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Sample records for exchange bias effect

  1. Exchange bias training effect in coupled all ferromagnetic bilayer structures.

    Science.gov (United States)

    Binek, Ch; Polisetty, S; He, Xi; Berger, A

    2006-02-17

    Exchange coupled bilayers of soft and hard ferromagnetic thin films show remarkable analogies to conventional antiferromagnetic/ferromagnetic exchange bias heterostructures. Not only do all these ferromagnetic bilayers exhibit a tunable exchange bias effect, they also show a distinct training behavior upon cycling the soft layer through consecutive hysteresis loops. In contrast with conventional exchange bias systems, such all ferromagnetic bilayer structures allow the observation of training induced changes in the bias-setting hardmagnetic layer by means of simple magnetometry. Our experiments show unambiguously that the exchange bias training effect is driven by deviations from equilibrium in the pinning layer. A comparison of our experimental data with predictions from a theory based upon triggered relaxation phenomena shows excellent agreement.

  2. Interfacial spin cluster effects in exchange bias systems

    Energy Technology Data Exchange (ETDEWEB)

    Carpenter, R., E-mail: rc548@york.ac.uk; Vallejo-Fernandez, G.; O' Grady, K. [Department of Physics, The University of York, York YO10 5DD (United Kingdom)

    2014-05-07

    In this work, the effect of exchange bias on the hysteresis loop of CoFe is observed. The evolution of the coercivities and the shift of the hysteresis loop during the annealing process has been measured for films deposited on NiCr and Cu seed layers. Through comparison of the as deposited and field annealed loops, it is clear that for an exchange biased material, the two coercivities are due to different reversal processes. This behaviour is attributed to spin clusters at the ferromagnet/antiferromagnet interface, which behave in a similar manner to a fine particle system.

  3. Antiferromagnetic exchange spring as the reason of exchange bias training effect

    Science.gov (United States)

    Dobrynin, A. N.; Maccherozzi, F.; Dhesi, S. S.; Fan, R.; Bencok, P.; Steadman, P.

    2014-07-01

    We observe recovery of the exchange bias training effect in a Co/CoO bilayer after warming the sample up to the blocking temperature and cooling it back to a low measuring temperature in zero magnetic field. Variation of the magnitude of X-ray magnetic linear dichroism in the sample for the system in the high unidirectional anisotropy state (after field cooling) and in the low unidirectional anisotropy state (after training) suggests rearrangement of antiferromagnetic structure during the initial field cycling in exchange biased state. Our results suggest formation of an antiferromagnetic exchange spring at the frustrated ferromagnetic-antiferromagnetic interface being the reason of the training effect.

  4. Exchange Bias Effects in Iron Oxide-Based Nanoparticle Systems

    Science.gov (United States)

    Phan, Manh-Huong; Alonso, Javier; Khurshid, Hafsa; Lampen-Kelley, Paula; Chandra, Sayan; Stojak Repa, Kristen; Nemati, Zohreh; Das, Raja; Iglesias, Óscar; Srikanth, Hariharan

    2016-01-01

    The exploration of exchange bias (EB) on the nanoscale provides a novel approach to improving the anisotropic properties of magnetic nanoparticles for prospective applications in nanospintronics and nanomedicine. However, the physical origin of EB is not fully understood. Recent advances in chemical synthesis provide a unique opportunity to explore EB in a variety of iron oxide-based nanostructures ranging from core/shell to hollow and hybrid composite nanoparticles. Experimental and atomistic Monte Carlo studies have shed light on the roles of interface and surface spins in these nanosystems. This review paper aims to provide a thorough understanding of the EB and related phenomena in iron oxide-based nanoparticle systems, knowledge of which is essential to tune the anisotropic magnetic properties of exchange-coupled nanoparticle systems for potential applications. PMID:28335349

  5. Exchange bias effect in Ti doped nanocrystalline SrFeO3-δ

    Directory of Open Access Journals (Sweden)

    A. Sendil Kumar

    2014-08-01

    Full Text Available Materials of Ti doped nanocrystalline SrFeO3-δ were synthesized through solid state reaction. Detailed magnetization measurements were carried out in zero field cooled (ZFC and field cooled (FC conditions. Compounds of SrFe1-xTixO3-δ (x = 0.1 to 0.3 are found to be spin glass and parent compound is a helical antiferromagnet. Non magnetic Ti4+ reduces the strength of exchange interactions and the curvature of hysteresis is changed towards concave nature. Exchange bias is observed below the peak temperature (irreversibility in magnetization (TIrr in ZFC-FC of SrFe1-xTixO3-δ (x = 0 to 0.3. The coercivity and exchange bias field values are found to be decreases with increase in temperature. Observed exchange bias effect is attributed to competition between antiferromagnetic superexchange and ferromagnetic double exchange interactions.

  6. Exchange bias effect in spin glass CoCr{sub 2}O{sub 4} nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Changming; Tian, Zhaoming; Wang, Liguang; Yuan, Songliu, E-mail: yuansl@hust.edu.cn

    2015-11-01

    CoCr{sub 2}O{sub 4} nanoparticles are about 5.4 nm in diameter synthesized by a hydrothermal technique. Magnetization measurements reveal that the nanoparticles exhibit a spin glass behavior below glass transition temperature. Signature of memory effect is clear in reheating curve where the step-like shape increasing with the increase of temperature is recovered after cooling process. Magnetic relaxation is performed to prove memory effect. Ageing effect is also detected in CoCr{sub 2}O{sub 4} nanoparticles to verify the spin glass behavior. As temperature decreases to 5 K, which is far below the glass transition temperature, exchange bias effect can be observed clearly accompanied with a shift in field-cooled hysteresis loop. As particle size decreases to 5.4 nm, spin glass behavior appears due to the increased spin disorder effect. The spin glass phase providing a pinning force from some frozen spins to the rotatable spins gives the key to explain the exchange bias effects. - Highlights: • Existence of spin glass phase is verified in CoCr{sub 2}O{sub 4} nanoparticles. • Exchange bias effect with a shift in field-cooled loop is observed at 5 K. • It is proved that exchange bias effect is originated from the spin glass phase.

  7. Bridging exchange bias effect in NiO and Ni(core)@NiO(shell) nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Rinaldi-Montes, Natalia, E-mail: nataliarin@gmail.com [Departamento de Física, Universidad de Oviedo, E-33007 Oviedo (Spain); Gorria, Pedro [Departamento de Física & IUTA, EPI, Universidad de Oviedo, E-33203 Gijón (Spain); Martínez-Blanco, David [Servicios Científico-Técnicos, Universidad de Oviedo, E-33006 Oviedo (Spain); Fuertes, Antonio B. [Instituto Nacional del Carbón, CSIC, E-33080 Oviedo (Spain); Fernández Barquín, Luis [CITIMAC, Facultad de Ciencias, Universidad de Cantabria, E-39005 Santander (Spain); Puente-Orench, Inés [Instituto de Ciencia de Materiales de Aragón, CSIC-Universidad de Zaragoza and Institut Laue-Langevin, BP 156, F-38042 Grenoble Cedex 9 (France); Blanco, Jesús A. [Departamento de Física, Universidad de Oviedo, E-33007 Oviedo (Spain)

    2016-02-15

    Among all bi-magnetic core(transition metal)@shell(transition metal oxide) nanoparticles (NPs), Ni@NiO ones show an onset temperature for the exchange bias (EB) effect far below the Néel temperature of bulk antiferromagnetic NiO. In this framework, the role played by the magnetism of NiO at the nanoscale is investigated by comparing the microstructure and magnetic properties of NiO and Ni@NiO NPs. With the aim of bridging the two systems, the diameter of the NiO NPs (~4 nm) is chosen to be comparable to the shell thickness of Ni@NiO ones (~2 nm). The EB effect in Ni@NiO NPs is attributed to the exchange coupling between the core and the shell, with an interfacial exchange energy of ΔE~0.06 erg cm{sup −2}, thus comparable to previous reports on Ni/NiO interfaces both in thin film and NP morphologies. In contrast, the EB detected in NiO NPs is explained in a picture where uncompensated spins located on a magnetically disordered surface shell are exchange coupled to the antiferromagnetic core. In all the studied NPs, the variation of the EB field as a function of temperature is described according to a negative exponential law with a similar decay constant, yielding a vanishing EB effect around T~40–50 K. In addition, the onset temperature for the EB effect in both NiO and Ni@NiO NPs seems to follow a universal dependence with the NiO crystallite size. - Highlights: • Comparison of the exchange bias effect in NiO and Ni(core)@NiO(shell) nanoparticles. • Universal temperature dependence of the exchange bias effect. • Suggested similar physical origin of the effect in both systems. • Size and crystallinity of the NiO shell hold the key for exchange bias properties.

  8. Disclosure of double exchange bias effect in chromium (III) oxide nanoparticles

    Czech Academy of Sciences Publication Activity Database

    Rinaldi-Montes, N.; Gorria, P.; Fuertes, A.B.; Martinez-Blanco, D.; Olivi, L.; Puente-Orench, I.; Alonso, J.M.; Phan, M.-H.; Skrikanth, H.; Martí, Xavier; Blanco, J.A.

    2017-01-01

    Roč. 53, č. 1 (2017), s. 1-4, č. článku 2300204. ISSN 0018-9464 R&D Projects: GA ČR GB14-37427G Institutional support: RVO:68378271 Keywords : antiferromagnetism * exchange bias (EB) * magnetic nanoparticles * magnetoelectric effect Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.243, year: 2016

  9. Exchange-biased planar Hall effect sensor optimized for biosensor applications

    DEFF Research Database (Denmark)

    Damsgaard, Christian Danvad; Freitas, S.C.; Freitas, P.P.

    2008-01-01

    This article presents experimental investigations of exchange-biased Permalloy planar Hall effect sensor crosses with a fixed active area of w x w = 40 x 40 mu m(2) and Permalloy thicknesses of t = 20, 30, and 50 nm. It is shown that a single domain model describes the system well...

  10. Size-dependent effects in exchange-biased planar Hall effect sensor crosses

    DEFF Research Database (Denmark)

    Donolato, Marco; Dalslet, Bjarke Thomas; Damsgaard, Christian Danvad

    2011-01-01

    Exchange-biased planar Hall effect magnetic field sensor crosses with arm width w have been studied as function of w. For large values of w, the magnetic behavior is hysteresis-free and follows the single domain Stoner-Wohlfarth model. When w is decreased, hysteresis is observed in the sensor...... by an increasing magnetic shape anisotropy of the arms of the cross. We propose a simple analytical model that captures the essential physics of the observations and parameterizes the effects of the cross-shape on the central part of the cross. (C) 2011 American Institute of Physics. [doi:10.1063/1.3561364]...

  11. Electric control of exchange bias training.

    Science.gov (United States)

    Echtenkamp, W; Binek, Ch

    2013-11-01

    Voltage-controlled exchange bias training and tunability are introduced. Isothermal voltage pulses are used to reverse the antiferromagnetic order parameter of magnetoelectric Cr(2)O(3), and thus continuously tune the exchange bias of an adjacent CoPd film. Voltage-controlled exchange bias training is initialized by tuning the antiferromagnetic interface into a nonequilibrium state incommensurate with the underlying bulk. Interpretation of these hitherto unreported effects contributes to new understanding in electrically controlled magnetism.

  12. Observation of an atomic exchange bias effect in DyCo4 film

    Science.gov (United States)

    Chen, Kai; Lott, Dieter; Radu, Florin; Choueikani, Fadi; Otero, Edwige; Ohresser, Philippe

    2015-12-01

    The fundamental important and technologically widely employed exchange bias effect occurs in general in bilayers of magnetic thin films consisting of antiferromagnetic and ferromagnetic layers where the hard magnetization behavior of an antiferromagnetic thin film causes a shift in the magnetization curve of a soft ferromagnetic film. The minimization of the single magnetic grain size to increase the storage density and the subsequent demand for magnetic materials with very high magnetic anisotropy requires a system with high HEB. Here we report an extremely high HEB of 4 Tesla observed in a single amorphous DyCo4 film close to room temperature. The origin of the exchange bias can be associated with the variation of the magnetic behavior from the surface towards the bulk part of the film revealed by X-ray absorption spectroscopy and X-ray magnetic circular dichroism techniques utilizing the bulk sensitive transmission and the surface sensitive total electron yield modes. The competition between the atomic exchange coupling in the single film and the Zeeman interaction lead to an intrinsic exchanged coupled system and the so far highest exchange bias effect HEB = 4 Tesla reported in a single film, which is accommodated by a partial domain wall formation.

  13. Suppression of exchange bias effect in maghemite nanoparticles functionalized with H{sub 2}Y

    Energy Technology Data Exchange (ETDEWEB)

    Guivar, Juan A. Ramos, E-mail: juan.ramos5@unmsm.edu.pe [Faculty of Physical Sciences, National University of San Marcos, P. O. Box 14-0149, Lima, 14 Peru (Peru); Morales, M.A. [Departamento de Física Teórica e Experimental, UFRN, Natal, RN, 59078-970 Brazil (Brazil); Litterst, F. Jochen [Institut für Physik der Kondensierten Materie, Technische Universität Braunschweig, Braunschweig, 38110 Germany (Germany)

    2016-12-15

    The structural, vibrational, morphological and magnetic properties of maghemite (γ-Fe{sub 2}O{sub 3}) nanoparticles functionalized with polar molecules EDTA(or H{sub 4}Y) and H{sub 2}Y are reported. The samples were functionalized before and after total synthesis of γ-Fe{sub 2}O{sub 3} nanoparticles. The molecules are anchored on the monodentate mode on the nanoparticles surface. Transmission electron microscopy (TEM) revealed the formation of maghemite nanoparticles with small diameter of 4 nm for the sample functionalized upon synthesis and 7.6 and 6.9 nm for the samples functionalized with EDTA and H{sub 2}Y after the formation of nanoparticles. Exchange bias phenomena were observed in some of the samples functionalized with EDTA at temperatures below 70 K. The presence of the bias effect was discussed in terms of the formation of a thin layer of a secondary phase like lepidocrocite, and the absence of this effect was explained in terms of the chemisorption of carboxylic groups from EDTA which suppressed the canting. Studies of Mössbauer spectroscopy as a function of temperature showed slow relaxation effects and allowed discussion of the secondary phase. In the M–T curves a maximum around 116 K was associated with this secondary phase also in agreement with the Mössbauer studies. The dynamic properties were studied by AC susceptibility, the out of phase signal revealed a spin glass like regime below 36.5 K. - Highlights: • Coprecipitation in alkaline medium was used for the synthesis of EDTA functionalized small maghemite nanoparticles. • Exchange bias effect was observed due to a thin layer of lepidocrocite like second phase. • The sample coprecipitated in a weak base did not show exchange bias effect. • The bias effect is discussed in terms of suppression of canting due to chemisorption of carboxylic groups from EDTA.

  14. Observation of an atomic exchange bias effect in DyCo4 film

    OpenAIRE

    Chen, Kai; Lott, Dieter; Radu, Florin; Choueikani, Fadi; Otero, Edwige; Ohresser, Philippe

    2015-01-01

    The fundamental important and technologically widely employed exchange bias effect occurs in general in bilayers of magnetic thin films consisting of antiferromagnetic and ferromagnetic layers where the hard magnetization behavior of an antiferromagnetic thin film causes a shift in the magnetization curve of a soft ferromagnetic film. The minimization of the single magnetic grain size to increase the storage density and the subsequent demand for magnetic materials with very high magnetic anis...

  15. Temperature evolution of nickel sulphide phases from thiourea complex and their exchange bias effect

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Nitesh [Chemistry and Physics of Materials Unit and International Centre for Materials Science, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore-560 064 (India); Raman, N. [Department of Chemistry, VHNSN College, Virudhunagar-626 001 (India); Sundaresan, A., E-mail: sundaresan@jncasr.ac.in [Chemistry and Physics of Materials Unit and International Centre for Materials Science, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore-560 064 (India)

    2013-12-15

    Considering the very complex phase diagram of nickel sulphide, it is quite challenging to stabilize pure phases from a single precursor. Here, we obtain nanoparticles of various phases of nickel sulphide by decomposing nickel–thiourea complex at different temperatures. The first phase in the evolution is the one with the maximum sulphur content, namely, NiS{sub 2} nanoparticles obtained at 400 °C. As the temperature is increased, nanoparticles of phases with lesser sulphur content, NiS (600 °C) and Ni{sub 3}S{sub 2} (800 °C) are formed. NiS{sub 2} nanoparticles exhibit weak ferromagnetic transition at 30 K and show a large exchange bias at 2 K. NiS nanoparticles are antiferromagnetic and show relatively smaller exchange bias effect. On the other hand, Ni{sub 3}S{sub 2} nanoparticles exhibit very weak temperature dependent magnetization. Electrical measurements show that both NiS{sub 2} and NiS are semiconductors whereas Ni{sub 3}S{sub 2} is a metal. - Graphical abstract: Pure phases of NiS{sub 2}, NiS and Ni{sub 3}S{sub 2} have been obtained by thermal decomposition of nickel–thiourea complex wherein, NiS{sub 2} nanoparticles exhibit remarkable exchange bias effect at 2 K. - Highlights: • NiS{sub 2}, NiS and Ni{sub 3}S{sub 2} nanoparticles are obtained by thermal decomposition of nickel–thiourea complex at different temperatures. • As the temperature is increased, nickel sulphide phase with lesser sulphur content is obtained. • NiS{sub 2} nanoparticles show good exchange bias property which can be explained by antiferromagnetic core and ferromagnetic shell model. • NiS{sub 2} and NiS are semiconducting while Ni{sub 3}S{sub 2} shows metallic behavior.

  16. Pseudo exchange bias due to rotational anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Ehrmann, A., E-mail: andrea.ehrmann@fh-bielefeld.de [Faculty of Engineering and Mathematics, Bielefeld University of Applied Sciences, 33619 Bielefeld (Germany); Komraus, S.; Blachowicz, T.; Domino, K. [Institute of Physics – Center for Science and Education, Silesian University of Technology, 44-100 Gliwice (Poland); Nees, M.K.; Jakobs, P.J.; Leiste, H. [Karlsruhe Nano Micro Facility (KNMF), Karlsruhe Institute of Technology (KIT), 76344 Eggenstein-Leopoldshafen (Germany); Mathes, M.; Schaarschmidt, M. [ACCESS e. V., 57072 Aachen (Germany)

    2016-08-15

    Ferromagnetic nanostructure arrays with particle dimensions between 160 nm and 400 nm were created by electron-beam lithography. The permalloy structures consist of rectangular-shaped walls around a square open space. While measuring their magnetic properties using the Magneto-Optical Kerr Effect (MOKE), in some angular regions an exchange bias (EB) seemed to appear. This paper gives an overview of possible reasons for this “pseudo exchange bias” and shows experimentally and by means of micromagnetic simulations that this effect can be attributed to unintentionally measuring minor loops. - Highlights: • Pseudo exchange bias can be found in square Py nanorings of different dimensions. • Pseudo exchange bias stems from unintentionally measuring minor loops. • New approach in explaining “real” exchange bias effect in coupled FM/AFM systems. • Theoretical base to explain other measurements of a rotational anisotropy.

  17. Phase transformation and exchange bias effects in mechanically alloyed Fe/magnetite powders

    Energy Technology Data Exchange (ETDEWEB)

    Crisan, O., E-mail: ocrisan@yahoo.com [National Institute for Materials Physics, P.O. Box MG-7, 077125 Bucharest-Magurele (Romania); Crisan, A.D. [National Institute for Materials Physics, P.O. Box MG-7, 077125 Bucharest-Magurele (Romania)

    2011-06-09

    Highlights: > Phase evolution in Fe/Fe{sub 3}O{sub 4} nanopowder monitored by synchrotron X-ray diffraction. > Fe/Fe{sub 3}O{sub 4} nanopowder undergo an incomplete redox reaction with formation of FeO. > FeO decomposes gradually into initial constituents at T up to 500 deg. C. > At higher T the redox reaction is reversible, at 900 deg. C only FeO is observed. > For the first time a strong exchange bias effect, related to FeO content, is observed. - Abstract: Nanostructured powders processed by ball milling of a mixture of Fe and Fe{sub 3}O{sub 4} at room temperature are shown to undergo an incomplete redox reaction with formation of FeO during the milling process. This reaction is favored by the high energy introduced during the mechano-alloying process. Concurrent effects of milling such as grain refinement down to the nanometre scale lead at the end of the milling processes to a mixed multiphase powder of nanograins, with Fe and Fe oxide grains inter-dispersed. We show that in the as-milled Fe/Fe{sub 3}O{sub 4} powder, during milling process, wuestite (FeO) is formed as a consequence of the redox reaction. Moreover, with increasing temperature, the system undergoes an inverse phase transformation towards the initial Fe and Fe{sub 3}O{sub 4} phases until about 450 deg. C. Above this temperature the reduction reaction Fe + Fe{sub 3}O{sub 4} = 4FeO is reinitiated, resulting in sharp decrease of Fe and Fe{sub 3}O{sub 4} content from about 550 deg. C and almost complete disappearance of these phases at about 900 deg. C. This transformation was investigated via an energy-dispersive in situ X-ray diffraction experiment using the synchrotron radiation. This study allows direct collection of X-ray patterns after few minutes exposure, at selected temperatures, ranging between 20 deg. C and 1000 deg. C. The structural and magnetic characterizations of the nanograin powders, as-milled and annealed at several temperatures, are studied using XRD, SEM and magnetic measurements

  18. Temperature effects in exchange-biased planar Hall sensors for bioapplications

    DEFF Research Database (Denmark)

    Damsgaard, Christian Danvad; Dalslet, Bjarke Thomas; Freitas, S.C.

    2009-01-01

    The temperature dependence of exchange biased planar Hall effect sensors is investigated between T = −10 and 70 °C. It is shown that a single domain model describes the system well and that the temperature coefficient of the low-field sensitivity at T = 25 °C is 0.32%/°C. A procedure...... for temperature correction by use of a reference sensor is demonstrated. Consequences for magnetic biosensing are exemplified with calculations on M-280 Dynabeads®....

  19. The effects of exchange bias on Fe-Co/MgO magnetic nanoparticles with core/shell morphology

    Energy Technology Data Exchange (ETDEWEB)

    Martinez-Boubeta, C; Balcells, Ll; MartInez, B [Instituto de Ciencia de Materiales de Barcelona (ICMAB-CSIC), Campus UAB, 08193 Bellaterra (Spain); Monty, C, E-mail: ben.martinez@icmab.e [CNRS/Procedes, Materiaux et Energie Solaire (PROMES), 66120 Font Romeu (France)

    2010-01-20

    The effects of exchange bias on core/shell structured nanoparticles are analyzed. Nanoparticles are integrated with high moment Fe-Co crystallites covered epitaxially with MgO shells. It is observed that the coercive field H{sub C}(FeCo)>H{sub C}(Co)>H{sub C}(Fe); however, the exchange bias field H{sub E} of the Co sample is higher than that of the FeCo one, while H{sub E} = 0 for the Fe sample. It is suggested that the exchange bias is induced by the formation of a (Co, Mg)O solid solution. In fact, we show that it is possible to modify the exchange bias properties by manipulating the level of Mg dusting at the interface, as recently reported for thin films.

  20. Manipulation of perpendicular exchange bias effect in [Co/Ni]N/(Cu, Ta/TbCo multilayer structures

    Directory of Open Access Journals (Sweden)

    Minghong Tang

    2015-08-01

    Full Text Available With the demand for increasing storage density in spintronic applications, extensive work has been devoted to searching for perpendicular magnetic material systems with strong exchange bias effect. In this study we have investigated the exchange bias effect in perpendicular magnetized heterostructures of [Co/Ni]N/(Cu, Ta/TbCo. An interlayer of 0.8 nm Cu is capable of achieving separate magnetization switching, showing a quite large exchange bias field over 2.9 kOe. With increasing the interlayer thickness, both the Co/Ni bias field and TbCo switching field decrease much more rapidly for the samples with a Ta interlayer as compared to the Cu case, due to the better coverage ability of the amorphous nature. The influence of layer thickness and composition of the FM and FI layers has also been investigated and the variation tendencies are well interpreted.

  1. Effect of thermal cycle on the interfacial antiferromagnetic spin configuration and exchange bias in Ni-Mn-Sb alloy

    Directory of Open Access Journals (Sweden)

    R. L. Wang

    2012-09-01

    Full Text Available Effect of thermal cycle on the interfacial antiferromagnetic (AFM spin configuration and exchange bias in Ni50Mn36Sb14 alloy has been investigated. The results indicate thermal cycle can induce further martensitic transition from part of arrested FM phase to AFM phase, leading to the reconstruction of interfacial antiferromagnetic spin configuration. The shape of hysteresis loops at 5 K after cooling back can be tuned from a single-shifted loop to a nearly symmetric double-shifted loop gradually accompanied with exchange bias field increasing to peak value and then decreasing. The evolutions can be illustrated intuitively by a simple AFM bidomain model.

  2. Antisite disorder induced spin glass and exchange bias effect in Nd2NiMnO6 epitaxial thin film

    Science.gov (United States)

    Singh, Amit Kumar; Chauhan, Samta; Chandra, Ramesh

    2017-03-01

    We report the observation of the exchange bias effect and spin glass behaviour at low temperature in a ferromagnetic Nd2NiMnO6 epitaxial thin film. Along with the ferromagnetic transition at ˜194 K, an additional transition is observed at lower temperature (˜55 K) as seen from M-T curves of the sample. A shift in the ac susceptibility peak with frequency has been observed at low temperature, which is a signature of a glassy phase within the sample. The detailed investigation of the memory effect and time dependent magnetic relaxation measurements reveals the presence of a spin glass phase in the Nd2NiMnO6 thin film. The exchange bias effect observed at low temperature in the sample has been associated with an antisite disorder induced spin glass phase, which results in a ferromagnetic/spin glass interface at low temperature. The exchange bias behaviour has been further confirmed by performing cooling field and temperature dependence of exchange bias along with training effect measurements.

  3. Reversible and irreversible temperature-induced changes in exchange-biased planar Hall effect bridge (PHEB) magnetic field sensors

    DEFF Research Database (Denmark)

    Rizzi, G.; Lundtoft, N.C.; Østerberg, F.W.

    2012-01-01

    We investigate the changes of planar Hall effect bridge magnetic field sensors upon exposure to temperatures between 25° C and 90°C. From analyses of the sensor response vs. magnetic fields we extract the exchange bias field Hex, the uniaxial anisotropy field HK and the anisotropic...

  4. Observation of pure inverse spin Hall effect in ferromagnetic metals via ferromagnetic/antiferromagnetic exchange-bias structures

    Science.gov (United States)

    Wu, H.; Wan, C. H.; Yuan, Z. H.; Zhang, X.; Jiang, J.; Zhang, Q. T.; Wen, Z. C.; Han, X. F.

    2015-08-01

    We report that the spin current generated by the spin Seebeck effect (SSE) in yttrium iron garnet (YIG) can be detected by a ferromagnetic metal (NiFe). By using the ferromagnetic/antiferromagnetic (FM/AFM) exchange bias structure (NiFe/IrMn), the inverse spin Hall effect (ISHE) and planar Nernst effect (PNE) of NiFe can be unambiguously separated, allowing us to observe a pure ISHE signal. After eliminating the in-plane temperature gradient in NiFe, we can even observe a pure ISHE signal without PNE from NiFe itself. It is worth noting that a large spin Hall angle (0.098) of NiFe is obtained, which is comparable with Pt. This work provides a kind of FM/AFM exchange bias structure to detect the spin current by charge signals, and highlights that ISHE in ferromagnetic metals can be used in spintronic research and applications.

  5. Inverse spin Hall and spin rectification effects in NiFe/FeMn exchange-biased thin films

    Science.gov (United States)

    Garcia, W. J. S.; Seeger, R. L.; da Silva, R. B.; Harres, A.

    2017-11-01

    Materials presenting high spin-orbit coupling are able to convert spin currents in charge currents. The phenomenon, known as inverse spin Hall effect, promises to revolutionize spintronic technology enabling the electrical detection of spin currents. It has been observed in a variety of systems, usually non-magnetic metals. We study the voltage emerging in exchange biased Ta/NiFe/FeMn/Ta thin films near the ferromagnetic resonance. Measured signals are related to both inverse spin Hall and spin rectification effects, and two distinct protocols were employed to separate their contributions.The curve shift due to the exchange bias effect may enable high frequency applications without an external applied magnetic field.

  6. Dipole-induced exchange bias.

    Science.gov (United States)

    Torres, Felipe; Morales, Rafael; Schuller, Ivan K; Kiwi, Miguel

    2017-11-09

    The discovery of dipole-induced exchange bias (EB), switching from negative to positive sign, is reported in systems where the antiferromagnet and the ferromagnet are separated by a paramagnetic spacer (AFM-PM-FM). The magnitude and sign of the EB is determined by the cooling field strength and the PM thickness. The same cooling field yields negative EB for thin spacers, and positive EB for thicker ones. The EB decay profile as a function of the spacer thickness, and the change of sign, are attributed to long-ranged dipole coupling. Our model, which accounts quantitatively for the experimental results, ignores the short range interfacial exchange interactions of the usual EB theories. Instead, it retains solely the long range dipole field that allows for the coupling of the FM and AFM across the PM spacer. The experiments allow for novel switching capabilities of long range EB systems, while the theory allows description of the structures where the FM and AFM are not in atomic contact. The results provide a new approach to design novel interacting heterostructures.

  7. 45○ sign switching of effective exchange bias due to competing anisotropies in fully epitaxial Co3FeN/MnN bilayers.

    Science.gov (United States)

    Hajiri, Tetsuya; Yoshida, Takuya; Filianina, Mariia; Jaiswal, Samridh; Borie, Benjamin; Asano, H; Zabel, Hartmut; Klaui, Mathias

    2017-11-20

    We report an unusual angular-dependent exchange bias effect in ferromagnet/antiferromagnet bilayers, where both ferromagnet and antiferromagnet are epitaxially grown. Numerical model calculations predict an approximately 45$^\\circ$ period for the sign switching of the exchange-bias field, depending on the ratio between magnetocrystalline anisotropy and exchange-coupling constant. The switching of the sign is indicative of a competition between a fourfold magnetocrystalline anisotropy of the ferromagnet and a unidirectional anisotropy field of the exchange coupling. This predicted unusual angular-dependent exchange bias and its magnetization switching process are confirmed by measurements on fully epitaxial Co$_3$FeN/MnN bilayers by longitudinal and transverse magneto-optic Kerr effect magnetometry. These results provide a deeper understanding of the exchange coupling phenomena in fully epitaxial bilayers with tailored materials and open up a complex switching energy landscape engineering by anisotropies. © 2017 IOP Publishing Ltd.

  8. Exchange bias effect in martensitic epitaxial Ni-Mn-Sn thin films applied to pin CoFeB/MgO/CoFeB magnetic tunnel junctions

    Science.gov (United States)

    Teichert, N.; Boehnke, A.; Behler, A.; Weise, B.; Waske, A.; Hütten, A.

    2015-05-01

    The exchange bias effect is commonly used to shift the coercive field of a ferromagnet. This technique is crucial for the use of magnetic tunnel junctions as logic or memory devices. Therefore, an independent switching of the two ferromagnetic electrodes is necessary to guarantee a reliable readout. Here, we demonstrate that the intrinsic exchange bias effect of Ni-Mn-Sn can be used to apply a unidirectional anisotropy to magnetic tunnel junctions. For this, we use epitaxial Ni-Mn-Sn films as pinning layers for microfabricated CoFeB/MgO/CoFeB magnetic tunnel junctions. We compare the exchange bias field ( HEB ) measured after field cooling in -10 kOe external field by magnetization measurements with HEB obtained from tunnel magnetoresistance measurements. Consistent for both methods, we find an exchange bias of about HEB=130 Oe at 10 K, which decreases with increasing temperature and vanishes above 70 K.

  9. Tunable exchange bias-like effect in patterned hard-soft two-dimensional lateral composites with perpendicular magnetic anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Hierro-Rodriguez, A., E-mail: ahierro@fc.up.pt; Alvarez-Prado, L. M.; Martín, J. I.; Alameda, J. M. [Departamento de Física, Universidad de Oviedo, C/Calvo Sotelo S/N, 33007 Oviedo (Spain); Centro de Investigación en Nanomateriales y Nanotecnología—CINN (CSIC—Universidad de Oviedo—Principado de Asturias), Parque Tecnológico de Asturias, 33428 Llanera (Spain); Teixeira, J. M. [IN-IFIMUP, Departamento de Física e Astronomia, Faculdade de Ciências, Universidade do Porto, Rua Campo Alegre 687, 4169-007 Porto (Portugal); Vélez, M. [Departamento de Física, Universidad de Oviedo, C/Calvo Sotelo S/N, 33007 Oviedo (Spain)

    2014-09-08

    Patterned hard-soft 2D magnetic lateral composites have been fabricated by e-beam lithography plus dry etching techniques on sputter-deposited NdCo{sub 5} thin films with perpendicular magnetic anisotropy. Their magnetic behavior is strongly thickness dependent due to the interplay between out-of-plane anisotropy and magnetostatic energy. Thus, the spatial modulation of thicknesses leads to an exchange coupled system with hard/soft magnetic regions in which rotatable anisotropy of the thicker elements provides an extra tool to design the global magnetic behavior of the patterned lateral composite. Kerr microscopy studies (domain imaging and magneto-optical Kerr effect magnetometry) reveal that the resulting hysteresis loops exhibit a tunable exchange bias-like shift that can be switched on/off by the applied magnetic field.

  10. Magnetization reversal in circularly exchange-biased ferromagnetic disks.

    Energy Technology Data Exchange (ETDEWEB)

    Tanase, M.; Petford-Long, A. K.; Heinonen, O.; Buchanan, K.; Sort, J.; Nogues, J.; Seagate Tech.; Univ. Autonoma de Barcelona; Colorado State Univ.

    2009-01-01

    We investigate the reversal behavior of circularly exchange-biased micron-sized bilayer disks of Permalloy (Py)/IrMn and CoFe/IrMn. A circular exchange bias is induced by imprinting the vortex configuration of the ferromagnetic layer into the IrMn when the disks are cooled in zero external field through the blocking temperature of IrMn. The resulting circular exchange bias has a profound effect on the reversal behavior of the ferromagnetic magnetization. In Py/IrMn disks the reversal takes place via vortex motion only, and the behavior is controlled by the exchange bias; it is reversible over a range of small fields and the vortex maintains a single chirality throughout reversal, determined by the chirality of the exchange bias. In CoFe/IrMn disks the non-negligible magnetocrystalline anisotropy causes a reversal via both vortices and domain walls resulting in a finite coercivity, and the behavior is controlled by microstructure. We verify that circular exchange bias does not give rise to a hysteresis loop shift. It lowers coercivity with respect to the field-cooled case, and in Py/IrMn disks it even causes completely reversible magnetic behavior. In both Py/IrMn and CoFe/IrMn disks, circular exchange bias removes the randomness (i.e., stochastic processes due to thermal activation) inherent in single-layer ferromagnetic disks and causes the magnetic behavior to be reproducible over time.

  11. Exchange bias effect in polycrystalline NiO/NiMn{sub 2}O{sub 4} composite

    Energy Technology Data Exchange (ETDEWEB)

    Freitas Cabral, A.J. [Instituto de Ciências Exatas e Naturais, Universidade Federal do Pará (UFPA), Belém, PA (Brazil); Peña Serna, J.; Rache Salles, B.; Novak, M.A. [Instituto de Física, Universidade Federal do Rio de janeiro (UFRJ), Rio de Janeiro, RJ (Brazil); Pinto, A.L. [Centro Brasileiro de Pesquisas Físicas (CBPF), Rio de Janeiro, RJ (Brazil); Rocha Remédios, C.M. [Instituto de Ciências Exatas e Naturais, Universidade Federal do Pará (UFPA), Belém, PA (Brazil)

    2015-05-05

    Highlights: • Antiferromagnetic NiO/ferrimagnetic NiMn{sub 2}O{sub 4} oxide composites. • Grains are well faceted, indicating that the specimen was well crystallized. • The micrographs suggests that NiO and NiMn{sub 2}O{sub 4} may be stuck to each other. • EB effect in NiO/NiMn{sub 2}O{sub 4} oxide composites. • EB effect increases with the amount of NiO. - Abstract: Calcination of aqueous solutions formed by different molar ratios between the nickel and manganese chlorides led to the formation of antiferromagnetic NiO/ferrimagnetic NiMn{sub 2}O{sub 4} oxide composites, as determined by X-ray powder diffraction technique and Rietveld refinement. Low temperature zero field cooled and field cooled magnetic hysteresis cycles show an exchange bias effect, presumably due to interaction at the interfaces between the antiferromagnetic and ferrimagnetic materials.

  12. Exchange bias of mu-metal thin films

    Energy Technology Data Exchange (ETDEWEB)

    Kirby, H.F.; Eggers, T.M.; Jayathilaka, P.B.; Campbell, S.M. [Department of Physics, Center for Integrated Functional Materials, University of South Florida, 4202 East Fowler Avenue, Tampa, FL 33620 (United States); Miller, Casey W., E-mail: cmilleratphysics@gmail.com [Department of Physics, Center for Integrated Functional Materials, University of South Florida, 4202 East Fowler Avenue, Tampa, FL 33620 (United States)

    2012-12-15

    The exchange bias of the soft ferromagnet mu-metal, Ni{sub 77}Fe{sub 14}Cu{sub 5}Mo{sub 4}, with the metallic antiferromagnet Fe{sub 50}Mn{sub 50} has been studied as a function of ferromagnet thickness and buffer layer material. Mu-metal exhibits classic exchange bias behavior: the exchange bias (H{sub EB}) and coercive fields scale inversely with the ferromagnet's thickness, with H{sub EB} varying as the cosine of the in-plane applied field angle. Ta buffers, rather than Cu, allow the mu-metal to retain more of its soft magnetic character while exhibiting exchange bias. The ability to preserve soft ferromagnetic behavior in an exchange biased heterostructure may be useful for low field sensing and other device applications. - Highlights: Black-Right-Pointing-Pointer Mu-metal/FeMn bilayers exhibit classic exchange bias behavior. Black-Right-Pointing-Pointer Mu-metal's soft magnetic properties are retained most effectively with Ta buffers. Black-Right-Pointing-Pointer Differences in interfacial exchange energy are structural in origin.

  13. Induced ferro-ferromagnetic exchange bias in nanocrystalline systems

    Energy Technology Data Exchange (ETDEWEB)

    Martínez-García, J.C.; Rivas, M.; García, J.A.

    2015-03-01

    An unusual magnetic hysteresis consisting of horizontally shifted and distorted loops appears in some Co-based nanocrystalline systems in which soft and hard ferromagnetic phases coexist. The bias field can be tuned at room temperature by premagnetising treatments. Several works attributed the origin of this effect to the dipolar interaction, while little attention has been paid to the exchange interaction contribution due to its short-range nature. In this paper the relative importance of the dipolar and exchange interactions is investigated by means of micromagnetic simulations. It is demonstrated that the exchange coupling, though a nearest-neighbour interaction, has far-reaching repercussions in the magnetic configuration, and substantially prevails over the magnetostatic interaction as the cause of the asymmetrical magnetisation reversal. The straightforward conclusion is that we are dealing with a ferro-ferromagnetic exchange bias effect. - Highlights: • Magnetic biphase nanocrystalline systems with biased hysteresis loops are presented. • Computational calculations including magnetostatic and exchange interactions have been made. • Exchange interaction largely prevails as the cause of the biasing effect. • The biasing of HL is due to exchange coupling of both ferromagnetic phases. • Assuming monodomain behaviour for the crystals allows simulating the experimental HL.

  14. Tailoring the magnetization reversal of elliptical dots using exchange bias.

    Energy Technology Data Exchange (ETDEWEB)

    Sort, J.; Buchanan, K. S.; Pearson, J. E.; Hoffmann, A.; Menendez, E.; Salazar-Alvarez, G.; Baro, M. D.; Miron, M.; Rodamcq, B.; Dieny, B.; ICREA; Univ. Autonoma of Barcelona; Insti. Catala de Nanotecnologia; SPINTEC

    2008-01-01

    Exchange bias effects have been studied in elliptical dots composed of ferromagnetic Ni{sub 80}Fe{sub 20}-antiferromagnetic Ir{sub 20}Mn{sub 80} bilayers. The magnetization reversal mechanisms and magnetic configurations have been investigated by magneto-optic Kerr effect and magnetic force microscopy. Although the obtained bias fields in these dots are relatively small, the magnetization reversal is found to be influenced by the ferromagnetic-antiferromagnetic coupling. Namely, for some off-axis angles of measurement, the magnetization reversal mechanism of the Ni{sub 80}Fe{sub 20}-Ir{sub 20}Mn{sub 80} ellipses depends on whether exchange bias is induced along the minor or major axis of the ellipses. Hence, exchange bias is shown to be an effective means for tailoring the magnetization reversal of elliptical dots after sample fabrication.

  15. Growth of oxide exchange bias layers

    Science.gov (United States)

    Chaiken, A.; Michel, R.P.

    1998-07-21

    An oxide (NiO, CoO, NiCoO) antiferromagnetic exchange bias layer produced by ion beam sputtering of an oxide target in pure argon (Ar) sputtering gas, with no oxygen gas introduced into the system. Antiferromagnetic oxide layers are used, for example, in magnetoresistive readback heads to shift the hysteresis loops of ferromagnetic films away from the zero field axis. For example, NiO exchange bias layers have been fabricated using ion beam sputtering of an NiO target using Ar ions, with the substrate temperature at 200 C, the ion beam voltage at 1000V and the beam current at 20 mA, with a deposition rate of about 0.2 {angstrom}/sec. The resulting NiO film was amorphous. 4 figs.

  16. Bias-voltage-controlled interlayer exchange coupling.

    Energy Technology Data Exchange (ETDEWEB)

    You, C.-Y.

    1999-03-29

    We propose a new system whose magnetization direction can be controlled by an applied bias voltage without an external magnetic field. The system consists of a four layered structure F{sub 1}/S/I/F{sub 2} (F{sub 1}, F{sub 2}: ferromagnets, S: spacer, I: insulator). An analytic expression for bias-voltage-controlled interlayer exchange coupling in this system is developed within a simple free-electron-like, one-dimensional approximation. According to the approach, the magnetic configurations of the two magnetic layers oscillate from antiferromagnetic to ferromagnetic with applied bias voltage. This implies that we can switch/rotate the magnetization direction without an external magnetic field. Possible applications of such a system are also discussed.

  17. Tunable exchange bias effect in magnetic Bi0.9Gd0.1Fe0.9Ti0.1O3 nanoparticles at temperatures up to 250K

    DEFF Research Database (Denmark)

    Basith, M. A.; Khan, F. A.; Ahmmad, Bashir

    2015-01-01

    The exchange bias (EB) effect has been observed in magnetic Bi0.9Gd0.1Fe0.9Ti0.1O3 nanoparticles.The influence of magnetic field cooling on the exchange bias effect has also been investigated. The magnitude of the exchange bias field (HEB) increases with the cooling magnetic field, showing...... that the strength of the exchange bias effect is tunable by the field cooling. The HEB values are also found to be dependent on the temperature. This magnetically tunable exchange bias obtained at temperatures up to 250K in Bi0.9Gd0.1Fe0.9Ti0.1O3 nanoparticles may be worthwhile for potential applications....

  18. Magnetic stability in exchange-spring and exchange bias systems after multiple switching cycles.

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, J. S.; Inomata, A.; You, C.-Y.; Pearson, J. E.; Bader, S. D.

    2001-06-01

    We have studied the magnetic stability in exchange bias and exchange spring systems prepared via epitaxial sputter deposition. The two interfacial exchange coupled systems, Fe/Cr(211) double superlattices consisting of a ferromagnetic and an antiferromagnetic Fe/Cr superlattice that are exchange coupled through a Cr spacer, and Sin-Co/Fe exchange-spring bilayer structures with ferromagnetically coupled hard Sin-Co layer and soft Fe layer, were epitaxially grown on suitably prepared Cr buffer layers to give rise to different microstructure and magnetic anisotropy. The magnetic stability was investigated using the magneto-optic Kerr effect during repeated reversal of the soft layer magnetization by field cycling up to 10{sup 7} times. For uniaxial Fe/Cr exchange biased double superlattices and exchange spring bilayers with uniaxial Sin-Co, small but rapid initial decay in the exchange bias field HE and in the remanent magnetization is observed. However, the exchange spring bilayers with biaxial and random in-plane anisotropy in the Sin-Co layer shows gradual decay in H{sub E} and without large reduction of the magnetization. The different decay behaviors are attributed to the different microstructure and spin configuration of the pinning layers.

  19. Exchange bias in sputtered FeNi/FeMn systems: Effect of short low-temperature heat treatments

    Energy Technology Data Exchange (ETDEWEB)

    Savin, Peter, E-mail: peter.savin@urfu.ru [Department of Magnetism and Magnetic Nanomaterials, Laboratory of Magnetic Sensors, Ural Federal University, 620002 Ekaterinburg (Russian Federation); Guzmán, Jorge [Instituto de Ciencia de Materiales de Madrid-CSIC, 28049 Madrid (Spain); Lepalovskij, Vladimir [Department of Magnetism and Magnetic Nanomaterials, Laboratory of Magnetic Sensors, Ural Federal University, 620002 Ekaterinburg (Russian Federation); Svalov, Andrey; Kurlyandskaya, Galina [Department of Magnetism and Magnetic Nanomaterials, Laboratory of Magnetic Sensors, Ural Federal University, 620002 Ekaterinburg (Russian Federation); Departamento de Electricidad y Electrónica, Universidad del País Vasco (UPV/EHU), 48940 Leioa, Vizcaya (Spain); Asenjo, Agustina [Instituto de Ciencia de Materiales de Madrid-CSIC, 28049 Madrid (Spain); Vas’kovskiy, Vladimir [Department of Magnetism and Magnetic Nanomaterials, Laboratory of Magnetic Sensors, Ural Federal University, 620002 Ekaterinburg (Russian Federation); Vazquez, Manuel [Department of Magnetism and Magnetic Nanomaterials, Laboratory of Magnetic Sensors, Ural Federal University, 620002 Ekaterinburg (Russian Federation); Instituto de Ciencia de Materiales de Madrid-CSIC, 28049 Madrid (Spain)

    2016-03-15

    Short (5 min) post-deposition thermal treatments under magnetic field at low temperature (up to 200 °C) performed in exchange-coupled FeNi(40 nm)/FeMn(20 nm) bilayer thin films prepared by magnetron sputtering are shown to be effective to significantly modify their exchange field (from around 40 Oe down to 27 Oe) between FeNi and FeMn layers. A similar exchange field decrease was observed for the first deposited FeNi layer of the FeNi(40 nm)/FeMn(20 nm)/FeNi(40 nm) trilayer films after the same thermal treatments. The exchange field value for the second FeNi layer was not substantially changed. The X-ray diffraction patterns indicates that such a heat treatment has no effect on the grain size and crystalline texture of the films, while atomic force microscope studies reveal an increase of the surface roughness after the treatment which is more noticeable in the case of the trilayer film. Analysis of the experimental results leads us to conclude that the variations of the exchange field after heat treatment are likely caused by a modification of interfacial roughness and/or interfacial magnetic structure, but unlikely by the changes in the microstructure and/or changes of composition of the antiferromagnetic FeMn layer. - Highlights: • FeNi/FeMn bilayers and FeNi/FeMn/FeNi trilayers were prepared by magnetron sputtering. • Post-deposition heat treatments at the temperatures below 200 °C during 5 min were made. • Annealing reduces the exchange field for the first FeNi layer in trilayers. • The exchange field value for the second FeNi layer was not substantially changed. • Exchange field changes are most likely caused by a modification of interface roughness.

  20. Negative magnetization and zero-field cooled exchange bias effect in Eu0.9Pr0.1CrO3 ceramics

    Science.gov (United States)

    Huang, Ping; Deng, Dongmei; Zheng, Jiashun; Li, Qing; Feng, Zhenjie; Kang, Baojuan; Ren, Wei; Jing, Chao; Zhang, Jincang; Cao, Shixun

    2018-02-01

    Interesting magnetic behaviors, including negative magnetization, zero field fooled and field cooled exchange bias effects, have been observed in Eu0.9Pr0.1CrO3. The negative magnetization at low temperature results from the antiparallel coupling between the Pr3+ moment and the canted moment of Cr3+ sublattice. Left shift of zero field cooled M-H loops, and right shift of field cooled M-H loops have been observed, due to the growth and competition of two types of magnetic structures with GxFz (EuCrO3) and GzFx (PrCrO3) orderings under magnetic field. When the cooling field is high enough, the Pr3+ moment is frozen antiparallel with the applied field during the cooling process, giving rise to a positive exchange bias (right shift of M-H). However, when the cooling field is near zero, magnetic clusters with GxFz (EuCrO3) or GzFx (PrCrO3) orderings are formed and distribute randomly during the cooling process, and the net Pr3+ moment get aligned along the applied field during the initial magnetization process to lower the Zeeman energy, and then negative exchange bias (left shift of M-H) appears.

  1. Anisotropy engineering using exchange bias on antidot templates

    Directory of Open Access Journals (Sweden)

    F. J. T. Goncalves

    2015-06-01

    Full Text Available We explore an emerging device concept based on exchange bias used in conjunction with an antidot geometry to fine tune ferromagnetic resonances. Planar cavity ferromagnetic resonance is used to study the microwave response of NiO/NiFe bilayers with antidot structuring. A large frequency asymmetry with respect to an applied magnetic field is found across a broad field range whose underlying cause is linked to the distribution of magnetic poles at the antidot surfaces. This distribution is found to be particularly sensitive to the effects of exchange bias, and robust in regards to the quality of the antidot geometry. The template based antidot geometry we study offers advantages for practical device construction, and we show that it is suitable for broadband absorption and filtering applications, allowing tunable anisotropies via interface engineering.

  2. Robust isothermal electric control of exchange bias at room temperature

    Science.gov (United States)

    Binek, Christian

    2011-03-01

    Voltage-controlled spintronics is of particular importance to continue progress in information technology through reduced power consumption, enhanced processing speed, integration density, and functionality in comparison with present day CMOS electronics. Almost all existing and prototypical solid-state spintronic devices rely on tailored interface magnetism, enabling spin-selective transmission or scattering of electrons. Controlling magnetism at thin-film interfaces, preferably by purely electrical means, is a key challenge to better spintronics. Currently, most attempts to electrically control magnetism focus on potentially large magnetoelectric effects of multiferroics. We report on our interest in magnetoelectric Cr 2 O3 (chromia). Robust isothermal electric control of exchange bias is achieved at room temperature in perpendicular anisotropic Cr 2 O3 (0001)/CoPd exchange bias heterostructures. This discovery promises significant implications for potential spintronics. From the perspective of basic science, our finding serves as macroscopic evidence for roughness-insensitive and electrically controllable equilibrium boundary magnetization in magnetoelectric antiferromagnets. The latter evolves at chromia (0001) surfaces and interfaces when chromia is in one of its two degenerate antiferromagnetic single domain states selected via magnetoelectric annealing. Theoretical insight into the boundary magnetization and its role in electrically controlled exchange bias is gained from first-principles calculations and general symmetry arguments. Measurements of spin-resolved ultraviolet photoemission, magnetometry at Cr 2 O3 (0001) surfaces, and detailed investigations of the unique exchange bias properties of Cr 2 O3 (0001)/CoPd including its electric controllability provide macroscopically averaged information about the boundary magnetization of chromia. Laterally resolved X-ray PEEM and temperature dependent MFM reveal detailed microscopic information of the chromia

  3. Controllable positive exchange bias via redox-driven oxygen migration

    National Research Council Canada - National Science Library

    Gilbert, Dustin A; Olamit, Justin; Dumas, Randy K; Kirby, B J; Grutter, Alexander J; Maranville, Brian B; Arenholz, Elke; Borchers, Julie A; Liu, Kai

    2016-01-01

    .... Using the strong oxygen affinity of gadolinium, we design a model system of GdxFe1-x/NiCoO bilayer films, where the oxygen migration is observed and manifested in a controlled positive exchange bias...

  4. Role of the antiferromagnetic bulk spins in exchange bias

    Energy Technology Data Exchange (ETDEWEB)

    Schuller, Ivan K. [Center for Advanced Nanoscience and Physics Department, University of California San Diego, La Jolla, CA 92093 (United States); Morales, Rafael, E-mail: rafael.morales@ehu.es [Department of Chemical-Physics & BCMaterials, University of the Basque Country UPV/EHU (Spain); IKERBASQUE, Basque Foundation for Science, 48011 Bilbao (Spain); Batlle, Xavier [Departament Física Fonamental and Institut de Nanociència i Nanotecnologia, Universitat de Barcelona, c/ Martí i Franqués s/n, 08028 Barcelona, Catalonia (Spain); Nowak, Ulrich [Department of Physics, University of Konstanz, 78464 Konstanz (Germany); Güntherodt, Gernot [Physics Institute (IIA), RWTH Aachen University, Campus RWTH-Melaten, 52074 Aachen (Germany)

    2016-10-15

    This “Critical Focused Issue” presents a brief review of experiments and models which describe the origin of exchange bias in epitaxial or textured ferromagnetic/antiferromagnetic bilayers. Evidence is presented which clearly indicates that inner, uncompensated, pinned moments in the bulk of the antiferromagnet (AFM) play a very important role in setting the magnitude of the exchange bias. A critical evaluation of the extensive literature in the field indicates that it is useful to think of this bulk, pinned uncompensated moments as a new type of a ferromagnet which has a low total moment, an ordering temperature given by the AFM Néel temperature, with parallel aligned moments randomly distributed on the regular AFM lattice. - Highlights: • We address the role of bulk antiferromagnetic spins in the exchange bias phenomenon. • Significant experiments on how bulk AFM spins determine exchange bias are highlighted. • We explain the model that accounts for experimental results.

  5. Exchange Bias and Inverse Magnetocaloric Effect in Co and Mn Co-Doped Ni2MnGa Shape Memory Alloy

    Directory of Open Access Journals (Sweden)

    Yong Liu

    2013-01-01

    Full Text Available Exchange bias effect observed in the Ni1.68Co0.32Mn1.20Ga0.80 alloy confirms the coexistence of antiferromagnetic and ferromagnetic phases in the martensite phase. A large inverse magnetocaloric effect has been observed within the martensitic transformation temperature range, which is originated from modified magnetic order through magnetic-field-induced phase transformation from partially antiferromagnetic martensite to ferromagnetic austenite. The magnetic entropy change is 16.2 J kg−1 K−1 at 232 K under ΔH = 60 kOe, with the net refrigerant capacity of 68 J kg−1. These properties indicate Co and Mn co-doped Ni2MnGa alloy is a multifunctional material potentially suitable for magnetic refrigeration and spintronics applications.

  6. Magnetic properties of NiMn{sub 2}O{sub 4−δ} (nickel manganite): Multiple magnetic phase transitions and exchange bias effect

    Energy Technology Data Exchange (ETDEWEB)

    Tadic, Marin, E-mail: marint@vinca.rs [Condensed Matter Physics Laboratory, Vinca Institute of Nuclear Sciences, University of Belgrade, POB 522, 11001 Belgrade (Serbia); Savic, S.M. [Institute for Multidisciplinary Research, University of Belgrade, Kneza Viseslava 1, 11000 Belgrade (Serbia); Jaglicic, Z. [University of Ljubljana, Faculty of Civil Engineering and Geodesy and Institute of Mathematics, Physics and Mechanics, Jadranska 19, 1000 Ljubljana (Slovenia); Vojisavljevic, K.; Radojkovic, A.; Prsic, S. [Institute for Multidisciplinary Research, University of Belgrade, Kneza Viseslava 1, 11000 Belgrade (Serbia); Nikolic, Dobrica [Department of Physics, University of Belgrade Faculty of Mining and Geology, Belgrade (Serbia)

    2014-03-05

    Highlights: • We have successfully synthesized NiMn{sub 2}O{sub 4−δ} sample by complex polymerization synthesis. • Magnetic measurements reveal complex properties and triple magnetic phase transitions. • Magnetic measurements of M(H) show hysteretic behavior below 120 K. • Hysteresis properties after cooling of the sample in magnetic field show exchange bias effect. -- Abstract: We present magnetic properties of NiMn{sub 2}O{sub 4−δ} (nickel manganite) which was synthesized by complex polymerization synthesis method followed by successive heat treatment and final calcinations in air at 1200 °C. The sample was characterized by using X-ray powder diffractometer (XRPD), scanning electron microscopy (SEM), field-emission scanning electron microscopy (FE-SEM) and superconducting quantum interference device (SQUID) magnetometer. The XRPD and FE-SEM studies revealed NiMn{sub 2}O{sub 4−δ} phase and good crystallinity of particles. No other impurities have been observed by XRPD. The magnetic properties of the sample have been studied by measuring the temperature and field dependence of magnetization. Magnetic measurements of M(T) reveal rather complex magnetic properties and multiple magnetic phase transitions. We show three magnetic phase transitions with transition temperatures at T{sub M1} = 35 K (long-range antiferromagnetic transition), T{sub M2} = 101 K (antiferromagnetic-type transition) and T{sub M3} = 120 K (ferromagnetic-like transition). We found that the T{sub M1} transition is strongly dependent on the strength of the applied magnetic field (T{sub M1} decreases with increasing applied field) whereas the T{sub M3} is field independent. Otherwise, the T{sub M2} maximum almost disappears in higher applied magnetic fields (H = 1 kOe and 10 kOe). Magnetic measurements of M(H) show hysteretic behavior below T{sub M3}. Moreover, hysteresis properties measured after cooling of the sample in magnetic field of 10 kOe show exchange bias effect with an

  7. Thickness dependent exchange bias in martensitic epitaxial Ni-Mn-Sn thin films

    Directory of Open Access Journals (Sweden)

    Anna Behler

    2013-12-01

    Full Text Available A thickness dependent exchange bias in the low temperature martensitic state of epitaxial Ni-Mn-Sn thin films is found. The effect can be retained down to very small thicknesses. For a Ni50Mn32Sn18 thin film, which does not undergo a martensitic transformation, no exchange bias is observed. Our results suggest that a significant interplay between ferromagnetic and antiferromagnetic regions, which is the origin for exchange bias, is only present in the martensite. The finding is supported by ab initio calculations showing that the antiferromagnetic order is stabilized in the phase.

  8. Thickness dependent exchange bias in martensitic epitaxial Ni-Mn-Sn thin films

    Energy Technology Data Exchange (ETDEWEB)

    Behler, Anna [IFW Dresden, Institute for Complex Materials, P.O. Box 27 01 16, 01171 Dresden (Germany); Department of Physics, Institute for Solid State Physics, Dresden University of Technology, 01062 Dresden (Germany); Teichert, Niclas; Auge, Alexander; Hütten, Andreas [Department of Physics, Thin Films and Physics of Nanostructures, Bielefeld University, 33501 Bielefeld (Germany); Dutta, Biswanath; Hickel, Tilmann [Max-Planck Institut für Eisenforschung, 40237 Düsseldorf (Germany); Waske, Anja [IFW Dresden, Institute for Complex Materials, P.O. Box 27 01 16, 01171 Dresden (Germany); Eckert, Jürgen [IFW Dresden, Institute for Complex Materials, P.O. Box 27 01 16, 01171 Dresden (Germany); Institute of Materials Science, Dresden University of Technology, 01062 Dresden (Germany)

    2013-12-15

    A thickness dependent exchange bias in the low temperature martensitic state of epitaxial Ni-Mn-Sn thin films is found. The effect can be retained down to very small thicknesses. For a Ni{sub 50}Mn{sub 32}Sn{sub 18} thin film, which does not undergo a martensitic transformation, no exchange bias is observed. Our results suggest that a significant interplay between ferromagnetic and antiferromagnetic regions, which is the origin for exchange bias, is only present in the martensite. The finding is supported by ab initio calculations showing that the antiferromagnetic order is stabilized in the phase.

  9. Thickness dependent exchange bias in martensitic epitaxial Ni-Mn-Sn thin films

    Science.gov (United States)

    Behler, Anna; Teichert, Niclas; Dutta, Biswanath; Waske, Anja; Hickel, Tilmann; Auge, Alexander; Hütten, Andreas; Eckert, Jürgen

    2013-12-01

    A thickness dependent exchange bias in the low temperature martensitic state of epitaxial Ni-Mn-Sn thin films is found. The effect can be retained down to very small thicknesses. For a Ni50Mn32Sn18 thin film, which does not undergo a martensitic transformation, no exchange bias is observed. Our results suggest that a significant interplay between ferromagnetic and antiferromagnetic regions, which is the origin for exchange bias, is only present in the martensite. The finding is supported by ab initio calculations showing that the antiferromagnetic order is stabilized in the phase.

  10. Postannealing of magnetic tunnel junctions with ion-bombardment-modified exchange bias

    Science.gov (United States)

    Höink, V.; Sacher, M. D.; Schmalhorst, J.; Reiss, G.; Engel, D.; Junk, D.; Ehresmann, A.

    2005-04-01

    The influence of a postannealing procedure on the transport properties of magnetic tunnel junctions with ion-bombardment-manipulated exchange bias is investigated. The controlled manipulation of the direction of the exchange bias field in magnetic tunnel junctions by He ion bombardment usually is accompanied by a reduction of the tunneling magnetoresistance and an increase in the resistance. Here, we demonstrate that it is possible to reduce these negative effects of the ion bombardment considerably by postannealing without a magnetic field. For optimized combinations of ion dose and postannealing temperature, the tunneling magnetoresistance recovers completely (>50% resistance change) while the exchange bias direction set by the ion bombardement is preserved.

  11. Tunable giant exchange bias in the single-phase rare-earth-transition-metal intermetallics YM n12 -xF ex with highly homogenous intersublattice exchange coupling

    Science.gov (United States)

    Xia, Yuanhua; Wu, Rui; Zhang, Yinfeng; Liu, Shunquan; Du, Honglin; Han, Jingzhi; Wang, Changsheng; Chen, Xiping; Xie, Lei; Yang, Yingchang; Yang, Jinbo

    2017-08-01

    A tunable giant exchange bias effect is discovered in a family of bulk intermetallic compounds YM n12 -xF ex . Experimental data demonstrate that the exchange bias effect originates from global interactions among ferromagnetic and antiferromagnetic sublattices but not the interfacial exchange coupling or inhomogeneous magnetic clusters. A giant exchange bias with a loop shift of up to 6.1 kOe has been observed in YM n4.4F e7.6 compound. In a narrow temperature range, the exchange bias field shows a sudden switching-off whereas the coercivity shows a sudden switching-on with increasing temperature. This unique feature indicates that the intersublattice exchange coupling is highly homogenous. Our theoretical calculations reveal this switching feature, which agrees very well with the experiments and provides insights into the physical underpinnings of the observed exchange bias and coercivity.

  12. Determining the sign of exchange coupling in a chromia based perpendicular exchange bias heterostructure

    Science.gov (United States)

    Singh, Uday; Street, Mike; Echtenkamp, Will; Binek, Christian; Adenwalla, Shireen

    Exchange bias arises from the coupling at the AFM/FM interface and, has been observed and studied in a wide range of systems. A key property of exchange bias systems is the sign of the coupling between the ferromagnet spins and the interfacial antiferromagnet spins, which may be aligned either ferromagnetically (parallel) or antiferromagnetically (antiparallel). Antiferromagnetic exchange coupling is known to be the generic cause of positive exchange bias. Determining the sign of exchange coupling is straight forward in system where the coupling is weak and can be overcome by Zeeman energy on field -cooling. It is, however, a challenging task when the available magnetic field is low or the magnitude of the exchange coupling is high. Here, we present a technique to determine the sign of the exchange coupling using low fields. We measure the exchange bias field as a function of ferromagnet magnetization during field cooling and the resultant behavior of the exchange bias vs. the magnetization uniquely determines the sign of the coupling. We use this to measure the sign of the exchange coupling in a Cr2O3(300 nm)/Pd(0.5 nm)/[Co(0.3 nm)/Pd(1 nm)]3 heterostructure thin film system and verify our results with the conventional high field method. This work was supported by the National Science Foundation (NSF) through Grant No. DMR-1409622 and the Nebraska Materials Research Science and Engineering Center (MRSEC) (Grant No. DMR-1420645).

  13. Exchange bias in zinc ferrite-FeNiMoB based metallic glass composite thin films

    Energy Technology Data Exchange (ETDEWEB)

    R, Lisha; P, Geetha; B, Aravind P.; Anantharaman, M. R., E-mail: mraiyer@yahoo.com [Cochin University of Science and Technology, Cochin-682022 (India); T, Hysen [Christian College, Chengannur, Kerala-689121 (India); Ojha, S.; Avasthi, D. K. [Inter University Accelerator Centre, Vasant Kunj, New Delhi-110067 (India); Ramanujan, R. V. [School of Materials Science and Engineering, Nanyang Technological University (Singapore)

    2015-06-24

    The Exchange bias phenomenon and methods to manipulate the bias field in a controlled manner are thrust areas in magnetism due to its sophisticated theoretical concepts as well as advanced technological utility in the field of spintronics. The Exchange bias effect is observed as a result of ferromagnetic-antiferromagnetic (FM-AFM) exchange interaction, usually observed as a loop shift on field cooling below the Neel temperature of AFM. In the present study, we have chosen zinc ferrite which is a well known antiferromagnet, and FeNiMoB based metallic glass as the ferromagnet. The films were prepared by RF sputtering technique. The thickness and composition was obtained by RBS. The magnetic studies using SQUID VSM indicate exchange bias effect in the system. The effect of thermal annealing on exchange bias effect was studied. The observed exchange bias in the zinc ferrite-FeNiMoB system is not due to FM-AFM coupling but due to spin glass-ferromagnetic interaction.

  14. Exchange bias and strain effect co-modulated magnetic symmetry in La0.6Sr0.4MnO3/orthorhombic-YMnO3 multiferroic heterostructures

    Science.gov (United States)

    Zheng, Dongxing; Gong, Junlu; Jin, Chao; Li, Peng; Feng, Liefeng; Bai, Haili

    2017-06-01

    The exchange bias and strain effect co-modulated magnetic symmetry in all oxide La0.6Sr0.4MnO3 (LSMO) and orthorhombic YMnO3 (YMO) multiferroic heterostructures were studied. Because of the lattice mismatch between the LSMO and YMO layers, the LSMO layer exhibits a 90° rotation growth on the YMO layer. The strain induced growth not only leads to a 90° phase shift in the anisotropic magnetoresistance (AMR) curves, but also brings a two-fold symmetric magnetoelastic coupling energy along the LSMO [1 1 0] direction. With the incorporation of magnetoelastic coupling energy and exchange coupling energy, the exchange bias induced torque shows a phase shift and causes the asymmetry of the peak position and value in the AMR curves. This work illustrates a modulated magnetic symmetry in ferromagnetic/multiferroic systems by interfacial exchange coupling and strain effect, which will benefit the design of magnetoelectric devices.

  15. Exchange bias and strain effect co-modulated magnetic symmetry in La0.6Sr0.4MnO3/orthorhombic-YMnO3 multiferroic heterostructures

    KAUST Repository

    Zheng, Dongxing

    2017-05-03

    The exchange bias and strain effect co-modulated magnetic symmetry in all oxide La0.6Sr0.4MnO3 (LSMO) and orthorhombic YMnO3 (YMO) multiferroic heterostructures were studied. Because of the lattice mismatch between the LSMO and YMO layers, the LSMO layer exhibits a 90° rotation growth on the YMO layer. The strain induced growth not only leads to a 90° phase shift in the anisotropic magnetoresistance (AMR) curves, but also brings a two-fold symmetric magnetoelastic coupling energy along the LSMO $[1\\\\,1\\\\,0]$ direction. With the incorporation of magnetoelastic coupling energy and exchange coupling energy, the exchange bias induced torque shows a phase shift and causes the asymmetry of the peak position and value in the AMR curves. This work illustrates a modulated magnetic symmetry in ferromagnetic/multiferroic systems by interfacial exchange coupling and strain effect, which will benefit the design of magnetoelectric devices.

  16. Magnetoelectricity coupled exchange bias in BaMnF4

    National Research Council Canada - National Science Library

    Zhou, Shuang; Wang, Ji; Chang, Xiaofeng; Wang, Shuangbao; Qian, Bin; Han, Zhida; Xu, Qingyu; Du, Jun; Wang, Peng; Dong, Shuai

    2015-01-01

    .... The blocking temperature of 65 K for exchange bias coincides well with the peak at 65 K in the zero-field cooled temperature-dependent magnetization curve, which has been assigned to the onset temperature of two-dimensional antiferromagnetism...

  17. Exchange bias in Co/CoO/Co{sub 3}O{sub 4} nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Ahmadvand, Hossein, E-mail: ahmadvand@cc.iut.ac.ir [Department of Physics, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Safdari, Sayed Reza [Department of Physics, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Nozad Golikand, Ahmad [Material Research Center, Isfahan 81465-1589 (Iran, Islamic Republic of); Dasgupta, Papri; Poddar, Asok [Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064 (India); Salamati, Hadi [Department of Physics, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of)

    2015-03-01

    Nanostructures of Co/CoO/Co{sub 3}O{sub 4} were synthesized by a chemical method at different temperatures between 300 and 600 °C. The samples were characterized by TG, XRD, TEM and SQUID magnetometry. The lower temperature sample (300 °C) is composed of Co, CoO and Co{sub 3}O{sub 4}, while the higher temperature sample only contains Co{sub 3}O{sub 4}. All the samples exhibit exchange bias effect. The exchange bias is observed below 205 K (below the CoO blocking temperature) for the sample prepared at lower temperature (300 °C), while for other samples (350–600 °C), the effect is observed below 35 K (below the Néel temperature of Co{sub 3}O{sub 4}, T{sub N}=40 K). The roles of CoO and Co{sub 3}O{sub 4} on the magnetic properties and the mechanisms governing exchange bias effect have been discussed. - Highlights: • Synthesis of Co/CoO/Co{sub 3}O{sub 4} nanostructure by a simple method. • Study of exchange bias in a cobalt/cobalt-oxide nanostructure containing both cobalt oxides. • Discussion on the role of CoO and Co3O4 on the exchange bias properties of the nanostructure.

