bluuebunny/crossref_metadata_2025 huggingface dataset:
Planar Hall effect and magnetic anisotropy in epitaxially strained chromium dioxide thin films
Authors: Goennenwein S. T. B. , Keizer R. S. , Schink S. W. , van Dijk I. , Klapwijk T. M. , Miao G. X. , Xiao G. , Gupta A.
Published: April 2007

We have measured the in-plane anisotropic magnetoresistance of 100nm thick CrO2 thin films at liquid He temperatures. In low magnetic fields H, both the longitudinal and the transverse (planar Hall) resistance show abrupt switches, which characteristically depend on the orientation of H. All the experimental findings consistently demonstrate that the magnetic anisotropy in these CrO2 thin films is biaxial. We show that the biaxial magnetic anisotropy is due to epitaxial coherency strain, and that it naturally explains the complex magnetic switching behavior reported recently in CrO2 films with thicknesses of 50nm⩽d⩽250nm.
Generalized fractional Schrödinger equation with space-time fractional derivatives
Authors: Wang Shaowei , Xu Mingyu
Published: April 2007

In this paper the generalized fractional Schrödinger equation with space and time fractional derivatives is constructed. The equation is solved for free particle and for a square potential well by the method of integral transforms, Fourier transform and Laplace transform, and the solution can be expressed in terms of Mittag-Leffler function. The Green function for free particle is also presented in this paper. Finally, we discuss the relationship between the cases of the generalized fractional Schrödinger equation and the ones in standard quantum.
Porous, self-supported Ni3S2∕Ni nanoarchitectured electrode operating through efficient lithium-driven conversion reactions
Authors: Wang Qiang , Gao Rui , Li Jinghong
Published: April 2007

To benefit from the large capacity gain advantages offered by lithium-driven conversion reactions and to overcome intrinsic kinetic limitations, a porous, self-supported Ni3S2∕Ni nanoarchitectured electrode concept is reported. The originality of this electrode configuration is rooted in low-temperature hydrothermal techniques, which provide an efficient way to enable the realization of a better interface contact in order to easily fuel electrons to the active material and to add mechanical cohesion to the electrode. A preliminary result shows that the nanoarchitectured electrode exhibits a sustained reversible capacity at 2C rate with a loss of only 18% after 20cycles and outstanding rate capability even at a rate of 16C.
Electromagnetic and microwave absorption properties of (Co2+–Si4+) substituted barium hexaferrites and its polymer composite
Authors: Abbas S. M. , Chatterjee R. , Dixit A. K. , Kumar A. V. R. , Goel T. C.
Published: April 2007

The electromagnetic (EM) and microwave absorption properties of (Co2+–Si4+) substituted barium hexaferrite compositions BaCox2+Fey+2Six+y4+Fe12−2x−2y+3O19 (x=0.9 and y=0.0, 0.05, and 0.2) and its polymer composites prepared from hexaferrite, polyaniline, and carbon powders dispersed in polyurethane matrix have been investigated at the microwave frequency range of the X band (8.2–12.4GHz). The hexaferrite compositions were synthesized by solid-state reaction technique, whereas polyaniline, by chemical route. The permeabilities of a ferrite are drastically reduced at higher gigahertz frequencies. The permittivities, however, can be enhanced by appropriate choice of composition and processing temperature. In the present ferrite composition, silicon content is taken in excess so as to convert some of the Fe3+ ions to Fe2+ ions. This conversion has been shown to enhance EM and absorption properties. Mössbauer spectroscopy on the samples establishes that addition of excess Si4+ converts some of the Fe3+ to Fe2+. The sintered ferrites have shown resonance phenomena, but the composites do not. The EM parameters ε′, ε″, μ′, and μ″ were measured using a vector network analyzer (Agilent, model PNA E8364B). These measured EM parameters were used to determine the absorption spectra at different sample thicknesses based on a model of a single layered plane wave absorber backed by a perfect conductor. The sintered ferrite composition (x=0.9 and y=0.05) showed the best absorption properties [a minimum reflection loss of −17.7to−14.3dB over the whole frequency range of the X band (8.2–12.4) for a sample thickness of just 0.8mm], and it is used in the composite absorbers in powder form along with other constituents. The optimized composite absorber has shown dielectric constant ε′∼11.5, dielectric loss ε″∼2.3, and a minimum reflection loss of −29dB at 10.97GHz with the −20dB bandwidth over the frequency range of 9.7–12.2GHz for a sample thickness of 2.0mm. The magnetic parameters μ′ and μ″ for the composite remained nearly 1 and 0, respectively, throughout the measured frequency range. Both sintered ferrite and composite absorbers can fruitfully be utilized for suppression of electromagnetic interference and reduction of radar signatures (stealth technology).
Optical transmission through gold film with Archimedean-like subwavelength hole arrays
Authors: Li Jia-Qi , Yang Wei-Qing , Zhang Yan-Ting , Wang Qian-Jin , Huang Cheng-Ping , Zhu Yong-Yuan
Published: April 2007

In this paper, two kinds of Archimedean-like hole arrays [Archimedean 4 (A4) and Archimedean 7 (A7)] that have been fabricated in gold films and the optical transmission spectra from the visible to near-infrared region have been measured. With A4 and A7 hole arrays, the Fourier coefficients of reciprocal lattice vectors are manipulated, with which the transmission suppression and enhancement have been experimentally observed. The results provide the possibility to manipulate the light transmission through the design of both reciprocal vectors and Fourier coefficients by engineering the metal surface.
Theory of electron localization at dielectric-metal interfaces: A continuum model
Authors: Zharikov A. A. , Fischer S. F.
Published: April 2007

