bluuebunny/crossref_metadata_2025 huggingface dataset:
AR-C155858 is a potent inhibitor of monocarboxylate transporters MCT1 and MCT2 that binds to an intracellular site involving transmembrane helices 7–10
Authors: Ovens Matthew J. , Davies Andrew J. , Wilson Marieangela C. , Murray Clare M. , Halestrap Andrew P.
Published: November 2009

In the present study we characterize the properties of the potent MCT1 (monocarboxylate transporter 1) inhibitor AR-C155858. Inhibitor titrations of L-lactate transport by MCT1 in rat erythrocytes were used to determine the Ki value and number of AR-C155858-binding sites (Et) on MCT1 and the turnover number of the transporter (kcat). Derived values were 2.3±1.4 nM, 1.29±0.09 nmol per ml of packed cells and 12.2±1.1 s−1 respectively. When expressed in Xenopus laevis oocytes, MCT1 and MCT2 were potently inhibited by AR-C155858, whereas MCT4 was not. Inhibition of MCT1 was shown to be time-dependent, and the compound was also active when microinjected, suggesting that AR-C155858 probably enters the cell before binding to an intracellular site on MCT1. Measurement of the inhibitor sensitivity of several chimaeric transporters combining different domains of MCT1 and MCT4 revealed that the binding site for AR-C155858 is contained within the C-terminal half of MCT1, and involves TM (transmembrane) domains 7–10. This is consistent with previous data identifying Phe360 (in TM10) and Asp302 plus Arg306 (TM8) as key residues in substrate binding and translocation by MCT1. Measurement of the Km values of the chimaeras for L-lactate and pyruvate demonstrate that both the C- and N-terminal halves of the molecule influence transport kinetics consistent with our proposed molecular model of MCT1 and its translocation mechanism that requires Lys38 in TM1 in addition to Asp302 and Arg306 in TM8 [Wilson, Meredith, Bunnun, Sessions and Halestrap (2009) J. Biol. Chem. 284, 20011–20021].
Evaluation of the in vitro cytotoxicity of the antimicrobial peptide P34
Authors: Vaucher Rodrigo Almeida , De da Motta Souza Amanda , Brandelli Adriano
Published: November 2009

The in vitro cytotoxicity of the antimicrobial peptide P34 was evaluated in different eukaryotic cells. The food‐grade bacteriocin nisin was also analysed for comparison. Vero cells were treated with different concentrations (0.02–2.5 μg·ml−1) of antimicrobial peptide P34 and nisin. Cell viability and plasma membrane integrity were checked by MTT [3‐(4,5‐dimethylthiazole‐2‐yl)‐2,5‐diphenyltetrazolium bromide], NRU (Neutral Red dye uptake) and LDH (lactate dehydrogenase) assays. The EC50 values of the peptide P34 in MTT and NRU assays were 0.60 and 1.25 μg·ml−1 respectively, while values of nisin found were 0.50 and 1.04 μg·ml−1. In the LDH assay, the EC50 values were 0.65 and 0.62 μg·ml−1 for P34 and nisin, respectively. The peptide P34 revealed similar haemolytic activity on human erythrocytes (5.8%) when compared with nisin (4.9%). The effects on viability, motility and acrosomal exocytosis of human sperm were also evaluated. Nisin and P34 showed similar effects on sperm parameters. The evaluation of cytotoxicity of antimicrobial peptides is a critical step to guarantee their safe use.
Insulin resistance and hyperinsulinaemia in the development and progression of cancer
Authors: Godsland Ian F.
Published: November 2009

Experimental, epidemiological and clinical evidence implicates insulin resistance and its accompanying hyperinsulinaemia in the development of cancer, but the relative importance of these disturbances in cancer remains unclear. There are, however, theoretical mechanisms by which hyperinsulinaemia could amplify such growth-promoting effects as insulin may have, as well as the growth-promoting effects of other, more potent, growth factors. Hyperinsulinaemia may also induce other changes, particularly in the IGF (insulin-like growth factor) system, that could promote cell proliferation and survival. Several factors can independently modify both cancer risk and insulin resistance, including subclinical inflammation and obesity. The possibility that some of the effects of hyperinsulinaemia might then augment pro-carcinogenic changes associated with disturbances in these factors emphasizes how, rather than being a single causative factor, insulin resistance may be most usefully viewed as one strand in a network of interacting disturbances that promote the development and progression of cancer.
Tourism Relationship Model and Intermediary for Sustainable Tourism Management: Case Study of the Kiritappu Wetland Trust in Hamanaka, Hokkaido
Authors: Shikida Asami , Yoda Mami , Kino Akiko , Morishige Masayuki
Published: November 2009

This article proposes a simple model that depicts the relationship between community and extra-community stakeholders that will enable the effective development of sustainable tourism. ‘Sustainable tourism’ in this article is defined as tourism that utilizes community resources for tourism development and re-invests the returns from tourism to the destination resources based on the previous studies. The tourism relationship model, with a community-based intermediary as its sub-system, is introduced and applied to a case in Hokkaido, Japan. The application demonstrates that the model is a valid tool to identify two important factors for successful development of sustainable tourism, which are a ‘circulation mechanism’ that connects community resources and extra-community stakeholders through community-based intermediaries, and a ‘balancing mechanism’ that considers the existence value and economic value, supplemented by the community-based intermediary's functions to transfer financial capital from non-tourist sources.
Atomistic analysis of strain relaxation in [11¯]-oriented biaxially strained ultrathin copper films
Authors: Kolluri Kedarnath , Gungor M. Rauf , Maroudas Dimitrios
Published: November 2009

