WorldWideScience

Sample records for rotatory dispersion electronic

  1. Quantum optical rotatory dispersion

    Science.gov (United States)

    Tischler, Nora; Krenn, Mario; Fickler, Robert; Vidal, Xavier; Zeilinger, Anton; Molina-Terriza, Gabriel

    2016-01-01

    The phenomenon of molecular optical activity manifests itself as the rotation of the plane of linear polarization when light passes through chiral media. Measurements of optical activity and its wavelength dependence, that is, optical rotatory dispersion, can reveal information about intricate properties of molecules, such as the three-dimensional arrangement of atoms comprising a molecule. Given a limited probe power, quantum metrology offers the possibility of outperforming classical measurements. This has particular appeal when samples may be damaged by high power, which is a potential concern for chiroptical studies. We present the first experiment in which multiwavelength polarization-entangled photon pairs are used to measure the optical activity and optical rotatory dispersion exhibited by a solution of chiral molecules. Our work paves the way for quantum-enhanced measurements of chirality, with potential applications in chemistry, biology, materials science, and the pharmaceutical industry. The scheme that we use for probing wavelength dependence not only allows one to surpass the information extracted per photon in a classical measurement but also can be used for more general differential measurements. PMID:27713928

  2. Stereochemistry of the tadalafil diastereoisomers: a critical assessment of vibrational circular dichroism, electronic circular dichroism, and optical rotatory dispersion.

    Science.gov (United States)

    Qiu, Shi; De Gussem, Ewoud; Tehrani, Kourosch Abbaspour; Sergeyev, Sergey; Bultinck, Patrick; Herrebout, Wouter

    2013-11-14

    The stereochemistry of all four stereoisomers of tadalafil is determined using vibrational circular dichroism (VCD), electronic circular dichroism (ECD), and optical rotatory dispersion (ORD) spectroscopy. By comparing experimentally obtained VCD spectra to computationally simulated ones, the absolute configuration of the enantiomeric pair (6R, 12aR)/(6S, 12aS) can be confidently assigned without prior knowledge of their relative stereochemistry. IR and NMR spectra are used to aid the assignment of the relative stereochemistry. The IR and VCD difference spectra further confirm the assignment of all stereoisomers. ECD and ORD spectra are used to investigate the complementarity of the three chiroptical techniques. VCD spectroscopy itself is found to have the ability to identify diastereoisomers, and simultaneous use of these chiroptical spectroscopic methods and NMR chemical shifts aids in increasing the reliability of stereochemistry assignment of diastereoisomers.

  3. Absolute configuration of an axially chiral sulfonate determined from its optical rotatory dispersion, electronic circular dichroism, and vibrational circular dichroism spectra.

    Science.gov (United States)

    Covington, Cody L; Raghavan, Vijay; Smuts, Jonathan P; Armstrong, Daniel W; Polavarapu, Prasad L

    2017-11-01

    The absolute configuration (AC) of an axially chiral sulfonate (aCSO), 3,5-dimethyl-2-(naphthalen-1-yl)-6-(naphthalen-1-yl)benzenesulfonate (labeled as aCSO5), was investigated using optical rotatory dispersion (ORD), electronic circular dichroism (ECD), and vibrational circular dichroism (VCD) spectroscopies. All three methods led to the same conclusion and the AC of aCSO5 is reliably determined to be (-)-(aR, aR), or conversely (+)-(aS, aS). © 2017 Wiley Periodicals, Inc.

  4. Kramers-Kronig transformation of experimental electronic circular dichroism: application to the analysis of optical rotatory dispersion in dimethyl-L-tartrate.

    Science.gov (United States)

    Polavarapu, Prasad L; Petrovic, Ana G; Zhang, Peng

    2006-09-01

    When a limited region of the experimental electronic circular dichroism (ECD) spectrum is subjected to Kramers-Kronig (KK) transformation, the resulting optical rotatory dispersion (ORD) may or may not reproduce the experimentally measured ORD in the long-wavelength nonresonant region. If the KK transform of experimentally measured ECD in a limited wavelength region reproduces the experimentally measured ORD in the long-wavelength nonresonant region, then that observation indicates that the ORD in the long-wavelength nonresonant region should be satisfactorily predicted from the correspondingly limited number of electronic transitions in a reliable quantum mechanical calculation. On the other hand, if the KK transform of experimentally measured ECD in a limited region does not reproduce the experimentally measured ORD in the long-wavelength nonresonant region, then it should be possible to identify the ECD bands in the shorter wavelength region that are responsible for the differences between experimentally observed ORD and KK-transformed ECD. This approach helps to identify the role of ECD associated with higher energy-excited states in the nature of ORD in the long-wavelength nonresonant region. These concepts are demonstrated here by measuring the experimental ECD and ORD for dimethyl-L-tartrate in different solvents. While ECD spectra of dimethyl-L-tartrate in different solvents show little variation, ORD spectra in the long-wavelength nonresonant region show marked solvent dependence. These observations are explained using the difference between experimental ORD and KK-transformed ECD. Quantum mechanical predictions of ECD and ORD are also presented for isolated (R, R)-dimethyl tartrate at the B3LYP/aug-cc-pVDZ level.

  5. Bragg reflection band width and optical rotatory dispersion of cubic blue-phase liquid crystals

    Science.gov (United States)

    Yoshida, Hiroyuki; Anucha, Konkanok; Ogawa, Yasuhiro; Kawata, Yuto; Ozaki, Masanori; Fukuda, Jun-ichi; Kikuchi, Hirotsugu

    2016-10-01

    The Bragg reflection band width and optical rotatory dispersion of liquid crystalline cholesteric blue phases (BPs) I and II are compared by numerical simulations. Attention is paid to the wavelength regions for which the reflection bands with lowest photon energies appear, i.e., the [110 ] direction for BP I and the [100 ] direction for BP II. Finite difference time domain and 4 ×4 matrix calculations performed on the theoretical director tensor distribution of BPs with the same material parameters show that BP II, which has simple cubic symmetry, has a wider photonic band gap than BP I, which has body centered cubic symmetry, possibly due to the fact that the density of the double-twist cylinders in BP II are twice that in BP I. The theoretical results on the Bragg reflection band width are supported by reflectance measurements performed on BPs I and II for light incident along the [110 ] and [100 ] directions, respectively.

  6. New method to determine the optical rotatory dispersion of inorganic crystals applied to some samples of Carpathian Quartz.

    Science.gov (United States)

    Dimitriu, Dan Gheorghe; Dorohoi, Dana Ortansa

    2014-10-15

    A new method to determine the optical rotatory dispersion (ORD) in the visible range, based on a channeled spectrum obtained with a uniax inorganic crystal introduced between two crossed polarizers with its optical axis parallel to the light propagation direction is detailed in this paper. When the studied inorganic crystals are transparent, this method permits the estimation of the optical rotatory dispersion in the visible range, for which the cheap polarizers are available. The speed of the measurements is very high, because the estimations are made from the channeled spectrum obtained for a single arrangement of the optical components. By using a computer, ORD is quickly determined for the visible range. The results obtained by this method for some Carpathian Quartz samples are consistent with those from literature. The proposed method can be also applied in UV and IR spectral ranges, when the anisotropic layers are transparent and the linearly polarized radiations can be obtained.

  7. Solvent, temperature and concentration effects on the optical rotatory dispersion of (R)-3-methylcyclohexanone

    Science.gov (United States)

    Alenaizan, Asem; Al-Basheer, Watheq; Musa, Musa M.

    2017-02-01

    Optical rotatory dispersion (ORD) spectra are reported for isolated and solvated (R)-3-methylcyclohexanone (R-3MCH) in 10 solvents, of wide polarity range, and over the spectral range 350-650 nm. Sample concentration effects on ORD spectra of R-3MCH were also recorded and investigated over widely varying concentrations from 2.5 × 10-3 to 2.5 × 10-1 g/mL where an observed sensitivity of optical rotation (OR) to incident light wavelength at low concentrations is correlated to solvent effects. Temperature effects were also studied by recording ORD spectra over the temperature range 0-65 °C in toluene. Recorded specific OR was plotted against various solvent parameters, namely, dipole moment, polarity, refractive index and polarizability to probe solvent effects. Furthermore, solvent effects were studied by incorporating Kamlet's and Taft's solvent parameters in the multi-parametric linear fitting. Theoretically, ORD spectra and populations of optimized geometries of equatorial and axial conformers of R-3MCH were calculated in the gas and solvated phases. All theoretical calculations were performed employing the polarizable continuum model using density functional theoretical and composite scheme (G4) methods with aug-cc-pVTZ and aug-cc-pVDZ basis sets. Net ORD spectra of R-3MCH were generated by the Boltzmann-weighted sum of the contributions of the dominant conformers. Upon comparing theoretical and experimental ORD spectra, a very good agreement is observed for the ORD spectra in the gas phase and high polarity solvents compared to relatively lesser agreement in low polarity solvents.

  8. Quartz optical filter for wavelength selection of frequency-doubled laser based on optical rotatory dispersion effect

    Institute of Scientific and Technical Information of China (English)

    Shan Zhang; Fuquan Wu; Wendi Wu; Haifeng Wang

    2007-01-01

    Based on the optical rotatory dispersion effect, an optical filter for selecting the second harmonic of a frequency-doubled laser is constructed from quartz in combination with polarizers. The operating principle is analyzed by matrix formulation, and the result indicates that the second harmonic of a frequency-doubled laser will be obtained when the rotation angle has a difference of (2n + 1)π/2 (n = 0, 1, 2, 3,… ) between the two polarizations of the second-harmonic laser and the fundamental laser. The spectrum of the output laser is taken by the AQ-6315A spectrometer, and the experimental results are in good agreement with the theoretical results.

  9. Faraday rotation dispersion measurements of diamagnetic organic liquids and simultaneous determination of natural optical rotatory dispersion using a pulsed magnetic field.

    Science.gov (United States)

    Suwa, Masayori; Miyamoto, Kayoko; Watarai, Hitoshi

    2013-01-01

    We constructed an apparatus to measure the wavelength dispersion of the Faraday rotation in the visible region, and determined the Verdet constants of diamagnetic organic liquids, including aliphatic compounds, benzene derivatives, and naphthalene derivatives. These three groups were easily distinguished by the magnitudes of their Verdet constants. Based on the theory developed by Serber, we determined the enhancing effect of π*←π transitions on the visible-light Faraday rotation angles observed for aromatic compounds. Furthermore, we propose a novel approach for simultaneously observing Faraday rotation dispersion and natural optical rotatory dispersion.

  10. Radioracemization and radiation-induced chiral amplification of chiral terpenes measured by optical rotatory dispersion (ORD) spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Cataldo, Franco [Lupi Chemical Research Institute, Via Casilina 1626/A, 00133 Rome (Italy); INAF-Osservatorio Astrofisico di Catania, Via S. Sofia 78, 95123 Catania (Italy)], E-mail: franco.cataldo@fastwebnet.it; Ursini, Ornella; Angelini, Giancarlo [Institute of Chemical Methodologies, CNR Via Salaria Km. 29300 00016 Monterotondo Stazione, Rome (Italy)

    2008-08-15

    For the first time the radioracemization of {alpha}(+)pinene and {alpha}(-)pinene, of turpentine and of R(-)-{alpha}-phellandrene has been studied by optical rotatory dispersion (ORD) spectroscopy. For all these compounds, the radioracemization implies a shift of the ORD curves toward lower levels of specific optical rotation. The radioracemization degree (R{sub R}) has been defined and calculated for all the compounds studied. It has been found that for radiation dose of 1 MGy the radioracemization degree is about 4.5% for the compound with the highest optical purity and reaches 7-8% for the less optically pure compounds, demonstrating that impurities can affect greatly the radioracemization. In contrast with the general radioracemization effect exerted by high-energy radiation on chiral molecules, {beta}(-)pinene, {beta}(+)pinene when irradiated show an increment of their specific optical rotation. This fact has been measured for the first time by ORD spectroscopy and the amplification degree of chirality can reach 1000% in the near UV. This phenomenon is due to the formation of a chiral polymer, poly-{beta}-pinene, which forms a solution with the monomer enhancing its optical activity. The implications for the theories of the origin of life of such unexpected phenomenon are discussed briefly.

  11. Influence of Physical and Chemical Modification on the Optical Rotatory Dispersion and Biological Activity of Chitosan Films

    Directory of Open Access Journals (Sweden)

    A. B. Shipovskaya

    2013-01-01

    Full Text Available The optical and bactericidal properties of acetic and basic chitosan films were studied. By the ORD technique, we found that these films differed in the values of their specific optical rotation and of their rotary and dispersive constants. A sign inversion of was observed when the acetic chitosan films were heat-treated. The bactericidal activity of the initial and dehydrated acetic films was analyzed, and their moisture content and optical and biological activities were compared.

  12. Measurement of Rotatory Optics Element in Tensor Dielectric Matrix for Rotatory Optical Fiber

    Institute of Scientific and Technical Information of China (English)

    LIU Jinghao; ZHANG Xiaofan; LI Huazhou; BAO Zhenwu

    2005-01-01

    The rotatory optics element in the tensor dielectric coefficient matrix is an important parameter for analyzing and calculating a rotatory optical fiber by electromagnetic theory. But the mea-surement of rotatory optics element is difficult for the rotatory optical fiber. A simple principle and method for measuring rotatory optics element are put forward in this paper. Firstly by using electromagnetic theory it was demonstrated that the rotatory optics element has a simple linear relation with the rotatory angle, and then the rotatory optics element has a simple linear relation with the magnetic field strength (or bias current in the helix coil) . Secondly a measurement system for the rotatory optics element in the rotatory optical fiber was designed. Using the measurement system the rotatory element can be obtained by measuring the bias current simply.

  13. Atlantoaxial rotatory dislocation. A case report.

    Science.gov (United States)

    Niibayashi, H

    1998-07-01

    Report of a child who sustained an acute atlantoaxial rotatory dislocation, associated with fractures of the clavicle and the temporal bone, and rupture of the alar ligament demonstrated by magnetic resonance imaging. To describe the radiographic and pathoanatomic characteristics of the injury process. Only five cases of traumatic atlantoaxial rotatory dislocation associated with fracture of the clavicle have been reported previously. This is the first report of a ruptured alar ligament demonstrated on magnetic resonance imaging in a patient with atlantoaxial rotatory dislocation associated with fractures of the clavicle and the temporal bone. Computed tomography revealed the Type 1 rotatory dislocation described by Fielding and Hawkins, and magnetic resonance imaging delineated the ruptured alar ligament. Traction in a halter, followed by 6 weeks of immobilization with a cervical collar, was successful in the management of the injury. Concomitant fractures of the right temporal bone and the right clavicle may yield excessive left rotation of the atlas on the axis, resulting in the rupture of the right alar ligament. Awareness of this condition allows early diagnosis and effective conservative treatment.

  14. Microstructural change on electron irradiated oxide dispersion strengthened ferritic steels

    Science.gov (United States)

    Kinoshita, H.; Akasaka, N.; Takahashi, H.; Shibahara, I.; Onose, S.

    1992-09-01

    Oxide dispersion strengthened (ODS) ferritic steels were irradiated in a high voltage electron microscope (HVEM) to study their response to irradiation. Fe-13Cr with 0.25 wt% Y2O3 as dispersed particles and containing additions of either 0.45% Nb, 0.45% V and 0.67% Zr were irradiated at 673 and 723 K up to 15 dpa. The Y2O3 particles in all specimens were stable under these irradiation conditions. During irradiation, two types of dislocations were formed but observable voids were not formed. Furthermore, plate-like and granular-like precipitates formed in both the irradiated and nonirradiated regions.

  15. Evolution of Modulated Dispersive Electron Waves in a Plasma

    DEFF Research Database (Denmark)

    Sugai, H.; Lynov, Jens-Peter; Michelsen, Poul

    1979-01-01

    The linear propagation of amplitude-modulated electron waves was examined in a low-density Q-machine plasma. Three effects of the strong dispersion on the modulated wave have been demonstrated: (i) a wavepacket expands along its direction of propagation, followed by a shift of the frequency through...... the wavepacket, (ii) the number of oscillations in the temporally observed packet is not identical with that in the spatially observed packet and (iii) continuously modulated waves exhibit recurrence of modulation. The experimental results agree with both a simple analysis based on the Schrodinger equation...

  16. Lateral atlantoaxial joint arthrography in atlantoaxial rotatory fixation.

    Science.gov (United States)

    Hosono, Noboru; Yonenobu, Kazuo; Tada, Koichi; Yoshikawa, Hideki

    2003-04-01

    There has been much debate about the pathogenesis of atlantoaxial rotatory fixation. Intraarticular abnormality has not been well documented thus far. This is the first case of chronic atlantoaxial rotatory fixation in which atlantoaxial joints were examined by consecutive arthrography. A 7-year-old girl was diagnosed with atlantoaxial rotatory fixation on a three-dimensional CT scan. Arthrography of the lateral atlantoaxial joints indicated a rupture of the joint capsule on the dislocated side at first, followed by a successful repair after 5 weeks' immobilization with a halo apparatus. Because torticollis recurred after taking off the halo vest, we performed surgery in which severe adhesion of the cartilage surface of facet joint was noted on the undislocated side and release of the adhesion was needed to mobilize the atlas. Atlantoaxial arthrodesis by screw fixation facilitated a solid fusion of the segment.

  17. Velocity dispersion of correlated energy spread electron beams in the free electron laser

    Science.gov (United States)

    Campbell, L. T.; Maier, A. R.

    2017-03-01

    The effects of a correlated linear energy/velocity chirp in the electron beam in the free electron laser (FEL), and how to compensate for its effects by using an appropriate taper (or reverse-taper) of the undulator magnetic field, is well known. The theory, as described thus far, ignores velocity dispersion from the chirp in the undulator, taking the limit of a ‘small’ chirp. In the following, the physics of compensating for chirp in the beam is revisited, including the effects of velocity dispersion, or beam compression or decompression, in the undulator. It is found that the limit of negligible velocity dispersion in the undulator is different from that previously identified as the small chirp limit, and is more significant than previously considered. The velocity dispersion requires a taper which is nonlinear to properly compensate for the effects of the detuning, and also results in a varying peak current (end thus a varying gain length) over the length of the undulator. The results may be especially significant for plasma driven FELs and low energy linac driven FEL test facilities.

  18. Velocity Dispersion of Correlated Energy Spread Electron Beams in the Free Electron Laser

    CERN Document Server

    Campbell, L T

    2016-01-01

    The effects of a correlated linear energy/velocity chirp in the electron beam in the FEL, and how to compensate for its effects by using an appropriate taper (or reverse-taper) of the undulator magnetic field, is well known. The theory, as described thus far, ignores velocity dispersion from the chirp in the undulator, taking the limit of a `small' chirp. In the following, the physics of compensating for chirp in the beam is revisited, including the effects of velocity dispersion, or beam compression or decompression, in the undulator. It is found that the limit of negligible velocity dispersion in the undulator is different from that previously identified as the small chirp limit, and is more significant than previously considered. The velocity dispersion requires a taper which is non-linear to properly compensate for the effects of the detuning, and also results in a varying peak current (end thus a varying gain length) over the length of the undulator. The results may be especially significant for plasma d...

  19. Temperature Dependence of Polarizability and Dispersion in Three, Two and One Dimensional Electron Gases

    Institute of Scientific and Technical Information of China (English)

    YAN Baorong; KONG Linghua; LV Jianhong; HU Xiwei

    2009-01-01

    Both temperature dependence of polarizability and plasmon dispersion in unmagnetized metal (or semiconductor) electron gases are investigated in this paper.It is obtained that,with a continuous variation of temperature in a large region,the polarizability and dispersion change non-monotonously.The static polarizability x(q,ω=0,μ,T) and dispersion ωp(q,T) for finite T in three,two and one dimensional electron gases are calculated numerically.In addition,dispersion relation ω(q) at a definite temperature (T≠0) is similar to that at T=0.

  20. Dispersal

    Science.gov (United States)

    Clobert, J.; Danchin, E.; Dhondt, A.A.; Nichols, J.D.

    2001-01-01

    The ability of species to migrate and disperse is a trait that has interested ecologists for many years. Now that so many species and ecosystems face major environmental threats from habitat fragmentation and global climate change, the ability of species to adapt to these changes by dispersing, migrating, or moving between patches of habitat can be crucial to ensuring their survival. This book provides a timely and wide-ranging overview of the study of dispersal and incorporates much of the latest research. The causes, mechanisms, and consequences of dispersal at the individual, population, species and community levels are considered. The potential of new techniques and models for studying dispersal, drawn from molecular biology and demography, is also explored. Perspectives and insights are offered from the fields of evolution, conservation biology and genetics. Throughout the book, theoretical approaches are combined with empirical data, and care has been taken to include examples from as wide a range of species as possible.

  1. Simulation-Based Design of a Rotatory SMA Drive

    Science.gov (United States)

    Dilthey, Sascha; Meier, Horst

    2009-08-01

    The design and optimization of a rotatory drive powered by shape memory alloy (SMA) actuators is described in this paper. SMA actuators used in technical applications are parameterized by the use of trial-and-error methods, because there is a lack of computer-aided design tools for this active material. A numerical modeling approach was developed to design and optimize the geometry and the load and heating conditions of SMA actuators in a technical system to achieve a good dynamic and a high reliability. The shape memory effect used in most technical systems is the extrinsic two way effect (2WE). This effect can be simulated with the numerical model which was implemented in MATLAB/SIMULINK. The focus of the model is on the activation behavior of the SMA actuator, which defines its rate of heating and cooling. Different load conditions and various actuator geometries and shapes, e.g. wire or spring actuator, are simulated by the calculation of the energetic balance of the whole system. The numerical model can be used to simulate time variant heating currents in order to obtain an optimal system performance. The model was used to design a rotatory SMA-drive system, which is based on the moving concept of a wave drive gear set. In contrast to the conventional system, which is driven by an electric motor, the SMA drive consists of a strain wave gear and SMA wire actuators that are applied circularly to generate a rotatory movement. Special characteristics of this drive system are a high torque density and a high positioning accuracy.

  2. Long-term sequel of posterolateral rotatory instability of the elbow: a case report

    Directory of Open Access Journals (Sweden)

    Cheng Chun-Ying

    2010-01-01

    Full Text Available Abstract The natural course of untreated posterior lateral rotatory instability of the elbow is unclear. A case of elbow arthrosis with progressing deformity and flexion contracture after an episode of elbow dislocation about 20 years ago presented the possibility the long term outcome of untreated posterior lateral rotatory instability of the elbow.

  3. Energy dispersive X-ray analysis in the electron microscope

    CERN Document Server

    Bell, DC

    2003-01-01

    This book provides an in-depth description of x-ray microanalysis in the electron microscope. It is sufficiently detailed to ensure that novices will understand the nuances of high-quality EDX analysis. Includes information about hardware design as well as the physics of x-ray generation, absorption and detection, and most post-detection data processing. Details on electron optics and electron probe formation allow the novice to make sensible adjustments to the electron microscope in order to set up a system which optimises analysis. It also helps the reader determine which microanalytical me

  4. Measurement of Electron Clouds in Large Accelerators by Microwave Dispersion

    Energy Technology Data Exchange (ETDEWEB)

    De Santis, S.; Byrd, J.M.; /LBL, Berkeley; Caspers, F.; /CERN; Krasnykh, A.; /SLAC; Kroyer, T.; /CERN; Pivi, M.T.F.; /SLAC; Sonnad, K.G.; /LBL, Berkeley

    2008-03-19

    Clouds of low energy electrons in the vacuum beam pipes of accelerators of positively charged particle beams present a serious limitation for operation at high currents. Furthermore, it is difficult to probe their density over substantial lengths of the beam pipe. We have developed a novel technique to directly measure the electron cloud density via the phase shift induced in a TE wave transmitted over a section of the accelerator and used it to measure the average electron cloud density over a 50 m section in the positron ring of the PEP-II collider at the Stanford Linear Accelerator Center.

  5. Electron dispersion events in the morningside auroral zone and their relationship with VLF emissions

    Energy Technology Data Exchange (ETDEWEB)

    Hardy, D.A.; Burke, W.J. (Hanscom Air Force Base, MA (United States)); Villalon, E. (Northeastern Univ., Boston, MA (United States))

    1990-05-01

    Energy/time dispersion events have been observed in the precipitating electron data in the energy range from 630 eV to 20 keV recorded by the J sensor on the low-altitude, polar-orbiting HILAT satellite. The dispersions are such that the higher-energy electrons are observed earlier in time than the lower-energy electrons The time interval for single dispersion event is from 1 to 2 s. Within an auroral pass in which such energy/time dispersion events are observed, there are typically several such events, and they can be spaced within the pass in either a periodic or aperiodic manner. The events are typically observed within and toward the equatorward edge of the region of diffuse auroral electron precipitation. During a given pass the events can be observed over a wide range of L shells. The occurrence of these events maximizes in the interval 0600-1,200 hours MLT. The energy/time dispersion is generally consistent with the electrons originating from a common source. The events are seen at L shells from 3.7 to greater than 15. The source distance for the electrons is inferred to be generally beyond the equator for events at L shells less than approximately 8 and before the equator for events at higher L shells. Because of the low energies at which the dispersions are observed, it is unlikely that their occurrence can be explained by resonant interaction with VLF waves. Based on circumstantial evidence from other reported observations common to the morning sector, and alternative theoretical explanation is presented. According to this model the dispersion events result from impulsive interactions of the electrons with intense, asymmetric packets of VLF waves via the nonlinear, ponderomotive force.

  6. THz-radiation production using dispersively-selected flat electron bunches

    CERN Document Server

    Thangaraj, Jayakar

    2013-01-01

    We propose an alternative scheme for a tunable THz radiation source generated by relativistic electron bunches. This technique relies on the combination of dispersive selection and flat electron bunch. The dispersive selection uses a slit mask inside a bunch compressor to transform the energy-chirped electron beam into a bunch train. The flat beam transformation boosts the frequency range of the THz source by reducing the beam emittance in one plane. This technique generates narrow-band THz radiation with a tuning range between 0.2 - 4 THz. Single frequency THz spectrum can also be generated by properly choosing the slit spacing, slit width, and the energy chirp.

  7. Effect of electron inertia on dispersive properties of Alfvén waves in cold plasmas

    Science.gov (United States)

    Jana, Sayanee; Ghosh, Samiran; Chakrabarti, Nikhil

    2017-10-01

    The effect of electron inertia on Alfvén wave propagation is investigated in the framework of the two-fluid theory in a compressible magnetized plasma. The linear analysis of the governing equations manifests the dispersion relation of the circularly polarized Alfvén waves where the electron inertia is found to act as a source of dispersion. In the finite amplitude limit, the nonlinear Alfvén wave may be described by the Derivative Nonlinear Schrödinger equation (DNLSE) modified by third order dispersion arising due to finite electron inertia. The derived equation seems to be novel with respect to what exists in the literature of Alfvén wave dynamics. We have shown that this electron inertia modified DNLSE is completely integrable and an analytical solution is demonstrated with vanishing boundary conditions. The results are expected to be of special importance in the context of space and laboratory plasmas.

  8. Electron dispersion events in the morningside auroral zone and their relationship with VLF emissions

    Science.gov (United States)

    Hardy, David A.; Burke, William J.; Villalon, Elena

    1990-05-01

    This paper reports on observations of electron precipitation bursts observed in the morningside auroral zone with the J sensor, an electron detector aboard the Hilat satellite. The characteristics of these precipitation events are documented, and a theoretical explanation that could account for the observed properties is presented. According to this model, the dispersion events result from impulsive interactions of the electrons with intense asymmetric packets of VLF waves via the nonlinear ponderomotive force.

  9. A linear dispersion relation for the hybrid kinetic-ion/fluid-electron model of plasma physics

    CERN Document Server

    Told, Daniel; Astfalk, Patrick; Jenko, Frank

    2016-01-01

    A dispersion relation for a commonly used hybrid model of plasma physics is developed, which combines fully kinetic ions and a massless-electron fluid description. Although this model and variations of it have been used to describe plasma phenomena for about 40 years, to date there exists no general dispersion relation to describe the linear wave physics contained in the model. Previous efforts along these lines are extended here to retain arbitrary wave propagation angles, temperature anisotropy effects, as well as additional terms in the generalized Ohm's law which determines the electric field. A numerical solver for the dispersion relation is developed, and linear wave physics is benchmarked against solutions of a full Vlasov-Maxwell dispersion relation solver. This work opens the door to a more accurate interpretation of existing and future wave and turbulence simulations using this type of hybrid model.

  10. The dispersion modification of electrostatic geodesic acoustic mode by electron geodesic drift current

    OpenAIRE

    Zhang, Shuangxi

    2014-01-01

    The past studies treated the perturbed distribution of circulating electrons as adiabatic one when studying the dispersion relation of electrostatic geodesic acoustic mode(GAM). In this paper, the flow of electron geodesic current (FEGC) is added to modify this adiabatic distribution. Based on the drift kinetic theory, it is found that FEGC obviously increases the magnitude of the standard GAM's frequency and reduces its damping rate. The increase of frequency results from the contribution of...

  11. Lorentz Dispersion Law from classical Hydrogen electron orbits in AC electric field via geometric algebra

    CERN Document Server

    Perez, Uzziel; Sugon, Quirino M; McNamara, Daniel J; Yoshikawa, Akimasa

    2015-01-01

    We studied the orbit of an electron revolving around an infinitely massive nucleus of a large classical Hydrogen atom subject to an AC electric field oscillating perpendicular to the electron's circular orbit. Using perturbation theory in geometric algebra, we show that the equation of motion of the electron perpendicular to the unperturbed orbital plane satisfies a forced simple harmonic oscillator equation found in Lorentz dispersion law in Optics. We show that even though we did not introduce a damping term, the initial orbital position and velocity of the electron results to a solution whose absorbed energies are finite at the dominant resonant frequency $\\omega=\\omega_0$; the electron slowly increases its amplitude of oscillation until it becomes ionized. We computed the average power absorbed by the electron both at the perturbing frequency and at the electron's orbital frequency. We graphed the trace of the angular momentum vector at different frequencies. We showed that at different perturbing frequen...

  12. Oxide dispersion strengthened Fe–12Cr steel in three dimensions: An electron tomography study

    Energy Technology Data Exchange (ETDEWEB)

    Castro, V. de, E-mail: vanessa.decastro@uc3m.es [Department of Materials, University of Oxford, Oxford OX1 3PH (United Kingdom); Departamento de Física, Universidad Carlos III de Madrid, Avenida de la Universidad 30, 28911 Leganés, Madrid (Spain); Rodrigo, P. [Departamento de Ciencia e Ingeniería de Materiales, Universidad Rey Juan Carlos, c/Tulipán s.n., 28933 Móstoles, Madrid (Spain); Marquis, E.A. [Department of Materials, University of Oxford, Oxford OX1 3PH (United Kingdom); Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI (United States); Lozano-Perez, S. [Department of Materials, University of Oxford, Oxford OX1 3PH (United Kingdom)

    2014-01-15

    Highlights: • An ODS Fe–12Cr steel was reconstructed in 3D using electron tomography. • Electron tomography allowed reconstruction of nanoparticles down to 5 nm. • Reconstruction showed that some particles are found within Cr-rich precipitates. -- Abstract: In this work, scanning-transmission electron microscope tomography and atom-probe tomography were successfully applied to characterize the Y- and Cr-rich secondary phases present in an oxide dispersion strengthened reduced activation Fe–12Cr alloy in three dimensions. Electron energy loss spectroscopy, energy dispersive spectroscopy and energy filtered transmission electron microscopy were used to obtain analytical information about the region used for electron tomography reconstruction. The results obtained with these techniques provided accurate information regarding the Y-rich nanoparticle dispersion and chemistry and their association with the Cr-rich precipitates present in the alloy. Reconstructions show that Y-rich nanoparticles are frequently found to be embedded within the larger Cr-rich carbides and oxides, which would decrease the amount of nanoparticles capable of strengthening the matrix.

  13. 1H relaxation dispersion in solutions of nitroxide radicals: Influence of electron spin relaxation

    Science.gov (United States)

    Kruk, D.; Korpała, A.; Kubica, A.; Kowalewski, J.; Rössler, E. A.; Moscicki, J.

    2013-03-01

    The work presents a theory of nuclear (1H) spin-lattice relaxation dispersion for solutions of 15N and 14N radicals, including electron spin relaxation effects. The theory is a generalization of the approach presented by Kruk et al. [J. Chem. Phys. 137, 044512 (2012)], 10.1063/1.4736854. The electron spin relaxation is attributed to the anisotropic part of the electron spin-nitrogen spin hyperfine interaction modulated by rotational dynamics of the paramagnetic molecule, and described by means of Redfield relaxation theory. The 1H relaxation is caused by electron spin-proton spin dipole-dipole interactions which are modulated by relative translational motion of the solvent and solute molecules. The spectral density characterizing the translational dynamics is described by the force-free-hard-sphere model. The electronic relaxation influences the 1H relaxation by contributing to the fluctuations of the inter-molecular dipolar interactions. The developed theory is tested against 1H spin-lattice relaxation dispersion data for glycerol solutions of 4-oxo-TEMPO-d16-15N and 4-oxo-TEMPO-d16-14N covering the frequency range of 10 kHz-20 MHz. The studies are carried out as a function of temperature starting at 328 K and going down to 290 K. The theory gives a consistent overall interpretation of the experimental data for both 14N and 15N systems and explains the features of 1H relaxation dispersion resulting from the electron spin relaxation.

  14. Evaluating E. coli degradation using a rotatory disk photoreactor

    Directory of Open Access Journals (Sweden)

    Gina María Hincapié Mejía

    2010-04-01

    Full Text Available Degradation of the bacterium E. coli was studied using a rotatory disk photoreactor manufactured in stainless steel to ascertain this photoreaction system’s behaviour in different operating conditions. The photoreactor was equipped with 6 black light bulbs (BLB used as a source of UV light and fitted with 7 removable disks made of common frosted glass impregnated with TiO2 photocatalyzer which were coupled to a rotation system. TiO2 was impregnated on the disks using the sol-gel method varying molar precursor gel ratios. Abrasion resistance, disk adhesion and surface uniformity tests were carried out for selecting the film presenting the best characteristics. Bacterial photodegradation studies were carried out using the following variable parameters: the disks’ rotation speed, radiation intensity and the number of discs which were directly related to the concentration of photo-catalyzer in the system. Up to 64.3% degradation was achieved in 4 hours using 7 disks, low intensity and low rotation speed.

  15. Development of wavelength-dispersive soft X-ray emission spectrometers for transmission electron microscopes--an introduction of valence electron spectroscopy for transmission electron microscopy.

    Science.gov (United States)

    Terauchi, Masami; Koike, Masato; Fukushima, Kurio; Kimura, Atsushi

    2010-01-01

    Two types of wavelength-dispersive soft X-ray spectrometers, a high-dispersion type and a conventional one, for transmission electron microscopes were constructed. Those spectrometers were used to study the electronic states of valence electrons (bonding electrons). Both spectrometers extended the acceptable energy regions to higher than 2000 eV. The best energy resolution of 0.08 eV was obtained for an Al L-emission spectrum by using the high-dispersion type spectrometer. By using the spectrometer, C K-emission of carbon allotropes, Cu L-emission of Cu(1-x)Zn(x) alloys and Pt M-emission spectra were presented. The FWHM value of 12 eV was obtained for the Pt Malpha-emission peak. The performance of the conventional one was also presented for ZnS and a section specimen of a multilayer device. W-M and Si-K emissions were clearly resolved. Soft X-ray emission spectroscopy based on transmission electron microscopy (TEM) has an advantage for obtaining spectra from a single crystalline specimen with a defined crystal setting. As an example of anisotropic soft X-ray emission, C K-emission spectra of single crystalline graphite with different crystal settings were presented. From the spectra, density of states of pi- and sigma-bondings were separately derived. These results demonstrated a method to analyse the electronic states of valence electrons of materials in the nanometre scale based on TEM.

  16. The Wavelength-Dispersive Spectrometer and Its Proposed Use in the Analytical Electron Microscope

    Science.gov (United States)

    Goldstein, Joseph I.; Lyman, Charles E.; Williams, David B.

    1989-01-01

    The Analytical Electron Microscope (AEM) equipped with a wavelength-dispersive spectrometer (WDS) should have the ability to resolve peaks which normally overlap in the spectra from an energy-dispersive spectrometer (EDS). With a WDS it should also be possible to measure lower concentrations of elements in thin foils due to the increased peak-to-background ratio compared with EDS. The WDS will measure X-ray from the light elements (4 less than Z less than 1O) more effectively. This paper addresses the possibility of interfacing a compact WDS with a focussing circle of approximately 4 cm to a modem AEM with a high-brightness (field emission) source of electrons.

  17. Energy-spread measurement of triple-pulse electron beams based on the magnetic dispersion principle

    CERN Document Server

    Wang, Yi; Yang, Zhiyong; Zhang, Huang; Ding, Hengsong; Yang, Anmin; Wang, Minhong

    2016-01-01

    The energy-spread of the triple-pulse electron beam generated by the Dragon-II linear induction accelerator is measured using the method of energy dispersion in the magnetic field. A sector magnet is applied for energy analyzing of the electron beam, which has a bending radius of 300 mm and a deflection angle of 90 degrees. For each pulse, both the time-resolved and the integral images of the electron position at the output port of the bending beam line are recorded by a streak camera and a CCD camera, respectively. Experimental results demonstrate an energy-spread of less than +-2.0% for the electron pulses. The cavity voltage waveforms obtained by different detectors are also analyzed for comparison.

  18. Traumatic atlantoaxial rotatory fixation associated with C2 articular facet fracture in adult patient: Case report

    Directory of Open Access Journals (Sweden)

    Mehdi Bellil

    2014-01-01

    Full Text Available Traumatic atlantoaxial rotatory fixation is a very rare injury in adults which is often misdiagnosed initially. Its combination with C2 fractures is predominated by dens lesions. Therapeutic management is challenging because of the difficulty to achieve optimal reduction and permanent stability. We report a rare case of traumatic atlantoaxial rotatory fixation in a 56-year-old women associated with C2 articular facet fracture successfully treated by conservative means after patient-awake manual reduction with optimal functional and radiographic outcome.

  19. Ion-dispersion and rapid electron fluctuations in the cusp: a case study

    Directory of Open Access Journals (Sweden)

    J. Lunde

    2008-08-01

    Full Text Available We present results from co-ordinated measurements with the low altitude REIMEI satellite and the ESR (EISCAT Svalbard Radar, together with other ground-based instruments carried out in February 2006. The results mainly relate to the dayside cusp where clear signatures of so-called ion-dispersion are seen in the satellite data. The cusp ion-dispersion is important for helping to understand the temporal and spatial structure of magnetopause reconnection. Whenever a satellite crosses boundaries of flux tubes or convection cells, cusp structures such as ion-dispersion will always be encountered. In our case we observed 3 distinct steps in the ion energy, but it includes at least 2 more steps as well, which we interpret as temporal features in relation to pulsed reconnection at the magnetopause. In addition, fast variations of the electron flux and energy occurring during these events have been studied in detail. The variations of the electron population, if interpreted as structures crossed by the REIMEI satellite, would map near the magnetopause to similar features as observed previously with the Cluster satellites. These were explained as Alfvén waves originating from an X-line of magnetic reconnection.

  20. Growth, dispersion, and electronic devices of nitrogen-doped single-wall carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Oikonomou, Antonios [School of Computer Science, The University of Manchester, Oxford Road, Manchester M13 9PL (United Kingdom); Susi, Toma; Kauppinen, Esko I. [Nanomaterials Group, Department of Applied Physics, Aalto University School of Science, PO Box 15100, 00076 Aalto (Finland); Vijayaraghavan, Aravind [School of Computer Science, The University of Manchester, Oxford Road, Manchester M13 9PL (United Kingdom); Centre for Mesoscience and Nanotechnology, The University of Manchester, Oxford Road, Manchester M13 9PL (United Kingdom)

    2012-12-15

    This paper describes the complete processes from growth to electronic devices of nitrogen-doped single-wall carbon nanotubes (N-SWCNTs). The N-SWCNTs were synthesized using a floating catalyst chemical vapor deposition method. The dry-deposited N-SWCNT films were dispersed in N-methylpyrolidone followed by sonication and centrifugation steps to yield a stable dispersion of N-SWCNTs in solution. The length and diameter distribution as well as concentration of N-SWCNTs in solution were measured by atomic force microscopy and optical absorption spectroscopy, respectively. The N-SWCNTs were then assembled into electronic devices using bottom-up dielectrophoresis and characterized as field-effect transistors. Finally, the potential for application of N-SWCNTs in sensors is discussed. The three stages of N-doped SWCNT processing: (a) growth and collection on filter, (b) dispersion in NMP, and (c) dielectrophoretic assembly into transistor device. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  1. Direct visualization of dispersed lipid bicontinuous cubic phases by cryo-electron tomography

    Science.gov (United States)

    Demurtas, Davide; Guichard, Paul; Martiel, Isabelle; Mezzenga, Raffaele; Hébert, Cécile; Sagalowicz, Laurent

    2015-11-01

    Bulk and dispersed cubic liquid crystalline phases (cubosomes), present in the body and in living cell membranes, are believed to play an essential role in biological phenomena. Moreover, their biocompatibility is attractive for nutrient or drug delivery system applications. Here the three-dimensional organization of dispersed cubic lipid self-assembled phases is fully revealed by cryo-electron tomography and compared with simulated structures. It is demonstrated that the interior is constituted of a perfect bicontinuous cubic phase, while the outside shows interlamellar attachments, which represent a transition state between the liquid crystalline interior phase and the outside vesicular structure. Therefore, compositional gradients within cubosomes are inferred, with a lipid bilayer separating at least one water channel set from the external aqueous phase. This is crucial to understand and enhance controlled release of target molecules and calls for a revision of postulated transport mechanisms from cubosomes to the aqueous phase.

  2. 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.

  3. Fluid simulation of dispersive and nondispersive ion acoustic waves in the presence of superthermal electrons

    Science.gov (United States)

    Lotekar, Ajay; Kakad, Amar; Kakad, Bharati

    2016-10-01

    One-dimensional fluid simulation is performed for the unmagnetized plasma consisting of cold fluid ions and superthermal electrons. Such a plasma system supports the generation of ion acoustic (IA) waves. A standard Gaussian type perturbation is used in both electron and ion equilibrium densities to excite the IA waves. The evolutionary profiles of the IA waves are obtained by varying the superthermal index and the amplitude of the initial perturbation. This simulation demonstrates that the amplitude of the initial perturbation and the superthermal index play an important role in determining the time evolution and the characteristics of the generated IA waves. The initial density perturbation in the system creates charge separation that drives the finite electrostatic potential in the system. This electrostatic potential later evolves into the dispersive and nondispersive IA waves in the simulation system. The density perturbation with the amplitude smaller than 10% of the equilibrium plasma density evolves into the dispersive IA waves, whereas larger density perturbations evolve into both dispersive and nondispersive IA waves for lower and higher superthermal index. The dispersive IA waves are the IA oscillations that propagate with constant ion plasma frequency, whereas the nondispersive IA waves are the IA solitary pulses (termed as IA solitons in the stability region) that propagate with the constant wave speed. The characteristics of the stable nondispersive IA solitons are found to be consistent with the nonlinear fluid theory. To the best of our knowledge, this is the first fluid simulation study that has considered the superthermal distributions for the plasma species to model the electrostatic solitary waves.

  4. Electron and phonon dispersions of the two-dimensional Holstein model: effects of vertex and non-local corrections

    CERN Document Server

    Hague, J P

    2003-01-01

    I apply the newly developed dynamical cluster approximation (DCA) to the calculation of the electron and phonon dispersions in the two-dimensional Holstein model. In contrast to previous work, the DCA enables the effects of spatial fluctuations (non-local corrections) to be examined. Approximations neglecting and incorporating lowest-order vertex corrections are investigated. I calculate the phonon density of states, the renormalized phonon dispersion, the electron dispersion and electron spectral functions. I demonstrate how vertex corrections stabilize the solution, stopping a catastrophic softening of the (pi, pi) phonon mode. A kink in the electron dispersion is found in the normal state along the (zeta, zeta) symmetry direction in both the vertex- and non-vertex-corrected theories for low phonon frequencies, corresponding directly to the renormalized phonon frequency at the (pi, 0) point. This kink is accompanied by a sudden drop in the quasi-particle lifetime. Vertex and non-local corrections enhance th...

  5. Time Resolved Measurement of Electron Cloud Densities from Dispersion of Transverse Electric Pulses

    CERN Document Server

    Sonnad, Kiran G

    2015-01-01

    The measurement of electron cloud densities in particle accelerators using microwaves has proven to be an effective, non-invasive and inexpensive method. So far the experimental schemes have used continuous waves. This has either been in the form of travelling waves that are propagated, or standing waves that are trapped, in both cases within a segment of the accelerator chamber. The variation in the wave dispersion relation caused by the periodic creation and decay of the electron cloud leads to a phase modulation in the former case, and a frequency modulation in the latter. In general, these methods enable the measurement of a time averaged electron cloud density. In this paper we propose a time resolved measurement by using pulses propagated over a finite length of the accelerator chamber. The pulses are launched periodically, once after a bunch train has passed and then again half a revolution period later. This results in pulses alternating between a dispersion that is either affected by a cloud or not. ...

  6. First principles electronic band structure and phonon dispersion curves for zinc blend beryllium chalcogenide

    Energy Technology Data Exchange (ETDEWEB)

    Dabhi, Shweta, E-mail: venu.mankad@gmail.com; Mankad, Venu, E-mail: venu.mankad@gmail.com; Jha, Prafulla K., E-mail: venu.mankad@gmail.com [Department of Physics, Maharaja Krishnakumasinhji Bhavnagar University, Bhavnagar-364001 (India)

    2014-04-24

    A detailed theoretical study of structural, electronic and Vibrational properties of BeX compound is presented by performing ab-initio calculations based on density-functional theory using the Espresso package. The calculated value of lattice constant and bulk modulus are compared with the available experimental and other theoretical data and agree reasonably well. BeX (X = S,Se,Te) compounds in the ZB phase are indirect wide band gap semiconductors with an ionic contribution. The phonon dispersion curves are represented which shows that these compounds are dynamically stable in ZB phase.

  7. Corrections for shear and rotatory inertia on flexural vibrations of beams

    NARCIS (Netherlands)

    Nederveen, C.J.; Schwarzl, F.R.

    1964-01-01

    Different correction formulae for the influence of shear and rotatory inertia on flexural vibrations of freely supported beams are compared with the exact solution. It appears that in most cases a simple formula is sufficient because of the appearance of a constant which is not accurately known, viz

  8. A C1-2 locked facet in a child with atlantoaxial rotatory fixation. Case report.

    Science.gov (United States)

    Missori, Paolo; Miscusi, Massimo; Paolini, Sergio; DiBiasi, Claudio; Finocchi, Vannina; Peschillo, Simone; Delfini, Roberto

    2005-12-01

    Conservative treatment is reported in a child with atlantoaxial rotatory fixation. Three-dimensional (3D) computerized tomography (CT) and magnetic resonance (MR) imaging demonstrated the degree of dislocation and alar ligament damage. A rigid cervical collar and muscle relaxant agents without any traction allowed full recovery. Control 3D CT scanning and MR imaging findings are reported.

  9. Design of a transversal equalizer for electronic dispersion compensation in optical communication links

    Institute of Scientific and Technical Information of China (English)

    GAO Zhen-bin; SHI Yong; WANG Bo; ZENG Xiang-ye

    2011-01-01

    @@ A programmable transversal equalizer for electronic dispersion compensation (EDC) in optical fiber communication systems is developed.Based on the SiGe technology with a cut-off frequency of 80 GHz, the equalizer consists of 6 seriesparallel amplifiers as delay units and 7 Gilbert variable gain amplifiers as taps, which ensure that the equalizer can work at the bit rate of 10 Gb/s.With different tap gains, the forward voltage gain of the transversal equalizer varies, which demonstrates that the equalizer has various filtering characteristics such as low pass filtering, band pass filtering, band reject filtering, and notch filtering, so it can effectively simulate the inverse transfer function of dispersive channels in optical communications, and can be used for compensating the inter-symbol interference and other nonlinear problems caused by dispersion.The equalizer (including pads) occupies an area of 0.40 mm × 1.08 mm, and its total power dissipation is 400 mW with 3.3 V power supply.

  10. Design of a transversal equalizer for electronic dispersion compensation in optical communication links

    Science.gov (United States)

    Gao, Zhen-bin; Shi, Yong; Wang, Bo; Zeng, Xiang-ye

    2011-01-01

    A programmable transversal equalizer for electronic dispersion compensation (EDC) in optical fiber communication systems is developed. Based on the SiGe technology with a cut-off frequency of 80 GHz, the equalizer consists of 6 seriesparallel amplifiers as delay units and 7 Gilbert variable gain amplifiers as taps, which ensure that the equalizer can work at the bit rate of 10 Gb/s. With different tap gains, the forward voltage gain of the transversal equalizer varies, which demonstrates that the equalizer has various filtering characteristics such as low pass filtering, band pass filtering, band reject filtering, and notch filtering, so it can effectively simulate the inverse transfer function of dispersive channels in optical communications, and can be used for compensating the inter-symbol interference and other nonlinear problems caused by dispersion. The equalizer (including pads) occupies an area of 0.40 mm×1.08 mm, and its total power dissipation is 400 mW with 3.3 V power supply.

  11. The dispersion modification of electrostatic geodesic acoustic mode by electron geodesic drift current

    CERN Document Server

    Zhang, Shuangxi

    2014-01-01

    The past studies treated the perturbed distribution of circulating electrons as adiabatic one when studying the dispersion relation of electrostatic geodesic acoustic mode(GAM). In this paper, the flow of electron geodesic current (FEGC) is added to modify this adiabatic distribution. Based on the drift kinetic theory, it is found that FEGC obviously increases the magnitude of the standard GAM's frequency and reduces its damping rate. The increase of frequency results from the contribution of FEGC to the radial flow. The reason for the reduction of damping rate is that when the effect of FEGC counts, the new resonant velocity becomes much larger than ions thermal velocity with equilibrium distribution obeying Maxwellian distribution, compared with unmodified Landau resonant velocity. Especially, FEGC changes the characters of the frequency and damping rate of low-frequency GAM as functions of safety factor $q$ .

  12. Void swelling of an oxide dispersion strengthened ferritic alloy in a high voltage electron microscope

    Science.gov (United States)

    Snykers, M.

    1980-03-01

    An oxide dispersion strengthened ferritic alloy with nominal composition Fe-13Cr-3.5Ti-1.5Mo-2TiO 2 and a cast alloy with a composition close to that of the matrix of the oxide dispersion strengthened alloy are irradiated in a high voltage electron microscope in the temperature range 380-550°C. The alloys are doped with 0-30 ppm helium. For alloys containing 10 ppm He a peak swelling temperature at 450°C is found. A maximum swelling of 1.1% is found at an irradiation dose of 20 dpa. In the absence of He no swelling is found in the temperature range 430-470°C. The swelling rate is highest at the onset of swelling. The results obtained here are quite similar to those for some ferritic steels such as FV607, EM 12 and HT9, except for the influence of He and for the dose dependence.

  13. Performance of carrier phase recovery for electronically dispersion compensated coherent systems.

    Science.gov (United States)

    Farhoudi, Ramtin; Ghazisaeidi, Amirhossein; Rusch, Leslie Ann

    2012-11-19

    An analytical approach taking into account carrier phase estimation (CPE) is presented to predict performance of quadrature phase shift-keying (QPSK) systems using coherent detection. Using this approach, system performance is found as a function of symbol rate, local oscillator (LO) linewidth, chromatic dispersion (CD) and signal-to-noise ratio (SNR). A new expression is derived for the covariance matrix of the conditional probability density function (pdf) of the decision statistic. This pdf is used to find bit error rate (BER) semi-analytically. Our analytical derivation assumes perfect removal of data modulation which corresponds to an ideal decision feedback (DF) carrier recovery. The validity of the analytical pdf for predicting BER is verified for a wide range of system parameters of interest in long haul systems. In addition, our semi-analytical BER provides a lower bound for the Viterbi-Viterbi (VV) BER, while showing the analytical BER previously proposed in the literature shows an overly pessimistic prediction of VV BER performance. We show that inaccuracy in previous analysis stems from overly simple model for the CPE when compensating large accumulated dispersion electronically. Finally, we study extension of our results to quadrature amplitude modulation (QAM). Preliminary simulation results are promising but the accuracy of our semi-analytical approach for predicting BER should be investigated further.

  14. Submicron writing by laser irradiation on metal nano-particle dispersed films toward flexible electronics

    Science.gov (United States)

    Watanabe, Akira; Aminuzzaman, Mohammod; Miyashita, Tokuji

    2009-02-01

    The requirement for microwiring technology by a wet process has significantly increased recently toward the achievement of printable and flexible electronics. We have developed the metal microwiring with a resolution higher than 1 μm by the laser direct writing technique using Ag and Cu nano-particle-dispersed films as precursors. The technique was applied to the microwiring on a flexible and transparent polymer film. The metallization is caused in a micro-region by focused laser beam, which reduces the thermal damage of the flexible polymer substrate during the metallization process. The laser direct writing technique is based on the efficient and fast conversion of photon energy to thermal energy by direct excitation of the plasmon absorption of a metal nano-particle, which provides Cu microwiring with a low resistivity owing to the inhibition of the surface oxidation of the Cu nano-particle.

  15. Effects of cation compositions on the electronic properties and optical dispersion of indium zinc tin oxide thin films by electron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Denny, Yus Rama [Department of Electrical Engineering, University of Sultan Ageng Tirtayasa, Banten 42435 (Indonesia); Seo, Soonjoo [Division of Materials Science, Korea Basic Science Institute, Daejeon 305-806 (Korea, Republic of); Lee, Kangil; Oh, Suhk Kun [Department of Physics, Chungbuk National University, Cheongju 361-763 (Korea, Republic of); Kang, Hee Jae, E-mail: hjkang@cbu.ac.kr [Department of Physics, Chungbuk National University, Cheongju 361-763 (Korea, Republic of); Heo, Sung; Chung, Jae Gwan; Lee, Jae Cheol [Analytical Engineering Center, Samsung Advanced Institute of Technology, Suwon 440-600 (Korea, Republic of); Tougaard, Sven [Department of Physics, Chemistry, and Pharmacy, University of Southern Denmark, DK-5230 Odense M. (Denmark)

    2015-02-15

    Highlights: • REELS analysis can provide optical dispersion and electronic properties of oxide materials. • The band gap varied with In/Zn/Sn compositions and increased after annealing. • The optical properties were examined using REELS in conjunction with the Tougaard–Yubero model. • The dispersion parameters were determined by a single-oscillator Wemple–DiDomenico model. • The Zn and Sn contents play a crucial role in determining the single-oscillator constant and dispersion energy of IZTO thin films. - Abstract: The electronic properties and optical dispersion of indium zinc tin oxide (IZTO) films with different cation compositions were investigated by reflection electron energy loss spectroscopy (REELS). The REELS spectra of IZTO films revealed that the band gap varied with different Sn/Zn ratios and In content. The optical properties were examined with REELS data using Tougaard–Yubero model and the results were compared with the envelope of the transmission spectra obtained using a UV-spectrometer. The dispersion behavior of the refractive index from REELS results was studied in terms of the single-oscillator Wemple–DiDomenico model. The results showed that the different compositions of In/Zn/Sn caused a change in the dispersion parameters of IZTO thin films in contrast to the static values of refractive indices and dielectric constant which remained the same. Our work demonstrated that REELS is an efficient tool to study the optical properties of a material by obtaining the optical parameters.

  16. On the dispersion law of low-frequency electron whistler waves in a multi-ion plasma

    Directory of Open Access Journals (Sweden)

    B. V. Lundin

    2008-06-01

    Full Text Available A new and simple dispersion law for extra-low-frequency electron whistler waves in a multi-ion plasma is derived. It is valid in a plasma with finite ratio ωcpe of electron gyro-to-plasma frequency and is suitable for wave frequencies much less than ωpe but well above the gyrofrequencies of most heavy ions. The resultant contribution of the ions to the dispersion law is expressed by means of the lower hybrid resonance frequency, the highest ion cutoff frequency and the relative content of the lightest ion. In a frequency domain well above the ions' gyrofrequencies, this new dispersion law merges with the "modified electron whistler dispersion law" determined in previous works by the authors. It is shown that it fits well to the total cold plasma electron whistler dispersion law, for different orientations of the wave vectors and different ion constituents, including negative ions or negatively charged dust grains.

  17. KINEMATIC ANALYSIS OF THE POSTERIOR ELEMENT OF LUMBAR SPINE IN ROTATORY CHIROPRACTIC

    Institute of Scientific and Technical Information of China (English)

    侯筱魁; 董凡; 戴克戎; 汤荣光; 魏晋兵

    1993-01-01

    Rotatory chiropractic is one of the key manipulations in the treatment of low-er backache. The present paper reports the kinematic changes in the posterior element oflumbar spine during rotatory manipulation, using motion segments of lumbar spine fromfresh cadavers as specimens and an electromechanical system for the measurements. Theanalysis of the angle-displacement curve and the load-angle curve reveals that rotatorychiropractic is a kind of complicated 3-D. 6-degree-of-freedom motion. Correctmanipulation may adjust the volume of the nerve root canal and relax the articulation be-tween the upper and lower joint processes so as to relieve the adhesion of the enclosuresin the nerve root canal and relieve the adhesion of the facet joints, and bring aboutimprovement of local circulation and amelioration of symptoms.

  18. Atlantoaxial Rotatory Subluxation after Removal of a Ventriculoperitoneal Shunt in the Supine-Lateral Position.

    Science.gov (United States)

    Hashide, Shusei; Aihara, Yasuo; Nagahara, Ayumi; Mitsuyama, Tetsuryu; Okada, Yoshikazu

    2015-01-01

    Atlantoaxial rotatory subluxation (AARS) is an uncommon disease with a greater prevalence in children than adults. So far there has only been one report of AARS after surgery related to ventriculoperitoneal (VP) shunting. We present a new case of AARS closed reduction treatment after VP shunt removal in an 8-year-old girl with wound pain on the back of her head and torticollis after surgery. Her head was rotated in the spine-lateral position during surgery. The diagnosis of AARS was established by 3D-computed tomography. The rotatory subluxation was cured after cervical traction therapy. The successful closed reduction was the consequence of early detection and conservative treatment, which are important constituents in the management of AARS. © 2015 S. Karger AG, Basel.

  19. Atlanto axial rotatory dislocation in adults: a rare complication of an epileptic seizure--case report.

    Science.gov (United States)

    Tarantino, Roberto; Donnarumma, Pasquale; Marotta, Nicola; Missori, Paolo; Viozzi, Ilaria; Landi, Alessandro; Delfini, Roberto

    2014-01-01

    Atlanto Axial Rotatory Dislocations (AARDs) are a heterogeneous group of post-traumatic pathologies typical of the pediatric age, and rare in adults. We describe the case of a 34-year-old woman, developing Atlanto Axial Rotatory Fixation (AARF) after a generalized tonic-clonic epileptic seizure, an extremely rare traumatic cause never described in literature. AARF was detected only 1 month after the accident and nonsurgical treatment was attempted at the beginning. The patient underwent surgery only 2 months after the accident. The best treatment should be conservative reduction within 1 month; when it is not possible, it is advisable to perform surgery as soon as possible. C1-C2 fixation with Harm's technique is the gold standard for fixed luxations. Delay of treatment makes intraoperative reduction more difficult and increase the establishment of the chronic permanent change of neck muscles and ligaments.

  20. Atlanto Axial Rotatory Dislocation in Adults: A Rare Complication of an Epileptic Seizure—Case Report

    Science.gov (United States)

    TARANTINO, Roberto; DONNARUMMA, Pasquale; MAROTTA, Nicola; MISSORI, Paolo; VIOZZI, Ilaria; LANDI, Alessandro; DELFINI, Roberto

    2014-01-01

    Atlanto Axial Rotatory Dislocations (AARDs) are a heterogeneous group of post-traumatic pathologies typical of the pediatric age, and rare in adults. We describe the case of a 34-year-old woman, developing Atlanto Axial Rotatory Fixation (AARF) after a generalized tonic-clonic epileptic seizure, an extremely rare traumatic cause never described in literature. AARF was detected only 1 month after the accident and nonsurgical treatment was attempted at the beginning. The patient underwent surgery only 2 months after the accident. The best treatment should be conservative reduction within 1 month; when it is not possible, it is advisable to perform surgery as soon as possible. C1–C2 fixation with Harm's technique is the gold standard for fixed luxations. Delay of treatment makes intraoperative reduction more difficult and increase the establishment of the chronic permanent change of neck muscles and ligaments. PMID:24201098

  1. Posterolateral rotatory instability of the elbow: a case report and literature review.

    Science.gov (United States)

    Yang, Chen; Li, Wei; Gong, Yu-bao; Li, Shu-qiang; Qi, Xin

    2010-12-01

    Posterolateral rotatory instability of the elbow describes a condition that radial head subluxation or dislocation occurs when forearm rotates externally in relation to humerus. It is difficult to diagnose and treat. We reported a typical case which was confirmed by physical examination and MR images. Ligamentous insufficiency was confirmed under direct vision, and was reconstructed with triceps fascia as described by Gong et al with slight modification. Regain of full function was achieved one year after surgery.

  2. Posterolateral rotatory instability of the elbow: a case report and literature review

    Institute of Scientific and Technical Information of China (English)

    YANG Chen; LI Wei; GONG Yu-bao; LI Shu-qiang; QI Xin

    2010-01-01

    Posterolateral rotatory instability of the elbow describes a condition that radial head subluxation or dislocation occurs when forearm rotates externally in relation to humerus. It is difficult to diagnose and treat. We reported a typical case which was confirmed by physical examination and MR images. Ligamentous insufficiency was confirmed under direct vision, and was reconstructed with triceps fascia as described by Gong et al with slight modification. Regain of full function was achieved one year after surgery.

  3. The effect of betahistine on vestibular habituation: comparison of rotatory and sway habituation training.

    Science.gov (United States)

    Mierzwinski, J; Kazmierczak, H; Pawlak-Osinska, K; Piziewicz, A

    2001-07-01

    This study was designed to investigate the effect of histaminergic agonists and antagonists on the acquisition of vestibular habituation. The experimental animals, pigeons, were subjected to unilateral rotatory and sway habituation training sessions. The habituation of postural reflexes and post-rotatory head nystagmus was assessed. Vestibular habituation in the control group was achieved by adopting the kinetic reflex posture after approximately 9 training sessions, and after 10 and 14 training sessions, respectively for 50% reduction of the total number of beats (TNB) and the duration of post-rotatory head nystagmus. In the sway adaptation test control pigeons needed nearly 15 training sessions while pigeons receiving betahistine adapted after approximately 8 sessions. Administration of histamine and, most notably, betahistine accelerated the process, while both H1 and H2 antagonists (clemastine, cimetidine) tended to retard it, indicating a less significant contribution of H2 receptors. The cholinergic agent physostigmine strongly retarded habituation while the anticholinergic agent scopolamine markedly accelerated it. In addition the adrenomimetic agent ephedrine also accelerated habituation while the adrenolytic agent droperidol retarded reduction of nystagmus beats. The results indicate that histaminergic receptors play a significant role in the vestibular habituation mechanism but are intricately involved with other types of receptors. Betahistine is clearly the agent of choice for attenuating vestibular effects.

  4. Toward transferable interatomic van der Waals potentials: The role of multipole electrostatics and many-body dispersion without electrons

    CERN Document Server

    Bereau, Tristan

    2014-01-01

    We estimate polarizabilities of atoms in molecules without electron density, using a Voronoi partitioning approach instead. The resulting atomic dispersion coefficients are calculated, as well as many-body dispersion effects on intermolecular potential energies. We also estimate contributions from multipole electrostatics and compare them to dispersion. We assess the performance of the resulting intermolecular potential from dispersion and electrostatics for more than 1,300 neutral and charged, small organic molecular dimers. Applications to water clusters, the benzene crystal, the anti-cancer drug ellipticine---intercalated between two Watson-Crick DNA base pairs, as well as six macro-molecular host-guest complexes highlight the potential of this method and help to identify points of future improvement. Overall, the method achieves an accuracy well within sophisticated empirical force fields, such as OPLS and Amber FF03, while exhibiting a simple parametrization protocol without the need for experimental inp...

  5. Subtracted dispersion relation formalism for the two-photon exchange correction to elastic electron-proton scattering: Comparison with data

    Energy Technology Data Exchange (ETDEWEB)

    Tomalak, O. [Johannes Gutenberg Universitaet, Institut fuer Kernphysik, Mainz (Germany); Johannes Gutenberg-Universitaet, PRISMA Cluster of Excellence, Mainz (Germany); Taras Shevchenko National University of Kyiv, Department of Physics, Kyiv (Ukraine); Vanderhaeghen, M. [Johannes Gutenberg Universitaet, Institut fuer Kernphysik, Mainz (Germany); Johannes Gutenberg-Universitaet, PRISMA Cluster of Excellence, Mainz (Germany)

    2015-02-01

    We apply a subtracted dispersion relation formalism with the aim to improve predictions for the two-photon exchange corrections to elastic electron-proton scattering observables at finite momentum transfers. We study the formalism on the elastic contribution, and make a detailed comparison with existing data for unpolarized cross sections as well as polarization transfer observables. (orig.)

