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1

Longitudinal Spin Seebeck Effect  

NASA Astrophysics Data System (ADS)

The spin Seebeck effect (SSE) refers to the generation of a spin voltage as a result of a temperature gradient in magnetic materials [1-7]. Here, a spin voltage is a potential for electron spins to drive a nonequilibrium spin current; when a conductor is attached to a magnet with a finite spin voltage, it induces a spin injection into the conductor. The SSE is of crucial importance in spintronics and spin caloritronics, since it enables simple and versatile generation of a spin current from heat. The simplest and most straightforward setup of the SSE is the longitudinal configuration [4], in which a spin current flowing parallel to a temperature gradient is measured via the inverse spin Hall effect (ISHE). The longitudinal SSE device consists of a ferromagnetic or ferrimagnetic insulator (FI, e.g. YIG) covered with a paramagnetic metal (PM, e.g. Pt) film. When a temperature gradient is applied perpendicular to the FI/PM interface, an ISHE-induced voltage is generated in the PM layer. In this talk, we report the observation of the longitudinal SSE in various FI/PM systems and provide evidence that the longitudinal SSE is free from thermoelectric artefact [7], i.e., the anomalous Nernst effect caused by extrinsic magnetic proximity [8]. Then, we discuss the longitudinal SSE from an application point of view [6]. We thank E. Saitoh, S. Maekawa, G. E. W. Bauer, X.-F. Jin, H. Adachi, D. Hou, D. Tian, T. Kikkawa, A. Kirihara, and M. Ishida for their support and valuable discussions. [4pt] [1] K. Uchida et al., Nature 455, 778 (2008).[0pt] [2] K. Uchida et al., Nature Mater. 9, 894 (2010).[0pt] [3] C. M. Jaworski et al., Nature Mater. 9, 898 (2010).[0pt] [4] K. Uchida et al., Appl. Phys. Lett. 97, 172505 (2010).[0pt] [5] K. Uchida et al., Nature Mater. 10, 737 (2011).[0pt] [6] A. Kirihara et al., Nature Mater. 11, 686 (2012).[0pt] [7] T. Kikkawa et al., arXiv:1211.0139 (2012). [0pt] [8] S. Y. Huang et al., Phys. Rev. Lett. 109, 107204 (2012).

Uchida, Ken-Ichi

2013-03-01

2

Theory of the spin Seebeck effect  

NASA Astrophysics Data System (ADS)

The spin Seebeck effect refers to the generation of a spin voltage caused by a temperature gradient in a ferromagnet, which enables the thermal injection of spin currents from the ferromagnet into an attached nonmagnetic metal over a macroscopic scale of several millimeters. The inverse spin Hall effect converts the injected spin current into a transverse charge voltage, thereby producing electromotive force as in the conventional charge Seebeck device. Recent theoretical and experimental efforts have shown that the magnon and phonon degrees of freedom play crucial roles in the spin Seebeck effect. In this paper, we present the theoretical basis for understanding the spin Seebeck effect and briefly discuss other thermal spin effects.

Adachi, Hiroto; Uchida, Ken-ichi; Saitoh, Eiji; Maekawa, Sadamichi

2013-03-01

3

Seebeck effect in magnetic tunnel junctions  

NASA Astrophysics Data System (ADS)

Creating temperature gradients in magnetic nanostructures has resulted in a new research direction, that is, the combination of magneto- and thermoelectric effects. Here, we demonstrate the observation of one important effect of this class: the magneto-Seebeck effect. It is observed when a magnetic configuration changes the charge-based Seebeck coefficient. In particular, the Seebeck coefficient changes during the transition from a parallel to an antiparallel magnetic configuration in a tunnel junction. In this respect, it is the analogue to the tunnelling magnetoresistance. The Seebeck coefficients in parallel and antiparallel configurations are of the order of the voltages known from the charge-Seebeck effect. The size and sign of the effect can be controlled by the composition of the electrodes’ atomic layers adjacent to the barrier and the temperature. The geometric centre of the electronic density of states relative to the Fermi level determines the size of the Seebeck effect. Experimentally, we realized 8.8% magneto-Seebeck effect, which results from a voltage change of about -8.7??V?K-1 from the antiparallel to the parallel direction close to the predicted value of -12.1??V?K-1. In contrast to the spin-Seebeck effect, it can be measured as a voltage change directly without conversion of a spin current.

Walter, Marvin; Walowski, Jakob; Zbarsky, Vladyslav; Münzenberg, Markus; Schäfers, Markus; Ebke, Daniel; Reiss, Günter; Thomas, Andy; Peretzki, Patrick; Seibt, Michael; Moodera, Jagadeesh S.; Czerner, Michael; Bachmann, Michael; Heiliger, Christian

2011-10-01

4

Theory of the spin Seebeck effect.  

PubMed

The spin Seebeck effect refers to the generation of a spin voltage caused by a temperature gradient in a ferromagnet, which enables the thermal injection of spin currents from the ferromagnet into an attached nonmagnetic metal over a macroscopic scale of several millimeters. The inverse spin Hall effect converts the injected spin current into a transverse charge voltage, thereby producing electromotive force as in the conventional charge Seebeck device. Recent theoretical and experimental efforts have shown that the magnon and phonon degrees of freedom play crucial roles in the spin Seebeck effect. In this paper, we present the theoretical basis for understanding the spin Seebeck effect and briefly discuss other thermal spin effects. PMID:23420561

Adachi, Hiroto; Uchida, Ken-ichi; Saitoh, Eiji; Maekawa, Sadamichi

2013-02-19

5

Evidence for a magnetic seebeck effect.  

PubMed

The irreversible thermodynamics of a continuous medium with magnetic dipoles predicts that a temperature gradient in the presence of magnetization waves induces a magnetic induction field, which is the magnetic analog of the Seebeck effect. This thermal gradient modulates the precession and relaxation. The magnetic Seebeck effect implies that magnetization waves propagating in the direction of the temperature gradient and the external magnetic induction field are less attenuated, while magnetization waves propagating in the opposite direction are more attenuated. PMID:24010472

Brechet, Sylvain D; Vetro, Francesco A; Papa, Elisa; Barnes, Stewart E; Ansermet, Jean-Philippe

2013-08-22

6

Spin pumping and spin Seebeck effect  

NASA Astrophysics Data System (ADS)

Utilization of a spin current, a flow of electrons' spins in a solid, is the key technology in spintronics that will allow the achievement of efficient magnetic memories and computing devices. In this technology, generation and detection of spin currents are necessary. Here, we review inverse spin-Hall effect and spin-current-generation phenomena recently discovered both in metals and insulators: inverse spin-Hall effect, spin pumping, and spin Seebeck effect. (1)Spin pumping and spin torque in a Mott insulator system We found that spin pumping and spin torque effects appear also at an interface between Pt and an insulator YIG.. This means that we can connect a spin current carried by conduction electrons and a spin-wave spin current flowing in insulators. We demonstrate electric signal transmission by using these effects and interconversion of the spin currents [1]. (2) Spin Seebeck effect We have observed, by using the inverse spin-Hall effect [2], spin voltage generation from a heat current in a NiFe, named the spin-Seebeck effect [3]. Surprisingly, spin-Seebeck effect was found to appear even in insulators [4], a situation completely different from conventional charge Seebeck effect. The result implies an important role of elementary excitation in solids beside charge in the spin Seebeck effect. In the talk, we review the recent progress of the research on this effect. This research is collaboration with K. Ando, K. Uchida, Y. Kajiwara, S. Maekawa, G. E. W. Bauer, S. Takahashi, and J. Ieda. [4pt] [1] Y. Kajiwara and E. Saitoh et al. Nature 464 (2010) 262. [0pt] [2] E. Saitoh et al., Appl. Phys. Lett. 88 (2006) 182509. [0pt] [3] K. Uchida and E. Saitoh et al., Nature 455 (2008)778. [0pt] [4] K. Uchida and E. Saitoh et al.,Nature materials 9 (2010) 894 - 897.

Saitoh, Eiji

2012-02-01

7

Simple Demonstration of the Seebeck Effect  

ERIC Educational Resources Information Center

In this article we propose a simple and low-cost experimental set-up through which science educators can demonstrate the Seebeck effect using a thermocouple and an instrumentation amplifier. The experiment can be set up and conducted during a 1-hour laboratory session. (Contains 3 tables and 3 figures.)

Molki, Arman

2010-01-01

8

Magnons, Spin Current and Spin Seebeck Effect  

NASA Astrophysics Data System (ADS)

When metals and semiconductors are placed in a temperature gradient, the electric voltage is generated. This mechanism to convert heat into electricity, the so-called Seebeck effect, has attracted much attention recently as the mechanism for utilizing wasted heat energy. [1]. Ferromagnetic insulators are good conductors of spin current, i.e., the flow of electron spins [2]. When they are placed in a temperature gradient, generated are magnons, spin current and the spin voltage [3], i.e., spin accumulation. Once the spin voltage is converted into the electric voltage by inverse spin Hall effect in attached metal films such as Pt, the electric voltage is obtained from heat energy [4-5]. This is called the spin Seebeck effect. Here, we present the linear-response theory of spin Seebeck effect based on the fluctuation-dissipation theorem [6-8] and discuss a variety of the devices. [4pt] [1] S. Maekawa et al, Physics of Transition Metal Oxides (Springer, 2004). [0pt] [2] S. Maekawa: Nature Materials 8, 777 (2009). [0pt] [3] Concept in Spin Electronics, eds. S. Maekawa (Oxford University Press, 2006). [0pt] [4] K. Uchida et al., Nature 455, 778 (2008). [0pt] [5] K. Uchida et al., Nature Materials 9, 894 (2010) [0pt] [6] H. Adachi et al., APL 97, 252506 (2010) and Phys. Rev. B 83, 094410 (2011). [0pt] [7] J. Ohe et al., Phys. Rev. B (2011) [0pt] [8] K. Uchida et al., Appl. Phys. Lett. 97, 104419 (2010).

Maekawa, Sadamichi

2012-02-01

9

Theory of phonon-driven spin Seebeck effect  

NASA Astrophysics Data System (ADS)

Spin Seebeck effect refers to a thermal spin injection occurring over millimeter scales from a ferromagnet into an attached nonmagnetic metal [Uchida et al., Nature 455, 778 (2008)]. We discuss the importance of the phonon-drag process in the spin Seebeck effect. Our theory of phonon-drag spin Seebeck effect [Adachi et al., Appl. Phys. Lett. 97, 252506 (2010)] explains simultaneously the local nature of the spin Seebeck effect [Jaworski et al., Nature Materials 9, 898 (2010); Uchida et al., Nature Materials 10, 737 (2011)] and the signal enhancement at low temperatures [Jaworski et al., Phys. Rev. Lett. 106, 186601 (2011)]. We also discuss the difference between our approach and that developed in Xiao et al., Phys. Rev. B 81, 214418 (2010).

Adachi, Hiroto; Ohe, Jun-Ichiro; Takahashi, Saburo; Maekawa, Sadamichi

2012-02-01

10

Spin-Seebeck Effect in III-V Based Semiconductors  

NASA Astrophysics Data System (ADS)

The spin-Seebeck effect has now been observed in metals^1 (NiFe), semiconductors^2 (GaMnAs), and insulators^3 (YIG). It consists of a thermally generated spin distribution that is phonon driven. Here we extend our measurements of the spin-Seebeck effect to other group III-V based magnetic semiconductors and present measurements of conventional thermomagnetic and galvanomagnetic properties as well as the spin-Seebeck effect. Work supported by the National Science Foundation, NSF-CBET-1133589 1. K. Uchida, et al., Nature 455 778 (2008) 2. C.M. Jaworski et al., Nature Materials 8 898 (2010), Phys. Rev. Lett. 106 186601 (2011) 3. K. Uchida, et al., Nature Materials 8 893 (2010)

Jaworski, Christopher M.; Myers, Roberto C.; Heremans, Joseph P.

2012-02-01

11

Gigantic enhancement of spin Seebeck effect by phonon drag  

NASA Astrophysics Data System (ADS)

We investigate both theoretically and experimentally a gigantic enhancement of the spin Seebeck effect [K. Uchida et al., Nature 455, 778 (2008); C. M. Jaworski et al., Nature Mater. 9, 898 (2010); K. Uchida et al., Nature Mater. 9, 894 (2010)] in a prototypical magnet LaY2Fe5O12 at low temperatures. Our theoretical analysis sheds light on the important role of phonons; the spin Seebeck effect is enormously enhanced by nonequilibrium phonons that drag the low-lying spin excitations. We further argue that this scenario gives a clue to understand the observation of the spin Seebeck effect that is unaccompanied by a global spin current, and predict that the substrate condition affects the observed signal.

Adachi, Hiroto; Uchida, Ken-Ichi; Saitoh, Eiji; Ohe, Jun-Ichiro; Takahashi, Saburo; Maekawa, Sadamichi

2011-03-01

12

Spin-seebeck effect: a phonon driven spin distribution.  

PubMed

Here we report on measurements of the spin-Seebeck effect in GaMnAs over an extended temperature range alongside the thermal conductivity, specific heat, magnetization, and thermoelectric power. The amplitude of the spin-Seebeck effect in GaMnAs scales with the thermal conductivity of the GaAs substrate and the phonon-drag contribution to the thermoelectric power of the GaMnAs, demonstrating that phonons drive the spin redistribution. A phenomenological model involving phonon-magnon drag explains the spatial and temperature dependence of the measured spin distribution. PMID:21635114

Jaworski, C M; Yang, J; Mack, S; Awschalom, D D; Myers, R C; Heremans, J P

2011-05-02

13

Theory of magnon-driven spin Seebeck effect  

Microsoft Academic Search

The spin Seebeck effect is a spin-motive force generated by a temperature gradient in a ferromagnet that can be detected via normal metal contacts through the inverse spin Hall effect [K. Uchida , Nature (London) 455, 778 (2008)]. We explain this effect by spin pumping at the contact that is proportional to the spin-mixing conductance of the interface, the inverse

Jiang Xiao; Gerrit E. W. Bauer; Ken-Chi Uchida; Eiji Saitoh; Sadamichi Maekawa

2010-01-01

14

Spin Seebeck effect in antiferromagnets and compensated ferrimagnets  

NASA Astrophysics Data System (ADS)

We theoretically investigate the spin Seebeck effect (SSE) in antiferromagnets and ferrimagnets, and show that the SSE vanishes in antiferromagnets but survives in ferrimagnets even at the magnetization compensation point despite the absence of its saturation magnetization. The nonvanishing SSE in ferrimagnets stems from two nondegenerate magnons. We demonstrate that the magnitude of the SSE in ferrimagnets is unchanged across the magnetization compensation point.

Ohnuma, Yuichi; Adachi, Hiroto; Saitoh, Eiji; Maekawa, Sadamichi

2013-01-01

15

Longitudinal spin Seebeck effect free from the proximity Nernst effect.  

PubMed

This Letter provides evidence for intrinsic longitudinal spin Seebeck effects (LSSEs) that are free from the anomalous Nernst effect (ANE) caused by an extrinsic proximity effect. We report the observation of LSSEs in Au/Y(3)Fe(5)O(12) (YIG) and Pt/Cu/YIG systems, showing that the LSSE appears even when the mechanism of the proximity ANE is clearly removed. In the conventional Pt/YIG structure, furthermore, we separate the LSSE from the ANE by comparing the voltages in different magnetization and temperature-gradient configurations; the ANE contamination was found to be negligibly small even in the Pt/YIG structure. PMID:23432302

Kikkawa, T; Uchida, K; Shiomi, Y; Qiu, Z; Hou, D; Tian, D; Nakayama, H; Jin, X-F; Saitoh, E

2013-02-07

16

Gigantic enhancement of spin Seebeck effect by phonon drag  

Microsoft Academic Search

We investigate both theoretically and experimentally a gigantic enhancement of the spin Seebeck effect [K. Uchida et al., Nature 455, 778 (2008); C. M. Jaworski et al., Nature Mater. 9, 898 (2010); K. Uchida et al., Nature Mater. 9, 894 (2010)] in a prototypical magnet LaY2Fe5O12 at low temperatures. Our theoretical analysis sheds light on the important role of phonons;

Hiroto Adachi; Ken-Ichi Uchida; Eiji Saitoh; Jun-Ichiro Ohe; Saburo Takahashi; Sadamichi Maekawa

2011-01-01

17

Theory of magnon-driven spin Seebeck effect  

NASA Astrophysics Data System (ADS)

The spin Seebeck effect is a spin-motive force generated by a temperature gradient in a ferromagnet that can be detected via normal metal contacts through the inverse spin Hall effect [K. Uchida , Nature (London) 455, 778 (2008)]. We explain this effect by spin pumping at the contact that is proportional to the spin-mixing conductance of the interface, the inverse of a temperature-dependent magnetic coherence volume, and the difference between the magnon temperature in the ferromagnet and the electron temperature in the normal metal [D. J. Sanders and D. Walton, Phys. Rev. B 15, 1489 (1977)].

Xiao, Jiang; Bauer, Gerrit E. W.; Uchida, Ken-Chi; Saitoh, Eiji; Maekawa, Sadamichi

2010-06-01

18

Spin-Seebeck effect in amorphous ferromagnetic alloys  

NASA Astrophysics Data System (ADS)

Since its first discovery in 2008 [1], continuous research on spin-Seebeck effect (SSE) has established a theory for the driving mechanisms of SSE: in the presence of a thermal gradient, the spin waves (magnons) present in ferromagnets are brought out of thermal equilibrium. It is suspected that their return to thermal equilibrium is what launches a spin flux, which then is converted into a voltage in a separate material by strong spin-orbit interactions. While it is proven that substrate phonons affect the spin-Seebeck signals [2], another possible mechanism that can drive magnons out of equilibrium can be magnon thermal conductivity. Here, to isolate the magnon and phonon contributions, we investigate the relation between SSE and magnon thermal conductivity in amorphous ferromagnetic alloys (Metglas). Because Metglas has high Curie temperature, yet mostly localized phonon modes, the magnon contribution to SSE is expected to be larger than in crystalline ferromagnets. Experimental SSE data as well as magneto-thermal conductivity data will be presented. [4pt] [1] K. Uchida et al., Nature 455, 778 (2008).[0pt] [2] C.M. Jaworski et al., PRL 106, 186601 (2011).

Jin, Hyungyu; Yang, Zihao; Myers, Roberto; Heremans, Joseph

2013-03-01

19

Tailoring of Seebeck coefficient with surface roughness effects in silicon sub-50-nm films  

PubMed Central

The effect of surface roughness on the Seebeck coefficient in the sub-50-nm scale silicon ultra thin films is investigated theoretically using nonequilibrium Green's function formalism. For systematic studies, the surface roughness is modelled by varying thickness periodically with square wave profile characterized by two parameters: amplitude (A0) and wavelength (?). Since high Seebeck coefficient is obtained if the temperature difference between the ends of device produces higher currents and higher induced voltages, we investigate how the generated current and induced voltage is affected with increasing A0 and ?. The theoretical investigations show that pseudoperiodicity of the device structure gives rise to two effects: firstly the threshold energy at which the transmission of current starts is shifted towards higher energy sides and secondly transmission spectra of current possess pseudobands and pseudogaps. The width of the pseudobands and their occupancies determine the total generated current. It is found that current decreases with increasing A0 but shows a complicated trend with ?. The trends of threshold energy determine the trends of Seebeck voltage with roughness parameters. The increase in threshold energy makes the current flow in higher energy levels. Thus, the Seebeck voltage, i.e. voltage required to nullify this current, increases. Increase in Seebeck voltage results in increase in Seebeck coefficient. We find that threshold energy increases with increasing A0 and frequency (1/?). Hence, Seebeck voltage and Seebeck coefficient increase vice versa. It is observed that Seebeck coefficient is tuneable with surface roughness parameters.

2012-01-01

20

Designing a study of the Spin Seebeck Effect  

NASA Astrophysics Data System (ADS)

The Spin Seebeck Effect (SSE) refers to the recently discovered generation of a spin voltage as a result of an applied temperature gradient. The SSE has been observed in ferromagnetic (FM) metals, semiconductors, and insulators. This area of research has attracted much interest because it may provide a means to make use of waste heat from electronic devices. While several theories have been presented, there are still open questions regarding the physical mechanism of this effect. Recent experimental evidence suggests that magnons and phonons play a role in thermal spin physics; however, the experiments done to date are performed primarily through detection of a voltage via the Inverse Spin Hall Effect that is due to the steady-state accumulation of a spin distribution across the FM material and consequently provide only indirect information on the magnons. Here we will discuss an experimental setup that we have designed to explore the role of magnons in the SSE using Brillouin light scattering.

Riley, Grant; Liu, Jason; Roberts, Gerri; Buchanan, Kristen

2012-10-01

21

The Effect of Binding Groups on the Seebeck Coefficient of Phenyl Derivative Molecular Junctions  

NASA Astrophysics Data System (ADS)

Thermoelectrics currently suffer from low efficiencies due to inverse coupling of the Seebeck coefficient and electrical conductivity, limiting the power factor. Decoupling of these two physical properties has previously been demonstrated in molecular junctions. Using an STM break junction measurement technique, we demonstrate the effect that the direct binding group Au-C has on the Seebeck coefficient. Phenyl derivative molecules with an Au-C direct binding group show a significantly lower Seebeck coefficient than molecules with an Au-S binding group. This lower Seebeck coefficient is explained by theoretical calculations as a broadening in the transmission function due to the direct bonding group. This demonstrates the importance of the metal-molecule interface and binding group selection in tuning the transmission function, and the resultant conductance and Seebeck coefficient. This result will lend further insight in rational design for molecules with higher power factors.

Chang, William; Mai, Chengkang; Kotiuga, Michele; Urban, Jeffrey; Neaton, Jeffrey; Bazan, Gui; Segalman, Rachel

2013-03-01

22

Long-range spin Seebeck effect and acoustic spin pumping  

NASA Astrophysics Data System (ADS)

Imagine that a metallic wire is attached to a part of a large insulator, which itself exhibits no magnetization. It seems impossible for electrons in the wire to register where the wire is positioned on the insulator. Here we found that, using a Ni81Fe19/Pt bilayer wire on an insulating sapphire plate, electrons in the wire recognize their position on the sapphire. Under a temperature gradient in the sapphire, surprisingly, the voltage generated in the Pt layer is shown to reflect the wire position, although the wire is isolated both electrically and magnetically. This non-local voltage is due to the coupling of spins and phonons: the only possible carrier of information in this system. We demonstrate this coupling by directly injecting sound waves, which realizes the acoustic spin pumping. Our finding provides a persuasive answer to the long-range nature of the spin Seebeck effect, and it opens the door to ‘acoustic spintronics’ in which sound waves are exploited for constructing spin-based devices.

Uchida, K.; Adachi, H.; An, T.; Ota, T.; Toda, M.; Hillebrands, B.; Maekawa, S.; Saitoh, E.

2011-10-01

23

Spin-Seebeck effect: Local nature of thermally induced spin currents in GaMnAs  

Microsoft Academic Search

The spin-Seebeck effect refers to a spatial distribution of spins in a ferromagnetic material induced by a thermal gradient. This macroscopic spatial distribution of spins is several orders of magnitude larger than the spin diffusion length [1]. Here we describe measurements of the spin-Seebeck effect in the ferromagnetic semiconductor, GaMnAs [2]. The thermally induced spatial distribution of spins is inferred

Roberto Myers

2011-01-01

24

Linear-response theory of spin Seebeck effect in ferromagnetic insulators  

Microsoft Academic Search

We formulate a linear response theory of spin Seebeck effect, i.e., a spin\\u000avoltage generation from heat current flowing in a ferromagnet. Our approach\\u000afocuses on the collective magnetic excitation of spins, i.e., magnons. We show\\u000athat the linear-response formulation provides us with a qualitative as well as\\u000aquantitative understanding of the spin Seebeck effect observed in a\\u000aprototypical magnet

Hiroto Adachi; Jun-ichiro Ohe; Saburo Takahashi; Sadamichi Maekawa

2010-01-01

25

Spin-Seebeck effect: Local nature of thermally induced spin currents in GaMnAs  

NASA Astrophysics Data System (ADS)

The spin-Seebeck effect refers to a spatial distribution of spins in a ferromagnetic material induced by a thermal gradient. This macroscopic spatial distribution of spins is several orders of magnitude larger than the spin diffusion length [1]. Here we describe measurements of the spin-Seebeck effect in the ferromagnetic semiconductor, GaMnAs [2]. The thermally induced spatial distribution of spins is inferred from the sign and magnitude of the inverse spin Hall voltage generated from local spin currents in platinum bars that are in electrical contact with the ferromagnetic material. From an experimental point of view, GaMnAs provides unique measurement geometries since the magnetic easy axes can be engineered in different directions and the low Curie temperature makes it convenient to perform spin-Seebeck measurements across the magnetic phase transition. Using different experimental configurations we measure either the isolated spin-Seebeck signal, the planar and transverse Nernst effect, or a combination of the spin-Seebeck and Nernst effects. One of the most intriguing aspects of the spin-Seebeck effect is the observation that the spatial distribution of spins is maintained across electrical breaks revealing that the effect does not arise from a longitudinal spin current of charge carriers. [4pt] [1] K. Uchida, S. Takahashi, K. Harii, J. Ieda, W. Koshibae, K. Ando, S. Maekawa, E. Saitoh, Nature 455, 778 (2008). [0pt] [2] C. M. Jaworski, J. Yang, S. Mack, D. D. Awschalom, J. P. Heremans, R. C. Myers, Nature Materials 9, 898 (2010).

Myers, Roberto

2011-03-01

26

Two Exponentials Associated with Temperature in Spin-Seebeck Effect Geometry  

Microsoft Academic Search

Recent experiments report the observation of a Spin-Seebeck effect, where an applied thermal gradient along (x) a very thin (z), narrow (y) ferromagnetic sample F is associated with a spin current. ootnotetextK. Uchida et al, Nature 455, 778 (2008). In present geometries this spin current is measured indirectly via a Pt bar above (z) the sample; a voltage difference V

Wayne Saslow; Matthew Sears

2011-01-01

27

Magnon, phonon, and electron temperature profiles and the spin Seebeck effect in magnetic insulator/normal metal hybrid structures  

NASA Astrophysics Data System (ADS)

We calculate the phonon, electron, and magnon temperature profiles in yttrium iron garnet/platinum bilayers by diffusive theory with appropriate boundary conditions, in particular taking into account interfacial thermal resistances. Our calculations show that in thin film hybrids, the interface magnetic heat conductance qualitatively affects the magnon temperature. Based on published material parameters we assess the degree of nonequilibrium at the yttrium iron garnet/platinum interface. The magnitude of the spin Seebeck effect derived from this approach compares well with experimental results for the longitudinal spin Seebeck effect. Additionally, we address the temperature profiles in the transverse spin Seebeck effect.

Schreier, Michael; Kamra, Akashdeep; Weiler, Mathias; Xiao, Jiang; Bauer, Gerrit E. W.; Gross, Rudolf; Goennenwein, Sebastian T. B.

2013-09-01

28

On the exceptional negative Seebeck effect in 3d-doped ?-rhombohedral boron  

Microsoft Academic Search

Interstitial doping with 3d-elements impact the electronic properties of ?-rhombohedral boron significantly; in some cases high negative Seebeck coefficients occur. The explanation by simple charge transfer is excluded. We attribute these effects to the correlation among the diluted 3d atoms generating a specific system of electronic states in the band gap. The interaction with Ogitsu’s antiferromagnetic Ising model, describing the

H. Werheit

2011-01-01

29

The Seebeck effect as used for the nondestructive evaluation of metals  

SciTech Connect

The thermoelectric measurement of conductive materials is being applied increasingly to the nondestructive sorting and identifying of metals and alloys. In theory, thermoelectrics as used for this application has long been recognized as valid. However, only with recent advances in solid state electronics has this method become reliable and practical for field use. In this paper the principle of the Seebeck Effect in measuring the electromotive force created at the heated junctions of dissimilar metals is employed as a technique for nondestructively sorting metals and alloys.

Stuart, C.M.

1983-01-01

30

Spin-dependent Seebeck effect in non-local spin valve devices  

NASA Astrophysics Data System (ADS)

We performed measurements of Py/Cu and Py/Ag lateral spin valves as a function of injection current direction and magnitude. Above a ``critical'' current, there is an unexpected dependence of spin injection on current direction. Positive currents show higher polarization of spin injection than negative. This implies that in addition to current-induced spin injection, there is a thermally induced injection from a spin-dependent Seebeck effect. A temperature gradient in the Py electrode, caused by Joule heating, is responsible for injecting excess spins into the non-magnetic channel. This effect has important consequences for understanding high-current spin-based devices, such as spin transfer torque devices.

Erekhinsky, Mikhail; Casanova, Fèlix; Schuller, Ivan K.; Sharoni, Amos

2012-05-01

31

Spin Seebeck effect in thin films of the Heusler compound Co2MnSi  

NASA Astrophysics Data System (ADS)

The recently discovered spin Seebeck effect (SSE) which generates spin voltage due to a temperature gradient in ferromagnets, was systematically studied in half-metallic Heusler compound Co2MnSi (CMS)/Pt thin films to investigate the effect of spin polarization of ferromagnetic layer on SSE. An epitaxial thin film of CMS with an almost perfect B2-ordered structure was prepared directly on a MgO(001) substrate. The measurement was performed at room temperature for various temperature differences, ?T = 0-20 K between higher (300 K+?T) and lower (300 K) temperature ends along the film. The clear sign reversal of the thermally induced spin voltage due to SSE at the higher and lower temperature ends of the CMS film was detected by means of inverse spin-Hall effect in a Pt wire. The SSE was also investigated in a Py thin film deposited on a MgO(001) substrate and compared to that with CMS to verify the effect of spin polarization on SSE. Comparable signals of SSE in CMS and Py thin films suggested that thermal excitation of magnons might have more vital effects in SSE than the degree of spin polarization in ferromagnetic metals.

Bosu, S.; Sakuraba, Y.; Uchida, K.; Saito, K.; Ota, T.; Saitoh, E.; Takanashi, K.

2011-06-01

32

Spectral non-uniform temperature and non-local heat transfer in the spin Seebeck effect  

NASA Astrophysics Data System (ADS)

Recently discovered spin-dependent thermoelectric effects have merged spin, charge, and thermal physics, known as spin caloritronics, of which the spin Seebeck effect is its most puzzling. Here we present a theory of this effect driven by subthermal non-local phonon heat transfer and spectral non-uniform temperature. The theory explains its non-local behaviour from the fact that phonons that store the energy (thermal) and the phonons that transfer it (subthermal) are located in different parts of the spectrum and have different kinetics. This gives rise to a spectral phonon distribution that deviates from local equilibrium along the substrate and is sensitive to boundary conditions. The theory also predicts a non-magnon origin of the effect in ferromagnetic metals in agreement with observations in recent experiments. Equilibration of the heat flow from the substrate to the Pt probe and backwards leads to a vertical spin current produced by the spin-polarized electrons dragged by the thermal phonons.

Tikhonov, Konstantin S.; Sinova, Jairo; Finkel'Stein, Alexander M.

2013-06-01

33

Spectral non-uniform temperature and non-local heat transfer in the spin Seebeck effect.  

PubMed

Recently discovered spin-dependent thermoelectric effects have merged spin, charge, and thermal physics, known as spin caloritronics, of which the spin Seebeck effect is its most puzzling. Here we present a theory of this effect driven by subthermal non-local phonon heat transfer and spectral non-uniform temperature. The theory explains its non-local behaviour from the fact that phonons that store the energy (thermal) and the phonons that transfer it (subthermal) are located in different parts of the spectrum and have different kinetics. This gives rise to a spectral phonon distribution that deviates from local equilibrium along the substrate and is sensitive to boundary conditions. The theory also predicts a non-magnon origin of the effect in ferromagnetic metals in agreement with observations in recent experiments. Equilibration of the heat flow from the substrate to the Pt probe and backwards leads to a vertical spin current produced by the spin-polarized electrons dragged by the thermal phonons. PMID:23735931

Tikhonov, Konstantin S; Sinova, Jairo; Finkel'stein, Alexander M

2013-01-01

34

Two Exponentials Associated with Temperature in Spin-Seebeck Effect Geometry  

NASA Astrophysics Data System (ADS)

Recent experiments report the observation of a Spin-Seebeck effect, where an applied thermal gradient along (x) a very thin (z), narrow (y) ferromagnetic sample F is associated with a spin current.ootnotetextK. Uchida et al, Nature 455, 778 (2008). In present geometries this spin current is measured indirectly via a Pt bar above (z) the sample; a voltage difference V along y is measured and interpreted as being due to a spin current js into (z) the Pt, which then causes an inverse Spin Hall effect (js causes transverse V). Measured voltages often show a sinh(x/s) dependence, where s is long compared to any relevant spin-diffusion length.ootnotetextC. M. Jaworski et al, Nature Materials 9, 898 (2010). The spin current has been interpreted as accompanying a temperature disequilibrium between the phonons and magnons in F.ootnotetextJ. Xiao et al, Phys. Rev. B 81, 214418 (2010). The present work uses irreversible thermodynamics to include magnon-phonon equilibration in F and the thermal properties of the (non-magnetic) substrate S. We find two exponentials describing the overall thermal response along x, the second one associated with equilibration between F and S. If the thermal coupling between F and S is poor, then the second length can be rather long.

Saslow, Wayne; Sears, Matthew

2011-03-01

35

High Seebeck effects from conducting polymer: Poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) based thin-film device with hybrid metal/polymer/metal architecture  

SciTech Connect

Conductive polymers are of particular interest for thermoelectric applications due to their low thermal conductivity and relatively high electrical conductivity. In this study, commercially available conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) was used in a hybrid metal/polymer/metal thin film design in order to achieve a high Seebeck coefficient with the value of 252lV/k on a relatively low temperature scale. Polymer film thickness was varied in order to investigate its influence on the Seebeck effect. The high Seebeck coefficient indicates that the metal/polymer/metal design can develop a large entropy difference in internal energy of charge carriers between high and low-temperature metal electrodes to develop electrical potential due to charge transport in conducting polymer film through metal/polymer interface. Therefore, the metal/polymer/metal structure presents a new design to combine inorganic metals and organic polymers in thin-film form to develop Seebeck devices

Stanford, Michael G [ORNL; Wang, Hsin [ORNL; Ivanov, Ilia N [ORNL; Hu, Bin [University of Tennessee, Knoxville (UTK)

2012-01-01

36

A high-performance laser energy meter based on anisotropic Seebeck effect in a strongly correlated electronic thin film  

NASA Astrophysics Data System (ADS)

We have developed a high-performance laser energy meter based on anisotropic Seebeck effect in a strongly correlated electronic (SCE) thin film. SCE thin films, typically represented by high-temperature superconductor (HTS) cuprate and colossal magnetoresistance (CMR) manganite thin films, demonstrate tremendous anisotropic Seebeck effect. In this study, a La2/3Ca1/3MnO3 thin film grown on a tilted LaAlO3 substrate is tested with the fundamental, the second, the third, and the fourth harmonics (1064, 532, 355, 266 nm, respectively) of a Q-switched Nd:YAG laser over a wide range of temperatures from room temperature to 16 K. The peak-value of the laser-induced thermoelectric voltage signal shows a good linear relationship with the laser energy per pulse in the measured wavelength and temperature ranges. The combined advantages over other commercial laser detectors such as nanosecond-order response and spectrally broad and flat response over a wide range of temperatures, in situ real-time measurement, and energy savings, make the device an ideal candidate for next-generation laser detectors and laser power/energy meters.

Zhang, G.-Y.; Zheng, H.-R.; Huang, W.-H.; Zhang, X.-Y.; Gao, D.-L.; Zhang, H.; Zhang, P.-X.; Tseng, T.-Y.; Habermeier, H.-U.; Lin, C.-T.; Cheng, H.-H.

2013-11-01

37

High temperature Seebeck coefficient metrology  

SciTech Connect

We present an overview of the challenges and practices of thermoelectric metrology on bulk materials at high temperature (300 to 1300 K). The Seebeck coefficient, when combined with thermal and electrical conductivity, is an essential property measurement for evaluating the potential performance of novel thermoelectric materials. However, there is some question as to which measurement technique(s) provides the most accurate determination of the Seebeck coefficient at high temperature. This has led to the implementation of nonideal practices that have further complicated the confirmation of reported high ZT materials. To ensure meaningful interlaboratory comparison of data, thermoelectric measurements must be reliable, accurate, and consistent. This article will summarize and compare the relevant measurement techniques and apparatus designs required to effectively manage uncertainty, while also providing a reference resource of previous advances in high temperature thermoelectric metrology.

Martin, J. [Materials Science and Engineering Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); Tritt, T. [Department of Physics and Astronomy, Clemson University, Clemson, South Carolina 29634 (United States); Uher, C. [Department of Physics, University of Michigan, Ann Arbor, Michigan 48109 (United States)

2010-12-15

38

Seebeck and Shubnikov-de Haas Effects in a Two Dimensional p-type HgTe/CdTe Superlattice  

NASA Astrophysics Data System (ADS)

We report here the band structure performed in the envelope function formalism, new X-ray diffraction, Seebeck and Shubnikov-de Haas (SDH) effects in a two dimensional p-type HgTe (56 Å) / CdTe (30 Å) superlattice. At 4.2 K, the sample exhibits p type conductivity with a Hall mobility of 8200 cm2/Vs. This allowed us to observe the SDH effect with p = 1.80×1012 cm-2. The observed SDH oscillations minima are justified by the calculated Landau levels as a function of applied magnetic field. At low temperature, the thermoelectric power ? ~T0.8 indicated a collision time ? ~ E3/2, a Fermi energy at 12 meV and an effective masse of the degenerated heavy holes gas of m*HHl=0.308 m0. In the intrinsic regime, ? ~T-3/2 and RH T3/2 indicates a gap Eg of 190 meV in agreement with calculated Eg(?, 300 K) =178 meV. This sample is a medium-infrared detector, narrow gap and two-dimensional p-type semiconductor.

Nafidi, A.; El Abidi, A.; El Kaaouachi, A.

2006-09-01

39

Time-resolved measurement of the tunnel magneto-Seebeck effect in a single magnetic tunnel junction  

NASA Astrophysics Data System (ADS)

Recently, several groups have reported spin-dependent thermoelectric effects in magnetic tunnel junctions. In this paper, we present a setup for time-resolved measurements of thermovoltages and thermocurrents of a single micro- to nanometer-scaled tunnel junction. An electrically modulated diode laser is used to create a temperature gradient across the tunnel junction layer stack. This laser modulation technique enables the recording of time-dependent thermovoltage signals with a temporal resolution only limited by the preamplifier for the thermovoltage. So far, time-dependent thermovoltage could not be interpreted. Now, with the setup presented in this paper, it is possible to distinguish different Seebeck voltage contributions to the overall measured voltage signal in the ?s time regime. A model circuit is developed that explains those voltage contributions on different sample types. Further, it will be shown that a voltage signal arising from the magnetic tunnel junction can only be observed when the laser spot is directly centered on top of the magnetic tunnel junction, which allows a lateral separation of the effects.

Boehnke, Alexander; Walter, Marvin; Roschewsky, Niklas; Eggebrecht, Tim; Drewello, Volker; Rott, Karsten; Münzenberg, Markus; Thomas, Andy; Reiss, Günter

2013-06-01

40

Time-resolved measurement of the tunnel magneto-Seebeck effect in a single magnetic tunnel junction.  

PubMed

Recently, several groups have reported spin-dependent thermoelectric effects in magnetic tunnel junctions. In this paper, we present a setup for time-resolved measurements of thermovoltages and thermocurrents of a single micro- to nanometer-scaled tunnel junction. An electrically modulated diode laser is used to create a temperature gradient across the tunnel junction layer stack. This laser modulation technique enables the recording of time-dependent thermovoltage signals with a temporal resolution only limited by the preamplifier for the thermovoltage. So far, time-dependent thermovoltage could not be interpreted. Now, with the setup presented in this paper, it is possible to distinguish different Seebeck voltage contributions to the overall measured voltage signal in the ?s time regime. A model circuit is developed that explains those voltage contributions on different sample types. Further, it will be shown that a voltage signal arising from the magnetic tunnel junction can only be observed when the laser spot is directly centered on top of the magnetic tunnel junction, which allows a lateral separation of the effects. PMID:23822355

Boehnke, Alexander; Walter, Marvin; Roschewsky, Niklas; Eggebrecht, Tim; Drewello, Volker; Rott, Karsten; Münzenberg, Markus; Thomas, Andy; Reiss, Günter

2013-06-01

41

Coupled polaron-phonon effects on Seebeck coefficient and lattice conductivity of B13C2 from first principles  

NASA Astrophysics Data System (ADS)

The anomalous temperature-independent behavior of the Seebeck coefficient and the lattice thermal conductivity of B13C2 are explained through polaron and phonon evolutions found using ab initio molecular dynamics (AIMD). Analyses of lattice dynamics show that the unique icosahedron structures dominate the optical phonon modes and CBC intericosahedral bonds dominate the local acoustic vibration. We identify that the temperature-induced Jahn-Teller distortion and electron-phonon coupling in icosahedron structures create small polarons (i.e., charge trapping and phonon softening). We also verify that large-displacement chain atoms scatter heat-conducting phonons. Using equilibrium and nonequilibrium AIMD methods (including entropy and energy analyses), we predict the Seebeck coefficient and its components as well as the lattice thermal conductivity, and we find good agreement with experiments. Softened and localized phonons make a significant vibrational contribution to the Seebeck coefficient and allow for an amorphous-like lattice thermal conductivity.

Kim, Hyoungchul; Kaviany, Massoud

2013-04-01

42

Effect of Magnetic Doping on Electrical and Thermal Conductivities and Seebeck Coefficient of Suspended Bismuth Telluride Nanoplates  

NASA Astrophysics Data System (ADS)

Bismuth telluride has been investigated intensively as a model system for topological insulators. In this work, we have studied electrical and thermal transport properties of suspended bismuth telluride nanoplates grown by the vapor-solid method. The thin crystals were transferred onto micro-fabricated suspended structures with built-in electrodes and thermometers, which allowed us to measure electrical (?) and thermal (?) conductivities as well as the Seebeck coefficient (S). The through-etched hole in the devices enabled us to evaporate Cr layers on both surfaces of the crystal. After H2 annealing at 500 K, we measured enhanced ?, ?, and S values by 40, 10, and 20%, respectively. In comparison, H2 annealing without Cr evaporation resulted in 10, 10, and -8% changes of ?, ?, and S values, respectively. The effect of magnetic doping by Cr will be discussed. Additionally, magneto-transport measurements were performed on the samples to resolve the transport properties of the surface states. We observed a pronounced weak anti-localization feature in undoped samples. Changes in this feature after Cr doping will be presented.

Jo, Insun; Thompson Pettes, Michael; Yao, Zhen; Shi, Li

2013-03-01

43

Seebeck tuning in chalcogenide nanoplate assemblies by nanoscale heterostructuring.  

PubMed

Chalcogenide nanostructures offer promise for obtaining nanomaterials with high electrical conductivity, low thermal conductivity, and high Seebeck coefficient. Here, we demonstrate a new approach of tuning the Seebeck coefficient of nanoplate assemblies of single-crystal pnictogen chalcogenides by heterostructuring the nanoplates with tellurium nanocrystals. We synthesized bismuth telluride and antimony telluride nanoplates decorated with tellurium nanorods and nanofins using a rapid, scalable, microwave-stimulated organic surfactant-directed technique. Heterostructuring permits two- to three-fold factorial tuning of the Seebeck coefficient, and yields a 40% higher value than the highest reported for bulk antimony telluride. Microscopy and spectroscopy analyses of the nanostructures suggest that Seebeck tunability arises from carrier-energy filtration effects at the Te-chalcogenide heterointerfaces. Our approach of heterostructuring nanoscale building blocks is attractive for realizing high figure-of-merit thermoelectric nanomaterials. PMID:20812700

Mehta, Rutvik J; Karthik, Chinnathambi; Singh, Binay; Teki, Ranganath; Borca-Tasciuc, Theo; Ramanath, Ganpati

2010-09-28

44

Thermal creation of a spin current by Seebeck spin tunneling  

NASA Astrophysics Data System (ADS)

The thermoelectric analog of spin-polarized tunneling, namely Seebeck spin tunneling, is a recently discovered phenomenon that arises from the spin-dependent Seebeck coefficient of a magnetic tunnel contact. In a tunnel junction with one ferromagnetic electrode and one non-magnetic electrode, a temperature difference between the two electrodes creates a spin current across the contact. Here, the basic principle and the observation of Seebeck spin tunneling are described. It is shown how it can be used to create a spin accumulation in silicon driven by a heat flow across a magnetic tunnel contact, without a charge tunnel current. The sign of the spin current depends on the direction of the heat flow, whereas its magnitude is anisotropic, i.e., dependent on the absolute orientation of the magnetization of the ferromagnet. The connection between Seebeck spin tunneling and the tunnel magneto-Seebeck effect, observed in metal magnetic tunnel junctions, is also clarified. Seebeck spin tunneling may be used to convert waste heat into useful thermal spin currents that aid or replace electrical spin current, and thereby improve the energy efficiency of spintronic devices and technologies.

Jansen, R.; Le Breton, J. C.; Deac, A. M.; Saito, H.; Yuasa, S.

2013-09-01

45

Apparatus for measuring the Seebeck coefficients of highly resistive organic semiconducting materials.  

PubMed

A Seebeck coefficient measurement apparatus for high resistance organic semiconductor materials has been designed and built. It can measure materials with resistance over 7?×?10(12) ?. This is the highest material resistance value ever reported for Seebeck coefficient measurement. A cyclic temperature gradient generation technique and a corresponding algorithm are proposed to eliminate the negative effects of the long term drift of Seebeck voltage. Sources of errors in these measurements are discussed. PMID:23635216

Cai, H Y; Cui, D F; Li, Y T; Chen, X; Zhang, L L; Sun, J H

2013-04-01

46

Interplay between charge stripes and sign reversals of Hall and Seebeck effects in stripe-ordered La1.6-xNd0.4SrxCuO4 superconductors  

NASA Astrophysics Data System (ADS)

The Hall and Seebeck effects of the stripe-ordered superconductor La1.6-xNd0.4SrxCuO4 single crystals (x = 0.10, 0.12 and 0.15) were investigated systematically. The sign change of Hall and Seebeck coefficients (RH and S) from positive to negative with decreasing temperature suggests the presence of electron pockets in the Fermi surface due to the stripe ordering. We successfully tune this behavior through an epitaxial strain induced by the mismatch between the thin film and the substrate. The negative RH disappears in the thinner film in which the static charge stripe is greatly suppressed by the strong epitaxial strain, and for a strain released thicker film the negative RH recovers. These results indicate the possibility of Fermi surface reconstruction caused by the static charge stripe order in the system.