Results are reported of a systematic atomic-scale computational analysis of strain relaxation mechanisms and the associated defect dynamics in nanometer-scale thin or ultrathin Cu films that are subjected to a broad range of biaxial tensile strains. The films contain pre-existing voids and the film planes are oriented normal to the [11¯0] crystallographic direction. The analysis is based on isothermal-isostrain molecular-dynamics simulations according to an embedded-atom-method parameterization for Cu and employing multimillion-atom slab supercells. In addition to an initial elastic response for an applied biaxial strain level ε<2%, our analysis reveals three regimes in the thin-film mechanical response as ε increases. For 2%≤ε≤6%, biaxial strain relaxation is dominated by emission and propagation of dislocations (plastic flow) from the surface of the void accompanied by ductile void growth. For 6%<ε<10%, the biaxial strain in the thin film is relaxed by both ductile void growth and emission of dislocations from the surfaces of the thin film. For ε≥10%, strain relaxation is dominated by dislocation emission from the surfaces of the thin film, leading to a structural transformation from the face-centered cubic to a hexagonal close-packed phase. The defect nucleation mechanisms and the high-strain response of the thin films are found to be significantly different from those observed in ⟨111⟩-oriented Cu thin films [M. R. Gungor and D. Maroudas, J. Appl. Phys. 97, 113527 (2005); M. R. Gungor and D. Maroudas, Appl. Phys. Lett. 87, 171913 (2005)].
Ultrafast pulsed-laser dissociation of Mn–H complexes in GaAs
Authors: Farshchi R. , Hwang D. J. , Chopdekar R. V. , Ashby P. D. , Grigoropoulos C. P. , Dubon O. D.
Published: November 2009

We demonstrate direct writing of ferromagnetism in hydrogenated Ga0.96Mn0.04As using femtosecond laser pulses. Tight beam focusing results in the local dissociation of Mn–H defect complexes with sub-500 nm resolution and no detected surface damage. Dot, line, and Hall-bar patterns were drawn in the hydrogenated films by translating the sample during laser irradiation. Magnetotransport measurements on the Hall-bar patterns reveal recovery of hole-mediated ferromagnetism with a Curie temperature of 50 K while magnetic anisotropy is similar to prehydrogenated Ga0.96Mn0.04As. Interruption of the laser beam during writing leads to the formation of a paramagnetic gap with controllable conductance separating two ferromagnetic line segments. These features, along with the laser tunability of magnetic and electrical properties in the activated regions, represent a planar approach to defining all-semiconductor spintronic structures for device applications.
Enhanced mass transport in ultrarapidly heated Ni/Si thin-film multilayers
Authors: Cook L. P. , Cavicchi R. E. , Bassim N. , Eustis S. , Wong-Ng W. , Levin I. , Kattner U. R. , Campbell C. E. , Montgomery C. B. , Egelhoff W. F. , Vaudin M. D.
Published: November 2009

We investigated multilayer and bilayer Ni/Si thin films by nanodifferential scanning calorimetry (nano-DSC) at ultrarapid scan rates, in a temperature-time regime not accessible with conventional apparatus. DSC experiments were completed at slower scan rates as well, where it was possible to conduct parallel rapid thermal annealing experiments for comparison. Postexperimental characterization was accomplished by x-ray diffraction, and by transmission electron microscopy (TEM) and energy-filtered TEM of thin cross sections prepared by focused ion beam milling. We found that rate of heating has a profound effect on the resulting microstructure, as well as on the DSC signal. After heating to 560 °C at 120 °C/s, the general microstructure of the multilayer was preserved, in spite of extensive interdiffusion of Ni and Si. By contrast, after heating to 560 °C at 16 000 °C/s, the multilayer films were completely homogeneous with no evidence of the original multilayer microstructure. For the slower scan rates, we interpret the results as indicating a solid state diffusion-nucleation-growth process. At the higher scan rates, we suggest that the temperature increased so rapidly that a metastable liquid was first formed, resulting in complete intermixing of the multilayer, followed by crystallization to form solid phases. The integrated DSC enthalpies for both multilayer and bilayer films are consistent with this interpretation, which is further supported by thermodynamic predictions of metastable Ni/Si melting and solid state Ni/Si interdiffusion. Our results suggest that use of heating rates >10 000 °C/s may open new avenues for intermetallic micro- and nanofabrication, at temperatures well below those prevailing during explosive silicidation.
Evidence of atomic-scale arsenic clustering in highly doped silicon
Authors: Duguay S. , Vurpillot F. , Philippe T. , Cadel E. , Lardé R. , Deconihout B. , Servanton G. , Pantel R.
Published: November 2009

Low temperature (675 °C) epitaxial in situ doped Si layers (As, 1.5 at. %) were analyzed by atom probe tomography (APT) to study clustering in a highly arsenic-doped silicon layer. The spatial distribution of As atoms in this layer was obtained by APT, and the distance distribution between first nearest neighbors between As atoms was studied. The result shows that the distribution of As atoms is nonhomogeneous, indicating clustering. Those clusters, homogeneously distributed in the volume, are found to be very small (a few atoms) with a high number density and contain more than 60% of the total number of As atoms.
Surface functionalized Ba0.6Sr0.4TiO3 /poly(vinylidene fluoride) nanocomposites with significantly enhanced dielectric properties
Authors: Li Kecheng , Wang Hong , Xiang Feng , Liu Weihong , Yang Haibo
Published: November 2009