  6. Biomedical and agricultural applications of energy dispersive X-ray spectroscopy in electron microscopy.

    Science.gov (United States)

    Wyroba, Elżbieta; Suski, Szymon; Miller, Karolina; Bartosiewicz, Rafał

    2015-09-01

    Energy dispersive X-ray spectroscopy (EDS) in electron microscopy has been widely used in many research areas since it provides precise information on the chemical composition of subcellular structures that may be correlated with their high resolution images. In EDS the characteristic X-rays typical of each element are analyzed and the new detectors - an example of which we describe - allow for setting precisely the area of measurements and acquiring signals as a point analysis, as a linescan or in the image format of the desired area. Mapping of the elements requires stringent methods of sample preparation to prevent redistribution/loss of the elements as well as elimination of the risk of overlapping spectra. Both qualitative and quantitative analyses may be performed at a low probe current suitable for thin biological samples. Descriptions of preparation techniques, drawbacks and precautions necessary to obtain reliable results are provided, including data on standards, effects of specimen roughness and quantification. Data on EPMA application in different fields of biomedical and agricultural studies are reviewed. In this review we refer to recent EDS/EPMA applications in medical diagnostics, studies on air pollution and agrochemicals as well as on plant models used to monitor the environment.

  7. Toward transferable interatomic van der Waals interactions without electrons: The role of multipole electrostatics and many-body dispersion

    Energy Technology Data Exchange (ETDEWEB)

    Bereau, Tristan, E-mail: bereau@mpip-mainz.mpg.de [Max-Planck-Institut für Polymerforschung, Ackermannweg 10, 55128 Mainz, Germany and Department of Chemistry, University of Basel, 4056 Basel (Switzerland); Lilienfeld, O. Anatole von [Department of Chemistry, Institute of Physical Chemistry, University of Basel, 4056 Basel, Switzerland and Argonne Leadership Computing Facility, Argonne National Laboratory, Argonne, Illinois 60439 (United States)

    2014-07-21

    We estimate polarizabilities of atoms in molecules without electron density, using a Voronoi tesselation approach instead of conventional density partitioning schemes. The resulting atomic dispersion coefficients are calculated, as well as many-body dispersion effects on intermolecular potential energies. We also estimate contributions from multipole electrostatics and compare them to dispersion. We assess the performance of the resulting intermolecular interaction model from dispersion and electrostatics for more than 1300 neutral and charged, small organic molecular dimers. Applications to water clusters, the benzene crystal, the anti-cancer drug ellipticine—intercalated between two Watson-Crick DNA base pairs, as well as six macro-molecular host-guest complexes highlight the potential of this method and help to identify points of future improvement. The mean absolute error made by the combination of static electrostatics with many-body dispersion reduces at larger distances, while it plateaus for two-body dispersion, in conflict with the common assumption that the simple 1/R{sup 6} correction will yield proper dissociative tails. Overall, the method achieves an accuracy well within conventional molecular force fields while exhibiting a simple parametrization protocol.

  8. Dispersion relation and growth rate for a corrugated channel free-electron laser with a helical wiggler pump

    Institute of Scientific and Technical Information of China (English)

    A.Hasanbeigi; H.Mehdian

    2013-01-01

    The effects of corrugated ion channels on electron trajectories and spatial growth rate for a free-electron laser with a one-dimensional helical wiggler have been investigated.Analysis of the steady-state electron trajectories is performed by solving the equations of motion.Our results show that the presence of a corrugated channel shifts the resonance frequency to smaller values of ion channel frequency.The sixth-order dispersion equation describing the coupling between the electrostatic beam mode and the electromagnetic mode has also been derived.The dispersion relation characteristic is analyzed in detail by numerical solution.Results show that the growth rate of instability in the presence of corrugated ion channels can be greatly enhanced relative to the case of an uniform ion channel.

  9. A comparative in vitro efficacy of conventional rotatory and chemomechanical caries removal: Influence on cariogenic flora, microhardness, and residual composition

    Directory of Open Access Journals (Sweden)

    Rene Garcia-Contreras

    2014-01-01

    Full Text Available Background: Chemomechanical caries removal system is part of the minimal invasive dentistry; the aim of the study was to compare the amount of bacteria after caries removal with chemomechanical system and conventional rotatory instruments and to test the Vickers microhardness and micro-RAMAN analysis of residual dentin after excavation. Materials and Methods: Molars were induced for demineralization, confirmed with DIAGNOdent; Streptococcus mutans were inoculated into the cavities and filled. Caries removal was performed with rotatory instruments and chemomechanical system; surviving bacteria were cultured for 24 and 48 hours at 37΀C. Vickers microhardness and micro-RAMAN analysis were tested after excavation. Data were analyzed with Wilcoxon, continuity correction, odds ratio, ANOVA post hoc Tukey test, and Spearman correlation. Results: Demineralization was significantly detectable at 240 hours of incubation; conventional rotatory instruments and chemomechanical caries removal were effective in 19.4%-22.6% and 25.8%-32.3%, respectively. Vickers microhardness of chemomechanical system was higher (P < 0.0001 than conventional rotatory instruments and comparable to healthy dentin. Micro-RAMAN analysis showed that healthy dentin is correlated to chemomechanical system (R 2 = 0.683, P < 0.00001 and drilling with burs (R 2 = 0.139, P < 0.00001. Conclusion: The chemomechanical system is effective for caries elimination, comparable to conventional rotatory instruments; the remaining Vickers microhardness and composition surface tissue are similar to healthy dentin.

  10. A comparative in vitro efficacy of conventional rotatory and chemomechanical caries removal: Influence on cariogenic flora, microhardness, and residual composition

    Science.gov (United States)

    Garcia-Contreras, Rene; Scougall-Vilchis, Rogelio Jose; Contreras-Bulnes, Rosalia; Sakagami, Hiroshi; Morales-Luckie, Raul Alberto; Nakajima, Hiroshi

    2014-01-01

    Background: Chemomechanical caries removal system is part of the minimal invasive dentistry; the aim of the study was to compare the amount of bacteria after caries removal with chemomechanical system and conventional rotatory instruments and to test the Vickers microhardness and micro-RAMAN analysis of residual dentin after excavation. Materials and Methods: Molars were induced for demineralization, confirmed with DIAGNOdent; Streptococcus mutans were inoculated into the cavities and filled. Caries removal was performed with rotatory instruments and chemomechanical system; surviving bacteria were cultured for 24 and 48 hours at 37°C. Vickers microhardness and micro-RAMAN analysis were tested after excavation. Data were analyzed with Wilcoxon, continuity correction, odds ratio, ANOVA post hoc Tukey test, and Spearman correlation. Results: Demineralization was significantly detectable at 240 hours of incubation; conventional rotatory instruments and chemomechanical caries removal were effective in 19.4%-22.6% and 25.8%-32.3%, respectively. Vickers microhardness of chemomechanical system was higher (P < 0.0001) than conventional rotatory instruments and comparable to healthy dentin. Micro-RAMAN analysis showed that healthy dentin is correlated to chemomechanical system (R2 = 0.683, P < 0.00001) and drilling with burs (R2 = 0.139, P < 0.00001). Conclusion: The chemomechanical system is effective for caries elimination, comparable to conventional rotatory instruments; the remaining Vickers microhardness and composition surface tissue are similar to healthy dentin. PMID:25506140

  11. Elemental analysis of occupational and environmental lung diseases by electron probe microanalyzer with wavelength dispersive spectrometer.

    Science.gov (United States)

    Takada, Toshinori; Moriyama, Hiroshi; Suzuki, Eiichi

    2014-01-01

    Occupational and environmental lung diseases are a group of pulmonary disorders caused by inhalation of harmful particles, mists, vapors or gases. Mineralogical analysis is not generally required in the diagnosis of most cases of these diseases. Apart from minerals that are encountered rarely or only in specific occupations, small quantities of mineral dusts are present in the healthy lung. As such when mineralogical analysis is required, quantitative or semi-quantitative methods must be employed. An electron probe microanalyzer with wavelength dispersive spectrometer (EPMA-WDS) enables analysis of human lung tissue for deposits of elements by both qualitative and semi-quantitative methods. Since 1993, we have analyzed 162 cases of suspected occupational and environmental lung diseases using an EPMA-WDS. Our institute has been accepting online requests for elemental analysis of lung tissue samples by EPMA-WDS since January 2011. Hard metal lung disease is an occupational interstitial lung disease that primarily affects workers exposed to the dust of tungsten carbide. The characteristic pathological findings of the disease are giant cell interstitial pneumonia (GIP) with centrilobular fibrosis, surrounded by mild alveolitis with giant cells within the alveolar space. EPMA-WDS analysis of biopsied lung tissue from patients with GIP has demonstrated that tungsten and/or cobalt is distributed in the giant cells and centrilobular fibrosing lesion in GIP. Pneumoconiosis, caused by amorphous silica, and acute interstitial pneumonia, associated with the giant tsunami, were also elementally analyzed by EPMA-WDS. The results suggest that commonly found elements, such as silicon, aluminum, and iron, may cause occupational and environmental lung diseases.

  12. Backscattered electron imaging and windowless energy dispersive x-ray microanalysis: a new technique for gallstone analysis

    Energy Technology Data Exchange (ETDEWEB)

    Kaufman, H.S.; Lillemoe, K.D.; Magnuson, T.H.; Frasca, P.; Pitt, H.A. (Johns Hopkins Univ. School of Medicine, Baltimore, MD (USA))

    1990-12-01

    Scanning electron microscopy with or without conventional energy dispersive x-ray microanalysis is currently used to identify gallstone microstructure and inorganic composition. Organic calcium salts are among many biliary constituents thought to have a role in gallstone nidation and growth. However, current analytical techniques which identify these salts are destructive and compromise gallstone microstructural data. We have developed a new technique for gallstone analysis which provides simultaneous structural and compositional identification of calcium salts within gallstones. Backscattered electron imaging is used to localize calcium within cholesterol at minimum concentrations of 0.01%. Windowless energy dispersive x-ray microanalysis produces elemental spectra of gallstone calcium salts which are qualitatively and quantitatively different. These combined techniques provide simultaneous structural and compositional information obtained from intact gallstone cross-sections and have been used to identify calcium salts in gallstones obtained at cholecystectomy from 106 patients.

  13. Phonon dispersion and electron-phonon coupling in MgB2 and AlB2.

    Science.gov (United States)

    Bohnen, K P; Heid, R; Renker, B

    2001-06-18

    We present a first principles investigation of the lattice dynamics and electron-phonon coupling of the superconductor MgB2 and the isostructural AlB2 within the framework of density functional perturbation theory using a mixed-basis pseudopotential method. Complete phonon dispersion curves and Eliashberg functions alpha2F are calculated for both systems. The main differences are related to high frequency in-plane boron vibrations, which are strongly softened in MgB2 and exhibit an exceptionally strong electron-phonon coupling. We also report on Raman measurements, which support the theoretical findings. Implications for the superconducting transition temperature are briefly discussed.

  14. New insight into the dispersion characteristics of electrostatic waves in ultradense plasmas: electron degeneracy and relativistic effects

    Science.gov (United States)

    Kourakis, I.; McKerr, M.; Elkamash, I. S.; Haas, F.

    2017-10-01

    The dispersion properties of electrostatic waves propagating in ultrahigh density plasma are investigated, from first principles, in a one-dimensional geometry. A self-consistent multispecies plasma fluid model is taken as starting point, incorporating electron degeneracy and relativistic effects. The inertia of all plasma components is retained, for rigor. Exact expressions are obtained for the oscillation frequency, and the phase and group velocity of electrostatic waves is computed. Two branches are obtained, viz. an acoustic low-frequency dispersion branch and an upper (optic-like) branch: these may be interpreted as ion-acoustic and electron plasma (Langmuir) waves, respectively, as in classical plasmas, yet bearing an explicit correction in account of relativistic and electron degeneracy effects. The electron plasma frequency is shown to reduce significantly at high values of the density, due to the relativistic effect. The result is compared with approximate models, wherein either electrons are considered inertialess (low-frequency ionic scale) or ions are considered to be stationary (Langmuir-wave limit).

  15. Influence of Rotation Increments on Imaging Performance for a Rotatory Dual-Head PET System

    Directory of Open Access Journals (Sweden)

    Fanzhen Meng

    2017-01-01

    Full Text Available For a rotatory dual-head positron emission tomography (PET system, how to determine the rotation increments is an open problem. In this study, we simulated the characteristics of a rotatory dual-head PET system. The influences of different rotation increments were compared and analyzed. Based on this simulation, the imaging performance of a prototype system was verified. A reconstruction flowchart was proposed based on a precalculated system response matrix (SRM. The SRM made the relationships between the voxels and lines of response (LORs fixed; therefore, we added the interpolation method into the flowchart. Five metrics, including spatial resolution, normalized mean squared error (NMSE, peak signal-to-noise ratio (PSNR, contrast-to-noise (CNR, and structure similarity (SSIM, were applied to assess the reconstructed image quality. The results indicated that the 60° rotation increments with the bilinear interpolation had advantages in resolution, PSNR, NMSE, and SSIM. In terms of CNR, the 90° rotation increments were better than other increments. In addition, the reconstructed images of 90° rotation increments were also flatter than that of 60° increments. Therefore, both the 60° and 90° rotation increments could be used in the real experiments, and which one to choose may depend on the application requirement.

  16. A diagnose not to miss: Rotatory Atlantoaxial subluxation in emergency service

    Directory of Open Access Journals (Sweden)

    Umut OCAK

    2016-03-01

    Full Text Available Objective: The objective of this study is to take attention to atlantoaxial subluxations especially in pediatric population that may be misdiagnosed in the emergency services easily. When diagnosed early in the emergency services, it may be corrected with ease and the treatment is more likely to be conservative. Method: Seven patients with atlantoaxial rotatory subluxation (AARS, between ages of 5 and 13, who admitted to our emergency service between 1 July 2013 - 1 September 2014 were examined retrospectively. Results: All patients were treated conservatively with bed rest, muscle relaxants and rigid cervical collar. None of them needed surgery. Conclusions: Atlantoaxial rotatory subluxation (AARS is one of the main types of cervical spine anomalies seen in pediatric patients and is a rare condition that is often misdiagnosed and therefore incorrectly managed especially in emergency services. The diagnosis requires a high index of suspicion. Many pediatric cervical spine injuries can be treated with external immobilization and AARS is almost always reducible. Pediatric population is prone to upper spine injuries due to ligamentous laxity and AARS should always be kept in mind especially in emergency services.

  17. Ion Bernstein instability dependence on the proton-to-electron mass ratio: Linear dispersion theory

    Science.gov (United States)

    Min, Kyungguk; Liu, Kaijun

    2016-07-01

    Fast magnetosonic waves, which have as their source ion Bernstein instabilities driven by tenuous ring-like proton velocity distributions, are frequently observed in the inner magnetosphere. One major difficulty in the simulation of these waves is that they are excited in a wide frequency range with discrete harmonic nature and require time-consuming computations. To overcome this difficulty, recent simulation studies assumed a reduced proton-to-electron mass ratio, mp/me, and a reduced light-to-Alfvén speed ratio, c/vA, to reduce the number of unstable modes and, therefore, computational costs. Although these studies argued that the physics of wave-particle interactions would essentially remain the same, detailed investigation of the effect of this reduced system on the excited waves has not been done. In this study, we investigate how the complex frequency, ω = ωr+iγ, of the ion Bernstein modes varies with mp/me for a sufficiently large c/vA (such that ωpe2/Ωe2≡(me/mp)(c/vA)2≫1) using linear dispersion theory assuming two different types of energetic proton velocity distributions, namely, ring and shell. The results show that low- and high-frequency harmonic modes respond differently to the change of mp/me. For the low harmonic modes (i.e., ωr˜Ωp), both ωr/Ωp and γ/Ωp are roughly independent of mp/me, where Ωp is the proton cyclotron frequency. For the high harmonic modes (i.e., Ωp≪ωr≲ωlh, where ωlh is the lower hybrid frequency), γ/ωlh (at fixed ωr/ωlh) stays independent of mp/me when the parallel wave number, k∥, is sufficiently large and becomes inversely proportional to (mp/me)1/4 when k∥ goes to zero. On the other hand, the frequency range of the unstable modes normalized to ωlh remains independent of mp/me, regardless of k∥.

  18. Studying dispersions of ferroelectric nanopowders in dioctyl phthalate as dielectric media for capacitive electronic components

    Science.gov (United States)

    Gorokhovskii, A. V.; Gorshkov, N. V.; Burmistrov, I. N.; Goffman, V. G.; Tret'yachenko, E. V.; Sevryugin, A. V.; Fedorov, F. S.; Kovyneva, N. N.

    2016-06-01

    The electrical properties of dispersions of a powdered ferroelectric nanocomposite based on ilmenite (FeTiO3) and hollandite (K1.46Ti7.2Fe0.8O16) in dioctyl phthalate have been studied by impedance spectroscopy techniques in a frequency range of 10-1-106 Hz. The influence of stabilizing additives of cationic and anionic surfactants and iron acetylacetonate on the permittivity, conductivity, and dielectric losses was determined for dispersions containing 40 mass % of the solid composite. The influence of composition on the mechanisms of relaxation processes in the system is discussed.

  19. On the transferability of atomic contributions to the optical rotatory power of hydrogen peroxide, methyl hydroperoxide and dimethyl peroxide

    DEFF Research Database (Denmark)

    Sánchez, Marina; Alkorta, Ibon; Elguero, José

    2014-01-01

    The chirality of molecules expresses itself, for example, in the fact that a solution of a chiral molecule rotates the plane of linear polarised light. The underlying molecular property is the optical rotatory power (ORP) tensor, which according to time-dependent perturbation theory can be calcul...

  20. A comparison between different oxide dispersion strengthened ferritic steel ongoing in situ oxide dissolution in High Voltage Electron Microscope

    Energy Technology Data Exchange (ETDEWEB)

    Monnet, I., E-mail: monnet@ganil.fr [Centre de Recherche sur les Ions, les Materiaux et la Photonique, CEA/CNRS/ENSICAEN/UCBN, BP5133-14070 Caen cedex 5 (France); Service de Recherches Metallurgiques Appliquees, CEA/DEN/DMN/SRMA, 91191 Gif sur Yvette cedex (France); Van den Berghe, T.; Dubuisson, Ph. [Service de Recherches Metallurgiques Appliquees, CEA/DEN/DMN/SRMA, 91191 Gif sur Yvette cedex (France)

    2012-05-15

    ODS materials are considered for nuclear applications but previous experimental studies have shown a partial dissolution of some oxides under neutron irradiation. In this work, electron irradiations were used to evaluate the stability of the oxides depending on the chemical composition of the oxide dispersion. Four ferritic steels based on EM10 (Fe-9Cr-1Mo) and reinforced respectively by Al{sub 2}O{sub 3}, MgO, MgAl{sub 2}O{sub 4} and Y{sub 2}O{sub 3}, were studied. These materials were irradiated with 1 MeV or 1.2 MeV electrons in a High Voltage Electron Microscope. This technique allows to follow one single oxide and to determine the evolution of its size during the irradiation. In situ HVEM observations indicate that the dissolution rate depends on the chemical composition of the oxide, on the temperature and on the irradiation dose.

  1. Treatment of atlantoaxial rotatory fixation with botulinum toxin muscle block and manipulation.

    Science.gov (United States)

    Lin, Chia-Hung; Chen, Chun-Jung; Chen, Chuan-Mu; Liao, Su-Lan; Raung, Shue-Ling; Tsai, Sen-Wei

    2010-04-01

    Slippage after reduction of atlantoaxial rotatory fixation (AARF) is usually treated with repeated cervical traction and brace immobilization. To date, no data have been published on the management of muscle spasm during treatment. Here, we describe the case of a 7-year-old girl with AARF for 1 month who visited our hospital for treatment. During physical examination, spasm of the sternocleidomastoid muscle was noted. The patient was treated with manipulative reduction, and slippage after reduction was managed with botulinum spasticity block of the sternocleidomastoid and splenius capitis muscles, and repeated manipulation. Cervical orthosis immobilization with a rehabilitation program of isometric contract-relax exercise for the neck was conducted for 3 months. The subject had full recovery from AARF at 1-year follow-up. This report demonstrates that, in selected cases of slippage after reduction from AARF, conservative management with manipulation under anesthesia is a good method, and the muscle components may play a crucial role in AARF.

  2. Arthroscopic and open management of posterolateral rotatory instability of the elbow.

    Science.gov (United States)

    O'Brien, Michael J; Savoie, Felix H

    2014-09-01

    Posterolateral rotatory instability (PLRI) is the most common cause of residual instability following a simple elbow dislocation. PLRI may result from trauma or iatrogenic injury to the radial ulnohumeral ligament during treatment for other conditions, such as lateral epicondylitis. PLRI can be identified through a combination of history and physical examination, and confirmed with magnetic resonance imaging arthrography. Once diagnosed, surgery is necessary to correct persistent instability. Instability can be confirmed arthroscopically through several findings, including subluxation of the radial head on the capitellum and the arthroscopic "drive through sign of the elbow." Acute repairs, both open and arthroscopic, heal with excellent patient outcomes. In the chronic setting, graft reconstruction may be required. This report describes arthroscopic repair of the radial ulnohumeral ligament and open reconstruction with associated outcomes. A high index of suspicion is necessary to correctly diagnosis this condition in patients with lateral elbow pain and feelings of instability.

  3. Vibration of prolate spheroidal shells with shear deformation and rotatory inertia: Axisymmetric case

    Science.gov (United States)

    Hayek, Sabih I.; Boisvert, Jeffrey E.

    2003-11-01

    This paper presents the derivation of the equations for nonaxisymmetric motion of prolate spheroidal shells of constant thickness. The equations include the effect of distributed mechanical surface forces and moments. The shell theory used in this derivation includes three displacements and two thickness shear rotations. Thus, the effects of membrane, bending, shear deformation, and rotatory inertia are included in this theory. The resulting five coupled partial differential equations are self-adjoint and positive definite. The frequency-wave-number spectrum has five branches, two acoustic and three optical branches representing flexural, extensional, torsional, and two thickness shear. For the case of axisymmetric motion, these were computed for various spheroidal shell eccentricities and thickness-to-length ratios for a large number of modes. The axisymmetric dynamic response for damped shells of various eccentricities and thicknesses under point and ring surface forces are presented.

  4. ASSESSMENT OF EFFECTIVENESS OF TB POSTING DURING THE COMPULSORY ROTATORY RESIDENTIAL INTERNSHIP (CRRI PROGRAMME

    Directory of Open Access Journals (Sweden)

    Pradeep Aggarwal

    2011-12-01

    Full Text Available Research Question: What is the effectiveness of TB posting during the Compulsory Rotatory Residential Internship (CRRI programme? Objectives: To assess the effectiveness of TB posting during the CRRI programme. To find out the need of making Tuberculosis & Respiratory Diseases Department posting mandatory during CRRI Programme. Study Design: Cross Sectional study. Study Duration: 12 months i.e. 01st April 2009 till 31st March 2010 Participants: 90 students who joined the CRRI programme formed the study group. Out of these 90 interns only 57 (64% of them joined their two months Compulsory Rotatory Internship in the Department of Community Medicine and these were posted in Tuberculosis & Respiratory Diseases Department for 15 days. Methodology: A pre-designed pre-tested self-administered questionnaire was administered to the participants on the first day and last day of their posting in Tuberculosis & Respiratory Diseases Department. The results were analysed by using suitable statistical package. Results: The mean pre-test score was 28 (49.6% and the mean post-test score was 38 (61.5%. It was observed that there was a 27% improvement in the knowledge of the participants when the question about the year of launching of RNTCP programme in India was asked. A remarkable improvement (46% was found in the difference between pre and post-test knowledge of the participants when the questions like “Who are the DOTS providers” and “What is the colour coding of boxes for different categories of patients” were asked. A significant difference in the knowledge was found in the pre and post-test assessment in reference to Tuberculosis and its National Programm

  5. High-Energy Kink Observed in the Electron Dispersion of High-Temperature Cuprate Superconductors

    Science.gov (United States)

    Valla, T.; Kidd, T. E.; Yin, W.-G.; Gu, G. D.; Johnson, P. D.; Pan, Z.-H.; Fedorov, A. V.

    2007-04-01

    Photoemission studies show the presence of a high-energy anomaly in the observed band dispersion for two families of cuprate superconductors, Bi2Sr2CaCu2O8+δ and La2-xBaxCuO4. The anomaly, which occurs at a binding energy of approximately 340 meV, is found to be anisotropic and relatively weakly doping dependent. Scattering from short range or nearest neighbor spin excitations is found to supply an adequate description of the observed phenomena.

  6. Relevance of GaAs(001) surface electronic structure for high frequency dispersion on n-type accumulation capacitance

    Science.gov (United States)

    Pi, T. W.; Chen, W. S.; Lin, Y. H.; Cheng, Y. T.; Wei, G. J.; Lin, K. Y.; Cheng, C.-P.; Kwo, J.; Hong, M.

    2017-01-01

    This study investigates the origin of long-puzzled high frequency dispersion on the accumulation region of capacitance-voltage characteristics in an n-type GaAs-based metal-oxide-semiconductor. Probed adatoms with a high Pauling electronegativity, Ag and Au, unexpectedly donate charge to the contacted As/Ga atoms of as-grown α2 GaAs(001)-2 × 4 surfaces. The GaAs surface atoms behave as charge acceptors, and if not properly passivated, they would trap those electrons accumulated at the oxide and semiconductor interface under a positive bias. The exemplified core-level spectra of the Al2O3/n-GaAs(001)-2 × 4 and the Al2O3/n-GaAs(001)-4 × 6 interfaces exhibit remnant of pristine surface As emission, thereby causing high frequency dispersion in the accumulation region. For the p-type GaAs, electrons under a negatively biased condition are expelled from the interface, thereby avoiding becoming trapped.

  7. Novel Synchronous Linear and Rotatory Micro Motors Based on Polymer Magnets with Organic and Inorganic Insulation Layers

    Directory of Open Access Journals (Sweden)

    Andreas WALDSCHIK

    2008-12-01

    Full Text Available In this work, we report on the development of several synchronous motors with rotatory or linear movements. The synchronous micro motors are brushless DC motors or stepper motors with electrically controlled commutation consisting of a stator and a rotor. The rotor is mounted onto the stator and is adjusted by an integrated guidance. Inside the stator different coil systems are realized, like double layer sector coils or special nested coils. The coil systems can be controlled by three or six phases depending on the operational mode. Furthermore, inorganic insulation layers were used in order to reduce the thickness of the system. By this means four layers of electrical conductors can be realized especially for the 2D devices. The smallest diameter of the rotatory motor is 1 mm and could be successfully driven.

  8. Transverse vibration of Bernoulli Euler beams carrying point masses and taking into account their rotatory inertia: Exact solution

    Science.gov (United States)

    Maiz, Santiago; Bambill, Diana V.; Rossit, Carlos A.; Laura, P. A. A.

    2007-06-01

    The situation of structural elements supporting motors or engines attached to them is usual in technological applications. The operation of the machine may introduce severe dynamic stresses on the beam. It is important, then, to know the natural frequencies of the coupled beam-mass system, in order to obtain a proper design of the structural elements. An exact solution for the title problem is obtained in closed-form fashion, considering general boundary conditions by means of translational and rotatory springs at both ends. The model allows to analyze the influence of the masses and their rotatory inertia on the dynamic behavior of beams with all the classic boundary conditions, and also, as particular cases, to determine the frequencies of continuous beams.

  9. Electron Correlation Models for Optical Activity

    DEFF Research Database (Denmark)

    Höhn, E. G.; O. E. Weigang, Jr.

    1968-01-01

    A two-system no-overlap model for rotatory strength is developed for electric-dipole forbidden as well as allowed transitions. General equations which allow for full utilization of symmetry in the chromophore and in the environment are obtained. The electron correlation terms are developed in full...

  10. Understanding the dramatic role of anomalous dispersion on the measurement of electron densities in plasmas using interferometers

    Energy Technology Data Exchange (ETDEWEB)

    Nilsen, J; Johnson, W R; Iglesias, C A; Scofield, J H

    2005-07-20

    For decades the electron density of plasmas has been measured using optical interferometers. With the availability of good X-ray laser sources in the last decade interferometers have been extended into the wavelength range 14-47 nm, which has enabled researchers to probe even higher density plasmas. The data analysis assumes the index of refraction is due only to the free electrons, which makes the index less than one. Recent interferometer experiments in Al plasmas observed plasmas with index of refraction greater than one at 14 nm and brought into question the validity of the usual formula for calculating the index. In this paper we show how the anomalous dispersion from bound electrons can dominate the free electron contribution to the index of refraction in many plasmas and make the index greater than one or enhance the contribution to the index such that one would greatly overestimate the density of the plasma using interferometers. Using a new average-atom code we calculate the index of refraction in many plasmas at different temperatures for photon energies from 0 to 100 eV and compare against calculations done with OPAL. We also present examples of other plasmas that may have index of refraction greater than one at X-ray laser energies. During the next decade X-ray free electron lasers and other X-ray sources will be available to probe a wider variety of plasmas at higher densities and shorter wavelengths so understanding the index of refraction in plasmas will be even more essential.

  11. Enhancement of energy dispersive residual stress analysis by consideration of detector electronic effects

    Science.gov (United States)

    Denks, I. A.; Genzel, Ch.

    2007-08-01

    The effects of the germanium detector electronics on diffraction line patterns is investigated. It is shown that not only the detector resolution and the throughput but also the energy stability depend on both the specific detector settings and the dead time. For a moderate resolution versus throughput setting a correction function is proposed and applied to the near-surface residual stress analysis of three samples with considerably different stress states. It is demonstrated that without the correction function ghost stresses up to hundreds of MPa in the near-surface region are obtained. The correction procedure is verified by conventional X-ray measurements. In conclusion, the authors strongly suggest quantifying the electronic shifts of any individual detector systems prior to the analysis of residual stresses.

  12. Method validation for chemical composition determination by electron microprobe with wavelength dispersive spectrometer

    Science.gov (United States)

    Herrera-Basurto, R.; Mercader-Trejo, F.; Muñoz-Madrigal, N.; Juárez-García, J. M.; Rodriguez-López, A.; Manzano-Ramírez, A.

    2016-07-01

    The main goal of method validation is to demonstrate that the method is suitable for its intended purpose. One of the advantages of analytical method validation is translated into a level of confidence about the measurement results reported to satisfy a specific objective. Elemental composition determination by wavelength dispersive spectrometer (WDS) microanalysis has been used over extremely wide areas, mainly in the field of materials science, impurity determinations in geological, biological and food samples. However, little information is reported about the validation of the applied methods. Herein, results of the in-house method validation for elemental composition determination by WDS are shown. SRM 482, a binary alloy Cu-Au of different compositions, was used during the validation protocol following the recommendations for method validation proposed by Eurachem. This paper can be taken as a reference for the evaluation of the validation parameters more frequently requested to get the accreditation under the requirements of the ISO/IEC 17025 standard: selectivity, limit of detection, linear interval, sensitivity, precision, trueness and uncertainty. A model for uncertainty estimation was proposed including systematic and random errors. In addition, parameters evaluated during the validation process were also considered as part of the uncertainty model.

  13. Synthesis and evaluation of changes induced by solvent and substituent in electronic absorption spectra of some azo disperse dyes.

    Science.gov (United States)

    Mohammadi, Asadollah; Yazdanbakhsh, Mohammad Reza; Farahnak, Lahya

    2012-04-01

    Five azo disperse dyes were prepared by diazotizing 4'-aminoacetophenone and p-anisidine and coupling with varies N-alkylated aromatic amines. Characterization of the dyes was carried out by using UV-vis, FTIR and 1H NMR spectroscopic techniques. The electronic absorption spectra of dyes are determined at room temperature in fifteen solvents with different polarities. The solvent dependent maximum absorption band shifts, were investigated using dielectric constant (ɛ), refractive index (n) and Kamlet-Taft polarity parameters (hydrogen bond donating ability (α), hydrogen bond accepting ability (β) and dipolarity/polarizability polarity scale (π*)). Acceptable agreement was found between the maximum absorption band of dyes and solvent polarity parameters especially with π*. The effect of substituents of coupler and/or diazo component on the color of dyes was investigated. The effects of acid and base on the visible absorption maxima of the dyes are also reported.

  14. Dispersion of the electron g factor anisotropy in InAs/InP self-assembled quantum dots

    Science.gov (United States)

    Belykh, V. V.; Yakovlev, D. R.; Schindler, J. J.; van Bree, J.; Koenraad, P. M.; Averkiev, N. S.; Bayer, M.; Silov, A. Yu.

    2016-08-01

    The electron g factor in an ensemble of InAs/InP quantum dots with emission wavelengths around 1.4 μm is measured using time-resolved pump-probe Faraday rotation spectroscopy in different magnetic field orientations. Thereby, we can extend recent single dot photoluminescence measurements significantly towards lower optical transition energies through 0.86 eV. This allows us to obtain detailed insight into the dispersion of the recently discovered g factor anisotropy in these infrared emitting quantum dots. We find with decreasing transition energy over a range of 50 meV a strong enhancement of the g factor difference between magnetic field normal and along the dot growth axis, namely, from 1 to 1.7. We argue that the g factor cannot be solely determined by the confinement energy, but the dot asymmetry underlying this anisotropy therefore has to increase with increasing dot size.

  15. Composition measurement in substitutionally disordered materials by atomic resolution energy dispersive X-ray spectroscopy in scanning transmission electron microscopy.

    Science.gov (United States)

    Chen, Z; Taplin, D J; Weyland, M; Allen, L J; Findlay, S D

    2016-10-21

    The increasing use of energy dispersive X-ray spectroscopy in atomic resolution scanning transmission electron microscopy invites the question of whether its success in precision composition determination at lower magnifications can be replicated in the atomic resolution regime. In this paper, we explore, through simulation, the prospects for composition measurement via the model system of AlxGa1-xAs, discussing the approximations used in the modelling, the variability in the signal due to changes in configuration at constant composition, and the ability to distinguish between different compositions. Results are presented in such a way that the number of X-ray counts, and thus the expected variation due to counting statistics, can be gauged for a range of operating conditions.

  16. Uranium aerosols at a nuclear fuel fabrication plant: Characterization using scanning electron microscopy and energy dispersive X-ray spectroscopy

    Science.gov (United States)

    Hansson, E.; Pettersson, H. B. L.; Fortin, C.; Eriksson, M.

    2017-05-01

    Detailed aerosol knowledge is essential in numerous applications, including risk assessment in nuclear industry. Cascade impactor sampling of uranium aerosols in the breathing zone of nuclear operators was carried out at a nuclear fuel fabrication plant. Collected aerosols were evaluated using scanning electron microscopy and energy dispersive X-ray spectroscopy. Imaging revealed remarkable variations in aerosol morphology at the different workshops, and a presence of very large particles (up to ≅ 100 × 50 μm2) in the operator breathing zone. Characteristic X-ray analysis showed varying uranium weight percentages of aerosols and, frequently, traces of nitrogen, fluorine and iron. The analysis method, in combination with cascade impactor sampling, can be a powerful tool for characterization of aerosols. The uranium aerosol source term for risk assessment in nuclear fuel fabrication appears to be highly complex.

  17. Nail Damage (Severe Onychodystrophy) Induced by Acrylate Glue: Scanning Electron Microscopy and Energy Dispersive X-Ray Investigations

    Science.gov (United States)

    Pinteala, Tudor; Chiriac, Anca Eduard; Rosca, Irina; Larese Filon, Francesca; Pinteala, Mariana; Chiriac, Anca; Podoleanu, Cristian; Stolnicu, Simona; Coros, Marius Florin; Coroaba, Adina

    2017-01-01

    Background Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) techniques have been used in various fields of medical research, including different pathologies of the nails; however, no studies have focused on obtaining high-resolution microscopic images and elemental analysis of disorders caused by synthetic nails and acrylic adhesives. Methods Damaged/injured fingernails caused by the use of acrylate glue and synthetic nails were investigated using SEM and EDX methods. Results SEM and EDX proved that synthetic nails, acrylic glue, and nails damaged by contact with acrylate glue have a different morphology and different composition compared to healthy human nails. Conclusions SEM and EDX analysis can give useful information about the aspects of topography (surface sample), morphology (shape and size), hardness or reflectivity, and the elemental composition of nails. PMID:28232921

  18. Electron beam dispersion measurements in nitrogen using two-dimensional imaging of N2(+) fluorescence

    Science.gov (United States)

    Clapp, L. H.; Twiss, R. G.; Cattolica, R. J.

    Experimental results are presented related to the radial spread of fluorescence excited by 10 and 20 KeV electron beams passing through nonflowing rarefied nitrogen at 293 K. An imaging technique for obtaining species distributions from measured beam-excited fluorescence is described, based on a signal inversion scheme mathematically equivalent to the inversion of the Abel integral equation. From fluorescence image data, measurements of beam radius, integrated signal intensity, and spatially resolved distributions of N2(+) first-negative-band fluorescence-emitting species have been made. Data are compared with earlier measurements and with an heuristic beam spread model.

  19. Quantification of C2 cervical spine rotatory fixation by X-ray, MRI and CT

    Energy Technology Data Exchange (ETDEWEB)

    Gradl, Georg [Chirurgische Klinik und Poliklinik der Universitaet Rostock, Abteilung Unfall- und Wiederherstellungschirurgie, Rostock (Germany); Maier-Bosse, Tamara; Staebler, Axel [Institut fuer Radiologische Diagnostik der Universitaet Muenchen, Klinikum Grobetahadern, Munich (Germany); Penning, Randolph [Institut fuer Rechtsmedizin der Universitaet Muenchen, Munich (Germany)

    2005-02-01

    Atlanto-axial rotatory displacement is known to be a cause of childhood torticollis and may as well be responsible for chronic neck pain after rear-end automobile collisions. The objective was to determine whether quantification of C2 malrotation is possible by plain radiographs in comparison to CT as the golden standard. MR imaging was evaluated as to whether it was of equal value in the detection of bony landmarks. C2 vertebra of five human cadaveric cervical spine specimens, ligamentously intact, were rotated using a Steinmann pin in steps of 5 up to 15 right and 15 left. Plain radiographs, CT and MRI images were taken in each rotational step. Data were analyzed for quantification of C2 rotation by three independent examiners. A rotation of 5 led to a spinous process deviation (SPD) from the midline of 3 mm as measured on an a.p. plain radiograph. A coefficient of rotation was calculated (1.62 mm{sup -1}). Data analyzed by three examiners revealed a small coefficient of variation (0.03). MRI and CT measurements showed comparable results for the quantification of rotation; however, in both techniques the 15 rotation was underestimated. Quantification of upper cervical spine malrotation was possible on plain radiographs using the SPD and a rotation coefficient. MRI and CT were equally successful in the assessment of C2 malrotation. (orig.)

  20. Void formation and microstructural development in oxide dispersion strengthened ferritic steels during electron-irradiation

    Science.gov (United States)

    Saito, J.; Suda, T.; Yamashita, S.; Ohnuki, S.; Takahashi, H.; Akasaka, N.; Nishida, M.; Ukai, S.

    1998-10-01

    ODS ferritic steels (13Cr-0.5Ti-0.2Y 2O 3) were prepared by the mechanical alloying method followed by the hot extrusion and several heat treatments including recrystallization. ODS steels with different heat treatment and a ferritic/martensitic (F/M) steel for the reference were irradiated to 12 dpa at 670-770 K in HVEM. After recrystallization, the dislocation density decreased with increasing grain size, however, the oxide particles did not show any obvious change in the size and the number density. During the electron-irradiation the microstructure was relatively stable, i.e. oxide particles showed good stability and the dislocation density remained almost constant. A limited void formation was observed in the specimens, and the suppressive effect due to dislocations with high number density was confirmed. From these results, the behavior of microstructure and the limited void formation in ODS steels have been discussed.

  1. Quantitative characterization of the mesothelioma-inducing erionite series minerals by transmission electron microscopy and energy dispersive spectroscopy.

    Science.gov (United States)

    Dogan, Meral

    2012-01-01

    Air-collected erionite series minerals from Cappadocia region of Turkey were characterized quantitatively by using transmission electron microscopy (TEM) equipped with energy dispersive spectroscopy (EDS). Field emission scanning electron microscopy aided identification of fibrous minerals. Quantitative characterization guidelines for positive identification of erionites proposed by Dogan and Dogan (2008) was applied and the modified balance error formula (E%mineral is erionite-K and a mean chemical formula is proposed based upon the TEM-EDS results. Among the 60 analyses, 11 passed E% test (18.3%), 33 passed Mg-content test (55.0%), and only 3 passed both E% and Mg-content tests (5.0%). This shows difficulty of quantitative characterization of the erionite series minerals. However, as erionite is the most carcinogenic mineral known and is classified by IARC as a Group-I (human) carcinogen, it requires special attention from the mineralogical community to help establish its true mineralogical properties. Quantitatively characterized erionite data are very scarce in literature. Correctly identified erionite mineral types will be useful to medical researchers in their search to find a possible cure for the deadly disease of mesothelioma. © Wiley Periodicals, Inc.

  2. Uniform Treatment of Solute-Solvent Dispersion in the Ground and Excited Electronic States of the Solute Based on a Solvation Model with State-Specific Polarizability.

    Science.gov (United States)

    Marenich, Aleksandr V; Cramer, Christopher J; Truhlar, Donald G

    2013-08-13

    We present a new kind of treatment of the solute-solvent dispersion contribution to the free energy of solvation using a solvation model with state-specific polarizability (SMSSP). To evaluate the solute-solvent dispersion contribution, the SMSSP model utilizes only two descriptors, namely, the spherically averaged dipole polarizability of the solute molecule (either in its ground or excited electronic state) and the refractive index of the solvent. The model was parametrized over 643 ground-state solvation free energy data for 231 solutes in 14 nonpolar, non-hydrogen-bonding solvents. We show that the SMSSP model is applicable to solutes in both the ground and the excited electronic state. For example, in comparison to available experimental data, the model yields qualitatively accurate predictions of the solvatochromic shifts for a number of systems where solute-solvent dispersion is the dominant contributor to the shift.

  3. Condylus tertius with atlanto-axial rotatory fixation: an unreported association

    Energy Technology Data Exchange (ETDEWEB)

    Udare, Ashlesha Satish [M.G.M. Hospital, Department of Radiology, Kamothe, Navi Mumbai (India); Global Hospital Super Speciality and Transplant Centre, Department of Radiology, Mumbai (India); Navi Mumbai, Maharashtra (India); Bansal, Divya; Patel, Bhavin [M.G.M. Hospital, Department of Radiology, Kamothe, Navi Mumbai (India); Mondel, Prabath Kumar [P.D. Hinduja Hospital, Department of Radiology, Mahim, Mumbai (India); Aiyer, Siddharth [Shatabdi Hospital, Department of Orthopedics, Chembur, Mumbai (India)

    2014-04-15

    The ''condylus tertius'' or the ''third occipital condyle'' is an embryological remnant of the proatlas sclerotome. Anatomically, it is attached to the basion and often articulates with the anterior arch of the atlas and the odontoid apex; hence, it is also called the ''median occipital condyle''. It is a rare anomaly of the cranio-vertebral junction (CVJ) that can lead to instability and compression of important surrounding neurovascular structures. We report a case of a 16-year-old boy who presented with suboccipital neck pain, torticollis and right sided hemiparesis. Plain radiographs revealed an increased atlanto-dental interspace (ADI) with a retroflexed odontoid. Open mouth view showed asymmetry of the articular processes of the atlas with respect to the dens. Computed tomography (CT) of the CVJ delineated the third occipital condyle. Furthermore, on dynamic CT study, a type 3 atlanto-axial rotatory fixation (AARF) was clearly demonstrated. Magnetic resonance imaging (MRI) of the CVJ revealed severe right-sided spinal cord compression by the retroflexed and rightward deviated dens. It also revealed disruption of the left alar and transverse ligaments. The patient was treated with 8 weeks of cranial traction and reasonable alignment was obtained. This was followed by C1-C2 lateral mass screw fixation and C1-C2 interlaminar wiring to maintain the alignment. A review of the literature did not reveal any cases of condylus tertius associated with non-traumatic AARF. An accurate knowledge of the embryology and imaging features of this rare CVJ anomaly is useful in the prompt diagnosis and management of such patients. (orig.)

  4. Cervical Rotatory Manipulation Decreases Uniaxial Tensile Properties of Rabbit Atherosclerotic Internal Carotid Artery

    Science.gov (United States)

    Qi, Ji; Zhang, Lei; Chen, Chao; Mondal, Shubhro; Ping, Kaike; Chen, Yili

    2017-01-01

    Objective. To investigate the effects of one of the Chinese massage therapies, cervical rotatory manipulation (CRM), on uniaxial tensile properties of rabbit atherosclerotic internal carotid artery (ICA). Methods. 40 male purebred New Zealand white rabbits were randomly divided into CRM-Model group, Non-CRM-Model group, CRM-Normal group, and Non-CRM-Normal group. After modeling (atherosclerotic model) and intervention (CRM or Non-CRM), uniaxial tensile tests were performed on the ICAs to assess the differences in tensile mechanical properties between the four groups. Results. Both CRM and modeling were the main effects affecting physiological elastic modulus (PEM) of ICA. PEM in CRM-Model group was 1.81 times as much as Non-CRM-Model group, while the value in CRM-Model group was 1.34 times as much as CRM-Normal group. Maximum elastic modulus in CRM-Model group was 1.80 times as much as CRM-Normal group. Max strains in CRM-Model group and Non-CRM-Model group were 30.98% and 28.71% lower than CRM-Normal group and Non-CRM-Normal group, respectively. However, whether treated with CRM or not, the uniaxial tensile properties of healthy ICAs were not statistically different. Conclusion. CRM may decrease the uniaxial tensile properties of rabbit arteriosclerotic ICA, but with no effect on normal group. The study will aid in the meaningful explanation of the controversy about the harmfulness of CRM and the suitable population of CRM. PMID:28303160

  5. CT findings and surgical treatment of atlanto-axial rotatory fixation. A case report

    Energy Technology Data Exchange (ETDEWEB)

    Shoji, Akira; Harano, Hideyuki; Okumura, Terufumi (Fukuroi Municipal Hospital, Shizuoka (Japan)); Nakagawa, Hiroshi; Sugiyama, Tadamitsu

    1984-07-01

    A case of atlanto-axial rotatory fixation (AARF) was presented in a 19-year-old female who developed sudden onset of neck pain and limitation of neck movement after direct carotid angiography for seizure disorder. Neurological examination was negative except for cock-robin posture and mild hypesthesia and hypalgesia in left C/sub 2/ distribution. Plain films of the cervical spine disclosed abnormal alignment of C/sub 1/-C/sub 2/ and possible rotational dislocation. Bilateral selective vertebral angiography showed marked anterior and posterior displacement of left and right vertebral artery, respectively, at the level of C/sub 1/. On CT metrizamide myelography, there was clockwise rotation of C/sub 1/ on C/sub 2/ with locked facet on the left but no evidence of cord compression was found. With diagnosis of AARF, manual reduction under general anesthesia and with fluoroscopic control was first attempted without success. Therefore, the patient underwent open reduction by using high speed air-drill and posterior fusion of C/sub 1/ to C/sub 3/ with acryl and wire. Postoperative course was uneventful and the patient went back to work as a computer operator in three months. The etiology of AARF was described by many authors, but in our case, congenital hypogenesis of transverse and alar ligaments plus minor trauma was most suggested. For neurological manifestations of AARF, occipital neuralgia, headache, neck pain, limitation of neck movement and cock-robin posture were reported, but the cock-robin posture was most characteristic and was an important symptom for the early diagnosis. In neuroradiological findings of AARF, plain CT and CT metrizamide myelography are very useful. Because they clearly demonstrate the degree of rotation and interlocking of atlanto-axial joints, and the presence of cord compression.

  6. Electroabsorption spectroscopy of electronic transition for room-temperature ionic liquid molecules dispersed in a polymer matrix

    Energy Technology Data Exchange (ETDEWEB)

    Ito, Ryuichi; Funamoto, Yuuki [Department of Applied Chemistry, Muroran Institute of Technology, Muroran 050-8585 (Japan); Ohta, Nobuhiro [Research Institute for Electronic Science, Hokkaido University, Sapporo 060-0812 (Japan); Iimori, Toshifumi, E-mail: iimori@mmm.muroran-it.ac.jp [Department of Applied Chemistry, Muroran Institute of Technology, Muroran 050-8585 (Japan)

    2015-07-29

    Highlights: • We measure electric field effects on absorption spectra of ionic liquids. • Changes in dipole moment and polarizability on photoexcitation are determined. • Pyridinium ions show reorientation along electric fields in polymer matrix. • Lower limit of electric dipole moment in the ground state is evaluated. - Abstract: Electroabsorption spectroscopy of electronic transitions in the room-temperature ionic liquids (RTILs) 1-butylpyridinium bis(trifluoromethylsulfonyl)imide ([C{sub 4}py][NTf{sub 2}]) and 1-butyl-3-methylpyridinium bis(trifluoromethylsulfonyl)imide ([C{sub 4}mpy][NTf{sub 2}]) dispersed in poly(methyl methacrylate) (PMMA) is reported. [C{sub 4}py][NTf{sub 2}] shows a π → π{sup ∗} transition of the cation [C{sub 4}py]{sup +} with an absorption maximum at 258 nm. The changes in the dipole moment and the electronic polarizability between the excited and ground states are determined by analysis of the Stark effect in the absorption band. A field-induced reorientation effect of the pyridinium chromophore is observed at room temperature. This observation implies that the cation [C{sub 4}py]{sup +} is not rigidly fixed to the polymer matrix, which is consistent with the results of previous studies on hybrid materials of RTILs and PMMA. The lower limit of the dipole moment in the ground state is derived from analysis of the field-induced reorientation effect, and the results for [C{sub 4}mpy][NTf{sub 2}] are essentially the same as those for [C{sub 4}py][NTf{sub 2}].

  7. Energy-dispersive spectroscopy and electron backscatter diffraction analysis of isothermally aged SAF 2507 type superduplex stainless steel

    Science.gov (United States)

    Dobranszky, J.; Szabo, P. J.; Berecz, T.; Hrotko, V.; Portko, M.

    2004-10-01

    Due to thermal effects, several precipitation and segregation processes are known in duplex stainless steels. These microstructural changes influence both of the original phases, but in different ways. Isothermal ageing in a large range of temperature was performed on SAF 2507 type steel. The temperature range was 300-1000 °C, the ageing time was between 100 s and 24 h. This paper discusses the results of ageing at 900 °C. Microstructural changes were investigated by electron microscopy, energy-dispersive spectroscopy and electron backscattered diffraction analysis. This technique allowed the determination of the microstructure of the secondary austenite and sigma phase and their mutual orientation properties. Beside this, thermoelectric power measurements were also performed, which gave information about the kinetics of the precipitation process. Results showed that sigma-phase precipitation started right after 200 s in the case of annealed steel, and faster than 100 s in the cold-rolled state. After 5000 s, the delta-ferrite disappeared. Chemical composition of sigma phase was independent on the ageing time. A small decrease in nickel content was observed with a slight increase of Cr content. Small amount of chi phase had also been observed on the ferrite-ferrite boundaries, but later they changed into sigma phase. Similarly to sigma phase, chi phase showed significant phosphorus enrichment. During ageing, small chrome nitride precipitates developed, which amount increased in time, and some vanadium could be measured in them. The orientation relationship between austenite and sigma phase deviated from Nenno-orientationship with about 24°, and seems to form a [110]‖[310] relationship, which was characteristic right from the beginning of the process, and remains more or less constant.

  8. Characterization of wood dust from furniture by scanning electron microscopy and energy-dispersive x-ray analysis.

    Science.gov (United States)

    Gómez Yepes, Milena Elizabeth; Cremades, Lázaro V

    2011-01-01

    Study characterized and analyzed form factor, elementary composition and particle size of wood dust, in order to understand its harmful health effects on carpenters in Quindío (Colombia). Once particle characteristics (size distributions, aerodynamic equivalent diameter (D(α)), elemental composition and shape factors) were analyzed, particles were then characterized via scanning electron microscopy (SEM) in conjunction with energy dispersive X-ray analysis (EDXRA). SEM analysis of particulate matter showed: 1) cone-shaped particle ranged from 2.09 to 48.79 µm D(α); 2) rectangular prism-shaped particle from 2.47 to 72.9 µm D(α); 3) cylindrically-shaped particle from 2.5 to 48.79 µm D(α); and 4) spherically-shaped particle from 2.61 to 51.93 µm D(α). EDXRA reveals presence of chemical elements from paints and varnishes such as Ca, K, Na and Cr. SEM/EDXRA contributes in a significant manner to the morphological characterization of wood dust. It is obvious that the type of particles sampled is a complex function of shapes and sizes of particles. Thus, it is important to investigate the influence of particles characteristics, morphology, shapes and D(α) that may affect the health of carpenters in Quindío.

  9. NASA Li/CF(x) cell problem analysis: Scanning electron microscopy with energy dispersive x ray spectrometry

    Science.gov (United States)

    Baker, John

    1991-01-01

    An analysis was made of Lithium/carbon fluoride cell parts for possible chloride contamination induced by exposure to thionyl chloride (SOCl2); various samples were submitted for analysis. Only a portion of the analysis which has been conducted is covered, herein, namely analysis by scanning electron microscopy with energy dispersive x ray spectrometry (SEM/EDS). A strip of nickel was exposed to SOCl2 vapors to observe variations in surface concentrations of sulfur and chlorine with time. By detecting chlorine one can not infer contamination by SOCl2 only that contamination is present. Six samples of stainless steel foil were analyzed for chlorine using EDS. Chlorine was not detected on background samples but was detected on the samples which had been handled including those which had been cleaned. Cell covers suspected of being contaminated while in storage and covers which were not exposed to the same storage conditions were analyzed for chlorine. Although no chlorine was found on the covers from cells, it was found on all stored covers. Results are presented with techniques shown for analysis and identification. Relevant photomicrographs are presented.

  10. Faults and foibles of quantitative scanning electron microscopy/energy dispersive x-ray spectrometry (SEM/EDS)

    Science.gov (United States)

    Newbury, Dale E.; Ritchie, Nicholas W. M.

    2012-06-01

    Scanning electron microscopy with energy dispersive x-ray spectrometry (SEM/EDS) is a powerful and flexible elemental analysis method that can identify and quantify elements with atomic numbers > 4 (Be) present as major constituents (where the concentration C > 0.1 mass fraction, or 10 weight percent), minor (0.01history of more than 40 years, and the sophistication of modern analytical software, the method is vulnerable to serious shortcomings that can lead to incorrect elemental identifications and quantification errors that significantly exceed reasonable expectations. This paper will describe shortcomings in peak identification procedures, limitations on the accuracy of quantitative analysis due to specimen topography or failures in physical models for matrix corrections, and quantitative artifacts encountered in xray elemental mapping. Effective solutions to these problems are based on understanding the causes and then establishing appropriate measurement science protocols. NIST DTSA II and Lispix are open source analytical software available free at www.nist.gov that can aid the analyst in overcoming significant limitations to SEM/EDS.

  11. NASA Li/CF(x) cell problem analysis: Scanning electron microscopy with energy dispersive x ray spectrometry

    Science.gov (United States)

    Baker, John

    1991-01-01

    An analysis was made of Lithium/carbon fluoride cell parts for possible chloride contamination induced by exposure to thionyl chloride (SOCl2); various samples were submitted for analysis. Only a portion of the analysis which has been conducted is covered, herein, namely analysis by scanning electron microscopy with energy dispersive x ray spectrometry (SEM/EDS). A strip of nickel was exposed to SOCl2 vapors to observe variations in surface concentrations of sulfur and chlorine with time. By detecting chlorine one can not infer contamination by SOCl2 only that contamination is present. Six samples of stainless steel foil were analyzed for chlorine using EDS. Chlorine was not detected on background samples but was detected on the samples which had been handled including those which had been cleaned. Cell covers suspected of being contaminated while in storage and covers which were not exposed to the same storage conditions were analyzed for chlorine. Although no chlorine was found on the covers from cells, it was found on all stored covers. Results are presented with techniques shown for analysis and identification. Relevant photomicrographs are presented.

  12. Evaluation of the effect of lichens on ceramic roofing tiles by scanning electron microscopy and energy-dispersive spectroscopy analyses.

    Science.gov (United States)

    Kiurski, Jelena S; Ranogajec, Jonjaua G; Ujhelji, Agnes L; Radeka, Miroslava M; Bokorov, Milos T

    2005-01-01

    The effect of the actions of some lichens on the quality of ceramic roofing tiles was investigated in view of textural and microstructural changes considering their biocorrosion resistance. Two types (extruded and pressed) of the real ceramic roofing tiles aged 6 to 10 years, as well as the ceramic model systems formed with the additives of the specific chemical composition Cu-slag powder (10 wt%) and CuO powder (1 wt%), treated with various concentrations of oxalic acid (0.01 wt%, 0.1 wt%, and 4 wt%) were investigated. The thalli of lichen (Verrucaria nigrescens) growth on ceramic roofing tile were examined by scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). Investigation by SEM and EDS gave information regarding the ultrastructure characteristics of the thallus and the lichen-ceramic tile contact zone, allowing the observation of the hyphal penetration and filling up of the fissures and cracks by the lichens' hyphae. The CuO as the raw mixture additive changed the quality of the surface of the ceramic model systems as it has increased resistance to oxalic acid actions. The textural changes in the ceramic model systems and the formation of the identified destructive crystal phase, whewellite, were slowed down. The fundamental interactions between lichens and ceramic materials of the model systems have been identified as physico-chemical processes based on oxalic acid actions, which could cause ceramic matrix deterioration and consequently aging of ceramic roofing tile systems.

  13. Delayed onset of rotatory self-motion perception, dysdiadochokinesia and disturbed eye pursuit caused by low-dose pregabalin

    OpenAIRE

    Hounnou, Patrice; Nicoucar, Keyvan

    2014-01-01

    A 30-year-old woman with chronic foot pain after an orthopaedic surgery and chronic neck pain presented to the emergency department (ED) with a history of self-rotatory vertigo with unsteadiness. She had started low-dose pregabalin, 25 mg two times a day 9 months before experiencing symptoms with the dose gradually increased to 150 mg two times a day over this period. Clinical examination revealed difficulty performing eye pursuit with left eye and dysdiadochokinesia of the left arm. Owing to...

  14. Scanning transmission electron microscopy/energy-dispersive spectroscopy analysis of the dentin adhesive interface using a labeled 2-hydroxyethylmethacrylate analogue.

    Science.gov (United States)

    Eick, J D; Robinson, S J; Byerley, T J; Chappell, R P; Spencer, P; Chappelow, C C

    1995-06-01

    In an attempt to compare the morphology of the dentin adhesive interface and the wetting and penetration of the adhesive in relation to the dentin surface, we studied four dentin adhesive systems using scanning transmission electron microscopy (STEM) and energy-dispersive spectroscopy (EDS). 2-Hydroxyethylmethacrylate (HEMA), a monomer common to many commercial dentin adhesive systems, was altered to produce a thiolated analogue (HETMA). Sulfur, traceable by EDS and STEM, was substituted for the oxygen atom in the backbone of the HEMA molecule. The resulting analogue, with solubility parameters and other wetting and physical properties very similar to those of HEMA, was applied to four sets of tooth specimens, each pre-treated with a different primer or etchant. Three separate pre-treatments--nitric acid, maleic acid, and citric acid/ferric chloride--created a demineralized zone approximately 1 to 3 microns thick at the dentin surface. The HETMA was found to permeate freely into this zone when either of the latter two pre-treatments was used. However, the band of dentin that was demineralized by the nitric acid pre-treatment appeared impermeable to the HETMA. The fourth pre-treatment, an alcohol-based solution including the phosphorus acid ester PENTA and HEMA, modified the smear layer of the tooth slightly and did not appear to demineralize the dentin. HETMA applied to the specimens pre-treated with PENTA and HEMA was clearly in intimate contact with the dentin or modified smear layer; however, it did not penetrate or diffuse into these areas. It did flow into the dentinal tubules, as was also evident with each of the other systems. It was concluded that the acid pre-treatment of the dentin greatly influenced the wetting behavior of the dentin adhesive and thus could substantially affect the resultant bond strength of the dentin adhesive systems.

  15. Chemical elements characterization of root canal sealers using scanning electron microscopy and energy dispersive X-ray analysis.

    Science.gov (United States)

    Sampaio, Felipe Cavalcanti; Alencar, Ana Helena Gonçalves; Guedes, Orlando Aguirre; Veloso, Heloisa Helena Pinho; Santos, Tatiane Oliveira; Estrela, Carlos

    2014-03-01

    The aim of this study was to evaluate the chemical elements composition of root canal filling materials using Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray analysis (EDX). Eighteen standard polyethylene tubes were filled with the following materials: Sealapex(®), Sealer 26(®), MTA Fillapex(®), Pulp Canal Sealer(®), Endofill(®) and AH Plus(®). After 48 hours at 37°C and 95% relative humidity, the samples were surface-sputtered with gold and analyzed using SEM at 5000X magnification. Their chemical composition and element distributionwere determined using EDX. Results were evaluated qualitatively (SEM images and elemental mapping) and quantitatively (weight percentage). Calcium oxide- and hydroxide-based sealers (Sealapex(®) and Sealer 26(®)) had calcium peaks of 53.58 wt% and 65.00 wt%. MTA Fillapex(®) had 30.58 wt% of calcium and high amounts of silicon (31.02 wt%) and bismuth (27.38 wt%). Zinc oxide- and eugenol-based sealers, Pulp Canal Sealer(®) and Endofill(®), had 67.74 wt% and 63.16 wt% of zinc each. AH Plus(®) had a higher amount of zirconium (64.24 wt%). All materials had elements other than those described by the manufacturers. Surface analysis using EDX revealed that regularity varied, element distribution was uniform, and particles had similar sizes and variable shapes. Most chemical elements were those described by the manufacturers, but percentages were different. The surface of root canal sealers had different regularity findings, uniform distribution and particles of similar sizes but variable shapes.

  16. Crystal and electronic structure of BiTeI, AuTeI, and PdTeI compounds: A dispersion-corrected density-functional study

    OpenAIRE

    Güler-Kılıç, Sümeyra; Kılıç, Çetin

    2015-01-01

    Semilocal and dispersion-corrected density-functional calculations have been performed to study the crystal structure, equation of state, and electronic structure of metal tellurohalides with chemical formula MeTeI where Me=Bi, Au, or Pd. A comparative investigation of the results of these calculations is conducted which reveals the role of van der Waals attraction. It is shown that the prediction of crystal structure of metal tellurohalides is systematically improved thanks to the inclusion ...

  17. Dispersion effect on the current voltage characteristic of AlGaN/GaN high electron mobility transistors

    Institute of Scientific and Technical Information of China (English)

    Pu Yan; Pang Lei; Chen Xiao-Juan; Yuan Ting-Ting; Luo Wei-Jun; Liu Xin-Yu

    2011-01-01

    The current voltage (IV) characteristics are greatly influenced by the dispersion effects in AlGaN/GaN highelectron mobility transistors. The direct current (DC) IV and pulsed IV measurements are performed to give a deep investigation into the dispersion effects,which are mainly related to the trap and self-heating mechanisms. The results show that traps play an important role in the kink effects,and high stress can introduce more traps and defects in the device. With the help of the pulsed IV measurements,the trapping effects and self-heating effects can be separated.The impact of time constants on the dispersion effects is also discussed. In order to achieve an accurate static DC IV measurement,the steady state of the bias points must be considered carefully to avoid the dispersion effects.

  18. Dynamic Electronic Dispersion Equalization in Coherent Optical Networks Using Variable-Step-Size Least-Mean-Square Algorithm

    CERN Document Server

    Li, Liang

    2016-01-01

    In coherent detection employing digital signal processing, chromatic dispersion (CD) can be compensated effectively in the electrical domain. In practical optical transport networks, the signal lightpaths between two terminal nodes can be different due to current network conditions. Accordingly, the transmission distance and the accumulated dispersion in the lightpath cannot be predicted. Therefore, the adaptive compensation of dynamic dispersion such as the use of least-mean-square (LMS) algorithm is necessary in such optical fiber networks to enable a flexible routing and switching. In this paper, we present a detailed analysis on the adaptive dispersion compensation using the LMS algorithms in coherent optical transmission networks. Numerical simulations have been carried out accordingly. It can be found that the variable-step-size LMS equalizer can achieve the adaptive CD equalization with a lower complexity, compared to the traditional LMS algorithm.

  19. Quantitative energy-dispersive electron probe X-ray microanalysis for single-particle analysis and its application for characterizing atmospheric aerosol particles

    Indian Academy of Sciences (India)

    Shila Maskey; Chul-Un Ro

    2011-02-01

    An energy-dispersive electron probe X-ray microanalysis (ED-EPMA) technique using an energy-dispersive X-ray detector with an ultra-thin window, designated as low-Z particle EPMA, has been developed. The low-Z particle EPMA allows the quantitative determination of concentrations of low-Z elements such as C, N and O, as well as higher-Z elements that can be analysed by conventional ED-EPMA. The quantitative determination of low-Z elements (using full Monte Carlo simulations, from the electron impact to the X-ray detection) in individual particles has improved the applicability of single-particle analysis, especially in atmospheric environmental aerosol research; many environmentally important atmospheric particles, e.g. sulphates, nitrates, ammonium and carbonaceous particles, contain low-Z elements. To demonstrate its practical applicability, the application of the low-Z particle EPMA for the characterization of Asian Dust, urban and subway aerosol particles is shown herein. In addition, it is demonstrated that the Monte Carlo calculation can also be applied in a quantitative single-particle analysis using transmission electron microscopy (TEM) coupled with energy-dispersive X-ray spectrometry (EDX), showing that the technique is useful and reliable for the characterization of submicron aerosol particles

  20. A correlative approach to segmenting phases and ferrite morphologies in transformation-induced plasticity steel using electron back-scattering diffraction and energy dispersive X-ray spectroscopy.