  18. Role of the antiferromagnetic bulk spins in exchange bias

    Science.gov (United States)

    Schuller, Ivan K.; Morales, Rafael; Batlle, Xavier; Nowak, Ulrich; Güntherodt, Gernot

    2016-10-01

    This "Critical Focused Issue" presents a brief review of experiments and models which describe the origin of exchange bias in epitaxial or textured ferromagnetic/antiferromagnetic bilayers. Evidence is presented which clearly indicates that inner, uncompensated, pinned moments in the bulk of the antiferromagnet (AFM) play a very important role in setting the magnitude of the exchange bias. A critical evaluation of the extensive literature in the field indicates that it is useful to think of this bulk, pinned uncompensated moments as a new type of a ferromagnet which has a low total moment, an ordering temperature given by the AFM Néel temperature, with parallel aligned moments randomly distributed on the regular AFM lattice.

  19. Exchange bias of patterned systems: Model and numerical simulation

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, Griselda [Facultad de Fisica, P. Universidad Catolica de Chile, Casilla 306, Santiago 7820436 (Chile); Centro para el Desarrollo de la Nanociencia y la Nanotecnologia, CEDENNA, Avda. Ecuador 3493, Santiago (Chile); Kiwi, Miguel, E-mail: mkiwi@puc.c [Facultad de Fisica, P. Universidad Catolica de Chile, Casilla 306, Santiago 7820436 (Chile); Centro para el Desarrollo de la Nanociencia y la Nanotecnologia, CEDENNA, Avda. Ecuador 3493, Santiago (Chile); Mejia-Lopez, Jose; Ramirez, Ricardo [Facultad de Fisica, P. Universidad Catolica de Chile, Casilla 306, Santiago 7820436 (Chile); Centro para el Desarrollo de la Nanociencia y la Nanotecnologia, CEDENNA, Avda. Ecuador 3493, Santiago (Chile)

    2010-11-15

    The magnitude of the exchange bias field of patterned systems exhibits a notable increase in relation to the usual bilayer systems, where a continuous ferromagnetic film is deposited on an antiferromagnet insulator. Here we develop a model, and implement a Monte Carlo calculation, to interpret the experimental observations which is consistent with experimental results, on the basis of assuming a small fraction of spins pinned ferromagnetically in the antiferromagnetic interface layer.

  20. Exchange bias training effect in phase separated polycrystalline Sm{sub 0.1}Ca{sub 0.7}Sr{sub 0.2}MnO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Markovich, V., E-mail: markoviv@bgu.ac.il [Department of Physics, Ben-Gurion University of the Negev, 84105, Beer-Sheva (Israel); Fita, I.; Wisniewski, A.; Puzniak, R. [Institute of Physics, Polish Academy of Sciences, Aleja Lotnikow 32/46, 02-668, Warsaw (Poland); Martin, C. [Laboratoire CRISMAT, UMR 6508, ISMRA, 14050, Caen Cedex (France); Jung, G. [Department of Physics, Ben-Gurion University of the Negev, 84105, Beer-Sheva (Israel); Institute of Physics, Polish Academy of Sciences, Aleja Lotnikow 32/46, 02-668, Warsaw (Poland); Gorodetsky, G. [Department of Physics, Ben-Gurion University of the Negev, 84105, Beer-Sheva (Israel)

    2016-12-01

    Magnetic properties of antiferromagnetic (AFM) electron doped manganite Sm{sub 0.1}Ca{sub 0.7}Sr{sub 0.2}MnO{sub 3} have been investigated, focusing mainly on the exchange bias (EB) effect and associated training effect. The studied compound exhibits the ground state with heterogeneous spin configuration, consisting of the C-type antiferromagnetic phase with the Néel temperature T{sub N-C} ≈ 120 K, the G-AFM phase with the Néel temperature T{sub N-G} ≈ 60 K, and ferromagnetic-like phase with a very weak spontaneous magnetic moment. Measurements of hysteresis loops have shown that the exchange bias field monotonously decreases with increasing temperature and vanishes above 40 K, while the coercivity disappears only above 70 K. The temperature variation of the exchange bias field has been successfully described by an exponential decay form. The stability of EB has been evaluated in the studies of the training effect, which has been discussed in the frame of the spin relaxation model, elucidating the important role of the AFM domain rearrangement at the interface. The complex phase separation and possible contributions from different interfaces between coexisting magnetic phases to the EB effect have also been discussed. - Highlights: • Sm{sub 0.1}Ca{sub 0.7}Sr{sub 0.2}MnO{sub 3} exhibits exchange bias (EB) effect at low temperatures T < 40 K. • The EB effect is associated with the phase separation and the presence of FM clusters as well as the G- and C-type AFM phases. • The training effect (TE) has been discussed in the frame of the spin relaxation model. • The TE is relatively small, indicating that AFM moment configuration is almost frozen during the magnetization reversal.

  1. Fundamentals for magnetic patterning by ion bombardment of exchange bias layer systems

    Science.gov (United States)

    Ehresmann, A.; Engel, D.; Weis, T.; Schindler, A.; Junk, D.; Schmalhorst, J.; Höink, V.; Sacher, M. D.; Reiss, G.

    2006-01-01

    In the present paper we investigate whether the ion bombardment induced magnetic modifications in exchange biased bilayers are stable in time, whether the direction of the exchange bias can be set to any arbitrary (in-plane) direction by the ion bombardment and whether the exchange bias field can be changed in successive bombardment steps. These three fundamental characteristics are prerequisites for ion bombardment used for an efficient, practical, and stable magnetic patterning of exchange biased layer systems.

  2. Annealing effect on the crystal structure and exchange bias in Heusler Ni{sub 45.5}Mn{sub 43.0}In{sub 11.5} alloy ribbons

    Energy Technology Data Exchange (ETDEWEB)

    González-Legarreta, L. [Department of Physics, University of Oviedo, Calvo Sotelo s/n, 33007 Oviedo (Spain); Rosa, W.O. [Centro Brasileiro de Pesquisas Físicas, Rua Dr. Xavier Sigaud, 150 Urca., 22290-180 Rio de Janeiro, RJ (Brazil); García, J. [Department of Physics, University of Oviedo, Calvo Sotelo s/n, 33007 Oviedo (Spain); Ipatov, M.; Nazmunnahar, M. [Department of Materials Physics, Faculty of Chemistry, University of the Basque Country, 20018 San Sebastian (Spain); Escoda, L.; Suñol, J.J. [Department of Physics, Campus Montilivi s/n, University of Girona, 17071 Girona (Spain); Prida, V.M. [Department of Physics, University of Oviedo, Calvo Sotelo s/n, 33007 Oviedo (Spain); Sommer, R.L. [Centro Brasileiro de Pesquisas Físicas, Rua Dr. Xavier Sigaud, 150 Urca., 22290-180 Rio de Janeiro, RJ (Brazil); González, J. [Department of Materials Physics, Faculty of Chemistry, University of the Basque Country, 20018 San Sebastian (Spain); Leoni, M. [Department of Material Engineering and Industrial Technologies, University of Trento, Via Mesiano 77, I-38123 Trento (Italy); Hernando, B., E-mail: grande@uniovi.es [Department of Physics, University of Oviedo, Calvo Sotelo s/n, 33007 Oviedo (Spain)

    2014-01-05

    Highlights: • Preparation of Ni–Mn–In Heusler alloys by melt spinning technique in ribbon shape. • Short annealing effects on the crystal structure, microstructure and magnetic properties. • Influence of annealing on the martensitic transformation. • Enhancement of the exchange bias effect. -- Abstract: A Heusler Ni{sub 45.5}Mn{sub 43.0}In{sub 11.5} alloy has been prepared by arc melting and produced in a ribbon shape by rapid solidification using melt spinning technique. Structural properties have been investigated, at different temperatures, by using X-ray diffraction. Austenite is the stable phase at room temperature with a L2{sub 1} cubic crystal structure. Exchange bias effect was observed after field cooling by means of hysteresis loop measurements. At 5 K, hysteresis loop shifts along the axis of the applied magnetic field and that shift magnitude decreases significantly with increasing temperature. A piece of ribbon was annealed at 973 K during 10 min in order to investigate the influence of annealing on crystal structure and magnetic properties. After annealing, a martensitic phase with a monoclinic 10M structure at room temperature is observed. The onset of the martensitic phase transformation shifts to 365 K, temperatures associated with both martensitic and reverse transitions do not change noticeably under an applied magnetic field up to 30 kOe, and a drastic decrease on magnetization is observed in comparison with the as-quenched ribbon meanwhile the exchange bias effect is enhanced.

  3. Manipulating exchange bias using all-optical helicity-dependent switching

    Science.gov (United States)

    Vallobra, P.; Fache, T.; Xu, Y.; Zhang, L.; Malinowski, G.; Hehn, M.; Rojas-Sánchez, J.-C.; Fullerton, E. E.; Mangin, S.

    2017-10-01

    Deterministic all-optical control of magnetization without an applied magnetic field has been reported for various materials such as ferrimagnetic and ferromagnetic thin films, as well as granular recording media. Here we demonstrate optical control of the magnetic configuration of an antiferromagnetic layer through the exchange bias interaction using the helicity of a femtosecond pulsed laser on IrMn /[Co/Pt ] xN antiferromagnetic/ferromagnetic heterostructures. We show that the magnitude and the sign of the exchange bias field can be deterministically controlled without any applied magnetic field, only by changing the helicity of the light, the laser fluence, or the number of light pulses. We also present the combined effects of laser pulses with an applied magnetic field. This study lays the foundation for the development of new applications based on spintronic devices where the exchange bias phenomenon is routinely used to pin the magnetization orientation of a magnetic layer in one direction.

  4. Tunable magnetic anisotropy of antiferromagnetic superlattice and resultant exchange bias of ferromagnetic layer on it

    Energy Technology Data Exchange (ETDEWEB)

    Tsunoda, Masakiyo [Department of Electonic Engineering, Tohoku University, Aobayama 6-6-05, Sendai 980-8579 (Japan)]. E-mail: tsunoda@ecei.tohoku.ac.jp; Naka, Mamiko [Department of Electonic Engineering, Tohoku University, Aobayama 6-6-05, Sendai 980-8579 (Japan); Kim, Dong Young [Department of Electonic Engineering, Tohoku University, Aobayama 6-6-05, Sendai 980-8579 (Japan); Research Center for Advanced Magnetic Materials, Chungnam National University, Daejeon 305-764 (Korea, Republic of); Takahashi, Migaku [Department of Electonic Engineering, Tohoku University, Aobayama 6-6-05, Sendai 980-8579 (Japan); New Industry Creation Hatchery Center, Tohoku University, Aobayama 6-6-10, Sendai 980-8579 (Japan)

    2006-09-15

    Exchange biasing of ferromagnetic layer deposited on the antiferromagnetic superlattice was investigated in (Co{sub 70}Fe{sub 30}/Ru){sub 29.5}/Ru/Co{sub 90}Fe{sub 10} multilayers. Uniaxial magnetic anisotropy (K {sub AF}) was induced and tuned in the antiferromagentic superlattice by uniaxial substrate bending method through the inverse effect of magnetostriction. The exchange bias increased and tended to be saturated with increasing the K {sub AF}, while it was not observed at K {sub AF}=0.

  5. Surface spin glass and exchange bias effect in Sm0.5Ca0.5MnO3 manganites nano particles

    Directory of Open Access Journals (Sweden)

    S. K. Giri

    2011-09-01

    Full Text Available In this letter, we report that the charge/orbital order state of bulk antiferromagnetic Sm0.5Ca0.5MnO3 is suppressed and confirms the appearance of weak ferromagnetism below 65 K followed by a low temperature spin glass like transition at 41 K in its nano metric counterpart. Exchange anisotropy effect has been observed in the nano manganites and can be tuned by the strength of the cooling magnetic field (Hcool. The values of exchange fields (HE, coercivity (HC, remanence asymmetry (ME and magnetic coercivity (MC are found to strongly depend on cooling magnetic field and temperature. HE increases with increasing Hcool but for larger Hcool, HE tends to decrease due to the growth of ferromagnetic cluster size. Magnetic training effect has also been observed and it has been analyzed thoroughly using spin relaxation model. A proposed phenomenological core-shell type model is attributed to an exchange coupling between the spin-glass like shell (surrounding and antiferromagnetic core of Sm0.5Ca0.5MnO3 nano manganites mainly on the basis of uncompensated surface spins. Results suggest that the intrinsic phase inhomogeneity due to the surface effects of the nanostructured manganites may cause exchange anisotropy, which is of special interests for potential application in multifunctional spintronic devices.

  6. Magnetically tunable bipolar switching of the exchange-bias field in Co2TiO4

    Science.gov (United States)

    Wei, A.; Tao, S.; Fang, Y.; Han, Z. D.; Qian, B.; Jiang, X. F.; Zhou, H.; Tang, R. J.; Wang, D. H.

    2017-11-01

    Coupling at the interfaces between antiferromagnetic and ferromagnetic constituents is known to be responsible for the exchange-bias effect, where external stimulus like temperature, electric or magnetic fields are supposed to influence the associated phenomenology. In this paper, we prepare the polycrystalline Co2TiO4 and investigate its temperature- and field-dependent magnetization, from which an unusual exchange-bias effect associated with magnetic reversals is extracted. At low temperature, a continuous crossover from negative to positive exchange-bias fields can be obtained with increment of the cooling magnetic field, showing a magnetically tunable effect. The bipolar switching of exchange-bias field in this compound depends on the relative orientation between Co2+ and [Co3+Ti3+] magnetic moments.

  7. Enhancement of exchange bias and training effect in ion-beam sputtered Fe{sub 46}Mn{sub 54}/Ni{sub 81}Fe{sub 19} bilayers

    Energy Technology Data Exchange (ETDEWEB)

    Fulara, Himanshu; Chaudhary, Sujeet, E-mail: sujeetc@physics.iitd.ac.in; Kashyap, Subhash C. [Thin Film Laboratory, Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016 (India); Granville, Simon [Callaghan Innovation, PO Box 31310, Lower Hutt 5040 (New Zealand); The MacDiarmid Institute for Advanced Materials and Nanotechnology, Lower Hutt (New Zealand)

    2014-01-28

    We present a remarkable enhancement by 300% of the exchange-bias field at room temperature, without affecting the coercivity value, via optimum magnetic annealing (250 °C/3 kOe) in ion-beam sputtered FeMn(30 nm)/NiFe(10 nm) bilayers. This specific behavior has been attributed to a higher degree of γ-FeMn(111) orientation that offers more interfacial FeMn moments to get pinned with the moments of the adjacent NiFe layer. Unlike the absence of training effect at room temperature, a pronounced training effect and an accompanying magnetization reversal asymmetry are evidenced upon field cooling below 50 K due to the presence of biaxial exchange induced anisotropy across the interdiffused FeMn/NiFe interface. The present findings not only have technological significance but also are of relevance to the understanding of interfacial spin disorder and frustration in these exchange-biased systems.

  8. Perspectives of voltage control for magnetic exchange bias in multiferroic heterostructures

    Science.gov (United States)

    Yang, Q.; Zhou, Z.; Sun, N. X.; Liu, M.

    2017-04-01

    Exchange bias, as an internal magnetic bias induced by a ferromagnetic-antiferromagnetic exchange coupling, is extremely important in many magnetic applications such as memories, sensors and other devices. Voltage control of exchange bias in multiferroics provides an energy-efficient way to achieve a rapidly 180° deterministic switching of magnetization, which has been considered as a key challenge in realizing next generation of fast, compact and ultra-low power magnetoelectric memories and sensors. Additionally, exchange bias can enhance dynamic magnetoelectric coupling strength in an external-field-free manner. In this paper, we provide a perspective on voltage control of exchange bias in different multiferroic heterostructures. Brief mechanization and related experiments are discussed as well as future trend and challenges that can be overcome by electrically tuning of exchange bias in state-of-the-art magnetoelectric devices.

  9. Effect of ball milling and thermal treatment on exchange bias and magnetocaloric properties of Ni{sub 48}Mn{sub 39.5}Sn{sub 10.5}Al{sub 2} ribbons

    Energy Technology Data Exchange (ETDEWEB)

    Czaja, P., E-mail: p.czaja@imim.pl [Institute of Metallurgy and Materials Science, Polish Academy of Sciences, 25 Reymonta Str., 30-059 Kraków (Poland); Przewoźnik, J. [AGH University of Science and Technology, Faculty of Physics and Applied Computer Science, Department of Solid State Physics, Al. Mickiewicza 30, 30-059 Krakow (Poland); Fitta, M.; Bałanda, M. [The Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, 152 Radzikowskiego Str., 31-342 Krakow (Poland); Chrobak, A. [A. Chelkowski Institute of Physics, University of Silesia, 4 Uniwersytecka Str., Katowice 40-007 (Poland); Kania, B. [Institute of Metallurgy and Materials Science, Polish Academy of Sciences, 25 Reymonta Str., 30-059 Kraków (Poland); Zackiewicz, P. [Institute of Non Ferrous Metals, 5 Sowinskiego Str., Gliwice 44-100 (Poland); Wójcik, A.; Szlezynger, M.; Maziarz, W. [Institute of Metallurgy and Materials Science, Polish Academy of Sciences, 25 Reymonta Str., 30-059 Kraków (Poland)

    2016-03-01

    The combined effect of ball milling and subsequent heat treatment on microstructure, magnetic, magnetocaloric and exchange bias properties of Ni{sub 48}Mn{sub 39.5}Sn{sub 10.5}Al{sub 2} ribbons is reported. The annealing treatment results in the increase of the critical martensitic transformation temperature. The magnetic entropy change ΔS{sub M} of the order of 7.9 and −2.3 J kg K{sup −1} for the annealed 50–32 µm powder fraction is determined. This is less than in the as melt spun ribbon but appears at a considerably higher temperature. At the same time EB is decreased due to annealing treatment. This decrease is attributed to the strengthened ferromagnetic exchange coupling due heat induced stress and structural relaxation. - Highlights: • Milling and annealing of Ni–Mn–Sn–Al ribbons increases the MT temperature. • ΔS{sub M} equal to 7.9 and −2.3 J kg K{sup −1} for the annealed 50–32 µm powder fraction. • Exchange Bias decreases due to annealing treatment. • Milling and annealing are useful for tuning of properties of Ni–Mn–Sn–Al alloys.

  10. Fundamentals for magnetic patterning by ion bombardment of exchange bias layer systems

    Energy Technology Data Exchange (ETDEWEB)

    Ehresmann, A.; Engel, D.; Weis, T. [Institute of Physics and Centre for Interdisciplinary Nanostructure Science and Technology (CINSaT), Kassel University, Heinrich-Plett-Str. 40, 34132 Kassel (Germany); Schindler, A. [Institut fuer Festkoerperforschung, Forschungszentrum Juelich GmbH, 52425 Juelich (Germany); Junk, D. [Technische Physik, Universitaet des Saarlandes, P.O. Box 151150, 66041 Saarbruecken (Germany); Schmalhorst, J.; Hoeink, V.; Sacher, M.D.; Reiss, G. [Faculty of Physics, Bielefeld University, P.O. Box 100131, 33501 Bielefeld (Germany)

    2006-01-01

    In the present paper we investigate whether the ion bombardment induced magnetic modifications in exchange biased bilayers are stable in time, whether the direction of the exchange bias can be set to any arbitrary (in-plane) direction by the ion bombardment and whether the exchange bias field can be changed in successive bombardment steps. These three fundamental characteristics are prerequisites for ion bombardment used for an efficient, practical, and stable magnetic patterning of exchange biased layer systems. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  11. Antisite-disorder driven large exchange bias effect in phase separated La{sub 1.5}Ca{sub 0.5}CoMnO{sub 6} double perovskite

    Energy Technology Data Exchange (ETDEWEB)

    Sahoo, R.C.; Paladhi, D. [Department of Physics, Indian Institute of Technology Kharagpur, West Bengal 721302 (India); Dasgupta, Papri; Poddar, A. [Experimental Condensed Matter Physics Division, Saha Institute of Nuclear Physics, West Bengal (India); Singh, Ripandeep; Das, A. [Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Nath, T.K., E-mail: tnath@phy.iitkgp.ernet.in [Department of Physics, Indian Institute of Technology Kharagpur, West Bengal 721302 (India)

    2017-04-15

    Investigations of structural and magnetic properties of polycrystalline hole doped double perovskite La{sub 1.5}Ca{sub 0.5}CoMnO{sub 6} has clearly revealed the existence of structural antisite-disorder (either, Co–O–Co or Mn–O–Mn) in the system. The ordering of Co{sup 2+} and Mn{sup 4+} gives rise to a ferromagnetic transition around 157 K. A spin-canted antiferromagnetic transition is found in this material at T{sub CAFM} ~9 K. The effect of antisite-disorder in the double perovskite structure is most likely the prime reason for antiferromagnetic interaction. The temperature dependent inverse susceptibility exhibits Curie-Weiss like behaviour and it yields an effective paramagnetic moment of 6.49 μ{sub B}. At very low temperature (Texchange bias (EB) field of H{sub EB} ~5.5 kOe and can be tuned by the cooling field. The presence of zero-field cooled spontaneous EB effect (P-type and N-type) is confirmed to be not an experimental artefact - an inherent property of this double perovskite material. A phenomenological model has been proposed to explain the exchange coupling between the ferromagnetic and canted-antiferromagnetic interfaces of antisite-disordered La{sub 1.5}Ca{sub 0.5}CoMnO{sub 6} mainly on the basis of uncompensated interface spins. - Highlights: • Large exchange bias (EB) effect has been observed in 25% Ca doped La{sub 2}CoMnO{sub 6} antisite-disordered system. • Neutron powder diffraction analysis clearly suggested canted antiferromagnetic spin ordering at low temperature in our phase separated system. • A phenomenological model has been proposed for experimental results. • The results may be useful to acquire enough information about exchange biased interfaces for various magnetic device applications.

  12. Exchange-bias effect at La0.75Sr0.25MnO3/LaNiO3 interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Rojas Sánchez, J. C. [Centro Atomico Bariloche-CNEA, Rio Negro (Argentina); National Scientific and Technical Research Council, Buenos Aires (Argentina); Nelson-Cheeseman, B. [Univ. of California, Berkeley, CA (United States); Granada, M. [Centro Atomico Bariloche-CNEA, Rio Negro (Argentina); National Scientific and Technical Research Council, Buenos Aires (Argentina); Arenholz, E. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Advanced Light Source (ALS); Steren, L. B. [National Scientific and Technical Research Council, Buenos Aires (Argentina); Centro Atomico Constituyentes-CNEA, San Martin (Argentina)

    2012-03-26

    In this paper, we show that ferromagnetic/paramagnetic La0.75Sr0.25MnO3/LaNiO3 multilayers present an unexpected magnetic exchange-bias effect (EBE), observed in field-cooled magnetization loops. The exchange-bias field and the enhancement of the coercivity vanish around 50 K. We demonstrate that the oxidation state of the Ni and Mn cations changes from Mn3+-Ni3+ to Mn4+-Ni2+ in the layers close to the interface probed by x-ray absorption spectroscopy measurements. The variation of the valence states is accompanied by a change in the magnetic behavior of the cations at the La0.75Sr0.25MnO3/LaNiO3 interface, possibly giving rise to the formation of magnetic or magnetically frustrated regions that may pin the ferromagnetic a0.75Sr0.25MnO3 layers and explain the EBE.

  13. Exchange bias coupling in NiO/Ni bilayer tubular nanostructures synthetized by electrodeposition and thermal oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Yu, T., E-mail: work_tian@scu.edu.cn [College of Physical Science and Technology, Sichuan University, Chengdu 610064 (China); Zhang, Z.W.; Xu, Y.H. [College of Physical Science and Technology, Sichuan University, Chengdu 610064 (China); Liu, Y. [Analytical & Testing Center, Sichuan University, Chengdu 610064 (China); Li, W.J. [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing 100190 (China); Nie, Y.; Zhang, X. [College of Physical Science and Technology, Sichuan University, Chengdu 610064 (China); Xiang, G., E-mail: gxiang@scu.edu.cn [College of Physical Science and Technology, Sichuan University, Chengdu 610064 (China)

    2017-05-01

    In this paper, we reported the synthesis of NiO/Ni bilayer nanotubes by electrodeposition and thermal oxidation using anodic aluminum oxide templates. The morphology, structure, chemical composition and magnetic properties, especially magnetic exchange bias induced by subsequent magnetic field cooling, in this one-dimensional antiferromagnetic/ferromagnetic hybrid system were investigated. It was found that the effect of the annealing temperature, which mainly dominated the thickness of the NiO layer, and the annealing time, which mainly dominated the grain size of the NiO, on the exchange bias field showed competitive relationship. The optimized exchange bias field was achieved by the combination of the shorter annealing time and higher annealing temperature. - Highlights: • NiO-Ni bilayer tubular nanotubes were fabricated by electrodeposition and thermal oxidation. • The exchange bias effect in NiO-Ni nanotubes was induced by magnetic field cooling. • The competitive effect of annealing temperature and annealing time on the exchange bias coupling was analyzed.

  14. Enhanced exchange bias fields for CoO/Co bilayers: influence of antiferromagnetic grains and mechanisms

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Cheng-Hsun-Tony; Chang, Shin-Chen [Department of Physics, National Taiwan Normal University, Taipei 116, Taiwan (China); Tsay, Jyh-Shen, E-mail: jstsay@phy.ntnu.edu.tw [Department of Physics, National Taiwan Normal University, Taipei 116, Taiwan (China); Yao, Yeong-Der [Institute of Physics, Academia Sinica, Nankang, Taipei 11529, Taiwan (China)

    2017-05-31

    Highlights: • An antiferromagnetic grain model on exchange bias phenomena is proposed. • Grain size and grain density are considered. • For smaller grain size, the dependence of t{sub CoO} on T{sub B} showed a less pronounced variation. • An increased grain density is responsible for the enhancement in the exchange bias fields. - Abstract: The emergence and optimization of devices that can be applied to spintronics have attracted considerable interest, and both experimental and theoretical approaches have been used in studies of exchange bias phenomena. A survey of the literature indicates that great efforts have been devoted to improving exchange bias fields, while only limited attempts have been made to control the temperature dependence of exchange bias. In this study, the influence of antiferromagnetic grains on exchange bias phenomena in CoO/Co bilayers on a semiconductor surface was investigated. Based on an antiferromagnetic grain model, a correlation between grain size, grain density, blocking temperature, and the exchange bias field was established. For crystallites with a smaller median diameter, the dependence of the thickness of the CoO layer on blocking temperature showed a less pronounced variation. This is due to the larger thermal agitation of the atomic spin moments in the grain, which causes a weaker exchange coupling between atomic spin moments. The enhanced density of antiferromagnetic/ferromagnetic pinning sites resulting from an increased grain density is responsible for the enhancement in the exchange bias fields. The results reported herein provide insights into our knowledge related to controlling the temperature dependence of exchange bias and related mechanisms.

  15. Evidence of spin-glass like ordering and exchange bias effect in antisite-disordered nanometric La1.5Ca0.5CoMnO6 double perovskite

    Science.gov (United States)

    Sahoo, R. C.; Paladhi, D.; Nath, T. K.

    2017-08-01

    Single-phase polycrystalline La1.5Ca0.5CoMnO6 double perovskite nanoparticles (∼25 nm) have been synthesized by chemical sol-gel method. We report here the structural, magnetic and transport properties using X-ray diffraction, dc magnetization, ac susceptibility, exchange bias and dc resistivity measurements. The Rietveld refinement of X-ray diffraction pattern reveals that the La1.5Ca0.5CoMnO6 (LCCMO) system crystallizes in orthorhombic structure with pbnm space group. Mn and Co ions are not completely ordered on the B sites due to the presence of about 30% antisite-disorder in the system. The ordering of Co2+ and Mn4+ gives rise to the ferromagnetism below 145 K. A spin glass like ground state has also been observed near 37.6(4) K, arising mainly due to the presence of competing magnetic interactions and antisite-disorder in the LCCMO nanoparticles. The frequency dependence peak shift of the Ac-susceptibility peak in the glassy state follows the critical slowing down model. The observed memory effect in ac susceptibility data reveals the existence of interacting clusters in a competing magnetic interactions state. The presence of noticeable exchange bias effect can be best explained on the basis of uncompensated interface (ferromagnetic/spin-glass) spins of antisite-disordered LCCMO system. This anti-site disordered nanocompound exhibits semiconducting behavior with variable range hopping kind of electronic conduction mechanism in the temperature range of 200-300 K. We have also observed large negative magnetoresistance (-30% at 100 K and 60 kOe) mainly due to the spin-polarized transport across the grain boundaries.

  16. Modification of the saturation magnetization of exchange bias thin film systems upon light-ion bombardment.

    Science.gov (United States)

    Huckfeldt, Henning; Gaul, Alexander; David Müglich, Nicolas; Holzinger, Dennis; Nissen, Dennis; Albrecht, Manfred; Emmrich, Daniel; Beyer, André; Gölzhäuser, Armin; Ehresmann, Arno

    2017-03-29

    The magnetic modification of exchange bias materials by 'ion bombardment induced magnetic patterning' has been established more than a decade ago. To understand these experimental findings several theoretical models were introduced. Few investigations, however, did focus on magnetic property modifications caused by effects of ion bombardment in the ferromagnetic layer. In the present study, the structural changes occurring under ion bombardment were investigated by Monte-Carlo simulations and in experiments. A strong reduction of the saturation magnetization scaling linearly with increasing ion doses is observed and our findings suggest that it is correlated to the swelling of the layer material based on helium implantation and vacancy creation.

  17. Reversal magnetization, spin reorientation, and exchange bias in YCr O3 doped with praseodymium

    Science.gov (United States)

    Durán, A.; Escamilla, R.; Escudero, R.; Morales, F.; Verdín, E.

    2018-01-01

    Crystal structure, thermal properties, and magnetic properties were studied systematically in Y1 -xP rxCr O3 with 0.0 ≤x ≤0.3 compositions. Magnetic susceptibility and specific-heat measurements show an increase in the antiferromagnetic transition temperature (TN) as Pr is substituted in the Y sites and notable magnetic features are observed below TN. Strong coupling between magnetic and crystalline parameters is observed in a small range of Pr compositions. A small perturbation in the lattice parameters by a Pr ion is sufficient to induce a spin-reorientation transition followed by magnetization reversal to finally induce the exchange-bias effect. The spin-reorientation temperature (TSR) is increased from 35 to 149 K for 0.025 ≤x ≤0.1 compositions. It is found that the Cr spin sublattice rotates continuously from TSR to a new spin configuration at lower temperature. In addition, magnetization reversal is observed at T*˜35 K for x =0.05 up to T*˜63 K for x =0.20 composition. The M -H curves show a negative exchange-bias effect induced by Pr ions, which are observed below 100 K and are more intense at 5 K. At 10 K, the magnetic contribution of the specific heat as well as the ZFC magnetization show the rise of a peak with increasing Pr content. The magnetic anomaly could be associated with the freezing of the Pr magnetic moment randomly distributed at the 4 c crystallographic site. A clear correspondence between spin reorientation, magnetization reversal, and exchange-bias anisotropy with the tilting and octahedral distortion is also discussed.

  18. Antiferromagnetic exchange bias of a ferromagnetic semiconductor by a ferromagnetic metal

    Energy Technology Data Exchange (ETDEWEB)

    Olejnik, K.; Wadley, P.; Haigh, J.; Edmonds, K. W.; Campion, R. P.; Rushforth, A. W.; Gallagher, B. L.; Foxon, C. T.; Jungwirth, T.; Wunderlich, J.; Dhesi, S. S.; Cavill, S.; van der Laan, G.; Arenholz, E.

    2009-11-05

    We demonstrate an exchange bias in (Ga,Mn)As induced by antiferromagnetic coupling to a thin overlayer of Fe. Bias fields of up to 240 Oe are observed. Using element-specific x-ray magnetic circular dichroism measurements, we distinguish an interface layer that is strongly pinned antiferromagnetically to the Fe. The interface layer remains polarized at room temperature.

  19. Nanoscale Control of Exchange Bias with BiFeO3 Thin Films

    NARCIS (Netherlands)

    Martin, Lane W.; Chu, Ying-Hao; Holcomb, Mikel B.; Huijben, Mark; Yu, Pu; Han, Shu-Jen; Lee, Donkoun; Wang, Shan X.; Ramesh, R.

    2008-01-01

    We demonstrate a direct correlation between the domain structure of multiferroic BiFeO3 thin films and exchange bias of Co0.9Fe0.1/BiFeO3 heterostructures. Two distinct types of interactions − an enhancement of the coercive field (exchange enhancement) and an enhancement of the coercive field

  20. NiO/Fe(001): Magnetic anisotropy, exchange bias, and interface structure

    Science.gov (United States)

    Młyńczak, E.; Luches, P.; Valeri, S.; Korecki, J.

    2013-06-01

    The magnetic and structural properties of NiO/Fe epitaxial bilayers grown on MgO(001) were studied using magnetooptic Kerr effect (MOKE) and conversion electron Mössbauer spectroscopy (CEMS). The bilayers were prepared under ultra high vacuum conditions using molecular beam epitaxy with oblique deposition. Two systems were compared: one showing the exchange bias (100ML-NiO/24ML-Fe), ML stands for a monolayer, and another where the exchange bias was not observed (50ML-NiO/50ML-Fe). For both, the magnetic anisotropy was found to be complex, yet dominated by the growth-induced uniaxial anisotropy. The training effect was observed for the 100ML-NiO/24ML-Fe system and quantitatively described using the spin glass model. The composition and magnetic state of the interfacial Fe layers were studied using 57Fe-CEMS. An iron oxide phase (Fe3+4Fe2+1O7), as thick as 31 Å, was identified at the NiO/Fe interface in the as-deposited samples. The ferrimagnetic nature of the interfacial iron oxide film explains the complex magnetic anisotropy observed in the samples.

  1. Cyanide single-molecule magnets exhibiting solvent dependent reversible "on" and "off" exchange bias behavior

    DEFF Research Database (Denmark)

    Pinkowicz, Dawid; Southerland, Heather I.; Avendaño, Carolina

    2015-01-01

    Co/Os analogue (PPN){[Mn(III)(salphen)(MeOH)]2[Co(III)0.92Os(III)0.08(CN)6]}·7MeOH were undertaken. It was found that all compounds exhibit switchable single-molecule magnet (SMM) and exchange-bias behavior depending on the interstitial methanol content. The pristine (PPN){[Mn(salphen)(MeOH)]2[Os......(CN)6]}·7MeOH (Mn2Os·7MeOH) behaves as an SMM with an effective barrier for the magnetization reversal, (Ueff/kB), of 17.1 K. Upon desolvation, Mn2Os exhibits an increase of Ueff/kB to 42.0 K and an opening of the hysteresis loop observable at 1.8 K. Mn2Os·7MeOH shows also exchange-bias behavior...... with magnetic hysteresis loops exhibiting a shift in the quantum tunneling to 0.25 T from zero-field. The Fe(III) and Ru(III) analogues were prepared as reference compounds for assessing the effect of the 5d versus 4d and 3d metal ions on the SMM properties. These compounds are also SMMs and exhibit similar...

  2. Tuning the ferromagnetic-antiferromagnetic interfaces of granular Co-CoO exchange bias systems by annealing

    Energy Technology Data Exchange (ETDEWEB)

    Menéndez, E., E-mail: Enric.MenendezDalmau@fys.kuleuven.be; Modarresi, H.; Pereira, L. M. C.; Temst, K.; Vantomme, A. [Instituut voor Kern- en Stralingsfysica, KU Leuven, Celestijnenlaan 200 D, BE-3001 Leuven (Belgium); Dias, T. [Instituut voor Kern- en Stralingsfysica, KU Leuven, Celestijnenlaan 200 D, BE-3001 Leuven (Belgium); Instituto de Física, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, 91501-970 Rio Grande do Sul (Brazil); Geshev, J. [Instituto de Física, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, 91501-970 Rio Grande do Sul (Brazil)

    2014-04-07

    The low-temperature magnetic behavior of granular Co-CoO exchange bias systems, prepared by oxygen ion implantation in Co thin films and subsequent annealing, is addressed. The thermal activation effects lead to an O migration which results in virtually pure Co areas embedded in a structurally relaxed and nearly stoichiometric CoO phase. This yields decreased training and exchange bias shifts, while the blocking temperature significantly increases, coming close to the Néel temperature of bulk CoO for samples implanted to a fluence above 1 × 10{sup 17} ions/cm{sup 2} (15% O). The dependence of the exchange bias shift on the pristine O-implanted content is analogous to that of the antiferromagnetic thickness in most ferromagnetic/antiferromagnetic systems (i.e., an increase in the exchange bias shift up to a maximum followed by a decrease until a steady state is reached), suggesting that, after annealing, the enriched Co areas might be rather similar in size for samples implanted above 1 × 10{sup 17} ions/cm{sup 2}, whereas the corresponding CoO counterparts become enlarged with pristine O content (i.e., effect of the antiferromagnet size). This study demonstrates that the magnetic properties of granular Co-CoO systems can be tailored by controllably modifying the local microstructure through annealing treatments.

  3. Temperature- and magnetic field-dependence of exchange bias in SrCoO2.29 ceramics

    Directory of Open Access Journals (Sweden)

    L. Xie

    2017-01-01

    Full Text Available A cation’s oxidation state in a transition metal oxide may significantly change its physical and chemical properties. In this work, magnetic properties of both cubic SrCoO2.29 and hexagonal SrCoO2.50 ceramics, annealed following a selected yet simple process, have been studied. The SrCoO2.50 ceramics annealed in air displays an unusual paramagnetic property, and the SrCoO2.29 quenched into water shows a short-range ferromagnetic coupling in the antiferromagnetic background. Exchange coupling at the ferromagnetic/antiferromagnetic interfaces brings out an obvious exchange bias effect in the SrCoO2.29 sample. Due to its complicated magnetic states, the exchange bias effect presents strong temperature and cooling field dependences.

  4. Magnetic compensation-induced sign reversal of exchange bias in a multi-glass perovskite SmFeO3

    Science.gov (United States)

    De, Chandan; Nayak, Ajaya K.; Nicklas, Michael; Sundaresan, A.

    2017-10-01

    We report an unusual sign reversal of exchange bias (EB) across a magnetic compensation point in an orthorhombic perovskite SmFeO3. A conventional negative EB with a positive vertical magnetization shift is observed below a cluster-glass freezing temperature (Tg ˜ 150 K). Upon further lowering of the temperature, the EB disappears at the magnetic compensation point before reversing its sign to a positive exchange bias below 4 K. The EB effect originates from an interfacial exchange interaction within a cluster glass phase, whereas its sign reversal arises from the reversal of the direction of the net magnetic moment as a result of dominance of Sm3+ over Fe3+ below the compensation temperature. The existence of a multi-glass state is demonstrated by ac-susceptibility and electrical permittivity measurements. A phenomenological model is presented to understand the EB effect and its sign reversal across the compensation point.

  5. Interface-induced spontaneous positive and conventional negative exchange bias effects in bilayer La^sub 0.7^Sr^sub 0.3^MnO3/Eu^sub 0.45^Sr^sub 0.55^MnO3 heterostructures

    National Research Council Canada - National Science Library

    J Krishna Murthy; P S Anil Kumar

    2017-01-01

    (ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image) We report zero-field-cooled spontaneous-positive and field-cooled conventional-negative exchange bias effects in epitaxial bilayer composed of La0.7Sr0.3MnO3 (LSMO...

  6. Evidence of spin-glass like ordering and exchange bias effect in antisite-disordered nanometric La{sub 1.5}Ca{sub 0.5}CoMnO{sub 6} double perovskite

    Energy Technology Data Exchange (ETDEWEB)

    Sahoo, R.C.; Paladhi, D.; Nath, T.K., E-mail: tnath@phy.iitkgp.ernet.in

    2017-08-15

    Highlights: • SG has been observed due to antisite disorder and different magnetic interactions. • The observed EB can be best explained on the basis of uncompensated interface spins. • −30% MR has been observed due to the spin-polarized transport at grain boundaries. - Abstract: Single-phase polycrystalline La{sub 1.5}Ca{sub 0.5}CoMnO{sub 6} double perovskite nanoparticles (∼25 nm) have been synthesized by chemical sol-gel method. We report here the structural, magnetic and transport properties using X-ray diffraction, dc magnetization, ac susceptibility, exchange bias and dc resistivity measurements. The Rietveld refinement of X-ray diffraction pattern reveals that the La{sub 1.5}Ca{sub 0.5}CoMnO{sub 6} (LCCMO) system crystallizes in orthorhombic structure with pbnm space group. Mn and Co ions are not completely ordered on the B sites due to the presence of about 30% antisite-disorder in the system. The ordering of Co{sup 2+} and Mn{sup 4+} gives rise to the ferromagnetism below 145 K. A spin glass like ground state has also been observed near 37.6(4) K, arising mainly due to the presence of competing magnetic interactions and antisite-disorder in the LCCMO nanoparticles. The frequency dependence peak shift of the Ac-susceptibility peak in the glassy state follows the critical slowing down model. The observed memory effect in ac susceptibility data reveals the existence of interacting clusters in a competing magnetic interactions state. The presence of noticeable exchange bias effect can be best explained on the basis of uncompensated interface (ferromagnetic/spin-glass) spins of antisite-disordered LCCMO system. This anti-site disordered nanocompound exhibits semiconducting behavior with variable range hopping kind of electronic conduction mechanism in the temperature range of 200–300 K. We have also observed large negative magnetoresistance (−30% at 100 K and 60 kOe) mainly due to the spin-polarized transport across the grain boundaries.

  7. Giant exchange bias and its angular dependence in Co/CoO core-shell nanowire assemblies

    Energy Technology Data Exchange (ETDEWEB)

    Gandha, Kinjal; Chaudhary, Rakesh P.; Mohapatra, Jeotikanta; Koymen, Ali R.; Liu, J. Ping, E-mail: pliu@uta.edu

    2017-07-12

    The exchange-bias field (H{sub EB}) and its angular dependence are systematically investigated in Co/CoO core-shell nanowire assemblies (∼15 nm in diameter and ∼200 nm in length) consisting of single-crystalline Co core and polycrystalline CoO shell. Giant exchange-bias field (H{sub EB}) up to 2.4 kOe is observed below a blocking temperature (T{sub EB} ∼150 K) in the aligned Co/CoO nanowire assemblies. It is also found that there is an angular dependence between the H{sub EB} and the applied magnetization direction. The H{sub EB} showed a peak at 30° between the applied field and the nanowire aligned direction, which may be attributed to the noncollinear spin orientations at the interface between the ferromagnetic core and the antiferromagnetic shell. This behavior is quantitatively supported by an analytical calculation based on Stoner–Wohlfarth model. This study underlines the importance of the competing magnetic anisotropies at the interface of Co/CoO core-shell nanowires. - Highlights: • Giant exchange bias is observed in oriented Co/CoO core-shell nanowire assemblies. • Study of angular and temperature dependence of the exchange bias effect. • Competing magnetic anisotropies at the interface of Co/CoO core-shell nanowires. • Effect of misaligned spins in FM/AFM interface on angular dependence of exchange bias. • We explain the analytical model that accounts for experimental results.

  8. A separation of antiferromagnetic spin motion modes in the training effect of exchange biased Co/CoO film with in-plane anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Wu, R. [State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871 (China); Department of Materials Science and Metallurgy, University of Cambridge, Cambridge CB3 0FS (United Kingdom); Yun, C.; Ding, S. L.; Wen, X.; Liu, S. Q.; Wang, C. S.; Han, J. Z.; Du, H. L. [State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871 (China); Yang, J. B., E-mail: jbyang@pku.edu.cn [State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871 (China); Collaborative Innovation Center of Quantum Matter, Beijing 100871 (China)

    2016-08-07

    The motion of antiferromagnetic interfacial spins is investigated through the temperature evolution of training effect in a Co/CoO film with in-plane biaxial anisotropy. Significant differences in the training effect and its temperature dependence are observed in the magnetic easy axis and hard axis (HA) and ascribed to the different motion modes of antiferromagnetic interfacial spins, the collective spin cluster rotation (CSR) and the single spin reversal (SSR), caused by different magnetization reversal modes of ferromagnetic layer. These motion modes of antiferromagnetic spins are successfully separated using a combination of an exponential function and a classic n{sup −1/2} function. A larger CSR to SSR ratio and a shorter lifetime of CSR found in the HA indicates that the domain rotation in the ferromagnetic layer tends to activate and accelerate a CSR mode in the antiferromagnetic spins.

  9. Piezostrain tuning exchange bias mediated by electric field in composite heterostructure

    Science.gov (United States)

    Li, Pingping; Zhou, Cai; Wang, Wenqiang; Cao, Cuimei; Yao, Jinli; Jiang, Changjun

    2017-12-01

    The change of unidirectional anisotropy and uniaxial anisotropy field turned by piezostrain in an IrMn/Co/Ta/Pb(Mg1/3Nb2/3)O3–PbTiO3 heterostructure with an exchange bias was investigated by ferromagnetic resonance at room temperature. The curve of the magnetic resonance field versus the electric fields showed an asymmetric butterfly-like behavior, which was consistent with the result of strain versus electric field curves. This butterfly-like behavior can be attributed to the piezostrain effect. Specifically, the non-volatile uniaxial anisotropy field and unidirectional anisotropy field behavior under different electric fields induced by piezostrain effect were obtained. Our result is crucial for further application of future multiferroic devices.

  10. Nanometer-size magnetic domains and coherent magnetization reversal in a giant exchange-bias system

    DEFF Research Database (Denmark)

    Dufour, C.; Fitzsimmons, M. R.; Borchers, J. A.

    2011-01-01

    The role of magnetic domains and domain walls in exchange bias has stimulated much contemporary deliberation. Here we present compelling evidence obtained with small-angle scattering of unpolarized- and polarized-neutron beams that magnetization reversal occurs via formation of 10-100s nm......-sized magnetic domains in an exchange-biased DyFe2/YFe2 superlattice. The reversal mechanism is observed to involve rotation of magnetization in and out of the sample plane. Remarkably, the domains are arranged in a quasiperiodic manner in the plane of the sample. The length scale of domain formation is similar...

  11. Direct observation of exchange bias related uncompensated spins at the CoO/Cu interface.

    Science.gov (United States)

    Valev, V K; Gruyters, M; Kirilyuk, A; Rasing, Th

    2006-02-17

    Magnetization-induced optical second harmonic generation (MSHG) from the exchange-biased CoO/Cu-(X)/Fe multilayer shows the presence of pinned uncompensated spins at the CoO/Cu interface. For increasing Cu spacer thickness, the exchange bias measured via the hysteresis loop shift diminishes and disappears at X = 3.5 nm, while the MSHG signal still shows a strong magnetic contribution from the CoO interface. This indicates that the magnetic interaction between Fe and CoO layers is sufficiently strong to induce order in the antiferromagnetic layer even at a spacer thickness for which there is no observable hysteresis loop shift.

  12. Observation of enhanced exchange bias behaviour in NiCoMnSb Heusler alloys

    Energy Technology Data Exchange (ETDEWEB)

    Nayak, Ajaya K; Suresh, K G [Magnetic Materials Laboratory, Department of Physics, Indian Institute of Technology Bombay, Mumbai-400076 (India); Nigam, A K [Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai-400005 (India)], E-mail: suresh@phy.iitb.ac.in

    2009-06-07

    We report the observation of large exchange bias (EB) in Ni{sub 50-x}Co{sub x}Mn{sub 38}Sb{sub 12} Heusler alloys with x = 0, 2, 3, 4, 5, which is attributed to the coexistence of ferromagnetic (FM) and antiferromagnetic (AFM) phases in the martensitic phase. The phase coexistence is possibly due to the supercooling of the high temperature FM phase and the predominant AFM component in the martensitic phase. The presence of EB is well supported by the observation of the training effect. The EB field increases with Co concentration. The maximum value of 480 Oe at T = 3 K is observed in x = 5 after field cooling in 50 kOe, which is almost double the highest value reported so far in any Heusler alloy system. Increase in the AFM coupling after Co substitution is found to be responsible for the increase in the EB.

  13. Ultrathin Limit of Exchange Bias Coupling at Oxide Multiferroic/Ferromagnetic Interfaces

    NARCIS (Netherlands)

    Huijben, Mark; Yu, P.; Martin, L.W.; Molegraaf, Hajo; Chu, Y.H.; Holcomb, M.B.; Balke, N.; Rijnders, Augustinus J.H.M.; Ramesh, R.

    2013-01-01

    Exchange bias coupling at the multiferroic- ferromagnetic interface in BiFeO3/La0.7Sr0.3MnO3 heterostructures exhibits a critical thickness for ultrathin BiFeO3 layers of 5 unit cells (2 nm). Linear dichroism measurements demonstrate the dependence on the BiFeO3 layer thickness with a strong

  14. Exchange bias and magnetic behaviour of iron nanoclusters prepared by the gas aggregation technique

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez-Marcos, J., E-mail: sanchej@icmm.csic.es [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientificas, Cantoblanco, 28049 Madrid (Spain); Laguna-Marco, M.A.; Martinez-Morillas, R. [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientificas, Cantoblanco, 28049 Madrid (Spain); Jimenez-Villacorta, F. [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientificas, Cantoblanco, 28049 Madrid (Spain); SpLine Spanish CRG Beamline at the European Synchrotron Radiation Facilities, ESRF-BP 220-38043 Grenoble Cedex (France); Cespedes, E. [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientificas, Cantoblanco, 28049 Madrid (Spain); Menendez, N. [Dep. Quimica-Fisica Aplicada, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Prieto, C. [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientificas, Cantoblanco, 28049 Madrid (Spain)

    2012-09-25

    Highlights: Black-Right-Pointing-Pointer Gas aggregation phase technique allows obtaining {alpha}-Fe{sub 2}O{sub 3} nanoparticles. Black-Right-Pointing-Pointer We have reported exchange bias up to 3250 Oe at 2 K. Black-Right-Pointing-Pointer Exchange bias may be tuned by different stoichiometry of {alpha}-Fe{sub 2}O{sub 3} nanoparticles. - Abstract: Iron nanoclusters have been deposited by the gas-phase aggregation technique to form multilayered structures with outstanding exchange-bias (H{sub E}) values up to H{sub E} = 3300 Oe at low temperatures. In order to explain the observed magnetic properties, composition and crystallographic phase have been determined by X-ray absorption spectroscopy. A metal-oxide core-shell arrangement has to be discarded to explain the large obtained values of H{sub E} since structural results show nanoclusters formed by the antiferromagnetic {alpha}-Fe{sub 2}O{sub 3} oxide. Moreover, nanoparticles of few nanometers formed by substoichiometric {alpha}-Fe{sub 2}O{sub 3} explain the observed weak ferromagnetism and let to understand the origin of large exchange bias by the interaction between different spin sublattice configurations provided by the low iron coordination at surface.

  15. Training-induced inversion of spontaneous exchange bias field on La{sub 1.5}Ca{sub 0.5}CoMnO{sub 6}

    Energy Technology Data Exchange (ETDEWEB)

    Bufaiçal, L., E-mail: lbufaical@ufg.br [Instituto de Física, Universidade Federal de Goiás, 74001-970 Goiânia, GO (Brazil); Finkler, R.; Coutrim, L.T. [Instituto de Física, Universidade Federal de Goiás, 74001-970 Goiânia, GO (Brazil); Pagliuso, P.G. [Instituto de Física “Gleb Wataghin”, UNICAMP, 13083-859 Campinas, SP (Brazil); Grossi, C.; Stavale, F.; Baggio-Saitovitch, E.; Bittar, E.M. [Centro Brasileiro de Pesquisas Físicas, Rua Dr. Xavier Sigaud 150, 22290-180 Rio de Janeiro, RJ (Brazil)

    2017-07-01

    Highlights: • La{sub 1.5}Ca{sub 0.5}CoMnO{sub 6} exhibits spontaneous exchange bias effect at low temperature. • For successive hysteresis cycles it inverts the shift sign from negative to positive. • For a field cooled hysteresis cycle, the exchange bias effect greatly enhances. • Our results are compared to those of the analogue compound La{sub 1.5}Sr{sub 0.5}CoMnO{sub 6}. - Abstract: In this work we report the synthesis and structural, electronic and magnetic properties of La{sub 1.5}Ca{sub 0.5}CoMnO{sub 6} double-perovskite. This is a re-entrant spin cluster material which exhibits a non-negligible negative exchange bias effect when it is cooled in zero magnetic field from an unmagnetized state down to low temperature. X-ray powder diffraction, X-ray photoelectron spectroscopy and magnetometry results indicate mixed valence state at Co site, leading to competing magnetic phases and uncompensated spins at the magnetic interfaces. We compare the results for this Ca-doped material with those reported for the resemblant compound La{sub 1.5}Sr{sub 0.5}CoMnO{sub 6}, and discuss the much smaller spontaneous exchange bias effect observed for the former in terms of its structural and magnetic particularities. For La{sub 1.5}Ca{sub 0.5}CoMnO{sub 6}, when successive magnetization loops are carried, the spontaneous exchange bias field inverts its sign from negative to positive from the first to the second measurement. We discuss this behavior based on the disorder at the magnetic interfaces, related to the presence of a glassy phase. This compound also exhibits a large conventional exchange bias, for which there is no sign inversion of the exchange bias field for consecutive cycles.

  16. Defect induced enhancement of exchange bias by swift heavy ion irradiation in zinc ferrite–FeNiMoB alloy based bilayer films

    Energy Technology Data Exchange (ETDEWEB)

    Lisha, R. [Cochin University of Science and Technology, Cochin 682022, Kerala (India); Hysen, T. [Christian College, Chengannur 689122, Kerala (India); Geetha, P.; Aravind, P.B. [Cochin University of Science and Technology, Cochin 682022, Kerala (India); Shareef, M.; Shamlath, A. [Central University of Kerala, Kasargod 671316, Kerala (India); Ojha, Sunil [Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067 (India); Ramanujan, R.V. [School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798 (Singapore); Anantharaman, M.R., E-mail: mraiyer@yahoo.com [Cochin University of Science and Technology, Cochin 682022, Kerala (India)

    2015-10-01

    Highlights: • Bilayer films of FeNiMoB–zinc ferrite exhibiting exchange bias was prepared by RF sputtering. • The films were irradiated using 100 MeV Ag ions. • At a particular fluence of 1 × 10{sup 12} ions/cm{sup 2} high exchange field of 210 Oe obtained. • At higher fluences the exchange bias is decreased. - Abstract: Exchange biased systems consisting of ferromagnetic (FM)–antiferromagnetic (AFM) interfaces are increasingly being investigated because of their application potential in spin valves and tunnel junctions. In bilayer systems, ion irradiation is capable of modifying the interface and thereby offers unique opportunities to tailor exchange field. In the present study, irradiation with 100 MeV Ag{sup 8+} ions is utilized to alter the exchange bias field in zinc ferrite–FeNiMoB bilayer system. The thin films which were deposited by RF sputtering technique and annealed at 600 °C were irradiated at various fluences. Structural and magnetic studies were carried out by using Glancing X Ray Diffractometer (GXRD) and Superconducting Quantum Interference Device Vibrating Sample Magnetometer (SQUID VSM) respectively. It was observed that the as deposited films exhibited exchange bias and on ion irradiation, bias field could be enhanced at certain fluences. The enhancement in bias field is attributed to defects created in the antiferromagnet as a result of ion irradiation. The experimental result is fitted in accordance with the diluted antiferromagnet model. Coercivity was also found to vary with ion fluence. Ion fluence was thus effectively used to enhance bias field as well as coercivity in the bilayer consisting of zinc ferrite–FeNiMoB.

  17. Thermal stability of magnetic nanostructures in ion-bombardment-modified exchange-bias systems

    Science.gov (United States)

    Höink, V.; Sacher, M. D.; Schmalhorst, J.; Reiss, G.; Engel, D.; Weis, T.; Ehresmann, A.

    2006-06-01

    In magnetic bilayer systems consisting of a ferromagnet and an antiferromagnet the strength and direction of the exchange bias coupling can be set by ion bombardment in an external magnetic field. Magnetic nanostructures with a laterally varying exchange bias direction can be produced by local ion bombardment (ion bombardment induced magnetic patterning). We have investigated the thermal stability of these magnetic nanostructures by in situ x-ray photoemission electron microscopy while heating the samples above their blocking temperature. The investigations have been done at a 10.4μm×10.4μm large checkered pattern with a minimum size of the magnetic patterns of 800nm×800nm on a field cooled MnIr/CoFe stack and a pattern with 1.6μm wide lines with a periodicity of 5μm on an as-prepared MnIr/Co stack. The temperature dependence of the magnetization pattern can be explained by the temperature dependence of the exchange bias interaction, the exchange interaction energy, and the stray field energy. No substantial change of the thermal stability of magnetic patterns in remanence by the ion bombardment was found.

  18. Heterogeneous Causal Effects and Sample Selection Bias

    DEFF Research Database (Denmark)

    Breen, Richard; Choi, Seongsoo; Holm, Anders

    2015-01-01

    causal effects might vary over individuals or groups. In this paper we point out one of the under-appreciated hazards of seeking to estimate heterogeneous causal effects: conventional selection bias (that is, selection on baseline differences) can easily be mistaken for heterogeneity of causal effects....... This might lead us to find heterogeneous effects when the true effect is homogenous, or to wrongly estimate not only the magnitude but also the sign of heterogeneous effects. We apply a test for the robustness of heterogeneous causal effects in the face of varying degrees and patterns of selection bias...

  19. Observation of magnetization rotation during the reversal in Co/CoO exchange-bias multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Gierlings, M.; Fritzsche, H.; Gruyters, M.; Riegel, D. [Hahn-Meitner Institut Berlin, Glienicker Strasse 100, 14109 Berlin (Germany); Prandolini, M.J. [Institut fuer Experimentalphysik (WE1), Freie Universitaet Berlin, 14195 Berlin (Germany)

    2002-07-01

    The magnetization-reversal processes of ferromagnetic Co in [Co/CoO/Au]{sub 20} exchange-bias multilayers are studied with polarized neutron reflectometry. The investigations were performed at 300 K, i.e. above the Neel temperature of CoO. We measured the non-spin-flip as well as the spin-flip intensities. Thus, we are able to distinguish between a magnetization rotation and a domain-wall movement. This is essential, in order to compare the obtained results to measurements performed below T{sub N} of CoO, when the sample is in the exchange-bias state (i.e. after field cooling). (orig.)

  20. Exchange Bias Tuning for Magnetoresistive Sensors by Inclusion of Non-Magnetic Impurities

    Directory of Open Access Journals (Sweden)

    Parikshit Pratim Sharma

    2016-07-01

    Full Text Available The fine control of the exchange coupling strength and blocking temperature ofexchange bias systems is an important requirement for the development of magnetoresistive sensors with two pinned electrodes. In this paper, we successfully tune these parameters in top- and bottom-pinned systems, comprising 5 nm thick Co40Fe40B20 and 6.5 nm thick Ir22Mn78 films. By inserting Ru impurities at different concentrations in the Ir22Mn78 layer, blocking temperatures ranging from 220 °C to 100 °C and exchange bias fields from 200 Oe to 60 Oe are obtained. This method is then applied to the fabrication of sensors based on magnetic tunneling junctions consisting of a pinned synthetic antiferromagnet reference layer and a top-pinned sensing layer. This work paves the way towards the development of new sensors with finely tuned magnetic anisotropies.

  1. The Behavioral Bias of Foreign Debt Usage in Foreign Exchange Risk Management

    DEFF Research Database (Denmark)

    Aabo, Tom

    We investigate the behavioral bias in the use of debt denominated in foreign currency (foreign debt) in managing foreign exchange risks. From a strictly financial (rational) point of view foreign debt and derivates are close substitutes. Whether e.g. a European firm sells forward US dollars against...... foreign exchange risk management in medium-sized, non-financial firms in Denmark and find a behavioral bias in the use of foreign debt. Among the firms that are internationally involved (operating revenues, costs and/or assets in foreign currency), on average a quarter of the financial debt is denominated...... distinguishes itself from the use of shortsighted currency derivatives such as forward contracts by not being significantly and positively related to the foreign sales ratio in a multivariate setting. Furthermore, while the degree of matching at the firm level - creating offsetting operating revenues and costs...

  2. Ultrathin Limit of Exchange Bias Coupling at Oxide Multiferroic/Ferromagnetic Interfaces

    Science.gov (United States)

    2013-07-12

    stabilizers in recording heads based on anisotropic magnetoresistance . [ 11 ] Exchange bias heterostructures based on multiferroic materials...epitaxial layers of LSMO and BFO, which were strained in-plane to the STO (001) substrate. Figure 1 c shows the presence of Kiessig fringes...drastically. This is generally interpreted by considering a strain -induced distortion of MnO 6 octahedra based on the Jahn-Teller distortion theory. [ 39

  3. Microplasma Jet Synthesis of Ni-Fe Oxide Films for Magnetic Exchange Bias and Electrocatalytic Studies

    Science.gov (United States)

    Pebley, Andrew Christian

    Ni-Fe oxides have received significant interest from the scientific community because they have attractive magnetic and electrochemical properties for use in next generation data storage and energy conversion technologies. For example, the NiFe2O4/NiO nanogranular system exhibits the exchange bias effect, a magnetic phenomenon occurring at the interface of a ferro- or ferrimagnet (FM or FiM) and an antiferromagnet (AFM), where the AFM acts to increase the magnetic hardness of the corresponding FM or FiM. Additionally, doping of NiO with Fe has resulted in remarkably high catalytic activities for water splitting, a potential clean energy alternative to fossil fuels. A key challenge in implementing these Ni-Fe oxides for magnetic and electrocatalytic applications is the ability to control film morphology, crystallinity, composition, chemical phase, and doping during synthesis. Moreover, how these physiochemical properties effect magnetic and electrochemical behavior in the Ni-Fe oxide system is not fully understood. This dissertation focuses on the development and use of a novel synthesis technique, known as microplasma (MP) jet-based deposition, for the fabrication of biphasic NiFe2O4 (FiM)/NiO (AFM) and Fe-doped NiO nanostructured films for fundamental studies of exchange bias and electrocatalysis, respectively. The goal of this work was to understand how MP operation and deposition conditions (e.g., precursor composition, flux, substrate temperature, and post-deposition heat treatment) influence Ni-Fe oxide growth and film microstructure. Specifically, the role of composition, phase fraction, grain size, temperature, and interfacial density on exchange bias phenomena in NiFe 2O4/NiO nanogranular films was investigated. MP jets were also used to realize metastable Fe-doped NiO films with high surface area to assess how doping affects the electrochemical properties of NiO for the oxygen evolution reaction (OER). Biphasic NiFe2O4/NiO films of different composition

  4. Enhancing the blocking temperature of perpendicular-exchange biased Cr2O3 thin films using buffer layers

    Directory of Open Access Journals (Sweden)

    Naoki Shimomura

    2017-02-01

    Full Text Available In this study, we investigated the effect of buffer layers on the blocking temperature (TB of perpendicular exchange bias of thin Cr2O3/Co exchange coupled films with a Ru spacer and revealed a high TB of 260 K for 20-nm-thick Cr2O3 thin films. By comparing the TB values of the 20-nm-thick Cr2O3 films on Pt and α-Fe2O3 buffers, we investigated the lattice strain effect on the TB. We show that higher TB values can be obtained using an α-Fe2O3 buffer, which is likely because of the lattice strain-induced increase in Cr2O3 magnetocrystalline anisotropy.

  5. Tuning exchange bias in core/shell FeO/Fe3O4 nanoparticles.

    Science.gov (United States)

    Sun, Xiaolian; Huls, Natalie Frey; Sigdel, Aruna; Sun, Shouheng

    2012-01-11

    Monodisperse 35 nm FeO nanoparticles (NPs) were synthesized and oxidized in a dry air atmosphere into core/shell FeO/Fe(3)O(4) NPs with both FeO core and Fe(3)O(4) shell dimensions controlled by reaction temperature and time. Temperature-dependent magnetic properties were studied on FeO/Fe(3)O(4) NPs obtained from the FeO NPs oxidized at 60 and 100 °C for 30 min. A large exchange bias (shift in the hysteresis loop) was observed in these core/shell NPs. The relative dimensions of the core and shell determine not only the coercivity and exchange field but also the dominant reversal mechanism of the ferrimagnetic Fe(3)O(4) component. This is the first time demonstration of tuning exchange bias and of controlling asymmetric magnetization reversal in FeO/Fe(3)O(4) NPs with antiferromagnetic core and ferrimagnetic shell. © 2011 American Chemical Society

  6. Electrical control of exchange bias via oxygen migration across CoO-ZnO nanocomposite barrier

    Science.gov (United States)

    Li, Q.; Yan, S. S.; Xu, J.; Li, S. D.; Zhao, G. X.; Long, Y. Z.; Shen, T. T.; Zhang, K.; Zhang, J.

    2016-12-01

    We proposed a nanocomposite barrier CoO-ZnO for magnetism manipulation in Co/CoO-ZnO/Ag heterojunctions. Both electrical control of magnetism and resistive switching were realized in this junction. An electrical tunable exchange bias of CoO1-v (v denotes O vacancies) on Co films was realized using voltages below 1 volt. The magnetism modulation associated with resistive switching can be attributed to the oxygen ions migration between the insulating CoO1-v layer and the semiconductive ZnO1-v layer, which can cause both ferromagnetic phase and resistance switching of CoO1-v layer.

  7. The Effect of Monetary Policy on Exchange Rates : How to Solve the Puzzles

    NARCIS (Netherlands)

    Kumah, F.Y.

    1996-01-01

    Recent empirical research on the effects of monetary policy shocks on exchange rate fluctuations have encountered the exchange rate puzzle and th e forward discount bias puzzle.The exchange rate puzzle is the tendency of the domestic currency (of non-US G-7 countries) to depreciate against the US

  8. Electronic control of interface ferromagnetic order and exchange-bias in paramagnetic-antiferromagnetic epitaxial bilayers.

    Science.gov (United States)

    Pandey, Parul; Das, Tanmay; Rana, Rakesh; Parmar, Jayesh B; Bhattacharyya, Somnath; Rana, Dhanvir Singh

    2015-02-21

    The hetero-epitaxially engineered magnetic phases, formed due to entanglement of the spin, charge and lattice degrees of freedom, at the atomically sharp interfaces of complex oxide heterostructures are indispensable for devising multifunctional devices. In the quest for novel and superior spintronics functionalities, we have explored the interface magnetism in the epitaxial bilayer of atypical magnetic and electronic states, i.e., of paramagnetic metallic and antiferromagnetic (AFM) insulating phases. In this framework, we observe an unusually strong ferromagnetic order and large exchange-bias fields generated at the interface of the bilayers of metallic CaRuO3 and AFM insulating manganite. The magnetic moment of the interface ferromagnetic order increases linearly with increasing thickness (7-90 nm) of the metallic CaRuO3 layer. This linear scaling signifying an electronic (non-magnetic) control of the interface magnetism and a non-monotonic dependence of the exchange-bias on metallic layers evolve as novel spintronics attributes in atypical bilayers.

  9. Charge ordering and exchange bias behaviors in Co3O4 porous nanoplatelets and nanorings

    Science.gov (United States)

    Debnath, J. C.; Wang, Jianli; Zeng, R.

    2017-01-01

    We present the synthesis of α-Co3O4 porous nanoplatelets and hexagonal nanorings using microwave-assisted hydrothermal and conventional chemical reaction methods. The x-ray diffraction (XRD) and refinement analyses indicate the α-Co3O4 crystal structure, and the x-ray photoelectron spectrum (XPS) indicates the high purity of the samples. The M-T (including 1/χ-T) curves indicate an antiferromagnetic transition at about 35 K in both kind of samples but the interesting finding was made that a charge-ordered (CO) state appears at 250 K for the nanoplatelets sample whereas it is inattentive for the nanorings. The antiferromagnetic transition temperature TN is lower than that of the bulk α-Co3O4 single crystal due to the nanosized structures. We observed quite significant exchange bias for nanorings. The exchange bias behavior of the α-Co3O4 hexagonal nanorings is consistent with an antiferromagnetic (AFM) Co3O4 core and spin-glass like shell.

  10. Triggering of spin-flipping-modulated exchange bias in FeCo nanoparticles by electronic excitation

    Science.gov (United States)

    Sarker, Debalaya; Bhattacharya, Saswata; Srivastava, Pankaj; Ghosh, Santanu

    2016-12-01

    The exchange coupling between ferromagnetic (FM)-antiferromagnetic (AF) interfaces is a key element of modern spintronic devices. We here introduce a new way of triggering exchange bias (EB) in swift heavy ion (SHI) irradiated FeCo-SiO2 films, which is a manifestation of spin-flipping at high irradiation fluence. The elongation of FeCo nanoparticles (NPs) in SiO2 matrix gives rise to perpendicular magnetic anisotropy at intermediate fluence. However, a clear shift in hysteresis loop is evident at the highest fluence. This reveals the existence of an AF exchange pinning domain in the NPs, which is identified not to be oxide shell from XANES analysis. Thermal spike calculations along with first-principles based simulations under the framework of density functional theory (DFT) demonstrate that spin flipping of 3d valence electrons is responsible for formation of these AF domains inside the FM NPs. EXAFS experiments at Fe and Co K-edges further unravel that spin-flipping in highest fluence irradiated film results in reduced bond lengths. The results highlight the possibility of miniaturization of magnetic storage devices by using irradiated NPs instead of conventionally used FM-AF multilayers.

