bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental study of the dehydration reactions gypsum-bassanite and bassanite-anhydrite at high pressure: Indication of anomalous behavior of H2O at high pressure in the temperature range of 50–300°C
Authors: Mirwald Peter W.
Published: February 2008

The system CaSO4–H2O, characterized by the three dehydration reactions gypsum-anhydrite, gypsum-bassanite, and bassanite-anhydrite, was reexamined by in situ differential pressure analysis in the temperature range of 60–350°C up to 3.5GPa pressure. The investigation revealed a fine structure in the dehydration boundaries of gypsum-bassanite and bassanite-anhydrite, each characterized by three inflections at 0.9–1.0, 1.9–2.0, and 2.6–28GPa. In addition, the phase transition of anhydrite high pressure anhydrite (monazite structure) was established for the first time at high P-T conditions intersecting the bassanite-anhydrite dehydration boundary at 2.15GPa∕250°C. Furthermore, the triple point gypsum-bassanite-anhydrite was redetermined with 235MPa∕80.5°C. The evaluation of the gypsum-bassanite dehydration boundary with respect to the volume and entropy change of the reaction, ΔVreact and ΔSreact, by means of the Clausius–Clapeyron relation yields for the entropy parameter an unusually large increase over the range of the noted inflections. This is interpreted as anomalous entropy behavior of H2O related presumably to a dramatic increase in fluctuations of the hydrogen network of the liquid leading possibly into a new structural state. The effect is strongly related to the three noted pressure levels of 0.9–1.0, 1.9–2.0, and 2.6–28GPa. In a synopsis of data including also a previous high pressure study in the temperature range between 0 and 80°C, a tentative P-T diagram of H2O is proposed.
A theoretical study for nanoparticle partitioning in the lamellae of diblock copolymers
Authors: Jin Jiezhu , Wu Jianzhong
Published: February 2008

Morphology control is important for practical applications of composite materials that consist of functional polymers and nanoparticles. Toward that end, block copolymers provide useful templates to arrange nanoparticles in the scaffold of self-organized polymer microdomains. This paper reports theoretical predictions for the distribution of nanoparticles in the lamellar structures of symmetric diblock copolymers on the basis of a polymer density functional theory (DFT) and the potential distribution theorem (PDT). The DFT predicts periodic spacing of lamellar structures in good agreement with molecular dynamics simulations. With the polymer structure from DFT as the input, the PDT is used to examine the effects of particle size, surface energy, polymer chain length, and compressibility on the distribution of nanoparticles in the limit of low particle density. It is found that the nanoparticle distribution depends not only on the particle size and surface energy but also on the local structure of the microdomain interface, polymer chain length, and compressibility. The theoretical predictions are compared well with experiments and simulations.
Model simulations of continuous ion injection into electron-beam ion source trap with slanted electrostatic mirror
Authors: Pikin A. , Kponou A. , Alessi J. G. , Beebe E. N. , Prelec K. , Raparia D.
Published: February 2008

The efficiency of trapping ions in an electron-beam ion source (EBIS) is of primary importance for many applications requiring operations with externally produced ions: RIA breeders, ion sources, and traps. At the present time, the most popular method of ion injection is pulsed injection, when short bunches of ions get trapped in a longitudinal trap while traversing the trap region. Continuous trapping is a challenge for EBIS devices because mechanisms which reduce the longitudinal ion energy per charge in a trap (cooling with residual gas, energy exchange with other ions, and ionization) are not very effective, and accumulation of ions is slow. A possible approach to increase trapping efficiency is to slant the mirror at the end of the trap which is opposite to the injection end. A slanted mirror will convert longitudinal motion of ions into transverse motion, and, by reducing their longitudinal velocity, prevent these ions from escaping the trap on their way out. The trade-off for the increased trapping efficiency this way is an increase in the initial transverse energy of the accumulated ions. The slanted mirror can be realized if the ends of two adjacent electrodes, drift tubes, which act as an electrostatic mirror, are machined to produce a slanted gap, rather than an upright one. Applying different voltages to these electrodes will produce a slanted mirror. The results of two-dimensional (2D) and three-dimensional (3D) computer simulations of the ion injection into an EBIS are presented using simplified models of an EBIS with conical (2D simulations) and slanted (3D simulations) mirror electrodes.
Surface discharge related properties of fiberglass reinforced plastic insulator for use in neutral beam injector of JT-60U
Authors: Yamano Y. , Takahashi M. , Kobayashi S. , Hanada M. , Ikeda Y.
Published: February 2008

Neutral beam injection (NBI) used for JT-60U is required to generate negative ions of 500keV energies. To produce such high-energy ions, three-stage electrostatic accelerators consisting of three insulator rings made of fiberglass reinforced plastic (FRP) are applied. The surface discharges along FRP insulators are one of the most serious problems in the development of NBI. To increase the hold-off voltage against surface flashover events, it is necessary to investigate the FRP insulator properties related to surface discharges in vacuum. This paper describes surface flashover characteristics for FRP and alumina samples under vacuum condition. The results show that the fold-off voltages for FRP samples are inferior to those of alumina ceramics. In addition, measurement results of surface resistivity and volume resistivity under vacuum and atmospheric conditions, secondary electron emission characteristics, and cathodoluminescence under some keV electron beam irradiation are also reported. These are important parameters to analyze surface discharge of insulators in vacuum.
Lithium cobalt oxide as electron injection material for high performance organic light-emitting diodes
Authors: Zhang Deqiang , Li Yang , Zhang Guohui , Gao Yudi , Duan Lian , Wang Liduo , Qiu Yong
Published: February 2008

