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Sample records for haas-van alphen effect

  1. The de Haas-van Alphen effect in nanostructures of cadmium fluoride

    SciTech Connect

    Bagraev, N. T.; Brilinskaya, E. S.; Danilovskii, E. Yu.; Klyachkin, L. E.; Malyarenko, A. M.; Romanov, V. V.

    2012-01-15

    Measurements of the field and temperature dependences of static magnetic susceptibility demonstrate de Haas-van Alphen oscillations at high temperatures and low magnetic fields in sandwich nanostructures, which are represented by an ultranarrow p-type CdF{sub 2} quantum well confined by {delta} barriers heavily doped with boron on the surface of an n-type CdF{sub 2} crystal. The temperature dependences of the de Haasvan Alphen oscillation amplitudes indicate a small value of the effective mass of two-dimensional holes, as a result of which, the strong field assumption, {mu}B Much-Greater-Than 1, is fulfilled at high temperatures. It is for the first time that a periodic variation in the de Haas-van Alphen oscillation frequency is detected and is accompanied by a diamagnetic response as temperature is increased. This phenomenon manifests itself as synchronous temperature oscillations of the density and effective mass of two-dimensional holes as a result of the mesoscopic properties of {delta} barriers.

  2. Berry Phase and de Haas van Alphen Effect in LaRhIn5

    NASA Astrophysics Data System (ADS)

    Mikitik, G. P.; Sharlai, Yu. V.

    2004-09-01

    We explain the experimental data on the magnetization of LaRhIn5 recently published by Goodrich et al. [

    Phys. Rev. Lett. 89, 026401 (2002)PRLTAO0031-900710.1103/PhysRevLett.89.026401
    ]. We show that the magnetization of a small electron group associated with a band-contact line was detected in that Letter. These data provide the first observation of the Berry phase of electrons in metals via the de Haas van Alphen effect.

  3. de Haas--van Alphen effect and Fermi surface of lutetium

    SciTech Connect

    Johanson, W.R.; Crabtree, G.W.; Schmidt, F.A.

    1984-03-01

    We report de Haas--van Alphen measurements of the Fermi surface of lutetium at temperatures down to 0.3 K and in fields up to 150 kG in the (1010) and (1120) planes. Lutetium, having a filled 4f shell, serves as a nonmagnetic prototype of the structurally similar (hcp), trivalent, heavy rare-earth elements from Gd to Tm. The fact that no complete frequency branches were observed indicates that there are no closed pieces of the Fermi surface. We observed all but one orbit predicted by relativistic augmented-plane-wave calculations of Keeton and Loucks and by recent spin-orbit--linearized-augmented-plane-wave calculations of Tibbetts and Harmon. The data support a geometry similar to that of yttrium, and in good qualitative agreement with energy-band theory.

  4. de Haas-van Alphen effect and Fermi surface of lutetium

    NASA Astrophysics Data System (ADS)

    Johanson, W. R.; Crabtree, G. W.; Schmidt, F. A.

    1984-03-01

    We report de Haas-van Alphen measurements of the Fermi surface of lutetium at temperatures down to 0.3 K and in fields up to 150 kG in the (101¯0) and (112¯0) planes. Lutetium, having a filled 4f shell, serves as a nonmagnetic prototype of the structurally similar (hcp), trivalent, heavy rare-earth elements from Gd to Tm. The fact that no complete frequency branches were observed indicates that there are no closed pieces of the Fermi surface. We observed all but one orbit predicted by relativistic augmented-plane-wave calculations of Keeton and Loucks and by recent spin-orbit-linearized-augmented-plane-wave calculations of Tibbetts and Harmon. The data support a geometry similar to that of yttrium, and in good qualitative agreement with energy-band theory.

  5. Fermiology and De Haas-van Alphen effect of {beta}-(ET){sub 2}IBr{sub 2}

    SciTech Connect

    Wosnitza, J.; Crabtree, G.W.; Carlson, K.D.; Wang, H.H.; Williams, J.M.

    1993-04-01

    The Fermi surface of the organic superconductor {beta}-(ET){sub 2}IBr{sub 2} investigated by measurements of the de Haas - van Alphen (dHvA) effect has been found to have the typical two-dimensional cylindrical form. A small amount of corrugation could be quantitatively determined by the distinctive angular dependence of beating nodes. the existence of up to four almost identical frequencies in the dHvA signal may be explained by magnetic interaction effects within the samples. Due to the 1/cos{Theta}- behavior of the effective mass spin-splitting zeros could be detected.

  6. Al{sub 70}Pd{sub 21.5}Mn{sub 8.5}: A quasicrystal showing the de haas-van Alphen effect

    SciTech Connect

    Haanappel, E.G.; Kycia, S.W.; Harmon, B.N.; Canfield, P.C.; Goldman, A.I.; Rabson, D.A.; Thompson, J.D.; Mueller, F.M.

    1995-07-01

    We have measured the de Haas-van Alphen effect in the icosahedral quasicrystal Al{sub 70}Pd{sub 21.5}Mn{sub 8.5}. We have found two well-defined frequencies with the magnetic field parallel to a five-fold axis, and two different ones with the field parallel to a two-fold axis. On increasing the temperature, the amplitude of the oscillations substantially decreased, suggesting that the carriers have large masses.

  7. de Haas-van Alphen effect measurements on cerium-lanthanum-M-indium (M = cobalt, rhodium, iridium) alloys

    NASA Astrophysics Data System (ADS)

    Alver, Umit

    The de Haas van Alphen (dHvA) effect, which measures the oscillatory component of the magnetization, in several CexLa1-x MIn5 (M = Rh, Co, Ir) alloys for 0 ≤ x ≤ 1 has been studied in detail using torque, pulse field and field modulation techniques. The frequencies, associated extremal cross sectional areas of the Fermi surface and effective masses of each sample throughout each of the series are reported. The energy band calculations of CeRhIn5, CeCoIn5 and CeIrIn5 assume that the 4f electrons in Ce are completely delocalized and these electrons make a significant contribution to the topology of the Fermi surface. It is observed that the band calculations are in agreement with the dHvA measurements for CexLa1-x CoIn5 and CexLa1-xIrIn5 . However, the dHvA measurements on CexLa1-xRhIn 5 show that the 4f electrons are entirely localized in CeRhIn5. The measurements show that the effective masses of carriers for each series vary slowly at low concentration and a dramatic increase is observed at high concentrations for B || [001]. In addition, for Co and Ir series at low concentrations (x ≤ 0.25), the mass enhancement agrees with the existing theory. The Dingle temperature measurements suggest that the replacement of La by Ce increases the scattering rate of the electrons for M = Co, Ir, not for M = Rh. For x = 0.5 and higher concentrations dHvA measurements on CexLa1-xRhIn5 show that dHvA oscillations originate from only one spin direction. However, dHvA measurements on Co and Ir series for x ≤ 0.10 show that there is no single spin dependence contributing to the oscillations.

  8. Shubnikov-de-Haas and de-Haas-van-Alphen oscillations in silicon nanostructures

    SciTech Connect

    Bagraev, N. T.; Brilinskaya, E. S.; Gets, D. S.; Klyachkin, L. E.; Malyarenko, A. M.; Romanov, V. V.

    2011-11-15

    The dependences of the longitudinal resistance and the static magnetic susceptibility on the magnetic field applied perpendicularly to the plane of an ultranarrow silicon quantum well confined by {delta} barriers heavily doped with boron demonstrate the high-temperature Shubnikov-de-Haas and de-Haas-van-Alphen oscillations in low magnetic fields. The results are indicative of the implementation of the high-field approximation {mu}B Much-Greater-Than 1 under these conditions due to the small effective mass of two-dimensional heavy holes, which is confirmed by measurements of temperature dependences of the de-Haas-van-Alphen oscillations.

  9. De Haas-van Alphen effect and energy gaps of a correlated two-dimensional electron system in an AlAs two-valley pseudospin system

    NASA Astrophysics Data System (ADS)

    Windisch, T.; Huang, X.; Dasgupta, S.; Rupprecht, B.; Heyn, Ch.; Bichler, M.; Fontcuberta I Morral, A.; Grayson, M.; Abstreiter, G.; Wilde, M. A.; Grundler, D.

    2009-11-01

    We report highly sensitive de Haas-van Alphen (dHvA) effect measurements on a high-mobility two-dimensional electron system in an AlAs quantum well. Here two valleys are occupied forming a pseudospin system. At 400 mK, the dHvA effect shows pronounced oscillations at filling factors ν=1 to four. In the quantum limit at ν=1 the data are consistent with an interaction-enhanced valley splitting, which exceeds the Zeeman spin splitting in a perpendicular field B . When tilting B the energy gap ΔE at ν=1 shows first an unexpectedly strong angular dependence and then remains constant. This suggests a crossover in the energy gap, most likely from a spin to a pseudospin gap. We attribute the strong initial dependence of ΔE on the tilt angle to skyrmion-type spin excitations. Surprisingly, the dHvA oscillation amplitudes do not display coincidence phenomena at higher filling factors. This is explained by the large valley splitting and avoided crossings of energy levels.

  10. de Haas-van Alphen oscillations for neutral atoms in electric fields

    NASA Astrophysics Data System (ADS)

    Farias, B.; Furtado, C.

    2016-07-01

    The de Haas-van Alphen (dHvA) effect is well known as an oscillatory variation of the magnetization of conductors as a function of the inverse magnetic field and the frequency is proportional to the area of the Fermi surface. Here, we show that an analogous effect can occur for neutral atoms with a nonvanishing magnetic moment interacting with an electric field. Under an appropriate field-dipole configuration, the neutral atoms subject to a synthetic magnetic field arrange themselves in Landau levels. Using the Landau-Aharonov-Casher (LAC) theory, we obtain the energy eigenfunctions and eigenvalues as well as the degeneracy of the system. In a strong effective magnetic field regime we present the quantum oscillations in the energy and effective magnetization of a two-dimensional (2D) atomic gas. From the dHvA period we determine the area of the Fermi circle of the atomic cloud.

  11. Small and nearly isotropic hole-like Fermi surfaces in LiFeAs detected through de Haas-van Alphen effect

    NASA Astrophysics Data System (ADS)

    Zeng, B.; Watanabe, D.; Zhang, Q. R.; Li, G.; Besara, T.; Siegrist, T.; Xing, L. Y.; Wang, X. C.; Jin, C. Q.; Goswami, P.; Johannes, M. D.; Balicas, L.

    2013-10-01

    LiFeAs is unique among the arsenic based Fe-pnictide superconductors because it is the only nearly stoichiometric compound which does not exhibit magnetic order. This is at odds with electronic structure calculations which find a very stable magnetic state and predict cylindrical hole- and electron-like Fermi surface sheets whose geometry suggests spin fluctuations and a possible instability toward long-range ordering at the nesting vector. In fact, a complex magnetic phase diagram is indeed observed in the isostructural NaFeAs compound. Previous angle-resolved photoemission (ARPES) experiments revealed the existence of both hole and electron-like surfaces, but with rather distinct cross-sectional areas and an absence of the nesting that is thought to underpin both magnetic order and superconductivity in the pnictide family of superconductors. These ARPES observations were challenged by subsequent de Haas-van Alphen (dHvA) measurements which detected a few, electron-like Fermi surface sheets in rough agreement with the original band calculations. Here, we show a detailed dHvA study unveiling additional, small and nearly isotropic Fermi surface sheets in LiFeAs single crystals, which ought to correspond to hole-like orbits, as previously observed by ARPES. Therefore, our results reconcile the apparent discrepancy between ARPES and the previous dHvA results. The small size of these Fermi surface pockets suggests a prominent role for the electronic correlations in LiFeAs. The absence of gap nodes, in combination with the coexistence of quasi-two-dimensional and three-dimensional Fermi surfaces, favor an s-wave pairing symmetry for LiFeAs. But similar electron-like Fermi surfaces combined with very different hole pockets between LiFeAs and LiFeP suggest that the nodes in the gap function of LiFeP might be located on the hole pockets. This would be difficult to reconcile with the current understanding of the s± scenario.

  12. de Haas van Alphen perspective on the origin of heavy fermions in UPt3

    NASA Astrophysics Data System (ADS)

    Rourke, Patrick; McCollam, Alix; McMullan, Greg; Norman, Mike; Julian, Stephen; Huxley, Andrew

    2006-03-01

    Precise de Haas van Alphen (dHvA) oscillation measurements on the heavy fermion superconductor UPt3 are available as a function of magnetic field angle. It was recently proposed that the heavy quasiparticles in this material arise from the localization of two of the three 5f electrons of the U ions [Zwicknagl et al., PRB 65, 081103R (2002)]. The predicted Fermi surface topology however differs from traditional bandstructure calculations. We will focus on the experimentally observed angle dependence of the hole-like δ-orbit, as this appears difficult to reconcile with the Fermi surface of Zwicknagl et al.

  13. Conduction electron g-factors in ruthenium and osmium from de Haas-van Alphen measurements

    NASA Astrophysics Data System (ADS)

    Startsev, V. E.; Coleridge, P. T.; Templeton, I. M.; Fawcett, E.; Muir, C.; Perz, J. M.

    1984-04-01

    Conduction electron g-factors have been deduced from de Haas-van Alphen line shapes in the hexagonal group VIII 4 d transition metal ruthenium and the electronically analogous 5 d metal osmium. The values for orbits normal to [0001] are 1.8±0.1 and 1.3±0.1 for the ellipsoids centered on the line LM in ruthenium and osmium, respectively, and 1.9±0.2 for the Γ-centered ellipsoid in ruthenium. The more marked suppression of the g-factor in osmium, where spin-orbit coupling is stronger, is consistent with recent theoretical studies of transition metal g-factor trends.

  14. de Haas-van Alphen study of role of 4 f electrons in antiferromagnetic CeZn11 as compared to its nonmagnetic analog LaZn11

    NASA Astrophysics Data System (ADS)

    Blake, S. F.; Hodovanets, H.; McCollam, A.; Bud'ko, S. L.; Canfield, P. C.; Coldea, A. I.

    2016-12-01

    We present a de Haas-van Alphen study of the Fermi surface of the low-temperature antiferromagnet CeZn11 and its nonmagnetic analog LaZn11, measured by torque magnetometry up to fields of 33 T and at temperatures down to 320 mK . Both systems possess similar de Haas-van Alphen frequencies, with three clear sets of features—ranging from 50 T to 4 kT —corresponding to three bands of a complex Fermi surface, with an expected fourth band also seen weakly in CeZn11. The effective masses of the charge carriers are very light (<1 me ) in LaZn11 but a factor of 2-4 larger in CeZn11, indicative of stronger electronic correlations. We perform detailed density functional theory (DFT) calculations for CeZn11 and find that only DFT+U calculations with U =1.5 eV , which localize the 4 f states, provide a good match to the measured de Haas-van Alphen frequencies, once the presence of magnetic breakdown orbits is also considered. Our study suggests that the Fermi surface of CeZn11 is very close to that of LaZn11 being dominated by Zn 3 d , as the Ce 4 f states are localized and have little influence on its electronic structure, however, they are responsible for its magnetic order and contribute to enhance electronic correlations.

  15. De Haas-van Alphen Oscillations In Quasi-two-dimensional Underdoped Cuprate Superconductors In The Canonical Ensemble

    SciTech Connect

    Harrison, N; Sebastian, S E

    2008-01-01

    We calculate the de Haas-van Alphen (dHvA) effect waveform using the canonical ensemble for different Fermi surface scenarios applicable to the underdoped cuprate superconductor YBa{sub 2}Cu{sub 3}O{sub 6.5}, in which quantum oscillations have recently been observed. The harmonic content of the dHvA waveform of the principal F{sub {alpha}} {approx} 500 T frequency is consistent with the existence of a second thermodynamically dominant section of Fermi surface that acts primarily as a charge reservoir. Oscillations in the charge density to and from this reservoir are shown to potentially contribute to the observed large quantum oscillations in the Hall resistance.

  16. de Haas van Alphen Oscillations in the Underdoped High-Temperature Superconductor YBa2Cu3O6.5

    NASA Astrophysics Data System (ADS)

    Jaudet, Cyril; Vignolles, David; Audouard, Alain; Levallois, Julien; Leboeuf, D.; Doiron-Leyraud, Nicolas; Vignolle, B.; Nardone, M.; Zitouni, A.; Liang, Ruixing; Bonn, D. A.; Hardy, W. N.; Taillefer, Louis; Proust, Cyril

    2008-05-01

    The de Haas van Alphen effect was observed in the underdoped cuprate YBa2Cu3O6.5 via a torque technique in pulsed magnetic fields up to 59 T. Above a field of ˜30T the magnetization exhibits clear quantum oscillations with a single frequency of 540 T and a cyclotron mass of 1.76 times the free electron mass, in excellent agreement with previously observed Shubnikov de Haas oscillations. The oscillations obey the standard Lifshitz-Kosevich formula of Fermi-liquid theory. This thermodynamic observation of quantum oscillations confirms the existence of a well-defined, closed, and coherent, Fermi surface in the pseudogap phase of cuprates.

  17. de Haas-van Alphen measurements on the antiferromagnet URhIn5

    NASA Astrophysics Data System (ADS)

    Yu, Jing Fei; Bartha, Attila; Custers, Jeroen; Julian, Stephen R.

    2017-09-01

    We report on the results of a de Haas-van Alphen (dHvA) measurement performed on the recently discovered antiferromagnet URhIn5 (TN=98 K), a 5 f analog of the well studied heavy fermion antiferromagnet CeRhIn5. We observe two small Fermi surfaces: a roughly spherical pocket β , with Fβ≃0.3 kT, and a pillow-shaped closed surface, α , with Fα≃1.1 kT. In addition, we observe two higher frequencies γ1 with Fγ1≃3.2 kT and γ2 with Fγ 2≃3.5 kT that are seen only near the c axis, and that may arise on cylindrical Fermi surfaces. The measured cyclotron masses range from 1.9 me to 4.3 me . A simple LDA+SO calculation performed for the paramagnetic ground state shows a very different Fermi surface topology, demonstrating a need for more advanced electronic structure calculations.

  18. de Haas-van Alphen studies and Fermi surface properties of organic superconductors (ET)[sub 2]X

    SciTech Connect

    Wosnitza, J. . Physikalisches Inst.); Crabtree, G.W.; Williams, J.M.; Wang, H.H.; Carlson, K.D.; Geiser, U. )

    1993-04-01

    de Haas-van Alphen (dHvA) measurements of organic superconductors (ET)[sub 2]X, where ET stands for bis(ethylene)dithiotetrathiafulvalene (or BEDT-TTF) and X = IBr[sub 2], (NH[sub 4])Hg(SCN)[sub 4] and Cu(NCS)[sub 2] are reported. The strong two-dimensionality of the Fermi surface (FS) is clearly seen by the perfect 1/cos([Theta])-behavior of the dHvA frequency. The distinctive kind of beating and the angular dependence of the dHvA signal in [beta]-(ET)[sub 2]IBr[sub 2] gives clear evidence for a lightly corrugated structure of the FS. Due to the nearly cylinder-shape of the FS the bare band structure effective mass, m[sub b], also shows a 1/cos([Theta])-dependence which is responsible for spin splitting zeros at certain angles. At these points, where the fundamental amplitude of the dHvA signal is vanishing, m[sub b] could exactly be determined and by comparison with the independently measured cyclotron effective mass the electron-phonon coupling constant could be estimated. 17 refs, 5 figs.

  19. de Haas-van Alphen studies and Fermi surface properties of organic superconductors (ET){sub 2}X

    SciTech Connect

    Wosnitza, J.; Crabtree, G.W.; Williams, J.M.; Wang, H.H.; Carlson, K.D.; Geiser, U.

    1993-04-01

    de Haas-van Alphen (dHvA) measurements of organic superconductors (ET){sub 2}X, where ET stands for bis(ethylene)dithiotetrathiafulvalene (or BEDT-TTF) and X = IBr{sub 2}, (NH{sub 4})Hg(SCN){sub 4} and Cu(NCS){sub 2} are reported. The strong two-dimensionality of the Fermi surface (FS) is clearly seen by the perfect 1/cos({Theta})-behavior of the dHvA frequency. The distinctive kind of beating and the angular dependence of the dHvA signal in {beta}-(ET){sub 2}IBr{sub 2} gives clear evidence for a lightly corrugated structure of the FS. Due to the nearly cylinder-shape of the FS the bare band structure effective mass, m{sub b}, also shows a 1/cos({Theta})-dependence which is responsible for spin splitting zeros at certain angles. At these points, where the fundamental amplitude of the dHvA signal is vanishing, m{sub b} could exactly be determined and by comparison with the independently measured cyclotron effective mass the electron-phonon coupling constant could be estimated. 17 refs, 5 figs.

  20. Nearly massless Dirac fermions and strong Zeeman splitting in the nodal-line semimetal ZrSiS probed by de Haas-van Alphen quantum oscillations

    NASA Astrophysics Data System (ADS)

    Hu, Jin; Tang, Zhijie; Liu, Jinyu; Zhu, Yanglin; Wei, Jiang; Mao, Zhiqiang

    2017-07-01

    Topological semimetals represent a new class of quantum materials hosting Dirac/Weyl fermions. The essential properties of topological fermions can be revealed by quantum oscillations. Here we present systematic de Haas-van Alphen (dHvA) oscillation studies on the recently discovered topological Dirac nodal-line semimetal ZrSiS. From the angular dependence of dHvA oscillations, we have revealed the anisotropic Dirac bands in ZrSiS and found surprisingly strong Zeeman splitting at low magnetic fields. The Landé g factor estimated from the separation of Zeeman splitting peaks is as large as 38. From the analyses of dHvA oscillations, we also revealed nearly zero effective mass and exceptionally high quantum mobility for Dirac fermions in ZrSiS. These results shed light on the nature of novel Dirac fermion physics of ZrSiS.

  1. New insights on frequency combinations and ‘forbidden frequencies’ in the de Haas-van Alphen spectrum of κ-(ET)2Cu(SCN)2

    NASA Astrophysics Data System (ADS)

    Audouard, Alain; Fortin, Jean-Yves; Vignolles, David; Laukhin, Vladimir N.; Kushch, Nataliya D.; Yagubskii, Eduard B.

    2016-07-01

    de Haas-van Alphen oscillations of the organic metal κ-(ET)2Cu(SCN)2 have been measured up to 55 T at liquid helium temperatures. The Fermi surface of this charge transfer salt is a textbook example of a linear chain of orbits coupled by magnetic breakdown. Accordingly, the oscillation spectrum is composed of linear combinations of the frequencies linked to the α and magnetic breakdown-induced β orbits. The field and temperature dependence of all the observed Fourier components, in particular the ‘forbidden frequency’ β -α which cannot correspond to a classical orbit, are quantitatively accounted for by analytical calculations based on a second order development of the free energy, i.e. beyond the first order Lifshitz-Kosevich formula.

  2. Quantum Hall conductance and de Haas-van Alphen oscillation in a tight-binding model with electron and hole pockets for (TMTSF) 2NO3

    NASA Astrophysics Data System (ADS)

    Kishigi, Keita; Hasegawa, Yasumasa

    2016-08-01

    Quantized Hall conductance and de Haas-van Alphen (dHvA) oscillation are studied theoretically in the tight-binding model for (TMTSF) 2NO3 , in which there are small pockets of electrons and holes due to the periodic potentials of anion ordering in the a direction. The magnetic field is treated by hoppings as complex numbers due to the phase caused by the vector potential, i.e., Peierls substitution. In realistic values of parameters and the magnetic field, the energy as a function of the magnetic field (Hofstadter butterfly diagram) is obtained. It is shown that the energy levels are broadened and the gaps are closed or almost closed periodically as a function of the inverse magnetic field, which is not seen in the semiclassical theory of the magnetic breakdown. The Hall conductance is quantized with an integer obtained by the Diophantine equation when the chemical potential lies in an energy gap. When electrons or holes are doped in this system, the Hall conductance is quantized in some regions of a magnetic field but it is not quantized in other regions of a magnetic field due to the broadening of the Landau levels. The amplitude of the dHvA oscillation at zero temperature decreases as the magnetic field increases, while it is constant in the semiclassical Lifshitz Kosevich formula.

  3. De Hass-van Alphen effect in YBCO

    SciTech Connect

    Smith, J.L.; Fowler, C.M.; Freeman, B.L.; Hults, W.L.; King, J.C.; Mueller, F.M.

    1990-01-01

    Measurement of the de Haas-van Alphen effect in YBa{sub 2}Cu{sub 3}O{sub 6.97} in pulsed, magnetic fields peaking at 100 T in powdered material with the field applied along the c-axis reveal two pieces of the Fermi surface. Their cross sections are 0.56 kT (0.054 {angstrom}{sup {minus}2}) and 0.78 kT (0.075 {angstrom}{sup {minus}2}) with effective masses of 2.8 and 4.4 respectively.

  4. Small and nearly isotropic hole-like Fermi surfaces in LiFeAs detected through de Haas-van Alphen effect

    NASA Astrophysics Data System (ADS)

    Zeng, Bin; Watanabe, Daiki; Zhang, Qiu; Li, Gang; Besara, Tiglet; Siegrist, Theo; Xing, Lingyi; Wang, Xiancheng; Jin, Changqing; Goswami, Pallab; Johannes, Michelle; Balicas, Luis

    2014-03-01

    We show a detailed dHvA study unveiling small and nearly isotropic Fermi surface sheets in LiFeAs single crystals, which is not observed by previous dHvA results, as well as the cylindrical electron-like Fermi surfaces. Our results are in partial agreement with the ARPES results, and the small, nearly isotropic Fermi surface should correspond to the hole-like pocket, suggesting a prominent role for the electronic correlations in LiFeAs. The absence of gap nodes, in combination with the coexistence of quasi-two-dimensional and three-dimensional Fermi surfaces, favor an s-wave pairing symmetry for LiFeAs.

  5. QED effective action at finite temperature and density

    NASA Astrophysics Data System (ADS)

    Elmfors, Per; Persson, David; Skagerstam, Bo-Sture

    1993-07-01

    Results are presented of calculations of the QED effective action at finite temperature and density to all orders in an external homogeneous and time-independent magnetic field, in the weak coupling limit. The free energy, obtained explicitly, exhibits the expected de Haas-van Alphen oscillations. An effective coupling at finite temperature and density is derived in a closed form and is compared with renormalization group results.

  6. Impurity effects in the magnetic oscillations on doped graphene with Zeeman splitting

    NASA Astrophysics Data System (ADS)

    Escudero, F.; Ardenghi, J. S.; Jasen, Paula; Juan, A.

    2017-08-01

    The aim of this work is to describe the electronic and magnetic properties of graphene in a constant magnetic field, in the long wavelength approximation with random disorder. Taking into account the Zeeman effect, the electronic density of states for each spin is found and the de Haas van Alphen oscillations (dHvA) are found. The magnetic field is found to modulate the de Haas-van Alphen magnetization through the ratio of the Zeeman coupling and pseudospin-Landau coupling. In turn, the Pauli magnetization is studied showing that the Zeeman splitting and disorder introduces a dHvA oscillation period that depends on the magnetic field strength and generalizes the Onsager relation. In turn, a beat frequency appears that does not depend on B but increase linearly with the chemical potential. These results, which are different from those obtained in the standard nonrelativistic 2D electron gas, are attributed to its anomalous Landau level spectrum in graphene.

  7. Effect of structural disorder on quantum oscillations in graphite

    SciTech Connect

    Camargo, B. C. Kopelevich, Y.; Usher, A.; Hubbard, S. B.

    2016-01-18

    We have studied the effect of structural disorder on the de Haas van Alphen and Shubnikov de Haas quantum oscillations measured in natural, Kish, and highly oriented pyrolytic graphite samples at temperatures down to 30 mK and at magnetic fields up to 14 T. The measurements were performed on different samples characterized by means of x-ray diffractometry, transmission electron microscopy, and atomic-force microscopy techniques. Our results reveal a correlation between the amplitude of quantum oscillations and the sample surface roughness.

  8. de Haas-van Alphen measurements in Ba{sub 0.6}K{sub 0.4}BiO{sub 3}

    SciTech Connect

    Goodrich, R.G.; Grienier, C.; Hall, D.

    1993-08-01

    dHvA measurements were made on the 32 K cubic superconductor Ba{sub 0.6}K{sub 0.4}BiO{sub 3} using a 50 Tesla pulsed field magnet at NHMFL (Los Alamos) and a 18 T superconducting magnet (LSU). Data were taken with the magnetic field aligned along the (001) direction, at 1.5 to 3.9 K. The pulsed fields were high enough to drive the system well into the normal state. Analysis shows that the frequencies of the observed dHvA oscillations arise from a several Fermi surface sheets. One cross section was nearly identical with that predicted by a new LDA calculation.

  9. Ground state magnetization of conduction electrons in graphene with Zeeman effect

    NASA Astrophysics Data System (ADS)

    Escudero, F.; Ardenghi, J. S.; Sourrouille, L.; Jasen, P.

    2017-05-01

    In this work we address the ground state magnetization in graphene, considering the Zeeman effect and taking into account the conduction electrons in the long wavelength approximation. We obtain analytical expressions for the magnetization at T=0 K, where the oscillations given by the de Haas van Alphen (dHvA) effect are present. We find that the Zeeman effect modifies the magnetization by introducing new peaks associated with the spin splitting of the Landau levels. These peaks are very small for typical carrier densities in graphene, but become more important for higher densities. The obtained results provide insight of the way in which the Zeeman effect modifies the magnetization, which can be useful to control and manipulate the spin degrees of freedom.

  10. Frequency anomaly in the Rashba-effect induced magnetization oscillations of a high-mobility two-dimensional electron system

    NASA Astrophysics Data System (ADS)

    Rupprecht, B.; Heedt, S.; Hardtdegen, H.; Schäpers, Th.; Heyn, Ch.; Wilde, M. A.; Grundler, D.

    2013-01-01

    With the direct measurement of the quantum oscillatory magnetization M of a two-dimensional electron system (2DES) in an InGaAs/InP asymmetric quantum well we discover a frequency anomaly of the de Haas-van Alphen effect which is not consistent with existing theories on spin-orbit interaction (SOI). Strikingly, the oscillatory magnetoresistance of the same heterostructure, that is, the Shubnikov-de Haas effect conventionally used to explore SOI, does not show the frequency anomaly. This explains why our finding has not been reported for almost three decades. The understanding of the ground state energy of a 2DES is evidenced to be incomplete when SOI is present.

  11. Confinement and inhomogeneous broadening effects in the quantum oscillatory magnetization of quantum dot ensembles

    NASA Astrophysics Data System (ADS)

    Herzog, F.; Heedt, S.; Goerke, S.; Ibrahim, A.; Rupprecht, B.; Heyn, Ch; Hardtdegen, H.; Schäpers, Th; Wilde, M. A.; Grundler, D.

    2016-02-01

    We report on the magnetization of ensembles of etched quantum dots with a lateral diameter of 460 nm, which we prepared from InGaAs/InP heterostructures. The quantum dots exhibit 1/B-periodic de-Haas-van-Alphen-type oscillations in the magnetization M(B) for external magnetic fields B  >  2 T, measured by torque magnetometry at 0.3 K. We compare the experimental data to model calculations assuming different confinement potentials and including ensemble broadening effects. The comparison shows that a hard wall potential with an edge depletion width of 100 nm explains the magnetic behavior. Beating patterns induced by Rashba spin-orbit interaction (SOI) as measured in unpatterned and nanopatterned InGaAs/InP heterostructures are not observed for the quantum dots. From our model we predict that signatures of SOI in the magnetization could be observed in larger dots in tilted magnetic fields.

  12. Split Fermi Surface Properties based on the Relativistic Effect in Superconductor PdBiSe with the Cubic Chiral Crystal Structure

    NASA Astrophysics Data System (ADS)

    Kakihana, Masashi; Nakamura, Ai; Teruya, Atsushi; Harima, Hisatomo; Haga, Yoshinori; Hedo, Masato; Nakama, Takao; Ōnuki, Yoshichika

    2015-03-01

    We grew single crystals of PdBiSe with the ullmannite-type cubic chiral structure and carried out de Haas-van Alphen (dHvA) experiments to clarify the Fermi surface properties. The Fermi surfaces are found to split into two different Fermi surfaces, reflecting the non-centrosymmetric crystal structure. A splitting energy between two nearly spherical Fermi surfaces named α and α' is determined as 1050-1260 K. These Fermi surfaces are identified to be due the band-149 and -150 electron Fermi surfaces centered at the Γ point from the results of full-potential linearized augmented plane wave (FLAPW) energy band calculations under consideration of a mass correction in the spin-orbit interaction for Bi-6p electrons based on the relativistic effect. The theoretical splitting energy between these Fermi surfaces is 1080-1150 K, which is in good agreement with the experimental value.

  13. Correlations and effects of pressure in Fe-pnictides

    NASA Astrophysics Data System (ADS)

    Valenti, Roser

    2014-03-01

    In this talk we will explore the effects of correlations and pressure in Fe-based superconductors by considering a combination of density functional theory calculations and dynamical mean field theory and compare our results with recent ARPES and de Haas van Alphen experiments. We will discuss the importance of orbital-selective correlations in the 111 (LiFeAs, LiFeP) and 122 families (BaFe2As2,CaFe2As2, KFe2As2) and indicate how the topology of the Fermi surface, specially in KFe2As2, is influenced by these effects. In this context, we will show why MgFeGe, an isostructural and isoelectronic system to LiFeAs, doesn't superconduct. In the case of the 122 systems, we will predict and analyze changes in the electronic and magnetic properties under hydrostatic, tensile and compressive pressure and will discuss our results in relation to (i) superconductivity, (ii) magnetism and (iii) the mechanisms involved in the detwinning process of an orthorhombic iron-pnictide crystal a. Funding has been provided by the German Science Foundation (DFG).

  14. High-temperature quantum kinetic effect in silicon nanosandwiches

    NASA Astrophysics Data System (ADS)

    Bagraev, N. T.; Grigoryev, V. Yu.; Klyachkin, L. E.; Malyarenko, A. M.; Mashkov, V. A.; Romanov, V. V.; Rul, N. I.

    2017-01-01

    The negative-U impurity stripes confining the edge channels of semiconductor quantum wells are shown to allow the effective cooling inside in the process of the spin-dependent transport, with the reduction of the electron-electron interaction. The aforesaid promotes also the creation of composite bosons and fermions by the capture of single magnetic flux quanta on the edge channels under the conditions of low sheet density of carriers, thus opening new opportunities for the registration of the quantum kinetic phenomena in weak magnetic fields at high-temperatures up to the room temperature. As a certain version noted above we present the first findings of the high temperature de Haas-van Alphen, 300 K, quantum Hall, 77 K, effects as well as quantum conductance staircase in the silicon sandwich structure that represents the ultra-narrow, 2 nm, p-type quantum well (Si-QW) confined by the delta barriers heavily doped with boron on the n-type Si (100) surface.

  15. A complete theory for the magnetism of an ideal gas of electrons

    SciTech Connect

    Biswas, Shyamal; Jana, Debnarayan; Sen, Swati

    2013-05-15

    We have explored Pauli paramagnetism, Landau diamagnetism, and de Haas-van Alphen effect in a single framework, and unified these three effects for all temperatures as well as for all strengths of magnetic field. Our result goes beyond Pauli-Landau result on the magnetism of the 3-D ideal gas of electrons, and is able to describe crossover of the de Haas-van Alphen oscillation to the saturation of magnetization. We also have obtained a novel asymptotic series expansion for the low temperature properties of the system.

  16. Fermi Surface Properties Based on the Relativistic Effect in SrBi3 with AuCu3-Type Cubic Structure

    NASA Astrophysics Data System (ADS)

    Kakihana, Masashi; Akamine, Hiromu; Yara, Tomoyuki; Teruya, Atsushi; Nakamura, Ai; Takeuchi, Tetsuya; Hedo, Masato; Nakama, Takao; Ōnuki, Yoshichika; Harima, Hisatomo

    2015-12-01

    Bi-6p electrons are well known to possess a strong spin-orbit interaction, but a mass correction based on the relativistic effect is scarcely discussed in the electronic state. To clarify the relativistic properties of Bi-6p electrons, we grew single crystals of SrBi3 with the AuCu3-type cubic structure by the Bi self-flux method and carried out electrical resistivity, specific heat, and de Haas-van Alphen (dHvA) experiments. Several kinds of closed Fermi surfaces are observed from the dHvA effect. Among them, three kinds of main Fermi surfaces are compared with the results of full-potential linearized augmented plane wave (FLAPW) energy band calculations under two considerations. One corresponds to the mass correction in the spin-orbit interaction for Bi-6p electrons. The other is without the mass correction. Detected two kinds of the main Fermi surfaces are well explained with and without the mass correction, but a remaining Fermi surface is explained only with the mass correction. The relativistic effects of the spin-orbit interaction and mass correction are essentially important for Bi-6p electrons in SrBi3.

  17. Magnetic Oscillations in Metals

    NASA Astrophysics Data System (ADS)

    Schoenberg, D.

    2009-09-01

    Preface; 1. Historical introduction; 2. Theory; 3. Observation of the de Haas-van Alphen effect; 4. Other oscillatory effects; 5. Fermi surfaces and cyclotron masses; 6. Magnetic interaction; 7. Magnetic breakdown; 8. The Dingle temperature; 9. Phase and spin-splitting; Appendices; Bibliography; Notes; Index.

  18. Influence of pressure on the Fermi surface of niobium

    SciTech Connect

    Anderson, J.R.; Papaconstantopoulos, D.A.; Schirber, J.E.

    1981-12-15

    The effects of pressure on selected de Haas--van Alphen frequencies in niobium have been measured. The frequency shifts, including a relatively large negative shift for the jungle-gym arms, can be explained by a model which uses a Slater-Koster interpolation of augmented-plane-wave X..cap alpha.. bands which had been calculated for two lattice spacings.

  19. Influence of pressure on the Fermi surface of niobium

    NASA Astrophysics Data System (ADS)

    Anderson, J. R.; Papaconstantopoulos, D. A.; Schirber, J. E.

    1981-12-01

    The effects of pressure on selected de Haas - van Alphen frequencies in niobium have been measured. The frequency shifts, including a relatively large negative shift for the jungle-gym arms, can be explained by a model which uses a Slater-Koster interpolation of augmented-plane-wave Xα bands which had been calculated for two lattice spacings.

  20. Spin Hall effect and Landau spectrum of Dirac electrons in bismuth

    NASA Astrophysics Data System (ADS)

    Fuseya, Yuki

    2015-03-01

    Bismuth has played an important role in solid-state physics. Many key phenomena were first discovered in bismuth, such as diamagnetism, Seebeck, Nernst, Shubnikov-de Haas, and de Haas-van Alphen effects. These phenomena result from particular electronic states of bismuth. The strong spin-orbit interaction (~ 1.5eV) causes strong spin-dependent interband couplings resulting in an anomalous spin magnetic moment. We investigate the spin Hall effect and the angular dependent Landau spectrum of bismuth paying special attention to the effect of the anomalous spin magnetic moment. It is shown that the spin Hall insulator is possible and there is a fundamental relationship between the spin Hall conductivity and orbital diamagnetism in the insulating state of the Dirac electrons. Based on this theoretical finding, the magnitude of spin Hall conductivity is estimated for bismuth by that of orbital susceptibility. The magnitude of spin Hall conductivity turns out to be as large as 104Ω-1 cm-1, which is about 100 times larger than that of Pt. It is also shown that the ratio of the Zeeman splitting to the cyclotron energy, which reflects the effect of crystalline spin-orbit interaction, for holes at the T-point can be larger than 1.0 (the maximum of previous theories) and exhibit strong angular dependence, which gives a possible solution to the long-standing mystery of holes at the T-point. In collaboration with Masao Ogata, Hidetoshi Fukuyama, Zengwei Zhu, Benoît Fauqué, Woun Kang, and Kamran Behnia. Supported by JSPS (KAKENHI 24244053, 25870231, and 13428660).

  1. Magnetic catalysis effect in the (2+1)-dimensional Gross-Neveu model with Zeeman interaction

    NASA Astrophysics Data System (ADS)

    Klimenko, K. G.; Zhokhov, R. N.

    2015-05-01

    Magnetic catalysis of the chiral symmetry breaking and other magnetic properties of the (2+1)-dimensional Gross-Neveu model are studied taking into account the Zeeman interaction of spin-1/2 quasi-particles (electrons) with tilted (with respect to a system plane) external magnetic field B = {B_ bot } + {B_allel }. The Zeeman interaction is proportional to magnetic moment μB of electrons. For simplicity, temperature and chemical potential are equal to zero throughout the paper. We compare in the framework of the model the above mentioned phenomena both at μB = 0 and μB ≠ 0. It is shown that at μB ≠ 0 the magnetic catalysis effect is drastically changed in comparison with the μB = 0 case. Namely, at μB ≠ 0 the chiral symmetry, being spontaneously broken by B at subcritical coupling constants, is always restored at |B| → ∞ (even at B_allel = 0). Moreover, it is proved in this case that chiral symmetry can be restored simply by tilting B to a system plane, and in the region B⊥ → 0 the de Haas - van Alphen oscillations of the magnetization are observed. At supercritical values of coupling constant we have found two chirally non-invariant phases which respond differently on the action of B. The first (at rather small values of |B|) is a diamagnetic phase, in which there is an enhancement of chiral condensate, whereas the second is a paramagnetic chirally broken phase. Numerical estimates show that phase transitions described in the paper can be achieved at low enough laboratory magnetic fields.

  2. High-field de Haas{endash}van Alphen measurements in Pd

    SciTech Connect

    Vuillemin, J.J.; Harrison, N.; Goodrich, R.G.

    1999-05-01

    The de Haas{endash}van Alphen (dHvA) effect in 99.999{percent} pure palladium has been observed in pulsed fields up to 60 T directed along [100]. We report a dHvA frequency of 73.5 kT with a cyclotron effective mass=12.5m{sub 0}. Such a frequency is not reported previously but is predicted by band theory for the open hole sheet of the Fermi surface. We also observe strong harmonic content near 50 T for the electron sheet and this is interpreted in terms of a field-dependent {ital g} factor. {copyright} {ital 1999} {ital The American Physical Society}

  3. De Hass-van Alphen and magnetoresistance reveal predominantly single-band transport behavior in PdTe2.

    PubMed

    Wang, Yongjian; Zhang, Jinglei; Zhu, Wenka; Zou, Youming; Xi, Chuanying; Ma, Long; Han, Tao; Yang, Jun; Wang, Jingrong; Xu, Junmin; Zhang, Lei; Pi, Li; Zhang, Changjin; Zhang, Yuheng

    2016-08-12

    Research on two-dimensional transition metal dichalcogenides (TMDs) has grown rapidly over the past several years, from fundamental studies to the development of next generation technologies. Recently, it has been reported that the MX2-type PdTe2 exhibits superconductivity with topological surface state, making this compound a promising candidate for investigating possible topological superconductivity. However, due to the multi-band feature of most of TMDs, the investigating of magnetoresistance and quantum oscillations of these TMDs proves to be quite complicated. Here we report a combined de Hass-van Alphen effect and magnetoresistance studies on the PdTe2 single crystal. Our high-field de Hass-van Alphen data measured at different temperature and different tilting angle suggest that though these is a well-defined multi-band feature, a predominant oscillation frequency has the largest oscillation magnitude in the fast Fourier transformation spectra, which is at least one order of magnitude larger than other oscillation frequencies. Thus it is likely that the transport behavior in PdTe2 system can be simplified into a single-band model. Meanwhile, the magnetoresistance results of the PdTe2 sample can be well-fitted according to the single-band models. The present results could be important in further investigation of the transport behaviors of two-dimensional TMDs.

  4. De Hass-van Alphen and magnetoresistance reveal predominantly single-band transport behavior in PdTe2

    PubMed Central

    Wang, Yongjian; Zhang, Jinglei; Zhu, Wenka; Zou, Youming; Xi, Chuanying; Ma, Long; Han, Tao; Yang, Jun; Wang, Jingrong; Xu, Junmin; Zhang, Lei; Pi, Li; Zhang, Changjin; Zhang, Yuheng

    2016-01-01

    Research on two-dimensional transition metal dichalcogenides (TMDs) has grown rapidly over the past several years, from fundamental studies to the development of next generation technologies. Recently, it has been reported that the MX2-type PdTe2 exhibits superconductivity with topological surface state, making this compound a promising candidate for investigating possible topological superconductivity. However, due to the multi-band feature of most of TMDs, the investigating of magnetoresistance and quantum oscillations of these TMDs proves to be quite complicated. Here we report a combined de Hass-van Alphen effect and magnetoresistance studies on the PdTe2 single crystal. Our high-field de Hass-van Alphen data measured at different temperature and different tilting angle suggest that though these is a well-defined multi-band feature, a predominant oscillation frequency has the largest oscillation magnitude in the fast Fourier transformation spectra, which is at least one order of magnitude larger than other oscillation frequencies. Thus it is likely that the transport behavior in PdTe2 system can be simplified into a single-band model. Meanwhile, the magnetoresistance results of the PdTe2 sample can be well-fitted according to the single-band models. The present results could be important in further investigation of the transport behaviors of two-dimensional TMDs. PMID:27516134

  5. De Hass-van Alphen and magnetoresistance reveal predominantly single-band transport behavior in PdTe2

    NASA Astrophysics Data System (ADS)

    Wang, Yongjian; Zhang, Jinglei; Zhu, Wenka; Zou, Youming; Xi, Chuanying; Ma, Long; Han, Tao; Yang, Jun; Wang, Jingrong; Xu, Junmin; Zhang, Lei; Pi, Li; Zhang, Changjin; Zhang, Yuheng

    2016-08-01

    Research on two-dimensional transition metal dichalcogenides (TMDs) has grown rapidly over the past several years, from fundamental studies to the development of next generation technologies. Recently, it has been reported that the MX2-type PdTe2 exhibits superconductivity with topological surface state, making this compound a promising candidate for investigating possible topological superconductivity. However, due to the multi-band feature of most of TMDs, the investigating of magnetoresistance and quantum oscillations of these TMDs proves to be quite complicated. Here we report a combined de Hass-van Alphen effect and magnetoresistance studies on the PdTe2 single crystal. Our high-field de Hass-van Alphen data measured at different temperature and different tilting angle suggest that though these is a well-defined multi-band feature, a predominant oscillation frequency has the largest oscillation magnitude in the fast Fourier transformation spectra, which is at least one order of magnitude larger than other oscillation frequencies. Thus it is likely that the transport behavior in PdTe2 system can be simplified into a single-band model. Meanwhile, the magnetoresistance results of the PdTe2 sample can be well-fitted according to the single-band models. The present results could be important in further investigation of the transport behaviors of two-dimensional TMDs.

  6. de Haas–van Alphen study of role of 4f electrons in antiferromagnetic CeZn11 as compared to its nonmagnetic analog LaZn11

    DOE PAGES

    Blake, S. F.; Hodovanets, H.; McCollam, A.; ...

    2016-12-02

    Here we present a de Haas–van Alphen study of the Fermi surface of the low-temperature antiferromagnet CeZn11 and its nonmagnetic analog LaZn11, measured by torque magnetometry up to fields of 33T and at temperatures down to 320 mK . Both systems possess similar de Haas–van Alphen frequencies, with three clear sets of features—ranging from 50 T to 4 kT —corresponding to three bands of a complex Fermi surface, with an expected fourth band also seen weakly in CeZn11 . The effective masses of the charge carriers are very light (<1 me) in LaZn11 but a factor of 2–4 larger inmore » CeZn11, indicative of stronger electronic correlations. We perform detailed density functional theory (DFT) calculations for CeZn11 and find that only DFT+ U calculations with U = 1.5 eV , which localize the 4 f states, provide a good match to the measured de Haas–van Alphen frequencies, once the presence of magnetic breakdown orbits is also considered. Finally, our study suggests that the Fermi surface of CeZn11 is very close to that of LaZn11 being dominated by Zn 3d , as the Ce 4 f states are localized and have little influence on its electronic structure, however, they are responsible for its magnetic order and contribute to enhance electronic correlations.« less

  7. Fermi surface, magnetic, and superconducting properties in actinide compounds

    NASA Astrophysics Data System (ADS)

    Ōnuki, Yoshichika; Settai, Rikio; Haga, Yoshinori; Machida, Yo; Izawa, Koichi; Honda, Fuminori; Aoki, Dai

    2014-08-01

    The de Haas-van Alphen effect, which is a powerful method to explore Fermi surface properties, has been observed in cerium, uranium, and nowadays even in neptunium and plutonium compounds. Here, we present the results of several studies concerning the Fermi surface properties of the heavy fermion superconductors UPt3 and NpPd5Al2, and of the ferromagnetic pressure-induced superconductor UGe2, together with those of some related compounds for which fascinating anisotropic superconductivity, magnetism, and heavy fermion behavior has been observed. xml:lang="fr"

  8. Theory of quantum oscillations of magnetization in Kondo insulators

    NASA Astrophysics Data System (ADS)

    Ram, Panch; Kumar, Brijesh

    2017-08-01

    The Kondo lattice model of spin-1/2 local moments coupled to the conduction electrons at half filling is studied for its orbital response to magnetic field on bipartite lattices. Through an effective charge dynamics, in a canonical representation of electrons that appropriately describes the Kondo insulating ground state, the magnetization is found to show de Haas-van Alphen oscillations from intermediate to weak Kondo coupling. These oscillations are ascribed to the inversion of a dispersion of the gapped charge quasiparticles, whose chemical potential surface is measured by the oscillation frequency. Such oscillations are also predicted to occur in spin-density wave insulators.

  9. Magnetic quantum oscillations in a monolayer graphene under a perpendicular magnetic field

    NASA Astrophysics Data System (ADS)

    Fu, Zhen-Guo; Wang, Zhi-Gang; Li, Shu-Shen; Zhang, Ping

    2011-05-01

    The de Haas-van Alphen (dHvA) oscillations of electronic magnetization in a monolayer graphene with structure-induced spin-orbit interaction (SOI) are studied. The results show that the dHvA oscillating centre in this system deviates from the well known (zero) value in a conventional two-dimensional electron gas. The inclusion of SOI will change the well-defined sawtooth pattern of magnetic quantum oscillations and result in a beating pattern. In addition, the SOI effects on Hall conductance and magnetic susceptibility are also discussed.

  10. Magnetism in a Mn modulation-doped InAs/InGaAs heterostructure with a two-dimensional hole system

    NASA Astrophysics Data System (ADS)

    Rupprecht, B.; Krenner, W.; Wurstbauer, U.; Heyn, Ch.; Windisch, T.; Wilde, M. A.; Wegscheider, W.; Grundler, D.