    Science.gov (United States)

    Gazder, Azdiar A; Al-Harbi, Fayez; Spanke, Hendrik Th; Mitchell, David R G; Pereloma, Elena V

    2014-12-01

    Using a combination of electron back-scattering diffraction and energy dispersive X-ray spectroscopy data, a segmentation procedure was developed to comprehensively distinguish austenite, martensite, polygonal ferrite, ferrite in granular bainite and bainitic ferrite laths in a thermo-mechanically processed low-Si, high-Al transformation-induced plasticity steel. The efficacy of the ferrite morphologies segmentation procedure was verified by transmission electron microscopy. The variation in carbon content between the ferrite in granular bainite and bainitic ferrite laths was explained on the basis of carbon partitioning during their growth. Copyright © 2014 Elsevier B.V. All rights reserved.

  1. Adult Case of Atlantoaxial Rotatory Fixation Treated with In Situ Fixation Using an Unusual Posterior Instrumentation Construct.

    Science.gov (United States)

    Miyao, Yasuyoshi; Sasaki, Manabu; Umegaki, Masao; Yonenobu, Kazuo

    2017-07-01

    Atlantoaxial rotatory fixation (AARF) occurs commonly in children who have undergone trauma. It is usually corrected with conservative therapy. In this report, however, the patient was an adult with AARF who was treated surgically. A 64-year-old woman presented with a 1-year history of spastic gait and hand clumsiness. Imaging studies revealed the presence of AARF, os odontoideum, and severe spinal cord compression at that spinal level. As the AARF had not been responded to head traction with a halo device, we decided to treat the patient with in situ posterior fixation. Because the rigid dislocation was present between the atlas and the axis, we were forced to make an unusual instrumentation construct. Neurological symptoms other than hand numbness diminished after the surgery, and arthrodesis was obtained between the occiput and the axis. It should be noted that surgical planning for posterior instrumentation construct is required when rigid AARF is treated surgically.

  2. Evaluation of a dispersion medium for the irradiation of blood products in a electron linear accelerator; Evaluacion de un medio dispersor para la irradiacion de hemoderivados en un acelerador lineal de electrones

    Energy Technology Data Exchange (ETDEWEB)

    Ordiales, J. M.; Falero, B.; Vazquez, M.; Alvarez, F. J.

    2013-07-01

    The use of bags of rice as dispersion medium in irradiation of blood products for medical use is less effective than the immersion from the point of view dosimetric water. However, given the wide range of dose values for a valid result and once subjected to quality control procedure, the method provides the necessary work for the irradiation of blood products in a linear electron accelerator. (Author)

  3. SIMULATION OF FORWARD AND BACKWARD WAVES EVOLUTION OF FEW-CYCLE PULSES PROPAGATING IN AN OPTICAL WAVEGUIDE WITH DISPERSION AND CUBIC NONLINEARITY OF ELECTRONIC AND ELECTRONIC-VIBRATION NATURE

    Directory of Open Access Journals (Sweden)

    L. S. Konev

    2015-09-01

    Full Text Available Numerical method for calculation of forward and backward waves of intense few-cycle laser pulses propagating in an optical waveguide with dispersion and cubic nonlinearity of electronic and electronic-vibration nature is described. Simulations made with the implemented algorithm show that accounting for Raman nonlinearity does not lead to qualitative changes in behavior of the backward wave. Speaking about quantitative changes, the increase of efficiency of energy transfer from the forward wave to the backward wave is observed. Presented method can be also used to simulate interaction of counterpropagating pulses.

  4. On the microstructure and strengthening mechanism in oxide dispersion-strengthened 316 steel: A coordinated electron microscopy, atom probe tomography and in situ synchrotron tensile investigation

    Energy Technology Data Exchange (ETDEWEB)

    Miao, Yinbin, E-mail: miao2@illinois.edu [Department of Nuclear, Plasma, and Radiological Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801 (United States); Mo, Kun [Nuclear Engineering Division, Argonne National Laboratory, Lemont, IL 60439 (United States); Zhou, Zhangjian [School of Material Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Liu, Xiang; Lan, Kuan-Che [Department of Nuclear, Plasma, and Radiological Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801 (United States); Zhang, Guangming [Department of Nuclear, Plasma, and Radiological Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801 (United States); School of Material Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Miller, Michael K.; Powers, Kathy A. [Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Mei, Zhi-Gang [Nuclear Engineering Division, Argonne National Laboratory, Lemont, IL 60439 (United States); Park, Jun-Sang; Almer, Jonathan [Advanced Photon Source, Argonne National Laboratory, Lemont, IL 60439 (United States); Stubbins, James F. [Department of Nuclear, Plasma, and Radiological Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801 (United States)

    2015-07-15

    An oxide dispersion-strengthened (ODS) 316 steel was developed to simultaneously provide the advantages of ODS steels in mechanical strength and radiation tolerance as well as the excellence of austenitic steels in creep performance and corrosion resistance. The precipitate phases within the austenite matrix were identified by the combined techniques of atom probe tomography (APT), scanning transmission electron microscopy equipped with electron dispersive X-ray spectroscopy (STEM-EDS), and synchrotron wide-angle and small-angle X-ray scattering (WAXS and SAXS). Coarse TiN, hexagonal YAlO{sub 3} and orthorhombic YAlO{sub 3} precipitates were found along with fine Y–Ti–O nanoparticles. In situ WAXS experiments were performed at room and elevated temperatures to examine the size effect on the load partitioning phenomenon for TiN, hexagonal YAlO{sub 3} and Y{sub 2}Ti{sub 2}O{sub 7} phases. In addition, the dislocation density evolution throughout the tensile tests was analyzed by the modified Williamson–Hall method and confirmed by transmission electron microscopy (TEM) observations, revealing the difference in plasticity at various temperatures.

  5. Performing elemental microanalysis with high accuracy and high precision by scanning electron microscopy/silicon drift detector energy-dispersive X-ray spectrometry (SEM/SDD-EDS).

    Science.gov (United States)

    Newbury, Dale E; Ritchie, Nicholas W M

    Electron-excited X-ray microanalysis performed in the scanning electron microscope with energy-dispersive X-ray spectrometry (EDS) is a core technique for characterization of the microstructure of materials. The recent advances in EDS performance with the silicon drift detector (SDD) enable accuracy and precision equivalent to that of the high spectral resolution wavelength-dispersive spectrometer employed on the electron probe microanalyzer platform. SDD-EDS throughput, resolution, and stability provide practical operating conditions for measurement of high-count spectra that form the basis for peak fitting procedures that recover the characteristic peak intensities even for elemental combination where severe peak overlaps occur, such PbS, MoS2, BaTiO3, SrWO4, and WSi2. Accurate analyses are also demonstrated for interferences involving large concentration ratios: a major constituent on a minor constituent (Ba at 0.4299 mass fraction on Ti at 0.0180) and a major constituent on a trace constituent (Ba at 0.2194 on Ce at 0.00407; Si at 0.1145 on Ta at 0.0041). Accurate analyses of low atomic number elements, C, N, O, and F, are demonstrated. Measurement of trace constituents with limits of detection below 0.001 mass fraction (1000 ppm) is possible within a practical measurement time of 500 s.

  6. Supervised Mineral Classification with Semi-automatic Training and Validation Set Generation in Scanning Electron Microscope Energy Dispersive Spectroscopy Images of Thin Sections

    DEFF Research Database (Denmark)

    Flesche, Harald; Nielsen, Allan Aasbjerg; Larsen, Rasmus

    2000-01-01

    This paper addresses the problem of classifying minerals common in siliciclastic and carbonate rocks. Twelve chemical elements are mapped from thin sections by energy dispersive spectroscopy in a scanning electron microscope (SEM). Extensions to traditional multivariate statistical methods...... are applied to perform the classification. First, training and validation sets are grown from one or a few seed points by a method that ensures spatial and spectral closeness of observations. Spectral closeness is obtained by excluding observations that have high Mahalanobis distances to the training class...

  7. Spurious dispersion effects at FLASH

    Energy Technology Data Exchange (ETDEWEB)

    Prat, Eduard

    2009-07-15

    The performance of the Free-Electron Laser (FEL) process imposes stringent demands on the transverse trajectory and size of the electron beam. Since transverse dispersion changes off-energy particle trajectories and increases the effective beam size, dispersion must be controlled. This thesis treats the concept of dispersion in linacs, and analyses the impact of dispersion on the electron beam and on the FEL process. It presents generation mechanisms for spurious dispersion, quantifying its importance for FLASH (Free-electron Laser in Hamburg) and the XFEL (European X-ray Free-Electron Laser). A method for measuring and correcting dispersion and its implementation in FLASH is described. Experiments of dispersion e ects on the transverse beam quality and on the FEL performance are presented. (orig.)

  8. Dispersive Liquid-Liquid Microextraction Based on Solidification of Floating Organic Drop Followed by Gas Chromatography-Electron Capture Detector for Determination of Some Pesticides in Water Samples

    Directory of Open Access Journals (Sweden)

    Mostafa Bashiri Juybari

    2011-01-01

    Full Text Available In this study dispersive liquid-liquid microextraction based on solidification of floating organic drop (DLLME-SFO followed by gas chromatography-electron capture detection (GC-ECD was developed for determination of some pesticides in the water samples. Some important parameters, such as type and volumes of extraction and disperser solvent and salt effect on the extraction recovery of analytes from aqueous solution were investigated. Under the optimum conditions (extraction solvent: 1-undecanol, 15.0 μL; disperser solvent: acetone, 1.0 mL, and without salt addition, the preconcentration factors were obtained ranged from 802 to 915 for analytes. The linear ranges were from 0.05 to 100 μg L−1, and detection limits ranged from 0.05 to 0.008 μg L−1. The relative standard deviations (RSDs%, =5 were between 3.2% and 6.7%. The proposed method was successfully applied to the determination of target analytes in the tap, sea, and river water samples, and satisfactory recoveries were obtained.

  9. Preparation of Highly Dispersed Reduced Graphene Oxide Decorated with Chitosan Oligosaccharide as Electrode Material for Enhancing the Direct Electron Transfer of Escherichia coli.

    Science.gov (United States)

    Luo, Zhimin; Yang, Dongliang; Qi, Guangqin; Yuwen, Lihui; Zhang, Yuqian; Weng, Lixing; Wang, Lianhui; Huang, Wei

    2015-04-29

    Water-dispersed reduced graphene oxide/chitosan oligosaccharide (RGO-CTSO) was prepared by chemical reduction of graphene oxide and synchronous functionalization with biocompatible chitosan oligosaccharide (CTSO). ζ potential measurement indicated that RGO-CTSO was highly stable in the acidic aqueous solution. RGO-CTSO was used to modify glassy carbon electrode (GCE) as the growth template of Escherichia coli (E. coli). The enhanced direct electron transfer of E. coli on the RGO-CTSO-modified GCE was studied by cyclic voltammetry. Compared with GCE or RGO-modified GCE, RGO-CTSO-modified GCE was more suitable for the adhesion growth of E. coli to improve direct electron transfer. The biocompatibility and versatility of RGO-CTSO made it promising for use as an anode material in microbial fuel cells.

  10. Rigorous quantitative elemental microanalysis by scanning electron microscopy/energy dispersive x-ray spectrometry (SEM/EDS) with spectrum processing by NIST DTSA-II

    Science.gov (United States)

    Newbury, Dale E.; Ritchie, Nicholas W. M.

    2014-09-01

    Quantitative electron-excited x-ray microanalysis by scanning electron microscopy/silicon drift detector energy dispersive x-ray spectrometry (SEM/SDD-EDS) is capable of achieving high accuracy and high precision equivalent to that of the high spectral resolution wavelength dispersive x-ray spectrometer even when severe peak interference occurs. The throughput of the SDD-EDS enables high count spectra to be measured that are stable in calibration and resolution (peak shape) across the full deadtime range. With this high spectral stability, multiple linear least squares peak fitting is successful for separating overlapping peaks and spectral background. Careful specimen preparation is necessary to remove topography on unknowns and standards. The standards-based matrix correction procedure embedded in the NIST DTSA-II software engine returns quantitative results supported by a complete error budget, including estimates of the uncertainties from measurement statistics and from the physical basis of the matrix corrections. NIST DTSA-II is available free for Java-platforms at: http://www.cstl.nist.gov/div837/837.02/epq/dtsa2/index.html).

  11. Long-term dispersion stability and adhesion promotion of aqueous Cu nano-ink for flexible printed electronics.

    Science.gov (United States)

    Seo, Yeong-Hui; Jeong, Sunho; Jo, Yejin; Choi, Youngmin; Ryu, Beyong-Hwan; Han, Gayoung; Lee, Minsu

    2013-08-01

    Aqueous Cu nanoparticles are synthesized using a reducing agent and surface capping molecule which prevents the interparticular agglomeration and surface oxidation. Aqueous conductive nano ink is prepared using the resulting Cu nanoparticles and conductive Cu layers are prepared via a wet coating process. The conductive Cu layers, metalized by annealing at 300 degrees C under vacuum atmosphere, exhibit excellent electrical resistivity, showing values as low as 12 microomega cm. The long-term dispersion stability for three months is monitored through an investigation on the rheological behavior of the conductive nano ink and the resistivity variation of the conductive Cu layer. The adhesion property of the conductive Cu layer is dramatically improved when using a primer-treated polyimide film, whereas the conductive Cu layer completely peels off on a pristine polyimide film. The epoxy-contained primer plays a critical role as an intermediary between the aqueous Cu nano ink and the polyimide film.

  12. CT-functional diagnostics of the rotatory instability of upper cervical spine. 1. An experimental study on cadavers.

    Science.gov (United States)

    Dvorak, J; Panjabi, M; Gerber, M; Wichmann, W

    1987-04-01

    Twelve specimens of the upper cervical spine were functionally examined by using radiography, cineradiography and computerized tomographic (CT) scan. The range of rotation was measured from CT images after maximal rotations to both sides. The left alar ligament was then cut and the examination repeated. The alar and transverse ligaments could be differentiated on CT images in axial, sagittal, and coronal views. Rotation at occiput-atlas was 4.35 degrees to the right and 5.9 degrees to the left and at atlas-axis it was 31.4 degrees to the right and 33 degrees to the left. After one-sided lesion of the alar ligament, there was an overall increase of 10.8 degrees or 30% of original rotation to the opposite side, divided about equally between the occiput-atlas and the atlas-axis. It is concluded that a lesion (irreversible overstretching or rupture of alar ligaments) can result in rotatory hypermobility or instability of the upper cervical spine.

  13. An adaptive method with weight matrix as a function of the state to design the rotatory flexible system control law

    Science.gov (United States)

    Souza, Luiz C. G.; Bigot, P.

    2016-10-01

    One of the most well-known techniques of optimal control is the theory of Linear Quadratic Regulator (LQR). This method was originally applied only to linear systems but has been generalized for non-linear systems: the State Dependent Riccati Equation (SDRE) technique. One of the advantages of SDRE is that the weight matrix selection is the same as in LQR. The difference is that weights are not necessarily constant: they can be state dependent. Then, it gives an additional flexibility to design the control law. Many are applications of SDRE for simulation or real time control but generally SDRE weights are chosen constant so no advantage of this flexibility is taken. This work serves to show through simulation that state dependent weights matrix can improve SDRE control performance. The system is a non-linear flexible rotatory beam. In a brief first part SDRE theory will be explained and the non-linear model detailed. Then, influence of SDRE weight matrix associated with the state Q will be analyzed to get some insight in order to assume a state dependent law. Finally, these laws are tested and compared to constant weight matrix Q. Based on simulation results; one concludes showing the benefits of using an adaptive weight Q rather than a constant one.

  14. Development of a multichannel dispersion interferometer for measurements of the plasma density distribution after massive gas injection and during the runaway electron phase in TEXTOR

    Energy Technology Data Exchange (ETDEWEB)

    Lvovskiy, Andrey

    2015-07-14

    The tokamak performance is limited both by technological and physical reasons. The crossing of operational limits often leads to a global loss of plasma confinement called disruption. Strong heat and electromagnetic loads are produced during the disruption. The applicability of massive injection of impurities for mitigation of thermal and electromagnetic stresses has been shown at many machines. The third issue of disruption is the generation of runaway electrons. A runaway electron beam with energy about 10 MeV and carried current up to 70% of initial plasma current could cause a serious damage in case of localized impact to the wall. It is theoretically predicted that significant increase of electron density could suppress the generation of runaway electron via collision mechanism. However, the consistent proof of this statement has never been done. The use of massive noble gas injection for the suppression of runaway electron generation is investigated in the present work. A reliable measurement of the electron density during disruption characterized by fast and significant change of plasma parameters is crucially important for that purpose. To solve this issue a multi-channel dispersion-interferometer has been developed on TEXTOR. This is a unique diagnostics allowing reliable measurement of line plasma density during disruption and post-disruption stage with high time resolution. The generation of runaway electrons has been investigated in deliberately induced disruption. The successful suppression of runaway electron generation has been found in the case of sufficient gas amount injection with proper timing not later than beginning of current quench. The critical density threshold has been found to be up to one order of magnitude below the theoretically predicted. The possible reasons are discussed in detail. The minimum of critical density threshold dependence on Z impurity number has been found. The different amount of electrons delivered into the plasma

  15. A comparative transmission electron microscopy, energy dispersive x-ray spectroscopy and spatially resolved micropillar compression study of the yttria partially stabilised zirconia - porcelain interface in dental prosthesis

    Energy Technology Data Exchange (ETDEWEB)

    Lunt, Alexander J.G., E-mail: alexander.lunt@chch.ox.ac.uk [Department of Engineering Science, University of Oxford, Parks Road, Oxford, Oxfordshire OX1 3PJ (United Kingdom); Mohanty, Gaurav, E-mail: gaurav.mohanty@empa.ch [EMPA Materials Science & Technology, Feuerwerkerstrasse 39, CH-3602 Thun (Switzerland); Ying, Siqi, E-mail: siqi.ying@eng.ox.ac.uk [Department of Engineering Science, University of Oxford, Parks Road, Oxford, Oxfordshire OX1 3PJ (United Kingdom); Dluhoš, Jiří, E-mail: jiri.dluhos@tescan.cz [TESCAN Brno, s.r.o., Libušina tř. 1, 623 00 Brno-Kohoutovice (Czech Republic); Sui, Tan, E-mail: tan.sui@eng.ox.ac.uk [Department of Engineering Science, University of Oxford, Parks Road, Oxford, Oxfordshire OX1 3PJ (United Kingdom); Neo, Tee K., E-mail: neophyte@singnet.com.sg [Specialist Dental Group, Mount Elizabeth Orchard, 3 Mount Elizabeth, #08-03/08-08/08-10, 228510 (Singapore); Michler, Johann, E-mail: johann.michler@empa.ch [EMPA Materials Science & Technology, Feuerwerkerstrasse 39, CH-3602 Thun (Switzerland); Korsunsky, Alexander M., E-mail: alexander.korsunsky@eng.ox.ac.uk [Department of Engineering Science, University of Oxford, Parks Road, Oxford, Oxfordshire OX1 3PJ (United Kingdom)

    2015-12-01

    Recent studies into the origins of failure of yttria partially stabilised zirconia–porcelain veneered prosthesis have revealed the importance of micro-to-nano scale characterisation of this interface zone. Current understanding suggests that the heat treatment, residual stresses and varying microstructure at this location may contribute to near-interface porcelain chipping. In this study the chemical, microstructural and mechanical property variation across the interfacial zone has been characterised at two differing length scales and using three independent techniques; energy dispersive X-ray spectroscopy, transmission electron microscopy and micropillar compression. Energy dispersive X-ray spectroscopy mapping of the near-interface region revealed, for the first time, that the diffusional lengths of twelve principal elements are limited to within 2–6 μm of the interface. This study also revealed that 0.2–2 μm diameter zirconia grains had become detached from the bulk and were embedded in the near-interface porcelain. Transmission electron microscopy analysis demonstrated the presence of nanoscale spherical features, indicative of tensile creep induced voiding, within the first 0.4–1.5 μm from the interface. Within zirconia, variations in grain size and atomistic structure were also observed within the 3 μm closest to the interface. Micropillar compression was performed over a 100 μm range on either side of the interface at the spatial resolution of 5 μm. This revealed an increase in zirconia and porcelain loading modulus at close proximities (< 5 μm) to the interface and a decrease in zirconia modulus at distances between 6 and 41 μm from this location. The combination of the three experimental techniques has revealed intricate details of the microstructural, chemical and consequently mechanical heterogeneities in the YPSZ–porcelain interface, and demonstrated that the length scales typically associated with this behaviour are approximately ± 5

  16. Dispersion-Corrected Density Functional Theory Investigations of Structural and Electronic Properties of Bulk MoS2: Effect of Uniaxial Strain.

    Science.gov (United States)

    Nguyen, Chuong V; Hieu, Nguyen N; Nguyen, Duong T

    2015-12-01

    Strain-dependent structural and electronic properties of MoS2 materials are investigated using first principles calculations. The structural and electronic band structures of the MoS2 with relaxed unit cells are optimized and calculated by the dispersion-corrected density functional theory (DFT-D2). Calculations within the local density approximation (LDA) and GGA using PAW potentials were also performed for specific cases for the purpose of comparison. The effect of strain on the band gap and the dependence of formation energy on strain of MoS2 are also studied and discussed using the DFT-D2 method. In bulk MoS2, the orbitals shift towards the higher/lower energy area when strain is applied along the z/x direction, respectively. The energy splitting of Mo4d states is in the range from 0 to 2 eV, which is due to the reduction of the electronic band gap of MoS2.

  17. Influences of acid on molecular forms of fluorescein and photoinduced electron transfer in fluorescein-dispersing sol-gel titania films.

    Science.gov (United States)

    Nishikiori, Hiromasa; Setiawan, Rudi Agus; Miyashita, Kyohei; Teshima, Katsuya; Fujii, Tsuneo

    2014-01-01

    Fluorescein-dispersing titania gel films were prepared by the acid-catalyzed sol-gel reaction using a titanium alkoxide solution containing fluorescein. The molecular forms of fluorescein in the films, depending on its acid-base equilibria, and the complex formation and photoinduced electron transfer process between the dye and titania surface were investigated by fluorescence and photoelectric measurements. The titanium species were coordinated to the carboxylate and phenolate-like groups of the fluorescein species. The quantum efficiencies of the fluorescence quenching and photoelectric conversion were higher upon excitation of the dianion species interacting with the titania, i.e. the dye-titania complex. This result indicated that the dianion form was the most favorable for formation of the dye-titania complex exhibiting the highest electron transfer efficiency. Using nitric acid as the catalyst, the titania surface bonded to the fluorescein instead of the adsorbed nitrate ion during the steam treatment. The dye-titania complex formation played an important role in the electron injection from the dye to the titania conduction band.

  18. SCANNING ELECTRON MICROSCOPY ANALYSIS OF FUEL/MATRIX INTERACTION LAYERS IN HIGHLY-IRRADIATED U-Mo DISPERSION FUEL PLATES WITH Al AND Al–Si ALLOY MATRICES

    Directory of Open Access Journals (Sweden)

    DENNIS D. KEISER, JR.

    2014-04-01

    Full Text Available In order to investigate how the microstructure of fuel/matrix-interaction (FMI layers change during irradiation, different U–7Mo dispersion fuel plates have been irradiated to high fission density and then characterized using scanning electron microscopy (SEM. Specifially, samples from irradiated U–7Mo dispersion fuel elements with pure Al, Al-2Si and AA4043 (∼4.5 wt.%Si matrices were SEM characterized using polished samples and samples that were prepared with a focused ion beam (FIB. Features not observable for the polished samples could be captured in SEM images taken of the FIB samples. For the Al matrix sample, a relatively large FMI layer develops, with enrichment of Xe at the FMI layer/Al matrix interface and evidence of debonding. Overall, a significant penetration of Si from the FMI layer into the U–7Mo fuel was observed for samples with Si in the Al matrix, which resulted in a change of the size (larger and shape (round of the fission gas bubbles. Additionally, solid fission product phases were observed to nucleate and grow within these bubbles. These changes in the localized regions of the microstructure of the U–7Mo may contribute to changes observed in the macroscopic swelling of fuel plates with Al-Si matrices.

  19. 10.7 Gb/s electronic predistortion transmitter using commercial FPGAs and D/A converters implementing real-time DSP for chromatic dispersion and SPM compensation.

    Science.gov (United States)

    Waegemans, Robert; Herbst, Stefan; Holbein, Ludwig; Watts, Philip; Bayvel, Polina; Fürst, Cornelius; Killey, Robert I

    2009-05-11

    We present an experimental demonstration of simultaneous chromatic dispersion and self-phase modulation compensation at 10.7 Gb/s using real-time electronic digital signal processing. This was achieved using a pre-distorting transmitter based on commercially available field programmable gate arrays and 21.4 GS/s, 6-bit resolution digital-to-analog converters. The digital signal processing employed look-up tables stored in RAM. This resulted in the achievement of a BER of 10(-6) at an OSNR of 16 dB after transmission over a 450 km link of uncompensated standard single mode fiber with + 4 dBm launch power.

  20. Supervised Mineral Classification with Semi-automatic Training and Validation Set Generation in Scanning Electron Microscope Energy Dispersive Spectroscopy Images of Thin Sections

    DEFF Research Database (Denmark)

    Flesche, Harald; Nielsen, Allan Aasbjerg; Larsen, Rasmus

    2000-01-01

    This paper addresses the problem of classifying minerals common in siliciclastic and carbonate rocks. Twelve chemical elements are mapped from thin sections by energy dispersive spectroscopy in a scanning electron microscope (SEM). Extensions to traditional multivariate statistical methods...... are applied to perform the classification. First, training and validation sets are grown from one or a few seed points by a method that ensures spatial and spectral closeness of observations. Spectral closeness is obtained by excluding observations that have high Mahalanobis distances to the training class......–Matusita distance and the posterior probability of a class mean being classified as another class. Fourth, the actual classification is carried out based on four supervised classifiers all assuming multinormal distributions: simple quadratic, a contextual quadratic, and two hierarchical quadratic classifiers...

  1. Unusual electronic structure and observation of dispersion kink in CeFeAsO parent compound of FeAs-based superconductors.

    Science.gov (United States)

    Liu, Haiyun; Chen, G F; Zhang, Wentao; Zhao, Lin; Liu, Guodong; Xia, T-L; Jia, Xiaowen; Mu, Daixiang; Liu, Shanyu; He, Shaolong; Peng, Yingying; He, Junfeng; Chen, Zhaoyu; Dong, Xiaoli; Zhang, Jun; Wang, Guiling; Zhu, Yong; Xu, Zuyan; Chen, Chuangtian; Zhou, X J

    2010-07-01

    We report the first comprehensive high-resolution angle-resolved photoemission measurements on CeFeAsO, a parent compound of FeAs-based high temperature superconductors with a magnetic-structural transition at ∼150 K. In the magnetic-ordering state, four holelike Fermi surface sheets are observed near Γ(0,0), and the Fermi surface near M(±π,±π) shows a tiny electronlike pocket at M surrounded by four strong spots. The unusual Fermi surface topology deviates strongly from the band structure calculations. The electronic signature of the magnetic-structural transition shows up in the dramatic change of the quasiparticle scattering rate. A dispersion kink at ∼25 meV is observed for the first time in the parent compound of Fe-based superconductors.

  2. Density of electronic states and dispersion of optical functions of defect chalcopyrite CdGa{sub 2}X{sub 4} (X = S, Se): DFT study

    Energy Technology Data Exchange (ETDEWEB)

    Reshak, A.H. [Institute of Complex Systems, FFPW, CENAKVA, University of South Bohemia in CB, Nove Hrady 37333 (Czech Republic); Center of Excellence Geopolymer and Green Technology, School of Material Engineering, University Malaysia Perlis, 01007 Kangar, Perlis (Malaysia); Khan, Saleem Ayaz, E-mail: sayaz_usb@yahoo.com [Institute of Complex Systems, FFPW, CENAKVA, University of South Bohemia in CB, Nove Hrady 37333 (Czech Republic)

    2013-11-15

    Graphical abstract: - Highlights: • FPLAPW method is used for calculating the electronic and optical properties of CdGa{sub 2}X{sub 4}. • Electronic and optical properties were calculated using LDA, GGA, EVGGA and mBJ. • Band gap conformed that CdGa{sub 2}X{sub 4} are semiconductors fit for UV and visible light. • The ECD shows that change in the bond length and bond nature affect the band gap. • The dielectric tensor components and its derivatives show considerable anisotropy. - Abstract: A density functional theory (DFT) based on full potential linear augmented plane wave (FPLAPW) was used for calculating the electronic structure, charge density and optical properties of CdGa{sub 2}X{sub 4} (X = S, Se) compounds. Local density approximation (LDA), generalized gradient approximation (GGA), Engle Vasko generalized gradient approximation (EVGGA) and recently modified Becke–Johnson (mBJ) were applied to calculate the band structure, total and partial density of states. The investigation of band structures and density of states of CdGa{sub 2}X{sub 4} (X = S, Se) elucidate that mBJ potential show close agreement to the experimental results. The mBJ potential was selected for further explanation of optical properties of CdGa{sub 2}X{sub 4} (X = S, Se). The study of electronic charge density contours shows that change in the bond lengths and bond nature affect the band gap of the compounds. The two non-zero dielectric tensor components and its derivatives show considerable anisotropy between the perpendicular and parallel components. The present work provide accurate information about the combination (hybridization) of orbital, formation of bands and dispersion of non-zero tensor components of CdGa{sub 2}X{sub 4} (X = S, Se)

  3. Scanning electron microscopy coupled with energy-dispersive X-ray spectrometry for quick detection of sulfur-oxidizing bacteria in environmental water samples

    Science.gov (United States)

    Sun, Chengjun; Jiang, Fenghua; Gao, Wei; Li, Xiaoyun; Yu, Yanzhen; Yin, Xiaofei; Wang, Yong; Ding, Haibing

    2017-01-01

    Detection of sulfur-oxidizing bacteria has largely been dependent on targeted gene sequencing technology or traditional cell cultivation, which usually takes from days to months to carry out. This clearly does not meet the requirements of analysis for time-sensitive samples and/or complicated environmental samples. Since energy-dispersive X-ray spectrometry (EDS) can be used to simultaneously detect multiple elements in a sample, including sulfur, with minimal sample treatment, this technology was applied to detect sulfur-oxidizing bacteria using their high sulfur content within the cell. This article describes the application of scanning electron microscopy imaging coupled with EDS mapping for quick detection of sulfur oxidizers in contaminated environmental water samples, with minimal sample handling. Scanning electron microscopy imaging revealed the existence of dense granules within the bacterial cells, while EDS identified large amounts of sulfur within them. EDS mapping localized the sulfur to these granules. Subsequent 16S rRNA gene sequencing showed that the bacteria detected in our samples belonged to the genus Chromatium, which are sulfur oxidizers. Thus, EDS mapping made it possible to identify sulfur oxidizers in environmental samples based on localized sulfur within their cells, within a short time (within 24 h of sampling). This technique has wide ranging applications for detection of sulfur bacteria in environmental water samples.

  4. Effect of Li Adsorption on the Electronic and Hydrogen Storage Properties of Acenes: A Dispersion-Corrected TAO-DFT Study

    Science.gov (United States)

    Seenithurai, Sonai; Chai, Jeng-Da

    2016-09-01

    Due to the presence of strong static correlation effects and noncovalent interactions, accurate prediction of the electronic and hydrogen storage properties of Li-adsorbed acenes with n linearly fused benzene rings (n = 3-8) has been very challenging for conventional electronic structure methods. To meet the challenge, we study these properties using our recently developed thermally-assisted-occupation density functional theory (TAO-DFT) with dispersion corrections. In contrast to pure acenes, the binding energies of H2 molecules on Li-adsorbed acenes are in the ideal binding energy range (about 20 to 40 kJ/mol per H2). Besides, the H2 gravimetric storage capacities of Li-adsorbed acenes are in the range of 9.9 to 10.7 wt%, satisfying the United States Department of Energy (USDOE) ultimate target of 7.5 wt%. On the basis of our results, Li-adsorbed acenes can be high-capacity hydrogen storage materials for reversible hydrogen uptake and release at ambient conditions.

  5. Effect of Li Adsorption on the Electronic and Hydrogen Storage Properties of Acenes: A Dispersion-Corrected TAO-DFT Study

    CERN Document Server

    Seenithurai, Sonai

    2016-01-01

    Due to the presence of strong static correlation effects and noncovalent interactions, accurate prediction of the electronic and hydrogen storage properties of Li-adsorbed acenes with n linearly fused benzene rings (n = 3 - 8) has been very challenging for conventional electronic structure methods. To meet the challenge, we study these properties using our recently developed thermally-assisted-occupation density functional theory (TAO-DFT) with dispersion corrections. In contrast to pure acenes, the binding energies of H2 molecules on Li-adsorbed acenes are in the ideal binding energy range (about 20 to 40 kJ/mol per H2). Besides, the H2 gravimetric storage capacities of Li-adsorbed acenes are in the range of 9.9 to 10.7 wt%, satisfying the United States Department of Energy (USDOE) ultimate target of 7.5 wt%. On the basis of our results, Li-adsorbed acenes can be high-capacity hydrogen storage materials for reversible hydrogen uptake and release at ambient conditions.

  6. Investigation of passivation effects in AlGaN/GaN metal-insulator-semiconductor high electron-mobility transistor by gate-drain conductance dispersion study

    Institute of Scientific and Technical Information of China (English)

    Bi Zhi-Wei; Chang Yong-Ming; Li Zhi-Ming; Mei Nan; Hu Zhen-Hua; Mao Wei; Hao Yue; Feng Qian; Cao Yan-Rong; Gao Zhi-Yuan; Zhang Jin-Cheng; Ma Xiao-Hua

    2011-01-01

    This paper studies the drain current collapse of AlGaN/GaN metal-insulator-semiconductor high electron-mobility transistors(MIS-HEMTs)with NbAlO dielectric by applying dual-pulsed stress to the gate and drain of the device.For NbAlO MIS-HEMT,smaller current collapse is found,especially when the gate static voltage is-8 V.Through a thorough study of the gate-drain conductance dispersion,it is found that the growth of NbAlO can reduce the trap density of the AlGaN surface.Therefore,fewer traps can be filled by gate electrons,and hence the depletion effect in the channel is suppressed effectively.It is proved that the NbAlO gate dielectric can not only decrease gate leakage current but also passivate the AlGaN surface effectively,and weaken the current collapse effect accordingly.

  7. Scanning electron microscopy coupled with energy-dispersive X-ray spectrometry for quick detection of sulfur-oxidizing bacteria in environmental water samples

    Science.gov (United States)

    Sun, Chengjun; Jiang, Fenghua; Gao, Wei; Li, Xiaoyun; Yu, Yanzhen; Yin, Xiaofei; Wang, Yong; Ding, Haibing

    2016-03-01

    Detection of sulfur-oxidizing bacteria has largely been dependent on targeted gene sequencing technology or traditional cell cultivation, which usually takes from days to months to carry out. This clearly does not meet the requirements of analysis for time-sensitive samples and/or complicated environmental samples. Since energy-dispersive X-ray spectrometry (EDS) can be used to simultaneously detect multiple elements in a sample, including sulfur, with minimal sample treatment, this technology was applied to detect sulfur-oxidizing bacteria using their high sulfur content within the cell. This article describes the application of scanning electron microscopy imaging coupled with EDS mapping for quick detection of sulfur oxidizers in contaminated environmental water samples, with minimal sample handling. Scanning electron microscopy imaging revealed the existence of dense granules within the bacterial cells, while EDS identified large amounts of sulfur within them. EDS mapping localized the sulfur to these granules. Subsequent 16S rRNA gene sequencing showed that the bacteria detected in our samples belonged to the genus Chromatium, which are sulfur oxidizers. Thus, EDS mapping made it possible to identify sulfur oxidizers in environmental samples based on localized sulfur within their cells, within a short time (within 24 h of sampling). This technique has wide ranging applications for detection of sulfur bacteria in environmental water samples.

  8. A correlative approach to segmenting phases and ferrite morphologies in transformation-induced plasticity steel using electron back-scattering diffraction and energy dispersive X-ray spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Gazder, Azdiar A., E-mail: azdiar@uow.edu.au [Electron Microscopy Centre, University of Wollongong, New South Wales 2500 (Australia); Al-Harbi, Fayez; Spanke, Hendrik Th. [School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, New South Wales 2522 (Australia); Mitchell, David R.G. [Electron Microscopy Centre, University of Wollongong, New South Wales 2500 (Australia); Pereloma, Elena V. [Electron Microscopy Centre, University of Wollongong, New South Wales 2500 (Australia); School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, New South Wales 2522 (Australia)

    2014-12-15

    Using a combination of electron back-scattering diffraction and energy dispersive X-ray spectroscopy data, a segmentation procedure was developed to comprehensively distinguish austenite, martensite, polygonal ferrite, ferrite in granular bainite and bainitic ferrite laths in a thermo-mechanically processed low-Si, high-Al transformation-induced plasticity steel. The efficacy of the ferrite morphologies segmentation procedure was verified by transmission electron microscopy. The variation in carbon content between the ferrite in granular bainite and bainitic ferrite laths was explained on the basis of carbon partitioning during their growth. - Highlights: • Multi-condition segmentation of austenite, martensite, polygonal ferrite and ferrite in bainite. • Ferrites in granular bainite and bainitic ferrite segmented by variation in relative carbon counts. • Carbon partitioning during growth explains variation in carbon content of ferrites in bainites. • Developed EBSD image processing tools can be applied to the microstructures of a variety of alloys. • EBSD-based segmentation procedure verified by correlative TEM results.

  9. Modified Pippard relationship describing the Raman frequency shifts of the rotatory lattice mode of ammonia solid II in the vicinity of its melting point

    Indian Academy of Sciences (India)

    H Karacali; H Yurtseven

    2005-11-01

    We relate in this study the thermal expansivity, , to the Raman frequency shift (1/)( /) for the rotatory lattice (librational) mode in ammonia solid II near its melting point. We have used our calculated Raman frequencies of this mode for pressures of 3.65, 5.02 and 6.57 kbars for this crystalline system. The values of the slope, d/d, which we deduced from our spectroscopic relation, are compared with those obtained experimentally. In particular, our computed slope value for the pressure of 5.02 kbar is in very good agreement with the empirical result.

  10. Simultaneous detection of electronic structure changes from two elements of a bifunctional catalyst using wavelength-dispersive X-ray emission spectroscopy and in situ electrochemistry.

    Science.gov (United States)

    Gul, Sheraz; Ng, Jia Wei Desmond; Alonso-Mori, Roberto; Kern, Jan; Sokaras, Dimosthenis; Anzenberg, Eitan; Lassalle-Kaiser, Benedikt; Gorlin, Yelena; Weng, Tsu-Chien; Zwart, Petrus H; Zhang, Jin Z; Bergmann, Uwe; Yachandra, Vittal K; Jaramillo, Thomas F; Yano, Junko

    2015-04-14

    Multielectron catalytic reactions, such as water oxidation, nitrogen reduction, or hydrogen production in enzymes and inorganic catalysts often involve multimetallic clusters. In these systems, the reaction takes place between metals or metals and ligands to facilitate charge transfer, bond formation/breaking, substrate binding, and release of products. In this study, we present a method to detect X-ray emission signals from multiple elements simultaneously, which allows for the study of charge transfer and the sequential chemistry occurring between elements. Kβ X-ray emission spectroscopy (XES) probes charge and spin states of metals as well as their ligand environment. A wavelength-dispersive spectrometer based on the von Hamos geometry was used to disperse Kβ signals of multiple elements onto a position detector, enabling an XES spectrum to be measured in a single-shot mode. This overcomes the scanning needs of the scanning spectrometers, providing data free from temporal and normalization errors and therefore ideal to follow sequential chemistry at multiple sites. We have applied this method to study MnOx-based bifunctional electrocatalysts for the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR). In particular, we investigated the effects of adding a secondary element, Ni, to form MnNiOx and its impact on the chemical states and catalytic activity, by tracking the redox characteristics of each element upon sweeping the electrode potential. The detection scheme we describe here is general and can be applied to time-resolved studies of materials consisting of multiple elements, to follow the dynamics of catalytic and electron transfer reactions.

  11. Direct phase selection of initial phases from single-wavelength anomalous dispersion (SAD) for the improvement of electron density and ab initio structure determination

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Chung-De [National Synchrotron Radiation Research Center, 101 Hsin-Ann Road, Hsinchu 30076, Taiwan (China); National Tsing Hua University, Hsinchu, Taiwan (China); Huang, Yen-Chieh [National Synchrotron Radiation Research Center, 101 Hsin-Ann Road, Hsinchu 30076, Taiwan (China); Chiang, Hsin-Lin [National Tsing Hua University, Hsinchu, Taiwan (China); Hsieh, Yin-Cheng; Guan, Hong-Hsiang; Chuankhayan, Phimonphan [National Synchrotron Radiation Research Center, 101 Hsin-Ann Road, Hsinchu 30076, Taiwan (China); Chen, Chun-Jung, E-mail: cjchen@nsrrc.org.tw [National Synchrotron Radiation Research Center, 101 Hsin-Ann Road, Hsinchu 30076, Taiwan (China); National Tsing Hua University, Hsinchu, Taiwan (China); National Cheng Kung University, Tainan City 701, Taiwan (China); National Cheng Kung University, Tainan City 701, Taiwan (China)

    2014-09-01

    A novel direct phase-selection method to select optimized phases from the ambiguous phases of a subset of reflections to replace the corresponding initial SAD phases has been developed. With the improved phases, the completeness of built residues of protein molecules is enhanced for efficient structure determination. Optimization of the initial phasing has been a decisive factor in the success of the subsequent electron-density modification, model building and structure determination of biological macromolecules using the single-wavelength anomalous dispersion (SAD) method. Two possible phase solutions (ϕ{sub 1} and ϕ{sub 2}) generated from two symmetric phase triangles in the Harker construction for the SAD method cause the well known phase ambiguity. A novel direct phase-selection method utilizing the θ{sub DS} list as a criterion to select optimized phases ϕ{sub am} from ϕ{sub 1} or ϕ{sub 2} of a subset of reflections with a high percentage of correct phases to replace the corresponding initial SAD phases ϕ{sub SAD} has been developed. Based on this work, reflections with an angle θ{sub DS} in the range 35–145° are selected for an optimized improvement, where θ{sub DS} is the angle between the initial phase ϕ{sub SAD} and a preliminary density-modification (DM) phase ϕ{sub DM}{sup NHL}. The results show that utilizing the additional direct phase-selection step prior to simple solvent flattening without phase combination using existing DM programs, such as RESOLVE or DM from CCP4, significantly improves the final phases in terms of increased correlation coefficients of electron-density maps and diminished mean phase errors. With the improved phases and density maps from the direct phase-selection method, the completeness of residues of protein molecules built with main chains and side chains is enhanced for efficient structure determination.

  12. Gadolinium released from MR contrast agents is deposited in brain tumors: in situ demonstration using scanning electron microscopy with energy dispersive X-ray spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Xia, Daniel; Davis, Richard L.; Crawford, Judith A.; Abraham, Jerrold L. (Dept. of Pathology, SUNY Upstate Medical Univ., Syracuse, NY (United States)), e-mail: abrahamj@upstate.edu

    2010-12-15

    Background: Gadolinium (Gd)-containing MRI contrast agents (GdCA) are widely used in studies of brain tumors, and a number of reports suggest that under certain conditions, such as renal failure, Gd may be released from GdCA into patient's tissues. Whether this may happen in abnormal tissues in the absence of renal failure has not been studied. Purpose: To test the hypothesis that the local retention of GdCA resulting from brain tumor-associated alterations in the blood-brain barrier (BBB) may result in the deposition of Gd released from the GdCA, depending on stability. Material and Methods: In this retrospective study, 30 selected brain tumor biopsies from 28 patients (taken before and after an institutional switch from a less stable to an intermediate stable GdCA) were searched for Gd-containing deposits using scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS). Relevant histories and laboratory results were obtained through institutional electronic records. Associations between the presence of deposits and other variables were tested for statistical significance using the two-tailed Fisher's exact test. Results: Insoluble deposits containing Gd associated with phosphorus and calcium were found in seven biopsies from five patients. These deposits were found in patients with estimated GFRs above 53 ml/min, and were detected more often in those receiving GdCA before the switch from a less stable to an intermediate stable GdCA (P = 0.04), and may be more frequent in patients receiving more than one contrast-enhanced MR scan (P = 0.15). Conclusion: Gd-containing deposits are present in brain tumors following contrast-enhanced MR scans in patients without severe renal disease. Further studies are needed to assess the clinical importance of the deposits we observed and to determine whether they are also found in other conditions that alter the integrity of the BBB

  13. Rotatory subluxation of the scaphoid in Kienböck's disease is not a cause of scapholunate advanced collapse (SLAC) in the wrist.

    Science.gov (United States)

    Taniguchi, Y; Tamaki, T; Honda, T; Yoshida, M

    2002-07-01

    We have examined whether the rotatory subluxation of the scaphoid which is seen in patients with advanced Kienböck's disease is associated with scapholunate advanced collapse (SLAC) wrist. We studied 16 patients (11 men, 5 women) who had stage-IV Kienböck's disease with chronic subluxation of the scaphoid. All had received conservative treatment. The mean period of affection with Kienböck's disease was 30 years (14 to 49). No wrist had SLAC. In eight patients, 24 years or more after the onset of the disease, the articular surface of the radius had been remodelled by the subluxed scaphoid with maintenance of the joint space. The wrists of six patients were considered to be excellent, nine good, and one fair according to the clinical criteria of Dornan. Our findings have shown that rotatory subluxation of the scaphoid in Kienböck's disease is not a cause of SLAC wrist and therefore that scaphotrapeziotrapezoid arthrodesis is not required for the management of these patients.

  14. The role of the anterolateral ligament in ACL insufficient and reconstructed knees on rotatory stability: A biomechanical study on human cadavers.

    Science.gov (United States)

    Tavlo, M; Eljaja, S; Jensen, J T; Siersma, V D; Krogsgaard, M R

    2016-08-01

    Studies suggest that the anterolateral ligament (ALL) is important for knee stability. The purpose was to clarify ALL's effect on rotatory and anterior-posterior stability in the anterior cruciate ligament (ACL)-insufficient and reconstructed knees and the effect of reconstruction of an insufficient ALL. Eighteen cadaveric knees were included. Stability was tested for intact (+ALL), detached (-ALL) and reconstructed (+ reALL) ALL, with ACL removed (-ACL) and reconstructed (+ACL) in six combinations. All were tested in 0, 30, 60, and 90 °C flexion. Anterior-posterior stability was measured with a rolimeter. Rotation with a torque of 8.85 Nm was measured photographically. The ALL was well defined in 78% of knees. ACL reconstruction had a significant effect on anterior-posterior stability. Detaching the ALL had a significant effect on internal rotatory stability and on anterior-posterior stability in ACL-insufficient knees. Reconstruction of ACL and ALL reestablished knee stability. The appearance of the ALL was not uniform. The ALL was an internal rotational stabilizer. Anatomical ALL reconstruction in combination with ACL reconstruction could reestablish stability. ALL reconstruction might be considered in patients with combined ACL and ALL tears, but the clinical effect should be established in a controlled clinical study.

  15. Computer-aided screening system for cervical precancerous cells based on field emission scanning electron microscopy and energy dispersive x-ray images and spectra

    Science.gov (United States)

    Jusman, Yessi; Ng, Siew-Cheok; Hasikin, Khairunnisa; Kurnia, Rahmadi; Osman, Noor Azuan Bin Abu; Teoh, Kean Hooi

    2016-10-01

    The capability of field emission scanning electron microscopy and energy dispersive x-ray spectroscopy (FE-SEM/EDX) to scan material structures at the microlevel and characterize the material with its elemental properties has inspired this research, which has developed an FE-SEM/EDX-based cervical cancer screening system. The developed computer-aided screening system consisted of two parts, which were the automatic features of extraction and classification. For the automatic features extraction algorithm, the image and spectra of cervical cells features extraction algorithm for extracting the discriminant features of FE-SEM/EDX data was introduced. The system automatically extracted two types of features based on FE-SEM/EDX images and FE-SEM/EDX spectra. Textural features were extracted from the FE-SEM/EDX image using a gray level co-occurrence matrix technique, while the FE-SEM/EDX spectra features were calculated based on peak heights and corrected area under the peaks using an algorithm. A discriminant analysis technique was employed to predict the cervical precancerous stage into three classes: normal, low-grade intraepithelial squamous lesion (LSIL), and high-grade intraepithelial squamous lesion (HSIL). The capability of the developed screening system was tested using 700 FE-SEM/EDX spectra (300 normal, 200 LSIL, and 200 HSIL cases). The accuracy, sensitivity, and specificity performances were 98.2%, 99.0%, and 98.0%, respectively.

  16. Scanning electron microscopy and energy-dispersive X-ray microanalysis studies of early dental calculus on resin plates exposed to human oral cavities.

    Science.gov (United States)

    Kodaka, T; Ohohara, Y; Debari, K

    1992-06-01

    Dental calculus formed after 10 days on resin plates, applied to the lingual sides of the mandibular gingival regions in eight human subjects, was investigated by means of scanning electron microscopy (SEM) and energy-dispersive X-ray microanalysis (EDX). The mineral deposits were mainly divided into three types: A, B, and C. The type A deposits showing an average Ca/P molar ratio of 1.42 were densely packed with fine needle-shaped crystals formed by the intra- and extra-cellular calcification. The type A deposits, probably composed of Ca-deficient apatites and the transitional forms between apatite and octacalcium phosphate (OCP), were observed in all subjects. The type B deposits showing an average Ca/P molar ratio of 0.96 were aggregated with polygonal column, triangular plate-shaped, and rhombohedral crystals. These crystals identified as brushite (CaHPO4-2H2O:dicalcium phosphate dihydrate: DCPD) were found in four subjects. Platelet-shaped crystals of the type C deposits were observed in three subjects. Their Ca/P molar ratio of 1.26 and the crystal shape were similar to those of OCP. Whitlockite crystals were not found although Mg-containing hexagonal disk-like crystals were observed in two subjects.

  17. Investigation of Sn surface segregation during GeSn epitaxial growth by Auger electron spectroscopy and energy dispersive x-ray spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Tsukamoto, Takahiro; Suda, Yoshiyuki [Graduate School of Engineering, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo 184-8588 (Japan); Hirose, Nobumitsu; Kasamatsu, Akifumi; Mimura, Takashi; Matsui, Toshiaki [National Institute of Information and Communications Technology, 4-2-1 Nukui-Kitamachi, Koganei, Tokyo 184-8795 (Japan)

    2015-02-02

    The mechanism of Sn surface segregation during the epitaxial growth of GeSn on Si (001) substrates was investigated by Auger electron spectroscopy and energy dispersive X-ray spectroscopy. Sn surface segregation depends on the growth temperature and Sn content of GeSn layers. During Sn surface segregation, Sn-rich nanoparticles form and move on the surface during the deposition, which results in a rough surface owing to facet formation. The Sn-rich nanoparticles moving on the surface during the deposition absorb Sn from the periphery and yield a lower Sn content, not on the surface but within the layer, because the Sn surface segregation and the GeSn deposition occur simultaneously. Sn surface segregation can occur at a lower temperature during the deposition compared with that during postannealing. This suggests that the Sn surface segregation during the deposition is strongly promoted by the migration of deposited Ge and Sn adatoms on the surface originating from the thermal effect of substrate temperature, which also suggests that limiting the migration of deposited Ge and Sn adatoms can reduce the Sn surface segregation and improve the crystallinity of GeSn layers.

  18. Quick Detection of Sulfur Bacteria in Environmental Water Sample with SEM(scanning electron microscopy) coupled with Energy Dispersive X-ray Spectrometry

    Science.gov (United States)

    Sun, C.; Ding, H.; Wang, Y.; Jiang, F.; Li, X.; Gao, W.; Yin, X.

    2015-12-01

    Sulfur-oxidizing bacteria play important roles in global sulfur cycle. Sulfur bacteria detection has been largely dependent on targeted gene sequencing technology or traditional cell cultivation which usually takes from days to months to finish. This cannot meet the requirements of some time-sensitive samples and/or complicated environmental samples. Since Energy-Dispersive X-ray Spectrometry (EDS) can be used to simultaneously detect multiple elements including sulfur in a sample with minimal sample treatment, the technology was applied to detect sulfur bacteria through the high sulfur content in the bacteria cell. We report the application of SEM (scanning electron microscopy) imaging coupled with EDS mapping for direct and quick detection of sulfur oxidizer in contaminated environmental water samples. The presence of sulfur bacteria can be confirmed within 24 hours after sampling. Subsequent 16S RNA gene sequencing results found the bacteria detected had over 99% similarity to Chromatium Okenii, confirming the bacterium was a sulfur oxidizer. The developed technique made it possible to quickly detect sulfur oxidizer in environmental sample and could have wide applications in sulfur bacteria detection in environmental water samples.

  19. Application of Scanning Electron Microscopy/Energy-Dispersive X-Ray Spectroscopy for Characterization of Detrital Minerals in Karst Cave Speleothems.

    Science.gov (United States)

    Zupančič, Nina; Miler, Miloš; Šebela, Stanka; Jarc, Simona

    2016-02-01

    Micro-scale observations in karst caves help to identify different processes that shaped local morphology. Scanning electron microscopy/energy-dispersive X-ray spectroscopy inspection of speleothems from two karst caves in Slovenia, Predjama and Črna Jama, confirmed the presence of sub-angular to sub-rounded detrital fragments of clay minerals, feldspars, quartz, Fe-oxides/hydroxides, rutile and Nb-rutile, xenotime, kassite, allanite, fluorapatite, epidote, ilmenite, monazite, sphene, and zircon, between 2 and 50 μm across. These occur in porous layers separating calcite laminae in the clayey coating on the layer below the surface of the speleothems, and are also incorporated within actual crystals. It is likely that they are derived from the weathered rocks of the Eocene flysch. Probably they were first transported into the caves by floodwaters forming cave sediments. Later, depending upon the climate conditions, they were moved by air currents or by water to the surface of active speleothems. They might also be redeposited from overlying soils enriched with wind-transported minerals from the flysch, or from higher passages filled with weathered flysch sediment, by drip water percolating through the fissured limestone. As some of the identified minerals are carriers of rare earth elements, Ti and Zr, their presence could affect any palaeoclimatic interpretations that are based upon the geochemical composition of the speleothems.

  20. A simple method for detection of gunshot residue particles from hands, hair, face, and clothing using scanning electron microscopy/wavelength dispersive X-ray (SEM/WDX).

    Science.gov (United States)

    Kage, S; Kudo, K; Kaizoji, A; Ryumoto, J; Ikeda, H; Ikeda, N

    2001-07-01

    We devised a simple and rapid method for detection of gunshot residue (GSR) particles, using scanning electron microscopy/wavelength dispersive X-ray (SEM/WDX) analysis. Experiments were done on samples containing GSR particles obtained from hands, hair, face, and clothing, using double-sided adhesive coated aluminum stubs (tape-lift method). SEM/WDX analyses for GSR were carried out in three steps: the first step was map analysis for barium (Ba) to search for GSR particles from lead styphnate primed ammunition, or tin (Sn) to search for GSR particles from mercury fulminate primed ammunition. The second step was determination of the location of GSR particles by X-ray imaging of Ba or Sn at a magnification of x 1000-2000 in the SEM, using data of map analysis, and the third step was identification of GSR particles, using WDX spectrometers. Analysis of samples from each primer of a stub took about 3 h. Practical applications were shown for utility of this method.

  1. Preparation of highly conjugated water-dispersible graphene-butyric acid for the enhancement of electron transfer within polyamic acid-benzoxazole: potential applications in electrochemical sensing.

    Science.gov (United States)

    Chen, Hsiao-Chien; Chen, Yen-Hsuan; Chen, Shi-Liang; Chern, Yaw-Terng; Tsai, Rung-Ywan; Hua, Mu-Yi

    2013-08-15

    To break through the long time and complex procedures for the preparation of highly conjugated reduced graphene oxide (r-GO) in developing electrochemical sensor, a time-saving and simple method is investigated in this study. One novel step of the exfoliated accompanying carboxylated graphene sheet from pristine is achieved via Friedel-Crafts acylation. By electrophilic aromatic substitution, the succinic anhydride ring is opened and attaches covalently to the graphene sheet (Gs) to form exfoliated graphene with grafted 1-one-butyric acid (Gs-BA). The grafting chain converts anions in aqueous solution to maintain Gs-BA in a stable dispersion and noticeably decreases the π-π stacking of the exfoliated Gs during the drying process. The analytical results of the absorption spectroscopy demonstrate that the conjugation of Gs-BA is not significantly destroyed by this chemical modification; Gs-BA retains the Gs electrical properties favorable for developing electrochemical sensors. When polyamic acid-benzoxazole (PAA-BO), a hydrogen peroxide (H₂O₂)-sensitive probe, hybridizes with Gs-BA to form Gs-BA-PAA-BO, the electron transfer rate relating to the response time improves markedly from 1.09 s(-1) to 38.8 s(-1). Additionally, it offers a high performance for H₂O₂ sensing in terms of sensitivity and response time, making this method applicable for developing glucose and choline biosensors.

  2. Chemical Differentiation of Osseous and Nonosseous Materials Using Scanning Electron Microscopy-Energy-Dispersive X-Ray Spectrometry and Multivariate Statistical Analysis.

    Science.gov (United States)

    Meizel-Lambert, Cayli J; Schultz, John J; Sigman, Michael E

    2015-11-01

    Identification of osseous materials is generally established on gross anatomical features. However, highly fragmented or taphonomically altered materials may be problematic and may require chemical analysis. This research was designed to assess the use of scanning electron microscopy-energy-dispersive X-ray spectrometry (SEM/EDX), elemental analysis, and multivariate statistical analysis (principal component analysis) for discrimination of osseous and nonosseous materials of similar chemical composition. Sixty samples consisting of osseous (human and nonhuman bone and dental) and non-osseous samples were assessed. After outliers were removed a high overall correct classification of 97.97% was achieved, with 99.86% correct classification for osseous materials. In addition, a blind study was conducted using 20 samples to assess the applicability for using this method to classify unknown materials. All of the blind study samples were correctly classified resulting in 100% correct classification, further demonstrating the efficiency of SEM/EDX and statistical analysis for differentiation of osseous and nonosseous materials. © 2015 American Academy of Forensic Sciences.

  3. Evaluation of the Forensic Utility of Scanning Electron Microscopy-Energy Dispersive Spectroscopy and Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry for Printing Ink Examinations.

    Science.gov (United States)

    Corzo, Ruthmara; Subedi, Kiran; Trejos, Tatiana; Almirall, José R

    2016-05-01

    Improvements in printing technology have exacerbated the problem of document counterfeiting, prompting the need for analytical techniques that better characterize inks for forensic analysis and comparisons. In this study, 319 printing inks (toner, inkjet, offset, and Intaglio) were analyzed directly on the paper substrate using scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) and Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS). As anticipated, the high sensitivity of LA-ICP-MS pairwise comparisons resulted in excellent discrimination (average of ~ 99.6%) between different ink samples from each of the four ink types and almost 100% correct associations between ink samples known to originate from the same source. SEM-EDS analysis also resulted in very good discrimination for different toner and intaglio inks (>97%) and 100% correct association for samples from the same source. SEM-EDS provided complementary information to LA-ICP-MS for certain ink types but showed limited utility for the discrimination of inkjet and offset inks.

  4. Femtosecond time-resolved X-ray absorption spectroscopy of liquid using a hard X-ray free electron laser in a dual-beam dispersive detection method.

    Science.gov (United States)

    Obara, Yuki; Katayama, Tetsuo; Ogi, Yoshihiro; Suzuki, Takayuki; Kurahashi, Naoya; Karashima, Shutaro; Chiba, Yuhei; Isokawa, Yusuke; Togashi, Tadashi; Inubushi, Yuichi; Yabashi, Makina; Suzuki, Toshinori; Misawa, Kazuhiko

    2014-01-13

    We present femtosecond time-resolved X-ray absorption spectroscopy of aqueous solution using a hard x-ray free electron laser (SACLA) and a synchronized Ti:sapphire laser. The instrumental response time is 200 fs, and the repetition rate of measurement is 10 Hz. A cylindrical liquid beam 100 μm in diameter of aqueous ammonium iron(III) oxalate solution is photoexcited at 400 nm, and the transient X-ray absorption spectra are measured in the K-edge region of iron, 7.10 - 7.26 keV, using a dual X-ray beam dispersive detection method. Each of the dual beams has the pulse energy of 1.4 μJ, and pump-induced absorbance change on the order of 10(-3) is successfully detected. The photoexcited iron complex exhibits a red shifted iron K-edge with the appearance time constant of 260 fs. The X-ray absorption difference spectra, with and without the pump pulses, are independent of time delay after 1.5 ps up to 100 ps, indicating that the photoexcited species is long-lived.

  5. A case of hut lung: scanning electron microscopy with energy dispersive x-ray spectroscopy analysis of a domestically acquired form of pneumoconiosis.

    Science.gov (United States)

    Mukhopadhyay, Sanjay; Gujral, Manmeet; Abraham, Jerrold L; Scalzetti, Ernest M; Iannuzzi, Michael C

    2013-07-01

    Hut lung is a pneumoconiosis caused by exposure to smoke derived from biomass fuels used for cooking in poorly ventilated huts. We report, to our knowledge, the first analysis of the dust deposited in the lungs in hut lung by scanning electron microscopy with energy dispersive x-ray spectroscopy (SEM/EDS). A Bhutanese woman presented with shortness of breath and an abnormal chest radiograph. Chest CT scan showed innumerable tiny bilateral upper lobe centrilobular nodules. Transbronchial biopsy revealed mild interstitial fibrosis with heavy interstitial deposition of black dust. SEM/EDS showed that the dust was carbonaceous, with smaller yet substantial numbers of silica and silicate particles. Additional history revealed use of a wood/coal-fueled stove in a small, poorly ventilated hut for 45 years. The possibility of hut lung should be considered in women from countries where use of biomass-fueled stoves for cooking is common. Our findings support the classification of this condition as a mixed-dust pneumoconiosis.

  6. Nanocomposites from Stable Dispersions of Carbon Nanotubes in Polymeric Matrices Using Dispersion Interaction

    Science.gov (United States)

    Wise, Kristopher Eric (Inventor); Park, Cheol (Inventor); Kang, Jin Ho (Inventor); Siochi, Emilie J. (Inventor); Harrison, Joycelyn S. (Inventor)

    2016-01-01

    Stable dispersions of carbon nanotubes (CNTs) in polymeric matrices include CNTs dispersed in a host polymer or copolymer whose monomers have delocalized electron orbitals, so that a dispersion interaction results between the host polymer or copolymer and the CNTs dispersed therein. Nanocomposite products, which are presented in bulk, or when fabricated as a film, fiber, foam, coating, adhesive, paste, or molding, are prepared by standard means from the present stable dispersions of CNTs in polymeric matrices, employing dispersion interactions, as presented hereinabove.

  7. Dispersion Forces

    CERN Document Server

    Buhmann, Stefan Yoshi

    2012-01-01

    In this book, a modern unified theory of dispersion forces on atoms and bodies is presented which covers a broad range of advanced aspects and scenarios. Macroscopic quantum electrodynamics is shown to provide a powerful framework for dispersion forces which allows for discussing general properties like their non-additivity and the relation between microscopic and macroscopic interactions. It is demonstrated how the general results can be used to obtain dispersion forces on atoms in the presence of bodies of various shapes and materials. Starting with a brief recapitulation of volume I, this volume II deals especially with bodies of irregular shapes, universal scaling laws, dynamical forces on excited atoms, enhanced forces in cavity quantum electrodynamics, non-equilibrium forces in thermal environments and quantum friction. The book gives both the specialist and those new to the field a thorough overview over recent results in the field. It provides a toolbox for studying dispersion forces in various contex...

  8. Dispersive liquid-liquid microextraction combined with gas chromatography-electron capture detection for the determination of polychlorinated biphenyls in soils

    Energy Technology Data Exchange (ETDEWEB)

    Hu Jia [Department of Chemical Engineering, Zhejiang University, Hangzhou, Zhejiang 310027 (China); Key Laboratory of Pesticide and Chemical Biology of Ministry of Education, Central China Normal University, Wuhan 430079 (China); Fu Lingyan; Zhao Xinna; Liu Xiujuan [Key Laboratory of Pesticide and Chemical Biology of Ministry of Education, Central China Normal University, Wuhan 430079 (China); Wang Huili; Wang Xuedong [School of Environmental Science and Public Health, Wenzhou Medical College, Wenzhou 325035 (China); Dai Liyan, E-mail: dailiyan@zju.edu.cn [Department of Chemical Engineering, Zhejiang University, Hangzhou, Zhejiang 310027 (China)

    2009-04-27

    In this article, dispersive liquid-liquid microextraction (DLLME) and gas chromatography-electron capture detection (GC-ECD) were presented for the extraction and determination of five polychlorinated biphenyls (PCBs) in soil samples. Acetone was used as extraction solvent for the extraction of PCBs from soil samples. In DLLME, the target analytes in the extraction solvent were rapidly transferred from the acetone extract to chlorobenzene when the extraction process began. The main advantages of this method are quick speed, high enrichment factor, high recovery and good repeatability. Under the optimum conditions, the method yields a linear calibration curve in the concentration range from 2 to 2000 {mu}g kg{sup -1}for PCB 52, and 0.4 to 400 {mu}g kg{sup -1} for other target analytes. Coefficients of correlation (r{sup 2}) ranged from 0.9993 to 0.9999. The repeatability was tested by spiking soil samples at a concentration level of 10 {mu}g kg{sup -1} for PCBs. The relative standard deviations (RSDs, n = 11) varied between 2.2% and 6.4%. The limits of detection (LODs), based on signal-to-noise (S/N) of 3, were between 0.20 and 0.50 {mu}g kg{sup -1}. The relative recoveries of the five PCBs from soil S1, S2 and S3 at spiking levels of 10, 20 and 50 {mu}g kg{sup -1} were in the range of 88.70-103.8%, 82.50-106.3% and 82.30-113.6%, respectively. Therefore, DLLME combined with GC-ECD can be successfully applied for the determination of trace PCB residues in real soil samples.

