WorldWideScience

Sample records for atomic attenuation cross

  1. The Mass Attenuation Coefficients, Electronic, Atomic, and Molecular Cross Sections, Effective Atomic Numbers, and Electron Densities for Compounds of Some Biomedically Important Elements at 59.5 keV

    OpenAIRE

    Burcu Akça; Erzeneoğlu, Salih Z.

    2014-01-01

    The mass attenuation coefficients for compounds of biomedically important some elements (Na, Mg, Al, Ca, and Fe) have been measured by using an extremely narrow collimated-beam transmission method in the energy 59.5 keV. Total electronic, atomic, and molecular cross sections, effective atomic numbers, and electron densities have been obtained by using these results. Gamma-rays of 241Am passed through compounds have been detected by a high-resolution Si(Li) detector and by using energy dispers...

  2. The Mass Attenuation Coefficients, Electronic, Atomic, and Molecular Cross Sections, Effective Atomic Numbers, and Electron Densities for Compounds of Some Biomedically Important Elements at 59.5 keV

    Directory of Open Access Journals (Sweden)

    Burcu Akça

    2014-01-01

    Full Text Available The mass attenuation coefficients for compounds of biomedically important some elements (Na, Mg, Al, Ca, and Fe have been measured by using an extremely narrow collimated-beam transmission method in the energy 59.5 keV. Total electronic, atomic, and molecular cross sections, effective atomic numbers, and electron densities have been obtained by using these results. Gamma-rays of 241Am passed through compounds have been detected by a high-resolution Si(Li detector and by using energy dispersive X-ray fluorescence spectrometer (EDXRF. Obtained results have been compared with theoretically calculated values of WinXCom and FFAST. The relative difference between the experimental and theoretical values are −9.4% to +11.9% with WinXCom and −11.8% to +11.7% FFAST. Results have been presented and discussed in this paper.

  3. Measurement of atomic number and mass attenuation coefficient in magnesium ferrite

    Indian Academy of Sciences (India)

    R H Kadam; S T Alone; G K Bichile; K M Jadhav

    2007-05-01

    Pure magnesium ferrite sample was prepared by standard ceramic technique and characterized by X-ray diffraction method. XRD pattern revealed that the sample possess single-phase cubic spinel structure. The linear attenuation coefficient (), mass attenuation coefficient (/ρ), total atomic cross-section (tot), total electronic cross-section (ele) and the effective atomic number (eff) were calculated for pure magnesium ferrite (MgFe2O4). The values of -ray mass attenuation coefficient were obtained using a NaI energy selective scintillation counter with radioactive -ray sources having energy 0.36, 0.511, 0.662, 1.17 and 1.28 MeV. The experimentally obtained values of /ρ and eff agreed fairly well with those obtained theoretically.

  4. Gamma attenuation characteristics and effective atomic numbers of polypropylene and polystyrene

    International Nuclear Information System (INIS)

    Gamma attenuation characteristics of polymer materials polypropylene and polystyrene are studied along with lead, iron and aluminum by subjecting them to gamma ray fields of known energies. A precise method for determination of mass attenuation coefficient of gamma rays using NaI (Tl) detector with 8k MCA is described in this paper. In order to minimize the effect of multiple scattering on the mass attenuation coefficient (μ/ρ) value, a good geometry arrangement was setup. For standardization purposes the mass attenuation coefficients of elemental shields like lead, iron and aluminum were measured and then, this method is applied for polymers of interest. The total atomic cross-section (σt,a) and total electronic cross-section (σt,el) were determined and by knowing the values of (σt,a) and (σt,el) the effective atomic numbers were estimated using the NIST XCOM. The experimental values were compared with the theoretical values. The agreement of experimental values of mass attenuation coefficients and effective atomic numbers with the theory has been found to be quite satisfactory. (author)

  5. Studies on effective atomic numbers, electron densities and mass attenuation coefficients in Au alloys.

    Science.gov (United States)

    Han, I; Demir, L

    2010-01-01

    The total mass attenuation coefficients (mu/rho) for pure Au and Au99Be1, Au88Ge12, Au95Zn5 alloys were measured at 59.5 and 88.0 keV photon energies. The samples were irradiated with 241Am and 109Cd radioactive point source using transmission arrangement. The gamma- rays were counted by a Si(Li) detector with resolution of 160 eV at 5.9 keV. Total atomic and electronic cross-sections (sigmat and sigmae), effective atomic and electron densities (Zeff and Nel) were determined using the obtained mass attenuation coefficients for investigated Au alloys. The theoretical mass attenuation coefficients of each alloy were estimated using mixture rule. PMID:20421703

  6. Calculation of radiation attenuation coefficients, effective atomic numbers and electron densities for some building materials

    International Nuclear Information System (INIS)

    Some building materials, regularly used in Turkey, such as sand, cement, gas concrete (lightweight, aerated concrete), tile and brick, have been investigated in terms of mass attenuation coefficient, effective atomic, numbers (Zeff), effective electron densities (Ne) and photon interaction cross section (σa) at 14 different energies from 81- to 1332-keV gamma-ray energies. The gamma rays were detected by using gamma-ray spectroscopy, a High Purity Germanium (HPGe) detector. The elemental compositions of samples were analysed using an energy dispersive X-ray fluorescence spectrometer. Mass attenuation coefficients of these samples have been compared with tabulations based upon the results of WinXcom. The theoretical mass attenuation coefficients were estimated using the mixture rule and the experimental values of investigated parameters were compared with the calculated values. The agreement of measured values of mass attenuation coefficient, effective atomic numbers, effective electron densities and photon interaction cross section with the theory has been found to be quite satisfactory. (authors)

  7. Calculation of radiation attenuation coefficients, effective atomic numbers and electron densities for some building materials.

    Science.gov (United States)

    Damla, N; Baltas, H; Celik, A; Kiris, E; Cevik, U

    2012-07-01

    Some building materials, regularly used in Turkey, such as sand, cement, gas concrete (lightweight, aerated concrete), tile and brick, have been investigated in terms of mass attenuation coefficient (μ/ρ), effective atomic, numbers (Z(eff)), effective electron densities (N(e)) and photon interaction cross section (σ(a)) at 14 different energies from 81- to 1332-keV gamma-ray energies. The gamma rays were detected by using gamma-ray spectroscopy, a High Purity Germanium (HPGe) detector. The elemental compositions of samples were analysed using an energy dispersive X-ray fluorescence spectrometer. Mass attenuation coefficients of these samples have been compared with tabulations based upon the results of WinXcom. The theoretical mass attenuation coefficients were estimated using the mixture rule and the experimental values of investigated parameters were compared with the calculated values. The agreement of measured values of mass attenuation coefficient, effective atomic numbers, effective electron densities and photon interaction cross section with the theory has been found to be quite satisfactory. PMID:22128356

  8. Photon mass attenuation coefficients, effective atomic numbers and electron densities of some thermoluminescent dosimetric compounds

    Indian Academy of Sciences (India)

    Shivalinge Gowda; S Krishnaveni; T Yashoda; T K Umesh; Ramakrishna Gowda

    2004-09-01

    Photon mass attenuation coefficients of some thermoluminescent dosimetric (TLD) compounds, such as LiF, CaCO3, CaSO4, CaSO4·2H2O, SrSO4, CdSO4, BaSO4, C4H6BaO4 and 3CdSO4·8H2O were determined at 279.2, 320.07, 514.0, 661.6, 1115.5, 1173.2 and 1332.5 keV in a well-collimated narrow beam good geometry set-up using a high resolution, hyper pure germanium detector. The attenuation coefficient data were then used to compute the effective atomic number and the electron density of TLD compounds. The interpolation of total attenuation cross-sections of photons of energy in elements of atomic number was performed using the logarithmic regression analysis of the data measured by the authors and reported earlier. The best-fit coefficients so obtained in the photon energy range of 279.2 to 320.07 keV, 514.0 to 661.6 keV and 1115.5 to 1332.5 keV by a piece-wise interpolation method were then used to find the effective atomic number and electron density of the compounds. These values are found to be in agreement with other available published values.

  9. Study of the mass attenuation coefficients and effective atomic numbers in some gemstones

    International Nuclear Information System (INIS)

    The total mass attenuation coefficients for natural beryl, corundum, garnet, pearl, and tourmaline gemstones were measured at 81, 356.5, 661.6, 1173.2, and 1332.5 keV photon energies. The samples were irradiated with 133Ba, 137Cs and 60Co radioactive point sources using gamma ray transmission method. Total atomic and electronic cross-sections, effective atomic numbers and electron densities were determined experimentally and theoretically. The experimental values were compared with the calculated values for all samples. The calculations were extended for total photon interactions in a wide energy range (1 keV-100 GeV) using WinXCom program of the most commonly irradiated gemstones with different sources of ionized radiation. The values of these parameters have been found to vary with photon energy and chemical composition of the gemstones. All variations of these parameters against energy are shown graphically for total photon interactions. (author)

  10. Mass Attenuation Coefficients and Effective Atomic Numbers of Thermoluminescent Aluminum Oxide Based Glasses

    International Nuclear Information System (INIS)

    The photon mass attenuation coefficient of a newly prepared 15Al2O3-35P2O5- xCaO-(50-x)Na2CO3 glass system (symbolized as APCN), where x=5, 10, 15, 20, 25, 30, 35, 40 all in mol%, have been calculated at photon energies of 0.662 MeV (137Cs source) and 1.25 MeV (60Co source). In addition, the photon mass attenuation coefficient of 15Al2O3-35P2O5-25CaO-25Na2CO3 glass system (symbolized as APCN25-25), all in mol%, doped with different concentrations of SiO2 have been calculated. The WinXCOM software program on the basis of mixture rule was utilized in calculations. The total atomic (σt) and electronic (σe) cross sections, effective atomic number (Zeff) and electron density (Nel) were calculated. The results showed that the total mass attenuation coefficient showed an extremely dependence on incoherent scattering processes where it varies with Na2CO3 contents in the APCN composition while changing the concentrations of SiO2 in APCN25-25 glass showed slight changes in the values. Otherwise, the mass attenuation coefficient (µm) had higher values at 0.662 MeV than those of 1.25 MeV in both APCN and APCN25-25 glass systems. The values of Zeff showed a decrease with increasing Na2CO3 contents in the APCN composition. The should highly be considered in dealing with such prepared APCN glass system as a gamma ray detector, specially as thermoluminescence dosimeter.

  11. Measurement of attenuation coefficient, effective atomic number and electron density of oxides of lanthanides by using simplified ATM-method

    International Nuclear Information System (INIS)

    Highlights: • Measurement of linear attenuation coefficient by simplified ATM method for the oxides of Lanthanides. • Atomic parameters are calculated from linear attenuation coefficients. • Geometrical setup has been validated with metallic targets of uniform thickness. • Experimental results are in good agreement with theoretical results within error limits. - Abstract: The linear and mass attenuation coefficient of non-uniform thick samples of oxides of lanthanide (Pr6O11, Nd2O3, Gd2O3, Tb4O7, Ho2O3 and Er2O3) has been measured by gamma ray photons of energy 59.54 keV obtained from 100 mCi radioactive source of 241Am. Advanced Two Media (ATM) methods Gupta et al. (2013) is simplified by considering air as first medium and metallic foil as second medium. In the present measurements this consideration simplifies the mathematical complexities and laboratory work to find the attenuation coefficients of non-uniform thick samples. The values of attenuation coefficient were then used to calculate effective atomic numbers (Zeff), interaction cross-section (σ) and effective electron densities (Neff) of lanthanide oxides. The method is validated by measuring linear/mass attenuation coefficient and other parameters for Mo, Ag, Sn, W and Pb of uniform thickness. The measured results are compared with the theoretical values from WinXcom Gerward et al. (2001). It is found that measured values are in agreement within 2% of theoretical results. The measurement of linear attenuation coefficient, effective atomic numbers (Zeff), interaction cross-section and effective electron densities (Neff) enhances the understanding of material characteristics. Presently studied materials i.e. oxides of Lanthanide are widely used as glass colouring agent and in electronic sensing devices

  12. Measurement of attenuation coefficient, effective atomic number and electron density of oxides of lanthanides by using simplified ATM-method

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Gurinderjeet; Gupta, Manoj Kumar, E-mail: mkgupta.sliet@gmail.com; Dhaliwal, A.S.; Kahlon, K.S.

    2015-01-15

    Highlights: • Measurement of linear attenuation coefficient by simplified ATM method for the oxides of Lanthanides. • Atomic parameters are calculated from linear attenuation coefficients. • Geometrical setup has been validated with metallic targets of uniform thickness. • Experimental results are in good agreement with theoretical results within error limits. - Abstract: The linear and mass attenuation coefficient of non-uniform thick samples of oxides of lanthanide (Pr{sub 6}O{sub 11}, Nd{sub 2}O{sub 3}, Gd{sub 2}O{sub 3}, Tb{sub 4}O{sub 7}, Ho{sub 2}O{sub 3} and Er{sub 2}O{sub 3}) has been measured by gamma ray photons of energy 59.54 keV obtained from 100 mCi radioactive source of {sup 241}Am. Advanced Two Media (ATM) methods Gupta et al. (2013) is simplified by considering air as first medium and metallic foil as second medium. In the present measurements this consideration simplifies the mathematical complexities and laboratory work to find the attenuation coefficients of non-uniform thick samples. The values of attenuation coefficient were then used to calculate effective atomic numbers (Z{sub eff}), interaction cross-section (σ) and effective electron densities (N{sub eff}) of lanthanide oxides. The method is validated by measuring linear/mass attenuation coefficient and other parameters for Mo, Ag, Sn, W and Pb of uniform thickness. The measured results are compared with the theoretical values from WinXcom Gerward et al. (2001). It is found that measured values are in agreement within 2% of theoretical results. The measurement of linear attenuation coefficient, effective atomic numbers (Z{sub eff}), interaction cross-section and effective electron densities (N{sub eff}) enhances the understanding of material characteristics. Presently studied materials i.e. oxides of Lanthanide are widely used as glass colouring agent and in electronic sensing devices.

  13. Simulated mixed absorbers and effective atomic numbers for attenuation

    Indian Academy of Sciences (India)

    K Karunakaran Nair; N Ramachandran; K K Abdullah; K M Varier

    2006-09-01

    The total -ray interaction crosss-sections on mixed absorbers were determined at 662 keV with a view to study the effective atomic numbers for -ray absorption under narrow beam good geometry set-up. The measurements were taken for the combination of metallic absorbers like aluminium, copper, lead and mercury and also for the simulated absorbers by rotating the targets. ORTEC HPGe and NaI(Tl) detectors were used for detection of -rays.The experimental results compare favourably with theoretical values derived from XCOM package and suggest the usefulness of the concept of effective atomic numbers and the utility of the rotating absorbers technique.

  14. Removal cross sections and total mass attenuation coefficients of fast neutrons and gamma rays for steel

    CERN Document Server

    Elsayed, A A

    2003-01-01

    The present work deals with the study of the attenuation properties and determination of the cross sections of fast neutrons and gamma rays for structure steel used in different applications in nuclear power plants, particle accelerators, research reactors and different radiation attenuation fields. Investigation has been performed by measuring the transmitted fast neutron and gamma ray spectra behind cylindrical samples of steel (rho=7.87 gem sup - sup 3) of different thicknesses. A reactor collimated beam and neutron - gamma spectrometer with stiblbene scintillator were used for measurements. The pluse shape disriminate technique based on zero cross over method was used to discriminate between neutron and gamma ray pulses. Effective removal cross-section (sigma sub R) and total mass attenuation coefficient (mu) of neureons and gamma rays have been achieved using the attenuation relations. Microscopic removal cross sections sigma sup 9 sup 8 and mass removal cross sections sigma sub R sub / subrho of fast ne...

  15. Blocking of diffusion transitions of metal atoms at excitation of weakly attenuating plasmons

    CERN Document Server

    Gorelov, B M; Ogenko, V M; Shalyapina, G M

    2001-01-01

    One studies blocking transitions of metal atoms in YBa sub 2 Cu sub 3 O sub 7 high-temperature superconductor at excitation of weakly attenuating acoustic plasmons and at thermodesorption of 01 atoms. Ni and Au atoms were as diffusates. YBa sub 2 Cu sub 3 O sub 7 sub - subdelta specimens were irradiated by 9.4 GHz frequency and 10 sup 4 W power pulsed UHF-field. Temperature dependences of diffusion coefficient of Ni and Au atoms prior and subsequent to UHF irradiation and thermodesorption of 0 atoms are analyzed. It is pointed out that subsequent to UHF irradiation resistance of a specimen increases near transition into superconducting state. One makes a conclusion that blocking of space and surface transitions of Ni and Au atoms results from accumulation a large number of interstitial atoms in the surface layer of crystallites

  16. Cold atom dynamics in crossed laser beam waveguides

    CERN Document Server

    Torrontegui, E; Ruschhaupt, A; Guéry-Odelin, D; Muga, J G

    2010-01-01

    We study the dynamics of neutral cold atoms in an $L$-shaped crossed-beam optical waveguide formed by two perpendicular red-detuned lasers of different intensities and a blue-detuned laser at the corner. Complemented with a vibrational cooling process this setting works as a one-way device or "atom diode".

  17. Mass attenuation coefficients, effective atomic numbers and effective electron densities for some polymers

    International Nuclear Information System (INIS)

    In this study, the total mass attenuation coefficients (mm) for some homo- and hetero-chain polymers, namely polyamide-6 (PA-6), poly-methyl methacrylate (PMMA), low-density polyethylene (LDPE), polypropylene (PP) and polystyrene (PS) were measured at 59.5, 511, 661.6, 1173.2, 1274.5 and 1332.5 keV photon energies. The samples were separately irradiated with 241Am, 22Na, 137Cs and 60Co (638 kBq) radioactive gamma sources. The measurements were made by performing transmission experiments with a '2 x 2' NaI(Tl) scintillation detector having an energy resolution of 7 % at 662 keV gamma ray from the decay of 137Cs. The effective atomic numbers (Zeff) and the effective electron densities (Neff) were determined experimentally and theoretically using the obtained μm values for the investigated samples. Furthermore, Zeff and Neff of each polymer were computed for total photon interaction cross-sections using theoretical data over a wide energy region from 1 keV to 10 MeV. The experimental values of the selected polymers were found to be in good agreement with the theoretical values. (authors)

  18. Mass attenuation coefficients, effective atomic numbers and effective electron densities for some polymers.

    Science.gov (United States)

    Kucuk, Nil; Cakir, Merve; Isitman, Nihat Ali

    2013-01-01

    In this study, the total mass attenuation coefficients (μ(m)) for some homo- and hetero-chain polymers, namely polyamide-6 (PA-6), poly-methyl methacrylate (PMMA), low-density polyethylene (LDPE), polypropylene (PP) and polystyrene (PS) were measured at 59.5, 511, 661.6, 1173.2, 1274.5 and 1332.5 keV photon energies. The samples were separately irradiated with (241)Am, (22)Na, (137)Cs and (60)Co (638 kBq) radioactive gamma sources. The measurements were made by performing transmission experiments with a 2″×2″ NaI(Tl) scintillation detector having an energy resolution of 7 % at 662 keV gamma ray from the decay of (137)Cs. The effective atomic numbers (Z(eff)) and the effective electron densities (N(eff)) were determined experimentally and theoretically using the obtained μ(m) values for the investigated samples. Furthermore, Z(eff) and N(eff) of each polymer were computed for total photon interaction cross-sections using theoretical data over a wide energy region from 1 keV to 10 MeV. The experimental values of the selected polymers were found to be in good agreement with the theoretical values. PMID:22645382

  19. Measurement of attenuation cross-sections of some fatty acids in the energy range 122–1330 keV

    Indian Academy of Sciences (India)

    GAIKWAD D K; PAWAR P P

    2016-07-01

    The mass attenuation coefficients $(\\mu m)$ have been measured for undecylic acid (C$_{11}$H$_{22}$O$_2$), lauric acid (C$_{12}$H$_{24}$O$_2$), tridecylic acid (C$_{13}$H$_{26}$O$_2$), myristic acid (C$_{14}$H$_{28}$O$_2$), pentadecylic acid (C$_{15}$H$_{30}$O$_2$) andpalmitic acid (C$_{16}$H$_{32}$O$_2$) using $^{57}$Co, $^{133}$Ba, $^{137}$Cs, $^{60}$Co and $^{22}$Na emitted γ radiation with energies 122, 356,511, 662, 1170, 1275 and 1330 keV, respectively. The accurate values of the effective atomic number (Zeff), atomic cross-section $(\\sigma t,)$, electronic cross-section $(\\sigma e)$ and the effective electron density (Neff) have great significance in radiation protection and dosimetry. These quantities were obtained by utilizing experimentally measured values of mass attenuation coefficients $(\\mu m)$. A NaI(Tl) scintillation detector with 8.2% (at 662 keV) resolution was used for detecting of attenuated γ -photons. The variation in Zeff and Neff of fatty acids with energy is discussed. The experimental and theoretical results are in good agreement within 2% deviation.

  20. Selected K and L X-Ray mass attenuation coefficients for low atomic number materials

    International Nuclear Information System (INIS)

    X-ray attenuation coefficients for low atomic mumbers elements were obtained for characteristic K and L X-ray of a number of selected elements using the fitting of a third degree polynomial to the values tabulated by Storm and Israel

  1. Determination of total mass attenuation coefficients, effective atomic numbers and electron densities for different shielding materials

    International Nuclear Information System (INIS)

    Highlights: • The gamma shielding properties of eight shielding materials have been investigated. • We calculated the total mass attenuation coefficients by using WinXCom program. • The values of effective atomic number and electron density are also calculated. • All parameters depend on chemical content and the incident photon energy. • The Field castable Heat Resistant is the most effective shielding material. - Abstract: In this paper, the interaction of gamma rays with some shielding materials has been studied. The total mass attenuation coefficient (μt) for eight shielding materials has been calculated by using WinXCOM program in the energy range from 1 keV to 100 GeV. Also, the effective atomic number (Zeff) and the effective electron density (Neff) were calculated using the values of the total mass attenuation coefficient. The dependence of these parameters on the incident photon energy and the chemical composition has been examined

  2. Scaling of Cross Sections for Ion-atom Impact Ionization

    CERN Document Server

    Kaganovich, I D; Startsev, E

    2003-01-01

    The values of ion-atom ionization cross sections are frequently needed for many applications that utilize the propagation of fast ions through matter. When experimental data and theoretical calculations are not available, approximate formulas are frequently used. This paper briefly summarizes the most important theoretical results and approaches to cross section calculations in order to place the discussion in historical perspective and offer a concise introduction to the topic. Based on experimental data and theoretical predictions, a new fit for ionization cross sections is proposed. The range of validity and accuracy of several frequently used approximations (classical trajectory, the Born approximation, and so forth) are discussed using, as examples, the ionization cross sections of hydrogen and helium atoms by various fully stripped ions.

  3. Scaling Cross Sections for Ion-atom Impact Ionization

    Energy Technology Data Exchange (ETDEWEB)

    Igor D. Kaganovich; Edward Startsev; Ronald C. Davidson

    2003-06-06

    The values of ion-atom ionization cross sections are frequently needed for many applications that utilize the propagation of fast ions through matter. When experimental data and theoretical calculations are not available, approximate formulas are frequently used. This paper briefly summarizes the most important theoretical results and approaches to cross section calculations in order to place the discussion in historical perspective and offer a concise introduction to the topic. Based on experimental data and theoretical predictions, a new fit for ionization cross sections is proposed. The range of validity and accuracy of several frequently used approximations (classical trajectory, the Born approximation, and so forth) are discussed using, as examples, the ionization cross sections of hydrogen and helium atoms by various fully stripped ions.

  4. Scaling of Cross Sections for Ion-atom Impact Ionization

    International Nuclear Information System (INIS)

    The values of ion-atom ionization cross sections are frequently needed for many applications that utilize the propagation of fast ions through matter. When experimental data and theoretical calculations are not available, approximate formulas are frequently used. This paper briefly summarizes the most important theoretical results and approaches to cross section calculations in order to place the discussion in historical perspective and offer a concise introduction to the topic. Based on experimental data and theoretical predictions, a new fit for ionization cross sections is proposed. The range of validity and accuracy of several frequently used approximations (classical trajectory, the Born approximation, and so forth) are discussed using, as examples, the ionization cross sections of hydrogen and helium atoms by various fully stripped ions

  5. Attenuation of Cross-Flow Fan Noise Using Porous Stabilizers

    Directory of Open Access Journals (Sweden)

    Huanxin Lai

    2011-01-01

    Full Text Available This paper presents a qualitative analysis of controlling the cross-flow fan noise by using porous stabilizers. The stabilizer was originally a folded plate. It is changed into a porous structure which has a plenum chamber and vent holes on the front wall. In order to investigate the influences of using the porous stabilizers, experiments are carried out to measure the cross-flow fan aerodynamic performances and sound radiation. Meanwhile, the internal flow field of the fan is numerically simulated. The results show that the porous stabilizers have not produced considerable effect on the cross-flow fan's performance curve, but the noise radiated from the fan is strongly affected. This indicates the feasibility of controlling the cross-flow fan noise by using the porous stabilizers with selected porosity.

  6. Removal cross sections and total mass attenuation coefficients of fast neutrons and gamma rays for steel

    International Nuclear Information System (INIS)

    The present work deals with the study of the attenuation properties and determination of the cross sections of fast neutrons and gamma rays for structure steel used in different applications in nuclear power plants, particle accelerators, research reactors and different radiation attenuation fields. Investigation has been performed by measuring the transmitted fast neutron and gamma ray spectra behind cylindrical samples of steel (ρ=7.87 gem-3) of different thicknesses. A reactor collimated beam and neutron - gamma spectrometer with stiblbene scintillator were used for measurements. The pluse shape disriminate technique based on zero cross over method was used to discriminate between neutron and gamma ray pulses. Effective removal cross-section (σR) and total mass attenuation coefficient (μ) of neureons and gamma rays have been achieved using the attenuation relations. Microscopic removal cross sections σ98 and mass removal cross sections σR/ρ of fast neutrons have been evaluated based on measured results and definite energies. Also, total mass attenuation coefficients (μ/σ) of gamma rays have been evalusted and calculated using measured results and XCOM code respectively. Comparison between measured and calculated results shows a resonable agreement between the two

  7. The photon scattering cross-sections of atomic hydrogen

    CERN Document Server

    Grunefeld, Swaantje J; Cheng, Yongjun

    2016-01-01

    We present a unified view of the frequency dependence of the various scattering processes involved when a neutral hydrogen atom interacts with a monochromatic, linearly-polarized photon. A computational approach is employed of the atom trapped by a finite-sized-box due to a finite basis-set expansion, which generates a set of transition matrix elements between $E0$ pseudostates. We introduce a general computational methodology that enables the computation of the frequency-dependent dipole transition polarizability with one real and two different imaginary contributions. These dipole transition polarizabilities are related to the cross-sections of one-photon photoionization, Rayleigh, Raman, and Compton scattering. Our numerical calculations reveal individual Raman scattering cross-sections above threshold that can rapidly vanish and revive. Furthermore, our numerical Compton cross-sections do not overtly suffer from the infra-red divergence problem, and are three orders-of-magnitude higher than previous analy...

  8. Total Born approximation cross sections for single electron loss by atoms and ions colliding with atoms

    Science.gov (United States)

    Rule, D. W.

    1977-01-01

    The first born approximation (FBA) is applied to the calculation of single electron loss cross sections for various ions and atoms containing from one to seven electrons. Screened hydrogenic wave functions were used for the states of the electron ejected from the projectile, and Hartree-Fock elastic and incoherent scattering factors were used to describe the target. The effect of the target atom on the scaling of projectile ionization cross sections with respect to the projectile nuclear charge was explored in the case of hydrogen-like ions. Scaling of the cross section with respect to the target nuclear charge for electron loss by Fe (+25) in collision with neutral atoms ranging from H to Fe is also examined. These results were compared to those of the binary encounter approximation and to the FBA for the case of ionization by completely stripped target ions.

  9. Electron and positron atomic elastic scattering cross sections

    Energy Technology Data Exchange (ETDEWEB)

    Stepanek, Jiri E-mail: jiri.stepanek@psi.ch

    2003-02-01

    A method was developed to calculate the total and differential elastic-scattering cross sections for incident electrons and positrons in the energy range from 0.01 eV to 1 MeV for atoms of Z=1-100. For electrons, hydrogen, helium, nitrogen, oxygen, krypton, and xenon, and for positrons, helium, neon, and argon atoms were considered for comparison with experimental data. First, the variationally optimized atomic static potentials were calculated for each atom by solving the Dirac equations for bound electron states. Second, the Dirac equations for a free electron or positron are solved for an atom using the previously calculated static potential accomplished (in the case of electrons) by 'adjusted' Hara's exchange potential for a free-state particle. Additional to the exchange effects, the charge cloud polarization effects are considered applying the correlation-polarization potential of O'Connell and Lane (with correction of Padial and Norcross) for incident electrons, and of Jain for incident positrons. The total, cutoff and differential elastic-scattering cross sections are calculated for incident electrons and positrons with the help of the relativistic partial wave analysis. The solid state effects for scattering in solids are described by means of a muffin-tin model, i.e. the potentials of neighboring atoms are superpositioned in such a way that the resulting potential and its derivative are zero in the middle distance between the atoms. The potential of isolated atom is calculated up to the radius at which the long-range polarization potential becomes a value of -10{sup -8}.

  10. Effective atomic numbers and mass attenuation coefficients of some thermoluminescent dosimetric compounds for total photon interaction

    International Nuclear Information System (INIS)

    Effective atomic numbers for total gamma-ray interaction with some selected thermoluminescent dosimetric compounds such as barium acetate, barium sulfate, calcium carbonate, calcium sulfate, calcium sulfate dihydrate, cadmium sulfate (anhydrous), cadmium sulfate, strontium sulfate, and lithium fluoride have been calculated in the 1-keV to 20-MeV energy region. Experimental mass attenuation coefficients and effective atomic numbers for these compounds at selected photon energies of 26.3, 33.2, 59.54, and 661.6 keV have been obtained from good geometry transmission measurements and compared with theoretical values. The effect of absorption edge on effective atomic numbers and its variation with energy, and nonvalidity of the Bragg's mixture rule at incident photon energies closer to the absorption edges of constituent elements of compounds are discussed

  11. Measurements of mass attenuation coefficient, effective atomic number and electron density of some amino acids

    International Nuclear Information System (INIS)

    The mass attenuation coefficients of some amino acids, such as DL-aspartic acid-LR(C4H7NO4), L-glutamine (C4H10N2O3), creatine monohydrate LR(C4H9N3O2H2O), creatinine hydrochloride (C4H7N3O·HCl) L-asparagine monohydrate(C4H9N3O2H2O), L-methionine LR(C5H11NO2S), were measured at 122, 356, 511, 662, 1170, 1275 and 1330 keV photon energies using a well-collimated narrow beam good geometry set-up. The gamma-rays were detected using NaI (Tl) scintillation detection system with a resolution of 0.101785 at 662 keV. The attenuation coefficient data were then used to obtain the effective atomic numbers (Zeff), and effective electron densities (Neff) of amino acids. It was observed that the effective atomic number (Zeff) and effective electron densities (Neff) initially decrease and tend to be almost constant as a function of gamma-ray energy. Zeff and Neff experimental values showed good agreement with the theoretical values with less than 1% error for amino acids. - Highlights: • We report the values of mass attenuation coefficients (μ/ρ). • The values of (Zeff) i.e. effective atomic number are calculated. • Measurement of effective electron density (Neff) of some amino acids. • Comparison of all μ/ρ values with XCOM programme

  12. Near threshold photodetachment cross section of negative atomic oxygen ions

    Institute of Scientific and Technical Information of China (English)

    Wu Jian-Hua(吴建华); Yuan Jian-Min(袁建民); Vo Ky Lan

    2003-01-01

    A 40-target state close-coupling calculation for the photodetachment cross section of negative atomic oxygen near threshold is carried out with core-valence electron correlation by using the R-matrix method. It was shown that after considering the excitations of two electrons from the 2s shell, the electron affinity of O- (2s22p5 2po) agrees with the experimental result much better than that just considering the excitations of electrons only from the 2p shell as well as only one electron from the 2s shell. Total cross section as well as the main contribution of the ionization channels to the partial cross section are illustrated to show the structure near threshold clearly.

  13. Inelastic cross sections for positron scattering from atomic hydrogen

    International Nuclear Information System (INIS)

    Positronium formation (Ps) cross sections for positrons impinging on atomic hydrogen were measured in the impact energy range from 13eV to 255eV at the High Intensity Positron (HIP) beam at Brookhaven National Laboratory (BNL). The Ps-formation cross section was found to rise rapidly from the threshold at 6.8eV to a maximum value of (2.98 ± 0.18) x 10-16 cm2 for ∼ 15eV positrons. By 75eV it drops below the detection limit of 0.17 x 10-16 cm2 which is the present level of statistical uncertainty. The experiment was modified to enable the measurement of doubly differential scattering cross sections

  14. Inelastic cross sections for positron scattering from atomic hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Weber, M.; Hofmann, A.; Raith, W.; Sperber, W. [Bielefeld Univ. (Germany). Fakultaet fuer Physik; Jacobsen, F.; Lynn, K.G. [Brookhaven National Lab., Upton, NY (United States)

    1994-12-31

    Positronium formation (Ps) cross sections for positrons impinging on atomic hydrogen were measured in the impact energy range from 13eV to 255eV at the High Intensity Positron (HIP) beam at Brookhaven National Laboratory (BNL). The Ps-formation cross section was found to rise rapidly from the threshold at 6.8eV to a maximum value of (2.98 {plus_minus} 0.18) {times} 10{sup {minus}16} cm{sup 2} for {approx} 15eV positrons. By 75eV it drops below the detection limit of 0.17 {times} 10{sup {minus}16} cm{sup 2} which is the present level of statistical uncertainty. The experiment was modified to enable the measurement of doubly differential scattering cross sections.

  15. Determination of mass attenuation coefficients and effective atomic numbers for Inconel 738 alloy for different energies obtained from Compton scattering

    International Nuclear Information System (INIS)

    Highlights: ► Mass attenuation coefficient of Inconel 738 superalloy was measured. ► Gamma-ray energies were changed by Compton scattering technique. ► Effective atomic number and electron density are also calculated. ► All parameters decrease with increased energy. ► The experimental values are in good agreement with theoretical ones. - Abstract: The mass attenuation coefficient of Inconel 738 superalloy has been measured at different gamma ray energies by using the Compton scattering technique. The theoretical values of mass attenuation coefficient of a glass sample were calculated using WinXCom program. The effective atomic number and electron density are also calculated. The results showed that the mass attenuation coefficients, effective atomic number and electron density increase with the decrease in gamma ray energies which is in good agreement with theoretical values (less than 2% error)

  16. Measurements of mass attenuation coefficient, effective atomic number and electron density of some amino acids

    Science.gov (United States)

    Kore, Prashant S.; Pawar, Pravina P.

    2014-05-01

    The mass attenuation coefficients of some amino acids, such as DL-aspartic acid-LR(C4H7NO4), L-glutamine (C4H10N2O3), creatine monohydrate LR(C4H9N3O2H2O), creatinine hydrochloride (C4H7N3O·HCl) L-asparagine monohydrate(C4H9N3O2H2O), L-methionine LR(C5H11NO2S), were measured at 122, 356, 511, 662, 1170, 1275 and 1330 keV photon energies using a well-collimated narrow beam good geometry set-up. The gamma-rays were detected using NaI (Tl) scintillation detection system with a resolution of 0.101785 at 662 keV. The attenuation coefficient data were then used to obtain the effective atomic numbers (Zeff), and effective electron densities (Neff) of amino acids. It was observed that the effective atomic number (Zeff) and effective electron densities (Neff) initially decrease and tend to be almost constant as a function of gamma-ray energy. Zeff and Neff experimental values showed good agreement with the theoretical values with less than 1% error for amino acids.

  17. Studies on mass energy-absorption coefficients and effective atomic energy-absorption cross sections for carbohydrates

    International Nuclear Information System (INIS)

    We measured here the mass attenuation coefficients (μ/ρ) of carbohydrates, Esculine (C15H16O9), Sucrose (C12H22O11), Sorbitol (C6H14O6), D-Galactose (C6H12O6), Inositol (C6H12O6), D-Xylose (C5H10O5) covering the energy range from 122 keV up to 1330 keV photon energies by using gamma ray transmission method in a narrow beam good geometry set-up. The gamma-rays were detected using NaI(Tl) scintillation detection system with a resolution of 8.2% at 662 keV. The attenuation coefficient data were then used to obtain the total attenuation cross-section (σtot), molar extinction coefficients (ε), mass-energy absorption coefficients (μen/ρ) and effective (average) atomic energy-absorption cross section (σa,en) of the compounds. These values are found to be in good agreement with the theoretical values calculated based on XCOM data. - Highlights: • Compute the values of mass attenuation coefficients (μ/ρ) of some carbohydrates. • The values of (μen/ρ) i.e. mass energy-absorption coefficient are calculated. • Effective atomic energy-absorption cross sections (σa,en). • Comparison of all (μ/ρ), (μen/ρ), (σa,en) values with XCOM program. • The measured data for carbohydrates are useful in radiation dosimetry and other fields

  18. Quantum atomic lithography via cross-cavity optical Stern-Gerlach setup

    Science.gov (United States)

    Máximo, C. E.; Batalhão, T. B.; Bachelard, R.; de Moraes Neto, G. D.; de Ponte, M. A.; Moussa, M. H. Y.

    2014-10-01

    We present a fully quantum scheme to perform 2D atomic lithography based on a cross-cavity optical Stern-Gerlach setup: an array of two mutually orthogonal cavities crossed by an atomic beam perpendicular to their optical axes, which is made to interact with two identical modes. After deriving an analytical solution for the atomic momentum distribution, we introduce a protocol allowing us to control the atomic deflection by manipulating the amplitudes and phases of the cavity field states.

  19. Analytical Absorption Cross-Section for Photon by a Hydrogen 2s Atom

    Institute of Scientific and Technical Information of China (English)

    Boniface Otieno Ndinya; Stephen Onyango Okeyo

    2011-01-01

    We calculate the absorption cross-section for photon by a hydrogen 2s atom using the quantum-classical approximation for the total photo cross-section of many electron atoms.With the application of the first-order term of the Baker-Hausdorf expansion, the absorption cross-section for the hydrogen 2s atom decreases to a minimum, the Cooper pair minimum, at low photon energy.Such a minimum is absent in the exact absorption cross-section for photon by a hydrogen 2s atom.We have extended the calculation for the absorption cross-section of the hydrogen 2s atom using the quantum-classical approximation for the total photo cross-section of many electron to include the second-order term of the Baker-Hausdorf expansion and observed a great reduction in the dip associated with the Cooper pair minimum at the zero crossing.

  20. Coplanar (, 3) differential cross-section of He atom

    Indian Academy of Sciences (India)

    R Choubisa; A S Bhullar; K K Sud

    2003-06-01

    We present in this paper the results of our calculation of five-fold differential cross-section (FDCS) for (, 3) process on He atom in low momentum transfer and high electron impact energy in shake-off mechanism. The formalism has been developed in Born approximation using plane waves, Byron and Joachain as well as Le Sech and correlated BBK-type wave functions respectively for incident and scattered, bound and ejected electrons. The angular distribution of FDCS of our calculation is presented in various modes of coplanar geometry and comparison is made with the available experimental data. We observe that the present calculation is able to reproduce the trend of the experimental data. However, it differs in magnitude from the experiment. The present theory does not predict four-peak structure in summed mutual angle mode for lower excess ejected electron energies. We also discuss the importance of momentum transfer, post-collision interaction (PCI) and ion participation in the (, 3) process in constant 12 mode.

  1. Studies on mass energy-absorption coefficients and effective atomic energy-absorption cross sections for carbohydrates

    Science.gov (United States)

    Ladhaf, Bibifatima M.; Pawar, Pravina P.

    2015-04-01

    We measured here the mass attenuation coefficients (μ/ρ) of carbohydrates, Esculine (C15H16O9), Sucrose (C12H22O11), Sorbitol (C6H14O6), D-Galactose (C6H12O6), Inositol (C6H12O6), D-Xylose (C5H10O5) covering the energy range from 122 keV up to 1330 keV photon energies by using gamma ray transmission method in a narrow beam good geometry set-up. The gamma-rays were detected using NaI(Tl) scintillation detection system with a resolution of 8.2% at 662 keV. The attenuation coefficient data were then used to obtain the total attenuation cross-section (σtot), molar extinction coefficients (ε), mass-energy absorption coefficients (μen/ρ) and effective (average) atomic energy-absorption cross section (σa,en) of the compounds. These values are found to be in good agreement with the theoretical values calculated based on XCOM data.

  2. Studies on mass attenuation coefficients, effective atomic numbers and electron densities for CoCuAg alloy thin film

    Science.gov (United States)

    Apaydın, G.; Cengiz, E.; Tıraşoğlu, E.; Aylıkcı, V.; Bakkaloğlu, Ö. F.

    2009-05-01

    The mass attenuation coefficients for the elements Co, Cu and Ag and a thin film of CoCuAg alloy were measured in the energy range 4.029-38.729 keV. Effective atomic numbers and electron densities were calculated by using these coefficients. The energies were obtained by using secondary targets that were irradiated with gamma-ray photons of 241Am. The x-rays were counted by using a Canberra Ultra-LEGe detector with a resolution of 150 eV at 5.9 keV. The results were compared with theoretical calculated values and fairly good agreement was found between them within an average experimental error. The mass attenuation coefficients, effective atomic numbers and electron densities were plotted versus photon energy.

  3. Studies on mass attenuation coefficients, effective atomic numbers and electron densities for CoCuAg alloy thin film

    International Nuclear Information System (INIS)

    The mass attenuation coefficients for the elements Co, Cu and Ag and a thin film of CoCuAg alloy were measured in the energy range 4.029-38.729 keV. Effective atomic numbers and electron densities were calculated by using these coefficients. The energies were obtained by using secondary targets that were irradiated with gamma-ray photons of 241Am. The x-rays were counted by using a Canberra Ultra-LEGe detector with a resolution of 150 eV at 5.9 keV. The results were compared with theoretical calculated values and fairly good agreement was found between them within an average experimental error. The mass attenuation coefficients, effective atomic numbers and electron densities were plotted versus photon energy.

  4. On cross sections of intercombination transitions between high-excited levels in electron-atom collisions

    International Nuclear Information System (INIS)

    The cross sections of intercombination transitions (ICT) between high-excited levels of atoms during the collisions of the latter with electrons are considered. A method is proposed for calculating ICT cross sections which are orbital quantum number totals. A comparison with the cross section calculated within the scope of quasiclassic approach is performed. Both methods yield close results

  5. Pharmacologic attenuation of cross-modal sensory augmentation within the chronic pain insula.

    Science.gov (United States)

    Harte, Steven E; Ichesco, Eric; Hampson, Johnson P; Peltier, Scott J; Schmidt-Wilcke, Tobias; Clauw, Daniel J; Harris, Richard E

    2016-09-01

    Pain can be elicited through all mammalian sensory pathways yet cross-modal sensory integration, and its relationship to clinical pain, is largely unexplored. Centralized chronic pain conditions such as fibromyalgia are often associated with symptoms of multisensory hypersensitivity. In this study, female patients with fibromyalgia demonstrated cross-modal hypersensitivity to visual and pressure stimuli compared with age- and sex-matched healthy controls. Functional magnetic resonance imaging revealed that insular activity evoked by an aversive level of visual stimulation was associated with the intensity of fibromyalgia pain. Moreover, attenuation of this insular activity by the analgesic pregabalin was accompanied by concomitant reductions in clinical pain. A multivariate classification method using support vector machines (SVM) applied to visual-evoked brain activity distinguished patients with fibromyalgia from healthy controls with 82% accuracy. A separate SVM classification of treatment effects on visual-evoked activity reliably identified when patients were administered pregabalin as compared with placebo. Both SVM analyses identified significant weights within the insular cortex during aversive visual stimulation. These data suggest that abnormal integration of multisensory and pain pathways within the insula may represent a pathophysiological mechanism in some chronic pain conditions and that insular response to aversive visual stimulation may have utility as a marker for analgesic drug development. PMID:27101425

  6. Variation of photoabsorption cross section of atomic silver from isolated to condensed conditions*

    Institute of Scientific and Technical Information of China (English)

    Ma Xiao-Guang; Gong Yu-Bing; Qu Zhao-Jun

    2009-01-01

    The influence of the local-field on the photoabsorption cross section of the atomic silver is studied in detail by using the Clausius-Mossotti(CM)model and the Onsager model separately.The variations of the photoabsorption cross section of atomic silver with number density and radius of the environmental interaction cavity are studied systematically by using more general expressions for the photoabsorption cross sections,proposed by Sun et al recently.It has proved to be reasonable to model the optical response properties of bulky material by coupling the property of isolated atom with the environmental effccts in the present work.

  7. Total Born-approximation cross sections for single-electron loss by atoms and ions colliding with atoms

    Science.gov (United States)

    Rule, D. W.

    1977-01-01

    The first Born approximation (FBA) is applied to the calculation of single-electron-loss cross sections for various ions and atoms containing from one to seven electrons. Screened hydrogenic wave functions are used for the states of the electron ejected from the projectile, and Hartree-Fock elastic and incoherent scattering factors are used to describe the target. The effect of the target atom on the scaling of projectile ionization cross sections with respect to the projectile nuclear charge is explored in the case of hydrogenlike ions. Also examined is the scaling of the cross section with respect to the target nuclear charge for electron loss by Fe(25+) in collision with neutral atoms ranging from H to Fe. These results are compared with those of the binary-encounter approximation (BEA) and with the FBA for the case of ionization by completely stripped target ions. Electron-loss cross sections are also calculated for the ions O(i+) (i = 3-7) and N(i+) (i = 0-6) in collision with He targets in the energy range of approximately 0.1 to 100 MeV/nucleon. These results are found to be in excellent agreement with the available data near the peak of the ionization cross section.

  8. Dynamics of Cold Atoms Crossing a One-Way Barrier

    OpenAIRE

    Thorn, Jeremy J.; Schoene, Elizabeth A.; Li, Tao; Steck, Daniel A.

    2009-01-01

    We implemented an optical one-way potential barrier that allows ultracold $^{87}$Rb atoms to transmit through when incident on one side of the barrier but reflect from the other. This asymmetric barrier is a realization of Maxwell's demon, which can be employed to produce phase-space compression and has implications for cooling atoms and molecules not amenable to standard laser-cooling techniques. The barrier comprises two focused, Gaussian laser beams that intersect the focus of a far-off-re...

  9. Magnetic levitation for effective loading of cold cesium atoms in a crossed dipole trap

    Science.gov (United States)

    Li, Yuqing; Feng, Guosheng; Xu, Rundong; Wang, Xiaofeng; Wu, Jizhou; Chen, Gang; Dai, Xingcan; Ma, Jie; Xiao, Liantuan; Jia, Suotang

    2015-05-01

    We report a detailed study of effective magnetically levitated loading of cold atoms in a crossed dipole trap: an appropriate magnetic field gradient precisely compensates for the destructive gravitational force of the atoms and an additional bias field simultaneously eliminates the antitrapping potential induced by the magnetic field gradient. The magnetic levitation is required for a large-volume crossed dipole trap to form a shallow but very effective loading potential, making it a promising method for loading and trapping more cold atoms. For cold cesium atoms in the F =3 , m F =3 state prepared by three-dimensional degenerated Raman sideband cooling, a large number of atoms ˜3.2 ×106 have been loaded into a large-volume crossed dipole trap with the help of the magnetic levitation technique. The dependence of the number of atoms loaded and trapped in the dipole trap on the magnetic field gradient and bias field, respectively, is in good agreement with the theoretical analysis. The optimum magnetic field gradient of 31.13 G/cm matches the theoretical value of 31.3 G/cm well. This method can be used to obtain more cold atoms or a large number of Bose-Einstein condensation atoms for many atomic species in high-field seeking states.

  10. Effective atomic number and mass attenuation coefficient of PbO-BaO-B2O3 glass system

    Science.gov (United States)

    Issa, Shams A. M.

    2016-03-01

    Gamma-rays attenuation coefficient, half-value layer, mean free path, effective atomic number and electron density have been measured in glass system of xPbO-(50-x) BaO-50B2O3 (where 5≤x≤45 mol%) for gamma ray photon energies of 0.356, 0.662, 1.173 and 1.33 MeV. The emitted gamma ray was detected by 3×3 in. NaI(Tl) scintillation gamma ray spectrometers. The results were found in good agreement with the theoretical values which calculated from WinXcom.

  11. Study of mass attenuation coefficients and effective atomic numbers of bismuth-ground granulated blast furnace slag concretes

    Science.gov (United States)

    Kumar, Sandeep; Singh, Sukhpal

    2016-05-01

    Five samples of Bismuth-Ground granulated blast furnace slag (Bi-GGBFS) concretes were prepared using composition (0.6 cement + x Bi2O3 + (0.4-x) GGBFS, x = 0.05, 0.10, 0.15, 0.20 and 0.25) by keeping constant water (W) cement (C) ratio. Mass attenuation coefficients (μm) of these prepared samples were calculated using a computer program winXCOM at different gamma ray energies, whereas effective atomic numbers (Zeff) is calculated using mathematical formulas. The radiation shielding properties of Bi-GGBFS concrete has been compared with standard radiation shielding concretes.

  12. Studies on effective atomic numbers, electron densities from mass attenuation coefficients near the K edge in some samarium compounds.

    Science.gov (United States)

    Akman, F; Durak, R; Turhan, M F; Kaçal, M R

    2015-07-01

    The effective atomic numbers and electron densities of some samarium compounds were determined using the experimental total mass attenuation coefficient values near the K edge in the X-ray energy range from 36.847 up to 57.142 keV. The measurements, in the region from 36.847 to 57.142 keV, were done in a transmission geometry utilizing the Kα2, Kα1, Kβ1 and Kβ2 X-rays from different secondary source targets excited by the 59.54 keV gamma-photons from an Am-241 annular source. This paper presents the first measurement of the effective atomic numbers and electron densities for some samarium compounds near the K edge. The results of the study showed that the measured values were in good agreement with the theoretically calculated ones. PMID:25880612

  13. Attenuation and cross-attenuation in taste aversion learning in the rat: Studies with ionizing radiation, lithium chloride and ethanol

    International Nuclear Information System (INIS)

    The preexposure paradigm was utilized to evaluate the similarity of ionizing radiation, lithium chloride and ethanol as unconditioned stimuli for the acquisition of a conditioned taste aversion. Three unpaired preexposures to lithium chloride (3.0 mEq/kg, IP) blocked the acquisition of a taste aversion when a novel sucrose solution was paired with either the injection of the same dose of lithium chloride or exposure to ionizing radiation (100 rad). Similar pretreatment with radiation blocked the acquisition of a radiation-induced aversion, but had no effect on taste aversions produced by lithium chloride (3.0 or 1.5 mEq/kg). Preexposure to ethanol (4 g/kg, PO) disrupted the acquisition of an ethanol-induced taste aversion, but not radiation- or lithium chloride-induced aversions. In contrast, preexposure to either radiation or lithium chloride attenuated an ethanol-induced taste aversion in intact rats, but not in rats with lesions of the area postrema. The results are discussed in terms of relationships between these three unconditioned stimuli and in terms of implications of these results for understanding the nature of the proximal unconditioned stimulus in taste aversion learning

  14. Cross-section measurements for electron-impact ionization of atoms

    Science.gov (United States)

    Freund, Robert S.; Wetzel, Robert C.; Shul, Randy J.; Hayes, Todd R.

    1990-04-01

    Absolute electron-impact cross sections have been measured from 0 to 200 eV for single ionization of 16 atoms (Mg, Fe, Cu, Ag, Al, Si, Ge, Sn, Pb, P, As, Sb, Bi, S, Se, and Te) with an estimated accuracy of +/-10%. Combined with our recent measurements of He, Ne, Ar, Kr, Xe, F, Cl, Br, I, Ga, and In [Wetzel et al., Phys. Rev. A 35, 559 (1987); Hayes et al., ibid. 35, 578 (1987); Shul, Wetzel, and Freund, ibid. 39, 5588 (1989)], a set of 27 atomic single-ionization cross sections has now been measured with the same apparatus. In addition, cross sections are reported for double ionization of ten atoms and triple ionization of eight atoms. The measurements are made by crossing an electron beam with a 3-keV beam of neutral atoms, prepared by charge-transfer neutralization of a mass-selected ion beam. The critical measurement of absolute neutral beam flux is made with a calibrated pyroelectric crystal. The magnitudes of the single-ionization-peak cross sections decrease monotonically across rows of the periodic table from group IIIA (Al,Ga,In) to group VIIIA (Ar,Kr,Xe), varying much more than predicted by various empirical formulas and classical and quantum-mechanical theories.

  15. Analysis of the differential cross section for the hydrogen atom ionization by fast electrons in an uniform electric field

    International Nuclear Information System (INIS)

    Quantitative analysis of the differential cross section for a hydrogen atom ionization by fast electrons in the Born nonrelativistic approximation in the external homogeneous electric field, is carried out. It is shown that the cross section obtained may essentially differ from the similar cross section of an isolated atom ionization by angular distribution of the secondary pulses, oscillation components and magnitude

  16. Tomography of atomic number and density of materials using dual-energy imaging and the Alvarez and Macovski attenuation model

    Science.gov (United States)

    Paziresh, M.; Kingston, A. M.; Latham, S. J.; Fullagar, W. K.; Myers, G. M.

