bluuebunny/crossref_metadata_2025 huggingface dataset:
Processes and boreal summer impacts of the 2004 El Niño Modoki: An AGCM study
Authors: Ashok Karumuri , Iizuka Satoshi , Rao S. A. , Saji N. H. , Lee W.‐J.
Published: February 2009

The sea surface temperature anomalies (SSTA) of tropical Pacific in the boreal summer of 2004 show a distinct tripolar pattern with warm SSTA in the central tropical Pacific, flanked on both sides by cold SSTA. The distinct conditions during the boreal summer of 2004 and the following winter were catalogued as a new coupled phenomenon named El Niño Modoki in a recent generalized study. The 2004 event is unique in the sense that it occurred without any co‐occurring IOD, thereby without any possibility of external modulation of its processes and impacts in the tropics. Using observed data since 1979, we show that the 2004 event indeed involves the distinct equatorial coupled ocean‐atmosphere dynamics different from the conventional El Niño. Further, using an AGCM, we confirm that during boreal summer anomalous twin Walker circulation cells associated with the El Niño Modoki SSTA give rise to observed rainfall anomalies in the tropics.
Evaluating how photochemistry and transport determine stratospheric inorganic chlorine in coupled chemistry‐climate models
Authors: Struthers H. , Bodeker G. E. , Smale D. , Rozanov E. , Schraner M. , Peter T.
Published: February 2009

This study examines how the stratospheric conversion of organic molecules containing chlorine (CCly) to inorganic forms (Cly) can be comprehensively evaluated in three‐dimensional coupled chemistry‐climate models (CCMs) using results from two models (SOCOL and UMETRAC) as examples. Stratospheric inorganic chlorine concentrations depend on both photochemistry and transport. The CCly to Cly conversion process is the first step towards chlorine catalyzed destruction of stratospheric ozone. It is therefore important that models used for the prediction of future stratospheric change accurately simulate this process. Also, because there are multiple processes influencing Cly in CCMs, direct comparison of Cly by itself is of limited use as a validation diagnostic for CCMs. Results show that SOCOL's representation of the photochemical conversion of CCly to Cly is more realistic than UMETRAC's. The CCly to Cly parameterization used in UMETRAC masks transport deficiencies in the model which means that Cly in the polar lower stratosphere from UMETRAC compares better with observations than SOCOL.
Effects of station relocation in the aa index
Authors: Lukianova R. , Alekseev G. , Mursula K.
Published: February 2009

Earlier studies have shown that the long‐term measure of geomagnetic activity, the aa index, is inhomogeneous and depicts an excessively large (about 12 nT) centennial increase. This has preliminarily been suggested to be due to possible station intercalibration problems in 1957 when the northern aa station was changed from Abinger to Hartland. In the present paper we show that the 3‐hourly aa index time series is not uniform but includes systematic jump‐like changes in the distribution of the various aa values with each change of stations in 1920, 1926, 1957, and 1980. We estimate how large a change to the aa index was caused by each particular aa value. We find that the changes to the aa index due to different ranges of activity are smooth and fairly similar for all jumps. In 1957 the largest aa values had, at the expense of more moderate aa values, a relatively larger contribution to the jump than in other station changes because the relative station coefficient was somewhat larger in 1957, leading to larger spreading and a higher average level of aa values. However, while this difference could cause a slight overestimate of the aa values, we find that the total changes in the aa index over jumps are in agreement, in both sign and magnitude, with the solar cycle variation. So it is unlikely that the excessive increase of the aa index would be due to erroneously estimated station coefficients.
Scaling relations for large Martian valleys
Authors: Som Sanjoy M. , Montgomery David R. , Greenberg Harvey M.
Published: February 2009

The dendritic morphology of Martian valley networks, particularly in the Noachian highlands, has long been argued to imply a warmer, wetter early Martian climate, but the character and extent of this period remains controversial. We analyzed scaling relations for the 10 large valley systems incised in terrain of various ages, resolvable using the Mars Orbiter Laser Altimeter (MOLA) and the Thermal Emission Imaging System (THEMIS). Four of the valleys originate in point sources with negligible contributions from tributaries, three are very poorly dissected with a few large tributaries separated by long uninterrupted trunks, and three exhibit the dendritic, branching morphology typical of terrestrial channel networks. We generated width‐area and slope‐area relationships for each because these relations are identified as either theoretically predicted or robust terrestrial empiricisms for graded precipitation‐fed, perennial channels. We also generated distance‐area relationships (Hack's law) because they similarly represent robust characteristics of terrestrial channels (whether perennial or ephemeral). We find that the studied Martian valleys, even the dendritic ones, do not satisfy those empiricisms. On Mars, the width‐area scaling exponent b of −0.7–4.7 contrasts with values of 0.3–0.6 typical of terrestrial channels; the slope‐area scaling exponent θ ranges from −25.6–5.5, whereas values of 0.3–0.5 are typical on Earth; the length‐area, or Hack's exponent n ranges from 0.47 to 19.2, while values of 0.5–0.6 are found on Earth. None of the valleys analyzed satisfy all three relations typical of terrestrial perennial channels. As such, our analysis supports the hypotheses that ephemeral and/or immature channel morphologies provide the closest terrestrial analogs to the dendritic networks on Mars, and point source discharges provide terrestrial analogs best suited to describe the other large Martian valleys.
Spatial time domain reflectometry and its application for the measurement of water content distributions along flat ribbon cables in a full‐scale levee model
Authors: Scheuermann Alexander , Huebner Christof , Schlaeger Stefan , Wagner Norman , Becker Rolf , Bieberstein Andreas
Published: February 2009

