bluuebunny/crossref_metadata_2025 huggingface dataset:
Antiferromagnetically coupled patterned media
Authors: Piramanayagam S. N. , Aung K. O. , Deng S. , Sbiaa R.
Published: March 2009

Magnetostatic interactions in patterned media are responsible for increasing the switching field distribution and reducing the thermal stability. Micromagnetic simulations indicate that a reduced saturation magnetization (Ms) and increased anisotropy constant (Ku) lead to better thermal stability. However, writability will be a concern with this approach. Patterned media with an antiferromagnetically coupled (AFC) recording media structure is studied to obtain high thermal stability even with a larger Ms and larger Ku. With the AFC structure, the reduced remanence magnetization (Mr) leads to a reduced magnetostatic interaction, even though the Ms is larger. Magnetic force microscopy measurements indicate that the AFC media show a narrower switching field distribution.
Structural and dynamical properties of ionic liquids: The influence of charge location
Authors: Spohr H. V. , Patey G. N.
Published: March 2009

The properties of ionic liquids depend on the chemical structure of the constituent ions. An important difference between molten inorganic salts and room temperature ionic liquids (RTILs) is that in RTILs the charge is frequently not located at the center of mass. This paper describes a molecular dynamics investigation of the influence of charge location on the structure and transport properties of ionic liquids. The model considered consists of univalent spherical ions with the cation charge moved away from its center of mass. It is shown that the charge location has an important influence on the liquid properties. As the charge is moved off center, the electrical conductivity initially increases, and the shear viscosity decreases. However, when the charge exceeds a certain displacement, this behavior is reversed. With further charge displacement, the conductivity decreases sharply and the viscosity increases rapidly. This behavior reversal can be traced to the formation of directional ion pairs that are present in sufficient numbers, and have lifetimes sufficiently long to strongly influence the liquid properties. We suggest that the influence of directional ion pairing can explain what appear to be anomalously low conductivities and high viscosities observed for some RTILs. The rotational and reorientational motions of the cations are examined, and shown to be strongly influenced by ion-pair formation when the charge is far off center. The temperature dependence of the transport properties is considered for selected systems, and deviations from Arrhenius behavior are found to be most important for the conductivity. Based on our results, this possibly indicates that directional ion pairs create an additional “barrier” to charge transport in some ionic liquids.
Uniaxial magnetocrystalline anisotropy for c-plane oriented Co100−xMx (M: Cr, Mo, W) film with stacking faults
Authors: Hinata Shintaro , Yanagisawa Ryuichi , Saito Shin , Takahashi Migaku
Published: March 2009

Stacking faults (SFs) in Co-based alloy grains in a Co100−xMx (M: Cr, Mo, and W) film are evaluated by means of in-plane x-ray diffraction. Moreover, the correlation between SFs and uniaxial magnetocrystalline anisotropy Ku is discussed in connection with the spin-orbit interaction. The ratio of the integrated intensities of the (10.0) to (11.0) diffractions corrected by Lorentz and atomic scattering factors has been proposed as an index for SFs in hcp films with a c-plane sheet texture. This ratio is equal to 0.25 for perfect hcp stacking, while it is 0 for perfect fcc specific stacking. It has a one-to-one correspondence with the probability of -A-B-C- atomic-layer stacking Pfcc. Using this index, pure sputtered Co films are found to have a Pfcc of 10%. The addition of only 5 at. % of Mo or W into the Co grains reduces Pfcc to 2%. Ku was found to increase with the addition of material (e.g., Ku was 4.0×106 ergs/cm3 for 5 at. % Mo), although the atomic magnetic moment of Co decreases monotonously. A Pfcc of 10% is found to lower Ku in a pure Co film by more than a factor of 2 when the spin-orbit interaction is taken into account.
Thermal and electronic transport properties of CeTe2−xSnx compounds
Authors: Rhyee Jong-Soo , Cho Eunseog , Lee Kyu Hyoung , Kim Sang Il , Lee Eun Sung , Lee Sang Mock , Kwon Yong Seung
Published: March 2009

The thermal and electronic transport properties on rare-earth dichalcogenide compounds of CeTe2−xSnx (x≤0.1) were investigated by measuring electrical resistivity ρ, thermal conductivity κ, and Seebeck coefficient S. Compound of CeTe2 exhibited very low κ (1.25 W m−1 K−1) at 300 K, which was understood by the charge density wave lattice distortion. From the ρ(T) measurements, the metallic property of CeTe2 was significantly enhanced by Sn substitution. The temperature-dependent behavior of S(T) for CeTe2−xSnx (x=0.05 and 0.1) was well described by the inelastic Umklapp process and the phonon drag. The low Seebeck coefficient of CeTe2 (S≈2.5 μV/K at T≈300 K) was increased by Sn doping. From the band structure calculation, the semimetallic band character of CeTe2 was revealed with symmetric electron-hole band dispersion near the Fermi level. The symmetric electron-hole band dispersion of CeTe2 is responsible for the low Seebeck coefficient. The enhancement of the metallic property and Seebeck coefficient because of Sn substitution could be understood by the charge imbalance between electrons and holes caused by hole doping in the Te monolayer.
LASER-driven fast electron dynamics in gaseous media under the influence of large electric fields
Authors: Batani D. , Baton S. D. , Manclossi M. , Piazza D. , Koenig M. , Benuzzi-Mounaix A. , Popescu H. , Rousseaux C. , Borghesi M. , Cecchetti C. , Schiavi A.
Published: March 2009