A nanocomposite was prepared by embedding Ba0.6Sr0.4TiO3 (BST)/silver core/shell nanoparticles (BST@Ag) into polyvinylidene-fluoride (PVDF). Through functionalizing the surface of BST nanoparticles by silver coating, the relative permittivity of composites was significantly increased to 153 at 100 Hz which is 73% higher than that of the composite making of untreated BST nanoparticals. The loss tangent was still low (less than 0.2) when the filler content of BST@Ag was 0.55. Increasing the conductivity of the interlayer between BST and PVDF by silver enhances the space charge polarization and forms a nanocapacitance network through the interparticle junctions connecting the electrodes of sample.
Solution-processed conjugated polymer organic p-i-n light-emitting diodes with high built-in potential by solution- and solid-state doping
Authors: Sivaramakrishnan Sankaran , Zhou Mi , Kumar Aravind C. , Chen Zhi-Li , Png Rui-Qi , Chua Lay-Lay , Ho Peter K. H.
Published: November 2009

Polymer p-i-n homojunction light-emitting diodes (LEDs) comprising p-doped poly(dioctylfluorene-alt-benzothiadiazole) (F8BT) hole-injection, intrinsic F8BT emitter, and n-doped F8BT electron-injection layers have been demonstrated. A thin F8BT film was photocrosslinked and bulk p-doped by nitronium oxidation, then overcoated with an F8BT layer which was then surface n-doped by contact printing with naphthalenide on an elastomeric stamp. These LEDs exhibit high built-in potential (Vbi=2.2 V), efficient bipolar injection, and greatly improved external electroluminescence efficiency compared to control devices without the p-i-n structure. A modulated photocurrent technique was used to measure this Vbi, which systematically improves with diode structure.
Real-time ellipsometric modeling and characterization of the evolution of nanometer-scale Ge islands and pits in Ge homoepitaxy
Authors: Akazawa Housei
Published: November 2009

Nanometer-scale Ge islands and pits are self-organized during GeH4 vacuum-ultraviolet-excited chemical vapor deposition on a Ge(001) substrate. We carried out simulation and fitting on real-time ellipsometric Ψ−Δ trajectories that reflect undergoing changes in the surface morphology. The islanded Ge epitaxial layer was optically represented by multiple stacked slabs with linearly varying graded indices from the bottom to the top of the islands. The dielectric function of each slab was calculated by mixing the dielectric functions of Ge with that of voids under Bruggeman effective medium approximation. The only model that could reproduce the roughening Ψ−Δ trajectory was preferential nucleation of Ge on the top surface of truncated pyramidal islands after almost 100% of the initial surface had been wet. The smoothing section was consistent with the model assuming nucleation on the sidewalls of islands as well as on the top surface, which led to simultaneous deepening and narrowing of the valleys or pits between the islands. This smoothing model was supported by atomic force microscopy images.
Electron paramagnetic resonance characterization of defects in monoclinic HfO2 and ZrO2 powders
Authors: Wright Sandra , Barklie R. C.
Published: November 2009

Electron paramagnetic resonance (EPR) measurements have been made at X-band and room temperature on monoclinic HfO2 and ZrO2 powders from several suppliers. They reveal the presence of eight main paramagnetic centers H1, H2, H3, H4, and Z1, Z2, Z3, and Z4. H1 and Z1 are analogous as H4 and Z4 and H2 and Z2 are similar as H3 and Z3. H1 and Z1 have axial symmetry with g∥<g⊥<ge, where ge is the free electron g value. H1 is found in all, and Z1 in all but one, of the samples in their as-received state but with a wide range of concentrations. However, annealing the samples in air up to 900 °C reduces the volume concentration range and the areal concentrations all become of order 1011 cm−2. Irradiation with γ-rays does not affect their concentration. The Z1 centers are found to be the same as those previously observed in ZrO2 powders that were attributed to Zr3+ ions in coordinatively unsaturated (cus) sites at and/or near the surface. Our results are consistent with this model for Z1 and with an analogous model of cus Hf3+ for H1. H4 and Z4 are centers of isotropic symmetry with g values that are both within ±0.0004 of 2.0027; they are produced in all HfO2 and ZrO2 samples, respectively, that are heated in vacuum at ≥300 °C. Their concentration reaches a maximum of order 1017 cm−3 or 1012 cm−2 in the range of 550–750 °C. They are also most likely to be mainly at and/or near the surface and to involve an electron trapped in an oxygen vacancy cluster. The EPR spectra of H2 and Z2 are consistent with those of S=1/2 centers of orthorhombic symmetry with principal g values about equal to or just less than ge suggesting that they are trapped electron centers. The electrons produced by γ-irradiation are trapped at precursors to H2 but are easily detrapped. Z2 centers also appear to be shallow electron traps. Their identity is uncertain; they have some characteristics of electrons trapped in oxygen vacancies and of CO2− radicals. H3 and Z3 are likely to involve holes trapped on oxygen, possibly as O− and O2− type centers, respectively, but their location in not known. Their concentration increases to an upper limit as the γ-ray dose is increased and this shows that their precursors are trapping charge generated by the γ-rays. Like the H2 and Z2 centers, even annealing at 100 °C releases the charge but their precursors, at least in HfO2, are not destroyed. The significance of these centers is discussed.
Radical oxidation of germanium for interface gate dielectric GeO2 formation in metal-insulator-semiconductor gate stack
Authors: Kobayashi Masaharu , Thareja Gaurav , Ishibashi Masato , Sun Yun , Griffin Peter , McVittie Jim , Pianetta Piero , Saraswat Krishna , Nishi Yoshio
Published: November 2009