Localization of electrons at dielectric-metal interfaces is studied in the framework of a continuum model. The layer of thickness L, with a negative electron affinity, is characterized by the static dielectric constant εs and by the optical dielectric constant ε∞. It is found that the electron localization along the plane of the interface occurs if the layer thickness exceeds a critical value Lc. In the case of a high polar layer, the electron energy of the localized ground state shows a nonmonotonic dependence on the layer thickness. A strong correlation between low-lying excitations and the spread of the localized state has been established. The magnitude of the correlation parameter is close to the analogous correlation for the solvated electron in the bulk. The localization dynamics is discussed in terms of relaxation along a polarization coordinate, which is directly connected to the polarization energy of the layer.
Crystallization process and amorphous state stability of Si-Sb-Te films for phase change memory
Authors: Feng J. , Zhang Z. F. , Zhang Y. , Cai B. C. , Lin Y. Y. , Tang T. A. , Chen Bomy
Published: April 2007

Crystallization process and amorphous state stability of Si-Sb-Te films with different Si concentration (10, 20 at. %) and Sb/Te ratio (2:3 and 1:1) have been studied and compared with Ge2Sb2Te5 (GST) film by in situ film resistance measurements. The effects of Si concentration and Sb content on crystalline resistivity, crystallization temperature, activation energy of crystallization, and amorphous state stability of films have been studied. The activation energy Ea of crystallization of GST film was confirmed to be 2.34 eV, while the activation energy Ea of Si10Sb36Te54 film increased to 2.99 eV and further reached to 3.65 eV for Si20Sb32Te48 film when the Si content increased to 20 at. %. Si addition increased the crystallization temperature and crystalline resistivity of Si-Sb-Te films largely, and enhanced the amorphous state stability of the films, while Sb revealed contrary effects to Si. The microstructures of Si-Sb-Te films were analyzed through x-ray diffraction and high resolution transmission electron microscopy. Phase separation has been observed in annealed Si-Sb-Te films, and Si-Sb-Te films crystallized into rhombohedral Sb2Te3 phase surrounded by amorphous Si-rich grain boundaries with high resistance, which would be helpful to reduce the writing current of phase change memory.
Protein destruction by a helium atmospheric pressure glow discharge: Capability and mechanisms
Authors: Deng X. T. , Shi J. J. , Kong M. G.
Published: April 2007

Biological sterilization represents one of the most exciting applications of atmospheric pressure glow discharges (APGD). Despite the fact that surgical instruments are contaminated by both microorganisms and proteinaceous matters, sterilization effects of APGD have so far been studied almost exclusively for microbial inactivation. This work presents the results of a detailed investigation of the capability of a helium-oxygen APGD to inactivate proteins deposited on stainless-steel surfaces. Using a laser-induced fluorescence technique for surface protein measurement, a maximum protein reduction of 4.5 logs is achieved by varying the amount of the oxygen admixture into the background helium gas. This corresponds to a minimum surface protein of 0.36 femtomole/mm2. It is found that plasma reduction of surface-borne protein is through protein destruction and degradation, and that its typically biphasic reduction kinetics is influenced largely by the thickness profile of the surface protein. Also presented is a complementary study of possible APGD protein inactivation mechanisms. By interplaying the protein inactivation kinetics with optical emission spectroscopy, it is shown that the main protein-destructing agents are excited atomic oxygen (via the 777 and 844 nm emission channels) and excited nitride oxide (via the 226, 236, and 246 nm emission channels). It is also demonstrated that the most effective protein reduction is achieved possibly through a synergistic effect between atomic oxygen and nitride oxide. This study is a useful step toward a full confirmation of the efficacy of APGD as a sterilization technology for surgical instruments contaminated by prion proteins.
Thermoelectric properties of n-type nanocrystalline bismuth-telluride-based thin films deposited by flash evaporation
Authors: Takashiri M. , Takiishi M. , Tanaka S. , Miyazaki K. , Tsukamoto H.
Published: April 2007

The thermal conductivity of n-type nanocrystalline bismuth-telluride-based thin films (Bi2.0Te2.7Se0.3) is investigated by a differential 3ω method at room temperature. The nanocrystalline thin films are grown on a glass substrate by a flash evaporation method, followed by hydrogen annealing at 250 °C. The structure of the thin films is studied by means of atomic force microscopy, x-ray diffraction, and energy-dispersive x-ray spectroscopy. The thin films exhibit an average grain size of 60 nm and a cross-plane thermal conductivity of 0.8 W∕m K. The in-plane electrical conductivity and in-plane Seebeck coefficient are also investigated. Assuming that the in-plane thermal conductivity of the thin films is identical to that of the cross-plane direction, the in-plane figure of merit of the thin films is estimated to be ZT=0.7. As compared with a sintered bulk sample with average grain size of 30 μm and nearly the same composition as the thin films, the nanocrystalline thin films show approximately a 50% reduction in the thermal conductivity, but the electrical conductivity also falls 40%. The reduced thermal and electrical conductivities are attributed to increased carrier trapping and scattering in the nanocrystalline film.
Surface-state related luminescence in ZnO nanocrystals
Authors: Fallert Johannes , Hauschild Robert , Stelzl Felix , Urban Alex , Wissinger Markus , Zhou Huijuan , Klingshirn Claus , Kalt Heinz
Published: April 2007