Lithium cobalt oxide was introduced into organic light-emitting diodes as the electron injection layer. The device with tris(8-hydroxyquinolato) aluminum doped with 10-(2-benzothiazolyl)-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H,11H-[1]benzopyrano[6,7,8-ij]quinolizin-11-one as the light-emitting layer and LiCoO2 as the electron injection layer showed promising efficiency (10.74cd∕A at 11V) and longer lifetime (2.8 times as much as LiF∕Al control device). Lithium cobalt oxide proved to be thermally decomposed in vacuum to form lithium oxide, which was responsible for the enhanced electron injection.
A temperature control technique for nonequilibrium molecular simulation
Authors: Leimkuhler Ben , Legoll Frédéric , Noorizadeh Emad
Published: February 2008

We describe a dynamical approach to thermal regulation in molecular dynamics. Temperature is moderated by a control law and an additional variable, as in Nosé dynamics, but whose influence on the system decreases as the system approaches equilibrium. This device enables approximation of microcanonical averages and autocorrelation functions consistent with a given target temperature. Moreover, we demonstrate that the suggested technique is effective for the control of heat dissipation in a nonequilibrium setting, first by showing that the temperature control correctly regulates heat introduced by a rapid change to the system, and then by studying the slow relaxation of vibrational degrees of freedom (e.g., due to bonded atoms) in a solvent bath.
A hybrid local/global optimal control algorithm for dissipative systems with time-dependent targets: Formulation and application to relaxing adsorbates
Authors: Beyvers Stephanie , Saalfrank Peter
Published: February 2008

Open-system quantum optimal control theory for optical control of the dynamics of a quantum system in contact with a dissipative bath is used here for explicitly time-dependent target operators, Ô(t). Global and local control strategies are combined in a novel algorithm by defining a set of time slices, into which the total control time is subdivided. The optimization then proceeds locally forward in time from subinterval to subinterval, while within each subinterval global control theory is used with iterative forward-backward propagation. The subintervals are connected by appropriate boundary conditions. In the present paper, all operators are represented in the basis of the eigenstates of the field-free system Hamiltonian. The algorithm is first applied to and its computational performance tested for a two-level system with energy and phase relaxation, and later extended to a many-level model. Model parameters are chosen to represent the IR pulse excitation of the adsorbate-surface stretch mode of vibrationally relaxing CO on a Cu(100) surface. Various time-dependent targets are formulated to achieve (i) population inversion, (ii) the creation of a wavepacket, and (iii) overtone excitation by “ladder climbing.”
One-dimensional ablation in multiwire arrays
Authors: Sasorov P. V. , Oliver B. V. , Yu E. P. , Mehlhorn T. A.
Published: February 2008

The main physical processes responsible for plasma ablation in multiwire Z pinches are considered via eigensolutions to one-dimensional steady state magnetohydrodynamics. A double scale-length structure of the plasma accelerating layer is demonstrated. The width of the resistive scale-length that defines the current layer structure is significantly larger than the thermal scale-length, where transport of energy toward the cores and plasma pressure play important roles. The transport of energy is provided mainly by radiation, though electron thermal conduction is also important very close to the plasma-core interface. Another type of solution of the steady state problem is revealed, when local Ohmic heating is important down to the interface. Selection between these two types of solutions is considered from multiple points of view. Although the one-dimensional problem is mainly considered in this paper, it is shown how the one-dimensional results may help to understand results of two-dimensional models.
Magnetism of ZnO nanoparticles doped with 3d cations prepared by a solvothermal method
Authors: Alaria J. , Venkatesan M. , Coey J. M. D.
Published: February 2008

A systematic procedure for producing ZnO nanoparticles by heating ethanol and salt under pressure has been used to make pure ZnO and ZnO doped with cations of all 3d metals from Sc to Cu. When the ZnO is uniformly doped with the 3d cations, the nanoparticles show no ferromagnetism down to 4.2K. However, when the precursors are imperfectly dissolved in ethanol, ferromagnetism is found for Fe, Co, and Ni doping only.
Spin transfer torque in current-perpendicular-to-plane multilayer structure induced by spin relaxation in the capping layer
Authors: Kumar S. Bala , Tan S. G. , Jalil M. B. A. , Guo J. , Girgis E. , Jiang Yong
Published: February 2008

We study the effect of spin relaxation (SR) in the capping layer on spin-injection (SI) efficiency and spin torque (Γ) in a current-perpendicular-to-plane multilayer device comprising fixed(FM1)-spacer(NM1)-free(FM2)-capping(NM2) layers. In spin transfer switching of spin valves, high SI into free layer increases the net spin flux in the free layer and thus induces high Γ for magnetization switching. Our results show that the effect of capping layer SR on SI and Γ depends on the FM1 thickness (dFM1). The relationship between SR, SI, and dFM1 is explained by analyzing the spatial variation of spin accumulation across the device. The results of our calculations provide the theoretical basis for enhancing (minimizing) Γ by the localized manipulation of SR within the capping layer for magnetic random access memory (sensor) applications.
Effects of the magnetoelastic anisotropy in Ni nanowire arrays
Authors: Navas D. , Pirota K. R. , Mendoza Zelis P. , Velazquez D. , Ross C. A. , Vazquez M.
Published: February 2008