Spatial time domain reflectometry (spatial TDR) is a new measurement method for determining water content profiles along elongated probes (transmission lines). The method is based on the inverse modeling of TDR reflectograms using an optimization algorithm. By means of using flat ribbon cables it is possible to take two independent TDR measurements from both ends of the probe, which are used to improve the spatial information content of the optimization results and to consider effects caused by electrical conductivity. The method has been used for monitoring water content distributions on a full‐scale levee model made of well‐graded clean sand. Flood simulation tests, irrigation tests, and long‐term observations were carried out on the model. The results show that spatial TDR is able to determine water content distributions with an accuracy of the spatial resolution of about ±3 cm compared to pore pressure measurements and an average deviation of ±2 vol % compared to measurements made using another independent TDR measurement system.
Assessing the accuracy of monitoring wells in tidal wetlands
Authors: Gardner Leonard Robert
Published: February 2009

Groundwater movement in marshes is driven by tidal fluctuations, evapotranspiration, and the infiltration of rainwater. These forcings act on time scales of several hours. Monitoring wells in marshes must, therefore, be able to react rapidly and accurately to changes in these forcings. To assess the response characteristics of a given well design, I define a well's time constant as the square of its radius divided by the product of the aquifer conductivity and the length of its screen. Using numerical simulations, I show that the logarithm of the mean deviation over a tidal cycle between the head in the well and the head in the adjoining undisturbed aquifer is linearly related to the logarithm of the well time constant. Similar logarithmic relationships occur for the maximum deviations on flood and ebb tides and the well time constant. Thus, wells in soils with low hydraulic conductivity must have smaller radii and longer screens than those in more conductive soils in order to have similar accuracy. Alternatively, the time constant can be lowered by incorporating the pressure sensor in a slug that displaces most of the water above the sensor and thereby greatly reduces the volume of water that must move between the well and the aquifer.
Magnetic assembles of FePt (001) nanoparticles with SiO2 addition
Authors: Wei D. H.
Published: February 2009

Isolated FePt (001) nanoparticles surrounded with amorphous SiO2 have been fabricated by electron beam evaporation onto MgO (001) single-crystal substrates via the introduction of a SiO2 intermediate layer into the FePt film structures. The formation of two-dimensional magnetic assemblies of ordered FePt (001) nanoparticles with an average size of about 6nm was directly obtained with this process at only 400°C due to the interpenetration of SiO2, which has a lower surface energy. Studies of angular dependent coercivity show a tendency of a domain-wall motion to weaken toward rotation of reverse-domain type upon thickness of SiO2 additive layer into the FePt film structures. On the other hand, the exchange coupling between neighboring particles in the FePt nanostructures could be reduced with ultrathin SiO2 addition, which is confirmed from the Kelly–Henkel (δM) plot.
Magnetostriction and texture relationships in annealed galfenol alloys
Authors: Summers Eric M. , Meloy Rob , Na Suok-Min
Published: February 2009

An investigation into the relationship between the measured bulk magnetostriction in rolled galfenol alloy sheet and the measured texture components was conducted. Galfenol rolled sheet was prepared using different texture annealing parameters such as temperature (1000–1300 °C), cooling rate, and dwell time (1–24 h), with their saturation magnetostrictions measured, followed by electron backscattered diffraction to determine the degree of texture that each sample possessed. The dominate orientation in all samples analyzed was the {011}⟨100⟩, along the desired η-fiber. Measurement results indicate that as the η-fiber texture improves the bulk magnetostriction increases in a linear fashion with a maximum strain value of 154 ppm measured for sheet samples containing 45 area % η-fiber texture.
Effect of surface domain structure on wall mobility in amorphous microwires
Authors: Chiriac H. , Óvári T.-A. , Ţibu M.
Published: February 2009

Recently reported results on domain wall propagation within the inner core of bistable Fe-based positive magnetostrictive amorphous microwires opened up the way for future spintronic applications of amorphous microwires. Domain wall propagation has also been investigated in Co-based nearly zero magnetostrictive microwires, which become bistable under certain conditions. Wall velocity and mobility values were found to be superior in the latter type of microwires due to their much smaller magnetoelastic anisotropy. In this paper, the key role played by the surface domain structure of microwires in determining the wall mobility is investigated. Wall velocity measurements have been performed on (Co0.94Fe0.06)72.5Si12.5B15 microwires in as-cast glass-coated state and after glass removal with a hydrofluoric acid solution. Surface magnetization has been studied employing magneto-optical Kerr effect. The results show that both as-cast glass-coated microwires and microwires with the glass coating removed, which are bistable, display a helical magnetization in the surface region. The direction of the magnetization in this region affects the mobility of the propagating wall due to the stray fields associated with the preponderant components of the magnetization.
Reliability of HfSiON gate dielectric silicon MOS devices under [110] mechanical stress: Time dependent dielectric breakdown
Authors: Choi Youn Sung , Park Hyunwoo , Nishida Toshikazu , Thompson Scott E.
Published: February 2009