We present the results of experiments performed at the LULI laboratory, using the 100 TW laser facility, on the study of the propagation of fast electrons in gas targets. The implemented diagnostics included chirped shadowgraphy and proton imaging. Proton images showed the presence of very large fields in the gas (produced by charge separation). In turn, these imply a strong inhibition of propagation, and a slowing down of the fast electron cloud as it penetrates in the gas. Indeed chirped shadowgraphy images show a reduction in time of the velocity of the electron cloud from the initial value, of the order of a fraction of c, over a time scale of a few picoseconds.
Response to “Comment on ‘On the Crooks fluctuation theorem and the Jaraynski equality’ and ‘Nonequilibrium fluctuation dissipation theorem of Brownian dynamics’ [J. Chem. Phys. 130, 107101 (2009)]”
Authors: Chen L. Y.
Published: March 2009

Contrary to what Crooks asserts, the self-consistency requirement put forward in J. Chem. Phys.129, 091101 (2008) is necessary for the Jarzynski equality (JE) and the Crooks fluctuation theorem (CFT) to be valid regardless which definition of work one uses, the force-displacement definition or the thermodynamic definition. The self-consistency check limits the applicability of the JE/CFT to linear systems and reversible processes in nonlinear systems. The fluctuation-dissipation theorem of J. Chem. Phys.129, 144113 (2008) is valid where the JE/CFT is applicable and where the JE/CFT is inapplicable.
Water dynamics on the hydrate lattice of a tetrabutyl ammonium bromide semiclathrate
Authors: Schildmann S. , Nowaczyk A. , Geil B. , Gainaru C. , Böhmer R.
Published: March 2009

Deuteron nuclear magnetic resonance (NMR) and dielectric spectroscopy are utilized to investigate the dynamics of the water molecules in the semiclathrate (tetra-n-butyl ammonium bromide) ⋅26 H2O. Stimulated-echo spectroscopy reveals a nonexponential correlation function predominantly due to rotational motion with jump angles that are broadly distributed around the tetrahedral angle. The reorientational correlation times from this technique agree excellently with those from dielectric measurements, both resulting in an activation energy of (43±1) kJ/mol. Large, spatially varying electrical dipolar fields, set up by the Br− and the N+ ions located on the hydrate lattice, are held responsible for the pronounced stretching of the correlation functions. Solid-echo spectra were acquired over a broad temperature range. They exhibit an apparent two-phase character discussed in terms of various scenarios. Two-dimensional NMR spectra and four-time stimulated echoes were recorded, but an exchange of slow and fast subensembles could not be detected. Spin-lattice relaxation does not directly reflect the local reorientational motion and its nonexponentiality is interpreted with reference to the translational dynamics of the water molecules.
Multiscale Maxwell–Schrödinger modeling: A split field finite-difference time-domain approach to molecular nanopolaritonics
Authors: Lopata Kenneth , Neuhauser Daniel
Published: March 2009

We present a combined finite-difference time-domain/linear response approach for modeling plasmon/molecule systems. The self-interaction of the molecule is avoided by splitting the fields and currents into two parts: those due to the molecule and those from everything else. This approach is suitable for describing surface plasmons on metal nanostructures interacting in the near field with nearby dipolar molecules or semiconductor nanostructures. The approach is applied to three collinear 5 nm diameter gold nanoparticles; the results demonstrate that a nearby molecule strongly affects surface plasmon transfer along the array. Specifically, an xy oriented molecule situated midway between the second and third nanoparticles exhibits a symmetric Fano-type inference effect. Transmission of incident x-polarized energy from the second nanoparticle to the third is enhanced over a frequency range below the molecular resonance, and partially scattered into y-polarized currents for frequencies above. At the molecule’s resonance frequency, the magnitude of the resulting y-current is approximately 20% of the x-current.
The stabilities of gallium nanowires with different phases encapsulated in a carbon nanotube
Authors: Li K. , He H. Y. , Xu B. , Pan B. C.
Published: March 2009

For C–Ga systems, a classical potential is developed to describe the interaction between C and Ga atoms. By using this potential, we study the stabilities of the Ga nanowires with different phases encapsulated in a carbon nanotube (CNT). Simulations show that the encapsulated β-Ga and γ-Ga nanowires are more stable than the α-Ga nanowire in the CNT. Moreover, we find that such relative stabilities are mainly originated from the size effect of the Ga nanowires and the influence of the CNT. With performing molecular dynamics simulation at finite temperatures, the linear thermal expansion coefficient of an encapsulated Ga nanowire is predicted to be 1.38×10−4 K−1, being very close to the bulk value. The obtained stabilities as well as the thermal expansion feature of the concerned Ga nanowires are all consistent with experimental observations.
Observation of ion cyclotron range of frequencies mode conversion plasma flow drive on Alcator C-Mod
Authors: Lin Y. , Rice J. E. , Wukitch S. J. , Greenwald M. J. , Hubbard A. E. , Ince-Cushman A. , Lin L. , Marmar E. S. , Porkolab M. , Reinke M. L. , Tsujii N. , Wright J. C. ,   Alcator C-Mod Team
Published: March 2009