Nanoporous anodic alumina films on Al substrates have been used as templates for the growth of electrodeposited Ni nanowires. The nanowire diameter ranges between 35 and 65nm, and the hexagonal symmetry lattice constant is 105nm. The magnetization curves for these nanowire arrays with and without the Al substrate have been measured in a temperature range from 5to300K, from which the effective magnetic anisotropy, coercivity, and remanence have been determined. The effective easy magnetization axis changes from parallel to perpendicular to the Ni nanowire axis as temperature decreases, as a result of the magnetocrystalline and the magnetoelastic anisotropy terms, arising from the different thermal expansion coefficients of the ferromagnetic nanowires, the alumina and Al.
Effect of packing fraction on granular jetting from solid sphere entry into aerated and fluidized beds
Authors: Marston J. O. , Seville J. P. K. , Cheun Y-V. , Ingram A. , Decent S. P. , Simmons M. J. H.
Published: February 2008

When a solid sphere impacts on a granular bed, a high-speed vertical jet can arise following the collapse of the cavity that is formed by the penetration of the sphere into the bed. The jet then becomes unstable and breaks into discrete clusters due to density inhomogeneities. In this study, the jetting process was observed using high-speed photography and determined to be a function not only of impact velocity and particle size, but also of the packing fraction in the bed during the impact. Experiments were performed for two different bed diameters, two bed heights, and two impact velocities. Under certain conditions, below a threshold packing fraction, the jet is seen to divide into two distinct parts: a thin upper section followed by a thick base. Geometrical constraints are also shown to be critical in determining the dynamics of the jet.
Uniaxial magnetic anisotropy in Co and Co–Pt based perpendicular films in relation to lattice deformation
Authors: Shimatsu T. , Okazaki Y. , Sato H. , Muraoka H. , Aoi H. , Sakurai T. , Okamoto S. , Kitakami O. , Tanii S. , Sakuma A.
Published: February 2008

The relationship between uniaxial magnetic anisotropy Ku and lattice deformation was investigated for Co–Pt and Co perpendicular films and compared with theoretical results. A study of Co100−xPtx∕Ru perpendicular films (x=10,14,20) of various thickness showed that Ku increased as the c∕a ratio of the hcp Co–Pt lattice decreased, and the increase of Ku for a 1% reduction of c∕a was (8–10)×106erg∕cm3. The c∕a reduction was accompanied by an increase of the lattice volume Vlattice of about 2%. An examination of Co75Pt25 films deposited on various seed layer materials showed almost the same relationship between the value of Ku, the c∕a ratio, and Vlattice. Moreover, the rate of increase of Ku on reducing c∕a for single crystal Co perpendicular films was nearly the same as for the Co–Pt films. A theoretical calculation of Ku based on the linear muffin-tin orbital method in the atomic-sphere approximation revealed that both a decrease in the c∕a ratio and an increase in Vlattice enhance the Ku value of hcp-Co. The theoretical evaluation was qualitatively in good agreement with the experimental results, although the rate of increase of Ku evaluated experimentally was three to four times larger than the theoretical calculation.
Three-dimensional effects in trailing mass in the wire-array Z pinch
Authors: Yu Edmund P. , Cuneo M. E. , Desjarlais M. P. , Lemke R. W. , Sinars D. B. , Haill T. A. , Waisman E. M. , Bennett G. R. , Jennings C. A. , Mehlhorn T. A. , Brunner T. A. , Hanshaw H. L. , Porter J. L. , Stygar W. A. , Rudakov L. I.
Published: February 2008

The implosion phase of a wire-array Z pinch is investigated using three-dimensional (3D) simulations, which model the mass ablation phase and its associated axial instability using a mass injection boundary condition. The physical mechanisms driving the trailing mass network are explored, and it is found that in 3D the current paths though the trailing mass can reduce bubble growth on the imploding plasma sheath, relative to the 2D (r,z) equivalent. Comparison between the simulations and a high quality set of experimental radiographs is presented.
Spin-dependent transport in a ZnMnO∕ZnO heterostructure
Authors: Masuko K. , Ashida A. , Yoshimura T. , Fujimura N.
Published: February 2008

We report a spin-dependent transport property in modulation-doped ZnMnO:Al∕ZnMnO∕ZnO heterostructures. Using ZnO (0001¯) single crystal substrates, the heterostructures with atomically smooth surface and interface were prepared. For the sample with the Mn concentration of 12at.%, the electron confinement at the ZnMnO∕ZnO interface was recognized, indicating that ZnMnO layer acted as a barrier layer. In this paper, we investigated if an s-d exchange interaction exists between s electron conducting in the ZnO channel layer and Mn d spin in the ZnMnO barrier layer at the interface. To eliminate the Lorentz force and weak localization effects from the magnetoresistance (MR), the MR was measured under the magnetic field parallel to the sample surface. For a ZnMnO∕ZnO heterostructure with the sheet carrier concentration of 5.46×1012cm−2, at 1.85K, the parallel-field MR revealed that a positive MR was dominant below 0.8T, while a negative MR was recognized above 0.8T. The positive MR was well fitted to a Brillouin function, suggesting the existence of an s-d exchange interaction at the ZnMnO∕ZnO interface. The effect of the sheet carrier concentration on the MR behavior was also discussed.
Comment on “Accuracy limits and window corrections for photon Doppler velocimetry” [J. Appl. Phys. 101, 013523 (2007)]
Authors: Buttler W. T.
Published: February 2008

