retardation and roughness effects reduces the value of the apparent Hamaker constant and its ionic strength dependence with respect to the case of ideally smooth surfaces.

  19. Elementary particles

    NASA Astrophysics Data System (ADS)

    Fritzsch, Harald; Heusch, Karin

    Introduction -- Electrons and atomic nuclei -- Quantum properties of atoms and particles -- The knives of Democritus -- Quarks inside atomic nuclei -- Quantum electrodynamics -- Quantum chromodynamics -- Mesons, baryons, and quarks -- Electroweak interactions -- Grand unification -- Conclusion.

  20. MODELING REFLECTANCE AND TRANSMITTANCE OF QUARTZ-FIBER FILTER SAMPLES CONTAINING ELEMENTAL CARBON PARTICLES: IMPLICATIONS FOR THERMAL/OPTICAL ANALYSIS. (R831086)

    EPA Science Inventory

    A radiative transfer scheme that considers absorption, scattering, and distribution of light-absorbing elemental carbon (EC) particles collected on a quartz-fiber filter was developed to explain simultaneous filter reflectance and transmittance observations prior to and during...

  1. Human Injury From Atomic Particles and Photon Exposure: Fears, Myths, Risks, and Mortality

    PubMed Central

    2010-01-01

    Energy absorbtion from particles and photons moving at relativistic speeds has been a fundamental part of life on earth and wherever else life might exist. Heat and visible light have deeply influenced the course of human evolution, affecting habitat and nutrition. The photons of ionizing radiation that over time can possibly affect evolution, contribute to the more immediate problem of morbidity and mortality of cancer. This review addresses our radiative energy absorbtion, from both natural and manmade sources, and its relationship with disease and death. Educational Public Health efforts to offset the dangers of solar ultraviolet overexposure are presented, together with data on the significant mortality of metastatic melanoma. PMID:20481234

  2. Single-particle cryoEM analysis at near-atomic resolution from several thousand asymmetric subunits.

    PubMed

    Passos, Dario Oliveira; Lyumkis, Dmitry

    2015-11-01

    A single-particle cryoEM reconstruction of the large ribosomal subunit from Saccharomyces cerevisiae was obtained from a dataset of ∼75,000 particles. The gold-standard and frequency-limited approaches to single-particle refinement were each independently used to determine orientation parameters for the final reconstruction. Both approaches showed similar resolution curves and nominal resolution values for the 60S dataset, estimated at 2.9 Å. The amount of over-fitting present during frequency-limited refinement was quantitatively analyzed using the high-resolution phase-randomization test, and the results showed no apparent over-fitting. The number of asymmetric subunits required to reach specific resolutions was subsequently analyzed by refining subsets of the data in an ab initio manner. With our data collection and processing strategies, sub-nanometer resolution was obtained with ∼200 asymmetric subunits (or, equivalently for the ribosomal subunit, particles). Resolutions of 5.6 Å, 4.5 Å, and 3.8 Å were reached with ∼1000, ∼1600, and ∼5000 asymmetric subunits, respectively. At these resolutions, one would expect to detect alpha-helical pitch, separation of beta-strands, and separation of Cα atoms, respectively. Using this map, together with strategies for ab initio model building and model refinement, we built a region of the ribosomal protein eL6, which was missing in previous models of the yeast ribosome. The relevance for more routine high-resolution structure determination is discussed. PMID:26470814

  3. Optically sensitive devices based on Pt nano particles fabricated by atomic layer deposition and embedded in a dielectric stack

    NASA Astrophysics Data System (ADS)

    Mikhelashvili, V.; Padmanabhan, R.; Meyler, B.; Yofis, S.; Atiya, G.; Cohen-Hyams, Z.; Weindling, S.; Ankonina, G.; Salzman, J.; Kaplan, W. D.; Eisenstein, G.

    2015-10-01

    We report a series of metal insulator semiconductor devices with embedded Pt nano particles (NPs) fabricated using a low temperature atomic layer deposition process. Optically sensitive nonvolatile memory cells as well as optical sensors: (i) varactors, whose capacitance-voltage characteristics, nonlinearity, and peak capacitance are strongly dependent on illumination intensity; (ii) highly linear photo detectors whose responsivity is enhanced due to the Pt NPs. Both single devices and back to back pairs of diodes were used. The different configurations enable a variety of functionalities with many potential applications in biomedical sensing, environmental surveying, simple imagers for consumer electronics and military uses. The simplicity and planar configuration of the proposed devices makes them suitable for standard CMOS fabrication technology.

  4. Optimizing the flux coupling between a nanoSQUID and a magnetic particle using atomic force microscope nanolithography

    NASA Astrophysics Data System (ADS)

    Faucher, M.; Jubert, P. O.; Fruchart, O.; Wernsdorfer, W.; Bouchiat, V.

    2009-06-01

    We present results of niobium based SQUID magnetometers for which the weak links are engineered by the local oxidation of thin films using an atomic force microscope (AFM). Firstly, we show that this technique allows the creation of variable thickness bridges with 10 nm lateral resolution. Precise control of the weak link milling is offered by the possibility to monitor, in real-time, the weak link conductance. Such a process is shown to enhance the magnetic field modulation and hence the sensitivity of the magnetometer. Secondly, AFM lithography is used to provide a precise alignment of nanoSQUID weak links with respect to a ferromagnetic iron dot. The magnetization switching of the near-field coupled particle is studied as a function of the applied magnetic field direction.

  5. Optically sensitive devices based on Pt nano particles fabricated by atomic layer deposition and embedded in a dielectric stack

    SciTech Connect

    Mikhelashvili, V.; Padmanabhan, R.; Eisenstein, G.; Meyler, B.; Yofis, S.; Weindling, S.; Salzman, J.; Atiya, G.; Cohen-Hyams, Z.; Kaplan, W. D.; Ankonina, G.

    2015-10-07

    We report a series of metal insulator semiconductor devices with embedded Pt nano particles (NPs) fabricated using a low temperature atomic layer deposition process. Optically sensitive nonvolatile memory cells as well as optical sensors: (i) varactors, whose capacitance-voltage characteristics, nonlinearity, and peak capacitance are strongly dependent on illumination intensity; (ii) highly linear photo detectors whose responsivity is enhanced due to the Pt NPs. Both single devices and back to back pairs of diodes were used. The different configurations enable a variety of functionalities with many potential applications in biomedical sensing, environmental surveying, simple imagers for consumer electronics and military uses. The simplicity and planar configuration of the proposed devices makes them suitable for standard CMOS fabrication technology.

  6. Transport of charge and atomic particles in Rydberg state-rich plasmas

    NASA Astrophysics Data System (ADS)

    Hagström, Magnus; Davidsson, Jan; Holmlid, Leif

    1998-02-01

    New methods make it possible to form considerable flux densities of Rydberg atoms of alkali metals. It is now possible to study the transport processes in regions where the density of Rydberg atoms is large. Examples of such studies have been given by Svensson and coworkers. In the present study, 0022-3727/31/4/013/img1 ions and Rydberg states 0022-3727/31/4/013/img2 are formed by desorption at 1300-1800 K from an Ir surface covered by a thin graphite layer. Due to the very large cross sections for collision processes involving Rydberg species, the Rydberg state-rich plasma between the Ir emitter and a cold grid electrode is not collision free, even at a pressure of 0022-3727/31/4/013/img3 mbar. Electron or 0022-3727/31/4/013/img4 emission takes place from the grid at a rate controlled by the flux of 0022-3727/31/4/013/img1 and 0022-3727/31/4/013/img2. The transition to penetration of 0022-3727/31/4/013/img1 and 0022-3727/31/4/013/img2 through the cloud of excited species between the emitter and grid is observed directly by molecular beam and ion sampling to detectors in a separate chamber. There is a space-charge limited behaviour for the positive current through the plasma as well as, in some modes, a clear positive saturation current, which shows that little gas phase ionization takes place. A current larger than expected from the saturation current as well as maxima in the voltage dependences are observed at high Rydberg densities. These effects are probably caused by space charge compensation due to a dielectric phase of condensed excited species, which means, for example, that the effective distance between the emitter and grid is decreased, as observed. The temperature variation of the space charge limited behaviour gives an activation energy of 0022-3727/31/4/013/img9, while the saturation current gives an activation energy of 0022-3727/31/4/013/img10. This agrees well with the electronic excitations 0022-3727/31/4/013/img11 at 0.90 eV and 0022

  7. Atomic effects of beta decay in astrophysics and in elementary particle physics

    NASA Astrophysics Data System (ADS)

    Chen, Zonghua

    The bound-state beta decay of Re-187 and its application in Astrophysics is studied. There existed an uncertainty in the ratio of rhop of bound-state to continuum beta decay of Re-187 in both theory and experiment. A more definite theoretical result of rhop of approximately 1 percent is obtained by using single-configuration and multi-configuration Hartree-Fock-Dirac approximations. The results obtained are close to those obtained by Williams, Fowler, and Koonin by a modified Thomas-Fermi model. The bound-state beta decay of Re-187 at high temperatures is also studied. A generalization of the Thomas-Fermi results of various energy contributions to the ground-state energy of a neutral atom is also presented. An analytical expression for the ratio of the electron-electron to electron-nuclear interaction is obtained by the corrected Thomas-Fermi result, the ratio obtained gives a better agreement with the Hartree-Fock numerical results.

  8. Atomic force microscopy measurements of bacterial adhesion and biofilm formation onto clay-sized particles

    NASA Astrophysics Data System (ADS)

    Huang, Qiaoyun; Wu, Huayong; Cai, Peng; Fein, Jeremy B.; Chen, Wenli

    2015-11-01

    Bacterial adhesion onto mineral surfaces and subsequent biofilm formation play key roles in aggregate stability, mineral weathering, and the fate of contaminants in soils. However, the mechanisms of bacteria-mineral interactions are not fully understood. Atomic force microscopy (AFM) was used to determine the adhesion forces between bacteria and goethite in water and to gain insight into the nanoscale surface morphology of the bacteria-mineral aggregates and biofilms formed on clay-sized minerals. This study yields direct evidence of a range of different association mechanisms between bacteria and minerals. All strains studied adhered predominantly to the edge surfaces of kaolinite rather than to the basal surfaces. Bacteria rarely formed aggregates with montmorillonite, but were more tightly adsorbed onto goethite surfaces. This study reports the first measured interaction force between bacteria and a clay surface, and the approach curves exhibited jump-in events with attractive forces of 97 ± 34 pN between E. coli and goethite. Bond strengthening between them occurred within 4 s to the maximum adhesion forces and energies of -3.0 ± 0.4 nN and -330 ± 43 aJ (10-18 J), respectively. Under the conditions studied, bacteria tended to form more extensive biofilms on minerals under low rather than high nutrient conditions.