At modest H3e levels (n3He/ne∼8%–12%), in relatively low density D(H3e) plasmas, n¯e≤1.3×1020 m−3, heated with 50 MHz rf power at Bt0∼5.1 T, strong (up to 90 km/s) toroidal rotation (Vϕ) in the cocurrent direction has been observed by high-resolution x-ray spectroscopy on Alcator C-Mod. The change in central Vϕ scales with the applied rf power (≤30 km s−1 MW−1), and is generally at least a factor of 2 higher than the empirically determined intrinsic plasma rotation scaling. The rotation in the inner plasma (r/a≤0.3) responds to the rf power more quickly than that of the outer region (r/a≥0.7), and the rotation profile is broadly peaked for r/a≤0.5. Localized poloidal rotation (0.3≤r/a≤0.6) in the ion diamagnetic drift direction (∼2 km/s at 3 MW) is also observed, and similarly increases with rf power. Changing the toroidal phase of the antenna does not affect the rotation direction, and it only weakly affects the rotation magnitude. The mode converted ion cyclotron wave (MC ICW) has been detected by a phase contrast imaging system and the MC process is confirmed by two-dimensional full wave TORIC simulations. The simulations also show that the MC ICW is strongly damped on H3e ions in the vicinity of the MC layer, approximately on the same flux surfaces where the rf driven flow is observed. The flow shear in our experiment is marginally sufficient for plasma confinement enhancement based on the comparison of the E×B shearing rate and gyrokinetic linear stability analysis.
The dissipation rate coefficient of turbulence is not universal and depends on the internal stagnation point structure
Authors: Goto Susumu , Vassilicos J. C.
Published: March 2009

The energy dissipation rate coefficient of statistically stationary homogeneous isotropic turbulence depends on the external force sustaining the turbulence irrespective of Reynolds number. This nonuniversality is established by proving that the Taylor length is proportional to the mean distance between stagnation points and thereby relating the energy dissipation rate coefficient to the stagnation point structure of the turbulence which is shown to depend on the structure of the large eddies. Confirmation of these relations is obtained at moderate Reynolds numbers by a series of direct numerical simulations where the large-scale forcing is systematically varied.
Electromagnetic characteristic and microwave absorption properties of carbon nanotubes/epoxy composites in the frequency range from 2 to 6 GHz
Authors: Zhang Haiyan , Zeng Guoxun , Ge Ying , Chen Tianli , Hu Lichu
Published: March 2009

The preparation and characterization of carbon nanotubes (CNTs)/epoxy composites were studied for microwave absorption, which frequency is from 2 to 6 GHz. The absorbing coating with a loading of 15 wt % CNTs/epoxy resin, which thickness is 3 mm, exhibited an absorbing peak of 10.5 dB at 3.85GHz. After being treated by HNO3–H2SO4 acid at the temperature of 100 °C, the real and imaginary part values of permittivity of CNTs have a larger increase in quantity, and the absorbing peak position moves to lower frequency of 3.35 GHz showing an increasing the dielectric loss in lower microwave frequency. Two-layer coating with CNTs/epoxy resin and graphite/epoxy resin composites have been also investigated in order to widen the frequencies range of CNTs microwave sorbent in the low microwave frequency application. The results indicated that two-layer coating (15 wt % loading CNTs/epoxy resin and 9 wt % loading graphite/epoxy resin) can obtain 2.4 GHz broad frequencies band for absorption of 5.0 dB. The absorbing peak intensity and position can be adjusted by changing the thickness of each layer coating in the case of fixed total thickness. The two-layer coating of 15 wt % loading CNTs/epoxy resin (dtop=2 mm) and 9 wt % loading graphite/epoxy resin (dbottom=1 mm) has a strong absorbing peak at 5.52 GHz and achieves an absorbing value of 20.79 dB.
Rhombohedral superhard structure of BC2N
Authors: Li Quan , Wang Mei , Oganov Artem R. , Cui Tian , Ma Yanming , Zou Guangtian
Published: March 2009

Ab initio evolutionary algorithm was employed to resolve the crystal structure of the observed superhard BC2N. We uncovered two polymorphs with rhombohedral (2 f.u./cell) and orthorhombic (2 f.u./cell) symmetries, with which the experimental x-ray diffraction pattern is well reproduced. Analysis of the total energy results and the simulated energy-loss near-edge spectroscopy suggests that the rhombohedral structure is the best candidate for the superhard BC2N. We further demonstrated that earlier proposed high density and low density forms are likely from this single rhombohedral phase.
Some equivalences between the auxiliary field method and envelope theory
Authors: Buisseret Fabien , Semay Claude , Silvestre-Brac Bernard
Published: March 2009

The auxiliary field method has been recently proposed as an efficient technique to compute analytical approximate solutions of eigenequations in quantum mechanics. We show that the auxiliary field method is completely equivalent to the envelope theory, which is another well-known procedure to analytically solve eigenequations, although relying on different principles a priori. This equivalence leads to a deeper understanding of both frameworks.
Interface screening and imprint in poly(vinylidene fluoride/trifluoroethylene) ferroelectric field effect transistors
Authors: Lazareva I. , Koval Y. , Müller P. , Müller K. , Henkel K. , Schmeisser D.
Published: March 2009

We investigated the imprint effect in ferroelectric capacitors and field effect transistors (FETs) with a poly(vinylidene fluoride/trifluoroethylene) [P(VDF-TrFE)] ferroelectric insulator. The shift in switching voltages and the change in the ferroelectric FET (FeFET) channel conductance were measured as a function of time and the thickness of the ferroelectric layer. Analyzing our experimental data, we show that the imprint originates from interface-induced processes, which effectively screen polarization charges in P(VDF-TrFE). This phenomenon significantly influences the retention of FeFET channel conductance and the memory functionality of FeFET with P(VDF-TrFE).
Efficient near-infrared down conversion in Zn2SiO4:Tb3+,Yb3+ thin-films
Authors: Huang X. Y. , Zhang Q. Y.
Published: March 2009