  9. Dispersive liquid-liquid microextraction method based on solidification of floating organic drop combined with gas chromatography with electron-capture or mass spectrometry detection.

    Science.gov (United States)

    Leong, Mei-I; Huang, Shang-Da

    2008-11-21

    A simple dispersive liquid-liquid microextraction (DLLME) method based on solidification of a floating organic drop (DLLME-SFO) technique combined with gas chromatography/electron-capture detection (GC/ECD) or gas chromatography/mass spectrometry (GC/MS) has been developed. The proposed method is simple, low in cost, and of high precision. It overcomes the most important problem in DLLME, the high-toxic solvent used. Halogenated organic compounds (HOCs) in water samples were determined as the model compounds. The parameters optimized for the DLLME-SFO technique were as follows: A mixture of 0.5 mL acetone, containing 10 microL 2-dodecanol (2-DD-OH), was rapidly injected by syringe into the 5 mL water sample. After centrifugation, the fine 2-DD-OH droplets (8+/-0.5 microL) were floated at the top of the screwcap test tube. The test tube was then cooled in an ice bath. After 5 min the 2-DD-OH solvent had solidified and was then transferred into a conical vial; it melted quickly at room temperature and 3 microL (for GC/ECD) or 2 microL (for GC/MS) of it was injected into a gas chromatograph for analysis. The limit of detection (LOD) for this technique was 0.005-0.05microgL(-1) for GC/ECD and was 0.005-0.047 microgL(-1) for GC/MS, respectively. The linear range of the calibration curve of DLLME-SFO was from 0.01 to 500 microgL(-1) with a coefficient of estimation (r2)>0.996 for GC/ECD and was from 0.02 to 500 microgL(-1) with a coefficient of estimation (r2)>0.996 for GC/MS.

  10. Direct electron transfer of glucose oxidase and dual hydrogen peroxide and glucose detection based on water-dispersible carbon nanotubes derivative

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Hsiao-Chien [Department of Biochemistry and Molecular Cell Biology, School of Medicine, College of Medicine, Taipei Medical University, 250, Wuxing St., Taipei 11031, Taiwan (China); Tu, Yi-Ming; Hou, Chung-Che [Department of Chemical and Materials Engineering, Chang Gung University, 259 Wen-Hwa 1st Rd., Tao-Yuan 33302, Taiwan (China); Lin, Yu-Chen [Wah Hong industrial Co. Ltd., 6 Lixing St., Guantian Dist., Tainan City 72046,Taiwan (China); Chen, Ching-Hsiang [Graduate Institute of Applied Science and Technology, National Taiwan University of Science and Technology, 43 Keelung Rd., Sec. 4, Taipei 10607, Taiwan (China); Yang, Kuang-Hsuan, E-mail: khy@mail.vnu.edu.tw [Department of Food and Beverage Management, Vanung University, 1, Van Nung Rd., Shuei-Wei Li, Chung-Li City 32061, Taiwan (China)

    2015-03-31

    Highlights: • Dual hydrogen peroxide and glucose sensor. • Direct electrochemistry of glucose oxidase used MWCNT-Py/GC electrode. • Change sensing function by adjusting pH value. - Abstract: A water-dispersible multi-walled carbon nanotubes (MWCNTs) derivative, MWCNTs-1-one-dihydroxypyridine (MWCNTs-Py) was synthesis via Friedel–Crafts chemical acylation. Raman spectra demonstrated the conjugated level of MWCNTs-Py was retained after this chemical modification. MWCNTs-Py showed dual hydrogen peroxide (H{sub 2}O{sub 2}) and glucose detections without mutual interference by adjusting pH value. It was sensitive to H{sub 2}O{sub 2} in acidic solution and displayed the high performances of sensitivity, linear range, response time and stability; meanwhile it did not respond to H{sub 2}O{sub 2} in neutral solution. In addition, this positively charged MWCNTs-Py could adsorb glucose oxidase (GOD) by electrostatic attraction. MWCNTs-Py-GOD/GC electrode showed the direct electron transfer (DET) of GOD with a pair of well-defined redox peaks, attesting the bioactivity of GOD was retained due to the non-destroyed immobilization. The high surface coverage of active GOD (3.5 × 10{sup −9} mol cm{sup −2}) resulted in exhibiting a good electrocatalytic activity toward glucose. This glucose sensor showed high sensitivity (68.1 μA mM{sup −1} cm{sup −2}) in a linear range from 3 μM to 7 mM in neutral buffer solution. The proposed sensor could distinguish H{sub 2}O{sub 2} and glucose, thus owning high selectivity and reliability.

  11. Synthesis and Evaluation of Changes Induced by Solvent and Substituent in Electronic Absorption Spectra of New Azo Disperse Dyes Containig Barbiturate Ring

    OpenAIRE

    2013-01-01

    Six azo disperse dyes were prepared by diazotizing 4-amino hippuric acid and coupled with barbituric acid and 2-thiobarbituric acid. Then, the products were reacted with aromatic aldehyde, sodium acetate, and acetic anhydride, and oxazolone derivatives were formed. Characterization of the dyes was carried out by using UV-Vis, FT-IR, 1H NMR and 13C NMR, and mass spectroscopic techniques. The solvatochromic behavior of azo disperse dyes was evaluated in various solvents. The effects of substitu...

  12. Dispersion Modeling.

    Science.gov (United States)

    Budiansky, Stephen

    1980-01-01

    This article discusses the need for more accurate and complete input data and field verification of the various models of air pollutant dispension. Consideration should be given to changing the form of air quality standards based on enhanced dispersion modeling techniques. (Author/RE)

  13. Chemical dispersants

    NARCIS (Netherlands)

    Rahsepar, Shokouhalsadat; Smit, Martijn P.J.; Murk, Albertinka J.; Rijnaarts, Huub H.M.; Langenhoff, Alette A.M.

    2016-01-01

    Chemical dispersants were used in response to the Deepwater Horizon oil spill in the Gulf of Mexico, both at the sea surface and the wellhead. Their effect on oil biodegradation is unclear, as studies showed both inhibition and enhancement. This study addresses the effect of Corexit on oil biodeg

  14. Chemical dispersants

    NARCIS (Netherlands)

    Rahsepar, Shokouhalsadat; Smit, Martijn P.J.; Murk, Albertinka J.; Rijnaarts, Huub H.M.; Langenhoff, Alette A.M.

    2016-01-01

    Chemical dispersants were used in response to the Deepwater Horizon oil spill in the Gulf of Mexico, both at the sea surface and the wellhead. Their effect on oil biodegradation is unclear, as studies showed both inhibition and enhancement. This study addresses the effect of Corexit on oil

  15. Synthesis and Evaluation of Changes Induced by Solvent and Substituent in Electronic Absorption Spectra of New Azo Disperse Dyes Containig Barbiturate Ring

    Directory of Open Access Journals (Sweden)

    Hooshang Hamidian

    2013-01-01

    Full Text Available Six azo disperse dyes were prepared by diazotizing 4-amino hippuric acid and coupled with barbituric acid and 2-thiobarbituric acid. Then, the products were reacted with aromatic aldehyde, sodium acetate, and acetic anhydride, and oxazolone derivatives were formed. Characterization of the dyes was carried out by using UV-Vis, FT-IR, 1H NMR and 13C NMR, and mass spectroscopic techniques. The solvatochromic behavior of azo disperse dyes was evaluated in various solvents. The effects of substituents of aromatic aldehyde, barbiturate, and thiobarbiturate ring on the color of dyes were investigated.

  16. Intercomparison of dispersed radiation readings among film dosimetry, electronic and OSL with X-rays for low dose; Intercomparacion de lecturas de radiacion dispersa entre dosimetria film, electronica y OSL con rayos X para dosis bajas

    Energy Technology Data Exchange (ETDEWEB)

    Andisco, D. [Universidad de Buenos Aires, Facultad de Medicina, Paraguay 2155, C1121AAA Buenos Aires (Argentina); Blanco, S. [CONICET, Saavedra 15, C1083ACA Buenos Aires (Argentina); Bourel, V.; Schmidt, L. [Universidad Favaloro, Facultad de Ciencias e Ingenieria, Solis 453, C1078AAI, Buenos Aires (Argentina); Di Risio, C., E-mail: dandisco@fmed.uba.ar [Universidad de Belgrano, Facultad de Ingenieria, Zabala 1837, C1426DQG, Buenos Aires (Argentina)

    2014-08-15

    One of the personal dosimetry methods more used for several decades is the dosimetry type film, characterized to possess readings with certain margin of trust. Today other methods exist that many times are presupposed more reliable due to the nature of the detection like the electronic dosimeters or the OSL (Optically Stimulated Luminescence) dosimetry. With the purpose of comparing different methods and to can determining the existent differences among each method has been carried out an intercomparison assay. The different dosimeters have been exposed to dispersed radiation generated by a Hemodynamics equipment of the type -arch in C- and a dispersing system of the primary beam. Film dosimeters have been used; OSL (In Light), OSL (Nano Dots) and Electronic with the purpose of knowing and to valorize the existent differences among its readings. Always, the intercomparison exercises have demonstrated to be an useful tool when establishing the measurement capacity and the quality of the results emitted by the laboratories of personal dosimetry services. Also, this type of assays allows obtaining quality indicators of the laboratory performance and they are habitual part of the procedures for accreditation of the same ones. The Optically Stimulated Luminescence is a technology that has grown in Argentina so much in the area of personal dosimetry as in dosimetry in vivo (radiotherapy area). In this intercomparison study, the answers corresponding to each technology were looked for oneself irradiation of the disperse type, that is to say, of very low energy. (Author)

  17. Role of the upper branch of the hour-glass magnetic spectrum in the formation of the main kink in the electronic dispersion of high-Tc cuprate superconductors

    Science.gov (United States)

    Geffroy, Dominique; Chaloupka, Jiří; Dahm, Thomas; Munzar, Dominik

    2016-04-01

    We investigate the electronic dispersion of the high-Tc cuprate superconductors using the fully self-consistent version of the phenomenological model, where charge planar quasiparticles are coupled to spin fluctuations. The inputs we use, the underlying (bare) band structure and the spin susceptibility χ , are extracted from fits of angle-resolved photoemission and inelastic neutron scattering data of underdoped YBa2Cu3O6.6 by T. Dahm and coworkers [Nat. Phys. 5, 217 (2009), 10.1038/nphys1180]. Our main results are as follows: (i) We have confirmed the finding by Dahm and coworkers that the main nodal kink is, for the present values of the input parameters, determined by the upper branch of the hourglass of χ . We demonstrate that the properties of the kink depend qualitatively on the strength of the charge-spin coupling. (ii) The effect of the resonance mode of χ on the electronic dispersion strongly depends on its kurtosis in the quasimomentum space. A low (high) kurtosis implies a negligible (considerable) effect of the mode on the dispersion in the near-nodal region. (iii) The energy of the kink decreases as a function of the angle θ between the Fermi surface cut and the nodal direction, in qualitative agreement with recent experimental observations. We clarify the trend and make a specific prediction concerning the angular dependence of the kink energy in underdoped YBa2Cu3O6.6 .

  18. Characterization of toners and inkjets by laser ablation spectrochemical methods and Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Trejos, Tatiana, E-mail: trejost@fiu.edu; Corzo, Ruthmara, E-mail: rcorz001@fiu.edu; Subedi, Kiran, E-mail: ksube001@fiu.edu; Almirall, José, E-mail: almirall@fiu.edu

    2014-02-01

    Detection and sourcing of counterfeit currency, examination of counterfeit security documents and determination of authenticity of medical records are examples of common forensic document investigations. In these cases, the physical and chemical composition of the ink entries can provide important information for the assessment of the authenticity of the document or for making inferences about common source. Previous results reported by our group have demonstrated that elemental analysis, using either Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) or Laser Ablation Induced Breakdown Spectroscopy (LIBS), provides an effective, practical and robust technique for the discrimination of document substrates and writing inks with minimal damage to the document. In this study, laser-based methods and Scanning Electron Microscopy-Energy Dispersive X-Ray Spectroscopy (SEM-EDS) methods were developed, optimized and validated for the forensic analysis of more complex inks such as toners and inkjets, to determine if their elemental composition can differentiate documents printed from different sources and to associate documents that originated from the same printing source. Comparison of the performance of each of these methods is presented, including the analytical figures of merit, discrimination capability and error rates. Different calibration strategies resulting in semi-quantitative and qualitative analysis, comparison methods (match criteria) and data analysis and interpretation tools were also developed. A total of 27 black laser toners originating from different manufacturing sources and/or batches were examined to evaluate the discrimination capability of each method. The results suggest that SEM-EDS offers relatively poor discrimination capability for this set (∼ 70.7% discrimination of all the possible comparison pairs or a 29.3% type II error rate). Nonetheless, SEM-EDS can still be used as a complementary method of analysis since it has

  19. Characterization of toners and inkjets by laser ablation spectrochemical methods and Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy

    Science.gov (United States)

    Trejos, Tatiana; Corzo, Ruthmara; Subedi, Kiran; Almirall, José

    2014-02-01

    Detection and sourcing of counterfeit currency, examination of counterfeit security documents and determination of authenticity of medical records are examples of common forensic document investigations. In these cases, the physical and chemical composition of the ink entries can provide important information for the assessment of the authenticity of the document or for making inferences about common source. Previous results reported by our group have demonstrated that elemental analysis, using either Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) or Laser Ablation Induced Breakdown Spectroscopy (LIBS), provides an effective, practical and robust technique for the discrimination of document substrates and writing inks with minimal damage to the document. In this study, laser-based methods and Scanning Electron Microscopy-Energy Dispersive X-Ray Spectroscopy (SEM-EDS) methods were developed, optimized and validated for the forensic analysis of more complex inks such as toners and inkjets, to determine if their elemental composition can differentiate documents printed from different sources and to associate documents that originated from the same printing source. Comparison of the performance of each of these methods is presented, including the analytical figures of merit, discrimination capability and error rates. Different calibration strategies resulting in semi-quantitative and qualitative analysis, comparison methods (match criteria) and data analysis and interpretation tools were also developed. A total of 27 black laser toners originating from different manufacturing sources and/or batches were examined to evaluate the discrimination capability of each method. The results suggest that SEM-EDS offers relatively poor discrimination capability for this set (~ 70.7% discrimination of all the possible comparison pairs or a 29.3% type II error rate). Nonetheless, SEM-EDS can still be used as a complementary method of analysis since it has

  20. Dispersion Relation Tool for generalized lower-hybrid mode with, density gradient, equilibrium ExB drift, collisions and finite electron Larmor radius

    CERN Document Server

    Romadanov, Ivan; Frias, Winston; Chapurin, Oleksandr; Koshkarov, Oleksandr

    2016-01-01

    MATLAB solver has been developed for studies of local instabilities in partially magnetized plasmas typical for ExB discharge plasmas. Examples for the Simon-Hoh, lower-hybrid and ion-sound instabilities in Penning discharge. The detailed behavior of the local dispersion relation can be investigated, plotted and saved with this solver. It allows to include various effects, change plasma parameters and obtain eigen-frequencies as a function of the wavenumbers in x or y directions.

  1. Mobility of the ankle joint: recording of rotatory movements in the talocrural joint in vitro with and without the lateral collateral ligaments of the ankle.

    Science.gov (United States)

    Rasmussen, O; Tovborg-Jensen, I

    1982-02-01

    A method for graphic recording of rotatory movements in osteoligamentous ankle preparations is described. By this method it is possible to record characteristic mobility patterns in two planes at the same time. The ankle is affected by a known torque, so that the individual mobility patterns are reproducible with unchanged condition of the ligaments. Six amputated legs were investigated in the sagittal and horizontal planes and another six in the sagittal and frontal planes. Mobility patterns were recorded with intact ligaments and after successive cutting of the lateral collateral ligaments of the ankle in the anteroposterior direction. In the sagittal plane increased dorsiflexion was observed after total cutting of the lateral ligaments, while plantar flexion remained unchanged. In the horizontal plane the internal rotation of the talus increased in step with increasing injury to the ligament, particularly when the ankle was plantar flexed. When all collateral ligaments had been cut, an increase in external rotation occurred, especially in dorsiflexion. In the frontal plane the talar tilt increased gradually with increasing injury to the ligaments. Talar tilt was at a maximum in the neutral position of the ankle or in plantar flexion. After total severing of the collateral ligaments, however, talar tilt was most marked in dorsiflexion of the ankle.

  2. 颈椎定点旋转手法"点"的数字化解剖%Digital anatomical position of the "point" in cervical vertebra fixed-point rotatory technique

    Institute of Scientific and Technical Information of China (English)

    袁元杏; 万磊; 李义凯; 陈静

    2011-01-01

    背景:虽然颈椎定点旋转复位手法效果显著,但其机制一直缺乏深入的研究.临床上对所要实施的推拿力和旋转节段无法做到精确控制,有时会造成手法的医源性损伤.目的:从颈椎定点旋转手法旋转中心点的角度分析旋转手法的作用途径.方法:在64排螺旋CT工作平台扫描标本,层距1 mm.在PHILIPS MEDICAL SYSTEMS图像处理功能模块中提取图片中轮廓线数据,进行上颈椎三维结构重建和图像显示.取枢椎棘突顶点(A点)、齿突垂直轴心(B点)以及两者之间连线的中点(C点)为旋转轴心(模拟中的旋转中心点),分别以各点为原点建立球坐标系.观察枢椎棘突顶点与下颌尖旋转前后的连线夹角,以及齿突垂直轴心与下颌尖旋转前后的连线夹角.结果与结论:做定点手法旋转时其中心并非是施术者利手作用的枢椎棘突顶点,而是枢椎齿突垂直轴心;实际轴心旋转角>术者观察角.提示应建立颈椎定轴旋转的新概念,并掌握颈椎定轴旋转手法的原则,以指导临床正确应用脊柱旋转类手法.%BACKGROUND: Although the fixed-point cervical vertebra rotating reduction has a notable treatment effect, yet it has not been deeply studied in the medical field. Some clinical surgeons feel difficult to make an accurate control on the power and rotatory joint position while operating, even results in iatrogenic injury. OBJECTIVE: To discuss the action mechanism of rotatory technique based on the central rotatory point of cervical vertebra fixed-point rotatory technique. METHODS: Samples were scanned through a 64-row spiral CT working platform at 1-mm layer distance. The picture's profilogram data were extracted from the image processing functional module in PHILIPS MEDICAL SYSTEMS, and then the three-dimensional structure of the upper cervical vertebra was reconstructed and displayed. Taking the axis spinous process peak (point A), odontoid process vertical axes (point B

  3. Hydrodynamic and kinetic models for spin-1/2 electron-positron quantum plasmas: Annihilation interaction, helicity conservation, and wave dispersion in magnetized plasmas

    CERN Document Server

    Andreev, Pavel A

    2014-01-01

    We discuss complete theory of spin-1/2 electron-positron quantum plasmas, when electrons and positrons move with velocities mach smaller than the speed of light. We derive a set of two fluid quantum hydrodynamic equations consisting of the continuity, Euler, spin (magnetic moment) evolution equations for each species. We explicitly include the Coulomb, spin-spin, Darwin and annihilation interactions. The annihilation interaction is the main topic of the paper. We consider contribution of the annihilation interaction in the quantum hydrodynamic equations and in spectrum of waves in magnetized electron-positron plasmas. We consider propagation of waves parallel and perpendicular to an external magnetic field. We also consider oblique propagation of longitudinal waves. We derive set of quantum kinetic equations for electron-positron plasmas with the Darwin and annihilation interactions. We apply the kinetic theory for the linear wave behavior in absence of external fields. We calculate contribution of the Darwin...

  4. Hydrodynamic and kinetic models for spin-1/2 electron-positron quantum plasmas: Annihilation interaction, helicity conservation, and wave dispersion in magnetized plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Andreev, Pavel A., E-mail: andreevpa@physics.msu.ru [Faculty of Physics, Lomonosov Moscow State University, Moscow (Russian Federation)

    2015-06-15

    We discuss the complete theory of spin-1/2 electron-positron quantum plasmas, when electrons and positrons move with velocities mach smaller than the speed of light. We derive a set of two fluid quantum hydrodynamic equations consisting of the continuity, Euler, spin (magnetic moment) evolution equations for each species. We explicitly include the Coulomb, spin-spin, Darwin and annihilation interactions. The annihilation interaction is the main topic of the paper. We consider the contribution of the annihilation interaction in the quantum hydrodynamic equations and in the spectrum of waves in magnetized electron-positron plasmas. We consider the propagation of waves parallel and perpendicular to an external magnetic field. We also consider the oblique propagation of longitudinal waves. We derive the set of quantum kinetic equations for electron-positron plasmas with the Darwin and annihilation interactions. We apply the kinetic theory to the linear wave behavior in absence of external fields. We calculate the contribution of the Darwin and annihilation interactions in the Landau damping of the Langmuir waves. We should mention that the annihilation interaction does not change number of particles in the system. It does not related to annihilation itself, but it exists as a result of interaction of an electron-positron pair via conversion of the pair into virtual photon. A pair of the non-linear Schrodinger equations for the electron-positron plasmas including the Darwin and annihilation interactions is derived. Existence of the conserving helicity in electron-positron quantum plasmas of spinning particles with the Darwin and annihilation interactions is demonstrated. We show that the annihilation interaction plays an important role in the quantum electron-positron plasmas giving the contribution of the same magnitude as the spin-spin interaction.

  5. Hydrodynamic and kinetic models for spin-1/2 electron-positron quantum plasmas: Annihilation interaction, helicity conservation, and wave dispersion in magnetized plasmas

    Science.gov (United States)

    Andreev, Pavel A.

    2015-06-01

    We discuss the complete theory of spin-1/2 electron-positron quantum plasmas, when electrons and positrons move with velocities mach smaller than the speed of light. We derive a set of two fluid quantum hydrodynamic equations consisting of the continuity, Euler, spin (magnetic moment) evolution equations for each species. We explicitly include the Coulomb, spin-spin, Darwin and annihilation interactions. The annihilation interaction is the main topic of the paper. We consider the contribution of the annihilation interaction in the quantum hydrodynamic equations and in the spectrum of waves in magnetized electron-positron plasmas. We consider the propagation of waves parallel and perpendicular to an external magnetic field. We also consider the oblique propagation of longitudinal waves. We derive the set of quantum kinetic equations for electron-positron plasmas with the Darwin and annihilation interactions. We apply the kinetic theory to the linear wave behavior in absence of external fields. We calculate the contribution of the Darwin and annihilation interactions in the Landau damping of the Langmuir waves. We should mention that the annihilation interaction does not change number of particles in the system. It does not related to annihilation itself, but it exists as a result of interaction of an electron-positron pair via conversion of the pair into virtual photon. A pair of the non-linear Schrodinger equations for the electron-positron plasmas including the Darwin and annihilation interactions is derived. Existence of the conserving helicity in electron-positron quantum plasmas of spinning particles with the Darwin and annihilation interactions is demonstrated. We show that the annihilation interaction plays an important role in the quantum electron-positron plasmas giving the contribution of the same magnitude as the spin-spin interaction.

  6. Interpretation of transconductance dispersion in AlGaAs/InGaAs pseudomorphic high electron mobility transistor by capacitance deep level transient spectroscopy

    CERN Document Server

    Choi, K J; Yoo, H M; Lee, G Y

    1998-01-01

    The transconductance dispersion in AlGaAs/InGaAs PHEMT grown by MBE was interpreted by means of capacitance DLTS technique. When the gate bias was -0.2 V, the transconductance decreased at a very broad frequency range of 5.5 Hz -1.7x10 sup 4 Hz. However, when a positive bias was applied to the gate, the transconductance increased at a low frequency range and then decreased at a high frequency range. In the transconductance dispersion measurement as a function of temperature, the transition frequency shifted to higher frequency region with the increase in temperature. The emission energy for the change in the transition frequency was determined to be 0.394 eV from the temperature dependency of the transition frequency. In the capacitance DLTS measurements, we observed DX-center with thermal activation energy of 0.420 eV and two hole trap-like signals. The DX-center peak decreased as the filling pulse decreased from +0.6 V and disappeared at the bias of -0.1 V. Comparing the activation energy of DX-center in DL...

  7. Dispersed Indeterminacy

    CERN Document Server

    Fayngold, Moses

    2013-01-01

    A state of a single particle can be represented by a quantum blob in the corresponding phase space, or a patch (granule) in its 2-D subspace. Its area is frequently stated to be no less than, implying that such a granule is an indivisible quantum of the 2-D phase space. But this is generally not true, as is evident, for instance, from representation of some states in the basis of innately discrete observables like angular momentum. Here we consider some dispersed states involving the evanescent waves different from that in the total internal reflection. Such states are represented by a set of separated granules with individual areas, but with the total indeterminacy . An idealized model has a discrete Wigner function and is described by a superposition of eigenstates with eigenvalues and forming an infinite periodic array of dots on the phase plane. The question about the total indeterminacy in such state is discussed. We argue that the eigenstates corresponding to the considered EW cannot be singled out by a...

  8. Dispersion Properties of TIRPCF under Compton Scattering

    Institute of Scientific and Technical Information of China (English)

    HAO Dong-shan; YU Ding-chen

    2006-01-01

    The dispersion properties in the short wavelength region of total internal reflective photonic crystal fiber(TIRPCF) in Compton scattering have been studied by using the model of the equivalent twin waveguide soliton coupling,dispersion management solitons and effective refractive index. It is shown that the positive dispersion of the cladding waveguide of TIRPCF and the negative dispersion of its core waveguide are quickly increased by the square of the collision non-elastic composition between the electron and photons,and they are lessened by the increase of the electron absorption photon number. Under the one-photon nonlinear Compton scattering,the method of the compensated probing laser diffraction by the phase hole induced by the stationary pumping laser in the cladding waveguide enables the average dispersion value of TIRPCF to be close to zero,and the zero dispersion point quickly shifts to the short wavelength region.

  9. Transverse dispersion laws in ultra-relativistic plasma with fast electron distribution%极端相对论快电子分布等离子体中横振荡色散关系

    Institute of Scientific and Technical Information of China (English)

    刘三秋; 国洪梅

    2011-01-01

    本文对各向同性极端相对论快电子呈幂律分布等离子体中横振荡色散关系进行了解析和数值研究.得到长波支和短波支色散关系的解析表达式.由于解析近似对波数的限制,无法得到全波数空间色散曲线,因此对色散方程进行了数值求解.研究表明,在满足长波支和短波支条件时,解析色散曲线与数值色散曲线完全符合.此外,利用多项式回归的方法对数值结果进行拟合,得到不同参数下快电子分布等离子体横振荡色散关系近似表达式,该结果为进一步研究快电子分布等离子体的性质提供了重要的理论依据.%Analytic and numerical study of electromagnetic oscillations of isotropic relativistic plasma with fast electron distribution is presented. Different analytic formulas for the long-wavelength and short-wavelength branches are obtained.The numerical study gives the dispersion curve in the whole wavenumber range. It is shown that analytical dispersion curves in the long-wavelength and short-wavelength regions are coincident with the numerical ones. Furthermore, the approximate expression of the dispersion law for the different parameters is given by fitting numerical curves with the polynomial regression method, which provides a reference for further study.

  10. Influence of Pd/Pd2 decoration on the structural, electronic and sensing properties of monolayer graphene in the presence of methane molecule: A dispersion-corrected DFT study

    Science.gov (United States)

    Nasresfahani, Sh.; Safaiee, R.; Sheikhi, M. H.

    2017-08-01

    This paper is devoted to study on the methane (CH4) adsorption ability of graphene decorated by a single palladium (Pd) atom and its dimer (Pd2), using dispersion-corrected density functional theory (DFT-D2). The adsorption energy, optimum geometry and electronic structure in terms of density of states, band structure, and charge transfer are calculated. Our results show that van der Waals interactions lead to physisorption of CH4 on the prisitine graphene with the adsorption energy of -112 meV, which is close to its experimental value. The calculations also show that hybridization of Pd and graphene electronic states strongly binds Pd atoms to graphene surface, inducing chemisorption of the adsorbate. The adsorption energies of Pd atom and its dimer have been found to be -1.43 eV and -2.27 eV, respectively. Furthermore symmetry breaking of the graphene structure, due to the Pd/Pd2-decoration, leads to opening a band gap, bringing graphene from semimetalic to semiconducting state. In the presence of methane molecule, the electronic band gap of Pd-decorated graphene is increased from 73 meV to 90 meV, while for Pd dimer it is decreased from 185 meV to 55 meV. As a result, compared to Pd-decorated graphene, Pd2-decorated graphene has a stronger interaction with the methane molecule and may provide a more sensitive signal for methane gas detection.

  11. Magerl technique for children atlantoaxial rotatory subluxation%Magerl技术治疗儿童寰枢关节旋转半脱位

    Institute of Scientific and Technical Information of China (English)

    唐明星; 张宏其; 刘金洋; 王昱翔; 郭超峰; 刘少华; 邓盎; 高琪乐; 王龙杰

    2016-01-01

    Objective To discuss the feasibility and prognosis of magerl technique for children.Atlantoaxial Rotatory Subluxation.Methods 63 patients with Atlantoaxial Rotatory Subluxation were treated in our hospital,and 16 of whom were treated with bilateral C1,2 posterior transarticular screw fixation and fusion.All cases aged from 8 to 14,with an average age of 11±2.3 years old.According to Fielding classification,10 cases were in type II,and 6 in type Ⅲ.1 patient showed dizziness,11 patients showed obvious appearance of deviation of head and neck;14 patients showed varying degrees of occipito-cervical pain,and one patient showed incomplete paralysis.All patients had undergone Halo traction,then the Magerl surgery for atlantoaxial fixation fusion.Through follow-up and photograph of atlantoaxial mouth opening,lateral cervical X-ray and atlantoaxial 3D CT,the screw position and bone graft fusion were evaluated.The clinical and radiological outcomes were evaluated according to the Symon and Lavender clinical standard,the imaging index space available for the cord (SAC),and the atlas-dens interval (ADI).Results All cases were followed up for 3 to 98 months (mean 38±14.6 months).All patients had completed the bilateral UCSS screw fixation,and the symptoms were improved significantly,without neurological symptoms aggravated or complications such as neurovascular injury.All UCSS screw position through the atlantoaxial joint was accurate,without atlanto occipital joint activity limitation.All patients got bony fusion 3 to 6 months post-operation.The clinical recovery rate was 93.8%.The SAC of C1,2 segment increased by 6.06± 1.29 mm postoperatively,which showed a significant difference compared with preoperative SAC.The SAC at the latest follow-up was 15.31±0.79 mm,showing no significant difference compared with that just postoperatively.The ADI at one month postoperatively decreased by 5.75 ± 1.53 mm,showing a significant difference compared with preoperative SAC.The ADI

  12. Relativistic energy loss in a dispersive medium

    DEFF Research Database (Denmark)

    Houlrik, Jens Madsen

    2002-01-01

    The electron energy loss in a dispersive medium is obtained using macroscopic electrodynamics taking advantage of a static frame of reference. Relativistic corrections are described in terms of a dispersive Lorentz factor obtained by replacing the vacuum velocity c by the characteristic phase...

  13. Relativistic energy loss in a dispersive medium

    DEFF Research Database (Denmark)

    Houlrik, Jens Madsen

    2002-01-01

    The electron energy loss in a dispersive medium is obtained using macroscopic electrodynamics taking advantage of a static frame of reference. Relativistic corrections are described in terms of a dispersive Lorentz factor obtained by replacing the vacuum velocity c by the characteristic phase...

  14. Seed dispersal in fens

    NARCIS (Netherlands)

    Middleton, Beth; van Diggelen, Rudy; Jensen, Kai

    2006-01-01

    Question: How does seed dispersal reduce fen isolation and contribute to biodiversity? Location: European and North American fens. Methods: This paper reviews the literature on seed dispersal to fens. Results: Landscape fragmentation may reduce dispersal opportunities thereby isolating fens and

  15. Scanning Electron Microscopy Coupled with Energy Dispersive Spectrometric Analysis Reveals for the First Time Weddellite and Sylvite Crystals on the Surface of Involucral Bracts and Petals of two Xeranthemum L. (Compositae) Species.

    Science.gov (United States)

    Gavrilović, Milan; Erić, Suzana; Marin, Petar D; Garcia-Jacas, Núria; Susanna, Alfonso; Janaćković, Pedja

    2017-06-01

    In this work, weddellite and sylvite crystals are identified for the first time on the involucral bracts and petals of Xeranthemum annuum and Xeranthemum cylindraceum using scanning electron microscopy coupled with energy dispersive spectrometric (SEM-EDS) analysis. Well-developed crystals of weddellite (CaC2O4·2H2O) occur in the form of a tetragonal bipyramid (hhl), rarely in combination of a bipyramid and tetragonal prism (h00). Indumentum of involucral bracts of X. cylindraceum consists of nonglandular and glandular trichomes. Sylvite (KCl) crystals are observed only on the petal surface of X. cylindraceum. The crystals of sylvite occur in the form of perfect cubes (hexahedrons), but some crystals are deformed, i.e., partially elongated. Taxonomic significance of investigated microcharacters as well as the use of SEM-EDS analysis in taxonomic studies of plants are discussed.

  16. The identification of the pigments used to paint statues of Feixiange Cliff in China in late 19th century by micro-Raman spectroscopy and scanning electron microscopy/energy dispersive X-ray analysis

    Science.gov (United States)

    Jin, Pu-jun; Huang, Wei; Jianhua-Wang; Zhao, Gang; Wang, Xiao-ling

    2010-11-01

    The application of micro-Raman spectroscopy (μ-RS) and scanning electron microscopy (SEM)/energy dispersive X-ray spectrometer (EDS) to the research of pigments collected from Statues of Feixiange Cliff No. 67 and No. 69 niche of Tang Dynasty in China is reported. Five kinds of pigments were found in the experimental data, including black (carbon), white (gypsum + quartz), blue (lapis lazuli) and green (Paris green + Barium sulphate). After synthesized in 1814, Paris green was reported for a large import as a light and bright green pigment to paint architectures in China from the late 19th century. The analyzed blue pigment demonstrated the similar Raman spectra to the Lâjvardina blue glazed ceramics, which indicated lapis lazuli was an artificial product. This confirmed the painting of Feixiange Cliff in the early Republic of China as the historical record, and also reveals that some pigments were imported from abroad.

  17. Component analyses of urinary nanocrystallites of uric acid stone formers by combination of high-resolution transmission electron microscopy, fast Fourier transformation, energy dispersive X-ray spectroscopy, X-ray diffraction and Fourier transform infrared spectroscopy.

    Science.gov (United States)

    Sun, Xin-Yuan; Xue, Jun-Fa; Xia, Zhi-Yue; Ouyang, Jian-Ming

    2015-06-01

    This study aimed to analyse the components of nanocrystallites in urines of patients with uric acid (UA) stones. X-ray diffraction (XRD), Fourier transform infrared spectroscopy, high-resolution transmission electron microscopy (HRTEM), fast Fourier transformation (FFT) of HRTEM, and energy dispersive X-ray spectroscopy (EDS) were performed to analyse the components of these nanocrystallites. XRD and FFT showed that the main component of urinary nanocrystallites was UA, which contains a small amount of calcium oxalate monohydrate and phosphates. EDS showed the characteristic absorption peaks of C, O, Ca and P. The formation of UA stones was closely related to a large number of UA nanocrystallites in urine. A combination of HRTEM, FFT, EDS and XRD analyses could be performed accurately to analyse the components of urinary nanocrystallites.

  18. Scanning electron microscopy (SEM) and X-ray dispersive spectrometry evaluation of direct laser metal sintering surface and human bone interface: a case series.

    Science.gov (United States)

    Mangano, Carlo; Piattelli, Adriano; Raspanti, Mario; Mangano, Francesco; Cassoni, Alessandra; Iezzi, Giovanna; Shibli, Jamil Awad

    2011-01-01

    Recent studies have shown that direct laser metal sintering (DLMS) produces structures with complex geometry and consequently that allow better osteoconductive properties. The aim of this patient report was to evaluate the early bone response to DLMS implant surface retrieved from human jaws. Four experimental DLMS implants were inserted in the posterior mandible of four patients during conventional dental implant surgery. After 8 weeks, the micro-implants and the surrounding tissue were removed and prepared for scanning electron microscopy (SEM) and histomorphometric analysis to evaluate the bone-implant interface. The SEM and EDX evaluations showed a newly formed tissue composed of calcium and phosphorus. The bone-to-implant contact presented a mean of 60.5 ± 11.6%. Within the limits of this patient report, data suggest that the DLMS surfaces presented a close contact with the human bone after a healing period of 8 weeks.

  19. Design and Application of Novel Dispersants for Coatings and Other System

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    1 Results Dispersants are defined as liquids or gases that can be added to a mixture to promote dispersion or to maintain dispersed particles in suspension. A good dispersant not only helps to provide good dispersion, but also good performance, stability and rheological properties. Therefore, dispersants are widely used in many applications such as coating, ink, electronic materials, plastics, and so on[1]. There are different ways to categorize the many dispersants available on the market. From a molec...

  20. Attenuated total reflectance FT-IR imaging and quantitative energy dispersive-electron probe X-ray microanalysis techniques for single particle analysis of atmospheric aerosol particles.

    Science.gov (United States)

    Ryu, JiYeon; Ro, Chul-Un

    2009-08-15

    This work demonstrates the practical applicability of the combined use of attenuated total reflectance (ATR) FT-IR imaging and low-Z particle electron probe X-ray microanalysis (EPMA) techniques for the characterization of individual aerosol particles. These two single particle analytical techniques provide complementary information on the physicochemical characteristics of the same individual particles, that is, the low-Z particle EPMA for the information on the morphology and elemental concentration and the ATR-FT-IR imaging on the functional group, molecular species, and crystal structure. It was confirmed that the ATR-FT-IR imaging technique can provide sufficient FT-IR absorption signals to perform molecular speciation of individual particles of micrometer size when applied to artificially generated aerosol particles such as ascorbic acid and NaNO(3) aerosols. An exemplar indoor atmospheric aerosol sample was investigated to demonstrate the practical feasibility of the combined application of ATR-FT-IR imaging and low-Z particle EPMA techniques for the characterization of individual airborne particles.

  1. Investigation of slice emittance using an energy-chirped electron beam in a dispersive section for photo injector characterization at PITZ

    Energy Technology Data Exchange (ETDEWEB)

    Ivanisenko, Yevgeniy

    2012-06-15

    This work describes a transverse slice emittance diagnostics with an RMS temporal resolution down to 2 ps that was implemented at the Photo Injector Test facility in Zeuthen (PITZ). The measurements were performed for several bunch charges generated by a laser pulse that has a flat-top temporal profile of 21-22 ps FWHM duration. This diagnostics allows to study the beam projected emittance compensation with a solenoid magnetic field experimentally and therefore contributes to the beam emittance optimization for the needs of short wavelength linac-based FELs in particular. The diagnostics is based upon the usage of electron bunches which have a correlation between the longitudinal position and the momentum of the bunch particles. This property allows to convert the bunch longitudinal distribution into a transverse one in a dipole magnet. A slit with a narrow opening at the dipole exit selects a fraction of the particle ensemble, a slice, which emittance is analyzed at a screen downstream. Slit scan and quadrupole scan techniques can be used to measure the emittance of the slices. In the experiments it was found that the slice emittance values are 5-10% lower than the projected emittance values, indicating a good effectivity of the solenoid compensation. The emittance obtained using quadrupole scan technique has shown different results when compared to slit scan technique due to a beam halo. The observed beam halo in phase space contributes up to 40% of the emittance value while having only 10% of the bunch charge.

  2. Low density solvent based dispersive liquid-liquid microextraction with gas chromatography-electron capture detection for the determination of cypermethrin in tissues and blood of cypermethrin treated rats.

    Science.gov (United States)

    Mudiam, Mohana Krishna Reddy; Jain, Rajeev; Maurya, Shailendra Kumar; Khan, Haider A; Bandyopadhyay, Sanghamitra; Murthy, R C

    2012-05-01

    A simple and rapid method to determine the cypermethrin (CYP) insecticide in rat tissues (kidney, liver and brain) and blood has been developed for the first time using low density solvent-dispersive liquid-liquid microextraction (LDS-DLLME) followed by gas chromatography-electron capture detector (GC-ECD) analysis. Initially, tissue samples containing CYP were homoginized in acetone. Subsequently, homogenate was mixed with n-hexane (extraction solvent) and the mixture was rapidly injected into water. The upper n-hexane layer was collected in a separate microtube and injected into GC-ECD for analysis. Blood samples were diluted with ultrapure water and subjected to DLLME through similar procedure. Parameters such as type and volume of disperser and extraction solvent, salting out effect and extraction time, which can affect the extraction efficiency of DLLME, were optimized. Method was validated by investigating linearity, precision, recovery, limit of detection (LOD) and quantification (LOQ). LODs in tissue were in the range of 0.043-0.314 ng mg(-1) and for blood it was 8.6 ng mL(-1) with a signal to noise ratio of 3:1. LOQs in tissue were in the range of 0.143-1.03 ng mg(-1) and for blood it was 28.3 ng mL(-1) with a signal to noise ratio of 10:1. Mean recoveries of CYP at three different concentation levels in all the matrices were found to be in the range of 81.6-103.67%. The results show that, LDS-DLLME coupled with GC-ECD offers a simple, rapid and efficient technique for extraction and determination of CYP in rat tissues and blood samples, which in turn would be useful for toxicological studies of CYP.

  3. Dispersion engineering of surface plasmons.

    Science.gov (United States)

    Mandel, Isroel M; Bendoym, Igor; Jung, Young U; Golovin, Andrii B; Crouse, David T

    2013-12-30

    In this work, it is shown how the shapes of surface plasmon dispersion curves can be engineered by manipulating the distribution of the electromagnetic fields in multilayer structures, which themselves are controlled by the free electron density in metal-like materials, such as doped semiconductors in the THz spectral range. By having a nonuniform free electron density profile, reduced relative to that in typical bulk metals, the electromagnetic fields of surface plasmons are distributed in different metallic materials that have different complex dielectric permittivities. As the in-plane component of surface plasmon's wave-vector increases, they become more confined to a particular layer of the multilayer structure and have energies that are predictable by considering the permittivity of the layer in which the fields are most concentrated. Unusual and arbitrary shapes of surface plasmon dispersion curves can be designed, including stair steps and dovetails shapes.

  4. Theoretical Magnon Dispersion Curves for Gd

    DEFF Research Database (Denmark)

    Lindgård, Per-Anker; Harmon, B. N.; Freeman, A. J.

    1975-01-01

    The magnon dispersion curve of Gd metal has been determined from first principles by use of augmented-plane-wave energy bands and wave functions. The exchange matrix elements I(k⃗, k⃗′) between the 4f electrons and the conduction electrons from the first six energy bands were calculated under...

  5. New insights into the chemical structure of Y2Ti2O7-δ nanoparticles in oxide dispersion-strengthened steels designed for sodium fast reactors by electron energy-loss spectroscopy

    Science.gov (United States)

    Badjeck, V.; Walls, M. G.; Chaffron, L.; Malaplate, J.; March, K.

    2015-01-01

    In this paper we study by high resolution scanning transmission electron microscopy coupled with electron energy-loss spectroscopy (STEM-EELS) an oxide dispersion-strengthened (ODS) steel with the nominal composition Fe-14Cr-1W-0.3TiH2-0.3Y2O3 (wt.%) designed to withstand the extreme conditions met in Gen. IV nuclear reactors. After denoising via principal component analysis (PCA) the data are analyzed using independent component analysis (ICA) which is useful in the investigation of the physical properties and chemical structure of the material by separating the individual spectral responses. The Y-Ti-O nanoparticles are found to be homogeneously distributed in the ferritic matrix, sized from 1 to 20 nm and match a non-stoichiometric pyrochlore-Y2Ti2O7-δ structure for sizes greater than 5 nm. We show that they adopt a (Y-Ti-O)-Cr core-shell structure and that Cr also segregates at the matrix grain boundaries, which may slightly modify the corrosion properties of the steel. Using Ti-L2,3 and O-K fine structure (ELNES) the Ti oxidation state is shown to vary from the center of the nanoparticles to their periphery, from Ti4+ in distorted Oh symmetry to a valency often lower than 3+. The sensitivity of the Ti "white lines" ELNES to local symmetry distortions is also shown to be useful when investigating the strain induced in the nanoparticles by the surrounding matrix. The Cr-shell and the variation of the Ti valence state highlight a complex nanoparticle-matrix interface.

  6. Elemental composition of strawberry plants inoculated with the plant growth-promoting bacterium Azospirillum brasilense REC3, assessed with scanning electron microscopy and energy dispersive X-ray analysis.

    Science.gov (United States)

    Guerrero-Molina, M F; Lovaisa, N C; Salazar, S M; Díaz-Ricci, J C; Pedraza, R O

    2014-07-01

    The elemental composition of strawberry plants (Fragaria ananassa cv. Macarena) inoculated with the plant growth-promoting bacterium Azospirillum brasilense REC3, and non-inoculated controls, was studied using scanning electron microscopy (SEM) and energy dispersive X-ray (EDS) analysis. This allowed simultaneous semi-quantification of different elements in a small, solid sample. Plants were inoculated and grown hydroponically in 50% or 100% Hoagland solution, corresponding to limited or optimum nutrient medium, respectively. Bacteria-inoculated plants increased the growth index 45% and 80% compared to controls when grown in 100% and 50% Hoagland solution, respectively. Thus, inoculation with A. brasilense REC3 in a nutrient-limited medium had the strongest effect in terms of increasing both shoot and root biomass and growth index, as already described for Azospirillum inoculated into nutrient-poor soils. SEM-EDS spectra and maps showed the elemental composition and relative distribution of nutrients in strawberry tissues. Leaves contained C, O, N, Na, P, K, Ca and Cu, while roots also had Si and Cl. The organic fraction (C, O and N) accounted for over 96.3% of the total chemical composition; of the mineral fraction, Na had higher accumulation in both leaves and roots. Azospirillum-inoculated and control plants had similar elemental quantities; however, in bacteria-inoculated roots, P was significantly increased (34.33%), which constitutes a major benefit for plant nutrition, while Cu content decreased (35.16%).

  7. Method development for analysis of urban dust using scanning electron microscopy with energy dispersive x-ray spectrometry to detect the possible presence of world trade center dust constituents

    Science.gov (United States)

    Bern, A.M.; Lowers, H.A.; Meeker, G.P.; Rosati, J.A.

    2009-01-01

    The collapse of the World Trade Center Towers on September 11, 2001, sent dust and debris across much of Manhattan and in the surrounding areas. Indoor and outdoor dust samples were collected and characterized by U.S. Geological Survey (USGS) scientists using scanning electron microscopy with energy-dispersive spectrometry (SEM/EDS). From this characterization, the U.S. Environmental Protection Agency and USGS developed a particulate screening method to determine the presence of residual World Trade Center dust in the indoor environment using slag wool as a primary "signature". The method describes a procedure that includes splitting, ashing, and sieving of collected dust. From one split, a 10 mg/mL dust/ isopropanol suspension was prepared and 10-30 ??L aliquots of the suspension placed on an SEM substrate. Analyses were performed using SEM/EDS manual point counting for slag wool fibers. Poisson regression was used to identify some of the sources of uncertainty, which are directly related to the small number of fibers present on each sample stub. Preliminary results indicate that the procedure is promising for screening urban background dust for the presence of WTC dust. Consistent sample preparation of reference materials and samples must be performed by each laboratory wishing to use this method to obtain meaningful and accurate results. ?? 2009 American Chemical Society.

  8. Scanning electron microscopy-energy dispersive X-ray spectrometry (SEM-EDX) and aerosol time-of-flight mass spectrometry (ATOFMS) single particle analysis of metallurgy plant emissions.

    Science.gov (United States)

    Arndt, J; Deboudt, K; Anderson, A; Blondel, A; Eliet, S; Flament, P; Fourmentin, M; Healy, R M; Savary, V; Setyan, A; Wenger, J C

    2016-03-01

    The chemical composition of single particles deposited on industrial filters located in three different chimneys of an iron-manganese (Fe-Mn) alloy manufacturing plant have been compared using aerosol time-of-flight mass spectrometry (ATOFMS) and scanning electron microscopy-energy dispersive X-ray spectrometry (SEM-EDX). Very similar types of particles were observed using both analytical techniques. Calcium-containing particles dominated in the firing area of the sintering unit, Mn and/or Al-bearing particles were observed at the cooling area of the sintering unit, while Mn-containing particles were dominant at the smelting unit. SEM-EDX analysis of particles collected downstream of the industrial filters showed that the composition of the particles emitted from the chimneys is very similar to those collected on the filters. ATOFMS analysis of ore samples was also performed to identify particulate emissions that could be generated by wind erosion and manual activities. Specific particle types have been identified for each emission source (chimneys and ore piles) and can be used as tracers for source apportionment of ambient PM measured in the vicinity of the industrial site.

  9. Field-emission scanning electron microscopy and energy-dispersive x-ray analysis to understand the role of tannin-based dyes in the degradation of historical wool textiles.

    Science.gov (United States)

    Restivo, Annalaura; Degano, Ilaria; Ribechini, Erika; Pérez-Arantegui, Josefina; Colombini, Maria Perla

    2014-10-01

    An innovative approach, combining field-emission scanning electron microscopy (FESEM) with energy dispersive X-ray spectroscopy (EDX) analysis, is presented to investigate the degradation mechanisms affecting tannin-dyed wool. In fact, tannin-dyed textiles are more sensitive to degradation then those dyed with other dyestuffs, even in the same conservation conditions. FESEM-EDX was first used to study a set of 48 wool specimens (artificially aged) dyed with several raw materials and mordants, and prepared according to historical dyeing recipes. EDX analysis was performed on the surface of wool threads and on their cross-sections. In addition, in order to validate the model formulated by the analysis of reference materials, several samples collected from historical and archaeological textiles were subjected to FESEM-EDX analysis. FESEM-EDX investigations enabled us to reveal the correlation between elemental composition and morphological changes. In addition, aging processes were clarified by studying changes in the elemental composition of wool from the protective cuticle to the fiber core in cross-sections. Morphological and elemental analysis of wool specimens and of archaeological and historical textiles showed that the presence of tannins increases wool damage, primarily by causing a sulfur decrease and fiber oxidation.

  10. Dispersing powders in liquids

    CERN Document Server

    Nelson, RD

    1988-01-01

    This book provides powder technologists with laboratory procedures for selecting dispersing agents and preparing stable dispersions that can then be used in particle size characterization instruments. Its broader goal is to introduce industrial chemists and engineers to the phenomena, terminology, physical principles, and chemical considerations involved in preparing and handling dispersions on a commercial scale. The book introduces novices to: - industrial problems due to improper degree of dispersion; - the nomenclature used in describing particles; - the basic physica

  11. Valence holes observed in nanodiamonds dispersed in water.

    Science.gov (United States)

    Petit, Tristan; Pflüger, Mika; Tolksdorf, Daniel; Xiao, Jie; Aziz, Emad F

    2015-02-21

    Colloidal dispersion is essential for most nanodiamond applications, but its influence on nanodiamond electronic properties remains unknown. Here we have probed the electronic structure of oxidized detonation nanodiamonds dispersed in water by using soft X-ray absorption and emission spectroscopies at the carbon and oxygen K edges. Upon dispersion in water, the π* transitions from sp(2)-hybridized carbon disappear, and holes in the valence band are observed.

  12. Dispersion y dinamica poblacional

    Science.gov (United States)

    Dispersal behavior of fruit flies is appetitive. Measures of dispersion involve two different parameter: the maximum distance and the standard distance. Standard distance is a parameter that describes the probalility of dispersion and is mathematically equivalent to the standard deviation around ...

  13. Seed dispersal in fens

    NARCIS (Netherlands)

    Middleton, Beth; van Diggelen, Rudy; Jensen, Kai

    2006-01-01

    Question: How does seed dispersal reduce fen isolation and contribute to biodiversity? Location: European and North American fens. Methods: This paper reviews the literature on seed dispersal to fens. Results: Landscape fragmentation may reduce dispersal opportunities thereby isolating fens and redu

  14. Dispersion based beam tilt correction

    CERN Document Server

    Guetg, Marc W; Prat, Eduard; Reiche, Sven

    2013-01-01

    In Free Electron Lasers (FEL), a transverse centroid misalignment of longitudinal slices in an electron bunch reduces the effective overlap between radiation field and electron bunch and therefore the FEL performance. The dominant sources of slice misalignments for FELs are the incoherent and coherent synchrotron radiation within bunch compressors as well as transverse wake fields in the accelerating cavities. This is of particular importance for over-compression which is required for one of the key operation modes for the SwissFEL planned at the Paul Scherrer Institute. The centroid shift is corrected using corrector magnets in dispersive sections, e.g. the bunch compressors. First and second order corrections are achieved by pairs of sextupole and quadrupole magnets in the horizontal plane while skew quadrupoles correct to first order in the vertical plane. Simulations and measurements at the SwissFEL Injector Test Facility are done to investigate the proposed correction scheme for SwissFEL. This paper pres...

  15. Conservation of Moroccan manuscript papers aged 150, 200 and 800 years. Analysis by infrared spectroscopy (ATR-FTIR), X-ray diffraction (XRD), and scanning electron microscopy energy dispersive spectrometry (SEM-EDS).

    Science.gov (United States)

    Hajji, Latifa; Boukir, Abdellatif; Assouik, Jamal; Lakhiari, Hamid; Kerbal, Abdelali; Doumenq, Pierre; Mille, Gilbert; De Carvalho, Maria Luisa

    2015-02-05

    The preservation of manuscripts and archive materials is a serious problem for librarians and restorers. Paper manuscript is subjected to numerous degradation factors affecting their conservation state. This research represents an attempt to evaluate the conservation restoration process applied in Moroccan libraries, especially the alkaline treatment for strengthening weakened paper. In this study, we focused on six samples of degraded and restored paper taken from three different Moroccan manuscripts aged 150, 200 and 800 years. In addition, the Japanese paper used in restoration has been characterized. A modern paper was also analyzed as reference. A three-step analytical methodology based on infrared spectroscopy (ATR-FTIR), X-ray diffraction (XRD) and scanning electron microscopy coupled to energy dispersive spectrometry (SEM-EDS) analysis was developed before and after restoration in order to determine the effect of the consolidation treatment on the paper structure. The results obtained by XRD and ATR-FTIR disclosed the presence of barium sulfate (BaSO4) in all restored paper manuscripts. The presence of calcium carbonate (CaCO3) in all considered samples was confirmed by FTIR spectroscopy. The application of de-acidification treatment causes significant changes connected with the increase of intensity mostly in the region 1426 cm(-1), assigned to the asymmetric and symmetric CO stretching mode of calcite, indicating the effectiveness of de-acidification procedure proved by the rise of the alkaline reserve content allowing the long term preservation of paper. Observations performed by SEM magnify the typical paper morphology and the structure of fibbers, highlighting the effect of the restoration process, manifested by the reduction of impurities.

  16. Dispersion management with metamaterials

    Energy Technology Data Exchange (ETDEWEB)

    Tassin, Philippe; Koschny, Thomas; Soukoulis, Costas M.

    2017-03-07

    An apparatus, system, and method to counteract group velocity dispersion in fibers, or any other propagation of electromagnetic signals at any wavelength (microwave, terahertz, optical, etc.) in any other medium. A dispersion compensation step or device based on dispersion-engineered metamaterials is included and avoids the need of a long section of specialty fiber or the need for Bragg gratings (which have insertion loss).

  17. Vowel dispersion in Truku

    OpenAIRE

    Chiang, Wen-yu; Chiang, Fang-mei

    2013-01-01

    This study investigates the dispersion of vowel space in Truku, an endangered Austronesian language in Taiwan. Adaptive Dispersion (Liljencrants and Lindblom, 1972; Lindblom, 1986, 1990) proposes that the distinctive sounds of a language tend to be positioned in phonetic space in a way that maximizes perceptual contrast. For example, languages with large vowel inventories tend to expand the overall acoustic vowel space. Adaptive Dispersion predicts that the distance between the point vowels w...

  18. Seed dispersal in fens

    Science.gov (United States)

    Middleton, B.; Van Diggelen, R.; Jensen, K.

    2006-01-01

    Question: How does seed dispersal reduce fen isolation and contribute to biodiversity? Location: European and North American fens. Methods: This paper reviews the literature on seed dispersal to fens. Results: Landscape fragmentation may reduce dispersal opportunities thereby isolating fens and reducing genetic exchange. Species in fragmented wetlands may have lower reproductive success, which can lead to biodiversity loss. While fens may have always been relatively isolated from each other, they have become increasingly fragmented in modern times within agricultural and urban landscapes in both Europe and North America. Dispersal by water, animals and wind has been hampered by changes related to development in landscapes surrounding fens. Because the seeds of certain species are long-lived in the seed bank, frequent episodes of dispersal are not always necessary to maintain the biodiversity of fens. However, of particular concern to restoration is that some dominant species, such as the tussock sedge Carex stricta, may not disperse readily between fens. Conclusions: Knowledge of seed dispersal can be used to maintain and restore the biodiversity of fens in fragmented landscapes. Given that development has fragmented landscapes and that this situation is not likely to change, the dispersal of seeds might be enhanced by moving hay or cattle from fens to damaged sites, or by reestablishing lost hydrological connections. ?? IAVS; Opulus Press.

  19. Visualizing Dispersion Interactions

    Science.gov (United States)

    Gottschalk, Elinor; Venkataraman, Bhawani

    2014-01-01

    An animation and accompanying activity has been developed to help students visualize how dispersion interactions arise. The animation uses the gecko's ability to walk on vertical surfaces to illustrate how dispersion interactions play a role in macroscale outcomes. Assessment of student learning reveals that students were able to develop…

  20. Visualizing Dispersion Interactions

    Science.gov (United States)

    Gottschalk, Elinor; Venkataraman, Bhawani

    2014-01-01

    An animation and accompanying activity has been developed to help students visualize how dispersion interactions arise. The animation uses the gecko's ability to walk on vertical surfaces to illustrate how dispersion interactions play a role in macroscale outcomes. Assessment of student learning reveals that students were able to develop…

  1. Perfect Dispersive Medium

    CERN Document Server

    Gupta, Shulabh

    2015-01-01

    Dispersion is at the heart of all ultrafast real-time signal processing systems across the entire electromagnetic spectrum ranging from radio-frequencies to optics. However, following Kramer-Kronig relations, these signal processing systems have been plagued with the parasitic amplitude distortions due to frequency dependent, and non-flat amplitude transmission of naturally dispersive media. This issue puts a serious limitation on the applicability and performance of these signal processing systems. To solve the above mentioned issue, a perfect dispersive medium is proposed in this work, which artificially violates the Kramer-Kronig relations, while satisfying all causality requirements. The proposed dispersive metamaterial is based on loss-gain metasurface pairs and exhibit a perfectly flat transmission response along with arbitrary dispersion in a broad bandwidth, thereby solving a seemingly unavoidable issue in all ultrafast signal processing systems. Such a metamaterial is further shown using sub-waveleng...

  2. Evolution of dispersal distance.

    Science.gov (United States)

    Durrett, Rick; Remenik, Daniel

    2012-03-01

    The problem of how often to disperse in a randomly fluctuating environment has long been investigated, primarily using patch models with uniform dispersal. Here, we consider the problem of choice of seed size for plants in a stable environment when there is a trade off between survivability and dispersal range. Ezoe (J Theor Biol 190:287-293, 1998) and Levin and Muller-Landau (Evol Ecol Res 2:409-435, 2000) approached this problem using models that were essentially deterministic, and used calculus to find optimal dispersal parameters. Here we follow Hiebeler (Theor Pop Biol 66:205-218, 2004) and use a stochastic spatial model to study the competition of different dispersal strategies. Most work on such systems is done by simulation or nonrigorous methods such as pair approximation. Here, we use machinery developed by Cox et al. (Voter model perturbations and reaction diffusion equations 2011) to rigorously and explicitly compute evolutionarily stable strategies.

  3. Finite element analysis of lumbar pelvic and proximal femur model with simulate lumbar rotatory manipulation%旋转手法对腰椎骨盆和股骨上端结构有限元模型的分析

    Institute of Scientific and Technical Information of China (English)

    胡华; 熊昌源; 韩国武

    2012-01-01

    目的:研究腰椎旋转手法时腰椎骨盆和股骨上端各结构位移和应力的特点.方法:使用腰椎CT片,以Mimics 10.01软件建立腰椎骨盆和股骨上端几何模型,经Geomagic 9对模型进行修改后导入Hypermesh 10划分4面体网格并添加椎间盘与韧带.根据手法作用原理,将腰椎旋转手法进行分解,把各项力学参数导入三维有限元模型.利用Abaqus求解模块对4工况下模型的位移和应力进行计算分析,得到腰椎旋转手法作用时腰椎骨盆和股骨上端各结构位移和应力的变化.结果:①相同工况下腰椎位移的大小顺序是:L1>L2>L3>L4>L5,前柱>中柱>后柱.②不同工况下腰椎的位移大小顺序是:工况3>工况1>工况4>工况2.③相同工况下椎间盘从L1,2-L5S1各椎间盘位移大小顺序是:L1,2>L2,3>L3,4>L4,5>L5S1,同一椎间盘内各象限位移大小顺序为:第2象限>第3象限>第1象限>第4象限.④不同工况下各椎间盘的位移大小顺序是:L1,2>L2,3>L3,4>L4.5> L5S1,同一椎间盘不同工况下位移大小顺序是:工况3>工况4>工况1>工况2.⑤骨盆和髋关节在手法作用过程中存在明显的位移和应力集中.结论:①旋转手法的作用原理与腰椎骨盆和股骨上端各相应解剖部位因旋转而引起的相对位移有关;②在手法的操作过程中,不能随意加大侧弯和前屈的角度;③在腰椎旋转手法的施术过程中,必须综合考虑腰椎骨盆和股骨上端各部位的具体情况以确定适应证和禁忌证.%Objective: To study the changes of displacement and stress in the model of lumbar pelvic and proximal femur during lumbar rotatory manipulation. MethodS:The date of lumbar pelvic and proximal femur CT scan by Mimics 10.01 software was established a lumbar pelvic and proximal femur geometric model, then the model was modified with Geomagic 9, at last the modified model was imported into hypermesh 10 and meshed with

  4. Nondestructive characterization of municipal-solid-waste-contaminated surface soil by energy-dispersive X-ray fluorescence and low-Z (atomic number) particle electron probe X-ray microanalysis.

    Science.gov (United States)

    Gupta, Dhrubajyoti; Ghosh, Rita; Mitra, Ajoy K; Roy, Subinit; Sarkar, Manoranjan; Chowdhury, Subhajit; Bhowmik, Asit; Mukhopadhyay, Ujjal; Maskey, Shila; Ro, Chul-Un

    2011-11-01

    The long-term environmental impact of municipal solid waste (MSW) landfilling is still under investigation due to the lack of detailed characterization studies. A MSW landfill site, popularly known as Dhapa, in the eastern fringe of the metropolis of Kolkata, India, is the subject of present study. A vast area of Dhapa, adjoining the current core MSW dump site and evolving from the raw MSW dumping in the past, is presently used for the cultivation of vegetables. The inorganic chemical characteristics of the MSW-contaminated Dhapa surface soil (covering a 2-km stretch of the area) along with a natural composite (geogenic) soil sample (from a small countryside farm), for comparison, were investigated using two complementary nondestructive analytical techniques, energy-dispersive X-ray fluorescence (EDXRF) for bulk analysis and low-Z (atomic number) particle electron probe X-ray microanalysis (low-Z particle EPMA) for single-particle analysis. The bulk concentrations of K, Rb, and Zr remain almost unchanged in all the soil samples. The Dhapa soil is found to be polluted with heavy metals such as Cu, Zn, and Pb (highly elevated) and Ti, Cr, Mn, Fe, Ni, and Sr (moderately elevated), compared to the natural countryside soil. These high bulk concentration levels of heavy metals were compared with the Ecological Soil Screening Levels for these elements (U.S. Environment Protection Agency) to assess the potential risk on the immediate biotic environment. Low-Z particle EPMA results showed that the aluminosilicate-containing particles were the most abundant, followed by SiO2, CaCO3-containing, and carbonaceous particles in the Dhapa samples, whereas in the countryside sample only aluminosilicate-containing and SiO2 particles were observed. The mineral particles encountered in the countryside sample are solely of geogenic origin, whereas those from the Dhapa samples seem to have evolved from a mixture of raw dumped MSW, urban dust, and other contributing factors such as wind

  5. Energy-dispersed ions in the plasma sheet boundary layer and associated phenomena: Ion heating, electron acceleration, Alfvén waves, broadband waves, perpendicular electric field spikes, and auroral emissions

    Directory of Open Access Journals (Sweden)

    A. Keiling

    2006-10-01

    Full Text Available Recent Cluster studies reported properties of multiple energy-dispersed ion structures in the plasma sheet boundary layer (PSBL that showed substructure with several well separated ion beamlets, covering energies from 3 keV up to 100 keV (Keiling et al., 2004a, b. Here we report observations from two PSBL crossings, which show a number of identified one-to-one correlations between this beamlet substructure and several plasma-field characteristics: (a bimodal ion conics (<1 keV, (b field-aligned electron flow (<1 keV, (c perpendicular electric field spikes (~20 mV/m, (d broadband electrostatic ELF wave packets (<12.5 Hz, and (e enhanced broadband electromagnetic waves (<4 kHz. The one-to-one correlations strongly suggest that these phenomena were energetically driven by the ion beamlets, also noting that the energy flux of the ion beamlets was 1–2 orders of magnitude larger than, for example, the energy flux of the ion outflow. In addition, several more loosely associated correspondences were observed within the extended region containing the beamlets: (f electrostatic waves (BEN (up to 4 kHz, (g traveling and standing ULF Alfvén waves, (h field-aligned currents (FAC, and (i auroral emissions on conjugate magnetic field lines. Possible generation scenarios for these phenomena are discussed. In conclusion, it is argued that the free energy of magnetotail ion beamlets drove a variety of phenomena and that the spatial fine structure of the beamlets dictated the locations of where some of these phenomena occurred. This emphasizes the notion that PSBL ion beams are important for magnetosphere-ionosphere coupling. However, it is also shown that the dissipation of electromagnetic energy flux (at altitudes below Cluster of the simultaneously occurring Alfvén waves and FAC was larger (FAC being the largest than the dissipation of beam kinetic energy flux, and thus these two energy carriers contributed more to the energy transport on PSBL field lines

  6. Preparation of natural brucite nanofibers by the dispersion method

    Institute of Scientific and Technical Information of China (English)

    Li Xu; Wen Ni; Wenping Li; Xingde Liu; Hailong Yang; Xiaoguang Yang

    2008-01-01

    The preparation of natural brucite nanofibers through dispersion by the wet process is described. The test results indicate that brucite fibers can be well dispersed by using sodium dioctyl sulfosuccinate (OT) as the dispersant at a dispersant/fiber mass ratio of 0.15:1, dispersing for 30 min at a water/solid mass ratio of 20:1. The prepared nanofibers were characterized with X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscope (TEM). It is shown that the prepared single brucite nanofiber is around 30 run in diameter and the talus of the nonsingle brucite nanofibers is about 50-150 nm in diameter. Natural brucite mineral fibers were treated by the dispersion method to obtain nanomaterials. These fibers have significant advantages over artificial nanofibers both in yield and in cost.