The time dependent dielectric breakdown (TDDB) of 7–8 nm thick nitrided hafnium silicate (HfSiON) dielectric silicon (Si) metal-oxide-semiconductor capacitors are measured under uniaxial mechanical stress using four point wafer bending along the [110] direction. Both applied tensile and compressive stresses are observed to degrade TDDB. The degradation for both stress polarity is consistent with a previously reported increase in mechanical stress-induced gate leakage via Poole–Frenkel emission. The independence of the charge to breakdown on HfSiON thickness suggests that the degradation under mechanical stress is primary mediated at the HfSiON/Si interface during constant negative gate voltage stressing.
Reflectionless sharp bends and corners in waveguides using epsilon-near-zero effects
Authors: Edwards B. , Alù A. , Silveirinha M. G. , Engheta N.
Published: February 2009

Following our recent theoretical and experimental results that show how zero-permittivity metamaterials may provide anomalous tunneling and energy squeezing through ultranarrow waveguide channels, here we report an experimental investigation of the bending features relative to this counterintuitive resonant effect. We generate the required effectively zero permittivity using a waveguide operating at the cutoff of its dominant mode, and we show how sharp and narrow bends may be inserted within the propagation channel without causing any sensible reflection or loss and without affecting its tunneling properties.
Probing rotational relaxation in HBr (v=1) using double resonance spectroscopy
Authors: Kabir Md. Humayun , Antonov Ivan O. , Heaven Michael C.
Published: February 2009

Rotational energy transfer in HBr(v=1)+HBr collisions has been investigated using an optical pump-probe double resonance technique at ambient temperature. Rotationally state selective excitation of v=1 for rotational levels in the range J=0–9 was achieved by stimulated Raman pumping, and the evolution of population was monitored using (2+1) resonantly enhanced multiphoton ionization spectroscopy of the g 3∑−-X ∑1+(0–1) band. Collision-induced population transfer events with ΔJ≤8 were observed at a pressure of 0.32 Torr. State-to-field rate constants for loss of population from the initially prepared states ranged from 8.3×10−10 to 4.9×10−10 cm3 s−1. The full state-to-state rate constant set was analyzed by fitting to numerical solutions of the coupled differential equations describing the relaxation processes. Rate constant matrices were generated using fitting and scaling functions. The rate coefficients were best represented by the statistical power exponential gap law.
Anisotropic magnetic phase diagrams of HoB4 single crystal
Authors: Kim J. Y. , Cho B. K. , Han S. H.
Published: February 2009

We have investigated the magnetic and electronic properties of a single-crystal HoB4. Antiferromagneticlike transitions were revealed by the temperature-dependent magnetization exhibiting two transition temperatures at TN1=7.1 K and TN2=5.7 K for an applied magnetic field along the c-axis, and showed only one transition at T=5.7 K for an applied magnetic field perpendicular to the c-axis. The isothermal magnetization with an applied magnetic field along the c-axis exhibited three distinct metamagnetic phase transitions at Hc1=2 T, Hc2=3.5 T, and Hc3=3.9 T at T=2 K. On the other hand, the isothermal magnetization with an applied magnetic field perpendicular to the c-axis showed two metamagneticlike transitions. A rapid change in the temperature and the field-dependent resistivity was found to be intimately correlated with magnetic transitions. Based on the isothermal magnetization and field-dependent resistivity for both magnetic field directions (H∥c and H⊥c), anisotropic phase diagrams of HoB4 were constructed. From the comparison of the phase diagram of HoB4 with that of DyB4, it was deduced that HoB4 has a geometrical quadrupolar frustration of Ho3+ moment.
Pd
2
N
2
, a proteiform molecule: Matrix isolation spectroscopy and density functional theory calculations
Authors: Souvi S. M. , Tremblay B. , Perchard J. P. , Alikhani M. E.
Published: February 2009

The formation of Pd2N2 from the cocondensation of effusive beams of Pd and N2 in neon and argon matrices is evidenced by absorptions in the range of 2200–1800 cm−1. In argon, selective irradiation in the near-infrared and visible ranges leads to interconversions between three structures, distinguished by the stretching frequency of the diatomic N2: Bridged T-shaped (νNN at 1990 cm−1), side on (νNN at 2178 cm−1) and parallel (νNN at 1823 cm−1). For the first two structures, the νNN mode is also accompanied by another signal below 500 cm−1. An extra feature close to 490 cm−1, not sensitive to irradiation at λirr>400 nm and also assignable to a molecule with the same Pd:N2 stoichiometry (2:1), corresponds to a centrosymmetrical Pd–N–N–Pd structure with an inactive νNN mode close to 2141 cm−1, as deduced from the observation of a weak signal close to 2630 cm−1 associated with this species and assignable to the combination νNN+νPdN. All these experimental data and their structural implications are fully supported by theoretical calculations [density functional theory (DFT)]. On the basis of this comparative study, we have obtained a reliable theoretical description of the spectroscopic data using the metageneralized gradient approximation functional within the unrestricted DFT (UDFT) formalism for all spin multiplets. We have also searched a stable electronic solution for each multiplet (particularly for the singlet state), in order to account for the nondynamic correlations.
Structural properties of hyperbranched polymers in the melt under shear via nonequilibrium molecular dynamics simulation
Authors: Le Tu C. , Todd B. D. , Daivis P. J. , Uhlherr A.
Published: February 2009

