bluuebunny/crossref_metadata_2025 huggingface dataset:
Determination of the nanoscale dielectric constant by means of a double pass method using electrostatic force microscopy
Authors: Riedel C. , Arinero R. , Tordjeman Ph. , Ramonda M. , Lévêque G. , Schwartz G. A. , Oteyza D. G. de , Alegria A. , Colmenero J.
Published: August 2009

We present a method to determine the local dielectric permittivity of thin insulating layers. The measurement is based on the detection of force gradients in electric force microscopy by means of a double pass method. The proposed experimental protocol is simple to implement and does not need any modification of standard commercial devices. Numerical simulations based on the equivalent charge method make it possible to carry out quantification whatever the thickness of film, the radius of the tip, and the tip-sample distance. This method has been validated on a thin SiO2 sample for which the dielectric permittivity at the nanoscale has been characterized in the literature. We also show how we can quantitatively measure the local dielectric permittivity for ultrathin polymer film of poly(vinyl acetate) and polystyrene.
The design and application of virtual ion meter based on LABVIEW 8.0
Authors: Meng Hu , Li Jiangyuan , Tang Yonghuai
Published: August 2009

The virtual ion meter is developed based on LABVIEW 8.0 by homemade adjusting circuit, data acquisition (DAQ) board, and computer. This note provides details of the structure of testing system and flow chart of DAQ program. This virtual instrument system is applied to multitask testing such as determining rate constant of second-order reaction by pX, pX potentiometric titration, determining oscillating reaction by potential, etc. The result of application indicates that this test system not only has function of real-time data acquiring, displaying, storage, but also realizes remote monitoring and controlling test-control spots through internet, automatic analyzing and processing of data, reporting of result according to the different testing task; moreover, the veracity and repeatability of data processing result are higher than the results of manual data processing.
Monte Carlo simulation study of scanning Auger electron images
Authors: Li Y. G. , Ding Z. J. , Zhang Z. M.
Published: August 2009

Simulation of contrast formation in Auger electron imaging of surfaces is helpful for analyzing scanning Auger microscopy/microanalysis (SAM) images. In this work, we have extended our previous Monte Carlo model and the simulation method for calculation of scanning electron microscopy (SEM) images to SAM images of complex structures. The essentials of the simulation method are as follows. (1) We use a constructive solid geometry modeling for a sample geometry, which is complex in elemental distribution, as well as in topographical configuration and a ray-tracing technique in the calculation procedure of electron flight steps that across the different element zones. The combination of the basic objects filled with elements, alloys, or compounds enables the simulation to a variety of sample geometries. (2) Sampled Auger signal electrons with a characteristic energy are generated in the simulation following an inner-shell ionization event, whose description is based on the Castani’s inner-shell ionization cross section. This paper discusses in detail the features of simulated SAM images and of line scans for structured samples, i.e., the objects embedded in a matrix, under various experimental conditions (object size, location depth, beam energy, and the incident angle). Several effects are predicted and explained, such as the contrast reversion for nanoparticles in sizes of 10–60 nm, the contrast enhancement for particles made of different elements and wholly embedded in a matrix, and the artifact contrast due to nearby objects containing different elements. The simulated SAM images are also compared with the simulated SEM images of secondary electrons and of backscattered electrons. The results indicate that the Monte Carlo simulation can play an important role in quantitative SAM mapping.
Performance of nano superconducting quantum interference devices for small spin cluster detection
Authors: Granata C. , Vettoliere A. , Walke P. , Nappi C. , Russo M.
Published: August 2009

In the present paper, performance of nano-superconducting-quantum-interference devices (SQUIDs) has been investigated in view of their employment in the detection of small spin populations. The analysis has been focused on nano-SQUID sensors having a square loop with a side length of 200 nm. We calculate the spin sensitivity and the magnetic response relative to the single Bohr magneton (single spin), as a function of its position within the SQUID hole. The results show that the SQUID response depends strongly on the spin position; the ratio between the spin sensitivity evaluated in the center of the loop and the minimum one is as high as a factor of 3 for a spin at a reasonable distance z′ of 10 nm from the SQUID plane. Furthermore, the magnetic flux due to several hundred of spins has been evaluated by considering different random spin distributions within the SQUID hole. Due to the both nonuniform SQUID response and the random distribution process, the results show a statistical uncertainty which has been evaluated as a function of the spin number. The estimated informations are very useful to optimize the sensor performance in view of the most nanomagnetism applications.
Fast-switching system for injection seeding of a high-power Ti:sapphire laser
Authors: Khalesifard Hamid R. , Fix Andreas , Ehret Gerhard , Schiller Max , Wulfmeyer Volker
Published: August 2009