  9. Atomic force microscopy measurements of bacterial adhesion and biofilm formation onto clay-sized particles

    PubMed Central

    Huang, Qiaoyun; Wu, Huayong; Cai, Peng; Fein, Jeremy B.; Chen, Wenli

    2015-01-01

    Bacterial adhesion onto mineral surfaces and subsequent biofilm formation play key roles in aggregate stability, mineral weathering, and the fate of contaminants in soils. However, the mechanisms of bacteria-mineral interactions are not fully understood. Atomic force microscopy (AFM) was used to determine the adhesion forces between bacteria and goethite in water and to gain insight into the nanoscale surface morphology of the bacteria-mineral aggregates and biofilms formed on clay-sized minerals. This study yields direct evidence of a range of different association mechanisms between bacteria and minerals. All strains studied adhered predominantly to the edge surfaces of kaolinite rather than to the basal surfaces. Bacteria rarely formed aggregates with montmorillonite, but were more tightly adsorbed onto goethite surfaces. This study reports the first measured interaction force between bacteria and a clay surface, and the approach curves exhibited jump-in events with attractive forces of 97 ± 34 pN between E. coli and goethite. Bond strengthening between them occurred within 4 s to the maximum adhesion forces and energies of −3.0 ± 0.4 nN and −330 ± 43 aJ (10−18 J), respectively. Under the conditions studied, bacteria tended to form more extensive biofilms on minerals under low rather than high nutrient conditions. PMID:26585552

  10. Atomic force microscopy measurements of bacterial adhesion and biofilm formation onto clay-sized particles.

    PubMed

    Huang, Qiaoyun; Wu, Huayong; Cai, Peng; Fein, Jeremy B; Chen, Wenli

    2015-01-01

    Bacterial adhesion onto mineral surfaces and subsequent biofilm formation play key roles in aggregate stability, mineral weathering, and the fate of contaminants in soils. However, the mechanisms of bacteria-mineral interactions are not fully understood. Atomic force microscopy (AFM) was used to determine the adhesion forces between bacteria and goethite in water and to gain insight into the nanoscale surface morphology of the bacteria-mineral aggregates and biofilms formed on clay-sized minerals. This study yields direct evidence of a range of different association mechanisms between bacteria and minerals. All strains studied adhered predominantly to the edge surfaces of kaolinite rather than to the basal surfaces. Bacteria rarely formed aggregates with montmorillonite, but were more tightly adsorbed onto goethite surfaces. This study reports the first measured interaction force between bacteria and a clay surface, and the approach curves exhibited jump-in events with attractive forces of 97 ± 34 pN between E. coli and goethite. Bond strengthening between them occurred within 4 s to the maximum adhesion forces and energies of -3.0 ± 0.4 nN and -330 ± 43 aJ (10(-18) J), respectively. Under the conditions studied, bacteria tended to form more extensive biofilms on minerals under low rather than high nutrient conditions. PMID:26585552

  11. Optical and morphological study of misoriented GaAs substrates exposed to bismuth flow using in situ spectral reflectance and atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Massoudi, I.; Habchi, M. M.; Rebey, A.; El Jani, B.

    2012-08-01

    (100) GaAs substrates with different misorientations were exposed to trimethyl-bismuth (TMBi) flow. The wafers were examined after exposure times of 9 and 43 min. The wafers growth was carried out at atmospheric pressure, in a metalorganic vapor phase epitaxy (MOVPE) reactor, at a temperature of 375 °C. The in situ spectral reflectance (SR) in the spectral range 400-1000 nm was used to monitor the deposition. The reflectivity is marked by two temporal phases, an increase followed by a slow decrease. The atomic force microscopy (AFM) measurements show two different growth modes of bismuth, big isolated islands for early exposure time and a high density of small islands for long exposure times. We also note that the islands' density and size change greatly with the misorientation of the substrate. The correlation between the results given by ex situ AFM and in situ SR is performed via theoretical simulations. We show that roughness, as well as optical and thermal effects are mainly responsible for the reflectivity behavior. We have successfully quantified the spectral evolution of the sensitivity σSR of the incident beam wavelength to the surface undulations.

  12. Observation of different reflected high-energy electron diffraction patterns during atomic layer epitaxy growth of CdTe epilayers

    NASA Astrophysics Data System (ADS)

    Faschinger, W.; Juza, P.; Sitter, H.

    1991-12-01

    We present the first RHEED observations during atomic layer epitaxy growth of CdTe on GaAs substrates. The evolution of the RHEED pattern shows that, despite the large lattice mismatch, growth becomes two-dimensional after the deposition of a few monolayers. We observe intensity variations of two RHEED spots under surface resonance conditions and show that this new approach is superior to the observation of the specular spot for the measurement of surface coverages and adsorption kinetics. From the variation of the spot intensities with substrate temperature, we deduce that the Cd and Te surface coverages drop to 0.5 at substrate temperatures higher than 315°C.

  13. The Development of Dalton's Atomic Theory as a Case Study in the History of Science: Reflections for Educators in Chemistry

    NASA Astrophysics Data System (ADS)

    Viana, Hélio Elael Bonini; Porto, Paulo Alves

    2010-01-01

    The inclusion of the history of science in science curricula—and specially, in the curricula of science teachers—is a trend that has been followed in several countries. The reasons advanced for the study of the history of science are manifold. This paper presents a case study in the history of chemistry, on the early developments of John Dalton’s atomic theory. Based on the case study, several questions that are worth discussing in educational contexts are pointed out. It is argued that the kind of history of science that was made in the first decades of the twentieth century (encyclopaedic, continuist, essentially anachronistic) is not appropriate for the development of the competences that are expected from the students of sciences in the present. Science teaching for current days will benefit from the approach that may be termed the “new historiography of science”.

  14. Effects of viewing geometry, aggregation state, and particle size on reflectance spectra of the Murchison CM2 chondrite deconvolved to Dawn FC band passes

    NASA Astrophysics Data System (ADS)

    Izawa, Matthew R. M.; Schäfer, Tanja; Pietrasz, Valerie B.; Cloutis, Edward A.; Mann, Paul; Nathues, Andreas; Mengel, Kurt; Schäfer, Michael; Thangjam, Guneshwar; Hoffmann, Martin; Tait, Kimberly T.; Applin, Daniel M.

    2016-03-01

    Several current and soon-to-launch missions will investigate 'dark' asteroids, whose spectra have few weak or no distinct spectral features. Some carbonaceous chondrites, particularly the CI and CM groups, are reasonable material analogues for many dark asteroid surfaces. In addition to compositional variations, many non-compositional effects, including viewing geometry, surface particle size and particle sorting, can influence reflectance spectra, potentially complicating mineralogical interpretation of such data from remote surfaces. We have carried out an investigation of the effects of phase angle, particle size, aggregation state, and intra-sample heterogeneity on the reflectance spectra (0.4-1.0 μm) of the Murchison CM2 carbonaceous chondrite, deconvolved to Dawn Framing Camera (FC) band passes. This study was motivated by the desire to derive information about the surface of Ceres from Dawn FC data. Key spectral parameters derived from the FC multispectral data include various two-band reflectance ratios as well as three-band ratios that have been derived for mineralogical analysis. Phase angle effects include increased visible slope with increasing phase angle, a trend that may reverse at very high phase angles. Fine-grained particles exert a strong influence on spectral properties relative to their volumetric proportion. Grain size variation effects include a decrease in spectral contrast and increased visible spectral slope with decreasing grain size. Intra-sample heterogeneity, while spectrally detectable, is of relatively limited magnitude.

  15. Si (111) surface cleaning using atomic hydrogen and SiH2 studied using reflection high-energy electron diffraction

    NASA Astrophysics Data System (ADS)

    Hirayama, Hiroyuki; Tatsumi, Toru

    1989-07-01

    The Si(111) wafer covered by a thin protective oxide layer was cleaned in disilane gas source Si molecular-beam epitaxy chamber. The effect of the electron cyclotron resonance (ECR) cracked/uncracked disilane or hydrogen irradiation on the initial surface cleaning was studied by observing the reflection high-energy electron diffraction pattern change. The ECR-cracked disilane irradiation was the most effective for lowering the cleaning temperature and the surface cleaning was achieved at 680 °C. The uncracked disilane and the ECR-cracked hydrogen irradiation were also effective for lowering the cleaning temperature. The uncracked hydrogen irradiation has no effect for lowering the cleaning temperature. The SiH2 and H were main species of the ECR-cracked disilane and these played important roles in the cleaning process.

  16. Reflectance spectroscopy of low atomic weight and Na-rich minerals: Borates, hydroxides, nitrates, nitrites, and peroxides

    NASA Astrophysics Data System (ADS)

    Cloutis, E.; Berg, B.; Mann, P.; Applin, D.

    2016-01-01

    We have measured reflectance spectra (0.35-20 μm) of a suite of minerals and synthetic compounds that contain low-Z (⩽Na) elements as the major cation and/or the major anion in oxides/oxyhydroxides, and are relevant to planetary geology and astrobiology. The suite comprises Na-borates, Na-, K-, Ca-hydroxides, nitrates, nitrites, and peroxides. Na-borate spectra exhibit B-O fundamental vibrations between 7 and 14 μm, and overtones/combinations of these bands in the 1.55, 1.75, 2.15, and 2.25 μm regions. Na-, K-, and Ca-hydroxide reflectance spectra are characterized by OH and metal-OH fundamental vibrations near 3, 8, and 18 μm, and a number of overtone and combination absorption bands at shorter wavelengths, and a characteristic metal-OH band near 2.35 μm. The nitrate and nitrite spectra exhibit fundamental N-O vibrations in the 7-14 μm region and numerous combinations and overtones that are still detectable to as low as ∼1.8 μm. Na-peroxide is largely spectrally featureless below 24 μm, making its detection problematic, while H-peroxide has many OH-related absorption features below 2.5 μm that differ in position from those of H2O ice and liquid. The results of this study indicate that the borates, hydroxides, nitrates, nitrite, and hydrogen peroxide can all be uniquely identified using characteristic absorption features that are present below 2.5 μm. However, some of these features are weak, and their detectability will depend on the types and abundances of any accessory phases that may be present.