We demonstrate a facile approach for the synthesis of Zn2SiO4:Tb3+,Yb3+ transparent thin films. The thin film phosphor was characterized by various methods including x-ray diffraction, atom force microscope, and photoluminescence studies. Upon excitation with a UV-blue photon in the range of 350–485 nm, an intense near-infrared (NIR) emission at around 900–1100 nm has been obtained, which is assigned to the electronic transition F27/2→F25/2 of Yb3+ upon exploring the cooperative down conversion mechanism from Tb3+ to Yb3+. The dependence of Yb3+ doping concentration on the visible- and NIR-emissions, decay lifetime, and quantum efficiencies of the thin-films has been investigated. The optimal internal NIR quantum efficiency could be as high as 154.1%.
Temperature dependence of the thermal expansion of AlN
Authors: Figge Stephan , Kröncke Hanno , Hommel Detlef , Epelbaum Boris M.
Published: March 2009

The thermal expansion of wurtzite AlN bulk crystals grown by physical vapor transport was studied by high resolution x-ray diffraction in a temperature range from 20 to 1250 K. The temperature dependence of the derived anisotropic thermal expansion coefficients along the a- and c-directions could be well described over the entire temperature range within both the Debye model and the Einstein model. In comparison to GaN, larger expansion coefficients and higher characteristic temperatures have been found. The resulting thermal mismatch of AlGaN/GaN heterostructures are presented.
BiFeO
3
/
TiO
2
core-shell structured nanocomposites as visible-active photocatalysts and their optical response mechanism
Authors: Li Shun , Lin Yuan-Hua , Zhang Bo-Ping , Li Jing-Feng , Nan Ce-Wen
Published: March 2009

Anatase titania-coated bismuth ferrite nanocomposites (BiFeO3/TiO2) have been fabricated via a hydrothermal approach combined with a hydrolysis precipitation processing. Analysis of the microstructure and phase composition reveals that a core-shell BiFeO3/TiO2 structure can be formed, which results in a significant redshift in the UV-vis absorption spectra as compared to a simple mechanical mixture of BiFeO3–TiO2 nanopowders. The core-shell structured BiFeO3/TiO2 nanocomposites exhibit higher photocatalytic activity for photodegradation of Congo red under visible-light (λ>400 nm) irradiation, which should be attributed to the enhancement of the quantum efficiency by separating the electrons and holes effectively. The obtained BiFeO3/TiO2 nanocomposites can be used as potential visible-light driven photocatalysts.
ZnO-nanowires modified polypyrrole films as highly selective and sensitive chlorine sensors
Authors: Joshi Aditee , Aswal D. K. , Gupta S. K. , Yakhmi J. V. , Gangal S. A.
Published: March 2009

Room temperature sensing characteristics of the polypyrrole (PPy) films modified with different weight percentages of ZnO nanowires (ZnO-NWs) have been studied for various oxidizing (NO2 and Cl2) as well as reducing (H2S, NH3, CH4, and CO) gases. We demonstrate that ZnO-NW (50 wt %):PPy composite films are highly selective to Cl2 along with high-sensitivity (40 at 10 ppm), fast-response (55 s), and highly reproducible response curves. It has been shown that negatively charged O2− surfaces of ZnO-NW transfer electrons to PPy, making it in a highly reduced form. A strong localization of charge carriers in the reduced PPy makes composite film highly resistive (>1010 Ω cm) as well insensitive to interaction with most of the gases except Cl2. Cl2 being highly oxidizing gas interacts with composite films and causes a sharp reduction in its resistivity.
Shape transition in very large germanium islands on Si(111)
Authors: MacLeod J. M. , Lipton-Duffin J. A. , Lanke U. , Urquhart S. G. , Rosei F.
Published: March 2009

Ge islands with areas up to hundreds of μm2 were grown on Si(111). These islands, grown above 750 °C and at a deposition rate of 1 monolayer/min, become decreasingly compact with increasing size and can have nonuniform cross sections with heights reaching over 500 nm. The largest islands are ramified, often comprising multiple discrete parts. X-ray photoemission electron microscopy absorption maps show that the islands have a higher concentration of Ge at their centers, with more Si near the edges. We propose that the shape transformation is driven by strain relief at the island perimeters.
Optically pumped nanolaser based on two magnetic plasmon resonance modes
Authors: Zhu Z. H. , Liu H. , Wang S. M. , Li T. , Cao J. X. , Ye W. M. , Yuan X. D. , Zhu S. N.
Published: March 2009

We propose and analyze theoretically a double magnetic plasmon resonance nanolaser, in which ytterbium-erbium codoped material is used as the gain medium. Through design of the double magnetic resonance modes, pumping light (980 nm) can be resonantly absorbed and laser light (1550 nm) can be resonantly generated simultaneously. We introduce a set of rate equations combined to describe the operation of the laser and predict the lasing condition. According to our calculations, the disadvantage that pumping light is difficult to be absorbed by a thin slab of gain materials can be overcome.
Illumination-induced errors associated with suns-VOC measurements of silicon solar cells
Authors: Roth Thomas , Hohl-Ebinger Jochen , Grote Daniela , Schmich Evelyn , Warta Wilhelm , Glunz Stefan W. , Sinton Ronald A.
Published: March 2009