We investigate the optical properties of four different samples of ZnO nanocrystals, with a particle size average varying from 70 up to 380nm. The photoluminescence (PL) of all samples shows at low temperature an emission band around 3.31eV, which is several orders of magnitude stronger compared to the PL of bulk ZnO at this energy. This band shows a clear dependence on the surface to volume ratio of the nanocrystals and is therefore assigned to surface states. Temperature dependent measurements reveal that this band plays a major role up to room temperature for all examined ZnO powders. Additionally, intensity dependent measurements display that the origin of this emission band can be assigned to bound exciton complexes (BECs). Compared to the well known shallow BECs the measured lifetimes of these relatively strong bound excitons states are much longer.
Kinetic self-organization of trenched templates for the fabrication of versatile ferromagnetic nanowires
Authors: Borca B. , Fruchart O. , David Ph. , Rousseau A. , Meyer C.
Published: April 2007

The authors have self-organized versatile magnetic nanowires, i.e., with variable period and adjustable magnetic anisotropy energy (MAE). First, using the kinetic roughening of W(110), uniaxial templates of trenches were grown on commercial sapphire wafers. Unlike most templates used for self-organization, those have a variable period; 4–12nm are demonstrated here. Fe deposition then results in the formation of wires in the trenches. The magnitude of MAE could be engineered up or down by changing the capping layer or underlayer, in turn affecting the mean superparamagnetic temperature, raised to 175K so far.
Accurate calculation of anharmonic vibrational frequencies of medium sized molecules using local coupled cluster methods
Authors: Hrenar Tomica , Werner Hans-Joachim , Rauhut Guntram
Published: April 2007

Local coupled cluster methods were applied for the automated generation of accurate multidimensional potential energy surfaces for a set of test molecules ranging from six to nine atoms. Based on these surfaces anharmonic fundamental frequencies were computed using vibrational self-consistent field and configuration interaction methods. The computed vibrational frequencies are compared to those obtained from similar calculations using conventional coupled cluster methods and to experimental values. The results from local and conventional methods are found to be of similar accuracy and in close agreement with experimental values. In addition, an efficient parallelization of the fully automated surface generation code is presented.
Resonance-antiresonance electromagnetic behavior in a disordered dielectric composite
Authors: Zhen L. , Jiang J. T. , Shao W. Z. , Xu C. Y.
Published: April 2007

In the present study, a kind of SiCw/wax composite was prepared and its electromagnetic properties were studied experimentally. It is found that Mie resonance can occur in this composite in spite of its disordered structure. The Mie resonance is believed to lead to the resonant-antiresonant electromagnetic behavior accompanied by a negative ε″ in the SiCw/wax composite in the 2–18GHz band range. The resulted magnetic behavior in the current composite is believed to be weakened by the random orientation of the whiskers.
Frequency-dependent magnetoresistance and magnetocapacitance properties of magnetic tunnel junctions with MgO tunnel barrier
Authors: Padhan P. , LeClair P. , Gupta A. , Tsunekawa K. , Djayaprawira D. D.
Published: April 2007

The frequency-dependent impedance of magnetic tunnel junctions (MTJs) with MgO barriers was investigated. The capacitance of the MTJs switches from high to low when the relative electrode magnetizations change from parallel to antiparallel, opposite the resistance change. Additionally, for parallel magnetizations, the capacitance varies with temperature though resistance remains approximately constant. The low frequency resistance and the tunneling magnetoresistance are in agreement with dc values. The capacitance is found to be larger than the expected (geometrical) capacitance, in contrast to MTJs with Al2O3 barriers. These results are explained by screening due to charge and spin accumulation at the interfaces.
Nd
3
+
ion shift under domain inversion by electron beam writing in LiNbO3
Authors: Molina P. , Sarkar D. , Ramírez M. O. , García Solé J. , Bausá L. E. , García B. J. , Muñoz Santiuste J. E.
Published: April 2007

Ferroelectric domain inversion has been obtained in Nd3+ doped lithium niobate by means of direct electron beam writing. The local effects of the polarization inversion on the optical transitions of Nd3+ ions have been studied by low temperature high resolution site selective spectroscopy. Inverted regions present different axial crystal field acting over Nd3+ ions compared with noninverted (original) regions. The results can be interpreted in terms of slight shifts of Nd3+ ions along the ferroelectric c axis within the Li+ octahedrons, as a result of the lattice rearrangement after the domain inversion processes.
Evidence for segregation of Te in Ge2Sb2Te5 films: Effect on the “phase-change” stress
Authors: Krusin-Elbaum L. , Cabral C. , Chen K. N. , Copel M. , Abraham D. W. , Reuter K. B. , Rossnagel S. M. , Bruley J. , Deline V. R.
Published: April 2007

The authors present direct evidence for Te segregation to the grain boundaries in chalcogenide Ge2Sb2Te5 films by using transmission electron microscopy scans with a 0.5nm diameter focused probe. This finding is consistent with the observed impeded grain growth and with the post-transition relief of a “spikelike” stress, fully to the pretransition level. Te motion shows up in void formation below 200°C, a pileup of Te at the surface and its loss at higher (above 400°C) temperatures. Tuning the driving force for this segregation may be key for the optimal phase-change material design.
Quantum mechanical effects in nanometer field effect transistors
Authors: Luo Jun-Wei , Li Shu-Shen , Xia Jian-Bai , Wang Lin-Wang
Published: April 2007

The atomistic pseudopotential quantum mechanical calculations for million atom nanosized metal-oxide-semiconductor field-effect transistors (MOSFETs) are presented. When compared with semiclassical Thomas-Fermi simulation results, there are significant differences in I-V curve, electron threshold voltage, and gate capacitance. In many aspects, the quantum mechanical effects exacerbate the problems encountered during device minimization, and it also presents different mechanisms in controlling the behaviors of a nanometer device than the classical one.
Bias current effects on the magnetoresistance of a ferromagnetic-semiconductor-ferromagnetic trilayer
Authors: Bala Kumar S. , Tan S. G. , Jalil M. B. A.
Published: April 2007