Xie, L.; Ding, J. F.; Guo, R. R.; Sun, X. F.; Li, X. G.

2011-09-01

47

Data analysis for Seebeck coefficient measurements.  

PubMed

The Seebeck coefficient is one of the key quantities of thermoelectric materials and routinely measured in various laboratories. There are, however, several ways to calculate the Seebeck coefficient from the raw measurement data. We compare these different ways to extract the Seebeck coefficient, evaluate the accuracy of the results, and show methods to increase this accuracy. We furthermore point out experimental and data analysis parameters that can be used to evaluate the trustworthiness of the obtained result. The shown analysis can be used to find and minimize errors in the Seebeck coefficient measurement and therefore increase the reliability of the measured material properties. PMID:23822373

de Boor, J; Müller, E

2013-06-01

48

Nernst, Seebeck, and Hall effects in the mixed state of YBa2Cu3O7-delta and Bi2Sr2CaCu2O8+x thin films: A comparative study  

Microsoft Academic Search

The anisotropy of the high-temperature superconductors has strong impact on their transport properties in the mixed state. We have performed a comparative study of the Nernst, Seebeck, and Hall effects of the anisotropic and extremely anisotropic high-temperature superconductors YBa2Cu3O7-delta and Bi2Sr2CaCu2O8+x, respectively. High-quality, c-axis-oriented epitaxial thin films have been used for our study. The temperature and the magnetic-field dependence of

H.-C. Ri; R. Gross; F. Gollnik; A. Beck; R. P. Huebener; P. Wagner; H. Adrian

1994-01-01

49

Seebeck coefficient of nanowires interconnected into large area networks.  

PubMed

We measured the macroscopic Seebeck coefficient of silicon nanowires (SiNWs), organized in a highly interconnected networks on large areas (order of mm(2)). The fabricated networks are very reliable with respect to random nanowire failure and are electrically and thermally equivalent to many SiNWs placed in parallel between the electrical contacts. The equivalent SiNWs have a macroscopic length of the order of millimeters and are very narrow (width smaller than 100 nm) so that they can be used to exploit thermoelectric properties at nanoscale for macroscopic electrical power generation and/or cooling. The measurement of the Seebeck coefficient S, facilitated by the macroscopic dimensions of the network, gives an insight into two questions, nanowire effective doping and carrier mobility, which are widely discussed in the literature. We found that the measured value of S is compatible with an effective doping that is higher than that of the original wafer. This higher doping is consistent with the value estimated from the measured electrical conductivity of the SiNWs with the assumption that the electron mobility inside the nanowire is equal to that of bulk silicon. PMID:23668777

Pennelli, Giovanni; Totaro, Massimo; Piotto, Massimo; Bruschi, Paolo

2013-06-12

50

Giant Seebeck coefficient of the graphene/h-BN superlattices  

NASA Astrophysics Data System (ADS)

The electronic structures and Seebeck coefficients of the graphene/h-BN superlattices which consist of zigzag graphene nanoribbons (ZGNRs) and zigzag BN nanoribbons (ZBNNRs) have been investigated using ab initio calculations based on the density functional theory. It has been shown that a ZGNR/ZBNNR marks up to 20 times larger in the Seebeck coefficient than graphene. The Seebeck coefficients of the superlattices increase with decreasing width of the constituent ZGNR. It has been revealed that the giant Seebeck coefficients of the superlattices stem from the so-called pudding mold band with a finite energy gap.

Yokomizo, Yushi; Nakamura, Jun

2013-09-01

51

The conductivity and Seebeck coefficient in the nearest-neighbour hopping regime of a Fermi glass  

Microsoft Academic Search

An effective medium theory is used to calculate the conductivity activation energy and the Seebeck coefficient for nearest-neighbour hopping in a band of Anderson localised states at the Fermi level. The results of these calculations are compared with experimental observations on cerium sulphide, fluorine-substituted magnetite and 'pure' magnetite Fe3O4.

T. E. Whall

1981-01-01

52

The impact of commonly used approximations on the computation of the Seebeck coefficient and mobility of polar semiconductors  

NASA Astrophysics Data System (ADS)

Seebeck coefficient modeling and measurement has important applications in direct thermal to electrical energy conversion and solid-state physics. The computations of the Seebeck coefficient and mobility of polar semiconductors in the literature often employ certain approximations, notably the relaxation time approximation (RTA) and the truncation of the Boltzmann transport equation. We study the accuracy of these approximations as a function of the effective mass, temperature, and carrier concentration using a recently developed technique for rigorous solution of the Boltzmann transport equation. We find that the approximations give rise to considerable error in the computed Seebeck coefficients of heavily doped semiconductors with a low effective mass, and that the RTA is entirely inapplicable for the accurate computation of the mobility of several important materials.

Ramu, Ashok T.; Bowers, John E.

2012-10-01

53

Thermal spin current from a ferromagnet to silicon by Seebeck spin tunnelling  

NASA Astrophysics Data System (ADS)

Heat generation by electric current, which is ubiquitous in electronic devices and circuits, raises energy consumption and will become increasingly problematic in future generations of high-density electronics. The control and re-use of heat are therefore important topics for existing and emerging technologies, including spintronics. Recently it was reported that heat flow within a ferromagnet can produce a flow of spin angular momentum--a spin current--and an associated voltage. This spin Seebeck effect has been observed in metallic, insulating and semiconductor ferromagnets with temperature gradients across them. Here we describe and report the demonstration of Seebeck spin tunnelling--a distinctly different thermal spin flow, of purely interfacial nature--generated in a tunnel contact between electrodes of different temperatures when at least one of the electrodes is a ferromagnet. The Seebeck spin current is governed by the energy derivative of the tunnel spin polarization. By exploiting this in ferromagnet-oxide-silicon tunnel junctions, we observe thermal transfer of spins from the ferromagnet to the silicon without a net tunnel charge current. The induced spin accumulation scales linearly with heating power and changes sign when the temperature differential is reversed. This thermal spin current can be used by itself, or in combination with electrical spin injection, to increase device efficiency. The results highlight the engineering of heat transport in spintronic devices and facilitate the functional use of heat.

Le Breton, Jean-Christophe; Sharma, Sandeep; Saito, Hidekazu; Yuasa, Shinji; Jansen, Ron

2011-07-01

54

A high temperature apparatus for measurement of the Seebeck coefficient  

NASA Astrophysics Data System (ADS)

A high temperature Seebeck coefficient measurement apparatus with various features to minimize typical sources of error is designed and built. Common sources of temperature and voltage measurement error are described and principles to overcome these are proposed. With these guiding principles, a high temperature Seebeck measurement apparatus with a uniaxial 4-point contact geometry is designed to operate from room temperature to over 1200 K. This instrument design is simple to operate, and suitable for bulk samples with a broad range of physical types and shapes.

Iwanaga, Shiho; Toberer, Eric S.; Lalonde, Aaron; Snyder, G. Jeffrey

2011-06-01

55

High-Temperature Measurement of Seebeck Coefficient and Electrical Conductivity  

NASA Astrophysics Data System (ADS)

We have developed a system for simultaneous measurement of the electrical conductivity and Seebeck coefficient for thermoelectric samples in the temperature region of 300 K to 1000 K. The system features flexibility in sample dimensions and easy sample exchange. To verify the accuracy of the setup we have referenced our system against the NIST standard reference material 3451 and other setups and can show good agreement. The developed system has been used in the search for a possible high-temperature Seebeck standard material. FeSi2 emerges as a possible candidate, as this material combines properties typical of thermoelectric materials with large-scale fabrication, good spatial homogeneity, and thermal stability up to 1000 K.

de Boor, J.; Stiewe, C.; Ziolkowski, P.; Dasgupta, T.; Karpinski, G.; Lenz, E.; Edler, F.; Mueller, E.

2013-07-01

56

Enhanced Seebeck coefficient of bismuth telluride compounds with graded doping profiles  

NASA Astrophysics Data System (ADS)

Thermoelectric properties of Bi-Sb-Te and Bi-Se-Te compounds with graded Ag doping profiles are reported. A junction structure with graded doping is formed in the Bi-Te based compounds through thermally driven Ag diffusion, which has demonstrated a greatly enhanced Seebeck coefficient when a thermal gradient is applied in the same direction of carrier concentration gradient. A mechanism based on the spatial variation of bandgap narrowing induced by heavy-doping effect is proposed to explain the anomalous thermoelectric property of Bi-Te based compounds with graded doping profiles.

Huang, Hung-Hsien; Lu, Meng-Pei; Chiu, Chien-Hao; Su, Lin-Chieh; Liao, Chien-Neng; Huang, Jing-Yi; Hsieh, Huey-Lin

2013-10-01

57

Seebeck Coefficient of Lithium and Lithium-Tin Alloys  

NASA Astrophysics Data System (ADS)

Experiments into the viability of lithium as a first wall material in a fusion device have shown that it offers great benefits in reducing recycling of hydrogenic species at the wall, increasing energy confinement times, and gettering impurities. However, concerns have been raised about its practicality in regions of high heat fluxes, and one of the greatest is whether or not a lithium divertor concept can function at high steady state temperatures without significant evaporation of the lithium. Lithium-tin alloys might offer a solution by suppressing evaporation, but their performance in a TEMHD driven device such as the LIMIT device under development at UIUC is directly dependent on their thermoelectric properties, namely their unknown Seebeck coefficient. In support of the use of lithium-tin alloys in such a device, experiments are performed to recover the Seebeck coefficient of several different compositions of lithium-tin alloys. Experiments previously performed at the University of Illinois of the Seebeck coefficient of lithium [1] were confirmed and expanded upon by this study. Values of ranging from 12 +/-1 uV/K at 82C to 28 +/-1 uV/K at 240C were obtained.[4pt] [1] V. Surla et al. Journal of Nuclear Materials 415 (2011) 18-22.

Kirsch, L.; Fiflis, P.; Andruczyk, D.; Curreli, D.; Ruzic, D. N.

2012-10-01

58

Traceable Thermoelectric Measurements of Seebeck Coefficients in the Temperature Range from 300 K to 900 K  

NASA Astrophysics Data System (ADS)

This work is focused on the characterization of thermoelectric reference materials with traceable Seebeck coefficients in the temperature range from 300 K to 900 K. The presented measurement system will provide a relative uncertainty of the measurement of the Seebeck coefficient of about 5 %. The Seebeck coefficient represents an important component of the figure of merit ZT and thus the low uncertainty of the Seebeck coefficient will also lower the uncertainty of the ZT value. We also present data which lead to the launch of the certification process of a NiCu-alloy according to the ISO Guide 35.

Lenz, Ernst; Edler, Frank; Ziolkowski, Pawel

2013-10-01

59

Theory of asymmetric and negative differential magnon tunneling under temperature bias: Towards a spin Seebeck diode and transistor  

NASA Astrophysics Data System (ADS)

We study the nonequilibrium transport for the asymmetric and negative differential magnon tunneling driven by temperature bias. We demonstrate that the many-body magnon interaction that makes the magnonic spectrum temperature-dependent is the crucial factor for the emergence of rectification and negative differential spin Seebeck effects in magnon tunneling junctions. When magnonic junctions have temperature-dependent density of states, reversing the temperature bias is able to give asymmetric spin currents and increasing temperature bias could give an anomalously decreasing magnonic spin current. We show that these properties are relevant for building spin Seebeck diodes and transistors, which could play important roles in controlling information and energy in magnonics and spin caloritronics.

Ren, Jie; Zhu, Jian-Xin

2013-09-01

60

High Temperature Seebeck Coefficient and Electrical Resistivity of Ge2Sb2Te5 Thin Films  

NASA Astrophysics Data System (ADS)

Phase-change memory (PCM) is a promising memory technology in which a small volume of a chalcogenide material can be reversibly and rapidly switched between amorphous and crystalline phases by an electrical pulse that brings it above crystallization (˜ 150-200 C) or melting (˜ 700 C) temperature. The large temperature levels involved and small dimensions of PCM devices give rise to very large temperature gradients (˜ 10 K/nm and higher) which result in strong thermoelectric effects. High-temperature characterization of the temperature-dependent thermoelectric properties of these materials is therefore critical to understand for the operation of these devices but to date there is only limited experimental data available. We have performed simultaneous measurements of Seebeck coefficient and electrical resistance of thin films of GST with different thicknesses, deposited on silicon dioxide, from room temperature to ˜ 600 C, under small temperature gradients. Two-point current-voltage (I-V) measurements were performed using a semiconductor parameter analyzer. The resistance of the material and the Seebeck voltage (open-circuit voltage) are calculated from the slope and intercept of the I-V characteristics. The details of the measurements and S(T) and R(T) results for the GST thin film samples will be presented and discussed.

Adnane, Lhacene; Dirisaglik, Faruk; Akbulut, Mustafa; Zhu, Yu; Lam, Chung; Gokirmak, Ali; Silva, Helena

2012-02-01

61

Multiple potential barriers as a possible mechanism to increase the Seebeck coefficient and electrical power factor  

Microsoft Academic Search

In this paper, a possible mechanism to increase the Seebeck coefficient of semiconductors is proposed. Multiple potential barriers are used to reduce the mean-free-path of carriers at the cold end without significantly affecting those at the hot end. This results in an increase in the Seebeck coefficient. Theoretical calculation based upon a simplified model indicates that an increase in the

D. M. Rowe; Gao Min

1994-01-01

62

Round-robin studies of two potential seebeck coefficient standard reference materials  

Microsoft Academic Search

The scientific activities of NIST include the development and distribution of standard reference materials (SRMtrade) for instrument calibration and inter-laboratory data comparison. Full characterization of a thermoelectric material requires measurement of the electrical resistivity, thermal conductivity, and Seebeck coefficient. While standard reference materials exist or have existed for the first two properties, Seebeck coefficient standard reference materials are not available.

Nathan D. Lowhorn; W. Wong-Ng; W. Zhang; Z. Q. Lu; M. Otani; E. Thomas; M. Green; T. N. Tran; N. Dilley; N. Elsner; T. Hogan; Q. Li; H. Obara; J. Sharp; R. Venkatasubramanian; R. Willigan; J. Yang; G. Nolas; T. Tritt

2007-01-01

63

Space- and time-resolved Seebeck and Nernst voltages in laser-heated permalloy/gold microstructures  

NASA Astrophysics Data System (ADS)

Thermoelectric effects in microstructured permalloy (Py)/Au wires are investigated using space- and time-resolved measurements based on scanning focused laser heating. Supported by numerical simulations of the temperature distribution, we identify two major contributions to the laser-induced signals: (i) the Seebeck effect due to thermocouples of Py/Au and (ii) the anomalous Nernst effect (ANE) in Py with a coefficient of NANE~1.6 ?V/K. ANE-based magnetic imaging of magnetic domains and magnetization reversal is demonstrated with a lateral resolution on the ?m scale.

von Bieren, Arndt; Brandl, Florian; Grundler, Dirk; Ansermet, Jean-Philippe

2013-02-01

64

Conductivities and Seebeck Coefficients of Boron Carbides: ''Softening-Bipolaron'' Hopping  

SciTech Connect

The most conspicuous feature of boron carbides' electronic transport properties is their having both high carrier densities and large Seebeck coefficients. The magnitudes and temperature dependencies of the Seebeck coefficients are consistent with large contributions from softening bipolarons: singlet bipolarons whose stabilization is significantly affected by their softening of local vibrations. Boron carbides' high carrier densities, small activation energies for hopping ({approx} 0.16 eV), and anomalously large Seebeck coefficients combine with their low, glass-like thermal conductivities to make them unexpectedly efficient high-temperature thermoelectrics.

ASELAGE,TERRENCE L.; EMIN,DAVID JACOB; MCCREADY,STEVEN S.

2000-07-20

65

Dynamic spin Seebeck coefficient and thermo-spin Hall conductivity in systems with Rashba and Dresselhaus spin-orbit coupling  

NASA Astrophysics Data System (ADS)

The generation of spin currents by thermal gradients is a central issue of spin caloritronics. In addition to the recently observed spin Seebeck effect, a transverse thermoelectric effect has been proposed. This is the generation of a spin Hall current by a temperature gradient in a two-dimensional electron gas (2DEG) with Rashba spin-orbit interaction (SOI). We calculate the spin Seebeck coefficient and the thermo-spin Hall conductivity tensor of the spin current response induced by a frequency dependent temperature gradient in a 2DEG with Rashba and Dresselhaus SOI. We consider quantum wells grown in the main crystallographic directions. The spin splitting caused by SOI opens the possibility of resonant effects due to transitions between the spin-split subbands in response to alternating thermoelectric fields and temperature gradients in the THz regime. The spin current response shows characteristic spectral features in notable contrast to the pure Rashba coupling case. Such behavior is caused by the reduced symmetry of the momentum space available for transitions and the presence of critical points. This anisotropic dynamic response could be useful for spin manipulation via thermal means.

Maytorena, Jesus; Iglesias, Priscilla

2013-03-01

66

Landau-Lifshitz theory of the longitudinal spin Seebeck effect  

NASA Astrophysics Data System (ADS)

Thermal-bias-induced spin angular momentum transfer between a paramagnetic metal and ferromagnetic insulator is studied theoretically based on the stochastic Landau-Lifshitz-Gilbert (LLG) phenomenology. Magnons in the ferromagnet establish a nonequilibrium steady state by equilibrating with phonons via bulk Gilbert damping and electrons in the paramagnet via spin pumping, according to the fluctuation-dissipation theorem. Subthermal magnons and the associated spin currents are treated classically, while the appropriate quantum crossover is imposed on high-frequency magnetic fluctuations. We identify several length scales in the ferromagnet, which govern qualitative changes in the dependence of the thermally induced spin current on the magnetic film thickness.

Hoffman, Silas; Sato, Koji; Tserkovnyak, Yaroslav

2013-08-01

67

Oscillatory and sign-alternating behaviors of the Seebeck coefficients in carbon monatomic junctions  

NASA Astrophysics Data System (ADS)

In the framework of density functional theory combined with the Lippmann-Schwinger formalism in scattering approaches, we calculate the Seebeck coefficients for carbon atom chains sandwiched between aluminum electrodes from first principles. The most striking feature is that the Seebeck coefficients are length dependent, and can be negative (n type) or positive (p type) for odd- or even-numbered carbon atom chains. Alternating n-type and p-type material properties of carbon atom chains are due to the full- and half-filled ?*-orbital states near the chemical potential.

Hsu, Bailey C.; Yao, Hsuan-Te; Liu, Wei-Lin; Chen, Yu-Chang

2013-09-01

68

Cross-plane Seebeck coefficient and thermal conductivity of CuFeSe2 thin film  

NASA Astrophysics Data System (ADS)

The CuFeSe2 is a member of the I-III-VI2 semiconductors, whereas it shows different physical properties from the chalcopyrite family, include the tetragonal structure, the small band gap ~0.16 eV and the weak magnetic behavior. Only a few articles focused on this material in recent years. The measurements of the Seebeck coefficient and thermal conductivity of the high quality CuFeSe2 thin film could provide valuable information for its thermal application. In this report, a CuFeSe2 thin film with thickness ~200 nm on SiO2/Si substrate was prepared by pulse laser deposition (PLD). The highly crystallized film shows a preferred orientation (h 0 0) normal to the film surface. Two pairs of heater/sensor Au strips were thermally deposited on the thin film and substrate separately for thermal conductivity measurement using differential 3? method. The Seebeck coefficient across the film plane was directly measured by two additional EMF probes below and above the film with temperature gradient generated by heater/sensor at frequency 2?. The temperature dependence of thermal conductivity and Seebeck coefficient were measured in a wide temperature range from 150 to 300 K. The room-temperature thermal conductivity and Seebeck coefficient are obtained to be 3.5 W/m-K and -108 ?V/K respectively.

Lee, P. C.; Ou, M. N.; Luo, J. Y.; Wu, M. K.; Chen, Y. Y.

2012-06-01

69

Seebeck and thermal conductivity analysis in amorphous/crystalline {beta}-K{<_2}Bi{<_8}Se{<_13} nanocomposite materials.  

SciTech Connect

In this work, ball milling is applied on {beta}-K{sub 2}Bi{sub 8}Se{sub 13} compounds in order to explore the potential of the process for the fabrication of nano-based material. Polycrystalline {beta}-K{sub 2}Bi{sub 8}Se{sub 13}, synthesized from melt, was ball milled under inert atmosphere. Powder x-ray diffraction showed a significantly increased disorder with ball milling time. TEM studies confirmed the presence of nanocrystalline material in an amorphous matrix, suggesting the development of crystalline/amorphous {beta}-K{sub 2}Bi{sub 8}Se{sub 13} nanocomposite material via ball milling process. Seebeck coefficient and thermal conductivity were analyzed based on the effective medium theory and show a significant contribution of a nanocrystalline phase.

Kyratsi, Th.; Hatzikraniotis, E.; Ioannou, M.; Chung, D. Y.; Tsiaoussis, I. (Materials Science Division); (Univ. Cyprus); (Aristotle Univ. Thessaloniki)

2011-01-01

70

High temperature Seebeck coefficient and resistance measurement system for thermoelectric materials in the thin disk geometry  

NASA Astrophysics Data System (ADS)

A versatile apparatus to measure the cross-plane Seebeck coefficient and the resistivity of bulk samples shaped as disks or thin plates, over a temperature range of 300 K-620 K with possible extension to higher temperatures, is presented. It is constructed from readily available equipment and instrumentation with parts that are easily manufactured. The Seebeck coefficient is measured over an average region of the sample under steady-state conditions. The sample resistance is measured using a four-point alternating current method and scaled to room temperature measurements with known geometry to calculate resistivity. A variety of sample shapes are supported. Most importantly, the support of the thin disk geometry allows for the very same samples to be used in a laser flash instrument. The design allows for rough vacuum, high vacuum, or purging with inert gases in the sample chamber. Measurements on thermoelectric ZnSb and a Ni reference material are presented.

Böttger, P. H. Michael; Flage-Larsen, E.; Karlsen, O. B.; Finstad, Terje G.

2012-02-01

71

Correlation of Seebeck coefficient and electric conductivity in polyaniline and polypyrrole  

SciTech Connect

We have measured the Seebeck coefficient and electric conductivity in the air-stable conducting polymers polyaniline and polypyrrole at different doping levels. We find, at 300 K, the general correlation that the logarithm of the electrical conductivity varies linearly with the Seebeck coefficient on doping, but with a proportionality substantially in excess of a prediction from simple theory for a single type of mobile carrier. The correlation is unexpected in its universality and unfavorable in its consequences for thermoelectric applications. A standard model suggests that conduction by carriers of both signs may occur in these doped polymers, which thus leads to reduced thermoelectric efficiency. We also show that polyacetylene (which is not air stable), does exhibit the correlation with the expected proportionality, and, thus, its properties could be more favorable for thermoelectricity. {copyright} {ital 1998 American Institute of Physics.}

Mateeva, N.; Niculescu, H.; Schlenoff, J.; Testardi, L.R. [TecOne, Inc., 1803 Sageway Drive, Tallahassee, Florida 32303 (United States)

1998-03-01

72

Seebeck Coefficient and Optical Studies of Cadmium Doped CuInS2 Single Crystal  

NASA Astrophysics Data System (ADS)

Full Text PDF Single crystals of CuInS2 were successfully grown by chemical vapor transport technique using iodine as transporting agent. The as grown chemical vapor transport CuInS2 single crystals were found to have large resistivity. To decrease the resistivity of the crystals they were doped with three different cadmium concentrations. Seebeck coefficient variation with temperature is measured for all the three doped samples. Optical bandgaps were determined for these three doped samples using optical absorption spectra. The obtained results are discussed in detail.

Chaki, S. H.

2009-08-01

73

Economical Route to Produce High Seebeck Coefficient Calcium Cobaltate for Bulk Thermoelectric Applications  

SciTech Connect

Phase pure calcium cobaltate (Ca1.24Co1.62O3.86) was prepared by Self-propagating High-temperature Synthesis (SHS) followed by a short post heat treatment. Prepared powders were characterized by XRD for phase purity, and SEM for particle size and distribution. Temperature histories at the center and on the surface of reaction pellet during the SHS process were monitored and recorded. Particles size of synthesized powders was reduced using a planetary mill to increase its specific surface area. Electrical conductivity, thermal conductivity and Seebeck coefficient of the prepared power were measured and figure of merit was reported.

Selig, Jiri [Lamar University; Lin, Sidney [Lamar University; Lin, Hua-Tay [ORNL; Johnson, D Ray [ORNL; Wang, Hsin [ORNL

2011-01-01

74

Carrier Concentrations and Seebeck Measurements on CuSc_1-xMg_xO_2+y Transparent Conductive Thin Films  

Microsoft Academic Search

A series of seven magnesium-doped copper scandium oxide films were made by radio frequency sputtering, and intercalated at various oxygen pressures to create different oxygen concentrations in each film. Results of the room temperature Seebeck measurements show that the p-type nature of the carriers persists for all intercalation pressures. Small Seebeck coefficients characteristic of metals corresponded to high oxygen intercalation

Dara L. Easley; Janet Tate; Allen L. Wasserman

2003-01-01

75

Thermal spin injection and accumulation in CoFe/MgO tunnel contacts to n-type Si through Seebeck spin tunneling  

NASA Astrophysics Data System (ADS)

We report the thermal spin injection and accumulation in crystalline CoFe/MgO tunnel contacts to n-type Si through Seebeck spin tunneling (SST). With the Joule heating (laser heating) of Si (CoFe), the thermally induced spin accumulation is detected by means of the Hanle effect for both polarities of the temperature gradient across the tunnel contact. The magnitude of the thermal spin signal scales linearly with the heating power, and its sign is reversed as we invert the temperature gradient, demonstrating the major features of SST and thermal spin accumulation. Based on a quantitative comparison of the thermal and electrical spin signals, the thermal spin injection through SST is suggested as an effective route to inject the spin accumulation.

Jeon, Kun-Rok; Min, Byoung-Chul; Park, Seung-Young; Lee, Kyeong-Dong; Song, Hyon-Seok; Park, Youn-Ho; Shin, Sung-Chul

2013-09-01

76

A sintered nanoparticle p-n junction observed by a Seebeck microscan  

NASA Astrophysics Data System (ADS)

A nanoparticular p-n junction was realized by a field-assisted sintering process, using p-type and n-type doped silicon nanoparticles. A spatially resolved Seebeck microscan showed a broad transition from the positively doped to the negatively doped range. Overshoots on both sides are characteristic for the transition. Despite the tip size being much larger than the mean particle size, information about the dopant distribution between the particles is deduced from modeling the measured data under different assumptions, including the limited spatial resolution of the tip. The best match between measured and modeled data is achieved by the idea of doping compensation, due to the sintering process. Due to a short time at high temperature during the field-assisted sintering process, solid state diffusion is too slow to be solely responsible for the observed compensation of donors and acceptors over a wide range. Therefore, these measurements support a densification mechanism based on (partial) melting and recrystallization.

Becker, A.; Schierning, G.; Theissmann, R.; Meseth, M.; Benson, N.; Schmechel, R.; Schwesig, D.; Petermann, N.; Wiggers, H.; Ziolkowski, P.

2012-03-01

77

Thermal conductivity and Seebeck coefficients of icosahedral boron arsenide films on silicon carbide  

NASA Astrophysics Data System (ADS)

The thermal conductivity of icosahedral boron arsenide (B12As2) films grown on (0001) 6H-SiC substrates by chemical vapor deposition was studied by the 3? technique. The room temperature thermal conductivity decreased from 27.0 to 15.3 W/m K as the growth temperature was decreased from 1450 to 1275 °C. This is mainly attributed to the differences in the impurity concentration and microstructure, determined from secondary ion mass spectrometry and high resolution transmission electron microscopy, respectively. Callaway's theory was applied to calculate the temperature-dependent thermal conductivity, and the results are in good agreement with the experimental data. Seebeck coefficients were determined as 107 ?V/K and 136 ?V/K for samples grown at 1350 °C with AsH3/B2H6 flow ratio equals to 1:1 and 3:5, respectively.

Gong, Y.; Zhang, Y.; Dudley, M.; Zhang, Y.; Edgar, J. H.; Heard, P. J.; Kuball, M.

2010-10-01

78

Carrier Concentrations and Seebeck Measurements on CuSc_1-xMg_xO_2+y Transparent Conductive Thin Films.  

NASA Astrophysics Data System (ADS)

A series of seven magnesium-doped copper scandium oxide films were made by radio frequency sputtering, and intercalated at various oxygen pressures to create different oxygen concentrations in each film. Results of the room temperature Seebeck measurements show that the p-type nature of the carriers persists for all intercalation pressures. Small Seebeck coefficients characteristic of metals corresponded to high oxygen intercalation pressures, whereas larger coefficients characteristic of semiconductors corresponded to the low intercalation pressures. Further analysis of the Seebeck coefficients using a model developed in house gave reasonable qualitative values for the carrier concentrations of the films. This work was supported by the National Science Foundation.

Easley, Dara L.; Tate, Janet; Wasserman, Allen L.

2003-05-01

79

Measurement setup for the simultaneous determination of diffusivity and Seebeck coefficient in a multi-anvil apparatus.  

PubMed

In this paper, a high pressure setup is presented for performing simultaneous measurements of Seebeck coefficient and thermal diffusivity in multianvil apparatus for the purpose of enhancing the study of transport phenomena. Procedures for the derivation of Seebeck coefficient and thermal diffusivity/conductivity, as well as their associated sources of errors, are presented in detail, using results obtained on the filled skutterudite, Ce(0.8)Fe(3)CoSb(12,) up to 12 GPa at ambient temperature. Together with recent resistivity and sound velocity measurements in the same apparatus, these developments not only provide the necessary data for a self-consistent and complete characterization of the figure of merit of thermoelectric materials under pressure, but also serve as an important tool for furthering our knowledge of the dynamics and interplay between these transport phenomena. PMID:23020390

Jacobsen, M K; Liu, W; Li, B

2012-09-01

80

In-situ conductivity and Seebeck measurements of highly efficient n-dopants in fullerene C60  

NASA Astrophysics Data System (ADS)

We present two organic dimetal complexes Cr2(hpp)4 and W2(hpp)4 as n-dopants investigated in the model system of fullerene C60 for the application in organic electronic devices. Conductivity and Seebeck measurements on doped layers are carried out in vacuum at different doping concentrations and various substrate temperatures to compare the two dopants. Very high conductivities of up to 4 S/cm are achieved for both organic dopants. The thermal activation energy of the conductivity as well as the measured Seebeck coefficient are found to decrease with increasing doping concentration, indicating a shift of the Fermi level towards the electron transport level of the n-doped C60.

Menke, Torben; Ray, Debdutta; Meiss, Jan; Leo, Karl; Riede, Moritz

2012-02-01

81

Measurements of the Thermal Conductivity and Seebeck Coefficient of Natural Nanolaminate Materials  

NASA Astrophysics Data System (ADS)

We report thermal transport measurements of materials in the general family M_nAX_n-1, where M is an early transition metal, A is an A-group element (mostly IIIA and IVA) and X is C and/or N and n = 1 to 3. We have measured Ti_3AlC_2, Ti_3SiC_2, and materials with Ge substituted for some of the Si. The results of these measurements suggest that materials in the Â"312Â" family, have a value of thermal conductivity near room temperature of roughly 40W/Km, with the primary mechanism for heat transport attributed to the entropy of free charge carriers. However, as temperature decreases, the phonon contribution and impurity scattering become more important and differences emerge. These differences with be discussed, as well as differences observed in the thermal transport of Ti_4AlN3 and V_2AlC. We also present Seebeck Coefficient measurements on the same materials and discuss the implications of these results.

Palma, J.; Lofland, S.; Finkel, P.; Hettinger, J.; Seaman, B.; Gupta, S.; Barsoum, M.

2003-03-01

82

Spin Seebeck Effect and Thermal Colossal Magnetoresistance in Graphene Nanoribbon Heterojunction  

PubMed Central

Spin caloritronics devices are very important for future development of low-power-consumption technology. We propose a new spin caloritronics device based on zigzag graphene nanoribbon (ZGNR), which is a heterojunction consisting of single-hydrogen-terminated ZGNR (ZGNR-H) and double-hydrogen-terminated ZGNR (ZGNR-H2). We predict that spin-up and spin-down currents flowing in opposite directions can be induced by temperature difference instead of external electrical bias. The thermal spin-up current is considerably large and greatly improved compared with previous work in graphene. Moreover, the thermal colossal magnetoresistance is obtained in our research, which could be used to fabricate highly-efficient spin caloritronics MR devices.

Ni, Yun; Yao, Kailun; Fu, Huahua; Gao, Guoying; Zhu, Sicong; Wang, Shuling

2013-01-01

83

Observations of Co4+ in a Higher Spin State and the Increase in the Seebeck Coefficient of Thermoelectric Ca3Co4O9  

SciTech Connect

Ca{sub 3}Co{sub 4}O{sub 9} has a unique structure that leads to exceptionally high thermoelectric transport. Here we report the achievement of a 27% increase in the room-temperature in-plane Seebeck coefficient of Ca{sub 3}Co{sub 4}O{sub 9} thin films. We combine aberration-corrected Z-contrast imaging, atomic-column resolved electron energy-loss spectroscopy, and density-functional calculations to show that the increase is caused by stacking faults with Co4+-ions in a higher spin state compared to that of bulk Ca{sub 3}Co{sub 4}O{sub 9}. The higher Seebeck coefficient makes the Ca{sub 3}Co{sub 4}O{sub 9} system suitable for many high temperature waste-heat-recovery applications.

Klie, Robert F [University of Illinois, Chicago; Qiao, Q. [University of Illinois, Chicago; Paulauskas, T. [University of Illinois, Chicago; Gulec, A. [University of Illinois, Chicago; Rebola, A. [University of Illinois, Chicago; Ogut, Serdar [University of Illinois, Chicago; Prange, Micah P [Vanderbilt University; Idrobo Tapia, Juan C [ORNL; Pantelides, Sokrates T. [Vanderbilt University; Kolesnik, S. [Northern Illinois University; Dabrowski, B. [Argonne National Laboratory (ANL); Ozdemir, M. [University of Alabama, Tuscaloosa; Boyraz, C. [University of Alabama, Tuscaloosa; Mazumdar, Dipanjan [University of Alabama, Tuscaloosa; Gupta, Dr. Arunava [University of Alabama, Tuscaloosa

2012-01-01

84

Thermospin effects of a quasi-one-dimensional system in the presence of spin-orbit interaction  

NASA Astrophysics Data System (ADS)

The authors investigate the effect of Rashba spin-orbit interaction (SOI) and external magnetic field on the thermospin properties of a quasi-one-dimensional ballistic electron system. Spin analogs to the thermoelectric Seebeck coefficient and figure of merit (FOM) are defined and studied. Sign reversal and oscillation of spin Seebeck coefficient are indicated as a function of junction parameters. With the increase of SOI strength, the spin Seebeck coefficient oscillates more rapidly and the intervals between adjacent peaks are narrowed. Because large thermal conductance is induced by the more conducting paths, spin-FOM in the presence system is smaller than that of a quantum dot device.

Lü, Hai-Feng; Zhu, Liang-Chen; Zu, Xiao-Tao; Zhang, Huai-Wu

2010-03-01

85

Seebeck effect and neutron diffraction of NdSrBaCu3O6+z. Effect of argon annealing  

NASA Astrophysics Data System (ADS)

We have performed neutron-diffraction and thermopower experiments on two samples of NdSrBaCu3O6+z. One was a conventionally annealed sample at 450°C in oxygen [O] and the other was heated in argon at 850°C followed by oxygen annealing [AO]. The Tc of the sample [O] was 68 K and that of [AO] was 78 K. The neutron data showed that the [O] sample had a higher impurity level arising from Nd entering the Sr/Ba sites that may result in a decrease in the carrier density (p) which was also confirmed by our thermopower measurements. The increase in p and in-phase purity for the [AO] sample may account for the observed increase in Tc.

Zelenay, I.; Nafidi, A.; Greaves, C.; Suryanarayanan, R.

1994-09-01

86

Electrical conductivity and seebeck coefficient of nonstoichiometric La sub 1 minus x Sr sub x CoO sub 3 minus. delta  

SciTech Connect

This paper reports the conductivity and Seebeck coefficient of the perovskite-type oxides La{sub 1 {minus} x}Sr{sub x}CoO{sub 3 {minus} {delta}}(x = 0-0.7) measured in 10{sup {minus} 5}-1 atm O{sub 2} gas at temperatures 25{degrees}-1000{degrees}C. The results are discussed in relation to the lattice-parameter and oxygen nonstoichiometry. Close relationships were found between the temperature dependence of the conductivity and the rhombohedral angle, {alpha}. For La{sub 1 {minus} x}Sr{sub x}CoO{sub 3 {minus} {delta}} {lt} 60.3{degrees}-60.4{degrees} (LaCoO{sub 3 {minus} {delta}} above 800{degrees}C and La{sub 1 {minus} x}Sr{sub x}CoO{sub 3 {minus} {delta}} with x {gt} 0.5 at room temperature), the conductivity decreases with temperature, suggesting metallic conduction. For La{sub 1 {minus} x}Sr{sub x}CoO{sub 3 {minus} {delta}} with {alpha} {gt} 60.4{degrees}, the conductivity increases with temperature like semiconductors. In the oxides with metallic conduction, the conductivity was found to decrease with increase in the oxygen vacancy concentration. Because the conduction band is composed of the Co-O-Co network, it is considered that the band is distributed by the formation of oxygen vacancies and becomes narrower, resulting in the decrease in conductivity.

Mizusaki, J. (Inst. of Environmental Science and Technology, Yokohama National Univ., Tokiwadai, Hodogaya-ku, Yokohama 240 (JP)); Tabuchi, J. (Fundamental Research Laboratories, NEC Corporation, Miyamae-ku, Kawasaki 213 (JP)); Matsuura, T. (Research Inst. of Electrical Communication, Tohoku Univ., Katahira, Sendai 980 (JP)); Yamauchi, S. (Research Inst., National Rehabilitation Center of Disabled, Namiki, Tokorozawa, Saitama 359 (JP)); Fucki, K. (Dept. of Industrial Chemistry, Science Univ. of Tokyo, Yamazaki, Noda, Chiba 278 (JP))

1989-07-01

87

Pressure-Temperature Effects on Charge-Transport in Transition-Metal Oxides.  

National Technical Information Service (NTIS)

Effects of pressure and temperature on electrical conductivity and thermoelectric power of NiO, CoO, Fe2O3, and Cu2O were measured. The temperature dependence of conductivity and Seebeck coefficient in lithium doped NiO and CoO single crystals indicated t...

A. P. Young C. M. Schwartz P. J. Freud

1968-01-01

88

High-throughput characterization of the Seebeck coefficient of a-(Cr1 - xSix)1 - yOy thin film materials libraries as verification of the extended thermopower formula  

NASA Astrophysics Data System (ADS)

In a previous paper (Sonntag 2010 J. Phys.: Condens. Matter 22 235501) the classical thermopower formula has been argued to be incomplete, because it only takes into account the scattering properties of the carriers, but not the temperature dependence of the electrochemical potential ? caused by variation of the carrier density and/or band edge shift with temperature T. This argument is now checked experimentally by high-throughput measurements of the thermopower (Seebeck coefficient) S of a-(Cr1 - xSix)1 - yOy thin film materials libraries. The concentration dependences of S differ depending on whether the measurements are done with the complete film (where x ranges continuously from x?0.3 to 0.8; y?0.1-0.2) or with the separated pieces (each piece with another average value of x). These differences are especially large if, in addition, an oxygen gradient is present.

Sonntag, Joachim; Ziolkowski, Pawel; Savan, Alan; Kieschnick, Michael; Ludwig, Alfred

2011-07-01

89

Thermoelectric effect of correlated metals: Band-structure effects and the breakdown of Mott's formula  

NASA Astrophysics Data System (ADS)

We study the thermoelectric effect of two-dimensional metals on a square lattice within semiclassical Boltzmann transport theory with particular focus on electron-electron scattering. We compute the electrical conductivity and the Seebeck coefficient as a function of band filling and temperature for generically chosen hopping parameters in a two-dimensional tight-binding model. The Boltzmann equation is solved numerically after computing the full collision integral, taking the angular and radial degrees of freedom into account. These degrees of freedom of the collision integral, neglected in the standard single-relaxation-time approximation, play an important role if the transport coefficients show unconventional features. Within our detailed numerical simulation, we show that the widely used Mott formula to compute the Seebeck effect is not sufficient to describe the thermoelectric effect in the presence of strong electron-electron scattering. Furthermore, we study the Seebeck coefficient and its temperature dependence in the vicinity of a Lifshitz transition and demonstrate that it shows remarkable parallels to transport features near a quantum critical point.

Buhmann, Jonathan M.; Sigrist, Manfred

2013-09-01

90

Effect of aluminum on the thermoelectric properties of nanostructured PbTe.  

PubMed

In the present work, the effect of aluminum (Al) on the thermoelectric properties of PbTe is studied. Aluminum doped PbTe samples, fabricated by a ball milling and hot pressing, have Seebeck coefficients between -100 and -200 ?V K-1 and electrical conductivities of (3.6-18) × 104 S m-1 at room temperature, which means that Al is an effective donor in PbTe. The first principle calculations clearly show an increase of the density of states close to the Fermi level in the conduction band due to Al doping, which averages up the energy and effective mass of electrons, resulting in enhancement of the Seebeck coefficient. The maximum figure-of-merit ZT of 1.2 is reached at 770 K in the Al0.03PbTe sample. PMID:23912680

Zhang, Qinyong; Yang, Siqi; Zhang, Qian; Chen, Shuo; Liu, Weishu; Wang, Hui; Tian, Zhiting; Broido, David; Chen, Gang; Ren, Zhifeng

2013-08-30

91

Large and tunable photothermoelectric effect in single-layer MoS2.  

PubMed

We study the photoresponse of single-layer MoS(2) field-effect transistors by scanning photocurrent microscopy. We find that, unlike in many other semiconductors, the photocurrent generation in single-layer MoS(2) is dominated by the photothermoelectric effect and not by the separation of photoexcited electron-hole pairs across the Schottky barriers at the MoS(2)/electrode interfaces. We observe a large value for the Seebeck coefficient for single-layer MoS(2) that by an external electric field can be tuned between -4 × 10(2) and -1 × 10(5) ?V K(-1). This large and tunable Seebeck coefficient of the single-layer MoS(2) paves the way to new applications of this material such as on-chip thermopower generation and waste thermal energy harvesting. PMID:23301811

Buscema, Michele; Barkelid, Maria; Zwiller, Val; van der Zant, Herre S J; Steele, Gary A; Castellanos-Gomez, Andres

2013-01-11

92

Large and Tunable Photothermoelectric Effect in Single-Layer MoS2  

NASA Astrophysics Data System (ADS)

We study the photoresponse of single-layer MoS2 field-effect transistors by scanning photocurrent microscopy. We find that, unlike in many other semiconductors, the photocurrent generation in single-layer MoS2 is dominated by the photo-thermoelectric effect and not by the separation of photoexcited electron-hole pairs across the Schottky barriers at the MoS2/electrode interfaces. We observe a large value for the Seebeck coefficient for single-layer MoS2 that, by an external electric field, can be tuned between -4x10^2 uV/K and -1x10^5 uV/K. This large and tunable Seebeck coefficient of the single-layer MoS2 paves the way to new applications of this material such as on-chip thermopower generation and waste thermal energy harvesting.

Buscema, Michele; Barkelid, Maria; Zwiller, Val; van der Zant, Herre S. J.; Steele, Gary A.; Castellanos-Gomez, Andres

2013-02-01

93

Electrical transport, electrothermal transport, and effective electron mass in single-crystalline In2O3 films  

NASA Astrophysics Data System (ADS)

A comprehensive study of the room-temperature electrical and electrothermal transport of single-crystalline indium oxide (In2O3) and indium tin oxide (ITO) films over a wide range of electron concentrations is reported. We measured the room-temperature Hall mobility ?H and Seebeck coefficient S of unintentionally doped and Sn-doped high-quality, plasma-assisted molecular-beam-epitaxy-grown In2O3 for volume Hall electron concentrations nH from 7×1016 cm?3 (unintentionally doped) to 1×1021 cm?3 (highly Sn-doped, ITO). The resulting empirical S(nH) relation can be directly used in other In2O3 samples to estimate the volume electron concentration from simple Seebeck coefficient measurements. The mobility and Seebeck coefficient were modeled by a numerical solution of the Boltzmann transport equation. Ionized impurity scattering and polar optical phonon scattering were found to be the dominant scattering mechanisms. Acoustic phonon scattering was found to be negligible. Fitting the temperature-dependent mobility above room temperature of an In2O3 film with high mobility allowed us to find the effective Debye temperature (?D=700 K) and number of phonon modes (NOPML=1.33) that best describe the polar optical phonon scattering. The modeling also yielded the Hall scattering factor rH as a function of electron concentration, which is not negligible (rH?1.4) at nondegenerate electron concentrations. Fitting the Hall-scattering-factor corrected concentration-dependent Seebeck coefficient S(n) for nondegenerate samples to the numerical solution of the Boltzmann transport equation and to widely used, simplified equations allowed us to extract an effective electron mass of m*=(0.30±0.03)me (with free electron mass me). The modeled mobility and Seebeck coefficient based on polar optical phonon and ionized impurity scattering describes the experimental results very accurately up to electron concentrations of 1019 cm?3, and qualitatively explains a mobility plateau or local maximum around 1020 cm?3. Ionized impurity scattering with doubly charged donors best describes the mobility in our unintentionally doped films, consistent with oxygen vacancies as unintentional shallow donors, whereas singly charged donors best describe our Sn-doped films. Our modeling yields a (phonon-limited) maximum theoretical drift mobility and Hall mobility of ?=190 cm2/Vs and ?H=270 cm2/Vs, respectively. Simplified equations for the Seebeck coefficient describe the measured values in the nondegenerate regime using a Seebeck scattering parameter of r=?0.55 (which is consistent with the determined Debye temperature), and provide an estimate of the Seebeck coefficient to lower electron concentrations. The simplified equations fail to describe the Seebeck coefficient around the Mott transition (nMott=5.5×1018 cm?3) from nondegenerate to degenerate electron concentrations, whereas the numerical modeling accurately describes this region.

Preissler, Natalie; Bierwagen, Oliver; Ramu, Ashok T.; Speck, James S.