GeO 2 was grown by a slot-plane-antenna (SPA) high density radical oxidation, and the oxidation kinetics of radical oxidation GeO2 was examined. By the SPA radical oxidation, no substrate orientation dependence of growth rate attributed to highly reactive oxygen radicals with low oxidation activation energy was demonstrated, which is highly beneficial to three-dimensional structure devices, such as multigate field-effect transistors, to form conformal gate dielectrics. The electrical properties of an aluminum oxide (Al2O3) metal-oxide-semiconductor gate stack with a GeO2 interfacial layer were investigated, showing very low interface state density (Dit), 1.4×1011 cm−2 eV−1. By synchrotron radiation photoemission spectroscopy, the conduction and the valence band offsets of GeO2 with respect to Ge were estimated to be 1.2±0.3 and 3.6±0.1 eV, which are sufficiently high to suppress gate leakage.
Optical transitions of positively charged excitons and biexcitons in single InAs quantum dots
Authors: Chang X. Y. , Dou X. M. , Sun B. Q. , Xiong Y. H. , Niu Z. C. , Ni H. Q. , Jiang D. S.
Published: November 2009

We investigate fine structures observed in the optical transitions of positively charged excitons and biexcitons in single quantum dots. We show that double charged biexciton XX2+ emits into a hot double charged exciton X2+∗ at first, and then relaxes into charged excitons X2+ or X+ states via phonon scattering or Auger process respectively. XX2+ gives rise to two elliptically polarized emission lines due to the mixing of two lower-levels in the final state. X2+ causes two optical transitions with different polarizations, i.e., a linearly polarized emission with a fine structure splitting of 45 μeV and a circularly polarized emission with twofold degeneracy.
Modeling of atmospheric-pressure anodic carbon arc producing carbon nanotubes
Authors: Keidar M. , Beilis I. I.
Published: November 2009

Global model of atmospheric-pressure anodic arc in helium is developed. This type of discharge is currently used for efficient synthesis of various carbon nanostructures including carbon nanotubes. The model features include coupling between interelectrode plasma and electrodes, current continuity at electrodes, thermal regime of electrodes, and anode erosion. It is taken into account that arc radius increases linearly with the arc current according to experimental observation. Results indicate that substantial fraction of the current at the cathode is conducted by ions (0.7–0.9 of the total current). Calculated anode erosion rate and nonmonotonic voltage-current characteristic of the arc predicted by the model are in agreement with experimental data. It is concluded that nonmonotonic behavior of the arc voltage can be only reproduced by considering experimentally observed dependence of the arc radius on arc current.
A short pulse (7 μs FWHM) and high repetition rate (dc-5kHz) cantilever piezovalve for pulsed atomic and molecular beams
Authors: Irimia Daniel , Dobrikov Dimitar , Kortekaas Rob , Voet Han , van den Ende Daan A. , Groen Wilhelm A. , Janssen Maurice H. M.
Published: November 2009

In this paper we report on the design and operation of a novel piezovalve for the production of short pulsed atomic or molecular beams. The high speed valve operates on the principle of a cantilever piezo. The only moving part, besides the cantilever piezo itself, is a very small O-ring that forms the vacuum seal. The valve can operate continuous (dc) and in pulsed mode with the same drive electronics. Pulsed operation has been tested at repetition frequencies up to 5 kHz. The static deflection of the cantilever, as mounted in the valve body, was measured as a function of driving field strength with a confocal microscope. The deflection and high speed dynamical response of the cantilever can be easily changed and optimized for a particular nozzle diameter or repetition rate by a simple adjustment of the free cantilever length. Pulsed molecular beams with a full width at half maximum pulse width as low as 7 μs have been measured at a position 10 cm downstream of the nozzle exit. This represents a gas pulse with a length of only 10 mm making it well matched to for instance experiments using laser beams. Such a short pulse with 6 bar backing pressure behind a 150 μm nozzle releases about 1016 particles/pulse and the beam brightness was estimated to be 4×1022 particles/(s str). The short pulses of the cantilever piezovalve result in a much reduced gas load in the vacuum system. We demonstrate operation of the pulsed valve with skimmer in a single vacuum chamber pumped by a 520 l/s turbomolecular pump maintaining a pressure of 5×10−6 Torr, which is an excellent vacuum to have the strong and cold skimmed molecular beam interact with laser beams only 10 cm downstream of the nozzle to do velocity map slice imaging with a microchannel-plate imaging detector in a single chamber. The piezovalve produces cold and narrow (Δv/v=2%–3%) velocity distributions of molecules seeded in helium or neon at modest backing pressures of only 6 bar. The low gas load of the cantilever valve makes it possible to design very compact single chamber molecular beam machines with high quality cold and intense supersonic beams. The high speed cantilever piezovalve may find broad applicability in experiments where short and strong gas pulses are needed with only modest pumping, the effective use of (expensive) samples, or the production of cold atomic and molecular beams.
Binary rototranslational hyper-Rayleigh spectra of H2–He gas mixture
Authors: Godet J.-L. , Bancewicz T. , Głaz W. , Maroulis G. , Haskopoulos A.
Published: November 2009

The collision-induced rototranslational hyper-Rayleigh spectra of gaseous H2–He mixture are computed and discussed in the binary regime. As the input data we use our ab initio computed H2–He collision-induced first dipole hyperpolarizability tensor Δβ(R). Both the vector and the septor part of the H2–He hyper-Rayleigh spectra are evaluated at room temperature (T=295 K). The spectra are calculated assuming the full quantum computations based on the Schrödinger equation of the relative translational motion in the isotropic H2–He potential as well as using semiclassical methods.
Near-field evidence of local polarized emission centers in InGaN/GaN materials
Authors: Micheletto Ruggero , Allegrini Maria , Kawakami Yoichi
Published: November 2009