    2010-05-01

    For an InAs quantum well which is modulation-doped with Mn we measure directly and simultaneously the magnetization and magnetic anisotropy of, both, the two dimensional hole system (2DHS) and Mn dopants. Using highly sensitive micromechanical torque magnetometry at 400 mK we observe the de Haas-van Alphen effect of the 2DHS in a magnetic field B up to 14 T. Around B =0 we find a magnetic hysteresis which we attribute to the spontaneous ordering of magnetic moments in the interacting Mn-hole system. Tilted field experiments suggest a uniaxial magnetic anisotropy with the easy axis in (001) growth direction.

  11. Effects of chiral imbalance and magnetic field on pion superfluidity and color superconductivity

    NASA Astrophysics Data System (ADS)

    Cao, Gaoqing; Zhuang, Pengfei

    2015-11-01

    The effects of chiral imbalance and external magnetic field on pion superfluidity and color superconductivity are investigated in extended Nambu-Jona-Lasinio models. We take the Schwinger approach to treat the interaction between the charged pion condensate and magnetic field at finite isospin density and include simultaneously the chiral imbalance and magnetic field at finite baryon density. For the superfluidity, the chiral imbalance and magnetic field lead to catalysis and inverse catalysis effects, respectively. For the superconductivity, the chiral imbalance enhances the critical baryon density, and the magnetic field results in a de Haas-van Alphan oscillation on the phase transition line.

  12. Quasi-two-dimensional Fermi surfaces with localized f electrons in the layered heavy-fermion compound CePt2In7

    NASA Astrophysics Data System (ADS)

    Götze, K.; Krupko, Y.; Bruin, J. A. N.; Klotz, J.; Hinlopen, R. D. H.; Ota, S.; Hirose, Y.; Harima, H.; Settai, R.; McCollam, A.; Sheikin, I.

    2017-08-01

    We report measurements of the de Haas-van Alphen effect in the layered heavy-fermion compound CePt2In7 in high magnetic fields up to 35 T. Above an angle-dependent threshold field, we observed several de Haas-van Alphen frequencies originating from almost ideally two-dimensional Fermi surfaces. The frequencies are similar to those previously observed to develop only above a much higher field of 45 T, where a clear anomaly was detected and proposed to originate from a change in the electronic structure [M. M. Altarawneh et al., Phys. Rev. B 83, 081103 (2011), 10.1103/PhysRevB.83.081103]. Our experimental results are compared with band structure calculations performed for both CePt2In7 and LaPt2In7 , and the comparison suggests localized f electrons in CePt2In7 . This conclusion is further supported by comparing experimentally observed Fermi surfaces in CePt2In7 and PrPt2In7 , which are found to be almost identical. The measured effective masses in CePt2In7 are only moderately enhanced above the bare electron mass m0, from 2 m0 to 6 m0 .

  13. Effect of Octahedron Rotation in (Ba_(1-x) K_x)BiO3 (x ~ 0.4)

    NASA Astrophysics Data System (ADS)

    McMullan, Greg; Koelling, Dale; Sterne, Philip

    1998-03-01

    In trying to understand the Fermi surface by assuming Ba-K ordering (P.A. Sterne, BAPS 40):448(1995), a minimum total energy was found for a rocksalt structure of twice the lattice constant. The resulting folded back Fermi surface can explain the additional de Haas-van Alphen orbits footnote R.G. Goodrich, et al, J. Phys. Chem. Solids 54:1251(1993) not realized in the unmodified perovskite structure. Recent XFAS data (Y. Yacoby, et al), Sol. St. Commun. 101:801(1997) indicate local alternating rotations of the oxygen octahedra by ~ 4.5^o about an <111> axis. Such a (more typical) perovskite distortion produces a larger-celled fcc lattice and a similar folding. Despite the local symmetry reduction introduced, neutron scattering (S. Pei, et al), Phys. Rev B41:4126(1990) finds the crystal to be on average cubic. The initial assumption is of disordered domains of the four <111> axes requiring that one consider not only how the observed orbits are obtained but also how quantum oscillations can be preserved.

  14. Requirements for the observation of Fermi surfaces in disordered alloys

    SciTech Connect

    Faulkner, J S; Stocks, G M

    1991-01-01

    The proposal is made that it may be possible to use de Haas-van Alphen measurements to gain a deeper understanding of the electronic states in concentrated, disordered, substitutional, metallic alloys. The reasons for this are the increased availability of high magnetic fields and the development of a quantitative alloy theory. 16 refs., 5 figs.

  15. de Haas–van Alphen study of role of 4f electrons in antiferromagnetic CeZn11 as compared to its nonmagnetic analog LaZn11

    SciTech Connect

    Blake, S. F.; Hodovanets, H.; McCollam, A.; Bud'ko, S. L.; Canfield, P. C.; Coldea, A. I.

    2016-12-02

    Here we present a de Haas–van Alphen study of the Fermi surface of the low-temperature antiferromagnet CeZn11 and its nonmagnetic analog LaZn11, measured by torque magnetometry up to fields of 33T and at temperatures down to 320 mK . Both systems possess similar de Haas–van Alphen frequencies, with three clear sets of features—ranging from 50 T to 4 kT —corresponding to three bands of a complex Fermi surface, with an expected fourth band also seen weakly in CeZn11 . The effective masses of the charge carriers are very light (<1 me) in LaZn11 but a factor of 2–4 larger in CeZn11, indicative of stronger electronic correlations. We perform detailed density functional theory (DFT) calculations for CeZn11 and find that only DFT+ U calculations with U = 1.5 eV , which localize the 4 f states, provide a good match to the measured de Haas–van Alphen frequencies, once the presence of magnetic breakdown orbits is also considered. Finally, our study suggests that the Fermi surface of CeZn11 is very close to that of LaZn11 being dominated by Zn 3d , as the Ce 4 f states are localized and have little influence on its electronic structure, however, they are responsible for its magnetic order and contribute to enhance electronic correlations.

  16. Enhanced quantum oscillatory magnetization and nonequilibrium currents in an interacting two-dimensional electron system in MgZnO/ZnO with repulsive scatterers

    NASA Astrophysics Data System (ADS)

    Brasse, M.; Sauther, S. M.; Falson, J.; Kozuka, Y.; Tsukazaki, A.; Heyn, Ch.; Wilde, M. A.; Kawasaki, M.; Grundler, D.

    2014-02-01

    Torque magnetometry at low temperature and in high magnetic fields B is performed on MgZnO/ZnO heterostructures incorporating high-mobility two-dimensional electron systems. We find a sawtoothlike quantum oscillatory magnetization M (B), i.e., the de Haas-van Alphen (dHvA) effect. At the same time, nonequilibrium currents and unexpected spikelike overshoots in M are observed which allow us to identify the microscopic nature and density of the residual disorder. The acceptorlike scatterers give rise to a magnetic thaw down effect which enhances the dHvA amplitude beyond the electron-electron interaction effects being present in the MgZnO/ZnO heterostructures.

  17. Ultrasonic probe of the AuZn Fermi surface.

    SciTech Connect

    Svitelskiy, O.; Suslov, A. V.; Singleton, J. M.; Lashley, J. C.

    2005-01-01

    We, for the first time, apply the ultrasonic pulse-echo technique to explore the Fermi surface of the martensite phase of the single crystalline AuZn shape memory alloy. The ultrasonic measurements were performed in the magnetic fields of up to 45 T in the temperature range of 0.07 < T < 300 K. In the martensite phase (T < 64 K), the oscillations of the speed of the longitudinal sound wave propagating in the (110) direction indicated a strong acoustic de Haas - van Alphen effect. In addition to the earlier described oscillations with frequencies of 1140 and 4720 Tesla, we observed a new frequency of 120 Tesla, which was predicted theoretically. Corresponding effective masses were in favorable agreement with those expected from band structure calculations.

  18. Quasi-two-dimensional Fermi surface topography of the delafossite PdRhO2

    NASA Astrophysics Data System (ADS)

    Arnold, F.; Naumann, M.; Khim, S.; Rosner, H.; Sunko, V.; Mazzola, F.; King, P. D. C.; Mackenzie, A. P.; Hassinger, E.

    2017-08-01

    We report on a combined study of the de Haas-van Alphen effect and angle-resolved photoemission spectroscopy on single crystals of the metallic delafossite PdRhO2 rounded off by ab initio band structure calculations. A high-sensitivity torque magnetometry setup with superconducting quantum interference device readout and synchrotron-based photoemission with a light spot size of 50 μ m enabled high-resolution data to be obtained from samples as small as 150 ×100 ×20 (μm ) 3 . The Fermi surface shape is nearly cylindrical with a rounded hexagonal cross section enclosing a Luttinger volume of 1.00(1) electrons per formula unit.

  19. On the quantum magnetic oscillations of electrical and thermal conductivities of graphene

    NASA Astrophysics Data System (ADS)

    Alisultanov, Z. Z.; Reis, M. S.

    2016-05-01

    Oscillating thermodynamic quantities of diamagnetic materials, specially graphene, have been attracting attention of the scientific community due to the possibility to experimentally map the Fermi surface of the material. These have been the case of the de Haas-van Alphen and Shubnikov-de Haas effects, found on the magnetization and electrical conductivity, respectively. In this direction, managing the thermodynamic oscillations is of practical purpose, since from the reconstructed Fermi surface it is possible to access, for instance, the electronic density. The present work theoretically explores the quantum oscillations of electrical and thermal conductivities of a monolayer graphene under a crossed magnetic and electric fields. We found that the longitudinal electric field can increase the amplitude of the oscillations and this result is of practical and broad interest for both, experimental and device physics.

  20. Theoretical reconsideration of antiferromagnetic Fermi surfaces in URu2Su2

    NASA Astrophysics Data System (ADS)

    Yamagami, Hiroshi

    2011-01-01

    In an itinerant 5f-band model, the antiferromagnetic (AFM) Fermi surfaces of URu2Si2 are reconsidered using a relativistic LAPW method within a local spin-density approximation, especially taking into account the lattice parameters dependent on pressures. The reduction of the z-coordinate of the Si sites results in the effect of flattening the Ru-Si layers of URu2Si2 crystal structure, thus weakening a hybridization/mixing between the U-5f and Ru-4d states in the band structure. Consequently the 5f bands around the Fermi level are more flat in the dispersion with decreasing the z-coordinate, thus producing three closed Fermi surfaces like "curing-stone", "rugby-ball " and "ball". The origins of de Haas-van Alphen branches can be qualitatively interpreted from the obtained AFM Fermi surfaces.

  1. Berry phase and band structure analysis of the Weyl semimetal NbP

    PubMed Central

    Sergelius, Philip; Gooth, Johannes; Bäßler, Svenja; Zierold, Robert; Wiegand, Christoph; Niemann, Anna; Reith, Heiko; Shekhar, Chandra; Felser, Claudia; Yan, Binghai; Nielsch, Kornelius

    2016-01-01

    Weyl semimetals are often considered the 3D-analogon of graphene or topological insulators. The evaluation of quantum oscillations in these systems remains challenging because there are often multiple conduction bands. We observe de Haas-van Alphen oscillations with several frequencies in a single crystal of the Weyl semimetal niobium phosphide. For each fundamental crystal axis, we can fit the raw data to a superposition of sinusoidal functions, which enables us to calculate the characteristic parameters of all individual bulk conduction bands using Fourier transform with an analysis of the temperature and magnetic field-dependent oscillation amplitude decay. Our experimental results indicate that the band structure consists of Dirac bands with low cyclotron mass, a non-trivial Berry phase and parabolic bands with a higher effective mass and trivial Berry phase. PMID:27667203

  2. The Fermi surface and f-valence electron count of UPt{sub 3}.

    SciTech Connect

    McMullan, G. J.; Rourke, P. M. C.; Norman, M. R.; Huxley, A. D.; Doiron-Layraud, N.; Flouquet, J.; Lonzarich, G. G.; McCollam, A.; Julian, S. R.; Materials Science Division; MRC Lab. Molecular Biology; Univ. of Toronto; School of Phys. Edinburgh; Univ. de Sherbrooke; CEA Univ. of Cambridge

    2008-01-01

    Combining old and new de Haas-van Alphen (dHvA) and magnetoresistance data, we arrive at a detailed picture of the Fermi surface of the heavy fermion superconductor UPt{sub 3}. Our work was partially motivated by a new proposal that two 5f valence electrons per formula unit in UPt{sub 3} are localized by correlation effects--agreement with previous dHvA measurements of the Fermi surface was invoked in its support. Comprehensive comparison with our new observations shows that this 'partially localized' model fails to predict the existence of a major sheet of the Fermi surface, and is therefore less compatible with experiment than the originally proposed 'fully itinerant' model of the electronic structure of UPt{sub 3}. In support of this conclusion, we offer a more complete analysis of the fully itinerant band structure calculation, where we find a number of previously unrecognized extremal orbits on the Fermi surface.

  3. Topological change of the Fermi surface in ternary iron-pnictides with reduced c/a ratio: A dHvA study of CaFe2P2

    SciTech Connect

    Coldea, Amalia I.; Andrew, C.M.J.; Analytis, J.G.; McDonald, R.D.; Bangura, A.F.; Chu, J.-H.; Fisher, I.R.; Carrington, A.; /Bristol U.

    2010-05-26

    We report a de Haas-van Alphen effect study of the Fermi surface of CaFe{sub 2}P{sub 2} using low temperature torque magnetometry up to 45 T. This system is a close structural analogue of the collapsed tetragonal non-magnetic phase of CaFe{sub 2}As{sub 2}. We find the Fermi surface of CaFe{sub 2}P{sub 2} to differ from other related ternary phosphides in that its topology is highly dispersive in the c-axis, being three-dimensional in character and with identical mass enhancement on both electron and hole pockets ({approx} 1.5). The dramatic change in topology of the Fermi surface suggests that in a state with reduced (c/a) ratio, when bonding between pnictogen layers becomes important, the Fermi surface sheets are unlikely to be nested.

  4. Fermi surface of YBCO by DHVA

    SciTech Connect

    Smith, J.L.; Fowler, C.M.; Freeman, B.L.; Hults, W.L.; King, J.C.; Mueller, F.M.

    1991-01-01

    These proceedings demonstrate how far scientist have come in the last four years of high temperature superconductivity. Knowledge of the energy bands and Fermi surfaces from experiment has come rather late. Photoemission, first showed proof of the validity of the energy band calculations. Positron annihilation, presented by West, after a rough start, is now giving evidence of the Fermi surface. Both of these techniques involve electronic excitations and hence, although they show the Fermi surface, do not put as severe a constraint on various models for superconductivity as does the de Haas-van Alphen (dHvA) effect. This is a true measurement of the electronic ground state in an applied magnetic field where the frequency of oscillatory magnetization yields extremal cross-sectional areas of the Fermi surface. The authors have already reported some of their Fermi surface work at two conferences but present here discussion of several more important aspects of the work. 11 refs., 2 figs.

  5. The Fermi surfaces and the magnetic properties of Ce xLa 1- xP

    NASA Astrophysics Data System (ADS)

    Uesawa, A.; Haga, Y.; Suzuki, T.

    1997-02-01

    The measurement of the transport properties, the magnetic susceptibility, the magnetization, the magnetic specific heat and the de Haas-van Alphen (dHvA) effect are carried out for the dilute system Ce xLa 1- xP ( x = 0.02, 0.10, 0.50, 0.90) prepared by the mineralization method. The experiments for x = 0.02 and 0.10 are well explained by the isolate Ce 3+ ion with 4f Γ 7 ground state and weak interactions between them. It is show for the x = 0.50 sample that magnetization curve breaks its slope at 7 T with the antiferromagnetically ordering below TN = 3.4 K and that its moment is larger than the value expected from Γ 7 ground state. This indicates an appearance of the frist excited Γ 8 moments in spite of large crystalline splitting energy.

  6. Thermal expansion, heat capacity and magnetostriction of RAl3 (R = Tm, Yb, Lu) single crystals

    SciTech Connect

    Bud'ko, S.; Frenerick, J.; Mun, E.; Canfield, P.; Schmiedeshoff, G.

    2007-12-13

    We present thermal expansion and longitudinal magnetostriction data for cubic RAl{sub 3} (R = Tm, Yb, Lu) single crystals. The thermal expansion coefficient for YbAl{sub 3} is consistent with an intermediate valence of the Yb ion, whereas the data for TmAl{sub 3} show crystal electric field contributions and have strong magnetic field dependences. de Haas-van Alphen like oscillations were observed in the magnetostriction data for YbAl{sub 3} and LuAl{sub 3}, several new extreme orbits were measured and their effective masses were estimated. Specific heat data taken at 0 and 140 kOe for both LuAl{sub 3} and TmAl{sub 3} for T {le} 200 K allow for the determination of a crystal electric field splitting scheme for TmAl{sub 3}.

  7. Small plastic piston-cylinder cell for pulsed magnetic field studies at cryogenic temperatures

    NASA Astrophysics Data System (ADS)

    Coniglio, William A.; Graf, David E.; Tozer, Stanley W.

    2013-06-01

    A plastic piston-cylinder cell based on a thick wall test-tube has been designed for pulsed magnetic field studies. The small 12.7 mm diameter and overall height of 19.3 mm allow the cell to freely rotate in a cryostat with a diameter of 21.5 mm. Electrical leads, coax cable or microstrip transmission lines can be introduced into the pressure chamber for a variety of measurements such as electrical transport, de Haas-van Alphen, Shubnikov-de Haas and Hall effect. A fiber optic has been introduced for the purpose of calibrating the pressure via a ruby manometer. The fiber optic opens up additional experimental techniques such as photoluminescence, photoconductivity and, with use of a special fiber with a Bragg grating, magnetostriction and thermal expansion. Maximum pressures of 0.35 GPa at room temperature have been obtained.

  8. Magnetization in two-dimensional electron gas in a perpendicular magnetic field: The roles of edge states and spin-orbit coupling

    NASA Astrophysics Data System (ADS)

    Wang, Zhigang; Zhang, Wei; Zhang, Ping

    2009-06-01

    We study the de Haas-van Alphen (dHvA) oscillations in the magnetization of a two-dimensional electron gas under the influence of the edge states and/or the Rashba spin-orbit interaction (SOI). The boundaries of the systems lift partially the degeneracies of Landau levels (LLs) and the resulting edge states lead to the changes in both the center and the amplitude of the sawtoothlike magnetization oscillation. The SOI mixes the spin-up and spin-down states of neighboring LLs into two unequally spaced energy branches. The inclusion of SOI changes the well-defined sawtooth pattern of the dHvA oscillations in the magnetization. The weaker the magnetic field is, the larger the change in the dHvA oscillations is due to the edge effect and/or the spin-orbit coupling. Some theoretical results are compared with the experimental data.

  9. Fermi Surface Properties of Eu-Divalent and Eu-Trivalent Electronic States with the AuCu3-type Cubic Structure

    NASA Astrophysics Data System (ADS)

    Nakamura, Ai; Takeuchi, Tetsuya; Tatetsu, Yasutomi; Maehira, Takahiro; Harima, Hisatomo; Hedo, Masato; Nakama, Takao; Ōnuki, Yoshichika

    2015-03-01

    The electronic states in EuBi3 and EuPd3 are known to be Eu-divalent and Eu- trivalent, respectively, from the previous studies using polycrystal samples. In the present study, we succeeded in growing high-quality single crystals, and carried out the de Haas-van Alphen (dHvA) measurements and energy band calculations to clarify the Fermi surface properties.

  10. The Diamagnetic Phase Transition of Dense Electron Gas: Astrophysical Applications

    NASA Astrophysics Data System (ADS)

    Wang, Zhaojun; Lü, Guoliang; Zhu, Chunhua; Wu, Baoshan

    2016-10-01

    Neutron stars are ideal astrophysical laboratories for testing theories of the de Haas-van Alphen effect and diamagnetic phase transition which is associated with magnetic domain formation. The “magnetic interaction” between delocalized magnetic moments of electrons (the Shoenberg effect), can result in an effect of the diamagnetic phase transition into domains of alternating magnetization (Condon's domains). Associated with the domain formation are prominent magnetic field oscillation and anisotropic magnetic stress which may be large enough to fracture the crust of magnetar with a super-strong field. Even if the fracture is impossible as in “low-field” magnetar, the depinning phase transition of domain wall (DW) motion driven by low field rate (mainly due to the Hall effect) in the randomly perturbed crust can result in a catastrophically variation of magnetic field. This intermittent motion, similar to the avalanche process, makes the Hall effect be dissipative. These qualitative consequences about magnetized electron gas are consistent with observations of magnetar emission, and especially the threshold critical dynamics of driven DW can partially overcome the difficulties of “low-field” magnetar bursts and the heating mechanism of transient, or “outbursting” magnetar.

  11. Magnetotransport properties of the triply degenerate node topological semimetal tungsten carbide

    NASA Astrophysics Data System (ADS)

    He, J. B.; Chen, D.; Zhu, W. L.; Zhang, S.; Zhao, L. X.; Ren, Z. A.; Chen, G. F.

    2017-05-01

    We report the magnetoresistance (MR), Hall effect, and de Haas-van Alphen (dHvA) effect studies of single crystals of tungsten carbide, WC, which is predicted to be a new type of topological semimetal with triply degenerate nodes. With the magnetic field rotated in the plane perpendicular to the current, WC shows a field induced metal-to-insulator-like transition and large nonsaturating quadratic MR at low temperatures. As the magnetic field parallel to the current, a pronounced negative longitudinal MR only can be observed for a certain direction of current flow. The Hall effect indicates WC is a perfect compensated semimetal, which may be related to the large nonsaturating quadratic MR. The analysis of dHvA oscillations reveals that WC is a multiband system with small cross-sectional areas of Fermi surface and light cyclotron effective masses. Our results indicate that WC is an ideal platform to study the recently proposed "new fermions" with triply degenerate crossing points.

  12. Robust Resistive Critical Field in Noncentrosymmetric B20 AuBe

    NASA Astrophysics Data System (ADS)

    Rebar, Dj; Ditusa, Jf; Adams, P.; Ball, J.; Browne, D.; Vekhter, I.; Young, D.; Prestigiacomo, J.; Chan, Jy

    AuBe is a chiral-structured (B20 structure) superconductor. The B20 structure in magnetic systems was discovered to host a magnetic topological structure, the Skyrmion lattice, and our research focused on what behavior the same structure would effect in a superconducting system. Samples were arc-melted in an Ar atmosphere and characterized via powder XRD. Specific heat measurement revealed bulk superconductivity with an exponential form below Tc while magnetization showed Type I behavior near the Tc of 3.2 K and a crossover to Type II behavior at approximately 1.2 K. Resistance measurement revealed a critical field that deviates from that found in magnetization measurements at approximately 2.4 K linearly rising with decreasing T to approximately 3.5x Hc2 at T =0.3K. The resistive critical field was also found to be robust against a Cr film deposited on the surface of AuBe. We find similarity between this superconductivity crossover behavior and robust low temperature critical field with other noncentrosymmetric superconductors in literature. Additionally, we measured the de Haas-van Alphen effect in polycrystalline samples and derived an effective electron mass of 0.16mo for a small spherical piece of Fermi surface.

  13. Fermi Surface of the Pnictide Superconductor LaRu2 P 2 studied by quantum oscillations

    NASA Astrophysics Data System (ADS)

    Moll, Philip; Balakirev, Fedor; McDonald, Ross; Karpinski, Janusz; Bukowski, Zbigniew; Blaha, Peter; Schwarz, Karlheinz; Batlogg, Bertram

    2011-03-01

    LaRu 2 P2 is a stochiometric pnictide superconductor (Tc ~ 4.1 K) and crystallizes in the ThCr 2 Si 2 structure (the ``122'' pnictide family). We have mapped out its Fermi surface via the deHaas-vanAlphen effect in pulsed magnetic fields up to 60T (LANL/NHMFL). Pronounced oscillations were observed in the magnetic torque measured with a microcantilever setup. Two features are particularly noteworthy: The oscillations can be followed to surprisingly high temperatures beyond 20K, and the main frequency component at θ = 20circ; (θ = 0circ; at HIIc) is at 349T (α -peak), significantly lower than in the related compounds LaFe 2 P2 . A second frequency originating from a larger Fermi surface cross-section at 1921 T (β -peak) is identified. The temperature dependence of the amplitudes is well described by the Lifshitz- Kosevich formalism and gives low effective masses m*/m = 0.80 (α sheet) and 1.09 (β sheet). Therefore, most ``122'' metals appear to have similarly low effective masses.

  14. Anomalous behaviour of critical fields near a superconducting quantum critical point in BaFe2(As1-xPx)2

    NASA Astrophysics Data System (ADS)

    Putzke, C.; Carrington, A.; Walmsley, P.; Malone, L.; Fletcher, J. D.; See, P.; Vignolles, D.; Proust, C.; Badoux, S.; Kasahara, S.; Mazukami, Y.; Shibauchi, T.; Matsuda, Y.

    2014-03-01

    BaFe2(As1-xPx)2 presents one of the cleanest and clearest systems in which to study the influence of quantum critical fluctuations on high temperature superconductivity. In this material a sharp maximum in the magnetic penetration depth has been found at the quantum critical point (QCP x = 0 . 3) where Tc is maximal1. Specific heat and de Haas-van Alphen effect measurements2 show that this peak is driven by a corresponding increase in the quasiparticle effective mass. Based on these previous results a simple one-band theory would suggest that at the QCP we should expect a large increase in Hc 2 and a corresponding dip in Hc 1 . Actual measurements of these critical fields, which we present here, shows quite different behavior which we suggest is caused by an anomalous enhancement in the vortex core energy close to the QCP. 1 K.Hashimoto et.al., Science 336, 1554 (2012) 2 P.Walmsley, C.Putzke et.al., Phys. Rev. Lett. 110, 257002 (2013) This work was supported by the Engineering and Physical Sciences Research Council, EuroMagNET II, and KAKENHI from JSPS.

  15. Magnetic properties of multiferroics-semiconductors Eu1-xCexMn2O5

    NASA Astrophysics Data System (ADS)

    Sanina, V. A.; Golovenchits, E. I.; Zalesskii, V. G.; Scheglov, M. P.

    2011-11-01

    Studies of magnetization, magnetoresistance, and magnetic oscillations in semiconductor-multiferroics Eu1-xCexMn2O5 (x = 0.2-0.25) (ECMO) at temperatures ranging from 5 to 350 K in magnetic fields up to 6 T are presented. It is shown that phase separation and charge carrier self-organization in the crystals give rise to a layered superstructure perpendicular to the c axis. An effect of magnetic field cycling on the superstructure, magnetization, and magnetoresistance is demonstrated. X-ray diffraction studies of ECMO demonstrating the effect of magnetic field on the superstructure are presented. The de Haas-van Alphen magnetization oscillations in high magnetic fields and the temperature-induced magnetic oscillations in a fixed magnetic field are observed at low temperatures. Below 10 K the quantum corrections to magnetization due to the weak charge carrier localization in 2D superlattice layers occur. It is shown that at all the temperatures the Eu1-xCexMn2O5 magnetic state is dictated by superparamagnetism of isolated ferromagnetic domains.

  16. Quantum oscillations in iron-based superconductors: BaFe2As2 vs. KFe2As2

    NASA Astrophysics Data System (ADS)

    Terashima, Taichi; Kurita, Nobuyuki; Kimata, Motoi; Tomita, Megumi; Tsuchiya, Satoshi; Satsukawa, Hidetaka; Harada, Atsushi; Hazama, Kaori; Imai, Motoharu; Sato, Akira; Uji, Shinya; Kihou, Kunihiro; Lee, Chul-Ho; Kito, Hijiri; Tomioka, Yasuhide; Ito, Toshimitsu; Iyo, Akira; Eisaki, Hiroshi; Liang, Tian; Nakajima, Masamichi; Ishida, Shigeyuki; Uchida, Shin-ichi; Saito, Taku; Fukazawa, Hideto; Kohori, Yoh; Harima, Hisatomo

    2013-07-01

    We present results of Shubnikov-de Haas oscillation measurements on detwinned BaFe2As2 and de Haas-van Alphen oscillation measurements on KFe2As2. The Fermi surface of BaFe2As2 in the antiferromagnetic phase is found to consist of one hole and two electron pockets, all of which are three-dimensional and closed, and can reasonably be accounted for by LSD A band calculations. We find only moderate mass enhancements m*/mband of 2-3. In the case of KFe2As2, four quasi-two-dimensional Fermi surface cylinders epsilon, α, ζ, and β are observed in qualitative agreement with previous ARPES data. In sharp contrast to BaFe2As2, agreement between the observed and LDA-calculated Fermi surface is poor: LDA calculations seem to predict wrong crystal-field splitting of Fe 3d states. Large effective masses up to 20 me, me being the free electron mass, are found. The Sommerfeld coefficient estimated from the observed Fermi surface and effective masses is consistent with the measured value of 93 mJ/K2mol [H. Fukazawa et al., J. Phys. Soc. Jpn. 80, SA118 (2011)] and is 8-9 times larger than the band value, indicating strong electronic correlations in KFe2As2.

  17. Low-Temperature Magnetic Orderings and Fermi Surface Properties of LaCd11, CeCd11, and PrCd11 with a Caged Crystal Structure

    NASA Astrophysics Data System (ADS)

    Yoshiuchi, Shingo; Takeuchi, Tetsuya; Ohya, Masahiro; Katayama, Keisuke; Matsushita, Masaki; Yoshitani, Naohisa; Nishimura, Naoto; Ota, Hisashi; Tateiwa, Naoyuki; Yamamoto, Etsuji; Haga, Yoshinori; Yamagami, Hiroshi; Honda, Fuminori; Settai, Rikio; Ōnuki, Yoshichika

    2010-04-01

    We succeeded in growing single crystals of cage-structure compounds RCd11 (R: La, Ce, and Pr) and precisely studied their low-temperature magnetic and electronic properties by measuring electrical resistivity, magnetic susceptibility, magnetization, specific heat, and the de Haas-van Alphen (dHvA) effect. We found antiferromagnetic ordering at 0.44 and 0.39 K in CeCd11 and PrCd11, respectively, and clarified the magnetic phase diagrams of the compounds. In addition, low-lying crystalline electric field (CEF) schemes were proposed from the specific heat results of both compounds. From the present study, the antiferromagnetic ordering in PrCd11 is found to be of the exchange-induced type with a singlet ground state. From the dHvA experiment, we detected small dHvA branches ranging from 7× 105 to 2× 107 Oe, which correspond to small Fermi surfaces. This is mainly due to a small Brillouin zone based on a large unit cell. Moreover, the dHvA frequencies and cyclotron masses are approximately the same among RCd11, revealing a localized character of 4f electrons in CeCd11 and PrCd11.

  18. Quantum oscillations in a lead chalcogenide three-dimensional Dirac system

    NASA Astrophysics Data System (ADS)

    Orbanić, Filip; Novak, Mario; Baćani, Mirko; Kokanović, Ivan

    2017-01-01

    The de Haas-van Alphen (dHvA) and the Shubnikov-de Haas (SdH) oscillations were used to probe the properties of the Fermi surface in single crystals of Pb0.83Sn0.17Se with reduced charge concentration. Pronounced low-frequency oscillations of ˜8 T in the [001] direction were observed, confirming the single Fermi surface cross section. Due to the low effective charge concentration, the ultraquantum limit is reached already at ˜10 T. We observe π -Berry phase shift in the phase of both dHvA and SdH oscillations, which confirms the 3D Dirac nature of the energy band dispersion. In the construction of the Landau level diagram we use a combined indexing method for conductivity, magnetic susceptibility, and magnetization, which is based on the indexing used in the topological insulators. Moreover, the reliability of the indexing method is increased because we use, beside minima and maxima, zeros of the oscillations as well. Different microscopic parameters were calculated from the quantum oscillations in the magnetization, conductivity, and resistivity.

  19. A multi-component Fermi surface in the vortex state of an underdoped high-Tc superconductor.

    PubMed

    Sebastian, Suchitra E; Harrison, N; Palm, E; Murphy, T P; Mielke, C H; Liang, Ruixing; Bonn, D A; Hardy, W N; Lonzarich, G G

    2008-07-10

    To understand the origin of superconductivity, it is crucial to ascertain the nature and origin of the primary carriers available to participate in pairing. Recent quantum oscillation experiments on high-transition-temperature (high-T(c)) copper oxide superconductors have revealed the existence of a Fermi surface akin to that in normal metals, comprising fermionic carriers that undergo orbital quantization. The unexpectedly small size of the observed carrier pocket, however, leaves open a variety of possibilities for the existence or form of any underlying magnetic order, and its relation to d-wave superconductivity. Here we report experiments on quantum oscillations in the magnetization (the de Haas-van Alphen effect) in superconducting YBa(2)Cu(3)O(6.51) that reveal more than one carrier pocket. In particular, we find evidence for the existence of a much larger pocket of heavier mass carriers playing a thermodynamically dominant role in this hole-doped superconductor. Importantly, characteristics of the multiple pockets within this more complete Fermi surface impose constraints on the wavevector of any underlying order and the location of the carriers in momentum space. These constraints enable us to construct a possible density-wave model with spiral or related modulated magnetic order, consistent with experimental observations.

  20. Evidence from Fermi surface analysis for the low-temperature structure of lithium

    NASA Astrophysics Data System (ADS)

    Elatresh, Sabri F.; Cai, Weizhao; Ashcroft, N. W.; Hoffmann, Roald; Deemyad, Shanti; Bonev, Stanimir A.

    2017-05-01

    The low-temperature crystal structure of elemental lithium, the prototypical simple metal, is a several-decades-old problem. At 1 atm pressure and 298 K, Li forms a body-centered cubic lattice, which is common to all alkali metals. However, a low-temperature phase transition was experimentally detected to a structure initially identified as having the 9R stacking. This structure, proposed by Overhauser in 1984, has been questioned repeatedly but has not been confirmed. Here we present a theoretical analysis of the Fermi surface of lithium in several relevant structures. We demonstrate that experimental measurements of the Fermi surface based on the de Haas-van Alphen effect can be used as a diagnostic method to investigate the low-temperature phase diagram of lithium. This approach may overcome the limitations of X-ray and neutron diffraction techniques and makes possible, in principle, the determination of the lithium low-temperature structure (and that of other metals) at both ambient and high pressure. The theoretical results are compared with existing low-temperature ambient pressure experimental data, which are shown to be inconsistent with a 9R phase for the low-temperature structure of lithium.

  1. Fermi-surface topologies and low-temperature phases of the filled skutterudite compounds CeOs4Sb12 and NdOs4Sb12

    DOE PAGES

    Ho, Pei Chun; Singleton, John; Goddard, Paul A.; ...

    2016-11-28

    We use MHz conductivity, torque magnetometer, and magnetization measurements to report on single crystals of CeOs 4 Sb 12 and NdOs 4 Sb 12 using temperatures down to 0.5 K and magnetic fields of up to 60 tesla. The field-orientation dependence of the de Haas-van Alphen and Shubnikov-de Haas oscillations is deduced by rotating the samples about the [ 010 ] and [ 0more » $$\\bar{1}$$ 1 1 ] directions. Our results indicate that NdOs 4 Sb 12 has a similar Fermi surface topology to that of the unusual superconductor PrOs 4 Sb 12 , but with significantly smaller effective masses, supporting the importance of local phonon modes in contributing to the low-temperature heat capacity of NdOs 4 Sb 12 . By contrast, CeOs 4 Sb 12 undergoes a field-induced transition from an unusual semimetal into a high-field, high-temperature state characterized by a single, almost spherical Fermi-surface section. Furthermore, the behavior of the phase boundary and comparisons with models of the band structure lead us to propose that the field-induced phase transition in CeOs 4 Sb 12 is similar in origin to the well-known α - γ transition in Ce and its alloys.« less

  2. Fermi-surface topologies and low-temperature phases of the filled skutterudite compounds CeOs4Sb12 and NdOs4Sb12

    SciTech Connect

    Ho, Pei Chun; Singleton, John; Goddard, Paul A.; Balakirev, Fedor F.; Chikara, Shalinee; Yanagisawa, Tatsuya; Maple, M. Brian; Shrekenhamer, David B.; Lee, Xia; Thomas, Avraham T.

    2016-11-28

    We use MHz conductivity, torque magnetometer, and magnetization measurements to report on single crystals of CeOs 4 Sb 12 and NdOs 4 Sb 12 using temperatures down to 0.5 K and magnetic fields of up to 60 tesla. The field-orientation dependence of the de Haas-van Alphen and Shubnikov-de Haas oscillations is deduced by rotating the samples about the [ 010 ] and [ 0 $\\bar{1}$ 1 1 ] directions. Our results indicate that NdOs 4 Sb 12 has a similar Fermi surface topology to that of the unusual superconductor PrOs 4 Sb 12 , but with significantly smaller effective masses, supporting the importance of local phonon modes in contributing to the low-temperature heat capacity of NdOs 4 Sb 12 . By contrast, CeOs 4 Sb 12 undergoes a field-induced transition from an unusual semimetal into a high-field, high-temperature state characterized by a single, almost spherical Fermi-surface section. Furthermore, the behavior of the phase boundary and comparisons with models of the band structure lead us to propose that the field-induced phase transition in CeOs 4 Sb 12 is similar in origin to the well-known α - γ transition in Ce and its alloys.

  3. Fermi-surface topologies and low-temperature phases of the filled skutterudite compounds CeOs4Sb12 and NdOs4Sb12

    NASA Astrophysics Data System (ADS)

    Ho, Pei Chun; Singleton, John; Goddard, Paul A.; Balakirev, Fedor F.; Chikara, Shalinee; Yanagisawa, Tatsuya; Maple, M. Brian; Shrekenhamer, David B.; Lee, Xia; Thomas, Avraham T.

    2016-11-01

    MHz conductivity, torque magnetometer, and magnetization measurements are reported on single crystals of CeOs4Sb12 and NdOs4Sb12 using temperatures down to 0.5 K and magnetic fields of up to 60 tesla. The field-orientation dependence of the de Haas-van Alphen and Shubnikov-de Haas oscillations is deduced by rotating the samples about the [010 ] and [0 1 ¯1 ] directions. The results indicate that NdOs4Sb12 has a similar Fermi surface topology to that of the unusual superconductor PrOs4Sb12 , but with significantly smaller effective masses, supporting the importance of local phonon modes in contributing to the low-temperature heat capacity of NdOs4Sb12 . By contrast, CeOs4Sb12 undergoes a field-induced transition from an unusual semimetal into a high-field, high-temperature state characterized by a single, almost spherical Fermi-surface section. The behavior of the phase boundary and comparisons with models of the band structure lead us to propose that the field-induced phase transition in CeOs4Sb12 is similar in origin to the well-known α -γ transition in Ce and its alloys.

  4. A Local-Density Band Theory for the Fermi Surface of the Heavy-Electron Compound CeRu2Si2

    NASA Astrophysics Data System (ADS)

    Yamagami, Hiroshi; Hasegawa, Akira

    1993-02-01

    On the basis of the itinerant-electron model for the 4f electrons, the energy band structure and the Fermi surface are calculated for the metamagnetic heavy-electron compound CeRu2Si2 having the low-temperature electronic specific heat coefficient γ of 350 mJ/K2 mol. by a self-consistent symmetrized relativistic APW method with the exchange and correlation potential in a local-density approximation. The main Fermi surface consists of a large closed hole sheet and a complicated electron sheet like a jungle gym. The Fermi surface topology is consistent with the experimental result for the high-field magneto-resistance. By comparison with the electronic structure of LaRu2Si2, effects of the 4f bands on the Bloch states on the Fermi surface in CeRu2Si2 are investigated in detail. Strong evidences for existence of the electron sheet are found in available experimental de Haas-van Alphen frequencies. The enhancement factor for γ is estimated as 38.

  5. Investigation of the production and properties of lattice defects induced by low temperature reactor irradiation

    NASA Astrophysics Data System (ADS)

    Mansel, W.; Mueller, P.; Marangos, J.; Wahl, D.; Wallner, G.; Weck, W.; Riem, R.; Glaeser, W.

    1984-03-01

    Defects in irradiated metals were investigated. In the project defect production rate neutron spectra in the irradiated position of a low temperature irradiation stand are determined using the multiple probe activation method. In the project Mossbauer spectroscopy the trapping of interstitial atoms on 57C-impurity atoms in W and V is observed. It is found that in W interstitial atoms are mobile at 25 K. For Mo57Co a detailed understanding of the reactions between impurity and interstitial atoms is obtained. In the project alkali metals the mobility of interstitial atoms in K, Na and Li at 5K is demonstrated by resistivity measurements; step III lies at 16K. The investigations of the magnetic resistance on irradiated or worked K show that the macroscopic, residual defect systems in the samples are responsible for the anomalous linear evolution of the longitudinal high field magnetic resistance. In the project Fermi surfaces of Bi with lattice defects de Haas-van Alphen effect measurements on irradiated Bi show an increase up to 100% of the Fermi surface cross sections of the electron ellipsoid and a simultaneous decrease of the vacancies Fermi surface cross sections.

  6. Magnetic properties of Ce3+ in PbCeA (A= Te, Se, S)

    NASA Astrophysics Data System (ADS)

    Isber, S.; Gratens, X.; Charar, S.; Golacki, Z.

    2013-01-01

    The magnetic susceptibility of Pb1-xCexA (A = S, Se and Te) crystals with 0.006 ≤ x ≤ 0.036 were studied in the temperature range from 20 mK up to room temperature. X-band (~9.5 GHz) Electron Paramagnetic Resonance (EPR) showed small shifts in the effective Landé factors that were attributed to crystal-field admixture. The EPR measurements were correlated with the magnetic susceptibility data and resulted in estimating the crystal-field splitting Δ = E(Γ8) - E(Γ7) of the lowest 2F5/2 manifold for Ce3+ ions in PbA (A = S, Se and Te) of about 340 K, 440 K and 540 K for Pb1-xCexTe, Pb1-xCexSe, and Pb1-xCexS, respectively. The values for the crystal-field splitting deduced from the magnetic data were found to be in agreement with the calculated ones based on the point charge model. Moreover, the deHaas van-Alphen magnetic oscillations in the susceptibility measurements of Pb1-xCexTe (x~ 0.05 and 0.07) were observed at ultra-low temperature (20 mK); The oscillations were investigated and the values of the oscillatory period for Pb1-xCexTe (x = 0.0048 and 0.007) are reported.

  7. Evidence from Fermi surface analysis for the low-temperature structure of lithium.

    PubMed

    Elatresh, Sabri F; Cai, Weizhao; Ashcroft, N W; Hoffmann, Roald; Deemyad, Shanti; Bonev, Stanimir A

    2017-05-23

    The low-temperature crystal structure of elemental lithium, the prototypical simple metal, is a several-decades-old problem. At 1 atm pressure and 298 K, Li forms a body-centered cubic lattice, which is common to all alkali metals. However, a low-temperature phase transition was experimentally detected to a structure initially identified as having the 9R stacking. This structure, proposed by Overhauser in 1984, has been questioned repeatedly but has not been confirmed. Here we present a theoretical analysis of the Fermi surface of lithium in several relevant structures. We demonstrate that experimental measurements of the Fermi surface based on the de Haas-van Alphen effect can be used as a diagnostic method to investigate the low-temperature phase diagram of lithium. This approach may overcome the limitations of X-ray and neutron diffraction techniques and makes possible, in principle, the determination of the lithium low-temperature structure (and that of other metals) at both ambient and high pressure. The theoretical results are compared with existing low-temperature ambient pressure experimental data, which are shown to be inconsistent with a 9R phase for the low-temperature structure of lithium.

  8. Two-dimensional Fermi surfaces in Kondo insulating SmB6

    NASA Astrophysics Data System (ADS)

    Li, Gang

    There has been renewed interest in Samarium Hexaboride, which is a strongly correlated heavy Fermion material. Hybridization between itinerant electrons and localized orbitals lead to an opening of charge gap at low temperature. However, the resistivity of SmB6 does not diverge at low temperature. Former studies suggested that this residual conductance is contributed by various origins. Recent theoretical developments suggest that the particular symmetry of energy bands of SmB6 may host a topologically non-trivial surface state, i.e., a topological Kondo insulator. To probe the Fermiology of the possible metallic surface state, we use sensitive torque magnetometry to detect the de Haas van Alphen (dHvA) effect due to Landau level quantization on flux-grown crystals, down to He-3 temperature and up to 45 Tesla. Our angular and temperature dependent data suggest two-dimensional Fermi Surfaces lie in both crystalline (001) and (101) surface planes of SmB6.

  9. Quantum oscillations of the superconductor LaRu2P2: Comparable mass enhancement λ≈1 in Ru and Fe phosphides

    NASA Astrophysics Data System (ADS)

    Moll, Philip J. W.; Kanter, Jakob; McDonald, Ross D.; Balakirev, Fedor; Blaha, Peter; Schwarz, Karlheinz; Bukowski, Zbigniew; Zhigadlo, Nikolai D.; Katrych, Sergiy; Mattenberger, Kurt; Karpinski, Janusz; Batlogg, Bertram

    2011-12-01

    We have studied the angular-dependent de Haas-van Alphen oscillations of LaRu2P2 using magnetic torque in pulsed magnetic fields up to 60 T. The observed oscillation frequencies are in excellent agreement with the geometry of the calculated Fermi surface. The temperature dependence of the oscillation amplitudes reveals effective masses m*(α)=0.71 and m*(β)=0.99 me, which are enhanced over the calculated band mass by λcyc of 0.8. We find a similar enhancement of λγ≈1 in comparing the measured electronic specific heat (γ=11.5 mJ/mol K2) with the total density of states from band-structure calculations. Remarkably, very similar mass enhancements have been reported in other pnictides, LaFe2P2, LaFePO (Tc≈4K), and LaRuPO, independent of whether they are superconducting or not. This is contrary to the common perceptions that the normal-state quasiparticle renormalizations reflect the strength of the superconducting pairing mechanism and leads to new questions about pairing in isostructural and isoelectronic Ru- and Fe-pnictide superconductors.

  10. Quantum oscillations in superconductors in magnetic field

    NASA Astrophysics Data System (ADS)

    Gvozdikov, Vladimir M.; Gvozdikova, Mariya V.

    2000-07-01

    The Aharonov-Bohm oscillations (ABO) of the free energy, the critical temperature, and the magnetic susceptibility in a stack of hollow mesoscopic cylinders are calculated. It is shown that sinusoidal (in flux) ABO crosses over to the parabolic Little-Parks oscillations (LPO) when the diameter of cylinders exceeds the coherence length. The exponential temperature behaviour of the magnetic susceptibility is like that found in Ag cylinders with thin Nb coating [Czech. J. Physics 46 (1996) 2317]. The formal analogy between oscillations of the free energy in the Aharonov-Bohm system in question and the de Haas-van Alphen oscillations (dHvAO) in layered superconductors is discussed.

  11. The electronic structure of Lu

    NASA Astrophysics Data System (ADS)

    Tibbetts, T. A.; Harmon, B. N.

    1982-12-01

    The electronic structure of hcp Lu has been calculated using a linearized augmented plane wave (LAPW) method and the Hedin-Lundqvist local density approximation for exchange and correlation. Although complete self-consistency was hindered by the proximity of the 4f levels to the Fermi energy, the valence bands were converged and the calculation yielded a Fermi surface remarkably similar to that calculated by Keeton and Loucks. Comparison is made with recent de Haas-van Alphen and neutron magnetic form factor experiments.

  12. High-frequency magnetic oscillations of the organic metal θ-(ET)4ZnBr4(C6H4Cl2) in pulsed magnetic field of up to 81 T

    NASA Astrophysics Data System (ADS)

    Béard, J.; Billette, J.; Suleiman, M.; Frings, P.; Knafo, W.; Scheerer, G. W.; Duc, F.; Vignolles, D.; Nardone, M.; Zitouni, A.; Delescluse, P.; Lagarrigue, J.-M.; Giquel, F.; Griffe, B.; Bruyant, N.; Nicolin, J.-P.; Rikken, G. L. J. A.; Lyubovskii, R. B.; Shilov, G. V.; Zhilyaeva, E. I.; Lyubovskaya, R. N.; Audouard, A.

    2012-09-01

    De Haas-van Alphen oscillations of the organic metal θ-(ET)4ZnBr4(C6H4Cl2) are studied in pulsed magnetic fields up to 81 T. The long decay time of the pulse allows determining reliable field-dependent amplitudes of Fourier components with frequencies up to several kiloteslas. The Fourier spectrum is in agreement with the model of a linear chain of coupled orbits. In this model, all the observed frequencies are linear combinations of the frequency linked to the basic orbit α and to the magnetic-breakdown orbit β.

  13. Thermodynamic anomaly above the superconducting critical temperature in the quasi-one-dimensional superconductor Ta4Pd3Te16

    NASA Astrophysics Data System (ADS)

    Helm, T.; Flicker, F.; Kealhofer, R.; Moll, P. J. W.; Hayes, I. M.; Breznay, N. P.; Li, Z.; Louie, S. G.; Zhang, Q. R.; Balicas, L.; Moore, J. E.; Analytis, J. G.

    2017-02-01

    We study the intrinsic electronic anisotropy and fermiology of the quasi-one-dimensional superconductor Ta4Pd3Te16 . Below T*=20 K, we detect a thermodynamic phase transition that predominantly affects the conductivity perpendicular to the quasi-one-dimensional chains. The transition relates to the presence of charge order that precedes superconductivity. Remarkably, the Fermi surface pockets detected by de Haas-van Alphen oscillations are unaffected by this transition, suggesting that the ordered state does not break any translational symmetries but rather alters the scattering of the quasiparticles themselves.

  14. Effects of oxygen plasma etching on Sb{sub 2}Te{sub 3} explored by torque detected quantum oscillations

    SciTech Connect

    Yan, Yuan E-mail: martin.dressel@pi1.physik.uni-stuttgart.de; Heintze, Eric; Pracht, Uwe S.; Blankenhorn, Marian; Dressel, Martin E-mail: martin.dressel@pi1.physik.uni-stuttgart.de

    2016-04-25

    De Haas–van Alphen measurements evidence that oxygen plasma etching strongly affects the properties of the three-dimensional topological insulator Sb{sub 2}Te{sub 3}. The quantum oscillations in magnetization down to low temperature (T ≥ 2 K) and high magnetic field (B ≤ 7 T) have been systematically investigated using a high-sensitive cantilever torque magnetometer. The effective mass and the oscillation frequency obtained from de Haas–van Alphen measurements first increase and then decrease as the oxygen plasma etching time increases from 0 to 12 min, corresponding to an up- and down-shift of the Dirac point. We establish the cantilever torque magnetometer as a powerful contactless tool to investigate the oxygen sensitivity of the surface state in topological insulators.

  15. Superconducting properties of K1-xNaxFe2As2 under pressure

    NASA Astrophysics Data System (ADS)

    Grinenko, V.; Schottenhamel, W.; Wolter, A. U. B.; Efremov, D. V.; Drechsler, S.-L.; Aswartham, S.; Kumar, M.; Wurmehl, S.; Roslova, M.; Morozov, I. V.; Holzapfel, B.; Büchner, B.; Ahrens, E.; Troyanov, S. I.; Köhler, S.; Gati, E.; Knöner, S.; Hoang, N. H.; Lang, M.; Ricci, F.; Profeta, G.