This comment addresses limitations of optical Doppler velocimetry in the presence of ejecta.
Temperature compensation of lamb wave sensor by combined antisymmetric mode and symmetric mode
Authors: Li Feng , Wu Yihui , Manceau Jean-François , Bastien François
Published: February 2008

Both thermal sensitivity and mass sensitivity in liquid of the first antisymmetric (A0) mode and the first symmetric (S0) mode of Lamb wave biosensor were investigated. A0 and S0 modes are sensitive to the mass change on the surface of the sensor but A0 mode is also sensitive to the liquid in the region of evanescent wave associated with Lamb wave. By combining A0 mode and S0 mode, the measurement error due to the environmental temperature drift decreased by a large factor, therefore, the environmental temperature was efficiently compensated without changing the structure of Lamb wave sensor.
Molecular mechanics modeling for properties of carbon nanotubes
Authors: Wang Q. , Liew K. M.
Published: February 2008

Molecular mechanics calculations for in-plane stiffness, shear modulus, and the bending rigidity of single-walled carbon nanotubes are reported in this work through the calculations of the strain energy for carbon nanotubes and graphite sheets subjected to various types of loading. Elastic rod and plate theories are employed to link the material properties of carbon nanotubes directly to the molecular mechanics calculations. The in-plane stiffness of carbon nanotubes is about 372–376J∕m2. The bending rigidity is found to be around 1.78eV for relatively large tubes and graphite sheets.
A model for the propagation of strain solitary waves in solids with relaxing atomic defects
Authors: Mirzade F. Kh.
Published: February 2008

A model for the propagation of nonlinear dispersive one-dimensional longitudinal strain waves in an isotropic solid with quadratic nonlinearity of elastic continuum is proposed by taking into account the interaction of the longitudinal displacements with the temperature field and the field of concentration of nonequilibrium (recombining) atomic point defects (vacancies and interstitial atoms). The governing nonlinear equation describing the evolution of the self-consistent strain fields is derived. It is shown that the thermoelastic effect on the strain waves manifests itself in the appearance of dissipative terms, which describe the heat transfer and the thermoelastic interaction caused by the strain-induced heat release due to the recombination of atomic defects. The equation that describes the evolution of the amplitude of nonlinear traveling localized waves with time in the single-wave approximation is derived, and on the basis of this equation, the damping increments of these waves are determined with allowance the dissipative losses. The influence of stress-induced decay of defect complexes on the evolution of nonlinear strain waves is considered.
Phase evolution, magnetic and electrical properties in Sm-doped bismuth ferrite
Authors: Nalwa Kanwar Singh , Garg Ashish
Published: February 2008

In this paper, we report on the effect of Sm doping on the phase evolution and properties of phase-pure Bi1−xSmxFeO3 (BSFO) ceramics synthesized via a conventional solid-state-reaction method. We find that upon calcination, Sm doping of bismuth ferrite promotes the formation of perovskitic phase and leads to the elimination of the secondary phases. On the other hand, undoped compositions do not yield completely phase-pure samples and contain secondary phases such as Bi25FeO40. Differential thermal analysis corroborates the sequence of phase evolution as examined from the x-ray diffraction patterns. A thermodynamic analysis, based on the bond energy, has been carried out to explain the effect of doping on the stabilization of perovskite structured phase upon Sm doping and is well supported by the thermal analysis results. Vibrating sample magnetometry measurements show that BSFO samples possess higher room temperature remnant magnetization than the undoped samples. Temperature dependent magnetic measurements suggest an antiferromagnetic behavior in the BSFO samples with a Néel temperature of ∼370°C, absent in the undoped samples. Mössbauer spectroscopy on Sm-doped specimens reveals the presence of phase-pure BSFO with absence of any Fe+2 ions. Interestingly, doped samples exhibit an order of magnitude increase in the leakage current density.
Impedance and magnetic properties of chemically synthesized CrO2∕Ag nanocomposite particles
Authors: Singh G. P. , Ram S.
Published: February 2008

The impedance of CrO2∕Ag nanocomposite particles has been investigated in the frequency range of 100Hz–1MHz at a temperature of 300–475K. The impedance in the form of Cole-Cole plot reveals that the resistivity contribution primarily comes from bulk grain interior below 375K and above those from both the grain interior and grain boundaries. The grain interior resistance decreases from 163kΩ at 300Kto6kΩ at 475K with a typical semiconductor like behavior. Above 375K, the impurities at grain boundaries are thermally activated and, thus, contribute to the dielectric relaxation. The electrical conductivity of the CrO2∕Ag nanocomposite follows an Arrhenius law with an activation energy/dielectric transition from 0.18to0.82eV at 400K. The dielectric transition is explained as the change of the crystal field caused by the thermal expansion or by the surface bond contraction in the small CrO2∕Ag particles. At 300K, the nanocomposite has an increased coercivity of 650Oe, with a saturation magnetization of 75emu∕g (equivalent to 1.13μB per Cr4+ ion), which is attributed to the spin pinning in the single domain CrO2∕Ag particles.
Magnetoelectric coefficient in BiFeO3 compounds
Authors: Caicedo J. M. , Zapata J. A. , Gómez M. E. , Prieto P.
Published: February 2008