    2016-06-01

    Dual-energy computed tomography and the Alvarez and Macovski [Phys. Med. Biol. 21, 733 (1976)] transmitted intensity (AMTI) model were used in this study to estimate the maps of density (ρ) and atomic number (Z) of mineralogical samples. In this method, the attenuation coefficients are represented [Alvarez and Macovski, Phys. Med. Biol. 21, 733 (1976)] in the form of the two most important interactions of X-rays with atoms that is, photoelectric absorption (PE) and Compton scattering (CS). This enables material discrimination as PE and CS are, respectively, dependent on the atomic number (Z) and density (ρ) of materials [Alvarez and Macovski, Phys. Med. Biol. 21, 733 (1976)]. Dual-energy imaging is able to identify sample materials even if the materials have similar attenuation coefficients at single-energy spectrum. We use the full model rather than applying one of several applied simplified forms [Alvarez and Macovski, Phys. Med. Biol. 21, 733 (1976); Siddiqui et al., SPE Annual Technical Conference and Exhibition (Society of Petroleum Engineers, 2004); Derzhi, U.S. patent application 13/527,660 (2012); Heismann et al., J. Appl. Phys. 94, 2073-2079 (2003); Park and Kim, J. Korean Phys. Soc. 59, 2709 (2011); Abudurexiti et al., Radiol. Phys. Technol. 3, 127-135 (2010); and Kaewkhao et al., J. Quant. Spectrosc. Radiat. Transfer 109, 1260-1265 (2008)]. This paper describes the tomographic reconstruction of ρ and Z maps of mineralogical samples using the AMTI model. The full model requires precise knowledge of the X-ray energy spectra and calibration of PE and CS constants and exponents of atomic number and energy that were estimated based on fits to simulations and calibration measurements. The estimated ρ and Z images of the samples used in this paper yield average relative errors of 2.62% and 1.19% and maximum relative errors of 2.64% and 7.85%, respectively. Furthermore, we demonstrate that the method accounts for the beam hardening effect in density (ρ) and

  17. Improved calculation of displacements per atom cross section in solids by gamma and electron irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Piñera, Ibrahin, E-mail: ipinera@ceaden.edu.cu [Centro de Aplicaciones Tecnológicas y Desarrollo Nuclear, CEADEN, 30 St. 502, Playa 11300, Havana (Cuba); Cruz, Carlos M.; Leyva, Antonio; Abreu, Yamiel; Cabal, Ana E. [Centro de Aplicaciones Tecnológicas y Desarrollo Nuclear, CEADEN, 30 St. 502, Playa 11300, Havana (Cuba); Espen, Piet Van; Remortel, Nick Van [University of Antwerp, CGB, Groenenborgerlaan 171, 2020 Antwerpen (Belgium)

    2014-11-15

    Highlights: • We present a calculation procedure for dpa cross section in solids under irradiation. • Improvement about 10–90% for the gamma irradiation induced dpa cross section. • Improvement about 5–50% for the electron irradiation induced dpa cross section. • More precise results (20–70%) for thin samples irradiated with electrons. - Abstract: Several authors had estimated the displacements per atom cross sections under different approximations and models, including most of the main gamma- and electron-material interaction processes. These previous works used numerical approximation formulas which are applicable for limited energy ranges. We proposed the Monte Carlo assisted Classical Method (MCCM), which relates the established theories about atom displacements to the electron and positron secondary fluence distributions calculated from the Monte Carlo simulation. In this study the MCCM procedure is adapted in order to estimate the displacements per atom cross sections for gamma and electron irradiation. The results obtained through this procedure are compared with previous theoretical calculations. An improvement in about 10–90% for the gamma irradiation induced dpa cross section is observed in our results on regard to the previous evaluations for the studied incident energies. On the other hand, the dpa cross section values produced by irradiation with electrons are improved by our calculations in about 5–50% when compared with the theoretical approximations. When thin samples are irradiated with electrons, more precise results are obtained through the MCCM (in about 20–70%) with respect to the previous studies.

  18. Cross-sections for neutral atoms and molecules collisions with charged spherical nanoparticle

    CERN Document Server

    Shneider, M N

    2016-01-01

    The paper presents cross sections for collisions of neutral atoms/molecules with a charged nanoparticle, which is the source of the dipole potential. The accuracy of the orbital limited motion (OLM) approximation is estimated. It is shown that simple analytical formulas for the atoms/molecules and heat fluxes, obtained in the OLM approximation, give an error of not more than 15%, and are applicable in all reasonable range of nanoparticles and weakly ionized plasma parameters.

  19. Enhanced Optical Cross Section via Collective Coupling of Atomic Dipoles in a 2D Array

    Science.gov (United States)

    Bettles, Robert J.; Gardiner, Simon A.; Adams, Charles S.

    2016-03-01

    Enhancing the optical cross section is an enticing goal in light-matter interactions, due to its fundamental role in quantum and nonlinear optics. Here, we show how dipolar interactions can suppress off-axis scattering in a two-dimensional atomic array, leading to a subradiant collective mode where the optical cross section is enhanced by almost an order of magnitude. As a consequence, it is possible to attain an optical depth which implies high-fidelity extinction, from a monolayer. Using realistic experimental parameters, we also model how lattice vacancies and the atomic trapping depth affect the transmission, concluding that such high extinction should be possible, using current experimental techniques.

  20. Enhanced optical cross section via collective coupling of atomic dipoles in a 2D array

    CERN Document Server

    Bettles, Robert J; Adams, Charles S

    2015-01-01

    Enhancing the optical cross section is an enticing goal in light-matter interactions, due to its fundamental role in quantum and non-linear optics. Here, we show how dipolar interactions can suppress off-axis scattering in a two-dimensional atomic array, leading to a subradiant collective mode where the optical cross section is enhanced by an order of magnitude. As a consequence, it is possible to attain an optical depth which implies high fidelity extinction, from a monolayer. Using realistic experimental parameters, we also model how lattice vacancies and the atomic trapping depth affect the transmission, concluding that such high extinction should be possible, using current experimental techniques.

  1. An Empirical Formula of Atomic K-Shell Ionization Cross Sections by Electron Impact

    Institute of Scientific and Technical Information of China (English)

    唐昶环; 安竹; 罗正明; 范晓强

    2001-01-01

    An empirical formula is proposed to describe the K-shell ionization cross sections by electron impact over a wide range of atomic numbers and overvoltages U (the ratio between the electron incident energy and the bindingenergy of the electrons in the K-shell). The study is based on the analysis of existing experimental data of K-shell ionization cross sections. The expression shows the results in good agreement with the data for Z<6 atoms as well as for 6<Z<79.

  2. Effect of static electric field on cross sections in antiproton impact ionization of atomic helium

    International Nuclear Information System (INIS)

    We report the effect of static electric fields in different geometrical features on the collisional ionization of helium atoms by antiproton. The Classical Trajectory Monte Carlo (CTMC) method with a model interaction potential has been used to simulate the differential and total ionization cross sections in antiproton–helium atom collisions in the energy range of 10–500 keV with and without electric fields. The calculated ionization cross sections are in reasonable agreement with the recently reported experimental and theoretical results. The effects of the external electric fields are seen to be quite prominent.

  3. Fast compression of a cold atomic cloud using a blue detuned crossed dipole trap

    CERN Document Server

    Bienaime, Tom; de Lepinay, Laure Mercier; Bellando, Louis; Chabe, Julien; Kaiser, Robin

    2012-01-01

    We present the experimental realization of a compressible blue detuned crossed dipole trap for cold atoms allowing for fast dynamical compression (~ 5 - 10 ms) of 5x10^7 Rubidium atoms up to densities of ~ 10^13 cm^-3. The dipole trap consists of two intersecting tubes of blue-detuned laser light. These tubes are formed using a single, rapidly rotating laser beam which, for sufficiently fast rotation frequencies, can be accurately described by a quasi-static potential. The atomic cloud is compressed by dynamically reducing the trap volume leading to densities close to the Ioffe-Reggel criterion for light localization.

  4. Reaction Mechanism of Oxygen Atoms with Unsaturated Hydrocarbons by the Crossed-Molecular-Beams Method

    Science.gov (United States)

    Buss, R. J.; Baseman, R. J.; Guozhong, H.; Lee, Y. T.

    1982-04-01

    From a series of studies of the reaction of oxygen atoms with unsaturated hydrocarbons using the crossed molecular beam method, the dominant reaction mechanisms were found to be the simple substitution reactions with oxygen atoms replacing H, Cl, Br atom or alkyl groups. Complication due to secondary reaction was avoided by carrying out experiments under single collisions and observing primary products directly. Primary products were identified by measuring the angular and velocity distributions of products at all the mass numbers which could be detected by the mass spectrometer, and from comparison of these distributions, applying the requirement of energy and momentum conservation.

  5. The cross-over from tunnelling to multiphoton ionization of atoms

    CERN Document Server

    Klaiber, Michael

    2016-01-01

    We present a theory illuminating the cross-over from strong-field tunnelling ionization to weak-field multiphoton ionization in the interaction of a classical laser field with a hydrogen atom. A simple formula is derived in which the ionization amplitude appears as a product of two separate amplitudes. The first describes the initial polarization of the atom by virtual multiphoton absorption and the second the subsequent tunnelling out of the polarized atom. Tunnelling directly from the ground state and multiphoton absorption without tunnelling appear naturally as the limits of the theory.

  6. Scaling and Formulary cross sections for ion-atom impact ionization

    OpenAIRE

    Kaganovich, Igor D.; Startsev, Edward; Davidson, Ronald C.

    2004-01-01

    The values of ion-atom ionization cross sections are frequently needed for many applications that utilize the propagation of fast ions through matter. When experimental data and theoretical calculations are not available, approximate formulas are frequently used. This paper briefly summarizes the most important theoretical results and approaches to cross section calculations in order to place the discussion in historical perspective and offer a concise introduction to the topic. Based on expe...

  7. Differential cross section for photoionization of a hydrogen atom in a uniform electric field

    International Nuclear Information System (INIS)

    The differential cross section for the photoionisation of an atom in a uniform electric field can be observed if the photocurrent is registered on a plane screen perpendicular to the uniform field axis. It manifests a complicated structure due to both resonance and interference effects which are interpreted in terms of the classical electron trajectories. In certain experimental conditions, the pattern can achieve a macroscopic size. Tentative suggestions for the applications of the differential cross section observation are discussed. (Author)

  8. Ericson fluctuations in the chaotic ionization of the hydrogen atom in crossed magnetic and electric fields

    International Nuclear Information System (INIS)

    We report exact quantum calculations for the hydrogen atom in crossed magnetic and electric fields. Employing the complex-coordinate-rotation method we are able to extend the calculations of eigenstates far into the continuum region. Calculated photoionization cross sections are found to exhibit strong Ericson fluctuations, a characteristic feature of chaotic scattering. This interpretation is supported by classical trajectory calculations which reveal a fractal dependence of the classical ionization time on the initial conditions

  9. Ionization cross sections of state selective atomic hydrogen by impact of multiply charged ions

    International Nuclear Information System (INIS)

    Ionization cross sections of atomic hydrogen in ground state and in metastable 2s state in collision with bare projectiles over a wide energy range have been calculated. The final state wave function considers the distortion due to Coulomb fields of both the projectile and the target nucleus. The present calculated total ionization cross-section values show good accord with the measurements for He2+, Li3- and C6+ impact at intermediate and high energy region. (author)

  10. Determination of total mass attenuation coefficients, effective atomic numbers and electron densities for different shielding materials used in radiation protection

    Energy Technology Data Exchange (ETDEWEB)

    Almeida J, A. T. [FUNDACENTRO, Centro Regional de Minas Gerais, Brazilian Institute for Safety and Health at Work, Belo Horizonte, 30180-100 Minas Gerais (Brazil); Nogueira, M. S. [Center of Development of Nuclear Technology / CNEN, Av. Pte. Antonio Carlos 6627, 31270-901 Belo Horizonte, Minas Gerais (Brazil); Santos, M. A. P., E-mail: mnogue@cdtn.br [Regional Center for Nuclear Science / CNEN, 50.740-540 Recife, Pernambuco (Brazil)

    2015-10-15

    Full text: In this paper, the interaction of X-rays with some shielding materials has been studied for materials containing different amounts of barite and aggregates. The total mass attenuation coefficient (μ{sub t}) for three shielding materials has been calculated by using WinXCOM program in the energy range from RQR qualities (RQR-4, RQR-6, RQR-9, and RQR-10). They were: cream barite (density 2.99 g/cm{sup 3} collected in the State of Sao Paulo), purple barite (density 2.95 g/cm{sup 3} collected in the State of Bahia) and white barite (density 3.10 g/cm{sup 3} collected in the State of Paraiba). The chemical analysis was carried out by an X-ray fluorescence spectrometer model EDX-720, through dispersive energy. The six elements of the higher concentration found in the sample and analyzed by Spectrophotometry of Energy Dispersive X-ray for the samples were Ba(60.9% - white barite), Ca(17,92% - cream barite), Ce(3,60% - white barite), Fe(17,16% - purple barite), S(12,11% - white barite) and Si(29,61% - purple barite). Also, the effective atomic number (Z{sub eff}) and the effective electron density (N{sub eff}) were calculated using the values of the total mass attenuation coefficient. The dependence of these parameters on the incident photon energy and the chemical composition has been examined. (Author)

  11. Determination of total mass attenuation coefficients, effective atomic numbers and electron densities for different shielding materials used in radiation protection

    International Nuclear Information System (INIS)

    Full text: In this paper, the interaction of X-rays with some shielding materials has been studied for materials containing different amounts of barite and aggregates. The total mass attenuation coefficient (μt) for three shielding materials has been calculated by using WinXCOM program in the energy range from RQR qualities (RQR-4, RQR-6, RQR-9, and RQR-10). They were: cream barite (density 2.99 g/cm3 collected in the State of Sao Paulo), purple barite (density 2.95 g/cm3 collected in the State of Bahia) and white barite (density 3.10 g/cm3 collected in the State of Paraiba). The chemical analysis was carried out by an X-ray fluorescence spectrometer model EDX-720, through dispersive energy. The six elements of the higher concentration found in the sample and analyzed by Spectrophotometry of Energy Dispersive X-ray for the samples were Ba(60.9% - white barite), Ca(17,92% - cream barite), Ce(3,60% - white barite), Fe(17,16% - purple barite), S(12,11% - white barite) and Si(29,61% - purple barite). Also, the effective atomic number (Zeff) and the effective electron density (Neff) were calculated using the values of the total mass attenuation coefficient. The dependence of these parameters on the incident photon energy and the chemical composition has been examined. (Author)

  12. Deriving effective atomic numbers from DECT based on a parameterization of the ratio of high and low linear attenuation coefficients

    Science.gov (United States)

    Landry, Guillaume; Seco, Joao; Gaudreault, Mathieu; Verhaegen, Frank

    2013-10-01

    Dual energy computed tomography (DECT) can provide simultaneous estimation of relative electron density ρe and effective atomic number Zeff. The ability to obtain these quantities (ρe, Zeff) has been shown to benefit selected radiotherapy applications where tissue characterization is required. The conventional analysis method (spectral method) relies on knowledge of the CT scanner photon spectra which may be difficult to obtain accurately. Furthermore an approximate empirical attenuation correction of the photon spectrum through the patient is necessary. We present an alternative approach based on a parameterization of the measured ratio of low and high kVp linear attenuation coefficients for deriving Zeff which does not require the estimation of the CT scanner spectra. In a first approach, the tissue substitute method (TSM), the Rutherford parameterization of the linear attenuation coefficients was employed to derive a relation between Zeff and the ratio of the linear attenuation coefficients measured at the low and high kVp of the CT scanner. A phantom containing 16 tissue mimicking inserts was scanned with a dual source DECT scanner at 80 and 140 kVp. The data from the 16 inserts phantom was used to obtain model parameters for the relation between Zeff and \\mu \\big|_{140kVp}^{80kVp}. The accuracy of the method was evaluated with a second phantom containing 4 tissue mimicking inserts. The TSM was compared to a more complex approach, the reference tissue method (RTM), which requires the derivation of stoichiometric fit parameters. These were derived from the 16 inserts phantom scans and used to calculate CT numbers at 80 and 140 kVp for a set of tabulated reference human tissues. Model parameters for the parameterization of \\mu \\big|_{140\\;kVp}^{80\\;kVp} were estimated for this reference tissue dataset and compared to the results of the TSM. Residuals on Zeff for the reference tissue dataset for both TSM and RTM were compared to those obtained from the

  13. Photoionization cross-sections for atoms and ions of aluminum, silicon, and argon.

    Science.gov (United States)

    Chapman, R. D.; Henry, R. J. W.

    1972-01-01

    Photoionization cross sections for all levels belonging to the configurations of atoms and ions of aluminum, silicon, and argon have been calculated using Hartree-Fock bound-electron wave functions and close-coupling approximation free-electron wave functions. The results are presented in the form of a computationally convenient interpolation formula and should find wide astrophysical application.

  14. Quantum-mechanical calculations of cross sections for electron collisions with atoms and molecules

    CERN Document Server

    Bartschat, Klaus; Zatsarinny, Oleg

    2016-01-01

    An overview of quantum-mechanical methods to generate cross-section data for electron collisions with atoms and molecules is presented. Particular emphasis is placed on the time-independent close-coupling approach, since it is particularly suitable for low-energy collisions and also allows for systematic improvements as well as uncertainty estimates. The basic ideas are illustrated with examples for electron collisions with argon atoms and methane. For many atomic systems, such as e-Ar collisions, highly reliable cross sections can now be computed with quantified uncertainties. On the other hand, while electron collision calculations with molecules do provide key input data for plasma models, the methods and computer codes presently used require further development to make these inputs robust.

  15. Effect of viscous cross coupling between two immiscible fluids on elastic wave propagation and attenuation in unsaturated porous media

    Science.gov (United States)

    Lo, Wei-Cheng; Yeh, Chao-Lung; Lee, Jhe-Wei

    2015-09-01

    A central issue in the theoretical treatment of a multiphase system is the proper mathematical description of momentum transfer across fluid-solid and fluid-fluid interfaces. Although recent studies have advanced our knowledge on modeling the coupling behavior between a porous framework and the fluids permeating it, the effect of viscous resistance caused by two-fluid flow on elastic wave behavior in unsaturated porous media still remains elusive. In the present study, the theoretical model developed for describing immiscible two-phase fluid flows in a deformable porous medium related to harmonic wave perturbation is generalized to account for viscous cross coupling due to relative velocity between two adjacent fluids. The corresponding dispersion relations whose coefficients feature all elasticity, inertial-drag, and viscous-drag parameters are then precisely formulated, in a physical context characterizing three compressional waves and one shear wave. To evaluate quantitatively this as-yet unknown effect, numerical calculations are conducted to solve the dispersion relations for Columbia fine sandy loam bearing an oil-water mixture as a function of water saturation and excitation frequency. Our results show that the phase speed and attenuation coefficient of the P3 wave which has the smallest speed is strongly sensitive to the presence of viscous cross coupling, as expected since this wave is attributed primarily to the out-of-phase motion of the two pore fluids. Viscous cross coupling also exerts an impact on the attenuation coefficient of the shear wave and the P1 wave whose speed is greatest, which exhibits two opposite trends at different ranges of low and high water contents. Relative differences in these wave attributes are principally independent of excitation frequency. A sensitivity analysis is carried out to assess how changes in viscous cross coupling affect these differences, revealing that some of them become more significant as viscous cross

  16. Nearside-farside analysis of differential cross sections: Diffraction and rainbow scattering in atom-atom and atom-molecule rotationally inelastic sudden collisions

    Science.gov (United States)

    McCabe, P.; Connor, J. N. L.

    1996-02-01

    Nearside-farside (NF) theory, as used to understand nuclear heavy-ion differential cross sections, is applied for the first time to the angular scattering of atom-atom and atom-diatom collisions. A NF decomposition of the partial wave series (PWS) for the scattering amplitude has the following advantages: (a) it is exact, (b) it uses PW scattering matrix elements (quantum or semiclassical) as calculated by standard computer programs, (c) it is easily incorporated into existing computer programs which calculate angular distributions, (d) semiclassical techniques, such as stationary phase or saddle point integration, are not invoked for the PWS, although the semiclassical picture is still evident. A disadvantage of a NF decomposition is that it is not unique. The Fuller and Hatchell NF decompositions are used to analyze the angular scattering of four collision systems whose PWS involve Legendre polynomials: (a) atom-atom He+Ne elastic diffraction scattering, (b) atom-atom H++Ar elastic rainbow scattering, (c) atom rigid-rotator Ne+D2(j=0) →Ne+D2(j) diffraction scattering under sudden conditions so that the infinite-order-sudden (IOS) approximation is valid, (d) atom rigid-rotator He+N2(j=0)→He+N2(j) rotational rainbow IOS scattering. The utility of these two NF decompositions is assessed by comparison with results from the semiclassical complex angular momentum (CAM) representation of the scattering amplitude. This is chosen because it allows an unambiguous separation of the scattering amplitude into nearside and farside subamplitudes under semiclassical conditions. The Fuller NF decomposition, unlike the Hatchell NF decomposition, provides a physically clear explanation of the angular scattering, which always agrees with the semiclassical CAM interpretation (except for scattering angles ≊180°). The Fuller NF decomposition is therefore recommended for applications to atomic and molecular collisions. The NF theory for the decomposition of Legendre polynomials

  17. Study of mass attenuation coefficients, effective atomic numbers and electron densities for some low Z compounds of dosimetry interest at 59.54 keV incident photon energy

    International Nuclear Information System (INIS)

    Highlights: ► Gamma-ray interaction parameters of some low Z compounds have been measured at 59.54 keV. ► Values of effective atomic numbers (Zeff) have been obtained using an alternative approach based upon interpolation method. ► Composite materials investigated behave as incoherent scatters. ► Selected compounds can be represented by single (valued) mean atomic number 〈Z〉 at incident photon energy. ► Data presented is expected to be useful in medical based applications of nuclear radiation. - Abstract: Total mass attenuation coefficient, total photon interaction cross-section, effective atomic numbers (Zeff) and electron densities (Ne) of Aniline (C6H5NH2), Cyclohexane (C6H12), Glycerine (C3H5(OH)3), Butyl alcohol N-(C4H9OH), DMSO – dimethyl sulfoxide (C2H6OS), Methyl ethyl-ketone (C4H8O), Xylene (C8H10), Acetophenone (C8H8O) and Triethyl amine (C6H15N) have been measured at 59.54 keV energy photon emitted by 100 mCi 241Am point source employing narrow beam transmission geometry. Obtained results have been compared with theoretically calculated values of XCOM (Berger and Hubbel, 1987) and FFAST (). Mixture rule was employed to calculated theoretical mass attenuation coefficient values for each sample. Good agreement has been observed between experimental and theoretical values within experimental uncertainties.

  18. Scaled plane-wave Born cross sections for atoms and molecules

    Science.gov (United States)

    Tanaka, H.; Brunger, M. J.; Campbell, L.; Kato, H.; Hoshino, M.; Rau, A. R. P.

    2016-04-01

    Integral cross sections for optically allowed electronic-state excitations of atoms and molecules by electron impact, by applying scaled plane-wave Born models, are reviewed. Over 40 years ago, Inokuti presented an influential review of charged-particle scattering, based on the theory pioneered by Bethe forty years earlier, which emphasized the importance of reliable cross-section data from low eV energies to high keV energies that are needed in many areas of radiation science with applications to astronomy, plasmas, and medicine. Yet, with a couple of possible exceptions, most computational methods in electron-atom scattering do not, in general, overlap each other's validity range in the region from threshold up to 300 eV and, in particular, in the intermediate region from 30 to 300 eV. This is even more so for electron-molecule scattering. In fact this entire energy range is of great importance and, to bridge the gap between the two regions of low and high energy, scaled plane-wave Born models were developed to provide reliable, comprehensive, and absolute integral cross sections, first for ionization by Kim and Rudd and then extended to optically allowed electronic-state excitation by Kim. These and other scaling models in a broad, general application to electron scattering from atoms and molecules, their theoretical basis, and their results for cross sections along with comparison to experimental measurements are reviewed. Where possible, these data are also compared to results from other computational approaches.

  19. Calculation of the ionization differential effective cross sections in fast ion-atom collisions

    CERN Document Server

    Kaminskij, A K

    2002-01-01

    The method of the calculations of the ionization effective cross sections d sigma/d OMEGA differential in the incident ion scattering angle is described in fast collisions of light ions and atoms. The calculated values of angular distributions of the ions Al, Mg (for the different values of charge and energy of ions) after their collisions with the Ne, Mg atoms being ionized are reported. The dependence of such angular distributions on the incident ion charge and energy and the initial state of ejected electron is investigated

  20. Application of sampling theory in modeling of continuum processes: photoionization cross-sections of atoms

    CERN Document Server

    Kozlov, Alex; Quiney, Harry

    2016-01-01

    We describe a method for the calculation of photoionization cross-sections using square-integrable amplitudes obtained from the diagonalization of finite-basis set representations of the electronic Hamiltonian. Three examples are considered: a model example in which the final state is a free particle, the hydrogen atom and neutral atomic sodium. The method exploits the Whittaker-Shannon-Kotel'nikov sampling theorem, which is widely used in digital signal sampling and reconstruction. The approach reproduces known data with very good accuracy and converges to the exact solution with increase of the basis set size.

  1. The ionized electron return phenomenon of Rydberg atom in crossed-fields

    Science.gov (United States)

    Dong, Chengwei; Wang, Peijie; Du, Mengli; Uzer, Turgay; Lan, Yueheng

    2016-05-01

    Rydberg atom is highly excited with one valence electron being in a high quantum state, which is very far away from the nucleus. The energy level is similar to that of the hydrogen atom. Introducing externally perpendicular electric and magnetic fields breaks the rotation symmetry and the traditional view is that the ionized electron crosses from the bound into the unbound region and will never return. However, we find that when the field is strong enough, the electron does not move off to infinity and there is a certain possibility of return. Three new periodic orbits are found by the variational method and the physical significance of the phenomenon is also discussed.

  2. Cross section database for collision processes of helium atom with charged particles. 1. Electron impact processes

    International Nuclear Information System (INIS)

    A comprehensive and critically assessed cross section database for the inelastic collision processes of ground state and excited helium atoms colliding with electrons, protons and multiply-charged ions has been prepared at the Data and Planning Center at NIFS. The present report describes the first part of the database containing the recommended data for electron impact excitation and ionization of neutral helium. An states (atomic terms) with n ≤ 4 are treated individually while the states with n > 4 are considered degenerate. For the processes involving transitions to and from n > 4 levels, suitable cross section scaling relations are presented. For a large number of electron impact transitions, both from the ground and excited states, new convergent close coupling (CCC) calculations were performed to achieve a high accuracy of the data. The evaluated/recommended cross section data are presented by analytic fit functions which preserve the correct asymptotic behavior of the cross sections. The cross sections are also displayed in a graphical form. (author)

  3. Low viscosity and high attenuation in MgSiO3 post-perovskite inferred from atomic-scale calculations

    Science.gov (United States)

    Goryaeva, Alexandra M.; Carrez, Philippe; Cordier, Patrick

    2016-10-01

    This work represents a numerical study of the thermal activation for dislocation glide of the [100](010) slip system in MgSiO3 post-perovskite (Mg-ppv) at 120 GPa. We propose an approach based on a one-dimensional line tension model in conjunction with atomic-scale calculations. In this model, the key parameters, namely, the line tension and the Peierls barrier, are obtained from density functional theory calculations. We find a Peierls stress σp = 2.1 GPa and a line tension Γ = 9.2 eV/Å, which lead to a kink-pair enthalpy (under zero stress) of 2.69 eV. These values confirm that this slip system bears a very low lattice friction because it vanishes for temperatures above approximately 500 K under mantle conditions. In the Earth’s mantle, high-pressure Mg-ppv silicate is thus expected to become as ductile as ferropericlase. These results confirm the hypothesis of a weak layer in the D″ layer where Mg-ppv is present. Easy glide along [100](010) suggests strong preferred orientations with (010) planes aligned. Highly mobile [100] dislocations are also likely to respond to stresses related to seismic waves, leading to energy dissipation and strong attenuation.

  4. Threshold ionization dynamics of the hydrogen atom in crossed electric and magnetic fields

    International Nuclear Information System (INIS)

    In crossed electric and magnetic fields the hydrogen atom undergoes a transition to chaotic scattering associated with a critical point in the Hamiltonian flow. The stability of the critical point is determined and leads to an accurate prediction of the transition to scattering that is independent of the magnetic-field strength. Nevertheless, observed variations in the apparent ionization threshold with magnetic-field strength are explained

  5. An empirical curve describing the ionization cross-sections in atomic collisions involving heavy ions

    International Nuclear Information System (INIS)

    In a recent paper, a fifth order polynomial curve was presented which fits very well to the existing experimental data on K-shell ionization cross-sections induced by protons. It is a universal curve, in the sense that it includes target atoms of any Z number at any projectile (proton) energy. In principle, it is possible to fit in the same curve the cross-sections obtained with any ion as a projectile, by means of a scaling law derived from the plane wave Born approximation (PWBA) and the binary encounter approximation (BEA) models. Experimental data with deuterons, alpha particles and 3He ions were fit into the same curve, with a good agreement. The agreement was poorer for experimental cross-sections obtained with heavier ions, like 12C, 14N and 40Ar. The discrepancies are attributable to several aspects of the ion-atom interaction, not considered in the derivation of such scaling law. The ECPSSR model has been more successful on predicting the cross-sections for heavy ions. Within the considerations in the ECPSSR and other models, arguments are given to explain the former discrepancies and suggestions are made to generalize the scaling law to fit the heavy ion data in a single curve

  6. Preliminary measurements of doubly differential cross sections for ejection of electrons from atomic hydrogen by 70 keV protons

    International Nuclear Information System (INIS)

    A Slevin atomic hydrogen source has been used to produce a thermal beam of H and H2 as a target for 70 keV protons. A method has been devised which yields atomic to molecular hydrogen cross section ratios. Since the electron ejection cross sections for H2 are known, the atomic hydrogen cross sections can be determined. The angular and energy ranges of the detected electrons, differential in angle and energy, are 20 degrees-160 degrees and 1.5-250 eV respectively

  7. Preliminary measurements of doubly differential cross sections for ejection of electrons from atomic hydrogen by 70 keV protons

    Energy Technology Data Exchange (ETDEWEB)

    Kerby, G.W.; Gealy, M.W.; Hsu, Y.Y.; Rudd, M.E. [Univ. of Nebraska, Lincoln, NB (United States)

    1993-05-01

    A Slevin atomic hydrogen source has been used to produce a thermal beam of H and H{sub 2} as a target for 70 keV protons. A method has been devised which yields atomic to molecular hydrogen cross section ratios. Since the electron ejection cross sections for H{sub 2} are known, the atomic hydrogen cross sections can be determined. The angular and energy ranges of the detected electrons, differential in angle and energy, are 20{degrees}-160{degrees} and 1.5-250 eV respectively.

  8. Studies on mass attenuation coefficient, effective atomic number and electron density of some amino acids in the energy range 0.122-1.330 MeV

    Science.gov (United States)

    Pawar, Pravina P.; Bichile, Govind K.

    2013-11-01

    The total mass attenuation coefficients of some amino acids, such as Glycine (C2H5NO2), DL-Alanine (C3H7NO2), Proline (C5H9NO2), L-Leucine (C6H13NO2 ), L-Arginine (C6H14N4O2) and L-Arginine Monohydrochloride (C6H15ClN4O2), were measured at 122, 356, 511, 662, 1170, 1275 and 1330 keV photon energies using a well-collimated narrow beam good geometry set-up. The gamma rays were detected using NaI (Tl) scintillation detection system with a resolution of 10.2% at 662 keV. The attenuation coefficient data were then used to obtain the effective atomic numbers (Zeff) and effective electron densities (Neff) of amino acids. It was observed that the effective atomic number (Zeff) and effective electron densities (Neff) tend to be almost constant as a function of gamma-ray energy. The results show that, the experimental values of mass attenuation coefficients, effective atomic numbers and effective electron densities are in good agreement with the theoretical values with less than 1% error.

  9. Bibliography of electron and photon cross sections with atoms and molecules. Published in the 20th century. Methane

    International Nuclear Information System (INIS)

    Bibliographies of original and review reports of experiments or theories of electron and photon cross sections and also electron swarm data are presented for atomic or molecular species with specified targets. These works covered 17 atoms and 51 molecules. The present bibliography is only for methane (CH4). About 1050 papers were compiled. A comprehensive author index is included. The bibliography covers the period 1924 through 2000 for CH4. Finally, author's comments for CH4 electron collision cross sections are given. (author)

  10. Semiclassical Calculation of Recurrence Spectra of Li Rydberg Atom in Crossed Electric and Magnetic Field

    Institute of Scientific and Technical Information of China (English)

    WANGDe-Hua; DINGShi-Liang

    2003-01-01

    Closed-orbit theory is a semiclassical technique for explaining the spectra of Rydberg atoms in external fields. Using the dosed-orblt theory and classical perturbation theory, we calculate the scaled recurrence spectra of Lithium atom in magnetic field plus a weak perpendicular electric field. The results show when the crossed electric field is added, the recurrence spectra are weakened greatly. As the scaled electric field f increases, the peaks of the recurrence spectra lose strength. Some recurrences are very sensitive and fall off rapidly as f increases, others persist till much higher f. As the electric field is stronger, some of the peaks revive. This phenomenon, caused by the interference among the electron waves that return to the nucleus, can be computed from the azimuthal dependence of the classical closed orbits.

  11. Semiclassical Calculation of Recurrence Spectra of Li Rydberg Atom in Crossed Electric and Magnetic Field

    Institute of Scientific and Technical Information of China (English)

    WANG De-Hua; DING Shi-Liang

    2003-01-01

    Closed-orbit theory is a semiclassical technique for explaining the spectra of Rydberg atoms in external fields. Using the closed-orbit theory and classical perturbation theory, we calculate the scaled recurrence spectra of Lithium atom in magnetic field plus a weak perpendicular electric field. The results show when the crossed electric field is added, the recurrence spectra are weakened greatly. As the scaled electric field f increases, the peaks of the recurrence spectra lose strength. Some recurrences are very sensitive and fall off rapidly as f increases; others persist till much higher f . As the electric field is stronger, some of the peaks revive. This phenomenon, caused by the interference among the electron waves that return to the nucleus, can be computed from the azimuthal dependence of the classical closed orbits.

  12. Absolute total cross sections for the scattering of 2--18-eV electrons by cesium atoms

    International Nuclear Information System (INIS)

    Absolute total cross sections for the scattering of electrons by cesium atoms between 2 and 18 eV have been measured using the atomic-recoil technique in the scattering-out mode. Our results are somewhat lower than those of Visconti, Slevin, and Rubin [Phys. Rev. A 3, 1310 (1971)] above 2 eV

  13. Absolute total cross sections for the scattering of 2--18-eV electrons by cesium atoms

    Energy Technology Data Exchange (ETDEWEB)

    Jaduszliwer, B.; Chan, Y.C. (Electronics Technology Center, The Aerospace Corporation, P. O. Box 92957, Los Angeles, California 90009 (United States))

    1992-01-01

    Absolute total cross sections for the scattering of electrons by cesium atoms between 2 and 18 eV have been measured using the atomic-recoil technique in the scattering-out mode. Our results are somewhat lower than those of Visconti, Slevin, and Rubin (Phys. Rev. A 3, 1310 (1971)) above 2 eV.

  14. Design and optimization of a harmonic probe with step cross section in multifrequency atomic force microscopy.

    Science.gov (United States)

    Cai, Jiandong; Wang, Michael Yu; Zhang, Li

    2015-12-01

    In multifrequency atomic force microscopy (AFM), probe's characteristic of assigning resonance frequencies to integer harmonics results in a remarkable improvement of detection sensitivity at specific harmonic components. The selection criterion of harmonic order is based on its amplitude's sensitivity on material properties, e.g., elasticity. Previous studies on designing harmonic probe are unable to provide a large design capability along with maintaining the structural integrity. Herein, we propose a harmonic probe with step cross section, in which it has variable width in top and bottom steps, while the middle step in cross section is kept constant. Higher order resonance frequencies are tailored to be integer times of fundamental resonance frequency. The probe design is implemented within a structural optimization framework. The optimally designed probe is micromachined using focused ion beam milling technique, and then measured with an AFM. The measurement results agree well with our resonance frequency assignment requirement. PMID:26724066

  15. Design and optimization of a harmonic probe with step cross section in multifrequency atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Cai, Jiandong; Zhang, Li [Department of Mechanical and Automation Engineering, The Chinese University of Hong Kong, Shatin, NT (Hong Kong); Wang, Michael Yu, E-mail: michael.wang@nus.edu.sg [Department of Mechanical and Automation Engineering, The Chinese University of Hong Kong, Shatin, NT (Hong Kong); Department of Mechanical Engineering, National University of Singapore, Singapore 117575 (Singapore)

    2015-12-15

    In multifrequency atomic force microscopy (AFM), probe’s characteristic of assigning resonance frequencies to integer harmonics results in a remarkable improvement of detection sensitivity at specific harmonic components. The selection criterion of harmonic order is based on its amplitude’s sensitivity on material properties, e.g., elasticity. Previous studies on designing harmonic probe are unable to provide a large design capability along with maintaining the structural integrity. Herein, we propose a harmonic probe with step cross section, in which it has variable width in top and bottom steps, while the middle step in cross section is kept constant. Higher order resonance frequencies are tailored to be integer times of fundamental resonance frequency. The probe design is implemented within a structural optimization framework. The optimally designed probe is micromachined using focused ion beam milling technique, and then measured with an AFM. The measurement results agree well with our resonance frequency assignment requirement.

  16. Atoms

    Institute of Scientific and Technical Information of China (English)

    刘洪毓

    2007-01-01

    Atoms(原子)are all around us.They are something like the bricks (砖块)of which everything is made. The size of an atom is very,very small.In just one grain of salt are held millions of atoms. Atoms are very important.The way one object acts depends on what

  17. Rovibrationally Inelastic Atom-Molecule Collision Cross Sections from a Hard Sphere Model

    Science.gov (United States)

    Lashner, Jacob; Stewart, Brian

    2016-05-01

    Hard-shell models have long been used to elucidate the principal features of molecular energy transfer and exchange reaction in the A + BC system. Nevertheless, no three-dimensional hard-shell calculation of inelastic collision cross sections has been reported. This work aims to fill that void. A particular motivation comes from our experimental results, which show the importance of equatorial impacts in the vibrational excitation process. Working with the simple hard-sphere model, we incorporated secondary impacts, defined as those in which A strikes C after striking B. Such collisions are important in systems such as Li2 - X, in which vibrational energy transfer occurs principally through side impacts. We discuss the complexity this adds to the model and present fully three-dimensional cross sections for rovibrational excitation of an initially stationary molecule in the homonuclear A + B2 system, examining the cross section as a function of the masses and radii of the atoms. We show how the features in the cross section evolve as these parameters are varied and calculate the contribution of secondary (near-equatorial) impacts to the dynamics. We compare with recent measurements in our laboratory and with the results of quasiclassical trajectories.

  18. Comparison of electron elastic-scattering cross sections calculated from two commonly used atomic potentials

    International Nuclear Information System (INIS)

    We have analyzed differential cross sections (DCSs) for the elastic scattering of electrons by neutral atoms that have been derived from two commonly used atomic potentials: the Thomas-Fermi-Dirac (TFD) potential and the Dirac-Hartree-Fock (DHF) potential. DCSs from the latter potential are believed to be more accurate. We compared DCSs for six atoms (H, Al, Ni, Ag, Au, and Cm) at four energies (100, 500, 1000, and 10 000 eV) from two databases issued by the National Institute of Standards and Technology in which DCSs had been obtained from the TFD and DHF potentials. While the DCSs from the two potentials had similar shapes and magnitudes, there can be pronounced deviations (up to 70%) for small scattering angles for Al, Ag, Au, and Cm. In addition, there were differences of up to 400% at scattering angles for which there were deep minima in the DCSs; at other angles, the differences were typically less than 20%. The DCS differences decreased with increasing electron energy. DCSs calculated from the two potentials were compared with measured DCSs for six atoms (He, Ne, Ar, Kr, Xe, and Hg) at energies between 50 eV and 3 keV. For Ar, the atom for which experimental data are available over the largest energy range there is good agreement between the measured DCSs and those calculated from the TFD and DHF potentials at 2 and 3 keV, but the experimental DCSs agree better with the DCSs from the DHF potential at lower energies. A similar trend is found for the other atoms. At energies less than about 1 keV, there are increasing differences between the measured DCSs and the DCSs calculated from the DHF potential. These differences were attributed to the neglect of absorption and polarizability effects in the calculations. We compare transport cross sections for H, Al, Ni, Ag, Au, and Cm obtained from the DCSs for each potential. For energies between 200 eV and 1 keV, the largest differences are about 20% (for H, Au, and Cm); at higher energies, the differences are

  19. Calculation Of Change-Changing Cross Sections Of IONS Or Atoms Colliding With Fast IONS Using The Classical Trajectory Method

    Energy Technology Data Exchange (ETDEWEB)

    Kaganovich, I. D., Shnidman, Ariel, Mebane, Harrison, Davidson, R.C.

    2008-10-10

    Evaluation of ion-atom charge-changing cross sections is needed for many accelerator applications. A classical trajectory Monte Carlo (CTMC) simulation has been used to calculate ionization and charge exchange cross sections. For benchmarking purposes, an extensive study has been performed for the simple case of hydrogen and helium targets in collisions with various ions. Despite the fact that the simulation only accounts for classical mechanics, the calculations are comparable to experimental results for projectile velocities in the region corresponding to the vicinity of the maximum cross section. Shortcomings of the CTMC method for multielectron target atoms are discussed.

  20. Calculation Of Change-Changing Cross Sections Of IONS Or Atoms Colliding With Fast IONS Using The Classical Trajectory Method

    International Nuclear Information System (INIS)

    Evaluation of ion-atom charge-changing cross sections is needed for many accelerator applications. A classical trajectory Monte Carlo (CTMC) simulation has been used to calculate ionization and charge exchange cross sections. For benchmarking purposes, an extensive study has been performed for the simple case of hydrogen and helium targets in collisions with various ions. Despite the fact that the simulation only accounts for classical mechanics, the calculations are comparable to experimental results for projectile velocities in the region corresponding to the vicinity of the maximum cross section. Shortcomings of the CTMC method for multielectron target atoms are discussed

  1. Atomic-scale mapping of electronic structures across heterointerfaces by cross-sectional scanning tunneling microscopy

    International Nuclear Information System (INIS)

    Interfacial science has received much attention recently based on the development of state-of-the-art analytical tools that can create and manipulate the charge, spin, orbital, and lattice degrees of freedom at interfaces. Motivated by the importance of nanoscale interfacial science that governs device operation, we present a technique to probe the electronic characteristics of heterointerfaces with atomic resolution. In this work, the interfacial characteristics of heteroepitaxial structures are investigated and the fundamental mechanisms that pertain in these systems are elucidated through cross-sectional scanning tunneling microscopy (XSTM). The XSTM technique is employed here to directly observe epitaxial interfacial structures and probe local electronic properties with atomic-level capability. Scanning tunneling microscopy and spectroscopy experiments with atomic precision provide insight into the origin and spatial distribution of electronic properties across heterointerfaces. The first part of this report provides a brief description of the cleavage technique and spectroscopy analysis in XSTM measurements. The second part addresses interfacial electronic structures of several model heterostructures in current condensed matter research using XSTM. Topics to be discussed include high-κ‘s/III–V’s semiconductors, polymer heterojunctions, and complex oxide heterostructures, which are all material systems whose investigation using this technique is expected to benefit the research community. Finally, practical aspects and perspectives of using XSTM in interface science are presented. (topical review)

  2. Determining the mass attenuation coefficient, effective atomic number, and electron density of raw wood and binderless particleboards of Rhizophora spp. by using Monte Carlo simulation

    Directory of Open Access Journals (Sweden)

    Mohammad W. Marashdeh

    2015-01-01

    Full Text Available Rhizophora spp. wood has the potential to serve as a solid water or tissue equivalent phantom for photon and electron beam dosimetry. In this study, the effective atomic number (Zeff and effective electron density (Neff of raw wood and binderless Rhizophora spp. particleboards in four different particle sizes were determined in the 10–60 keV energy region. The mass attenuation coefficients used in the calculations were obtained using the Monte Carlo N-Particle (MCNP5 simulation code. The MCNP5 calculations of the attenuation parameters for the Rhizophora spp. samples were plotted graphically against photon energy and discussed in terms of their relative differences compared with those of water and breast tissue. Moreover, the validity of the MCNP5 code was examined by comparing the calculated attenuation parameters with the theoretical values obtained by the XCOM program based on the mixture rule. The results indicated that the MCNP5 process can be followed to determine the attenuation of gamma rays with several photon energies in other materials.

  3. Determining the mass attenuation coefficient, effective atomic number, and electron density of raw wood and binderless particleboards of Rhizophora spp. by using Monte Carlo simulation

    Science.gov (United States)

    Marashdeh, Mohammad W.; Al-Hamarneh, Ibrahim F.; Abdel Munem, Eid M.; Tajuddin, A. A.; Ariffin, Alawiah; Al-Omari, Saleh

    Rhizophora spp. wood has the potential to serve as a solid water or tissue equivalent phantom for photon and electron beam dosimetry. In this study, the effective atomic number (Zeff) and effective electron density (Neff) of raw wood and binderless Rhizophora spp. particleboards in four different particle sizes were determined in the 10-60 keV energy region. The mass attenuation coefficients used in the calculations were obtained using the Monte Carlo N-Particle (MCNP5) simulation code. The MCNP5 calculations of the attenuation parameters for the Rhizophora spp. samples were plotted graphically against photon energy and discussed in terms of their relative differences compared with those of water and breast tissue. Moreover, the validity of the MCNP5 code was examined by comparing the calculated attenuation parameters with the theoretical values obtained by the XCOM program based on the mixture rule. The results indicated that the MCNP5 process can be followed to determine the attenuation of gamma rays with several photon energies in other materials.

  4. Fully differential cross sections for low to intermediate energy perpendicular plane ionization of xenon atoms

    International Nuclear Information System (INIS)

    Highlights: • We present triply differential cross section (TDCS) results for the perpendicular plane ionization of xenon atoms. • The TDCS has been calculated in the modified distorted wave Born approximation formalism. • The effects of target polarization and post collision interaction have also been included. • The polarization potential, higher order effects and PCI has been found to be useful in the description of TDCS. - Abstract: Triple differential cross section (TDCS) results are reported for the perpendicular plane ionization of Xe (5p) at incident electron energies 5 eV, 10 eV, 20 eV, and 40 eV above ionization potential. The modified distorted wave Born approximation formalism with first as well as the second order Born terms has been used to calculate the TDCS. Effects of target polarization and post collision interaction have also been included. We compare the (e, 2e) TDCS results of our calculation with the recent available experimental data and theoretical results and discuss the process contributing to structure seen in the differential cross section. It has been observed from the present study that the second order effect and target polarization make significant contribution in description of collision dynamics of xenon at the low and intermediate energy for the perpendicular emission of electrons

  5. Mass attenuation coefficient (μ/ρ), effective atomic number (Zeff) and measurement of x-ray energy spectra using based calcium phosphate biomaterials: a comparative study

    International Nuclear Information System (INIS)

    In dentistry, alveolar bone regeneration procedures using based calcium phosphate biomaterials have been shown effective. However,there are not reports in the literature of studies the interaction of low energy radiation in these biomaterials used as attenuator and not being then allowed a comparison between the theoretical values and experimental.The objective of this study was to determine the interaction of radiation parameters of four dental biomaterials - BioOss, Cerasorb M Dental, Straumann Boneceramic and Osteogen for diagnostic radiology qualities. As a material and methods, the composition of the biomaterials was determined by the analytical techniques. The samples with 0.181 cm to 0,297 cm thickness were experimentally used as attenuators for the measurement of the transmitted X-rays spectra in X-ray equipment with 50 to 90 kV range by spectrometric system comprising the Cd Te detector. After this procedure, the mass attenuation coefficient, the effective atomic number were determined and compared between all the specimens analyzed, using the program WinXCOM in the range of 10 to 200 keV. In all strains examined observed that the energy spectrum of x-rays transmitted through the BioOss has the mean energy slightly smaller than the others biomaterials for close thickness. The μ/ρ and Zeff of the biomaterials showed its dependence on photon energy and atomic number of the elements of the material analyzed. It is concluded according to the methodology employed in this study that the measurements of x-ray spectrum, μ/ρ and Zeff using biomaterials as attenuators confirmed that the thickness, density, composition of the samples, the incident photon energy are factors that determine the characteristics of radiation in a tissue or equivalent material. (Author)

  6. Determining the mass attenuation coefficient, effective atomic number, and electron density of raw wood and binderless particleboards of Rhizophora spp. by using Monte Carlo simulation

    OpenAIRE

    Mohammad W. Marashdeh; Ibrahim F. Al-Hamarneh; Eid M. Abdel Munem; A.A. Tajuddin; Alawiah Ariffin; Saleh Al-Omari

    2015-01-01

    Rhizophora spp. wood has the potential to serve as a solid water or tissue equivalent phantom for photon and electron beam dosimetry. In this study, the effective atomic number (Zeff) and effective electron density (Neff) of raw wood and binderless Rhizophora spp. particleboards in four different particle sizes were determined in the 10–60 keV energy region. The mass attenuation coefficients used in the calculations were obtained using the Monte Carlo N-Particle (MCNP5) simulation code. The M...

  7. Observation on Surface and Cross Section of Thin Film Solar Cells Using Atomic Force Microscope

    Institute of Scientific and Technical Information of China (English)

    FENG Liang-huan; WU Li-li; CAI Wei; CAI Ya-ping; ZHENG Jia-gui; ZHANG Jing-quan; LI Bing; LI Wei

    2005-01-01

    Atomic force microscope (AFM) is able to produce three-dimensional digital data in both forcemode and height-mode and its applications are not limited to map the surfaces of conducting materials. It can use the force-mode to image the repulsive and attractive force patterns. The cross sections of polycrystalline CdS/CdTe and amorphous silicon heterojunction solar cells are observed with AFM. In case of short circuit,the microstructures of different layers in the samples are clearly displayed. When the cells are open circuit, the topographical images are altered, the potential outline due to the space charge in junction region is observed.Obviously, AFM can be employed to investigate experimentally built-in potential in junction of semiconductor devices, such as solar cells.

  8. Lateral vibration attenuation of a beam with circular cross-section by a support with integrated piezoelectric transducers shunted to negative capacitances

    Science.gov (United States)

    Götz, Benedict; Schaeffner, Maximilian; Platz, Roland; Melz, Tobias

    2016-09-01

    Undesired vibration may occur in lightweight structures due to excitation and low damping. For the purpose of lateral vibration attenuation in beam structures, piezoelectric transducers shunted to negative capacitances can be an appropriate measure. In this paper, a new concept for lateral vibration attenuation by integrated piezoelectric stack transducers in the elastic support of a beam with circular cross-section is presented. In the piezoelastic support, bending of the beam in an arbitrary direction is transformed into a significant axial deformation of three stack transducers and, thus, the beam’s surface may remain free from transducers. For multimodal vibration attenuation, each piezoelectric transducer is shunted to a negative capacitance. It is shown by numerical simulation and experiment that the concept of an elastic beam support with integrated shunted piezoelectric stack transducers is capable of reducing the lateral vibration of the beam in an arbitrary direction.

  9. Measurement of Absolute Atomic Collision Cross Section with Helium Using 87Rb Atoms Confined in Magneto-Optic and Magnetic Traps

    Institute of Scientific and Technical Information of China (English)

    WANG Ji-Cheng; ZHOU Ke-Ya; WANG Yue-Yuan; LIAO Qing-Hong; LIU Shu-Tian

    2011-01-01

    We present the measurements and calculations of the absolute total collision cross sections for a room-temperature gas of helium using 87 Rb atoms confined in either a magneto-optic or a magnetic quadrupole trap. The loss rates from the magneto-optic trap and the pure magnetic trap are compared and show significant differences. The collision cross sections as a function of trap depth for helium gas are obtained. These findings are significant for extracting the information about the different cross sections when the trap depth is changed.%@@ We present the measurements and calculations of the absolute total collision cross sections for a room-temperature gas of helium using 87Rb atoms confined in either a magneto-optic or a magnetic quadrupole trap.The loss rates from the magneto-optic trap and the pure magnetic trap are compared and show significant differences.The collision cross sections as a function of trap depth for helium gas are obtained.These findings are significant for extracting the information about the different cross sections when the trap depth is changed.

  10. Photoionization of Xe inside C60: Atom-fullerene hybridization, giant cross-section enhancement, and correlation confinement resonances

    International Nuclear Information System (INIS)

    A theoretical study of the subshell photoionization of the Xe atom endohedrally confined in C60 is presented. Powerful hybridization of the Xe 5s state with the bottom edge of C60 π band is found that induces strong structures in the 5s ionization, causing the cross section to differ significantly from earlier results that omit this hybridization. The hybridization also affects the angular distribution asymmetry parameter of Xe 5p ionization near the Cooper minimum. The 5p cross section, on the other hand, is greatly enhanced by borrowing considerable oscillator strength from the C60 giant plasmon resonance via the atom-fullerene dynamical interchannel coupling. Beyond the C60 plasmon energy range the atomic subshell cross sections display confinement-induced oscillations in which, over the large 4d shape resonance region, the dominant 4d oscillations induce their ''clones'' in all degenerate weaker channels known as correlation confinement resonances.

  11. Status of Charge Exchange Cross Section Measurements for Highly Charged Ions on Atomic Hydrogen

    Science.gov (United States)

    Draganic, I. N.; Havener, C. C.; Schultz, D. R.; Seely, D. G.; Schultz, P. C.

    2011-05-01

    Total cross sections of charge exchange (CX) for C5+, N6+, and O7+ ions on ground state atomic hydrogen are measured in an extended collision energy range of 1 - 20,000 eV/u. Absolute CX measurements are performed using an improved merged-beams technique with intense highly charged ion beams extracted from a 14.5 GHz ECR ion source mounted on a high voltage platform. In order to improve the problematic H+ signal collection for these exoergic CX collisions at low relative energies, a new double focusing electrostatic analyzer was installed. Experimental CX data are in good agreement with all previous H-oven relative measurements at higher collision energies. We compare our results with the most recent molecular orbital close-coupling (MOCC) and atomic orbital close-coupling (AOCC) theoretical calculations. Work supported by the NASA Solar & Heliospheric Physics Program NNH07ZDA001N, the Office of Fusion Energy Sciences and the Division of Chemical Sciences, Geosciences, and Biosciences, and the Office of Basic Energy Sciences of the U.S. DoE.

  12. Cross sections for medium energy He ions scattered from Hf and Au atoms

    Energy Technology Data Exchange (ETDEWEB)

    Nishimura, Tomoaki, E-mail: t-nishi@hosei.ac.jp [Research Center of Ion Beam Technology and College of Engineering, Hosei University, Koganei, Tokyo 184-8584 (Japan); Mitsuhara, Kei; Visikovskiy, Anton; Kido, Yoshiaki [Department of Physics, Ritsumeikan University, Kusatsu, Shiga-ken 525-8577 (Japan)

    2012-06-01

    The elastic scattering cross sections for medium energy He ions incident on Ni, Hf and Au atoms were measured precisely using a toroidal electrostatic analyzer. We prepared the targets of Ni({approx}1 nm)/HfO{sub 2}(1.5 nm)/Si(0 0 1) and Ni({approx}1 nm)/Au({approx}0.5 nm)/Si(1 1 1) and performed in situ ion scattering measurement under ultrahigh vacuum condition. The absolute amounts of Ni, Hf and Au were determined by Rutherford backscattering using 1.5 MeV He ions at a scattering angle of 150 Degree-Sign . The scattering cross sections for Hf and Au were normalized by those for Ni to avoid the ambiguities of the number of incident particles, solid angle subtended by a detector, detection efficiency and the He{sup +} fractions for the emerging He ions from the surfaces. The results obtained are compared with the simple Lee-Hart formula and the calculated values using the Moliere and ZBL potentials and the potentials derived from the Hartree-Fock-Slater wave functions.