The authors apply a self-consistent ballistic-diffusive theoretical model to study the bias current j effect on the magnetoresistance of a ferromagnet (FM)-semiconductor (SC)-FM trilayer, with SC highly doped (n++). The interfacial resistance becomes a dynamic parameter and its decrease with increasing j would be responsible for the decrease of magnetoresistance (MR) with j. The underlying physics of this model is based on a self-consistent treatment between the spin drift diffusion transport of electrons in the bulk and ballistic transmission at the interfaces. This model applies qualitatively to the more common FM-nonmagnetic-FM, metal-based current-perpendicular-to-plane spin valve, which has shown experimentally observed decline of MR with j.
Transition between grain boundary and intragrain scattering transport mechanisms in boron-doped zinc oxide thin films
Authors: Steinhauser J. , Faÿ S. , Oliveira N. , Vallat-Sauvain E. , Ballif C.
Published: April 2007

A comprehensive model for the electronic transport in polycrystalline ZnO:B thin films grown by low pressure chemical vapor deposition is presented. The optical mobilities and carrier concentration calculated from reflectance spectra using the Drude model were compared with the data obtained by Hall measurements. By analyzing the results for samples with large variation of grain size and doping level, the respective influences on the transport of potential barriers at grain boundaries and intragrain scattering could be separated unambiguously. A continuous transition from grain boundary scattering to intragrain scattering is observed for doping level increasing from 3×1019to2×1020cm−3.
Enhancement of terahertz wave generation from laser induced plasma
Authors: Xie Xu , Xu Jingzhou , Dai Jianming , Zhang X.-C.
Published: April 2007

It is well known that air plasma induced by ultrashort laser pulses emits broadband terahertz waves. The authors report the study of terahertz wave generation from the laser induced plasma where there is a preexisting plasma background. When a laser beam from a Ti:sapphire amplifier is used to generate a terahertz wave, enhancement of the generation is observed if there is another laser beam creating a plasma background. The enhancement of the terahertz wave amplitude lasts hundreds of picoseconds after the preionized background is created, with a maximum enhancement up to 250% observed.
Event-driven Brownian dynamics for hard spheres
Authors: Scala A. , Voigtmann Th. , De Michele C.
Published: April 2007

Brownian dynamics algorithms integrate Langevin equations numerically and allow to probe long time scales in simulations. A common requirement for such algorithms is that interactions in the system should vary little during an integration time step; therefore, computational efficiency worsens as the interactions become steeper. In the extreme case of hard-body interactions, standard numerical integrators become ill defined. Several approximate schemes have been invented to handle such cases, but little emphasis has been placed on testing the correctness of the integration scheme. Starting from the two-body Smoluchowski equation, the authors discuss a general method for the overdamped Brownian dynamics of hard spheres, recently developed by one of the authors. They test the accuracy of the algorithm and demonstrate its convergence for a number of analytically tractable test cases.
Influence of hole transport units on the efficiency of polymer light emitting diodes
Authors: Laquai Frédéric , Hertel Dirk
Published: April 2007

Charge transport and electroluminescence efficiency in spirobifluorene polymers containing triarylamine as hole transport unit have been studied. The hole mobility as measured by the time-of-flight technique was found to be on the order of 10−4cm2V−1s−1. The field and temperature dependences of the mobility are in accord with the Gaussian disorder model. Best device efficiencies of the blue emitting materials are in the range of 2.9cd∕A. The influence of the hole transport unit on charge transport and device efficiency is analyzed. The efficiency depends critically on the amount of the hole transport unit and decreases with increasing hole mobility.
Effects of octahedral thickness variance on the temperature coefficient of resonant frequency of the B-site deficient hexagonal perovskites
Authors: Zhao Fei , Yue Zhenxing , Pei Jing , Gui Zhilun , Li Longtu
Published: April 2007

The temperature coefficient of resonant frequency (τf) and the structure of B-site deficient hexagonal perovskite materials have been assembled with the intention of understanding the structure-property relationship. Based on the refined structure data, the authors proposed a structure-related parameter v to characterize the octahedral thickness variance. Therefore, a correlation between the value of τf and the octahedral thickness variance has been established. This approach illustrates that the octahedral thickness variance plays an important role in the value and sign of τf. It also gives a satisfying explanation for the variation of τf in the Ba5Nb4O15–Ba5Ta4O15 system.
Thermal conductance of single-walled carbon nanotube embedded in an elastic half-space
Authors: Prasher Ravi
Published: April 2007

Calculations of ballistic thermal conductance of single-walled carbon nanotube (CNT) embedded in an elastic half-space are presented. The conductance is very different than the conductance of freestanding CNT due to change in phonon velocity and maximum cutoff frequency. Depending on the temperature, the conductance of embedded CNT can be higher or lower than that of freestanding CNT. Applications of the formulation are in CNT-based nanocomposites or CNT in contact with an elastic substrate. Good agreement with experimental thermal conductivity of nanocomposites made from single-walled CNT and epoxy is found.
Pressure-dependent Raman scattering and photoluminescence of Zn1−xCdxSe epilayers
Authors: Lin Y. C. , Chiu C. H. , Fan W. C. , Yang S. L. , Chuu D. S. , Chou W. C.
Published: April 2007