Hyperbranched polymer melts have been simulated using a coarse-grained model and nonequilibrium molecular dynamics (NEMD) techniques. In order to determine the shear-induced changes in the structural properties of hyperbranched polymers, various parameters were calculated at different strain rates. The radii of gyration which characterize the size of the polymer were evaluated. The tensor of gyration was analyzed and results indicate that hyperbranched polymer molecules have a prolate ellipsoid shape under shear. As hyperbranched polymers have compact, highly branched architecture and layers of beads have increasing densities which might lead to an unusual distribution of mass, the distribution of beads was also studied. The distribution of terminal beads was investigated to understand the spatial arrangement of these groups which is very important for hyperbranched polymer applications, especially in drug delivery.
Turbulence-driven zonal flows in helical systems with radial electric fields
Authors: Sugama H. , Watanabe T.-H.
Published: February 2009

Collisionless long-time responses of the zonal-flow potential to the initial condition and turbulence source in helical systems having radial electric fields are derived theoretically. All classes of particles in passing, toroidally trapped, and helical-ripple-trapped states are considered. The transitions between the toroidally trapped and helical-ripple-trapped states are taken into account while solving the gyrokinetic equation analytically by taking its average along the particle orbits. When the radial displacements of helical-ripple-trapped particles are reduced either by neoclassical optimization of the helical geometry lowering the radial drift or by strengthening the radial electric field Er to boost the poloidal rotation, enhanced zonal-flow responses are obtained. Under the identical conditions on the magnitude of Er and the magnetic geometry, using ions with a heavier mass gives rise to a higher zonal-flow response, and therefore the turbulent transport is expected to show a more favorable ion-mass dependence than the conventional gyro-Bohm scaling.
First principles study of the graphene/Ru(0001) interface
Authors: Jiang De-en , Du Mao-Hua , Dai Sheng
Published: February 2009

Annealing the Ru metal that typically contains residual carbon impurities offers a facile way to grow graphene on Ru(0001) at the macroscopic scale. Two superstructures of the graphene/Ru(0001) interface with periodicities of 3.0 and 2.7 nm, respectively, were previously observed by scanning tunneling microscopy. Using first principles density functional theory, we optimized the observed superstructures and found interfacial C–Ru bonding of C atoms atop Ru atoms for both superstructures, which causes the graphene sheet to buckle and form periodic humps of ∼1.7 Å in height within the graphene sheet. The flat region of the graphene sheet, which is 2.2–2.3 Å above the top Ru layer and has more C atoms occupying the atop sites, interacts more strongly with the substrate than does the hump region. We found that interfacial adhesion is much stronger for the 3.0 nm superstructure than for the 2.7 nm superstructure, suggesting that the former is the thermodynamically more stable phase. We explained the 3.0 nm superstructure’s stability in terms of the interplay between C–Ru bonding and lattice matching.
Miniature anvil cell for high-pressure measurements in a commercial superconducting quantum interference device magnetometer
Authors: Alireza Patricia Lebre , Lonzarich Gilbert George
Published: February 2009

We describe a miniature diamond anvil cell that can be used in a commercial superconducting quantum interference device (SQUID) magnetometer to detect magnetic and superconducting transitions at applied pressures above 100 kbar. The cell is of simple design but constructed out of ultralow susceptibility materials that allow us to detect changes in the magnetic moment of the specimen at the full sensitivity of the SQUID magnetometer (typically 10−7 emu). We present examples of the use of the cell to detect ferromagnetic, antiferromagnetic, and superconducting transitions at pressures and temperatures in the range of 0≤P≤100 kbar, 1.8 K≤T≤290 K, respectively.
Electrode kinetics of Cu–SiO2-based resistive switching cells: Overcoming the voltage-time dilemma of electrochemical metallization memories
Authors: Schindler C. , Staikov G. , Waser R.
Published: February 2009

The kinetics of the switching process in Cu–SiO2-based electrochemical metallization memory cells was investigated as a function of the switching voltage and the SiO2 film thickness. We observe an exponential dependence of the switching rate on the switching voltage and no significant thickness dependence in the range from 5to20nm SiO2. We conclude from our data that the cathodic electrodeposition represents the rate-limiting step of the switching kinetics. The voltage-time dilemma seems to be overcome by the exponential dependence of the switching rate in combination with a threshold voltage presumably originating from a nucleation overpotential.
Dielectric relaxation of lanthanum doped zirconium oxide
Authors: Zhao C. Z. , Taylor S. , Werner M. , Chalker P. R. , Murray R. T. , Gaskell J. M. , Jones A. C.
Published: February 2009

Lanthanum doped zirconium oxide (Lax–Zr1−xO2−δ) films, with La contents, up to x=0.35, were studied. Films were annealed at 900 °C to crystallize them into phases with higher κ-values. Increasing the La content suppressed the monoclinic phase and stabilized the tetragonal or cubic phase. The highest dielectric constant was obtained for a lightly doped film with a La content of x=0.09, for which a κ-value of 40 was obtained. This was accompanied by a significant dielectric relaxation, following a single Curie–von Schweidler power-law dependency with frequency, changing to a mixed Curie–von Schweidler and Kohlrausch–Williams–Watts relationships after annealing. The dielectric relaxation was most severe for lightly doped films, which had the highest κ-values. The dielectric relaxation appears to be related to the size of crystal grains formed during annealing, which was dependent on the doping level.
Si substrates texturing and vapor-solid-solid Si nanowhiskers growth using pure hydrogen as source gas
Authors: Nordmark H. , Nagayoshi H. , Matsumoto N. , Nishimura S. , Terashima K. , Marioara C. D. , Walmsley J. C. , Holmestad R. , Ulyashin A.
Published: February 2009