  17. Experiences and Reflections about Teaching Atomic Structure in a Jigsaw Classroom in Lower Secondary School Chemistry Lessons

    NASA Astrophysics Data System (ADS)

    Eilks, Ingo

    2005-02-01

    This article describes and discusses an example of how atomic structure can be taught in lower secondary chemistry using a modified jigsaw-classroom method. The lesson was taught in grades 9 and 10 (age range 15 17 years) chemistry in 13 learning groups with a total of 313 students in various grammar, middle, and comprehensive schools in Germany. The written evaluation of the lesson focused on determining the students’ opinions on the teaching methods that were used. Emphasis was on gathering information from the students’ viewpoint. Did the students think that these methods could make science lessons more attractive? Could these methods help to promote more active student learning, cooperative learning, or communicative and social abilities? Additional data that were derived from a cognitive test and teacher feedback are also presented. The results of the study show that teaching methods like the jigsaw classroom have potential to improve students’ attitude towards science. The results may also indicate that it is appropriate to demand that student-oriented and cooperative-learning methods be used more often in secondary level science education.

  18. Single atomic particle at rest in free space : new value for electron radius

    NASA Astrophysics Data System (ADS)

    Dehmelt, H.

    Zero-point confinement in a suitable trap is briefly discussed as a quantum-mechanical equivalent of the classical single particle at rest in free space. So far, such confinement has been realized only for the 150 GHz cyclotron motion in geonium, a single electron permanently confined in a Penning trap. The most important result of mono-ion spectroscopy is a new, 10 000 times smaller, radius for the electron. This result was obtained by analyzing our g-factor data, g/2 = 1.001 159 652 193 (4), on the basis of a near-Dirac particle model. RF spectroscopy in geonium relies on the Continuous Stem Gerlach Effect in which a spin flip is detected as a small change in the ~ 60 MHz axial oscillation frequency of the electron in the trap. The Kaufmann Effect or relativistic mass shift may become a superior alternative : operating a geonium apparatus as a frequency selective mini-synchro-cyclotron has produced an easily detectable shift in the axial frequency. Like in Habann's 1926 split-anode magnetron, energy is quickly transferred from the oscillating electron to a resonant circuit, but by us for the purpose of detection, damping and cooling of the oscillatory motion. Conversely, localizing the electron to ~ 60 μm in the node of a standing wave in the trap cavity, where this cavity looks like a short, when it is resonant with the cyclotron motion, has made it possible to decrease the natural line width ten-fold. By driving the axial frequency not on resonance but on a side band higher by the ~ 12 kHz magnetron frequency, it has been possible to force the magnetron motion to absorb the excess in the photon energy and thereby shrink the magnetron radius to ~ 15 μm. By an analogous laser spectroscopic procedure the oscillation amplitude of a Ba+ ion in a different trap has been reduced to ~ 120 nm or less. Like in Nuclear Magnetic Resonance, confinement is now much smaller than the wave length and no motional side bands appear in the optical spectrum. Such a mono

  19. Design and demonstration of a system for the deposition of atomic-oxygen durable coatings for reflective solar dynamic power system concentrators

    NASA Technical Reports Server (NTRS)

    Mcclure, Donald J.

    1988-01-01

    A system for the vacuum deposition of atomic-oxygen durable coatings for reflective solar dynamic power systems (SDPS) concentrators was designed and demonstrated. The design issues pertinent to SDPS were developed by the Government Aerospace Systems Division of the Harris Corporation and are described in NASA-CR-179489. Both design and demonstration phases have been completed. At the time of this report the deposition system was ready for coating of facets for SDPS concentrators. The materials issue relevant to the coating work were not entirely resolved. These issues can only be resolved when substrates which are comparable to those which will be used in flight hardware are available. The substrates available during the contract period were deficient in the areas of surface roughness and contamination. These issues are discussed more thoroughly in the body of the report.

  20. An international conference in honour of the centennial of the birth of Ya.B. Zeldovich, "Subatomic Particles, Nucleons, Atoms, the Universe: Processes and Structure"

    NASA Astrophysics Data System (ADS)

    Kilin, S. Ya.; Ruffini, R.; Vereshchagin, G.

    2015-06-01

    An international conference in honour of the centennial of the birth of Ya.B. Zeldovich, "Subatomic Particles, Nucleons, Atoms, the Universe: Processes and Structure" was held in Minsk, Belarus on March 10-14, 2014. Scientific papers based on plenary presentations made at this conference are being published in Volumes 6 and 7, 2015 of "Astronomy Reports."

  1. Transfer of a weakly bound electron in collisions of Rydberg atoms with neutral particles. II. Ion-pair formation and resonant quenching of the Rb(nl) and Ne(nl) States by Ca, Sr, and Ba atoms

    SciTech Connect

    Narits, A. A.; Mironchuk, E. S.; Lebedev, V. S.

    2013-10-15

    Electron-transfer processes are studied in thermal collisions of Rydberg atoms with alkaline-earth Ca(4s{sup 2}), Sr(5s{sup 2}), and Ba(6s{sup 2}) atoms capable of forming negative ions with a weakly bound outermost p-electron. We consider the ion-pair formation and resonant quenching of highly excited atomic states caused by transitions between Rydberg covalent and ionic terms of a quasi-molecule produced in collisions of particles. The contributions of these reaction channels to the total depopulation cross section of Rydberg states of Rb(nl) and Ne(nl) atoms as functions of the principal quantum number n are compared for selectively excited nl-levels with l Much-Less-Than n and for states with large orbital quantum numbers l = n - 1, n - 2. It is shown that the contribution from resonant quenching dominates at small values of n, and the ion-pair formation process begins to dominate with increasing n. The values and positions of the maxima of cross sections for both processes strongly depend on the electron affinity of an alkaline-earth atom and on the orbital angular momentum l of a highly excited atom. It is shown that in the case of Rydberg atoms in states with large l {approx} n - 1, the rate constants of ion-pair formation and collisional quenching are considerably lower than those for nl-levels with l Much-Less-Than n.

  2. Visible and Near-Infrared (VNIR) reflectance spectroscopy of glassy igneous material: Spectral variation, retrieving optical constants and particle sizes by Hapke model

    NASA Astrophysics Data System (ADS)

    Carli, C.; Roush, T. L.; Pedrazzi, G.; Capaccioni, F.

    2016-03-01

    Silicate glasses with igneous compositions can be an important constituent of planetary surface material via effusive volcanism or impact cratering processes. Different planetary surfaces are mapped with hyper-spectrometers in the VNIR, and in this spectral range crystal field absorptions are useful in discriminating iron bearing silicate components. For these reasons studying glassy materials, and their optical constants, is an important effort to better document and understand spectral features of Solar System silicate crusts where glasses are present, but may be difficult to map. In our work we present a set of four different synthetic glasses, produced under terrestrial conditions, with variable composition and in particular an increasing amount of iron. The VNIR spectra show, for all the compositions, two absorptions are present near 1.1 and 1.9 μm but reflectance, slope and absorption shape varies with composition. We measured the reflectance of different particle sizes of the samples and used radiative transfer models to estimate the optical constants as a function of wavelength. We used the retrieved optical constants to estimate the particle size from the measured reflectances and the results fall within the known sieve range. We qualitatively discuss the effect of the shape and distribution of particles on the application of the model.

  3. Structure of single-supported DMPC lipid bilayer membranes as a function of hydration level studied by neutron reflectivity and Atomic Force Microscopy

    NASA Astrophysics Data System (ADS)

    Miskowiec, A.; Schnase, P.; Bai, M.; Taub, H.; Hansen, F. Y.; Dubey, M.; Singh, S.; Majewski, J.

    2012-02-01

    We have recently been investigating the diffusion of water on single-supported DMPC lipid bilayer membranes at different levels of hydration, using high-resolution quasielastic neutron scattering (QNS). To aid in the interpretation of these QNS studies, we have conducted neutron reflectivity (NR) measurements on SPEAR at LANSCE to characterize the structure of similarly prepared samples. Protonated DMPC membranes were deposited onto SiO2-coated Si(100) substrates and characterized by Atomic Force Microscopy (AFM) at different levels of hydration. We find reasonable agreement between the membrane thickness determined by NR and AFM at room temperature. We also find consistency between the scattering length density (SLD) profile in the vicinity of the upper leaflet of the supported DMPC membrane and that found in a molecular dynamics simulation of a freestanding membrane at 303 K. However, the fit to the reflectivity curve can be improved by modifying the SLD profile near the leaflet closest to the SiO2 surface.

  4. SUPPRESSION OF REFLECTED ELECTRONS BY KINETIC ALFVEN TURBULENCE IN A QUASI-PERPENDICULAR SHOCK: PARTICLE-IN-CELL SIMULATIONS

    SciTech Connect

    Saito, S.; Umeda, T.

    2011-07-20

    Shock drift acceleration is one of the important mechanisms for electron acceleration associated with magnetic mirror reflection along the magnetic field in a quasi-perpendicular collisionless shock. We study the influence of a rippled shock surface in the in-plane magnetic field on the magnetic mirror reflection of electrons. Simulation results show that the number of reflected electrons reduces after generation of the rippled shock surface. Electric and magnetic wavenumber spectra of the generated fluctuations in the shock transition region indicate the existence of kinetic Alfven turbulence. The kinetic Alfven turbulence decreases the electron pitch angle by parallel scattering, which reduces the magnetic mirror force acting on the electrons. These results suggest that the shock-generated kinetic Alfven turbulence suppresses the magnetic mirror reflection of electrons during the shock drift acceleration.

  5. Analytic expressions for Atomic Layer Deposition: coverage, throughput, and materials utilization in cross-flow, particle coating, and spatial ALD

    SciTech Connect

    Yanguas-Gil, Angel; Elam, Jeffrey W.