A high frequency switching and tunable seed laser system has been designed and constructed for injection seeding of a high-power pulsed Ti:sapphire laser. The whole laser system operates as the transmitter of a scanning, ground-based, water-vapor differential absorption lidar (DIAL). The output of two seed lasers can be tuned in the wavelength range of 815–840 nm up to the power of 20 mW and switched between the online and offline wavelengths of the DIAL at frequencies of 0–1 kHz. The frequency stability of online and offline seed lasers is better than ±20 MHz rms and the mode-hop-free tuning range is greater than 40 GHz with external cavity diode lasers. The advantage of this system for efficient injection seeding of the Ti:sapphire cavity is that it is modular, robust, fully fiber-coupled, and polarization maintaining.
Relativistic theory of nuclear magnetic resonance parameters in a Gaussian basis representation
Authors: Kutzelnigg Werner , Liu Wenjian
Published: August 2009

The calculation of NMR parameters from relativistic quantum theory in a Gaussian basis expansion requires some care. While in the absence of a magnetic field the expansion in a kinetically balanced basis converges for the wave function in the mean and for the energy with any desired accuracy, this is not necessarily the case for magnetic properties. The results for the magnetizability or the nuclear magnetic shielding are not even correct in the nonrelativistic limit (nrl) if one expands the original Dirac equation in a kinetically balanced Gaussian basis. This defect disappears if one starts from the unitary transformed Dirac equation as suggested by Kutzelnigg [Phys. Rev. A 67, 032109 (2003)]. However, a new difficulty can arise instead if one applies the transformation in the presence of the magnetic field of a point nucleus. If one decomposes certain contributions, the individual terms may diverge, although their sum is regular. A controlled cancellation may become difficult and numerical instabilities can arise. Various ways exist to avoid these singularities and at the same time get the correct nrl. There are essentially three approaches intermediate between the transformed and the untransformed formulation, namely, the bispinor decomposition, the decomposition of the lower component, and the hybrid unitary transformation partially at operator and partially at matrix level. All three possibilities were first considered by Xiao et al. [J. Chem. Phys. 126, 214101 (2007)] in a different context and in a different nomenclature. Their analysis and classification in a more general context are given here for the first time. Use of an extended balanced basis has no advantages and has other drawbacks and is not competitive, while the use of a restricted magnetic balance basis can be justified.
Analytic continuation average spectrum method for quantum liquids
Authors: Reichman David R. , Rabani Eran
Published: August 2009

We revisit the problem of determining the real-frequency density response in quantum fluids via analytical continuation of imaginary-time quantum Monte Carlo data. We demonstrate that the average spectrum method (ASM) is capable of revealing resolved modes in the dynamic structure factor of both ortho-deuterium and liquid para-hydrogen, in agreement with experiments and quantum mode-coupling theories, while the maximum entropy approach yields only a smooth unimodal spectrum. Outstanding issues are discussed. Our work provides the first application of the ASM method in realistic off-lattice systems.
Dielectric and piezoelectric properties of K0.5Na0.5NbO3–AgSbO3 lead-free ceramics
Authors: Lin Dunmin , Kwok K. W. , Chan H. L. W.
Published: August 2009

Lead-free piezoelectric ceramics (1−x)K0.5Na0.5NbO3–xAgSbO3+0.75 mol % MnO2 were prepared by a conventional solid-state sintering technique, and the piezoelectric and dielectric properties of the ceramics were studied. The results of x-ray diffraction suggest that AgSbO3 diffuses into the K0.5Na0.5NbO3 lattices to form a new solid solution with a single-phase orthorhombic perovskite structure. After the addition of AgSbO3, the paraelectric cubic-ferroelectric tetragonal phase transition temperature (TC) and the ferroelectric tetragonal-ferroelectric orthorhombic phase transition temperature (TO-T) decrease, and the ceramics become “softened,” resulting in significant improvements in the ferroelectric and piezoelectric properties. The ceramics with x=0.03–0.10 exhibit excellent piezoelectric properties: d33=130–216 pC/N, kp=0.44–0.51, and kt=0.40–0.52. The ceramics also exhibit a good thermal stability up to high TO-T, suggesting that the ceramics are promising candidates for lead-free piezoelectric ceramics.
Molecular dynamics simulation of effective thermal conductivity of vapor-filled nanogap and nanocavity
Authors: Hwang G. S. , Kaviany M.
Published: August 2009