We study the optical polarization properties of confined structures in InGaN/GaN single quantum well devices. Using a near-field optical setup we investigated the photoluminescence maps with a polarization-modulation method. If the optical emissions have a preferred polarization orientation, our apparatus yields a signal that is proportional to the degree of polarization. We could demonstrate that within the quantum well there are localized submicrometer centers that emit strongly oriented light. This points toward the existence of quantum-dot like confined asymmetric domains hidden within the quantum well.
Extrapolating MP2 and CCSD explicitly correlated correlation energies to the complete basis set limit with first and second row correlation consistent basis sets
Authors: Hill J. Grant , Peterson Kirk A. , Knizia Gerald , Werner Hans-Joachim
Published: November 2009

Accurate extrapolation to the complete basis set (CBS) limit of valence correlation energies calculated with explicitly correlated MP2-F12 and CCSD(T)-F12b methods have been investigated using a Schwenke-style approach for molecules containing both first and second row atoms. Extrapolation coefficients that are optimal for molecular systems containing first row elements differ from those optimized for second row analogs, hence values optimized for a combined set of first and second row systems are also presented. The new coefficients are shown to produce excellent results in both Schwenke-style and equivalent power-law-based two-point CBS extrapolations, with the MP2-F12/cc-pV(D,T)Z-F12 extrapolations producing an average error of just 0.17 mEh with a maximum error of 0.49 for a collection of 23 small molecules. The use of larger basis sets, i.e., cc-pV(T,Q)Z-F12 and aug-cc-pV(Q,5)Z, in extrapolations of the MP2-F12 correlation energy leads to average errors that are smaller than the degree of confidence in the reference data (∼0.1 mEh). The latter were obtained through use of very large basis sets in MP2-F12 calculations on small molecules containing both first and second row elements. CBS limits obtained from optimized coefficients for conventional MP2 are only comparable to the accuracy of the MP2-F12/cc-pV(D,T)Z-F12 extrapolation when the aug-cc-pV(5+d)Z and aug-cc-pV(6+d)Z basis sets are used. The CCSD(T)-F12b correlation energy is extrapolated as two distinct parts: CCSD-F12b and (T). While the CCSD-F12b extrapolations with smaller basis sets are statistically less accurate than those of the MP2-F12 correlation energies, this is presumably due to the slower basis set convergence of the CCSD-F12b method compared to MP2-F12. The use of larger basis sets in the CCSD-F12b extrapolations produces correlation energies with accuracies exceeding the confidence in the reference data (also obtained in large basis set F12 calculations). It is demonstrated that the use of the 3C(D) Ansatz is preferred for MP2-F12 CBS extrapolations. Optimal values of the geminal Slater exponent are presented for the diagonal, fixed amplitude Ansatz in MP2-F12 calculations, and these are also recommended for CCSD-F12b calculations.
Effects of combined current injection and laser irradiation on Permalloy microwire switching
Authors: Franken J. H. , Möhrke P. , Kläui M. , Rhensius J. , Heyderman L. J. , Thiele J.-U. , Swagten H. J. M. , Gibson U. J. , Rüdiger U.
Published: November 2009

Combined field- and current-induced domain wall (DW) motion in Permalloy microwires is studied using fast magneto-optical Kerr-microscopy. On increasing the current density, we find a decrease of Kerr signal contrast, corresponding to a reduction in the magnetization, which is attributed to Joule heating of the sample. Resistance measurements on samples with varying substrates confirm that the Curie temperature is reached when the magneto-optical contrast vanishes and reveal the importance of the heat flow into the substrate. By tuning the laser power, DWs can be pinned in the laser spot, which can thus act as a flexible pinning site for DW devices.
Interfacial layer dependence on device property of high-κ TiLaO Ge/Si N-type metal-oxide-semiconductor capacitors at small equivalent-oxide thickness
Authors: Chen W. B. , Chin Albert
Published: November 2009

We have investigated the device property dependence of high dielectric-constant (high-κ) TiLaO epitaxial-Ge/Si n-type metal-oxide-semiconductor (n-MOS) capacitors on different GeO2 and SiO2 interfacial layers. Large capacitance density of 3.3 μF/cm2, small equivalent-oxide thickness (EOT) of 0.81 nm and small C-V hysteresis of 19 mV are obtained simultaneously for MOS capacitor using ultrathin SiO2 interfacial layer, while the device with ultrathin interfacial GeO2 shows inferior performance of larger 1.1 nm EOT and poor C-V hysteresis of 93 mV. From cross-sectional transmission electron microscopy, secondary ion mass spectroscopy, and x-ray photoelectron spectroscopy analysis, the degraded device performance using GeO2 interfacial layer is due to the severe Ge outdiffusion, thinned interfacial GeO2 and thicker gate dielectric after 550 °C rapid-thermal anneal.
Semiclassical electron correlation operator
Authors: Rassolov Vitaly A.
Published: November 2009

The concept of the correlation operator, introduced 10 years ago as a possible method to model the electron correlation effects with single determinant wave functions [Rassolov, J. Chem. Phys. 110, 3672 (1999)], is revisited. We derive a semiclassical limit of the correlation operator in weakly correlated systems and give its coordinate space representation. Application of this operator to the atomic systems, such as computations of energies of the neutral atoms, energies of the cations, and spin states energy gaps, demonstrates capabilities and limitations of this concept.
Probing magnetic singularities during magnetization process in FePd films
Authors: Masseboeuf Aurélien , Jourdan Thomas , Lançon Frédéric , Bayle-Guillemaud Pascale , Marty Alain
Published: November 2009