    2014-05-01

    In this work, the authors present analytic models for atomic layer deposition (ALD) in three common experimental configurations: cross-flow, particle coating, and spatial ALD. These models, based on the plug-flow and well-mixed approximations, allow us to determine the minimum dose times and materials utilization for all three configurations. A comparison between the three models shows that throughput and precursor utilization can each be expressed by universal equations, in which the particularity of the experimental system is contained in a single parameter related to the residence time of the precursor in the reactor. For the case of cross-flow reactors, the authors show how simple analytic expressions for the reactor saturation profiles agree well with experimental results. Consequently, the analytic model can be used to extract information about the ALD surface chemistry (e. g., the reaction probability) by comparing the analytic and experimental saturation profiles, providing a useful tool for characterizing new and existing ALD processes. (C) 2014 American Vacuum Society

  6. Imaging the fine-scale structure of the cellular actin cytoskeleton by Single Particle Tracking and Atomic Force Microscopy

    NASA Astrophysics Data System (ADS)

    Mustata, Gina-Mirela

    It has been proposed that diffusion in the plasma membrane of eukaryotic cells it is compartmentalized due to the interaction with the underlying actin-based membrane skeleton that comes into close proximity to the lipid bilayer. The cytoskeleton is a dynamic structure that maintains cell shape, enables cell motion, and plays important roles in both intra-cellular transport and cellular division. We show here the evidence of plasma membrane compartmentalization using Single Particle Tracking (SPT) and Atomic Force Microscopy (AFM) imaging. SPT of Quantum dot labeled lipid in the plasma membrane of live normal rat kidney cells show compartments ranging from 325 nm to 391 nm depending on the sampling time. Using AFM imaging of live NRK cell in the presence of phalloidin, the membrane compartmentalization it is visible with the average size of the compartments of 325 +/- 10 nm (the main peak is centered at 260 nm). Further, the underlying membrane skeleton in fixed cells was directly imaged after partial removal of the plasma membrane to reveal size of the membrane skeleton meshwork of 339 +/- 10 nm. A new method of measuring the characteristics of the actin meshwork was proposed. Probing the local compliance of the plasma membrane through the deflection of a soft AFM cantilever we can expect that the stiffness of the membrane will be higher at locations directly above a cortical actin. This new method provided information about the structure of the skeletal meshwork of neuronal cell body predicting an average compartment size of about 132 nm. This was confirmed through SPT of QD-lipid incorporated into the neuronal cell membrane.

  7. Effect of Deficit Irrigation and Kaolin-based Foliar Reflectant Particle Film on Aroma of cv. Merlot (Vitis vinifera L.)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Water deficit during development of red-skinned wine grape enhances berry composition for wine production but increases risk of fruit exposure to deleterious levels of heat and/or solar radiation. Foliar application of a kaolin-based particle film has been shown in many crops to alleviate stress sym...

  8. PHOTOACOUSTIC DETERMINATION OF OPTICAL PROPERTIES OF AEROSOL PARTICLES COLLECTED ON FILTERS: DEVELOPMENT OF A METHOD TAKING INTO ACCOUNT SUBSTRATE REFLECTIVITY

    EPA Science Inventory

    The absorptivity and imaginary index of refraction for carbon and methylene blue particles were inferred from the photoacoustic spectra of samples collected on Teflon filter substrates. Three models of varying complexity were developed to describe the photoacoustic signal as a fu...

  9. Three-dimensional particle tracking around microstructures in water via total internal reflection fluorescence microscopy and refractive-index-matching method

    NASA Astrophysics Data System (ADS)

    Unno, Noriyuki; Nakata, Shuichiro; Satake, Shin-ichi; Taniguchi, Jun

    2016-07-01

    Multilayer nanoparticle image velocimetry (MnPIV) with a refractive-index-matching method is powerful technique for x- y- z (3D) flow measurement, because it can detect the 3D position of fluorescent particles with submicron resolution. In MnPIV, the intensity of fluorescence of a particle is used to estimate its z-position. However, it has been difficult to measure 3D flows around microstructures in water by total internal reflection fluorescence microscopy because of light scattering caused by the different refractive indices of the structures and the working fluid. By using a thermal nanoimprinting technique, we succeeded in fabricating microstructures from a polymer resin whose refractive index is equal to that of water, and we used these microstructures to perform MnPIV in water. As a result of the match between the refractive index of water and that of the microstructures, we were able to perform 3D tracking of nanoparticles around the microstructures in water.

  10. Atomizing nozzle and process

    DOEpatents

    Anderson, Iver E.; Figliola, Richard S.; Molnar, Holly M.

    1993-07-20

    High pressure atomizing nozzle includes a high pressure gas manifold having a divergent expansion chamber between a gas inlet and arcuate manifold segment to minimize standing shock wave patterns in the manifold and thereby improve filling of the manifold with high pressure gas for improved melt atomization. The atomizing nozzle is especially useful in atomizing rare earth-transition metal alloys to form fine powder particles wherein a majority of the powder particles exhibit particle sizes having near-optimum magnetic properties.

  11. Atomizing nozzle and process

    DOEpatents

    Anderson, Iver E.; Figliola, Richard S.; Molnar, Holly M.

    1992-06-30

    High pressure atomizing nozzle includes a high pressure gas manifold having a divergent expansion chamber between a gas inlet and arcuate manifold segment to minimize standing shock wave patterns in the manifold and thereby improve filling of the manifold with high pressure gas for improved melt atomization. The atomizing nozzle is especially useful in atomizing rare earth-transition metal alloys to form fine powder particles wherein a majority of the powder particles exhibit particle sizes having near-optimum magnetic properties.

  12. Manipulation of gold colloidal nanoparticles with atomic force microscopy in dynamic mode: influence of particle-substrate chemistry and morphology, and of operating conditions.

    PubMed

    Darwich, Samer; Mougin, Karine; Rao, Akshata; Gnecco, Enrico; Jayaraman, Shrisudersan; Haidara, Hamidou

    2011-01-01

    One key component in the assembly of nanoparticles is their precise positioning to enable the creation of new complex nano-objects. Controlling the nanoscale interactions is crucial for the prediction and understanding of the behaviour of nanoparticles (NPs) during their assembly. In the present work, we have manipulated bare and functionalized gold nanoparticles on flat and patterned silicon and silicon coated substrates with dynamic atomic force microscopy (AFM). Under ambient conditions, the particles adhere to silicon until a critical drive amplitude is reached by oscillations of the probing tip. Beyond that threshold, the particles start to follow different directions, depending on their geometry, size and adhesion to the substrate. Higher and respectively, lower mobility was observed when the gold particles were coated with methyl (-CH(3)) and hydroxyl (-OH) terminated thiol groups. This major result suggests that the adhesion of the particles to the substrate is strongly reduced by the presence of hydrophobic interfaces. The influence of critical parameters on the manipulation was investigated and discussed viz. the shape, size and grafting of the NPs, as well as the surface chemistry and the patterning of the substrate, and finally the operating conditions (temperature, humidity and scan velocity). Whereas the operating conditions and substrate structure are shown to have a strong effect on the mobility of the particles, we did not find any differences when manipulating ordered vs random distributed particles. PMID:21977418

  13. Synthesis and Characterization of Surface Grafted Poly(N-isopropylacrylamide) and Poly(Carboxylic Acid)– Iron Particles via Atom Transfer Radical Polymerization for Biomedical Applications

    PubMed Central

    Sutrisno, Joko; Fuchs, Alan; Evrensel, Cahit

    2014-01-01

    This research relates to the preparation and characterization of surface grafted poly(N-isopropylacrylamide) and poly(carboxylic acid)–micron-size iron particles via atom transfer radical polymerization (ATRP). The surface grafted polymers–iron particles result in multifunctional materials which can be used in biomedical applications. The functionalities consist of cell targeting, imaging, drug delivery, and immunological response. The multifunctional materials are synthesized in two steps. First, surface grafting is used to place polymer molecules on the iron particles surface. The second step, is conjugation of the bio-molecules onto the polymer backbone. Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy were used to confirm the presence of polymers on the iron particles. The thickness of the grafted polymers and glass transition temperature of the surface grafted polymers were determined by transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). The covalent bond between grafted polymers and iron particles caused higher glass transition temperature as compared with non-grafted polymers. The ability to target the bio-molecule and provide fluorescent imaging was simulated by conjugation of rat immunoglobulin and fluorescein isothiocyanate (FITC) labeled anti-rat. The fluorescence intensity was determined using flow cytometry and conjugated IgG-FITC anti-rat on iron particles which was imaged using a fluorescence microscopy. PMID:25382869

  14. Evaluation of effervescent atomizer internal design on the spray unsteadiness using a phase/Doppler particle analyzer

    SciTech Connect

    Liu, Meng; Duan, YuFeng; Zhang, TieNan

    2010-09-15

    The purpose of this research was to investigate the dependence of effervescent spray unsteadiness on operational conditions and atomizer internal design by the ideal spray theory of Edwards and Marx. The convergent-divergent effervescent atomizer spraying water with air as atomizing medium in the ''outside-in'' gas injection was used in this study. Results demonstrated that droplet formation process at various air to liquid ratio (ALR) led to the spray unsteadiness and all droplet size classes exhibited unsteadiness behavior in spray. The spray unsteadiness reduced quickly at ALR of 3% and decreased moderately at ALR of other values as the axial distance increased. When the axial distance was 200 mm, the spray unsteadiness reduced dramatically with the increase in radial distance, but lower spray unsteadiness at the center of spray and higher spray unsteadiness at the edge of spray were shown as the axial distance increased. The spray unsteadiness at the center region of spray increased with the injection pressure. Low spray unsteadiness and good atomization performance can be obtained when the diameter of incline aeration holes increased at ALR of 10%. Although short mixing chamber with large discharge orifice diameter for convergent-divergent effervescent atomizer produced good atomization, the center region of spay showed high spray unsteadiness and maybe formed the droplet clustering. (author)

  15. The Nature of Atoms.

    ERIC Educational Resources Information Center

    Holden, Alan

    This monograph was written for the purpose of presenting physics to college students who are not preparing for careers in physics. It deals with the nature of atoms, and treats the following topics: (1) the atomic hypothesis, (2) the chemical elements, (3) models of an atom, (4) a particle in a one-dimensional well, (5) a particle in a central…

  16. PREFACE: Advanced Science Research Symposium 2009 Positron, Muon and other exotic particle beams for materials and atomic/molecular sciences (ASR2009)

    NASA Astrophysics Data System (ADS)

    Higemoto, Wataru; Kawasuso, Atsuo

    2010-05-01

    It is our great pleasure to deliver the proceedings of ASR2009, the Advanced Science Research International Symposium 2009. ASR2009 is part of a series of symposia which is hosted by the Japan Atomic Energy Agency, Advanced Science Research Center (JAEA-ASRC), and held every year with different scientific topics. ASR2009 was held at Tokai in Japan from 10-12 November 2009. In total, 102 participants, including 29 overseas scientists, made 44 oral presentations and 64 poster presentations. In ASR2009 we have focused on material and atomic/molecular science research using positrons, muons and other exotic particle beams. The symposium covered all the fields of materials science which use such exotic particle beams. Positrons, muons and other beams have similar and different features. For example, although positrons and muons are both leptons having charge and spin, they give quite different information about materials. A muon mainly detects the local magnetic state of the solid, while a positron detects crystal imperfections and electron momenta in solids. Other exotic particle beams also provide useful information about materials which is not able to be obtained with muons or positrons. Therefore, the complementary use of particle beams, coupled with an understanding of their relative advantages, leads to greater excellence in materials research. This symposium crossed the fields of muon science, positron science, unstable-nuclei science, and other exotic particle-beam science. We therefore believe that ASR2009 became an especially important meeting for finding new science with exotic particle beams. Finally, we would like to extend our appreciation to all the participants, committee members, and support staff for their great efforts to make ASR2009 a fruitful symposium. ASR2009 Chairs Wataru Higemoto and Atsuo Kawasuso Advanced Science Research Center, Japan Atomic Energy Agency Organizing committee Y Hatano, JAEA (Director of ASRC) M Fujinami, Chiba Univ. R H

  17. Transfer of a weakly bound electron in collisions of Rydberg atoms with neutral particles. I. Long-range interaction effects in the ionic-covalent coupling

    SciTech Connect

    Lebedev, V. S. Narits, A. A.