  13. Bibliography of electron and photon cross sections with atoms and molecules published in the 20th century. Argon

    Energy Technology Data Exchange (ETDEWEB)

    Hayashi, Makoto [Gaseous Electronics Institute, Nagoya, Aichi (Japan)

    2003-01-01

    A bibliography of original and review reports of experiments or theories of electron and photon cross sections and also electron swarm data are presented for atomic or molecular species with specified targets. These works covered 17 atoms and 51 molecules. The present bibliography is only for argon (Ar). About 1,960 papers were compiled. A comprehensive author index is included. The bibliography covers the period 1921 through 2000 for Ar. Finally, author's recommended Ar electron collision cross section set is given in numerical tables. (author)

  14. Bibliography of electron and photon cross sections with atoms and molecules published in the 20th century. Carbon dioxide

    Energy Technology Data Exchange (ETDEWEB)

    Hayashi, Makoto [Gaseous Electronics Institute, Nagoya, Aichi (Japan)

    2003-04-01

    A bibliography of original and review reports of experiments or theories of electron and photon cross sections and also electron swarm data are presented for atomic or molecular species with specified targets. These works covered 17 atoms and 51 molecules. The present bibliography is only for carbon dioxide (CO{sub 2}). About 1,240 papers were compiled. A comprehensive author index is included. The bibliography covers the period 1901 through 2000 for CO{sub 2}. Finally, author's comments for CO{sub 2} electron collision cross sections are given. (author)

  15. Bibliography of electron and photon cross sections with atoms and molecules published in the 20th century. Water vapour

    International Nuclear Information System (INIS)

    Bibliographies of original and review reports of experiments or theories of electron and photon cross sections and also electron swarm data are presented for atomic or molecular species with specified targets. These works covered 17 atoms and 51 molecules. The present bibliography is only for water vapour (H2O, D2O and HDO). About 1200 papers were compiled. A comprehensive author index is included. The bibliography covers the period 1915 through 2000 for H2O. Finally, author's comments for electron collision cross sections and photodissociation processes of H2O are given. (author)

  16. Bibliography of electron and photon cross sections with atoms and molecules published in the 20th century. Nitrogen molecule

    International Nuclear Information System (INIS)

    A bibliography of original and review reports of experiments or theories of electron and photon cross sections and also electron swarm data are presented for atomic or molecular species with specified targets. These works covered 17 atoms and 51 molecules. The present bibliography is only for nitrogen molecule (N2). About 2240 papers were compiled. A comprehensive author index is include. The bibliography covers the period 1906 through 2000 for N2. Finally, author's comments for N2 electron collision cross section are given. (author)

  17. Bibliography of electron and photon cross sections with atoms and molecules published in the 20th century. Ammonia and phosphine

    International Nuclear Information System (INIS)

    Bibliographies of original and review reports of experiments or theories of electron and photon cross sections and also electron swarm data are presented for atomic or molecular species with specified targets. These works covered 17 atoms and 51 molecules. The present bibliography is only for ammonia (NH3) and phosphine (PH3). About 820 (NH3) and 190 (PH3) papers were compiled respectively. Comprehensive author indexes for each molecule are included. The bibliography covers the period 1922 through 2000 for NH3 and 1928 through 2000 for PH3. Finally, author's comments for NH3 electron collision cross sections are given. (author)

  18. Bibliography of electron and photon cross sections with atoms and molecules published in the 20th century. Sulphur hexafluoride

    International Nuclear Information System (INIS)

    A bibliography of original and review reports of experiments or theories of electron and photon cross sections and also electron swarm data are presented for atomic or molecular species with specified targets. These works covered 17 atoms and 51 molecules. The present bibliography is only for sulphur hexafluoride (SF6). About 920 papers were compiled. A comprehensive author index is included. The bibliography covers the period 1934 through 2000 for SF6. Finally, author's comments for SF6 electron collision cross section are given. (author)

  19. Bibliography of electron and photon cross sections with atoms and molecules published in the 20th century. Hydrogen halide molecules

    International Nuclear Information System (INIS)

    Bibliographies of original and review reports of experiments or theories of electron and photon cross sections and also electron swarm data are presented for atomic or molecular species with specified targets. These works covered 17 atoms and 51 molecules. The present bibliography is only for hydrogen halide molecules (HF, HCL, HBr, HI). About 330 (HF), 420 (HCl) 220 (HBr) and 150 (HI) papers were compiled respectively. Comprehensive author indexes for each molecule are included. The bibliography covers the period 1903 through 2000 for HF-HI. Finally, author's comments for HBr electron collision cross sections are given. (author)

  20. Bibliography of electron and photon cross sections with atoms and molecules published in the 20th century. Sulphur hexafluoride

    Energy Technology Data Exchange (ETDEWEB)

    Hayashi, Makoto [Gaseous Electronics Institute, Nagoya, Aichi (Japan)

    2003-05-01

    A bibliography of original and review reports of experiments or theories of electron and photon cross sections and also electron swarm data are presented for atomic or molecular species with specified targets. These works covered 17 atoms and 51 molecules. The present bibliography is only for sulphur hexafluoride (SF{sub 6}). About 920 papers were compiled. A comprehensive author index is included. The bibliography covers the period 1934 through 2000 for SF{sub 6}. Finally, author's comments for SF{sub 6} electron collision cross section are given. (author)

  1. Bibliography of electron and photon cross sections with atoms and molecules published in the 20th century. Hydrogen molecules

    International Nuclear Information System (INIS)

    Bibliographies of original and review reports of experiments or theories of electron and photon cross sections and also electron swarm data are presented for atomic or molecular species with specified targets. These works covered 17 atoms and 51 molecules. The present bibliography is only for hydrogen molecules (H2, HD, HT, D2, DT, T2). About 2200 papers were compiled. A comprehensive author index is included. The bibliography covers the period 1901 through 2000 for H2. Finally, author's comments for H2 electron collision cross sections are given. (author)

  2. Bibliography of electron and photon cross sections with atoms and molecules published in the 20th century. Xenon

    International Nuclear Information System (INIS)

    A bibliographies of original and review reports of experiments or theories of electron and photon cross sections and also electron swarm data are presented for atomic or molecular species with specified targets. These works covered 17 atoms and 51 molecules. The present bibliography is only for xenon (Xe). About 1180 papers were compiled. A comprehensive author index is included. The bibliography covers the period 1921 through 2000 for Xe. Finally, author's recommended Xe electron collision cross section set is given by number tables. (author)

  3. Bibliography of electron and photon cross sections with atoms and molecules published in the 20th century. Argon

    International Nuclear Information System (INIS)

    A bibliography of original and review reports of experiments or theories of electron and photon cross sections and also electron swarm data are presented for atomic or molecular species with specified targets. These works covered 17 atoms and 51 molecules. The present bibliography is only for argon (Ar). About 1,960 papers were compiled. A comprehensive author index is included. The bibliography covers the period 1921 through 2000 for Ar. Finally, author's recommended Ar electron collision cross section set is given in numerical tables. (author)

  4. Preliminary measurements of doubly differential cross sections for ejection of electrons from atomic and molecular hydrogen by 70-keV helium ions

    International Nuclear Information System (INIS)

    A mixture of atomic and molecular hydrogen, generated by a Slevin hydrogen atom source, was used as the target for 70-keV He+ ions. Procedures were devised to extract the ratio of the cross sections for hydrogen atoms to hydrogen molecules. The cross sections for hydrogen molecules were then measured separately and the cross sections for hydrogen atoms obtained. The cross sections for ejection of electrons, differential in the angle and energy of ejection, were measured over the 15 degrees-160 degrees range of angles and at electron energies from 1.5 to 130 eV

  5. Preliminary measurements of doubly differential cross sections for ejection of electrons from atomic and molecular hydrogen by 70-keV helium ions

    Energy Technology Data Exchange (ETDEWEB)

    Hsu, Y.Y.; Gealy, M.W.; Kerby, G.W.; Rudd, M.E. [Univ. of Nebraska, Lincoln, NB (United States)

    1993-05-01

    A mixture of atomic and molecular hydrogen, generated by a Slevin hydrogen atom source, was used as the target for 70-keV He{sup +} ions. Procedures were devised to extract the ratio of the cross sections for hydrogen atoms to hydrogen molecules. The cross sections for hydrogen molecules were then measured separately and the cross sections for hydrogen atoms obtained. The cross sections for ejection of electrons, differential in the angle and energy of ejection, were measured over the 15{degrees}-160{degrees} range of angles and at electron energies from 1.5 to 130 eV.

  6. Stripping and multiple electron loss cross sections for heavy ions incident on various atomic and molecular gases

    International Nuclear Information System (INIS)

    Differential cross sections for charge change resulting from the scattering of 20-MeV 127I5+ and 20-MeV 35Cl4+ ions from thin gaseous targets of Xe, Ar, and N2 were measured and published. Total electron loss cross sections were measured for 20-MeV Fe4+ ions transmitted through a variety of atomic and molecular gaseous targets. All low-charge-state peaks were well resolved. The measured total cross sections per target atom for loss of one to eleven electrons in a single collision for 20-MeV Fe4+ ions transmitted through gases of N2, SF6, Ar, Kr, and Xe are shown as a function of the final charge state q. There is an overall rather steep decrease for increasing q, interrupted by a weaker decrease between q = 6 and q = 8. For the highest q values, the cross sections follow a nearly exponential decrease with q. The cross sections are smaller and the decrease at high q values is more pronounced, the lighter the target atoms. The cross sections are smaller for molecular targets than for the noble gases. 2 figures

  7. Mass energy-absorption coefficients and average atomic energy-absorption cross-sections for amino acids in the energy range 0.122-1.330 MeV

    Science.gov (United States)

    More, Chaitali V.; Lokhande, Rajkumar M.; Pawar, Pravina. P.

    2016-05-01

    Mass attenuation coefficients of amino acids such as n-acetyl-l-tryptophan, n-acetyl-l-tyrosine and d-tryptophan were measured in the energy range 0.122-1.330 MeV. NaI (Tl) scintillation detection system was used to detect gamma rays with a resolution of 8.2% at 0.662 MeV. The measured attenuation coefficient values were then used to determine the mass energy-absorption coefficients (σa,en) and average atomic energy-absorption cross sections (μen/ρ) of the amino acids. Theoretical values were calculated based on XCOM data. Theoretical and experimental values are found to be in good agreement.

  8. Velocity dependence of the Penning and associative ionization cross sections of Ar atoms by He(23S) and He(21S) atoms

    International Nuclear Information System (INIS)

    The velocity dependence of both the Penning and associative ionization cross sections sigma/sub PI/ and sigma/sub AI/ of Ar atoms by He(2 3S) and He(2 1S) metastable atoms, and of their sum sigma/subT/ = sigma/sub PI/ + sigma/sub AI/, is measured in the velocity range 1200--4500 m/sec (30--400 meV) in a crossed-beam experiment by a time-of-flight technique. Characteristic cross-section ratios sigma/sub AI//sigma/subT/ and sigma/subT/(singlet)/sigma/subT/(triplet) are reported along with the relative magnitude of the cross sections sigma/sub AI/, sigma/sub PI/, sigma/subT/. The measurements clearly show a difference in the reaction mechanisms involving He(2 3S) and He(2 1S). This difference appears not only in the ratio sigma/sub AI//sigma/subT/, whose magnitude reaches 19% and 38% for He(2 3S) and He(2 1S), respectively, at the velocity v = 1200 m/sec (30 meV), and in the ratio sigma/subT/(singlet)/sigma/subT/ (triplet), which increases from 0.5 to 3.8 for velocity decreasing from 4500 m/sec to 1200 m/sec, but also in the different shapes of the sigma/sub AI/ and sigma/sub PI/ cross sections for He(2 3S) and He(2 1S). The experimental results for He(2 3S) are also compared to theoretical calculations made in the classical impact parameter formulation. The model gives a total ionization cross section sigma/subT/ and partial ionization cross sections sigma/sub AI/ and sigma/sub PI/ in good agreement with the data. Information on both the coupling width and the He + Ar+ interaction potential well are obtained

  9. Partial and total electronic stopping cross sections of atoms for a singly charged helium ion, Part 2

    International Nuclear Information System (INIS)

    Partial and total electronic stopping cross sections of atoms with Z (55 ≤ Z ≤ 92) for a He+ ion are tabulated as the second part of NIFS-DATA-11 (1991) on the basis of the wave-packet theory. (author)

  10. The study of interaction potentials and differential cross sections for collisions between He atoms and hydrogen halide molecules

    Institute of Scientific and Technical Information of China (English)

    孙桂华; 杨向东; 朱俊; 王彩霞

    2002-01-01

    In this paper, we present the uniform interaction potentials for helium atoms and halogen hydride molecules (HF,HC1 and HBr). The differential cross sections are calculated using the above interaction potentials for the He-HF,HCl and HBr systems, respectively, and the results of the calculations are found to be in agreement with the existingtheoretical results and experimental data.

  11. Investigating the effect of electric field on ionization cross sections in antiproton–hydrogen/deuterium atoms collisions

    International Nuclear Information System (INIS)

    The Classical Trajectory Monte Carlo (CTMC) method has been used to investigate the effects of aligned electric field on the ionization cross sections in antiproton and hydrogen atoms collisions. The cross sections for the ionization of hydrogen/deuterium collision with antiproton in the energy range 10–500 keV/amu have been calculated and compared with the available experiment and theoretical results. The ionization cross sections are in reasonable agreement with the recently reported experimental and theoretical results. Isotope effect in the ionization cross section is reported to be negligible. The effects of the external electric field are seen to be quite prominent. Differential cross sections for ionization at the scattering angle up to 0.1° are also reported in this paper.

  12. Use of Activated Carbon in Packaging to Attenuate Formaldehyde-Induced and Formic Acid-Induced Degradation and Reduce Gelatin Cross-Linking in Solid Dosage Forms.

    Science.gov (United States)

    Colgan, Stephen T; Zelesky, Todd C; Chen, Raymond; Likar, Michael D; MacDonald, Bruce C; Hawkins, Joel M; Carroll, Sophia C; Johnson, Gail M; Space, J Sean; Jensen, James F; DeMatteo, Vincent A

    2016-07-01

    Formaldehyde and formic acid are reactive impurities found in commonly used excipients and can be responsible for limiting drug product shelf-life. Described here is the use of activated carbon in drug product packaging to attenuate formaldehyde-induced and formic acid-induced drug degradation in tablets and cross-linking in hard gelatin capsules. Several pharmaceutical products with known or potential vulnerabilities to formaldehyde-induced or formic acid-induced degradation or gelatin cross-linking were subjected to accelerated stability challenges in the presence and absence of activated carbon. The effects of time and storage conditions were determined. For all of the products studied, activated carbon attenuated drug degradation or gelatin cross-linking. This novel use of activated carbon in pharmaceutical packaging may be useful for enhancing the chemical stability of drug products or the dissolution stability of gelatin-containing dosage forms and may allow for the 1) extension of a drug product's shelf-life when the limiting attribute is a degradation product induced by a reactive impurity, 2) marketing of a drug product in hotter and more humid climatic zones than currently supported without the use of activated carbon, and 3) enhanced dissolution stability of products that are vulnerable to gelatin cross-linking.

  13. Use of Activated Carbon in Packaging to Attenuate Formaldehyde-Induced and Formic Acid-Induced Degradation and Reduce Gelatin Cross-Linking in Solid Dosage Forms.

    Science.gov (United States)

    Colgan, Stephen T; Zelesky, Todd C; Chen, Raymond; Likar, Michael D; MacDonald, Bruce C; Hawkins, Joel M; Carroll, Sophia C; Johnson, Gail M; Space, J Sean; Jensen, James F; DeMatteo, Vincent A

    2016-07-01

    Formaldehyde and formic acid are reactive impurities found in commonly used excipients and can be responsible for limiting drug product shelf-life. Described here is the use of activated carbon in drug product packaging to attenuate formaldehyde-induced and formic acid-induced drug degradation in tablets and cross-linking in hard gelatin capsules. Several pharmaceutical products with known or potential vulnerabilities to formaldehyde-induced or formic acid-induced degradation or gelatin cross-linking were subjected to accelerated stability challenges in the presence and absence of activated carbon. The effects of time and storage conditions were determined. For all of the products studied, activated carbon attenuated drug degradation or gelatin cross-linking. This novel use of activated carbon in pharmaceutical packaging may be useful for enhancing the chemical stability of drug products or the dissolution stability of gelatin-containing dosage forms and may allow for the 1) extension of a drug product's shelf-life when the limiting attribute is a degradation product induced by a reactive impurity, 2) marketing of a drug product in hotter and more humid climatic zones than currently supported without the use of activated carbon, and 3) enhanced dissolution stability of products that are vulnerable to gelatin cross-linking. PMID:27262203

  14. Studies on mass attenuation coefficient, effective atomic number and electron density of some amino acids in the energy range 0.122–1.330 MeV

    International Nuclear Information System (INIS)

    The total mass attenuation coefficients of some amino acids, such as Glycine (C2H5NO2), DL-Alanine (C3H7NO2), Proline (C5H9NO2), L-Leucine (C6H13NO2 ), L-Arginine (C6H14N4O2) and L-Arginine Monohydrochloride (C6H15ClN4O2), were measured at 122, 356, 511, 662, 1170, 1275 and 1330 keV photon energies using a well-collimated narrow beam good geometry set-up. The gamma rays were detected using NaI (Tl) scintillation detection system with a resolution of 10.2% at 662 keV. The attenuation coefficient data were then used to obtain the effective atomic numbers (Zeff) and effective electron densities (Neff) of amino acids. It was observed that the effective atomic number (Zeff) and effective electron densities (Neff) tend to be almost constant as a function of gamma-ray energy. The results show that, the experimental values of mass attenuation coefficients, effective atomic numbers and effective electron densities are in good agreement with the theoretical values with less than 1% error. - Highlights: • Compute the Mass Attenuation Coefficient, effective atomic number and electron density of some amino acids. • Gamma ray attenuation studies on biologically important molecules have been carried out using narrow beam good geometry set up. • The values of Mass Attenuation Coefficient, effective atomic number and electron density of some amino acids are in agreement with the XCOM programme. • The measured mass attenuation coefficient for some amino acids are useful in medical field. • The data is useful in radiation dosimetry and other fields

  15. Theoretical investigation of the hypothesized crossing between the Penning and atomic autoionizing states of He+K

    Energy Technology Data Exchange (ETDEWEB)

    Padial, N.T.; Martin, R.L.; Cohen, J.S.; Lane, N.F.

    1989-03-01

    The Penning ionization interaction He(12s/sup 3/S)+K(3p/sup 6/4s) and the atomic autoionizing state interaction He(1s/sup 2/)+K(3p/sup 5/4s/sup 2/) have been determined in a configuration-interaction calculation utilizing a basis set designed to treat these two states equitably. In contrast to an earlier calculation, the corresponding two potential curves are found not to cross. This finding puts in question the original speculation that the observed large He/sup */+K ionization cross section is due partially to collisional excitation of atomic states that subsequently autoionize. However, the calculated Penning ionization cross section is still in agreement with the experimental measurement.

  16. Atomic structure of the non-polar GaN(anti 2110) surface by cross-sectional scanning tunneling microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Krueger, David; Kuhr, Simon; Schmidt, Thomas; Hommel, Detlef; Falta, Jens [Institute of Solid State Physics, University of Bremen (Germany)

    2009-05-15

    The (anti 2110) plane of gallium nitride, exposed by cleaving a GaN single crystal under ultra-high vacuum conditions, has been atomically resolved for the first time, using cross-sectional scanning tunneling microscopy. The spatial period length supports a (1 x 1) unit mesh size, i.e., the absence of a reconstruction. The contrast observed in the experimental data is well explained by the atomic arrangement expected for a truncated-bulk structure. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  17. Approximate analytical formulas for total cross sections and for mass attenuation coefficients of narrow gamma beams for 3 to 100 MeV

    International Nuclear Information System (INIS)

    Tabulated data by Storm and Israel for total cross sections and mass attenuation coefficients for narrow gamma beams of 3 to 100 MeV and elements with Z equal to 26 to 94 were approximated by an analytical formula analogous to the ultrarelativistic case of Compton scattering and pair creation. The reproduction accuracy of the tabulated data is better than 1 to 2% in a region of 3 to 60 MeV and better than 3 to 4% from 60 to 100 MeV. In the analytical formula three constants were needed for each Z, the tables of which are given. (author)

  18. Enhanced Cross-Phase Modulation Based on a Double Electromagnetically Induced Transparency in a Four-Level Tripod Atomic System

    International Nuclear Information System (INIS)

    We report experimental observations on the simultaneous electromagnetically induced transparency (EIT) effects for probe and trigger fields (double EIT) as well as the enhanced cross-phase modulation (XPM) between the two fields in a four-level tripod EIT system of the D1 line of 87Rb atoms. The XPM coefficients (larger than 2x10-5 cm2/W) and the accompanying transmissions (higher than 60%) are measured at a slight detuning of the probe field from the exact EIT-resonance condition. The system and enhanced cross-Kerr nonlinearities presented here can be applied to quantum information processes

  19. Single and double electron capture cross sections in keV-collisions between fully stripped ions with helium atom

    OpenAIRE

    Ibaaz, Aicha; Dubois, Alain

    2015-01-01

    International audience We present cross section calculations for single-, double-capture, and double capture to auto-ionizing states occurring in the course of collisions between fully stripped ions Aq+ (q≤10) and helium atom at impact energies ranging from 0.25 to 625 keV/u. These calculations were performed by applying a semiclassical nonperturbative close coupling approach, based on the expansion of the scattering wave function into asymptotic bielectronic states with proper translation...

  20. Photoionization cross section of atomic cadmium using the multi-configuration Tamm-Dancoff approximation

    Science.gov (United States)

    Pradhan, G. B.; Jose, J.; Radojević, V.; Manson, S. T.; Deshmukh, P. C.

    2009-11-01

    The Multiconfiguration Tamm-Dancoff approximation (MCTD) is used to calculate the photoionization cross section of cadmium. Results are compared with available experimental data and also with earlier computations of the cross-section. We find that while earlier computations overestimated the photoionization cross section compared to experiment, the present MCTD computation underestimates the same.

  1. Photoionization cross section of atomic cadmium using the multi-configuration Tamm-Dancoff approximation

    International Nuclear Information System (INIS)

    The Multiconfiguration Tamm-Dancoff approximation (MCTD) is used to calculate the photoionization cross section of cadmium. Results are compared with available experimental data and also with earlier computations of the cross-section. We find that while earlier computations overestimated the photoionization cross section compared to experiment, the present MCTD computation underestimates the same.

  2. T- and B-Cell-Mediated Protection Induced by Novel, Live Attenuated Pertussis Vaccine in Mice. Cross Protection against Parapertussis

    OpenAIRE

    Pascal Feunou Feunou; Julie Bertout; Camille Locht

    2010-01-01

    BACKGROUND: Despite the extensive use of efficacious vaccines, pertussis still ranks among the major causes of childhood mortality worldwide. Two types of pertussis vaccines are currently available, whole-cell, and the more recent acellular vaccines. Because of reduced reactogenicity and comparable efficacy acellular vaccines progressively replace whole-cell vaccines. However, both types require repeated administrations for optimal efficacy. We have recently developed a live attenuated vaccin...

  3. ALiCCE: Atomic Lines Calibration using the Cross-Entropy Algorithm

    CERN Document Server

    Martins, Lucimara; Caproni, Anderson; Vitoriano, Roberto

    2014-01-01

    Atomic line opacities play a crucial role in stellar astrophysics. They strongly modify the radiative transfer in stars, therefore impacting their physical structure. Ultimately, most of our knowledge of stellar population systems (stars, clusters, galaxies, etc.) relies on the accuracy with which we understand and reproduce the stellar spectra. With such a wide impact on Astronomy, it would be ideal to have access to a complete, accurate and precise list of atomic transitions. This, unfortunately, is not the case. Few atomic transitions had their parameters actually measured in the laboratory, and for most of the lines the parameters were calculated with low precision atomic energy levels. Only a small fraction of the lines were calibrated empirically. For the purpose of computing a stellar spectral grid with a complete coverage of spectral types and luminosity classes, this situation is rather limiting. We have implemented an innovative method to perform a robust calibration of atomic line lists used by spe...

  4. Improved adiabatic calculation of muonic-hydrogen-atom cross sections. II. Hyperfine transitions and elastic scattering in symmetric collisions

    International Nuclear Information System (INIS)

    The improved adiabatic representation is used in calculations of elastic and hyperfine-transition cross sections for symmetric collisions of pμ, dμ, and tμ with bare p, d, and t nuclei and with H, D, and T atoms, respectively. The cross sections for dμ+d and tμ+t are in excellent agreement with other recent determinations, while those for pμ+p are about 30% larger at low energies. The electronic screening is calculated nonperturbatively and found to be about 30% smaller in magnitude than the previously calculated value at large internuclear distances, and to deviate considerably from the asymptotic form in the molecular region. The resulting screened elastic cross sections are up to 60% smaller than those obtained using the old screening potential. The reactance matrices, needed for calculations of molecular-target effects, are given in tables

  5. Displacement cross sections and PKA spectra: tables and applications. [Neutron damage energy cross sections to 20 MeV, primary knockon atom spectra to 15 MeV

    Energy Technology Data Exchange (ETDEWEB)

    Doran, D G; Graves, N J

    1976-12-01

    Damage energy cross sections to 20 MeV are given for aluminum, vanadium, chromium, iron, nickel, copper, zirconium, niobium, molybdenum, tantalum, tungsten, lead, and 18Cr10Ni stainless steel. They are based on ENDF/B-IV nuclear data and the Lindhard energy partition model. Primary knockon atom (PKA) spectra are given for aluminum, iron, niobium, tantalum, and lead for neutron energies up to 15 MeV at approximately one-quarter lethargy intervals. The contributions of various reactions to both the displacement cross sections (taken to be proportional to the damage energy cross sections) and the PKA spectra are presented graphically. Spectral-averaged values of the displacement cross sections are given for several spectra, including approximate maps for the Experimental Breeder Reactor-II (EBR-II) and several positions in the Fast Test Reactor (FTR). Flux values are included to permit estimation of displacement rates. Graphs show integral PKA spectra for the five metals listed above for neutron spectra corresponding to locations in the EBR-II, the High Flux Isotope Reactor (HFIR), and a conceptual fusion reactor (UWMAK-I). Detailed calculations are given only for cases not previously documented. Uncertainty estimates are included.

  6. Development of a Supersonic Atomic Oxygen Nozzle Beam Source for Crossed Beam Scattering Experiments

    Science.gov (United States)

    Sibener, S. J.; Buss, R. J.; Lee, Y. T.

    1978-05-01

    A high pressure, supersonic, radio frequency discharge nozzle beam source was developed for the production of intense beams of ground state oxygen atoms. An efficient impedance matching scheme was devised for coupling the radio frequency power to the plasma as a function of both gas pressure and composition. Techniques for localizing the discharge directly behind the orifice of a water-cooled quartz nozzle were also developed. The above combine to yield an atomic oxygen beam source which produces high molecular dissociation in oxygen seeded rare gas mixtures at total pressures up to 200 torr: 80 to 90% dissociation for oxygen/argon mixtures and 60 to 70% for oxygen/helium mixtures. Atomic oxygen intensities are found to be greater than 10{sup 17} atom sr{sup -1} sec{sup -1}. A brief discussion of the reaction dynamics of 0 + IC1 ..-->.. I0 + C1 is also presented.

  7. Atomic Rayleigh scattering cross-sections and the associated anomalous dispersion in the X-ray regions

    International Nuclear Information System (INIS)

    Elastic scattering cross-sections for Pd, Ag, Cd, In, Sn, Sb, Pt, Au and Pb are measured at an angle of 90 circle in the X-ray region 5.41≤E≤8.04 keV. These energies fall between the high-energy side of the L- and M-shell absorption edges of the atoms considered. The present atomic region is significant for solid X-rays to assess the contribution of resonance and solid-state environmental effects. Also it is the anomalous scattering region for many of the atoms of the periodic table. Experimental results are compared with theoretical calculations based on form factor formalisms including the anomalous corrections and available recent S-matrix values. Based on the experimental evidence, the present results indicate the influence of solid-state environmental effects, the importance of anomalous corrections nearer to absorption edges, the correctness of revised high-energy limit values, the superiority of S-matrix predictions over form factor values on measured elastic scattering cross-sections in the X-ray regime and also show the resonance behavior around K,L and M absorption edges. (orig.)

  8. Determination of the 1s-2s two-photon excitation cross-section in atomic hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Bickel, G.A.; McRae, G.A

    2000-07-01

    Hydrogen atoms are ablated from zirconium alloys into the gas phase by a pulsed Nd:YAG laser and photo-ionized with three photons at 243 nm via the two-photon 1s {sup 2}S{sub 1/2}-2s {sup 2}S{sub 1/2} resonant transition. A determination of the effective 1s-2s two-photon excitation cross-section is necessary to quantify the hydrogen atom density in the ablation plume. A measurement of the ion signal vs photo-ionization beam energy is fitted to an expression derived from the rate equations. The temporal and spatial properties of the photo-ionization laser beam, transit of the H atoms through the beam, and detector geometry are taken into account. The effective two-photon cross-section for this experimental configuration, derived with the rate equation formalism, is 3.3 {+-} 0.8 X 10{sup -28} cm{sup 4} W{sup -1}. This compares well with the ab initio prediction of 5 {+-} 1 X 10{sup -28} cm{sup 4} W{sup -1} under these experimental conditions. (author)

  9. Total cross sections for electrons scattering from simple molecules containing the larger atom sulfur at 30-5000eV

    Institute of Scientific and Technical Information of China (English)

    Shi De-Heng; Liu Yu-Fang; Sun Jin-Feng; Yang Xiang-Dong; Zhu Zun-Lue

    2005-01-01

    A complex optical model potential modified by the concept of bonded atom, which takes into consideration the overlapping effect of electron clouds, is employed to calculate the total cross sections for electrons scattering from simple molecules (SO2, H2S, OCS, CS2 and SO3) containing the larger atom, sulfur, at 30-5000eV by using the additivity rule model at Hartree-Fock level. The quantitative molecular total cross section results are compared with those obtained in experiments and other calculations wherever available, and good agreement is obtained. It is shown that the additivity rule model together with the complex optical model potential modified by the concept of bonded atom can give the results closer to the experiments than the one unmodified by it. So, the introduction of bonded-atom concept in complex optical model potential betters the accuracy of the total cross section calculations of electrons from the molecules containing the larger atom, sulfur.

  10. Plasma out of thermodynamical equilibrium: influence of the plasma environment on atomic structure and collisional cross sections

    International Nuclear Information System (INIS)

    In hot dense plasmas, the free-electron and ion spatial distribution may strongly affect the atomic structure. To account for such effects we have implemented a potential correction based on the uniform electron gas model and on a Thomas-Fermi Approach in the Flexible Atomic Code (FAC). This code has been applied to obtain energies, wave-functions and radiative rates modified by the plasma environment. In hydrogen-like ions, these numerical results have been successfully compared to an analytical calculation based on first-order perturbation theory. In the case of multi-electron ions, we observe level crossings in agreement with another recent model calculation. Various methods for the collision cross-section calculations are reviewed. The influence of plasma environment on these cross-sections is analyzed in detail. Some analytical expressions are proposed for hydrogen-like ions in the limit where Born or Lotz approximations apply and are compared to the numerical results from the FAC code. Finally, from this work, we study the influence of the plasma environment on our collisional-radiative model so-called Foch. Because of this environment, the mean charge state of the ions increases. The line shift is observed on the bound-bound emission spectra. A good agreement is found between our work and experimental data on a Titanium plasma. (author)

  11. Live, attenuated influenza A H5N1 candidate vaccines provide broad cross-protection in mice and ferrets.

    Directory of Open Access Journals (Sweden)

    Amorsolo L Suguitan

    2006-09-01

    Full Text Available BACKGROUND: Recent outbreaks of highly pathogenic influenza A H5N1 viruses in humans and avian species that began in Asia and have spread to other continents underscore an urgent need to develop vaccines that would protect the human population in the event of a pandemic. METHODS AND FINDINGS: Live, attenuated candidate vaccines possessing genes encoding a modified H5 hemagglutinin (HA and a wild-type (wt N1 neuraminidase from influenza A H5N1 viruses isolated in Hong Kong and Vietnam in 1997, 2003, and 2004, and remaining gene segments derived from the cold-adapted (ca influenza A vaccine donor strain, influenza A/Ann Arbor/6/60 ca (H2N2, were generated by reverse genetics. The H5N1 ca vaccine viruses required trypsin for efficient growth in vitro, as predicted by the modification engineered in the gene encoding the HA, and possessed the temperature-sensitive and attenuation phenotypes specified by the internal protein genes of the ca vaccine donor strain. More importantly, the candidate vaccines were immunogenic in mice. Four weeks after receiving a single dose of 10(6 50% tissue culture infectious doses of intranasally administered vaccines, mice were fully protected from lethality following challenge with homologous and antigenically distinct heterologous wt H5N1 viruses from different genetic sublineages (clades 1, 2, and 3 that were isolated in Asia between 1997 and 2005. Four weeks after receiving two doses of the vaccines, mice and ferrets were fully protected against pulmonary replication of homologous and heterologous wt H5N1 viruses. CONCLUSIONS: The promising findings in these preclinical studies of safety, immunogenicity, and efficacy of the H5N1 ca vaccines against antigenically diverse H5N1 vaccines provide support for their careful evaluation in Phase 1 clinical trials in humans.

  12. Precision measurements of cross sections of inelastic processes realized in collisions of alkali metal ions with atoms of rare gases

    CERN Document Server

    Lomsadze, R A; Mosulishvili, N O; Kezerashvili, R Ya

    2015-01-01

    This work presents a multifaceted experimental study of collisions of Na$^{+}$ and K$^{+}$ ions in the energy range 0.5 -- 10 keV with He and Ar atoms. Absolute cross sections for charge-exchange, ionization, stripping and excitation were measured using a refined version of the transfer electric field method, angle- and energy-dependent collection of product ions, energy loss, and optical spectroscopy. The experimental data and the schematic correlation diagrams have been employed to analyze and determine the mechanisms for these processes.

  13. Computational study of elastic and electronically inelastic scattering of Br by ground state I atoms: Role of potential curve crossing

    International Nuclear Information System (INIS)

    Two-state, close-coupled quantal computations of the elastic and inelastic scattering of ground-state I atoms by ground-state Br and spin--orbit excited Br* atoms have been carried out over a range of total energies E from 0.01 to 0.94 eV. The possibility of translational--electronic energy transfer arises from the 3Pi0+ potential curve crossing at E=0.25 eV, responsible for the well-known IBr predissociation. The Y, B, and V12(R) diabatic potentials have been obtained by judicious extension (and manipulation) of the spectroscopically derived B and B' adiabats. At energies below the threshold for Br* formation (E/sub th/=0.457 eV) collisions of I+Br are necessarily elastic, exhibiting both shape and compound-state resonances. These produce interesting interference patterns in the differential cross sections, but no significant inverse-predissociation resonance (which might have been anticipated for E> or =0.25 eV). The main features of the elastic scattering can be fairly well approximated considering only the lower adiabat, even at post threshold energies where the inelastic process becomes important. An oscillatory pattern found in the total elastic cross section has been identified with a barrier effect associated with the maximum in this B adiabat. Total inelastic cross sections are well reproduced by the closed-form Landau--Zener--Stueckelberg (LZS) approximation. The Boltzmann-averaged LZS rate constant for the collisional deactivation I+Br*→I+Br is calculated to be 1.8x10-11 cm3 sec-1 at 300 K (with only a slight temperature dependence over the range 300--1000 K). This large rate is due to the inverse predissociation mechanism, common

  14. Calculation of charge-changing cross-sections of ions or atoms colliding with fast ions using the classical trajectory method

    International Nuclear Information System (INIS)

    Evaluation of ion-atom charge-changing cross-sections is needed for many accelerator applications. A Classical Trajectory Monte Carlo (CTMC) simulation has been used to calculate ionization and charge-exchange cross-sections. For benchmarking purposes, an extensive study has been performed for the simple case of hydrogen and helium targets in collisions with various ions. Despite the fact that the simulation only accounts for classical mechanics, the calculations are comparable to experimental results for projectile velocities in the region corresponding to the vicinity of the maximum cross-section. The shortcomings of the CTMC method for multielectron target atoms are discussed.

  15. Simulations of the atomic structure, energetics, and cross slip of screw dislocations in copper

    DEFF Research Database (Denmark)

    Rasmussen, Torben; Jacobsen, Karsten Wedel; Leffers, Torben;

    1997-01-01

    Using nanoscale atomistic simulations it has been possible to address the problem of cross slip of a dissociated screw dislocation in an fee metal (Cu) by a method not suffering from the limitations imposed by elasticity theory. The focus has been on different dislocation configurations relevant ...

  16. Crossed beam reactive scattering of oxygen atoms and surface scattering studies of gaseous condensation

    Energy Technology Data Exchange (ETDEWEB)

    Sibener, S.J.

    1979-09-01

    A high pressure, radio frequency discharge nozzle beam source was developed for the production of very intense (greater than or equal to 10/sup 18/ atoms sr/sup -1/ sec/sup -1/) supersonic beams of oxygen atoms. This source is capable of producing seeded beams of ground state O(/sup 3/P/sub J/) atoms when dilute oxygen-argon mixtures are used, with molecular dissociation levels exceeding 80% being realized for operation at pressures up to 350 torr. When dilute oxygen-helium mixtures are employed both ground state O(/sup 3/P/sub J/) and excited state O(/sup 1/D/sub 2/) atoms are present in the terminal beam, with molecular dissociation levels typically exceeding 60% being achieved for operation at pressures up to 200 torr. Atomic oxygen mean translational energies from 0.14 to 0.50 eV were obtained using the seeded beams technique, with Mach numbers as high as 10 (FWHM ..delta.. v/v approx. = 20%) being realized. The IC1, CF/sub 3/I, C/sub 6/H/sub 6/, and C/sub 6/D/sub 6/ reactions are discussed in detail. The IC1 and CF/sub 3/I studies have enabled us to determine an improved value for the bond energy of the IO radical: D/sub o/(IO) = 55 +- 2 kcal/mole. The IO product angular and velocity distributions have been used to generate center-of-mass flux contour maps, which indicate that these two reactions proceed via relatively long-lived collision complexes whose mean lifetimes are slightly shorter than their respective rotational periods. The O(/sup 3/P/sub J/) + C/sub 6/H/sub 6/ and C/sub 6/D/sub 6/ reactions were studied in order to elucidate the reaction mechanism, and, in particular, to identify the primary reaction products produced in these reactions. Finally, a series of beam-surface scattering experiments are described which examined the internal and translational energy dependence of molecular condensation probabilities for collisions involving either CC1/sub 4/ or SF/sub 6/ and their respective condensed phases. 117 references. (JFP)

  17. Crossed beam reactive scattering of oxygen atoms and surface scattering studies of gaseous condensation

    International Nuclear Information System (INIS)

    A high pressure, radio frequency discharge nozzle beam source was developed for the production of very intense (greater than or equal to 1018 atoms sr-1 sec-1) supersonic beams of oxygen atoms. This source is capable of producing seeded beams of ground state O(3P/sub J/) atoms when dilute oxygen-argon mixtures are used, with molecular dissociation levels exceeding 80% being realized for operation at pressures up to 350 torr. When dilute oxygen-helium mixtures are employed both ground state O(3P/sub J/) and excited state O(1D2) atoms are present in the terminal beam, with molecular dissociation levels typically exceeding 60% being achieved for operation at pressures up to 200 torr. Atomic oxygen mean translational energies from 0.14 to 0.50 eV were obtained using the seeded beams technique, with Mach numbers as high as 10 (FWHM Δ v/v approx. = 20%) being realized. The IC1, CF3I, C6H6, and C6D6 reactions are discussed in detail. The IC1 and CF3I studies have enabled us to determine an improved value for the bond energy of the IO radical: D/sub o/(IO) = 55 +- 2 kcal/mole. The IO product angular and velocity distributions have been used to generate center-of-mass flux contour maps, which indicate that these two reactions proceed via relatively long-lived collision complexes whose mean lifetimes are slightly shorter than their respective rotational periods. The O(3P/sub J/) + C6H6 and C6D6 reactions were studied in order to elucidate the reaction mechanism, and, in particular, to identify the primary reaction products produced in these reactions. Finally, a series of beam-surface scattering experiments are described which examined the internal and translational energy dependence of molecular condensation probabilities for collisions involving either CC14 or SF6 and their respective condensed phases. 117 references

  18. Absolute vacuum ultraviolet photoabsorption cross section studies of atomic and molecular species: Techniques and observational data

    Science.gov (United States)

    Judge, D. L.; Wu, C. Y. R.

    1990-01-01

    Absorption of a high energy photon (greater than 6 eV) by an isolated molecule results in the formation of highly excited quasi-discrete or continuum states which evolve through a wide range of direct and indirect photochemical processes. These are: photoionization and autoionization, photodissociation and predissociation, and fluorescence. The ultimate goal is to understand the dynamics of the excitation and decay processes and to quantitatively measure the absolute partial cross sections for all processes which occur in photoabsorption. Typical experimental techniques and the status of observational results of particular interest to solar system observations are presented.

  19. Cross-Sectional Investigations on Epitaxial Silicon Solar Cells by Kelvin and Conducting Probe Atomic Force Microscopy: Effect of Illumination.

    Science.gov (United States)

    Narchi, Paul; Alvarez, Jose; Chrétien, Pascal; Picardi, Gennaro; Cariou, Romain; Foldyna, Martin; Prod'homme, Patricia; Kleider, Jean-Paul; I Cabarrocas, Pere Roca

    2016-12-01

    Both surface photovoltage and photocurrent enable to assess the effect of visible light illumination on the electrical behavior of a solar cell. We report on photovoltage and photocurrent measurements with nanometer scale resolution performed on the cross section of an epitaxial crystalline silicon solar cell, using respectively Kelvin probe force microscopy and conducting probe atomic force microscopy. Even though two different setups are used, the scans were performed on locations within 100-μm distance in order to compare data from the same area and provide a consistent interpretation. In both measurements, modifications under illumination are observed in accordance with the theory of PIN junctions. Moreover, an unintentional doping during the deposition of the epitaxial silicon intrinsic layer in the solar cell is suggested from the comparison between photovoltage and photocurrent measurements. PMID:26831693

  20. On the Coulomb corrections to the total cross section of the interaction of the $\\pi^{+}\\pi^{-}$ atom with ordinary atoms at high energy

    CERN Document Server

    Ivanov, D Yu

    1999-01-01

    The size of $\\pi^+\\pi^-$ atom in the low lying states is considerably smaller than the radius of atomic screening. Due to that we can neglect this screening calculating the contribution of multi-photon exchanges. We obtain the analytic formula for Coulomb corrections which works with a very good accuracy for the ground state of $\\pi^+\\pi^-$ atom.

  1. Absolute Doubly Differential Cross Sections for Ejection of Electrons in - and Five-Body Collisions of 20 TO 114-KEV Protons on Atomic and Molecular Hydrogen.

    Science.gov (United States)

    Kerby, George W., III

    A crossed-beam experiment was performed to detect ejected electrons from ground-state atomic and molecular hydrogen after collisions with 20- to 114-keV protons. Because a pure atomic hydrogen target is not readily attainable, a method has been devised which yields atomic to molecular hydrogen doubly differential cross section (DDCS) ratios. Since the molecular hydrogen DDCS's were independently measured, the atomic cross sections could be directly calculated. Absolute cross sections differential in electron energy and angle were measured for electron energies ranging from 1.5 to 400 eV and scattering angles from 15^circ to 165^circ with respect to the fast beam. Electrons and ions were energy analyzed by an electrostatic hemispherical analyzer, which has an energy resolution of 5% and is rotatable in the scattering plane about the collision center. Atomic hydrogen is produced by a radio-frequency discharge of the type devised by J. Slevin. Hydrogen gas effuses from a 1 mm diameter nozzle in a nearly cos theta distribution. The projectile beam intersects the thermal gas targets 4 mm below the tip of the nozzle. Dissociation fractions of 74% and atomic hydrogen densities of 7 times 10 ^{11} cm^ {-3} were typical. The fraction of dissociated hydrogen was measured by detecting the reduced 9-eV ion signal from the molecular target when the RF is on. This characteristic ion signal originates from the coulomb breakup of the molecule and dissociative channels of excited H _sp{2}{+}. An auxiliary experiment was performed to determine the target densities with the aid of a low-resolution magnetic mass spectrometer after the slow recoil ions were extracted from the collision volume by a weak electric field. Comparisons of the atomic cross sections are made with theories such as the classical-trajectory Monte Carlo (CTMC) method, the plane-wave Born approximation (PWBA) and the continuum-distorted-wave eikonal-initial-state (CDW-EIS) approximation.

  2. Atomic force microscopy imaging reveals the formation of ASIC/ENaC cross-clade ion channels

    Energy Technology Data Exchange (ETDEWEB)

    Jeggle, Pia; Smith, Ewan St. J.; Stewart, Andrew P. [Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD (United Kingdom); Haerteis, Silke; Korbmacher, Christoph [Institut für Zelluläre und Molekulare Physiologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Waldstrasse 6, 91054 Erlangen (Germany); Edwardson, J. Michael, E-mail: jme1000@cam.ac.uk [Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD (United Kingdom)

    2015-08-14

    ASIC and ENaC are co-expressed in various cell types, and there is evidence for a close association between them. Here, we used atomic force microscopy (AFM) to determine whether ASIC1a and ENaC subunits are able to form cross-clade hybrid ion channels. ASIC1a and ENaC could be co-isolated from detergent extracts of tsA 201 cells co-expressing the two subunits. Isolated proteins were incubated with antibodies against ENaC and Fab fragments against ASIC1a. AFM imaging revealed proteins that were decorated by both an antibody and a Fab fragment with an angle of ∼120° between them, indicating the formation of ASIC1a/ENaC heterotrimers. - Highlights: • There is evidence for a close association between ASIC and ENaC. • We used AFM to test whether ASIC1a and ENaC subunits form cross-clade ion channels. • Isolated proteins were incubated with subunit-specific antibodies and Fab fragments. • Some proteins were doubly decorated at ∼120° by an antibody and a Fab fragment. • Our results indicate the formation of ASIC1a/ENaC heterotrimers.

  3. Differential cross sections of muonic atoms scattering. Asymmetric collisions: pμ + (d,t), dμ + (p,t) and tμ + (p,d)

    International Nuclear Information System (INIS)

    We present the differential cross sections dσ(E,Ω)/dΩ for elastic and inelastic (isotopic exchange) scattering of muonic hydrogen, deuterium and tritium on hydrogen isotopes nuclei for the case of difference in masses of the projectile μ-atom and the target nucleus. Available partial phase shifts have been used in the calculations and the results are presented in tables and figures for different CMS collision energies. The cross sections are important for description of the slowing down and diffusion of μ-atoms in matter and particularly for description of kinetics of muon catalyzed nuclear fusion. 12 refs., 11 figs., 12 tabs

  4. Pyridoxine hydrochloride attenuate and decrease the depressant effects of meclizine on human psychomotor performance: Randomized clinical trial, cross-over study.

    Directory of Open Access Journals (Sweden)

    Hayder M. Al-kuraishy

    2011-12-01

    Full Text Available The present study was conducted to assess and compare the cognitive and psychomotor effects of Pyridoxine HCl 50mg and meclizine 25mg or both in 30healthy adult volunteers in a single blind, randomized cross over study. Following single dose of each drug, the volunteers were subjected to perform a series of tests of cognitive and psychomotor performance at 2 hours post dose. The Leeds Battery Psychomotor Instrument test consisted of both subjective and objective tests which were further grouped into Instrumental tests which included Simple reaction time (SRT, Choice Reaction Time Task (CRT and Critical Flicker Fusion frequency threshold (CFFT. Meclizine at dose of 25mg was significantly different from placebo (p0.05. The dual and combined effects of pyridoxine HCl 50mg plus meclizine 25mg attenuate and remove the depressant effects that mediated via meclizine. These results allow the conclusion that pyridoxine at its recommended therapeutic dose of 50mg is needed to be mixed with meclizine or others antihistamine to eliminate psychomotor and cognitive impairment as usual adverse effect of meclizine

  5. Mass attenuation coefficient (μ/ρ), effective atomic number (Z{sub eff}) and measurement of x-ray energy spectra using based calcium phosphate biomaterials: a comparative study

    Energy Technology Data Exchange (ETDEWEB)

    Fernandes Z, M. A.; Da Silva, T. A.; Nogueira, M. S. [Centro de Desenvolvimento da Tecnologia Nuclear / CNEN, Pte. Antonio Carlos 6627, Belo Horizonte 31270-901, Minas Gerais (Brazil); Goncalves Z, E., E-mail: madelon@cdtn.br [Pontifice Catholic University of Minas Gerais, Av. Dom Jose Gaspar 500, Belo Horizonte 30535-901, Minas Gerais (Brazil)

    2015-10-15

    In dentistry, alveolar bone regeneration procedures using based calcium phosphate biomaterials have been shown effective. However,there are not reports in the literature of studies the interaction of low energy radiation in these biomaterials used as attenuator and not being then allowed a comparison between the theoretical values and experimental.The objective of this study was to determine the interaction of radiation parameters of four dental biomaterials - BioOss, Cerasorb M Dental, Straumann Boneceramic and Osteogen for diagnostic radiology qualities. As a material and methods, the composition of the biomaterials was determined by the analytical techniques. The samples with 0.181 cm to 0,297 cm thickness were experimentally used as attenuators for the measurement of the transmitted X-rays spectra in X-ray equipment with 50 to 90 kV range by spectrometric system comprising the Cd Te detector. After this procedure, the mass attenuation coefficient, the effective atomic number were determined and compared between all the specimens analyzed, using the program WinXCOM in the range of 10 to 200 keV. In all strains examined observed that the energy spectrum of x-rays transmitted through the BioOss has the mean energy slightly smaller than the others biomaterials for close thickness. The μ/ρ and Z{sub eff} of the biomaterials showed its dependence on photon energy and atomic number of the elements of the material analyzed. It is concluded according to the methodology employed in this study that the measurements of x-ray spectrum, μ/ρ and Z{sub eff} using biomaterials as attenuators confirmed that the thickness, density, composition of the samples, the incident photon energy are factors that determine the characteristics of radiation in a tissue or equivalent material. (Author)

  6. Doubly Differential Cross Sections for Ejection of Electrons from Atomic and Molecular Hydrogen by 30-120 KEV HELIUM(+) Ion Impact

    Science.gov (United States)

    Hsu, Ying-Yuan

    Electrons ejected from atomic and molecular hydrogen in He^+ ion impacts were observed with projectile energies ranging from 30 to 120 keV. The ejection angles observed were 15^circ, 30^circ, 50^circ, 70^ circ, 90^circ, 110^circ, 130^circ and 160^circ with electron energies ranging from 1.5 to 130 eV. Ejected electrons were energy analyzed by an electrostatic analyzer with 5% resolution and were detected by a channel electron multiplier. A Slevin-type RF hydrogen atom source was used to generate a mixed target of atomic and molecular hydrogen. The dissociation fraction of the target was determined from the measurement of 9-eV H^+ ions coming from the break-up of the 2psigma_ {u} state of the H_2 ^+ molecular ion. Methods were devised to extract the electron ejection cross section ratio between hydrogen atoms and molecules. Cross sections for the hydrogen atom were then calculated from additional measurements on pure H_2.. The results are compared to plane-wave-Born approximation (PWBA) calculations, classical-trajectory-Monte-Carlo (CTMC) calculations, and continuum-distorted-wave-eikonal-initial -state (CDW-EIS) calculations for proton impact. Electron loss cross sections are calculated with PWBA and used as a correction to the above calculations.

  7. The influence of isotope substitution of neon atom on the integral cross sections of rotational excitation in Ne-Na2 collisions

    Institute of Scientific and Technical Information of China (English)

    Zang Hua-Ping; Li Wen-Feng; Linghu Rong-Feng; Cheng Xin-Lu; Yang Xiang-Dong

    2011-01-01

    This paper applies the multiple ellipsoid model to the 16Ne (20Ne, 28Ne, 34Ne)-Na2 collision systems, and calculates integral cross sections for rotational excitation at the incident energy of 190 meV. It can be seen that the accuracy of the integral cross sections can be improved by increasing the number of equipotential ellipsoid surfaces. Moreover, by analysing the differences of these integral cross sections, it obtains the change rules of the integral cross sections with the increase of rotational angular quantum number J', and with the change of the mass of isotope substitution neon atom. Finally, the contribution of different regions of the potential to inelastic cross sections for 20Ne-Na2 collision system is investigated at relative incident energy of 190 meV.

  8. Attenuation of microwaves by poly-disperse small spheroid particles

    Science.gov (United States)

    Zhang, Peichang; Wang, Zhenhui

    1998-08-01

    Expressions for calculating the attenuation cross sections of poly-disperse, small spheroids, whose rotatory axes are in specific status, have been derived from a universal formula for calculating the attenuation cross section of a particle of arbitrary shape. Attenuation cross sections of liquid, ice, and spongy spheroidal droplets in different size and eccentricity at different wave lengths have been computed and analyzed.

  9. Successful cross-protective efficacy induced by heat-adapted live attenuated nephropathogenic infectious bronchitis virus derived from a natural recombinant strain.

    Science.gov (United States)

    Lim, Tae-Hyun; Youn, Ha-Na; Yuk, Seong-Su; Kwon, Jung-Hoon; Hong, Woo-Tack; Gwon, Gyeong-Bin; Lee, Jung-Ah; Lee, Joong-Bok; Lee, Sang-Won; Song, Chang-Seon

    2015-12-16

    A natural recombinant nephropathogenic K40/09 strain of infectious bronchitis virus (IBV) was heat-adapted for possible future use as live attenuated vaccine. The K40/09 strain was selected during successive serial passages in specific-pathogen free (SPF) embryonated eggs at sub-optimal higher temperature (56°C). Unlike the parental strain, the attenuated strain, designated K40/09 HP50, was found to be safe in 1-day-old SPF chicks, which showed neither mortality nor signs of morbidity, and rarely induced ciliostasis or histological changes in the trachea and kidney after intraocular and fine-spray administration. K40/09 HP50 provided almost complete protection against two distinct subgroups of a nephropathogenic strain (KM91-like and QX-like subgroup) and elicited the production of high titers of neutralizing antibody (neutralization index of 3.6). We conclude that the K40/09 HP50 vaccine virus is rapidly attenuated by heat adaptation and exhibits the desired level of attenuation, immunogenicity, and protective efficacy required for a live attenuated vaccine. These results indicate that the K40/09 vaccine could be helpful for the reduction of economic losses caused by recently emergent nephropathogenic IBV infection in many countries.

  10. Effective atomic numbers of some H-, C-, N- and O-based composite materials derived from differential incoherent scattering cross-sections

    Indian Academy of Sciences (India)

    S Prasanna Kumar; V Manjunathaguru; T K Umesh

    2010-04-01

    In this work, we have made an effort to determine whether the effective atomic numbers of H-, C-, N- and O-based composite materials would indeed remain a constant over the energy grid of 280–1200 keV wherein incoherent scattering dominates their interaction with photons. For this purpose, the differential incoherent scattering cross-sections of Be, C, Mg, Al, Ca and Ti were measured for three scattering angles 60°, 80° and 100° at 279.1, 661.6 and 1115.5 keV using which an expression for the effective atomic number was derived. The differential incoherent scattering cross-sections of the composite materials of interest measured at these three angles in the same set-up and substituted in this expression would yield their effective atomic number at the three energies. Results obtained in this manner for bakelite, nylon, epoxy, teflon, perspex and some sugars, fatty acids as well as amino acids agreed to within 2% of some of the other available values. It was also observed that for each of these samples, eff was almost a constant at the three energies which unambiguously justified the conclusions drawn by other authors earlier [Manjunathaguru and Umesh, J. Phys. B: At. Mol. Opt. Phys. 39, 3969 (2006); Manohara et al, Nucl. Instrum. Methods B266, 3906 (2008); Manohara et al Phys. Med. Biol. 53, M377 (2008)] based on total interaction cross-sections in the energy grid of interest.