2013-08-01

94

Effect of chemical doping on the thermoelectric properties of FeGa3  

NASA Astrophysics Data System (ADS)

Thermoelectric properties of the chemically-doped intermetallic narrow-band semiconductor FeGa3 are reported. The parent compound shows semiconductor-like behavior with a small bandgap (Eg = 0.2 eV), a carrier density of ~1018 cm-3, and a large n-type Seebeck coefficient (S ~ - 400 ?V/K) at room temperature. Hall effect measurements indicate that chemical doping significantly increases the carrier density, resulting in a metallic state, while the Seebeck coefficient still remains fairly large (~- 150 ?V/K). The largest power factor (S2/? = 62 ?W/m K2) was observed for Fe0.99Co0.01(Ga0.997Ge0.003)3, and its corresponding figure of merit (ZT = 1.3 × 10-2) at 390 K improved by over a factor of 5 from the pure material.

Haldolaarachchige, N.; Karki, A. B.; Phelan, W. Adam; Xiong, Y. M.; Jin, R.; Chan, Julia Y.; Stadler, S.; Young, D. P.

2011-05-01

95

Observation of the planar Nernst effect in permalloy and nickel thin films with in-plane thermal gradients.  

PubMed

We present experimental evidence of a transverse thermopower, or planar Nernst effect, in ferromagnetic metal thin films driven by thermal gradients applied in the plane of the films. Samples of 20 nm thick Ni and Ni(80)Fe(20) were deposited on 500 nm thick suspended Si-N thermal isolation platforms with integrated platinum strips designed originally to allow measurement of thermally generated spin currents (the spin Seebeck effect). The low thermal conductivity of the thin supporting Si-N structure results in an essentially 2D geometry that approaches the zero substrate limit, dramatically reducing the contribution of thermal gradients perpendicular to the sample plane typically found in similar experiments on bulk substrates. The voltage on the platinum strips generated transverse to the applied thermal gradient (V(T)) is linear with increasing ?T and exhibits a sign reversal on hot and cold sides of the sample. However, V(T) is always even in applied magnetic field and shows a sin? cos? angular dependence, both key indicators of the planar Nernst effect. Within the 5 nV estimated error of our experiment there is no evidence of a signal from the spin Seebeck effect, which would have cos? angular dependence, suggesting a reduced spin Seebeck coefficient in a planar, entirely thin-film geometry. PMID:23215412

Avery, A D; Pufall, M R; Zink, B L

2012-11-07

96

Transport magnetic proximity effects in platinum.  

PubMed

Platinum (Pt) metal, being nonmagnetic and with a strong spin-orbit coupling interaction, has been central in detecting the pure spin current and establishing most of the recent spin-based phenomena. Magnetotransport measurements, both electrical and thermal, conclusively show strong ferromagnetic characteristics in thin Pt films on the ferromagnetic insulator due to the magnetic proximity effects. The pure spin current phenomena measured by Pt, including the inverse spin Hall and the spin Seebeck effects, are thus contaminated and not exclusively established. PMID:23005323

Huang, S Y; Fan, X; Qu, D; Chen, Y P; Wang, W G; Wu, J; Chen, T Y; Xiao, J Q; Chien, C L

2012-09-07

97

Synthetic conditions and their doping effect on {Beta}-K{sub 2}Bi{sub 8}Se{sub 13}.  

SciTech Connect

In this work the synthetic conditions for K{sub 2}Bi{sub 8}Se{sub 13} and their effect on its thermoelectric properties were investigated. K{sub 2}Bi{sub 8}Se{sub 13} was prepared as a single phase using K{sub 2}Se and Bi{sub 2}Se{sub 3} as starting materials in a furnace or via a reaction using direct flame, followed by remelting or annealing. Seebeck coefficient measurements showed that the doping level in the material is sensitive to the synthetic conditions. Higher synthesis temperatures as well as the flame reaction technique followed by annealing gave more homogenous samples with higher Seebeck coefficient. IR optical spectroscopic measurements showed a wide range of doping level achieved among the different synthetic conditions. These findings suggest that synthetic conditions can act as a useful tool for the optimization of the thermoelectric properties of these materials.

Kyratsi, Th.; Kika, I.; Hatzikraniotis, E.; Paraskevopoulos, K. M.; Chrissafis, K.; Kanatzidis, M. G. (Materials Science Division); (Univ. Cyprus); (Aristotle Univ. Thessaloniki); (Northwestern Univ.)

2009-04-01

98

Electric detection ofmagnetization dynamics through inverse spin Hall effects  

NASA Astrophysics Data System (ADS)

Spin currents, flows of spin angular momentum, are essential in spintronics. To explore the physics of spin currents, effective methods for detecting and generating spin currents should be established. Here we report the observation of the inverse/direct spin-Hall effects in metallic films. These effects enable electric generation and detection of spin currents. We have applied these effects to the observation of the spin-Seebeck effect. The inverse spin-Hall effect (ISHE) is the generation of a charge current from a spin current via the spin-orbit interaction. We have observed ISHE in metallic films at room temperature. The sample used in the present study is a bilayer film comprising a 10-nm-thick ferromagnetic NiFe layer and a 7- nm-thick nonmagnetic metallic (NM=Pt, Pd, Cu, Nb, and Au) layer. In our sample system, a pure spin current is injected from the NiFe layer into the NM layer using the spin-pumping effect operated by ferromagnetic resonance (FMR). ISHE in the NM layer converts the spin current into an electric current, which causes charge accumulation at the edges of the NM layer, or a difference of electric potential between the edges. By measuring this potential difference, this method allows us to detect ISHE in the films. We also demonstrated that the reverse effect of this spin- pumping induced ISHE allows the electric manipulation of magnetization relaxation even in a large-area film. This result can be argued in terms of the combination of the spin-torque effect and the direct spin-Hall effect. A model calculation reproduces the experimental data. This effect can be applied to a quantitative measurement of spin currents without assuming microscopic parameters. We have applied ISHE to the observation of the spin-Seebeck effect. By means of ISHE, we measured spin voltage generated from a temperature gradient in NiFe. This thermally induced spin voltage persists even at distances far from the sample ends and its sign is reversed between the ends of the sample along the temperature gradient. These behaviors are consistent with a phenomenological two-band model for the spin-Seebeck effect. The spin-Seebeck effect can be applied directly to constructing thermal spin generators for driving spintronics devices, thereby opening the door to thermo-spintronics.

Saitoh, Eiji

2010-03-01

99

Effect of Deposition Conditions on the Microstructure and the Thermoelectric Properties of Galvanostatically Electrodeposited Bi2Te3 Film  

NASA Astrophysics Data System (ADS)

Bismuth Telluride (Bi2Te3) films were deposited by a simple and cost-effective galvanostatic electrodeposition process from a solution containing bismuth tri-nitrate penta-hydrate and tellurium dioxide of different concentration ratios in 1 M nitric acid onto gold sputtered silicon substrate at various current densities. The effect of distinct current densities, electrolyte concentrations and electrodes distances on the microstructure and the thermoelectric properties of Bi2Te3 films were investigated. X-Ray diffraction (XRD) and field emission scanning electron microscope (FESEM) analysis ensured a high density, homogenous and near stoichiometric film. The surface morphology, crystalline structure and grain size were correlated with the applied current density. A prominent orientation (110) was observed for all the films and the grain size was acquired from 21 to 45 nm. The Seebeck measurement affirmed n-type semiconductor behavior of the deposited films. Enhancement in carrier mobility without significant change of the carrier concentration and Seebeck coefficient was achieved by tuning the electrodes distance. The thermoelectric film has a maximum measured Seebeck coefficient of -61.215 ?V/K and a very high electrical conductivity of 2.13 × 103 ?-1 ? cmn-1. The maximum calculated power factor was 8.2 ?W?K-2 ? cm-1.

Rashid, Mohammad Mamunur; Chung, Gwiy-Sang

2013-10-01

100

Giant intrinsic thermomagnetic effects in thin MgO magnetic tunnel junctions  

NASA Astrophysics Data System (ADS)

An intrinsic spin-dependent Seebeck effect in the linear tunneling transport regime of magnetic tunneling junctions (MTJs) was discovered recently. This effect leads to a nonlinear correction of Ohm's law in the dc response. We analyze this intrinsic magneto-thermoelectrical effect for MTJs with different MgO barrier (tb=0.7-1.35 nm) thicknesses. We report strong intrinsic effects in MTJs with thin MgO barriers (1189%), upon reversal of the magnetization of the two CoFeB layers. Such large effects are promising for useful spin caloritronic devices, integrating charge, heat, and spin tunnel transport.

Teixeira, J. M.; Costa, J. D.; Ventura, J.; Fernandez-Garcia, M. P.; Azevedo, J.; Araujo, J. P.; Sousa, J. B.; Wisniowski, P.; Cardoso, S.; Freitas, P. P.

2013-05-01

101

Influence of electron scatterings on thermoelectric effect  

NASA Astrophysics Data System (ADS)

In this work, we employed non-equilibrium Green's function to investigate the electron transport properties in a nanowire in the presence of scatterings. The scattering mechanism is modelled by the Büttiker probe. The effect of electron scattering is analyzed under three conditions: absence of external field; with a bias voltage; and with a finite temperature difference. It is found that weak and strong scattering strengths affect the electron transport in different ways. In the case of weak scattering strength, electron trapping increases the electron density, thereby boosting the conductance significantly. Although the increment in conductance would reduce the Seebeck coefficient slightly, the power factor still increases. In the case of strong scattering strength, electron diffraction causes the redistribution of electrons; accumulation of electrons at the ends of the wire blocks current flow; hence the conductance is reduced significantly. Although the Seebeck coefficient increases slightly, the power factor still decreases. The power factor is enhanced by 6%-18%, at the optimum scattering strength.

Li, Jing; Cheung Au Yeung, Tin; Hin Kam, Chan

2012-08-01

102

Spin-dependent thermoelectric effects in graphene-based spin valves  

NASA Astrophysics Data System (ADS)

Using first-principles calculations combined with non-equilibrium Green's function (NEGF), we investigate spin-dependent thermoelectric effects in a spin valve which consists of zigzag graphene nanoribbon (ZGNR) electrodes with different magnetic configurations. We find that electron transport properties in the ZGNR-based spin valve are strongly dependent on the magnetic configurations. As a result, with a temperature bias, thermally-induced currents can be controlled by switching the magnetic configurations, indicating a thermal magnetoresistance (MR) effect. Moreover, based on the linear response assumption, our study shows that the remarkably different Seebeck coefficients in the various magnetic configurations lead to a very large and controllable magneto Seebeck ratio. In addition, we evaluate thermoelectric properties, such as the power factor, electron thermal conductance and figure of merit (ZT), of the ZGNR-based spin valve. Our results indicate that the power factor and the electron thermal conductance are strongly related to the transmission gap and electron-hole symmetry of the transmission spectrum. Moreover, the value of ZT can reach 0.15 at room temperature without considering phonon scattering. In addition, we investigate the thermally-controlled magnetic distributions in the ZGNR-based spin valve and find that the magnetic distribution, especially the local magnetic moment around the Ni atom, is strongly related to the thermal bias. The very large, multi-valued and controllable thermal magnetoresistance and Seebeck effects indicate the strong potential of ZGNR-based spin valves for extremely low-power consuming spin caloritronics applications. The thermally-controlled magnetic moment in the ZGNR-based spin valve indicates its possible applications for information storage.

Zeng, Minggang; Huang, Wen; Liang, Gengchiau

2012-12-01

103

Enhanced thermoelectric performance through energy-filtering effects in nanocomposites dispersed with metallic particles  

NASA Astrophysics Data System (ADS)

The thermoelectric properties of semiconductor materials with metallic nanoinclusions were investigated by using the Boltzmann transport equation under the relaxation time approximation. The results showed that the Seebeck coefficient can be significantly enhanced due to interface potential barrier induced by metallic nanoinclusions, leading to the optimized power factor at T < 700 K as barrier height is around kBT larger than the Fermi energy (here, kB is the Boltzmann constant). Additionally, it was found that high-concentration nanoinclusions with radius 1-2 nm can effectively enhance the thermoelectric performance of nanocomposites through energy-selective carrier scattering.

Liu, M.; Qin, X. Y.

2012-09-01

104

Effect of hot-press sintering temperature on thermal transport properties of TiSe2  

NASA Astrophysics Data System (ADS)

Titanium diselenide (TiSe2) alloy was prepared using solid state reaction method and hot press sintering. The effects of hot press sintering temperatures on TiSe2 were studied on the thermal transport properties of the material. As grown material shows pure TiSe2 phase and layer structure. Increasing sintering temperature results in reduced electrical resistivity ? whereas the Seebeck coefficient, ? show no significant relative change. Reduced electrical resistivity may be attributed to the increased crystalline nature. This results in improved power factor showing the optimum condition for producing better TiSe2 thermoelectric material.

Bhatt, R.; Bhattacharya, S.; Basu, R.; Patel, M.; Singh, A.; Bhatt, P.; Aswal, D. K.; Gupta, S. K.

2013-06-01

105

Effects of YSZ Additions on Thermoelectric Properties of Nb-Doped Strontium Titanate  

NASA Astrophysics Data System (ADS)

The effect of yttria-stabilized zirconia (YSZ) with a low thermal conductivity on the thermoelectric properties of Nb-doped SrTiO3 bulk materials, which were fabricated by the conventional normal pressure sintering method in an Ar atmosphere, was examined. YSZ additions reduced the thermal conductivity but significantly enhanced the electrical conductivity. However, the Seebeck coefficient was nearly independent of YSZ content. Thus, the ZT value was enhanced, and a sample with 3 wt.% YSZ displayed the maximum ZT value, 0.21, at 900 K. Additionally, the reason for the reduced thermal conductivity and enhanced electrical conductivity by YSZ additions was investigated in detail.

Wang, Ning; Li, Huawei; Ba, Yaoshuai; Wang, Yifeng; Wan, Chunlei; Fujinami, Kyoichi; Koumoto, Kunihito

2010-09-01

106

Effect of Ti Substitution on Thermoelectric Properties of W-Doped Heusler Fe2VAl Alloy  

NASA Astrophysics Data System (ADS)

Effects of element substitutions on thermoelectric properties of Heusler Fe2VAl alloys were evaluated. By W substitution at the V site, the thermal conductivity is reduced effectively because of the enhancement of phonon scattering resulting from the introduction of W atoms, which have much greater atomic mass and volume than the constituent elements of Fe2VAl alloy. W substitution is also effective to obtain a large negative Seebeck coefficient and high electrical conductivity through an electron injection effect. To change the conduction type from n-type to p-type, additional Ti substitution at the V site, which reduces the valence electron density, was examined. A positive Seebeck coefficient as high as that of conventional p-type Fe2VAl alloy was obtained using a sufficient amount of Ti substitution. Electrical resistivity was reduced by the hole doping effect of the Ti substitution while maintaining low thermal conductivity. Compared with the conventional solo-Ti-substituted p-type Fe2VAl alloy, the ZT value was improved, reaching 0.13 at 450 K.

Mikami, M.; Ozaki, K.; Takazawa, H.; Yamamoto, A.; Terazawa, Y.; Takeuchi, T.

2013-07-01

107

Effects of annealing temperature on thermoelectric properties of Bi2Te3 films prepared by co-sputtering  

NASA Astrophysics Data System (ADS)

N-type thermoelectric bismuth telluride (Bi2Te3) films were grown on SiO2/Si substrates by RF magnetron co-sputtering without intentional substrate heating. The effects of annealing temperature (150-350 °C) on surface morphology, crystal structure and thermoelectric properties of the Bi2Te3 films were investigated. Its crystallization was significantly improved by increasing the annealing temperature, giving rise to the enhanced charge carrier mobility. It is found that the optimum of Seebeck coefficient and power factor was about -242 ?V/K and 21 ?W/K2cm, respectively, obtained at the annealing temperature of 300 °C.

Wang, Xing; He, Hongcai; Wang, Ning; Miao, Lei

2013-07-01

108

Replace `van Hove singularity' by `negative- U singularity' and proceed: a comment on the analysis of HTSC Seebeck data by McIntosh and Kaiser - and related matters concerning the mechanism  

NASA Astrophysics Data System (ADS)

It is shown how recent simple modelling and interpretation of the transport data from high temperature superconducting (HTSC) systems can be recast in terms of a negative-U model rather than through a standard van Hove singularity. Since it seems that 0953-8984/9/28/005/img1 should be 0953-8984/9/28/005/img2 for a negative-U circumstance to be optimally effective in raising 0953-8984/9/28/005/img3, the ideas of Khodel et al concerning fermion condensation are worked into the presentation.

Wilson, John A.

1997-07-01

109

Strain effect analysis on the thermoelectric figure of merit in n-type Si/Ge nanocomposites  

NASA Astrophysics Data System (ADS)

In this paper, the effect of strain on the thermoelectric figure of merit is investigated in n-type Ge nanowire-Si host nanocomposite materials. The Seebeck coefficient and electrical conductivity of the Si-Ge nanocomposites are calculated using an analytical model derived from the Boltzmann transport equation (BTE) under the relaxation-time approximation. The effect of strain is incorporated into the BTE through the strain induced energy shift and effective mass variation calculated from the deformation potential theory and a degenerate k.p method at the zone-boundary X point. The effect of strain on the phonon thermal conductivity in the nanocomposites is computed with a model combining the strain dependent lattice dynamics and the ballistic phonon BTE. The electronic thermal conductivity is computed from the electrical conductivity using the Wiedemann-Franz law. Normal and shear strains are applied in the transverse plane of the Si-Ge nanocomposites. Thermoelectric properties, including the electrical conductivity, thermal conductivity, Seebeck coefficient, and dimensionless figure of merit, are computed for Si-Ge nanocomposites under these strain conditions.

Xu, Y.; Li, G.

2012-03-01

110

Thermal Cycling Effects on the Thermoelectric Properties of n-Type In, Ce based Skutterudite Compounds  

SciTech Connect

N-type In-filled CoSb3 are known skutterudite compounds that have shown promising thermoelectric (TE) properties resulting in high dimensionless figure of merit values at elevated temperatures. Their use in various waste heat recovery applications will require that they survive and operate after exposure to harsh thermal cycling environments. This research focused on uncovering the thermal cycling effects on thermoelectric properties of n-type In0.2Co4Sb12 and In0.2Ce0.15Co4Sb12 skutterudite compositions as well as quantifying their temperature-dependent structural properties (elastic modulus, shear modulus, and Poisson's ratio). It was observed that the Seebeck coefficient and resistivity increased only slightly in the double-filled In,Ce skutterudite materials upon thermal cycling. In the In-filled skutterudites the Seebeck coefficient remained approximately the same on thermal cycling, while electrical resistivity increased significantly after thermal cycling. Results also show that thermal conductivity marginally decreases in the case of In-filled skutterudites, whereas the reduction is more pronounced in In, Ce-based skutterudite compounds. The possible reason for this kind of reduction can be attributed to grain pinning effects due to formation of nano inclusions. High temperature structural property measurements (i.e., Young's modulus and shear modulus) are also reported and the results show that these structural properties decrease slowly as temperature increases and the compounds are structurally stable after numerous thermal cycles.

Biswas, Krishnendu; Subramanian, Mas A.; Good, Morris S.; Roberts, Kamandi C.; Hendricks, Terry J.

2012-06-14

111

A Quantitative Model for the Thermocouple Effect Using Statistical and Quantum Mechanics  

NASA Astrophysics Data System (ADS)

This paper employs statistical and quantum mechanics to develop a model for the mechanism underlying the Seebeck effect. The conventional view of the equilibrium criterion for valence electrons in a material is that the Fermi Energy should be constant throughout the system. However, this criterion is an approximation and it is shown to be inadequate for thermocouple systems. An improved equilibrium criterion is developed by applying statistical and quantum mechanics to determine the total flow of electrons across an arbitrary boundary within a system. Dynamic equilibrium is then considered to be the situation where the Fermi Energy either side of the boundary is such that the flow of electrons in each direction is the same. This equilibrium criterion is then applied to the conditions along the thermocouple wires and at the junctions in order to generate a model for the Seebeck effect. The equations involved for calculating the electronic structure of a material cannot be solved analytically, so a solution is achieved using numeric models employing CASTEP code running on a Sun Beowulf cluster and iterative algorithms written in the Excel™ VBA language on a PC. The model is used to calculate the EMF versus temperature function for the gold versus platinum thermocouple, which is then compared with established experimental data.

Bramley, Paul; Clark, Stewart

2003-09-01

112

Giant spin-dependent thermoelectric effect in magnetic tunnel junctions.  

PubMed

Thermoelectric effects in magnetic nanostructures and the so-called spin caloritronics are attracting much interest. Indeed it provides a new way to control and manipulate spin currents, which are key elements of spin-based electronics. Here we report on a giant magnetothermoelectric effect in a magnetic tunnel junction. The thermovoltage in this geometry can reach 1 mV. Moreover a magnetothermovoltage effect could be measured with ratio similar to the tunnel magnetoresistance ratio. The Seebeck coefficient can then be tuned by changing the relative magnetization orientation of the two magnetic layers in the tunnel junction. Therefore, our experiments extend the range of spintronic devices application to thermoelectricity and provide a crucial piece of information for understanding the physics of thermal spin transport. PMID:22434187

Lin, Weiwei; Hehn, Michel; Chaput, Laurent; Negulescu, Béatrice; Andrieu, Stéphane; Montaigne, François; Mangin, Stéphane

2012-03-20

113

Strain Effects in Thermoelectric Ca3Co4O9 Thin Films  

NASA Astrophysics Data System (ADS)

Thermoelectric oxides have attracted increasing attention due to their high thermal power and temperature stability. In particular, Ca3Co4O9 (CCO), a misfit layered structure consisting of single layer hole-doped CoO2 sandwiched between insulating Ca2CoO3 rocksalt layers, exhibits a high Seebeck coefficient at 1000 K.^ It was suggested that the Seebeck-coefficient can be further increased by growing doped thin films with controlled defects structures. This study combines pulsed layer deposition thin film synthesis of pristine CCO on several oxide substrates, as well as CCO thin films doped with Ti, Bi or La, with aberration-corrected scanning transmission electron microscopy and electron energy loss spectroscopy (EELS) to examine the effects of interfacial strain and doping on the atomic and electronic structures of CCO. The thermoelectric properties will be measured and correlated to the local changes in the atomic and electronic structures. We will further evaluate the role of CoO2 stacking faults, as well as film thickness on the thermoelectric properties of CCO.

Klie, Robert; Qiao, Qiao; Gulec, Ahmet; Paulauskas, Tadas; Kolesnik, Stanislaw; Dabrowski, Bogdan; Boyraz, Cihat; Ozdemir, Mehmet; Mazumdar, Dipanjan; Gupta, Arun

2011-03-01

114

The Effect of Adding Nano-Bi2Te3 on Properties of GeTe-Based Thermoelectric Material  

NASA Astrophysics Data System (ADS)

The efficient thermoelectric materials (GeTe)0.85- x (Mn0.6Sn0.4Te)0.15(Bi2Te3) x (0 ? x ? 0.05), in which Bi2Te3 is nanopowder, were prepared by hot pressing. The effect of adding neutral nano-Bi2Te3 content on the thermoelectric properties of germanium telluride was investigated. With increasing x, the thermal conductivity of the prepared samples decreased significantly and the Seebeck coefficient declined slightly, while there was no obvious change in electrical conductivity. In both electrical conductivity and Seebeck coefficient curves at different x values, there are inflection points around 600 K. The maximum dimensionless figure of merit ZT of the prepared materials is 1.54, attained in the temperature range from 700 K to 750 K for x = 0.03. The x-ray diffraction (XRD) pattern shows that Bi2Te3 has been alloyed into the GeTe-MnTe-SnTe alloy, which is consistent with the high-resolution scanning electron microscopy (HRSEM) images. Adding nano-Bi2Te3 to GeTe-based materials could also increase their performance stability at high temperature as a result of decreasing the phase-transition temperature T c.

Zhang, Lili; Wang, Wei; Ren, Baoguo; Guo, Jinjuan

2013-07-01

115

Thermoelectric Effects in Simulations of Phase Change Memory Mushroom Cells  

NASA Astrophysics Data System (ADS)

Phase change memory is a potential candidate for the future of high-speed non-volatile memory, however significant improvements in cell design is crucial for its success in the mainstream market. Due to the asymmetric geometry of phase change mushroom cells and the high temperature gradients generated, thermoelectric effects play a key role in determining energy consumption, cell performance, and reliability. In this study, rotationally symmetric 2D finite element simulations using COMSOL Multiphysics are implemented for GeSbTe (GST). Temperature dependent material parameters (electrical conductivity, thermal conductivity, heat capacity, and Seebeck coefficient) are included in the model for accuracy. Switching the direction of current shows a large change in peak molten volume within the cell, as well as current and power consumption.

Faraclas, Azer; Bakan, Gokhan; Gokirmak, Ali; Silva, Helena

2012-02-01

116

Effects of oxygen gas pressure on structural, electrical, and thermoelectric properties of (ZnO){sub 3}In{sub 2}O{sub 3} thin films deposited by rf magnetron sputtering  

SciTech Connect

Zinc indium oxide films were deposited by the rf magnetron sputtering method using a (ZnO){sub 3}In{sub 2}O{sub 3} target. The films were prepared at 573 K in various Ar/O{sub 2} sputtering gases (O{sub 2} content: 0%-25%). The effect of the oxygen gas content in the sputtering gas on the structural, optical, electrical, and thermoelectric properties of the films was investigated. The films had a c-axis oriented layer structure. The films deposited at 0%-3% oxygen gas contents exhibited a high electrical conductivity with a high carrier concentration, n{approx_equal}10{sup 20} cm{sup -3}, while the conductivity of the films significantly decreased above the 3% oxygen gas content, having a carrier concentration below 10{sup 18} cm{sup -3}. From the optical transmission measurement, the band gap of the films was estimated to be 3.01 eV. The films deposited at 3%-8% oxygen gas contents showed a high Seebeck coefficient, -300 {mu}V/K, while the maximum power factor, 4.78x10{sup -5} W/m K{sup 2}, was obtained at the 2% oxygen gas content. The Seebeck coefficient and the power factor were calculated on the basis of degenerate semiconductors. These results suggest that zinc indium oxide films have the possibility of being high performance thermoelectric materials.

Orikasa, Yuki; Hayashi, Naoaki; Muranaka, Shigetoshi [Department of Interdisciplinary Environment, Graduate School of Human and Environmental Studies, Kyoto University, Sakyo-ku, Kyoto 606-8501 (Japan)

2008-06-01

117

Effects of interdot hopping and Coulomb blockade on the thermoelectric properties of serially coupled quantum dots  

PubMed Central

We have theoretically studied the thermoelectric properties of serially coupled quantum dots (SCQDs) embedded in an insulator connected to metallic electrodes. In the framework of Keldysh Green’s function technique, the Landauer formula of transmission factor is obtained using the equation of motion method. Based on such analytical expressions of charge and heat currents, we calculate the electrical conductance, Seebeck coefficient, electron thermal conductance, and figure of merit (ZT) of SCQDs in the linear response regime. The effects of interdot hopping and electron Coulomb interactions on ZT are analyzed. We demonstrate that ZT is not a monotonic increasing function of interdot electron hopping strength (tc). We also show that in the absence of phonon thermal conductance, SCQD can reach the Carnot efficiency as tcapproaches zero.

2012-01-01

118

Effects of interdot hopping and Coulomb blockade on the thermoelectric properties of serially coupled quantum dots.  

PubMed

: We have theoretically studied the thermoelectric properties of serially coupled quantum dots (SCQDs) embedded in an insulator connected to metallic electrodes. In the framework of Keldysh Green's function technique, the Landauer formula of transmission factor is obtained using the equation of motion method. Based on such analytical expressions of charge and heat currents, we calculate the electrical conductance, Seebeck coefficient, electron thermal conductance, and figure of merit (ZT) of SCQDs in the linear response regime. The effects of interdot hopping and electron Coulomb interactions on ZT are analyzed. We demonstrate that ZT is not a monotonic increasing function of interdot electron hopping strength (tc). We also show that in the absence of phonon thermal conductance, SCQD can reach the Carnot efficiency as tcapproaches zero. PMID:22591807

T Kuo, David M; Chang, Yia-Chung

2012-05-16

119

Effect of Gamma Irradiation on The Dielectric Properties of La Doped CuZn Ferrite  

NASA Astrophysics Data System (ADS)

The electrical Properties of Lanthanum doped Cu-Zn ferrite of the general formula Cu.0.5Zn0.5La0.35Fe1.65O4 was carried out at different temperatures as a function of the applied frequency. The studied samples were prepared by double sintering ceramic technique. X-ray diffraction analysis was performed to assure the formation of the sample in single phases. The effect of gamma irradiation on the investigated samples was also studied. Two types of charge carriers were found in the form of two types of conduction, n-type and p- type as it was found by Seebeck measurements. Hopping mechanisms was the most predominant one that exists in the conduction processes. The variation of dielectric loss with gamma irradiation dose illustrates the different responses which enhances the change of magnetic ordering from ferromagnetic to paramagnetic state.

Ahmed, M. A.; Ramadan, A. A.; El-Ahdal, M. A.; Kamal, M. M.; Yousef, A.

2007-02-01

120

Effects of Fe substitution on the transport properties of the superconductor MgB2  

NASA Astrophysics Data System (ADS)

A systematic study has been made on the effect of Fe substitution by means of resistivity, thermal conductivity, and Seebeck coefficient of the Mg1-xFexB2 superconductor involving 0%, 0.3%, 0.6%, 1.2%, and 3.0% Fe content. The superconducting transition has been found to be very sharp (˜0.2K) for a pristine sample and substitution of Fe results in the decrease of TC with the increase in the transition width. Thermal conductivity is found to decrease with Fe content in general, such that the shoulder present in the pristine sample tends to fade away with increasing Fe. An analysis has been made on the normal state resistivity in terms of a two-band model, and of the thermal conductivity in terms of the Wiedemann-Franz law and the lattice thermal conductivity, and the information obtained on the basis of this analysis has been discussed. Besides, the electronic density of states (DOS) near the Fermi level remains nearly unaffected upon Fe substitution, as evidenced by the Seebeck coefficient measurements. When compared with Mn, Fe behaves like a nonmagnetic element with a modest variation in TC and on the other hand, the TC depression is much stronger when compared with other elements like Al, Cu, etc. Therefore, the observed variation in TC for the presently investigated concentrations of Fe is attributed to the specific nature of the given substituent element (Fe) in altering the phonon frequency and/or electron-phonon coupling strength rather than spin-flip scattering or change in DOS or disorder.

Gahtori, Bhasker; Lal, Ratan; Agarwal, S. K.; Kuo, Y. K.; Sivakumar, K. M.; Hsu, J. K.; Lin, J. Y.; Rao, Ashok; Chen, S. K.; MacManus-Driscoll, J. L.

2007-05-01

121

Electron effective mass in n-type electron-induced ferromagnetic semiconductor (In,Fe)As: Evidence of conduction band transport  

NASA Astrophysics Data System (ADS)

The electron effective mass (m*) in n-type carrier-induced ferromagnetic semiconductor (In,Fe)As was estimated by using the thermoelectric Seebeck effect. It was found that m* is 0.03 ~ 0.17m0 depending on the electron concentration, where m0 is the free electron mass. These values are similar to those of electrons in the conduction band of n+ InAs. The Fermi level EF in (In,Fe)As is located at least 0.15 eV above the conduction band bottom. Our results indicate that electron carriers in (In,Fe)As reside in the conduction band, rather than in a hypothetical Fe-related itinerant impurity band.

Nam Hai, Pham; Anh, Le Duc; Tanaka, Masaaki

2012-12-01

122

Large transverse thermoelectric voltage effect in incline-oriented SrTi1-xNbxO3 films with cubic structure  

NASA Astrophysics Data System (ADS)

SrTi1-xNbxO3 films with cubic structure were grown on LaAlO3 single crystal substrates by pulsed laser deposition, in which the inclination angle of the (001) plane orientation was in strict accordance with 10° against the film surface. The maximal peak value of transverse thermoelectric voltage of up to 6.88 V was obtained for the sample with the optimum thickness around 500 nm. The large voltage signals indicate SrTi1-xNbxO3 films have considerable anisotropy of the Seebeck coefficient ?S which reaches to ~25 ?V/K. The results demonstrate cubic structure materials also can be used to develop large transverse thermoelectric voltage effect.

Qin, Yi; Zhao, Ting; Zhang, Hai-Hong; Wang, Bo; Zhang, Peng-Xiang; Yang, Jian-Feng

2013-06-01

123

Thermo-electric effect in a nano-sized crossed Permalloy/Cu junction under high bias current  

NASA Astrophysics Data System (ADS)

We show that the difference in the Seebeck coefficients between two voltage probes produces an additional electric signal in the local resistance measurement of the submicron-sized junction. This is because the temperature increase at the junction induced by the Joule heating produces unnegligible Seebeck voltage in addition to the Ohmic voltage. In nanostructured systems, since the temperature variation becomes quite high under the high-bias current, the Seebeck voltage dominates the detected electrical voltage. This provides a consistent description for unusual bias-current dependences of the differential resistance in nano-sized metallic junction systems.

Mu, Congpu; Hu, Shaojie; Wang, Jianbo; Kimura, Takashi

2013-09-01

124

Induced Magneto-transport Effects in Non-magnetic Metals on Yttrium Iron Garnet  

NASA Astrophysics Data System (ADS)

Yttrium iron garnet (YIG) was called ``spin Seebeck insulator,'' for it supports heat-generated pure spin currents. Pt thin film, with strong spin-orbit interaction, is used as a spin current generator or detector based on the spin Hall effect or the inverse spin Hall effect. The combination of these two materials plays a very important role in spintronics. A recent magnetotransport study shows strong evidence of a magnetic proximity effect in thin Pt films deposited on YIG. Here, we present a magneto-transport study of several non-magnetic (NM) metal films (e.g. Pt, Pd) on YIG films grown on gadolinium gallium garnet substrates with laser molecular beam epitaxy. The anisotropic magnetoresistance (AMR) and anomalous Hall effect (AHE) reveal clear ferromagnetic characteristics in NM films. The magnitude of the AHE angle ? in Pd/YIG structure increases with decreasing temperature, while ? in Pt/YIG structure has a sign reversal at an intermediate temperature. Both AMR and AHE have been investigated as the NM film thickness is varied and an optimal effective thickness is identified. The effect of annealing has also been studied and the results are consistent with the observed thickness dependence. In thin NM films, a ln(T) temperature dependence with a resistivity minimum is observed at low temperatures, suggesting that the Kondo effect may be relevant. Detailed discussions about the origin of these effects will be presented.

Lin, Tao; Tang, Chi; Shi, Jing

2013-03-01

125

Thermomagnonic spin transfer and Peltier effects in insulating magnets  

NASA Astrophysics Data System (ADS)

The recent discovery of the spin Seebeck effect [1] in metals, insulators and semiconductors stimulated development of spincaloritronics [2]. The possibility of measuring the Onsager reciprocal spin Peltier effect has been investigated recently as well. In our theoretical work [3], we study the fictitious electromagnetic fields induced by magnetic textures which may offer an alternative route for observing the spin Peltier effect. Particularly, in an insulating ferromagnet a moving magnetic texture should effectively drive the spin (wave) current which in turn should lead to the heat current by the spin Peltier effect. We further study the coupled magnon energy transport and collective magnetization dynamics in ferromagnets with magnetic textures. We conclude that the analogy between the fictitious electromagnetic fields and real fields should lead to magnonic counterparts of such effects as the Hall effect, the Ettingshausen effect, the Nernst effect, and the Righi-Leduc effect. By constructing a phenomenological theory based on irreversible thermodynamics, we describe motion of domain walls by thermal gradients and generation of heat flows by magnetization dynamics. From microscopic description based on magnon kinetics, we estimate the transport coefficients and analyze the feasibility of energy-related applications (e.g. nanoscale heat pumps [4]) in insulating ferromagnets, such as yttrium iron garnet and europium oxide. Our estimates show that the viscous coupling effects between magnetization dynamics and magnon flows can be strong in materials with low spin densities (e.g. dilute magnetic systems) and narrow domain walls, which can allow the magnonic manipulation of magnetization dynamics and heat pumping.[4pt] [1] K. Uchida et al. Nature 455, 778 (2008).[0pt] [2] G. E. W. Bauer, A. H. MacDonald, S. Maekawa, Solid State Commun. 150, 459 (2010).[0pt] [3] A. A. Kovalev and Y. Tserkovnayk, arXiv:1106.3135.[0pt] [4] A. A. Kovalev and Y. Tserkovnyak, Solid State Commun. 150, 500 (2010).

Kovalev, Alexey A.

2012-02-01

126

MeV Si ion beam modification effects on the thermoelectric generator from Er0.1Fe1.9SbGe0.4 thin film  

NASA Astrophysics Data System (ADS)

Effective thermoelectric materials and devices have a low thermal conductivity and a high electrical conductivity. The performance of the thermoelectric materials and devices is shown by a dimensionless figure of merit, ZT. The purpose of this study is to improve the figure of merit of the single layer of Er0.1Fe1.9SbGe0.4 thin film used as thermoelectric generators. We have deposited the monolayer of Er0.1Fe1.9SbGe0.4 thin film on silicon and silica substrates with thickness of 302 nm using ion beam assisted deposition (IBAD). Rutherford backscattering spectrometry (RBS) was used to determine the total film thickness and stoichiometry. The MeV Si ion bombardments were performed on single layer of Er0.1Fe1.9SbGe0.4 thin films at five different fluences between 5 × 1013-5 × 1015 ions/cm2.The defect and disorder in the lattice caused by ion beam modification and the grain boundaries of these nanoscale clusters increase phonon scattering and increase the chance of annihilation of the phonon. The increase of the electron density of states in the miniband of the quantum dot structure formed by bombardment also increases the Seebeck coefficient and the electrical conductivity. We measured the thermoelectric efficiency of the fabricated device by measuring the cross plane thermal conductivity by the 3rd harmonic (3?) method, the cross plane Seebeck coefficient, and the electrical conductivity using the Van Der Pauw method before and after the MeV ion bombardments.

Budak, S.; Guner, S.; Muntele, C.; Ila, D.

2009-05-01

127

Giant Nernst effect in CeCoIn5.  

PubMed

We present a study of Nernst and Seebeck coefficients of the heavy-fermion superconductor CeCoIn5. Below 18 K, concomitant with a field-dependent Seebeck coefficient, a large sublinear Nernst signal emerges with a magnitude drastically exceeding what is expected for a multiband Fermi-liquid metal. In the mixed state, in contrast with all other superconductors studied before, this signal overwhelms the one associated with the motion of superconducting vortices. The results point to a hitherto unknown source of transverse thermoelectricity in strongly interacting electrons. PMID:15245310

Bel, R; Behnia, K; Nakajima, Y; Izawa, K; Matsuda, Y; Shishido, H; Settai, R; Onuki, Y

2004-05-27

128

Spin thermoelectric effects in Kondo quantum dots coupled to ferromagnetic leads  

NASA Astrophysics Data System (ADS)

Thermoelectric effects in transport through a quantum dot coupled to external ferromagnetic leads are investigated theoretically. The basic thermoelectric transport characteristics, such as thermopower, electronic contribution to the heat conductance, and the corresponding figure of merit, are calculated in the linear response regime by means of the density-matrix numerical renormalization group method. The case of a nonzero spin splitting of the electrochemical potential in the electrodes is also considered and the associated spin thermoelectric effects are analyzed. It is shown that the spin-dependent thermoelectric phenomena in the local moment regime depend generally on the exchange field induced by ferromagnetic contacts. In addition, the temperature dependence of the Seebeck coefficient is rather nontrivial, and depends on the spin polarization and spin relaxation in the leads. In the presence of ferromagnetic leads, the thermopower as a function of temperature may change sign more times than the thermopower for nonmagnetic leads. These changes can be thus used to determine the relevant Kondo behavior and Kondo energy scale in the system. Moreover, the effects of external magnetic field and different spin polarization of ferromagnetic leads are also analyzed.

Weymann, I.; Barna?, J.

2013-08-01

129

Density-of-states effective mass and scattering parameter measurements by transport phenomena in thin films  

NASA Astrophysics Data System (ADS)

A novel machine has been developed to measure transport coefficients in the temperature range of 50-350 K of thin films deposited on electrically insulating substrates. The measured coefficients-resistivity, Hall, Seebeck, and Nernst-are applied to solutions of the Boltzmann transport equation to give information about the film's density-of-states effective mass, the Fermi energy level, and an energy-dependent scattering parameter. The machine is designed to eliminate or compensate for simultaneously occurring transport phenomena that would interfere with the desired measured quantity, while allowing for all four coefficients to be measured on the same sample. An average density-of-states effective mass value of 0.29+/-0.04me was measured on the transparent conductive oxide, cadmium stannate (CTO), over a carrier concentration range of 2-7×1020 cm-3. This effective mass value matched previous results obtained by optical and thermoelectric modeling. The measured scattering parameter indicates that neutral impurities or a mixture of scattering mechanisms may inhibit the transport of carriers in CTO.

Young, D. L.; Coutts, T. J.; Kaydanov, V. I.

2000-02-01

130

Effect of NiTe Nanoinclusions on Thermoelectric Properties of Bi2Te3  

NASA Astrophysics Data System (ADS)

Metal nanoinclusions in bulk thermoelectric matrix create metal-semiconductor interfaces, which can result in improvement in the thermoelectric power factor due to low-energy electron filtering and a simultaneous reduction in lattice thermal conductivity due to increased phonon scattering at grain boundaries. The combined effect results in enhancement of the thermoelectric figure of merit. We report the effect of NiTe nanoinclusions in a Bi2Te3 matrix. The Bi2Te3/NiTe nanocomposite was synthesized by planetary ball milling. Different volume fractions of NiTe nanoinclusions were incorporated into the bulk (Bi2Te3) matrix and uniaxially hot pressed at 100 MPa and 500°C. The presence of nanoinclusions was confirmed by x-ray diffraction and transmission electron microscopy. The Seebeck coefficient, electrical conductivity, and thermal diffusivity were measured from room temperature to 150°C. The carrier concentration of the matrix (Bi2Te3) and the nanocomposites (NiTe/Bi2Te3) at room temperature were deduced from Hall-effect measurements. Addition of NiTe decreased the carrier concentration, and the power factor increased in the 1 vol.% NiTe/Bi2Te3 compared with inclusion-free Bi2Te3 matrix due to an increase in mobility.

Sumithra, S.; Takas, Nathan J.; Nolting, Westly M.; Sapkota, Sanshrut; Poudeu, Pierre F. P.; Stokes, Kevin L.

2012-06-01

131

Large Seebeck magnetic anisotropy in thin Co films embedded in Cu determined by ab initio investigations  

NASA Astrophysics Data System (ADS)

The longitudinal thermopower of a Cu/Co/Cu trilayer system exhibits an oscillatory dependence on the thickness of the Co layer, a behavior related to the formation of quantum well states in the minority spin channel. In addition, it is found to be very sensitive to a switching between an in-plane and out-of-plane magnetization. The resulting magnetothermopower (MTP) is therefore much larger than anticipated from the conventional anisotropic magnetoresistance (AMR). Our calculations establish a direct connection between the magnitude of the MTP signal and the asymmetry of the AMR around the Fermi energy. An enhancement of MTP based on this understanding may offer the possibility of implementing an efficient spin read-out thermoelectric device based on a single ferromagnetic layer.

Popescu, Voicu; Kratzer, Peter

2013-09-01

132

Temporal evolution of Seebeck coefficient in an ac driven strongly correlated quantum dot  

NASA Astrophysics Data System (ADS)

We study the response of the thermopower of a quantum dot in the Kondo regime to sinusoidal displacement of the dot energy level via a gate voltage using time dependent non-crossing approximation and linear response Onsager relations. Instantaneous thermopower begins to exhibit complex fluctuations when the driving amplitude is increased at constant driving frequency. We also find that the time averaged thermopower decreases steadily until it saturates at constant driving amplitude as a function of inverse driving frequency. On the other hand, time averaged thermopower is found to be quite sensitive to ambient temperature at all driving frequencies for large driving amplitudes. We discuss the underlying microscopic mechanism for these peculiarities based on the behaviour of the dot density of states.

Goker, Ali Ihsan; Gedik, Elif

2013-03-01

133

Temporal evolution of the Seebeck coefficient in an ac driven strongly correlated quantum dot  

NASA Astrophysics Data System (ADS)

We study the response of the thermopower of a quantum dot in the Kondo regime to sinusoidal displacement of the dot energy level via a gate voltage using time dependent non-crossing approximation and linear response Onsager relations. Instantaneous thermopower begins to exhibit complex fluctuations when the driving amplitude is increased at constant driving frequency. We also find that the time averaged thermopower decreases steadily until it saturates at constant driving amplitude as a function of inverse driving frequency. On the other hand, time averaged thermopower is found to be quite sensitive to ambient temperature at all driving frequencies for large driving amplitudes. We discuss the underlying microscopic mechanism for these peculiarities based on the behaviour of the dot density of states.

Goker, A.; Gedik, E.

2013-03-01

134

Thermoelectric effect of silicon films prepared by aluminum-induced crystallization  

NASA Astrophysics Data System (ADS)

Aluminum-induced crystallized silicon films were prepared on glass substrates by magnetron sputtering. Aluminum was added in the silicon films intermittently by the regular pulse sputtering of an aluminum target. The amount of aluminum in the silicon films can be controlled by regulating the aluminum sputtering power and the sputtering time of the undoped silicon layer; thus, the Seebeck coefficient and electrical resistivity of the polycrystalline silicon films can be adjusted. It is found that, when the sputtering power ratio of aluminum to silicon is 16%, both the Seebeck coefficient and the electrical resistivity decrease with the increasing amount of aluminum as expected; the Seebeck coefficient and the electrical resistivity at room temperature are 0.185-0.285 mV/K and 0.30-2.4 ?·cm, respectively. By reducing the sputtering power ratio to 7%, however, the Seebeck coefficient does not change much, though the electrical resistivity still decreases with the amount of aluminum increasing; the Seebeck coefficient and electrical resistivity at room temperature are 0.219-0.263 mV/K and 0.26-0.80 ?·cm, respectively.