    2013-10-15

    Ion-pair formation processes are studied in collisions of Rydberg atoms with neutral particles possessing small electron affinities. Nonadiabatic transitions from a Rydberg covalent term to an ionic term of a quasi-molecule are considered using the modified Landau-Zener theory supplemented with calculation of survival factors of an anion decaying in the Coulomb field of a positive ion core. Using the technique of irreducible tensor operators and the momentum representation of the wavefunction of a highly excited atom, exact expressions are obtained for transition matrix elements and the ionic-covalent coupling parameter. The approach developed in the paper provides the description beyond the scope of a conventional assumption about a small variation of the wavefunction of the Rydberg atom on the range of electron coordinates determined by the characteristic radius of the wavefunction of the anion. This allows one to correctly consider long-range effects of the interaction between a weakly bound electron and the neutral core of a negative ion in processes under study. It is shown by the example of thermal collisions of Xe(nf) atoms with CH{sub 3}CN molecules that this is very important for a reliable quantitative description of anion formation with a low binding energy. The results are compared with experiments and calculations performed within the framework of a number of approximate methods.

  18. Comprehensive size-determination of whole virus vaccine particles using gas-phase electrophoretic mobility macromolecular analyzer, atomic force microscopy, and transmission electron microscopy.

    PubMed

    Havlik, Marlene; Marchetti-Deschmann, Martina; Friedbacher, Gernot; Winkler, Wolfgang; Messner, Paul; Perez-Burgos, Laura; Tauer, Christa; Allmaier, Günter

    2015-09-01

    Biophysical properties including particle size distribution, integrity, and shape of whole virus vaccine particles at different stages in tick-borne encephalitis (TBE) vaccines formulation were analyzed by a new set of methods. Size-exclusion chromatography (SEC) was used as a conservative sample preparation for vaccine particle fractionation and gas-phase electrophoretic mobility macromolecular analyzer (GEMMA) for analyzing electrophoretic mobility diameters of isolated TBE virions. The derived particle diameter was then correlated with molecular weight. The diameter of the TBE virions determined after SEC by GEMMA instrumentation was 46.8 ± 1.1 nm. Atomic force microscopy (AFM) and transmission electron microscopy (TEM) were implemented for comparison purposes and to gain morphological information on the virion particle. Western blotting (Dot Blot) as an immunological method confirmed biological activity of the particles at various stages of the developed analytical strategy. AFM and TEM measurements revealed higher diameters with much higher SD for a limited number of virions, 60.4 ± 8.5 and 53.5 ± 5.3 nm, respectively. GEMMA instrumentation was also used for fractionation of virions with specifically selected diameters in the gas-phase, which were finally collected by means of an electrostatic sampler. At that point (i.e., after particle collection), AFM and TEM showed that the sampled virions were still intact, exhibiting a narrow size distribution (i.e., 59.8 ± 7.8 nm for AFM and 47.5 ± 5.2 nm for TEM images), and most importantly, dot blotting confirmed immunological activity of the collected samples. Furthermore dimers and virion artifacts were detected, too. PMID:26266988

  19. Comprehensive Size-Determination of Whole Virus Vaccine Particles Using Gas-Phase Electrophoretic Mobility Macromolecular Analyzer, Atomic Force Microscopy, and Transmission Electron Microscopy

    PubMed Central

    Havlik, Marlene; Marchetti-Deschmann, Martina; Friedbacher, Gernot; Winkler, Wolfgang; Messner, Paul; Perez-Burgos, Laura; Tauer, Christa; Allmaier, Günter

    2015-01-01

    Biophysical properties including particle size distribution, integrity, and shape of whole virus vaccine particles at different stages in tick-borne encephalitis (TBE) vaccines formulation were analyzed by a new set of methods. Size-exclusion chromatography (SEC) was used as a conservative sample preparation for vaccine particle fractionation and gas-phase electrophoretic mobility macromolecular analyzer (GEMMA) for analyzing electrophoretic mobility diameters of isolated TBE virions. The derived particle diameter was then correlated with molecular weight. The diameter of the TBE virions determined after SEC by GEMMA instrumentation was 46.8 ± 1.1 nm. Atomic force microscopy (AFM) and transmission electron microscopy (TEM) were implemented for comparison purposes and to gain morphological information on the virion particle. Western blotting (Dot Blot) as an immunological method confirmed biological activity of the particles at various stages of the developed analytical strategy. AFM and TEM measurements revealed higher diameters with much higher SD for a limited number of virions, 60.4 ± 8.5 and 53.5 ± 5.3 nm, respectively. GEMMA instrumentation was also used for fractionation of virions with specifically selected diameters in the gas-phase, which were finally collected by means of an electrostatic sampler. At that point (i.e., after particle collection), AFM and TEM showed that the sampled virions were still intact, exhibiting a narrow size distribution (i.e., 59.8 ± 7.8 nm for AFM and 47.5 ± 5.2 nm for TEM images), and most importantly, dot blotting confirmed immunological activity of the collected samples. Furthermore dimers and virion artifacts were detected, too. PMID:26266988

  20. Reflecting Reflective Practice

    ERIC Educational Resources Information Center

    Galea, Simone

    2012-01-01

    This paper demystifies reflective practice on teaching by focusing on the idea of reflection itself and how it has been conceived by two philosophers, Plato and Irigaray. It argues that reflective practice has become a standardized method of defining the teacher in teacher education and teacher accreditation systems. It explores how practices of…

  1. Cold Atoms

    NASA Astrophysics Data System (ADS)

    Bellac, Michel Le

    2014-11-01

    This chapter and the following one address collective effects of quantum particles, that is, the effects which are observed when we put together a large number of identical particles, for example, electrons, helium-4 or rubidium-85 atoms. We shall see that quantum particles can be classified into two categories, bosons and fermions, whose collective behavior is radically different. Bosons have a tendency to pile up in the same quantum state, while fermions have a tendency to avoid each other. We say that bosons and fermions obey two different quantum statistics, the Bose-Einstein and the Fermi-Dirac statistics, respectively. Temperature is a collective effect, and in Section 5.1 we shall explain the concept of absolute temperature and its relation to the average kinetic energy of molecules. We shall describe in Section 5.2 how we can cool atoms down thanks to the Doppler effect, and explain how cold atoms can be used to improve the accuracy of atomic clocks by a factor of about 100. The effects of quantum statistics are prominent at low temperatures, and atom cooling will be used to obtain Bose-Einstein condensates at low enough temperatures, when the atoms are bosons.

  2. The n-particle picture and the calculation of the electronic structure of atoms, molecules, and solids

    SciTech Connect

    Gonis, A.; Turchi, P.E.A.; Schulthess, T.C.; Ek, J. van

    1997-08-01

    The works referred to above indicate the usefulness of viewing an N-particle system from a higher-dimensional perspective. In doing so, one should attempt to strike a balance between conceptual clarity and computational efficiency, which mitigates against considering calculations in 3n-dimensional space except for rather small values of n. It appears that such a procedure may be profitably employed if a system of N particles were to be considered as consisting of a collection of units or sets, (I{sub k}), each containing n{sub k} particles so that {Sigma}{sub k} n{sub k} = N. The resulting problem associated with these sets of particles that interact with one another is obviously formally identical to the original one. However, it possesses the formal advantage of allowing, in principle, the systematic approach to an exact solution by treating the entire system as a single unit. The operative words here are in principle, as practical applications do not seem to be possible but for the smallest number of particles in a unit, say n = 2 or n = 3. However, in such an implementation, the interparticle correlation is treated directly and explicitly within a unit, resulting in a more accurate treatment of the system the larger the number of particle in a unit.

  3. Davisson-Germer Prize in Atomic or Surface Physics: The COLTRIMS multi-particle imaging technique-new Insight into the World of Correlation

    NASA Astrophysics Data System (ADS)

    Schmidt-Bocking, Horst

    2008-05-01

    The correlated many-particle dynamics in Coulombic systems, which is one of the unsolved fundamental problems in AMO-physics, can now be experimentally approached with so far unprecedented completeness and precision. The recent development of the COLTRIMS technique (COLd Target Recoil Ion Momentum Spectroscopy) provides a coincident multi-fragment imaging technique for eV and sub-eV fragment detection. In its completeness it is as powerful as the bubble chamber in high energy physics. In recent benchmark experiments quasi snapshots (duration as short as an atto-sec) of the correlated dynamics between electrons and nuclei has been made for atomic and molecular objects. This new imaging technique has opened a powerful observation window into the hidden world of many-particle dynamics. Recent multiple-ionization studies will be presented and the observation of correlated electron pairs will be discussed.

  4. Predicting the stability of atom-like and molecule-like unit-charge Coulomb three-particle systems

    SciTech Connect

    King, Andrew W.; Herlihy, Patrick E.; Cox, Hazel

    2014-07-28

    Non-relativistic quantum chemical calculations of the particle mass, m{sub 2}{sup ±}, corresponding to the dissociation threshold in a range of Coulomb three-particle systems of the form (m{sub 1}{sup ±}m{sub 2}{sup ±}m{sub 3}{sup ∓}), are performed variationally using a series solution method with a Laguerre-based wavefunction. These masses are used to calculate an accurate stability boundary, i.e., the line that separates the stability domain from the instability domains, in a reciprocal mass fraction ternary diagram. This result is compared to a lower bound to the stability domain derived from symmetric systems and reveals the importance of the asymmetric (mass-symmetry breaking) terms in the Hamiltonian at dissociation. A functional fit to the stability boundary data provides a simple analytical expression for calculating the minimum mass of a third particle required for stable binding to a two-particle system, i.e., for predicting the bound state stability of any unit-charge three-particle system.