Scanning and transmission electron microscopies have been used to study silicon substrate texturing and whisker growth on Si substrates using pure hydrogen source gas in a tungsten hot filament reactor. Substrate texturing, in the nanometer to micrometer range of mono- and as-cut multicrystalline silicon, was observed after deposition of WSi2 particles that acted as a mask for subsequent hydrogen radical etching. Simultaneous Si whisker growth was observed for long residence time of the source gas and low H2 flow rate with high pressure. The whiskers formed via vapor-solid-solid growth, in which the deposited WSi2 particles acted as catalysts for a subsequent metal-induced layer exchange process well below the eutectic temperature. In this process, SiHx species, formed by substrate etching by the H radicals, diffuse through the metal particles. This leads to growth of crystalline Si whiskers via metal-induced solid-phase crystallization. Transmission electron microscopy, electron diffraction, and x-ray energy dispersive spectroscopy were used to study the WSi2 particles and the structure of the Si substrates in detail. It has been established that the whiskers are partly crystalline and partly amorphous, consisting of pure Si with WSi2 particles on their tips as well as sometimes being incorporated into their structure.
The gravitational ellipse
Authors: D’Eliseo Maurizio M.
Published: February 2009

The elliptical orbit of the classical gravitational two-body problem can be determined by studying the free oscillations about a circular motion or the small motions around a fixed point in a rotating reference frame. In this last schematization we approximate the differential equation of motion by a succession of simple equations we solve iteratively, obtaining a piecemeal determination of the position vector r formally expressed in terms of Laurent polynomials, from which we quickly deduce the explicit time-dependent expressions in the form of complex trigonometric polynomials. This approach can also be used in the presence of perturbing forces and, by way of illustration, we study the effects of a small linear repulsive force on the elliptical orbit.
Prediction of graphitelike BC4N from first-principles calculations
Authors: Luo Xiaoguang , Liu Zhongyun , He Julong , Xu Bo , Yu Dongli , Wang Hui-Tian , Tian Yongjun
Published: February 2009

We present first-principles calculations of the structural and electronic properties of possible graphitelike BC4N constructed from 3r-graphite structure. Our calculation results show that the hexagonal BC4N structure stacked with one B-N layer and two C-C layers has the lowest total energy among all constructed BC4N structures. The calculated negative formation energy indicates that it may be synthesized from 3r-graphite and 3r-BN. Its stability has been further confirmed by mechanical stability criteria. The electronic properties show that it is a narrow band gap semiconductor.
Electronic properties of a strained ⟨100⟩ silicon nanowire
Authors: Sajjad Redwan Noor , Alam Khairul
Published: February 2009

The effects of uniaxial strain on the electronic properties of silicon nanowires grown in ⟨100⟩ direction are studied using a tight binding sp3d5s∗ orbital basis quantum simulation. Calculations are performed using both Harrison and Boykin formalisms (discussed in Sec. II). The energy difference between the fourfold (Δ4) and the twofold (Δ2) degenerate valleys of conduction bands reduces with compressive strain and the nanowire becomes an indirect band gap material when the compressive strain exceeds a certain value. With tensile strain, this energy difference increases and the nanowire band structures remain direct. The conduction band edge is downshifted with compressive strain and is upshifted with tensile strain. However, the valence band edge is upshifted with both types of strain that results in band gap reduction with strain. The four-valley degeneracy of conduction band at the center of one dimensional wire Brillouin zone is slightly lifted with both types of strain. The energy difference between the top two valence bands is insensitive to tensile strain and is significantly changed with compressive strain. The strain has no effect on conduction band effective mass but changes the valence band effective mass significantly. A 1% strain can change the hole effective mass by ≈53%. Harrison and Boykin formalisms produce very similar valence band edge and hole and electron effective masses and significantly different conduction band edge and band gap. In Boykin formalism, strain affects the energy levels of both the Δ4 and Δ2 valleys of conduction band while the energy level of only Δ2 valleys is affected by strain in Harrison calculations. The direct to indirect transition occurs at a slightly higher compressive strain in Boykin formalism.
Formation and distribution of compounds at the Ru–Si(001) ultrathin film interface
Authors: Pasquali L. , Mahne N. , Montecchi M. , Mattarello V. , Nannarone S.
Published: February 2009

Interface formation between Ru and Si(001) has been studied by x-ray and ultraviolet photoemissions. The film properties were investigated, for metal deposition at room temperature, as a function of the Ru film thickness and as a function of the annealing temperature of a thick grown film. From the evolution of the Ru and Si core levels, we find that alloying takes place at the interface during growth and estimate the thickness of the intermixed region to be of the order of 15–20 ML. Annealing at increasingly high temperatures causes the formation of different silicide phases, which are discussed in relation to theoretical and experimental data on related transition metal silicides.
Logic gates with a single graphene transistor
Authors: Sordan Roman , Traversi Floriano , Russo Valeria
Published: February 2009