  11. Accurate evaluation of pressure effects on the electronic stopping cross section and mean excitation energy of atomic hydrogen beyond the Bethe approximation

    Energy Technology Data Exchange (ETDEWEB)

    Cabrera-Trujillo, R., E-mail: trujillo@fis.unam.mx [Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, Ap. Postal 48-3, Cuernavaca, Morelos 62251 (Mexico); Departamento de Física, Universidad Autónoma Metropolitana-Iztapalapa, Ap. Postal 55-534, 09340 México, D.F. (Mexico); Cruz, S.A., E-mail: cruz@xanum.uam.mx [Departamento de Física, Universidad Autónoma Metropolitana-Iztapalapa, Ap. Postal 55-534, 09340 México, D.F. (Mexico)

    2014-02-01

    Atomic hydrogen is used as a fundamental reference target system to explore pressure effects on the electronic stopping cross section, S{sub e}, of swift bare ions such as protons and α-particles. This is achieved by considering the hydrogen atom under pressure as a padded spherically-confined quantum system. Within this scheme, S{sub e} is calculated rigorously in the first Born approximation taking into account the full target excitation spectrum and momentum transfer distribution for different confinement conditions (pressures) and fixed projectile charge states. Pressure effects on the target mean excitation energy, I, are also formally calculated and compared with corresponding accurate calculations based on the Local Plasma Approximation (LPA). Even though atomic hydrogen is the simplest target system, its accurate treatment to account for the role of pressure in the stopping dynamics is found to provide useful means to understand the behavior of more complex systems under similar conditions. It is found that: (i) the region of projectile velocities for which the Bethe approximation remains valid is shifted towards higher values as pressure increases; (ii) shell corrections are enhanced relative to the free-atom case as pressure increases, and (iii) the LPA seems to underestimate I as pressure is increased. The results of this work for atomic hydrogen may serve as accurate benchmark reference values for studies of pressure effects on S{sub e} and I using different methodologies.

  12. Interpretation of ES, CS, and IOS approximations within a translational-internal coupling scheme. II. Application to atom-diatom kinetic cross sections

    Science.gov (United States)

    Coombe, D. A.; Snider, R. F.

    1980-02-01

    ES, CS, and IOS approximations to atom-diatom kinetic cross sections are derived. In doing so, reduced S-matrices in a translational-internal coupling scheme are stressed. This entails the insertion of recently obtained approximate reduced S-matrices in the translational-internal coupling scheme into previously derived general expressions for the kinetic cross sections. Of special interest is the structure (rotational j quantum number dependence) of the kinetic cross sections associated with the Senftleben Beenakker effects and of pure internal state relaxation phenomena. The viscomagnetic effect is used as an illustrative example. It is found in particular that there is a great similarity of structure between the energy sudden (and IOS) approximation and the previously derived distorted wave Born results.

  13. Measurements of the X-ray linear attenuation coefficient for low atomic number materials at energies 32-66 and 140 keV

    Science.gov (United States)

    Midgley, S. M.

    2005-03-01

    The X-ray linear attenuation coefficient was measured for materials containing elements hydrogen to calcium. Characteristic X-rays with energies 32- 66 keV were produced by X-ray fluorescence using a secondary target system, and 140 keV gamma rays were obtained from an unsealed 99 mTc source. The photon beams were highly collimated and recorded using energy dispersive detection. A high-purity germanium detector was utilised to distinguish between measurements with K α and K β characteristic X-rays, and the gamma ray measurements used a sodium iodide detector. Samples were selected on the basis of having known composition and mass densities were measured using a pycnometer. The samples comprised six plastics, seven crystalline materials, three tissue substitute materials, three liquids and six salt solutions. Our results have an uncertainty of less than 2% and are a few percent lower than values predicted by the tabulations.

  14. Measurements of the X-ray linear attenuation coefficient for low atomic number materials at energies 32-66 and 140 keV

    International Nuclear Information System (INIS)

    The X-ray linear attenuation coefficient was measured for materials containing elements hydrogen to calcium. Characteristic X-rays with energies 32-66 keV were produced by X-ray fluorescence using a secondary target system, and 140 keV gamma rays were obtained from an unsealed 99mTc source. The photon beams were highly collimated and recorded using energy dispersive detection. A high-purity germanium detector was utilised to distinguish between measurements with Kα and Kβ characteristic X-rays, and the gamma ray measurements used a sodium iodide detector. Samples were selected on the basis of having known composition and mass densities were measured using a pycnometer. The samples comprised six plastics, seven crystalline materials, three tissue substitute materials, three liquids and six salt solutions. Our results have an uncertainty of less than 2% and are a few percent lower than values predicted by the tabulations

  15. A comprehensive study on the atom flow in the cross-field discharge of a Hall thruster

    International Nuclear Information System (INIS)

    The flow properties of Xe atoms were investigated in the 1 kW class PPS100-ML Hall effect thruster by means of Doppler-shifted laser-induced fluorescence spectroscopy in the near infrared. Fluorescence spectra of the 6s [1/2]2o resonant level and the 6s [3/2]2o metastable level have been acquired inside and outside the thruster channel under several operating conditions. Analytical treatment and modelling of the measured lineshapes indicate the atom axial velocity increases inside the channel to a value well above the sound speed before decreasing quickly in the near-field plume. Numerical simulations performed with a fluid/kinetic hybrid approach allow us to explain the shape of the velocity profile. Atomic flow acceleration originates in the combination of three processes, namely the selective ionization of slow atoms, the flow expansion and the creation of fast neutrals on BN-SiO2 walls owing to recombination of ions. Deceleration results from the invasion of the atomic jet by slow and relatively cold atoms from the residual background gas and from the cathode. In addition, it is shown that charge-exchange collisions have a non-negligible impact on the atom velocity in spite of the low background pressure in test chambers.

  16. Analysis of Collisional Cross Sections of Rydberg nS and nD States of Ultracold Caesium Atoms

    Science.gov (United States)

    Feng, Zhigang; Miao, Jingyuan; Zhao, Kejia; Li, Difei; Yang, Zhijun; Wu, Fan; Wu, Zhaochun; Zhao, Jianming; Jia, Suotang

    2016-05-01

    We present a simple analytical formula derived from an existing theoretical model and a detailed theoretical investigation of effects of the van der Waals interaction and dipole–dipole interaction on collisional cross sections as functions of various parameters. We analyze the main mechanism leading to large collisional cross sections on the basis of our previous experimental results using the present formula and also analyze the effects of some other factors on collisional cross sections.

  17. Enhanced cross-Kerr nonlinearity via electromagnetically induced transparency in a four-level tripod atomic system

    International Nuclear Information System (INIS)

    We investigate, both theoretically and experimentally, the cross-Kerr nonlinearity generated in a four-level tripod system in the 87Rb D1 line. The system exhibits simultaneous electromagnetically induced transparency (EIT) windows for two weak (probe and trigger) fields and the enhanced cross-Kerr nonlinearity by EIT. The cross-Kerr nonlinear phase shifts for probe (trigger) field are measured at several different intensities of trigger (probe) field. The results show that large cross-phase modulation (XPM) coefficients can be achieved at low light intensities.

  18. Enhanced cross-Kerr nonlinearity via electromagnetically induced transparency in a four-level tripod atomic system

    Energy Technology Data Exchange (ETDEWEB)

    Yang Xudong; Li Shujing; Zhang Chunhong; Wang Hai [State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan 030006 (China)

    2009-07-15

    We investigate, both theoretically and experimentally, the cross-Kerr nonlinearity generated in a four-level tripod system in the {sup 87}Rb D1 line. The system exhibits simultaneous electromagnetically induced transparency (EIT) windows for two weak (probe and trigger) fields and the enhanced cross-Kerr nonlinearity by EIT. The cross-Kerr nonlinear phase shifts for probe (trigger) field are measured at several different intensities of trigger (probe) field. The results show that large cross-phase modulation (XPM) coefficients can be achieved at low light intensities.

  19. Withdrawal of Chinese Physics Letters 28 (2011) 043401 “Measurement of Absolute Atomic Collision Cross Section with Helium Using 87Rb Atoms Confined in Magneto-Optic and Magnetic Traps” by WANG Ji-Cheng et al.

    Institute of Scientific and Technical Information of China (English)

    WANG Ji-Cheng; ZHOU Ke-Ya; WANG Yue-Yuan; LIAO Qing-Hong; LIU Shu-Tian

    2011-01-01

    We announce the withdrawal of the article entitled “Measurement of Absolute Atomic Collision Cross Section with Helium Using 87Rb Atoms Confined in Magneto-Optic and Magnetic Traps”,which was published in Chinese Physics Letters [28(4)(2011)043401].The first author,Jicheng Wang,had participated in related research with Professor Kirk Madison's group at the Department of Physics & Astronomy at the University of British Columbia,Canada from September 2008 to February 2010.Even though consent had been granted for some of the experimental data to be used by Jicheng Wang in his own thesis,its publication had not been authorized.We apologize to Professor K.Madison for the misunderstanding,and to Chinese Physics Letters and the readers of Chinese Physics Letters for any inconvenience this mistake may have caused.%We announce the withdrawal of the article entitled "Measurement of Absolute Atomic Collision Cross Section with Helium Using 87Rb Atoms Confined in Magneto-Optic and Magnetic Traps", which was published in Chinese Physics Letters [28(4) (2011)043401]. The first author, Jicheng Wang, had participated in related research with Professor Kirk Madison's group at the Department of Physics & Astronomy at the University of British Columbia, Canada from September 2008 to February 2010. Even though consent had been granted for some of the experimental data to be used by Jicheng Wang in his own thesis, its publication had not been authorized. We apologize to Professor K. Madison for the misunderstanding, and to Chinese Physics Letters ad the readers of Chinese Physics Letters for any inconvenience this mistake may have caused.

  20. Design of an experimental setup to measure the K-shell photoelectric cross sections and other atomic parameters at K edge

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Alvarez, J.A.; Lopez-Pino, N.; Rizo, O. Diaz; Corrales, Y.; Padilla-Cabal, F.; Perez-Liva, M.; Alessandro, K.D.; Maidana, N.L. [Instituto Superior de Tecnologia y Ciencias Aplicadas (InSTEC), La Habana (Cuba)

    2010-07-01

    Full text: An experimental setup to measure the K shell jump ratio, jump factor and the ratio of total to K-shell photo-electric cross section at K edge was designed with Monte Carlo (MC) simulations, using the MCNPX V 2.6 code. In our arrangement, Bremsstrahlung photons, produced by beta particles from a {sup 90}Sr- {sup 90}Y source (activity - 0.1 mCi) hitting a thin Nickel converter, were used to irradiate the targets. The incident and transmitted spectra were measured with an HPGe detector coupled to conventional electronics. A sharp decrease in intensity at the K-shell binding energy was observed in the transmitted spectra, which, after corrections for photon attenuation, showed the known behavior for the photoelectric cross section as function of photon energy. The photon beam divergence effects were corrected with a calibration curve calculated with MC from simulations of a parallel and a divergent beam. Targets of Dy, Ta, Pt and Au were used to test the setup. The obtained data were processed by fitting either the total cross section to a sigmoidal function or the cross section branches around the K edge to the empirical law {sigma} = (A/E){sup n}. The results obtained using the first method show the influence of detector energy resolution in the data, because the measured jump at the K edge is not so sharp as it should be. Furthermore, additional calculations were done to obtain the anomalous scattering factors and the K-shell oscillator strengths. The values obtained for the K-shell photoelectric cross sections were compared with theoretical and other experimental data. In most cases, relative deviations below 10% were found. (author)

  1. Non-adiabatic dynamics of reactions of O(1D) with Xe, CO, NO2, and CO2 from crossed atomic and molecular beam experiments

    Science.gov (United States)

    Boering, Kristie

    2015-03-01

    Reactions of the first excited state of atomic oxygen, O(1D), with small molecules such as CO, NO2, and CO2 continue to be of interest in aeronomy and atmospheric chemistry, thus providing additional motivation to understand the dynamics of these reactions and how well they are predicted by theory. In collaboration with Prof. Jim Lin of the Institute of Atomic and Molecular Sciences, Academia Sinica, Taiwan, we have studied the dynamics of quenching and non-quenching reactions between O(1D) and various small molecules using a universal crossed atomic and molecular beam apparatus. New experimental results for the dynamics of quenching of O(1D) by Xe and CO will be presented and compared with previous results for NO2 (K.A. Mar, A.L. Van Wyngarden, C.-W. Liang, Y.T. Lee, J.J. Lin, K.A. Boering, J. Chem. Phys., 137, 044302, doi: 10.1063/1.4736567, 2012) and CO2 (M.J. Perri, A.L. Van Wyngarden, K.A. Boering, J.J. Lin, and Y.T. Lee, J. Chem. Phys., 119(16), 8213-8216, 2003; M.J. Perri, A.L. Van Wyngarden, J.J. Lin, Y.T. Lee, and K.A. Boering, J. Phys. Chem. A, 108(39), 7995-8001, doi: 10.1021/jp0485845, 2004). Among the most intriguing of the new results are for quenching of O(1D) by Xe, for which marked oscillations in the differential cross sections were observed for the O(3P) and Xe products. The shape and relative phase of the oscillatory structure depended strongly on collision energy. This behavior is likely due to the quantum nature of the collision dynamics, caused by interferences among multiple curve crossing pathways accessible during electronic quenching, known as Stueckelberg oscillations.

  2. On the calculation of cross-sections for electron neutral atom collisions in the Born approximation to the reactance matrix

    International Nuclear Information System (INIS)

    Born partial wave integrals are considered for electron-neutral atom collisions. It is shown that for relatively general atomic wave functions these may be evaluated analytically. These form the Born reactance matrix Rsub(B) and can be used to calculate the collision strengths in the approximations Ωsup(I), Ωsup(II). It is shown how to modify Ωsup(I) to take some account of exchange using the simple Ochkur approximation. A result is presented for the coupling coefficients that occur in Seaton's multiplication theorem for spherical Bessel functions. (author)

  3. Generalized Coulomb-projected Born-approximation cross sections for atomic excitation by charged-particle impact

    International Nuclear Information System (INIS)

    An expression is given for the (n/sub i/,l = 0 → n/sub f/,l/sub f/ = 0) excitation cross section in terms of a single one-dimensional integral with the aid of a transformation to prolate spheroidal coordinates. Results are given for the 1s-2s excitation of arbitrary-Z hydrogenic targets. For our choice of wave functions the cross sections are found to scale as Z-4 at fixed E/sub inc//Z2. The principal difference between the Coulomb-projected Born-approximation (CPBA) and Born results is in the large-angle portion of the differential cross section. This, however, leads to CPBA and Born momentum-transfer cross sections which differ by less than 20% at high energies for 1s-2s transitions

  4. Computation of triple differential cross-sections with the inclusion of exchange effects in atomic K-shell ionization by relativistic electrons for symmetric geometry

    Indian Academy of Sciences (India)

    S Dhar; M R Alam

    2007-09-01

    The triple differential cross-section for K-shell ionization of silver and copper atoms by relativistic electrons have been computed in the coplanar symmetric geometry with the inclusion of exchange effects following the multiple scattering theory of Das and Seal [1] multiplied by suitable spinors. Present computed results are marginally improved in some cases from the previous computed results [2]. Present results are compared with measured values [3] and with previous computation results [2]. Some other theoretical computational results are also presented here for comparison.

  5. Calculation of total excitation cross section in the collision of bare ions with atomic hydrogen for transition from ground to and states using Born-Faddeev approximation

    Directory of Open Access Journals (Sweden)

    R Fathi

    2013-09-01

    Full Text Available  In this work, total excitation cross section of atomic hydrogen in the collision of bare ion was calculated employing a three body Faddeev formalism. In the present calculation, initially the first order electronic amplitude was calculated using the interaction potential which led to inelastic form factor. Secondly, the first order nuclear amplitude was calculated and added to the first order electronic amplitude. This second term was calculated employing the near-the-shell two body transition operator. The interaction energy was assumed to be in the intermediate and high energy limits . Finally, the results were compared with the relevant cross sections calculated under monocentric close-coupling data in the literature.

  6. Theoretical state-selective and total cross sections for electron capture from helium atoms by fully stripped ions

    Science.gov (United States)

    Mančev, I.; Milojević, N.; Belkić, Dž.

    2015-03-01

    The four-body boundary-corrected first Born (CB1-4B) approximation is used to compute cross sections for single electron capture from helium targets by fully stripped ions. The projectile ions are H+, He2+, Li3+, Be4+, B5+, C6+, N7+, O8+, and F9+. An extensive list of theoretical state-to-state cross sections in these collisions at energies ranging from 20 to 10 000 keV/amu is given. This list includes the state-selective cross sections Qnlm for each individual triple of the usual quantum numbers { n , l , m } of the final hydrogen-like states alongside Qnl and Qn for the pertinent sub-shells and shells where the respective summations over m and { l , m } have been carried out. The maximal value of the principal quantum number n was chosen to vary from 4 (H+) to 10 (F9+) so as to satisfy the condition n ≥ZP, where ZP is the nuclear charge of the projectile. Usually, the largest cross sections stem from those values of n that match the projectile charge (n =ZP) . The total cross sections for capture summed over all the quantum numbers { n , l , m } are also tabulated. The overall goal of this study is to fill in lacunae in the existing databases of charge exchange cross sections that are needed in several inter-disciplinary fields. For example, in particle transport physics, which is of utmost importance in such emerging branches as hadron therapy, these cross sections constitute a part of the multifaceted input data for stochastic simulations of energy losses of multiply charged ions in matter, including tissue. Other significant uses of the present data are anticipated in charge exchange diagnostics within thermonuclear research project as well as in applications covering the relevant parts of plasma physics and astrophysics.

  7. Resonances in the Photoionization Cross Sections of Atomic Nitrogen Shape the Far-Ultraviolet Spectrum of the Bright Star in 47 Tucanae

    CERN Document Server

    Dixon, William V

    2013-01-01

    The far-ultraviolet (FUV) spectrum of the Bright Star (B8 III) in 47 Tuc (NGC 104) shows a remarkable pattern: it is well fit by LTE models at wavelengths longer than Lyman beta, but at shorter wavelengths it is fainter than the models by a factor of two. A spectrum of this star obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE) shows broad absorption troughs with sharp edges at 995 and 1010 A and a deep absorption feature at 1072 A, none of which are predicted by the models. We find that these features are caused by resonances in the photoionization cross sections of the first and second excited states of atomic nitrogen (2s$^2$ 2p$^3$ $^2$D$^0$ and $^2$P$^0$). Using cross sections from the Opacity Project, we can reproduce these features, but only if we use the cross sections at their full resolution, rather than the resonance-averaged cross sections usually employed to model stellar atmospheres. These resonances are strongest in stellar atmospheres with enhanced nitrogen and depleted carbon ab...

  8. Atomic and plasma-material interaction data for fusion. V. 8. Elastic and related transport cross sections for collisions among isotopomers of H+ + H, H+ + H2, H+ + He, H + H, and H + H2

    International Nuclear Information System (INIS)

    The Volume 8 of the 'Atomic and Plasma-Material Interaction Data for Fusion' provides an exhaustive source of information on elastic scattering, momentum transfer and viscosity cross sections for collisions of hydrogenic ions, atoms and molecules, and their isotopes, in the energy range pertinent to fusion reactor divertor plasmas and extending (in its low-energy part) to collision conditions that are relevant for astrophysics. Hydrogen ion-helium atom collisions are also included. The reported cross sections are obtained from extensive quantum-mechanical calculations and can be regarded as having very high accuracy

  9. State-Selective and Total Single-Capture Cross Sections for Fast Collisions of Multiply Charged Ions with Helium Atoms

    Science.gov (United States)

    Mančev, Ivan; Milojević, Nenad; Belkić, Dževad

    2013-11-01

    The four-body boundary corrected first Born approximation (CB1-4B) is used to calculate the single electron capture cross sections for collisions between fully stripped ions (He2+, Be4+, B5+ and C6+) and helium target at intermediate and high impact energies. The main goal of this study is to assess the usefulness of the CB1-4B method at intermediate and high impact energies for these collisions. Detailed comparisons with the measurements are carried out and the obtained theoretical cross sections are in reasonable agreement with the available experimental data.

  10. Analytical formulae for total cross sections for electron scattering by atoms (N, O, F, Ne, P, S, Cl, Ar, As, Se, Br, Kr) between 0.5-10 keV

    Energy Technology Data Exchange (ETDEWEB)

    Williart, A. [Univ. Nacional de Educacion a Distancia, Madrid (Spain). Dept. de Fisica de los Materiales; Garcia, G. [Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas, Madrid (Spain)

    2001-10-01

    Analytical formulae for total cross sections for electron scattering by atoms which are close to the noble gases (Ne, Ar and Kr), for electron energies ranging from 0.5 to 10 keV, have been obtained in this study. We have shown, previously, that molecular total cross sections, at these energies, depend on target polarizability and the number of target electrons. A similar behaviour has been supposed for total cross sections of some atoms (N, O, F, P, S, Cl, As, Se and Br). The obtained expression depends on atomic parameters and it is based in some correlation derived from noble gases. The applicability of the formula has been checked by comparison with available data for atomic oxygen. (orig.)

  11. A semi-empirical formula for calculation of absolute cross sections for ionization and excitation of atoms by electrons

    NARCIS (Netherlands)

    Vriens, L.

    1965-01-01

    A simple analytical expression for the absolute ionization and (optically allowed) excitation cross sections, as a function of the electron energy, is “derived”. In this expression there are two parameters. The first one is proportional to the optical oscillator strength and the second one is depend

  12. Cross-sections for electron capture by multiply charged ions from hydrogen atoms and molecules and population of electronic states of created ions

    International Nuclear Information System (INIS)

    The cross-sections for single electron capture by alpha-particles and multiply charged ions Ne3+, Ne4+, Ar4+, Ar5+, Ar6+ from hydrogen atoms and molecules have been measured using registration of coincidences between incident and recoil ions after collision to separate this process. Population of different electronic states of ions with lower charges produced at single electron capture has been measured by collision spectroscopy method. Cross-sections for one electron capture by He2+, ArZ+ (Z = 6, 5, 4) and NeZ+ (Z = 3-4) have been measured in the kinetic energy range of incident multiply charged ions from 1xZ to 12xZ keV (Z is charge of multiply charged ions). Cross-sections for the population of electronic states at electron capture from H2 molecules have been measured in the velocity range from V = 1·107 cm/s to V5,5·107 cm/s (in the collision energy range 3.0xZ Kev - 21.0xZ KeV) at collisions of ArZ+ ions (Z=3-6) and NeZ+ (Z3-4). The double electron capture cross-sections at incident alpha-particles and hydrogen molecules collision have been measured in the energy range from 1 KeV up to 100 KeV (V=0, 235/2, 58·108 cm/s). Errors of measured values of cross-sections are ∼10-15% The results of the measurements are presented in Tables 1-8. (author)

  13. Differential and total excitation cross sections in the collision of protons with He atoms at intermediate and high energies under a three body formalism

    Directory of Open Access Journals (Sweden)

    R Fathi

    2011-09-01

    Full Text Available  A three-body model is devised to study differential and total cross sections for the excitation of helium atom under impact of energetic protons. The actual process is a four body one but in the present model the process is simplified into a three-body one. In this model, an electron of helium atom is assumed to be inactive and only one electron of the atom is active. Therefore, the active electron is assumed to be in an atomic state with a potential of the nucleus, T, being screened by the inactive electron, e, and, thus, an effective charge of Ze. As a result, the ground state, 11S, or the excited states, 21S and 21P, wave function of the active electron is deduced from similar hydrogenic wave functions assuming effective charge, Ze for the combined nucleus (T+e. In this three-body model, the Faddeev-Watson-Lovelace formalism for excitation channel is used to calculate the transition amplitude. In the first order approximation, electronic and nuclear interaction is assumed in the collision to be A(1e= and A(1n=, respectively. Here, A(1, Txy, |i> and |f> are the first order transition amplitude, the transition matrix for the interaction between particles x and y, the initial state and the final state, respectively. The transition matrix for the first order electronic interaction implemented into A(1e is approximated as the corresponding two-body interaction, Vxy. In order to calculate first order nuclear amplitude A(1n, the near-the-shell form of transition matrix TPT is used. Calculations are performed in the energy range of 50 keV up to 1MeV. The results are then compared with those of theoretical and experimental works in the literature.

  14. Enhancement of level-crossing resonances in rubidium atoms by frequency control of the exciting radiation field

    CERN Document Server

    Auzinsh, Marcis; Ferber, Ruvin; Gahbauer, Florian; Kalvans, Linards; Mozers, Arturs; Spiss, Agris

    2013-01-01

    We studied magneto-optical resonances caused by excited-state level crossings in a nonzero magnetic field. Experimental measurements were performed on the transitions of the $D_2$ line of rubidium. These measured signals were described by a theoretical model that takes into account all neighboring hyperfine transitions, the mixing of magnetic sublevels in an external magnetic field, the coherence properties of the exciting laser radiation, and the Doppler effect. Good agreement between the experimental measurements and the theoretical model could be achieved over a wide range of laser power densities. We further showed that the contrasts of the level-crossing peaks can be sensitive to changes in the frequency of the exciting laser radiation as small as several tens of megahertz when the hyperfine splitting of the exciting state is larger than the Doppler broadening.

  15. Formation of very low energy states crossing the ionization threshold of argon atoms in strong mid-infrared fields

    CERN Document Server

    Wolter, Benjamin; Baudisch, Matthias; Pullen, Michael G; Tong, Xiao-Min; Hemmer, Michaël; Senftleben, Arne; Schröter, Claus Dieter; Ullrich, Joachim; Moshammer, Robert; Biegert, Jens; Burgdörfer, Joachim

    2014-01-01

    Atomic ionization by intense mid-infrared (mid-IR) pulses produces low electron energy features that the strong-field approximation, which is expected to be valid in the tunneling ionization regime characterized by small Keldysh parameters ($\\gamma \\ll 1$), cannot describe. These features include the low-energy structure (LES), the very-low-energy structure (VLES), and the more recently found zero-energy structure (ZES). They result from the interplay between the laser electric field and the atomic Coulomb field which controls the low-energy spectrum also for small $\\gamma$. In the present joint experimental and theoretical study we investigate the vectorial momentum spectrum at very low energies. Using a reaction microscope optimized for the detection of very low energy electrons, we have performed a thorough study of the three-dimensional momentum spectrum well below 1 eV. Our measurements are complemented by quantum and classical simulations, which allow for an interpretation of the LES, VLES and of the ne...

  16. Retraction notice to "Measurements of total absolute collision cross section of ultracold Rb atom using magneto-optic and pure magnetic traps" [Chinese Optics Letters 9, 060201 (2011)

    Institute of Scientific and Technical Information of China (English)

    Jicheng Wang; Yueyuan Wang; Yueke Wang; Guangyu Fang; Shutian Liu

    2011-01-01

    This article "Measurements of total absolute collision cross section of ultracold Rb atom using magneto-optic and pure magnetic traps",which was published on Chinese Optics Letters (9,060201 (2011)) has been retracted at the request of the authors.Reason:The first author,Jicheng Wang,participated in a related research in Professor Kirk Madison's group in the Department of Physics & Astronomy at the University of British Columbia,Canada from September 2008 to February 2010.Some of the experimental data have not been authorized for publication,even though they have been consented to be used by Jicheng Wang in his own research.The authors apologize to Professor K.Madison for misunderstanding,and to Chinese Optics Letters and the readers of Chinese Optics Letters for any inconvenience this mistake may have caused.

  17. Functionalization of cross linked chitosan with 2-aminopyridine-3-carboxylic acid for solid phase extraction of cadmium and zinc ions and their determination by atomic absorption spectrometry

    International Nuclear Information System (INIS)

    We have developed a new method for solid phase extraction (SPE) and preconcentration of trace amounts of cadmium and zinc using cross linked chitosan that was functionalized with 2-aminopyridine-3-carboxy acid. Analytical parameters, sample pH, effect of flow rate, sample volume, and concentration of eluent on column SPE were investigated. The effect of matrix ions on the recovery of cadmium and zinc has been investigated and were found not to interfere with preconcentration. Under the optimum experimental conditions, the preconcentration factors for Cd(II) and Zn(II) were found to be 90. The two elements were quantified via atomic absorption spectrometry. The detection limits for cadmium and zinc are 21 and 65 ng L -1, respectively. The method was evaluated by analyzing a certified reference material (NIST 1643e; water) and has been successfully applied to the analysis of cadmium and zinc in environmental water samples. (author)

  18. High-performance HfO x /AlO y -based resistive switching memory cross-point array fabricated by atomic layer deposition.

    Science.gov (United States)

    Chen, Zhe; Zhang, Feifei; Chen, Bing; Zheng, Yang; Gao, Bin; Liu, Lifeng; Liu, Xiaoyan; Kang, Jinfeng

    2015-01-01

    Resistive switching memory cross-point arrays with TiN/HfO x /AlO y /Pt structure were fabricated. The bi-layered resistive switching films of 5-nm HfO x and 3-nm AlO y were deposited by atomic layer deposition (ALD). Excellent device performances such as low switching voltage, large resistance ratio, good cycle-to-cycle and device-to-device uniformity, and high yield were demonstrated in the fabricated 24 by 24 arrays. In addition, multi-level data storage capability and robust reliability characteristics were also presented. The achievements demonstrated the great potential of ALD-fabricated HfO x /AlO y bi-layers for the application of next-generation nonvolatile memory.

  19. Feedback based simultaneous correction of imaging artifacts due to geometrical and mechanical cross-talk and tip-sample stick in atomic force microscopy

    Science.gov (United States)

    Shegaonkar, Ajit C.; Salapaka, Srinivasa M.

    2007-10-01

    This paper presents a feedback scheme that simultaneously corrects, in real time, for the imaging artifacts caused by cantilever and photosensor misalignments as well as misinterpretations in relative lateral position of the tip with respect to the sample due to the tip-sample stick in atomic force microscopy (AFM). The optical beam bounce method, typically used in AFM for imaging, is sensitive to inaccuracies of cantilever geometry and the relative misalignment of the laser source, cantilever, and the laser sensitive diode from the intended design. These inaccuracies, which contribute to the geometrical cross-talk between the normal and the lateral signals, become prominent at the atomic and subnanometer scales, and thereby impede high resolution imaging studies. The feedback scheme accounts for these artifacts and makes imaging insensitive to, in fact, practically independent of these inaccuracies. This scheme counteracts the lateral twisting dynamics of the cantilever, and as a result, it avoids the misinterpretation problem of the relative lateral position of the cantilever tip from the sample and thereby avoids the corresponding imaging artifacts that are typically prominent in contact mode friction force microscopy (FFM). The feedback scheme consists of simultaneously regulating the normal as well as the lateral cantilever deflection signal at their respective set points. This not only removes the imaging artifacts due to geometrical misalignments, mechanical cross-talk, and irregular sliding but also the corresponding compensatory control signal gives a more accurate real time measure of the lateral interaction force between the sample and the cantilever as compared to the lateral deflection signal used in FFM. Experimental results show significant improvement, and in some cases, practical elimination of the artifacts. The design and implementation of a split piezoassembly needed for the lateral actuation for the feedback scheme are also presented.

  20. Cardiovascular responses to the ingestion of sugary drinks using a randomised cross-over study design: does glucose attenuate the blood pressure-elevating effect of fructose?

    OpenAIRE

    Grasser, Erik K; Dulloo, Abdul; Montani, Jean-Pierre

    2014-01-01

    Overconsumption of sugar-sweetened beverages has been implicated in the pathogenesis of CVD. The objective of the present study was to elucidate acute haemodynamic and microcirculatory responses to the ingestion of sugary drinks made from sucrose, glucose or fructose at concentrations similar to those often found in commercial soft drinks. In a randomised cross-over study design, twelve young healthy human subjects (seven men) ingested 500 ml tap water in which was dissolved 60 g of either su...

  1. Experiments and modeling on droplet motion and atomization of diesel and bio-diesel fuels in a cross-flowed air stream

    International Nuclear Information System (INIS)

    This paper describes an experimental and numerical modeling on microscopic droplet behaviors and macroscopic atomization characteristics of diesel and bio-diesel fuels under the conditions of air cross-flow. In order to obtain the experimental air-assisted-droplet behavior and breakup characteristics, deformation ratio, droplet trajectory, and droplet size distribution were investigated quantitatively for different droplet breakup mechanisms. In order to assess prediction accuracies of the original spray models contained in the standard CFD code and validate the currently modified and suggested models, the computations were implemented using the KIVA-3V code with a three dimensional computational mesh and compared to the experimental results. Because the original TAB model and droplet drag model tend to predict the unphysical breakup characteristics, to improve the calculation accuracy, the model constants of the droplet motion equation in the TAB model and the droplet drag model were modified and optimized. In addition, a new model for determining the droplet size after breakup is currently suggested, because original model does not consider the frictional flow inside a droplet, resulting in impractical droplet size results. Based on inspections of the measured and calculated results, outcomes of atomization characteristics from modified models give a reasonable droplet deformation rate and also show the appropriate droplet trajectory at the first breakup stage. In the results of droplet breakup and atomization, the modified models give improved prediction accuracy on the droplet size distribution better than the standard models. But there still shows a little discrepancy between calculated and measured droplet size and its distribution pattern. It seems to be caused by the own assumption of the TAB model which is based only on the vibration and breakup mechanism.

  2. Icariin Attenuates OGD/R-Induced Autophagy via Bcl-2-Dependent Cross Talk between Apoptosis and Autophagy in PC12 Cells

    Science.gov (United States)

    2016-01-01

    Icariin (ICA), an active component of Epimedium brevicornum Maxim, exerts a variety of neuroprotective effects such as antiapoptosis. However, the mechanisms underlying antiapoptosis of ICA in neurons exposed to oxygen-glucose deprivation and reperfusion (OGD/R) are unclear. The B-cell lymphoma-2 (Bcl-2) protein family plays an important role in the regulation of apoptosis and autophagy through Bcl-2-dependent cross talk. Bcl-2 suppresses apoptosis by binding to Bax and inhibits autophagy by binding to Beclin-1 which is an autophagy related protein. In the present study, MTT result showed that ICA increased cell viability significantly in OGD/R treated PC12 cells (P < 0.01). Results of western blotting analysis showed that ICA increased Bcl-2 expression significantly and decreased expressions of Bax, cleaved Caspase-3, Beclin-1, and LC3-II significantly in OGD/R treated PC12 cells (P < 0.01). These results suggest that ICA protects PC12 cells from OGD/R induced autophagy via Bcl-2-dependent cross talk between apoptosis and autophagy. PMID:27610184

  3. Measurements of differential cross sections with electrons of intermediate energy (300-1000 eV) scattered by atom and molecule

    International Nuclear Information System (INIS)

    Differential Elastic Cross Sections for electrons scattered by osub(2) and Ar in the angular range 5 sup(0)- 140 sup(0) were measured in the energy range between 300 and 1000 eV. The Relative Flow Technique proposed by SRIVASTAVA et alii (1975) was used. Absolute Differential Elastic Cross Section data from DuBOIS and RUDD (1976) for Nsub(2) were stablished as a secondary standard. Our obtained results for Ar at 400, 800 and 1000 eV were compared against experimental and theoretical results available in the literature. For molecular Oxygen at 300, 400, 800 and 1000 eV our experimental data were compared with values from other authors and also theoretical values from Independent Atom Model including Multiple Intramolecular Scattering. Results for Ar at 1000 eV in the angular range between 60 sup(0) and 140 sup(0) and for osub(2) at 800 and 100 eV, between 5 sup(0) and 120 sup(0), were reported for the first time. (author)

  4. Photoionization of iodine atoms: Angular distributions and relative partial photoionization cross-sections in the energy region 11.0-23.0 eV

    Science.gov (United States)

    Eypper, Marie; Innocenti, Fabrizio; Morris, Alan; Dyke, John M.; Stranges, Stefano; West, John B.; King, George C.

    2010-08-01

    Relative partial photoionization cross-sections and angular distribution parameters, β, have been measured for the first, I+(P32)←I(P23/2), and fourth, I+(D12)←I(P23/2), (5p)-1 photoelectron (PE) bands of atomic iodine, by performing angle-resolved constant-ionic-state (CIS) measurements on these PE bands in the photon energy range 11.0-23.0 eV. Three Rydberg series, two ns and one nd series, which converge to the I+ P31 limit at 11.33 eV and four Rydberg series, two ns and two nd series, which converge to the I+ D12 limit at 12.15 eV were observed in the first PE band CIS spectra. The fourth band CIS spectrum showed structure in the 12.9-14.1eV photon energy range, which is also seen in the first band CIS spectra. This structure arises from excitation to ns and nd Rydberg states that are parts of series converging to the I+ S10 limit we reported on earlier, as well as 5s→5p excitations in the photon energy range 17.5-22.5 eV. These atomic iodine CIS spectra show reasonably good agreement with the equivalent spectra obtained for atomic bromine. The β-plots for the first PE band recorded up to the I+ P31 and I+ D12 limits only show resonances corresponding to some of the 5p→nd excitations observed in the first band CIS spectra scanned to the I+ D12 limit (12.15 eV). These plots are interpreted in terms of an angular momentum transfer model with the positive values of β obtained on resonances corresponding to parity allowed jt=1 and 3 channels and the off-resonance negative β values corresponding to parity unfavored channels, where jt is the quantum number for angular momentum transfer between the molecule, and the ion and photoelectron. The β-plots recorded for iodine are significantly different from those obtained for atomic bromine. Comparison of the experimental CIS spectra and β-plots with available theoretical results highlights the need for higher level calculations which include factors such as configuration interaction in the initial and final

  5. Cardiovascular responses to the ingestion of sugary drinks using a randomised cross-over study design: Does glucose attenuate the blood pressure-elevating effect of fructose?

    Science.gov (United States)

    Grasser, Erik K; Dulloo, Abdul; Montani, Jean-Pierre

    2014-07-28

    Overconsumption of sugar-sweetened beverages has been implicated in the pathogenesis of CVD. The objective of the present study was to elucidate acute haemodynamic and microcirculatory responses to the ingestion of sugary drinks made from sucrose, glucose or fructose at concentrations similar to those often found in commercial soft drinks. In a randomised cross-over study design, twelve young healthy human subjects (seven men) ingested 500 ml tap water in which was dissolved 60 g of either sucrose, glucose or fructose, or an amount of fructose equivalent to that present in sucrose (i.e. 30 g fructose). Continuous cardiovascular monitoring was performed for 30 min before and at 60 min after ingestion of sugary drinks, and measurements included beat-to-beat blood pressure (BP) and impedance cardiography. Additionally, microvascular endothelial function testing was performed after iontophoresis of acetylcholine and sodium nitroprusside using laser Doppler flowmetry. Ingestion of fructose (60 or 30 g) increased diastolic and mean BP to a greater extent than the ingestion of 60 g of either glucose or sucrose (Psugary drinks. In conclusion, ingestion of fructose, but not sucrose, increases BP in healthy human subjects. Although sucrose comprises glucose and fructose, its changes in TPR and CO are more related to glucose than to fructose.

  6. Cardiovascular responses to the ingestion of sugary drinks using a randomised cross-over study design: Does glucose attenuate the blood pressure-elevating effect of fructose?

    Science.gov (United States)

    Grasser, Erik K; Dulloo, Abdul; Montani, Jean-Pierre

    2014-07-28

    Overconsumption of sugar-sweetened beverages has been implicated in the pathogenesis of CVD. The objective of the present study was to elucidate acute haemodynamic and microcirculatory responses to the ingestion of sugary drinks made from sucrose, glucose or fructose at concentrations similar to those often found in commercial soft drinks. In a randomised cross-over study design, twelve young healthy human subjects (seven men) ingested 500 ml tap water in which was dissolved 60 g of either sucrose, glucose or fructose, or an amount of fructose equivalent to that present in sucrose (i.e. 30 g fructose). Continuous cardiovascular monitoring was performed for 30 min before and at 60 min after ingestion of sugary drinks, and measurements included beat-to-beat blood pressure (BP) and impedance cardiography. Additionally, microvascular endothelial function testing was performed after iontophoresis of acetylcholine and sodium nitroprusside using laser Doppler flowmetry. Ingestion of fructose (60 or 30 g) increased diastolic and mean BP to a greater extent than the ingestion of 60 g of either glucose or sucrose (Psugary drinks. In conclusion, ingestion of fructose, but not sucrose, increases BP in healthy human subjects. Although sucrose comprises glucose and fructose, its changes in TPR and CO are more related to glucose than to fructose. PMID:24780643

  7. Imaging Rayleigh wave attenuation with USArray

    Science.gov (United States)

    Bao, Xueyang; Dalton, Colleen A.; Jin, Ge; Gaherty, James B.; Shen, Yang

    2016-07-01

    The EarthScope USArray provides an opportunity to obtain detailed images of the continental upper mantle at an unprecedented scale. The majority of mantle models derived from USArray data to date contain spatial variations in seismic-wave speed; however, in many cases these data sets do not by themselves allow a non-unique interpretation. Joint interpretation of seismic attenuation and velocity models can improve upon the interpretations based only on velocity and provide important constraints on the temperature, composition, melt content, and volatile content of the mantle. The surface wave amplitudes that constrain upper-mantle attenuation are sensitive to factors in addition to attenuation, including the earthquake source excitation, focusing and defocusing by elastic structure, and local site amplification. Because of the difficulty of isolating attenuation from these other factors, little is known about the attenuation structure of the North American upper mantle. In this study, Rayleigh wave traveltime and amplitude in the period range 25-100 s are measured using an interstation cross-correlation technique, which takes advantage of waveform similarity at nearby stations. Several estimates of Rayleigh wave attenuation and site amplification are generated at each period, using different approaches to separate the effects of attenuation and local site amplification on amplitude. It is assumed that focusing and defocusing effects can be described by the Laplacian of the traveltime field. All approaches identify the same large-scale patterns in attenuation, including areas where the attenuation values are likely contaminated by unmodelled focusing and defocusing effects. Regionally averaged attenuation maps are constructed after removal of the contaminated attenuation values, and the variations in intrinsic shear attenuation that are suggested by these Rayleigh wave attenuation maps are explored.

  8. Polyphenol- and fibre-rich dried fruits with green tea attenuate starch-derived postprandial blood glucose and insulin: a randomised, controlled, single-blind, cross-over intervention.

    Science.gov (United States)

    Nyambe-Silavwe, H; Williamson, G

    2016-08-01

    Polyphenol- and fibre-rich foods (PFRF) have the potential to affect postprandial glycaemic responses by reducing glucose absorption, and thus decreasing the glycaemic response of foods when consumed together. A randomised, single-blind, cross-over study was conducted on sixteen healthy volunteers to test whether PFRF could attenuate postprandial blood glucose in healthy volunteers when added to a source of carbohydrate (starch in bread). This is the first study to examine the effects of a meal comprised of components to inhibit each stage of the biochemical pathway, leading up to the appearance of glucose in the blood. The volunteers were fasted and attended four visits: two control visits (bread, water, balancing sugars) and two test visits (single and double dose of PFRF) where they consumed bread, water and PFRF. Blood samples were collected at 0 (fasted), 15, 30, 45, 60, 90, 120, 150 and 180 min after consumption. The PFRF components were tested for α-amylase and α-glucosidase inhibitory potential in vitro. Plasma glucose was lower after consumption of both doses compared with controls: lower dose, change in mean incremental areas under the glucose curves (IAUC)=-27·4 (sd 7·5) %, Pamylase (green tea, strawberry, blackberry and blackcurrant) and α-glucosidase (green tea) activities in vitro. The PFRF have a pronounced and significant lowering effect on postprandial blood glucose and insulin response in humans, due in part to inhibition of α-amylase and α-glucosidase, as well as glucose transport. PMID:27278405

  9. Gamma-ray attenuation coefficients in some heavy metal oxide borate glasses at 662 keV

    International Nuclear Information System (INIS)

    The linear attenuation coefficient (μ) and mass attenuation coefficients (μ/ρ) of glasses in three systems: xPbO(1-x)B2O3, 0.25PbO.xCdO(0.75-x)B2O3 and xBi2O3(1-x)B2O3 were measured at 662 keV. Appreciable variations were noted in the attenuation coefficients due to changes in the chemical composition of glasses. In addition to this, absorption cross-sections per atom were also calculated. A comparison of shielding properties of these glasses with standar d shielding materials like lead, lead glass and concrete has proven that these glasses have a potential application as transparent radiation shielding. (orig.)

  10. Effective atomic numbers and electron densities of some biologically important compounds containing H, C, N and O in the energy range 145 1330 keV

    Science.gov (United States)

    Manjunathaguru, V.; Umesh, T. K.

    2006-09-01

    A semi-empirical relation which can be used to determine the total attenuation cross sections of samples containing H, C, N and O in the energy range 145-1332 keV has been derived based on the total attenuation cross sections of several sugars, amino acids and fatty acids. The cross sections have been measured by performing transmission experiments in a narrow beam good geometry set-up by employing a high-resolution hyperpure germanium detector at seven energies of biological importance such as 145.4 keV, 279.2 keV, 514 keV, 661.6 keV, 1115.5 keV, 1173.2 keV and 1332.1 keV. The semi-empirical relation can reproduce the experimental values within 1-2%. The total attenuation cross sections of five elements carbon, aluminium, titanium, copper and zirconium measured in the same experimental set-up at the energies mentioned above have been used in a new matrix method to evaluate the effective atomic numbers and the effective electron densities of samples such as cholesterol, fatty acids, sugars and amino acids containing H, C, N and O atoms from their effective atomic cross sections. The effective atomic cross sections are the total attenuation cross sections divided by the total number of atoms of all types in a particular sample. Further, a quantity called the effective atomic weight was defined as the ratio of the molecular weight of a sample to the total number of atoms of all types in it. The variation of the effective atomic number was systematically studied with respect to the effective atomic weight and a new semi-empirical relation for Zeff has been evolved. It is felt that this relation can be very useful to determine the effective atomic number of any sample having H, C, N and O atoms in the energy range 145-1332 keV irrespective of its chemical structure.

  11. Rydberg atom ionization by slow collisions with alkali element atoms

    International Nuclear Information System (INIS)

    A new mechanism for ionization of highexcited atoms due to the electron capture into the autoionization state of a negative ion is suggested. Calculations of cross-sections and the ionization rate for sodium and lithium atoms collisions are performed

  12. The attenuation coefficients in CT: Didactic review

    International Nuclear Information System (INIS)

    The review article refers details about the derivation of the Attenuation coefficient of the CT-Number, the electron density and physical density, the effective atomic number, dual KV scanning, the performance of different scanners, furtheron the CT-numbers of intracranial structures, the attempts of characterization of tissue by CT, measurements of effective atomic number and electron density, distribution and probability of occurance of CT-numbers, and distribution of CT-numbers in space. (AJ)

  13. Combined crossed molecular beam and ab initio investigation of the multichannel reaction of boron monoxide (BO; X2Σ+) with Propylene (CH3CHCH2; X1A'): competing atomic hydrogen and methyl loss pathways.

    Science.gov (United States)

    Maity, Surajit; Dangi, Beni B; Parker, Dorian S N; Kaiser, Ralf I; An, Yi; Sun, Bing-Jian; Chang, A H H

    2014-10-16

    The reaction dynamics of boron monoxide ((11)BO; X(2)Σ(+)) with propylene (CH(3)CHCH(2); X(1)A') were investigated under single collision conditions at a collision energy of 22.5 ± 1.3 kJ mol(-1). The crossed molecular beam investigation combined with ab initio electronic structure and statistical (RRKM) calculations reveals that the reaction follows indirect scattering dynamics and proceeds via the barrierless addition of boron monoxide radical with its radical center located at the boron atom. This addition takes place to either the terminal carbon atom (C1) and/or the central carbon atom (C2) of propylene reactant forming (11)BOC(3)H(6) intermediate(s). The long-lived (11)BOC(3)H(6) doublet intermediate(s) underwent unimolecular decomposition involving at least three competing reaction mechanisms via an atomic hydrogen loss from the vinyl group, an atomic hydrogen loss from the methyl group, and a methyl group elimination to form cis-/trans-1-propenyl-oxo-borane (CH(3)CHCH(11)BO), 3-propenyl-oxo-borane (CH(2)CHCH(2)(11)BO), and ethenyl-oxo-borane (CH(2)CH(11)BO), respectively. Utilizing partially deuterated propylene (CD(3)CHCH(2) and CH(3)CDCD(2)), we reveal that the loss of a vinyl hydrogen atom is the dominant hydrogen elimination pathway (85 ± 10%) forming cis-/trans-1-propenyl-oxo-borane, compared to the loss of a methyl hydrogen atom (15 ± 10%) leading to 3-propenyl-oxo-borane. The branching ratios for an atomic hydrogen loss from the vinyl group, an atomic hydrogen loss from the methyl group, and a methyl group loss are experimentally derived to be 26 ± 8%:5 ± 3%:69 ± 15%, respectively; these data correlate nicely with the branching ratios calculated via RRKM theory of 19%:5%:75%, respectively.

  14. The chaperone-like activity of α-synuclein attenuates aggregation of its alternatively spliced isoform, 112-synuclein in vitro: plausible cross-talk between isoforms in protein aggregation.

    Science.gov (United States)

    Manda, Krishna Madhuri; Yedlapudi, Deepthi; Korukonda, Srikanth; Bojja, Sreedhar; Kalivendi, Shasi V

    2014-01-01

    Abnormal oligomerization and aggregation of α-synuclein (α-syn/WT-syn) has been shown to be a precipitating factor in the pathophysiology of Parkinson's disease (PD). Earlier observations on the induced-alternative splicing of α-syn by Parkinsonism mimetics as well as identification of region specific abnormalities in the transcript levels of 112-synuclein (112-syn) in diseased subjects underscores the role of 112-syn in the pathophysiology of PD. In the present study, we sought to identify the aggregation potential of 112-syn in the presence or absence of WT-syn to predict its plausible role in protein aggregation events. Results demonstrate that unlike WT-syn, lack of 28 aa in the C-terminus results in the loss of chaperone-like activity with a concomitant gain in vulnerability to heat-induced aggregation and time-dependent fibrillation. The effects were dose and time-dependent and a significant aggregation of 112-syn was evident at as low as 45 °C following 10 min of incubation. The heat-induced aggregates were found to be ill-defined structures and weakly positive towards Thioflavin-T (ThT) staining as compared to clearly distinguishable ThT positive extended fibrils resulting upon 24 h of incubation at 37 °C. Further, the chaperone-like activity of WT-syn significantly attenuated heat-induced aggregation of 112-syn in a dose and time-dependent manner. On contrary, WT-syn synergistically enhanced fibrillation of 112-syn. Overall, the present findings highlight a plausible cross-talk between isoforms of α-syn and the relative abundance of these isoforms may dictate the nature and fate of protein aggregates.

  15. The influence of electron beam direction and atomic weight on the ionization cross-section of metals by high-energy electrons

    International Nuclear Information System (INIS)

    The intensities of X-rays generated from samples of Ni3Al, Ni15 at.%Al and (TiNb)3Al were examined over a range of accelerating voltages as a function of diffracting conditions. It was found that the intensities of the X-rays from the heavier element in the alloys may be enhanced, with respect to the signal from the lighter element, when the sample is oriented at symmetry. This occurs for Ni and Ti with respect to the Al intensity in Ni3Al and (TiNb)3Al, even when the systematic row which is excited does not contain a superlattice reflection, and in Ni15 at.%Al which is effectively a disordered alloy. The situation in (TiNb)3Al is more complex, since although the Ti signal is enhanced with respect to the Al signal at symmetry for all reflections, the NbK intensity is not increased relative to the Ti signal but is increased relative to the Al intensity; the magnitude of this increase is about twice as great for reflections which lie in rows which contain superlattice reflections than for rows which do not. In contrast, the NbL intensity is decreased with respect to the TiK intensity when the crystal is set at symmetry for all types of systematic rows. These observations are interpreted in terms of the influence of atomic number on the sizes of electron shells and hence on their ionization cross-sections. The results are briefly discussed in terms of the technique of ALCHEMI, which is used to determine site occupancy in alloys, and in terms of the quantification of energy dispersive X-ray data from thin samples. (author)

  16. Photonic Crystal Fiber Attenuator

    Institute of Scientific and Technical Information of China (English)

    Joo Beom Eom; Hokyung Kim; Jinchae Kim; Un-Chul Paek; Byeong Ha Lee

    2003-01-01

    We propose a novel fiber attenuator based on photonic crystal fibers. The difference in the modal field diameters of a conventional single mode fiber and a photonic crystal fiber was used. A variable optical attenuator was also achieved by applying macro-bending on the PCF part of the proposed attenuator

  17. Photon attenuation properties of some thorium, uranium and plutonium compounds

    Energy Technology Data Exchange (ETDEWEB)

    Singh, V. P.; Badiger, N. M. [Karnatak University, Department of Physics, Dharwad-580003, Karnataka (India); Vega C, H. R., E-mail: kudphyvps@rediffmail.com [Universidad Autonoma de Zacatecas, Unidad Academica de Estudios Nucleares, Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas, Zac. (Mexico)

    2015-10-15

    Mass attenuation coefficients, effective atomic numbers, effective electron densities for nuclear materials; thorium, uranium and plutonium compounds have been studied. The photon attenuation properties for the compounds have been investigated for partial photon interaction processes by photoelectric effect, Compton scattering and pair production. The values of these parameters have been found to change with photon energy and interaction process. The variations of mass attenuation coefficients, effective atomic number and electron density with energy are shown graphically. Moreover, results have shown that these compounds are better shielding and suggesting smaller dimensions. The study would be useful for applications of these materials for gamma ray shielding requirement. (Author)

  18. Photon attenuation properties of some thorium, uranium and plutonium compounds

    International Nuclear Information System (INIS)

    Mass attenuation coefficients, effective atomic numbers, effective electron densities for nuclear materials; thorium, uranium and plutonium compounds have been studied. The photon attenuation properties for the compounds have been investigated for partial photon interaction processes by photoelectric effect, Compton scattering and pair production. The values of these parameters have been found to change with photon energy and interaction process. The variations of mass attenuation coefficients, effective atomic number and electron density with energy are shown graphically. Moreover, results have shown that these compounds are better shielding and suggesting smaller dimensions. The study would be useful for applications of these materials for gamma ray shielding requirement. (Author)

  19. On the influence of the distortion of the initial atomic state by the field of a multicharged ion on double differential cross sections

    International Nuclear Information System (INIS)

    The theoretical description of atom ionization by multicharged ions is suggested; besides interaction in the finite state at Z1/Vi1 is a charge of an incident particle, Vi is a velocity of colliding particles) the distortion of the initial state of the target atom by the field of an incident ion is correctly taken into account. It is shown that the effect of the distortion of the initial state on the angular and energy distributions of electrons increases with the charge increase and the ion velocity decrease. The results of calculations for ion collisions with the helium atom are compared with experimental data

  20. Experimental atomic physics

    International Nuclear Information System (INIS)

    The atomic structure and collision phenomena of highly stripped ions in the range Z = 6 to 35 were studied. Charge-transfer and multiple-electron-loss cross sections were determined. Absolute x-ray-production cross sections for incident heavy ions were measured. 10 figures, 1 table

  1. Variable laser attenuator

    Science.gov (United States)

    Foltyn, Stephen R.