  5. Orbital motion of dust particles in an rf magnetron discharge. Ion drag force or neutral atom wind force

    SciTech Connect

    Pal, A. F.; Ryabinkin, A. N.; Serov, A. O.; Dyatko, N. A.; Starostin, A. N.; Filippov, A. V.

    2012-03-15

    Microparticles with sizes up to 130 {mu}m have been confined and the velocity and diameter of particles in a plasma trap of an rf magnetron discharge with an arc magnetic field have been simultaneously measured. The motion of the gas induced by electron and ion cyclotron currents has been numerically simulated using the Navier-Stokes equation. The experimental and numerical results confirm the mechanism of the orbital motion of dust particles in the magnetron discharge plasma that is associated with the orbital motion of the neutral gas accelerated by electron and ion drift flows in crossed electric and magnetic fields.

  6. Alpha Particle

    NASA Astrophysics Data System (ADS)

    Murdin, P.

    2000-11-01

    Term that is sometimes used to describe a helium nucleus, a positively charged particle that consists of two protons and two neutrons, bound together. Alpha particles, which were discovered by Ernest Rutherford (1871-1937) in 1898, are emitted by atomic nuclei that are undergoing alpha radioactivity. During this process, an unstable heavy nucleus spontaneously emits an alpha particle and transmut...

  7. Waves and Particles--The Orbital Atom, Parts One & Two of an Integrated Science Sequence, Student Guide, 1971 Edition.

    ERIC Educational Resources Information Center

    Portland Project Committee, OR.

    The third year of the Portland Project, a three-year secondary school curriculum in integrated science, consists of four parts, the first two of which are covered in this student guide. The reading assignments for part one, "Waves and Particles," are listed in the student guide and are to be read in the Harvard Project Physics textbook. The…

  8. Calculation of effective atomic number and electron density of essential biomolecules for electron, proton, alpha particle and multi-energetic photon interactions

    NASA Astrophysics Data System (ADS)

    Kurudirek, Murat; Onaran, Tayfur

    2015-07-01

    Effective atomic numbers (Zeff) and electron densities (Ne) of some essential biomolecules have been calculated for total electron interaction, total proton interaction and total alpha particle interaction using an interpolation method in the energy region 10 keV-1 GeV. Also, the spectrum weighted Zeff for multi-energetic photons has been calculated using Auto-Zeff program. Biomolecules consist of fatty acids, amino acids, carbohydrates and basic nucleotides of DNA and RNA. Variations of Zeff and Ne with kinetic energy of ionizing charged particles and effective photon energies of heterogeneous sources have been studied for the given materials. Significant variations in Zeff and Ne have been observed through the entire energy region for electron, proton and alpha particle interactions. Non-uniform variation has been observed for protons and alpha particles in low and intermediate energy regions, respectively. The maximum values of Zeff have found to be in higher energies for total electron interaction whereas maximum values have found to be in relatively low energies for total proton and total alpha particle interactions. When it comes to the multi-energetic photon sources, it has to be noted that the highest Zeff values were found at low energy region where photoelectric absorption is the pre-dominant interaction process. The lowest values of Zeff have been shown in biomolecules such as stearic acid, leucine, mannitol and thymine, which have highest H content in their groups. Variation in Ne seems to be more or less the same with the variation in Zeff for the given materials as expected.

  9. Formation of the muonic helium atom /alpha particle-muon-electron/ and observation of its Larmor precession

    NASA Technical Reports Server (NTRS)

    Souder, P. A.; Casperson, D. E.; Crane, T. W.; Hughes, V. W.; Lu, D. C.; Yam, M. H.; Orth, H.; Reist, H. W.; Zu Putlitz, G.

    1975-01-01

    Experiments are described in which it proved possible to form the muonic helium atom by stopping polarized negative muons in a helium gas with a 2% xenon admixture at a pressure of 14 atm. The observed Larmor precession amplitudes are plotted against the gyromagnetic ratio for both muons and antimuons stopped in He + 2% Xe. In addition, a non-zero residual polarization of 0.06 plus or minus 0.01 was measured for muons stopped in pure helium gas, which corresponds to a depolarization factor of 18 plus or minus 3.

  10. [Study of the last glacial loess-like deposits in the coastal area of South China with diffuse reflectance spectroscopy and laser particle size analysis].

    PubMed

    Wang, Jing; Chen, Zhen; Chen, Guo-neng

    2014-11-01

    Newly discovered yellow silt widely distributed in the coastal area of south China was analyzed using diffuse reflectance spectroscopy (DRS) and laser particle size (LPS) methods in the present paper. The authors take the lead in trying to synthetically judge the depositional environment, transporting agent and forming mechanism of the yellow silt from angles of output forms of iron minerals as well as grain size distribution features of the samples chose from three representative sections and a drill core. The DRS first derivative curves show the peak height of iron minerals decreasing from hematite (565 nm) to goethite (505 and 435 nm), which reflects a relatively dry, cold climate that coincides with the aeolian loess widely distributed in the northwest China, but reverses of the fluvial and marine deposits which experienced a well hydration in humid conditions over a long period of time in study area. LPS analysis show that grain size from top to bottom of the sections and drill core are homogeneous and typical of aeolian sediments. The grain size distribution in the yellow silt is characterized by double peaks with main peak of 10-50 μm and a secondary peak of < 5 μm, similar to that of loess in northwest China but quite different from associated fluvial and marine deposits featured by unidirectional change of allocation mode of the grain size groups. Based on grain size analysis, DRS results, age range of 10-80 ka, and spatial distribution that both of the positive landforms and buried topographies in the coastal area of south China have this kind of sediments, the yellow silt is considered to represent an aeolian deposit formed during the last glacial period, which is called "loess-like deposits" in our study. PMID:25752028

  11. Computer simulations of the effect of atomic structure and coordination on the stabilities and melting behaviour of copper surfaces and nano-particles

    NASA Astrophysics Data System (ADS)

    Daff, Thomas D.; Saadoune, Iman; Lisiecki, Isabelle; de Leeuw, Nora H.

    2009-02-01

    We have studied the structures and stabilities of copper nano-particles and the melting properties of copper surfaces using interatomic potential-based molecular dynamics simulations, where the (1 1 1) surface has been shown to be the most stable in terms of surface energy and melting behaviour. Low energy shapes of nano-particles are influenced by the surfaces present and therefore have a higher proportion of (1 1 1) surface. The effect of surface structure on stability becomes less marked as the size of the nano-particle is increased. Melting is observed to occur below the bulk melting temperature in all the surfaces investigated, at increasingly lower temperatures from the (1 1 1), (1 0 0), (1 1 0) down to the (2 1 0) surface, confirming their order of decreasing stability. The melting processes of defective close-packed copper surfaces were also simulated. Steps, kinks, and facets were all shown to accelerate the melting of the surfaces. The melting is shown to initiate at the site of the defect and the results demonstrate that it is the low-coordinated atoms, at the step edge or kink, that are more mobile at lower temperatures. These features facilitate surface melting even further below the melting temperature than was observed for the perfect surfaces. Furthermore, facets of (1 0 0) surface were shown to be unstable even at moderate temperatures on the close-packed surface.

  12. Commercial and Cost Effective Production of Two-Dimensional Read-Out Boards for Sub-Atomic Particle Detectors

    SciTech Connect

    Crary, David; Majka, Richard

    2010-10-22

    We report results from research aimed at developing and demonstrating production of 2-D readout structures for GEM (Gas Electron Multiplier) charged particle tracking chambers at Tech-Etch. Readout boards of two types, bi-planar and single plane, were fabricated and evaluated. The results show that Tech-Etch can produce suitable boards of either type however the single plane board has a number of advantages both in production and use that will likely make it the preferred choice for GEM tracking chambers.

  13. Density relaxation and particle motion characteristics in a non-ionic deep eutectic solvent (acetamide + urea): Time-resolved fluorescence measurements and all-atom molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Das, Anuradha; Das, Suman; Biswas, Ranjit

    2015-01-01

    Temperature dependent relaxation dynamics, particle motion characteristics, and heterogeneity aspects of deep eutectic solvents (DESs) made of acetamide (CH3CONH2) and urea (NH2CONH2) have been investigated by employing time-resolved fluorescence measurements and all-atom molecular dynamics simulations. Three different compositions (f) for the mixture [fCH3CONH2 + (1 - f)NH2CONH2] have been studied in a temperature range of 328-353 K which is ˜120-145 K above the measured glass transition temperatures (˜207 K) of these DESs but much lower than the individual melting temperature of either of the constituents. Steady state fluorescence emission measurements using probe solutes with sharply different lifetimes do not indicate any dependence on excitation wavelength in these metastable molten systems. Time-resolved fluorescence anisotropy measurements reveal near-hydrodynamic coupling between medium viscosity and rotation of a dissolved dipolar solute. Stokes shift dynamics have been found to be too fast to be detected by the time-resolution (˜70 ps) employed, suggesting extremely rapid medium polarization relaxation. All-atom simulations reveal Gaussian distribution for particle displacements and van Hove correlations, and significant overlap between non-Gaussian (α2) and new non-Gaussian (γ) heterogeneity parameters. In addition, no stretched exponential relaxations have been detected in the simulated wavenumber dependent acetamide dynamic structure factors. All these results are in sharp contrast to earlier observations for ionic deep eutectics with acetamide [Guchhait et al., J. Chem. Phys. 140, 104514 (2014)] and suggest a fundamental difference in interaction and dynamics between ionic and non-ionic deep eutectic solvent systems.

  14. Density relaxation and particle motion characteristics in a non-ionic deep eutectic solvent (acetamide + urea): time-resolved fluorescence measurements and all-atom molecular dynamics simulations.