Hou, Qing-run; Gu, Bing-fu; Chen, Yi-bao; He, Yuan-jin

2012-10-01

135

Thermal Cycling, Mechanical Degradation, and the Effective Figure of Merit of a Thermoelectric Module  

NASA Astrophysics Data System (ADS)

Thermoelectric modules experience performance reduction and mechanical failure due to thermomechanical stresses induced by thermal cycling. The present study subjects a thermoelectric module to thermal cycling and evaluates the evolution of its thermoelectric performance through measurements of the thermoelectric figure of merit, ZT, and its individual components. The Seebeck coefficient and thermal conductivity are measured using steady-state infrared microscopy, and the electrical conductivity and ZT are evaluated using the Harman technique. These properties are tracked over many cycles until device failure after 45,000 thermal cycles. The mechanical failure of the TE module is analyzed using high-resolution infrared microscopy and scanning electron microscopy. A reduction in electrical conductivity is the primary mechanism of performance reduction and is likely associated with defects observed during cycling. The effective figure of merit is reduced by 20% through 40,000 cycles and drops by 97% at 45,000 cycles. These results quantify the effect of thermal cycling on a commercial TE module and provide insight into the packaging of a complete TE module for reliable operation.

Barako, M. T.; Park, W.; Marconnet, A. M.; Asheghi, M.; Goodson, K. E.

2013-03-01

136

Thermal Hall effect in YBCO: Probing Fermi-surface reconstruction inside the superconducting state  

NASA Astrophysics Data System (ADS)

The thermal Hall (Righi-Leduc) effect was measured in the cuprate superconductor YBCO at a doping p = 0.11, as a function of magnetic field H up to 29 T. At temperatures well below the zero-field superconducting Tc, the thermal Hall conductivity ?xy is positive at low field and then turns over to become negative at fields above 15 T. The negative ?xy is consistent with the negative Hall and Seebeck coefficients observed in the normal state above 25 T [1,2]. This further supports our interpretation: the Fermi surface of YBCO contains a small electron-like pocket [3] in that region of the phase diagram, the result of a Fermi-surface reconstruction attributed to stripe order [4]. In the T = 0 limit at H = 29 T, we find reasonable agreement with the Wiedemann-Franz law, ?xy/T=L0?xy. The fact that ?xy changes sign at H 15 T is consistent with a scenario of phase competition whereby stripe order emerges only at finite field, in agreement with recent NMR studies that detect the onset of charge-stripe order above 15 T [5]. [4pt] [1] LeBoeuf et al., PRB 83, 054056 (2011); [2] Lalibert'e et al., Nat. Commun. 2, 432 (2011); [3] LeBoeuf et al., Nature 450, 533 (2007); [4] Chang et al., PRL 104, 057005 (2010); [5] Wu et al., Nature 477, 191 (2011).

Cyr-Choinière, Olivier; Laliberté, Francis; Dufour-Beauséjour, Sophie; Grissonnanche, Gaël.; Gordon, Ryan T.; Doiron-Leyraud, Nicolas; Taillefer, Louis; Ramshaw, Brad J.; Liang, Ruixing; Bonn, Doug A.; Hardy, Walter N.; Proust, Cyril

2012-02-01

137

The effect of element substitution on high-temperature thermoelectric properties of Ca3Co2O6 compounds  

NASA Astrophysics Data System (ADS)

Polycrystalline Ca3Co1.8M0.2O6 (M=Mn, Fe, Co, Ni, Cu) and Ca2.7Na0.3Co2O6 were synthesized by solid-state reaction to evaluate the effect of substitution on the thermoelectric properties of Ca3Co2O6. Substitution by Mn, Cu and Na appears to increase carrier density, given that electrical resistivity (?) and the Seebeck coefficient (S) were simultaneously reduced. Conversely, Fe substitution seems to reduce carrier density, resulting in a simultaneous increase in S and ?. Cu and Na substitution resulted in a significant decrease in ? due to enhancement of grain size and grain boundary connectivity, which could have a strong impact on ?. Not only the intrinsic substitution effect on the electronic state but also this modification of the microstructure plays an important role in improvement of the thermoelectric power factor, particularly in the case of the Na-substituted sample.Graphical abstractSEM images of fracture cross-sections of Ca3Co1.8M0.2O6 (M=Mn, Fe, Co, Ni and Cu) and Ca2.7Na0.3Co2O6 pellets.

Mikami, Masashi; Funahashi, Ryoji

2005-05-01

138

Exploring the doping effects of Ag in p-type PbSe compounds with enhanced thermoelectric performance  

NASA Astrophysics Data System (ADS)

In this study, we prepared a series of Ag-doped PbSe bulk materials by a melting-quenching process combined with a subsequent spark plasma sintering process, and systematically investigated the doping effects of Ag on the thermoelectric properties. Ag substitution in the Pb site does not introduce resonant levels near the valence band edge or detectable change in the density of state in the vicinity of the Fermi level, but moves the Fermi level down and increases the carrier concentration to a maximum value of ~4.7 × 1019 cm-3 which is still insufficient for heavily doped PbSe compounds. Nonetheless, the non-monotonic variation in carrier concentration with increasing Ag content indicates that Ag doping reaches the solution limit at ~1.0% and the excessive Ag presumably acts as donors in the materials. Moreover, the large energy gap of the PbSe-based material wipes off significant 'roll-over' in the Seebeck coefficient at elevated temperatures which gives rise to high power factors, being comparable to p-type Te analogues. Consequently, the maximum ZT reaches ~1.0 for the 1.5% Ag-doped samples with optimized carrier density, which is ~70% improvement in comparison with an undoped sample and also superior to the commercialized p-type PbTe materials.

Wang, Shanyu; Zheng, Gang; Luo, Tingting; She, Xiaoyu; Li, Han; Tang, Xinfeng

2011-11-01

139

Effect of grain size on thermoelectric properties of n-type nanocrystalline bismuth-telluride based thin films  

NASA Astrophysics Data System (ADS)

The effect of grain size on the thermoelectric properties of n-type nanocrystalline bismuth-telluride based thin films is investigated. We prepare the nanocrystalline thin films with average grain sizes of 10, 27, and 60 nm by a flash-evaporation method followed by a hydrogen annealing process. The thermoelectric properties, in terms of the thermal conductivity by a differential 3? method, the electrical conductivity, and the Seebeck coefficient are measured at room temperature and used to evaluate the figure of merit. The minimum thermal conductivity is 0.61 W m-1 K-1 at the average grain size of 10 nm. We also estimate the lattice thermal conductivity of the nanocrystalline thin films and compare it with a simplified theory of phonon scattering on grain boundaries. For nanosized grains, the lattice thermal conductivity of nanocrystalline thin films decreases rapidly for smaller grains, corresponding to the theoretical calculation. The figure of merit is also decreased as the grain size decreases, which is attributed to the increased number of defects at the grain boundaries.

Takashiri, M.; Miyazaki, K.; Tanaka, S.; Kurosaki, J.; Nagai, D.; Tsukamoto, H.

2008-10-01

140

Grain size effects on reductions in lattice thermal conductivity of TiNiSn half-Heusler alloys  

NASA Astrophysics Data System (ADS)

TiNiSn half-Heusler alloys are currently being investigated for their potential as thermoelectric materials. They exhibit large Seebeck coefficients (-40 to -250 ?V/K) and favorable electrical resistivities (0.1 to 8m?-cm), resulting into promising power factors (?^2?T) ( ˜ 1.0 W/m-K at 300K and ˜ 4.2 W/m-K at 650K). Unfortunately, the thermal conductivity (composed mainly of lattice contribution) in these materials is also high ( ˜ 10W/m-K). Hence, attempts to tune the lattice thermal conductivity, by point defect or mass fluctuation scattering and grain boundary scattering effects have been investigated. A correlation between the grain size (D <10?m) and the lattice thermal conductivity in these materials, in good agreement with theoretical predictions by Sharp et. al. have been observed. Reductions in grain size ( ˜ sub-micron or nano-sized grains) have been achieved by ball milling and shock compaction of original ingots. Significant reductions in lattice thermal conductivity ( ˜ 3W/m-K at 300K) in these nano-grained samples have been observed. Results on the correlation of lattice thermal conductivity and grain size will be presented and discussed.

Bhattacharya, S.; Tritt, Terry M.; Xia, Y.; Ponnambalam, V.; Poon, S. J.; Thadhani, N.

2002-10-01

141

The Effect of Annealing in Controlled Vapor Pressure on the Thermoelectric Properties of RF-Sputtered Bi2Te3 Film  

NASA Astrophysics Data System (ADS)

To investigate the effect of annealing in controlled atmosphere on the thermoelectric properties of Bi-Te film, Te-deficient Bi-Te film was deposited by sputtering, and then annealed with various Bi-Te alloy powders with different Te concentrations in a closed system at 250°C for 24 h. Bi-Te phases other than Bi2Te3 in the as-deposited film could be removed when the film was annealed with Bi-Te source powder containing 62 at.% or higher content of Te. At the same time, the values of Seebeck coefficient and carrier concentration of the films approach -105 ?V/K and 3 × 1019 cm-3 to 6 × 1019 cm-3, respectively. This result indicates that mass transport of Te to the film takes place, resulting in the formation of Bi2Te3 phase and reduction of the amount of p-type carriers due to compositional change of the film from Te-deficient to stoichiometric. Annealing in controlled Te-vapor atmosphere is an effective method to improve the thermoelectric properties of Bi-Te film by changing the composition and phase of Te-deficient film to stoichiometric Bi2Te3 film.

Kim, Hyo-Jung; Yim, Ju-Hyuk; Choi, Won Chel; Park, Chan; Kim, Jin-Sang

2012-06-01

142

Impact of interfacial resistance switching on thermoelectric effect of Nb-doped SrTiO3 single crystalline  

NASA Astrophysics Data System (ADS)

The thermoelectric properties of the bistable resistance states in Nb doped SrTiO3 single crystal have been investigated. The Seebeck coefficients for both low and high resistance states change linearly with temperature. The three-terminals contrast measurement demonstrates that a large fraction of the voltage drop is applied at the tiny volume near the bottom interface between the electrode and the oxide bulk. Therefore, the metallic oxide bulk plays a dominant role in the temperature dependence of Seebeck coefficients. The thermoelectric properties of new resistance switching (RS) devices with minimized non-RS volume could be exploited for the RS mechanism and novel applications.

Zhang, Peijian; Meng, Yang; Liu, Ziyu; Li, Dong; Su, Tao; Meng, Qingyu; Mao, Qi; Pan, Xinyu; Chen, Dongmin; Zhao, Hongwu

2012-03-01

143

Effects of Gd, Co, and Ni doping in La{sub 2/3}Ca{sub 1/3}MnO{sub 3}: Resistivity, thermopower, and paramagnetic resonance  

SciTech Connect

The effect of elemental substitutions on the properties of the ferromagnetic, conducting, highly magnetoresistive compound La{sub 2/3}Ca{sub 1/3}MnO{sub 3} has been studied. The results of Co doping and Ni doping on the Mn site and Gd doping on the La site are reported. These compounds were investigated by x-ray diffraction, magnetization measurements, resistivity measurements, thermopower measurements, and by paramagnetic resonance. The result of replacing La by Gd atoms is to lower the ferromagnetic (or metal-insulator) transition temperature, an effect which is shown to be due to bond bending caused by the lattice adjusting to the size differential between the La and Gd ions. On the other hand, the reduction of the magnetic transition temperature when Mn ions are replaced with Co or Ni ions is {ital not} attributed to changes in the size of the ions. Instead, we ascribe the lowering of the ferromagnetic transition temperature to a weakening of the double-exchange interaction between two unlike ions. The resistivity and Seebeck coefficient in these materials have been investigated as a function of elemental substitution. The magnetic polaron theory of Zhang is used, phenomenologically, to provide a quantitative explanation of these transport properties. In addition, the effect of these elemental substitutions on the linewidths of the paramagnetic resonances is studied and is discussed in terms of exchange narrowing and spin-lattice relaxation.

Rubinstein, M.; Gillespie, D.J.; Snyder, J.E. [U.S. Naval Research Laboratory, Washington, D.C. 20390 (United States); Tritt, T.M. [Clemson University, Clemson, South Carolina 29634 (United States)

1997-09-01

144

Thermoelectric Terminology in Metrology and Standards.  

National Technical Information Service (NTIS)

In metrology and standards, thermoelectricity is most often associated with thermometry. Therefore, this paper emphasizes thermoelectricity in thermometry and it focuses on the Seebeck effect. Yet, the thermoelectric terminology applies generally to all t...

R. P. Reed

1989-01-01

145

Effects of SiC Nanodispersion on the Thermoelectric Properties of p-Type and n-Type Bi2Te3-Based Alloys  

NASA Astrophysics Data System (ADS)

Polycrystalline p-type Bi0.5Sb1.5Te3 and n-type Bi2Te2.7Se0.3 thermoelectric (TE) alloys containing a small amount (vol.% ?5) of SiC nanoparticles were fabricated by mechanical alloying and spark plasma sintering. It was revealed that the effects of SiC addition on TE properties can be different between p-type and n-type Bi2Te3-based alloys. SiC addition slightly increased the power factor of the p-type materials by decreasing both the electrical resistivity ( ?) and Seebeck coefficient ( ?), but decreased the power factor of n-type materials by increasing both ? and ?. Regardless of the conductivity type, the thermal conductivity was reduced by dispersing SiC nanoparticles in the Bi2Te3-based alloy matrix. As a result, a small amount (0.1 vol.%) of SiC addition increased the maximum dimensionless figure of merit ( ZT max) of the p-type Bi0.5Sb1.5Te3 alloys from 0.88 for the SiC-free sample to 0.97 at 323 K, though no improvement in TE performance was obtained in the case of n-type Bi2Te2.7Se0.3 alloys. Importantly, the SiC-dispersed alloys showed better mechanical properties, which can improve material machinability and device reliability.

Liu, Da-Wei; Li, Jing-Feng; Chen, Chen; Zhang, Bo-Ping

2011-05-01

146

Spray pyrolysis of tin selenide thin-film semiconductors: the effect of selenium concentration on the properties of the thin films  

NASA Astrophysics Data System (ADS)

Thin films of tin selenide (SnxSey) with an atomic ratio of , 1 and 1.5 were prepared on a glass substrate at T = 470°C using a spray pyrolysis technique. The initial materials for the preparation of the thin films were an alcoholic solution consisting of tin chloride (SnCl4· 5H2O) and selenide acide (H2SeO3). The prepared thin films were characterized by X-ray diffraction (XRD), scanning electron microscopy, scanning tunneling microscopy, scanning helium ion microscopy, and UV-vis spectroscopy. The photoconductivity and thermoelectric effects of the SnxSey thin films were then studied. The SnxSey thin films had a polycrystalline structure with an almost uniform surface and cluster type growth. The increasing atomic ratio of r in the films, the optical gap, photosensitivity and Seebeck coefficient were changed from 1.6 to 1.37 eV, 0.01 to 0.31 and ?26.2 to ?42.7 mV/K (at T = 350 K), respectively. In addition, the XRD patterns indicated intensity peaks in r = 1 that corresponded to the increase in the SnSe and SnSe2 phases.

Fadavieslam, M. R.; Bagheri-Mohagheghi, M. M.

2013-08-01

147

Post-annealing Effect on Microstructures and Thermoelectric Properties of Bi0.45Sb1.55Te3 Thin Films Deposited by Co-sputtering  

NASA Astrophysics Data System (ADS)

p-Type Bi0.45Sb1.55Te3 thermoelectric (TE) thin films have been prepared at room temperature by a magnetron cosputtering process. The effect of postannealing on the microstructure and TE properties of Bi0.45Sb1.55Te3 films has been investigated in the temperature range from room temperature to 350°C. x-Ray diffraction analysis shows that the annealed films have polycrystalline rhombohedral crystal structure, and the average grain size increases from 36 nm to 64 nm with increasing annealing temperature from room temperature to 350°C. Electron probe microanalysis shows that annealing above 250°C can cause Te reevaporation, which induces porous thin films and dramatically affects electrical transport properties of the thin films. TE properties of the films have been investigated at room temperature. The hole concentration shows a trend from descent to ascent and has a minimum value at the annealing temperature of 200°C, while the Seebeck coefficient shows an opposite trend and a maximum value of 245 ?V K-1. The electrical resistivity monotonically decreases from 19.8 m? cm to 1.4 m? cm with increasing annealing temperature. Correspondingly, a maximum value of power factor, 27.4 ?W K-2 cm-1, was obtained at the annealing temperature of 250°C.

Song, Junqiang; Chen, Xihong; Tang, Yunshan; Yao, Qin; Chen, Lidong

2012-11-01

148

Effect of ruthenium substitution in layered sodium cobaltate Na{sub x}CoO{sub 2}: Synthesis, structural and physical properties  

SciTech Connect

Solid-state synthesis of Na{sub 0.71}Co{sub 1-x}Ru{sub x}O{sub 2} compositions shows that ruthenium can be substituted for cobalt in the hexagonal Na{sub 0.71}CoO{sub 2} phase up to x=0.5. The cell expands continuously with increasing ruthenium content. All mixed Co-Ru phases show a Curie-Weiss behaviour with no evidence of magnetic ordering down to 2 K. Unlike the parent phase Na{sub 0.71}CoO{sub 2}, ruthenium-substituted phases are all semiconducting. They exhibit high thermoelectric power, with a maximum of 165 muV/K at 300 K for x=0.3. The Curie constant C and Seebeck coefficient S show a non-monotonic evolution as a function of ruthenium content, demonstrating a remarkable interplay between magnetic properties and thermoelectricity. The presence of ruthenium has a detrimental effect on water intercalation and superconductivity in this system. Applying to Ru-substituted phases the oxidative intercalation of water known to lead to superconductivity in the Na{sub x}CoO{sub 2} system yields a 2-water layer hydrate only for x=0.1, and this phase is not superconducting down to 2 K. - Graphical Abstract: Effect of ruthenium substitution on thermoelectric power in Na{sub 0.71}Co{sub 1-x}Ru{sub x}O{sub 2} (left) and on low-temperature ac susceptibility in hydrated derivative (right).

Strobel, Pierre, E-mail: pierre.strobel@grenoble.cnrs.f [Institut Neel, CNRS, and Universite Joseph Fourier, B.P. 166, 38042 Grenoble, Cedex 9 (France); Muguerra, Herve [Institut Neel, CNRS, and Universite Joseph Fourier, B.P. 166, 38042 Grenoble, Cedex 9 (France); Hebert, Sylvie [CRISMAT (UMR CNRS 6508), ENSI-Caen, F-14050 Caen Cedex (France); Pachoud, Elise [Institut Neel, CNRS, and Universite Joseph Fourier, B.P. 166, 38042 Grenoble, Cedex 9 (France); CRISMAT (UMR CNRS 6508), ENSI-Caen, F-14050 Caen Cedex (France); Colin, Claire [Institut Neel, CNRS, and Universite Joseph Fourier, B.P. 166, 38042 Grenoble, Cedex 9 (France); Julien, Marc-Henri [Laboratoire de Spectrometrie Physique, UMR CNRS 5588 and Universite Joseph Fourier, 38402 Saint Martin d'Heres (France)

2009-07-15

149

Thermoelectric effects in silicene nanoribbons  

NASA Astrophysics Data System (ADS)

Transport and thermoelectric coefficients (including also spin thermopower) of silicene nanoribbons with zigzag edges are investigated by ab initio numerical methods. Local spin density of such nanoribbons reveals edge magnetism. As in graphene, one finds antiferromagnetic and ferromagnetic ordering, with spin polarization at one edge antiparallel or parallel to that at the other edge, respectively. Thermoelectric properties, especially the Seebeck coefficient, significantly depend on the electronic band structure and are enhanced when the Fermi level is in the energy gap. However, the thermoelectric efficiency is significantly reduced when the phonon contribution to the heat conductance is included. This phonon contribution has been calculated numerically by two different methods. Transition from antiferromagnetic to ferromagnetic states leads to a large magnetoresistance as well as to a considerable magnetothermopower. Thermoelectric parameters in the antiparallel configuration, when spin polarization in the left part of the nanoribbon is opposite to that in the right part, are also analyzed.

Zberecki, K.; Wierzbicki, M.; Barna?, J.; Swirkowicz, R.

2013-09-01

150

Effect of doping MoSe2 single crystals with rhenium  

NASA Astrophysics Data System (ADS)

Single crystals of Mo0.005Se2 have been grown by direct vapour transport technique to the maximum size 21 mm×15 mm. Growth conditions, growth mechanism and lattice parameters are determined. Room temperature resistivity, low temperature resistivity and thermoelectric power of the specimens have been measured. Seebeck coefficient and Hall coefficient measurements reveal that all the samples are n-type in nature.

Agarwal, M. K.; Patel, P. D.; Gupta, S. K.

1993-04-01

151

Electronic structure and volume effect on thermoelectric transport in p -type Bi and Sb tellurides  

Microsoft Academic Search

Thermoelectric transport properties (Seebeck coefficient, S , and electrical conductivity, sigma ) of p -type Bi and Sb tellurides are investigated using a first-principles all-electron density-functional approach. We demonstrate that the carrier concentration, band gap, and lattice constants have an important influence on the temperature behavior of S and that the volume expansion by 5.5% in Sb2Te3 results in an

Min Sik Park; Jung-Hwan Song; Julia E. Medvedeva; Miyoung Kim; In Gee Kim; Arthur J. Freeman

2010-01-01

152

Chemical Doping Effect on the Thermoelectric Properties of TGa3 (T = Fe, Ru, Os)  

NASA Astrophysics Data System (ADS)

Thermoelectric properties of chemically-doped intermetallic narrow-band semiconductors: TGa3 (T = Fe, Ru, Os) are reported. The parent compounds show semiconductor-like behavior (Eg ˜ 0.2 eV, n290K ˜ 10^18 cm^3) with large n-type Seebeck coefficients at room temperature (S290K ˜ -300 ?V/K). The semiconductor-like FeGa3 becomes metallic upon chemical doping (adding electron carriers), but RuGa3 and OsGa3 remain semiconducting. While the electrical resistivity and the Seebeck coefficients of all the compounds decrease with electron doping, the Seebeck coefficients remain fairly large and n-type, which leads to larger power factors than those of the pure samples. The thermal conductivity (?290K = 1.6 W/m K) of electron-doped FeGa3 decreases, which increases the room temperature power factor by a large percentage (S^2/?290K = 60 ?W/m K^2) over that of pure FeGa3. This improvement in the power factor leads to a corresponding enhancement in the thermoelectric figure of merit (ZT) -- a factor of 5 increases above undoped polycrystalline FeGa3 and two orders of magnitude improvement over that of pure single crystalline FeGa3.

Haldolaarachchige, Neel; Karki, Amar; Phelan, Adam; Xiong, Yimin; Jin, Rongying; Chan, Julia; Stadler, Shane; Young, David

2011-03-01

153

Effect of partial La filling on the local electronic properties of LaxCo4Sb12 studied using 59Co NMR  

NASA Astrophysics Data System (ADS)

We present a systematic investigation of the LaxCo4Sb12 skutterudites with x<=0.2 using 59Co nuclear magnetic resonance (NMR) spectroscopy. The NMR line shape, the quadrupole splitting, the Knight shift and the spin lattice relation rate of each compound have been identified. For LaxCo4Sb12, the central transition and the quadrupole linewidths increase with the La concentration because of the effect of the inhomogeneous electric field gradient. In addition, each linewidth exhibits a temperature-independent behavior, confirming the non-magnetic characteristic of these materials. The results of the isotropic Knight shift and the spin-lattice relaxation rate provide further information on the electronic structure around the Fermi surfaces of these compounds. In La0.1Co4Sb12 and La0.2Co4Sb12, the low-temperature NMR relaxation rates follow the Korringa behavior, indicating a finite density of carriers at the Fermi level. The high-temperature relaxation rates go over to a semiconductor-like activated form, being consistent with a semimetallic response. A detailed analysis of the spin-lattice relaxation rate established that the partial Co 3d Fermi-level density of states (DOS) increases with the La content. The NMR observations were interpreted in terms of a two-band scenario that consists of predominant d-electron features at low temperatures and exotic behavior of s-character electrons at high temperatures. Moreover, the obtained Fermi-level DOS show good agreement with those observed from the electrical conductivity and the Seebeck coefficient measurements in these La-filled skutterudites.

Lue, C. S.; Huang, S. M.; Kuo, C. N.; Huang, F.-T.; Chu, M.-W.

2008-08-01

154

Effect of Mixed Grain Sizes on the Thermoelectric Properties of Ca0.9Yb0.1MnO3  

NASA Astrophysics Data System (ADS)

Ca0.9Yb0.1MnO3 has been identified as a material that might be suitable for thermoelectric applications. We fabricated micro/nanograined Ca0.9Yb0.1MnO3 composites, with the aim of controlling the passage of electrons and phonons simultaneously. Micro/nanograined Ca0.9Yb0.1MnO3 composites containing various fractions of nanosized powder were prepared by sintering mixtures of microparticulate and nanoparticulate Ca0.9Yb0.1MnO3, obtained by solid-state reaction and by gas-phase reaction, respectively. The electrical resistivity increased markedly when the weight fraction of nanosized powder exceeded 50%, probably as a result of a percolation phenomenon. However, the thermal conductivity was considerably reduced when the weight fraction of nanosized powder exceeded 25%, but then remained almost constant. The absolute values of the Seebeck coefficient of micro/nanograined Ca0.9Yb0.1MnO3 composites were larger than those of monolithic micro- or nanograin Ca0.9Yb0.1MnO3, probably as a result of the effects of potential-barrier scattering. The highest dimensionless figure of merit ZT value of 0.09 at 973 K was achieved with a sample containing 50% nanosized powder, and this value is 10% larger than that of monolithic micrograined Ca0.9Yb0.1MnO3.

Fukui, Tsubasa; Matsuzawa, Mie; Funahashi, Ryoji; Kosuga, Atsuko

2013-10-01

155

Ion-induced changes in semiconductor properties of hydrogenated amorphous silicon  

NASA Astrophysics Data System (ADS)

Undoped, phosphorus doped (n-type), and boron doped (p-type) hydrogenated amorphous silicon (a-Si:H) thin films are irradiated with 3.0 MeV protons, 100 keV protons, and 2.8 MeV silicon ions, and the electric conductivity variations as a function of ion fluence are investigated. The Seebeck coefficient variations as a function of ion fluence are also investigated and are compared to the electric conductivity variations. As a result, a systematic interpretation of radiation effects on a-Si:H semiconductors is obtained. In the fluence regime of below 10?6 dpa, the increase in electric conductivity and the emergence of negative Seebeck effect are observed in the undoped a-Si:H because of donor-center generation. In the fluence regime from 10?6 dpa to 10?4 dpa, the decrease in electric conductivity and the decrease in absolute value of Seebeck coefficient are observed in the doped a-Si:H, since the carrier removal effect is caused by radiation defects, which are thought to be mainly dangling bonds. In the fluence regime of above 10?4 dpa, the increase in electric conductivity caused by the enhancement of hopping transport via localized states is observed. The absolute value of Seebeck coefficient of doped a-Si:H decreases in this fluence regime, whereas no Seebeck effect is observed in the undoped a-Si:H.

Sato, Shin-ichiro; Ohshima, Takeshi

2013-11-01

156

Thermoelectric properties of electrolessly etched silicon nanowire arrays  

NASA Astrophysics Data System (ADS)

Patterning silicon as nanowires with roughened sidewalls enhances the thermoelectric figure-of-merit ZT by order of magnitude compared to the bulk at 300 K [1]. The enhancement is mainly achieved by the remarkable reduction in the thermal conductivity below 5 W/mK at 300 K with only a negligible effect on the power factor of these nanowires. While the focus remained on understanding the implications of surface disorder on the thermal conductivity, the phonon transport effects on the Seebeck coefficient of these wires remains largely unexplored. We developed an electroless etching technique to generate nanowire arrays (NWAs) with controlled surface roughness, morphology, porosity and doping [2]. We conduct the simultaneous device-level measurements of the Seebeck coefficient and thermal conductivity of the NWAs using frequency domain techniques. We observe that nano-structuring quenches the phonon drag [3] in NWAs thereby reducing the Seebeck coefficient by ˜25% compared to the bulk at degenerate doping levels. Further, we observe that the sidewall roughness greater than 3 nm roughness height lowers the thermal conductivity 75% below the Casimir limit [4] with 10% - 15% increase in Seebeck coefficient. The porous NWAs show thermal conductivity close to the amorphous limit of Si with enhancement in the Seebeck coefficient primarily due to the carrier depletion. References: [1] A. I. Hochbaum et al, Nature 451, 163-167 (2008). [2] K. Balasundaram et. al., Nanotechnology 23, 305304 (2012). [3] C. Herring, Phys. Rev. 96, 1163 (1954). [4] H. G. B. Casimir, Physica 5, 495 (1938).

Sadhu, Jyothi; Tian, Hongxiang; Ma, Jun; Valavala, Krishna; Singh, Piyush; Sinha, Sanjiv

2013-03-01

157

Effects of Sb compensation on microstructure, thermoelectric properties and point defect of CoSb3 compound  

NASA Astrophysics Data System (ADS)

Volatilization of Sb during the fabrication of CoSb3 by mechanical alloying and then spark plasma sintering has been successfully compensated by adding excess Sb. The average grain size increases apparently with excess Sb content, abnormally grown by about 100 times as the excess Sb is up to 4 at.%. A liquid-phase-related mechanism is used to explain the abnormal growth. The uncompensated sample shows a negative Seebeck coefficient near room temperature, while the sample compensated with 6 at.% excess Sb shows an intrinsic positive Seebeck coefficient and an enhanced ZT value, which has a maximum of about 0.1 at 350 °C, which is two times higher than the uncompensated one. The transition of electrical conductivity from n- to p-type relative to the Sb compensation is discussed in relation to the point defect. A defect equation is given to show the nature of electron generation due to Sb deficiency. The Sb-vacancy not only provides extrinsic carrier but also generates a significant impact on the band gap and hence on the Seebeck coefficient.

Liu, Wei-Shu; Zhang, Bo-Ping; Li, Jing-Feng; Zhao, Li-Dong

2007-11-01

158

Microchips for the Investigation of Thermal and Electrical Properties of Individual Nanowires  

NASA Astrophysics Data System (ADS)

This paper focuses on the determination of thermal and electrical properties of individual thermoelectric nanowires, primarily bismuth and bismuth compound nanowires, as functions of their crystallinity, diameter, and composition. For measurements of the Seebeck coefficient and the electrical and thermal conductivity, specially designed microchips have been developed and employed. Finite-element simulations demonstrate that the temperature profiles of the microchips provide suitable temperature gradients for Seebeck-effect measurements and heat-sink conditions for thermal conductivity investigations. First measurements of thermal conductivity of metallic nanowires and of Seebeck coefficients of granular nanowires prepared by focused electron-beam-induced deposition are presented. Some of these results are discussed in the framework of finite-size-effect theory.

Völklein, F.; Reith, H.; Schmitt, M. C.; Huth, M.; Rauber, M.; Neumann, R.

2010-09-01

159

Anomalous enhancement of the thermoelectric power in gallium-doped p-(Bi{sub 1-x}Sb{sub x}){sub 2}Te{sub 3} single crystals  

SciTech Connect

The effect of gallium on the temperature dependences (5 K {<=} T {<=} 300 K) of Seebeck coefficient {alpha}, electrical conductivity {sigma}, thermal conductivity k, and thermoelectric efficiency Z of mixed p-(Bi{sub 0.5}Sb{sub 0.5}){sub 2}Te{sub 3} semiconductor single crystals is studied. The hole concentration decreases upon gallium doping; that is, gallium causes a donor effect. The Seebeck coefficient increases anomalously, i.e., much higher than it should be at the detected decrease in the hole concentration. This leads to an enhancement of the thermoelectric power. The observed changes in the Seebeck coefficient indicate a noticeable gallium-induced change in the density of states in the valence band.

Kulbachinskii, V. A., E-mail: kulb@mig.phys.msu.ru; Kytin, V. G.; Tarasov, P. M. [Moscow State University (Russian Federation)

2010-04-15

160

Temporal Donor Generation in Undoped Hydrogenated Amorphous Silicon Induced by Swift Proton Bombardment  

NASA Astrophysics Data System (ADS)

Seebeck coefficient variations of undoped hydrogenated amorphous silicon (a-Si:H) semiconductors due to swift proton irradiation were investigated using an in-situ thermoelectric power measurement system. Undoped a-Si:H irradiated with 3.0 MeV protons at a fluence regime of 3.1× 1011--5.0× 1012/cm2 showed a negative Seebeck coefficient although the Seebeck effect was not observed at fluences above 5.3× 1013/cm2. These results suggest that donor like centers are generated by low fluence proton irradiation, whereas the donor centers are compensated by radiation-induced defects or themselves disappear after high fluence proton irradiation. These effects decay with time, giving the donor centers a temporal nature.

Sato, Shin-ichiro; Sai, Hitoshi; Ohshima, Takeshi; Imaizumi, Mitsuru; Shimazaki, Kazunori; Kondo, Michio

2011-06-01

161

Advertising Effects and Effectiveness  

Microsoft Academic Search

The results of the application of an integrated econometric time-series model for advertising effectiveness is presented. The model form gives rise to three possible advertising effects: brand loyalty, current effects (both simple and compound) and carryover effects. The inherent nature of these effects is related to the degree of involvement and the affective or cognitive aspects of the purchase decision.

Mike T. Bendixen

1993-01-01

162

Impurity Band Effects in Thermoelectric Materials  

NASA Astrophysics Data System (ADS)

The possibility of improvement of the power factor through introduction of impurity bands is considered. The contributions to the Seebeck coefficient and electrical conductivity from carriers in an impurity band are expressed in terms of the Fermi energy and the position of the impurity levels relative to the edge of the main band. Surprisingly, it is found that the presence of an impurity band generally brings little benefit, and in fact, when it lies near the edge of the main band, the power factor may be significantly reduced. Our findings are consistent with the observation that the figure of merit of PbTe is improved by the presence of deep-lying thallium states. They also indicate that, for Bi2Te3, compensation for nonstoichiometry by counterdoping may not yield the highest power factor.

Goldsmid, H. J.

2012-08-01

163

MeV Si ions bombardments effects on thermoelectric properties of SiO2/SiO2+Ge nanolayers  

NASA Astrophysics Data System (ADS)

The performance of the thermoelectric materials and devices is shown by a dimensionless figure of merit, ZT=S2?T/K, where S is the Seebeck coefficient, ? is the electrical conductivity, T is the absolute temperature and K is the thermal conductivity. ZT can be increased by increasing S, increasing ?, or decreasing K. We have prepared the thermoelectric generator device of SiO2/SiO2+Ge multilayer superlattice films using the ion beam assisted deposition (IBAD). The 5 MeV Si ion bombardments have been performed using the AAMU Pelletron ion beam accelerator at five different fluences to make quantum structures (nanodots and/or nanoclusters) in the multilayer superlattice thin films to decrease the cross plane thermal conductivity, increase the cross plane Seebeck coefficient and cross plane electrical conductivity. To characterize the thermoelectric generator devices before and after MeV Si ions bombardments at the different fluences we have measured the cross-plane Seebeck coefficient, the cross-plane electrical conductivity, and the cross-plane thermal conductivity, Raman spectra to get some information about the sample structure and bond structures among the used elements in the superlattice thin film systems.

Budak, S.; Smith, C.; Pugh, M.; Heidary, K.; Colon, T.; Johnson, R. B.; Muntele, C.; Ila, D.

2012-04-01

164

Implications of nanostructuring on the thermoelectric properties in half-Heusler alloys  

NASA Astrophysics Data System (ADS)

High energy ball milled Zr0.25Hf0.75NiSn alloys subjected to spark plasma sintering show an enhanced thermoelectric figure of merit in comparison with its normal bulk material synthesized by arc-melting process. The enhancement is due to increase in Seebeck coefficient with simultaneous decrease in thermal conductivity which follows due to increase in the cell volume. Theoretical calculations find that volume expansion facilitates band narrowing effects leading to high Seebeck coefficient and that decreasing orbital overlap which results in weak bonding leads to dampening the phonon propagation in addition to the interface scattering of phonons from phase boundaries.

Bhardwaj, A.; Misra, D. K.; Pulikkotil, J. J.; Auluck, S.; Dhar, A.; Budhani, R. C.

2012-09-01

165

Effect of Nickel Substitution on Defect Chemistry, Electrical Properties, and Dimensional Stability of Calcium-Doped Yttrium Chromite  

SciTech Connect

The effect of nickel substitution on defect chemistry, electrical properties, and dimensional stability of calcium-doped yttrium chromite was studied for use as an interconnect material in high temperature solid oxide fuel cells (SOFCs). The compositions of Y0.8Ca0.2Cr1-xNixO3±? (x=0-0.15), prepared using the glycine nitrate process, showed single phase orthorhombic perovskite structures over a wide range of oxygen partial pressures (10^-17 atm ? pO2 ? 0.21 atm). X-ray diffraction (XRD) analysis indicated that most of the nickel ions replacing chromium ions are divalent and act as acceptor dopants, leading to a substantial increase in conductivity. In particular, the conductivity at 900 degree C in air increased from 10 S/cm to 34 S/cm with 15% nickel substitution, and an increase in charge carrier density was confirmed by Seebeck measurements. A point defect model was derived, and the relationship between electrical conductivity and oxygen partial pressure was successfully fitted into the proposed model. The defect modeling results indicated that nickel substitution improves the stability of calcium-doped yttrium chromite toward reduction and suppresses the oxygen vacancy formation, which results in significantly increased electrical conductivity in reducing environment. The electrical conductivity of Y0.8Ca0.2Cr0.85Ni0.15O3±? at 900 degree C in reducing atmosphere (pO2=10^-17 atm) was 5.8 S/cm, which was more than an order of magnitude higher than that of Y0.8Ca0.2CrO3±? (0.2 S/cm). Improved stability in reducing atmosphere was further confirmed by dilatometry measurements showing reduced isothermal "chemical" expansion, and the isothermal expansion in reducing atmosphere (pO2=10^-17 atm) at 900 degree C decreased from 0.07% for Y0.8Ca0.2CrO3±? to 0.03% for Y0.8Ca0.2Cr0.85Ni0.15O3±?. Based on these results, enhanced electrical performance and mechanical integrity is expected with nickel substitution on calcium-doped yttrium chromite in SOFC operating conditions.

Yoon, Kyung J.; Stevenson, Jeffry W.; Marina, Olga A.

2011-06-30

166

Effect of Fe Substitution on Thermoelectric Properties of Fe x In4- x Se3 Compounds  

NASA Astrophysics Data System (ADS)

Starting from elemental powder mixtures of Fe x In4- x Se3 ( x = 0, 0.05, 0.1, 0.15), polycrystalline In4Se3-based compounds with homogeneous microstructures were prepared by mechanical alloying (MA) and hot pressing (HP). With the increase of x from 0 to 0.15, the electrical resistivity and the absolute value of the Seebeck coefficient increased, while the thermal conductivity first decreased and then increased. The maximal dimensionless figure of merit ZT of 0.44 was obtained for the Fe x In4- x Se3 ( x = 0.05) sample at 723 K.

Li, Gen; Yang, Junyou; Xiao, Ye; Fu, Liangwei; Peng, Jiangying; Deng, Yuan; Zhu, Pinwen; Yan, Haixue

2013-04-01

167

Nonstoichiometry and chemical purity effects in thermoelectric Ba8Ga16Ge30 clathrate  

NASA Astrophysics Data System (ADS)

Zone melting purification experiments have been carried out on the clathrate, Ba8Ga16Ge30. The impurities present have been identified and their approximate concentrations measured. Trace impurities were determined to be approximately 240 parts per million (ppm) in the most impure sample to 17 ppm in the most pure sample. The temperature-dependent Seebeck coefficient, thermal conductivity, and electrical conductivity are reported as a function of sample purity as well as the room-temperature Hall coefficient. Microprobe analysis suggests that the samples are nonstoichiometric with excess Ge relative to Ga, and there are indications of the presence of defects. Single-crystal x-ray investigations as well as synchrotron powder diffraction measurements support the presence of defects, but the x-ray data cannot accurately determine the relative amounts of Ga and Ge. Band-structure calculations in the generalized gradient approximation show that the measured Hall and Seebeck coefficients are consistent with a defect lattice of approximate stoichiometry Ba8Ga14Ge31. Although the figure of merit (ZT) is found to be the highest for the purest sample, the dominant contribution to transport is conjectured to arise from deviations from the ideal stoichiometry and not impurities.

Bryan, J. Daniel; Blake, Nick P.; Metiu, Horia; Stucky, Galen D.; Iversen, Bo B.; Poulsen, Rasmus D.; Bentien, Anders

2002-12-01

168

Thermoelectric Effect of Silicon Films with - and Deep-Level Acceptors  

NASA Astrophysics Data System (ADS)

Crystalline Si films with both shallow- and deep-level acceptors, Al and Cu, have been prepared on glass and quartz substrates by the methods of magnetron sputtering and Al-induced crystallization. Al and Cu are co-added in the Si films intermittently by regular pulse sputtering of Al and Cu targets during deposition of the Si films. By regulating the sputtering times of Al and Cu targets, the amounts of Al and Cu in the Si films can be controlled, and thus the Seebeck coefficient and electrical resistivity of the silicon films can be adjusted. It is found that the Al and Cu co-doped Si film has a larger Seebeck coefficient and a lower electrical resistivity at higher temperatures, as compared with that of only Al-doped Si film. As a result, the thermoelectric power factor of the Al and Cu co-doped Si film is greatly enhanced. The present experimental results will not only help us to understand the basic thermoelectric properties of semiconductors doubly doped with shallow- and deep-level impurities, but also open the possibility of enhancement of thermoelectric power factor by using this concept.

Hou, Q. R.; Sun, J. L.; Gu, B. F.; Chen, Y. B.; He, Y. J.

2012-12-01

169

Effect of substrate on the atomic structure and physical properties of thermoelectric Ca3Co4O9 thin films  

NASA Astrophysics Data System (ADS)

The incommensurately layered cobalt oxide Ca3Co4O9 exhibits an unusually high Seebeck coefficient as a polycrystalline bulk material, making it ideally suited for many high temperature thermoelectric applications. In this paper, we investigate properties of Ca3Co4O9 thin films grown on cubic perovskite SrTiO3, LaAlO3, and (La0.3Sr0.7)(Al0.65Ta0.35)O3 substrates and on hexagonal Al2O3 (sapphire) substrates using the pulsed laser deposition technique. X-ray diffraction and transmission electron microscopy analysis indicate strain-free growth of films, irrespective of the substrate. However, depending on the lattice and symmetry mismatch, defect-free growth of the hexagonal CoO2 layer is stabilized only after a critical thickness and, in general, we observe the formation of a stable Ca2CoO3 buffer layer near the substrate-film interface. Beyond this critical thickness, a large concentration of CoO2 stacking faults is observed, possibly due to weak interlayer interaction in this layered material. We propose that these stacking faults have a significant impact on the Seebeck coefficient and we report higher values in thinner Ca3Co4O9 films due to additional phonon scattering sites, necessary for improved thermoelectric properties.

Qiao, Q.; Gulec, A.; Paulauskas, T.; Kolesnik, S.; Dabrowski, B.; Ozdemir, M.; Boyraz, C.; Mazumdar, D.; Gupta, A.; Klie, R. F.

2011-08-01

170

Doppler Effect  

NSDL National Science Digital Library

Doppler effect followed from water waves to sound waves to light waves. Red shift of the universe is also explored. What is doppler effect? It is the change in frequency of a wave for an observer moving relative to the source of the wave. What does that mean? Watch this: moving doppler effect video What does the doppler effect look like in a stationary and moving object? dooppler effect views What does doppler effect have to do with stars and galaxies??? View the following ...

Clemons, Mrs.

2010-11-10

171

Doppler Effect  

NSDL National Science Digital Library

Doppler effect followed from water waves to sound waves to light waves. Red shift of the universe is also explored. What is doppler effect? It is the change in frequency of a wave for an observer moving relative to the source of the wave. What does that mean? Watch this: moving doppler effect video What does the doppler effect look like in a stationary and moving object? dooppler effect views What does doppler effect have to do with stars and galaxies??? View the following ...

Brown, Mrs.

2010-10-26

172

Greenhouse Effect  

NSDL National Science Digital Library

This activity is a greenhouse-effect-in-a-bottle experiment. The lesson includes readings from NEED.org and an inquiry lab measuring the effect of carbon dioxide and temperature change in an enclosed environment.

Education, Connecticut E.

173

Chemotherapy Effects  

MedlinePLUS

... saved articles window. My Saved Articles » My ACS » Chemotherapy Effects Chemotherapy drugs are powerful medicines that can cause side ... on the side effects most commonly caused by chemotherapy, this is a good place to start. Managing ...

174

Effects of \\  

Microsoft Academic Search

Brainstorming instruction is an effective method for increasing the production of good ideas in a particular type of creative thinking problems, and is even more effective if preceded by extensive training in its use. (5 tables)

Sidney J. Parnes; Arnold Meadow

1959-01-01

175

Thermal effects  

SciTech Connect

Literature dealing with the following topics was reviewed: effects of power plant once-through cooling on aquatic systems; site studies; producers - effects on growth and production; consumers; decomposers; diseases and parasites; and beneficial uses of power plant condenser cooling water. (DAD)

Talmage, S.S.; Coutant, C.C.

1980-06-01

176

Thermal effects  

Microsoft Academic Search

Literature dealing with the following topics was reviewed: effects of power plant once-through cooling on aquatic systems; site studies; producers - effects on growth and production; consumers; decomposers; diseases and parasites; and beneficial uses of power plant condenser cooling water. (DAD)

S. S. Talmage; C. C. Coutant

1980-01-01

177

Naloxone: Effects and Side Effects  

Center for Drug Evaluation (CDER)

Text Version... Cardiovascular effects ?Hypertension morbidity (eg, vascular aneurysms) ... Hypertension morbidity (eg, vascular aneurysms) ... More results from www.fda.gov/downloads/drugs/newsevents

178

Thermal effects  

Microsoft Academic Search

Literature concerning the effects of temperature on aquatic organisms is reviewed. Subjects include: site studies, producers, consumers, decomposers, diseases and parasites, and beneficial uses. Specific topics involve growth, reproduction, temperature tolerance, preferred temperature, feeding, distribution, oxygen metabolism, and morphology.

1976-01-01

179

Position Effects  

Microsoft Academic Search

Position effects describe the observed alteration in protein-coding gene expression that may accompany a change in genomic\\u000a position of a given gene. A position effect may result from chromosomal translocation or other genomic rearrangements. Recent\\u000a advances in chromatin studies in several different species including yeast, Drosophila, and mouse have contributed significantly\\u000a to better understanding of human diseases resulting from abnormal

Pawel Stankiewicz

180

Modeling thermoelectric transport in organic materials.  