    2014-09-01

    The effects of hydrostatic pressure and partial Na substitution on the normal-state properties and the superconducting transition temperature (Tc) of K1-xNaxFe2As2 single crystals were investigated. It was found that a partial Na substitution leads to a deviation from the standard T2 Fermi-liquid behavior in the temperature dependence of the normal-state resistivity. It was demonstrated that non-Fermi-liquid like behavior of the resistivity for K1-xNaxFe2As2 and some KFe2As2 samples can be explained by a disorder effect in the multiband system with rather different quasiparticle effective masses. Concerning the superconducting state our data support the presence of a shallow minimum around 2 GPa in the pressure dependence of Tc for stoichiometric KFe2As2. The analysis of Tc in K1-xNaxFe2As2 at pressures below 1.5 GPa showed that the reduction of Tc with Na substitution follows the Abrikosov-Gor'kov law with the critical temperature Tc0 of the clean system (without pair breaking), which linearly depends on the pressure. Our observations also suggest that Tc of K1-xNaxFe2As2 is nearly independent of the lattice compression produced by the Na substitution. Further, we theoretically analyzed the behavior of the band structure under pressure within the generalized gradient approximation (GGA). A qualitative agreement between the calculated and the recently measured—in de Haas-van Alphen experiments [T. Terashima et al., Phys. Rev. B 89, 134520 (2014), 10.1103/PhysRevB.89.134520]—pressure dependencies of the Fermi-surface cross sections has been found. These calculations also indicate that the observed minimum around 2 GPa in the pressure dependence of Tc may occur without a change of the pairing symmetry.

  16. Superconductivity on the verge of electronic topological transition in Fe based superconductors

    NASA Astrophysics Data System (ADS)

    Ghosh, Haranath; Sen, Smritijit

    2017-04-01

    A comprehensive first principles study on the electronic topological transition in a number of 122 family of Fe based superconductors is presented. Doping as well as temperature driven Lifshitz transitions are predicted from ab-initio simulations in a variety of Fe based superconductors that are consistent with experimental findings. In all the studied compounds the Lifshitz transitions are consistently found to take place at a doping concentration just around where superconductivity is known to acquire the highest Tc and magnetism disappears. This indicates the intriguing heed to the inter-relationship between superconductivity and Lifshitz transition in Fe-based 122 materials. Systematically, the Lifshitz transition occurs (above certain threshold doping) in some of the electronic Fermi surfaces for hole doped 122 compounds, whereas in hole Fermi surfaces for electron as well as iso-electronic doped 122 compounds. Temperature driven Lifshitz transition is found to occur in the iso-electronic Ru-doped BaFe2As2 compounds. A systematic study of Fermi surface area e.g., variations of (i) areas of each individual Fermi surfaces, (ii) sum total areas of all the electron Fermi Surfaces, (iii) sum total areas of all the hole Fermi Surfaces, (iv) sum total areas of all the five Fermi Surfaces, (v) difference of all hole and all electron Fermi surface areas as a function of doping is a rare wealth of information that can be verified by the de Haas-van Alphen and allied effects (i.e. , Shubnikov-de Haas effect) are presented. Fermi surface area are found to carry sensitivity of topological modifications more acutely than the band structures and can be used as a better experimental tool to identify ETT/LT.

  17. Three-quarter Dirac points, Landau levels, and magnetization in α -(BEDT-TTF ) 2I3

    NASA Astrophysics Data System (ADS)

    Kishigi, Keita; Hasegawa, Yasumasa

    2017-08-01

    The energies as a function of the magnetic field (H ) and the pressure are studied theoretically in the tight-binding model for the two-dimensional organic conductor α -(BEDT-TTF ) 2I3 , in which massless Dirac fermions are realized. The effects of the uniaxial pressure (P ) are studied by using the pressure-dependent hopping parameters. The system is semimetallic with the same area of an electron pocket and a hole pocket at P <3.0 kbar, where the energies (ɛD0 ) at the Dirac points locate below the Fermi energy (ɛF0 ) when H =0 . We find that at P =2.3 kbar the Dirac cones are critically tilted. In that case a type of band crossing occurs at "three-quarter" Dirac points; i.e., the dispersion is quadratic in one direction and linear in the other three directions. We obtain magnetic field dependencies of the Landau levels (ɛn) : ɛn-ɛD0∝(nH ) 4 /5 at P =2.3 kbar (three-quarter Dirac points) and | ɛn-ɛF0|∝(nH ) 2 at P =3.0 kbar (the critical pressure for the semimetallic state). We also study the magnetization as a function of the inverse magnetic field. We obtain two types of quantum oscillations. One is the usual de Haas-van Alphen (dHvA) oscillation, and the other is the unusual dHvA-like oscillation which is seen even in the system without the Fermi surface.

  18. Edge states, Aharonov-Bohm oscillations, and thermodynamic and spectral properties in a two-dimensional electron gas with an antidot

    SciTech Connect

    Bogachek, E.N.; Landman, U.

    1995-11-15

    The thermodynamic and spectral properties of a two-dimensional electron gas with an antidot in a strong magnetic field, {ital r}{sub {ital c}}{le}{ital r}{sub 0}, where {ital r}{sub {ital c}} is the cyclotron radius and {ital r}{sub 0} is the antidot effective radius, are studied via a solvable model with the antidot confinement potential {ital U}{similar_to}1/{ital r}{sup 2}. The edge states localized at the antidot boundary result in an Aharonov-Bohm-type oscillatory dependence of the magnetization as a function of the magnetic field flux through the antidot. These oscillations are superimposed on the de Haas--van Alphen oscillations. In the strong-field limit, {h_bar}{omega}{sub {ital c}}{similar_to}{epsilon}{sub {ital F}}, where {omega}{sub {ital c}} is the cyclotron frequency and {epsilon}{sub {ital F}} is the Fermi energy, the amplitude of the Aharonov-Bohm-type oscillations of the magnetization due to the contribution of the lowest edge state is {similar_to}{mu}{sub {ital B}}{ital k}{sub {ital F}}{ital r}{sub {ital c}} ({mu}{sub {ital B}} is the Bohr magneton and {ital k}{sub {ital F}} is the Fermi wave vector). When the magnetic field is decreased, higher edge states can contribute to the magnetization, leading to the appearance of a beating pattern in the Aharonov-Bohm oscillations. The role of temperature in suppressing the oscillatory contribution due to higher edge states is analyzed. Rapid oscillations of the magnetization as a function of the Aharonov-Bohm flux, occurring on a scale of a small fraction of the flux quantum {ital hc}/{ital e}, are demonstrated. The appearance of a manifold of non- equidistant frequencies in the magneto-optical-absorption spectrum, due to transitions between electronic edge states localized near the antidot boundary, is predicted.

  19. Low Temperature Physics at Yale in the late 30's through the early 50's

    NASA Astrophysics Data System (ADS)

    Wheeler, Robert

    2006-03-01

    The low temperature program at Yale was initiated by C. T. Lane (1904-1991) in the fall of 1937 when he was appointed to the teaching staff as an instructor in the department of Physics. Following his doctorate from McGill in 1929 he investigated the magnetic susceptibilities of ``soft'' metals supported by the National Research Council of Canada, the Commissioners of the 1851 Exhibition and a Sterling Fellowship at Yale. Arranged by Louis McKeehan, with 5000 from the new George Sheffield research fund, he started the construction of a Kapitza type helium liquefier. The machine was largely completed in the fall of 1939, yet liquid helium was not made until early December 1940 due to the need for extensive on line purification of the gas. Returning in 1945 from war research, Lane and Henry A. Fairbank (Ph.D 1944) continued the metals work along with new thrusts into Second Sound , properties of helium^ three impurities in liquid helium and starting in the 50's on rotating He II. In 1933 both Lane and Onsager were awarded Sterling Fellowships, which initiated a stimulating experimental- theoretical exchange continuing until they both retired. The best-known example was the rediscovery at Yale of the deHaas-van Alphen effect, previously observed only in bismuth, in zinc; where upon Onsager and his students provided new insights into our understanding of the Fermi surface of metals. With the development of new instrumentation one observed vast changes in experimental style during this period. The evolution of the production of liquid helium from Lane's device though the Collins machine to the commodity business of today now makes experiments of huge size and importance possible.

  20. Entropy and Fermi surface considerations in the nematic phase of Sr3Ru2O7

    NASA Astrophysics Data System (ADS)

    MacKenzie, Andrew

    2010-03-01

    The layered perovskite metal Sr3Ru2O7 has generated interest because of the discovery of nematic-like electrical transport properties at low temperatures [1]. The unusual properties are seen in the vicinity of a metamagnetic quantum critical point. They appear to be the result of the formation of a new phase, which can be observed only in the highest purity single crystals, with mean free paths of several thousand angstroms. Recently, my group has concentrated on understanding this phase and determining its boundaries using thermodynamic probes. In this talk I will review the physics that we believe underlies our observations, and then report on the recent progress, showing how measurements of the specific heat and magneto-caloric effect enable the determination of a complete ``entropy landscape'' of phase formation in the vicinity of a quantum critical point [2]. I will also discuss the discovery of de Haas-van Alphen oscillations within the putative electronic nematic phase [3]. [4pt] [1] R.A. Borzi, S.A. Grigera, J. Farrell, R.S. Perry, S. Lister, S.L. Lee, D.A. Tennant, Y. Maeno & A.P. Mackenzie, Science 315, 214 (2007). [0pt] [2] A.W. Rost, R.S. Perry, J.F. Mercure, A.P. Mackenzie & S.A. Grigera, Science 325, 1360 (2009). [0pt] [3] J.-F. Mercure, S. K. Goh, E. C. T. O'Farrell, R. S. Perry, M. L. Sutherland, A. Rost, S. A. Grigera, R. A. Borzi, P. Gegenwart and A. P. Mackenzie, Phys. Rev. Lett. 103, 176401 (2009).

  1. Fermi Surface and Van Hove Singularities in the Itinerant Metamagnet Sr(3)Ru(2)O(7)

    SciTech Connect

    Tamai, A.; Allan, M.P.; Mercure, J.F.; Meevasana, W.; Dunkel, R.; Lu, D.H.; Perry, R.S.; Mackenzie, A.P.; Singh, D.J.; Shen, Z.-X.; Baumberger, F.; /Scottish U. Research Reactor Ctr. /St. Andrews U.

    2011-01-04

    The low-energy electronic structure of the itinerant metamagnet Sr{sub 3}Ru{sub 2}O{sub 7} is investigated by angle resolved photoemission and density functional calculations. We find well-defined quasiparticle bands with resolution limited line widths and Fermi velocities up to an order of magnitude lower than in single layer Sr{sub 2}RuO{sub 4}. The complete topography, the cyclotron masses and the orbital character of the Fermi surface are determined, in agreement with bulk sensitive de Haas - van Alphen measurements. An analysis of the dxy band dispersion reveals a complex density of states with van Hove singularities (vHs) near the Fermi level; a situation which is favorable for magnetic instabilities.

  2. Fermi surface measurements of lutetium

    NASA Astrophysics Data System (ADS)

    Johanson, W. R.; Crabtree, G. W.; Schmidt, F. A.

    1982-03-01

    We report de Haas-van Alphen (dHvA) measurements of the Fermi surface of lutetium at temperatures down to 0.3 K and in fields up to 150 kG in the (101¯0) and (112¯0) planes. Lutetium, having a filled 4f shell, serves as a nonmagnetic prototype of the structurally similar (hcp), trivalent, heavy rare earths from Gd to Tm. No complete frequency branches were observed, indicating that there are no closed pieces of surface. We observed all but one orbit predicted by relativistic-augmented-plane wave (RAPW) calculations of Keeton and Loucks, and the data support a geometry that is in good qualitative agreement with the existence of nested open electron and hole sheets.

  3. Fermi surface measurements of lutetium

    SciTech Connect

    Johanson, W.R.; Crabtree, G.W.; Schmidt, F.A.

    1982-03-01

    We report de Haas-van Alphen (dHvA) measurements of the Fermi surface of lutetium at temperatures down to 0.3 K and in fields up to 150 kG in the (1010) and (1120) planes. Lutetium, having a filled 4f shell, serves as a nonmagnetic prototype of the structurally similar (hcp), trivalent, heavy rare earths from Gd to Tm. No complete frequency branches were observed, indicating that there are no closed pieces of surface. We observed all but one orbit predicted by relativistic-augmented-plane wave (RAPW) calculations of Keeton and Loucks, and the data support a geometry that is in good qualitative agreement with the existence of nested open electron and hole sheets.

  4. Fermi surface measurements of lutetium

    SciTech Connect

    Johanson, W.R.; Crabtree, G.W.; Schmidt, F.A.

    1982-01-01

    We report de Haas-van Alphen (dHvA) measurements of the Fermi surface of Lutetium at temperatures down to .3K and in fields up to 150 kG in the (1010) and (1120) planes. Lutetium, having a filled 4f shell, serves as a non-magnetic prototype of the structurally similar (hcp), trivalent, heavy rare-earths from Gd to Tm. No complete frequency branches were observed, indicating that there are no closed pieces of surface. We observed all but one orbit predicted by relativistic-augmented-plane wave (RAPW) calculations of Keeton and Loucks, and the data support a geometry that is in good qualitative agreement with the existence of nested open electron and hole sheets.

  5. Organic Superconductors

    SciTech Connect

    Charles Mielke

    2009-02-27

    Intense magnetic fields are an essential tool for understanding layered superconductors. Fundamental electronic properties of organic superconductors are revealed in intense (60 tesla) magnetic fields. Properties such as the topology of the Fermi surface and the nature of the superconducting order parameter are revealed. With modest maximum critical temperatures~13K the charge transfer salt organic superconductors prove to be incredibly valuable materials as their electronically clean nature and layered (highly anisotropic) structures yield insights to the high temperature superconductors. Observation of de Haas-van Alphen and Shubnikov-de Haas quantum oscillatory phenomena, magnetic field induced superconductivity and re-entrant superconductivity are some of the physical phenomena observed in the charge transfer organic superconductors. In this talk, I will discuss the nature of organic superconductors and give an overview of the generation of intense magnetic fields; from the 60 tesla millisecond duration to the extreme 1000 tesla microsecond pulsed magnetic fields.

  6. Quantum oscillations without magnetic field

    NASA Astrophysics Data System (ADS)

    Liu, Tianyu; Pikulin, D. I.; Franz, M.

    2017-01-01

    When the magnetic field B is applied to a metal, nearly all observable quantities exhibit oscillations periodic in 1 /B . Such quantum oscillations reflect the fundamental reorganization of electron states into Landau levels as a canonical response of the metal to the applied magnetic field. We predict here that, remarkably, in the recently discovered Dirac and Weyl semimetals, quantum oscillations can occur in the complete absence of magnetic field. These zero-field quantum oscillations are driven by elastic strain which, in the space of the low-energy Dirac fermions, acts as a chiral gauge potential. We propose an experimental setup in which the strain in a thin film (or nanowire) can generate a pseudomagnetic field b as large as 15 T and demonstrate the resulting de Haas-van Alphen and Shubnikov-de Haas oscillations periodic in 1 /b .

  7. Field-induced gapless electron pocket in the superconducting vortex phase of YNi2B2C as probed by magnetoacoustic quantum oscillations

    NASA Astrophysics Data System (ADS)

    Nössler, J.; Seerig, R.; Yasin, S.; Uhlarz, M.; Zherlitsyn, S.; Behr, G.; Drechsler, S.-L.; Fuchs, G.; Rosner, H.; Wosnitza, J.

    2017-01-01

    By use of ultrasound studies we resolved magnetoacoustic quantum oscillation deep into the mixed state of the multiband nonmagnetic superconductor YNi2B2C . Below the upper critical field, only a very weak additional damping appears that can be well explained by the field inhomogeneity caused by the flux-line lattice in the mixed state. This is clear evidence for no or a vanishingly small gap for one of the bands, namely, the spheroidal α band. This contrasts de Haas-van Alphen data obtained by use of torque magnetometry for the same sample, with a rapidly vanishing oscillation signal in the mixed state. This points to a strongly distorted flux-line lattice in the latter case that, in general, can hamper a reliable extraction of gap parameters by use of such techniques.

  8. Phase analysis of quantum oscillations in graphite.

    PubMed

    Luk'yanchuk, Igor A; Kopelevich, Yakov

    2004-10-15

    The quantum de Haas-van Alphen (dHvA) and Shubnikov-de Haas oscillations measured in graphite were decomposed by pass-band filtering onto contributions from three different groups of carriers. Generalizing the theory of dHvA oscillations for 2D carriers with an arbitrary spectrum and by detecting the oscillation frequencies using a method of two-dimensional phase-frequency analysis which we developed, we identified these carriers as (i) minority holes having a 2D parabolic massive spectrum p(2)(perpendicular)/2m(perpendicular), (ii) massive majority electrons with a 3D spectrum and (iii) majority holes with a 2D Dirac-like spectrum +/-vp(perpendicular) which seems to be responsible for the unusual strongly-correlated electronic phenomena in graphite.

  9. Kinetic phenomena in organic conductors in high magnetic fields (Review Article)

    NASA Astrophysics Data System (ADS)

    Peschansky, V. G.; Stepanenko, D. I.

    2016-11-01

    A review of experimental and theoretical studies of transport phenomena in strongly anisotropic organic conductors is presented. Considerable attention is paid to the phenomena that are specific to quasi-2D and quasi-1D conductive structures and have no analogues both in ordinary metals and in truly 2D or 1D conducting systems. Angular magnetoresistance oscillations, de Haas-van Alphen and Shubnikov-de Haas phenomena, high-temperature quantum oscillations of the magnetoresistance, and high-frequency resonances, including those arising due to the motion of electrons open trajectories, are discussed. The resonant angular oscillations of high-frequency conductivity and weakly damped electromagnetic waves in quasi-2D organic conductors under strong spatial dispersion are considered.

  10. The Fermi surface and f-valence electron count of UPt3

    NASA Astrophysics Data System (ADS)

    McMullan, G. J.; Rourke, P. M. C.; Norman, M. R.; Huxley, A. D.; Doiron-Leyraud, N.; Flouquet, J.; Lonzarich, G. G.; McCollam, A.; Julian, S. R.

    2008-05-01

    Combining old and new de Haas-van Alphen (dHvA) and magnetoresistance data, we arrive at a detailed picture of the Fermi surface of the heavy fermion superconductor UPt3. Our work was partially motivated by a new proposal that two 5f valence electrons per formula unit in UPt3 are localized by correlation effects—agreement with previous dHvA measurements of the Fermi surface was invoked in its support. Comprehensive comparison with our new observations shows that this 'partially localized' model fails to predict the existence of a major sheet of the Fermi surface, and is therefore less compatible with experiment than the originally proposed 'fully itinerant' model of the electronic structure of UPt3. In support of this conclusion, we offer a more complete analysis of the fully itinerant band structure calculation, where we find a number of previously unrecognized extremal orbits on the Fermi surface.

  11. Layered Kondo lattice model for quantum critical beta-YbAlB4.

    PubMed

    Nevidomskyy, Andriy H; Coleman, P

    2009-02-20

    We analyze the magnetic and electronic properties of the quantum critical heavy fermion superconductor beta-YbAlB4, calculating the Fermi surface and the angular dependence of the extremal orbits relevant to the de Haas-van Alphen measurements. Using a combination of the realistic materials modeling and single-ion crystal field analysis, we are led to propose a layered Kondo lattice model for this system, in which two-dimensional boron layers are Kondo coupled via interlayer Yb moments in a Jz=+/-5/2 state. This model fits the measured single-ion magnetic susceptibility and predicts a substantial change in the electronic anisotropy as the system is pressure tuned through the quantum critical point.

  12. Two-dimensional magnetic quantum oscillations observed in an organic metal

    SciTech Connect

    Hagel, J.; Wanka, S.; Wosnitza, J.; Balthes, E.; Schlueter, J. A.; Kini, A. M.; Geiser, U.; Mohtasham, J.; Winter, R. W.; Gard, G. L.

    2000-07-24

    The de Haas-van Alphen (dHvA) signal of the organic superconductor {beta}{double_prime}-(BEDT-TTF){sub 2}SF{sub 5}CH{sub 2}CF{sub 2}SO{sub 3} shows an inverse-sawtooth wave form which proves the existence of an ideal two-dimensional (2D) Fermi surface. The dHvA wave shape can almost perfectly be described by a 2D theory assuming a constant chemical potential. This either implies the existence of the predicted quasi-one-dimensional band with an exceptionally large density of states or the chemical potential may be pinned due to localized states near the Fermi energy.

  13. Hole Fermi surface in Bi2Se3 probed by quantum oscillations

    NASA Astrophysics Data System (ADS)

    Piot, B. A.; Desrat, W.; Maude, D. K.; Orlita, M.; Potemski, M.; Martinez, G.; Hor, Y. S.

    2016-04-01

    Transport and torque magnetometry measurements are performed at high magnetic fields and low temperatures in a series of p-type (Ca-doped) Bi2Se3 crystals. The angular dependence of the Shubnikov-de Haas and de Haas-van Alphen quantum oscillations enables us to determine the Fermi surface of the bulk valence band states as a function of the carrier density. At low density, the angular dependence exhibits a downturn in the oscillations frequency between 0∘ and 90∘, reflecting a bag-shaped hole Fermi surface. The detection of a single frequency for all tilt angles rules out the existence of a Fermi surface with different extremal cross sections down to 24 meV. There is therefore no signature of a camelback in the valence band of our bulk samples, in accordance with the direct band gap predicted by G W calculations.

  14. Nontrivial Berry phase and type-II Dirac transport in the layered material PdT e2

    NASA Astrophysics Data System (ADS)

    Fei, Fucong; Bo, Xiangyan; Wang, Rui; Wu, Bin; Jiang, Juan; Fu, Dongzhi; Gao, Ming; Zheng, Hao; Chen, Yulin; Wang, Xuefeng; Bu, Haijun; Song, Fengqi; Wan, Xiangang; Wang, Baigeng; Wang, Guanghou

    2017-07-01

    We report on a systematic study of type-II Dirac fermions in a layered crystal of PdT e2 . De Haas-van Alphen oscillations show a small Fermi-surface pocket with a cross section of 0.077 n m-2 with a nontrivial Berry phase. First-principles calculation reveals that the nontrivial Berry phase originates from a hole pocket formed by the tilted Dirac cone. In addition, the band dispersion measured with angle-resolved photoemission spectroscopy is found to be consistent with that of a type-II Dirac cone dispersion. We propose that PdT e2 is an improved platform to host topological superconductors.

  15. Magnetic measurements of rare earth hexaborides

    NASA Astrophysics Data System (ADS)

    Teklu, Alem Abraha

    2000-10-01

    The de Haas van Alphen (dHvA) effect is used, using the field modulation method, to study the orientation dependence of the extremal cross-sectional areas of the Fermi surface (FS) and effective masses of CexLa 1--xB6 alloys for x between 0 and 0.05. Previous measurements on these samples, using the pulsed field method, up to x = 1 showed that the FS was spin polarized at very low Ce concentration, at x = 0.05, indicating a spin polarity-dependent scattering mechanism. Moreover, the effective mass was enhanced by the increase of Ce concentration. This was the motivation for the present work which is to study in detail the topology of the FS and measure effective masses at these low Ce concentrations. The dHvA frequency corresponding to the alpha3 orbit of pure LaB 6 for the magnetic field parallel to the [100] axis has a value of (7.89 +/- 0.004)kT, which is in very good agreement with the original measurements on this sample. The effective mass of such an orbit is also found to be (0.66 +/- 0.03)me, which agrees with these measurements. The measurements on all samples 0 ≤ x ≤ 0.05, for this field direction, indicate that the frequencies corresponding to the alpha3 and alpha 1,2 orbits increase in a simple way with the increase of Ce concentration up to 5%. Similarly, the effective mass and the charge carrier density exhibit such behavior showing the gradual transformation of the ground state from light metal LaB6 to heavy Fermion CeB6. The angular dependence of the dHvA frequencies corresponding to the (alpha 3 and alpha1,2 orbits confirms the assumption that the FS is an ellipsoid of revolution centered at the X points of the Brillouin zone. The development of the FS from spin unpolarized LaB6 to complete polarization to the spin up state at 5% Ce in LaB6 is shown in great detail. This is in agreement with one of the existing theories. Similar measurements were performed on ferromagnetic EuB6, and the FS and effective masses were determined.

  16. Magnetic and transport properties of nanostructured materials and other novel systems

    NASA Astrophysics Data System (ADS)

    Bleiweiss, Michael Craig

    2001-07-01

    The structural, static magnetic and electrical transport properties of several novel and interesting systems were studied. The first system, a manganite class of ABO3 perovskites, appropriately doped with a divalent alkali (La1-xCaxMnO3), that exhibit colossal magnetoresistance (CMR). In addition to the typical high field negative magnetoresistance, an unusual low field positive magnetoresistance was discovered. Paramagnetic data, obtained via SQUID susceptometry, yield a Curie temperature of 277.2 K +/- 1.8 K. Transport properties show small polaron and double magnon effects in the temperature dependent resistivity, while the Hall coefficient was analyzed and found to possess both ordinary and anomalous components. The second group of substances was inverse opal structures or opal replicas with structure sizes on the order of 35 nm. Due to the three-dimensional nanostructuring, quantum effects were observed at temperatures far higher than have been previously reported. Fermi surface effects, namely deHaas-vanAlphen oscillations at 60 K, yield a net carrier concentration of 4 x 1018 carriers/cm3. One-dimensional weak localization (below 14 K), finite size effects, magnetic localization (up to 200 K), giant magnetoresistance (GMR) of more than 500% and both electron-like and hole-like Hall behaviors were also observed in the bismuth inverse opal samples. The carbon opal replicas, with n = 3.57 x 1022 carriers/cm3, show interesting effects such as one-dimensional variable range hopping (VRH) below 30 K, three-dimensional weak localization, Shubnikov-deHaas oscillations and quantum Hall effects (QHE). Never before have QHE been observed at such low fields (<2.5 T) and temperatures several times that of liquid helium (>30 K). The last material studied was magnesium diboride (MgB2). MgB 2 was doped with a variety of materials viz., Li, Bi, Cu, Zn and others. The addition of Li produced an increase in superconducting transition temperature approximately 1 K above that of

  17. Electronic Properties of Ferric Chloride Intercalated Graphite Compounds

    NASA Astrophysics Data System (ADS)

    Powers, Robert E., Jr.

    This dissertation reports electronic transport measurements on ferric chloride (FeCl_3) graphite intercalation compounds (GIC's). The c-axis conductivity is measured as a function of temperature from 1K to 293K in various stages of FeCl _3 acceptor GIC's and there are marked changes in the behavior of the conductivity as a function of stage. An attempt is made to explain these results on the basis of current theories of c-axis conduction in GIC's, notably the various hopping mechanisms assisted by phonons and impurities in parallel with band conduction. The in-plane resistivity of various stages of FeCl_3 GIC's at temperatures from 1K to 293K is measured and it is found that the absolute conductivity is enhanced from that of highly-oriented pyrolytic graphite and that the temperature behavior is metal-like and stage dependent. The hall effect and magnetoresistance of the samples are measured at low and high applied magnetic fields (up to 20T) and at various fixed point temperatures (1K, 4K, 77K, and 293K). Besides qualitative features obtained from these measurements such as the sign of the predominant carrier and the shape of the fermi surface, the Lorentz -Drude Single Carrier Model is used to obtain the carrier densities and mobilities as a function of stage. Shubnikov-deHaas (SdH) oscillations are observed in the samples at high field and at various temperatures from 1K to about 30K. The data are used to determine the effective carrier masses, relaxation times, and mobilities for some stages. DeHaas-VanAlphen oscillations are also observed in the AC susceptibility in independently measured samples. The frequencies observed are comparable to those observed in the SdH measurements but in the cases of both types of measurements, frequencies which are present in some samples are not found in others. The data is in good agreement with previous preliminary measurements by other investigators. ftn*All degree requirements completed in 1993, but degree will be granted

  18. Determination of surface structure of cleaved (001) USb2 single crystal

    SciTech Connect

    Chen, Shao-ping; Hawley, Marilyn; Bauer, Eric D; Stockum, Phil B; Manoharan, Hari C

    2009-01-01

    ), and the presence of contaminants, all of which are averaged over when probed in photoemission studies. The quasi two-dimensional USb{sub 2} has a layered tetragonal structure that is easily cleaved and has been extensively studied by a number of different techniques, such as resistivity, Hall effect measurements, photoemission and angle-resolved photoemission spectroscopy, de Haas-van Alphen, neutron diffraction, nuclear magnetic resonance, and U{sup 238} Mossbauer spectroscopy techniques. Here, we provide local information about the surfaces of this interesting compound, which we find to contain a high density of defects.

  19. Structure of cleaved (001) USb2 single crystal

    SciTech Connect

    Chen, Shao-ping; Hawley, Marilyn; Bauer, Eric D; Stockum, Phil B; Manoharan, Hari C

    2009-01-01

    , all of which are averaged over when probed in photoemission studies. The quasi two-dimensional USb{sub 2} has a layered tetragonal structure that is easily cleaved and has been extensively studied by a number of different techniques, such as resistivity, Hall effect measurements, photoemission and angle-resolved photoemission spectroscopy, de Haas-van Alphen, neutron diffraction, nuclear magnetic resonance, and U{sup 238} Mossbauer spectroscopy techniques. Here, we provide local information about the surfaces of this interesting compound, which we find to contain a high density of defects.

  20. PREFACE: Correlated Electrons (Japan)

    NASA Astrophysics Data System (ADS)

    Miyake, Kazumasa

    2007-03-01

    This issue of Journal of Physics: Condensed Matter is dedicated to results in the field of strongly correlated electron systems under multiple-environment. The physics of strongly correlated electron systems (SCES) has attracted much attention since the discovery of superconductivity in CeCu_2 Si_2 by Steglich and his co-workers a quater-century ago. Its interest has been intensified by the discovery of high-Tc superconductivity in a series of cuprates with layered perovskite structure which are still under active debate. The present issue of Journal of Physics: Condensed Matter present some aspects of SCES physics on the basis of activities of a late project "Centre-Of-Excellence" supported by MEXT (Ministry of Education, Sports, Science, Culture and Technology of the Japanese Government). This project has been performed by a condensed matter physics group in the faculties of science and engineering science of Osaka University. Although this project also covers correlated phenomena in optics and nano-scale systems, we focus here on the issues of SCES related to superconductivity, mainly unconventional. The present issue covers the discussions on a new mechanism of superconductivity with electronic origin (critical valence fluctuation mechanism), interplay and unification of magnetism and superconductivity in SCES based on a systematic study of NQR under pressure, varieties of Fermi surface of Ce- and U-based SCES probed by the de Haas-van Alphen effect, electronic states probed by a bulk sensitive photoemission spectroscopy with soft X-ray, pressure induced superconductivity of heavy electron materials, pressure dependence of superconducting transition temperature based on a first-principle calculation, and new superconductors under very high-pressure. Some papers offer readers' reviews of the relevant fields and/or include new developments of this intriguing research field of SCES. Altogether, the papers within this issue outline some aspects of electronic states

  1. Ultrasensitive measurements of magnetism in carbon-based materials

    NASA Astrophysics Data System (ADS)

    Scozzaro, Nicolas Joseph

    In this dissertation I present MRFM measurements of spin dynamics across the interface between pure a diamond region and a region of densely implanted spins, which we call a spin wire. These measurements demonstrate that spin diffusion mediated by spin flip-flops can be the dominant effect that determines the lifetime of spins in nanoscale volumes. In particular, the ability to measure nanoscale volumes illuminates the need to specify exactly what one means by spin lifetime, which most commonly refers to T1, the ensemble spin lattice relaxation time. As the measured ensemble shrinks down to small numbers of spins, or even a single spin, the notion of spin lifetime most intuitively means the amount of time it takes for a spin to flip from up to down. We show that on an individual-spin basis, the spin lifetime can be much less than T1. Although MRFM has reached a number of milestones, one significant capability which has not yet been accomplished is direct measurement of the transverse component of the magnetization. Such a capability would open MRFM to a wealth of techniques commonly used for conventional NMR, which detects the transverse moment inductively. This capability would require matching the nuclear Larmor precession frequency to the mechanical resonance frequency, which is in the MHz regime for typical applied fields. While cantilevers typically have kHz frequencies, there are membrane mechanical resonators that have MHz frequencies. To this end, we began MRFM studies using membranes. In this dissertation I demonstrate the first MRFM measurements of the longitudinal magnetization using a membrane resonator. I show that membranes have a number of advantages compared to cantilevers for MRFM applications, and are a promising candidate for transverse mechanical detection of magnetic resonance. Finally, I use the sensitive technique of cantilever magnetometry to study two-dimensional van der Waals materials. En route to measuring graphene, I measure de Haas van

  2. Oscillating magnetocaloric effect in size-quantized diamagnetic film

    SciTech Connect

    Alisultanov, Z. Z.

    2014-03-21

    We investigate the oscillating magnetocaloric effect on a size-quantized diamagnetic film in a transverse magnetic field. We obtain the analytical expression for the thermodynamic potential in case of the arbitrary spectrum of carriers. The entropy change is shown to be the oscillating function of the magnetic field and the film thickness. The nature of this effect is the same as for the de Haas–van Alphen effect. The magnetic part of entropy has a maximal value at some temperature. Such behavior of the entropy is not observed in magneto-ordered materials. We discuss the nature of unusual behavior of the magnetic entropy. We compare our results with the data obtained for 2D and 3D cases.

  3. Self-energies in itinerant magnets: A focus on Fe and Ni

    NASA Astrophysics Data System (ADS)

    Sponza, Lorenzo; Pisanti, Paolo; Vishina, Alena; Pashov, Dimitar; Weber, Cedric; van Schilfgaarde, Mark; Acharya, Swagata; Vidal, Julien; Kotliar, Gabriel

    2017-01-01

    We present a detailed study of local and nonlocal correlations in the electronic structure of elemental transition metals carried out by means of the quasiparticle self-consistent GW (QS GW ) and dynamical mean field theory (DMFT). Recent high resolution ARPES and Haas-van Alphen data of two typical transition metal systems (Fe and Ni) are used as a case study. (i) We find that the properties of Fe are very well described by QS GW . Agreement with cyclotron and very clean ARPES measurements is excellent, provided that final-state scattering is taken into account. This establishes the exceptional reliability of QS GW also in metallic systems. (ii) Nonetheless QS GW alone is not able to provide an adequate description of the Ni ARPES data due to strong local spin fluctuations. We surmount this deficiency by combining nonlocal charge fluctuations in QS GW with local spin fluctuations in DMFT. (iii) Finally we show that the dynamics of the local fluctuations are actually not crucial. The addition of an external static field can lead to similarly good results if nonlocal correlations are included through QS GW .

  4. Electrical Transport Experiments at High Pressure

    SciTech Connect

    Weir, S

    2009-02-11

    High-pressure electrical measurements have a long history of use in the study of materials under ultra-high pressures. In recent years, electrical transport experiments have played a key role in the study of many interesting high pressure phenomena including pressure-induced superconductivity, insulator-to-metal transitions, and quantum critical behavior. High-pressure electrical transport experiments also play an important function in geophysics and the study of the Earth's interior. Besides electrical conductivity measurements, electrical transport experiments also encompass techniques for the study of the optoelectronic and thermoelectric properties of materials under high pressures. In addition, electrical transport techniques, i.e., the ability to extend electrically conductive wires from outside instrumentation into the high pressure sample chamber have been utilized to perform other types of experiments as well, such as high-pressure magnetic susceptibility and de Haas-van Alphen Fermi surface experiments. Finally, electrical transport techniques have also been utilized for delivering significant amounts of electrical power to high pressure samples, for the purpose of performing high-pressure and -temperature experiments. Thus, not only do high-pressure electrical transport experiments provide much interesting and valuable data on the physical properties of materials extreme compression, but the underlying high-pressure electrical transport techniques can be used in a number of ways to develop additional diagnostic techniques and to advance high pressure capabilities.

  5. Occupied and unoccupied band structure of Ag(100) determined by photoemission from Ag quantum wells and bulk samples

    NASA Astrophysics Data System (ADS)

    Paggel, J. J.; Miller, T.; Chiang, T.-C.

    2000-01-01

    Angle-resolved photoemission spectra taken from atomically uniform films of Ag on Fe(100) show layer-resolved quantum-well peaks. The measured peak positions as a function of film thickness permit a unique determination of the initial band dispersion via the Bohr-Sommerfeld quantization rule. This information, combined with normal-emission data taken from a single crystal Ag(100), leads to a unique determination of the final band dispersion. In this study, we employ a two-band model with four adjustable parameters for a simultaneous fit to these experimental results. The initial and final band dispersions deduced from the fit are accurate to better than 0.03 eV at any wave vector k within the range of measurement. The analytic formula for the band dispersions and the parameters for the best fit are given for future reference. The Fermi wave vector along [100], normalized to the Brillouin-zone size, is determined to be kF/kΓX=0.828+/-0.001, which is more accurate than the de Haas-van Alphen result. The corresponding Fermi velocity is νF=1.06 in units of the free-electron value. The combined reflection phase for the electron wave at the two boundaries is also deduced and compared with a semiempirical formula. This comparison allows us to deduce the edges of the hybridization gap in the Fe substrate.

  6. Electrons at the monkey saddle: A multicritical Lifshitz point

    NASA Astrophysics Data System (ADS)

    Shtyk, A.; Goldstein, G.; Chamon, C.

    2017-01-01

    We consider two-dimensional interacting electrons at a monkey saddle with dispersion ∝px3-3 pxpy2 . Such a dispersion naturally arises at the multicritical Lifshitz point when three Van Hove saddles merge in an elliptical umbilic elementary catastrophe, which we show can be realized in biased bilayer graphene. A multicritical Lifshitz point of this kind can be identified by its signature Landau level behavior Em∝(Bm ) 3 /2 and related oscillations in thermodynamic and transport properties, such as de Haas-Van Alphen and Shubnikov-de Haas oscillations, whose period triples as the system crosses the singularity. We show, in the case of a single monkey saddle, that the noninteracting electron fixed point is unstable to interactions under the renormalization-group flow, developing either a superconducting instability or non-Fermi-liquid features. Biased bilayer graphene, where there are two non-nested monkey saddles at the K and K' points, exhibits an interplay of competing many-body instabilities, namely, s -wave superconductivity, ferromagnetism, and spin- and charge-density waves.

  7. Phase separation and charge carrier self-organization in semiconductor-multiferroic Eu0.8Ce0.2Mn2O5

    NASA Astrophysics Data System (ADS)

    Sanina, V. A.; Golovenchits, E. I.; Zalesskii, V. G.; Lushnikov, S. G.; Scheglov, M. P.; Gvasaliya, S. N.; Savvinov, A.; Katiyar, R. S.; Kawaji, H.; Atake, T.

    2009-12-01

    The state with a giant permittivity (ɛ'˜104) and ferromagnetism have been observed above 185 K (including room temperature) in single crystals of diluted semiconductor manganite-multiferroic Eu0.8Ce0.2Mn2O5 in the investigations of x-ray diffraction, heat capacity, dielectric and magnetic properties, conductivity, and Raman light-scattering spectra of this material. X-ray diffraction study has revealed a layered superstructure along the c axis at room temperature. A model of the state with a giant ɛ' including as-grown two-dimensional layers with doping impurities, charge carriers, and double-exchange-coupled Mn3+-Mn4+ ion pairs is suggested. At low temperatures these layers form isolated electrically neutral small-size one-dimensional superlattices, in which de Haas-van Alphen oscillations were observed. As temperature grows and hopping conductivity increases, the charge carrier self-organization in the crystal causes formation of a layered superstructure consisting of charged layers (with an excess Mn3+ concentration) alternating with dielectric layers of the initial crystal—the ferroelectricity due to charge-ordering state. Ferromagnetism results from double exchange between Mn3+ and Mn4+ ions by means of charge carriers in the charged layers. Temperature evolution of frequency shifts of Ag modes and quasielastic scattering in Raman-scattering spectra agree with the pattern of phase transitions in ECMO suggested.

  8. Evidence of Topological Nodal-Line Fermions in ZrSiSe and ZrSiTe

    NASA Astrophysics Data System (ADS)

    Hu, Jin; Tang, Zhijie; Liu, Jinyu; Liu, Xue; Zhu, Yanglin; Graf, David; Myhro, Kevin; Tran, Son; Lau, Chun Ning; Wei, Jiang; Mao, Zhiqiang

    2016-07-01

    A Dirac nodal-line semimetal phase, which represents a new quantum state of topological materials, has been experimentally realized only in a few systems, including PbTaSe2 , PtSn4 , and ZrSiS. In this Letter, we report evidence of nodal-line fermions in ZrSiSe and ZrSiTe probed in de Haas-van Alphen quantum oscillations. Although ZrSiSe and ZrSiTe share a similar layered structure with ZrSiS, our studies show the Fermi surface (FS) enclosing a Dirac nodal line has a 2D character in ZrSiTe, in contrast with 3D-like FS in ZrSiSe and ZrSiS. Another important property revealed in our experiment is that the nodal-line fermion density in this family of materials (˜1020 cm-3 ) is much higher than the Dirac fermion density of other topological materials with discrete nodes. In addition, we have demonstrated ZrSiSe and ZrSiTe single crystals can be thinned down to 2D atomic thin layers through microexfoliation, which offers the first platform to explore exotic properties of topological nodal-line fermions in low dimensions.

  9. Evidence of Topological Nodal-Line Fermions in ZrSiSe and ZrSiTe.

    PubMed

    Hu, Jin; Tang, Zhijie; Liu, Jinyu; Liu, Xue; Zhu, Yanglin; Graf, David; Myhro, Kevin; Tran, Son; Lau, Chun Ning; Wei, Jiang; Mao, Zhiqiang

    2016-07-01

    A Dirac nodal-line semimetal phase, which represents a new quantum state of topological materials, has been experimentally realized only in a few systems, including PbTaSe_{2}, PtSn_{4}, and ZrSiS. In this Letter, we report evidence of nodal-line fermions in ZrSiSe and ZrSiTe probed in de Haas-van Alphen quantum oscillations. Although ZrSiSe and ZrSiTe share a similar layered structure with ZrSiS, our studies show the Fermi surface (FS) enclosing a Dirac nodal line has a 2D character in ZrSiTe, in contrast with 3D-like FS in ZrSiSe and ZrSiS. Another important property revealed in our experiment is that the nodal-line fermion density in this family of materials (∼10^{20}  cm^{-3}) is much higher than the Dirac fermion density of other topological materials with discrete nodes. In addition, we have demonstrated ZrSiSe and ZrSiTe single crystals can be thinned down to 2D atomic thin layers through microexfoliation, which offers the first platform to explore exotic properties of topological nodal-line fermions in low dimensions.

  10. Direct, experimental evidence of the Fermi surface in YBa sub 2 Cu sub 3 O sub 7-x

    SciTech Connect

    Haghighi, H.; Kaiser, J.H.; Rayner, S.L.; West, R.N. ); Liu, J.Z.; Shelton, R. ); Howell, R.H.; Sterne, P.A.; Solal, F.; Fluss, M.J. )

    1991-04-29

    We report new measurements of the electron-positron momentum spectra of YBa{sub 2}Cu{sub 3}O{sub 7-x} performed with ultra-high statistical precision. These data differ from previous results in two significant respects: They show the D{sub 2} symmetry appropriate for untwinned crystals and, more importantly, they show unmistakable, statistically significant, discontinuities that are evidence of a major Fermi surface section. These results provide a partial answer to a question of special significance to the study of high temperature superconductors i.e. the distribution of the electrons in the material, the electronic structure. Special consideration has been given both experimentally and theoretically to the existence and shape of a Fermi surface in the materials and to the superconducting gap. There are only three experimental techniques that can provide details of the electronic structure at useful resolutions. They are angular correlation of positron annihilation radiation, ACAR, angle resolved photo emission, PE, and de Haas van Alphen measurements. 11 refs., 4 figs.

  11. Heavy fermions, quantum criticality, and unconventional superconductivity in filled skutterudites and related materials

    SciTech Connect

    Andraka, Bohdan

    2015-05-14

    The main goal of this program was to explore the possibility of novel states and behaviors in Pr-based system exhibiting quantum critical behavior, PrOs₄Sb₁₂. Upon small changes of external parameter, such as magnetic field, physical properties of PrOs₄Sb₁₂ are drastically altered from those corresponding to a superconductor, to heavy fermion, to field-induced ordered phase with primary quadrupolar order parameter. All these states are highly unconventional and not understood in terms of current theories thus offer an opportunity to expand our knowledge and understanding of condensed matter. At the same time, these novel states and behaviors are subjects to intense international controversies. In particular, two superconducting phases with different transition temperatures were observed in some samples and not observed in others leading to speculations that sample defects might be partially responsible for these exotic behaviors. This work clearly established that crystal disorder is important consideration, but contrary to current consensus this disorder suppresses exotic behavior. Superconducting properties imply unconventional inhomogeneous state that emerges from unconventional homogeneous normal state. Comprehensive structural investigations demonstrated that upper superconducting transition is intrinsic, bulk, and unconventional. The high quality of in-house synthesized single crystals was indirectly confirmed by de Haas-van Alphen quantum oscillation measurements. These measurements, for the first time ever reported, spanned several different phases, offering unprecedented possibility of studying quantum oscillations across phase boundaries.

  12. Fermi Surfaces in the Antiferromagnetic, Paramagnetic and Polarized Paramagnetic States of CeRh2Si2 Compared with Quantum Oscillation Experiments

    NASA Astrophysics Data System (ADS)

    Pourret, Alexandre; Suzuki, Michi-To; Palaccio Morales, Alexandra; Seyfarth, Gabriel; Knebel, Georg; Aoki, Dai; Flouquet, Jacques

    2017-08-01

    The large quantum oscillations observed in the thermoelectric power in the antiferromagnetic (AF) state of the heavy-fermion compound CeRh2Si2 disappear suddenly when entering in the polarized paramagnetic (PPM) state at Hc ˜ 26.5 T, indicating an abrupt reconstruction of the Fermi surface. The electronic band structure was calculated using [LDA+U] for the AF state taking the correct magnetic structure into account, for the PPM state, and for the paramagnetic state (PM). Different Fermi surfaces were obtained for the AF, PM, and PPM states. Due to band folding, a large number of branches was expected and observed in the AF state. The LDA+U calculation was compared with the previous LDA calculations. Furthermore, we compared both calculations with previously published de Haas-van Alphen experiments. The better agreement with the LDA approach suggests that above the critical pressure pc CeRh2Si2 enters in a mixed-valence state. In the PPM state under a high magnetic field, the 4f contribution at the Fermi level EF drops significantly compared with that in the PM state, and the 4f electrons contribute only weakly to the Fermi surface in our approach.

  13. Unusual magnetotransport from Si-square nets in topological semimetal HfSiS

    NASA Astrophysics Data System (ADS)

    Kumar, Nitesh; Manna, Kaustuv; Qi, Yanpeng; Wu, Shu-Chun; Wang, Lei; Yan, Binghai; Felser, Claudia; Shekhar, Chandra

    2017-03-01

    The class of topological semimetals comprises a large pool of compounds. Together they provide a wide platform to realize exotic quasiparticles, for example, Dirac, nodal-line Dirac, and Weyl fermions. In this Rapid Communication, we report the Berry phase, Fermi-surface topology, and anisotropic magnetoresistance of HfSiS which has recently been predicted to be a nodal-line semimetal. This compound contains a large carrier density, higher than most of the known semimetals. Massive amplitudes of de Haas-van Alphen and Shubnikov-de Haas oscillations up to 20 K in 7 T assist us in witnessing a nontrivial π-Berry phase, which is a consequence of topological Dirac-type dispersion of bands originating from the hybridization of px+py and dx2-y2 orbitals of square-net plane of Si and Hf atoms, respectively. Furthermore, we establish the three-dimensional Fermi surface which consists of very asymmetric water caltroplike electrons and barley seedlike hole pockets which account for the anisotropic magnetoresistance in HfSiS.

  14. Quantum oscillations of magnetization in tight-binding electrons on a honeycomb lattice

    NASA Astrophysics Data System (ADS)

    Kishigi, Keita; Hasegawa, Yasumasa

    2014-08-01

    We show that quantum oscillations of the magnetization can occur when the Fermi surface consists of points (massless Dirac points) or even when the chemical potential is in an energy gap by studying tight-binding electrons on a honeycomb lattice in a uniform magnetic field. The quantum oscillations of the magnetization as a function of the inverse magnetic field are known as de Haas-van Alphen (dHvA) oscillations and the frequency is proportional to the area of the Fermi surface. The dominant period of the oscillations shown in this paper corresponds to the area of the first Brillouin zone and its phase is zero. The origin of these quantum oscillations is the characteristic magnetic field dependence of the energy known as the Hofstadter butterfly and the Harper broadening of Landau levels. These oscillations are not caused by the crossing of the chemical potential and Landau levels, which is the case in dHvA oscillations. These oscillations can be observed experimentally in systems with a large supercell such as a graphene antidot lattice or ultracold atoms in an optical lattice at an external magnetic field of a few Tesla when the area of the supercell is 104 times larger than that of graphene.

  15. Magnetic properties of Dirac fermions in a buckled honeycomb lattice

    NASA Astrophysics Data System (ADS)

    Tabert, C. J.; Carbotte, J. P.; Nicol, E. J.

    2015-01-01

    We calculate the magnetic response of a buckled honeycomb lattice with intrinsic spin-orbit coupling (such as silicene) which supports valley-spin polarized energy bands when subjected to a perpendicular electric field Ez. By changing the magnitude of the external electric field, the size of the two band gaps involved can be tuned, and a transition from a topological insulator (TI) to a trivial band insulator (BI) is induced as one of the gaps becomes zero, and the system enters a valley-spin polarized metallic state (VSPM). In an external magnetic field (B ), a distinct signature of the transition is seen in the derivative of the magnetization with respect to chemical potential μ , which gives the quantization of the Hall plateaus through the Streda relation. When plotted as a function of the external electric field, the magnetization has an abrupt change in slope at its minimum, which signals the VSPM state. The magnetic susceptibility χ shows jumps as a function of μ when a band gap is crossed, which provides a measure of the gaps' variation as a function of external electric field. Alternatively, at fixed μ , the susceptibility displays an increasingly large diamagnetic response as the electric field approaches the critical value of the VSPM phase. In the VSPM state, magnetic oscillations exist for any value of chemical potential while for the TI and BI states, μ must be larger than the minimum gap in the system. When μ is larger than both gaps, there are two fundamental cyclotron frequencies (which can also be tuned by Ez) involved in the de-Haas van-Alphen oscillations that are close in magnitude. This causes a prominent beating pattern to emerge.