    PubMed

    Das, Anuradha; Das, Suman; Biswas, Ranjit

    2015-01-21

    Temperature dependent relaxation dynamics, particle motion characteristics, and heterogeneity aspects of deep eutectic solvents (DESs) made of acetamide (CH3CONH2) and urea (NH2CONH2) have been investigated by employing time-resolved fluorescence measurements and all-atom molecular dynamics simulations. Three different compositions (f) for the mixture [fCH3CONH2 + (1 - f)NH2CONH2] have been studied in a temperature range of 328-353 K which is ∼120-145 K above the measured glass transition temperatures (∼207 K) of these DESs but much lower than the individual melting temperature of either of the constituents. Steady state fluorescence emission measurements using probe solutes with sharply different lifetimes do not indicate any dependence on excitation wavelength in these metastable molten systems. Time-resolved fluorescence anisotropy measurements reveal near-hydrodynamic coupling between medium viscosity and rotation of a dissolved dipolar solute. Stokes shift dynamics have been found to be too fast to be detected by the time-resolution (∼70 ps) employed, suggesting extremely rapid medium polarization relaxation. All-atom simulations reveal Gaussian distribution for particle displacements and van Hove correlations, and significant overlap between non-Gaussian (α2) and new non-Gaussian (γ) heterogeneity parameters. In addition, no stretched exponential relaxations have been detected in the simulated wavenumber dependent acetamide dynamic structure factors. All these results are in sharp contrast to earlier observations for ionic deep eutectics with acetamide [Guchhait et al., J. Chem. Phys. 140, 104514 (2014)] and suggest a fundamental difference in interaction and dynamics between ionic and non-ionic deep eutectic solvent systems. PMID:25612718

  15. Density relaxation and particle motion characteristics in a non-ionic deep eutectic solvent (acetamide + urea): Time-resolved fluorescence measurements and all-atom molecular dynamics simulations

    SciTech Connect

    Das, Anuradha; Das, Suman; Biswas, Ranjit

    2015-01-21

    Temperature dependent relaxation dynamics, particle motion characteristics, and heterogeneity aspects of deep eutectic solvents (DESs) made of acetamide (CH{sub 3}CONH{sub 2}) and urea (NH{sub 2}CONH{sub 2}) have been investigated by employing time-resolved fluorescence measurements and all-atom molecular dynamics simulations. Three different compositions (f) for the mixture [fCH{sub 3}CONH{sub 2} + (1 − f)NH{sub 2}CONH{sub 2}] have been studied in a temperature range of 328-353 K which is ∼120-145 K above the measured glass transition temperatures (∼207 K) of these DESs but much lower than the individual melting temperature of either of the constituents. Steady state fluorescence emission measurements using probe solutes with sharply different lifetimes do not indicate any dependence on excitation wavelength in these metastable molten systems. Time-resolved fluorescence anisotropy measurements reveal near-hydrodynamic coupling between medium viscosity and rotation of a dissolved dipolar solute. Stokes shift dynamics have been found to be too fast to be detected by the time-resolution (∼70 ps) employed, suggesting extremely rapid medium polarization relaxation. All-atom simulations reveal Gaussian distribution for particle displacements and van Hove correlations, and significant overlap between non-Gaussian (α{sub 2}) and new non-Gaussian (γ) heterogeneity parameters. In addition, no stretched exponential relaxations have been detected in the simulated wavenumber dependent acetamide dynamic structure factors. All these results are in sharp contrast to earlier observations for ionic deep eutectics with acetamide [Guchhait et al., J. Chem. Phys. 140, 104514 (2014)] and suggest a fundamental difference in interaction and dynamics between ionic and non-ionic deep eutectic solvent systems.

  16. The Response of the Ionospheric Cusp to the Solar Wind Through Two Perspectives: Low Energy Charged Particle In-Situ Measurements and Low-Energy Neutral Atom Imaging

    NASA Technical Reports Server (NTRS)

    Coffey, V. N.; Moore, T. E.; Chandler, M. O.; Giles, B. L.; Craven, P. D.; Rose, M. Franklin (Technical Monitor)

    2000-01-01

    The Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) mission provides a new perspective on the study of the response of the magnetosphere/ionosphere system to changing solar wind conditions, particularly the variability of ion outflow. Learning to interpret this new type of data becomes an essential step in the process of melding these results with the wealth of in-situ charged particle observations obtained over the past 25 years. In order to understand how the in-situ data correspond to and contrast with IMAGE results we will perform a conjunctive study of event data from two instruments to shed light on the coupling of the solar wind and ionosphere from these different perspectives. We will use the Low Energy Neutral Atom instrument (LENA) which images energetic neutral atom emissions from upward flowing ionospheric ions and the Thermal Ion Dynamics Instrument (TIDE) on the Polar satellite which measures in-situ ion outflow from 0.3-300 eV. Our primary goal will be to understand how comparing the imaging and in-situ perspectives can aid in the analysis of both data sets.

  17. The Response of the Ionospheric Cusp to the Solar Through Two Perspectives: Low Energy Changed Particle In-Situ Measurements and Low- Energy Neutral Atom Imaging

    NASA Technical Reports Server (NTRS)

    Coffey, V. N.; Moore, T. E.; Chandler, M. O.; Craven, P. D.

    2000-01-01

    The IMAGE mission provides a new perspective on the study of the response of the magnetosphere/ionosphere system to changing solar wind conditions, particularly the variability of ion outflow. Learning to interpret this new type of data becomes an essential step in the process of melding these results with the wealth of in-situ charged particle observations obtained over the past 25 years. In order to understand how the in-situ data correspond to and contrast with IMAGE results we will perform a conjunctive study of event data from two instruments to shed light on the coupling of the solar wind and ionosphere from these different perspectives. We will use the Low Energy Neutral Atom instrument (LENA) which images energetic neutral atom emissions from upward flowing ionospheric ions and the Thermal Ion Dynamics Instrument (TIDE) on the Polar satellite which measures in-situ ion outflow from 0.3-300 eV. Our primary goal will be to understand how comparing the imaging and in-situ perspectives can aid in the analysis of both data sets.

  18. Clustering of metal atoms in organic media. 9. High-activity Ni/MgO catalysts prepared by metal vapor methods. Surface area and particle size effects

    SciTech Connect

    Matsuo, K.; Klabunde, K.J.

    1982-02-01

    A metal vapor method was employed to prepare highly dispersed Ni metal catalysts (solvated metal atom dispersed = SMAD catalyst) supported on MgO. Compared with conventional Ni/MgO compositions, the SMAD catalysts showed much greater activities for all reactions studied (hydrogenolysis of methylcyclopentane, MCP; hydrogenation/hydrogenolysis of toluene, TOL; methanation of carbon monoxide, CO; dehydration of isopropyl alcohol, IPA). These high activities for the SMAD catalysts are attributed to the high surface area of Ni on MgO and the high percentage of this Ni in a zero-valent state (reduction degree). Conventional methods for preparing Ni/MgO catalysts did not yield nearly such favorable surface areas or reduction degrees. Nickel particle size effects were observed during hydrogenolysis studies of MCP and hydrogenation studies of TOL. These phenomena are explained by assuming the size of an active Ni particle to be largest for hydrogenolysis of MCP > hydrogenation of TOL > methanation of CO approx. = dehydrogenation of IPA. 8 figures, 2 tables.

  19. Commercial and Cost Effective Production of Two-Dimensional Read-Out Boards for Sub-Atomic Particle Detectors

    SciTech Connect

    Crary, David; Majka, Richard

    2010-10-22

    Tech-Etch has considerable experience in numerous related high precision etched Kapton® products including production of GEM foils. The required precision and production process for 2-D readout boards is similar to that developed for GEM foil production. Additionally, Tech-Etch has strong ties with several research institutions (namely Brookhaven National Laboratory, MIT and Yale University) that can help design and evaluate the performance of the readout boards produced at Tech-Etch. Since Tech-Etch is a small company, it also has the capability to produce a large variety of part configurations, optimized for a particular customer's requirements. We report results from research aimed at developing and demonstrating production of 2-D readout structures for GEM (Gas Electron Multiplier) charged particle tracking chambers at Tech-Etch. Readout boards of two types, bi-planar and single plane, were fabricated and evaluated. The results show that Tech-Etch can produce suitable boards of either type however the single plane board has a number of advantages both in production and use that will likely make it the preferred choice for GEM tracking chambers.

  20. Reflective Teaching

    ERIC Educational Resources Information Center

    Farrell, Thomas S. C.

    2013-01-01

    Thomas Farrell's "Reflective Teaching" outlines four principles that take teachers from just doing reflection to making it a way of being. Using the four principles, Reflective Practice Is Evidence Based, Reflective Practice Involves Dialogue, Reflective Practice Links Beliefs and Practices, and Reflective Practice Is a Way of Life,…

  1. Single molecule investigations of DNA looping using the tethered particle method and translocation by acto-myosin using polarized total internal reflection fluorescence microscopy

    NASA Astrophysics Data System (ADS)

    Beausang, John F.

    Single molecule biophysics aims to understand biological processes by studying them at the single molecule level in real time. The proteins and nucleic acids under investigation typically exist in an aqueous environment within ˜ ten degrees of room temperature. These seemingly benign conditions are actually quite chaotic at the nanoscale, where single bio-molecules perform their function. As a result, sensitive experiments and statistical analyses are required to separate the weak single molecule signal from its background. Protein-DNA interactions were investigated by monitoring DNA looping events in tethered particle experiments. A new analysis technique, called the Diffusive hidden Markov method, was developed to extract kinetic rate constants from experimental data without any filtering of the raw data; a common step that improves the signal to noise ratio, but at the expense of lower time resolution. In the second system, translocation of the molecular motor myosin along its actin filament track was studied using polarized total internal reflection (polTIRF) microscopy, a technique that determines the orientation and wobble of a single fluorophore attached to the bio-molecule of interest. The range of resolvable angles was increased 4-fold to include a hemisphere of possible orientations. As a result, the handedness of actin filament twirling as it translocated along a myosin-coated surface was determined to be left-handed. The maximum time resolution of a polTIRF setup was increased 50-fold, in part by recording the arrival times and polarization state of single photons using a modified time-correlated single photon counting device. A new analysis, the Multiple Intensity Change Point algorithm, was developed to detect changes in molecular orientation and wobble using the raw time-stamped data with no user-defined bins or thresholds. The analysis objectively identified changes in the orientation of a bifunctional-rhodamine labeled calmodulin that was attached

  2. [The new atherogenic plasma index reflects the triglyceride and HDL-cholesterol ratio, the lipoprotein particle size and the cholesterol esterification rate: changes during lipanor therapy].