Raman and photoluminescence spectra of cubic Zn1−xCdxSe (0≦x≦0.32) epilayers were obtained at high pressure. The impurity mode I observed in the phonon Raman spectra at low temperature confirms the intermediate phonon mode behavior. A split transverse optical phonon mode was found in the down-stroke high-pressure Raman scattering. Additionally, the pressure-dependent longitudinal optical (LO) phonon frequencies and the Grüneisen parameter (γLO) were obtained by quadratic polynomial fitting. Pressure-driven resonant Raman scattering effect was observed in samples with a high Cd concentration (x≧0.18). The critical pressure of semiconductor-to-metal phase transition (Pt) decreases as the Cd content increases. As the Cd concentration increases from 0 to 0.32, Pt falls from 13.6to9.4GPa, according to Pt (GPa)=13.6−6.8x−20.3x2.
High insulating quality CaF2 pseudomorphic films on Si(111)
Authors: Sokolov N. S. , Kaveev A. K. , Krupin A. V. , Tyaginov S. E. , Vexler M. I. , Ikeda S. , Tsutsui K. , Saiki K.
Published: April 2007

Current-voltage characteristics of epitaxially grown Au∕CaF2∕Si(111) metal-insulator-semiconductor structures with thin (1.5–6nm) pseudomorphic fluoride layer have been studied. It was found that CaF2 films in these structures are of better insulating quality than those in the devices reported previously. Typical breakdown field for the fluorite layers was about 8×106V∕cm and the tunnel current did not exceed the values predicted by simulations with realistic parameters.
Rectifying properties of magnetite-based Schottky diode and the effects of magnetic field
Authors: Chen Y. Z. , Sun J. R. , Xie Y. W. , Wang D. J. , Lu W. M. , Liang S. , Shen B. G.
Published: April 2007

Rectifying properties, with and without magnetic field, of a high quality Fe3O4∕SrTiO3:Nb Schottky diode have been experimentally studied. The junction exhibits an excellent rectifying behavior both below and above the Verwey temperature (TV) of Fe3O4. Magnetic field has a weak but visible effect on the transport process of the junction, producing a negative magnetoresistance for TTV. Based on an analysis of the current-voltage characteristics, the spin polarization of Fe3O4 has been deduced. It is a strong function of temperature, varying between −78% and 18%.
All-optical nondemolition measurement of single hole spin in a quantum-dot molecule
Authors: Troiani F. , Wilson-Rae I. , Tejedor C.
Published: April 2007

The authors propose an all-optical scheme to perform a nondemolition measurement of a single hole spin localized in a quantum-dot molecule. The latter is embedded in a microcavity and driven by two lasers. This allows them to induce Raman transitions which entangle the spin state with the polarization of the emitted photons. They find that the measurement can be completed with high fidelity on a time scale T∼102ps, shorter than the typical decoherence time.
Thermal annealing effects on the electrical characteristics of the back interface in nano-silicon-on-insulator channel
Authors: Cho Won-Ju , Ahn Chang-Geun
Published: April 2007

The electrical properties of the back interface between the thin silicon and buried-oxide layers of nano-silicon-on-insulator substrate were evaluated. The effects of rapid thermal annealing (RTA) process were investigated, and the distributions of interface states at the thin silicon/buried-oxide interface were estimated by using metal-point-contact field-effect-transistor method. The interface-states at the back interface were considerably increased by RTA process. The RTA higher than 800°C contributes to the increase of acceptor-type interface states. The increased interface states were effectively reduced by conventional furnace annealing at 500°C in nitrogen ambient.
Vapor pressure critical amplitudes from the normal boiling point
Authors: Velasco S. , Román F. L. , White J. A. , Mulero A.
Published: April 2007

The authors propose a method to estimate the two first critical amplitudes for the vapor pressure of a fluid in terms only of the reduced pressure, Pbr=Pb∕Pc, and temperature, Tbr=Tb∕Tc, of the normal boiling point. The method is based on the fact that the product (1−Tr)Pr presents a maximum near the critical region. Based on a study of 43 fluids, the authors found that the reduced pressure and temperature of that maximum can be obtained from simple relations in terms of the parameter h≡TbrlnPbr∕(Tbr−1). These relations are checked against additional data for 1608 fluids.
Low-power switching in magnetoresistive random access memory bits using enhanced permeability dielectric films
Authors: Pietambaram Srinivas V. , Rizzo N. D. , Dave R. W. , Goggin J. , Smith K. , Slaughter J. M. , Tehrani S.
Published: April 2007

We reduced the switching field (Hsw) in arrays of single-layer magnetoresistive random access memory elements using enhanced permeability dielectric (EPD) films. This reduction is due to an increased magnetic flux density produced at the bit by increasing the permeability μ of the surrounding dielectric. The authors produced EPD films by embedding superparamagnetic nanoparticles of various sizes in oxides of Al, Mg, or Si. For bits surrounded by EPD, Hsw decreased linearly as μ increased. Using this approach, we reduced Hsw by ≈40% for μ=3.5, without changing the energy barrier to magnetization reversal.
Epitaxial growth of Ba0.3Sr0.7TiO3 thin films on Al2O3(0001) using ultrathin TiN layer as a sacrificial template
Authors: Yamada Tomoaki , Muralt Paul , Sherman Vladimir O. , Sandu Cosmin S. , Setter Nava
Published: April 2007