  16. Skutterudites under pressure: An ab initio study

    SciTech Connect

    Ram, Swetarekha; Kanchana, V.; Valsakumar, M. C.

    2014-03-07

    Ab initio results on the band structure, density of states, and Fermi surface (FS) properties of LaRu{sub 4}X{sub 12} (X = P, As, Sb) are presented at ambient pressure as well as under compression. The analysis of density of states reveals the major contribution at the Fermi level to be mainly from the Ru-d and X-p states. We have a complicated Fermi surface with both electron and hole characters for all the three compounds which is derived mainly from the Ru-d and X-p states. There is also a simpler FS with hole character derived from the P-p{sub z} orbital for LaRu{sub 4}P{sub 12} and Ru-d{sub z{sup 2}} orbital in the case of As and Sb containing compounds. More interestingly, Fermi surface nesting feature is observed only in the case of the LaRu{sub 4}P{sub 12}. Under compression, we observe the topology of the complicated FS sheet of LaRu{sub 4}As{sub 12} to change around V/V{sub 0} = 0.85, leading to a behaviour similar to that of a multiband superconductor, and in addition, we have two more hole pockets centered around Γ at V/V{sub 0} = 0.8 for the same compound. Apart from this, we find the hole pocket to vanish at V/V{sub 0} = 0.8 in the case of LaRu{sub 4}Sb{sub 12} and the opening of the complicated FS sheet gets reduced. The de Haas van Alphen calculation shows the number of extremal orbits in the complicated sheet to change in As and Sb containing compounds under compression, where we also observe the FS topology to change.

  17. Photoemission studies of classic and novel thermoelectric materials

    NASA Astrophysics Data System (ADS)

    Greanya, Viktoria Augusta

    Thermoelectric materials have been studied vigorously since the 1950s. Recent advances in materials synthesis and theory have rejuvinated the field in the last decade. The thermoelectric properties of materials are related to their electronic structure. In addition, many of these materials behave quasi-low-dimensionally, making them ideal candidates for study using angle resolved and angle integrated photoelectron spectroscopy (ARPES and AIPES). We report the first detailed study of the valence band electronic structure of Bi2Te3, Bi2Se3 and CsBi 4Te6 using ARPES and AIPES. Experimental results are compared with local density approximation (LDA) band structure calculations and (when available) with de Haas-van Alphen and Shubnikov-de Haas experiments. Bi2Te3 is currently the best room temperature thermoelectric material known. Dispersions of the valence bands were determined using ARPES. A six-fold k-space degeneracy in the valence band maximum is found. The quasi-two-dimensional nature of the electronic structure was demonstrated by the weakly dispersive bands along the Gamma-Z direction. The density of states (DOS) for this material was also studied using AIPES. Spectra were taken at multiple photon energies. Six valence band peaks were found. Good correspondence with the calculated DOS was found. Bi2Se3 is isostructural to Bi2Te 3 but its thermoelectric performance is significantly worse. The valence band dispersions for this material have been determined, as well as the DOS. We find the valence band maximum to be located at Gamma. Ten easily identifiable bands are seen within 4 eV of the Fermi level. The energy bands in the Gamma-Z direction are found to be flatter than those predicted by theory. The APES measurements revealed a total of nine bands, which correspond well to the calculated DOS. CsBi4Te6 is a novel thermoelectric material, recently discovered in the chemistry department of Michigan State University. This material exhibits quasi

  18. Application du groupe de renormalisation aux conducteurs organiques quasi-unidimensionnels soumis a un champ magnetique

    NASA Astrophysics Data System (ADS)

    Hubert, Laurent

    Des conducteurs organiques fortement anisotropes presentent, sous l'effet d'un champ magnetique, une etonnante variete de proprietes physiques tel que: l'effet Shubnikov-de Haas, l'effet de Haas-van-Alphen, l'existence de cascades d'ondes de densite de spin apparentees a l'effet Hall quantique, reentrance vers la phase metallique pouvant provenir d'un 'breakdown' magnetique, et tout recemment la possibilite d'un confinement charge induit par le champ magnetique. A cela s'ajoute les nombreuses caracteristiques deja apparues en variant la pression hydrostatique ou la substitution chimique: separation spin-charge, localisation de la charge, transition spin-Peierls, antiferromagnetisme itinerant ou non, supraconductivite, et l'existence d'une frontiere commune entre les phases supraconductrice et antiferromagnetique. En vue de completer la description theorique du diagramme de phase generalise des conducteurs organiques, nous adaptons et elargissons la methode du groupe de renormalisation quantique (GRQ) au cas ou le champ magnetique est non nul. On sait deja que cette methode permet de resoudre le dilemme tout particulier des composes Q-1D, soit leur capacite de produire des transitions de phase malgre leur forte anisotropie et consequemment de leur faible dimensionalite. Cette methode est deja utilisee pour decrire le diagramme de phase temperature versus pression des sels de Bechgaard, de leurs analogues souffres et mixtes. Le GRQ permet aussi de comprendre comment des systemes anisotropes comme les conducteurs organiques peuvent se comporter comme des liquides de Luttinger a haute temperature et comme des liquides de Fermi ou condenses a basse temperature. Nous montrons que l'introduction d'un champ magnetique dans un regime de saut coherent interchai ne a deux particules n'apporte que de simples corrections aux lois d'echelles dans le canal zero son, alors qu'il introduit un mecanisme de brisure de paire dans le canal Cooper. Dans le regime de saut coherent a une

  19. Are Effective Properties Effective?

    SciTech Connect

    Han, Ru; Ingber, Marc S.; Hsiao, S.-C.

    2008-02-15

    The effective moduli (effective Young's modulus, effective Poisson's ratio, effective shear modulus, and effective bulk modulus) of dispersed-phase-reinforced composite materials are determined at the mesoscopic level using three-dimensional parallel boundary element simulations. By comparing the mesoscopic BEM results and the macroscopic results based on effective properties, limitations in the effective property approach have been examined.

  20. A Poetic Journey: The Transfer and Transformation of German Strategies for Moral Education in Late Eighteenth-Century Dutch Poetry for Children

    ERIC Educational Resources Information Center

    Parlevliet, Sanne; Dekker, Jeroen J. H.

    2013-01-01

    One of the most popular Dutch educational enlightenment authors was Hieronymus van Alphen. His three volumes of "Little Poems for Children" published in 1778 and 1782 were extremely successful, both in the Netherlands and abroad. Inspired by the German poets Christian Felix Weisse and Gottlob Wilhelm Burmann, Van Alphen brought about an…

  1. A Poetic Journey: The Transfer and Transformation of German Strategies for Moral Education in Late Eighteenth-Century Dutch Poetry for Children

    ERIC Educational Resources Information Center

    Parlevliet, Sanne; Dekker, Jeroen J. H.

    2013-01-01

    One of the most popular Dutch educational enlightenment authors was Hieronymus van Alphen. His three volumes of "Little Poems for Children" published in 1778 and 1782 were extremely successful, both in the Netherlands and abroad. Inspired by the German poets Christian Felix Weisse and Gottlob Wilhelm Burmann, Van Alphen brought about an…

  2. CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Magnetization of two-dimensional heavy holes with boundaries in a perpendicular magnetic field

    NASA Astrophysics Data System (ADS)

    Fang, Cheng; Wang, Zhi-Gang; Li, Shu-Shen; Zhang, Ping

    2009-10-01

    The magnetisation of heavy holes in III-V semiconductor quantum wells with Rashba spin-orbit coupling (SOC) in an external perpendicular magnetic field is studied theoretically. We concentrate on the effects on the magnetisation induced by the system boundary, the Rashba SOC and the temperature. It is found that the sawtooth-like de Haasvan Alphen (dHvA) oscillations of the magnetisation will change dramatically in the presence of such three factors. Especially, the effects of the edge states and Rashba SOC on the magnetisation are more evident when the magnetic field is smaller. The oscillation center will shift when the boundary effect is considered and the Rashba SOC will bring beating patterns to the dHvA oscillations. These effects on the dHvA oscillations are preferably observed at low temperatures. With increasing temperature, the dHvA oscillations turn to be blurred and eventually disappear.

  3. Development of the High-Field Heavy-Fermion Ground State in Ce{sub x }La{sub 1 {minus}x}B{sub 6} Intermetallics

    SciTech Connect

    Goodrich, R.G.; Teklu, A.; Harrison, N.; Young, D.; Fisk, Z.

    1999-05-01

    de Haas{endash}van Alphen measurements in Ce{sub x}La {sub 1{minus}x}B{sub 6} intermetallics reveal the existence of long-lived quasiparticles for all 0{lt}x{lt}1 . This is accompanied by the enhancement of the field-dependent effective mass, together with changes to the topology of the Fermi surface developing very early in the series, and with the effective mass eventually exhibiting a maximum near x{approximately}0.9 . One of the spin contributions to the signal is also observed to disappear at very low x , indicating a spin polarity-dependent scattering mechanism. {copyright} {ital 1999} {ital The American Physical Society}

  4. Phase-space noncommutativity and the thermodynamics of the Landau system

    NASA Astrophysics Data System (ADS)

    Halder, Aslam; Gangopadhyay, Sunandan

    2017-06-01

    Thermodynamics of the Landau system in noncommutative phase-space (NCPS) has been studied in this paper. The analysis involves the use of generalized Bopp-shift transformations to map the noncommutative (NC) system to its commutative equivalent system. The partition function of the system is computed and from this, the magnetization and the susceptibility of the Landau system are obtained. The results reveal that the magnetization and the susceptibility get modified by both the spatial and momentum NC parameters 𝜃 and 𝜃¯. We then investigate the de Hass-van Alphen effect in NCPS. Here, the oscillation of the magnetization and the susceptibility get corrected by both the spatial and momentum NC parameters 𝜃 and 𝜃¯.

  5. Thermodynamics of a Charged Particle in a Noncommutative Plane in a Background Magnetic Field

    NASA Astrophysics Data System (ADS)

    Halder, Aslam; Gangopadhyay, Sunandan

    2017-03-01

    Landau system in noncommutative space has been considered. To take into account the issue of gauge invariance in noncommutative space, we incorporate the Seiberg-Witten map in our analysis. Generalised Bopp-shift transformation is then used to map the noncommutative system to its commutative equivalent system. In particular we have computed the partition function of the system and from this we obtained the susceptibility of the Landau system and found that the result gets modified by the spatial noncommutative parameter θ. We also investigate the de Hass-van Alphen effect in noncommutative space and observe that the oscillation of the magnetization and the susceptibility gets noncommutative corrections. Interestingly, the susceptibility in the noncommutative scenario is non-zero in the range of the magnetic field greater than the threshold value which is in contrast to its commutative counterpart. The results obtained are valid upto all orders in the noncommutative parameter θ.

  6. Thermodynamics of a Charged Particle in a Noncommutative Plane in a Background Magnetic Field

    NASA Astrophysics Data System (ADS)

    Halder, Aslam; Gangopadhyay, Sunandan

    2017-06-01

    Landau system in noncommutative space has been considered. To take into account the issue of gauge invariance in noncommutative space, we incorporate the Seiberg-Witten map in our analysis. Generalised Bopp-shift transformation is then used to map the noncommutative system to its commutative equivalent system. In particular we have computed the partition function of the system and from this we obtained the susceptibility of the Landau system and found that the result gets modified by the spatial noncommutative parameter θ. We also investigate the de Hass-van Alphen effect in noncommutative space and observe that the oscillation of the magnetization and the susceptibility gets noncommutative corrections. Interestingly, the susceptibility in the noncommutative scenario is non-zero in the range of the magnetic field greater than the threshold value which is in contrast to its commutative counterpart. The results obtained are valid upto all orders in the noncommutative parameter θ.

  7. Physical properties of single crystalline BaSn{sub 5}

    SciTech Connect

    Lin, Xiao; Budko, Sergey; Canfield, Paul

    2012-01-30

    We present a comprehensive study of the binary intermetallic superconductor, BaSn{sub 5}. High-quality single crystalline BaSn{sub 5} was grown out of a Sn flux. Detailed thermodynamic and transport measurements were performed to study BaSn{sub 5}'s normal and superconducting state properties. This material appears to be a strongly coupled, multiband superconductor. H{sub c2}(T) is almost isotropic. De Haas–van Alphen oscillations were observed and two effective masses were estimated from the FFT spectra. Hydrostatic pressure causes a decrease in the superconducting transition temperature at the rate of ≈−0.053 ± 0.001 K/kbar.

  8. Side Effects

    Cancer.gov

    Side effects are problems that occur when treatment affects healthy tissues or organs. Learn about side effects caused by cancer treatment. Know what signs and symptoms to call your doctor about, ways to manage these problems, and treatment options.

  9. Placebo Effect

    MedlinePlus

    ... David C. Spencer, MD Steven Karceski, MD The placebo effect Joseph H. Friedman, MD Richard Dubinsky, MD ... truly effective, it is often compared to a placebo. WHAT IS A PLACEBO? Placebos are usually thought ...

  10. Chemotherapy Effects

    MedlinePlus

    ... Falling Fatigue Fertility and Sexual Side Effects Fever Hair ... Cancers Caused by Cancer Treatment Some cancer treatments such as chemotherapy and radiation therapy may increase a person's risk ...

  11. Thermal Effects.

    ERIC Educational Resources Information Center

    Talmage, Sylvia S.; Coutant, Charles C.

    1978-01-01

    Presents a literature review of the effect of temperature on the biosphere water, covering publications of 1976-77. This review includes the effects of temperature on growth, production, and embryonic and larval development. A list of 401 references is also presented. (HM)

  12. "Further Effects"

    NASA Astrophysics Data System (ADS)

    Kinigstein, Steven Michael

    In writing Further Effects, I intended to illustrate the benefits that are to be had from the use of effects - processing, when applied at the compositional level, rather than as a post-compositional afterthought. When effects are used creatively in the compositional stage, they will influence the very nature of a piece. They are capable of expressing rhythmic and metric ideas. They can alter the natural timbre of an instrument. This can be done on levels of abstraction ranging from discreet subtlety to disguise beyond recognition. There is one effect (known as "pitch shift.") that allows an instrument to play pitches that are well outside of its range. In Further Effects, I direct the performers to use a volume pedal (which I view as a tool, rather than an effect) for the broadened creative use of dynamics that it so efficiently grants. The use of an effects processor and volume pedal creates a need for ancillary equipment. An amplifier, cables, and an electric hook-up (a microphone or a pickup) will be required for each instrument. While an amplifier serves to project the processed sound, there must also be a device or method to suppress unprocessed sound. A great deal of thought and work goes into the use of effects; yet I feel it is wasteful to use this musical resource merely as post-compositional decoration.

  13. Gauging Effectiveness

    ERIC Educational Resources Information Center

    Foord, Kathleen A.; Haar, Jean M.

    2012-01-01

    Books by education experts and speakers at national professional conferences have inspired many school leaders to initiate professional learning communities (PLCs). Sustaining them effectively to raise student achievement is another matter. How can one know whether a PLC is moving toward a desired outcome? Measuring effectiveness requires an…

  14. Effective Schools Require Effective Principals

    ERIC Educational Resources Information Center

    LaPointe, Michelle; Davis, Stephen H.

    2006-01-01

    At long last, scholars and policy makers have come to realize what most school administrators have known for years--that effective schools require both outstanding teachers and strong leaders. Although there is considerable research about the characteristics of effective school leaders and the strategies principals can use to help manage…

  15. Psychopharmaceuticals: effects and side effects

    PubMed Central

    Kline, Nathan S.

    1959-01-01

    Drugs which affect psychological behaviour are being used in vast amounts nowadays, with, in all too many cases, but scant regard for their exact uses or possible side effects. This article contains a clinical classification of these drugs, followed by an account of their principal side effects and the means of obviating them. PMID:14409889

  16. Effective Parenting

    MedlinePlus

    ... Listen Español Text Size Email Print Share Effective Parenting Page Content Article Body Now that our children ... school play and his soccer games. Your Current Parenting Experiences Spend some time thinking about how you ...

  17. Erosion Effects

    NASA Image and Video Library

    2003-01-22

    The impact crater in this NASA Mars Odyssey image is a model illustration of the effects of erosion on Mars. The degraded crater rim and several landslides observed in crater walls are evidence of the mass wasting of materials.

  18. Effects and Effectiveness of Telemedicine

    PubMed Central

    Grigsby, Jim; Kaehny, Margaret M.; Sandberg, Elliot J.; Schlenker, Robert E.; Shaughnessy, Peter W.

    1995-01-01

    The use of telemedicine has recently undergone rapid growth and proliferation. Although the feasibility of many applications has been tested for nearly 30 years, data concerning the costs, effects, and effectiveness of telemedicine are limited. Consequently, the development of a strategy for coverage, payment, and utilization policy has been hindered. Telemedicine continues to expand, and pressure for policy development increases in the context of Federal budget cuts and major changes in health service financing. This article reviews the literature on the effects and medical effectiveness of telemedicine. It concludes with several recommendations for research, followed by a discussion of several specific questions, the answers to which might have a bearing on policy development. PMID:10153466

  19. Listening Effectively

    DTIC Science & Technology

    1996-04-01

    Force managers unique in this regard. Far from it—business organizations with a profit motive have long recognized the value of listening effectively...Far from it—business organizations with a profit motive have long recognized the value of listening effectively. Chief ex - ecutive officers and chief...Hello, Daddy . This is Missy.” I was amused that she called me Daddy and then iden - tified herself, but I decided to play along. “Missy who?” I asked

  20. Tectonomagnetic effects

    USGS Publications Warehouse

    Johnston, M.

    1978-01-01

    We know that earthquakes result from the sudden release of elastic strain, the end product, most likely, of a long period of gradual stress accumulation in the crust. At the U.S Geological Survey, our magnetic fields studies have two main directions. First, a determination of the magnetic behavior accompanying shallow earthquakes (seismomagnetic effects). Second, a long-term monitoring of the magnetic field in the vicinity of an active fault to detect magnetic changes due to general tectonic activity, particularly that which ultimately leads to earthquakes. These magnetic changes are generally termed "tectonomagnetic effects." 

  1. Sleeper Effects

    ERIC Educational Resources Information Center

    Maurer, Daphne; Mondloch, Catherine J.; Lewis, Terri L.

    2007-01-01

    Early experience preserves and refines many capabilities that emerge prenatally. Here we describe another role that it plays--establishing the neural substrate for capabilities that emerge at a much later point in development. The evidence comes from sleeper effects: permanent deficits when early experience was absent in capabilities that normally…

  2. Sleeper Effects

    ERIC Educational Resources Information Center

    Maurer, Daphne; Mondloch, Catherine J.; Lewis, Terri L.

    2007-01-01

    Early experience preserves and refines many capabilities that emerge prenatally. Here we describe another role that it plays--establishing the neural substrate for capabilities that emerge at a much later point in development. The evidence comes from sleeper effects: permanent deficits when early experience was absent in capabilities that normally…

  3. Communicating Effectively

    Cancer.gov

    The seventh module of the EPEC-O (Education in Palliative and End-of-Life Care for Oncology) Self-Study: Cultural Considerations When Caring for African Americans explores communication issues pertinent to African Americans with cancer and their health care providers, discusses strategies for culturally sensitive communication, and presents the SPIKES protocol, a practical framework for effective communication.

  4. System Effectiveness

    SciTech Connect

    Powell, Danny H; Elwood Jr, Robert H

    2011-01-01

    An effective risk assessment system is needed to address the threat posed by an active or passive insider who, acting alone or in collusion, could attempt diversion or theft of nuclear material. It is critical that a nuclear facility conduct a thorough self-assessment of the material protection, control, and accountability (MPC&A) system to evaluate system effectiveness. Self-assessment involves vulnerability analysis and performance testing of the MPC&A system. The process should lead to confirmation that mitigating features of the system effectively minimize the threat, or it could lead to the conclusion that system improvements or upgrades are necessary to achieve acceptable protection against the threat. Analysis of the MPC&A system is necessary to understand the limits and vulnerabilities of the system to internal threats. Self-assessment helps the facility be prepared to respond to internal threats and reduce the risk of theft or diversion of nuclear material. MSET is a self-assessment or inspection tool utilizing probabilistic risk assessment (PRA) methodology to calculate the system effectiveness of a nuclear facility's MPC&A system. MSET analyzes the effectiveness of an MPC&A system based on defined performance metrics for MPC&A functions based on U.S. and international best practices and regulations. A facility's MC&A system can be evaluated at a point in time and reevaluated after upgrades are implemented or after other system changes occur. The total system or specific subareas within the system can be evaluated. Areas of potential performance improvement or system upgrade can be assessed to determine where the most beneficial and cost-effective improvements should be made. Analyses of risk importance factors show that sustainability is essential for optimal performance. The analyses reveal where performance degradation has the greatest detrimental impact on total system risk and where performance improvements have the greatest reduction in system risk

  5. Blazhko Effect

    NASA Technical Reports Server (NTRS)

    Teays, Terry

    1996-01-01

    The cause of the Blazhko effect, the long-term modulation of the light and radial velocity curves of some RR Lyr stars, is still not understood. The observational characteristics of the Blazhko effect are discussed. Some preliminary results are presented from two recent campaigns to observe RR Lyr, using the International Ultraviolet Explorer along with ground-based spectroscopy and photometry, throughout a pulsation cycle, at a variety of Blazhko phases. A set of ultraviolet light curves have been generated from low dispersion IUE spectra. In addition, the (visual) light curves from IUE's Fine Error Sensor are analyzed using the Fourier decomposition technique. The values of the parameters Psi(sub 21) and R(sub 21) at different Blazhko phases of RR Lyr span the range of values found for non-Blazhko variables of similar period.

  6. Thermal Effects.

    PubMed

    Yan, Ming; Zhang, Panyue; Zeng, Guangming

    2016-10-01

    This review focuses on the research literatures published in 2015 relating to topics of thermal effects in water pollution control. This review is divided into the following sections: biological nitrogen and phosphorus removal, wastewater treatment for organic conversion, industrial wastewater treatment, anaerobic digestion of sewage sludge and solid waste, sludge biochar preparation and application, pyrolysis of sewage sludge, reduction heavy metal in sewage sludge and soil, and other issues of wastewater and sludge treatment.

  7. Zeeman Effect

    NASA Astrophysics Data System (ADS)

    Murdin, P.

    2000-11-01

    The splitting of a spectral line into two, three or more components, that occurs when the source of that line lies within a magnetic field. This phenomenon is named after the Dutch physicist, Pieter Zeeman (1865-1943), who discovered the effect in the laboratory, in 1896. The separation of the components of a line is proportional to the strength of the magnetic field and the number of components,...

  8. Erosion Effects

    NASA Technical Reports Server (NTRS)

    2003-01-01

    [figure removed for brevity, see original site]

    The impact crater in this THEMIS image is a model illustration to the effects of erosion on Mars. The degraded crater rim and several landslides observed in crater walls is evidence to the mass wasting of materials. Layering in crater walls also suggests the presence of materials that erode at varying rates.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

    Image information: VIS instrument. Latitude 31.6, Longitude 44.3 East (315.7 West). 19 meter/pixel resolution.

  9. Erosion Effects

    NASA Technical Reports Server (NTRS)

    2003-01-01

    [figure removed for brevity, see original site]

    The impact crater in this THEMIS image is a model illustration to the effects of erosion on Mars. The degraded crater rim and several landslides observed in crater walls is evidence to the mass wasting of materials. Layering in crater walls also suggests the presence of materials that erode at varying rates.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

    Image information: VIS instrument. Latitude 31.6, Longitude 44.3 East (315.7 West). 19 meter/pixel resolution.

  10. Radiation effects.

    PubMed

    Preston, R J

    2012-01-01

    International Commission on Radiological Protection (ICRP) Committee 1 (C1) considers the risk of induction of cancer and heritable disease; the underlying mechanisms of radiation action; and the risks, severity, and mechanisms of induction of tissue reactions (formerly 'deterministic effects'). C1 relies upon the interpretation of current knowledge of radio-epidemiological studies; current information on the underlying mechanisms of diseases and radiation-induced disease; and current radiobiological studies at the whole animal, tissue, cell, and molecular levels. This overview will describe the activities of C1 in the context of the 2007 Recommendations of ICRP. In particular, the conclusions from the most recent C1 Task Group deliberations on radon and lung cancer, and tissue reactions will be discussed. Other activities are described in summary fashion to illustrate those areas that C1 judge to be likely to influence the development of the risk estimates and nominal risk coefficients used for radiation protection purposes.

  11. CONFERENCES AND SYMPOSIA: Scientific session of the Division of General Physics and Astronomy of the Russian Academy of Sciences (May 14, 1997)

    NASA Astrophysics Data System (ADS)

    Mineev, V. P.; Vavilov, M. G.; Volkov, V. A.; Takhtamirov, E. E.; Sukhorukov, Anatolii P.; Bogatov, Alexandr P.; Korovin, S. D.; Ardelyan, N. V.; Bisnovatyi-Kogan, Gennadiĭ S.; Moiseenko, S. G.; Slysh, V. I.

    1997-10-01

    A scientific session of the Division of General Physics and Astronomy of the Russian Academy of Sciences was held on May 14, 1997 at the P L Kapitza Institute for Physical Problems, RAS. The following reports were presented at the session: (1) Mineev V P, Vavilov M G (Landau Institute of Theoretical Physics, RAS, Chernogolovka, Moscow Region) ''De Haas—van Alphen effect in superconductors''; (2) Volkov V A, Takhtamirov E E (Institute of Radio-Engineering and Electronics, RAS, Moscow) ''Dynamics of an electron with space-dependent mass and the effective-mass method for semiconductor heterostructures''; (3) Sukhorukov A P (M V Lomonosov Moscow State University, Moscow) ''New avenue of investigation in the physics of solitons: parametrically-coupled solitons in a quadratically-nonlinear medium''; (4) Bogatov A P (P N Lebedev Physics Institute, RAS, Moscow) ''Optics of semiconductor lasers''; (5) Korovin S D (Institute of High-Power Electronics, Tomsk) ''Generation of high-power microwave radiation on the base of high-current nanosecond electron beams''; (6) Ardelyan N V, Bisnovatyi-Kogan G S, Moiseenko S G (M V Lomonosov Moscow State University, Moscow; Institute of Space Research, Moscow) ''Explosion mechanisms of supernovae: the magnetorotational model''; (7) Slysh V I (Astrocosmic Centre of the P N Lebedev Physics Institute, RAS, Moscow) ''Stars, planets, and cosmic masers''. Summaries of four (1, 2, 6, 7) of the reports are given below.

  12. Magnetic field-induced Fermi surface reconstruction and quantum criticality in CeRhIn5

    DOE PAGES

    Jiao, Lin; Weng, Z. F.; Smidman, Michael; ...

    2017-02-06

    Here, we present detailed results of the field evolution of the de Haas–van Alphen (dHvA) effect in CeRhIn5. A magnetic field-induced reconstruction of the Fermi surface is clearly shown to occur inside the antiferromagnetic state, in an applied field of around B* ≃ 30 T, which is evidenced by the appearance of several new dHvA branches. The angular dependence of the dHvA frequencies reveals that the Fermi surfaces of CeRhIn5 at B > B* and CeCoIn5 are similar. The results suggest that the Ce-4f electrons in become itinerant at B > B* due to the Kondo effect, prior to themore » field-induced quantum critical point (QCP) at Bc0 ≃ 50 T. The electronic states at the field-induced QCP are therefore different from that of the pressure-induced QCP where a dramatic Fermi surface reconstruction occurs exactly at the critical pressure, indicating that multiple types of QCP may exist in CeRhIn5.« less

  13. On Effect Size

    ERIC Educational Resources Information Center

    Kelley, Ken; Preacher, Kristopher J.

    2012-01-01

    The call for researchers to report and interpret effect sizes and their corresponding confidence intervals has never been stronger. However, there is confusion in the literature on the definition of effect size, and consequently the term is used inconsistently. We propose a definition for effect size, discuss 3 facets of effect size (dimension,…

  14. Improving School Effectiveness.

    ERIC Educational Resources Information Center

    MacBeath, John, Ed.; Mortimore, Peter, Ed.

    School effectiveness is an issue that has preoccupied researchers and policymakers for 3 decades. To study how ineffective schools become effective and what constitutes an effective school, the Improving School Effectiveness Project was carried out in Scotland from 1995 to 1997. This project forms the basis of discussion in this book, which has 11…

  15. On Effect Size

    ERIC Educational Resources Information Center

    Kelley, Ken; Preacher, Kristopher J.

    2012-01-01

    The call for researchers to report and interpret effect sizes and their corresponding confidence intervals has never been stronger. However, there is confusion in the literature on the definition of effect size, and consequently the term is used inconsistently. We propose a definition for effect size, discuss 3 facets of effect size (dimension,…

  16. Gravitational Casimir Effect

    NASA Astrophysics Data System (ADS)

    Quach, James Q.

    2015-02-01

    We derive the gravitonic Casimir effect with nonidealized boundary conditions. This allows the quantification of the gravitonic contribution to the Casimir effect from real bodies. We quantify the meagerness of the gravitonic Casimir effect in ordinary matter. We also quantify the enhanced effect produced by the speculated Heisenberg-Couloumb (HC) effect in superconductors, thereby providing a test for the validity of the HC theory, and, consequently, the existence of gravitons.

  17. Gravitational Casimir effect.

    PubMed

    Quach, James Q

    2015-02-27

    We derive the gravitonic Casimir effect with nonidealized boundary conditions. This allows the quantification of the gravitonic contribution to the Casimir effect from real bodies. We quantify the meagerness of the gravitonic Casimir effect in ordinary matter. We also quantify the enhanced effect produced by the speculated Heisenberg-Couloumb (HC) effect in superconductors, thereby providing a test for the validity of the HC theory, and, consequently, the existence of gravitons.

  18. On effect size.

    PubMed

    Kelley, Ken; Preacher, Kristopher J

    2012-06-01

    The call for researchers to report and interpret effect sizes and their corresponding confidence intervals has never been stronger. However, there is confusion in the literature on the definition of effect size, and consequently the term is used inconsistently. We propose a definition for effect size, discuss 3 facets of effect size (dimension, measure/index, and value), outline 10 corollaries that follow from our definition, and review ideal qualities of effect sizes. Our definition of effect size is general and subsumes many existing definitions of effect size. We define effect size as a quantitative reflection of the magnitude of some phenomenon that is used for the purpose of addressing a question of interest. Our definition of effect size is purposely more inclusive than the way many have defined and conceptualized effect size, and it is unique with regard to linking effect size to a question of interest. Additionally, we review some important developments in the effect size literature and discuss the importance of accompanying an effect size with an interval estimate that acknowledges the uncertainty with which the population value of the effect size has been estimated. We hope that this article will facilitate discussion and improve the practice of reporting and interpreting effect sizes. (c) 2012 APA, all rights reserved)

  19. Regulation with placebo effects.

    PubMed

    Malani, Anup

    2008-12-01

    A growing scientific literature supports the existence of placebo effects from a wide range of health interventions and for a range of medical conditions. This Article reviews this literature, examines the implications for law and policy, and suggests future areas for research on placebo effects. In particular, it makes the case for altering the drug approval process to account for, if not credit, placebo effects. It recommends that evidence of placebo effects be permitted as a defense in cases alleging violations of informed consent or false advertising. Finally, it finds that tort law already has doctrines such as joint and several liability to account for placebo effects. Future research on placebo effects should focus on whether awareness of placebo effects can disable these effects and whether subjects can control their own placebo effects.

  20. Stormwater BMP Effectiveness Toolkit

    EPA Science Inventory

    US EPA has identified the effectiveness of Stormwater Best Management Practices (BMPs) as a priority research need. Effective protection of biotic integrity requires that processes maintaining the diversity of physical habitats be protected. Methods are needed to evaluate the e...

  1. Stormwater BMP Effectiveness Toolkit

    EPA Science Inventory

    US EPA has identified the effectiveness of Stormwater Best Management Practices (BMPs) as a priority research need. Effective protection of biotic integrity requires that processes maintaining the diversity of physical habitats be protected. Methods are needed to evaluate the e...

  2. Side Effects (Management)

    MedlinePlus

    ... Cancer is Treated Side Effects Dating, Sex, and Reproduction Advanced Cancer For Children For Teens For Young ... Cancer is Treated Side Effects Dating, Sex, and Reproduction Advanced Cancer For Children For Teens For Young ...

  3. The Hydrophobic Effect.

    ERIC Educational Resources Information Center

    Huque, Entazul M.

    1989-01-01

    Discusses the physical basis and current understanding of hydrophobic effects. The thermodynamic background of the effects, hydrophobic hydration, and hydrophobic interactions are described. Four existing controversies are outlined. (YP)

  4. Skills for Effective Consultation.

    ERIC Educational Resources Information Center

    Dustin, Dick; Ehly, Stewart

    1984-01-01

    Discusses counselor skills that promote effective consultation. Reviews research on effective school consultation and presents a five-stage model which involves phasing in, problem identification, implementation, evaluation, and termination. Provides recommendations for the process and products of consultation. (JAC)

  5. Hormonal effects in newborns

    MedlinePlus

    ... page: //medlineplus.gov/ency/article/001911.htm Hormonal effects in newborns To use the sharing features on this page, please enable JavaScript. Hormonal effects in newborns occur because in the womb, babies ...

  6. Medications and Side Effects

    MedlinePlus

    ... to fully work. You might feel some side effects of your medication before your feel the benefits – ... as sleepiness, anxiety or headache) is a side effect or a symptom of your illness. Many side ...

  7. The Hydrophobic Effect.

    ERIC Educational Resources Information Center

    Huque, Entazul M.

    1989-01-01

    Discusses the physical basis and current understanding of hydrophobic effects. The thermodynamic background of the effects, hydrophobic hydration, and hydrophobic interactions are described. Four existing controversies are outlined. (YP)

  8. Effective College Teaching.

    ERIC Educational Resources Information Center

    Caraway, James E.

    1978-01-01

    The author discusses other writings on effective college teaching and then presents his list of necessary characteristics for the effective teacher, stressing the interpersonal dimension of the teaching-learning situation. (MF)

  9. Memory effects in turbulence

    NASA Technical Reports Server (NTRS)

    Hinze, J. O.

    1979-01-01

    Experimental investigations of the wake flow of a hemisphere and cylinder show that such memory effects can be substantial and have a significant influence on momentum transport. Memory effects are described in terms of suitable memory functions.

  10. Skills for Effective Consultation.

    ERIC Educational Resources Information Center

    Dustin, Dick; Ehly, Stewart

    1984-01-01

    Discusses counselor skills that promote effective consultation. Reviews research on effective school consultation and presents a five-stage model which involves phasing in, problem identification, implementation, evaluation, and termination. Provides recommendations for the process and products of consultation. (JAC)

  11. Prooxidant effects of nitrofurantoin.

    PubMed

    Novikov, O O; Pokrovskii, M V; Konovalenko, A B

    2002-08-01

    We studied the possibility of using prooxidant effects of nitrofurantoin (furadonin) for stimulation of the natural antioxidant systems for preventing myocardial damage after coronary occlusion. A pronounced cardioprotective effect of the drug was observed.

  12. Vocational Education Effectiveness Indicators.

    ERIC Educational Resources Information Center

    White, Barbara

    This paper provides an overview of some of the issues involved in developing and implementing vocational education effectiveness indicators and systems. The paper first discusses educational effectiveness indicator systems--with the emphasis on "systems" in contrast to individual effectiveness indicators taken alone--and stresses the…

  13. Effects of Nuclear Weapons.

    ERIC Educational Resources Information Center

    Sartori, Leo

    1983-01-01

    Fundamental principles governing nuclear explosions and their effects are discussed, including three components of a nuclear explosion (thermal radiation, shock wave, nuclear radiation). Describes how effects of these components depend on the weapon's yield, its height of burst, and distance of detonation point. Includes effects of three…

  14. Effects of Nuclear Weapons.

    ERIC Educational Resources Information Center

    Sartori, Leo

    1983-01-01

    Fundamental principles governing nuclear explosions and their effects are discussed, including three components of a nuclear explosion (thermal radiation, shock wave, nuclear radiation). Describes how effects of these components depend on the weapon's yield, its height of burst, and distance of detonation point. Includes effects of three…

  15. Special Effects Activity Guide.

    ERIC Educational Resources Information Center

    Boxer, Jennifer; Valenta, Carol

    This guide accompanies "Special Effects," a 40-minute IMAX film and "Special Effects II", a multimedia, interactive traveling exhibit designed by the California Museum of Science and Industry. The exhibit focuses on the underlying scientific and technical processes of special effects from the earliest motion picture to state-of-the-art digital…

  16. Effective Schools Research.

    ERIC Educational Resources Information Center

    Levine, Daniel U.; Lezotte, Lawrence W.

    Research studies that have focused on identifying the characteristics or correlates of elementary and secondary schools that are unusually effective are reviewed, concentrating on the "effective schools" movement. Research on effective schools supports the conclusion that they rank high on certain characteristics frequently referred to as…

  17. Effective Internships for Effective New Administrators.

    ERIC Educational Resources Information Center

    Edmonson, Stacey

    One challenge faced by any educational leadership program is how to develop effective entry-level school administrators. Many administrative interns receive no real administrative practice at all through their internship, and yet upon completion of the internship, they are expected to be competent administrators. The internship at Sam Houston…

  18. Enhanced magnetocaloric effect material

    DOEpatents

    Lewis, Laura J. H.

    2006-07-18

    A magnetocaloric effect heterostructure having a core layer of a magnetostructural material with a giant magnetocaloric effect having a magnetic transition temperature equal to or greater than 150 K, and a constricting material layer coated on at least one surface of the magnetocaloric material core layer. The constricting material layer may enhance the magnetocaloric effect by restriction of volume changes of the core layer during application of a magnetic field to the heterostructure. A magnetocaloric effect heterostructure powder comprising a plurality of core particles of a magnetostructural material with a giant magnetocaloric effect having a magnetic transition temperature equal to or greater than 150 K, wherein each of the core particles is encapsulated within a coating of a constricting material is also disclosed. A method for enhancing the magnetocaloric effect within a giant magnetocaloric material including the step of coating a surface of the magnetocaloric material with a constricting material is disclosed.

  19. Addressing diversion effects

    PubMed Central

    Resnik, David B.

    2015-01-01

    Alan Wertheimer argues that those who promulgate principles of research ethics have a responsibility to take into account the diversion effects of those principles. In this commentary, I argue that Wertheimer's proposal that diversion effects should be considered when promulgating principles of research ethics makes sense, but it often may be best to deal with these effects once a principle has been accepted and implemented, rather than focusing on them at the outset. PMID:27774202

  20. Dynamic ground effects

    NASA Technical Reports Server (NTRS)

    Paulson, John W., Jr.; Kemmerly, Guy T.; Gilbert, William P.

    1990-01-01

    A research program is underway at the NASA Langley Research Center to study the effect of rate of descent on ground effects. A series of powered models were tested in the Vortex Research Facility under conditions with rate of descent and in the 14 x 22 Foot Subsonic Tunnel under identical conditions but without rate of descent. These results indicate that the rate of descent can have a significant impact on ground effects particularly if vectored or reversed thrust is used.

  1. Addressing diversion effects.

    PubMed

    Resnik, David B

    2015-07-01

    Alan Wertheimer argues that those who promulgate principles of research ethics have a responsibility to take into account the diversion effects of those principles. In this commentary, I argue that Wertheimer's proposal that diversion effects should be considered when promulgating principles of research ethics makes sense, but it often may be best to deal with these effects once a principle has been accepted and implemented, rather than focusing on them at the outset.

  2. Atomic lighthouse effect

    NASA Astrophysics Data System (ADS)

    Máximo, C. E.; Kaiser, R.; Courteille, Ph. W.; Bachelard, R.

    2014-11-01

    We investigate the deflection of light by a cold atomic cloud when the light-matter interaction is locally tuned via the Zeeman effect using magnetic field gradients. This "lighthouse" effect is strongest in the single-scattering regime, where deviation of the incident field is largest. For optically dense samples, the deviation is reduced by collective effects, as the increase in linewidth leads to a decrease of the magnetic field efficiency.

  3. Atomic lighthouse effect.

    PubMed

    Máximo, C E; Kaiser, R; Courteille, Ph W; Bachelard, R

    2014-11-01

    We investigate the deflection of light by a cold atomic cloud when the light-matter interaction is locally tuned via the Zeeman effect using magnetic field gradients. This "lighthouse" effect is strongest in the single-scattering regime, where deviation of the incident field is largest. For optically dense samples, the deviation is reduced by collective effects, as the increase in linewidth leads to a decrease in magnetic field efficiency.

  4. Practical and effective ALARA.

    PubMed

    Bevelacqua, Joseph John

    2010-05-01

    The ALARA Principle ensures that the total effective dose equivalent is minimized subject to economic and social factors. Effective ALARA programs must include the participation of all facility workgroups, management support, teamwork, and strong leadership. The development and sustainability of effective ALARA programs require the establishment and monitoring of goals, rewarding the successful achievement of those goals, and incorporating lessons learned from tasks that fail to meet their goals.

  5. HALL EFFECT INVESTIGATIONS

    DTIC Science & Technology

    INTERMETALLIC COMPOUNDS, *SEMICONDUCTING FILMS, *THIN FILM STORAGE DEVICES, ANTIMONY ALLOYS, CRYSTALLIZATION, ELECTRODES, ELECTROMAGNETIC PROPERTIES, EVAPORATION, HALL EFFECT , HEAT TREATMENT, INDIUM ALLOYS, ELECTRICAL RESISTANCE.

  6. Volcano-electromagnetic effects

    USGS Publications Warehouse

    Johnston, Malcolm J. S.

    2007-01-01

    Volcano-electromagnetic effects—electromagnetic (EM) signals generated by volcanic activity—derive from a variety of physical processes. These include piezomagnetic effects, electrokinetic effects, fluid vaporization, thermal demagnetization/remagnetization, resistivity changes, thermochemical effects, magnetohydrodynamic effects, and blast-excited traveling ionospheric disturbances (TIDs). Identification of different physical processes and their interdependence is often possible with multiparameter monitoring, now common on volcanoes, since many of these processes occur with different timescales and some are simultaneously identified in other geophysical data (deformation, seismic, gas, ionospheric disturbances, etc.). EM monitoring plays an important part in understanding these processes.

  7. Effective lecture presentation skills.

    PubMed

    Gelula, M H

    1997-02-01

    Lectures are the most popular form of teaching in medical education. As much as preparation and organization are key to the lecture's success, the actual presentation also depends upon the presenter's ability to reach the audience. Teaching is a lively activity. It calls for more than just offering ideas and data to an audience. It calls for direct contact with the audience, effective use of language, capability to use limited time effectively, and the ability to be entertaining. This article offers a structure to effective lecturing by highlighting the importance of voice clarity and speaking speed, approaches to using audiovisual aids, effectively using the audience to the lecture, and ways to be entertaining.

  8. Multicaloric effect: An outlook

    NASA Astrophysics Data System (ADS)

    Vopson, Melvin M.

    2017-05-01

    In 2017 the scientific community celebrates 100 years since Weiss and Piccard made the first observation of a caloric effect in magnetic materials, when studying temperature changes in Nickel subjected to applied magnetic fields near the Curie transition temperature [1]. The effect was called the magneto-caloric effect. A thermodynamic formulation of the adiabatic magneto-caloric refrigeration was given independently by Debye [2] and Giauque [3] in 1920s, followed by the first experimental confirmation of adiabatic refrigeration in 1933 [4]. Since then, the research field has expanded considerably and other interesting caloric effects have been discovered in materials displaying different forms of ferroic order.

  9. Volcanic effects on climate

    NASA Technical Reports Server (NTRS)

    Robock, Alan

    1991-01-01

    Volcanic eruptions which inject large amounts of sulfur-rich gas into the stratosphere produce dust veils which last years and cool the earth's surface. At the same time, these dust veils absorb enough solar radiation to warm the stratosphere. Since these temperature changes at the earth's surface and in the stratosphere are both in the opposite direction of hypothesized effects from greenhouse gases, they act to delay and mask the detection of greenhouse effects on the climate system. Tantalizing recent research results have suggested regional effects of volcanic eruptions, including effects on El Nino/Southern Oscillation (ENSO). In addition, a large portion of the global climate change of the past 100 years may be due to the effects of volcanoes, but a definite answer is not yet clear. While effects of several years were demonstrated with both data studies and numerical models, long-term effects, while found in climate model calculations, await confirmation with more realistic models. Extremely large explosive prehistoric eruptions may have produced severe weather and climate effects, sometimes called a 'volcanic winter'. Complete understanding of the above effects of volcanoes is hampered by inadequacies of data sets on volcanic dust veils and on climate change. Space observations can play an increasingly important role in an observing program in the future. The effects of volcanoes are not adequately separated from ENSO events, and climate modeling of the effects of volcanoes is in its infancy. Specific suggestions are made for future work to improve the knowledge of this important component of the climate system.

  10. Presenting Food Science Effectively

    ERIC Educational Resources Information Center

    Winter, Carl K.

    2016-01-01

    While the need to present food science information effectively is viewed as a critical competency for food scientists by the Institute of Food Technologists, most food scientists may not receive adequate training in this area. Effective presentations combine both scientific content and delivery mechanisms that demonstrate presenter enthusiasm for…

  11. Nonlocal Anomalous Hall Effect.

    PubMed

    Zhang, Steven S-L; Vignale, Giovanni

    2016-04-01

    The anomalous Hall (AH) effect is deemed to be a unique transport property of ferromagnetic metals, caused by the concerted action of spin polarization and spin-orbit coupling. Nevertheless, recent experiments have shown that the effect also occurs in a nonmagnetic metal (Pt) in contact with a magnetic insulator [yttrium iron garnet (YIG)], even when precautions are taken to ensure that there is no induced magnetization in the metal. We propose a theory of this effect based on the combined action of spin-dependent scattering from the magnetic interface and the spin-Hall effect in the bulk of the metal. At variance with previous theories, we predict the effect to be of first order in the spin-orbit coupling, just as the conventional anomalous Hall effect-the only difference being the spatial separation of the spin-orbit interaction and the magnetization. For this reason we name this effect the nonlocal anomalous Hall effect and predict that its sign will be determined by the sign of the spin-Hall angle in the metal. The AH conductivity that we calculate from our theory is in order of magnitude agreement with the measured values in Pt/YIG structures.

  12. Music Teacher Effectiveness Research.

    ERIC Educational Resources Information Center

    Brand, Manny

    Although relatively few studies exist, a review of the research reveals some common characteristics of an effective music teacher. Effective music teachers tend to be extroverted, enthusiastic, and care sincerely for their students. Such teachers are competent in musicianship (particularly in diagnosing and correcting musical errors and in using…

  13. Defining Effective Teaching

    ERIC Educational Resources Information Center

    Layne, L.

    2012-01-01

    The author looks at the meaning of specific terminology commonly used in student surveys: "effective teaching." The research seeks to determine if there is a difference in how "effective teaching" is defined by those taking student surveys and those interpreting the results. To investigate this difference, a sample group of professors and students…

  14. The Kaye Effect

    ERIC Educational Resources Information Center

    Binder, J. M.; Landig, A. J.

    2009-01-01

    The International Young Physicists' Tournament (IYPT) is a worldwide, annual competition for secondary school students. This is our solution to problem number 10, "The Kaye effect", as presented in the final round of the 21st IYPT in Trogir, Croatia. The Kaye effect occurs when a thin stream of shampoo or a different adequate non-Newtonian liquid…

  15. Cardiovascular Effects Of Weightlessness

    NASA Technical Reports Server (NTRS)

    Sandler, Harold

    1992-01-01

    NASA technical memorandum presents study of effects of weightlessness and simulations upon cardiovascular systems of humans and animals. Reviews research up to year 1987 in United States and Soviet space programs on such topics as physiological changes induced by weightlessness in outer space and by subsequent return to Earth gravity and also reviews deconditioning effects of prolonged bed rest on ground.

  16. Organizational Effectiveness of Schools.

    ERIC Educational Resources Information Center

    Miskel, Cecil

    1982-01-01

    Because organizational effectiveness of schools is difficult to define, a model is needed to explain the complexities of the concept. Two models offer some promise. One is the goal model, which defines effectiveness as the degree to which organizations meet or surpass their goals (either official or operational). The other is the system resource…

  17. A ''Voice Inversion Effect?''

    ERIC Educational Resources Information Center

    Bedard, Catherine; Belin, Pascal

    2004-01-01

    Voice is the carrier of speech but is also an ''auditory face'' rich in information on the speaker's identity and affective state. Three experiments explored the possibility of a ''voice inversion effect,'' by analogy to the classical ''face inversion effect,'' which could support the hypothesis of a voice-specific module. Experiment 1 consisted…

  18. A ''Voice Inversion Effect?''

    ERIC Educational Resources Information Center

    Bedard, Catherine; Belin, Pascal

    2004-01-01

    Voice is the carrier of speech but is also an ''auditory face'' rich in information on the speaker's identity and affective state. Three experiments explored the possibility of a ''voice inversion effect,'' by analogy to the classical ''face inversion effect,'' which could support the hypothesis of a voice-specific module. Experiment 1 consisted…

  19. [Side effects of antibiotics].

    PubMed

    Hoigné, R

    1975-03-01

    The clinically severe and newer forms of antibiotic side effects are reviewed. The study covers the following antibiotics: penicillins, cephalosporins, aminoglycosides and polymyxins, tetracyclines, chloramphenicol and thiamphenicol, macrolides and lincomycin, rifamycins and sulfonamides. Special reference is made to (1) hematologic side effects, and (2) general evaluation of drug reactions. The relationship between reaction time and clinical symptoms is of particular practical significance.

  20. Presenting Food Science Effectively

    ERIC Educational Resources Information Center

    Winter, Carl K.

    2016-01-01

    While the need to present food science information effectively is viewed as a critical competency for food scientists by the Institute of Food Technologists, most food scientists may not receive adequate training in this area. Effective presentations combine both scientific content and delivery mechanisms that demonstrate presenter enthusiasm for…

  1. Effectiveness and efficiency *

    PubMed Central

    McCormick, J. S.

    1981-01-01

    This paper proposes that doctors need to accept the technical meaning of terms used in economics such as effectiveness, efficiency, cost, input, process, cost benefit and outcome. The usefulness of these terms is discussed, with examples, and it is agreed that effectiveness and efficiency are best examined by those whose behaviour must alter as a result of the analysis. PMID:6796680

  2. Radiation effects in space

    SciTech Connect

    Fry, R.J.M.

    1987-07-01

    As more people spend more time in space, and the return to the moon and exploratory missions are considered, the risks require continuing examination. The effects of microgravity and radiation are two potential risks in space. These risks increase with increasing mission duration. This document considers the risk of radiation effects in space workers and explorers. 17 refs., 1 fig., 4 tabs.