In this work, we report magnetoelectric coefficient measurements in BiFeO3 (BFO) compounds using dynamic lock-in technique to evidence magnetoelectric coupling behavior. The response of the magnetoelectric coefficient shows rapid increase from low frequencies (0.1kHz) to around 5kHz, reaching a maximum, and then decreasing monotonously to 100kHz. For a constant frequency at 7kHz, the maximum magnetoelectric coefficient was close to 7mV∕cmOe, obtained at a bias magnetic field of H=120Oe. Thus, we demonstrated the feasibility of this technique for characterizing multiferroic materials.
MULTIMODE quantum calculations of intramolecular vibrational energies of the water dimer and trimer using ab initio-based potential energy surfaces
Authors: Wang Yimin , Carter Stuart , Braams Bastiaan J. , Bowman Joel M.
Published: February 2008

We report vibrational configuration interaction calculations of the monomer fundamentals of (H2O)2, (D2O)2, (H2O)3, and (D2O)3 using the code MULTIMODE and full dimensional ab initio-based global potential energies surfaces (PESs). For the dimer the HBB PES [Huang et al., J. Chem. Phys 128, 034312 (2008)] is used and for the trimer a new PES, reported here, is used. The salient properties of the new trimer PES are presented and compared to previous single-point calculations and the vibrational energies are compared with experiments.
Light scattering from an ordered array of needle-shaped organic nanoaggregates: Evidence for optical mode launching
Authors: Fiutowski J. , Bordo V. G. , Jozefowski L. , Madsen M. , Rubahn H.-G.
Published: February 2008

Pronounced peaks in both photoluminescence and light scattering from an array of almost parallel oriented, needle-shaped organic nanoaggregates on mica are observed as a function of angle of incidence. Within the framework of a simple theoretical model, we identify those peaks as originating from the launching of normal modes in the nanofibers, both radiative and waveguiding. Quantitative information is obtained about the mode spectrum and morphology of nanoscaled objects from a simple far field scattering measurement.
Soft magnetic properties of FeCo films with high saturation magnetization
Authors: Liu Xiaoxi , Morisako Akimitsu
Published: February 2008

The magnetic properties of multilayer composed of Fe65Co35 and thin layers of Co (less than 5nm) have been investigated. It is found that the microstructure, crystallographic texture, and magnetic softness of the multilayers depended on the initial layer. Multilayers with saturation magnetic induction higher than 23kG and hard axis coercivity smaller than 2Oe have been successfully prepared by using Co as the initial layer. Furthermore, the structure provided an effective process to tailor the in-plane magnetic anisotropy field without deteriorating the magnetic softness of the multilayers.
A unique dosing system for the production of OH under high vacuum for the study of environmental heterogeneous reactions
Authors: Brown Matthew A. , Johánek Viktor , Hemminger John C.
Published: February 2008

A unique dosing system for the production of hydroxyl radicals under high vacuum for the study of environmental heterogeneous reactions is described. Hydroxyl radicals are produced by the photodissociation of a hydrogen peroxide aqueous gas mixture with 254nm radiation according to the reaction H2O2+hν (254nm)→OH+OH. Under the conditions of the current design, 0.6% conversion of hydrogen peroxide is expected yielding a hydroxyl number density on the order of 1010molecules∕cm3. The flux distribution of the dosing system is calculated using a Monte Carlo simulation method and compared with the experimentally determined results. The performance of this unique hydroxyl dosing system is demonstrated for the heterogeneous reaction with a solid surface of potassium iodide. Coupling of the hydroxyl radical dosing system to a quantitative surface analysis system should help provide molecular level insight into detailed reaction mechanisms.
Building a better cell trap: Applying Lagrangian modeling to the design of microfluidic devices for cell biology
Authors: Kim Min-Cheol , Wang Zhanhui , Lam Raymond H. W. , Thorsen Todd
Published: February 2008

In this report, we show how computational fluid dynamics can be applied to the design of efficient hydrodynamic cell traps in microfluidic devices. Modeled hydrodynamic trap designs included a large, multiple-aperture “C-type” sieve for trapping hundreds of cells, flat single-aperture arrays for single cells, and “U-type” hydrodynamic structures with one or two apertures to confine small clusters of cells (∼10–15 cells per trap). Using 3T3 cells as a model system, the motion of each individual cell was calculated using a one-way coupled Lagrangian method. The cell was assumed to be a solid sphere, and interactions with other cells were only considered when a cell sedimented in the trap. The ordinary differential equations were solved along the cell trajectory for the three components of the velocity and location vector by using the Rosenbrock method based on an adaptive time-stepping technique. Validation of the predictive value of modeling, using 3T3 cells flowed through microfluidic devices containing “U-type sieves” under the simulation flow parameters, showed excellent agreement between experiment and simulation with respect to cell number per trap and the uniformity of cell distribution within individual microchambers. For applications such as on-chip cell culture or high-throughput screening of cell populations within a lab-on-a-chip environment, Lagrangian simulations have the potential to greatly simplify the design process.
Fully integrated detection of single magnetic beads in complementary metal-oxide-semiconductor
Authors: Florescu Octavian , Mattmann Moritz , Boser Bernhard
Published: February 2008