  7. Dipolar structures in colloidal magnetite dispersions

    NARCIS (Netherlands)

    Klokkenburg, Mark

    2007-01-01

    Dipolar structures in liquid colloidal dispersions comprising well-defined magnetite (Fe3O4) nanoparticles with a permanent magnetic dipole moment are analyzed on a single-particle level by in situ cryogenic transmission electron microscopy (2D). Compared to conventional ferrofluids, these dispersio

  8. Dipolar structures in colloidal magnetite dispersions

    NARCIS (Netherlands)

    Klokkenburg, Mark

    2007-01-01

    Dipolar structures in liquid colloidal dispersions comprising well-defined magnetite (Fe3O4) nanoparticles with a permanent magnetic dipole moment are analyzed on a single-particle level by in situ cryogenic transmission electron microscopy (2D). Compared to conventional ferrofluids, these dispersio

  9. Clinical Observation on TuiNa and Rotatory Manual Reduction in Treating Lumbar Disc Herniation%推拿结合旋转复位手法治疗腰椎间盘突出症的临床观察

    Institute of Scientific and Technical Information of China (English)

    张沛桃

    2012-01-01

    Objective: To explore clinical effects of TuiNa and rotatory manual reduction in treating lumbar disc herniation (LDH). Method: A total of 100 patients with LDH were randomly divided into treatment group and control group, 50 cases each group. Treatment group were given with manipulation including kneading, one-finger pushing manipulation to relax muscles and ligament, point-pressing manipulation at acupoints of She Shu (BL23), DaChangShu (BL25), HuanTiao(GB30), WeiZhong (BL40), KunLun(BL60) and others, fixed rotatory manual reduction and traction, traction weight from 30 to 60 kg, 30 min once, once per day, one session was 15 days, the interval was one to two days. Control group received traction. Clinical effects of both groups and changes of visual analogue scale (VAS) before and after treating were observed. Result: Cure rate of treatment group was 76.00%, higher than 50.00% of control group with statistical meaning (P<0.05); total effective rate of treatment group was 96.00%, superior to 74.00% of control group with statistical meaning (P<0.05). VAS of both groups after treating decreased compared with that before treating with statistical meaning (P<0.05); comparison between both groups suggested statistical meaning after the treatment (P<0.05). Conclusion: TuiNa and rotatory manual reduction can obtain notable clinical effects and can obviously alleviate the pain in treating LDH.%目的:观察推拿结合旋转复位手法治疗腰椎间盘突出症(LDH)的临床疗效.方法:将符合病例入选标准的100例LDH 患者随机分为治疗组、对照组各50 例.治疗组患者先用揉、一指禅推法等放松腰臀腿部肌肉韧带,同时在肾俞、大肠俞、环跳、委中、昆仑等穴位给予点按手法,再行定点旋转复位术,同时给予牵引治疗,牵引质量30~60 kg,30 min/次,1次/d,治疗15 天,中间休息1~2 天.对照组给予牵引治疗(方法同治疗组).观察2组临床疗效及治疗前后疼痛评分变化情况.结

  10. Rates of Gravel Dispersion

    Science.gov (United States)

    Haschenburger, J. K.

    2010-12-01

    Sediment transfers in gravel-bed rivers involve the three-dimensional dispersion of mixed size sediment. From a kinematics standpoint, few studies are available to inform on the streamwise and vertical rates of sediment dispersion in natural channels. This research uses a gravel tracing program to quantify dispersion rates over 19 flood seasons. Empirical observations come from Carnation Creek, a small gravel-bed river with large woody debris located on the west coast of Vancouver Island, Canada. Frequent floods and the relatively limited armor layer facilitate streambed activity and relatively high bedload transport rates, typically under partial sediment transport conditions. Over 2500 magnetically tagged stones, ranging in size from 16 to 180 mm, were deployed on the bed surface between 1989 and 1992 in four generations. To quantify gravel dispersion over distances up to 2.6 km, observations are taken from 11 recoveries. Over 280 floods capable of moving bedload occurred during this period, with five exceeding the estimated bankfull discharge. Streamwise dispersion is quantified by virtual velocity, while dispersion into the streambed is quantified by a vertical burial rate. The temporal trend in streamwise dispersion rates is described by a power function. Initial virtual velocities decline rapidly from around 1.4 m/hr to approach an asymptote value of about 0.2 m/hr. The rapid change corresponds to a significant increase in the proportion of buried tracers due to vertical mixing. Initial burial rates reflect the magnitude of the first flood after tracer deployment and range from 0.07 to 0.46 cm/hr depending on tracer generation. Burial rates converge to about 0.06 cm/hr after the fourth flood season and then gradually decline to about 0.01 cm/hr. Thus, the rate of streamwise dispersion exceeds that of vertical dispersion by three orders of magnitude when the movement of sediment routinely activated by floods is considered.

  11. Dispersive hydrodynamics: Preface

    Science.gov (United States)

    Biondini, G.; El, G. A.; Hoefer, M. A.; Miller, P. D.

    2016-10-01

    This Special Issue on Dispersive Hydrodynamics is dedicated to the memory and work of G.B. Whitham who was one of the pioneers in this field of physical applied mathematics. Some of the papers appearing here are related to work reported on at the workshop "Dispersive Hydrodynamics: The Mathematics of Dispersive Shock Waves and Applications" held in May 2015 at the Banff International Research Station. This Preface provides a broad overview of the field and summaries of the various contributions to the Special Issue, placing them in a unified context.

  12. Influence of dispersant on Y_2O_3:Eu~(3+) powders synthesized by combustion method

    Institute of Scientific and Technical Information of China (English)

    王超男; 赵江波; 李勇; 张慰萍; 尹民

    2009-01-01

    Y2O3:Eu3+ powders were synthesized by combustion method and the influence of dispersant was investigated.XRD analysis indicated that the particle size increased with a small amount of dispersant firstly and then decreased with a further increase of dispersant.The morphologies of the powders were studied by scanning electron microscopy(SEM) and high-resolution transmission electron microscopy(HRTEM).SEM images revealed that an appropriate amount of dispersant could reduce the agglomeration significantly.Due ...

  13. Dispersion forces in methane

    NARCIS (Netherlands)

    Lekkerkerker, H.N.W.; Coulon, P.; Luyckx, R.

    1977-01-01

    The coefficients of the R-6 and R-7 terms in the series representation of the dispersion interaction between two methane molecules and between methane and helium, neon and argon are calculated by a variation method.

  14. Fickian dispersion is anomalous

    Science.gov (United States)

    Cushman, John H.; O'Malley, Dan

    2015-12-01

    The thesis put forward here is that the occurrence of Fickian dispersion in geophysical settings is a rare event and consequently should be labeled as anomalous. What people classically call anomalous is really the norm. In a Lagrangian setting, a process with mean square displacement which is proportional to time is generally labeled as Fickian dispersion. With a number of counter examples we show why this definition is fraught with difficulty. In a related discussion, we show an infinite second moment does not necessarily imply the process is super dispersive. By employing a rigorous mathematical definition of Fickian dispersion we illustrate why it is so hard to find a Fickian process. We go on to employ a number of renormalization group approaches to classify non-Fickian dispersive behavior. Scaling laws for the probability density function for a dispersive process, the distribution for the first passage times, the mean first passage time, and the finite-size Lyapunov exponent are presented for fixed points of both deterministic and stochastic renormalization group operators. The fixed points of the renormalization group operators are p-self-similar processes. A generalized renormalization group operator is introduced whose fixed points form a set of generalized self-similar processes. Power-law clocks are introduced to examine multi-scaling behavior. Several examples of these ideas are presented and discussed.

  15. Interaction Study of an Amorphous Solid Dispersion of Cyclosporin A in Poly-Alpha-Cyclodextrin with Model Membranes by 1H-, 2H-, 31P-NMR and Electron Spin Resonance

    Directory of Open Access Journals (Sweden)

    Jean-Claude Debouzy

    2014-01-01

    Full Text Available The properties of an amorphous solid dispersion of cyclosporine A (ASD prepared with the copolymer alpha cyclodextrin (POLYA and cyclosporine A (CYSP were investigated by 1H-NMR in solution and its membrane interactions were studied by 1H-NMR in small unilamellar vesicles and by 31P 2H NMR in phospholipidic dispersions of DMPC (dimyristoylphosphatidylcholine in comparison with those of POLYA and CYSP alone. 1H-NMR chemical shift variations showed that CYSP really interacts with POLYA, with possible adduct formation, dispersion in the solid matrix of the POLYA, and also complex formation. A coarse approach to the latter mechanism was tested using the continuous variations method, indicating an apparent 1 : 1 stoichiometry. Calculations gave an apparent association constant of log Ka = 4.5. A study of the interactions with phospholipidic dispersions of DMPC showed that only limited interactions occurred at the polar head group level (31P. Conversely, by comparison with the expected chain rigidification induced by CYSP, POLYA induced an increase in the fluidity of the layer while ASD formation led to these effects almost being overcome at 298 K. At higher temperature, while the effect of CYSP seems to vanish, a resulting global increase in chain fluidity was found in the presence of ASD.

  16. The Function of the Magnetic-Optic Modulation in the Very Small Rotatory Angle of Polarization%磁光调制技术在光偏振微小旋转角精密测量中的应用

    Institute of Scientific and Technical Information of China (English)

    钱小陵; 常悦

    2001-01-01

    An experimental device is introduced which improves themeasurement accuracy of polarimetry very small rotatory angle of polarization to the magnitude of 10-4 degree by applying the magnetic-optic modulation. The working principles of the device is described in details and the data obtained from the experiment is also provided%提供了一种实验装置,在光偏振微小旋转角的测量中,应用磁光调制技术,对薄膜样品的克尔效应、药物原料的旋光效应和化学试剂的费尔德常数进行了观测、测量.其中在费尔德常数的测量中,精度达到了亚毫度的数量级.详细介绍了该装置的工作原理,以及在实验中获得的数据.

  17. Coping with power dispersion?

    DEFF Research Database (Denmark)

    2014-01-01

    The last decades have witnessed a significant shift in policy competences away from central governments in Europe. The reallocation of competences spans over three dimensions: upwards; sideways; and downwards. This collection takes the dispersion of powers as a starting point and seeks to assess...... how the actors involved cope with the new configurations. In this introduction, we discuss the conceptualization of power dispersion and highlight the ways in which the contributions add to this research agenda. We then outline some general conclusions and end by indicating future avenues of research...

  18. Valence holes observed in nanodiamonds dispersed in water

    Science.gov (United States)

    Petit, Tristan; Pflüger, Mika; Tolksdorf, Daniel; Xiao, Jie; Aziz, Emad F.

    2015-02-01

    Colloidal dispersion is essential for most nanodiamond applications, but its influence on nanodiamond electronic properties remains unknown. Here we have probed the electronic structure of oxidized detonation nanodiamonds dispersed in water by using soft X-ray absorption and emission spectroscopies at the carbon and oxygen K edges. Upon dispersion in water, the π* transitions from sp2-hybridized carbon disappear, and holes in the valence band are observed.Colloidal dispersion is essential for most nanodiamond applications, but its influence on nanodiamond electronic properties remains unknown. Here we have probed the electronic structure of oxidized detonation nanodiamonds dispersed in water by using soft X-ray absorption and emission spectroscopies at the carbon and oxygen K edges. Upon dispersion in water, the π* transitions from sp2-hybridized carbon disappear, and holes in the valence band are observed. Electronic supplementary information (ESI) available: Experimental methods, details on XAS/XES normalization and background correction procedures. See DOI: 10.1039/c4nr06639a

  19. Cotton Effect in Copper-Proline Complexes in the Visible Region

    Science.gov (United States)

    Volkov, Victor; Pfister, Rolf

    2005-01-01

    The electronic properties of Cu(II) complex with proline are considered to demonstrate the Cotton effect in the visible region. A series of experiments in optical rotatory dispersion spectroscopy with free D- and L-proline and their complexes with the Cu(II) ion in aqueous solution is suggested.

  20. NEXT Ion Thruster Performance Dispersion Analyses

    Science.gov (United States)

    Soulas, George C.; Patterson, Michael J.

    2008-01-01

    The NEXT ion thruster is a low specific mass, high performance thruster with a nominal throttling range of 0.5 to 7 kW. Numerous engineering model and one prototype model thrusters have been manufactured and tested. Of significant importance to propulsion system performance is thruster-to-thruster performance dispersions. This type of information can provide a bandwidth of expected performance variations both on a thruster and a component level. Knowledge of these dispersions can be used to more conservatively predict thruster service life capability and thruster performance for mission planning, facilitate future thruster performance comparisons, and verify power processor capabilities are compatible with the thruster design. This study compiles the test results of five engineering model thrusters and one flight-like thruster to determine unit-to-unit dispersions in thruster performance. Component level performance dispersion analyses will include discharge chamber voltages, currents, and losses; accelerator currents, electron backstreaming limits, and perveance limits; and neutralizer keeper and coupling voltages and the spot-to-plume mode transition flow rates. Thruster level performance dispersion analyses will include thrust efficiency.

  1. Dispersion Distance and the Matter Distribution of the Universe in Dispersion Space.

    Science.gov (United States)

    Masui, Kiyoshi Wesley; Sigurdson, Kris

    2015-09-18

    We propose that "standard pings," brief broadband radio impulses, can be used to study the three-dimensional clustering of matter in the Universe even in the absence of redshift information. The dispersion of radio waves as they travel through the intervening plasma can, like redshift, be used as a cosmological distance measure. Because of inhomogeneities in the electron density along the line of sight, dispersion is an imperfect proxy for radial distance and we show that this leads to calculable dispersion-space distortions in the apparent clustering of sources. Fast radio bursts (FRBs) are a new class of radio transients that are the prototypical standard ping and, due to their high observed dispersion, have been interpreted as originating at cosmological distances. The rate of fast radio bursts has been estimated to be several thousand over the whole sky per day and, if cosmological, the sources of these events should trace the large-scale structure of the Universe. We calculate the dispersion-space power spectra for a simple model where electrons and FRBs are biased tracers of the large-scale structure of the Universe, and we show that the clustering signal could be measured using as few as 10 000 events. Such a survey is in line with what may be achieved with upcoming wide-field radio telescopes.

  2. Exchange Coulomb interaction in nanotubes: Dispersion of Langmuir waves

    CERN Document Server

    Andreev, P A

    2015-01-01

    Microscopic derivation of the Coulomb exchange interaction for electrons located on the nanotubes is presented. Our derivation is based on the many-particle quantum hydrodynamic method. We demonstrate the role of the curvature of the nanocylinders on the force of the exchange interaction. We calculate corresponding dispersion dependencies for electron oscillations on the nanotubes.

  3. Individual dispersion of synthetic imogolite nanotubes via droplet evaporation

    Institute of Scientific and Technical Information of China (English)

    YANG HuiXian; SU ZhaoHui

    2007-01-01

    Morphology of synthetic imogolite nanotubes formed in droplet evaporation was investigated by transmission electron microscopy and electron diffraction. The nanotubes form a dense entangled network at higher concentrations, while at lower concentrations the nanotubes are liable to form oriented bundles. Under enthanol atmosphere, individual dispersion of nanotubes was observed for the first time, which reveals the length polydispersity of synthetic imogolite nanotubes.

  4. Large, dispersive photoelectron Fermi edge and the electronic structure of YBa/sub 2/Cu/sub 3/O/sub 6. 9/ single crystals measured at 20 K

    Energy Technology Data Exchange (ETDEWEB)

    Arko, A. J.; List, R. S.; Bartlett, R. J.; Cheong, S.; Fisk, Z.; Thompson, J. D.; Olson, C. G.; Yang, A.; Liu, R.; Gu, C.; and others

    1989-08-01

    We have performed angle-integrated photoemission measurements at 20 K on well-oxygenated (/ital T//sub /ital c//=92 K) single crystals of YBa/sub 2/Cu/sub 3/O/sub 6.9/ cleaved /ital n/ /ital situ/, and find a relatively large, resolution-limited Fermi edge which shows large amplitude variations with photon energy, indicative of band-structure final-state effects. Some dispersion is seen even in our angle-integrated measurements. Our best estimate of /ital N/(/ital E//sub /ital F//) per Cu atom is that it is about 20% that of Cu metal with about a 20-80 mix of Cu 3/ital d/ and O 2/ital p/ orbitals. Dispersive and final-state effects are seen throughout the valence bands. The line shapes of the spectra as a function of photon energy are very well reproduced by band-structure predictions, indicating a correct mix of 2/ital p/ and 3/ital d/ orbitals in the calculations, while the energy positions of the peak agree with calculated bands to within /approx/0.5 eV. We conclude that a Fermi-liquid approach to conductivity is appropriate.

  5. Nanocrystals for electronics.

    Science.gov (United States)

    Panthani, Matthew G; Korgel, Brian A

    2012-01-01

    Semiconductor nanocrystals are promising materials for low-cost large-area electronic device fabrication. They can be synthesized with a wide variety of chemical compositions and size-tunable optical and electronic properties as well as dispersed in solvents for room-temperature deposition using various types of printing processes. This review addresses research progress in large-area electronic device applications using nanocrystal-based electrically active thin films, including thin-film transistors, light-emitting diodes, photovoltaics, and thermoelectrics.

  6. Compensation of chromatic and polarization mode dispersion in fiber-optic communication lines in microwave signals transmittion.

    Science.gov (United States)

    Ermolaev, A. N.; Krishpents, G. P.; Davydov, V. V.; Vysoczkiy, M. G.

    2016-08-01

    Methods of dispersion compensation in fiber-optic communication lines. A new proposed method of electronic dispersion compensation in the transmission of microwave signals through fiber-optic lines. Represents is proposed the results of experimental studies of this method.

  7. Spatially Dispersed Employee Recovery

    DEFF Research Database (Denmark)

    Hvass, Kristian Anders; Torfadóttir, Embla

    2014-01-01

    Employee recovery addresses either employee well-being or management's practices in aiding employees in recovering themselves following a service failure. This paper surveys the cabin crew at a small, European, low-cost carrier and investigates employees' perceptions of management practices to aid...... personnel achieve service recovery. Employee recovery within service research often focuses on front-line employees that work in a fixed location, however a contribution to the field is made by investigating the recovery of spatially dispersed personnel, such as operational personnel in the transport sector......, who have a work place away from a fixed or central location and have minimal management contact. Results suggest that the support employees receive from management, such as recognition, information sharing, training, and strategic awareness are all important for spatially dispersed front...

  8. Light dispersion in space

    Science.gov (United States)

    Barbosa, L. C.

    2015-09-01

    Considering an idea of F. Arago in 1853 regarding light dispersion through the light ether in the interstellar space, this paper presents a new idea on an alternative interpretation of the cosmological red shift of the galaxies in the universe. The model is based on an analogy with the temporal material dispersion that occurs with light in the optical fiber core. Since intergalactic space is transparent, according to the model, this phenomenon is related to the gravitational potential existing in the whole space. Thus, it is possible to find a new interpretation to Hubble's constant. In space, light undergoes a dispersion process in its path, which is interpreted by a red shift equation of the type Δz = HL, since H = (d2n/dλ2 Δv Δλ), where H means the Hubble constant, n is the refractive index of the intergalactic space, Δλ is the spectral width of the extragalactic source, and Δv is the variation of the speed of light caused by the gravitational potential. We observe that this "constant" is governed by three new parameters. Light traveling the intergalactic space undergoes red shift due to this mechanism, while light amplitude decreases with time, and the wavelength always increases, thus producing the same type of behavior given by Hubble's Law. It can be demonstrated that the dark matter phenomenon is produced by the apparent speed of light of the stars on the periphery of the galaxies, without the existence of dark energy. Based on this new idea, the model of the universe is static, lacking expansion. Other phenomena may be interpreted based on this new model of the universe. We have what we call temporal gravitational dispersion of light in space produced by the variations of the speed of light, due to the presence of the gravitational potential in the whole space.

  9. Disabling Radiological Dispersal Terror

    Energy Technology Data Exchange (ETDEWEB)

    Hart, M

    2002-11-08

    Terror resulting from the use of a radiological dispersal device (RDD) relies upon an individual's lack of knowledge and understanding regarding its significance. Disabling this terror will depend upon realistic reviews of the current conservative radiation protection regulatory standards. It will also depend upon individuals being able to make their own informed decisions merging perceived risks with reality. Preparation in these areas will reduce the effectiveness of the RDD and may even reduce the possibility of its use.

  10. A new chiral residue analysis method for triazole fungicides in water using dispersive liquid-liquid microextraction (DLLME).

    Science.gov (United States)

    Luo, Mai; Liu, Donghui; Zhou, Zhiqiang; Wang, Peng

    2013-09-01

    A rapid, simple, reliable, and environment-friendly method for the residue analysis of the enantiomers of four chiral fungicides including hexaconazole, triadimefon, tebuconazole, and penconazole in water samples was developed by dispersive liquid-liquid microextraction (DLLME) pretreatment followed by chiral high-performance liquid chromatography (HPLC)-DAD detection. The enantiomers were separated on a Chiralpak IC column by HPLC applying n-hexane or petroleum ether as mobile phase and ethanol or isopropanol as modifier. The influences of mobile phase composition and temperature on the resolution were investigated and most of the enantiomers could be completely separated in 20 min under optimized conditions. The thermodynamic parameters indicated that the separation was enthalpy-driven. The elution orders were detected by both circular dichroism detector (CD) and optical rotatory dispersion detector (ORD). Parameters affecting the DLLME performance for pretreatment of the chiral fungicides residue in water samples, such as the extraction and dispersive solvents and their volume, were studied and optimized. Under the optimum microextraction condition the enrichment factors were over 121 and the linearities were 30-1500 µg L(-1) with the correlation coefficients (R(2)) over 0.9988 and the recoveries were between 88.7% and 103.7% at the spiking levels of 0.5, 0.25, and 0.05 mg L(-1) (for each enantiomer) with relative standard deviations varying from 1.38% to 6.70% (n = 6) The limits of detection (LODs) ranged from 8.5 to 29.0 µg L(-1) (S/N = 3).

  11. Stable zinc oxide nanoparticle dispersions in ionic liquids

    Science.gov (United States)

    Wittmar, Alexandra; Gautam, Devendraprakash; Schilling, Carolin; Dörfler, Udo; Mayer-Zaika, Wolfgang; Winterer, Markus; Ulbricht, Mathias

    2014-05-01

    The influence of the hydrophilicity and length of the cation alkyl chain in imidazolium-based ionic liquids on the dispersability of ZnO nanoparticles by ultrasound treatment was studied by dynamic light scattering and advanced rheology. ZnO nanopowder synthesized by chemical vapor synthesis was used in parallel with one commercially available material. Before preparation of the dispersion, the nanoparticles characteristics were determined by transmission electron microscopy, X-ray diffraction, nitrogen adsorption with BET analysis, and FT-IR spectroscopy. Hydrophilic ionic liquids dispersed all studied nanopowders better and in the series of hydrophilic ionic liquids, an improvement of the dispersion quality with increasing length of the alkyl chain of the cation was observed. Especially, for ionic liquids with short alkyl chain, additional factors like nanoparticle concentration in the dispersion and the period of the ultrasonic treatment had significant influence on the dispersion quality. Additionally, nanopowder characteristics (crystallite shape and size as well as the agglomeration level) influenced the dispersion quality. The results indicate that the studied ionic liquids are promising candidates for absorber media at the end of the gas phase synthesis reactor allowing the direct preparation of non-agglomerated nanoparticle dispersions without supplementary addition of dispersants and stabilizers.

  12. Nozzle for electric dispersion reactor

    Science.gov (United States)

    Sisson, Warren G.; Basaran, Osman A.; Harris, Michael T.

    1995-01-01

    A nozzle for an electric dispersion reactor includes two concentric electrodes, the inner one of the two delivering disperse phase fluid into a continuous phase fluid. A potential difference generated by a voltage source creates a dispersing electric field at the end of the inner electrode.

  13. Dispersion of oil into water using lecithin-Tween 80 blends: The role of spontaneous emulsification.

    Science.gov (United States)

    Riehm, David A; Rokke, David J; Paul, Prakash G; Lee, Han Seung; Vizanko, Brent S; McCormick, Alon V

    2017-02-01

    Lecithin-rich mixtures of the nontoxic surfactants lecithin and Tween 80 are effective marine oil spill dispersants, but produce much higher oil-water interfacial tension than other, comparably effective dispersants. This suggests interfacial phenomena other than interfacial tension influence lecithin-Tween 80 dispersants' effectiveness. The interface between seawater and dispersant-crude oil mixtures was studied using light microscopy, cryogenic scanning electron microscopy, and droplet coalescence tests. Lecithin:Tween 80 ratio was varied from 100:0 to 0:100 and wt% dispersant in the oil was varied from 1.25 to 10wt%. Tween 80-rich dispersants cause oil-into-water spontaneous emulsification, while lecithin-rich dispersants primarily cause water-into-oil spontaneous emulsification. Possible mechanisms for this spontaneous emulsification are discussed, in light of images of spontaneously emulsifying interfaces showing no bursting microstructures, interfacial gel, or phase inversion, and negligible interfacial turbulence. Dispersant loss into seawater due to oil-into-water spontaneous emulsification may explain why Tween 80-rich dispersants are less effective than lecithin-rich dispersants with comparable interfacial tension, although longer droplet coalescence times observed for Tween 80-rich, self-emulsifying dispersant-oil mixtures may mitigate the effects of dispersant leaching. Conversely, surfactant retention in oil via lecithin-rich dispersants' water-into-oil emulsification may explain why lecithin-Tween 80 dispersants are as effective as dispersants containing other surfactant blends which produce lower interfacial tension.

  14. Synthesis and characterization of stable aqueous dispersions of graphene

    Indian Academy of Sciences (India)

    Ujjal Kumar Sur; Abhijit Saha; Aparna Datta; Balaprasad Ankamwar; Farah Surti; Sannak Dutta Roy; Debasish Roy

    2016-02-01

    A stable aqueous dispersion (5 mg ml$^{−1}$) of graphene was synthesized by a simple protocol based on three-step reduction of graphene oxide (GO) dispersion synthesized using the modified version of Hummers and Offeman method. Reduction of GO was carried out using sodium borohydride, hydrazine hydrate and dimethyl hydrazine as reducing agents. The chemically synthesized graphene was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–visible absorption spectroscopy, Fourier transform infrared (FTIR) and Raman spectroscopy, thermogravimetric analysis (TGA), optical microscopy. The stability of aqueous dispersions of graphene was confirmed through zeta potential measurements and the negative zeta potentials of 55–60 mV were obtained indicating the high stability of aqueous graphene dispersions.

  15. Modelling the dispersion energy for Van der Waals complexes

    CERN Document Server

    Sanz-Garcia, A

    2002-01-01

    Strictly ab initio calculations of the dispersion energy are unfeasible in practice but for the smallest systems. A sensible alternative is to model the dispersion contribution through a damped multipolar expansion. This thesis proposes to represent the dispersion energy by means of a non-empirical, atom-atom model using damping functions scaled from 'exact' results for one electron-one electron systems. We start by investigating the scalability of ab initio calculated damping functions for closed-shell atom-atom dimers. Ab initio scaling parameters are employed to assess the quality of the damping functions yielded by a predictor scheme based on the charge overlap between the interacting monomers. The investigation of the scaling properties is extended to atom-linear molecule systems, focusing on the dependence on orientation of the short-range dispersion energy and how to account for it using isotropic damping parameters. We study the possibilities of an 'atomic' (multicentre) representation of the dispersi...

  16. Validity condition of separating dispersion of PCFs into material dispersion and geometrical dispersion

    Institute of Scientific and Technical Information of China (English)

    Wei Wang; Lantian Hou; Zhaolun Liu; Guiyao Zhou

    2009-01-01

    When using normalized dispersion method for the dispersion design of photonic crystal fibers(PCFs),it is vital that the group velocity dispersion of PCF can be seen as the sum of geometrical dispersion and material dispersion.However,the error induced by this way of calculation will deteriorate the final results.Taking 5 ps/(km·nm)and 5% as absolute error and relative error limits,respectively,the structure parameter boundaries of PCFs about when separating total dispersion into geometrical and material components is valid are provided for wavelength shorter than 1700 nm.By using these two criteria together,it is adequate to evaluate the simulatcd dispersion of PCFs when normalized dispersion method is employed.

  17. INFLUENCE OF CHROMATIC DISPERSION, DISPERSION SLOPE, DISPERSION CURVATURE ON MICROWAVE GENERATION USING TWO CASCADE MODULATORS

    OpenAIRE

    Mandeep Singh; S.K. Raghuwanshi

    2013-01-01

    This work presents a theoretical study of harmonic generation of microwave signals after detection of a modulated optical carrier in cascaded two electro-optic modulators. Dispersion is one of the major limiting factors for microwave generation in microwave photonics. In this paper, we analyze influence of chromatic dispersion, dispersion slope, dispersion curvature on microwave generation using two cascaded MZMs and it has been found that output intensity of photodetector reduces when disper...

  18. Developing a dispersant spraying capability

    Energy Technology Data Exchange (ETDEWEB)

    Gill, S.D.

    1979-01-01

    In developing a national dispersant spraying capability, the Canadian Coast Guard (CCG) has undertaken a modification program to enable the conventional offshore spraying gear to be mounted on almost any vessel of convenience. Smaller, more versatile inshore spraying vessels and pumps have been designed and built. With the popularization of concentrated dispersants, the inshore pumping equipment can be used aboard hovercraft for special application situations. A program of acquiring mobile dispersant storage tanks has been undertaken with auxiliary equipment that will facilitate the shipment of dispersants in bulk by air freight. Work also has commenced on extending the dispersant application program to include the CCG fleet of helicopters.

  19. Dispersion relations in heavily-doped nanostructures

    CERN Document Server

    Ghatak, Kamakhya Prasad

    2016-01-01

    This book presents the dispersion relation in heavily doped nano-structures. The materials considered are III-V, II-VI, IV-VI, GaP, Ge, Platinum Antimonide, stressed, GaSb, Te, II-V, HgTe/CdTe superlattices and Bismuth Telluride semiconductors. The dispersion relation is discussed under magnetic quantization and on the basis of carrier energy spectra. The influences of magnetic field, magneto inversion, and magneto nipi structures on nano-structures is analyzed. The band structure of optoelectronic materials changes with photo-excitation in a fundamental way according to newly formulated electron dispersion laws. They control the quantum effect in optoelectronic devices in the presence of light. The measurement of band gaps in optoelectronic materials in the presence of external photo-excitation is displayed. The influences of magnetic quantization, crossed electric and quantizing fields, intense electric fields on the on the dispersion relation in heavily doped semiconductors and super-lattices are also disc...

  20. Dispersion Interactions in Water Clusters.

    Science.gov (United States)

    Guidez, Emilie B; Gordon, Mark S

    2017-05-18

    The importance of dispersion forces in water clusters is examined using the effective fragment potential (EFP) method. Since the original EFP1 water potential does not include dispersion, a dispersion correction to the EFP1 potential (EFP1-D) was derived and implemented. The addition of dispersion to the EFP1 potential yields improved geometries for water clusters that contain 2-6 molecules. The importance of the odd E7 contribution to the dispersion energy is investigated. The E7 dispersion term is repulsive for all of the water clusters studied here and can have a magnitude that is as large as half of the E6 value. The E7 term therefore contributes to larger intermolecular distances for the optimized geometries. Inclusion of many-body effects and/or higher order terms may be necessary to further improve dispersion energies and optimized geometries.

  1. 基质固相分散-气相色谱热能检测法测定电子烟烟油中的TSNAs%Determination of TSNAs in electronic cigarette liquids by GC-TEA with matrix solid phase dispersion

    Institute of Scientific and Technical Information of China (English)

    张凤梅; 杨光宇; 刘志华; 朱瑞芝; 司晓喜; 刘春波; 申钦鹏; 何沛; 王昆淼

    2016-01-01

    利用基质固相分散-气相色谱热能检测法测定电子烟烟油中的烟草特有亚硝胺(TSNAs).电子烟烟油用碱性氧化铝分散处理,然后用带柱层析净化功能的索氏提取器净化.经净化后的样品用气相色谱热能进行检测分析.在选定条件下,NNK、NNN、NAB、NAT的4种烟草特有亚硝胺检出限分别为7.6、12.8、13.2、4.0 ng/mL,方法的回收率为89.6%~ 94.7%;对样品进行7次测定,日内相对标准偏差为3.2% ~4.0%;日间相对标准偏差为4.2% ~4.6%,结果令人满意.%A matrix solid phase dispersion and gas chromatography method are used to determine N-nitrosamines (TSNAs) in electronic cigarette liquids in combination with matrix solid phase dispersion.The electronic cigarette liquids samples are firstly dispersed with basic alumina and purified by basic alumina column chromatography combined with cable extraction.The purified samples are analyzed by gas chromatouraphy equipped with thermal energy analyser (TEA).The detection limits for four TSNAs (NNK、NNN、NAB、NAT) are 7.6,12.8,13.2,and 4.0 ng/mL,respectively.The developed method provides spiked recoveries of 89.6%-94.7% for TSNAs.The intra-day relative standard deviations are 3.2%-4.0% and the inter-day relative standard deviations are 4.2%-4.6%.This method is applied for the determination of TSNAs in electronic cigarette liquids with good results.

  2. Effects of yichan tang on rotatory behavior, substance nigra cells and neurotransmitter of rats with Parkinson disease%抑颤汤对帕金森病大鼠旋转行为、黑质细胞及神经递质的影响

    Institute of Scientific and Technical Information of China (English)

    窦永起; 杨明会; 王炜; 刘毅

    2006-01-01

    g xianlingpi, 10 g roucongrong, 15 g gouqizi, 15 g danshen and 8 g wugong,etc., and provided by Dispensary of Chinese herb of General Hospital of Chinese PLA. Drug was decocted for 30 minutes to filter the solution and then concentrated into decoction including 1.0 g/mL raw materials.METHODS: The experiment was carried out at the Animal Laboratory of General Hospital of Chinese PLA from September to December 2001. PD rat model were established with 6-hydroxy-dopa to observe behavior of rats.The administration of rats (body mass/kg) in yichan tang group was 10 times as the administration of the adults (60 kg) (5 g/kg). Rats were perfused once a day and weighted once a week. The dosage of administration was regulated as the body mass changing, and the administration lasted for 8 weeks. Rats in saline group and normal control group were perfused with the same volume of saline as the criteria of body mass. Rotatory behaviors of rats in normal group, saline group (model group before administration)and yichan tang group were observed before administration and at 5, 6, 7 and 8 weeks after administration. Changes of content of catecholamines in extracellular fluid of cerebral tissue were measured with micro-dialysis technique and high performance liquid chromatography (HPLC), meanwhile, changes of substantia nigra nerve cells on both sides of corpus striatum were observed under 20-time and 40-time optic microscopes.MAIN OUTCOME MEASURES: Effect of yichan tang on medium of cranial nerve of PD rats; changes of substantia nigra nerve cells on both sides of corpus striatum with optic microscope and electron microscope; evaluation of yichan tang.RESULTS: Among 100 rats, 6 rats in yichan tang group died because of failure perfusion, 5 in saline group and 2 in normal control group. Therefore, 87 rats were involved in the final analysis. ① At 5, 6, 7 and 8 weeks after treatment, rotatory times within 40 minutes were all shorter in yichan tang group than those in saline group

  3. 定点旋转手法配合中频治疗椎动脉型颈椎病%Vertebral Artery Type Cervical Spondylosis Treated with Cervical Rotatory and Local Manipulation Combined with Modulated Medium Frequency Electrotherapy

    Institute of Scientific and Technical Information of China (English)

    范斌; 冯敬

    2013-01-01

    To explore the curative effect of the combined traditional Chinese medical therapy for vertebral artery type cervical spondylosis.Metheds:238 cases of vertebral artery type cervical spondylosis were randomly divided into treatment group (128 cases) and controlled group (110 cases),the treatment group were treated with cervical rotatory and local manipulation and modulated medium frequency electrotherapy; the controlled group of 110 cases were treated with Tui Na manipulation.Results:After two courses of treatment,the significant effective rate was 68.75% (88 cases) ; the effective rate was27.34% (35 cases) ;the non effective rate was 3.91% (5 eases),the total effectiverate was 96.09% (133 cases) of the treatment group.To compare with the controlled group,there was statistical difference (P<0.001).Conclusion:Local manipulation combined with modulated medium frequency electrotherapy for vertebral artery type cervical spondylosis can alleviate symptoms significantly better and sooner than Tui Na treatment simply.%目的:探讨中医综合治疗推动脉型颈椎病的临床效果.方法:随机将238例患者分为治疗组128例,对照组110例,治疗组采用定点旋转手法配合中频治疗;对照组采用单纯推拿治疗.观察两组的治疗效果.结果:通过两个疗程治疗,治疗组显效88例(68.75%),有效35例(27.34%)无效5例(3.91%)总有效率133例(96.09%),与对照组相比,差异有显著性意义(P< 0.001).结论:定点旋转手法配合中频治疗椎动脉型颈椎病椎动脉型颈椎病起效快且疗效确切,疗效优于单纯推拿治疗.

  4. QT dispersion and P wave dispersion in patients with fibromyalgia.

    Science.gov (United States)

    Yolbaş, Servet; Yıldırım, Ahmet; Düzenci, Deccane; Karakaya, Bülent; Dağlı, Mustafa Necati; Koca, Süleyman Serdar

    2016-12-01

    Fibromyalgia (FM) is a chronic disease characterized by widespread pain. Somatic complaints associated with the cardiovascular system, such as chest pain and palpitations, are frequently seen in FM patients. P and QT dispersions are simple and inexpensive measurements reflecting the regional heterogeneity of atrial and ventricular repolarization, respectively. QT dispersion can cause serious ventricular arrhythmias. The aim of the present study was to evaluate QT dispersion and P wave dispersion in patients with FM. The study involved 48 FM patients who fulfilled the established criteria and 32 healthy controls (HC). A standard 12-lead electrocardiogram was performed on all participants. QT dispersion was defined as the difference between the longest and the shortest QT intervals. Similarly, the differences between the shortest and longest P waves were defined as P wave dispersion. The QT dispersion and corrected QT dispersion were shorter in the FM group compared with the HC group (pdispersion value, there was no significant difference between the FM and HC groups (p=0.088). Longer QT and P wave dispersions are not problems in patients with FM. Therefore, it may be concluded that fibromyalgia does not include an increased risk of atrial and/or ventricular arrhythmias.

  5. SMED - Sulphur MEditerranean Dispersion

    Science.gov (United States)

    Salerno, Giuseppe G.; Sellitto, Pasquale; Corradini, Stefano; Di Sarra, Alcide Giorgio; Merucci, Luca; Caltabiano, Tommaso; La Spina, Alessandro

    2016-04-01

    Emissions of volcanic gases and particles can have profound impacts on terrestrial environment, atmospheric composition, climate forcing, and then on human health at various temporal and spatial scales. Volcanic emissions have been identified as one of the largest sources of uncertainty in our understanding of recent climate change trends. In particular, a primary role is acted by sulphur dioxide emission due to its conversion to volcanic sulphate aerosol via atmospheric oxidation. Aerosols may play a key role in the radiative budget and then in photochemistry and tropospheric composition. Mt. Etna is one of the most prodigious and persistent emitters of gasses and particles on Earth, accounting for about 10% of global average volcanic emission of CO2 and SO2. Its sulphur emissions stand for 0.7 × 106 t S/yr9 and then about 10 times bigger than anthropogenic sulphur emissions in the Mediterranean area. Centrepiece of the SMED project is to advance the understanding of volcanogenic sulphur dioxide and sulphate aerosol particles dispersion and radiative impact on the downwind Mediterranean region by an integrated approach between ground- and space-based observations and modelling. Research is addressed by exploring the potential relationship between proximal SO2 flux and aerosol measured remotely in the volcanic plume of Mt. Etna between 2000 and 2014 and distal aerosol ground-based measurements in Lampedusa, Greece, and Malta from AERONET network. Ground data are combined with satellite multispectral polar and geostationary imagers able to detect and retrieve volcanic ash and SO2. The high repetition time of SEVIRI (15 minutes) will ensure the potential opportunity to follow the entire evolution of the volcanic cloud, while, the higher spatial resolution of MODIS (1x1 km2), are exploited for investigating the probability to retrieve volcanic SO2 abundances from passive degassing. Ground and space observations are complemented with atmospheric Lagrangian model

  6. Dispersive transport across interfaces

    Science.gov (United States)

    Berkowitz, Brian; Adler, Pierre

    2015-04-01

    Experiments demonstrating asymmetrical dispersive transport of a conservative tracer across interfaces between different porous materials have recently been performed. Here, this phenomenon is studied numerically on the pore scale. The flow field is derived by solving the Stokes equation. The dispersive transport is simulated by a large number of particles undergoing random walks under the simultaneous action of convection and diffusion. Two main two-dimensional configurations are studied; each consists of two segments (called coarse and fine) with the same structure, porosity, and length along the main flow, but different characteristic solid/pore sizes. One structure consists of two channels containing cavities of different sizes, and the second of square "grains" of different sizes. At time t=0, a large number of particles is injected (as a pulse) around a given cross-section. The corresponding breakthrough curves (BTCs) are registered as functions of time at six different cross sections. Calculations are made twice; in the first case (CtoF), particles are injected in the coarse side and are transported towards the fine one; in the second one (FtoC), the opposite case is studied. These calculations are performed for various Péclet numbers (Pe). Comparison of the resulting BTCs shows features that are similar to experimental observations, but with qualitative and quantitative differences. The influences of the medium, of the injection and observation planes, and of Pe are detailed and discussed. A BTC for pulse injection can be characterized by its maximum M(t_M) and the time tM at which it occurs. The observed differences for channels bounded by cavities are very small. However for the granular structures, M(t_M) is always larger for FtoC than for CtoF ; tM depends on all the parameters, namely Pe, the size ratio between the large and small grains, the injection and the observation planes. The numerical results are systematically compared with solutions of one

  7. Comparison of three techniques for skin total irradiation with electrons; Comparacao de tres tecnicas de irradiacao total da pele com eletrons

    Energy Technology Data Exchange (ETDEWEB)

    Batista, Delano V.S., E-mail: dbatista@ird.gov.b [Instituto de Radioprotecao e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil); Instituto Nacional de Cancer (INCa), Rio de Janeiro, RJ (Brazil); Bardella, Lucia H. [Instituto Nacional de Cancer (INCa), Rio de Janeiro, RJ (Brazil); Rosa, Luiz A.R. da, E-mail: lrosa@ird.gov.b [Instituto de Radioprotecao e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil)

    2011-10-26

    This paper compared three techniques of skin total irradiation with electrons: 1) horizontal positioning, 2) vertical positioning - rotatory technique and 3) vertical positioning - six fields technique. For that, a anthropomorphic phantom was positioned according to the recommendation for each technique and was i radiated at the linear accelerator by using the 6 MeV electrons. Radiochromic films were positioned on the surface in various regions of the phantom for measurement of absorbed dose. A ionization chamber was positioned inside of equivalent issue plates for dose evaluation due to the photons produced by electron stopping. The technique 2 and 3 have shown too similar in the results and number or discrepant points (8 and 10 respectively) of prescription lower than the technique 1 (22 points). The total body dose of photons of the 1, 2 and 3 techniques was 2.2%, 5.3% and 5.2% respectively

  8. Amplified Dispersive Optical Tomography

    CERN Document Server

    Goda, Keisuke; Jalali, Bahram

    2008-01-01

    Optical coherence tomography (OCT) has proven to be a powerful technique for studying tissue morphology in ophthalmology, cardiology, and endomicroscopy. Its performance is limited by the fundamental trade-off between the imaging sensitivity and acquisition speed -- a predicament common in virtually all imaging systems. In this paper, we circumvent this limit by using distributed Raman post-amplification of the reflection from the sample. We combine the amplification with simultaneously performed dispersive Fourier transformation, a process that maps the optical spectrum into an easily measured time-domain waveform. The Raman amplification enables measurement of weak signals which are otherwise buried in noise. It extends the depth range without sacrificing the acquisition speed or causing damage to the sample. As proof of concept, single-shot imaging with 15 dB improvement in sensitivity at an axial scan rate of 36.6 MHz is demonstrated.

  9. Natural dispersion revisited.

    Science.gov (United States)

    Johansen, Øistein; Reed, Mark; Bodsberg, Nils Rune

    2015-04-15

    This paper presents a new semi-empirical model for oil droplet size distributions generated by single breaking wave events. Empirical data was obtained from laboratory experiments with different crude oils at different stages of weathering. The paper starts with a review of the most commonly used model for natural dispersion, which is followed by a presentation of the laboratory study on oil droplet size distributions formed by breaking waves conducted by SINTEF on behalf of the NOAA/UNH Coastal Response Research Center. The next section presents the theoretical and empirical foundation for the new model. The model is based on dimensional analysis and contains two non-dimensional groups; the Weber and Reynolds number. The model was validated with data from a full scale experimental oil spill conducted in the Haltenbanken area offshore Norway in July 1982, as described in the last section of the paper.

  10. Acoustic Rectification in Dispersive Media

    Science.gov (United States)

    Cantrell, John H.

    2008-01-01

    It is shown that the shapes of acoustic radiation-induced static strain and displacement pulses (rectified acoustic pulses) are defined locally by the energy density of the generating waveform. Dispersive properties are introduced analytically by assuming that the rectified pulses are functionally dependent on a phase factor that includes both dispersive and nonlinear terms. The dispersion causes an evolutionary change in the shape of the energy density profile that leads to the generation of solitons experimentally observed in fused silica.

  11. Progress in urban dispersion studies

    DEFF Research Database (Denmark)

    Batchvarova, E.; Gryning, Sven-Erik

    2006-01-01

    The present Study addresses recent achievements in better representation Of the urban area structure in meteorology and dispersion parameterisations. The setup and Main Outcome of several recent dispersion experiments in Urban areas and their use in model validation are discussed. The maximum...... BUBBLE Tracer Experiment) the horizontal spread of the plume corresponds to a Lagrangian time scale bigger than the value for ground Sources. Turbulence measurements LIP to 3-5 times the building height Lire needed for direct use in dispersion Calculations....

  12. Seed dispersal of desert annuals.

    Science.gov (United States)

    Venable, D Lawrence; Flores-Martinez, Arturo; Muller-Landau, Helene C; Barron-Gafford, Greg; Becerra, Judith X

    2008-08-01

    We quantified seed dispersal in a guild of Sonoran Desert winter desert annuals at a protected natural field site in Tucson, Arizona, USA. Seed production was suppressed under shrub canopies, in the open areas between shrubs, or both by applying an herbicide prior to seed set in large, randomly assigned removal plots (10-30 m diameter). Seedlings were censused along transects crossing the reproductive suppression borders shortly after germination. Dispersal kernels were estimated for Pectocarya recurvata and Schismus barbatus from the change in seedling densities with distance from these borders via inverse modeling. Estimated dispersal distances were short, with most seeds traveling less than a meter. The adhesive seeds of P. recurvata went farther than the small S. barbatus seeds, which have no obvious dispersal adaptation. Seeds dispersed farther downslope than upslope and farther when dispersing into open areas than when dispersing into shrubs. Dispersal distances were short relative to the pattern of spatial heterogeneity created by the shrub and open space mosaic. This suggests that dispersal could contribute to local population buildup, possibly facilitating species coexistence. Overall, these results support the hypothesis that escape in time via delayed germination is likely to be more important for desert annuals than escape in space.

  13. Statistical Thermodynamics of Disperse Systems

    DEFF Research Database (Denmark)

    Shapiro, Alexander

    1996-01-01

    Principles of statistical physics are applied for the description of thermodynamic equilibrium in disperse systems. The cells of disperse systems are shown to possess a number of non-standard thermodynamic parameters. A random distribution of these parameters in the system is determined....... On the basis of this distribution, it is established that the disperse system has an additional degree of freedom called the macro-entropy. A large set of bounded ideal disperse systems allows exact evaluation of thermodynamic characteristics. The theory developed is applied to the description of equilibrium...

  14. 驾驶摩托车致膝关节前内侧旋转不稳定的手术治疗%SURGICAL TREATMENT OF ANTERO-MEDIAL ROTATORY INSTABILITY OF KNEE JOINT CAUSED BY MOTORCYCLE

    Institute of Scientific and Technical Information of China (English)

    周炎; 丰峰; 瞿新丛; 方祖怡; 刘祥; 潘晓辉; 许来峰

    2012-01-01

    Objective To discuss the effectiveness of operation technique for antero-medial rotatory instability (AMRI) of the knee joint caused by motorcycle. Methods Between June 2007 and December 2009, 32 cases of AMRI caused by motorcycle were treated. There were 28 males and 4 females with an average age of 35.5 years (range, 20-50 years). The interval between injury and surgery was 5-10 days (mean, 7 days). The anterior cruciate ligament (ACL) was injured at the attachment point of the condyles crest; the medial collateral ligament (MCL) was injured at central site in 19 cases, at medial condyles of femur in 10 cases, and at medial condyles of tibia in 3 cases, which were all closed injuries. The bone avulsion of condyles crest was fixed by steel wire and MCL was repaired. Results Red swelling and a little effusion occurred at the incision in 1 case, and the other incisions healed by first intention. Traumatic arthritis of the knee occurred in 5 cases. Thirty-two cases were followed up 16-22 months (mean, 18.5 months). The X-ray examination showed that the fracture union time was 5-8 weeks (mean, 6 weeks) after operation. At last follow-up, the extension of knee joint was 0° and the flexion of the knee joint was 110-170° (mean, 155°). According to the synthetic evaluating standard of International Knee Documentation Committee, 24 cases were rated as A level, 6 cases as B, 1 case as C, and 1 case as D at last follow-up. Lysholm knee score was 85.93 ± 3.76 at last follow-up, which was significantly higher (t=53.785, P=0.000) than preoperative score 37.54 ± 3.43. Conclusion In patients with AMRI caused by motorcycle, steel wire is used to fix the bone avulsion of condyles crest and MCL should be repaired simultaneously as far as possible. And associating with the early postoperative functional exercise, the short-term effectiveness is satisfactory, but long-term effectiveness still need further follow-up observation.%目的 探讨手术治疗驾驶摩托车致膝关

  15. INFLUENCE OF CHROMATIC DISPERSION, DISPERSION SLOPE, DISPERSION CURVATURE ON MICROWAVE GENERATION USING TWO CASCADE MODULATORS

    Directory of Open Access Journals (Sweden)

    Mandeep Singh

    2013-03-01

    Full Text Available This work presents a theoretical study of harmonic generation of microwave signals after detection of a modulated optical carrier in cascaded two electro-optic modulators. Dispersion is one of the major limiting factors for microwave generation in microwave photonics. In this paper, we analyze influence of chromatic dispersion, dispersion slope, dispersion curvature on microwave generation using two cascaded MZMs and it has been found that output intensity of photodetector reduces when dispersion term up to fifth order are added. We have used the two cascaded Mach-Zehnder Modulators for our proposed model and tried to show the dispersion effect with the help of modulation depth factor of MZM, which have been not discussed earlier.

  16. Additive strengthening mechanisms in dispersion hardened polycrystals

    DEFF Research Database (Denmark)

    Hansen, Niels; Ralph, B.

    1986-01-01

    Tensile data from polycrystalline samples of copper dispersion strengthened by alumina are analysed. The basis of this analysis is to look at the strain range from 0.05 to 0.20 where the stress-strain curves show a parabolic hardening behaviour and are parallel to one another. The means by which...... the dislocation density contributions from each of these three sources. The type of additivity suggested here not only gives very good agreement with the stress-strain data but it also uses and is in accord with the experimental measurements of dislocation densities made using transmission electron microscopy....

  17. Hybrid compensation arrangement in dispersed generation systems

    DEFF Research Database (Denmark)

    Chen, Zhe; Blaabjerg, Frede; Pedersen, John Kim

    2005-01-01

    This paper presents a hybrid compensation system consisting of an active filter and distributed passive filters. In the system, each individual passive filter is connected to a distortion source and designed to eliminate main harmonics and supply reactive power for the distortion source, while...... are performed for a power system including the dispersed generation units connected into the system through power electronic converters and diode rectifier loads, which produce the distorted waveforms. The simulation results have demonstrated that good compensation effects can be achieved by using the combined...

  18. Electron-Cyclotron Waves

    NARCIS (Netherlands)

    Westerhof, E.

    1994-01-01

    The essential elements of the theory of electron cyclotron waves are reviewed, The two main electro-magnetic modes of propagation are identified and their dispersion and absorption properties are discussed. The importance of the use of the relativistic resonance condition is stressed.

  19. Toward Uniformly Dispersed Battery Electrode Composite Materials: Characteristics and Performance.

    Science.gov (United States)

    Kwon, Yo Han; Huie, Matthew M; Choi, Dalsu; Chang, Mincheol; Marschilok, Amy C; Takeuchi, Kenneth J; Takeuchi, Esther S; Reichmanis, Elsa

    2016-02-10

    Battery electrodes are complex mesoscale systems comprised of electroactive components, conductive additives, and binders. In this report, methods for processing electrodes with dispersion of the components are described. To investigate the degree of material dispersion, a spin-coating technique was adopted to provide a thin, uniform layer that enabled observation of the morphology. Distinct differences in the distribution profile of the electrode components arising from individual materials physical affinities were readily identified. Hansen solubility parameter (HSP) analysis revealed pertinent surface interactions associated with materials dispersivity. Further studies demonstrated that HSPs can provide an effective strategy to identify surface modification approaches for improved dispersions of battery electrode materials. Specifically, introduction of surfactantlike functionality such as oleic acid (OA) capping and P3HT-conjugated polymer wrapping on the surface of nanomaterials significantly enhanced material dispersity over the composite electrode. The approach to the surface treatment on the basis of HSP study can facilitate design of composite electrodes with uniformly dispersed morphology and may contribute to enhancing their electrical and electrochemical behaviors. The conductivity of the composites and their electrochemical performance was also characterized. The study illustrates the importance of considering electronic conductivity, electron transfer, and ion transport in the design of environments incorporating active nanomaterials.

  20. The NET effect of dispersants

    NARCIS (Netherlands)

    Marieke Zeinstra-Helfrich; Wierd Koops; Albertinka J. Murk

    2015-01-01

    Application of chemical dispersants or mechanical dispersion on surface oil is a trade-off between surface effects (impact of floating oil) and sub-surface effects (impact of suspended oil). Making an informed decision regarding such response, requires insight in the induced change in fate and

  1. Fermion dispersion in axion medium

    OpenAIRE

    Mikheev, N. V.; Narynskaya, E. N.

    2008-01-01

    The interaction of a fermion with the dense axion medium is investigated for the purpose of finding an axion medium effect on the fermion dispersion. It is shown that axion medium influence on the fermion dispersion under astrophysical conditions is negligible small if the correct Lagrangian of the axion-fermion interaction is used.

  2. Large deviations in Taylor dispersion

    Science.gov (United States)

    Kahlen, Marcel; Engel, Andreas; Van den Broeck, Christian

    2017-01-01

    We establish a link between the phenomenon of Taylor dispersion and the theory of empirical distributions. Using this connection, we derive, upon applying the theory of large deviations, an alternative and much more precise description of the long-time regime for Taylor dispersion.

  3. Pigment dispersion syndrome

    Directory of Open Access Journals (Sweden)

    C.S. Sandhya

    2013-10-01

    Full Text Available We report of the rare occurrence of pigment dispersion syndrome (PDS with posterior subcapsular cataract in both eyes in a young male patient. The patient presented with complaints of progressive decrease in vision of one year duration. The patient also had high myopia with mild iridodonesis, phacodonesis and anterior insertion of zonules. Classical signs of PDS like Krukenberg's spindle on the posterior corneal surface were evident on slit lamp examination; transillumination defects in the iris could not be elicited by retroillumination as the iris was heavily pigmented. Gonioscopy revealed heavy and uniform pigmentation of trabecular meshwork. Evidence of a characteristic iris configuration on optical coherence tomography (OCT, namely, posterior bowing of iris in the mid periphery suggested the diagnosis of PDS. This case highlights the importance of OCT in identifying the iris configuration characteristically seen in PDS even in the absence of transillumination defects in the iris and reiterates the need to look for subtle signs like phacodonesis which are important when surgical intervention is planned.

  4. Dispersion in unit disks

    CERN Document Server

    Dumitrescu, Adrian

    2009-01-01

    We present two new approximation algorithms with (improved) constant ratios for selecting $n$ points in $n$ unit disks such that the minimum pairwise distance among the points is maximized. (I) A very simple $O(n \\log{n})$-time algorithm with ratio 0.5110 for disjoint unit disks. In combination with an algorithm of Cabello \\cite{Ca07}, it yields a $O(n^2)$-time algorithm with ratio of 0.4487 for dispersion in $n$ not necessarily disjoint unit disks. (II) A more sophisticated LP-based algorithm with ratio 0.6495 for disjoint unit disks that uses a linear number of variables and constraints, and runs in polynomial time. The algorithm introduces a novel technique which combines linear programming and projections for approximating distances. The previous best approximation ratio for disjoint unit disks was 1/2. Our results give a partial answer to an open question raised by Cabello \\cite{Ca07}, who asked whether 1/2 could be improved.

  5. Dispersal and migration

    Directory of Open Access Journals (Sweden)

    Schwarz, C.

    2004-06-01

    Full Text Available Ringing of birds unveiled many aspects of avian migration and dispersal movements. However, there is even much more to be explored by the use of ringing and other marks. Dispersal is crucial in understanding the initial phase of migration in migrating birds as it is to understand patterns and processes of distribution and gene flow. So far, the analysis of migration was largely based on analysing spatial and temporal patters of recoveries of ringed birds. However, there are considerable biases and pitfalls in using recoveries due to spatial and temporal variation in reporting probabilities. Novel methods are required for future studies separating the confounding effects of spatial and temporal heterogeneity of recovery data and heterogeneity of the landscape as well. These novel approaches should aim a more intensive and novel use of the existing recovery data by taking advantage of, for instance, dynamic and multistate modeling, should elaborate schemes for future studies, and should also include other marks that allow a more rapid data collection, like telemetry, geolocation and global positioning systems, and chemical and molecular markers. The latter appear to be very useful in the delineating origin of birds and connectivity between breeding and non–breeding grounds. Many studies of migration are purely descriptive. However, King and Brooks (King & Brooks, 2004 examine if movement patterns of dolphins change after the introduction of a gillnet ban. Bayesian methods are an interesting approach to this problem as they provide a meaningful measure of the probability that such a change occurred rather than simple yes/no response that is often the result of classical statistical methods. However, the key difficulty of a general implementation of Bayesian methods is the complexity of the modelling —there is no general userfriendly package that is easily accessible to most scientists. Drake and Alisauskas (Drake & Alisauskas, 2004 examine the

  6. Air Flow and Dispersion Section

    Energy Technology Data Exchange (ETDEWEB)

    Slinn, W. G.N.; Nicola, P. W.; Powell, D. C.; Davis, W. E.

    1976-03-01

    There are eight papers in this section. Some of the fundamentals of atmospheric dispersion of pollutants are examined with theoretical analyses as well as detailed experimental investigations. Emphasis has been placed on analyzing and summarizing previous experimental dispersion data with more realistic and fundamentally sound approaches to plume behavior. The goal is to finalize improved short-range dispersion models from existing data, removing inconsistencies and inadequacies in presently applied assessment models. Dispersion and transport efforts in the future should aim toward evaluating plume behavior on meso and regional scales. The complex features of flow and dispersion through storms, and in the vicinity of significant terrain characteristics influencing local to regional circulations must receive future emphasis. (auth)

  7. Suppression of Instability in Rotatory Hydromagnetic Convection

    Indian Academy of Sciences (India)

    Joginder S Dhiman

    2000-08-01

    Recently discovered hydrodynamic instability [1], in a simple Bénard configuration in the parameter regime 02 > 1 under the action of a nonadverse temperature gradient, is shown to be suppressed by the simultaneous action of a uniform rotation and a uniform magnetic field both acting parallel to gravity for oscillatory perturbations whenever $(\\mathscr{Q}_1/^2+\\mathscr{J}/^4) > 1$ and the effective Rayleigh number $\\mathcal{R}$(1-02) is dominated by either 274(1 + 1/1)/4 or 274/2 according as 1 ≥ 1 or 1 ≤ 1 respectively. Here 0 is the temperature of the lower boundary while 2 is the coefficient of specific heat at constant volume due to temperature variation and 1, $\\mathcal{R}, \\mathscr{Q}$ and $\\mathscr{T}$ respectively denote the magnetic Prandtl number, the Rayleigh number, the Chandrasekhar number and the Taylor number.

  8. Electronics and electronic systems

    CERN Document Server

    Olsen, George H

    1987-01-01

    Electronics and Electronic Systems explores the significant developments in the field of electronics and electronic devices. This book is organized into three parts encompassing 11 chapters that discuss the fundamental circuit theory and the principles of analog and digital electronics. This book deals first with the passive components of electronic systems, such as resistors, capacitors, and inductors. These topics are followed by a discussion on the analysis of electronic circuits, which involves three ways, namely, the actual circuit, graphical techniques, and rule of thumb. The remaining p

  9. Strong interactions in spacelike and timelike domains dispersive approach

    CERN Document Server

    Nesterenko, Alexander V

    2017-01-01

    Strong Interactions in Spacelike and Timelike Domains: Dispersive Approach provides the theoretical basis for the description of the strong interactions in the spacelike and timelike domains. The book primarily focuses on the hadronic vacuum polarization function, R-ratio of electron-positron annihilation into hadrons, and the Adler function, which govern a variety of the strong interaction processes at various energy scales. Specifically, the book presents the essentials of the dispersion relations for these functions, recaps their perturbative calculation, and delineates the dispersively improved perturbation theory. The book also elucidates the peculiarities of the continuation of the spacelike perturbative results into the timelike domain, which is indispensable for the studies of electron-positron annihilation into hadrons and the related processes.

  10. Dispersive suspended microextraction.

    Science.gov (United States)

    Yang, Zhong-Hua; Liu, Yu; Lu, Yue-Le; Wu, Tong; Zhou, Zhi-Qiang; Liu, Dong-Hui

    2011-11-14

    A novel sample pre-treatment technique termed dispersive suspended microextraction (DSME) coupled with gas chromatography-flame photometric detection (GC-FPD) has been developed for the determination of eight organophosphorus pesticides (ethoprophos, malathion, chlorpyrifos, isocarbophos, methidathion, fenamiphos, profenofos, triazophos) in aqueous samples. In this method, both extraction and two phases' separation process were performed by the assistance of magnetic stirring. After separating the two phases, 1 μL of the suspended phase was injected into GC for further instrument analysis. Varieties of experiment factors which could affect the experiment results were optimized and the following were selected: 12.0 μL p-xylene was selected as extraction solvent, extraction speed was 1200 rpm, extraction time was 30 s, the restoration speed was 800 rpm, the restoration time was 8 min, and no salt was added. Under the optimum conditions, limits of detections (LODs) varied between 0.01 and 0.05 μg L(-1). The relative standard deviation (RSDs, n=6) ranged from 4.6% to 12.1%. The linearity was obtained by five points in the concentration range of 0.1-100.0 μg L(-1). Correlation coefficients (r) varied from 0.9964 to 0.9995. The enrichment factors (EFs) were between 206 and 243. In the final experiment, the developed method has been successfully applied to the determination of organophosphorus pesticides in wine and tap water samples and the obtained recoveries were between 83.8% and 101.3%. Compared with other pre-treatment methods, DSME has its own features and could achieve satisfied results for the analysis of trace components in complicated matrices.

  11. Dispersion-strengthened Aluminium Products Manufactured by Powder Blending

    DEFF Research Database (Denmark)

    Hansen, Niels

    1969-01-01

    Detailed experiments carried out to examine relationship between microstructure and mechanical properties of powder-blended aluminum products are reported; their results as well as structural studies by transmission electron microscopy and tensile-and creep- testing, are given; as dispersed phase...