    1988-01-01

    The disclosure relates to low loss, high power variable attenuators comprng one or more transmissive and/or reflective multilayer dielectric filters. The attenuator is particularly suitable to use with unpolarized lasers such as excimer lasers. Beam attenuation is a function of beam polarization and the angle of incidence between the beam and the filter and is controlled by adjusting the angle of incidence the beam makes to the filter or filters. Filters are selected in accordance with beam wavelength.

  2. X-Ray Form Factor, Attenuation and Scattering Tables

    Science.gov (United States)

    SRD 66 X-Ray Form Factor, Attenuation and Scattering Tables (Web, free access)   This database collects tables and graphs of the form factors, the photoabsorption cross section, and the total attenuation coefficient for any element (Z <= 92).

  3. Free radical hydrogen atom abstraction from saturated hydrocarbons: A crossed-molecular-beams study of the reaction Cl + C{sub 3}H{sub 8} {yields} HCl + C{sub 3}H{sub 7}

    Energy Technology Data Exchange (ETDEWEB)

    Blank, D.A.; Hemmi, N.; Suits, A.G.; Lee, Y.T. [Lawrence Berkeley National Lab., CA (United States)

    1997-04-01

    The abstraction of hydrogen atoms from saturated hydrocarbons are reactions of fundamental importance in combustion as well as often being the rate limiting step in free radical substitution reactions. The authors have begun studying these reactions under single collision conditions using the crossed molecular beam technique on beamline 9.0.2.1, utilizing VUV undulator radiation to selectively ionize the scattered hydrocarbon free radical products (C{sub x}H{sub 2x+1}). The crossed molecular beam technique involves two reactant molecular beams fixed at 90{degrees}. The molecular beam sources are rotatable in the plane defined by the two beams. The scattered neutral products travel 12.0 cm where they are photoionized using the VUV undulator radiation, mass selected, and counted as a function of time. In the authors initial investigations they are using halogen atoms as protypical free radicals to abstract hydrogen atoms from small alkanes. Their first study has been looking at the reaction of Cl + propane {r_arrow} HCl + propyl radical. In their preliminary efforts the authors have measured the laboratory scattering angular distribution and time of flight spectra for the propyl radical products at collision energies of 9.6 kcal/mol and 14.9 kcal/mol.

  4. Comparison of quantum mechanical and classical trajectory calculations of cross sections for ion-atom impact ionization of negative - and positive -ions for heavy ion fusion applications

    CERN Document Server

    Kaganovich, I D; Davidson, R C; Kaganovich, Igor D.; Startsev, Edward A.; Davidson, Ronald C.

    2003-01-01

    Stripping cross sections in nitrogen have been calculated using the classical trajectory approximation and the Born approximation of quantum mechanics for the outer shell electrons of 3.2GeV I$^{-}$ and Cs$^{+}$ ions. A large difference in cross section, up to a factor of six, calculated in quantum mechanics and classical mechanics, has been obtained. Because at such high velocities the Born approximation is well validated, the classical trajectory approach fails to correctly predict the stripping cross sections at high energies for electron orbitals with low ionization potential.

  5. Comparison of quantum mechanical and classical trajectory calculations of cross sections for ion-atom impact ionization of negative - and positive -ions for heavy ion fusion applications

    OpenAIRE

    Kaganovich, Igor D.; Startsev, Edward A.; Davidson, Ronald C.

    2003-01-01

    Stripping cross sections in nitrogen have been calculated using the classical trajectory approximation and the Born approximation of quantum mechanics for the outer shell electrons of 3.2GeV I$^{-}$ and Cs$^{+}$ ions. A large difference in cross section, up to a factor of six, calculated in quantum mechanics and classical mechanics, has been obtained. Because at such high velocities the Born approximation is well validated, the classical trajectory approach fails to correctly predict the stri...

  6. Landing gear noise attenuation

    Science.gov (United States)

    Moe, Jeffrey W. (Inventor); Whitmire, Julia (Inventor); Kwan, Hwa-Wan (Inventor); Abeysinghe, Amal (Inventor)

    2011-01-01

    A landing gear noise attenuator mitigates noise generated by airframe deployable landing gear. The noise attenuator can have a first position when the landing gear is in its deployed or down position, and a second position when the landing gear is in its up or stowed position. The noise attenuator may be an inflatable fairing that does not compromise limited space constraints associated with landing gear retraction and stowage. A truck fairing mounted under a truck beam can have a compliant edge to allow for non-destructive impingement of a deflected fire during certain conditions.

  7. Multiple-cascade model for the filling of hollow Ne atoms moving below an Al surface

    International Nuclear Information System (INIS)

    Analytic expressions for a multiple-cascade model were derived to study the filling of L and K vacancies of hollow Ne atoms moving in shallow layers of an Al surface. The model requires cross sections for charge transfer into the L shell of the projectile that were determined from molecular-orbital calculations including screening effects of hollow atoms and asymptotic solid-state energies. The analysis accounts for mechanisms of Landau-Zener curve crossing and Fano-Lichten promotion. To describe the transport of the electrons within the solid, absorption and buildup effects were taken into account. The results from the cascade model show good agreement with angular distributions of Ne K Auger electrons recently measured. Attenuation effects were found to produce shifts in the K Auger spectra at varying observation angles. The significant difference previously observed for the mean L-shell occupation numbers during L and K Auger emission is explained by the present model

  8. Crossed-beam reaction of carbon atoms with hydrocarbon molecules. V. Chemical dynamics of n-C4H3 formation from reaction of C(3Pj) with allene, H2CCCH2(X 1A1)

    Science.gov (United States)

    Kaiser, R. I.; Mebel, A. M.; Chang, A. H. H.; Lin, S. H.; Lee, Y. T.

    1999-06-01

    The crossed molecular beams technique was employed to investigate the reaction between ground state carbon atoms, C(3Pj), and allene, H2CCCH2(X 1A1), at two averaged collision energies of 19.6 and 38.8 kJ mol-1. Product angular distributions and time-of-flight spectra of C4H3 were recorded. Forward-convolution fitting of the data yields weakly polarized center-of-mass angular flux distributions isotropic at lower, but forward scattered with respect to the carbon beam at a higher collision energy. The maximum translational energy release and the angular distributions combined with ab initio and RRKM calculations are consistent with the formation of the n-C4H3 radical in its electronic ground state. The channel to the i-C4H3 isomer contributes less than 1.5%. Reaction dynamics inferred from the experimental data indicate that the carbon atom attacks the π-orbitals of the allenic carbon-carbon double bond barrierless via a loose, reactant-like transition state located at the centrifugal barrier. The initially formed cyclopropylidene derivative rotates in a plane almost perpendicular to the total angular momentum vector around its C-axis and undergoes ring opening to triplet butatriene. At higher collision energy, the butatriene complex decomposes within 0.6 ps via hydrogen emission to form the n-C4H3 isomer and atomic hydrogen through an exit transition state located 9.2 kJ mol-1 above the products. The explicit identification of the n-C4H3 radical under single collision represents a further example of a carbon-hydrogen exchange in reactions of ground state carbon atoms with unsaturated hydrocarbons. This channel opens a barrierless route to synthesize extremely reactive hydrocarbon radicals in combustion processes, interstellar chemistry, and hydrocarbon-rich atmospheres of Jupiter, Saturn, Titan, as well as Triton.

  9. A crossed molecular beam and ab-initio investigation of the reaction of boron monoxide (BO; X2Σ+) with methylacetylene (CH3CCH; X1A1): competing atomic hydrogen and methyl loss pathways.

    Science.gov (United States)

    Maity, Surajit; Parker, Dorian S N; Dangi, Beni B; Kaiser, Ralf I; Fau, Stefan; Perera, Ajith; Bartlett, Rodney J

    2013-11-21

    The gas-phase reaction of boron monoxide ((11)BO; X(2)Σ(+)) with methylacetylene (CH3CCH; X(1)A1) was investigated experimentally using crossed molecular beam technique at a collision energy of 22.7 kJ mol(-1) and theoretically using state of the art electronic structure calculation, for the first time. The scattering dynamics were found to be indirect (complex forming reaction) and the reaction proceeded through the barrier-less formation of a van-der-Waals complex ((11)BOC3H4) followed by isomerization via the addition of (11)BO(X(2)Σ(+)) to the C1 and/or C2 carbon atom of methylacetylene through submerged barriers. The resulting (11)BOC3H4 doublet radical intermediates underwent unimolecular decomposition involving three competing reaction mechanisms via two distinct atomic hydrogen losses and a methyl group elimination. Utilizing partially deuterated methylacetylene reactants (CD3CCH; CH3CCD), we revealed that the initial addition of (11)BO(X(2)Σ(+)) to the C1 carbon atom of methylacetylene was followed by hydrogen loss from the acetylenic carbon atom (C1) and from the methyl group (C3) leading to 1-propynyl boron monoxide (CH3CC(11)BO) and propadienyl boron monoxide (CH2CCH(11)BO), respectively. Addition of (11)BO(X(2)Σ(+)) to the C1 of methylacetylene followed by the migration of the boronyl group to the C2 carbon atom and/or an initial addition of (11)BO(X(2)Σ(+)) to the sterically less accessible C2 carbon atom of methylacetylene was followed by loss of a methyl group leading to the ethynyl boron monoxide product (HCC(11)BO) in an overall exoergic reaction (78 ± 23 kJ mol(-1)). The branching ratios of these channels forming CH2CCH(11)BO, CH3CC(11)BO, and HCC(11)BO were derived to be 4 ± 3%, 40 ± 5%, and 56 ± 15%, respectively; these data are in excellent agreement with the calculated branching ratios using statistical RRKM theory yielding 1%, 38%, and 61%, respectively. PMID:23651442

  10. A crossed molecular beam and ab-initio investigation of the reaction of boron monoxide (BO; X2Σ+) with methylacetylene (CH3CCH; X1A1): competing atomic hydrogen and methyl loss pathways.

    Science.gov (United States)

    Maity, Surajit; Parker, Dorian S N; Dangi, Beni B; Kaiser, Ralf I; Fau, Stefan; Perera, Ajith; Bartlett, Rodney J

    2013-11-21

    The gas-phase reaction of boron monoxide ((11)BO; X(2)Σ(+)) with methylacetylene (CH3CCH; X(1)A1) was investigated experimentally using crossed molecular beam technique at a collision energy of 22.7 kJ mol(-1) and theoretically using state of the art electronic structure calculation, for the first time. The scattering dynamics were found to be indirect (complex forming reaction) and the reaction proceeded through the barrier-less formation of a van-der-Waals complex ((11)BOC3H4) followed by isomerization via the addition of (11)BO(X(2)Σ(+)) to the C1 and/or C2 carbon atom of methylacetylene through submerged barriers. The resulting (11)BOC3H4 doublet radical intermediates underwent unimolecular decomposition involving three competing reaction mechanisms via two distinct atomic hydrogen losses and a methyl group elimination. Utilizing partially deuterated methylacetylene reactants (CD3CCH; CH3CCD), we revealed that the initial addition of (11)BO(X(2)Σ(+)) to the C1 carbon atom of methylacetylene was followed by hydrogen loss from the acetylenic carbon atom (C1) and from the methyl group (C3) leading to 1-propynyl boron monoxide (CH3CC(11)BO) and propadienyl boron monoxide (CH2CCH(11)BO), respectively. Addition of (11)BO(X(2)Σ(+)) to the C1 of methylacetylene followed by the migration of the boronyl group to the C2 carbon atom and/or an initial addition of (11)BO(X(2)Σ(+)) to the sterically less accessible C2 carbon atom of methylacetylene was followed by loss of a methyl group leading to the ethynyl boron monoxide product (HCC(11)BO) in an overall exoergic reaction (78 ± 23 kJ mol(-1)). The branching ratios of these channels forming CH2CCH(11)BO, CH3CC(11)BO, and HCC(11)BO were derived to be 4 ± 3%, 40 ± 5%, and 56 ± 15%, respectively; these data are in excellent agreement with the calculated branching ratios using statistical RRKM theory yielding 1%, 38%, and 61%, respectively.

  11. Measurement of K-Shell Ionization Cross Sections of Cr, Ni and Cu Atoms by 7.5-25 keV Electron Impact

    Institute of Scientific and Technical Information of China (English)

    安竹; 唐昶环; 罗正明

    2001-01-01

    The K-shell ionization cross sections of Cr, Ni and Cu elements by 7.5-25 keV electron impact have been measured.The experimental data have also been compared with the theoretical predictions of the Hippler and Mayol-Salvat models. In general, it seems that the Mayol-Salvat model can provide a better description to our experimental data.

  12. Atom Chips

    CERN Document Server

    Folman, R; Cassettari, D; Hessmo, B; Maier, T; Schmiedmayer, J; Folman, Ron; Krüger, Peter; Cassettari, Donatella; Hessmo, Björn; Maier, Thomas

    1999-01-01

    Atoms can be trapped and guided using nano-fabricated wires on surfaces, achieving the scales required by quantum information proposals. These Atom Chips form the basis for robust and widespread applications of cold atoms ranging from atom optics to fundamental questions in mesoscopic physics, and possibly quantum information systems.

  13. Ge Implantation to Improve Crystallinity and Productivity for Solid Phase Epitaxy Prepared by Atomic Mass Unit Cross Contamination-Free Technique

    Science.gov (United States)

    Lee, Kong-Soo; Yoo, Dae-Han; Han, Jae-Jong; Son, Gil-Hwan; Lee, Chang-Hun; Noh, Ju-Hee; Kim, Seok-Jae; Kim, Yong-Kwon; You, Young-Sub; Hyung, Yong-Woo; Lee, Hyeon-Deok

    2006-11-01

    Germanium (Ge) ion implantation was investigated for crystallinity enhancement during solid phase epitaxial (SPE) regrowth. Electron back-scatter diffraction (EBSD) measurement showed numerical increase of 19% of (100) signal, which might be due to the effect of pre-amorphization implantation (PAI) on silicon layer. On the other hand, electrical property such as off-leakage current of n-channel metal oxide semiconductor (NMOS) transistor degraded in specific regions of wafers. It was confirmed that arsenic (As) atoms were incorporated into channel area during Ge ion implantation. Since the equipment for Ge PAI was using several source gases such as BF3 and AsH3, atomic mass unit (AMU) contamination during PAI of Ge with AMU 74 caused the incorporation of As with AMU 75 which resided in arc-chamber and other parts of the equipment. It was effective to use Ge isotope of AMU 72 to suppress AMU contamination. It was effective to use enriched Ge source gas with AMU 72 in order to improve productivity.

  14. Planetary Ices Attenuation Properties

    Science.gov (United States)

    McCarthy, Christine; Castillo-Rogez, Julie C.

    In this chapter, we review the topic of energy dissipation in the context of icy satellites experiencing tidal forcing. We describe the physics of mechanical dissipation, also known as attenuation, in polycrystalline ice and discuss the history of laboratory methods used to measure and understand it. Because many factors - such as microstructure, composition and defect state - can influence rheological behavior, we review what is known about the mechanisms responsible for attenuation in ice and what can be inferred from the properties of rocks, metals and ceramics. Since attenuation measured in the laboratory must be carefully scaled to geologic time and to planetary conditions in order to provide realistic extrapolation, we discuss various mechanical models that have been used, with varying degrees of success, to describe attenuation as a function of forcing frequency and temperature. We review the literature in which these models have been used to describe dissipation in the moons of Jupiter and Saturn. Finally, we address gaps in our present knowledge of planetary ice attenuation and provide suggestions for future inquiry.

  15. Cross-Sectional Conductive Atomic Force Microscopy of CdTe/CdS Solar Cells: Effects of Etching and Back-Contact Processes; Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Moutinho, H. R.; Dhere, R. G.; Jiang, C.-S.; Gessert, T. A.; Duda, A. M.; Young, M.; Metzger, W. K.; Li, X.; Al-Jassim, M. M.

    2006-05-01

    We investigated the effects of the etching processes using bromine and nitric-phosphoric acid solutions, as well as of Cu, in the bulk electrical conductivity of CdTe/CdS solar cells using conductive atomic force microscopy (C-AFM). Although the etching process can create a conductive layer on the surface of the CdTe, the layer is very shallow. In contrast, the addition of a thin layer of Cu to the surface creates a conductive layer inside the CdTe that is not uniform in depth, is concentrated at grains boundaries, and may short circuit the device if the CdTe is too thin. The etching process facilitates the Cu diffusion and results in thicker conductive layers. The existence of this inhomogeneous conductive layer directly affects the current transport and is probably the reason for needing thick CdTe in these devices.

  16. Frequency Dependent Attenuation Revisited

    CERN Document Server

    Richard, Kowar; Xavier, Bonnefond

    2009-01-01

    The work is inspired by thermo-and photoacoustic imaging, where recent efforts are devoted to take into account attenuation and varying wave speed parameters. In this paper we study causal equations describing propagation of attenuated pressure waves. We review standard models like frequency power laws and and the thermo-viscous equation. The lack of causality of standard models in the parameter range relevant for photoacoustic imaging requires to derive novel equations. The main ingredients for deriving causal equations are the Kramers-Kronig relation and the mathematical concept of linear system theory. The theoretical results of this work are underpined by numerical experiments.

  17. Bonds Between Atoms.

    Science.gov (United States)

    Holden, Alan

    The field of inquiry into how atoms are bonded together to form molecules and solids crosses the borderlines between physics and chemistry encompassing methods characteristic of both sciences. At one extreme, the inquiry is pursued with care and rigor into the simplest cases; at the other extreme, suggestions derived from the more careful inquiry…

  18. Inulin crystal initiation via a glucose-fructose cross-link of adjacent polymer chains: atomic force microscopy and static molecular modelling.

    Science.gov (United States)

    Cooper, Peter D; Rajapaksha, K Harinda; Barclay, Thomas G; Ginic-Markovic, Milena; Gerson, Andrea R; Petrovsky, Nikolai

    2015-03-01

    Semi-crystalline microparticles of inulin (MPI) have clinical utility as potent human vaccine adjuvants but their relevant surface structure and crystal assembly remain undefined. We show inulin crystal surfaces to resemble multi-layered, discoid radial spherulites resulting from very rapid formation of complex tertiary structures, implying directed crystal initiation. Physical and in silico molecular modelling of unit cells confirm steric feasibility of initiation by hydrogen-bonded cross-linking of terminal glucose to a fructose of another chain, mimicking bonding in sucrose crystals. A strong, chelate-like dual H-bond is proposed to compel the known antiparallel alignment of inulin chains. Such cross-linking would require one extra fructose per chain in the native inulin crystal, as observed. Completion of five H-bonded internal ring-domains would 'lock in' each new 6-fructose structural unit of each antiparallel helix pair to create a new isoform. All known properties of inulin isoforms follow readily from these concepts.

  19. XCOM: Photon Cross Sections Database

    Science.gov (United States)

    SRD 8 XCOM: Photon Cross Sections Database (Web, free access)   A web database is provided which can be used to calculate photon cross sections for scattering, photoelectric absorption and pair production, as well as total attenuation coefficients, for any element, compound or mixture (Z energies from 1 keV to 100 GeV.

  20. Quantum synapse for cold atoms

    CERN Document Server

    Kouzaev, G A

    2007-01-01

    In this paper, the quantum synaptic effect is studied that arisen in the system of two crossed wires excited by the static (DC) and radio-frequency (RF) currents. The potential barrier between the two orthogonal atom streams is controlled electronically and the atoms can be transferred from one wire to another under certain critical values of the RF and DC currents. The results are interesting in the study of quantum interferometry and quantum registering of cold atoms.

  1. Is there seismic attenuation in the mantle?

    Science.gov (United States)

    Ricard, Y.; Durand, S.; Montagner, J.-P.; Chambat, F.

    2014-02-01

    The small scale heterogeneity of the mantle is mostly due to the mixing of petrological heterogeneities by a smooth but chaotic convection and should consist in a laminated structure (marble cake) with a power spectrum S(k) varying as 1/k, where k is the wavenumber of the anomalies. This distribution of heterogeneities during convective stirring with negligible diffusion, called Batchelor regime is documented by fluid dynamic experiments and corresponds to what can be inferred from geochemistry and seismic tomography. This laminated structure imposes density, seismic velocity and potentially, anisotropic heterogeneities with similar 1/k spectra. A seismic wave of wavenumber k0 crossing such a medium is partly reflected by the heterogeneities and we show that the scattered energy is proportional to k0S(2k0). The reduction of energy for the propagating wave appears therefore equivalent to a quality factor 1/Q∝k0S(2k0). With the specific 1/k spectrum of the mantle, the resulting apparent attenuation should therefore be frequency independent. We show that the total contribution of 6-9% RMS density, velocity and anisotropy would explain the observed S and P attenuation of the mantle. Although these values are large, they are not unreasonable and we discuss how they depend on the range of frequencies over which the attenuation is explained. If such a level of heterogeneity were present, most of the attenuation of the Earth would be due to small scale scattering by laminations, not by intrinsic dissipation. Intrinsic dissipation must certainly exist but might correspond to a larger, yet unobserved Q. This provocative result would explain the very weak frequency dependence of the attenuation, and the fact that bulk attenuation seems negligible, two observations that have been difficult to explain for 50 years.

  2. Atom cooling with an atom-optical diode on a ring

    OpenAIRE

    Ruschhaupt, A.; Muga, J. G.

    2008-01-01

    We propose a method to cool atoms on a ring by combining an atom diode -a laser valve for one-way atomic motion which induces robust internal state excitation- and a trap. We demonstrate numerically that the atom is efficiently slowed down at each diode crossing, and it is finally trapped when its velocity is below the trap threshold.

  3. Atom chips

    CERN Document Server

    Reichel, Jakob

    2010-01-01

    This book provides a stimulating and multifaceted picture of a rapidly developing field. The first part reviews fundamentals of atom chip research in tutorial style, while subsequent parts focus on the topics of atom-surface interaction, coherence on atom chips, and possible future directions of atom chip research. The articles are written by leading researchers in the field in their characteristic and individual styles.

  4. Dynamics of the Q2Π1u(1 ) state studied from the isotope effect on the cross sections for the formation of the 2 p atom pair in the photoexcitation of H2 and D2

    Science.gov (United States)

    Hosaka, Kouichi; Shiino, Kennichi; Nakanishi, Yuko; Odagiri, Takeshi; Kitajima, Masashi; Kouchi, Noriyuki

    2016-06-01

    The absolute values of the cross section for formation of a 2 p atom pair in the photoexcitation of H2 and D2 are measured against the incident photon energy in the range of doubly excited states by means of the coincidence detection of two Lyman-α photons. The cross-section curves are explained only by the contribution of the doubly excited Q2Π1u(1 ) state. The isotope effect on the oscillator strengths of 2 p +2 p pair formation for H2 and D2 from the Q2Π1u(1 ) state is almost the same as that on the oscillator strengths of 2 s +2 p pair formation from the Q2Π1u(1 ) state obtained by our group [T. Odagiri et al., Phys. Rev. A 84, 053401 (2011), 10.1103/PhysRevA.84.053401]. This channel independence indicates that both isotope effects are dominated by the early dynamics of the Q2Π1u(1 ) state, before reaching the branching point into 2 p +2 p pair formation and 2 s +2 p pair formation.

  5. Atomic Physics

    CERN Document Server

    Foot, Christopher J

    2007-01-01

    This text will thoroughly update the existing literature on atomic physics. Intended to accompany an advanced undergraduate course in atomic physics, the book will lead the students up to the latest advances and the applications to Bose-Einstein Condensation of atoms, matter-wave inter-ferometry and quantum computing with trapped ions. The elementary atomic physics covered in the early chapters should be accessible to undergraduates when they are first introduced to the subject. To complement. the usual quantum mechanical treatment of atomic structure the book strongly emphasizes the experimen

  6. Atom interferometry

    International Nuclear Information System (INIS)

    We will first present a development of the fundamental principles of atom interferometers. Next we will discuss a few of the various methods now available to split and recombine atomic De Broglie waves, with special emphasis on atom interferometers based on optical pulses. We will also be particularly concerned with high precision interferometers with long measurement times such those made with atomic fountains. The application of atom interferometry to the measurement of the acceleration due to gravity will be detailed. We will also develop the atom interferometry based on adiabatic transfer and we will apply it to the measurement of the photon recoil in the case of the Doppler shift of an atomic resonance caused by the momentum recoil from an absorbed photon. Finally the outlook of future developments will be given. (A.C.)

  7. Polarized atomic hydrogen beam

    Energy Technology Data Exchange (ETDEWEB)

    Chan, N.; Crowe, D.M.; Lubell, M.S.; Tang, F.C.; Vasilakis, A.; Mulligan, F.J.; Slevin, J.

    1988-12-01

    We describe the design and operating characteristics of a simple polarized atomic hydrogen beam particularly suitable for applications to crossed beams experiments. In addition to experimental measurements, we present the results of detailed computer models, using Monte-Carlo ray tracing techniques, optical analogs, and phase-space methods, that not only provide us with a confirmation of our measurement, but also allow us to characterize the density, polarization, and atomic fraction of the beam at all points along its path. As a subsidiary result, we also present measurements of the relative and absolute efficiencies of the V/G Supavac mass analyzer for masses 1 and 2.

  8. Control algorithms for dynamic attenuators

    Energy Technology Data Exchange (ETDEWEB)

    Hsieh, Scott S., E-mail: sshsieh@stanford.edu [Department of Radiology, Stanford University, Stanford, California 94305 and Department of Electrical Engineering, Stanford University, Stanford, California 94305 (United States); Pelc, Norbert J. [Department of Radiology, Stanford University, Stanford California 94305 and Department of Bioengineering, Stanford University, Stanford, California 94305 (United States)

    2014-06-15

    Purpose: The authors describe algorithms to control dynamic attenuators in CT and compare their performance using simulated scans. Dynamic attenuators are prepatient beam shaping filters that modulate the distribution of x-ray fluence incident on the patient on a view-by-view basis. These attenuators can reduce dose while improving key image quality metrics such as peak or mean variance. In each view, the attenuator presents several degrees of freedom which may be individually adjusted. The total number of degrees of freedom across all views is very large, making many optimization techniques impractical. The authors develop a theory for optimally controlling these attenuators. Special attention is paid to a theoretically perfect attenuator which controls the fluence for each ray individually, but the authors also investigate and compare three other, practical attenuator designs which have been previously proposed: the piecewise-linear attenuator, the translating attenuator, and the double wedge attenuator. Methods: The authors pose and solve the optimization problems of minimizing the mean and peak variance subject to a fixed dose limit. For a perfect attenuator and mean variance minimization, this problem can be solved in simple, closed form. For other attenuator designs, the problem can be decomposed into separate problems for each view to greatly reduce the computational complexity. Peak variance minimization can be approximately solved using iterated, weighted mean variance (WMV) minimization. Also, the authors develop heuristics for the perfect and piecewise-linear attenuators which do not requirea priori knowledge of the patient anatomy. The authors compare these control algorithms on different types of dynamic attenuators using simulated raw data from forward projected DICOM files of a thorax and an abdomen. Results: The translating and double wedge attenuators reduce dose by an average of 30% relative to current techniques (bowtie filter with tube current

  9. Atomic and molecular science with synchrotron radiation

    International Nuclear Information System (INIS)

    This paper discusses the following topics: electron correlation in atoms; atomic innershell excitation and decay mechanisms; timing experiments; x-ray scattering; properties of ionized species; electronic properties of actinide atoms; total photon-interaction cross sections; and molecular physics. 66 refs

  10. "Zipped Synthesis" by Cross-Metathesis Provides a Cystathionine β-Synthase Inhibitor that Attenuates Cellular H2S Levels and Reduces Neuronal Infarction in a Rat Ischemic Stroke Model.

    Science.gov (United States)

    McCune, Christopher D; Chan, Su Jing; Beio, Matthew L; Shen, Weijun; Chung, Woo Jin; Szczesniak, Laura M; Chai, Chou; Koh, Shu Qing; Wong, Peter T-H; Berkowitz, David B

    2016-04-27

    The gaseous neuromodulator H2S is associated with neuronal cell death pursuant to cerebral ischemia. As cystathionine β-synthase (CBS) is the primary mediator of H2S biogenesis in the brain, it has emerged as a potential target for the treatment of stroke. Herein, a "zipped" approach by alkene cross-metathesis into CBS inhibitor candidate synthesis is demonstrated. The inhibitors are modeled after the pseudo-C 2-symmetric CBS product (l,l)-cystathionine. The "zipped" concept means only half of the inhibitor needs be constructed; the two halves are then fused by olefin cross-metathesis. Inhibitor design is also mechanism-based, exploiting the favorable kinetics associated with hydrazine-imine interchange as opposed to the usual imine-imine interchange. It is demonstrated that the most potent "zipped" inhibitor 6S reduces H2S production in SH-SY5Y cells overexpressing CBS, thereby reducing cell death. Most importantly, CBS inhibitor 6S dramatically reduces infarct volume (1 h post-stroke treatment; ∼70% reduction) in a rat transient middle cerebral artery occlusion model for ischemia. PMID:27163055

  11. “Zipped Synthesis” by Cross-Metathesis Provides a Cystathionine β-Synthase Inhibitor that Attenuates Cellular H2S Levels and Reduces Neuronal Infarction in a Rat Ischemic Stroke Model

    Science.gov (United States)

    2016-01-01

    The gaseous neuromodulator H2S is associated with neuronal cell death pursuant to cerebral ischemia. As cystathionine β-synthase (CBS) is the primary mediator of H2S biogenesis in the brain, it has emerged as a potential target for the treatment of stroke. Herein, a “zipped” approach by alkene cross-metathesis into CBS inhibitor candidate synthesis is demonstrated. The inhibitors are modeled after the pseudo-C2-symmetric CBS product (l,l)-cystathionine. The “zipped” concept means only half of the inhibitor needs be constructed; the two halves are then fused by olefin cross-metathesis. Inhibitor design is also mechanism-based, exploiting the favorable kinetics associated with hydrazine-imine interchange as opposed to the usual imine–imine interchange. It is demonstrated that the most potent “zipped” inhibitor 6S reduces H2S production in SH-SY5Y cells overexpressing CBS, thereby reducing cell death. Most importantly, CBS inhibitor 6S dramatically reduces infarct volume (1 h post-stroke treatment; ∼70% reduction) in a rat transient middle cerebral artery occlusion model for ischemia. PMID:27163055

  12. Atomic physics

    International Nuclear Information System (INIS)

    Research activities in atomic physics at Lawrence Berkeley Laboratory during 1976 are described. Topics covered include: experiments on stored ions; test for parity violation in neutral weak currents; energy conservation and astrophysics; atomic absorption spectroscopy, atomic and molecular detectors; theoretical studies of quantum electrodynamics and high-z ions; atomic beam magnetic resonance; radiative decay from the 23Po,2 levels of helium-like argon; quenching of the metastable 2S/sub 1/2/ state of hydrogen-like argon in an external electric field; and lifetime of the 23Po level of helium-like krypton

  13. Atomic physics

    CERN Document Server

    Born, Max

    1989-01-01

    The Nobel Laureate's brilliant exposition of the kinetic theory of gases, elementary particles, the nuclear atom, wave-corpuscles, atomic structure and spectral lines, electron spin and Pauli's principle, quantum statistics, molecular structure and nuclear physics. Over 40 appendices, a bibliography, numerous figures and graphs.

  14. 正电子碰撞Ag,In,Sn原子L壳层电离截面的理论计算%Theoretical calculation of L-shell ionization cross section of Ag, In, and Sn atoms by positron impact

    Institute of Scientific and Technical Information of China (English)

    何彪; 何建新; 易有根; 江少恩; 郑志坚

    2011-01-01

    在David Botz分析模型的基础上,综合考虑正电子及电子碰撞电离的库仑效应和电子交换效应,引入离子效应和相对论效应修正因子,计算了Ag,In,Sn原子的L壳层电离截面.计算结果表明,引入了修正因子的计算结果明显优于平面波波恩近似和扭曲波波恩近似的计算结果,并和最近文献的实验值符合得较好.其计算结果可为激光等离子体模拟提供准确参数.%Based on the analytical formulas of David Botz, considering the Coulomb effect and exchange effect in the ionization by positron and electron impact, the total cross sections of positron-impact Lshell ionization of Ag? In, Sn atomic are calculated by incorporating both ionic and relativistic corrections in it. In comparison with the quantum mechanical predictions of plane-wave and distorted-wave Born approximations, it is found that the improved analytical formulas are in better agreement with the experimental results. The calculated results can be used to simlate the laser plasma.

  15. The determination of lead in ore slurries by gamma-ray attenuation

    International Nuclear Information System (INIS)

    The preferential attenuation of low energy gamma radiation by high atomic number elements has been applied to the determination of the lead content of ore slurries containing up to 50 wt% solids. For ores containing between about 0.16 and 10% lead, a linear relationship was found between lead content and gamma attenuation. The determination of the solids content (density) of the slurries, based on the attenuation of high energy gamma radiation, has also been investigated, and was shown to be effectively independent of the atomic number of the absorber. An equation is given that predicts the effect of changes in density and elemental composition in the slurry on the attenuation of gamma radiation. Also, an analysis of the errors in both gamma-ray attenuation methods is presented. (author)

  16. Attenuation of neutrons through ducts and labyrinths

    CERN Document Server

    Mauro, Egidio

    2009-01-01

    Monte Carlo simulations have been performed for the attenuation of neutron radiation produced at proton accelerators through ducts and labyrinths of various design, and the results are compared with the predictions made by analytical expressions available in the literature. The results show that the so-called universal transmission curves are an appropriate and simple tool applicable in many situations, when the radiation source is not in direct view of the duct mouth. This is not the case for point sources located in front of the duct. The simulations showed that it is not possible to apply the same models because the transmission factor is strongly dependent on the cross-sectional area of the duct. A universal expression has been derived to estimate the neutron transmission through a straight duct of length d and cross-sectional area A in direct view of the source, which only depends on A and on a small set of numerical coefficients.

  17. A polarized atomic hydrogen beam

    OpenAIRE

    Chan, N; Crowe, D.M.; Lubell, M. S.; Tang, F.C.; Vasilakis, A.; Mulligan, F. J.; Slevin, J.

    1988-01-01

    We describe the design and operating characteristics of a simple polarized atomic hydrogen beam particularly suitable for applications to crossed beams experiments. In addition to experimental measurements, we present the results of detailed computer models, using Monte-Carlo ray tracing techniques, optical analogs, and phase-space methods, that not only provide us with a confirmation of our measurement, but also allow us to characterize the density, polarization, and atomic fraction of the b...

  18. Effective atomic number and electron density of amino acids within the energy range of 0.122-1.330 MeV

    Science.gov (United States)

    More, Chaitali V.; Lokhande, Rajkumar M.; Pawar, Pravina P.

    2016-08-01

    Photon attenuation coefficient calculation methods have been widely used to accurately study the properties of amino acids such as n-acetyl-L-tryptophan, n-acetyl-L-tyrosine, D-tryptophan, n-acetyl-L-glutamic acid, D-phenylalanine, and D-threonine. In this study, mass attenuation coefficients (μm) of these amino acids for 0.122-, 0.356-, 0.511-, 0.662-, 0.884-, 1.170, 1.275-, 1.330-MeV photons are determined using the radio-nuclides Co57, Ba133, Cs137, Na22, Mn54, and Co60. NaI (Tl) scintillation detection system was used to detect gamma rays with a resolution of 8.2% at 0.662 MeV. The calculated attenuation coefficient values were then used to determine total atomic cross sections (σt), molar extinction coefficients (ε), electronic cross sections (σe), effective atomic numbers (Zeff), and effective electron densities (Neff) of the amino acids. Theoretical values were calculated based on the XCOM data. Theoretical and experimental values are found to be in a good agreement (error<5%). The variations of μm, σt, ε, σe, Zeff, and Neff with energy are shown graphically. The values of μm, σt, ε, σe are higher at lower energies, and they decrease sharply as energy increases; by contrast, Zeff and Neff were found to be almost constant.

  19. Trapping atoms on a transparent permanent-magnet atom chip

    CERN Document Server

    Shevchenko, A; Jaakkola, A; Kaivola, M; Lindvall, T; Pfau, T; Tittonen, I

    2006-01-01

    We describe experiments on trapping of atoms in microscopic magneto-optical traps on an optically transparent permanent-magnet atom chip. The chip is made of magnetically hard ferrite-garnet material deposited on a dielectric substrate. The confining magnetic fields are produced by miniature magnetized patterns recorded in the film by magneto-optical techniques. We trap Rb atoms on these structures by applying three crossed pairs of counter-propagating laser beams in the conventional magneto-optical trapping (MOT) geometry. We demonstrate the flexibility of the concept in creation and in-situ modification of the trapping geometries through several experiments.

  20. Manipulating nanoscale atom-atom interactions with cavity QED

    CERN Document Server

    Pal, Arpita; Deb, Bimalendu

    2016-01-01

    We theoretically explore manipulation of interactions between excited and ground state atoms at nanoscale separations by cavity quantum electrodynamics (CQED). We develop an adiabatic molecular dressed state formalism and show that it is possible to generate Fano-Feshbach resonances between ground and long-lived excited-state atoms inside a cavity. The resonances are shown to arise due to non-adiabatic coupling near a pseudo-crossing between the dressed state potentials. We illustrate our results with a model study using fermionic $^{171}$Yb atoms in a two-modal cavity. Our study is important for manipulation of interatomic interactions at low energy by cavity field.

  1. Doping Scheme of Semiconducting Atomic Chains

    Science.gov (United States)

    Toshishige, Yamada; Saini, Subhash (Technical Monitor)

    1998-01-01

    Atomic chains, precise structures of atomic scale created on an atomically regulated substrate surface, are candidates for future electronics. A doping scheme for intrinsic semiconducting Mg chains is considered. In order to suppress the unwanted Anderson localization and minimize the deformation of the original band shape, atomic modulation doping is considered, which is to place dopant atoms beside the chain periodically. Group I atoms are donors, and group VI or VII atoms are acceptors. As long as the lattice constant is long so that the s-p band crossing has not occurred, whether dopant atoms behave as donors or acceptors is closely related to the energy level alignment of isolated atomic levels. Band structures are calculated for Br-doped (p-type) and Cs-doped (n-type) Mg chains using the tight-binding theory with universal parameters, and it is shown that the band deformation is minimized and only the Fermi energy position is modified.

  2. Observation of relativistic antihydrogen atoms

    Science.gov (United States)

    Blanford, Glenn Delfosse, Jr.

    1997-09-01

    An observation of relativistic antihydrogen atoms is reported in this dissertation. Experiment 862 at Fermi National Accelerator Laboratory observed antihydrogen atoms produced by the interaction of a circulating beam of high momentum (3 production is outlined within. The cross section corresponds to the process where a high momentum antiproton causes e+e/sp- pair creation near a nucleus with the e+ being captured by the antiproton. Antihydrogen is the first atom made exclusively of antimatter to be detected. The observation experiment's results are the first step towards an antihydrogen spectroscopy experiment which would measure the n = 2 Lamb shift and fine structure.

  3. Gamma and neutron attenuation behaviours of boron carbide–silicon carbide composites

    International Nuclear Information System (INIS)

    Highlights: • Gamma and neutron attenuation behaviours of B4C–SiC composites were investigated. • Increasing SiC ratio increases gamma attenuation behaviour of the B4C–SiC composites. • Increasing SiC ratio decrease attenuation behaviour of the B4C–SiC composites. • HVT values of the B4C–SiC composites were calculated for Cs-137, Co-60 and Pu–Be sources. • Experimental mass attenuation coefficient are compatible with theoretical (XCOM) values. - Abstract: In this study, the gamma and neutron attenuation behaviors of pure boron carbide and boron carbide–silicon carbide composites which include three different silicon carbide ratios (20%, 30%, and 40%) by volume were investigated against Cs-137, Co-60 gamma radioisotope sources and Pu–Be neutron source. Transmission technique was used in the experiments to investigate the gamma and neutron attenuation properties of the materials. Linear and mass attenuation coefficients of the samples were determined for 0.662 (Cs-137) and 1.25 MeV (Co-60) energetic gamma rays. In addition the total macroscopic cross-sections (∑T) were calculated for the materials against Pu–Be neutron source. Theoretical mass attenuation coefficients were calculated from XCOM computer code. The experimental and theoretical mass attenuation coefficients were compared and evaluated with each other. In addition half value thickness (HVT) calculations were carried out by using linear attenuation coefficients and total macroscopic cross-sections. The results showed that increasing silicon carbide ratio decreases HVTs against Cs-137 and Co-60 gamma radioisotope sources whereas increases HVTs against Pu–Be neutron source. The mass attenuation coefficients were compatible with the theoretical (XCOM) values. Increasing silicon carbide ratio in boron carbide–silicon carbide composites causes higher gamma attenuation and lower neutron attenuation values

  4. Atomic secrecy

    International Nuclear Information System (INIS)

    An article, The H-Bomb Secret: How We Got It, Why We're Telling It, by Howard Morland was to be published in The Progressive magazine in February, 1979. The government, after learning of the author's and the editors' intention to publish the article and failing to persuade them to voluntarily delete about 20% of the text and all of the diagrams showing how an H-bomb works, requested a court injunction against publication. Acting under the Atomic Energy Act of 1954, US District Court Judge Robert W. Warren granted the government's request on March 26. Events dealing with the case are discussed in this publication. Section 1, Progressive Hydrogen Bomb Case, is discussed under the following: Court Order Blocking Magazine Report; Origins of the Howard Morland Article; Author's Motives, Defense of Publication; and Government Arguments Against Disclosure. Section 2, Access to Atomic Data Since 1939, contains information on need for secrecy during World War II; 1946 Atomic Energy Act and its effects; Soviet A-Bomb and the US H-Bomb; and consequences of 1954 Atomic Energy Act. Section 3, Disputed Need for Atomic Secrecy, contains papers entitled: Lack of Studies on H-Bomb Proliferation; Administration's Position on H-Bombs; and National Security Needs vs Free Press

  5. Zitterbewegung in Cold Atoms

    Science.gov (United States)

    Penteado, Poliana; Egues, J. Carlos

    2013-03-01

    In condensed matter systems, the coupling between spatial and spin degrees of freedom through the spin-orbit (SO) interaction offers the possibility of manipulating the electron spin via its orbital motion. The proposal by Datta and Das of a `spin transistor' for example, highlights the use of the SO interaction to control the electron spin via electrical means. Recently, arrangements of crossed lasers and magnetic fields have been used to trap and cool atoms in optical lattices and also to create light-induced gauge potentials, which mimic the SO interactions in real solids. In this work, we investigate the Zitterbewegung in cold atoms by starting from the effective SO Hamiltonian derived in Ref.. Cross-dressed atoms as effective spins can provide a proper setting in which to observe this effect, as the relevant parameter range of SO strengths may be more easily attainable in this context. We find a variety of peculiar Zitterbewegung orbits in real and pseudo-spin spaces, e.g., cycloids and ellipses - all of which obtained with realistic parameters. This work is supported by FAPESP, CAPES and CNPq.

  6. Seismic attenuation in fractured media

    International Nuclear Information System (INIS)

    The prime objective of this paper is to quantitatively estimate seismic attenuation caused by fractures with different physical parameters. In seismic wave simulation, the fractured media are treated as the anisotropic media and fractures are represented by frequency-dependent elastic constants. Based on numerical experiments with three different parameters, namely viscosity, porosity and the Lamé parameters, this paper has the following observations. First, seismic attenuation is not affected by the viscosity within fractures, although it increases with the increase of porosity and decreases with the increase of the Lamé parameters within fractures. Among the latter two parameters, seismic attenuation is more sensitive to the Lamé parameters than to the porosity. Second, for the attenuation anisotropy, low frequencies have more anisotropic effect than high frequencies. For example, a 50 Hz wavefield has the strongest anisotropy effect if compared to 100 and 150 Hz wavefields. The attenuation anisotropy for low frequency (say 50 Hz) is more sensitive to the viscosity than the porosity and the Lamé parameters have the weakest effect among these three parameters. These observations suggest that low-frequency seismic attenuation, and especially the attenuation anisotropy in low frequency, would have great potential for fluid discrimination within fractured media. (paper)

  7. Atomic theories

    CERN Document Server

    Loring, FH

    2014-01-01

    Summarising the most novel facts and theories which were coming into prominence at the time, particularly those which had not yet been incorporated into standard textbooks, this important work was first published in 1921. The subjects treated cover a wide range of research that was being conducted into the atom, and include Quantum Theory, the Bohr Theory, the Sommerfield extension of Bohr's work, the Octet Theory and Isotopes, as well as Ionisation Potentials and Solar Phenomena. Because much of the material of Atomic Theories lies on the boundary between experimentally verified fact and spec

  8. Studies on effective atomic numbers and electron densities in amino acids and sugars in the energy range 30-1333 keV

    Energy Technology Data Exchange (ETDEWEB)

    Gowda, Shivalinge [Department of Studies in Physics, University of Mysore, Manasagangotri, Mysore 570 006 (India); Krishnaveni, S. [Department of Studies in Physics, University of Mysore, Manasagangotri, Mysore 570 006 (India); Gowda, Ramakrishna [Department of Studies in Physics, University of Mysore, Manasagangotri, Mysore 570 006 (India)]. E-mail: ramakrishnagowda@yahoo.com

    2005-10-15

    The effective atomic numbers and electron densities of the amino acids glycine, alanine, serine, valine, threonine, leucine, isoleucine, aspartic acid, lysine, glutamic acid, histidine, phenylalanine, arginine, tyrosine, tryptophane and the sugars arabinose, ribose, glucose, galactose, mannose, fructose, rhamnose, maltose, melibiose, melezitose and raffinose at the energies 30.8, 35.0, 81.0, 145, 276.4, 302.9, 356, 383.9, 661.6, 1173 and 1332.5 keV were calculated by using the measured total attenuation cross-sections. The interpolations of total attenuation cross-sections for photons of energy E in elements of atomic number Z was performed using the logarithmic regression analysis of the XCOM data in the photon energy region 30-1500 keV. The best-fit coefficients obtained by a piece wise interpolation method were used to find the effective atomic number and electron density of the compounds. These values are found to be in good agreement with the theoretical values calculated based on XCOM data.

  9. Atomic and molecular data for radiotherapy

    International Nuclear Information System (INIS)

    An Advisory Group Meeting devoted solely to review the atomic and molecular data needed for radiotherapy was held in Vienna from 13 to 16 June 1988. The following items as related to the atoms and molecules of human tissues were reviewed: Cross sections differential in energy loss for electrons and other charged particles. Secondary electron spectra, or differential ionization cross sections. Total cross sections for ionization and excitation. Subexcitation electrons. Cross sections for charged-particle collisions in condensed matter. Stopping power for low-energy electrons and ions. Initial yields of atomic and molecular ions and their excited states and electron degradation spectra. Rapid conversion of these initial ions and their excited states through thermal collisions with other atoms and molecules. Track-structure quantities. Other relevant data. Refs, figs and tabs

  10. Anomalous scattering factors of some rare earth elements evaluated using photon interaction cross-sections

    Indian Academy of Sciences (India)

    S B Appaji Gowda; M L Mallikarjuna; R Gowda; T K Umesh

    2003-09-01

    The real and imaginary parts, '() and ''() of the dispersion corrections to the forward Rayleigh scattering amplitude (also called anomalous scattering factors) for the elements La, Ce, Pr, Nd, Sm, Gd, Dy, Ho and Er, have been determined by a numerical evaluation of the dispersion integral that relates them through the optical theorem to the photoeffect cross-sections. The photoeffect cross-sections are derived from the total attenuation cross-section data set experimentally determined using high resolution high purity germanium detector in a narrow beam good geometry set-up for these elements in the photon energy range 5 to 1332 keV and reported earlier by the authors. Below 5 keV, Scofield’s photoeffect cross-sections compiled in XCOM program have been interpolated and used. Simple formulae for '' in terms of atomic number and energy have also been obtained. The data cover the energy region from 6 to 85 keV and atomic number from 57–68. The results obtained are found to agree fairly well with the other available data.

  11. Collision-produced atomic states

    International Nuclear Information System (INIS)

    The last 10-15 years have witnessed the development of a new, powerful class of experimental techniques for atomic collision studies, allowing partial or complete determination of the state of the atoms after a collision event, i.e. the full set of quantum-mechanical scattering amplitudes or - more generally - the density matrix describing the system. Evidently, such studies, involving determination of alignment and orientation parameters, provide much more severe tests of state-of-the-art scattering theories than do total or differential cross section measurements which depend on diagonal elements of the density matrix. The off-diagonal elements give us detailed information about the shape and dynamics of the atomic states. Therefore, close studies of collision-produced atomic states are currently leading to deeper insights into the fundamental physical mechanisms governing the dynamics of atomic collision events. The first part of the lectures deals with the language used to describe atomic states, while the second part presents a selection of recent results for model systems which display fundamental aspects of the collision physics in particularly instructive ways. I shall here restrict myself to atom-atom collisions. The discussion will be focused on states decaying by photon emission though most of the ideas can be easily modified to include electron emission as well. (orig./AH)

  12. Total and elastic electron scattering cross sections from Xe at intermediate and high energies

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, G [Instituto de Matematicas y Fisica Fundamental, CSIC, Serrano 123, 28006 Madrid (Spain); Pablos, J L de [Departamento de Fusion y Particulas Elementales, CIEMAT, Avenida Complutense 22, 28040 Madrid (Spain); Blanco, F [Departamento de Fisica Atomica Molecular y Nuclear, Universidad Complutense de Madrid, 28040 Madrid (Spain); Williart, A [Departamento de Fisica de los Materiales, UNED, Senda del Rey 9, 28040 Madrid (Spain)

    2002-11-28

    Experimental total electron scattering cross sections from Xe in the energy range 300-5000 eV have been obtained with experimental errors of about 3%. The method was based on the measurement of the attenuation of a linear electron beam through a Xe gas cell in combination with an electron spectroscopy technique to analyse the energy of the transmitted electrons. Differential and integral elastic cross sections have been calculated using a scattering potential method which includes relativistic effects. The consistency of our theoretical and experimental results is also discussed in the paper. Finally, analytical formulae depending on two parameters, namely the number of target electrons and the atomic polarizability, are given to reproduce the experimental data for Ne, Ar, Kr and Xe in the energy range 500-10 000 eV.

  13. The new approach of polarimetric attenuation correction for improving radar quantitative precipitation estimation(QPE)

    Science.gov (United States)

    Gu, Ji-Young; Suk, Mi-Kyung; Nam, Kyung-Yeub; Ko, Jeong-Seok; Ryzhkov, Alexander

    2016-04-01

    To obtain high-quality radar quantitative precipitation estimation data, reliable radar calibration and efficient attenuation correction are very important. Because microwave radiation at shorter wavelength experiences strong attenuation in precipitation, accounting for this attenuation is the essential work at shorter wavelength radar. In this study, the performance of different attenuation/differential attenuation correction schemes at C band is tested for two strong rain events which occurred in central Oklahoma. And also, a new attenuation correction scheme (combination of self-consistency and hot-spot concept methodology) that separates relative contributions of strong convective cells and the rest of the storm to the path-integrated total and differential attenuation is among the algorithms explored. A quantitative use of weather radar measurement such as rainfall estimation relies on the reliable attenuation correction. We examined the impact of attenuation correction on estimates of rainfall in heavy rain events by using cross-checking with S-band radar measurements which are much less affected by attenuation and compared the storm rain totals obtained from the corrected Z and KDP and rain gages in these cases. This new approach can be utilized at shorter wavelength radars efficiently. Therefore, it is very useful to Weather Radar Center of Korea Meteorological Administration preparing X-band research dual Pol radar network.

  14. Atomic data for fusion

    International Nuclear Information System (INIS)

    This report provides a handbook of recommended cross-section and rate-coefficient data for inelastic collisions between hydrogen, helium and lithium atoms, molecules and ions, and encompasses more than 400 different reactions of primary interest in fusion research. Published experimental and theoretical data have been collected and evaluated, and the recommended data are presented in tabular, graphical and parametrized form. Processes include excitation and spectral line emission, charge exchange, ionization, stripping, dissociation and particle interchange reactions. The range of collision energies is appropriate to applications in fusion-energy research

  15. Atomic data for fusion

    Energy Technology Data Exchange (ETDEWEB)

    Hunter, H.T.; Kirkpatrick, M.I.; Alvarez, I.; Cisneros, C.; Phaneuf, R.A. (eds.); Barnett, C.F.

    1990-07-01

    This report provides a handbook of recommended cross-section and rate-coefficient data for inelastic collisions between hydrogen, helium and lithium atoms, molecules and ions, and encompasses more than 400 different reactions of primary interest in fusion research. Published experimental and theoretical data have been collected and evaluated, and the recommended data are presented in tabular, graphical and parametrized form. Processes include excitation and spectral line emission, charge exchange, ionization, stripping, dissociation and particle interchange reactions. The range of collision energies is appropriate to applications in fusion-energy research.

  16. Positronium collisions with rare-gas atoms

    CERN Document Server

    Gribakin, G F; Wilde, R S; Fabrikant, I I

    2015-01-01

    We calculate elastic scattering of positronium (Ps) by the Xe atom using the recently developed pseudopotential method [Fabrikant I I and Gribakin G F 2014 Phys. Rev. A 90 052717] and review general features of Ps scattering from heavier rare-gas atoms: Ar, Kr and Xe. The total scattering cross section is dominated by two contributions: elastic scattering and Ps ionization (break-up). To calculate the Ps ionization cross sections we use the binary-encounter method for Ps collisions with an atomic target. Our results for the ionization cross section agree well with previous calculations carried out in the impulse approximation. Our total Ps-Xe cross section, when plotted as a function of the projectile velocity, exhibits similarity with the electron-Xe cross section for the collision velocities higher than 0.8 a.u., and agrees very well with the measurements at Ps velocities above 0.5 a.u.

  17. Attenuation of gamma-radiation by multilayer polymer disperse-filled structures

    International Nuclear Information System (INIS)

    The results of attenuation of gamma-radiation in multilayered structures containing polymer matrix and super-dispersed powders are presented. These structures, which represented as combination of layers with gradient of effective atomic number, reveal anisotropy of attenuation of low-energy gamma-radiation in normal direction relative to plane of layers. Application of structures in engineering materials of containers for radioactive waste or spent fuel provide reduction of their weight comparatively of containers made from steel and concrete.