Microcoils are integrated with n-well Hall sensors in a complementary metal-oxide-semiconductor (CMOS) integrated circuit for the detection of individual superparamagnetic beads. The 4.2-μm-wide microcoils, generating magnetic fields of 800μT with 10mA of current, are used to polarize beads of 2.8μm in diameter. The resulting 10.8μT magnetization field induced in the bead is measured by a 4.7μm Hall sensor, stacked below the microcoil. The detection system has a sensitivity and resolution of 34V∕AT and 300nT∕√Hz, respectively. Integration of the magnetic bead detection onto a CMOS platform drastically reduces system cost, complexity, and power consumption, and marks an important milestone on the road to implementing low-cost, easy-to-use, point-of-care diagnostic assay.
Magnetic behavior and magnetocaloric effect of neodymium-based amorphous alloy
Authors: Gorsse S. , Orveillon G. , Chevalier B.
Published: February 2008

The Nd49Al13Ni38 amorphous alloy has been prepared by melt-spinning in the form of ribbons. Its magnetic properties have been investigated via superconducting quantum interference device magnetometry and its magnetic phase diagram was established. Hysteresis and temperature-dependent magnetization measurements show the occurrence of a reentrant spin-glass behavior on cooling. With increasing applied field, the spin-freezing temperature decreases and disappears at very high field, and the Curie temperature increases, broadening the temperature range of the ferromagnetic state. The resulting magnetocaloric effect was evaluated and compared to other interesting magnetic refrigerant materials.
High density platinum nanocrystals for non-volatile memory applications
Authors: Dufourcq J. , Bodnar S. , Gay G. , Lafond D. , Mur P. , Molas G. , Nieto J. P. , Vandroux L. , Jodin L. , Gustavo F. , Baron Th.
Published: February 2008

High density self-assembled platinum nanodots are elaborated using a radio frequence sputtering technique and embedded in memory structures. Electronic microscopy methods are used to characterize the morphology. Scanning electron microscopy and scanning transmission electron microscopy observations allow quantification of the density (>3×1012cm−2) and size (2–3nm) of the nanocrystals, whereas their crystallinity is investigated using high-resolution transmission electron microscopy. Then, capacitance-voltage sweep measurements give excellent memory characteristics with a 7.1V maximal memory window. Promising retention performances and an estimation of the number of electrons stored in the metallic nanodots are also given in this paper.
Influence of chirality on the interfacial bonding characteristics of carbon nanotube polymer composites
Authors: Zheng Qingbin , Xue Qingzhong , Yan Keyou , Gao Xili , Li Qun , Hao Lanzhong
Published: February 2008

The influence of chirality on the interfacial bonding characteristics of single-walled nanotubes (SWNTs) reinforced polymer composites was investigated using molecular mechanics and molecular dynamics simulations. The simulations indicate that the interfacial bonding and shear stress between the SWNT and the poly(methyl methacrylate) depends on the chirality. For SWNTs with similar molecular weights, diameters, and lengths, nanotubes with larger chiral angles achieve higher bonding energy and the armchair nanotube may be the best nanotube type for reinforcement. The general conclusions derived from this work may be of importance in devising advanced nanotube reinforced composites.
Interfacial thermodynamics of compressible polymer solutions
Authors: Ghiass Majid , Rey Alejandro D.
Published: February 2008

A variational model is developed to compute the coupled density and concentration fields that define the structure of planar interface between equilibrium phases of a compressible polymer solution. The solution of the model in conjunction with the modified Sanchez—Lacombe, with parametric data relevant to real polymer solutions, quantifies the role of compressibility on interfacial thermodynamics and interfacial tension. In particular, it is found that pressure pulses originating from density changes compensate chemical stresses. The interfacial tension, based on Bakker’s equation, between equilibrium polymer solution phases and corresponding interfacial thickness exhibits pressure scaling behavior analogous to that predicted with temperature for incompressible polymer solutions.
X-ray photoemission study of the Au∕La0.67Sr0.33MnO3 interface formation
Authors: Petti D. , Bertacco R. , Brivio S. , Cantoni M. , Cattoni A. , Ciccacci F.
Published: February 2008

We report an x-ray photoemission spectroscopy study of the Au∕La0.67Sr0.33MnO3 interface formation, aiming to investigate interface abruptness and possible chemical interdiffusion. Our results indicate that the gold deposition does not affect the chemical properties of manganite film and no interdiffusion or segregation takes place.
Diagnostics for low-energy electrons in a two-frequency capacitively coupled plasma in Ar
Authors: Ishimaru M. , Ohba T. , Ohmori T. , Yagisawa T. , Kitajima T. , Makabe T.
Published: February 2008

An experimental procedure to investigate the spatiotemporal characteristics of electrons in the vicinity of mean energy in a radiofrequency plasma is proposed by using optical emission and absorption spectroscopy in Ar. The method employs optical kinetics of long-lived metastable atom Ar(1s5) and short-lived excited Ar(2p9). The electron density distribution ne(z,t) is demonstrated in a typical condition in a two-frequency capacitively coupled plasma, excited at 100MHz and biased at 500kHz in pure Ar. The density shows almost time independent characteristics in the bulk plasma and a strong time dependence in the sheath in front of the bias electrode.
An analytical model of effective electrical conductivity of carbon nanotube composites
Authors: Deng Fei , Zheng Quan-Shui
Published: February 2008