  12. PREPARATION OF POLYMER DISPERSED LIQUID CRYSTALS USING PHOTOPOLYMERIZATION

    Institute of Scientific and Technical Information of China (English)

    Xing-he Fan; Xiao-feng Xie; Yasuo Hatate

    2001-01-01

    2-Hydroxyethyl methacrylate (HEMA) and styrene copolymers are prepared by photopolymerization. The electrooptical behavior and microstructure of the polymer dispersed liquid crystal films are investigated by using He-Ne laser and scanning electron micro scopy, respectively. With increasing E7 content in the copolymer, droplet size increased, threshold voltage decreased.

  13. 超大型空心钢锭翻转变形均匀性和压实效果研究%Research on Rotatory Deformation Uniformity and Compaction Effect of Super-heavy Hollow Steel Ingot

    Institute of Scientific and Technical Information of China (English)

    刘敏; 马庆贤; 刘功梅

    2016-01-01

    20Mn5超大型空心钢锭在上平下V砧翻转芯轴拔长过程中采用普通V砧进行顺序翻转,锻件变形极不均匀且存在密集型疏松缺陷。通过DEFORM-3D数值模拟和理论推导,定量给出发散角和理论翻转角度与V砧角度和压下率的关系,提出不同压下率下的普通V砧翻转新工艺。数值模拟和物理试验结果表明,单砧压下时大圆角V砧和凸型V砧两种新型V砧的变形均匀性和压实效果均要优于普通V砧。翻转拔长模拟结果表明,不同压下率下凸型V砧、大圆角V砧和普通V砧翻转新工艺的变形均匀性和压实效果均要优于普通V砧顺序翻转,其中大圆角V砧翻转新工艺的变形均匀性最优,凸型V砧翻转新工艺的压实效果最优。研究结果可为国产大型筒体锻件空心钢锭锻造工艺规范的制定提供重要理论参考。%Sequenced rotation with ordinary V-shaped anvil is used in the upper flat and lower V-shaped anvils mandrel drawing process of 20Mn5 super-heavy hollow steel ingot, but the forging deforms unevenly and contains intensive porosities. By numerical simulation using DEFORM-3D and theoretical derivation, the relationship between divergence angle, theoretical rotation angle, V-shaped anvil angle and reduction rate is given quantificationally, and the new rotation processes with ordinary V-shaped anvil at different reduction rates are proposed. Numerical simulation and physical experiment results show that the deformation uniformity and compaction effect of big fillet V-shaped anvil and convex V-shaped anvil is better than that of ordinary V-shaped anvil for single press. Simulation results of rotatory drawing show the deformation uniformity and compaction effect of new rotation processes with convex V-shaped anvil, big fillet V-shaped anvil and ordinary V-shaped anvil is better than that of sequenced rotation with ordinary V-shaped anvil at different reduction rates, while the deformation

  14. Wave-equation dispersion inversion

    KAUST Repository

    Li, Jing

    2016-12-08

    We present the theory for wave-equation inversion of dispersion curves, where the misfit function is the sum of the squared differences between the wavenumbers along the predicted and observed dispersion curves. The dispersion curves are obtained from Rayleigh waves recorded by vertical-component geophones. Similar to wave-equation traveltime tomography, the complicated surface wave arrivals in traces are skeletonized as simpler data, namely the picked dispersion curves in the phase-velocity and frequency domains. Solutions to the elastic wave equation and an iterative optimization method are then used to invert these curves for 2-D or 3-D S-wave velocity models. This procedure, denoted as wave-equation dispersion inversion (WD), does not require the assumption of a layered model and is significantly less prone to the cycle-skipping problems of full waveform inversion. The synthetic and field data examples demonstrate that WD can approximately reconstruct the S-wave velocity distributions in laterally heterogeneous media if the dispersion curves can be identified and picked. The WD method is easily extended to anisotropic data and the inversion of dispersion curves associated with Love waves.

  15. The incomplete plasma dispersion function: properties and application to waves in bounded plasmas

    OpenAIRE

    Baalrud, Scott D.

    2013-01-01

    The incomplete plasma dispersion function is a generalization of the plasma dispersion function in which the defining integral spans a semi-infinite, rather than infinite, domain. It is useful for describing the linear dielectric response and wave dispersion in non-Maxwellian plasmas when the distribution functions can be approximated as Maxwellian over finite, or semi-infinite, intervals in velocity phase-space. A ubiquitous example is the depleted Maxwellian electron distribution found near...

  16. [Compared with colloidal silica and porous silica as baicalin solid dispersion carrier].

    Science.gov (United States)

    Yan, Hong-Mei; Ding, Dong-Mei; Wang, Jing; Sun, E; Jia, Xiao-Bin; Zhang, Zhen-Hai

    2014-07-01

    To compare the dissolution characteristics of colloidal silica and porous silica as the solid dispersion carrier, with baicalin as the model drug. The baicalin solid dispersion was prepared by the solvent method, with colloidal silica and porous silica as the carriers. In the in vitro dissolution experiment, the solid dispersion was identified by scanning electron microscopy, differential scanning and X-ray diffraction. The solid dispersion carriers prepared with both colloidal silica and porous silica could achieve the purpose of rapid release. Along with the increase in the proportion of the carriers, the dissolution rate is accelerated to more than 80% within 60 min. Baicalin existed in the solid dispersion carriers in the non-crystalline form. The release behaviors of the baicalin solid dispersion prepared with two types of carrier were different. Among the two solid dispersion carriers, porous silica dissolved slowly than colloidal silica within 60 min, and they showed similar dissolutions after 60 min.

  17. Dispersion scenarios over complex terrain

    DEFF Research Database (Denmark)

    Thykier-Nielsen, S.; Mikkelsen, T.; Moreno, J.

    1993-01-01

    A presentation of preliminary results from a real-time simulation of full-scale dispersion experiments carried out over complex terrain in Northern Spain is given. Actual wind and turbulence measurements as observed during the experiments were analysed and used as input data for a series of simul......A presentation of preliminary results from a real-time simulation of full-scale dispersion experiments carried out over complex terrain in Northern Spain is given. Actual wind and turbulence measurements as observed during the experiments were analysed and used as input data for a series...... are suitable for subsequent comparison with observed mean dispersion data when they become available....

  18. Dispersion Decay and Scattering Theory

    CERN Document Server

    Komech, Alexander

    2012-01-01

    A simplified, yet rigorous treatment of scattering theory methods and their applications Dispersion Decay and Scattering Theory provides thorough, easy-to-understand guidance on the application of scattering theory methods to modern problems in mathematics, quantum physics, and mathematical physics. Introducing spectral methods with applications to dispersion time-decay and scattering theory, this book presents, for the first time, the Agmon-Jensen-Kato spectral theory for the Schr?dinger equation, extending the theory to the Klein-Gordon equation. The dispersion decay plays a crucial role i

  19. Semiconductor opto-electronics

    CERN Document Server

    Moss, TS; Ellis, B

    1972-01-01

    Semiconductor Opto-Electronics focuses on opto-electronics, covering the basic physical phenomena and device behavior that arise from the interaction between electromagnetic radiation and electrons in a solid. The first nine chapters of this book are devoted to theoretical topics, discussing the interaction of electromagnetic waves with solids, dispersion theory and absorption processes, magneto-optical effects, and non-linear phenomena. Theories of photo-effects and photo-detectors are treated in detail, including the theories of radiation generation and the behavior of semiconductor lasers a

  20. DISPERSION RELATION OF A MAGNETIZED PLASMA-FILLED BACKWARD WAVE OSCILLATOR

    Institute of Scientific and Technical Information of China (English)

    GAO HONG; LIU SHENG-GANG

    2000-01-01

    A linear theory and a more general dispersion relation of electromagnetic radiation from a magnetized plasma-filled backward wave oscillator with sinusoidally corrugated slow-wave structure driven by a solid intense relativistic electron beam have been given. The comparisons show good agreement with the previous works when B0 → ∞ and ωb = 0 from this dispersion relation.

  1. The conservation physiology of seed dispersal

    National Research Council Canada - National Science Library

    Graeme D. Ruxton; H. Martin Schaefer

    2012-01-01

    ...—dispersal interactions. We argue that large-bodied seed dispersers may be particularly important for plant conservation because seed dispersal of large-seeded plants is often more specialized and because large-bodied...

  2. Superradiant scattering of dispersive fields

    CERN Document Server

    Richartz, Maurício; Weinfurtner, Silke; Liberati, Stefano

    2013-01-01

    Motivated by analogue models of classical and quantum field theory in curved spacetimes and their recent experimental realizations, we consider wave scattering processes of dispersive fields exhibiting two extra degrees of freedom. In particular, we investigate how standard superradiant scattering processes are affected by subluminal or superluminal modifications of the dispersion relation. We analyze simple 1-dimensional toy-models based on fourth-order corrections to the standard second order wave equation and show that low-frequency waves impinging on generic scattering potentials can be amplified during the process. In specific cases, by assuming a simple step potential, we determine quantitatively the deviations in the amplification spectrum that arise due to dispersion, and demonstrate that the amplification can be further enhanced due to the presence of extra degrees of freedom. We also consider dispersive scattering processes in which the medium where the scattering takes place is moving with respect ...

  3. Asphaltene dispersants as demulsification aids

    Energy Technology Data Exchange (ETDEWEB)

    Manek, M.B.

    1995-11-01

    Destabilization of petroleum asphaltenes may cause a multitude of problems in crude oil recovery and production. One major problem is their agglomeration at the water-oil interface of crude oil emulsions. Once agglomeration occurs, destabilized asphaltenes can form a thick pad in the dehydration equipment, which significantly reduces the demulsification rate. Certain polymeric dispersants increase asphaltene solubilization in hydrocarbon media, and when used in conjunction with emulsion breakers, facilitate the demulsification process. Two case studies are presented that demonstrate how asphaltene dispersants can efficiently inhibit pad formation and help reduce demulsifier dosage. Criteria for dispersant application and selection are discussed, which include the application of a novel laboratory technique to assess asphaltene stabilization in the crude oil. The technique monitors asphaltene agglomeration while undergoing titration with an incompatible solvent (precipitant). The method was used to evaluate stabilization of asphaltenes in the crude oil and to screen asphaltene dispersants.

  4. Dispersion engineering for integrated nanophotonics

    CERN Document Server

    Vanbésien, Olivier

    2014-01-01

    This book shows how dispersion engineering in two dimensional dielectric photonic crystals can provide new effects for the precise control of light propagation for integrated nanophotonics.Dispersion engineering in regular and graded photonic crystals to promote anomalous refraction effects is studied from the concepts to experimental demonstration via nanofabrication considerations. Self collimation, ultra and negative refraction, second harmonic generation, mirage and invisibility effects which lead to an unprecedented control of light propagation at the (sub-)wavelength scale for the

  5. Dispersion in alluvial convergent estuaries

    Science.gov (United States)

    Zhang, Zhilin; Savenije, Hubert H. G.

    2016-04-01

    The Van der Burgh's equation for longitudinal effective dispersion is a purely empirical method with practical implications. Its application to the effective tidal average dispersion under equilibrium conditions appears to have excellent performance in a wide range of alluvial estuaries. In this research, we try to find out the physical meaning of Van der Burgh's coefficient. Researchers like MacCready, Fischer, Kuijper, Hansen and Rattray have tried to split up dispersion into its constituents which did not do much to explain overall behaviour. In addition, traditional literature on dispersion is mostly related to flumes with constant cross-section. This research is about understanding the Van der Burgh's coefficient facing the fact that natural estuaries have exponentially varying cross-section. The objective is to derive a simple 1-D model considering both longitudinal and lateral mixing processes based on field observations (theoretical derivation). To that effect, we connect dispersion with salinity using the salt balance equation. Then we calculate the salinity along the longitudinal direction and compare it to the observed salinity. Calibrated dispersion coefficients in a range of estuaries are then compared with new expressions for the Van der Burgh's coefficient K and it is analysed if K varies from estuary to estuary. The set of reliable data used will be from estuaries: Kurau, Perak, Bernam, Selangor, Muar, Endau, Maputo, Thames, Corantijn, Sinnamary, Mae Klong, Lalang, Limpopo, Tha Chin, Chao Phraya, Edisto and Elbe.

  6. Polyol-assisted vermiculite dispersion in polyurethane nanocomposites.

    Science.gov (United States)

    Park, Yong Tae; Qian, Yuqiang; Lindsay, Chris I; Nijs, Conny; Camargo, Rafael E; Stein, Andreas; Macosko, Christopher W

    2013-04-24

    The largest use of polyurethane (PU) is as closed cell rigid foams for thermal insulation. One problem is loss of blowing gases, which leads to slow increase in thermal conductivity. PU composites with plate-like nanofillers create a diffusion barrier, reducing gas transport and slowing insulation aging. In this research, a new in situ intercalative polymerization is described to disperse vermiculite (VMT) in PU. When VMT was modified by cation exchange with long-chain quaternary ammonium, the dispersion in methylene diphenyl diisocyanate (MDI) was significantly improved. Dispersion of clay in MDI was further improved by combining high intensity dispersive mixing with a polyol-clay preblend (master-batch). The VMT dispersibility was characterized using rheology, microscopy, and X-ray scattering/diffraction. With the method of polyol-assisted VMT dispersion, electron microscopy revealed extensive intercalation and exfoliation of clay particles. In contrast, simple mixing of organoclay in MDI resulted in macroscopic localization and poor distribution of clay particles in PU. The final nanocomposites prepared by the master-batch method showed enhancement of mechanical properties (85% increase in elastic modulus) and reduction in permeability to CO2, as much as 40%, at a low clay concentration of 3.3 wt %.

  7. Dispersion and decay of collective modes in neutron star cores

    Science.gov (United States)

    Kobyakov, D. N.; Pethick, C. J.; Reddy, S.; Schwenk, A.

    2017-08-01

    We calculate the frequencies of collective modes of neutrons, protons, and electrons in the outer core of neutron stars. The neutrons and protons are treated in a hydrodynamic approximation and the electrons are regarded as collisionless. The coupling of the nucleons to the electrons leads to Landau damping of the collective modes and to significant dispersion of the low-lying modes. We investigate the sensitivity of the mode frequencies to the strength of entrainment between neutrons and protons, which is not well characterized. The contribution of collective modes to the thermal conductivity is evaluated.

  8. Crossing of manifolds leads to flat dispersion: Blazed Littrow waveguides

    Energy Technology Data Exchange (ETDEWEB)

    Benisty, H.; Khayam, O. [Laboratoire Charles Fabry, Institut d' Optique, Universite Paris-Sud, CNRS, FR-91127 Palaiseau (France); Piskunov, N. [Laboratoire Charles Fabry, Institut d' Optique, Universite Paris-Sud, CNRS, FR-91127 Palaiseau (France); Faculty of Physics, M. V. Lomonosov Moscow State University, Moscow, 119991 (Russian Federation); Kashkarov, P. K. [Faculty of Physics, M. V. Lomonosov Moscow State University, Moscow, 119991 (Russian Federation)

    2011-12-15

    We display a photonic embodiment of the Demkov-Ostrovsky solution to the crossing of two manifolds made of equidistant modes thanks to broad periodic waveguides. We find clearly narrowing resonances that signal the singular, flat dispersion case that we had termed ''critical coupling.'' The reconciliation of band-edge confinement and cavity confinement, two pillars of photonics, appear from the guide length dependence of spectra. We suggest the generality of the Demkov-Ostrovsky or critical coupling flat dispersion across all kinds of waves, e.g., electronic and acoustic.

  9. Carbon nanotube suspensions, dispersions, & composites

    Science.gov (United States)

    Simmons, Trevor John

    Carbon Nanotubes (CNTs) are amazing structures that hold the potential to revolutionize many areas of scientific research. CNTs can be behave both as semiconductors and metals, can be grown in highly ordered arrays and patterns or in random orientation, and can be comprised of one graphene cylinder (single wall nanotube, SWNT) or several concentric graphene cylinders (multi-wall nanotube, MWNT). Although these structures are usually only a few nanometers wide, they can be grown up to centimeter lengths, and in massive quantities. CNTs can be produced in a variety of processes ranging from repeated combustion of organic material such as dried grass, arc-discharge with graphite electrodes, laser ablation of a graphitic target, to sophisticated chemical vapor deposition (CVD) techniques. CNTs are stronger than steel but lighter than aluminum, and can be more conductive than copper or semiconducting like silicon. This variety of properties has been matched by the wide variety of applications that have been developed for CNTs. Many of these applications have been limited by the inability of researchers to tame these structures, and incorporating CNTs into existing technologies can be exceedingly difficult and prohibitively expensive. It is therefore the aim of the current study to develop strategies for the solution processing and deposition of CNTs and CNT-composites, which will enable the use of CNTs in existing and emerging technologies. CNTs are not easily suspended in polar solvents and are extremely hydrophobic materials, which has limited much of the solution processing to organic solvents, which also cannot afford high quality dispersions of CNTs. The current study has developed a variety of aqueous CNT solutions that employ surfactants, water-soluble polymers, or both to create suspensions of CNTs. These CNT 'ink' solutions were deposited with a variety of techniques that have afforded many interesting structures, both randomly oriented as well as highly

  10. Dispersion properties of photonic Bandgap Fibres

    DEFF Research Database (Denmark)

    Broeng, Jes; Barkou, Stig Eigil; Søndergaard, Thomas

    1999-01-01

    Dispersion properties of new low-index core photonic crystal fibres are presented. Both wideband nearzero despersion and very large dispersion is shown possible in the 1550 nm wavelength range.......Dispersion properties of new low-index core photonic crystal fibres are presented. Both wideband nearzero despersion and very large dispersion is shown possible in the 1550 nm wavelength range....

  11. Dispersion Management with Higher Order Mode Fibers

    Institute of Scientific and Technical Information of China (English)

    Siddharth Ramachandran

    2003-01-01

    Dispersion compensation with few-mode fibers is emerging as a promising technique that can provide full dispersion and dispersion-slope compensation. The inherent modal path diversity of these fibers allows implementation of static as well as tunable dispersion management schemes. In addition, the low nonlinearityof this technology can improve system OSNR, leading to enhancements in transmission distances.

  12. Dispersion Management with Higher Order Mode Fibers

    Institute of Scientific and Technical Information of China (English)

    Siddharth; Ramachandran

    2003-01-01

    Dispersion compensation with few-mode fibers is emerging as a promising technique that can provide full dispersion and dispersion-slope compensation. The inherent modal path diversity of these fibers allows implementation of static as well as tunable dispersion management schemes. In addition, the low non-linearity of this technology can improve system OSNR, leading to enhancements in transmission distances.

  13. The complex dispersion relation of surface plasmon polaritons at gold/para-hexaphenylene interfaces

    DEFF Research Database (Denmark)

    Lemke, Christoph; Leißner, Till; Klick, Alwin;

    2014-01-01

    Two-photon photoemission electron microscopy (2P-PEEM) is used to measure the real and imaginary part of the dispersion relation of surface plasmon polaritons at different interface systems. A comparison of calculated and measured dispersion data for a gold/vacuum interface demonstrates the capab......Two-photon photoemission electron microscopy (2P-PEEM) is used to measure the real and imaginary part of the dispersion relation of surface plasmon polaritons at different interface systems. A comparison of calculated and measured dispersion data for a gold/vacuum interface demonstrates...... the capability of the presented experimental approach. A systematic 2P-PEEM study on the dispersion relation of dielectric-loaded gold surfaces shows how effective the propagation of surface plasmon polaritons at a gold/para-hexaphenylene interface can be tuned by adjustment of the dielectric film thickness...

  14. Drying mechanism of poly(N-isopropylacrylamide) microgel dispersions.

    Science.gov (United States)

    Horigome, Koji; Suzuki, Daisuke

    2012-09-11

    The drying mechanism of poly(N-isopropylacrylamide) (pNIPAm) microgel dispersions was investigated. The microgels were synthesized by temperature-programmed aqueous free radical precipitation polymerization using NIPAm, N,N'-methylenebis(acrylamide), and water-soluble initiator. Drying processes of the microgel dispersions were observed with a digital camera and an optical microscope, and the resultant dried structures were observed by scanning electron microscopy. We found that the presence of the microgels changed the behavior of the drying process of water. In particular, the microgels were adsorbed at the air/water interface selectively within a few minutes irrespective of the microgel concentration. The relationship between the drying mechanism and structure of the resultant microgel thin film has been clarified by changing the microgel concentration of the dispersions.

  15. Recrystallization characteristics of oxide dispersion strengthened nickel-base alloys

    Science.gov (United States)

    Hotzler, R. K.; Glasgow, T. K.

    1980-01-01

    Electron microscopy was employed to study the process of recrystallization in two oxide dispersion strengthened (ODS) mechanically alloyed nickel-base alloys, MA 754 and MA 6000E. MA 754 contained both fine, uniformly dispersed particles and coarser oxides aligned along the working direction. Hot rolled MA 754 had a grain size of 0.5 microns and high dislocation densities. After partial primary recrystallization, the fine grains transformed to large elongated grains via secondary (or abnormal) grain growth. Extruded and rolled MA 6000E contained equiaxed grains of 0.2 micron diameter. Primary recrystallization occurring during working eliminated virtually all dislocations. Conversion from fine to coarse grains was triggered by gamma prime dissolution; this was also a process of secondary or abnormal grain growth. Comparisons were made to conventional and oxide dispersion strengthened nickel-base alloys.

  16. Dispersion Synthesis with Multi-Ordered Metatronic Filters

    CERN Document Server

    Li, Yue; Engheta, Nader

    2016-01-01

    We propose the synthesis of frequency dispersion of layered structures based on the design of multi-ordered optical filters using nanocircuit concepts. Following the well known insertion loss method commonly employed in the design of electronic and microwave filters, here we theoretically show how we can tailor optical dispersion as we carry out the design of several low-pass, high-pass, band-pass and band-stop filters of different order with a (maximally flat) Butterworth response. We numerically demonstrate that these filters can be designed by combining metasurfaces made of one or two materials acting as optical lumped elements, and, hence, leading to simple, easy to apply, design rules. The theoretical results based on this circuital approach are validated with full-wave numerical simulations. The results presented here can be extended to virtually any frequency dispersion synthesis, filter design procedure and/or functionality, thus opening up exciting possibilities in the design of composite materials w...

  17. Particle Scattering off of Right-Handed Dispersive Waves

    CERN Document Server

    Schreiner, Cedric; Spanier, Felix

    2016-01-01

    Resonant scattering of fast particles off low frequency plasma waves is a major process determining transport characteristics of energetic particles in the heliosphere and contributing to their acceleration. Usually, only Alfv\\'en waves are considered for this process, although dispersive waves are also present throughout the heliosphere. We investigate resonant interaction of energetic electrons with dispersive, right-handed waves. For the interaction of particles and a single wave a variable transformation into the rest frame of the wave can be performed. Here, wellestablished analytic models derived in the framework of magnetostatic quasi-linear theory (QLT) can be used as a reference to validate simulation results. However, this approach fails as soon as several dispersive waves are involved. Based on analytic solutions modeling the scattering amplitude in the magnetostatic limit, we present an approach to modify these equations for the use in the plasma frame. Thereby we aim at a description of particle ...

  18. Plasma Treated TiO2 Nanoparticles for Dispersion Enhancement

    Institute of Scientific and Technical Information of China (English)

    WANG Ying; LI Chun; ZHANG Jing

    2009-01-01

    TiO2 nanoparticles were treated in a fluidized reactor by introducing Hexamethyldisiloxane(HMDSO)plasma monomer.The organic HMDSO-polymer vapor was condensed on the nanoparticles and lowered their surface energy.This plasma treatment was harmless to the crystal lattice of the TiO2 nanoparticles.The treated nanoparticles were mixed in glycol solutions and polymerized into TiO2-polyester composites for studying the effect of plasma deposition on dispersion.It Was found that the dispersion of the TiO2 nanoparticles in both glycol and the polyester matrix Was significantly improved due to lower surface energy and HMDSO plasma treatment, as from ultraviolet absorbency measurements and scanning electron microscopy observation.The theory of colloid stability successfully explained the dispersion enhancement of TiO2 nanoparticles in glycol.

  19. HYPERBRANCHED POLYMERIC DISPERSANTS AND NON-AQUEOUS PIGMENT DISPERSIONS

    NARCIS (Netherlands)

    ANDRE, XAVIER; Bernaerts, Katrien

    2011-01-01

    A polymeric dispersant having a hyperbranched polyurethane architecture obtained by reacting a polyisocyanate core with a mixture of a) 40 to 65 mol% of an anchor represented by Formula (I) and/or (II) wherein n represents an integer selected from 0 to 7; and X and Y each independently represent a p

  20. Hyperbranched polymeric dispersants and non-aqueous pigment dispersions

    NARCIS (Netherlands)

    ANDRE, XAVIER; Bernaerts, Katrien

    2012-01-01

    The invention discloses a polymeric dispersant having a hyperbranched polyurethane architecture obtained by reacting a polyisocyanate core with a mixture of a) 40 to 65 mol% of an anchor represented by Formula (I) and/or (II) wherein n represents an integer selected from 0 to 7; and X and Y each ind

  1. HYPERBRANCHED POLYMERIC DISPERSANTS AND NON-AQUEOUS PIGMENT DISPERSIONS

    NARCIS (Netherlands)

    ANCRE, XAVIER; BERNAERTS, KATRIEN; ANDRE, XAVIER

    2012-01-01

    A polymeric dispersant having a hyperbranched polyurethane architecture obtained by reacting a polyisocyanate core with a mixture of: a) 40 to 65 mol % of an anchor represented by Formula (I) and/or (II): wherein n represents an integer selected from 0 to 7; and X and Y each independently represent

  2. Catalysis on singly dispersed bimetallic sites

    Science.gov (United States)

    Zhang, Shiran; Nguyen, Luan; Liang, Jin-Xia; Shan, Junjun; Liu, Jingyue; Frenkel, Anatoly I.; Patlolla, Anitha; Huang, Weixin; Li, Jun; Tao, Franklin

    2015-08-01

    A catalytic site typically consists of one or more atoms of a catalyst surface that arrange into a configuration offering a specific electronic structure for adsorbing or dissociating reactant molecules. The catalytic activity of adjacent bimetallic sites of metallic nanoparticles has been studied previously. An isolated bimetallic site supported on a non-metallic surface could exhibit a distinctly different catalytic performance owing to the cationic state of the singly dispersed bimetallic site and the minimized choices of binding configurations of a reactant molecule compared with continuously packed bimetallic sites. Here we report that isolated Rh1Co3 bimetallic sites exhibit a distinctly different catalytic performance in reduction of nitric oxide with carbon monoxide at low temperature, resulting from strong adsorption of two nitric oxide molecules and a nitrous oxide intermediate on Rh1Co3 sites and following a low-barrier pathway dissociation to dinitrogen and an oxygen atom. This observation suggests a method to develop catalysts with high selectivity.

  3. Stochastic models for atmospheric dispersion

    DEFF Research Database (Denmark)

    Ditlevsen, Ove Dalager

    2003-01-01

    Simple stochastic differential equation models have been applied by several researchers to describe the dispersion of tracer particles in the planetary atmospheric boundary layer and to form the basis for computer simulations of particle paths. To obtain the drift coefficient, empirical vertical...... velocity distributions that depend on height above the ground both with respect to standard deviation and skewness are substituted into the stationary Fokker/Planck equation. The particle position distribution is taken to be uniform *the well/mixed condition( and also a given dispersion coefficient...

  4. A generalized advection dispersion equation

    Indian Academy of Sciences (India)

    Abdon Atangana

    2014-02-01

    This paper examines a possible effect of uncertainties, variability or heterogeneity of any dynamic system when being included in its evolution rule; the notion is illustrated with the advection dispersion equation, which describes the groundwater pollution model. An uncertain derivative is defined; some properties of the operator are presented. The operator is used to generalize the advection dispersion equation. The generalized equation differs from the standard equation in four properties. The generalized equation is solved via the variational iteration technique. Some illustrative figures are presented.

  5. Dispersion scenarios over complex terrain

    DEFF Research Database (Denmark)

    Thykier-Nielsen, S.; Mikkelsen, T.; Moreno, J.

    1993-01-01

    A presentation of preliminary results from a real-time simulation of full-scale dispersion experiments carried out over complex terrain in Northern Spain is given. Actual wind and turbulence measurements as observed during the experiments were analysed and used as input data for a series of simul......A presentation of preliminary results from a real-time simulation of full-scale dispersion experiments carried out over complex terrain in Northern Spain is given. Actual wind and turbulence measurements as observed during the experiments were analysed and used as input data for a series...

  6. Preparation of aqueous dispersion of thermoplastic sizing agent for carbon fiber by emulsion/solvent evaporation

    Science.gov (United States)

    Giraud, Isabelle; Franceschi-Messant, Sophie; Perez, Emile; Lacabanne, Colette; Dantras, Eric

    2013-02-01

    In this work, different sizing agent aqueous dispersions based on polyetherimide (PEI) were elaborated in order to improve the interface between carbon fibers and a thermoplastic matrix (PEEK). The dispersions were obtained by the emulsion/solvent evaporation technique. To optimize the stability and the film formation on the fibers, two surfactants were tested at different concentrations, with different concentrations of PEI. The dispersions obtained were characterized by dynamic light scattering (DLS) and the stability evaluated by analytical centrifugation (LUMiFuge). The selected dispersions were tested for film formation ability by scanning electron microscopy (SEM), and the sizing performance was assessed by observation of the fiber/matrix interface by SEM. The results revealed that an aqueous dispersion of PEI, stabilized by sodium dodecyl sulfate as the surfactant, led to very stable sizing agent aqueous dispersion with ideal film formation and better interface adhesion.

  7. Synthesis,characterization and hydrodesulfurization activity of silica-dispersed NiMoW trimetallic catalysts

    Institute of Scientific and Technical Information of China (English)

    Di Liu; Lihua Liu; Guangci Li; Chenguang Liu

    2010-01-01

    Silica-dispersed NiMoW trimetallic hydrodesulfurization catalysts were prepared by deposition-precipitation method.For comparative purposes,bulk NiMoW trimetallic catalysts were obtained by co-precipitation.Silica was employed to disperse active metals for full utilization of active components and silica-dispersed NiMoW catalyst had high active metal content.BET analysis showed that silica-dispersed NiMoW trimetallic catalysts had a high surface area(165.1 m2/g)and pore volume(0.27 ml/g).Transmission electron microscopy results proved that active components were well dispersed.Hydrodesulfurization activity of silica-dispersed NiMoW catalysts was much higher than that of comparative catalysts and up to twice greater than those of commercial NiMo alumina-supported systems per gram of catalyst.

  8. Inferences from the Distributions of Fast Radio Burst Pulse Widths, Dispersion Measures and Fluences

    CERN Document Server

    Katz, J I

    2015-01-01

    The widths, dispersion measures, dispersion indices and fluences of Fast Radio Bursts (FRB) impose coupled constraints that all models must satisfy. Observation of dispersion indices close to their low density limit of $-2$ sets a model-independent upper bound on the electron density and a lower bound on the size of any dispersive plasma cloud. The non-monotonic dependence of burst widths (after deconvolution of instrumental effects) on dispersion measure excludes the intergalactic medium as the location of scattering that broadens the FRB in time. Temporal broadening far greater than that of pulsars at similar high Galactic latitudes implies that scattering occurs close to the sources, where high densities and strong turbulence are plausible. FRB energetics are consistent with supergiant pulses from young, fast, high-field pulsars at cosmological distances. The distribution of FRB dispersion measures is inconsistent with expanding clouds (such as SNR). It excludes space-limited distributions (such as the loc...

  9. Observations of Obliquely Propagating Electron Bernstein Waves

    DEFF Research Database (Denmark)

    Armstrong, R. J.; Juul Rasmussen, Jens; Stenzel, R. L.

    1981-01-01

    Plane electron Bernstein waves propagating obliquely to the magnetic field are investigated. The waves are excited by a plane grid antenna in a large volume magnetoplasma. The observations compare favorably with the predictions of the linear dispersion relation.......Plane electron Bernstein waves propagating obliquely to the magnetic field are investigated. The waves are excited by a plane grid antenna in a large volume magnetoplasma. The observations compare favorably with the predictions of the linear dispersion relation....

  10. On Dispersion in Visual Photoreceptors

    NARCIS (Netherlands)

    Stavenga, D.G.; Barneveld, H.H. van

    1975-01-01

    An idealized visual pigment absorbance spectrum is used together with a Kramers-Kronig dispersion relation to calculate the contribution of the visual pigment to the refractive index of the fly photoreceptor. It appears that an absorption coefficient of 0.010 µm-1 results in a refractive index varia

  11. Magnetic exciton dispersion in praseodymium

    DEFF Research Database (Denmark)

    Rainford, B. D.; Houmann, Jens Christian Gylden

    1971-01-01

    Measurements of the dispersion of magnetic excitons have been made in a single crystal of praseodymium metal using inelastic neutron scattering. A preliminary analysis of the data yields the first detailed information about the exchange interactions and the crystal field splittings in the light...

  12. Dispersion-Enhanced Laser Gyroscope

    Science.gov (United States)

    Smith, David D.; Chang, Hongrok; Arissian, L.; Diels, J. C.

    2008-01-01

    We analyze the effect of a highly dispersive element placed inside a modulated optical cavity on the frequency and amplitude of the output modulation to determine the conditions for enhanced gyroscopic sensitivities. The element is treated as both a phase and amplitude filter, and the time-dependence of the cavity field is considered. Both atomic gases (two-level and multi-level) and optical resonators (single and coupled) are considered and compared as dispersive elements. We find that it is possible to simultaneously enhance the gyro scale factor sensitivity and suppress the dead band by using an element with anomalous dispersion that has greater loss at the carrier frequency than at the side-band frequencies, i.e., an element that simultaneously pushes and intensifies the perturbed cavity modes, e.g. a two-level absorber or an under-coupled optical resonator. The sensitivity enhancement is inversely proportional to the effective group index, becoming infinite at a group index of zero. However, the number of round trips required to reach a steady-state also becomes infinite when the group index is zero (or two). For even larger dispersions a steady-state cannot be achieved, and nonlinear dynamic effects such as bistability and periodic oscillations are predicted in the gyro response.

  13. DIMO, a plant dispersal model

    NARCIS (Netherlands)

    Wamelink, G.W.W.; Jochem, R.; Greft, van der J.G.M.; Franke, J.; Malinowska, A.H.; Geertsema, W.; Prins, A.H.; Ozinga, W.A.; Hoek, van der D.C.J.; Grashof-Bokdam, C.J.

    2014-01-01

    Due to human activities many natural habitats have become isolated. As a result the dispersal of many plant species is hampered. Isolated populations may become extinct and have a lower probability to become reestablished in a natural way. Moreover, plant species may be forced to migrate to new area

  14. Molecular mobility in glassy dispersions

    Science.gov (United States)

    Mehta, Mehak; McKenna, Gregory B.; Suryanarayanan, Raj

    2016-05-01

    Dielectric spectroscopy was used to characterize the structural relaxation in pharmaceutical dispersions containing nifedipine (NIF) and either poly(vinyl) pyrrolidone (PVP) or hydroxypropyl methylcellulose acetate succinate (HPMCAS). The shape of the dielectric response (permittivity versus log time) curve was observed to be independent of temperature. Thus, for the pure NIF as well as the dispersions, the validity of the time-temperature superposition principle was established. Furthermore, though the shape of the full dielectric response varied with polymer concentration, the regime related to the α- or structural relaxation was found to superimpose for the dispersions, though not with the response of the NIF itself. Hence, there is a limited time-temperature-concentration superposition for these systems as well. Therefore, in this polymer concentration range, calculation of long relaxation times in these glass-forming systems becomes possible. We found that strong drug-polymer hydrogen bonding interactions improved the physical stability (i.e., delayed crystallization) by reducing the molecular mobility. The strength of hydrogen bonding, structural relaxation time, and crystallization followed the order: NIF-PV P>NIF-HPMCAS>NIF. With an increase in polymer concentration, the relaxation times were longer indicating a decrease in molecular mobility. The temperature dependence of relaxation time, in other words fragility, was independent of polymer concentration. This is the first application of the superposition principle to characterize structural relaxation in glassy pharmaceutical dispersions.

  15. Wireless Communication over Dispersive Channels

    NARCIS (Netherlands)

    Fang, K.

    2010-01-01

    Broadband wireless communication systems require high transmission rates, where the bandwidth of the transmitted signal is larger than the channel coherence bandwidth. This gives rise to time dispersion of the transmitted symbols or frequency-selectivity with different frequency components exhibitin

  16. Molecular mobility in glassy dispersions

    Energy Technology Data Exchange (ETDEWEB)

    Mehta, Mehak [Univ. of Minnesota, Minneapolis, MN (United States). Dept. of Pharmaceutics; McKenna, Gregory B. [Texas Tech Univ., Lubbock, TX (United States). Dept. of Chemical Engineering; Suryanarayanan, Raj [Univ. of Minnesota, Minneapolis, MN (United States). Dept. of Pharmaceutics

    2016-05-27

    Dielectric spectroscopy was used to characterize the structural relaxation in pharmaceutical dispersions containing nifedipine (NIF) and either poly(vinyl) pyrrolidone (PVP) or hydroxypropyl methylcellulose acetate succinate (HPMCAS). The shape of the dielectric response (permittivity versus log time) curve was observed to be independent of temperature. Thus, for the pure NIF as well as the dispersions, the validity of the time-temperature superposition principle was established. Furthermore, though the shape of the full dielectric response varied with polymer concentration, the regime related to the α- or structural relaxation was found to superimpose for the dispersions, though not with the response of the NIF itself. Hence, there is a limited time-temperature-concentration superposition for these systems as well. Therefore, in this polymer concentration range, calculation of long relaxation times in these glass-forming systems becomes possible. We found that strong drug-polymer hydrogen bonding interactions improved the physical stability (i.e., delayed crystallization) by reducing the molecular mobility. The strength of hydrogen bonding, structural relaxation time, and crystallization followed the order: NIF$-$PV P>NIF$-$HPMCAS>NIF. With an increase in polymer concentration, the relaxation times were longer indicating a decrease in molecular mobility. The temperature dependence of relaxation time, in other words fragility, was independent of polymer concentration. This is the first application of the superposition principle to characterize structural relaxation in glassy pharmaceutical dispersions.

  17. Dispersion-enhanced laser gyroscope

    Science.gov (United States)

    Smith, David D.; Chang, Hongrok; Arissian, L.; Diels, J. C.

    2008-11-01

    We analyze the effect of a highly dispersive element placed inside a modulated optical cavity on the frequency and amplitude of the output modulation to determine the conditions for enhanced gyroscopic sensitivities. The element is treated as both a phase and amplitude filter, and the time dependence of the cavity field is considered. Both atomic gases (two level and multilevel) and optical resonators (single and coupled) are considered and compared as dispersive elements. We find that it is possible to simultaneously enhance the gyro scale factor sensitivity and suppress the dead band by using an element with anomalous dispersion that has greater loss at the carrier frequency than at the sideband frequencies, i.e., an element that simultaneously pushes and intensifies the perturbed cavity modes, e.g. a two-level absorber or an undercoupled optical resonator. The sensitivity enhancement is inversely proportional to the effective group index, becoming infinite at a group index of zero. However, the number of round trips required to reach a steady state also becomes infinite when the group index is zero (or two). For even larger dispersions a steady state cannot be achieved, and nonlinear dynamic effects such as bistability and periodic oscillations are predicted in the gyro response.

  18. Seed dispersal: Size does matter

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    @@ Many small seed-eating rodents bury their food in an erratic manner called scatter-hoarding because they are unable to defend one large hoard. This process has a complicated influence on seed dispersal,as shown in the work by ZHANG Zhibin at the CAS Institute of Zoology and hisco-workers.

  19. Anomalous dispersions of `hedgehog' particles

    Science.gov (United States)

    Bahng, Joong Hwan; Yeom, Bongjun; Wang, Yichun; Tung, Siu On; Hoff, J. Damon; Kotov, Nicholas

    2015-01-01

    Hydrophobic particles in water and hydrophilic particles in oil aggregate, but can form colloidal dispersions if their surfaces are chemically camouflaged with surfactants, organic tethers, adsorbed polymers or other particles that impart affinity for the solvent and increase interparticle repulsion. A different strategy for modulating the interaction between a solid and a liquid uses surface corrugation, which gives rise to unique wetting behaviour. Here we show that this topographical effect can also be used to disperse particles in a wide range of solvents without recourse to chemicals to camouflage the particles' surfaces: we produce micrometre-sized particles that are coated with stiff, nanoscale spikes and exhibit long-term colloidal stability in both hydrophilic and hydrophobic media. We find that these `hedgehog' particles do not interpenetrate each other with their spikes, which markedly decreases the contact area between the particles and, therefore, the attractive forces between them. The trapping of air in aqueous dispersions, solvent autoionization at highly developed interfaces, and long-range electrostatic repulsion in organic media also contribute to the colloidal stability of our particles. The unusual dispersion behaviour of our hedgehog particles, overturning the notion that like dissolves like, might help to mitigate adverse environmental effects of the use of surfactants and volatile organic solvents, and deepens our understanding of interparticle interactions and nanoscale colloidal chemistry.

  20. An Introduction to Dispersive Interactions

    Science.gov (United States)

    Taddei, M. M.; Mendes, T. N. C.; Farina, C.

    2010-01-01

    Dispersive forces are a kind of van der Waals intermolecular force which could only be fully understood with the establishment of quantum mechanics and, in particular, of quantum electrodynamics. In this pedagogical paper, we introduce the subject in a more elementary approach, aiming at students with basic knowledge of quantum mechanics. We…

  1. Dispersive mudslide-induced tsunamis

    Directory of Open Access Journals (Sweden)

    A. Rubino

    1998-01-01

    Full Text Available A nonlinear nested model for mudslide-induced tsunamis is proposed in which three phases of the life of the wave, i.e. the generation, far-field propagation and costal run-up are described by means of different mathematical models, that are coupled through appropriate matching procedures. The generation and run-up dynamics are simulated through a nonlinear shallow-water model with movable lateral boundaries: in the generation region two active layers are present, the lower one describing the slide descending on a sloping topography. For the intermediate phase, representing wave propagation far from the generation region, the hydrostatic assumption is not assumed as appropriate in general and, therefore, a nonlinear model allowing for weak phase dispersion, namely a Kadomtsev-Petviashvili equation, is used. This choice is made in order to assess the relevance of dispersive features such as solitary waves and dispersive tails. It is shown that in some realistic circumstances dispersive mudslide-induced tsunami waves can be produced over relatively short, distances. In such cases the use of a hydrostatic model throughout the whole tsunami history turns out to give erroneous results. In particular, when solitary waves are generated during the tsunami propagation in the open sea, the resulting run-up process yields peculiar wave forms leading to amplified coastal inundations with respect to a mere hydrostatic context.

  2. Promoting cell proliferation using water dispersible germanium nanowires.

    Directory of Open Access Journals (Sweden)

    Michael Bezuidenhout

    Full Text Available Group IV Nanowires have strong potential for several biomedical applications. However, to date their use remains limited because many are synthesised using heavy metal seeds and functionalised using organic ligands to make the materials water dispersible. This can result in unpredicted toxic side effects for mammalian cells cultured on the wires. Here, we describe an approach to make seedless and ligand free Germanium nanowires water dispersible using glutamic acid, a natural occurring amino acid that alleviates the environmental and health hazards associated with traditional functionalisation materials. We analysed the treated material extensively using Transmission electron microscopy (TEM, High resolution-TEM, and scanning electron microscope (SEM. Using a series of state of the art biochemical and morphological assays, together with a series of complimentary and synergistic cellular and molecular approaches, we show that the water dispersible germanium nanowires are non-toxic and are biocompatible. We monitored the behaviour of the cells growing on the treated germanium nanowires using a real time impedance based platform (xCELLigence which revealed that the treated germanium nanowires promote cell adhesion and cell proliferation which we believe is as a result of the presence of an etched surface giving rise to a collagen like structure and an oxide layer. Furthermore this study is the first to evaluate the associated effect of Germanium nanowires on mammalian cells. Our studies highlight the potential use of water dispersible Germanium Nanowires in biological platforms that encourage anchorage-dependent cell growth.

  3. Cast aluminum alloys containing dispersions of zircon particles

    Science.gov (United States)

    Banerji, A.; Surappa, M. K.; Rohatgi, P. K.

    1983-06-01

    A process for preparing Al-alloy castings containing dispersions of zircon particles is described. Composites were prepared by stirring zircon particles (40 to 200 µm size) in commercially pure Al (99.5 pct)* and Al-11.8 pct Si melts and subsequently casting these melts in permanent molds. It was found to be necessary to alloy the above two melts with 3 pct Mg to disperse substantial amounts of zircon particles (25 to 30 pct). Further, it was possible to disperse up to 60 wt pct zircon by adding up to 5 pct Mg; however, the melts containing above 30 wt pct zircon showed insufficient fluidity for gravity diecasting and had to be pressure diecast. Microstructural studies of cast composites indicated the presence of a reaction zone at the periphery of zircon particles, and electron probe microanalysis showed concentrations of Mg and Si at the particle-matrix interface. Hardness, abrasive wear resistance, elastic modulus, 0.2 pct proof stress, and tensile strength of cast Al-3 pct Mg alloy were found to improve with the dispersions of zircon particles. Scanning electron micrographs of abraded and fractured surfaces did not show any evidence of particle pull-outs or voids at the particle matrix interface, indicating strong continuous bonding.

  4. Enhanced convective heat transfer using graphene dispersed nanofluids.

    Science.gov (United States)

    Baby, Tessy Theres; Ramaprabhu, Sundara

    2011-04-04

    Nanofluids are having wide area of application in electronic and cooling industry. In the present work, hydrogen exfoliated graphene (HEG) dispersed deionized (DI) water, and ethylene glycol (EG) based nanofluids were developed. Further, thermal conductivity and heat transfer properties of these nanofluids were systematically investigated. HEG was synthesized by exfoliating graphite oxide in H2 atmosphere at 200°C. The nanofluids were prepared by dispersing functionalized HEG (f-HEG) in DI water and EG without the use of any surfactant. HEG and f-HEG were characterized by powder X-ray diffractometry, electron microscopy, Raman and FTIR spectroscopy. Thermal and electrical conductivities of f-HEG dispersed DI water and EG based nanofluids were measured for different volume fractions and at different temperatures. A 0.05% volume fraction of f-HEG dispersed DI water based nanofluid shows an enhancement in thermal conductivity of about 16% at 25°C and 75% at 50°C. The enhancement in Nusselts number for these nanofluids is more than that of thermal conductivity.

  5. Enhanced convective heat transfer using graphene dispersed nanofluids

    Directory of Open Access Journals (Sweden)

    Baby Tessy

    2011-01-01

    Full Text Available Abstract Nanofluids are having wide area of application in electronic and cooling industry. In the present work, hydrogen exfoliated graphene (HEG dispersed deionized (DI water, and ethylene glycol (EG based nanofluids were developed. Further, thermal conductivity and heat transfer properties of these nanofluids were systematically investigated. HEG was synthesized by exfoliating graphite oxide in H2 atmosphere at 200°C. The nanofluids were prepared by dispersing functionalized HEG (f-HEG in DI water and EG without the use of any surfactant. HEG and f-HEG were characterized by powder X-ray diffractometry, electron microscopy, Raman and FTIR spectroscopy. Thermal and electrical conductivities of f-HEG dispersed DI water and EG based nanofluids were measured for different volume fractions and at different temperatures. A 0.05% volume fraction of f-HEG dispersed DI water based nanofluid shows an enhancement in thermal conductivity of about 16% at 25°C and 75% at 50°C. The enhancement in Nusselts number for these nanofluids is more than that of thermal conductivity.

  6. Dispersions of non-covalently functionalized graphene with minimal stabilizer

    Science.gov (United States)

    Parviz, Dorsa; Das, Sriya; Irin, Fahmida; Green, Micah

    2013-03-01

    Pyrene derivatives are promising substitutes of surfactants and polymers for stabilization of graphene in aqueous dispersions. We demonstrate that pyrene derivatives stabilize single- to few-layer graphene sheets, yielding exceptionally higher graphene/stabilizer ratio in comparison with conventional stabilizers. Parameters such as stabilizer concentration, initial graphite concentration, type and number of functional groups, counterions, the pH and the polarity of dispersion media were shown to affect the adsorption process and final graphene concentration. The effectiveness of pyrene derivatives is determined by the type, number and electronegativity of functional groups and counterion. It also depends on the distance between functional group and pyrene basal plan, the pH of the dispersion (as shown by zeta potential measurements) and the relative polarity between stabilizer and solvent. Stability of the dispersions against centrifugation, pH and temperature changes and lyophilization was investigated. These dispersions also show promise for applications to polymer nanocomposites, organic solar cells, conductive films, and inkjet-printed electronic devices.

  7. Optimization of dispersing agents for preparing YAG transparent ceramics

    Institute of Scientific and Technical Information of China (English)

    BA Xuewei; LI Jiang; PAN Yubai; LIU Jing; JIANG Benxue; LIU Wenbin; KOU Huamin

    2013-01-01

    The suspensions of the powder mixture of yttria and alumina were prepared by the aqueous tape casting method.Rodia DP270,Dolapix CE64,citric acid and Dammonium 3008 were used as dispersing agents.The morphologies of the powders and the fiacture surface of the green body were observed by scanning electron microscopy (SEM).The zeta potential test was employed to characterize the surface charge states of different suspensions.The dispersion of the suspensions was analyzed by the rheological tests and the sedimentation experiments.The results indicated that the yttria and alumina powder mixtures were well dispersed by the dispersing agents.The rheological curves showed shear thinning behavior.The most efficient dispersing agent was Dammonium 3008.The optimum usage of Dammonium 3008 was 1.0 wt.%.The green body was dense and no interface between the adjacent layers was found.The in-line transmittance of the as-sintered YAG ceramic was higher than 80% between 400 and 1100 nm.

  8. The dispersion and aggregation of graphene oxide in aqueous media

    Science.gov (United States)

    Wang, Meng; Niu, Yang; Zhou, Jihan; Wen, Hao; Zhang, Zhenyu; Luo, Da; Gao, Dongliang; Yang, Juan; Liang, Dehai; Li, Yan

    2016-07-01

    dispersion of GO may be applied in the solution processing of GO. It also expands the scope of the design and preparation of new GO-based hybrid materials with different functions. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr03503e

  9. Interdependence of waveguide and material dispersion.

    Science.gov (United States)

    Marcuse, D

    1979-09-01

    Theoretical work on dispersion in single-mode fibers sometimes uses the assumption that waveguide dispersion D(w) and material dispersion D(m) are separate effects that contribute additively to the total amount of dispersion D(m+w). Using Gloge's LP-mode approximation we compute the dispersion of the LP(0l) (HE(11)) mode by solving the eigenvalue equation taking dispersion of core and cladding materials into account. The dispersion of the LP(01) mode is computed by numerical differentiation of the solution of the eigenvalue equation. The difference D(m+w) - D(w) is compared to waveguide dispersion D(w), which is computed by ignoring the dispersive properties of the core and cladding materials. We find large percentage deviations between D(m+w) - D(m) and D(w). The assumption of additivity of material and waveguide dispersion is thus not quite correct. However, because of the small contribution of waveguide dispersion to the total dispersion of the LP(01) mode, even a large percentage error in the waveguide dispersion has little influence on the over-all dispersion of the LP(01) mode.

  10. 旋转式伽玛刀治疗功能性垂体微腺瘤的远期疗效和安全性%The Long-term Therapeutic Effect and Safety of Rotatory Gamma Knife Treatment for Secretory Pituitary Microadenomas

    Institute of Scientific and Technical Information of China (English)

    石松生; 杨卫忠; 梁日生; 陈阵; 陈建乐

    2011-01-01

    目的 探讨旋转式伽玛刀治疗功能性垂体微腺瘤的远期疗效和安全性.方法 总结分析1998年3月-2006年2月经旋转式伽玛刀治疗5年以上且获得随访的功能性垂体微腺瘤患者66例,男性11例,女性55例,年龄(31.3±10.6)岁,病程(36.7±14.8)月,治疗剂量(30/9~60/30)Gy.结果 临床表现缓解63例、无变化2例、加重1例,肿瘤消失或缩小59例、无变化6例、增大1例;原异常升高的垂体激素恢复正常或下降62例、无明显变化3例、升高1例,其中2例出现垂体内分泌功能低下,但只有1例有相应的临床症状且需激素替代治疗.结论 旋转式伽玛刀治疗功能性垂体微腺瘤的远期效果好而且安全,引起垂体功能低下的可能性极小.%Objective To investigate the long-term therapeutic effect and safety of rotatory gam ma knife treatment for secretory pituitary microadenomas. Methods The clinical and follow-up results of 66 patients of secretory pituitary microadenomas from March 1998 to February 2006 , who had been treated with rotatory gamma knife for at least 5 years, were retrospectively summarized and analysed. In this se ries, 55 patients were female and 11 were male, ranging in age from 16 to 68 years (mean 31. 3 + 10. 6 years). The illness duration ranged from 3 months to 12 years (mean 36. 7 + 14. 8 months). The thera peutic dose was 30/9~60/30 Gy. Result The clinical manifestations relieved in 63 cases, did not change in 2 cases and aggravated in one; the tumor disappeared or shrinked in 59 cases, remained the same size in 6 cases and enlarged in one; and the pre-treatment elevated pituitary hormone restored to normal level or decreased in 62 cases, did not show obvious change in 3 cases and increased in one. Hypopituitarism was found in only two cases, but only one presented relative clinical symptoms and needed hormone replace ment therapy. Conclusion Rotatory gamma knife treatment for secretory pituitary microadenomas is se cure and

  11. Observation on the curative effect of Feng' s rotatory reduction manipulation at fixed points of spine in the treatment of acute lumbar sprain%冯氏脊柱定点旋转复位手法治疗急性腰扭伤的疗效观察

    Institute of Scientific and Technical Information of China (English)

    杜诚恳; 董倔强; 王海磊; 翁文水

    2012-01-01

    目的:观察冯氏脊柱定点旋转复位手法治疗急性腰扭伤的临床疗效.方法:将纳入研究的90例急性腰扭伤患者随机分成2组,每组45例.治疗组采用冯氏脊柱定点旋转复位手法治疗,对照组采用传统斜扳手法治疗 手法治疗每天1次,共治疗3次.分别于治疗前和治疗结束后采用自拟腰痛疾患疗效评定标准对2组患者的疗效进行评定.结果:治疗前2组患者腰痛评分比较,差异无统计学意义(t=0.028,P=0.978);治疗后2组患者腰痛评分均增加(t=18.183,P=0.000;t=13.726,P=0.000),治疗组增加更明显(t=2.039,P=0.044).结论:冯氏脊柱定点旋转复位手法治疗急性腰扭伤疗效显著,值得临床推广应用.%Objective:To observe the clinical curative effect of Feng' s rotatory reduction manipulation at fked points of spine in the treatment of acute lumbar sprain( ALS). Methods:Ninety ALS patients enrolled in the study were randomly divider! into 2 groups,45 cases in each group. Patients in the treatment group were administrated with Feng's rotatory reduction manipulation at fixed points of spine, while the others in the control group were administrated with traditional oblique-pulling manipulation,once a day for consecutive 3 days. The cura-tive effects were evaluated according to the self-designed standard for curative effect evaluation of low back pain before and after the treat-ment respectively. Results:There was no statistical difference in the low back pain scores between the 2 groups before the treatment (t = 0. 028, P = 0.978). The low back pain scores of the 2 groups were all increased after the ireatmen(t = 18. 183 ,P = 0. 000;/ = 13.726.t = 0. 000) ,and scores increased more significantly in the treatment group(t =2. 039 ,P=0. 044 ). Conclusion;The method of Feng' s rotatory reduction manipulation at fixed points of spine performs well in ihe. treatment of acute lumbar sprain.it is worth popularizing in the clinic.

  12. Hard electronics; Hard electronics

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-03-01

    In the fields of power conversion devices and broadcasting/communication amplifiers, high power, high frequency and low losses are desirable. Further, for electronic elements in aerospace/aeronautical/geothermal surveys, etc., heat resistance to 500degC is required. Devices which respond to such hard specifications are called hard electronic devices. However, with Si which is at the core of the present electronics, the specifications cannot fully be fulfilled because of the restrictions arising from physical values. Accordingly, taking up new device materials/structures necessary to construct hard electronics, technologies to develop these to a level of IC were examined and studied. They are a technology to make devices/IC of new semiconductors such as SiC, diamond, etc. which can handle higher temperature, higher power and higher frequency than Si and also is possible of reducing losses, a technology to make devices of hard semiconducter materials such as a vacuum microelectronics technology using ultra-micro/high-luminance electronic emitter using negative electron affinity which diamond, etc. have, a technology to make devices of oxides which have various electric properties, etc. 321 refs., 194 figs., 8 tabs.

  13. Optimized dispersion of nanoparticles for biological in vitro and in vivo studies

    Directory of Open Access Journals (Sweden)

    Coester Conrad

    2008-11-01

    Full Text Available Abstract Background The aim of this study was to establish and validate a practical method to disperse nanoparticles in physiological solutions for biological in vitro and in vivo studies. Results TiO2 (rutile dispersions were prepared in distilled water, PBS, or RPMI 1640 cell culture medium. Different ultrasound energies, various dispersion stabilizers (human, bovine, and mouse serum albumin, Tween 80, and mouse serum, various concentrations of stabilizers, and different sequences of preparation steps were applied. The size distribution of dispersed nanoparticles was analyzed by dynamic light scattering and zeta potential was measured using phase analysis light scattering. Nanoparticle size was also verified by transmission electron microscopy. A specific ultrasound energy of 4.2 × 105 kJ/m3 was sufficient to disaggregate TiO2 (rutile nanoparticles, whereas higher energy input did not further improve size reduction. The optimal sequence was first to sonicate the nanoparticles in water, then to add dispersion stabilizers, and finally to add buffered salt solution to the dispersion. The formation of coarse TiO2 (rutile agglomerates in PBS or RPMI was prevented by addition of 1.5 mg/ml of human, bovine or mouse serum albumin, or mouse serum. The required concentration of albumin to stabilize the nanoparticle dispersion depended on the concentration of the nanoparticles in the dispersion. TiO2 (rutile particle dispersions at a concentration lower than 0.2 mg/ml could be stabilized by the addition of 1.5 mg/ml albumin. TiO2 (rutile particle dispersions prepared by this method were stable for up to at least 1 week. This method was suitable for preparing dispersions without coarse agglomerates (average diameter 2 (rutile, ZnO, Ag, SiOx, SWNT, MWNT, and diesel SRM2975 particulate matter. Conclusion The optimized dispersion method presented here appears to be effective and practicable for preparing dispersions of nanoparticles in physiological

  14. Analysis of Wave Nonlinear Dispersion Relation

    Institute of Scientific and Technical Information of China (English)

    LI Rui-jie; TAO Jian-fu

    2005-01-01

    The nonlinear dispersion relations and modified relations proposed by Kirby and Hedges have the limitation of intermediate minimum value. To overcome the shortcoming, a new nonlinear dispersion relation is proposed. Based on the summarization and comparison of existing nonlinear dispersion relations, it can be found that the new nonlinear dispersion relation not only keeps the advantages of other nonlinear dispersion relations, but also significantly reduces the relative errors of the nonlinear dispersion relations for a range of the relative water depth of 1<kh<1.5 and has sufficient accuracy for practical purposes.

  15. Dispersion compensation based on prism compressor

    Science.gov (United States)

    Liu, Hongying; Lan, Tian; Chen, Xiaomei; Ni, Guoqiang

    2017-04-01

    A prism compressor can compensate dispersion of femtosecond light pulses travelling in air for laser ranging. An accurate expression of the group delay dispersion (GDD) of a prism compressor at arbitrary incident angle and at arbitrary incident point is obtained, which is of benefit to finely compensating dispersion of femtosecond pulses. Influences of several parameters on group delay dispersion are analyzed for the active compensation of dispersion of femtosecond pulses. These expressions are convenient to applications of intra- and extra-cavity dispersion compensation of ultra-short laser pulses, as well as fine compensation of satellite laser ranging and laser altimetry.

  16. Seed dispersal distances: a typology based on dispersal modes and plant traits

    OpenAIRE

    Vittoz, P.; Engler, R.

    2007-01-01

    The ability of plants to disperse seeds may be critical for their survival under the current constraints of landscape fragmentation and climate change. Seed dispersal distance would therefore be an important variable to include in species distribution models. Unfortunately, data on dispersal distances are scarce, and seed dispersion models only exist for some species with particular dispersal modes. To overcome this lack of knowledge, we propose a simple approach to estimate seed dispersal di...

  17. Effects of oil dispersants on photodegradation of pyrene in marine water

    Energy Technology Data Exchange (ETDEWEB)

    Gong, Yanyan [Environmental Engineering Program, Department of Civil Engineering, Auburn University, Auburn, AL 36849 (United States); College of Environmental Science and Engineering, Nankai University, Tianjin 300071 (China); Fu, Jie [Environmental Engineering Program, Department of Civil Engineering, Auburn University, Auburn, AL 36849 (United States); O’Reilly, S.E. [U.S. Department of the Interior, Gulf of Mexico OCS, Office of Environment, New Orleans, LA 70123 (United States); Zhao, Dongye, E-mail: zhaodon@auburn.edu [Environmental Engineering Program, Department of Civil Engineering, Auburn University, Auburn, AL 36849 (United States)

    2015-04-28

    Highlights: • Oil dispersant enhances pyrene photodegradation in seawater. • Oil dispersant increases formation of superoxide radicals. • Pyrene photodegradation shows a two-stage kinetics and follows first-order rate law. • Pyrene is degraded mainly through electron transfer from excited pyrene to oxygen. • Higher ionic strength and temperature and lower HA favor pyrene photodegradation. - Abstract: This work investigated effects of a popular oil dispersant (Corexit EC9500A) on UV- or sunlight-mediated photodegradation of pyrene (a model polycyclic aromatic hydrocarbon) in seawater. The presence of 18 and 180 mg/L of the dispersant increased the first-order photodegradation rate by 5.5% and 16.7%, respectively, and reduced or ceased pyrene volatilization. By combining individual first-order rate laws for volatilization and photodegradation, we proposed an integrated kinetic model that can adequately predict the overall dissipation of pyrene from seawater. Mechanistic studies indicated that superoxide radicals played a predominant role in pyrene photodegradation, and the dispersant enhanced formation of superoxide radicals. 1-Hydroxypyrene was the main intermediate regardless of the dispersant, suggesting that electrons were transferred from excited pyrene to oxygen. In the presence of 18 mg/L of the dispersant, the photodegradation rate increased with increasing ionic strength and temperature, but decreased with increasing HA concentration, and remained independent of solution pH. The results are important in understanding roles of oil dispersants on environmental fate of persistent oil components in natural and engineered systems.

  18. Dispersing perylene diimide/SWCNT hybrids: structural insights at the molecular level and fabricating advanced materials.

    Science.gov (United States)

    Tsarfati, Yael; Strauss, Volker; Kuhri, Susanne; Krieg, Elisha; Weissman, Haim; Shimoni, Eyal; Baram, Jonathan; Guldi, Dirk M; Rybtchinski, Boris

    2015-06-17

    The unique properties of carbon nanotubes (CNT) are advantageous for emerging applications. Yet, the CNT insolubility hampers their potential. Approaches based on covalent and noncovalent methodologies have been tested to realize stable dispersions of CNTs. Noncovalent approaches are of particular interest as they preserve the CNT's structures and properties. We report on hybrids, in which perylene diimide (PDI) amphiphiles are noncovalently immobilized onto single wall carbon nanotubes (SWCNT). The resulting hybrids were dispersed and exfoliated both in water and organic solvents in the presence of two different PDI derivatives, PP2b and PP3a. The dispersions were investigated using cryogenic transmission electron microscopy (cryo-TEM), providing unique structural insights into the exfoliation. A helical arrangement of PP2b assemblies on SWCNTs dominates in aqueous dispersions, while a single layer of PP2b and PP3a was found on SWCNTs in organic dispersions. The dispersions were probed by steady-state and time-resolved spectroscopies, revealing appreciable charge redistribution in the ground state, and an efficient electron transfer from SWCNTs to PDIs in the excited state. We also fabricated hybrid materials from the PP2b/SWCNT dispersions. A supramolecular membrane was prepared from aqueous dispersions and used for size-selective separation of gold nanoparticles. Hybrid buckypaper films were prepared from the organic dispersions. In the latter, high conductivity results from enhanced electronic communication and favorable morphology within the hybrid material. Our findings shed light onto SWCNT/dispersant molecular interactions, and introduce a versatile approach toward universal solution processing of SWCNT-based materials.

  19. Phonon dispersion and lifetimes in MgB2.

    Science.gov (United States)

    Shukla, Abhay; Calandra, Matteo; D'Astuto, Matteo; Lazzeri, Michele; Mauri, Francesco; Bellin, Christophe; Krisch, Michael; Karpinski, J; Kazakov, S M; Jun, J; Daghero, D; Parlinski, K

    2003-03-01

    We measure phonon dispersion and linewidth in a single crystal of MgB2 along the Gamma-A, Gamma-M, and A-L directions using inelastic x-ray scattering. We use density functional theory to compute the effect of both electron-phonon coupling and anharmonicity on the linewidth, obtaining excellent agreement with experiment. Anomalous broadening of the E(2g) phonon mode is found all along Gamma-A. The dominant contribution to the linewidth is always the electron-phonon coupling.

  20. Electronic Cigarettes

    Science.gov (United States)

    ... New FDA Regulations Text Size: A A A Electronic Cigarettes Electronic cigarettes (e-cigarettes) are battery operated products designed ... more about: The latest news and events about electronic cigarettes on this FDA page Electronic cigarette basics ...