PubMed

Thermoelectric energy converters can directly convert heat to electricity using semiconducting materials via the Seebeck effect and electricity to heat via the Peltier effect. Their efficiency depends on the dimensionless thermoelectric figure of merit of the material, which is defined as zT = S(2)?T/? with S, ?, ?, and T being the Seebeck coefficient, electrical conductivity, thermal conductivity, and absolute temperature respectively. Organic materials for thermoelectric applications have attracted great attention. In this review, we present our recent progress made in developing theories and computational schemes to predict the thermoelectric figure of merit at the first-principles level. The methods have been applied to model thermoelectric transport in closely-packed molecular crystals and one-dimensional conducting polymer chains. The physical insight gained in these studies will help in the design of efficient organic thermoelectric materials. PMID:23086525

Wang, Dong; Shi, Wen; Chen, Jianming; Xi, Jinyang; Shuai, Zhigang

2012-10-19

181

Thermoelectric properties of magnesium silicide fabricated using vacuum plasma thermal spray  

NASA Astrophysics Data System (ADS)

The thermoelectric properties of magnesium silicide samples prepared by Vacuum Plasma Spray (VPS) are compared with those made from the conventional hot press method using the same feedstock powder. Thermal conductivity, electrical conductivity, Seebeck coefficient, and figure of merit are characterized from room temperature to 700 K. X-ray diffraction and scanning electron microscopy of the samples are obtained to assess how phase and microstructure influence the thermoelectric properties. Carrier concentration and Hall mobility are obtained from Hall Effect measurements, which provide further insight into the electrical conductivity and Seebeck coefficient mechanisms. Low-temperature electrical conductivity measurements suggest a 3D variable range hopping effect in the samples. VPS samples achieved a maximum ZT = 0.16 at 700 K, which is around 30% of the hot press sample ZT = 0.55 at 700 K using the same raw powder. The results suggest that thermal spray is a potential deposition technique for thermoelectric materials.

Fu, Gaosheng; Zuo, Lei; Longtin, Jon; Nie, Chao; Gambino, Richard

2013-10-01

182

Peltier cooling and onsager reciprocity in ferromagnetic thin films.  

PubMed

We present direct measurements of the Peltier effect as a function of temperature from 77 to 325 K in Ni, Ni_{80}Fe_{20}, and Fe thin films made using a suspended Si-N membrane structure. Measurement of the Seebeck effect in the same films allows us to directly test predictions of Onsager reciprocity between the Peltier and Seebeck effects. The Peltier coefficient ? is negative for both Ni and Ni_{80}Fe_{20} films and positive for the Fe film. The Fe film also exhibits a peak associated with the magnon drag Peltier effect. The observation of magnon drag in the Fe film verifies that the coupling between the phonon, magnon, and electron systems in the film is the same whether driven by heat current or charge current. The excellent agreement between ? values predicted using the experimentally determined Seebeck coefficient for these films and measured values offers direct experimental confirmation of the Onsager reciprocity between these thermoelectric effects in ferromagnetic thin films near room temperature. PMID:24093285

Avery, A D; Zink, B L

2013-09-17

183

Peltier Cooling and Onsager Reciprocity in Ferromagnetic Thin Films  

NASA Astrophysics Data System (ADS)

We present direct measurements of the Peltier effect as a function of temperature from 77 to 325 K in Ni, Ni80Fe20, and Fe thin films made using a suspended Si-N membrane structure. Measurement of the Seebeck effect in the same films allows us to directly test predictions of Onsager reciprocity between the Peltier and Seebeck effects. The Peltier coefficient ? is negative for both Ni and Ni80Fe20 films and positive for the Fe film. The Fe film also exhibits a peak associated with the magnon drag Peltier effect. The observation of magnon drag in the Fe film verifies that the coupling between the phonon, magnon, and electron systems in the film is the same whether driven by heat current or charge current. The excellent agreement between ? values predicted using the experimentally determined Seebeck coefficient for these films and measured values offers direct experimental confirmation of the Onsager reciprocity between these thermoelectric effects in ferromagnetic thin films near room temperature.

Avery, A. D.; Zink, B. L.

2013-09-01

184

Enhanced thermoelectric properties of Nb-doped SrTiO 3 polycrystalline ceramic by titanate nanotube addition  

Microsoft Academic Search

The effects of titanate nanotube (TNT) addition on the thermoelectric properties of Nb-doped SrTiO3 polycrystalline ceramic are discussed. Nb-doped SrTiO3 ceramic composite with TNT addition was fabricated by the pressure-less sintering method in an Ar atmosphere. TNT addition significantly enhanced the ratio of the electrical conductivity to thermal conductivity. Meanwhile, the Seebeck coefficient was almost independent of TNT addition, thus,

Ning Wang; Hongcai He; Xiao Li; Li Han; Chunqiu Zhang

2010-01-01

185

Electrical and thermal transport properties of Ba 6C 60 compound  

Microsoft Academic Search

Bulk Ba6C60 fulleride has been prepared by solid-state reaction and spark plasma sintering (SPS) technique. We report measurements of electrical resistivity, Seebeck coefficient, thermal conductivity and Hall effect. The compound is metallic with high electron concentration and low mobility. The values of electrical resistivity and thermopower are also low, consistent with the Hall data. The lattice thermal conductivity for Ba6C60

X. Shi; L. D. Chen; S. Q. Bai; W. B. Zhang; X. Y. Zhao

2005-01-01

186

Electrical and thermal transport properties of Ba6C60 compound  

Microsoft Academic Search

Bulk Ba6C60 fulleride has been prepared by solid-state reaction and spark plasma sintering (SPS) technique. We report measurements of electrical resistivity, Seebeck coefficient, thermal conductivity and Hall effect. The compound is metallic with high electron concentration and low mobility. The values of electrical resistivity and thermopower are also low, consistent with the Hall data. The lattice thermal conductivity for Ba6C60

X. Shi; L. D. Chen; S. Q. Bai; W. B. Zhang; X. Y. Zhao

2005-01-01

187

Studies on transport properties of MoSe2-xTex single crystals  

NASA Astrophysics Data System (ADS)

Single crystals of MoSe2-xTex (x = 0.25, 0.5, 1, 1.5, 1.75) were grown by chemical vapor transport technique. The stoichiometric composition of grown crystals was confirmed by energy dispersive X-ray spectroscopy. Transport properties like electrical resistivity, Seebeck co-efficient measurements at high temperature and Hall effect at room temperature were studied on these samples. The obtained results are discussed in details in this paper.

Bhavsar, Divyesh N.; Jani, Ashvinkumar R.

2013-08-01

188

Transport phenomena in (Bi1.6Pb0.4)(Sr1.8Ba0.2)Ca2(Cu1-XFeX)3Oy thin films  

Microsoft Academic Search

Measurements of resistivity, Nernst, Seebeck and Hall effects in the mixed state and in the fluctuation regime above Tco of Bi 2223 doped with Fe (0 <= x <= 0.05) epitaxial thin films for magnetic fields between 0 and 5 T and temperature range 4-150 K are reported. The critical field slope dBc2\\/dT, zetaab and lambdaab dependence of iron content

G. Ilonca; A. V. Pop; D. Ciurchea; C. Corega; M. Ilonca; R. Deltour

1997-01-01

189

Thermoelectric properties of p-type antimony bismuth telluride alloys prepared by cold pressing  

Microsoft Academic Search

Sb2 ? xBixTe3 (x = 0.43–0.51) thermoelectric materials were prepared by the powder metallurgy method. The effects of grinding and sintering processes on the Seebeck coefficient, electrical conductivity, and thermoelectric figure of merit were investigated. For different particle sizes, a shift in maximum of Z = f(x) dependence was found. This shift can be explained by the presence of point

J. Navrátil; Z. Starý

1996-01-01

190

Design, Calibration, and Testing of a New Tian-Calvet Heat-Flow Microcalorimeter for Measurement of Differential Heats of Adsorption  

Microsoft Academic Search

A Tian-Calvet heat-flow microcalorimeter system is described for measurement of heats of adsorption and reaction on porous solids. Heat-flow signals are measured in transducer assemblies consisting of several hundred Seebeck-effect thermoelements connected in series and arranged in a square configuration. These transducers surround a stainless steel calorimeter cell connected to a high-vacuum volumetric adsorption system. The sensitivity of the calorimeter

V. Garcia-Cuello; J. C. Moreno-Pirajan; L. Giraldo-Gutierrez; K. Sapag; G. Zgrablich

2008-01-01

191

New position-sensitive detector for pulsed or CW laser beam alignment  

Microsoft Academic Search

A new class of position-sensitive detectors has been developed at Los Alamos Scientific Laboratory (LASL). These detectors utilize Seebeck effect and thermal diffusion in the detector material (Si). Large area (up to 125 cm²) detectors with only four electrodes yield accurate x-y position sensing for CW and pulsed laser beams. The detectors are sensitive to any laser wavelength and feature

Hammond

1979-01-01

192

Mechanism of the Electrical Conduction in Li-Doped NiO  

Microsoft Academic Search

The electrical conductivity and the Seebeck effect are measured in the temperature region of 100 to 1300°K in NiO doped with Li. From the results it is concluded that the mobility of the charge carriers involves no activation energy. The temperature dependence of the conductivity is almost completely determined by the charge-carrier concentration. In order to calculate from the measurements

A. J. Bosman; C. Crevecoeur

1966-01-01

193

Electronic transport phenomena in single-crystal NiO and CoO  

Microsoft Academic Search

Hall effect, conductivity and Seebeck measurements have been made on a series of NiO and CoO crystals containing up to approximately 0.6 at.% Li in the range 150-1100 °K. The results are interpreted in terms of 3d conduction in a narrow band and indicate that impurity conduction is dominant in many samples up to 200-300 °K, even when no Li

I G Austin; A J Springthorpe; B A Smith; C E Turner

1967-01-01

194

New Concept of Laboratory Exercise on Temperature Measurements Using Thermocouple  

NASA Astrophysics Data System (ADS)

The proposed exercise is focused on the measurement of temperature using thermocouple, students acquire theoretical knowledge of the Seebeck effect, the design and application of thermocouples including the differences between their various types. The students measure the voltage at the thermocouple by various methods: directly with a compensation box, using operational amplifiers and USB module. The exercise explains also general principles of low voltage measurements, error compensation and uncertainty evaluation.

Slavata, Old?ich; Sou?ek, Pavel; Holub, Jan

2013-09-01

195

Interpersonal Effectiveness  

NSDL National Science Digital Library

Interpersonal Effectiveness provides participants with an opportunity to develop their interpersonal skills through interactive exercises conducted in a team setting. Debriefing these exercises with all members of the class helps ensure that the exercises translate into personal and interpersonal learning for the participants. After completing this module, students should be able to identify the principles of good teamwork and effective communication and demonstrate those skills during a series of interactive exercises. Note: This module is part of a modularized manufacturing technology curriculum created by the PSCME, found at www.pscme.org/educators.html.

Alston, Michele; King, John

2010-07-26

196

Photoelectric Effect  

NSDL National Science Digital Library

This is a series of simulations of aspects of the photoelectric effect. There is an animation of the experiment with four choices of incident radiation - low and high intensity "red", to represent low energy light and low and high intensity "blue" to represent higher energy light. Electron production is animated and there is an ammeter to simulate current flow. Additional simulations show the effect of light frequency and intensity. There is a link to a spreadsheet that allows students to choose a sample from among five metals. The spreadsheet includes several questions to be answered after working through the materials.

197

Coriolis Effect  

NSDL National Science Digital Library

This set of four animated slides illustrates the Coriolis effect, a manifestation of one of Newton's laws which says that objects move in a straight line, in an "inertial" frame of reference, unless acted upon by a force. The slides use the analogy of a ball thrown on a rotating carousel.

198

Thermal effects  

Microsoft Academic Search

The 1976 literature on thermal effects was reviewed under the following categories: reviews; power plant studies; producers; consumer reproduction, development, morphology, distribution, thermal tolerance, growth, feeding, activity, oxygen metabolism, temperature and other stresses; decomposers; diseases and parasites and beneficial uses. Many of the studies are summarized in tabular form.

C. C. Coutant; S. S. Talmadge

1977-01-01

199

Slingshot Effect  

NSDL National Science Digital Library

This web page demonstrates the slingshot effect through a Flash simulation. The user places an object at some distance from Jupiter, sets up its initial velocity, then choose the appropriate time to lunch it. Once the simulation begins, the path of the projectile and its speed are shown.

Fowler, Michael; Ching, Jacquie H.

2008-09-20

200

Atmospheric Effect  

Microsoft Academic Search

AN atmospheric effect, which is sometimes observed in England, displayed itself here in great beauty yesterday. The western sun had been cut off from us by an intervening ridge, while the upper atmosphere was still filled with his light. There was a good deal of opalescent haze in the atmosphere, which, had the sun shone upon it uniformly, would have

John Tyndall

1872-01-01

201

Sleeper Effects  

ERIC Educational Resources Information Center

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

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

2007-01-01

202

Greenhouse Effect  

NSDL National Science Digital Library

This HyperPhysics webpage contains information and diagrams on global warming, the greenhouse effect, and greenhouse gases. Numerous graphs and diagrams illustrate the measurements and concepts. Also, this page displays the famous "Keeling curve" showing atmospheric carbon dioxide concentration versus time from 1958 to 2004. This page page is part of the HyperPhysics Collection, which contains many short, illustrated pages on various areas of physics and astronomy.

Nave, Carl R.

2013-04-29

203

Effective Presentations  

PubMed Central

Where the purpose of presentations is to inform, effective delivery is important to ensure that audiences receive the educational message. We offer six suggestions: introduce the topic in an interesting way; speak loudly enough; do not read; involve the audience actively; respect the attention span of the audience; and limit the amount of content. We conclude that the skills of live public presentation can be learned, but that the art of presentation is innate. Imagesp2063-ap2064-a

Spooner, H. James; Swanson, Richard W.

1990-01-01

204

Magnon gap formation and charge density wave effect on thermoelectric properties in the SmNiC2 compound  

NASA Astrophysics Data System (ADS)

We studied the electrical, thermal, and thermoelectric properties of the polycrystalline compound of SmNiC2. The electrical resistivity and magnetization measurement show the interplay between the charge density wave at TCDW=150 K and the ferromagnetic ordering of Tc=18 K. Below the ferromagnetic transition temperature, we observed the magnon gap formation of ??4.3-4.4 meV by ?(T) and Cp(T) measurements. The charge density wave is attributed to the increase of the Seebeck coefficient resulting in the increase of the power factor S2?. The thermal conductivity anomalously increases with increasing temperature along the whole measured temperature range, which implies the weak attribution of Umklapp phonon scattering. The thermoelectric figure of merit ZT significantly increases due to the increase of the power factor at TCDW=150 K. Here we argue that the competing interaction between electron-phonon and electron-magnon couplings exhibits the unconventional behavior of electrical and thermal properties.

Kim, Jin Hee; Rhyee, Jong-Soo; Kwon, Yong Seung

2012-12-01

205

Effect of antisite defects on band structure and thermoelectric performance of ZrNiSn half-Heusler alloys  

NASA Astrophysics Data System (ADS)

Band structures for ZrNiSn with Zr/Sn antisite defects are calculated with ab initio methods. Antisite defects shrink the band gap and enhance the density of states slope near the Fermi level, which are favorable to electrical transport properties for intrinsic semiconductors. The degree of Zr/Sn antisite defects are controlled by annealing time experimentally, and measurements show low electrical resistivity and high Seebeck coefficient for unannealed ZrNiSn, which benefits from the modified electronic structure caused by antisite defects. The maximum ZT is 0.64 at 800 K for unannealed ZrNiSn, which is the highest value for ZrNiSn systems without exterior doping.

Qiu, Pengfei; Yang, Jiong; Huang, Xiangyang; Chen, Xihong; Chen, Lidong

2010-04-01

206

Influence of the rare-earth element on the effects of the structural and magnetic phase transitions in CeFeAsO, PrFeAsO, and NdFeAsO  

SciTech Connect

We present results of transport and magnetic properties and heat capacity measurements on polycrystalline CeFeAsO, PrFeAsO and NdFeAsO. These materials undergo structural phase transitions, spin density wave-like magnetic ordering of small moments on iron and antiferromagnetic ordering of rare-earth moments. The temperature dependence of the electrical resistivity, Seebeck coefficient, thermal conductivity, Hall coefficient and magnetoresistance are reported. The magnetic behavior of the materials have been investigated using Moessbauer spectroscopy and magnetization measurements. Transport and magnetic properties are affected strongly by the structural and magnetic transitions, suggesting significant changes in the band structure and/or carrier mobilities occur, and phonon-phonon scattering is reduced upon transformation to the low-temperature structure. Results are compared with recent reports for LaFeAsO, and systematic variations in properties as the identity of Ln is changed are observed and discussed. As Ln progresses across the rare-earth series from La to Nd, an increase in the hole contributions to the Seebeck coefficient and increases in magnetoresistance and the Hall coefficient are observed in the low-temperature phase. Analysis of hyperfine fields at the iron nuclei determined from Moessbauer spectra indicates that the moment on Fe in the orthorhombic phase is nearly independent of the identity of Ln, in apparent contrast to reports of powder neutron diffraction refinements.

McGuire, Michael A [ORNL; Hermann, Raphael P. [Forschungszentrum Julich, Julich, Germany; Safa-Sefat, Athena [ORNL; Sales, Brian C [ORNL; Jin, Rongying [ORNL; Mandrus, David [ORNL; Grandjean, F. [University of Liege, Belgium; Long, Gary J. [University of Missouri, Rolla

2009-01-01

207

ERRATUM: Replace `van Hove singularity' by `negative- U singularity' and proceed: a comment on the analysis of HTSC Seebeck data by McIntosh and Kaiser - and related matters concerning the mechanism  

NASA Astrophysics Data System (ADS)

In the abstract and on page 6065 of this article an error of terminology occurred. The situation where the negative-U doubly loaded state $^{10}{\\rm Cu}^{2-}_{III}$

Wilson, John A.

1997-10-01

208

Electric and thermoelectric properties of electrodeposited bismuth telluride (Bi2Te3) films  

NASA Astrophysics Data System (ADS)

We investigated the relationships among the deposition potential, the electric properties, and the thermoelectric properties of Bi2Te3 films electrodeposited from a solution containing 1.00 mM TeO2 and 0.86 mM Bi-EDTA complex. From the results of the Hall-effect measurements, the films formed at >-0.27 V vs Ag/AgCl were Te-rich n-Bi2Te3, and the carrier concentration increased with more negative deposition potential. The films formed at <-0.35 V were Bi-rich p-Bi2Te3, and the carrier concentration showed a constant value. A depth profile showed that all the electrodeposited films were composed of two layers, and that an n-type layer containing a large excess of Te existed near the substrate surface. From the Seebeck coefficient measurements, the electrical type of all the films was n type, and the maximum Seebeck coefficient (-70+/-10 ?V K-1) was observed for the film deposited at -0.20 V. The electrical type obtained by the Seebeck coefficient measurements was completely different from the electrical type determined by the Hall-effect measurements. This difference could be explained by the p-n junction formation near the substrate surface.

Takahashi, Makoto; Kojima, Masashi; Sato, Shoji; Ohnisi, Naoyuki; Nishiwaki, Akira; Wakita, Koichi; Miyuki, Takuma; Ikeda, Shoichiro; Muramatsu, Yasuhiko

2004-11-01

209

Piezoelectric Effect  

NSDL National Science Digital Library

In this activity, by the Concord Consortium's Molecular Literacy project, students explore the piezoelectric effect, which is the conversion between electricity and mechanical motion. The model used in this activity shows this conversion and users can manipulate the model to change the voltage and observe changes to a crystal. The activity itself is a java-based interactive resource built upon the free, open source Molecular Workbench software. In these activities, students are allowed to explore at their own pace in a digital environment full of demonstrations, illustrations, and models they can manipulate. In addition to the activity, visitors will find an overview of the activity and central and key concepts.

2008-10-23

210

Radiation effects.  

PubMed

International Commission on Radiological Protection (ICRP) Committee 1 (C1) considers the risk of induction of cancer and heritable disease; the underlying mechanisms of radiation action; and the risks, severity, and mechanisms of induction of tissue reactions (formerly 'deterministic effects'). C1 relies upon the interpretation of current knowledge of radio-epidemiological studies; current information on the underlying mechanisms of diseases and radiation-induced disease; and current radiobiological studies at the whole animal, tissue, cell, and molecular levels. This overview will describe the activities of C1 in the context of the 2007 Recommendations of ICRP. In particular, the conclusions from the most recent C1 Task Group deliberations on radon and lung cancer, and tissue reactions will be discussed. Other activities are described in summary fashion to illustrate those areas that C1 judge to be likely to influence the development of the risk estimates and nominal risk coefficients used for radiation protection purposes. PMID:23088999

Preston, R J

2012-08-22

211

Magnetic and electronic properties of misfit-layered cobalt oxide (Ca1-? OH)xCoO2  

NASA Astrophysics Data System (ADS)

The magnetic and electronic properties of non- and hole-doped samples of misfit-layered cobalt oxide (Ca1-?OH)xCoO2 were investigated using the data obtained from measurements of the magnetization, specific heat, resistivity, and Seebeck coefficient. A Curie-Weiss-like behavior was observed for all samples. In a highly doped sample, a magnetic transition at 13 K and metamagnetism, due to long-range antiferromagnetic ordering, were observed. This long-range ordering coexists with a nonordered paramagnetic moment, most likely enhanced by ferromagnetic fluctuations. Large Sommerfeld constants, ?=32 and 46 mJ mol-1 K-2, were obtained from the specific heat of the doped samples. This indicates that a large effective mass of the carriers exists in the hole-doped phase of this compound. The observation of both the finite value of ? and the semiconducting resistivity indicates that the carrier is localized by the Anderson localization mechanism. The Seebeck coefficient decreases with hole doping. In low temperature, the Seebeck coefficients for the doped samples exhibit abrupt enhancements with decreasing temperature, which implies an existence of pseudogap.

Shizuya, Mitsuyuki; Isobe, Masaaki; Takayama-Muromachi, Eiji

2007-07-01

212

Optimization of Dimensionless Figure of Merit in Oxide Thin Film Thermoelectrics  

NASA Astrophysics Data System (ADS)

The ability of uniquely functional thermoelectric materials to convert waste heat directly into electricity is critical considering the global energy economy. Profitable, energy-efficient thermoelectrics possess thermoelectric figures of merit ZT >= 1. We examined the effect of metal nanoparticle -- oxide film interfaces on the thermal conductivity ? and Seebeck coefficient S in bilayer and multilayer thin film oxide thermoelectrics in an effort to improve the dimensionless figure of merit ZT. Since a thermoelectric's figure of merit ZT is directly proportional to S/?, reducing ? and increasing S are key strategies to optimize ZT. We reduced ? by phonon scattering due to the inclusion of metal nanoparticles in the bulk of the thermoelectric thin film, and increased S due to energy-dependent electron scattering at the metal - oxide interfaces. Doped strontium titanate (STO) thin film/Au nanoparticle composites were synthesized by alternate ablation of Au and Nb-doped STO targets during pulsed laser deposition. Characterization of the thermoelectric films involve XRD, XPS, and TEM analyses, Seebeck coefficient measurements, and also measurements of the thermal conductivity via time-domain thermoreflectance. The measured thermal conductivities and Seebeck coefficients of the thin films shows a strong dependence on the nanoscale interfaces of the films.

Osborne, Daniel; Huxtable, Scott; Tiwari, Ashutosh; Abiade, Jeremiah

2010-03-01

213

Side Effects of Chemotherapy  

MedlinePLUS

... Men Living with Prostate Cancer Side Effects of Chemotherapy Side Effects Urinary Dysfunction Bowel Dysfunction Erectile Dysfunction ... Side Effects of Hormone Therapy Side Effects of Chemotherapy Side Effects: When to Seek Help PSA Rising ...

214

Effective Teaching/Effective Urban Teaching  

ERIC Educational Resources Information Center

|This article considers the ways in which 17 novice teachers define and describe effective urban teaching and the stark contrasts that these teachers draw between effective urban teaching and effective teaching. The authors find that descriptions of students played a considerable role when participants made distinctions between effective teaching…

Watson, Dyan; Charner-Laird, Megin; Kirkpatrick, Cheryl L.; Szczesiul, Stacy Agee; Gordon, Pamela J.

2006-01-01

215

The Ranschburg effect  

Microsoft Academic Search

Summarizes recent research on the Ranschburg effect, an inhibitory effect on short-term recall observed when a stimulus string contains a repeated element, and attempts to identify the conditions associated with the effect. The theoretical bases for the Ranschburg effect, including a new analysis of the effect are considered and the results of 2 experiments designed as a 1st test of

John C. Jahnke

1969-01-01

216

Mercury: Health Effects  

MedlinePLUS

... toxicological profile for mercury . Top of page Elemental mercury effects Elemental (metallic) mercury primarily causes health effects ... 0370.htm . Top of page Effects of other mercury compounds (inorganic and organic) High exposures to inorganic ...

217

Effect of doping on the electronic structure and transport properties of half-Heusler compounds  

NASA Astrophysics Data System (ADS)

Narrow-band-gap half-Heusler semiconductors are promising candidates for high-temperature thermoelectrics due to large power factor S^2,, S is Seebeck coefficient and ? is the electrical conductivity. S^2, is usually maximized by changing the carrier concentration through doping. We have carried out transport measurements in Hf0.5Zr0.5CoxIr1-xSb0.99Sn0.01 for different x and temperatures (T). The nominal hole concentration n=1.78x10^20/cm^3. Measured Svalues (?V/K) are in the range 14-122 at 300 K and 90-216 at 750 K. The systems we have chosen to calculate S are (Hf,Zr)(Co,Ir)Sb. We have used ab intio band structure, Boltzmann transport equation (assuming constant relaxation time) and the rigid band approximation (RBA). We find values in the range 121-257 at 300 K and 262-390 at 750 K. To understand the origin of these differences, we have examined the validity of RBA. We observe that isovalent impurities do not change the band structure significantly, whereas charged impurities change the host band structure. Transport properties are also influenced by the change in the band structure.

Lee, Mal-Soon; Mahanti, S. D.; Takas, Nathan J.; Maji, Paramathesh; Poudeu, Ferdinand P.

2010-03-01

218

On Effect Size  

ERIC Educational Resources Information Center

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

Kelley, Ken; Preacher, Kristopher J.

2012-01-01

219

Effect Lines for Specifying Animation Effects  

Microsoft Academic Search

Abstract When we create 2D animations on a desktop computer using programs such as Microsoft PowerPoint or Macrome- dia Flash, we assign effects to objects and define their pa- rameters, such as their path, speed, and time of movement. To do this, we use conventional interfaces like menus or dia- log boxes. However, the motion effects associated with each object

Yoshikazu Kato; Etsuya Shibayama; Shin Takahashi

2004-01-01

220

Regulation with placebo effects.  

PubMed

A growing scientific literature supports the existence of placebo effects from a wide range of health interventions and for a range of medical conditions. This Article reviews this literature, examines the implications for law and policy, and suggests future areas for research on placebo effects. In particular, it makes the case for altering the drug approval process to account for, if not credit, placebo effects. It recommends that evidence of placebo effects be permitted as a defense in cases alleging violations of informed consent or false advertising. Finally, it finds that tort law already has doctrines such as joint and several liability to account for placebo effects. Future research on placebo effects should focus on whether awareness of placebo effects can disable these effects and whether subjects can control their own placebo effects. PMID:19353835

Malani, Anup

2008-12-01

221

Transport Properties of Ni and PbTe Under Pressure  

NASA Astrophysics Data System (ADS)

The high-pressure transport properties have been determined for nickel and PbTe. Nickel shows a reduction in electrical resistivity, an increase in thermal conductivity, and a variable effect on the Seebeck coefficient with pressure. In PbTe, a dramatic decrease in resistivity and a slow increase in thermal conductivity have been observed with increasing pressure. The three transport properties in PbTe are affected by a pressure-induced structural phase transition. The measurements show that the high-pressure phase is likely a more effective thermoelectric material than the ambient-pressure phase.

Jacobsen, Matthew K.; Kumar, Ravhi S.; Cornelius, Andrew L.

2012-04-01

222

Thermokinetic considerations about spin-dependent voltage generated by heat currents  

NASA Astrophysics Data System (ADS)

Thermokinetic considerations are appled to the case of a generic spintronic device in which a magneto-voltaic response is measured, in the absence of electric current, on an electrode placed perpendicular to a ferromagnetic layer (see Fig. 1). The magnetovoltaic signal is a response to a power excitation, that is related to the ferromagnetic degrees of freedom. This excitation can be performed by ferromagnetic resonance (electromagnetic excitations), by a temperature gradient, by magnetomechanical coupling or by magneto optic coupling (see these proceedings). The description of this generic device allows the so-called spin-Seebeck effects and spin-pumping effects17-16 to be addressed.

Wegrowe, Jean-Eric; Drouhin, Henri-Jean

2013-09-01

223

Kite Pseudo Effect Algebras  

NASA Astrophysics Data System (ADS)

We define a new class of pseudo effect algebras, called kite pseudo effect algebras, which is connected with partially ordered groups not necessarily with strong unit. In such a case, starting even with an Abelian po-group, we can obtain a noncommutative pseudo effect algebra. We show how such kite pseudo effect algebras are tied with different types of the Riesz Decomposition Properties. Kites are so-called perfect pseudo effect algebras, and we define conditions when kite pseudo effect algebras have the least non-trivial normal ideal.

Dvure?enskij, Anatolij

2013-10-01

224

The Mossbauer Effect.  

National Technical Information Service (NTIS)

The theory of the nuclear Mossbauer effect and its optical analogue is presented. Introductory paragraphs deal with the destruction of resonance fluorescence in case of a freely recoiling nucleus. The partial restoration of resonance by Doppler effect and...

A. Mukerji C. A. Coulter

1966-01-01

225

Stormwater BMP Effectiveness Toolkit  

EPA Science Inventory

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

226

Effects of Stroke  

MedlinePLUS

... Davis Legacy Fund Stay Informed Share » Effects of Stroke After Stroke Effects of Stroke Pediatric Stroke Rehabilitation ... PDF file. Content Updated: August 2012 Get Involved Stroke and You Stroke Survivors Caregivers and Families Healthcare ...

227

The Stimulated Raman Effect.  

National Technical Information Service (NTIS)

The paper reviews the main experimental and theoretical developments in stimulated Raman scattering of light, which has been actively investigated since 1962. The effect cannot be discussed properly without paying attention to related nonlinear effects wh...

N. Bloembergen

1967-01-01

228

Effective Frequency Technique.  

National Technical Information Service (NTIS)

An effective monochromatic frequency technique is described to represent the effects of finite spectral bandwidth for active and passive measurements centered on an absorption line, a trough region, or a slowly varying spectral feature. For Gaussian and r...

C. L. Korb C. Y. Weng

2003-01-01

229

Leadership Effectiveness and Gender.  

National Technical Information Service (NTIS)

This research paper on the subject of Leadership Effectiveness and Gender attempts to conduct a focused amount of research to answer the question about the correlation between gender and leadership effectiveness. It specifically looks at the current defin...

C. R. Gedney

1999-01-01

230

Global Effects Simulation Studies.  

National Technical Information Service (NTIS)

This document reviews the initial rise of a fire plume in the atmosphere, including effects of the condensation of entrained moisture. The condensation, expansion, and evaporation of the water cloud are examined, as are the relative effects of scattering ...

C. Chandler E. Bauer F. A. Albini

1986-01-01

231

Health effects of ozone  

Microsoft Academic Search

The 1989 Critical Review on Health Effects of Ozone by Morton Lippmann is a valuable contribution to the literature on criteria air pollutants. In a comprehensive fashion, the paper methodically examines key areas relevant to understanding effects of ozone on human health: exposure and dosimetry, populations and responses of concern, research approaches, and effects upon specific pulmonary endpoints from single

Utell

1989-01-01

232

Health effects of ozone  

Microsoft Academic Search

Dr. Morton Lippmann prepared, at the request of the A WMA Review Committee, an extensive update of the available information on the biological effects of ozone. His review is a thorough and well-written summary of what is known about respiratory effects of low ozone concentrations. The authors is well qualified to evaluate clinical data on ozone effects since a substantial

Vostal

1989-01-01

233

Special Effects Activity Guide.  

ERIC Educational Resources Information Center

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

Boxer, Jennifer; Valenta, Carol

234

How effective are models?  

Microsoft Academic Search

This article discusses a number of common interpretations of 'implementation' in the literature, and how these have been confused. Various different levels of implementation are then discussed, including the concept of model effectiveness. This is concerned with both the operational effectiveness of the model, as shown by a tangible improvement in the system modelled, and the personal effectiveness in helping

John Fripp

1985-01-01

235

Special Effects Activity Guide.  

ERIC Educational Resources Information Center

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

Boxer, Jennifer; Valenta, Carol

236

Irradiation Effects on Zircaloy.  

National Technical Information Service (NTIS)

In a water cooled reactor, the neutron effect on zirconium base alloys which are used in the core, is a twofold one: - indirect effect, by means of modifications to the alloy environment; - direct effect occurence of irradiation defects in the material. T...

P. Morize

1983-01-01

237

Nonlinear Talbot Effect  

NASA Astrophysics Data System (ADS)

We propose and experimentally demonstrate the nonlinear Talbot effect from nonlinear photonic crystals. The nonlinear Talbot effect results from self-imaging of the generated periodic intensity pattern at the output surface of the crystal. To illustrate the effect, we experimentally observed second-harmonic Talbot self-imaging from 1D and 2D periodically poled LiTaO3 crystals. Both integer and fractional nonlinear Talbot effects were investigated. The observation not only conceptually extends the conventional Talbot effect, but also opens the door for a variety of new applications in imaging technologies.

Zhang, Yong; Wen, Jianming; Zhu, S. N.; Xiao, Min

2010-05-01

238

Nonlinear Talbot effect.  

PubMed

We propose and experimentally demonstrate the nonlinear Talbot effect from nonlinear photonic crystals. The nonlinear Talbot effect results from self-imaging of the generated periodic intensity pattern at the output surface of the crystal. To illustrate the effect, we experimentally observed second-harmonic Talbot self-imaging from 1D and 2D periodically poled LiTaO(3) crystals. Both integer and fractional nonlinear Talbot effects were investigated. The observation not only conceptually extends the conventional Talbot effect, but also opens the door for a variety of new applications in imaging technologies. PMID:20482176

Zhang, Yong; Wen, Jianming; Zhu, S N; Xiao, Min

2010-05-07

239

Enhanced thermoelectric performance in zinc substituted p-type filled skutterudites CeFe{sub 4-x}Zn{sub x}Sb{sub 12}  

SciTech Connect

In this study, Zn-substituted polycrystalline skutterudites CeFe{sub 4-x}Zn{sub x}Sb{sub 12} (x=0, 0.05, 0.1, 0.2, 0.3) were successfully prepared by a traditional melting-annealing method. The solubility of Zn in Fe site is {approx}1.2%, exceeding which trace amount of ZnSb phase can be detected in the XRD. This ZnSb impurity phase, with size of several hundred nanometers for the sample with x=0.2 but showing surprisingly small size of {approx}10 nm for the sample with x=0.3, selectively distributes on the grain boundaries. In particular, the introduction of Zn in Fe site effectively improves the Seebeck coefficient in a manner of enhancement in hole effective mass, but it has negligible influence on both electrical and thermal conductivities though the hole concentration is increased. Consequently the corresponding improvement in power factor leads to an improved thermoelectric figure of merit (ZT) of 0.9 at 800 K for the sample with x=0.1, which is {approx}15% higher than that of Zn-free sample. This study demonstrates a favorable effect of Zn iso-substitution and opens a new strategy to improve the thermoelectric properties of p-type Fe-based skutterudites beyond the sole phonon engineering. - Graphical abstract: (a)-(c) ZnSb nanoinclusions emerge when Zn exceeds its solubility limit. (d), (e) The introduction of Zn boosts the Seebeck coefficient and thus enhances the ZT value. Highlights: Black-Right-Pointing-Pointer Zn is successfully employed to substitute Fe atom for the first time. Black-Right-Pointing-Pointer ZnSb nanoinclusions emerge when Zn exceeds its solubility limit {approx}0.12. Black-Right-Pointing-Pointer The introduction of Zn boosts the Seebeck coefficient and enhances the ZT value.

Tan Gangjian; Wang Shanyu; Li Han; Yan Yonggao [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Luoshi Road 122, Hongshan district, Wuhan 430070 (China); Tang Xinfeng, E-mail: tangxf@whut.edu.cn [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Luoshi Road 122, Hongshan district, Wuhan 430070 (China)

2012-03-15

240

The butterfly effect of the "butterfly effect".  

PubMed

The "Butterfly Effect" metaphor states with variance that the flap of a butterfly's wings in Brazil can cause a tornado in Texas. This metaphor has become part of the common vernacular of Western culture. In this paper I discuss the origins of the metaphor, examine its current usage within popular culture, and present an argument as to why it is popular. I propose that the metaphor is a type of semantic attractor, a narrative device with invariant meaning but audience-specific contextualization. Finally I address whether the Butterfly Effect metaphor is a good example of itself. PMID:19527619

Dooley, Kevin J

2009-07-01

241

Amplification of Spin Waves by Thermal Spin-Transfer Torque  

NASA Astrophysics Data System (ADS)

We observe amplification of spin-wave packets propagating along a film of single-crystal yttrium iron garnet subject to a transverse temperature gradient. The spin waves are excited and detected with standard techniques used in magnetostatic microwave delay lines in the 1-2 GHz frequency range. The amplification is attributed to the action of a thermal spin-transfer torque acting on the magnetization that opposes the relaxation and which is created by spin currents generated through the spin-Seebeck effect. The experimental data are interpreted with a spin-wave model that gives an amplification gain in very good agreement with the data.

Padrón-Hernández, E.; Azevedo, A.; Rezende, S. M.

2011-11-01

242

Thermomicrocapillaries as temperature biosensors in single cells  

NASA Astrophysics Data System (ADS)

Temperature is an important physical parameter in biology and its deviation from optimum can cause damage in biosystems. Thermocouples based on the Seebeck effect can be structured on glass microcapillaries to obtain thermomicrocapillaries (TMCs) usable in a micromanipulation setup. The suitability of the setup was proven by monitoring the temperature increase upon illumination of leaves and single cells following insertion of the TMC. The increase was 1.5 K in green tissue and 0.75 K in white leaf sections due to lower absorption. In single cells of trichomes, the increase was 0.5 K due to heat dissipation to the surrounding air.

Herth, Simone; Giesguth, Miriam; Wedel, Waldemar; Reiss, Günther; Dietz, Karl-Josef

2013-03-01

243

Lattice thermal conductivity diminution and high thermoelectric power factor retention in nanoporous macroassemblies of sulfur-doped bismuth telluride nanocrystals  

NASA Astrophysics Data System (ADS)

We report ultralow lattice thermal conductivity in the 0.3 <= ?L <= 0.6 W m-1 K-1 range in nanoporous bulk bismuth telluride pellets obtained by sintering chemically synthesized nanostructures, together with single-crystal-like electron mobilities and Seebeck coefficients at comparable charge carrier concentrations. The observed ?L is up to 35% lower than classical effective medium predictions, and can be quantitatively explained by increased phonon scattering at nanopores and nanograins. Our findings are germane to tailoring nanoporous thermoelectric materials for efficient solid-state refrigeration, thermal energy harvesting, and thermal management applications.

Zhang, Yanliang; Mehta, Rutvik J.; Belley, Matthew; Han, Liang; Ramanath, Ganpati; Borca-Tasciuc, Theodorian

2012-05-01

244

Giant improvement of thermoelectric power factor of Bi2Te3 under pressure  

Microsoft Academic Search

The pressure (P) dependencies of both the thermopower (Seebeck effect) S and the electrical resistance (R) for p-type single crystals of Bi2Te3 and indium-doped bismuth telluride (InxBi2-xTe3,0.04<=x<=0.10) are reported on a pressure range of 0-8.5 GPa. The thermoelectric power factor (efficiency) (æ=S2\\/R) exhibits two maxima: the first one near ~1 GPa and the second near ~2.5-4.5 GPa. These features evidence

Sergey V. Ovsyannikov; Vladimir V. Shchennikov; Grigoriy V. Vorontsov; Andrey Y. Manakov; Anna Y. Likhacheva; Vladimir A. Kulbachinskii

2008-01-01

245

Thermoelectric properties of P-type antimony bismuth telluride alloys prepared by cold pressing  

SciTech Connect

Sb{sub 2{minus}x}Bi{sub x}Te{sub 3} (x = 0.43--0.51) thermoelectric materials were prepared by the powder metallurgy method. The effects of grinding and sintering processes on the Seebeck coefficient, electrical conductivity, and thermoelectric figure of merit were investigated. For different particle sizes, a shift in maximum of Z = f(x) dependence was found. This shift can be explained by the presence of point defects and their interaction. Cold-pressed material with Z {approximately} 3.1 {times} 10{sup {minus}3} K{sup {minus}1} was prepared.

Navratil, J.; Stary, Z.; Plechacek, T. [Academy of Sciences of the Czech Republic and Univ. of Pardubice (Czech Republic). Joint Lab. of Solid State Chemistry

1996-12-01

246

Enhancing high-temperature thermoelectric properties of PtAs2 by Rh doping  

NASA Astrophysics Data System (ADS)

The effects of Rh doping on the thermoelectric properties of Pt1-xRhxAs2 (x = 0, 0.005, and 0.01) with pyrite structure were studied by conducting measurements of electrical resistivity ?, Seebeck coefficient S, and thermal conductivity ?. The sample with x = 0.005 exhibited large S and low ?, resulting in a maximum power factor (S2/?) of 65 ?W/cmK2 at 440 K. The peculiarly shaped ``corrugated flat band'' predicted for PtSb2 might explain the enhanced thermoelectric properties of doped PtAs2.

Kudo, Kazutaka; Nakano, Seiya; Mizukami, Tasuku; Takabatake, Toshiro; Nohara, Minoru

2013-08-01

247

Enhanced room temperature electronic and thermoelectric properties of the dilute bismuthide InGaBiAs  

SciTech Connect

We report room temperature electronic and thermoelectric properties of Si-doped In{sub 0.52}Ga{sub 0.48}Bi{sub y}As{sub 1-y} with varying Bi concentrations. These films were grown epitaxially on a semi-insulating InP substrate by molecular beam epitaxy. We show that low Bi concentrations are optimal in improving the conductivity, Seebeck coefficient, and thermoelectric power factor, possibly due to the surfactant effects of bismuth. We observed a reduction in thermal conductivity with increasing Bi concentration, which is expected because of alloy scattering. We report a peak ZT of 0.23 at 300 K.

Dongmo, Pernell; Zhong Yujun; Bomberger, Cory; Zide, Joshua [Department of Materials Science and Engineering, University of Delaware, Newark, Delaware 19716 (United States); Attia, Peter [Department of Chemical Engineering, University of Delaware, Newark, Delaware 19716 (United States); Cheaito, Ramez; Hopkins, Patrick E. [Department of Mechanical and Aerospace Engineering, University of Virginia, Charlottesville, Virginia 2294 (United States); Ihlefeld, Jon F. [Sandia National Laboratories, P.O. Box 5800, M.S. 1069, Albuquerque, New Mexico 87185 (United States)

2012-11-01

248

On the posedness of thermoelectrochemical coupled systems  

NASA Astrophysics Data System (ADS)

We examine the complete coupled thermoelectrochemical system that describes reaction problems. The cross effects, namely the thermoelectric (Peltier-Seebeck), the thermodiffusion (Dufour-Soret), and the electrochemical diffusion, occur as reciprocal phenomena of irreversible processes. We deal with convective/radiative heat-transfer boundary conditions on a part of the boundary. The objective is their application to electrolysis, Li batteries, and fuel cells. The existence of stationary solutions for the theoretical model is found, under different smallness conditions on the data, via a fixed point argument.

Consiglieri, Luisa

2013-05-01

249

Feasibility of enhancing the thermoelectric power factor in GaNxAs1-x  

NASA Astrophysics Data System (ADS)

This study was motivated by the possibility of using N resonant levels interacting with the GaAs conduction band, in GaNxAs1-x (0effective mass (md) and consequently the thermoelectric power factor (S2?)—where S is the Seebeck coefficient and ? is the electrical conductivity. However, it was observed that, compared with GaAs, the power factor was reduced in spite of a small increase in the md. The influences of carrier passivation and dopant type, as well as the changes in the carrier scattering mechanism, which degrades the carrier mobility, are discussed.

Pichanusakorn, P.; Kuang, Y. J.; Patel, C.; Tu, C. W.; Bandaru, P. R.

2012-08-01

250

Graphene nanoribbon thermopower as a tool for molecular spectroscopy  

NASA Astrophysics Data System (ADS)

In this work, we study thermoelectric properties of graphene nanoribbons with side-attached organic molecules. By adopting a single-band tight binding Hamiltonian and the Green's function formalism, we calculated the transmission and Seebeck coefficients for different hybrid systems. The corresponding thermopower profiles exhibit a series of sharp peaks at the eigenenergies of the isolated molecule indicating that the system can be proposed as a molecular thermo-device. We have studied the effects of the temperature on the thermoelectric response, and considered random configurations of molecule distributions, in different disorder regimes. We have found that the main features of the thermopower are robust under temperature and disorder.

Rosales, L.; Nunez, C. D.; Pacheco, M.; Latgé, A.; Orellana, P. A.

2013-10-01

251

Band Structure And Electronic Transport Properties In Ii-Vi Nano-Semiconductors. Application To Infrared Detectors Superlattices And Alloys  

NASA Astrophysics Data System (ADS)

We report here electronic transport properties measurements, scattering mechanisms and theoretical results on Fermi energy, donor state energy and modeling carrier charge mobility in the ternary alloys Hg1- x Cd x Te (x = 0.22) medium-infrared detector. We report again the band structure, magneto-transport results, X-ray diffraction, Seebeck and Shubnikov-de Haas effects (SDH) in the medium-infrared detector, narrow gap and two-dimensional p-type semiconductor HgTe(5.6 nm)/CdTe(3 nm) superlattice. The later sample is an alternative to the investigated alloy.

Abidi, A. El; Nafidi, A.; Kaaouachi, A. El; Chaib, H.

252

Transparent p-type conducting CuScO2+x films  

NASA Astrophysics Data System (ADS)

Transparent films of CuScO2+x have been prepared which show p-type electrical conductivity. The temperature dependence of the conductivity indicates semiconducting behavior with an apparent room temperature activation energy of 0.11 eV. The highest room temperature conductivity observed was 30 S cm-1. Films 110 nm thick show 40% transparency in most of the visible spectrum and become much more transparent in the infrared spectrum. The p-type behavior was confirmed by the Seebeck effect.