We report the use of Lorentz microscopy to observe the domain wall structure during the magnetization process in iron-palladium thin foils. We have focused on the magnetic structure of domain walls of bubble-shaped magnetic domains near saturation. Regions are found along the domain walls where the magnetization abruptly reverses. Multiresolution magnetic simulations showed that these regions are vertical Bloch lines (VBL) and that the different bubble shapes observed are related to the inner structure of the VBL. Combining these two complementary methods, we were thus able to probe the presence of magnetic singularities as small as Bloch points in the inner magnetization of the domain walls.
Recombination mechanisms in highly efficient thin film Zn(S,O)/Cu(In,Ga)S2 based solar cells
Authors: Merdes S. , Sáez-Araoz R. , Ennaoui A. , Klaer J. , Lux-Steiner M. Ch. , Klenk R.
Published: November 2009

Progress in fabricating Cu(In,Ga)S2 based solar cells with Zn(S,O) buffer is presented. An efficiency of 12.9% was achieved. Using spectral response, current-voltage and temperature dependent current-voltage measurements, current transport in this junction was studied and compared to that of a highly efficient CdS/Cu(In,Ga)S2 solar cell with a special focus on recombination mechanisms. Independently of the buffer type and despite the difference in band alignment of the two junctions, interface recombination is found to be the main recombination channel in both cases. This was unexpected since it is generally assumed that a cliff facilitates interface recombination while a spike suppresses it.
Emission properties of Ag/dielectric/Ag plasmonic thermal emitter with different lattice type, hole shape, and dielectric material
Authors: Chang Yi-Tsung , Wu Yi-Tin , Lee Jheng-Han , Chen Hung-Hsin , Hsueh Chun-Yuan , Huang Hao-Fu , Jiang Yu-Wei , Chang Pei-En , Lee Si-Chen
Published: November 2009

The emission spectra of the trilayer Ag/dielectric/Ag plasmonic thermal emitter (PTE) with different lattice type, hole shape, and dielectric material were investigated. It is found that the position and number of thermal emission peak of the PTE are determined by the lattice type not by the hole shape and dielectric materials. The PTE with hexagonal lattice generates only one strong (1,0) Ag/dielectric emission peak, whereas a similar PTE with square lattice generates two strong (1,0) and (1,1) Ag/dielectric emission peaks, their relative intensities follow the blackbody radiation law. This phenomenon suggests the coupling of Ag/dielectric and Ag/air modes.
Damping of surface acoustic vibration induced by electrons trapped on SnO2 nanocrystal surface
Authors: Gao F. , Li T. H. , Wu X. L. , Cheng Y. C. , Shen J. C. , Chu Paul K.
Published: November 2009

Broad full widths of half maxima (dampings) are observed from the low-frequency Raman spectra of hydrothermally prepared SnO2 nanocrystal congeries. No matrix exists between these nanocrystals and the complex-frequency model is thus unable to explain the damping in the low-frequency Raman peaks. An alternative model in which damping is induced by the interaction between confined surface acoustic vibrations and localized electrons near the nanocrystal surface is proposed to explain the phenomenon. This model which suggests that damping is proportional to d−3/2, where d is the average diameter of nanocrystals, is corroborated by our experimental results.
Synergistic information encoding by combinatorial pulse operation of ferroelectrics
Authors: Ricinschi Dan , Nicastro Damian , Kanashima Takeshi , Okuyama Masanori
Published: November 2009

We explore beyond binary memory capability of ferroelectrics, aiming to render them able to encode multiple bit information, based on operation in a regime spanning several polarization reversal mechanisms. Accessing a Pb(Zr,Ti)O3 ceramic capacitor with combinatorial sequences of pulses whose amplitude, width, and polarity are all allowed to vary during polarization reversal, eight partially switched multiple-level memory states are reproducibly generated. We demonstrate, with aid of applied mathematics, that this operation protocol summons the electric-field-dependent microstructure assembly laws of the material into allowing multiple bit data encoding and storage of up to 64 bits of information in a single ferroelectric capacitor.
Heavy atom nitroxyl radicals. III. Identification of the Cl2P=S free radical in the gas phase by laser spectroscopy and ab initio calculations
Authors: Yang Jie , Zhang Xiaopeng , Clouthier Dennis J. , Tarroni Riccardo
Published: November 2009

The dichlorothiophosphoryl (Cl2PS) free radical has been identified in the gas phase for the first time by a combination of laser-induced fluorescence and single vibronic level emission spectroscopy. High level ab initio calculations of the properties of the ground and first two excited states have been undertaken to aid in the interpretation of the data. The radicals were produced by an electric discharge through a dilute mixture of Cl3PS in high pressure argon at the exit of a pulsed supersonic expansion. An extensive band system was observed in the 760–560 nm region and has been assigned as the B̃ A2′-X̃ A2′ electronic transition in which an electron in the ground state π orbital is promoted to the π∗ orbital. Three excited state and four ground state vibrational frequencies and their chlorine isotope effects have been measured and found to be in good accord with the theoretical predictions. Theory indicates that the radical is nonplanar in the ground state with increased pyramidalization and a longer PS bond in the first (Ã A2″n-π∗) and second excited electronic states.
Observation of space-charge-limited current due to charge generation at interface of molybdenum dioxide and organic layer
Authors: Matsushima Toshinori , Murata Hideyuki
Published: November 2009