  3. The Pygmalion Effect Lives

    ERIC Educational Resources Information Center

    Rosenthal, Robert

    1973-01-01

    Briefly reviewing his own research, and that of critics of the Pygmalion Effect, the author proposes a four-factor "theory" of the influences that produce the effect: the relationship of teachers to special students differs in climate, input, feedback, and output. (JM)

  4. Teacher Work Group Effectiveness

    ERIC Educational Resources Information Center

    Conley, Sharon; Fauske, Janice; Pounder, Diana G.

    2004-01-01

    Recent research links the development of a collaborative community of educators to enhanced teaching and learning effectiveness. This study contributes to this research by testing a work group effectiveness model with a sample of teachers from middle school teams. The study assesses the interrelationships among the model's antecedent variables…

  5. Effective Online Teachers

    ERIC Educational Resources Information Center

    Muirhead, Brent

    2006-01-01

    Effective online teaching is a popular topic in today's educational technology journals due to the vital role that educators play in the teaching and learning process. The author will provide insights into effective online teachers and highlight training and mentoring practices for online instructors at the University of Phoenix.

  6. Correlational effect size benchmarks.

    PubMed

    Bosco, Frank A; Aguinis, Herman; Singh, Kulraj; Field, James G; Pierce, Charles A

    2015-03-01

    Effect size information is essential for the scientific enterprise and plays an increasingly central role in the scientific process. We extracted 147,328 correlations and developed a hierarchical taxonomy of variables reported in Journal of Applied Psychology and Personnel Psychology from 1980 to 2010 to produce empirical effect size benchmarks at the omnibus level, for 20 common research domains, and for an even finer grained level of generality. Results indicate that the usual interpretation and classification of effect sizes as small, medium, and large bear almost no resemblance to findings in the field, because distributions of effect sizes exhibit tertile partitions at values approximately one-half to one-third those intuited by Cohen (1988). Our results offer information that can be used for research planning and design purposes, such as producing better informed non-nil hypotheses and estimating statistical power and planning sample size accordingly. We also offer information useful for understanding the relative importance of the effect sizes found in a particular study in relationship to others and which research domains have advanced more or less, given that larger effect sizes indicate a better understanding of a phenomenon. Also, our study offers information about research domains for which the investigation of moderating effects may be more fruitful and provide information that is likely to facilitate the implementation of Bayesian analysis. Finally, our study offers information that practitioners can use to evaluate the relative effectiveness of various types of interventions. PsycINFO Database Record (c) 2015 APA, all rights reserved.

  7. Assessing Effective Teaching.

    ERIC Educational Resources Information Center

    Tuckman, Bruce W.

    1995-01-01

    Teacher effectiveness can be evaluated by traditional performance-based evaluation, though that method has some limitations. Alternative approaches to teacher evaluation include student evaluation of teacher performance and portfolio assessment. The Tuckman Teacher Feedback Form is presented as a more effective self-improvement system than a…

  8. The polarized EMC effect

    SciTech Connect

    W. Bentz; I. C. Cloet; A. W. Thomas

    2007-02-01

    We calculate both the spin independent and spin dependent nuclear structure functions in an effective quark theory. The nucleon is described as a composite quark-diquark state, and the nucleus is treated in the mean field approximation. We predict a sizable polarized EMC effect, which could be confirmed in future experiments.

  9. The Kaye Effect

    ERIC Educational Resources Information Center

    Binder, J. M.; Landig, A. J.

    2009-01-01

    The International Young Physicists' Tournament (IYPT) is a worldwide, annual competition for secondary school students. This is our solution to problem number 10, "The Kaye effect", as presented in the final round of the 21st IYPT in Trogir, Croatia. The Kaye effect occurs when a thin stream of shampoo or a different adequate non-Newtonian liquid…

  10. Effective survey automation

    Treesearch

    John Weisberg; Jay Beaman

    2001-01-01

    Progress in the options for survey data collection and its effective processing continues. This paper focuses on the rapidly evolving capabilities of handheld computers, and their effective exploitation including links to data captured from scanned questionnaires (OMR and barcodes). The paper describes events in Parks Canada that led to the creation of survey software...

  11. Developing Effective Managers.

    ERIC Educational Resources Information Center

    Roberts, T.J.

    In this introductory work, the main principles on which British companies are basing management development programs are presented, and stages in assuring a supply of effective managerial talent are set forth: stages in assuring a supply of effective managerial t"lent are set forth: program planning based on clear objectives and…

  12. [Providing Effective Behavior Support.

    ERIC Educational Resources Information Center

    SAIL: Technical Assistance Journal, 1996

    1996-01-01

    This theme issue addresses the provision of behavioral support for students with behavior disorders. The first article, "Providing Effective Behavior Support to All Students: Procedures and Processes" (George Sugai), summarizes the literature on the effectiveness of various interventions and offers several models for examining the…

  13. PLEIOTROPIC EFFECTS OF STATINS

    PubMed Central

    Liao, James K.; Laufs, Ulrich

    2009-01-01

    Statins are potent inhibitors of cholesterol biosynthesis. In clinical trials, statins are beneficial in the primary and secondary prevention of coronary heart disease. However, the overall benefits observed with statins appear to be greater than what might be expected from changes in lipid levels alone, suggesting effects beyond cholesterol lowering. Indeed, recent studies indicate that some of the cholesterol-independent or “pleiotropic” effects of statins involve improving endothelial function, enhancing the stability of atherosclerotic plaques, decreasing oxidative stress and inflammation, and inhibiting the thrombogenic response. Furthermore, statins have beneficial extrahepatic effects on the immune system, CNS, and bone. Many of these pleiotropic effects are mediated by inhibition of isoprenoids, which serve as lipid attachments for intracellular signaling molecules. In particular, inhibition of small GTP-binding proteins, Rho, Ras, and Rac, whose proper membrane localization and function are dependent on isoprenylation, may play an important role in mediating the pleiotropic effects of statins. PMID:15822172

  14. [Psychoanalysis and Side Effect].

    PubMed

    Shirahase, Joichiro

    2015-01-01

    A study of psychoanalysis from the perspective of side effects reveals that its history was a succession of measures to deal with its own side effects. This, however, does not merely suggest that, as a treatment method, psychoanalysis is incomplete and weak: rather, its history is a record of the growth and development of psychoanalysis that discovered therapeutic significance from phenomena that were initially regarded as side effects, made use of these discoveries, and elaborated them as a treatment method. The approach of research seen during the course of these developments is linked to the basic therapeutic approach of psychoanalysis. A therapist therefore does not draw conclusions about a patient's words and behaviors from a single aspect, but continues to make efforts to actively discover a variety of meanings and values from them, and to make the patient's life richer and more productive. This therapeutic approach is undoubtedly one of the unique aspects of psychoanalysis. I discuss the issue of psychoanalysis and side effects with the aim of clarifying this unique characteristic of psychoanalysis. The phenomenon called resistance inevitably emerges during the process of psychoanalytic treatment. Resistance can not only obstruct the progress of therapy; it also carries the risk of causing a variety of disadvantages to the patient. It can therefore be seen as an adverse effect. However, if we re-examine this phenomenon from the perspective of transference, we find that resistance is in fact a crucial tool in psychoanalysis, and included in its main effect, rather than a side effect. From the perspective of minimizing the character of resistance as a side effect and maximizing its character as a main effect, I have reviewed logical organization, dynamic evaluation, the structuring of treatment, the therapist's attitudes, and the training of therapists. I conclude by stating that psychoanalysis has aspects that do not match the perspective known as a side

  15. Proton Damage Effects on Carbon Nanotube Field-Effect Transistors

    DTIC Science & Technology

    2014-06-19

    PROTON DAMAGE EFFECTS ON CARBON NANOTUBE FIELD-EFFECT TRANSISTORS THESIS Evan R. Kemp, Ctr...United States. AFIT-ENP-T-14-J-39 PROTON DAMAGE EFFECTS ON CARBON NANOTUBE FIELD-EFFECT TRANSISTORS THESIS Presented to...PROTON DAMAGE EFFECTS ON CARBON NANOTUBE FIELD-EFFECT TRANSISTORS Evan R. Kemp, BS Ctr, USAF Approved: // Signed

  16. Nonlocal Anomalous Hall Effect

    NASA Astrophysics Data System (ADS)

    Zhang, Steven S.-L.; Vignale, Giovanni

    2016-04-01

    The anomalous Hall (AH) effect is deemed to be a unique transport property of ferromagnetic metals, caused by the concerted action of spin polarization and spin-orbit coupling. Nevertheless, recent experiments have shown that the effect also occurs in a nonmagnetic metal (Pt) in contact with a magnetic insulator [yttrium iron garnet (YIG)], even when precautions are taken to ensure that there is no induced magnetization in the metal. We propose a theory of this effect based on the combined action of spin-dependent scattering from the magnetic interface and the spin-Hall effect in the bulk of the metal. At variance with previous theories, we predict the effect to be of first order in the spin-orbit coupling, just as the conventional anomalous Hall effect—the only difference being the spatial separation of the spin-orbit interaction and the magnetization. For this reason we name this effect the nonlocal anomalous Hall effect and predict that its sign will be determined by the sign of the spin-Hall angle in the metal. The AH conductivity that we calculate from our theory is in order of magnitude agreement with the measured values in Pt /YIG structures.

  17. Cardiovascular Effects of Felypressin

    PubMed Central

    Cecanho, Rodrigo; De Luca, Laurival Antonio; Ranali, José

    2006-01-01

    Cardiovascular effects of felypressin (FEL) were studied in Wistar rats. Heart rate and mean arterial pressure measurements were taken in awake rats treated with vasopressin (AVP), FEL, or epinephrine (EPI). Each group received either an intravenous (IV) or an intracerebroventricular V1 receptor antagonist, saline, area postrema removal, or sham surgery. Analysis of variance and Student-Newman-Keuls (P < .05) were applied. Felypressin and AVP induced a pressor effect, and bradycardia was inhibited by IV V1 antagonist. Intracerebroventricular V1 antagonist and area postrema removal enhanced their pressor effects. Epinephrine induced a higher pressor effect and a similar bradycardia that was not affected by the treatments. It was concluded that FEL depends on V1 receptors to induce pressor and bradycardic effects, and that it produces a high relationship between bradycardia and mean arterial pressure variation depending on area postrema and central V1 receptors. These effects are potentially less harmful to the cardiovascular system than the effects of EPI. PMID:17177590

  18. Bystander effects and radiotherapy.

    PubMed

    Marín, Alicia; Martín, Margarita; Liñán, Olga; Alvarenga, Felipe; López, Mario; Fernández, Laura; Büchser, David; Cerezo, Laura

    2015-01-01

    Radiation-induced bystander effects are defined as biological effects expressed after irradiation by cells whose nuclei have not been directly irradiated. These effects include DNA damage, chromosomal instability, mutation, and apoptosis. There is considerable evidence that ionizing radiation affects cells located near the site of irradiation, which respond individually and collectively as part of a large interconnected web. These bystander signals can alter the dynamic equilibrium between proliferation, apoptosis, quiescence or differentiation. The aim of this review is to examine the most important biological effects of this phenomenon with regard to areas of major interest in radiotherapy. Such aspects include radiation-induced bystander effects during the cell cycle under hypoxic conditions when administering fractionated modalities or combined radio-chemotherapy. Other relevant aspects include individual variation and genetics in toxicity of bystander factors and normal tissue collateral damage. In advanced radiotherapy techniques, such as intensity-modulated radiation therapy (IMRT), the high degree of dose conformity to the target volume reduces the dose and, therefore, the risk of complications, to normal tissues. However, significant doses can accumulate out-of-field due to photon scattering and this may impact cellular response in these regions. Protons may offer a solution to reduce out-of-field doses. The bystander effect has numerous associated phenomena, including adaptive response, genomic instability, and abscopal effects. Also, the bystander effect can influence radiation protection and oxidative stress. It is essential that we understand the mechanisms underlying the bystander effect in order to more accurately assess radiation risk and to evaluate protocols for cancer radiotherapy.

  19. Bystander effects and radiotherapy

    PubMed Central

    Marín, Alicia; Martín, Margarita; Liñán, Olga; Alvarenga, Felipe; López, Mario; Fernández, Laura; Büchser, David; Cerezo, Laura

    2014-01-01

    Radiation-induced bystander effects are defined as biological effects expressed after irradiation by cells whose nuclei have not been directly irradiated. These effects include DNA damage, chromosomal instability, mutation, and apoptosis. There is considerable evidence that ionizing radiation affects cells located near the site of irradiation, which respond individually and collectively as part of a large interconnected web. These bystander signals can alter the dynamic equilibrium between proliferation, apoptosis, quiescence or differentiation. The aim of this review is to examine the most important biological effects of this phenomenon with regard to areas of major interest in radiotherapy. Such aspects include radiation-induced bystander effects during the cell cycle under hypoxic conditions when administering fractionated modalities or combined radio-chemotherapy. Other relevant aspects include individual variation and genetics in toxicity of bystander factors and normal tissue collateral damage. In advanced radiotherapy techniques, such as intensity-modulated radiation therapy (IMRT), the high degree of dose conformity to the target volume reduces the dose and, therefore, the risk of complications, to normal tissues. However, significant doses can accumulate out-of-field due to photon scattering and this may impact cellular response in these regions. Protons may offer a solution to reduce out-of-field doses. The bystander effect has numerous associated phenomena, including adaptive response, genomic instability, and abscopal effects. Also, the bystander effect can influence radiation protection and oxidative stress. It is essential that we understand the mechanisms underlying the bystander effect in order to more accurately assess radiation risk and to evaluate protocols for cancer radiotherapy. PMID:25535579

  20. Immunosuppressive effects of lead

    USGS Publications Warehouse

    Franson, J. Christian; Feierabend, J.Scott; Russell, A.Brooke

    1986-01-01

    Immunosuppressive effects of lead were reported as early as 1966, when it was noted that lead increased the sensitivity of rats to bacterial endotoxins (Selye et al. 1966). Since then a substantial body of literature has demonstrated adverse effects of lead on the immune system in a variety of laboratory animals, but very little has been done in this area with avian species. Such immunosuppressive effects could be of significance to waterfowl populations, considering the potential for lead ingestion by waterfowl and subsequent exposure of these birds to disease agents.

  1. Bustling argon: biological effect

    PubMed Central

    2013-01-01

    Argon is a noble gas in group 18 of the periodic table. Certificated to exist in air atmosphere merely one century ago, discovery of argon shows interesting stories of researching and exploring. It was assumed to have no chemical activity. However, argon indeed present its biological effect on mammals. Narcotic effect of argon in diving operation and neur-protective function of argon in cerebral injury demonstrate that argon has crucial effect and be concentrated on is necessary. Furthermore, consider to be harmless to human, argon clinical application in therapy would be another option. PMID:24088583

  2. Effective Frequency Technique

    NASA Technical Reports Server (NTRS)

    Kirk, C. Laurence; Weng, Chi Y.

    2002-01-01

    An effective monochromatic frequency technique is described to represent the effects of finite spectral bandwidth for active and passive measurements centered on an absorption line, a trough region, or a slowly varying spectral feature. For Gaussian and rectangular laser line shapes, the effective frequency is shown to have a simple form which depends only on the instrumental line shape and bandwidth and not on the absorption line profile. The technique yields accuracies better than 0.1% for bandwidths less than 0.2 times the atmospheric line width.

  3. Immunosuppressive effects of lead

    USGS Publications Warehouse

    Franson, J. Christian; Feierabend, J.Scott; Russell, A.Brooke

    1986-01-01

    Immunosuppressive effects of lead were reported as early as 1966, when it was noted that lead increased the sensitivity of rats to bacterial endotoxins (Selye et al. 1966). Since then a substantial body of literature has demonstrated adverse effects of lead on the immune system in a variety of laboratory animals, but very little has been done in this area with avian species. Such immunosuppressive effects could be of significance to waterfowl populations, considering the potential for lead ingestion by waterfowl and subsequent exposure of these birds to disease agents.

  4. Seebeck effect in electrolytes.

    PubMed

    Chikina, I; Shikin, V; Varlamov, A A

    2012-07-01

    We study Seebeck effect in liquid electrolytes, starting from its simple neutral analog--thermodiffusion (so-called Ludwig-Soret or Soret effect). It is observed that when two or more subsystems of mobile particles are subjected to the temperature gradient, various types of them respond to it differently. In the case when these fractions, with different mobility parameters (Soret coefficients), are oppositely charged (a case typical for electrolytes), the nonhomogeneous internal electric field is generated. The latter field prevents these fractions from space separation and determines the intensity of the appearing Seebeck effect.

  5. Improving engineering effectiveness

    NASA Technical Reports Server (NTRS)

    Fiero, J. D.

    1985-01-01

    Methodologies to improve engineering productivity were investigated. The rocky road to improving engineering effectiveness is reviewed utilizing a specific semiconductor engineering organization as a case study. The organization had a performance problem regarding new product introductions. With the help of this consultant as a change agent the engineering team used a systems approach to through variables that were effecting their output significantly. Critical factors for improving this engineering organization's effectiveness and the roles/responsibilities of management, the individual engineers and the internal consultant are discussed.

  6. Scattering Effects in Proximity Effect Tunneling Spectroscopy.

    NASA Astrophysics Data System (ADS)

    Gai, Wei

    PETS (Proximity Effect Tunneling Spectroscopy) technique has been applied to Niobium/Yttrium and Niobium/Lutetium bilayers. We have determined electron - phonon interaction parameter lambda_{rm e -ph} is 0.55 for Yttrium and 0.67 for Lutetium. Spin fluctuations parameter lambda_{ rm S} is 0.20 for Yttrium and 0.33 for Lutetium. We found that the large spin fluctuations in Yttrium and Lutetium has responsibility to the absence of superconductivity in them. Our results have given a reasonable explanation of high superconducting transition temperature in them under high pressure. The large reflection coefficient and strong diffuse scattering at Nb/Y and Nb/Lu interface has been discovered and it should have strong influence on the transport properties of metallic superlattices. From the modeling study of elastic scattering in proximity effect tunnel junctions, we have explained why some conventional made high {rm T_{C}} superconducting tunnel junctions give ideal like characteristics in the gap region but variable strength phonon structures in the phonon region.

  7. Cytogenetic effects of cyclamates

    SciTech Connect

    Jemison, E.W.; Brown, K.; Rivers, B.; Knight, R.

    1984-01-01

    PHA-stimulated human peripheral lymphocytes were used as a model system for assessing the in vitro effects of calcium cyclamate. Techniques of autoradiography, cytological staining, cell counting, liquid scintillation and karyotyping were used to study the cytogenetic damage and biochemical effects of calcium cyclamate when assayed in 24 hour intervals for 96 hours. The cells were exposed to 10(-2) and 10(-3) molar concentrations of calcium cyclamate in TC 199 medium with fetal calf serum and antibiotics. It was noted that the addition of cyclamate increased mitotic rate of lymphocyte cells in cultures. It was determined that calcium cyclamate impaired the synthesis of deoxribonunucleic acid (as depicted by decreased incorporation of tritiated thymidine), reduced grain counts in autoradiographs and increased chromosome aberrations in cyclamate treated PHA stimulated peripheral blood lymphocytes in vitro. Morphological changes and growth rates showed significant effects. These studies indicate that calcium cyclamate has variable significant effects on leucocytes growth and chromosome morphology.

  8. Polarization Effects with Pendulums.

    ERIC Educational Resources Information Center

    Morgan, Bruce H.

    1982-01-01

    Describes an apparatus used to demonstrate effects observed with polarized light. The apparatus employs two pendulums attached to threads crossing orthogonally over an overhead projector. Several demonstrations using the apparatus are provided. (Author/JN)

  9. Environmental and Welfare Effects

    EPA Pesticide Factsheets

    View English or Spanish-language version of a fact sheet that highlights the key effects that support the EPA’s determination that current and future concentrations of greenhouse gases endanger public welfare.

  10. Hydrodynamic effects in proteins.

    PubMed

    Szymczak, Piotr; Cieplak, Marek

    2011-01-26

    Experimental and numerical results pertaining to flow-induced effects in proteins are reviewed. Special emphasis is placed on shear-induced unfolding and on the role of solvent mediated hydrodynamic interactions in the conformational transitions in proteins.

  11. Vaccine herd effect.

    PubMed

    Kim, Tae Hyong; Johnstone, Jennie; Loeb, Mark

    2011-09-01

    Vaccination ideally protects susceptible populations at high risk for complications of the infection. However, vaccines for these subgroups do not always provide sufficient effectiveness. The herd effect or herd immunity is an attractive way to extend vaccine benefits beyond the directly targeted population. It refers to the indirect protection of unvaccinated persons, whereby an increase in the prevalence of immunity by the vaccine prevents circulation of infectious agents in susceptible populations. The herd effect has had a major impact in the eradication of smallpox, has reduced transmission of pertussis, and protects against influenza and pneumococcal disease. A high uptake of vaccines is generally needed for success. In this paper we aim to provide an update review on the herd effect, focusing on the clinical benefit, by reviewing data for specific vaccines.

  12. Side Effects: Fatigue

    Cancer.gov

    Fatigue is a common side effect of many cancer treatments such as chemotherapy, radiation therapy, immunotherapy, and surgery. Anemia and pain can also cause fatigue. Learn about symptoms and way to manage fatigue.

  13. Side Effects: Diarrhea

    Cancer.gov

    Diarrhea, a side effect of cancer treatment, may cause symptoms such as loose, watery stools. Diarrhea can lead to dehydration and malnutrition in cancer patients. Learn about ways to treat and manage diarrhea during cancer treatment.

  14. Side Effects: Pain

    Cancer.gov

    Controlling pain is an important part of your cancer treatment plan. Learn how to track levels of pain. Find out how pain, a side effect of cancer treatment, is treated using acupuncture, biofeedback, and physical therapy.

  15. The Effects: Economy

    EPA Pesticide Factsheets

    Nutrient pollution has diverse and far-reaching effects on the U.S. economy, impacting tourism, property values, commercial fishing, recreational businesses and many other sectors that depend on clean water.

  16. Ototoxic Medications (Medication Effects)

    MedlinePlus

    ... Information for the Public / Hearing and Balance Ototoxic Medications (Medication Effects) By Barbara Cone, Patricia Dorn, Dawn Konrad- ... Audiology Information Series [PDF]. What Is Ototoxicity? Certain medications can damage the ear, resulting in hearing loss, ...

  17. Coefficients of Effective Length.

    ERIC Educational Resources Information Center

    Edwards, Roger H.

    1981-01-01

    Under certain conditions, a validity Coefficient of Effective Length (CEL) can produce highly misleading results. A modified coefficent is suggested for use when empirical studies indicate that underlying assumptions have been violated. (Author/BW)

  18. Radiation effects in space

    SciTech Connect

    Fry, R.J.M.

    1986-01-01

    The paper discusses the radiation environment in space that astronauts are likely to be exposed to. Emphasis is on proton and HZE particle effects. Recommendations for radiation protection guidelines are presented. (ACR)

  19. Pictorial Superiority Effect

    ERIC Educational Resources Information Center

    Nelson, Douglas L.; And Others

    1976-01-01

    Pictures generally show superior recognition relative to their verbal labels. This experiment was designed to link this pictorial superiority effect to sensory or meaning codes associated with the two types of symbols. (Editor)

  20. [Physiologic effects of hypothermia].

    PubMed

    Kovács, Eniko; Jenei, Zsigmond; Horváth, Anikó; Gellér, László; Szilágyi, Szabolcs; Király, Akos; Molnár, Levente; Sótonyi, Péter; Merkely, Béla; Zima, Endre

    2011-01-30

    Therapeutic use of hypothermia has come to the frontline in the past decade again in the prevention and in mitigation of neurologic impairment. The application of hypothermia is considered as a successful therapeutic measure not just in neuro- or cardiac surgery, but also in states causing brain injury or damage. According to our present knowledge this is the only proven therapeutic tool, which improves the neurologic outcome after cardiac arrest, decreasing the oxygen demand of the brain. Besides influencing the nervous system, hypothermia influences the function of the whole organ system. Beside its beneficial effects, it has many side-effects, which may be harmful to the patient. Before using it for a therapeutic purpose, it is very important to be familiar with the physiology and complications of hypothermia, to know, how to prevent and treat its side-effects. The purpose of this article is to summarize the physiologic and pathophysiologic effects of hypothermia.

  1. Effects of New Technologies.

    ERIC Educational Resources Information Center

    Social and Labour Bulletin, 1980

    1980-01-01

    Transnational implications of technological change and innovation in telecommunications are discussed, including impact on jobs and industrial relations, computer security, access to information, and effects of technological innovation on international economic systems. (SK)

  2. Cardiovascular Effects of Weightlessness

    NASA Technical Reports Server (NTRS)

    Short, K.

    1985-01-01

    Physiological changes resulting from long term weightlessness are reviewed and activities conducted to study cardiovascular deconditioning at NASA Ames are discussed. Emphasis is on using monkeys in chair rest, water immersion, and tilt table studies to simulate space environment effects.

  3. Side Effects: Appetite Loss

    Cancer.gov

    Cancer treatments may lower your appetite. Side effects such as nausea, fatigue, or mouth sores can also making eating difficult. Learn how to eat well to avoid losing weight or becoming dehydrated, so you stay strong during treatment.

  4. Side Effects: Sleep Problems

    Cancer.gov

    Sleep problems are a common side effect during cancer treatment. Find out how a polysomnogram can assess sleep problems. Learn about the benefits of managing sleep disorders in men and women with cancer.

  5. [Cardiovascular effects of doping].

    PubMed

    Gauthier, J

    2001-09-01

    Cardiovascular effects of doping drugs are numerous, with different mechanisms: vasoconstriction of amphetamines, erythropoietin and cocaine; sodium water retention of anabolic steroids and corticosteroids; elevation in blood viscosity of erythropoietin, perflurocarbon emulsion, recombinant hemoglobin and anabolic steroids; sympathetic nervous system activation of amphetamines, beta 2 agonists and clenbuterol; lipids profile disorder of anabolic steroids. Physical activity consequences, particularly bradycardia and dehydration, are worsening. Thrombosis and arrythmogenic effects, with possibility of sudden death, are the severe immediate events. Hypertension and coronary diseases are medium-term effects; acute myocardial infarction is frequent. Heart failure can be secondary to cardiac muscle direct fibrosis, like with anabolic steroids. These cardiovascular effects are serious and it is necessary to early detect the doping drugs use in sporstmen; all prescribing physician should be aware of existing drugs and their clinical events.

  6. Theme: Effective Teaching.

    ERIC Educational Resources Information Center

    Luft, Vernon D.; And Others

    1993-01-01

    Discusses effective teaching and its relationship to learning styles, instructional processes, and teacher commitment. Stresses the importance of knowing the students and the subject matter and developing students' higher order thinking skills. (JOW)

  7. Climate Effects on Health

    MedlinePlus

    ... Chapter . Additional information regarding the health effects of climate change and references to supporting literature can be found ... globalchange.gov/engage/activities-products/NCA3/technical-inputs . Climate change, together with other natural and human-made health ...

  8. Cepheid/Blazhko Effect

    NASA Astrophysics Data System (ADS)

    Teays, Terry

    1995-03-01

    Two separate research projects were covered under this contract. The first project was to study the temperatures of Cepheid variable stars, while the second was a study of the Blazhko effect in RR Lyrae, both of them using IUE data.

  9. Dynamic Treatment Effects

    PubMed Central

    Heckman, James J.; Humphries, John Eric; Veramendi, Gregory

    2016-01-01

    This paper develops robust models for estimating and interpreting treatment effects arising from both ordered and unordered multistage decision problems. Identification is secured through instrumental variables and/or conditional independence (matching) assumptions. We decompose treatment effects into direct effects and continuation values associated with moving to the next stage of a decision problem. Using our framework, we decompose the IV estimator, showing that IV generally does not estimate economically interpretable or policy relevant parameters in prototypical dynamic discrete choice models, unless policy variables are instruments. Continuation values are an empirically important component of estimated total treatment effects of education. We use our analysis to estimate the components of what LATE estimates in a dynamic discrete choice model. PMID:27041793

  10. Dynamic Treatment Effects.

    PubMed

    Heckman, James J; Humphries, John Eric; Veramendi, Gregory

    2016-02-01

    This paper develops robust models for estimating and interpreting treatment effects arising from both ordered and unordered multistage decision problems. Identification is secured through instrumental variables and/or conditional independence (matching) assumptions. We decompose treatment effects into direct effects and continuation values associated with moving to the next stage of a decision problem. Using our framework, we decompose the IV estimator, showing that IV generally does not estimate economically interpretable or policy relevant parameters in prototypical dynamic discrete choice models, unless policy variables are instruments. Continuation values are an empirically important component of estimated total treatment effects of education. We use our analysis to estimate the components of what LATE estimates in a dynamic discrete choice model.

  11. Strategies for Effective Outsourcing.

    ERIC Educational Resources Information Center

    Moneta, Larry; Dillon, William L.

    2001-01-01

    Emphasizes strategies that can be employed for effective outsourcing in higher education settings. Several models of outsourcing are identified and described, and examples of institutions using each model are provided. (GCP)

  12. Developing Effective Performance Measures

    DTIC Science & Technology

    2014-10-14

    University When Performance Measurement Goes Bad Laziness Vanity Narcissism Too Many Pettiness Inanity 52 Developing Effective...Kasunic, October 14, 2014 © 2014 Carnegie Mellon University Narcissism Measuring performance from the organization’s point of view, rather than from

  13. Effects of Anesthesia

    MedlinePlus

    ... previous surgery, be sure to tell the physician anesthesiologist. Regional Anesthesia The potential side effects of regional ... with past surgeries or procedures, tell your physician anesthesiologist, who may be able to give you medicine ...

  14. Radiative transfer dynamo effect

    DOE PAGES

    Munirov, Vadim R.; Fisch, Nathaniel J.

    2017-01-17

    Here, magnetic fields in rotating and radiating astrophysical plasma can be produced due to a radiative interaction between plasma layers moving relative to each other. The efficiency of current drive, and with it the associated dynamo effect, is considered in a number of limits. It is shown here, however, that predictions for these generated magnetic fields can be significantly higher when kinetic effects, previously neglected, are taken into account.

  15. Hall Effect Spintronics

    DTIC Science & Technology

    2011-04-01

    spin-transfer torque gives rise to magnetization reversal and excitation of spin-waves in ferromagnet /normal- metal / ferromagnet trilayers (F/N/F...applications based on the extraordinary Hall effect (EHE). The work was focused on three major tasks: 1. Preparation and study of CoPd multilayers ...D. Rosenblatt, M. Karpovski and A. Gerber, Reversal of the Extraordinary Hall Effect polarity in thin Co-Pd multilayers ., Appl. Phys. Lett., 96

  16. Nocturnal aircraft noise effects.

    PubMed

    Basner, M; Samel, A

    2004-01-01

    Noise protection associated with the construction and extension of airports in the Federal Republic of Germany has been regulated by the law for protection against aircraft noise since 1971. This legislation is due for revision because of different aspects. One aspect is the growth of air traffic which has led many airports to the limits of their capacity and in search of new ways of adaptation to the increasing demand for flight services. Another aspect is the increasing concern of the population about noise effects which has to be addressed by better protection against the effects of aircraft noise. The framework conditions of policy in terms of society as a whole, its health and economic environment need to be put into effect by political action. Science can contribute to this goal by performing noise effects research and by providing recommendations to the political body. However, it remains controversial, what measures are necessary or adequate to assure effective protection of the population against aircraft noise. This is particularly true for the protection of rest and sleep at night. The problem of finding a common basis for adequate recommendations is associated with (1) the low number of primary studies, which also exhibited highly variable results and assessments, (2) the handling of acoustic or psycho-acoustic dimensions for quantifying psychological or physiological reactions, and (3) the conception of how far preventive measures have to go to prove effective. With this in mind, the DLR Institute for Aerospace Medicine is conducting a large-scale, multi-stage study for investigating the acute effects of nocturnal aircraft noise on human sleep. This enterprise is implemented in the framework of the HGF/DLR project "Quiet Air Traffic" for developing sustainable assessment criteria for human-specific effects of aircraft noise at night.

  17. Radiative transfer dynamo effect

    NASA Astrophysics Data System (ADS)

    Munirov, Vadim R.; Fisch, Nathaniel J.

    2017-01-01

    Magnetic fields in rotating and radiating astrophysical plasma can be produced due to a radiative interaction between plasma layers moving relative to each other. The efficiency of current drive, and with it the associated dynamo effect, is considered in a number of limits. It is shown here, however, that predictions for these generated magnetic fields can be significantly higher when kinetic effects, previously neglected, are taken into account.

  18. Strategies for effective meetings.

    PubMed

    Gerwick, Michele A

    2013-04-01

    This article provides basic strategies for conducting effective meetings and providing committee chairs and members with a sense of accomplishment. Health care professionals can become easily frustrated regarding the need to attend meetings. They may perceive that attending a meeting is a waste of their valuable time, that nothing is ever accomplished, and that their input is not valued. Committee leaders need to use effective strategies to enhance each committee member's sense of accomplishment. Copyright 2013, SLACK Incorporated.

  19. Effects of periodic discharges

    NASA Technical Reports Server (NTRS)

    Ford, F. E.

    1977-01-01

    Periodic capacity checks are assessed as well as the effects of periodic discharges on the cycle life and the performance of cells during the cycle life. Topics discussed include the effect of the amount of electrolyte on cell capacity at 35 C; battery design for spacecraft; electrolyte starvation theory; battery separator degradation; negative electrode stability; voltage regulation; operating temperatures; and integration of reconditioning systems using microprocessors.

  20. Secondary pool boiling effects

    NASA Astrophysics Data System (ADS)

    Kruse, C.; Tsubaki, A.; Zuhlke, C.; Anderson, T.; Alexander, D.; Gogos, G.; Ndao, S.

    2016-02-01

    A pool boiling phenomenon referred to as secondary boiling effects is discussed. Based on the experimental trends, a mechanism is proposed that identifies the parameters that lead to this phenomenon. Secondary boiling effects refer to a distinct decrease in the wall superheat temperature near the critical heat flux due to a significant increase in the heat transfer coefficient. Recent pool boiling heat transfer experiments using femtosecond laser processed Inconel, stainless steel, and copper multiscale surfaces consistently displayed secondary boiling effects, which were found to be a result of both temperature drop along the microstructures and nucleation characteristic length scales. The temperature drop is a function of microstructure height and thermal conductivity. An increased microstructure height and a decreased thermal conductivity result in a significant temperature drop along the microstructures. This temperature drop becomes more pronounced at higher heat fluxes and along with the right nucleation characteristic length scales results in a change of the boiling dynamics. Nucleation spreads from the bottom of the microstructure valleys to the top of the microstructures, resulting in a decreased surface superheat with an increasing heat flux. This decrease in the wall superheat at higher heat fluxes is reflected by a "hook back" of the traditional boiling curve and is thus referred to as secondary boiling effects. In addition, a boiling hysteresis during increasing and decreasing heat flux develops due to the secondary boiling effects. This hysteresis further validates the existence of secondary boiling effects.

  1. Potassium: more beneficial effects.

    PubMed

    He, F J; MacGregor, G A

    2003-10-01

    Over 70 years ago, potassium was found to have a natriuretic effect and was used in patients with heart failure. However, it took many years for its role in the control of blood pressure to be recognized. Recently, epidemiological and clinical studies in man and experimental studies in animals have shown that increasing potassium intake towers blood pressure and that communities with a high potassium intake tend to have lower population blood pressures. Several studies have shown an interaction between salt intake and potassium intake. However, the recent DASH-Sodium (Dietary Approaches to Stop Hypertension) study demonstrates an additive effect of a low salt and high potassium diet on blood pressure. Increasing potassium intake may have other beneficial effects, for example, reducing the risk of stroke and preventing the development of renal disease independent of its effect on blood pressure. A high potassium intake reduces calcium excretion and could play an important role in the management of hypercalciuria and kidney stone formation, as well as bone demineralization. Potassium intake may also play an important role in carbohydrate intolerance. A reduced serum potassium increases the risk of lethal ventricular arrhythmias in those at risk, i.e. patients with ischemic heart disease, heart failure or left ventricular hypertrophy, and increasing potassium intake may prevent this. In this article, we address the evidence for the important role of potassium intake in regulating blood pressure and other beneficial effects of potassium which may be independent of and additional to its effect on blood pressure.

  2. Effective Transport Properties

    NASA Astrophysics Data System (ADS)

    Mauri, Roberto

    In this chapter we study a particular case of multiphase systems, namely two-phase materials in which one of the phases is randomly dispersed in the other, so that the composite can be viewed on a macroscale as an effective continuum, with well defined properties. In general, the theoretical determination of the parameter for an effective medium requires, as a rule, the solution of a corresponding transport problem at the microscale, which takes into account the morphology of the system and its evolution. As the mathematical problem is well-posed on a microscale, this can be accomplished using, for example, the multiple scale approach shown in Chap. 11 ; however, the task requires massive computations and is therefore difficult to implement from the practical standpoint. Here, instead, we focus on a deterministic approach to the problem, where the geometry and spatial configuration of the particles comprising the included phase are given and the solution to the microscale problem is therefore sought analytically. As examples, we study the effective thermal conductivity of solid reinforced materials (Sect. 10.1), the effective viscosity of non-colloidal suspensions (Sect. 10.2), the effective permeability of porous materials (10.3) and the effective self- and gradient diffusivities of colloidal suspensions (Sect. 10.4). Then, in Sect. 10.5, an alternative dynamic definition of the transport coefficients is considered, which can also serve as a basis to determine the effective properties of complex systems.

  3. Spin Hall effects

    NASA Astrophysics Data System (ADS)

    Sinova, Jairo; Valenzuela, Sergio O.; Wunderlich, J.; Back, C. H.; Jungwirth, T.

    2015-10-01

    Spin Hall effects are a collection of relativistic spin-orbit coupling phenomena in which electrical currents can generate transverse spin currents and vice versa. Despite being observed only a decade ago, these effects are already ubiquitous within spintronics, as standard spin-current generators and detectors. Here the theoretical and experimental results that have established this subfield of spintronics are reviewed. The focus is on the results that have converged to give us the current understanding of the phenomena, which has evolved from a qualitative to a more quantitative measurement of spin currents and their associated spin accumulation. Within the experimental framework, optical-, transport-, and magnetization-dynamics-based measurements are reviewed and linked to both phenomenological and microscopic theories of the effect. Within the theoretical framework, the basic mechanisms in both the extrinsic and intrinsic regimes are reviewed, which are linked to the mechanisms present in their closely related phenomenon in ferromagnets, the anomalous Hall effect. Also reviewed is the connection to the phenomenological treatment based on spin-diffusion equations applicable to certain regimes, as well as the spin-pumping theory of spin generation used in many measurements of the spin Hall angle. A further connection to the spin-current-generating spin Hall effect to the inverse spin galvanic effect is given, in which an electrical current induces a nonequilibrium spin polarization. This effect often accompanies the spin Hall effect since they share common microscopic origins. Both can exhibit the same symmetries when present in structures comprising ferromagnetic and nonmagnetic layers through their induced current-driven spin torques or induced voltages. Although a short chronological overview of the evolution of the spin Hall effect field and the resolution of some early controversies is given, the main body of this review is structured from a pedagogical

  4. A "voice inversion effect?".

    PubMed

    Bédard, Catherine; Belin, Pascal

    2004-07-01

    Voice is the carrier of speech but is also an "auditory face" rich in information on the speaker's identity and affective state. Three experiments explored the possibility of a "voice inversion effect," by analogy to the classical "face inversion effect," which could support the hypothesis of a voice-specific module. Experiment 1 consisted of a gender identification task on two syllables pronounced by 90 speakers (boys, girls, men, and women). Experiment 2 consisted of a speaker discrimination task on pairs of syllables (8 men and 8 women). Experiment 3 consisted of an instrument discrimination task on pairs of melodies (8 string and 8 wind instruments). In all three experiments, stimuli were presented in 4 conditions: (1) no inversion; (2) temporal inversion (e.g., backwards speech); (3) frequency inversion centered around 4000 Hz; and (4) around 2500 Hz. Results indicated a significant decrease in performance caused by sound inversion, with a much stronger effect for frequency than for temporal inversion. Interestingly, although frequency inversion markedly affected timbre for both voices and instruments, subjects' performance was still above chance. However, performance at instrument discrimination was much higher than for voices, preventing comparison of inversion effects for voices vs. non-vocal stimuli. Additional experiments will be necessary to conclude on the existence of a possible "voice inversion effect."

  5. Knowledge of contraceptive effectiveness.

    PubMed

    Eisenberg, David L; Secura, Gina M; Madden, Tessa E; Allsworth, Jenifer E; Zhao, Qiuhong; Peipert, Jeffrey F

    2012-06-01

    The purpose of this study was to determine women's knowledge of contraceptive effectiveness. We performed a cross-sectional analysis of a contraceptive knowledge questionnaire that had been completed by 4144 women who were enrolled in the Contraceptive CHOICE Project before they received comprehensive contraceptive counseling and chose their method. For each contraceptive method, women were asked "what percentage would get pregnant in a year: <1%, 1-5%, 6-10%, >10%, don't know." Overall, 86% of subjects knew that the annual risk of pregnancy is >10% if no contraception is used. More than 45% of women overestimate the effectiveness of depo-medroxyprogesterone acetate, pills, the patch, the ring, and condoms. After adjustment for age, education, and contraceptive history, the data showed that women who chose the intrauterine device (adjusted relative risk, 6.9; 95% confidence interval, 5.6-8.5) or implant (adjusted relative risk, 5.9; 95% confidence interval, 4.7-7.3) were significantly more likely to identify the effectiveness of their method accurately compared with women who chose either the pill, patch, or ring. This cohort demonstrated significant knowledge gaps regarding contraceptive effectiveness and over-estimated the effectiveness of pills, the patch, the ring, depo-medroxyprogesterone acetate, and condoms. Copyright © 2012 Mosby, Inc. All rights reserved.

  6. Relativistic effects in chemistry

    SciTech Connect

    Yatsimirskii, K.B.

    1995-11-01

    Relativistic effects become apparent when the velocity of the electron is arbitrarily close to the speed of light (137 au) without actually attaining it (in heavy atoms of elements at the end of Mendeleev`s Periodic Table). At the orbital level, the relativistic effect is apparent in the radial contraction of penetrating s and p shells, expansion of nonpenetrating d and f shells, and the spin-orbit splitting of p-,d-, and f-shells. The appearance of a relativistic effect is indicated in the variation in the electronic configurations of the atoms in the Periodic Table, the appearance of new types of closed electron shells (6s{sub 1/2}{sup 2}, 6p{sub 1/2}{sup 2}, 7s{sub 1/2}{sup 2}, 5d{sub 3/2}{sup 4}), the stabilization of unstable oxidation states of heavy elements, the characteristic variation in the ionization enthalpies of heavy atoms, their electron affinity, hydration energies, redox potentials, and optical electronegativities. In the spectra of coordination compounds, a relativistic effect is observed when comparing the position of the charge transfer bands in analogous compounds, the parameters characterizing the ligand field strength (10Dq), the interatomic distances and angles in compounds of heavy elements. A relativistic effect is also apparent in the ability of heavy metals to form clusters and superclusters. Relativistic corrections also affect other properties of heavy metal compounds (force constants, dipole moments, biological activity, etc.).

  7. Mitochondrial threshold effects.

    PubMed Central

    Rossignol, Rodrigue; Faustin, Benjamin; Rocher, Christophe; Malgat, Monique; Mazat, Jean-Pierre; Letellier, Thierry

    2003-01-01

    The study of mitochondrial diseases has revealed dramatic variability in the phenotypic presentation of mitochondrial genetic defects. To attempt to understand this variability, different authors have studied energy metabolism in transmitochondrial cell lines carrying different proportions of various pathogenic mutations in their mitochondrial DNA. The same kinds of experiments have been performed on isolated mitochondria and on tissue biopsies taken from patients with mitochondrial diseases. The results have shown that, in most cases, phenotypic manifestation of the genetic defect occurs only when a threshold level is exceeded, and this phenomenon has been named the 'phenotypic threshold effect'. Subsequently, several authors showed that it was possible to inhibit considerably the activity of a respiratory chain complex, up to a critical value, without affecting the rate of mitochondrial respiration or ATP synthesis. This phenomenon was called the 'biochemical threshold effect'. More recently, quantitative analysis of the effects of various mutations in mitochondrial DNA on the rate of mitochondrial protein synthesis has revealed the existence of a 'translational threshold effect'. In this review these different mitochondrial threshold effects are discussed, along with their molecular bases and the roles that they play in the presentation of mitochondrial diseases. PMID:12467494

  8. Effective Documentation Tools

    NASA Technical Reports Server (NTRS)

    Sleboda, Claire

    1997-01-01

    Quality assurance programs provide a very effective means to monitor and evaluate medical care. Quality assurance involves: (1) Identify a problem; (2) Determine the source and nature of the problem; (3) Develop policies and methods to effect improvement; (4) Implement those polices; (5) Monitor the methods applied; and (6) Evaluate their effectiveness. Because this definition of quality assurance so closely resembles the Nursing Process, the health unit staff was able to use their knowledge of the nursing process to develop many forms which improve the quality of patient care. These forms include the NASA DFRC Service Report, the occupational injury form (Incident Report), the patient survey (Pre-hospital Evaluation/Care Report), the Laboratory Log Sheet, the 911 Run Sheet, and the Patient Assessment Stamp. Examples and steps which are followed to generate these reports are described.

  9. Giving effective presentations.

    PubMed

    Englehart, Nadine

    2004-03-01

    Apprehension about oral communication, or public speaking is rated as the number one fear among most individuals. Developing skill in, and comfort with, public speaking is important whether we are presenting oral reports and proposals, responding to questions, or training co-workers. Effective speakers are able to communicate information in a way that stimulates interest, helps the audience to understand and remember, and influences attitudes and behaviours. Many of us think that effective speakers are born rather than made. In truth most successful speakers work hard and invest a great deal of time and effort in to improving their speaking capabilities. Effective public speaking is a learned skill and activity that requires lots of practice. Like other learned skills, having a strategy with clear action steps can help you achieve your goal.

  10. Security effectiveness review (SER)

    SciTech Connect

    Kouprianova, I.; Ek, D.; Showalter, R.; Bergman, M.

    1998-08-01

    As part of the on-going DOE/Russian MPC and A activities at the Institute of Physics and Power Engineering (IPPE) and in order to provide a basis for planning MPC and A enhancements, an expedient method to review the effectiveness of the MPC and A system has been adopted. These reviews involve the identification of appropriate and cost-effective enhancements of facilities at IPPE. This effort requires a process that is thorough but far less intensive than a traditional vulnerability assessment. The SER results in a quick assessment of current and needed enhancements. The process requires preparation and coordination between US and Russian analysts before, during, and after information gathering at the facilities in order that the analysis is accurate, effective, and mutually agreeable. The goal of this paper is to discuss the SER process, including the objectives, time scale, and lessons learned at IPPE.

  11. The Mozart Effect.

    PubMed

    Hughes, John R.

    2001-10-01

    This review deals with the Mozart Effect, an improvement of performance while listening to Mozart music. Previous studies have shown improved spatial temporal reasoning and improved IQ test results and neurophysiological changes, mainly increased coherence among different groups of subjects. This review emphasizes the effect on epileptiform patterns, both generalized and focal; provides an example of a chronic effect over a period of 1-2 days; addresses the distinctive aspects of the music to account for this phenomenon and shows that long-term periodicity in the power of the music is a special quality; and deals with the melodic line and shows that Mozart repeats the melodic line much more frequently than other well-known composers. It is likely that the superorganization of the cerebral cortex resonates with great organization found in Mozart music.

  12. Aviation noise effects

    NASA Astrophysics Data System (ADS)

    Newman, J. S.; Beattie, K. R.

    1985-03-01

    This report summarizes the effects of aviation noise in many areas, ranging from human annoyance to impact on real estate values. It also synthesizes the findings of literature on several topics. Included in the literature were many original studies carried out under FAA and other Federal funding over the past two decades. Efforts have been made to present the critical findings and conclusions of pertinent research, providing, when possible, a bottom line conclusion, criterion or perspective. Issues related to aviation noise are highlighted, and current policy is presented. Specific topic addressed include: annoyance; Hearing and hearing loss; noise metrics; human response to noise; speech interference; sleep interference; non-auditory health effects of noise; effects of noise on wild and domesticated animals; low frequency acoustical energy; impulsive noise; time of day weightings; noise contours; land use compatibility; and real estate values. This document is designed for a variety of users, from the individual completely unfamiliar with aviation noise to experts in the field.

  13. Metallic field effect transistors

    NASA Astrophysics Data System (ADS)

    Farooq, Hassan

    This thesis investigates the principle of operation behind metallic-field effect transistors (METFETs) through a systematic study of atomistic simulations performed on metallic bulk, nanowire and transistor structures. In particular, density functional theory (DFT) and non-equilibrium green's function (NEGF) based models were used to study the effect on the bandstructure and density of states of highly scaled metallic nanowires with varying parameters such as crystal orientation, cross-sectional area, and applied external bias. Similarly, the effect of varying similar parameters on the transfer and output characteristics of highly scaled metallic transistors was studied. Furthermore, oxide interfaces with metallic channels were investigated. The simulation results show that a gold METFET in the [100] crystal orientation has an I ON /IOFF ratio of 41, ION of 29.5microA and fT of 6.7THz, outperforming similarly sized MOSFETs as a promising alternative for use in high-frequency circuits.

  14. Cosmological memory effect

    NASA Astrophysics Data System (ADS)

    Tolish, Alexander; Wald, Robert M.

    2016-08-01

    The "memory effect" is the permanent change in the relative separation of test particles resulting from the passage of gravitational radiation. We investigate the memory effect for a general, spatially flat Friedmann-Lemaître-Robertson-Walker (FLRW) cosmology by considering the radiation associated with emission events involving particle-like sources. We find that if the resulting perturbation is decomposed into scalar, vector, and tensor parts, only the tensor part contributes to memory. Furthermore, the tensor contribution to memory depends only on the cosmological scale factor at the source and observation events, not on the detailed expansion history of the universe. In particular, for sources at the same luminosity distance, the memory effect in a spatially flat FLRW spacetime is enhanced over the Minkowski case by a factor of (1 +z ).

  15. Unparticle Casimir effect

    NASA Astrophysics Data System (ADS)

    Frassino, Antonia M.; Nicolini, Piero; Panella, Orlando

    2017-09-01

    In this paper we present the un-Casimir effect, namely the study of the Casimir energy in the presence of an unparticle component in addition to the electromagnetic field contribution. The distinctive feature of the un-Casimir effect is a fractalization of metallic plates. This result emerges through a new dependence of the Casimir energy on the plate separation that scales with a continuous power controlled by the unparticle dimension. As long as the perfect conductor approximation is valid, we find bounds on the unparticle scale that are independent of the effective coupling constant between the scale invariant sector and ordinary matter. We find regions of the parameter space such that for plate distances around 5 μm and larger the un-Casimir bound wins over the other bounds.