I SC - V OC curves measured by the suns-VOC method are widely used for solar cell characterization due to its being unaffected by series resistance effects. A common setup for this measurement system uses a xenon photoflash for illumination purposes, resulting in a fast acquisition of the suns-VOC measurement data during the decaying edge of one flash. However, the use of a xenon photoflash accompanies also several disadvantages. Measurement errors are expected from the imperfect illumination homogeneity on the measurement stage. Also the discrepancy of the flash spectrum compared to the standard AM 1.5G spectrum leads to spectral mismatch between the sample and monitor cells when their spectral response differs. In addition, the divergence of the flash light leads to different illumination densities on the sample and the monitor cell if the height of these two cells differs. In this article these photoflash-caused measurement errors are investigated in detail, analyzing the resulting deviation in illumination density. The error due to an inhomogeneous illumination is negligible under most circumstances, while the error due to a spectral mismatch has to be considered but can be reduced drastically if an additional short-pass filter is used. The measurement error due to different cell highs should be taken into account but can be accounted for using an analytical correction.
Tunable thermal hysteresis in MnFe(P,Ge) compounds
Authors: Trung N. T. , Ou Z. Q. , Gortenmulder T. J. , Tegus O. , Buschow K. H. J. , Brück E.
Published: March 2009

Structural, magnetic, and magnetocaloric properties of the MnFe(P,Ge) compounds were systematically studied on both bulk alloys and melt-spun ribbons. The experimental results show that the critical behavior of the phase transition can be controlled by changing either the compositions or the annealing conditions. The thermal hysteresis is found to be tunable. It can reach very small values, while maintaining a large magnetocaloric effect in a large range of working temperatures and under field changes that may be produced by conventional permanent magnets. Consequently, an effective way in producing ideal magnetic refrigerants for room-temperature applications is suggested.
Formation of x-ray vortex dipoles using a single diffraction pattern and direct phase measurement using interferometry
Authors: Kohmura Yoshiki , Sawada Kei , Taguchi Munetaka , Ishikawa Tetsuya , Ohigashi Takuji , Suzuki Yoshio
Published: March 2009

We have devised a method for generating x-ray vortices by using a diffraction pattern from a simple aperture with illumination wave fronts with spherical curvatures. The interferometry visualized the x-ray vortex dipoles by the direct phase measurement. Our interference technique enabled us to sensitively detect and quantitatively measure various phase dislocations on the x-ray wave fronts, providing useful methodologies for beam diagnostics and materials science.
Directional ion emission from thin films under femtosecond laser irradiation
Authors: Williams Gareth O. , Favre Sébastian , O’Connor Gerard M.
Published: March 2009

Thin films of nickel have been irradiated using femtosecond laser pulses in vacuum. Subsequent emission of plasma ions is diagnosed using an ion probe. Angular distributions of the emitted ions are presented for a range of target film thicknesses. Data are compared to the Anisimov model of plasma expansion [S. I. Anisimov, D. Bauerle, and B. S. Luk’yanchuk, Phys. Rev. B 48, 12076 (1993)]. The tendency of the ions to be ejected at small angles to the normal of the target surface is explained in terms of the initial conditions of the plume. Results are explained in terms of the initial shape and adiabatic index of the plasma.
Contributions to Hanle lineshapes in Fe/GaAs nonlocal spin valve transport
Authors: Awo-Affouda C. , van ’t Erve O. M. J. , Kioseoglou G. , Hanbicki A. T. , Holub M. , Li C. H. , Jonker B. T.
Published: March 2009

The transport Hanle effect is commonly used to determine spin lifetimes in spin-polarized transport structures. We show that the domain structure of ferromagnetic contacts used to inject and detect the spin current introduces asymmetries to the Hanle lineshape. In addition, the nuclear spin polarization can produce anomalous narrowing and broadening of the Hanle linewidth depending upon the orientation of the transport spin and the applied field. Neither effect is included in the analysis typically applied. We illustrate how these contributions can significantly impact the apparent spin lifetime extracted from the transport Hanle lineshape, and how they can be compensated for.
Unique nanostructures and enhanced thermoelectric performance of melt-spun BiSbTe alloys
Authors: Xie Wenjie , Tang Xinfeng , Yan Yonggao , Zhang Qingjie , Tritt Terry M.
Published: March 2009

We report a melt spinning technique followed by a quick spark plasma sintering procedure to fabricate high-performance p-type Bi0.52Sb1.48Te3 bulk material with unique microstructures. The microstructures consist of nanocrystalline domains embedded in amorphous matrix and 5–15 nm nanocrystals with coherent grain boundary. The significantly reduced thermal conductivity leads to a state-of-the-art dimensionless figure of merit ZT∼1.56 at 300 K, more than 50% improvement of that of the commercial Bi2Te3 ingot materials.
Photoluminescence enhancement by gold nanoparticles in Eu3+ doped GeO2–Bi2O3 glasses
Authors: Kassab Luciana R. P. , da Silva Diego S. , de Almeida Ricardo , de Araújo Cid B.
Published: March 2009

We report large photoluminescence (PL) enhancement in Eu3+-doped GeO2–Bi2O3 glasses containing gold nanoparticles (NPs). Growth of ≈1000% in the PL intensity corresponding to the Eu3+ transition D50→F72, at 614 nm, was observed in comparison with a reference sample that does not contain gold NPs. Other PL bands from 580 to 700 nm are also enhanced. The enhancement of the PL intensity is attributed to the increased local field in the Eu3+ locations due to the presence of the NPs and the energy transfer from the excited NPs to the Eu3+ ions.
Thermal conductivities and phase transition temperatures of various phase-change materials measured by the 3ω method
Authors: Risk W. P. , Rettner C. T. , Raoux S.
Published: March 2009