  1. Hawking Radiation in Dispersive Media

    CERN Document Server

    Robertson, Scott James

    2011-01-01

    Hawking radiation, despite its presence in theoretical physics for over thirty years, remains elusive and undetected. It also suffers, in its original context of gravitational black holes, from conceptual difficulties. Of particular note is the trans-Planckian problem, which is concerned with the apparent origin of the radiation in absurdly high frequencies. In order to gain better theoretical understanding and, it is hoped, experimental verification of Hawking radiation, much study is being devoted to systems which model the spacetime geometry of black holes, and which, by analogy, are also thought to emit Hawking radiation. These analogue systems typically exhibit dispersion, which regularizes the wave behaviour at the horizon but does not lend itself well to analytic treatment, thus rendering Hawking's prediction less secure. A general analytic method for dealing with Hawking radiation in dispersive systems has proved difficult to find. This thesis presents new numerical and analytic results for Hawking em...

  2. Coupling constant in dispersive model

    Indian Academy of Sciences (India)

    R Saleh-Moghaddam; M E Zomorrodian

    2013-11-01

    The average of the moments for event shapes in + - → hadrons within the context of next-to-leading order (NLO) perturbative QCD prediction in dispersive model is studied. Moments used in this article are $\\langle 1 - T \\rangle, \\langle ρ \\rangle, \\langle B_{T} \\rangle$ and $\\langle B_{W} \\rangle$. We extract , the coupling constant in perturbative theory and α0 in the non-perturbative theory using the dispersive model. By fitting the experimental data, the values of $(M_{Z^{°}})$ = 0.1171 ± 0.00229 and 0 ($_{I} = 2{\\text{GeV}}$) = 0.5068 ± 0.0440 are found. Our results are consistent with the above model. Our results are also consistent with those obtained from other experiments at different energies. All these features are explained in this paper.

  3. Statistical description of turbulent dispersion

    Science.gov (United States)

    Brouwers, J. J. H.

    2012-12-01

    We derive a comprehensive statistical model for dispersion of passive or almost passive admixture particles such as fine particulate matter, aerosols, smoke, and fumes in turbulent flow. The model rests on the Markov limit for particle velocity. It is in accordance with the asymptotic structure of turbulence at large Reynolds number as described by Kolmogorov. The model consists of Langevin and diffusion equations in which the damping and diffusivity are expressed by expansions in powers of the reciprocal Kolmogorov constant C0. We derive solutions of O(C00) and O(C0-1). We truncate at O(C0-2) which is shown to result in an error of a few percentages in predicted dispersion statistics for representative cases of turbulent flow. We reveal analogies and remarkable differences between the solutions of classical statistical mechanics and those of statistical turbulence.

  4. Study of Dispersion Coefficient Channel

    Science.gov (United States)

    Akiyama, K. R.; Bressan, C. K.; Pires, M. S. G.; Canno, L. M.; Ribeiro, L. C. L. J.

    2016-08-01

    The issue of water pollution has worsened in recent times due to releases, intentional or not, of pollutants in natural water bodies. This causes several studies about the distribution of pollutants are carried out. The water quality models have been developed and widely used today as a preventative tool, ie to try to predict what will be the concentration distribution of constituent along a body of water in spatial and temporal scale. To understand and use such models, it is necessary to know some concepts of hydraulic high on their application, including the longitudinal dispersion coefficient. This study aims to conduct a theoretical and experimental study of the channel dispersion coefficient, yielding more information about their direct determination in the literature.

  5. Tachyonic Dispersion in Coherent Networks

    CERN Document Server

    Chong, Y D

    2015-01-01

    We propose a technique to realize a tachyonic band structure in a coherent network, such as an array of coupled ring resonators. This is achieved by adding "PT symmetric" spatially-balanced gain and loss to each node of the network. In a square-lattice network, the quasi-energy bandstructure exhibits a tachyonic dispersion relation, centered at either the center or corner of the Brillouin zone. There is one tachyonic hyperboloid in each gap, unlike in PT-symmetric tight-binding honeycomb lattices where the hyperboloids occur in pairs. The dispersion relation can be probed by measuring the peaks in transmission across a finite network as the gain/loss parameter is varied.

  6. Ability Dispersion and Team Performance

    DEFF Research Database (Denmark)

    Hoogendoorn, Sander; Parker, Simon C.; Van Praag, Mirjam

    What is the effect of dispersed levels of cognitive ability of members of a (business) team on their team's performance? This paper reports the results of a field experiment in which 573 students in 49 teams start up and manage real companies under identical circumstances for one year. We ensured...... exogenous variation in -otherwise random- team composition by assigning students to teams based on their measured cognitive abilities (Raven test). Each team performs a variety of tasks, often involving complex decision making. The key result of the experiment is that the performance of business teams first...... increases and then decreases with ability dispersion. We seek to understand this finding by developing a model in which team members of different ability levels form sub-teams with other team members with similar ability levels to specialize in different productive tasks. Diversity spreads production over...

  7. Ability Dispersion and Team Performance

    DEFF Research Database (Denmark)

    Hoogendoorn, Sander; Parker, Simon C.; Van Praag, Mirjam

    What is the effect of dispersed levels of cognitive ability of members of a (business) team on their team's performance? This paper reports the results of a field experiment in which 573 students in 49 (student) teams start up and manage real companies under identical circumstances for one year. We...... ensured exogenous variation in otherwise random team composition by assigning students to teams based on their measured cognitive abilities. Each team performs a variety of tasks, often involving complex decision making. The key result of the experiment is that the performance of business teams first...... increases and then decreases with ability dispersion. We seek to understand this finding by developing a model in which team members of different ability levels form sub- teams with other team members with similar ability levels to specialize in different productive tasks. Diversity spreads production over...

  8. Ability Dispersion and Team Performance

    DEFF Research Database (Denmark)

    Hoogendoorn, Sander; Parker, Simon C.; Van Praag, Mirjam

    What is the effect of dispersed levels of cognitive ability of members of a (business) team on their team's performance? This paper reports the results of a field experiment in which 573 students in 49 teams start up and manage real companies under identical circumstances. We ensured exogenous...... variation in - otherwise random - team composition by assigning students to teams based on their measured cognitive abilities (Raven test). Each team performs a variety of tasks, often involving complex decision making. The key result of the experiment is that the performance of business teams first...... increases and then decreases with ability dispersion. We seek to understand this finding by developing a model in which team members of different ability levels form sub-teams with other team members with similar ability levels to specialize in different productive tasks. Diversity spreads production over...

  9. Faraday anomalous dispersion optical tuners

    Science.gov (United States)

    Wanninger, P.; Valdez, E. C.; Shay, T. M.

    1992-01-01

    Common methods for frequency stabilizing diode lasers systems employ gratings, etalons, optical electric double feedback, atomic resonance, and a Faraday cell with low magnetic field. Our method, the Faraday Anomalous Dispersion Optical Transmitter (FADOT) laser locking, is much simpler than other schemes. The FADOT uses commercial laser diodes with no antireflection coatings, an atomic Faraday cell with a single polarizer, and an output coupler to form a compound cavity. This method is vibration insensitive, thermal expansion effects are minimal, and the system has a frequency pull in range of 443.2 GHz (9A). Our technique is based on the Faraday anomalous dispersion optical filter. This method has potential applications in optical communication, remote sensing, and pumping laser excited optical filters. We present the first theoretical model for the FADOT and compare the calculations to our experimental results.

  10. Thermodynamic approach to boron nitride nanotube solubility and dispersion

    Science.gov (United States)

    Tiano, A. L.; Gibbons, L.; Tsui, M.; Applin, S. I.; Silva, R.; Park, C.; Fay, C. C.

    2016-02-01

    improve dispersion include surface functionalization, surfactants, polymer wrapping, and sonication. Although these approaches have proven effective, they often achieve dispersion by altering the surface or structure of the nanomaterial and ultimately, their intrinsic properties. Co-solvents are commonly utilized in the polymer, paint, and art conservation industries to selectively dissolve materials. These co-solvents are utilized based on thermodynamic interaction parameters and are chosen so that the original materials are not affected. The same concept was applied to enhance the dispersion of boron nitride nanotubes (BNNTs) to facilitate the fabrication of BNNT nanocomposites. Of the solvents tested, dimethylacetamide (DMAc) exhibited the most stable, uniform dispersion of BNNTs, followed by N,N-dimethylformamide (DMF), acetone, and N-methyl-2-pyrrolidone (NMP). Utilizing the known Hansen solubility parameters of these solvents in comparison to the BNNT dispersion state, a region of good solubility was proposed. This solubility region was used to identify co-solvent systems that led to improved BNNT dispersion in poor solvents such as toluene, hexane, and ethanol. Incorporating the data from the co-solvent studies further refined the proposed solubility region. From this region, the Hansen solubility parameters for BNNTs are thought to lie at the midpoint of the solubility sphere: 16.8, 10.7, and 9.0 MPa1/2 for δd, δp, and δh, respectively, with a calculated Hildebrand parameter of 21.8 MPa1/2. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr08259e

  11. The Electron

    Energy Technology Data Exchange (ETDEWEB)

    Thomson, George

    1972-01-01

    Electrons are elementary particles of atoms that revolve around and outside the nucleus and have a negative charge. This booklet discusses how electrons relate to electricity, some applications of electrons, electrons as waves, electrons in atoms and solids, the electron microscope, among other things.

  12. Hydrodynamic dispersion within porous biofilms

    KAUST Repository

    Davit, Y.

    2013-01-23

    Many microorganisms live within surface-associated consortia, termed biofilms, that can form intricate porous structures interspersed with a network of fluid channels. In such systems, transport phenomena, including flow and advection, regulate various aspects of cell behavior by controlling nutrient supply, evacuation of waste products, and permeation of antimicrobial agents. This study presents multiscale analysis of solute transport in these porous biofilms. We start our analysis with a channel-scale description of mass transport and use the method of volume averaging to derive a set of homogenized equations at the biofilm-scale in the case where the width of the channels is significantly smaller than the thickness of the biofilm. We show that solute transport may be described via two coupled partial differential equations or telegrapher\\'s equations for the averaged concentrations. These models are particularly relevant for chemicals, such as some antimicrobial agents, that penetrate cell clusters very slowly. In most cases, especially for nutrients, solute penetration is faster, and transport can be described via an advection-dispersion equation. In this simpler case, the effective diffusion is characterized by a second-order tensor whose components depend on (1) the topology of the channels\\' network; (2) the solute\\'s diffusion coefficients in the fluid and the cell clusters; (3) hydrodynamic dispersion effects; and (4) an additional dispersion term intrinsic to the two-phase configuration. Although solute transport in biofilms is commonly thought to be diffusion dominated, this analysis shows that hydrodynamic dispersion effects may significantly contribute to transport. © 2013 American Physical Society.

  13. Dispersed Fringe Sensing Analysis - DFSA

    Science.gov (United States)

    Sigrist, Norbert; Shi, Fang; Redding, David C.; Basinger, Scott A.; Ohara, Catherine M.; Seo, Byoung-Joon; Bikkannavar, Siddarayappa A.; Spechler, Joshua A.

    2012-01-01

    Dispersed Fringe Sensing (DFS) is a technique for measuring and phasing segmented telescope mirrors using a dispersed broadband light image. DFS is capable of breaking the monochromatic light ambiguity, measuring absolute piston errors between segments of large segmented primary mirrors to tens of nanometers accuracy over a range of 100 micrometers or more. The DFSA software tool analyzes DFS images to extract DFS encoded segment piston errors, which can be used to measure piston distances between primary mirror segments of ground and space telescopes. This information is necessary to control mirror segments to establish a smooth, continuous primary figure needed to achieve high optical quality. The DFSA tool is versatile, allowing precise piston measurements from a variety of different optical configurations. DFSA technology may be used for measuring wavefront pistons from sub-apertures defined by adjacent segments (such as Keck Telescope), or from separated sub-apertures used for testing large optical systems (such as sub-aperture wavefront testing for large primary mirrors using auto-collimating flats). An experimental demonstration of the coarse-phasing technology with verification of DFSA was performed at the Keck Telescope. DFSA includes image processing, wavelength and source spectral calibration, fringe extraction line determination, dispersed fringe analysis, and wavefront piston sign determination. The code is robust against internal optical system aberrations and against spectral variations of the source. In addition to the DFSA tool, the software package contains a simple but sophisticated MATLAB model to generate dispersed fringe images of optical system configurations in order to quickly estimate the coarse phasing performance given the optical and operational design requirements. Combining MATLAB (a high-level language and interactive environment developed by MathWorks), MACOS (JPL s software package for Modeling and Analysis for Controlled Optical

  14. Dispersion as a Survival Strategy

    Science.gov (United States)

    Junior, Valdivino Vargas; Machado, Fábio Prates; Roldán-Correa, Alejandro

    2016-08-01

    We consider stochastic growth models to represent population subject to catastrophes. We analyze the subject from different set ups considering or not spatial restrictions, whether dispersion is a good strategy to increase the population viability. We find out it strongly depends on the effect of a catastrophic event, the spatial constraints of the environment and the probability that each exposed individual survives when a disaster strikes.

  15. Faraday anomalous dispersion optical filters

    Science.gov (United States)

    Shay, T. M.; Yin, B.; Alvarez, L. S.

    1993-01-01

    The effect of Faraday anomalous dispersion optical filters on infrared and blue transitions of some alkali atoms is calculated. A composite system is designed to further increase the background noise rejection. The measured results of the solar background rejection and image quality through the filter are presented. The results show that the filter may provide high transmission and high background noise rejection with excellent image quality.

  16. Hard electronics; Hard electronics

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-03-01

    Hard material technologies were surveyed to establish the hard electronic technology which offers superior characteristics under hard operational or environmental conditions as compared with conventional Si devices. The following technologies were separately surveyed: (1) The device and integration technologies of wide gap hard semiconductors such as SiC, diamond and nitride, (2) The technology of hard semiconductor devices for vacuum micro- electronics technology, and (3) The technology of hard new material devices for oxides. The formation technology of oxide thin films made remarkable progress after discovery of oxide superconductor materials, resulting in development of an atomic layer growth method and mist deposition method. This leading research is expected to solve such issues difficult to be easily realized by current Si technology as high-power, high-frequency and low-loss devices in power electronics, high temperature-proof and radiation-proof devices in ultimate electronics, and high-speed and dense- integrated devices in information electronics. 432 refs., 136 figs., 15 tabs.

  17. The dispersal of protoplanetary discs

    Directory of Open Access Journals (Sweden)

    Ercolano Barbara

    2013-04-01

    Full Text Available Protoplanetary discs are a natural consequence of the star formation process and as such are ubiquitous around low-mass stars. They are fundamental to planet formation as they hold the reservoir of material from which planets form. Their evolution and final dispersal and the timescales that regulate these process are therefore of particular interest. In this contribution I will review the observational evidence for the dispersal of discs being dominated by two timescales and for the final dispersal to occur quickly and from the inside out. I will discuss the current theoretical models, including X-ray photoevaporation, showing that the latter provides a natural explanation to the observed behaviour and review supporting and contrasting evidence. I will finally introduce a new mechanism based on the interaction between planet formation and photoevaporation that may explain a particular class of transition discs with large inner holes and high accretion rates that are problematic for photoevaporation models and planet formation models alone.

  18. Chromatic Dispersion Estimation in Digital Coherent Receivers

    DEFF Research Database (Denmark)

    Soriano, Ruben Andres; Hauske, Fabian N.; Guerrero Gonzalez, Neil

    2011-01-01

    Polarization-diverse coherent demodulation allows to compensate large values of accumulated linear distortion by digital signal processing. In particular, in uncompensated links without optical dispersion compensation, the parameter of the residual chromatic dispersion (CD) is vital to set...

  19. Contribution of the surface contamination of uranium-materials on the quantitative analysis results by electron probe microbeam analysis; Contributions des effets de surface des materiaux uraniferes aux resultats d'analyses quantitatives par microsonde electronique a dispersion de longueur d'onde

    Energy Technology Data Exchange (ETDEWEB)

    Bonino, O.; Fournier, C.; Fucili, C.; Dugne, O. [CEA Valrho, (DCC/DTE/SIM), 30 - Marcoule (France); Merlet, C. [Montpellier-2 Univ. (ISTEEM/CNRS), 34 (France)

    2000-07-01

    The analytical testing of uranium materials is necessary for quality research and development in nuclear industry applications (enrichment, safety studies, fuel, etc). Electron Probe Microbeam Analysis Wavelength Dispersive Spectrometry (EPMA-WDS) is a dependable non-destructive analytical technology. The characteristic X-ray signal is measured to identify and quantify the sample components, and the analyzed volume is about one micron cube. The surface contamination of uranium materials modifies and contributes to the quantitative analysis results of EPMA-WDS. This contribution is not representative of the bulk. A thin oxidized layer appears in the first instants after preparation (burnishing, cleaning) as well as a carbon contamination layer, due to metallographic preparation and carbon cracking under the impact of the electron probe. Several analytical difficulties subsequently arise, including an overlapping line between the carbon Ka ray and the Uranium U{sub NIVOVI} ray. Sensitivity and accuracy of the quantification of light elements like carbon and oxygen are also reduced by the presence of uranium. The aim of this study was to improve the accuracy of quantitative analysis on uranium materials by EPMA-WDS by taking account of the contribution of surface contamination. The first part of this paper is devoted to the study of the contaminated surface of the uranium materials U, UFe{sub 2} and U{sub 6}Fe a few hours after preparation. These oxidation conditions are selected so as to reproduce the same contamination surfaces occurring in microprobe analytical conditions. Surface characterization techniques were SIMS and Auger spectroscopy. The contaminated surfaces are shown. They consist of successive layers: a carbon layer, an oxidized iron layer, followed by an iron depletion layer (only in UFe{sub 2} and U{sub 6}Fe), and a ternary oxide layer (U-Fe-O for UFe{sub 2} et U{sub 6}Fe and UO{sub 2+x} for uranium). The second part of the paper addresses the

  20. Stochastic differential equations and turbulent dispersion

    Science.gov (United States)

    Durbin, P. A.

    1983-01-01

    Aspects of the theory of continuous stochastic processes that seem to contribute to an understanding of turbulent dispersion are introduced and the theory and philosophy of modelling turbulent transport is emphasized. Examples of eddy diffusion examined include shear dispersion, the surface layer, and channel flow. Modeling dispersion with finite-time scale is considered including the Langevin model for homogeneous turbulence, dispersion in nonhomogeneous turbulence, and the asymptotic behavior of the Langevin model for nonhomogeneous turbulence.

  1. Optical angular momentum in dispersive media

    CERN Document Server

    Philbin, T G

    2012-01-01

    The angular momentum density and flux of light in a dispersive, rotationally symmetric medium are derived from Noether's theorem. Optical angular momentum in a dispersive medium has no simple relation to optical linear momentum, even if the medium is homogeneous. A circularly polarized monochromatic beam in a homogeneous, dispersive medium carries a spin angular momentum per unit energy of $\\pm\\omega^{-1}$, as in vacuum. This result demonstrates the non-trivial interplay of dispersive contributions to optical angular momentum and energy.

  2. Dispersion climatology in a coastal zone

    DEFF Research Database (Denmark)

    Larsen, Søren Ejling; Gryning, Sven-Erik

    1986-01-01

    system should be used to describe the dispersion. This dispersion classification scheme is used to organize 3 years of data from two meteorological masts, one placed directly at a shoreline and the other roughly 1 km inland. Differences in the dispersion climatology over land and water are studied...

  3. Dispersion properties of photonic crystal fibres

    DEFF Research Database (Denmark)

    Bjarklev, Anders Overgaard; Broeng, Jes; Dridi, Kim;

    1998-01-01

    Approximate dispersion and bending properties of all-silica two-dimensional photonic crystal fibres are characterised by the combination of an effective-index model and classical analysis tools for optical fibres. We believe for the first time to have predicted the dispersion properties of photonic...... crystal fibres. The results strongly indicate that these fibres have potential applications as dispersion managing components...

  4. Renormalization of the graphene dispersion velocity determined from scanning tunneling spectroscopy.

    Science.gov (United States)

    Chae, Jungseok; Jung, Suyong; Young, Andrea F; Dean, Cory R; Wang, Lei; Gao, Yuanda; Watanabe, Kenji; Taniguchi, Takashi; Hone, James; Shepard, Kenneth L; Kim, Phillip; Zhitenev, Nikolai B; Stroscio, Joseph A

    2012-09-14

    In graphene, as in most metals, electron-electron interactions renormalize the properties of electrons but leave them behaving like noninteracting quasiparticles. Many measurements probe the renormalized properties of electrons right at the Fermi energy. Uniquely for graphene, the accessibility of the electrons at the surface offers the opportunity to use scanned probe techniques to examine the effect of interactions at energies away from the Fermi energy, over a broad range of densities, and on a local scale. Using scanning tunneling spectroscopy, we show that electron interactions leave the graphene energy dispersion linear as a function of excitation energy for energies within ±200  meV of the Fermi energy. However, the measured dispersion velocity depends on density and increases strongly as the density approaches zero near the charge neutrality point, revealing a squeezing of the Dirac cone due to interactions.

  5. Dispersion characteristics of planar grating with arbitrary grooves for terahertz Smith-Purcell radiation

    Energy Technology Data Exchange (ETDEWEB)

    Cao, Miaomiao, E-mail: mona486@yeah.net; Li, Ke, E-mail: like3714@163.com [Key Laboratory of High Power Microwave Sources and Technologies, Institute of Electronics, Chinese Academy of Sciences, Beijing 100190 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Liu, Wenxin, E-mail: lwenxin@mail.ie.ac.cn; Wang, Yong, E-mail: wangyong3845@sina.com [Key Laboratory of High Power Microwave Sources and Technologies, Institute of Electronics, Chinese Academy of Sciences, Beijing 100190 (China)

    2015-03-15

    In this paper, a novel method of getting the dispersion relations in planar grating with arbitrary grooves for terahertz Smith-Purcell radiation is investigated analytically. The continuous profile of the groove is approximately replaced by a series of rectangular steps. By making use of field matches method and the continuity of transverse admittance, the universal dispersion equation for grating with arbitrarily shaped grooves is derived. By solving the dispersion equation in presence of electron beam, the growth rate is obtained directly and the dependence on beam parameters is analyzed. Comparisons of the dispersion characteristics among some special groove shapes have been made by numerical calculation. The results show that the rectangular-step approximation method provides a novel approach to obtain the universal dispersion relation for grating with arbitrary grooves for Smith-Purcell radiation.

  6. The incomplete plasma dispersion function: properties and application to waves in bounded plasmas

    CERN Document Server

    Baalrud, Scott D

    2013-01-01

    The incomplete plasma dispersion function is a generalization of the plasma dispersion function in which the defining integral spans a semi-infinite, rather than infinite, domain. It is useful for describing the linear dielectric response and wave dispersion in non-Maxwellian plasmas when the distribution functions can be approximated as Maxwellian over finite, or semi-infinite, intervals in velocity phase-space. A ubiquitous example is the depleted Maxwellian electron distribution found near boundary sheaths or double layers, where the passing interval can be modeled as Maxwellian with a lower temperature than the trapped interval. The depleted Maxwellian is used as an example to demonstrate the utility of using the incomplete plasma dispersion function for calculating modifications to wave dispersion relations.

  7. Going against the flow: a case for upstream dispersal and detection of uncommon dispersal events

    NARCIS (Netherlands)

    Wubs, E.R.J.; Fraaije, Rob G.A.; Groot, de G.A.; Erkens, R.H.J.; Garsen, Annemarie G.; Kleyheeg, Erik; Raven, Bart M.; Soons, Merel B.

    2016-01-01

    1.Dispersal and colonisation are key processes determining species survival, and their importance is increasing as a consequence of ongoing habitat fragmentation, land-use change and climate change. Identification of long-distance dispersal events, including upstream dispersal, and of the dispersal

  8. Going against the flow: a case for upstream dispersal and detection of uncommon dispersal events

    NARCIS (Netherlands)

    Wubs, E. R. Jasper; Fraaije, Rob G. A.; de Groot, G. Arjen; Erkens, Roy H. J.; Garssen, Annemarie G.; Kleyheeg, Erik; Raven, Bart M.; Soons, Merel B.

    2016-01-01

    * Dispersal and colonisation are key processes determining species survival, and their importance is increasing as a consequence of ongoing habitat fragmentation, land-use change and climate change. Identification of long-distance dispersal events, including upstream dispersal, and of the dispersal

  9. Broadband dispersion compensation using microstructure fibers

    Institute of Scientific and Technical Information of China (English)

    Xia Zhang; Xiaomin Ren; Yongzhao Xu; Zinan Wang; Yongqing Huang; Xue Chen

    2007-01-01

    Beijing University of Posts and Telecommunications, Beijing 100876Dispersion and dispersion slope compensation of 10-Gb/s pulses using microstructure fibers (MFs) is demonstrated experimentally. A 26-m MF is used to compensate the dispersion of 2-km standard singe mode fiber in a 20-nm range in C band. The experimental results show that a significant improvement can be achieved in the quality of the observed pulses with the dispersion compensation. Moreover, the further research shows that the MF can compensate the anomalous dispersion of a single mode fiber within ±0.27 ps/(nm·km) over a 50-nm wavelength range from 1520 to 1570 nm.

  10. Normal-dispersion microresonator Kerr frequency combs

    Directory of Open Access Journals (Sweden)

    Xue Xiaoxiao

    2016-06-01

    Full Text Available Optical microresonator-based Kerr frequency comb generation has developed into a hot research area in the past decade. Microresonator combs are promising for portable applications due to their potential for chip-level integration and low power consumption. According to the group velocity dispersion of the microresonator employed, research in this field may be classified into two categories: the anomalous dispersion regime and the normal dispersion regime. In this paper, we discuss the physics of Kerr comb generation in the normal dispersion regime and review recent experimental advances. The potential advantages and future directions of normal dispersion combs are also discussed.

  11. Dispersion of coupled mode-gap cavities

    CERN Document Server

    Lian, Jin; Yüce, Emre; De Rossi, Sylvain Combrié Alfredo; Mosk, Allard P

    2015-01-01

    The dispersion of a CROW made of photonic crystal mode-gap cavities is pronouncedly asymmetric. This asymmetry cannot be explained by the standard tight binding model. We show that the fundamental cause of the asymmetric dispersion is the fact that the cavity mode profile itself is dispersive, i.e., the mode wave function depends on the driving frequency, not the eigenfrequency. This occurs because the photonic crystal cavity resonances do not form a complete set. By taking into account the dispersive mode profile, we formulate a mode coupling model that accurately describes the asymmetric dispersion without introducing any new free parameters.

  12. Bilayer dispersion-flattened waveguides with four zero-dispersion wavelengths.

    Science.gov (United States)

    Guo, Yuhao; Jafari, Zeinab; Agarwal, Anu M; Kimerling, Lionel C; Li, Guifang; Michel, Jurgen; Zhang, Lin

    2016-11-01

    We propose a new type of bilayer dispersion-flattened waveguides that have four zero-dispersion wavelengths. Low and flat dispersion can be achieved by using two different material combinations, with a much smaller index contrast as compared to the previously proposed slot-assisted dispersion-flattened waveguides. Without using a nano-slot, dispersion becomes less sensitive to waveguide dimensions, which is highly desirable for high-yield device fabrication. Ultra-low dispersion, high nonlinearity, and fabrication-friendly design would make it promising for practical implementation of nonlinear photonic functions. The proposed waveguide configuration deepens our understanding of the dispersion flattening principle.

  13. Rheology and structure of aqueous bentonite–polyvinyl alcohol dispersions

    Indian Academy of Sciences (India)

    S İşçı; C H Ünlü; O Atici; N Güngör

    2006-10-01

    The influence of polymer on flow behaviour of Balikesir, Turkey bentonite dispersions (2%, w/w) was studied for non-ionic polymer, polyvinyl alcohol (PVA). In a range of 3.3 × 10-6 – 3.3 × 105 mol/l, PVA was added to the bentonite dispersions in different concentrations and its behaviour was observed on rheology parameters. Thixotropy was detected by a hysteresis loop of the flow curves. The data were interpreted taking into account the interactions of colloidal clay particles, bentonitic clay concentrations, structure, and concentrations of added PVA. The particle size analysis was explained by surface orientation of PVA to the clay particles dispersed in aqueous solution. Zeta potential determination also emphasized that PVA molecules got attached on the face and edge surface of clay particles. The morphology of bentonite dispersions was analysed by scanning electron micrograph (SEM). FTIR studies carried out in parallel to rheology studies showed that hydrogen bonds were formed between surface of the clay, and absorbed PVA molecules and adsorbed water. The presence of PVA did not prevent extensive swelling of bentonite.

  14. Dispersion and Purification of Single-Wall Carbon Nanotubes Using Carboxymethylcellulose

    Science.gov (United States)

    Takahashi, Teruo; Tsunoda, Katsunori; Yajima, Hirofumi; Ishii, Tadahiro

    2004-06-01

    We have developed a novel method for the purification of single-wall carbon nanotubes (SWNTs) that involves annealing in air and dispersing the SWNTs in an aqueous solution of carboxymethylcellulose (CMC). The purity of the resulting SWNTs was evaluated by analytical techniques such as electron microscopy, Raman spectroscopy, and thermogravimetric analysis (TGA). As a result, it was revealed that CMC functioned as an effective dispersion reagent in the exfoliation of the SWNT bundles and thereby, SWNTs with appreciably high quality were prepared.

  15. Minimal dispersion refractive index profiles.

    Science.gov (United States)

    Feit, M D

    1979-09-01

    The analogy between optics and quantum mechanics is exploited by considering a 2-D quantum system whose Schroedinger equation is closely related to the wave equation for light propagation in an optical fiber. From this viewpoint, Marcatili's condition for minimal-dispersion-refractive-index profiles, and the Olshansky- Keck formula for rms pulse spreading in an alpha-profile fiber may be derived without recourse to the WKB approximation. Besides affording physical insight into these results, the present approach points out a possible limitation in their application to real fibers.

  16. Dispersive nanoSQUID magnetometry

    Science.gov (United States)

    Levenson-Falk, E. M.; Antler, N.; Siddiqi, I.

    2016-11-01

    We describe the theory and implementation of a dispersive magnetometer based on an aluminum nanoSQUID. The nanoSQUID consists of a superconducting loop interrupted by two variable-thickness weak-link nanobridge Josephson junctions. When the nanoSQUID is placed in parallel with a lumped-element capacitor, it acts as the inductive element in a resonant tank circuit. By performing microwave reflectometry on the circuit, the SQUID inductance can be measured, providing a sensitive meter of the flux threading the SQUID loop. In this review we provide the theoretical basis for the device, describe design and operation considerations, and present characterization results on several devices.

  17. Nonlinear Dispersion Effect on Wave Transformation

    Institute of Scientific and Technical Information of China (English)

    LI Ruijie; Dong-Young LEE

    2000-01-01

    A new nonlinear dispersion relation is given in this paper, which can overcome the limitation of the intermediate minimum value in the dispersion relation proposed by Kirby and Dalrymple (1986), and which has a better approximation to Hedges' empirical relation than the modilied relations by Hedges (1987). Kirby and Dahymple (1987) for shallow waters. The new dispersion relation is simple in form. thus it can be used easily in practice. Meanwhile. a general explicil approximalion to the new dispersion rela tion and olher nonlinear dispersion relations is given. By use of the explicit approximation to the new dispersion relation along with the mild slope equation taking inlo account weakly nonlinear effect, a mathematical model is obtained, and it is applied to laboratory data. The results show that the model developed vith the new dispersion relation predicts wave translornation over complicated topography quite well.

  18. Dispersive properties of tunnelling-induced transparency in an asymmetric double quantum well

    Institute of Scientific and Technical Information of China (English)

    苏雪梅; 卓仲畅; 王立军; 高锦岳

    2002-01-01

    We have investigated the dispersive properties of tunnelling-induced transparency in asymmetric double quantumwell structures where two excited states are coupled by resonant tunnelling through a thin barrier in a three-levelsystem of electronic subbands. The intersubband transitions exhibit high dispersion at zero absorption, which leads tothe slow light velocity in this medium as compared with that in vacuum (c=3× 108). The group velocity in a specificGaAs/AlGaAs sample is calculated to be vg=c/4.30. This structure can be used to compensate for the dispersion andenergy loss in fibre optical communications.

  19. Nanoparticle composites for printed electronics

    Science.gov (United States)

    Männl, U.; van den Berg, C.; Magunje, B.; Härting, M.; Britton, D. T.; Jones, S.; van Staden, M. J.; Scriba, M. R.

    2014-03-01

    Printed Electronics is a rapidly developing sector in the electronics industry, in which nanostructured materials are playing an increasingly important role. In particular, inks containing dispersions of semiconducting nanoparticles, can form nanocomposite materials with unique electronic properties when cured. In this study we have extended on our previous studies of functional nanoparticle electronic inks, with the development of a solvent-based silicon ink for printed electronics which is compatible with existing silver inks, and with the investigation of other metal nanoparticle based inks. It is shown that both solvent-based and water-based inks can be used for both silver conductors and semiconducting silicon, and that qualitatively there is no difference in the electronic properties of the materials printed with a soluble polymer binder to when an acrylic binder is used.

  20. Incorporating patterns of disperser behaviour into models of seed dispersal and its effects on estimated dispersal curves.

    Science.gov (United States)

    Westcott, David A; Bentrupperbäumer, Joan; Bradford, Matt G; McKeown, Adam

    2005-11-01

    The processes determining where seeds fall relative to their parent plant influence the spatial structure and dynamics of plant populations and communities. For animal dispersed species the factors influencing seed shadows are poorly understood. In this paper we test the hypothesis that the daily temporal distribution of disperser behaviours, for example, foraging and movement, influences dispersal outcomes, in particular the shape and scale of dispersal curves. To do this, we describe frugivory and the dispersal curves produced by the southern cassowary, Casuarius casuarius, the only large-bodied disperser in Australia's rainforests. We found C. casuarius consumed fruits of 238 species and of all fleshy-fruit types. In feeding trials, seeds of 11 species were retained on average for 309 min (+/-256 SD). Sampling radio-telemetry data randomly, that is, assuming foraging occurs at random times during the day, gives an estimated average dispersal distance of 239 m (+/-207 SD) for seeds consumed by C. casuarius. Approximately 4% of seeds were dispersed further than 1,000 m. However, observation of wild birds indicated that foraging and movement occur more frequently early and late in the day. Seeds consumed early in the day were estimated to receive dispersal distances 1.4 times the 'random' average estimate, while afternoon consumed seeds received estimated mean dispersal distances of 0.46 times the 'random' estimate. Sampling movement data according to the daily distribution of C. casuarius foraging gives an estimated mean dispersal distance of 337 m (+/-194 SD). Most animals' behaviour has a non-random temporal distribution. Consequently such effects should be common and need to be incorporated into seed shadow estimation. Our results point to dispersal curves being an emergent property of the plant-disperser interaction rather than being a property of a plant or species.

  1. Conductive nanomaterials for printed electronics.

    Science.gov (United States)

    Kamyshny, Alexander; Magdassi, Shlomo

    2014-09-10

    This is a review on recent developments in the field of conductive nanomaterials and their application in printed electronics, with particular emphasis on inkjet printing of ink formulations based on metal nanoparticles, carbon nanotubes, and graphene sheets. The review describes the basic properties of conductive nanomaterials suitable for printed electronics (metal nanoparticles, carbon nanotubes, and graphene), their stabilization in dispersions, formulations of conductive inks, and obtaining conductive patterns by using various sintering methods. Applications of conductive nanomaterials for electronic devices (transparent electrodes, metallization of solar cells, RFID antennas, TFTs, and light emitting devices) are also briefly reviewed.

  2. Ambient Electronics

    Science.gov (United States)

    Sekitani, Tsuyoshi; Someya, Takao

    2012-10-01

    We report the recent research progress and future prospects of flexible and printed electronics, focusing on molecular electronic material-based thin-film transistors, which are expected to usher in a new era of electronics.

  3. Introduction to nonlinear dispersive equations

    CERN Document Server

    Linares, Felipe

    2015-01-01

    This textbook introduces the well-posedness theory for initial-value problems of nonlinear, dispersive partial differential equations, with special focus on two key models, the Korteweg–de Vries equation and the nonlinear Schrödinger equation. A concise and self-contained treatment of background material (the Fourier transform, interpolation theory, Sobolev spaces, and the linear Schrödinger equation) prepares the reader to understand the main topics covered: the initial-value problem for the nonlinear Schrödinger equation and the generalized Korteweg–de Vries equation, properties of their solutions, and a survey of general classes of nonlinear dispersive equations of physical and mathematical significance. Each chapter ends with an expert account of recent developments and open problems, as well as exercises. The final chapter gives a detailed exposition of local well-posedness for the nonlinear Schrödinger equation, taking the reader to the forefront of recent research. The second edition of Introdu...

  4. Electron cooling

    Science.gov (United States)

    Meshkov, I.; Sidorin, A.

    2004-10-01

    The brief review of the most significant and interesting achievements in electron cooling method, which took place during last two years, is presented. The description of the electron cooling facilities-storage rings and traps being in operation or under development-is given. The applications of the electron cooling method are considered. The following modern fields of the method development are discussed: crystalline beam formation, expansion into middle and high energy electron cooling (the Fermilab Recycler Electron Cooler, the BNL cooler-recuperator, cooling with circulating electron beam, the GSI project), electron cooling in traps, antihydrogen generation, electron cooling of positrons (the LEPTA project).

  5. Development and characterization of nifedipine-amino methacrylate copolymer solid dispersion powders with various adsorbents

    Directory of Open Access Journals (Sweden)

    Yotsanan Weerapol

    2017-07-01

    Full Text Available Solid dispersions of nifedipine (NDP, a poorly water-soluble drug, and amino methacrylate copolymer (AMCP with aid of adsorbent, that is, fumed silica, talcum, calcium carbonate, titanium dioxide, and mesoporous silica from rice husks (SRH, were prepared by solvent method. The physicochemical properties of solid dispersions, compared to their physical mixtures, were determined using powder X-ray diffractometry (PXRD and differential scanning calorimetry (DSC. The surface morphology of the prepared solid dispersions was examined by scanning electron microscopy (SEM. The dissolution of NDP from solid dispersions was compared to NDP powders. The effect of adsorbent type on NDP dissolution was also examined. The dissolution of NDP increased with the ratio of NDP:AMCP:adsorbent of 1:4:1 when compared to the other formulations. As indicated from PXRD patterns, DSC thermograms and SEM images, NDP was molecularly dispersed within polymer carrier or in an amorphous form, which confirmed the better dissolution of solid dispersions. Solid dispersions containing SRH provided the highest NDP dissolution, due to a porous nature of SRH, allowing dissolved drug to fill in the pores and consequently dissolve in the medium. The results suggested that solid dispersions containing adsorbents (SRH in particular demonstrated improved dissolution of poorly water-soluble drug when compared to NDP powder.

  6. [Study on solid dispersion of precipitated calcium carbonate-based oleanolic acid].

    Science.gov (United States)

    Yan, Hong-mei; Zhang, Zhen-hai; Jia, Xiao-bin; Jiang, Yan-rong; Sun, E

    2015-05-01

    Oleanolic acid-precipitated calcium carbonate solid dispersion was prepared by using solvent evaporation method. The microscopic structure and physicochemical properties of solid dispersion were analyzed using differential scanning calorimetry and scanning electron microscopy (SEM). And its in vitro release also was investigated. The properties of the precipitated calcium carbonate was studied which was as a carrier of oleanolic acid solid dispersion. Differential scanning calorimetry analysis suggested that oleanolic acid may be present in solid dispersion as amorphous substance. The in vitro release determination results of oleanolic acid-precipitated calcium carbonate (1: 5) solid dispersion showed accumulated dissolution rate of.oleanolic acid was up to 90% at 45 min. Accelerating experiment showed that content and in vitro dissolution of oleanolic acid solid dispersion did not change after storing over 6 months. The results indicated that in vitro dissolution of oleanolic acid was improved greatly by the solid dispersion with precipitated calcium carbonate as a carrier. The solid dispersion is a stabilizing system which has actual applied value.

  7. Improvement of interaction between pre-dispersed multi-walled carbon nanotubes and unsaturated polyester resin

    Energy Technology Data Exchange (ETDEWEB)

    Beg, M. D. H., E-mail: dhbeg@yahoo.com; Moshiul Alam, A. K. M., E-mail: akmmalam@gmail.com; Yunus, R. M. [Universiti Malaysia Pahang, Faculty of Chemical and Natural Resources Engineering (Malaysia); Mina, M. F. [Bangladesh University of Engineering and Technology, Department of Physics (Bangladesh)

    2015-01-15

    Efforts are being given to the development of well-dispersed nanoparticle-reinforced polymer nanocomposites in order to tailor the material properties. In this perspective, well dispersion of multi-walled carbon nanotubes (MWCNTs) in unsaturated polyester resin (UPR) was prepared using pre-dispersed MWCNTs in tetrahydrofuran solvent with ultrasonication method. Then the well-dispersed MWCNTs reinforced UPR nanocomposites were fabricated through solvent evaporation. Fourier-transform infrared spectroscopy indicates a good interaction between matrix and MWCNTs. This along with homogeneous dispersion of nanotubes in matrix has been confirmed by the field emission scanning electron microscopy. At low shear rate, the value of viscosity of UPR is 8,593 mPa s and that of pre-dispersed MWCNT–UPR suspension is 43,491 mPa s, showing implicitly a good dispersion of nanotubes. A notable improvement in the crystallinity of UPR from 14 to 21 % after MWCNTs inclusion was observed by X-ray diffractometry. The mechanical properties, such as tensile strength, tensile modulus, impact strength, and elongation-at-break, of nanocomposite were found to be increased to 22, 20, 28, and 87 %, respectively. The estimated melting enthalpy per gram for composites as analyzed by differential scanning calorimetry is higher than that of UPR. The onset temperature of thermal decomposition in the nanocomposites as monitored by thermogravimetric analysis is found higher than that of UPR. Correlations among MWCNTs dispersion, nucleation, fracture morphology, and various properties were measured and reported.

  8. Enhancement of dispersion and bonding of graphene-polymer through wet transfer of functionalized graphene oxide

    Directory of Open Access Journals (Sweden)

    F. Sharif

    2012-12-01

    Full Text Available Dispersion of nanomaterials in polymeric matrices plays an important role in determining the final properties of the composites. Dispersion in nano scale, and especially in single layers, provides best opportunity for bonding. In this study, we propose that by proper functionalization and mixing strategy of graphene its dispersion, and bonding to the polymeric matrix can be improved. We then apply this strategy to graphene-epoxy system by amino functionalization of graphene oxide (GO. The process included two phase extraction, and resulted in better dispersion and higher loading of graphene in epoxy matrix. Rheological evaluation of different graphene-epoxy dispersions showed a rheological percolation threshold of 0.2 vol% which is an indication of highly dispersed nanosheets. Observation of the samples by optical microscopy, scanning electron microscopy (SEM, and atomic force microscopy (AFM, showed dispersion homogeneity of the sheets at micro and nano scales. Study of graphene-epoxy composites showed good bonding between graphene and epoxy. Mechanical properties of the samples were consistent with theoretical predictions for ideal composites indicating molecular level dispersion and good bonding between nanosheets and epoxy matrix.

  9. Improvement of interaction between pre-dispersed multi-walled carbon nanotubes and unsaturated polyester resin

    Science.gov (United States)

    Beg, M. D. H.; Moshiul Alam, A. K. M.; Yunus, R. M.; Mina, M. F.

    2015-01-01

    Efforts are being given to the development of well-dispersed nanoparticle-reinforced polymer nanocomposites in order to tailor the material properties. In this perspective, well dispersion of multi-walled carbon nanotubes (MWCNTs) in unsaturated polyester resin (UPR) was prepared using pre-dispersed MWCNTs in tetrahydrofuran solvent with ultrasonication method. Then the well-dispersed MWCNTs reinforced UPR nanocomposites were fabricated through solvent evaporation. Fourier-transform infrared spectroscopy indicates a good interaction between matrix and MWCNTs. This along with homogeneous dispersion of nanotubes in matrix has been confirmed by the field emission scanning electron microscopy. At low shear rate, the value of viscosity of UPR is 8,593 mPa s and that of pre-dispersed MWCNT-UPR suspension is 43,491 mPa s, showing implicitly a good dispersion of nanotubes. A notable improvement in the crystallinity of UPR from 14 to 21 % after MWCNTs inclusion was observed by X-ray diffractometry. The mechanical properties, such as tensile strength, tensile modulus, impact strength, and elongation-at-break, of nanocomposite were found to be increased to 22, 20, 28, and 87 %, respectively. The estimated melting enthalpy per gram for composites as analyzed by differential scanning calorimetry is higher than that of UPR. The onset temperature of thermal decomposition in the nanocomposites as monitored by thermogravimetric analysis is found higher than that of UPR. Correlations among MWCNTs dispersion, nucleation, fracture morphology, and various properties were measured and reported.

  10. Improved dissolution of Kaempferia parviflora extract for oral administration by preparing solid dispersion via solvent evaporation

    Directory of Open Access Journals (Sweden)

    Yotsanan Weerapol

    2017-03-01

    Full Text Available Kaempferia parviflora, a plant in the family Zingiberaceae, has been used in Thai traditional medicines for treating hypertension and promoting longevity with good health and well-being. However, its limited aqueous solubility and low dissolution restrict its bioavailability. The aim of the study was therefore to improve the dissolution rate of K. parviflora extracted with dichloromethane (KPD by solid dispersions. Different water-soluble polymers were applied to improve dissolution of KPD. The solid dispersions in different ratios were prepared by solvent evaporation method. Only hydroxypropyl methylcellulose (HPMC and polyvinyl alcohol-polyethylene glycol grafted copolymer (PVA-co-PEG could be used to produce homogeneous, powdered solid dispersions. Physical characterization by scanning electron microscopy, hot stage microscopy, differential scanning calorimetry and powder X-ray diffractometry, in comparison with corresponding physical mixtures, showed the changes in solid state during the formation of solid dispersions. Dissolution of a selected marker, 5,7,4′-trimethoxyflavone (TMF, from KPD/HPMC and KPD/PVA-co-PEG solid dispersions was significantly improved, compared with pure KPD. The dissolution enhancement by solid dispersion was influenced by both type and content of polymers. The stability of KPD/HPMC and KPD/PVA-co-PEG solid dispersions was also good after 6-month storage in both long-term and accelerated conditions. These results identified that the KPD/HPMC and KPD/PVA-co-PEG solid dispersions were an effective new approach for pharmaceutical application of K. parviflora.

  11. Cleavage nature, electrokinetics, aggregation and dispersion of kaolinite

    Institute of Scientific and Technical Information of China (English)

    胡岳华; 孙伟; 刘晓文; 王淀佐

    2003-01-01

    Quantum chemical simulation calculation shows that kaolinite is cleaved to produce(001)and(001)basal planes.(001)plane is dominant by [SiO4] tetrahedral,which interacted easily with hydrogen ion or other positive ions by electrostatic forces or hydrogen bonding.(001)plane is dominant hy [AlO2(OH)4],which interacted easily with high negativity group such as-O-,-N-,F-etc.The apparent zeta potential and surface points of zero charge(PZC)are different for hard and soft kaolinites depending on their crystallinity index(HI).The self-aggregation between edge and basal plane due to the electrostatic interactions may occur at acidic media.The dispersion of kaolinite particles at alkaline media may be attributed to the electrostatic repulsion between basal planes and/or edges.The aggregation or dispersion behavior is revealed by scan electron microscope and the transmittance measurements for the suspension of kaolinite particles.

  12. Curvature-Induced Asymmetric Spin-Wave Dispersion

    Science.gov (United States)

    Otálora, Jorge A.; Yan, Ming; Schultheiss, Helmut; Hertel, Riccardo; Kákay, Attila

    2016-11-01

    In magnonics, spin waves are conceived of as electron-charge-free information carriers. Their wave behavior has established them as the key elements to achieve low power consumption, fast operative rates, and good packaging in magnon-based computational technologies. Hence, knowing alternative ways that reveal certain properties of their undulatory motion is an important task. Here, we show using micromagnetic simulations and analytical calculations that spin-wave propagation in ferromagnetic nanotubes is fundamentally different than in thin films. The dispersion relation is asymmetric regarding the sign of the wave vector. It is a purely curvature-induced effect and its fundamental origin is identified to be the classical dipole-dipole interaction. The analytical expression of the dispersion relation has the same mathematical form as in thin films with the Dzyalonshiinsky-Moriya interaction. Therefore, this curvature-induced effect can be seen as a "dipole-induced Dzyalonshiinsky-Moriya-like" effect.

  13. Fast Pairwise Conversion of Supernova Neutrinos: A Dispersion Relation Approach

    Science.gov (United States)

    Izaguirre, Ignacio; Raffelt, Georg; Tamborra, Irene

    2017-01-01

    Collective pair conversion νeν¯ e↔νxν¯ x by forward scattering, where x =μ or τ , may be generic for supernova neutrino transport. Depending on the local angular intensity of the electron lepton number carried by neutrinos, the conversion rate can be "fast," i.e., of the order of √{2 }GF(nνe-nν¯e)≫Δ matm2/2 E . We present a novel approach to understand these phenomena: a dispersion relation for the frequency and wave number (Ω ,K ) of disturbances in the mean field of νeνx flavor coherence. Runaway solutions occur in "dispersion gaps," i.e., in "forbidden" intervals of Ω and/or K where propagating plane waves do not exist. We stress that the actual solutions also depend on the initial and/or boundary conditions, which need to be further investigated.

  14. Dispersion Relation of Linear Waves in Quantum Magnetoplasmas

    Science.gov (United States)

    Zhu, Jun

    2016-07-01

    The quantum magnetohydrodynamic (QMHD) model is applied in investigating the propagation of linear waves in quantum magnetoplasmas. Using the QMHD model, the dispersion equation for quantum magnetoplasmas and the dispersion relations of linear waves are deduced. Results show that quantum effects affect the propagation of electron plasma waves and extraordinary waves (X waves). When we select the plasma parameters of the laser-based plasma compression (LBPC) schemes for calculation, the quantum correction cannot be neglected. Meanwhile, the corrections produced by the Fermi degeneracy pressure and Bohm potential are compared under different plasma parameter conditions. supported by National Natural Science Foundation of China (No. 11447125) and the Research Training Program for Undergraduates of Shanxi University of China (Nos. 2014012167, 2015013182)

  15. Modeling the dispersion in electromechanically coupled myocardium

    Science.gov (United States)

    Eriksson, Thomas S. E.; Prassl, Anton J.; Plank, Gernot; Holzapfel, Gerhard A.

    2014-01-01

    SUMMARY We present an approach to model the dispersion of fiber and sheet orientations in the myocardium. By utilizing structure parameters, an existing orthotropic and invariant-based constitutive model developed to describe the passive behavior of the myocardium is augmented. Two dispersion parameters are fitted to experimentally observed angular dispersion data of the myocardial tissue. Computations are performed on a unit myocardium tissue cube and on a slice of the left ventricle indicating that the dispersion parameter has an effect on the myocardial deformation and stress development. The use of fiber dispersions relating to a pathological myocardium had a rather big effect. The final example represents an ellipsoidal model of the left ventricle indicating the influence of fiber and sheet dispersions upon contraction over a cardiac cycle. Although only a minor shift in the pressure–volume (PV) loops between the cases with no dispersions and with fiber and sheet dispersions for a healthy myocardium was observed, a remarkably different behavior is obtained with a fiber dispersion relating to a diseased myocardium. In future simulations, this dispersion model for myocardial tissue may advantageously be used together with models of, for example, growth and remodeling of various cardiac diseases. PMID:23868817

  16. Modeling the dispersion in electromechanically coupled myocardium.

    Science.gov (United States)

    Eriksson, Thomas S E; Prassl, Anton J; Plank, Gernot; Holzapfel, Gerhard A

    2013-11-01

    We present an approach to model the dispersion of fiber and sheet orientations in the myocardium. By utilizing structure parameters, an existing orthotropic and invariant-based constitutive model developed to describe the passive behavior of the myocardium is augmented. Two dispersion parameters are fitted to experimentally observed angular dispersion data of the myocardial tissue. Computations are performed on a unit myocardium tissue cube and on a slice of the left ventricle indicating that the dispersion parameter has an effect on the myocardial deformation and stress development. The use of fiber dispersions relating to a pathological myocardium had a rather big effect. The final example represents an ellipsoidal model of the left ventricle indicating the influence of fiber and sheet dispersions upon contraction over a cardiac cycle. Although only a minor shift in the pressure-volume (PV) loops between the cases with no dispersions and with fiber and sheet dispersions for a healthy myocardium was observed, a remarkably different behavior is obtained with a fiber dispersion relating to a diseased myocardium. In future simulations, this dispersion model for myocardial tissue may advantageously be used together with models of, for example, growth and remodeling of various cardiac diseases.

  17. Research progress in avian dispersal behavior

    Institute of Scientific and Technical Information of China (English)

    Yang LIU; Zhengwang ZHANG

    2008-01-01

    Dispersal, defined as a linear spreading move-ment of individuals away from others of the population is a fundamental characteristic of organisms in nature. Dispersal is a central concept in ecological, behavioral and evolutionary studies, driven by different forces such as avoidance of inbreeding depression, density-dependent competition and the need to change breeding locations. By effective dispersal, organisms can enlarge their geo-graphic range and adjust the dynamic, sex ratio and gen-etic compositions of a population. Birds are one of the groups that are studied intensively by human beings. Due to their diurnal habits, diverse life history strategies and complex movement, birds are also ideal models for the study of dispersal behaviors. Certain topics of avian dispersal including sex-biased, asymmetric dispersal caused by differences in body conditions, dispersal pro-cesses, habitat selection and long distance dispersal are discussed here. Bird-ringing or marking, radio-telemetry and genetic markers are useful tools widely applied in dispersal studies. There are three major challenges regard-ing theoretical study and methodology research of dis-persal: (1) improvement in research methodology is needed, (2) more in-depth theoretical research is neces-sary, and (3) application of theoretical research into the conservation efforts for threatened birds and the manage-ment of their habitats should be carried out immediately.

  18. Aerodynamics of puffball mushroom spore dispersal

    Science.gov (United States)

    Amador, Guillermo; Barberie, Alex; Hu, David

    2012-11-01

    Puffball mushrooms Lycoperdon are spherical fungi that release a cloud of spores in response to raindrop impacts. In this combined experimental and theoretical study, we elucidate the aerodynamics of this unique impact-based spore-dispersal. We characterize live puffball ejections by high speed video, the geometry and elasticity of their shells by cantilever experiments, and the packing fraction and size of their spores by scanning electron microscope. We build a dynamically similar puffball mimic composed of a tied-off latex balloon filled with baby powder and topped with a 1-cm slit. A jet of powder is elicited by steady lateral compression of the mimic between two plates. The jet height is a bell-shaped function of force applied, with a peak of 18 cm at loads of 45 N. We rationalize the increase in jet height with force using Darcy's Law: the applied force generates an overpressure maintained by the air-tight elastic membrane. Pressure is relieved as the air travels through the spore interstitial spaces, entrains spores, and exits through the puffball orifice. This mechanism demonstrates how powder-filled elastic shells can generate high-speed jets using energy harvested from rain.

  19. Soliton trapping of dispersive waves in photonic crystal fiber with two zero dispersive wavelengths.

    Science.gov (United States)

    Wang, Weibin; Yang, Hua; Tang, Pinghua; Zhao, Chujun; Gao, Jing

    2013-05-06

    Based on the generalized nonlinear Schrödinger equation, we present a numerical study of trapping of dispersive waves by solitons during supercontinuum generation in photonic crystal fibers pumped with femtosecond pulses in the anomalous dispersion region. Numerical simulation results show that the generated supercontinuum is bounded by two branches of dispersive waves, namely blue-shifted dispersive waves (B-DWs) and red-shifted dispersive waves (R-DWs). We find a novel phenomenon that not only B-DWs but also R-DWs can be trapped by solitons across the zero-dispersion wavelength when the group-velocity matching between the soliton and the dispersive wave is satisfied, which may led to the generation of new spectral components via mixing of solitons and dispersive waves. Mixing of solitons with dispersive waves has been shown to play an important role in shaping not only the edge of the supercontinuum, but also its central part around the higher zero-dispersion wavelength. Further, we show that the phenomenon of soliton trapping of dispersive waves in photonic crystal fibers with two zero-dispersion wavelengths has a very close relationship with pumping power and the interval between two zero-dispersion wavelengths. In order to clearly display the evolution of soliton trapping of dispersive waves, the spectrogram of output pulses is observed using cross-correlation frequency-resolved optical gating technique (XFROG).

  20. Dispersed publication of editorial research

    DEFF Research Database (Denmark)

    Rosenberg, Jacob; Pommergaard, Hans-Christian; Vinther, Siri

    2015-01-01

    INTRODUCTION: There seems to be no dedicated journals available for publication of editorial research in the biomedical sciences; that is research into editorial or publication process issues involving the scientific approach to writing, reviewing, editing and publishing. It is unknown where papers...... concerning these issues are typically published. We therefore set out to study the distribution of such papers in the biomedical literature. METHODS: In this pilot study, we conducted a MEDLINE search for papers on editorial research published in the year 2012. RESULTS: We found 445 articles published in 311...... journals with a median of one article per journal (range: 1-17). CONCLUSION: The publication of papers on editorial research seems to be dispersed. In order to increase the visibility of this research field, it may be reasonable to establish well-defined platforms such as dedicated journals or journal...

  1. Stochastic models for atmospheric dispersion

    DEFF Research Database (Denmark)

    Ditlevsen, Ove Dalager

    2003-01-01

    Simple stochastic differential equation models have been applied by several researchers to describe the dispersion of tracer particles in the planetary atmospheric boundary layer and to form the basis for computer simulations of particle paths. To obtain the drift coefficient, empirical vertical...... positions close to the boundaries. Different rules have been suggested in the literature with justifications based on simulation studies. Herein the relevant stochastic differential equation model is formulated in a particular way. The formulation is based on the marginal transformation of the position...... dependent particle velocity into a position independent Gaussian velocity. Boundary conditions are obtained from Itos rule of stochastic differentiation. The model directly point at a canonical rule of reflection for the approximating random walk with finite time step. This reflection rule is different from...

  2. Post-crash fuel dispersal

    Energy Technology Data Exchange (ETDEWEB)

    Tieszen, S.R.

    1997-03-01

    This paper is a brief overview of work over the last several decades in understanding what occurs to jet fuel stored in aircraft fuel tanks on impact with the ground. Fuel dispersal is discussed in terms of the overall crash dynamics process and impact regimes are identified. In a generic sense, the types of flow regimes which can occur are identified and general descriptions of the processes are given. Examples of engineering level tools, both computational and experimental, which have applicability to analyzing the complex environments are presented. Finally, risk based decision is discussed as a quick means of identifying requirements for development of preventative or mitigation strategies, such as further work on the development of an anti-misting agent.

  3. Dispersion relations for unphysical particles

    Science.gov (United States)

    Siringo, Fabio

    2017-03-01

    Generalized dispersion relations are discussed for unphysical particles, e.g. confined degrees of freedom that are not present in the physical spectra but can give rise to observable bound states. While in general the propagator of the unphysical particles can have complex poles and cannot be reconstructed from the knowledge of the imaginary part, under reasonable assumptions the missing piece of information is shown to be in the rational function that contains the poles and must be added to the integral representation. For pure Yang-Mills theory, the rational part and the spectral term are identified in the explicit analytical expressions provided by the massive expansion of the gluon propagator. The multi particle spectral term turns out to be very small and the simple rational part provides, from first principles, an approximate propagator that is equivalent to the tree-level result of simple phenomenological models like the refined Gribov-Zwanziger model.

  4. Dispersion and suburbanisation. New ethnoscapes.

    Directory of Open Access Journals (Sweden)

    Pau Serra del Pozo

    2011-11-01

    Full Text Available There are many deviations from the simple scheme of ethnic enclaves or ethnic centralities today, even in contemporary Little Havana in Miami. This scheme tends to be diluted by three processes: 1 the decentralization of some immigrant residents towards the suburbs or urban periphery; these suburban immigrants may be more settled or affluent than recent immigrants living in inner-city communities; 2 the dispersal of entrepreneurs of a particular ethnic minority in a large metropolitan area; and 3 the emergence and coexistence of multiple ethnic groups in the same zone or area. The three processes gradually cause the loss of the unity of the residententrepreneur coethnic tandem in the same neighbourhood.

  5. Dispersed publication of editorial research

    DEFF Research Database (Denmark)

    Rosenberg, Jacob; Pommergaard, Hans-Christian; Vinther, Siri;

    2015-01-01

    INTRODUCTION: There seems to be no dedicated journals available for publication of editorial research in the biomedical sciences; that is research into editorial or publication process issues involving the scientific approach to writing, reviewing, editing and publishing. It is unknown where papers...... concerning these issues are typically published. We therefore set out to study the distribution of such papers in the biomedical literature. METHODS: In this pilot study, we conducted a MEDLINE search for papers on editorial research published in the year 2012. RESULTS: We found 445 articles published in 311...... journals with a median of one article per journal (range: 1-17). CONCLUSION: The publication of papers on editorial research seems to be dispersed. In order to increase the visibility of this research field, it may be reasonable to establish well-defined platforms such as dedicated journals or journal...

  6. Dispersion of Co/CNTs via strong electrostatic adsorption method: Thermal treatment effect

    Science.gov (United States)

    Akbarzadeh, Omid; Zabidi, Noor Asmawati Mohd; Abdullah, Bawadi; Subbarao, Duvvuri

    2015-07-01

    The effect of different thermal treatment temperature on the structure of multi-walled carbon nanotubes (MWCNTs) and Co particle dispersion on CNTs support is studied using Strong electrostatic adsorption (SEA) method. The samples tested by N2-adsorption, field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). N2-adsorption results showed BET surface area increased using thermal treatment and TEM images showed that increasing the thermal treatment temperature lead to flaky CNTs and defects introduced on the outer surface and Co particle dispersion increased.

  7. Dispersion of Co/CNTs via strong electrostatic adsorption method: Thermal treatment effect

    Energy Technology Data Exchange (ETDEWEB)

    Akbarzadeh, Omid, E-mail: omid.akbarzadeh63@gmail.com; Abdullah, Bawadi, E-mail: bawadi-abdullah@petronas.com.my; Subbarao, Duvvuri, E-mail: duvvuri-subbarao@petronas.com.my [Department of Chemical Engineering, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 31750 Tronoh, Perak (Malaysia); Zabidi, Noor Asmawati Mohd, E-mail: noorasmawati-mzabidi@petronas.com.my [Department of Fundamental and Applied Sciences, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 31750 Tronoh, Perak (Malaysia)

    2015-07-22

    The effect of different thermal treatment temperature on the structure of multi-walled carbon nanotubes (MWCNTs) and Co particle dispersion on CNTs support is studied using Strong electrostatic adsorption (SEA) method. The samples tested by N{sub 2}-adsorption, field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). N{sub 2}-adsorption results showed BET surface area increased using thermal treatment and TEM images showed that increasing the thermal treatment temperature lead to flaky CNTs and defects introduced on the outer surface and Co particle dispersion increased.

  8. Formulation of disperse systems science and technology

    CERN Document Server

    Tadros, Tharwat F

    2014-01-01

    This book presents comprehensively the science and technology behind the formulation of disperse systems like emulsions, suspensions, foams and others. Starting with a general introduction, the book covers a broad range of topics like the role of different classes of surfactants, stability of disperse systems, formulation of different dispersions, evaluation of formulations and many more. Many examples are included, too. Written by the experienced author and editor Tharwart Tadros, this book is indispensable for every scientist working in the field.

  9. Electrostatic Stabilization of Graphene in Organic Dispersions

    OpenAIRE

    Rodgers, Andrew N J; Velicky, Matej; Dryfe, Robert A.W.

    2015-01-01

    The exfoliation of graphite to give graphene dispersions in nonaqueous solvents is an important area with regards to scalable production of graphene in bulk quantities and its ultimate application in devices. Understanding the mechanisms governing the stability of these dispersions is therefore of both scientific interest and technological importance. Herein, we have used addition of an indifferent electrolyte to perturb few-layer graphene dispersions in a nonaqueous solvent (1,2-dichloroetha...

  10. Phonon dispersion and heat capacity in polyfuran

    Science.gov (United States)

    Ali, Parvej; Srivastava, Seema; Ali Khan, Irfan; Gupta, V. D.; Ansari, Saif-ul-Islam

    A study of the normal modes of vibration and their dispersion in polyfuran (Pfu) based on the Urey-Bradley force field is reported. It provides a detailed interpretation of IR and Raman spectra. Characteristic features of dispersion curves such as regions of high density-of-states, repulsion and character mixing of dispersive modes are discussed. Predictive values of heat capacity as a function of temperature are calculated.

  11. Signal velocity for anomalous dispersive waves

    Energy Technology Data Exchange (ETDEWEB)

    Mainardi, F. (Bologna Univ. (Italy))

    1983-03-11

    The concept of signal velocity for dispersive waves is usually identified with that of group velocity. When the dispersion is anomalous, this interpretation is not correct since the group velocity can assume nonphysical values. In this note, by using the steepest descent method first introduced by Brillouin, the phase velocity is shown to be the signal velocity when the dispersion is anomalous in the full range of frequencies.