The operation of four basic two-input logic gates fabricated with a single graphene transistor is demonstrated. Single-transistor operation is obtained in a circuit designed to exploit the charge neutrality point of graphene to perform Boolean logic. The type of logic function is selected by offset of the input digital signals. The merits and limitations of the fabricated gates are assessed by comparing their performance with that of conventional logic gates.
A model for conductive percolation in ordered nanowire arrays
Authors: Silverberg J. L.
Published: February 2009

The combined processes of anodization and electrodeposition lead to highly ordered arrays of cylindrical nanowires. This template-based self-assembly fabrication method yields nanowires embedded in alumina. Commonly, chemical etching is used to remove the alumina and free the nanowires. However, it has been experimentally observed during the etching process that the nanowires tend to form clumps. In this work, the nanowires are modeled as elastic rods subject to surface interaction forces. The dynamics of the model give rise to the aforementioned clumping behavior, which is studied via percolation theory. This work finds that percolation takes place with probability P∼(t−tc)x, where the exponent x=2.8 and tc is the time at which percolation takes place. The critical exponents that entirely determine the system are found to be for (dimension) d=2, β=2.1, γ=0.57, Δ=2.7, α=−2.8, ν=2.4, and δ=1.3.
Magnetization switching without charge or spin currents
Authors: Stöhr J. , Siegmann H. C. , Kashuba A. , Gamble S. J.
Published: February 2009

We propose schemes of reversing the magnetization of a ferromagnet by electric fields alone, without charge or spin currents or external magnetic fields. The switching is triggered by picosecond manipulation of the atomic positions or subpicosecond distortion of the valence charge distribution, which through spin-orbit coupling modifies the magnetic anisotropy. We discuss how such time-even anisotropies can be used to switch the time-odd magnetization for in-plane and out-of-plane magnetization directions. In all cases the switching process is completely determined by the appropriately chosen orientation, magnitude, and temporal length of the electric field created by a voltage or photon pulse.
Boron-doped diamond heater and its application to large-volume, high-pressure, and high-temperature experiments
Authors: Shatskiy Anton , Yamazaki Daisuke , Morard Guillaume , Cooray Titus , Matsuzaki Takuya , Higo Yuji , Funakoshi Ken-ichi , Sumiya Hitoshi , Ito Eiji , Katsura Tomoo
Published: February 2009

A temperature of 3500 °C was generated using a diamond resistance heater in a large-volume Kawai-type high-pressure apparatus. Re and LaCrO3 have conventionally been used for heaters in high-pressure studies but they cannot generate temperatures higher than 2900 °C and make in situ x-ray observations difficult due to their high x-ray absorption. Using a boron-doped diamond heater overcomes these problems and achieves stable temperature generation for pressure over 10 GPa. The heater starting material is a cold-compressed mixture of graphite with boron used to avoid the manufacturing difficulties due to the extreme hardness of diamond. The diamond heater was synthesized in situ from the boron-graphite mixture at temperature of 1600±100 °C and pressure of 20 GPa. By using the proposed technique, we have employed the diamond heater for high-temperature generation in a large-volume high-pressure apparatus. Achievement of temperatures above 3000 °C allows us to measure the melting points of the important constituents in earth’s mantle (MgSiO3, SiO2, and Al2O3) and core (Fe and Ni) at extremely high pressures.
Magnetic structure of La0.7Sr0.3MnO3/La0.7Sr0.3FeO3 superlattices
Authors: Arenholz E. , van der Laan G. , Yang F. , Kemik N. , Biegalski M. D. , Christen H. M. , Takamura Y.
Published: February 2009

Using x-ray magnetic dichroism, we characterize the magnetic order in La0.7Sr0.3MnO3(LSMO)/La0.7Sr0.3FeO3(LSFO) superlattices with six unit cell thick sublayers. The LSMO layers exhibit a reduced Curie temperature compared to the bulk while antiferromagnetic order in the LSFO layers persists up to the bulk Néel temperature. Moreover, we find that aligning the LSMO magnetization by a magnetic field within the (001) surface plane leads to a reorientation of the Fe moments as well maintaining a perpendicular orientation of Fe and Mn moments. This perpendicular alignment is due to the frustrated exchange coupling at the LSMO/LSFO interface.
Effect of surface tension on nanotube nanofluids
Authors: Kumar Ranganathan , Milanova Denitsa
Published: February 2009

This letter presents heat transfer results that single-walled carbon nanotube (CNT) suspensions in a boiling environment can extend the saturated boiling regime and postpone catastrophic failure of the material even further than previously reported if the surface tension of the nanofluid is carefully controlled. The maximum enhancement in the critical heat flux is nearly four times for a surfactant to CNT concentration ratio of 1:5. The experimental results show that the material burnout is a strong function of the relaxation of the nanofluid surface tension with the base fluid.
In situ x-ray photoelectron spectroscopy analysis of SiOxFy passivation layer obtained in a SF6/O2 cryoetching process
Authors: Pereira J. , Pichon L. E. , Dussart R. , Cardinaud C. , Duluard C. Y. , Oubensaid E. H. , Lefaucheux P. , Boufnichel M. , Ranson P.
Published: February 2009