    PubMed

    Dobiásová, M; Frohlich, J

    2000-03-01

    The new atherogenic plasma index (AIP) is a logarithmic transformation of the ratio of the molar triglyceride (TG) concentration and high density lipoprotein cholesterol (HDL-C). AIP correlates closely with the size of LDL particles (r = 0.8) and esterification rate of plasma cholesterol devoid of apo B lipoproteins (FERHDL), r = 0.9 which are considered at present the most sensitive indicators of the atherogenic plasma profile. AIP was recommended by the authors, based on analysis of results of 11 previous studies (1156 subjects) where FERHDL and plasma lipid parameters were investigated in different groups of people who differed as to the atherogenic risk. The AIP index was moreover used for evaluation of a clinical study comprising 609 patients with hyperlipidaemia, who were treated for three months with ciprofibrate (Lipanor). The mean AIP values of non-risk groups (plasma from umbilical blood, children, healthy women etc.) equalled zero or were lower, while with an increasing atherogenic risk (men, women after the menopause) AIP reached positive values, incl. high positive values in risk groups (plasma of diabetic subjects, patients with HLP, patients with positive angiography, myocardial infarction etc.). In all groups women had lower AIP values as compared with males. In patients after Lipanor therapy the AIP declined (from 0.58 +/- 0.17 to 0.33_0.18 in men, from 0.50 +/- 0.18 to 0.21 +/- 0.19 in women). If we consider AIP values from negative ones to 0.15 as "safe" from the aspect of atherogenicity, before Lipanor treatment these "safe" levels were recorded in 1.5% men and in 5.2% women and after treatment in 32% men and 48% women. The results indicate, that AIP which reflects the plasma lipoprotein profile quantifies the relations between TG and HDL-C and thus can be an objective indicator of the atherogenic risk and effectiveness of treatment and it is useful because it can be assessed in any surgery. PMID:11048517

  3. Eliminated Phototoxicity of TiO2 Particles by an Atomic-Layer-Deposited Al2 O3 Coating Layer for UV-Protection Applications.

    PubMed

    Jang, Eunyong; Sridharan, Kishore; Park, Young Min; Park, Tae Joo

    2016-08-16

    We demonstrate the conformal coating of an ultrathin Al2 O3 layer on TiO2 nanoparticles through atomic layer deposition by using a specifically designed rotary reactor to eliminate the phototoxicity of the particles for cosmetic use. The ALD reactor is modified to improve the coating efficiency as well as the agitation of the particles for conformal coating. Elemental and microstructural analyses show that ultrathin Al2 O3 layers are conformally deposited on the TiO2 nanoparticles with a controlled thickness. Rhodamine B dye molecules on Al2 O3 -coated TiO2 exhibited a long life time under UV irradiation, that is, more than 2 h, compared to that on bare TiO2 , that is, 8 min, indicating mitigation of photocatalytic activity by the coated layer. The effect of carbon impurities in the film resulting from various deposition temperatures and thicknesses of the Al2 O3 layer on the photocatalytic activity are also thoroughly investigated with controlled experimental condition by using dye molecules on the surface. Our results reveal that an increased carbon impurity resulting from a low processing temperature provides a charge conduction path and generates reactive oxygen species causing the degradation of dye molecule. A thin coated layer, that is, less than 3 nm, also induced the tunneling of electrons and holes to the surface, hence oxidizing dye molecules. Furthermore, the introduction of an Al2 O3 layer on TiO2 improves the light trapping thus, enhances the UV absorption. PMID:27405514

  4. Facile Conversion of Hydroxy Double Salts to Metal-Organic Frameworks Using Metal Oxide Particles and Atomic Layer Deposition Thin-Film Templates.

    PubMed

    Zhao, Junjie; Nunn, William T; Lemaire, Paul C; Lin, Yiliang; Dickey, Michael D; Oldham, Christopher J; Walls, Howard J; Peterson, Gregory W; Losego, Mark D; Parsons, Gregory N

    2015-11-01

    Rapid room-temperature synthesis of metal-organic frameworks (MOFs) is highly desired for industrial implementation and commercialization. Here we find that a (Zn,Cu) hydroxy double salt (HDS) intermediate formed in situ from ZnO particles or thin films enables rapid growth (<1 min) of HKUST-1 (Cu3(BTC)2) at room temperature. The space-time-yield reaches >3 × 10(4) kg·m(-3)·d(-1), at least 1 order of magnitude greater than any prior report. The high anion exchange rate of (Zn,Cu) hydroxy nitrate HDS drives the ultrafast MOF formation. Similarly, we obtained Cu-BDC, ZIF-8, and IRMOF-3 structures from HDSs, demonstrating synthetic generality. Using ZnO thin films deposited via atomic layer deposition, MOF patterns are obtained on pre-patterned surfaces, and dense HKUST-1 coatings are grown onto various form factors, including polymer spheres, silicon wafers, and fibers. Breakthrough tests show that the MOF-functionalized fibers have high adsorption capacity for toxic gases. This rapid synthesis route is also promising for new MOF-based composite materials and applications. PMID:26456471

  5. Reflection Coefficients.

    ERIC Educational Resources Information Center

    Greenslade, Thomas B., Jr.

    1994-01-01

    Discusses and provides an example of reflectivity approximation to determine whether reflection will occur. Provides a method to show thin-film interference on a projection screen. Also applies the reflectivity concepts to electromagnetic wave systems. (MVL)

  6. Helium Atom Scattering from KTa0:7Nb0:3O3 (001): Anomalous Surface reflectivity with varying surface temperature and helium wave vector

    SciTech Connect

    Fatema, Rifat; Trelenberg, T. W.; Van Winkle, David; Skofronick, J. G.; Safron, Sanford A.; Flaherty, F. A.; Boatner, Lynn A

    2011-01-01

    Helium atom diraction experiments have been carried out on the (001) surface of KTaO3 doped with 30% Nb. The surfaces were produced by cleaving single crystals of the material in situ. After the samples were thermally cycled, the angular distributions measured in the <100> azimuth, but not those in the <110> azimuth, revealed half-order diraction peaks. These indicate the formation of small (21) surface domains. The scans of the specular and Bragg diraction peak intensities as the sample temperatures were varied from about 325K to 60-80K and back to 325K showed large hysteresis particularly in the <100> azimuth. In addition, these scans showed a distinct intensity dip at about 85K, which is far removed from any bulk phase transition temperature of this material. Most curious, the specular re ectivity of the surface was found to be a strong function of the He wavevector, decreasing rapidly as the wavevector was varied above or below an optimum value.

  7. Atom-atom inelastic collisions and three-body atomic recombination in weakly ionized argon plasmas

    NASA Technical Reports Server (NTRS)

    Braun, C. G.; Kunc, J. A.

    1989-01-01

    A stationary collisional-radiative model including both inelastic electron-atom and atom-atom collisions is used to examine nonequilibrium weakly ionized argon plasmas with atomic densities 10 to the 16th to 10 to the 20th/cu cm, temperatures below 6000 K, and with different degrees of radiation trapping. It is shown that three-body atomic recombination becomes important at high particle densities. Comparison is made between the present approach and Thomson's theory for atomic recombination.

  8. Reflected Glory

    NASA Astrophysics Data System (ADS)

    2011-02-01

    The nebula Messier 78 takes centre stage in this image taken with the Wide Field Imager on the MPG/ESO 2.2-metre telescope at the La Silla Observatory in Chile, while the stars powering the bright display take a backseat. The brilliant starlight ricochets off dust particles in the nebula, illuminating it with scattered blue light. Igor Chekalin was the overall winner of ESO's Hidden Treasures 2010 astrophotography competition with his image of this stunning object. Messier 78 is a fine example of a reflection nebula. The ultraviolet radiation from the stars that illuminate it is not intense enough to ionise the gas to make it glow - its dust particles simply reflect the starlight that falls on them. Despite this, Messier 78 can easily be observed with a small telescope, being one of the brightest reflection nebulae in the sky. It lies about 1350 light-years away in the constellation of Orion (The Hunter) and can be found northeast of the easternmost star of Orion's belt. This new image of Messier 78 from the MPG/ESO 2.2-metre telescope at the La Silla Observatory is based on data selected by Igor Chekalin in his winning entry to the Hidden Treasures competition [1]. The pale blue tint seen in the nebula in this picture is an accurate representation of its dominant colour. Blue hues are commonly seen in reflection nebulae because of the way the starlight is scattered by the tiny dust particles that they contain: the shorter wavelength of blue light is scattered more efficiently than the longer wavelength red light. This image contains many other striking features apart from the glowing nebula. A thick band of obscuring dust stretches across the image from the upper left to the lower right, blocking the light from background stars. In the bottom right corner, many curious pink structures are also visible, which are created by jets of material being ejected from stars that have recently formed and are still buried deep in dust clouds. Two bright stars, HD 38563A and

  9. Reflected Glory

    NASA Astrophysics Data System (ADS)

    2011-02-01

    The nebula Messier 78 takes centre stage in this image taken with the Wide Field Imager on the MPG/ESO 2.2-metre telescope at the La Silla Observatory in Chile, while the stars powering the bright display take a backseat. The brilliant starlight ricochets off dust particles in the nebula, illuminating it with scattered blue light. Igor Chekalin was the overall winner of ESO's Hidden Treasures 2010 astrophotography competition with his image of this stunning object. Messier 78 is a fine example of a reflection nebula. The ultraviolet radiation from the stars that illuminate it is not intense enough to ionise the gas to make it glow - its dust particles simply reflect the starlight that falls on them. Despite this, Messier 78 can easily be observed with a small telescope, being one of the brightest reflection nebulae in the sky. It lies about 1350 light-years away in the constellation of Orion (The Hunter) and can be found northeast of the easternmost star of Orion's belt. This new image of Messier 78 from the MPG/ESO 2.2-metre telescope at the La Silla Observatory is based on data selected by Igor Chekalin in his winning entry to the Hidden Treasures competition [1]. The pale blue tint seen in the nebula in this picture is an accurate representation of its dominant colour. Blue hues are commonly seen in reflection nebulae because of the way the starlight is scattered by the tiny dust particles that they contain: the shorter wavelength of blue light is scattered more efficiently than the longer wavelength red light. This image contains many other striking features apart from the glowing nebula. A thick band of obscuring dust stretches across the image from the upper left to the lower right, blocking the light from background stars. In the bottom right corner, many curious pink structures are also visible, which are created by jets of material being ejected from stars that have recently formed and are still buried deep in dust clouds. Two bright stars, HD 38563A and

  10. Solar Neutral Particles

    NASA Video Gallery

    This animation shows a neutral solar particle's path leaving the sun, following the magnetic field lines out to the heliosheath. The solar particle hits a hydrogen atom, stealing its electron, and ...