  12. Bed-Load Dispersion: A Literature Review

    Science.gov (United States)

    2016-12-01

    However, the work of Phillips et al. (2013) suggested that the asymptotic limit of bed-load dispersion is super- dispersive. Fischer et al. (1979...Olinde and Johnson 2015, Phillips et al. 2013, Martin et al. 2012 and 2014). Campagnol et al. (2015) showed that if the particles are exhibiting...vertical dispersion. Journal of Geophysical Research: Earth Surface 119(9): 1818–1832. Phillips , C. B., R. L. Martin, and D. J. Jerolmack. 2013

  13. The conservation physiology of seed dispersal.

    Science.gov (United States)

    Ruxton, Graeme D; Schaefer, H Martin

    2012-06-19

    At a time when plant species are experiencing increasing challenges from climate change, land-use change, harvesting and invasive species, dispersal has become a very important aspect of plant conservation. Seed dispersal by animals is particularly important because some animals disperse seeds to suitable sites in a directed fashion. Our review has two aims: (i) to highlight the various ways plant dispersal by animals can be affected by current anthropogenic change and (ii) to show the important role of plant and (particularly) animal physiology in shaping seed-dispersal interactions. We argue that large-bodied seed dispersers may be particularly important for plant conservation because seed dispersal of large-seeded plants is often more specialized and because large-bodied animals are targeted by human exploitation and have smaller population sizes. We further argue that more specialized seed-dispersal systems on island ecosystems might be particularly at risk from climate change both owing to small population sizes involved but also owing to the likely thermal specialization, particularly on tropical islands. More generally, the inherent vulnerability of seed-dispersal mutualisms to disruption driven by environmental change (as well as their ubiquity) demands that we continue to improve our understanding of their conservation physiology.

  14. Black Brant X third stage dispersion dynamics

    Science.gov (United States)

    Montag, W. H.; Maksimovic, V. M.; Lindahl, J. E.

    1982-01-01

    The successful development of the Black Brant X (BBX) launch vehicle resulted from the application of a gyroscopically stabilized, unguided third stage motor configuration. Design analyses indicated sufficient gyroscopic stability and acceptable impact dispersion could be realized by optimizing second/third stage separation time. By flying an unguided third stage motor, significant program cost savings were realized. One flight test and two operational missions demonstrated the feasibility of utilizing gyroscopic stability to achieve satisfactory trajectory dispersion on a high performance rocket. A detailed assessment of the major dispersion contributors identified for the first three BBX missions is presented, offering important insight into the dispersion sensitivity of unguided, spin-stabilized flight.

  15. RHEOLOGICAL BEHAVIOR OF EPOXY RESIN WATERBORNE DISPERSIONS

    Institute of Scientific and Technical Information of China (English)

    Zhen-zhong Yang; Yuan-ze Xu; De-lu Zhao

    2001-01-01

    The waterborne dispersions of epoxy resin were prepared by the phase inversion emulsification technique.Rheological behavior and its relationship with the structural change of the systems were studied. It was shown that the concentrated dispersions were highly viscoelastic and pseudoplastic, which was attributed to the formation of a physical network among the waterborne particles via hydrogen bond. The dilute dispersions were Newtonian fluids. The discrete clusters composed of small waterborne particles were found in diluted dispersions. With increasing solid content, there existed a structural transition via percolation through a cluster-cluster aggregation mode to form the physical network, which was qualitatively evidenced by the TEM morphologies.``

  16. Dispersal of Engineered Male Aedes aegypti Mosquitoes.

    Science.gov (United States)

    Winskill, Peter; Carvalho, Danilo O; Capurro, Margareth L; Alphey, Luke; Donnelly, Christl A; McKemey, Andrew R

    2015-11-01

    Aedes aegypti, the principal vector of dengue fever, have been genetically engineered for use in a sterile insect control programme. To improve our understanding of the dispersal ecology of mosquitoes and to inform appropriate release strategies of 'genetically sterile' male Aedes aegypti detailed knowledge of the dispersal ability of the released insects is needed. The dispersal ability of released 'genetically sterile' male Aedes aegypti at a field site in Brazil has been estimated. Dispersal kernels embedded within a generalized linear model framework were used to analyse data collected from three large scale mark release recapture studies. The methodology has been applied to previously published dispersal data to compare the dispersal ability of 'genetically sterile' male Aedes aegypti in contrasting environments. We parameterised dispersal kernels and estimated the mean distance travelled for insects in Brazil: 52.8 m (95% CI: 49.9 m, 56.8 m) and Malaysia: 58.0 m (95% CI: 51.1 m, 71.0 m). Our results provide specific, detailed estimates of the dispersal characteristics of released 'genetically sterile' male Aedes aegypti in the field. The comparative analysis indicates that despite differing environments and recapture rates, key features of the insects' dispersal kernels are conserved across the two studies. The results can be used to inform both risk assessments and release programmes using 'genetically sterile' male Aedes aegypti.

  17. Selection of Dispersivity in Groundwater Risk Assessment

    Institute of Scientific and Technical Information of China (English)

    武晓峰; 唐杰

    2004-01-01

    The Domenico model is used in combination with ASTM E 1739 in a Tier 2 risk assessment of chlorinated organic solvents contaminated groundwater sites to predict potential contaminant concentration in groundwater down-gradient from the point of exposure (POE). A knowledge of the dispersivity parameters is necessary for carrying out this calculation. A constant longitudinal dispersivity of 10 m is often used in analytical and numerical calculation. However, because of the scale effect of dispersion, two other main approaches are currently often used. From the viewpoint of conservative principle in risk assessment, it is necessary to determine which dispersivity data will give a higher predicted concentration, corresponding to a more conservative risk calculation. Generally, it is considered that a smaller dispersivity leads to a higher predicted concentration. This assumption is correct when dispersion is the only natural attenuation factor. However, degradation of commonly encountered chlorinated organic solvents in environment under natural condition has been widely reported. Calculations given in this paper of several representative cases show that a general consideration of the influence of dispersivity on concentration prediction is not always correct when a degradation term is included in the calculation. To give a conservative risk calculation, the scale effect of dispersion is considered. Calculations also show that the dispersivity parameters need to be determined by considering the POE distance from the source, the groundwater velocity, and the degradation rate of the contaminant.

  18. The conservation physiology of seed dispersal

    Science.gov (United States)

    Ruxton, Graeme D.; Schaefer, H. Martin

    2012-01-01

    At a time when plant species are experiencing increasing challenges from climate change, land-use change, harvesting and invasive species, dispersal has become a very important aspect of plant conservation. Seed dispersal by animals is particularly important because some animals disperse seeds to suitable sites in a directed fashion. Our review has two aims: (i) to highlight the various ways plant dispersal by animals can be affected by current anthropogenic change and (ii) to show the important role of plant and (particularly) animal physiology in shaping seed–dispersal interactions. We argue that large-bodied seed dispersers may be particularly important for plant conservation because seed dispersal of large-seeded plants is often more specialized and because large-bodied animals are targeted by human exploitation and have smaller population sizes. We further argue that more specialized seed-dispersal systems on island ecosystems might be particularly at risk from climate change both owing to small population sizes involved but also owing to the likely thermal specialization, particularly on tropical islands. More generally, the inherent vulnerability of seed-dispersal mutualisms to disruption driven by environmental change (as well as their ubiquity) demands that we continue to improve our understanding of their conservation physiology. PMID:22566677

  19. Discrete dispersion models and their Tweedie asymptotics

    DEFF Research Database (Denmark)

    Jørgensen, Bent; Kokonendji, Célestin C.

    2016-01-01

    in this approach, whereas several overdispersed discrete distributions, such as the Neyman Type A, Pólya-Aeppli, negative binomial and Poisson-inverse Gaussian, turn out to be Poisson-Tweedie factorial dispersion models with power dispersion functions, analogous to ordinary Tweedie exponential dispersion models...... with power variance functions. Using the factorial cumulant generating function as tool, we introduce a dilation operation as a discrete analogue of scaling, generalizing binomial thinning. The Poisson-Tweedie factorial dispersion models are closed under dilation, which in turn leads to a Poisson...

  20. Investigation of Surfactant Type, Dosage and Ultrasonication Temperature Control on Dispersity of Metal-Coated Multi-Walled Carbon Nanotubes.

    Science.gov (United States)

    Liang, Xiaoning; Li, Wei

    2016-04-01

    We studied the dispersity of multi-walled carbon nanotubes (MWNTs) combined with different metal- lic particles (Ni and Fe). An ultrasonic-assisted water-bath dispersion process was used to dis- perse the metal-coated MWNTs in different solutions and the dispersity was measured using an ultraviolet-visible spectrophotometer. The dispersity and morphology of the MWNTs were characterized using field-emission scanning electron microscopy (FE-SEM) together with digital image processing technology. Effects of dispersant type (sodium dodecyl benzene sulfonate (SDBS), oleic acid, and polymer (TNEDIS)) and surfactant dosage on the dispersity of the metal-coated MWNTs were investigated under controlled and uncontrolled temperatures and results were compared with those from the untreated MWNTs. The results showed that the negative effects of temperature on the ultrasonic dispersion process could be eliminated through a temperature-controlled system. Moreover, the TNEDIS, SDBS, and oleic acid were arranged in the descending order of the dispersion effect degree. The untreated MWNTs, Ni-coated MWNTs, and Fe-coated MWNTs were arranged in the descending degree of dispersity order. Since the metal coating makes the MWNTs harder and more fragile, the metal-coated MWNTs are more likely to fracture during the ultrasonic dispersion process.

  1. Development of megestrol acetate solid dispersion nanoparticles for enhanced oral delivery by using a supercritical antisolvent process.

    Science.gov (United States)

    Ha, Eun-Sol; Kim, Jeong-Soo; Baek, In-Hwan; Yoo, Jin-Wook; Jung, Yunjin; Moon, Hyung Ryong; Kim, Min-Soo

    2015-01-01

    In the present study, solid dispersion nanoparticles with a hydrophilic polymer and surfactant were developed using the supercritical antisolvent (SAS) process to improve the dissolution and oral absorption of megestrol acetate. The physicochemical properties of the megestrol acetate solid dispersion nanoparticles were characterized using scanning electron microscopy, differential scanning calorimetry, powder X-ray diffraction, and a particle-size analyzer. The dissolution and oral bioavailability of the nanoparticles were also evaluated in rats. The mean particle size of all solid dispersion nanoparticles that were prepared was dispersion state within the solid dispersion nanoparticles. Hydroxypropylmethyl cellulose (HPMC) solid dispersion nanoparticles significantly increased the maximum dissolution when compared with polyvinylpyrrolidone K30 solid dispersion nanoparticles. The extent and rate of dissolution of megestrol acetate increased after the addition of a surfactant into the HPMC solid dispersion nanoparticles. The most effective surfactant was Ryoto sugar ester L1695, followed by D-α-tocopheryl polyethylene glycol 1000 succinate. In this study, the solid dispersion nanoparticles with a drug:HPMC:Ryoto sugar ester L1695 ratio of 1:2:1 showed >95% rapid dissolution within 30 minutes, in addition to good oral bioavailability, with approximately 4.0- and 5.5-fold higher area under the curve (0-24 hours) and maximum concentration, respectively, than raw megestrol acetate powder. These results suggest that the preparation of megestrol acetate solid dispersion nanoparticles using the supercritical antisolvent process is a promising approach to improve the dissolution and absorption properties of megestrol acetate.

  2. Dispersion-strengthened Aluminium Products Manufactured by Powder Blending

    DEFF Research Database (Denmark)

    Hansen, Niels

    1969-01-01

    Detailed experiments carried out to examine relationship between microstructure and mechanical properties of powder-blended aluminum products are reported; their results as well as structural studies by transmission electron microscopy and tensile-and creep- testing, are given; as dispersed phase......, various oxide powders were selected on criterion that during manufacturing no reaction must taken place between metal and oxide phase; strength of powder-blended aluminum products increases and elongation decreases with decreasing particle size of aluminum powder and with increasing concentration of oxide...

  3. Bunch length modulation in highly dispersive storage rings

    Directory of Open Access Journals (Sweden)

    C. Biscari

    2005-09-01

    Full Text Available Modulation of the bunch length in an electron storage ring appears with the combination of a high rf voltage derivative and large dispersion in the dipoles, producing drifting of the longitudinal phase plane along the closed orbit. The comparison is done between two different regimes: the one corresponding to high momentum compaction structures, in which the drifting in all dipoles has always the same direction, and the other one corresponding to low momentum compaction in which the drifting changes sign along the ring. Expressions for the longitudinal Twiss functions, energy spread and longitudinal emittance are given. The generalization to multiple rf systems is mentioned.

  4. Nongeneric dispersion of excitons in the bulk of WSe2

    Science.gov (United States)

    Schuster, R.; Wan, Y.; Knupfer, M.; Büchner, B.

    2016-08-01

    We combine electron energy-loss spectroscopy (EELS) and density functional theory (DFT) calculations to study the dispersion and effective mass of excitons in the bulk of WSe2. Our EELS data suggest substantial deviations from the generic quadratic momentum dependence along the Γ K direction. From the DFT-derived Kohn-Sham states we deduce the EELS response without the inclusion of particle-hole attraction to study the possible role of the single-particle band structure on the exciton behavior. Based on this analysis we argue in favor of a strongly momentum dependent particle-hole interaction in WSe2 and other group-VI-transition-metal dichalcogenides.

  5. Dispersion Characteristics of a New Slow-Wave Structure

    Institute of Scientific and Technical Information of China (English)

    WU Jian-Qiang

    2004-01-01

    @@ The microwave excitation in a new slow-wave structure, i.e. the plasma-filled coaxial cylindrical dielectric-loaded cylindrical waveguide, is investigated by using the self-consistent linear field theory in considering the collision effect between electrons and ions in the plasma via the collision frequency term. The determinant dispersion equation of the beam-wave interaction with a complex value of angular frequency is derived. The effects of plasma collision frequency on the output frequency and the wave growth rate of the beam-wave interaction are calculated and discussed.

  6. Acoustoelectric effect in graphene with degenerate energy dispersion

    Science.gov (United States)

    Dompreh, K. A.; Mensah, N. G.; Mensah, S. Y.

    2017-01-01

    Acoustoelectric current (jac) in Free-Standing Graphene (FSG) having degenerate energy dispersion at low temperatures T ≪TBG (TBG is the Block-Gruneisen temperature) was studied theoretically. We considered electron interaction with in-plain acoustic phonons in the hypersound regime (sound vibration in the range 109 -1012 Hz). The obtained expression for jac was numerically analyzed for various temperatures (T) and frequencies (ωq) and graphically presented. The non-linear dependence of jac on ωq varied with temperature. This qualitatively agreed with an experimentally obtained result which deals with temperature dependent acoustoelectric current in graphene [21].

  7. Dispersal-mediated trophic interactions can generate apparent patterns of dispersal limitation in aquatic metacommunities

    NARCIS (Netherlands)

    Verreydt, D.; De Meester, L.; Decaestecker, E.; Villena, M.J.; Van der Gucht, K.; Vannormelingen, P.; Vyverman, W.; Declerck, S.A.J.

    2012-01-01

    Dispersal is a major organising force in metacommunities, which may facilitate compositional responses of local communities to environmental change and affect ecosystem function. Organism groups differ widely in their dispersal abilities and their communities are therefore expected to have different

  8. Who dispersed the seeds? The use of DNA barcoding in frugivory and seed dispersal studies

    National Research Council Canada - National Science Library

    González‐Varo, Juan P; Arroyo, Juan M; Jordano, Pedro; Gilbert, M

    2014-01-01

    ... ‘which species dispersed the seeds’. This is essential for assessing how multiple frugivore species contribute distinctly to critical dispersal events such as seed delivery to safe sites, long...

  9. Evaluación in vitro de la preparación de conductos mesiales de molares con instrumentos manuales Ni-Ti y Protaper Universal rotatorio In vitro evaluation of mesial molars canals preparation with manual Ni-Ti instruments and rotatory Protaper Universal

    Directory of Open Access Journals (Sweden)

    D. Aracena Rojas

    2013-04-01

    Full Text Available Con la finalidad de disminuir los errores durante la preparación de los conductos radiculares, se han introducido diversas modificaciones en los sistemas de instrumentación mecanizados de níquel-titanio. Se realizó un estudio in vitro para comparar el grado de transporte que se presenta a nivel de la unión del tercio apical con el tercio medio de conductos radiculares con el sistema rotatorio Protaper Universal y el sistema manual de níquel-titanio, con la técnica de fuerzas balanceadas. Se trabajó con 52 conductos mesiales de 26 molares maxilares y mandibulares, las cuales fueron divididas en dos grupos. El primer grupo de conductos (n = 28 fueron instrumentados con Protaper Universal rotatorio y el segundo grupo de conductos (n = 24 fueron instrumentados con técnica manual de fuerzas balanceadas. Las raíces mesiales de los molares fueron sumergidas en una matriz de acrílico, la cual permitió manipular las preparaciones, realizar cortes transversales y comparar los conductos radiculares antes y después de la instrumentación, para establecer las diferencias que se apreciaron en cuanto al transporte apical. Las imágenes obtenidas fueron fotografiadas con un microscopio estereoscópico y analizadas mediante el programa Autodesk AutoCAD® 2007. Finalmente, los datos obtenidos fueron tabulados y analizados con el programa Stata® 9.0 v. En el presente trabajo Protaper provocó menos transporte apical comparado con la técnica manual de fuerzas balanceadas.In order to reduce errors during root canal preparation, there have been several changes in instrumentation with rotatory systems of nickel-titanium. This is an in vitro study and the aim was to compare the degree of transportation that occurs at the union between the apical third and half third of root canals with the rotaroty Protaper Universal and nickel titanium manual system with balanced force technique. We worked with 52 mesial canals of 26 first and second maxillary and

  10. Pollen Forecast and Dispersion Modelling

    Science.gov (United States)

    Costantini, Monica; Di Giuseppe, Fabio; Medaglia, Carlo Maria; Travaglini, Alessandro; Tocci, Raffaella; Brighetti, M. Antonia; Petitta, Marcello

    2014-05-01

    The aim of this study is monitoring, mapping and forecast of pollen distribution for the city of Rome using in-situ measurements of 10 species of common allergenic pollens and measurements of PM10. The production of daily concentration maps, associated to a mobile phone app, are innovative compared to existing dedicated services to people who suffer from respiratory allergies. The dispersal pollen is one of the most well-known causes of allergic disease that is manifested by disorders of the respiratory functions. Allergies are the third leading cause of chronic disease and it is estimated that tens millions of people in Italy suffer from it. Recent works reveal that during the last few years there was a progressive increase of affected subjects, especially in urban areas. This situation may depend: on the ability to transport of pollutants, on the ability to react between pollutants and pollen and from a combination of other irritants, existing in densely populated and polluted urban areas. The methodology used to produce maps is based on in-situ measurements time series relative to 2012, obtained from networks of air quality and pollen stations in the metropolitan area of Rome. The monitoring station aerobiological of University of Rome "Tor Vergata" is located at the Department of Biology. The instrument used to pollen monitoring is a volumetric sampler type Hirst (Hirst 1952), Model 2000 VPPS Lanzoni; the data acquisition is carried out as reported in Standard UNI 11008:2004 - "Qualità dell'aria - Metodo di campionamento e conteggio dei granuli pollinici e delle spore fungine aerodisperse" - the protocol that describes the procedure for measuring of the concentration of pollen grains and fungal spores dispersed into the atmosphere, and reported in the "Manuale di gestione e qualità della R.I.M.A" (Travaglini et. al. 2009). All 10 allergenic pollen are monitored since 1996. At Tor Vergata university is also operating a meteorological station (SP2000, CAE

  11. Ab initio Calculation of Intermolecular Dispersion Energy and Induction Energy of Nitramide Dimer

    Institute of Scientific and Technical Information of China (English)

    SONG, Hua-Jie(宋华杰); XIAO, He-Ming(肖鹤鸣); DONG, Hai-Shan(董海山); HUANG, Yi-Gang(黄奕刚); LONG, Xin-Ping(龙新平); TANG, Yei-Peng(汤业鹏)

    2004-01-01

    The dispersion energies, induction energies and their exchange counterparts (exchange-dispersion and exchange-induction energies) between two interacting nitramide molecules at several separations are derived based upon symmetry-adapted perturbation theory (SAPT). The results show that (1) the effect of intramonomer electron correlation on dispersion energies and induction energies for nitramide dimer system is remarkable especially in the region near the van der Waals minimum distance (0.42 nm). (2) At smaller separations the dispersion energies and the induction energies are largely quenched by their exchange counterparts, and this case in induction interaction is much more remarkable than in dispersion interaction. (3) Since at shorter distances there exists the strong short-range interaction due to electron transfer which quickly decays and even disappears at larger separations, the two different R-dependency formulae of induction energies were found: one is ca. R-12.7 at short distances, and the other ca. R-7.0 at large separations. The latter R-dependency is similar to that (ca. R-7.2) of dispersion. (4) In the case of strong polar interaction existing in nitramide dimer, the "true" induction correlation terms of higher order than tE(22)ind may be important.

  12. Who dispersed the seeds? The use of DNA barcoding in frugivory and seed dispersal studies

    OpenAIRE

    González-Varo, Juan P.; J.M. Arroyo; Jordano, Pedro

    2014-01-01

    Assessing dispersal events in plants faces important challenges and limitations. A methodological issue that limits advances in our understanding of seed dissemination by frugivorous animals is identifying 'which species dispersed the seeds'. This is essential for assessing how multiple frugivore species contribute distinctly to critical dispersal events such as seed delivery to safe sites, long-distance dispersal and the colonization of non-occupied habitats. Here, we describe DNA-barcoding ...

  13. Personality-dependent dispersal cancelled under predation risk.

    Science.gov (United States)

    Cote, Julien; Fogarty, Sean; Tymen, Blaise; Sih, Andrew; Brodin, Tomas

    2013-12-22

    Dispersal is a fundamental life-history trait for many ecological processes. Recent studies suggest that dispersers, in comparison to residents, display various phenotypic specializations increasing their dispersal inclination or success. Among them, dispersers are believed to be consistently more bold, exploratory, asocial or aggressive than residents. These links between behavioural types and dispersal should vary with the cause of dispersal. However, with the exception of one study, personality-dependent dispersal has not been studied in contrasting environments. Here, we used mosquitofish (Gambusia affinis) to test whether personality-dependent dispersal varies with predation risk, a factor that should induce boldness or sociability-dependent dispersal. Corroborating previous studies, we found that dispersing mosquitofish are less social than non-dispersing fish when there was no predation risk. However, personality-dependent dispersal is negated under predation risk, dispersers having similar personality types to residents. Our results suggest that adaptive dispersal decisions could commonly depend on interactions between phenotypes and ecological contexts.

  14. Does an ant-dispersed plant, Viola reichenbachiana, suffer from reduced seed dispersal under inundation disturbances?

    NARCIS (Netherlands)

    Prinzing, A.; Dauber, J.; Hammer, E.; Hammouti, N.; Bohning-Gaese, K.

    2008-01-01

    Many plant species use ants as seed dispersers. This dispersal mode is considered to be susceptible to disturbances, but the effect of natural, small-scale disturbances is still unknown. We investigated how small-scale disturbances due to inundation affect seed dispersal in Viola reichenbachiana, a

  15. 钉-棒系统与外固定支架固定骨盆不稳定损伤模型的生物力学比较%Biomechanical comparison of pedicle screw-rod system and pelvic external fixator in models of rotatory unstable pelvic injury

    Institute of Scientific and Technical Information of China (English)

    李尚政; 苏伟; 赵劲民; 谢能峰

    2013-01-01

    Objective To compare the biomechanical performances of pedicle screw-rod system versus pelvic ala ilium external fixator in cadaveric models of rotatory unstable pelvic injury.Methods Seven cadaveric specimens of normal adult pelvis were used for the test,retaining intact spines from the fifth lumbar vertebra to the proximal 20 centimeters of both femurs,intact pubic symphysis,bilateral hip joints,bilateral sacroiliac joints,bilateral sacrotuberous ligaments,bilateral sacrospinous ligaments,bilateral anterior sacroiliac ligaments and bilateral posterior sacroiliac ligaments.The pelvic specimens were put in an AGX biomechanical testing machine at a standing neutral posture and subjected to a vertical load of up to 500 N downward from the L5 body.The displacements of the symphysis pubis were recorded sequentially in the following 4 conditions:1.intact pelvis; 2.pelvic Tile B1 injury in simulation of rotatory unstable injury of the pelvis in which the symphysis pubis was cut off and accompanied with ruptures of ipsilateral sacrospinous and sacrotuberous ligaments; 3.pelvic Tile B1 injury fixated with the pedicle screw-rod system; 4.pelvic Tile B1 injury fixated with the pelvic ala ilium external fixator.Results Under the vertical load of 500 N,displacements of the symphysis pubis increased significantly from condition 1 (0.121 ± 0.025 mm),to condition 3 (0.656 ±0.103 mm),to condition 4 (1.512 ±0.101 mm) and last to condition 2 (4.512 ±0.391 mm).The difference between any two conditions was significant (P < 0.05).Conclusion Fixation by the pedicle screw-rod system is significantly better than that by the pelvic ala ilium external fixator for rotatory unstable pelvic injury,because the former can more effectively restore the biomechanical stability of the pelvic ring.%目的 通过对钉-棒系统和骨盆髂骨翼外固定支架固定骨盆水平旋转不稳定损伤模型的生物力学进行测试,对比两者固定骨盆的力学稳定性,为

  16. Dispersion-induced nonlinearities in semiconductors

    DEFF Research Database (Denmark)

    Mørk, Jesper; Mecozzi, A.

    2002-01-01

    A dispersive and saturable medium is shown, under very general conditions, to possess ultrafast dynamic behaviour due to non-adiabatic polarisation dynamics. Simple analytical expressions relating the effect to the refractive index dispersion of a semiconductor ire derived and the magnitude...... of the equivalent Kerr coefficient is shown to be in qualitative agreement with measurements on active semiconductor waveguides....

  17. Van der Waals forces and spatial dispersion

    OpenAIRE

    2009-01-01

    A version of the Green's functions theory of the Van der Waals forces which can be conveniently used in the presence of spatial dispersion is presented. The theory is based on the fluctuation-dissipation theorem and is valid for interacting bodies, separated by vacuum. Objections against theories acounting for the spatial dispersion are discussed.

  18. Are western juniper seeds dispersed through diplochory?

    Science.gov (United States)

    Seed dispersal of western juniper (Juniperus occidentalis) appears to be convergent on a strategy utilized by fruit-bearing trees in that this conifer produces fleshy female cones (a.k.a., juniper “berries”) that are consumed by frugivorous birds, which then disperse the seeds through endozoochory b...

  19. Dispersive and erodible soils - fundamental differences

    CSIR Research Space (South Africa)

    Paige-Green, P

    2008-11-01

    Full Text Available Dispersive, erodible and slaking soils are prevalent over wide areas of South Africa. Each of these materials increases the cost of construction, but dispersive soils are likely to lead to far more serious problems, particularly in dam construction...

  20. Phonon dispersion relation of liquid metals

    Indian Academy of Sciences (India)

    P B Thakor; P N Gajjar; A R Jani

    2009-06-01

    The phonon dispersion curves of some liquid metals, viz. Na ( = 1), Mg ( = 2), Al ( = 3) and Pb ( = 4), have been computed using our model potential. The charged hard sphere (CHS) reference system is applied to describe the structural information. Our model potential along with CHS reference system is capable of explaining the phonon dispersion relation for monovalent, divalent, trivalent and tetravalent liquid metals.

  1. Membranes as separators of dispersed emulsion phases

    NARCIS (Netherlands)

    Lefferts, A.G.

    1997-01-01

    The reuse or discharge of industrial waste waters, containing small fractions of dispersed oil, requires a purification treatment for which membranes can be used. If only little oil is present, removal of the dispersed phase might be preferable to the more commonly applied removal of the

  2. Hominoid dispersal patterns and human evolution.

    Science.gov (United States)

    Koenig, Andreas; Borries, Carola

    2012-05-01

    Recent advances in DNA and isotope analyses have allowed tentative reconstructions of dispersal strategies of Plio-Pleistocene hominins.(1,2) Comparing their findings to dispersal patterns of some extant apes and humans suggested groups of related males and unrelated females in Neandertals indicating patrilocality(2) and Pan-like male philopatry in australopiths.(1) Here we review the demographic, ethnographic, and genetic evidence of dispersal patterns in extant apes and humans and compare the results to the suggestions for Plio-Pleistocene hominins. We find that alternative dispersal patterns, for example among gorillas or gibbons, could explain the findings of related or natal males in a confined geographic area. Based on sexual size dimorphism, we speculate that gorillas might currently be the best model for reconstructing dispersal in robust australopiths. Given that the sexual size dimorphism in other australopiths is still hotly debated, the question of which hominoid model best matches their dispersal pattern must remain unanswered. Neandertal dispersal patterns have been compared to patrilocality of modern humans. However, the latter is related to the advent of food production. Consequently, hunter-gatherers exhibiting primarily multilocality appear to be the better comparison for Neandertals. Overall, human-like patrilocality and Pan-like male philopatry appear to be poor models for the reconstruction of dispersal patterns in Plio-Pleistocene hominins. Copyright © 2012 Wiley Periodicals, Inc.

  3. Seed dispersal effectiveness revisited: a conceptual review.

    Science.gov (United States)

    Schupp, Eugene W; Jordano, Pedro; Gómez, José María

    2010-10-01

    Growth in seed dispersal studies has been fast-paced since the seed disperser effectiveness (SDE) framework was developed 17 yr ago. Thus, the time is ripe to revisit the framework in light of accumulated new insight. Here, we first present an overview of the framework, how it has been applied, and what we know and do not know. We then introduce the SDE landscape as the two-dimensional representation of the possible combinations of the quantity and the quality of dispersal and with elevational contours representing isoclines of SDE. We discuss the structure of disperser assemblages on such landscapes. Following this we discuss recent advances and ideas in seed dispersal in the context of their impacts on SDE. Finally, we highlight a number of emerging issues that provide insight into SDE. Overall, the SDE framework successfully captures the complexities of seed dispersal. We advocate an expanded use of the term dispersal encompassing the multiple recruitment stages from fruit to adult. While this entails difficulties in estimating SDE, it is a necessary expansion if we are to understand the central relevance of seed dispersal in plant ecology and evolution.

  4. Method of dispersing a hydrocarbon using bacteria

    Science.gov (United States)

    Tyndall, Richard L.

    1996-01-01

    New protozoan derived microbial consortia and method for their isolation are provided. Consortia and bacteria isolated therefrom are useful for treating wastes such as trichloroethylene and trinitrotoluene. Consortia, bacteria isolated therefrom, and dispersants isolated therefrom are useful for dispersing hydrocarbons such as oil, creosote, wax, and grease.

  5. 21 CFR 178.3725 - Pigment dispersants.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Pigment dispersants. 178.3725 Section 178.3725 Food... regulation, the substances listed in this section may be safely used as pigment dispersants in food-contact... not to exceed 0.45 percent by weight of the pigment. The pigmented articles may contact all...

  6. "Dispersion modeling approaches for near road

    Science.gov (United States)

    Roadway design and roadside barriers can have significant effects on the dispersion of traffic-generated pollutants, especially in the near-road environment. Dispersion models that can accurately simulate these effects are needed to fully assess these impacts for a variety of app...

  7. Uncertainty in spatially explicit animal dispersal models

    NARCIS (Netherlands)

    Mooij, W.M.; DeAngelis, D.L.

    2003-01-01

    Uncertainty in estimates of survival of dispersing animals is a vexing difficulty in conservation biology. The current notion is that this uncertainty decreases the usefulness of spatially explicit population models in particular. We examined this problem by comparing dispersal models of three level

  8. Blends of ascarosides regulate dispersal in nematodes

    Science.gov (United States)

    Blends of ascarosides regulate dispersal in nematodes Presenter: Dr. Fatma Kaplan Dispersal is an important behavior for many organisms. It can easily be observed when infectious juveniles of entomopathogenic nematodes (Steinernema and Heterorhabditis) leave a consumed insect host. Dauer larvae of ...

  9. Intermolecular forces: a solution to dispersion interactions.

    Science.gov (United States)

    Shimizu, Ken D

    2013-12-01

    London dispersion forces have been cited as an important factor in protein folding, drug–receptor interactions, and catalyst selectivities. However, careful analysis of a model system finds that the dispersion interactions are only minor contributors to the formation of complexes in solution.

  10. Chromatic Dispersion Estimation in Digital Coherent Receivers

    DEFF Research Database (Denmark)

    Soriano, Ruben Andres; Hauske, Fabian N.; Guerrero Gonzalez, Neil;

    2011-01-01

    Polarization-diverse coherent demodulation allows to compensate large values of accumulated linear distortion by digital signal processing. In particular, in uncompensated links without optical dispersion compensation, the parameter of the residual chromatic dispersion (CD) is vital to set the ac...

  11. Dispersed and decentralised settlement system

    Directory of Open Access Journals (Sweden)

    Andrej Černe

    2004-01-01

    Full Text Available In the process of reintegration of the urban system new settlements are emerging on theurban rim, transitional zones are reurbanised, derelict areas within the cities are being developedand degraded urban areas of derelict industrial complexes are being renaturalised. Inthe periphery combined research and production parks are being set up, in the open landscapeintegrated business, trade and recreational centres are springing up. Decentralisationand recentralisation of focal points of development accompany the contemporary processesof reurbanisation and suburbanisation – they are simultaneous and move in two-direction i.e. to and from the city. We understand them as manifestation of a dynamic balance amongcontradiction existing between the centre and the rim. Deindustrialisation and relocation ofproduction and distribution from the centres of gravity to the periphery generate extensivedegraded urban areas within cities and between the city and suburbs. The periphery is beingurbanised with the creation of new, dispersed and nonhierachical poles of development, andthe city and inner city is undergoing reurbanization. The general environmental conditionsin the city and in the countryside are being equalised, the potentials of development arebeing sought in the comparative advantages of local conditions: be it attractive urban districts,be it suburban entities or countryside areas.

  12. Dispersive internal long wave models

    Energy Technology Data Exchange (ETDEWEB)

    Camassa, R.; Choi, W.; Holm, D.D. [Los Alamos National Lab., NM (United States); Levermore, C.D.; Lvov, Y. [Univ. of Arizona, Tucson, AZ (United States)

    1998-11-01

    This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). This work is a joint analytical and numerical study of internal dispersive water wave propagation in a stratified two-layer fluid, a problem that has important geophysical fluid dynamics applications. Two-layer models can capture the main density-dependent effects because they can support, unlike homogeneous fluid models, the observed large amplitude internal wave motion at the interface between layers. The authors have derived new model equations using multiscale asymptotics in combination with the method they have developed for vertically averaging velocity and vorticity fields across fluid layers within the original Euler equations. The authors have found new exact conservation laws for layer-mean vorticity that have exact counterparts in the models. With this approach, they have derived a class of equations that retain the full nonlinearity of the original Euler equations while preserving the simplicity of known weakly nonlinear models, thus providing the theoretical foundation for experimental results so far unexplained.

  13. Taylor dispersion analysis of mixtures.

    Science.gov (United States)

    Cottet, Hervé; Biron, Jean-Philippe; Martin, Michel

    2007-12-01

    Taylor dispersion analysis (TDA) is a fast and simple method for determining hydrodynamic radii. In the case of sample mixtures, TDA, as the other nonseparative methods, leads to an average diffusion coefficient on the different molecules constituting the mixture. We set in this work the equations giving, on a consistent basis, the average values obtained by TDA with detectors with linear response functions. These equations confronted TDA experiments of sample mixtures containing different proportions of a small molecule and a polymer standard. Very good agreement between theory and experiment was obtained. In a second part of this work, on the basis of monomodal or bimodal molar mass distributions of polymers, the different average diffusion coefficients corresponding to TDA were compared to the z-average diffusion coefficient (D(z)) obtained from dynamic light scattering (DLS) experiments and to the weight average diffusion coefficient (D(w)). This latter value is sometimes considered as the most representative of the sample mixture. From these results, it appears that, for monomodal distribution and relatively low polydispersity (I = 1.15), the average diffusion coefficient generally derived from TDA is very close to Dw. However, for highly polydisperse samples (e.g., bimodal polydisperse distributions), important differences could be obtained (up to 35% between TDA and D(w)). In all the cases, the average diffusion coefficient obtained by TDA for a mass concentration detector was closer to the Dw value than the z-average obtained by DLS.

  14. Databases of surface wave dispersion

    Directory of Open Access Journals (Sweden)

    L. Boschi

    2005-06-01

    Full Text Available Observations of seismic surface waves provide the most important constraint on the elastic properties of the Earth’s lithosphere and upper mantle. Two databases of fundamental mode surface wave dispersion were recently compiled and published by groups at Harvard (Ekström et al., 1997 and Utrecht/Oxford (Trampert and Woodhouse, 1995, 2001, and later employed in 3-d global tomographic studies. Although based on similar sets of seismic records, the two databases show some significant discrepancies. We derive phase velocity maps from both, and compare them to quantify the discrepancies and assess the relative quality of the data; in this endeavour, we take careful account of the effects of regularization and parametrization. At short periods, where Love waves are mostly sensitive to crustal structure and thickness, we refer our comparison to a map of the Earth’s crust derived from independent data. On the assumption that second-order effects like seismic anisotropy and scattering can be neglected, we find the measurements of Ekström et al. (1997 of better quality; those of Trampert and Woodhouse (2001 result in phase velocity maps of much higher spatial frequency and, accordingly, more difficult to explain and justify geophysically. The discrepancy is partly explained by the more conservative a priori selection of data implemented by Ekström et al. (1997. Nevertheless, it becomes more significant with decreasing period, which indicates that it could also be traced to the different measurement techniques employed by the authors.

  15. Graphene, a material for superfast electronics?

    Science.gov (United States)

    Courtney, Robert; Kattel, Shyam; Kiefer, Boris

    2011-10-01

    Physics Department, New Mexico State University: The performance of electronic devices has tremendously increased over the last few decades mainly due to miniaturization of electronic components. However, Moore's law suggests that a limiting minimal feature size of microprocessors may be reached as early as 2020. Thus, it is important to search for new technologies that allow overcoming this limitation. One possibility is to explore the feasibility of near speed of light electronics. Traditional metals have Fermi velocity on the order of 2000 km/s while the Fermi velocity of semiconductors is significantly lower. In contrast, the particular electronic structure of graphene may permit much faster electron transport than semiconductors and metals. This effect is due to the linear segments of the electronic dispersion in graphene below the Fermi energy, as opposed to the quadratic dispersion found in other materials. Here we have used density-functional-theory (DFT) to explore the effect of nitrogen doping on the electronic band structure of graphene, and especially its effect on the linear dispersion that is critical for near speed of light electronics.

  16. Co-processing of hydroxypropyl methylcellulose (HPMC) for improved aqueous dispersibility.

    Science.gov (United States)

    Sharma, Payal; Modi, Sameer R; Bansal, Arvind K

    2015-05-15

    Hydroxypropyl methylcellulose (HPMC), a widely employed film coating polymer, exhibits poor dispersibility in an aqueous medium. Rapid hydration leading to swelling and coherent gel formation is reported to be responsible for this problem. Present study focuses on the use of spray drying based approach for co-processing of HPMC to improve its dispersibility. Dispersion behavior of native HPMC showed formation of large lumps that did not dissolve completely for 40min. However, HPMC co-processed with lactose and sodium chloride exhibited improvement in dispersibility with complete dissolution attained within 20min. Mechanistic insights into improved dispersibility were obtained using contact angle studies, confocal laser scanning microscopy (CLSM), transmission electron microscopy (TEM) and scanning TEM (STEM) studies. Co-processed products exhibited higher immersional wetting as determined by sessile drop contact angle technique, which indicated spontaneous incursion of water. CLSM study revealed highly swollen and erodible gel in co-processed products. Novel application of TEM and STEM techniques was developed to understand the nature of mixing achieved during co-processing. Overall the improvement in dispersibility of co-processed products was predominantly due to the alteration in sub-particulate level properties during co-processing. The effect of excipients on the film properties of HPMC, like tensile strength and hygroscopicity, was also assessed. This study provides the comprehensive understanding of role of co-processing on improvement of dispersion behavior of HPMC and helps in the selection of suitable excipients for the same.

  17. Colloidal dispersions of maghemite nanoparticles produced by laser pyrolysis with application as NMR contrast agents

    Energy Technology Data Exchange (ETDEWEB)

    Veintemillas-Verdaguer, Sabino [Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, 28049 Madrid (Spain); Morales, Maria del Puerto [Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, 28049 Madrid (Spain); Bomati-Miguel, Oscar [Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, 28049 Madrid (Spain); Bautista, Carmen [Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, 28049 Madrid (Spain); Zhao, Xinqing [Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, 28049 Madrid (Spain); Bonville, Pierre [CEA, CE Saclay, DSM/DRECAM/SPEC, 91191 Gif-Sur-Yvette (France); Alejo, Rigoberto Perez de [Universidad Complutense de Madrid, Unidad de RMN, Paseo Juan XXIII, 1, 28040 Madrid (Spain); Ruiz-Cabello, Jesus [Universidad Complutense de Madrid, Unidad de RMN, Paseo Juan XXIII, 1, 28040 Madrid (Spain); Santos, Martin [Hospital Universitario Puerta de Hierro, Servicio de Cirugia Experimental. C/San Martin de Porres 4, 28035 Madrid (Spain); Tendillo-Cortijo, Francisco J [Hospital Universitario Puerta de Hierro, Servicio de Cirugia Experimental. C/San Martin de Porres 4, 28035 Madrid (Spain); Ferreiros, Joaquin [Hospital Clinico de Madrid ' San Carlos' , Ciudad Universitaria, 28040 Madrid (Spain)

    2004-08-07

    Biocompatible magnetic dispersions have been prepared from {gamma}-Fe{sub 2}O{sub 3} nanoparticles (5 nm) synthesized by continuous laser pyrolysis of Fe(CO){sub 5} vapours. The feasibility of using these dispersions as magnetic resonance imaging (MRI) contrast agents has been analysed in terms of chemical structure, magnetic properties, {sup 1}H NMR relaxation times and biokinetics. The magnetic nanoparticles were dispersed in a strong alkaline solution in the presence of dextran, yielding stable colloids in a single step. The dispersions consist of particle-aggregates 25 nm in diameter measured using transmission electron microscope and a hydrodynamic diameter of 42 nm measured using photon correlation spectroscopy. The magnetic and relaxometric properties of the dispersions were of the same order of magnitude as those of commercial contrast agents produced using coprecipitation. However, these dispersions, when injected intravenously in rats at standard doses showed a mono-exponential blood clearance instead of a biexponential one, with a blood half-life of 7 {+-} 1 min. Furthermore, an important enhancement of the image contrast was observed after the injection, mainly located at the liver and the spleen of the rat. In conclusion, the laser pyrolysis technique seems to be a good alternative to the coprecipitation method for producing MRI contrast agents, with the advantage of being a continuous synthesis method that leads to very uniform particles capable of being dispersed and therefore transformed in a biocompatible magnetic liquid.

  18. Effects of Various Surfactants on the Dispersion of MWCNTs-OH in Aqueous Solution.

    Science.gov (United States)

    Cui, Hongzhi; Yan, Xiantong; Monasterio, Manuel; Xing, Feng

    2017-09-06

    Dispersion of carbon nanotubes (CNTs) is a challenge for their application in the resulting matrixes. The present study conducted a comparison investigation of the effect of four surfactants: Alkylphenol polyoxyethylene ether (APEO), Silane modified polycarboxylate (Silane-PCE), I-Cationic polycarboxylate (I-C-PCE), and II-Cationic polycarboxylate (II-C-PCE) on the dispersion of hydroxyl functionalized multi-walled carbon nanotubes (MWCNTs-OH). Among the four surfactants, APEO and II-C-PCE provide the best and the worst dispersion effect of CNTs in water, respectively. Dispersion effect of MWCNTs-OH has been characterized by optical microscope (OM), field emission-scanning electron microscope (FE-SEM), and Ultraviolet-visible spectroscopy (UV-Vis).The OM images are well consistent with the UV-Vis results. Based on the chemical molecular structures of the four surfactants, the mechanism of MWCNTs-OH dispersion in water was investigated. For each kind of surfactant, an optimum surfactant/MWCNTs-OH ratio has been determined. This ratio showed a significant influence on the dispersion of MWCNTs-OH. Surfactant concentration higher or lower than this value can weaken the dispersion quality of MWCNTs-OH.

  19. Phthalimide containing donor-acceptor polymers for effective dispersion of single-walled carbon nanotubes

    Directory of Open Access Journals (Sweden)

    Baris Yilmaz

    2015-08-01

    Full Text Available Single-walled carbon nanotubes have been dispersed by novel phthalimide containing donor-acceptor type copolymers in organic media. Brominated phthalimide comonomer has been copolymerized with several electron rich structures using Suzuki and Stille coupling reactions. Carbon nanotube dispersion capability of the resultant polymers has been assessed by exploiting the non-covalent interaction of nanotube surface with the pi-system of conjugated backbone of polymers. Four polymers have been found to be good candidates for individually dispersing nanotubes in solution. In order to identify the dispersed nanotube species, 2D excitation-emission map and Raman spectroscopy have been performed. Molecular dynamics modelling has been utilized to reveal the binding energies of dispersants with the nanotube surface and the simulation results have been compared with the experimental findings. Both experimental and theoretical results imply the presence of a complex mechanism that governs the extent of dispersion capacity and selectivity of each conjugated polymeric dispersant in solubilizing carbon nanotubes.

  20. Dispersion of Metal Phthalocyanines on Surface of TiO2

    Institute of Scientific and Technical Information of China (English)

    ZHU Jian-Feng; WANG Chun-Ming; ZHU Yue-Xiang; ZHAO Bi-Ying; XIE You-Chang

    2005-01-01

    Dispersion of copper(Ⅱ) phthalocyanine (CuPc), copper(Ⅱ) phthalocyaninesulfonate (CuPcS) and cobalt(Ⅱ)phthalocyaninetetrasulfonate (CoPcTS) on the surface of titanium dioxide was investigated by XRD, XPS, FT-IR and UV-Vis techniques. Results show that interaction between CuPc and TiO2 was very weak and CuPc was difficult to disperse on the surface of the support. While partly sulfurized CuPcS could be dispersed on the surface of support through sulfo-groups and its dispersion capacity was determined to be 0.085 g CuPcS/g TiO2. Completely sulfurized CoPcTS could also be dispersed on the surface of TiO2 as a monolayer and its dispersion capacity was 0.12 g CoPcTS/g TiO2. Interactions of the sulfo-groups as well as the electrons of CoPcTS with the surface of TiO2could be evidenced by FT-IR characterization. Therefore, it was suggested that CoPcTS molecules be adsorbed on the surface of TiO2 in a flat-lying mode while CuPcS in a slanting one. UV-Vis spectra show that the dispersed CuPcS and CoPcTS molecules exist in both forms of monomers and dimers.

  1. Mechanical agitation induces counterintuitive aggregation of pre-dispersed carbon nanotubes.

    Science.gov (United States)

    Fernandes, Ricardo M F; Buzaglo, Matat; Regev, Oren; Furó, István; Marques, Eduardo F

    2017-05-01

    Mechanical agitation is commonly used to fragment and disperse insoluble materials in liquids. However, here we show that when pristine single-walled carbon nanotubes pre-dispersed in water are subject to vortex-shaking for very short periods (typically 10-60s, power density ∼0.002WmL(-1)), re-aggregation counterintuitively occurs. The initial dispersions are produced using surfactants as dispersants and powerful tip sonication (∼1WmL(-1)) followed by centrifugation. Detailed imaging by light and electron microscopies shows that the vortex-induced aggregates consist of loose networks (1-10(2)μm in size) of intertwined tubes and thin bundles. The average aggregate size increases with vortexing time in an apparently logarithmic manner and depends on the dispersant used, initial concentration of nanotubes and size distribution of bundles. The aggregation is, nonetheless, reversible: if the vortex-shaken dispersions are mildly bath-sonicated (∼0.03WmL(-1)), the flocs break down and re-dispersal occurs. Molecular insight for the mechanism behind this surprising phenomenon is put forth.

  2. Method of Obtaining a Composite Material Based on Small-Dispersed Particles

    Directory of Open Access Journals (Sweden)

    D.G. Batryshev

    2016-10-01

    Full Text Available In this work a method of obtaining a composite material based on small-dispersed particles is considered. Proposed method consists of two steps of separation, mechanical – rough separation and plasma – soft separation, and also of step of deposition a catalytic nanolayer by wet impregnation of separated particles in an aqueous solution of nickel nitrate. During such procedure a composite powder of small-dispersed zeolite particles with average diameter of 5 m and catalytic nickel layer was obtained. All obtained samples were studied on a Quanta 3D 200i scanning electron microscope. Microscopic analysis and obtained experimental results show, that increasing of dispersion of separated powder allows for increasing a mass of catalyst in the composite, and the used separation method in plasma for obtaining of particles with high dispersion do not erode a catalytic layer.

  3. Decoupling of epitaxial graphene via gold intercalation probed by dispersive Raman spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Pillai, P. B., E-mail: p.pillai@sheffield.ac.uk, E-mail: m.desouza@sheffield.ac.uk; DeSouza, M., E-mail: p.pillai@sheffield.ac.uk, E-mail: m.desouza@sheffield.ac.uk [Semiconductor Materials and Device Group, Electronic and Electrical Engineering, University of Sheffield, Mappin Street, S1 3JD Sheffield (United Kingdom); Narula, R.; Reich, S. [Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin (Germany); Wong, L. Y.; Batten, T. [Renishaw, Old Town, Wotton-under-Edge, GL12 7DW Gloucestershire (United Kingdom); Pokorny, J. [Department of Materials Science and Engineering, Sir Robert Hadfield Building, Mappin Street, S1 3JD Sheffield (United Kingdom); Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 182 21 Praha 8 (Czech Republic)

    2015-05-14

    Signatures of a superlattice structure composed of a quasi periodic arrangement of atomic gold clusters below an epitaxied graphene (EG) layer are examined using dispersive Raman spectroscopy. The gold-graphene system exhibits a laser excitation energy dependant red shift of the 2D mode as compared to pristine epitaxial graphene. The phonon dispersions in both the systems are mapped using the experimentally observed Raman signatures and a third-nearest neighbour tight binding electronic band structure model. Our results reveal that the observed excitation dependent Raman red shift in gold EG primarily arise from the modifications of the phonon dispersion in gold-graphene and shows that the extent of decoupling of graphene from the underlying SiC substrate can be monitored from the dispersive nature of the Raman 2D modes. The intercalated gold atoms restore the phonon band structure of epitaxial graphene towards free standing graphene.

  4. Progesterone and testosterone production by dispersed rat placental cells.

    Science.gov (United States)

    Matt, D W; Gibney, J A; Malamed, S; Macdonald, G J

    1986-04-01

    Isopycnic separation and unit gravity sedimentation were employed to identify the rat placental cell types capable of producing progesterone and testosterone. Subdivision of Day 12-dispersed placental cells in Percoll gradients revealed that fractions (less than 1.048 g/ml) containing giant cytotrophoblast cells produced greater quantities of progesterone (p less than 0.01) than did fractions (greater than 1.048 g/ml) with equal numbers of placental cells but void of giant cytotrophoblasts. Unit gravity sedimentation of Day 16-dispersed placental cells revealed that when incubated, isolated giant cytotrophoblast cells were capable of producing both progesterone and testosterone. Both of the separation studies strongly suggested that other cell types also produce steroids. However, the biosynthetic capacity of the giant cytotrophoblast cell appeared to be 1000-fold greater than that of the other cell types. Incubation of Day 12-dispersed placental cells with human chorionic gonadotropin or 3',5'-cyclic adenosine monophosphate did not further increase progesterone production as compared to untreated control incubates, suggesting rat placental steroidogenesis is not under trophic hormone control. Electron microscopic observations of giant cytotrophoblast cells revealed a complex ultrastructure suggesting a variety of physiological functions.

  5. Extension of the D3 dispersion coefficient model

    Science.gov (United States)

    Caldeweyher, Eike; Bannwarth, Christoph; Grimme, Stefan

    2017-07-01

    A new model, termed D4, for the efficient computation of molecular dipole-dipole dispersion coefficients is presented. As in the related, well established D3 scheme, these are obtained as a sum of atom-in-molecule dispersion coefficients over atom pairs. Both models make use of dynamic polarizabilities obtained from first-principles time-dependent density functional theory calculations for atoms in different chemical environments employing fractional atomic coordination numbers for interpolation. Different from the D3 model, the coefficients are obtained on-the-fly by numerical Casimir-Polder integration of the dynamic, atomic polarizabilities α (iω ). Most importantly, electronic density information is now incorporated via atomic partial charges computed at a semi-empirical quantum mechanical tight-binding level, which is used to scale the polarizabilities. Extended statistical measures show that errors for dispersion coefficients with the proposed D4 method are significantly lower than with D3 and other, computationally more involved schemes. Alongside, accurate isotropic charge and hybridization dependent, atom-in-molecule static polarizabilities are obtained with an unprecedented efficiency. Damping function parameters are provided for three standard density functionals, i.e., TPSS, PBE0, and B3LYP, allowing evaluation of the new DFT-D4 model for common non-covalent interaction energy benchmark sets.

  6. Phase behavior and shear alignment in SWNT-surfactant dispersions.

    Science.gov (United States)

    Nativ-Roth, Einat; Yerushalmi-Rozen, Rachel; Regev, Oren

    2008-09-01

    The effect of single-walled carbon nanotubes (SWNT) on the phase behavior of the cationic surfactant cetyltrimethylammonium bromide (CTAB) in aqueous solutions is investigated at room temperature. Small-angle X-ray scattering (SAXS) and cryogenic transmission electron microscopy (cryo-TEM) are used for characterization of bulk dispersions and nanometrically thin films. Additional carbonaceous additives (fullerenes, multi-walled carbon nanotubes, and carbon black) serve as reference systems. It is found that dispersions of carbonaceous additive (excluding fullerenes) at intermediate surfactant concentrations (below the liquid-crystalline region of the native surfactant) induce demixing and macroscopic phase separation in otherwise homogeneous solutions of CTAB. Two coexisting liquid phases of similar CTAB concentrations are observed, with the carbonaceous species residing within the lower phase. At high CTAB concentrations (liquid-crystal region) the SWNTs are found to incorporate into the ordered lyotropic liquid-crystalline phase while preserving the native d-spacing. Investigation of nanometrically thin films at intermediate surfactant concentrations under external shear reveals shear-induced structure (SIS) in the presence of minute amounts of SWNTs. The effect is found to be exclusive to SWNT and does not occur in dispersions of other carbonaceous additives.

  7. Pay Dispersion and Performance in Teams

    DEFF Research Database (Denmark)

    Bucciol, Alessandro; Foss, Nicolai J; Piovesan, Marco

    2014-01-01

    Extant research offers conflicting predictions about the effect of pay dispersion on team performance. We collected a unique dataset from the Italian soccer league to study the effect of intra-firm pay dispersion on team performance, under different definitions of what constitutes a "team......". This peculiarity of our dataset can explain the conflicting evidence. Indeed, we also find positive, null, and negative effects of pay dispersion on team performance, using the same data but different definitions of team. Our results show that when the team is considered to consist of only the members who directly...... contribute to the outcome, high pay dispersion has a detrimental impact on team performance. Enlarging the definition of the team causes this effect to disappear or even change direction. Finally, we find that the detrimental effect of pay dispersion is due to worse individual performance, rather than...

  8. High-dispersive mirrors for femtosecond lasers.

    Science.gov (United States)

    Pervak, V; Teisset, C; Sugita, A; Naumov, S; Krausz, F; Apolonski, A

    2008-07-07

    We report on the development of highly dispersive mirrors for chirped-pulse oscillators (CPO) and amplifiers (CPA). In this proof-of-concept study, we demonstrate the usability of highly dispersive multilayer mirrors for high-energy femtosecond oscillators, namely for i) a chirped-pulse Ti:Sa oscillator and ii) an Yb:YAG disk oscillator. In both cases a group delay dispersion (GDD) of the order of 2x10(4) fs(2) was introduced, accompanied with an overall transmission loss as low as approximately 2 per cent. This unprecedented combination of high dispersion and low loss over a sizeable bandwidth with multilayer structures opens the prospects for femtosecond CPA systems equipped with a compact, alignment-insensitive all-mirror compressors providing compensation of GDD as well as higher-order dispersion.

  9. Rheological behaviour of heated potato starch dispersions

    Science.gov (United States)

    Juszczak, L.; Witczak, M.; Ziêba, T.; Fortuna, T.

    2012-10-01

    The study was designed to investigate the rheological properties of heated potato starch dispersions. Water suspensions of starch were heated at 65, 80 or 95°C for 5, 15, 30 or 60 min. The dispersions obtained were examined for granule size distribution and rheology. It was found that the starch dispersions significantly differed in both respects. The mean diameters of starch granules were largest for the dispersion heated at 65°C and smallest for that heated at 95°C. As the heating temperature was raised, the yield stresses and consistency coefficients decreased, while the flow behaviour indexes and Casson plastic viscosities increased. There were also differences in the viscoelastic properties of the dispersions: for those heated at 65°C the storage and loss moduli increased with heating time whereas for those heated at 80°C both moduli decreased.

  10. Shock waves in dispersive Eulerian fluids

    CERN Document Server

    Hoefer, M A

    2013-01-01

    The long time behavior of an initial step resulting in a dispersive shock wave (DSW) for the one-dimensional isentropic Euler equations regularized by generic, third order dispersion is considered by use of Whitham averaging. Under modest assumptions, the jump conditions (DSW locus and speeds) for admissible, weak DSWs are characterized and found to depend only upon the sign of dispersion (convex or concave) and a general pressure law. Two mechanisms leading to the breakdown of this simple wave DSW theory for sufficiently large jumps are identified: a change in the sign of dispersion, leading to gradient catastrophe in the modulation equations, and the loss of genuine nonlinearity in the modulation equations. Large amplitude DSWs are constructed for several particular dispersive fluids with differing pressure laws modeled by the generalized nonlinear Schr\\"{o}dinger equation. These include superfluids (Bose-Einstein condensates and ultracold Fermions) and "optical fluids". Estimates of breaking times for smoo...

  11. Flow properties of acetylated chickpea protein dispersions.

    Science.gov (United States)

    Liu, Li H; Hung, Tran V

    2010-06-01

    Chickpea protein concentrate was acetylated with acetic anhydride at 5 levels. Acetylated chickpea protein (ACP) dispersions at 3 levels (6%, 45%, and 49%) were chosen for this flow property study. Effects of protein concentration, temperature, concentrations of salt addition and particularly, degree of acetylation on these properties were examined. Compared with native chickpea proteins, the ACP dispersions exhibited a strong shear thinning behavior. Within measured temperature range (15 to 55 degrees C), the apparent viscosities of native chickpea protein dispersions were temperature independent; those of ACP dispersions were thermally affected. The flow index (n), consistency coefficient (m), apparent yield stress, and apparent viscosities of ACP dispersions increased progressively up to 45% acetylation but decreased at 49% acetylation level. Conformational studies by gel filtration suggested that chickpea proteins were associated or polymerized at up to 45% acetylation but the associated subunits gradually dissociated to smaller units at higher levels (49%) of acetylation.

  12. Pay Dispersion and Performance in Teams

    DEFF Research Database (Denmark)

    Bucciol, Alessandro; Foss, Nicolai J; Piovesan, Marco

    2014-01-01

    Extant research offers conflicting predictions about the effect of pay dispersion on team performance. We collected a unique dataset from the Italian soccer league to study the effect of intra-firm pay dispersion on team performance, under different definitions of what constitutes a "team......". This peculiarity of our dataset can explain the conflicting evidence. Indeed, we also find positive, null, and negative effects of pay dispersion on team performance, using the same data but different definitions of team. Our results show that when the team is considered to consist of only the members who directly...... contribute to the outcome, high pay dispersion has a detrimental impact on team performance. Enlarging the definition of the team causes this effect to disappear or even change direction. Finally, we find that the detrimental effect of pay dispersion is due to worse individual performance, rather than...

  13. Pay Dispersion and Performance in Teams

    Science.gov (United States)

    Bucciol, Alessandro; Foss, Nicolai J.; Piovesan, Marco

    2014-01-01

    Extant research offers conflicting predictions about the effect of pay dispersion on team performance. We collected a unique dataset from the Italian soccer league to study the effect of intra-firm pay dispersion on team performance, under different definitions of what constitutes a “team”. This peculiarity of our dataset can explain the conflicting evidence. Indeed, we also find positive, null, and negative effects of pay dispersion on team performance, using the same data but different definitions of team. Our results show that when the team is considered to consist of only the members who directly contribute to the outcome, high pay dispersion has a detrimental impact on team performance. Enlarging the definition of the team causes this effect to disappear or even change direction. Finally, we find that the detrimental effect of pay dispersion is due to worse individual performance, rather than a reduction of team cooperation. PMID:25397615

  14. Laboratory effectiveness testing of oil spill dispersants

    Energy Technology Data Exchange (ETDEWEB)

    Fingas, M.F.; Kyle, D.A.; Wang, Z.; Handfield, D.; Ianuzzi, D.; Ackerman, F. [Environment Canada, Ottawa, Ontario (Canada)

    1995-06-01

    Dispersant effectiveness tests are reviewed. Studies have been conducted of the variances among several standard regulatory tests. Three main causes of differences have been identified, oil-to-water ratio, settling time and energy. Energy can be partially compensated for in high energy tests by correcting for natural dispersion. With this correction and with high oil-to-water ratios and a settling time of at least 10 minutes, five apparatuses yield very similar results for a variety of oils and dispersants. Recent studies into the energy variation of dispersant tests show that the energy level varies in many apparatuses. The repeatability of energy levels in apparatus is largely responsible for the variation in dispersant effectiveness values in certain apparatus. Studies of analytical procedures show that traditional extraction and analysis methods cause a bias to results. Methods to overcome these difficulties are presented.

  15. Longitudinal dielectric function and dispersion relation of electrostatic waves in relativistic plasmas

    Science.gov (United States)

    Touil, B.; Bendib, A.; Bendib-Kalache, K.

    2017-02-01

    The longitudinal dielectric function is derived analytically from the relativistic Vlasov equation for arbitrary values of the relevant parameters z = m c 2 / T , where m is the rest electron mass, c is the speed of light, and T is the electron temperature in energy units. A new analytical approach based on the Legendre polynomial expansion and continued fractions was used. Analytical expression of the electron distribution function was derived. The real part of the dispersion relation and the damping rate of electron plasma waves are calculated both analytically and numerically in the whole range of the parameter z . The results obtained improve significantly the previous results reported in the literature. For practical purposes, explicit expressions of the real part of the dispersion relation and the damping rate in the range z > 30 and strongly relativistic regime are also proposed.

  16. Electron Microscopy.

    Science.gov (United States)

    Beer, Michael

    1980-01-01

    Reviews technical aspects of structure determination in biological electron microscopy (EM). Discusses low dose EM, low temperature microscopy, electron energy loss spectra, determination of mass or molecular weight, and EM of labeled systems. Cites 34 references. (CS)

  17. Electron Microscopy.

    Science.gov (United States)

    Beer, Michael

    1980-01-01

    Reviews technical aspects of structure determination in biological electron microscopy (EM). Discusses low dose EM, low temperature microscopy, electron energy loss spectra, determination of mass or molecular weight, and EM of labeled systems. Cites 34 references. (CS)

  18. Understand electronics

    CERN Document Server

    Bishop, Owen

    2013-01-01

    Understand Electronics provides a readable introduction to the exciting world of electronics for the student or enthusiast with little previous knowledge. The subject is treated with the minimum of mathematics and the book is extensively illustrated.This is an essential guide for the newcomer to electronics, and replaces the author's best-selling Beginner's Guide to Electronics.The step-by-step approach makes this book ideal for introductory courses such as the Intermediate GNVQ.

  19. Electronic components

    CERN Document Server

    Colwell, Morris A

    1976-01-01

    Electronic Components provides a basic grounding in the practical aspects of using and selecting electronics components. The book describes the basic requirements needed to start practical work on electronic equipment, resistors and potentiometers, capacitance, and inductors and transformers. The text discusses semiconductor devices such as diodes, thyristors and triacs, transistors and heat sinks, logic and linear integrated circuits (I.C.s) and electromechanical devices. Common abbreviations applied to components are provided. Constructors and electronics engineers will find the book useful

  20. Can dispersion corrections annihilate the dispersion-driven nano-aggregation of non-polar groups? An ab initio molecular dynamics study of ionic liquid systems.

    Science.gov (United States)

    Firaha, Dzmitry S; Thomas, Martin; Hollóczki, Oldamur; Korth, Martin; Kirchner, Barbara

    2016-11-28

    In this study, we aim at understanding the influence of dispersion correction on the ab initio molecular dynamics simulations of ionic liquid (IL) systems. We investigated a large bulk system of the 1-butyl-3-methylimidazolium triflate IL and a small cluster system of ethylamine in ethylammonium nitrate both under periodic boundary conditions. The large system displays several changes upon neglect of dispersion correction, the most striking one is the surprising decrease of the well-known microheterogeneity which is accompanied by an increase of side chain hydrogen atom-anion interplay. For the diffusion coefficient, we observe a correction towards experimental behavior in terms of the cation becoming faster than the anion with dispersion correction. Changes in the electronic structure upon dispersion correction are reflected in larger/smaller dipole moments for anions/cations also seen in the calculated IR spectrum. The energetics of different ion pair dimer subsystems (polar and non-polar) are in accordance with the analysis of the trajectories: A detailed balance in the ionic liquid system determines its particular behavior. While the overall interaction terms for dispersion-corrected calculations are higher, the decrease in microheterogeneity upon inclusion of dispersion interaction becomes obvious due to the relation between all contributions to polar-polar terms. For the small system, we clearly observe the well known behavior that the hybrid functionals show higher reaction barriers than the pure generalized gradient approximation (GGA) functionals. The correction of dispersion reduces the discrepancies in some cases. Accounting for the number of jumps, we observe that dispersion correction reduces the discrepancies from 50% to less than 10%.