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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

Current heating induced spin Seebeck effect  

SciTech Connect

A measurement technique for the spin Seebeck effect is presented, wherein the normal metal layer used for its detection is exploited simultaneously as a resistive heater and thermometer. We show how the various contributions to the measured total signal can be disentangled, allowing to extract the voltage signal solely caused by the spin Seebeck effect. To this end, we performed measurements as a function of the external magnetic field strength and its orientation. We find that the effect scales linearly with the induced rise in temperature, as expected for the spin Seebeck effect.

Schreier, Michael, E-mail: michael.schreier@wmi.badw.de; Roschewsky, Niklas; Dobler, Erich; Meyer, Sibylle; Huebl, Hans; Goennenwein, Sebastian T. B. [Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, Garching (Germany)] [Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, Garching (Germany); Gross, Rudolf [Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, Garching (Germany) [Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, Garching (Germany); Physik-Department, Technische Universität München, Garching (Germany)

2013-12-09

3

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

2013-08-23

4

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

5

Exciton Seebeck effect in molecular systems  

NASA Astrophysics Data System (ADS)

We investigate the exciton dynamics under temperature difference with the hierarchical equations of motion. Through a nonperturbative simulation of the transient absorption of a heterogeneous trimer model, we show that the temperature difference causes exciton population redistribution and affects the exciton transfer time. It is found that one can reproduce not only the exciton population redistribution but also the change of the exciton transfer time induced by the temperature difference with a proper tuning of the site energies of the aggregate. In this sense, there exists a site energy shift equivalence for any temperature difference in a broad range. This phenomenon is similar to the Seebeck effect as well as spin Seebeck effect and can be named as exciton Seebeck effect.

Yan, Yun-An; Cai, Shaohong

2014-08-01

6

Time resolved spin Seebeck effect experiments  

NASA Astrophysics Data System (ADS)

In this Letter, we present the results of transient thermopower experiments, performed at room temperature on yttrium iron garnet/platinum bilayers. Upon application of a time-varying thermal gradient, we observe a characteristic low-pass frequency response of the ensuing thermopower voltage with cutoff frequencies of up to 37 MHz. We interpret our results in terms of the spin Seebeck effect, and argue that small wavevector magnons are of minor importance for the spin Seebeck effect in our thin film hybrid structures.

Roschewsky, Niklas; Schreier, Michael; Kamra, Akashdeep; Schade, Felix; Ganzhorn, Kathrin; Meyer, Sibylle; Huebl, Hans; Geprägs, Stephan; Gross, Rudolf; Goennenwein, Sebastian T. B.

2014-05-01

7

Time resolved spin Seebeck effect experiments  

SciTech Connect

In this Letter, we present the results of transient thermopower experiments, performed at room temperature on yttrium iron garnet/platinum bilayers. Upon application of a time-varying thermal gradient, we observe a characteristic low-pass frequency response of the ensuing thermopower voltage with cutoff frequencies of up to 37 MHz. We interpret our results in terms of the spin Seebeck effect, and argue that small wavevector magnons are of minor importance for the spin Seebeck effect in our thin film hybrid structures.

Roschewsky, Niklas, E-mail: niklas.roschewsky@wmi.badw.de; Schreier, Michael; Schade, Felix; Ganzhorn, Kathrin; Meyer, Sibylle; Geprägs, Stephan [Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, Garching (Germany); Kamra, Akashdeep [Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, Garching (Germany); Kavli Institute of Nanoscience, Delft University of Technology, Delft (Netherlands); Huebl, Hans; Goennenwein, Sebastian T. B. [Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, Garching (Germany); Nanosystems Initiative Munich (NIM), Munich (Germany); Gross, Rudolf [Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, Garching (Germany); Physik-Department, Technische Universität München, Garching (Germany); Nanosystems Initiative Munich (NIM), Munich (Germany)

2014-05-19

8

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

9

Photo-Seebeck effect of conjugated polymers  

NASA Astrophysics Data System (ADS)

Photo-Seebeck effect of conjugated polymers (CPs) from thiophenes and selenophenes were explored for a flexible energy conversion device. CP films were obtained by oxidative polymerizations, which grow conductive channels as polymerization proceeds. Through an optimized polymerization condition, highly conductive CP films were obtained with lower oxidation level. Taking advantage of their high electrical conductivity, the CP films were further explored as a transparent photo-thermo-electric film, because their absorption energy is easily controlled by the degree of oxidation or doping. Upon exposure to a near IR source, the CP films got heated, to result in temperature rise on a substrate. The generated heat was effectively converted into electricity to confirm a photo-Seebeck effect from the CP film under a light exposure. Efficient near-IR photothermal effect and heat to electric conversion have been realized in CP films that could benefit in exploiting multifunctional film displays, invisible NIR sensors, and hybrid energy harvesters.

Kim, B.; Lim, H.; Kim, E.

2014-08-01

10

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

11

Surface sensitivity of the spin Seebeck effect  

SciTech Connect

We have investigated the influence of the interface quality on the spin Seebeck effect (SSE) of the bilayer system yttrium iron garnet (YIG)–platinum (Pt). The magnitude and shape of the SSE is strongly influenced by mechanical treatment of the YIG single crystal surface. We observe that the saturation magnetic field (H{sub sat}{sup SSE}) for the SSE signal increases from 55.3?mT to 72.8?mT with mechanical treatment. The change in the magnitude of H{sub sat}{sup SSE} can be attributed to the presence of a perpendicular magnetic anisotropy due to the treatment induced surface strain or shape anisotropy in the Pt/YIG system. Our results show that the SSE is a powerful tool to investigate magnetic anisotropy at the interface.

Aqeel, A.; Vera-Marun, I. J.; Wees, B. J. van; Palstra, T. T. M., E-mail: t.t.m.palstra@rug.nl [Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen (Netherlands)

2014-10-21

12

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

13

Seebeck effects in two-dimensional spin transistors  

NASA Astrophysics Data System (ADS)

We consider a spin-orbit-coupled two-dimensional electron system under the influence of a thermal gradient externally applied to two attached reservoirs. We discuss the generated voltage bias (charge Seebeck effect), spin bias (spin Seebeck effect), and magnetization-dependent thermopower (magneto-Seebeck effect) in the ballistic regime of transport at linear response. We find that the charge thermopower is an oscillating function of both the spin-orbit strength and the quantum well width. We also observe that it is always negative for normal leads. We carefully compare the exact results for the linear response coefficients and a Sommerfeld approximation. When the contacts are ferromagnetic, we calculate the spin-resolved Seebeck coefficient for parallel and antiparallel magnetization configuration. Remarkably, the thermopower can change its sign by tuning the Fermi energy. This effect disappears when the Rashba coupling is absent. Additionally, we determine the magneto-Seebeck ratio, which shows dramatic changes in the presence of a the Rashba potential.

Alomar, M. I.; Serra, Llorenç; Sánchez, David

2015-02-01

14

Giant spin Seebeck effect in a non-magnetic material.  

PubMed

The spin Seebeck effect is observed when a thermal gradient applied to a spin-polarized material leads to a spatially varying transverse spin current in an adjacent non-spin-polarized material, where it gets converted into a measurable voltage. It has been previously observed with a magnitude of microvolts per kelvin in magnetically ordered materials, ferromagnetic metals, semiconductors and insulators. Here we describe a signal in a non-magnetic semiconductor (InSb) that has the hallmarks of being produced by the spin Seebeck effect, but is three orders of magnitude larger (millivolts per kelvin). We refer to the phenomenon that produces it as the giant spin Seebeck effect. Quantizing magnetic fields spin-polarize conduction electrons in semiconductors by means of Zeeman splitting, which spin-orbit coupling amplifies by a factor of ?25 in InSb. We propose that the giant spin Seebeck effect is mediated by phonon-electron drag, which changes the electrons' momentum and directly modifies the spin-splitting energy through spin-orbit interactions. Owing to the simultaneously strong phonon-electron drag and spin-orbit coupling in InSb, the magnitude of the giant spin Seebeck voltage is comparable to the largest known classical thermopower values. PMID:22785317

Jaworski, C M; Myers, R C; Johnston-Halperin, E; Heremans, J P

2012-07-12

15

Photo-Seebeck effect in ZnS  

NASA Astrophysics Data System (ADS)

To explore the thermoelectric transport nature of photo-excited carriers, the electrical conductivity and the Seebeck coefficient are measured under ultraviolet illumination in the wide-gap semiconductor ZnS near room temperature. The conductivity increases linearly as against the photon flux density with little dependence on temperature, indicating the conduction under illumination is mostly governed by the photo-doped carriers. We have found that, in high contrast to the temperature-insensitive photoconductivity, the temperature dependence of the Seebeck coefficient is dramatically varied by illumination, which is unexplained from a simple photo-doping effect for one majority carrier. Such a distinct difference in the transport quantities is rather understood within a two-carrier model, in which only the Seebeck coefficient is strongly affected by photo-excited minority carriers. The present result is also compared with earlier reports of the photo-Hall experiments to discuss the underlying photo-transport mechanism.

Shiraishi, Yuuka; Okazaki, Ryuji; Taniguchi, Hiroki; Terasaki, Ichiro

2015-03-01

16

Longitudinal spin Seebeck effect: from fundamentals to applications  

NASA Astrophysics Data System (ADS)

The spin Seebeck effect refers to the generation of spin voltage as a result of a temperature gradient in ferromagnetic or ferrimagnetic materials. When a conductor is attached to a magnet under a temperature gradient, the thermally generated spin voltage in the magnet injects a spin current into the conductor, which in turn produces electric voltage owing to the spin-orbit interaction. The spin Seebeck effect is of increasing importance in spintronics, since it enables direct generation of a spin current from heat and appears in a variety of magnets ranging from metals and semiconductors to insulators. Recent studies on the spin Seebeck effect have been conducted mainly in paramagnetic metal/ferrimagnetic insulator junction systems in the longitudinal configuration in which a spin current flowing parallel to the temperature gradient is measured. This ‘longitudinal spin Seebeck effect’ (LSSE) has been observed in various sample systems and exclusively established by separating the spin-current contribution from extrinsic artefacts, such as conventional thermoelectric and magnetic proximity effects. The LSSE in insulators also provides a novel and versatile pathway to thermoelectric generation in combination of the inverse spin-Hall effects. In this paper, we review basic experiments on the LSSE and discuss its potential thermoelectric applications with several demonstrations.

Uchida, K.; Ishida, M.; Kikkawa, T.; Kirihara, A.; Murakami, T.; Saitoh, E.

2014-08-01

17

How to Make a Cheap and Effective Seebeck Calorimeter  

Microsoft Academic Search

The Seebeck calorimeter is very effective in measuring heat generation over a wide range of power and with high sensitivity and stability. Such a device can be constructed cheaply and easily, although with considerable investment of time. A successful example is described.

Edmund Storms

2005-01-01

18

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

19

Enhanced thermoelectric performance and anomalous seebeck effects in topological insulators.  

PubMed

Improving the thermoelectric figure of merit zT is one of the greatest challenges in material science. The recent discovery of topological insulators (TIs) offers new promise in this prospect. In this work, we demonstrate theoretically that zT is strongly size dependent in TIs, and the size parameter can be tuned to enhance zT to be significantly greater than 1. Furthermore, we show that the lifetime of the edge states in TIs is strongly energy dependent, leading to large and anomalous Seebeck effects with an opposite sign to the Hall effect. These striking properties make TIs a promising material for thermoelectric science and technology. PMID:24949782

Xu, Yong; Gan, Zhongxue; Zhang, Shou-Cheng

2014-06-01

20

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. PMID:22390685

2012-01-01

21

Thermoelectric Seebeck effect in oxide-based resistive switching memory  

PubMed Central

Reversible resistive switching induced by an electric field in oxide-based resistive switching memory shows a promising application in future information storage and processing. It is believed that there are some local conductive filaments formed and ruptured in the resistive switching process. However, as a fundamental question, how electron transports in the formed conductive filament is still under debate due to the difficulty to directly characterize its physical and electrical properties. Here we investigate the intrinsic electronic transport mechanism in such conductive filament by measuring thermoelectric Seebeck effects. We show that the small-polaron hopping model can well describe the electronic transport process for all resistance states, although the corresponding temperature-dependent resistance behaviours are contrary. Moreover, at low resistance states, we observe a clear semiconductor–metal transition around 150?K. These results provide insight in understanding resistive switching process and establish a basic framework for modelling resistive switching behaviour. PMID:25141267

Wang, Ming; Bi, Chong; Li, Ling; Long, Shibing; Liu, Qi; Lv, Hangbing; Lu, Nianduan; Sun, Pengxiao; Liu, Ming

2014-01-01

22

Nonlinear thermokinetic phenomena due to the Seebeck effect.  

PubMed

We propose a novel mechanism to produce nonlinear thermokinetic vortex flows around a circular cylinder with ideally high thermal conductivity in an electrolyte. That is, the nonlinear thermokinetic slip velocity, which is proportional to the square of the temperature gradient [?(T)0(2)], is derived based on the electrolyte Seebeck effect, heat conduction equation, and Helmholtz–Smoluchowski formula. Different from conventional linear thermokinetic theory, our theory predicts that the inversion of the temperature gradient does not change the direction of the thermokinetic flows and thus a Janus particle using this phenomenon can move to the both hotter and colder regions in a temperature gradient field by changing the direction of its dielectric end. Our findings bridge the gap between the electro- and thermo-kinetic phenomena and provide an integrated physical viewpoint for the interface science. PMID:25003210

Sugioka, Hideyuki

2014-07-22

23

Thermoelectric Seebeck effect in oxide-based resistive switching memory.  

PubMed

Reversible resistive switching induced by an electric field in oxide-based resistive switching memory shows a promising application in future information storage and processing. It is believed that there are some local conductive filaments formed and ruptured in the resistive switching process. However, as a fundamental question, how electron transports in the formed conductive filament is still under debate due to the difficulty to directly characterize its physical and electrical properties. Here we investigate the intrinsic electronic transport mechanism in such conductive filament by measuring thermoelectric Seebeck effects. We show that the small-polaron hopping model can well describe the electronic transport process for all resistance states, although the corresponding temperature-dependent resistance behaviours are contrary. Moreover, at low resistance states, we observe a clear semiconductor-metal transition around 150?K. These results provide insight in understanding resistive switching process and establish a basic framework for modelling resistive switching behaviour. PMID:25141267

Wang, Ming; Bi, Chong; Li, Ling; Long, Shibing; Liu, Qi; Lv, Hangbing; Lu, Nianduan; Sun, Pengxiao; Liu, Ming

2014-01-01

24

Longitudinal spin Seebeck effect in various garnet ferrites  

NASA Astrophysics Data System (ADS)

The longitudinal spin Seebeck effect (LSSE) is investigated in various garnet ferrites Y3-xRxFe5-yMyO12 (R=Gd, Ca; M=Al, Mn, V, In, Zr) by means of the inverse spin Hall effect in Pt films. The magnitude of the LSSE voltage in the Pt/Y3-xRxFe5-yMyO12 samples is found to be enhanced with increasing concentration of Fe in the garnet ferrites, which can be explained by a change in the spin-mixing conductance at the Pt/Y3-xRxFe5-yMyO12 interfaces. We also investigate the dependence of the LSSE voltage on macroscopic magnetic parameters of Y3-xRxFe5-yMyO12. The experimental results show that the LSSE voltage in the Pt/Y3-xRxFe5-yMyO12 samples has a positive correlation with the Curie temperature and the saturation magnetization, but no clear correlation with the gyromagnetic ratio and the Gilbert damping constant of the samples.

Uchida, K.; Nonaka, T.; Kikkawa, T.; Kajiwara, Y.; Saitoh, E.

2013-03-01

25

Large spin Seebeck effects in zigzag-edge silicene nanoribbons  

SciTech Connect

Using the first-principles methods, we investigate the thermospin properties of a two-probe model based on zigzag-edge silicene nanoribbons (ZSiNRs). Compared with the odd-width ZSiNRs, the spin Seebeck coefficient of the even-width ZSiNRs is obviously enhanced at room temperature. This fact is attributed to a nearly perfect symmetry of the linear conductance gap with the different spin index with respect to the Fermi level induced by the different parity of the wave functions. More interestingly, the corresponding charge Seebeck coefficient is near zero. Therefore, when a thermal bias is presented in the even-width ZSiNRs, a nearly pure spin current is achieved. Meanwhile, the spin polarization of the current approaches infinite.

Yang, Xi-Feng; Liu, Yu-Shen, E-mail: ysliu@cslg.edu.cn; Feng, Jin-Fu, E-mail: fengjinfu@cslg.edu.cn [College of Physics and Engineering, Changshu Institute of Technology and Jiangsu Laboratory of Advanced Functional materials, Changshu 215500 (China); Wang, Xue-Feng, E-mail: xf-wang1969@yahoo.com [College of Physics, Optoelectronics and Energy, Soochow University, Suzhou 215006 (China)

2014-08-15

26

Large spin Seebeck effects in zigzag-edge silicene nanoribbons  

NASA Astrophysics Data System (ADS)

Using the first-principles methods, we investigate the thermospin properties of a two-probe model based on zigzag-edge silicene nanoribbons (ZSiNRs). Compared with the odd-width ZSiNRs, the spin Seebeck coefficient of the even-width ZSiNRs is obviously enhanced at room temperature. This fact is attributed to a nearly perfect symmetry of the linear conductance gap with the different spin index with respect to the Fermi level induced by the different parity of the wave functions. More interestingly, the corresponding charge Seebeck coefficient is near zero. Therefore, when a thermal bias is presented in the even-width ZSiNRs, a nearly pure spin current is achieved. Meanwhile, the spin polarization of the current approaches infinite.

Yang, Xi-Feng; Liu, Yu-Shen; Feng, Jin-Fu; Wang, Xue-Feng

2014-08-01

27

Observation of the spin Seebeck effect in epitaxial Fe3O4 thin films  

NASA Astrophysics Data System (ADS)

We report the experimental observation of the spin Seebeck effect in magnetite thin films. The signal observed at temperatures above the Verwey transition is a contribution from both the anomalous Nernst (ANE) and spin Seebeck (SSE) effects. The contribution from the ANE of the Fe3O4 layer to the SSE is found to be negligible due to the resistivity difference between Fe3O4 and Pt layers. Below the Verwey transition, the SSE is free from the ANE of the ferromagnetic layer and it is also found to dominate over the ANE due to magnetic proximity effect on the Pt layer.

Ramos, R.; Kikkawa, T.; Uchida, K.; Adachi, H.; Lucas, I.; Aguirre, M. H.; Algarabel, P.; Morellón, L.; Maekawa, S.; Saitoh, E.; Ibarra, M. R.

2013-02-01

28

Photo-Seebeck effect in tetragonal PbO single crystals  

SciTech Connect

We report the observation of photo-Seebeck effect in tetragonal PbO crystals. The photo-induced carriers contribute to the transport phenomena, and consequently the electrical conductivity increases and the Seebeck coefficient decreases with increasing photon flux density. A parallel-circuit model is used to evaluate the actual contributions of photo-excited carriers from the measured transport data. The photo-induced carrier concentration estimated from the Seebeck coefficient increases almost linearly with increasing photon flux density, indicating a successful photo-doping effect on the thermoelectric property. The mobility decreases by illumination but the reduction rate strongly depends on the illuminated photon energy. Possible mechanisms of such photon-energy-dependent mobility are discussed.

Mondal, P. S.; Okazaki, R.; Taniguchi, H.; Terasaki, I. [Department of Physics, Nagoya University, Nagoya 464-8602 (Japan)

2013-11-07

29

Communication Role of moisture in the Seebeck effect in cement-based materials  

E-print Network

.D.L. Chung* Composite Materials Research Laboratory, University at Buffalo, State University of New York, Buffalo, NY 14260-4400, USA Received 12 June 2003; accepted 24 May 2004 Abstract Moisture in the form of liquid water contributes little, if any, to the Seebeck effect in cement-based materials. Moisture loss

Chung, Deborah D.L.

30

Use of a Very Sensitive Seebeck Calorimeter to Study the Pons-Fleischmann and Letts Effects  

Microsoft Academic Search

Characteristics of a commercial Seebeck calorimeter are described. This very stable instrument is applied to a study of the Pons-Fleischmann effect using a palladium anode and a platinum cathode. The use of a laser to stimulate anomalous heat production (the Letts effect) is also described. Positive results were obtained for both effects and these reveal important aspects of the nuclear-active-environment.

Edmund Storms

2005-01-01

31

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

32

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

PubMed Central

Thermoelectric effects in magnetic tunnel junctions are promising to serve as the basis for logic devices or memories in a ”green” information technology. However, up to now the readout contrast achieved with Seebeck effects was magnitudes smaller compared to the well-established tunnel magnetoresistance effect. Here, we resolve this problem by demonstrating that the tunnel magneto-Seebeck effect (TMS) in CoFeB/MgO/CoFeB tunnel junctions can be switched on to a logic “1” state and off to “0” by simply changing the magnetic state of the CoFeB electrodes. This new functionality is achieved by combining a thermal gradient and an electric field. Our results show that the signal crosses zero and can be adjusted by tuning a bias voltage that is applied between the electrodes of the junction; hence, the name of the effect is bias-enhanced tunnel magneto-Seebeck effect (bTMS). Via the spin- and energy-dependent transmission of electrons in the junction, the bTMS effect can be configured using the bias voltage with much higher control than the tunnel magnetoresistance and even completely suppressed for only one magnetic configuration. Moreover, our measurements are a step towards the experimental realization of high TMS ratios without additional bias voltage, which are predicted for specific Co-Fe compositions. PMID:25755010

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

2015-01-01

33

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

NASA Astrophysics Data System (ADS)

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

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

2015-03-01

34

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

PubMed

Thermoelectric effects in magnetic tunnel junctions are promising to serve as the basis for logic devices or memories in a "green" information technology. However, up to now the readout contrast achieved with Seebeck effects was magnitudes smaller compared to the well-established tunnel magnetoresistance effect. Here, we resolve this problem by demonstrating that the tunnel magneto-Seebeck effect (TMS) in CoFeB/MgO/CoFeB tunnel junctions can be switched on to a logic "1" state and off to "0" by simply changing the magnetic state of the CoFeB electrodes. This new functionality is achieved by combining a thermal gradient and an electric field. Our results show that the signal crosses zero and can be adjusted by tuning a bias voltage that is applied between the electrodes of the junction; hence, the name of the effect is bias-enhanced tunnel magneto-Seebeck effect (bTMS). Via the spin- and energy-dependent transmission of electrons in the junction, the bTMS effect can be configured using the bias voltage with much higher control than the tunnel magnetoresistance and even completely suppressed for only one magnetic configuration. Moreover, our measurements are a step towards the experimental realization of high TMS ratios without additional bias voltage, which are predicted for specific Co-Fe compositions. PMID:25755010

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

2015-01-01

35

Spin-resolved Fano resonances induced large spin Seebeck effects in graphene-carbon-chain junctions  

SciTech Connect

We propose a high-efficiency thermospin device constructed by a carbon atomic chain sandwiched between two ferromagnetic (FM) zigzag graphene nanoribbon electrodes. In the low-temperature regime, the magnitude of the spin figure of merit is nearly equal to that of the corresponding charge figure of merit. This is attributed to the appearances of spin-resolved Fano resonances in the linear conductance spectrum resulting from the quantum interference effects between the localized states and the expanded states. The spin-dependent Seebeck effect is obviously enhanced near these Fano resonances with the same spin index; meanwhile, the Seebeck effect of the other spin component has a smaller value due to the smooth changing of the linear conductance with the spin index. Thus, a large spin Seebeck effect is achieved, and the magnitude of the spin figure of merit can reach 1.2 at T?=?25?K. Our results indicate that the FM graphene-carbon-chain junctions can be used to design the high-efficiency thermospin devices.

Liu, Yu-Shen; Zhang, Xue; Feng, Jin-Fu, E-mail: fengjinfu@cslg.edu.cn [Jiangsu Laboratory of Advanced Functional Materials and College of Physics and Engineering, Changshu Institute of Technology, Changshu 215500 (China); Wang, Xue-Feng, E-mail: xf-wang1969@yahoo.com [Department of Physics, Soochow University, Suzhou 215006 (China)

2014-06-16

36

Seebeck coefficient of one electron  

SciTech Connect

The Seebeck coefficient of one electron, driven thermally into a semiconductor single-electron box, is investigated theoretically. With a finite temperature difference ?T between the source and charging island, a single electron can charge the island in equilibrium, directly generating a Seebeck effect. Seebeck coefficients for small and finite ?T are calculated and a thermally driven Coulomb staircase is predicted. Single-electron Seebeck oscillations occur with increasing ?T, as one electron at a time charges the box. A method is proposed for experimental verification of these effects.

Durrani, Zahid A. K., E-mail: z.durrani@imperial.ac.uk [Department of Electrical and Electronic Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ (United Kingdom)

2014-03-07

37

Effect of phonon transport on the Seebeck coefficient and thermal conductivity of silicon nanowire arrays  

NASA Astrophysics Data System (ADS)

Thermoelectrics enable solid-state conversion of heat to electricity by the Seebeck effect, but must provide scalable and cost-effective technology for practical waste heat harvesting. This dissertation explores the thermoelectric properties of electrochemically etched silicon nanowires through experiments, complemented by charge and thermal transport theories. Electrolessly etched silicon nanowires show anomalously low thermal conductivity that has been attributed to the increased scattering of heat conducting phonons from the surface disorder introduced by etching. The reduction is below the incoherent limit for phonon scattering at the boundary, the so-called Casimir limit. A new model of partially coherent phonon transport shows that correlated multiple scattering of phonons off resonantly matched rough surfaces can indeed lead to thermal conductivity below the Casimir limit. Using design guidelines from the theory, silicon nanowires of controllable surface roughness are fabricated using metal-assisted chemical etching. Extensive characterization of the nanowire surfaces using transmission electron microscopy provides surface roughness parameters that are important in testing transport theories. The second part of the dissertation focuses on the implications of increased phonon scattering on the Seebeck coefficient, which is a cumulative effect of non-equilibrium amongst charge carriers and phonons. A novel frequency-domain technique enables simultaneous measurements of the Seebeck coefficient and the thermal conductivity of nanowire arrays. The frequency response measurements isolate the parasitic contributions thus improving upon existing techniques for cross-plane thermoelectric measurements. While the thermal conductivity of nanowires reduces significantly with increased roughness, there is also a significant reduction in the Seebeck coefficient over a wide range of doping. Theoretical fitting of the data reveals that such reduction results from the annihilation of phonon drag in nanowires due to phonon boundary scattering. By exploring the effect of surface roughness and employing lattice non-equilibrium theories, the measurements are able to distinguish between long wavelength phonons that contribute to phonon drag and shorter wavelengths that contribute to heat conduction near room temperature. Phonon drag quenching in nanostructures has implications beyond silicon and this thesis paves the way toward spectrally selective phonon scattering for improving nanoscale thermoelectrics.

Sadhu, Jyothi Swaroop

38

Enhanced spin Seebeck effect in a germanene p-n junction  

NASA Astrophysics Data System (ADS)

Spin Seebeck effect in a germanene p-n junction is studied by using the nonequilibrium Green's function method combined with the tight-binding Hamiltonian. We find that the thermal bias ?T can generate spin thermopower when a local exchange field is applied on one edge of the germanene nano-ribbon. The magnitude of the spin thermopower can be modulated by the potential drop across the two terminals of the p-n junction. When the value of the potential drop is smaller than the spin-orbit interaction strength, the spin thermopower is enhanced by two orders of magnitude larger as compared to the case of zero p-n voltage. Optimal temperature corresponding to maximum spin thermopower is insensitive to the potential drop. In the p-n region, maximum spin thermopower can be obtained at relatively higher temperatures. When the value of the potential drop is larger than that of the spin-orbit interaction, however, the spin Seebeck effect decays rapidly with increasing potential drop or temperature. By optimizing the structure parameters, the magnitude of the spin thermopower can be remarkably enhanced due to the coexistence of the exchange field and the potential drop.

Zheng, Jun; Chi, Feng; Guo, Yong

2014-12-01

39

Surface polarization enhanced Seebeck effects in vertical multi-layer metal-polymer-metal thin-film devices.  

PubMed

We explore a new mechanism to develop Seebeck effects by using temperature-dependent surface polarization based on vertical multi-layer Al-P3HT:PCBM-Al thin-film devices. Here, the temperature-dependent surface polarization functions as an additional driving force, as compared with the traditional driving force from the entropy difference, to diffuse the charge carriers under a temperature gradient towards the development of Seebeck effects. The temperature-dependent surface polarization is essentially generated by both the thermally dependent polarization through the charge-phonon coupling mechanism and the thermally modulated interface dipoles by Fermi electrons. It is noted that the entropy difference often causes an inverse relationship between the Seebeck coefficient and electrical conductivity in thermoelectric developments. However, this temperature-dependent surface polarization provides a mechanism allowing a co-operative relationship between the Seebeck coefficient and electrical conductivity. We demonstrate simultaneously the enhanced Seebeck coefficient and electrical conductivity by using the dielectric interface through the temperature-dependent surface polarization to diffuse charge carriers in the Al-MoO3-P3HT:PCBM-Al thin-film device. PMID:25213557

Liu, Qing; Hu, Dehua; Wang, Hongfeng; Stanford, Michael; Wang, Hsin; Hu, Bin

2014-10-28

40

Enhancement of spin-Seebeck effect by inserting ultra-thin Fe70Cu30 interlayer  

NASA Astrophysics Data System (ADS)

We report the longitudinal spin-Seebeck effects (LSSEs) for Pt/Fe70Cu30/BiY2Fe5O12 (BiYIG) and Pt/BiYIG devices. The LSSE voltage was found to be enhanced by inserting an ultra-thin Fe70Cu30 interlayer. This enhancement decays sharply with increasing the Fe70Cu30 thickness, suggesting that it is not due to bulk phenomena, such as a superposition of conventional thermoelectric effects, but due to interface effects related to the Fe70Cu30 interlayer. Combined with control experiments using Pt/Fe70Cu30 devices, we conclude that the enhancement of the LSSE voltage in the Pt/Fe70Cu30/BiYIG devices is attributed to the improvement of the spin-mixing conductance at the Pt/BiYIG interfaces.

Kikuchi, D.; Ishida, M.; Uchida, K.; Qiu, Z.; Murakami, T.; Saitoh, E.

2015-02-01

41

Investigation of the magnetic properties of insulating thin films using the longitudinal spin Seebeck effect  

NASA Astrophysics Data System (ADS)

The longitudinal spin Seebeck effect is used as a detector for the magnetic properties and switching characteristics of magnetic thin insulating films. We use a 300 nm and a 20 nm thick Yttrium Iron Garnet (YIG, Y3Fe5O12) film prepared by pulsed laser deposition and afterwards coated by platinum for the detection of the thermally excited magnons by the inverse spin Hall effect. The inverse spin Hall signals reveal a magnetic uniaxial anisotropy along the direction of the platinum stripe in the thicker film. For the thin film we find a more isotropic behavior, which is complementarily observed using the magnetoresistance occurring at the platinum/YIG interface. We explain our results on the basis of x-ray diffraction data, which reveal a miscut of the substrate and film surface and an expansion of the YIG lattice. Both findings favor a growth-induced magnetic anisotropy that we observe.

Kehlberger, A.; Jakob, G.; Onbasli, M. C.; Kim, D. H.; Ross, C. A.; Kläui, M.

2014-05-01

42

Investigation of the magnetic properties of insulating thin films using the longitudinal spin Seebeck effect  

SciTech Connect

The longitudinal spin Seebeck effect is used as a detector for the magnetic properties and switching characteristics of magnetic thin insulating films. We use a 300 nm and a 20?nm thick Yttrium Iron Garnet (YIG, Y{sub 3}Fe{sub 5}O{sub 12}) film prepared by pulsed laser deposition and afterwards coated by platinum for the detection of the thermally excited magnons by the inverse spin Hall effect. The inverse spin Hall signals reveal a magnetic uniaxial anisotropy along the direction of the platinum stripe in the thicker film. For the thin film we find a more isotropic behavior, which is complementarily observed using the magnetoresistance occurring at the platinum/YIG interface. We explain our results on the basis of x-ray diffraction data, which reveal a miscut of the substrate and film surface and an expansion of the YIG lattice. Both findings favor a growth-induced magnetic anisotropy that we observe.

Kehlberger, A., E-mail: kehlberg@uni-mainz.de; Jakob, G.; Kläui, M. [Institute of Physics, University of Mainz, 55099 Mainz (Germany); Onbasli, M. C.; Kim, D. H.; Ross, C. A. [Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

2014-05-07

43

Large-tunneling anisotropic magneto-Seebeck effect in a CoPt/MgO/Pt tunnel junction  

NASA Astrophysics Data System (ADS)

We theoretically investigate the tunneling anisotropic magneto-Seebeck effect in a realistically modeled CoPt /MgO /Pt tunnel junction using coherent transport calculations. For comparison we study the tunneling magneto-Seebeck effect in CoPt /MgO /CoPt as well. We find that the magneto-Seebeck ratio of CoPt /MgO /Pt exceeds that of CoPt /MgO /CoPt for small barrier widths, reaching 175 % at room temperature. This provides a sharp contrast to the magnetoresistance, in which CoPt /MgO /CoPt performs better by one order of magnitude for all barrier widths. Thus, by switching from two ferromagnetic layers to one (so that spin-orbit coupling alone governs the magnetic transport anisotropy), the magnetoresistance ratio diminishes while the magneto-Seebeck ratio remains comparable or improves considerably. We therefore demonstrate that magnetic tunability can increase when caused solely by spin-orbit coupling. This result sheds light on the role that spin-orbit coupling plays in magnetically tuning the properties of tunnel junctions.

Amin, V. P.; Zemen, J.; Železný, J.; Jungwirth, T.; Sinova, Jairo

2014-10-01

44

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

45

Robust longitudinal spin-Seebeck effect in Bi-YIG thin films.  

PubMed

In recent years, the coupling of magnetic insulators (bismuth-doped yttrium iron garnet, Bi-YIG) with platinum has garnered significant interest in spintronics research due to applicability as spin-current-driven thermoelectric coatings. These coatings bridge the gap between spintronics technologies and thermoelectric materials, providing a novel means of transforming waste heat into electricity. However, there remain questions regarding the origins of the spin-Seebeck effect (SSE) as well as claims that observed effects are a manifestation of magnetic proximity effects, which would induce magnetic behavior in platinum. Herewith we provide support that the voltages observed in the Bi-YIG/Pt films are purely SSE voltages. We reaffirm claims that magnon transport theory provides an ample basis for explaining SSE behavior. Finally, we illustrate the advantages of pulsed-laser deposition, as these Bi-YIG films possess large SSE voltages (even in absence of an external magnetic field), as much as twice those of films fabricated via solution-based methods. PMID:24651124

Siegel, Gene; Prestgard, Megan Campbell; Teng, Shiang; Tiwari, Ashutosh

2014-01-01

46

Robust longitudinal spin-Seebeck effect in Bi-YIG thin films  

NASA Astrophysics Data System (ADS)

In recent years, the coupling of magnetic insulators (bismuth-doped yttrium iron garnet, Bi-YIG) with platinum has garnered significant interest in spintronics research due to applicability as spin-current-driven thermoelectric coatings. These coatings bridge the gap between spintronics technologies and thermoelectric materials, providing a novel means of transforming waste heat into electricity. However, there remain questions regarding the origins of the spin-Seebeck effect (SSE) as well as claims that observed effects are a manifestation of magnetic proximity effects, which would induce magnetic behavior in platinum. Herewith we provide support that the voltages observed in the Bi-YIG/Pt films are purely SSE voltages. We reaffirm claims that magnon transport theory provides an ample basis for explaining SSE behavior. Finally, we illustrate the advantages of pulsed-laser deposition, as these Bi-YIG films possess large SSE voltages (even in absence of an external magnetic field), as much as twice those of films fabricated via solution-based methods.

Siegel, Gene; Prestgard, Megan Campbell; Teng, Shiang; Tiwari, Ashutosh

2014-03-01

47

Robust longitudinal spin-Seebeck effect in Bi-YIG thin films  

PubMed Central

In recent years, the coupling of magnetic insulators (bismuth-doped yttrium iron garnet, Bi-YIG) with platinum has garnered significant interest in spintronics research due to applicability as spin-current-driven thermoelectric coatings. These coatings bridge the gap between spintronics technologies and thermoelectric materials, providing a novel means of transforming waste heat into electricity. However, there remain questions regarding the origins of the spin-Seebeck effect (SSE) as well as claims that observed effects are a manifestation of magnetic proximity effects, which would induce magnetic behavior in platinum. Herewith we provide support that the voltages observed in the Bi-YIG/Pt films are purely SSE voltages. We reaffirm claims that magnon transport theory provides an ample basis for explaining SSE behavior. Finally, we illustrate the advantages of pulsed-laser deposition, as these Bi-YIG films possess large SSE voltages (even in absence of an external magnetic field), as much as twice those of films fabricated via solution-based methods. PMID:24651124

Siegel, Gene; Prestgard, Megan Campbell; Teng, Shiang; Tiwari, Ashutosh

2014-01-01

48

Room-temperature synthesis and seebeck effect of lead chalcogenide nanocubes  

NASA Astrophysics Data System (ADS)

The pure face-centered cubic lead chalcogenide nanocubes have been synthesized in hydrazine hydrate saturated alkaline solution under the conditions of room temperature, ambient pressure, and a short growth time, with advantages of being simple, high yield and cost effective. The size of PbS, PbSe and PbTe nanocubes is 200-300 nm, 50-120 nm, and 30-60 nm, respectively. It was found that the growth steps of lead chalcogenides (especially PbTe) nanostructures could be controlled in the strong hydrazine hydrate alkaline environment. Thermoelectric properties of the films made from the PbS, PbSe and PbTe nanocubes have been investigated comparatively for the first time. The results indicate that the room-temperature Seebeck coefficient value of the PbS, PbSe and PbTe nanocube films is up to 154.4 ?V/K, 199.8 ?V/K and 451.1 ?V/K, respectively.

Wan, Buyong; Hu, Chenguo; Xi, Yi; Xu, Jing; He, Xiaoshan

2010-01-01

49

A novel strongly correlated electronic thin-film laser energy/power meter based on anisotropic Seebeck effect  

NASA Astrophysics Data System (ADS)

Strongly correlated electronic (SCE) materials including high-temperature superconducting cuprate and colossal magnetoresistance manganite thin films demonstrate tremendous anisotropic Seebeck effect which makes them very promising for developing high-performance laser detectors. In this work, laser-induced thermoelectric voltage (LITV) signals with nanosecond response time have been measured in SCE La1- x Pb x MnO3 thin films based on anisotropic Seebeck effect at room temperature. The magnitude of the LITV signals increases linearly with laser energy/power density in a wide range of laser wavelengths from ultraviolet, visible to infrared based on which a novel SCE thin-film laser energy/power meter has been developed.

Zhang, G.-Y.; Zhang, H.; Tan, S.-L.; Zhang, P.-X.; Tseng, T.-Y.; Habermeier, H.-U.; Lin, C.-T.; Singjai, P.

2014-09-01

50

Unambiguous separation of the inverse spin Hall and anomalous Nernst effects within a ferromagnetic metal using the spin Seebeck effect  

NASA Astrophysics Data System (ADS)

The longitudinal spin Seebeck effect is measured on the ferromagnetic insulator Fe3O4 with the ferromagnetic metal Co0.2Fe0.6B0.2 (CoFeB) as the spin detector. By using a non-magnetic spacer material between the two materials (Ti), it is possible to decouple the two ferromagnetic materials and directly observe pure spin flow from Fe3O4 into CoFeB. It is shown that in a single ferromagnetic metal, the inverse spin Hall effect (ISHE) and anomalous Nernst effect (ANE) can occur simultaneously with opposite polarity. Using this and the large difference in the coercive fields between the two magnets, it is possible to unambiguously separate the contributions of the spin Seebeck effect from the ANE and observe the degree to which each effect contributes to the total response. These experiments show conclusively that the ISHE and ANE in CoFeB are separate phenomena with different origins and can coexist in the same material with opposite response to a thermal gradient.

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

2014-09-01

51

Unambiguous separation of the inverse spin Hall and anomalous Nernst effects within a ferromagnetic metal using the spin Seebeck effect  

SciTech Connect

The longitudinal spin Seebeck effect is measured on the ferromagnetic insulator Fe{sub 3}O{sub 4} with the ferromagnetic metal Co{sub 0.2}Fe{sub 0.6}B{sub 0.2} (CoFeB) as the spin detector. By using a non-magnetic spacer material between the two materials (Ti), it is possible to decouple the two ferromagnetic materials and directly observe pure spin flow from Fe{sub 3}O{sub 4} into CoFeB. It is shown that in a single ferromagnetic metal, the inverse spin Hall effect (ISHE) and anomalous Nernst effect (ANE) can occur simultaneously with opposite polarity. Using this and the large difference in the coercive fields between the two magnets, it is possible to unambiguously separate the contributions of the spin Seebeck effect from the ANE and observe the degree to which each effect contributes to the total response. These experiments show conclusively that the ISHE and ANE in CoFeB are separate phenomena with different origins and can coexist in the same material with opposite response to a thermal gradient.

Wu, Stephen M., E-mail: swu@anl.gov; Hoffman, Jason; Pearson, John E.; Bhattacharya, Anand [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States)

2014-09-01

52

Spin Seebeck power generators  

SciTech Connect

We derive expressions for the efficiency and figure of merit of two spin caloritronic devices based on the spin Seebeck effect (SSE), i.e., the generation of spin currents by a temperature gradient. The inverse spin Hall effect is conventionally used to detect the SSE and offers advantages for large area applications. We also propose a device that converts spin current into electric one by means of a spin-valve detector, which scales favorably to small sizes and approaches a figure of merit of 0.5 at room temperature.