  18. Influence of the chemical composition on gamma ray attenuation by fatty acids.

    Science.gov (United States)

    Bhandal, G S; Singh, K

    1992-04-01

    The dependence of gamma ray attenuation on the chemical composition of fatty acids is investigated in the energy range from 10(-3) to 10(5) MeV. The mass attenuation coefficients (muF) and effective atomic numbers (Zeff) have been calculated for 27 different fatty acids. They show appreciable variation with the chemical composition of fatty acids in the region of gamma ray energies from 10(-3) to 10(5) MeV. PMID:1314792

  19. Atomic arias

    Science.gov (United States)

    Crease, Robert P.

    2009-01-01

    The American composer John Adams uses opera to dramatize controversial current events. His 1987 work Nixon in China was about the landmark meeting in 1972 between US President Richard Nixon and Chairman Mao Zedong of China; The Death of Klinghoffer (1991) was a musical re-enactment of an incident in 1985 when Palestinian terrorists kidnapped and murdered a wheelchair-bound Jewish tourist on a cruise ship. Adams's latest opera, Doctor Atomic, is also tied to a controversial event: the first atomic-bomb test in Alamogordo, New Mexico, on 16 June 1945. The opera premièred in San Francisco in 2005, had a highly publicized debut at the Metropolitan Opera in New York in 2008, and will have another debut on 25 February - with essentially the same cast - at the English National Opera in London.

  20. Atomic physics

    Energy Technology Data Exchange (ETDEWEB)

    Livingston, A.E.; Kukla, K.; Cheng, S. [Univ. of Toledo, OH (United States)] [and others

    1995-08-01

    In a collaboration with the Atomic Physics group at Argonne and the University of Toledo, the Atomic Physics group at the University of Notre Dame is measuring the fine structure transition energies in highly-charged lithium-like and helium-like ions using beam-foil spectroscopy. Precise measurements of 2s-2p transition energies in simple (few-electron) atomic systems provide stringent tests of several classes of current atomic- structure calculations. Analyses of measurements in helium-like Ar{sup 16+} have been completed, and the results submitted for publication. A current goal is to measure the 1s2s{sup 3}S{sub 1} - 1s2p{sup 3}P{sub 0} transition wavelength in helium-like Ni{sup 26+}. Measurements of the 1s2s{sup 2}S{sub 1/2} - 1s2p{sup 2}P{sub 1/2,3/2} transition wavelengths in lithium-like Kr{sup 33+} is planned. Wavelength and lifetime measurements in copper-like U{sup 63+} are also expected to be initiated. The group is also participating in measurements of forbidden transitions in helium-like ions. A measurement of the lifetime of the 1s2s{sup 3}S{sub 1} state in Kr{sup 34+} was published recently. In a collaboration including P. Mokler of GSI, Darmstadt, measurements have been made of the spectral distribution of the 2E1 decay continuum in helium-like Kr{sup 34+}. Initial results have been reported and further measurements are planned.

  1. Estimation of Water Vapour Attenuation And Rain Attenuation

    Directory of Open Access Journals (Sweden)

    K.Kalyana Srinivas

    2015-04-01

    Full Text Available Attenuation due to and water vapour and rain can severely degrade the radio wave propagation at centimeter or millimeter wavelengths. It restricts the path length of radio communication systems and limits the use of higher frequencies for line-of-sight microwave links and satellite communications. The attenuation will pose a greater problem to communication as the frequency of occurrence of heavy rain increases.In a tropical region, like Malaysia, where excessive rainfall is a common phenomenon throughout the year, the knowledge of the rain attenuation at the frequency of operation is extremely required for the design of a reliable terrestrial and earth space communication link at a particular location.

  2. The attenuation and the attenuators: strategies and tactics

    Directory of Open Access Journals (Sweden)

    Antonio Briz

    2013-12-01

    Full Text Available This work is inscribed in a research project (ES.POR.ATENUAÇÃO that seeks to analyze and explain the attenuator activity in different regional varieties of Spanish and Portuguese, in order to perform, subsequently, different contrastive intralinguistic and interlinguistic studies. In this article, we explain some of the theoretical and methodological principles on which are based the qualitative and quantitative analysis. And especially, we will refer to the concept of attenuation (Briz 1995, 2002, 2003, 2005, 2007a, 2012.

  3. Multi-transmitting formula for attenuating waves

    Institute of Scientific and Technical Information of China (English)

    陈少林; 廖振鹏

    2003-01-01

    The MTF is extended to case of attenuating incident wave by introducing an attenuation coefficient. The reflection coefficients of this modified MTF and MTF areevaluated and compared when an attenuating wave impinges on the boundary, and the results demonstrate that MTF can be used to absorb slightly attenuating wavesand the modified MTF is more capable of absorbing heavily attenuating waves than MTF. The accuracy of modified MTF is also tested by numerical examples of fluid saturated porous media.

  4. Photoacoustic Imaging Taking into Account Attenuation

    CERN Document Server

    Kowar, Richard

    2010-01-01

    First, we review existing attenuation models and discuss their causality properties, which we believe to be essential for algorithms for inversion with attenuated data. Then, we survey causality properties of common attenuation models. We also derive integro-differential equations which the attenuated waves are satisfying. In addition we discuss the ill--conditionness of the inverse problem for calculating the unattenuated wave from the attenuated one.

  5. Classical approach in atomic physics

    Energy Technology Data Exchange (ETDEWEB)

    Solov' ev, E.A. [Bogoliubov Laboratory of Theoretical Physics, Joint Institute for Nuclear Research, 141980 Dubna (Russian Federation)

    2011-12-15

    The application of a classical approach to various quantum problems - the secular perturbation approach to quantization of a hydrogen atom in external fields and a helium atom, the adiabatic switching method for calculation of a semiclassical spectrum of a hydrogen atom in crossed electric and magnetic fields, a spontaneous decay of excited states of a hydrogen atom, Gutzwiller's approach to Stark problem, long-lived excited states of a helium atom discovered with the help of Poincare section, inelastic transitions in slow and fast electron-atom and ion-atom collisions - is reviewed. Further, a classical representation in quantum theory is discussed. In this representation the quantum states are treated as an ensemble of classical states. This approach opens the way to an accurate description of the initial and final states in classical trajectory Monte Carlo (CTMC) method and a purely classical explanation of tunneling phenomenon. The general aspects of the structure of the semiclassical series such as renormalization group symmetry, criterion of accuracy and so on are reviewed as well. (author)

  6. Collisional properties of trapped cold chromium atoms

    CERN Document Server

    Pavlovich, Z; Côté, R; Sadeghpour, H R; Pavlovic, Zoran; Roos, Bjoern O.; Côté, Robin

    2004-01-01

    We report on calculations of the elastic cross section and thermalization rate for collision between two maximally spin-polarized chromium atoms in the cold and ultracold regimes, relevant to buffer-gas and magneto-optical cooling of chromium atoms. We calculate ab initio potential energy curves for Cr2 and the van der Waals coefficient C6, and construct interaction potentials between two colliding Cr atoms. We explore the effect of shape resonances on elastic cross section, and find that they dramatically affect the thermalization rate. Our calculated value for the s-wave scattering length is compared in magnitude with a recent measurement at ultracold temperatures.

  7. Use of ultrasonic attenuation and backscatter measurement for determining the grain size of austenitic steel OX18H12T

    International Nuclear Information System (INIS)

    A nondestructive method is described for the rapid determination of the grain size of nuclear piping. The method is based upon ultrasonic attenuation measurement, the coefficient of attenuation serving as a characteristic measure. The backscatter method is used to determine grain size distribution over the entire cross section. (author)

  8. Sound attenuation in magnetorheological fluids

    Science.gov (United States)

    Rodríguez-López, J.; Elvira, L.; Resa, P.; Montero de Espinosa, F.

    2013-02-01

    In this work, the attenuation of ultrasonic elastic waves propagating through magnetorheological (MR) fluids is analysed as a function of the particle volume fraction and the magnetic field intensity. Non-commercial MR fluids made with iron ferromagnetic particles and two different solvents (an olive oil based solution and an Araldite-epoxy) were used. Particle volume fractions of up to 0.25 were analysed. It is shown that the attenuation of sound depends strongly on the solvent used and the volume fraction. The influence of a magnetic field up to 212 mT was studied and it was found that the sound attenuation increases with the magnetic intensity until saturation is reached. A hysteretic effect is evident once the magnetic field is removed.

  9. Josephson tunnel junction microwave attenuator

    DEFF Research Database (Denmark)

    Koshelets, V. P.; Shitov, S. V.; Shchukin, A. V.;

    1993-01-01

    A new element for superconducting electronic circuitry-a variable attenuator-has been proposed, designed, and successfully tested. The principle of operation is based on the change in the microwave impedance of a superconductor-insulator-superconductor (SIS) Josephson tunnel junction when dc biased...... at different points in the current-voltage characteristic. Both numerical calculations based on the Tien-Gordon theory and 70-GHz microwave experiments have confirmed the wide dynamic range (more than 15-dB attenuation for one stage) and the low insertion loss in the ''open'' state. The performance of a fully...... integrated submillimeter receiver circuit which comprises a flux-flow oscillator (FFO) as local oscillator, a superconducting variable attenuator, and a microwave SIS detector with tuned-out capacitance is also reported....

  10. Light element opacities from ATOMIC

    Science.gov (United States)

    Colgan, J.; Kilcrease, D. P.; Magee, N. H.; Armstrong, G. S. J.; Abdallah, J.; Sherrill, M. E.; Fontes, C. J.; Zhang, H. L.; Hakel, P.

    2013-06-01

    We present new calculations of local-thermodynamic-equilibrium (LTE) light element opacities from the Los Alamos ATOMIC code. ATOMIC is a multi-purpose code that can generate LTE or non-LTE quantities of interest at various levels of approximation. A program of work is currently underway to compute new LTE opacity data for all elements H through Zn. New opacity tables for H through Ne are complete, and a new Fe opacity table will be available soon. Our calculations, which include fine-structure detail, represent a systematic improvement over previous Los Alamos opacity calculations using the LEDCOP legacy code. Our opacity calculations incorporate atomic structure data computed from the CATS code, which is based on Cowan's atomic structure codes, and photoionization cross section data computed from the Los Alamos ionization code GIPPER. We make use of a new equation-of-state (EOS) model based on the chemical picture. ATOMIC incorporates some physics packages from LEDCOP and also includes additional physical processes, such as improved free-free cross sections and additional scattering mechanisms. In this report, we briefly discuss the physics improvements included in our new opacity calculations and present comparisons of our new opacities with other work for C, O, and Fe at selected conditions.

  11. Energetics and dynamics of atomic uranium levels

    International Nuclear Information System (INIS)

    New methods for discovering and identifying new electronic levels of atomic uranium and measuring parameters, such as radiative lifetimes and absorption cross-sections, are described. The uranium atoms are produced within an especially designed induction-heated oven. The uranium vapor is irradiated by nitrogen laser pumped, pulsed dye lasers. The various measurements are accomplished by detection of laser induced fluorescence from selectively excited levels. 138 atomic-uranium odd levels in the region 32260-34900 cm-1 and 16 even levels in the region 49500-49900 cm-1 are reported. Unique J values are presented for 64 levels and partial assignment (two possibilities) for 42 levels. Radiative lifetimes are presented for 134 levels. Absorption cross sections were measured for 12 transitions. Isotope shifts of 17 levels are given. Cross-sections for internal excitation transfer in uranium which are induced by collisions with argon atoms, are presented for 11 levels. (author)

  12. X-Ray Attenuation Cell

    Energy Technology Data Exchange (ETDEWEB)

    Ryutov, D.; Toor, A.

    2000-03-03

    To minimize the pulse-to-pulse variation, the LCLS FEL must operate at saturation, i.e. 10 orders of magnitude brighter spectral brilliance than 3rd-generation light sources. At this intensity, ultra-high vacuums and windowless transport are required. Many of the experiments, however, will need to be conducted at a much lower intensity thereby requiring a reliable means to reduce the x-ray intensity by many orders of magnitude without increasing the pulse-to-pulse variation. In this report we consider a possible solution for controlled attenuation of the LCLS x-ray radiation. We suggest using for this purpose a windowless gas-filled cell with the differential pumping. Although this scheme is easily realizable in principle, it has to be demonstrated that the attenuator can be made short enough to be practical and that the gas loads delivered to the vacuum line of sight (LOS) are acceptable. We are not going to present a final, optimized design. Instead, we will provide a preliminary analysis showing that the whole concept is robust and is worth further study. The spatial structure of the LCLS x-ray pulse at the location of the attenuator is shown in Fig. 1. The central high-intensity component, due to the FEL, has a FWHM of {approx}100 {micro}m. A second component, due to the undulator's broad band spontaneous radiation is seen as a much lower intensity ''halo'' with a FWHM of 1 mm. We discuss two versions of the attenuation cell. The first is directed towards a controlled attenuation of the FEL up to the 4 orders of magnitude in the intensity, with the spontaneous radiation halo being eliminated by collimators. In the second version, the spontaneous radiation is not sacrificed but the FEL component (as well as the first harmonic of the spontaneous radiation) gets attenuated by a more modest factor up to 100. We will make all the estimates assuming that the gas used in the attenuator is Xenon and that the energy of the FEL is 8.25 keV. At

  13. Atom Skimmers and Atom Lasers Utilizing Them

    Science.gov (United States)

    Hulet, Randall; Tollett, Jeff; Franke, Kurt; Moss, Steve; Sackett, Charles; Gerton, Jordan; Ghaffari, Bita; McAlexander, W.; Strecker, K.; Homan, D.

    2005-01-01

    Atom skimmers are devices that act as low-pass velocity filters for atoms in thermal atomic beams. An atom skimmer operating in conjunction with a suitable thermal atomic-beam source (e.g., an oven in which cesium is heated) can serve as a source of slow atoms for a magneto-optical trap or other apparatus in an atomic-physics experiment. Phenomena that are studied in such apparatuses include Bose-Einstein condensation of atomic gases, spectra of trapped atoms, and collisions of slowly moving atoms. An atom skimmer includes a curved, low-thermal-conduction tube that leads from the outlet of a thermal atomic-beam source to the inlet of a magneto-optical trap or other device in which the selected low-velocity atoms are to be used. Permanent rare-earth magnets are placed around the tube in a yoke of high-magnetic-permeability material to establish a quadrupole or octupole magnetic field leading from the source to the trap. The atoms are attracted to the locus of minimum magnetic-field intensity in the middle of the tube, and the gradient of the magnetic field provides centripetal force that guides the atoms around the curve along the axis of the tube. The threshold velocity for guiding is dictated by the gradient of the magnetic field and the radius of curvature of the tube. Atoms moving at lesser velocities are successfully guided; faster atoms strike the tube wall and are lost from the beam.

  14. Atomic data for controlled fusion research

    International Nuclear Information System (INIS)

    Presented is an evaluated graphical and tabular compilation of atomic and molecular cross sections of interest to controlled thermonuclear research. The cross sections are tabulated and graphed as a function of energy for collision processes involving heavy particles, electrons, and photons with atoms and ions. Also included are sections on data for particle penetration through macroscopic matter, particle transport properties, particle interactions with surfaces, and pertinent charged particle nuclear cross sections and reaction rates. In most cases estimates have been made of the data accuracy

  15. Semiempirical potentials for positron scattering by atoms

    Energy Technology Data Exchange (ETDEWEB)

    Assafrao, Denise; Walters, H. R. J.; Arretche, Felipe; Dutra, Adriano; Mohallem, J. R. [Departamento de Fisica, Universidade Federal do Espirito Santo, 29075-910, Vitoria, ES (Brazil); Department of Applied Mathematics and Theoretical Physics, Queen' s University, Belfast, BT7 1NN (United Kingdom); Departamento de Fisica, Universidade do Estado de Santa Catarina, 89223-100, Joinville, SC (Brazil); Laboratorio de Atomos e Moleculas Especiais, Departamento de Fisica, ICEx, Universidade Federal de Minas Gerais, PO Box 702, 30123-970, Belo Horizonte, MG (Brazil)

    2011-08-15

    We report calculations of differential and integral cross sections for positron scattering by noble gas and alkaline-earth atoms within the same methodology. The scattering potentials are constructed by scaling adiabatic potentials so that their minima coincide with the covalent radii of the target atoms. Elastic differential and integral cross sections are calculated for Ne, Ar, Be, and Mg, and the results are very close to experimental and best theoretical data. Particularly, elastic differential cross sections for Be and Mg at low energies are reported.

  16. Formation of positron-atom bound states in collisions between Rydberg Ps and neutral atoms

    CERN Document Server

    Swann, A R; Deller, A; Gribakin, G F

    2016-01-01

    Predicted twenty years ago, positron binding to neutral atoms has not yet been observed experimentally. A new scheme is proposed to detect positron-atom bound states by colliding Rydberg positronium (Ps) with neutral atoms. Estimates of the charge-transfer-reaction cross section are obtained using the first Born approximation for a selection of neutral atom targets and a wide range of incident Ps energies and principal quantum numbers. We also estimate the corresponding Ps ionization cross section. The accuracy of the calculations is tested by comparison with earlier predictions for Ps charge transfer in collisions with hydrogen and antihydrogen. We describe an existing Rydberg Ps beam suitable for producing positron-atom bound states and estimate signal rates based on the calculated cross sections and realistic experimental parameters. We conclude that the proposed methodology is capable of producing such states and of testing theoretical predictions of their binding energies.

  17. Positron impact ionization of atomic hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Jones, G.O.; Charlton, M.; Slevin, J.; Laricchia, G.; Kover, A.; Poulsen, M.R.; Chormaic, S.N. (University Coll., London (United Kingdom). Dept. of Physics and Astronomy)

    1993-08-14

    Ionization cross sections for positrons impacting on atomic hydrogen have been measured for kinetic energies in the range 15-700 eV. This has been done in a crossed-beam geometry where a magnetically guided positron beam intersects a hydrogen gas jet emanating from a radio frequency discharge tube. Electron impact ionization cross sections were also measured with the same apparatus thus facilitating comparison with, and normalization to, published results. (author).

  18. Positron impact ionization of atomic hydrogen

    International Nuclear Information System (INIS)

    Ionization cross sections for positrons impacting on atomic hydrogen have been measured for kinetic energies in the range 15-700 eV. This has been done in a crossed-beam geometry where a magnetically guided positron beam intersects a hydrogen gas jet emanating from a radio frequency discharge tube. Electron impact ionization cross sections were also measured with the same apparatus thus facilitating comparison with, and normalization to, published results. (author)

  19. A polarized atomic hydrogen beam

    International Nuclear Information System (INIS)

    We describe the design and operating characteristics of a simple polarized atomic hydrogen beam particularly suitable for applications to crossed beams experiments. In addition to experimental measurements, we present the results of detailed computer models, using Monte-Carlo ray tracing techniques, optical analogs, and phase-space methods, that not only provide us with a confirmation of our measurement, but also allow us to characterize the density, polarization, and atomic fraction of the beam at all points along its path. As a subsidiary result, we also present measurements of the relative and absolute efficiencies of the V/G Supavac mass analyzer for masses 1 and 2. (orig.)

  20. Atom-atom interactions around the band edge of a photonic crystal waveguide.

    Science.gov (United States)

    Hood, Jonathan D; Goban, Akihisa; Asenjo-Garcia, Ana; Lu, Mingwu; Yu, Su-Peng; Chang, Darrick E; Kimble, H J

    2016-09-20

    Tailoring the interactions between quantum emitters and single photons constitutes one of the cornerstones of quantum optics. Coupling a quantum emitter to the band edge of a photonic crystal waveguide (PCW) provides a unique platform for tuning these interactions. In particular, the cross-over from propagating fields [Formula: see text] outside the bandgap to localized fields [Formula: see text] within the bandgap should be accompanied by a transition from largely dissipative atom-atom interactions to a regime where dispersive atom-atom interactions are dominant. Here, we experimentally observe this transition by shifting the band edge frequency of the PCW relative to the [Formula: see text] line of atomic cesium for [Formula: see text] atoms trapped along the PCW. Our results are the initial demonstration of this paradigm for coherent atom-atom interactions with low dissipation into the guided mode.

  1. Determination of rain attenuation from electromagnetic scattering by spherical raindrops: Theory and experiment

    Science.gov (United States)

    Odedina, M. O.; Afullo, T. J.

    2010-02-01

    The forward scattering amplitudes for the spherical raindrops are determined for all raindrop sizes at different frequencies by using the Mie scattering theory. The real parts of the extinction cross sections are used to generate power law models at different frequencies. These are integrated over different established raindrop-size distribution models to formulate rain attenuation models. Using the developed rain attenuation models with 5 year rain rate statistics at R0.01 determined in previous work, the specific rain attenuation is computed. The experimental results obtained from the horizontally polarized signal level measurements recorded in Durban for different rain attenuation bounds are compared with the theoretical results. Finally, the best theoretical model is used to estimate the seasonal cumulative distribution of rain attenuation for Durban, South Africa.

  2. Cold heteronuclear atom-ion collisions

    CERN Document Server

    Zipkes, Christoph; Ratschbacher, Lothar; Sias, Carlo; Köhl, Michael

    2010-01-01

    We study cold heteronuclear atom ion collisions by immersing a trapped single ion into an ultracold atomic cloud. Using ultracold atoms as reaction targets, our measurement is sensitive to elastic collisions with extremely small energy transfer. The observed energy-dependent elastic atom-ion scattering rate deviates significantly from the prediction of Langevin but is in full agreement with the quantum mechanical cross section. Additionally, we characterize inelastic collisions leading to chemical reactions at the single particle level and measure the energy-dependent reaction rate constants. The reaction products are identified by in-trap mass spectrometry, revealing the branching ratio between radiative and non-radiative charge exchange processes.

  3. Comparison of quantum-mechanical and classical trajectory calculations of cross sections for ion-atom impact ionization of negative and positive ions for heavy-ion fusion applications

    International Nuclear Information System (INIS)

    Stripping cross sections in nitrogen have been calculated using the classical trajectory approximation and the Born approximation of quantum mechanics for the outer shell electrons of 3.2 GeV I- and Cs+ ions. A large difference in cross section, up to a factor of 6, calculated in quantum mechanics and classical mechanics, has been obtained. Because at such high velocities the Born approximation is well validated, the classical trajectory approach fails to correctly predict the stripping cross sections at high energies for electron orbitals with low ionization potential

  4. Compact plasmonic variable optical attenuator

    DEFF Research Database (Denmark)

    Leosson, Kristjan; Rosenzveig, Tiberiu; Hermannsson, Pétur Gordon;

    2008-01-01

    We demonstrate plasmonic nanowire-based thermo-optic variable optical attenuators operating in the 1525-1625 nm wavelength range. The devices have a footprint as low as 1 mm, extinction ratio exceeding 40 dB, driving voltage below 3 V, and full modulation bandwidth of 1 kHz. The polarization...

  5. Stormwater Attenuation by Green Roofs

    Science.gov (United States)

    Sims, A.; O'Carroll, D. M.; Robinson, C. E.; Smart, C. C.

    2014-12-01

    Innovative municipal stormwater management technologies are urgently required in urban centers. Inadequate stormwater management can lead to excessive flooding, channel erosion, decreased stream baseflows, and degraded water quality. A major source of urban stormwater is unused roof space. Green roofs can be used as a stormwater management tool to reduce roof generated stormwater and generally improve the quality of runoff. With recent legislation in some North American cities, including Toronto, requiring the installation of green roofs on large buildings, research on the effectiveness of green roofs for stormwater management is important. This study aims to assess the hydrologic response of an extensive sedum green roof in London, Ontario, with emphasis on the response to large precipitation events that stress municipal stormwater infrastructure. A green roof rapidly reaches field capacity during large storm events and can show significantly different behavior before and after field capacity. At field capacity a green roof has no capillary storage left for retention of stormwater, but may still be an effective tool to attenuate peak runoff rates by transport through the green roof substrate. The attenuation of green roofs after field capacity is linked to gravity storage, where gravity storage is the water that is temporarily stored and can drain freely over time after field capacity has been established. Stormwater attenuation of a modular experimental green roof is determined from water balance calculations at 1-minute intervals. Data is used to evaluate green roof attenuation and the impact of field capacity on peak flow rates and gravity storage. In addition, a numerical model is used to simulate event based stormwater attenuation. This model is based off of the Richards equation and supporting theory of multiphase flow through porous media.

  6. Atom as a "Dressed" Nucleus

    CERN Document Server

    Kalitvianski, V

    2008-01-01

    It is shown that electrostatic potential of atomic nucleus seen by a fast charged projectile at short distances is quite smeared due to nucleus motion around the atomic center of inertia. For example, the size of positive charge cloud in the Hydrogen ground state is much larger than the proper proton size. It is even bigger for the target atom in an excited state. Therefore the elastic scattering at large angles is generally weaker than the Rutherford one. In other words, the resulting elastic interaction with an atom at short distances is softer than the Colombian one due to a natural cutoff. In addition, the large angle scattering leads to the target atom excitations due to hitting the nucleus (inelastic processes). It is also shown that the Rutherford cross section is in fact the inclusive rather than the elastic one. These results are analogous to the QED ones. The difference and the value of the presented below non relativistic atomic calculations is in non perturbatively (exact) dressing that immediatel...

  7. Modeling transmission and scatter for photon beam attenuators.

    Science.gov (United States)

    Ahnesjö, A; Weber, L; Nilsson, P

    1995-11-01

    The development of treatment planning methods in radiation therapy requires dose calculation methods that are both accurate and general enough to provide a dose per unit monitor setting for a broad variety of fields and beam modifiers. The purpose of this work was to develop models for calculation of scatter and transmission for photon beam attenuators such as compensating filters, wedges, and block trays. The attenuation of the beam is calculated using a spectrum of the beam, and a correction factor based on attenuation measurements. Small angle coherent scatter and electron binding effects on scattering cross sections are considered by use of a correction factor. Quality changes in beam penetrability and energy fluence to dose conversion are modeled by use of the calculated primary beam spectrum after passage through the attenuator. The beam spectra are derived by the depth dose effective method, i.e., by minimizing the difference between measured and calculated depth dose distributions, where the calculated distributions are derived by superposing data from a database for monoenergetic photons. The attenuator scatter is integrated over the area viewed from the calculation point of view using first scatter theory. Calculations are simplified by replacing the energy and angular-dependent cross-section formulas with the forward scatter constant r2(0) and a set of parametrized correction functions. The set of corrections include functions for the Compton energy loss, scatter attenuation, and secondary bremsstrahlung production. The effect of charged particle contamination is bypassed by avoiding use of dmax for absolute dose calibrations. The results of the model are compared with scatter measurements in air for copper and lead filters and with dose to a water phantom for lead filters for 4 and 18 MV. For attenuated beams, downstream of the buildup region, the calculated results agree with measurements on the 1.5% level. The accuracy was slightly less in situations

  8. Modeling transmission and scatter for photon beam attenuators.

    Science.gov (United States)

    Ahnesjö, A; Weber, L; Nilsson, P

    1995-11-01

    The development of treatment planning methods in radiation therapy requires dose calculation methods that are both accurate and general enough to provide a dose per unit monitor setting for a broad variety of fields and beam modifiers. The purpose of this work was to develop models for calculation of scatter and transmission for photon beam attenuators such as compensating filters, wedges, and block trays. The attenuation of the beam is calculated using a spectrum of the beam, and a correction factor based on attenuation measurements. Small angle coherent scatter and electron binding effects on scattering cross sections are considered by use of a correction factor. Quality changes in beam penetrability and energy fluence to dose conversion are modeled by use of the calculated primary beam spectrum after passage through the attenuator. The beam spectra are derived by the depth dose effective method, i.e., by minimizing the difference between measured and calculated depth dose distributions, where the calculated distributions are derived by superposing data from a database for monoenergetic photons. The attenuator scatter is integrated over the area viewed from the calculation point of view using first scatter theory. Calculations are simplified by replacing the energy and angular-dependent cross-section formulas with the forward scatter constant r2(0) and a set of parametrized correction functions. The set of corrections include functions for the Compton energy loss, scatter attenuation, and secondary bremsstrahlung production. The effect of charged particle contamination is bypassed by avoiding use of dmax for absolute dose calibrations. The results of the model are compared with scatter measurements in air for copper and lead filters and with dose to a water phantom for lead filters for 4 and 18 MV. For attenuated beams, downstream of the buildup region, the calculated results agree with measurements on the 1.5% level. The accuracy was slightly less in situations

  9. NIST Databases on Atomic Spectra

    Science.gov (United States)

    Reader, J.; Wiese, W. L.; Martin, W. C.; Musgrove, A.; Fuhr, J. R.

    2002-11-01

    The NIST atomic and molecular spectroscopic databases now available on the World Wide Web through the NIST Physics Laboratory homepage include Atomic Spectra Database, Ground Levels and Ionization Energies for the Neutral Atoms, Spectrum of Platinum Lamp for Ultraviolet Spectrograph Calibration, Bibliographic Database on Atomic Transition Probabilities, Bibliographic Database on Atomic Spectral Line Broadening, and Electron-Impact Ionization Cross Section Database. The Atomic Spectra Database (ASD) [1] offers evaluated data on energy levels, wavelengths, and transition probabilities for atoms and atomic ions. Data are given for some 950 spectra and 70,000 energy levels. About 91,000 spectral lines are included, with transition probabilities for about half of these. Additional data resulting from our ongoing critical compilations will be included in successive new versions of ASD. We plan to include, for example, our recently published data for some 16,000 transitions covering most ions of the iron-group elements, as well as Cu, Kr, and Mo [2]. Our compilations benefit greatly from experimental and theoretical atomic-data research being carried out in the NIST Atomic Physics Division. A new compilation covering spectra of the rare gases in all stages of ionization, for example, revealed a need for improved data in the infrared. We have thus measured these needed data with our high-resolution Fourier transform spectrometer [3]. An upcoming new database will give wavelengths and intensities for the stronger lines of all neutral and singly-ionized atoms, along with energy levels and transition probabilities for the persistent lines [4]. A critical compilation of the transition probabilities of Ba I and Ba II [5] has been completed and several other compilations of atomic transition probabilities are nearing completion. These include data for all spectra of Na, Mg, Al, and Si [6]. Newly compiled data for selected ions of Ne, Mg, Si and S, will form the basis for a new

  10. Muonium/muonic hydrogen formation in atomic hydrogen

    Indian Academy of Sciences (India)

    V S Kulhar

    2004-09-01

    The muonium/muonic hydrogen atom formation in ± –H collisions is investigated, using a two-state approximation in a time dependent formalism. It is found that muonium cross-section results are similar to the cross-section results obtained for positronium formation in + –H collision. Muonic hydrogen atom formation cross-sections in - –H collision are found to be significant in a narrow range of energy (5 eV–25 eV).

  11. Characteristics of liver tissue for attenuate the gamma radiation

    International Nuclear Information System (INIS)

    It was determined the lineal attenuation coefficient of hepatic tissue before gamma radiation of a source of 137 Cs. When exposing organic material before X or gamma radiation fields, part of the energy of the photons is absorbed by the material, while another part crosses it without producing any effect. The quantity of energy that is absorbed is a measure of the dose that receives the material. The three main mechanisms by means of which the gamma rays interacting with the matter are: The Photoelectric Effect, the Compton dispersion and the Even production; the sum of these three processes is translated in the attenuation coefficient of the radiation. In this work we have used hepatic tissue of bovine, as substitute of the human hepatic tissue, and we have measured the lineal attenuation coefficient for photons of 0.662 MeV. Through a series of calculations we have determined the lineal attenuation coefficient for photons from 10-3 to 10-5 MeV and the measured coefficient was compared with the one calculated. (Author)

  12. Magnetic Trapping of Cold Bromine Atoms

    CERN Document Server

    Rennick, C J; Doherty, W G; Softley, T P

    2014-01-01

    Magnetic trapping of bromine atoms at temperatures in the milliKelvin regime is demonstrated for the first time. The atoms are produced by photodissociation of Br$_2$ molecules in a molecular beam. The lab-frame velocity of Br atoms is controlled by the wavelength and polarization of the photodissociation laser. Careful selection of the wavelength results in one of the pair of atoms having sufficient velocity to exactly cancel that of the parent molecule, and it remains stationary in the lab frame. A trap is formed at the null point between two opposing neodymium permanent magnets. Dissociation of molecules at the field minimum results in the slowest fraction of photofragments remaining trapped. After the ballistic escape of the fastest atoms, the trapped slow atoms are only lost by elastic collisions with the chamber background gas. The measured loss rate is consistent with estimates of the total cross section for only those collisions transferring sufficient kinetic energy to overcome the trapping potential...

  13. Ex Vacuo Atom Chip Bose-Einstein Condensate (BEC)

    CERN Document Server

    Squires, Matthew B; Kasch, Brian; Stickney, James A; Erickson, Christopher J; Crow, Jonathan A R; Carlson, Evan J; Burke, John H

    2016-01-01

    Ex vacuo atom chips, used in conjunction with a custom thin walled vacuum chamber, have enabled the rapid replacement of atom chips for magnetically trapped cold atom experiments. Atoms were trapped in $>2$ kHz magnetic traps created using high power atom chips. The thin walled vacuum chamber allowed the atoms to be trapped $\\lesssim1$ mm from the atom chip conductors which were located outside of the vacuum system. Placing the atom chip outside of the vacuum simplified the electrical connections and improved thermal management. Using a multi-lead Z-wire chip design, a Bose-Einstein condensate was produced with an external atom chip. Vacuum and optical conditions were maintained while replacing the Z-wire chip with a newly designed cross-wire chip. The atom chips were exchanged and an initial magnetic trap was achieved in less than three hours.

  14. ENHANCEMENTS TO NATURAL ATTENUATION: SELECTED CASE STUDIES

    Energy Technology Data Exchange (ETDEWEB)

    Vangelas, K; W. H. Albright, W; E. S. Becvar, E; C. H. Benson, C; T. O. Early, T; E. Hood, E; P. M. Jardine, P; M. Lorah, M; E. Majche, E; D. Major, D; W. J. Waugh, W; G. Wein, G; O. R. West, O

    2007-05-15

    In 2003 the US Department of Energy (DOE) embarked on a project to explore an innovative approach to remediation of subsurface contaminant plumes that focused on introducing mechanisms for augmenting natural attenuation to achieve site closure. Termed enhanced attenuation (EA), this approach has drawn its inspiration from the concept of monitored natural attenuation (MNA).

  15. Gamma-ray attenuation coefficients in bismuth borate glasses

    International Nuclear Information System (INIS)

    Mass attenuation coefficients of glasses in the system: xBi2O3(1-x)B2O3 (x=0.30, 0.35, 0.40, 0.45 and 0.55) were determined at 356, 662, 1173 and 1332 keV photon energies using a narrow beam transmission method. Appreciable variations were observed in these coefficients due to changes in the chemical composition of glasses. These coefficients were then used to determine effective atomic numbers of glass samples, which were found to be constant with bismuth concentration and energy

  16. SEISMIC ATTENUATION FOR RESERVOIR CHARACTERIZATION

    Energy Technology Data Exchange (ETDEWEB)

    Joel Walls; M.T. Taner; Gary Mavko; Jack Dvorkin

    2002-01-01

    In Section 1 of this first report we will describe the work we are doing to collect and analyze rock physics data for the purpose of modeling seismic attenuation from other measurable quantities such as porosity, water saturation, clay content and net stress. This work and other empirical methods to be presented later, will form the basis for ''Q pseudo-well modeling'' that is a key part of this project. In Section 2 of this report, we will show the fundamentals of a new method to extract Q, dispersion, and attenuation from field seismic data. The method is called Gabor-Morlet time-frequency decomposition. This technique has a number of advantages including greater stability and better time resolution than spectral ratio methods.

  17. Chlorine signal attenuation in concrete.

    Science.gov (United States)

    Naqvi, A A; Maslehuddin, M; ur-Rehman, Khateeb; Al-Amoudi, O S B

    2015-11-01

    The intensity of prompt gamma-ray was measured at various depths from chlorine-contaminated silica fume (SF) concrete slab concrete specimens using portable neutron generator-based prompt gamma-ray setup. The intensity of 6.11MeV chloride gamma-rays was measured from the chloride contaminated slab at distance of 15.25, 20.25, 25.25, 30.25 and 35.25cm from neutron target in a SF cement concrete slab specimens. Due to attenuation of thermal neutron flux and emitted gamma-ray intensity in SF cement concrete at various depths, the measured intensity of chlorine gamma-rays decreases non-linearly with increasing depth in concrete. A good agreement was noted between the experimental results and the results of Monte Carlo simulation. This study has provided useful experimental data for evaluating the chloride contamination in the SF concrete utilizing gamma-ray attenuation method.

  18. Ghost Imaging with Atoms

    CERN Document Server

    Khakimov, R I; Shin, D K; Hodgman, S S; Dall, R G; Baldwin, K G H; Truscott, A G

    2016-01-01

    Ghost imaging is a technique -- first realized in quantum optics -- in which the image emerges from cross-correlation between particles in two separate beams. One beam passes through the object to a bucket (single-pixel) detector, while the second beam's spatial profile is measured by a high resolution (multi-pixel) detector but never interacts with the object. Neither detector can reconstruct the image independently. However, until now ghost imaging has only been demonstrated with photons. Here we report the first realisation of ghost imaging of an object using massive particles. In our experiment, the two beams are formed by correlated pairs of ultracold metastable helium atoms, originating from two colliding Bose-Einstein condensates (BECs) via $s$-wave scattering. We use the higher-order Kapitza-Dirac effect to generate the large number of correlated atom pairs required, enabling the creation of a ghost image with good visibility and sub-millimetre resolution. Future extensions could include ghost interfe...

  19. Electron-Impact Ionization Cross Section Database

    Science.gov (United States)

    SRD 107 Electron-Impact Ionization Cross Section Database (Web, free access)   This is a database primarily of total ionization cross sections of molecules by electron impact. The database also includes cross sections for a small number of atoms and energy distributions of ejected electrons for H, He, and H2. The cross sections were calculated using the Binary-Encounter-Bethe (BEB) model, which combines the Mott cross section with the high-incident energy behavior of the Bethe cross section. Selected experimental data are included.

  20. "Bohr's Atomic Model."

    Science.gov (United States)

    Willden, Jeff

    2001-01-01

    "Bohr's Atomic Model" is a small interactive multimedia program that introduces the viewer to a simplified model of the atom. This interactive simulation lets students build an atom using an atomic construction set. The underlying design methodology for "Bohr's Atomic Model" is model-centered instruction, which means the central model of the…

  1. Mechanisms of geometrical seismic attenuation

    Directory of Open Access Journals (Sweden)

    Igor B. Morozov

    2011-07-01

    Full Text Available In several recent reports, we have explained the frequency dependence of the apparent seismic quality-factor (Q observed in many studies according to the effects of geometrical attenuation, which was defined as the zero-frequency limit of the temporal attenuation coefficient. In particular, geometrical attenuation was found to be positive for most waves traveling within the lithosphere. Here, we present three theoretical models that illustrate the origin of this geometrical attenuation, and we investigate the causes of its preferential positive values. In addition, we discuss the physical basis and limitations of both the conventional and new attenuation models. For waves in media with slowly varying properties, geometrical attenuation is caused by variations in the wavefront curvature, which can be both positive (for defocusing and negative (for focusing. In media with velocity/density contrasts, incoherent reflectivity leads to geometrical-attenuation coefficients which are proportional to the mean squared reflectivity and are always positive. For «coherent» reflectivity, the geometrical attenuation is approximately zero, and the attenuation process can be described according to the concept of «scattering Q». However, the true meaning of this parameter is in describing the mean reflectivity within the medium, and not that of the traditional resonator quality factor known in mechanics. The general conclusion from these models is that non-zero and often positive levels of geometrical attenuation are common in realistic, heterogeneous media, both observationally and theoretically. When transformed into the conventional Q-factor form, this positive geometrical attenuation leads to Q values that quickly increase with frequency. These predictions show that the positive frequency-dependent Q observed in many datasets might represent artifacts of the transformations of the attenuation coefficients into Q.

  1. Imaging subtle microstructural variations in ceramics with precision ultrasonic velocity and attenuation measurements

    Energy Technology Data Exchange (ETDEWEB)

    Generazio, E.R.; Roth, D.J.; Baaklini, G.Y.

    1987-11-01

    Acoustic images of a silicon carbide ceramic disk were obtained using a precision scanning contact pulse echo technique. Phase and cross-correlation velocity, and attenuation maps were used to form color images of microstructural variations. These acoustic images reveal microstructural variations not observable with x-ray radiography.

  2. Imaging subtle microstructural variations in ceramics with precision ultrasonic velocity and attenuation measurements

    Science.gov (United States)

    Generazio, Edward R.; Roth, Don J.; Baaklini, George Y.

    1987-01-01

    Acoustic images of a silicon carbide ceramic disk were obtained using a precision scanning contact pulse echo technique. Phase and cross-correlation velocity, and attenuation maps were used to form color images of microstructural variations. These acoustic images reveal microstructural variations not observable with X-ray radiography.

  3. Influence of magnetite and boron carbide on radiation attenuation of cement-fiber/composite

    International Nuclear Information System (INIS)

    Trial was made to create composites from agriculture fibers, which have good mechanical, physical and radiation attenuation properties for different applications. Fast neutron and gamma ray spectra, as well as, slow neutron fluxes behind samples of cement-fiber (CF) (ρ=2.095 g cm-3) and cement-fiber-magnetite (CFM) (ρ=2.858 g cm-3)/composites have been investigated. Neutron and gamma spectra have been measured using a collimated reactor beam and neutron- gamma spectrometer with stilbene scintillator. A pulse shape discrimination technique based on zero cross over method was used to discriminate between neutron and gamma ray pulses. While, slow neutron fluxes have been measured using a collimated reactor beam and BF3 counter. Results were used to achieve removal cross sections (ΣR,meas.), total attenuation coefficients (μ) and macroscopic cross sections (Σ) of fast neutrons, gamma rays and slow neutrons respectively from the attenuation relations. Also, removal cross sections (ΣR,cal.) and total mass attenuation coefficients (μ/ρ) of fast neutrons and gamma rays have been calculated using the composites elemental composition and XCOM code respectively. Measured and calculated results were compared and a reasonable agreement was found

  4. Determination of mass attenuation coefficients of dilute solutions of sulphates of some elements

    International Nuclear Information System (INIS)

    The narrow beam transmission methods have been employed for the determination of linear mass attenuation coefficients of the aqueous solutions of some sulphates of alkaline earth elements in the concentration range 0.05 to 0.25 g/cm3 at 81, 356, 511, 662, 1173 and 1332 keV gamma ray energies. From the precisely measured densities of these solutions, mass attenuation coefficients were then obtained. These coefficients were then successfully used to determine the effective atomic numbers of the solutions. A very good agreement is observed between the theoretical and experimental values. (author)

  5. MULTIPHOTON IONIZATION OF ATOMS

    OpenAIRE

    Mainfray, G.

    1985-01-01

    Multiphoton ionization of one-electron atoms, such as atomic hydrogen and alkaline atoms, is well understood and correctly described by rigorous theoretical models. The present paper will be devoted to collisionless multiphoton ionization of many-electron atoms as rare gases. It induces removal of several electrons and the production of multiply charged ions. Up to Xe5+ ions are produced in Xe atoms. Doubly charged ions can be produced, either by simultaneous excitation of two electrons, or b...

  6. Stable atomic hydrogen: Polarized atomic beam source

    International Nuclear Information System (INIS)

    We have carried out experiments with stable atomic hydrogen with a view to possible applications in polarized targets or polarized atomic beam sources. Recent results from the stabilization apparatus are described. The first stable atomic hydrogen beam source based on the microwave extraction method (which is being tested ) is presented. The effect of the stabilized hydrogen gas density on the properties of the source is discussed. (orig.)

  7. Ultrasound fields in an attenuating medium

    DEFF Research Database (Denmark)

    Jensen, Jørgen Arendt; Gandhi,, D; O'Brien,, W.D., Jr.

    1993-01-01

    Ultrasound fields propagating in tissue will undergo changes in shape not only due to diffraction, but also due to the frequency dependent attenuation. Linear fields can be fairly well predicted for a non-attenuating medium like water by using the Tupholme-Stepanishen method for calculating...... it into a frequency dependent part and frequency independent part. The latter results in an attenuation factor that is multiplied onto the responses from the individual elements, and the frequency dependent part is handled by attenuating the basic one-dimensional pulse. The influence on ultrasound fields from...

  8. Simulating atmospheric free-space optical propagation: rainfall attenuation

    Science.gov (United States)

    Achour, Maha

    2002-04-01

    With recent advances and interest in Free-Space Optics (FSO) for commercial deployments, more attention has been placed on FSO weather effects and the availability of global weather databases. The Meteorological Visual Range (Visibility) is considered one of the main weather parameters necessary to estimate FSO attenuation due to haze, fog and low clouds. Proper understanding of visibility measurements conducted throughout the years is essential. Unfortunately, such information is missing from most of the databases, leaving FSO players no choice but to use the standard visibility equation based on 2% contrast and other assumptions on the source luminance and its background. Another challenge is that visibility is measured using the visual wavelength of 550 nm. Extrapolating the measured attenuations to longer infrared wavelengths is not trivial and involves extensive experimentations. Scattering of electromagnetic waves by spherical droplets of different sizes is considered to simulate FSO scattering effects. This paper serves as an introduction to a series of publications regarding simulation of FSO atmospheric propagation. This first part focuses on attenuation due to rainfall. Additional weather parameters, such as rainfall rate, temperature and relative humidity are considered to effectively build the rain model. Comparison with already published experimental measurement is performed to validate the model. The scattering cross section due to rain is derived from the density of different raindrop sizes and the raindrops fall velocity is derived from the overall rainfall rate. Absorption due the presence of water vapor is computed using the temperature and relative humidity measurements.

  9. Ultrasonic attenuation in cuprate superconductors

    Indian Academy of Sciences (India)

    T Gupta; D M Gaitonde

    2002-05-01

    We calculate the longitudinal ultrasonic attenuation rate (UAR) in clean d-wave superconductors in the Meissner and the mixed phases. In the Meissner phase we calculate the contribution of previously ignored processes involving the excitation of a pair of quasi-holes or quasi-particles. There is a contribution ∝ in the regime B ≪ F ≪ 0 and a contribution ∝ 1/ in the regime F ≪ B ≪ 0. We find that these contributions to the UAR are large and cannot be ignored. In the mixed phase, using a semi-classical description, we calculate the electronic quasi-particle contribution to the UAR which at very low , has a independent term proportional to $\\sqrt{H}$.

  10. Attenuation characteristics of gypsum wallboard

    International Nuclear Information System (INIS)

    Increased cost of lead is promoting enhanced usage of common building materials for shielding in diagnostic medical and dental facilities where only a few half-value layers (HVLs) are needed. Attenuation of primary beam X-ray photons in gypsum wallboard as a function of kVp, filtration, and wallboard thickness have been measured. Findings, obtained using a Victoreen 555 with an 0.1 DAS probe in poor geometry, are substantially in agreement with the sparse data in the literature but extend to thicker wall configurations and different kVp and filtration parameters. These findings are of value in maximizing the benefit/cost ratio for diagnostic shielding, and strengthen the conviction that, where used for shielding purposes, common building materials must be installed carefully and HVL-depth dependence considered thoroughly. (author)

  11. Electron-impact ionization of heavy atomic ions

    International Nuclear Information System (INIS)

    General theoretical methods for the calculation of direct and indirect processes in the electron-impact ionization of heavy atomic ions are reviewed. Cross section results for Xe8+ and U89+ are presented. 12 refs., 4 figs

  12. Atomic and molecular collision processes

    International Nuclear Information System (INIS)

    530Accomplishments during the course of a 44-month program of code development and high precision calculations for electron collisions with atoms, atomic ions, and molecules are summarized. In electron-atom and -ion collisions, we were primarily concerned with the fundamental physics of the process that controls excitation in high temperature plasmas. In the molecular work, we pursued the development of techniques for accurate calculations of ro-vibrational excitation of polyatomic molecules, to the modeling of gas-phase laser systems. Highlights from the seven technical paper published as a result of this contract include: The resolution of a long history of unexplained anomalies and experimental/theoretical discrepancies by a demonstration that the Coulomb phase must be included in scattering amplitudes for electron-ion collisions. Definitive close-coupling calculations of cross sections for electron impact excitation of Be+, using a very elaborate expansion for the collision system and inclusion of both one- and two-body terms for the effect of core polarization. Detailed state-of-the-art calculations for electron-impact excitation of the sodium-like ion A ell 2+ that included core-polarization interactions, and which also produced new data on bound-state energy levels for the magnesium-like ion A ell + and oscillator strengths for A ell 2+. Partial cross sections for excitation of the 3p level of sodium at energies just above threshold calculated using a four-state close-coupling approach, including both total cross sections and those for excitation as a function of the change in the spin and orbital angular momentum projection quantum numbers of the target electron. Generalization of our electron-molecule scattering code to carry out full vibrational close-coupling calculations with an exact treatment of exchange and with a parameter-free representation of correlation and polarization interactions, and application to HF and H2

  13. Advances in atomic spectroscopy

    CERN Document Server

    Sneddon, J

    2000-01-01

    This fifth volume of the successful series Advances in Atomic Spectroscopy continues to discuss and investigate the area of atomic spectroscopy.It begins with a description of the use of various atomic spectroscopic methods and applications of speciation studies in atomic spectroscopy. The emphasis is on combining atomic spectroscopy with gas and liquid chromatography. In chapter two the authors describe new developments in tunable lasers and the impact they will have on atomic spectroscopy. The traditional methods of detection, such as photography and the photomultiplier, and how they are being replaced by new detectors is discussed in chapter three. The very active area of glow discharge atomic spectrometry is presented in chapter four where, after a brief introduction and historical review, the use of glow discharge lamps for atomic spectroscopy and mass spectrometry are discussed. Included in this discussion is geometry and radiofrequency power. The future of this source in atomic spectroscopy is also dis...

  14. Atomic and molecular manipulation

    CERN Document Server

    Mayne, Andrew J

    2011-01-01

    Work with individual atoms and molecules aims to demonstrate that miniaturized electronic, optical, magnetic, and mechanical devices can operate ultimately even at the level of a single atom or molecule. As such, atomic and molecular manipulation has played an emblematic role in the development of the field of nanoscience. New methods based on the use of the scanning tunnelling microscope (STM) have been developed to characterize and manipulate all the degrees of freedom of individual atoms and molecules with an unprecedented precision. In the meantime, new concepts have emerged to design molecules and substrates having specific optical, mechanical and electronic functions, thus opening the way to the fabrication of real nano-machines. Manipulation of individual atoms and molecules has also opened up completely new areas of research and knowledge, raising fundamental questions of "Optics at the atomic scale", "Mechanics at the atomic scale", Electronics at the atomic scale", "Quantum physics at the atomic sca...

  15. Positronium impact ionization of Alkali atoms

    CERN Document Server

    Ghosh, D

    2015-01-01

    Target ionization processes of alkali atoms by Positronium impact are investigated. Calculations are performed in the frame work of model potential formalism using the Coulomb distorted eikonal approximation. Interesting qualitative features are noted both in the scattered Ps and the ejected electron distributions in differential as well as double differential levels of the collision cross sections.

  16. Filtered back-projection reconstruction for attenuation proton CT along most likely paths

    Science.gov (United States)

    Quiñones, C. T.; Létang, J. M.; Rit, S.

    2016-05-01

    This work investigates the attenuation of a proton beam to reconstruct the map of the linear attenuation coefficient of a material which is mainly caused by the inelastic interactions of protons with matter. Attenuation proton computed tomography (pCT) suffers from a poor spatial resolution due to multiple Coulomb scattering (MCS) of protons in matter, similarly to the conventional energy-loss pCT. We therefore adapted a recent filtered back-projection algorithm along the most likely path (MLP) of protons for energy-loss pCT (Rit et al 2013) to attenuation pCT assuming a pCT scanner that can track the position and the direction of protons before and after the scanned object. Monte Carlo simulations of pCT acquisitions of density and spatial resolution phantoms were performed to characterize the new algorithm using Geant4 (via Gate). Attenuation pCT assumes an energy-independent inelastic cross-section, and the impact of the energy dependence of the inelastic cross-section below 100 MeV showed a capping artifact when the residual energy was below 100 MeV behind the object. The statistical limitation has been determined analytically and it was found that the noise in attenuation pCT images is 411 times and 278 times higher than the noise in energy-loss pCT images for the same imaging dose at 200 MeV and 300 MeV, respectively. Comparison of the spatial resolution of attenuation pCT images with a conventional straight-line path binning showed that incorporating the MLP estimates during reconstruction improves the spatial resolution of attenuation pCT. Moreover, regardless of the significant noise in attenuation pCT images, the spatial resolution of attenuation pCT was better than that of conventional energy-loss pCT in some studied situations thanks to the interplay of MCS and attenuation known as the West–Sherwood effect.

  17. Atomic structure and electron correlations

    International Nuclear Information System (INIS)

    Synchrotron experiments combined with theoretical calculations have already given much information on atomic structure and the effects of electron correlations, and this combination of theory and experiment is expected to yield much new information in coming years. In the calculations of photoabsorption cross sections, it is almost always necessary to include electron correlations in both initial and final states to obtain good agreement with experiment. The main theoretical approaches which include effects of electron correlations have been R-matrix theory, random phase approximation with exchange (RPAE), relativistic random phase approximation with exchange, and many-body perturbation theory

  18. Cognitive, Medical, and Neuroimaging Characteristics of Attenuated Mucopolysaccharidosis Type II

    Science.gov (United States)

    Yund, Brianna; Rudser, Kyle; Ahmed, Alia; Kovac, Victor; Nestrasil, Igor; Raiman, Julian; Mamak, Eva; Harmatz, Paul; Steiner, Robert; Lau, Heather; Vekaria, Pooja; Wozniak, Jeffrey R.; Lim, Kelvin O.; Delaney, Kathleen; Whitley, Chester; Shapiro, Elsa G.

    2014-01-01

    The phenotype of attenuated mucopolysaccharidosis type II (MPS II), also called Hunter syndrome, has not been previously studied in systematic manner. In contrast to the “severe” phenotype, the “attenuated” phenotype does not present with behavioral or cognitive impairment; however the presence of mild behavior and cognitive impairment that might impact long term functional outcomes is unknown. Previously, significant MRI abnormalities have been found in MPS II. Recent evidence suggests white matter abnormalities in many MPS disorders. Methods As the initial cross-sectional analysis of a longitudinal study, we studied the association of brain volumes and somatic disease burden with neuropsychological outcomes, including measures of intelligence, memory and attention in 20 patients with attenuated MPS II with a mean age of 15.8. MRI volumes were compared to 55 normal controls. Results While IQ and memory were average, measures of attention were one standard deviation below the average range. Corpus callosum volumes were significantly different from age-matched controls, differing by 22%. Normal age-related volume increases in white matter were not seen in MPS II patients as they were in controls. Somatic disease burden and white matter and corpus callosum volumes were significantly associated with attention deficits. Neither age at evaluation nor age at starting treatment predicted attention outcomes. Conclusions Despite average intelligence, attention is compromised in attenuated MPS II. Results confirm an important role of corpus callosum and cortical white matter abnormality in MPS II as well as the somatic disease burden in contributing to attention difficulties. Awareness by the patient and caregivers with appropriate management and symptomatic support will benefit the attenuated MPS II patient. PMID:25541100

  19. THE ORNL ATOM PROBE

    OpenAIRE

    Miller, M

    1986-01-01

    The ORNL Atom Probe is a microanalytical tool for studies in materials science. The instrument is a combination of a customized version of the vacuum system of the VG FIM-100 atom probe, an ORNL-designed microcomputer-controlled digital timing system, and a double curved CEMA Imaging Atom Probe detector. The atom probe combines four instruments into one - namely a field ion microscope, an energy compensated time-of-flight mass spectrometer, an imaging atom probe, and a pulsed laser atom probe.