  11. Approach to Exchange Bias Effect in La2/3Ca1/3MnO3/BiFeO3 and BiFeO3/ La2/3Ca1/3MnO3 Bilayers

    Science.gov (United States)

    Dominguez, Claribel; Ordonez, John; Diez, Sandra; Gomez, Maria; Guénon, Stefan; Schuller, Ivan

    2013-03-01

    We have grown bilayers of ferromagnetic La2/3Ca1/3MnO3 (LCMO) and multiferroic BiFeO3 (BFO) on (100) SrTiO3 (STO) substrates, by DC- and magnetron RF -sputtering technique, respectively, at high-oxygen pressures. We maintain constant the thickness of the layers (tBFO=72nm; tLCMO=80nm). Temperature dependence of the resistivity indicates that the MI-transition temperature of the manganite in the BFO/LCMO/STO is affected by the presence of the BFO layer in comparison with TMI for the single LCMO layer. Furthermore, temperature dependence of magnetization shows that the BFO/LCMO/STO bilayer has higher Curie temperature than that for LCMO/BFO/STO, indicating a strong structural dependence of the LCMO layer with magnetic response. The dependence of the magnetic moment with magnetic field after field cooling gives indication of the existence of Exchange Bias effect in the LCMO/BFO/STO bilayer. Isothermal loops also display dependence of the Exchange Bias magnitude with field cooling. This work has been supported by UNIVALLE Research Project CI 7864, and ``El Patrimonio Autónomo Fondo Nacional de Financiamiento para CT&I FJC,'' Contract RC - No. 275-2011, COLCIENCIAS-CENM, Colombia

  12. Direct observation of rotatable uncompensated spins in the exchange bias system Co/CoO-MgO.

    Science.gov (United States)

    Ge, Chuannan; Wan, Xiangang; Pellegrin, Eric; Hu, Zhiwei; Manuel Valvidares, S; Barla, Alessandro; Liang, Wen-I; Chu, Ying-Hao; Zou, Wenqin; Du, Youwei

    2013-11-07

    We have observed a large exchange bias field HE ≈ 2460 Oe and a large coercive field HC ≈ 6200 Oe at T = 2 K for Co/CoO core-shell nanoparticles (~4 nm diameter Co metal core and CoO shell with ~1 nm thickness) embedded in a non-magnetic MgO matrix. Our results are in sharp contrast to the small exchange bias and coercive field in the case of a non-magnetic Al2O3 or C matrix materials reported in previous studies. Using soft X-ray magnetic circular dichroism at the Co-L2,3 edge, we have observed a ferromagnetic signal originating from the antiferromagnetic CoO shell. This gives direct evidence for the existence of rotatable interfacial uncompensated Co spins in the nominally antiferromagnetic CoO shell, thus supporting the uncompensated spin model as a microscopic description of the exchange bias mechanism.

  13. Placebo effect studies are susceptible to response bias and to other types of biases

    DEFF Research Database (Denmark)

    Hróbjartsson, Asbjørn; Kaptchuk, Ted J; Miller, Franklin G

    2011-01-01

    Investigations of the effect of placebo are often challenging to conduct and interpret. The history of placebo shows that assessment of its clinical significance has a real potential to be biased. We analyze and discuss typical types of bias in studies on placebo.......Investigations of the effect of placebo are often challenging to conduct and interpret. The history of placebo shows that assessment of its clinical significance has a real potential to be biased. We analyze and discuss typical types of bias in studies on placebo....

  14. The origin of exchange bias, observation of pinned orbital moments at iron L2,3 in FeMn/Co

    Energy Technology Data Exchange (ETDEWEB)

    Audehm, Patrick; Schuetz, G.; Goering, Eberhard [Max Planck Institute for Metals Research, Stuttgart (Germany); Brueck, Sebastian [University of Wuerzburg, Physikalisches Institut, Wuerzburg (Germany)

    2010-07-01

    The exchange anisotropy was discovered by Meiklejohn and Bean in 1956. Since then there have been many attempts to model the behavior of a system with exchange bias effect. Exchange bias (EB) results in a shift of the hysteresis loop and secondly in an increase of the coercive field. We investigated a widely studied EB-system, consisting of polycrystalline iron (Fe)-manganese (Mn) as an antiferromagnet and cobalt as a ferromagnet. We used X-ray magnetic circular dichroism (XMCD) and X-ray resonant magnetic reflectivity (XRMR) at the Fe L2,3 and Mn L2,3 edges, simultaneously performed in surface sensitive total electron yield (TEY) and bulk sensitive total fluorescence yield (TFY) at room and low temperatures. For the first time, we measured pinned magnetic Fe moments in iron-manganese. Mn shows nearly no XMCD effect, while the Fe provides a sizeable signal from the rotatable moments and a very small (about 0.7 per mill of the total signal) signal from the pinned uncompensated moments. According to the well established sum rules of XMCD the non-rotatable Fe L2,3 edge spectra reveal nearly pure orbital character. These results suggest a different view on the origin of exchange bias, based on locally loaded spin-orbit-coupling, and new possibilities understanding the origin of EB.

  15. Bias effects in implicit memory tasks.

    Science.gov (United States)

    Ratcliff, R; McKoon, G

    1996-12-01

    A major focus of recent research in memory has been performance on implicit tasks. The phenomenon of most interest has been repetition priming, the effect that prior exposure to a stimulus has on later perception of the stimulus or on a later decision about the stimulus. Picture naming, word identification, and word production in stem- and fragment-completion tasks all show repetition priming effects. The separation of implicit from explicit memory systems provides one account of this data, but a different theoretical view is proposed here: Repetition-priming effects come about because the processes that perform a task are biased products, temporary modifications of the processes, which influence later processing. The aim of this article is to demonstrate the potential of this view for developing new theories and for prompting new empirical questions.

  16. Placebo effect studies are susceptible to response bias and to other types of biases

    DEFF Research Database (Denmark)

    Hróbjartsson, Asbjørn; Kaptchuk, Ted J; Miller, Franklin G

    2011-01-01

    Investigations of the effect of placebo are often challenging to conduct and interpret. The history of placebo shows that assessment of its clinical significance has a real potential to be biased. We analyze and discuss typical types of bias in studies on placebo....

  17. Exchange bias behavior in Ni{sub 50.0}Mn{sub 35.5} In{sub 14.5} ribbons annealed at different temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez, T. [Dept. de Fisica, Universidad de Oviedo, Calvo Sotelo s/n, 33007 Oviedo (Spain); Sato Turtelli, R.; Groessinger, R. [Institut fur Festkoerperphysik, Technische Universitaet Wien, Wiedner Hauptstr. 8-10, 1040 Vienna (Austria); Sanchez, M.L.; Santos, J.D.; Rosa, W.O.; Prida, V.M. [Dept. de Fisica, Universidad de Oviedo, Calvo Sotelo s/n, 33007 Oviedo (Spain); Escoda, Ll.; Sunol, J.J. [Campus de Montilivi, Universidad de Girona, edifici PII, Lluis Santalo s/n. 17003 Girona (Spain); Koledov, V. [Kotelnikov Institute of Radio Engineering and Electronics, RAS, Moscow 125009 (Russian Federation); Hernando, B., E-mail: grande@uniovi.es [Dept. de Fisica, Universidad de Oviedo, Calvo Sotelo s/n, 33007 Oviedo (Spain)

    2012-10-15

    Heusler alloy Ni{sub 50.0}Mn{sub 35.5}In{sub 14.5} ribbons were prepared by melt-spinning technique. Several short time annealings were carried out in order to enhance the exchange bias effect in this alloy ribbon. The magnetic transition temperature increases with the annealing, compared to the as-spun sample, however no significant differences in respective Curie temperatures were observed for austenite and martensite phases in such annealed samples. Exchange bias effect is observed at low temperatures for all samples and practically vanishes at 60 K for the as-spun sample, whereas for the annealed ribbons it vanishes at 100 K.

  18. Exchange bias properties of 140 nm-sized dipolarly interacting circular dots with ultrafine IrMn and NiFe layers

    Energy Technology Data Exchange (ETDEWEB)

    Spizzo, F., E-mail: spizzo@fe.infn.it [Dipartimento di Fisica e Scienze della Terra and CNISM, Università di Ferrara, I-44122 Ferrara (Italy); Tamisari, M. [Dipartimento di Fisica e Scienze della Terra and CNISM, Università di Ferrara, I-44122 Ferrara (Italy); Dipartimento di Fisica e Geologia and CNISM, Università di Perugia, I-06123 Perugia (Italy); Chinni, F.; Bonfiglioli, E. [Dipartimento di Fisica e Scienze della Terra and CNISM, Università di Ferrara, I-44122 Ferrara (Italy); Gerardino, A. [Istituto di Fotonica e Nanotecnologie, CNR, I-00156 Roma (Italy); Barucca, G. [Dipartimento SIMAU, Università Politecnica delle Marche, I-60131 Ancona (Italy); Bisero, D.; Fin, S.; Del Bianco, L. [Dipartimento di Fisica e Scienze della Terra and CNISM, Università di Ferrara, I-44122 Ferrara (Italy)

    2016-02-15

    We studied the exchange bias effect in an array of IrMn(3 nm)/NiFe(3 nm) circular dots (size ~140 nm and center-to-center distance ~200 nm, as revealed by microscopy analyses), prepared on a large area (3×3 mm{sup 2}) by electron beam lithography and lift-off, using dc sputtering deposition. Hysteresis loops were measured by SQUID magnetometer at increasing values of temperature T (in the 5–300 K range) after cooling from 300 K down to 5 K in zero field (ZFC mode) and in a saturating magnetic field (FC mode). The exchange bias effect disappears above T~200 K and, at each temperature, the exchange field H{sub EX} measured in ZFC is substantially lower than the FC one. Micromagnetic calculations indicate that, at room temperature, each dot is in high-remanence ground state, but magnetic dipolar interactions establish a low-remanence configuration of the array as a whole. Hence, at low temperature, following the ZFC procedure, the exchange anisotropy in the dot array is averaged out, tending to zero. However, even the FC values of H{sub EX} and of the coercivity H{sub C} are definitely smaller compared to those measured in a reference continuous film with the same stack configuration (at T=5 K, H{sub EX}~90 Oe and H{sub C}~180 Oe in the dots and H{sub EX}~1270 Oe and H{sub C}~860 Oe in the film). Our explanation is based on the proven glassy magnetic nature of the ultrathin IrMn layer, implying the existence of magnetic correlations among the spins, culminating in a collective freezing below T~100 K. We propose, also by the light of micromagnetic simulations, that the small dot size imposes a spatial constraint on the magnetic correlation length among the IrMn spins so that, even at the lowest temperature, their thermal stability, especially at the dot border, is compromised. - Highlights: • Exchange bias in 140 nm-sized IrMn(3 nm)/NiFe(3 nm) dots much weaker than in a film. • Glassy magnetic nature of the IrMn phase and collective spin freezing at T<100 K

  19. Thermal simulation of magnetization reversals for size-distributed assemblies of core-shell exchange biased nanoparticles

    Science.gov (United States)

    Richy, J.; Jay, J.-Ph.; Pogossian, S. P.; Ben Youssef, J.; Sheppard, C. J.; Prinsloo, A. R. E.; Spenato, D.; Dekadjevi, D. T.

    2016-08-01

    A temperature dependent coherent magnetization reversal model is proposed for size-distributed assemblies of ferromagnetic nanoparticles and ferromagnetic-antiferromagnetic (AF) core-shell nanoparticles. The nanoparticles are assumed to be of uniaxial anisotropy and all aligned along their easy axis. The thermal dependence is included by considering thermal fluctuations, implemented via the Néel-Arrhenius theory. Thermal and angular dependence of magnetization reversal loops, coercive field, and exchange-bias field are obtained, showing that ferromagnetic-antiferromagnetic size-distributed exchange-coupled nanoparticles exhibit temperature-dependent asymmetric magnetization reversal. Also, non-monotonic evolutions of exchange-bias and coercive fields with temperature are demonstrated. The angular dependence of coercive field with temperature exhibits a complex behavior, with the presence of an apex, whose position and amplitude are strongly temperature-dependent. The angular dependence of exchange bias with temperature exhibits complex behaviors, which depends on the AF anisotropy and exchange coupling. The resulting angular behavior demonstrates the key role of the size distribution and temperature in the magnetic response of nanoparticles.

  20. Selection Bias and the Degree Effect.

    Science.gov (United States)

    Frazis, Harley

    1993-01-01

    Analysis of National Longitudinal Study data used an ordered probit model of schooling choice to correct for selection bias. Evidence indicates that selection bias does not account for the high rate of return for completing college compared to having "some college." (SK)

  1. Magnetic stability under magnetic cycling of MgO-based magnetic tunneling junctions with an exchange-biased synthetic antiferromagnetic pinned layer

    Directory of Open Access Journals (Sweden)

    Qiang Hao

    2016-02-01

    Full Text Available We investigate the magnetic stability and endurance of MgO-based magnetic tunnel junctions (MTJs with an exchange-biased synthetic antiferromagnetic (SAF pinned layer. When a uniaxially cycling switching field is applied along the easy axis of the free magnetic layer, the magnetoresistance varies only by 1.7% logarithmically with the number of cycles, while no such change appears in the case of a rotating field. This observation is consistent with the effect of the formation and motion of domain walls in the free layer, which create significant stray fields within the pinned hard layer. Unlike in previous studies, the decay we observed only occurs during the first few starting cycles (<20, at which point there is no further variance in all performance parameters up to 107 cycles. Exchange-biased SAF structure is ideally suited for solid-state magnetic sensors and magnetic memory devices.

  2. Multilevel Thermally Assisted Magnetoresistive Random-Access Memory Based on Exchange-Biased Vortex Configurations

    Science.gov (United States)

    de Araujo, C. I. L.; Alves, S. G.; Buda-Prejbeanu, L. D.; Dieny, B.

    2016-08-01

    A concept of multilevel thermally assisted magnetoresistive random-access memory is proposed and investigated by micromagnetic simulations. The storage cells are magnetic tunnel junctions in which the storage layer is exchange biased and in a vortex configuration. The reference layer is an unpinned soft magnetic layer. The stored information is encoded via the position of the vortex core in the storage layer. This position can be varied along two degrees of freedom: the radius and the in-plane angle. The information is read out from the amplitude and phase of the tunnel magnetoresistance signal obtained by applying a rotating field on the cell without heating the cell. Various configurations are compared in which the soft reference layer consists of either a simple ferromagnetic layer or a synthetic antiferromagnetic sandwich (SAF). Among those, the most practical one comprises a SAF reference layer in which the magnetostatic interaction between the SAF and storage layer is minimized. This type of cell should allow one to store at least 40 different states per cell representing more than five bits per cell.

  3. Manipulation of Superparamagnetic Beads on Patterned Exchange-Bias Layer Systems for Biosensing Applications.

    Science.gov (United States)

    Ehresmann, Arno; Koch, Iris; Holzinger, Dennis

    2015-11-13

    A technology platform based on a remotely controlled and stepwise transport of an array arrangement of superparamagnetic beads (SPB) for efficient molecular uptake, delivery and accumulation in the context of highly specific and sensitive analyte molecule detection for the application in lab-on-a-chip devices is presented. The near-surface transport of SPBs is realized via the dynamic transformation of the SPBs' magnetic potential energy landscape above a magnetically stripe patterned Exchange-Bias (EB) thin film layer systems due to the application of sub-mT external magnetic field pulses. In this concept, the SPB velocity is dramatically influenced by the magnitude and gradient of the magnetic field landscape (MFL) above the magnetically stripe patterned EB substrate, the SPB to substrate distance, the magnetic properties of both the SPBs and the EB layer system, respectively, as well as by the properties of the external magnetic field pulses and the surrounding fluid. The focus of this review is laid on the specific MFL design in EB layer systems via light-ion bombardment induced magnetic patterning (IBMP). A numerical approach is introduced for the theoretical description of the MFL in comparison to experimental characterization via scanning Hall probe microscopy. The SPB transport mechanism will be outlined in terms of the dynamic interplay between the EB substrate's MFL and the pulse scheme of the external magnetic field.

  4. Exchange bias in a ferromagnetic semiconductor induced by a ferromagnetic metal: Fe/(Ga,Mn)As bilayer films studied by XMCD measurements and SQUID magnetometry

    Science.gov (United States)

    Olejnik, K.; Wadley, P.; Haigh, J. A.; Edmonds, K. W.; Campion, R. P.; Rushforth, A. W.; Gallagher, B. L.; Foxon, C. T.; Jungwirth, T.; Wunderlich, J.; Dhesi, S. S.; Cavill, S. A.; van der Laan, G.; Arenholz, E.

    2010-03-01

    We demonstrate an exchange bias in (Ga,Mn)As induced by antiferromagnetic coupling to a thin overlayer of Fe. Bias fields of up to 240 Oe are observed. Using element-specific x-ray magnetic circular dichroism measurements, we distinguish a strongly exchange-coupled (Ga,Mn)As interface layer in addition to the biased bulk of the (Ga,Mn)As film. The interface layer remains polarized at room temperature.

  5. Synthesis and controllable oxidation of monodisperse cobalt-doped wüstite nanoparticles and their core-shell stability and exchange-bias stabilization.

    Science.gov (United States)

    Chen, Chih-Jung; Chiang, Ray-Kuang; Kamali, Saeed; Wang, Sue-Lein

    2015-09-14

    Cobalt-doped wüstite (CWT), Co0.33Fe0.67O, nanoparticles were prepared via the thermal decomposition of CoFe2-oleate complexes in organic solvents. A controllable oxidation process was then performed to obtain Co0.33Fe0.67O/CoFe2O4 core-shell structures with different core-to-shell volume ratios and exchange bias properties. The oxidized core-shell samples with a ∼4 nm CoFe2O4 shell showed good resistance to oxygen transmission. Thus, it is inferred that the cobalt ferrite shell provides a better oxidation barrier performance than magnetite in the un-doped case. The hysteresis loops of the oxidized 19 nm samples exhibited a high exchange bias field (H(E)), an enhanced coercivity field (H(C)), and a pronounced vertical shift, thus indicating the presence of a strong exchange bias coupling effect. More importantly, the onset temperature of H(E) was found to be higher than 200 K, which suggests that cobalt doping increases the Néel temperature (T(N)) of the CWT core. In general, the results show that the homogeneous dispersion of Co in iron precursors improves the stability of the final CWT nanoparticles. Moreover, the CoFe2O4 shells formed following oxidation increase the oxidation resistance of the CWT cores and enhance their anisotropy energy.

  6. Placebo effect studies are susceptible to response bias and to other types of biases.

    Science.gov (United States)

    Hróbjartsson, Asbjørn; Kaptchuk, Ted J; Miller, Franklin G

    2011-11-01

    Investigations of the effect of placebo are often challenging to conduct and interpret. The history of placebo shows that assessment of its clinical significance has a real potential to be biased. We analyze and discuss typical types of bias in studies on placebo. A methodological analysis and discussion. The inherent nonblinded comparison between placebo and no-treatment is the best research design we have in estimating effects of placebo, both in a clinical and in an experimental setting, but the difference between placebo and no-treatment remains an approximate and fairly crude reflection of the true effect of placebo interventions. A main problem is response bias in trials with outcomes that are based on patients' reports. Other biases involve differential co-intervention and patient dropouts, publication bias, and outcome reporting bias. Furthermore, extrapolation of results to a clinical settings are challenging because of a lack of clear identification of the causal factors in many clinical trials, and the nonclinical setting and short duration of most laboratory experiments. Creative experimental efforts are needed to assess rigorously the clinical significance of placebo interventions and investigate the component elements that may contribute to the therapeutic benefit. Copyright © 2011 Elsevier Inc. All rights reserved.

  7. Placebo effect studies are susceptible to response bias and to other types of biases

    Science.gov (United States)

    Hróbjartsson, Asbjørn; Kaptchuk, Ted J; Miller, Franklin G

    2011-01-01

    OBJECTIVE Investigations of the effect of placebo are often challenging to conduct and interpret. The history of placebo shows that assessment of its clinical significance has a real potential to be biased. We analyse and discuss typical types of bias in studies on placebo. STUDY DESIGN AND SETTING a methodological analysis and discussion. RESULTS The inherent nonblinded comparison between placebo and no-treatment is the best research design we have in estimating effects of placebo, both in a clinical and in an experimental setting, but the difference between placebo and no-treatment remains an approximate and fairly crude reflection of the true effect of placebo interventions. A main problem is response bias in trials with outcomes that are based on patients reports. Other biases involve differential co-intervention and patient drop-outs, publication bias, and outcome reporting bias. Furthermore, extrapolation of results to a clinical settings are challenging because of lack of clear identification of the causal factors in many clinical trials, and the non-clinical setting and short duration of most laboratory experiments. CONCLUSIONS Creative experimental efforts are needed to assess rigorously the clinical significance of placebo interventions and investigate the component elements that may contribute to therapeutic benefit. PMID:21524568

  8. Observation of magnetization and exchange bias reversals in NdFe0.5Cr0.5O3

    Science.gov (United States)

    Sharannia, M. P.; De, Santanu; Singh, Ripandeep; Das, A.; Nirmala, R.; Santhosh, P. N.

    2017-05-01

    Polycrystalline NdFe0.5Cr0.5O3 has orthorhombic structure with Pnma space group and is magnetically ordered at room temperature as confirmed by neutron diffraction. The magnetic structure involves CxGyFz type ordering of Fe3+/Cr3+ ions. NdFe0.5Cr0.5O3 shows magnetization reversal and sign reversal of exchange bias at 16 K. Nd3+ moments that get induced by the internal field of |Fe+Cr| sublattice couple antiferromagnetically with the ferromagnetic component of |Fe+Cr| sublattice. Nd3+ moments overcome the |Fe+Cr| moments at 16 K below which the material shows negative magnetization and positive exchange bias.

  9. Charge ordering and exchange bias behaviors in Co{sub 3}O{sub 4} porous nanoplatelets and nanorings

    Energy Technology Data Exchange (ETDEWEB)

    Debnath, J.C., E-mail: jcd341@uowmail.edu.au [Institute for Frontier Materials, Deakin University, Geelong, VIC 3216 (Australia); Wang, Jianli [Institute for Superconductivity and Electronic Materials, University of Wollongong, Wollongong, NSW 2522 (Australia); Zeng, R. [Institute for Superconductivity and Electronic Materials, University of Wollongong, Wollongong, NSW 2522 (Australia); School of Materials Science and Engineering, Faculty of Science, UNSW, Sydney NSW 2052 (Australia)

    2017-01-01

    We present the synthesis of α-Co{sub 3}O{sub 4} porous nanoplatelets and hexagonal nanorings using microwave-assisted hydrothermal and conventional chemical reaction methods. The x-ray diffraction (XRD) and refinement analyses indicate the α-Co{sub 3}O{sub 4} crystal structure, and the x-ray photoelectron spectrum (XPS) indicates the high purity of the samples. The M–T (including 1/χ–T) curves indicate an antiferromagnetic transition at about 35 K in both kind of samples but the interesting finding was made that a charge-ordered (CO) state appears at 250 K for the nanoplatelets sample whereas it is inattentive for the nanorings. The antiferromagnetic transition temperature T{sub N} is lower than that of the bulk α-Co{sub 3}O{sub 4} single crystal due to the nanosized structures. We observed quite significant exchange bias for nanorings. The exchange bias behavior of the α-Co{sub 3}O{sub 4} hexagonal nanorings is consistent with an antiferromagnetic (AFM) Co{sub 3}O{sub 4} core and spin-glass like shell. - Highlights: ●Charge-ordered state appears for the Co{sub 3}O{sub 4} nanoplatelets but absent for the nanorings. ●Quite significant exchange bias is only observed for Co{sub 3}O{sub 4} nanorings. ●Exchange bias behavior of Co{sub 3}O{sub 4} nanorings is consistent with spin-glass like shell. ●Potential for ultrahigh-density magnetic recording and spin valve devices.

  10. Cognitive bias modification training in adolescents: persistence of training effects

    OpenAIRE

    Belli, Stefano R.; Lau, Jennifer Y.F.

    2014-01-01

    Negative biases in the interpretation of social information are associated with anxious symptoms in adolescents. Previous studies have attempted to modify interpretive biases to alleviate anxious mood responses but the longevity of such training effects has not been established. A cognitive bias modification of interpretations (CBM-I) paradigm was administered to sixty-nine 15–17 year-olds. Participants were either trained to interpret ambiguous social situations positively, or received contr...

  11. Exchange scattering as the driving force for ultrafast all-optical and bias-controlled reversal in ferrimagnetic metallic structures

    Science.gov (United States)

    Kalashnikova, A. M.; Kozub, V. I.

    2016-02-01

    Experimentally observed ultrafast all-optical magnetization reversal in ferrimagnetic metals and heterostructures based on antiferromagnetically coupled ferromagnetic d - and f -metallic layers relies on intricate energy and angular momentum flow between electrons, phonons, and spins. Here we treat the problem of angular momentum transfer in the course of ultrafast laser-induced dynamics in a ferrimagnetic metallic system using microscopical approach based on the system of rate equations. We show that the magnetization reversal is supported by a coupling of d and f subsystems to delocalized s or p electrons. The latter can transfer spin between the two subsystems in an incoherent way owing to the (s ;p )-(d ;f ) exchange scattering. Since the effect of the external excitation in this process is reduced to the transient heating of the mobile electron subsystem, we also discuss the possibility to trigger the magnetization reversal by applying a voltage bias pulse to antiferromagnetically coupled metallic ferromagnetic layers embedded in point contact or tunneling structures. We argue that such devices allow controlling reversal with high accuracy. We also suggest using the anomalous Hall effect to register the reversal, thus playing a role of reading probes.

  12. Exchange effects in a cold plasma

    CERN Document Server

    Ekman, Robin; Brodin, Gert

    2015-01-01

    We have studied the exchange corrections to linear electrostatic wave propagation in a plasma using a quantum kinetic formalism. Specifically we have considered the zero temperature limit. In order to simplify the calculations we have focused on the long wavelength limit, i.e. wavelengths much longer than the de Broglie wavelength. For the case of ion-acoustic waves we have calculated the exchange correction both to the damping rate and the real part of the frequency. For Langmuir waves the frequency shift due to exchange effects is found. Our results are compared with the frequency shifts deduced from commonly used exchange potentials which are computed from density functional theory.

  13. Battling Bias: Effects of Training and Training Context

    NARCIS (Netherlands)

    Poos, Jackie; van den Bosch, Karel; Janssen, C.P.

    2017-01-01

    This study investigates whether cognitive bias in judgment and decision making can be reduced by training, and whether the effects are affected by the nature of the training environment. Theory suggests that biases can be overcome by training in critical reflective thinking. In addition, applied

  14. Battling bias : Effects of training and training context

    NARCIS (Netherlands)

    Poos, J.M.; Bosch, K. van den; Janssen, C.P.

    2017-01-01

    This study investigates whether cognitive bias in judgment and decision making can be reduced by training, and whether the effects are affected by the nature of the training environment. Theory suggests that biases can be overcome by training in critical reflective thinking. In addition, applied

  15. Friendship Network in the Classroom: Parents Bias and Peer Effects

    DEFF Research Database (Denmark)

    Landini, Fabio; Montinari, Natalia; Pin, Paolo

    : parents expect peer effects on school achievement to be stronger than what they really are. Thus, parents of low-performing students report their children to be friends of high-performing students. Our numerical simulations indicate that when this bias is combined with a bias on how some children target...

  16. Observation of giant exchange bias in bulk Mn{sub 50}Ni{sub 42}Sn{sub 8} Heusler alloy

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Jyoti; Suresh, K. G., E-mail: suresh@iitb.ac.in [Magnetic Materials Laboratory, Department of Physics, Indian institute of Technology Bombay, Mumbai, Maharashtra 400076 (India)

    2015-02-16

    We report a giant exchange bias (EB) field of 3520 Oe in bulk Mn{sub 50}Ni{sub 42}Sn{sub 8} Heusler alloy. The low temperature magnetic state of the martensite phase has been studied by DC magnetization and AC susceptibility measurements. Frequency dependence of spin freezing temperature (T{sub f}) on critical slowing down relation and observation of memory effect in zero field cooling mode confirms the super spin glass (SSG) phase at low temperatures. Large EB is attributed to the strong exchange coupling between the SSG clusters formed by small regions of ferromagnetic order embedded in an antiferromagnetic (AFM) matrix. The temperature and cooling field dependence of EB have been studied and related to the change in unidirectional anisotropy at SSG/AFM interface. The training effect also corroborates with the presence of frozen (SSG) moments at the interface and their role in EB.

  17. Magnetism and associated exchange bias in Ni{sub 2−x}Co{sub x}Mn{sub 1.4}Ga{sub 0.6}

    Energy Technology Data Exchange (ETDEWEB)

    Chapai, Ramakanta; Khan, Mahmud, E-mail: khanm2@miamioh.edu

    2016-04-01

    A series of Ni{sub 2−x}Co{sub x}Mn{sub 1.4}Ga{sub 0.6} Heusler alloys have been systematically investigated by x-ray diffraction, dc magnetization, and ac susceptibility measurements. For all Co concentration, the alloys exhibit the L1{sub 0} martensitic structure at room temperature. Interestingly, Co doping simultaneously causes a reduction in the ferromagnetic exchange interaction and enhancement of magnetic anisotropy in Ni{sub 2−x}Co{sub x}Mn{sub 1.4}Ga{sub 0.6}. Exchange bias effects under both zero field cooled and field cooled condition have been observed in all alloys for x<0.3. The ac susceptibility data show frequency dependence that changes with increasing Co concentration, indicating a change of ground state from spin glass to super spin glass. The experimental results are explained considering the atomic radii of Ni and Co and the fundamental magnetic interactions in Heusler alloys. - Highlights: • The magnetic properties and associated exchange bias of Ni2-xCoxMn1.4Ga0.6 have been investigated. • Ferromagnetic and antiferromagnetic interactions co-exist in the alloys. • The competing interactions results in interesting magnetic properties. • AC susceptibility data shows the existence of spin glass and super spin glass interactions.

  18. Enhanced magnetic behavior, exchange bias effect, and dielectric property of BiFeO{sub 3} incorporated in (BiFeO{sub 3}){sub 0.50} (Co{sub 0.4}Zn{sub 0.4}Cu{sub 0.2} Fe{sub 2}O{sub 4}){sub 0.5} nanocomposite

    Energy Technology Data Exchange (ETDEWEB)

    Mukhopadhyay, K.; Mahapatra, A. S.; Sutradhar, S.; Chakrabarti, P. K., E-mail: pabitra-c@hotmail.com [Solid State Research Laboratory, Department of Physics, Burdwan University, Burdwan-713104, West Bengal (India)

    2014-03-15

    Nanoparticles of BiFeO{sub 3} (BFO) are incorporated in the nanocomposite of (BiFeO{sub 3}){sub 0.50} (Co{sub 0.4}Zn{sub 0.4}Cu{sub 0.2} Fe{sub 2}O{sub 4}){sub 0.5}, (BFO-CZCF) and these are prepared by chemical route. The formation of pure crystallographic phase of each component (BFO and CZCF) in the nanocomposite of BFO-CZCF has been confirmed by Rietveld analysis of the X-ray diffractograms using FULLPROF program. Morphology, average particle size and its distribution, crystallographic phase etc. are obtained from the high-resolution transmission electron microscopy of BFO-CZCF. Magnetic measurements of BFO-CZCF have been carried out to explore the modulation of magnetic behavior of BFO in BFO-CZCF. Interestingly, magnetization of BFO-CZCF has been drastically enhanced compared to that of the pristine BFO. An exchange bias effect is also observed in the M vs. H loops of BFO-CZCF recorded in field cooled and zero field cooled conditions, which suggest that nanoparticles of BFO (AFM) are encapsulated by nanoparticles of CZCF (FM) in BFO-CZCF. Thermal variation of dielectric constant of BFO-CZCF is recorded in the range of 300 to 1073 K and a ferroelectric to paraelectric transition is observed at ∼728 K. Enhanced magnetic property of BFO would quite interesting for this important multiferroic.

  19. Enhanced magnetic behavior, exchange bias effect, and dielectric property of BiFeO3 incorporated in (BiFeO3)0.50 (Co0.4Zn0.4Cu0.2 Fe2O4)0.5 nanocomposite

    Science.gov (United States)

    Mukhopadhyay, K.; Mahapatra, A. S.; Sutradhar, S.; Chakrabarti, P. K.

    2014-03-01

    Nanoparticles of BiFeO3 (BFO) are incorporated in the nanocomposite of (BiFeO3)0.50 (Co0.4Zn0.4Cu0.2 Fe2O4)0.5, (BFO-CZCF) and these are prepared by chemical route. The formation of pure crystallographic phase of each component (BFO and CZCF) in the nanocomposite of BFO-CZCF has been confirmed by Rietveld analysis of the X-ray diffractograms using FULLPROF program. Morphology, average particle size and its distribution, crystallographic phase etc. are obtained from the high-resolution transmission electron microscopy of BFO-CZCF. Magnetic measurements of BFO-CZCF have been carried out to explore the modulation of magnetic behavior of BFO in BFO-CZCF. Interestingly, magnetization of BFO-CZCF has been drastically enhanced compared to that of the pristine BFO. An exchange bias effect is also observed in the M vs. H loops of BFO-CZCF recorded in field cooled and zero field cooled conditions, which suggest that nanoparticles of BFO (AFM) are encapsulated by nanoparticles of CZCF (FM) in BFO-CZCF. Thermal variation of dielectric constant of BFO-CZCF is recorded in the range of 300 to 1073 K and a ferroelectric to paraelectric transition is observed at ˜728 K. Enhanced magnetic property of BFO would quite interesting for this important multiferroic.

  20. Enhanced magnetic behavior, exchange bias effect, and dielectric property of BiFeO3 incorporated in (BiFeO30.50 (Co0.4Zn0.4Cu0.2 Fe2O40.5 nanocomposite

    Directory of Open Access Journals (Sweden)

    K. Mukhopadhyay

    2014-03-01

    Full Text Available Nanoparticles of BiFeO3 (BFO are incorporated in the nanocomposite of (BiFeO30.50 (Co0.4Zn0.4Cu0.2 Fe2O40.5, (BFO-CZCF and these are prepared by chemical route. The formation of pure crystallographic phase of each component (BFO and CZCF in the nanocomposite of BFO-CZCF has been confirmed by Rietveld analysis of the X-ray diffractograms using FULLPROF program. Morphology, average particle size and its distribution, crystallographic phase etc. are obtained from the high-resolution transmission electron microscopy of BFO-CZCF. Magnetic measurements of BFO-CZCF have been carried out to explore the modulation of magnetic behavior of BFO in BFO-CZCF. Interestingly, magnetization of BFO-CZCF has been drastically enhanced compared to that of the pristine BFO. An exchange bias effect is also observed in the M vs. H loops of BFO-CZCF recorded in field cooled and zero field cooled conditions, which suggest that nanoparticles of BFO (AFM are encapsulated by nanoparticles of CZCF (FM in BFO-CZCF. Thermal variation of dielectric constant of BFO-CZCF is recorded in the range of 300 to 1073 K and a ferroelectric to paraelectric transition is observed at ∼728 K. Enhanced magnetic property of BFO would quite interesting for this important multiferroic.

  1. Effects of Inventory Bias on Landslide Susceptibility Calculations

    Science.gov (United States)

    Stanley, T. A.; Kirschbaum, D. B.

    2017-01-01

    Many landslide inventories are known to be biased, especially inventories for large regions such as Oregon's SLIDO or NASA's Global Landslide Catalog. These biases must affect the results of empirically derived susceptibility models to some degree. We evaluated the strength of the susceptibility model distortion from postulated biases by truncating an unbiased inventory. We generated a synthetic inventory from an existing landslide susceptibility map of Oregon, then removed landslides from this inventory to simulate the effects of reporting biases likely to affect inventories in this region, namely population and infrastructure effects. Logistic regression models were fitted to the modified inventories. Then the process of biasing a susceptibility model was repeated with SLIDO data. We evaluated each susceptibility model with qualitative and quantitative methods. Results suggest that the effects of landslide inventory bias on empirical models should not be ignored, even if those models are, in some cases, useful. We suggest fitting models in well-documented areas and extrapolating across the study region as a possible approach to modeling landslide susceptibility with heavily biased inventories.

  2. Effects of Inventory Bias on Landslide Susceptibility Calculations

    Science.gov (United States)

    Stanley, Thomas; Kirschbaum, Dalia B.

    2017-01-01

    Many landslide inventories are known to be biased, especially inventories for large regions such as Oregons SLIDO or NASAs Global Landslide Catalog. These biases must affect the results of empirically derived susceptibility models to some degree. We evaluated the strength of the susceptibility model distortion from postulated biases by truncating an unbiased inventory. We generated a synthetic inventory from an existing landslide susceptibility map of Oregon, then removed landslides from this inventory to simulate the effects of reporting biases likely to affect inventories in this region, namely population and infrastructure effects. Logistic regression models were fitted to the modified inventories. Then the process of biasing a susceptibility model was repeated with SLIDO data. We evaluated each susceptibility model with qualitative and quantitative methods. Results suggest that the effects of landslide inventory bias on empirical models should not be ignored, even if those models are, in some cases, useful. We suggest fitting models in well-documented areas and extrapolating across the study region as a possible approach to modelling landslide susceptibility with heavily biased inventories.

  3. The effects of interfacial exchange coupling in Fe/ErFeO3 heterostructures

    Science.gov (United States)

    Tang, J.; Ke, Y. J.; He, W.; Zhang, X. Q.; Zhang, Y. S.; Zhang, W.; Li, Y.; Ahmad, S. S.; Cheng, Z. H.

    2017-05-01

    Exploring exchange bias in ferromagnetic (FM)/antiferromagnetic (AFM) heterostructures is vital for both fundamental magnetism and practical application. However, in the case of conventional FM/AFM systems, the essential field cooling process above the Néel temperature of AFM materials hinders their application if the Néel temperature is far higher than room-temperature. Here, we report the effects of interfacial exchange coupling in Fe/ErFeO3 heterostructures. The magnetic-field-induced switchable exchange bias, originating from the AFM exchange coupling between Fe film and Dzyaloshinskii-Moriya-interaction-induced net moment of ErFeO3 along c axis, is successfully achieved without field cooling or in-field growth process of AFM. Different from the most previous pinning layer using a hard FM or traditional AFM, ErFeO3 pinning layer has the advantages of both the magnetic field sensitivity (~780 Oe) and ultrahigh dynamic frequency. In addition, although Fe film is polycrystalline, it exhibits a strong uniaxial magnetic anisotropy resulted from the so-called ‘spin-flop-coupling effect’, i.e. the magnetic coupling between Fe film and the compensated G-type AFM spins of EFO along a axis. Interestingly, the exchange bias field and asymmetric switching field offer entirely different information about the asymmetry of magnetization reversal near hard axis. The asymmetric switching field is further proved to be an effective measure to determine the weak unidirectional magnetic anisotropy for film with nearly 180° domain wall displacement. Our experimental results provide a practical method to establish room-temperature exchange bias in FM/G-type AFM without field cooling. Furthermore, the magnetic-field-induced switchable exchange-bias, the spin-flop coupling effect and the angular dependent asymmetry of magnetization reversal in the vicinity of hard axis in Fe/ErFeO3 heterostructures may provide new insights on the interfacial exchange coupling in FM/AFM systems.

  4. Effects of Cognitive Bias Modification Training via Smartphones

    OpenAIRE

    Ranming Yang; Lixia Cui; Feng Li; Jing Xiao; Qin Zhang; Oei, Tian P. S.

    2017-01-01

    Background and Objectives: Negative cognitive biases have been linked to anxiety and mood problems. Accumulated data from laboratory studies show that positive and negative interpretation styles with accompanying changes in mood can be induced through cognitive bias modification (CBM) paradigms. Despite the therapeutic potential of positive training effects, few studies have explored training paradigms administered via smartphones. The current study aimed to compare the effectiveness of three...

  5. Exchange bias properties of 140 nm-sized dipolarly interacting circular dots with ultrafine IrMn and NiFe layers

    Science.gov (United States)

    Spizzo, F.; Tamisari, M.; Chinni, F.; Bonfiglioli, E.; Gerardino, A.; Barucca, G.; Bisero, D.; Fin, S.; Del Bianco, L.

    2016-02-01

    We studied the exchange bias effect in an array of IrMn(3 nm)/NiFe(3 nm) circular dots (size 140 nm and center-to-center distance 200 nm, as revealed by microscopy analyses), prepared on a large area (3×3 mm2) by electron beam lithography and lift-off, using dc sputtering deposition. Hysteresis loops were measured by SQUID magnetometer at increasing values of temperature T (in the 5-300 K range) after cooling from 300 K down to 5 K in zero field (ZFC mode) and in a saturating magnetic field (FC mode). The exchange bias effect disappears above T 200 K and, at each temperature, the exchange field HEX measured in ZFC is substantially lower than the FC one. Micromagnetic calculations indicate that, at room temperature, each dot is in high-remanence ground state, but magnetic dipolar interactions establish a low-remanence configuration of the array as a whole. Hence, at low temperature, following the ZFC procedure, the exchange anisotropy in the dot array is averaged out, tending to zero. However, even the FC values of HEX and of the coercivity HC are definitely smaller compared to those measured in a reference continuous film with the same stack configuration (at T=5 K, HEX 90 Oe and HC 180 Oe in the dots and HEX 1270 Oe and HC 860 Oe in the film). Our explanation is based on the proven glassy magnetic nature of the ultrathin IrMn layer, implying the existence of magnetic correlations among the spins, culminating in a collective freezing below T 100 K. We propose, also by the light of micromagnetic simulations, that the small dot size imposes a spatial constraint on the magnetic correlation length among the IrMn spins so that, even at the lowest temperature, their thermal stability, especially at the dot border, is compromised.

  6. Magnetic charge distribution and stray field landscape of asymmetric néel walls in a magnetically patterned exchange bias layer system

    Science.gov (United States)

    Zingsem, Norbert; Ahrend, Florian; Vock, Silvia; Gottlob, Daniel; Krug, Ingo; Doganay, Hatice; Holzinger, Dennis; Neu, Volker; Ehresmann, Arno

    2017-12-01

    The 3D stray field landscape above an exchange bias layer system with engineered domain walls has been fully characterized by quantitative magnetic force microscopy (qMFM) measurements. This method is based on a complete quantification of the MFM tip’s imaging properties and the subtraction of its contribution from the measured MFM data by deconvolution in Fourier space. The magnetically patterned Ir17Mn83/Co70Fe30-exchange-bias-multilayers have been designed to contain asymmetric head-to-head (hh)/tail-to-tail (tt) Néel walls between domains of different magnetic anisotropies for potential use in guided particle transport. In the current application, qMFM reveals the effective magnetic charge profile on the surface of the sample—with high spatial resolution and in an absolute quantitative manner. These data enable to calculate the magnetostatic potential and the full stray field landscape above the sample surface. It has been successfully tested against: (i) micromagnetic simulations of the magnetization structure of a comparable exchange-bias layer system, (ii) measurements of the magnetization profile across the domain boundary with x-ray photoemission electron microscopy, and (iii) direct stray field measurements obtained by scanning Hall probe microscopy at elevated scan heights. This approach results in a quantitative determination of the stray field landscape at close distances to the sample surface, which will be of importance for remote magnetic particle transport applications in lab-on-a-chip devices. Furthermore, the highly resolving and quantitative MFM approach reveals details of the domain transition across the artificially structured phase boundary, which have to be attributed to a continuous change in the materials parameters across this boundary, rather than an abrupt one.

  7. Real effective exchange rate misalignment in Nigeria

    OpenAIRE

    Nwachukwu, Ngozi E.; Adebayo, Racheal O.; Shettima, Abdullahi M.; Anigwe, John O.; Udechukwu-Peterclaver, Chidinma T.

    2016-01-01

    The study analyzed the relationship between relevant macroeconomic variables and the real effective exchange rate (REER) in Nigeria based on the Behavioural Equilibrium Exchange Rate (BEER) approach. An Autoregressive Distributed Lag (ARDL) model was estimated to obtain the equilibrium REER while the resultant levels of misalignment were computed for the period 1990 - 2014. Model results indicated that terms of trade and degree of trade openness are significant determinants of the REER, imply...

  8. Biases of Professional Exchange Rate Forecasts: Psychological Explanations and an Experimentally-Based Comparison to Novices

    OpenAIRE

    Bofinger, Peter; Leitner, Johannes; Schmidt, Robert

    2004-01-01

    The empirical performance of macroeconomic exchange rate models is more than disappointing. This dismal result is also reflected in the forecasting capabilities of professional analysts: all in all, analysts are not in a position to beat naïve random walk forecasts. The root for this deficient outcome stems from the fact that professional forecasts are to a large extend influenced by actual changes in exchange rates. A reasonable explanation for this behaviour can be taken from the behavioura...

  9. Context effects and observer bias--implications for forensic odontology.

    Science.gov (United States)

    Page, Mark; Taylor, Jane; Blenkin, Matt

    2012-01-01

    Psychologists have long recognized the effects of contextual and extraneous information on decision making. Such information renders the subject susceptible to both motivational and cognitive bias; yet, it is difficult to assess the extent to which these influence forensic odontologists opinions as there have been no studies to date on this subject. This article explores the various types of contextual effects and biasing influences that potentially impact on the analysis of bitemarks in forensic odontology. It appears that the current practice of bitemark analysis is rich in sources of potentially biasing influences. In addition to the fundamental recognition that some form of bias is likely to exist, ways in which these should be minimized include: separation of the collection and analysis phases; limiting the amount of contextual information available to the odontologist responsible for the analysis; and ensuring that evidence that is ambiguous or of poor quality is identified as such prior to analysis. © 2011 American Academy of Forensic Sciences.

  10. Effects of Cognitive Bias Modification Training via Smartphones

    Science.gov (United States)

    Yang, Ranming; Cui, Lixia; Li, Feng; Xiao, Jing; Zhang, Qin; Oei, Tian P. S.

    2017-01-01

    Background and Objectives: Negative cognitive biases have been linked to anxiety and mood problems. Accumulated data from laboratory studies show that positive and negative interpretation styles with accompanying changes in mood can be induced through cognitive bias modification (CBM) paradigms. Despite the therapeutic potential of positive training effects, few studies have explored training paradigms administered via smartphones. The current study aimed to compare the effectiveness of three different types of training programmes (cognitive bias modification-attention, CBM-A; cognitive bias modification-interpretation, CBM-I; attention and interpretation modification, AIM) administered via smart-phones by using a control condition (CC). Methods: Seventy-six undergraduate participants with high social anxiety (Liebowitz Social Anxiety Scale, LSAS ≥ 30) were randomly assigned to four groups: CBM-A (n = 20), CBM-I (n = 20), AIM (n = 16), and CC (n = 20). Results: The results showed that the effects of CBM training, CBM-I training, or AIM training vs. CC for attention yielded no significant differences in dot-probe attention bias scores. The CBM-I group showed significantly less threat interpretation and more benign interpretation than the CC group on interpretation bias scores. Conclusions: The present results supported the feasibility of delivering CBM-I via smartphones, but the effectiveness of CBM-A and AIM training via smartphones was limited. PMID:28855880

  11. Effects of Cognitive Bias Modification Training via Smartphones.

    Science.gov (United States)

    Yang, Ranming; Cui, Lixia; Li, Feng; Xiao, Jing; Zhang, Qin; Oei, Tian P S

    2017-01-01

    Background and Objectives: Negative cognitive biases have been linked to anxiety and mood problems. Accumulated data from laboratory studies show that positive and negative interpretation styles with accompanying changes in mood can be induced through cognitive bias modification (CBM) paradigms. Despite the therapeutic potential of positive training effects, few studies have explored training paradigms administered via smartphones. The current study aimed to compare the effectiveness of three different types of training programmes (cognitive bias modification-attention, CBM-A; cognitive bias modification-interpretation, CBM-I; attention and interpretation modification, AIM) administered via smart-phones by using a control condition (CC). Methods:Seventy-six undergraduate participants with high social anxiety (Liebowitz Social Anxiety Scale, LSAS ≥ 30) were randomly assigned to four groups: CBM-A (n = 20), CBM-I (n = 20), AIM (n = 16), and CC (n = 20). Results: The results showed that the effects of CBM training, CBM-I training, or AIM training vs. CC for attention yielded no significant differences in dot-probe attention bias scores. The CBM-I group showed significantly less threat interpretation and more benign interpretation than the CC group on interpretation bias scores. Conclusions: The present results supported the feasibility of delivering CBM-I via smartphones, but the effectiveness of CBM-A and AIM training via smartphones was limited.

  12. Effects of Cognitive Bias Modification Training via Smartphones

    Directory of Open Access Journals (Sweden)

    Ranming Yang

    2017-08-01

    Full Text Available Background and Objectives: Negative cognitive biases have been linked to anxiety and mood problems. Accumulated data from laboratory studies show that positive and negative interpretation styles with accompanying changes in mood can be induced through cognitive bias modification (CBM paradigms. Despite the therapeutic potential of positive training effects, few studies have explored training paradigms administered via smartphones. The current study aimed to compare the effectiveness of three different types of training programmes (cognitive bias modification-attention, CBM-A; cognitive bias modification-interpretation, CBM-I; attention and interpretation modification, AIM administered via smart-phones by using a control condition (CC.Methods:Seventy-six undergraduate participants with high social anxiety (Liebowitz Social Anxiety Scale, LSAS ≥ 30 were randomly assigned to four groups: CBM-A (n = 20, CBM-I (n = 20, AIM (n = 16, and CC (n = 20.Results: The results showed that the effects of CBM training, CBM-I training, or AIM training vs. CC for attention yielded no significant differences in dot-probe attention bias scores. The CBM-I group showed significantly less threat interpretation and more benign interpretation than the CC group on interpretation bias scores.Conclusions: The present results supported the feasibility of delivering CBM-I via smartphones, but the effectiveness of CBM-A and AIM training via smartphones was limited.

  13. Investigating Exchange Bias and Coercivity in Fe3O4–γ-Fe2O3 Core–Shell Nanoparticles of Fixed Core Diameter and Variable Shell Thicknesses

    Directory of Open Access Journals (Sweden)

    Ihab M. Obaidat

    2017-11-01

    Full Text Available We have carried out extensive measurements on novel Fe3O4–γ-Fe2O3 core–shell nanoparticles of nearly similar core diameter (8 nm and of various shell thicknesses of 1 nm (sample S1, 3 nm (sample S2, and 5 nm (sample S3. The structure and morphology of the samples were studied using X-ray diffraction (XRD, transmission electron microscopy (TEM, and selected area electron diffraction (SAED. The direct current (DC magnetic measurements were carried out using a superconducting quantum interference device (SQUID. Exchange bias and coercivity were investigated at several temperatures where the applied field was varied between 3 and −3 T. Several key results are obtained, such as: (a the complete absence of exchange bias effect in sample S3; (b the occurrence of nonconventional exchange bias effect in samples S2 and S1; (c the sign-change of exchange bias field in sample S2; (d the monotonic increase of coercivity with temperature above 100 K in all samples; (e the existence of a critical temperature (100 K at which the coercivity is minimum; (f the surprising suppression of coercivity upon field-cooling; and (g the observation of coercivity at all temperatures, even at 300 K. The results are discussed and attributed to the existence of spin glass clusters at the core–shell interface.

  14. Effects of imaging gradients in sequences with varying longitudinal storage time-Case of diffusion exchange imaging

    DEFF Research Database (Denmark)

    Lasic, Samo; Lundell, Henrik; Topgaard, Daniel

    2017-01-01

    Purpose: To illustrate the potential bias caused by imaging gradients in correlation MRI sequences using longitudinal magnetization storage (LS) and examine the case of filter exchange imaging (FEXI) yielding maps of the apparent exchange rate (AXR). Methods: The effects of imaging gradients...... low-pass diffusion filtering during the LS interval, which is more pronounced at lower exchange rates. For a total exchange rate constant larger than 1 s-1, the AXR bias is expected to be negligible when slices thicker than 2.5mm are used. Conclusion: In correlation experiments like FEXI, relying...... in FEXI were observed on yeast cells. To analyze the AXR bias, signal evolution was calculated by applying matrix exponential operators. Results: A sharp threshold for the slice thickness was identified, below which the AXR is increasingly underestimated. The bias can be understood in terms of an extended...

  15. Methods for preparing polymer-decorated single exchange-biased magnetic nanoparticles for application in flexible polymer-based films

    Directory of Open Access Journals (Sweden)

    Laurence Ourry

    2017-02-01

    Full Text Available Background: Magnetic nanoparticles (NPs must not only be well-defined in composition, shape and size to exhibit the desired properties (e.g., exchange-bias for thermal stability of the magnetization but also judiciously functionalized to ensure their stability in air and their compatibility with a polymer matrix, in order to avoid aggregation which may seriously affect their physical properties. Dipolar interactions between NPs too close to each other favour a collective magnetic glass state with lower magnetization and coercivity because of inhomogeneous and frustrated macrospin cluster freezing. Consequently, tailoring chemically (through surface functionalization and magnetically stable NPs for technological applications is of primary importance.Results: In this work, well-characterized exchange-biased perfectly epitaxial CoxFe3−xO4@CoO core@shell NPs, which were isotropic in shape and of about 10 nm in diameter, were decorated by two different polymers, poly(methyl methacrylate (PMMA or polystyrene (PS, using radical-controlled polymerization under various processing conditions. We compared the influence of the synthesis parameters on the structural and microstructural properties of the resulting hybrid systems, with special emphasis on significantly reducing their mutual magnetic attraction. For this, we followed two routes: the first one consists of the direct grafting of bromopropionyl ester groups at the surface of the NPs, which were previously recovered and redispersed in a suitable solvent. The second route deals with an “all in solution” process, based on the decoration of NPs by oleic acid followed by ligand exchange with the desired bromopropionyl ester groups. We then built various assemblies of NPs directly on a substrate or suspended in PMMA.Conclusion: The alternative two-step strategy leads to better dispersed polymer-decorated magnetic particles, and the resulting nanohybrids can be considered as valuable building

  16. Effects of ESP forecast bias-correction on deterministic optimization method biases.

    Science.gov (United States)

    Arsenault, R.; Côté, P.; Latraverse, M.

    2016-12-01

    Rio Tinto is a multinational metal and natural resources producer with energy-intensive aluminium smelters in Quebec, Canada. Rio Tinto also owns and operates power houses on the Péribonka and Saguenay Rivers in Quebec. The system, which is run by Rio Tinto's Quebec Power Operations Division, consists of 6 generating stations and 3 major reservoirs. One of the significant issues that had to be resolved for effective operation of this system was to determine the volume of weekly water releases for all generating stations. Several challenges had to be dealt with before a suitable solution could be found. In the past two years, we developed a rolling horizon test bed that mimics the day to day system operation. With this test bed, we compared four different algorithms (three stochastic and one deterministic) and found that using an anticipative deterministic approach to calculate the release decisions for the first period is an inadequate strategy. The results also showed that methods based on scenarios prove superior to methods based on probability distributions. The test bed was also used to assess the quality of the Ensemble Streamflow Prediction (ESP) forecast. It was found that under-dispersion in ESPs impacted the quality of the results and that the optimization methods did not all react in the same way. We show that the bias introduced by the use of a deterministic optimization method can hinder the efforts placed in bias-correcting ESP forecasts. We also show that biasing the ESP members (or alternatively by selecting a decision scenario other than the median one) it was possible to negate the deterministic bias and consistently improve the overall power generation.

  17. Radiation effects on ion exchange materials

    Energy Technology Data Exchange (ETDEWEB)

    Gangwer, T.E.; Goldstein, M.; Pillay, K.K.S.

    1977-11-01

    An extensive literature review and data compilation has been completed on the radiation-damage of ion exchange resins. The primary goal of the study has been to review the available literature on ion exchange materials used in, as well as those with potential for use in, the nuclear fuel and waste reprocessing areas. The physical and chemical properties of ion exchangers are reviewed. Experimental parameters useful in characterizing the effects of radiation on synthetic ion exchange resins are identified or defined. In compiling the diverse types of data, an effort was made to present the experimental data or experimentally based parameters in a format that would be useful for inter-comparing radiation effects on resins. When subject to radiation there are various general trends or qualitative effects displayed by the different types of resins. These radiation-trends and effects have been formulated into qualitative statements. The present day level of understanding of the behavior of resins under ionizing radiation is too limited to justify quantitative predictive modeling. The limitations and deficiencies of the literature are discussed and the experimentation needed to achieve quantitative modeling are outlined. 14 figs., 108 references.

  18. Effects of positive interpretive bias modification in highly anxious individuals.

    Science.gov (United States)

    Salemink, Elske; van den Hout, Marcel; Kindt, Merel

    2009-06-01

    Over the past 20 years evidence has accumulated that individuals suffering from anxiety tend to interpret ambiguous information as threatening. Considering the causal role of this interpretive bias in anxiety, it was recently established that modifying interpretive biases influences anxiety. This suggests that anxiety can be clinically treated by directly targeting this interpretive bias. The present study was designed to modify a negative interpretive bias in highly anxious individuals, and subsequently assess the hypothesized beneficial effects on clinical measures. High trait-anxious participants were randomly assigned to one of two conditions: a positive interpretational Cognitive Bias Modification (CBM-I) or a control condition (n=2 x 17). The program was offered online for eight consecutive days. Upon completing the program, participants who had followed positive CBM-I were less state and trait-anxious compared to the control group. Additionally, positively trained participants scored lower on a measure of general psychopathology (SCL-90). No effects were observed on social anxiety and stress vulnerability. The mixed pattern of findings renders them rather inconclusive, leaving interpretations of the potential therapeutic merits of CBM-I open for future research.

  19. Origins of the Exchange-Bias Phenomenology, Coercivity Enhancement, and Asymmetric Hysteretic Shearing in Core-Surface Smart Nanoparticles

    Directory of Open Access Journals (Sweden)

    Rıza Erdem

    2016-01-01

    Full Text Available We have used a spin-1 Ising model Hamiltonian with dipolar (bilinear, J, quadrupolar (biquadratic, K, and dipolar-quadrupolar (odd, L interactions in pair approximation to investigate the exchange-bias (EB, coercive field, and asymmetric hysteretic shearing properties peculiar to core/surface (C/S composite nanoparticles (NPs. Shifted hysteresis loops with an asymmetry and coercivity enhancement are observed only in the presence of the odd interaction term in the Hamiltonian expression and their magnitudes show strong dependence on the value of L. The observed coercivity and EB in C/S NPs originated from nonzero odd coupling energies and their dependence on temperature (T and particle size (R are also discussed in relation to experimental findings.

  20. Exchange biased FeNi/FeMn bilayers with coercivity and switching field enhanced by FeMn surface oxidation

    Directory of Open Access Journals (Sweden)

    A. V. Svalov

    2013-09-01

    Full Text Available FeNi/FeMn bilayers were grown in a magnetic field and subjected to heat treatments at temperatures of 50 to 350 °C in vacuum or in a gas mixture containing oxygen. In the as-deposited state, the hysteresis loop of 30 nm FeNi layer was shifted. Low temperature annealing leads to a decrease of the exchange bias field. Heat treatments at higher temperatures in gas mixture result in partial oxidation of 20 nm thick FeMn layer leading to a nonlinear dependence of coercivity and a switching field of FeNi layer on annealing temperature. The maximum of coercivity and switching field were observed after annealing at 300 °C.

  1. Investigating the effects of liquidity and exchange rate on Tehran Stock Exchange

    Directory of Open Access Journals (Sweden)

    Younos Vakil Alroaia

    2014-08-01

    Full Text Available This paper presents an empirical investigation to study the effects of two macroeconomic factors; namely exchange rate and liquidity on stock index. The proposed study was applied in Iran and on major index of Tehran Stock Exchange over the period 2001-2011. They reported that the currency exchange maintained negative impact on stock exchange for the period of investigation. This is due to the fact that when currency devalued, working capital decreases and firms did not enough money to purchase raw materials, pay wages, etc. In addition, liquidity marinated a direct and positive relationship with exchange index. However, the impact of liquidity seems to be bigger than currency exchange.

  2. Evaluating Gender Bias in Ratings of University Instructors' Teaching Effectiveness

    Science.gov (United States)

    Young, Suzanne; Rush, Leslie; Shaw, Dale

    2009-01-01

    The purpose of this study was to examine the gender bias in student ratings of effective teaching. Students in five colleges were invited to rate instructors on three factors: interpersonal characteristics, pedagogical characteristics, and course content characteristics. We analyzed group differences based on student gender, instructor gender, and…

  3. The influence of oxidation process on exchange bias in egg-shaped FeO/Fe3O4 core/shell nanoparticles

    Science.gov (United States)

    Leszczyński, Błażej; Hadjipanayis, George C.; El-Gendy, Ahmed A.; Załęski, Karol; Śniadecki, Zbigniew; Musiał, Andrzej; Jarek, Marcin; Jurga, Stefan; Skumiel, Andrzej

    2016-10-01

    Egg-shaped nanoparticles with a core-shell morphology were synthesized by thermal decomposition of an iron oleate complex. XRD and M(T) magnetic measurements confirmed the presence of FeO (wustite) and Fe3O4 (magnetite) phases in the nanoparticles. Oxidation of FeO to Fe3O4 was found to be the mechanism for the shell formation. As-made nanoparticles exhibited high values of exchange bias at 2 K. Oxidation led to decrease of exchange field from 2880 Oe (in as-made sample) to 330 Oe (in oxidized sample). At temperatures higher than the Néel temperature of FeO (200 K) there was no exchange bias. An interesting observation was made showing the exchange field to be higher than the coercive field at temperatures close to magnetite's Verwey transition.

  4. Cognitive Bias Modification Training in Adolescents: Effects on Interpretation Biases and Mood

    Science.gov (United States)

    Lothmann, Claudia; Holmes, Emily A.; Chan, Stella W. Y.; Lau, Jennifer Y. F.

    2011-01-01

    Background: Negative biases in the interpretation of ambiguous material have been linked to anxiety and mood problems. Accumulating data from adults show that positive and negative interpretation styles can be induced through cognitive bias modification (CBM) paradigms with accompanying changes in mood. Despite the therapeutic potential of…

  5. Bias in the exchange of arguments: the case of scientists' evaluation of lay viewpoints on GM food.

    Science.gov (United States)

    Cuppen, Eefje; Hisschemøller, Matthijs; Midden, Cees

    2009-09-01

    Most perspectives on public participation share the notion that dialogues should be open, allowing participants to articulate and evaluate different views and knowledge claims. We hypothesize that participants' evaluation of claims may be biased because participants have a preference for a particular type or source of a claim. This would hamper an open dialogue. We tested the effect of three variables on scientists' evaluation of claims of the general public about GM food: the claim's favorability towards GM food, the phrasing, and the source of the claim. Results are based on a survey-experiment among 73 biotechnology-scientists. Biased processing occurred when scientists evaluated claims. Claims that were corresponding with the attitude of the scientists and that were phrased in a cognitive way were evaluated more positively than claims that were contrasting the attitude of the scientists and that were phrased in an affective way. Contrary to our expectation, scientists evaluated claims of the public more positively than claims of experts.

  6. Electric field induced reversible 180° magnetization switching through tuning of interfacial exchange bias along magnetic easy-axis in multiferroic laminates.

    Science.gov (United States)

    Xue, Xu; Zhou, Ziyao; Peng, Bin; Zhu, Mingmin; Zhang, Yijun; Ren, Wei; Ren, Tao; Yang, Xi; Nan, Tianxiang; Sun, Nian X; Liu, Ming

    2015-11-18

    E-field control of interfacial exchange coupling and deterministic switching of magnetization have been demonstrated in two sets of ferromagnetic(FM)/antiferromagnetic(AFM)/ferroelectric(FE) multiferroic heterostructures, including NiFe/NiCoO/glass/PZN-PT (011) and NiFe/FeMn/glass/PZN-PT (011). We designed this experiment to achieve exchange bias tuning along the magnetic easy axis, which is critical for realizing reversible 180° magnetization deterministic switching at zero or small magnetic bias. Strong exchange coupling were established across AFM-FM interfaces, which plays an important role in voltage control of magnetization switching. Through the competition between the E-field induced uniaxial anisotropy in ferromagnetic layer and unidirectional anisotropy in antiferromagnetic layer, the exchange bias was significantly shifted by up to |∆Hex|/Hex = 8% in NiFe/FeMn/glass/PZN-PT (011) and 13% in NiFe/NiCoO/glass/PZN-PT (011). In addition, the square shape of the hysteresis loop, as well as a strong shape tunability of |∆Hex|/Hc = 67.5 ~ 125% in NiFe/FeMn/glass/PZN-PT and 30 ~ 38% in NiFe/NiCoO/glass/PZN-PT were achieved, which lead to a near 180° magnetization switching. Electrical tuning of interfacial exchange coupling in FM/AFM/FE systems paves a new way for realizing magnetoelectric random access memories and other memory technologies.

  7. The influence of oxidation process on exchange bias in egg-shaped FeO/Fe{sub 3}O{sub 4} core/shell nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Leszczyński, Błażej, E-mail: b.leszczynski@amu.edu.pl [NanoBioMedical Centre, Adam Mickiewicz University, Umultowska 85, 61-614 Poznań (Poland); Faculty of Physics, Adam Mickiewicz University, Umultowska 85, 61-614 Poznań (Poland); Hadjipanayis, George C.; El-Gendy, Ahmed A. [Department of Physics and Astronomy, University of Delaware, 217 Sharp Lab, Newark, DE 19716 (United States); Załęski, Karol [NanoBioMedical Centre, Adam Mickiewicz University, Umultowska 85, 61-614 Poznań (Poland); Śniadecki, Zbigniew [Institute of Molecular Physics, Polish Academy of Sciences, M. Smoluchowskiego 17, 60-179 Poznań (Poland); Musiał, Andrzej [NanoBioMedical Centre, Adam Mickiewicz University, Umultowska 85, 61-614 Poznań (Poland); Institute of Molecular Physics, Polish Academy of Sciences, M. Smoluchowskiego 17, 60-179 Poznań (Poland); Jarek, Marcin [NanoBioMedical Centre, Adam Mickiewicz University, Umultowska 85, 61-614 Poznań (Poland); Jurga, Stefan [NanoBioMedical Centre, Adam Mickiewicz University, Umultowska 85, 61-614 Poznań (Poland); Faculty of Physics, Adam Mickiewicz University, Umultowska 85, 61-614 Poznań (Poland); Skumiel, Andrzej [Faculty of Physics, Adam Mickiewicz University, Umultowska 85, 61-614 Poznań (Poland)

    2016-10-15

    Egg-shaped nanoparticles with a core–shell morphology were synthesized by thermal decomposition of an iron oleate complex. XRD and M(T) magnetic measurements confirmed the presence of FeO (wustite) and Fe{sub 3}O{sub 4} (magnetite) phases in the nanoparticles. Oxidation of FeO to Fe{sub 3}O{sub 4} was found to be the mechanism for the shell formation. As-made nanoparticles exhibited high values of exchange bias at 2 K. Oxidation led to decrease of exchange field from 2880 Oe (in as-made sample) to 330 Oe (in oxidized sample). At temperatures higher than the Néel temperature of FeO (200 K) there was no exchange bias. An interesting observation was made showing the exchange field to be higher than the coercive field at temperatures close to magnetite's Verwey transition. - Highlights: • Synthesis of monodispersed FeO nanoparticles is shown. • As-made FeO nanoparticle is antiferromagnetically ordered, when it is oxidized to Fe{sub 3}O{sub 4}, the FeO core becomes small and disordered. • Exchange bias in well-ordered and disordered core is different.

  8. Sex-biased genetic effects on gene regulation in humans

    Science.gov (United States)

    Dimas, Antigone S.; Nica, Alexandra C.; Montgomery, Stephen B.; Stranger, Barbara E.; Raj, Towfique; Buil, Alfonso; Giger, Thomas; Lappalainen, Tuuli; Gutierrez-Arcelus, Maria; McCarthy, Mark I.; Dermitzakis, Emmanouil T.

    2012-01-01

    Human regulatory variation, reported as expression quantitative trait loci (eQTLs), contributes to differences between populations and tissues. The contribution of eQTLs to differences between sexes, however, has not been investigated to date. Here we explore regulatory variation in females and males and demonstrate that 12%–15% of autosomal eQTLs function in a sex-biased manner. We show that genes possessing sex-biased eQTLs are expressed at similar levels across the sexes and highlight cases of genes controlling sexually dimorphic and shared traits that are under the control of distinct regulatory elements in females and males. This study illustrates that sex provides important context that can modify the effects of functional genetic variants. PMID:22960374

  9. Meson exchange-current effects in heavy nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Dehesa, J.S.; Lallena, A. (Granada Univ. (Spain). Dept. de Fisica Nuclear); Krewald, S. (Kernforschungsanlage Juelich G.m.b.H. (Germany, F.R.). Inst. fuer Kernphysik); Donnelly, T.W. (Massachusetts Inst. of Tech., Cambridge (USA). Lab. for Nuclear Science; Massachusetts Inst. of Tech., Cambridge (USA). Dept. of Physics)

    1985-04-15

    Meson exchange-current effects in the electroexcitation of magnetic states are evaluated in /sup 16/O and /sup 208/Pb. A new method is suggested which properly includes the influence of the nuclear mean field on meson exchange-current effects. In addition, an effective meson exchange-current operator is developed which considerably simplifies the evaluation of meson exchange-current effects. Over a wide range of momentum transfers, the magnetic cross sections for the electroexcitation of high-spin, stretched 1 plh states are found to be smoothly enhanced by meson exchange currents.