The oxyfluorinated silicon passivation layer created during various cryoetching processes is of interest in order to improve high aspect ratio profiles. In this work, the desorption of a SiOxFy layer obtained in an overpassivating SF6/O2 regime was investigated during the wafer warm-up from the cryogenic temperature to room temperature. An in situ x-ray photoelectron spectroscopy (XPS) device is used in order to probe the top-surface layer and understand the desorption mechanism. A new mechanism can be proposed using the evolution of fluorine, oxygen, silicon, and carbon contributions evidenced by XPS.
High minority carrier lifetime in Ga-doped Czochralski-grown silicon by Ge codoping
Authors: Arivanandhan Mukannan , Gotoh Raira , Fujiwara Kozo , Uda Satoshi
Published: February 2009

Higher minority carrier lifetimes (76 μs) were measured in Ga and Ge codoped Czochralski-silicon (CZ-Si) crystal compared to Ga-doped CZ-Si (28 μs). The minority carrier lifetime increase was associated with a decrease in etch pit density related to grown-in microdefects (GMD) in as-grown CZ-Si with increasing Ge concentration. Furthermore, oxygen (O) precipitation was enhanced in CZ-Si by increased Ge concentration, but this had a lesser limiting influence on minority carrier lifetime. The mechanism by which Ga and Ge codoping affects GMD suppression and enhances O precipitation in CZ-Si is discussed on the basis of the behavior of Ge-vacancy-O related complexes.
Fabrication, photoemission studies, and sensor of Hg nanoparticles templated on plasmid DNA
Authors: Majumder Subrata , Priyadarshini M. , Subudhi U. , Umananda M. , Chainy G. B. N. , Satyam P. V. , Varma Shikha
Published: February 2009

Fabrication of Hg nanoparticles (NPs) templated on plasmid DNA has been investigated here. The Hg NPs get embedded inside the DNA scaffold through local melting of double helix due to the strong and exclusive interaction of the NPs with the nitrogen of the nucleic acid bases. The interaction of the Hg NPs with the guanine-cytosine base pair sites is responsible for the formation of two Hg metal-base complexes that can find application as the signature of ion-DNA interactions. The modifications in the transport properties of metal conjugated DNA can be utilized as sensor for mercury contamination.
High efficiency photoluminescence from silica-coated CdSe quantum dots
Authors: Qian Lei , Bera Debasis , Tseng Teng-Kuan , Holloway Paul. H.
Published: February 2009

The effects on the luminescent properties of coating CdSe quantum dots with silica are presented. Coating increased the quantum yields from ∼10%–20% to ∼80% at a maximum. The changes in quantum yields and photoluminescence peak at wavelength were discussed in terms of the effects of surface charge. By neutralizing surface charge, the emission from CdSe quantum dots was initially blueshifted followed by redshifting, and the quantum yield increased dramatically.
The thermal-field emission model for carrier injection characteristics of an organic field effect transistor
Authors: Kimura Yasuo , Oba Tomohisa , Shimakura Naoko , Niwano Michio
Published: February 2009

We have investigated the influence of carrier injection on the characteristics of an organic field effect transistor (OFET) using a rubrene single crystal. The mobility estimated from the transfer characteristic of the OFET depended strongly on the channel length and the thickness of the rubrene single crystal although the mobility is intrinsically independent of the dimensions of an OFET. On the other hand, the temperature dependence of the saturation drain current was in good agreement with the thermal-field emission theory. These suggest that OFETs are controlled not only by the carrier accumulation at the channel but also by the carrier injection.
Tunable emission based on the composite of Au nanoparticles and CdSe quantum dots deposited on elastomeric film
Authors: Chen C. W. , Wang C. H. , Wei C. M. , Chen Y. F.
Published: February 2009

A simple approach to investigate the dependence of emission on the separation distance between metal nanoparticles and semiconductor quantum dots is demonstrated. Without varying the mixed concentrations, a tunable emission is achieved based on the deposition of the composite of Au nanoparticles and CdSe quantum dots on elastomeric film. By utilizing the inherent nature of the elasticity of the elastomeric film, it is found that depending on the separation distance, the emission intensity can be quenched or enhanced. The underlying mechanism can be explained quite well by the interplay between the local field excitation due to surface plasmons and electrons transfer to metal nanoparticles.
High mobility InGaZnO4 thin-film transistors on paper
Authors: Lim Wantae , Douglas E. A. , Kim S.-H. , Norton D. P. , Pearton S. J. , Ren F. , Shen H. , Chang W. H.
Published: February 2009

We report on the fabrication and the electrical properties of amorphous (α-)InGaZnO4 thin-film transistors deposited on cellulose paper by sputtering at room temperature. The 150-μm-thick paper was used as both a gate dielectric and a substrate for device structural support. The transistors on paper were patterned by lithography and operated in enhancement mode with a threshold voltage of 3.75 V, and exhibited saturation mobility, subthreshold gate-voltage swing, and drain current on-to-off ratio of ∼35 cm2 V−1 s−1, 2.4 V decade−1, and ∼104, respectively. These results verify that simple cellulose paper is a good gate dielectric as well as a low-cost substrate for flexible electronic devices such as paper-based displays.
High-temperature electrical transport behaviors in textured Ca3Co4O9-based polycrystalline ceramics
Authors: Lin Yuan-Hua , Lan Jinle , Shen Zhijian , Liu Yuheng , Nan Ce-Wen , Li Jing-Feng
Published: February 2009