Cahaya, Adam B.; Tretiakov, O. A. [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Bauer, Gerrit E. W. [Institute for Materials Research and WPI-AIMR, Tohoku University, Sendai 980-8577 (Japan); Kavli Institute of NanoScience, TU Delft Lorentzweg 1, 2628 CJ Delft (Netherlands)

2014-01-27

53

Theoretical Expectation of Large Seebeck Effect in PtAs2 and PtP2  

NASA Astrophysics Data System (ADS)

Motivated by a recent observation of good thermoelectric properties in PtSb2, we theoretically study related pyrites in an attempt to seek for a material that overcomes the suppression of the Seebeck coefficient at high temperatures. We find that PtAs2 and PtP2 are good candidates, where their larger band gaps than that of PtSb2 combined with the overall flatness of their band top gives rise to a monotonically increasing Seebeck coefficient up to high temperatures. This expectation has been confirmed quite recently for hole-doped PtAs2, where a very large power factor of ˜65 µW cm?1 K?2 at T = 400 K is observed.

Mori, Kouta; Usui, Hidetomo; Sakakibara, Hirofumi; Kuroki, Kazuhiko

2014-02-01

54

Effect of silicide/silicon hetero-junction structure on thermal conductivity and Seebeck coefficient.  

PubMed

We fabricated a thermoelectric device with a silicide/silicon laminated hetero-structure by using RF sputtering and rapid thermal annealing. The device was observed to have Ohmic characteristics by I-V measurement. The temperature differences and Seebeck coefficients of the proposed silicide/silicon laminated and bulk structure were measured. The laminated thermoelectric device shows suppression of heat flow from the hot to cold side. This is supported by the theory that the atomic mass difference between silicide and silicon creates a scattering center for phonons. The major impact of our work is that phonon transmission is suppressed at the interface between silicide and silicon without degrading electrical conductivity. The estimated thermal conductivity of the 3-layer laminated device is 126.2 +/- 3.7 W/m. K. Thus, by using the 3-layer laminated structure, thermal conductivity is reduced by around 16% compared to bulk silicon. However, the Seebeck coefficient of the thermoelectric device is degraded compared to that of bulk silicon. It is understood that electrical conductivity is improved by using silicide as a scattering center. PMID:24266143

Choi, Wonchul; Park, Young-Sam; Hyun, Younghoon; Zyung, Taehyoung; Kim, Jaehyeon; Kim, Soojung; Jeon, Hyojin; Shin, Mincheol; Jang, Moongyu

2013-12-01

55

Half-metallic properties, single-spin negative differential resistance, and large single-spin Seebeck effects induced by chemical doping in zigzag-edged graphene nanoribbons  

NASA Astrophysics Data System (ADS)

Ab initio calculations combining density-functional theory and nonequilibrium Green's function are performed to investigate the effects of either single B atom or single N atom dopant in zigzag-edged graphene nanoribbons (ZGNRs) with the ferromagnetic state on the spin-dependent transport properties and thermospin performances. A spin-up (spin-down) localized state near the Fermi level can be induced by these dopants, resulting in a half-metallic property with 100% negative (positive) spin polarization at the Fermi level due to the destructive quantum interference effects. In addition, the highly spin-polarized electric current in the low bias-voltage regime and single-spin negative differential resistance in the high bias-voltage regime are also observed in these doped ZGNRs. Moreover, the large spin-up (spin-down) Seebeck coefficient and the very weak spin-down (spin-up) Seebeck effect of the B(N)-doped ZGNRs near the Fermi level are simultaneously achieved, indicating that the spin Seebeck effect is comparable to the corresponding charge Seebeck effect.

Yang, Xi-Feng; Zhou, Wen-Qian; Hong, Xue-Kun; Liu, Yu-Shen; Wang, Xue-Feng; Feng, Jin-Fu

2015-01-01

56

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

57

The Low-Temperature Seebeck Coefficient in Insulators  

NASA Astrophysics Data System (ADS)

We show the existence of a space-charge effect in the measurement of the low-temperature Seebeck coefficient in insulators. The Seebeck coefficient is obtained by measurement of the voltage due to a temperature gradient . The space-charge effect makes the voltage go to zero in insulators, even if the Seebeck coefficient does not vanish. We propose that the Seebeck coefficient does not actually vanish in insulators, contrary to common belief. We also propose that variable-range hopping is not observed in conductivity measurements.

Mahan, G. D.

2015-01-01

58

Joule heating-induced coexisted spin Seebeck effect and spin Hall magnetoresistance in the platinum/Y{sub 3}Fe{sub 5}O{sub 12} structure  

SciTech Connect

Spin Seebeck effect (SSE) and spin Hall magnetoresistance (SMR) are observed simultaneously in the Pt/Y{sub 3}Fe{sub 5}O{sub 12} hybrid structure when thermal gradient is produced by Joule heating. According to their dependences on applied current, these two effects can be separated. Their dependence on heating power and magnetic field is systematically studied. With the increase of heating power, the SSE enhances linearly, whereas the SMR decreases slowly. The origin of the spin currents is further analyzed. The heating power dependences of the spin currents associated with the SSE and the SMR are found to be different.

Wang, W. X. [State Key Laboratory of Advance Technology for Material Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China); Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Wang, S. H.; Zou, L. K.; Cai, J. W.; Sun, J. R., E-mail: jrsun@iphy.ac.cn, E-mail: sun-zg@whut.edu.cn [Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Sun, Z. G. [State Key Laboratory of Advance Technology for Material Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China)

2014-11-03

59

Reference Material for Seebeck Coefficients  

NASA Astrophysics Data System (ADS)

This paper describes a measurement method and a measuring system to determine absolute Seebeck coefficients of thermoelectric bulk materials with the aim of establishing reference materials for Seebeck coefficients. Reference materials with known thermoelectric properties are essential to allow a reliable benchmarking of different thermoelectric materials for application in thermoelectric generators to convert thermal into electrical energy or vice versa. A temperature gradient (1 to 8) K is induced across the sample, and the resulting voltage is measured by using two differential Au/Pt thermocouples. On the basis of the known absolute Seebeck coefficients of Au and Pt, the unknown Seebeck coefficient of the sample is calculated. The measurements are performed in inert atmospheres and at low pressure (30 to 60) mbar in the temperature range between 300 K and 860 K. The measurement results of the Seebeck coefficients of metallic and semiconducting samples are presented. Achievable relative measurement uncertainties of the Seebeck coefficient are on the order of a few percent.

Edler, F.; Lenz, E.; Haupt, S.

2015-03-01

60

The Method and Results Using Seebeck Calorimetry  

Microsoft Academic Search

The characteristics of and errors associated with Seebeck calorimeters, as applied to the Fleischmann-Pons Effect, are described. This type of calorimeter as well as a flow type calorimeter were used to measured apparent excess energy from the same sample of platinum plated with palladium and other materials.

Edmund Storms

61

Nanoscale Spin Seebeck Rectifier: Controlling Thermal Spin Transport across Insulating Magnetic Junctions with Localized Spin  

NASA Astrophysics Data System (ADS)

The spin Seebeck effect is studied across a charge insulating magnetic junction, in which thermal-spin conjugate transport is assisted by the exchange interactions between the localized spin in the center and electrons in metallic leads. We show that, in contrast with bulk spin Seebeck effect, the figure of merit of such nanoscale thermal-spin conversion can be infinite, leading to the ideal Carnot efficiency in the linear response regime. We also find that in the nonlinear spin Seebeck transport regime the device possesses the asymmetric and negative differential spin Seebeck effects. In the last, the situations with leaking electron tunneling are also discussed. This nanoscale thermal spin rectifier, by tuning the junction parameters, can act as a spin Seebeck diode, spin Seebeck transistor, and spin Seebeck switch, which could have substantial implications for flexible thermal and information control in molecular spin caloritronics.

Ren, Jie; Fransson, Jonas; Zhu, Jian-Xin

2014-06-01

62

The Seebeck coefficient of iodine  

E-print Network

THE SEEBECK COEFFICIENT OF IODINE A Thesis By DOMINGO M. PEREZ-F~EZ Submitted to the Graduate College of the Texas A&M University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE January 1968 Major Subject...; Physics THE SEEBECK COEFFICIENT OF IODINE A Thesis By DOMINGO M. PEREZ-FERNANDEZ Approved as to style and content by: ( airman of Co ittee) (Member) (Head of Depa ment) (Member) ( ember) (Member) (Member) January 1968 ACKNONLEDGEMENTS...

Perez-Fernandez, Domingo Miguel

1968-01-01

63

Simultaneous detection of the spin-Hall magnetoresistance and the spin-Seebeck effect in platinum and tantalum on yttrium iron garnet  

NASA Astrophysics Data System (ADS)

The spin-Seebeck effect (SSE) in platinum (Pt) and tantalum (Ta) on yttrium iron garnet has been investigated by both externally heating the sample (using an on-chip Pt heater on top of the device) and by current-induced heating. For SSE measurements, external heating is the most common method to obtain clear signals. Here we show that also by current-induced heating it is possible to directly observe the SSE, separate from the also present spin-Hall magnetoresistance (SMR) signal, by using a lock-in detection technique. Using this measurement technique, the presence of additional second-order signals at low applied magnetic fields and high heating currents is revealed. These signals are caused by current-induced magnetic fields (Oersted fields) generated by the used ac current, resulting in dynamic SMR signals.

Vlietstra, N.; Shan, J.; van Wees, B. J.; Isasa, M.; Casanova, F.; Ben Youssef, J.

2014-11-01

64

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

65

GMAG PhD Dissertation Research Award: The Planar Nernst and Seebeck Effects in Ferromagnetic Metal Films with In-Plane Thermal Gradients  

NASA Astrophysics Data System (ADS)

Recently, the spin Seebeck effect (SSE) has attracted a great deal of attention as one possible source of pure spin currents. In response to a thermal gradient (?T), the SSE is thought to produce a pure spin current detectable by measuring a transverse voltage (VT) generated by the inverse spin Hall effect. However, recent work on spin-dependent transport in thin film nanostructures supported by bulk substrates suggests that early SSE experiments may have been strongly affected by unintended ?T through the supporting substrates. They may also have been affected by thermoelectric effects generated from planar thermal gradients such as transverse thermopower, also known as the planar Nernst effect (PNE), in which a VT develops in response to a ?T applied in the plane of a film with in-plane magnetization. In this talk, we present the first results from experiments designed to probe the SSE and related effects such as the PNE and longitudinal thermopower in 20 nm thick nickel and permalloy thin films deposited on suspended Si-N platforms. In our experiments, the background thermal conduction of the 500 nm thick platforms is at least 1000x smaller than the bulk substrates used previous experiments, thus confining ?T to the plane of the film. The results exhibit the ?? angular dependence predicted by the PNE, where ? is the angle between film magnetization and thermal gradient, rather than the ? dependence expected from SSE predictions. We demonstrate that the magnetic field dependence of the PNE, anisotropic magnetoresistance, and longitudinal thermopower (?) is generated by spin-dependent scattering and present results confirming the Onsager reciprocity between ? and the Peltier coefficient. Finally, we present an upper limit for the SSE coefficient in our experiment that is at least an order of magnitude smaller than previously reported by experiments conducted using bulk substrates. I would like to thank my collaborators Barry L. Zink and Matthew R. Pufall and gratefully acknowledge support from the NSF CAREER Grant No. DMR-0847796.

Avery, Azure

2013-03-01

66

Uncertainty analysis for common Seebeck and electrical resistivity measurement systems  

NASA Astrophysics Data System (ADS)

This work establishes the level of uncertainty for electrical measurements commonly made on thermoelectric samples. The analysis targets measurement systems based on the four probe method. Sources of uncertainty for both electrical resistivity and Seebeck coefficient were identified and evaluated. Included are reasonable estimates on the magnitude of each source, and cumulative propagation of error. Uncertainty for the Seebeck coefficient includes the cold-finger effect which has been quantified with thermal finite element analysis. The cold-finger effect, which is a result of parasitic heat transfer down the thermocouple probes, leads to an asymmetric over-estimation of the Seebeck coefficient. A silicon germanium thermoelectric sample has been characterized to provide an understanding of the total measurement uncertainty. The electrical resistivity was determined to contain uncertainty of ±7.0% across any measurement temperature. The Seebeck coefficient of the system is +1.0%/-13.1% at high temperature and ±1.0% near room temperature. The power factor has a combined uncertainty of +7.3%/-27.0% at high temperature and ±7.5% near room temperature. These ranges are calculated to be typical values for a general four probe Seebeck and resistivity measurement configuration.

Mackey, Jon; Dynys, Frederick; Sehirlioglu, Alp

2014-08-01

67

Thermal and transport properties of the Heusler-type Fe2VAl1-xGex(0?x?0.20) alloys: Effect of doping on lattice thermal conductivity, electrical resistivity, and Seebeck coefficient  

NASA Astrophysics Data System (ADS)

We report on the thermoelectric properties of the Heusler-type Fe2VAl1-xGex alloys with compositions 0?x?0.20 . While Fe2VAl(x=0) exhibits a semiconductorlike behavior in electrical resistivity, a slight substitution of Ge for Al causes a significant decrease in the low-temperature resistivity and a large enhancement in the Seebeck coefficient, reaching -130?V/K for x=0.05 at around room temperature. Comparison with the Fe2VAl1-xSix system demonstrates that the compositional variation of the Seebeck coefficient falls on a universal curve irrespective of the doping elements (Ge and Si), both of which are isoelectronic elements. The net effect of doping is most likely to cause a rigid-bandlike shift of the Fermi level from the central region in the pseudogap. In spite of a similar decrease in the electrical resistivity with composition of Ge and Si, the thermal conductivity decreases more rapidly for the Ge substitution. It is concluded that doping of heavier atoms such as Ge reduces more effectively the lattice thermal conductivity while retaining the low electrical resistivity as well as the large Seebeck coefficient.

Nishino, Y.; Deguchi, S.; Mizutani, U.

2006-09-01

68

Seebeck Coefficient Measured With Differential Heat Pulses  

NASA Technical Reports Server (NTRS)

Common experimental errors reduced because pulse technique suppresses drifts in thermoelectric measurements. Differential-heat-pulse apparatus measures Seebeck coefficient in semiconductors at temperatures up to 1,900 K. Sample heated to measuring temperature in furnace. Ends of sample then differentially heated a few degrees more by lamps. Differential temperature rise and consequent Seebeck voltage measured via thermocouple leads. Because pulse technique used, errors that often arise from long-term drifts in thermoelectric measurements suppressed. Apparatus works with temperature differences of only few degrees, further increasing accuracy of coefficients obtained.

Zoltan, L.; Wood, C.; Stapfer, G.

1986-01-01

69

Huge Seebeck coefficients in non-aqueous electrolytes  

E-print Network

The Seeebeck coefficients of the non-aqueous electrolytes tetrabutylammonium nitrate, tetraoctylphosphonium bromide and tetradodecylammonium nitrate in 1-octanol, 1-dodecanol and ethylene-glycol are measured in a temperature range from T=30 to T=45 C. The Seebeck coefficient is generally of the order of a few hundreds of microvolts per Kelvin for aqueous solution of inorganic ions. Here we report huge values of 7 mV/K at 0.1M concentration for tetrabutylammonium nitrate in 1-dodecanol. These striking results open the question of unexpectedly large kosmotrope or "structure making" effects of tetraalkylammonium ions on the structure of alcohols.

M. Bonetti; S. Nakamae; M. Roger; P. Guenoun

2011-02-11

70

Combination of PVA with Graphene to Improve the Seebeck Coefficient for Thermoelectric Generator Applications  

NASA Astrophysics Data System (ADS)

Ultrasensitive thermoelectric (TE) materials are essential for the next generation of self-powered electronic devices. In this work, a graphene-based TE generator was fabricated. For 50 to 1000 graphene layers the average Seebeck coefficient was 90 ?V/K. We also report improvement of the Seebeck coefficient by use of a hybrid material containing 10% poly(vinyl alcohol) (PVA) and 90% graphene oxide prepared and tested under the same conditions. The results show that the Seebeck coefficient is improved by an average of 30% compared with graphene alone. Because the fabrication process is facile, scalable, and cost effective, it could also be applicable to other fields of science and engineering.

Mahmoud, L.; Abdul Samad, Y.; Alhawari, M.; Mohammad, B.; Liao, K.; Ismail, M.

2015-01-01

71

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

72

Description of a Sensitive Seebeck Calorimeter Used for Cold Fusion Studies  

Microsoft Academic Search

A sensitive and stable Seebeck calorimeter is described and used to determine the heat of formation of PdD. This determination can be used to show that such calorimeters are sufficiently accurate to measure the LENR effect and give support to the claims.

Edmund Storms

2006-01-01

73

Description of a Sensitive Seebeck Calorimeter Used for Cold Fusion Studies  

NASA Astrophysics Data System (ADS)

A sensitive and stable Seebeck calorimeter is described and used to determine the heat of formation of PdD. This determination can be used to show that such calorimeters are sufficiently accurate to measure the LENR effect and give support to the claims.

Storms, Edmund

74

Measurement of Seebeck coefficient using a light pulse  

NASA Technical Reports Server (NTRS)

A high-temperature (1900 K) Seebeck coefficient apparatus is described in which small thermal gradients are generated in a sample by light pulses transmitted via light pipes. By employing an analog subtraction circuit, the Seebeck coefficient is displayed directly on an X-Y recorder. This technique presents a convenient, accurate, and rapid method for measuring the Seebeck coefficient in highly doped semiconductors as a function of temperature. The nature of the resulting display (X-Y recording) is a valuable tool in determining validity of the data. A straight line results (i.e., a minimum of hysteresis) only if all potential experimental errors are minimized. Under these conditions, the error of measurements of the Seebeck coefficient is estimated to be less than + or - 1 percent.

Wood, C.; Zoltan, D.; Stapfer, G.

1985-01-01

75

System to Measure Thermal Conductivity and Seebeck Coefficient for Thermoelectrics  

NASA Technical Reports Server (NTRS)

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 elevated temperatures. This has led to the implementation of nonstandardized practices that have further complicated the confirmation of reported high ZT materials. The major objective of the procedure described is for the simultaneous measurement of the Seebeck coefficient and thermal diffusivity within a given temperature range. These thermoelectric measurements must be precise, accurate, and reproducible to ensure meaningful interlaboratory comparison of data. The custom-built thermal characterization system described in this NASA-TM is specifically designed to measure the inplane thermal diffusivity, and the Seebeck coefficient for materials in the ranging from 73 K through 373 K.

Kim, Hyun-Jung; Skuza, Jonathan R.; Park, Yeonjoon; King, Glen C.; Choi, Sang H.; Nagavalli, Anita

2012-01-01

76

Nanoscale Thermoelectrics: A Study of the Absolute Seebeck Coefficient of Thin Films  

NASA Astrophysics Data System (ADS)

The worlds demand for energy is ever increasing. Likewise, the environmental impact of climate change due generating that energy through combustion of fossil fuels is increasingly alarming. Due to these factors new sources of renewable energies are constantly being sought out. Thermoelectric devices have the ability to generate clean, renewable, energy out of waste heat. However promising that is, their inefficiency severely inhibits applicability and practical use. The usefulness of a thermoelectric material increases with the dimensionless quantity, ZT, which depends on the Seebeck coefficient and electrical and thermal conductivity. These characteristic material parameters have interdependent energy transport contributions that classically prohibit the optimization of one with out the detriment of another. Encouraging advancements of ZT have occurred in the past ten years due to the decoupling of the thermal and electrical conductivity. Further advancements are necessary in order to produce applicable devices. One auspicious way of decoupling or tuning energy transport properties, is through size reduction to the nanoscale. However, with reduced dimensions come complications in measuring material properties. Measurements of properties such as the Seebeck coefficient, S, are primarily contingent upon the measurement apparatus. The Seebeck coefficient is defined as the amount of voltage generated by a thermal gradient. Measuring a thermally generated voltage by traditional methods gives, the voltage measured as a linear function of the Seebeck coefficient of the leads and of the material being tested divided by the applied thermal gradient. If accurate values of the Seebeck coefficients of the leads are available, simple subtraction provides the answer. This is rarely the case in nanoscale measurement devices with leads exclusively made from thin film materials that do not have well known bulk-like thermopower values. We have developed a technique to directly measure, S, as a function of temperature using a micro-machined thermal isolation platform consisting of a suspended, patterned SiN membrane. By measuring a series of thicknesses of metallic films up to the infinitely thin film limit, in which the electrical resistivity is no longer decreasing with increasing film thickness, but still not at bulk values, along with the effective electron mean free path, we are able to show the contribution of the leads needed to measure this property. Having a comprehensive understanding of the background contribution we are able to determine the absolute Seebeck coefficient of a wide variety of thin films. The nature of the design of the SiN membrane also allows the ability to accurately and directly measure thermal and electrical transport of the thin films yielding a comprehensive measurement of the three quantities that characterize a material's efficiency. This can serve to further the development of thermoelectric materials through precise measurements of the material properties that dictate efficiency.

Mason, Sarah J.

77

Seebeck Coefficient Metrology: Do Contemporary Protocols Measure Up?  

NASA Astrophysics Data System (ADS)

Comparative measurements of the Seebeck coefficient are challenging due to the diversity of instrumentation and measurement protocols. With the implementation of standardized measurement protocols and the use of Standard Reference Materials (SRMs®), for example, the recently certified National Institute of Standards and Technology (NIST) SRM® 3451 ``Low Temperature Seebeck Coefficient Standard (10-390 K)'', researchers can reliably analyze and compare data, both intra- and inter-laboratory, thereby accelerating the development of more efficient thermoelectric materials and devices. We present a comparative overview of commonly adopted Seebeck coefficient measurement practices. First, we examine the influence of asynchronous temporal and spatial measurement of electric potential and temperature. Temporal asynchronicity introduces error in the absolute Seebeck coefficient of the order of ?10%, whereas spatial asynchronicity introduces error of the order of a few percent. Second, we examine the influence of poor thermal contact between the measurement probes and the sample. This is especially critical at high temperature, wherein the prevalent mode of measuring surface temperature is facilitated by pressure contact. Each topic will include the comparison of data measured using different measurement techniques and using different probe arrangements. We demonstrate that the probe arrangement is the primary limit to high accuracy, wherein the Seebeck coefficients measured by the 2-probe arrangement and those measured by the 4-probe arrangement diverge with the increase in temperature, approaching ?14% at 900 K. Using these analyses, we provide recommended measurement protocols to guide members of the thermoelectric materials community in performing more accurate measurements and in evaluating more comprehensive uncertainty limits.

Martin, Joshua; Wong-Ng, Winnie; Green, Martin L.

2015-01-01

78

First Principles Explanation of the Positive Seebeck Coefficient of Lithium  

NASA Astrophysics Data System (ADS)

Lithium is one of the simplest metals, with negative charge carriers and a close reproduction of free-electron dispersion. Experimentally, however, Li is one of a handful of elemental solids (along with Cu, Ag, and Au) where the sign of the Seebeck coefficient (S) is opposite to that of the carrier. This counterintuitive behavior still lacks a satisfactory interpretation. We calculate S fully from first principles, within the framework of Allen's formulation of Boltzmann transport theory. Here it is crucial to avoid the constant relaxation time approximation, which gives a sign for S which is necessarily that of the carriers. Our calculated S are in excellent agreement with experimental data, up to the melting point. In comparison with another alkali metal, Na, we demonstrate that within the simplest nontrivial model for the energy dependency of the electron lifetimes, the rapidly increasing density of states (DOS) across the Fermi energy is related to the sign of S in Li. The exceptional energy dependence of the DOS is beyond the free-electron model, as the dispersion is distorted by the Brillouin zone edge; this has a stronger effect in Li than other alkali metals. The electron lifetime dependency on energy is central, but the details of the electron-phonon interaction are found to be less important, contrary to what has been believed for several decades. Band engineering combined with the mechanism exposed here may open the door to new "ambipolar" thermoelectric materials, with a tunable sign for the thermopower even if either n- or p-type doping is impossible.

Xu, Bin; Verstraete, Matthieu J.

2014-05-01

79

Design of seebeck coefficient measurement probe for powder library.  

PubMed

A thermoelectric evaluation system, attachable to our developed materials exploration system "M-ist Combi" based on the electrostatic spray deposition method, was designed and established for high-throughput to explore new candidate thermoelectric materials. The developed Seebeck coefficient measurement probe consists of two chromel-alumel thermocouples, and one of thermocouples is able to control its own temperature to ensure a temperature difference between thermocouples. The measurement time for each sample was about 5 s. This provides a stabilized time for the thermoelectric power for each sample. And, it was found that the Seebeck coefficient measurement probe could be used as a high-throughput screening tool for exploring candidate thermoelectric materials. PMID:24367887

Fujimoto, Kenjiro; Taguchi, Toru; Yoshida, Shogo; Ito, Shigeru

2014-02-10

80

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

81

Simultaneous Enhancement of the Electrical Conductivity and Seebeck Coefficient of PEDOT-block-PEG/SWCNTs Nanocomposites  

NASA Astrophysics Data System (ADS)

In this study, the thermoelectric (TE) performance of poly(3,4-ethylenedioxythiophene)-block-poly(ethylene glycol) (PEDOT-block-PEG), one of the most important poly(3,4-ethylenedioxythiophene) (PEDOT) derivatives, was studied. To improve its TE performance, different mass fractions of single-walled carbon nanotubes (SWCNTs) were incorporated by physical mixing. Blending with SWCNTs resulted in simultaneous enhancement of the electrical conductivity and Seebeck coefficient of the PEDOT-block-PEG/SWCNTs nanocomposites. At 300 K, the maximum electrical conductivity was increased from 0.51 to 78.6 S/cm, and the Seebeck coefficient was increased from 5.1 to 46.3 ?V/K. The thermal conductivity of the composite films was low (0.24-0.34 W/m/K). The maximum ZT of PEDOT-block-PEG/SWCNTs nanocomposites was 1.24 × 10-2 when the SWCNTs content was 66.7 wt.%. This study suggests that constructing PEDOT-block-PEG/SWCNTs nanocomposites might be an effective way of improving the TE properties of PEDOT-block-PEG.

Jiang, Qinglin; Liu, Congcong; Zhu, Danhua; Song, Haijun; Xu, Jingkun; Shi, Hui; Mo, Daize; Wang, Zhipeng; Zhu, Zhengyou

2014-11-01

82

Seebeck rectification enabled by intrinsic thermoelectrical coupling in magnetic tunneling junctions.  

PubMed

An intrinsic thermoelectric coupling effect in the linear response regime of magnetic tunneling junctions (MTJ) is reported. In the dc response, it leads to a nonlinear correction to Ohm's law. Dynamically, it enables a novel Seebeck rectification and second harmonic generation, which apply for a broad frequency range and can be magnetically controlled. A phenomenological model on the footing of the Onsager reciprocal relation and the principle of energy conservation explains very well the experimental results obtained from both dc and frequency-dependent transport measurements performed up to GHz frequencies. Our work refines previous understanding of magnetotransport and microwave rectification in MTJs. It forms a new foundation for utilizing spin caloritronics in high-frequency applications. PMID:22861893

Zhang, Z H; Gui, Y S; Fu, L; Fan, X L; Cao, J W; Xue, D S; Freitas, P P; Houssameddine, D; Hemour, S; Wu, K; Hu, C-M

2012-07-20

83

Cross-plane Seebeck coefficient of ErAs:InGaAs/InGaAlAs superlattices Gehong Zenga  

E-print Network

Cross-plane Seebeck coefficient of ErAs:InGaAs/InGaAlAs superlattices Gehong Zenga Department; published online 6 February 2007 We characterize cross-plane and in-plane Seebeck coefficients for Er. The microheater creates a local temperature difference, and the cross-plane Seebeck coefficients

Bowers, John

84

Multifold Seebeck increase in RuO{sub 2} films by quantum-guided lanthanide dilute alloying  

SciTech Connect

Ab initio predictions indicating that alloying RuO{sub 2} with La, Eu, or Lu can increase the Seebeck coefficient ? manifold due to quantum confinement effects are validated in sputter-deposited La-alloyed RuO{sub 2} films showing fourfold ? increase. Combinatorial screening reveals that ? enhancement correlates with La-induced lattice distortion, which also decreases the thermal conductivity twentyfold, conducive for high thermoelectric figures of merit. These insights should facilitate the rational design of high efficiency oxide-based thermoelectrics through quantum-guided alloying.

Music, Denis, E-mail: music@mch.rwth-aachen.de; Basse, Felix H.-U.; Schneider, Jochen M. [Materials Chemistry, RWTH Aachen University, Kopernikusstr. 10, D-52074 Aachen (Germany); Han, Liang; Borca-Tasciuc, Theo [Department of Mechanical, Aerospace and Nuclear Engineering, Rensselaer Polytechnic Institute, 110 8th St., Troy, New York 12180 (United States); Devender [Materials Science and Engineering Department, Rensselaer Polytechnic Institute, 110 8th St., Troy, New York 12180 (United States); Gengler, Jamie J. [Air Force Research Laboratory, Materials and Manufacturing Directorate, WPAFB, Ohio 45433 (United States); Spectral Energies, LLC, Dayton, Ohio 45431 (United States); Voevodin, Andrey A. [Air Force Research Laboratory, Materials and Manufacturing Directorate, WPAFB, Ohio 45433 (United States); Ramanath, Ganpati [Materials Chemistry, RWTH Aachen University, Kopernikusstr. 10, D-52074 Aachen (Germany); Materials Science and Engineering Department, Rensselaer Polytechnic Institute, 110 8th St., Troy, New York 12180 (United States)

2014-02-03

85

Characterization of Lorenz number with Seebeck coefficient measurement  

NASA Astrophysics Data System (ADS)

In analyzing zT improvements due to lattice thermal conductivity (?L) reduction, electrical conductivity (?) and total thermal conductivity (?Total) are often used to estimate the electronic component of the thermal conductivity (?E) and in turn ?L from ?L = ˜ ?Total - L?T. The Wiedemann-Franz law, ?E = L?T, where L is Lorenz number, is widely used to estimate ?E from ? measurements. It is a common practice to treat L as a universal factor with 2.44 × 10-8 W?K-2 (degenerate limit). However, significant deviations from the degenerate limit (approximately 40% or more for Kane bands) are known to occur for non-degenerate semiconductors where L converges to 1.5 × 10-8 W?K-2 for acoustic phonon scattering. The decrease in L is correlated with an increase in thermopower (absolute value of Seebeck coefficient (S)). Thus, a first order correction to the degenerate limit of L can be based on the measured thermopower, |S|, independent of temperature or doping. We propose the equation: L = 1 . 5 + exp [- /| S | 116] (where L is in 10-8 W?K-2 and S in ?V/K) as a satisfactory approximation for L. This equation is accurate within 5% for single parabolic band/acoustic phonon scattering assumption and within 20% for PbSe, PbS, PbTe, Si0.8Ge0.2 where more complexity is introduced, such as non-parabolic Kane bands, multiple bands, and/or alternate scattering mechanisms. The use of this equation for L rather than a constant value (when detailed band structure and scattering mechanism is not known) will significantly improve the estimation of lattice thermal conductivity.

Kim, Hyun-Sik; Gibbs, Zachary M.; Tang, Yinglu; Wang, Heng; Snyder, G. Jeffrey

2015-04-01

86

Profiling the Local Seebeck Coefficient with Nanometer Resolution Using Scanning Thermoelectric Microscopy (SThEM)  

NASA Astrophysics Data System (ADS)

Thermoelectric (TE) devices offer a method of recovering waste heat through solid state conversion of heat to electricity. Nanostructured thermoelectric materials may provide the key to increased efficiencies, which are sensitive to the Seebeck coefficients (S) However, traditional bulk measurement techniques can only provide a spatially averaged measurement of S over the whole sample, which can hardly investigate the effects of nanostructures on S on the nanoscale. A novel technique known as scanning thermoelectric microscopy (SThEM) has recently been developed to measure induced thermal voltages with nanometer resolution In SThEM, an unheated scanning tunneling microscopy tip acts as a high-resolution voltmeter probe to measure the thermally-induced voltage, V, in a heated sample. Here we present a local S measurement using SThEM across an InGaAs P-N junction. The thermovoltage shows an abrupt change of sign within 10 nanometers, which reveals nanometer spatial resolution. We will discuss local S measurements of AlAs/GaAs superlattices (SLs) with various SL periods and compare the local S with scanning tunneling spectroscopy measurements, which will reveal how local electronic states influence thermoelectric properties.

Lin, Yen-Hsiang; Walrath, Jenna; Goldman, Rachel

2013-03-01

87

Critical evaluation of the colossal Seebeck coefficient of nanostructured rutile MnO2.  

PubMed

We have explored the correlation between the Seebeck coefficient and the electronic structure of nanostructured rutile MnO2 using density functional theory to critically appraise the three orders of magnitude scatter in literature data. Our hypothesis is that the microstructure and morphology on the nanoscale is causing this behaviour, which we have tested by comparing the Seebeck coefficient of bulk MnO2 with two low-energy surfaces: MnO2(1?1?0) and MnO2(0?0?1). From these data, it is evident that variations over two orders of magnitude in the Seebeck coefficient can be attained by affecting domain size and texture on the nanoscale. This may be understood by analysing the electronic structure. Surface hybridized Mn d-O p states fill the band gap of MnO2 and thus substantially alter the transport properties. PMID:25730181

Music, Denis; Schneider, Jochen M

2015-03-25

88

Critical evaluation of the colossal Seebeck coefficient of nanostructured rutile MnO2  

NASA Astrophysics Data System (ADS)

We have explored the correlation between the Seebeck coefficient and the electronic structure of nanostructured rutile MnO2 using density functional theory to critically appraise the three orders of magnitude scatter in literature data. Our hypothesis is that the microstructure and morphology on the nanoscale is causing this behaviour, which we have tested by comparing the Seebeck coefficient of bulk MnO2 with two low-energy surfaces: MnO2(1?1?0) and MnO2(0?0?1). From these data, it is evident that variations over two orders of magnitude in the Seebeck coefficient can be attained by affecting domain size and texture on the nanoscale. This may be understood by analysing the electronic structure. Surface hybridized Mn d–O p states fill the band gap of MnO2 and thus substantially alter the transport properties.

Music, Denis; Schneider, Jochen M.

2015-03-01

89

Ultrahigh resolution characterizing nanoscale Seebeck coefficient via the heated, conductive AFM probe  

NASA Astrophysics Data System (ADS)

An ultrahigh resolution probe technique for charactering nanoscale Seebeck coefficient was developed based on a modified conductive AFM probe with local heating function. The heated AFM conductive tip realizes nanoscale thermal contact between the AFM tip and the thermoelectric samples and successfully excites nanoscale thermoelectric signal. Excellent agreement was found between nanoscale Seebeck coefficient values and their corresponding macroscopy measurements in thermoelectric bulk and thin films. Such AFM-based thermoelectric probe technique provides a very convenient and promising tool for measuring nanoscale thermoelectric parameters with ultrahigh resolution up to 15 nm.

Xu, K. Q.; Zeng, H. R.; Yu, H. Z.; Zhao, K. Y.; Li, G. R.; Song, J. Q.; Shi, X.; Chen, L. D.

2015-01-01

90

Carbon nanotubes enhanced Seebeck coefficient and power factor of rutile TiO2.  

PubMed

The Seebeck coefficient, according to Ioffe's approximation, is inversely proportional to carrier density and decreases with doping. Herein, we find that the incorporation of multi-walled carbon nanotubes into rutile TiO2 improves the electrical conductivity and Seebeck coefficient at a low filling fraction of tubes; moreover, the former was due to the lengthening of the mean free path and doping modified carrier mobility for the latter. Tube-oxide mixing also causes significant phonon drag at the interfaces and the reduced thermal conductivity was verified by the promoted figure of merit. PMID:25729788

Lai, Yao-Cheng; Tsai, Hsin-Jung; Hung, Chia-I; Fujishiro, Hiroyuki; Naito, Tomoyuki; Hsu, Wen-Kuang

2015-03-11

91

Simultaneous measurement of the Seebeck coefficient and thermal diffusivity for bulk thermoelectric materials  

NASA Astrophysics Data System (ADS)

We simultaneously measured the Seebeck coefficient and thermal diffusivity of a rectangular parallelepiped bulk thermoelectric material. We used one-dimensional heat conduction equation to show that a periodic heat cycle produces not only the thermoelectromotive force but also a certain phase shift angle between the edge and intermediate points of a sample along the length of the material. Based on the equation of the modified Angström method, an experiment at 300 K was performed using NIST standard material (SRM 3451, Bi2Te3 material) to measure the Seebeck coefficient and thermal diffusivity. The measured Seebeck coefficient was ?231 ± 3 µV/K, which corresponds to the published value. Using the same experimental setup as that for the thermal diffusivity measurement, the dependence of the phase shift angle on frequency was measured from 5 mHz to 10 Hz for the phase shift angle from ?8.2 to ?450°. The estimated thermal diffusivity was (1.53 ± 0.05) × 10?6 m2/s. We conclude that the modified Angström method can be used to measure the Seebeck coefficient and thermal diffusivity simultaneously.

Homma, Ryoei; Hasegawa, Yasuhiro; Terakado, Hiroki; Morita, Hiroyuki; Komine, Takashi

2015-02-01

92

Ribosomal Synthesis of Dehydroalanine-Containing Peptides Florian P. Seebeck and Jack W. Szostak*  

E-print Network

Ribosomal Synthesis of Dehydroalanine-Containing Peptides Florian P. Seebeck and Jack W. Szostak synthesis by large multifunctional syn- thetases complicates the construction and sampling of large Due to its moderate electrophilicity, Ala may also serve as a warhead in protein- reactive compounds15

Heller, Eric

93

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

94

Development and application of an instrument for spatially resolved Seebeck coefficient measurements  

NASA Astrophysics Data System (ADS)

The Seebeck coefficient is a key indicator of the majority carrier type (electrons or holes) in a material. The recent trend toward the development of combinatorial materials research methods has necessitated the development of a new high-throughput approach to measuring the Seebeck coefficient at spatially distinct points across any sample. The overall strategy of the high-throughput experiments is to quickly identify the region of interest on the sample at some expense of accuracy, and then study this region by more conventional techniques. The instrument for spatially resolved Seebeck coefficient measurements reported here relies on establishing a temperature difference across the entire compositionally graded thin-film and consecutive mapping of the resulting voltage as a function of position, which facilitates the temperature-dependent measurements up to 400 °C. The results of the designed instrument are verified at ambient temperature to be repeatable over 10 identical samples and accurate to within 10% versus conventional Seebeck coefficient measurements over the -100 to +150 ?V/K range using both n-type and p-type conductive oxides as test cases. The developed instrument was used to determine the sign of electrical carriers of compositionally graded Zn-Co-O and Ni-Co-O libraries prepared by combinatorial sputtering. As a result of this study, both cobalt-based materials were determined to have p-type conduction over a broad single-phase region of chemical compositions and small variation of the Seebeck coefficient over the entire investigated range of compositions and temperature.

Zakutayev, Andriy; Luciano, Frank J.; Bollinger, Vincent P.; Sigdel, Ajaya K.; Ndione, Paul F.; Perkins, John D.; Berry, Joseph J.; Parilla, Philip A.; Ginley, David S.

2013-05-01

95

Simultaneous increase in electrical conductivity and Seebeck coefficient in highly boron-doped nanocrystalline Si.  

PubMed

A large thermoelectric power factor in heavily boron-doped p-type nanograined Si with grain sizes ?30 nm and grain boundary regions of ?2 nm is reported. The reported power factor is ?5 times higher than in bulk Si. It originates from the surprising observation that for a specific range of carrier concentrations, the electrical conductivity and Seebeck coefficient increase simultaneously. The two essential ingredients for this observation are nanocrystallinity and extremely high boron doping levels. This experimental finding is interpreted within a theoretical model that considers both electron and phonon transport within the semiclassical Boltzmann approach. It is shown that transport takes place through two phases so that high conductivity is achieved in the grains, and high Seebeck coefficient by the grain boundaries. This together with the drastic reduction in the thermal conductivity due to boundary scattering could lead to a significant increase of the figure of merit ZT. This is one of the rare observations of a simultaneous increase in the electrical conductivity and Seebeck coefficient, resulting in enhanced thermoelectric power factor. PMID:23598565

Neophytou, Neophytos; Zianni, Xanthippi; Kosina, Hans; Frabboni, Stefano; Lorenzi, Bruno; Narducci, Dario

2013-05-24

96

Measurements of the Seebeck coefficient of thermoelectric materials by an ac method  

SciTech Connect

An ac method for measurement of the Seebeck coefficient was developed. Specimens were heated periodically at frequencies in the range 0.2--10 Hz using a semiconductor laser. The small temperature increase and the resultant thermoelectric power were measured with a Pt-Pt 13% Rh thermocouple (25 {micro}m in diameter) through a lock-in amplifier. The Seebeck coefficient of a Pt{sub 90}Rh{sub 10} foil measured by the ac method was in agreement with that obtained from the standard table. The optimum frequency and specimen thickness for the ac method were 0.2 Hz and 0.1--0.2 mm, respectively. The Seebeck coefficients of silicon single crystal and several thermoelectric semiconductors (Si{sub 80}Ge{sub 20}, PbTc, FeSi{sub 2}, SiB{sub 14}) measured by the ac method agreed with those measured by a conventional dc method in the temperature range between room temperature and 1200 K. The time needed for each measurement was less than a few tens of minutes, significantly shorter than that for a conventional dc method.