Epitaxial Ba0.3Sr0.7TiO3 (BST) films with significantly improved tunable performance were grown on c-plane sapphire [Al2O3(0001)] substrates using ultrathin TiN seed layers by pulsed laser deposition. A very thin (111) epitaxial TiN layer deposited at room temperature acted as a sacrificial epitaxial template for the BST film in the initial growth stage. The BST films grew with (111) orientation having BST[21¯1¯]‖Al2O3[112¯0] and BST[21¯1¯]‖Al2O3[21¯1¯0] epitaxial relationships. Planar capacitors fabricated on the epitaxial BST film showed significantly higher tunability as compared to those on a polycrystalline BST film directly deposited on the substrate.
Complete genetic linkage can subvert natural selection
Authors: Gerrish Philip J. , Colato Alexandre , Perelson Alan S. , Sniegowski Paul D.
Published: April 2007

The intricate adjustment of organisms to their environment demonstrates the effectiveness of natural selection. But Darwin himself recognized that certain biological features could limit this effectiveness, features that generally reduce the efficiency of natural selection or yield suboptimal adaptation. Genetic linkage is known to be one such feature, and here we show theoretically that it can introduce a more sinister flaw: when there is complete linkage between loci affecting fitness and loci affecting mutation rate, positive natural selection and recurrent mutation can drive mutation rates in an adapting population to intolerable levels. We discuss potential implications of this finding for the early establishment of recombination, the evolutionary fate of asexual populations, and immunological clearance of clonal pathogens.
Extracellular RNA constitutes a natural procoagulant cofactor in blood coagulation
Authors: Kannemeier Christian , Shibamiya Aya , Nakazawa Fumie , Trusheim Heidi , Ruppert Clemens , Markart Philipp , Song Yutong , Tzima Eleni , Kennerknecht Elisabeth , Niepmann Michael , von Bruehl Marie-Luise , Sedding Daniel , Massberg Steffen , Günther Andreas , Engelmann Bernd , Preissner Klaus T.
Published: April 2007

Upon vascular injury, locally controlled haemostasis prevents life-threatening blood loss and ensures wound healing. Intracellular material derived from damaged cells at these sites will become exposed to blood components and could contribute to blood coagulation and pathological thrombus formation. So far, the functional and mechanistic consequences of this concept are not understood. Here, we present
in vivo
and
in vitro
evidence that different forms of eukaryotic and prokaryotic RNA serve as promoters of blood coagulation. Extracellular RNA was found to augment (auto-)activation of proteases of the contact phase pathway of blood coagulation such as factors XII and XI, both exhibiting strong RNA binding. Moreover, administration of exogenous RNA provoked a significant procoagulant response in rabbits. In mice that underwent an arterial thrombosis model, extracellular RNA was found associated with fibrin-rich thrombi, and pretreatment with RNase (but not DNase) significantly delayed occlusive thrombus formation. Thus, extracellular RNA derived from damaged or necrotic cells particularly under pathological conditions or severe tissue damage represents the long sought natural “foreign surface” and provides a procoagulant cofactor template for the factors XII/XI-induced contact activation/amplification of blood coagulation. Extracellular RNA thereby reveals a yet unrecognized target for antithrombotic intervention, using RNase or related therapeutic strategies.
Microarray analysis of newly synthesized RNA in cells and animals
Authors: Kenzelmann M. , Maertens S. , Hergenhahn M. , Kueffer S. , Hotz-Wagenblatt A. , Li L. , Wang S. , Ittrich C. , Lemberger T. , Arribas R. , Jonnakuty S. , Hollstein M. C. , Schmid W. , Gretz N. , Gröne H. J. , Schütz G.
Published: April 2007

Current methods to analyze gene expression measure steady-state levels of mRNA. To specifically analyze mRNA transcription, we have developed a technique that can be applied
in vivo
in intact cells and animals. Our method makes use of the cellular pyrimidine salvage pathway and is based on affinity-chromatographic isolation of thiolated mRNA. When combined with data on mRNA steady-state levels, this method is able to assess the relative contributions of mRNA synthesis and degradation/stabilization. It overcomes limitations associated with currently available methods such as mechanistic intervention that disrupts cellular physiology, or the inability to apply the techniques
in vivo
. Our method was first tested in serum response of cultured fibroblast cells and then applied to the study of renal ischemia reperfusion injury, demonstrating its applicability for whole organs
in vivo
. Combined with data on mRNA steady-state levels, this method provided a detailed analysis of regulatory mechanisms of mRNA expression and the relative contributions of RNA synthesis and turnover within distinct pathways, and identification of genes expressed at low abundance at the transcriptional level.
Structure and evolution of the Ivy protein family, unexpected lysozyme inhibitors in Gram-negative bacteria
Authors: Abergel Chantal , Monchois Vincent , Byrne Deborah , Chenivesse Sabine , Lembo Frédérique , Lazzaroni Jean-Claude , Claverie Jean-Michel
Published: April 2007

Part of an ancestral bactericidal system, vertebrate C-type lysozyme targets the peptidoglycan moiety of bacterial cell walls. We report the crystal structure of a protein inhibitor of C-type lysozyme, the
Escherichia coli
Ivy protein, alone and in complex with hen egg white lysozyme. Ivy exhibits a novel fold in which a protruding five-residue loop appears essential to its inhibitory effect. This feature guided the identification of Ivy orthologues in other Gram-negative bacteria. The structure of the evolutionary distant
Pseudomonas aeruginosa
Ivy orthologue was also determined in complex with hen egg white lysozyme, and its antilysozyme activity was confirmed. Ivy expression protects porous cell-wall
E. coli
mutants from the lytic effect of lysozyme, suggesting that it is a response against the permeabilizing effects of the innate vertebrate immune system. As such, Ivy acts as a virulence factor for a number of Gram-negative bacteria-infecting vertebrates.
ATM deficiency impairs thymocyte maturation because of defective resolution of T cell receptor α locus coding end breaks
Authors: Vacchio Melanie S. , Olaru Alexandru , Livak Ferenc , Hodes Richard J.
Published: April 2007