  16. Effective Nutritional Supplement Combinations

    NASA Astrophysics Data System (ADS)

    Cooke, Matt; Cribb, Paul J.

    Few supplement combinations that are marketed to athletes are supported by scientific evidence of their effectiveness. Quite often, under the rigor of scientific investigation, the patented combination fails to provide any greater benefit than a group given the active (generic) ingredient. The focus of this chapter is supplement combinations and dosing strategies that are effective at promoting an acute physiological response that may improve/enhance exercise performance or influence chronic adaptations desired from training. In recent years, there has been a particular focus on two nutritional ergogenic aids—creatine monohydrate and protein/amino acids—in combination with specific nutrients in an effort to augment or add to their already established independent ergogenic effects. These combinations and others are discussed in this chapter.

  17. Paramagnetic Spin Seebeck Effect

    NASA Astrophysics Data System (ADS)

    Wu, Stephen M.; Pearson, John E.; Bhattacharya, Anand

    2015-05-01

    We report the observation of the longitudinal spin Seebeck effect in paramagnetic insulators. By using a microscale on-chip local heater, we generate a large thermal gradient confined to the chip surface without a large increase in the total sample temperature. Using this technique at low temperatures (<20 K ), we resolve the paramagnetic spin Seebeck effect in the insulating paramagnets Gd3Ga5O12 (gadolinium gallium garnet) and DyScO3 (DSO), using either W or Pt as the spin detector layer. By taking advantage of the strong magnetocrystalline anisotropy of DSO, we eliminate contributions from the Nernst effect in W or Pt, which produces a phenomenologically similar signal.

  18. Paramagnetic spin seebeck effect.

    PubMed

    Wu, Stephen M; Pearson, John E; Bhattacharya, Anand

    2015-05-08

    We report the observation of the longitudinal spin Seebeck effect in paramagnetic insulators. By using a microscale on-chip local heater, we generate a large thermal gradient confined to the chip surface without a large increase in the total sample temperature. Using this technique at low temperatures (<20  K), we resolve the paramagnetic spin Seebeck effect in the insulating paramagnets Gd3Ga5O12 (gadolinium gallium garnet) and DyScO3 (DSO), using either W or Pt as the spin detector layer. By taking advantage of the strong magnetocrystalline anisotropy of DSO, we eliminate contributions from the Nernst effect in W or Pt, which produces a phenomenologically similar signal.

  19. Paramagnetic Spin Seebeck Effect

    SciTech Connect

    Wu, Stephen M.; Pearson, John E.; Bhattacharya, Anand

    2015-05-01

    We report the observation of the longitudinal spin Seebeck effect in paramagnetic insulators. By using a microscale on-chip local heater, we generate a large thermal gradient confined to the chip surface without a large increase in the total sample temperature. Using this technique at low temperatures (< 20 K), we resolve the paramagnetic spin Seebeck effect in the insulating paramagnets Gd3Ga5O12 (gadolinium gallium garnet) and DyScO3 (DSO), using either W or Pt as the spin detector layer. By taking advantage of the strong magnetocrystalline anisotropy of DSO, we eliminate contributions from the Nernst effect in W or Pt, which produces a phenomenologically similar signal.

  20. Effective string theory revisited

    NASA Astrophysics Data System (ADS)

    Dubovsky, Sergei; Flauger, Raphael; Gorbenko, Victor

    2012-09-01

    We revisit the effective field theory of long relativistic strings such as confining flux tubes in QCD. We derive the Polchinski-Strominger interaction by a calculation in static gauge. This interaction implies that a non-critical string which initially oscillates in one direction gets excited in orthogonal directions as well. In static gauge no additional term in the effective action is needed to obtain this effect. It results from a one-loop calculation using the Nambu-Goto action. Non-linearly realized Lorentz symmetry is manifest at all stages in dimensional regularization. We also explain that independent of the number of dimensions non-covariant counterterms have to be added to the action in the commonly used zeta-function regularization.

  1. Cost effective lighting

    SciTech Connect

    Morse, O.; Verderber, R.

    1987-07-01

    Long-life replacement lamps for the incandescent lamp have been evaluated with regard to their cost effectiveness. The replacements include the use of energy buttons that extend lamp life as well as an adaptive fluorescent circline lamp that will fit into existing incandescent lamp sockets. The initial, operating, and replacement costs for one million lumen-hours are determined for each lamp system. We find the most important lighting cost component is the operating cost. Using lamps that are less efficient or devices that cause lamps to operate less efficiently are not cost-effective. The adaptive fluorescent circline lamp, even at an initial cost of $15.00, is the most cost effective source of illumination compared to the incandescent lamp and lamp systems examined. 3 refs., 6 tabs.

  2. Relative age effect: implications for effective practice.

    PubMed

    Andronikos, Georgios; Elumaro, Adeboye Israel; Westbury, Tony; Martindale, Russell J J

    2016-01-01

    Physical and psychological differences related to birthdate amongst athletes of the same selection year have been characterised as the "relative age effects" (RAEs). RAEs have been identified in a variety of sports, both at youth and adult level, and are linked with dropout of athletes and a reduction of the talent pool. This study examined the existence, mechanisms and possible solutions to RAEs using qualitative methodology. Seven experts in the field of talent identification and development were interviewed. Inductive analysis of the data showed that, while there was mixed evidence for the existence of RAEs across sports, the eradication of RAEs was attributed to controllable features of the development environment. The factors reported included the structure of "categories" used to group athletes within the sport (e.g. age, weight, size, skills), recognition and prioritisation of long-term development over "short term win focus." Education of relevant parties (e.g. coaches, scouts, clubs) about RAEs and the nature of "talent" within a long-term context was suggested, along with careful consideration of the structure of the development environment (e.g. delayed selection, provision for late developers, focus on skills not results, use of challenge). Implications for research and practice are discussed.

  3. Cytogenetic effects of cyclamates.

    PubMed

    Jemison, E W; Brown, K; Rivers, B; Knight, R

    1984-01-01

    PHA-stimulated human peripheral lymphocytes were used as a model system for assessing the in vitro effects of calcium cyclamate. Techniques of autoradiography, cytological staining, cell counting, liquid scintillation and karyotyping were used to study the cytogenetic damage and biochemical effects of calcium cyclamate when assayed in 24 hour intervals for 96 hours. The cells were exposed to 10(-2) and 10(-3) molar concentrations of calcium cyclamate in TC 199 medium with fetal calf serum and antibiotics. These studies were carried out in three (3) phases. Phase I was primarily orientation studies of the effects of cyclamates and included running preliminary test checks, the establishment of parameters of dosage, assessing growth patterns and selecting key chromosomal aberrations. Sixty four (64) of the metaphase spreads showed morphologically detectable changes and aberrations. It was also noted that the addition of cyclamate increased mitotic rate of lymphocyte cells in cultures. Phase III arranged research designs to determine more precise characterization of chromosomal observations and morphological effects. Among other findings it was noted that of 13 types of observations only ten were found in the experimental group. The introduction of cyclamates increased the stability of the leucocyte cultures. These studies reinforced the findings on the increase of mitotic rate. Phase III extended protocols to include autoradiography and scintillation counting. It was determined that calcium cyclamate impaired the synthesis of deoxribonunucleic acid (as depicted by decreased incorporation of tritiated thymidine), reduced grain counts in autoradiographs and increased chromosome aberrations in cyclamate treated PHA stimulated peripheral blood lymphocytes in vitro. Morphological changes and growth rates showed significant effects. These studies indicate that calcium cyclamate has variable significant effects on leucocytes growth and chromosome morphology.

  4. Hyperthermic effects on behavior.

    PubMed

    Wetsel, William C

    2011-01-01

    This review focuses upon the past 8 years of research on hyperthermic effects on behavior. Heat stress and heat stoke become severe conditions when body temperatures exceed 40°C as this can lead to delirium, convulsions, coma, and death. The animal literature indicates that hyperthermia can increase glutamatergic and decrease GABAergic neurotransmission. Interestingly, µ-opiate receptor antagonists can attenuate the morphological and biochemical changes in brain, as well as, ameliorate some behavioral deficits induced by heart stress. In humans, heat stress can produce detrimental effects on motor and cognitive performance. Since most cognitive tasks require a motor response, some cognitive deficiencies may be attributed to decreased motor performance. Although hyperthermia may exert more deleterious effects on complex than simple cognitive tasks, systematic studies are needed to examine the effects of different levels and durations of hyperthermia (irrespective of dehydration) on cognition. Additionally, body temperatures should be carefully monitored where controls are run for baseline or brief exposures to a hyperthermic environment. Acute radiofrequency exposure can disrupt behavior when body temperatures increase >1°C with whole body SAR between 3.2-8.4 W/kg and time-averaged power densities at 8-140 mW/cm(2). Effects of lower levels of radiation are conflicting and some experiments fail to replicate even with the original investigators. This suggests either that brief exposure to the radiation is at a threshold where some individuals are affected while others are not, or that these levels are innocuous. Nevertheless, thermal changes appear to account for almost all of the behavioral effects reported.

  5. Habituation of reinforcer effectiveness.

    PubMed

    Lloyd, David R; Medina, Douglas J; Hawk, Larry W; Fosco, Whitney D; Richards, Jerry B

    2014-01-09

    In this paper we propose an integrative model of habituation of reinforcer effectiveness (HRE) that links behavioral- and neural-based explanations of reinforcement. We argue that HRE is a fundamental property of reinforcing stimuli. Most reinforcement models implicitly suggest that the effectiveness of a reinforcer is stable across repeated presentations. In contrast, an HRE approach predicts decreased effectiveness due to repeated presentation. We argue that repeated presentation of reinforcing stimuli decreases their effectiveness and that these decreases are described by the behavioral characteristics of habituation (McSweeney and Murphy, 2009; Rankin etal., 2009). We describe a neural model that postulates a positive association between dopamine neurotransmission and HRE. We present evidence that stimulant drugs, which artificially increase dopamine neurotransmission, disrupt (slow) normally occurring HRE and also provide evidence that stimulant drugs have differential effects on operant responding maintained by reinforcers with rapid vs. slow HRE rates. We hypothesize that abnormal HRE due to genetic and/or environmental factors may underlie some behavioral disorders. For example, recent research indicates that slow-HRE is predictive of obesity. In contrast ADHD may reflect "accelerated-HRE." Consideration of HRE is important for the development of effective reinforcement-based treatments. Finally, we point out that most of the reinforcing stimuli that regulate daily behavior are non-consumable environmental/social reinforcers which have rapid-HRE. The almost exclusive use of consumable reinforcers with slow-HRE in pre-clinical studies with animals may have caused the importance of HRE to be overlooked. Further study of reinforcing stimuli with rapid-HRE is needed in order to understand how habituation and reinforcement interact and regulate behavior.

  6. Habituation of reinforcer effectiveness

    PubMed Central

    Lloyd, David R.; Medina, Douglas J.; Hawk, Larry W.; Fosco, Whitney D.; Richards, Jerry B.

    2014-01-01

    In this paper we propose an integrative model of habituation of reinforcer effectiveness (HRE) that links behavioral- and neural-based explanations of reinforcement. We argue that HRE is a fundamental property of reinforcing stimuli. Most reinforcement models implicitly suggest that the effectiveness of a reinforcer is stable across repeated presentations. In contrast, an HRE approach predicts decreased effectiveness due to repeated presentation. We argue that repeated presentation of reinforcing stimuli decreases their effectiveness and that these decreases are described by the behavioral characteristics of habituation (McSweeney and Murphy, 2009; Rankin etal., 2009). We describe a neural model that postulates a positive association between dopamine neurotransmission and HRE. We present evidence that stimulant drugs, which artificially increase dopamine neurotransmission, disrupt (slow) normally occurring HRE and also provide evidence that stimulant drugs have differential effects on operant responding maintained by reinforcers with rapid vs. slow HRE rates. We hypothesize that abnormal HRE due to genetic and/or environmental factors may underlie some behavioral disorders. For example, recent research indicates that slow-HRE is predictive of obesity. In contrast ADHD may reflect “accelerated-HRE.” Consideration of HRE is important for the development of effective reinforcement-based treatments. Finally, we point out that most of the reinforcing stimuli that regulate daily behavior are non-consumable environmental/social reinforcers which have rapid-HRE. The almost exclusive use of consumable reinforcers with slow-HRE in pre-clinical studies with animals may have caused the importance of HRE to be overlooked. Further study of reinforcing stimuli with rapid-HRE is needed in order to understand how habituation and reinforcement interact and regulate behavior. PMID:24409128

  7. Aharonov-Bohm effect revisited

    NASA Astrophysics Data System (ADS)

    Eskin, Gregory

    2015-04-01

    Aharonov-Bohm effect is a quantum mechanical phenomenon that attracted the attention of many physicists and mathematicians since the publication of the seminal paper of Aharonov and Bohm [1] in 1959. We consider different types of Aharonov-Bohm effects such as the magnetic AB effect, electric AB effect, combined electromagnetic AB effect, AB effect for the Schrödinger equations with Yang-Mills potentials, and the gravitational analog of AB effect. We shall describe different approaches to prove the AB effect based on the inverse scattering problems, the inverse boundary value problems in the presence of obstacles, spectral asymptotics, and the direct proofs of the AB effect.

  8. Picosecond Spin Seebeck Effect

    NASA Astrophysics Data System (ADS)

    Kimling, Johannes; Choi, Gyung-Min; Brangham, Jack T.; Matalla-Wagner, Tristan; Huebner, Torsten; Kuschel, Timo; Yang, Fengyuan; Cahill, David G.

    2017-02-01

    We report time-resolved magneto-optic Kerr effect measurements of the longitudinal spin Seebeck effect in normal metal /Y3Fe5 O12 bilayers driven by an interfacial temperature difference between electrons and magnons. The measured time evolution of spin accumulation induced by laser excitation indicates transfer of angular momentum across normal metal /Y3Fe5 O12 interfaces on a picosecond time scale, too short for contributions from a bulk temperature gradient in an yttrium iron garnet. The product of spin-mixing conductance and the interfacial spin Seebeck coefficient determined is of the order of 108 A m-2 K-1 .

  9. Magnetic Nernst effect

    NASA Astrophysics Data System (ADS)

    Brechet, Sylvain D.; Ansermet, Jean-Philippe

    2015-09-01

    The thermodynamics of irreversible processes in continuous media predicts the existence of a magnetic Nernst effect that results from a magnetic analog to the Seebeck effect in a ferromagnet and magnetophoresis occurring in a paramagnetic electrode in contact with the ferromagnet. Thus, a voltage that has DC and AC components is expected across a Pt electrode as a response to the inhomogeneous magnetic induction field generated by magnetostatic waves of an adjacent YIG slab subject to a temperature gradient. The voltage frequency and dependence on the orientation of the applied magnetic induction field are quite distinct from that of spin pumping.

  10. Effective Temperature of Mutations

    NASA Astrophysics Data System (ADS)

    Derényi, Imre; Szöllősi, Gergely J.

    2015-02-01

    Biological macromolecules experience two seemingly very different types of noise acting on different time scales: (i) point mutations corresponding to changes in molecular sequence and (ii) thermal fluctuations. Examining the secondary structures of a large number of microRNA precursor sequences and model lattice proteins, we show that the effects of single point mutations are statistically indistinguishable from those of an increase in temperature by a few tens of kelvins. The existence of such an effective mutational temperature establishes a quantitative connection between robustness to genetic (mutational) and environmental (thermal) perturbations.

  11. Erythropoietin and Nonhematopoietic Effects.

    PubMed

    Nekoui, Alireza; Blaise, Gilbert

    2017-01-01

    Erythropoietin (EPO) is the main regulator of red blood cell production. Since the 1990s, EPO has been used for the treatment of anemia associated with end-stage renal failure and chemotherapy. The erythropoietin receptors were found on other organs such as the brain, spinal cord, heart and skin. In addition, it has been shown that many tissues produce and locally release EPO in response to hypoxic, biochemical and physical stress. In cellular, animal and clinical studies, EPO protects tissues from ischemia and reperfusion injury, has antiapoptotic effects and improves regeneration after injury. In this article, we mainly review the nonhematopoietic effects and new possible clinical indications for EPO.

  12. Quantum Spin Hall Effect

    SciTech Connect

    Bernevig, B.Andrei; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.

    2010-01-15

    The quantum Hall liquid is a novel state of matter with profound emergent properties such as fractional charge and statistics. Existence of the quantum Hall effect requires breaking of the time reversal symmetry caused by an external magnetic field. In this work, we predict a quantized spin Hall effect in the absence of any magnetic field, where the intrinsic spin Hall conductance is quantized in units of 2 e/4{pi}. The degenerate quantum Landau levels are created by the spin-orbit coupling in conventional semiconductors in the presence of a strain gradient. This new state of matter has many profound correlated properties described by a topological field theory.

  13. Contamination effects study

    NASA Technical Reports Server (NTRS)

    1988-01-01

    The in-situ optical surface measurement system is a facility designed to study the deleterious effects of particulate materials on the surface reflectivities of optical materials in the vacuum ultraviolet (VUV). This arrangement is designed to simulate the on-orbit effects of contamination and degradation of optical surfaces. This simulation is accomplished through the use of non-coherent VUV sources illuminating optical surfaces located in a high vacuum chamber. Several sources of contamination are employed. The reflectivity is measured both at the specular reflection as well as at two scattered positions, forward and reverse. The system components are described and an operating procedure is given.

  14. Effects Based Operations (EBO)

    DTIC Science & Technology

    2005-09-01

    new declarative executable action specification language ( Tapir ) and simulation definition language (Krill); improved models of morale and defeat...The new Action Models and Defeat Mechanisms provide CtF with a much broader range of measurable effects. Krill and Tapir make it possible to describe...1 2.0.1 Tapir : A better action language................................................................................................... 5

  15. Explaining Charter School Effectiveness

    ERIC Educational Resources Information Center

    Angrist, Joshua D.; Pathak, Parag A.; Walters, Christopher R.

    2012-01-01

    This study uses entrance lotteries to explore heterogeneity in the achievement effects of charter schools across demographic groups and between urban and non-urban areas in Massachusetts. The authors develop a framework for interpreting this heterogeneity using both student- and school-level explanatory variables. (Contains 4 tables.)

  16. Holding Effective Board Meetings.

    ERIC Educational Resources Information Center

    American Association of School Administrators, Arlington, VA.

    Advice and tested methods for management of meetings from superintendents and board members are combined in this reference book on conducting effective school board meetings. Intended for a wide readership, it contains three chapters and an exhibit section comprising over one-third of the document. Following a brief introduction, chapter 1,…

  17. Camp's "Disneyland" Effect.

    ERIC Educational Resources Information Center

    Renville, Gary

    1999-01-01

    Describes the positive mental, physical, and social growth impacts that the camping experience had on the author, and urges camp program evaluation to plan and implement such changes. Sidebar lists steps of effective evaluation: program goals and objectives, goals of evaluation, implementation of evaluation, data analysis, and findings and…

  18. Effective Staff Development.

    ERIC Educational Resources Information Center

    Bush, Robert N.

    Beginning with the observation that educators are faced with rising public expectations, declining resources, and increased public criticism, this paper describes a six-fold model for determining how staff development is operating and how it can be made to operate more effectively, in a self-renewing manner. The six dimensions consist of the…

  19. Building Effective Afterschool Programs.

    ERIC Educational Resources Information Center

    Fashola, Olatokunbo S.

    Through a comprehensive review of various afterschool programs across the United States, this resource provides a practical overview of the research and best practices that can be easily adapted and applied in the development of highly effective afterschool programs. chapters focus on: (1) "Why Afterschool Programs?" (benefits, challenges, and…

  20. Cause and effect

    NASA Astrophysics Data System (ADS)

    Clement, Charles; Dawson, Peter

    2017-06-01

    In response to Kate Brown’s article “Chernobyl’s hidden legacy (Physics World Focus on Nuclear Energy 2017 pp9-11) in which she argues that researchers today should be looking at Soviet-era information on the medical effects of the Chernobyl disaster.

  1. Giving effective poster presentations

    SciTech Connect

    Rice, J A

    1998-08-27

    Giving an effective poster presentation can be easy and rewarding with attention to a few proven concepts. Define your audience. Keep the words and graphics clear, concise, and eye-catching. Remember, you have three seconds to attract attention and 30 seconds to get your message across.

  2. Qualities of Effective Principals

    ERIC Educational Resources Information Center

    Stronge, James H.; Richard, Holly B.; Catano, Nancy

    2008-01-01

    You know how important principals are in advancing student achievement and school success, but it's not been exactly clear which components of the principal's job are the highest priority... until now. Following on the results-based approach from the ASCD best-seller "Qualities of Effective Teachers", James Stronge and his coauthors…

  3. Is Effective Teaching Stable?

    ERIC Educational Resources Information Center

    Patrick, Helen; Mantzicopoulos, Panayota

    2016-01-01

    The authors examined the ecological validity of using observation-based scores to evaluate individual teachers' effectiveness, mirroring their use by school administrators. Using the Classroom Assessment Scoring System, the authors asked (a) how similar are teachers' emotional support, classroom organization, and instructional support scores from…

  4. The Training Effectiveness Algorithm.

    ERIC Educational Resources Information Center

    Cantor, Jeffrey A.

    1988-01-01

    Describes the Training Effectiveness Algorithm, a systematic procedure for identifying the cause of reported training problems which was developed for use in the U.S. Navy. A two-step review by subject matter experts is explained, and applications of the algorithm to other organizations and training systems are discussed. (Author/LRW)

  5. Microcircuit radiation effects databank

    NASA Technical Reports Server (NTRS)

    1983-01-01

    Radiation test data submitted by many testers is collated to serve as a reference for engineers who are concerned with and have some knowledge of the effects of the natural radiation environment on microcircuits. Total dose damage information and single event upset cross sections, i.e., the probability of a soft error (bit flip) or of a hard error (latchup) are presented.

  6. Effective Classroom Management

    ERIC Educational Resources Information Center

    Mansor, Azlin Norhaini; Eng, Wong Kim; Rasul, Mohamad Sattar; Hamzah, Mohd Izham Mohd; Hamid, Aida Hanim A.

    2012-01-01

    This paper attempts to explore and identify the characteristics of an effective teacher who teaches English as a second language to 10 year old students from different ethnics, various social economic background and multi-level language ability, at a private primary school in Malaysia. The study focused on classroom management using a case study…

  7. Effects of Drug Use

    MedlinePlus

    ... work or losing a job trouble in relationships child abuse or neglect driving crashes arrests and jail Visit the Easy-to-Read Drug Facts webpages listed under Drugs That People Abuse to learn more about effects of specific drugs. Previous Index Next English Español ...

  8. Tips for Effective Management

    ERIC Educational Resources Information Center

    Supple, Kevin F.

    2009-01-01

    School business officials' days are filled with numbers and reports--audits, balance sheets, check registers, financial statements, journal entries, vouchers, and warrant reports, just to name a few. Those are all important tools that school business officers use to manage the financial resources of the district effectively. However, they are also…

  9. Making Effective Assignments.

    ERIC Educational Resources Information Center

    McLeod, Alan M., Ed.

    1982-01-01

    Although the focus of this issue of the "Virginia English Bulletin" is on making effective assignments, most of the articles also emphasize the importance and power of writing. Articles deal with the following topics: (1) the use of I-search (as explained by Kenneth Macrorie in "Searching Writing") as a form of research paper…

  10. Measuring Teacher Effectiveness

    ERIC Educational Resources Information Center

    Jacobo, Amber Leann

    2012-01-01

    Prior research has shown that there is a correlation between teacher characteristics (e.g., pedagogical knowledge, teacher preparation/certification) and student achievement. Current political contexts call for the utilization of student achievement data to measure the effectiveness of our education systems. A solid research base of how teacher…

  11. Effective Monitor Display Design.

    ERIC Educational Resources Information Center

    Harrell, William

    1999-01-01

    Describes some of the factors that affect computer monitor display design and provides suggestions and insights into how screen displays can be designed more effectively. Topics include color, font choices, organizational structure of text, space outline, and general principles. (Author/LRW)

  12. The Negative Repetition Effect

    ERIC Educational Resources Information Center

    Mulligan, Neil W.; Peterson, Daniel J.

    2013-01-01

    A fundamental property of human memory is that repetition enhances memory. Peterson and Mulligan (2012) recently documented a surprising "negative repetition effect," in which participants who studied a list of cue-target pairs twice recalled fewer targets than a group who studied the pairs only once. Words within a pair rhymed, and…

  13. Creating Effective Multimedia Instruction.

    ERIC Educational Resources Information Center

    Sales, Gregory C.

    1999-01-01

    Presents information on several critical themes related to multimedia instruction for those involved in the design, development, or use of computer delivered instruction. Addresses software product life cycle; systematic approach to design; multimedia design and development teams; production values; critical components of effective multimedia;…

  14. Commentary: Expanding on Effectiveness

    ERIC Educational Resources Information Center

    Pelham, William E., Jr.; Massetti, Greta M.

    2003-01-01

    Atkins, Graczyk, Frazier, and Abdul-Adil (2003) make the point that there have been three limitations of mental health services for children and families in low-income, urban settings: (a) accessibility; (b) effectiveness; and (c) sustainability. Their article focuses extensively on improving access and addressing issues of sustainability in…

  15. Contaminant effects on fisheries

    SciTech Connect

    Cairns, V.W.; Hodson, P.V.; Nriagu, J.O.

    1984-01-01

    These proceedings collect papers on the effects of water pollution on fish and fisheries. Topics include: monitoring lead pollution in fish, metallothionein and acclimation to heavy metals in fish, modeling approaches, appraising the status of fisheries, and assessing the health of aquatic ecosystems.

  16. Effective Thinking Outdoors.

    ERIC Educational Resources Information Center

    Hyde, Rod

    1997-01-01

    Effective Thinking Outdoors (ETO) is an organization that teaches thinking skills and strategies via significant outdoor experiences. Identifies the three elements of thinking as creativity, play, and persistence; presents a graphic depiction of the problem-solving process and aims; and describes an ETO exercise, determining old routes of travel…

  17. Effect of New Technologies.

    ERIC Educational Resources Information Center

    Social and Labour Bulletin, 1983

    1983-01-01

    This series of articles cites a variety of sources and synthesizes a number of studies on the effects of new technologies on the world of work and on social and economic life in general. These studies are related to several industrial nations and are also concerned with the new information-oriented society. (SSH)

  18. Cost Effective Prototyping

    NASA Technical Reports Server (NTRS)

    Wickman, Jerry L.; Kundu, Nikhil K.

    1996-01-01

    This laboratory exercise seeks to develop a cost effective prototype development. The exercise has the potential of linking part design, CAD, mold development, quality control, metrology, mold flow, materials testing, fixture design, automation, limited parts production and other issues as related to plastics manufacturing.

  19. Commentary: Expanding on Effectiveness

    ERIC Educational Resources Information Center

    Pelham, William E., Jr.; Massetti, Greta M.

    2003-01-01

    Atkins, Graczyk, Frazier, and Abdul-Adil (2003) make the point that there have been three limitations of mental health services for children and families in low-income, urban settings: (a) accessibility; (b) effectiveness; and (c) sustainability. Their article focuses extensively on improving access and addressing issues of sustainability in…

  20. Qualities of Effective Principals

    ERIC Educational Resources Information Center

    Stronge, James H.; Richard, Holly B.; Catano, Nancy

    2008-01-01

    You know how important principals are in advancing student achievement and school success, but it's not been exactly clear which components of the principal's job are the highest priority... until now. Following on the results-based approach from the ASCD best-seller "Qualities of Effective Teachers", James Stronge and his coauthors…

  1. Commonalities across Effective Collaboratives.

    ERIC Educational Resources Information Center

    Russell, Jill F.; Flynn, Richard B.

    2000-01-01

    Examined effective collaborations involving schools and colleges of education and other organizations, identifying commonly voiced reasons for collaboration and factors perceived as important in collaboration. Data come from research, case descriptions, survey responses, and input from collaborators. Willingness to listen, mutual respect,…

  2. Cardiovascular effects of alcohol.

    PubMed Central

    Davidson, D M

    1989-01-01

    The effects of alcohol on the heart include modification of the risk of coronary artery disease, the development of alcoholic cardiomyopathy, exacerbation of conduction disorders, atrial and ventricular dysrhythmias, and an increased risk of hypertension, hemorrhagic stroke, infectious endocarditis, and fetal heart abnormalities. PMID:2686174

  3. Coanda effect in valves

    NASA Astrophysics Data System (ADS)

    Uruba, Václav; Procházka, Pavel; Skála, Vladislav

    2016-11-01

    Coanda effect takes place in flow within valves diffuser for certain conditions. The valve plug in half-closed position forms wall-jet, which could be stable or instable, depending on geometry and other conditions. This phenomenon was subject of experimental study using time-resolved PIV technique. For the acquired data analysis the special spatio-temporal methods have been used.

  4. The Negative Repetition Effect

    ERIC Educational Resources Information Center

    Mulligan, Neil W.; Peterson, Daniel J.

    2013-01-01

    A fundamental property of human memory is that repetition enhances memory. Peterson and Mulligan (2012) recently documented a surprising "negative repetition effect," in which participants who studied a list of cue-target pairs twice recalled fewer targets than a group who studied the pairs only once. Words within a pair rhymed, and…

  5. Analgesic effects of calcitonin.

    PubMed

    Lyritis, G P; Trovas, G

    2002-05-01

    The analgesic activity of salmon calcitonin (subcutaneous or intranasal) has been demonstrated in several prospective clinical trials, in patients suffering different painful skeletal conditions, including recent nontraumatic osteoporotic vertebral fractures. The mechanism of the analgesic effect of calcitonin is not clear. It is possible that specific binding sites for salmon calcitonin exist in the brain. Another explanation is that changes in descending serotonergic modification on the sensory transmission mediated by C afferents contribute to the analgesic effects of calcitonin on pain in osteoporotic patients. From the clinical point of use, the analgesic effect of calcitonin is beneficial throughout the whole period of medical treatment of osteoporotic patients. Salmon calcitonin in a daily dose of 100 IU subcutaneously or 200 IU intranasally reduces dramatically the back pain (p < 0.0005) after a recent osteoporotic vertebral fracture, and promotes the early mobility of patients. The finding that injectable or intranasally administered salmon calcitonin effectively controls severe pain in osteoporotic patients with a recent vertebral fracture, allowing them earlier mobility in combination with a reduction of the urinary hydroxyproline excretion, and a limitation of the considerable bone loss that may occur during prolonged bed rest, make this therapeutic scheme attractive.

  6. Effects on saltwater organisms

    SciTech Connect

    Reish, D.J.; Oshida, P.S.; Wilkes, F.G.; Mearns, A.J.; Ginn, T.C.; Carr, R.S.

    1984-06-01

    A review of the literature reveals numerous articles dealing with the uptake of metals by marine organisms. Cadmium, copper, zinc, and methyl mercury have been shown to have toxic effects on fish, oysters, clams, lobsters, and other marine animals. Both genetic and environmental factors are involved in the accumulation of these metals. 237 references.

  7. Radiation: Doses, Effects, Risks.

    ERIC Educational Resources Information Center

    Lean, Geoffrey, Ed.

    Few scientific issues arouse as much public controversy as the effects of radiation. This booklet is an attempt to summarize what is known about radiation and provide a basis for further discussion and debate. The first four chapters of the booklet are based on the most recent reports to the United Nations' General Assembly by the United Nations…

  8. Effective Thinking Outdoors.

    ERIC Educational Resources Information Center

    Hyde, Rod

    1997-01-01

    Effective Thinking Outdoors (ETO) is an organization that teaches thinking skills and strategies via significant outdoor experiences. Identifies the three elements of thinking as creativity, play, and persistence; presents a graphic depiction of the problem-solving process and aims; and describes an ETO exercise, determining old routes of travel…

  9. Measuring Teacher Effectiveness

    ERIC Educational Resources Information Center

    Jacobo, Amber Leann

    2012-01-01

    Prior research has shown that there is a correlation between teacher characteristics (e.g., pedagogical knowledge, teacher preparation/certification) and student achievement. Current political contexts call for the utilization of student achievement data to measure the effectiveness of our education systems. A solid research base of how teacher…

  10. Effective Staff Development.

    ERIC Educational Resources Information Center

    Bush, Robert N.

    Beginning with the observation that educators are faced with rising public expectations, declining resources, and increased public criticism, this paper describes a six-fold model for determining how staff development is operating and how it can be made to operate more effectively, in a self-renewing manner. The six dimensions consist of the…

  11. Reporting Research Results Effectively

    ERIC Educational Resources Information Center

    Volkwein, J. Fredericks

    2010-01-01

    Assessment research is at its best when it packages research results and data so that they can be digested by multiple audiences. Too many assessment researchers spend all their efforts planning and executing the research project with little attention to closing the loop at the end. If assessment findings are not communicated effectively, the…

  12. Effectively Communicating Qualitative Research

    ERIC Educational Resources Information Center

    Ponterotto, Joseph G.; Grieger, Ingrid

    2007-01-01

    This article is a guide for counseling researchers wishing to communicate the methods and results of their qualitative research to varied audiences. The authors posit that the first step in effectively communicating qualitative research is the development of strong qualitative research skills. To this end, the authors review a process model for…

  13. Reading and Writing Effectively.

    ERIC Educational Resources Information Center

    Lewandowski, Carol; Burt, Lorna

    This workbook, designed for workplace literacy courses, covers effective reading and writing. Introductory materials include objectives, a topical outline, sources, and information on time for the course and continuing education credits. The 16 sessions of the course cover the following topics: job terms; abbreviations, acronyms, and pictorial…

  14. Institutional Effectiveness Resource Manual.

    ERIC Educational Resources Information Center

    Cannon, Delinda T.; And Others

    This resource manual was produced to assist the South Carolina Technical College System's efforts to improve institutional effectiveness and accountability. The first two sections of the manual provide a brief foreword, a description of state initiatives for research and academic excellence in South Carolina, the text of state legislation…

  15. Matthew Effects for Whom?

    ERIC Educational Resources Information Center

    Morgan, Paul L.; Farkas, George; Hibel, Jacob

    2008-01-01

    Which children are most at risk of experiencing a Matthew effect in reading? We investigated this question using population-based methodology. First, we identified children entering kindergarten on socio-demographic factors (i.e., gender, race/ethnicity, and socioeconomic status) known to index the relative risks and resources available to them as…

  16. Effective Free Surfaces

    NASA Astrophysics Data System (ADS)

    Yapalparvi, Ramesh; Protas, Bartosz

    2010-11-01

    In this investigation we introduce the concept of an "effective free surface" arising as a solution of time--averaged equations in the presence of free boundaries. This work is motivated by applications of optimization theory to problems involving free surfaces, such as droplets impinging on the weld pool surface in welding processes. In such problems the time--dependent governing equations lead to technical difficulties, many of which are alleviated when methods of optimization are applied to a steady problem with effective free surfaces. The corresponding equations are obtained by performing the Reynolds decomposition and averaging of the time--dependent free--boundary equations based on the volume--of--fluid (VoF) formalism. We identify the terms representing the average effect of fluctuating free boundaries which, in analogy with the Reynolds stresses in classical turbulence models, need to be modelled and propose some simple algebraic closures for these terms. We argue that effective free boundaries can be computed using methods of shape optimization and present some results.

  17. Cost Effective Prototyping

    NASA Technical Reports Server (NTRS)

    Wickman, Jerry L.; Kundu, Nikhil K.

    1996-01-01

    This laboratory exercise seeks to develop a cost effective prototype development. The exercise has the potential of linking part design, CAD, mold development, quality control, metrology, mold flow, materials testing, fixture design, automation, limited parts production and other issues as related to plastics manufacturing.

  18. Alexandrite effect spectropyrometer

    NASA Astrophysics Data System (ADS)

    Liu, Yan

    2006-08-01

    Alexandrite crystal is commonly used for making alexandrite laser, and it also has a less-known phenomenon called the alexandrite effect that refers to the color change between different light sources. A novel spectropyrometer for temperature measurement of a radiating body utilizing the alexandrite effect is introduced. The alexandrite effect method for temperature measurement is based on the relationship between the temperature of blackbody and the hue-angle in the CIELAB color space. The alexandrite effect spectropyrometer consists of an optical probe, a spectrometer, a computer, and an alexandrite filter. It measures the spectral power distribution of a radiating body through the alexandrite filter, calculates the hue-angle, and determines the temperature. The spectropyrometer is suitable for temperature measurement of any radiating body with or without spectral lines in its spectral power distribution from 1000 K to 100000 K. The spectropyrometer is particularly useful for high to ultrahigh temperature measurement of any radiating bodies with spectral line emissions, such as electric arcs and discharges, plasmas, and high temperature flames.

  19. Building Effective Afterschool Programs.

    ERIC Educational Resources Information Center

    Fashola, Olatokunbo S.

    Through a comprehensive review of various afterschool programs across the United States, this resource provides a practical overview of the research and best practices that can be easily adapted and applied in the development of highly effective afterschool programs. chapters focus on: (1) "Why Afterschool Programs?" (benefits, challenges, and…

  20. Is Effective Teaching Stable?

    ERIC Educational Resources Information Center

    Patrick, Helen; Mantzicopoulos, Panayota

    2016-01-01

    The authors examined the ecological validity of using observation-based scores to evaluate individual teachers' effectiveness, mirroring their use by school administrators. Using the Classroom Assessment Scoring System, the authors asked (a) how similar are teachers' emotional support, classroom organization, and instructional support scores from…

  1. Fast and effective?

    PubMed

    Trueland, Jennifer

    2013-12-18

    The 5.2 diet involves two days of fasting each week. It is being promoted as the key to sustained weight loss, as well as wider health benefits, despite the lack of evidence on the long-term effects. Nurses need to support patients who wish to try intermittent fasting.

  2. Teacher Effectiveness: A Position.

    ERIC Educational Resources Information Center

    Scott, Myrtle

    1969-01-01

    This document summarizes the highlights of research on teacher effectiveness and concludes with recommendations based on a synthesis of this past work. The various methodologies that have been used are discussed, from rating scales to objective observation techniques, such as OScAR and the ecological studies. The major problems in teacher…

  3. Effects of Induced Astigmatism.

    ERIC Educational Resources Information Center

    Schubert, Delwyn G.; Walton, Howard N.

    1968-01-01

    The relationship of astigmatism to reading and the possible detrimental effects it might have on reading were investigated. The greatest incidence of astigmatism was for the with-the-rule type ranging from .50 to 1.00 diopter. This type of astigmatism was induced in 35 seniors from the Los Angeles College of Optometry by placing cylindrical lenses…

  4. Biasing Effects of Experimenters.

    ERIC Educational Resources Information Center

    Rosenthal, Robert

    1977-01-01

    Explains the types of effects, usually unintentional, that psychologists can have upon the results of their research; describes the "Pygmalion Experiment," in which teachers' expectations for children's behavior proved to be self-fulfilling prophecies; and points to research needs in the area of interpersonal expectations. (GT)

  5. What Effective Schools Do

    ERIC Educational Resources Information Center

    West, Martin R.; Gabrieli, Christopher F. O.; Finn, Amy S.; Kraft, Matthew A.; Gabrieli, John D. E.

    2014-01-01

    Research has been showing that the most important development in K-12 education over the past decade has been the emergence of a growing number of urban schools that have been convincingly shown to have dramatic positive effects on the achievement of disadvantaged students. Those with the strongest evidence of success are oversubscribed charter…

  6. Effects of Induced Astigmatism.

    ERIC Educational Resources Information Center

    Schubert, Delwyn G.; Walton, Howard N.

    1968-01-01

    The relationship of astigmatism to reading and the possible detrimental effects it might have on reading were investigated. The greatest incidence of astigmatism was for the with-the-rule type ranging from .50 to 1.00 diopter. This type of astigmatism was induced in 35 seniors from the Los Angeles College of Optometry by placing cylindrical lenses…

  7. Reporting Research Results Effectively

    ERIC Educational Resources Information Center

    Volkwein, J. Fredericks

    2010-01-01

    Assessment research is at its best when it packages research results and data so that they can be digested by multiple audiences. Too many assessment researchers spend all their efforts planning and executing the research project with little attention to closing the loop at the end. If assessment findings are not communicated effectively, the…

  8. [Pharmacological effects of hordenine].

    PubMed

    Hapke, H J; Strathmann, W

    1995-06-01

    Hordenine is an ingredient of some plants which are used as feed for animals, i.e. in sprouting barley. After ingestion of such feed hordenine may be detected in blood or urine of horses which in case of racing horses may be the facts of using prohibited compounds. Results of some experiments in pharmacological models show that hordenine is an indirectly acting adrenergic drug. It liberates norepinephrine from stores. In isolated organs and those structures with reduced epinephrine contents the hordenine-effect is only very poor. Experiments in intact animals (rats, dogs) show that hordenine has a positive inotropic effect upon the heart, increases systolic and diastolic blood pressure, peripheral blood flow volume, inhibits gut movements but has no effect upon the psychomotorical behaviour of mice. All effects are short and only possible after high doses which are not to be expected after ingestion of hordenine containing feed for horses. A measurable increase of the performance of racing horses is quite improbable.

  9. Effective Team Participation.

    ERIC Educational Resources Information Center

    Male, Mary

    1991-01-01

    The Student Study Team (SST) is described as a California intervention model that encourages effective multidisciplinary team participation. The development, training, operation, and evaluation of such teams are discussed, and implementation recommendations are offered. The article includes a flow chart of the SST process, a meeting competency…

  10. Confirming Testlet Effects

    ERIC Educational Resources Information Center

    DeMars, Christine E.

    2012-01-01

    A testlet is a cluster of items that share a common passage, scenario, or other context. These items might measure something in common beyond the trait measured by the test as a whole; if so, the model for the item responses should allow for this testlet trait. But modeling testlet effects that are negligible makes the model unnecessarily…

  11. The Effective, Efficient Professor.

    ERIC Educational Resources Information Center

    Felder, Richard M.

    2002-01-01

    Presents a succinct overview of the book "The Effective, Efficient Professor" (P. Wankat) that presents a wealth of strategies and techniques for successful faculty members. Sections of the book focus on time management, teaching, students, and scholarship and service. Includes some practical tips from the book ranging from instructional…

  12. Conducting Effective Simulator Training.

    ERIC Educational Resources Information Center

    Gerling, Kenneth D.

    This paper describes the simulator phase of Commonwealth Edison's program for training and licensing operators of nuclear power stations. Topics covered include (1) preparing the students before starting the simulator phase; (2) the simulator schedule and the number of students that can be trained effectively in a class; (3) format and structure…

  13. The Effectiveness of DISCOVER.

    ERIC Educational Resources Information Center

    Engel, Elaine Frances

    Computer assisted career guidance (CACG) systems have been around for at least the past 20 years in career guidance centers. There are two types of systems: information retrieval and guidance interaction. This study investigated the effectiveness of DISCOVER in facilitating career decisions among college students. DISCOVER is a systematic career…

  14. Effectively Communicating Qualitative Research

    ERIC Educational Resources Information Center

    Ponterotto, Joseph G.; Grieger, Ingrid

    2007-01-01

    This article is a guide for counseling researchers wishing to communicate the methods and results of their qualitative research to varied audiences. The authors posit that the first step in effectively communicating qualitative research is the development of strong qualitative research skills. To this end, the authors review a process model for…

  15. Learning to Effect.

    ERIC Educational Resources Information Center

    Barnett, Ronald, Ed.

    This book presents 14 papers which discuss contemporary issues of curriculum change and instructional effectiveness in higher education primarily from a British perspective. Papers address curriculum purpose, curriculum delivery, and curriculum impact on the wider society. In addition, the book covers experiential learning, skills and training,…

  16. Creating an Effective Newsletter

    ERIC Educational Resources Information Center

    Shackelford, Ray; Griffis, Kurt

    2006-01-01

    Newsletters are an important resource or form of media. They offer a cost-effective way to keep people informed, as well as to promote events and programs. Production of a newsletter makes an excellent project, relevant to real-world communication, for technology students. This article presents an activity on how to create a short newsletter. The…

  17. Side Effects: Lymphedema

    Cancer.gov

    Lymphedema is a side effect that can be caused when part of the lymph system is damaged or blocked, such as during surgery to remove lymph nodes, or radiation therapy. Cancer patients may notice symptoms during treatment or lymphedema may start years afte

  18. Camp's "Disneyland" Effect.

    ERIC Educational Resources Information Center

    Renville, Gary

    1999-01-01

    Describes the positive mental, physical, and social growth impacts that the camping experience had on the author, and urges camp program evaluation to plan and implement such changes. Sidebar lists steps of effective evaluation: program goals and objectives, goals of evaluation, implementation of evaluation, data analysis, and findings and…

  19. Educator Effectiveness Administrative Manual

    ERIC Educational Resources Information Center

    Pennsylvania Department of Education, 2014

    2014-01-01

    The goal of this manual is to provide guidance in the evaluation of educators, highlight critical components of effectiveness training, and offer opportunities for professional growth. The term "educator" includes teachers, all professional and temporary professional employees, education specialists, and school administrators/principals.…

  20. Appraising fire effects

    Treesearch

    Robert M. Loomis; Donna M. Paananen

    1989-01-01

    Fire effects in the central hardwood forest vary greatly. Depending on a number of factors, some trees will be killed immediately; others will be injured and die in a year or more; still others will incur basal wounds that can provide entry for decay; and some trees will not be affected.

  1. Marijuana: respiratory tract effects.

    PubMed

    Owen, Kelly P; Sutter, Mark E; Albertson, Timothy E

    2014-02-01

    Marijuana is the most commonly used drug of abuse in the USA. It is commonly abused through inhalation and therefore has effects on the lung that are similar to tobacco smoke, including increased cough, sputum production, hyperinflation, and upper lobe emphysematous changes. However, at this time, it does not appear that marijuana smoke contributes to the development of chronic obstructive pulmonary disease. Marijuana can have multiple physiologic effects such as tachycardia, peripheral vasodilatation, behavioral and emotional changes, and possible prolonged cognitive impairment. The carcinogenic effects of marijuana are unclear at this time. Studies are mixed on the ability of marijuana smoke to increase the risk for head and neck squamous cell carcinoma, lung cancer, prostate cancer, and cervical cancer. Some studies show that marijuana is protective for development of malignancy. Marijuana smoke has been shown to have an inhibitory effect on the immune system. Components of cannabis are under investigation as treatment for autoimmune diseases and malignancy. As marijuana becomes legalized in many states for medical and recreational use, other forms of tetrahydrocannabinol (THC) have been developed, such as food products and beverages. As most research on marijuana at this time has been on whole marijuana smoke, rather than THC, it is difficult to determine if the currently available data is applicable to these newer products.

  2. Effects of New Technologies.

    ERIC Educational Resources Information Center

    Social and Labour Bulletin, 1983

    1983-01-01

    This group of articles studies the effects of microelectronics technologies on the world of work and on the social and economic life in general. These studies are related to several industrial nations and are also concerned with the international division of labor. (SSH)

  3. Effective Instructional Management.

    ERIC Educational Resources Information Center

    Zakariya, Sally Banks; Steller, Arthur, Ed.

    Effective instructional management processes come in many guises, but all share four essential components: (1) a set of educational goals toward which progress can be measured; (2) a means of assessing students' instructional needs and determining placement and grouping; (3) an organizational structure and instructional delivery process capable of…

  4. Coteratogenic effects of caffeine.

    PubMed

    Sivak, A

    1994-02-01

    Coteratogenicity studies have been carried out using various physical and chemical agents along with caffeine. For ionizing radiation in mice, enhancement of teratogenic responses (cleft palate, limb malformations) was noted with single systemic bolus doses of 50 to 200 mg/kg. Studies in rats with ethanol or nicotine reveal only an additive effect with caffeine. There are mixed results with chemical carcinogens and caffeine with some studies showing enhancement and others showing that caffeine inhibits the teratogenic effect of some carcinogens. The time of treatment, at the time of carcinogen exposure for the inhibition and later in the gestation period for the enhancement, appears to be the critical factor. For a variety of pharmaceutical agents (acetazolamide, mitomycin C, hydroxyurea, 5-fluorouracil), caffeine was shown to enhance the teratogenic effect of the agent. With 5-azacytidine in rats, caffeine suppressed limb malformations. Administration of inhibitors of beta-adrenergic function reduces the teratogenic effect of caffeine in mice. The interpretation of the experimental studies in terms of human hazard is complicated by the general use of high-dose bolus exposures which are not typical of human exposures, and the use of test systems that are not readily applicable to humans. The studies in human populations show clearly that caffeine itself has no link to negative birth outcome, and in the few instances where it has been examined there appears to be no interaction between coffee consumption and either alcohol consumption or smoking on pregnancy outcome.

  5. Space Environmental Effects Knowledgebase

    NASA Technical Reports Server (NTRS)

    Wood, B. E.

    2007-01-01

    This report describes the results of an NRA funded program entitled Space Environmental Effects Knowledgebase that received funding through a NASA NRA (NRA8-31) and was monitored by personnel in the NASA Space Environmental Effects (SEE) Program. The NASA Project number was 02029. The Satellite Contamination and Materials Outgassing Knowledgebase (SCMOK) was created as a part of the earlier NRA8-20. One of the previous tasks and part of the previously developed Knowledgebase was to accumulate data from facilities using QCMs to measure the outgassing data for satellite materials. The main object of this current program was to increase the number of material outgassing datasets from 250 up to approximately 500. As a part of this effort, a round-robin series of materials outgassing measurements program was also executed that allowed comparison of the results for the same materials tested in 10 different test facilities. Other programs tasks included obtaining datasets or information packages for 1) optical effects of contaminants on optical surfaces, thermal radiators, and sensor systems and 2) space environmental effects data and incorporating these data into the already existing NASA/SEE Knowledgebase.

  6. What Effective Schools Do

    ERIC Educational Resources Information Center

    West, Martin R.; Gabrieli, Christopher F. O.; Finn, Amy S.; Kraft, Matthew A.; Gabrieli, John D. E.