Goto, T.; Li, J.H.; Hirai, T. [Tohoku Univ., Sendai (Japan). Inst. for Materials Research; Maeda, Y.; Kato, R.; Maesono, A. [SHINKO-RIKO Inc., Yokohama (Japan)

1997-03-01

97

Uncertainty Analysis of Seebeck Coefficient and Electrical Resistivity Characterization  

NASA Technical Reports Server (NTRS)

In order to provide a complete description of a materials thermoelectric power factor, in addition to the measured nominal value, an uncertainty interval is required. The uncertainty may contain sources of measurement error including systematic bias error and precision error of a statistical nature. The work focuses specifically on the popular ZEM-3 (Ulvac Technologies) measurement system, but the methods apply to any measurement system. The analysis accounts for sources of systematic error including sample preparation tolerance, measurement probe placement, thermocouple cold-finger effect, and measurement parameters; in addition to including uncertainty of a statistical nature. Complete uncertainty analysis of a measurement system allows for more reliable comparison of measurement data between laboratories.

Mackey, Jon; Sehirlioglu, Alp; Dynys, Fred

2014-01-01

98

Laser Synthesis of Nanometric Iron Oxide Films with High Seebeck Coefficient and High Thermoelectric Figure of Merit  

NASA Astrophysics Data System (ADS)

Radiation of a KrF-laser ( ? = 248 nm) was used for the synthesis by reactive pulsed laser deposition (RPLD) of nanometric iron oxide [Fe2O3-X (0?×?1)] films with variable thickness, stoichiometry and electrical properties. Film deposition was carried out on <100>Si at its temperature to have being increased from 293 to 800 K. XRD analysis showed that films deposited on Si substrate had polycrystalline structure. Films demonstrated semiconductor temperature trend with variable band gap Eg about 1.0 eV or less depending on oxygen pressure, the number of laser pulses and substrate temperature. Film thickness (13-60 nm) depended on oxygen pressure, substrate temperature and number of laser pulses. The higher substrate temperature, the more crystallinity of the deposited iron oxides' films was resulting in increasing of thermo electromotive force coefficient (Seebeck coefficient, S). It was found out the optimum oxygen pressure in the reactor, substrate temperature and film thickness when the S coefficient was high as 12-4 mV/K in the range 240-330 K. The thermoelectric figure of merit (ZT) was high as 1-6 in the range 280-330 K. This makes nanometric Fe2O3-X films, synthesized by UV photons using RPLD method, an exceptionally strong candidate for effective thermo sensors and thermo converters operating at moderate temperature.

Mulenko, S. A.; Gorbachuk, N. T.; Stefan, N.

2014-12-01

99

Seebeck and resistance diagnostics in the ESA MSL facility for the ISS  

NASA Astrophysics Data System (ADS)

The new generation of furnaces, used to study materials in microgravity on board the International Space Station, is defined to perform long duration experiments requiring optimised growth parameters of the material under study. Seebeck and Resistance diagnostics are to be able to perform in-situ and non-invasive observations and give scientists a means to influence their experiment, thus implementing the Telescience concept. A breadboard model and an engineering model of the "Seebeck and Resistance Measurement Device" (S&RMD) have been realised under an ESA contract. Two flight models are soon to be realised. They will be placed on board the International Space Station (ISS) in 2004/2005 for use by scientists. The aim of this presentation is to inform the scientific community and programmatics managers of the performances of such a device to attract their interest in view of future scientific experiment proposals on board the International Space Station, in the ESA Materials Science Laboratory (MSL) facility. The MSL will be integrated in the NASA first Material Science Research Rack (MSRR-1), which will be installed in the US Laboratory of the ISS.

Pissard, J.-P.; Le Grand, G.; Salvi, C.; Garandet, J.-P.; Drevet, B.; Martella, M.

2002-07-01

100

Seebeck Coefficient of Manganese Oxide Nanoparticles as a Function of Ohmic Resistance  

NASA Astrophysics Data System (ADS)

Due to the ever increasing energy demand and growing global concern over the environmental impact of CO2 emissions, there is an urging need to seek solutions to transit from fossil fuels to sustainable energy. Thermoelectric (TE) materials show great promise for converting waste heat energy into electricity. TE systems have many unique advantages such as silent operationality, time reliability, and dimensional scalability. Most recently, researchers Song et al. [1] found that MnO2 nanoparticles show a giant Seebeck coefficient of S = 20 mV/K, which is100 times higher than bismuth telluride, one of the best TE materials. Song et al.[1] concluded the paper claiming that the giant S is related to the surface density of the electronic states (DOS). However, they provided very little information about the S as a function of Ohmic resistance [R] for different nano particle sizes which can give information about the DOS. Our preliminary results show that there is a sudden increase of S from 0.33-0.63 mV/K as R increases from 80-110 Ohms. This transition has never been seen before and it can give clues as to the existence of the Giant S observed in this material.[4pt] [1] F. Song, L. Wu and S. Liang, Giant Seebeck coefficient thermoelectric device of MnO2 powder, Nano. 23, 085401 (2012).

Francis, Nicholas; Hedden, Morgan; Constantin, Costel

2013-03-01

101

Record Seebeck coefficient and extremely low thermal conductivity in nanostructured SnSe  

NASA Astrophysics Data System (ADS)

SnSe has been prepared by arc-melting, as mechanically robust pellets, consisting of highly oriented polycrystals. This material has been characterized by neutron powder diffraction (NPD), scanning electron microscopy, and transport measurements. A microscopic analysis from NPD data demonstrates a quite perfect stoichiometry SnSe0.98(2) and a fair amount of anharmonicity of the chemical bonds. The Seebeck coefficient reaches a record maximum value of 668 ?V K-1 at 380 K; simultaneously, this highly oriented sample exhibits an extremely low thermal conductivity lower than 0.1 W m-1 K-1 around room temperature, which are two of the main ingredients of good thermoelectric materials. These excellent features exceed the reported values for this semiconducting compound in single crystalline form in the moderate-temperatures region and highlight its possibilities as a potential thermoelectric material.

Serrano-Sánchez, F.; Gharsallah, M.; Nemes, N. M.; Mompean, F. J.; Martínez, J. L.; Alonso, J. A.

2015-02-01

102

Size effects on thermoelectric behavior of ultrathin NaxCoO2 films  

NASA Astrophysics Data System (ADS)

Size effects in thermoelectric NaxCoO2 thin films are studied, focusing on the electrical resisitivity and Seebeck coefficient. For very thin films below 10 nm, we have observed an increase in resistivity, which is in agreement with theoretical models. In contrast to a predicted simultaneous suppression of the Seebeck coefficient for ultrathin films, we observe a constant Seebeck coefficient as a function of layer thickness due to changes in the structural properties as well as the presence of strong electron correlations. This preserved high Seebeck coefficient opens up new directions for NaxCoO2 ultrathin films as basic building blocks in thermoelectric superlattices with enhanced phonon scattering.

Brinks, Peter; Rijnders, Guus; Huijben, Mark

2014-11-01

103

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

104

Thermoelectric performance of poly(3-hexylthiophene) films doped by iodine vapor with promising high seebeck coefficient  

NASA Astrophysics Data System (ADS)

Poly(3-hexylthiophene) (P3HT) films doped with iodine vapor have been prepared by casting a P3HT solution on glass substrates and their thermoelectric (TE) performances has been investigated. The maximum Seebeck coefficient and electrical conductivity of iodine-doped P3HT films were 386 µV·K-1 (at room temperature) and 4.7 × 10-1 S·cm-1, which is about five orders of magnitude higher than that of pristine P3HT films. The power factor of these iodine-doped P3HT films was estimated to be 7.0 µW·m-1·K-2 at room temperature, which is a relative high value for organic TE materials. The UV-vis spectra of iodine-doped P3HT films showed a slight red shift of the iodine-doped P3HT compared to those of pristine P3HT films. Atomic force microscopy images indicated the conformational changes in P3HT chains after treatment with iodine vapor. During this treatment, the P3HT chains self-organized into a more ordered structure, this organization improved the charge carrier transport capability and the TE performance of P3HT the films.

Zhu, Hongfei; Liu, Congcong; Song, Haijun; Xu, Jingkun; Kong, Fangfang; Wang, Jianmin

2014-03-01

105

Evaluation of Seebeck coefficients in n- and p-type silicon nanowires fabricated by complementary metal-oxide-semiconductor technology.  

PubMed

Silicon-based thermoelectric nanowires were fabricated by using complementary metal-oxide-semiconductor (CMOS) technology. 50 nm width n- and p-type silicon nanowires (SiNWs) were manufactured using a conventional photolithography method on 8 inch silicon wafer. For the evaluation of the Seebeck coefficients of the silicon nanowires, heater and temperature sensor embedded test patterns were fabricated. Moreover, for the elimination of electrical and thermal contact resistance issues, the SiNWs, heater and temperature sensors were fabricated monolithically using a CMOS process. For validation of the temperature measurement by an electrical method, scanning thermal microscopy analysis was carried out. The highest Seebeck coefficients were - 169.97 ?V K(-1) and 152.82 ?V K(-1) and the highest power factors were 2.77 mW m(-1) K(-2) and 0.65 mW m(-1) K(-2) for n- and p-type SiNWs, respectively, in the temperature range from 200 to 300 K. The larger power factor value for n-type SiNW was due to the higher electrical conductivity. The total Seebeck coefficient and total power factor for the n- and p-leg unit device were 157.66 ?V K(-1) and 9.30 mW m(-1) K(-2) at 300 K, respectively. PMID:22995969

Hyun, Younghoon; Park, Youngsam; Choi, Wonchul; Kim, Jaehyeon; Zyung, Taehyoung; Jang, Moongyu

2012-10-12

106

Vacancy filling effect in thermoelectric NbO  

NASA Astrophysics Data System (ADS)

Using density functional theory, we have systematically explored the 1a and 1b vacancy filling in NbO (space group Pm-3m) with Nb and N, respectively, to design compounds with large Seebeck coefficients. The most dominating effect was identified for filling of 1b Wyckoff sites with N giving rise to a fivefold increase in the Seebeck coefficient. This may be understood based on the electronic structure. Nb d—nonmetal p hybridization induces quantum confinement and hence enables the enhancement of the Seebeck coefficient. This was validated by measuring the Seebeck coefficient of reactively sputtered thin films. At 800 °C these electrically conductive oxynitrides exhibit the Seebeck coefficient of ?70 µV K?1, which is the largest absolute value ever reported for these compounds.

Music, Denis; Geyer, Richard W.; Bliem, Pascal; Hans, Marcus; Primetzhofer, Daniel

2015-03-01

107

Vacancy filling effect in thermoelectric NbO.  

PubMed

Using density functional theory, we have systematically explored the 1a and 1b vacancy filling in NbO (space group Pm-3m) with Nb and N, respectively, to design compounds with large Seebeck coefficients. The most dominating effect was identified for filling of 1b Wyckoff sites with N giving rise to a fivefold increase in the Seebeck coefficient. This may be understood based on the electronic structure. Nb d-nonmetal p hybridization induces quantum confinement and hence enables the enhancement of the Seebeck coefficient. This was validated by measuring the Seebeck coefficient of reactively sputtered thin films. At 800 °C these electrically conductive oxynitrides exhibit the Seebeck coefficient of -70 µV K(-1), which is the largest absolute value ever reported for these compounds. PMID:25730353

Music, Denis; Geyer, Richard W; Bliem, Pascal; Hans, Marcus; Primetzhofer, Daniel

2015-03-25

108

Charging of heated colloidal particles using the electrolyte Seebeck effect Arghya Majee and Alois Wrger  

E-print Network

of self- propulsion and Brownian motion leads to a complex dif- fusion behavior [8--11]. Locally modifying to a temperature variation along its sur- face; the resulting self-propulsion adds a ballistic velocity component

Boyer, Edmond

109

Nernst and Seebeck Coefficients of the Cuprate Superconductor YBa2Cu3O6.67: A Study of Fermi Surface Reconstruction  

NASA Astrophysics Data System (ADS)

The Seebeck and Nernst coefficients S and ? of the cuprate superconductor YBa2Cu3Oy (YBCO) were measured in a single crystal with doping p=0.12 in magnetic fields up to H=28T. Down to T=9K, ? becomes independent of field by H?30T, showing that superconducting fluctuations have become negligible. In this field-induced normal state, S/T and ?/T are both large and negative in the T?0 limit, with the magnitude and sign of S/T consistent with the small electronlike Fermi surface pocket detected previously by quantum oscillations and the Hall effect. The change of sign in S(T) at T?50K is remarkably similar to that observed in La2-xBaxCuO4, La2-x-yNdySrxCuO4, and La2-x-yEuySrxCuO4, where it is clearly associated with the onset of stripe order. We propose that a similar density-wave mechanism causes the Fermi surface reconstruction in YBCO.

Chang, J.; Daou, R.; Proust, Cyril; Leboeuf, David; Doiron-Leyraud, Nicolas; Laliberté, Francis; Pingault, B.; Ramshaw, B. J.; Liang, Ruixing; Bonn, D. A.; Hardy, W. N.; Takagi, H.; Antunes, A. B.; Sheikin, I.; Behnia, K.; Taillefer, Louis

2010-02-01

110

Seebeck and figure of merit enhancement in nanostructured antimony telluride by antisite defect suppression through sulfur doping.  

PubMed

Antimony telluride has a low thermoelectric figure of merit (ZT < ?0.3) because of a low Seebeck coefficient ? arising from high degenerate hole concentrations generated by antimony antisite defects. Here, we mitigate this key problem by suppressing antisite defect formation using subatomic percent sulfur doping. The resultant 10-25% higher ? in bulk nanocrystalline antimony telluride leads to ZT ? 0.95 at 423 K, which is superior to the best non-nanostructured antimony telluride alloys. Density functional theory calculations indicate that sulfur increases the antisite formation activation energy and presage further improvements leading to ZT ? 2 through optimized doping. Our findings are promising for designing novel thermoelectric materials for refrigeration, waste heat recovery, and solar thermal applications. PMID:22891784

Mehta, Rutvik J; Zhang, Yanliang; Zhu, Hong; Parker, David S; Belley, Matthew; Singh, David J; Ramprasad, Ramamurthy; Borca-Tasciuc, Theodorian; Ramanath, Ganpati

2012-09-12

111

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

112

Observations of Co4+ in a higher spin state and the increase in the Seebeck coefficient of thermoelectric Ca3Co4O9.  

PubMed

Ca3Co4O9 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 Ca3Co4O9 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 Ca3Co4O9. The higher Seebeck coefficient makes the Ca3Co4O9 system suitable for many high temperature waste-heat-recovery applications. PMID:23003068

Klie, R F; Qiao, Q; Paulauskas, T; Gulec, A; Rebola, A; Ö?üt, S; Prange, M P; Idrobo, J C; Pantelides, S T; Kolesnik, S; Dabrowski, B; Ozdemir, M; Boyraz, C; Mazumdar, D; Gupta, A

2012-05-11

113

Transport Properties of Bulk Thermoelectrics An International Round-Robin Study, Part I: Seebeck Coefficient and Electrical Resistivity  

SciTech Connect

Recent research and development of high temperature thermoelectric materials has demonstrated great potential of converting automobile exhaust heat directly into electricity. Thermoelectrics based on classic bismuth telluride have also started to impact the automotive industry by enhancing air conditioning efficiency and integrated cabin climate control. In addition to engineering challenges of making reliable and efficient devices to withstand thermal and mechanical cycling, the remaining issues in thermoelectric power generation and refrigeration are mostly materials related. The figure-of-merit, ZT, still needs to improve from the current value of 1.0 - 1.5 to above 2 to be competitive to other alternative technologies. In the meantime, the thermoelectric community could greatly benefit from the development of international test standards, improved test methods and better characterization tools. Internationally, thermoelectrics have been recognized by many countries as an important area for improving energy efficiency. The International Energy Agency (IEA) group under the implementing agreement for Advanced Materials for Transportation (AMT) identified thermoelectric materials as an important area in 2009. This paper is Part I of the international round-robin testing of transport properties of bulk thermoelectrics. The main focuses in Part I are on two electronic transport properties: Seebeck coefficient and electrical resistivity.

Wang, Hsin [ORNL; Porter, Wallace D [ORNL; Bottner, Harold [Fraunhofer-Institute, Freiburg, Germany; Konig, Jan [Fraunhofer-Institute, Freiburg, Germany; Chen, Lidong [Chinese Academy of Sciences; Bai, Shengqiang [Chinese Academy of Sciences; Tritt, Terry M. [Clemson University; Mayolett, Alex [Corning, Inc; Senawiratne, Jayantha [Corning, Inc; Smith, Charlene [Corning, Inc; Harris, Fred [ZT-Plus; Gilbert, Partricia [Marlow Industries, Inc; Sharp, Jeff [Marlow Industries, Inc; Lo, Jason [CANMET - Materials Technology Laboratory, Natural Resources of Canada; Keinke, Holger [University of Waterloo, Canada; Kiss, Laszlo I. [University of Quebec at Chicoutimi

2013-01-01

114

Thermal conductivity and Seebeck coefficient of 12CaO?7Al2O3 electride with a cage structure  

NASA Astrophysics Data System (ADS)

Thermal conductivity (?) and Seebeck coefficient (?) of electron-doped light-metal oxide 12CaO?7Al2O3 (C12A7 electride) with a subnanometer-sized cage structure are reported on single crystals with various electron concentrations (Ne) . The semiconducting C12A7 electride exhibits n -type conduction with the highest ? value of -100?VK-1 at 300 K. The ? exhibits an amorphouslike T2 dependence at low temperatures and varies between 2.3 and 4.5Wm-1K-1 at 300 K. This is an order-of-magnitude lower than that of the constituents, CaO (15Wm-1K-1) and Al2O3 (30Wm-1K-1) . These properties are attributed to the cage structure, suggesting that the semiconducting electride should be regarded as a phonon glass and electron crystal material. The thermoelectric performance of electrides evaluated by a dimensionless figure of merit (ZT) shows an optimized value of 2×10-3 at 300 K for the semiconducting electride with Ne of 5×1020cm-3 .

Kim, Sung Wng; Tarumi, Ryuichi; Iwasaki, Hideo; Ohta, Hiromichi; Hirano, Masahiro; Hosono, Hideo

2009-08-01

115

Ratchet effects in graphene and quantum wells with lateral superlattice  

NASA Astrophysics Data System (ADS)

Theoretical and experimental studies on the ratchet effects in graphene and in quantum wells with a lateral superlattice excited by alternating electric fields of terahertz frequency range are presented. We discuss the Seebeck ratchet effect and helicity driven photocurrents and show that the photocurrent generation is based on the combined action of a spatially periodic in-plane potential and a spatially modulated light.

Golub, L. E.; Nalitov, A. V.; Ivchenko, E. L.; Olbrich, P.; Kamann, J.; Eroms, J.; Weiss, D.; Ganichev, S. D.

2013-12-01

116

Hall, Seebeck, and Nernst Coefficients of Underdoped HgBa2CuO4+?: Fermi-Surface Reconstruction in an Archetypal Cuprate Superconductor  

DOE PAGESBeta

Charge-density-wave order has been observed in cuprate superconductors whose crystal structure breaks the square symmetry of the CuO2 planes, such as orthorhombic YBa2Cu3Oy (YBCO), but not so far in cuprates that preserve that symmetry, such as tetragonal HgBa2CuO4+? (Hg1201). We have measured the Hall (RH), Seebeck (S), and Nernst (?) coefficients of underdoped Hg1201 in magnetic fields large enough to suppress superconductivity. The high-field RH(T) and S(T) are found to drop with decreasing temperature and become negative, as also observed in YBCO at comparable doping. In YBCO, the negative RH and S are signatures of a small electron pocket caused by Fermi-surface reconstruction, attributed to charge-density-wave modulations observed in the same range of doping and temperature. We deduce that a similar Fermi-surface reconstruction takes place in Hg1201, evidence that density-wave order exists in this material. A striking similarity is also found in the normal-state Nernst coefficient ?(T), further supporting this interpretation. Given the model nature of Hg1201, Fermi-surface reconstruction appears to be common to all hole-doped cuprates, suggesting that density-wave order is a fundamental property of these materials.

Doiron-Leyraud, Nicolas; Lepault, S.; Cyr-Choinière, O.; Vignolle, B.; Grissonnanche, G.; Laliberté, F.; Chang, J.; Bariši?, N.; Chan, M. K.; Ji, L.; Zhao, X.; Li, Y.; Greven, M.; Proust, C.; Taillefer, Louis

2013-06-01

117

Anomalous Enhancement of Seebeck Coefficient in Pr-Based 1-2-20 System with Non-Kramers Doublet Ground States  

NASA Astrophysics Data System (ADS)

Low-temperature Seebeck coefficient S/T measurements have been performed on Pr-based 1-2-20 system, PrTr2X20 (Tr = Ti, Ta, V, Ir, X = Al, Zn) with non-Kramers doublet ground states. For PrTr2X20 with X = Al, we find a large S/T, which amounts to those of heavy fermion metals. By contrast, S/T for PrIr2Zn20 is found to be considerably small as the same order of magnitude as those of ordinary metals, despite the commonly enhanced Sommerfeld coefficient ? throughout the system. A satisfactory of the quasi-universal relation between S/T and ? as well as the Kadowaki-Woods relation demonstrates that the mass enhancement is realized in PrTr2Al20 due to the hybridization between f-electrons and the conduction electrons. We also find that the small S/T of PrIr2Zn20 is enhanced at low temperatures under the fields on the verge of quadrupole ordered phase, and in the same regime, the electrical resistivity follows the quadratic temperature dependence with a steep slope as a characteristic of Fermi liquid. The results imply an emergence of a nontrivial coherent state with sizable mass enhancement associated with the quadrupole degree of freedom.

Machida, Y.; Yoshida, T.; Ikeura, T.; Izawa, K.; Nakama, A.; Higashinaka, R.; Aoki, Y.; Sato, H.; Sakai, A.; Nakatsuji, S.; Nagasawa, N.; Matsumoto, K.; Onimaru, T.; Takabatake, T.

2015-03-01

118

Seebeck coefficient in organic semiconductors  

E-print Network

stories. Stephen went out of his way to introduce me to all things quintessentially English, an act for which I shall remain very thankful. He is a man with a big heart, and great dreams for a better world. I really consider myself lucky having met him... ,4-ethylenedioxythiophene) doped with poly(styrenesulphonate) (PEDOT:PSS) [14]. In an alternate report on PEDOT, its ZT value was controlled depending on its oxidation level, achieving a maximum of ZT ? 0.25 [15]. There are not many reports documenting ZT in many organic...

Venkateshvaran, Deepak

2014-07-01

119

Analysis of Residual Acceleration Effects on Transport and Segregation During Directional Solidification of Tin-Bismuth in the MEPHISTO Furnace Facility  

NASA Technical Reports Server (NTRS)

The objective of this work is to approach the problem of determining the transport conditions (and effects of residual acceleration) during the plane-front directional solidification of a tin-bismuth alloy under low gravity conditions. The work involves using a combination of 2- and 3-D numerical models, scaling analyses, ID models and the results of ground-based and low-gravity experiments. The latter are to be conducted during the MEPHISTO experiment scheduled for USMP-3 in early 1996. The models will be used to predict the response of the transport conditions and consequent solute segregation in directionally solidifying tin-bismuth melt. Real-time Seebeck voltage variations across a Sn-Bi melt during directional solidification in MEPHISTO on USMP-1 show a distinct variation which can be correlated with thruster firings. The Seebeck voltage measurement is related to the response of the instantaneous average melt composition at the melt-solid interface. This allows a direct comparison of numerical simulations with the Seebeck signals obtained on USMP-1. The effects of such accelerations on composition for a directionally solidifying Sn-Bi alloy have been simulated numerically. USMP-1 acceleration data was used to assist in our choice of acceleration magnitude and orientation. The results show good agreement with experimental observations. The USMP-3 experiments took place earlier this year (February 22 through March 6). There were several differences between the USMP-3 experiments as compared to USMP-1. Firstly a more concentrated alloy was solidified and, secondly, Primary Reaction Control System thruster burns were requested at particular times during four separate growth runs. This allowed us to monitor the response Seebeck response under well-characterized growth conditions. In addition, we carried out simulations during the experiment in order to interpret the Seebeck signal. Preliminary results are described here.

Alexander J. Iwan D. (Principal Investigator)

1996-01-01

120

Effects of yttrium doping on the thermoelectric properties of Hf0.6Zr0.4NiSn0.98Sb0.02 half-Heusler alloys  

NASA Astrophysics Data System (ADS)

The (Y,Sb) codoped (Hf0.6Zr0.4)1-xYxNiSn0.98Sb0.02 (x=0, 0.01, 0.015, 0.02, and 0.025) half-Heusler alloys were prepared by levitation melting and spark plasma sintering. The effects of Y doping on the electrical conductivity, the Seebeck coefficient, and the thermal conductivity have been investigated in the temperature range of 300-900 K. It was found that the Y doping decreased the carrier concentration and electrical conductivity due to the introduction of hole carriers. The thermal conductivity was also reduced upon Y doping, mainly due to the reduced carrier thermal conductivity. The Y-doping substantially increased the Seebeck coefficient because of the decrease in carrier concentration. Pisarenko plot showed that the measured room temperature Seebeck coefficients agrees well with the predicted single parabolic band behavior as a function of the carrier concentration, suggesting that no additional mechanisms cause the extra enhancement of Seebeck coefficient in the Y-Sb codoped half-Heusler alloys. The figure of merit ZT of 1% Y-doped sample was increased by a factor of about 25% than that of the undoped sample.

Zhu, T. J.; Xiao, K.; Yu, C.; Shen, J. J.; Yang, S. H.; Zhou, A. J.; Zhao, X. B.; He, J.

2010-08-01

121

Doping effects on thermoelectric properties of the off-stoichiometric Heusler compounds Fe{sub 2?x}V{sub 1+x}Al  

SciTech Connect

The thermoelectric properties of Heusler-type Fe{sub 2?x}V{sub 1+x}Al{sub 1?y}Si{sub y} and Fe{sub 2?x}V{sub 1+x?y}Ti{sub y}Al alloys have been investigated to clarify which off-stoichiometric alloy, i.e., V-rich (x?>?0) or V-poor (x?effective in enhancing the Seebeck coefficient when doped by Si and Ti, while retaining a low electrical resistivity. Large Seebeck coefficients of ?182??V/K and 110??V/K at 300?K are obtained for n-type Fe{sub 1.95}V{sub 1.05}Al{sub 0.97}Si{sub 0.03} and p-type Fe{sub 2.04}V{sub 0.93}Ti{sub 0.03}Al, respectively. When the Seebeck coefficient is plotted as a function of valence electron concentration (VEC), the VEC dependence for the doped off-stoichiometric alloys falls on characteristic curves depending on the off-stoichiometric composition x. It is concluded that a larger Seebeck coefficient with a negative sign can be obtained for the V-rich alloys rather than the V-poor alloys, whilst good p-type materials are always derived from the V-poor alloys. Substantial enhancements in the Seebeck coefficient for the off-stoichiometric alloys could be achieved by a favorable modification in the electronic structure around the Fermi level through the antisite V or Fe defect formation.

Nishino, Y., E-mail: nishino@nitech.ac.jp; Tamada, Y. [Department of Frontier Materials, Nagoya Institute of Technology, Nagoya 466-8555 (Japan)

2014-03-28

122

Thermoelectric effects in graphene nanostructures.  

PubMed

The thermoelectric properties of graphene and graphene nanostructures have recently attracted significant attention from the physics and engineering communities. In fundamental physics, the analysis of Seebeck and Nernst effects is very useful in elucidating some details of the electronic band structure of graphene that cannot be probed by conductance measurements alone, due in particular to the ambipolar nature of this gapless material. For applications in thermoelectric energy conversion, graphene has two major disadvantages. It is gapless, which leads to a small Seebeck coefficient due to the opposite contributions of electrons and holes, and it is an excellent thermal conductor. The thermoelectric figure of merit ZT of a two-dimensional (2D) graphene sheet is thus very limited. However, many works have demonstrated recently that appropriate nanostructuring and bandgap engineering of graphene can concomitantly strongly reduce the lattice thermal conductance and enhance the Seebeck coefficient without dramatically degrading the electronic conductance. Hence, in various graphene nanostructures, ZT has been predicted to be high enough to make them attractive for energy conversion. In this article, we review the main results obtained experimentally and theoretically on the thermoelectric properties of graphene and its nanostructures, emphasizing the physical effects that govern these properties. Beyond pure graphene structures, we discuss also the thermoelectric properties of some hybrid graphene structures, as graphane, layered carbon allotropes such as graphynes and graphdiynes, and graphene/hexagonal boron nitride heterostructures which offer new opportunities. Finally, we briefly review the recent activities on other atomically thin 2D semiconductors with finite bandgap, i.e. dichalcogenides and phosphorene, which have attracted great attention for various kinds of applications, including thermoelectrics. PMID:25779989

Dollfus, Philippe; Hung Nguyen, Viet; Saint-Martin, Jérôme

2015-04-10

123

Thermoelectric effects in graphene nanostructures  

NASA Astrophysics Data System (ADS)

The thermoelectric properties of graphene and graphene nanostructures have recently attracted significant attention from the physics and engineering communities. In fundamental physics, the analysis of Seebeck and Nernst effects is very useful in elucidating some details of the electronic band structure of graphene that cannot be probed by conductance measurements alone, due in particular to the ambipolar nature of this gapless material. For applications in thermoelectric energy conversion, graphene has two major disadvantages. It is gapless, which leads to a small Seebeck coefficient due to the opposite contributions of electrons and holes, and it is an excellent thermal conductor. The thermoelectric figure of merit ZT of a two-dimensional (2D) graphene sheet is thus very limited. However, many works have demonstrated recently that appropriate nanostructuring and bandgap engineering of graphene can concomitantly strongly reduce the lattice thermal conductance and enhance the Seebeck coefficient without dramatically degrading the electronic conductance. Hence, in various graphene nanostructures, ZT has been predicted to be high enough to make them attractive for energy conversion. In this article, we review the main results obtained experimentally and theoretically on the thermoelectric properties of graphene and its nanostructures, emphasizing the physical effects that govern these properties. Beyond pure graphene structures, we discuss also the thermoelectric properties of some hybrid graphene structures, as graphane, layered carbon allotropes such as graphynes and graphdiynes, and graphene/hexagonal boron nitride heterostructures which offer new opportunities. Finally, we briefly review the recent activities on other atomically thin 2D semiconductors with finite bandgap, i.e. dichalcogenides and phosphorene, which have attracted great attention for various kinds of applications, including thermoelectrics.

Dollfus, Philippe; Nguyen, Viet Hung; Saint-Martin, Jérôme

2015-04-01

124

On the Quantum Hall Effect in mono(bi)-layer graphene  

NASA Astrophysics Data System (ADS)

Based on a thermodynamic approach, we have calculated the specific resistivity of mono(bi)-layer graphene assumed dissipationless in quantizing magnetic field. The resistivity arises from combination of Peltier and Seebeck effects. The current I causes heating (cooling) at the first (second) sample contacts, due to the Peltier effect. The voltage measured across the sample is equal to the Seebeck thermoemf, and thus provides finite resistivity as I?0. The resistivity is a universal function of the magnetic field, e-h plasma density and temperature, expressed in fundamental units h/e2. At fixed magnetic field the magneto-transport problem is resolved in the vicinity of the Dirac point taking into account the splitting of zeroth Landau level. For mono(bi)- layer graphene the B-dependent splitting of zeroth Landau level is recovered from experimental data.

Cheremisin, M. V.

2014-11-01

125

Chemical pressure effect on the transport and electronic band structure of Fe2V1-xNbxAl  

NASA Astrophysics Data System (ADS)

We report the effects of partial substitution of Nb onto the V sites of Fe2VAl by measuring the electrical resistivity, Seebeck coefficient, and thermal conductivity as a function of temperature. It is found that the Nb substitution effectively produces a negative chemical pressure in the system. As a result, the Nb-substituted materials show enhanced semiconductinglike behavior in their electrical resistivity. In addition, the Seebeck coefficient changes sign from positive to negative while replacing V with Nb. These phenomena have been associated with the change of the band features, mainly due to the decrease in the number of the hole carriers. To identify this scenario, we performed ab initio calculations to investigate the electronic band structures of Fe2V1-xNbxAl , focusing on the band variation around the Fermi level. Theoretical results indicate a significant reduction in the hole pockets through Nb substitution, which is consistent with experimental observations.

Lue, C. S.; Liu, R. F.; Song, M. Y.; Wu, K. K.; Kuo, Y. K.

2008-10-01

126

Compensation of voltage drops in solid-state switches used with thermoelectric generators  

NASA Technical Reports Server (NTRS)

Seebeck effect solid state switch was developed eliminating thermoelectric generator switch voltage drops. Semiconductor switches were fabricated from materials with large Seebeck coefficients, arranged such that Seebeck potential is generated with such polarity that current flow is aided.

Shimada, K.

1972-01-01

127

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

2012-11-01

128

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

129

Anomalous effect of vanadium boride seeding on thermoelectric properties of YB{sub 22}C{sub 2}N  

SciTech Connect

Highlights: ? We doped YB{sub 22}C{sub 2}N; the long awaited n-type counterpart to p-type boron carbide. ? VB{sub 2} seeding of YB{sub 22}C{sub 2}N showed striking results. ? Thermal treatment effects led to VB{sub 2} being intrinsically doped. ? Large increase of both Seebeck coefficient and electrical conductivity was obtained. - Abstract: Vanadium boride seeded YB{sub 22}C{sub 2}N were synthesized and the thermoelectric properties investigated. YB{sub 22}C{sub 2}N is representative of the series of rare earth borocarbonitrides which is the potential long awaited n-type counterpart to p-type boron carbide. VB{sub 2} seeded samples of YB{sub 22}C{sub 2}N were prepared using VB{sub 2} directly as an initial additive and V{sub 2}O{sub 3} which also results in formation of vanadium diboride in the final product. The resistivity and Seebeck coefficient of samples were measured in the temperature range of 323 K to 1073 K. A dramatic effect of thermal treatment on the Seebeck coefficient of VB{sub 2} seeded samples was observed, and it is indicated that there is possible partial intrinsic doping of vanadium into YB{sub 22}C{sub 2}N. VB{sub 2} is revealed to be a promising additive to improve the thermoelectric properties of YB{sub 22}C{sub 2}N. An enhancement of more than 220% of the maximum absolute value of the Seebeck coefficient was obtained while the resistivity was also reduced considerably.

Prytuliak, A.; Maruyama, S. [International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), Namiki 1-1, Tsukuba 305-0044 (Japan); Mori, T., E-mail: MORI.Takao@nims.go.jp [International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), Namiki 1-1, Tsukuba 305-0044 (Japan)

2013-05-15

130

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

131

Effect of Heavy Element Substitution and Off-Stoichiometric Composition on Thermoelectric Properties of Fe2VAl-Based Heusler Phase  

NASA Astrophysics Data System (ADS)

The thermoelectric performance of Fe2VAl-based alloys was improved by using the effects of (a) heavy element substitution and (b) off-stoichiometric (Fe/V ? 2) composition. The former method led to a significant reduction of lattice thermal conductivity, whereas the latter to an evolution of the Seebeck coefficient. As a result of sample preparation, we confirmed that the dimensionless figure of merit with n-type behavior was increased up to 0.25 at 420 K for the sample obtained at the optimized composition of Fe1.98V0.97Ta0.05Al0.9Si0.1. Electronic structure calculations revealed that the increase of the Seebeck coefficient observed for Fe-poor samples was caused by a reduction of the density of states near the chemical potential.

Takeuchi, Tsunehiro; Terazawa, Yuichi; Furuta, Yukihiro; Yamamoto, Akio; Mikami, Masashi

2013-07-01

132

Photo-controllable thermoelectric properties with reversibility and photo-thermoelectric effects of tungsten trioxide accompanied by its photochromic phenomenon  

NASA Astrophysics Data System (ADS)

The addition of photo-controllable properties to tungsten trioxide (WO3) is of interest for developing practical applications of WO3 as well as for interpreting such phenomena from scientific viewpoints. Here, a sputtered crystalline WO3 thin film generated thermoelectric power due to ultraviolet (UV) light-induced band-gap excitation and was accompanied by a photochromic reaction resulting from generating W5+ ions. The thermoelectric properties (electrical conductivity (?) and Seebeck coefficient (S)) and coloration of WO3 could be reversibly switched by alternating the external stimulus between UV light irradiation and dark storage. After irradiating the film with UV light, ? increased, whereas the absolute value of S decreased, and the photochromic (coloration) reaction was detected. Notably, the opposite behavior was exhibited by WO3 after dark storage, and this reversible cycle could be repeated at least three times. Moreover, photo-thermoelectric effects (photo-conductive effect (photo-conductivity, ?photo) and photo-Seebeck effect (photo-Seebeck coefficient, Sphoto)) were also detected in response to visible-light irradiation of the colored WO3 thin films. Under visible-light irradiation, ?photo and the absolute value of Sphoto increased and decreased, respectively. These effects are likely attributable to the excitation of electrons from the mid-gap visible light absorption band (W5+ state) to the conduction band of WO3. Our findings demonstrate that the simultaneous, reversible switching of multiple properties of WO3 thin film is achieved by the application of an external stimulus and that this material exhibits photo-thermoelectric effects when irradiated with visible-light.

Azuma, Chiori; Kawano, Takuto; Kakemoto, Hirofumi; Irie, Hiroshi

2014-11-01

133

Photo-controllable thermoelectric properties with reversibility and photo-thermoelectric effects of tungsten trioxide accompanied by its photochromic phenomenon  

SciTech Connect

The addition of photo-controllable properties to tungsten trioxide (WO{sub 3}) is of interest for developing practical applications of WO{sub 3} as well as for interpreting such phenomena from scientific viewpoints. Here, a sputtered crystalline WO{sub 3} thin film generated thermoelectric power due to ultraviolet (UV) light-induced band-gap excitation and was accompanied by a photochromic reaction resulting from generating W{sup 5+} ions. The thermoelectric properties (electrical conductivity (?) and Seebeck coefficient (S)) and coloration of WO{sub 3} could be reversibly switched by alternating the external stimulus between UV light irradiation and dark storage. After irradiating the film with UV light, ? increased, whereas the absolute value of S decreased, and the photochromic (coloration) reaction was detected. Notably, the opposite behavior was exhibited by WO{sub 3} after dark storage, and this reversible cycle could be repeated at least three times. Moreover, photo-thermoelectric effects (photo-conductive effect (photo-conductivity, ?{sub photo}) and photo-Seebeck effect (photo-Seebeck coefficient, S{sub photo})) were also detected in response to visible-light irradiation of the colored WO{sub 3} thin films. Under visible-light irradiation, ?{sub photo} and the absolute value of S{sub photo} increased and decreased, respectively. These effects are likely attributable to the excitation of electrons from the mid-gap visible light absorption band (W{sup 5+} state) to the conduction band of WO{sub 3}. Our findings demonstrate that the simultaneous, reversible switching of multiple properties of WO{sub 3} thin film is achieved by the application of an external stimulus and that this material exhibits photo-thermoelectric effects when irradiated with visible-light.

Azuma, Chiori [Faculty of Engineering, University of Yamanashi, 4-3-11 Takeda, Kofu, Yamanashi 400-8511 (Japan); Kawano, Takuto [Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, 4-3-11 Takeda, Kofu, Yamanashi 400-8511 (Japan); Kakemoto, Hirofumi; Irie, Hiroshi, E-mail: hirie@yamanashi.ac.jp [Clean Energy Research Center, University of Yamanashi, 4-3-11 Takeda, Kofu, Yamanashi 400-8511 (Japan)

2014-11-07

134

Effects of Ni, Pd, and Pt Substitutions on Thermoelectric Properties of CoSi Alloys  

NASA Astrophysics Data System (ADS)

Ni-, Pd-, and Pt-substituted CoSi samples have been prepared by an arc melting and annealing procedure. The x-ray diffraction and scanning electron microscopy results show that Ni and Pd are effective n-type dopants for CoSi, while Pt is immiscible with CoSi and forms an impurity phase with a possible chemical formula of PtCoSi2. The thermoelectric properties were measured from 80 K to 300 K. For Ni- and Pd-doped samples, the electrical resistivity and Seebeck coefficient decrease simultaneously due to the increasing carrier concentration. For Pt-substituted samples, the electrical resistivity also decreases. However, this reduction is thought to be not due to an increase in carriers but rather to originate from the effect of the Pt-rich impurity phase at the grain boundaries. The Seebeck coefficient is not affected by 1% Pt substitution; however, further increase of the Pt level also causes a decrease in the Seebeck coefficient. The room-temperature power factor is 63 ?W K-2 cm-1 for pure CoSi and 73 ?W K-2 cm-1 for the Co0.99Pt0.01Si sample. Although the thermal conductivity is reduced for both n-type-doped and Pt-substituted samples around 80 K, the room-temperature values are still close to that of pure CoSi. As a result, ZT of 0.13 is obtained at room temperature for Co0.99Pt0.01Si, an 18% increase compared with CoSi.

Sun, Hui; Lu, Xu; Morelli, Donald T.

2013-07-01

135

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

136

Specific salt effects on thermophoresis of charged colloids.  