  10. Effect of bias in ferroelectric-antiferroelectric relaxation

    Science.gov (United States)

    Geday, M. A.; Medialdea, D. P.; Cerrolaza, B.; Bennis, N.; Quintana, X.; Otón, J. M.

    2009-06-01

    The ferroelectric-antiferroelectric transition in greyscale generation of antiferroelectric liquid crystal displays (AFLC) is a heterogeneous process. The process has been described as the growth of finger-like domains [1]. We have previously studied the ferroelectric-antiferroelectric phase transition, relaxation that follows the data pulse in surface stabilized asymmetric antiferroelectric liquid crystal displays using biasless video frequency waveforms [2]. This relaxation involves an intensity decay of the light transmitted by a pixel and depends on several parameters such as surface stabilization, rotational viscosity of the AFLC, magnitude of the data pulse, and bias voltage. The usual multiplexed driving of AFLC displays leads to long-term stabilisation of the grey levels induced by the data pulses within the selection time. However, depending on the bias level, alternative greyscale mechanisms may be obtained by allowing the grey levels to decay during the frametime. These greyscales may be advantageous in some instances since they improve the dynamic response of the AFLC device and reduce the reset time of the waveform. In this study we extend the previous work to include the effect of bias. We present the measured data, in terms of growth pattern and speed and present an extension of the previously model on order to explain the results.

  11. Lineup Identification by Children: Effects of Clothing Bias

    Science.gov (United States)

    Freire, Alejo; Lee, Kang; Williamson, Karen S.; Stuart, Sarah J. E.; Lindsay, R. C. L.

    2008-01-01

    This study examined effects of clothing cues on children's identification accuracy from lineups. Four- to 14-year-olds (n = 228) saw 12 video clips of individuals, each wearing a distinctly colored shirt. After watching each clip children were presented with a target-present or target-absent photo lineup. Three clothing conditions were included. In 2 conditions all lineup members wore the same colored shirt; in the third, biased condition, the shirt color of only one individual matched that seen in the preceding clip (the target in target-present trials and the replacement in target-absent trials). Correct identifications of the target in target-present trials were most frequent in the biased condition, whereas in target-absent trials the biased condition led to more false identifications of the target replacement. Older children were more accurate than younger children, both in choosing the target from target-present lineups and rejecting target-absent lineups. These findings suggest that a simple clothing cue such as shirt color can have a significant impact on children's lineup identification accuracy. PMID:15264450

  12. Thickness and bilayer number dependence on exchange bias in ferromagnetic/antiferromagnetic multilayers based on La{sub 1−x}Ca{sub x}MnO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Restrepo-Parra, E., E-mail: erestrepopa@unal.edu.co [Departamento de Física y Química, Universidad Nacional de Colombia-Sede Manizales, A.A. 127 Manizales (Colombia); Agudelo-Giraldo, J.D. [Departamento de Física y Química, Universidad Nacional de Colombia-Sede Manizales, A.A. 127 Manizales (Colombia); Grupo de Investigación y Desarrollo en Informática y Telecomunicaciones, Universidad de Manizales, Manizales (Colombia); Restrepo, J. [Grupo de Magnetismo y Simulación, Instituto de Física, Universidad de Antioquia, A.A. 1226 Medellín (Colombia)

    2014-05-01

    In this work, simulations of ferromagnetic/antiferromagnetic multilayers of La{sub 1−x}Ca{sub x}MnO{sub 3} have been carried out by using the Monte Carlo method combined with the Metropolis algorithm and the classical Heisenberg model. In the Hamiltonian we have considered three contributions: nearest neighbor exchange interaction, magnetocrystalline anisotropy and Zeeman interaction. Samples were built by including three types of Mn ions depending on their valence state and type of ionic orbital. Both the number of layers and the antiferromagnetic layer thickness influence on the exchange bias phenomenon are analyzed. Hysteresis loops results exhibit not only a shift as evidence of exchange bias but also the formation of plateaus or steps caused by the presence of more than one interface and the low layers thickness. Each layer presents a strong magnetic behavior because the magneto static energy favors formation of multi-domains in contrast with the single-domains of a single layer FM producing one sub-Loop of each domain (each layer). On the other hand, as the number of layers (n) increases, the sub-cycles tend to disappear. As the plateaus disappear, the system is more effective, increasing the coercive and bias fields. Moreover, domain sizes (layers thickness) also affect the shape of the hysteresis loop. On increasing the thickness of the AFM layer, a decrease in the plateaus produced by the uncoupling is generated.

  13. Robust Interfacial Exchange Bias and Metal-Insulator Transition Influenced by the LaNiO3 Layer Thickness in La0.7Sr0.3MnO3/LaNiO3 Superlattices.

    Science.gov (United States)

    Zhou, Guowei; Song, Cheng; Bai, Yuhao; Quan, Zhiyong; Jiang, Fengxian; Liu, Wenqing; Xu, Yongbing; Dhesi, Sarnjeet S; Xu, Xiaohong

    2017-01-25

    Artificial heterostructures based on LaNiO3 (LNO) have been widely investigated with the aim to realize the insulating antiferromagnetic state of LNO. In this work, we grew [(La0.7Sr0.3MnO3)5-(LaNiO3)n]12 superlattices on (001)-oriented SrTiO3 substrates by pulsed laser deposition and observed an unexpected exchange bias effect in field-cooled hysteresis loops. Through X-ray absorption spectroscopy and magnetic circular dichroism experiments, we found that the charge transfer at the interfacial Mn and Ni ions can induce a localized magnetic moment. A remarkable increase of exchange bias field and a transition from metal to insulator were simultaneously observed upon decreasing the thickness of the LNO layer, indicating the antiferromagnetic insulator state in 2 unit cells LNO ultrathin layers. The robust exchange bias of 745 Oe in the superlattice is caused by an interfacial localized magnetic moment and an antiferromagnetic state in the ultrathin LNO layer, pinning the ferromagnetic La0.7Sr0.3MnO3 layers together. Our results demonstrate that artificial interface engineering is a useful method to realize novel magnetic and transport properties.

  14. Media Bias

    OpenAIRE

    Sendhil Mullainathan; Andrei Shleifer

    2002-01-01

    There are two different types of media bias. One bias, which we refer to as ideology, reflects a news outlet's desire to affect reader opinions in a particular direction. The second bias, which we refer to as spin, reflects the outlet's attempt to simply create a memorable story. We examine competition among media outlets in the presence of these biases. Whereas competition can eliminate the effect of ideological bias, it actually exaggerates the incentive to spin stories.

  15. Spin structure of exchange biased heterostructures. Fe/MnF{sub 2} and Fe/FeF{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Sahoo, B.

    2006-12-18

    In this work, the {sup 57}Fe probe layer technique is used in order to investigate the depth- and temperature-dependent Fe-layer spin structure of exchange biased Fe/MnF{sub 2} and Fe/FeF{sub 2} (pseudo-twinned) antiferromagnetic (AFM) systems by conversion electron Moessbauer spectroscopy (CEMS) and nuclear resonant scattering (NRS) of synchrotron radiation. Two kinds of samples with a 10 A {sup 57}Fe probe layer directly at or 35 A away from the interface, labeled as interface and center sample, respectively, were studied in this work. The results obtained by CEMS for Fe/MnF{sub 2} suggests that, at 80 K, i.e., above T{sub N}=67 K of MnF{sub 2}, the remanent state Fe-layer spin structure of the two studied samples are slightly different due to their different microstructure. In the temperature range from 300 K to 80 K, the Fe-layer spin structure does not change just by zero-field cooling the sample in remanence. For Fe/FeF{sub 2}, a continuous non-monotonic change of the remanent-state Fe spin structure was observed by cooling from 300 K to 18 K. NRS of synchrotron radiation was used to investigate the temperature- and depth-dependent Fe-layer spin structure during magnetization reversal in pseudo-twinned Fe/MnF{sub 2}. A depthdependent Fe spin structure in an applied magnetic field (applied along the bisector of the twin domains) was observed at 10 K, where the Fe spins closer to the interface are not aligned along the field direction. The depth-dependence disappears at 150 K. (orig.)

  16. Can positive social exchanges buffer the detrimental effects of negative social exchanges? Age and gender differences.

    Science.gov (United States)

    Fiori, Katherine L; Windsor, Tim D; Pearson, Elissa L; Crisp, Dimity A

    2013-01-01

    Findings from existing research exploring whether positive social exchanges can help to offset (or 'buffer' against) the harmful effects of negative social exchanges on mental health have been inconsistent. This could be because the existing research is characterized by different approaches to studying various contexts of 'cross-domain' and 'within-domain' buffering, and/or because the nature of buffering effects varies according to sociodemographic characteristics that underlie different aspects of social network structure and function. The purpose of this study was to examine whether the buffering effects of global perceptions of positive exchanges on the link between global negative exchanges and mental health varied as a function of age and gender. We used a series of regressions in a sample of 556 Australian older adults (ages 55-94) to test for three-way interactions among gender, positive social exchanges, and negative social exchanges, as well as age and positive and negative social exchanges, in predicting mental health, controlling for years of education, partner status, and physical functioning. We found that positive exchanges buffered against negative exchanges for younger old adults, but not for older old adults, and for women, but not for men. Our findings are interpreted in light of research on individual differences in coping responses and interpersonal goals among late middle-aged and older adults. Our findings are in line with gerontological theories (e.g., socioemotional selectivity theory), and imply that an intervention aimed at using positive social exchanges as a means of coping with negative social exchanges might be more successful among particular populations (i.e., women, 'younger' old adults). Copyright © 2012 S. Karger AG, Basel.

  17. Establishing exchange bias below T-N with polycrystalline Ni0.52Co0.48O/Co bilayers

    DEFF Research Database (Denmark)

    Berkowitz, A.E.; Hansen, Mikkel Fougt; Tang, Y.J.

    2005-01-01

    Exchange-coupled bilayers of polycrystalline ferromagnetic (FM) Co on antiferromagnetic (AFM) Ni0.52Co0.48O were investigated with emphasis on the issue of establishing an exchange-bias field, H-E, below the AFM ordering temperature, T-N. It was found that field-cooling the bilayers through T......-N provided very little, if any, increase in H-E over that produced by deposition of the Co at temperatures far below T-N. Further significant aspects of this issue were also examined. The biasing field, H-B, needed to be applied only during the deposition of a small fraction (1 nm) of the FM film below T...

  18. Observation of magnetization and exchange bias reversals in NdFe{sub 0.5}Cr{sub 0.5}O{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Sharannia, M.P.; De, Santanu [Department of Physics, Indian Institute of Technology Madras, Chennai 600036 (India); Singh, Ripandeep; Das, A. [Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Nirmala, R. [Department of Physics, Indian Institute of Technology Madras, Chennai 600036 (India); Santhosh, P.N., E-mail: santhosh@iitm.ac.in [Department of Physics, Indian Institute of Technology Madras, Chennai 600036 (India)

    2017-05-15

    Polycrystalline NdFe{sub 0.5}Cr{sub 0.5}O{sub 3} has orthorhombic structure with Pnma space group and is magnetically ordered at room temperature as confirmed by neutron diffraction. The magnetic structure involves C{sub x}G{sub y}F{sub z} type ordering of Fe{sup 3+}/Cr{sup 3+} ions. NdFe{sub 0.5}Cr{sub 0.5}O{sub 3} shows magnetization reversal and sign reversal of exchange bias at ~16 K. Nd{sup 3+} moments that get induced by the internal field of |Fe+Cr| sublattice couple antiferromagnetically with the ferromagnetic component of |Fe+Cr| sublattice. Nd{sup 3+} moments overcome the |Fe+Cr| moments at ~16 K below which the material shows negative magnetization and positive exchange bias. - Highlights: • Neutron diffraction confirms magnetic ordering at 300 K in NdFe{sub 0.5}Cr{sub 0.5}O{sub 3}. • Magnetic structure involves C{sub x}G{sub y}F{sub z} type ordering of Fe{sup 3+}/Cr{sup 3+} ions. • Nd{sup 3+} moments couple antiferromagnetically with |Fe+Cr| ferromagnetic moments. • Shows magnetization reversal and exchange bias reversal.

  19. Magnetization reversal and tunable exchange bias in GdCr{sub 1−x}Mn{sub x}O{sub 3} (x=0−0.50)

    Energy Technology Data Exchange (ETDEWEB)

    Dash, Bibhuti B.; Ravi, S., E-mail: sravi@iitg.ernet.in

    2017-05-01

    Single phase samples of GdCr{sub 1-x}Mn{sub x}O{sub 3} (x=0−0.50) were prepared and their magnetic properties were studied by measuring temperature and field variations of magnetization. The Neel temperature, T{sub N} is found to decrease from T{sub N}=174 K for x=0 to 91 K for x=0.50. The magnetization reversal persists upto 5 at% of Mn substitution with a magnetic compensation temperature, T{sub comp} of 136 K and 139 K for x=0 and 0.05 respectively. However, spin reorientation induced magnetization reversal emerges for x=0.40 and 0.50 samples around 30 K. Tunable positive and negative exchange bias fields in the range of −1.0 kOe to +1.6 kOe have been observed. The origin of magnetization reversal and exchange bias field is explained in terms of antiparallel alignment of canted ferromagnetic component of Cr{sup 3+} ions and the paramagnetic moments of Gd{sup 3+} and Mn{sup 3+} ions under the influence of negative internal field due to antiferromagnetically ordered Cr{sup 3+} ions. - Highlights: • Magnetization reversal and bipolar switching in Mn substituted GdCrO{sub 3} • Tunable exchange bias field in the range of −1.0 kOe to +1.6 kOe. • Low temperature spin reorientation transition is observed.

  20. Acute Alcohol Effects on Attentional Bias in Heavy and Moderate Drinkers

    OpenAIRE

    Weafer, Jessica; Fillmore, Mark T.

    2012-01-01

    Heavy drinkers show an increased attentional bias to alcohol-related stimuli compared to moderate drinkers, and this bias is thought to promote motivation for alcohol consumption (Field & Cox, 2008). Studies have begun to examine acute alcohol effects on attentional bias, however little is known regarding how these effects might differ based on drinker type. Further, the degree to which attentional bias in response to alcohol is associated with excessive alcohol consumption remains unexplored...

  1. Electrochemical migration in electronics: effect of contamination and bias conditions

    DEFF Research Database (Denmark)

    Verdingovas, Vadimas; Jellesen, Morten Stendahl; Ambat, Rajan

    climate, contamination, and bias conditions. In this work, the effect of ionic contamination such as sodium chloride and weak organic acids, as they are used in no-clean fluxes, was studied under water droplet and humidity elevation at room temperature conditions. The effect of pH and tin ion dissolution...... droplet. Overall the tendency of increase in time to electrochemical migration with decrease of duty cycle was observed. The testing of the printed circuit boards under humid conditions showed a correlation between the hygroscopic property of contaminants and leakage current measured on the boards....... A significant increase of leakage current was observed at humidity levels close to the critical or deliquescence of the contaminants....

  2. Entanglement of lock-in transition and exchange bias in Co(Cr{sub 0.9}Co{sub 0.1}){sub 2}O{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Padam, R.; Ravi, S.; Pal, D., E-mail: dpal@iitg.ernet.in

    2014-09-01

    We report here the structural, magnetic and exchange bias in a well characterized single phase sample of Co(Cr{sub 0.9}Co{sub 0.1}){sub 2}O{sub 4}. A pronounced signature of thermal hysteresis in temperature dependent magnetic susceptibility curves is obtained across the lock-in transition T{sub L}≃10K. Concomitantly, exchange bias is observed only below the lock-in transition (T{sub L}≃10K). This indicates a possible coupling of exchange bias to the lock-in transition in this system.

  3. Two-photon exchange effect on deuteron electromagnetic form factors

    OpenAIRE

    Dong, Yu Bing; Chen, D. Y.

    2009-01-01

    Corrections of two-photon exchange to proton and neutron electromagnetic form factors are employed to study the effect of two-photon exchange on the deuteron electromagnetic form factors. Numerical results of the effect are given. It is suggested to test the effect in the measurement of $P_z$ in a small angle limit.

  4. The role of magnetic interactions in exchange bias properties of MnFe2O4@γ-Fe2O3 core/shell nanoparticles

    Science.gov (United States)

    Silva, F. G.; Aquino, R.; Tourinho, F. A.; Stepanov, V. I.; Raikher, Yu L.; Perzynski, R.; Depeyrot, J.

    2013-07-01

    Low-temperature magnetic properties of assemblies of 3.3 nm sized nanoparticles (NPs) based on a MnFe2O4 core protected by a maghemite shell are investigated. These NPs are obtained by a chemical core/shell method developed for the synthesis of the electrostatically stabilized ferrofluid colloidal dispersions that we probe here. They are model systems where the interparticle interaction is tuned by the NP volume fractions, ranging here between 0.4% and 13.9%. It has been shown that these NPs consist of a well-ordered ferrimagnetic core surrounded by a disordered spin glass-like surface layer and that they display uniaxial magnetic anisotropy. We compare the magnetic hysteresis loops of non-textured frozen dispersions (with magnetic anisotropy axis of NPs distributed at random) with those of a powder based on the same NPs. After cooling under field the hysteresis loops shift along the H axis, expressing the coupling between the spin-ordered cores and the disordered surface layers. The negative H-shift provides an evaluation for the exchange bias (EB) field. The EB field is optimum for a cooling field of the order of the anisotropy field. A comparison between frozen dispersions and disordered powder allows us to distinguish the influence of intra- and interparticle interactions on the EB. Interparticle collective effects dominate in the powder while an intraparticle EB, eventually hindered by dipolar interactions at large volume fraction, is observed in frozen dispersions.

  5. Plasma acceleration using a radio frequency self-bias effect

    Energy Technology Data Exchange (ETDEWEB)

    Rafalskyi, D.; Aanesland, A. [Laboratoire de Physique des Plasmas (CNRS, Ecole Polytechnique, Sorbonne Universités, UPMC Univ Paris 06, Univ Paris-Sud), Ecole Polytechnique, 91128 Palaiseau (France)

    2015-06-15

    In this work plasma acceleration using a RF self-bias effect is experimentally studied. The experiments are conducted using a novel plasma accelerator system, called Neptune, consisting of an inductively coupled plasma source and a RF-biased set of grids. The plasma accelerator can operate in a steady state mode, producing a plasma flow with separately controlled plasma flux and velocity without any magnetic configuration. The operating pressure at the source output is as low as 0.2 mTorr and can further be decreased. The ion and electron flows are investigated by measuring the ion and electron energy distribution functions both space resolved and with different orientations with respect to the flow direction. It is found that the flow of electrons from the source is highly anisotropic and directed along the ion flow and this global flow of accelerated plasma is well localized in the plasma transport chamber. The maximum flux is about 7.5·10{sup 15} ions s{sup −1} m{sup −2} (at standard conditions) on the axis and decreasing to almost zero at a radial distances of more than 15 cm from the flow axis. Varying the RF acceleration voltage in the range 20–350 V, the plasma flow velocity can be changed between 10 and 35 km/s. The system is prospective for different technology such as space propulsion and surface modification and also interesting for fundamental studies for space-related plasma simulations and investigation of the dynamo effect using accelerated rotating plasmas.

  6. Effect of cross-type bias in a two-dimensional array of short Josephson junctions

    DEFF Research Database (Denmark)

    Filatrella, G.; Pedersen, Niels Falsig; Wiesenfeld, K.

    1998-01-01

    We investigate numerically the effect of cross-type bias on two-dimensional arrays of short Josephson junctions. We have demonstrated that, for the simplest circuit, this type of bias is able to phase lock the junctions yielding a substantial improvement over ordinary biasing schemes. (C) 1998 Am...... American Institute of Physics....

  7. Surprise, Memory, and Retrospective Judgment Making: Testing Cognitive Reconstruction Theories of the Hindsight Bias Effect

    Science.gov (United States)

    Ash, Ivan K.

    2009-01-01

    Hindsight bias has been shown to be a pervasive and potentially harmful decision-making bias. A review of 4 competing cognitive reconstruction theories of hindsight bias revealed conflicting predictions about the role and effect of expectation or surprise in retrospective judgment formation. Two experiments tested these predictions examining the…

  8. Influence of Alternate Biasing on TID Effects of Irradiated Mixed-Signal Programmable Arrays

    Science.gov (United States)

    Balen, Tiago R.; Vaz, Rafael G.; Fernandes, Gustavo S.; Gonçalez, Odair L.

    2016-08-01

    This work investigates the influence of alternate biasing on TID effects in mixed-signal programmable devices. By reducing the time the device is biased when exposed to ionizing radiation, the severity of TID effects is also reduced, due to the increasing in the initial recombination of electron-hole pairs and the radiation induced charge neutralization effect. These effects are investigated considering a switched capacitor filter prototyped in a Field Programmable Analog Array. Eight samples of such device were exposed to gamma radiation while the devices were alternately biased, by repeatedly turning the power on and off, corresponding to different equivalent total biasing times and duty-cycles. Results show increase in radiation tolerance to the alternate biased devices, which is dependent also on the biasing duty-cycle. Considering this behavior, a novel system level radiation hardening technique, based on modular redundancy, associated to an alternate biasing scheme, is also proposed in this paper.

  9. NSAIDs and spontaneous abortions - true effect or an indication bias?

    Science.gov (United States)

    Daniel, Sharon; Koren, Gideon; Lunenfeld, Eitan; Levy, Amalia

    2015-10-01

    The aim of the study was to characterize the extent of indication bias resulting from the excessive use of NSAIDs on the days preceding a spontaneous abortion to relieve pain. We used data from a retrospective cohort study assessing the risk for spontaneous abortions following exposure to NSAIDs. Three definitions of exposure for cases of spontaneous abortions were compared, from the first day of pregnancy until the day of spontaneous abortion and until 3 and 2 days before a spontaneous abortion. Statistical analysis was performed using multivariate time programmed Cox regression. A sharp increase was observed in the dispensation of indomethacin, diclofenac and naproxen, and a milder increase was found in the use of ibuprofen during the week before a spontaneous abortion. Non- selective COX inhibitors in general and specifically diclofenac and indomethacin were found to be associated with spontaneous abortions when the exposure period was defined until the day of spontaneous abortion (hazard ratio (HR) 1.15, 95% confidence interval (CI) 1.04, 1.28; HR 1.31, 95% CI 1.08, 1.59 and HR 3.33, 95% CI 2.09, 5.29, respectively). The effect disappears by excluding exposures occurring on the day before the spontaneous abortion for non-selective COX inhibitors and on the last week before the spontaneous abortion for indomethacin. In general, decreasing HRs were found with the exclusion of exposures occurring on the days immediately before the spontaneous abortion. The increased use of NSAIDs during the last few days that preceded a spontaneous abortion to relieve pain associated with the miscarriage could bias studies assessing the association between exposure to NSAIDs and spontaneous abortions. © 2015 The British Pharmacological Society.

  10. Effect of bias voltage on microstructure and mechanical properties of ...

    Indian Academy of Sciences (India)

    Mechanical properties were deduced from nano-indentation measurements. The residual stress in all the coatings was compressive and increased with increasing bias voltage in a manner similar to that reported in literature for Ti–Al–N coatings deposited with CAE. The bias voltage was also found to significantly influence ...

  11. Cognitive Bias Modification for Interpretation in Major Depression: Effects on Memory and Stress Reactivity.

    Science.gov (United States)

    Joormann, Jutta; Waugh, Christian E; Gotlib, Ian H

    2015-01-01

    Interpreting ambiguous stimuli in a negative manner is a core bias associated with depression. Investigators have used cognitive bias modification for interpretation (CBM-I) to demonstrate that it is possible to experimentally induce and modify these biases. This study extends previous research by examining whether CBM-I affects not only interpretation, but also memory and physiological stress response in individuals diagnosed with Major Depressive Disorder (MDD). We found that CBM-I was effective in inducing an interpretive bias. Participants also exhibited memory biases that corresponded to their training condition and demonstrated differential physiological responding in a stress task. These results suggest that interpretation biases in depression can be modified, and that this training can lead to corresponding changes in memory and to decreases in stress reactivity. Findings from this study highlight the importance of examining the relations among different cognitive biases in MDD and the possibility of modifying cognitive biases.

  12. Jeans instability with exchange effects in quantum dusty magnetoplasmas

    Energy Technology Data Exchange (ETDEWEB)

    Jamil, M., E-mail: jamil.gcu@gmail.com [Department of Physics, COMSATS Institute of Information Technology, Lahore 54000 (Pakistan); Rasheed, A. [Department of Physics, Government College University, Faisalabad 38000 (Pakistan); Rozina, Ch. [Department of Physics, Lahore College for Women University, Lahore 54000 (Pakistan); Jung, Y.-D. [Department of Applied Physics and Department of Bionanotechnology, Hanyang University, Ansan, Kyunggi-Do 426-791 (Korea, Republic of); Salimullah, M. [Department of Physics, Jahangirnagar University, Savar, Dhaka 1342 (Bangladesh)

    2015-08-15

    Jeans instability is examined in magnetized quantum dusty plasmas using the quantum hydrodynamic model. The quantum effects are considered via exchange-correlation potential, recoil effect, and Fermi degenerate pressure, in addition to thermal effects of plasma species. It is found that the electron exchange and correlation potential have significant effects over the threshold value of wave vector and Jeans instability. The presence of electron exchange and correlation effect shortens the time of dust sound that comparatively stabilizes the self gravitational collapse. The results at quantum scale are helpful in understanding the collapse of the self-gravitating dusty plasma systems.

  13. Brazilian exchange rate complexity: Financial crisis effects

    Science.gov (United States)

    Piqueira, José Roberto C.; Mortoza, Letícia Pelluci D.

    2012-04-01

    With the financial market globalization, foreign investments became vital for the economies, mainly in emerging countries. In the last decades, Brazilian exchange rates appeared as a good indicator to measure either investors' confidence or risk aversion. Here, some events of global or national financial crisis are analyzed, trying to understand how they influenced the "dollar-real" rate evolution. The theoretical tool to be used is the López-Mancini-Calbet (LMC) complexity measure that, applied to real exchange rate data, has shown good fitness between critical events and measured patterns.

  14. Effects of biasing on the galaxy power spectrum at large scales

    Science.gov (United States)

    Beltrán Jiménez, José; Durrer, Ruth

    2011-05-01

    In this paper we study the effect of biasing on the power spectrum at large scales. We show that even though nonlinear biasing does introduce a white noise contribution on large scales, the P(k)∝kn behavior of the matter power spectrum on large scales may still be visible and above the white noise for about one decade. We show, that the Kaiser biasing scheme which leads to linear bias of the correlation function on large scales, also generates a linear bias of the power spectrum on rather small scales. This is a consequence of the divergence on small scales of the pure Harrison-Zeldovich spectrum. However, biasing becomes k dependent if we damp the underlying power spectrum on small scales. We also discuss the effect of biasing on the baryon acoustic oscillations.

  15. ESTIMATING THE EFFECTS OF EXCHANGE AND INTEREST ...

    African Journals Online (AJOL)

    Common stock value is affected by two important economic and financial risk factors namely interest rate and exchange rate. Interest rate which reflects the price of money also affects other variables in the financial market. Valuation of stock prices is indirectly affected by interest rates while directly its volatility causes a shift ...

  16. Recognition memory for pictorial stimuli: biasing effects of stimulus emotionality.

    Science.gov (United States)

    Fernández-Rey, José; Redondo, Jaime

    2007-08-01

    The possibility that stimulus emotionality might influence recognition bias in a long-term memory task was studied with respect to both the valence and arousal dimensions of emotion. For this purpose, we used 108 International Affective Picture System pictures that were representative of all regions of this two-dimensional space. Signal detection theory analysis was applied using A'and B'' D as discrimination and bias measures, respectively. In general, the results showed that greater discrimination was accompanied by a response bias that was more conservative for pleasant and for unarousing pictures than for unpleasant and for arousing ones. These results provide new evidence in connection with the emotion-induced recognition bias in long-term memory performance.

  17. Treatment effect on biases in size estimation in spider phobia.

    Science.gov (United States)

    Shiban, Youssef; Fruth, Martina B; Pauli, Paul; Kinateder, Max; Reichenberger, Jonas; Mühlberger, Andreas

    2016-12-01

    The current study investigates biases in size estimations made by spider-phobic and healthy participants before and after treatment. Forty-one spider-phobic and 20 healthy participants received virtual reality (VR) exposure treatment and were then asked to rate the size of a real spider immediately before and, on average, 15days after the treatment. During the VR exposure treatment skin conductance response was assessed. Prior to the treatment, both groups tended to overestimate the size of the spider, but this size estimation bias was significantly larger in the phobic group than in the control group. The VR exposure treatment reduced this bias, which was reflected in a significantly smaller size rating post treatment. However, the size estimation bias was unrelated to the skin conductance response. Our results confirm the hypothesis that size estimation by spider-phobic patients is biased. This bias is not stable over time and can be decreased with adequate treatment. Copyright © 2016 Elsevier B.V. All rights reserved.

  18. Temperature and magnetic field-assisted switching of magnetization and observation of exchange bias in YbCrO3 nanocrystals.

    Science.gov (United States)

    Gupta, Preeti; Poddar, Pankaj

    2015-10-05

    In this paper, we demonstrate an interesting feature in YbCrO3 (YCO) nanocrystals, in which the material shows temperature and external magnetic field-assisted switching (a complete sign reversal) of zero field cooled magnetization (MZFC) and observation of exchange bias (EB) as a result of competing spin interaction at low temperature. This feature can be applied in nonvolatile memories, where, simply by changing the magnitude of the Hext and T, the polarity of the magnetization can be switched between negative and positive. We also observed negative magnetization in YCO. Our results showed that, below its Nèel temperature (TN ≈ 119 K), the MZFC crosses over to negative sign for H < 1000 Oe. At 60 K, YCO showed a significant negative MZFC ≈ -0.05 emu/g (at 100 Oe) due to the competing effects of Yb(3+), Cr(3+) spins, thermal activation energy, and Hext. At further lower temperatures, the MZFC showed a crossover to positive values, and the crossover temperature showed the dependence on Hext (∼19 K for 100 Oe curve). The YCO also showed Hext and T-dependent HEB, which changed its sign with T. The observed T-dependent sign reversal in the EB was closely associated with the sign reversal of MZFC. The symmetric shift in field-cooled isothermal hysteresis curves confirmed that the observed EB was not due to the unsaturated minor loop. The training cycle further confirmed that the HEB value decreased to ∼2% of the initial value of observed EB, which was very small compared to the observed HEB in YCO, which indicated stable spin configuration at the locally formed ferromagnetic/antiferromagnetic interface.

  19. Effects of GC bias in next-generation-sequencing data on de novo genome assembly.

    Directory of Open Access Journals (Sweden)

    Yen-Chun Chen

    Full Text Available Next-generation-sequencing (NGS has revolutionized the field of genome assembly because of its much higher data throughput and much lower cost compared with traditional Sanger sequencing. However, NGS poses new computational challenges to de novo genome assembly. Among the challenges, GC bias in NGS data is known to aggravate genome assembly. However, it is not clear to what extent GC bias affects genome assembly in general. In this work, we conduct a systematic analysis on the effects of GC bias on genome assembly. Our analyses reveal that GC bias only lowers assembly completeness when the degree of GC bias is above a threshold. At a strong GC bias, the assembly fragmentation due to GC bias can be explained by the low coverage of reads in the GC-poor or GC-rich regions of a genome. This effect is observed for all the assemblers under study. Increasing the total amount of NGS data thus rescues the assembly fragmentation because of GC bias. However, the amount of data needed for a full rescue depends on the distribution of GC contents. Both low and high coverage depths due to GC bias lower the accuracy of assembly. These pieces of information provide guidance toward a better de novo genome assembly in the presence of GC bias.

  20. Effects of GC bias in next-generation-sequencing data on de novo genome assembly.

    Science.gov (United States)

    Chen, Yen-Chun; Liu, Tsunglin; Yu, Chun-Hui; Chiang, Tzen-Yuh; Hwang, Chi-Chuan

    2013-01-01

    Next-generation-sequencing (NGS) has revolutionized the field of genome assembly because of its much higher data throughput and much lower cost compared with traditional Sanger sequencing. However, NGS poses new computational challenges to de novo genome assembly. Among the challenges, GC bias in NGS data is known to aggravate genome assembly. However, it is not clear to what extent GC bias affects genome assembly in general. In this work, we conduct a systematic analysis on the effects of GC bias on genome assembly. Our analyses reveal that GC bias only lowers assembly completeness when the degree of GC bias is above a threshold. At a strong GC bias, the assembly fragmentation due to GC bias can be explained by the low coverage of reads in the GC-poor or GC-rich regions of a genome. This effect is observed for all the assemblers under study. Increasing the total amount of NGS data thus rescues the assembly fragmentation because of GC bias. However, the amount of data needed for a full rescue depends on the distribution of GC contents. Both low and high coverage depths due to GC bias lower the accuracy of assembly. These pieces of information provide guidance toward a better de novo genome assembly in the presence of GC bias.

  1. Investigating the effect of externalizing perspectives on cognitives biases

    DEFF Research Database (Denmark)

    Madsen, Fredrik Huitfeldt; Hicks, David L., David

    2007-01-01

    the number of attacks that “get through”. There are many subproblems of this main problem, one of which is that relative quality of the intelligence analysis is too low [39, We observe that the analysts suffer from cognitive biases, and we assume that this is one of the reasons behind “low” quality...... of intelligence analysis. We propose that complexity of maintaining multiple different perspectives the same data is one of the reasons for this. We further propose that a tool that facillitates the externalization multiple perspectives would reduce these biases and hence increase the overall quality...

  2. Evidence of nicotine replacement's effectiveness dissolves when meta-regression accommodates multiple sources of bias.

    Science.gov (United States)

    Stanley, T D; Massey, Shelby

    2016-11-01

    To accommodate and correct identifiable bias and risks of bias among clinical trials of nicotine replacement therapy (NRT). Meta-regression analysis of a published Cochrane Collaboration systematic review of 122 placebo-controlled clinical trials. Both identified risks of bias and potential publication (or reporting or small sample) bias are associated with an increase in the reported effectiveness of NRT. Whenever multiple sources of biases are accommodated by meta-regression, no evidence of a practically notable or statistically significant overall increased rate of smoking cessation remains. Our findings are in stark contrast with the 50% to 70% increase in smoking cessation reported by the Cochrane Collaboration systematic review. After more than 100 randomized clinical trials have been conducted, the overall effectiveness of NRT is in doubt. Simple, well-established meta-regression methods can test, accommodate, and correct multiple sources biases, often mentioned but dismissed by conventional systematic reviews. Copyright © 2016 Elsevier Inc. All rights reserved.

  3. Bias Corrections for Standardized Effect Size Estimates Used with Single-Subject Experimental Designs

    Science.gov (United States)

    Ugille, Maaike; Moeyaert, Mariola; Beretvas, S. Natasha; Ferron, John M.; Van den Noortgate, Wim

    2014-01-01

    A multilevel meta-analysis can combine the results of several single-subject experimental design studies. However, the estimated effects are biased if the effect sizes are standardized and the number of measurement occasions is small. In this study, the authors investigated 4 approaches to correct for this bias. First, the standardized effect…

  4. Sustainability of teacher expectation bias effects on long-term student performance

    NARCIS (Netherlands)

    de Boer, Hester; Bosker, R.J.; Van der Werf, M.P.C.

    In this article, we address the relationship between teacher expectation bias and student characteristics, its effect on long-term student performance, and the development of this effect over time. Expectation bias was defined as the difference between observed and predicted teacher expectation.

  5. Effects of personal characteristics on susceptibility to decision bias : a literature study

    NARCIS (Netherlands)

    Toet, A.; Brouwer, A.M.; Bosch, K. van den; Korteling, J.E.

    2016-01-01

    Cognitive biases and heuristics are pervasive simplifications and distortions in judgement and reasoning that systematically affect human decision making. Knowledge in this area may enable us to foresee and reduce detrimental effects of biases or to influence others more effectively. We therefore

  6. Temperature Dependence of Faraday Effect-Induced Bias Error in a Fiber Optic Gyroscope.

    Science.gov (United States)

    Li, Xuyou; Liu, Pan; Guang, Xingxing; Xu, Zhenlong; Guan, Lianwu; Li, Guangchun

    2017-09-07

    Improving the performance of interferometric fiber optic gyroscope (IFOG) in harsh environments, such as magnetic field and temperature field variation, is necessary for its practical applications. This paper presents an investigation of Faraday effect-induced bias error of IFOG under varying temperature. Jones matrix method is utilized to formulize the temperature dependence of Faraday effect-induced bias error. Theoretical results show that the Faraday effect-induced bias error changes with the temperature in the non-skeleton polarization maintaining (PM) fiber coil. This phenomenon is caused by the temperature dependence of linear birefringence and Verdet constant of PM fiber. Particularly, Faraday effect-induced bias errors of two polarizations always have opposite signs that can be compensated optically regardless of the changes of the temperature. Two experiments with a 1000 m non-skeleton PM fiber coil are performed, and the experimental results support these theoretical predictions. This study is promising for improving the bias stability of IFOG.

  7. SPICE Modeling of Body Bias Effect in 4H-SiC Integrated Circuit Resistors

    Science.gov (United States)

    Neudeck, Philip G.

    2017-01-01

    The DC electrical behavior of n-type 4H-SiC resistors used for realizing 500C durable integrated circuits (ICs) is studied as a function of substrate bias and temperature. Improved fidelity electrical simulation is described using SPICE NMOS model to simulate resistor substrate body bias effect that is absent from the SPICE semiconductor resistor model.

  8. Impact of exchange-correlation effects on the IV characteristics of a molecular junction

    DEFF Research Database (Denmark)

    Thygesen, Kristian Sommer

    2008-01-01

    The role of exchange-correlation effects in nonequilibrium quantum transport through molecular junctions is assessed by analyzing the IV curve of a generic two-level model using self-consistent many-body perturbation theory (second Born and GW approximations) on the Keldysh contour. It is demonst......The role of exchange-correlation effects in nonequilibrium quantum transport through molecular junctions is assessed by analyzing the IV curve of a generic two-level model using self-consistent many-body perturbation theory (second Born and GW approximations) on the Keldysh contour....... It is demonstrated how the variation of the molecule's energy levels with the bias voltage can produce anomalous peaks in the dI/dV curve. This effect is suppressed by electronic self-interactions and is therefore underestimated in standard transport calculations based on density functional theory. Inclusion...... of dynamic correlations introduces quasiparticle (QP) scattering which in turn broadens the molecular resonances. The broadening increases strongly with bias and can have a large impact on the calculated IV characteristic....

  9. Acute alcohol effects on attentional bias in heavy and moderate drinkers.

    Science.gov (United States)

    Weafer, Jessica; Fillmore, Mark T

    2013-03-01

    Heavy drinkers show an increased attentional bias to alcohol-related stimuli compared to moderate drinkers, and this bias is thought to promote motivation for alcohol consumption (Field & Cox, 2008). Studies have begun to examine acute alcohol effects on attentional bias; however, little is known regarding how these effects might differ based on drinker type. Further, the degree to which attentional bias in response to alcohol is associated with excessive alcohol consumption remains unexplored. For the current study, 20 heavy drinkers and 20 moderate drinkers completed a visual probe task in response to placebo and two active doses of alcohol (0.45g/kg and 0.65g/kg). Participants' eye-movements were monitored and attentional bias was calculated as the difference in time spent focused on alcohol compared to neutral images. Participants' alcohol consumption was assessed by a timeline follow-back calendar and a laboratory ad lib consumption task. Results showed that heavy drinkers displayed significantly greater attentional bias than did moderate drinkers following placebo. However, heavy drinkers displayed a dose-dependent decrease in attentional bias following alcohol, whereas the drug had no effect in moderate drinkers. Individual differences in attentional bias under placebo were strongly associated with both self-reported and laboratory alcohol consumption, yet bias following alcohol administration did not predict either measure of consumption. These findings suggest that attentional bias is strongest before a drinking episode begins. As such, an attentional bias might be most influential in terms of initiation of alcohol consumption, and less of a factor in promoting continued consumption within the drinking episode. (PsycINFO Database Record (c) 2013 APA, all rights reserved).

  10. Effects of a low dose of alcohol on cognitive biases and craving in heavy drinkers.

    Science.gov (United States)

    Schoenmakers, Tim; Wiers, Reinout W; Field, Matt

    2008-03-01

    Heavy alcohol drinking increases the incentive salience of alcohol-related cues. This leads to increased appetitive motivation to drink alcohol as measured by subjective craving and cognitive biases such as attentional bias and approach bias. Although these measures relate to the same construct, correlations between these variables are often very low. Alcohol consumption might not only increase different aspects of appetitive motivation, but also correlations between those aspects. To investigate the effect of a low alcohol dose on changes in various measures of appetitive motivation. Twenty-three heavy social drinkers were tested in 2 sessions, once after receiving an alcohol prime dose and once after receiving a placebo drink. After drink administration, attentional bias was measured with a visual-probe task using concurrent eye movement monitoring. Furthermore, we measured the approach bias with a stimulus response compatibility task and subjective craving with the Desires for Alcohol Questionnaire. After the alcohol prime dose, participants had higher levels of craving and more pronounced attentional bias (faster reaction times to probes that replaced alcohol rather than control pictures, increased maintenance of gaze on alcohol pictures, and a higher percentage of first eye movements directed toward alcohol pictures). Approach bias was not influenced by the alcohol prime dose. The correlation between attentional bias and approach bias was significantly higher after the alcohol than after the placebo drink. A low alcohol dose increased most measures of appetitive motivation for alcohol and increased the interrelation between cognitive measures of this construct.

  11. The Fox News Effect: Media Bias and Voting

    OpenAIRE

    DellaVigna, Stefano; Kaplan, Ethan

    2006-01-01

    Does media bias affect voting? We address this question by looking at the entry of Fox News in cable markets and its impact on voting. Between October 1996 and November 2000, the conservative Fox News Channel was introduced in the cable programming of 20 percent of US towns. Fox News availability in 2000 appears to be largely idiosyncratic. Using a data set of voting data for 9,256 towns, we investigate if Republicans gained vote share in towns where Fox News entered the cable market by the y...

  12. Effect of short-term SSRI treatment on cognitive bias in generalised anxiety disorder.

    Science.gov (United States)

    Mogg, Karin; Baldwin, David S; Brodrick, Paul; Bradley, Brendan P

    2004-11-01

    There is considerable evidence showing that individuals with generalised anxiety disorder (GAD) selectively process threat-related information, e.g. they have a bias to interpret ambiguous information in a threat-related manner. Cognitive theories of anxiety, which provide the basis of cognitive-behaviour therapy, propose that such processing biases play an important role in causing and maintaining anxiety. Given that treatment with selective serotonin re-uptake inhibitors (SSRIs) appears to be effective for GAD, we examined whether it is successful in removing cognitive bias. The clinical group included 19 patients with a diagnosis of GAD, and the control group consisted of a non-clinical sample of volunteers, matched for age, gender and years in education. The patients were assessed on measures of interpretative bias (homophone task), anxiety and depression before being prescribed an SSRI (paroxetine or citalopram). After 4 weeks, the cognitive task and mood measures were repeated in the patient group. Prior to treatment, the GAD group showed a significantly greater level of threat-related interpretive bias than controls. Following SSRI treatment, there were significant reductions in both interpretive bias and in anxiety levels in the GAD group. Furthermore, individuals who showed greater clinical improvement (e.g. reflected by reduced anxiety scores) showed a correspondingly greater reduction in their cognitive bias. The results suggest that SSRIs are effective in modifying both subjective anxiety levels and threat-related interpretive bias.

  13. Ultrafiltration Membrane Fouling and the Effect of Ion Exchange Resins

    KAUST Repository

    Jamaly, Sanaa

    2011-12-01

    Membrane fouling is a challenging process for the ultrafiltration membrane during wastewater treatment. This research paper determines the organic character of foulants of different kinds of wastewater before and after adding some ion exchange resins. Two advanced organic characterization methods are compared in terms of concentration of dissolved organic carbons: The liquid chromatography with organic carbon (LC-OCD) and Shimadzu total organic carbon (TOC). In this study, two secondary wastewater effluents were treated using ultrafiltration membrane. To reduce fouling, pretreatment using some adsorbents were used in the study. Six ion exchange resins out of twenty were chosen to compare the effect of adsorbents on fouling membrane. Based on the percent of dissolved organic carbon’s removal, three adsorbents were determined to be the most efficient (DOWEX Marathon 11 anion exchange resin, DOWEX Optipore SD2 polymeric adsorbent, and DOWEX PSR2 anion exchange), and three other ones were determined to the least efficient (DOWEX Marathon A2 anion exchange resin, DOWEX SAR anion exchange resin, and DOWEX Optipore L493 polymeric adsorbent). Organic characterization for feed, permeate, and backwash samples were tested using LC-OCD and TOC to better understand the characteristics of foulants to prevent ultrafiltration membrane fouling. The results suggested that the polymeric ion exchange resin, DOWEX SD2, reduced fouling potential for both treated wastewaters. All the six ion exchange resins removed more humic fraction than other organic fractions in different percent, so this fraction is not the main for cause for UF membrane fouling. The fouling of colloids was tested before and after adding calcium. There is a severe fouling after adding Ca2+ to effluent colloids.

  14. Effects of electrode biasing in STOR-M Tokamak

    Science.gov (United States)

    Basu, Debjyoti; Nakajima, Masaru; Rohollahi, Akbar; McColl, David; Adegun, Joseph; Xiao, Chijin; Hirose, Akira

    2015-11-01

    STOR-M is an iron-core, limiter based tokamak with major and minor radii of 46cm and 12 cm, respectively. Recently, electrode biasing experiments have been carried to study the improved confinement. For this purpose we have developed a DC power supply which can be gated by a high power SCR. The rectangular SS electrode has a height of 10 cm, a width of 2 cm and a thickness of 0.2 cm. The radial position of the electrode throughout the experiments is kept around 4mm inside the limiter in the plasma edge region. After application of positive bias with voltages between +90 V to +110 V during the plasma discharge current flat top with slightly higher edge-qa (nearly 5 to 6), noticeable increment of average plasma density and soft x-ray intensity along the central chord have been observed. No distinguishable change in H α emission has been measured. These phenomena may be attributed to improved confinement formed at the inner region but not at the edge. In the upcoming experimental campaign, Ion Doppler spectroscopy will be used to measure possible velocity shear inside the inner plasma region. Edge plasma pressure gradient will also be measured using Langmuir probes. Detailed experimental results will be presented.

  15. Effect of bias voltages on the synthesis of nanostructured carbon nitride films

    Science.gov (United States)

    Feng, P. X.; Yang, P.; Shi, Y. C.

    2006-05-01

    XPS, Raman scattering and SEM were used to study effect of DC bias voltages (0-400 V) on the synthesis of high nitrogen content of carbon nitride (CN x) films. Maximal N/C ratio up to 0.81 was first obtained at the bias voltage of 250 V, and the maximal fraction of sp 3 CN bond inside the film was up to 40%. Either too high or too low bias voltages would result in decrease of nitrogen content inside the CN x films. Typical G and D bands were identified. Intensities of G and D bands showed periodic development following an increase of bias voltages. Several groups of nanoscale particles were observed at the pulsed bias voltage of 5 kV. Each group of particles appeared sunflower type of distribution where the biggest (85 nm) particle at the center was surrounded by many small sizes (35 nm) of CN particles.

  16. Bias dependence of synergistic radiation effects induced by electrons and protons on silicon bipolar junction transistors

    Science.gov (United States)

    Liu, Chaoming; Li, Xingji; Yang, Jianqun; Ma, Guoliang; Xiao, Liyi

    2015-06-01

    Bias dependence on synergistic radiation effects caused by 110 keV electrons and 170 keV protons on the current gain of 3DG130 NPN bipolar junction transistors (BJTs) is studied in this paper. Experimental results indicate that the influence induced by 170 keV protons is always enhancement effect during the sequential irradiation. However, the influence induced by 110 keV electrons on the BJT under various bias cases is different during the sequential irradiation. The transition fluence of 110 keV electrons is dependent on the bias case on the emitter-base junction of BJT.

  17. Orange peel coupling in multilayers with perpendicular magnetic anisotropy: Application to (Co/Pt)-based exchange-biased spin-valves

    Science.gov (United States)

    Moritz, J.; Garcia, F.; Toussaint, J. C.; Dieny, B.; Nozières, J. P.

    2004-01-01

    Néel's theory of magnetostatic coupling between two magnetic layers with in-plane magnetization separated by a non-magnetic spacer has been extended to the case of multilayers with perpendicular anisotropy. It is shown that the presence of a correlated roughness between the successive interfaces induces an interlayer coupling through the spacer analogous to the well-known orange peel coupling. However, depending on the parameters describing the interfacial roughness, the magnetic anisotropy and the exchange stiffness constant, this coupling can favor either parallel or an antiparallel alignment of the magnetization in the two ferromagnetic layers. This model was used to quantitatively interpret the variation of interlayer coupling vs. thickness of Pt spacer layer in out-of-plane magnetized exchange-biased spin-valves comprising (Pt/Co) multilayers as free and pinned layers. It is shown that the net coupling can be interpreted by the coexistence of perpendicular orange peel and oscillatory RKKY couplings. Interestingly, since these two couplings have different thickness dependence, in certain range of Pt thickness, the coupling changes sign during growth, being antiferromagnetic at the early stage of the growth of the top (Co/Pt) multilayer but ferromagnetic once the growth is completed.

  18. Empirical evidence of bias in treatment effect estimates in controlled trials with different interventions and outcomes

    DEFF Research Database (Denmark)

    Wood, Lesley; Egger, Matthias; Gluud, Lise Lotte

    2008-01-01

    To examine whether the association of inadequate or unclear allocation concealment and lack of blinding with biased estimates of intervention effects varies with the nature of the intervention or outcome....

  19. Memory bias for negative emotional words in recognition memory is driven by effects of category membership.

    Science.gov (United States)

    White, Corey N; Kapucu, Aycan; Bruno, Davide; Rotello, Caren M; Ratcliff, Roger

    2014-01-01

    Recognition memory studies often find that emotional items are more likely than neutral items to be labelled as studied. Previous work suggests this bias is driven by increased memory strength/familiarity for emotional items. We explored strength and bias interpretations of this effect with the conjecture that emotional stimuli might seem more familiar because they share features with studied items from the same category. Categorical effects were manipulated in a recognition task by presenting lists with a small, medium or large proportion of emotional words. The liberal memory bias for emotional words was only observed when a medium or large proportion of categorised words were presented in the lists. Similar, though weaker, effects were observed with categorised words that were not emotional (animal names). These results suggest that liberal memory bias for emotional items may be largely driven by effects of category membership.

  20. Transient plasma potential in pulsed dual frequency inductively coupled plasmas and effect of substrate biasing

    National Research Council Canada - National Science Library

    Mishra, Anurag; Yeom, Geun Young

    2016-01-01

    An electron emitting probe in saturated floating potential mode has been used to investigate the temporal evolution of plasma potential and the effect of substrate RF biasing on it for pulsed dual frequency (2 MHz/13.56 MHz...

  1. Effect of interlayer exchange coupling on magnetic chiral structures

    Energy Technology Data Exchange (ETDEWEB)

    Kang, S. P.; Kwon, H. Y.; Kim, H. S.; Shim, J. H.; Won, C. [Department of Physics, Kyung Hee University, Seoul 130-701 (Korea, Republic of)

    2015-07-28

    We numerically investigated the effect of interlayer exchange coupling on magnetic chiral structures, such as a helical/cycloidal spin structure and magnetic skyrmion crystal (SkX), which are produced in a magnetic system involving the Dzyaloshinskii-Moriya interaction (DMI). We report the existence of a phase transition where the length scale of magnetic structure discontinuously changes, and that there can be a novel magnetic structure around the phase boundary that exhibits double-ordering lengths of magnetic structure. Therefore, the system has multiple ground phases determined by the ratio of interlayer exchange coupling strength and DMI strength. Furthermore, we investigated the critical condition of the external perpendicular field required for the SkX. The critical field is significantly reduced under the effect of interlayer exchange coupling, which can stabilize the SkX without the external field.

  2. Students as effective harm reductionists and needle exchange organizers.

    Science.gov (United States)

    Barbour, Kyle; McQuade, Miriam; Brown, Brandon

    2017-03-17

    Needle exchange programs are safe, highly effective programs for promoting health among people who inject drugs. However, they remain poorly funded, and often illegal, in many places worldwide due to fear and stigma surrounding drug use. Continued advocacy, education, and implementation of new needle exchanges are thus essential to improve public health and reduce structural inequality. We argue that students, and especially professional and graduate students, have the potential to play an important role in advancing harm reduction. Students benefit from the respect given to the professions they are training to enter, which gives them leverage to navigate the political hurdles often faced by needle exchange organizers, especially in areas that presently lack services. In addition, due to their relative simplicity, needle exchanges do not require much of the licensing, clinical knowledge, and infrastructure associated with more traditional student programs, such as student-run free medical clinics. Students are capable of learning harm reduction cultural approaches and techniques if they remain humble, open-minded, and seek the help of the harm reduction community. Consequently, students can generate tremendous benefits to their community without performing beyond their appropriate clinical limitations. Students benefit from organizing needle exchanges by gaining applied experience in advocacy, organization-building, and political finesse. Working in a needle exchange significantly helps erode stigma against multiple marginalized populations. Students in health-related professions additionally learn clinically-relevant knowledge that is often lacking from their formal training, such as an understanding of structural violence and inequality, root causes of substance use, client-centered approaches to health services, and interacting with clients as peers, rather than through the standard hierarchical medical interaction. We therefore encourage students to learn about

  3. The Effectiveness of Cognitive Bias Modification Interventions for Substance Addictions: A Meta-Analysis

    DEFF Research Database (Denmark)

    Cristea, Ioana; Kok, Robin; Cuijpers, Pim

    2016-01-01

    Background and Aims Cognitive bias modification (CBM) interventions, presumably targeting automatic processes, are considered particularly promising for addictions. We conducted a meta-analysis examining randomized controlled trials (RCTs) of CBM for substance addiction outcomes. Methods Studies...... were identified through systematic searches in bibliographical databases. We included RCTs of CBM interventions, alone or in combination with other treatments, for any type of addiction. We examined trial risk of bias, publication bias and possible moderators. Effects sizes were computed for post......-test and follow-up, using a random-effects model. We grouped outcome measures and reported results for addiction (all related measures), craving and cognitive bias. Results We identified 25 trials, 18 for alcohol problems, and 7 for smoking. At post-test, there was no significant effect of CBM for addiction, g...

  4. Asymmetrical transfer effects of cognitive bias modification: Modifying attention to threat influences interpretation of emotional ambiguity, but not vice versa.

    Science.gov (United States)

    Bowler, J O; Hoppitt, L; Illingworth, J; Dalgleish, T; Ononaiye, M; Perez-Olivas, G; Mackintosh, B

    2017-03-01

    It is well established that attention bias and interpretation bias each have a key role in the development and continuation of anxiety. How the biases may interact with one another in anxiety is, however, poorly understood. Using cognitive bias modification techniques, the present study examined whether training a more positive interpretation bias or attention bias resulted in transfer of effects to the untrained cognitive domain. Differences in anxiety reactivity to a real-world stressor were also assessed. Ninety-seven first year undergraduates who had self-reported anxiety were allocated to one of four groups: attention bias training (n = 24), interpretation bias training (n = 26), control task training (n = 25) and no training (n = 22). Training was computer-based and comprised eight sessions over four weeks. Baseline and follow-up measures of attention and interpretation bias, anxiety and depression were taken. A significant reduction in threat-related attention bias and an increase in positive interpretation bias occurred in the attention bias training group. The interpretation bias training group did not exhibit a significant change in attention bias, only interpretation bias. The effect of attention bias training on interpretation bias was significant as compared with the two control groups. There were no effects on self-report measures. The extent to which interpretive training can modify attentional processing remains unclear. Findings support the idea that attentional training might have broad cognitive consequences, impacting downstream on interpretive bias. However, they do not fully support a common mechanism hypothesis, as interpretive training did not impact on attentional bias. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

  5. The Effectiveness of Cognitive Bias Modification Interventions for Substance Addictions: A Meta-Analysis.

    Directory of Open Access Journals (Sweden)

    Ioana A Cristea

    Full Text Available Cognitive bias modification (CBM interventions, presumably targeting automatic processes, are considered particularly promising for addictions. We conducted a meta-analysis examining randomized controlled trials (RCTs of CBM for substance addiction outcomes.Studies were identified through systematic searches in bibliographical databases. We included RCTs of CBM interventions, alone or in combination with other treatments, for any type of addiction. We examined trial risk of bias, publication bias and possible moderators. Effects sizes were computed for post-test and follow-up, using a random-effects model. We grouped outcome measures and reported results for addiction (all related measures, craving and cognitive bias.We identified 25 trials, 18 for alcohol problems, and 7 for smoking. At post-test, there was no significant effect of CBM for addiction, g = 0.08 (95% CI -0.02 to 0.18 or craving, g = 0.05 (95% CI -0.06 to 0.16, but there was a significant, moderate effect on cognitive bias, g = 0.60 (95% CI 0.39 to 0.79. Results were similar for alcohol and smoking outcomes taken separately. Follow-up addiction outcomes were reported in 7 trials, resulting in a small but significant effect of CBM, g = 0.18 (95% CI 0.03 to 0.32. Results for addiction and craving did not differ by substance type, sample type, delivery setting, bias targeted or number of sessions. Risk of bias was high or uncertain in most trials, for most criteria considered. Meta-regression analyses revealed significant inverse relationships between risk of bias and effect sizes for addiction outcomes and craving. The relationship between cognitive bias and respectively addiction ESs was not significant. There was consistent evidence of publication bias in the form of funnel plot asymmetry.Our results cast serious doubts on the clinical utility of CBM interventions for addiction problems, but sounder methodological trials are necessary before this issue can be settled. We found no

  6. Effects of Cross-Border Engineer Exchange on Innovation

    DEFF Research Database (Denmark)

    Machikita, Tomohiro

    2012-01-01

    Using data from a survey to manufacturing firms, this paper attempts to detect sources of new technologies transferred to a well-established industrial district in Calabarzon, the Philippines, and a rapidly growing agglomeration in Hanoi, Vietnam. We find significant effects of exchange of engine...

  7. The effect of exchange rate devaluation on selected agricultural ...

    African Journals Online (AJOL)

    This work examined and evaluated in comparative terms, the effect of exchange rate devaluation on selected agricultural export commodities as well as on the total agricultural export commodities in the Pre-SAP (1972-1985) and the SAP era (1986-2010) in Nigeria. Based on the data collected from Central Bank of Nigeria ...

  8. Conditions on exchange mechanisms for polarization effects in inclusive reactions

    CERN Document Server

    Salin, P

    1974-01-01

    In the framework of Mueller-Regge phenomenology the conditions under which one could expect to observe polarization effects in the fragmentation region for inclusive relations are investigated. On the basis of kinematical considerations and parity relations only, it is found that this requires exchange of states with mixed naturalities. (9 refs).

  9. The Indirect Effect of Source Information on Psychological Reactance Against Antismoking Messages Through Perceived Bias.

    Science.gov (United States)

    Kim, Hyunjung

    2017-05-01

    This study investigates the indirect effect of source information on attitudes toward antismoking campaigns through perceived bias and psychological reactance by employing a survey experiment (N = 416). Findings demonstrate that an editorial advocating antismoking campaigns from ideologically congruent media is perceived as less biased than the same editorial from hostile media. The perceived bias is linked to perceived threat to freedom, which, in turn, is linked to psychological reactance against the editorial, resulting in less favorable attitudes toward antismoking campaigns. Smokers are more likely to show the linkages than nonsmokers. Implications of the findings are discussed.

  10. Finale furioso: referee-biased injury times and their effects on home advantage in football.

    Science.gov (United States)

    Riedl, Dennis; Strauss, Bernd; Heuer, Andreas; Rubner, Oliver

    2015-01-01

    The role of referees has become a central issue in the investigation of home advantage. The main aim of this study was a thorough examination of the referee bias concerning injury time in football, which is currently seen as an important example for the assertion that referees contribute to home advantage. First, we use archival data from the German Bundesliga (seasons 2000/2001-2010/2011) to confirm the existence of an asymmetry in the allocation of injury time. We show this asymmetry to be a bias by ruling out hitherto remaining alternative explanations (effect = 18 s, P referee bias, stating that referees systematically accord more injury time when one team leads in the game compared to a draw (effect = 21 s, P = 0.004, R2(adj) = 0.06). Third, the quantitative benefit of home or away teams in goals and points due to these biases is assessed. Overall, referee decisions on injury time indeed reveal biases, but they do not contribute to the home advantage, that is, there is no significant effect on goals scored by the teams. The qualitative findings (a new bias on injury time) as well as the quantitative findings (no overall effect) shed new light on the role of referees for home advantage.

  11. Exchange bias of MnFe2O4@γFe2O3 and CoFe2O4@γFe2O3 core/shell nanoparticles

    Science.gov (United States)

    Cabreira-Gomes, R.; G. Silva, F.; Aquino, R.; Bonville, P.; Tourinho, F. A.; Perzynski, R.; Depeyrot, J.

    2014-11-01

    We compare here exchange bias (EB) properties of chemically synthesized core-shell nanoparticles (NPs), based either on a core of soft ferrite (MnFe2O4) or hard ferrite (CoFe2O4) protected by a maghemite shell (γ-Fe2O3). These NPs dispersed in acidic solutions are electrostatically stabilized, yielding to stable colloidal dispersions with a strong interparticle repulsion and negligible dipolar interactions in the probed range of temperatures. Field cooled (FC) magnetic hysteresis loops of non-textured frozen dispersions (with magnetic anisotropy axis of NPs distributed at random) and those of a powder based on the same NPs present a shift along the H-axis, expressing the coupling between the spin-ordered cores and the disordered surface layer of the NPs. The bias field is found to present a maximum, larger for NPs based on harder ferrite core. It is obtained for a cooling field of the order of one half of the anisotropy field, which is much larger for the CoFe2O4 cores than for MnFe2O4 ones. In powders, particles are in contact leading to an interparticle exchange which is not present in the dilute solutions where exchange bias properties are only due to an intraparticle exchange between core and surface. The thermal dependence of the bias field is well described by a reduced exponential behavior with a characteristic freezing temperature of about 8 K.

  12. Alcohol-cue exposure effects on craving and attentional bias in underage college-student drinkers.

    Science.gov (United States)

    Ramirez, Jason J; Monti, Peter M; Colwill, Ruth M

    2015-06-01

    The effect of alcohol-cue exposure on eliciting craving has been well documented, and numerous theoretical models assert that craving is a clinically significant construct central to the motivation and maintenance of alcohol-seeking behavior. Furthermore, some theories propose a relationship between craving and attention, such that cue-induced increases in craving bias attention toward alcohol cues, which, in turn, perpetuates craving. This study examined the extent to which alcohol cues induce craving and bias attention toward alcohol cues among underage college-student drinkers. We designed within-subject cue-reactivity and visual-probe tasks to assess in vivo alcohol-cue exposure effects on craving and attentional bias on 39 undergraduate college drinkers (ages 18-20). Participants expressed greater subjective craving to drink alcohol following in vivo cue exposure to a commonly consumed beer compared with water exposure. Furthermore, following alcohol-cue exposure, participants exhibited greater attentional biases toward alcohol cues as measured by a visual-probe task. In addition to the cue-exposure effects on craving and attentional bias, within-subject differences in craving across sessions marginally predicted within-subject differences in attentional bias. Implications for both theory and practice are discussed. (PsycINFO Database Record (c) 2015 APA, all rights reserved).

  13. The effect of small-wave modulation on the electromagnetic bias

    Science.gov (United States)

    Rodriguez, Ernesto; Kim, Yunjin; Martin, Jan M.

    1992-01-01

    The effect of the modulation of small ocean waves by large waves on the physical mechanism of the EM bias is examined by conducting a numerical scattering experiment which does not assume the applicability of geometric optics. The modulation effect of the large waves on the small waves is modeled using the principle of conservation of wave action and includes the modulation of gravity-capillary waves. The frequency dependence and magnitude of the EM bias is examined for a simplified ocean spectral model as a function of wind speed. These calculations make it possible to assess the validity of previous assumptions made in the theory of the EM bias, with respect to both scattering and hydrodynamic effects. It is found that the geometric optics approximation is inadequate for predictions of the EM bias at typical radar altimeter frequencies, while the improved scattering calculations provide a frequency dependence of the EM bias which is in qualitative agreement with observation. For typical wind speeds, the EM bias contribution due to small-wave modulation is of the same order as that due to modulation by the nonlinearities of the large-scale waves.

  14. Attention bias modification for major depressive disorder: Effects on attention bias, resting state connectivity, and symptom change.

    Science.gov (United States)

    Beevers, Christopher G; Clasen, Peter C; Enock, Philip M; Schnyer, David M

    2015-08-01

    Cognitive theories of depression posit that selective attention for negative information contributes to the maintenance of depression. The current study experimentally tested this idea by randomly assigning adults with Major Depressive Disorder (MDD) to 4 weeks of computer-based attention bias modification designed to reduce negative attention bias or 4 weeks of placebo attention training. Findings indicate that compared to placebo training, attention bias modification reduced negative attention bias and increased resting-state connectivity within a neural circuit (i.e., middle frontal gyrus and dorsal anterior cingulate cortex) that supports control over emotional information. Further, pre- to post-training change in negative attention bias was significantly correlated with depression symptom change only in the active training condition. Exploratory analyses indicated that pre- to post-training changes in resting state connectivity within a circuit associated with sustained attention to visual information (i.e., precuenus and middle frontal gyrus) contributed to symptom improvement in the placebo condition. Importantly, depression symptoms did not change differentially between the training groups-overall, a 40% decrease in symptoms was observed across attention training conditions. Findings suggest that negative attention bias is associated with the maintenance of depression; however, deficits in general attentional control may also maintain depression symptoms, as evidenced by resting state connectivity and depression symptom improvement in the placebo training condition. (c) 2015 APA, all rights reserved).

  15. Attention Bias Modification for Major Depressive Disorder: Effects on Attention Bias, Resting State Connectivity, and Symptom Change

    Science.gov (United States)

    Beevers, Christopher G.; Clasen, Peter C.; Enock, Philip M.; Schnyer, David M.

    2015-01-01

    Cognitive theories of depression posit that selective attention for negative information contributes to the maintenance of depression. The current study experimentally tested this idea by randomly assigning adults with Major Depressive Disorder (MDD) to four weeks of computer-based attention bias modification designed to reduce negative attention bias or four weeks of placebo attention training. Findings indicate that compared to placebo training, attention bias modification reduced negative attention bias and increased resting-state connectivity within a neural circuit (i.e., middle frontal gyrus and dorsal anterior cingulate cortex) that supports control over emotional information. Further, pre- to post-training change in negative attention bias was significantly correlated with depression symptom change only in the active training condition. Exploratory analyses indicated that pre- to post-training changes in resting state connectivity within a circuit associated with sustained attention to visual information (i.e., precuenus and middle frontal gyrus) contributed to symptom improvement in the placebo condition. Importantly, depression symptoms did not change differentially between the training groups—overall, a 40% decrease in symptoms was observed across attention training conditions. Findings suggest that negative attention bias is associated with the maintenance of depression; however, general attentional control may also maintain depression symptoms, as evidenced by resting state connectivity and depression symptom improvement in the placebo training condition. PMID:25894440

  16. Effects of varying light bias on an optically-addressed two-terminal multicolor photodetector

    Science.gov (United States)

    Steenbergen, E. H.; DiNezza, M. J.; Dettlaff, W. H. G.; Lim, S. H.; Zhang, Y.-H.

    2011-05-01

    Multicolor photodetectors often require more than two terminals, making it very difficult to construct multicolor FPAs, due to the increased processing complexity. A novel approach is proposed to overcome this problem: an optically-addressed two-terminal multicolor photodetector. This two-terminal detector design is important for FPAs because it maximizes the fill factor and simplifies the necessary ROICs. This novel device concept is demonstrated using LEDs as the optical bias sources and a three-color detector. Varying light bias levels expose the effects of, luminescence coupling, optical leakage, and shunt leakage currents on the detector performance. The measured dark current, responsivity, and linear dynamic range of the detector reveal a tradeoff between low optical bias for minimal dark current and maximum responsivity and high optical bias for maximum dynamic range for optimal detector performance.

  17. The effect of dc bias on the poled states in PNZST antiferroelectric thin films

    Energy Technology Data Exchange (ETDEWEB)

    Zhai Jiwei [Functional Materials Research Laboratory, Tongji University, Shanghai 200092 (China); Yao Xi [Functional Materials Research Laboratory, Tongji University, Shanghai 200092 (China); Xu Zhengkui [Department of Physics and Materials Science, City University of Hong Kong Kowloon, Hong Kong (China); Chen, Haydn [Department of Physics and Materials Science, City University of Hong Kong Kowloon, Hong Kong (China)

    2007-03-21

    The effect on the polarization of antiferroelectric (AFE) PNZST ((Pb,Nb)(Zr,Sn,Ti)O{sub 3}) thin films by {epsilon}-E (dc bias field) cycles was studied. It was shown that in these films the AFE ordering is destroyed by the application of a dc electrical field bias along the surface normal direction. After removing the dc bias the film relaxes slowly back to the initial AFE state. This phenomenon is dependent on the film thickness. The relaxation time decreases with increasing film thickness. With increasing storage time of the sample after removing the dc bias at room temperature or heat treatment above the Curie temperature, the AFE ordering can return. From the characteristics of hysteresis loops and {epsilon}-E behaviours, we can ascertain that this phenomenon could be attributed to the difference in the poled volume at the interfaces between the electrode and the film.