Current density-voltage characteristics of hole-only devices are influenced by thicknesses of molybdenum dioxide (MoO2) and molybdenum trioxide (MoO3) as buffer layers. A space-charge-limited current of N,N′-diphenyl-N,N′-bis(1-naphthyl)-1,1′-biphenyl-4,4′-diamine (α-NPD) is observed in a wide range of MoO2 thicknesses from 0.25 to 10 nm and at a specific MoO3 thickness of 0.75 nm. Charge transfer characteristics at interfaces of MoO2/α-NPD and MoO3/α-NPD are investigated from changes in fluorescence intensity of α-NPD. Reasons of the improved device characteristics are discussed in terms of interfacial charge generation composed of charged transfer and charge separation.
High-speed tuning of visible laser wavelength using a nanoimprinted grating optical tunable filter
Authors: Huang Nien-Tsu , Truxal Steven C. , Tung Yi-Chung , Hsiao Amy , Takayama Shuichi , Kurabayashi Katsuo
Published: November 2009

We report on a microelectromechanical tunable optical filter incorporating strain-tunable nanoimprinted elastomeric grating with a pitch varied by 18%. This device enables tuning of optical fiber-guided laser wavelength between λ=473 and 532 nm within 0.5 ms by mechanically modulating the pitch with a silicon microactuator. We also demonstrate the use of the device for obtaining two-color images of live/dead-stained cells with the color intensity ratio varied by the actuator voltage applied. The small structure of the device integrated on a silicon chip may be used in portable systems for optical switching and spectroscopy.
dc electrokinetic transport of cylindrical cells in straight microchannels
Authors: Ai Ye , Beskok Ali , Gauthier David T. , Joo Sang W. , Qian Shizhi
Published: November 2009

Electrokinetic transport of cylindrical cells under dc electric fields in a straight microfluidic channel is experimentally and numerically investigated with emphasis on the dielectrophoretic (DEP) effect on their orientation variations. A two-dimensional multiphysics model, composed of the Navier–Stokes equations for the fluid flow and the Laplace equation for the electric potential defined in an arbitrary Lagrangian–Eulerian framework, is employed to capture the transient electrokinetic motion of cylindrical cells. The numerical predictions of the particle transport are in quantitative agreement with the obtained experimental results, suggesting that the DEP effect should be taken into account to study the electrokinetic transport of cylindrical particles even in a straight microchannel with uniform cross-sectional area. A comprehensive parametric study indicates that cylindrical particles would experience an oscillatory motion under low electric fields. However, they are aligned with their longest axis parallel to the imposed electric field under high electric fields due to the induced DEP effect.
Interaction of La2O3 capping layers with HfO2 gate dielectrics
Authors: Copel M. , Guha S. , Bojarczuk N. , Cartier E. , Narayanan V. , Paruchuri V.
Published: November 2009

We report the effect of La2O3 capping layers on HfO2/SiO2/Si dielectrics, proposed for use in threshold voltage tuning of field effect transistors. Depth profiling with medium energy ion scattering shows that an initial surface layer of La2O3 diffuses through the HfO2 at elevated temperatures, ultimately converting some of the thin interfacial SiO2 into a silicate. Core-level photoemission measurements indicate that the additional band-bending induced by the La2O3 only appears after diffusion, and the added charge resides between the HfO2 and the substrate.
Electrically interconnected assemblies of microscale device components by printing and molding
Authors: Kim Mo Joon , Yoon Jongseung , Park Sang-Il , Rogers John A.
Published: November 2009

This letter presents approaches for assembly and electrical interconnection of micro/nanoscale devices into functional systems with useful characteristics. Transfer printing techniques provide deterministic control over an assembly process that occurs prior to or simultaneously with a soft lithographic molding step that defines relief features in a receiving polymer. Filling these features with conducting materials that are processable in the form of liquids or pastes yields integrated interconnects and contacts aligned to the devices. Studies of the underlying aspects and application to representative systems in photovoltaics and solid state lighting indicators provide insights into the process and its practical use.
Smooth potential energy surface for cavitation, dispersion, and repulsion free energies in polarizable continuum model
Authors: Wang Yali , Li Hui
Published: November 2009

Smooth potential energy surfaces and analytic gradients are obtained for cavitation, dispersion, and repulsion free energies in the polarizable continuum model using the fixed points with variable areas (FIXPVA) tessellation scheme. In addition, it is shown that FIXPVA can reproduce the standard GEPOL results to within 1 kcal/mol.
Selection among genotypes in final stage sugarcane trials: effects of time of year
Authors: Rattey A. R. , Jackson P. A. , Hogarth D. M. , McRae T. A.
Published: November 2009

Low levels of commercial cane sugar (CCS) reduce relative economic value (REV) in sugarcane. In the Australian sugarcane industry, CCS is lower early (June) compared with the completion (November) of the harvest period. Performance of sugarcane genotypes in 2 Central region series and 1 Burdekin region series of final stage selection trials was examined to determine if independent selection programs are required to select elite genotypes for 2 target periods: (a) early (before July), and (b) mature (from July on). Across series, CCS (16.83 v. 12.02% fresh cane weight) and REV (AU$3937/ha v. $3123/ha) were significantly higher in the mature than in the early period, while genotypic variance for CCS (0.76 v. 0.33), and broad-sense heritability for CCS (0.96 v. 0.86) and REV (0.79 v. 0.69), were higher in the early than in the mature period. Genetic correlations between sample times less than 3 months apart were usually ≥0.9 for CCS, but generally declined to ≤0.6 for times greater than 3 months apart. Consequently, genotype × period (early compared with mature) interaction effects on CCS affected selection decisions, especially in the Central region, and genetic improvements for CCS would be expected via specific targeting of early and mature periods. However, genotype × period interaction effects were not important for cane yield or REV, such that selection for specific adaptation to early or mature periods would not improve gains in REV across the entire harvest period. Some final stage selection trials should be harvested early in the harvest period, when heritability and genotypic variance are highest, to capture high early CCS genotypes with acceptable cane yield for recycling in breeding activities. This protocol should enhance genetic gain for early CCS and simultaneously increase REV early in the harvesting period of the Australian sugar industry.
Use of high throughput sequencing to observe genome dynamics at a single cell level
Authors: Parkhomchuk D. , Amstislavskiy V. , Soldatov A. , Ogryzko V.
Published: November 2009