We have employed the “3ω method” to determine the thermal conductivities of the amorphous and crystalline phases of the technologically important materials Ge2Sb2Te5, nitrogen-doped Ge2Sb2Te5, Ag- and In-doped Sb2Te, and Ge15Sb85. We used the “3ω voltage” as a monitor of thermal conductivity that allowed us to observe the amorphous-to-crystalline phase transition as the material was annealed. For these materials, our results reveal that the thermal conductivity κ is related to the electrical conductivity σ by an empirical relationship of the form κ=σLT+0.175 W/m K, where L is the Lorenz number and T is temperature.
Microcavity top-emitting organic light-emitting devices integrated with diffusers for simultaneous enhancement of efficiencies and viewing characteristics
Authors: Liu Chih-Che , Liu Su-Hao , Tien Kun-Cheng , Hsu Min-Hung , Chang Hong-Wei , Chang Chih-Kai , Yang Chih-Jen , Wu Chung-Chih
Published: March 2009

We show that integrating diffuser films with microcavity top-emitting organic light-emitting devices (OLEDs) provide a convenient approach for simultaneously achieving large quantum- efficiency enhancement (1.38 times compared to top-emitting devices without diffusers and 2.1 times compared to conventional bottom-emitting devices) and improving viewing characteristics (more saturated/stable colors over angles, emission patterns more Lambertian, pixel sharpness remained) of top-emitting microcavity OLEDs for display applications. Most importantly, the fabrication of the diffuser films is simple and effective. These features may make it attractive for use in enhancing OLED performances in various applications.
Step-terraced morphology of GaAs(001) substrates prepared at quasiequilibrium conditions
Authors: Alperovich V. L. , Akhundov I. O. , Rudaya N. S. , Sheglov D. V. , Rodyakina E. E. , Latyshev A. V. , Terekhov A. S.
Published: March 2009

“Step and terrace” surface morphology with regular arrays of atomically flat terraces separated by monatomic steps was obtained by annealing GaAs(001) substrates in the conditions close to equilibrium. These conditions were realized under molecular hydrogen ambient in a narrow slit (“capillary”) between two adjacent GaAs substrates or in a graphite cassette containing saturated Ga–GaAs melt. The evolution of the step and terrace morphology was characterized by the length of monatomic steps, which was proved to be a more adequate characteristic of flattening process as compared to the root mean square roughness.
Magnetic properties of Mn-doped 6H-SiC
Authors: Song Bo , Bao Huiqiang , Li Hui , Lei Ming , Jian Jikang , Han Jiecai , Zhang Xinghong , Meng Songhe , Wang Wanyan , Chen Xiaolong
Published: March 2009

We report the synthesis and characterizations of low Mn-doped (<10−3 molar fraction) 6H-SiC. Raman scattering studies show an unusual shift in Raman peak with altering Mn contents. The magnetic properties measurement shows the typical ferromagnetic order was established at as low Mn-doped concentration as 10−4 molar fraction at around 250 K. It is speculated that the defects-related effects other than the Mn content play a more important role to determine the magnetic ordering.
Laser direct write printing of sensitive and robust light emitting organic molecules
Authors: Kattamis Nicholas T. , McDaniel Neal D. , Bernhard Stefan , Arnold Craig B.
Published: March 2009

We examine the effects of three laser direct-write (LDW) printing techniques on 9-anthracenemethanol and tris(8-hydroxyquinoline)aluminum (Alq3) organic luminophores in order to link the differences in transfer mechanism to the resulting material properties. Degradation can occur where laser light and elevated temperatures are transferred to the molecules, such as those printed via matrix-assisted or thin metal absorptive layer LDW. In contrast, thick film polyimide absorbing layer techniques eliminate damage in these sensitive materials by shielding them from excessive heat and laser illumination.
Si/SiC bonded wafer: A route to carbon free SiO2 on SiC
Authors: Pérez-Tomás A. , Lodzinski M. , Guy O. J. , Jennings M. R. , Placidi M. , Llobet J. , Gammon P. M. , Davis M. C. , Covington J. A. , Burrows S. E. , Mawby P. A.
Published: March 2009

This paper describes the thermal oxidation of Si/SiC heterojunction structures, produced using a layer-transfer process, as an alternative solution to fabricating SiC metal-oxide-semiconductor (MOS) devices with lower interface state densities (Dit). Physical characterization demonstrate that the transferred Si layer is relatively smooth, uniform, and essentially monocrystalline. The Si on SiC has been totally or partially thermally oxidized at 900–1150 °C. Dit for both partially and completely oxidized silicon layers on SiC were significantly lower than Dit values for MOS capacitors fabricated via conventional thermal oxidation of SiC. The quality of the SiO2, formed by oxidation of a wafer-bonded silicon layer reported here has the potential to realize a number of innovative heterojunction concepts and devices, including the fabrication of high quality and reliable SiO2 gate oxides.
Observations of ultraslow light-based photon logic gates: NAND/OR
Authors: Ham B. S. , Hahn J.
Published: March 2009

We report observations of photon logic gate operations using ultraslow light phenomena in a rare-earth doped solid medium. Unlike conventional optical logic gates based on semiconductor optical amplifiers, the present photon logic gate utilizes spin coherence, which is completely free from the optical population constraint and gives potential for ultrahigh speed operations. In addition to the possibility of ultralow power operations, the usage of ultraslow light gives a benefit of all-optical buffer memory functions. Thus, the present demonstration has potential applications to cascadable photon logic devices.
Polarization tunable selective polariton generator
Authors: Sedoglavich N. , Künnemeyer R. , Sharpe J. C.
Published: March 2009