  20. Elastic Scattering Properties of Ultracold Strontium Atoms

    Institute of Scientific and Technical Information of China (English)

    张计才; 朱遵略; 刘玉芳; 孙金锋

    2011-01-01

    We investigate the elastic scattering properties of strontium atoms at ultracold temperatures.The scattering parameters,such as s-wave scattering lengths,effective ranges and p-wave scattering lengths,are calculated for all stable isotope combinations of Sr atoms by the quantal method and semiclassical method,respectively.Good agreements are obtained.The scattering parameters are very sensitive to small changes of the reduced mass.Due to the repulsive interisotope and intraisotope s-wave scattering length and large elastic cross sections,84Sr-86Srmixture is a good candidate to realize Bose-Bose quantum degenerate atomic gases.%We investigate the elastic scattering properties of strontium atoms at ultracold temperatures. The scattering parameters, such as s-wave scattering lengths, effective ranges and p-wave scattering lengths, are calculated for all stable isotope combinations of Sr atoms by the quantal method and semiclassical method, respectively. Good agreements are obtained. The scattering parameters are very sensitive to small changes of the reduced mass. Due to the repulsive interisotope and intraisotope s-wave scattering length and large elastic cross sections, MSr-s(iSr mixture is a good candidate to realize Bose-Bose quantum degenerate atomic gases.

  1. Crossing Filaments

    CERN Document Server

    Filippov, Boris

    2011-01-01

    Solar filaments show the position of large scale polarity inversion lines and are used for the reconstruction of large-scale solar magnetic field structure on the basis of H{\\alpha} synoptic charts for the periods when magnetographic measurements were not available. Sometimes crossing filaments are seen in H{\\alpha} filtergrams. We analyze daily H{\\alpha} filtergrams from the archive of Big Bear Solar Observatory for the period of 1999-2003 to find crossing and interacting filaments. A number of examples are presented and filament patterns are compared with photospheric magnetic field distributions. We have found that all crossing filaments reveal quadrupolar magnetic configurations of the photospheric field and presume the presence of null points in the corona.

  2. Lung attenuation measurements in healthy young adults.

    NARCIS (Netherlands)

    Smit, H.J.M.; Golding, R.P.; Schramel, F.M.N.H.; Devillé, W.L.; Manoliu, R.A.; Postmus, P.E.

    2003-01-01

    Background: High-resolution computed tomography (HRCT) attenuation measurements may be more sensitive in finding early emphysematous changes in relatively young subjects than lung function measurements. Objectives: To define lung attenuation parameters in smokers and never-smokers. Methods: A prospe

  3. Simple parameterization of nuclear attenuation data

    CERN Document Server

    Akopov, N; Akopov, Z

    2007-01-01

    Based on the nuclear attenuation data obtained by the HERMES experiment on nitrogen and krypton nuclei, it is shown that the nuclear attenuation $R_M^{h}$ can be parametrised in a form of a linear polynomial $P_1=a_{11}$ + $\\tau a_{12}$, where $\\tau$ is the formation time, which depends on the energy of the virtual photon $\

  4. Precision Model for Microwave Rotary Vane Attenuator

    DEFF Research Database (Denmark)

    Guldbrandsen, Tom

    1979-01-01

    A model for a rotary vane attenuator is developed to describe the attenuator reflection and transmission coefficients in detail. All the parameters of the model can be measured in situ, i.e., without diassembling any part. The tranmission errors caused by internal reflections are calculated from ...

  5. Multichannel eikonal treatment of electron--atom collisions

    International Nuclear Information System (INIS)

    A multichannel treatment of atomic collisions is presented and applied to the excitation of atomic hydrogen and helium by electrons with incident energy above the ionization threshold. The calculated cross sections compare very favorably with other refined theoretical procedures and with various experiments

  6. Photoabsorption by atoms in external fields near the ionization threshold

    International Nuclear Information System (INIS)

    An expression is obtained for the photoabsorption cross section of atoms near the ionization threshold in an external static magnetic field. The results satisfactorily describe quasi-Landau resonances observed experimentally in the photoabsorption by hydrogen atoms in a magnetic field. A similar expression is obtained for the photoabsorption in an electric field

  7. Measurements of photon mass attenuation coefficients for Ge and BGO crystals at 10 MeV

    International Nuclear Information System (INIS)

    The photon mass attenuation coefficients of the important materials for γ-ray detection, Ge and BGO (Bi4Ge3O12) crystals, have been measured for 10.0 MeV γ-rays. The measurement system using the laser-Compton backscattering γ-rays and the high-resolution high-energy photon spectrometer has been developed and utilized. The effectiveness of the system achieving the total systematic uncertainties of 0.5% for the measurements of the photon mass attenuation coefficients was demonstrated. It was shown that the measured photon mass attenuation coefficients, 318.1±1.7 [cm2/g] for the Ge crystal and 425.2±2.4 [cm2/g] for the BGO crystal, agree within the achieved experimental uncertainties with the evaluated values including atomic and nuclear processes at 10.0 MeV. (author)

  8. Presenting the Bohr Atom.

    Science.gov (United States)

    Haendler, Blanca L.

    1982-01-01

    Discusses the importance of teaching the Bohr atom at both freshman and advanced levels. Focuses on the development of Bohr's ideas, derivation of the energies of the stationary states, and the Bohr atom in the chemistry curriculum. (SK)

  9. Comparison of Reg. Guide 1.99 fluence attenuation methods

    Energy Technology Data Exchange (ETDEWEB)

    Jones, E.N. [TransWare Enterprises Inc., 1565 Mediterranean Dr., Sycamore, IL 60178 (United States)

    2011-07-01

    U.S. Regulatory Guide 1.99 Revision 2 (U.S. Nuclear Regulatory Commission, 1988, 'Radiation Embrittlement of Reactor Vessel Materials,' Regulatory Guide 1.99, Revision 2, Washington, D.C.) provides for the use of two substantially different methods for determining through-wall fluence in nuclear reactor pressure vessels. One method is a generic attenuation curve based on a simplistic exponential decay equation. Partly due to the simplicity of its application, the generic attenuation method is predominantly used for licensing calculations. However, it has a limitation in that at increasing distances away from the core belt-line, it becomes increasingly less accurate because it cannot account for neutron streaming effects in the cavity region surrounding the pressure vessel. The other attenuation method is based on a displacement per atom (dpa) calculation specific to the reactor vessel structure. The dpa method provides a more accurate representation of fluence attenuation through the reactor pressure vessel (RPV) wall at all elevations of the pressure vessel because it does account for neutron streaming in the cavity region. A requirement for using the dpa method, however, is an accurate flux solution through the RPV wall. This requirement has limited the use of traditional transport methods, such as discrete ordinates, that are limited by their treatment of cavity regions (i.e., air) outside the pressure vessel wall. TransWare Enterprises, under the sponsorship of EPRI and BWRVIR has developed an advanced three-dimensional transport methodology capable of producing fully converged flux solutions throughout the entire reactor system, including in the cavity region and primary shield structures. This methodology provides an accurate and reliable determination of through-wall fluence in boiling water reactor (BWR) and pressurized water reactor (PWR) pressure vessels, thus allowing the dpa method to be implemented with high reliability. Using this advanced 3

  10. Imaging Rayleigh wave attenuation and phase velocity in the western and central United States

    Science.gov (United States)

    Bao, X.; Dalton, C. A.; Jin, G.; Gaherty, J. B.

    2013-12-01

    The EarthScope USArray provides an opportunity to obtain detailed images of the continental upper mantle at an unprecedented scale. The majority of mantle models derived from USArray data to date contain spatial variations in seismic-wave speed; however, little is known about the attenuation structure of the North American upper mantle. Joint interpretation of seismic attenuation and velocity models can improve upon the interpretations based only on velocity, and provide important constraints on the temperature, composition, melt content, and volatile content of the mantle. We jointly invert Rayleigh wave phase and amplitude observations for phase velocity and attenuation maps for the western and central United States using USArray data. This approach exploits the amplitudes' sensitivity to velocity and the phase delays' sensitivity to attenuation. The phase and amplitude data are measured in the period range 20--100 s using a new interstation cross-correlation approach, based on the Generalized Seismological Data Functional algorithm, that takes advantage of waveform similarity at nearby stations. The Rayleigh waves are generated from 670 large teleseismic earthquakes that occurred between 2006 and 2012, and measured from all available Transportable Array stations. We consider two separate and complementary approaches for imaging attenuation variations: (1) the Helmholtz tomography (Lin et al., 2012) and (2) two-station path tomography. Results obtained from the two methods are contrasted. We provide a preliminary interpretation based on the observed relationship between Rayleigh wave attenuation and phase velocity.

  11. Antiprotonic Helium Atoms

    OpenAIRE

    Kartavtsev, O. I.

    1995-01-01

    Metastable antiprotonic helium atoms $^{3,4}\\! H\\! e\\bar pe$ have been discovered recently in experiments of the delayed annihilation of antiprotons in helium media. These exotic atoms survive for an enormous time (about tens of microseconds) and carry the extremely large total angular momentum $L\\sim 30-40$. The theoretical treatment of the intrinsic properties of antiprotonic helium atoms, their formation and collisions with atoms and molecules is discussed.

  12. Atomic Scale Plasmonic Switch

    OpenAIRE

    Emboras, A.; Niegemann, J.; Ma, P; Haffner, C; Pedersen, A.; Luisier, M.; Hafner, C; Schimmel, T.; Leuthold, J.

    2016-01-01

    The atom sets an ultimate scaling limit to Moore’s law in the electronics industry. While electronics research already explores atomic scales devices, photonics research still deals with devices at the micrometer scale. Here we demonstrate that photonic scaling, similar to electronics, is only limited by the atom. More precisely, we introduce an electrically controlled plasmonic switch operating at the atomic scale. The switch allows for fast and reproducible switching by means of the relocat...

  13. Atomizing nozzle and process

    Science.gov (United States)

    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.

  14. Atoms Talking to SQUIDs

    CERN Document Server

    Hoffman, J E; Kim, Z; Wood, A K; Anderson, J R; Dragt, A J; Hafezi, M; Lobb, C J; Orozco, L A; Rolston, S L; Taylor, J M; Vlahacos, C P; Wellstood, F C

    2011-01-01

    We present a scheme to couple trapped $^{87}$Rb atoms to a superconducting flux qubit through a magnetic dipole transition. We plan to trap atoms on the evanescent wave outside an ultrathin fiber to bring the atoms to less than 10 $\\mu$m above the surface of the superconductor. This hybrid setup lends itself to probing sources of decoherence in superconducting qubits. Our current plan has the intermediate goal of coupling the atoms to a superconducting LC resonator.

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

    Science.gov (United States)

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

    1989-02-01

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

  16. Atomic Spectra Database (ASD)

    Science.gov (United States)

    SRD 78 NIST Atomic Spectra Database (ASD) (Web, free access)   This database provides access and search capability for NIST critically evaluated data on atomic energy levels, wavelengths, and transition probabilities that are reasonably up-to-date. The NIST Atomic Spectroscopy Data Center has carried out these critical compilations.

  17. Estimation of the matrix attenuation in heterogeneous radioactive waste drums using dual-energy computed tomography

    International Nuclear Information System (INIS)

    Gamma spectroscopy measurements of the activity of radionuclides in nuclear waste drums must be corrected for the attenuation due to the non-homogeneous waste matrix. The attenuation factors depend on the matrix local density and effective atomic number, and on the energy of the gamma rays emitted by the radionuclides. The requirements for the system presented in this paper are to estimate the attenuation in low-density (3), 120 l drums containing radionuclides emitting in the (59.5 keV, 1.4 MeV) energy range. A series of three-dimensional (3D) attenuation maps of the drum are computed using a dual-energy computerized tomography (DE-CT) system with an external, polychromatic X-ray source. The system successively records low-energy (mean energy about 62 keV) and high-energy (about 300 keV) projections using different tube voltages, anode current, and filtration. Each projection is acquired by 22 BGO scintillators - PM detectors in fan-beam geometry. The drum is rotated and elevated in a helical scan. A DE calibration transforms pairs of DE projections into pairs of 'equivalent basis materials (BM)' projections. This non-linear transformation allows to correct for polychromaticity. After reconstruction, the two 'equivalent BM' 3D maps are used, together with tabulated attenuation data of the BMs, in order to extrapolate the 3D attenuation map at any energy peak. Maps of the mass density and of the effective atomic number can also be computed. The total examination time is less than 5 min. Experimental images are shown

  18. Live attenuated intranasal influenza vaccine.

    Science.gov (United States)

    Esposito, Susanna; Montinaro, Valentina; Groppali, Elena; Tenconi, Rossana; Semino, Margherita; Principi, Nicola

    2012-01-01

    Annual vaccination is the most effective means of preventing and controlling influenza epidemics, and the traditional trivalent inactivated vaccine (TIV) is by far the most widely used. Unfortunately, it has a number of limitations, the most important of which is its poor immunogenicity in younger children and the elderly, the populations at greatest risk of severe influenza. Live attenuated influenza vaccine (LAIV) has characteristics that can overcome some of these limitations. It does not have to be injected because it is administered intranasally. It is very effective in children and adolescents, among whom it prevents significantly more cases of influenza than the traditional TIV. However, its efficacy in adults has not been adequately documented, which is why it has not been licensed for use by adults by the European health authorities. LAIV is safe and well tolerated by children aged > 2 y and adults, but some concerns arisen regarding its safety in younger children and subjects with previous asthma or with recurrent wheezing. Further studies are needed to solve these problems and to evaluate the possible role of LAIV in the annual vaccination of the general population.

  19. Beta attenuation transmission system (BATS)

    Energy Technology Data Exchange (ETDEWEB)

    Hagan, R.C.; Fullbright, H.J.

    1977-01-01

    The beta attenuation transmission system (BATS) is an automated radiation gauge designed for quantitative measurement of component thickness in explosive detonators. The BATS was designed and built by Group M-1, the Nondestructive Testing Group, of the Los Alamos Scientific Laboratory to measure the areal thickness, in mg/cm/sup 2/, of a cylinder of high explosive (HE) enclosed within a plastic holder. The problem is to determine the density of the HE. A /sup 90/Sr source is collimated by a 0.25 x 1.59-mm slit, and the transmitted beta-particle flux is detected by a plastic scintillator, coupled to a photomultiplier tube. The detonator is transported through the radiation beam by a leadscrew, ballnut, stepping-motor combination. Continuous analog position data are available, derived from the output from a linear-actuated potentiometer attached to the scanner. A linear electrometer amplifies the detected signal, which is then integrated for a preselected time, to obtain the desired statistical accuracy. A microprocessor (..mu..P) is used to control the scanner position and to make the data readings at the assigned positions. The data are stored, and, at the completion of the scan, are processed into the desired format. The final answer is displayed to the operator or output to a peripheral device for permanent record. The characteristics of the radiation source, the collimator, the signal detection and conditioning, and the final results are described in detail. The scanner and the microprocessor control system are briefly outlined.

  20. Attenuation of diacylglycerol second messengers

    Energy Technology Data Exchange (ETDEWEB)

    Bishop, W.R.; Ganong, B.R.; Bell, R.M.

    1986-05-01

    Diacylglycerol(DAG) derived from phosphatidylinositol activates protein kinase C in agonist-stimulated cells. At least two pathways may contribute to the attenuation of the DAG signal: (1) phosphorylation to phosphatidic acid(PA) by DAG kinase(DGK), and (2) deacylation by DAG and monoacylglycerol lipases. A number of DAG analogs were tested as substrates and inhibitors of partially purified pig brain DGK. Two analogs were potent inhibitors in vitro, 1-monooleoylglycerol(MOG,K/sub I/ = 91 ..mu..M) and diotanoylethyleneglycol (diC/sub 8/EG, K/sub I/ = 58 ..mu..M). These compounds were tested in human platelets. DiC/sub 8/EG inhibited (70 - 100%) (/sup 32/P/sub i/) incorporation into PA in thrombin-stimulated platelets. Under these conditions the DAG signal was somewhat long-lived but was still metabolized, presumably by the lipase pathway. MOG treatment elevated DAG levels up to 4-fold in unstimulated platelets. The DAG formed was in a pool where it did not activate protein kinase C. Thrombin-stimulation of MOG-treated platelets resulted in DAG levels 10-fold higher than control platelets. This appears to be due to the inability of these platelets to metabolize agonist-linked DAG via the lipase pathway. The development of specific inhibitors of DAG kinase and DAG lipase, in conjunction with mass quantification of DAG levels as used here, will provide further insights into the regulation of DAG second messengers.

  1. Ponderomotive light squeezing with atomic cavity optomechanics

    CERN Document Server

    Brooks, Daniel W C; Brahms, Nathan; Purdy, Thomas P; Schreppler, Sydney; Stamper-Kurn, Dan M

    2011-01-01

    Accessing distinctly quantum aspects of the interaction between light and the position of a mechanical object has been an outstanding challenge to cavity-optomechanical systems. Only cold-atom implementations of cavity optomechanics have indicated effects of the quantum fluctuations in the optical radiation pressure force. Here we use such a system, in which quantum photon-number fluctuations significantly drive the center of mass of an atomic ensemble inside a Fabry-Perot cavity. We show that the optomechanical response both amplifies and ponderomotively squeezes the quantum light field. We also demonstrate that classical optical fluctuations can be attenuated by 26 dB or amplified by 20 dB with a weak input pump power of < 40 pW, and characterize the optomechanical amplifier's frequency-dependent gain and phase response in both the amplitude and phase-modulation quadratures.

  2. The influence of noise sources on cross-correlation amplitudes

    CERN Document Server

    Hanasoge, Shravan M

    2012-01-01

    We use analytical examples and asymptotic forms to examine the mathematical structure and physical meaning of the seismic cross correlation measurement. We show that in general, cross correlations are not Green's functions of medium, and may be very different depending on the source distribution. The modeling of noise sources using spatial distributions as opposed to discrete collections of sources is emphasized. When stations are illuminated by spatially complex source distributions, cross correlations show arrivals at a variety of time lags, from zero to the maximum surface-wave arrival time. Here, we demonstrate the possibility of inverting for the source distribution using the energy of the full cross-correlation waveform. The interplay between the source distribution and wave attenuation in determining the functional dependence of cross correlation energies on station-pair distance is quantified. Without question, energies contain information about wave attenuation. However, the accurate interpretation o...

  3. Graphene-based Electronically Tuneable Microstrip Attenuator

    Directory of Open Access Journals (Sweden)

    L. Pierantoni

    2014-06-01

    Full Text Available This paper presents the design of a graphene- based electronically tuneable microstrip attenuator operating at a frequency of 5 GHz. The use of graphene as a variable resistor is discussed and the modelling of its electromagnetic properties at microwave frequencies is fully addressed. The design of the graphene-based attenuator is described. The structure integrates a patch of graphene, whose characteristics can range from being a fairly good conductor to a highly lossy material, depending on the applied voltage. By applying the proper voltage through two high-impedance bias lines, the surface resistivity of graphene can be modified, thereby changing the insertion loss of the microstrip attenuator.

  4. Single Atom Plasmonic Switch

    CERN Document Server

    Emboras, Alexandros; Ma, Ping; Haffner, Christian; Luisier, Mathieu; Hafner, Christian; Schimmel, Thomas; Leuthold, Juerg

    2015-01-01

    The atom sets an ultimate scaling limit to Moores law in the electronics industry. And while electronics research already explores atomic scales devices, photonics research still deals with devices at the micrometer scale. Here we demonstrate that photonic scaling-similar to electronics-is only limited by the atom. More precisely, we introduce an electrically controlled single atom plasmonic switch. The switch allows for fast and reproducible switching by means of the relocation of an individual or at most - a few atoms in a plasmonic cavity. Depending on the location of the atom either of two distinct plasmonic cavity resonance states are supported. Experimental results show reversible digital optical switching with an extinction ration of 10 dB and operation at room temperature with femtojoule (fJ) power consumption for a single switch operation. This demonstration of a CMOS compatible, integrated quantum device allowing to control photons at the single-atom level opens intriguing perspectives for a fully i...

  5. Interferometry with atoms

    International Nuclear Information System (INIS)

    Optics and interferometry with matter waves is the art of coherently manipulating the translational motion of particles like neutrons, atoms and molecules. Coherent atom optics is an extension of techniques that were developed for manipulating internal quantum states. Applying these ideas to translational motion required the development of techniques to localize atoms and transfer population coherently between distant localities. In this view position and momentum are (continuous) quantum mechanical degrees of freedom analogous to discrete internal quantum states. In our contribution we start with an introduction into matter wave optics in sect. 1, discuss coherent atom optics and atom interferometry techniques for molecular beams in sect. 2 and for trapped atoms in sect. 3. In sect. 4 we then describe tools and experiments that allow to probe the evolution of quantum states of many-body systems by atom interference.

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

    International Nuclear Information System (INIS)

    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 C60.

  7. Attenuation layer for magnetostatic wave (MSW) absorbers

    Science.gov (United States)

    Glass, H. L.; Adkins, L. R.; Stearns, F. S.

    1984-09-01

    A new technique has been developed for the suppression of MSW end reflections which give rise to passband ripple. The basic idea is to provide a thin film of highly attenuating epitaxial material at the ends of a MSW delay line while preserving high quality YIG in the active region of the device. The GGG wafer preparation is a three step process which involves: (1) the growth of the attenuation layer, (2) the removal of this layer from the central region of the wafer and (3) the growth of high quality YIG on the remaining structure. Delay lines using the attenuation layer for end terminations have been evaluated experimentally and compared to devices utilizing other termination methods. The results indicate that the attenuation layer method produces ripple suppression characteristics which are the equal of those obtained with other termination techniques. The advantage of this new method lies in its suitability for large quantity fabrication requirements.

  8. Radiation-attenuated vaccine for lungworm disease

    International Nuclear Information System (INIS)

    The work done at the Indian Veternary Research Institute, Izatnagar, on the development of a vaccine for lungworm diseases is reported. Research work done includes: (1) studies on the epidemiology and the incidence of the lungworm infections, (ii) studies on the radiation-attenuated lungworm Dictyocaulus filaria vaccine, (iii) studies on other parasites using ionizing radiation, (iv) incidence of lungworm infection in sheep in Jammu and Kashmir State, (v) suitable dose of gamma radiation for attenuation, (vi) laboratory studies with radiation-attenuated D. filaria vaccine, (vii) serology of D. filaria infection, (viii) field trials with the radiation-attenuated vaccine, (ix) immune response of previously exposed lambs to vaccination, (x) comparative susceptibility of sheep and goats to infection with D. filaria, (xi) quantitative studies of D. filaria in lambs and (xii) production and supply of lungworm vaccine. (A.K.)

  9. Electron Effective-Attenuation-Length Database

    Science.gov (United States)

    SRD 82 NIST Electron Effective-Attenuation-Length Database (PC database, no charge)   This database provides values of electron effective attenuation lengths (EALs) in solid elements and compounds at selected electron energies between 50 eV and 2,000 eV. The database was designed mainly to provide EALs (to account for effects of elastic-eletron scattering) for applications in surface analysis by Auger-electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS).

  10. ATTENUATION AND FLANKING TRANSMISSION IN LIGHTWEIGHT STRUCTURES

    DEFF Research Database (Denmark)

    Brunskog, Jonas; Lhomond, Alice; Ohlrich, Mogens

    2007-01-01

    In this paper the attenuation and flanking transmissions of impact noise in lightweight building structures is studied using a modal approach. The structural field is mainly analysed, putting the main attention to the parts being important in the modelling. The amount of attenuation produced by the...... periodically reinforcing beams used in lightweight building structures is analysed. The consequence of these factors in modelling flanking transmission is also discussed....

  11. Two dipolar atoms in a harmonic trap

    Science.gov (United States)

    Ołdziejewski, Rafał; Górecki, Wojciech; Rzążewski, Kazimierz

    2016-05-01

    Two identical dipolar atoms moving in a harmonic trap without an external magnetic field are investigated. Using the algebra of angular momentum we reduce the problem to a simple numerics. We show that the internal spin-spin interactions between the atoms couple to the orbital angular momentum causing an analogue of the Einstein-de Haas effect. We show a possibility of adiabatically pumping our system from the s-wave to the d-wave relative motion. The effective spin-orbit coupling occurs at anti-crossings of the energy levels.

  12. Techniques for Measuring Aerosol Attenuation using the Central Laser Facility at the Pierre Auger Observatory

    CERN Document Server

    ,

    2013-01-01

    The Pierre Auger Observatory in Malarg\\"ue, Argentina, is designed to study the properties of ultra-high energy cosmic rays with energies above 1018 eV. It is a hybrid facility that employs a Fluorescence Detector to perform nearly calorimetric measurements of Extensive Air Shower energies. To obtain reliable calorimetric information from the FD, the atmospheric conditions at the observatory need to be continuously monitored during data acquisition. In particular, light attenuation due to aerosols is an important atmospheric correction. The aerosol concentration is highly variable, so that the aerosol attenuation needs to be evaluated hourly. We use light from the Central Laser Facility, located near the center of the observatory site, having an optical signature comparable to that of the highest energy showers detected by the FD. This paper presents two procedures developed to retrieve the aerosol attenuation of fluorescence light from CLF laser shots. Cross checks between the two methods demonstrate that re...

  13. Monte Carlo calculations for gamma-ray mass attenuation coefficients of some soil samples

    International Nuclear Information System (INIS)

    Highlights: • Gamma-ray mass attenuation coefficients of soils. • Radiation shielding properties of soil. • Comparison of calculated results with the theoretical and experimental ones. • The method can be applied to various media. - Abstract: We developed a simple Monte Carlo code to determine the mass attenuation coefficients of some soil samples at nine different gamma-ray energies (59.5, 80.9, 122.1, 159.0, 356.5, 511.0, 661.6, 1173.2 and 1332.5 keV). Results of the Monte Carlo calculations have been compared with tabulations based upon the results of photon cross section database (XCOM) and with experimental results by other researchers for the same samples. The calculated mass attenuation coefficients were found to be very close to the theoretical values and the experimental results

  14. Long range intermolecular forces in triatomic systems: connecting the atom-diatom and atom-atom-atom representations

    OpenAIRE

    Cvitas, Marko T.; Soldan, Pavel; Hutson, Jeremy M.

    2005-01-01

    The long-range forces that act between three atoms are analysed in both atom-diatom and atom-atom-atom representations. Expressions for atom-diatom dispersion coefficients are obtained in terms of 3-body nonadditive coefficients. The anisotropy of atom-diatom C_6 dispersion coefficients arises primarily from nonadditive triple-dipole and quadruple-dipole forces, while pairwise-additive forces and nonadditive triple-dipole and dipole-dipole-quadrupole forces contribute significantly to atom-di...

  15. Atomic and Molecular Data Activities at NIFS in 2009 - 2011

    International Nuclear Information System (INIS)

    We open and maintain the NIFS atomic and molecular numerical databases. Numbers of data records increase to 476,048 in total (as of Aug. 23, 2011) and mainly new data are added for AMDIS (electron impact ionization, excitation, and recombination cross sections and rate coefficients) and CHART (charge transfer of atom - ion collisions cross sections) during last two years. A collaboration group has started for research on atomic and molecular processes in plasma using the Large Helical Device and we measure visible and extreme ultraviolet spectra of W and rare earth elements. We also organize a collaboration group with atomic physicists from Japanese universities for research on W to study atomic data, spectra and collisional-radiative models for W ions. (author)

  16. Atom-interferometric measurement of Stark level splittings

    Science.gov (United States)

    Zhao, Jianming; Raithel, Georg

    2016-05-01

    Rydberg atoms are highly sensitive to external electric fields due to their large polarizability, scaling as n7 (n is the principal quantum number). In cesium, nS Rydberg levels mix with nearby (n-4) high- l states, forming sequences of avoided crossings. Mixed adiabatic/diabatic passages through these crossings are employed as beam splitters and recombiners in an atom-interferometric measurement of energy level splittings. We subject cold cesium atoms to laser-excitation, electric-field and detection sequences that constitute an (internal-state) atom interferometer. For the read-out of the interferometer we utilize state-dependent collisions, which selectively remove atoms of one kind from the detected signal. We investigate the dependence of the interferometric signal on timing and field parameters, and find good agreement with quantum simulations of the interferometer. Fourier analysis of the interferometric signals yield coherence frequencies that agree with corresponding energy-level differences in calculated Stark maps.

  17. Comparison of electrothermal atomization diode laser Zeeman- and wavelength-modulated atomic absorption and coherent forward scattering spectrometry

    International Nuclear Information System (INIS)

    Atomic absorption and coherent forward scattering spectrometry by using a near-infrared diode laser with and without Zeeman and wavelength modulation were carried out with graphite furnace electrothermal atomization. Analytical curves and limits of detection were compared. The magnetic field was modulated with 50 Hz, and the wavelength of the diode laser with 10 kHz. Coherent forward scattering was measured with crossed and slightly uncrossed polarizers. The results show that the detection limits of atomic absorption spectrometry are roughly the same as those of coherent forward scattering spectrometry with crossed polarizers. According to the theory with bright flicker noise limited laser sources the detection limits and linear ranges obtained with coherent forward scattering spectrometry with slightly uncrossed polarizers are significantly better than those obtained with crossed polarizers and with atomic absorption spectrometry. This is due to the fact that employing approaches of polarization spectroscopy reduce laser intensity fluctuations to their signal carried fractions

  18. Atom-atom interactions around the band edge of a photonic crystal waveguide

    Science.gov (United States)

    Hood, Jonathan D.; Goban, Akihisa; Asenjo-Garcia, Ana; Lu, Mingwu; Yu, Su-Peng; Chang, Darrick E.; Kimble, H. J.

    2016-09-01

    Tailoring the interactions between quantum emitters and single photons constitutes one of the cornerstones of quantum optics. Coupling a quantum emitter to the band edge of a photonic crystal waveguide (PCW) provides a unique platform for tuning these interactions. In particular, the cross-over from propagating fields E(x)∝e±ikxxE(x)∝e±ikxx outside the bandgap to localized fields E(x)∝e-κx|x|E(x)∝e-κx|x| within the bandgap should be accompanied by a transition from largely dissipative atom-atom interactions to a regime where dispersive atom-atom interactions are dominant. Here, we experimentally observe this transition by shifting the band edge frequency of the PCW relative to the D1D1 line of atomic cesium for N¯=3.0±0.5N¯=3.0±0.5 atoms trapped along the PCW. Our results are the initial demonstration of this paradigm for coherent atom-atom interactions with low dissipation into the guided mode.

  19. Analytical evaluation of atomic form factors: application to Rayleigh scattering

    CERN Document Server

    Safari, L; Amaro, P; Jänkälä, K; Fratini, F

    2014-01-01

    Atomic form factors are widely used for the characterization of targets and specimens, from crystallography to biology. By using recent mathematical results, here we derive an analytical expression for the atomic form factor within the independent particle model constructed from nonrelativistic screened hydrogenic wavefunctions. The range of validity of this analytical expression is checked by comparing the analytically obtained form factors with the ones obtained within the Hartee-Fock method. As an example, we apply our analytical expression for the atomic form factor to evaluate the differential cross section for Rayleigh scattering off neutral atoms.

  20. Analytical evaluation of atomic form factors: Application to Rayleigh scattering

    Energy Technology Data Exchange (ETDEWEB)

    Safari, L., E-mail: laleh.safari@ist.ac.at [IST Austria (Institute of Science and Technology Austria), Am Campus 1, 3400 Klosterneuburg (Austria); Department of Physics, University of Oulu, Box 3000, FI-90014 Oulu (Finland); Santos, J. P. [Laboratório de Instrumentação, Engenharia Biomédica e Física da Radiação (LIBPhys-UNL), Departamento de Física, Faculdade de Ciências e Tecnologia, FCT, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal); Amaro, P. [Laboratório de Instrumentação, Engenharia Biomédica e Física da Radiação (LIBPhys-UNL), Departamento de Física, Faculdade de Ciências e Tecnologia, FCT, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal); Physikalisches Institut, Universität Heidelberg, D-69120 Heidelberg (Germany); Jänkälä, K. [Department of Physics, University of Oulu, Box 3000, FI-90014 Oulu (Finland); Fratini, F. [Department of Physics, University of Oulu, Box 3000, FI-90014 Oulu (Finland); Institute of Atomic and Subatomic Physics, TU Wien, Stadionallee 2, 1020 Wien (Austria); Departamento de Física, Instituto de Ciências Exatas, Universidade Federal de Minas Gerais, 31270-901 Belo Horizonte, MG (Brazil)

    2015-05-15

    Atomic form factors are widely used for the characterization of targets and specimens, from crystallography to biology. By using recent mathematical results, here we derive an analytical expression for the atomic form factor within the independent particle model constructed from nonrelativistic screened hydrogenic wave functions. The range of validity of this analytical expression is checked by comparing the analytically obtained form factors with the ones obtained within the Hartee-Fock method. As an example, we apply our analytical expression for the atomic form factor to evaluate the differential cross section for Rayleigh scattering off neutral atoms.

  1. Electron Elastic-Scattering Cross-Section Database

    Science.gov (United States)

    SRD 64 NIST Electron Elastic-Scattering Cross-Section Database (PC database, no charge)   This database provides values of differential elastic-scattering cross sections, corresponding total elastic-scattering cross sections, phase shifts, and transport cross sections for elements with atomic numbers from 1 to 96 and for electron energies between 50 eV and 20,000 eV (in steps of 1 eV).

  2. Single atom microscopy.

    Science.gov (United States)

    Zhou, Wu; Oxley, Mark P; Lupini, Andrew R; Krivanek, Ondrej L; Pennycook, Stephen J; Idrobo, Juan-Carlos

    2012-12-01

    We show that aberration-corrected scanning transmission electron microscopy operating at low accelerating voltages is able to analyze, simultaneously and with single atom resolution and sensitivity, the local atomic configuration, chemical identities, and optical response at point defect sites in monolayer graphene. Sequential fast-scan annular dark-field (ADF) imaging provides direct visualization of point defect diffusion within the graphene lattice, with all atoms clearly resolved and identified via quantitative image analysis. Summing multiple ADF frames of stationary defects produce images with minimized statistical noise and reduced distortions of atomic positions. Electron energy-loss spectrum imaging of single atoms allows the delocalization of inelastic scattering to be quantified, and full quantum mechanical calculations are able to describe the delocalization effect with good accuracy. These capabilities open new opportunities to probe the defect structure, defect dynamics, and local optical properties in 2D materials with single atom sensitivity. PMID:23146658

  3. Ionization of atomic hydrogen by 30 1000 keV antiprotons

    Energy Technology Data Exchange (ETDEWEB)

    Knudsen, H.; Mikkelsen, U.; Paludan, K. [Institute of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C (Denmark); Kirsebom, K.; Moller, S.P.; Uggerhoj, E. [Institute for Synchrotron Radiation, University of Aarhus, DK-8000 Aarhus C (Denmark); Slevin, J. [Department of Experimental Physics, St. Patrick`s College, Maynooth (Ireland); Charlton, M. [Department of Physics and Astronomy, University College London, London WC1E 6BT (United Kingdom); Morenzoni, E. [Paul Scherrer Institut, Villigen, CH-4234 (Switzerland)

    1995-06-05

    Ionization in collisions between antiprotons and atomic hydrogen is perhaps the least complicated and most fundamental process that can be treated by atomic-collision theory. We present measurements of the ionization cross section for 30--1000 keV antiprotons colliding with atomic hydrogen.

  4. Atomic homodyne detection of weak atomic transitions.

    Science.gov (United States)

    Gunawardena, Mevan; Elliott, D S

    2007-01-26

    We have developed a two-color, two-pathway coherent control technique to detect and measure weak optical transitions in atoms by coherently beating the transition amplitude for the weak transition with that of a much stronger transition. We demonstrate the technique in atomic cesium, exciting the 6s(2)S(1/2) --> 8s(2)S(1/2) transition via a strong two-photon transition and a weak controllable Stark-induced transition. We discuss the enhancement in the signal-to-noise ratio for this measurement technique over that of direct detection of the weak transition rate, and project future refinements that may further improve its sensitivity and application to the measurement of other weak atomic interactions.

  5. Metal atom oxidation laser

    International Nuclear Information System (INIS)

    A chemical laser which operates by formation of metal or carbon atoms and reaction of such atoms with a gaseous oxidizer in an optical resonant cavity is described. The lasing species are diatomic or polyatomic in nature and are readily produced by exchange or other abstraction reactions between the metal or carbon atoms and the oxidizer. The lasing molecules may be metal or carbon monohalides or monoxides

  6. Advances in atomic physics

    Directory of Open Access Journals (Sweden)

    Tharwat M. El-Sherbini

    2015-09-01

    Full Text Available In this review article, important developments in the field of atomic physics are highlighted and linked to research works the author was involved in himself as a leader of the Cairo University – Atomic Physics Group. Starting from the late 1960s – when the author first engaged in research – an overview is provided of the milestones in the fascinating landscape of atomic physics.

  7. Advances in atomic physics

    OpenAIRE

    Tharwat M. El-Sherbini

    2015-01-01

    Graphical abstract In this review article, important developments in the field of atomic physics are highlighted and linked to research works the author was involved in himself as a leader of the Cairo University – Atomic Physics Group. Starting from the late 1960s – when the author first engaged in research - an overview is provided of the milestones in the fascinating landscape of atomic physics.

  8. Atomic and Molecular Physics

    OpenAIRE

    Cohen-Tannoudji, Claude

    2015-01-01

    When physicists began to explore the world of atoms more precisely, as they endeavoured to understand its structure and the laws governing its behaviour, they soon encountered serious difficulties. Our intuitive concepts, based on our daily experience of the macroscopic world around us, proved to be completely erroneous on the atomic scale; the atom was incomprehensible within the framework of classical physics. In order to uncover these new mysteries, after a great deal of trial and error, e...

  9. Advances in atomic spectroscopy

    CERN Document Server

    Sneddon, J

    1997-01-01

    This series describes selected advances in the area of atomic spectroscopy. It is primarily intended for the reader who has a background in atmoic spectroscopy; suitable to the novice and expert. Although a widely used and accepted method for metal and non-metal analysis in a variety of complex samples, Advances in Atomic Spectroscopy covers a wide range of materials. Each Chapter will completely cover an area of atomic spectroscopy where rapid development has occurred.

  10. Advances in atomic spectroscopy

    CERN Document Server

    Sneddon, J

    1995-01-01

    This series describes selected advances in the area of atomic spectroscopy. It is promarily intended for the reader who has a background in atmoic spectroscopy; suitable to the novice and expert. Although a widely used and accepted method for metal and non-metal analysis in a variety of complex samples, Advances in Atomic Spectroscopy covers a wide range of materials. Each Chapter will completely cover an area of atomic spectroscopy where rapid development has occurred.

  11. Metal atom oxidation laser

    Science.gov (United States)

    Jensen, R.J.; Rice, W.W.; Beattie, W.H.

    1975-10-28

    A chemical laser which operates by formation of metal or carbon atoms and reaction of such atoms with a gaseous oxidizer in an optical resonant cavity is described. The lasing species are diatomic or polyatomic in nature and are readily produced by exchange or other abstraction reactions between the metal or carbon atoms and the oxidizer. The lasing molecules may be metal or carbon monohalides or monoxides. (auth)

  12. Atomic Oxygen Effects

    Science.gov (United States)

    Miller, Sharon K. R.

    2014-01-01

    Atomic oxygen, which is the most predominant species in low Earth orbit, is highly reactive and can break chemical bonds on the surface of a wide variety of materials leading to volatilization or surface oxidation which can result in failure of spacecraft materials and components. This presentation will give an overview of how atomic oxygen reacts with spacecraft materials, results of space exposure testing of a variety of materials, and examples of failures caused by atomic oxygen.

  13. The Software Atom

    CERN Document Server

    Javanainen, Juha

    2016-01-01

    By putting together an abstract view on quantum mechanics and a quantum-optics picture of the interactions of an atom with light, we develop a corresponding set of C++ classes that set up the numerical analysis of an atom with an arbitrary set of angular-momentum degenerate energy levels, arbitrary light fields, and an applied magnetic field. As an example, we develop and implement perturbation theory to compute the polarizability of an atom in an experimentally relevant situation.

  14. Dissociative excitation of cesium atom upon e-CsOH collisions

    International Nuclear Information System (INIS)

    The process of dissociative excitation of cesium atom in collisions with mono-kinetic molecules of cesium hydroxide is studied. It is established that behaviour of dissociative excitations the cesium atom in spectral series corresponds of to the grade dependence of cross sections on the main quantum number of the upper level. The values of constants, characterizing the behaviour of cross sections in the eight spectral series of the cesium atom are determined

  15. Ionization of hydrogen atom by electron impact in the presence of elliptically polarized laser field

    International Nuclear Information System (INIS)

    The problem of ionization in electron hydrogen atom collision in the presence of elliptically polarized laser field, is investigated. The use of the higher order modification of the atomic bound state wave function shows that there is a strong enhancement in the cross section when the laser frequency is half the atomic transition frequency. The dependence of the cross section on the polarization of the laser field is also discussed. (author). 3 refs., 2 figs

  16. Maximum likelihood estimation of the attenuated ultrasound pulse

    DEFF Research Database (Denmark)

    Rasmussen, Klaus Bolding

    1994-01-01

    The attenuated ultrasound pulse is divided into two parts: a stationary basic pulse and a nonstationary attenuation pulse. A standard ARMA model is used for the basic pulse, and a nonstandard ARMA model is derived for the attenuation pulse. The maximum likelihood estimator of the attenuated ultra...

  17. Memory effects in attenuation and amplification quantum processes

    CERN Document Server

    Lupo, Cosmo; Mancini, Stefano

    2010-01-01

    With increasing communication rates via quantum channels, memory effects become unavoidable whenever the use rate of the channel is comparable with the typical relaxation time of the channel environment. We then introduce a model of bosonic memory channel, describing correlated noise effects in quantum optical processes via attenuating or amplifying media. To study such a channel model we make use of a proper set of collective field variables, which allows us to unravel the memory effects, mapping the n-fold concatenation of the memory channel to a, unitarily equivalent, direct product of n single-mode bosonic channels. We hence estimate the channel capacities by relying on known results for the memoryless setting. Our findings show that the model is characterized by two different regimes, in which the cross-correlations induced by the noise among different channel uses are either exponentially enhanced or exponentially reduced.

  18. Neutron attenuation in the laser ducts of an inertial-confinement fusion reactor

    International Nuclear Information System (INIS)

    This report deals with the problem of neutron streaming through the laser beam ducts of an inertial confinement fusion power plant. The neutron flux through these ducts must be attenuated by a factor of 1012 to meet radiological safety limits. The problem is dealt with by using mirrors to bend the path of the laser beam while cutting off a line of sight path for neutrons. The Monte Carlo Code MCNP was used to analyze the two mirror SOLASE design, which only attenuated the neutron flux by a factor of 103. The Westinghouse design, initially assuming four mirrors, attenuated the neutron flux by 104 per mirror bend, and hence only three mirror bends were needed. Further studies also revealed that the large length/diameter ratio of the ducts and the thinner mirror design were crucial to the large attenuation. It may also be possible to develop a two mirror system, at 106 attenuation per mirror bend, utilizing improvements such as point cross overs, a second flux trap, and acute column-to-column angles. Further studies are needed to check this possibility

  19. Evanescent Wave Atomic Mirror

    Science.gov (United States)

    Ghezali, S.; Taleb, A.

    2008-09-01

    A research project at the "Laboratoire d'électronique quantique" consists in a theoretical study of the reflection and diffraction phenomena via an atomic mirror. This poster presents the principle of an atomic mirror. Many groups in the world have constructed this type of atom optics experiments such as in Paris-Orsay-Villetaneuse (France), Stanford-Gaithersburg (USA), Munich-Heidelberg (Germany), etc. A laser beam goes into a prism with an incidence bigger than the critical incidence. It undergoes a total reflection on the plane face of the prism and then exits. The transmitted resulting wave out of the prism is evanescent and repulsive as the frequency detuning of the laser beam compared to the atomic transition δ = ωL-ω0 is positive. The cold atomic sample interacts with this evanescent wave and undergoes one or more elastic bounces by passing into backward points in its trajectory because the atoms' kinetic energy (of the order of the μeV) is less than the maximum of the dipolar potential barrier ℏΩ2/Δ where Ω is the Rabi frequency [1]. In fact, the atoms are cooled and captured in a magneto-optical trap placed at a distance of the order of the cm above the prism surface. The dipolar potential with which interact the slow atoms is obtained for a two level atom in a case of a dipolar electric transition (D2 Rubidium transition at a wavelength of 780nm delivered by a Titane-Saphir laser between a fundamental state Jf = l/2 and an excited state Je = 3/2). This potential is corrected by an attractive Van der Waals term which varies as 1/z3 in the Lennard-Jones approximation (typical atomic distance of the order of λ0/2π where λ0 is the laser wavelength) and in 1/z4 if the distance between the atom and its image in the dielectric is big in front of λ0/2π. This last case is obtained in a quantum electrodynamic calculation by taking into account an orthornormal base [2]. We'll examine the role of spontaneous emission for which the rate is inversely

  20. Electron collisions with coherently prepared atomic targets

    Energy Technology Data Exchange (ETDEWEB)

    Trajmar, S.; Kanik, I.; LeClair, L.R.; Khakoo, M.S. [California Inst. of Tech., Pasadena, CA (United States). Jet Propulsion Lab.; Bray, I.; Fursa, D. [Flinders Univ. of South Australia, Adelaide (Australia). Electronics Structure of Materials Centre; Csanak, G. [Los Alamos National Lab., NM (United States)

    1998-02-01

    The subject of electron scattering by laser-excited atoms is briefly reviewed. To demonstrate some aspects of these electron collision processes, the authors describe the procedures and the results of a joint experimental and theoretical study concerning elastic scattering by coherently excited {sup 138}Ba (...6s6p {sup 1}P{sub 1}) atoms. Examples of experimental and theoretical collision parameters and magnetic sublevel differential cross sections for elastic scattering are given and compared. The convergent close coupling calculations (with the neglect of spin-orbit interaction) are in good agreement with experiment at 20 eV impact energy and 10, 15 and 20{degree} scattering angles and can be expected to yield reliable integral magnetic sublevel and alignment creation cross sections. The role of these quantities in plasma polarization spectroscopy is pointed out.

  1. Fully differential cross sections for heavy particle impact ionization

    Energy Technology Data Exchange (ETDEWEB)

    McGovern, M; Walters, H R J [Department of Applied Mathematics and Theoretical Physics, Queen' s University, Belfast BT7 1NN (United Kingdom); Assafrao, D; Mohallem, J R [Laboratorio de Atomos e Moleculas Especiais, Departamento de Fisica, ICEx, Universidade Federal de Minas Gerais, P.O Box 702, 30123-970 Belo Horizonte, MG (Brazil); Whelan, Colm T, E-mail: mmcgovern06@qub.ac.u [Department of Physics, Old Dominion University, Norfolk, VA 23529-0116 (United States)

    2009-11-15

    We describe a procedure for extracting fully differential ionization cross sections from an impact parameter coupled pseudostate treatment of the collision. Some examples from antiproton impact ionization of atomic Hydrogen are given.

  2. Disciplinary Crossings.

    Science.gov (United States)

    Singh, Ilina

    2016-09-01

    Eighteen months ago, I left a permanent professorship in a generously interdisciplinary department of sociology and took an impermanent, lower-paying job at a university where I had to apply to something called the "Committee on Distinction" to retain the title of "Professor." Some people say, "That's what happens when Oxford calls." But it wasn't just that. It was the opportunity to engage in a groundbreaking experiment: to embed and integrate ethics within the Oxford Department of Psychiatry and Neuroscience. It's a dream job, for which I was willing to cross the disciplinary line into the medical sciences. In the United Kingdom, many bioethicists still work in departments outside science and medicine; similarly, those of us who work on neuroethics and psychiatric ethics tend to inhabit departments of philosophy, law, or sociology. I can report already that interdisciplinarity from this side feels and looks different. PMID:27649834

  3. Crossing Borders

    Directory of Open Access Journals (Sweden)

    Erik D. Barton, MD, MS, MBA

    2016-01-01

    Full Text Available As emergency physicians, we are privileged to be in a field that crosses more boundaries than any other medical specialty. It is a calling. Our skills are portable and transferable across cultural and geographic disparities. For these reasons, many of us are drawn to sharing our knowledge and training across the globe – towards treating patients in underserved and austere environments abroad. The rapid growth of international and global health educational initiatives across our U.S. residency training programs is a direct result of those undeniable forces. Additionally, inclusion of such rotations becomes a powerful resident recruitment tool as more and more of our trainees are looking for these opportunities during their formative years.

  4. Comparison of non-attenuation corrected and attenuation corrected myocardial perfusion SPE

    Directory of Open Access Journals (Sweden)

    Hasan Raza

    2016-09-01

    Conclusion: This study demonstrates that CT based attenuation corrected Tc-99mm sestamibi SPECT myocardial perfusion imaging significantly improved the specificity of the RCA territory compared with non-attenuation corrected Tc-99mm sestamibi SPECT myocardial perfusion imaging in both genders irrespective of BMI.

  5. Fast metastable hydrogen atoms from H2 molecules: twin atoms

    Directory of Open Access Journals (Sweden)

    Trimèche A.

    2015-01-01

    Full Text Available It is a difficult task to obtain “twin atoms”, i.e. pairs of massive particles such that one can perform experiments in the same fashion that is routinely done with “twin photons”. One possible route to obtain such pairs is by dissociating homonuclear diatomic molecules. We address this possibility by investigating the production of metastable H(2s atoms coming from the dissociation of cold H2 molecules produced in a Campargue nozzle beam crossing an electron beam from a high intensity pulsed electron gun. Dissociation by electron impact was chosen to avoid limitations of target molecular excited states due to selection rules. Detectors placed several centimeters away from the collision center, and aligned with respect to possible common molecular dissociation channel, analyze the neutral fragments as a function of their time-of-flight (TOF through Lyman-α detection. Evidence for the first time observed coincidence of pairs of H(2s atoms obtained this way is presented.

  6. Atoms, Molecules, and Compounds

    CERN Document Server

    Manning, Phillip

    2007-01-01

    Explores the atoms that govern chemical processes. This book shows how the interactions between simple substances such as salt and water are crucial to life on Earth and how those interactions are predestined by the atoms that make up the molecules.

  7. Multiphoton ionization of atoms

    International Nuclear Information System (INIS)

    The paper is devoted to the analysis of high intensity effects which result from multiphoton ionization of atoms in a high laser intensity, ranging from 1010 to 1015 W cm-2. Resonant multiphoton ionization of atoms, the production of multiply charged ions, and electron energy spectra, are all discussed. (U.K.)

  8. When Atoms Want

    Science.gov (United States)

    Talanquer, Vicente

    2013-01-01

    Chemistry students and teachers often explain the chemical reactivity of atoms, molecules, and chemical substances in terms of purposes or needs (e.g., atoms want or need to gain, lose, or share electrons in order to become more stable). These teleological explanations seem to have pedagogical value as they help students understand and use…

  9. Atomic Energy Control Board

    International Nuclear Information System (INIS)

    This paper has been prepared to provide an overview of the responsibilities and activities of the Atomic Energy Control Board. It is designed to address questions that are often asked concerning the establishment of the Atomic Energy Control Board, its enabling legislation, licensing and compliance activities, federal-provincial relationships, international obligations, and communications with the public

  10. Tyre Volume and Pressure Effects on Impact Attenuation during Mountain Bike Riding

    OpenAIRE

    Paul W. Macdermid; Matthew C. Miller; Fiona M. Macdermid; Fink, Philip W.

    2015-01-01

    Exposure to impacts and vibrations has been shown to be detrimental to cross country mountain bike performance and health. Therefore, any strategy aimed at attenuating such exposure is useful to participants and/or industry. The purpose of this study was to assess the influence of tyre size and tyre inflation pressure on exposure to impacts. Participants completed nine trials of a technical section (controlled for initial speed and route taken) including nine separate conditions involving thr...

  11. Atomic Rydberg Reservoirs for Polar Molecules

    CERN Document Server

    Zhao, Bo; Pupillo, Guido; Zoller, Peter

    2011-01-01

    We discuss laser dressed dipolar and Van der Waals interactions between atoms and polar molecules, so that a cold atomic gas with laser admixed Rydberg levels acts as a designed reservoir for both elastic and inelastic collisional processes. The elastic scattering channel is characterized by large elastic scattering cross sections and repulsive shields to protect from close encounter collisions. In addition, we discuss a dissipative (inelastic) collision where a spontaneously emitted photon carries away (kinetic) energy of the collision partners, thus providing a significant energy loss in a single collision. This leads to the scenario of rapid thermalization and cooling of a molecule in the mK down to the \\mu K regime by cold atoms.

  12. Atomic Rydberg Reservoirs for Polar Molecules

    Science.gov (United States)

    Zhao, B.; Glaetzle, A. W.; Pupillo, G.; Zoller, P.

    2012-05-01

    We discuss laser-dressed dipolar and van der Waals interactions between atoms and polar molecules, so that a cold atomic gas with laser admixed Rydberg levels acts as a designed reservoir for both elastic and inelastic collisional processes. The elastic scattering channel is characterized by large elastic scattering cross sections and repulsive shields to protect from close encounter collisions. In addition, we discuss a dissipative (inelastic) collision where a spontaneously emitted photon carries away (kinetic) energy of the collision partners, thus providing a significant energy loss in a single collision. This leads to the scenario of rapid thermalization and cooling of a molecule in the mK down to the μK regime by cold atoms.