PubMed

We study the Soret effect of charged polystyrene particles as a function of temperature and electrolyte composition. As a main result we find that the Soret coefficient is determined by charge effects, and that non-ionic contributions are small. In view of the well-known electric-double layer interactions, our thermal field-flow fractionation data lead us to the conclusion that the Soret effect originates to a large extent from diffusiophoresis in the salt gradient and from the electrolyte Seebeck effect, both of which show strong specific-ion effects. Moreover, we find that thermophoresis of polystyrene beads is fundamentally different from proteins and aqueous polymer solutions, which show a strong non-ionic contribution. PMID:24652409

Eslahian, Kyriakos A; Majee, Arghya; Maskos, Michael; Würger, Alois

2014-03-28

137

Enhancement of the thermoelectric figure of merit in DNA-like systems induced by Fano and Dicke effects.  

PubMed

We report a theoretical study highlighting the thermoelectric properties of biological and synthetic DNA molecules. Based on an effective tight-binding model of duplex DNA and by using the nonequilibrium Green's function technique, the thermal conductance, electrical conductance, Seebeck coefficient and thermoelectric figure of merit in the system are numerically calculated by varying the asymmetries of energies and electronic hoppings in the backbone sites to simulate the environmental complications and fluctuations. We find that due to the multiple transport paths in the DNA molecule, the Fano antiresonance occurs, and enhances the Seebeck coefficient and the figure of merit. When the energy difference is produced in every opposite backbone site, the Dicke effect appears. This effect gives rise to a semiconducting-metallic transition, and enhances the thermoelectric efficiency of the DNA molecule remarkably. Moreover, as the Fano antiresonance point is close to the Dicke resonance one, a giant enhancement in the thermoelectric figure of merit in the DNA molecule has been found. These results provide a scenario to obtain effective routes to enhance the thermoelectric efficiency in the DNA molecules, and suggest perspectives for future experiments intending to control the thermoelectric transport in DNA-like nanodevices. PMID:25826287

Fu, Hua-Hua; Gu, Lei; Wu, Dan-Dan; Zhang, Zu-Quan

2015-04-01

138

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

139

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

140

Influence of Thallium on the Shubnikov - de Haas effect and Thermoelectric Properties of Sb2Te3 and Bi2Se3  

NASA Astrophysics Data System (ADS)

Influence of Tl-doping on the Shubnikov de Haas effect (SdH) at T=4.2 K in magnetic field up to 38 T of p-Sb2-xTlxTe3 (x=0; 0.005; 0.015; 0.05) and n-Bi2-xTlxSe3 (x=0, 0.01; 0.02; 0.04; 0.06) single crystals has been investigated. By increasing the Tl content, the frequency of the SdH effect and hence the extremal cross-sections of the Fermi-surface decreases in both materials. The hole concentration decreases in Sb2-xTlxTe3 due to a donor effect of Tl and the electron concentration decreases in n-Bi2-xTlxSe3 due to an acceptor effect of Tl. Temperature dependence of the Seebeck coefficient S, electrical conductivity ?, thermal conductivity k and the figure of merit ZT single crystals were measured in the temperature range 77 K - 300 K. The values of k and ? decrease due to Tl doping in Sb2-xTlxTe3 and n-Bi2-xTlxSe3 and the Seebeck coefficient S for all compositions increases in the whole temperature range. The figure of merit ZT increases in both materials. The preferential scattering mechanism in Tl-doped samples changes from the acoustic phonon scattering to the ionized impurity scattering.

Kulbachinskii, V. A.; Kudryashov, A. A.; Kytin, V. G.

2014-12-01

141

Giant thermovoltage in single InAs nanowire field-effect transistors.  

PubMed

Millivolt range thermovoltage is demonstrated in single InAs nanowire based field effect transistors. Thanks to a buried heating scheme, we drive both a large thermal bias ?T > 10 K and a strong field-effect modulation of electric conductance on the nanostructures. This allows the precise mapping of the evolution of the Seebeck coefficient S as a function of the gate-controlled conductivity ? between room temperature and 100 K. Based on these experimental data a novel estimate of the electron mobility is given. This value is compared with the result of standard field-effect based mobility estimates and discussed in relation to the effect of charge traps in the devices. PMID:23869467

Roddaro, Stefano; Ercolani, Daniele; Safeen, Mian Akif; Suomalainen, Soile; Rossella, Francesco; Giazotto, Francesco; Sorba, Lucia; Beltram, Fabio

2013-08-14

142

Competing spin pumping effects in magnetic hybrid structures  

NASA Astrophysics Data System (ADS)

Pure spin current can be detected by its conversion into charge current in nanometer thick nonmagnetic metal layer with large spin-orbit coupling by means of the inverse spin Hall effect (ISHE). Recently, it has been shown that the metallic ferromagnet Permalloy (Py) can also be used as spin current detector in experiments in which an ISHE voltage is created in a Py layer in contact with the insulating ferromagnet yttrium iron garnet (YIG) under a thermal gradient in the longitudinal spin Seebeck configuration. Here, we report experiments with microwave driven spin pumping in heterostructures made with single crystal YIG film and a nanometer thick Py or Pt layer that show that Py behaves differently than nonmagnetic metals as a spin current detector. The results are attributed to the competition between the spin currents generated by the dynamics of the magnetizations in YIG and in Py, which are exchange coupled at the interface.

Azevedo, A.; Alves Santos, O.; Fonseca Guerra, G. A.; Cunha, R. O.; Rodríguez-Suárez, R.; Rezende, S. M.

2014-02-01

143

Thermoelectric effect enhanced by resonant states in graphene  

NASA Astrophysics Data System (ADS)

Thermoelectric effects in graphene are considered theoretically with particular attention paid to the role of resonant scattering on impurities. Using the T -matrix method we calculate the impurity resonant states and the momentum relaxation time due to scattering on impurities. The Boltzmann kinetic equation is used to determine the thermoelectric coefficients. It is shown that the resonant impurity states near the Fermi level give rise to a resonant enhancement of the Seebeck coefficient and figure of merit Z T . The Wiedemann-Franz ratio deviates from that known for ordinary metals, where this ratio is constant and equal to the Lorentz number. This deviation appears for small chemical potentials and in the vicinity of the resonant states. In the limit of a constant relaxation time, this ratio has been calculated analytically for ? =0 .

Inglot, M.; Dyrda?, A.; Dugaev, V. K.; Barna?, J.

2015-03-01

144

Seebeck and Peltier coefficients of hydrogen electrodes related to the  

E-print Network

and Technology #12;#12;Thermopower of concentration cell with hydrogen electrodes related to PEMFC Papy Mutuwa of a person who likes to learn new things all the time. After reading what NTNU had to offer, I decided to go with a specialization in Energy and gas Technology. This was a little bit different from Physical Chemistry. I

Kjelstrup, Signe

145

Giant Seebeck Coefficient in V-TCNE thin films  

NASA Astrophysics Data System (ADS)

The disordered structure of organic conductors results in a naturally low thermal conductivity (?) but their ZT is known to be low because of their low thermopower (S) and electrical conductivity (?). Here we report an exception, with results obtained from 220 to 320K for the thermopower of V-TCNEx (V-(C2(CN)4)x) thin films deposited on a Si wafer (111). At room temperature S=+21.8 mV/K and increases with decreasing temperature. Those values are matched only by very pure semiconductors such as Si at low temperature, Bi nanowires, or strongly correlated electron systems like FeSb2. The valence band of V-TCNE has a very high density of states over a very narrow energy range, ascribed mostly to vanadium 3d(t2g) orbitals,ootnotetextY-J Yoo et al., Nat. Mat. 9 638 2010 which is consistent with the exceptionally large value of S. The dependence of S and ? upon illumination will also be shown, alongside preliminary estimates for the ZT.

Chamoire, Audrey; Jaworski, Christopher; Kao, Chi-Yueh; Heremans, Joseph; Epstein, Arthur

2011-03-01

146

Seebeck nanoantennas for the detection and characterization of infrared radiation.  

PubMed

Arrays of metallic thermocouples in the shape of spiral nanoantennas are proposed as infrared detectors, which use the thermoelectric properties of the metallic interfaces to generate electrical DC signals. The responsivity of these types of antennas is evaluated from both theoretical and numerical perspectives pointing out its potential as infrared sensors. Moreover, the same structures can be used to characterize the state of polarization of the optical near fields with a spatial resolution comparable to the wavelength. PMID:25607310

Briones, Edgar; Cuadrado, Alexander; Briones, Joel; Díaz de León, Ramón; Martínez-Antón, Juan Carlos; McMurtry, Stefan; Hehn, Michel; Montaigne, François; Alda, Javier; González, Francisco Javier

2014-10-20

147

Effect of Heat Treatment in Air on Thermoelectric Properties of Polycrystalline Type-I Silicon-Based Clathrate: Ba8Al15Si31  

NASA Astrophysics Data System (ADS)

The effect of heat treatment in air on the thermoelectric properties was investigated for polycrystalline Ba8Al15Si31, where the Al content is almost at the maximum in the Ba8Al x Si46-x system, to evaluate the thermal stability in air at high temperatures, which is indispensable for practical use in thermoelectric applications. Samples were prepared by combining arc melting and spark plasma sintering techniques. Heat treatments were performed in air at 873 K for 10 days and 20 days. The Seebeck coefficient, electrical conductivity, and thermal conductivity were measured before and after the heat treatments. The microstructure and chemical composition were also analyzed before and after the heat treatments, using scanning electron microscopy with energy-dispersive x-ray spectroscopy. Although an oxidation layer was formed on the surface by the heat treatment in air, the chemical composition of the interior of Ba8Al15Si31 was found to be stable in air at 873 K for 10 days and 20 days. The Seebeck coefficient, the electrical conductivity, and the thermal conductivity were found to be almost unchanged after the heat treatment, indicating that Ba8Al15Si31 clathrate is promising as a thermoelectric material with high thermal stability for use in air at 873 K.

Anno, Hiroaki; Shirataki, Ritsuko

2014-09-01

148

Spin Hall magnetoresistance at Pt/CoFe2O4 interfaces and texture effects  

NASA Astrophysics Data System (ADS)

We report magnetoresistance measurements on thin Pt bars grown on epitaxial (001) and (111) CoFe2O4 (CFO) ferrimagnetic insulating films. The results can be described in terms of the recently discovered spin Hall magnetoresistance (SMR). The magnitude of the SMR depends on the interface preparation conditions, being optimal when the Pt/CFO samples are prepared in situ, in a single process. The spin-mixing interface conductance, the key parameter governing SMR and other relevant spin-dependent phenomena, such as spin pumping or spin Seebeck effect, is found to be different depending on the crystallographic orientation of CFO, highlighting the role of the composition and density of magnetic ions at the interface on spin mixing.

Isasa, Miren; Bedoya-Pinto, Amilcar; Vélez, Saül; Golmar, Federico; Sánchez, Florencio; Hueso, Luis E.; Fontcuberta, Josep; Casanova, Fèlix

2014-10-01

149

Effects of temperature and composition on the thermal and electrical conductivities of Ni3Al  

NASA Astrophysics Data System (ADS)

The results of a study of the thermal conductivity, electrical resistivity, and Seebeck coefficient of Ni3Al are described. The thermal and electrical conductivities are sensitive to composition and attain their maximum values in well-ordered, stoichiometric Ni3Al. Nonstoichiometry (antisite defects), and Fe (a substitutional solute) and B (an interstitial solute) contents are all about equally effective in reducing the transport properties. Even for stoichiometric Ni3Al, the temperature variation of the thermal and electrical conductivities resembles that of an alloy, and this is attributed to scattering associated with the loss of ferromagnetic order at ˜60 K. Experimental data and a theoretical analysis show that phonon conduction is an important part of the thermal conductivity and not very sensitive to composition or stoichiometry.

Williams, R. K.; Graves, R. S.; Weaver, F. J.

1987-02-01

150

Ultraviolet fast-response photoelectric effect in tilted orientation SrTiO{sub 3} single crystals  

SciTech Connect

Ultraviolet photoelectricity based on the vicinal cut as-supplied SrTiO{sub 3} single crystals has been experimentally studied in the absence of an applied bias at room temperature. An open-circuit photovoltage of 130 ps rise time and 230 ps full width at half maximum was observed under the irradiation of a 355 nm pulsed laser of 25 ps in duration. The dependence of the photoelectric effect on the tilting angles was studied, and the optimum angle is 20.9 deg. . Seebeck effect is proposed to elucidate the tilting angle dependence of laser-induced photovoltage. This work demonstrates the potential of SrTiO{sub 3} single crystals in ultraviolet detection.

Zhao Kun; Jin Kuijuan; Huang Yanhong; Zhao Songqing; Lu Huibin; He Meng; Chen Zhenghao; Zhou Yueliang; Yang Guozhen [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100080 (China) and Department of Mathematics and Physics, China University of Petroleum, Beijing 102249 (China) and International Center for Materials Physics, Chinese Academy of Sciences, Shenyang 110016 (China); Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100080 (China)

2006-10-23

151

Al insertion and additive effects on the thermoelectric properties of yttrium boride  

NASA Astrophysics Data System (ADS)

The aluminoboride YxAlyB14 (x ˜ 0.57, 0.41 ? y ? 0.63) has been found to show striking p-n control of the thermoelectric properties through variations of the y occupancy of the Al site. The effect of Al was investigated in further extremes. Polycrystalline samples of Al-free YxB14(x ˜ 0.55; "YB25") were successfully synthesized in sufficient amounts for bulk spark plasma sintering (SPS) samples and their thermoelectric properties were investigated. Y0.56Al0.57B14 was also prepared in comparison, and further Al was added to the samples through SPS treatment. We observed that Y0.55B14 exhibits large positive Seebeck coefficients, ˜1000 ?V K-1, around room temperature and the absolute value of the Seebeck coefficient largely decreases with increase of temperature while that of Y0.56Al0.57B14 is proportional to T-1/2, indicating a strong effect of Al on the electronic structure around the Fermi level. Y0.55B14 was found to be strongly disordered with a relatively low thermal conductivity and short localization length of 0.65 Å which is close to that previously determined for the disordered and thermally glass-like compound YB66. Occupancy of Al could not be increased further for the Al-rich sample, although Al was discovered to act as a sintering aid to enhance density and ZT could be significantly improved by 50%.

Maruyama, Satofumi; Prytuliak, Anastasiia; Miyazaki, Yuzuru; Hayashi, Kei; Kajitani, Tsuyoshi; Mori, Takao

2014-03-01

152

Al insertion and additive effects on the thermoelectric properties of yttrium boride  

SciTech Connect

The aluminoboride Y{sub x}Al{sub y}B{sub 14} (x???0.57, 0.41 ? y ? 0.63) has been found to show striking p-n control of the thermoelectric properties through variations of the y occupancy of the Al site. The effect of Al was investigated in further extremes. Polycrystalline samples of Al-free Y{sub x}B{sub 14}(x???0.55; “YB{sub 25}”) were successfully synthesized in sufficient amounts for bulk spark plasma sintering (SPS) samples and their thermoelectric properties were investigated. Y{sub 0.56}Al{sub 0.57}B{sub 14} was also prepared in comparison, and further Al was added to the samples through SPS treatment. We observed that Y{sub 0.55}B{sub 14} exhibits large positive Seebeck coefficients, ?1000??V K{sup ?1}, around room temperature and the absolute value of the Seebeck coefficient largely decreases with increase of temperature while that of Y{sub 0.56}Al{sub 0.57}B{sub 14} is proportional to T{sup ?1/2}, indicating a strong effect of Al on the electronic structure around the Fermi level. Y{sub 0.55}B{sub 14} was found to be strongly disordered with a relatively low thermal conductivity and short localization length of 0.65?Å which is close to that previously determined for the disordered and thermally glass-like compound YB{sub 66}. Occupancy of Al could not be increased further for the Al-rich sample, although Al was discovered to act as a sintering aid to enhance density and ZT could be significantly improved by 50%.

Maruyama, Satofumi [National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba 305-0044 (Japan); Department of Applied Physics, Graduate School of Engineering, Tohoku University, 6-6-05 Aoba, Aramaki, Aoba-ku, Sendai 980-8579 (Japan); Prytuliak, Anastasiia [National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba 305-0044 (Japan); Miyazaki, Yuzuru; Hayashi, Kei; Kajitani, Tsuyoshi [Department of Applied Physics, Graduate School of Engineering, Tohoku University, 6-6-05 Aoba, Aramaki, Aoba-ku, Sendai 980-8579 (Japan); Mori, Takao, E-mail: MORI.Takao@nims.go.jp [National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba 305-0044 (Japan); University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577 (Japan)

2014-03-28

153

The Effect of Multivalley Bandstructure on Thermoelectric Properties of Al x Ga1- x As  

NASA Astrophysics Data System (ADS)

We present the theoretical modeling of the thermoelectric properties of Al x Ga1- x As. It was shown that, contrary to the known good thermoelectric materials, the optimum composition happens far from the point at which the multiple bands meet. This unexpected optimum material composition is related to the detrimental effect of multivalley bandstructure. A semi-empirical model was employed to predict the thermoelectric properties versus alloy composition, temperature, and doping concentration. The electrical conductivity, Seebeck coefficient and figure-of-merit ( ZT) were calculated with consideration of the energy-dependent relaxation time and multivalley band structure for Al x Ga1- x As. The theoretical model was verified by comparison with different sets of experimental data on both electrical and thermal transport properties. It was shown that the multivalley bandstructure in Al x Ga1- x As affects the Seebeck coefficient in two counteracting processes; however, it always reduces the electrical conductivity and the electronic thermal conductivity. It was shown that the multivalley bandstructure also affects the lattice thermal conductivity. In contrast to several good thermoelectric materials in which their multivalley band structure enhances the ZT, in Al x Ga1- x As, the ZT reduces at the composition x at which the three bands of ?, X, and L meet each other. Therefore, the maximum ZT happens far from this point. The optimum x also depends on temperature and reduces with temperature. Therefore, the Al concentration must decrease across the thermoelectric leg from the cold to the hot side. At the optimum composition, the ZT of Al x Ga1- x As is predicted to be comparable to that of good thermoelectric materials at high temperatures.

Norouzzadeh, Payam; Vashaee, Daryoosh

2015-02-01

154

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

155

Effects of Pr doping on thermoelectric transport properties of Ca 3- xPr xCo 4O 9  

NASA Astrophysics Data System (ADS)

The rare earth praseodymium doped Ca 3- xPr xCo 4O 9 ( x = 0.05, 0.1, 0.2 and 0.3) thermoelectric bulk materials are fabricated by combining sol-gel with spark plasma sintering method. The bulk specimens are characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The effects of Pr doping on thermoelectric transport properties have been investigated. The results show that all specimens are single-phased; the grain orientated bulks present deteriorated texture. The polaron carrier conduction mechanism is not changed and the electrical conduction is tuned as a result of carrier concentration modification, thereby an enhanced Seebeck coefficient. The total thermal conductivity is suppressed mainly due to the phonon thermal conduction confinement. The thermoelectric performance of the bulk material is optimized at x = 0.2.

Zhang, F. P.; Zhang, X.; Lu, Q. M.; Zhang, J. X.; Liu, Y. Q.; Zhang, G. Z.

2011-07-01

156

Effects of Nano-?-Al2O3 Dispersion on the Thermoelectric and Mechanical Properties of CoSb3 Composites  

NASA Astrophysics Data System (ADS)

Nano-?-Al2O3/CoSb3 composites with different ?-Al2O3 contents were prepared by spark plasma sintering. The effects of ?-Al2O3 addition on the microstructure, the thermoelectric properties, and the mechanical properties were studied in this article. It is found that ?-Al2O3 nanoparticles locate mainly at grain boundaries of the matrix. The dispersed particles decrease both the electrical conductivity and the thermal conductivity, but make the Seebeck coefficient increase. The dimensionless figure of merit is nearly unchanged by the dispersion. However, the introduction of nano-?-Al2O3 is very effective in improving the mechanical performance of the composites. The compressive strength and flexural strength of the 1.0 wt.% nano-?-Al2O3 dispersed samples are improved by 42.7 and 52.0%, respectively, compared with the nondispersed samples.

Wen, Pengfei; Mei, Hong; Zhai, Pengcheng; Duan, Bo

2013-11-01

157

Effects of Mn substitution on the thermoelectric properties of the electron-doped perovskite Sr1-xLaxTiO3  

NASA Astrophysics Data System (ADS)

We have tried to improve the n-type thermoelectric properties of the electron- doped Perovskite Sr1-xLaxTiO3 by a Mn substitution. The 1 ~ 2 % Mn substitution enhances the Seebeck coefficient (S) and reduces the thermal conductivity (?) by about 50 % at room temperature (RT) without largely increasing the resistivity for the 5 % electron-doped SrTiO3. Consequently, the power factor at RT keeps a large value comparable to that of Bi2Te3 and the dimensionless figure-of-merits at RT increases twofold by the slight Mn substitution. Such a large reduction of ? at RT is perhaps due to the effect of Jahn-Teller active Mn3+ ions, around which dynamical local lattice distortion may occur.

Okuda, T.; Hata, H.; Eto, T.; Nishina, K.; Kuwahara, H.; Nakamura, M.; Kajimoto, R.

2014-12-01

158

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

159

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

160

Thermoelectric effects and magnetic anisotropy of Ga1-xMnxAs thin films  

NASA Astrophysics Data System (ADS)

The transverse voltages generated in a Ga1-xMnxAs ferromagnetic semiconductor in planar Hall effect and transverse spin Seebeck effect configurations are systematically analyzed. The observed field dependences consist of symmetric and asymmetric contributions. The former is attributed to the planar Nernst effect in the magnetic film in the presence of an in-plane temperature gradient, while the latter is caused by the anomalous Nernst effect due to spurious out-of-plane temperature gradients with a coefficient as high as 500 ?V/K. We also report on the experimental observation of the planar Hall effect measured at different temperatures. Using a Stoner-Wohlfarth model for data analysis, the anisotropy constants Ku and Kc of superimposed uniaxial and cubic anisotropies in the magnetic film are determined. The temperature dependence of the Ku/Kc ratio reveals a gradual substitution of the cubic anisotropy dominating at low temperatures with the uniaxial anisotropy as the temperature rises. This behavior is confirmed by the simultaneous domain observation using Kerr microscopy, demonstrating different field evolutions of the domain structure at different temperatures.

Soldatov, I. V.; Panarina, N.; Hess, C.; Schultz, L.; Schäfer, R.

2014-09-01

161

Spin transport and spin-caloric effects in (Cr,Zn)Te half-metallic nanostructures: Effect of spin disorder at elevated temperatures from first principles  

NASA Astrophysics Data System (ADS)

An important contribution to the thermoelectric and spin-caloric transport properties in magnetic materials at elevated temperatures is the formation of a spin-disordered state due to local moment fluctuations. This effect has not been largely investigated so far. We focus on various magnetic nanostructures of CrTe in the form of thin layers or nanowires embedded in ZnTe matrix, motivated by the miniaturization of spintronics devices and by recent suggestions that magnetic nanostructures can lead to extraordinary thermoelectric effects due to quantum confinement. The electronic structure of the studied systems is calculated within the multiple scattering screened Korringa-Kohn-Rostoker Green function (KKR-GF) framework. The Monte Carlo method is used to simulate the magnetization in the temperature induced spin disorder. The transport properties are evaluated from the transmission probability obtained using the Baranger-Stone approach within the KKR-GF framework. We find qualitative and quantitative changes in the thermoelectric and spin-caloric coefficients when spin disorder is included in the calculation. Furthermore, we show that substitutional impurities in CrTe nanowires could considerably enhance the Seebeck coefficient and the thermoelectric figure of merit.

Ková?ik, Roman; Mavropoulos, Phivos; Blügel, Stefan

2015-01-01

162

Photothermoelectric and photovoltaic effects both present in MoS2  

PubMed Central

As a finite-energy-bandgap alternative to graphene, semiconducting molybdenum disulfide (MoS2) has recently attracted extensive interest for energy and sensor applications. In particular for broad-spectral photodetectors, multilayer MoS2 is more appealing than its monolayer counterpart. However, little is understood regarding the physics underlying the photoresponse of multilayer MoS2. Here, we employ scanning photocurrent microscopy to identify the nature of photocurrent generated in multilayer MoS2 transistors. The generation and transport of photocurrent in multilayer MoS2 are found to differ from those in other low-dimensional materials that only contribute with either photovoltaic effect (PVE) or photothermoelectric effect (PTE). In multilayer MoS2, the PVE at the MoS2-metal interface dominates in the accumulation regime whereas the hot-carrier-assisted PTE prevails in the depletion regime. Besides, the anomalously large Seebeck coefficient observed in multilayer MoS2, which has also been reported by others, is caused by hot photo-excited carriers that are not in thermal equilibrium with the MoS2 lattice. PMID:25605348

Zhang, Youwei; Li, Hui; Wang, Lu; Wang, Haomin; Xie, Xiaomin; Zhang, Shi-Li; Liu, Ran; Qiu, Zhi-Jun

2015-01-01

163

Effects of doping on transport properties in Cu-Bi-Se-based thermoelectric materials.  

PubMed

The thermoelectric properties of Zn-, In-, and I-doped Cu1.7Bi4.7Se8 pavonite homologues were investigated in the temperature range from 300 to 560 K. On the basis of the comprehensive structural analysis using Rietveld refinement of synchrotron radiation diffraction for Cu(x+y)Bi(5-y)Se8 compounds with the inherently disordered crystallographic sites, we demonstrate a doping strategy that provides a simultaneous control for enhanced electronic transport properties by the optimization of carrier concentration and exceptionally low lattice thermal conductivity by the formation of point defects. Substituted Zn or In ions on Cu site was found to be an effective phonon scattering center as well as an electron donor, while doping on Bi site showed a moderate effect for phonon scattering. In addition, we achieved largely enhanced power factor in small amount of In doping on Cu site by increased electrical conductivity and moderately decreased Seebeck coefficient. Coupled with a low lattice thermal conductivity originated from intensified point defect phonon scattering by substituted In ions with host Cu ions, a thermoelectric figure of merit ZT of 0.24 at 560 K for Cu1.6915In0.0085Bi4.7Se8 was achieved, yielding 30% enhancement compared with that of a pristine Cu1.7Bi4.7Se8 at the same temperature. PMID:25402498

Hwang, Jae-Yeol; Mun, Hyeon A; Kim, Sang Il; Lee, Ki Moon; Kim, Jungeun; Lee, Kyu Hyoung; Kim, Sung Wng

2014-12-15

164

Photothermoelectric and photovoltaic effects both present in MoS2  

NASA Astrophysics Data System (ADS)

As a finite-energy-bandgap alternative to graphene, semiconducting molybdenum disulfide (MoS2) has recently attracted extensive interest for energy and sensor applications. In particular for broad-spectral photodetectors, multilayer MoS2 is more appealing than its monolayer counterpart. However, little is understood regarding the physics underlying the photoresponse of multilayer MoS2. Here, we employ scanning photocurrent microscopy to identify the nature of photocurrent generated in multilayer MoS2 transistors. The generation and transport of photocurrent in multilayer MoS2 are found to differ from those in other low-dimensional materials that only contribute with either photovoltaic effect (PVE) or photothermoelectric effect (PTE). In multilayer MoS2, the PVE at the MoS2-metal interface dominates in the accumulation regime whereas the hot-carrier-assisted PTE prevails in the depletion regime. Besides, the anomalously large Seebeck coefficient observed in multilayer MoS2, which has also been reported by others, is caused by hot photo-excited carriers that are not in thermal equilibrium with the MoS2 lattice.

Zhang, Youwei; Li, Hui; Wang, Lu; Wang, Haomin; Xie, Xiaomin; Zhang, Shi-Li; Liu, Ran; Qiu, Zhi-Jun

2015-01-01

165

Photothermoelectric and photovoltaic effects both present in MoS2.  

PubMed

As a finite-energy-bandgap alternative to graphene, semiconducting molybdenum disulfide (MoS2) has recently attracted extensive interest for energy and sensor applications. In particular for broad-spectral photodetectors, multilayer MoS2 is more appealing than its monolayer counterpart. However, little is understood regarding the physics underlying the photoresponse of multilayer MoS2. Here, we employ scanning photocurrent microscopy to identify the nature of photocurrent generated in multilayer MoS2 transistors. The generation and transport of photocurrent in multilayer MoS2 are found to differ from those in other low-dimensional materials that only contribute with either photovoltaic effect (PVE) or photothermoelectric effect (PTE). In multilayer MoS2, the PVE at the MoS2-metal interface dominates in the accumulation regime whereas the hot-carrier-assisted PTE prevails in the depletion regime. Besides, the anomalously large Seebeck coefficient observed in multilayer MoS2, which has also been reported by others, is caused by hot photo-excited carriers that are not in thermal equilibrium with the MoS2 lattice. PMID:25605348

Zhang, Youwei; Li, Hui; Wang, Lu; Wang, Haomin; Xie, Xiaomin; Zhang, Shi-Li; Liu, Ran; Qiu, Zhi-Jun

2015-01-01

166

Poole-Frenkel effect in sputter-deposited CuAlO(2+x) nanocrystals.  

PubMed

Field-assisted thermionic emission within a sputter-deposited, nanocrystalline thin film of CuAlO2.06 is observed for the first time, and explained in terms of the Poole-Frenkel model. The presence of adsorbed oxygen ions as trap-states at the grain boundary regions of the nanostructured thin film is considered to manifest this phenomenon. Under an applied field, the barrier of the trap potential is lowered and thermal emission of charge carriers takes place at different sample temperatures to induce nonlinearity in the current (I)-voltage (V) characteristics of the nanomaterial. Fitting of the Poole-Frenkel model with the I-V data shows that the nonlinearity is effective above 50 V under the operating conditions. Calculations of the energy of the trap level, acceptor level and Fermi level reveal the existence of deep level trap-states and a shallow acceptor level with acceptor concentration considerably higher than the trap-states. Hall measurements confirm the p-type semiconductivity of the film, with a hole concentration around 10(18) cm(-3). Thermopower measurements give a room-temperature Seebeck coefficient around 130 ?V K(-1). This temperature-dependent conductivity enhancement within CuAlO2 nanomaterial may find interesting applications in transparent electronics and high-voltage applications for power supply networks. PMID:23535666

Banerjee, Arghya Narayan; Joo, Sang Woo

2013-04-26

167

?he Effect of Ge on Mg2Si0.6-x Sn0.4Ge x Materials  

NASA Astrophysics Data System (ADS)

In this work, we investigate the influence of the introduction of Ge on the thermoelectric properties of Bi-doped quaternary Mg2Si0.6- x Sn0.4Ge x alloys. Mg2Si0.58- x Sn0.4Bi0.02Ge x materials were fabricated by a low temperature reaction method, followed by hot pressing. Structure and phase composition of the obtained hot-pressed pellets were observed by x-ray diffraction. Morphology and chemical composition were monitored by scanning electron microscopy equipped with energy-dispersive x-ray spectroscopy. The results indicate a natural tendency of the material to phase separate into Si-rich, Sn-rich, and Ge-rich regions, which seem to become finer in size with Ge concentration. The compounds have been characterized by electrical conductivity, Seebeck coefficient, and thermal conductivity measurements in the temperature range of 300-823 K. The effect of Ge in the lattice thermal conductivity is discussed in terms of solid solution formation as well as effective medium theory.

Vlachos, N.; Hatzikraniotis, E.; Mihailescu, C. N.; Giapintzakis, J.; Kyratsi, Th.

2014-10-01

168

Effects of Heavy Element Substitution on Electronic Structure and Lattice Thermal Conductivity of Fe2VAl Thermoelectric Material  

NASA Astrophysics Data System (ADS)

By using first-principles cluster calculations, we identified that Ta or W substitution for V is useful for decreasing the lattice thermal conductivity of the Fe2VAl Heusler alloy without greatly affecting the electron transport properties. It was clearly confirmed that the Fe2(V1- x Ta x )Al0.95Si0.05 ( x = 0, 0.025, 0.05), Fe2(V0.9- x Ta x Ti0.1)Al ( x = 0, 0.10, 0.20), and Fe2(V0.9-2 x W x Ti0.1+ x )Al ( x = 0, 0.05, 0.10) alloys indeed possessed large Seebeck coefficient regardless of the amounts of substituted elements, while their lattice thermal conductivity was effectively reduced. As a result of partial substitution of Ta for V, we succeeded in increasing the magnitude of the dimensionless figure of merit of the Heusler phase up to 0.2, which is five times as large as the Ta-free compound.

Terazawa, Yuichi; Mikami, Masashi; Itoh, Takashi; Takeuchi, Tsunehiro

2012-06-01

169

The effect of Cu substitution on microstructure and thermoelectric properties of LaCoO3 ceramics.  

PubMed

La(Co, Cu)O(3-?) ceramics were prepared by pressureless sintering of citrate precursor powders, and their thermoelectric properties were investigated with an emphasis on the influence of Cu doping and phase structure as well as microstructure. It was found that a secondary phase first appeared in the form of a network along the grain boundaries and then changed to dispersion with increasing Cu content, which effectively reduced the lattice thermal conductivity of the materials. The thermal conductivity was only 1.21 W m(-1) K(-1) for the sample LaCo(0.75)Cu(0.25)O(3-?), being much lower as for the thermoelectric oxide materials. In addition, a small amount of Cu substitution for Co increased the electrical conductivity greatly and the absolute Seebeck coefficient, whose sign was also reversed from negative to positive. The dimensionless figure of merit, ZT, of LaCoO(3-?) oxides at low and middle temperatures can be remarkably enhanced by substituting Co with Cu. PMID:22858990

Li, Fu; Li, Jing-Feng; Li, Jian-Hui; Yao, Fang-Zhou

2012-09-21

170

Effect of Sn Doping on the Thermoelectric Properties of n-type Bi2(Te,Se)3 Alloys  

NASA Astrophysics Data System (ADS)

In the present work, 0.01-0.05wt.% Sn-doped Bi2(Te0.9Se0.1)3 alloys were prepared by mechanical deformation followed by hot pressing, and their thermoelectric properties were studied. We observed that the Sn element is a very effective dopant as an acceptor to control the carrier concentration in the n-type Bi2(Te0.9Se0.1)3 alloys to optimize their thermoelectric property. The n-type carrier concentration can be controlled from 4.2 × 1019/cm3 to 2.4 × 1019/cm3 by 0.05wt.% Sn-doping. While the Seebeck coefficient and the electrical resistivity are both increased with doping, the power factor remains the same. Therefore, we found that the thermoelectric figure-of-merit becomes maximized at 0.75 when the thermal conductivity has a minimum value for the 0.03wt.% Sn-doped sample.

Lee, Jae-Uk; Lee, Deuk-Hee; Kwon, Beomjin; Hyun, Dow-Bin; Nahm, Sahn; Baek, Seung-Hyub; Kim, Jin-Sang

2015-01-01

171

Effect of microstructure on the thermoelectric properties of CSD-grown Bi2Sr2Co2Oy thin films  

NASA Astrophysics Data System (ADS)

Three Bi2Sr2Co2Oy thin films with different microstructures have been prepared by chemical solution deposition on LaAlO3(001) through varying the annealing temperature. With the decrease in the annealing temperature, both the size and c-axis alignment degree of grains in the film decrease as well, leading to an increase in the film resistivity. In addition, the decrease in the annealing temperature also results in a slight increase in the Seebeck coefficient due to the enhanced energy filtering effect of the small-grain film. The nanostructured Bi2Sr2Co2Oy film with an average grain size of about 100 nm shows a power factor comparable to that of films with larger grains. Since the thermal conductivity of the nanostructured films can be depressed due to the enhanced phonon scattering by grain boundary, a higher figure of merit is expected in Bi2Sr2Co2Oy thin film with grains in nanometer size.

Wang, Shu-Fang; Yan, Guo-Ying; Chen, Shan-Shan; Bai, Zi-Long; Wang, Jiang-Long; Yu, Wei; Fu, Guang-Sheng

2013-03-01

172

Effect of copper doping on kinetic phenomena in n-Bi{sub 2}Te{sub 2.85}Se{sub 0.15}  

SciTech Connect

In single crystals of copper-doped and undoped Bi{sub 2}Te{sub 2.85}Se{sub 0.15} solid solutions with an electron concentration close to 1 x 10{sup 19} cm{sup -3}, the temperature dependences are investigated for the Hall (R{sub 123}, R{sub 321}) and Seebeck (S{sub 11}) kinetic coefficients, the electrical-conductivity ({sigma}{sub 11}), Nernst-Ettingshausen (Q{sub 123}), and thermal conductivity (k{sub 11}) coefficients in the temperature range of 77-400 K. The absence of noticeable anomalies in the temperature dependences of the kinetic coefficients makes it possible to use the one-band model when analyzing the experimental results. Within the framework of the one-band model, the effective mass of density of states (m{sub d} {approx} 0.8m{sub 0}), the energy gap ({epsilon}{sub g} {approx} 0.2 eV), and the effective scattering parameter (r{sub eff} {approx} 0.2) are estimated. The obtained value of the parameter r{sub eff} is indicative of the mixed electron-scattering mechanism with the dominant scattering by acoustic phonons. Data on the thermal conductivity and the lattice resistivity obtained by subtracting the electron contribution according to the Wiedemann-Franz law are presented.

Zhitinskaya, M. K.; Nemov, S. A. [St. Petersburg State Technical University (Russian Federation)], E-mail: nemov_s@mail.ru; Svechnikova, T. E. [Russian Academy of Sciences, Baikov Institute of Metallurgy and Materials Science (Russian Federation)

2007-10-15

173

The feasibility of electrophoretic repair of impoundment leaks  

E-print Network

- osmosis Electro-osmosis Chemical osmosis Heat Current Ion Isothermal heat transfer Streaming current Streaming current Thermal conduction Fourier's law Thermo- electricity Seebeck effect Thermal diffusion of electrolyte Soret effect...

Han, Ji-Seok

2002-01-01

174

Oxide based thermoelectric materials for large scale power generation  

E-print Network

The thermoelectric (TE) devices are based on the Seebeck and Peltier effects, which describe the conversion between temperature gradient and electricity. The effectiveness of the material performance can be described by ...

Song, Yang, M. Eng. Massachusetts Institute of Technology

2008-01-01

175

Optical and electrical properties and phonon drag effect in low temperature TEP measurements of AgSbSe2 thin films  

NASA Astrophysics Data System (ADS)

Polycrystalline thin films of silver antimony selenide have been deposited using a reactive evaporation technique onto an ultrasonically cleaned glass substrate at a vacuum of 10-5 torr. The preparative parameters, like substrate temperature and incident fluxes, have been properly controlled in order to get stoichiometric, good quality and reproducible thin film samples. The samples are characterized by XRD, SEM, AFM and a UV—vis—NIR spectrophotometer. The prepared sample is found to be polycrystalline in nature. From the XRD pattern, the average particle size and lattice constant are calculated. The dislocation density, strain and number of crystallites per unit area are evaluated using the average particle size. The dependence of the electrical conductivity on the temperature has also been studied and the prepared AgSbSe2 samples are semiconducting in nature. The AgSbSe2 thin films exhibited an indirect allowed optical transition with a band gap of 0.64 eV. The compound exhibits promising thermoelectric properties, a large Seebeck coefficient of 30 mV/K at 48 K due to strong phonon electron interaction. It shows a strong temperature dependence on thermoelectric properties, including the inversion of a dominant carrier type from p to n over a low temperature range 9-300 K, which is explained on the basis of a phonon drag effect.

Namitha Asokan, T.; Urmila, K. S.; Jacob, Rajani; Reena Philip, Rachel; Okram, G. S.; Ganesan, V.; Pradeep, B.

2014-05-01

176

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

177

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

178

Effects of (Al,Ge) double doping on the thermoelectric properties of higher manganese silicides  

NASA Astrophysics Data System (ADS)

Experiments and analysis have been carried out to investigate the effects of Al and (Al,Ge) doping on the microstructure and thermoelectric properties of polycrystalline higher manganese silicide (HMS) samples, which were prepared by solid-state reaction, ball milling, and followed by spark plasma sintering. It has been found that Al doping effectively increases the hole concentration, which leads to an increase in the electrical conductivity and power factor. By introducing the second dopant Ge into Al-doped HMS, the electrical conductivity is increased, and the Seebeck coefficient is decreased as a result of further increased hole concentration. The peak power factor is found to occur at a hole concentration between 1.8 × 1021 and 2.2 × 1021 cm-3 measured at room temperature. The (Al,Ge)-doped HMS samples show lower power factors owing to their higher hole concentrations. The mobility of Mn(Al0.0035GeySi0.9965-y)1.8 with y = 0.035 varies approximately as T-3/2 above 200 K, suggesting acoustic phonon scattering is the dominant scattering mechanism. The thermal conductivity of HMS does not change appreciably by Al or (Al,Ge) doping. The maximum ZT of (Al,Ge)-doped HMS is 0.57 at 823 K, which is similar to the highest value found in the Al-doped HMS samples. The ZT values were reduced in the Mn(Al0.0035GeySi0.9965-y)1.8 samples with high Ge concentration of y = 0.025 and 0.035, because of reduced power factor. In addition, a two-band model was employed to show that the hole contribution to the thermal conductivity dominates the bipolar and electron contributions for all samples from 300 to 823 K and accounts for about 12% of the total thermal conductivity at about 800 K.