A selective polariton generator (SPG) design, based on surface plasmon antennae principles, is demonstrated to provide a selective light transmission peak. The polarization-sensitive structure selectively generates and transports polaritons of a desired wavelength through a circular subwavelength aperture. By varying the SPG structure around a central nanohole, we are able to control the peak optical transmission wavelengths via the polarization state of the incident photons. We find good agreement between simulations and experimental results.
Utilization of phononic-crystal reflective gratings in a layered surface acoustic wave device
Authors: Wu Tsung-Tsong , Wang Wei-Shan , Sun Jia-Hong , Hsu Jin-Chen , Chen Yung-Yu
Published: March 2009

In this paper, a design that combines two-port surface acoustic wave (SAW) devices and phononic crystals (PCs) acting as reflected gratings is demonstrated. Finite-difference time-domain method is used to analyze SAWs encountering the PC and optimize the design. A layered ZnO/Si SAW device and a square lattice PC composing of cylindrical holes on silicon were fabricated. With the PC of 15-layer cylinders, experimental insertion loss shows a 7 dB improvement at 212 MHz at central frequency. In addition, the size of gratings is reduced significantly as compared to the traditional gratings with hundreds of metal strips.
Phenotypes and tolerances in the design space of biochemical systems
Authors: Savageau Michael A. , Coelho Pedro M. B. M. , Fasani Rick A. , Tolla Dean A. , Salvador Armindo
Published: March 2009

One of the major unsolved problems of modern biology is deep understanding of the complex relationship between the information encoded in the genome of an organism and the phenotypic properties manifested by that organism. Fundamental advances must be made before we can begin to approach the goal of predicting the phenotypic consequences of a given mutation or an organism's response to a novel environmental challenge. Although this problem is often portrayed as if the task were to find a more or less direct link between genotypic and phenotypic levels, on closer examination the relationship is far more layered and complex. Although there are some intuitive notions of what is meant by phenotype at the level of the organism, it is far from clear what this term means at the biochemical level. We have described design principles that are readily revealed by representation of molecular systems in an appropriate design space. Here, we first describe a generic approach to the construction of such a design space in which qualitatively distinct phenotypes can be identified and counted. Second, we show how the boundaries between these phenotypic regions provide a method of characterizing a system's tolerance to large changes in the values of its parameters. Third, we illustrate the approach for one of the most basic modules of biochemical networks and describe an associated design principle. Finally, we discuss the scaling of this approach to large systems.
Biochemical analyses of indole-3-acetaldoxime-dependent auxin biosynthesis in
Arabidopsis
Authors: Sugawara Satoko , Hishiyama Shojiro , Jikumaru Yusuke , Hanada Atsushi , Nishimura Takeshi , Koshiba Tomokazu , Zhao Yunde , Kamiya Yuji , Kasahara Hiroyuki
Published: March 2009

Auxins are hormones that regulate many aspects of plant growth and development. The main plant auxin is indole-3-acetic acid (IAA), whose biosynthetic pathway is not fully understood. Indole-3-acetaldoxime (IAOx) has been proposed to be a key intermediate in the synthesis of IAA and several other indolic compounds. Genetic studies of IAA biosynthesis in
Arabidopsis
have suggested that 2 distinct pathways involving the
CYP79B
or
YUCCA
(
YUC
) genes may contribute to IAOx synthesis and that several pathways are also involved in the conversion of IAOx to IAA. Here we report the biochemical dissection of IAOx biosynthesis and metabolism in plants by analyzing IAA biosynthesis intermediates. We demonstrated that the majority of IAOx is produced by
CYP79B
genes in
Arabidopsis
because IAOx production was abolished in
CYP79B
-deficient mutants. IAOx was not detected from rice, maize, and tobacco, which do not have apparent
CYP79B
orthologues. IAOx levels were not significantly altered in the
yuc1 yuc2 yuc4 yuc6
quadruple mutants, suggesting that the
YUC
gene family probably does not contribute to IAOx synthesis. We determined the pathway for conversion of IAOx to IAA by identifying 2 likely intermediates, indole-3-acetamide (IAM) and indole-3-acetonitrile (IAN), in
Arabidopsis
. When
13
C
6
-labeled IAOx was fed to
CYP79B
-deficient mutants,
13
C
6
atoms were efficiently incorporated to IAM, IAN, and IAA. This biochemical evidence indicates that IAOx-dependent IAA biosynthesis, which involves IAM and IAN as intermediates, is not a common but a species-specific pathway in plants; thus IAA biosynthesis may differ among plant species.
An embryonic stem cell chromatin remodeling complex, esBAF, is essential for embryonic stem cell self-renewal and pluripotency
Authors: Ho Lena , Ronan Jehnna L. , Wu Jiang , Staahl Brett T. , Chen Lei , Kuo Ann , Lessard Julie , Nesvizhskii Alexey I. , Ranish Jeff , Crabtree Gerald R.
Published: March 2009

Mammalian SWI/SNF [also called BAF (Brg/Brahma-associated factors)] ATP-dependent chromatin remodeling complexes are essential for formation of the totipotent and pluripotent cells of the early embryo. In addition, subunits of this complex have been recovered in screens for genes required for nuclear reprogramming in
Xenopus
and mouse embryonic stem cell (ES) morphology. However, the mechanism underlying the roles of these complexes is unclear. Here, we show that BAF complexes are required for the self-renewal and pluripotency of mouse ES cells but not for the proliferation of fibroblasts or other cells. Proteomic studies reveal that ES cells express distinctive complexes (esBAF) defined by the presence of Brg (Brahma-related gene), BAF155, and BAF60A, and the absence of Brm (Brahma), BAF170, and BAF60C. We show that this specialized subunit composition is required for ES cell maintenance and pluripotency. Our proteomic analysis also reveals that esBAF complexes interact directly with key regulators of pluripotency, suggesting that esBAF complexes are specialized to interact with ES cell-specific regulators, providing a potential explanation for the requirement of BAF complexes in pluripotency.
TNF/iNOS-producing dendritic cells are the necessary evil of lethal influenza virus infection
Authors: Aldridge Jerry R. , Moseley Carson E. , Boltz David A. , Negovetich Nicholas J. , Reynolds Cory , Franks John , Brown Scott A. , Doherty Peter C. , Webster Robert G. , Thomas Paul G.
Published: March 2009