The ATM (ataxia telangiectasia mutated) protein plays a central role in sensing and responding to DNA double-strand breaks. Lymphoid cells are unique in undergoing physiologic double-strand breaks in the processes of Ig class switch recombination and T or B cell receptor V(D)J recombination, and a role for ATM in these processes has been suggested by clinical observations in ataxia telangiectasia patients as well as in engineered mice with mutations in the
Atm
gene. We demonstrate here a defect in thymocyte maturation in ATM-deficient mice that is associated with decreased efficiency in V-J rearrangement of the endogenous T cell receptor (TCR)α locus, accompanied by increased frequency of unresolved TCR Jα coding end breaks. We also demonstrate that a functionally rearranged TCRαβ transgene is sufficient to restore thymocyte maturation, whereas increased thymocyte survival by bcl-2 cannot improve TCRα recombination and T cell development. These data indicate a direct role for ATM in TCR gene recombination
in vivo
that is critical for surface TCR expression in CD4
+
CD8
+
cells and for efficient thymocyte selection. We propose a unified model for the two major clinical characteristics of ATM deficiency, defective T cell maturation and increased genomic instability, frequently affecting the TCRα locus. In the absence of ATM, delayed TCRα coding joint formation results both in a reduction of αβ TCR-expressing immature cells, leading to inefficient thymocyte selection, and in accumulation of unstable open chromosomal DNA breaks, predisposing to TCRα locus-associated chromosomal abnormalities.
Structural basis for ligand and heparin binding to neuropilin B domains
Authors: Vander Kooi Craig W. , Jusino Manuel A. , Perman Benjamin , Neau David B. , Bellamy Henry D. , Leahy Daniel J.
Published: April 2007

Neuropilin (Nrp) is a cell surface receptor with essential roles in angiogenesis and axon guidance. Interactions between Nrp and the positively charged C termini of its ligands, VEGF and semaphorin, are mediated by Nrp domains b1 and b2, which share homology to coagulation factor domains. We report here the crystal structure of the tandem b1 and b2 domains of Nrp-1 (N1b1b2) and show that they form a single structural unit. Cocrystallization of N1b1b2 with Tuftsin, a peptide mimic of the VEGF C terminus, reveals the site of interaction with the basic tail of VEGF on the b1 domain. We also show that heparin promotes N1b1b2 dimerization and map the heparin binding site on N1b1b2. These results provide a detailed picture of interactions at the core of the Nrp signaling complex and establish a molecular basis for the synergistic effects of heparin on Nrp-mediated signaling.
Prenatal Organophosphate Metabolite and Organochlorine Levels and Performance on the Brazelton Neonatal Behavioral Assessment Scale in a Multiethnic Pregnancy Cohort
Authors: Engel Stephanie M. , Berkowitz Gertrud S. , Barr Dana B. , Teitelbaum Susan L. , Siskind Jodi , Meisel Stefanie J. , Wetmur James G. , Wolff Mary S.
Published: April 2007

Prenatal exposures to organophosphate pesticides and polychlorinated biphenyls have been associated with abnormal neonatal behavior and/or primitive reflexes. In 1998–2002, the Mount Sinai Children's Environmental Health Center (New York City) investigated the effects of indoor pesticide use and exposure to polychlorinated biphenyls on pregnancy outcome and child neurodevelopment in an inner-city multiethnic cohort. The Brazelton Neonatal Behavioral Assessment Scale was administered before hospital discharge (n = 311). Maternal urine samples were analyzed for six dialkylphosphate metabolites and malathion dicarboxylic acid. A random subset of maternal peripheral blood samples from the entire cohort (n = 194) was analyzed for polychlorinated biphenyls and 1,1′-dichloro-2,2′-bis(4-chlorophenyl)ethylene. Malathion dicarboxylic acid levels above the limit of detection were associated with a 2.24-fold increase in the number of abnormal reflexes (95% confidence interval: 1.55, 3.24). Likewise, higher levels of total diethylphosphates and total dialkylphosphates were associated with an increase in abnormal reflexes, as was total dimethylphosphates after paraoxonase expression was considered. No adverse associations were found with polychlorinated biphenyl or 1,1′-dichloro-2,2′-bis(4-chlorophenyl)ethylene levels and any behavior. The authors uncovered additional evidence that prenatal levels of organophosphate pesticide metabolites are associated with anomalies in primitive reflexes, which are a critical marker of neurologic integrity.
I. Harding v Wealands
Authors: McEleavy Peter , Dougherty Charles , Wyles Lucy
Published: April 2007

In Harding v Wealands1 the House of Lords had to consider the vexed question of where the dividing line between substance and procedure should lie in private international law. The specific issue before their Lordships was whether matters relating to the assessment of damages in tort should be treated as matters of substance, and thus be for the applicable law, or whether they should be treated as matters of procedure, and therefore be left for the law of the forum. The decision of the House of Lords has resolved this difficult question in favour of a procedural characterization. The result of the House of Lords' decision is that in all such cases, regardless of the foreign law element, the assessment of damages will be conducted in accordance with English (Northern Irish or Scottish) law, as the law of the forum. Nonetheless, some reservations do exist as to the justification for the decision and as to how likely it is to remain the last word on the subject.
Regulation of angiogenesis in the bone marrow of myelodysplastic syndromes transforming to overt leukaemia
Authors: Keith Tamara , Araki Yuko , Ohyagi Masaki , Hasegawa Maki , Yamamoto Kouhei , Kurata Morito , Nakagawa Yasunori , Suzuki Kenshi , Kitagawa Masanobu
Published: April 2007