With the development of high throughput sequencing technology, it becomes possible to directly analyze mutation distribution in a genome-wide fashion, dissociating mutation rate measurements from the traditional underlying assumptions. Here, we sequenced several genomes of
Escherichia coli
from colonies obtained after chemical mutagenesis and observed a strikingly nonrandom distribution of the induced mutations. These include long stretches of exclusively G to A or C to T transitions along the genome and orders of magnitude intra- and intergenomic differences in mutation density. Whereas most of these observations can be explained by the known features of enzymatic processes, the others could reflect stochasticity in the molecular processes at the single-cell level. Our results demonstrate how analysis of the molecular records left in the genomes of the descendants of an individual mutagenized cell allows for genome-scale observations of fixation and segregation of mutations, as well as recombination events, in the single genome of their progenitor.
Peripheral modulation of worker bee responses to queen mandibular pheromone
Authors: Vergoz Vanina , McQuillan H. James , Geddes Lisa H. , Pullar Kiri , Nicholson Brad J. , Paulin Michael G. , Mercer Alison R.
Published: November 2009

It is generally accepted that young worker bees (
Apis mellifera
L.) are highly attracted to queen mandibular pheromone (QMP). Our results challenge this widely held view. We have found that unless young workers are exposed to QMP early in adult life, they, like foragers, avoid contact with this pheromone. Our data indicate that responses to QMP are regulated peripherally, at the level of the antennal sensory neurons, and that a window of opportunity exists in which QMP can alter a young bee's response to this critically important pheromone. Exposing young bees to QMP from the time of adult emergence reduces expression in the antennae of the D1-like dopamine receptor gene,
Amdop1
. Levels of
Amdop3
transcript, on the other hand, and of the octopamine receptor gene
Amoa1
, are significantly higher in the antennae of bees strongly attracted to QMP than in bees showing no attraction to this pheromone. A decline in QMP attraction with age is accompanied by a fall in expression in worker antennae of the D2-like dopamine receptor,
Am
DOP3, a receptor that is selectively activated by QMP. Taken together, our findings suggest that QMP's actions peripherally not only suppress avoidance behavior, but also enhance attraction to QMP, thereby facilitating attendance of the queen.
Med8, Med18, and Med20 subunits of the Mediator head domain are interdependent upon each other for folding and complex formation
Authors: Adler David , Rahaman Hamidur , Wittung-Stafshede Pernilla , Björklund Stefan
Published: November 2009

We have studied folding and complex formation of the yeast Mediator head-module protein subunits Med8, Med18, and Med20. Using a combination of immunoprecipitation, far-UV circular dichroism, and fluorescence measurements on recombinantly expressed and denatured proteins that were allowed to renature separately or in different combinations, we found that Med8, Med18, and Med20 can fold in different ways to form both soluble monomeric proteins and different distinct subcomplexes. However, the concurrent presence of all three protein subunits during the renaturation process is required for proper folding and trimer complex formation.
Warming increases the risk of civil war in Africa
Authors: Burke Marshall B. , Miguel Edward , Satyanath Shanker , Dykema John A. , Lobell David B.
Published: November 2009

Armed conflict within nations has had disastrous humanitarian consequences throughout much of the world. Here we undertake the first comprehensive examination of the potential impact of global climate change on armed conflict in sub-Saharan Africa. We find strong historical linkages between civil war and temperature in Africa, with warmer years leading to significant increases in the likelihood of war. When combined with climate model projections of future temperature trends, this historical response to temperature suggests a roughly 54% increase in armed conflict incidence by 2030, or an additional 393,000 battle deaths if future wars are as deadly as recent wars. Our results suggest an urgent need to reform African governments' and foreign aid donors' policies to deal with rising temperatures.
Inositol pyrophosphate mediated pyrophosphorylation of AP3B1 regulates HIV-1 Gag release
Authors: Azevedo Cristina , Burton Adam , Ruiz-Mateos Ezequiel , Marsh Mark , Saiardi Adolfo
Published: November 2009

High-energy inositol pyrophosphates, such as IP
7
(diphosphoinositol pentakisphosphate), can directly donate a β-phosphate to a prephosphorylated serine residue generating pyrophosphorylated proteins. Here, we show that the β subunit of AP-3, a clathrin-associated protein complex required for HIV-1 release, is a target of IP
7
-mediated pyrophosphorylation. We have identified Kif3A, a motor protein of the kinesin superfamily, as an AP3B1-binding partner and demonstrate that Kif3A, like the AP-3 complex, is involved in an intracellular process required for HIV-1 Gag release. Importantly, IP
7
-mediated pyrophosphorylation of AP3B1 modulates the interaction with Kif3A and, as a consequence, affects the release of HIV-1 virus-like particles. This study identifies a cellular process that is regulated by IP
7
-mediated pyrophosphorylation.