Respiratory infection with highly pathogenic influenza A viruses is characterized by the exuberant production of cytokines and chemokines and the enhanced recruitment of innate inflammatory cells. Here, we show that challenging mice with virulent influenza A viruses, including currently circulating H5N1 strains, causes the increased selective accumulation of a particular dendritic cell subset, the tipDCs, in the pneumonic airways. These tipDCs are required for the further proliferation of influenza-specific CD8+T cells in the infected lung, because blocking their recruitment in CCR2−/−mice decreases the numbers of CD8+effectors and ultimately compromises virus clearance. However, diminution rather than total elimination of tipDC trafficking by treatment with the peroxisome proliferator-activated receptor-γ agonist pioglitazone moderates the potentially lethal consequences of excessive tipDC recruitment without abrogating CD8+T cell expansion or compromising virus control. Targeting the tipDCs in this way thus offers possibilities for therapeutic intervention in the face of a catastrophic pandemic.
National Depression Screening Day: An Undergraduate Practicum Experience
Authors: Kay Theresa S. , Rangel Dianna K.
Published: March 2009

Several authors have described the many benefits of undergraduate practica, how to organize an undergraduate practicum experience, and different undergraduate practicum activities. This article provides a description of the process of organizing and implementing National Depression Screening Day at a university campus as an undergraduate practicum activity.
Paying it Forward as a Teacher-Mentor: An Interview with Bill Hill
Authors: Noble Linda M.
Published: March 2009

Bill Hill received his PhD from the University of Georgia in 1979 and has been on the faculty at Kennesaw State University (KSU) ever since. He is currently director of the KSU Center for Excellence in Teaching and Learning. His professional activities and research revolve around faculty development. In 1989, he founded, and continues to coordinate, the annual Southeastern Conference on the Teaching of Psychology. He has held leadership roles in the Society for the Teaching of Psychology, serving as president (2001–2002) and director of programming (2004–2008); he also coordinated the annual “best practices” in teaching psychology conference from 2002 to 2008. He received the 1985 KSU Distinguished Teaching Award and the 2004 American Psychological Foundation Charles L. Brewer Distinguished Teaching Award. Bill is a Fellow of Divisions 1, 2, and 52 in the American Psychological Association.

Linda Noble completed her PhD at the University of Georgia in 1985 and began her career at KSU the same year. She served as chair of the Psychology Department, dean of the College of Humanities and Social Sciences, and associate director of the Center for Excellence in Teaching and Learning. She has held several leadership positions in the Society for the Teaching of Psychology, including president (2003) and editor of the Methods and Techniques section of Teaching of Psychology. She is now serving as the assistant vice chancellor for Faculty Affairs at the Board of Regents of the University System of Georgia, where she oversees faculty policies and procedures at all 35 state institutions and coordinates systemwide faculty development events.
The Power of Situations: Jonestown and the Fundamental Attribution Error
Authors: Riggio Heidi R. , Garcia Amber L.
Published: March 2009

The fundamental attribution error (FAE) is the tendency to overestimate dispositional and underestimate situational causes for others' behavior (Ross, 1977). Undergraduate students ( N = 155) explained the causes of a person's “bad day.” The experimental group completed responses after viewing a documentary on Jonestown and discussing situational factors in that environment; 3 other groups completed responses after a research methods lecture (control) or lectures on the FAE. Participants exposed to the film made significantly fewer dispositional and more situational attributions in explaining the target's bad day compared to control participants and more situational attributions compared to lecture participants. We discuss implications for teaching psychological principles using real-life events.
APA's Learning Objectives for Research Methods and Statistics in Practice: A Multimethod Analysis
Authors: Tomcho Thomas J. , Rice Diana , Foels Rob , Folmsbee Leah , Vladescu Jason , Lissman Rachel , Matulewicz Ryan , Bopp Kara
Published: March 2009

Research methods and statistics courses constitute a core undergraduate psychology requirement. We analyzed course syllabi and faculty self-reported coverage of both research methods and statistics course learning objectives to assess the concordance with APA's learning objectives (American Psychological Association, 2007). We obtained a sample of 64 research methods and 56 statistics syllabi (return rates: 16%, 14%) from 400 randomly selected psychology departments in colleges and universities in the United States. Course syllabi generally contained appropriate research methods and statistics content. However, certain APA learning objectives consistently were absent from course syllabi, and we found discrepancies between listed objectives and faculty self-reports of topics covered.
Incorporating Active Learning with PowerPoint-Based Lectures Using Content-Based Questions
Authors: Gier Vicki S. , Kreiner David S.
Published: March 2009

Instructors often use Microsoft PowerPoint lectures and handouts as support tools to provide students with the main concepts of the lectures. Some instructors and researchers believe that PowerPoint encourages student passivity. We conducted 2 studies to determine whether the use of content-based questions (CBQs) would enhance learning when combined with traditional PowerPoint lectures. Our results indicated significantly higher quiz scores and exam scores when students used CBQs in comparison to using only the traditional PowerPoint lecture and handouts. The results suggest that it is possible to incorporate effective active learning methods into PowerPoint-based lectures.