  13. Consistency of atomic data for the interpretation of beam emission spectra

    Energy Technology Data Exchange (ETDEWEB)

    Delabie, E; Von Hellermann, M G [FOM Institute for Plasma Physics Rijnhuizen, Association EURATOM-FOM, PO Box 1207, 3430 BE Nieuwegein (Netherlands); Brix, M; Giroud, C; Surrey, E; Zastrow, K D [EURATOM/CCFE Association, Culham Science Centre, Abingdon, OX14 3DB (United Kingdom); Jaspers, R J E [Eindhoven University of Technology, Postbus 513, 5600 MB Eindhoven (Netherlands); Marchuk, O [Forschungszentrum Juelich, Association EURATOM-FZJ, 52425, Juelich (Germany); O' Mullane, M G [Department of Physics, University of Strathclyde, 107 Rottenrow, Glasgow G4 0NG (United Kingdom); Ralchenko, Yu, E-mail: e.delabie@fz-juelich.d [Atomic Physics Division, National Institute of Standards and Technology, Gaithersburg, MD 20899-8422 (United States)

    2010-12-15

    Several collisional-radiative (CR) models (Anderson et al 2000 Plasma Phys. Control. Fusion 42 781-806, Hutchinson 2002 Plasma Phys. Control. Fusion 44 71-82, Marchuk et al 2008 Rev. Sci. Instrum. 79 10F532) have been developed to calculate the attenuation and the population of excited states of hydrogen or deuterium beams injected into tokamak plasmas. The datasets generated by these CR models are needed for the modelling of beam ion deposition and (excited) beam densities in current experiments, and the reliability of these data will be crucial to obtain helium ash densities on ITER combining charge exchange and beam emission spectroscopy. Good agreement between the different CR models for the neutral beam (NB) is found, if corrections to the fundamental cross sections are taken into account. First the H{sub {alpha}} and H{sub {beta}} beam emission spectra from JET are compared with the expected intensities. Second, the line ratios within the Stark multiplet are compared with the predictions of a sublevel resolved model. The measured intensity of the full multiplet is {approx}30% lower than expected on the basis of beam attenuation codes and the updated beam emission rates, but apart from the atomic data this could also be due to the characterization of the NB path and line of sight integration and the absolute calibration of the optics. The modelled n = 3 to n = 4 population agrees very well with the ratio of the measured H{sub {alpha}} to H{sub {beta}} beam emission intensities. Good agreement is found as well between the NB power fractions measured with beam emission in plasma and on the JET Neutral Beam Test Bed. The Stark line ratios and {sigma}/{pi} intensity ratio deviate from a statistical distribution, in agreement with the CR model in parabolic states from Marchuk et al (2010 J. Phys. B: At. Mol. Opt. Phys. 43 011002).

  14. Cine CT for Attenuation Correction in Cardiac PET/CT

    OpenAIRE

    Alessio, Adam M.; Kohlmyer, Steve; Branch, Kelley; Chen, Grace; Caldwell, James; Kinahan, Paul

    2007-01-01

    In dual-modality PET/CT systems, the CT scan provides the attenuation map for PET attenuation correction. The current clinical practice of obtaining a single helical CT scan provides only a snapshot of the respiratory cycle, whereas PET occurs over multiple respiratory cycles. Misalignment of the attenuation map and emission image because of respiratory motion causes errors in the attenuation correction factors and artifacts in the attenuation-corrected PET image. To rectify this problem, we ...

  15. Elastic cross sections for electron-carbon scattering

    Institute of Scientific and Technical Information of China (English)

    Liu Jun-Bo; Wang Yang; Zhou Ya-Jun

    2007-01-01

    We used the close-coupling optical (CCO) approach to investigate the open-shell carbon atom. The elastic cross sections have been presented at the energies below 90eV, and the present CCO results have been compared with other theoretical results. We found that polarization and the continuum states have significant contributions to the elastic cross sections. The present calculations show that the CCO method is capable of calculating electron scattering from open-shell atoms.

  16. Atomic diffusion in stars

    CERN Document Server

    Michaud, Georges; Richer, Jacques

    2015-01-01

    This book gives an overview of atomic diffusion, a fundamental physical process, as applied to all types of stars, from the main sequence to neutron stars. The superficial abundances of stars as well as their evolution can be significantly affected. The authors show where atomic diffusion plays an essential role and how it can be implemented in modelling.  In Part I, the authors describe the tools that are required to include atomic diffusion in models of stellar interiors and atmospheres. An important role is played by the gradient of partial radiative pressure, or radiative acceleration, which is usually neglected in stellar evolution. In Part II, the authors systematically review the contribution of atomic diffusion to each evolutionary step. The dominant effects of atomic diffusion are accompanied by more subtle effects on a large number of structural properties throughout evolution. One of the goals of this book is to provide the means for the astrophysicist or graduate student to evaluate the importanc...

  17. Antiprotonic-hydrogen atoms

    International Nuclear Information System (INIS)

    Experimental studies of antiprotonic-hydrogen atoms have recently made great progress following the commissioning of the low energy antiproton facility (LEAR) at CERN in 1983. At the same time our understanding of the atomic cascade has increased considerably through measurements of the X-ray spectra. The life history of the p-bar-p atom is considered in some detail, from the initial capture of the antiproton when stopping in hydrogen, through the atomic cascade with the emission of X-rays, to the final antiproton annihilation and production of mesons. The experiments carried out at LEAR are described and the results compared with atomic cascade calculations and predictions of strong interaction effects. (author)

  18. Moving Single Atoms

    Science.gov (United States)

    Stuart, Dustin

    2016-05-01

    Single neutral atoms are promising candidates for qubits, the fundamental unit of quantum information. We have built a set of optical tweezers for trapping and moving single Rubidium atoms. The tweezers are based on a far off-resonant dipole trapping laser focussed to a 1 μm spot with a single aspheric lens. We use a digital micromirror device (DMD) to generate dynamic holograms of the desired arrangement of traps. The DMD has a frame rate of 20 kHz which, when combined with fast algorithms, allows for rapid reconfiguration of the traps. We demonstrate trapping of up to 20 atoms in arbitrary arrangements, and the transport of a single-atom over a distance of 14 μm with continuous laser cooling, and 5 μm without. In the meantime, we are developing high-finesse fibre-tip cavities, which we plan to use to couple pairs of single atoms to form a quantum network.

  19. Plasma diagnostics and atomic processes

    International Nuclear Information System (INIS)

    Spectroscopic plasma diagnostics with the use of atomic processes are discussed relating to three subjects in the followings. i) Time resolved X-ray spectra of titanium helium-like ions from tokamaks. X-ray spectra observed from tokamak plasmas are analysed with a non-ionization equilibrium model which could explain the time behavior of both spectra and ion abundances. ii) Line intensity ratios of OV ions for temperature and density diagnostics. Intensity ratios of emission lines from OV ions are calculated for use in temperature and density diagnostics. The line emissions from a tokamak are analysed for the diagnostics of plasma periphery. iii) Collisional processes in hot dense plasmas. The collisional ladder-like excitation and ionization in a hot dense plasma are discussed for the dielectronic states. This process enhances the excitation rate coefficients and decreases the resonance contributions to the excitation cross section. (author)

  20. Atomic Ionization by Electron Impact

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The field of atomic ionization by electron impact is several decades old. In that period of time, significant progress has been made in several aspects of the problem and we have learned a lot about ionizing collisions as a result of this work. Over the years, both the experiments and theories have improved dramatically. Experiments are now able to measure absolute triple differential cross sections for both in-plane or out-of-plane geometries. Theories have been getting better and better at including all the 3-body interactions in the wavefunction for the system. However, during the history of the field, experiment has been ahead of theory and it is just very recently that theory has started to catch up. In this paper, we will show that theory is now able to accurately predict the results of electron impact ionization of hydrogen for intermediate and higher energies.

  1. Self-assembled multilayer films of sulfonated graphene and polystyrene-based diazonium salt as photo-cross-linkable supercapacitor electrodes.

    Science.gov (United States)

    Xiong, Zhiyuan; Gu, Tonghan; Wang, Xiaogong

    2014-01-21

    Photo-cross-linkable multilayer films composed of sulfonated reduced graphene oxide (SRGO) and polystyrene-based diazonium salt (PSDAS) were fabricated by electrostatic layer-by-layer (LbL) self-assembly. Polystyrene with narrow molecular weight distribution was synthesized by atom transfer radical polymerization (ATRP), and cationic PSDAS was prepared through nitration, reduction, and diazotization reactions. Negatively charged SRGO nanosheets were prepared through prereduced by NaBH4, modified by diazonium salt of sulfanilic acid, and then further reduced by hydrazine. The multilayer films were obtained by alternately dipping substrates in the PSDAS solution and SRGO dispersion in acidic conditions. The cross-linking between the components occurred during the multilayer formation process and was further achieved by the UV light irradiation after the film preparation. The assembling process and surface morphology of LbL multilayer films were monitored by UV-vis spectroscopy, atomic force microscopy (AFM), and scanning electron microscopy (SEM). The cross-linking between SRGO and PSDAS was verified by attenuated total reflectance FTIR (ATR-FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and contact angle measurement. The graphene nanosheets were found to be homogeneously distributed in the cross-linked network of the films. The large accessible surface area of graphene nanosheets and the cross-linking structure afforded the LbL films with high specific capacitance and excellent cyclic stability when used as supercapacitor electrodes. At a sweeping rate of 10 mV/s, the film with nine bilayers exhibited a specific capacitance of 150.4 F/g with ideal rectangular cyclic voltammogram. Large capacitance retention of 97% was observed after 10 000 charge-discharge cycles under the scanning rate of 1000 mV/s. This new approach for preparing graphene-containing multilayer films can be used to develop supercapacitor electrodes and other functional devices.

  2. Scattering cross section of metal catalyst atoms in silicon nanowires

    DEFF Research Database (Denmark)

    Markussen, Troels; Rurali, R.; Cartoixa, X.;

    2010-01-01

    A common technique to fabricate silicon nanowires is to use metal particles (e.g., Au, Ag, Cu, Al) to catalyze the growth reaction. As a consequence, the fabricated nanowires contain small concentrations of these metals as impurities. In this work we investigate the effect of the metallic impurit...

  3. Attenuation of ear muffs in Canadian mines

    Energy Technology Data Exchange (ETDEWEB)

    Savich, M.U.

    1979-12-01

    The main characteristics of eleven commercially available ear muffs were investigated in the laboratory and analyzed by a psychophysical and a physical method. Nine ear muffs were tested in mines. The three best muffs had bands passing behind the head. The ear muff with a support strap, which improves comfort and maintains a good fit during wear, showed the best attenuation. Causes of poor attenuation are listed. None of the ear muffs tested had all the characteristics desirable in an ideal unit. Because of unsatisfactory attenuation in working conditions, it should be a mandatory requirement that workers wear both ear muffs and ear plugs if the noise level is higher than 105 dBA.

  4. Research on Nanosecond Pulse Corona Discharge Attenuation

    International Nuclear Information System (INIS)

    A line-to-plate reactor was set-up in the experimental study on the application of nanosecond pulsed corona discharge plasma technology in environmental pollution control. Investigation on the attenuation and distortion of the amplitude of the pulse wave front and the discharge image as well as the waveform along the corona wire was conducted. The results show that the wave front decreases sharply during the corona discharge along the corona wire. The higher the amplitude of the applied pulse is, the more the amplitude of the wave front decreased. The wave attenuation responds in a lower corona discharge inversely. To get a higher efficiency of the line-to-plate reactor a sharp attenuation of the corona has to be considered in practical design

  5. Finite Element Analysis of Honeycomb Impact Attenuator

    Science.gov (United States)

    Yang, Seung-Yong; Choi, Seung-Kyu; Kim, Nohyu

    To participate in Student Formula Society of Automotive Engineers (SAE) competitions, it is necessary to build an impact attenuator that would give an average deceleration not to exceed 20g when it runs into a rigid wall. Students can use numerical simulations or experimental test data to show that their car satisfies this safety requirement. A student group to study formula cars at the Korea University of Technology and Education has designed a vehicle to take part in a SAE competition, and a honeycomb structure was adopted as the impact attenuator. In this paper, finite element calculations were carried out to investigate the dynamic behavior of the honeycomb attenuator. Deceleration and deformation behaviors were studied. Effect of the yield strength was checked by comparing the numerical results. ABAQUS/Explicit finite element code was used.

  6. Live attenuated vaccines for invasive Salmonella infections.

    Science.gov (United States)

    Tennant, Sharon M; Levine, Myron M

    2015-06-19

    Salmonella enterica serovar Typhi produces significant morbidity and mortality worldwide despite the fact that there are licensed Salmonella Typhi vaccines available. This is primarily due to the fact that these vaccines are not used in the countries that most need them. There is growing recognition that an effective invasive Salmonella vaccine formulation must also prevent infection due to other Salmonella serovars. We anticipate that a multivalent vaccine that targets the following serovars will be needed to control invasive Salmonella infections worldwide: Salmonella Typhi, Salmonella Paratyphi A, Salmonella Paratyphi B (currently uncommon but may become dominant again), Salmonella Typhimurium, Salmonella Enteritidis and Salmonella Choleraesuis (as well as other Group C Salmonella). Live attenuated vaccines are an attractive vaccine formulation for use in developing as well as developed countries. Here, we describe the methods of attenuation that have been used to date to create live attenuated Salmonella vaccines and provide an update on the progress that has been made on these vaccines.

  7. Research on Nanosecond Pulse Corona Discharge Attenuation

    Institute of Scientific and Technical Information of China (English)

    HE Zheng-hao; XU Huai-li; BAI Jing; YU Fu-sheng; HU Feng; LI Jin

    2007-01-01

    A line-to-plate reactor was set-up in the experimental study on the application of nanosecond pulsed corona discharge plasma technology in environmental pollution control.Investigation on the attenuation and distortion of the amplitude of the pulse wave front and the discharge image as well as the waveform along the corona wire was conducted.The results show that the wave front decreases sharply during the corona discharge along the corona wire.The higher the amplitude of the applied pulse is,the more the amplitude of the wave front decreased.The wave attenuation responds in a lower corona discharge inversely.To get a higher efficiency of the line-to-plate reactor a sharp attenuation of the corona has to be considered in practical design.

  8. Graphene-Based Waveguide Terahertz Wave Attenuator

    Science.gov (United States)

    Jian-rong, Hu; Jiu-sheng, Li; Guo-hua, Qiu

    2016-07-01

    We design an electrically controllable terahertz wave attenuator by using graphene. We show that terahertz wave can be confined and propagate on S-shaped graphene waveguide with little radiation losses, and the confined terahertz wave is further manipulated and controlled via external applied voltage bias. The simulated results show that, when chemical potential changes from 0.03 into 0.05 eV, the extinction ratio of the terahertz wave attenuator can be tuned from 1.28 to 39.42 dB. Besides the simplicity, this novel terahertz wave attenuator has advantages of small size (24 × 30 μm2), a low insertion loss, and good controllability. It has a potential application for forthcoming planar terahertz wave integrated circuit fields.

  9. Avoided level crossings in very highly charged ions

    Science.gov (United States)

    Beiersdorfer, P.; Scofield, J. H.; Brown, G. V.; Chen, M. H.; Hell, N.; Osterheld, A. L.; Vogel, D. A.; Wong, K. L.

    2016-05-01

    We report a systematic measurement of the (2p1/2 -13 d3/2) J =1 and (2s1/2 -13 p1/2) J =1 levels in 14 neonlike ions between Ba46 + and Pb72 + and document the effects of their avoided crossing near Z =68 . Strong mixing affects the oscillator strengths over a surprisingly wide range of atomic numbers and leads to the vanishing of one transition two atomic numbers below the crossing. The crossing voids the otherwise correct expectation that the (2p1/2 -13 d3/2) J =1 level energy is only weakly affected by quantum electrodynamics (QED). For about 10 atomic numbers surrounding the crossing, its QED contributions are anomalously large, attaining almost equality to those affecting the (2s1/2 -13 p1/2) J =1 level. As a result, the accuracy of energy level calculations appears compromised near the crossing.

  10. A Scheme of Generating and Spatially Separating Two-Component Entangled Atom Lasers

    OpenAIRE

    Liu, Xiong-Jun; Jing, Hui; Liu, Xin; Zhan, Ming-sheng; Ge, Mo-Lin

    2005-01-01

    Entanglement of remote atom lasers is obtained via quantum state transfer technique from lights to matter waves in a five-level $M$-type system. The considered atom-atom collisions can yield an effective Kerr susceptibility for this system and lead to the self- and cross- phase modulation between the two output atom lasers. This effect results in generation of entangled states of output fields. Particularly, under different conditions of space-dependent control fields, the entanglement of ato...

  11. Symmetric charge transfer cross section of uranium

    International Nuclear Information System (INIS)

    Symmetric charge transfer cross section of uranium was calculated under consideration of reaction paths. In the charge transfer reaction a d3/2 electron in the U atom transfers into the d-electron site of U+(4I9/2) ion. The J value of the U atom produced after the reaction is 6, 5, 4 or 3, at impact energy below several tens eV, only resonant charge transfer in which the product atom is ground state (J=6) takes place. Therefore, the cross section is very small (4-5 x 10-15 cm2) compared with that considered so far. In the energy range of 100-1000eV the cross section increases with the impact energy because near resonant charge transfer in which an s-electron in the U atom transfers into the d-electron site of U+ ion. Charge transfer cross section between U+ in the first excited state (289 cm-1) and U in the ground state was also obtained. (author)

  12. Linear atomic quantum coupler

    CERN Document Server

    El-Orany, Faisal A A

    2009-01-01

    In this paper, we develop the notion of the linear atomic quantum coupler. This device consists of two modes propagating into two waveguides, each of them includes a localized and/or a trapped atom. These waveguides are placed close enough to allow exchanging energy between them via evanescent waves. Each mode interacts with the atom in the same waveguide in the standard way, i.e. as the Jaynes-Cummings model (JCM), and with the atom-mode in the second waveguide via evanescent wave. We present the Hamiltonian for the system and deduce the exact form for the wavefunction. We investigate the atomic inversions and the second-order correlation function. In contrast to the conventional linear coupler, the atomic quantum coupler is able to generate nonclassical effects. The atomic inversions can exhibit long revival-collapse phenomenon as well as subsidiary revivals based on the competition among the switching mechanisms in the system. Finally, under certain conditions, the system can yield the results of the two-m...

  13. 78 FR 58571 - Maine Yankee Atomic Power Company, Connecticut Yankee Atomic Power Company, and The Yankee Atomic...

    Science.gov (United States)

    2013-09-24

    ... Atomic Power Company, Connecticut Yankee Atomic Power Company, and The Yankee Atomic Electric Company... Power Company (Maine Yankee), Connecticut Yankee Atomic Power Company (Connecticut Yankee), and the Yankee Atomic Electric Company (Yankee Atomic) (together, ``licensees'' or ``the Yankee Companies'')...

  14. Small angle elastic scattering of electrons by noble gas atoms

    International Nuclear Information System (INIS)

    In this thesis, measurements are carried out to obtain small angle elastic differential cross sections in order to check the validity of Kramers-Kronig dispersion relations for electrons scattered by noble gas atoms. First, total cross sections are obtained for argon, krypton and xenon. Next, a parallel plate electrostatic energy analyser for the simultaneous measurement of doubly differential cross section for small angle electron scattering is described. Also absolute differential cross sections are reported. Finally the forward dispersion relation for electron-helium collisions is dealt with. (Auth.)

  15. Multigroup Free-atom Doppler-broadening Approximation. Theory

    Energy Technology Data Exchange (ETDEWEB)

    Gray, Mark Girard [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2015-11-06

    Multigroup cross sections at a one target temperature can be Doppler-broadened to multigroup cross sections at a higher target temperature by matrix multiplication if the group structure suf- ficiently resolves the original temperature continuous energy cross section. Matrix elements are the higher temperature group weighted averages of the integral over the lower temperature group boundaries of the free-atom Doppler-broadening kernel. The results match theory for constant and 1/v multigroup cross sections at 618 lanl group structure resolution.

  16. Atomic Dark Matter

    OpenAIRE

    Kaplan, David E.; Krnjaic, Gordan Z.; Rehermann, Keith R.; Wells, Christopher M.

    2009-01-01

    We propose that dark matter is dominantly comprised of atomic bound states. We build a simple model and map the parameter space that results in the early universe formation of hydrogen-like dark atoms. We find that atomic dark matter has interesting implications for cosmology as well as direct detection: Protohalo formation can be suppressed below $M_{proto} \\sim 10^3 - 10^6 M_{\\odot}$ for weak scale dark matter due to Ion-Radiation interactions in the dark sector. Moreover, weak-scale dark a...

  17. EINSTEIN, SCHROEDINGER, AND ATOM

    Directory of Open Access Journals (Sweden)

    Trunev A. P.

    2014-03-01

    Full Text Available In this paper, we consider gravitation theory in multidimensional space. The model of the metric satisfying the basic requirements of quantum theory is proposed. It is shown that gravitational waves are described by the Liouville equation and the Schrodinger equation as well. The solutions of the Einstein equations describing the stationary states of arbitrary quantum and classical systems with central symmetry have been obtained. Einstein’s atom model has been developed, and proved that atoms and atomic nuclei can be represented as standing gravitational waves

  18. Atoms, molecules, solids

    International Nuclear Information System (INIS)

    This book is an introduction to modern physics for undergraduate students of physics or students of related fields. After an introduction to the wave-particle dualism the structure of atoms is considered with regards to atomic models. Then the foundations of quantum mechanics are introduced with regards to their application to atomic structure calculations. Thereafter the chemical bond and the molecular structure are discussed. Then classical and quantum statistical mechanics are introduced. Thereafter the crystal binding, the crystal structure, and the specific heat of solids are considered. Finally the band theory of solids is briefly introduced. Every chapter contains exercise problems. (HSI)

  19. Single-atom nanoelectronics

    CERN Document Server

    Prati, Enrico

    2013-01-01

    Single-Atom Nanoelectronics covers the fabrication of single-atom devices and related technology, as well as the relevant electronic equipment and the intriguing new phenomena related to single-atom and single-electron effects in quantum devices. It also covers the alternative approaches related to both silicon- and carbon-based technologies, also from the point of view of large-scale industrial production. The publication provides a comprehensive picture of the state of the art at the cutting edge and constitutes a milestone in the emerging field of beyond-CMOS technology. Although there are

  20. Atom probe tomography today

    Directory of Open Access Journals (Sweden)

    Alfred Cerezo

    2007-12-01

    Full Text Available This review aims to describe and illustrate the advances in the application of atom probe tomography that have been made possible by recent developments, particularly in specimen preparation techniques (using dual-beam focused-ion beam instruments but also of the more routine use of laser pulsing. The combination of these two developments now permits atomic-scale investigation of site-specific regions within engineering alloys (e.g. at grain boundaries and in the vicinity of cracks and also the atomic-level characterization of interfaces in multilayers, oxide films, and semiconductor materials and devices.

  1. Atom trap trace analysis

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Z.-T.; Bailey, K.; Chen, C.-Y.; Du, X.; Li, Y.-M.; O' Connor, T. P.; Young, L.

    2000-05-25

    A new method of ultrasensitive trace-isotope analysis has been developed based upon the technique of laser manipulation of neutral atoms. It has been used to count individual {sup 85}Kr and {sup 81}Kr atoms present in a natural krypton sample with isotopic abundances in the range of 10{sup {minus}11} and 10{sup {minus}13}, respectively. The atom counts are free of contamination from other isotopes, elements,or molecules. The method is applicable to other trace-isotopes that can be efficiently captured with a magneto-optical trap, and has a broad range of potential applications.

  2. Division of atomic physics

    International Nuclear Information System (INIS)

    The Division of Atomic Physics, Lund Institute of Technology (LTH), is responsible for the basic physics teaching in all subjects at LTH and for specialized teaching in Optics, Atomic Physics, Atomic and Molecular Spectroscopy and Laser Physics. The Division has research activities in basic and applied optical spectroscopy, to a large extent based on lasers. It is also part of the Physics Department, Lund University, where it forms one of eight divisions. Since the beginning of 1980 the research activities of our division have been centred around the use of lasers. The activities during the period 1991-1992 is described in this progress reports

  3. Inside the Hydrogen Atom

    CERN Document Server

    Nowakowski, M; Fierro, D Bedoya; Manjarres, A D Bermudez

    2016-01-01

    We apply the non-linear Euler-Heisenberg theory to calculate the electric field inside the hydrogen atom. We will demonstrate that the electric field calculated in the Euler-Heisenberg theory can be much smaller than the corresponding field emerging from the Maxwellian theory. In the hydrogen atom this happens only at very small distances. This effect reduces the large electric field inside the hydrogen atom calculated from the electromagnetic form-factors via the Maxwell equations. The energy content of the field is below the pair production threshold.

  4. The CHIANTI atomic database

    CERN Document Server

    Young, Peter R; Landi, Enrico; Del Zanna, Giulio; Mason, Helen

    2015-01-01

    The CHIANTI atomic database was first released in 1996 and has had a huge impact on the analysis and modeling of emissions from astrophysical plasmas. The database has continued to be updated, with version 8 released in 2015. Atomic data for modeling the emissivities of 246 ions and neutrals are contained in CHIANTI, together with data for deriving the ionization fractions of all elements up to zinc. The different types of atomic data are summarized here and their formats discussed. Statistics on the impact of CHIANTI to the astrophysical community are given and examples of the diverse range of applications are presented.

  5. Ultrasound transmission attenuation tomography using energy-scaled amplitude ratios

    Science.gov (United States)

    Chen, Ting; Shin, Junseob; Huang, Lianjie

    2016-04-01

    Ultrasound attenuation of breast tumors is related to their types and pathological states, and can be used to detect and characterize breast cancer. Particularly, ultrasound scattering attenuation can infer the margin properties of breast tumors. Ultrasound attenuation tomography quantitatively reconstructs the attenuation properties of the breast. Our synthetic-aperture breast ultrasound tomography system with two parallel transducer arrays records both ultrasound reflection and transmission signals. We develop an ultrasound attenuation tomography method using ultrasound energy-scaled amplitude decays of ultrasound transmission signals and conduct ultrasound attenuation tomography using a known sound-speed model. We apply our ultrasound transmission attenuation tomography method to a breast phantom dataset, and compare the ultrasound attenuation tomography results with conventional beamforming ultrasound images obtained using reflection signals. We show that ultrasound transmission attenuation tomography complements beamforming images in identifying breast lesions.

  6. Hamiltonian chaos with a cold atom in an optical lattice

    CERN Document Server

    Prants, S V

    2012-01-01

    We consider a basic model of the lossless interaction between a moving two-level atom and a standing-wave single-mode laser field. Classical treatment of the translational atomic motion provides the semiclassical Hamilton-Schrodinger equations which are a 5D nonlinear dynamical system with two integrals of motion. The atomic dynamics can be regular or chaotic in dependence on values of the control parameters, the atom-field detuning and recoil frequency. We develop a semiclassical theory of the chaotic atomic transport in terms of a random walk of the atomic electric dipole moment $u$. Based on a jump-like behavior of this variable for atoms crossing nodes of the standing wave, we construct a stochastic map that specifies the center-of-mass motion. We find the relations between the detuning, recoil frequency and the atomic energy, under which atoms may move in a optical lattice in a chaotic way. We obtain the analytical conditions under which deterministic atomic transport has fractal properties and explain a...

  7. The role of fullerene shell upon stuffed atom polarization potential

    Science.gov (United States)

    Amusia, Miron; Chernysheva, Larissa

    2016-05-01

    We have demonstrated that the polarization of the fullerene shell considerably alters the polarization potential of an atom, stuffed inside a fullerene. This essentially affects the electron elastic scattering phases as well as corresponding cross-sections. We illustrate the general trend by concrete examples of electron scattering upon endohedrals that are formed when Ne and Ar atom are stuffed inside fullerene C60. To obtain the presented results, we have suggested a simplified approach that permits to incorporate the effect of fullerenes polarizability into the endohedrals polarization potential. By applying this approach, we obtained numeric results that show strong variations in shape and magnitudes of scattering phases and cross-sections due to effect of fullerene polarization upon the endohedral polarization potential. Using concrete examples we have demonstrated that the elastic scattering of electrons upon endohedrals is an entirely quantum mechanical process, where addition of even a single atom can qualitatively alter the multi-particle cross-section.

  8. Atomic hydrogen interaction with Ru(1010).

    Science.gov (United States)

    Vesselli, E; Comelli, G; Rosei, R

    2004-05-01

    The interaction of atomic hydrogen with clean and deuterium precovered Ru(1010) was studied by means of temperature-programmed desorption (TPD) spectroscopy. Compared to molecular hydrogen experiments, after exposure of the clean surface to gas-phase atomic hydrogen at 90 K, two additional peaks grow in the desorption spectra at 115 and 150 K. The surface saturation coverage, determined by equilibrium between abstraction and adsorption reactions, is 2.5 monolayers. Preadsorbed deuterium abstraction experiments with gas-phase atomic hydrogen show that a pure Eley-Rideal mechanism is not involved in the process, while a hot atom (HA) kinetics describes well the reaction. By least-squares fitting of the experimental data, a simplified HA kinetic model yields an abstraction cross section value of 0.5 +/- 0.2 angstroms2. The atomic hydrogen interaction with an oxygen precovered surface was also studied by means of both TPD and x-ray photoelectron spectroscopy: oxygen hydrogenation and water production take place already at very low temperature (90 K).

  9. Towards a random laser with cold atoms

    CERN Document Server

    Guerin, William; Michaud, Franck; Brivio, Davide; Froufe-Pérez, Luis S; Carminati, Rémi; Eremeev, Vitalie; Goetschy, Arthur; Skipetrov, Sergey S; Kaiser, Robin

    2009-01-01

    Atoms can scatter light and they can also amplify it by stimulated emission. From this simple starting point, we examine the possibility of realizing a random laser in a cloud of laser-cooled atoms. The answer is not obvious as both processes (elastic scattering and stimulated emission) seem to exclude one another: pumping atoms to make them behave as amplifier reduces drastically their scattering cross-section. However, we show that even the simplest atom model allows the efficient combination of gain and scattering. Moreover, supplementary degrees of freedom that atoms offer allow the use of several gain mechanisms, depending on the pumping scheme. We thus first study these different gain mechanisms and show experimentally that they can induce (standard) lasing. We then present how the constraint of combining scattering and gain can be quantified, which leads to an evaluation of the random laser threshold. The results are promising and we draw some prospects for a practical realization of a random laser wit...

  10. Theoretical atomic physics code development I: CATS: Cowan Atomic Structure Code

    International Nuclear Information System (INIS)

    An adaptation of R.D. Cowan's Atomic Structure program, CATS, has been developed as part of the Theoretical Atomic Physics (TAPS) code development effort at Los Alamos. CATS has been designed to be easy to run and to produce data files that can interface with other programs easily. The CATS produced data files currently include wave functions, energy levels, oscillator strengths, plane-wave-Born electron-ion collision strengths, photoionization cross sections, and a variety of other quantities. This paper describes the use of CATS. 10 refs

  11. Advances in atomic spectroscopy

    CERN Document Server

    Sneddon, J

    1998-01-01

    This volume continues the series'' cutting-edge reviews on developments in this field. Since its invention in the 1920s, electrostatic precipitation has been extensively used in industrial hygiene to remove dust and particulate matter from gases before entering the atmosphere. This combination of electrostatic precipitation is reported upon in the first chapter. Following this, chapter two reviews recent advances in the area of chemical modification in electrothermal atomization. Chapter three consists of a review which deal with advances and uses of electrothermal atomization atomic absorption spectrometry. Flow injection atomic spectroscopy has developed rapidly in recent years and after a general introduction, various aspects of this technique are looked at in chapter four. Finally, in chapter five the use of various spectrometric techniques for the determination of mercury are described.

  12. Atomic and Molecular Interactions

    International Nuclear Information System (INIS)

    The Gordon Research Conference (GRC) on Atomic and Molecular Interactions was held at Roger Williams University, Bristol, RI. Emphasis was placed on current unpublished research and discussion of the future target areas in this field

  13. Atomic Interferometry Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Vertical cavity surface emitting lasers (VCSELs) is a new technology which can be used for developing high performance laser components for atom-based sensors...

  14. Atom chip gravimeter

    Science.gov (United States)

    Schubert, Christian; Abend, Sven; Gebbe, Martina; Gersemann, Matthias; Ahlers, Holger; Müntinga, Hauke; Matthias, Jonas; Sahelgozin, Maral; Herr, Waldemar; Lämmerzahl, Claus; Ertmer, Wolfgang; Rasel, Ernst

    2016-04-01

    Atom interferometry has developed into a tool for measuring rotations [1], accelerations [2], and testing fundamental physics [3]. Gravimeters based on laser cooled atoms demonstrated residual uncertainties of few microgal [2,4] and were simplified for field applications [5]. Atomic gravimeters rely on the interference of matter waves which are coherently manipulated by laser light fields. The latter can be interpreted as rulers to which the position of the atoms is compared. At three points in time separated by a free evolution, the light fields are pulsed onto the atoms. First, a coherent superposition of two momentum states is produced, then the momentum is inverted, and finally the two trajectories are recombined. Depending on the acceleration the atoms experienced, the number of atoms detected in the output ports will change. Consequently, the acceleration can be determined from the output signal. The laser cooled atoms with microkelvin temperatures used in state-of-the-art gravimeters impose limits on the accuracy [4]. Therefore, ultra-cold atoms generated by Bose-Einstein condensation and delta-kick collimation [6,7] are expected to be the key for further improvements. These sources suffered from a low flux implying an incompatible noise floor, but a competitive performance was demonstrated recently with atom chips [8]. In the compact and robust setup constructed for operation in the drop tower [6] we demonstrated all steps necessary for an atom chip gravimeter with Bose-Einstein condensates in a ground based operation. We will discuss the principle of operation, the current performance, and the perspectives to supersede the state of the art. The authors thank the QUANTUS cooperation for contributions to the drop tower project in the earlier stages. This work is supported by the German Space Agency (DLR) with funds provided by the Federal Ministry for Economic Affairs and Energy (BMWi) due to an enactment of the German Bundestag under grant numbers DLR 50WM

  15. Topics in atomic physics

    CERN Document Server

    Burkhardt, Charles E

    2006-01-01

    The study of atomic physics propelled us into the quantum age in the early twentieth century and carried us into the twenty-first century with a wealth of new and, in some cases, unexplained phenomena. Topics in Atomic Physics provides a foundation for students to begin research in modern atomic physics. It can also serve as a reference because it contains material that is not easily located in other sources. A distinguishing feature is the thorough exposition of the quantum mechanical hydrogen atom using both the traditional formulation and an alternative treatment not usually found in textbooks. The alternative treatment exploits the preeminent nature of the pure Coulomb potential and places the Lenz vector operator on an equal footing with other operators corresponding to classically conserved quantities. A number of difficult to find proofs and derivations are included as is development of operator formalism that permits facile solution of the Stark effect in hydrogen. Discussion of the classical hydrogen...

  16. Switching Control for Adaptive Disturbance Attenuation

    NARCIS (Netherlands)

    Battistelli, Giorgio; Mari, Daniele; Selvi, Daniela; Tesi, Alberto; Tesi, Pietro

    2014-01-01

    The problem of adaptive disturbance attenuation is addressed in this paper using a switching control approach. A finite family of stabilizing controllers is pre-designed, with the assumption that, for any possible operating condition, at least one controller is able to achieve a prescribed level of

  17. Microwave attenuation with composite of copper microwires

    Energy Technology Data Exchange (ETDEWEB)

    Gorriti, A.G.; Marin, P. [Instituto de Magnetismo Aplicado, (UCM-ADIF-CSIC) and Departamento de Fisica de Materiales (UCM). P.O. Box 155, Las Rozas, Madrid 28230 (Spain); Cortina, D. [Micromag S.L., Las Rozas, Madrid 28230 (Spain); Hernando, A., E-mail: antonio.hernando@adif.e [Instituto de Magnetismo Aplicado, (UCM-ADIF-CSIC) and Departamento de Fisica de Materiales (UCM). P.O. Box 155, Las Rozas, Madrid 28230 (Spain); Micromag S.L., Las Rozas, Madrid 28230 (Spain)

    2010-05-15

    It is shown that copper microwires composite media attenuates microwave reflection of metallic surfaces. We show how the distance to the metallic surface, as well as the length and volume fraction of microwires, determine the frequency of maximum absorption and the return loss level. Furthermore, we were able to fit the experimental results with a theoretical model based on Maxwell-Garnett mixing formula.

  18. Attenuation of PRRSV by chimera construction

    Science.gov (United States)

    Two genetically distinct infectious recombinant virus clones (pMLV, constructed from Ingelvac® PRRS MLV and pMN184, constructed from virulent strain MN184) were developed to study attenuation of contemporary PRRSV. Two reciprocal chimeric clones (pMLVORF1/MN184 and pMN184ORF1/MLV) were then constru...

  19. ULTRASONIC ATTENUATION IN MIXED STATE OF NIOBIUM

    OpenAIRE

    Dominec, J.; MÍŠek, K.

    1987-01-01

    We have investigated the attenuation of ultrasonic waves in the mixed state of niobium, where a remarkable dip appears near the lower critical field . The measurement has been performed on one sample for various orientations of the wave vector and of the principal crystallographic axes of the sample with respect to external magnetic field.

  20. Hadron attenuation at HERMES and JLab

    OpenAIRE

    Falter, T.; Cassing, W.; Gallmeister, K.; Mosel, U.

    2005-01-01

    We investigate the attenuation of hadrons in deep inelastic lepton-nucleus scattering in the kinematical regime of the HERMES and Jefferson Lab experiments. The calculation is carried out in the framework of a BUU transport model. Our results indicate a strong influence of (pre)hadronic final state interactions on the observed multiplicity ratios.

  1. Attenuation correction for small animal PET tomographs

    Energy Technology Data Exchange (ETDEWEB)

    Chow, Patrick L [David Geffen School of Medicine at UCLA, Crump Institute for Molecular Imaging, University of California, 700 Westwood Plaza, Los Angeles, CA 90095 (United States); Rannou, Fernando R [Departamento de Ingenieria Informatica, Universidad de Santiago de Chile (USACH), Av. Ecuador 3659, Santiago (Chile); Chatziioannou, Arion F [David Geffen School of Medicine at UCLA, Crump Institute for Molecular Imaging, University of California, 700 Westwood Plaza, Los Angeles, CA 90095 (United States)

    2005-04-21

    Attenuation correction is one of the important corrections required for quantitative positron emission tomography (PET). This work will compare the quantitative accuracy of attenuation correction using a simple global scale factor with traditional transmission-based methods acquired either with a small animal PET or a small animal x-ray computed tomography (CT) scanner. Two phantoms (one mouse-sized and one rat-sized) and two animal subjects (one mouse and one rat) were scanned in CTI Concorde Microsystem's microPET (registered) Focus{sup TM} for emission and transmission data and in ImTek's MicroCAT{sup TM} II for transmission data. PET emission image values were calibrated against a scintillation well counter. Results indicate that the scale factor method of attenuation correction places the average measured activity concentration about the expected value, without correcting for the cupping artefact from attenuation. Noise analysis in the phantom studies with the PET-based method shows that noise in the transmission data increases the noise in the corrected emission data. The CT-based method was accurate and delivered low-noise images suitable for both PET data correction and PET tracer localization.

  2. Hirshfeld atom refinement.

    Science.gov (United States)

    Capelli, Silvia C; Bürgi, Hans-Beat; Dittrich, Birger; Grabowsky, Simon; Jayatilaka, Dylan

    2014-09-01

    Hirshfeld atom refinement (HAR) is a method which determines structural parameters from single-crystal X-ray diffraction data by using an aspherical atom partitioning of tailor-made ab initio quantum mechanical molecular electron densities without any further approximation. Here the original HAR method is extended by implementing an iterative procedure of successive cycles of electron density calculations, Hirshfeld atom scattering factor calculations and structural least-squares refinements, repeated until convergence. The importance of this iterative procedure is illustrated via the example of crystalline ammonia. The new HAR method is then applied to X-ray diffraction data of the dipeptide Gly-l-Ala measured at 12, 50, 100, 150, 220 and 295 K, using Hartree-Fock and BLYP density functional theory electron densities and three different basis sets. All positions and anisotropic displacement parameters (ADPs) are freely refined without constraints or restraints - even those for hydrogen atoms. The results are systematically compared with those from neutron diffraction experiments at the temperatures 12, 50, 150 and 295 K. Although non-hydrogen-atom ADPs differ by up to three combined standard uncertainties (csu's), all other structural parameters agree within less than 2 csu's. Using our best calculations (BLYP/cc-pVTZ, recommended for organic molecules), the accuracy of determining bond lengths involving hydrogen atoms from HAR is better than 0.009 Å for temperatures of 150 K or below; for hydrogen-atom ADPs it is better than 0.006 Å(2) as judged from the mean absolute X-ray minus neutron differences. These results are among the best ever obtained. Remarkably, the precision of determining bond lengths and ADPs for the hydrogen atoms from the HAR procedure is comparable with that from the neutron measurements - an outcome which is obtained with a routinely achievable resolution of the X-ray data of 0.65 Å.

  3. Dangerous Energy : Atomic

    International Nuclear Information System (INIS)

    This book describes the disaster in Chernobyl, Russia. Through the accident It reveals the dangerous nuclear energy with a lot of problems on the nuclear power plants which includes four reasons about propelling development of atomic and criticism about that, eight reasons against development of atomic, the problem in 11 -12 nuclear power plant, the movement of antagonism towards nuclear waste in Anmyon island, cases of antinuclear in foreign country and building of new energy system.

  4. Atom laser divergence

    OpenAIRE

    Le Coq, Yann; Thywissen, Joseph H.; Rangwala, Sadiq A.; Gerbier, Fabrice; Richard, Simon; Delannoy, Guillaume; Bouyer, Philippe; Aspect, Alain

    2001-01-01

    We measure the angular divergence of a quasi-continuous, rf-outcoupled, free-falling atom laser as a function of the outcoupling frequency. The data is compared to a Gaussian-beam model of laser propagation that generalizes the standard formalism of photonic lasers. Our treatment includes diffraction, magnetic lensing, and interaction between the atom laser and the condensate. We find that the dominant source of divergence is the condensate-laser interaction.

  5. Guided Quasicontinuous Atom Laser

    OpenAIRE

    Guerin, William; Riou, Jean-Félix; Gaebler, John,; Josse, Vincent; Bouyer, Philippe; Aspect, Alain

    2006-01-01

    version published in Phys. Rev. Lett. 97, 200402 (2006) International audience We report the first realization of a guided quasicontinuous atom laser by rf outcoupling a Bose-Einstein condensate from a hybrid optomagnetic trap into a horizontal atomic waveguide. This configuration allows us to cancel the acceleration due to gravity and keep the de Broglie wavelength constant at 0.5 µm during 0.1 s of propagation. We also show that our configuration, equivalent to pigtailing an optical f...

  6. Metal atomization spray nozzle

    Science.gov (United States)

    Huxford, Theodore J.

    1993-01-01

    A spray nozzle for a magnetohydrodynamic atomization apparatus has a feed passage for molten metal and a pair of spray electrodes mounted in the feed passage. The electrodes, diverging surfaces which define a nozzle throat and diverge at an acute angle from the throat. Current passes through molten metal when fed through the throat which creates the Lorentz force necessary to provide atomization of the molten metal.

  7. Atoms, molecules & elements

    CERN Document Server

    Graybill, George

    2007-01-01

    Young scientists will be thrilled to explore the invisible world of atoms, molecules and elements. Our resource provides ready-to-use information and activities for remedial students using simplified language and vocabulary. Students will label each part of the atom, learn what compounds are, and explore the patterns in the periodic table of elements to find calcium (Ca), chlorine (Cl), and helium (He) through hands-on activities.

  8. Theoretical atomic collision physics

    Energy Technology Data Exchange (ETDEWEB)

    Lane, N.F. (Rice Univ., Houston, TX (USA) Rice Univ., Houston, TX (USA). Quantum Inst.)

    1990-01-01

    The theoretical atomic physics at Rice University focuses on obtaining a better understanding of the mechanisms that control inelastic collisions between excited atoms and atoms, molecules and ions. Particular attention is given to systems and processes that are of potential importance to advanced energy technologies. In the current year, significant progress has been made in quantitative studies of: quenching of low-Rydberg Na atoms in thermal energy collisions with He, Ne and Ar atoms; selective excitation resulting from charge transfer in collisions of highly stripped ions of He, Li, C, and with Li, Na and He atoms and H{sub 2} molecules at keV energies; differential elastic and single, and double electron transfer in He{sup ++} collisions with He at keV energies; inelastic electron-transfer in ultra-low-energy-energy (T=8 to 80K) collisions between {sup 3}He{sup +} and {sup 4}He and {sup 4}He{sup +} and {sup 3}He; a formalism for ionization by electron impact of ions in dense, high temperature plasmas.

  9. Cross section data for electron collisions in plasma physics

    Energy Technology Data Exchange (ETDEWEB)

    Marinkovic, B P [Institute of Physics, Belgrade, P. O. Box 68, Pregrevica 118, 11080 Belgrade (Serbia); Pejcev, V [Institute of Physics, Belgrade, P. O. Box 68, Pregrevica 118, 11080 Belgrade (Serbia); Filipovic, D M [Institute of Physics, Belgrade, P. O. Box 68, Pregrevica 118, 11080 Belgrade (Serbia); Sevic, D [Institute of Physics, Belgrade, P. O. Box 68, Pregrevica 118, 11080 Belgrade (Serbia); Milosavljevic, A R [Institute of Physics, Belgrade, P. O. Box 68, Pregrevica 118, 11080 Belgrade (Serbia); Milisavljevic, S [Institute of Physics, Belgrade, P. O. Box 68, Pregrevica 118, 11080 Belgrade (Serbia); Rabasovic, M S [Institute of Physics, Belgrade, P. O. Box 68, Pregrevica 118, 11080 Belgrade (Serbia); Pavlovic, D [Institute of Physics, Belgrade, P. O. Box 68, Pregrevica 118, 11080 Belgrade (Serbia); Maljkovic, J B [Institute of Physics, Belgrade, P. O. Box 68, Pregrevica 118, 11080 Belgrade (Serbia)

    2007-10-15

    We present a survey of cross section data for electron collisions used in plasma physics. Needs for cross section data have been identified in different fields of plasma physics and a brief review of existing data on electron/radical data has been presented. Experimental capabilities and recent results obtained in the Belgrade Laboratory for Atomic Collision Processes have been discussed.

  10. Effective atomic number of dental smalt

    International Nuclear Information System (INIS)

    The effective atomic numbers Z are enough utilized for to characterize the interactions of ionizing radiation with matter. Particularly for the Z calculation in biological tissues and/or composed materials we need to know the relationship between the cross sections of the diverse radiations interactions with mattera and the atomic numbers Z of the constituent elements in the tissue or composed material. Normally the cross section by atom σ 2 is proportional to Zm. The m value depends of the iterative process type and the energy of the incident photons. In the case of the photoelectric interaction, the m vary will vary between 4,698 and 4,799 for energies between 10 to 200 keV. It was verified that constituent elements with high Z (>20) they had a major contribution. The m values for the Compton interation and the coherent scattering were calculated of similar way. Knowing the m values, we calculate the partials Z of a composed material. For the calculation of total Z, we can use alternatives starting from the equivalent atomic number corresponding to the total cross section σ d tot, mc of the composed material. In this work for the calculation of Z values corresponding to diverse interations, we applied a linear regression at the values of Ln σ a x LnZ for different energies. In general, to characterize a simulator material of a tissue or composed material we need to know the total Z in function of the photon energy applied to dental smalt increases until some hundreds of keV the partial values of Z owing to photoelectric effect and the coherent scattering this is owing to the smalt has a great concentration of elements with high Z. (Author)

  11. Variable Optical Attenuator Based on Long-Range Surface Plasmon Polariton Multimode Interference Coupler

    Directory of Open Access Journals (Sweden)

    Xiaoqiang Sun

    2014-01-01

    Full Text Available The fabrication and characterization of a thermal variable optical attenuator based on long-range surface plasmon polariton (LRSPP waveguide with multimode interference architecture were investigated. The surface morphology and waveguide configuration of Au stripe were studied by atomic force microscopy. The fluctuation of refractive index of poly(methyl-methacrylate-glycidyl-methacrylate polymer cladding was confirmed to be less than 3×10-4 within 8 h curing at 120°C. The end-fire excitation of LRSPP mode guiding at 1550 nm along Au stripe indicated that the extinction ratio of attenuator was about 12 dB at a driving power of 69 mW. The measured optical rise time and fall time are 0.57 and 0.87 ms, respectively. These favorable properties promise potentials of this plasmonic device in the application of optical interconnection.

  12. Influence of dental resin material composition on cross-polarization-optical coherence tomography imaging

    Science.gov (United States)

    Lammeier, Carmen; Li, YuPing; Lunos, Scott; Fok, Alex; Rudney, Joel; Jones, Robert S.

    2012-10-01

    The purpose of this study was to investigate cross-polarization-optical coherence tomography (CP-OCT) signal attenuation through different resin material compositions. Four distinct composite systems were used: Filtek supreme ultra (FSU) (3M ESPE), IPS empress direct (EMD) (Ivoclar Vivadent), estelite sigma quick (SQK) (Tokuyama Dental), and Z100 (3M ESPE). Cross-sectional images of different composite-demineralized phantoms (n=108) were collected using a 1310-nm intraoral cross-polarization swept source OCT (CP-OCT) imaging system. %T quantified the CP-OCT signal attenuation. Scanning electron microscopy, transmission electron microscopy, and energy-dispersive x-ray spectrometer chemical analysis was utilized to determine how different matrix/filler compositions affected attenuation of the near infrared (NIR) signal. CP-OCT imaging of dental resin composites showed enormous variation in signal attenuation. For each of our composite systems, there was not a consistent attenuation difference in the NIR signal for A to D shades. The four composites had similar measured backscattering values but attenuated the overall signal to different degrees. When comparing the A2 shades between the four different composite systems, the order of highest to lowest of %T was EMD>Z100, FSU>SQK (ANOVA, Tukey, p<0.0001). As a result, we demonstrate the importance of understanding how the constituents of composite materials affect CP-OCT signal attenuation.

  13. Ionization of atoms by lasers and electric fields

    International Nuclear Information System (INIS)

    A ring dye laser was monitored 5890 A line by a sodium fluorescence cell. The laser was orthogonally directed to interact with a sodium effusive atomic beam. Light radiation from a lamp shifted the excited sodium to near continuum level. The highly excited states are more susceptible to an external field, thus shifting the highly external atoms to the continuum level. The interaction of the electric field causes an increase of two orders of magnitude as compared to two photonionization only. The high signal recorded was due to the probability of the ionization cross section approaching the excited cross section which is several orders of magnitude higher

  14. Charge exchange between hydrogen atoms and fully stripped heavy ions

    International Nuclear Information System (INIS)

    Charge exchange between multicharged ions and background atomic and molecular gases represents one of the limitations to the attainment of high charge states in heavy ion sources, particularly containment sources. An attempt is made to study systematically a particularly simple but in many respects representative class of such reactions, namely charge transfer between atomic hydrogen and fully stripped heavy ions. Approximate cross sections for these processes in the low keV range of collision energies were obtained using a multistate Landau--Zener method. The energy and Z dependences of the cross sections are discussed

  15. Attenuation data of point isotropic neutron sources up to 400MeV in water, ordinary concrete and iron

    Energy Technology Data Exchange (ETDEWEB)

    Kotegawa, Hiroshi; Tanaka, Shun-ichi; Sakamoto, Yukio; Nakane, Yoshihiro; Nakashima, Hiroshi [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    1994-08-01

    A comprehensive attenuation data of dose equivalent for point isotropic monoenergetic neutron sources up to 400MeV in infinite shields of water, ordinary concrete and iron has been calculated using the ANISN-JR code and a neutron-photon multigroup macroscopic cross section HIL086R. The attenuation factors were fitted to a 4th order polynomial exponent formula, making possible to use easily for point kernel codes. Additional data in finite shielding geometry was also calculated to correct the effect due to infinite medium, giving the maximum correction of 0.23 in the region for more 400 cm distance from neutron source of 400 MeV in iron shield. Effective attenuation length for monoenergetic neutrons have been studied in detail. Subsequently, it was shown that the attenuation length was strongly dependent upon the penetration length and the Moyer`s formula using a single attenuation length brought large error into the dose estimation behind thick shields for the intermediate energy neutrons up to 400 MeV. Furthermore, it was demonstrated that there was difference more than 50 % in the attenuation length of iron between the calculations with HIL086R and HIL086 because of the self-shielding effect. (author).

  16. Border Crossing/Entry Data - Boarder Crossing

    Data.gov (United States)

    Department of Transportation — Border Crossing/Entry Data provides summary statistics for incoming crossings at the U.S.-Canadian and the U.S.-Mexican border at the port level. Data are available...

  17. Atomic data for integrated tokamak modelling

    International Nuclear Information System (INIS)

    The Integrated Tokamak Modeling Task Force (ITM-TF) was set up in 2004. The main target is to coordinate the European fusion modeling effort and providing a complete European modeling structure for International Thermonuclear Experimental Reactor (ITER), with the highest degree of flexibility. For the accurate simulation of the processes in the active fusion reactor in the ITM-TF, numerous atomic, molecular, nuclear and surface related data are required. In this work we present total-, single- and multiple-ionization and charge exchange cross sections in close connection to the ITM-TF. Interpretation of these cross sections in multi-electron ion-atom collisions is a challenging task for theories. The main difficulty is caused by the many-body feature of the collision, involving the projectile, projectile electron(s), target nucleus, and target electron(s). The classical trajectory Monte Carlo (CTMC) method has been quite successful in dealing with the atomic processes in ion-atom collisions. One of the advantages of the CTMC method is that many-body interactions are exactly taken into account related CTMC simulations for a various collision systems are presented. To highlight the efficiency of the method we present electron emission cross sections in collision between dressed Alq+ ions with He target. The theory delivers separate spectra for electrons emitted from the target and the projectile. By summing these two components in the rest frame of the target we may make a comparison with available experimental data. For the collision system in question, a significant contribution from Fermi-shuttle ionization has to be expected in the spectra at energies higher than E=0.5 me (nV)2, where me is the mass of the electron, V the projectile velocity and n an integer greater than 1. We found enhanced electron yields compared to first order theory in this region of CTMC spectra, which can be directly attributed to the contribution of Fermi-shuttle type multiple scattering

  18. Positron-Lithium Atom and Electron-Lithium Atom Scattering Systems at Intermediate and High Energies

    Institute of Scientific and Technical Information of China (English)

    K. Ratnavelu; S. Y. Ng

    2006-01-01

    @@ The coupled-channel optical method is used to study positron scattering by atomic lithium at energies ranging from the ionization threshold to 60 eV. The present method simultaneously treats the target channels and the positronium (Ps) channels in the coupled-channel method together with the continuum effects via an ab-initio optical potential. Ionization, elastic and inelastic cross sections in target channels, and the total cross section are also reported and compared with other theoretical and experimental data. A comparative study with the corresponding electron-lithium data is also reported.

  19. KAERI charged particle cross section library for radioisotope production

    CERN Document Server

    Chang, J H; Kim, D H; Lee, Y O; Zhuang, Y X

    2001-01-01

    This report summarized information and figures describing the 'KAERI Charged Particle Cross Section Library for Radioisotope production' The library contains proton-, deutron-, He-3-, and alpha-induced monitor cross sections, and gamma- and positron-emitter production cross sections. Experimental data and evaluation methods are described, and the evaluated cross sections are compared with those of the IAEA, MENDL, and LA150. The library has cross sections and emission spectra suitable for the transport analysis in the design of radioisotope production system, and are available at http://atom.kaeri.re.kr/ in ENDF-6 format.

  20. Effective potentials for atom-atom interaction at low temperatures

    OpenAIRE

    Gao, Bo

    2002-01-01

    We discuss the concept and design of effective atom-atom potentials that accurately describe any physical processes involving only states around the threshold. The existence of such potentials gives hope to a quantitative, and systematic, understanding of quantum few-atom and quantum many-atom systems at relatively low temperatures.