  18. Systemic racism moderates effects of provider racial biases on adherence to hypertension treatment for African Americans.

    Science.gov (United States)

    Greer, Tawanda M; Brondolo, Elizabeth; Brown, Porschia

    2014-01-01

    The purpose of the current study was to examine perceived exposure to systemic racism as a moderator of the effects of perceived exposure to provider racial biases on treatment adherence and mistrust of health care for a sample of African American hypertensive patients. We hypothesized that patients who endorsed high levels of systemic racism would exhibit poor adherence to hypertension treatment and increased mistrust in health care in relation to perceptions of exposure to provider racial biases. The sample consisted of 100 African American patients who ranged in age from 24 to 82 years. All were diagnosed with hypertension and were recruited from an outpatient clinic located in the Southeastern region of the United States. Moderated regression analyses were performed to test the study hypotheses. Findings revealed a positive, significant main effect for perceived provider racial biases in predicting mistrust of care. This finding suggested that an increase in mistrust of health care was associated with increased perceptions of provider biases. In predicting treatment adherence, a significant interaction revealed that patients who endorsed low and moderate degrees of exposure to systemic racism displayed poor adherence to treatment in relation to greater perceptions of provider racial biases. The overall findings suggest that patients who perceive themselves as infrequently exposed to systemic racism possess the greatest risk for nonadherence to hypertension treatment in relation to increased perceptions of provider racial biases. Implications of the findings are discussed. 2014 APA, all rights reserved

  19. Potential Effects of Horizontal Gene Exchange in the Human Gut

    Directory of Open Access Journals (Sweden)

    Aaron Lerner

    2017-11-01

    Full Text Available Many essential functions of the human body are dependent on the symbiotic microbiota, which is present at especially high numbers and diversity in the gut. This intricate host–microbe relationship is a result of the long-term coevolution between the two. While the inheritance of mutational changes in the host evolution is almost exclusively vertical, the main mechanism of bacterial evolution is horizontal gene exchange. The gut conditions, with stable temperature, continuous food supply, constant physicochemical conditions, extremely high concentration of microbial cells and phages, and plenty of opportunities for conjugation on the surfaces of food particles and host tissues, represent one of the most favorable ecological niches for horizontal gene exchange. Thus, the gut microbial system genetically is very dynamic and capable of rapid response, at the genetic level, to selection, for example, by antibiotics. There are many other factors to which the microbiota may dynamically respond including lifestyle, therapy, diet, refined food, food additives, consumption of pre- and probiotics, and many others. The impact of the changing selective pressures on gut microbiota, however, is poorly understood. Presumably, the gut microbiome responds to these changes by genetic restructuring of gut populations, driven mainly via horizontal gene exchange. Thus, our main goal is to reveal the role played by horizontal gene exchange in the changing landscape of the gastrointestinal microbiome and potential effect of these changes on human health in general and autoimmune diseases in particular.

  20. Effects of habitat features on size-biased predation on salmon by bears.

    Science.gov (United States)

    Andersson, Luke C; Reynolds, John D

    2017-05-01

    Predators can drive trait divergence among populations of prey by imposing differential selection on prey traits. Habitat characteristics can mediate predator selectivity by providing refuge for prey. We quantified the effects of stream characteristics on biases in the sizes of spawning salmon caught by bears (Ursus arctos and U. americanus) on the central coast of British Columbia, Canada by measuring size-biased predation on spawning chum (Oncorhynchus keta) and pink (O. gorbuscha) salmon in 12 streams with varying habitat characteristics. We tested the hypotheses that bears would catch larger than average salmon (size-biased predation) and that this bias toward larger fish would be higher in streams that provide less protection to spawning salmon from predation (e.g., less pools, wood, undercut banks). We then we tested for how such size biases in turn translate into differences among populations in the sizes of the fish. Bears caught larger-than-average salmon as the spawning season progressed and as predicted, this was most pronounced in streams with fewer refugia for the fish (i.e., wood and undercut banks). Salmon were marginally smaller in streams with more pronounced size-biased predation but this predictor was less reliable than physical characteristics of streams, with larger fish in wider, deeper streams. These results support the hypothesis that selective forces imposed by predators can be mediated by habitat characteristics, with potential consequences for physical traits of prey.

  1. The effects of self-focus on attentional biases in social anxiety:An ERP study.

    Science.gov (United States)

    Judah, Matt R; Grant, DeMond M; Carlisle, Nancy B

    2016-06-01

    Cognitive theories of social anxiety disorder suggest that biased attention plays a key role in maintaining symptoms. These biases include self-focus and attention to socially threatening stimuli in the environment. The goal of this study was to utilize ERPs that are elicited by a change detection task to examine biases in selective attention (i.e., N2pc) and working memory maintenance (i.e., contralateral delay activity; CDA). Additionally, the effect of self-focus was examined using false heart rate feedback. In support of the manipulation, self-focus cues resulted in greater self-reported self-consciousness and task interference, enhanced anterior P2 amplitude and reduced SPN amplitude. Moreover, P2 amplitude for self-focus cues was correlated with reduced task performance for socially anxious subjects only. The difference in P2 amplitude between self-focus and standard cues was correlated with social anxiety independent of depression. As hypothesized, socially anxious participants (n = 20) showed early selection and maintenance of disgust faces relative to neutral faces as indicated by the N2pc and CDA components. Nonanxious controls (n = 22) did not show these biases. During self-focus cues, controls showed marginal evidence of biased selection for disgust faces, whereas socially anxious subjects showed no bias in this condition. Controls showed an ipsilateral delay activity after being cued to attend to one hemifield. Overall, this study supports early and persistent attentional bias for social threat in socially anxious individuals. Furthermore, self-focus may disrupt these biases. These findings and supplementary data are discussed in light of cognitive models of social anxiety disorder, recent empirical findings, and treatment.

  2. Effects of cognitive bias modification on social anxiety: A meta-analysis

    Science.gov (United States)

    Liu, Haining; Li, Xianwen; Han, Buxin; Liu, Xiaoqian

    2017-01-01

    Background Cognitive bias modification (CBM), a set of techniques for modifying bias in information processing—is considered a novel intervention for social anxiety disorder (SAD), which has drawn considerable interest from researchers. However, the effects of CBM on SAD are not consistent. Some studies have demonstrated significant positive effects compared to control groups, while others have found no such effects. Aims We conducted a meta-analysis aimed at quantitatively assessing the effects of CBM on SAD at post-test. Method Through a systematic literature search by two independent raters, 34 articles (36 randomized studies) including 2,550 participants were identified. A multilevel modeling approach was employed to assess the effects of CBM on SAD, and to explore the potentially crucial procedures and sample characteristics that enhance the effectiveness of benign training. Results In general, there were small but significant effects of CBM on the primary symptoms of SAD (g = 0.17), cognitive bias (CB) toward threat (g = 0.32), and reactivity in stressful situations (g = 0.25), but non-significant effects on secondary symptoms. However, the interpretation modification program was more effective than was attentional bias modification in reducing SAD primary symptoms and negative CB. Laboratory training procedures produced larger primary symptom reductions compared to Internet-based training, whereas the percentage of contingency and feedback about training performance boosted cognitive effects only. Finally, the following groups were more likely to benefit from CBM: younger participants (primary symptoms and cognitive effects), women (primary symptom effects), and samples with stronger CB (stressor effects). The quality of the randomized controlled trials was less than desirable, as there was some indication of publication bias in our study. Conclusions Current findings broadly supported cognitive theories of SAD that consider a bidirectional or mutually

  3. Effects of cognitive bias modification on social anxiety: A meta-analysis.

    Directory of Open Access Journals (Sweden)

    Haining Liu

    Full Text Available Cognitive bias modification (CBM, a set of techniques for modifying bias in information processing-is considered a novel intervention for social anxiety disorder (SAD, which has drawn considerable interest from researchers. However, the effects of CBM on SAD are not consistent. Some studies have demonstrated significant positive effects compared to control groups, while others have found no such effects.We conducted a meta-analysis aimed at quantitatively assessing the effects of CBM on SAD at post-test.Through a systematic literature search by two independent raters, 34 articles (36 randomized studies including 2,550 participants were identified. A multilevel modeling approach was employed to assess the effects of CBM on SAD, and to explore the potentially crucial procedures and sample characteristics that enhance the effectiveness of benign training.In general, there were small but significant effects of CBM on the primary symptoms of SAD (g = 0.17, cognitive bias (CB toward threat (g = 0.32, and reactivity in stressful situations (g = 0.25, but non-significant effects on secondary symptoms. However, the interpretation modification program was more effective than was attentional bias modification in reducing SAD primary symptoms and negative CB. Laboratory training procedures produced larger primary symptom reductions compared to Internet-based training, whereas the percentage of contingency and feedback about training performance boosted cognitive effects only. Finally, the following groups were more likely to benefit from CBM: younger participants (primary symptoms and cognitive effects, women (primary symptom effects, and samples with stronger CB (stressor effects. The quality of the randomized controlled trials was less than desirable, as there was some indication of publication bias in our study.Current findings broadly supported cognitive theories of SAD that consider a bidirectional or mutually reinforcing relationship between symptoms

  4. Quantum dust magnetosonic waves with spin and exchange correlation effects

    Energy Technology Data Exchange (ETDEWEB)

    Maroof, R.; Qamar, A. [Department of Physics, University of Peshawar, Peshawar 25000 (Pakistan); Mushtaq, A. [Department of Physics, Abdul Wali Khan University, Mardan 23200 (Pakistan); National Center for Physics, Shahdra Valley Road, Islamabad 44000 (Pakistan)

    2016-01-15

    Dust magnetosonic waves are studied in degenerate dusty plasmas with spin and exchange correlation effects. Using the fluid equations of magnetoplasma with quantum corrections due to the Bohm potential, temperature degeneracy, spin magnetization energy, and exchange correlation, a generalized dispersion relation is derived. Spin effects are incorporated via spin force and macroscopic spin magnetization current. The exchange-correlation potentials are used, based on the adiabatic local-density approximation, and can be described as a function of the electron density. For three different values of angle, the dispersion relation is reduced to three different modes under the low frequency magnetohydrodynamic assumptions. It is found that the effects of quantum corrections in the presence of dust concentration significantly modify the dispersive properties of these modes. The results are useful for understanding numerous collective phenomena in quantum plasmas, such as those in compact astrophysical objects (e.g., the cores of white dwarf stars and giant planets) and in plasma-assisted nanotechnology (e.g., quantum diodes, quantum free-electron lasers, etc.)

  5. Effect of external and internal magnetic fields on the bias stability in a Zeeman laser gyroscope

    Energy Technology Data Exchange (ETDEWEB)

    Kolbas, Yu Yu; Saveliev, I I; Khokhlov, N I [Open Joint-Stock Company M.F. Stel' makh Polyus Research Institute, Moscow (Russian Federation)

    2015-06-30

    With the specific features of electronic systems of a Zeeman laser gyroscope taken into account, the basic physical mechanisms of the magnetic field effect on the bias stability and the factors giving rise to the internal magnetic fields are revealed. The hardware-based methods of reducing the effect of external and internal magnetic fields are considered, as well as the algorithmic methods for increasing the stability of the bias magnetic component by taking into account its reproducible temperature and time dependences. Typical experimental temperature and time dependences of the magnetic component of the Zeeman laser gyro bias are presented, and by their example the efficiency of the proposed methods for reducing the effect of magnetic fields is shown. (laser gyroscopes)

  6. [Negative bias on self-referent processing in depression: focused on mood congruent effects].

    Science.gov (United States)

    Tagami, Kyoko

    2002-12-01

    The purpose of this study was to investigate negative bias on self-referent processing in depression, focused on the mood congruent effects in a natural depressed state and an experimentally induced transient depressed mood state. In Experiment 1, autobiographical memories and self-relevant ratings of personality trait words were examined in a natural depressed state or non-depressed state, which were measured by Beck Depression Inventory. Results revealed the mood congruent effects on both tasks. In Experiment 2, the same tasks as Experiment 1 were conducted in a transient depressed mood state or non-depressed mood state, which were induced through listening music. Unlike Experiment 1, there were no effects in both tasks, and a positive bias was observed in both mood states. It was suggested that transient mood state did not bias self-referent processing in depression, and Beck's schema hypothesis was supported.

  7. Impulsivity moderates the effect of approach bias modification on healthy food consumption.

    Science.gov (United States)

    Kakoschke, Naomi; Kemps, Eva; Tiggemann, Marika

    2017-10-01

    The study aimed to modify approach bias for healthy and unhealthy food and to determine its effect on subsequent food consumption. In addition, we investigated the potential moderating role of impulsivity in the effect of approach bias re-training on food consumption. Participants were 200 undergraduate women (17-26 years) who were randomly allocated to one of five conditions of an approach-avoidance task varying in the training of an approach bias for healthy food, unhealthy food, and non-food cues in a single session of 10 min. Outcome variables were approach bias for healthy and unhealthy food and the proportion of healthy relative to unhealthy snack food consumed. As predicted, approach bias for healthy food significantly increased in the 'avoid unhealthy food/approach healthy food' condition. Importantly, the effect of training on snack consumption was moderated by trait impulsivity. Participants high in impulsivity consumed a greater proportion of healthy snack food following the 'avoid unhealthy food/approach healthy food' training. This finding supports the suggestion that automatic processing of appetitive cues has a greater influence on consumption behaviour in individuals with poor self-regulatory control. Copyright © 2017 Elsevier Ltd. All rights reserved.

  8. Effects of Asymmetries on the Dynamics of Motorized Momentum Exchange Tether and Payloads Injection Precision

    Directory of Open Access Journals (Sweden)

    Naiming Qi

    2015-01-01

    Full Text Available This paper presents the error dynamic model of motorized momentum exchange tether (MMET based on the momentum exchange principle of space tether. The error dynamics are caused by the structural bias of the differences in tethers’ length and the difference in payloads’ mass. After that, the coupling analysis between orbit and attitude is presented. It is shown that, with increasing the differences in tethers’ length and payloads’ mass, the COM deviation of the MMET increases linearly. The numerical simulations of the MMET by considering the structural asymmetries are presented; the results show that the asymmetries have tiny influences on the orbit of the chief satellite by decreasing the apogee, which will change the instantaneous velocity at the apogee and affect the payload injection precision. What is more, the structural asymmetries have effects on the attitude elements (including the pitch angle and yaw angle; however, the effects could be weakened by the external torque. The structural asymmetries and gravity gradient torque have composite effects on the angular velocity of the propulsion tether.

  9. Attentional Retraining Administered to Cigarette Smokers in the Field: Effects on Attentional Bias, Craving, and Smoking

    Science.gov (United States)

    2013-08-30

    have greater effects on attentional bias. In a novel study of the effects of the drug d-Cycloserine (DCS; partial agonist at NMDA glutamate ...measures included a demographics questionnaire which asked participants to provide their age, gender, race/ ethnicity , income, and other demographic data

  10. On/off switching of bit readout in bias-enhanced tunnel magneto-Seebeck effect.

    Science.gov (United States)

    Boehnke, Alexander; Milnikel, Marius; von der Ehe, Marvin; Franz, Christian; Zbarsky, Vladyslav; Czerner, Michael; Rott, Karsten; Thomas, Andy; Heiliger, Christian; Reiss, Günter; Münzenberg, Markus

    2015-03-10

    Thermoelectric effects in magnetic tunnel junctions are promising to serve as the basis for logic devices or memories in a "green" information technology. However, up to now the readout contrast achieved with Seebeck effects was magnitudes smaller compared to the well-established tunnel magnetoresistance effect. Here, we resolve this problem by demonstrating that the tunnel magneto-Seebeck effect (TMS) in CoFeB/MgO/CoFeB tunnel junctions can be switched on to a logic "1" state and off to "0" by simply changing the magnetic state of the CoFeB electrodes. This new functionality is achieved by combining a thermal gradient and an electric field. Our results show that the signal crosses zero and can be adjusted by tuning a bias voltage that is applied between the electrodes of the junction; hence, the name of the effect is bias-enhanced tunnel magneto-Seebeck effect (bTMS). Via the spin- and energy-dependent transmission of electrons in the junction, the bTMS effect can be configured using the bias voltage with much higher control than the tunnel magnetoresistance and even completely suppressed for only one magnetic configuration. Moreover, our measurements are a step towards the experimental realization of high TMS ratios without additional bias voltage, which are predicted for specific Co-Fe compositions.

  11. Probing the antiferromagnetism of Ni{sub x}Mn{sub 100-X} with ferromagnetic Ni in exchange-biased bilayers and trilayers on Cu{sub 3}Au(001)

    Energy Technology Data Exchange (ETDEWEB)

    Khan, Muhammad Yaqoob

    2012-07-11

    In this thesis the antiferromagnetism of Ni{sub x}Mn{sub 100-x} thin films in contact with ferromagnetic Ni film(s) in exchange-biased bilayers and trilayers on Cu{sub 3}Au(001) is investigated by means of magneto-optical Kerr effect (MOKE). Ni{sub x}Mn{sub 100-x} ultrathin films (10{<=}x{<=}77) grow in layer-by-layer mode on Cu{sub 3}Au(001) with face-centered tetragonal structure similar to its bulk form. Ni{sub x}Mn{sub 100-x} can couple to out-of-plane (OoP) as well as in-plane (IP) magnetized Ni films, the latter stabilized by Co under-layer deposition. The antiferromagnetic (AFM) ordering temperature (T{sub AFM}) of Ni{sub x}Mn{sub 100-x} films coupled to IP magnetized Ni increases significantly with decreasing x from {approx} 50 to {approx} 20%, whereas only a slight change in T{sub AFM} is observed for bilayers with OoP magnetized Ni as a function of x. The blocking temperature (T{sub b}) is always higher for the IP case than for the OoP except for Ni{sub 50}Mn{sub 50}, where the reverse is true. The critical thickness of Ni{sub x}Mn{sub 100-x} for the onset of exchange bias (EB) decreases significantly for both coupling directions when decreasing x. These results suggest that for decreasing x, the non-collinear 3Q-like spin structure of Ni{sub x}Mn{sub 100-x} deviates, driven by composition-dependent strain, from a more-OoP to a more-IP configuration with an associated increase in magnetic anisotropic energy to establish EB at smaller Ni{sub x}Mn{sub 100-x} thicknesses. Trilayers of Ni/Ni{sub x}Mn{sub 100-x}/Ni (17{>=}x{>=}25) on Cu{sub 3}Au(001) are studied in detail, while manipulating the easy axis of magnetization of one or both of the FM Ni layers by the deposition of an adjacent Co layer. For the trilayers the exchange bias field H{sub eb} is found to be always smaller than in the corresponding bilayers at similar temperatures. This difference of Heb increases as the thickness of the Ni{sub x}Mn{sub 100-x} layer decreases. At reduced thickness (27 ML

  12. Fluency and belief bias in deductive reasoning: New indices for old effects

    Directory of Open Access Journals (Sweden)

    Dries eTrippas

    2014-06-01

    Full Text Available Models based on signal detection theory (SDT have occupied a prominent role in domains such as perception, categorisation, and memory. Recent work by Dube et al. (2010 suggests that the framework may also offer important insights in the domain of deductive reasoning. Belief bias in reasoning has traditionally been examined using indices based on raw endorsement rates – indices that critics have claimed are highly problematic. We discuss a new set of SDT indices fit for the investigation belief bias and apply them to new data examining the effect of perceptual disfluency on belief bias in syllogisms. In contrast to the traditional approach, the SDT indices do not violate important statistical assumptions, resulting in a decreased Type 1 error rate. Based on analyses using these novel indices we demonstrate that disfluency leads to decreased reasoning accuracy, contrary to predictions. Disfluency also appears to eliminate the typical link found between cognitive ability and the effect of beliefs on accuracy. Finally, replicating previous work, we demonstrate that cognitive ability leads to an increase in reasoning accuracy and a decrease in the response bias component of belief bias.

  13. [Comparison of the effects of exchange forms on social solidarity].

    Science.gov (United States)

    Inaba, Misato; Takahashi, Nobuyuki

    2012-04-01

    Although social solidarity is an essential component that helps maintaining social order, what produces solidarity and how does it work have not been fully investigated. We conducted an experiment to examine whether experiencing different forms of social exchange produces different levels of solidarity. We compared four forms of social exchange: reciprocal exchange (exchange resources without negotiation), negotiated exchange (with negotiation), pure-generalized exchange (giver can choose who to give) and chain-generalized exchange (giver cannot choose who to give). Two dimensions classify these exchanges: the number of players (two vs. more than two), and involvement of negotiation. Reciprocal and negotiated exchanges occur within dyads, while pure- and chain-generalized exchanges involve three or more players. Only the negotiated exchange involves negotiation process; the other exchanges are purely unilateral giving. Participants played a one-shot social dilemma game (SDG) before and after social exchange session. The more the players cooperated in SDG, the stronger the social solidarity. Results show that the cooperation rate in SDG increased more in the reciprocal, pure- and chain-generalized exchange conditions than that in the negotiated exchange condition, suggesting that social solidarity is facilitated by experiencing social exchange which does not involve negotiation.

  14. Theoretical and experimental insights into effects of wind on leaf heat and gas exchange

    Science.gov (United States)

    Schymanski, Stanislaus J.; Or, Dani

    2014-05-01

    Transpiration and heat exchange by plant leaves are coupled physiological processes of significant importance for surface-climate interactions and ecohydrology. The common practice of modelling transpiration as an isothermal process (assuming equal leaf and air temperatures) may introduce significant bias into estimates of transpiration rates and water use efficiency (WUE, the amount of carbon gained by photosynthesis per unit of water lost by transpiration). In contrast, explicit consideration of stomatal and leaf boundary layer resistances in series and the leaf energy balance in a physically-based model led to some surprising results, such as suppressed transpiration rates for increasing wind speed at constant stomatal conductance. The model predicts that for high wind velocities, the same leaf conductance (for water vapour and carbon dioxide) can be maintained with less evaporative losses. If this leaf-scale effect is consistent across most leaves, it may have profound implications for canopy-scale water use efficiency under globally decreasing wind speeds. This presentation reports the results of a systematic study of the effect of wind speed on leaf heat and gas exchange rates and introduces a novel experimental design to verify the modelling results using an insulated wind tunnel and artificial leaves with defined pore geometries, allowing to measure leaf-scale latent and sensible heat fluxes independently. First experimental results and new insights will be highlighted.

  15. Effect of verification bias on the sensitivity of fecal occult blood testing: a meta-analysis.

    Science.gov (United States)

    Rosman, Alan S; Korsten, Mark A

    2010-11-01

    There is controversy regarding the sensitivity of fecal occult blood tests (FOBT) for detecting colorectal cancer. Many of the published studies failed to correct for verification bias which may have increased the sensitivity. A meta-analysis of published studies evaluating the sensitivity and specificity of chemical-based FOBT for colorectal cancer was performed. Studies were included if both cancer and control subjects underwent confirmatory testing. We also included studies that attempted to correct for verification bias by either performing colonoscopy on all subjects regardless of the FOBT result or by using longitudinal follow-up. We then compared the sensitivity, specificity, and other diagnostic characteristics of the studies that attempted to correct for verification (n=10) vs. those that did not correct for this bias (n=19). The pooled sensitivity of guaiac-based FOBT for colorectal cancer of studies without verification bias was significantly lower than those studies with this bias [0.36 (95% CI 0.25-0.47) vs. 0.70 (95% CI 0.60-0.80), p=0.001]. The pooled specificity of the studies without verification bias was higher [0.96 (95% CI 0.94-0.97) vs. 0.88 (95% CI 0.84-0.91), p<0.005]. There was no significant difference in the area under the summary receiver operating characteristic curves. More sensitive chemical-based FOBT methods (e.g., Hemoccult® SENSA®) had a higher sensitivity but a lower specificity than standard guaiac methods. The sensitivity of guaiac-based FOBT for colorectal cancer has been overestimated as a result of verification bias. This test may not be sensitive enough to serve as an effective screening option for colorectal cancer.

  16. Galaxy bias and its effects on the Baryon acoustic oscillations measurements

    Energy Technology Data Exchange (ETDEWEB)

    Mehta, Kushal T. [Univ. of Arizona, Tucson, AZ (United States); Seo, Hee -Jong [Univ. of California, Berkeley, CA (United States); Fermi National Accelerator Lab., Batavia, IL (United States); Eckel, Jonathan [Univ. of Arizona, Tucson, AZ (United States); Eisenstein, Daniel J. [Univ. of Arizona, Tucson, AZ (United States); Harvard Univ., Cambridge, MA (United States); Metchnik, Marc [Univ. of Arizona, Tucson, AZ (United States); Pinto, Philip [Univ. of Arizona, Tucson, AZ (United States); Xu, Xiaoying [Univ. of Arizona, Tucson, AZ (United States)

    2011-05-31

    The baryon acoustic oscillation (BAO) feature in the clustering of matter in the universe serves as a robust standard ruler and hence can be used to map the expansion history of the universe. We use high force resolution simulations to analyze the effects of galaxy bias on the measurements of the BAO signal. We apply a variety of Halo Occupation Distributions (HODs) and produce biased mass tracers to mimic different galaxy populations. We investigate whether galaxy bias changes the non-linear shifts on the acoustic scale relative to the underlying dark matter distribution presented by Seo et al. (2009). For the less biased HOD models (b < 3), we do not detect any shift in the acoustic scale relative to the no-bias case, typically 0.10% ± 0.10%. However, the most biased HOD models (b > 3) show a shift at moderate significance (0.79% ± 0.31% for the most extreme case). We test the one-step reconstruction technique introduced by Eisenstein et al. (2007) in the case of realistic galaxy bias and shot noise. The reconstruction scheme increases the correlation between the initial and final (z = 1) density fields achieving an equivalent level of correlation at nearly twice the wavenumber after reconstruction. Reconstruction reduces the shifts and errors on the shifts. We find that after reconstruction the shifts from the galaxy cases and the dark matter case are consistent with each other and with no shift. The 1σ systematic errors on the distance measurements inferred from our BAO measurements with various HODs after reconstruction are about 0.07%-0.15%.

  17. Geometric phase effects in ultracold hydrogen exchange reaction

    Science.gov (United States)

    Hazra, Jisha; Kendrick, Brian K.; Balakrishnan, N.

    2016-10-01

    The role of the geometric phase effect on chemical reaction dynamics is explored by examining the hydrogen exchange process in the fundamental H+HD reaction. Results are presented for vibrationally excited HD molecules in the v = 4 vibrational level and for collision energies ranging from 1 μK to 100 K. It is found that, for collision energies below 3 K, inclusion of the geometric phase leads to dramatic enhancement or suppression of the reaction rates depending on the final quantum state of the HD molecule. The effect was found to be the most prominent for rotationally resolved integral and differential cross sections but it persists to a lesser extent in the vibrationally resolved and total reaction rate coefficients. However, no significant GP effect is present in the reactive channel leading to the D+H2 product or in the D+H2 (v=4,j=0) \\to HD+H reaction. A simple interference mechanism involving inelastic (nonreactive) and exchange scattering amplitudes is invoked to account for the observed GP effects. The computed results also reveal a shape resonance in the H+HD reaction near 1 K and the GP effect is found to influence the magnitude of the resonant part of the cross section. Experimental detection of the resonance may allow a sensitive probe of the GP effect in the H+HD reaction.

  18. The effect of cognitive bias modification for interpretation on avoidance of pain during an acute experimental pain task.

    Science.gov (United States)

    Jones, Emma Blaisdale; Sharpe, Louise

    2014-08-01

    Research confirms that patients with chronic pain show a tendency to interpret ambiguous stimuli as pain related. However, whether modifying these interpretive pain biases impacts pain outcomes is unknown. This study aimed to demonstrate that interpretation biases towards pain can be modified, and that changing these biases influences pain outcomes in the cold pressor task. One hundred and six undergraduate students were randomly allocated to receive either threatening or reassuring information regarding the cold pressor. They also were randomly allocated to 1 of 2 conditions in the Ambiguous Scenarios Task, in which they were trained to have either a threatening interpretation of pain (pain bias condition) or a nonthreatening interpretation of pain (no pain bias condition). Therefore, the study had a 2 (threat/reassuring)×2 (pain bias/no pain bias) design. Analyses showed that a bias was induced contingent on condition, and that the threat manipulation was effective. Participants in the pain bias condition hesitated more before doing the cold pressor task than those in the no pain bias condition, as did those in the threat compared with the reassurance condition. The major finding was that interpretive bias mediated the relationship between bias condition and hesitance time, supporting the causal role of interpretive biases for avoidance behaviors in current chronic pain models. No differences were found on other pain outcomes regarding bias or threat, and the efficacy of the bias modification was not impacted by different levels of threat. These results suggest that cognitive bias modification should be further explored as a potential intervention in pain. Crown Copyright © 2014. Published by Elsevier B.V. All rights reserved.

  19. Regulatory fit effects on perceived fiscal exchange and tax compliance.

    Science.gov (United States)

    Leder, Susanne; Mannetti, Lucia; Hölzl, Erik; Kirchler, Erich

    2010-04-01

    Paying taxes can be considered a contribution to the welfare of a society. But even though tax payments are redistributed to citizens in the form of public goods and services, taxpayers often do not perceive many benefits from paying taxes. Information campaigns about the use of taxes for financing public goods and services could increase taxpayers' understanding of the importance of taxes, strengthen their perception of fiscal exchange and consequently also increase tax compliance. Two studies examined how fit between framing of information and taxpayers' regulatory focus affects perceived fiscal exchange and tax compliance. Taxpayers should perceive the exchange between tax payments and provision of public goods and services as higher if information framing suits their regulatory focus. Study 1 supported this hypothesis for induced regulatory focus. Study 2 replicated the findings for chronic regulatory focus and further demonstrated that regulatory fit also affects tax compliance. The results provide further evidence for findings from previous studies concerning regulatory fit effects on tax attitudes and extend these findings to a context with low tax morale.

  20. Publication bias & small-study effects in pediatric dentistry meta-analyses.

    Science.gov (United States)

    Papageorgiou, Spyridon N; Dimitraki, Dionysia; Coolidge, Trilby; Kotsanos, Nikolaos

    2015-03-01

    The aim of this study was to examine the presence and extent of publication bias and small-study effects in meta-analyses (MAs) investigating pediatric dentistry-related subjects. Following a literature search, 46 MAs including 882 studies were analyzed qualitatively. Of these, 39 provided enough data to be re-analyzed. Publication bias was assessed with the following methods: contour-enhanced funnel plots, Begg and Mazumdar's rank correlation and Egger's linear regression tests, Rosenthal's failsafe N, and Duval and Tweedie's "trim and fill" procedure. Only a few MAs adequately assessed the existence and effect of publication bias. Inspection of the funnel plots indicated asymmetry, which was confirmed by Begg-Mazumdar's test in 18% and by Egger's test in 33% of the MAs. According to Rosenthal's criterion, 80% of the MAs were robust, while adjusted effects with unpublished studies differed from little to great from the unadjusted ones. Pooling of the Egger's intercepts indicated that evidence of asymmetry was found in the pediatric dental literature, which was accentuated in dental journals and in diagnostic MAs. Since indications of small-study effects and publication bias in pediatric dentistry were found, the influence of small or missing trials on estimated treatment effects should be routinely assessed in future MAs. Copyright © 2015 Elsevier Inc. All rights reserved.

  1. The effects of ageing on self-reported aggression measures are partly explained by response bias.

    Science.gov (United States)

    Vigil-Colet, Andreu; Lorenzo-Seva, Urbano; Morales-Vives, Fabia

    2015-01-01

    Recent studies have suggested that the age-personality relationship may be partly explained by age-related changes in response bias. In the present study, we analysed how age affected social desirability and acquiescence, and how this effect impacted the age-aggression relationship. We used the Indirect-Direct Aggression Questionnaire, which provides response bias and physical, verbal and indirect aggression scores independently of each other. We applied this test to a sample of 616 individuals aged between 18 and 96 (M = 49.24, SD = 24.81) and analysed the relationships between age and aggression measures with and without response bias. We found that social desirability and acquiescence increased by between one and two standard deviations between adulthood and old age. This affected the age-aggression relationship for all aggression scales and, especially for verbal and indirect aggression, whose relationships with age decreased from r = -.192 and r = -.309 to r = .012 and r = -.159, respectively, when response biases were controlled. When response bias and, in particular social desirability, are not controlled, elderly people tend to show aggression scores that are considerably lower than their true aggression levels.

  2. Effect of dc-bias on the dielectric behavior of CNT/ABS nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    El Ghanem, Hasan M., E-mail: hmel@just.edu.jo [Physics Department, Jordan University of Science and Technology, P.O. Box 3030, Irbid 22110 (Jordan); Abdul Jawad, Saa' di [Physics Department, Hashemite University, P.O. Box 150459, Zarqa 13115 (Jordan); Al-Saleh, Mohammed H.; Hussain, Yazan A [Department of Chemical Engineering, Jordan University of Science and Technology, P.O. Box 3030, Irbid 22110 (Jordan); Salah, Wael [Physics Department, Hashemite University, P.O. Box 150459, Zarqa 13115 (Jordan)

    2013-06-01

    Several aspects of the dielectric behavior of multi-walled carbon nanotube (MWCNT)/acrylonitrile–butadiene–styrene (ABS) nanocomposites were studied. MWCNT/ABS nanocomposites with filler content between 2 wt% and 15 wt% were prepared by melt mixing and characterized by the impedance technique. The results showed that the dc and ac conductivities increase with increasing dc bias and MWCNT content. The effect of dc bias was more pronounced for nanocomposites with low MWCNT content. The bode diagram of the real impedance for nanocomposites containing 2 wt% MWCNT or higher exhibited a frequency independent plateau in the low frequency region revealing that dc conduction is the dominant conduction mechanism. The critical frequency at which ac conductivity becomes frequency dependent increased with increasing dc bias and MWCNT content.

  3. Effect of a Biased Probe on the Afterglow Operation of an ECR4 Ion Source

    CERN Document Server

    Hill, C E; Wenander, F; Wolf, B H

    2000-01-01

    Various experiments have been performed on a 14.5 GHz ECR4 in order to improve the ion yield. The source runs in pulsed afterglow mode, and provides currents ~120 emA of Pb27+ to the CERN Heavy Ion Facility on an operational basis. In the search for higher beam intensities, the effects of a pulsed biased disk on axis at the injection side were investigated with different pulse timing and voltage settings. No proof for absolute higher intensities was seen for any of these modifications. However, the yield from a poorly tuned/low-performing source could be improved and the extracted pulse was less noisy with bias voltage applied. The fast response on the bias implies that increases/decreases are not due to ionisation processes. A good tune for high yield of high charge states during the afterglow coincides with a high plasma potential.

  4. Towards a de-biased social psychology: The effects of ideological perspective go beyond politics.

    Science.gov (United States)

    Funder, David C

    2015-01-01

    Reasonable conservatives are in short supply and will not arrive to save social psychology any time soon. The field needs to save itself through de-biasing. The effects of a liberal worldview permeate and distort discussion of many topics that are not overtly political, including behavioral genetics and evolutionary psychology, the fundamental attribution error, and the remarkably persistent consistency controversy.

  5. Gate-bias assisted charge injection in organic field-effect transistors

    NARCIS (Netherlands)

    Brondijk, J. J.; Torricelli, F.; Smits, E. C. P.; Blom, P. W. M.; de Leeuw, D. M.

    The charge injection barriers in organic field-effect transistors (OFETs) seem to be far less critical as compared to organic light-emitting diodes (OLEDs). Counter intuitively, we show that the origin is image-force lowering of the barrier due to the gate bias at the source contact, although the

  6. Gate-bias assisted charge injection in organic field-effect transistors

    NARCIS (Netherlands)

    Brondijk, J.J.; Torricelli, F.; Smits, E.C.P.; Blom, P.W.M.; Leeuw, D.M. de

    2012-01-01

    The charge injection barriers in organic field-effect transistors (OFETs) seem to be far less critical as compared to organic light-emitting diodes (OLEDs). Counter intuitively, we show that the origin is image-force lowering of the barrier due to the gate bias at the source contact, although the

  7. Effects of sertraline, duloxetine, vortioxetine, and idazoxan in the rat affective bias test

    DEFF Research Database (Denmark)

    Refsgaard, Louise Konradsen; Haubro, Kia; Pickering, Darryl S

    2016-01-01

    lead to improved mood. Objectives Using two conventional antidepressants, sertraline and duloxetine, we aimed to forward the characterization of a newly developed affective bias test (ABT) for rats. Further, we examined the effect of vortioxetine, a recently approved antidepressant, and the α2...

  8. Can statistical linkage of missing variables reduce bias in treatment effect estimates in comparative effectiveness research studies?

    Science.gov (United States)

    Crown, William; Chang, Jessica; Olson, Melvin; Kahler, Kristijan; Swindle, Jason; Buzinec, Paul; Shah, Nilay; Borah, Bijan

    2015-09-01

    Missing data, particularly missing variables, can create serious analytic challenges in observational comparative effectiveness research studies. Statistical linkage of datasets is a potential method for incorporating missing variables. Prior studies have focused upon the bias introduced by imperfect linkage. This analysis uses a case study of hepatitis C patients to estimate the net effect of statistical linkage on bias, also accounting for the potential reduction in missing variable bias. The results show that statistical linkage can reduce bias while also enabling parameter estimates to be obtained for the formerly missing variables. The usefulness of statistical linkage will vary depending upon the strength of the correlations of the missing variables with the treatment variable, as well as the outcome variable of interest.

  9. Hostile Attributional Bias, Negative Emotional Responding, and Aggression in Adults: Moderating Effects of Gender and Impulsivity

    OpenAIRE

    Chen, Pan; Coccaro, Emil F.; Jacobson, Kristen C.

    2012-01-01

    The current study examined the main effects of hostile attributional bias (HAB) and negative emotional responding on a variety of aggressive behaviors in adults, including general aggression, physical aggression, relational aggression, and verbal aggression. Effects of both externalizing (anger) and internalizing (embarrassment/upset) negative emotions were considered. In addition, the moderating roles of gender and impulsivity on the effects of HAB and negative emotional responding were expl...

  10. Performance analyses of helical coil heat exchangers. The effect of external coil surface modification on heat exchanger effectiveness

    Science.gov (United States)

    Andrzejczyk, Rafał; Muszyński, Tomasz

    2016-12-01

    The shell and coil heat exchangers are commonly used in heating, ventilation, nuclear industry, process plant, heat recovery and air conditioning systems. This type of recuperators benefits from simple construction, the low value of pressure drops and high heat transfer. In helical coil, centrifugal force is acting on the moving fluid due to the curvature of the tube results in the development. It has been long recognized that the heat transfer in the helical tube is much better than in the straight ones because of the occurrence of secondary flow in planes normal to the main flow inside the helical structure. Helical tubes show good performance in heat transfer enhancement, while the uniform curvature of spiral structure is inconvenient in pipe installation in heat exchangers. Authors have presented their own construction of shell and tube heat exchanger with intensified heat transfer. The purpose of this article is to assess the influence of the surface modification over the performance coefficient and effectiveness. The experiments have been performed for the steady-state heat transfer. Experimental data points were gathered for both laminar and turbulent flow, both for co current- and countercurrent flow arrangement. To find optimal heat transfer intensification on the shell-side authors applied the number of transfer units analysis.

  11. Industry-specific Real Effective Exchange Rates in Asia

    OpenAIRE

    SATO Kiyotaka; SHIMIZU Junko; Nagendra SHRESTHA; Shajuan ZHANG

    2015-01-01

    This study constructs a monthly series of industry-specific real effective exchange rates (I-REERs) based on the producer price indices of nine Asian economies from 2001 to 2014. To check the usefulness of the I-REERs as a measurement of international price competitiveness, we calculated the aggregated I-REER (Avg-I-REER) and compared it with the REER published by the Bank for International Settlements (BIS-REER). We found that in some Asian economies, the Avg-I-REER exhibited different movem...

  12. Mobile phase modifier effects in multimodal cation exchange chromatography.

    Science.gov (United States)

    Holstein, Melissa A; Parimal, Siddharth; McCallum, Scott A; Cramer, Steven M

    2012-01-01

    This study examines protein adsorption behavior and the effects of mobile phase modifiers in multimodal chromatographic systems. Chromatography results with a diverse protein library indicate that multimodal and ion exchange resins have markedly different protein binding behavior and selectivity. NMR results corroborate the stronger binding observed for the multimodal system and provide insight into the structural basis for the observed binding behavior. Protein-binding affinity and selectivity in multimodal and ion exchange systems are then examined using a variety of mobile phase modifiers. Arginine and guanidine are found to have dramatic effects on protein adsorption, yielding changes in selectivity in both chromatographic systems. While sodium caprylate leads to slightly weaker chromatographic retention for most proteins, certain proteins exhibit significant losses in retention in both systems. The presence of a competitive binding mechanism between the multimodal ligand and sodium caprylate for binding to ubiquitin is confirmed using STD NMR. Polyol mobile phase modifiers are shown to result in increased retention for weakly bound proteins and decreased retention for strongly bound proteins, indicating that the overall retention behavior is determined by a balance between changes in electrostatic and hydrophobic interactions. This work provides an improved understanding of protein adsorption and mobile phase modifier effects in multimodal chromatographic systems and sets the stage for future work to develop more selective protein separation systems. Copyright © 2011 Wiley Periodicals, Inc.

  13. Reduction of Pavlovian Bias in Schizophrenia: Enhanced Effects in Clozapine-Administered Patients.

    Directory of Open Access Journals (Sweden)

    Matthew A Albrecht

    Full Text Available The negative symptoms of schizophrenia (SZ are associated with a pattern of reinforcement learning (RL deficits likely related to degraded representations of reward values. However, the RL tasks used to date have required active responses to both reward and punishing stimuli. Pavlovian biases have been shown to affect performance on these tasks through invigoration of action to reward and inhibition of action to punishment, and may be partially responsible for the effects found in patients. Forty-five patients with schizophrenia and 30 demographically-matched controls completed a four-stimulus reinforcement learning task that crossed action ("Go" or "NoGo" and the valence of the optimal outcome (reward or punishment-avoidance, such that all combinations of action and outcome valence were tested. Behaviour was modelled using a six-parameter RL model and EEG was simultaneously recorded. Patients demonstrated a reduction in Pavlovian performance bias that was evident in a reduced Go bias across the full group. In a subset of patients administered clozapine, the reduction in Pavlovian bias was enhanced. The reduction in Pavlovian bias in SZ patients was accompanied by feedback processing differences at the time of the P3a component. The reduced Pavlovian bias in patients is suggested to be due to reduced fidelity in the communication between striatal regions and frontal cortex. It may also partially account for previous findings of poorer "Go-learning" in schizophrenia where "Go" responses or Pavlovian consistent responses are required for optimal performance. An attenuated P3a component dynamic in patients is consistent with a view that deficits in operant learning are due to impairments in adaptively using feedback to update representations of stimulus value.

  14. Quantifying attentional effects on the fidelity and biases of visual working memory in young children.

    Science.gov (United States)

    Guillory, Sylvia B; Gliga, Teodora; Kaldy, Zsuzsa

    2018-03-01

    Attentional control enables us to direct our limited resources to accomplish goals. The ability to flexibly allocate resources helps to prioritize information and inhibit irrelevant/distracting information. We examined developmental changes in visual working memory (VWM) fidelity in 4- to 7-year-old children and the effects that a distracting non-target object can exert in biasing their memory representations. First, we showed that VWM fidelity improves from early childhood to adulthood. Second, we found evidence of working memory load on recall variability in children and adults. Next, using cues to manipulate attention, we found that older children are able to construct a more durable memory representation for an object presented following a non-target using a pre-cue (that biases encoding before presentation) compared with a retro-cue (that signals which item to recall after presentation). In addition, younger children had greater difficulties maintaining an item in memory when an intervening item was presented. Lastly, we found that memory representations are biased toward a non-target when it is presented following the target and away from a non-target when it precedes the target. These bias effects were more pronounced in children compared with adults. Together, these results demonstrate changes in attention over development that influence VWM memory fidelity. Copyright © 2017 Elsevier Inc. All rights reserved.

  15. Effect of Reverse Bias Stress on Leakage Currents and Breakdown Voltages of Solid Tantalum Capacitors

    Science.gov (United States)

    Teverovsky, Alexander A.

    2011-01-01

    the processes under reverse bias conditions. In practice, there were instances when, due to unforeseen events, the system operated at conditions when capacitors experience periodically a relatively small reverse bias for some time followed by normal, forward bias conditions. In such a case an assessment should be made on the degree to which these capacitors are degraded by application of low-voltage reverse bias, and whether this degradation can be reversed by normal operating conditions. In this study, reverse currents in different types of tantalum capacitors were monitored at different reverse voltages below 15%VR and temperatures in the range from room to 145 C for up to 150 hours to get better understanding of the degradation process and determine conditions favorable to the unstable mode of operation. The reversibility of RB degradation has been evaluated after operation of the capacitors at forward bias conditions. The effect of reverse bias stress (RBS) on reliability at normal operating conditions was evaluated using highly accelerated life testing at voltages of 1.5VR and 2 VR and by analysis of changes in distributions of breakdown voltages. Possible mechanisms of RB degradation are discussed.

  16. The facing bias in biological motion perception: Effects of stimulus gender and observer sex.

    Science.gov (United States)

    Schouten, Ben; Troje, Nikolaus F; Brooks, Anna; van der Zwan, Rick; Verfaillie, Karl

    2010-07-01

    Under orthographic projection, biological motion point-light walkers offer no cues to the order of the dots in depth: Views from the front and from the back result in the very same stimulus. Yet observers show a bias toward seeing a walker facing the viewer (Vanrie, Dekeyser, & Verfaillie, 2004). Recently, we reported that this facing bias strongly depends on the gender of the walker (Brooks et al., 2008). The goal of the present study was, first, to examine the robustness of the effect by testing a much larger subject sample and, second, to investigate whether the effect depends on observer sex. Despite the fact that we found a significant effect of figure gender, we clearly failed to replicate the strong effect observed in the original study. We did, however, observe a significant interaction between figure gender and observer sex.

  17. Publication Bias in Psychology: A Diagnosis Based on the Correlation between Effect Size and Sample Size

    Science.gov (United States)

    Kühberger, Anton; Fritz, Astrid; Scherndl, Thomas

    2014-01-01

    Background The p value obtained from a significance test provides no information about the magnitude or importance of the underlying phenomenon. Therefore, additional reporting of effect size is often recommended. Effect sizes are theoretically independent from sample size. Yet this may not hold true empirically: non-independence could indicate publication bias. Methods We investigate whether effect size is independent from sample size in psychological research. We randomly sampled 1,000 psychological articles from all areas of psychological research. We extracted p values, effect sizes, and sample sizes of all empirical papers, and calculated the correlation between effect size and sample size, and investigated the distribution of p values. Results We found a negative correlation of r = −.45 [95% CI: −.53; −.35] between effect size and sample size. In addition, we found an inordinately high number of p values just passing the boundary of significance. Additional data showed that neither implicit nor explicit power analysis could account for this pattern of findings. Conclusion The negative correlation between effect size and samples size, and the biased distribution of p values indicate pervasive publication bias in the entire field of psychology. PMID:25192357

  18. Publication bias in psychology: a diagnosis based on the correlation between effect size and sample size.

    Science.gov (United States)

    Kühberger, Anton; Fritz, Astrid; Scherndl, Thomas

    2014-01-01

    The p value obtained from a significance test provides no information about the magnitude or importance of the underlying phenomenon. Therefore, additional reporting of effect size is often recommended. Effect sizes are theoretically independent from sample size. Yet this may not hold true empirically: non-independence could indicate publication bias. We investigate whether effect size is independent from sample size in psychological research. We randomly sampled 1,000 psychological articles from all areas of psychological research. We extracted p values, effect sizes, and sample sizes of all empirical papers, and calculated the correlation between effect size and sample size, and investigated the distribution of p values. We found a negative correlation of r = -.45 [95% CI: -.53; -.35] between effect size and sample size. In addition, we found an inordinately high number of p values just passing the boundary of significance. Additional data showed that neither implicit nor explicit power analysis could account for this pattern of findings. The negative correlation between effect size and samples size, and the biased distribution of p values indicate pervasive publication bias in the entire field of psychology.

  19. Effects of standard and explicit cognitive bias modification and computer-administered cognitive-behaviour therapy on cognitive biases and social anxiety☆

    Science.gov (United States)

    Mobini, Sirous; Mackintosh, Bundy; Illingworth, Jo; Gega, Lina; Langdon, Peter; Hoppitt, Laura

    2014-01-01

    Background and objectives This study examines the effects of a single session of Cognitive Bias Modification to induce positive Interpretative bias (CBM-I) using standard or explicit instructions and an analogue of computer-administered CBT (c-CBT) program on modifying cognitive biases and social anxiety. Methods A sample of 76 volunteers with social anxiety attended a research site. At both pre- and post-test, participants completed two computer-administered tests of interpretative and attentional biases and a self-report measure of social anxiety. Participants in the training conditions completed a single session of either standard or explicit CBM-I positive training and a c-CBT program. Participants in the Control (no training) condition completed a CBM-I neutral task matched the active CBM-I intervention in format and duration but did not encourage positive disambiguation of socially ambiguous or threatening scenarios. Results Participants in both CBM-I programs (either standard or explicit instructions) and the c-CBT condition exhibited more positive interpretations of ambiguous social scenarios at post-test and one-week follow-up as compared to the Control condition. Moreover, the results showed that CBM-I and c-CBT, to some extent, changed negative attention biases in a positive direction. Furthermore, the results showed that both CBM-I training conditions and c-CBT reduced social anxiety symptoms at one-week follow-up. Limitations This study used a single session of CBM-I training, however multi-sessions intervention might result in more endurable positive CBM-I changes. Conclusions A computerised single session of CBM-I and an analogue of c-CBT program reduced negative interpretative biases and social anxiety. PMID:24412966

  20. Legume-rhizobia signal exchange: promiscuity and environmental effects

    Directory of Open Access Journals (Sweden)

    Mario Andrade Lira Junior

    2015-09-01

    Full Text Available Although signal exchange between legumes and their rhizobia is among the best-known examples of this biological process, most of the more characterized data comes from just a few legume species and environmental stresses. Although a relative wealth of information is available for some model legumes and some of the major pulses such as soybean, little is known about tropical legumes. This relative disparity in current knowledge is also apparent in the research on the effects of environmental stress on signal exchange; cool-climate stresses, such as low-soil temperature, comprise a relatively large body of research, whereas high-temperature stresses and drought are not nearly as well understood. Both tropical legumes and their environmental stress-induced effects are increasingly important due to global population growth (the demand for protein, climate change (increasing temperatures and more extreme climate behavior, and urbanization (and thus heavy metals. This knowledge gap for both legumes and their environmental stresses is compounded because whereas most temperate legume-rhizobia symbioses are relatively specific and cultivated under relatively stable environments, the converse is true for tropical legumes, which tend to be promiscuous and grow in highly variable conditions. This review will clarify some of this missing information and highlight fields in which further research would benefit our current knowledge.

  1. Effects of Copper Exchange Levels on Complexation of Ammonia in ...

    African Journals Online (AJOL)

    NJD

    Cation exchange, catalysis, copper, complexation, copper ammines. 1. Introduction. Copper-exchanged zeolites ... characterization of cation-exchanged zeolites is ammonia.7. Ammonia is small enough (ca. 3.70 × 3.99 .... quartz glass sample cuvettes and the diffuse reflectance spec- troscopy measurements obtained from ...

  2. Effects Of Real Exchange Rate Uncertainty On Private Investment In ...

    African Journals Online (AJOL)

    The results of the study indicated that real exchange rate uncertainty is a significant determinant of private investment and that real exchange rate uncertainty has a negative impact on private investment in Ghana. The policy implication of the findings is that government should pursue sound exchange rate policies that ...

  3. Effectiveness of two web-based cognitive bias modification interventions targeting approach and attentional bias in gambling problems: study protocol for a pilot randomised controlled trial.

    Science.gov (United States)

    Boffo, Marilisa; Willemen, Ronny; Pronk, Thomas; Wiers, Reinout W; Dom, Geert

    2017-10-03

    Disordered gamblers have phenotypical and pathological similarities to those with substance use disorders (SUD), including exaggerated automatic cognitive processing of motivationally salient gambling cues in the environment (i.e., attentional and approach bias). Cognitive bias modification (CBM) is a family of computerised interventions that have proved effective in successfully re-training these automatic cognitive biases in SUD. CBM interventions can, in principle, be administered online, thus showing potential of being a low-cost, low-threshold addition to conventional treatments. This paper presents the design of a pilot randomised controlled trial exploring the effectiveness of two web-based CBM interventions targeting attentional and approach bias towards gambling cues in a sample of Dutch and Belgian problematic and pathological gamblers. Participants (N = 182) are community-recruited adults experiencing gambling problems, who have gambled at least twice in the past 6 months and are motivated to change their gambling behaviour. After a baseline assessment session, participants are randomly assigned to one of four experimental conditions (attentional or approach bias training, or the placebo version of the two trainings) and complete six sessions of training. At baseline and before each training session, participants receive automated personalised feedback on their gambling motives and reasons to quit or reduce gambling. The post-intervention, 1-month, and 3-month follow-up assessments will examine changes in gambling behaviour, with frequency and expenditure as primary outcomes, and depressive symptoms and gambling-related attentional and approach biases as secondary outcomes. Secondary analyses will explore possible moderators (interference control capacity and trait impulsivity) and mediators (change in cognitive bias) of training effects on the primary outcomes. This study is the first to explore the effectiveness of an online CBM intervention for

  4. Mendelian randomization with invalid instruments: effect estimation and bias detection through Egger regression.

    Science.gov (United States)

    Bowden, Jack; Davey Smith, George; Burgess, Stephen

    2015-04-01

    The number of Mendelian randomization analyses including large numbers of genetic variants is rapidly increasing. This is due to the proliferation of genome-wide association studies, and the desire to obtain more precise estimates of causal effects. However, some genetic variants may not be valid instrumental variables, in particular due to them having more than one proximal phenotypic correlate (pleiotropy). We view Mendelian randomization with multiple instruments as a meta-analysis, and show that bias caused by pleiotropy can be regarded as analogous to small study bias. Causal estimates using each instrument can be displayed visually by a funnel plot to assess potential asymmetry. Egger regression, a tool to detect small study bias in meta-analysis, can be adapted to test for bias from pleiotropy, and the slope coefficient from Egger regression provides an estimate of the causal effect. Under the assumption that the association of each genetic variant with the exposure is independent of the pleiotropic effect of the variant (not via the exposure), Egger's test gives a valid test of the null causal hypothesis and a consistent causal effect estimate even when all the genetic variants are invalid instrumental variables. We illustrate the use of this approach by re-analysing two published Mendelian randomization studies of the causal effect of height on lung function, and the causal effect of blood pressure on coronary artery disease risk. The conservative nature of this approach is illustrated with these examples. An adaption of Egger regression (which we call MR-Egger) can detect some violations of the standard instrumental variable assumptions, and provide an effect estimate which is not subject to these violations. The approach provides a sensitivity analysis for the robustness of the findings from a Mendelian randomization investigation. © The Author 2015; Published by Oxford University Press on behalf of the International Epidemiological Association.

  5. Prejudice and the Plate: Effects of Weight Bias in Nutrition Judgments.

    Science.gov (United States)

    Schuldt, Jonathon P; Guillory, Jamie E; Gay, Geri K

    2016-01-01

    As millions of people turn to social media for health information, better understanding the factors that guide health-related judgments and perceptions in this context is imperative. We report on two Web experiments (n>400 total) examining the power of society's widespread weight bias and related stereotypes to influence nutrition judgments in social media spaces. In Experiment 1, meals were judged as lower in nutritional quality when the person who recommended them (the source) was depicted as obese rather than of normal weight, an effect mediated by stereotypic beliefs about the source as a generally unhealthy person. Experiment 2 replicated this effect, which--notably--remained significant when controlling for objective nutritional information (calories and fat content). Results highlight spillover effects of weight bias that extend beyond person perception to color impressions of objects (here, food) that are associated with stigmatized attributes. Implications for everyday nutrition judgments and public health are considered.

  6. Phantom behavioral assimilation effects: systematic biases in social comparison choice studies.

    Science.gov (United States)

    Marsh, Herbert W; Seaton, Marjorie; Kuyper, Hans; Dumas, Florence; Huguet, Pascal; Régner, Isabelle; Buunk, Abraham P; Monteil, Jean-Marc; Gibbons, Frederick X

    2010-04-01

    Consistent with social comparison theory (SCT), Blanton, Buunk, Gibbons, and Kuyper (1999) and Huguet, Dumas, Monteil, and Genestoux (2001) found that students tended to choose comparison targets who slightly outperformed them (i.e., upward comparison choices), and this had a beneficial effect on subsequent performance--a behavioral assimilation effect (BAE). We show (Studies 1 and 2) that this apparent BAE is due, in part, to uncontrolled measurement error in pretest achievement. However, using simulated data (Study 3), these phantom BAEs were eliminated with latent-variable models with multiple indicators. In Studies 4 and 5, latent-variable models were applied to the Blanton et al. and Huguet et al. data, resulting in substantially smaller but still significantly positive BAEs. More generally in personality research based on correlational data, failure to control measurement error in pretest/background variables will positively bias the apparent effects of personality variables of interest, but widely applicable approaches demonstrated here can correct for these biases.

  7. Making simple sentences hard: Verb bias effects in simple direct object sentences

    Science.gov (United States)

    Wilson, Michael P.; Garnsey, Susan M.

    2009-01-01

    Constraint-based lexical models of language processing assume that readers resolve temporary ambiguities by relying on a variety of cues, including particular knowledge of how verbs combine with nouns. Previous experiments have demonstrated verb bias effects only in structurally complex sentences, and have been criticized on the grounds that such effects could be due to a rapid reanalysis stage in a two-stage modular processing system. In a self-paced reading experiment and an eyetracking experiment, we demonstrate verb bias effects in sentences with simple structures that should require no reanalyis, and thus provide evidence that the combinatorial properties of individual words influence the earliest stages of sentence comprehension. PMID:20160997

  8. [The effects of interpretation bias for social events and automatic thoughts on social anxiety].

    Science.gov (United States)

    Aizawa, Naoki

    2015-08-01

    Many studies have demonstrated that individuals with social anxiety interpret ambiguous social situations negatively. It is, however, not clear whether the interpretation bias discriminatively contributes to social anxiety in comparison with depressive automatic thoughts. The present study investigated the effects of negative interpretation bias and automatic thoughts on social anxiety. The Social Intent Interpretation-Questionnaire, which measures the tendency to interpret ambiguous social events as implying other's rejective intents, the short Japanese version of the Automatic Thoughts Questionnaire-Revised, and the Anthropophobic Tendency Scale were administered to 317 university students. Covariance structure analysis indicated that both rejective intent interpretation bias and negative automatic thoughts contributed to mental distress in social situations mediated by a sense of powerlessness and excessive concern about self and others in social situations. Positive automatic thoughts reduced mental distress. These results indicate the importance of interpretation bias and negative automatic thoughts in the development and maintenance of social anxiety. Implications for understanding of the cognitive features of social anxiety were discussed.

  9. Bias Errors due to Leakage Effects When Estimating Frequency Response Functions

    Directory of Open Access Journals (Sweden)

    Andreas Josefsson

    2012-01-01

    Full Text Available Frequency response functions are often utilized to characterize a system's dynamic response. For a wide range of engineering applications, it is desirable to determine frequency response functions for a system under stochastic excitation. In practice, the measurement data is contaminated by noise and some form of averaging is needed in order to obtain a consistent estimator. With Welch's method, the discrete Fourier transform is used and the data is segmented into smaller blocks so that averaging can be performed when estimating the spectrum. However, this segmentation introduces leakage effects. As a result, the estimated frequency response function suffers from both systematic (bias and random errors due to leakage. In this paper the bias error in the H1 and H2-estimate is studied and a new method is proposed to derive an approximate expression for the relative bias error at the resonance frequency with different window functions. The method is based on using a sum of real exponentials to describe the window's deterministic autocorrelation function. Simple expressions are derived for a rectangular window and a Hanning window. The theoretical expressions are verified with numerical simulations and a very good agreement is found between the results from the proposed bias expressions and the empirical results.

  10. Room temperature magnetic ordering, enhanced magnetization and exchange bias of GdMnO3 nanoparticles in (GdMnO3)0.70(CoFe2O4)0.30

    Science.gov (United States)

    Mitra, A.; Mahapatra, A. S.; Mallick, A.; Chakrabarti, P. K.

    2017-02-01

    Nanoparticles of GdMnO3 (GMO) are prepared by sol-gel method. To enhance the magnetic property and also to obtain the magnetic ordering at room temperature (RT), nanoparticles of GMO are incorporated in the matrix of CoFe2O4 (CFO). Desired crystallographic phases of CFO, GMO and GMO-CFO are confirmed by analyzing X-ray diffractrograms (XRD) using Rietveld method. The average size of nanoparticles and their distribution, crystallographic phase, nanocrystallinity etc. are studied by high-resolution transmission electron microscope (HRTEM). Magnetic hysteresis loops (M-H) of GMO-CFO under zero field cooled (ZFC) and field cooled (FC) conditions are observed at different temperatures down to 5 K. Magnetization vs. temperature (M-T) under ZFC and FC conditions are also recorded. Interestingly, exchange bias (EB) is found at low temperature which suggests the encapsulation of the ferromagnetic (FM) nanoparticles of GMO by the ferrimagnetic nanoparticles of CFO below 100 K. Enhanced magnetization, EB effect and RT magnetic ordering of GMO-CFO would be interesting for both theoretical and experimental investigations.

  11. Do Methodological Choices in Environmental Modeling Bias Rebound Effects? A Case Study on Electric Cars.

    Science.gov (United States)

    Font Vivanco, David; Tukker, Arnold; Kemp, René

    2016-10-18

    Improvements in resource efficiency often underperform because of rebound effects. Calculations of the size of rebound effects are subject to various types of bias, among which methodological choices have received particular attention. Modellers have primarily focused on choices related to changes in demand, however, choices related to modeling the environmental burdens from such changes have received less attention. In this study, we analyze choices in the environmental assessment methods (life cycle assessment (LCA) and hybrid LCA) and environmental input-output databases (E3IOT, Exiobase and WIOD) used as a source of bias. The analysis is done for a case study on battery electric and hydrogen cars in Europe. The results describe moderate rebound effects for both technologies in the short term. Additionally, long-run scenarios are calculated by simulating the total cost of ownership, which describe notable rebound effect sizes-from 26 to 59% and from 18 to 28%, respectively, depending on the methodological choices-with favorable economic conditions. Relevant sources of bias are found to be related to incomplete background systems, technology assumptions and sectorial aggregation. These findings highlight the importance of the method setup and of sensitivity analyses of choices related to environmental modeling in rebound effect assessments.

  12. Exchange bias in Ba0.4Sr0.6TiO3/La0.7Sr0.3MnO3 heterostructures

    Science.gov (United States)

    Singamaneni, Srinivasa Rao; Prater, John T.; Narayan, Jagdish

    2017-05-01

    This work relates to the integration of the two-layer stack of the proposed multiferroic structure onto silicon substrates. Ba1-xSrxTiO3 is an excellent material for room-temperature voltage-tunable dielectric applications due to its high (ɛ=6000) dielectric constant. In this study we choose a composition of Ba0.4Sr0.6TiO3 (BST), which is cubic and paraelectric at 300K, and transforms to a ferroelectric tetragonal phase upon cooling through the Curie temperature (TC) at 200K. The main focus of the present work is to study what happens when BST is placed in contact with a room temperature ferromagnetic layer such as La0.7Sr0.3MnO3 (LSMO). In this study, the magnetic properties of a BST (200nm)/LSMO (63nm) heterostructure was compared to that of a single LSMO layer (63nm). Both films were deposited onto MgO/TiN buffered Si (100) using pulsed laser deposition (PLD) and a domain matching epitaxy (DME) paradigm. X-ray diffraction (XRD) measurements showed that these films were of single phase and epitaxial in nature, with an unrelaxed lattice strain of ˜0.2% that was predominately composed of thermal and defect-induced strain. The magnetic measurements showed that the Curie temperature (TC) of LSMO remained unchanged at 350K when the BST was in contact with the LSMO layer. Interestingly, at 4K both the coercive field (Hc) and the exchange bias (HEB) of the BST/LSMO heterostructure as compared to the lone LSMO film increased significantly from 400 to 800 Oe and from 155 to 305 Oe, respectively. These differences were found to disappear above 200 K, the ferroelectric TC of the BST over-layer. This strongly suggests that the observed changes in the magnetic behavior of the heterostructure was the result of stress and/or charge redistributions that resulted when the BST layer transformed from the cubic (paraelectric) to tetragonal (ferroelectric) phase at low temperature.

  13. Leader-Member Exchange, the "Pelz Effect," and Cooperative Communication between Group Members.

    Science.gov (United States)

    Lee, Jaesub

    1997-01-01

    Explores effects of differential quality of leader-member exchange on cooperative communication among work group members. Suggests that the nature of an individual's exchange with his/her leader and his/her leader's upward leader-member exchange significantly impact perceived use of coworker cooperative communication. Provides evidence of linkage…

  14. An Econometric Analysis of the Effect of Exchange Rate Volatility on ...

    African Journals Online (AJOL)

    Exchange rate policy plays an important role in national economic development and management. Thus, the debate on exchange rate management has preoccupied economists and public sector managers for a very long time. The objective of this paper is to examine the effect of exchange rate volatility on tradable goods ...

  15. 78 FR 76685 - Self-Regulatory Organizations; EDGA Exchange, Inc.; Notice of Filing and Immediate Effectiveness...

    Science.gov (United States)

    2013-12-18

    ... From the Federal Register Online via the Government Publishing Office SECURITIES AND EXCHANGE COMMISSION Self-Regulatory Organizations; EDGA Exchange, Inc.; Notice of Filing and Immediate Effectiveness.... Pursuant to Section 19(b)(1) of the Securities Exchange Act of 1934 (the ``Act''),\\1\\ and Rule 19b-4...

  16. 78 FR 76693 - Self-Regulatory Organizations; EDGX Exchange, Inc.; Notice of Filing and Immediate Effectiveness...

    Science.gov (United States)

    2013-12-18

    ... From the Federal Register Online via the Government Publishing Office SECURITIES AND EXCHANGE COMMISSION Self-Regulatory Organizations; EDGX Exchange, Inc.; Notice of Filing and Immediate Effectiveness.... Pursuant to Section 19(b)(1) of the Securities Exchange Act of 1934 (the ``Act''),\\1\\ and Rule 19b-4...

  17. 78 FR 58359 - Self-Regulatory Organizations; Topaz Exchange, LLC; Notice of Filing and Immediate Effectiveness...

    Science.gov (United States)

    2013-09-23

    ... From the Federal Register Online via the Government Publishing Office SECURITIES AND EXCHANGE COMMISSION Self-Regulatory Organizations; Topaz Exchange, LLC; Notice of Filing and Immediate Effectiveness...) of the Securities Exchange Act of 1934 (the ``Act''),\\1\\ and Rule 19b-4 thereunder,\\2\\ notice is...

  18. 78 FR 56955 - Self-Regulatory Organizations; BATS Exchange, Inc.; Notice of Filing and Immediate Effectiveness...

    Science.gov (United States)

    2013-09-16

    ... From the Federal Register Online via the Government Publishing Office SECURITIES AND EXCHANGE COMMISSION Self-Regulatory Organizations; BATS Exchange, Inc.; Notice of Filing and Immediate Effectiveness... to Section 19(b)(1) of the Securities Exchange Act of 1934 (the ``Act''),\\1\\ and Rule 19b-4...

  19. (Re)integrating Simmel in Contemporary Social Exchange: The Effect of Nonpartisans on Relational Outcomes

    Science.gov (United States)

    Collett, Jessica L.

    2011-01-01

    Despite the increased prevalence of neutral third parties in both formal and informal exchange processes, social exchange theory has yet to consider the effect of nonpartisans on important cognitive and affective outcomes of exchange. This research integrates Simmel's conceptualization of small groups and nonpartisans with contemporary theory and…

  20. The effect of proximity to hurricanes Katrina and Rita on subsequent hurricane outlook and optimistic bias.

    Science.gov (United States)

    Trumbo, Craig; Lueck, Michelle; Marlatt, Holly; Peek, Lori

    2011-12-01

    This study evaluated how individuals living on the Gulf Coast perceived hurricane risk after Hurricanes Katrina and Rita. It was hypothesized that hurricane outlook and optimistic bias for hurricane risk would be associated positively with distance from the Katrina-Rita landfall (more optimism at greater distance), controlling for historically based hurricane risk and county population density, demographics, individual hurricane experience, and dispositional optimism. Data were collected in January 2006 through a mail survey sent to 1,375 households in 41 counties on the coast (n = 824, 60% response). The analysis used hierarchal regression to test hypotheses. Hurricane history and population density had no effect on outlook; individuals who were male, older, and with higher household incomes were associated with lower risk perception; individual hurricane experience and personal impacts from Katrina and Rita predicted greater risk perception; greater dispositional optimism predicted more optimistic outlook; distance had a small effect but predicted less optimistic outlook at greater distance (model R(2) = 0.21). The model for optimistic bias had fewer effects: age and community tenure were significant; dispositional optimism had a positive effect on optimistic bias; distance variables were not significant (model R(2) = 0.05). The study shows that an existing measure of hurricane outlook has utility, hurricane outlook appears to be a unique concept from hurricane optimistic bias, and proximity has at most small effects. Future extension of this research will include improved conceptualization and measurement of hurricane risk perception and will bring to focus several concepts involving risk communication. © 2011 Society for Risk Analysis.