Highly (00l) oriented Ca3Co4O9-based ceramics were fabricated by spark plasma sintering combined with a dynamic forging process. The grain orientation is effective in lowering the electrical resistivity and enhancing the thermoelectric power factor but with little influence on the Seebeck coefficient. A metallic-to-semiconducting transition temperature can be observed and the activation energy is almost independent of the La-doping. All of the Ca3Co4O9-based ceramic samples exhibit large thermoelectric power, and the figure of merit for La-doped Ca3Co4O9 sample can reach 0.26 at 975 K, which can be a promising candidate of p-type material for high-temperature thermoelectric application.
Interactions of MKrn+ (M = Cu, Ag, and Au; n = 1 - 3): Ab Initio Calculations
Authors: Xinying Li , Xue Cao , Yongfang Zhao
Published: February 2009

The equilibrium geometries, stabilities, and populations of the title species were investigated at the CCSD(T) level. The population analyses show covalent contribution occurs in the M–Kr bonding and the best theoretical estimate of the dissociation energies of the most stable AuKrn+ are 0.801, 1.743, and 2.193 eV. The electron correlation and relativistic effects on the interaction were investigated at the CCSD(T) level and both effects stabilize the title species.
The Synthesis of Potential DNA Intercalators. 2. Tri- and Tetra-Cyclic Heterocycles
Authors: Ebrahimlo Ali Reza Molla , Khalafy Jabbar , Prager Rolf H.
Published: February 2009

The reaction of 1,4-dichlorophthalazine and 2,3-dichloroquinoxaline with some isoxazolones gave their mono- and bis-isoxazolinyl derivatives. The base-catalyzed rearrangement of these derivatives afforded the corresponding tri- and tetracyclic heterocycles.
Cyclobutanes and Cyclobutenes from Photochemical Cleavage of Some Bicyclo[3.2.0]heptan-2-ones
Authors: Sydnes Leiv K. , Van Ha Doan
Published: February 2009

Irradiation of solutions of cyclopent-2-enone or 3-methylcyclopent-2-enone and allyl alcohol with light from a medium-pressure mercury lamp through a Pyrex filter with a cut-off at 295 nm furnishes excellent yields of isomeric mixtures of substituted bicyclo[3.2.0]heptan-2-ones as the primary products. Both enones give predominantly the head-to-head isomer with exo stereochemistry. The primary products turn out to be photolabile and undergo Norrish type I cleavage followed by hydrogen abstraction, but the outcome is influenced by the presence of a methyl group at C5. In the absence of such a methyl group the C1–C2 bond is cleaved, to give rise to two cyclobutenyl aldehydes in better than 90% combined yield; when a methyl group is attached at C5 both C–C bonds to the carbonyl group are broken and a mixture of cyclobutyl aldehydes and ketenes are formed in close to quantitative combined yield.
A gene regulatory network directed by zebrafish No tail accounts for its roles in mesoderm formation
Authors: Morley Rosalind H. , Lachani Kim , Keefe Damian , Gilchrist Michael J. , Flicek Paul , Smith James C. , Wardle Fiona C.
Published: February 2009

Using chromatin immunoprecipitation combined with genomic microarrays we have identified targets of No tail (Ntl), a zebrafish Brachyury ortholog that plays a central role in mesoderm formation. We show that Ntl regulates a downstream network of other transcription factors and identify an in vivo Ntl binding site that resembles the consensus T-box binding site (TBS) previously identified by in vitro studies. We show that the notochord-expressed genefloating head(flh) is a direct transcriptional target of Ntl and that a combination of TBSs in theflhupstream region are required for Ntl-directed expression. Using our genome-scale data we have assembled a preliminary gene regulatory network that begins to describe mesoderm formation and patterning in the early zebrafish embryo.
Long-term efficacy and safety of
all-trans
retinoic acid/arsenic trioxide-based therapy in newly diagnosed acute promyelocytic leukemia
Authors: Hu Jiong , Liu Yuan-Fang , Wu Chuan-Feng , Xu Fang , Shen Zhi-Xiang , Zhu Yong-Mei , Li Jun-Min , Tang Wei , Zhao Wei-Li , Wu Wen , Sun Hui-Ping , Chen Qiu-Sheng , Chen Bing , Zhou Guang-Biao , Zelent Arthur , Waxman Samuel , Wang Zhen-Yi , Chen Sai-Juan , Chen Zhu
Published: February 2009

All-
trans
retinoic acid (ATRA)/arsenic trioxide (ATO) combination-based therapy has benefitted newly diagnosed acute promyelocytic leukemia (APL) in short-term studies, but the long-term efficacy and safety remained unclear. From April 2001, we have followed 85 patients administrated ATRA/ATO with a median follow-up of 70 months. Eighty patients (94.1%) entered complete remission (CR). Kaplan–Meier estimates of the 5-year event-free survival (EFS) and overall survival (OS) for all patients were 89.2% ± 3.4% and 91.7% ± 3.0%, respectively, and the 5-year relapse-free survival (RFS) and OS for patients who achieved CR (
n
= 80) were 94.8% ± 2.5% and 97.4% ± 1.8%, respectively. Upon ATRA/ATO, prognosis was not influenced by initial white blood cell count, distinct
PML-RAR
α types, or
FLT3
mutations. The toxicity profile was mild and reversible. No secondary carcinoma was observed, and 24 months after the last dose of ATRA/ATO, patients had urine arsenic concentrations well below the safety limit. These results demonstrate the high efficacy and minimal toxicity of ATRA/ATO treatment for newly diagnosed APL in long-term follow-up, suggesting a potential frontline therapy for de novo APL.