Experiments on electrical properties of carbon nanotube (CNT) composites have shown that addition of CNTs may greatly enhance the electrical conductivity of the matrix. It has been a key but unresolved issue for years how to develop an analytical model of effective electrical conductivity of CNT composites that takes account of not only the CNT concentration and percolation, but also CNT conductivity anisotropy, aspect ratio, and nonstraightness. Such a model is established in this letter. The model predictions agree well with the measured data available in literatures and are also extended to account the effect of the orientation distribution of CNTs.
Preliminary evidence of field induced rhenium etching by XeF2 at high vacuum
Authors: Castano Giraldo C. H. , Aghazarian M. , Ruzic D. N.
Published: February 2008

Preliminary evidence of enhanced etching of rhenium by XeF2 under the influence of an electric field (3.36GV∕m) is presented. Scanning electron microscope photographs of sharp rhenium tips show etching of at least 0.40μm ±0.07 in 32min at the point of maximum electric field, indicating a field enhanced etching rate of 13nm∕min ±2. A control experiment shows a maximum spontaneous etching of rhenium by XeF2 of 0.1μm ±0.07 in 30min, indicating a maximum possible spontaneous etching rate of rhenium by XeF2 of 3nm∕min ±2. The spontaneous rate of tungsten by XeF2 reported in the literature is 0.2nm∕min.
GaAs interfacial self-cleaning by atomic layer deposition
Authors: Hinkle C. L. , Sonnet A. M. , Vogel E. M. , McDonnell S. , Hughes G. J. , Milojevic M. , Lee B. , Aguirre-Tostado F. S. , Choi K. J. , Kim H. C. , Kim J. , Wallace R. M.
Published: February 2008

The reduction and removal of surface oxides from GaAs substrates by atomic layer deposition (ALD) of Al2O3 and HfO2 are studied using in situ monochromatic x-ray photoelectron spectroscopy. Using the combination of in situ deposition and analysis techniques, the interfacial “self-cleaning” is shown to be oxidation state dependent as well as metal organic precursor dependent. Thermodynamics, charge balance, and oxygen coordination drive the removal of certain species of surface oxides while allowing others to remain. These factors suggest proper selection of surface treatments and ALD precursors can result in selective interfacial bonding arrangements.
Atomic-layer-deposited HfO2 on In0.53Ga0.47As: Passivation and energy-band parameters
Authors: Chang Y. C. , Huang M. L. , Lee K. Y. , Lee Y. J. , Lin T. D. , Hong M. , Kwo J. , Lay T. S. , Liao C. C. , Cheng K. Y.
Published: February 2008

Atomic-layer-deposited high κ dielectric HfO2 films on air-exposed In0.53Ga0.47As∕InP (100), using Hf(NCH3C2H5)4 and H2O as the precursors, were found to have an atomically sharp interface free of arsenic oxides, an important aspect for Fermi level unpinning. A careful and thorough probing, using high-resolution angular-resolved x-ray photoelectron spectroscopy (XPS) with synchrotron radiation, however, observed the existence of Ga2O3, In2O3, and In(OH)3 at the interface. The current transport of the metal-oxide-semiconductor capacitor for an oxide 7.8nm thick follows the Fowler–Nordheim tunneling mechanism and shows a low leakage current density of ∼10−8A∕cm2 at VFB+1V. Well behaved frequency-varying capacitance-voltage curves were measured and an interfacial density of states of 2×1012cm−2eV−1 was derived. A conduction-band offset of 1.8±0.1eV and a valence-band offset of 2.9±0.1eV have been determined using the current transport data and XPS, respectively.
Can results from a laboratory bioassay be used as an indicator of field performance of rice cultivars with allelopathic potential against Damasonium minus (starfruit)?
Authors: Seal Alexa N. , Pratley James E. , Haig Terry
Published: February 2008

Several weeds of rice in Australia have developed resistance to the main herbicide available for their control. Allelopathy is one phenomenon that could be incorporated into an integrated weed-management system as a supplement or alternative to synthetic herbicides. Several rice cultivars were screened both in the laboratory and the field for allelopathic potential against a major rice weed, Damasonium minus. Results from the laboratory bioassay showed that there were significant differences among cultivars in their ability to inhibit D. minus root growth. D. minus root lengths ranged from 2.0% (cv. Hungarian #1) to 32.6% (cv. Rexmont) that of the control. In the field study, significant differences existed in the D. minus dry matter grown in association with different cultivars, ranging from 4.6% (cv. Tono Brea) to 72.2% (cv. Rexmont) that of the control. Comparison between laboratory and field results indicated a strong relationship between performance in the field and in the laboratory (r2 = 0.713). Those cultivars ranked as allelopathic in the bioassay tended to have associated lower D. minus dry weight in the field. Eight of the top 10 allelopathic cultivars in the bioassay were among the top 10 suppressive cultivars in the field trial. This important finding indicates that at least some of the variation in field performance of cultivars may be predicted by their performance in bioassays.
Herbage accumulation, botanical composition, and nutritive value of five pasture types for dairy production in southern Australia
Authors: Tharmaraj J. , Chapman D. F. , Nie Z. N. , Lane A. P.
Published: February 2008