  1. Temperature effects on pitfall catches of epigeal arthropods: a model and method for bias correction.

    Science.gov (United States)

    Saska, Pavel; van der Werf, Wopke; Hemerik, Lia; Luff, Martin L; Hatten, Timothy D; Honek, Alois; Pocock, Michael

    2013-02-01

    Carabids and other epigeal arthropods make important contributions to biodiversity, food webs and biocontrol of invertebrate pests and weeds. Pitfall trapping is widely used for sampling carabid populations, but this technique yields biased estimates of abundance ('activity-density') because individual activity - which is affected by climatic factors - affects the rate of catch. To date, the impact of temperature on pitfall catches, while suspected to be large, has not been quantified, and no method is available to account for it. This lack of knowledge and the unavailability of a method for bias correction affect the confidence that can be placed on results of ecological field studies based on pitfall data.Here, we develop a simple model for the effect of temperature, assuming a constant proportional change in the rate of catch per °C change in temperature, r, consistent with an exponential Q10 response to temperature. We fit this model to 38 time series of pitfall catches and accompanying temperature records from the literature, using first differences and other detrending methods to account for seasonality. We use meta-analysis to assess consistency of the estimated parameter r among studies.The mean rate of increase in total catch across data sets was 0·0863 ± 0·0058 per °C of maximum temperature and 0·0497 ± 0·0107 per °C of minimum temperature. Multiple regression analyses of 19 data sets showed that temperature is the key climatic variable affecting total catch. Relationships between temperature and catch were also identified at species level. Correction for temperature bias had substantial effects on seasonal trends of carabid catches.Synthesis and Applications. The effect of temperature on pitfall catches is shown here to be substantial and worthy of consideration when interpreting results of pitfall trapping. The exponential model can be used both for effect estimation and for bias correction of observed data. Correcting for temperature

  2. p-Curve and Effect Size: Correcting for Publication Bias Using Only Significant Results.

    Science.gov (United States)

    Simonsohn, Uri; Nelson, Leif D; Simmons, Joseph P

    2014-11-01

    Journals tend to publish only statistically significant evidence, creating a scientific record that markedly overstates the size of effects. We provide a new tool that corrects for this bias without requiring access to nonsignificant results. It capitalizes on the fact that the distribution of significant p values, p-curve, is a function of the true underlying effect. Researchers armed only with sample sizes and test results of the published findings can correct for publication bias. We validate the technique with simulations and by reanalyzing data from the Many-Labs Replication project. We demonstrate that p-curve can arrive at conclusions opposite that of existing tools by reanalyzing the meta-analysis of the "choice overload" literature. © The Author(s) 2014.

  3. Contamination, potential bias and humidity effects on electrical performance and corrosion reliability of electronic devices

    DEFF Research Database (Denmark)

    Piotrowska, Kamila; Verdingovas, Vadimas; Jellesen, Morten S.

    2015-01-01

    This paper describes the interactions between flux contamination, humidity and po-tential bias and their effect on corrosion reliability. Water layer formation on laminate surfaces and behavior of different solder flux chemistries with humid conditions have been studied, together......-sponse of electronics is estimated as a function of contamination type under cycling humid conditions. The results show the correlation between the ionic contamination type and water layer formation on surfaces in the presence of the flux residue....

  4. Bias in the estimation of exposure effects with individual- or group-based exposure assessment.

    Science.gov (United States)

    Kim, Hyang-Mi; Richardson, David; Loomis, Dana; Van Tongeren, Martie; Burstyn, Igor

    2011-01-01

    In this paper, we develop models of bias in estimates of exposure-disease associations for epidemiological studies that use group- and individual-based exposure assessments. In a study that uses a group-based exposure assessment, individuals are grouped according to shared attributes, such as job title or work area, and assigned an exposure score, usually the mean of some concentration measurements made on samples drawn from the group. We considered bias in the estimation of exposure effects in the context of both linear and logistic regression disease models, and the classical measurement error in the exposure model. To understand group-based exposure assessment, we introduced a quasi-Berkson error structure that can be justified with a moderate number of exposure measurements from each group. In the quasi-Berkson error structure, the true value is equal to the observed one plus error, and the error is not independent of the observed value. The bias in estimates with individual-based assessment depends on all variance components in the exposure model and is smaller when the between-group and between-subject variances are large. In group-based exposure assessment, group means can be assumed to be either fixed or random effects. Regardless of this assumption, the behavior of estimates is similar: the estimates of regression coefficients were less attenuated with a large sample size used to estimate group means, when between-subject variability was small and the spread between group means was large. However, if groups are considered to be random effects, bias is present, even with large number of measurements from each group. This does not occur when group effects are treated as fixed. We illustrate these models in analyses of the associations between exposure to magnetic fields and cancer mortality among electric utility workers and respiratory symptoms due to carbon black.

  5. The effect of dental insurance on dental care use and selection bias.

    Science.gov (United States)

    Cooper, Philip F; Manski, Richard J; Pepper, John V

    2012-09-01

    We examine the effect of dental insurance coverage on the probability of having a dental care visit in light of selection bias. We use data from the 2003 Medical Expenditure Panel Survey and use 3 different approaches to control for selection bias. First, we use a probit specification and include a rich set of independent variables that we posit control for unobserved attitudes toward risk and health care. Second, we use an instrumental variable model with family employment status as our instrument. Finally, we use a nonparametric approach to identify the upper and lower bounds of a dental insurance effect. We also ran a base probit model that did not include controls for attitudes toward risk and health care. The base probit, the probit including measure of attitudes, and the instrumental variable models provided similar estimates of the effect of dental insurance on the probability to seek dental care. This may indicate that selection bias may not be a concern. All estimates were within the bounds obtained through the nonparametric approach. Despite concerns of the potential endogeneity of dental insurance in models that estimate dental care use, we find evidence that these concerns may be unfounded.

  6. Thermophysical Property Estimation by Transient Experiments: The Effect of a Biased Initial Temperature Distribution

    Directory of Open Access Journals (Sweden)

    Federico Scarpa

    2015-01-01

    Full Text Available The identification of thermophysical properties of materials in dynamic experiments can be conveniently performed by the inverse solution of the associated heat conduction problem (IHCP. The inverse technique demands the knowledge of the initial temperature distribution within the material. As only a limited number of temperature sensors (or no sensor at all are arranged inside the test specimen, the knowledge of the initial temperature distribution is affected by some uncertainty. This uncertainty, together with other possible sources of bias in the experimental procedure, will propagate in the estimation process and the accuracy of the reconstructed thermophysical property values could deteriorate. In this work the effect on the estimated thermophysical properties due to errors in the initial temperature distribution is investigated along with a practical method to quantify this effect. Furthermore, a technique for compensating this kind of bias is proposed. The method consists in including the initial temperature distribution among the unknown functions to be estimated. In this way the effect of the initial bias is removed and the accuracy of the identified thermophysical property values is highly improved.

  7. Enhanced effects of combined cognitive bias modification and computerised cognitive behaviour therapy on social anxiety

    Directory of Open Access Journals (Sweden)

    Emma Butler

    2015-12-01

    Full Text Available This study examines whether combined cognitive bias modification for interpretative biases (CBM-I and computerised cognitive behaviour therapy (C-CBT can produce enhanced positive effects on interpretation biases and social anxiety. Forty socially anxious students were randomly assigned into two conditions, an intervention group (positive CBM-I + C-CBT or an active control (neutral CBM-I + C-CBT. At pre-test, participants completed measures of social anxiety, interpretative bias, cognitive distortions, and social and work adjustment. They were exposed to 6 × 30 min sessions of web-based interventions including three sessions of either positive or neutral CBM-I and three sessions of C-CBT, one session per day. At post-test and two-week follow-up, participants completed the baseline measures. A combined positive CBM-I + C-CBT produced less negative interpretations of ambiguous situations than neutral CBM-I + C-CBT. The results also showed that both positive CBM-I + C-CBT and neutral CBM-I + C-CBT reduced social anxiety and cognitive distortions as well as improving work and social adjustment. However, greater effect sizes were observed in the positive CBM-I + C-CBT condition than the control. This indicates that adding positive CBM-I to C-CBT enhanced the training effects on social anxiety, cognitive distortions, and social and work adjustment compared to the neutral CBM-I + C-CBT condition.

  8. Inclusion of Body-Bias Effect in SPICE Modeling of 4H-SiC Integrated Circuit Resistors

    Science.gov (United States)

    Neudeck, Philip G.

    2017-01-01

    The DC electrical behavior of n-type 4H-SiC resistors used for realizing 500 C durable integrated circuits (ICs) is studied as a function of substrate bias and temperature. Improved fidelity electrical simulation is described using SPICE NMOS model to simulate resistor substrate body bias effect that is absent from the SPICE semiconductor resistor model.

  9. Evaluation of the thermal effect on separation selectivity in anion-exchange processes using superheated water ion-exchange chromatography.

    Science.gov (United States)

    Shibukawa, Masami; Taguchi, Akihiko; Suzuki, Yusuke; Saitoh, Kazunori; Hiaki, Toshihiko; Yarita, Takashi

    2012-07-07

    The thermal effect on retention and separation selectivity of inorganic anions and aromatic sulfonate ions in anion-exchange chromatography is studied on a quaternized styrene-divinylbenzene copolymer anion-exchange column in the temperature range of 40-120 °C using superheated water chromatography. The selectivity coefficient for a pair of identically charged anions approaches unity as temperature increases provided the ions have the same effective size, such that the retention of an analyte ion decreases with an increase in temperature when the analyte ion has stronger affinity for the ion-exchanger than that of the eluent counterion, whereas it increases when it has weaker affinity. The change in anion-exchange selectivity with temperature observed with superheated water chromatography has been discussed on the basis of the effect of temperature on hydration of the ions. At elevated temperatures, especially in superheated water, the electrostatic interaction or association of the ions with the fixed ion in the resin phase becomes a predominant factor resulting in a different separation selectivity from that obtained at ambient temperature.

  10. The effect of order of dwells on the first dwell gaze bias for eventually chosen items.

    Science.gov (United States)

    Onuma, Takuya; Penwannakul, Yuwadee; Fuchimoto, Jun; Sakai, Nobuyuki

    2017-01-01

    The relationship between choice and eye movement has gained marked interest. The gaze bias effect, i.e., the tendency to look longer at items that are eventually chosen, has been shown to occur in the first dwell (initial cohesion of fixations for an item). In the two-alternative forced-choice (2AFC) paradigm, participants would look at one of the items first (defined as first look; FL), and they would then move and look at another item (second look; SL). This study investigated how the order in which the chosen items were looked at modulates the first dwell gaze bias effect. Participants were asked to assert their preferences and perceptual 2AFC decisions about human faces (Experiment 1) and daily consumer products (Experiment 2), while their eye movements were recorded. The results showed that the first dwell gaze bias was found only when the eventually chosen item was looked at after another one; the chosen item was looked at for longer as compared to the not-chosen item in the SL, but not in the FL. These results indicate that participants actively allocate more time to looking at a subsequently chosen item only after they perceive both items in the SL. Therefore, the selective encoding seems to occur in the early comparison stage of visual decision making, and not in the initial encoding stage. These findings provide insight into the relationship between choice and eye movement.

  11. The effects of intranasal oxytocin on smoothie intake, cortisol and attentional bias in anorexia nervosa.

    Science.gov (United States)

    Leppanen, Jenni; Cardi, Valentina; Ng, Kah Wee; Paloyelis, Yannis; Stein, Daniel; Tchanturia, Kate; Treasure, Janet

    2017-05-01

    Anorexia nervosa (AN) is characterised by severe malnutrition as well as intense fear and anxiety around food and eating with associated anomalies in information processing. Previous studies have found that the neuropeptide, oxytocin, can influence eating behaviour, lower the neurobiological stress response and anxiety among clinical populations, and alter attentional processing of food and eating related images in AN. Thirty adult women with AN and twenty-nine healthy comparison (HC) women took part in the current study. The study used double blind, placebo controlled, crossover design to investigate the effects of a single dose of intranasal oxytocin (40 IU) on a standard laboratory smoothie challenge, and on salivary cortisol, anxiety, and attentional bias towards food images before and after the smoothie challenge in AN and HC participants. Attentional bias was assessed using a visual probe task. Relative to placebo intranasal oxytocin reduced salivary cortisol and altered anomalies in attentional bias towards food images in the AN group only. The oxytocin-induced reduction in attentional avoidance of food images correlated with oxytocin induced reduction in salivary cortisol in the AN group before the smoothie challenge. Intranasal oxytocin did not significantly alter subjective feelings of anxiety or intake during the smoothie challenge in the AN or HC groups. Intranasal oxytocin may moderate the automated information processing biases in AN and reduce neurobiological stress. Further investigation of the effects of repeated administration of oxytocin on these processes as well as on eating behaviour and subjective anxiety would be of interest. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

  12. Direct testing of the biasing effect of manipulations of endolymphatic pressure on cochlear mechanical function

    Science.gov (United States)

    LePage, Eric; Avan, Paul

    2015-12-01

    The history of cochlear mechanical investigations has been carried out in two largely separate sets of endeavours; those interested in auditory processing in animal models and those interested in the origin of adverse vestibular symptoms in humans. In respect of the first, mechanical vibratory data is considered pathological and not representative of pristine behaviour if it departs from the reigning model of sharp tuning and high hearing sensitivity. Conversely, when the description of the pathological behaviour is the focus, fluid movements responsible for hearing loss and vestibular symptoms dominate. Yet both extensive sets of data possess a common factor now being reconsidered for its potential to shed light on the mechanisms in general. The common factor is a mechanical bias — the departure of cochlear epithelial membranes from their usual resting position. In both cases the bias modulates hearing sensitivity and distorts tuning characteristics. Indeed several early sets of guinea pig mechanical data were dismissed as "pathological" when in hindsight, the primary effect influencing the data was not loss of outer hair cell function per se, but a mechanical bias unknowingly introduced in process of making the measurement. Such biases in the displacement of the basilar membrane from its position are common, and may be caused by low-frequency sounds (topically including infrasound) or by variations in fluid volume in the chambers particularly applying the case of endolymphatic hydrops. Most biases are quantified in terms of visualisation of fluid volume change, electric potential changes and otoacoustic emissions. Notably many previous studies have also searched for raised pressures with negative results. Yet these repeated findings are contrary to the widespread notion that, at least when homeostasis is lost, it is a rise in endolymphatic pressure which is responsible for membrane rupture and Meniere's attacks. This current investigation in Mongolian gerbils

  13. Lay Evaluation of Financial Experts: The Action Advice Effect and Confirmation Bias

    Directory of Open Access Journals (Sweden)

    Tomasz Zaleskiewicz

    2016-09-01

    Full Text Available The goal of this experimental project was to investigate lay peoples’ perceptions of epistemic authority (EA in the field of finance. EA is defined as the extent to which a source of information is treated as evidence for judgments independently of its objective expertise and based on subjective beliefs. Previous research suggested that EA evaluations are biased and that lay people tend to ascribe higher EA to experts who advise action (in the case of medical experts or confirm clients’ expectations (in the case of politicians. However, there has been no research into biases in lay evaluations of financial experts and this project is aimed to fill this gap. Experiment 1 showed that lay people tended to ascribe greater authority to financial consultants who gave more active advice to clients considering taking out a mortgage. Experiment 2 confirmed the action advice effect found in Experiment 1. However, the outcomes of Experiments 2 and – particularly – 3 suggested that this bias might also be due to clients’ desire to confirm their own opinions. Experiment 2 showed that the action advice effect was moderated by clients’ own opinions on taking loans. Lay people ascribed the greatest EA to the advisor in the scenario in which he advised taking action and where this coincided with the client’s positive opinion on the advisability of taking out a loan. In Experiment 3 only participants with a positive opinion on the financial product ascribed greater authority to experts who recommended it; participants whose opinion was negative tended to rate consultants who advised rejecting the product more highly. To conclude, these three experiments revealed that lay people ascribe higher EA to financial consultants who advise action rather than maintenance of the status quo, but this effect is limited by confirmation bias: when the client’s a priori opinion is salient, greater authority is ascribed to experts whose advice confirms it. In this

  14. Foreign Exchange: Making International Payments More Cost Effective.

    Science.gov (United States)

    Ruesch, Otto J.

    1993-01-01

    College business officers can save money, adhere better to budgets, and improve relations with international vendors through foreign monetary exchange. By comparing exchange rates and buying foreign currency when rates are good, institutions retain much more control over the transaction rate than if they delegate the task to the bank. (MSE)

  15. Thermoelectric effects in graphene at high bias current and under microwave irradiation.

    Science.gov (United States)

    Skoblin, Grigory; Sun, Jie; Yurgens, August

    2017-11-14

    We use a split top gate to induce doping of opposite signs in different parts of a graphene field-effect transistor, thereby effectively forming a graphene thermocouple. The thermocouple is sensitive to the electronic temperature in graphene, which can be several hundred kelvin higher than the ambient one at sufficiently high bias current. Combined with the high thermoelectric power of graphene, this allows for i) simple measurements of the electronic temperature and ii) building thermoelectric radiation detectors. A simple prototype graphene thermoelectric detector shows a temperature-independent optical responsivity of around 400 V/W at 94 GHz at temperatures of 4-50 K.

  16. Own-Group Face Recognition Bias: The Effects of Location and Reputation

    Directory of Open Access Journals (Sweden)

    Linlin Yan

    2017-10-01

    Full Text Available In the present study, we examined whether social categorization based on university affiliation can induce an advantage in recognizing faces. Moreover, we investigated how the reputation or location of the university affected face recognition performance using an old/new paradigm. We assigned five different university labels to the faces: participants’ own university and four other universities. Among the four other university labels, we manipulated the academic reputation and geographical location of these universities relative to the participants’ own university. The results showed that an own-group face recognition bias emerged for faces with own-university labels comparing to those with other-university labels. Furthermore, we found a robust own-group face recognition bias only when the other university was located in a different city far away from participants’ own university. Interestingly, we failed to find the influence of university reputation on own-group face recognition bias. These results suggest that categorizing a face as a member of one’s own university is sufficient to enhance recognition accuracy and the location will play a more important role in the effect of social categorization on face recognition than reputation. The results provide insight into the role of motivational factors underlying the university membership in face perception.

  17. Neighborhood Effects of Intergroup Contact on Change in Youth Intergroup Bias.

    Science.gov (United States)

    Merrilees, Christine E; Taylor, Laura K; Baird, Rachel; Goeke-Morey, Marcie C; Shirlow, Peter; Cummings, E Mark

    2018-01-01

    Intergroup contact plays a critical role in the reduction of prejudice; however, there is limited research examining the multiple ways through which contact can impact trajectories of development for adolescents in divided societies. Thus, the goal of the current study was to examine individual- and context-level effects of intergroup contact on change in intergroup bias through adolescence. Hierarchical linear modeling was used to analyze five waves of data from 933 youth (M age  = 15.5, SD = 4.03; range: 10-20 years old; 52% female) living in 38 neighborhoods in Belfast, Northern Ireland. The results suggest that youth increase in bias with age. Adolescents with more frequent intergroup contact increase more quickly, and those who report higher quality of contact increase more slowly. Both frequency and quality of contact at the neighborhood level predicted slower increases in bias across adolescence. The results add to a growing literature that combines social and developmental approaches to understanding how intergroup processes and intergroup divide impact youth development of intergroup attitudes and behaviors. The results are discussed in terms of the importance of both individual experiences and the context of intergroup contact for youth development in divided contexts.

  18. Effects of a chirped bias voltage on ion energy distributions in inductively coupled plasma reactors

    Science.gov (United States)

    Lanham, Steven J.; Kushner, Mark J.

    2017-08-01

    The metrics for controlling reactive fluxes to wafers for microelectronics processing are becoming more stringent as feature sizes continue to shrink. Recent strategies for controlling ion energy distributions to the wafer involve using several different frequencies and/or pulsed powers. Although effective, these strategies are often costly or present challenges in impedance matching. With the advent of matching schemes for wide band amplifiers, other strategies to customize ion energy distributions become available. In this paper, we discuss results from a computational investigation of biasing substrates using chirped frequencies in high density, electronegative inductively coupled plasmas. Depending on the frequency range and chirp duration, the resulting ion energy distributions exhibit components sampled from the entire frequency range. However, the chirping process also produces transient shifts in the self-generated dc bias due to the reapportionment of displacement and conduction with frequency to balance the current in the system. The dynamics of the dc bias can also be leveraged towards customizing ion energy distributions.

  19. The adverse effect of real effective exchange rate change on trade balance in European transition countries

    Directory of Open Access Journals (Sweden)

    Selena Begović

    2017-12-01

    Full Text Available Most European transition countries have fixed or highly managed flexible exchange rate regimes. This exchange rate rigidity is sometimes argued to worsen the trade balance by keeping the currency overvalued. However, there is no unambiguous evidence that currency depreciation/devaluation positively affects trade balance and leads towards the adjustment, even in the short-run. Therefore, we examine the effect of real effective exchange rate (hereafter REER on trade balance in European transition economies over the period 2000-2015. By using fixed effect model for static and generalised method of moments for dynamic estimation, we find that there is an adverse effect of the REER on trade balance in European transition countries over the period 2000-2015. Namely, depreciation of REER deteriorates trade balance in European transition countries, which could be explained by high import dependence and low export capacity. This implies that policymakers in European transition countries should not use exchange rate policy to improve trade balance. This is important in the light of their accession towards European economic and monetary integration, implying that these countries should focus more on using fiscal, rather than monetary (and exchange rate, policy to adjust trade balance, which is one of the required real convergence towards the EU standards.

  20. Effect of size sprinkled heat exchange surface on developing boiling

    Directory of Open Access Journals (Sweden)

    Petr Kracík

    2016-06-01

    Full Text Available This article presents research of sprinkled heat exchangers. This type of research has become rather topical in relation to sea water desalination. This process uses sprinkling of exchangers which rapidly separates vapour phase from a liquid phase. Applications help better utilize low-potential heat which is commonly wasted in utility systems. Low-potential heat may increase utilization of primary materials. Our ambition is to analyse and describe the whole sprinkled exchanger. Two heat exchangers were tested with a similar tube pitch: heat exchanger no. 1 had a four-tube bundle and heat exchanger no. 2 had eight-tube bundle. Efforts were made to maintain similar physical characteristics. They were tested at two flow rates (ca 0.07 and 0.11 kg s−1 m−1 and progress of boiling on the bundle was observed. Initial pressure was ca 10 kPa (abs at which no liquid was boiling at any part of the exchanger; the pressure was then lowered. Other input parameters were roughly similar for both flow rates. Temperature of heating water was ca 50°C at a constant flow rate of ca 7.2 L min−1. Results of our experiments provide optimum parameters for the given conditions for both tube bundles.

  1. Ecological bias in studies of the short-term effects of air pollution on health

    Science.gov (United States)

    Shaddick, Gavin; Lee, Duncan; Wakefield, Jonathan

    2013-06-01

    There has been a great deal of research into the short-term effects of air pollution on health with a large number of studies modelling the association between aggregate disease counts and environmental exposures measured at point locations, for example via air pollution monitors. In such cases, the standard approach is to average the observed measurements from the individual monitors and use this in a log-linear health model. Hence such studies are ecological in nature being based on spatially aggregated health and exposure data. Here we investigate the potential for bias in the estimates of the effects on health when estimating the short-term effects of air pollution on health. Such ecological bias may occur if a simple summary measure, such as a daily mean, is not a suitable summary of a spatially variable pollution surface. We assess the performance of commonly used models when confronted with such issues using simulation studies and compare their performance with a model specifically designed to acknowledge the effects of exposure aggregation. In addition to simulation studies, we apply the models to a case study of the short-term effects of particulate matter on respiratory mortality using data from Greater London for the period 2002-2005. We found a significant increased risk of 3% (95% CI 1-5%) associated with the average of the previous three days exposure to particulate matter (per 10 μg m-3 PM10).

  2. The joint effect of bias awareness and self-reported prejudice on intergroup anxiety and intentions for intergroup contact.

    Science.gov (United States)

    Perry, Sylvia P; Dovidio, John F; Murphy, Mary C; van Ryn, Michelle

    2015-01-01

    Two correlational studies investigated the joint effect of bias awareness-a new individual difference measure that assesses Whites' awareness and concern about their propensity to be biased-and prejudice on Whites' intergroup anxiety and intended intergroup contact. Using a community sample (Study 1), we found the predicted Bias Awareness × Prejudice interaction. Prejudice was more strongly related to interracial anxiety among those high (vs. low) in bias awareness. Study 2 investigated potential behavioral consequences in an important real world context: medical students' intentions for working primarily with minority patients. Study 2 replicated the Bias Awareness × Prejudice interaction and further demonstrated that interracial anxiety mediated medical students' intentions to work with minority populations. (PsycINFO Database Record (c) 2015 APA, all rights reserved).

  3. How to Boost Positive Interpretations? A Meta-Analysis of the Effectiveness of Cognitive Bias Modification for Interpretation

    Science.gov (United States)

    Menne-Lothmann, Claudia; Viechtbauer, Wolfgang; Höhn, Petra; Kasanova, Zuzana; Haller, Simone P.; Drukker, Marjan; van Os, Jim; Wichers, Marieke; Lau, Jennifer Y. F.

    2014-01-01

    The current meta-analysis explores the strength of effects of cognitive bias modification training for interpretation bias (CBM-I) on positive (i.e., adaptive) interpretations and mood as well as the training and sample characteristics influencing these effects. Data-bases were searched with the key words “interpret* bias AND training” and “interpret* bias AND modif*”. Reference lists of identified articles were checked and authors of identified articles were contacted for further relevant articles and unpublished data. Studies were reviewed for inclusion with eligibility criteria being that the study (a) aimed to target interpretation biases through any kind of training, (b) assessed mood and/or interpretation bias as outcome measures, (c) allocated individuals to training conditions at random, and (d) recruited adult samples. A meta-analytic multilevel mixed-effects model was employed to assess standardized mean changes in interpretation bias, negative mood, and emotional reactivity. In addition, several training and sample characteristics were explored for their potential to enhance benign training effectiveness. On average, benign CBM-I resulted in an increase in positive interpretation bias (pnegative mood state (pmood effects, whereas feedback about training performance and inclusion of non-benign training items (instead of including benign items only) boosted cognitive effects only. Finally, training was more effective in women (cognitive and mood effects) and presumably samples with symptomatic emotional dysregulation (cognitive effects). Although the effects of emotional dysregulation and number of training sessions could not well be distinguished, there is an indication that when used with imagery instructions and more training sessions, benign CBM-I can be employed as a useful complementary treatment to usual psychotherapies. PMID:24968234

  4. THE EFFECT OF EXCHANGE RATE ON THE CONSTRUCTION PROJECTS AND PROTECTION METHODS

    Directory of Open Access Journals (Sweden)

    Handan AKSUYEK,

    2017-02-01

    Full Text Available As with all sectors, recent extreme changes occurred in the exchange rates have substantially affected the construction operations. While the rise in foreign exchange rates leads to harmful effects in the negative direction at the operations having foreign exchange – based debt or it provides also advantageous effect in the positive direction at the construction companies having foreign exchange – indexed investments. In this context, this sudden change in foreign exchange rates which cannot be predicted beforehand and emerges as a result of speculative events. As with all operations carrying out foreign exchange – based tasks, these fluctuations in the foreign exchange rate head first among the factors which affect the achievement or failure of the cost or profit targets previously determined by the construction companies as well. Therefore, the companies whose costs and profits consist of different units of currency in their construction agreements should apply to the hedging methods in order to be protected against the exchange rate. As for the main tools of protection method are the derivative products such as forward, futures, swap and optional contracts. In this study, the effect of exchange rate fluctuations on the completion costs of construction projects is scrutinized. Moreover, the tools which may be employed by the construction companies in order to get rid of exchange rate which adversely influence the building companies in both directions have been comparatively evaluated.

  5. High Effectiveness Heat Exchanger for Cryogenic Refrigerators Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose an innovative high performance cryogenic heat exchanger manufactured of titanium by photo-etching and diffusion bonding. This is a parallel plate design...

  6. Effects of interest and exchange rate policies on Brazilian exports

    Directory of Open Access Journals (Sweden)

    Cláudia Maria Sonaglio

    2016-01-01

    Full Text Available In heterodox literature, the industrial sector is considered strategic for economic development. Consequently, reducing the contribution of this sector in the production of the country before it has reached the stage of economic maturity, affects the productive dynamics and slow technical progress. The appreciation of the real exchange rate is seen as one of the factors responsible for the reduction of the external competitiveness of Brazilian manufactures, and this exchange rate valuation may be occurring due to the differences between domestic and international interest rates. Given this context, the aim of this study is to evaluate the impact of changes in the monetary and exchange rate policy and in the composition of the total exports on the performance of the Brazilian economy using a structuralist model. The results reinforce the importance of the manufacturing sector to economic growth, especially in a competitive exchange rate environment.

  7. The Effectiveness of an Attention Bias Modification Program as an Adjunctive Treatment for Post-Traumatic Stress Disorder

    Science.gov (United States)

    Kuckertz, Jennie M.; Amir, Nader; Boffa, Joseph W.; Warren, Ciara K.; Rindt, Susan E. M.; Norman, Sonya; Ram, Vasudha; Ziajko, Lauretta; Webb-Murphy, Jennifer; McLay, Robert

    2014-01-01

    Attention bias modification (ABM) may be an effective treatment for anxiety disorders (Beard, Sawyer, & Hofmann, 2012). As individuals with PTSD possess an attentional bias towards threat-relevant information ABM may prove effective in reducing PTSD symptoms. We examined the efficacy of ABM as an adjunct treatment for PTSD in a real-world setting. We administered ABM in conjunction with prolonged exposure or cognitive-processing therapy and medication in a community inpatient treatment facility for military personnel diagnosed with PTSD. Participants were randomized to either ABM or an attention control condition (ACC). While all participants experienced reductions in PTSD symptoms, participants in the ABM group experienced significantly fewer PTSD and depressive symptoms at post-treatment when compared to the ACC group. Moreover, change in plasticity of attentional bias mediated this change in symptoms and initial attentional bias moderated the effects of the treatment. These results suggest that ABM may be an effective adjunct treatment for PTSD. PMID:25277496

  8. The effect of real exchange rate on unemployment

    OpenAIRE

    Zahra Bakhshi; Mehrzad Ebrahimi

    2016-01-01

    Unemployment is one of the problems that global economics, especially the economy of developing countries such as Iran is faced with. Therefore, there have been many studies to investigate the variables which affect unemployment in macroeconomics. Considering exchange rate volatility in recent years which have affected most of major variables of economy in Iran, this study tried to investigate the relationship between exchange rate and unemployment in Iran using the annual data of 30 years (f...

  9. Bias in the measure of the effectiveness of seasonal influenza vaccination among diabetics.

    Science.gov (United States)

    Casanova, Ludovic; Gobin, Nirvina; Villani, Patrick; Verger, Pierre

    2016-12-01

    The influenza virus is an important cause of morbidity and mortality for diabetics. The seasonal influenza vaccine's immunologic effectiveness is proven within the type 1 and type 2 diabetic populations, but the level of evidence is low. This article presents a systematic review for the bias in the measure of the effectiveness of seasonal influenza vaccination among diabetics. Using systematic review methods, we searched three electronic databases for published literature (MEDLINE, EMBASE and the Cochrane Library) and two grey literature (SIGLE and NHS EED) databases, to identify studies published between 1997 and 2013, examining the effect of seasonal influenza vaccination, among diabetics, on any measure for influenza morbidity or mortality. 725 records were identified from the three databases and screening, short-listing was undertaken independently by two reviewers. After de-duplication, all records were screened by title and then abstract, and 34 short-listed records were reviewed in full, with 7 studies included: 4 cohort studies and 3 case-control studies, conducted in 7 countries. The most common outcome of interest in studies (n=4) was all-cause mortality among elderly diabetics (>65 years), with individual studies reporting reductions in risk of between 33% [95%CI: 4%-54%] and 68% [95%CI: 58%-75%]. We found only two studies for working-age adult diabetics: one reporting that vaccination prevented hospitalizations due to pneumonia or influenza (vaccine effectiveness [VE] 43%, [95%CI: 28%-54%]) and all-cause hospitalizations (VE: 28% [95%CI: 24%-32%]); and, another reporting no significant decrease in all-cause mortality for working-age adult diabetics. We have identified three major biases: the use of indirect health outcomes, a risk of selection bias (health-seeking bias), and no adjustment for participant pneumococcal vaccination status. The most recent included article finds that morbimortality is still lower during off-season influenza in both

  10. Effects of enterectomy on postoperative visceral organ glucose exchange.

    Science.gov (United States)

    Souba, W W; Roughneen, P T; Goldwater, D L; Reed, R L; Rowlands, B J

    1989-01-01

    The effects of a 60% small-bowel resection on postoperative visceral organ glucose exchange was studied in order to gain further understanding of the role of the intestinal tract as a supplier of gluconeogenic substrate to the liver following operative stress. We determined the flux of glucose across the gastrointestinal tract, liver, and kidneys in 20 postoperative dogs. With enterectomy portal bloodflow and total hepatic bloodflow were diminished by 33% and 25%, respectively. Arterial glucose was slightly lower in the enterectomized group 6 hr following the operation. Intestinal glucose uptake was diminished by more than 50% in the enterectomized dogs (p less than 0.01). Net hepatic glucose release fell from 22 mumole/kg/min to 8 mumole/kg/min (p less than 0.01). In control animals the kidney was an organ of slight glucose uptake while in the enterectomized group, the kidney released glucose at the rate of 4.1 mumole/kg/min (p less than 0.05). The data suggest that the gut is an important supplier of gluconeogenic precursors to the liver which are used to support gluconeogenesis in the postoperative period. The ability of the kidney to accelerate glucose production in this setting suggests that metabolic adaptation and cooperation between organs occurs during organ absence or dysfunction which helps preserve glucose homeostasis.

  11. Effects of stomata clustering on leaf gas exchange.

    Science.gov (United States)

    Lehmann, Peter; Or, Dani

    2015-09-01

    A general theoretical framework for quantifying the stomatal clustering effects on leaf gaseous diffusive conductance was developed and tested. The theory accounts for stomatal spacing and interactions among 'gaseous concentration shells'. The theory was tested using the unique measurements of Dow et al. (2014) that have shown lower leaf diffusive conductance for a genotype of Arabidopsis thaliana with clustered stomata relative to uniformly distributed stomata of similar size and density. The model accounts for gaseous diffusion: through stomatal pores; via concentration shells forming at pore apertures that vary with stomata spacing and are thus altered by clustering; and across the adjacent air boundary layer. Analytical approximations were derived and validated using a numerical model for 3D diffusion equation. Stomata clustering increases the interactions among concentration shells resulting in larger diffusive resistance that may reduce fluxes by 5-15%. A similar reduction in conductance was found for clusters formed by networks of veins. The study resolves ambiguities found in the literature concerning stomata end-corrections and stomatal shape, and provides a new stomata density threshold for diffusive interactions of overlapping vapor shells. The predicted reduction in gaseous exchange due to clustering, suggests that guard cell function is impaired, limiting stomatal aperture opening. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

  12. The Effectiveness of Web-Based Foreign Exchange Trading Simulation in an International Finance Course

    Science.gov (United States)

    Chou, Chen-Huei; Liu, Hao-Chen

    2013-01-01

    The purpose of this article is to study if trading simulation is an effective tool to increase students' knowledge of the foreign exchange market. We developed a real-time multiuser web-based trading system that replicates an electronic brokerage foreign exchange market. To assess the effectiveness of the program, we conducted surveys in three…

  13. Light Effects on the Bias Stability of Transparent ZnO Thin Film Transistors

    National Research Council Canada - National Science Library

    Shin, Jae‐Heon; Lee, Ji‐Su; Hwang, Chi‐Sun; Park, Sang‐Hee Ko; Cheong, Woo‐Seok; Ryu, Minki; Byun, Chun‐Won; Lee, Jeong‐Ik; Chu, Hye Yong

    2009-01-01

    ...) under visible light illumination. The transfer curve shows virtually no change under positive gate bias stress with light illumination, while it shows dramatic negative shifts under negative gate bias stress...

  14. The Nature of Bias Crime Injuries: A Comparative Analysis of Physical and Psychological Victimization Effects.

    Science.gov (United States)

    Fetzer, Matthew D; Pezzella, Frank S

    2016-10-13

    The core justification of bias crime statutes concerns whether bias-motivated crimes are qualitatively different from otherwise motivated crimes. We test the hypothesis that bias crimes are more detrimental than non-bias crimes by testing for multi-dimensional injuries to victims of bias and non-bias-motivated criminal conduct. Using National Crime Victimization Survey (NCVS) Extract 2013 Collection Year Incident-level Extract File, we analyzed physical injuries and psychological trauma to NCVS victims during 2013. We found a range of covariates consistent with the likelihood of physical injury and psychological trauma. These included whether the incident was bias motivated, whether weapons (firearms, knives, other or unknown type of weapons) were involved, whether the incident involved multiple offenders or strangers, or whether drugs or alcohol were involved. Our findings reinforce previous studies that detected empirical evidence of multi-dimensional physical and psychological injuries to bias crime victims. © The Author(s) 2016.

  15. Investigation of Body Bias Dependence of Gate-Induced Drain Leakage Current for Body-Tied Fin Field Effect Transistor

    Science.gov (United States)

    Yoshida, Makoto; Lee, Chul; Jung, Kyoung-Ho; Kim, Chang-Kyu; Kim, Hui-Jung; Park, Heungsik; Lee, Won-Sok; Kim, Keunnam; Kahng, Jae-Rok; Yang, Wouns; Park, Donggun

    2008-09-01

    The body bias dependence of gate-induced drain leakage (GIDL) current for a fin field effect transistor fabricated on a bulk Si wafer (bulk FinFET) is investigated. The local damascene (LD) bulk FinFET is measured under various bias conditions and the effect of the body-bias-induced lateral electric field on GIDL current is evaluated. A lateral electric field shield effect under fin depleted condition is proposed and it is validated by the three-terminal band-to-band tunneling current model. The GIDL current of the bulk FinFET can be reduced by reducing the body bias, and an improvement in retention characteristics is expected.

  16. The effects of sampling bias and model complexity on the predictive performance of MaxEnt species distribution models.

    Directory of Open Access Journals (Sweden)

    Mindy M Syfert

    Full Text Available Species distribution models (SDMs trained on presence-only data are frequently used in ecological research and conservation planning. However, users of SDM software are faced with a variety of options, and it is not always obvious how selecting one option over another will affect model performance. Working with MaxEnt software and with tree fern presence data from New Zealand, we assessed whether (a choosing to correct for geographical sampling bias and (b using complex environmental response curves have strong effects on goodness of fit. SDMs were trained on tree fern data, obtained from an online biodiversity data portal, with two sources that differed in size and geographical sampling bias: a small, widely-distributed set of herbarium specimens and a large, spatially clustered set of ecological survey records. We attempted to correct for geographical sampling bias by incorporating sampling bias grids in the SDMs, created from all georeferenced vascular plants in the datasets, and explored model complexity issues by fitting a wide variety of environmental response curves (known as "feature types" in MaxEnt. In each case, goodness of fit was assessed by comparing predicted range maps with tree fern presences and absences using an independent national dataset to validate the SDMs. We found that correcting for geographical sampling bias led to major improvements in goodness of fit, but did not entirely resolve the problem: predictions made with clustered ecological data were inferior to those made with the herbarium dataset, even after sampling bias correction. We also found that the choice of feature type had negligible effects on predictive performance, indicating that simple feature types may be sufficient once sampling bias is accounted for. Our study emphasizes the importance of reducing geographical sampling bias, where possible, in datasets used to train SDMs, and the effectiveness and essentialness of sampling bias correction within MaxEnt.

  17. Bias-corrected estimator for intraclass correlation coefficient in the balanced one-way random effects model

    Directory of Open Access Journals (Sweden)

    Atenafu Eshetu G

    2012-08-01

    Full Text Available Abstract Background Intraclass correlation coefficients (ICCs are used in a wide range of applications. However, most commonly used estimators for the ICC are known to be subject to bias. Methods Using second order Taylor series expansion, we propose a new bias-corrected estimator for one type of intraclass correlation coefficient, for the ICC that arises in the context of the balanced one-way random effects model. A simulation study is performed to assess the performance of the proposed estimator. Data have been generated under normal as well as non-normal scenarios. Results Our simulation results show that the new estimator has reduced bias compared to the least square estimator which is often referred to as the conventional or analytical estimator. The results also show marked bias reduction both in normal and non-normal data scenarios. In particular, our estimator outperforms the analytical estimator in a non-normal setting producing estimates that are very close to the true ICC values. Conclusions The proposed bias-corrected estimator for the ICC from a one-way random effects analysis of variance model appears to perform well in the scenarios we considered in this paper and can be used as a motivation to construct bias-corrected estimators for other types of ICCs that arise in more complex scenarios. It would also be interesting to investigate the bias-variance trade-off.

  18. Bias-corrected estimator for intraclass correlation coefficient in the balanced one-way random effects model.

    Science.gov (United States)

    Atenafu, Eshetu G; Hamid, Jemila S; To, Teresa; Willan, Andrew R; Feldman, Brian M; Beyene, Joseph

    2012-08-20

    Intraclass correlation coefficients (ICCs) are used in a wide range of applications. However, most commonly used estimators for the ICC are known to be subject to bias. Using second order Taylor series expansion, we propose a new bias-corrected estimator for one type of intraclass correlation coefficient, for the ICC that arises in the context of the balanced one-way random effects model. A simulation study is performed to assess the performance of the proposed estimator. Data have been generated under normal as well as non-normal scenarios. Our simulation results show that the new estimator has reduced bias compared to the least square estimator which is often referred to as the conventional or analytical estimator. The results also show marked bias reduction both in normal and non-normal data scenarios. In particular, our estimator outperforms the analytical estimator in a non-normal setting producing estimates that are very close to the true ICC values. The proposed bias-corrected estimator for the ICC from a one-way random effects analysis of variance model appears to perform well in the scenarios we considered in this paper and can be used as a motivation to construct bias-corrected estimators for other types of ICCs that arise in more complex scenarios. It would also be interesting to investigate the bias-variance trade-off.

  19. A Meta-Analysis of the Effect of Cognitive Bias Modification on Anxiety and Depression

    Science.gov (United States)

    Hallion, Lauren S.; Ruscio, Ayelet Meron

    2011-01-01

    Cognitive biases have been theorized to play a critical role in the onset and maintenance of anxiety and depression. Cognitive bias modification (CBM), an experimental paradigm that uses training to induce maladaptive or adaptive cognitive biases, was developed to test these causal models. Although CBM has generated considerable interest in the…

  20. Effects of a low dose of alcohol on cognitive biases and craving in heavy drinkers

    NARCIS (Netherlands)

    Schoenmakers, T.; Wiers, R.W.H.J.; Field, M.

    2008-01-01

    Rationale Heavy alcohol drinking increases the incentive salience of alcohol-related cues. This leads to increased appetitive motivation to drink alcohol as measured by subjective craving and cognitive biases such as attentional bias and approach bias. Although these measures relate to the same

  1. Practical investigation of the gate bias effect on the reverse recovery behavior of the body diode in power MOSFETs

    DEFF Research Database (Denmark)

    Lindberg-Poulsen, Kristian; Petersen, Lars Press; Ouyang, Ziwei

    2014-01-01

    This work considers an alternative method of reducing the body diode reverse recovery by taking advantage of the MOSFET body effect, and applying a bias voltage to the gate before reverse recovery. A test method is presented, allowing the accurate measurement of voltage and current waveforms during...... reverse recovery at high di=dt. Different bias voltages and dead times are combined, giving a loss map which makes it possible to evaluate the practical efficacy of gate bias on reducing the MOSFET body diode reverse recovery, while comparing it to the well known methods of dead time optimization...

  2. Quantitative evaluation of the memory bias effect in ROC studies with PET/CT

    Science.gov (United States)

    Kallergi, Maria; Pianou, Nicoletta; Georgakopoulos, Alexandros; Kafiri, Georgia; Pavlou, Spiros; Chatziioannou, Sofia

    2012-02-01

    PURPOSE. The purpose of the study was to evaluate the memory bias effect in ROC experiments with tomographic data and, specifically, in the evaluation of two different PET/CT protocols for the detection and diagnosis of recurrent thyroid cancer. MATERIALS AND METHODS. Two readers participated in an ROC experiment that evaluated tomographic images from 43 patients followed up for thyroid cancer recurrence. Readers evaluated first whole body PET/CT scans of the patients and then a combination of whole body and high-resolution head and neck scans of the same patients. The second set was read twice. Once within 48 hours of the first set and the second time at least a month later. The detection and diagnostic performances of the readers in the three reading sessions were assessed with the DBMMRMC and LABMRMC software using the area under the ROC curve as a performance index. Performances were also evaluated by comparing the number and the size of the detected abnormal foci among the three readings. RESULTS. There was no performance difference between first and second treatments. There were statistically significant differences between first and third, and second and third treatments showing that memory can seriously affect the outcome of ROC studies. CONCLUSION. Despite the fact that tomographic data involve numerous image slices per patient, the memory bias effect is present and substantial and should be carefully eliminated from analogous ROC experiments.

  3. Effect of biased feedback on motor imagery learning in BCI-teleoperation system

    Directory of Open Access Journals (Sweden)

    Maryam eAlimardani

    2014-04-01

    Full Text Available Feedback design is an important issue in motor imagery BCI systems. Regardless, to date it has not been reported how feedback presentation can optimize co-adaptation between a human brain and such systems. This paper assesses the effect of realistic visual feedback on users’ BC performance and motor imagery skills. We previously developed a tele-operation system for a pair of humanlike robotic hands and showed that BCI control of such hands along with first-person perspective visual feedback of movements can arouse a sense of embodiment in the operators. In the first stage of this study, we found that the intensity of this ownership illusion was associated with feedback presentation and subjects’ performance during BCI motion control. In the second stage, we probed the effect of positive and negative feedback bias on subjects’ BCI performance and motor imagery skills. Although the subject specific classifier, which was set up at the beginning of experiment, detected no significant change in the subjects’ online performance, evaluation of brain activity patterns revealed that subjects’ self-regulation of motor imagery features improved due to a positive bias of feedback and a possible occurrence of ownership illusion. Our findings suggest that in general training protocols for BCIs, manipulation of feedback can play an important role in the optimization of subjects’ motor imagery skills.

  4. Neutralizing substitutes for leadership theory: leadership effects and common-source bias.

    Science.gov (United States)

    Dionne, Shelley D; Yammarino, Francis J; Atwater, Leanne E; James, Lawrence R

    2002-06-01

    The purpose of this research was to examine alternative models of substitutes for leadership theory given the general lack of empirical support for the moderating effects postulated by the theory. On this basis, the research posited that the effects of substitutes also could be conceptualized as mediated relations. The research examined moderated and mediated relations for several sets of leader behaviors and substitutes that have been examined in the literature. The research design sampled 49 organizations, with 940 subordinates rating 156 leaders. Results, although generally not supportive of the moderator or mediator hypotheses, essentially demonstrated that leadership matters. The findings also suggest that prior significant effects in substitutes literature may be merely a statistical artifact, resulting from common-source bias.

  5. Marijuana’s Acute Effects on Cognitive Bias for Affective and Marijuana Cues

    Science.gov (United States)

    Metrik, Jane; Aston, Elizabeth R.; Kahler, Christopher W.; Rohsenow, Damaris J.; McGeary, John E.; Knopik, Valerie S.

    2015-01-01

    Marijuana produces acute increases in positive subjective effects and decreased reactivity to negative affective stimuli, though may also acutely induce anxiety. Implicit attentional and evaluative processes may explicate marijuana’s ability to acutely increase positive and negative emotions. This within-subjects study examined whether smoked marijuana with 2.7–3.0 % delta-9-tetrahydrocannabinol (THC), relative to placebo, acutely changed attentional processing of rewarding and negative affective stimuli as well as marijuana-specific stimuli. On two separate days, regular marijuana users (N=89) smoked placebo or active THC cigarette and completed subjective ratings of mood, intoxication, urge to smoke marijuana, and two experimental tasks: Pleasantness Rating (response latency and perceived pleasantness of affective and marijuana-related stimuli) and Emotional Stroop (attentional bias to affective stimuli). On the Pleasantness Rating task, active marijuana increased response latency to negatively-valenced and marijuana-related (vs. neutral) visual stimuli, beyond a general slowing of response. Active marijuana also increased pleasantness ratings of marijuana images, although to a lesser extent than placebo due to reduced marijuana urge after smoking. Overall, active marijuana did not acutely change processing of positive emotional stimuli. There was no evidence of attentional bias to affective word stimuli on the Emotional Stroop task with the exception of attentional bias to positive word stimuli in the subgroup of marijuana users with cannabis dependence. Marijuana may increase allocation of attentional resources towards marijuana-specific and negatively-valenced visual stimuli without altering processing of positively-valenced stimuli. Marijuana-specific cues may be more attractive with higher levels of marijuana craving and less wanted with low craving levels. PMID:26167716

  6. Patient race and perceived illness responsibility: effects on provider helping and bias.

    Science.gov (United States)

    Nazione, Samantha; Silk, Kami J

    2013-08-01

    Health care disparities represent a major issue impacting the quality of care in the USA. Provider biases have been identified as contributing to health care disparities. This study examined the helping intentions and biases reported by medical students based on patient race and perceived patient responsibility. The study was guided by the responsibility-affect-helping model (RAHM), which proposes that helping behaviour is a function of perceived responsibility and affect. In a 2 × 3 online experiment, medical students (n = 231) viewed a health chart and dialogue for either a Black or a White patient, in which the dialogue included a manipulation of the patient's rationales for his non-compliance with diet recommendations (responsible, not responsible, no responsibility assigned). After viewing the manipulation, medical students completed measures regarding perceived patient responsibility, affect, intention to help, perceptions of the patient and ethnocentrism. The RAHM was supported, such that increased perceived patient responsibility led to increased provider anger and reduced provider helping intentions, whereas decreased perceived patient responsibility led to increased provider empathy and helping intentions. Additionally, an interaction effect between race and perceived patient responsibility occurred such that bias toward the Black patient was most likely to occur in the control condition. Perceived patient responsibility affects provider helping intentions and interacts with patient race to influence provider perceptions of patient characteristics. Communication on rationales for non-compliance as associated with perceived responsibility may lead to better or worse patient care as providers make attributions about patients based on these factors. © 2013 John Wiley & Sons Ltd.

  7. Voluntary vs. compulsory student evaluation of clerkships: effect on validity and potential bias.

    Science.gov (United States)

    Aoun Bahous, Sola; Salameh, Pascale; Salloum, Angelique; Salameh, Wael; Park, Yoon Soo; Tekian, Ara

    2018-01-05

    Students evaluations of their learning experiences can provide a useful source of information about clerkship effectiveness in undergraduate medical education. However, low response rates in clerkship evaluation surveys remain an important limitation. This study examined the impact of increasing response rates using a compulsory approach on validity evidence. Data included 192 responses obtained voluntarily from 49 third-year students in 2014-2015, and 171 responses obtained compulsorily from 49 students in the first six months of the consecutive year at one medical school in Lebanon. Evidence supporting internal structure and response process validity was compared between the two administration modalities. The authors also tested for potential bias introduced by the use of the compulsory approach by examining students' responses to a sham item that was added to the last survey administration. Response rates increased from 56% in the voluntary group to 100% in the compulsory group (P Students in both groups provided comparable clerkship rating except for one clerkship that received higher rating in the voluntary group (P = 0.02). Respondents in the voluntary group had higher academic performance compared to the compulsory group but this difference diminished when whole class grades were compared. Reliability of ratings was adequately high and comparable between the two consecutive years. Testing for non-response bias in the voluntary group showed that females were more frequent responders in two clerkships. Testing for authority-induced bias revealed that students might complete the evaluation randomly without attention to content. While increasing response rates is often a policy requirement aimed to improve the credibility of ratings, using authority to enforce responses may not increase reliability and can raise concerns over the meaningfulness of the evaluation. Administrators are urged to consider not only response rates, but also representativeness and

  8. Effects and Implications for Adoption of Brokerage System in Korea's Foreign Exchange Market

    Directory of Open Access Journals (Sweden)

    Yunjong Wang

    1999-03-01

    Full Text Available Since January 1st 1999, the South Korean government has begun to establish the understructure of the foreign exchange market in order to achieve the liberalization of foreign exchange. As one of the plans, the trade of foreign exchange which was under the monopolized mediation of the capital medium of financial settlement center will be in the charge of several commercial brokers. In the developed countries, the foreign exchange & stock system and the liberalization of foreign exchange are both widely used in a flexible way. So it is predicted that the introduction of commercial foreign exchange & stock system will bring positive effect to the enhancement of the market efficiency and the function of price both in South Korean market and overseas market, the foster of competitive power of the domestic broker and the improvement of the understructure of domestic foreign exchange market. But more importantly is that the foreign exchange market must expand the scale of its participator, bring in various relevant foreign exchange products and develop the bond market which has a close relationship with the foreign exchange market for further development.

  9. The effects of priming in a cued dot-probe task on appearance-related attentional biases in women.

    Science.gov (United States)

    Lane, Ben R; Mulgrew, Kate E; Mahar, Doug; White, Melanie J; Loughnan, Siobhan A

    2017-07-01

    The dot-probe task (DPT) is a reaction time measure of attentional bias. Research using this task has found inconsistent patterns of appearance-related attentional biases in women. This study examined the effects of a novel priming variation of the DPT, which incorporated additional cues into each trial of the task, on measurement of such biases. The study also examined associations between these biases and body image, a component of eating disorder symptomatology. A convenience sample of women from the general community (N = 103) completed body image measures online and attended a laboratory session to complete one of four DPTs: (1) an appearance-cued DPT containing images of thin-ideal models between each trial; (2) neutral-cued DPT containing images of forests; (3) time-delayed DPT controlling for time in place of an image; or (4) typical DPT containing only word stimuli. Women who completed the appearance-cued DPT demonstrated a stronger attentional bias for positive, but not negative, appearance words than women who completed the other DPT versions. Furthermore, for the appearance-cued and time-delayed DPTs, this bias correlated with poorer body image across several indicators (appearance evaluation, body dissatisfaction, self-evaluative salience of appearance, and state body satisfaction). Although it was unexpected that no attentional bias for negative-appearance words was found, the attentional bias for positive-appearance words may suggest that effects were driven by the ego-threat of positive-appearance words. Further research is warranted to determine whether such biases contribute to and maintain body image disturbance and disordered eating. © 2017 Wiley Periodicals, Inc.

  10. Effects of perturbative exchanges in a QCD-string model

    Energy Technology Data Exchange (ETDEWEB)

    J. Weda; J. Tjon

    2004-03-01

    The QCD-string model for baryons derived by Simonov and used for the calculation of baryon magnetic moments in a previous paper is extended to include also perturbative gluon and meson exchanges. The mass spectrum of the baryon multiplet is studied. For the meson interaction either the pseudoscalar or pseudovector coupling is used. Predictions are compared with the experimental data. Besides these exchanges the influence of excited quark orbitals on the baryon ground state are considered by performing a multichannel calculation. The nucleon-Delta splitting increases due to the mixing of higher quark states while the baryon magnetic momenta decrease. The multichannel calculation with perturbative exchanges is shown to yield reasonable magnetic moments while the mass spectrum is close to experiment.

  11. Effects of drain bias on the statistical variation of double-gate tunnel field-effect transistors

    Science.gov (United States)

    Choi, Woo Young

    2017-04-01

    The effects of drain bias on the statistical variation of double-gate (DG) tunnel field-effect transistors (TFETs) are discussed in comparison with DG metal-oxide-semiconductor FETs (MOSFETs). Statistical variation corresponds to the variation of threshold voltage (V th), subthreshold swing (SS), and drain-induced barrier thinning (DIBT). The unique statistical variation characteristics of DG TFETs and DG MOSFETs with the variation of drain bias are analyzed by using full three-dimensional technology computer-aided design (TCAD) simulation in terms of the three dominant variation sources: line-edge roughness (LER), random dopant fluctuation (RDF) and workfunction variation (WFV). It is observed than DG TFETs suffer from less severe statistical variation as drain voltage increases unlike DG MOSFETs.

  12. The generalizability of gender bias: Testing the effects of contextual, explicit, and implicit sexism on labor arbitration decisions.

    Science.gov (United States)

    Girvan, Erik J; Deason, Grace; Borgida, Eugene

    2015-10-01

    Decades of social-psychological research show that gender bias can result from features of the social context and from individual-level psychological predispositions. Do these sources of bias impact legal decisions, which are frequently made by people subject to factors that have been proposed to reduce bias (training and accountability)? To answer the question, we examined the potential for 3 major social-psychological theories of gender bias (role-congruity theory, ambivalent sexism, and implicit bias) to predict outcomes of labor arbitration decisions. In the first study, undergraduate students and professional arbitrators made decisions about 2 mock arbitration cases in which the gender of the employee-grievants was experimentally manipulated. Student participants' decisions showed the predicted gender bias, whereas the decisions of experienced professionals did not. Individual-level attitudes did not predict the extent of the observed bias and accountability did not attenuate it. In the second study, arbitrators' explicit and implicit gender attitudes were significant predictors of their decisions in published cases. The laboratory and field results suggest that context, expertise, and implicit and explicit attitudes are relevant to legal decision-making, but that laboratory experiments alone may not fully capture the nature of their effect on legal professionals' decisions in real cases. (c) 2015 APA, all rights reserved).

  13. The intraday effects of central bank intervention on exchange rate spreads

    DEFF Research Database (Denmark)

    Fatum, Rasmus; Pedersen, Jesper; Sørensen, Peter Norman

    2013-01-01

    We investigate the intraday effects of intra-marginal intervention in a horizontal band on the exchange rate spread. Official intraday data on Danish intervention transactions in the ERM II, the Exchange Rate Mechanism of the European Union, facilitates our analysis. We show that intervention...... purchases and sales both exert a significant influence on the exchange rate spread, but in opposite directions. Intervention purchases of the small currency, on average, narrow the spread while intervention sales of the small currency, on average, widen the spread. This is a novel finding that differs from...... those of existing studies that find intervention always widens the exchange rate spread and increases market uncertainty...

  14. Effects of Monetary Shocks on Exchange Rate: Empirical Evidence from India

    Directory of Open Access Journals (Sweden)

    Sharma Chandan

    2017-08-01

    Full Text Available This paper examines the effect of monetary policy shocks on exchange rate in a Multiple Indicator Approach (MIA framework. This study has employed a monetary policy index of key monetary policy instruments in India (Bank rate, Cash Reserve Ratio, Repo and Reverse Repo rates. The study finds the empirical evidence for puzzling behavior of price level and exchange rate. Both price and exchange rate increase initially in response to a contractionary policy shock. Policy shocks affect output, inflation and exchange rate to an appreciable extent over a forecasting horizon of one year.

  15. Just like a woman? Effects of gender-biased perceptions of friendship network brokerage on attributions and performance

    OpenAIRE

    Brands, R. A.; kilduff, M.

    2014-01-01

    Do women face bias in the social realm in which they are purported to excel? Across two different studies (one organizational and one comprising MBA teams), we examined whether the friendship networks around women tend to be systematically misperceived and whether there were effects of these misperceptions on the women themselves and their teammates. Thus, we investigated the possibility (hitherto neglected in the network literature) that biases in friendship networks are triggered not just b...

  16. Does attention redirection contribute to the effectiveness of attention bias modification on social anxiety?

    Science.gov (United States)

    Yao, Nisha; Yu, Hongyu; Qian, Mingyi; Li, Songwei

    2015-12-01

    Attention bias modification (ABM) is designed to modify threat-related attention bias and thus alleviate anxiety. The current research examined whether consistently directing attention towards targeted goals per se contributes to ABM efficacy. We randomly assigned 68 non-clinical college students with elevated social anxiety to non-valence-specific attend-to-geometrics (AGC), attention modification (AMC), or attention control (ACC) conditions. We assessed subjective, behavioral, and physiological reactivity to a speech task and self-reported social anxiety symptoms. After training, participants in the AMC exhibited an attention avoidance from threat, and those in the AGC responded more rapidly toward targeted geometrics. There was a significant pre- to post-reduction in subjective speech distress across groups, but behavioral and physiological reactivity to speech, as well as self-report social anxiety symptoms, remained unchanged. These results lead to questions concerning effectiveness of ABM training for reducing social anxiety. Further examination of the current ABM protocol is required. Copyright © 2015 Elsevier Ltd. All rights reserved.

  17. Exaggerated intergroup bias in economical decision making games: differential effects of primary and secondary psychopathic traits.

    Directory of Open Access Journals (Sweden)

    Steven M Gillespie

    Full Text Available Psychopathic personality traits are linked with selfish and non-cooperative responses during economical decision making games. However, the possibility that these responses may vary when responding to members of the in-group and the out-group has not yet been explored. We aimed to examine the effects of primary (selfish, uncaring and secondary (impulsive, irresponsible psychopathic personality traits on the responses of non-offending participants to the in-group and the out-group (defined in terms of affiliation to a UK University across a series of economical decision making games. We asked a total of 60 participants to act as the proposer in both the dictator game and the ultimatum game. We found that across both tasks, those who scored highly for secondary psychopathic traits showed an elevated intergroup bias, making more generous offers toward members of the in-group relative to the out-group. An exaggerated intergroup bias may therefore represent a motivational factor for the antisocial behavior of those with elevated secondary psychopathic traits.

  18. The foreign-language effect: thinking in a foreign tongue reduces decision biases.

    Science.gov (United States)

    Keysar, Boaz; Hayakawa, Sayuri L; An, Sun Gyu

    2012-06-01

    Would you make the same decisions in a foreign language as you would in your native tongue? It may be intuitive that people would make the same choices regardless of the language they are using, or that the difficulty of using a foreign language would make decisions less systematic. We discovered, however, that the opposite is true: Using a foreign language reduces decision-making biases. Four experiments show that the framing effect disappears when choices are presented in a foreign tongue. Whereas people were risk averse for gains and risk seeking for losses when choices were presented in their native tongue, they were not influenced by this framing manipulation in a foreign language. Two additional experiments show that using a foreign language reduces loss aversion, increasing the acceptance of both hypothetical and real bets with positive expected value. We propose that these effects arise because a foreign language provides greater cognitive and emotional distance than a native tongue does.

  19. The effects of social evaluation and looming threat on self-attentional biases and social anxiety.

    Science.gov (United States)

    Haikal, Muhammad; Hong, Ryan Y

    2010-04-01

    This paper examines how two proposed cognitive vulnerabilities of social anxiety, the fear of negative evaluation, and looming cognitive style may combine with socially demanding situations in predicting social anxiety symptoms and performance deficits. Fifty-two individuals previously identified as possessing these two cognitive vulnerabilities were randomly assigned to conditions in a 2 (high versus low social evaluation)x2 (high versus low temporal looming) experimental design. Significant interaction effects were found for: (a) residual change in anxiety symptoms from baseline level, and (b) performance on a speech task. Specifically, cognitively at-risk individuals exhibited the most increase in anxiety and the most performance deficits in the condition where social evaluation and temporal looming were high. In addition, a mediational effect of illusion of transparency (a form of self-attentional bias) between situational demands and residual change in anxiety was found. Implications arising from these results are discussed. (c) 2010 Elsevier Ltd. All rights reserved.

  20. Effect of psychological treatment on cognitive bias in generalized anxiety disorder.

    Science.gov (United States)

    Mathews, A; Mogg, K; Kentish, J; Eysenck, M

    1995-03-01

    Measures of attention and implicit memory for threatening words were obtained from anxious patients before and after psychological treatment, and compared with data from non-anxious control Ss collected over the same period. Findings confirmed the expectation that the presence of threatening distractors would be associated with greater interference with the performance of anxious patients than with that of controls, in both color-naming and attentional search tasks, but failed to confirm the previous finding of related differences in priming on a word completion task. Treatment significantly reduced selective interference effects in anxious patients, and abolished evidence of differences between the treated patients and controls. It is suggested that cognitive bias effects in anxiety may either depend on state factors alone, or may represent a more enduring individual difference that becomes apparent only when vulnerable individuals are primed by mood state or stressful events.

  1. 78 FR 78457 - Self-Regulatory Organizations; Topaz Exchange, LLC; Notice of Filing and Immediate Effectiveness...

    Science.gov (United States)

    2013-12-26

    ... express their true prices to buy and sell options for the benefit of all market participants. B. Self... From the Federal Register Online via the Government Publishing Office SECURITIES AND EXCHANGE COMMISSION Self-Regulatory Organizations; Topaz Exchange, LLC; Notice of Filing and Immediate Effectiveness...

  2. Effects of ionizing radiation on perfluorosulfonic acid ion-exchange polymer. [Nafion

    Energy Technology Data Exchange (ETDEWEB)

    Balko, E.N.; Chaklos, J.T.

    1981-05-01

    The effects of ..beta.. and ..gamma.. radiation on the Nafion perfluorinated ion-exchange polymer have been examined and the radiolysis products have been identified. The polymer degrades by simple chain scission, and the rate of degradation is not affected by the state of polymer hydration or the nature of the ion which occupies an exchange site.

  3. Spin-lattice coupling effects in the Holstein double-exchange model

    Energy Technology Data Exchange (ETDEWEB)

    Weisse, Alexander [School of Physics, University of New South Wales, Sydney NSW 2052 (Australia); Fehske, Holger [Institut fuer Physik, Ernst-Moritz-Arndt Universitaet Greifswald, 17487 Greifswald (Germany); Ihle, Dieter [Institut fuer Theoretische Physik, Universitaet Leipzig, Augustusplatz 10-11, 04109 Leipzig (Germany)]. E-mail: dieter.ihle@itp.uni-leipzig.de

    2005-04-30

    Based on the Holstein double-exchange model and a highly efficient single cluster Monte Carlo approach we study the interplay of double-exchange and polaron effects in doped colossal magneto-resistance (CMR) manganites. The CMR transition is shown to be appreciably influenced by lattice polaron formation.

  4. 76 FR 63686 - Self-Regulatory Organizations; BATS Exchange, Inc.; Notice of Filing and Immediate Effectiveness...

    Science.gov (United States)

    2011-10-13

    ...-2011-041] Self-Regulatory Organizations; BATS Exchange, Inc.; Notice of Filing and Immediate Effectiveness of Proposed Rule Change To Adopt a Definition of Professional and Require That All Professional... Organization's Statement of the Terms of Substance of the Proposed Rule Change The Exchange filed a proposal...

  5. 77 FR 47152 - Self-Regulatory Organizations; EDGX Exchange, Inc.; Notice of Filing and Immediate Effectiveness...

    Science.gov (United States)

    2012-08-07

    ... receive (and pay for) additional market data based on their own internal analysis of the need for such... COMMISSION Self-Regulatory Organizations; EDGX Exchange, Inc.; Notice of Filing and Immediate Effectiveness...'' or ``EDGX'') filed with the Securities and Exchange Commission (``Commission'') the proposed rule...

  6. 77 FR 47150 - Self-Regulatory Organizations; EDGA Exchange, Inc.; Notice of Filing and Immediate Effectiveness...

    Science.gov (United States)

    2012-08-07

    ... receive (and pay for) additional market data based on their own internal analysis of the need for such... COMMISSION Self-Regulatory Organizations; EDGA Exchange, Inc.; Notice of Filing and Immediate Effectiveness...'' or ``EDGA'') filed with the Securities and Exchange Commission (``Commission'') the proposed rule...

  7. Overcoming the effects of false positives and threshold bias in graph theoretical analyses of neuroimaging data.

    Science.gov (United States)

    Drakesmith, M; Caeyenberghs, K; Dutt, A; Lewis, G; David, A S; Jones, D K

    2015-09-01

    Graph theory (GT) is a powerful framework for quantifying topological features of neuroimaging-derived functional and structural networks. However, false positive (FP) connections arise frequently and influence the inferred topology of networks. Thresholding is often used to overcome this problem, but an appropriate threshold often relies on a priori assumptions, which will alter inferred network topologies. Four common network metrics (global efficiency, mean clustering coefficient, mean betweenness and smallworldness) were tested using a model tractography dataset. It was found that all four network metrics were significantly affected even by just one FP. Results also show that thresholding effectively dampens the impact of FPs, but at the expense of adding significant bias to network metrics. In a larger number (n=248) of tractography datasets, statistics were computed across random group permutations for a range of thresholds, revealing that statistics for network metrics varied significantly more than for non-network metrics (i.e., number of streamlines and number of edges). Varying degrees of network atrophy were introduced artificially to half the datasets, to test sensitivity to genuine group differences. For some network metrics, this atrophy was detected as significant (pcluster-enhanced permutation correction approach, to identify sustained significant effects across clusters of thresholds. This approach minimises requirements to determine a single threshold a priori. We demonstrate improved sensitivity of MTPC-corrected metrics to genuine group effects compared to an existing approach and demonstrate the use of MTPC on a previously published network analysis of tractography data derived from a clinical population. In conclusion, we show that there are large biases and instability induced by thresholding, making statistical comparisons of network metrics difficult. However, by testing for effects across multiple thresholds using MTPC, true group

  8. Effect of exogenous methyl jasmonate on growth, gas exchange and ...

    African Journals Online (AJOL)

    plants subjected to water stress. The soybean plants were grown under normal water supply conditions till blooming and were then subjected to moisture stress by withholding water followed by foliar application of MJ at the rate of 50 μM. Drought stress severely hampered the growth, leaf gas-exchange attributes as well as ...

  9. Effects of Copper Exchange Levels on Complexation of Ammonia in ...

    African Journals Online (AJOL)

    The copper ammine complexes of the various copper levels per unit cell were characterized and analyzed by a combination of diffuse reflectance, X-ray powder diffraction, FT-infrared spectroscopy, electron paramagnetic resonance and nuclear magnetic resonance spectroscopic methods. At low copper exchange levels ...

  10. Intergroup biases of the intermediate-status group: the effect of stability and instability of social stratification.