    2014-01-01

    Research has been showing that the most important development in K-12 education over the past decade has been the emergence of a growing number of urban schools that have been convincingly shown to have dramatic positive effects on the achievement of disadvantaged students. Those with the strongest evidence of success are oversubscribed charter…

  7. Calculation of effective dose.

    PubMed

    McCollough, C H; Schueler, B A

    2000-05-01

    The concept of "effective dose" was introduced in 1975 to provide a mechanism for assessing the radiation detriment from partial body irradiations in terms of data derived from whole body irradiations. The effective dose is the mean absorbed dose from a uniform whole-body irradiation that results in the same total radiation detriment as from the nonuniform, partial-body irradiation in question. The effective dose is calculated as the weighted average of the mean absorbed dose to the various body organs and tissues, where the weighting factor is the radiation detriment for a given organ (from a whole-body irradiation) as a fraction of the total radiation detriment. In this review, effective dose equivalent and effective dose, as established by the International Commission on Radiological Protection in 1977 and 1990, respectively, are defined and various methods of calculating these quantities are presented for radionuclides, radiography, fluoroscopy, computed tomography and mammography. In order to calculate either quantity, it is first necessary to estimate the radiation dose to individual organs. One common method of determining organ doses is through Monte Carlo simulations of photon interactions within a simplified mathematical model of the human body. Several groups have performed these calculations and published their results in the form of data tables of organ dose per unit activity or exposure. These data tables are specified according to particular examination parameters, such as radiopharmaceutical, x-ray projection, x-ray beam energy spectra or patient size. Sources of these organ dose conversion coefficients are presented and differences between them are examined. The estimates of effective dose equivalent or effective dose calculated using these data, although not intended to describe the dose to an individual, can be used as a relative measure of stochastic radiation detriment. The calculated values, in units of sievert (or rem), indicate the amount of

  8. Adverse effects of cannabis.

    PubMed

    2011-01-01

    Cannabis, Cannabis sativa L., is used to produce a resin that contains high levels of cannabinoids, particularly delta9-tetrahydrocannabinol (THC), which are psychoactive substances. Although cannabis use is illegal in France and in many other countries, it is widely used for its relaxing or euphoric effects, especially by adolescents and young adults. What are the adverse effects of cannabis on health? During consumption? And in the long term? Does cannabis predispose users to the development of psychotic disorders? To answer these questions, we reviewed the available evidence using the standard Prescrire methodology. The long-term adverse effects of cannabis are difficult to evaluate. Since and associated substances, with or without the user's knowledge. Tobacco and alcohol consumption, and particular lifestyles and behaviours are often associated with cannabis use. Some traits predispose individuals to the use of psychoactive substances in general. The effects of cannabis are dosedependent.The most frequently report-ed adverse effects are mental slowness, impaired reaction times, and sometimes accentuation of anxiety. Serious psychological disorders have been reported with high levels of intoxication. The relationship between poor school performance and early, regular, and frequent cannabis use seems to be a vicious circle, in which each sustains the other. Many studies have focused on the long-term effects of cannabis on memory, but their results have been inconclusive. There do not * About fifteen longitudinal cohort studies that examined the influence of cannabis on depressive thoughts or suicidal ideation have yielded conflicting results and are inconclusive. Several longitudinal cohort studies have shown a statistical association between psychotic illness and self-reported cannabis use. However, the results are difficult to interpret due to methodological problems, particularly the unknown reliability of self-reported data. It has not been possible to

  9. Stormwater BMP Effectiveness Assessment Toolkit

    EPA Science Inventory

    US EPA has identified stormwater BMP effectiveness as a priority research need. Effective protection of biotic integrity requires that processes maintaining the diversity of physical habitats be protected. Methods are needed to evaluate the effectiveness of existing Stormwater ...

  10. Health Effects of Air Pollution

    MedlinePlus

    ... Health effects of air pollution Health effects of air pollution Breathing air that is not clean can hurt ... important to know about the health effects that air pollution can have on you and others. Once you ...

  11. Stormwater BMP Effectiveness Assessment Toolkit

    EPA Science Inventory

    US EPA has identified stormwater BMP effectiveness as a priority research need. Effective protection of biotic integrity requires that processes maintaining the diversity of physical habitats be protected. Methods are needed to evaluate the effectiveness of existing Stormwater ...

  12. Separating Gender Composition Effects from Peer Effects in Education

    ERIC Educational Resources Information Center

    Jahanshahi, Babak

    2017-01-01

    This paper aims to demonstrate the importance of controlling for endogenous peer effects in estimating the influence of gender peer effects on educational outcomes. Using Manski's linear-in-means model, this paper illustrates that the estimation of gender peer effects is potentially biased in the presence of endogenous peer effect in education.…

  13. Separating Gender Composition Effects from Peer Effects in Education

    ERIC Educational Resources Information Center

    Jahanshahi, Babak

    2017-01-01

    This paper aims to demonstrate the importance of controlling for endogenous peer effects in estimating the influence of gender peer effects on educational outcomes. Using Manski's linear-in-means model, this paper illustrates that the estimation of gender peer effects is potentially biased in the presence of endogenous peer effect in education.…

  14. Effects and Side Effects of Flemish School Inspection

    ERIC Educational Resources Information Center

    Penninckx, Maarten; Vanhoof, Jan; De Maeyer, Sven; Van Petegem, Peter

    2016-01-01

    Despite the increased importance of school inspection in recent years, the current knowledge base does not provide a clear view on the effects and side effects of being inspected. More evidence is needed in more diverse educational contexts. This article responds to this need with a quantitative study on the effects and side effects of school…

  15. Effects and Side Effects of Flemish School Inspection

    ERIC Educational Resources Information Center

    Penninckx, Maarten; Vanhoof, Jan; De Maeyer, Sven; Van Petegem, Peter

    2016-01-01

    Despite the increased importance of school inspection in recent years, the current knowledge base does not provide a clear view on the effects and side effects of being inspected. More evidence is needed in more diverse educational contexts. This article responds to this need with a quantitative study on the effects and side effects of school…

  16. Genotoxic effects of metronidazole.

    PubMed

    Elizondo, G; Gonsebatt, M E; Salazar, A M; Lares, I; Santiago, P; Herrera, J; Hong, E; Ostrosky-Wegman, P

    1996-09-13

    Metronidazole (MTZ) is an effective agent used in the treatment of parasitic infections. Its genotoxic effects have been shown in a variety of prokaryotic systems; however, negative results have been reported in human in vivo studies. Due to its wide spread use, a study was performed to evaluate the chromosomal aberration frequencies in peripheral blood lymphocyte cultures from 10 individuals, before and after metronidazole treatment. A significant increase in the percentage of cells with chromatid and isochromatid breaks was observed after metronidazole treatment (1500 mg per day for 10 days). The percentages of cells with aberrations did not correlate with the levels of MTZ found in plasma. Individual variability was observed with respect to both the induction of aberrations and the concentration of MTZ in plasma. They could represent differences at the metabolic level, since metronidazole is known to be biotransformed by a polymorphic P450 cytochrome, and its metabolites have shown mutagenic activity.

  17. Conducting effective tailgate trainings.

    PubMed

    Harrington, David; Materna, Barbara; Vannoy, Jim; Scholz, Peter

    2009-07-01

    The California Department of Health Services' Occupational Health Branch and others have identified the construction industry as being at high risk for injuries, illnesses, and fatalities. Effective tailgate trainings (brief job site safety meetings) can be a powerful tool to promote hazard awareness and safe work practices. The authors found that many contractors and supervisors conducted ineffective tailgate trainings. They developed the BuildSafe California Project to assist contractors to have more effective programs by holding 25 training-of-trainers sessions reaching 1,525 participants. The needs assessment, intervention, and evaluation results from the first 18 trainings are presented. Eighty-six percent of the participants found the program "very helpful." Participants used the materials and made improvements in the quality and frequency of trainings. Supervisors must be skilled at conducting tailgate trainings as part of their responsibilities. There is a serious need to provide more culturally appropriate safety training in a workforce increasingly made up of Latino workers.

  18. Being an effective speaker.

    PubMed

    Davidhizar, R; Cosgray, R

    1991-08-01

    Communication in a group is an essential quality for success in nursing. Despite this, many nurses who must have communication skills to advance have little training in public speaking. Some nurses seek to correct such deficiencies in their education by taking courses in the evenings or on weekends to improve their understanding of the elements of effective speaking. Other nurses learn by self-reflection, study, and ongoing practice. This article has presented guidelines for speaking in a group that can offer assistance in mastering this important nursing skill. Elements of nonverbal communication are crucial for effective communication. However, despite the importance of non-verbal communication to the message, language is what makes communication possible. It is language that allows people to communicate new ideas and thoughts and to solve problems.

  19. Aerodynamic Leidenfrost effect

    NASA Astrophysics Data System (ADS)

    Gauthier, Anaïs; Bird, James C.; Clanet, Christophe; Quéré, David

    2016-12-01

    When deposited on a plate moving quickly enough, any liquid can levitate as it does when it is volatile on a very hot solid (Leidenfrost effect). In the aerodynamic Leidenfrost situation, air gets inserted between the liquid and the moving solid, a situation that we analyze. We observe two types of entrainment. (i) The thickness of the air gap is found to increase with the plate speed, which is interpreted in the Landau-Levich-Derjaguin frame: Air is dynamically dragged along the surface and its thickness results from a balance between capillary and viscous effects. (ii) Air set in motion by the plate exerts a force on the levitating liquid. We discuss the magnitude of this aerodynamic force and show that it can be exploited to control the liquid and even to drive it against gravity.

  20. Unexpected transient effect.

    PubMed

    Chame, A; Villain, J

    2001-02-01

    When a grooved periodic profile cut in a crystalline surface relaxes through surface diffusion, flatter parts appear at the top and bottom in the transient state which precedes complete smoothing. This has been attributed to a tendency of successive steps of identical sign to draw closer to one another. This kind of kinetic interaction is a consequence of the finite value of the interatomic distance, and is present even if no interaction between steps is taken into account. We investigate this effect in a very simplified model, namely, a one-dimensional profile with alternating pairs of up and down steps, where no annihilation of steps is allowed. The quantitative effect is partly treated analytically.

  1. Lightning Physics and Effects

    NASA Astrophysics Data System (ADS)

    Orville, Richard E.

    2004-03-01

    Lightning Physics and Effects is not a lightning book; it is a lightning encyclopedia. Rarely in the history of science has one contribution covered a subject with such depth and thoroughness as to set the enduring standard for years, perhaps even decades, to come. This contribution covers all aspects of lightning, including lightning physics, lightning protection, and the interaction of lightning with a variety of objects and systems as well as the environment. The style of writing is well within the ability of the technical non-expert and anyone interested in lightning and its effects. Potential readers will include physicists; engineers working in the power industry, communications, computer, and aviation industries; atmospheric scientists; geophysicists; meteorologists; atmospheric chemists; foresters; ecologists; physicians working in the area of electrical trauma; and, lastly, architects. This comprehensive reference volume contains over 300 illustrations, 70 tables with quantitative information, and over 6000 reference and bibliography entries.

  2. Measuring marketing effectiveness.

    PubMed

    Gluckman, J; Michaelis, T

    1987-09-01

    The most frequent question about the marketing function in hospitals today is, What are we getting for our money? To answer this, marketing directors must convince the board first of the need for marketing, then of marketing's effectiveness. To measure marketing effectiveness, some basic needs are a staff, equipment, cooperation between departments, utilization data, and a research budget. Some steps to be followed include developing a marketing data base--consisting of demographic projections, demand projections, and market share--testing a marketing strategy through experimentation, documenting the expected results and measurement techniques, and calculating the expected return on investments. In dealing with those "impossible-to-measure" cases, such as a physician who is not advertising but finds that a competitor is, a decision tree can help determine whether to advertise and how much to spend by indicating what the return on investment might be.

  3. Fatigue and Barkhausen effect

    NASA Astrophysics Data System (ADS)

    Tong, Wei

    Piezomagnetism designates a change in the magnetization of materials induced by mechanical actions such as tension or compression. The type of Barkhausen effect that occurs in this work consists of sudden, discontinuous jumps in a material's magnetization that appear in response to smooth (continuous) stress variations. A series of strain controlled fatigue tests with an alternating sinusoidal waveform were carried out to study the relationship between the endurance limit and the Barkhausen effect. Results of fatigue tests on steel specimens exhibiting Barkhausen pulses at various stages are reported and a threshold-crossing analysis is applied to the test results. These studies show that when the fatigue limit is approached, the Barkhausen pulses become, in general, more intense in amplitude and quantity than at other stress levels. A hypothetical mechanism is proposed that relates the intensity of the Barkhausen response to the inception of micro-cracking and rearrangements of the mechanical lattice at the microscopic level.

  4. Fuel Vaporization Effects

    NASA Technical Reports Server (NTRS)

    Bosque, M. A.

    1983-01-01

    A study of the effects of fuel-air preparation characteristics on combustor performance and emissions at temperature and pressure ranges representative of actual gas turbine combustors is discussed. The effect of flameholding devices on the vaporization process and NOx formation is discussed. Flameholder blockage and geometry are some of the elements that affect the recirculation zone characteristics and subsequently alter combustion stability, emissions and performance. A water cooled combustor is used as the test rig. Preheated air and Jet A fuel are mixed at the entrance of the apparatus. A vaporization probe is used to determine percentage of vaporization and a gas sample probe to determine concentration of emissions in the exhaust gases. The experimental design is presented and experimental expected results are discussed.

  5. Polarization effects. Volume 2

    SciTech Connect

    Courant, E.

    1981-01-01

    The use of polarized proton beams in ISABELLE is important for several general reasons: (1) With a single longitudinally polarized proton beam, effects involving parity violation can be identified and hence processes involving weak interactions can be separated from those involving strong and electromagnetic interactions. (2) Spin effects are important in the strong interactions and can be useful for testing QCD. The technique for obtaining polarized proton beams in ISABELLE appears promising, particularly in view of the present development of a polarized proton beam for the AGS. Projections for the luminosity in ISABELLE for collisions of polarized protons - one or both beams polarized with longitudinal or transverse polarization - range from 1/100 to 1 times the luminosity for unpolarized protons.

  6. NEURODEVELOPMENTAL EFFECTS OF COCAINE

    PubMed Central

    Singer, Lynn; Arendt, Robert; Minnes, Sonia

    2014-01-01

    The United States has recently been compelled to acknowledge and to cope with an alarming increase in incidence of drug exposure in newborns owing to a new cocaine epidemic. Perhaps because of the sudden onset of national recognition of the problem, the lack of a firm knowledge base regarding the mechanisms of the effects of cocaine on child development, and the sheer magnitude of the problem in urban areas of the United States, the issue of cocaine exposure in children has been characterized by medical, legal, and social policy controversies. This article focuses on elucidating what is and what is not known about cocaine’s neurodevelopmental effects and aims to inform perinatologists about the complex issues associated with understanding and caring for the cocaine-exposed newborn. PMID:8458168

  7. Latent effects decision analysis

    DOEpatents

    Cooper, J Arlin [Albuquerque, NM; Werner, Paul W [Albuquerque, NM

    2004-08-24

    Latent effects on a system are broken down into components ranging from those far removed in time from the system under study (latent) to those which closely effect changes in the system. Each component is provided with weighted inputs either by a user or from outputs of other components. A non-linear mathematical process known as `soft aggregation` is performed on the inputs to each component to provide information relating to the component. This information is combined in decreasing order of latency to the system to provide a quantifiable measure of an attribute of a system (e.g., safety) or to test hypotheses (e.g., for forensic deduction or decisions about various system design options).

  8. Estimating Absolute Site Effects

    SciTech Connect

    Malagnini, L; Mayeda, K M; Akinci, A; Bragato, P L

    2004-07-15

    The authors use previously determined direct-wave attenuation functions as well as stable, coda-derived source excitation spectra to isolate the absolute S-wave site effect for the horizontal and vertical components of weak ground motion. They used selected stations in the seismic network of the eastern Alps, and find the following: (1) all ''hard rock'' sites exhibited deamplification phenomena due to absorption at frequencies ranging between 0.5 and 12 Hz (the available bandwidth), on both the horizontal and vertical components; (2) ''hard rock'' site transfer functions showed large variability at high-frequency; (3) vertical-motion site transfer functions show strong frequency-dependence, and (4) H/V spectral ratios do not reproduce the characteristics of the true horizontal site transfer functions; (5) traditional, relative site terms obtained by using reference ''rock sites'' can be misleading in inferring the behaviors of true site transfer functions, since most rock sites have non-flat responses due to shallow heterogeneities resulting from varying degrees of weathering. They also use their stable source spectra to estimate total radiated seismic energy and compare against previous results. they find that the earthquakes in this region exhibit non-constant dynamic stress drop scaling which gives further support for a fundamental difference in rupture dynamics between small and large earthquakes. To correct the vertical and horizontal S-wave spectra for attenuation, they used detailed regional attenuation functions derived by Malagnini et al. (2002) who determined frequency-dependent geometrical spreading and Q for the region. These corrections account for the gross path effects (i.e., all distance-dependent effects), although the source and site effects are still present in the distance-corrected spectra. The main goal of this study is to isolate the absolute site effect (as a function of frequency) by removing the source spectrum (moment-rate spectrum) from

  9. Developmental effects of dioxins.

    PubMed Central

    Birnbaum, L S

    1995-01-01

    The potent developmental toxicity of dioxin in multiple species has been known for a number of years. However, recent studies have indicated that dioxin also induces functional developmental defects, many of which are delayed. Subtle structural deficits, not detectable at birth, have also been described in multiple species and in both sexes. Certain defects have been reported not only in animals but also in children prenatally exposed to complex mixtures containing dioxinlike compounds. None of the effects can be attributed to modulation of any one endocrine system. For example, dioxin does not bind to the estrogen receptor, but it can cause effects that are both estrogenic and antiestrogenic. However, viewing dioxin and related compounds as endocrine disruptors that may alter multiple pathways sheds some light on the complexities of this potent class of growth dysregulators. PMID:8593882

  10. Neuroprotective effects of creatine.

    PubMed

    Beal, M Flint

    2011-05-01

    There is a substantial body of literature, which has demonstrated that creatine has neuroprotective effects both in vitro and in vivo. Creatine can protect against excitotoxicity as well as against β-amyloid toxicity in vitro. We carried out studies examining the efficacy of creatine as a neuroprotective agent in vivo. We demonstrated that creatine can protect against excitotoxic lesions produced by N-methyl-D: -aspartate. We also showed that creatine is neuroprotective against lesions produced by the toxins malonate and 3-nitropropionic acid (3-NP) which are reversible and irreversible inhibitors of succinate dehydrogenase, respectively. Creatine produced dose-dependent neuroprotective effects against MPTP toxicity reducing the loss of dopamine within the striatum and the loss of dopaminergic neurons in the substantia nigra. We carried out a number of studies of the neuroprotective effects of creatine in transgenic mouse models of neurodegenerative diseases. We demonstrated that creatine produced an extension of survival, improved motor performance, and a reduction in loss of motor neurons in a transgenic mouse model of amyotrophic lateral sclerosis (ALS). Creatine produced an extension of survival, as well as improved motor function, and a reduction in striatal atrophy in the R6/2 and the N-171-82Q transgenic mouse models of Huntington's disease (HD), even when its administration was delayed until the onset of disease symptoms. We recently examined the neuroprotective effects of a combination of coenzyme Q10 (CoQ10) with creatine against both MPTP and 3-NP toxicity. We found that the combination of CoQ and creatine together produced additive neuroprotective effects in a chronic MPTP model, and it blocked the development of alpha-synuclein aggregates. In the 3-NP model of HD, CoQ and creatine produced additive neuroprotective effects against the size of the striatal lesions. In the R6/2 transgenic mouse model of HD, the combination of CoQ and creatine produced

  11. Safety Intervention Effectiveness

    SciTech Connect

    ZIMMERMAN, R.O.

    2001-10-16

    Judging safety intervention effectiveness is often left up to the eye of the beholder. Safety and Health Professionals must increase skills and increase their body of knowledge, based on scientific evidence, that can be applied confidently in the workplace. Evidence must be collected and analyzed to separate the interventions of the month with those that stand the test of time. The book Guide to Evaluating the Effectiveness of Strategies for Preventing Work injuries DHHS (NIOSH) Publication No. 2001-119, April 2001, serves as a primary reference. An example study related to biorhythms, popular in the late 1970s, is used to illustrate the separating of scientific evidence and pseudo-science hype. The cited biorhythm study focuses on the relationship of the accident dates and the three biorhythmic cycles (physical, emotional, and intelligence).

  12. Chromatic Vasarely effect.

    PubMed

    Tsofe, Avital; Yucht, Yulia; Beyil, Jenny; Einav, Shmuel; Spitzer, Hedva

    2010-10-28

    Vasarely's 'nested-squares' illusion is the perception of a glowing "X" along the diagonals of concentric squares with a luminance gradient. We present here the chromatic Vasarely effect, where the concentric angles have a chromatic gradient, under iso-brightness conditions. The strength of the effect was tested psychophysically by two measures, the length and the color of the illusory folds. The color of the illusory fold is perceived as the complementary color of the color of the nested-squares (or angles). The experimental results show that a large repertoire of stimuli with different colors and angles yielded significantly perceived colors. The results show that the strength of the perceived illusory fold (of both the length and the chroma) is significantly larger at sharper angles of the stimuli. The chromatic first-order adaptation computational model predicts most of the above results. Copyright © 2010 Elsevier Ltd. All rights reserved.

  13. Picosecond Spin Seebeck Effect.

    PubMed

    Kimling, Johannes; Choi, Gyung-Min; Brangham, Jack T; Matalla-Wagner, Tristan; Huebner, Torsten; Kuschel, Timo; Yang, Fengyuan; Cahill, David G

    2017-02-03

    We report time-resolved magneto-optic Kerr effect measurements of the longitudinal spin Seebeck effect in normal metal/Y_{3}Fe_{5}O_{12} bilayers driven by an interfacial temperature difference between electrons and magnons. The measured time evolution of spin accumulation induced by laser excitation indicates transfer of angular momentum across normal metal/Y_{3}Fe_{5}O_{12} interfaces on a picosecond time scale, too short for contributions from a bulk temperature gradient in an yttrium iron garnet. The product of spin-mixing conductance and the interfacial spin Seebeck coefficient determined is of the order of 10^{8}  A m^{-2} K^{-1}.

  14. Neurotoxic effects of methamphetamine.

    PubMed

    Thrash, Bessy; Karuppagounder, Senthilkumar S; Uthayathas, Subramaniam; Suppiramaniam, Vishnu; Dhanasekaran, Muralikrishnan

    2010-01-01

    In Parkinson's disease, depletion of dopamine in the striatum leads to various symptoms such as tremor, rigidity and akinesia. Methamphetamine use has significantly increased in USA and around the world and there are several reports showing that its long-term use increases the risk for dopamine depletion. However, the toxic mechanisms of methamphetamine are not well understood. This study was undertaken to gain greater mechanistic understanding of the toxicity induced by methamphetamine. We evaluated the effect of methamphetamine on the generation of reactive oxygen species, mitochondrial monoamine oxidase, complex I & IV activities. Behavioral analysis evaluated the effect on catalepsy, akinesia and swim score. Neurotransmitter levels were evaluated using high pressure liquid chromatography (HPLC) electrochemical detection (ECD). Results showed that methamphetamine caused significant generation of reactive oxygen species and decreased complex I activity in the mitochondria leading to dopamine depletion in the striatum.

  15. [Herbs and cardiotoxic effects].

    PubMed

    Maffè, Stefano; Paffoni, Paola; Laura Colombo, Maria; Davanzo, Franca; Dellavesa, Pierfranco; Cucchi, Lorenzo; Zenone, Franco; Paino, Anna Maria; Franchetti Pardo, Nicolò; Bergamasco, Luca; Signorotti, Fabiana; Parravicini, Umberto

    2013-06-01

    Accidental or deliberate ingestion of poisonous herbs has become an increasingly common phenomenon over the last years. From existing literature data and case reports from emergency room visits or poison control centers, an overview is presented of the potential cardiotoxic manifestations following intoxication by wild herbal plants of the territory. The effects of the consumption of cardiac glycoside-containing plants (e.g., digitalis) are discussed along with tachyarrhythmias induced by Aconitum napellus L., Atropa belladonna L., Mandragora officinarum L. or Ephedra distachya L. herbs, and hypertensive crises associated with licorice abuse. For each plant, a brief historical and botanical background is provided, focusing on pathophysiology of intoxication and cardiotoxic effects on the basis of the most recent literature. Finally, medical management of intoxication, from both a general and cardiological viewpoint, is reviewed.

  16. Effective Vaccination Policies

    PubMed Central

    Shaw, L.; Spears, W.; Billings, L.; Maxim, P.

    2010-01-01

    We present a framework for modeling the spread of pathogens throughout a population and generating policies that minimize the impact of those pathogens on the population. This framework is used to study the spread of human viruses between cities via airplane travel. It combines agent-based simulation, mathematical analysis, and an Evolutionary Algorithm (EA) optimizer. The goal of this study is to develop tools that determine the optimal distribution of a vaccine supply in the model. Using plausible benchmark vaccine allocation policies of uniform and proportional distribution, we compared their effectiveness to policies found by the EA. We then designed and tested a new, more effective policy which increased the importance of vaccinating smaller cities that are flown to more often. This “importance factor” was validated using U.S. influenza data from the last four years. PMID:21057602

  17. The Uniform Rugosity Effect

    NASA Astrophysics Data System (ADS)

    Bonnivard, Matthieu; Bucur, Dorin

    2012-06-01

    Relying on the effect of microscopic asperities, one can mathematically justify that viscous fluids adhere completely on the boundary of an impermeable domain. The rugosity effect accounts asymptotically for the transformation of complete slip boundary conditions on a rough surface in total adherence boundary conditions, as the amplitude of the rugosities vanishes. The decreasing rate (average velocity divided by the amplitude of the rugosities) computed on close flat layers is definitely influenced by the geometry. Recent results prove that this ratio has a uniform upper bound for certain geometries, like periodical and "almost Lipschitz" boundaries. The purpose of this paper is to prove that such a result holds for arbitrary (non-periodical) crystalline boundaries and general (non-smooth) periodical boundaries.

  18. The Kaye effect

    NASA Astrophysics Data System (ADS)

    Binder, J. M.; Landig, A. J.

    2009-11-01

    The International Young Physicists' Tournament (IYPT) is a worldwide, annual competition for secondary school students. This is our solution to problem number 10, The Kaye effect, as presented in the final round of the 21st IYPT in Trogir, Croatia. The Kaye effect occurs when a thin stream of shampoo or a different adequate non-Newtonian liquid is poured onto a surface. Suddenly, a jet leaves the heap that is formed by the shampoo and begins to 'dance' around the primary jet like a lasso. The phenomenon ends when the 'dancing' jet hits the primary jet and subsequently collapses. We started our investigations based on available literature (Kaye 1963 Nature 197 1001, Versluis et al 2006 J. Stat. Mech., Collyer and Fischer 1976 Nature 261 682). We made experiments with a similar experimental set-up in which we could determine the velocities of both shampoo streams as well as the angle of the 'dancing' stream. From there on, we developed a theoretical model for the energy loss of the jet in the heap. We discovered that the air layer between the jet and the heap is a necessity for the Kaye effect to occur. At this point, our observations differ from the aforementioned literature. This also accounts for the shampoo beam acting as a light guide. Further experiments concerning the viscoelasticity of the shampoo revealed that the elastic property of the shampoo is necessary for the effect to occur. This article is a written version of the oral contribution of the German team to the 21st IYPT competition, which was awarded first prize by an international jury. The article has been edited by European Journal of Physics.

  19. Disaster Response: Improving Effectiveness

    DTIC Science & Technology

    2007-12-01

    2005, had winds of 130-150 mph winds and produced an enormous amount of rain . The energy of the hurricane created a storm surge as high as 27 feet...were hoping for a speedy evacuation. Finally, late on 4 September, the last of individuals residing in the Superdome were evacuated. Hurricane ...REPORT TYPE AND DATES COVERED Master’s Thesis 4. TITLE AND SUBTITLE Disaster Response: Improving Effectiveness 6. AUTHOR( S ) Matt Benivegna 5

  20. Nonlocal anomalous Hall effect

    NASA Astrophysics Data System (ADS)

    Zhang, Shulei; Vignale, Giovanni

    Anomalous Hall effect (AHE) is a distinctive transport property of ferromagnetic metals arising from spin orbit coupling (SOC) in concert with spontaneous spin polarization. Nonetheless, recent experiments have shown that the effect also appears in a nonmagnetic metal in contact with a magnetic insulator. The main puzzle lies in the apparent absence of spin polarized electrons in the non-magnetic metal. Here, we theoretically demonstrate that the scattering of electrons from a rough metal-insulator interface is generally spin-dependent, which results in mutual conversion between spin and charge currents flowing in the plane of the layer. It is the current-carrying spin polarized electrons and the spin Hall effect in the bulk of the metal layer that conspire to generate the AH current. This novel AHE differs from the conventional one only in the spatial separation of the SOC and the magnetization, so we name it as nonlocal AHE. In contrast to other previously proposed mechanisms (e.g., spin Hall AHE and magnetic proximity effect (MPE)), the nonlocal AHE appears on the first order of spin Hall angle and does not rely on the induced moments in the metal layer, which make it experimentally detectable by contrasting the AH current directions of two layered structures such as Pt/Cu/YIG and β -Ta/Cu/YIG (with a thin inserted Cu layer to eliminate the MPE). We predict that the directions of the AH currents in these two trilayers would be opposite since the spin Hall angles of Pt and β -Ta are of opposite signs. Work supported by NSF Grants DMR-1406568.

  1. Lightning effects on aircraft

    NASA Technical Reports Server (NTRS)

    1977-01-01

    Direct and indirect effects of lightning on aircraft were examined in relation to aircraft design. Specific trends in design leading to more frequent lightning strikes were individually investigated. These trends included the increasing use of miniaturized, solid state components in aircraft electronics and electric power systems. A second trend studied was the increasing use of reinforced plastics and other nonconducting materials in place of aluminum skins, a practice that reduces the electromagnetic shielding furnished by a conductive skin.

  2. Tasting edge effects

    NASA Astrophysics Data System (ADS)

    Bocquet, Lydéric

    2007-02-01

    We show that the baking of potato wedges constitutes a crunchy example of edge effects, which are usually demonstrated in electrostatics. A simple model of the diffusive transport of water vapor around the potato wedges shows that the water vapor flux diverges at the sharp edges in analogy with its electrostatic counterpart. This increased evaporation at the edges leads to the crispy taste of these parts of the potatoes.

  3. Geomagnetic and atmospheric effects

    NASA Astrophysics Data System (ADS)

    Stoker, P. H.

    1983-08-01

    Geomagnetic and atmospheric processes affecting cosmic-ray earthbound spectrometry are analyzed. The topics discussed include: cutoff rigidities and asymptotic directions; cosmic ray secondaries in the atmosphere and magnetosphere; neutron counters without lead and neutron monitors; and coupling coefficients/yield functions and response functions of cosmic ray detectors. Theoretical simulations of the atmosphere and geomagnetism are presented, taking into account such factors as geomagnetic ring currents and meteorological effects. Diagrams and cutoff rigidity contours are included.

  4. Effect of Thermal Cycling

    DTIC Science & Technology

    1988-05-01

    MEASUREMENT METHOD To characterize the surfaces, a real time Twyman -Green phase shifting interferometer was mounted on an air-suspended 8000 lb granite... interferometer and mirror mounts were augmented to decrease their natural resonance frequency. To minimize thermal effects, a thermal insulation... INTERFEROMETER INTERFACE HP COMPUTER Fig. 8. RTI test arrangement. 22 1𔃺a wa M VIl. SURFACE FIGURE RESULTS 1. Uniform heating - 60 K/hr (Figs. 9a

  5. Magnetic effects on thermocouples

    NASA Astrophysics Data System (ADS)

    Beguš, Samo; Bojkovski, Jovan; Drnovšek, Janko; Geršak, Gregor

    2014-03-01

    Thermometers in laboratory environment and industrial applications are often subject to extraneous, usually unwanted and uncontrolled magnetic fields. Magnetic field influence can be minimized, but cannot be fully cancelled out. Even more, in most cases, there is no awareness of the existence of magnetic fields, let alone their effect on measurement instrumentation. In the past, sensitivity to high dc magnetic fields has been investigated in cryogenics and at high temperatures. More recently, the magnetic effect on weak dc magnetic fields was presented. The goal of this paper was to analyse and empirically and experimentally prove the magnetic sensitivity of thermocouples exposed to low magnetic fields: both dc and ac. Precision and uniform alternating and direct magnetic flux densities were generated by means of permanent magnets and power amplifiers with air-cored coils. The magnetic effect on ferromagnetic and non-ferromagnetic thermocouples at liquid-nitrogen-boiling point (-196 °C), ice point (0 °C), in water (17 °C) and at melting point of gallium fixed point cell (29.7646 °C) was investigated. Magnetic-field-dependent temperature errors of up to 700 mK (at 5.3 mT: dc) and up to 1 °C (at 10 mT: ac 50 Hz magnetic fields) were detected. From the results, it can be concluded that, ideally for temperature measurements of the highest accuracy in the above-cryogenic temperature range, magnetic sensitivity should be estimated and taken into account either as the correction of an error and/or as an additional source of measurement uncertainty. Special consideration should be given to thermocouple orientation relative to the magnetic field direction, influence of metal enclosures and magnetization effects on ferromagnetic components of thermocouples.

  6. Quantized Field Effects

    NASA Astrophysics Data System (ADS)

    Freyberger, Matthias; Vogel, Karl; Schleich, Wolfgang; O'Connell, Robert

    The electromagnetic field appears almost everywhere in physics. Following the introduction of Maxwell's equations in 1864, Max Planck initiated quantum theory when he discovered h = 2πℏ in the laws of black-body radiation. In 1905 Albert Einstein explained the photoelectric effect on the hypothesis of a corpuscular nature of radiation and in 1917 this paradigm led to a description of the interaction between atoms and electromagnetic radiation.

  7. Understaning the "funding effect"

    NASA Astrophysics Data System (ADS)

    Oreskes, N.

    2016-12-01

    There is a long history of industry funding of scientific and engineering research in the USA. Much of this work has been of high quality. Research demonstrates, however, that corporate funding can represent a threat to scientific independence and integrity. Studies show that sponsors' interests can affect research results, particularly when sponsors have a strong interest in a particular research outcome. The effects may occur through the impact of subconscious bias on sampling, study design, data interpretation, and/or reporting of results. Corporate funding can also skew research toward investigating certain questions at the expense of others, downplaying the significance of adverse findings, and/or failing to report adverse results. Gifts can affect behavior, even when they are unrelated to research activities. These impacts that are so substantial that they have a name: "the funding effect."[i] Evidence shows that scientists who strive to be objective and fair-minded may nonetheless fall prey to the funding effect. In many cases, the challenges of corporate gifts and funding can be addressed through education and improved self-awareness, agreements that protect researchers' freedom to publish without sponsor approval, sensible disclosure policies, and reasonable sanctions for failures of disclosure. However, in some cases, it may be appropriate for researchers and scientific societies to decline funding.

  8. Cascading Effects Following Intervention

    PubMed Central

    Patterson, Gerald R.; Forgatch, Marion S.; DeGarmo, David S.

    2010-01-01

    Four different sources for cascade effects were examined using 9-year process and outcome data from a randomized controlled trial (RCT) of a preventive intervention using Parent Management Training – Oregon Model (PMTO™). The social interaction learning (SIL) model of child antisocial behavior serves as one basis for predicting change. A second source addresses the issue of comorbid relationships among clinical diagnoses. The third source, collateral changes, describes events in which changes in one family member correlate with changes in another. The fourth component is based on the long-term effects of reducing coercion and increasing positive interpersonal processes within the family. New findings from the 9-year follow-up show that mothers experienced benefits as measured by standard of living (i.e., income, occupation, education, and financial stress) and frequency of police arrests. It is assumed that PMTO reduces the level of coercion, which sets the stage for a massive increase in positive social interaction. In effect, PMTO alters the family environment and thereby opens doors to healthy new social environments. PMID:20883592

  9. Background Pressure Effects on Krypton Hall Effect Thruster Internal Acceleration

    DTIC Science & Technology

    2013-08-01

    Technical Paper 3. DATES COVERED (From - To) August 2013- September 2013 4. TITLE AND SUBTITLE Background Pressure Effects on Krypton Hall Effect...Conference 2013, Washington, D.C., 6-10 October 2013. 14. ABSTRACT This study uses krypton propellant in a medium power Hall effect to amplify the...effect of background pressure due to the greater mobility of neutral krypton compared to neutral xenon. The use of krypton amplifies the effect of

  10. Effects of Agent Transparency on Multi-Robot Management Effectiveness

    DTIC Science & Technology

    2015-09-01

    ARL-TR-7466 ● SEP 2015 US Army Research Laboratory Effects of Agent Transparency on Multi- Robot Management Effectiveness by...SEP 2015 US Army Research Laboratory Effects of Agent Transparency on Multi- Robot Management Effectiveness by Joseph E Mercado Oak...Final 3. DATES COVERED (From - To) October 2013–September 2014 4. TITLE AND SUBTITLE Effects of Agent Transparency on Multi- Robot Management

  11. The Giant Magnetocaloric Effect

    NASA Astrophysics Data System (ADS)

    Pecharsky, Vitalij K.

    1998-03-01

    Since the discovery of the magnetocaloric effect in pure iron by E.Warburg in 1881, it has been measured experimentally on many magnetic metals and compounds. The majority of the materials studied order magnetically undergoing a second order phase transformation. The magnetocaloric effect, typically peaking near the Curie or the Néel temperature, generally ranges from 0.5 to 2 K (in terms of adiabatic temperature change) or at 1 to 4 J/kg K (in terms of isothermal magnetic entropy change) per 1 T magnetic field change. The giant magnetocaloric effect recently discovered in Gd_5(Si_xGe_1-x)4 alloys, where x <= 0.5, is associated with a first order magnetic phase transition and it reaches values of 3 to 4 K and 6 to 10 J/kg K per 1 T field change, respectively. The refrigerant capacity, which is the measure of how much heat can be transferred from a cold to a hot reservoir in one ideal thermodynamic cycle, is larger than that of the best second order phase transition materials by 25 to 100%. When the Gd_5(Si_xGe_1-x)4 alloys are compared with other known materials, which show first order magnetic phase transition, such as Dy, Ho, Er, HoCo_2, NdMn_2Si_2, Fe_0.49Rh_0.51, and (Hf_0.83Ta_0.17)Fe_2+x, only Fe_0.49Rh_0.51 has comparable magnetocaloric properties. However, the first order magnetic phase transition in Fe_0.49Rh_0.51 is irreversible, and the magnetocaloric effect disappears after one magnetizing/demagnetizing cycle. A study of the crystal structure, thermodynamics, and magnetism of the Gd_5(Si_xGe_1-x)4 alloys, where 0 <= x <= 1 allowed us to obtain a qualitative understanding of the basic relations between the composition, the crystal structure, and the change in thermodynamics and magnetocaloric properties, which occur in the Gd_5(Si_xGe_1-x)4 system, and which brings about the giant magnetocaloric effect when x <= 0.5.

  12. Effects of 5-FU.

    PubMed

    Wigmore, Peter M; Mustafa, Sarah; El-Beltagy, Maha; Lyons, Laura; Umka, Jariya; Bennett, Geoff

    2010-01-01

    5-fluorouracil (5-FU) is a chemotherapeutical agent used to treat cancers including breast and colorectal. Working as an antimetabolite to prevent cell proliferation, it primarily inhibits the enzyme thymidylate synthase blocking the thymidine formation required for DNA synthesis. Although having a relatively short half-life (< 30 mins) it readily enters the brain by passive diffusion. Clinically, it is used both as a single agent or in combination with other chemotherapies and has been associated with the long-term side effects of cognitive impairment, known as "chemo brain" or "chemo fog" These accounts have come primarily from patients undergoing treatment for breast cancer who report symptoms including confusion and memory impairment, which can last for months to years. Psychometric studies of patients have suffered from confounding variables, which has led to the use of rodent models to assess the cognitive effects of this drug. Researchers have used behavioral and physiological tests including the Morris water maze, novel object location/recognition tests, shock motivated T-maze, sensory gating and conditioning, to investigate the effect of this drug on cognition. The variety of cognitive tests and the difference in dosing and administration of 5-FU has led to varied results, possibly due to the different brain regions associated with each test and the subtlety of the drug's effect, but overall these studies indicates that 5-FU has a negative effect on memory, executive function and sensory gating. 5-FU has also been demonstrated to have biochemical and structural changes on specific regions of the brain. Evidence shows it can induce apoptosis and depress cell proliferation in the neurogenic regions of the adult brain including the sub granular zone (SGZ) within the hippocampus and in oligodendrocyte precursor populations within white matter tracts. Furthermore, investigations indicate levels ofdoublecortin, a marker for newly formed neurons and brain derived

  13. The Fire Effects Information System

    Treesearch

    William C. Fischer

    1987-01-01

    Lack of information regarding fire effects is perceived by many fire and resource managers as a barrier to the effective application of prescribed fire. This lack of information, in many instances, is the result of poor diffusion of existing knowledge rather than lack of knowledge. A computerized Fire Effects Information System can make existing fire effects knowledge...

  14. SOLAR EFFECTS ON BUILDING DESIGN.

    ERIC Educational Resources Information Center

    Building Research Inst., Inc., Washington, DC.

    A REPORT OF A PROGRAM HELD AS PART OF THE BUILDING RESEARCH INSTITUTE 1962 SPRING CONFERENCE ON THE SOLAR EFFECTS ON BUILDING DESIGN. TOPICS DISCUSSED ARE--(1) SOLAR ENERGY DATA APPLICABLE TO BUILDING DESIGN, (2) THERMAL EFFECTS OF SOLAR RADIATION ON MAN, (3) SOLAR EFFECTS ON ARCHITECTURE, (4) SOLAR EFFECTS ON BUILDING COSTS, (5) SELECTION OF…

  15. Epidemiologic studies of microwave effects

    SciTech Connect

    Silverman, C.

    1980-01-01

    Presented is a selective review of human epidemiological studies and related information concerning biological and health effects of microwave (MW) radiation. Two unpublished studies of MW effects are discussed: a study of U.S. Navy personnel occupationally exposed to radar, and a study of U.S. Embassy personnel in Moscow. MW effects in the following categories are discussed: ocular effects, nervous and behavioral effects, congenital anomalies, and cancer. Areas for future research are outlined.

  16. Quantum Effects in Biology

    NASA Astrophysics Data System (ADS)

    Mohseni, Masoud; Omar, Yasser; Engel, Gregory S.; Plenio, Martin B.

    2014-08-01

    List of contributors; Preface; Part I. Introduction: 1. Quantum biology: introduction Graham R. Fleming and Gregory D. Scholes; 2. Open quantum system approaches to biological systems Alireza Shabani, Masoud Mohseni, Seogjoo Jang, Akihito Ishizaki, Martin Plenio, Patrick Rebentrost, Alàn Aspuru-Guzik, Jianshu Cao, Seth Lloyd and Robert Silbey; 3. Generalized Förster resonance energy transfer Seogjoo Jang, Hoda Hossein-Nejad and Gregory D. Scholes; 4. Multidimensional electronic spectroscopy Tomáš Mančal; Part II. Quantum Effects in Bacterial Photosynthetic Energy Transfer: 5. Structure, function, and quantum dynamics of pigment protein complexes Ioan Kosztin and Klaus Schulten; 6. Direct observation of quantum coherence Gregory S. Engel; 7. Environment-assisted quantum transport Masoud Mohseni, Alàn Aspuru-Guzik, Patrick Rebentrost, Alireza Shabani, Seth Lloyd, Susana F. Huelga and Martin B. Plenio; Part III. Quantum Effects in Higher Organisms and Applications: 8. Excitation energy transfer in higher plants Elisabet Romero, Vladimir I. Novoderezhkin and Rienk van Grondelle; 9. Electron transfer in proteins Spiros S. Skourtis; 10. A chemical compass for bird navigation Ilia A. Solov'yov, Thorsten Ritz, Klaus Schulten and Peter J. Hore; 11. Quantum biology of retinal Klaus Schulten and Shigehiko Hayashi; 12. Quantum vibrational effects on sense of smell A. M. Stoneham, L. Turin, J. C. Brookes and A. P. Horsfield; 13. A perspective on possible manifestations of entanglement in biological systems Hans J. Briegel and Sandu Popescu; 14. Design and applications of bio-inspired quantum materials Mohan Sarovar, Dörthe M. Eisele and K. Birgitta Whaley; 15. Coherent excitons in carbon nanotubes Leonas Valkunas and Darius Abramavicius; Glossary; References; Index.

  17. 'The Kesterson effect'

    USGS Publications Warehouse

    Presser, T.S.

    1994-01-01

    Hypothesized to be derived from Cretaceous marine sedimentary rocks, selenium contamination of the Kesterson National Wildlife Refuge is traced through irrigation drainage to the source bedrock of the California Coast Ranges. This biogeochemical pathway of selenium is defined here as the 'Kesterson effect.' At the refuge ponds, this effect culminated in 1983 in a 64% rate of deformity and death of embryos and hatchlings of wild aquatic birds. From the previous companion paper on irrigation drainage, the Kesterson effect has been implicated in nine of 11 reconnaissance areas studied in the western United States. Deformities have resulted in at least five of these sites. Climatic, geologic, hydrologic, and soil conditions in these reconnaissance areas are similar to those in the area surrounding Kesterson National Wildlife Refuge in the west-central San Joaquin Valley of California, in California, selenium as selenate, was ultimately found weathered with sulfur from marine sources in soluble sodium and magnesium sulfate salts, which are concentrated by evaporation on farmland soils. The Se, mobilized by irrigation drainage, is bioaccumulated to toxic levels in refuge wetland ponds that are located mainly in hydrologically closed basins and thus act as concentrating disposal points. The depositional environment of the ponds may be similar to that of the nutrient-rich continental shelf edge and slope in which Cretaceous, Eocene, and Miocene sediments found to be seleniferous in the California Coast Ranges were deposited. Bioaccumulation may be therefore a primary mechanism of selenium enrichment in ancient sediments in addition to that of the formerly suggested Cretaceous volcanic pathway.

  18. The Flash Grab Effect

    PubMed Central

    Cavanagh, Patrick; Anstis, Stuart

    2013-01-01

    When an object moves back and forth, its trajectory appears significantly shorter than it actually is. The object appears to stop and reverse well before its actual reversal point, as if there is some averaging of location within a window of about 100 ms (Sinico et al, 2009). Surprisingly, if a bar is flashed at the physical end point of the trajectory, right on top of the object, just as it reverses direction, the flash is also shifted – grabbed by the object – and is seen at the perceived endpoint of the trajectory rather than the physical endpoint. This can shift the perceived location of the flash by as much as 2 or 3 times its physical size and by up to several degrees of visual angle. We first show that the position shift of the flash is generated by the trajectory shortening, as the same shift is seen with or without the flash. The flash itself is only grabbed if it is presented within a small spatiotemporal attraction zone around the physical end point of the trajectory. Any flash falling in that zone is pulled toward the perceived endpoint. The effect scales linearly with speed, up to a maximum, and is independent of the contrast of the moving stimulus once it is above 5%. Finally, we demonstrate that this position shift requires attention. These results reveal a new “flash grab” effect in the family of motion-induced position shifts. Although it most resembles the flash drag effect, it differs from this in the following ways: 1) it has a different temporal profile, 2) it requires attention, 3) it is about 10 times larger. PMID:23872166

  19. The flash grab effect.

    PubMed

    Cavanagh, Patrick; Anstis, Stuart

    2013-10-18

    When an object moves back and forth, its trajectory appears significantly shorter than it actually is. The object appears to stop and reverse well before its actual reversal point, as if there is some averaging of location within a window of about 100 ms (Sinico et al., 2009). Surprisingly, if a bar is flashed at the physical end point of the trajectory, right on top of the object, just as it reverses direction, the flash is also shifted - grabbed by the object - and is seen at the perceived endpoint of the trajectory rather than the physical endpoint. This can shift the perceived location of the flash by as much as 2 or 3 times its physical size and by up to several degrees of visual angle. We first show that the position shift of the flash is generated by the trajectory shortening, as the same shift is seen with or without the flash. The flash itself is only grabbed if it is presented within a small spatiotemporal attraction zone around the physical end point of the trajectory. Any flash falling in that zone is pulled toward the perceived endpoint. The effect scales linearly with speed, up to a maximum, and is independent of the contrast of the moving stimulus once it is above 5%. Finally, we demonstrate that this position shift requires attention. These results reveal a new "flash grab" effect in the family of motion-induced position shifts. Although it most resembles the flash drag effect, it differs from this in the following ways: (1) it has a different temporal profile, (2) it requires attention, (3) it is about 10 times larger. Copyright © 2013 Elsevier Ltd. All rights reserved.

  20. Environmental Effects of BPA

    PubMed Central

    Canesi, Laura

    2015-01-01

    Research on bisphenol A (BPA) as an environmental contaminant has now major regulatory implications toward the ecosystem health, and hence it is incumbent on scientists to do their research to the highest standards possible, in order that the most appropriate decisions are made to mitigate the impacts to aquatic wildlife. However, the contribution given so far appears rather fragmented. The present overview aims to collect available information on the effects of BPA on aquatic vertebrates and invertebrates to provide a general scenario and to suggest future developments toward more comprehensive approaches useful for aquatic species protection. PMID:26674307

  1. Microcircuit radiation effects databank

    NASA Technical Reports Server (NTRS)

    1983-01-01

    This databank is the collation of radiation test data submitted by many testers and serves as a reference for engineers who are concerned with and have some knowledge of the effects of the natural radiation environment on microcircuits. It contains radiation sensitivity results from ground tests and is divided into two sections. Section A lists total dose damage information, and section B lists single event upset cross sections, I.E., the probability of a soft error (bit flip) or of a hard error (latchup).

  2. Photochemical Effects of Sunlight

    PubMed Central

    Daniels, Farrington

    1972-01-01

    The importance of sunlight in bringing about not only photosynthesis in plants, but also other photochemical effects, is reviewed. More effort should be devoted to photochemical storage of the sun's energy without the living plant. There is no theoretical reason to believe that such reactions are impossible. Ground rules for searching for suitable solar photochemical reactions are given, and a few attempts are described, but nothing successful has yet been found. Future possibilities are suggested. Photogalvanic cells which convert sunlight into electricity deserve further research. Eugene Rabinowitch has been an active pioneer in these fields. PMID:5037333

  3. Photochemical effects of sunlight.

    PubMed

    Daniels, F

    1972-07-01

    The importance of sunlight in bringing about not only photosynthesis in plants, but also other photochemical effects, is reviewed. More effort should be devoted to photochemical storage of the sun's energy without the living plant. There is no theoretical reason to believe that such reactions are impossible. Ground rules for searching for suitable solar photochemical reactions are given, and a few attempts are described, but nothing successful has yet been found. Future possibilities are suggested. Photogalvanic cells which convert sunlight into electricity deserve further research. Eugene Rabinowitch has been an active pioneer in these fields.

  4. Assuring reliability program effectiveness.

    NASA Technical Reports Server (NTRS)

    Ball, L. W.

    1973-01-01

    An attempt is made to provide simple identification and description of techniques that have proved to be most useful either in developing a new product or in improving reliability of an established product. The first reliability task is obtaining and organizing parts failure rate data. Other tasks are parts screening, tabulation of general failure rates, preventive maintenance, prediction of new product reliability, and statistical demonstration of achieved reliability. Five principal tasks for improving reliability involve the physics of failure research, derating of internal stresses, control of external stresses, functional redundancy, and failure effects control. A final task is the training and motivation of reliability specialist engineers.