Four pasture treatments were compared with a perennial ryegrass (Lolium perenne) and white clover (Trifolium repens) mixture, the commonly sown pasture type, at 3 sites in south-western Victoria, to determine the extent to which total annual herbage accumulation and seasonal growth pattern could be manipulated in non-irrigated dairy systems. The pasture treatments were: (1) short-term winter-active (STW), based on Italian ryegrass (Lolium multiflorum); (2) long-term winter-active (LTW), based on Mediterranean tall fescue (Festuca arundinaceae) or cool-season active perennial ryegrass; (3) long-term summer-active (LTS), based on Continental tall fescue; and (4) perennial ryegrass pasture receiving moderately high nitrogen (N) inputs in winter and spring (total of 210 kg N/ha.year) to increase herbage accumulation during the ryegrass growing season (RHN). The perennial ryegrass and white clover mixture served as the control treatment. The 3 sites were Heytesbury (heavy clay soil), Terang (duplex soil), and Naringal (light soil). All pasture treatments were grazed by dairy cows. Herbage accumulation rate, botanical composition, and nutritive value of all pasture treatments were measured for 3 years. The winter-active pasture types had little effect on the overall seasonal distribution of forage supply or total annual yield compared with the control treatment. By contrast, the long-term summer-active pasture type significantly increased herbage accumulation during summer compared with all other pasture types (mean of an additional 1.3 t DM/ha during summer compared with the control treatment across all sites and years). However, this came at the cost of lower winter production (mean 0.8 t DM/ha). The LTS pasture also produced less dry matter than all other treatments in the first year after sowing at 2 of the 3 sites, reflecting the slower establishment of tall fescue. Ryegrass receiving high N inputs grew more total herbage on an annual basis than LTS. Mean total annual herbage accumulation (kg DM/ha.year) over the 3 years and 3 sites was in the order: RHN (14400) > LTS (13760) = Control (13170) > STW (12450) = LTW (12170) (P < 0.01). The results demonstrated that improvements over the industry ‘standard’ perennial ryegrass/white clover pasture management system in total herbage accumulation and the seasonal pattern of pasture growth are possible using existing pasture technology (mixtures of different species and cultivars, and N fertiliser inputs). However, significant interactions among sites, years and pasture treatments for several variables reinforced the need to understand limitations to plant growth on a site-by-site basis, to select plants that match the environmental conditions, and to then manage them appropriately to reach their growth potential.
Genetic analysis of grain yield conditioned on its component traits in rice (Oryza sativa L.)
Authors: Liu G. F. , Yang J. , Xu H. M. , Hayat Y. , Zhu J.
Published: February 2008

Grain yield (GY) of rice is a complex trait consisting of several yield components. It is of great importance to reveal the genetic relationships between GY and its yield components at the QTL (quantitative trait loci) level for multi-trait improvement in rice. In the present study, GY per plant in rice and its 3 yield component traits, panicle number per plant (PN), grain number per panicle (GN), and 1000-grain weight (GW), were investigated using a doubled-haploid population derived from a cross of an indica variety IR64 and a japonica variety Azucena. The phenotypic values collected from 2 cropping seasons were analysed by QTLNetwork 2.0 for mapping QTLs with additive (a) and/or additive × environment interaction (ae) effects. Furthermore, conditional QTL analysis was conducted to detect QTLs for GY independent of yield components. The results showed that the general genetic variation in GY was largely influenced by GN with the contribution ratio of 29.2%, and PN and GN contributed 10.5% and 74.6% of the genotype × environment interaction variation in GY, respectively. Four QTLs were detected with additive and/or additive × environment interaction effects for GY by the unconditional mapping method. However, for GY conditioned on PN, GN, and GW, 6 additional loci were identified by the conditional mapping method. All of the detected QTLs affecting GY were associated with at least one of the 3 yield components. The results revealed that QTL expressions of GY were contributed differently by 3 yield component traits, and provide valuable information for effectively improving GY in rice.
The collective-risk social dilemma and the prevention of simulated dangerous climate change
Authors: Milinski Manfred , Sommerfeld Ralf D. , Krambeck Hans-Jürgen , Reed Floyd A. , Marotzke Jochem
Published: February 2008

Will a group of people reach a collective target through individual contributions when everyone suffers individually if the target is missed? This “collective-risk social dilemma” exists in various social scenarios, the globally most challenging one being the prevention of dangerous climate change. Reaching the collective target requires individual sacrifice, with benefits to all but no guarantee that others will also contribute. It even seems tempting to contribute less and save money to induce others to contribute more, hence the dilemma and the risk of failure. Here, we introduce the collective-risk social dilemma and simulate it in a controlled experiment: Will a group of people reach a fixed target sum through successive monetary contributions, when they know they will lose all their remaining money with a certain probability if they fail to reach the target sum? We find that, under high risk of simulated dangerous climate change, half of the groups succeed in reaching the target sum, whereas the others only marginally fail. When the risk of loss is only as high as the necessary average investment or even lower, the groups generally fail to reach the target sum. We conclude that one possible strategy to relieve the collective-risk dilemma in high-risk situations is to convince people that failure to invest enough is very likely to cause grave financial loss to the individual. Our analysis describes the social window humankind has to prevent dangerous climate change.