    Science.gov (United States)

    Caricati, Luca; Monacelli, Nadia

    2012-01-01

    In two studies, the effect of instability of social stratification on intergroup behaviour of the intermediate-status group was investigated. In both studies, participants were categorised in the intermediate-status group. In Study 1, perceived instability was measured. Results show that the more social stratification was perceived as stable, the more intermediate-status group members were biased against the high-status group. Biases against both high- and low-status groups tended to become similar as social stratification was perceived as more unstable. In Study 2, instability was manipulated in upward and downward conditions. Results showed that, in the upwardly unstable condition, intermediate-status group members were more biased against high-status group, while in the downwardly unstable condition they were more biased against the low-status group.

  11. The power of social influence over food intake: examining the effects of attentional bias and impulsivity.

    Science.gov (United States)

    Hermans, Roel C J; Larsen, Junilla K; Lochbuehler, Kirsten; Nederkoorn, Chantal; Herman, C Peter; Engels, Rutger C M E

    2013-02-14

    Numerous studies have shown that people adjust their intake directly to that of their eating companions. A potential explanation for this modelling effect is that the eating behaviour of others operates as an external eating cue that stimulates food intake. The present study explored whether this cue-reactive mechanism can account for modelling effects on intake. It was investigated whether attentional bias towards dynamic eating cues and impulsivity would influence the degree of modelling. Participants completed one individual session and one session in which an experimental confederate accompanied them. In the first session, eye movements were recorded as an index of attentional bias to dynamic eating cues. In addition, self-reported impulsivity and response inhibition were assessed. The second session employed a between-participants design with three experimental conditions in which participants were exposed to a same-sex confederate instructed to eat nothing, a low or a large amount of M&Ms. A total of eighty-five young women participated. The participants' self-reported impulsivity determined the occurrence of modelling; only low-impulsive women adjusted their intake to that of their eating companion. Attention towards eating cues and response inhibition, however, did not moderate modelling of food intake. The present study suggests that cue-reactive mechanisms may not underlie modelling of food intake. Instead, the results emphasise the importance of social norms in explaining modelling effects, whereas it is suggested that the degree of impulsivity may play a role in whether or not women adhere to the intake norms set by their eating companion.

  12. Intergroup bias.

    Science.gov (United States)

    Hewstone, Miles; Rubin, Mark; Willis, Hazel

    2002-01-01

    This chapter reviews the extensive literature on bias in favor of in-groups at the expense of out-groups. We focus on five issues and identify areas for future research: (a) measurement and conceptual issues (especially in-group favoritism vs. out-group derogation, and explicit vs. implicit measures of bias); (b) modern theories of bias highlighting motivational explanations (social identity, optimal distinctiveness, uncertainty reduction, social dominance, terror management); (c) key moderators of bias, especially those that exacerbate bias (identification, group size, status and power, threat, positive-negative asymmetry, personality and individual differences); (d) reduction of bias (individual vs. intergroup approaches, especially models of social categorization); and (e) the link between intergroup bias and more corrosive forms of social hostility.

  13. Cognitive Bias Modification for Interpretation in Major Depression: Effects on Memory and Stress Reactivity

    OpenAIRE

    Joormann, Jutta; WAUGH, CHRISTIAN E.; Gotlib, Ian H.

    2015-01-01

    Interpreting ambiguous stimuli in a negative manner is a core bias associated with depression. Investigators have used cognitive bias modification for interpretation (CBM-I) to demonstrate that it is possible to experimentally induce and modify these biases. This study extends previous research by examining whether CBM-I affects not only interpretation, but also memory and physiological stress response in individuals diagnosed with Major Depressive Disorder (MDD). We found that CBM-I was effe...

  14. The cognitive and emotional effects of cognitive bias modification in interpretations in behaviorally inhibited youth

    OpenAIRE

    White, Lauren K.; Suway, Jenna G; Pine, Daniel S.; Field, Andy P.; Lester, Kathryn J; Muris, Peter; Bar-Haim, Yair; Fox, Nathan A.

    2016-01-01

    Cognitive bias modification (CBM) procedures follow from the view that interpretive biases play an important role in the development and maintenance of anxiety. As such, understanding the link between interpretive biases and anxiety in youth at risk for anxiety (e.g., behaviorally inhibited children) could elucidate the mechanisms involved in the development of pediatric anxiety. However, to date, the majority of CBM-I work only studies adult populations. The present article presents the resu...

  15. Combination of light-induced effect and gate bias stress in organic phototransistors

    Science.gov (United States)

    Liguori, R.; Sheets, W. C.; Bezzeccheri, E.; Facchetti, A.; Rubino, A.

    2016-05-01

    In this work, the photoresponse of pentacene-based thin film transistors fabricated with a photocurable polymer insulator was investigated under visible and ultraviolet illumination. A simple model was developed to distinguish a photoconductive and a photovoltaic effect, that is, a direct photocurrent and a current enhancement caused by a threshold voltage shift. The direction of the light-induced threshold translation is affected by measurement conditions (e.g. integration time and voltage range) and is related to the nature of the trap states, specifically those located in the pentacene film near the interface with the polymer. In particular, it was shown that, thanks to this phenomenon, the photosensitivity of the fabricated phototransistors could be modulated by the gate bias applied during illumination.

  16. Humidity Bias and Effect on Simulated Aerosol Optical Properties during the Ganges Valley Experiment

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Yan; Cadeddu, M.; Kotamarthi, V. R.; Renju, R.; Suresh Raju, C.

    2016-07-10

    The radiosonde humidity profiles available during the Ganges Valley Experiment were compared to those simulated from the regional Weather Research and Forecasting (WRF) model coupled with a chemistry module (WRF -Chern) and the global reanalysis datasets. Large biases were revealed. On a monthly mean basis at Nainital, located in northern India, the WRFChern model simulates a large moist bias in the free troposphere (up to +20%) as well as a large dry bias in the boundary layer (up to -30%). While the overall pattern of the biases is similar, the magnitude of the biases varies from time to time and from one location to another. At Thiruvananthapuram, the magnitude of the dry bias is smaller, and in contrast to Nainital, the higher-resolution regional WRF -Chern model generates larger moist biases in the upper troposphere than the global reanalysis data. Furthermore, the humidity biases in the upper troposphere, while significant, have little impact on the model estimation of column aerosol optical depth (AOD). The frequent occurrences of the dry boundary-layer bias simulated by the large-scale models tend to lead to the underestimation of AOD. It is thus important to quantify the humidity vertical profiles for aerosol simulations over South Asia.

  17. Climate change effects on irrigation demands and minimum stream discharge: impact of bias-correction method

    Directory of Open Access Journals (Sweden)

    J. Rasmussen

    2012-12-01

    Full Text Available Climate changes are expected to result in a warmer global climate, with increased inter-annual variability. In this study, the possible impacts of these climate changes on irrigation and low stream flow are investigated using a distributed hydrological model of a sandy catchment in western Denmark. The IPCC climate scenario A1B was chosen as the basis for the study, and meteorological forcings (precipitation, reference evapotranspiration and temperature derived from the ECHAM5-RACMO regional climate model for the period 2071–2100 was applied to the model. Two bias correction methods, delta change and Distribution-Based Scaling, were used to evaluate the importance of the bias correction method. Using the annual irrigation amounts, the 5-percentile stream flow, the median minimum stream flow and the mean stream flow as indicators, the irrigation and the stream flow predicted using the two methods were compared. The study found that irrigation is significantly underestimated when using the delta change method, due to the inability of this method to account for changes in inter-annual variability of precipitation and reference ET and the resulting effects on irrigation demands. However, this underestimation of irrigation did not result in a significantly higher summer stream flow, because the summer stream flow in the studied catchment is controlled by the winter and spring recharge, rather than the summer precipitation. Additionally, future increases in CO2 are found to have a significant effect on both irrigation and low flow, due to reduced transpiration from plants.

  18. The effect of gas mixing and biased disc voltage on the preglow transient of electron cyclotron resonance ion source.

    Science.gov (United States)

    Tarvainen, O; Toivanen, V; Komppula, J; Kalvas, T; Koivisto, H

    2012-02-01

    The effect of gas mixing and biased disc voltage on the preglow of electron cyclotron resonance ion source plasma has been studied with the AECR-U type 14 GHz ion source. It was found that gas mixing has a significant effect on the preglow. The extracted transient beam currents and efficiency of the heavier species increase, while the currents and efficiency of the lighter species decrease when gas mixing is applied. The effect of the biased disc was found to be pronounced in continuous operation mode in comparison to preglow. The data provide information on the time scales of the plasma processes explaining the effects of gas mixing and biased disc. The results also have implications on production of radioactive ion beams in preglow mode for the proposed Beta Beam neutrino factory.

  19. The Effects of Trade Openness on Malaysian Exchange Rate

    OpenAIRE

    Lee, Chin; Law, Chee-Hong

    2013-01-01

    This study investigates the impact of trade openness on Malaysian exchange rate. The findings show that most of the variables are statistically significant and carried the expected signs. As predicted by the theory, the rise of the income level and stock market index in Malaysia will lead to the appreciation of domestic currency. On the other hand, the increase in trade openness and interest rate can lead to depreciation of Malaysian Ringgit. In addition, the results suggested that a rise in ...

  20. Analysis of a vector-bias effect in the spread of malaria between two different incidence areas.

    Science.gov (United States)

    Kim, Sungchan; Masud, M A; Cho, Giphil; Jung, Il Hyo

    2017-04-21

    In 2005, Lacroix et al. demonstrated that infected humans are more attractive to mosquitoes, a phenomenon known as the vector-bias effect. The aim of this study was to determine how a vector-bias effect affects the changes in the dynamics of malaria transmission, and the changes in control strategies and cost-effectiveness for optimal control considering the regional characteristics or force of infections for different transmission rates. We used a vector-bias mathematical model and considered two different incidence areas: a high transmission area and a low transmission area. Our results showed that the dynamics in the two areas differed; as bias exists and the strategy for optimal control could be changed in the different areas. Thus, this work may give that considering the vector-bias effect in different areas facilitates prediction of the future dynamics and make decisions for establishing controls. We also mention the evolution of malaria parasites in this study. Copyright © 2017 Elsevier Ltd. All rights reserved.

  1. Fabrication and characterization of a charge-biased CMOS-MEMS resonant gate field effect transistor

    Science.gov (United States)

    Chin, C. H.; Li, C. S.; Li, M. H.; Wang, Y. L.; Li, S. S.

    2014-09-01

    A high-frequency charge-biased CMOS-MEMS resonant gate field effect transistor (RGFET) composed of a metal-oxide composite resonant-gate structure and an FET transducer has been demonstrated utilizing the TSMC 0.35 μm CMOS technology with Q > 1700 and a signal-to-feedthrough ratio greater than 35 dB under a direct two-port measurement configuration. As compared to the conventional capacitive-type MEMS resonators, the proposed CMOS-MEMS RGFET features an inherent transconductance gain (gm) offered by the FET transduction capable of enhancing the motional signal of the resonator and relaxing the impedance mismatch issue to its succeeding electronics or 50 Ω-based test facilities. In this work, we design a clamped-clamped beam resonant-gate structure right above a floating gate FET transducer as a high-Q building block through a maskless post-CMOS process to combine merits from the large capacitive transduction areas of the large-width beam resonator and the high gain of the underneath FET. An analytical model is also provided to simulate the behavior of the charge-biased RGFET; the theoretical prediction is in good agreement with the experimental results. Thanks to the deep-submicrometer gap spacing enabled by the post-CMOS polysilicon release process, the proposed resonator under a purely capacitive transduction already attains motional impedance less than 10 kΩ, a record-low value among CMOS-MEMS capacitive resonators. To go one step further, the motional signal of the proposed RGFET is greatly enhanced through the FET transduction. Such a strong transmission and a sharp phase transition across 0° pave a way for future RGFET-type oscillators in RF and sensor applications. A time-elapsed characterization of the charge leakage rate for the floating gate is also carried out.

  2. Effects of cognitive bias modification training on neural alcohol cue reactivity in alcohol dependence

    NARCIS (Netherlands)

    Wiers, C.E.; Stelzel, C.; Gladwin, T.E.; Park, S.Q.; Pawelczack, S.; Gawron, C.K.; Stuke, H.; Heinz, A.; Wiers, R.W.; Rinck, M.; Lindenmeyer, J.; Walter, H.; Bermpohl, F.

    2015-01-01

    Objective: In alcohol-dependent patients, alcohol cues evoke increased activation in mesolimbic brain areas, such as the nucleus accumbens and the amygdala. Moreover, patients show an alcohol approach bias, a tendency to more quickly approach than avoid alcohol cues. Cognitive bias modification

  3. Effects of cognitive bias modification training on neural alcohol cue reactivity in alcohol dependence

    NARCIS (Netherlands)

    Wiers, C.E.; Stelzel, C.; Gladwin, T.E.; Park, S.Q.; Pawelczack, S.; Gawron, C.K.; Stuke, H.; Heinz, A.; Wiers, R.W.H.J.; Rinck, M.; Lindenmeyer, J.; Walter, H.; Bermpohl, F.

    2015-01-01

    OBJECTIVE: In alcohol-dependent patients, alcohol cues evoke increased activation in mesolimbic brain areas, such as the nucleus accumbens and the amygdala. Moreover, patients show an alcohol approach bias, a tendency to more quickly approach than avoid alcohol cues. Cognitive bias modification

  4. The beneficial effects of a positive attention bias amongst children with a history of psychosocial deprivation.

    Science.gov (United States)

    Troller-Renfree, Sonya; McLaughlin, Katie A; Sheridan, Margaret A; Nelson, Charles A; Zeanah, Charles H; Fox, Nathan A

    2017-01-01

    Children raised in institutions experience psychosocial deprivation that has detrimental influences on attention and mental health. The current study examined patterns of attention biases in children from institutions who were randomized at approximately 21.6 months to receive either a high-quality foster care intervention or care-as-usual. At age 12, children performed a dot-probe task and indices of attention bias were calculated. Additionally, children completed a social stress paradigm and cortisol reactivity was computed. Children randomized into foster care (N=40) exhibited an attention bias toward positive stimuli but not threat, whereas children who received care-as-usual (N=40) and a never-institutionalized comparison group (N=47) showed no bias. Stability of foster care placement was related to positive bias, while instability of foster care placement was related to threat bias. The magnitude of the positive bias was associated with fewer internalizing problems and better coping mechanisms. Within the foster care group, positive attention bias was related to less blunted cortisol reactivity. Copyright © 2016 Elsevier B.V. All rights reserved.

  5. On commercial media bias

    OpenAIRE

    Germano, Fabrizio

    2008-01-01

    Within the spokes model of Chen and Riordan (2007) that allows for non-localized competition among arbitrary numbers of media outlets, we quantify the effect of concentration of ownership on quality and bias of media content. A main result shows that too few commercial outlets, or better, too few separate owners of commercial outlets can lead to substantial bias in equilibrium. Increasing the number of outlets (commercial and non-commercial) tends to bring down this bias; but the strongest ef...

  6. The effects of early foster care intervention on attention biases in previously institutionalized children in Romania.

    Science.gov (United States)

    Troller-Renfree, Sonya; McDermott, Jennifer Martin; Nelson, Charles A; Zeanah, Charles H; Fox, Nathan A

    2015-09-01

    Children raised in institutions experience psychosocial deprivation that can negatively impact attention skills and emotion regulation, which subsequently may influence behavioral regulation and social relationships. The current study examined visual attention biases in 8-year-old children who were part of the Bucharest Early Intervention Project (BEIP). Relations among attention biases and concurrent social outcomes were also investigated. In early childhood, 136 children abandoned at birth or shortly thereafter into institutional care were randomized to receive a high-quality foster care intervention or care-as-usual within the context of the Bucharest Early Intervention Project (BEIP). At 8 years of age, 50 care-as-usual, 55 foster care, and 52 community controls performed a behavioral dot-probe task, and indices of attention biases to threat and positive stimuli were calculated. Concurrent data on social behavior were collected. Children placed into the foster care intervention had a significant attention bias toward positive stimuli, while children who received care-as-usual had a significant bias toward threat. Children in the foster care intervention had a significantly larger positive bias when compared to the care-as-usual group. A positive bias was related to more social engagement, more prosocial behavior, less externalizing disorders, and less emotionally withdrawn behavior. The magnitude of positive bias was predicted by age of placement into foster care among children with a history of institutionalization. An attention bias towards positive stimuli was associated with reduced risk for behavioral problems amongst children who experienced early psychosocial deprivation. Research assessing attention biases in children experiencing early environmental stress may refine our understanding of the mechanisms underlying risk for later psychiatric and social disorders and inform prevention efforts. © 2014 John Wiley & Sons Ltd.

  7. Benthic solute exchange and carbon mineralization in two shallow subtidal sandy sediments: Effect of advective pore-water exchange

    DEFF Research Database (Denmark)

    Cook, Perran L. M.; Wenzhofer, Frank; Glud, Ronnie N.

    2007-01-01

    We conducted four field campaigns to evaluate benthic O-2 consumption and the effect of advective pore-water flow in nearshore permeable sediments in the North Sea and Baltic Sea. Advective pore-water transport had a marked effect on the benthic exchange of O-2 and TCO2 in benthic chamber...... of O-2 distribution across ripples, and also deep subsurface O-2 pools, being observed. Mineralization pathways were predominantly aerobic when benthic mineralization rates were low and advective pore-water flow high as a result of well-developed sediment topography. By contrast, mineralization...... proceeded predominantly through sulfate reduction when benthic mineralization rates were high and advective pore-water flow low as a result of poorly developed topography. Previous studies of benthic mineralization in shallow sandy sediments have generally ignored these dynamics and, hence, have overlooked...

  8. Biased Exposure-Health Effect Estimates from Selection in Cohort Studies: Are Environmental Studies at Particular Risk?

    Science.gov (United States)

    Weisskopf, Marc G; Sparrow, David; Hu, Howard; Power, Melinda C

    2015-11-01

    The process of creating a cohort or cohort substudy may induce misleading exposure-health effect associations through collider stratification bias (i.e., selection bias) or bias due to conditioning on an intermediate. Studies of environmental risk factors may be at particular risk. We aimed to demonstrate how such biases of the exposure-health effect association arise and how one may mitigate them. We used directed acyclic graphs and the example of bone lead and mortality (all-cause, cardiovascular, and ischemic heart disease) among 835 white men in the Normative Aging Study (NAS) to illustrate potential bias related to recruitment into the NAS and the bone lead substudy. We then applied methods (adjustment, restriction, and inverse probability of attrition weighting) to mitigate these biases in analyses using Cox proportional hazards models to estimate adjusted hazard ratios (HRs) and 95% confidence intervals (CIs). Analyses adjusted for age at bone lead measurement, smoking, and education among all men found HRs (95% CI) for the highest versus lowest tertile of patella lead of 1.34 (0.90, 2.00), 1.46 (0.86, 2.48), and 2.01 (0.86, 4.68) for all-cause, cardiovascular, and ischemic heart disease mortality, respectively. After applying methods to mitigate the biases, the HR (95% CI) among the 637 men analyzed were 1.86 (1.12, 3.09), 2.47 (1.23, 4.96), and 5.20 (1.61, 16.8), respectively. Careful attention to the underlying structure of the observed data is critical to identifying potential biases and methods to mitigate them. Understanding factors that influence initial study participation and study loss to follow-up is critical. Recruitment of population-based samples and enrolling participants at a younger age, before the potential onset of exposure-related health effects, can help reduce these potential pitfalls. Weisskopf MG, Sparrow D, Hu H, Power MC. 2015. Biased exposure-health effect estimates from selection in cohort studies: are environmental studies at

  9. Hostile Attributional Bias, Negative Emotional Responding, and Aggression in Adults: Moderating Effects of Gender and Impulsivity

    Science.gov (United States)

    Chen, Pan; Coccaro, Emil F.; Jacobson, Kristen C.

    2012-01-01

    The current study examined the main effects of hostile attributional bias (HAB) and negative emotional responding on a variety of aggressive behaviors in adults, including general aggression, physical aggression, relational aggression, and verbal aggression. Effects of both externalizing (anger) and internalizing (embarrassment/upset) negative emotions were considered. In addition, the moderating roles of gender and impulsivity on the effects of HAB and negative emotional responding were explored. Multilevel models were fitted to data from 2,749 adult twins aged 20–55 from the PennTwins cohort. HAB was positively associated with all four forms of aggression. There was also a significant interaction between impulsivity and HAB for general aggression. Specifically, the relationship between HAB and general aggression was only significant for individuals with average or above-average levels of impulsivity. Negative emotional responding was also found to predict all measures of aggression, although in different ways. Anger was positively associated with all forms of aggression, whereas embarrassment/upset predicted decreased levels of general, physical, and verbal aggression but increased levels of relational aggression. The associations between negative emotional responding and aggression were generally stronger for males than females. The current study provides evidence for the utility of HAB and negative emotional responding as predictors of adult aggression and further suggests that gender and impulsivity may moderate their links with aggression. PMID:24833604

  10. Hostile attributional bias, negative emotional responding, and aggression in adults: moderating effects of gender and impulsivity.

    Science.gov (United States)

    Chen, Pan; Coccaro, Emil F; Jacobson, Kristen C

    2012-01-01

    The current study examined the main effects of hostile attributional bias (HAB) and negative emotional responding on a variety of aggressive behaviors in adults, including general aggression, physical aggression, relational aggression, and verbal aggression. Effects of both externalizing (anger) and internalizing (embarrassment/upset) negative emotions were considered. In addition, the moderating roles of gender and impulsivity on the effects of HAB and negative emotional responding were explored. Multilevel models were fitted to data from 2,749 adult twins aged 20-55 from the PennTwins cohort. HAB was positively associated with all four forms of aggression. There was also a significant interaction between impulsivity and HAB for general aggression. Specifically, the relationship between HAB and general aggression was only significant for individuals with average or above-average levels of impulsivity. Negative emotional responding was also found to predict all measures of aggression, although in different ways. Anger was positively associated with all forms of aggression, whereas embarrassment/upset predicted decreased levels of general, physical, and verbal aggression but increased levels of relational aggression. The associations between negative emotional responding and aggression were generally stronger for males than females. The current study provides evidence for the utility of HAB and negative emotional responding as predictors of adult aggression and further suggests that gender and impulsivity may moderate their links with aggression. © 2011 Wiley Periodicals, Inc.

  11. THE EFFECT OF MACROECONOMIC VARIABLES ON BANKING STOCK PRICE INDEX IN INDONESIA STOCK EXCHANGE

    Directory of Open Access Journals (Sweden)

    Laduna R.

    2018-01-01

    Full Text Available Stock price index can be regarded as a barometer in the measuremet of a nation’s economic condition, besides it can also be used in conducting statistical analysis on the current market. Stock is the proof of one’s share in a company in the form of securities issued by the listed go-public companies. This study was conducted to measure the effect of macroeconomic variables such as inflation, interest rate, and exchange rate on banking stock price index in Indonesia stock exchange or Bursa Efek Indonesia (BEI. The results of study show that inflation and exchange rate posively influence the stock price index. The positive effect of the exchange rate shows that issuers who were positively affected by Rupiah (IDR depreciation appear to be the most dominant group. Meanwhile, the interest rate or Suku Bunga (SBI has a negative effect. Lower interest rate stimulates higher investments and better economic activities which increase the stock price.

  12. Membrane-type Total Heat Exchanger Performance Simulation with Consideration of Entrance Effects

    Science.gov (United States)

    Duan, J. F.; Min, J. C.

    2017-11-01

    Membrane-type total heat exchanger (THX) is an air-to-air heat exchanger used to reduce the building energy consumption associated with forced ventilation by recovering both heat and moisture from ventilation air. It contains a heat/moisture exchange core made of a water vapour permeable membrane, supply outdoor air and exhaust indoor air flow through the membrane channels in the core in a crossflow manner and exchange heat and moisture across the membranes. The present work numerically investigates the airflow channel entrance effects on the THX performance. The results show that such effects on the air temperature and humidity distributions are inconspicuous and so are they on the THX effectiveness, it is therefore appropriate to use the constant Nusselt number to evaluate the THX performance.

  13. The Effects Of Asymmetric Transmission Of Exchange Rate On Inflation In Iran: Application Of Threshold Models

    Directory of Open Access Journals (Sweden)

    Naghdi Yazdan

    2015-08-01

    Full Text Available Given the recent fluctuation in the exchange rate and the presence of several factors such as the various economy-political sanctions (mainly embargos on oil and banking, extreme volatility in different economic fields, and consequently the devaluation of national and public procurement -A landmark that is emanating from exchange rate fluctuation - two points should be noted: First, it is essential to review the effect of exchange rate fluctuation on macro economic variables such as inflation and to provide appropriate policies. Second, the existence of this condition provides the chance to study the relation between exchange rate and inflation in a non-linear and asymmetric method. Hence, the present study seeks to use TAR model and, on the basis of monthly time series data over the period March 2002 to March 2014, to analyze the cross-asymmetric and non-linear exchange rate on consumer price index (CPI in Iran. The results also show the presence of an asymmetric long-term relationship between these variables (exchange rate and CPI. Also, in the Iranian economy, the effect of negative shocks of exchange rate on inflation is more sustainable than the one from positive shocks.

  14. Selection bias, vote counting, and money-priming effects: A comment on Rohrer, Pashler, and Harris (2015) and Vohs (2015).

    Science.gov (United States)

    Vadillo, Miguel A; Hardwicke, Tom E; Shanks, David R

    2016-05-01

    When a series of studies fails to replicate a well-documented effect, researchers might be tempted to use a "vote counting" approach to decide whether the effect is reliable-that is, simply comparing the number of successful and unsuccessful replications. Vohs's (2015) response to the absence of money priming effects reported by Rohrer, Pashler, and Harris (2015) provides an example of this approach. Unfortunately, vote counting is a poor strategy to assess the reliability of psychological findings because it neglects the impact of selection bias and questionable research practices. In the present comment, we show that a range of meta-analytic tools indicate irregularities in the money priming literature discussed by Rohrer et al. and Vohs, which all point to the conclusion that these effects are distorted by selection bias, reporting biases, or p-hacking. This could help to explain why money-priming effects have proven unreliable in a number of direct replication attempts in which biases have been minimized through preregistration or transparent reporting. Our major conclusion is that the simple proportion of significant findings is a poor guide to the reliability of research and that preregistered replications are an essential means to assess the reliability of money-priming effects. (c) 2016 APA, all rights reserved).

  15. Selection Bias, Vote Counting, and Money-Priming Effects: A Comment on Rohrer, Pashler, and Harris (2015) and Vohs (2015)

    Science.gov (United States)

    2016-01-01

    When a series of studies fails to replicate a well-documented effect, researchers might be tempted to use a “vote counting” approach to decide whether the effect is reliable—that is, simply comparing the number of successful and unsuccessful replications. Vohs’s (2015) response to the absence of money priming effects reported by Rohrer, Pashler, and Harris (2015) provides an example of this approach. Unfortunately, vote counting is a poor strategy to assess the reliability of psychological findings because it neglects the impact of selection bias and questionable research practices. In the present comment, we show that a range of meta-analytic tools indicate irregularities in the money priming literature discussed by Rohrer et al. and Vohs, which all point to the conclusion that these effects are distorted by selection bias, reporting biases, or p-hacking. This could help to explain why money-priming effects have proven unreliable in a number of direct replication attempts in which biases have been minimized through preregistration or transparent reporting. Our major conclusion is that the simple proportion of significant findings is a poor guide to the reliability of research and that preregistered replications are an essential means to assess the reliability of money-priming effects. PMID:27077759

  16. Effect of an Intervention to Break the Gender Bias Habit for Faculty at One Institution: A Cluster Randomized, Controlled Trial

    Science.gov (United States)

    Carnes, Molly; Devine, Patricia G.; Manwell, Linda Baier; Byars-Winston, Angela; Fine, Eve; Ford, Cecilia E.; Forscher, Patrick; Isaac, Carol; Kaatz, Anna; Magua, Wairimu; Palta, Mari; Sheridan, Jennifer

    2014-01-01

    Purpose Despite sincere commitment to egalitarian, meritocratic principles, subtle gender bias persists, constraining women’s opportunities for academic advancement. The authors implemented a pair-matched, single-blind, cluster-randomized, controlled study of a gender bias habit-changing intervention at a large public university. Method Participants were faculty in 92 departments or divisions at the University of Wisconsin-Madison. Between September 2010 and March 2012, experimental departments were offered a gender bias habit-changing intervention as a 2.5 hour workshop. Surveys measured gender bias awareness; motivation, self-efficacy, and outcome expectations to reduce bias; and gender equity action. A timed word categorization task measured implicit gender/leadership bias. Faculty completed a worklife survey before and after all experimental departments received the intervention. Control departments were offered workshops after data were collected. Results Linear mixed-effects models showed significantly greater changes post-intervention for faculty in experimental vs. control departments on several outcome measures, including self-efficacy to engage in gender equity promoting behaviors (P = .013). When ≥ 25% of a department’s faculty attended the workshop (26 of 46 departments), significant increases in self-reported action to promote gender equity occurred at 3 months (P = .007). Post-intervention, faculty in experimental departments expressed greater perceptions of fit (P = .024), valuing of their research (P = .019), and comfort in raising personal and professional conflicts (P = .025). Conclusions An intervention that facilitates intentional behavioral change can help faculty break the gender bias habit and change department climate in ways that should support the career advancement of women in academic medicine, science, and engineering. PMID:25374039

  17. Effect of Inspiratory Time and Lung Compliance on Flow Bias Generated During Manual Hyperinflation: A Bench Study.

    Science.gov (United States)

    Bennett, Bradley G; Thomas, Peter; Ntoumenopoulos, George

    2015-10-01

    Manual hyperinflation can be used to assist mucus clearance in intubated patients. The technique's effectiveness to move mucus is underpinned by its ability to generate flow bias in the direction of expiration, and this must exceed specific thresholds. It is unclear whether the inspiratory times commonly used by physiotherapists generate sufficient expiratory flow bias based on previously published thresholds and whether factors such as lung compliance affect this. In a series of laboratory experiments, we applied manual hyperinflation to a bench model to examine the role of 3 target inspiratory times and 2 lung compliance settings on 3 measures of expiratory flow bias. Longer inspiratory times and lower lung compliances were associated with improvements in all measures of expiratory flow bias. In normal compliance lungs, achievement of the expiratory flow bias thresholds were (1) never achieved with an inspiratory time of 1 s, (2) rarely achieved with an inspiratory time of 2 s, and (3) commonly achieved with an inspiratory time of 3 s. In lower compliance lungs, achievement of the expiratory flow bias thresholds was (1) rarely achieved with an inspiratory time of 1 s, (2) sometimes achieved with an inspiratory time of 2 s, and (3) nearly always achieved with an inspiratory time of 3 s. Peak inspiratory pressures exceeded 40 cm H2O in normal compliance lungs with inspiratory times of 1 s and in lower compliance lungs with inspiratory times of 1 and 2 s. Inspiratory times of at least 3 s with normal compliance lungs and at least 2 s with lower compliance lungs appear necessary to achieve expiratory flow bias thresholds during manual hyperinflation. Inspiratory times shorter than this may lead to excessive peak inspiratory pressures. Verification of these findings in relation to the movement of mucus should be examined in further bench or animal models and/or human clinical trials. Copyright © 2015 by Daedalus Enterprises.

  18. Analyzing the effect of ion exchange on flexural strength of cermaco II and colorlogic veneer porcelains

    Directory of Open Access Journals (Sweden)

    N. Rashidan

    1998-04-01

    Full Text Available   The major foible of dental ceramics is their brittle nature. Therefore, the producers of these materials have focused on the “strength” issue. A method of increasing strength is ion exchange on porcelain surface which leads to formation of a compressive crust that opposing forces should overcome before developing a crack. In current study, ion exchange in two types of porcelain, Ceramco II which is used in PFM restorations and Colorloic veneer which is used for laminates, veneers, inlays and onlays, are evaluated. Additionally, laminate porcelains, etching effect on strength of porcelain and interaction of acid etching and ion exchange have been studied.

  19. Automation bias: a systematic review of frequency, effect mediators, and mitigators.

    Science.gov (United States)

    Goddard, Kate; Roudsari, Abdul; Wyatt, Jeremy C

    2012-01-01

    Automation bias (AB)--the tendency to over-rely on automation--has been studied in various academic fields. Clinical decision support systems (CDSS) aim to benefit the clinical decision-making process. Although most research shows overall improved performance with use, there is often a failure to recognize the new errors that CDSS can introduce. With a focus on healthcare, a systematic review of the literature from a variety of research fields has been carried out, assessing the frequency and severity of AB, the effect mediators, and interventions potentially mitigating this effect. This is discussed alongside automation-induced complacency, or insufficient monitoring of automation output. A mix of subject specific and freetext terms around the themes of automation, human-automation interaction, and task performance and error were used to search article databases. Of 13 821 retrieved papers, 74 met the inclusion criteria. User factors such as cognitive style, decision support systems (DSS), and task specific experience mediated AB, as did attitudinal driving factors such as trust and confidence. Environmental mediators included workload, task complexity, and time constraint, which pressurized cognitive resources. Mitigators of AB included implementation factors such as training and emphasizing user accountability, and DSS design factors such as the position of advice on the screen, updated confidence levels attached to DSS output, and the provision of information versus recommendation. By uncovering the mechanisms by which AB operates, this review aims to help optimize the clinical decision-making process for CDSS developers and healthcare practitioners.

  20. [Potential sponsorship bias in cost-effectiveness analyses of healthcare interventions: A cross-sectional analysis].

    Science.gov (United States)

    Catalá-López, Ferrán; Ridao, Manuel

    To examine the relationship between the funding source of cost-effectiveness analyses of healthcare interventions published in Spain and study conclusions. Descriptive cross-sectional study. Scientific literature databases (until December 2014). Cohort of cost-effectiveness analysis of healthcare interventions published in Spain between 1989-2014 (n=223) presenting quality-adjusted life years (QALYs) as the outcome measure. The relationship between qualitative conclusions of the studies and the type of funding source were established using Fisher's exact test in contingency tables. Distributions of the incremental cost-effectiveness ratios by source of funding in relation to hypothetical willingness to pay thresholds between €30,000-€50,000 per QALY were explored. A total of 136 (61.0%) studies were funded by industry. The industry-funded studies were less likely to report unfavorable or neutral conclusions than studies non-funded by industry (2.2% vs. 23.0%; P<.0001), largely driven by studies evaluating drugs (0.9% vs. 21.4%; P<.0001). The incremental cost-effectiveness ratios in studies funded by industry were more likely to be below the hypothetical willingness to pay threshold of €30,000 (73.8% vs. 56.3%; P<.0001) and €50,000 (89.4% vs. 68.2%; P<.0001) per QALY. This study reveals a potential sponsorship bias in cost-effectiveness analyses of healthcare interventions. Studies funded by industry could be favoring the efficiency profile of their products. Copyright © 2016 Elsevier España, S.L.U. All rights reserved.

  1. In the shadow of the boss's boss: effects of supervisors' upward exchange relationships on employees.

    Science.gov (United States)

    Tangirala, Subrahmaniam; Green, Stephen G; Ramanujam, Rangaraj

    2007-03-01

    Dyadic relationships in an organizational hierarchy are often nested within one another. For instance, the relationship between a supervisor and an employee is nested within the relationship between that supervisor and his or her boss. In that context, the authors propose that the supervisor's relationship with his or her boss (leader-leader exchange) moderates the effects of the supervisor's relationship with the employee (leader-member exchange). Specifically, the authors argue that leader-member exchange has a stronger positive effect on employees' attitudes toward the organization and its customers when leader-leader exchange is higher. Cross-level analysis of data from 581 frontline nurses and 29 supervisors in a midwestern hospital supports this contention. Implications for research and practice are discussed. (c) 2007 APA, all rights reserved.

  2. High effectiveness liquid droplet/gas heat exchanger for space power applications

    Science.gov (United States)

    Bruckner, A. P.; Mattick, A. T.

    1983-01-01

    A high-effectiveness liquid droplet/gas heat exchanger (LDHX) concept for thermal management in space is described. Heat is transferred by direct contact between fine droplets (approximately 100-300 microns in diameter) of a suitable low vapor pressure liquid and an inert working gas. Complete separation of the droplet and gas media in the zero-g environment is accomplished by configuring the LDHX as a vortex chamber.The large heat transfer area presented by the small droplets permits heat exchanger effectiveness of 0.9-0.95 in a compact, lightweight geometry which avoids many of the limitations of conventional plate and fin or tube and shell heat exchangers, such as their tendency toward single point failure. The application of the LDHX in a high temperature Brayton cycle is discussed to illustrate the performance and operational characteristics of this new heat exchanger concept.

  3. Effect of Malmquist bias on correlation studies with IRAS data base

    Science.gov (United States)

    Verter, Frances

    1993-01-01

    The relationships between galaxy properties in the sample of Trinchieri et al. (1989) are reexamined with corrections for Malmquist bias. The linear correlations are tested and linear regressions are fit for log-log plots of L(FIR), L(H-alpha), and L(B) as well as ratios of these quantities. The linear correlations for Malmquist bias are corrected using the method of Verter (1988), in which each galaxy observation is weighted by the inverse of its sampling volume. The linear regressions are corrected for Malmquist bias by a new method invented here in which each galaxy observation is weighted by its sampling volume. The results of correlation and regressions among the sample are significantly changed in the anticipated sense that the corrected correlation confidences are lower and the corrected slopes of the linear regressions are lower. The elimination of Malmquist bias eliminates the nonlinear rise in luminosity that has caused some authors to hypothesize additional components of FIR emission.

  4. Effect of oxygen on the bias-enhanced nucleation of diamond on silicon

    DEFF Research Database (Denmark)

    Schreck, M.; Christensen, Carsten; Stritzker, B.

    1999-01-01

    The influence of traces of oxygen in the process gas on the bias-enhanced nucleation (BEN) of diamond on silicon has been studied in the present work. CO2 in concentrations ranging from 0 to 3000 ppm was added during the nucleation procedure at U-bias = -200 V in microwave plasma chemical vapour...... deposition (MPCVD). A significant influence of CO2 could already be detected for a concentration of 75 ppm, corresponding to a C:O ratio of 600:1. It resulted in a continuous reduction of the biasing current and a delay in the nucleation process accompanied by a decrease of the final diamond......-covered substrate surface area with increasing CO2 concentration. At 3000 ppm, the nucleation was completely suppressed. An etching of diamond nuclei by the oxygen could be excluded from in-situ growth rate measurements under bias. Instead, optical emission spectra of the IIB Balmer line indicated a decrease...

  5. Effects of the location of a biased limiter on turbulent transport in the IR-T1 tokamak plasma

    Science.gov (United States)

    Alipour, Ramin; Ghoranneviss, Mahmood; Elahi, Ahmad Salar; Meshkani, Sakineh

    2017-09-01

    Plasma confinement plays an important role in fusion study. Applying an external voltage using limiter biasing system is proved to be an efficient approach for plasma confinement. In this study, the position of the limiter biasing system was changed to investigate the effect of applying external voltages at different places to the plasma. The external voltages of ±200 V were applied at the different positions of edge, 5 mm and 10 mm inside the plasma. Then, the main plasma parameters were measured. The results show that the poloidal turbulent transport and radial electric field increased about 25-35% and 35-45%, respectively (specially when the limiter biasing system was placed 5 mm inside the plasma). Also, the Reynolds stress is experienced its maximum reduction about 5-10% when the limiter biasing system was at 5 mm inside the plasma and the voltage of +200 V was applied to the plasma. When the limiter biasing system move 10 mm inside the plasma, the main plasma parameters experienced more instabilities and fluctuations than other positions.

  6. Benefits of being biased!

    Indian Academy of Sciences (India)

    Administrator

    The genetic code is degenerate: most amino acids are coded by multiple codons. However, it is known that certain ... tems, under certain conditions, it is possible to empirically demonstrate the effects of codon bias at the ... ing the metabolic costs incurred in terms of nonfunctional/ misfunctional proteins. Hence, codon bias ...

  7. Nanofiltration: ion exchange system for effective surfactant removal from water solutions

    OpenAIRE

    Kowalska, I.

    2014-01-01

    A system combining nanofiltration and ion exchange for highly effective separation of anionic surfactant from water solutions was proposed. The subjects of the study were nanofiltration polyethersulfone membranes and ion-exchange resins differing in type and structure. The quality of the treated solution was affected by numerous parameters, such as quality of the feed solution, membrane cut-off, resin type, dose and the solution contact time with the resin. A properly designed purification sy...

  8. Collider Bias in Trauma Comparative Effectiveness Research: The Stratification Blues for Systematic Reviews

    Science.gov (United States)

    2015-05-01

    survival bias, or the failure to exclude antecedent survival time that the intervention under study could not possibly affect , has cast doubt on many...explain the incongruous findings. Methods: The two most recent HSD trials, a single-site pilot and a multi-site pivotal study, provided data for a...overall findings has been challenging [18–26]. We hypothesised that a preventable type of collider bias could explain the incongruities . Methods Source

  9. Implementing a generic method for bias correction in statistical models using random effects, with spatial and population dynamics examples

    DEFF Research Database (Denmark)

    Thorson, James T.; Kristensen, Kasper

    2016-01-01

    Statistical models play an important role in fisheries science when reconciling ecological theory with available data for wild populations or experimental studies. Ecological models increasingly include both fixed and random effects, and are often estimated using maximum likelihood techniques...... configurations of an age-structured population dynamics model. This simulation experiment shows that the epsilon-method and the existing bias-correction method perform equally well in data-rich contexts, but the epsilon-method is slightly less biased in data-poor contexts. We then apply the epsilon......-method to a spatial regression model when estimating an index of population abundance, and compare results with an alternative bias-correction algorithm that involves Markov-chain Monte Carlo sampling. This example shows that the epsilon-method leads to a biologically significant difference in estimates of average...

  10. An attitude of gratitude: The effects of body-focused gratitude on weight bias internalization and body image.

    Science.gov (United States)

    Dunaev, Jamie; Markey, Charlotte H; Brochu, Paula M

    2018-02-08

    Internalized weight bias and body dissatisfaction are associated with a number of negative psychological and physical health outcomes. The current study examined the effectiveness of body-focused gratitude, through a short writing exercise, as a strategy to reduce internalized weight bias and improve body image. Young adults (M age  = 22.71, SD = 2.08, 51.2% female) were randomly assigned to either a body gratitude condition (n = 185) or a control condition (n = 184). Results indicated that participants in the gratitude condition reported significantly lower weight bias internalization and significantly more favorable appearance evaluation and greater body satisfaction when compared to the control condition. These effects were in the small range (ds = 0.27-0.33), and neither gender nor BMI moderated these effects. These findings provide preliminary support for body-focused gratitude writing exercises as an effective individual-level strategy for both reducing internalized weight bias and improving body image. Copyright © 2018 Elsevier Ltd. All rights reserved.

  11. Children's Hostile Attribution Bias Is Reduced after Watching Realistic Playful Fighting, and the Effect Is Mediated by Prosocial Thoughts

    Science.gov (United States)

    Boulton, Michael J.

    2012-01-01

    Hostile attribution bias (HAB) has been found to characterize aggressive children. Watching prosocial media has been shown to have positive effects on children, and the general learning model has been used to account for these observations. This study tested the hypotheses derived from this theory that exposure to playful fighting would lead to a…

  12. Effects of Grading Leniency and Low Workload on Students' Evaluations of Teaching: Popular Myth, Bias, Validity, or Innocent Bystanders?

    Science.gov (United States)

    Marsh, Herbert W.; Roche, Lawrence A.

    2000-01-01

    Discusses two studies that debunk the popular myths that student evaluations of teaching (SETs) are substantially biased by low workload and grading leniency. Results imply teaching effects were related to SETs. Contrary to predictions workload, expected grades, and their relations to SETs were stable over 12 years. (Author/MKA)

  13. Mothers' mental illness and child behavior problems: cause-effect association or observation bias?

    Science.gov (United States)

    Najman, J M; Williams, G M; Nikles, J; Spence, S; Bor, W; O'Callaghan, M; Le Brocque, R; Andersen, M J

    2000-05-01

    A number of studies have consistently found that a mother's mental health (particularly her level of depression) is a strong predictor of mental health problems experienced by her child(ren). However, the validity of this finding is in doubt because the majority of these studies have relied on maternal reports as indicators of children's behavior. This prospective, longitudinal study examines data on the mental health of the mother from prior to the birth of her child to when the child reaches 14 years of age. Child behavior is measured at 14 years of age using reports from mother and child. Mother and child responses are compared to provide an indication of the possible magnitude of maternal observation bias in the reporting of child behavior problems. Anxious and/or depressed mothers tend to report more cases of child behavior problems than do their mentally healthy counterparts or children themselves. Differences between mothers and youths in reporting behavior problems appear to be related to the mothers' mental health. Current maternal mental health impairment appears to have a substantial effect on the reporting of child behavior problems by the mother, thereby raising questions about the validity of reports of child behavior by persons who are currently emotionally distressed.

  14. Untold stories: biases and selection effects in research with victims of trafficking for sexual exploitation.

    Science.gov (United States)

    Brunovskis, Anette; Surtees, Rebecca

    2010-01-01

    Recent discussions of trafficking research have included calls for more innovative studies and new methodologies in order to move beyond the current trafficking narrative, which is often based on unrepresentative samples and overly simplified images. While new methods can potentially play a role in expanding the knowledge base on trafficking, this article argues that the solution is not entirely about applying new methods, but as much about using current methods to greater effect and with careful attention to their limitations and ethical constraints. Drawing on the authors' experience in researching trafficking issues in a number of projects over the past decade, the article outlines and exemplifies some of the methodological and ethical issues to be considered and accommodated when conducting research with trafficked persons -- including unrepresentative samples; access to respondents; selection biases by "gatekeepers" and self selection by potential respondents. Such considerations should inform not only how research is undertaken but also how this information is read and understood. Moreover, many of these considerations equally apply when considering the application of new methods within this field. The article maintains that a better understanding of how these issues come into play and inform trafficking research will translate into tools for conducting improved research in this field and, by implication, new perspectives on human trafficking.

  15. Negativity bias and task motivation: testing the effectiveness of positively versus negatively framed incentives.

    Science.gov (United States)

    Goldsmith, Kelly; Dhar, Ravi

    2013-12-01

    People are frequently challenged by goals that demand effort and persistence. As a consequence, philosophers, psychologists, economists, and others have studied the factors that enhance task motivation. Using a sample of undergraduate students and a sample of working adults, we demonstrate that the manner in which an incentive is framed has implications for individuals' task motivation. In both samples we find that individuals are less motivated when an incentive is framed as a means to accrue a gain (positive framing) as compared with when the same incentive is framed as a means to avoid a loss (negative framing). Further, we provide evidence for the role of the negativity bias in this effect, and highlight specific populations for whom positive framing may be least motivating. Interestingly, we find that people's intuitions about when they will be more motivated show the opposite pattern, with people predicting that positively framed incentives will be more motivating than negatively framed incentives. We identify a lay belief in the positive correlation between enjoyment and task motivation as one possible factor contributing to the disparity between predicted and actual motivation as a result of the framing of the incentive. We conclude with a discussion of the managerial implications for these findings. PsycINFO Database Record (c) 2013 APA, all rights reserved.

  16. Height bias and scale effect induced by antenna gravitational deformations in geodetic VLBI data analysis

    Science.gov (United States)

    Sarti, Pierguido; Abbondanza, Claudio; Petrov, Leonid; Negusini, Monia

    2011-01-01

    The impact of signal path variations (SPVs) caused by antenna gravitational deformations on geodetic very long baseline interferometry (VLBI) results is evaluated for the first time. Elevation-dependent models of SPV for Medicina and Noto (Italy) telescopes were derived from a combination of terrestrial surveying methods to account for gravitational deformations. After applying these models in geodetic VLBI data analysis, estimates of the antenna reference point positions are shifted upward by 8.9 and 6.7 mm, respectively. The impact on other parameters is negligible. To simulate the impact of antenna gravitational deformations on the entire VLBI network, lacking measurements for other telescopes, we rescaled the SPV models of Medicina and Noto for other antennas according to their size. The effects of the simulations are changes in VLBI heights in the range [-3, 73] mm and a net scale increase of 0.3-0.8 ppb. The height bias is larger than random errors of VLBI position estimates, implying the possibility of significant scale distortions related to antenna gravitational deformations. This demonstrates the need to precisely measure gravitational deformations of other VLBI telescopes, to derive their precise SPV models and to apply them in routine geodetic data analysis.

  17. Sex-specific effects of a parasite evolving in a female-biased host population

    Directory of Open Access Journals (Sweden)

    Duneau David

    2012-12-01

    Full Text Available Abstract Background Males and females differ in many ways and might present different opportunities and challenges to their parasites. In the same way that parasites adapt to the most common host type, they may adapt to the characteristics of the host sex they encounter most often. To explore this hypothesis, we characterized host sex-specific effects of the parasite Pasteuria ramosa, a bacterium evolving in naturally, strongly, female-biased populations of its host Daphnia magna. Results We show that the parasite proliferates more successfully in female hosts than in male hosts, even though males and females are genetically identical. In addition, when exposure occurred when hosts expressed a sexual dimorphism, females were more infected. In both host sexes, the parasite causes a similar reduction in longevity and leads to some level of castration. However, only in females does parasite-induced castration result in the gigantism that increases the carrying capacity for the proliferating parasite. Conclusions We show that mature male and female Daphnia represent different environments and reveal one parasite-induced symptom (host castration, which leads to increased carrying capacity for parasite proliferation in female but not male hosts. We propose that parasite induced host castration is a property of parasites that evolved as an adaptation to specifically exploit female hosts.

  18. Interpretation biases in paranoia.

    Science.gov (United States)

    Savulich, George; Freeman, Daniel; Shergill, Sukhi; Yiend, Jenny

    2015-01-01

    Information in the environment is frequently ambiguous in meaning. Emotional ambiguity, such as the stare of a stranger, or the scream of a child, encompasses possible good or bad emotional consequences. Those with elevated vulnerability to affective disorders tend to interpret such material more negatively than those without, a phenomenon known as "negative interpretation bias." In this study we examined the relationship between vulnerability to psychosis, measured by trait paranoia, and interpretation bias. One set of material permitted broadly positive/negative (valenced) interpretations, while another allowed more or less paranoid interpretations, allowing us to also investigate the content specificity of interpretation biases associated with paranoia. Regression analyses (n=70) revealed that trait paranoia, trait anxiety, and cognitive inflexibility predicted paranoid interpretation bias, whereas trait anxiety and cognitive inflexibility predicted negative interpretation bias. In a group comparison those with high levels of trait paranoia were negatively biased in their interpretations of ambiguous information relative to those with low trait paranoia, and this effect was most pronounced for material directly related to paranoid concerns. Together these data suggest that a negative interpretation bias occurs in those with elevated vulnerability to paranoia, and that this bias may be strongest for material matching paranoid beliefs. We conclude that content-specific biases may be important in the cause and maintenance of paranoid symptoms. Copyright © 2014. Published by Elsevier Ltd.

  19. Is the Effect of Parental Education on Offspring Biased or Moderated by Genotype?

    Directory of Open Access Journals (Sweden)

    Dalton Conley

    2015-02-01

    Full Text Available Parental education is the strongest measured predictor of offspring education, and thus many scholars see the parent–child correlation in educational attainment as an important measure of social mobility. But if social changes or policy interventions are going to have dynastic effects, we need to know what accounts for this intergenerational association, that is, whether it is primarily environmental or genetic in origin. Thus, to understand whether the estimated social influence of parental education on offspring education is biased owing to genetic inheritance (or moderated by it, we exploit the findings from a recent large genome-wide association study of educational attainment to construct a genetic score designed to predict educational attainment. Using data from two independent samples, we find that our genetic score significantly predicts years of schooling in both between-family and within-family analyses. We report three findings that should be of interest to scholars in the stratification and education fields. First, raw parent–child correlations in education may reflect one-sixth genetic transmission and five-sixths social inheritance. Second, conditional on a child’s genetic score, a parental genetic score has no statistically significant relationship to the child’s educational attainment. Third, the effects of offspring genotype do not seem to be moderated by measured sociodemographic variables at the parental level (but parent–child genetic interaction effects are significant. These results are consistent with the existence of two separate systems of ascription: genetic inheritance (a random lottery within families and social inheritance (across-family ascription. We caution, however, that at the presently attainable levels of explanatory power, these results are preliminary and may change when better-powered genetic risk scores are developed.

  20. Effect of Depreciation of the Exchange Rate on the Trade Balance of Albania

    Directory of Open Access Journals (Sweden)

    Kurtović Safet

    2017-09-01

    Full Text Available The paper investigates the effect of the real effective exchange rate depreciation of the lek on the trade balance of Albania using quarterly data from 1994 to 2015. Bounds testing cointegration approach, vector error correction model (VECM, and impulse response were used for the empirical analysis. The results of the study show a long-term cointegration between the real effective exchange rate (REER and the trade balance (TB. Specifically, the REER depreciation positively affects the trade balance of Albania in both the long and short run, indicating the weak presence of the J-curve effect. Important recommendations were derived from the results.

  1. Study on Return and Volatility Spillover Effects among Stock, CDS, and Foreign Exchange Markets in Korea

    Directory of Open Access Journals (Sweden)

    Taly I

    2015-09-01

    Full Text Available The key objective of this study is to investigate the return and volatility spillover effects among stock market, credit default swap (CDS market and foreign exchange market for three countries: Korea, the US and Japan. Using the trivariate VAR BEKK GARCH (1,1 model, the study finds that there are significant return and volatility spillover effects between the Korean CDS market and the Korean stock market. In addition, the return spillover effects from foreign exchange markets and the US stock market to the Korean stock market, and the volatility spillover effect from the Japanese stock market to the Korean stock market are both significant.

  2. Simulation of Electron Energy Spectra of a Biased Paracentric Hemispherical Deflection Analyzer as a Function of Entry Bias: Effects of Misalignments

    Directory of Open Access Journals (Sweden)

    O. Sise

    2014-01-01

    Full Text Available The performance of a biased paracentric hemispherical deflection analyzer (HDA, including fringing fields and their effect on focusing and energy resolution, is investigated using numerical methods. Electron energy spectra are calculated for three entry positions R0=84 mm, 100 mm, and 112 mm and compared with the recent experimental measurements. In both experiment and calculation, the two different paracentric entry positions R0=84 mm and R0=112 mm, on either side of the mean radius of 100 mm, are found to have a base energy resolution of about two times better than the conventional centric entry position R0=100 mm. In order to explain the discrepancies (6–30% between the simulated and the experimental resolutions the focusing characteristics are further investigated for different displacements of the input lens (ΔR0 with respect to the entry position R0 and the tilted input beam axis by αshift in the dispersive direction. We have found that the blame does not in fact lie with the theory and we have shown that the input lens may have been misaligned in the experiment. Slight misalignments affect both the true energy resolution measurement and the transmission of the beam.

  3. Analysis of the effect of attachment point bias during large space debris removal using a tethered space tug

    Science.gov (United States)

    Chu, Zhongyi; Di, Jingnan; Cui, Jing

    2017-10-01

    Space debris occupies a valuable orbital resource and is an inevitable and urgent problem, especially for large space debris because of its high risk and the possible crippling effects of a collision. Space debris has attracted much attention in recent years. A tethered system used in an active debris removal scenario is a promising method to de-orbit large debris in a safe manner. In a tethered system, the flexibility of the tether used in debris removal can possibly induce tangling, which is dangerous and should be avoided. In particular, attachment point bias due to capture error can significantly affect the motion of debris relative to the tether and increase the tangling risk. Hence, in this paper, the effect of attachment point bias on the tethered system is studied based on a dynamic model established based on a Newtonian approach. Next, a safety metric of avoiding a tangle when a tether is tensioned with attachment point bias is designed to analyse the tangling risk of the tethered system. Finally, several numerical cases are established and simulated to validate the effects of attachment point bias on a space tethered system.

  4. Effect of alcohol on risk of coronary heart disease and stroke: causality, bias, or a bit of both?

    Science.gov (United States)

    Emberson, Jonathan R; Bennett, Derrick A

    2006-01-01

    Epidemiological studies of middle-aged populations generally find the relationship between alcohol intake and the risk of coronary heart disease (CHD) and stroke to be either U- or J-shaped. This review describes the extent that these relationships are likely to be causal, and the extent that they may be due to specific methodological weaknesses in epidemiological studies. The consistency in the vascular benefit associated with moderate drinking (compared with non-drinking) observed across different studies, together with the existence of credible biological pathways, strongly suggests that at least some of this benefit is real. However, because of biases introduced by: choice of reference categories; reverse causality bias; variations in alcohol intake over time; and confounding, some of it is likely to be an artefact. For heavy drinking, different study biases have the potential to act in opposing directions, and as such, the true effects of heavy drinking on vascular risk are uncertain. However, because of the known harmful effects of heavy drinking on non-vascular mortality, the problem is an academic one. Studies of the effects of alcohol consumption on health outcomes should recognise the methodological biases they are likely to face, and design, analyse and interpret their studies accordingly. While regular moderate alcohol consumption during middle-age probably does reduce vascular risk, care should be taken when making general recommendations about safe levels of alcohol intake. In particular, it is likely that any promotion of alcohol for health reasons would do substantially more harm than good.

  5. Junctionless Diode Enabled by Self-Bias Effect of Ion Gel in Single-Layer MoS2 Device.

    Science.gov (United States)

    Khan, Muhammad Atif; Rathi, Servin; Park, Jinwoo; Lim, Dongsuk; Lee, Yoontae; Yun, Sun Jin; Youn, Doo-Hyeb; Kim, Gil-Ho

    2017-08-16

    The self-biasing effects of ion gel from source and drain electrodes on electrical characteristics of single layer and few layer molybdenum disulfide (MoS2) field-effect transistor (FET) have been studied. The self-biasing effect of ion gel is tested for two different configurations, covered and open, where ion gel is in contact with either one or both, source and drain electrodes, respectively. In open configuration, the linear output characteristics of the pristine device becomes nonlinear and on-off ratio drops by 3 orders of magnitude due to the increase in "off" current for both single and few layer MoS2 FETs. However, the covered configuration results in a highly asymmetric output characteristics with a rectification of around 103 and an ideality factor of 1.9. This diode like behavior has been attributed to the reduction of Schottky barrier width by the electric field of self-biased ion gel, which enables an efficient injection of electrons by tunneling at metal-MoS2 interface. Finally, finite element method based simulations are carried out and the simulated results matches well in principle with the experimental analysis. These self-biased diodes can perform a crucial role in the development of high-frequency optoelectronic and valleytronic devices.

  6. Examination of the effects of public spending and trade policy on real exchange rate in Cameroon

    Directory of Open Access Journals (Sweden)

    Victalice Ngimanang ACHAMOH

    2015-11-01

    Full Text Available The study adopts the inter-temporal model of Rodríguez (1989 and Edward (1989 extended in Elbadawi and Soto (1997 to empirically examine the effect of public expenditure and trade openness on the real exchange rate using Cameroon data from 1977 to 2010. After exploring some issues on exchange rate and reviewing the relevant literature, the study employs residual based-cointegration technique. All the variables were stationary at level form or first differences. Public spending significantly appreciates the real exchange likewise the trade openness variable in the longrun. The results of the study suggests that appreciation of real exchange rate could be prevented by contracting public spending or adopting restrictive trade measures especially in the long run.

  7. The Effects of Oil Price Changes And Exchange Rate Volatility On Unemployment: Evidence From Malaysia

    Directory of Open Access Journals (Sweden)

    Mohd Shahidan Shaari

    2016-01-01

    Full Text Available The study aims to examine the effects of oil price and exchange rate on unemployment in Malaysia. The empirical analysis commence by analyzing the time series property of data. The Johansen VAR-based co-integration technique was applied to examine the long run relationship between exchange rate, oil price and unemployment and found the long run relationship does exist. The vector error correction model was performed to check the short run dynamics and found that the short run dynamics are influenced by the estimated long run equilibrium. Granger causality was done and found that oil price does not affect unemployment but exchange rate has an influence on unemployment. Therefore, putting the exchange rate under control should be implemented to control unemployment.

  8. The effect of the correlation and exchange interactions on the electronic and magnetic properties of the hexagonal NiS using the onsite exact exchange/hybrid functionals

    Science.gov (United States)

    Reggad, A.; Lardjani, R.; Baghdad, R.; Bouhafs, B.

    2017-12-01

    We have performed ab initio calculations using the onsite exact exchange/hybrid functionals within the density functional theory to study the effect of the correlation and exchange interactions on the structural, electronic and magnetic properties of the hexagonal nickel sulphide (NiS) by varying the Fock exchange parameter value. The Perdew- Burke- Ernzerhof (PBE) calculation shows that the non magnetic state is the most stable, but the application of the onsite exact exchange/hybrid functionals for the correlated d electrons leads to get the anti-ferromagnetic AFM I state the most stable which is consistent with the experimental results. To get the semiconductor state we should use a α parameter value more than 0.05 which represents 5% of the Fock exchange. The α parameter has a big effect on the unit cell volume but there is a little effect on the c/a ratio. The magnetic moment and band gap are widely influenced by the exchange and correlation interactions. We have also investigated the effect of the lattice parameters on the magnetic and electronic properties.

  9. Quantum Anomalous Hall Effect in Graphene from Rashba and Exchange Effects

    OpenAIRE

    Qiao, Zhenhua; Yang, Shengyuan A.; Feng, Wanxiang; Tse, Wang-Kong; Ding, Jun; Yao, Yugui; Wang, Jian; Niu, Qian

    2010-01-01

    We investigate the possibility of realizing quantum anomalous Hall effect in graphene. We show that a bulk energy gap can be opened in the presence of both Rashba spin-orbit coupling and an exchange field. We calculate the Berry curvature distribution and find a non-zero Chern number for the valence bands and demonstrate the existence of gapless edge states. Inspired by this finding, we also study, by first principles method, a concrete example of graphene with Fe atoms adsorbed on top, obtai...

  10. Quantum anomalous Hall effect in graphene from Rashba and exchange effects

    Science.gov (United States)

    Qiao, Zhenhua; Yang, Shengyuan A.; Feng, Wanxiang; Tse, Wang-Kong; Ding, Jun; Yao, Yugui; Wang, Jian; Niu, Qian

    2010-10-01

    We investigate the possibility of realizing quantum anomalous Hall effect in graphene. We show that a bulk energy gap can be opened in the presence of both Rashba spin-orbit coupling and an exchange field. We calculate the Berry curvature distribution and find a nonzero Chern number for the valence bands and demonstrate the existence of gapless edge states. Inspired by this finding, we also study, by first-principles method, a concrete example of graphene with Fe atoms adsorbed on top, obtaining the same result.

  11. The Effects of Training Contingency Awareness During Attention Bias Modification on Learning and Stress Reactivity.

    Science.gov (United States)

    Lazarov, Amit; Abend, Rany; Seidner, Shiran; Pine, Daniel S; Bar-Haim, Yair

    2017-09-01

    Current attention bias modification (ABM) procedures are designed to implicitly train attention away from threatening stimuli with the hope of reducing stress reactivity and anxiety symptoms. However, the mechanisms underlying effective ABM delivery are not well understood, with awareness of the training contingency suggested as one possible factor contributing to ABM efficacy. Here, 45 high-anxious participants were trained to divert attention away from threat in two ABM sessions. They were randomly assigned to one of three training protocols: an implicit protocol, comprising two standard implicit ABM training sessions; an explicit protocol, comprising two sessions with explicit instruction as to the attention training contingency; and an implicit-explicit protocol, in which participants were not informed of the training contingency in the first ABM session and informed of it at the start of the second session. We examined learning processes and stress reactivity following a stress-induction task. Results indicate that relative to implicit instructions, explicit instructions led to stronger learning during the first training session. Following rest, the explicit and implicit groups exhibited consolidation-related improvement in performance, whereas no such improvement was noted for the implicit-explicit group. Finally, although stress reactivity was reduced after training, contingency awareness did not yield a differential effect on stress reactivity measured using both self-reports and skin conductance, within and across sessions. These results suggest that explicit ABM administration leads to greater initial learning during the training protocol while not differing from standard implicit administration in terms of off-line learning and stress reactivity. Copyright © 2017. Published by Elsevier Ltd.

  12. The effects of juvenile stress on anxiety, cognitive bias and decision making in adulthood: a rat model.

    Directory of Open Access Journals (Sweden)

    Nichola M Brydges

    Full Text Available Stress experienced in childhood is associated with an increased risk of developing psychiatric disorders in adulthood. These disorders are particularly characterized by disturbances to emotional and cognitive processes, which are not currently fully modeled in animals. Assays of cognitive bias have recently been used with animals to give an indication of their emotional/cognitive state. We used a cognitive bias test, alongside a traditional measure of anxiety (elevated plus maze, to investigate the effects of juvenile stress (JS on adulthood behaviour using a rodent model. During the cognitive bias test, animals were trained to discriminate between two reward bowls based on a stimulus (rough/smooth sandpaper encountered before they reached the bowls. One stimulus (e.g. rough was associated with a lower value reward than the other (e.g. smooth. Once rats were trained, their cognitive bias was explored through the presentation of an ambiguous stimulus (intermediate grade sandpaper: a rat was classed as optimistic if it chose the bowl ordinarily associated with the high value reward. JS animals were lighter than controls, exhibited increased anxiety-like behaviour in the elevated plus maze and were more optimistic in the cognitive bias test. This increased optimism may represent an optimal foraging strategy for these underweight animals. JS animals were also faster than controls to make a decision when presented with an ambiguous stimulus, suggesting altered decision making. These results demonstrate that stress in the juvenile phase can increase anxiety-like behaviour and alter cognitive bias and decision making in adulthood in a rat model.

  13. Investigating Uncertainty in Predicting Carbon Dynamics in North American Biomes: Putting Support-Effect Bias in Perspective

    Science.gov (United States)

    Dungan, Jennifer L.; Brass, Jim (Technical Monitor)

    2001-01-01

    A fundamental strategy in NASA's Earth Observing System's (EOS) monitoring of vegetation and its contribution to the global carbon cycle is to rely on deterministic, process-based ecosystem models to make predictions of carbon flux over large regions. These models are parameterized (that is, the input variables are derived) using remotely sensed images such as those from the Moderate Resolution Imaging Spectroradiometer (MODIS), ground measurements and interpolated maps. Since early applications of these models, investigators have noted that results depend partly on the spatial support of the input variables. In general, the larger the support of the input data, the greater the chance that the effects of important components of the ecosystem will be averaged out. A review of previous work shows that using large supports can cause either positive or negative bias in carbon flux predictions. To put the magnitude and direction of these biases in perspective, we must quantify the range of uncertainty on our best measurements of carbon-related variables made on equivalent areas. In other words, support-effect bias should be placed in the context of prediction uncertainty from other sources. If the range of uncertainty at the smallest support is less than the support-effect bias, more research emphasis should probably be placed on support sizes that are intermediate between those of field measurements and MODIS. If the uncertainty range at the smallest support is larger than the support-effect bias, the accuracy of MODIS-based predictions will be difficult to quantify and more emphasis should be placed on field-scale characterization and sampling. This talk will describe methods to address these issues using a field measurement campaign in North America and "upscaling" using geostatistical estimation and simulation.

  14. Effectiveness of attentional bias modification and cognitive behavioral therapy on the reduction of pain intensity in patients with chronic pain

    Directory of Open Access Journals (Sweden)

    Fateme Babai

    2016-08-01

    Full Text Available The aim of the study was to determine the effectiveness of Attentional Bias Modification (ABM and Cognitive Behavioral Therapy (CBT on the reduction of pain intensityin patients with chronic pain. This study was a quasiexperimental pretest-posttest design with control group. All patients who referred to physiotherapy clinics for pain during 2015 were participated in the study. They completed the Brief Pain Inventory-short form (BPI-SF for assessing severity of pain. Attentional bias was evaluated using computerized Dot-Probe task. The patients with chronic pain were screened by diagnostic criteria of DSM-V; neurologic diagnosis, and interview. 36 people were selected and randomly divided to three groups computer-based ABM, CBT, and control (12 cases in each group. Group A was trained in 8 sessions-each 15 minutes with the modified computerized Dot-Probe task for attentional bias modification. Group B was trained in 11 sessions-each 45 minutes with CBT program of Turk and Ferry for the chronic pain treatment. And Placebo program was administered for group C in which they completed 8 classic DotProbe sessions. In the end, for the posttest (T2 the participants were tested to identify the changes in biased attention to the emotional stimuli using classing Dot-Probe tasks, and BPI questionnaire to evaluate the changes of severity of pain. Data were analyzed using one-way variance analysis(ANOVA. On the BPI-SF, CBT more reduced the pain intensitythan computer-based ABM.In addition ABM treatment is more effective in reduction of attentional bias.Both of treatments are effective but CBT is more effective than ABM in reduction of pain intensity.

  15. Econometric Analysis of Determinants of Real Effective Exchange Rate in Nigeria (1960-2015

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    Ibrahim Waheed

    2016-06-01

    Full Text Available This study investigates the determinants of real effective exchange rate in Nigeria for the period between 1960 and 2015 using the vector error correction mechanism to separate long run from the short run fundamentals. The findings from the regression estimates revealed that; terms of trade, openness of the economy, net capital inflow and total government expenditure were the major long run determinants of real effective exchange rate in the country while variables such as; broad money supply (M2, nominal effective exchange rate, structural adjustment program dummy, June 12 crisis and change to civil rule dummies were revealed as the major short run determinants of exchange rate in Nigeria between 1960 and 2015. The study concludes by recommending that since the major variable of terms of trade (crude oil price is out of the government control, the effect of shocks due to the fluctuations of crude oil price can be minimized by shifting the economy from a mono-product nation and diversify the economy to increase productive capacity. Also, the change to civil rule dummy used in the study revealed that the system has not been friendly with the country’s real effective exchange rate, thus needing to review the system and bringing out all negative activities there in to ensure Nigeria’s currency appreciation. Guided openness is also suggested to avert the danger that unguided trade liberalization may bring into the country.