  5. Shock effects in meteorites

    NASA Technical Reports Server (NTRS)

    Stoeffler, D.; Bischoff, A.; Buchwald, V.; Rubin, A. E.

    1988-01-01

    The impacts that can occur between objects on intersecting solar system orbits can generate shock-induced deformations and transformations, creating new mineral phases or melting old ones. These shock-metamorphic effects affect not only the petrography but the chemical and isotopic properties and the ages of primordial meteoritic materials. A fuller understanding of shock metamorphism and breccia formation in meteorites will be essential not only in the study of early accretion, differentiation, and regolith-evolution processes, but in the characterization of the primordial composition of the accreted material itself.

  6. On nature's scaling effects

    NASA Technical Reports Server (NTRS)

    Wilkins, Dick J.

    1994-01-01

    This presentation afforded the opportunity to look back in the literature to discover scaling effects in nature that might be relevant to composites. Numerous examples were found in nature's approaches to wood, teeth, horns, leaves, eggs, feathers, etc. Nature transmits tensile forces rigidly with cohesive bonds, while dealing with compression forces usually through noncompressible hydraulics. The optimum design scaling approaches for aircraft were also reviewed for comparison with similitude laws. Finally, some historical evidence for the use of Weibull scaling in composites was reviewed.

  7. Capsaicin effects on blinking.

    PubMed

    Leon-Sarmiento, Fidias E; Bayona-Prieto, Jaime; Leon-S, Marta E

    2005-09-01

    Blinking is a normal human phenomenon involving trigeminal and facial pathways. To gain understanding on the neurobiology of blinking, five normal subjects were investigated before and after application of transdermal capsaicin at the forehead for two weeks. No effects of topical capsaicin were detected in eye blink rates. However, when capsaicin was applied to a female subject with blepharospasm, she showed a dramatic restoration of her vision subsequent to blinking modification. Deactivation of abnormal A-to-C fibers cross talks at the trigeminal-facial pathways seems to be the most likely mechanism of such improvement.

  8. Ion propulsion cost effectivity

    NASA Technical Reports Server (NTRS)

    Zafran, S.; Biess, J. J.

    1978-01-01

    Ion propulsion modules employing 8-cm thrusters and 30-cm thrusters were studied for Multimission Modular Spacecraft (MMS) applications. Recurring and nonrecurring cost elements were generated for these modules. As a result, ion propulsion cost drivers were identified to be Shuttle charges, solar array, power processing, and thruster costs. Cost effective design approaches included short length module configurations, array power sharing, operation at reduced thruster input power, simplified power processing units, and power processor output switching. The MMS mission model employed indicated that nonrecurring costs have to be shared with other programs unless the mission model grows. Extended performance missions exhibited the greatest benefits when compared with monopropellant hydrazine propulsion.

  9. Antipyretic effect of ketoprofen.

    PubMed

    Celebi, S; Hacimustafaoglu, M; Aygun, D; Arisoy, E S; Karali, Y; Akgoz, S; Citak Kurt, A N; Seringec, M

    2009-03-01

    The aim of this study was to investigate the efficacy and side effect profile of ketoprofen as well as compliance with respect to the taste of the drug and compare these parameters with those of acetaminophen and ibuprofen. A total of 301 patients between 1-14 years of age who applied to emergency rooms of three medical centers with the complaint of fever that required antipyretic therapy were included in the study. Fever was measured with the aid of a tympanic thermometer (Braun Kronberg 6014) and followed for 4-6 hours. The measurement was repeated at 30, 60, 120 minutes, and again 4-6 hours after the initial assessment. The mean age of the patients was 47.8+/-41.1 months. The patients randomly received 15 mg/kg/dose of acetaminophen (n=112 group 1), 0.5 mg/kg/dose of ketoprofen (n=105, group 2), or 10 mg/kg/dose of ibuprofen (n=84, group 3). Fever was 38.4+/-0.7 degrees C, 38.4+/-0.7 degrees C, and 38.5+/-0.5 degrees C at 30 minutes; 38.0+/-0.7 degrees C, 37.9+/-0.7 degrees C, and 38.0+/-0.6 degrees C at 60 minutes (p>0.05), 37.7+/-0.6 degrees C, 37.6+/-0.7 degrees C, and 37.7+/-0.5 degrees C at 120 minutes (p>0.05); 37.5+/-0.7 degrees C, 37.3+/-0.6 degrees C, and 37.4+/-0.6 degrees C at 4-6 hours after admission (p>0.05). The fever was significantly lower at 30, 60, and 120 minutes in all group s (p<0.05). Early vomiting after medication (<6 hours) was observed in 3.8%, 13.5%, and 9.6% whereas late vomiting (6-48 hours) occurred in 1.3%, 2.7%, and 5.8% respectively (p>0.05). Bad taste was expressed by 5.1%, 12.2%, and 5.8% early (<6 hours), and 3.9%, 8.1%, and 3.8% late (6-48 hours) (p>0.05). There were no differences between age groups for antipyretic effect, taste and adverse effect in three drugs (p>0.05). All three drugs were similar in terms of efficacy, adverse effects, and compliance within 48 hours of therapy. These results suggest that ketoprofen may be used for antipyresis as an alternative to acetaminophen and ibuprofen.

  10. Assessments of astronaut effectiveness

    NASA Technical Reports Server (NTRS)

    Rose, Robert M.; Helmreich, Robert L.; Fogg, Louis; Mcfadden, Terry J.

    1993-01-01

    This study examined the reliability and convergent validity of three methods of peer and supervisory ratings of the effectiveness of individual NASA astronauts and their relationships with flight assignments. These two techniques were found to be reliable and relatively convergent. Seniority and a peer-rated Performance and Competence factor proved to be most closely associated with flight assignments, while supervisor ratings and a peer-rated Group Living and Personality factor were found to be unrelated. Results have implications for the selection and training of astronauts.

  11. Interfacial effects in multilayers

    SciTech Connect

    Barbee, T.W., Jr.

    1998-04-01

    Interfacial structure and the atomic interactions between atoms at interfaces in multilayers or nano-laminates have significant impact on the physical properties of these materials. A technique for the experimental evaluation of interfacial structure and interfacial structure effects is presented and compared to experiment. In this paper the impact of interfacial structure on the performance of x-ray, soft x-ray and extreme ultra-violet multilayer optic structures is emphasized. The paper is concluded with summary of these results and an assessment of their implications relative to multilayer development and the study of buried interfaces in solids in general.

  12. Earthquake occurrence and effects.

    PubMed

    Adams, R D

    1990-01-01

    Although earthquakes are mainly concentrated in zones close to boundaries of tectonic plates of the Earth's lithosphere, infrequent events away from the main seismic regions can cause major disasters. The major cause of damage and injury following earthquakes is elastic vibration, rather than fault displacement. This vibration at a particular site will depend not only on the size and distance of the earthquake but also on the local soil conditions. Earthquake prediction is not yet generally fruitful in avoiding earthquake disasters, but much useful planning to reduce earthquake effects can be done by studying the general earthquake hazard in an area, and taking some simple precautions.

  13. Assuring reliability program effectiveness.

    NASA Technical Reports Server (NTRS)

    Ball, L. W.

    1973-01-01

    An attempt is made to provide simple identification and description of techniques that have proved to be most useful either in developing a new product or in improving reliability of an established product. The first reliability task is obtaining and organizing parts failure rate data. Other tasks are parts screening, tabulation of general failure rates, preventive maintenance, prediction of new product reliability, and statistical demonstration of achieved reliability. Five principal tasks for improving reliability involve the physics of failure research, derating of internal stresses, control of external stresses, functional redundancy, and failure effects control. A final task is the training and motivation of reliability specialist engineers.

  14. Radiative Effects of Aerosols

    NASA Technical Reports Server (NTRS)

    Valero, Francisco P. J.

    1997-01-01

    During the Atlantic Stratocumulus Transition Experiment (ASTEX) in June 1992, two descents in cloud-free regions allowed comparison of the change in aerosol optical depth as determined by an onboard total-direct-diffuse radiometer (TDDR) to the change calculated from measured size resolved aerosol microphysics and chemistry. Both profiles included pollution haze layer from Europe but the second also included the effect of a Saharan dust layer above the haze. The separate contributions of supermicrometer (coarse) and submicrometer (fine) aerosol were determined and thermal analysis of the pollution haze indicated that the fine aerosol was composed primarily of a sulfate/water mixture with a refractory soot-like core.

  15. Direct effects protection

    NASA Technical Reports Server (NTRS)

    1977-01-01

    Protection of an aircraft and each of its various systems against the direct effects of lightning were analyzed. Components located in different sections of the aircraft were individually examined since they are likely to experience different degrees of susceptibility to lightning, and may be vulnerable to different components of the lightning flash. The basic steps to be followed in establishing lightning protection were presented by discussing the varieties of arc entry and current flow-through damage. The lightning-strike zones and lightning current environments are established, since environmental conditions in the zones are those under which specific protective measures must perform. Airworthiness regulations which apply to lightning protection are cited.

  16. Terrorism Effects on Turkey

    DTIC Science & Technology

    1991-03-05

    1980’ s many changes took place among these countries; however, there are many indications that the IsB still controls these countries’ intelligence ...for opm Zblkadom vote TERRORISM EFFECTS ON TURKEY BY COLONEL TURAN OLCAY Turkish Army ~Is~RI~~tO S EMHT A’: A~pproved for publ~c 03. RMYWARCOLLG...Distribution is unlimited. 4. PERFORMING ORGANIZATION REPORT NUMBER( S ) S . MONITORING ORGANIZATION REPORT NUMBER( S ) Ga. NAME OF PERFORMING ORGANIZATION 6b

  17. Photoprotective effects of nicotinamide.

    PubMed

    Damian, Diona L

    2010-04-01

    Sun protective measures can reduce numbers of both precancerous actinic keratoses and cutaneous squamous cell carcinomas within relatively short periods of time even in high-risk populations. Sunscreens, which tend to provide greater protection against shortwave UVB than against longer wavelength UVA radiation, can however provide only partial protection from the mutagenic and immune suppressive effects of sunlight. In large part, this reflects poor compliance with proper sunscreen application and reapplication. Skin cancer is by far the most common malignancy in Caucasian populations, and additional strategies to reduce the morbidity and economic burden of this disease are now urgently needed. Nicotinamide, the amide form of vitamin B3, is an inexpensive agent which is used for a variety of dermatological applications with little or no toxicity even at high doses. Nicotinamide has photoprotective effects against carcinogenesis and immune suppression in mice, and is photoimmunoprotective in humans when used as a lotion or orally. UV irradiation depletes keratinocytes of cellular energy and nicotinamide, which is a precursor of nicotinamide adenine dinucleotide, may act at least in part by providing energy repletion to irradiated cells.

  18. When Is Selection Effective?

    PubMed

    Gravel, Simon

    2016-05-01

    Deleterious alleles can reach high frequency in small populations because of random fluctuations in allele frequency. This may lead, over time, to reduced average fitness. In this sense, selection is more "effective" in larger populations. Recent studies have considered whether the different demographic histories across human populations have resulted in differences in the number, distribution, and severity of deleterious variants, leading to an animated debate. This article first seeks to clarify some terms of the debate by identifying differences in definitions and assumptions used in recent studies. We argue that variants of Morton, Crow, and Muller's "total mutational damage" provide the soundest and most practical basis for such comparisons. Using simulations, analytical calculations, and 1000 Genomes Project data, we provide an intuitive and quantitative explanation for the observed similarity in genetic load across populations. We show that recent demography has likely modulated the effect of selection and still affects it, but the net result of the accumulated differences is small. Direct observation of differential efficacy of selection for specific allele classes is nevertheless possible with contemporary data sets. By contrast, identifying average genome-wide differences in the efficacy of selection across populations will require many modeling assumptions and is unlikely to provide much biological insight about human populations.

  19. Strategies for effective feedback.

    PubMed

    Kritek, Patricia A

    2015-04-01

    Provision of regular feedback to trainees on clinical performance by supervising providers is increasingly recognized as an essential component of undergraduate and graduate health sciences education; however, many individuals have not been formally trained in this pedagogical skill. At the bedside or in the clinic, effective performance feedback can be accomplished by following four key steps. Begin by setting expectations that incorporate the trainee's personal goals and external objectives. Delineate how and when you will provide feedback to the learner. Next, directly observe the trainee's performance. This can be challenging while engaged on a busy clinical service, but a focus on discrete activities or interactions (e.g., family meeting, intravascular volume assessment using bedside ultrasound, or obtaining informed consent) is helpful. The third step is to plan and prioritize the feedback session. Feedback is most effective when given in a timely fashion and delivered in a safe environment. Limit the issues addressed because learners often disengage if confronted with too many deficiencies. Finally, when delivering feedback, begin by listening to the trainee's self-evaluation and then take a balanced approach. Describe in detail what the trainee does well and discuss opportunities for improvement with emphasis on specific, modifiable behaviors. The feedback loop is completed with a plan for follow-up reassessment. Through the use of these relatively simple practices, both the trainee and teacher can have a more productive learning experience.

  20. The Creative Stereotype Effect.

    PubMed

    Dumas, Denis; Dunbar, Kevin N

    2016-01-01

    Because of its fundamental relevance to scientific innovation, artistic expression, and human ingenuity, creativity has long been the subject of systematic psychological investigation. Concomitantly, the far-reaching effects of stereotypes on various cognitive and social processes have been widely researched. Bridging these two literatures, we show in a series of two studies that stereotypes related to creativity can both enhance and diminish individuals' performance on a divergent thinking task. Specifically, Study 1 demonstrated that participants asked to take on a stereotypically uninhibited perspective performed significantly better on a divergent thinking task than those participants who took on a stereotypically inhibited perspective, and a control group. Relatedly, Study 2 showed that the same effect is found within-subjects, with divergent thinking significantly improving when participants invoke an uninhibited stereotype. Moreover, we demonstrate the efficacy of Latent Semantic Analysis as an objective measure of the originality of ideas, and discuss implications of our findings for the nature of creativity. Namely, that creativity may not be best described as a stable individual trait, but as a malleable product of context and perspective.

  1. The Effective Equation Method

    NASA Astrophysics Data System (ADS)

    Kuksin, Sergei; Maiocchi, Alberto

    In this chapter we present a general method of constructing the effective equation which describes the behavior of small-amplitude solutions for a nonlinear PDE in finite volume, provided that the linear part of the equation is a hamiltonian system with a pure imaginary discrete spectrum. The effective equation is obtained by retaining only the resonant terms of the nonlinearity (which may be hamiltonian, or may be not); the assertion that it describes the limiting behavior of small-amplitude solutions is a rigorous mathematical theorem. In particular, the method applies to the three- and four-wave systems. We demonstrate that different possible types of energy transport are covered by this method, depending on whether the set of resonances splits into finite clusters (this happens, e.g. in case of the Charney-Hasegawa-Mima equation), or is connected (this happens, e.g. in the case of the NLS equation if the space-dimension is at least two). For equations of the first type the energy transition to high frequencies does not hold, while for equations of the second type it may take place. Our method applies to various weakly nonlinear wave systems, appearing in plasma, meteorology and oceanography.

  2. Anomalous spin Josephson effect

    NASA Astrophysics Data System (ADS)

    Wang, Mei-Juan; Wang, Jun; Hao, Lei; Liu, Jun-Feng

    2016-10-01

    We report a theoretical study on the spin Josephson effect arising from the exchange coupling of the two ferromagnets (Fs), which are deposited on a two-dimensional (2D) time-reversal-invariant topological insulator. An anomalous spin supercurrent Js z˜sin(α +α0) is found to flow in between the two Fs and the ground state of the system is not limited to the magnetically collinear configuration (α =n π ,n is an integer) but determined by a controllable angle α0, where α is the crossed angle between the two F magnetizations. The angle α0 is the dynamic phase of the electrons traveling in between the two Fs and can be controlled electrically by a gate voltage. This anomalous spin Josephson effect, similar to the conventional φ0 superconductor junction, originates from the definite electron chirality of the helical edge states in the 2D topological insulator. These results indicate that the magnetic coupling in a topological system is different from the usual one in conventional materials.

  3. The Creative Stereotype Effect

    PubMed Central

    Dumas, Denis; Dunbar, Kevin N.

    2016-01-01

    Because of its fundamental relevance to scientific innovation, artistic expression, and human ingenuity, creativity has long been the subject of systematic psychological investigation. Concomitantly, the far-reaching effects of stereotypes on various cognitive and social processes have been widely researched. Bridging these two literatures, we show in a series of two studies that stereotypes related to creativity can both enhance and diminish individuals’ performance on a divergent thinking task. Specifically, Study 1 demonstrated that participants asked to take on a stereotypically uninhibited perspective performed significantly better on a divergent thinking task than those participants who took on a stereotypically inhibited perspective, and a control group. Relatedly, Study 2 showed that the same effect is found within-subjects, with divergent thinking significantly improving when participants invoke an uninhibited stereotype. Moreover, we demonstrate the efficacy of Latent Semantic Analysis as an objective measure of the originality of ideas, and discuss implications of our findings for the nature of creativity. Namely, that creativity may not be best described as a stable individual trait, but as a malleable product of context and perspective. PMID:26863143

  4. JPL Test Effectiveness Analysis

    NASA Technical Reports Server (NTRS)

    Shreck, Stephanie; Sharratt, Stephen; Smith, Joseph F.; Strong, Edward

    2008-01-01

    1) The pilot study provided meaningful conclusions that are generally consistent with the earlier Test Effectiveness work done between 1992 and 1994: a) Analysis of pre-launch problem/failure reports is consistent with earlier work. b) Analysis of post-launch early mission anomaly reports indicates that there are more software issues in newer missions, and the no-test category for identification of post-launch failures is more significant than in the earlier analysis. 2) Future work includes understanding how differences in Missions effect these analyses: a) There are large variations in the number of problem reports and issues that are documented by the different Projects/Missions. b) Some missions do not have any reported environmental test anomalies, even though environmental tests were performed. 3) Each project/mission has different standards and conventions for filling out the PFR forms, the industry may wish to address this issue: a) Existing problem reporting forms are to document and track problems, failures, and issues (etc.) for the projects, to ensure high quality. b) Existing problem reporting forms are not intended for data mining.

  5. Antiferromagnetic Spin Seebeck Effect.

    PubMed

    Wu, Stephen M; Zhang, Wei; Kc, Amit; Borisov, Pavel; Pearson, John E; Jiang, J Samuel; Lederman, David; Hoffmann, Axel; Bhattacharya, Anand

    2016-03-04

    We report on the observation of the spin Seebeck effect in antiferromagnetic MnF_{2}. A device scale on-chip heater is deposited on a bilayer of MnF_{2} (110) (30  nm)/Pt (4 nm) grown by molecular beam epitaxy on a MgF_{2} (110) substrate. Using Pt as a spin detector layer, it is possible to measure the thermally generated spin current from MnF_{2} through the inverse spin Hall effect. The low temperature (2-80 K) and high magnetic field (up to 140 kOe) regime is explored. A clear spin-flop transition corresponding to the sudden rotation of antiferromagnetic spins out of the easy axis is observed in the spin Seebeck signal when large magnetic fields (>9  T) are applied parallel to the easy axis of the MnF_{2} thin film. When the magnetic field is applied perpendicular to the easy axis, the spin-flop transition is absent, as expected.

  6. Antiferromagnetic Spin Seebeck Effect

    NASA Astrophysics Data System (ADS)

    Wu, Stephen M.; Zhang, Wei; KC, Amit; Borisov, Pavel; Pearson, John E.; Jiang, J. Samuel; Lederman, David; Hoffmann, Axel; Bhattacharya, Anand

    2016-03-01

    We report on the observation of the spin Seebeck effect in antiferromagnetic MnF2 . A device scale on-chip heater is deposited on a bilayer of MnF2 (110) (30 nm )/Pt (4 nm) grown by molecular beam epitaxy on a MgF2 (110) substrate. Using Pt as a spin detector layer, it is possible to measure the thermally generated spin current from MnF2 through the inverse spin Hall effect. The low temperature (2-80 K) and high magnetic field (up to 140 kOe) regime is explored. A clear spin-flop transition corresponding to the sudden rotation of antiferromagnetic spins out of the easy axis is observed in the spin Seebeck signal when large magnetic fields (>9 T ) are applied parallel to the easy axis of the MnF2 thin film. When the magnetic field is applied perpendicular to the easy axis, the spin-flop transition is absent, as expected.

  7. Meditation: Process and effects.

    PubMed

    Sharma, Hari

    2015-01-01

    Meditation has become popular in many Western nations, especially the USA. An increasing body of research shows various health benefits associated with meditation and these findings have sparked interest in the field of medicine. The practice of meditation originated in the ancient Vedic times of India and is described in the ancient Vedic texts. Meditation is one of the modalities used in Ayurveda (Science of Life), the comprehensive, natural health care system that originated in the ancient Vedic times of India. The term "meditation" is now loosely used to refer to a large number of diverse techniques. According to Vedic science, the true purpose of meditation is to connect oneself to one's deep inner Self. Techniques which achieve that goal serve the true purpose of meditation. Neurological and physiological correlates of meditation have been investigated previously. This article describes the process of meditation at a more fundamental level and aims to shed light on the deeper underlying mechanism of the beneficial effects associated with meditation. Research on the effects of meditation is summarized.

  8. Meditation: Process and effects

    PubMed Central

    Sharma, Hari

    2015-01-01

    Meditation has become popular in many Western nations, especially the USA. An increasing body of research shows various health benefits associated with meditation and these findings have sparked interest in the field of medicine. The practice of meditation originated in the ancient Vedic times of India and is described in the ancient Vedic texts. Meditation is one of the modalities used in Ayurveda (Science of Life), the comprehensive, natural health care system that originated in the ancient Vedic times of India. The term “meditation” is now loosely used to refer to a large number of diverse techniques. According to Vedic science, the true purpose of meditation is to connect oneself to one's deep inner Self. Techniques which achieve that goal serve the true purpose of meditation. Neurological and physiological correlates of meditation have been investigated previously. This article describes the process of meditation at a more fundamental level and aims to shed light on the deeper underlying mechanism of the beneficial effects associated with meditation. Research on the effects of meditation is summarized. PMID:27313408

  9. Radiation effects in space.

    PubMed

    Fry, R J

    1986-01-01

    The radiation protection guidelines of the National Aeronautics and Space Administration (NASA) are under review by Scientific Committee 75 of the National Council Protection and Measurements. The re-evaluation of the current guidelines is necessary, first, because of the increase in information about radiation risks since 1970 when the original recommendations were made and second, the population at risk has changed. For example, women have joined the ranks of the astronauts. Two types of radiation, protons and heavy ions, are of particular concern in space. Unfortunately, there is less information about the effects on tissues and cancer by these radiations than by other radiations. The choice of Quality Factors (Q) for obtaining dose equivalents for these radiations, is an important aspect of the risk estimate for space travel. There are not sufficient data for the induction of late effects by either protons or by heavy ions. The current information suggests a RBE for the relative protons of about 1, whereas, a RBE of 20 for tumor induction by heavy ions, such as iron-56, appears appropriate. The recommendations for the dose equivalent career limits for skin and the lens of the eye have been reduced but the 30-day and annual limits have been raised.

  10. Ecotoxicological effects extrapolation models

    SciTech Connect

    Suter, G.W. II

    1996-09-01

    One of the central problems of ecological risk assessment is modeling the relationship between test endpoints (numerical summaries of the results of toxicity tests) and assessment endpoints (formal expressions of the properties of the environment that are to be protected). For example, one may wish to estimate the reduction in species richness of fishes in a stream reach exposed to an effluent and have only a fathead minnow 96 hr LC50 as an effects metric. The problem is to extrapolate from what is known (the fathead minnow LC50) to what matters to the decision maker, the loss of fish species. Models used for this purpose may be termed Effects Extrapolation Models (EEMs) or Activity-Activity Relationships (AARs), by analogy to Structure-Activity Relationships (SARs). These models have been previously reviewed in Ch. 7 and 9 of and by an OECD workshop. This paper updates those reviews and attempts to further clarify the issues involved in the development and use of EEMs. Although there is some overlap, this paper does not repeat those reviews and the reader is referred to the previous reviews for a more complete historical perspective, and for treatment of additional extrapolation issues.

  11. Acrolein health effects.

    PubMed

    Faroon, O; Roney, N; Taylor, J; Ashizawa, A; Lumpkin, M H; Plewak, D J

    2008-08-01

    Acrolein is a chemical used as an intermediate reactive aldehyde in chemical industry. It is used for synthesis of many organic substances, methionine production, and methyl chloride refrigerant. The general population is exposed to acrolein via smoking, second-hand smoke, exposure to wood and plastic smoke. Firefighters and population living or working in areas with heavy automotive traffic may expose to higher level of acrolein via inhalation of smoke or automotive exhaust. Degradation of acrolein in all environmental media occurs rapidly, therefore, environmental accumulation is not expected. Acrolein degrade in 6A days when applied to surface water, and it has not been found as a contaminant in municipal drinking water. Acrolein vapor may cause eye, nasal and respiratory tract irritations in low level exposure. A decrease in breathing rate was reported by volunteers acutely exposed to 0.3A ppm of acrolein. At similar level, mild nasal epithelial dysplasia, necrosis, and focal basal cell metaplasia have been observed in rats. The acrolein effects on gastrointestinal mucosa in the animals include epithelial hyperplasia, ulceration, and hemorrhage. The severity of the effects is dose dependent. Acrolein induces the respiratory, ocular, and gastrointestinal irritations by inducing the release of peptides in nerve terminals innervating these systems. Levels of acrolein between 22 and 249 ppm for 10 min induced a dose-related decrease in substance P (a short-chain polypeptide that functions as a neurotransmitter or neuromodulator).

  12. An effective Z'

    SciTech Connect

    Fox, Patrick J.; Liu, Jia; Tucker-Smith, David; Weiner, Neal

    2011-12-06

    We describe a method to couple Z' gauge bosons to the standard model (SM), without charging the SM fields under the U(1)', but instead through effective higher-dimension operators. This method allows complete control over the tree-level couplings of the Z' and does not require altering the structure of any of the SM couplings, nor does it contain anomalies or require introduction of fields in nonstandard SM representations. Moreover, such interactions arise from simple renormalizable extensions of the SM—the addition of vectorlike matter that mixes with SM fermions when the U(1)' is broken. We apply effective Z' models as explanations of various recent anomalies: the D0 same-sign dimuon asymmetry, the CDF W+di-jet excess and the CDF top forward-backward asymmetry. In the case of the W+di-jet excess we also discuss several complementary analyses that may shed light on the nature of the discrepancy. We consider the possibility of non-Abelian groups, and discuss implications for the phenomenology of dark matter as well.

  13. An effective Z'

    DOE PAGES

    Fox, Patrick J.; Liu, Jia; Tucker-Smith, David; ...

    2011-12-06

    We describe a method to couple Z' gauge bosons to the standard model (SM), without charging the SM fields under the U(1)', but instead through effective higher-dimension operators. This method allows complete control over the tree-level couplings of the Z' and does not require altering the structure of any of the SM couplings, nor does it contain anomalies or require introduction of fields in nonstandard SM representations. Moreover, such interactions arise from simple renormalizable extensions of the SM—the addition of vectorlike matter that mixes with SM fermions when the U(1)' is broken. We apply effective Z' models as explanations ofmore » various recent anomalies: the D0 same-sign dimuon asymmetry, the CDF W+di-jet excess and the CDF top forward-backward asymmetry. In the case of the W+di-jet excess we also discuss several complementary analyses that may shed light on the nature of the discrepancy. We consider the possibility of non-Abelian groups, and discuss implications for the phenomenology of dark matter as well.« less

  14. Antidepressant effect of Stillen.

    PubMed

    Jeong, Hyun-Ja; Kim, Jeong-Hwa; Kim, Na-Rae; Yoou, Myoung-schook; Nam, Sun-Young; Kim, Kyu-Youb; Choi, Youngjin; Jang, Jae-Bum; Kang, In-Cheol; Baek, Nam-In; Kim, Hyung-Min

    2015-06-01

    Stillen has been used to treat patients with gastric mucosal ulcers and has an anti-inflammatory effect. It is well-known that neuro-inflammatory reactions are related to depression. Here we evaluated the antidepressant-like effect of Stillen on mice subjected to the forced swimming test (FST). Stillen and eupatilin (a major component of Stillen) significantly decreased immobility times compared with the FST control group. In the Stillen-administered group, increased levels of 5-hydroxytryptamine (serotonin) and brain-derived neurotrophic factor protein were observed in the hippocampus. Nissl bodies also increased in the hippocampus neuronal cytoplasm of the Stillen-administered group. Stillen decreased levels of interleukin (IL)-1β, IL-6, and tumor necrosis factor-α (at the mRNA and protein levels) in the hippocampus and serum, compared with the control group. In addition, the mRNA expression of estrogen receptor-β increased after Stillen administration in the hippocampus. These findings suggest that Stillen should be viewed as a candidate antidepressant.

  15. Matthew Effects for Whom?

    PubMed Central

    Morgan, Paul L.; Farkas, George; Hibel, Jacob

    2015-01-01

    Which children are most at risk of experiencing a Matthew effect in reading? We investigated this question using population-based methodology. First, we identified children entering kindergarten on socio-demographic factors (i.e., gender, race/ethnicity, and socioeconomic status) well known to index the relative risks and resources available to them as beginning readers. Second, we fitted growth curve models to the kindergarten—3rd grade reading scores of these children as they participated in the Early Childhood Longitudinal Study–Kindergarten Class (ECLS-K) study. Third, we compared the children’s relative reading achievement (as measured in standard deviation units from the sample’s overall mean across the study’s time points) of those children most and least at risk for learning disabilities. We found that those population subgroups most at risk for learning disabilities fall further behind typical readers over time. By contrast, those least at risk for learning disabilities do not move further ahead. We conclude that a one-sided Matthew effect exists and, moreover, it exists for those children at greatest risk for learning disabilities. PMID:26339117

  16. Microwave field effect transistor

    NASA Technical Reports Server (NTRS)

    Huang, Ho-Chung (Inventor)

    1989-01-01

    Electrodes of a high power, microwave field effect transistor are substantially matched to external input and output networks. The field effect transistor includes a metal ground plane layer, a dielectric layer on the ground plane layer, a gallium arsenide active region on the dielectric layer, and substantially coplanar spaced source, gate, and drain electrodes having active segments covering the active region. The active segment of the gate electrode is located between edges of the active segments of the source and drain electrodes. The gate and drain electrodes include inactive pads remote from the active segments. The pads are connected directly to the input and output networks. The source electrode is connected to the ground plane layer. The space between the electrodes and the geometry of the electrodes extablish parasitic shunt capacitances and series inductances that provide substantial matches between the input network and the gate electrode and between the output network and the drain electrode. Many of the devices are connected in parallel and share a common active region, so that each pair of adjacent devices shares the same source electrodes and each pair of adjacent devices shares the same drain electrodes. The gate electrodes for the parallel devices are formed by a continuous stripe that extends between adjacent devices and is connected at different points to the common gate pad.

  17. Antiferromagnetic spin Seebeck effect.

    SciTech Connect

    Wu, Stephen M.; Zhang, Wei; KC, Amit; Borisov, Pavel; Pearson, John E.; Jiang, J. Samuel; Lederman, David; Hoffmann, Axel; Bhattacharya, Anand

    2016-03-03

    We report on the observation of the spin Seebeck effect in antiferromagnetic MnF2. A device scale on-chip heater is deposited on a bilayer of MnF2 (110) (30nm)/Pt (4 nm) grown by molecular beam epitaxy on a MgF2(110) substrate. Using Pt as a spin detector layer, it is possible to measure the thermally generated spin current from MnF2 through the inverse spin Hall effect. The low temperature (2–80 K) and high magnetic field (up to 140 kOe) regime is explored. A clear spin-flop transition corresponding to the sudden rotation of antiferromagnetic spins out of the easy axis is observed in the spin Seebeck signal when large magnetic fields (>9T) are applied parallel to the easy axis of the MnF2 thin film. When the magnetic field is applied perpendicular to the easy axis, the spin-flop transition is absent, as expected.

  18. Oblique effect in stereopsis?

    NASA Astrophysics Data System (ADS)

    Davis, Elizabeth T.; King, Robert A.; Anoskey, Alana M.

    1992-08-01

    Contrast thresholds are lower for detection of a vertical pattern than for an obliquely-oriented pattern. Is there an analogous oblique effect for the depth threshold of a stereoscopic luminance pattern? If so, why? Are the causes different from those for an oblique effect with monocular vision? To explore these issues, we used stereoscopic blurry bar (D6) luminance patterns with a peak spatial frequency of 2 or 4 cycles/degree (cpd) and either a vertical or an oblique orientation. We obtained psychometric functions for data obtained from a method of constant stimuli procedure, using 100 forced-choice trials for each datum. For each of three observers we estimated stereoacuity with a maximum-likelihood curve-fitting procedure. Subjects showed better stereoacuity for the vertical spatial patterns than for the oblique patterns. Some possible causes are that for oblique patterns (unlike vertical patterns) (1) the total vertical extent of the pattern is shrunk by a factor of sin((theta) ), where (theta) equals 90 degree(s) for vertical; (2) the pattern is 'stretched out' in the horizontal direction by a factor of csc((theta) ); (3) there are vertical as well as horizontal retinal disparities. Perhaps the resulting sparseness of horizontal disparity information or the potential vertical disparities in the oblique patterns reduce stereoacuity. To disentangle these causes, we used several different experimental conditions (e.g., elongation of oblique patterns) run in randomized blocks of trials. We will discuss these results and implications for stereopsis.

  19. Handbook of radiation effects

    SciTech Connect

    Holmes-Siedle, A. Univ. of West London ); Adams, L. . Radiation Effects and Analysis Techniques Unit)

    1993-01-01

    This handbook is intended to serve as a tool for designers of equipment and scientific instruments in cases where they are required to ensure the survival of the equipment in radiation environments. High-technology materials, especially semiconductors and optics, tend to degrade on exposure to radiation in many different ways. Intense high-energy radiation environments are found in nuclear reactors and accelerators, machines for radiation therapy, industrial sterilization, and space. Some engineers have to build equipment which will survive a nuclear explosion from a hostile source. Proper handling of a disaster with radioactive materials requires equipment which depends utterly on semiconductor microelectronics and imaging devices. Thus the technology of radiation-tolerant electronics is an instrument for good social spheres as diverse as disaster planning and the exploration of Mars. In order to design equipment for intense environments like those described above, then degradation from high-energy irradiation must be seen as a basic design parameter. The aim of this handbook is to assist the engineer or student in that thought; to make it possible to write intelligent specifications; to offer some understanding of the complex variety of effects which occur when high-technology components encounter high-energy radiation; and to go thoroughly into the balance of choices of how to alleviate the effects and hence achieve the design aims of the project. Separate abstracts were prepared for 15 chapters of this book.

  20. [Neuropsychic effects of dehydroepiandrosterone].

    PubMed

    Rigaud, A S; Pellerin, J

    2001-04-01

    Dehydroepiandrosterone (DHEA) and DHEA sulfate (DHEA-S) are secreted primarily by the adrenal glands. DHEA could also be a neuroactive steroidal hormone. Because basal levels of DHEA and DHEA-S in humans decrease significantly with age, these hormones have been assumed to be involved in the aging process and in a number of pathologies which develop with aging: immunosenescence, increased mortality, increased incidence of cancer, osteoporosis and cardiovascular diseases. However, its role is still unknown. In humans, cross sectional and longitudinal studies have shown that DHEA might be associated with global measures of well-being and functioning, but positive effects on measures of memory and attention could not be found. Studies investigating DHEA and DHEA-S levels in dementia have produced controversial results. Short-term experimental studies have not shown significant improvement in global measures of well-being and functioning in healthy subjects but have revealed preliminary evidence for mood enhancing and antidepressant effects of DHEA. There is no evidence that DHEA could induce addiction in human beings.

  1. Effects of Therapist's Nonverbal Communication on Rated Skill and Effectiveness.

    ERIC Educational Resources Information Center

    Sherer, Mark; Rogers, Ronald W.

    1980-01-01

    Nonverbal cues of immediacy significantly improved ratings of the therapist's interpersonal skills and effectiveness. A therapist's nonverbal behavior is a basis for interpretations of empathy, warmth, genuineness, and effectiveness. (Author)

  2. Basic optics of effect materials.

    PubMed

    Jones, Steven A

    2010-01-01

    Effect materials derive their color and effect primarily from thin-film interference. Effect materials have evolved over the decades from simple guanine crystals to the complex multilayer optical structures of today. The development of new complex effect materials requires an understanding of the optics of effect materials. Such an understanding would also benefit the cosmetic formulator as these new effect materials are introduced. The root of this understanding begins with basic optics. This paper covers the nature of light, interference of waves, thin-film interference, color from interference, and color travel.

  3. [Pharmacology of misoprostol (pharmacokinetic data, adverse effects and teratogenic effects)].

    PubMed

    Aubert, J; Bejan-Angoulvant, T; Jonville-Bera, A-P

    2014-02-01

    Misoprostol is a synthetic analogue of prostaglandin E1. It is used in gynaecology because of its properties of myometrium smooth muscle cells contraction and its effects on the cervix. Misoprostol oral bioavailability is low and several authors have assessed whether the administration by other routes increased its pharmacodynamic effects. This paper summarizes the pharmacokinetic studies after other routes of administration: vaginal, sublingual, buccal or rectal. It also provides an update on its adverse effects and teratogenic effects.

  4. Effect Sizes, Confidence Intervals, and Confidence Intervals for Effect Sizes

    ERIC Educational Resources Information Center

    Thompson, Bruce

    2007-01-01

    The present article provides a primer on (a) effect sizes, (b) confidence intervals, and (c) confidence intervals for effect sizes. Additionally, various admonitions for reformed statistical practice are presented. For example, a very important implication of the realization that there are dozens of effect size statistics is that "authors must…

  5. Action languages: Dimensions, effects

    NASA Technical Reports Server (NTRS)

    Hayes, Daniel G.; Streeter, Gordon

    1989-01-01

    Dimensions of action languages are discussed for communication between humans and machines, and the message handling capabilities of object oriented programming systems are examined. Design of action languages is seen to be very contextual. Economical and effective design will depend on features of situations, the tasks intended to be accomplished, and the nature of the devices themselves. Current object oriented systems turn out to have fairly simple and straightforward message handling facilities, which in themselves do little to buffer action or even in some cases to handle competing messages. Even so, it is possible to program a certain amount of discretion about how they react to messages. Such thoughtfulness and perhaps relative autonomy of program modules seems prerequisite to future systems to handle complex interactions in changing situations.

  6. Biological effects of minerals

    SciTech Connect

    Guthrie, G.D. Jr.

    1991-09-01

    In general, clay materials exhibit a range of biological activities, from apparently inactive or slightly active, such as hematite, to highly fibrogenic and carcinogenic, such as fibrous brucite (nemalite). The zeolites also exhibit such as range, with some mordenite being slightly active and erionite being highly active; however, erionite is the only zeolite that has been studied extensively. The diversity of mineral species holds great potential for probing these mechanisms, especially when mineralogical data are integrated with biological data. Unfortunately, many of the studies reporting data on the biological effects of clays and zeolites fail to report detailed mineralogical information; hence, it is difficult at present to interpret the biological activities of minerals in terms of their physical and chemical properties. Important mineralogical data that are only rarely considered in biological research include exact mineralogy of the specimen (i.e., identification and abundance of contaminants), physical and chemical properties of minerals, and surface properties of minerals. 141 refs., 1 fig., 8 tabs.

  7. Dynamic effects of combustion

    NASA Technical Reports Server (NTRS)

    Oppenheim, A. K.

    1982-01-01

    The dynamic effects of combustion are due to the evolution of exothermic energy and its deposition in the compressible medium where the process takes place. The paper examines the dynamics of combustion phenomena, including ignition, turbulent flame propagation (inflammation), explosion, and detonation, with emphasis on their exothermic characteristics. Ignition and explosion are treated as problems of nonlinear mechanics, and their dynamic behavior is described in terms of phase space models and cinematographic laser shear interferograms. The results of a numerical random vortex model of turbulent flame propagation are confirmed in a combustion tunnel experiment, where it was observed that a fresh mixture of burnt and unburnt gases can sustain combustion with a relatively small expenditure of overall mass flow, due to the increasing specific volume of burnt gases inside the flame front. An isentropic pressure wave is found to precede the accelerating flame in the process of detonation, and components of this presssure wave are shown to propagate at local sonic velocities.

  8. The hot chocolate effect

    SciTech Connect

    Crawford, Frank S.

    1982-05-01

    The "hot chocolate effect" was investigated quantitatively, using water. If a tall glass cylinder is filled nearly completely with water and tapped on the bottom with a softened mallet one can detect the lowest longitudinal mode of the water column, for which the height of the water column is one quarter wavelength. If the cylinder is rapidly filled with hot tap water containing dissolved air the pitch of that mode may descend by nearly three octaves during the first few seconds as the air comes out of solution and forms bubbles. Then the pitch gradually rises as the bubbles float to the top. A simple theoretical expression for the pitch ratio is derived and compared with experiment. The agreement is good to within the ten percent accuracy of the experiments.

  9. Radiation Effects in Graphite

    SciTech Connect

    Burchell, Timothy D

    2012-01-01

    The requirements for a solid moderator are reviewed and the reasons that graphite has become the solid moderator of choice discussed. The manufacture and properties of some currently available near-isotropic and isotropic grades are described. The major features of a graphite moderated reactors are briefly outlined. Displacement damage and the induced structural and dimensional changes in graphite are described. Recent characterization work on nano-carbons and oriented pyrolytic graphites that have shed new light on graphite defect structures are reviewed, and the effect of irradiation temperature on the defect structures is highlighted. Changes in the physical properties of nuclear graphite caused by neutron irradiation are reported. Finally, the importance of irradiation induced creep is presented, along with current models and their deficiencies.

  10. Biological effects of ozone

    SciTech Connect

    Lippmann, M. )

    1989-09-01

    Tropospheric ozone, a classic anthropogenic air pollutant, is going to remain a troublesome byproduct of contemporary civilization for many decades. We have known for some time that the hydrocarbons and nitrogen oxides from motor vehicles, together with actinic radiation, account for local and regional photochemistry leading to prolonged afternoon ozone peaks. We also now know that agricultural burning and intensive animal husbandry elevate regional and mesoscale concentrations of ozone and its precursors, and that remote background levels of ozone have been rising steadily throughout this century. The changes we will have to make in emission controls to appreciably reduce current tropospheric ozone levels will have profound effects on our transportation systems, consumer products, and lifestyles. As a society, we will have to make difficult choices about the levels of ozone-associated health, welfare, and natural system damage we will tolerate, or conversely, how much we are willing to pay for controls which can minimize the damage.

  11. 'Special effects' burn injuries.

    PubMed

    Peters, W

    1991-02-01

    Three patients are presented with significant flame burns, resulting from accidents occurring during 'special effects' situations in the entertainment industry. These occurred as a result of the spontaneous combustion of various materials, during events in live theatre (gun powder), a television commercial (artificial 'rocket fuel'), and a video presentation (magnesium oxide). All three patients sustained flash burns to the face and hands. One patient sustained a significant bilateral corneal injury, a gamekeeper's thumb, and a permanent continuous right-sided high frequency tinnitus, in addition to his burn injury. Photographic documentation of all three patients is presented. The total loss of time from work for all patients was 6 months. All these injuries were potentially preventable.

  12. Respiratory effects of sevoflurane.

    PubMed

    Doi, M; Ikeda, K

    1987-03-01

    The respiratory effects of sevoflurane were studied in seven patients and compared with values obtained in another seven patients anesthetized with halothane. Resting ventilation, resting PaCO2, and ventilatory response to CO2 were measured awake and at 1.1 and 1.4 MAC levels of both anesthetic agents. We found that with sevoflurane, tidal volume and the slopes of the CO2 response curves decreased and PaCO2 increased with increasing depth of anesthesia, as with other inhaled anesthetics. A compensatory increase in respiratory frequency was not enough to prevent a decrease in minute volume with increasing depth of anesthesia. At 1.1 MAC, sevoflurane produced almost the same degree of respiratory depression as halothane. At 1.4 MAC, sevoflurane produced more profound respiratory depression than halothane.

  13. Nonequilibrium effects in fragmentation

    NASA Astrophysics Data System (ADS)

    Chernomoretz, A.; Ison, M.; Ortiz, S.; Dorso, C. O.

    2001-08-01

    We study, using molecular dynamics techniques, how boundary conditions affect the process of fragmentation of finite, highly excited, Lennard-Jones systems. We analyze the behavior of the caloric curves (CC), the associated thermal response functions (TRF), and cluster mass distributions for constrained and unconstrained hot drops. It is shown that the resulting CC for the constrained case differ from the one in the unconstrained case, mainly in the presence of a ``vapor branch.'' This branch is absent in the free expanding case even at high energies. This effect is traced to the role played by the collective expansion motion. On the other hand, we found that the recently proposed characteristic features of a first order phase transition taking place in a finite isolated system, i.e., abnormally large kinetic energy fluctuations and a negative branch in the TRF, are present for the constrained (dilute) as well as the unconstrained case. The microscopic origin of this behavior is also analyzed.

  14. TOWARD MORE EFFECTIVE REGULATION

    SciTech Connect

    J. GRAF

    2000-06-01

    This paper proposes a model relationship between the operator engaged in a hazardous activity, the regulator of that activity, and the general public. The roles and responsibilities of each entity are described in a way that allows effective communication flow. The role of the regulator is developed using the steam boiler as an example of a hazard subject to regulation; however, the model applies to any regulated activity. In this model the safety analyst has the extremely important role of communicating sometimes difficult technical information to the regulator in a way that the regulator can provide credible assurance to the general public as to the adequacy of the control of the hazardous activity. The conclusion asserts that acceptance of the model, understanding of the roles and responsibilities and definition of who communicates what information to whom will mitigate frustration on the part of each of the three entities.

  15. Photoplastic effect on ice

    SciTech Connect

    Khusnatdinov, N.N.; Petrenko, V.F.

    1995-09-01

    The study of photoplastic effect (PPE) on ice is essential for both fundamental and applied reasons. It is important for an understanding of dislocation motion as well as the flow of glaciers in cold regions that occurs under intensive solar radiation. It was found that the illumination of ice with UV light ({lambda}<300 nm) leads to its irreversible hardening. A prolonged irradiation with a total light exposure of about 8{center_dot}10{sup {minus}5} J/cm{sup 2} at {lambda} = 260 nm can change the creep rate up to 60 percent. Even more pronounced PPE was found in HCl-doped ice with the concentration, n = 10{sup 18} cm{sup {minus}3}. It is suggested that PPE is caused by the excitation of ``autoionization`` reaction which was found responsible for the photoconductivity of ice.

  16. [Are antidepressants really effective?].

    PubMed

    Ammendola, S; Kornreich, C

    2015-01-01

    Antidepressants are widely used for a long time and it is estimated that about 10 % of the belgian population is taking some of them each year. However, there are important controversies about their real efficacy. We review successively arguments for and against their efficacy. On the one hand, meta-analysis have shown no big efficacy differences between antidepressants and placebo. On the other hand, those meta-analysis have been criticized for their methodology. Animal models show a real effect of antidepressants on the brain and clinical observations, such as an impact on suicide prevention, the possibility of induced manic switch, and an efficacy on anxiety disorders are in favour of a real efficacy. Given our current state of knowledge about them it seems appropriate to continue to use anti-depressants in the treatment of depressive patients.

  17. [New effect biomarkers].

    PubMed

    De Palma, G; Corradi, M; Mutti, A; Baccarelli, A; Pesatori, A; Bertazzi, P A

    2004-01-01

    The major research goals for researchers developing biomarkers of effect are the development and validation of biomarkers that permit the prediction of the risk of disease in individuals and groups. One important objective is to prevent human cancer. This article reviews the most recent analytical methodologies, validation studies and field trials together with auditing and quality assessment of the necessary data based on scientific grounds. Consideration is given to new developments in the relatively young field of toxicogenomics, possibly leading to the identification of early changes that may lead to both cancer and non-cancer end points. Although the creation and development of reliable databases integrating information from genomic and proteomic research programmes should offer a contribution to the prediction of risks and prevention of diseases related to chemical exposure, the most promising future application of these technologies lies in the molecular diagnosis of diseases whose nosography will probably be redefined.

  18. The hot chocolate effect

    NASA Astrophysics Data System (ADS)

    Crawford, Frank S.

    1982-05-01

    The ''hot chocolate effect'' was investigated quantitatively, using water. If a tall glass cylinder is filled nearly completely with water and tapped on the bottom with a softened mallet one can detect the lowest longitudinal mode of the water column, for which the height of the water column is one-quarter wavelength. If the cylinder is rapidly filled with hot tap water containing dissolved air the pitch of that mode may descend by nearly three octaves during the first few seconds as the air comes out of solution and forms bubbles. Then the pitch gradually rises as the bubbles float to the top. A simple theoretical expression for the pitch ratio is derived and compared with experiment. The agreement is good to within the 10% accuracy of the experiments.

  19. [Side effects of caffeine].

    PubMed

    Dworzański, Wojciech; Opielak, Grzegorz; Burdan, Franciszek

    2009-11-01

    Caffeine is one of the most commonly ingested alkaloids worldwide. It is present in coffee, tea, soft and energy drinks, chocolate, etc. Currently published data has been stressed that the metyloxantine consumption increases the risk of coronary heart disease, arterial hypertension, arterial stiffness, and an elevation of cholesterol and homocysteine plasma concentration. The acute high consumption may also modulate insulin sensitivity and glucose blood level. However, the long-term consumption reduces the incidence of the type 2 diabetes mellitus. When administered in high doses the substance may cause various side effects, related to abnormal stimulation of the central nervous system, decrease tonus of the lower esophageal sphincter, as well as increase risk of miscarriage and intrauterine growth retardation. The final manifestation of side reactions is dependent on the genotype, especially polymorphisms of genes associated with caffeine metabolism, i.e., cytochrome P450-CYP1A2 and catechol-O-methyltransferase (COMT).

  20. Remarks on Effect Algebras

    NASA Astrophysics Data System (ADS)

    Majewski, Władysław A.; Tylec, Tomasz I.

    2010-12-01

    Erik M. Alfsen and Frederic W. Shultz had recently developed the characterisation of state spaces of operator algebras. It established full equivalence (in the mathematical sense) between the Heisenberg and the Schrödinger picture, i.e. given a physical system we are able to construct its state space out of its observables as well as to construct algebra of observables from its state space. As an underlying mathematical structure they used the theory of duality of ordered linear spaces and obtained results are valid for various types of operator algebras (namely C *, von Neumann, JB and JBW algebras). Here, we show that the language they developed also admits a representation of an effect algebra.