Chen, Xi; Weathers, Annie; Salta, Daniel; Zhang, Libin; Zhou, Jianshi; Goodenough, John B.; Shi, Li

2013-11-01

179

Effect of Processing Temperature on the Thermoelectric and Optical Properties of Copper Manganite-based Spinels  

NASA Astrophysics Data System (ADS)

This research is focused on investigation of the effect of doping and processing on the microstructure and phase evolution, and the effect of the microstructure and phases on the thermoelectric and optical properties of doped Copper Manganites. Undoped CuMn2O4 and four doped compositions, with nickel and cobalt, were investigated. Detailed processing protocols, including green state processing, were developed to make samples with a range of densities between 65 to 95%. Densification kinetics studies (dilatometry), together with phase and microstructural evolution (XRD, SEM and EDS) were used to demonstrate the role of second phases and especially liquid phase in controlling the densification. It is shown that the Cu content of the oxides plays an important role in controlling the densification and optimum sintering temperature. X-ray diffraction analysis showed that all the majority phase in all materials maintained a cubic spine] structure at all sintering temperatures. The thermoelectric and optical properties were also characterized. Electronic conduction in these oxides is through polaron hopping between Mn3+ and Mn4+. Thus, the thermoelectric properties were controlled largely by the nature of the primary phase, as the secondary phase was too Mn-deficient to support such conduction. Seebeck coefficient ranged from 16 to 185 microV/K, with both composition and the sintering temperature affecting it. The electrical resistivity spanned a wide range of 1.4--2537 O-cm, and was also affected by both the composition, and sintering temperature. Although no general trend was established for the thermal conductivity, it was apparent that the thermal diffusivity was dependent on the density as expected. The FTIR results show that these materials are transparent in the mid-infrared region, showing appreciable transmittance in the range of 12--18 microm. Finally, XPS analysis indicated that the Mn valence states ranged from Mn4+ to Mn2.5+ and generally decreased as sintering temperature increased, in agreement with the results of previous studies on thin films.

Leslie, Clifford J.

180

Nano-scale effects in bulk nanostructured thermoelectrics  

NASA Astrophysics Data System (ADS)

The technique of energy harvesting via thermoelectric (TE) materials is one of the favorable directions towards manifesting sustainable energy resources. The ability of TE materials to directly convert heat energy to electricity facilitates the reduction in consumption of natural resources for power generation. The requirements of high electrical conductivity and Seebeck coefficient while maintaining a low thermal conductivity for attaining higher TE performance introduced newer material processing techniques. Several efficient techniques for nano-scale structural modifications such as alloying, point defects, nanostructuring etc. were implemented for improvement in the figure-of-merit. Quantum confinement techniques based on nanostructuring of compounds gained prominence due to the resulting reduction of the lattice thermal conductivity. In this dissertation, various aspects of theoretical and experimental techniques pertaining to the nano-scale effects in TE materials were investigated. As a first step, in order to better understand the advantages and disadvantages of nanostructuring, TE characteristics of silicide based materials such as Mg2Si and Si1-xGex were theoretically modeled. A comprehensive comparison of effects of nanostructuring in both the materials was deduced. The fact that nanostructuring may not always be beneficial was highlighted through estimation of phonon mean free path in nanostructured compounds. In the second phase of this dissertation, a novel technique through mixing of a conductive glass-frit for improving the mechanical stability of Mg2Si was successfully developed. The studies were followed up by investigations on the benefits of combinatorial effects of nano-inclusions, nanostructuring and long duration annealing based on Bi2Te 3. In the final phase of this dissertation work, the technique of rapid decrystallization of single crystal silicon by high energy microwaves was introduced and the beneficial effects of rapid decrystallization were experimentally deduced. It was shown that a significant reduction in room temperature thermal conductivity of single crystal silicon could be achieved by means of grain size reduction via microwave energy. The advantages of nanostructuring in thermoelectric materials combined with techniques such as nano-inclusions, long duration annealing and rapid decrystallization have been explored comprehensively in this dissertation work. Such combinatorial techniques could be beneficially used to further enhance the efficiencies of thermoelectric materials.

Satyala, Nikhil

181

Effect of ceramic dispersion on thermoelectric properties of nano-ZrO{sub 2}/CoSb{sub 3} composites  

SciTech Connect

In the present work, nano-ZrO{sub 2}/CoSb{sub 3} composites were fabricated by milling ZrO{sub 2} and CoSb{sub 3} powders and hot pressing at different sintering temperatures. For the prepared compacts, the phase purity, microstructure, and temperature-dependent thermoelectric properties were characterized. The effect of nano-ZrO{sub 2} dispersion on composite electrical conductivity and thermal conductivity is strictly clarified by comparing the transport properties of the nondispersed and dispersed CoSb{sub 3} at identical porosity, so that the effect of porosity on thermoelectric parameters could be eliminated. The effect of the insulating inclusion itself on transport properties is also considered and eliminated using effective media theories. It is clearly verified that charge carrier scattering and phonon scattering occur simultaneously to lower the electrical conductivity and the thermal conductivity of CoSb{sub 3} due to the introduction of nano-ZrO{sub 2} inclusions. The investigated composites show higher electrical conductivity due to existence of metallic Sb and lower thermal conductivity because of nanodispersion. At the ranges of high measuring temperature (673-723 K) and low porosity (6%-9%), the ratio of electrical conductivity to thermal conductivity of the dispersed CoSb{sub 3} is higher than that of nondispersed CoSb{sub 3}, and the dimensionless figure of merit (ZT) of the composite could probably be improved at these ranges with the enhanced ratio of electrical conductivity to thermal conductivity and Seebeck coefficient, which is assumed to be increased by a potential barrier scattering.

He, Zeming; Stiewe, Christian; Platzek, Dieter; Karpinski, Gabriele; Mueller, Eckhard; Li, Shanghua; Toprak, Muhammet; Muhammed, Mamoun [Institute of Materials Research, German Aerospace Center (DLR), D-51170 Cologne (Germany); Materials Chemistry Division, Royal Institute of Technology (KTH), SE-10044 Stockholm (Sweden)

2007-02-15

182

The effects of the size and the doping concentration on the power factor of n-type lead telluride nanocrystals for thermoelectric energy conversion.  

PubMed

For the first time, we demonstrate a successful synthesis of colloidal n-type lead telluride nanocrystals doped with iodine. By tuning the reaction time and iodine concentration in the precursor solution, nanocrystals with different sizes and doping concentrations are synthesized. The Seebeck coefficient and electrical conductivity of the nanocrystals are measured on nanocrystal thin films fabricated by dip-coating glass substrates in the nanocrystals solution. Investigations on the influence of size and doping concentration on the electrical properties have been performed. The results show that the size of the nanocrystals significantly influences the electrical conductivity but not the Seebeck coefficient of nanocrystal films, while higher doping concentration leads to lower Seebeck coefficient but higher electrical conductivity in the nanocrystal films. Proof-of-concept thin-film thermoelectric modules are also fabricated using both p-type and n-type PbTe nanocrystals for the conversion of thermal energy into electrical energy. PMID:24527850

Fang, Haiyu; Luo, Zhiqiang; Yang, Haoran; Wu, Yue

2014-03-12

183

Are Effective Properties Effective?  

SciTech Connect

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

Han, Ru; Ingber, Marc S. [Department of Mechanical Engineering, University of New Mexico, NM 87131 (United States); Hsiao, S.-C. [Department of Hydraulic and Ocean Engineering, National Cheng-Kung University No. 1, Ta-Hsueh Road Tainan 701, Taiwan (China)

2008-02-15

184

The effect of structural vacancies on the thermoelectric properties of (Cu{sub 2}Te){sub 1?x}(Ga{sub 2}Te{sub 3}){sub x}  

SciTech Connect

We have studied the effects of structural vacancies on the thermoelectric properties of the ternary compounds (Cu{sub 2}Te){sub 1?x}(Ga{sub 2}Te{sub 3}){sub x} (x=0.5, 0.55, 0.571, 0.6, 0.625, 0.667 and 0.75), which are solid solutions found in the pseudo-binary phase diagram for Cu{sub 2}Te and Ga{sub 2}Te{sub 3}, and possesses tunable structural vacancy concentrations. This materials system is not suitable due to the cost and scarcity of the constituent elements, but the vacancy behavior is well understood and will provide a valuable test case for other systems more suitable from the standpoint of cost and abundance of raw materials, which also possesses these vacancy features, but whose structural characterization is lacking at this stage. We find that the nominally defect free phase CuGaTe{sub 2} possess the highest ZT (ZT=S{sup 2}T/??, where S is the Seebeck coefficient and ? is the electrical resistivity ? is the thermal conductivity and T is the absolute temperature) which approaches 1 at 840 K and seems to continuously increase above this temperature. This result is due to the unexpectedly low thermal conductivity found for this material at high temperature. The low thermal conductivity was caused by strong Umklapp (thermally resistive scattering processes involving three phonons) phonon scattering. We find that due to the coincidentally strong scattering of carriers by the structural defects that higher concentrations of these features lead to poor electrical transport properties and decreased ZT. - Graphical abstract: Thermal conductivity and zT as a function of temperature for a series of compounds of the type (Cu{sub 2}Te){sub 1-x}(Ga{sub 2}Te{sub 3})x (x=0.5, 0.55, 0.571, 0.6, 0.625, 0.667 and 0.75). Highlights: ? All the samples show p-type semiconducting behavior in the temperature dependence of the Seebeck and Hall coefficients. ? The increased carrier concentration and the introduction of vacancies diminish the carrier mobility and power factor. ? The low temperature k decreases significantly as the Ga{sub 2}Te{sub 3} content increases due to increasing point defects. ? The highest ZT ? 1.0 at 840 K among the samples in this study was found in CuGaTe2, which contains no vacancies.

Ye, Zuxin; Young Cho, Jung; Tessema, Misle M. [Optimal Inc., Plymouth Township, MI 48170 (United States); Salvador, James R., E-mail: james.salvador@gm.com [GM Global R and D, Warren, MI 48090 (United States); Waldo, Richard A. [GM Global R and D, Warren, MI 48090 (United States); Wang, Hsin; Cai, Wei [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States)

2013-05-15

185

Microwave-induced spin currents in ferromagnetic-insulator|normal-metal bilayer system  

SciTech Connect

A microwave technique is employed to simultaneously examine the spin pumping and the spin Seebeck effect processes in a YIG|Pt bilayer system. The experimental results show that for these two processes, the spin current flows in opposite directions. The temporal dynamics of the longitudinal spin Seebeck effect exhibits that the effect depends on the diffusion of bulk thermal-magnons in the thermal gradient in the ferromagnetic-insulator|normal-metal system.

Agrawal, Milan, E-mail: magrawal@physik.uni-kl.de [Fachbereich Physik and Landesforschungszentrum OPTIMAS, Technische Universität Kaiserslautern, 67663 Kaiserslautern (Germany); Graduate School Materials Science in Mainz, Gottlieb-Daimler-Strasse 47, 67663 Kaiserslautern (Germany); Serga, Alexander A.; Lauer, Viktor; Papaioannou, Evangelos Th.; Hillebrands, Burkard; Vasyuchka, Vitaliy I. [Fachbereich Physik and Landesforschungszentrum OPTIMAS, Technische Universität Kaiserslautern, 67663 Kaiserslautern (Germany)

2014-09-01

186

Atomic Layer-by-Layer Thermoelectric Conversion in Topological Insulator Bismuth/Antimony Tellurides  

E-print Network

Atomic Layer-by-Layer Thermoelectric Conversion in Topological Insulator Bismuth efficiency essentially requires cooperative control of electrical and thermal transport. Bismuth telluride, Seebeck Effects, Topological Insulator, Bismuth Telluride, Antimony Telluride Thermoelectric conversion

Jo, Moon-Ho

187

Modeling of solar thermal selective surfaces and thermoelectric generators  

E-print Network

A thermoelectric generator is a solid-state device that converts a heat flux into electrical power via the Seebeck effect. When a thermoelectric generator is inserted between a solar-absorbing surface and a heat sink, a ...

McEnaney, Kenneth

2010-01-01

188

Solar thermoelectrics for small scale power generation  

E-print Network

In the past two decades, there has been a surge in the research of new thermoelectric (TE) materials, driven party by the need for clean and sustainable power generation technology. Utilizing the Seebeck effect, the ...

Amatya, Reja

2012-01-01

189

Field effect controlled ferromagnetism in transition metal doped ZnO  

NASA Astrophysics Data System (ADS)

The ability to externally control the properties of magnetic materials would be highly desirable both from fundamental and technological point of views. In this respect, dilute magnetic semiconductor (DMS), in which a fraction of atoms of the nonmagnetic semiconductor host is replaced by magnetic ions, have recently attracted broad interest for their potential application in spintronics. In this work, we focused on transition metal (TM) (Co, Mn and Cu) doped Zinc oxide (ZnO) because room temperature ferromagnetism was both theoretically predicted and experimentally observed. However, the origin of such ferromagnetism, in particular whether it is a signature of a true DMS behaviour (long range magnetic interaction between the doping ions) or it arises from the formation of secondary phases, segregation or clustering is still under debate. Measuring the dependence of the magnetic properties on the carrier concentration can clarify the underlying physics. The samples were characterized by resistivity, Hall effect, magnetoresistance, Seebeck effect, synchrotron X-ray adsorption spectra (XAS) and magnetic dichroism (XMD) while modulating the carrier density by electric field. The insulating-gate field-effect transistor structures are realized in ZnO/Strontium Titanate (SrTiO 3) heterostructures by pulsed laser deposition. These devices offers the capability to modulate the carrier density of a probe accessible (light, AFM tip, ...) channel, by more than 5 orders of magnitude (from ~10 15 to ~10 20 e -/cm 3, estimated by Hall effect measurements under FE). The Co and Mn films measured by DC SQUID magnetometer result ferromagnetic and anomalous Hall effect was observed at low temperature but nor ferromagnetic nor antiferromagnetic signal was detectable in the XMD spectra. Cu doped films are insulating and nonmagnetic. Photo Emission Electron Microscopy (x-PEEM) and magnetic force microscopy (MFM) showed that the sample are homogeneus and no clustering of TM were detected. A large effect of the magnetic ions, strongly dependent on the carrier concentration, was observed on the transport properties and this effect according can be explained by a giant s-d exchange leading to spin splitting of the s-type conduction band. Since the filling of such band can be modified by field effect a electric field control of the spin polarization can be achieved.

Bellingeri, E.; Pellegrino, L.; Biasotti, M.; Pallecchi, I.; Canu, G.; Gerbi, A.; Vignolo, M.; Siri, A. S.; Marré, D.; Rusponi, S.; Lehnert, A.; Nolting, F.

2008-02-01

190

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

191

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

192

Temperature gradient measurements by using thermoelectric effect in CNTs-silicone adhesive composite.  

PubMed

This work presents the fabrication and investigation of thermoelectric cells based on composite of carbon nanotubes (CNT) and silicone adhesive. The composite contains CNT and silicon adhesive 1?1 by weight. The current-voltage characteristics and dependences of voltage, current and Seebeck coefficient on the temperature gradient of cell were studied. It was observed that with increase in temperature gradient the open circuit voltage, short circuit current and the Seebeck coefficient of the cells increase. Approximately 7 times increase in temperature gradient increases the open circuit voltage and short circuit current up to 40 and 5 times, respectively. The simulation of experimental results is also carried out; the simulated results are well matched with experimental results. PMID:24748375

Chani, Muhammad Tariq Saeed; Karimov, Kh S; Asiri, Abdullah M; Ahmed, Nisar; Bashir, Muhammad Mehran; Khan, Sher Bahadar; Rub, Malik Abdul; Azum, Naved

2014-01-01

193

Effects of surface band bending and scattering on thermoelectric transport in suspended bismuth telluride nanoplates.  

PubMed

A microdevice was used to measure the in-plane thermoelectric properties of suspended bismuth telluride nanoplates from 9 to 25 nm thick. The results reveal a suppressed Seebeck coefficient together with a general trend of decreasing electrical conductivity and thermal conductivity with decreasing thickness. While the electrical conductivity of the nanoplates is still within the range reported for bulk Bi2Te3, the total thermal conductivity for nanoplates less than 20 nm thick is well below the reported bulk range. These results are explained by the presence of surface band bending and diffuse surface scattering of electrons and phonons in the nanoplates, where pronounced n-type surface band bending can yield suppressed and even negative Seebeck coefficient in unintentionally p-type doped nanoplates. PMID:24164564

Pettes, Michael Thompson; Maassen, Jesse; Jo, Insun; Lundstrom, Mark S; Shi, Li

2013-11-13

194

Temperature Gradient Measurements by Using Thermoelectric Effect in CNTs-Silicone Adhesive Composite  

PubMed Central

This work presents the fabrication and investigation of thermoelectric cells based on composite of carbon nanotubes (CNT) and silicone adhesive. The composite contains CNT and silicon adhesive 1?1 by weight. The current-voltage characteristics and dependences of voltage, current and Seebeck coefficient on the temperature gradient of cell were studied. It was observed that with increase in temperature gradient the open circuit voltage, short circuit current and the Seebeck coefficient of the cells increase. Approximately 7 times increase in temperature gradient increases the open circuit voltage and short circuit current up to 40 and 5 times, respectively. The simulation of experimental results is also carried out; the simulated results are well matched with experimental results. PMID:24748375

Chani, Muhammad Tariq Saeed; Karimov, Kh. S.; Asiri, Abdullah M.; Ahmed, Nisar; Bashir, Muhammad Mehran; Khan, Sher Bahadar; Rub, Malik Abdul; Azum, Naved

2014-01-01

195

Effects of (Al,Ge) double doping on the thermoelectric properties of higher manganese silicides  

SciTech Connect

Experiments and analysis have been carried out to investigate the effects of Al and (Al,Ge) doping on the microstructure and thermoelectric properties of polycrystalline higher manganese silicide (HMS) samples, which were prepared by solid-state reaction, ball milling, and followed by spark plasma sintering. It has been found that Al doping effectively increases the hole concentration, which leads to an increase in the electrical conductivity and power factor. By introducing the second dopant Ge into Al-doped HMS, the electrical conductivity is increased, and the Seebeck coefficient is decreased as a result of further increased hole concentration. The peak power factor is found to occur at a hole concentration between 1.8?×?10{sup 21} and 2.2?×?10{sup 21}?cm{sup ?3} measured at room temperature. The (Al,Ge)-doped HMS samples show lower power factors owing to their higher hole concentrations. The mobility of Mn(Al{sub 0.0035}Ge{sub y}Si{sub 0.9965-y}){sub 1.8} with y?=?0.035 varies approximately as T{sup ?3/2} above 200?K, suggesting acoustic phonon scattering is the dominant scattering mechanism. The thermal conductivity of HMS does not change appreciably by Al or (Al,Ge) doping. The maximum ZT of (Al,Ge)-doped HMS is 0.57 at 823?K, which is similar to the highest value found in the Al-doped HMS samples. The ZT values were reduced in the Mn(Al{sub 0.0035}Ge{sub y}Si{sub 0.9965-y}){sub 1.8} samples with high Ge concentration of y?=?0.025 and 0.035, because of reduced power factor. In addition, a two-band model was employed to show that the hole contribution to the thermal conductivity dominates the bipolar and electron contributions for all samples from 300 to 823?K and accounts for about 12% of the total thermal conductivity at about 800?K.

Chen, Xi; Salta, Daniel; Zhang, Libin [Materials Science and Engineering Program, Texas Materials Institute, The University of Texas at Austin, Austin, Texas 78712 (United States); Weathers, Annie [Department of Mechanical Engineering, The University of Texas at Austin, Austin, Texas 78712 (United States); Zhou, Jianshi; Goodenough, John B.; Shi, Li [Materials Science and Engineering Program, Texas Materials Institute, The University of Texas at Austin, Austin, Texas 78712 (United States); Department of Mechanical Engineering, The University of Texas at Austin, Austin, Texas 78712 (United States)

2013-11-07

196

Doppler Effect  

NSDL National Science Digital Library

This site offers information on the classical doppler effect, the relativistic doppler effect, aberration, and the transverse doppler effect. It also discusses wave fronts, first-order and second order effect, light-time correction, Galilean transformation, and parallax.

Calvert, J.B.

197

Effect of rare earth radius and concentration on the structural and transport properties of doped Mn Zn ferrite  

Microsoft Academic Search

Dielectric constant (?'), AC conductivity (sigma), and seebeck coefficient (S) have been measured for the ferrite samples of the general formula Mn0.5Zn0.5RyFe2O4; where R=Dy, Gd, Sm, Ce, and La prepared by standard ceramic technique and sintered at 1200 °C with a heating rate 4 °C\\/min. X-ray diffractograms show that all samples posses the spinel structure with the appearance of small

E. Ateia; M. A. Ahmed; A. K. El-Aziz

2007-01-01

198

Effect of rare earth radius and concentration on the structural and transport properties of doped Mn–Zn ferrite  

Microsoft Academic Search

Dielectric constant (??), AC conductivity (?), and seebeck coefficient (S) have been measured for the ferrite samples of the general formula Mn0.5Zn0.5RyFe2O4; where R=Dy, Gd, Sm, Ce, and La prepared by standard ceramic technique and sintered at 1200°C with a heating rate 4°C\\/min. X-ray diffractograms show that all samples posses the spinel structure with the appearance of small peaks representing

E. Ateia; M. A. Ahmed; A. K. El-Aziz

2007-01-01

199

Effect of Heat Treatment on the Thermoelectric Properties of Bismuth-Antimony-Telluride Prepared by Mechanical Deformation and Mechanical Alloying  

NASA Astrophysics Data System (ADS)

In this work, p-type 20%Bi2Te3-80%Sb2Te3 bulk thermoelectric (TE) materials were prepared by mechanical deformation (MD) of pre-melted ingot and by mechanical alloying (MA) of elemental Bi, Sb, and Te granules followed by cold-pressing. The dependence on annealing time of changes of microstructure and TE properties of the prepared samples, including Seebeck coefficient, electrical resistivity, thermal conductivity, and figure-of-merit, was investigated. For both samples, saturation of the Seebeck coefficient and electrical resistivity were observed after annealing for 1 h at 380°C. It is suggested that energy stored in samples prepared by both MA and MD facilitated their recrystallization within short annealing times. The 20%Bi2Te3-80%Sb2Te3 sample prepared by MA followed by heat treatment had higher a Seebeck coefficient and electrical resistivity than specimens fabricated by MD. Maximum figures-of-merit of 3.00 × 10-3/K and 2.85 × 10-3/K were achieved for samples prepared by MA and MD, respectively.

Lee, Deuk-Hee; Lee, Jae-Uk; Jung, Sung-Jin; Baek, Seung-Hyub; Kim, Ju-Heon; Kim, Dong-Ik; Hyun, Dow-Bin; Kim, Jin-Sang

2014-06-01

200

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

201

Model for Increasing the Power Obtained from a Thermoelectric Generator Module  

NASA Astrophysics Data System (ADS)

We have developed a model for finding the most efficient way of increasing the power obtained from a thermoelectric generator (TEG) module with a variety of operating conditions and limitations. The model is based on both thermoelectric principles and thermal resistance circuits, because a TEG converts heat into electricity consistent with these two theories. It is essential to take into account thermal contact resistance when estimating power generation. Thermal contact resistance causes overestimation of the measured temperature difference between the hot and cold sides of a TEG in calculation of the theoretical power generated, i.e. the theoretical power is larger than the experimental power. The ratio of the experimental open-loop voltage to the measured temperature difference, the effective Seebeck coefficient, can be used to estimate the thermal contact resistance in the model. The ratio of the effective Seebeck coefficient to the theoretical Seebeck coefficient, the Seebeck coefficient ratio, represents the contact conditions. From this ratio, a relationship between performance and different variables can be developed. The measured power generated by a TEG module (TMH400302055; Wise Life Technology, Taiwan) is consistent with the result obtained by use of the model; the relative deviation is 10%. Use of this model to evaluate the most efficient means of increasing the generated power reveals that the TEG module generates 0.14 W when the temperature difference is 25°C and the Seebeck coefficient ratio is 0.4. Several methods can be used triple the amount of power generated. For example, increasing the temperature difference to 43°C generates 0.41 W power; improving the Seebeck coefficient ratio to 0.65 increases the power to 0.39 W; simultaneously increasing the temperature difference to 34°C and improving the Seebeck coefficient ratio to 0.5 increases the power to 0.41 W. Choice of the appropriate method depends on the limitations of system, the cost, and the environment.

Huang, Gia-Yeh; Hsu, Cheng-Ting; Yao, Da-Jeng

2014-06-01

202

High temperature experimental characterization of microscale thermoelectric effects  

NASA Astrophysics Data System (ADS)

Thermoelectric devices have been employed for many years as a reliable energy conversion technology for applications ranging from the cooling of sensors or charge coupled devices to the direct conversion of heat into electricity for remote power generation. However, its relatively low conversion efficiency has limited the implementation of thermoelectric materials for large scale cooling and waste heat recovery applications. Recent advances in semiconductor growth technology have enabled the precise and selective engineering of material properties to improve the thermoelectric figure of merit and thus the efficiency of thermoelectric devices. Accurate characterization at the intended operational temperature of novel thermoelectric materials is a crucial component of the optimization process in order to fundamentally understand material behavior and evaluate performance. The objective of this work is to provide the tools necessary to characterize high efficiency bulk and thin-film materials for thermoelectric energy conversion. The techniques developed here are not bound to specific material or devices, but can be generalized to any material system. Thermoreflectance imaging microscopy has proven to be invaluable for device thermometry owing to its high spatial and temporal resolutions. It has been utilized in this work to create two-dimensional temperature profiles of thermoelectric devices during operation used for performance analysis of novel materials, identification of defects, and visualization of high speed transients in a high-temperature imaging thermostat. We report the development of a high temperature imaging thermostat capable of high speed transient thermoelectric characterization. In addition, we present a noninvasive method for thermoreflectance coefficient calibration ideally suited for vacuum and thus high temperature employment. This is the first analysis of the thermoreflectance coefficient of commonly used metals at high-temperatures. High temperature vacuum thermostats are designed and fabricated with optical imaging capability and interchangeable measurement stages for various electrical and thermoelectric characterizations. We demonstrate the simultaneous measurement of in-plane electrical conductivity and Seebeck coefficient of thin-film or bulk thermoelectric materials. Furthermore, we utilize high-speed circuitry to implement the transient Harman technique and directly determine the cross-plane figure of merit of thin film thermoelectric materials at high temperatures. Transient measurements on thin film devices are subject to complications from the growth substrate, non-ideal contacts and other detrimental thermal and electrical effects. A strategy is presented for optimizing device geometry to mitigate the impact of these parasitics. This design enabled us to determine the cross-plane thermoelectric material properties in a single high temperature measurement of a 25mum InGaAs thin film with embedded ErAs (0.2%) nanoparticles using the bipolar transient Harman technique in conjunction with thermoreflectance thermal imaging. This approach eliminates discrepancies and potential device degradation from the multiple measurements necessary to obtain individual material parameters. Finite element method simulations are used to analyze non-uniform current and temperature distributions over the device area and determine the three dimensional current path for accurate extraction of material properties from the thermal images. Results match with independent measurements of thermoelectric material properties for the same material composition, validating this approach. We apply high magnification thermoreflectance imaging to create temperature maps of vanadium dioxide nanobeams and examine electro-thermal energy conversion along the nanobeam length. The metal to insulator transition of strongly correlated materials is subject to strong lattice coupling which brings about the unique one-dimensional alignment of metal-insulator domains along nanobeams. Many studies have investigated the effects of stress o

Favaloro, Tela

203

Numerical Calculation of Density of States and Band Structure A Thesis Submitted in Partial Satisfaction  

E-print Network

combustion engines, with the majority of energy lost in terms of waste heat. In theory, the waste heat can be recycled and generate electrical energy via Thermoelectric Effect. Thermoelectric Effect converts heat directly into electricity. One of the main components of thermoelectric effect, the Seebeck effect

Belanger, David P.

204

Measurement of Inhomogeneities in MIMS Thermocouples Using a Linear-Gradient Furnace and Dual Heat-Pipe Scanner  

NASA Astrophysics Data System (ADS)

This paper describes a linear-gradient furnace and a thermocouple homogeneity scanner that, together, measure changes in the Seebeck coefficient as a function of time and temperature. The furnace first exposes the test thermocouple to all temperatures in the range spanned by the furnace gradient. The homogeneity scanner then measures the Seebeck coefficient along the length of the thermocouple. By correlating the position on the thermocouple with the temperature in the furnace, changes in the Seebeck coefficient can be correlated with the temperature to which that part of the thermocouple was exposed. Repeat exposures for different durations allow the rapid accumulation of data describing drift versus temperature and time. The known profile of the furnace combined with the high resolution of the dual heat-pipe scanner enable the detection of Seebeck coefficient changes of less than 0.02 % over sub-millimeter distances. The high resolution of the scanner also minimizes the underestimation of short-range changes in the Seebeck coefficient. With the addition of other treatment processes, such as annealing, quenching, and cold work, the system can assess the full variety of reversible and irreversible effects in thermocouples. Preliminary experiments on base-metal thermocouples confirm much of the known long-term behavior. However, the system has also exposed the rapid onset of some of these effects at low temperatures, the large amount and variability of cold work in new thermocouples, and large variations between different thermocouples of the same type.

Webster, E. S.; White, D. R.; Edgar, H.

2015-03-01

205

Synthesis and thermoelectric properties of RuO{sub 2} nanorods  

SciTech Connect

We have explored the effect of the O/Ru ratio on the morphology and the Seebeck coefficient of RuO{sub 2} nanorods (space group P4{sub 2}/mnm) synthesized by reactive sputtering. At an O/Ru ratio of 1.69, a faceted surface is observed, while nanorod formation occurs at O/Ru ratios of 2.03 and 2.24. Using classical molecular dynamics with the potential parameters derived in this work, we show that volatile species enable nanorod formation. Based on ab initio calculations, two effects of the nanorod formation on the Seebeck coefficient are observed: (i) increase due to additional states in the vicinity of the Fermi level and (ii) decrease due to oxygen point defects (volatile species). These two competing effects give rise to a moderate increase in the Seebeck coefficient upon nanorod formation.

Music, Denis; Basse, Felix H.-U.; Schneider, Jochen M. [Materials Chemistry, RWTH Aachen University, D-52056 Aachen (Germany); Hassdorf, Ralf [Institute of Materials Research, German Aerospace Centre (DLR), D-51147 Cologne (Germany)

2010-07-15

206

Spin density wave order and fluctuations in Mn3Si : A transport study  

NASA Astrophysics Data System (ADS)

We present a comprehensive transport investigation of the itinerant antiferromagnet Mn3Si which undergoes a spin density wave (SDW) order below TN˜21.3K. The electrical resistivity, the thermal conductivity, and the Hall, Seebeck, and Nernst effects exhibit pronounced anomalies at the SDW transition. At temperatures higher than TN our data provide strong evidence for a large fluctuation regime which extends up to ˜200K in the resistivity, the Seebeck effect, and the Nernst effect. From the comparison of our results with other prototype SDW materials, viz., LaFeAsO and chromium, we conclude that many of the observed features are of generic character.

Steckel, Frank; Rodan, Steven; Hermann, Regina; Blum, Christian G. F.; Wurmehl, Sabine; Büchner, Bernd; Hess, Christian

2014-10-01

207

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 ...

Mrs. Clemons

2010-11-10

208

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 ...

Mrs. Brown

2010-10-26

209

Low effective mass and carrier concentration optimization for high performance p-type Mg2(1-x)Li2xSi0.3Sn0.7 solid solutions.  

PubMed

Mg2Si1-xSnx solid solutions are promising thermoelectric materials for power generation applications in the 500-800 K range. Outstanding n-type forms of these solid solutions have been developed in the past few years with the thermoelectric figure of merit ZT as high as 1.4. Unfortunately, no comparable performance has been achieved so far with p-type forms of the structure. In this work, we use Li doping on Mg sites in an attempt to enhance and control the concentration of hole carriers. We show that Li as well as Ga is a far more effective p-type dopant in comparison to Na or K. With the increasing content of Li, the electrical conductivity rises rapidly on account of a significantly enhanced density of holes. While the Seebeck coefficient decreases concomitantly, the power factor retains robust values supported by a rather high mobility of holes. Theoretical calculations indicate that Mg2Si0.3Sn0.7 intrinsically possesses the almost convergent double valence band structure (the light and heavy band), and Li doping retains a low density of states (DOS) on the top of the valence band, contrary to the Ga doping at the sites of Si/Sn. Low temperature specific heat capacity studies attest to a low DOS effective mass in Li-doped samples and consequently their larger hole mobility. The overall effect is a large power factor of Li-doped solid solutions. Although the thermal conductivity increases as more Li is incorporated in the structure, the enhanced carrier density effectively shifts the onset of intrinsic excitations (bipolar effect) to higher temperatures, and the beneficial role of phonon Umklapp processes as the primary limiting factor to the lattice thermal conductivity is thus extended. The final outcome is the figure of merit ZT ? 0.5 at 750 K for x = 0.07. This represents a 30% improvement in the figure of merit of p-type Mg2Si1-xSnx solid solutions over the literature values. Hence, designing low DOS near Fermi level EF for given carrier pockets can serve as an effective approach to optimize the PF and thus ZT value. PMID:25178356

Zhang, Qiang; Cheng, Long; Liu, Wei; Zheng, Yun; Su, Xianli; Chi, Hang; Liu, Huijun; Yan, Yonggao; Tang, Xinfeng; Uher, Ctirad

2014-11-21

210

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.

Connecticut Energy Education

211

Thermoelectric properties of Yb-filled CoSb3 skutterudites  

NASA Astrophysics Data System (ADS)

Yb-filled skutterudites Yb z Co4Sb12 (z = 0, 0.1, 0.2, 0.3, 0.4) were prepared by encapsulated melting and hot pressing. The filling effects of Yb on the transport and the thermoelectric properties of the skutterudites were examined. In the case of z ? 0.3, a secondary phase (YbSb2) was formed, indicating that the filling fraction limit of Yb was z = 0.2 - 0.3. The intrinsic CoSb3 had a high positive Seebeck coefficient, but Yb-filled CoSb3 exhibited a negative Seebeck coefficient. In the case of z ? 0.1, the maximum absolute value of the Seebeck coefficient was | -231| ?VK-1, and in the case of z ? 0.2, the absolute value of the Seebeck coefficient increased with increasing temperature. The electrical conductivity increased and the Seebeck coefficient decreased with increasing Yb filling content due to the increased carrier concentration. The thermal conductivity was reduced significantly by Yb filling, mainly due to a decrease in the lattice thermal conductivity. Also, the lattice thermal conductivity decreased with increasing Yb filling content, indicating that the phonon scattering was caused by the rattling of Yb fillers in the voids of the skutterudite structure. Yb0.2Co4Sb12 showed the highest figure of merit of 1.0 at 823 K.

Park, Kwan-Ho; Seo, Won-Seon; Shin, Dong-Kil; Kim, Il-Ho

2014-08-01

212

Tuning the Thermal Properties of Magnetic Tunnel Junctions  

E-print Network

/TMR) . . . . . . . . . . . 52 3.3 Tunneling Anisotropic Magnetoresistance (TAMR) . . . . . . . . . . 54 4. THERMOELECTRIC PHENOMENON . . . . . . . . . . . . . . . . . . . 56 4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 4.2 Traditional... Thermoelectric Effects . . . . . . . . . . . . . . . . . . . . 57 vii 4.2.1 Seebeck Effect . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 4.2.2 Peltier Effect . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 4.3 Spin Caloritronics...

Amin, Vivek Pravin

2014-04-18

213

School Effectiveness and Effectiveness Indicators.  

ERIC Educational Resources Information Center

Examines connections between Alberta practitioners' perceptions of current school effectiveness in elementary and junior high schools and the relative importance of various effectiveness indicators. Because of differences in practioners' perceptions, schools and school systems need to continually probe the dimensions of school-effectiveness

Holdaway, Edward A.; Johnson, Neil A.

1993-01-01

214

Health Effects  

MedlinePLUS

... Possible Health Effects Short-term Strong hallucinations including perceptions of otherworldly imagery, altered visual and auditory perceptions; increased blood pressure, vomiting. Long-term Unknown. Other ...

215

Photo-transport properties of Pb2CrO5 single crystals  

NASA Astrophysics Data System (ADS)

We report photo-thermoelectric transport phenomena in Pb2CrO5 single crystals. Without illumination, this material exhibits an insulating behavior characterized by an activation-type temperature variation of the electrical conductivity. The Seebeck coefficient contrastingly shows a crossover from high-temperature insulating to low-temperature metallic behavior, which is attributed to degenerate carriers in a donor level. We have found that under illumination, both the conductivity and the Seebeck coefficient increase in magnitude with increasing photon flux density in the degenerate-conduction regime. This result is difficult to understand within a simple photo-doping effect, which usually leads to a decrease in the Seebeck coefficient under illumination. The observed phenomenon is discussed in terms of a two-carrier contribution to the transport properties.

Mondal, P. S.; Okazaki, R.; Taniguchi, H.; Terasaki, I.

2014-11-01

216

Tailoring thermopower of single-molecular junctions by temperature-induced surface reconstruction  

NASA Astrophysics Data System (ADS)

Recent experiments revealed that surface reconstruction occurs at around 300-400 K in the interface of C60 adsorbed on Cu(111) substrate by scanning tunneling microscope techniques. To understand effects of such reconstruction on thermopower, we investigate the Seebeck coefficients of C60 single-molecular junctions without and with surface reconstruction as a function of temperature at different tip-to-molecule heights from first-principles. Our calculations show that surface reconstruction can enhance or suppress Seebeck coefficients according to junctions at different tip heights. We further observe that the Seebeck coefficient of the junction at d = 3.4 Å may change from p- to n-type under surface reconstruction.

Hsu, Bailey C.; Lin, Chiung-Yuan; Hsieh, Yau-Shian; Chen, Yu-Chang

2012-12-01

217

Gauging Effectiveness  

ERIC Educational Resources Information Center

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

Foord, Kathleen A.; Haar, Jean M.

2012-01-01

218

Thermal Effects.  

ERIC Educational Resources Information Center

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

Talmage, Sylvia S.; Coutant, Charles C.

1978-01-01

219

Doppler Effect  

NSDL National Science Digital Library

In this activity, learners use a tuning fork to explore how the Doppler effect works. They strike the tuning fork to produce a sound, then observe as the tone changes as the fork is swung back and forth. Learners also explore applications of the Doppler effect in technology.

2014-02-03

220

Technische Universitt Mnchen Fakultt fr Physik  

E-print Network

of dissipationless spin currents but also by the possibility of exploiting waste heat in devices to induce those decreasing the device size while trying to increase the transistor speed results in heat dissipation due (SSE) in analogy to the conventional Seebeck effect, a thermoelectric effect known since 1823 [3

Gross, Rudolf

221

Modern Thermocouple Experiment.  

ERIC Educational Resources Information Center

Describes a thermocouple circuit used to measure Joule heating as well as Peltier heating and cooling for a copper-Constantan metallic junction. Shows how the Seebeck effect from a thermocouple can monitor the temperature condition of a junction with regard to input power and Peltier effect. (Author/GA)

Chang, K. N.; And Others

1978-01-01

222

High thermoelectric figure of merit in nanocrystalline polyaniline at low temperatures  

NASA Astrophysics Data System (ADS)

Thermoelectric coolers with figure of merit (ZT) close to unity at low temperatures are the need of the hour with new advances in high temperature superconductors, superconducting microelectronic circuits, quantum computers, and photonics. Here, we demonstrate that the conducting polymer polyaniline (Pani) doped with camphor sulfonic acid synthesized in semi-crystalline nanostructures, possesses a giant Seebeck effect at low temperatures. The resulting enormously large Seebeck coefficient (up to 0.6 V/K) combined with an intrinsically low electrical conductivity and thermal conductivity give rise to a ZT = 0.77 at 45 K and ZT = 2.17 at 17 K.

Nath, Chandrani; Kumar, Ashok; Kuo, Yung-Kang; Okram, Gunadhor Singh

2014-09-01

223

Doppler Effect  

NSDL National Science Digital Library

- The Doppler Effect explains why we hear a sonic boom when an airplane flies faster than the speed of sound. - Applying the Doppler Effect is how we have Doppler Radar used to track weather. - The Doppler Effect can be applied to outerspace and it evidence that the universe is expanding. Sound is energy traveling through a medium. A medium can be a gas, liquid, or solid. Therefore sound can not travel in outerspace since it is a vacuum which means there is nothing not even air. Energy traveling through a medium or even a vacuum is considered a wave. ...

Mr. Leet

2008-03-16

224

Doppler Effect  

NSDL National Science Digital Library

Control the velocity of two sound sources in which the wave crests are visually represented. As the sound sources move, interference patterns and evidence of the Doppler effect can be observed and measured.

2007-12-12

225

Chemotherapy Effects  

MedlinePLUS

... Basics Cancer Prevention & Detection Signs & Symptoms of Cancer Treatments & Side Effects Cancer Facts & Statistics News About Cancer Expert Voices Blog Programs & Services Breast Cancer Support TLC Hair Loss & Mastectomy Products Hope ...

226

Health Effects  

MedlinePLUS

... Chapter . Additional information regarding the health effects of climate change and references to supporting literature can be found ... http://nca2014.globalchange.gov/report/sectors/human-health . Climate change, together with other natural and human-made health ...