  16. Exchange bias in (1 1 0)-orientated Bi{sub 0.9}La{sub 0.1}FeO{sub 3}/La{sub 0.5}Ca{sub 0.5}MnO{sub 3} films

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, J.L.; Gao, R.L.; Gao, W.W.; Shen, B.G. [Beijing National Laboratory for Condensed Matter Physics and the Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Sun, J.R., E-mail: jrsun@aphy.iphy.ac.cn [Beijing National Laboratory for Condensed Matter Physics and the Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China)

    2012-07-15

    We performed a systematic study on the exchange bias in (1 1 0)-orientated Bi{sub 0.9}La{sub 0.1}FeO{sub 3}/La{sub 0.5}Ca{sub 0.5}MnO{sub 3} (BLFO/LCMO) heterostructure with a fixed BLFO film thickness of 600 nm and different LCMO layers ranging from t=0 to 30 nm. The LCMO is found to be weakly ferromagnetic, with the Curie temperature descending from {approx}225 K to 0 as the layer thickness decreases from 30 nm to 3 nm. The main magnetic contributions come from the BLFO film, and the areal magnetization ratio is 1:0.07 for t=5 nm and 1:0.82 for t=30 nm for BLFO to LCMO at the temperature of 5 K. Further experiments show the presence of significant exchange bias, and it is, at the temperature of 10 K, {approx}40 Oe for t=0 and {approx}260 Oe for t=30 nm. The exchange bias reduces dramatically upon warming and disappears above the blocking temperature of the spin-glasslike behavior observed in the samples. The possible origin for exchange bias is discussed.

  17. Magnetization switching behavior with competing anisotropies in epitaxial Co3FeN /MnN exchange-coupled bilayers

    Science.gov (United States)

    Hajiri, T.; Yoshida, T.; Jaiswal, S.; Filianina, M.; Borie, B.; Ando, H.; Asano, H.; Zabel, H.; Kläui, M.

    2016-11-01

    We report unusual magnetization switching processes and angular-dependent exchange bias effects in fully epitaxial Co3FeN /MnN bilayers, where magnetocrystalline anisotropy and exchange coupling compete, probed by longitudinal and transverse magneto-optic Kerr effect (MOKE) magnetometry. The MOKE loops show multistep jumps corresponding to the nucleation and propagation of 90∘ domain walls in as-grown bilayers. By inducing exchange coupling, we confirm changes of the magnetization switching process due to the unidirectional anisotropy field of the exchange coupling. Taking into account the experimentally obtained values of the fourfold magnetocrystalline anisotropy, the unidirectional anisotropy field, the exchange-coupling constant, and the uniaxial anisotropy including its direction, the calculated angular-dependent exchange bias reproduces the experimental results. These results demonstrate the essential role of the competition between magnetocrystalline anisotropy and exchange coupling for understanding and tailoring exchange-coupling phenomena usable for engineering switching in fully epitaxial bilayers made of tailored materials.

  18. Effect of bias condition on heavy ion radiation in bipolar junction transistors

    Science.gov (United States)

    Liu, Chao-Ming; Li, Xing-Ji; Geng, Hong-Bin; Yang, De-Zhuang; He, Shi-Yu

    2012-08-01

    The characteristic degradations in a silicon NPN bipolar junction transistor (BJT) of 3DG142 type are examined under irradiation with 40-MeV chlorine (Cl) ions under forward, grounded, and reverse bias conditions, respectively. Different electrical parameters are in-situ measured during the exposure under each bias condition. From the experimental data, a larger variation of base current (IB) is observed after irradiation at a given value of base-emitter voltage (VBE), while the collector current is slightly affected by irradiation at a given VBE. The gain degradation is affected mostly by the behaviour of the base current. From the experimental data, the variation of current gain in the case of forward bias is much smaller than that in the other conditions. Moreover, for 3DG142 BJT, the current gain degradation in the case of reverse bias is more severe than that in the grounded case at low fluence, while at high fluence, the gain degradation in the reverse bias case becomes smaller than that in the grounded case.

  19. Balassa-Samuelson Effect in Won/Dollar and Won/Yen Exchange Rates

    Directory of Open Access Journals (Sweden)

    Donghwan Oh

    2010-06-01

    Full Text Available This paper examines, using various models including a non-linear one, that the Balassa-Samuelson (BS effect can account for the persistence of deviations from PPP in the long-run movements of won/dollar and won/yen real exchange rates. In test for PPP hypothesis that incorporates the BS effect, using the generalized Johansen' cointegration method, it is found that a cointegration relationship exists between each of won/dollar and won/yen real exchange rate and the productivity variables of two countries. And in test for PPP hypothesis that incorporates other fundamentals such as cumulative current account balance, foreign exchange reserve, terms of trade as well as productivity differentials, using a behavioral equilibrium exchange rate approach, it is found that a cointegration relationship exists between each of won/dollar and won/yen real exchange rate and all of these fundamentals. However, the plus sign of the estimated coefficient of the productivity differentials variable, which means that domestic productivity improvement produces increase in each of won/dollar and won/yen real exchange rate is not coincident with the result that the BS effect expects theoretically. Finally, in test for PPP hypothesis that incorporates the BS effect, using a non-linear STAR model, it is found that the adjustment process in case of won/dollar real exchange rate from the long-run equilibrium level can be adequately explained by a non-linear LSTAR model. But, the evidence of diagnostic statistics, which shows the existence of autocorrelation of the residuals in most of lags, might suggest the inadequacy of LSTAR model specification.

  20. The Body Mass Index-Mortality Link across the Life Course: Two Selection Biases and Their Effects.

    Science.gov (United States)

    Zheng, Hui; Dirlam, Jonathan

    2016-01-01

    In this study, we investigated two selection biases that may affect the obesity-mortality link over the life course: mortality selection and healthy participant effects. If these selection mechanisms are stronger among obese adults than among non-obese adults, they may contribute to the weakening obesity-mortality link over the life course. We used data from the National Health and Nutrition Examination Survey 1988-2010 with linked mortality files from 1988-2011. We employed weighted Cox models to test and adjust for these two selection biases. We also used complementary log-log models, adjusted for a normal distribution of frailty, to test for mortality selection effects; accelerated failure-time models to mitigate the mortality selection effect; and ordinary least squares regression to test for healthy participant effects. The link between class II/III obesity and mortality weakens at older ages. We did not find evidence for significant mortality selection or healthy participant effects. Also, even if the healthy participant effects were stronger among obese adults, they are not strong enough to produce a weakening association between obesity and morbidity at higher ages at the time of the survey. Therefore, neither of these selection biases explains the diminishing effect of class II/III obesity on mortality over the life course.

  1. The effect of selection bias in studies of fads and fashions.

    Directory of Open Access Journals (Sweden)

    Jerker Denrell

    Full Text Available Most studies of fashion and fads focus on objects and practices that once were popular. We argue that limiting the sample to such trajectories generates a selection bias that obscures the underlying process and generates biased estimates. Through simulations and the analysis of a data set that has previously not been used to analyze the rise and fall of cultural practices, the New York Times text archive, we show that studying a whole range of cultural objects, both popular and less popular, is essential for understanding the drivers of popularity. In particular, we show that estimates of statistical models of the drivers of popularity will be biased if researchers use only trajectories of those practices that once were popular.

  2. The effect of selection bias in studies of fads and fashions.

    Science.gov (United States)

    Denrell, Jerker; Kovács, Balázs

    2015-01-01

    Most studies of fashion and fads focus on objects and practices that once were popular. We argue that limiting the sample to such trajectories generates a selection bias that obscures the underlying process and generates biased estimates. Through simulations and the analysis of a data set that has previously not been used to analyze the rise and fall of cultural practices, the New York Times text archive, we show that studying a whole range of cultural objects, both popular and less popular, is essential for understanding the drivers of popularity. In particular, we show that estimates of statistical models of the drivers of popularity will be biased if researchers use only trajectories of those practices that once were popular.

  3. Predicting intergroup bias: the interactive effects of implicit theory and social identity.

    Science.gov (United States)

    Hong, Ying-yi; Coleman, Jill; Chan, Gloria; Wong, Rosanna Y M; Chiu, Chi-yue; Hansen, Ian G; Lee, Sau-lai; Tong, Yuk-yue; Fu, Ho-ying

    2004-08-01

    This research sought to integrate the implicit theory approach and the social identity approach to understanding biases in intergroup judgment. The authors hypothesized that a belief in fixed human character would be associated with negative bias and prejudice against a maligned group regardless of the perceiver's social identity. By contrast, a belief in malleable human character would allow the perceiver's social identity to guide intergroup perception, such that a common ingroup identity that includes the maligned group would be associated with less negative bias and prejudice against the maligned group than would an exclusive identity. To test these hypotheses, a correlational study was conducted in the context of the Hong Kong 1997 political transition to examine Hong Kong Chinese's perceptions of Chinese Mainlanders, and an experimental study was conducted in the United States to examine Asian Americans' perception of African Americans. Results from both studies supported the authors' predictions.

  4. Effects of DC bias on magnetic performance of high grades grain-oriented silicon steels

    Science.gov (United States)

    Ma, Guang; Cheng, Ling; Lu, Licheng; Yang, Fuyao; Chen, Xin; Zhu, Chengzhi

    2017-03-01

    When high voltage direct current (HVDC) transmission adopting mono-polar ground return operation mode or unbalanced bipolar operation mode, the invasion of DC current into neutral point of alternating current (AC) transformer will cause core saturation, temperature increasing, and vibration acceleration. Based on the MPG-200D soft magnetic measurement system, the influence of DC bias on magnetic performance of 0.23 mm and 0.27 mm series (P1.7=0.70-1.05 W/kg, B8>1.89 T) grain-oriented (GO) silicon steels under condition of AC / DC hybrid excitation were systematically realized in this paper. For the high magnetic induction GO steels (core losses are the same), greater thickness can lead to stronger ability of resisting DC bias, and the reasons for it were analyzed. Finally, the magnetostriction and A-weighted magnetostriction velocity level of GO steel under DC biased magnetization were researched.

  5. The mechanism of asymmetric pipe-wall thinning behind an orifice by combined effect of swirling flow and orifice bias

    Energy Technology Data Exchange (ETDEWEB)

    Fujisawa, Nobuyuki [Visualization Research Center, Niigata University, 8050, Ikarashi 2-Nocho, Nishi-ku, Niigata 950-2181 (Japan); Yamagata, Takayuki, E-mail: yamagata@eng.niigata-u.ac.jp [Visualization Research Center, Niigata University, 8050, Ikarashi 2-Nocho, Nishi-ku, Niigata 950-2181 (Japan); Kanno, Syo; Ito, Akihiro [Graduate School of Science and Technology, Niigata University, 8050, Ikarashi 2-Nocho, Nishi-ku, Niigata 950-2181 (Japan); Takano, Tsuyoshi [Visualization Research Center, Niigata University, 8050, Ikarashi 2-Nocho, Nishi-ku, Niigata 950-2181 (Japan)

    2012-11-15

    Highlights: Black-Right-Pointing-Pointer The mechanism of asymmetric pipe-wall thinning is clarified. Black-Right-Pointing-Pointer Flow fields and pipe-wall thinning are evaluated experimentally for orifice flow. Black-Right-Pointing-Pointer We demonstrate combined effects of swirling flows and orifice biases on flows. Black-Right-Pointing-Pointer Strong swirling flows and orifice biases cause an asymmetric pipe-wall thinning. - Abstract: In this paper, the mechanism of asymmetric pipe-wall thinning caused by flow accelerated corrosion behind an orifice in a circular pipe is studied by measuring the velocity fields by PIV and the mass transfer coefficients by naphthalene sublimation method. An attention is placed on the variations of the velocity fields and mass flux under the combined effect of swirling flow and orifice bias. The present measurement indicates that the flow field become asymmetric about the pipe axis due to the influence of swirling flow at large swirl intensity S = 0.3 in combination with an allowable orifice bias as small as 0.8% of a pipe diameter of standard steel pipes. This flow phenomenon results in the asymmetric distribution of mass transfer coefficient along the pipe-wall behind the orifice. The position of enhanced mass transfer occurs on the shorter orifice side near the orifice due to the flow reattachment, while the flow on the longer orifice side remains the same distribution of mass transfer coefficient as the case without swirl. These variations of velocity field and mass transfer data suggest that the mechanism of asymmetric pipe-wall thinning behind the orifice is due to the combined effect of swirling flow and orifice bias.

  6. Brillouin/Raman compensation of the Kerr-effect-induced bias in a nonlinear ring laser gyroscope.

    Science.gov (United States)

    Luo, Zhang; Yuan, Xiaodong; Zhu, Zhihong; Liu, Ken; Ye, Weimin; Zeng, Chun; Ji, Jiarong

    2013-04-01

    In this Letter, the beat frequency at rest of a ring laser gyroscope with nonlinear effects is discussed in detail. Even without an additional intensity-stabilizing system, the random nullshift bias induced by the Kerr effect is compensated by the phase shift associated with the stimulated Brillouin/Raman scattering. And the nonlinear stimulated scattering also serves as the gain mechanism of the gyroscope. And thus the influence of the fluctuation of the injected pump intensity on the beat frequency is eliminated.

  7. An Exploration Based Cognitive Bias Test for Mice: Effects of Handling Method and Stereotypic Behaviour.

    Directory of Open Access Journals (Sweden)

    Janja Novak

    Full Text Available Behavioural tests to assess affective states are widely used in human research and have recently been extended to animals. These tests assume that affective state influences cognitive processing, and that animals in a negative affective state interpret ambiguous information as expecting a negative outcome (displaying a negative cognitive bias. Most of these tests however, require long discrimination training. The aim of the study was to validate an exploration based cognitive bias test, using two different handling methods, as previous studies have shown that standard tail handling of mice increases physiological and behavioural measures of anxiety compared to cupped handling. Therefore, we hypothesised that tail handled mice would display a negative cognitive bias. We handled 28 female CD-1 mice for 16 weeks using either tail handling or cupped handling. The mice were then trained in an eight arm radial maze, where two adjacent arms predicted a positive outcome (darkness and food, while the two opposite arms predicted a negative outcome (no food, white noise and light. After six days of training, the mice were also given access to the four previously unavailable intermediate ambiguous arms of the radial maze and tested for cognitive bias. We were unable to validate this test, as mice from both handling groups displayed a similar pattern of exploration. Furthermore, we examined whether maze exploration is affected by the expression of stereotypic behaviour in the home cage. Mice with higher levels of stereotypic behaviour spent more time in positive arms and avoided ambiguous arms, displaying a negative cognitive bias. While this test needs further validation, our results indicate that it may allow the assessment of affective state in mice with minimal training-a major confound in current cognitive bias paradigms.

  8. The Frontal View of the Nose: Lighting Effects and Photographic Bias.

    Science.gov (United States)

    Strub, Benedikt; Mende, Konrad; Meuli-Simmen, Claudia; Bessler, Stephan

    2015-07-01

    Most aesthetic rhinosurgeons rely on proper photographic documentation of the nose using several different views. The frontal view is probably the most important, but it is also the most demanding. In the frontal view, delicate, 3-dimensional (3D) anatomic structures require special photographic skills. Lighting is crucial for detail rendition and 3D reproduction of the nose, and for apparent photographic bias. We compared the quality of reproduction and photographic bias with different symmetric and asymmetric lighting in common clinical practice described in the literature. The photographs were compared for anatomic reproduction, shadowing, 3-dimensionality, and apparent changes of nasal shape (bias). Symmetric lighting did not satisfy the demands of the rhinosurgeons because of marginal 3-dimensionality, reduced detail rendition, or photographic bias. Strongly asymmetric lighting altered the nasal shape adversely for bias depending on the side of illumination, but led to very good 3-dimensionality. Slightly asymmetric lighting demonstrated the best results for detail rendition and 3-dimensionality. Classic symmetric quarter light is a practicable lighting technique with limitations in the rendition of detail and 3-dimensionality. Slightly asymmetric lighting offered a perfect compromise, with substantially improved detail rendition and 3-dimensionality. Strongly asymmetric lighting may lead to photographic bias depending on the side of illumination. Frontal documentation of the nose with asymmetric lighting should, therefore, always be performed in duplicate, with asymmetric lighting from the right side and from the left side, to prevent misleading interpretations. © 2015 The American Society for Aesthetic Plastic Surgery, Inc. Reprints and permission: journals.permissions@oup.com.

  9. SEMICONDUCTOR DEVICES Effect of collector bias current on the linearity of common-emitter BJT amplifiers

    Science.gov (United States)

    Kun, Li; Jianfu, Teng; Xiuwei, Xuan

    2010-12-01

    Using a Volterra series, an explicit formula is derived for the connection between input 3rd-order intercept point and collector bias current (ICQ) in a common-emitter bipolar junction transistor amplifier. The analysis indicates that the larger ICQ is, the more linear the amplifier is. Furthermore, this has been verified by experiment. This study also integrates a method called dynamic bias current for expanding the dynamic range of an LNA (low noise amplifier) as an application of the analysis result obtained above. IMR3 (3rd-order intermodulation rate) is applied to evaluate the LNA's performance with and without adopting this method in this study.

  10. Nonlinear excitation kinetics of biased quantum wells. Coherent dynamical screening effect

    DEFF Research Database (Denmark)

    Turchinovich, Dmitry; Jepsen, Peter Uhd

    2006-01-01

    In this paper we describe a strongly nonlinear process of ultrafast photoexcitation of a biased quantum well. This process is governed by coherent dynamical screening, where the instantaneously polarized photoexcited carriers screen initial bias field. This results in a dynamic modification...... of the bandstructure of the quantum well, which is totally coherent with the temporal intensity distribution of the excitation laser pulse. We developed a time-resolved theoretical model of coherent dynamical screening, which predicts interesting fundamental consequences, such as nonlinear absorption and ultra...

  11. Acceleration bias in visually perceived velocity change and effects of Parkinson's bradykinesia.

    Science.gov (United States)

    Beudel, Martijn; de Geus, Crista M; Leenders, Klaus L; de Jong, Bauke M

    2013-10-02

    In Parkinson's disease (PD), basal ganglia dysfunction leads to disturbed sensorimotor integration and associated timing. Previous functional MRI and behavioural PD studies on timing indicated a specific striatal contribution to assessing spatial displacement in velocity estimation. In this computation, cerebral processing time implies demarcating discrete intervals of spatial change. To quantify these putative intervals, the threshold of perceived velocity change of a moving ball was assessed in healthy volunteers and PD patients. After rebound from the upper side of a monitor screen, the ball's velocity increased or decreased with variable magnitudes while participants indicated whether they noticed this velocity change. The threshold for detecting velocity change was around 0.014 rad/s in both groups. Moreover, velocity was perceived as equal when the ball decelerated; unchanged velocity was perceived as acceleration. This shift was 0.009 rad/s for healthy volunteers and 0.007 rad/s for PD patients, and was negatively correlated with the severity of bradykinesia. As the trajectory length before and after velocity change was the same, velocity change was also expressed as a change in stimulus duration (relative to 1 s initial duration). The temporal equivalent of a threshold for perceived velocity change was around 75 ms in both groups. The perceptual 'acceleration bias' is in line with the 'flash-lag' effect: the position of a moving stimulus is projected ahead compared with a stationary landmark. Such an extrapolation over adjacent past and predicted locations enables 'real-time' visuomotor control, notwithstanding delays because of intrinsic cerebral processing time. In PD, such impaired perceptual feed-forward processing may result in slow movements.

  12. Experimental modification of interpretation bias about animal fear in young children: effects on cognition, avoidance behavior, anxiety vulnerability, and physiological responding.

    Science.gov (United States)

    Lester, Kathryn J; Field, Andy P; Muris, Peter

    2011-01-01

    This study investigated the effects of experimentally modifying interpretation biases for children's cognitions, avoidance behavior, anxiety vulnerability, and physiological responding. Sixty-seven children (6-11 years) were randomly assigned to receive a positive or negative interpretation bias modification procedure to induce interpretation biases toward or away from threat about ambiguous situations involving Australian marsupials. Children rapidly learned to select outcomes of ambiguous situations, which were congruent with their assigned condition. Furthermore, following positive modification, children's threat biases about novel ambiguous situations significantly decreased, whereas threat biases significantly increased after negative modification. In response to a stress-evoking behavioral avoidance test, positive modification attenuated behavioral avoidance compared to negative modification. However, no significant effects of bias modification on anxiety vulnerability or physiological responses to this stress-evoking Behavioral Avoidance Task were observed.

  13. Exchange rate effect on stock returns in the East European emerging markets: A quantile regression approach

    Directory of Open Access Journals (Sweden)

    Živkov Dejan

    2014-01-01

    Full Text Available This paper investigates relationship between returns of stock prices and exchange rate changes in four East European emerging markets (Serbia, Poland, Hungary and Czech Republic using weekly data from January 2003 to June 2013. Two theories explain the connection in the economic literature - flow-oriented and portfolio-balance models, without a finite and conclusive answer on which one is predominant. Considering our relatively large sample period which also includes world crisis outbreak, the used empirical data have been compromised by structural breaks and heterogeneous unconditional distribution. To avoid parameter bias and wrong conclusions, authors used four auto-regressive distributed lag ADL(2,2 models assessed with quantile regression method, robust to non-normality problems. The results indicate that relationship between these variables is in accordance with portfolio-balance models in three out of four analyzed countries.

  14. Trends in Effective Diffusion Coefficients for Ion-Exchange Strengthening of Soda-Lime-Silicate Glasses

    Directory of Open Access Journals (Sweden)

    Stefan Karlsson

    2017-04-01

    Full Text Available Monovalent cations enable efficient ion-exchange processes due to their high mobility in silicate glasses. Numerous properties can be modified in this way, e.g., mechanical, optical, electrical, or chemical performance. In particular, alkali cation exchange has received significant attention, primarily with respect to introducing compressive stress into the surface region of a glass, which increases mechanical durability. However, most of the present applications rely on specifically tailored matrix compositions in which the cation mobility is enhanced. This largely excludes the major area of soda-lime-silicates (SLS such as are commodity in almost all large-scale applications of glasses. Basic understanding of the relations between structural parameters and the effective diffusion coefficients may help to improve ion-exchanged SLS glass products, on the one hand in terms of obtainable strength and on the other in terms of cost. In the present paper, we discuss the trends in the effective diffusion coefficients when exchanging Na+ for various monovalent cations (K+, Cu+, Ag+, Rb+, and Cs+ by drawing relations to physicochemical properties. Correlations of effective diffusion coefficients were found for the bond dissociation energy and the electronic cation polarizability, indicating that localization and rupture of bonds are of importance for the ion-exchange rate.

  15. Trends in Effective Diffusion Coefficients for Ion-exchange Strengthening of Soda Lime Silicate Glasses

    Science.gov (United States)

    Karlsson, Stefan; Wondraczek, Lothar; Ali, Sharafat; Jonson, Bo

    2017-04-01

    Monovalent cations enable efficient ion exchange processes due to their high mobility in silicate glasses. Numerous properties can be modified in this way, e.g., mechanical, optical, electrical or chemical performance. In particular, alkali cation exchange has received significant attention, primarily with respect to introducing compressive stress into the surface region of a glass, which increases mechanical durability. However, most of the present applications rely on specifically tailored matrix compositions in which the cation mobility is enhanced. This largely excludes the major area of soda lime silicates (SLS) such as are commodity in almost all large-scale applications of glasses. Basic understanding of the relations between structural parameters and the effective diffusion coefficients may help to improve ion-exchanged SLS glass products, on the one hand in terms of obtainable strength and on the other in terms of cost. In the present paper, we discuss the trends in the effective diffusion coefficients when exchanging Na+ for various monovalent cations (K+, Cu+, Ag+, Rb+ and Cs+) by drawing relations to physico-chemical properties. Correlations of effective diffusion coefficients were found for the bond dissociation energy and the electronic cation polarizability, indicating that localization and rupture of bonds are of importance for the ion exchange rate.

  16. The effects of a low-permeability lens on hyporheic exchange intensity

    Science.gov (United States)

    Su, X. R.; Shu, L. C.; Zhao, G.; Wang, M. M.; Lu, C. P.; Yao, C. C.

    2017-08-01

    Hyporheic exchange induced by dunes is a key process controlling water fluxes and biogeochemical process in river network, which has gained significant advances. Owing to the limitation of instrumental detection at small spatial scales, previous studies mainly focused on dune-induced hyporheic exchange in homogeneous systems and the impacts of a low-permeability lens on hyporheic process is still unknown. 2-D laboratory flume experiments were conducted in this study to quantitatively analyze the response mechanism of hyporheic exchange to the spatial locations of a low-permeability lens. Results indicated that the lens has hindering effects on the hyporheic exchange process and when located at the center of the horizontal location, the hindering effects were the weakest. The effect weakens when the vertical locations of the lens getting deeper. With the lens moving from the locations closer to the upstream face to that closer to the downstream face of the dunes, or moving from a shallow depth to a deep depth, the flowing path of hyporheic exchange become less influenced by the lens and the area of HZ is getting larger.

  17. Laterality effects in the spinning dancer illusion: The viewing-from-above bias is only part of the story.

    Science.gov (United States)

    Lucafò, Chiara; Marzoli, Daniele; Prete, Giulia; Tommasi, Luca

    2016-11-01

    The 'silhouette illusion', representing the silhouette of a female dancer pirouetting about her vertical axis, is a bistable stimulus created by Japanese web designer Nobuyuki Kayahara. Although the dancer can be perceived as spinning either clockwise or counterclockwise, the clockwise rotation is usually preferred. Troje and McAdam (i-Perception, 2010, 1, 143) showed that this clockwise bias can be attributed to the tendency to assume a viewpoint from above rather than from below, given that the dancer is portrayed from a vantage point that is not perpendicular to the axis of rotation. Here, we tested whether another possible factor contributing to the observers' interpretation of this bistable stimulus might be the tendency to perceive movements of the right rather than the left foot. We confirmed both the viewing-from-above bias and our hypothesis. The bias to perceive movements of the right leg might be a generalization to lower limbs of a perceptual frequency effect already observed for upper limbs. Such a perceptual and attentional bias towards the right hand/foot could account for the greater ability to predict the outcome of sport actions when observing right- rather than left-limbed movements, and thus the left-handers' and left-footers' advantage observed in a variety of interactive sports. © 2015 The British Psychological Society.

  18. Differential effects of approach bias and eating style on unhealthy food consumption in overweight and normal weight women.

    Science.gov (United States)

    Kakoschke, Naomi; Kemps, Eva; Tiggemann, Marika

    2017-11-01

    The current study aimed to examine the effects of approach bias for unhealthy food and trait eating style on consumption of unhealthy food in overweight and normal weight individuals. Participants were 245 undergraduate women aged 17 - 26 years. They completed an Approach-Avoidance Task, the Dutch Eating Behaviour Questionnaire (to assess restrained, emotional, and external eating), and a taste test to measure consumption of unhealthy food. An external eating style predicted increased consumption of unhealthy food. Among overweight participants, external and emotional eating style individually moderated the relationship between approach bias for unhealthy food and subsequent consumption. Specifically, approach bias was positively related to consumption in high external and emotional eaters, but negatively related to consumption in low emotional eaters. These interactions were not observed among normal weight participants. Practically, the results suggest that overweight individuals who are external or emotional eaters may benefit from interventions that aim to modify approach bias towards unhealthy food cues to reduce problematic eating behaviour.

  19. Atomoxetine effects on attentional bias to drug-related cues in cocaine dependent individuals

    NARCIS (Netherlands)

    Passamonti, L. (Luca); M. Luijten (Maartje); Ziauddeen, H.; I. Coyle-Gilchrist (Ian); Rittman, T.; Brain, S.A.E.; Regenthal, R.; I.H.A. Franken (Ingmar); Sahakian, B.J.; Bullmore, E.T.; Robbins, T.W.; Ersche, K.D.

    2017-01-01

    textabstractRationale: Biased attention towards drug-related cues and reduced inhibitory control over the regulation of drug-intake characterize drug addiction. The noradrenaline system has been critically implicated in both attentional and response inhibitory processes and is directly affected by

  20. Atomoxetine effects on attentional bias to drug-related cues in cocaine dependent individuals

    NARCIS (Netherlands)

    Passamonti, L.; Luijten, M.; Ziauddeen, H.; Coyle-Gilchrist, I.T.S.; Rittman, T.; Brain, S.A.E.; Regenthal, R.; Franken, I.H.A.; Sahakian, B.J.; Bullmore, E.T.; Robbins, T.W.; Ersche, K.D.

    2017-01-01

    Rationale: Biased attention towards drug-related cues and reduced inhibitory control over the regulation of drug-intake characterize drug addiction. The noradrenaline system has been critically implicated in both attentional and response inhibitory processes and is directly affected by drugs such as

  1. The Biasing Effects of Labels on Direct Observation by Preservice Teachers

    Science.gov (United States)

    Allday, R. Allan; Duhon, Gary J.; Blackburn-Ellis, Sarah; Van Dycke, Jamie L.

    2011-01-01

    Observational bias can significantly affect results attained through observation. This study focused on 122 preservice teacher educators who conducted a structured observation, using momentary time sampling procedures with 10-second intervals, to measure student on-task and off-task behaviors. The experimental variable altered was the…

  2. Information bias in contingent valuation: effects of personal relevance, quality of information, and motivational orientation

    Science.gov (United States)

    Icek Ajzen; Thomas C. Brown; Lori H. Rosenthal

    1996-01-01

    A laboratory experiment examined the potential for information bias in contingent valuation (CV). Consistent with the view that information about a public or private good can function as a persuasive communication, willingness to pay (WTP) was found to increase with the quality of arguments used to describe the good, especially under conditions of high personal...

  3. Prolonged recruitment efforts in health surveys: effects on response, costs, and potential bias.

    Science.gov (United States)

    Holle, Rolf; Hochadel, Matthias; Reitmeir, Peter; Meisinger, Christa; Wichmann, H Erich

    2006-11-01

    In health surveys, considerable effort and expense are invested to achieve a high response proportion and thereby to reduce selection bias. We investigated the interrelation of recruitment efforts and expense with potential nonresponse bias based on data from a large health survey. In a population-based health survey, a stratified sample of 6640 residents of the Augsburg (Germany) region was selected, of whom 4261 attended the main study between October 1999 and April 2001. A short telephone interview yielded additional information on nearly half of the nonparticipants. All recruitment contacts were documented, and expenses were estimated on the basis of unit costs. Different recruitment strategies were modeled retrospectively. We compared their cost savings as well as their influence on the response proportion and on prevalence estimates. The distribution of total contacting cost per individual was highly skewed with 50% of the total sum spent on 17% of the sample. Late responders showed many similarities with nonresponders; both included a higher percentage of people with impaired health and with greater behavioral health risks. We were able to identify recruitment strategies that may save up to 25% of the recruitment costs without significant shift in the parameter estimates. Data collected in the short nonresponder interview proved to be important to correct for possible nonresponse bias. In general, prolonged recruitment efforts lead to a larger and more representative sample but at increasing marginal costs. Specific cost-saving recruitment strategies that do not enhance response bias can be suggested. Interviews of nonresponders are also useful.

  4. Effects of reverse bias on the efficiency of dye solar cells

    CSIR Research Space (South Africa)

    Le Roux, Lukas J

    2009-08-01

    Full Text Available cell that was subjected to 4.5 V reverse bias was irreversibly damaged. The UV-vis spectra showed a blue shift (higher energy), the Raman showed no peak at 1713 cm-1 (which indicates the absence of free carboxylate groups) and the FT-IR showed...

  5. Effect of affect on social cost bias in social anxiety disorder

    NARCIS (Netherlands)

    Bitran, S.; Hofmann, S.G.

    2010-01-01

    The cognitive model of social anxiety disorder (SAD) assumes that cognitive biases are important maintaining factors of the disorder. Research and theory have highlighted the impact of cognitive self-regulatory processes on affect, but have not sufficiently focused on the influence of affect on

  6. A Rational Analysis of the Effects of Memory Biases on Serial Reproduction

    Science.gov (United States)

    Xu, Jing; Griffiths, Thomas L.

    2010-01-01

    Many human interactions involve pieces of information being passed from one person to another, raising the question of how this process of information transmission is affected by the cognitive capacities of the agents involved. Bartlett (1932) explored the influence of memory biases on the "serial reproduction" of information, in which one…

  7. The Effect of Colour and Size on Attentional Bias to Alcohol-Related Pictures

    Science.gov (United States)

    Harrison, Neil R.; McCann, Amy

    2014-01-01

    Attentional bias plays an important role in the development and maintenance of alcohol addiction, and has often been measured with a visual probe task, where reaction times are compared for probes replacing either a substance-related cue or a neutral cue. Systematic low-level differences between image classes are a potential cause of low internal…

  8. Controllable substrate bias voltages effectively tailoring nanocomposite Nb–B–Al–O film properties

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Na [Energy & Materials Engineering Centre, College of Physics and Materials Science, Tianjin Normal University, Tianjin 300387 (China); Dong, Lei, E-mail: dlei0008@126.com [Energy & Materials Engineering Centre, College of Physics and Materials Science, Tianjin Normal University, Tianjin 300387 (China); Li, Xifei, E-mail: xfli2011@hotmail.com [Energy & Materials Engineering Centre, College of Physics and Materials Science, Tianjin Normal University, Tianjin 300387 (China); Li, Dejun, E-mail: dejunli@mail.tjnu.edu.cn [Energy & Materials Engineering Centre, College of Physics and Materials Science, Tianjin Normal University, Tianjin 300387 (China); Wan, Rongxin; Gu, Hanqing [Tianjin Institute of Urological Surgery, Tianjin Medical University, Tianjin 300070 (China)

    2015-07-05

    Graphical abstract: Nb–B–Al–O nanocomposite films were synthesized by multi-target magnetron co-sputtering. Different substrate bias voltages can influence properties of obtained nanocomposite films. The maximum hardness at −160 V bias also showed the better thermostability and oxidation resistance properties at 300 °C in the air. More significantly, the TEM images and XRD results of the nanocomposite films at different bias obviously interpreted the change in mechanical properties, which provides a powerful inspiration to better understand the strategies to improve these films’ engineering applications. - Highlights: • The films were prepared by multi-target magnetron co-sputtering. • The structure and properties were influenced obviously by substrate bias voltages. • Maximum hardness and modulus at −160 V were higher than monolithic films. • The film at −160 V also showed better thermostability and oxidation resistance. - Abstract: The nanocomposite Nb–B–Al–O films based on NbB{sub 2} and Al{sub 2}O{sub 3} were successfully deposited on Si substrate via multi-target magnetron co-sputtering method. The influences of substrate bias on microstructure, mechanical, thermostability and oxidation resistance properties of the films were investigated in detail. Transmission Electron Microscopy (TEM), X-ray diffractometry (XRD), Scanning Electron Microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were performed to study the structural properties such as crystallinity, binding energy and chemical composition of as-prepared films. The combination of monocrystalline NbB{sub 2} (1 0 0) texture and Al{sub 2}O{sub 3} (1 1 3) crystal plane affected the mechanical properties of the films at different bias voltages. The best crystallization appeared at −160 V. The maximum hardness (23.4 GPa) and elastic modulus (274.5 GPa) of the films were obtained at optimal substrate bias of −160 V. The hardest film at −160 V also showed the better

  9. The effect of leader-member exchange, trust, supervisor support on organizational citizenship behavior in nurses.

    Science.gov (United States)

    Chen, Chun-Hsi Vivian; Wang, Shih-Jon; Chang, Wei-Chieh; Hu, Chin-Shin

    2008-12-01

    This study examined from a social exchange perspective the influence of leader-member exchange (LMX) on the trust of subordinates in their supervisors as well as their perception of support received from their medical organization supervisors and the subsequent effect of such on organizational citizenship behavior (OCB) in subordinates. Two hundred valid supervisor-subordinate (head nurses-nurses) dyads from 3 medical centers and 3 regional hospitals took part in this study, which found that the quality of leader-member exchange affects nurse trust in their supervisors as well as their perception of supervisor support, which consequently promotes OCB on the part of nurses. Findings imply that a higher level of LMX can enhance nurses' commitment, significantly reduce turnover, and promote their OCB, resulting in greater organizational effectiveness.

  10. The Moderating Effect of Leader-member Exchange on the Job Insecurity-Organizational Commitment Relationship

    Science.gov (United States)

    Hu, Sanman; Zuo, Bin

    Job insecurity has become an important issue for society and organizations in the last decades due to uncertain economic conditions, global competition, and the advancement of information technology. As job insecurity have detrimental consequences for employees and organizations, it is vital to identify variables that could buffer against the negative effects of job insecurity. In this study, we examined the moderating effect of Leader-member exchange on the relation between job insecurity and organizational commitment. Data collected from 314 employees indicated that the negative relationship between qualitative insecurity and affective commitment was alleviated as Leader-member exchange increased. Furthermore, the positive relation between quantitative insecurity and continuance commitment decreased as Leader-member exchange increased.

  11. A Comparison of Cognitive Bias Modification for Interpretation and Computerized Cognitive Behavior Therapy: Effects on Anxiety, Depression, Attentional Control, and Interpretive Bias

    Science.gov (United States)

    Bowler, Jennifer O.; Mackintosh, Bundy; Dunn, Barnaby D.; Mathews, Andrew; Dalgleish, Tim; Hoppitt, Laura

    2012-01-01

    Objective: Computerized cognitive behavioral therapy (cCBT) and cognitive bias modification for interpretation (CBM-I) both have demonstrated efficacy in alleviating social anxiety, but how they compare with each other has not been investigated. The present study tested the prediction that both interventions would reduce anxiety relative to a…

  12. The Effects of Exchange Rate Market in the Economy of Kosova

    Directory of Open Access Journals (Sweden)

    Argjira Kadrijaj Dushi

    2014-08-01

    Full Text Available From a conducted centralized economy, Kosovo‟s economy became a free market after 1999. This made the economy of Kosovo to face a lot of challenges. One of them and still a topic not studied among Kosovo economists is the Kosovo currency. Kosovo is not yet a member of EU but since 2002 is using euro currency. What are the advantages and disadvantages of using euro currency for the economy of Kosovo? This was not questionable in 2002, because Kosovo was still in the first steps of creating a financial system. But, today the importance of exchange rates in economy is crucial as a result of the internationalization of businesses, the constant increase of world trade with the national one and the rapid change of money transfer technology. In this research, through quantitative and qualitative methods is analyzed the development of exchange rate market in Kosovo and the effects of exchange rates movements in Kosovo economy, its GDP and inflation and in consumer price index. The research will point out the importance of exchange rates as an interest variable for some of Kosovo businesses and its effects in the transition economy of Kosovo which has not been exposed to exchange rates risk on macroeconomic variables.

  13. Promoting medical competencies through international exchange programs: benefits on communication and effective doctor-patient relationships.

    Science.gov (United States)

    Jacobs, Fabian; Stegmann, Karsten; Siebeck, Matthias

    2014-03-04

    Universities are increasingly organizing international exchange programs to meet the requirements of growing globalisation in the field of health care. Analyses based on the programs' fundamental theoretical background are needed to confirm the learning value for participants. This study investigated the extent of sociocultural learning in an exchange program and how sociocultural learning affects the acquisition of domain-specific competencies. Sociocultural learning theories were applied to study the learning effect for German medical students from the LMU Munich, Munich, Germany, of participation in the medical exchange program with Jimma University, Jimma, Ethiopia. First, we performed a qualitative study consisting of interviews with five of the first program participants. The results were used to develop a questionnaire for the subsequent, quantitative study, in which 29 program participants and 23 matched controls performed self-assessments of competencies as defined in the Tuning Project for Health Professionals. The two interrelated studies were combined to answer three different research questions. The participants rated their competence significantly higher than the control group in the fields of doctor-patient relationships and communication in a medical context. Participant responses in the two interrelated studies supported the link between the findings and the suggested theoretical background. Overall, we found that the exchange program affected the areas of doctor-patient relationships and effective communication in a medical context. Vygotsky's sociocultural learning theory contributed to explaining the learning mechanisms of the exchange program.

  14. Promoting medical competencies through international exchange programs: benefits on communication and effective doctor-patient relationships

    Science.gov (United States)

    2014-01-01

    Background Universities are increasingly organizing international exchange programs to meet the requirements of growing globalisation in the field of health care. Analyses based on the programs’ fundamental theoretical background are needed to confirm the learning value for participants. This study investigated the extent of sociocultural learning in an exchange program and how sociocultural learning affects the acquisition of domain-specific competencies. Methods Sociocultural learning theories were applied to study the learning effect for German medical students from the LMU Munich, Munich, Germany, of participation in the medical exchange program with Jimma University, Jimma, Ethiopia. First, we performed a qualitative study consisting of interviews with five of the first program participants. The results were used to develop a questionnaire for the subsequent, quantitative study, in which 29 program participants and 23 matched controls performed self-assessments of competencies as defined in the Tuning Project for Health Professionals. The two interrelated studies were combined to answer three different research questions. Results The participants rated their competence significantly higher than the control group in the fields of doctor-patient relationships and communication in a medical context. Participant responses in the two interrelated studies supported the link between the findings and the suggested theoretical background. Conclusion Overall, we found that the exchange program affected the areas of doctor-patient relationships and effective communication in a medical context. Vygotsky’s sociocultural learning theory contributed to explaining the learning mechanisms of the exchange program. PMID:24589133

  15. Effect of length biased sampling of unobserved sojourn times on the survival distribution when disease is screen detected.

    Science.gov (United States)

    Kafadar, Karen; Prorok, Philip C

    2009-07-20

    Data can arise as a length-biased sample rather than as a random sample; e.g. a sample of patients in hospitals or of network cable lines (experimental units with longer stays or longer lines have greater likelihoods of being sampled). The distribution arising from a single length-biased sampling (LBS) time has been derived (e.g. (The Statistical Analysis of Discrete Time Events. Oxford Press: London, 1972)) and applies when the observed outcome relates to the random variable subjected to LBS. Zelen (Breast Cancer: Trends in Research and Treatment. Raven Press: New York, 1976; 287-301) noted that cases of disease detected from a screening program likewise form a length-biased sample among all cases, since longer sojourn times afford greater likelihoods of being screen detected. In contrast to the samples on hospital stays and cable lines, however, the length-biased sojourns (preclinical durations) cannot be observed, although their subsequent clinical durations (survival times) are. This article quantifies the effect of LBS of the sojourn times (or pre-clinical durations) on the distribution of the observed clinical durations when cases undergo periodic screening for the early detection of disease. We show that, when preclinical and clinical durations are positively correlated, the mean, median, and quartiles of the distribution of the clinical duration from screen-detected cases can be substantially inflated-even in the absence of any benefit on survival from the screening procedure. Screening studies that report mean survival time need to take account of the fact that, even in the absence of any real benefit, the mean survival among cases in the screen-detected group will be longer than that among interval cases or among cases that arise in the control arm, above and beyond lead time bias, simply by virtue of the LBS phenomenon

  16. The effect of sex-biased dispersal on opposite-sexed spatial genetic structure and inbreeding risk.

    Science.gov (United States)

    Blyton, Michaela D J; Banks, Sam C; Peakall, Rod

    2015-04-01

    Natal sex-biased dispersal has long been thought to reduce the risk of inbreeding by spatially separating opposite-sexed kin. Yet, comprehensive and quantitative evaluations of this hypothesis are lacking. In this study, we quantified the effectiveness of sex-biased dispersal as an inbreeding avoidance strategy by combining spatially explicit simulations and empirical data. We quantified the extent of kin clustering by measuring the degree of spatial autocorrelation among opposite-sexed individuals (FM structure). This allowed us to systematically explore how the extent of sex-biased dispersal, generational overlap, and mate searching distance, influenced both kin clustering, and the resulting inbreeding in the absence of complementary inbreeding avoidance strategies. Simulations revealed that when sex-biased dispersal was limited, positive FM genetic structure developed quickly and increased as the mate searching distance decreased or as generational overlap increased. Interestingly, complete long-range sex-biased dispersal did not prevent the development of FM genetic structure when generations overlapped. We found a very strong correlation between FM genetic structure and both FIS under random mating, and pedigree-based measures of inbreeding. Thus, we show that the detection of FM genetic structure can be a strong indicator of inbreeding risk. Empirical data for two species with different life history strategies yielded patterns congruent with our simulations. Our study illustrates a new application of spatial genetic autocorrelation analysis that offers a framework for quantifying the risk of inbreeding that is easily extendable to other species. Furthermore, our findings provide other researchers with a context for interpreting observed patterns of opposite-sexed spatial genetic structure. © 2015 John Wiley & Sons Ltd.

  17. Correlation theory of crystal field and anisotropic exchange effects

    DEFF Research Database (Denmark)

    Lindgård, Per-Anker

    1985-01-01

    A general theory for including correlation effects in static and dynamic properties is presented in terms of Raccah or Stevens operators. It is explicitly developed for general crystal fields and anisotropic interactions and systems with several sublattices, like the rare earth compounds....... The theory gives explicitly a temperature dependent renormalization of both the crystal field and the interactions, and a damping of the excitations and in addition a central park component. The general theory is illustrated by a discussion of the singlet-doublet system. The correlation effects...

  18. The effect of Arabian Sea optical properties on SST biases and the South Asian summer monsoon in a coupled GCM

    Energy Technology Data Exchange (ETDEWEB)

    Turner, A.G.; Joshi, M.; Robertson, E.S.; Woolnough, S.J. [University of Reading, NCAS-Climate, Walker Institute for Climate System Research, Department of Meteorology, Reading (United Kingdom)

    2012-08-15

    This study examines the effect of seasonally varying chlorophyll on the climate of the Arabian Sea and South Asian monsoon. The effect of such seasonality on the radiative properties of the upper ocean is often a missing process in coupled general circulation models and its large amplitude in the region makes it a pertinent choice for study to determine any impact on systematic biases in the mean and seasonality of the Arabian Sea. In this study we examine the effects of incorporating a seasonal cycle in chlorophyll due to phytoplankton blooms in the UK Met Office coupled atmosphere-ocean GCM HadCM3. This is achieved by performing experiments in which the optical properties of water in the Arabian Sea - a key signal of the semi-annual cycle of phytoplankton blooms in the region - are calculated from a chlorophyll climatology derived from Sea-viewing Wide Field-of-View Sensor (SeaWiFS) data. The SeaWiFS chlorophyll is prescribed in annual mean and seasonally-varying experiments. In response to the chlorophyll bloom in late spring, biases in mixed layer depth are reduced by up to 50% and the surface is warmed, leading to increases in monsoon rainfall during the onset period. However when the monsoons are fully established in boreal winter and summer and there are strong surface winds and a deep mixed layer, biases in the mixed layer depth are reduced but the surface undergoes cooling. The seasonality of the response of SST to chlorophyll is found to depend on the relative depth of the mixed layer to that of the anomalous penetration depth of solar fluxes. Thus the inclusion of the effects of chlorophyll on radiative properties of the upper ocean acts to reduce biases in mixed layer depth and increase seasonality in SST. (orig.)

  19. Solder void position and size effects on electro thermal behaviour of MOSFET transistors in forward bias conditions

    OpenAIRE

    TRAN, S.H.; Dupont, Laurent; Khatir, Zoubir

    2014-01-01

    ESREF-25th European Symposium on Reliability of Electron Devices, Failure Physics and Analysis, BERLIN, ALLEMAGNE, 29-/09/2014 - 02/10/2014; This research aims to enhance the understanding on position and size effects on the electro thermal behaviour of low voltage power MOSFET transistors in forward bias condition. The numerical simulations are based on a fractional design of experiments (DoE). The performance of a finite elements model is discussed by comparing thermal and electrical measur...

  20. Effect of different Rates of Wood Ash on Exchangeable Aluminum ...

    African Journals Online (AJOL)

    Response of soybean grown on acidic soil to wood ash applied at 0, 2, 4, 6, and 8 t ha-1 was studied in two field experiments in 2003 and 2004 at Umudike in the rainforest zone of Southeast Nigeria. Treatments were fitted in a randomized complete block design (RCBD) replicated three times. Effect of treatments on some ...

  1. Investigation of cholesterol bias due to a matrix effect of external quality assurance samples: how true is your cholesterol method?

    Science.gov (United States)

    Pretorius, Carel J; Klingberg, Sandra; Johnson, Leslie; Park, Rodney; Wilgen, Urs; Ungerer, Jacobus P J

    2012-11-01

    Comparability of cholesterol measurement is clinically required and external quality assurance (EQA) programmes are important to verify the trueness of routine methods. We developed a gas chromatography-isotope dilution mass spectrometry (GC-IDMS) total cholesterol assay to investigate the cause of a suspected matrix-related negative bias with the Beckman Coulter enzymatic method discovered in an EQA programme. The GC-IDMS method was calibrated with certified reference material and verified against a secondary reference method. Bias between the GC-IDMS and Beckman Coulter methods was estimated according to Clinical and Laboratory Standards Institute (CLSI) protocol EP9-A2 with 40 clinical samples. At clinically important decision levels, no significant bias was demonstrated on patients' samples (all results within a ±3% limit). A matrix effect confined to the EQA material that affected the Beckman Coulter total cholesterol method was confirmed. The GC-IDMS method is suitable as a higher order total cholesterol method in a routine clinical laboratory. Matrix effects defeat the objectives of EQA schemes by preventing the verification of trueness. Given the importance of obtaining a true cholesterol result without systematic error, we recommend that EQA material without matrix effects should be used.

  2. Influence of trial duration on the bias of the estimated treatment effect in clinical trials when individual heterogeneity is ignored.

    Science.gov (United States)

    Cécilia-Joseph, Elsa; Auvert, Bertran; Broët, Philippe; Moreau, Thierry

    2015-05-01

    In randomized clinical trials where the times to event of two treatment groups are compared under a proportional hazards assumption, it has been established that omitting prognostic factors from the model entails an underestimation of the hazards ratio. Heterogeneity due to unobserved covariates in cancer patient populations is a concern since genomic investigations have revealed molecular and clinical heterogeneity in these populations. In HIV prevention trials, heterogeneity is unavoidable and has been shown to decrease the treatment effect over time. This article assesses the influence of trial duration on the bias of the estimated hazards ratio resulting from omitting covariates from the Cox analysis. The true model is defined by including an unobserved random frailty term in the individual hazard that reflects the omitted covariate. Three frailty distributions are investigated: gamma, log-normal, and binary, and the asymptotic bias of the hazards ratio estimator is calculated. We show that the attenuation of the treatment effect resulting from unobserved heterogeneity strongly increases with trial duration, especially for continuous frailties that are likely to reflect omitted covariates, as they are often encountered in practice. The possibility of interpreting the long-term decrease in treatment effects as a bias induced by heterogeneity and trial duration is illustrated by a trial in oncology where adjuvant chemotherapy in stage 1B NSCLC was investigated. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Effect of collector bias current on the linearity of common-emitter BJT amplifiers

    Energy Technology Data Exchange (ETDEWEB)

    Li Kun; Teng Jianfu [School of Electronic and Information Engineering, Tianjin University of Technology, Tianjin 300384 (China); Xuan Xiuwei, E-mail: likun@tju.edu.cn [School of Electronic and Information Engineering, Tianjin University, Tianjin 300072 (China)

    2010-12-15

    Using a Volterra series, an explicit formula is derived for the connection between input 3rd-order intercept point and collector bias current (I{sub CQ}) in a common-emitter bipolar junction transistor amplifier. The analysis indicates that the larger I{sub CQ} is, the more linear the amplifier is. Furthermore, this has been verified by experiment. This study also integrates a method called dynamic bias current for expanding the dynamic range of an LNA (low noise amplifier) as an application of the analysis result obtained above. IMR3 (3rd-order intermodulation rate) is applied to evaluate the LNA's performance with and without adopting this method in this study. (semiconductor devices)

  4. The effect of question order on evaluations of test performance: Can the bias dissolve?

    Science.gov (United States)

    Bard, Gabriele; Weinstein, Yana

    2017-10-01

    Question difficulty order has been shown to affect students' global postdictions of test performance. We attempted to eliminate the bias by letting participants experience the question order manipulation multiple times. In all three experiments, participants answered general knowledge questions and self-evaluated their performance. In Experiment 1, participants studied questions and answers in easy-hard or hard-easy question order prior to taking a test in the same order. In Experiment 2, participants took the same test twice in the opposite question order (easy-hard then hard-easy, or hard-easy then easy-hard). In Experiment 3, participants took two different tests in the opposite question order (easy-hard then hard-easy, or hard-easy then easy-hard). In all three experiments, we were unable to eliminate the bias, which suggests that repeated exposure is insufficient to overcome a strong initial anchor.

  5. Effects of Voltage-Bias Annealing on Metastable Defect Populations in CIGS and CZTSe Solar Cells

    Energy Technology Data Exchange (ETDEWEB)

    Harvey, Steven P.; Johnston, Steve; Teeter, Glenn

    2016-11-21

    We report on voltage-bias annealing (VBA) experiments performed on CIGS and CZTSe solar cells. In these experiments, completed devices were annealed at moderate temperatures and subsequently quenched with continuously applied voltage bias. These treatments resulted in substantial reversible changes in device characteristics. Photovoltaic (PV) conversion efficiency of the CIGS device varied from below 3% to above 15%, with corresponding changes in CIGS hole density from ~1014 cm-3 to ~1017 cm-3. In the CZTSe device, open-circuit voltage varied from 289 meV to 446 meV, caused by an approximately factor of fifty change in the CZTSe hole density. We interpret these findings in terms of reversible changes to the metastable point-defect populations that control key properties in these materials. Implications for optimization of PV materials and connections to long-term stability of PV devices are discussed.

  6. Rovno Amber Ant Assamblage: Bias toward Arboreal Strata or Sampling Effect?

    Directory of Open Access Journals (Sweden)

    Perkovsky E. E.

    2016-06-01

    Full Text Available In 2015 B. Guenard with co-authors indicated that the Rovno amber ant assemblage, as described by G. Dlussky and A. Rasnitsyn (2009, showed modest support for a bias towards arboreal origin comparing the Baltic and Bitterfeld assemblages, although it is not clear whether this reflects a sampling error or a signal of real deviation. Since 2009, the Rovno ant collection has now grown more than twice in volume which makes possible to check if the above inference about the essentially arboreal character of the assemblage is real or due to a sampling error. The comparison provided suggests in favour of the latter reason for the bias revealed by B. Guenard and co-authors. The new and larger data on the Rovno assemblage show that the share of non-arboreal ants is now well comparable with those concerning the Baltic and Bitterfeld assemblages. This holds true for the both total assemblages and subassemblages of worker ants only.

  7. Experimental study on the effects of the number of heat exchanger modules on thermal characteristics in a premixed combustion system

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Byeonghun; Lee, Chang-Eon [Inha University, Incheon (Korea, Republic of); Kum, Sung Min [Halla University, Wonju (Korea, Republic of); Lee, Seungro [Chonbuk National University, Jeonju (Korea, Republic of)

    2016-01-15

    The effects of the number of heat exchanger modules on thermal characteristics were experimentally studied in a premixed combustion system with a cross-flow staggered-tube heat exchanger. The various heat exchanger modules, from 4 to 8, combined with a premixed burner were tested to investigate the performance of the heat exchanger through the surface area of the heat exchanger at various equivalence ratios. Additionally, the performance of the heat exchanger was analyzed by applying entropy generation theory to the heat exchanger system. As a result, although the heat transfer rate increases with the increase of the equivalence ratio, the NOx and CO concentrations also increase due to the increasing flame temperature. In addition, the entropy generation increases with an increase of the equivalence ratio. Furthermore, the heat transfer rate and the effectiveness are increased with the increase of the number of the heat exchanger modules. Also, the effectiveness is sharply increased when the number of the heat exchanger modules is increased from 4 to 5. Consequently, the optimal operating conditions regarding pollutant emission, effectiveness and entropy generation in this experimental range are 0.85 for the equivalence ratio and 8 for the number of heat exchanger modules.

  8. Effect of alcohol on risk of coronary heart disease and stroke: causality, bias, or a bit of both?

    Directory of Open Access Journals (Sweden)

    Jonathan R Emberson

    2006-09-01

    Full Text Available Jonathan R Emberson, Derrick A BennettClinical Trial Service Unit, Richard Doll Building, University of Oxford, Oxford, UKAbstract: Epidemiological studies of middle-aged populations generally find the relationship between alcohol intake and the risk of coronary heart disease (CHD and stroke to be either U- or J-shaped. This review describes the extent that these relationships are likely to be causal, and the extent that they may be due to specific methodological weaknesses in epidemiological studies. The consistency in the vascular benefit associated with moderate drinking (compared with non-drinking observed across different studies, together with the existence of credible biological pathways, strongly suggests that at least some of this benefit is real. However, because of biases introduced by: choice of reference categories; reverse causality bias; variations in alcohol intake over time; and confounding, some of it is likely to be an artefact. For heavy drinking, different study biases have the potential to act in opposing directions, and as such, the true effects of heavy drinking on vascular risk are uncertain. However, because of the known harmful effects of heavy drinking on non-vascular mortality, the problem is an academic one. Studies of the effects of alcohol consumption on health outcomes should recognise the methodological biases they are likely to face, and design, analyse and interpret their studies accordingly. While regular moderate alcohol consumption during middle-age probably does reduce vascular risk, care should be taken when making general recommendations about safe levels of alcohol intake. In particular, it is likely that any promotion of alcohol for health reasons would do substantially more harm than good. Keywords: alcohol, coronary heart disease, stroke

  9. Nanofiltration: ion exchange system for effective surfactant removal from water solutions

    Directory of Open Access Journals (Sweden)

    I. Kowalska

    2014-12-01

    Full Text Available A system combining nanofiltration and ion exchange for highly effective separation of anionic surfactant from water solutions was proposed. The subjects of the study were nanofiltration polyethersulfone membranes and ion-exchange resins differing in type and structure. The quality of the treated solution was affected by numerous parameters, such as quality of the feed solution, membrane cut-off, resin type, dose and the solution contact time with the resin. A properly designed purification system made it possible to reduce the concentration of anionic surfactant below 1 mg L-1 from feed solutions containing surfactant in concentrations above the CMC value.

  10. The Effects of Oil Price Changes And Exchange Rate Volatility On Unemployment: Evidence From Malaysia

    OpenAIRE

    Mohd Shahidan Shaari; Nor Ermawati Hussain; Hafizah Abdul Rahim

    2013-01-01

    The study aims to examine the effects of oil price and exchange rate on unemployment in Malaysia. The empirical analysis commence by analyzing the time series property of data. The Johansen VAR-based co-integration technique was applied to examine the long run relationship between exchange rate, oil price and unemployment and found the long run relationship does exist. The vector error correction model was performed to check the short run dynamics and found that the short run dynamics are inf...

  11. Leader - Member Exchange in Different Organizational Cultures and Effects to Organizational Burnout

    Directory of Open Access Journals (Sweden)

    Erdem Kırkbeşoğlu

    2014-06-01

    Full Text Available The purpose of this study is to examine the effect of leader- member exchange to burnout syndrome in different organizational cultures. Sample of the study is constituted by 183 participants who work in life insurance companies which represent organic organizational culture and non-life insurance companies which represent mechanical organizational culture. As a result of regression and correlation analysis, it is determined that leader-member exchange in organic organizational culture affects organizational culture negatively and in higher level compared to mechanical organizational cultures.

  12. Nursing keypal exchange: an effective acculturation strategy to prepare for an international experience.

    Science.gov (United States)

    Maas-Garcia, Lillian

    2009-03-01

    The aim of this paper is to provide arguments for incorporating keypal exchanges prior to an international exchange. At Rotterdam University of Applied Science in the Netherlands, the Master's in Advanced Nursing Practice Program/Nurse Practitioner Program focuses on the role of the nurse practitioner and places emphasis on internationalization within the curriculum. The students must complete a short-term immersion experience to the USA during the 2-year programme. An effective teaching strategy to acculturate students to the American culture, healthcare and nursing system differences was utilized by incorporating keypal communication within the international preparation programme.

  13. Are the Intraday Effects of Central Bank Intervention on Exchange Rate Spreads Asymmetric and State Dependent?

    DEFF Research Database (Denmark)

    Fatum, Rasmus; Pedersen, Jesper; Sørensen, Peter Norman

    This paper investigates the intraday effects of unannounced foreign exchange intervention on bid-ask exchange rate spreads using official intraday intervention data provided by the Danish central bank. Our starting point is a simple theoretical model of the bid-ask spread which we use to formulate...... testable hypotheses regarding how unannounced intervention purchases and intervention sales influence the market asymmetrically. To test these hypotheses we estimate weighted least squares (WLS) time-series models of the intraday bid-ask spread. Our main result is that intervention purchases and sales both...

  14. Introduction to Unconscious Bias

    Science.gov (United States)

    Schmelz, Joan T.

    2010-05-01

    We all have biases, and we are (for the most part) unaware of them. In general, men and women BOTH unconsciously devalue the contributions of women. This can have a detrimental effect on grant proposals, job applications, and performance reviews. Sociology is way ahead of astronomy in these studies. When evaluating identical application packages, male and female University psychology professors preferred 2:1 to hire "Brian” over "Karen” as an assistant professor. When evaluating a more experienced record (at the point of promotion to tenure), reservations were expressed four times more often when the name was female. This unconscious bias has a repeated negative effect on Karen's career. This talk will introduce the concept of unconscious bias and also give recommendations on how to address it using an example for a faculty search committee. The process of eliminating unconscious bias begins with awareness, then moves to policy and practice, and ends with accountability.

  15. The exchange interaction effects on magnetic properties of the nanostructured CoPt particles

    Energy Technology Data Exchange (ETDEWEB)

    Komogortsev, S.V., E-mail: komogor@iph.krasn.ru [Kirensky Institute of Physics, SB RAS, 660036 Krasnoyarsk (Russian Federation); Iskhakov, R.S. [Kirensky Institute of Physics, SB RAS, 660036 Krasnoyarsk (Russian Federation); Zimin, A.A. [Siberian Federal University, 660041 Krasnoyarsk (Russian Federation); Filatov, E.Yu.; Korenev, S.V.; Shubin, Yu.V. [Nikolaev Institute of Inorganic Chemistry, SB RAS, 630090 Novosibirsk (Russian Federation); Novosibirsk State University, 630090 Novosibirsk (Russian Federation); Chizhik, N.A. [Siberian Federal University, 660041 Krasnoyarsk (Russian Federation); Yurkin, G.Yu.; Eremin, E.V. [Kirensky Institute of Physics, SB RAS, 660036 Krasnoyarsk (Russian Federation)

    2016-03-01

    Various manifestations of the exchange interaction effects in magnetization curves of the CoPt nanostructured particles are demonstrated and discussed. The inter-grain exchange constant A in the sponge-like agglomerates of crystallites is estimated as A=(7±1) pJ/m from the approach magnetization to saturation curves that is in good agreement with A=(6.6±0.5) pJ/m obtained from Bloch T {sup 3/2} law. The fractal dimensionality of the exchange coupled crystallite system in the porous media of the disordered CoPt alloy d=(2.60±0.18) was estimated from the approach magnetization to saturation curve. Coercive force decreases with temperature as H{sub c}~T {sup 3/2} which is assumed to be a consequence of the magnetic anisotropy energy reduction due to the thermal spin wave excitations in the investigated CoPt particles. - Highlights: • Nanostructured CoPt particles were synthesized and then annealed in He atmosphere. • The structure of the material and magnetization curves were studied. • The maximum on reduced coercivity vs grain size dependence was observed. • The dimensionality d of exchange coupled crystallite system was estimated. • Exchange stiffness constant A was estimated.

  16. The nature of three-body interactions in DFT: Exchange and polarization effects

    Science.gov (United States)

    Hapka, Michał; Rajchel, Łukasz; Modrzejewski, Marcin; Schäffer, Rainer; Chałasiński, Grzegorz; Szcześniak, Małgorzata M.

    2017-08-01

    We propose a physically motivated decomposition of density functional theory (DFT) 3-body nonadditive interaction energies into the exchange and density-deformation (polarization) components. The exchange component represents the effect of the Pauli exclusion in the wave function of the trimer and is found to be challenging for density functional approximations (DFAs). The remaining density-deformation nonadditivity is less dependent upon the DFAs. Numerical demonstration is carried out for rare gas atom trimers, Ar2-HX (X = F, Cl) complexes, and small hydrogen-bonded and van der Waals molecular systems. None of the tested semilocal, hybrid, and range-separated DFAs properly accounts for the nonadditive exchange in dispersion-bonded trimers. By contrast, for hydrogen-bonded systems, range-separated DFAs achieve a qualitative agreement to within 20% of the reference exchange energy. A reliable performance for all systems is obtained only when the monomers interact through the Hartree-Fock potential in the dispersion-free Pauli blockade scheme. Additionally, we identify the nonadditive second-order exchange-dispersion energy as an important but overlooked contribution in force-field-like dispersion corrections. Our results suggest that range-separated functionals do not include this component, although semilocal and global hybrid DFAs appear to imitate it in the short range.

  17. Effects of model chemistry and data biases on stratospheric ozone assimilation

    Directory of Open Access Journals (Sweden)

    L. Coy

    2007-06-01

    Full Text Available The innovations or observation minus forecast (O–F residuals produced by a data assimilation system provide a convenient metric of evaluating global analyses. In this study, O–F statistics from the Global Ozone Assimilation Testing System (GOATS are used to examine how ozone assimilation products and their associated O–F statistics depend on input data biases and ozone photochemistry parameterizations (OPP. All the GOATS results shown are based on a 6-h forecast and analysis cycle using observations from SBUV/2 (Solar Backscatter UltraViolet instrument-2 during September–October 2002. Results show that zonal mean ozone analyses are more independent of observation biases and drifts when using an OPP, while the mean ozone O–Fs are more sensitive to observation drifts when using an OPP. In addition, SD O–Fs (standard deviations are reduced in the upper stratosphere when using an OPP due to a reduction of forecast model noise and to increased covariance between the forecast model and the observations. Experiments that changed the OPP reference state to match the observations by using an "adaptive" OPP scheme reduced the mean ozone O–Fs at the expense of zonal mean ozone analyses being more susceptible to data biases and drifts. Additional experiments showed that the upper boundary of the ozone DAS can affect the quality of the ozone analysis and therefore should be placed well above (at least a scale height the region of interest.

  18. Bias in retrospective assessment of perceived dental treatment effects when using the Oral Health Impact Profile.

    Science.gov (United States)

    Reissmann, Daniel R; Erler, Antje; Hirsch, Christian; Sierwald, Ira; Machuca, Carolina; Schierz, Oliver

    2017-10-23

    Aim of this exploratory study was to investigate whether a retrospective assessment of oral health-related quality of life (OHRQoL) using the Oral Health Impact Profile (OHIP) is susceptible to bias such as implicit theory of change and cognitive dissonance. In this prospective clinical study, a sample of 126 adult patients (age 17-83 years, 49% women) requiring prosthodontic treatment was consecutively recruited. The OHRQoL was assessed using the 49-item OHIP at baseline and at follow-up. Additionally, patients were asked at follow-up to retrospectively rate their oral health status at baseline (retrospective pretest or then-test) and the change in oral health status using a global transition question. Furthermore, patients' ratings of overall oral health and general health were used as validity criteria for the OHRQoL assessments. Response shift was calculated as the difference between the initial and retrospective baseline assessments. Baseline and retrospective pretest did not differ substantially in terms of internal consistency and convergent validity. Response shift was more pronounced when patients perceived a large change in OHRQoL during treatment. Retrospective pretests were more highly correlated with the baseline than with the follow-up assessment. Findings suggest that retrospective assessments of OHRQoL using the OHIP-49 are susceptible to bias. Cognitive dissonance is more likely to appear as a source of bias than implicit theory of change.

  19. Attentional biases to foods: The effects of caloric content and cognitive restraint.

    Science.gov (United States)

    Forestell, Catherine A; Lau, Pia; Gyurovski, Ivo I; Dickter, Cheryl L; Haque, Sabrina S

    2012-12-01

    The goal of the present study was to determine whether female restrained and unrestrained eaters demonstrated differential levels of attentional bias to high calorie foods when they were presented as distractors in a flanker task. This task consisted of four blocks of 68 trials in which three food pictures were briefly presented simultaneously on a computer screen. On each trial a high or low calorie target food was presented in the center of a pair of high or low calorie food flanker pictures and participants' reaction times to answer a basic question about whether they would consume the target food for breakfast were recorded. In Experiment 1, in which all participants were fed a snack prior to engaging in the flanker task, there was no evidence that restrained (n=29) or unrestrained (n=37) eaters had an attentional bias. However, in Experiment 2, when participants completed the flanker task while hungry, restrained eaters (n=27) experienced response conflict only when low calorie targets were flanked by high calorie distractors, whereas unrestrained eaters (n=46) were distracted by high calorie flankers regardless of the caloric content of the target cue. The results from this implicit task indicate that flankers interfere with hungry participants' responses to varying degrees depending on their cognitive restraint. Whether attentional bias to food cues subsequently affects food choices and eating behavior is a topic for further investigation. Published by Elsevier Ltd.

  20. Social-Communicative Effects of the Picture Exchange Communication System (PECS) in Autism Spectrum Disorders

    Science.gov (United States)

    Lerna, Anna; Esposito, Dalila; Conson, Massimiliano; Russo, Luigi; Massagli, Angelo

    2012-01-01

    Background: The Picture Exchange Communication System (PECS) is a common treatment choice for non-verbal children with autism. However, little empirical evidence is available on the usefulness of PECS in treating social-communication impairments in autism. Aims: To test the effects of PECS on social-communicative skills in children with autism,…