To investigate the regulatory mechanisms of angiogenesis in the development of myelodysplastic syndromes (MDS) and its progression to overt leukaemia (OL), bone marrow samples from control, paired samples from MDS patients before and after transformation to OL (MDS → OL) and de novo acute myeloid leukaemia (AML) were analysed. Immunohistochemical staining showed a significant increase of bone marrow microvascular density (MVD) in MDS and de novo AML compared with controls. Surprisingly, in MDS, MVD significantly decreased upon transformation to OL, which was also significantly lower than the MVD of de novo AML. This evidence was strengthened by the pattern of angiogenic mediator gene expression, confirming the importance of various angiogenic mediators including vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), tumour necrosis factor α (TNFα), hepatocyte growth factor (HGF) and the angiopoietin family of mediators (Ang‐1 and Ang‐2) as well as the receptors for angiogenic mediators, such as VEGF receptor 2 (VEGFR2) and the tyrosine kinase receptor, TIE2. By contrast, the anti‐angiogenic mediator, transforming growth factor‐β (TGFβ) exhibited significantly higher expression in the bone marrow of MDS → OL, indicating the importance of this cytokine as the suppressive factor of angiogenesis in MDS. These findings indicate that the bone marrow microenvironment in MDS → OL and de novo AML differs remarkably, suggesting the different efficacy of anti‐angiogenic therapy between de novo AML and leukaemia secondary to MDS.
Cl‐IB‐MECA inhibits human erythropoiesis
Authors: Bhanu Natarajan V. , Aerbajinai Wulin , Gantt Nicole M. , Jackson Edwin K. , Goh Sung‐Ho , Terry Lee Y. , Miller Jeffery L.
Published: April 2007

Candidate drugs are being sought for the suppression of human erythropoiesis. Cl‐IB‐MECA [2‐chloro‐N6‐(3‐iodobenzyl)‐adenosine‐5′‐N‐methyluronamide] is a derivative of adenosine that inhibits the growth of leukaemic cell lines. To determine the effects of Cl‐IB‐MECA upon erythropoiesis, studies were performed by using an ex vivo culture system of primary human CD34+ cells. Cl‐IB‐MECA suppressed erythroblast growth and maturation at doses ≥50 μmol/l through a mechanism of cell cycle inhibition and accumulation of cells in the G1/G0 phase. These findings demonstrate that Cl‐IB‐MECA inhibits human erythropoiesis, and suggest that further consideration of this drug is warranted for patients with erythrocytosis or polycythemia syndromes.
Iron deprivation blocks multilineage haematopoietic differentiation by inhibiting induction of p21(WAF1/CIP1)
Authors: Alcantara Orlando , Boldt David H.
Published: April 2007

Iron is required for the differentiation of HL‐60 cells along the monocyte lineage in vitro, reflecting a requirement for iron in the transcriptional induction of the p21(WAF1/CIP1) gene. To determine if the same requirement holds true for differentiation in other cell lineages and for primary human CD34+ bone marrow precursor cells, we induced granulocyte differentiation by treating HL‐60 cells with dimethyl sulphoxide, and erythroid or megakaryocytic differentiation by treating K562 cells with butyrate or phorbol myristate acetate, respectively. Nitro blue tetrazolium reduction, expression of haem, or expression of CD41 was used to assess granulocytic, erythroid, or megakaryocytic differentiation respectively. Purified CD34+ cells were cultured with granulocyte/macrophage‐colony stimulating factor and stem cell factor to induce myelomonocytic differentiation. Iron deprivation was induced by desferrioxamine. p21(WAF1/CIP1) antisense oligonucleotides were used to inhibit p21 expression. Iron deprivation blocked p21 induction as judged by real‐time polymerase chain reaction assays. In addition, both iron deprivation and p21 antisense blocked CD34+ cell differentiation. These observations were not explained by induction of widespread apoptosis under conditions of iron deprivation. We concluded that both iron and functional p21(WAF1/CIP1) are required for in vitro differentiation of human haematopoietic precursors along multiple cell lineages.
Prognostic value of serum free light chain ratio at diagnosis in multiple myeloma
Authors: Kyrtsonis Marie‐Christine , Vassilakopoulos Theodoros P. , Kafasi Nicoletta , Sachanas Sotirios , Tzenou Tatiana , Papadogiannis Argiroula , Galanis Zacharoula , Kalpadakis Christina , Dimou Maria , Kyriakou Elias , Angelopoulou Maria K. , Dimopoulou Maria N. , Siakantaris Marina P. , Dimitriadou Evangelia M. , Kokoris Styliani I. , Panayiotidis Panayiotis , Pangalis Gerassimos A.
Published: April 2007

The prognostic value of baseline serum free light chain ratio (sFLCR) was investigated in 94 multiple myeloma (MM) patients. sFLCR was calculated as κ/λ or λ/κ, depending on the patients’ dominating monoclonal light chain. Median baseline sFLCR was 3·57 in κ‐MM patients, 45·09 in λ‐MM. ‘High’ sFLCR (≥ the observed median value for κ‐ and λ‐MM respectively) correlated with elevated serum creatinine and lactate dehydrogenase, extensive marrow infiltration and light chain type MM. The 5‐year disease‐specific survival was 82% and 30% in patients with sFLCR lower than and equal or greater than the median, respectively (P = 0·0001). sFLCR was an independent prognostic factor.