227

The Effect of Structural Vacancies on the Thermoelectric Properties of (Cu2Te)1-x(Ga2Te3)x  

SciTech Connect

We have studied the effects of structural vacancies on the thermoelectric properties of the ternary compounds (Cu2Te)1-x(Ga2Te3)x (x = 0.5, 0.55, 0.571, 0.6, 0.625, 0.667 and 0.75), which are solid solutions found in the pseudo-binary phase diagram for Cu2Te and Ga2Te3. This system possesses tunable structural vacancy concentrations. The x= 0.5 phase, CuGaTe2, is nominally devoid of structural vacancies, while the rest of the compounds contain varying amounts of these features, and the volume density of vacancies increases with Ga2Te3 content. The sample with x = 0.5, 0.55, 0.571, 0.6, 0.625 crystallize in the chalcopyrite structure while the x = 0.667 and 0.75 adopt the Ga2Te3 defect zinc blende structure. Strong scattering of heat carrying phonons by structural defects, leads to the reduction of thermal conductivity, which is beneficial to the thermoelectric performance of materials. On the other hand, these defects also scatter charge carriers and reduce the electrical conductivity. All the samples investigated are p-type semiconductors as inferred by the signs of their respective Hall (RH) and Seebeck (S) coefficients. The structural vacancies were found to scatter phonons strongly, while a combination of increased carrier concentration, and vacancies decreases the Hall mobility ( H), degrading the overall thermoelectric performance. The room temperature H drops from 90 cm2/V s for CuGaTe2 to 13 cm2/V s in Cu9Ga11Te21 and 4.6 cm2/V s in CuGa3Te5. The low temperature thermal conductivity decreases significantly with higher Ga2Te3 concentrations (higher vacancy concentration) due to increased point defect scattering which dominate thermal resistance terms. At high temperatures, the dependence of thermal conductivity on the Ga2Te3 content is less significant. The presence of strong Umklapp scattering leads to low thermal conductivity at high temperatures for all samples investigated. The highest ZT among the samples in this study was found for the defect-free CuGaTe2 with ZT ~ 1.0 at 840K.

Ye, Zuxin [GM Research and Development Center; Cho, Jung Y [GM R& D and Planning, Warren, Michigan; Tessema, Misle [GM Research and Development Center; Salvador, James R. [GM R& D and Planning, Warren, Michigan; Waldo, Richard [GM R& D and Planning, Warren, Michigan; Wang, Hsin [ORNL; Cai, Wei [ORNL

2013-01-01

228

Effects and Effectiveness of Telemedicine  

PubMed Central

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

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

1995-01-01

229

Email Effects  

NSDL National Science Digital Library

This site caters to those in search of an easier way to create tables, flow charts, maps, chemical structure diagrams, and the like. Email Effects can also add fun pictures to the signatures at the bottom of email messages for Macintosh owners who use Qualcomm's Eudora or Claris Emailer. This $10 shareware offers an easy-to-use interface with a drawing-like toolbar to create or convert the items mentioned above into ASCII based text. To convert an item, just copy and paste it into the Email Effects window. The text can be saved and/or added to an email message with the click of a button. Email Effects is provided by Sig Software. The download comes with text clip art.

230

Plasma Effects  

NASA Technical Reports Server (NTRS)

Radio communication with space probes requires sending signals through the Earth's ionosphere and usually the solar wind. During planetary flybys, the signal may also pass through the ionosphere of another planet. These ionized media can perturb the radio signal in a variety of ways. Examples of these perturbations are variations in the electrical length between the spacecraft and the ground station, Faraday rotation of linearly polarized signals, amplitude and phase scintillations, and spectral and angular broadening. These plasma effects can have undesirable influences on telemetry performance and thus need to be understood from a communications engineering viewpoint. The plasma effects are, however, useful from a scientific viewpoint, since the effects on the communications link can often be inverted to estimate the physical conditions in the plasma.

Armstrong, J. W.

1983-01-01

231

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.

232

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

233

Effects of \\  

Microsoft Academic Search

Recorded the voices of white and black male college students reading instructions and questions for the Peabody Picture Vocabulary Test (PPVT). 124 black and 128 white children from the same school in Grades 1-4 completed the PPVT after listening to 1 of the examiner's voices. Analysis of PPVT scores indicates significant effects for race of voice and race of S,

Kenneth France

1973-01-01

234

Effective Mentoring  

Microsoft Academic Search

Effective mentoring is essential to the growth and success of librarianship in all types of library. This paper considers the possibilities for fostering mentoring activities among early career librarians, mid-career transitional librarians, and non-professional library workers. First, the paper describes existing studies to illuminate the urgency of mentoring activities to address the diminishing number of librarians and changing librarianship in

Shin Freedman

2009-01-01

235

Electrical Properties and Surface Microtopographic Studies of Tungsten Disulfide Single Crystals Grown by CVT Technique  

Microsoft Academic Search

The single crystals of tungsten disulphide (WS2) were grown by chemical vapor transport (CVT) technique, using iodine as the transporting agent. The stoichiometric composition and the crystallographic lattice parameters of the grown crystals were determined by EDAX and X?ray diffraction (XRD) techniques, respectively. The Hall effect measurement and the Seebeck coefficient variation with temperature confirmed that the single crystals were

Sunil Chaki; Ajay Agarwal

2008-01-01

236

november 2009 bo Akademi -TkF -Vrme-och strmningsteknik Biskopsgatan 8, 20500 bo  

E-print Network

driving forces: transport = coefficient � driving force ­ heat flux (W/m2)= conductivity (W/m2.K)�temperature-correlations such as ­ Mass transfer = coefficient � temperature gradient ("thermal diffusion") ­ For example Seebeck effect, or stagnant fluid) in the presence of a temperature gradient, heat is transferred from high to low temperature

Zevenhoven, Ron

237

Waste-Heat thermoelectric power source for industrial wireless transmitters  

Microsoft Academic Search

This paper presents Seebeck effect-based thermoelectric power source utilizing waste heat in manufacturing processes for industrial wireless transmitters. An industrial wireless transmitter can be supplied by its internal battery in combination with the proposed thermoelectric power source to conserve battery lifetime. Moreover, the proposed power source can operate as the backup power supply for new battery replacement without tuning the

Teerawat Thepmanee; Prasit Julsereewong; N. Taratanaphol

2010-01-01

238

Author's personal copy Pyroelectric energy converter using co-polymer P(VDF-TrFE) and Olsen cycle  

E-print Network

of waste heat [1]. To date, the effort has focused on thermoelectric generators based on the Seebeck effect for waste heat energy harvesting Hiep Nguyen, Ashcon Navid, Laurent Pilon* University of California, Los, building, and testing a pyroelectric energy converter to directly convert waste heat into electricity

Pilon, Laurent

239

Pyroelectric Nanogenerators for Harvesting Thermoelectric Energy Ken C. Pradel,  

E-print Network

contact, Seebeck effect Wasted heat is a rich source of energy that could be harvested. In 2010 of wasted heat,1 which presents us with a great opportunity to harvest this type of energy using nanoPyroelectric Nanogenerators for Harvesting Thermoelectric Energy Ya Yang, Wenxi Guo, Ken C. Pradel

Wang, Zhong L.

240

A novel thermally biased mechanical energy conversion cycle Ian M. McKinley, Sam Goljahi, Christopher S. Lynch, and Laurent Pilona)  

E-print Network

in the form of low grade waste heat.1 Methods for harvesting low grade waste heat include Stirling engines,2 organic Rankine cycles,3 and thermoelectric devices.4,5 Stirling engines and organic Rankine cycles convert thermal energy into mechanical energy. Thermoelectric devices make use of the Seebeck effect

Pilon, Laurent

241

A Glucose BioFuel Cell Implanted in Rats  

Microsoft Academic Search

Powering future generations of implanted medical devices will require cumbersome transcutaneous energy transfer or harvesting energy from the human body. No functional solution that harvests power from the body is currently available, despite attempts to use the Seebeck thermoelectric effect, vibrations or body movements. Glucose fuel cells appear more promising, since they produce electrical energy from glucose and dioxygen, two

Philippe Cinquin; Chantal Gondran; Fabien Giroud; Simon Mazabrard; Aymeric Pellissier; François Boucher; Jean-Pierre Alcaraz; Karine Gorgy; François Lenouvel; Stéphane Mathé; Paolo Porcu; Serge Cosnier; Richard Haverkamp

2010-01-01

242

System Effectiveness  

SciTech Connect

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

Powell, Danny H [ORNL] [ORNL; Elwood Jr, Robert H [ORNL] [ORNL

2011-01-01

243

Blazhko Effect  

NASA Technical Reports Server (NTRS)

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

Teays, Terry

1996-01-01

244

Ripple Effects  

E-print Network

of water. In another portion of the economics project, Amosson and Extension Associate Bridget Guerrero take the results a step further. Using a socio-economic planning model, they first incorporate economic data for the counties in each sub...-region and in particular crop production costs. Finally, they input the initial effects on farmers? incomes gained from the opti- mization models into the socio-economic modeling program. The results give an idea of what specific policies or technological advances...

Wythe, Kathy

2006-01-01

245

Performance analysis of a thermosize micro\\/nano heat engine  

Microsoft Academic Search

In a recent paper [A. Sisman, I. Muller, Phys. Lett. A 320 (2004) 360] the thermodynamic properties of ideal gases confined in a narrow box were examined theoretically. The so-called “thermosize effects” similar to thermoelectric effects, such as Seebeck-like thermosize effect, Peltier-like thermosize effect and Thomson-like thermosize effect, were analyzed. Like the thermoelectric generator, based on the thermosize effects we

Wenjie Nie; Jizhou He

2008-01-01

246

Erosion Effects  

NASA Technical Reports Server (NTRS)

[figure removed for brevity, see original site]

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

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

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

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

2003-01-01

247

Spin caloritronics of blue phosphorene nanoribbons.  

PubMed

We report a first-principles study of the magnetic properties and spin caloritronics of zigzag-type blue phosphorene nanoribbons (zBPNRs). It is found that the bare zBPNR (0H-zBPNR) or monohydrogenated zBPNR (1H-zBPNR) exhibit spin-semiconducting properties arising from the edge electronic states. We further confirm that the py orbitals of the edge P atoms have the main contributions to these states. The spin-semiconducting property has a natural advantage for fabricating perfect thermospin devices with a stronger spin Seebeck effect than charge Seebeck effect at the Fermi level. When a temperature difference is applied, the electric current with the different spin index displays a bipolar behavior, and the spin-filtering efficiency can reach 1200%. By changing the widths of 0H-zBPNR and 1H-zBPNR, the ratio of the spin Seebeck coefficient to the charge Seebeck coefficient at the Fermi level is about 10 at room temperature. PMID:25801010

Liu, Y S; Zhang, X; Yang, X F; Hong, X K; Feng, J F; Si, M S; Wang, X F

2015-04-01

248

Effects of Bi on the thermoelectric properties of Mg2Si-Mg2Ge solid solutions  

NASA Astrophysics Data System (ADS)

Mg2Si1- x Ge x :Bi m (0.3 ? x ? 0.7, m = 0 or 0.02) solid solutions were synthesized by using a solid-state reaction (SSR) and were consolidated by hot pressing (HP). In the case of the undoped Mg2Si1- x Ge x specimens, the electrical conduction changed from n-type to p-type at room temperature for x ? 0.7 due to the intrinsic properties of Mg2Ge. The electrical conductivity rapidly increased with increasing temperature, indicating a non-degenerate semiconducting behavior, and decreased with increasing Ge content. However, all Bi-doped Mg2Si1- x Ge x solutions showed n-type conduction. The carrier concentration was increased from 4.0 × 1017 to 1.9 × 1020 cm-3 by Bi doping, and the electrical conductivity was increased from 7.3 × 10 to 4.3 × 104 Sm-1. The absolute value of the Seebeck coefficient increased with increasing temperature, and the Seebeck coefficient ranged from -91 to -224 ?VK-1 for the Bi-doped specimens. Bi doping reduced the thermal conductivities of the Mg2Si1- x Ge x solid solutions at temperatures above 723 K. Mg2Si0.7Ge0.3:Bi0.02 exhibited a maximum dimensionless figure-of-merit of 0.79 at 823 K.

You, Sin-Wook; Shin, Dong-Kil; Kim, Il-Ho

2014-09-01

249

Effect of substrate on the atomic structure and physical properties of thermoelectric Ca?Co?O? thin films.  

PubMed

The incommensurately layered cobalt oxide Ca(3)Co(4)O(9) 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 Ca(3)Co(4)O(9) thin films grown on cubic perovskite SrTiO(3), LaAlO(3), and (La(0.3)Sr(0.7))(Al(0.65)Ta(0.35))O(3) substrates and on hexagonal Al(2)O(3) (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 CoO(2) layer is stabilized only after a critical thickness and, in general, we observe the formation of a stable Ca(2)CoO(3) buffer layer near the substrate-film interface. Beyond this critical thickness, a large concentration of CoO(2) 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 Ca(3)Co(4)O(9) films due to additional phonon scattering sites, necessary for improved thermoelectric properties. PMID:21719960

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

2011-08-01

250

Microbial effects  

SciTech Connect

The postulated doubling of atmospheric CO/sub 2/ is not likely to have direct effect on soil microbial activity because during the growing season, the concentration of CO/sub 2/ in the soil atmosphere is already ten to fifty times higher than existing atmospheric CO/sub 2/. Based on all available experimental information, it is estimated that a doubling of atmospheric CO/sub 2/ will cause an increase in primary productivity of 10 to 40% depending on locale. The increase in biomass will, in turn, produce a limitation of available soil nutrients, especially nitrogen and phosphorus. Increased organic carbon together with nitrogen and/or phosphorus limitation will result in a preferential increase in nitrogen fixation and mycorrhizal activities as the expedient means for supplying required nutrients to sustain the predicted increase in primary productivity. Therefore, increased emphasis should be placed on fundamental research related to soil microbiology with special reference to nitrogen-fixing, nitrifying and denitrifying bacteria, and to the mycorrhizal fungi. 111 references, 2 figures.

Lamborg, M.R.; Hardy, R.W.F.; Paul, E.A.

1983-01-01

251

Effect of C-face 4H-SiC(0001) deposition on thermopower of single and multilayer graphene in AA, AB and ABC stacking  

NASA Astrophysics Data System (ADS)

The Seebeck coefficient in multilayer graphene is investigated within the density-functional theory, using the semiclassical Boltzmann equations and interpolating the bands in a maximally-localized Wannier functions basis set. We compare various graphene stackings (AA, AB and ABC) both free-standing and deposited on the 4H-SiC(0001) C-terminated substrate. We find that the presence of the SiC substrate can significantly affect the thermopower properties of graphene layers, depending on the stacking, providing a promising way to tailor efficient graphene-based devices.

Wierzbowska, Ma?gorzata; Dominiak, Adam; Pizzi, Giovanni

2014-12-01

252

Effect of Y doping on magnetic and transport properties of La0.7Sr0.3CoO3  

NASA Astrophysics Data System (ADS)

The temperature variation of magnetization, resistivity and thermo electric power of undoped and Y-doped La0.7Sr0.3CoO3 samples have been investigated. Y-doping decreases the magnetization possibly due to the spin state transition of Co-ions. The low temperature conduction in (La1-yYy)0.7Sr0.3CoO3 is consistent with the variable range hopping. With Y doping, value of the Seebeck coefficient increases, as Y doping decreases bandwidth and increases distortion.

Dwivedi, G. D.; Shukla, K. K.; Shahi, P.; Jha, O. K.; Ghosh, A. K.; Nigam, A. K.; Chatterjee, Sandip

2013-02-01

253

Development of Flexible Micro-Thermo-electrochemical Generators Based on Ionic Liquids  

NASA Astrophysics Data System (ADS)

The unfavourable relationship between electrical and thermal conductivity limits the choice of solid-state materials for thermoelectric generators (TEG). Among ionic liquids (IOL), it appears that a large variety of thermoelectric (TE) materials with promising high Seebeck coefficients have potential for development. Furthermore, the novel solid-on-liquid deposition technology (SOLID) allows the encapsulation of liquid TE materials to create new, highly integrated TEG devices. Following this vision, this paper studies a large number of IOLs looking at TE-relevant parameters such as thermal and electrical conductivity, Seebeck coefficient and temperature-dependent viscosity. We show that positive and negative Seebeck coefficients can be obtained, depending on the molecular structure and the viscosity of the IOL. The properties of single-junction TEGs are presented in terms of I- V characteristics correlated with the IOL properties. We prove that the limiting effect of conversion efficiency is the current density that can be extracted from a device rather than the Seebeck coefficient.

Uhl, Stefanie; Laux, Edith; Journot, Tony; Jeandupeux, Laure; Charmet, Jérôme; Keppner, Herbert

2014-10-01

254

The effects of Sb on the thermoelectric properties of Mg2Si1-xGex prepared by using solid-state synthesis  

NASA Astrophysics Data System (ADS)

Sb-doped Mg2Si1-xGex solid solutions were successfully prepared by using a solid-state reaction and hot pressing. In the case of the undoped Mg2Si1-xGex specimens, the electrical conduction changed from n-type to p-type at room temperature for x ? 0.7 due to the intrinsic properties of Mg2Ge. The electrical conductivity rapidly increased with increasing temperature, indicating a non-degenerate semiconducting behavior, and decreased with increasing Ge content. However, the Sb-doped Mg2Si1-xGex specimens showed n-type conduction, and the carrier concentration was increased from 4.0 × 1017 to 3.2 × 1021 cm-3 by doping with Sb atoms, which acted as donors. The absolute value of the Seebeck coefficient increased with increasing temperature, and the Seebeck coefficient ranged from -131 to -259 ?V/K for the Sb-doped specimens. Sb doping reduced the thermal conductivities of the Mg2Si1-xGex solid solutions at temperatures above 723 K. Mg2Si0.5Ge0.5:Sb0.02 exhibited a maximum dimensionless figure-of-merit of 0.56 at 823 K.

You, Sin-Wook; Shin, Dong-Kil; Kim, Il-Ho

2014-05-01

255

Effects of Thermal Annealing on the Thermoelectric and Optical Properties of SiO2/SiO2+Cu Nanolayer Thin Films  

NASA Astrophysics Data System (ADS)

We have prepared multi-nanolayer superlattice thin-film systems comprising 36 alternating layers of SiO2 and SiO2+Cu nanolayers, of total thickness approximately 300 nm, by magnetron direct current-radio frequency sputtering. To modify their thermoelectric and optical properties, the films were placed in a furnace for annealing at temperatures between 500°C and 700°C, in air, for 1 h, to form quantum nano-dots and/or quantum clusters. Atomic force microscopy was used to analyze the surface of the thin-film systems. The thermoelectric and optical properties of the systems were characterized by study of ultraviolet-visible-near infrared absorption, fluorescence, and Raman spectroscopy, and by measurement of Seebeck coefficients. Seebeck coefficients increased from -70 ?V/K to -100 ?V/K when the temperature was increased from 0°C to 700°C. Optical absorption spectra showed that formation of nano-dots and/or nano-clustering also occurred as the temperature was increased. Thermal annealing affected the optical and thermal properties of the multi-nanolayer thermoelectric thin-film systems in the positive direction.

Budak, S.; Baker, M.; Lassiter, J.; Smith, C.; Muntele, C.; Johnson, R. B.

2014-09-01

256

Side Effects of Chemotherapy  

MedlinePLUS

... PCF Spotlight Glossary African American Men Living with Prostate Cancer Side Effects of Chemotherapy Side Effects Urinary Dysfunction ... side effects of docetaxel as used to treat prostate cancer are VERY different and less severe than the ...

257

Thermoelectric effects in graphene with local spin-orbit interaction  

NASA Astrophysics Data System (ADS)

We investigate the transport properties of a graphene layer in the presence of Rashba spin-orbit interaction. Quite generally, spin-orbit interactions induce spin splittings and modifications of the graphene band structure. We calculate within the scattering approach the linear electric and thermoelectric responses of a clean sample when the Rashba coupling is localized around a finite region. We find that the thermoelectric conductance, unlike its electric counterpart, is quite sensitive to external modulations of the Fermi energy. Therefore, our results suggest that thermocurrent measurements may serve as a useful tool to detect nonhomogeneous spin-orbit interactions present in a graphene-based device. Furthermore, we find that the junction thermopower is largely dominated by an intrinsic term independently of the spin-orbit potential scattering. We discuss the possibility of canceling the intrinsic thermopower by resolving the Seebeck coefficient in the subband space. This causes unbalanced populations of electronic modes which can be tuned with external gate voltages or applied temperature biases.

Alomar, M. I.; Sánchez, David

2014-03-01

258

Communicating Effectively PDF  

Cancer.gov

Effective communication is essential for the delivery of quality cancer palliative care. And yet, healthcare providers often lack the skills to communicate effectively with their patients and families.

259

Polymorphic effect systems  

Microsoft Academic Search

We present a new approach to programming languages for parallel computers that uses an effect system to discover expression scheduling constraints. This effect system is part of a 'kinded' type system with three base kinds: types, which describe the value that an expression may return; effects, which describe the side-effects that an expression may have; and regions, which describe the

John M. Lucassen; David K. Gifford

1988-01-01

260

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

261

Improving School Effectiveness.  

ERIC Educational Resources Information Center

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

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

262

AHSGE Cause and Effect  

NSDL National Science Digital Library

Cause and Effect practice to build skill knowledge for the reading portion of the graduation exam. Complete the Cause and Effect activities at your pace . Cause and Effect Match , Cause and Effect Mini Lesson and Game , What s the Cause?? Quiz . ...

Ms. Ufomadu

2013-06-13

263

Small-polaron versus band conduction in some transition-metal oxides  

Microsoft Academic Search

In this paper an attempt is made to establish the nature of free charge carriers and of charge carriers bound to centres in p-type NiO, CoO and MnO and in n-type MnO and ?-Fe2O3.For free charge carriers, d.c. conductivity, Seebeck coefficient and Hall effect are considered. Effects arising from inhomogeneous conduction and impurity conduction are discussed. Impurity conduction appears to

A. J. Bosman; H. J. van Daal

1970-01-01

264

Gravitational Casimir Effect  

NASA Astrophysics Data System (ADS)

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

Quach, James Q.

2015-02-01

265

WASC EDUCATIONAL EFFECTIVENESS REVIEW EDUCATIONAL EFFECTIVENESS APPROACH  

E-print Network

to its citizens, articulated in the Master Plan for Higher Education, UC Santa Cruz must continue to doWASC EDUCATIONAL EFFECTIVENESS REVIEW EDUCATIONAL EFFECTIVENESS APPROACH UC Santa Cruz ... ranked sought to maintain the high quality of our undergraduate education. We also seek to continue growth

California at Santa Cruz, University of

266

Dimensional Analysis of Thermoelectric Modules Under Constant Heat Flux  

NASA Astrophysics Data System (ADS)

Thermoelectric power generation is examined in the case of radiative heating. A constant heat flux is assumed in addition to consideration of the Seebeck effect, Peltier effect, and Joule heating with temperature-dependent material properties. Numerical evaluations are conducted using a combination of the finite-volume method and an original simultaneous solver for the heat transfer, thermoelectric, and electric transportation phenomena. Comparison with experimental results shows that the new solver could work well in the numerical calculations. The calculations predict that the Seebeck effect becomes larger for longer thermoelectric elements because of the larger temperature difference. The heat transfer to the cold surface is critical to determine the junction temperatures under a constant heat flux from the hot surface. The negative contribution from Peltier cooling and heating can be minimized when the current is smaller for longer elements. Therefore, a thicker TE module can generate more electric power even under a constant heat flux.

Suzuki, Ryosuke O.; Fujisaka, Takeyuki; Ito, Keita O.; Meng, Xiangning; Sui, Hong-Tao

2015-01-01

267

Spin caloritronics.  

PubMed

Spintronics is about the coupled electron spin and charge transport in condensed-matter structures and devices. The recently invigorated field of spin caloritronics focuses on the interaction of spins with heat currents, motivated by newly discovered physical effects and strategies to improve existing thermoelectric devices. Here we give an overview of our understanding and the experimental state-of-the-art concerning the coupling of spin, charge and heat currents in magnetic thin films and nanostructures. Known phenomena are classified either as independent electron (such as spin-dependent Seebeck) effects in metals that can be understood by a model of two parallel spin-transport channels with different thermoelectric properties, or as collective (such as spin Seebeck) effects, caused by spin waves, that also exist in insulating ferromagnets. The search to find applications--for example heat sensors and waste heat recyclers--is on. PMID:22522639

Bauer, Gerrit E W; Saitoh, Eiji; van Wees, Bart J

2012-05-01

268

Thermoelectric Properties of Nanocrystalline PbTe Synthesized by Mechanical Alloying  

NASA Astrophysics Data System (ADS)

In this work, nanocrystalline lead telluride powder was synthesized from high-purity elements by mechanical alloying by means of a planetary ball-milling procedure. The milling medium was tungsten carbide, and the diameter of the balls was varied in order to investigate the effect on the structural features of the material. Phase transformations and crystallite evolution during ball-milling were followed by powder x-ray diffraction (PXRD). The broadened PXRD peaks were analyzed with Voigt functions, revealing small crystalline size and stress introduced during the mechanical alloying process. Transmission electron microscopy (TEM) studies confirmed the material’s nanostructure, as well as the effect of ball diameter on the size of the crystals. Thermoelectric properties are discussed in terms of the Seebeck coefficient and the nominal carrier concentration, as determined by Hall-effect measurements. The enhancement of the Seebeck coefficient is reported to be higher compared with other PbTe-based nanocomposites.

Papageorgiou, Ch.; Hatzikraniotis, E.; Lioutas, Ch. B.; Frangis, N.; Valassiades, O.; Paraskevopoulos, K. M.; Kyratsi, Th.

2010-09-01

269

Effect of Ru Substitution for Mn in the Si2Ti-Type Al-Mn-Si Alloy  

NASA Astrophysics Data System (ADS)

The Al-Mn-Si C54-phase is characterized by a large magnitude of the Seebeck coefficient | S| exceeding 300 ?V/K. It also possesses large lattice thermal conductivity, and hence the magnitude of the dimensionless figure of merit ZT is limited to small values less than 0.1. To decrease the lattice thermal conductivity, we partially substituted heavier Ru for lighter Mn in the Al-Mn-Si C54-phase. Even though the solubility of Ru in the Al-Mn-Si C54-phase was limited to only a few at.%, 3 at.% Ru substitution led to ~10% reduction of the lattice thermal conductivity. Grain size reduction with the assistance of the liquid quenching technique further reduced the magnitude of the lattice thermal conductivity, resulting in a value 38% smaller than that of the Ru-free Al-Mn-Si C54-phase.

Yamamoto, Akio; Takeuchi, Tsunehiro

2012-06-01

270

Managing Physical Effects  

Cancer.gov

Browse a list of common side effects of cancer or cancer treatment with links to practical information for preventing or relieving these effects. Also find information on maintaining proper nutrition during cancer treatment.

271

Side Effects (Management)  

MedlinePLUS

... cancer care is relieving side effects, called symptom management, palliative care, or supportive care. It is important ... treat them. To learn about the symptoms and management of the long-term side effects of cancer ...

272

Effective College Teaching.  

ERIC Educational Resources Information Center

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

Caraway, James E.

1978-01-01

273

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...

274

Theoretical and experimental investigation of magnetotransport in iron chalcogenides  

NASA Astrophysics Data System (ADS)

We explore the electronic, transport and thermoelectric properties of Fe1+ySexTe1-x compounds to clarify the mechanisms of superconductivity in Fe-based compounds. We carry out first-principles density functional theory (DFT) calculations of structural, electronic, magnetic and transport properties and measure resistivity, Hall resistance and Seebeck effect curves. All the transport properties exhibit signatures of the structural/magnetic transitions, such as discontinuities and sign changes of the Seebeck coefficient and of the Hall resistance. These features are reproduced by calculations provided that antiferromagnetic correlations are taken into account and experimental values of lattice constants are considered in DFT calculations. On the other hand, the temperature dependences of the transport properties can not be fully reproduced, and to improve the agreement between experiment and DFT calculations it is necessary to go beyond the constant relaxation time approximation and take into account correlation effects.

Caglieris, Federico; Ricci, Fabio; Lamura, Gianrico; Martinelli, Albert; Palenzona, A.; Pallecchi, Ilaria; Sala, Alberto; Profeta, Gianni; Putti, Marina

2012-10-01

275

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

2012-12-28

276

Spin current generation from sputtered Y3Fe5O12 films  

NASA Astrophysics Data System (ADS)

Spin current injection from sputtered yttrium iron garnet (YIG) films into an adjacent platinum layer has been investigated by means of the spin pumping and the spin Seebeck effects. Films with a thickness of 83 and 96 nanometers were fabricated by on-axis magnetron rf sputtering at room temperature and subsequent post-annealing. From the frequency dependence of the ferromagnetic resonance linewidth, the damping constant has been estimated to be (7.0 ± 1.0) × 10-4. Magnitudes of the spin current generated by the spin pumping and the spin Seebeck effect are of the same order as values for YIG films prepared by liquid phase epitaxy. The efficient spin current injection can be ascribed to a good YIG|Pt interface, which is confirmed by the large spin-mixing conductance (2.0 ± 0.2) × 1018 m-2.

Lustikova, J.; Shiomi, Y.; Qiu, Z.; Kikkawa, T.; Iguchi, R.; Uchida, K.; Saitoh, E.

2014-10-01

277

Spin current generation from sputtered Y{sub 3}Fe{sub 5}O{sub 12} films  

SciTech Connect

Spin current injection from sputtered yttrium iron garnet (YIG) films into an adjacent platinum layer has been investigated by means of the spin pumping and the spin Seebeck effects. Films with a thickness of 83 and 96 nanometers were fabricated by on-axis magnetron rf sputtering at room temperature and subsequent post-annealing. From the frequency dependence of the ferromagnetic resonance linewidth, the damping constant has been estimated to be (7.0?±?1.0)?×?10{sup ?4}. Magnitudes of the spin current generated by the spin pumping and the spin Seebeck effect are of the same order as values for YIG films prepared by liquid phase epitaxy. The efficient spin current injection can be ascribed to a good YIG|Pt interface, which is confirmed by the large spin-mixing conductance (2.0?±?0.2)?×?10{sup 18?}m{sup ?2}.

Lustikova, J., E-mail: lustikova@imr.tohoku.ac.jp; Shiomi, Y.; Kikkawa, T.; Iguchi, R. [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Qiu, Z. [WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Uchida, K. [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); PRESTO, Japan Science and Technology Agency, Saitama 332-0012 (Japan); Saitoh, E. [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); CREST, Japan Science and Technology Agency, Tokyo 102-0076 (Japan); Advanced Science Research Center, Japan Atomic Energy Agency, Tokai 319-1195 (Japan)

2014-10-21

278

Thermoelectric properties of tungsten-substituted Heusler Fe2VAl alloy  

NASA Astrophysics Data System (ADS)

A Heusler Fe2V1-xWxAl sintered alloy was synthesized to evaluate the effect of W substitution on thermoelectric properties of the Heusler alloy. The Seebeck coefficient and the electrical conductivity are simultaneously enhanced through electron injection resulting from the W substitution. Comparison with the Si-substituted Fe2VAl alloy reveals that the additional electronic states derived from W 5d orbital in the vicinity of pseudogap are likely to degrade the Seebeck coefficient. Thermal conductivity is effectively reduced by the W substitution because of the large atomic mass and volume of W compared to the constituent elements of Fe2VAl alloy. The appreciable reduction of thermal conductivity, without a serious deterioration in electrical conduction, enhances the thermoelectric figure of merit in the Heusler alloy.

Mikami, M.; Kinemuchi, Y.; Ozaki, K.; Terazawa, Y.; Takeuchi, T.

2012-05-01

279

Nanocubes  

NASA Astrophysics Data System (ADS)

A giant Seebeck coefficient of -890 ?V/K at 500 °C has been observed in Y0.2Sr0.8TiO3 prepared using nanocubes. Doping rare earth elements, RE, has revealed that small RE is effective to enhance the Seebeck coefficient. Through soft mode observations by Raman spectroscopy and structural calculations based on density functional theory, it has been found that the breakdown of inversion symmetry of the perovskite structure near the surface of nanocubes can be recovered by doping with small RE. Because the dielectric constant is strongly related to the surface structure in this compound, we suggest that RE doping modulates the potential barrier at the grain boundary, resulting in a pronounced energy filtering effect in Y doped SrTiO3.

Kinemuchi, Yoshiaki; Mimura, Ken-ichi; Towata, Atsuya; Kato, Kazumi

2014-06-01

280

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

281

Electrocaloric effect on graphenes  

NASA Astrophysics Data System (ADS)

The present Letter explores the electrocaloric effect of graphene nano-ribbons, with a longitudinal electric field and transversal magnetic field. Special features of the effect can be ruled and tuned by the applied fields as, for instance, the unusual inverse effect, created by the Landau levels. These results open doors to enhance electrocaloric utility of materials.

Reis, M. S.; Soriano, S.

2013-03-01

282

Effects of Nuclear Weapons.  

ERIC Educational Resources Information Center

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

Sartori, Leo

1983-01-01

283

Side Effects of Hormone Therapy  

MedlinePLUS

... Men Living with Prostate Cancer Side Effects of Hormone Therapy Side Effects Urinary Dysfunction Bowel Dysfunction Erectile Dysfunction Loss of Fertility Side Effects of Hormone Therapy Side Effects of Chemotherapy Side Effects: When ...

284

Allee effects in ants.  

PubMed

1. Allee effects occur when the aggregation of individuals result in mutually beneficial intraspecific interactions whereby individual fitness, or per capita growth rate, increases with the number of individuals. Allee effects are common in social species due to their cooperative behaviours, such as breeding, feeding or defence. Allee effects have important implications for many aspects of basic and applied ecology. Over the past decades, the study of Allee effects has influenced population dynamics, community ecology, endangered species management and invasion biology. 2. Despite the fact that cooperation is the basis of their social structure, Allee effects have received little attention among eusocial insects. Extreme cooperation is common, and reproductive specialization of individuals occurs due to division of labour. These life-history traits suggest that the potential contribution of each caste to reproduction and survival may be differential and nonadditive. 3. We studied Allee effects in the invasive Argentine ant (Linepithema humile). In this species, many queens and workers are present in colonies, which allowed us to explore the differential effects of castes on the presence of Allee effects. In the laboratory, we measured brood production and individual survival in experimental colonies that differed in the initial numbers of queens and workers.4. Our results highlight the differential effect of queens and workers on survival and productivity. We found three positive density-dependent relationships indicative of component Allee effects at the colony level: both workers and queens had a positive effect on the productivity of the other caste, and queens had a positive effect on worker survivorship. 5. Our experimental results suggest a potential positive feedback between worker and queen abundance, which may have contributed to the evolution of large colony sizes. Our study provides the first evidence of Allee effects in eusocial insects and highlights the need to consider castes separately in population dynamics. Division of labour and differential reproductive rates are factors that should be integrated into the study of Allee effects. PMID:23672650

Luque, Gloria M; Giraud, Tatiana; Courchamp, Franck

2013-09-01

285

Thermoelectric Properties of Lanthanum Sulfide  

NASA Technical Reports Server (NTRS)

Report describes measurement of Seebeck coefficient, electrical resistivity, thermal conductivity, and Hall effect in gamma-phase lanthanum sulfide with composition of La3-x S4. Results of study, part of search for high-temperature thermoelectric energy-conversion materials, indicate this sulfide behaves like extrinsic semiconductor over temperature range of 300 to 1,400 K, with degenerate carrier concentration controlled by stoichiometric ratio of La to S.

Wood, C.; Lockwood, R.; Parker, J. B.; Zoltan, A.; Zoltan, L. D.; Danielson, L.; Raag, V.

1987-01-01

286

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

287

Thermally Driven Josephson Effect  

NASA Technical Reports Server (NTRS)

A concept is proposed of the thermally driven Josephson effect in superfluid helium. Heretofore, the Josephson effect in a superfluid has been recognized as an oscillatory flow that arises in response to a steady pressure difference between two superfluid reservoirs separated by an array of submicron-sized orifices, which act in unison as a single Josephson junction. Analogously, the thermally driven Josephson effect is an oscillatory flow that arises in response to a steady temperature difference. The thermally driven Josephson effect is partly a consequence of a quantum- mechanical effect known as the fountain effect, in which a temperature difference in a superfluid is accompanied by a pressure difference. The thermally driven Josephson effect may have significance for the development of a high-resolution gyroscope based on the Josephson effect in a superfluid: If the pressure-driven Josephson effect were used, then the fluid on the high-pressure side would become depleted, necessitating periodic interruption of operation to reverse the pressure difference. If the thermally driven Josephson effect were used, there would be no net flow and so the oscillatory flow could be maintained indefinitely by maintaining the required slightly different temperatures on both sides of the junction.

Penanen, Konstantin; Chui, Talso

2008-01-01

288

Enhanced magnetocaloric effect material  

DOEpatents

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

Lewis, Laura J. H.

2006-07-18

289

Blowing Ratio Effects on Film Cooling Effectiveness  

E-print Network

The research focuses on testing the film cooling effectiveness on a gas turbine blade suction side surface. The test is performed on a five bladed cascade with a blow down facility. Four different blowing ratios are used in this study, which are 0...

Liu, Kuo-Chun

2010-01-14

290

Effect Identification in Comparative Effectiveness Research  

PubMed Central

The widespread adoption of electronic medical records means there are now vast data resources available for comparative effectiveness research (CER). In concert with conventional randomized controlled trials, CER holds great promise for advancing our understanding of how different therapeutic treatments yield different health outcomes in different settings and with different populations. But in a research culture fixated on estimating correlations and p-values, the threat of misinterpretation of results and improper CER inferences is troubling. Accordingly, this paper aims to shore up the inferential foundations of CER by introducing the fundamentals of effect identification, which is the process of identifying or teasing out empirically defensible causal effects from competing explanations. Three primary requirements of effect identification—positivity, exchangeability, and consistency— are explained and simple exampled are given. The take home message is that so-called big data from medical records may not yield better or more useful results. Advances will come only when the right question is addressed with the appropriate data and methods.

Oakes, J. Michael

2013-01-01

291

The Hubble effective potential  

SciTech Connect

We generalize the effective potential to scalar field configurations which are proportional to the Hubble parameter of a homogeneous and isotropic background geometry. This may be useful in situations for which curvature effects are significant. We evaluate the one loop contribution to the Hubble Effective Potential for a massless scalar with arbitrary conformal and quartic couplings, on a background for which the deceleration parameter is constant. Among other things, we find that inflationary particle production leads to symmetry restoration at late times.

Janssen, T.M.; Miao, S.P.; Prokopec, T. [Institute for Theoretical Physics and Spinoza Institute, Utrecht University, Leuvenlaan 4, Postbus 80.195, 3508 TD Utrecht (Netherlands)] [Institute for Theoretical Physics and Spinoza Institute, Utrecht University, Leuvenlaan 4, Postbus 80.195, 3508 TD Utrecht (Netherlands); Woodard, R.P., E-mail: T.M.Janssen@uu.nl, E-mail: S.Miao@uu.nl, E-mail: T.Prokopec@uu.nl, E-mail: woodard@phys.ufl.edu [Department of Physics, University of Florida, Gainesville, FL 32611 (United States)

2009-05-15

292

Dynamic ground effects  

NASA Technical Reports Server (NTRS)

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

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

1990-01-01

293

Atomic lighthouse effect.  

PubMed

We investigate the deflection of light by a cold atomic cloud when the light-matter interaction is locally tuned via the Zeeman effect using magnetic field gradients. This "lighthouse" effect is strongest in the single-scattering regime, where deviation of the incident field is largest. For optically dense samples, the deviation is reduced by collective effects, as the increase in linewidth leads to a decrease in magnetic field efficiency. PMID:25401364

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

2014-11-01

294

The Atomic Lighthouse Effect  

E-print Network

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

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

2014-01-01

295

Large morphological sensitivity of the magneto-thermopower in Co/Cu multilayered systems  

NASA Astrophysics Data System (ADS)

We present results of first-principles calculations on the transport properties, both under an electric field or a temperature gradient, in Co/Cu multilayered systems. The various effects brought about by the changes in the morphological parameters, such as the number of repeats and the layer thickness, are discussed in a systematic way. Our calculations show that the Seebeck coefficient and the magneto-thermopower (MTP) converge rather rapidly with the number of Co repeats. In the range of thin Co layers, we find strong variations in the amplitude and sign of both the Seebeck coefficient and the MTP. These large variations, which have no correspondent in the (magneto)conductance, are shown to be the result of quantum well states present in the minority spin channel of thin Co layers.

Popescu, Voicu; Kratzer, Peter

2015-03-01

296

High temperature transport properties of thermoelectric CaMnO{sub 3??} — Indication of strongly interacting small polarons  

SciTech Connect

The conductivity and Seebeck coefficient of CaMnO{sub 3??} have been studied at temperatures up to 1000?°C and in atmospheres with controlled oxygen partial pressure. Both transport coefficients were varied in situ by the reversible formation of oxygen vacancies up to ??=?0.15. The charge carrier concentration was calculated using a defect chemical model. The Seebeck coefficient could be approximated by Heikes' formula, while the conductivity shows a maximum at a molar charge carrier concentration of 0.25. These results were interpreted as a signature of strong electronic correlation effects, and it was concluded that charge transport in CaMnO{sub 3??} occurs via strongly interacting small polarons. General prospects for strongly correlated materials as potential candidates for high temperature thermoelectric power generation were discussed.

Schrade, M., E-mail: matthias.schrade@smn.uio.no; Finstad, T. G. [Centre for Materials Science and Nanotechnology, Department of Physics, University of Oslo, Sem Sælandsvei 24, 0371 Oslo (Norway); Kabir, R.; Li, S. [School of Materials Science and Engineering, University of New South Wales, Sydney, New South Wales 2052 (Australia); Norby, T. [Centre for Materials Science and Nanotechnology, Department of Chemistry, University of Oslo, FERMiO, Gaustadalléen 21, 0349 Oslo (Norway)

2014-03-14

297

Giant spin thermoelectric efficiency in ferromagnetic graphene nanoribbons with antidots  

NASA Astrophysics Data System (ADS)

Thermoelectric effects in zigzag graphene nanoribbons with parallel alignment of the edge spin polarizations are investigated theoretically. Spin and charge thermopower, electrical and heat conductance, and charge and spin thermoelectric efficiency are calculated numerically for pristine nanoribbons as well as for nanoribbons with periodic one-dimensional lattice of structural defects in the form of antidots. It is shown that structural defects reduce thermal conductance due to phonons and open gaps in the corresponding electronic spectrum. This, in turn, leads to a significant enhancement of the Seebeck and spin Seebeck coefficients as well as of the thermoelectric efficiency. A giant enhancement appears in certain regions of chemical potential (controlled by doping or external gate) and survives at room temperatures.