Duan, N.; Sleight, A. W.; Jayaraj, M. K.; Tate, J.

2000-08-01

253

Amplification of spin waves by thermal spin-transfer torque.  

PubMed

We observe amplification of spin-wave packets propagating along a film of single-crystal yttrium iron garnet subject to a transverse temperature gradient. The spin waves are excited and detected with standard techniques used in magnetostatic microwave delay lines in the 1-2 GHz frequency range. The amplification is attributed to the action of a thermal spin-transfer torque acting on the magnetization that opposes the relaxation and which is created by spin currents generated through the spin-Seebeck effect. The experimental data are interpreted with a spin-wave model that gives an amplification gain in very good agreement with the data. PMID:22181640

Padrón-Hernández, E; Azevedo, A; Rezende, S M

2011-11-04

254

Virality, Network Effects and Advertising Effectiveness  

Microsoft Academic Search

Many video ads are designed to go viral, so that the total number of views they receive depends on customers sharing the ads with their friends. This paper explores the relationship between achieving this endogenous reach and the effectiveness of the ad at persuading a consumer to purchase or adopt a favorable attitude towards a product. The analysis combines data

Catherine Tucker

2011-01-01

255

Transport, thermal, and magnetic properties of the narrow-gap semiconductor CrSb2  

NASA Astrophysics Data System (ADS)

Resistivity, the Hall effect, the Seebeck coefficient, thermal conductivity, heat capacity, and magnetic susceptibility data are reported for CrSb2 single crystals. In spite of some unusual features in electrical transport and Hall measurements below 100 K, only one phase transition is found in the temperature range from 2 to 750 K corresponding to long-range antiferromagnetic order below TN ? 273 K. Many of the low-temperature properties can be explained by the thermal depopulation of carriers from the conduction band into a low-mobility band located approximately 16 meV below the conduction-band edge, as deduced from the Hall effect data. In analogy with what occurs in Ge, the low-mobility band is likely an impurity band. The Seebeck coefficient, S, is large and negative for temperatures from 2 to 300 K ranging from ?-70?V/K at 300 K to -4500?V/K at 18 K. A large maximum in |S| at 18 K is likely due to phonon drag, with the abrupt drop in |S| below 18 K due to the thermal depopulation of the high-mobility conduction band. The large thermal conductivity between 10 and 20 K (?350 W/m K) is consistent with this interpretation, as are detailed calculations of the Seebeck coefficient made using the complete calculated electronic structure. These data are compared to data reported for FeSb2, which crystallizes in the same marcasite structure, and FeSi, another unusual narrow-gap semiconductor.

Sales, Brian C.; May, Andrew F.; McGuire, Michael A.; Stone, Matthew B.; Singh, David J.; Mandrus, David

2012-12-01

256

Coexistence of qubit effects  

Microsoft Academic Search

Two quantum events, represented by positive operators (effects), are coexistent if they can occur as possible outcomes in a single measurement scheme. Equivalently, the corresponding effects are coexistent\\u000a if and only if they are contained in the ranges of a single (joint) observable. Here we give several equivalent characterizations\\u000a of coexistent pairs of qubit effects. We also establish the equivalence

Paul Busch; Heinz-Jürgen Schmidt

2010-01-01

257

Practical and effective ALARA.  

PubMed

The ALARA Principle ensures that the total effective dose equivalent is minimized subject to economic and social factors. Effective ALARA programs must include the participation of all facility workgroups, management support, teamwork, and strong leadership. The development and sustainability of effective ALARA programs require the establishment and monitoring of goals, rewarding the successful achievement of those goals, and incorporating lessons learned from tasks that fail to meet their goals. PMID:20386191

Bevelacqua, Joseph John

2010-05-01

258

Effective Strategies Brief  

NSDL National Science Digital Library

In this research brief the authors detail effective teaching strategies for teaching students with difficulties in math. The brief summarizes the work of over fifty research studies and details the practices that were seen as consistently effective across many of them. The brief details six instructional strategies and presents data describing the effectiveness of each on special education students and low-achieving students. The brief can be viewed on the webpage or downloaded as a PDF.

Gersten, Russell; Clarke, Benjamin S.

2007-01-01

259

Magnetic Casimir effect  

SciTech Connect

The Casimir effect results from alterations of the zero-point electromagnetic energy introduced by boundary conditions. For ferromagnetic layers separated by vacuum (or a dielectric), such boundary conditions are influenced by the magneto-optical Kerr effect. We will show that this gives rise to a long-range magnetic interaction and discuss the effect for two different configurations (magnetization parallel and perpendicular to the layers). Analytical expressions are derived for two models and compared to numerical calculations. Numerical calculations of the effect for Fe are also presented and the possibility of an experimental observation of the Casimir magnetic interaction is discussed.

Metalidis, G.; Bruno, P. [Max-Planck-Institut fuer Mikrostrukturphysik, Weinberg 2, D-06120 Halle (Germany)

2002-12-01

260

Pressure effect on the electronic transport properties of Fe1+yTe1-xSex  

NASA Astrophysics Data System (ADS)

We present a systematic study of electronic transport as function of pressure up to 25 kbar of Fe+yTe1-xSex single crystalline samples (with y=0.02, 0.05, and x=0, 0.2, and 0.3). Pressure is demonstrated to be a clean control parameter to drive the system with high Fe-excess through the metal-insulator (MIT) transition, in analogy with increasing the Se-doping or reducing the Fe-excess. The scaling of resistivity ?(T, p) below 50 K identified a critical pressure of pc=8 kbar which separates non-metallic and metallic temperature dependences. At the pc the low-temperature sheet resistance is in the 6.5 k?/square range. The Seebeck coefficient (S) at pc changes sign from negative to positive indicating a change in the electronic structure and in the balance between the electron and hole carriers. The S at the highest pressure exhibits low positive values similar to the metallic, superconducting cuprates. The critical MIT behavior, related to a quantum phase transition, indicates a universality of the Fe- and Cu-based high-Tc superconductors.

Arsenijevi?, Stevan; Gaál, Richard; Rønnow, Henrik; Viennois, Romain; Giannini, Enrico; van der Marel, Dirk; Forró, László

2012-02-01

261

The polarized EMC effect  

SciTech Connect

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

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

2007-02-01

262

Health effects of ozone  

Microsoft Academic Search

The author comments on Morton Lippmann's paper entitled Health Effects of Ozone which was presented at the 82nd Air and Waste Management Association Annual Meeting and Exhibition, held in Anaheim, California in June 1989. Thanks to the efforts of Dr. Lippmann we have a better understanding of the acute, prolonged and chronic exposure health effects of ozone and are in

McKee

1989-01-01

263

Cardiovascular effects of leptin  

Microsoft Academic Search

A wealth of investigations, ranging from clinical and animal model studies to in vitro analyses, have generated great interest in the cardiovascular effects of leptin. Accordingly, many studies have examined the contribution of leptin to cardiac remodeling in heart failure and whether the effects of leptin on metabolism, apoptosis, extracellular matrix remodeling, and hypertrophy could explain the so-called obesity paradox.

Gary Sweeney

2009-01-01

264

The Kaye Effect  

ERIC Educational Resources Information Center

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

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

2009-01-01

265

The effectiveness of decoupling  

Microsoft Academic Search

This paper examines the effectiveness of decoupling as an optimization technique for high-performance computer architectures. Decoupled access execute architectures are described, and the concept of control decoupling is introduced and justified. A description of a highly-decoupled architecture is given, and a metric for the effectiveness of decoupling on particular programs, the Loss of Decoupling frequency is introduced. Finally, a number

Peter L. Bird; Alasdair Rawsthorne; Nigel P. Topham

1993-01-01

266

Nitrogen oxides - animal effects  

Microsoft Academic Search

The results of animal studies investigating the effects of nitrogen dioxide are reviewed in an attempt to arrive at objective grounds for an NOâ standard. There appears to be no threshold level for NOâ so far as some detectable alteration of lung function or structure in animals is concerned. A threshold may be reached for an effect contributing to clinical

Crocker

1973-01-01

267

Defining Effective Teaching  

ERIC Educational Resources Information Center

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

Layne, L.

2012-01-01

268

Theorizing Interactivity's Effects  

Microsoft Academic Search

Noting that interactivity is often defined but seldom theorized in the literature, this article provides some pointers for developing theories about effects of interactivity, particularly as it applies to Web-based mass communication. It first makes the case that interactivity is an attribute of the technology and not that of the user. It exposes the tautology of studying the effects of

S. Shyam Sundar

2004-01-01

269

Effects of Mobile Communication  

Microsoft Academic Search

Before reviewing some of the key consequences of mobile communication technology, a brief discussion of how they fit within the media effects paradigm is in order. At the risk of oversimplification, we understand the media effects paradigm as a framework for understanding how mass media content influences attitudes and behavior of audience members. To be fair, it is important to

Scott W. Campbell

270

Carbon star effective temperatures  

Microsoft Academic Search

Possible methods for measuring the effective temperatures of individual carbon stars are discussed. Since calibrations of broad or narrow-band photometric colors is impractical at present, empirical corrections to narrow band color temperatures is the only valid procedure. The effective temperature of the star TW Oph is estimated, based on preliminary reduction of the occultation and associated photometry

S. T. Ridgway; G. H. Jacoby; R. R. Joyce; D. C. Wells

1981-01-01

271

Institutional Effectiveness Report.  

ERIC Educational Resources Information Center

This is the first edition of the College of the Canyon's (California) Institutional Effectiveness Report, which is modeled after the statewide report prepared by the Chancellor's Office. The college is measuring 60 effectiveness indicators in four mission areas: student access, student success, staff composition, and fiscal condition. A brief…

College of the Canyons, Santa Clarita, CA.

272

Side effects of clozapine  

Microsoft Academic Search

In addition to the low risk of agranulocytosis, several more frequent side effects are associated with clozapine therapy. We tried to estimate the incidence of these side effects. We analysed 391 treatments in 315 inptients, who received clozapine alone or combined with other neuroleptic and antidepressant drugs. Two thirds were combined treatments, one third were treatments with clozapine alone (i.e.,

Hans Jörg Gaertner; Eberhard Fischer; Joachim Hoss

1989-01-01

273

Earthquake Effects and Experiences  

NSDL National Science Digital Library

This portion of the United States Geological Survey's (USGS) frequently-asked-questions feature on earthquakes addresses what individuals might actually experience during an earthquake. Topics include earthquake motion (rolling or shaking), earthquake effects (ground shaking, surface faulting, ground failure, etc.), earthquake magnitude, what an earthquake feels like, and others. There are also links to additional resources on earthquake effects and experiences.

274

Earthquake Effects and Experiences  

NSDL National Science Digital Library

This portion of the United States Geological Survey's (USGS) frequently-asked-questions feature on earthquakes addresses what individuals might actually experience during an earthquake. Topics include earthquake motion (rolling or shaking), earthquake effects (ground shaking, surface faulting, ground failure, etc.), earthquake magnitude, what an earthquake feels like, and others. There are also links to additional resources on earthquake effects and experiences.

2010-11-23

275

Effects of nuclear weapons  

Microsoft Academic Search

The most recent data concerning the effects associated with explosions of nuclear weapons are presented. The data have been obtained from observations made of effects of nuclear bombing in Japan and tests carried out at the Eniwetok Proving Grounds and Nevada Test Site, as well as from experiments with conventional explosives, and mathematical calculations. The volume is intended for use

Glasstone

1957-01-01

276

Quantum Spin Hall Effect  

Microsoft Academic Search

The quantum Hall liquid is a novel state of matter with profound emergent properties such as fractional charge and statistics. Existence of the quantum Hall effect requires breaking of the time reversal symmetry caused by an external magnetic field. In this work, we predict a quantized spin Hall effect in the absence of any magnetic field, where the intrinsic spin

B. Andrei Bernevig; Shou-Cheng Zhang

2010-01-01

277

Quantum Spin Hall Effect  

Microsoft Academic Search

The quantum Hall liquid is a novel state of matter with profound emergent properties such as fractional charge and statistics. The existence of the quantum Hall effect requires breaking of the time reversal symmetry caused by an external magnetic field. In this work, we predict a quantized spin Hall effect in the absence of any magnetic field, where the intrinsic

B. Andrei Bernevig; Shou-Cheng Zhang

2006-01-01

278

School Quality and Effectiveness  

Microsoft Academic Search

One of the most robust and consistent findings in educational research is that a child's educational attainment is greatly affected by its family background. A crucial issue for policy is whether schools have any effect on children's attainment or whether it is all determined by family background and personality traits. If schools are differentially effective then the school attended matters

Arnaud Chevalier; Peter Dolton; Ros Levacic

2004-01-01

279

Effects on Plants.  

National Technical Information Service (NTIS)

Results of experiments with plants on the effects of low-dose and low-dose rates of low LET radiation are reported. Experiments were conducted on the effects of x and gamma radiation on the production of yellow-green sectors in maize leaves, growth inhibi...

H. H. Smith

1977-01-01

280

Effectiveness of active antennas  

Microsoft Academic Search

Active antennas are miniaturized radio-receiver antennas which use broadband transistor amplifiers to effect added voltage. The effectiveness of such an antenna is the signal to noise ratio at the input of the amplifier. This paper presents an analysis of the noise properties of the most widespread active antenna - a short asymmetrical vibrator with a high-impedance broadband amplifier. It is

B. V. Sosunov

1976-01-01

281

Effective Family Problem Solving.  

ERIC Educational Resources Information Center

Effective family problem solving was studied in 97 families of elementary-school-aged children with definite- and indefinite-solution tasks. Incentive and task independence were manipulated. It was found that definitions of effective problem solving based on directly observed measures of group interaction were more valid than definitions based on…

Blechman, Elaine A.; McEnroe, Michael J.

1985-01-01

282

[Antioxidant effects of melatonin].  

PubMed

Increase in knowledge about reactive oxygen species action mechanisms and oxidative stress effects in living organisms led to intensive seeking for new, more effective substances, which prevent extreme development of oxidative stress or are able to decrease its negative influence, damaging cell structures and many cell functions. These substances are called antioxidants, scavengers, trappers or quenchers. In nineties, melatonin became the centre of the interest in the filed of investigation of antioxidative properties of different chemical substances. This is in living organisms ubiquitous substance with relatively simple chemical structure, good physical properties and wide physiological effects. The main role of endogenous melatonin comprises receptor-mediated biological rhythms synchronisation. Among other functions mentioned later belong anti-gonadotropic, immunotropic and non-receptor-mediated antioxidative effects. Melatonin is said to have also antineoplastic properties. Its anti-aging effect is discutable. PMID:11417192

Konecná, I; Holecek, V; Racek, J; Trefil, L; Rokyta, R

2001-05-01

283

The greenhouse effect  

NASA Astrophysics Data System (ADS)

The greenhouse effect on the Earth is identified by the difference between the effective radiating temperature of the planet and its surface temperature. The difference between the energy emitted by the surface and that emitted upward to space by the upper atmosphere quantifies it; it can therefore be defined as the long wave energy trapped in the atmosphere. Climate forcing and the response of the climate system within which climate feedback mechanisms are contained, will be defined in this review. Quantitative examples will illustrate what could happen if the greenhouse effect is perturbed by the human activities, in particular if atmospheric CO2 concentrations would double in the future. Recent measurements by satellites of the greenhouse effect will be given. The net cooling effect of clouds on the Earth and whether or not there will be less cooling by clouds as the planet warms, are discussed following a series of papers recently published by Ramanathan and his collaborators.

Berger, A.; Tricot, Ch.

1992-11-01

284

Thermoelectric properties of polycrystalline La{sub 1-x}Sr{sub x}CoO{sub 3}  

SciTech Connect

Thermoelectric properties of polycrystalline La{sub 1-x}Sr{sub x}CoO{sub 3}, where Sr{sup 2+} is substituted in La{sup 3+} site in perovskite-type LaCoO{sub 3}, have been investigated. Sr-doping increases the electrical conductivity ({sigma}) of La{sub 1-x}Sr{sub x}CoO{sub 3}, and also decreases the Seebeck coefficient (S) for 0.01{<=}x{<=}0.40. A Hall coefficient measurement reveals that the increase in electrical conductivity arises from increases in both carrier concentration and the Hall mobility. The decrease in the Seebeck coefficient is caused by a decrease in carrier effective mass as well as increase in carrier concentration. The highest power factor ({sigma}S{sup 2}) is 3.7x10{sup -4} W m{sup -1} K{sup -2} at 250 K for x=0.10. The thermal conductivity ({kappa}) is about 2 W m{sup -1} K{sup -1} at 300 K for 0{<=}x{<=}0.04, and increases for x{>=}0.05 because of an increase in heat transport by conductive carrier. The thermoelectric properties of La{sub 1-x}Sr{sub x}CoO{sub 3} are improved by Sr-doping, and the figure of merit (Z={sigma}S{sup 2} {kappa}{sup -1}) reaches 1.6x10{sup -4} K{sup -1} for x=0.06 at 300 K (ZT=0.048). For heavily Sr-doped samples, the thermoelectric properties diminish mainly because of the decrease in the Seebeck coefficient and the increase in thermal conductivity. - Graphical abstract: Temperature and Sr-doping level dependencies of the power factor of La{sub 1-x}Sr{sub x}CoO{sub 3}.

Iwasaki, Kouta [Department of Materials, Physics and Energy Engineering, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan)], E-mail: k-iwasaki@nucl.nagoya-u.ac.jp; Ito, Tsuyoshi [Department of Materials, Physics and Energy Engineering, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Nagasaki, Takanori; Arita, Yuji [EcoTopia Science Institute, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Yoshino, Masahito [Department of Materials, Physics and Energy Engineering, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Matsui, Tsuneo [Department of Materials, Physics and Energy Engineering, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); EcoTopia Science Institute, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan)

2008-11-15

285

The thermoelectric properties of bulk crystalline n- and p-type Mg2Si prepared by the vertical Bridgman method  

NASA Astrophysics Data System (ADS)

Bulk Mg2Si crystals were grown using the vertical Bridgman melt growth method. The n-type and p-type dopants, bismuth (Bi) and silver (Ag), respectively, were incorporated during the growth. X-ray powder diffraction analysis revealed clear peaks of Mg2Si with no peaks associated with the metallic Mg and Si phases. Residual impurities and process induced contaminants were investigated by using glow discharge mass spectrometry (GDMS). A comparison between the results of GDMS and Hall effect measurements indicated that electrical activation of the Bi doping in the Mg2Si was sufficient, while activation of the Ag doping was relatively smaller. It was shown that an undoped n-type specimen contained a certain amount of aluminum (Al), which was due either to residual impurities in the Mg source or the incorporation of process-induced impurities. Thermoelectric properties such as the Seebeck coefficient and the electrical and thermal conductivities were measured as a function of temperature up to 850 K. The dimensionless figures of merit for Bi-doped and Ag-doped samples were 0.65 at 840 K and 0.1 at 566 K, respectively. Temperature dependence of the observed Seebeck coefficient was fitted well by the two-carrier model. The first-principles calculations were carried out by using the all-electron band-structure calculation package (ABCAP) in which the full-potential linearized augmented-plane-wave method was employed. The ABCAP calculation adequately presents characteristics of the Seebeck coefficients for the undoped and heavily Bi-doped samples over the whole measured temperature range from room temperature to 850 K. The agreement between the theory and the experiment is poorer for the Ag-doped p-type samples.

Akasaka, Masayasu; Iida, Tsutomu; Matsumoto, Atsunobu; Yamanaka, Kohei; Takanashi, Yoshifumi; Imai, Tomohiro; Hamada, Noriaki

2008-07-01

286

Thermoelectric properties and applications of sodium doped vanadium pentoxide thin films  

NASA Astrophysics Data System (ADS)

This thesis investigates sodium (Na) vanadium pentoxide (V 2O5) bronzes as a new class of thermoelectric material for thin film device applications. A systematic study of Na doping into the V 2O5 host lattice was undertaken in an attempt to fmd the phase that maximizes a power factor described by sigmaS2, where sigma and S are the electrical conductivity and Seebeck coefficient, respectively. Various materials characterization techniques were used to understand the charge and energy transport mechanisms of the various phases, and explain why a certain phase exhibits a higher power factor. Knowledge and experiences gained through processing techniques were implemented in creating sensor devices in which the thermoelectric effect is a transduction mechanism. A method to prepare Na doped V2O5 solution was developed, which can be the basis for creating thin film thermoelectric devices. This is a unique technique which incorporates Na directly into the solution, without causing precipitation. This solution can be deposited on substrates to make crystalline thin films by annealing in air. By controlling the process parameters such as annealing temperature, time, and substrate, the amount of Na incorporated in the thin film can be fine tuned, allowing the creation of the desired sodium bronze phase. Physical parameters including electrical conductivity, Seebeck coefficient, and output power were measured on thin films with various Na doping concentrations to determine what phases were achievable, and how the presence of these phases influences these parameters. The increase in the beta-phase formation has been observed to improve electrical conductivity by a factor of 3, while it decreased the Seebeck coefficient by less than half. Power measurements verified that, while these films have smaller Seebeck coefficients, the large increase in conductivity compensated for the loss, thus increasing the net power factor. Changes in important physical parameters including carrier concentration and electron mobility were determined by measurements including XPS and Hall Effect, to understand the reasons for the improved thermoelectric properties. At the end, the developed process techniques were used to create a prototype thermal sensor array, which was built and tested.

Iwanaga, Shiho

287

[Cholinergic effects of nootropics].  

PubMed

With respect to the enhancing effect of nootropics on learning and memory, the influence of some of these drugs on the high affinity choline uptake has been investigated. Meclofenoxate competes with choline uptake in vitro because of its similar side chain; other nootropics are without in vitro effects. A single dose of pramiracetam enhances the choline uptake in cortex and hippocampus. Application of meclofenoxate decreases the uptake of choline. Other nootropics lack acute effects. Possible increases of uptake after repeated dosage disappear within 24 h. PMID:3149192

Funk, K F; Schmidt, J

1988-01-01

288

From effective interactions to effective operators  

NASA Astrophysics Data System (ADS)

One of the most successful approaches to the nuclear structure of light nuclei is the no-core shell model (NCSM), which describes with very good precision the observed nuclear spectra. In its framework, by means of the Lee Suzuki procedure one derives effective interactions in finite model spaces starting from realistic nucleon-nucleon (NN) potentials; the low-lying energy spectrum is then obtain through the diagonalization of the ab initio effective interactions in large, translationally invariant, many-body basis. In addition to energy levels, one has to obtain good description of the nuclear wave functions; the latter can be tested by computing observables and transition strengths. With a few exceptions, transition strengths and expectation values of observables have been obtained using bare operators restricted to the model space. We have started recently to apply the Lee-Suzuki procedure to general operators and performed tests in restricted model spaces. In this work, we compute expectation values of selected scalar observables and electromagnetic transition strengths using realistic wave functions for nuclei in the p shell. I.S. and B.R.B acknowledge partial support by NFS grants PHY0070858 and PHY0244389. The work was performed in part under the auspices of the U. S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48. P.N. received support from LDRD contract 04-ERD-058.

Stetcu, Ionel; Barrett, Bruce R.; Navratil, Petr

2004-10-01

289

Effective Communication: Instructor Guide.  

National Technical Information Service (NTIS)

Effective Communications is part of the Professional Development Series (PDS) of courses developed under the supervision of the Emergency Management Institute (EMI) with the assistance of State and local subject-matter experts. The series includes seven 1...

2002-01-01

290

Physiological Effects of Training.  

National Technical Information Service (NTIS)

With the evolution of exercise science a vast amount of information concerning the physiological effects of training has been generated. Understanding the basic training responses and adaptations of various modes of conditioning can give the clinician ins...

W. J. Kraemer W. L. Daniels

1985-01-01

291

Flexoelectric Effect in Solids  

NASA Astrophysics Data System (ADS)

Flexoelectricity-the coupling between polarization and strain gradients-is a universal effect allowed by symmetry in all materials. Following its discovery several decades ago, studies of flexoelectricity in solids have been scarce due to the seemingly small magnitude of this effect in bulk samples. The development of nanoscale technologies, however, has renewed the interest in flexoelectricity, as the large strain gradients often present at the nanoscale can lead to strong flexoelectric effects. Here we review the fundamentals of the flexoelectric effect in solids, discuss its presence in many nanoscale systems, and look at potential applications of this electromechanical phenomenon. The review also emphasizes the many open questions and unresolved issues in this developing field.

Zubko, Pavlo; Catalan, Gustau; Tagantsev, Alexander K.

2013-07-01

292

Vaccine herd effect.  

PubMed

Vaccination ideally protects susceptible populations at high risk for complications of the infection. However, vaccines for these subgroups do not always provide sufficient effectiveness. The herd effect or herd immunity is an attractive way to extend vaccine benefits beyond the directly targeted population. It refers to the indirect protection of unvaccinated persons, whereby an increase in the prevalence of immunity by the vaccine prevents circulation of infectious agents in susceptible populations. The herd effect has had a major impact in the eradication of smallpox, has reduced transmission of pertussis, and protects against influenza and pneumococcal disease. A high uptake of vaccines is generally needed for success. In this paper we aim to provide an update review on the herd effect, focusing on the clinical benefit, by reviewing data for specific vaccines. PMID:21604922

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

2011-05-23

293

Vaccine herd effect  

PubMed Central

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

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

2011-01-01

294

Coping with Side Effects  

MedlinePLUS

... Depression When should I call my doctor? Side Effect Strategies for Coping Fatigue Lingering feeling of tiredness Most common symptom Some medications Plenty of rest, with short naps Light to moderate physical activity Ask others to help ...

295

Demonstrating Product Effectiveness  

Center for Drug Evaluation (CDER)

Text Version... know how to do this with appropriate correction, ... effect. If the trial did not have assay sensitivity, then ... That is, the trial itself does not show the study's ... More results from www.fda.gov/downloads/drugs/guidancecomplianceregulatoryinformation

296

Munroe Effect Breaching Device.  

National Technical Information Service (NTIS)

There is provided in the present invention an unlined, Munroe Effect device for breaching structures in urban terrain during combat or emergency operations. The device is constructed as an unlined, linear, shaped explosive charge which upon detonation dir...

J. S. Foster J. A. Zehmer

1982-01-01

297

Effectiveness of Navy Advertising.  

National Technical Information Service (NTIS)

This analysis was performed to evaluate the effectiveness of Navy recruiting advertising in producing fully qualified, first-term enlistments during calendar years 1976 and 1977. Advertising expenditures and enlistment data were allocated to the county le...

T. C. Williams

1978-01-01

298

Coherent Backscattering Opposition Effect.  

National Technical Information Service (NTIS)

We have measured the opposition effect, the nonlinear surge in reflectance seen in particulate materials as phase angle approaches zero degrees, in a suite of materials of varying particle size and reflectance. These samples were illuminated by linearly a...

R. M. Nelson B. W. Hapke W. D. Smythe V. Gharakanian P. Herrera

1993-01-01

299

[Genetic effects of radiation].  

PubMed

This paper is a short review of genetic effect of radiation. This includes methods and results of a large-scale genetic study on specific loci in mice and of various studies in the offspring of atomic-bomb survivors. As for the latter, there is no results obtained which suggest the effect of parental exposure to radiation. Further, in recent years, studies are conducted to the offspring born to parents who were survivors of childhood cancers. In several reports, the mean gonad dose is quite large whereas in most instances, the results do not indicate genetic effect following parental exposure to radiation. Possible reasons for the difficulties in detecting genetic effect of radiation are discussed. PMID:22514926

Nakamura, Nori

2012-03-01

300

Radiation effects in space  

SciTech Connect

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

Fry, R.J.M.

1986-01-01

301

Substituent Effect in Ketoferrocenes.  

National Technical Information Service (NTIS)

The effect of carbonyl-group on the redox potential and Moessbauer parameters was studied in ketoferrocenes and chalcone analogous ferrocene derivatives. Interaction of electron-donating and electron-withdrawing substituents and the carbonyl-group is disc...

A. G. Nagy

1983-01-01

302

Hall Effect Spintronics.  

National Technical Information Service (NTIS)

Following the original project continued research devoted to manufacture, study and optimization of materials suitable for spintronics applications based on the extraordinary Hall effect (EHE). The work was focused on three major tasks: 1. Preparation and...

A. Gerber

2011-01-01

303

Cost Effectiveness Analysis.  

National Technical Information Service (NTIS)

This section presents the general cost-effectiveness analysis procedures appropriate to small communal and onsite waste-water treatment systems design. The cost components of the analysis will first be defined and the general procedures for their determin...

1995-01-01

304

Chemical Structural Aging Effects.  

National Technical Information Service (NTIS)

This program is determining the individual chemical rate processes that govern the aging of ANB-3066 propellant, and it is attempting to establish the effect of chemical (compositional) changes upon the system's mechanical response to enable better utiliz...

G. E. Myers A. B. Tipton

1972-01-01

305

Coefficients of Effective Length.  

ERIC Educational Resources Information Center

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

Edwards, Roger H.

1981-01-01

306

Nocturnal aircraft noise effects.  

PubMed

Noise protection associated with the construction and extension of airports in the Federal Republic of Germany has been regulated by the law for protection against aircraft noise since 1971. This legislation is due for revision because of different aspects. One aspect is the growth of air traffic which has led many airports to the limits of their capacity and in search of new ways of adaptation to the increasing demand for flight services. Another aspect is the increasing concern of the population about noise effects which has to be addressed by better protection against the effects of aircraft noise. The framework conditions of policy in terms of society as a whole, its health and economic environment need to be put into effect by political action. Science can contribute to this goal by performing noise effects research and by providing recommendations to the political body. However, it remains controversial, what measures are necessary or adequate to assure effective protection of the population against aircraft noise. This is particularly true for the protection of rest and sleep at night. The problem of finding a common basis for adequate recommendations is associated with (1) the low number of primary studies, which also exhibited highly variable results and assessments, (2) the handling of acoustic or psycho-acoustic dimensions for quantifying psychological or physiological reactions, and (3) the conception of how far preventive measures have to go to prove effective. With this in mind, the DLR Institute for Aerospace Medicine is conducting a large-scale, multi-stage study for investigating the acute effects of nocturnal aircraft noise on human sleep. This enterprise is implemented in the framework of the HGF/DLR project "Quiet Air Traffic" for developing sustainable assessment criteria for human-specific effects of aircraft noise at night. PMID:15070533

Basner, M; Samel, A

307

Pupillary Stroop effects  

Microsoft Academic Search

We recorded the pupil diameters of participants performing the words’ color-naming Stroop task (i.e., naming the color of\\u000a a word that names a color). Non-color words were used as baseline to firmly establish the effects of semantic relatedness\\u000a induced by color word distractors. We replicated the classic Stroop effects of color congruency and color incongruency with\\u000a pupillary diameter recordings: relative

Bruno Laeng; Marte Ørbo; Terje Holmlund; Michele Miozzo

2011-01-01

308

Security effectiveness review (SER)  

Microsoft Academic Search

As part of the on-going DOE\\/Russian MPC and A activities at the Institute of Physics and Power Engineering (IPPE) and in order to provide a basis for planning MPC and A enhancements, an expedient method to review the effectiveness of the MPC and A system has been adopted. These reviews involve the identification of appropriate and cost-effective enhancements of facilities

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

1998-01-01

309

The Doppler Effect  

NSDL National Science Digital Library

This Flash animation provides a simulation of the Doppler effect. The user can change the speed of the wave source and can move a microphone to detect the wave frequency at different points relative to the moving source. The resulting wave pattern can be both observed and heard. Instructional notes outlining the details of the Doppler effect are provided. This material is part of a web site for a second semester physics course for majors covering gravity, fluids, waves, and thermodynamics.

Fowler, Michael; Welch, Heather

2008-07-31

310

Cytogenetic effects of cyclamates  

Microsoft Academic Search

PHA-stimulated human peripheral lymphocytes were used as a model system for assessing the in vitro effects of calcium cyclamate. Techniques of autoradiography, cytological staining, cell counting, liquid scintillation and karyotyping were used to study the cytogenetic damage and biochemical effects of calcium cyclamate when assayed in 24 hour intervals for 96 hours. The cells were exposed to 10(-2) and 10(-3)

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

1984-01-01

311

Health effects of ozone  

SciTech Connect

The author comments on Morton Lippmann's paper entitled Health Effects of Ozone which was presented at the 82nd Air and Waste Management Association Annual Meeting and Exhibition, held in Anaheim, California in June 1989. Thanks to the efforts of Dr. Lippmann we have a better understanding of the acute, prolonged and chronic exposure health effects of ozone and are in a better position to receive public support to clean the air.

McKee, D. (Environmental Protection Agency, Research Triangle Park, NC (USA))

1989-09-01

312

Doppler Effect Applet  

NSDL National Science Digital Library

This applet lets students interactively experience the Doppler effect. The user can adjust the position of an "observer" relative to the wave source (a jet plane), change the plane's speed, observe how the waveforms change in frequency and wavelength as the plane passes by the observer, and listen to the change in pitch of the sound. There are also links to additional information on the Doppler effect, the physics of sound, and other sound-based applets.

313

Acid Rain Effects  

NSDL National Science Digital Library

Learners conduct a simple experiment to model and explore the harmful effects of acid rain (vinegar) on living (green leaf and eggshell) and non-living (paper clip) objects. Learners observe the effects over a period of days. This activity has links to other activities which can be combined to make a larger lesson. Resource contains vocabulary definitions and suggestions for assessment, extensions, and scaling for different levels of learners.

Kolenbrander, Amy; Yowell, Janet; Mach, Natalie; Zarske, Malinda S.; Carlson, Denise

2004-01-01

314

The Disappearing Delaware Effect  

Microsoft Academic Search

Refining and extending the methodology introduced by Daines (2001), I present evidence that small Delaware firms were worth more than small non-Delaware firms during the period 1991--1996 but not afterwards. I also present evidence that larger firms, which comprise 98% of my sample by size, exhibit no Delaware effect for any year during the period 1991--2002. Thus the Delaware effect

Guhan Subramanian

2004-01-01

315

Spin Hall Effect Transistor  

Microsoft Academic Search

The field of semiconductor spintronics explores spin-related quantum relativistic phenomena in solid-state systems. Spin transistors and spin Hall effects have been two separate leading directions of research in this field. We have combined the two directions by realizing an all-semiconductor spin Hall effect transistor. The device uses diffusive transport and operates without electrical current in the active part of the

Jörg Wunderlich; Byong-Guk Park; Andrew C. Irvine; Liviu P. Zârbo; Eva Rozkotová; Petr Nemec; Vít Novák; Jairo Sinova; Tomás Jungwirth

2010-01-01

316

The extraterrestrial Casimir Effect  

NASA Astrophysics Data System (ADS)

Application of the Electro-Gravi-Magnetic (EGM) Photon radiation method to the Casimir Effect (CE), suggests that the experimentally verified (terrestrially) neutrally charged Parallel-Plate configuration force, may differ within extraterrestrial gravitational environments from the gravitationally independent formulation by Casimir. Consequently, the derivation presented herein implies that a gravitationally dependent CE may become an important design factor in nanotechnology for extraterrestrial applications (ignoring finite conductivity + temperature effects and evading the requirement for Casimir Force corrections due to surface roughness).

Storti, Riccardo C.

2011-09-01

317

The Uniform Rugosity Effect  

Microsoft Academic Search

Relying on the effect of microscopic asperities, one can mathematically justify that viscous fluids adhere completely on the\\u000a boundary of an impermeable domain. The rugosity effect accounts asymptotically for the transformation of complete slip boundary\\u000a conditions on a rough surface in total adherence boundary conditions, as the amplitude of the rugosities vanishes. The decreasing\\u000a rate (average velocity divided by the

Matthieu Bonnivard; Dorin Bucur

2011-01-01

318

Pleiotropic effects of pitavastatin.  

PubMed

3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) are established first line treatments for hypercholesterolaemia. In addition to the direct effects of statins in reducing concentrations of atherogenic low density lipoprotein cholesterol (LDL-C), several studies have indicated that the beneficial effects of statins may be due to some of their cholesterol-independent, multiple (pleiotropic) effects which may differ between different members of the class. Pitavastatin is a novel synthetic lipophilic statin that has a number of pharmacodynamic and pharmacokinetic properties distinct from those of other statins, which may underlie its potential pleiotropic benefits in reducing cardiovascular risk factors. This review examines the principal pleiotropic effects of pitavastatin on endothelial function, vascular inflammation, oxidative stress and thrombosis. The article is based on a systematic literature search carried out in December 2010, together with more recent relevant publications where appropriate. The available data from clinical trials and in vitro and animal studies suggest that pitavastatin is not only effective in reducing LDL-C and triglycerides, but also has a range of other effects. These include increasing high density lipoprotein cholesterol, decreasing markers of platelet activation, improving cardiac, renal and endothelial function, and reducing endothelial stress, lipoprotein oxidation and, ultimately, improving the signs and symptoms of atherosclerosis. It is concluded that the diverse pleiotropic actions of pitavastatin may contribute to reducing cardiovascular morbidity and mortality beyond that achieved through LDL-C reduction. PMID:22053916

Davignon, Jean

2012-04-01

319

Effective Transport Properties  

NASA Astrophysics Data System (ADS)

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

Mauri, Roberto

320

Magnetoelectric effects in manganites  

NASA Astrophysics Data System (ADS)

Research on manganites has been conducted for more than half century. Recent discoveries of colossal responses to external fields such as colossal magnetoresistance effects and correlation among spin, orbital, and lattice in phase separated manganites and multiferroic manganites have motivated me to understand these materials. The main purpose of this dissertation is to understand magnetoelectric effects in phase separated (La1-yPr y)1-xCaxMnO3 (LPCMO) thin films and multiferroic BiMnO3 (BMO) thin films. First, high quality phase separated manganite thin films have been successfully grown. To grow the high quality manganite thin films, extensive effort was devoted to fine tuning of oxygen pressure, temperature, and laser fluence during film growth. As-grown films were characterized with various ex-situ techniques: magnetization measurements, transport measurements, x-ray diffraction, atomic force microscopy, and/or transmission electron microscopy to remove the effects of impurities and unwanted strains except substrate induced strain. Second, three major results were obtained in high quality phase separated LPCMO thin films. These results are based on the dynamic nature of phases in LPCMO. 1) LPCMO thin films showed single domain to multi-domain transition during cooling. This transition can be tuned by substrate stress induced in-plane magnetic anisotropy. 2) Evidence for the origin of colossal electroresistance (CER) effect has been observed. The CER is triggered by dielectrophoresis, or movements of ferromagnetic metallic (FMM) phase, which is manifested in anisotropic transport properties in microfabricated LPCMO cross structures. This fluidic nature of the FMM phase in LPCMO under high electric fields lead to exotic magnetoelectric effects. 3) Electric field effects on magnetotransport properties have been observed. This phenomena can also be tuned by the combined effect of substrate strain and current flow. This combined effect of electric and magnetic fields and strain at the interface of LPCMO suggest new ways to control magnetism (magnetotransport) with electric fields. Third, impurity-free and epitaxial BMO thin films were grown. These films showed ferromagnetism and ferroelectricity at low temperature. Magnetoelectric effects are discussed, especially magnetization change due to electric fields.

Jeen, Hyoung Jeen

321

Nonperturbative effects in supergravity  

NASA Astrophysics Data System (ADS)

A promising candidate for a fundamental theory of nature, incorporating both general relativity and quantum mechanics, is string theory. This theory is based on one-dimensional extended objects that move through spacetime. However, string theory is most naturally formulated in ten dimensions. To consider string theory in four dimensions one can compactify six dimensions (by making them very small) and compute the effect on the theory. This yields a certain four-dimensional theory. Furthermore, string theory contains also extended objects of higher dimensions, these are called D-branes (think for example of a membrane). Their effect on the four-dimensional theory should be considered as well. This is what we have done, in a certain setting, and the results are presented in this thesis. We work in the supergravity approximation, which means that we restrict ourselves to length scales (much) smaller than the string length. In this approximation the D-branes are described by solitonic solutions to the supergravity equations of motion. We consider the N=2 supergravity theory in four dimensions resulting from compactifying type IIA supergravity (the low energy limit of type IIA string theory) on a six-dimensional Calabi-Yau manifold. Furthermore we consider the membrane and NS five-brane. In the four-dimensional theory they can be described by finite action solutions to the equations of motion. We then construct the effective action which incorporates the effects of the membrane and the five-brane, respectively. The effective N=2 supergravity action (the supergravity multiplet coupled to a hypermultiplet) in four dimensions incorporating the one-loop effects in the background of a NS five-brane is computed by a 'traditional' instanton calculation. The effective action incorporating the one-loop effect in the presence of a membrane is computed using knowledge of the symmetries of the action and their breaking by the membrane. These nonperturbative corrections affect the hypermultiplet sector of the N=2 supergravity theory. Furthermore, we gauge an isometry of the hypermultiplet sector. This produces a potential. This potential has certain minima and the effect of the nonperturbative membrane corrections is to produce a metastable minimum which can have a positive value: a de Sitter minimum.

Davidse, Marijn

2006-01-01

322

A "voice inversion effect?".  

PubMed

Voice is the carrier of speech but is also an "auditory face" rich in information on the speaker's identity and affective state. Three experiments explored the possibility of a "voice inversion effect," by analogy to the classical "face inversion effect," which could support the hypothesis of a voice-specific module. Experiment 1 consisted of a gender identification task on two syllables pronounced by 90 speakers (boys, girls, men, and women). Experiment 2 consisted of a speaker discrimination task on pairs of syllables (8 men and 8 women). Experiment 3 consisted of an instrument discrimination task on pairs of melodies (8 string and 8 wind instruments). In all three experiments, stimuli were presented in 4 conditions: (1) no inversion; (2) temporal inversion (e.g., backwards speech); (3) frequency inversion centered around 4000 Hz; and (4) around 2500 Hz. Results indicated a significant decrease in performance caused by sound inversion, with a much stronger effect for frequency than for temporal inversion. Interestingly, although frequency inversion markedly affected timbre for both voices and instruments, subjects' performance was still above chance. However, performance at instrument discrimination was much higher than for voices, preventing comparison of inversion effects for voices vs. non-vocal stimuli. Additional experiments will be necessary to conclude on the existence of a possible "voice inversion effect." PMID:15177788

Bédard, Catherine; Belin, Pascal

2004-07-01

323

System Effectiveness Model Formulation  

SciTech Connect

Evaluation of system effectiveness has numerous pitfalls. System objectives may be poorly defined, may shift during the system life or may be hard to quantify. Further, individual perceptions of the quantifications may differ. Whatever the cause, system effectiveness has been an elusive term to quantitatively define. The proposed model presents a quantitative system effectiveness model and establishes a utilitarian approach for its use with the illustrative application to a nuclear safeguards system. The model uses the Type I and Type II statistical error rates as input to the component or subsystem effectiveness calculation which, when combined using a utilitarian methodology, quantify the overall system effectiveness. The methodology will use a survey of expert judgment to determine the relative importance of the individual subsystems through a statistically designed web survey. The web based survey will be available to nuclear material protection, control, and accounting experts attending the 2008 INMM conference. This model and methodology will provide a repeatable quantifiable measure for any system but in this case a simple safeguards system is used as an example.

Coates, Cameron W [ORNL; Jackson, Denise F [ORNL

2008-01-01

324

Mitochondrial threshold effects.  

PubMed Central

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

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

2003-01-01

325

Effective Nutritional Supplement Combinations  

NASA Astrophysics Data System (ADS)

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

Cooke, Matt; Cribb, Paul J.

326

Photoelectric Effect Model  

NSDL National Science Digital Library

The EJS Photoelectric Effect model simulates the Photoelectric effect discovered by Hertz in 1887 and described theoretically by Einstein in 1905. Light of a given frequency (and energy) shines on a metal. If the frequency (energy) of the light is greater than the work function, W, of the metal, electrons are ejected and can form a current (which is shown in milliAmperes). These photoelectrons will also have a kinetic energy if the energy of the light is greater than the workfunction. they will have kinetic energy. If subjected to an electric potential the electrons can be stopped from reaching the plate and stop current from flowing in a circuit. The EJS Photoelectric Effect model was created using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_qm_photoelectric.jar file will run the program if Java is installed.

Palop, Jose I.

2010-07-16

327

??-Corrected Chiral Magnetic Effect  

NASA Astrophysics Data System (ADS)

Using the AdS/CFT correspondence, the effect of ??-correction on the value of Chiral Magnetic Effect (CME) is computed by adding a number of spinning probe D7-branes in the ??-corrected background. We numerically show that the magnitude of CME rises in the presence of ??-correction for massive solutions and this increase is more sensible at higher temperatures. However, this value does not change for massless solution. Although some of the D7-brane embeddings have no CME, after applying the ??-correction they find a non-zero value for the CME. We also show that the effect of ??-correction removes the singularity from some of the D7-brane embeddings.

Ali-Akbari, M.; Taghavi, S. F.

2013-07-01

328

Health effects of ozone  

SciTech Connect

The 1989 Critical Review on Health Effects of Ozone by Morton Lippmann is a valuable contribution to the literature on criteria air pollutants. In a comprehensive fashion, the paper methodically examines key areas relevant to understanding effects of ozone on human health: exposure and dosimetry, populations and responses of concern, research approaches, and effects upon specific pulmonary endpoints from single and multiple exposures. Dr. Lippmann has provided us with more than an excellent summary; whenever possible, he has thoughtfully integrated findings from the relevant disciplines of animal toxicology, epidemiology, field studies and controlled clinical studies, and has emphasized exposure-response relationship in arriving at his conclusions. Going beyond the call of duty, he has concluded with a Critical Preview recommending a shape and form for the ozone standard of the future.

Utell, M.J. (Univ. of Rochester School of Medicine, NY (USA))

1989-09-01

329

Spin Hall Effect Transistor  

NASA Astrophysics Data System (ADS)

The field of semiconductor spintronics explores spin-related quantum relativistic phenomena in solid-state systems. Spin transistors and spin Hall effects have been two separate leading directions of research in this field. We have combined the two directions by realizing an all-semiconductor spin Hall effect transistor. The device uses diffusive transport and operates without electrical current in the active part of the transistor. We demonstrate a spin AND logic function in a semiconductor channel with two gates. Our study shows the utility of the spin Hall effect in a microelectronic device geometry, realizes the spin transistor with electrical detection directly along the gated semiconductor channel, and provides an experimental tool for exploring spin Hall and spin precession phenomena in an electrically tunable semiconductor layer.

Wunderlich, Jörg; Park, Byong-Guk; Irvine, Andrew C.; Zârbo, Liviu P.; Rozkotová, Eva; Nemec, Petr; Novák, Vít; Sinova, Jairo; Jungwirth, Tomás

2010-12-01

330

Aviation noise effects  

NASA Astrophysics Data System (ADS)

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

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

1985-03-01

331

Spin Hall effect transistor.  