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

2013-12-01

298

Volcanic effects on climate  

NASA Technical Reports Server (NTRS)

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

Robock, Alan

1991-01-01

299

Effects on Insects  

Technology Transfer Automated Retrieval System (TEKTRAN)

The effects of controlled and modified atmospheres on insects is reviewed and summarized in this chapter. Traditionally, controlled and modified atmospheres are used to store and preserve fresh fruits and vegetables. The effects on insects and the potential of these treatments are secondary to the...

300

Comparative Effectiveness Research  

Cancer.gov

Comparative Effectiveness Research (CER) is the conduct and synthesis of systematic research comparing different interventions and strategies to prevent, diagnose, treat and monitor health conditions. The purpose of this research is to inform patients, providers, and decision-makers about which interventions are most effective for which patients under specific circumstances.

301

Relativistic effects in chemistry  

Microsoft Academic Search

Relativistic effects become apparent when the velocity of the electron is arbitrarily close to the speed of light (137 au) without actually attaining it (in heavy atoms of elements at the end of Mendeleev's Periodic Table). At the orbital level, the relativistic effect is apparent in the radial contraction of penetrating s and p shells, expansion of nonpenetrating d and

K. B. Yatsimirskii

1995-01-01

302

Legislative Effectiveness in Congress  

Microsoft Academic Search

We argue that congressional scholarship would benefit from an aggressive agenda to incorporate legislative effectiveness more fully into theoretical and empirical examinations of Congress. To facilitate this effort, we advance hypotheses from a foundational theory of lawmaking effectiveness that arises from members' innate abilities, cultivated skills, and institutional positioning. We develop a method for cardinally ranking members of the U.S.

Craig Volden; Alan E. Wiseman

303

effectively tax treaty?  

E-print Network

Is income effectively connected to US trade/ business? Is this exempt under the tax treaty? Does- employee comp? Is income "effectively connected"? Is payment subject to a lower tax rate? Is payment for rent or royalty? Individual completes IRS form 1001. Payment will not be taxed. (Code "N") Taxes

Krovi, Venkat

304

Gastrointestinal effects of aspirin  

Microsoft Academic Search

Aspirin is being used as an effective analgesic and anti-inflammatory agent at doses >325 mg daily. At low doses (75–325 mg daily), aspirin is the key antiplatelet drug in the pharmacological prevention of cardiovascular diseases. Topical and systemic effects of aspirin in the gastrointestinal mucosa are associated with mucosal damage in the upper and lower gastrointestinal tract. The risk of

Carlos Sostres; Angel Lanas

2011-01-01

305

Radiation effects in space  

SciTech Connect

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

Fry, R.J.M.

1987-07-01

306

Primacy Effects in Attributions.  

ERIC Educational Resources Information Center

Previous research has suggested the existence of a primacy effect in the attribution of ability. To test if the primacy effect occurs in situations where specific cues about the person and nature of the test materials are lacking or greatly reduced, college students corrected a multiple-choice test in which a phantom stimulus person correctly…

McAndrew, Francis T.

307

Serious video game effectiveness  

Microsoft Academic Search

Given the interactive media characteristics and intrinsically motivating appeal, computer games are often praised for their potential and value in education. However, comprehensive research testing these assumptions is still missing. Preliminary comparative studies on the learning effects of games versus traditional media have shown some promise. In this paper, we describe a comparative study that thoroughly investigates the effects of

Wee Ling Wong; Cuihua Shen; Luciano Nocera; Eduardo Carriazo; Fei Tang; Shiyamvar Bugga; Harishkumar Narayanan; Hua Wang; Ute Ritterfeld

2007-01-01

308

Effective Mentoring Rebecca Vandiver  

E-print Network

Effective Mentoring Rebecca Vandiver 9 October 2006 #12;I. RESPONSIBILITIES OF A MENTOR #12;WHAT DOES IT MEAN TO BE A MENTOR?? · Mentors... ­ offer continuing guidance and support ­ are willing's performance "Effective mentoring can be learned, but not taught. Good mentors discover their own objectives

Lega, Joceline

309

The Greenhouse Effect  

Microsoft Academic Search

The Greenhouse Effect is getting a lot of publicity as concern grows about trends in weather and pollution. The midwestern states of the US suffered a drought during 1988 coupled with an unsually hot summer throughout the country. Many people attributed this to the Greenhouse Effect. Palmer and Brankovic (Nature, Vol. 338, page 54, March 2, 1989) tied the drought

2009-01-01

310

The greenhouse effect  

Microsoft Academic Search

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

A. Berger; Ch. Tricot

1992-01-01

311

Lake Effect Snow  

NSDL National Science Digital Library

This MPEG shows lake effect precipitation resulting when cold air masses pass over the relatively warm Great Lakes, pick up moisture, and then precipitate when again encountering the cold land surface. Note the bands of lake effect snow apparent over Lake Superior and the lack of snow on the western shore of Lake Michigan. The animation can be replayed to stress important points.

NASA

312

Aharonov-Bohm Effect  

NSDL National Science Digital Library

This web page illustrates the effect of a magnetic flux on the interference of a quantum double-slit experiment. The time-dependent scattering patterns are shown with and without a magnetic field. In addition, the effects of changing the topology of the system are discussed and displayed. The webpage includes animations which demonstrate the concept.

De Raedt, Hans

313

Concerning Hertz' photoelectric effect  

E-print Network

Experimental evidence of the photoelectric effect goes back to H. Hertz. It occurred during the famous confirmation experiments of the Maxwellian theory. It is commonly held however that it cannot be explained in the framework of that theory. We are calling attention to some aspects linked with the interpretation of that effect on which, in our opinion, it is worthwhile reflecting.

S. L. Vesely; A. A. Vesely

2002-02-23

314

Evaluating Effective Management Learning.  

ERIC Educational Resources Information Center

A better way to assess the effectiveness of management development is to measure organizational effectiveness rather than individual improvement. Case studies support the Business Excellence Framework model, which assesses enablers (leadership, personnel management, policy, resources, processes) and results (personnel and customer satisfaction,…

Bramley, Peter

1999-01-01

315

Teacher Work Group Effectiveness  

ERIC Educational Resources Information Center

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

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

2004-01-01

316

JPL Radiation Effects Facilities  

NASA Technical Reports Server (NTRS)

Radiation Effects Group investigates the effects of space radiation on present and future microelectronic and optoelectronic technologies, evaluate the risk of using them in specific space missions, and recommend component and design techniques for JPL and NASA programs to reduce reliability risk from space radiation.

Thorbourn, Dennis

2013-01-01

317

Effects on aquatic ecosystems  

Microsoft Academic Search

Regarding the effects of UV-B radiation on aquatic ecosystems, recent scientific and public interest has focused on marine primary producers and on the aquatic web, which has resulted in a multitude of studies indicating mostly detrimental effects of UV-B radiation on aquatic organisms. The interest has expanded to include ecologically significant groups and major biomass producers using mesocosm studies, emphasizing

D.-P. Häder; H. D. Kumar; R. C. Smith; R. C. Worrest

1998-01-01

318

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

319

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.

320

Branch Effect Reduction Techniques  

Microsoft Academic Search

Branch effects are the biggest obstacle to gaining significant speedups when running general purpose code on instruction level parallel machines. The article presents a survey which compares current branch effect reduction techniques, offering hope for greater gains. We believe this survey is timely because research is bearing much fruit: speedups of 10 or more are being demonstrated in research simulations

Augustus K. Uht; Vijay Sindagi; Sajee Somanathan

1997-01-01

321

Generalized gravitomagnetic clock effect  

E-print Network

In General Relativity, the rotation of a gravitating body like the Earth influences the motion of orbiting test particles or satellites in a non-Newtonian way. This causes, e.g., a precession of the orbital plane known as the Lense-Thirring effect and a precession of the spin of a gyroscope known as the Schiff effect. Here, we discuss a third effect first introduced by Cohen and Mashhoon called the gravitomagnetic clock effect. It describes the difference in proper time of counterrevolving clocks after a revolution of $2\\pi$. For two clocks on counterrotating equatorial circular orbits around the Earth, the effect is about $10^{-7}$ seconds per revolution, which is quite large. We introduce a general relativistic definition of the gravitomagnetic clock effect which is valid for arbitrary pairs of orbits. This includes rotations in the same direction and different initial conditions, which are crucial if the effect can be detected with existing satellites or with payloads on nondedicated missions. We also derive the post-Newtonian expansion of the general relativistic expression and calculate the effect for the example of a satellite of a Global Navigation Satellite System compared to a geostationary satellite.

Eva Hackmann; Claus Lämmerzahl

2014-08-28

322

Generalized gravitomagnetic clock effect  

NASA Astrophysics Data System (ADS)

In general relativity, the rotation of a gravitating body like the Earth influences the motion of orbiting test particles or satellites in a non-Newtonian way. This causes, e.g., a precession of the orbital plane known as the Lense-Thirring effect and a precession of the spin of a gyroscope known as the Schiff effect. Here, we discuss a third effect first introduced by Cohen and Mashhoon called the gravitomagnetic clock effect. It describes the difference in proper time of counterrevolving clocks after a revolution of 2?. For two clocks on counterrotating equatorial circular orbits around the Earth, the effect is about 10-7 s per revolution, which is quite large. We introduce a general relativistic definition of the gravitomagnetic clock effect which is valid for arbitrary pairs of orbits. This includes rotations in the same direction and different initial conditions, which are crucial if the effect can be detected with existing satellites or with payloads on nondedicated missions. We also derive the post-Newtonian expansion of the general relativistic expression and calculate the effect for the example of a satellite of a global navigation satellite system compared to a geostationary satellite.

Hackmann, Eva; Lämmerzahl, Claus

2014-08-01

323

The precedence effect.  

PubMed

When two similar transient sounds are presented binaurally in rapid succession, observers hear a single sound from a location which depends mainly on the properties of the first sound to reach the ears. This phenomenon, known as the precedence effect, was explored using stimuli consisting of 20 mus pulses presented using earphones; experiments were carried out on both the classical precedence effect (in which interaural delays provide the cues to lateralization) and on an amplitude-based precedence effect, where interaural amplitude differences provide the cues. Some experiments on the amplitude-based precedence effect led to unexpected but highly consistent anomalous results. The spectral characteristics of stimuli used in studies of both the classical and amplitude-based precedence effect were considered and, provided the delay between the two pairs of pulses used in the experiments is 600 mus or less, observers' behaviour is simply related to the amplitude and phase spectra of the stimuli. PMID:6668254

Gaskell, H

1983-12-01

324

Cross-plane electrical and thermal transport in oxide metal/semiconductor superlattices  

NASA Astrophysics Data System (ADS)

Perovskite oxides display a rich variety of electronic properties as metals, ferroelectrics, ferromagnetics, multiferroics, and thermoelectrics. Cross-plane electron filtering transport in metal/semiconductor superlattices provides a potential approach to increase the thermoelectric figure of merit (ZT). La0.67Sr0.33MnO3 (LSMO) and LaMnO3 (LMO) thin-film depositions were optimized using pulsed laser deposition (PLD) to achieve low resistivity constituent materials for LSMO/LMO superlattice heterostructures on (100)-strontium titanate (STO) substrates. X-ray diffraction and high-resolution reciprocal space mapping (RSM) indicate that the superlattices are epitaxial and pseudomorphic. Cross-plane devices were fabricated by etching cylindrical pillar structures in superlattices using inductively-coupled-plasma reactive-ion etching. The cross-plane electrical conductivity data for LSMO/LMO superlattices reveal an effective barrier height of 220 meV. The cross-plane LSMO/LMO superlattices showed a giant Seebeck coefficient of 2560 microV/K at 300K that increases to 16640 microV/K at 360K. The large Seebeck coefficient may arise due to hot electron and spin filtering as LSMO/LMO superlattice constituent materials exhibit spintronic properties where charges and spin current are intertwined and can generate a spin-Seebeck effect. The room temperature thermal conductivity achieved in low resistivity superlattices was 0.92 W/mK, which indicates that cross-plane phonon scattering at interfaces reduces the lattice contribution to the thermal conductivity. The giant contribution of spin-Seebeck, the large temperature dependence of the cross-plane power factor, and the low thermal conductivity in low resistance LSMO/LMO superlattices may offer opportunities to realize spin-magnetic thermoelectric devices, and suggests a direction for further investigations of the potential of LSMO/LMO oxide superlattices for thermoelectric devices.

Jha, Pankaj

325

Analysis of high-temperature thermoelectric properties of p-type CoSb3 within a two-valence-band and two-conduction-band model  

NASA Astrophysics Data System (ADS)

Experimental data on the thermoelectric properties of p-type CoSb3 reported by Caillat et al. [J. Appl. Phys. 80, 4442 (1996)] have been analyzed, assuming not only a pair of the first valence (v1) and the first conduction (c1) bands but also the second valence (v2) and the second conduction (c2) bands. By taking into account the excitation of carriers into the v2 and the c2 bands, the behavior of the Hall coefficient as well as that of the Seebeck coefficient at high temperatures is well explained. By taking into account the nonparabolicity of the v1 band, the temperature dependence of mobility is well explained with assuming scattering due to acoustic phonons, nonpolar and polar optical phonons, and ionized impurities. Furthermore, various material parameters of CoSb3, such as the band-gap energy, effective masses, and deformation potentials, have been deduced from fitting the calculation to the experimental data on the temperature dependences of the Hall coefficient, the mobility, and the Seebeck coefficient. Among them, the band-gap energy and the effective mass of the v1 band have been corrected from the original values estimated by Caillat et al. In addition, it is shown that the experimental data on the hole-concentration dependences of both the room-temperature Seebeck coefficient and the cyclotron mass are well reproduced by the theoretical calculation using the deduced values for the nonparabolic v1 band.

Kajikawa, Y.

2014-05-01

326

Thermoelectric properties of quaternary Heusler alloys Fe2VAl1-xSix  

NASA Astrophysics Data System (ADS)

We report the effects of Si substitution on the temperature-dependent electrical resistivity, Seebeck coefficient, as well as thermal conductivity in the Heusler-type compound Fe2VAl . It is found that the substitution of Si onto the Al sites causes a significant decrease in the electrical resistivity and lattice thermal conductivity. A theoretical analysis indicated that the reduction of lattice thermal conductivity arises mainly from point-defect scattering of the phonons. With slight substitution, the Seebeck coefficient changes sign from positive to negative, accompanied by the appearance of a broad minimum at high temperatures. These features are associated with the change in the electronic band structure, where the Fermi level shifts upwards from the center of the pseudogap due to electron-doping effect. For x>0.1 in Fe2VAl1-xSix , no broad minimum in the Seebeck coefficient appears, indicative of a dramatic modification in the band structure of these materials. While the thermoelectric performance improves with increasing Si concentration, the largest figure-of-merit ZT value among these alloys is still an order of magnitude lower than conventional thermoelectric materials.

Lue, C. S.; Chen, C. F.; Lin, J. Y.; Yu, Y. T.; Kuo, Y. K.

2007-02-01

327

Greenhouse effect of NOX.  

PubMed

Through various processes the nitrogen oxides (NOX) interact with trace gases in the troposphere and stratosphere which do absorb in the spectral range relevant to the greenhouse effect (infrared wavelengths). The net effect is an enhancement of the greenhouse effect. The catalytic role of NOX in the production of tropospheric ozone provides the most prominent contribution. The global waming potential is estimated as GWP (NOX = 30 - 33 and 7 - 10 for the respective time horizons of 20 and 100 years, and is thereby comparable to that of methane. NOX emissions in rural areas of anthropogenically influenced regions, or those in the vicinity of the txopopause caused by air traffic, cause the greenhouse effectivity to be substantially more intense. We estimate an additional 5-23 % for Germany's contribution to the anthropogenic greenhouse effect as a result of the indirect greenhouse effects stemming from NOX. Furthermore, a small and still inaccurately defined amount of the deposited NOX which has primarily been converted into nitrates is again released from the soil into the atmosphere in the form of the long-lived greenhouse gas nitrous oxide (N2O). Thus, anthropogenically induced NOX emissions contribute to enhanced greenhouse effect and to stratospheric ozone depletion in the time scale of more than a century. PMID:24234471

Lammel, G; Graßl, H

1995-07-01

328

Molecular beam epitaxy growth and properties of Co2TiSi thin films on GaAs(0?0?1): the effect of growth temperature  

NASA Astrophysics Data System (ADS)

Molecular beam epitaxy growth of ferromagnetic Co2TiSi films on GasAs(0?0?1) substrates is presented and it is found that the optimum growth temperature is between 300–360?°C where the film is single phase and exhibits highly (0?0?1)-ordered crystal structure. The Co2TiSi films are ferromagnetic up to 300?K and the highest value of saturation magnetization obtained is of 0.8??B per formula unit. The Co2TiSi films also exhibit a very low degree of magnetic anisotropy along in-plane crystallographic directions. Expected values of Seebeck coefficient and resistivity measured at room temperature confirm good stoichiometry of the Co2TiSi films and indicate that this material is a promising candidate for both spincaloric and spintronic applications.

Dau, M. T.; Herfort, J.

2015-01-01

329

Hall effect in nanowires  

NASA Astrophysics Data System (ADS)

The classical Hall effect in thin semiconductor nanowires with lateral contacts is considered theoretically. Two new phenomena: (i) influence of diffusion currents in nanowires with radius comparable with the screening length of carriers and (ii) eddy currents in non-planar Hall contacts are taken into account. Both effects result in a noticeable reduction of the measured Hall voltage compared with the standard formula for bulk samples and hence the effective carrier concentration determined by using this formula may exceed the real concentration in nanowires in up to two orders of magnitude.

Fernandes, C.; Ruda, H. E.; Shik, A.

2014-06-01

330

Measuring Study Effectiveness  

NSDL National Science Digital Library

This model-eliciting activity challenges students to operationally define a construct (study effectiveness). Students are given a survey to review that rates different aspects of study behaviors. They are then given a set of data for a few students and asked to use their scores to determine an index of study effectiveness. After determining a method, they are then asked to use this index to put five students in rank order according to their scores on study effectiveness. Students write a report explaining the method they used to determine these scores and how they produced their ratings.

This page was authored by the CATALST Group at the University of Minnesota, based on an original activity by Richard Lesh at Purdue University.

331

Bustling argon: biological effect  

PubMed Central

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

2013-01-01

332

Finite Temperature Effective Actions  

E-print Network

We present, from first principles, a direct method for evaluating the exact fermion propagator in the presence of a general background field at finite temperature, which can be used to determine the finite temperature effective action for the system. As applications, we determine the complete one loop finite temperature effective actions for 0+1 dimensional QED as well as the Schwinger model. These effective actions, which are derived in the real time (closed time path) formalism, generate systematically all the Feynman amplitudes calculated in thermal perturbation theory and also show that the retarded (advanced) amplitudes vanish in these theories.

Ashok Das; J. Frenkel

2009-08-27

333

Improving engineering effectiveness  

NASA Technical Reports Server (NTRS)

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

Fiero, J. D.

1985-01-01

334

Conducting Effective Performance Evaluations  

E-print Network

Conducting Effective Performance Evaluations February 2013 #12;Performance Management v to prove that the employee did know the expectations and standards #12;Performance Evaluation Personnel your most talented employees · Satisfactory participation in the performance evaluation process

Lawrence, Rick L.

335

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

336

[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

337

Matthew: Effect or Fable?  

E-print Network

In a market context, a status effect occurs when actors are accorded differential recognition for their efforts depending on their location in a status ordering, holding constant the quality of these efforts. In practice, ...

Azoulay, Pierre

338

Creating effective character animation  

E-print Network

Several stages are involved in the creation of an graphics. effective, three-dimensional character animation. Before starting any work at the computer, the animator should consider what his characters will look like and how they will move, as well...

Gerwig, Jennifer

1999-01-01

339

Chesapeake Bay Impact Effects  

NSDL National Science Digital Library

This PowerPoint show depicts the effects (blast, heat, etc.) of the Chesapeake Bay impact. To emphasize the human consequences of asteroid and comet impacts, the slides show what would happen to East Coast communities if an identical object hit the same place today. (The impact actually happened roughly 35 million years ago.) Impact effects were estimated with the Earth Impact Effects Program (www.lpl.arizona.edu/impacteffects/). Effects shown on these slides are at best very approximate, and, consequently, these slides should only be used to stimulate discussions about impact hazards. Satellite images were obtained through the NASA Earth Observing System Higher Education Alliance (GeoBrain) which provided funding for this work. Graphics were created with the Environmental Systems Research Institute (ESRI) family of geographic information system (GIS) products.

Mark Abolins

340

Comparative effectiveness research.  

PubMed

The goal of comparative effectiveness research is to improve health care while dealing with the seemingly ever-rising cost. An understanding of comparative effectiveness research as a core topic is important for neuroradiologists. It can be used in a variety of ways. Its goal is to look at alternative methods of interacting with a clinical condition, ideally, while improving delivery of care. While the Patient-Centered Outcome Research initiative is the most mature US-based foray into comparative effectiveness research, it has been used more robustly in decision-making in other countries for quite some time. The National Institute for Health and Clinical Excellence of the United Kingdom is a noteworthy example of comparative effectiveness research in action. PMID:24874531

Hirsch, J A; Schaefer, P W; Romero, J M; Rabinov, J D; Sanelli, P C; Manchikanti, L

2014-09-01

341

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.

Amy Kolenbrander

2004-01-01

342

The Quadratic Zeeman Effect  

Microsoft Academic Search

The Zeeman effects of the principal series lines of sodium and potassium in the range n=10 to 35 are observed in absorption, using the new 60-inch cyclotron magnet. With a field of 27,000 gauss, the lines having n in the neighborhood of ten show a normal triplet representing the complete Paschen-Back effect of the narrow 2P doublet. From about n=12

F. A. Jenkins; E. Segrè

1939-01-01

343

Correlational effect size benchmarks.  

PubMed

Effect size information is essential for the scientific enterprise and plays an increasingly central role in the scientific process. We extracted 147,328 correlations and developed a hierarchical taxonomy of variables reported in Journal of Applied Psychology and Personnel Psychology from 1980 to 2010 to produce empirical effect size benchmarks at the omnibus level, for 20 common research domains, and for an even finer grained level of generality. Results indicate that the usual interpretation and classification of effect sizes as small, medium, and large bear almost no resemblance to findings in the field, because distributions of effect sizes exhibit tertile partitions at values approximately one-half to one-third those intuited by Cohen (1988). Our results offer information that can be used for research planning and design purposes, such as producing better informed non-nil hypotheses and estimating statistical power and planning sample size accordingly. We also offer information useful for understanding the relative importance of the effect sizes found in a particular study in relationship to others and which research domains have advanced more or less, given that larger effect sizes indicate a better understanding of a phenomenon. Also, our study offers information about research domains for which the investigation of moderating effects may be more fruitful and provide information that is likely to facilitate the implementation of Bayesian analysis. Finally, our study offers information that practitioners can use to evaluate the relative effectiveness of various types of interventions. (PsycINFO Database Record (c) 2015 APA, all rights reserved). PMID:25314367

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

2015-03-01

344

Gynaecologic effects of tamoxifen  

Microsoft Academic Search

Tamoxifen, an estrogen antagonist, is widely used as adjuvant therapy in patients with breast cancer. Its efficacy in increasing\\u000a survival and reducing recurrence rates has been demonstrated in several European and American studies. However, its effects\\u000a appear to be tissue specific. Tamoxifen exerts an estrogen effect (agonist) on the endometrium, myometrium and vagina. An\\u000a increase in uterine cancer has been

Dennis Yi-Shin Kuo; Carolyn D. Runowicz

1995-01-01

345

The Lisse effect revisited.  

PubMed

The Lisse effect is a rarely noted phenomenon occurring when infiltration caused by intense rain seals the surface soil layer to airflow, trapping air in the unsaturated zone. Compression of air by the advancing front results in a pressure increase that produces a water-level rise in an observation well screened below the water table that is several times as large as the distance penetrated by the wetting front. The effect is triggered by intense rains and results in a very rapid water-level rise, followed by a recession lasting a few days. The Lisse effect was first noted and explained by Thal Larsen in 1932 from water-level observations obtained in a shallow well in the village of Lisse, Holland. The original explanation does not account for the increased air pressure pushing up on the bottom of the wetting front. Analysis of the effect of this upward pressure indicates that a negative pressure head at the base of the wetting front, psi(f), analogous to that postulated by Green and Ampt (1911) to explain initially rapid infiltration rates into unsaturated soils, is involved in producing the Lisse effect. Analysis of recorded observations of the Lisse effect by Larsen and others indicates that the water-level rise, which typically ranges from 0.10 to 0.55 m, should be only slightly larger than psi(f) and that the depth of penetration of the wetting front is no more than several millimeters. PMID:12425353

Weeks, Edwin P

2002-01-01

346

Enhancing thermoelectric properties of FeSb2 by altering stoichiometry and nanostructure  

NASA Astrophysics Data System (ADS)

FeSb2 is a strongly correlated semiconductor that has been shown to have an extraordinarily large Seebeck coefficient in single crystal samples. Bentien et al. report a Seebeck Coefficient of -45000 microV/K at 10K. The peak value of the dimensionless figure of merit (ZTmax) for single crystal samples is calculated to be approximately 0.005 at 10 K and is constrained by its relatively high thermal conductivity. In our previous studies, we find that nanocomposites (NC) tend to decrease thermal conductivity substantially by introducing phonon mismatches between crystal grains. Given that the Seebeck coefficient on the FeSb2 system is quite sensitive to carrier concentration, we focus on the effects of stoichiometric changes that heighten thermoelectric properties of FeSbx where x=2.04, 2.00, 1.96, 1.92. By tuning the stoichiometry and using the nanocomposite method, the peak value of ZTmax was found to be 0.0123 at 43K. Carrier concentration and Hall-mobility measurements will also be discussed.

Pokharel, Mani; Zhao, Huaizhau; Lukas, Kevin; Ren, Zhifeng; Opeil, Cyril

2012-02-01

347

Thermoelectric properties of c-axis aligned Bi-Te materials  

NASA Astrophysics Data System (ADS)

Single crystalline Bi-Te thermoelectric materials have a rhombohedral structure with van der Waals bonding along c-axis direction. This structure gives intrinsic anisotropy in thermoelectric properties like electrical resistivity, thermal conductivity, Seebeck coefficient, as well as electron/hall mobility. Recent research works report that nano structures in polycrystalline thermoelectric materials improve thermoelectric performance by reducing thermal conductivity or by enhancing Seebeck coefficient. We investigated the effect of adjusting crystal orientation in the microstructures containing sub micro-sized grains on the thermoelectric properties for polycrystalline Bi-Te materials. Bi-Te powder, prepared through the conventional pulverization process, was sufficiently dispersed in an appropriate solvent, and then was formed into c-axis aligned green body under a designated high magnetic field. The green bodies were sintered with spark-plasma-sintering machine. The degree of crystal alignment of sintered bodies was examined with the electron-back-scatter-diffraction SEM and the X-ray diffraction patterns. It was observed that for p-type thermoelectric Bi-Te materials, aligning crystal orientation properly made electrical resistivity in the preferred direction decreased with keeping Seebeck coefficient and thermal conductivity remained unchanged.

Kim, Hoyoung; Kim, Dong Hwan; Kim, Cham; Park, SangHa

2012-06-01

348

Thermoelectric Properties of Double-Filled p-Type La1-z Yb z Fe4-x Co x Sb12 Skutterudites  

NASA Astrophysics Data System (ADS)

La and Yb double-filled p-type skutterudites (La1-z Yb z Fe4-x Co x Sb12; 0.25 ? z ? 0.75 and 0.5 ? x ? 1) were synthesized by encapsulated melting and homogenized by use of heat treatment. It was apparent from the positive signs of the Seebeck coefficient and the Hall coefficient that all specimens had p-type characteristics. The carrier concentration decreased with charge compensation. The thermal conductivity and the electrical conductivity decreased and the Seebeck coefficient increased with increasing substitution of Co for Fe. However, the carrier concentration was increased by increasing the Yb filling ratio. Electrical conductivity increased and the Seebeck coefficient decreased with increasing Yb filling, because the electron valence of Yb2+ was lower than that of La3+. The thermal conductivity decreased with charge compensation, and the lattice thermal conductivity decreased with increasing Yb filling. Yb was more effective than La at reducing lattice thermal conductivity. The power factor (PF) and dimensionless figure of merit (ZT) increased with increasing temperature up to a specific temperature. The maximum PF = 2.81 mW/mK2 at 823 K was obtained for La0.75Yb0.25Fe3.5Co0.5Sb12 and the maximum ZT = 0.74 at 723 K was achieved for La0.5Yb0.5Fe3CoSb12.

Joo, Gyeong-Seok; Shin, Dong-Kil; Kim, Il-Ho

2014-09-01

349

Anomalous Skin Effect Igor Kaganovich  

E-print Network

Anomalous Skin Effect Revisited Igor Kaganovich Princeton Plasma Physics Laboratory #12 to explain "simply" anomalous skin effect without abusing physics. #12;3 Outline Skin effect (Inductively Coupled Plasmas/ Lasers) ­ Normal skin effect ­ Concept of phase-mixing and scale ­ Anomalous skin effect

Kaganovich, Igor

350

CAUSE & EFFECT What Is It?  

E-print Network

effect has Marcel Duchamp's Nude Descending A Staircase had on Western culture's understanding of what questions: Is there really a cause and effect relationship between these two events? If there really is a cause and effect relationship, what is the exact connection between the cause(s) and the effect(s)? What

Boonstra, Rudy

351

Intrauterine position effects.  

PubMed

A review of the literature suggests that individual variability in sex-related traits may be influenced by variations in hormonal exposure during fetal development. In litter-bearing mammals, fetuses develop in utero and may be subjected to differing hormonal environments based upon the sex of neighboring fetuses. Female fetuses developing between two males tend to show masculinized anatomical, physiological and behavioral traits as adults. Female fetuses developing without adjacent males, on the other hand, tend to show more feminized traits as adults. These traits include permanently altered hormone levels, reproductive organs, aggressive behaviors, secondary sex ratios and susceptibility to endocrine disruption. This intrauterine effect is due to the transfer of testosterone from male fetuses to adjacent fetuses. While these effects have been most clearly demonstrated in mice, other rodents and swine also show intrauterine position (IUP) effects. Some of these effects are similar to the influence of prenatal stress on adult phenotypes. A few reports on human twins suggest that variability in some masculine and feminine traits may be due to intrauterine hormonal signals. IUP effects may impact a number of scientific fields of research such as endocrine disruption, toxicology, population biology, animal production and health. PMID:12479841

Ryan, Bryce C; Vandenbergh, John G

2002-10-01

352

The real butterfly effect  

NASA Astrophysics Data System (ADS)

Historical evidence is reviewed to show that what Ed Lorenz meant by the iconic phrase ‘the butterfly effect’ is not at all captured by the notion of sensitive dependence on initial conditions in low-order chaos. Rather, as presented in his 1969 Tellus paper, Lorenz intended the phrase to describe the existence of an absolute finite-time predicability barrier in certain multi-scale fluid systems, implying a breakdown of continuous dependence on initial conditions for large enough forecast lead times. To distinguish from ‘mere’ sensitive dependence, the effect discussed in Lorenz's Tellus paper is referred to as ‘the real butterfly effect’. Theoretical evidence for such a predictability barrier in a fluid described by the three-dimensional Navier-Stokes equations is discussed. Whilst it is still an open question whether the Navier-Stokes equation has this property, evidence from both idealized atmospheric simulators and analysis of operational weather forecasts suggests that the real butterfly effect exists in an asymptotic sense, i.e. for initial-time atmospheric perturbations that are small in scale and amplitude compared with (weather) scales of interest, but still large in scale and amplitude compared with variability in the viscous subrange. Despite this, the real butterfly effect is an intermittent phenomenon in the atmosphere, and its presence can be signalled a priori, and hence mitigated, by ensemble forecast methods.

Palmer, T. N.; Döring, A.; Seregin, G.

2014-09-01

353

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.

354

The Quantum Sweeper Effect  

E-print Network

We show that during stochastic beam attenuation in double slit experiments, there appear unexpected new effects for transmission factors below $a\\lesssim10^{-4}$, which can eventually be observed with the aid of weak measurement techniques. These are denoted as quantum sweeper effects, which are characterized by the bunching together of low counting rate particles within very narrow spatial domains. We employ a "superclassical" modeling procedure which we have previously shown to produce predictions identical with those of standard quantum theory. Thus it is demonstrated that in reaching down to ever weaker channel intensities, the nonlinear nature of the probability density currents becomes ever more important. We finally show that the resulting unexpected effects nevertheless implicitly also exist in standard quantum mechanics.

Gerhard Groessing; Siegfried Fussy; Johannes Mesa Pascasio; Herbert Schwabl

2015-02-13

355

Giving effective presentations.  

PubMed

Apprehension about oral communication, or public speaking is rated as the number one fear among most individuals. Developing skill in, and comfort with, public speaking is important whether we are presenting oral reports and proposals, responding to questions, or training co-workers. Effective speakers are able to communicate information in a way that stimulates interest, helps the audience to understand and remember, and influences attitudes and behaviours. Many of us think that effective speakers are born rather than made. In truth most successful speakers work hard and invest a great deal of time and effort in to improving their speaking capabilities. Effective public speaking is a learned skill and activity that requires lots of practice. Like other learned skills, having a strategy with clear action steps can help you achieve your goal. PMID:15116467

Englehart, Nadine

2004-03-01

356

Effective Documentation Tools  

NASA Technical Reports Server (NTRS)

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

Sleboda, Claire

1997-01-01

357

The Mozart Effect.  

PubMed

This review deals with the Mozart Effect, an improvement of performance while listening to Mozart music. Previous studies have shown improved spatial temporal reasoning and improved IQ test results and neurophysiological changes, mainly increased coherence among different groups of subjects. This review emphasizes the effect on epileptiform patterns, both generalized and focal; provides an example of a chronic effect over a period of 1-2 days; addresses the distinctive aspects of the music to account for this phenomenon and shows that long-term periodicity in the power of the music is a special quality; and deals with the melodic line and shows that Mozart repeats the melodic line much more frequently than other well-known composers. It is likely that the superorganization of the cerebral cortex resonates with great organization found in Mozart music. PMID:12609277

Hughes, John R.

2001-10-01

358

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 ...

359

Nonprofit Organizational Effectiveness: Contrasts Between Especially Effective and Less Effective Organizations  

Microsoft Academic Search

How do key stakeholders of nonprofit organizations (NPOs) judge the effectiveness of their organization? Are the judgments of stake- holders similar, and how are board effectiveness and the use of practitioner-identified correct management procedures related to judgments of effectiveness? This study focuses on a subset of espe- cially effective and less effective NPOs from a larger sample and finds that

Robert D. Herman; David O. Renz

1998-01-01

360

Habituation of reinforcer effectiveness  

PubMed Central

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

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

2014-01-01

361

Effective Temperature of Mutations  

NASA Astrophysics Data System (ADS)

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

Derényi, Imre; Szöll?si, Gergely J.

2015-02-01

362

Anticancer effects of fucoidan.  

PubMed

Recently, there has been an increased interest in the pharmacologically active natural compounds isolated and used for remedies of various kinds of diseases, including cancer. The great deal of interest has been developed to isolate bioactive compounds from marine resources because of their numerous health beneficial effects. Among marine resources, marine algae are valuable sources of structurally diverse bioactive compounds. Fucoidan is a sulfated polysaccharide derived from brown seaweeds and has been used as an ingredient in some dietary supplement products. Fucoidan has various biological activities including antibacterial, antioxidant, anti-inflammatory, anticoagulant, and antitumor activities. So this chapter deals with anticancer effects of fucoidan. PMID:25081084

Senthilkumar, Kalimuthu; Kim, Se-Kwon

2014-01-01

363

Contamination effects study  

NASA Technical Reports Server (NTRS)

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

1988-01-01

364

Quantum Spin Hall Effect  

SciTech Connect

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

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

2010-01-15

365

Giant thermoelectric effect in graphene-based topological insulators with heavy adatoms and nanopores.  

PubMed

Designing thermoelectric materials with high figure of merit ZT = S(2)GT/Ktot requires fulfilling three often irreconcilable conditions, that is, the high electrical conductance G, small thermal conductance Ktot, and high Seebeck coefficient S. Nanostructuring is one of the promising ways to achieve this goal as it can substantially suppress lattice contribution to Ktot. However, it may also unfavorably influence the electronic transport in an uncontrollable way. Here, we theoretically demonstrate that this issue can be ideally solved by fabricating graphene nanoribbons with heavy adatoms and nanopores. The adatoms locally enhance spin-orbit coupling in graphene thereby converting it into a two-dimensional topological insulator with a band gap in the bulk and robust helical edge states, which carry electrical current and generate a highly optimized power factor S(2)G per helical conducting channel due to narrow boxcar-function-shaped electronic transmission (surpassing even the Mahan-Sofo limit obtained for delta-function-shaped electronic transmission). Concurrently, the array of nanopores impedes the lattice thermal conduction through the bulk. Using quantum transport simulations coupled with first-principles electronic and phononic band structure calculations, the thermoelectric figure of merit is found to reach its maximum ZT ? 3 at low temperatures T ? 40 K. This paves a way to design high-ZT materials by exploiting the nontrivial topology of electronic states through nanostructuring. PMID:24932511

Chang, Po-Hao; Bahramy, Mohammad Saeed; Nagaosa, Naoto; Nikoli?, Branislav K

2014-07-01

366

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....

367

Microcircuit radiation effects databank  

NASA Technical Reports Server (NTRS)

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

1983-01-01

368

Conducting Effective Performance Evaluations  

E-print Network

Conducting Effective Performance Evaluations · February 13, 2012 · March 9, 2012 #12 with the ability to prove that the employee did know the expectations and standards #12;Performance Evaluation Practice · An annual performance evaluation is required for classified and contract professional employees

Dyer, Bill

369

Reporting Research Results Effectively  

ERIC Educational Resources Information Center

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

Volkwein, J. Fredericks

2010-01-01

370

Pleiotropic effects of incretins  

PubMed Central

Drugs that augment the incretin system [glucagon like peptide (GLP) agonists and dipeptidyl peptidase-4 (DPP-4) inhibitors] represent a novel class of anti-hyperglycemic agents that have shown to improve the health and survival of beta-cells (improvement in postprandial hyperglycemia) and suppress glucagon (improvement in fasting hyperglycemia). The incretins represent a large family of molecules referred to as the “glucagon superfamily of peptide hormones” of which more than 90% of the physiological effects of incretins are accomplished by GLP-17-37 and GLP17-36 amide and gastric insulinotropic peptide (GIP). GLP-1 mediates its effects via the GLP-1 receptor, which has a wide tissue distribution [pancreas, lung, heart, vascular smooth muscle cells, endothelial cells, macrophages and monocytes, kidney, gastrointestinal tract (stomach and intestine), central nervous system (neoortex, cerebellum, hypothalamus, hippocampus, brainstem nucleus tractus solitarius) and peripheral nervous system]. This would imply that the incretin system has effects outside the pancreas. Over time data has accumulated to suggest that therapies that augment the incretin system has beneficial pleiotrophic effects. The incretins have shown to possess a cardiac-friendly profile, preserve neuronal cells and safeguard from neuronal degeneration, improve hepatic inflammation and hepatosteatosis, improve insulin resistance, promote weight loss and induce satiety. There is growing evidence that they may also be renoprotective promoting wound healing and bone health. PMID:22701844

Gupta, Vishal

2012-01-01

371

Facilitating Online Discussions Effectively  

ERIC Educational Resources Information Center

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.…

Rovai, Alfred P.

2007-01-01

372

Effective 4-H Meetings  

E-print Network

are needed and their effects on their health. ? Use a variety of teaching techniques. In a meeting related to pet grooming and hygiene for example, provide several ways of learning by showing the tools to be used, discussing them, demonstrating them...

Howard, Jeff W.

2005-05-10

373

Physiological effects of hypnosis  

Microsoft Academic Search

There are many studies indicating that sensory, circulatory, gastrointestinal, and cutaneous functions can be altered by means of hypnosis. There also are many studies indicating that similar physiological effects can be produced by symbolic stimulation without hypnosis. The assumption that hypnotic behavior is a function of the trance state is open to question. From Psyc Abstracts 36:01:3II90B.

Theodore Xenophon Barber

1961-01-01

374

Effects of Acid Rain  

NSDL National Science Digital Library

This portal provides links to information on the potential damage caused to the environment by acid rain. An introductory paragraph briefly describes the damage to lakes and streams, building materials, and monuments. Each link access additional information on these topics: surface waters and aquatic animals, forests, automotive coatings, soluble building materials such as marble or limestone, atmospheric haze, and human health effects.

375

Explaining Charter School Effectiveness  

ERIC Educational Resources Information Center

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

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

2012-01-01

376

Effective management of ARDS.  

PubMed

Acute respiratory distress syndrome is a serious complication of critical illness that is associated with high morbidity and mortality. There are no effective treatment options, so prevention, early recognition, and appropriate supportive care are essential to improve outcomes. This article provides an overview of the disorder, including current treatment considerations. PMID:25299354

Carlucci, Melissa; Graf, Nicole; Simmons, James Q; Corbridge, Susan J

2014-12-13

377

Exploring the Lotus Effect  

NSDL National Science Digital Library

Students test and observe the "self-cleaning" 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.

2014-09-18

378

Longitudinal Effects of Kindergarten.  

ERIC Educational Resources Information Center

Examined longitudinal effects of kindergarten attendance on academic achievement through high school with students who attended public or nonpublic kindergarten, or neither one. Found that students with either kind of kindergarten experience had higher ACT scores and grade point averages. Found no significant differences in number of students…

Prince, Debra Lindsey; Hare, R. Dwight; Howard, Esther M.

2001-01-01

379

Interactive Pi Bonding Effects  

NSDL National Science Digital Library

This application demonstrates the effect of pi bonding on the one-electron ligand field splitting in an octahedral. By clicking on the appropriate buttons students can see how D changes when you move from ligands with no pi bonding capability to pi donor and pi acceptor ligands.

380

Wood Quality: The Effects  

E-print Network

Particle and Fiber Energy Veneer Lumber Posts & PolesRound wood Heat Chemicals $ $$$ #12;Mix High & Low to considerOther things to consider................ Stability: height/diameter ratios lower through reduced thinning can be expected to effectively lower future ratios Wilson and Oliver 2000 #12;ThinningThinning #12

381

The supergreenhouse effect  

NASA Astrophysics Data System (ADS)

Although the greenhouse effect as it applies to explain the Earth's climate system is understood, there are aspects of the effect that require further study. In particular, the character of change in emission of radiation to space in a warming atmosphere and its relation to surface temperature is a key component of the greenhouse effect and related feedbacks. Over most of the planet, the emission systematically increase with increasing surface temperature indicating the important function of the emission to space in removing heat from the warming Earth. In some regions of the planet, the emission decreases with increasing temperature. These are the so-called super-greenhouse regions of the planet and if left alone, these regions would produce a localized runaway warming. Using global observations extracted from the A-train satellites, the properties of these supergreenhouse regions will be reviewed and the factors that control them explained. A glimpse at how these regions evolve in a warming world based on CMIP5 results will be presented and the broader implication of the supergreenhouse effect will be underlined.

Stephens, G. L.; Kahn, B. H.

2012-12-01

382

Effective Thinking Outdoors.  

ERIC Educational Resources Information Center

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

Hyde, Rod

1997-01-01

383

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.

384

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

385

Cardiovascular effects of alcohol.  

PubMed Central

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

Davidson, D M

1989-01-01

386

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

387

Creating Effective Multimedia Instruction.  

ERIC Educational Resources Information Center

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

Sales, Gregory C.

1999-01-01

388

Effects of Induced Astigmatism.  

ERIC Educational Resources Information Center

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

Schubert, Delwyn G.; Walton, Howard N.

1968-01-01

389

Earth Impacts Effects Program  

NSDL National Science Digital Library

This interactive web site estimates the regional environmental consequences of an impact on Earth. The program will estimate the ejecta distribution, ground shaking, atmospheric blast wave, and thermal effects of an impact as well as the size of the crater produced.

Robert Marcus

390

Space Environmental Effects Knowledgebase  

NASA Technical Reports Server (NTRS)

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

Wood, B. E.

2007-01-01

391

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

392

Fast and effective?  

PubMed

The 5.2 diet involves two days of fasting each week. It is being promoted as the key to sustained weight loss, as well as wider health benefits, despite the lack of evidence on the long-term effects. Nurses need to support patients who wish to try intermittent fasting. PMID:24345130

Trueland, Jennifer

2013-12-18

393

Effective Staff Development.  

ERIC Educational Resources Information Center

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

Bush, Robert N.

394

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...

395

Effective Online Privacy Policies  

Microsoft Academic Search

Online privacy policies are important mechanisms for informing web site users about the level of information privacy protection afforded when visiting web sites. To date, societal mechanisms and technologies have been the focus of attempts to improve the quality and effectiveness of online privacy policies. Little attention, however, has been given to the development and use of organisational measures for

Sharman Lichtenstein; Paula M C Swatman; Kanchan Babu

396

Class Effects in ATI's.  

ERIC Educational Resources Information Center

Selected results from an aptitude-treatment interaction (ATI) study illustrate the importance of including class analyses in ATI research. The interactive effects of motivational aptitude (including locus of control, academic self confidence, and interests) and cognitive aptitude (as measured by a learning task and the Lorge-Thorndike verbal and…

Greene, Jennifer C.

397

BIOLOGICAL EFFECTS OF MANGANESE  

EPA Science Inventory

The biological effects of manganese were studied in a town on the coast of Dalmatia in which a ferromanganese plant has been operating since before World War II. The study focused on the question of whether the exposure to manganese can cause a higher incidence of respiratory dis...

398

The quadratic Zeeman effect  

Microsoft Academic Search

The hydrogen-atom quadratic Zeeman effect is treated by several techniques, and a new perturbation approach is suggested which involves numerical solution of a radial equation based on the s part of the potential. The low-field results appear to be more accurate than those of previous workers.

J. Killingbeck

1979-01-01

399

Tips for Effective Management  

ERIC Educational Resources Information Center

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

Supple, Kevin F.

2009-01-01

400

FIELD DISPERSANT EFFECTIVENESS TEST  

EPA Science Inventory

The EPA's OHMSETT facility has developed a rapid field test that includes some of the theoretical aspects and conditions of dispersion at sea. This Field Dispersant Effectiveness Test (FDET) has been used to evaluate the dispersibility of various commonly-transported oils and mak...

401

The Surface Photoelectric Effect  

Microsoft Academic Search

The probability of ejection of an electron in the surface photo-effect is expressed in terms of a function of the potential barrier, the energy of the electron after ejection, and the frequency. This function is dominated, for low energies of ejection, by the transmission coefficient of the surface. It is then assumed that the function can be expanded in a

W. V. Houston

1937-01-01

402

Measuring Teacher Effectiveness  

ERIC Educational Resources Information Center

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

Jacobo, Amber Leann

2012-01-01

403

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.

Jeff Radel

404

test collection retrieval effectiveness  

E-print Network

and provide means, in the form of a large XML test collection and appropriate scoring methodsINEX evaluation test collection retrieval effectiveness The INEX Evaluation Initiative Gabriella increases, so is the need to assess their benefit to users. The benefit to a given user depends largely

Lalmas, Mounia

405

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

406

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

2014-02-01

407

Anticancer effects of phytosterols  

Microsoft Academic Search

Phytosterol and stanol (or phytosterols) consumption reduces intestinal cholesterol absorption, leading to decreased blood LDL-cholesterol levels and lowered cardiovascular disease risk. However, other biological roles for plant sterols and stanols have also been proposed. The objective of this review is to critically examine results from recent research regarding the potential effects and mechanisms of action of phytosterols on forms of

T A Woyengo; V R Ramprasath; P J H Jones; PJH Jones

2009-01-01

408

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.

Dr. Michael Cross, Cal Tech

409

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.

410

Evolution of Earth's Greenhouse Effect  

Microsoft Academic Search

The major factors contributing to Earth's greenhouse effect are discussed along with various quantitative methods for determining the greenhouse effect. Earth's greenhouse effect has evolved over geologic time scales and continues to evolve. The magnitude of Earth's greenhouse effect is explored for particular time periods of Earth's evolution from the Neoproterozoic to present. Coupled climate model simulations for these various

J. T. Kiehl

2003-01-01

411

Ecotoxicological effects at contaminated sites  

Microsoft Academic Search

Contamination sites pose significant environmental hazards for terrestrial and aquatic ecosystems. They are important sources of pollution and may result in ecotoxicological effects on terrestrial, groundwater and aquatic ecosystems. At severely contaminated sites, acute effects occur, but the core problem lies in long-term chronic effects. Ecotoxicological effects occur at all levels of biological organization, from the molecular to the ecosystem

Karl Fent

2004-01-01

412

Strongly nonlinear thermovoltage and heat dissipation in interacting quantum dots  

NASA Astrophysics Data System (ADS)

We investigate the nonlinear regime of charge and energy transport through Coulomb-blockaded quantum dots. We discuss crossed effects that arise when electrons move in response to thermal gradients (Seebeck effect) or energy flows in reaction to voltage differences (Peltier effect). We find that the differential thermoelectric conductance shows a characteristic Coulomb butterfly structure due to charging effects. Importantly, we show that experimentally observed thermovoltage zeros are caused by the activation of Coulomb resonances at large thermal shifts. Furthermore, the power dissipation asymmetry between the two attached electrodes can be manipulated with the applied voltage, which has implications for the efficient design of nanoscale coolers.

Sierra, Miguel A.; Sánchez, David

2014-09-01

413

Nonequilibrium effects and baryogenesis  

SciTech Connect

Possible effects due to nonequilibrium dynamics in the Affleck-Dine mechanism of baryogenesis are examined. Using the closed-time-path formalism, the quantum fluctuation and the backreaction of the Affleck-Dine scalar field are incorporated self-consistently into the dynamical equations of the system by invoking a nonperturbative Hartree approximation. It is found that such nonequilibrium effects can significantly affect the amount of baryon asymmetry that can be generated. In particular, it is possible to generate the observed baryon asymmetry with suitable initial conditions. The methodology described in this paper as well as some of the results obtained are quite general, and can be applied to any complex scalar field in a cosmological background.

Charng, Y.-Y.; Ng, K.-W. [Institute of Physics, Academia Sinica, Taipei, Taiwan 115 (China); Lee, D.-S. [Department of Physics, National Dong Hwa University, Hua-Lien, Taiwan 974 (China); Theory Group, Blackett Laboratory, Imperial College, London SW7 2BZ (United Kingdom); Leung, C.N. [Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716 (United States)

2005-12-15

414

Latent effects decision analysis  

DOEpatents

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

Cooper, J. Arlin (Albuquerque, NM); Werner, Paul W. (Albuquerque, NM)

2004-08-24

415

Effective Vaccination Policies  

PubMed Central

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

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

2010-01-01

416

Neuroprotective effects of creatine.  

PubMed

There is a substantial body of literature, which has demonstrated that creatine has neuroprotective effects both in vitro and in vivo. Creatine can protect against excitotoxicity as well as against ?-amyloid toxicity in vitro. We carried out studies examining the efficacy of creatine as a neuroprotective agent in vivo. We demonstrated that creatine can protect against excitotoxic lesions produced by N-methyl-D: -aspartate. We also showed that creatine is neuroprotective against lesions produced by the toxins malonate and 3-nitropropionic acid (3-NP) which are reversible and irreversible inhibitors of succinate dehydrogenase, respectively. Creatine produced dose-dependent neuroprotective effects against MPTP toxicity reducing the loss of dopamine within the striatum and the loss of dopaminergic neurons in the substantia nigra. We carried out a number of studies of the neuroprotective effects of creatine in transgenic mouse models of neurodegenerative diseases. We demonstrated that creatine produced an extension of survival, improved motor performance, and a reduction in loss of motor neurons in a transgenic mouse model of amyotrophic lateral sclerosis (ALS). Creatine produced an extension of survival, as well as improved motor function, and a reduction in striatal atrophy in the R6/2 and the N-171-82Q transgenic mouse models of Huntington's disease (HD), even when its administration was delayed until the onset of disease symptoms. We recently examined the neuroprotective effects of a combination of coenzyme Q10 (CoQ10) with creatine against both MPTP and 3-NP toxicity. We found that the combination of CoQ and creatine together produced additive neuroprotective effects in a chronic MPTP model, and it blocked the development of alpha-synuclein aggregates. In the 3-NP model of HD, CoQ and creatine produced additive neuroprotective effects against the size of the striatal lesions. In the R6/2 transgenic mouse model of HD, the combination of CoQ and creatine produced additive effects on improving survival. Creatine may stabilize mitochondrial creatine kinase, and prevent activation of the mitochondrial permeability transition. Creatine, however, was still neuroprotective in mice, which were deficient in mitochondrial creatine kinase. Administration of creatine increases the brain levels of creatine and phosphocreatine. Due to its neuroprotective effects, creatine is now in clinical trials for the treatment of Parkinson's disease (PD) and HD. A phase 2 futility trial in PD showed approximately a 50% improvement in Unified Parkinson's Disease Rating Scale at one year, and the compound was judged to be non futile. Creatine is now in a phase III clinical trial being carried out by the NET PD consortium. Creatine reduced plasma levels of 8-hydroxy-2-deoxyguanosine in HD patients phase II trial and was well-tolerated. Creatine is now being studied in a phase III clinical trial in HD, the CREST trial. Creatine, therefore, shows great promise in the treatment of a variety of neurodegenerative diseases. PMID:21448659

Beal, M Flint

2011-05-01

417

Safety Intervention Effectiveness  

SciTech Connect

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

ZIMMERMAN, R.O.

2001-10-16

418

Relativistic Hall Effect  

NASA Astrophysics Data System (ADS)

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.

Bliokh, Konstantin Y.; Nori, Franco

2012-03-01

419

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

420

Measuring marketing effectiveness.  

PubMed

The most frequent question about the marketing function in hospitals today is, What are we getting for our money? To answer this, marketing directors must convince the board first of the need for marketing, then of marketing's effectiveness. To measure marketing effectiveness, some basic needs are a staff, equipment, cooperation between departments, utilization data, and a research budget. Some steps to be followed include developing a marketing data base--consisting of demographic projections, demand projections, and market share--testing a marketing strategy through experimentation, documenting the expected results and measurement techniques, and calculating the expected return on investments. In dealing with those "impossible-to-measure" cases, such as a physician who is not advertising but finds that a competitor is, a decision tree can help determine whether to advertise and how much to spend by indicating what the return on investment might be. PMID:10312197

Gluckman, J; Michaelis, T

1987-09-01

421

The reverse Stroop effect.  

PubMed

In classic Stroop interference, manual or oral identification of sensory colors presented as incongruent color words is delayed relative to simple color naming. In the experiment reported here, this effect was shown to all but disappear when the response was simply to point to a matching patch of color. Conversely, strong reverse Stroop interference occurred with the pointing task. That is, when the sensory color of a color word was incongruent with that word, responses to color words were delayed by an average of 69 msec relative to a word presented in gray. Thus, incongruently colored words interfere strongly with pointing to a color patch named by the words, but little interference from incongruent color words is found when the goal is to match the color of the word. These results suggest that Stroop effects arise from response compatibility of irrelevant information rather than automatic processing or habit strength. PMID:10780025

Durgin, F H

2000-03-01

422

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

423

Estimating Absolute Site Effects  

SciTech Connect

The authors use previously determined direct-wave attenuation functions as well as stable, coda-derived source excitation spectra to isolate the absolute S-wave site effect for the horizontal and vertical components of weak ground motion. They used selected stations in the seismic network of the eastern Alps, and find the following: (1) all ''hard rock'' sites exhibited deamplification phenomena due to absorption at frequencies ranging between 0.5 and 12 Hz (the available bandwidth), on both the horizontal and vertical components; (2) ''hard rock'' site transfer functions showed large variability at high-frequency; (3) vertical-motion site transfer functions show strong frequency-dependence, and (4) H/V spectral ratios do not reproduce the characteristics of the true horizontal site transfer functions; (5) traditional, relative site terms obtained by using reference ''rock sites'' can be misleading in inferring the behaviors of true site transfer functions, since most rock sites have non-flat responses due to shallow heterogeneities resulting from varying degrees of weathering. They also use their stable source spectra to estimate total radiated seismic energy and compare against previous results. they find that the earthquakes in this region exhibit non-constant dynamic stress drop scaling which gives further support for a fundamental difference in rupture dynamics between small and large earthquakes. To correct the vertical and horizontal S-wave spectra for attenuation, they used detailed regional attenuation functions derived by Malagnini et al. (2002) who determined frequency-dependent geometrical spreading and Q for the region. These corrections account for the gross path effects (i.e., all distance-dependent effects), although the source and site effects are still present in the distance-corrected spectra. The main goal of this study is to isolate the absolute site effect (as a function of frequency) by removing the source spectrum (moment-rate spectrum) from the distance-corrected S-wave spectra. Typically, removing the S-wave source spectrum is difficult because of inadequate corrections for the source radiation pattern, directivity and random interference. In addition to complexities near the source, 2-D and 3-D structure beneath the recording site will result in an azimuth-dependent site effect. Since the direct wave only samples a narrow range in take-off and back-azimuth angles, multi-station averaging is needed to minimize the inherent scatter. To minimize these complicating effects, they apply the coda methodology outlined by Mayeda et al., (2003) to obtain stable moment-rate spectra. This methodology provides source amplitude and derived source spectra that are a factor of 3-to-4 times more stable than those derived from direct waves. Since the coda is commonly thought of as scattered energy that samples all ray parameters and back-azimuths, it is not very sensitive to the source radiation pattern and 3-D structure. This property makes it an excellent choice for use in obtaining average properties of the source, site and path effects in a region. Due to the characteristics of the techniques used in this study, all the inverted quantities are azimuthally averaged, since the aximuthal information is lost in the processing.

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

2004-07-15

424

Ocular effects of adrenomedullin.  

PubMed

The purpose of this study was to determine the expression and effects of adrenomedullin (AM), a novel vasodilator peptide, in the eye. Expression of AM mRNA was examined in the rat iris-ciliary body using reverse transcription-polymerase chain reaction (RT-PCR). In rabbits, intraocular pressure (IOP) was measured periodically after intravitreal injection (20 microl) of AM (10(-7)-10(-4)m) into one eye. In separate groups of rabbits, 30 min after intravitreal injection of either AM-(22-52) (10(-3)m), a specific AM receptor antagonist, or CGRP-(8-37) (10(-3)m), a CGRP1 receptor antagonist, into one eye, AM (10(-6)m) was injected into both eyes, and IOP was measured. Using different rabbits, aqueous protein and cAMP concentrations were determined 6 hr after injection of AM. Expression of AM mRNA was detected in the rat iris-ciliary body. In rabbits, intravitreally administered AM (10(-6)-10(-4)m) profoundly lowered IOP, and the maximum effect was observed at 4-8 h. The ocular hypotensive effect of AM was dose-dependent (10(-7)-10(-4)m). Pretreatment with CGRP-(8-37) did not significantly inhibit the ocular hypotensive effect of AM (10(-6)m), whereas pretreatment with AM-(22-52) completely abolished it. AM (10(-6)m) did not significantly affect aqueous protein concentration. The higher dose of AM (10(-5)m) induced a significant increase in aqueous protein, which was not associated with an increase in the aqueous cAMP content and was significantly inhibited by AM-(22-52) and CGRP-(8-37). These results demonstrate that AM is expressed in the iris-ciliary body and decreases IOP mainly via specific AM receptors, and suggest that AM may play a role in controlling IOP. PMID:10548466

Taniguchi, T; Kawase, K; Gu, Z B; Kimura, M; Okano, Y; Kawakami, H; Tsuji, A; Kitazawa, Y

1999-11-01

425

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

426

Geomorphically effective floods  

NASA Astrophysics Data System (ADS)

Investigations of the hydrology and geomorphology of recent floods from the rapid failure of two small upland dams document the unusually large peak boundary shear stress and peak stream power per unit area for each flood. Downstream consequences to alluvial channels and floodplains, however, were minimal. Lack of geomorphic change is attributed to the short duration of the floods, which lasted about six and sixteen minutes each. Distribution of stream power over hydrographs of eight exceptional floods is constructed from channel geometry, discharge rating curves, and flood hydrographs; the resulting curve is defined as a stream-power graph. A stream-power graph gives a better portrayal of the potential for a flood to be geomorphically effective than simple statements of flow magnitude. From stream-power graphs, total energy expended over a flood hydrograph can be computed. Total flood energy may not be a sensitive measure of geomorphic effectiveness without consideration of channel and floodplain resistance. A conceptual model combining flow duration, peak stream power per unit area, flood energy, and alluvial and bedrock thresholds may represent the effectiveness of floods and can distinguish among such cases as (a) floods of long duration, moderate to large energy expenditure, but low peak stream power per unit area. These floods are ineffective in causing significant landform changes in alluvial or bedrock channels; (b) floods of medium to long duration, with medium to large total energy expenditure, and large peak stream power per unit area. These are believed to be the most effective geomorphic floods in any kind of channel because of the optimal combination of peak flood power, duration, and total energy expenditure; and (c) floods of very short duration, low total energy expenditure, but large peak stream power. These floods are also ineffective agents of geomorphic change in spite of record values of peak stream power per unit area because of their short duration, and resulting low energy expenditures.

Costa, John E.; O'Connor, Jim E.

427

Magnetic effects on thermocouples  

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

428

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

429

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

430

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.

2014-09-14

431

Effects on Development  

Microsoft Academic Search

This chapter will review the effects produced on neural development by maternal consumption of cannabinoids during gestation\\u000a and lactation, with emphasis in thematuration of several neurotransmitter systems (dopamine, serotonin, opioids, cannabinoids,\\u000a etc.) and possible modifications in their functional expression at the behavioral or neuroendocrine levels. In addition, we\\u000a have analyzed the possible existence of a sexual dimorphism in these ontogenic

J. A. Ramos; M. Gómez; R. de Miguel

432

Dark Matter Effective Theory  

E-print Network

We organize the effective (self)interaction terms for complex scalar dark matter candidates which are either an isosinglet, isodoublet or an isotriplet with respect to the weak interactions. The classification has been performed ordering the operators in inverse powers of the dark matter cutoff scale. We assume Lorentz invariance, color and charge neutrality. We also introduce potentially interesting dark matter induced flavor-changing operators. Our general framework allows for model independent investigations of dark matter properties.

Eugenio Del Nobile; Francesco Sannino

2012-04-18

433

Pulsed DF laser effects  

Microsoft Academic Search

Laser effects caused by pulsed DF laser beams have been investigated under one-dimensional plasma conditions. The high energy pulse from a 50-liter photoinitiated chemical laser was utilized to measure both metal and fiberglass target responses to incident fluences up to 150 J\\/sq cm. In thermal coupling experiments with aluminum, the absorbed fluence showed enhancement just above the plasma threshold, reaching

W. E. Maher; R. B. Hall

1981-01-01

434

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

435

[Bactericidal effect of lysozyme].  

PubMed

Isolation of lysozyme from hemolymph of Alveonasus lahorensis (Acari: Parasitiformes, Argasidae) and Hyalomma marginatum (Acari: Parasitiformes, Ixodidae) with using ultrasound is described. It was shown that the bactericidal effect of the ultrasound-extracted lysozyme against Staphylococcus aureus and Micrococcus luteus significantly exceeded that of the chicken egg lysozyme and lysozyme from ticks without ultrasound exposure. Disintegration of the hemolymph cells increased lysozyme production. PMID:24640148

Podborodov, V M; Shchelkanov, M Iu; Smirnova, I P; Burenkova, L A; Novikova, V P; Aristova, V A; Novikova, E L; Moskvitina, G G; Ioffe, A M

2013-01-01

436

Identifying Effective School Principals  

E-print Network

focus on three dimensions: student performance, teacher retention, and financial management. Data is derived from the Texas Education Agency (TEA) to develop a total of seven specific indicators to measure success in these three areas for Texas... tests and school accountability ratings. TEA data is used from 1996-2005 to develop indicators for these two measures. Since our goal was to capture the improvements in student performance attributable to principal effectiveness, we used a value...

Fernandez, Kandyce; Flores, Santa; Huang, Emily; Igwe, Carolyn; McDonald, Leslie; Stroud, Ryan; Willis, Rebecca; Dugat, Amber

2007-01-01

437

Interpersonal effectiveness training  

E-print Network

of the individual 's daily activities and encounters with his or her spouse. The frequency of occurrence of the six behaviors were analyzed by a 6 x 7 x 4 factorial repeated measures ANOVA. This analysis revealed a significant main effect of questions (y&. 01... & Siegel, 1973; Mix, 1972; Navran, 1967; Pearce, 1973; Raush, Barry, Hertel 8 Swaim, 1974; Tubbs 8 Moss, 1974; Watzlawick, Beavin & Jackson, 1967; Wicks, 1973). A person's concept of himself and others partially determines his behavior. Bienvenu (1971...

DeOtte, Dona Lou Lewis

1976-01-01

438

The Effects of Outliers  

NSDL National Science Digital Library

Created by Illuminations: Resources for Teaching Mathematics, this lesson is designed to help students understand the significance of outliers. This lesson includes thought questions and an applet to help students visualize the effect of an outlier. The authors divide the lesson into different groups, they include: learning objectives, materials, instructional plans, NCTM standards/expectations, and finally references. This is a great interactive resource for those wanting to learn more about correlation and regression.

439

Extra Housepayments Effect  

NSDL National Science Digital Library

How financial institutions use the monthly mortgage payment and mortgage amortization formulas can be a confusing concept to grasp. This lesson asks students to find a current interest mortgage rate for their city and state. This rate is then applied to an Internet based mortgage calculator to discover the effect that paying extra on a monthly house payment has on total interest paid and length of the loan. A student worksheet is included in the document.

2011-01-05

440

Estimating Absolute Site Effects  

Microsoft Academic Search

The authors use previously determined direct-wave attenuation functions as well as stable, coda-derived source excitation spectra to isolate the absolute S-wave site effect for the horizontal and vertical components of weak ground motion. They used selected stations in the seismic network of the eastern Alps, and find the following: (1) all ''hard rock'' sites exhibited deamplification phenomena due to absorption

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

2004-01-01

441

QCD Effects in Cosmology  

E-print Network

The cosmological evolution in the radiation dominated regimen is usually computed by assuming an ideal relativistic thermal bath. In this note, we discuss the deviation from the non-interaction assumption. In either the standard model (SM) and the minimal supersymmetric standard model (MSSM), the main contribution comes from the strong interaction. An understanding of these effects are important for precision measurements and for the evolution of scalar modes, where the commented corrections constitute the main source of the dynamics.

Cembranos, Jose A R

2009-01-01

442

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

443

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

444

Putting Instruction Sequences into Effect  

E-print Network

An attempt is made to define the concept of execution of an instruction sequence. It is found to be a special case of directly putting into effect of an instruction sequence. Directly putting into effect of an instruction sequences comprises interpretation as well as execution. Directly putting into effect is a special case of putting into effect with other special cases classified as indirectly putting into effect.

Bergstra, Jan A

2011-01-01

445

Neuroprotective effects of Asiaticoside.  

PubMed

In the central nervous system, Asiaticoside has been shown to attenuate in vitro neuronal damage caused by exposure to ?-amyloid. In vivo studies demonstrated that Asiaticoside could attenuate neurobehavioral, neurochemical and histological changes in transient focal middle cerebral artery occlusion animals. In addition, Asiaticoside showed anxiolytic effects in acute and chronic stress animals. However, its potential neuroprotective properties in glutamate-induced excitotoxicity have not been fully studied. We investigated the neuroprotective effects of Asiaticoside in primary cultured mouse cortical neurons exposed to glutamate-induced excitotoxicity invoked by N-methyl-D-aspartate. Pretreatment with Asiaticoside decreased neuronal cell loss in a concentration-dependent manner and restored changes in expression of apoptotic-related proteins Bcl-2 and Bax. Asiaticoside pretreatment also attenuated the upregulation of NR2B expression, a subunit of N-methyl-D-aspartate receptors, but did not affect expression of NR2A subunits. Additionally, in cultured neurons, Asiaticoside significantly inhibited Ca(2+) influx induced by N-methyl-D-aspartate. These experimental findings provide preliminary evidence that during excitotoxicity induced by N-methyl-D-aspartate exposure in cultured cortical neurons, the neuroprotective effects of Asiaticoside are mediated through inhibition of calcium influx. Aside from its anti-oxidant activity, down-regulation of NR2B-containing N-methyl-D-aspartate receptors may be one of the underlying mechanisms in Asiaticoside neuroprotection. PMID:25221579

Qi, Feng-Yan; Yang, Le; Tian, Zhen; Zhao, Ming-Gao; Liu, Shui-Bing; An, Jia-Ze

2014-07-01

446

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. PMID:20883592

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

2010-01-01

447

Cardioprotective effects of curcumin.  

PubMed

Curcumin, a major active component of turmeric, is extracted from the powdered dry rhizome of Curcuma longa Linn (Zingiberaceae) and it has been used for centuries in indigenous medicine. We have shown that curcumin has a protective role against myocardial necrosis in rats. The antioxidant activity of curcumin could be attributed to the phenolic and methoxy groups in conjunction with the 1,3-diketone-conjugated diene system, for scavenging of the oxygen radicals. In addition, curcumin is shown to enhance the activities of detoxifying enzymes such as glutathione-S-transferase in vivo. We have also shown that oxygen free radicals exacerbate cardiac damage and curcumin induces cardioprotective effect and it also inhibits free-radical generation in myocardial ischemia in rats. This chapter on the cardioprotective effects of curcumin covers the following aspects: (1) the history of curcumin and its discovery as a potent drug with relevance to cardiovascular diseases; (2) mechanistic role of curcumin in vitro, emphasizing the antiplatelet and anticoagulant effects; (3) cardiovascular properties of curcumin; (4) application of curcumin in different animal models (viz. myocardial ischemia, myocardial infarction, cardiomyopathy, and arrhythmia in vitro and in vivo); (5) curcumin free-radical scavenging activity, particularly against O2 radical and depletion of the oxidative stress. PMID:17569220

Miriyala, Sumitra; Panchatcharam, Manikandan; Rengarajulu, Puvanakrishnan

2007-01-01

448

Stringy effects in scrambling  

E-print Network

In [1] we gave a precise holographic calculation of chaos at the scrambling time scale. We studied the influence of a small perturbation, long in the past, on a two-sided correlation function in the thermofield double state. A similar analysis applies to squared commutators and other out-of-time-order one-sided correlators [2-4]. The essential bulk physics is a high energy scattering problem near the horizon of an AdS black hole. The above papers used Einstein gravity to study this problem; in the present paper we consider stringy and Planckian corrections. Elastic stringy corrections play an important role, effectively weakening and smearing out the development of chaos. We discuss their signature in the boundary field theory, commenting on the extension to weak coupling. Inelastic effects, although important for the evolution of the state, leave a parametrically small imprint on the correlators that we study. We briefly discuss ways to diagnose these small corrections, and we propose another correlator where inelastic effects are order one.

Stephen H. Shenker; Douglas Stanford

2015-03-20

449

Planetary Electrochemical Effects  

NASA Astrophysics Data System (ADS)

Lightning on a planet other than the Earth was first discovered by Voyager when it flew past Jupiter in 1979. Since then it has been reported on Saturn by Voyager and Cassini, and on Venus from Pioneer Venus and Venus Express. While lightning involves clouds formed from polar molecules such as water, or vulcanism, dusty environments often create electrostatic fields through triboelectric phenomena. In each instance, changes in local chemistry with profound global impact can occur, such as lightning-induced nitrogen fixation on earth. Perhaps the most dramatic effect occurs on Mars within its global dust storms and dust devils. Enhanced production of oxidants, such as hydrogen peroxide, sulfur and halogen species including perhaps perchlorates from minerals in airborne dust are some of the likely chemical effects. The oxidants may be responsible for the lack of organics on the surface of Mars and rapid destruction of methane in the atmosphere. On Titan, the surface organics may be altered by a different (charged particle) effect, a phenomena that may also operate in the polar regions of Mars and on the Galilean satellites. In this talk, we will discuss possible chemical and astrobiological implications of above electrical processes.

Atreya, S. K.; Mihalka, K. M.; Mahaffy, P. R.; Delory, G. T.; Farrell, W. M.

2008-12-01

450

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. PMID:24101881

Shahar, Eyal; Shahar, Doron J

2013-01-01

451

Effectiveness Review Analysis (Insert Effectiveness Review Name) Root Cause  

E-print Network

Effectiveness Review Analysis ­ (Insert Effectiveness Review Name) 1 of 1 Root Cause: Corrective action address the root cause? 2. Does the corrective action prevent recurrence of similar conditions due

452

'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

453

Asteroids without opposition effect  

NASA Astrophysics Data System (ADS)

Most of the observed asteroids show a nonlinear increase of brightness at small phase angles, typically less than 7°, known as the opposition effect. Its amplitude, relative to the extrapolation of the linear part of the phase curve, depends on an asteroid's albedo, decreasing for low-albedo asteroids (e.g., Belskaya and Shevchenko 2000). Recently, low-albedo asteroids without the nonlinear increase of brightness down to subdegree phase angles were observed among outer-belt asteroids and Jupiter Trojans (Shevchenko et al. 2012, 2013). These asteroids belong mainly to the P and D spectral classes that have featureless spectra with moderate to high slopes in the visual and near-infrared wavelengths (DeMeo et al. 2009, 2013). Their spectra are similar to the spectra of carbonaceous chondrite meteorites, in particular, to those of some CI meteorites (Alais, Tagish Lake) and some CM meteorites after thermal heating (Cloutis et al. 2011, 2012, Fornazier et al. 2011). We analyze possible relationships between surface composition of asteroids and their opposition effect behavior. Asteroids which do not show nonlinear opposition effect in their magnitude--phase angle dependencies tend to have very low surface albedos. However, the correlation is not very strong due to errors in asteroid albedo determinations. We note that the absolute magnitudes of these asteroids determined using the H, G function are systematically overestimated (Slyusarev et al. 2012, Shevchenko et al. 2014). An overestimate of the absolute brightness results in systematic overestimation of their albedos from the infrared data (Usui et al., 2011, Masiero et al., 2011). Advantages of using the new H, G_1, G_2 function (Muinonen et al. 2010) for the determination of asteroid absolute magnitudes are discussed.

Shevchenko, V.; Belskaya, I.; Slyusarev, I.

2014-07-01

454

Quantum Effects in Biology  

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

455

Transistors: The Field Effect  

NSDL National Science Digital Library

Transistors are the building blocks of modern electronic devices. Your cell phones, iPods, and computers all depend on them to operate. Thanks to today's microfabrication technology, transistors can be made very tiny and be massively produced. You are probably using billions of them while working with this activity now--as of 2006, a dual-core Intel microprocessor contains 1.7 billion transistors. The field effect transistor is the most common type of transistor. So we will focus on it in this activity.

The Concord Consortium

2011-12-11

456

Vibration by relativistic effects  

E-print Network

Relativity, time reversal invariance in mechanics and principle of causality can be in the bases of a type of vibration of the extensive objects. It is because, the detailed analysis of the relativistic movement of an extensive body entail that all the objects must have inherent a vibratory movement to their own size. Such effect does not happen when it works with point particles thus is not stranger who happens unnoticed in the traditional studies. Also we can find relation between the form of vibration of the extensive objects and the energy that calculates by quantum considerations.

Enrique Oradaz Romay

2005-12-27

457

Microcircuit radiation effects databank  

NASA Technical Reports Server (NTRS)

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

1983-01-01

458

Assessments of astronaut effectiveness  

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

459

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

2013-01-01

460

Earthquake occurrence and effects.  

PubMed

Although earthquakes are mainly concentrated in zones close to boundaries of tectonic plates of the Earth's lithosphere, infrequent events away from the main seismic regions can cause major disasters. The major cause of damage and injury following earthquakes is elastic vibration, rather than fault displacement. This vibration at a particular site will depend not only on the size and distance of the earthquake but also on the local soil conditions. Earthquake prediction is not yet generally fruitful in avoiding earthquake disasters, but much useful planning to reduce earthquake effects can be done by studying the general earthquake hazard in an area, and taking some simple precautions. PMID:2347628

Adams, R D

1990-01-01

461

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.

Krista Larsen

462

The Greenhouse Effect  

NSDL National Science Digital Library

This site provides an overview of the Earth's atmospheric greenhouse effect by briefly exploring the atmospheres of nearby planets and discussing the greenhouse gases of our atmosphere, such as, water vapor, carbon dioxide, methane, ozone, and nitrous oxide. Students will learn that the heat-trapping ability of a greenhouse is influenced by a number of factors, including the transparency of the greenhouse cover, and color and texture of the planet's surfaces. This site serves as a resource for and includes links to two classroom activities.

Carol McLaren

2000-01-01

463

Genotoxic effect of alkaloids.  

PubMed

Because of the increased use of alkaloids in general medical practice in recent years, it is of interest to determine genotoxic, mutagenic and recombinogenic response to different groups of alkaloids in prokaryotic and eucaryotic organisms. Reserpine, boldine and chelerythrine did not show genotoxicity response in the SOS-Chromotest whereas skimmianine showed genotoxicity in the presence of a metabolic activation mixture. Voacristine isolated from the leaves of Ervatamia coronaria shows in vivo cytostatic and mutagenic effects in Saccharomyces cerevisiae hapioids cells. The Rauwolfia alkaloid (reserpine) was not able to induce reverse mutation and recombinational mitotic events (crossing-over and gene conversion) in yeast diploid strain XS2316. PMID:1842017

Henriques, J A; Moreno, P R; Von Poser, G L; Querol, C C; Henriques, A T

1991-01-01

464

Intrinsic Transverse Size Effect  

E-print Network

Two recently proposed concepts to improve the perturbative calculation of exclusive amplitudes, gluonic radiative corrections (Sudakov factor) and confinement size effects (intrinsic transverse momentum) are combined to study the neutron magnetic form factor in the space-like region. We find that nucleon distribution amplitudes modelled on the basis of current QCD sum rules indicate overlap with the existing data at the highest measured values of momentum transfer. However, sizeable higher-order perturbative corrections (K-factor) and/or higher-twist contributions cannot be excluded, although they may be weaker than in the proton case.

J. Bolz; R. Jakob; P. Kroll; M. Bergmann; N. G. Stefanis

1994-07-11

465

Shock effects in meteorites  

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

466

Key to effective video retrieval: effective cataloging and browsing  

Microsoft Academic Search

-—— ——— — : 1. ABSTRACT Mukirnedia data is an increasingly important information medium today. Providing intelligent access for effective use of this information continues to offer challenges in digital Iibrary research. As computer vision, image processing and speech recognition research continue to progress, we examine the effectiveness of these fully automated techniques in architecting effective video retrieval systems. We

Dulce B. Ponceleon; Savitha Srinivasan; Arnon Amir; Dragutin Petkovic; Dan Diklic

1998-01-01

467

Effect Sizes, Confidence Intervals, and Confidence Intervals for Effect Sizes  

ERIC Educational Resources Information Center

The present article provides a primer on (a) effect sizes, (b) confidence intervals, and (c) confidence intervals for effect sizes. Additionally, various admonitions for reformed statistical practice are presented. For example, a very important implication of the realization that there are dozens of effect size statistics is that "authors must…

Thompson, Bruce

2007-01-01

468

Effects of Vendor-Managed Inventory on the Bullwhip Effect  

Microsoft Academic Search

The bullwhip effect means that demand variability increases as one moves up the supply chain. In the following article the bullwhip effect is quantified for each part of the supply chain which is presupposed to consist of a producer, a wholesaler, a retailer, and a consumer. After considering the causes of the bullwhip effect, it will be shown with the

Susanne Hohmann; Stephan Zelewski

2011-01-01

469

The Manhattan Effect 1 Running Head: THE MANHATTAN EFFECT  

E-print Network

and dismisses her relationship worries. After breaking up with Tracy for another woman, however, Isaac hasThe Manhattan Effect 1 Running Head: THE MANHATTAN EFFECT The Manhattan Effect: When Relationship on close relationships has frequently contrasted one's own interests with the interests of the partner

Reber, Paul J.

470

Ecotoxicological effects extrapolation models  

SciTech Connect

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

Suter, G.W. II

1996-09-01

471

NEUROPROTECTIVE EFFECTS OF CURCUMIN  

PubMed Central

Neurodegenerative diseases result in the loss of functional neurons and synapses. Although future stem cell therapies offer some hope, current treatments for most of these diseases are less than adequate and our best hope is to prevent these devastating diseases. Neuroprotective approaches work best prior to the initiation of damage, suggesting that some safe and effective prophylaxis would be highly desirable. Curcumin has an outstanding safety profile and a number of pleiotropic actions with potential for neuroprotective efficacy, including anti-inflammatory, antioxidant, and anti-protein-aggregate activities. These can be achieved at sub-micromolar levels. Curcumin’s dose–response curves are strongly dose dependent and often biphasic so that in vitro data need to be cautiously interpreted; many effects might not be achievable in target tissues in vivo with oral dosing. However, despite concerns about poor oral bioavailability, curcumin has at least 10 known neuroprotective actions and many of these might be realized in vivo. Indeed, accumulating cell culture and animal model data show that dietary curcumin is a strong candidate for use in the prevention or treatment of major disabling age-related neurodegenerative diseases like Alzheimer’s, Parkinson’s, and stroke. Promising results have already led to ongoing pilot clinical trials. PMID:17569212

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

2008-01-01

472

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

473

Quantum Zeno Effect  

E-print Network

We present the physics of the quantum Zeno effect, whose gist is often expressed by invoking the adage "a watched pot never boils". We review aspects of the theoretical and experimental work done on the effect since its inception in 1977, and mention some applications. We dedicate the article - with our very best wishes - to Rudolf Zahradnik at the occasion of his great jubilee. Perhaps Rudolf's lasting youthfulness and freshness are due to that he himself had been frequently observed throughout his life: until the political turn-around in 1989 by those who wished, by their surveillance, to prevent Rudolf from spoiling the youth by his personal culture and his passion for science and things beautiful and useful in general. This attempt had failed. Out of gratitude, the youth has infected Rudolf with its youthfulness. Chronically. Since 1989, Rudolf has been closely watched by the public at large. For the same traits of his as before, but with the opposite goal and for the benefit of all generations. We relish keeping him in sight ...

Mikhail Lemeshko; Bretislav Friedrich

2009-03-26