PubMed

The field of semiconductor spintronics explores spin-related quantum relativistic phenomena in solid-state systems. Spin transistors and spin Hall effects have been two separate leading directions of research in this field. We have combined the two directions by realizing an all-semiconductor spin Hall effect transistor. The device uses diffusive transport and operates without electrical current in the active part of the transistor. We demonstrate a spin AND logic function in a semiconductor channel with two gates. Our study shows the utility of the spin Hall effect in a microelectronic device geometry, realizes the spin transistor with electrical detection directly along the gated semiconductor channel, and provides an experimental tool for exploring spin Hall and spin precession phenomena in an electrically tunable semiconductor layer. PMID:21205664

Wunderlich, Jörg; Park, Byong-Guk; Irvine, Andrew C; Zârbo, Liviu P; Rozkotová, Eva; Nemec, Petr; Novák, Vít; Sinova, Jairo; Jungwirth, Tomás

2010-12-24

332

The uncontrollable placebo effect  

Microsoft Academic Search

Objective:\\u000a \\u000a \\u000a To analyse the role of the control group in the methodology of clinical placebo effect evaluating trials.\\u000a \\u000a \\u000a Setting:\\u000a \\u000a \\u000a Department of Medical Philosophy and Clinical Theory, University of Copenhagen.\\u000a \\u000a \\u000a Methods:\\u000a \\u000a \\u000a A theoretical methodological analysis.\\u000a \\u000a \\u000a Results:\\u000a \\u000a \\u000a At least with present trial designs, it is impossible, with certainty, to exclude a potential placebo effect from the so-called\\u000a control group. The placebo effect,

A. Hróbjartsson

1996-01-01

333

Pseudoprogression and treatment effect.  

PubMed

The standard of care for newly diagnosed malignant glioblastoma entails postoperative radiotherapy and adjuvant chemotherapy with temozolomide. There has been an increase in the incidence of enhancing and progressive lesions seen on magnetic resonance imaging (MRI) following treatment. Conventional MRI with gadolinium contrast is unable to distinguish between the effects of treatment and actual tumor recurrence. New modalities have provided additional information for distinguishing treatment effects from tumor progression but are not 100% sensitive or specific in diagnosing progression. Novel radiographic or nonradiographic biomarkers with sensitivity and specificity verified in large randomized clinical trials are needed to detect progression. PMID:22440871

Jahangiri, Arman; Aghi, Manish K

2012-02-14

334

Mesoscopic Josephson effect  

NASA Astrophysics Data System (ADS)

In the classical Josephson effect the phase difference across the junction is well defined, and the supercurrent is reduced only weakly by phase diffusion. For mesoscopic junctions with small capacitance the phase undergoes large quantum fluctuations, and the current is also decreased by Coulomb blockade effects. We discuss the behavior of the current-voltage characteristics in a large range of parameters comprising the phase diffusion regime with coherent Josephson current as well as the supercurrent peak due to incoherent Cooper pair tunneling in the Coulomb blockade regime.

Grabert, Hermann; Ingold, Gert-Ludwig

1999-05-01

335

Predicting drug effectiveness.  

PubMed

Two new diagnostic tests which evaluate a patient's HIV resistance to antiviral drugs were scheduled to be on the market in July. The tests are being marketed under the trademarks Antivirogram, by Laboratory Corporation of America, and VircoGEN by VIRCO. Both companies say that when the tests are used together, they will predict which drugs a patient will respond to, leading to more effective treatment decisions. Studies were conducted to predict the effectiveness of Ritonavir/Saquinavir therapy, and the results were very promising. PMID:11365696

1998-08-01

336

Chiral magnetic effect  

SciTech Connect

Topological charge changing transitions can induce chirality in the quark-gluon plasma by the axial anomaly. We study the equilibrium response of the quark-gluon plasma in such a situation to an external magnetic field. To mimic the effect of the topological charge changing transitions we will introduce a chiral chemical potential. We will show that an electromagnetic current is generated along the magnetic field. This is the chiral magnetic effect. We compute the magnitude of this current as a function of magnetic field, chirality, temperature, and baryon chemical potential.

Fukushima, Kenji [Yukawa Institute, Kyoto University, Kyoto (Japan); Kharzeev, Dmitri E.; Warringa, Harmen J. [Department of Physics, Brookhaven National Laboratory, Upton New York 11973 (United States)

2008-10-01

337

Stormwater BMP Effectiveness Assessment Toolkit  

EPA Science Inventory

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

338

The Effects of Nuclear War.  

National Technical Information Service (NTIS)

The study examines the full range of effects that nuclear war would have on civilians: direct effects from blast and radiation; and indirect effects from economic, social, and political disruption. Particular attention is devoted to the ways in which the ...

1979-01-01

339

Side Effects of Hormone Therapy  

MedlinePLUS

... PCF Spotlight Glossary African American Men Living with Prostate Cancer Side Effects of Hormone Therapy Side Effects Urinary ... to evaluate its use in men with advanced prostate cancer. If the approach proves to be as effective ...

340

Petroleum effects in the Arctic  

SciTech Connect

This book presents papers on the environmental and biological effects of oil spills. Topics considered include the Arctic marine ecosystem, the physical and chemical fate of spilled oil, the effects of hydrocarbons on microorganisms and petroleum biodegradation in arctic ecosystems, the effects of oil on arctic invertebrates, the effects of oil on fish, a risk assessment of oil on arctic marine birds, the effects of petroleum on marine mammals, and the effects of petroleum activities on the ecology of arctic man.

Engelhardt, F.R.

1985-01-01

341

Structural Effects on Daylighting  

Microsoft Academic Search

Optimum daylighting of interior spaces is most effectively achieved by pure archi- tectural (or: structural) measures of which the most basic ones are the dimension- ing and positioning of daylight openings in the building envelope as well as geome- try and surface characteristics of the considered space. Multidimensional regres- sion analyses with such parameters performed for a number of simple

Friedrich Sick

342

Effective classical partition functions  

SciTech Connect

We present a method by which a quantum-mechanical partition function can be approximated from below by an effective classical partition function. The associated potential is obtained by a simple smearing procedure. For a strongly anharmonic oscillator and a double-well potential, the lowest approximation gives a free energy which is accurate to a few percent, even at zero temperature.

Feynman, R.P.; Kleinert, H.

1986-12-01

343

Effective receivables management.  

PubMed

To prevent the accumulation of accounts in the "greater than 120 days" category, receivable management strategies must be revised. The keys to managing receivables in the current healthcare environment have been presented. With the healthcare industry likely to remain credit-oriented, those organizations that effectively manage receivables and minimize their cost of working capital will win a real competitive advantage. PMID:10303035

Raymond, G B

1988-12-01

344

EFFECTS ON SALTWATER ORGANISMS  

EPA Science Inventory

The literature review summarizes current data on the effects of pesticides and metals on marine organisms, aquatic environmental research methods, bioaccumulation of pollutants by estuarine and marine organisms and in water/sediment residues and biota. Results of studies of the e...

345

Cardiovascular Effects of Caffeine  

PubMed Central

A review of the literature on the cardiovascular effects of caffeine indicates that moderate caffeine consumption does not cause cardiac arrhythmias, hypertension, or an increased incidence of coronary heart disease. Caffeine use is often associated with atherogenic behavior, such as cigarette smoking. Failure to take into account covariables for cardiovascular disease could be responsible for commonly held misconceptions about caffeine and heart disease.

Myers, Martin G.

1992-01-01

346

Health effects of ozone  

Microsoft Academic Search

It is an honor to have the opportunity to comment on Dr. Morton Lippmann's excellent review on the health effects of ozone, which was presented at the 82nd Air and Waste Management Association Annual Meeting and Exhibition held in Anaheim, California in June 1989. It is comprehensive in citing all of the pertinent references, interpretative in its review of the

McClellan

1989-01-01

347

Developing Effective Training Programs.  

ERIC Educational Resources Information Center

Focusing on research administrators, discusses how an effective training program improves employee performance by including comprehensive needs assessment, employing appropriate training methodologies, and anticipating factors beyond the actual training event that influence the transfer of skills from the training environment to the work…

Wagonhurst, Carole

2002-01-01

348

Designing Effective Posters  

NSDL National Science Digital Library

This website presents an online tutorial about creating effective poster presentations. The site guides users through the basics of poster design, which should free the presenter to focus on discussion of essential elements of the work. Decisions about poster format and design which contribute to efficient and accurate transfer of information using this medium are also discussed.

Radel, Jeff; Center, Ku M.

349

The nonlinear Fano effect  

Microsoft Academic Search

The Fano effect is ubiquitous in the spectroscopy of, for instance, atoms, bulk solids and semiconductor heterostructures. It arises when quantum interference takes place between two competing optical pathways, one connecting the energy ground state and an excited discrete state, the other connecting the ground state with a continuum of energy states. The nature of the interference changes rapidly as

M. Kroner; A. O. Govorov; S. Remi; B. Biedermann; S. Seidl; A. Badolato; P. M. Petroff; W. Zhang; R. Barbour; B. D. Gerardot; R. J. Warburton; K. Karrai

2008-01-01

350

Effect of a \\  

Microsoft Academic Search

3 studies with 104 undergraduates investigated the effect of a chunked typography on the reading rate and comprehension of mature readers, reading at their normal rates. Passages and questions from a standardized reading test were displayed via an electromechanical device which allowed actual reading times to be recorded. 5 experimental chunked formats were compared with each other and 1 selected

Ronald P. Carver

1970-01-01

351

Desert Storm environmental effects  

Microsoft Academic Search

It is noted that after more than six months of operation of the Patriot launch station in the Saudi Arabian desert no problems that were attributed to high temperature occurred. The environmental anomalies that did occur were cosmetic in nature and related to dust and salt fog. It was concluded that the Desert Storm environmental effects were typical of worldwide

E. W. Kimball

1992-01-01

352

Desert Storm environmental effects  

NASA Astrophysics Data System (ADS)

It is noted that after more than six months of operation of the Patriot launch station in the Saudi Arabian desert no problems that were attributed to high temperature occurred. The environmental anomalies that did occur were cosmetic in nature and related to dust and salt fog. It was concluded that the Desert Storm environmental effects were typical of worldwide hot, dry climates.

Kimball, E. W.

353

Ground Effect in Flight  

Microsoft Academic Search

The present paper aims to analyze the propulsion of birds and fishes undergoing the ground effect as well as the lift of high-speed ground vehicle. Applying the analytical method which was developed for flutter of a soft plate placed at an arbitrary position in subsonic channel flows, calculations are carried out first for non-oscillatory case in compressible flow and then

Yoshimichi Tanida

2001-01-01

354

Matthew Effects for Whom?  

ERIC Educational Resources Information Center

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

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

2008-01-01

355

Local-Effect Games  

Microsoft Academic Search

We present a new class of games, local-effect games (LEGs), which exploit structure in a differ- ent way from other compact game representations studied in AI. We show both theoretically and em- pirically that these games often (but not always) have pure-strategy Nash equilibria. Finding a po- tential function is a good technique for finding such equilibria. We give a

Kevin Leyton-brown; Moshe Tennenholtz

2003-01-01

356

Cost Effective Buying  

NSDL National Science Digital Library

This lesson plan will help students learn to evaluate energy-related purchases in terms of cost-effectiveness. How long will it take for the new purchase to "pay for itself" in terms of energy savings? The lesson involves both sustainability and economics concepts. The lesson should take two or three class periods to complete.

2011-01-11

357

Camp's "Disneyland" Effect.  

ERIC Educational Resources Information Center

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

Renville, Gary

1999-01-01

358

Developing Effective Tourism Leadership  

Microsoft Academic Search

This study explores the development of effective leadership in the tourism industry from the perspective of current industry leaders in Hong Kong, China. The literature reviews the key themes in tourism leadership research, which is followed by an empirical qualitative study of 10 leaders in the tourism industry in Hong Kong. Findings are explored in relation to three key areas:

Karin Weber; Adele Ladkin

2010-01-01

359

Gauge Invariant Effective Potentials  

SciTech Connect

We make use of a dual formulation of the abelian Higgs model expressing it in terms of anti-symmetric tensor fields. In this dual form we obtain a gauge invariant derivation of the effective potential and also make the topological contributions (vortex-strings) explicit in the action.

Ramos, Rudnei O. [Departamento de Fisica Teorica, Universidade do Estado do Rio de Janeiro, 20550-013 Rio de Janeiro, RJ (Brazil); Medeiros Neto, J.F. [Departamento de Fisica, Universidade Federal do Para, 66075-110 Belem, PA (Brazil); Departamento de Fisica Teorica, Universidade do Estado do Rio de Janeiro, 20550-013 Rio de Janeiro, RJ (Brazil)

2004-12-02

360

Documentation: Effective AND Literate  

Microsoft Academic Search

The purpose of this paper is to show how documentation can be literate, in a stylistic sense, and still be effective. Literate prose is a powerful tool that, when properly used in computer documentation, can take advantage of the full power of the English language. This does not mean that all computer documentation must or can read like a Nobel

Paul S. Burdett Jr.

1985-01-01

361

Astrophysical chaotic gun effect  

Microsoft Academic Search

We propose a kinetic equation for a special kind of acceleration: chaotic gun effect. Then we infer a distribution function which can depict the instability condition. With this distribution function we derive the power spectrum of the synchrotron emission and we prove the power law form of the power spectrum. We show that the spectral index of the emission spectrum

Gheorghe Dumitrescu; Toma N. Socolescu

2009-01-01

362

Effective Internet Research.  

ERIC Educational Resources Information Center

|Describes how teachers can help students learn to use effectively the wealth of knowledge on the Internet by organizing research in advance, planning carefully and structuring assignments as students conduct their own research, and teaching students to evaluate web sites. (SR)|

Lim, Janine

2001-01-01

363

Lorenz Attractor -- Butterfly Effect  

NSDL National Science Digital Library

The "Butterfly Effect", or more technically the "sensitive dependence on initial conditions", is the essence of chaos. This is illustrated an applet of the Lorenz Attractor. The demonstration shows a graphical representation of the time variation of three variables X(t),Y(t) and Z(t), coupled by non-linear evolution equations.

Michael Cross, Cal T.

364

Effective Press Releases  

Microsoft Academic Search

Stresses the importance of the effective management of the release of information to the media and the development of media relations. Considers reasons for good and bad press. Advises on the presentation of press releases, the elements of their content and their structure. Looks at how additional information should be supplied, and how photographs can be used to illustrate a

Linda S. Ashcroft

1994-01-01

365

Stern-Gerlach effect  

NSDL National Science Digital Library

This web page illustrates the Stern-Gerlach effect on spin 1/2 particles. Movies and an illustration show the time-dependent properties of wavepackets in an inhomogeneous magnetic field. Examples are given for silver atoms, ions, and electrons.

Michielsen, Kristel; De Raedt, Hans

2010-03-11

366

Courtside: Private Effects?  

ERIC Educational Resources Information Center

After being accused of sexually harassing a student, a high school math teacher in New York was suspended with pay pending an impartial hearing. The district allowed the teacher to return to his classroom to collect his personal effects, which he had kept in boxes, desk drawers, and three filing cabinets, one of which was locked. He did not…

Zirkel, Perry A.

2004-01-01

367

Lightning Physics and Effects  

Microsoft Academic Search

Lightning Physics and Effects is not a lightning book; it is a lightning encyclopedia. Rarely in the history of science has one contribution covered a subject with such depth and thoroughness as to set the enduring standard for years, perhaps even decades, to come. This contribution covers all aspects of lightning, including lightning physics, lightning protection, and the interaction of

Richard E. Orville

2004-01-01

368

Media effect in commercial  

Microsoft Academic Search

Keywords Brand identity, Brand image, Consumer behaviour, Goodwill, Marketing communications, Sponsorship Abstract Various elements of brand identity contribute to brand image development; however, the role of marketing communications is particularly important in achieving brand image effects. In the case of advertising, two separate elements of communications, a message and a medium, combine to deliver particular brand image values. In the

David Shipley

369

Facilitating online discussions effectively  

Microsoft Academic Search

This article presents a synthesis of the theoretical and research literature on facilitating asynchronous online discussions effectively. Online courses need to be designed so that they provide motivation for students to engage in productive discussions and clearly describe what is expected, perhaps in the form of a discussion rubric. Additionally, instructors need to provide discussion forums for socio-emotional discussions that

Alfred P. Rovai

2007-01-01

370

The Energy Diameter Effect  

NASA Astrophysics Data System (ADS)

The diameter (size) effect is the well-known increase of detonation velocity with increasing radius. We ask if a similar effect is seen with the detonation energy. To see this, it is necessary to perform the Cylinder test on small-radius samples of non-ideal explosives, which detonate with a low velocity. We fired nine ammonium nitrate/aluminum and AN/NM Cylinder shots with diameters of 12.7 to 50.8 mm using Fabry and heterodyne velocimetry for the wall velocities and pins for the detonation velocity. It is the use of the ultra-narrow 12.7 mm copper cylinders that give us points low enough to be sure that the effect exists. We find that the detonation energies at the three standard Cylinder relative volumes (2.2, 4.4, 7.2) vary roughly as the square of the detonation velocity. This is confirmed in numerical simulation calculations. A simple derivation of the relations of energy, detonation velocity, reaction zone length and detonation rate are given. We define a generalized inverse radius that can be applied to data for both explosive cylinders and outwardly-detonating spheres. The relation that detonation rate is proportional to the diameter effect slope can be used to derive the inverse radius equation. This work was performed under the auspices of the U.S. Department of Energy by the University of California Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48.

Vitello, Peter; Souers, P. Clark

2007-06-01

371

Recruiting Effective Board Members.  

ERIC Educational Resources Information Center

Asserts that lack of seriousness in recruiting board members for child care agencies can create problems with organizational effectiveness. Addresses the following: (1) Do we need more board members?; (2) What do we need from new members?; and (3) How do we begin recruiting? Provides resources, such as the "Child Care Agency Board Skill Inventory"…

Bess, Gary; Ratekin, Cindy

1999-01-01

372

DESIGNING EFFECTIVE STUDY ENVIRONMENTS  

Microsoft Academic Search

The study setting (private or open-plan), environmental color (blue, red, or white), and study material (reading or math comprehension) were manipulated in a simulated study environment to determine their effects on adult students' mood, satisfaction, motivation, and performance. Students rated the reading task as more demanding and less enjoyable than the math task. Negative mood was slightly greater for students

NANCY J. STONE

2001-01-01

373

Defending Double Effect  

Microsoft Academic Search

According to the doctrine of double effect(DDE), there is a morally significantdifference between harm that is intended andharm that is merely foreseen and not intended.It is not difficult to explain why it is bad tointend harm as an end (you have a ``badattitude'' toward that harm) but it is hard toexplain why it is bad to intend harm as a

Alison Hills

2003-01-01

374

Effective Instructional Management.  

ERIC Educational Resources Information Center

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

Zakariya, Sally Banks; Steller, Arthur, Ed.

375

Evaluating Effective Supervision.  

ERIC Educational Resources Information Center

|This paper outlines the purposes, professional obligations, and key components to consider when providing effective evaluation in psychotherapy supervision. An overview of various methods for gathering supervision data for evaluation purposes is provided including self-reporting; process notes; video and audiotaping; live observation; co-therapy;…

Worthen, Vaughn E.; Dougher, M. Kirk

376

Effect of Shock Waves.  

National Technical Information Service (NTIS)

Studies of the pathogenetic effects of shock waves from explosions are reviewed. The characteristics of an air blast are described. The interaction of such a blast on the human body, and the mechanism of resulting damage are investigated with particular a...

P. I. Burenin

1974-01-01

377

Creating Effective Multimedia Instruction  

Microsoft Academic Search

English: This paper presents information on several critical themes related to multimedia instruction. An understanding of these issues will be helpful to anyone involved in the design, development or use of computer delivered instruction. Topics addressed in this paper focus on: software product life cycle; systematic approach to design; multimedia design and development teams; production values; critical components of effective

Gregory C Sales

1999-01-01

378

Marijuana: Respiratory Tract Effects.  

PubMed

Marijuana is the most commonly used drug of abuse in the USA. It is commonly abused through inhalation and therefore has effects on the lung that are similar to tobacco smoke, including increased cough, sputum production, hyperinflation, and upper lobe emphysematous changes. However, at this time, it does not appear that marijuana smoke contributes to the development of chronic obstructive pulmonary disease. Marijuana can have multiple physiologic effects such as tachycardia, peripheral vasodilatation, behavioral and emotional changes, and possible prolonged cognitive impairment. The carcinogenic effects of marijuana are unclear at this time. Studies are mixed on the ability of marijuana smoke to increase the risk for head and neck squamous cell carcinoma, lung cancer, prostate cancer, and cervical cancer. Some studies show that marijuana is protective for development of malignancy. Marijuana smoke has been shown to have an inhibitory effect on the immune system. Components of cannabis are under investigation as treatment for autoimmune diseases and malignancy. As marijuana becomes legalized in many states for medical and recreational use, other forms of tetrahydrocannabinol (THC) have been developed, such as food products and beverages. As most research on marijuana at this time has been on whole marijuana smoke, rather than THC, it is difficult to determine if the currently available data is applicable to these newer products. PMID:23715638

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

2013-05-29

379

The Stephen Lawrence Effect.  

ERIC Educational Resources Information Center

Discusses the effect of the Macpherson Inquiry Report into the murder of Stephen Lawrence, a black man, on efforts to reduce institutional bias in Great Britain, claiming that there has been much more institutional indifference than institutional change since the report was published. Notes the need to rid society of racism in education. (SM)

Ouseley, Herman

2000-01-01

380

Loop effects in ?-->?+?-?  

NASA Astrophysics Data System (ADS)

We show that the incorporation of the model consisting of a loop of charged kaons in the description of the ?-->ƒ;0? decay has important effects on the expected signal to background ratio for e+e--->?(?)-->?+?-?. On leave of absence from Escuela Ciencias Físico-Matemáticas, Universidad Autónoma de Sinaloa.

Lucio, J. L. M.; Napsuciale, M.

1994-07-01

381

Hall Effect Spintronics.  

National Technical Information Service (NTIS)

This report results from a contract tasking Tel Aviv University as follows: This project will attempt to develop a new type of magnetic memory devices based on the so-called Extraordinary Hall Effect (EHE) in which information is stored in nanometric magn...

A. Gerber

2008-01-01

382

Towards Hall effect spintronics  

Microsoft Academic Search

Major efforts in the current exploration of spintronics are focused on the giant magnetoresistance (GMR) phenomenon in metallic, semiconducting and tunnel junction magnetic heterostructures. I wish to present a different approach based on the extraordinary Hall effect (EHE). Since its discovery more than a century ago, the EHE was not considered seriously for technological applications because of its relatively small

A. Gerber

2007-01-01

383

Effects of nuclear war  

Microsoft Academic Search

The author reviews the subject rising the following topics and subtopics: I. Nuclear explosions: heat, nuclear radiation, and radioactive fallout; II. Effects: radiation sickness, burns, blast injuries, and equivalent areas of death; III. Nuclear war: battlefield, regional, intercontinental - counterforce, and intercontinental - counter-city and industry. There are two appendices. 34 references, 32 figures.

von Hippel

1983-01-01

384

Continuous electrowetting effect  

Microsoft Academic Search

We introduce a new electrowetting effect, continuous electrowetting (CEW), and show its advantages for applications to displays and other electro-optic devices. We demonstrate experimentally, by using CEW, fast and reversible electrowetting flow on the theoretically predicted scale of ?10 cm\\/s for ?1-V driving voltage.

G. Beni; S. Hackwood; J. L. Jackel

1982-01-01

385

Building Effective Afterschool Programs.  

ERIC Educational Resources Information Center

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

Fashola, Olatokunbo S.

386

Modelling tidal effects  

Microsoft Academic Search

Two models for demonstrating tides and experimenting with various tidal effects are presented. The first takes advantage of the approximately inverse-square nature of the force law for magnetic poles and exhibits symmetric tidal bulges on opposite sides of the planet, analogous to the tides of the earth. The second demonstration apparatus is a realization of the ``rubber sheet'' geometry analogy

Gary White; Tony Mondragon; David Slaughter; Dorothy Coates

1993-01-01

387

Learning to Effect.  

ERIC Educational Resources Information Center

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

Barnett, Ronald, Ed.

388

Exploring the Lotus Effect  

NSDL National Science Digital Library

Students test and observe the âself-cleaningâ lotus effect using a lotus leaf and cloth treated with a synthetic lotus-like superhydrophobic coating. They also observe the Wenzel and Cassie Baxter wetting states by creating and manipulating condensation droplets on the leaf surface. They consider the real-life engineering applications for these amazing water-repellent and self-cleaning properties.

NSF CAREER Award and RET Program, Mechanical Engineering and Material Science,

389

The Effective, Efficient Professor.  

ERIC Educational Resources Information Center

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

Felder, Richard M.

2002-01-01

390

On nature's scaling effects  

Microsoft Academic Search

This presentation afforded the opportunity to look back in the literature to discover scaling effects in nature that might be relevant to composites. Numerous examples were found in nature's approaches to wood, teeth, horns, leaves, eggs, feathers, etc. Nature transmits tensile forces rigidly with cohesive bonds, while dealing with compression forces usually through noncompressible hydraulics. The optimum design scaling approaches

Dick J. Wilkins

1994-01-01

391

Notes on Effective Bandwidths  

Microsoft Academic Search

This paper presents a personal view of work to date on effective bandwidths,emphasising the unifying role of the concept: as a summary of thestatistical characteristics of sources over different time and space scales;in bounds, limits and approximations for various models of multiplexingunder quality of service constraints; and as the basis for simple and robusttariffing and connection acceptance control mechanisms for

Frank Kelly

1996-01-01

392

Alexandrite effect spectropyrometer  

NASA Astrophysics Data System (ADS)

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

Liu, Yan

2006-08-01

393

Cutaneous Effects of Smoking  

Microsoft Academic Search

Background: Cigarette smoking is the single biggest preventable cause of death and disability in developed countries and is a significant public health concern. While known to be strongly associated with a number of cardiovascular and pulmonary diseases and cancers, smoking also leads to a variety of cutaneous manifestations. Objective: This article reviews the effects of cigarette smoking on the skin

Anatoli Freiman; Garrett Bird; Andrei I. Metelitsa; Benjamin Barankin; Gilles J. Lauzon

2004-01-01

394

The Contrail Effect  

NSDL National Science Digital Library

NOVA's The Contrail Effect describes how contrails form and how humidity determines how long they last. The webpage goes on to describe the study during the days of clear skies, without contrails, following 9/11. Three satellite images of contrail patterns are provided.

Foundation, Wgbh E.

2011-09-15

395

Effective family problem solving.  

PubMed

Effective family problem solving was studied in 97 families of elementary-school-aged children, with 2 definite-solution tasks--tower building (TWB) and 20 questions (TQ), and 1 indefinite-solution task--plan-something-together (PST). Incentive (for cooperation or competition) and task independence (members worked solo or jointly) were manipulated during TWB and TQ, yielding 4 counterbalanced conditions per task per family. On TQ, solo performance exceeded joint performance; on TWB, competition impaired joint performance. Families effective at problem solving in all conditions of both definite-solution tasks tried more problem-solving strategies during TWB and deliberated longer and reached more satisfactory agreements during PST. Family problem-solving effectiveness was moderately predicted by 2 parents' participation in the study. Parental education, parental occupational prestige, and membership in the family of an academically and socially competent child were weaker predictors. The results indicate that definitions of effective family problem solving that are based on directly observed measures of group interaction are more valid than definitions that rely primarily on family characteristics. PMID:3987417

Blechman, E A; McEnroe, M J

1985-04-01

396

Reading Effects of IBM's \\  

Microsoft Academic Search

This article reviews evaluations of IBM's Writing to Read program in kindergartens and first grades. In Writing to Read (WTR), students rotate through five learning stations to learn and practice phonics, to write stories, and to listen to recorded books. Two of these stations involve computers. Twenty-one studies of Writing to Read in kindergartens found a median effect size of

Robert E. Slavin

1991-01-01

397

The Placebo Effect  

Microsoft Academic Search

Placebos have been traditionally regarded as deceptive therapies and have not been understood in the broader context of social symbols and of interpersonal factors that surround the healing process itself. Although the power of inert substances to heal is well recognized, the placebo effect also influences the outcome of conventional therapies. The role of the placebo in modern medicine is

Curtis E Margo

1999-01-01

398

ENVIRONMENTAL RESIDUE EFFECTS DATABASE (ERED)  

EPA Science Inventory

US Army Corps of Engineers public web site for the "Environmental Residue Effects Database", a searchable database of adverse biological effects associated with tissue concentrations of various contaminants....

399

Adverse effects of cannabis.  

PubMed

Cannabis, Cannabis sativa L., is used to produce a resin that contains high levels of cannabinoids, particularly delta9-tetrahydrocannabinol (THC), which are psychoactive substances. Although cannabis use is illegal in France and in many other countries, it is widely used for its relaxing or euphoric effects, especially by adolescents and young adults. What are the adverse effects of cannabis on health? During consumption? And in the long term? Does cannabis predispose users to the development of psychotic disorders? To answer these questions, we reviewed the available evidence using the standard Prescrire methodology. The long-term adverse effects of cannabis are difficult to evaluate. Since and associated substances, with or without the user's knowledge. Tobacco and alcohol consumption, and particular lifestyles and behaviours are often associated with cannabis use. Some traits predispose individuals to the use of psychoactive substances in general. The effects of cannabis are dosedependent.The most frequently report-ed adverse effects are mental slowness, impaired reaction times, and sometimes accentuation of anxiety. Serious psychological disorders have been reported with high levels of intoxication. The relationship between poor school performance and early, regular, and frequent cannabis use seems to be a vicious circle, in which each sustains the other. Many studies have focused on the long-term effects of cannabis on memory, but their results have been inconclusive. There do not * About fifteen longitudinal cohort studies that examined the influence of cannabis on depressive thoughts or suicidal ideation have yielded conflicting results and are inconclusive. Several longitudinal cohort studies have shown a statistical association between psychotic illness and self-reported cannabis use. However, the results are difficult to interpret due to methodological problems, particularly the unknown reliability of self-reported data. It has not been possible to establish a causal relationship in either direction, because of these methodological limitations. In Australia, the marked increase in cannabis use has not been accompanied by an increased incidence of schizophrenia. On the basis of the available data, we cannot reach firm conclusions on whether or not cannabis use causes psychosis. It seems prudent to inform apparently vulnerable individuals that cannabis may cause acute psychotic decompensation, especially at high doses. Users can feel dependent on cannabis, but this dependence is usually psychological. Withdrawal symptoms tend to occur within 48 hours following cessation of regular cannabis use, and include increased irritability, anxiety, nervousness, restlessness, sleep difficulties and aggression. Symptoms subside within 2 to 12 weeks. Driving under the influence of cannabis doubles the risk of causing a fatal road accident. Alcohol consumption plays an even greater role. A few studies and a number of isolated reports suggest that cannabis has a role in the occurrence of cardiovascular adverse effects, especially in patients with coronary heart disease. Numerous case-control studies have investigated the role of cannabis in the incidence of some types of cancer. Its role has not been ruled out, but it is not possible to determine whether the risk is distinct from that of the tobacco with which it is often smoked. Studies that have examined the influence of cannabis use on the clinical course of hepatitis C are inconclusive. Alcohol remains the main toxic agent that hepatitis C patients should avoid. In practice, the adverse effects of low-level, recreational cannabis use are generally minor, although they can apparently be serious in vulnerable individuals. The adverse effects of cannabis appear overall to be less serious than those of alcohol, in terms of neuropsychological and somatic effects, accidents and violence. PMID:21462790

2011-01-01

400

Adverse effects of retinoids.  

PubMed

Oral retinoids, synthetic derivatives of vitamin A, have been used in the treatment of various dermatoses over the last decade. The most useful drugs have been isotretinoin (13-cis-retinoic acid) for nodulocystic acne and etretinate for psoriasis vulgaris. Retinoids are also effective in the treatment of papulosquamous dermatoses other than psoriasis (i.e. inherited disorders of keratinisation), cutaneous T-cell lymphoma and in chemotherapy and chemoprevention of cancer. However, systemic administration of these compounds is frequently associated with mucocutaneous side effects, liver toxicity and abnormalities of serum lipid profiles, which might be related to an increased risk of coronary heart disease. Of particular concern is the teratogenic effect of all retinoids, which limits their use in women of child-bearing potential. Chronic toxicities from long term therapy with retinoids may result in skeletal abnormalities, usually mimicking diffuse idiopathic hyperostosis syndrome. Furthermore, the chronic use of retinoids in children may inhibit their growth due to premature epiphyseal closure. In contrast to other side effects of retinoids which are dose dependent and reversible upon withdrawal of the drug, it seems unlikely that bone abnormalities will resolve after discontinuation of the medication. In view of the wide spectrum of toxicities, treatment with retinoids requires appropriate selection of patients, careful consideration of the benefit to risk ratio for each individual, periodic monitoring of clinical response and laboratory tests. Clinicians should use special management techniques in order to prevent or minimize slide effects. Extensive investigations are currently being conducted in an attempt to develop new retinoids which will improve the therapeutic efficacy and reduce unwanted reactions. PMID:3054426

David, M; Hodak, E; Lowe, N J

401

Electronic inhomogeneity in n- and p-type PbTe detected by 125Te NMR  

NASA Astrophysics Data System (ADS)

125Te nuclear magnetic resonance spectra and spin-lattice relaxation of n- and p-type PbTe, self-doping narrow band-gap semiconductors, have been studied and compared to those of p-type GeTe. Spin-lattice relaxation in GeTe can be fit by one component, while that in both PbTe samples must be fit by at least two components, showing electronically homogeneous and inhomogeneous materials, respectively. For PbTe-based materials, the spin-lattice relaxation rate 1/T1 increases linearly with carrier concentration. The data for GeTe fall on the same line and allow us to extend this plot to higher concentrations. Long and short T1 components in both PbTe samples reflect “low,” ˜1017 cm-3, and “high,” ˜1018 cm-3, carrier concentration components. Carrier concentrations in both n- and p-type PbTe samples obtained from the Hall and Seebeck effects generally match the “high” carrier concentration component, and to some extent, ignore the “low” one. This demonstrates that the Hall and Seebeck effects may have a limited ability for the determination of carrier concentration in complex thermoelectric PbTe-based and other multicomponent materials.

Levin, E. M.; Heremans, J. P.; Kanatzidis, M. G.; Schmidt-Rohr, K.

2013-09-01

402

Enhancement of the thermoelectric properties in doped FeSb2 bulk crystals  

NASA Astrophysics Data System (ADS)

Kondo insulator FeSb2 with large Seebeck coefficient would have potential in thermoelectric applications in cryogenic temperature range if it had not been for large thermal conductivity ?. Here we studied the influence of different chemical substitutions at Fe and Sb site on thermal conductivity and thermoelectric effect in high quality single crystals. At 5% of Te doping at Sb site, thermal conductivity is suppressed from ~250 W/Km in undoped sample to about 8 W/Km. However, Cr and Co doping at Fe site suppresses thermal conductivity more slowly than Te doping, and even at 20% Cr/Co doping the thermal conductivity remains ~30 W/Km. The analysis of different contributions to phonon scattering indicates that the giant suppression of ? with Te is due to the enhanced point defect scattering originating from the strain field fluctuations. In contrast, Te-doping has small influence on the correlation effects and then for small Te substitution the large magnitude of the Seebeck coefficient is still preserved, leading to the enhanced thermoelectric figure of merit (ZT ~0.05 at ~100 K) in Fe(Sb0.9Te0.1)2.

Wang, Kefeng; Hu, Rongwei; Warren, John; Petrovic, C.

2012-07-01

403

Thermoelectric properties of p-type perovskite compounds LaCoO3 systems containing the A-site vacancy  

NASA Astrophysics Data System (ADS)

Thermoelectric properties of Sr-doped LaCoO3 system which includes both La1-xSrxCoO3 and La0.95-xSrxsquare0.05CoO3 containing the A-site vacancy were prepared by solid state reaction. The crystal phases of the samples were investigated by X-ray diffraction method. The electrical conductivity, Seebeck coefficient, and thermal conductivity were investigated, focusing the effect of A-site vacancy. Doping of Sr to LaCoO3 improved the electrical conductivity but decreased the seebeck coefficient and increased the thermal conductivity. A-site vacancy of La0.95-xSrxsquare0.05CoO3 system, in comparison with La1-xSrxCoO3 system, increased electrical conductivity, and decreased lattice thermal conductivity. As a result, it was found that the thermoelectric properties of La0.95-xSrxsquare0.05CoO3 containing the A-site vacancy showed the higher values than those of La1-xSrxCoO3. The introduction of A-site vacancy was effective on the improvement of thermoelectric property.

Anzai, Mayuka; Kawakami, Hiroshi; Saito, Miwa; Yamamura, Hiroshi

2011-05-01

404

Introduction of resonant states and enhancement of thermoelectric properties in half-Heusler alloys  

NASA Astrophysics Data System (ADS)

The inclusion of small concentrations of vanadium (less than 1%) was found to produce a substantial increase in the Seebeck coefficient of polycrystalline n-type half-Heusler alloys based on Hf0.75Zr0.25NiSn. Some degree of vanadium-induced thermopower enhancement was found to be present even at temperatures as high as 800 K. Electrical resistivity values of the vanadium-doped samples, on the other hand, exhibited only modest increases, thereby resulting in a 120% increase in the thermoelectric power factor of Hf0.75Zr0.25NiSn above room temperature. Such augmentation of the Seebeck coefficient, however, was diminished at all measured temperatures with the addition of a sufficient quantity of antimony to dope this class of compounds optimally. These observations are discussed in terms of carrier concentration, mobility, effective mass, and calculations of the effective gap size. When taken in conjunction with low temperature heat capacity measurements, these results indicate an increase in the density of states at the Fermi level that is consistent with the resonant state phenomena investigated earlier by theoretical work on semiconductors.

Simonson, J. W.; Wu, D.; Xie, W. J.; Tritt, T. M.; Poon, S. J.

2011-06-01

405

LDRD final report backside localization of open and shorted IC interconnections LDRD Project (FY98 and FY 99)  

SciTech Connect

Two new failure analysis techniques have been developed for backside and front side localization of open and shorted interconnections on ICs. These scanning optical microscopy techniques take advantage of the interactions between IC defects and localized heating using a focused infrared laser ({lambda} = 1,340 nm). Images are produced by monitoring the voltage changes across a constant current supply used to power the IC as the laser beam is scanned across the sample. The methods utilize the Seebeck Effect to localize open interconnections and Thermally-Induced Voltage Alteration (TIVA) to detect shorts. Initial investigations demonstrated the feasibility of TIVA and Seebeck Effect Imaging (SEI). Subsequent improvements have greatly increased the sensitivity of the TIVA/SEI system, reducing the acquisition times by more than 20X and localizing previously unobserved defects. The interaction physics describing the signal generation process and several examples demonstrating the localization of opens and shorts are described. Operational guidelines and limitations are also discussed. The system improvements, non-linear response of IC defects to heating, modeling of laser heating and examples using the improved system for failure analysis are presented.

Cole, E.I. Jr.; Tangyunyong, P.; Benson, D.A.; Barton, D.L.

2000-01-01

406

The Effects of Procedural Variations on Lateralized Stroop Effects  

Microsoft Academic Search

Several issues in the classic Stroop effect remain open, including (i) the stage of processing which gives rise to the effect, (ii) the effect of some procedural manipulations, (iii) the effect of hemispheric specialization and of interhemispheric interactions, and (iv) the existence of individual differences. In this paper, we investigate these issues using a series of experiments with central, lateral,

N. Y. Weekes; E. Zaidel

1996-01-01

407

High energy Si ions bombardment effects on the properties of nano-layers of SiO2/SiO2 + Ag  

NASA Astrophysics Data System (ADS)

We grew 50 periodic SiO2/SiO2 + Ag multi-layers by electron beam deposition technique. The co-deposited SiO2 + Ag layers are 7.26 nm, SiO2 buffer layers are 4 nm, and total thickness of film was determined as 563 nm. We measured the thickness of the layers using in situ thickness monitoring during deposition, and optical interferometry afterwards. The concentration and distribution of Ag in SiO2 were determined using Rutherford backscattering spectrometry (RBS). In order to calculate the dimensionless figure of merit, ZT, the electrical conductivity, thermal conductivity and the Seebeck coefficient of the layered structure were measured at room temperature before and after bombardment with 5 MeV Si ions. The energy of the Si ions was chosen such that the ions are stopped deep inside the silicon substrate and only electronic energy due to ionization is deposited in the layered structure. Optical absorption (OA) spectra were taken in the range 200-900 nm to monitor the Ag nanocluster formation in the thin layers.

Güner, S.; Budak, S.; Muntele, C. I.; Ila, D.

2009-05-01

408

Cerebroprotective effect of flunarizine.  

PubMed

The cerebroprotective effect of flunarizine was studied using the following methods: hypobaric hypoxia in mice, complete ischemia by decapitation in mice, anoxic hypoxia in mice, hemic hypoxia in rats, incomplete ischemia by bilateral carotid ligation in rats and asphyxic hypoxia in cats. Piracetam, meclofenoxate, nicergoline, naftidrofuryl, cinnarizine and nifedipine were studied as reference drugs. Flunarizine increased the survival time in all survival models. Its effect was most pronounced in complete ischemia model, and considerably higher than that of reference drugs. In asphyxic hypoxia flunarizine increased cortical resistance and shortened cortical recovery. The EEG frequency-amplitude analysis during asphyxic hypoxia showed a significant decrease of the slow-waves amplitudes of delta and theta range, and an increase of the fast-waves amplitudes of beta-2 range, changes indicating protective action. PMID:2087140

Nikolov, R; Nikolova, M; Dikova, M; Mirzoyan, R S; Ganshina, T S; Volobueva, T I

409

Doppler Effect Model  

NSDL National Science Digital Library

The Doppler Effect model demonstrates the shift in frequency of a wave that is produced by the motion of either the wave source or the observer of the wave (or both). In this simulation, you can explore the change in the wave that is produced by source and/or observer motion, and you can even view what the situation looks like from the perspective of the medium (the standard reference frame), the source, or the observer. The Doppler Effect model was created using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_bu_Doppler.jar file will run the program if Java is installed.

Duffy, Andrew

2010-04-25

410

Radiation Damage Effects  

NASA Astrophysics Data System (ADS)

Radiation damage is an important issue for the particle detectors operated in a hostile environment where radiations from various sources are expected. This is particularly important for high energy physics detectors designed for the energy and intensity frontiers. This chapter describes the radiation damage effects in scintillating crystals, including the scintillation-mechanism damage, the radiation-induced phosphorescence, and the radiation-induced absorption. The radiation damage mechanism in crystal scintillators is also discussed. While the damage in halides is attributed to the oxygen/hydroxyl contamination, it is the structure defects, such as the oxygen vacancies, which cause the damage in oxides. Various material analysis methods used in investigations of the radiation damage effects as well as the improvement of crystal quality through systematic R&D are also presented.

Zhu, R.-Y.

411

The QCD Effective String  

NASA Astrophysics Data System (ADS)

QCD can be described in a certain kinematical regime by an effective string theory. This string must couple to background chiral fields in a chirally invariant manner, thus taking into account the true chirally non-invariant QCD vacuum. By requiring conformal symmetry of the string and the unitarity constraint on chiral fields we reconstruct the equations of motion for the latter ones. These provide a consistent background for the propagation of the string. By further requiring locality of the effective action we recover the Lagrangian of non-linear sigma model of pion interactions. The prediction is unambiguous and parameter-free. The estimated chiral structural constants of Gasser and Leutwyler fit very well the phenomenological values.

Espriu, Domenec

2003-10-01

412

Applications of effective Lagrangians  

SciTech Connect

This thesis contains some applications of effective field theories in particle physics. The impact of a fourth generation of quarks on neutral kaon mixing is considered, and the results are extended to the mixing and CP violating phenomenology of neutral bottom meson systems. A phenomenological Lagrangian is constructed to describe radiative vector meson decays. The measured decay rates are reproduced, and one prediction is made. It is shown that the large-N approximation in the standard model cannot explain the {Delta}I = {1/2} rule for kaon nonleptonic decays, even when short distance effects such as Penguins are included. Finally, the contribution of small instantons to the axion potential is calculated. The induced potential can be a large if the QCD coupling is non-decreasing at high energies, and if a suppression by light quark masses can be avoided using loops of scalars.

Flynn, J.M.

1987-01-01

413

Developmental effects of dioxins.  

PubMed Central

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

Birnbaum, L S

1995-01-01

414

Fire Effects Information System  

NSDL National Science Digital Library

The Fire Effects Information System (FEIS) provides up-to-date information about fire effects on plants and animals. It was developed at the USDA Forest Service Rocky Mountain Research Station's Fire Sciences Laboratory in Missoula, Montana. The FEIS database contains synoptic descriptions, taken from current English-language literature of almost 900 plant species, about 100 animal species, and 16 Kuchler plant communities found on the North American continent. The emphasis of each synopsis is fire and how it affects each species. Background information on taxonomy, distribution, basic biology and ecology of each species is also included. Synopses are thoroughly documented, and each contains a complete bibliography. Personnel from several land management agencies (USDA Forest Service, USDI-BIA, NPS, BLM, F&WS) identified the species to be included in the database. Those agencies funded the original work and continue to support maintenance and updating of the database.

1995-12-12

415

Health effects of ozone  

SciTech Connect

It is an honor to have the opportunity to comment on Dr. Morton Lippmann's excellent review on the health effects of ozone, which was presented at the 82nd Air and Waste Management Association Annual Meeting and Exhibition held in Anaheim, California in June 1989. It is comprehensive in citing all of the pertinent references, interpretative in its review of the literature, integrates critical information and is highly relevant in dealing with one of our nation's most difficult air pollution issues. I commend Dr. Lippmann for developing a critical review that serves in many ways as a case study in toxicology and risk assessment. It does this by integrating data obtained from various types of studies, emphasizing exposure-dose-response relations and underscoring the importance of understanding the mechanisms by which ozone produces health effects. In this commentary, I would like to briefly consider several of the points made by Lippmann, and in doing so, note various issues requiring additional research.

McClellan, R.O. (Chemical Industry Institute of Toxicology, Research Triangle Park, NC (USA))

1989-09-01

416

[Hypertensive effects of qat].  

PubMed

Chewing of Qat leaves which contain amphetamine alkaloids is a traditional drug practice in the horn of Africa. Cathine and cathinone are responsible for the desired psychogenic (suppression of hunger, mind stimulation, euphoria) and sympathicomimetic effects. In this study, we monitored seven volunteers during a traditional qat ritual. An increase in systolic and diastolic pressure was observed in three patients including one presenting predisposing chronic arterial hypertension. Peak pressure was observed approximately seven hours after beginning the ritual. The three patients presenting pressure changes were not significantly different from the four unaffected patients with regard to age or duration of qat use. These findings suggest that qat use by untreated hypertensive patients who react strongly to vasoconstrictive effects can lead to hypertension and resulting cardiovascular complications. PMID:10088104

Mion, G; Oberti, M; Ali, A W

1998-01-01

417

Evaluating Grandmother Effects  

PubMed Central

Women who have outlived child-bearing have long been described as post-reproductive. But contributions they make to the survival or fertility of their descendants enhance the reproduction of their genes. Consequently natural selection affects this characteristic stage of human life history. Grandmother effects can be measured in data sets that include births and deaths over several generations, but unmeasured covariates complicate the task. Here we focus on two complications: cohort shifts in mortality and fertility, and maternal age at death. We use the Utah Population Database to show that longevity of grandmothers may be associated with fewer grandchildren, as reported by Madrigal and Melendez-Obando (2008) for a Costa Rican sample, even when grandmother effects are actually positive.

Smith, Ken R.

2009-01-01

418

Nonopioid effect of ?-endorphin.  

PubMed

This review presents the generalized literature data and the results of our own research of the nonopioid effect of ?-endorphin, an opioid neuropeptide interacting not only with opioid but also with nonopioid (insensitive to the opioid antagonist naloxone) receptors. The roles of the hormone and its receptors in regulation of the immune, nervous, and endocrine systems are discussed. The effect of neuromediator on the immune system mediated by both opioid and nonopioid receptors is considered in detail. The data on distribution and function of the nonopioid ?-endorphin receptor in human and animal organisms are presented. All available data on the characteristics of the nonopioid ?-endorphin receptor obtained by means of radioligand analysis are given. The discussed information is supposed to extend our conceptions of the role of ?-endorphin in mammals and to be of extensive use in medicine and pharmacology. PMID:21585314

Kovalitskaya, Yu A; Navolotskaya, E V

2011-04-01

419

[Herbs and cardiotoxic effects].  

PubMed

Accidental or deliberate ingestion of poisonous herbs has become an increasingly common phenomenon over the last years. From existing literature data and case reports from emergency room visits or poison control centers, an overview is presented of the potential cardiotoxic manifestations following intoxication by wild herbal plants of the territory. The effects of the consumption of cardiac glycoside-containing plants (e.g., digitalis) are discussed along with tachyarrhythmias induced by Aconitum napellus L., Atropa belladonna L., Mandragora officinarum L. or Ephedra distachya L. herbs, and hypertensive crises associated with licorice abuse. For each plant, a brief historical and botanical background is provided, focusing on pathophysiology of intoxication and cardiotoxic effects on the basis of the most recent literature. Finally, medical management of intoxication, from both a general and cardiological viewpoint, is reviewed. PMID:23748541

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

2013-06-01

420

Spin Hall effect devices.  

PubMed

The spin Hall effect is a relativistic spin-orbit coupling phenomenon that can be used to electrically generate or detect spin currents in non-magnetic systems. Here we review the experimental results that, since the first experimental observation of the spin Hall effect less than 10 years ago, have established the basic physical understanding of the phenomenon, and the role that several of the spin Hall devices have had in the demonstration of spintronic functionalities and physical phenomena. We have attempted to organize the experiments in a chronological order, while simultaneously dividing the Review into sections on semiconductor or metal spin Hall devices, and on optical or electrical spin Hall experiments. The spin Hall device studies are placed in a broader context of the field of spin injection, manipulation, and detection in non-magnetic conductors. PMID:22522638

Jungwirth, Tomas; Wunderlich, Jörg; Olejník, Kamil

2012-04-23

421

Relativistic Hall effect.  

PubMed

We consider the relativistic deformation of quantum waves and mechanical bodies carrying intrinsic angular momentum (AM). When observed in a moving reference frame, the centroid of the object undergoes an AM-dependent transverse shift. This is the relativistic analogue of the spin-Hall effect, which occurs in free space without any external fields. Remarkably, the shifts of the geometric and energy centroids differ by a factor of 2, and both centroids are crucial for the Lorentz transformations of the AM tensor. We examine manifestations of the relativistic Hall effect in quantum vortices and mechanical flywheels and also discuss various fundamental aspects of this phenomenon. The perfect agreement of quantum and relativistic approaches allows applications at strikingly different scales, from elementary spinning particles, through classical light, to rotating black holes. PMID:22540559

Bliokh, Konstantin Y; Nori, Franco

2012-03-21

422

Lightning Physics and Effects  

NASA Astrophysics Data System (ADS)

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

Orville, Richard E.

2004-03-01

423

Temporary Retinal Effects  

Microsoft Academic Search

IN your present week's ``Notes'' you have referred to the curious experiences of MM. Macé de Lepinay and Nicati, in finding the town lights appear green, after five hours among snow-fields. On the Cima di Jazi, some 16,000 feet or more high, I found another effect. On removing my blue snow-glasses, the sky (at about 10 a.m.) appeared of the

J. Rand Capron

1882-01-01

424

Adipokine Effects on Bone  

Microsoft Academic Search

The adipocyte is an important source of factors that act as circulating regulators of bone metabolism. These include estrogens,\\u000a and the adipokines, leptin, resistin, adiponectin, and probably others. Leptin acts directly on bone cells, and in some experimental\\u000a models these effects are modified by its actions on the central nervous system, which impact on appetite, body weight, and\\u000a insulin sensitivity.

Ian R. Reid; J. B. Richards

2009-01-01

425

Ivabradine: Cardiovascular Effects  

Microsoft Academic Search

Ivabradine (a compound of the benzocyclobutane) is a highly selective If current inhibitor acting directly on the sino-atrial node, induces a rapid, sustained and dose-dependent reduction of heart rate at rest and during exercise without a significant effect on atrio-ventricular conduction, left ventricular contraction\\/relaxation or vascular tissues. These properties associated with an improvement in left ventricular loading related to bradycardia

Andrea Rognoni; Marzia Bertolazzi; Sergio Maccio; Giorgio Rognoni

2009-01-01

426

NEUROPROTECTIVE EFFECTS OF CURCUMIN  

Microsoft Academic Search

Neurodegenerative diseases result in the loss of functional neurons and synapses. Although future stem cell therapies offer\\u000a some hope, current treatments for most of these diseases are less than adequate and our best hope is to prevent these devastating\\u000a diseases. Neuroprotective approaches work best prior to the initiation of damage, suggesting that some safe and effective\\u000a prophylaxis would be highly

Greg M. Cole; Bruce Teter; Sally A. Frautschy

427

Local-Effect Games  

Microsoft Academic Search

Abstract We present a new class of games, local-effect games (LEGs), which exploit structure in a different way from other compact,game,representations studied in AI. We show both theoretically and empirically that these games,often (but not always) have pure-strategy Nash equilibria. Finding a potential function is a good technique for finding such equilibria. We give a complete,characterization of which LEGs have

Kevin Leyton-brown; Moshe Tennenholtz

2005-01-01

428

Neuroprotective effects of creatine  

Microsoft Academic Search

There is a substantial body of literature, which has demonstrated that creatine has neuroprotective effects both in vitro\\u000a and in vivo. Creatine can protect against excitotoxicity as well as against ?-amyloid toxicity in vitro. We carried out studies\\u000a examining the efficacy of creatine as a neuroprotective agent in vivo. We demonstrated that creatine can protect against excitotoxic\\u000a lesions produced by

M. Flint Beal

2011-01-01

429

Center for Effective Organizations  

Microsoft Academic Search

ABSTRACT In this chapter, we closely examine one set of factors that are critical for knowledge work team effectiveness --how organizations set and communicate,direction for teams. The variables we examine encompass,several related elements in the organization's direction-setting context: the clarity of the organization's strategy, the alignment of individual team, and organizational goals, and the measurability and specificity of those goals.

JAY R. GALBRAITH; SUSAN G. COHEN; CRISTINA B. GIBSON; JULIAN BIRKINSHAW

430

The reverse Stroop effect  

Microsoft Academic Search

In classic Stroop interference, manual or oral identification of sensory colors presented as incongruent color words is delayed\\u000a relative to simple color naming. In the experiment reported here, this effect was shown to all but disappear when the response\\u000a was simply to point to a matching patch of color. Conversely, strong reverse Stroop interference occurred with the pointing\\u000a task. That

Frank H. Durgin

2000-01-01

431

Writing Effective TAFs  

NSDL National Science Digital Library

This module provides an overview of some of the applicable TAF Amendment and Conditional Group usage rules, as presented in the latest version of the National Weather Service Instruction 10-813 on TAF directives. It also presents a methodology for TAF writing and development that will lead to an effective and user-friendly product. The focus is on the ceiling and visibility aspects of the TAF. This module is part of the Distance Learning Course 1: Forecasting Fog and Low Stratus

Spangler, Tim

2003-06-28

432

Side effects of benoxaprofen  

Microsoft Academic Search

A study was made of adverse dermatological reactions to the non-steroidal anti-inflammatory agent benoxaprofen. Photosensitivity was seen in several patients, confined to wavelengths less than 340 nm. Other cutaneous side effects were erythema multiforme, the Stevens-Johnson syndrome, milia, and onycholysis. One case of pancytopenia and toxic epidermal necrolysis was reported. patients were not rechallenged with the drug, but these reactions

Brian Diffey; Colin Hindson; F Lawlor

1982-01-01

433

Asking Effective Questions  

NSDL National Science Digital Library

This 8-page monograph offers strategies for effective questioning that engages students and that deepens their conceptual understanding in mathematics. It suggests questions and prompts that help students progress through various stages of the problem solving process and that help teachers assess the thinking of students. The article describes the purposes of questions at different stages of a lesson and describes situations when it is appropriate to convey information to students. A list of references is included.

2011-07-01

434

Antithyroid effects of lithium  

PubMed Central

Lithium has been reported to be goitrogenic when used for the treatment of manic-depressive psychosis. To investigate the effects of lithium on iodine metabolism, male Sprague-Dawley rats were placed on a low iodine (LID) or normal iodine diet (NID) containing enough Li2CO3 to give serum lithium levels of 0.23-0.86 mEq/liter (human therapeutic range is 0.6-1.6 mEq/liter). The following effects were noted with lithium treatment: (a) thyroid weight increased concomitant with a slowing of thyroidal iodine release; (b) the ability to concentrate iodide was increased only after goiters were established; (c) on the LID, 131I uptake was elevated throughout all phases of treatment, even when the release rate was normal; (d) iodine organification was unaffected but the proportion of 131I present as iodothyronines was decreased; (e) the thyroidal 127I content was increased; (f) despite these changes, the serum PBI remained normal as did the thyroxine turnover rate; and (g) thyrotropin (TSH) levels in serum were the same as controls except for a slight elevation early in the course of treatment; TSH levels did not correlate with goitrogenesis. When LiCl was injected in large doses into intact rats (giving serum lithium levels of 3.08-3.89 mEq/liter), the iodide concentrating mechanism, 131I uptake, and 131I release rates were depressed. Similar experiments in hypophysectomized rats receiving TSH demonstrated these to be local antithyroid effects not mediated through the pituitary. The discrepancy between acute and chronic responses to lithium, and the dissociation between the inhibition of iodine release and stimulatory effects is discussed.

Berens, S. C.; Bernstein, R. S.; Robbins, J.; Wolff, J.

1970-01-01

435

Antithyroid effects of lithium.  

PubMed

Lithium has been reported to be goitrogenic when used for the treatment of manic-depressive psychosis. To investigate the effects of lithium on iodine metabolism, male Sprague-Dawley rats were placed on a low iodine (LID) or normal iodine diet (NID) containing enough Li(2)CO(3) to give serum lithium levels of 0.23-0.86 mEq/liter (human therapeutic range is 0.6-1.6 mEq/liter). The following effects were noted with lithium treatment: (a) thyroid weight increased concomitant with a slowing of thyroidal iodine release; (b) the ability to concentrate iodide was increased only after goiters were established; (c) on the LID, (131)I uptake was elevated throughout all phases of treatment, even when the release rate was normal; (d) iodine organification was unaffected but the proportion of (131)I present as iodothyronines was decreased; (e) the thyroidal (127)I content was increased; (f) despite these changes, the serum PBI remained normal as did the thyroxine turnover rate; and (g) thyrotropin (TSH) levels in serum were the same as controls except for a slight elevation early in the course of treatment; TSH levels did not correlate with goitrogenesis. When LiCl was injected in large doses into intact rats (giving serum lithium levels of 3.08-3.89 mEq/liter), the iodide concentrating mechanism, (131)I uptake, and (131)I release rates were depressed. Similar experiments in hypophysectomized rats receiving TSH demonstrated these to be local antithyroid effects not mediated through the pituitary. The discrepancy between acute and chronic responses to lithium, and the dissociation between the inhibition of iodine release and stimulatory effects is discussed. PMID:4194189

Berens, S C; Bernstein, R S; Robbins, J; Wolff, J

1970-07-01

436

The Kaye effect  

NASA Astrophysics Data System (ADS)

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

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

2009-11-01

437

Effective Teaching with Technology  

Microsoft Academic Search

A course entitled effective teaching with technology (ETT) has been taught to PhD candidates and postdoctoral students in science, technology, engineering, and mathematics (STEM) during the Spring semester of 2004, 2005, and 2006, at the University of Wisconsin-Madison. The course is supported by the NSF-sponsored Center for Integration of Research, Teaching, and Learning (CIRTL). The course employs the three CIRTL

Gregory Moses; Barbara Ingham; Katherine Barnicle; Jake Blanchard; Jan Cheetham; Sandra Courter; Elizabeth DeVos; Margaret Immendorf; Michael Litzkow; Gina Svarovsky; Alan Wolf

2006-01-01

438

Doppler-Effect Omnirange  

Microsoft Academic Search

This paper describes an omnirange of a new design in which the transmitting antenna is caused either to move, or to appear to move along a circular path to produce low-deviation FM by Doppler effect. The FM envelope phase of the transmitted signal is directionally characterized. Deviation-expansion and selective-degeneration in an AFC circuit are used at the receiver to detect

Paul Hansel

1953-01-01

439

Botany: floral fluorescence effect.  

PubMed

The way flowers appear to insects is crucial for pollination. Here we describe an internal light-filtering effect in the flowers of Mirabilis jalapa, in which the visible fluorescence emitted by one pigment, a yellow betaxanthin, is absorbed by another, a violet betacyanin, to create a contrasting fluorescent pattern on the flower's petals. This finding opens up new possibilities for pollinator perception as fluorescence has not previously been considered as a potential signal in flowers. PMID:16163341

Gandía-Herrero, Fernando; García-Carmona, Francisco; Escribano, Josefa

2005-09-15

440

Quantum effects in biology  

Microsoft Academic Search

The idea that quantum-mechanical phenomena can play nontrivial roles in biology has fascinated researchers for a century. Here we review some examples of such effects, including light-harvesting in photosynthesis, vision, electron- and proton-tunneling, olfactory sensing, and magnetoreception. We examine how experimental tests have aided this field in recent years and discuss the importance of developing new experimental probes for future

Graham R. Fleming; Gregory D. Scholes; Yuan-Chung Cheng

2011-01-01

441

Cost-Effectiveness Analyses  

Microsoft Academic Search

Surgical research has traditionally focused on comparing health outcome measures of a new technique with accepted practice.\\u000a As health care resources become scarcer and options for newer, more expensive diagnostic tests and surgical interventions\\u000a increase, incorporating cost-effectiveness analysis (CEA) into surgical research studies becomes increasingly important. CEA\\u000a provides the information necessary to allow resource allocation decisions to be based on

Lynn Stothers

442

Hall Effect Measurements  

NSDL National Science Digital Library

The objective of this Web site is twofold: (1) to describe the Hall measurement technique for determining the carrier density and mobility in semiconductor materials and (2) to initiate an electronic interaction forum where workers interested in the Hall effect can exchange ideas and information. It includes an introductory description of the Hall measurement technique and covers basic principles, equipment, and recommended procedures. Keywords: Conductance, conductivity, resistance, resistivity

2012-07-26

443

Tasting edge effects  

NASA Astrophysics Data System (ADS)

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

Bocquet, Lydéric

2007-02-01

444

Designing effective instruction  

Microsoft Academic Search

Summary  We have usedDesigning Effective Instruction in introductory ID courses and experienced its use from both the instructors' and the learners' perspective. Our overall\\u000a conclusion is that it is highly usable and accessible to beginning ID students, including those whose first language may not\\u000a be English. The ID model presented is clear and the focus on the learner throughout is appropriate

Gary J. Anglin; Steven M. Ross; Jerrold E. Kemp

2002-01-01

445

Preattentive auditory context effects  

Microsoft Academic Search

The effects of auditory context on the preattentive and perceptual organization of tone sequences were investigated. Two sets\\u000a of experiments were conducted in which the pitch of contextual tones was varied, bringing about two different contextual manipulations.\\u000a Preattentive auditory organization was indexed by the mismatch negativity event-related potential, which is elicited by violations\\u000a of auditory regularities even when participants ignore

István Winkler; Elyse Sussman; Mari Tervaniemi; János Horváth; Walter Ritter; Risto Näätänen

2003-01-01

446

Phenotypic Effects of the \\  

Microsoft Academic Search

From outbred Hsd:ICR mice, we selectively bred 4 replicate lines for high running (High-Runner (HR) lines) on wheels while maintaining 4 nonselected lines as controls (C lines). An apparent Mendelian recessive, the ''mini-muscle'' (MM) allele, whose main phenotypic effect is to reduce hindlimb muscle mass by 50%, was discovered in 2 HR lines and 1 C line. This gene of

ROBERT M. HANNON; S COTT A. KELLY; K EVIN M. MIDDLETON; E. M. Kolb; D ANIEL POMP; THEODORE GARLAND JR

2008-01-01

447

Radiation effects on integrated microcircuits  

NASA Astrophysics Data System (ADS)

A theory describing the effects of ionizing radiation on integrated microcircuits is developed. The features of secondary ionization effects (e.g., radiation-induced secondary breakdown) are examined along with residual and transient ionization effects on the characteristics of standard components of digital and analog ICs. The radiation characteristics of LSI systems are also considered, with emphasis on microdosimetric and functional effects.

Agakhanian, Tatevos M.; Astvatsatur'ian, Evgenii R.; Skorobogatov, Petr K.

448

SOLAR EFFECTS ON BUILDING DESIGN.  

ERIC Educational Resources Information Center

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

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

449

Petroleum effects in the Arctic  

Microsoft Academic Search

This book presents papers on the environmental and biological effects of oil spills. Topics considered include the Arctic marine ecosystem, the physical and chemical fate of spilled oil, the effects of hydrocarbons on microorganisms and petroleum biodegradation in arctic ecosystems, the effects of oil on arctic invertebrates, the effects of oil on fish, a risk assessment of oil on arctic

Engelhardt

1985-01-01

450

[Biological effects of selenium].  

PubMed

The role of selenium concerning its biological effects particularly in relation to cardiovascular and tumor diseases has been in the focus of intensive studies. Selenium is a constituent part of the enzyme glutathion peroxidase (E.C.1.11.1.9) which catalyzes the conversion of hydrogen peroxide and organic hydroperoxides into water and corresponding alcohols. A review of epidemiological studies is presented focusing predominantly on countries where a low concentration of selenium in blood serum was found. The role of selenium in the etiology of cardiovascular diseases may probably be accounted for by its protective effect as it prevents platelet aggregation and protects the arterial endothelium from being damaged by lipid peroxides. The results of experimental studies, carried out in research institutes in many parts of the world, suggest that coordinated supplementation of food with selenium may reduce the risk of cancer and moreover, the effect of selenium can be modified by other dietary factors, such as vitamin A and E. (Fig. 2, Ref. 29.) PMID:1296855

Brtková, A

1992-12-01

451

Ejs Doppler Effect Model  

NSDL National Science Digital Library

The Ejs Doppler Effect model displays the detection of sound waves from a moving source and the change in frequency of the detected wave via the Doppler effect. In addition to the wave fronts from the source a graph depicting the time of emission and time of detection of each of the wave fronts is given. The speed of sound, the velocity of the source and the position and velocity of the detector can be changed via text boxes. You can modify this simulation if you have Ejs installed by right-clicking within the plot and selecting âOpen Ejs Modelâ from the pop-up menu item. Ejs Doppler Effect model was created using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_ehu_waves_doppler.jar file will run the program if Java is installed. Ejs is a part of the Open Source Physics Project and is designed to make it easier to access, modify, and generate computer models. Additional Ejs models for wave optics are available. They can be found by searching ComPADRE for Open Source Physics, OSP, or Ejs.

Aguirregabiria, Juan

2008-08-20

452

Cascading Effects Following Intervention  

PubMed Central

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

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

2010-01-01

453

Health effects of ozone  

SciTech Connect

Dr. Morton Lippmann prepared, at the request of the A WMA Review Committee, an extensive update of the available information on the biological effects of ozone. His review is a thorough and well-written summary of what is known about respiratory effects of low ozone concentrations. The authors is well qualified to evaluate clinical data on ozone effects since a substantial amount of work on this subject has been produced in his own laboratory. Years of experience in consultative functions for the Environmental Protection Agency and Clean Air Science Advisory Committee further characterize Dr. Lippmann as an especially qualified scientist for assessing this complex problem. For the same reasons, however, interpretation of some experimental data in the review may have been influenced by inherent personal biases of the author and may, in fact, differ from the views of other investigators. This possibility is recognized in the text and does not diminish the overall quality of the review. My comments will be limited primarily to the general aspects of the review and to the role of the current form of the standard in public health protection.

Vostal, J.J. (General Motors Environmental Activities Staff, Warren, MI (USA))

1989-09-01

454

Pairing correlations and effective mass  

SciTech Connect

We study the effect of effective mass on pairing correlations in the ground states of superfluid nuclei {sup 124}Sn and {sup 136}Sn. Various parameter sets of Skyrme interactions and relativistic Lagrangians are adopted to study pairing correlations across a wide range of effective mass. It is shown that surface-type pairing interaction gives an almost constant pairing gap as a function of the effective mass, while volume-type pairing interaction shows rather strong dependence of the pairing gap upon the effective mass. The local pair potentials of various effective interactions are also examined in relation to the effective mass.

Yoshida, Satoshi [Science Research Center, Hosei University, 2-17-1 Fujimi, Chiyoda, Tokyo 102-8160 (Japan); Sagawa, Hiroyuki [Center for Mathematical Sciences, University of Aizu Aizu-Wakamatsu, Fukushima 965-8580 (Japan)

2008-05-15

455

The Giant Magnetocaloric Effect  

NASA Astrophysics Data System (ADS)

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

Pecharsky, Vitalij K.

1998-03-01

456

Health effects of nonionizing radiation  

SciTech Connect

Electromagnetic energy in the microwave and radiofrequency bands can produce biologic effects, which are predominantly thermal. During therapeutic use under medical supervision, desired biologic effects are produced and potentially injurious effects minimized. The biologic effects of electromagnetic fields have materialized because of a recent concern that relatively low-level fields produced by everyday electrical appliances, wiring in the home, and power transmission lines may be causally related to a number of detrimental health effects.41 references.

Wilkening, G.M.; Sutton, C.H. (AT T Bell Laboratories, Murray Hill, NJ (USA))

1990-03-01

457

Causal diagrams, the placebo effect, and the expectation effect.  

PubMed

Using causal diagrams, a formal research methodology, we analyzed several definitions of placebo and the placebo effect. We conclude that placebo is an ambiguous, redundant term and that the so-called placebo effect conceals far more interesting effects that are attributed to the patient's expectation. Biomedical research will benefit from abandoning the term placebo effect and focusing instead on a deeper understanding of the expectation variable, including its causes, effects, and effect modifiers. This avenue of research should be pursued by observational cohorts that are nested within clinical trials. PMID:24101881

Shahar, Eyal; Shahar, Doron J

2013-09-27

458

Causal diagrams, the placebo effect, and the expectation effect  

PubMed Central

Using causal diagrams, a formal research methodology, we analyzed several definitions of placebo and the placebo effect. We conclude that placebo is an ambiguous, redundant term and that the so-called placebo effect conceals far more interesting effects that are attributed to the patient’s expectation. Biomedical research will benefit from abandoning the term placebo effect and focusing instead on a deeper understanding of the expectation variable, including its causes, effects, and effect modifiers. This avenue of research should be pursued by observational cohorts that are nested within clinical trials.

Shahar, Eyal; Shahar, Doron J

2013-01-01

459

The flash grab effect.  

PubMed

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

Cavanagh, Patrick; Anstis, Stuart

2013-07-18

460

Adverse antiepileptic drug effects  

PubMed Central

Background: Adverse effects (AEs) of antiepileptic drugs (AEDs) are a major impediment to optimal dosing for seizure control. Better understanding of clinical properties of AEs is a prerequisite for systematic research of their neurobiological underpinnings. This study aimed to define specific patterns of AE occurrence and determine their clinical relevance based on their association with subjective health status. Methods: Two hundred subjects with epilepsy completed validated self-report health assessments, including the Adverse Event Profile (AEP) and Quality of Life in Epilepsy Inventory (QOLIE)-89. Factor analysis was performed on the 19 AEP items to identify distinct classes of AEs. Correlations between AE class scores and QOLIE-89 scores were evaluated. Multivariate analysis was used to assess contributions of AE class scores to QOLIE-89 scores after controlling for depression and seizure frequency. Relationships between changes in AE class scores and changes in QOLIE-89 scores were also investigated in a subgroup of 62 subjects enrolled in a randomized trial. Results: The mean number of AEs per subject was 6.5. AEs were segregated into five classes: Cognition/Coordination, Mood/Emotion, Sleep, Weight/Cephalgia, and Tegument/Mucosa. Higher scores in each AE class were associated with lower QOLIE-89 scores. Cognition/Coordination scores were the strongest predictor of QOLIE-89 scores. Improvements in Cognition/Coordination, Mood/Emotion, and Tegument/Mucosa scores were associated with improvements in QOLIE-89 scores. Improved Cognition/Coordination was the only predictor of improved QOLIE-89. Conclusion: Adverse effects (AEs) of antiepileptic drugs can be classified in five biologically plausible factors. When specific classes of AEs are identified and attempts are made to reduce them, quality of life is significantly improved. GLOSSARY AE = adverse effect; AED = antiepileptic drug; AEP = Adverse Event Profile; BDI = Beck Depression Inventory; GABA = ?-aminobutyric acid; HRQOL = Health-Related Quality of Life; QOLIE = Quality of Life in Epilepsy Inventory.

Perucca, Piero; Carter, Jewell; Vahle, Victoria; Gilliam, Frank G.

2009-01-01

461

'The Kesterson effect'  

USGS Publications Warehouse

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

Presser, T. S.

1994-01-01

462

Immunosuppressive effects of defibrotide.  

PubMed

The effect of defibrotide (DF) alone or in combination with CsA was examined using in vitro proliferation assays with human PBLs and in vivo heterotopic heart allografts in rats. DF alone (12.5-50 mg/ml) inhibited in vitro PBL proliferation more effectively after PHA (50-56%) or OKT3 (50-95%), than after alloantigenic (25-30%), stimulation. Furthermore, the combination of DF (1-4 mg/ml) with CsA (10-40 ng/ml) caused an 85.2-86.8% reduction in proliferative responses after OKT3 stimulation. Median-effect analysis documented that the combination index for DF and CsA was consistently lower than 0.3 at various concentration ratios of the 2 agents. Combination index values below 1.0 reflect drug synergism; those equal to 1.0 show additive, and above 1.0, antagonistic, interactions. Daily intraperitoneal injections of DF (150 mg/kg) failed to prolong the survival of Buffalo (RT-1b) heart allografts in Wistar-Furth (RT-1u) recipients, namely mean survival times of 7.0 +/- 0.7 days with, vs. 6.5 +/- 0.5 days without, DF treatment. Similarly, intravenous or intra-arterial infusion of DF (280 mg/kg) delivered directly into the heart allograft by a 7-day osmotic pump was ineffective. However, a course of local, but not systemic, DF (280 mg/kg) combined with a 14-day i.v. administration of a subtherapeutic dose of CsA (1 mg/kg) significantly prolonged heart allograft survival to 22.8 +/- 5.0 days (P < 0.001). Thus, in vitro DF is immunosuppressive alone at high concentrations, and in combination with CsA at low concentrations. Continuous infusion of DF into the graft combined with systemic administration of CsA prolonged transplant survival in vivo. These findings suggest that high tissue levels of DF potentiate the immunosuppressive effects of CsA. PMID:8212219

Ferraresso, M; Rigotti, P; Stepkowski, S M; Chou, T C; Kahan, B D

1993-10-01

463

Greenhouse Effect Lab  

NSDL National Science Digital Library

In this simple lab, students collect data to demonstrate basic atmospheric science concepts. Groups of students measure the effect of carbon dioxide on temperature using soda bottles with thermometers inserted. One bottle is filled with air and capped. The second bottle is filled with carbon dioxide using a specific procedure. To conduct the experiment, both bottles are placed under a lamp while students record the increase in temperature over five minutes. The bottle containing carbon dioxide has a greater increase in temperature than the bottle containing air. This lab demonstrates the fundamental concept that underlies climate change science by providing data that are easy for students to interpret.

Larsen, Krista

464

Effect of Auxin  

Microsoft Academic Search

The effect of auxin on the physiology of protoplasts from growing oat (Avena sativa L.) coleoptiles was investigated. Protoplasts, iso- lated iso-osmotically from peeled oat coleoptile segments, were found to swell steadily over many hours. lncubated in 1 mM CaCI,, 1 O mM KCI, 1 O mM 2-(morpholino)ethanesulfonic acid\\/lJ-bis- Itris(hydroxymethyl)methylaminolpropane, pH 6.5, and mannitol to 300 milliosmolal, protoplasts swelled 28.9%

Christopher P. Keller; Elizabeth Van Volkenburgh

465

Is health education effective?  

PubMed

Primary health care (PHC) workers from 20 hospitals, PHC nurses, community health care nurses, and other PHC workers attended a session on health education and effectiveness in South Africa in September 1991. Discussion is directed to an overview of health education as presented in the day's session, the effectiveness of health education, and recommendations for improving health education. The first session on health education aimed to explore the breadth of possibilities for health education, and to emphasize some important problems, such as inconsistency in messages. Role plays were enacted within different groups: the 1991 Tintswalo PHC nurses class, the Tintswalo People's Awareness of Disability Issues group, and the Nkhensani PHC nurses group. The second session involved a panel discussion with 4 speakers. The first speaker directed attention to the need for an adequate education as insurance for effective health education. Modern trends have been responsible for the destruction of black culture. There is a problem of victim blaming, when in fact the problem of rural mortality is the system. Socioeconomic conditions and politics must be changed before health education can be effective. Health personnel as representatives of the middle class may be viewed as part of the problem. The second speaker spoke of the ineffectiveness of teaching someone what ought to be eaten but not providing the means to acquire the food. Oppression has led to blaming the oppressed. The third speaker noted that health workers were indeed part of the problem, e.g., health workers do not practice the advice given out and many times are junior personnel who are not evaluated. There are requirements for tracking what nurses do, but little on evaluation of appropriate messages. Appearance replaces substance. The fourth speaker felt health education is about training people and satisfying the educator and the system. Politics and health were related and too much time was misdirected to fighting with the community. Situation analysis was recommended before action was taken. Recommendations involved, for instance, building rapport with the community, and the need for a greater grasp of health knowledge by health educators. PMID:1356228

McKenzie, A; Ngobeni, O; Bonongo, F

1992-07-01

466

On nature's scaling effects  

NASA Astrophysics Data System (ADS)

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

Wilkins, Dick J.

1994-07-01

467

Hepatoprotective effects of mushrooms.  

PubMed

The particular characteristics of growth and development of mushrooms in nature result in the accumulation of a variety of secondary metabolites such as phenolic compounds, terpenes and steroids and essential cell wall components such as polysaccharides, b-glucans and proteins, several of them with biological activities. The present article outlines and discusses the available information about the protective effects of mushroom extracts against liver damage induced by exogenous compounds. Among mushrooms, Ganoderma lucidum is indubitably the most widely studied species. In this review, however, emphasis was given to studies using other mushrooms, especially those presenting efforts of attributing hepatoprotective activities to specific chemical components usually present in the mushroom extracts. PMID:23884116

Soares, Andréia Assunço; de Sá-Nakanishi, Anacharis Babeto; Bracht, Adelar; da Costa, Sandra Maria Gomes; Koehnlein, Eloá Angélica; de Souza, Cristina Giatti Marques; Peralta, Rosane Marina

2013-07-01

468

Interface effects on nanoelectronics  

NASA Astrophysics Data System (ADS)

Nanoelectronics consist of devices with active electronic components on the nanometer length scale. At such dimensions most, if not all, atoms or molecules composing the active device region must be on or near a surface. Also, materials effectively confined to two dimensions, or when subject to abrupt boundary conditions, generally do not behave the same as materials inside three dimensional, continuous structures. This dissertation is a quantitative determination of how surfaces and interfaces in organic nanoelectronic devices affect properties such as charge transport, electronic structure, and material fluctuations. Si/SiO2 is a model gate/gate dielectric for organic thin film transistors, therefore proper characterization and measurement of the effects of the SiO2/organic interface on device structures is extremely important. I fabricated pentacene thin film transistors on Si/SiO2 and varied the conduction channel thickness from effectively bulk (˜40nm) to 2 continuous conducting layers to examine the effect of substrate on noise generation. The electronic spectral noise was measured and the generator of the noise was determined to be due to the random spatial dependence of grain boundaries, independent of proximity to the gate oxide. This result led me to investigate the mechanisms of pentacene grain formation, including the role of small quantities of impurities, on silicon dioxide substrates. Through a series of nucleation, growth and morphology studies, I determined that impurities assist in nucleation on SiO2, decreasing the stable nucleus size by a third and increasing the overall number of grains. The pentacene growth and morphology studies prompted further exploration of pentacene crystal growth on SiO2. I developed a method of making atomically clean ultra-thin oxide films, with surface chemistry and growth properties similar to the standard thick oxides. These ultra-thin oxides were measured to be as smooth as cleaned silicon and then used as substrates for scanning tunneling microscopy of pentacene films. The increased spatial resolution of this technique allowed for the first molecular resolution characterization of the standing-up pentacene crystal structure near the gate dielectric, with molecules oriented perpendicular to the SiO2 surface. Further studies probed how growth of C60 films on SiO2 and pentacene surfaces affected C60 morphology and electronic structure to better understand solar cell heterojunctions.

Conrad, Brad Richard

469

Interfacial effects in multilayers  

SciTech Connect

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

Barbee, T.W., Jr.

1998-04-01

470

High temperature thermoelectric properties of Nb-doped ZnO ceramics  

NASA Astrophysics Data System (ADS)

Solid-state reaction processing technique was used to prepare ZnxNb1-xO (0?x?0.02) polycrystalline bulk samples. In the present study, we find that their lattice parameters a and c tend to decrease with increasing amount of Nb additive. The electrical conductivity of all the Zn1-xNbxO samples increased with increasing temperature, indicating a semiconducting behavior in the measured temperature range. The addition of Nb2O5 to ZnO led to an increase in the electrical conductivity and a decrease in the absolute value of the Seebeck coefficient. The best performance at 1000 K has been observed for nominal 0.5 at% Nb-doped ZnO, with an electrical resistivity of about 73.13 (S cm-1) and Seebeck coefficient of ˜257.36 ?V K-1, corresponding to a power factor (S2?) of 4.84×10-4 Wm-1 K-2. The thermal conductivity, ?, of the oxide decreased as compared to pure ZnO. The figure of merit ZT values of ZnO-doped Nb2O5 samples are higher than the ZnO pure sample, demonstrating that the Nb2O5 addition is fairly effective for enhancing thermoelectric properties.

Wang, N. N.; Xin, H. X.; Li, D.; Li, X. J.; Zhang, J.; Qin, X. Y.

2013-12-01

471

Thermoelectric properties of Ba8Ga16Ge30 with TiO2 nanoinclusions  

NASA Astrophysics Data System (ADS)

The effects on thermal and electrical properties of adding small amounts of TiO2 nanoinclusions to bulk Ba8Ga16Ge30 clathrate have been investigated. The thermal properties were analysed using the transient plane source technique and the analysis showed a significant decrease in thermal conductivity as the volume fraction of TiO2 increased from 0 vol. % to 1.2 vol. %. The introduction of TiO2 nanoparticles caused a shift in the peak value of the Seebeck coefficient towards lower temperatures. The maximum value of the Seebeck coefficient was, however, only little affected. The introduction of TiO2 nanoparticles into the bulk Ba8Ga16Ge30 resulted in an increased electrical resistivity of the sample, thus simultaneously reducing the charge carrier contribution to the thermal conductivity, partly explaining the decrease in total thermal conductivity. Due to the large increase in resistivity of the samples, ZT was only somewhat improved for the material with 0.4 vol. % TiO2 while the ZT values of the other materials were lower than for the reference Ba8Ga16Ge30 material without TiO2 nanoparticles. The combined results are consistent with a scenario where the nanoparticle introduction causes a light doping of the semiconductor matrix and an increased concentration of phonon scattering centres.

Heijl, R.; Cederkrantz, D.; Nygren, M.; Palmqvist, A. E. C.

2012-08-01

472

Thermoelectric properties of the multilayered Bi2Te3 with chalcogenide materials  

NASA Astrophysics Data System (ADS)

Chalcogenide materials have been known as good candidates for thermoelectric materials including bismuth telluride and antimony telluride. Especially Bi2(1-x)Sb2xTe3(1-y)Se3y semimetal alloys family has a room temperature ZT value of about. Bismuth telluride based BiTeSb and BiTeSe multilayered thin films have been fabricated using cosputtering on Si substrate with varying applied power and thermal treatment. Thermoelectric properties have been affected by the texturing, the mobility of charge carriers, and the density of imperfections. In order to confirm the texture of the films we investigated the microstructure through x-ray diffraction. Carrier density, mobility, and resistivity have been measured by Hall-effect measurement system and Seebeck coefficient has been measured using temperature difference method. Seebeck coefficient of double layered BiTe/BiTeSb and BiTeSb/BiTeSe films have been affected by the mobility change.

Ryu, H.; Hyun, S. M.; Song, J. Y.

2012-06-01

473

Thermoelectric properties of Ca3Co4O9 thin film  

NASA Astrophysics Data System (ADS)

Thermoelectric oxides have attracted increasing attention due to their high thermal power and temperature stability. In particular, Ca3Co4O9 (CCO), a misfit layered structure consisting of single layer hole-doped CoO2 sandwiched between insulating Ca2CoO3 rocksalt layers, exhibits a high Seebeck coefficient at 1000 K. It was suggested that the Seebeck-coefficient can be further increased by growing doped thin films with controlled defects structures. This study combines pulsed layer deposition thin film synthesis of pristine CCO on several oxide substrates, as well as CCO thin films doped with Ti, Bi or La, with aberration-corrected scanning transmission electron microscopy and electron energy loss spectroscopy (EELS) to examine the effects of interfacial strain and doping on the atomic and electronic structures of CCO. The thermoelectric properties will be measured and correlated to the local changes in the atomic and electronic structures. We will further evaluate the role of CoO2 stacking faults, as well as film thickness on the thermoelectric properties of CCO.

Klie, Robert; Qiao, Qiao; Gulec, Ahmet; Paulauskas, Tadas; Kolesnik, Stanislaw; Dabrowski, Bogdan; Boyraz, Cihat; Ozdemir, Mehmet; Mazumdar, Dipanjan; Gupta, Arun

2011-03-01

474

Thermoelectric Properties Of SiO2/SiO2+Au Nano-Layered Superlattices Modified By MeV Si Ions Beam  

NASA Astrophysics Data System (ADS)

The efficiency of thermoelectric devices and materials is limited by the properties of n- and p-type (semi)conductors. Effective thermoelectric materials have a low thermal conductivity and a high electrical conductivity. The performance of thermoelectric materials and devices is shown by a dimensionless figure of merit, The performance of thermoelectric materials and devices is shown by a dimensionless figure of merit, ZT = S2?T/K, where S is the Seebeck coefficient, ? is the electrical conductivity, T is the absolute temperature and K is the thermal conductivity. ZT can be increased by both increasing S and ?, or decreasing K. In this study we have prepared a thermoelectric generator from 100 alternating layers of SiO2/SiO2+Au superlattice films using ion beam assisted deposition (IBAD). In order to determine the stoichiometry of SiO2 and Au in the grown multilayer films, Rutherford Backscattering Spectrometry (RBS) was used. The 5 MeV Si ions bombardment was performed using the CIM Pelletron ion beam accelerator to make nanodots and/or nanoclusters in the multi-layer superlattice thin films to decrease the cross plane thermal conductivity, increase the cross plane Seebeck coefficient and increase the cross plane electrical conductivity.

Chacha, J.; Budak, S.; Smith, C.; McElhaney, D.; Pugh, M.; Ogbara, K.; Heidary, K.; Johnson, R. B.; Muntele, C.; Ila, D.

2011-06-01

475

Excess thermopower and the theory of thermopower waves.  

PubMed

Self-propagating exothermic chemical reactions can generate electrical pulses when guided along a conductive conduit such as a carbon nanotube. However, these thermopower waves are not described by an existing theory to explain the origin of power generation or why its magnitude exceeds the predictions of the Seebeck effect. In this work, we present a quantitative theory that describes the electrical dynamics of thermopower waves, showing that they produce an excess thermopower additive to the Seebeck prediction. Using synchronized, high-speed thermal, voltage, and wave velocity measurements, we link the additional power to the chemical potential gradient created by chemical reaction (up to 100 mV for picramide and sodium azide on carbon nanotubes). This theory accounts for the waves' unipolar voltage, their ability to propagate on good thermal conductors, and their high power, which is up to 120% larger than conventional thermopower from a fiber of all-semiconducting SWNTs. These results underscore the potential to exceed conventional figures of merit for thermoelectricity and allow us to bound the maximum power and efficiency attainable for such systems. PMID:23889080

Abrahamson, Joel T; Sempere, Bernat; Walsh, Michael P; Forman, Jared M; Sen, Fatih; Sen, Selda; Mahajan, Sayalee G; Paulus, Geraldine L C; Wang, Qing Hua; Choi, Wonjoon; Strano, Michael S

2013-08-07

476

CROSS-DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY: Synthesis and high temperature thermoelectric transport properties of Si-based type-I clathrates  

NASA Astrophysics Data System (ADS)

N-type Si-based type-I clathrates with different Ga content were synthesized by combining the solid-state reaction method, melting method and spark plasma sintering (SPS) method. The effects of Ga composition on high temperature thermoelectric transport properties were investigated. The results show that at room temperature, the carrier concentration decreases, while the carrier mobility increases slightly with increasing Ga content. The Seebeck coefficient increases with increasing Ga content. Among all the samples, Ba7.93Ga17.13Si28.72 exhibits higher Seebeck coefficient than the others and reaches -135 ?V.K-1 at 1000 K. The sample prepared by this method exhibits very high electrical conductivity, and reaches 1.95×105 S.m-1 for Ba8.01Ga16.61Si28.93 at room temperature. The thermal conductivity of all samples is almost temperature independent in the temperature range of 300-1000 K, indicating the behaviour of a typical metal. The maximum ZT value of 0.75 is obtained at 1000 K for the compound Ba7.93Ga17.13Si28.72.

Deng, Shu-Kang; Tang, Xin-Feng; Tang, Run-Sheng

2009-07-01

477

Effects of Time on the Effectiveness of Dispersants. Final Version.  

National Technical Information Service (NTIS)

The objective of this study was to determine whether dispersants will remain with treated oil slicks over time and retain effectiveness. If dispersants remain effective for significant periods ot time, oil spill responders can consider dispersants in scen...

I. Eide J. Guyomarch J. L. Resby P. J. Brandvik P. S. Daling

2007-01-01

478

Acrolein health effects.  

PubMed

Acrolein is a chemical used as an intermediate reactive aldehyde in chemical industry. It is used for synthesis of many organic substances, methionine production, and methyl chloride refrigerant. The general population is exposed to acrolein via smoking, second-hand smoke, exposure to wood and plastic smoke. Firefighters and population living or working in areas with heavy automotive traffic may expose to higher level of acrolein via inhalation of smoke or automotive exhaust. Degradation of acrolein in all environmental media occurs rapidly, therefore, environmental accumulation is not expected. Acrolein degrade in 6A days when applied to surface water, and it has not been found as a contaminant in municipal drinking water. Acrolein vapor may cause eye, nasal and respiratory tract irritations in low level exposure. A decrease in breathing rate was reported by volunteers acutely exposed to 0.3A ppm of acrolein. At similar level, mild nasal epithelial dysplasia, necrosis, and focal basal cell metaplasia have been observed in rats. The acrolein effects on gastrointestinal mucosa in the animals include epithelial hyperplasia, ulceration, and hemorrhage. The severity of the effects is dose dependent. Acrolein induces the respiratory, ocular, and gastrointestinal irritations by inducing the release of peptides in nerve terminals innervating these systems. Levels of acrolein between 22 and 249 ppm for 10 min induced a dose-related decrease in substance P (a short-chain polypeptide that functions as a neurotransmitter or neuromodulator). PMID:19028774

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

2008-08-01

479

Predicting Earthquake Effects  

NASA Astrophysics Data System (ADS)

Advances in the earth sciences and information technology have lead to dramatic improvements in our ability to respond to, as well as anticipate and mitigate, earthquake effects in our communities. The development of Geographic Information System (GIS) based tools such as ShakeMap and HAZUS have ushered in a new era of risk and emergency management. Real-time maps of strong ground motion, coupled with engineering-based descriptions of building and infrastructure inventory and vulnerability enable more accurate determinations of the location and severity of earthquake damage and the socio-economic consequences for emergency managers and officials following significant earthquakes. The ability to map the distribution and growth of seismic risk in the United States has long-term benefits for public policy as well. Long-term forecasts of seismic risk based on varying mitigation strategies can provide guidance for developing national and local earthquake policy. The successful performance of the Trans-Alaska pipeline during the 2002 Denali earthquake illustrates the dependence of performance-based engineering on the ability to predict earthquake effects (e.g., levels of strong ground motion, amounts of fault displacement or ground deformation). Being able to reduce the uncertainty in predicting these parameters has significant economic consequences and enables decision makers to more efficiently prioritize risk management strategies.

Nishenko, S.

2005-12-01