The effect of adsorption on momentum au and thermal aT accommodation coefficients and effective thermal conductivity ⟨kf⟩ of Ar vapor-filled Pt nanogap and nanocavity is examined using nonequilibrium molecular dynamics (MD) simulations. For the accommodation coefficients, the increase in solid-fluid or fluid-fluid interatomic interactions within adsorbed layer causes transitions in magnitudes of au and aT near Ar triple-point temperature. In the nanogap, ⟨kf⟩ MD results are in close agreement with the available closed-form solution for transition-flow regime, i.e., Knudsen number 0.1<KnL<10, using the MD results of aT. In the nanocavity, the adiabatic sidewalls do not significantly alter the gas mean free path and ⟨kf⟩, and the sparse adsorption coverage on the sidewalls results in a negligibly small fluid circulation by surface diffusion under a temperature gradient.
Microstrip resonators for electron paramagnetic resonance experiments
Authors: Torrezan A. C. , Mayer Alegre T. P. , Medeiros-Ribeiro G.
Published: August 2009

In this article we evaluate the performance of an electron paramagnetic resonance (EPR) setup using a microstrip resonator (MR). The design and characterization of the resonator are described and parameters of importance to EPR and spin manipulation are examined, including cavity quality factor, filling factor, and microwave magnetic field in the sample region. Simulated microwave electric and magnetic field distributions in the resonator are also presented and compared with qualitative measurements of the field distribution obtained by a perturbation technique. Based on EPR experiments carried out with a standard marker at room temperature and a MR resonating at 8.17 GHz, the minimum detectable number of spins was found to be 5×1010 spins/GHz1/2 despite the low MR unloaded quality factor Q0=60. The functionality of the EPR setup was further evaluated at low temperature, where the spin resonance of Cr dopants present in a GaAs wafer was detected at 2.3 K. The design and characterization of a more versatile MR targeting an improved EPR sensitivity and featuring an integrated biasing circuit for the study of samples that require an electrical contact are also discussed.
Development of a local vacuum system for focused ion beam machining
Authors: Masuzawa Tsuneaki , Yoshida Yoshikazu , Ikeda Hiromichi , Oguchi Keigo , Yamagishi Hikaru , Wakabayashi Yuji
Published: August 2009

A local vacuum system for focused ion beam (FIB) processing, with a workpiece set in the air, has been developed. The local vacuum apparatus had a double-wall cylinder structure, used a differential exhaust, and each cylinder was connected to a vacuum exhaust pump. When the gap between the workpiece and the apparatus was 10 μm, the pressure of beam line in the machining head achieved 2.1×10−3 Pa. In addition, a visualization system was developed by visualizing the current flow out from a sample by FIB irradiation. With this system, it is possible to conduct focus adjustments of the FIB and shape recognition on a workpiece in the order of microns.
Electron spin quantum beats and room temperature g factor in GaAsN
Authors: Zhao H. M. , Lombez L. , Liu B. L. , Sun B. Q. , Xue Q. K. , Chen D. M. , Marie X.
Published: August 2009

We report on the investigation of electron spin quantum beats at room temperature in GaAsN thin films by time-resolved Kerr rotation technique. The measurement of the quantum beats, which originate from the Larmor precession of electron spins in external transverse magnetic field, yields an accurate determination of the conduction electron g factor. We show that the g factor of GaAs1−xNx thin films is significantly changed by the introduction of a small nitrogen fraction.
Characterization of hydrogen storage materials by means of pressure concentration isotherms based on the mass flow method
Authors: Bielmann Michael , Kato Shunsuke , Mauron Philippe , Borgschulte Andreas , Züttel Andreas
Published: August 2009

The determination of the equilibrium thermodynamic parameters of hydrogen storage materials from quasiequilibrium pressure data using the mass flow pressure concentration isotherm (pcI) method is presented. The method bases on the acquisition of pcI curves at different flow rates using a thermal mass flow controller to determine the amount of ad/desorbed hydrogen. These measurements provide a set of corresponding quasiequilibrium pressure functions from, which the true equilibrium pressure of the hydride is calculated by extrapolation to zero flow. The governing thermodynamic parameters can then be determined to characterize the material by the construction of a van’t Hoff plot, extracting enthalpy of reaction ΔHr and entropy of reaction ΔSr from the equilibrium pressure peq as a function of temperature. Naturally, true equilibrium can never be reached and therefore can only be approximated by measurement––a drawback that all experimental techniques share. This complication is alleviated by the flow-pcI approach at different flow rates. The compilation of the peq(T) data from pcI-measurements can be performed by different methods, whereas the so called Sieverts apparatus is most commonly used. In this paper, we elaborate the differences and advantages of the mass flow-pcI over the Sieverts Apparatus and present measurements and results on LaNi5 as a benchmark. Measurements at different flow rates are presented and equilibrium pressures at zero flow are achieved by extrapolation. The obtained results of ΔHd=32.5 kJ mol−1 H2 and ΔSd=115 J K−1 mol−1 H2 (desorption process) perfectly match literature values, emphasizing the excellent quality of the measurements and the performance of this measurement apparatus.
Ultrafast H2 and D2 rotational Raman responses in near critical CO2: An experimental and theoretical study of anisotropic solvation dynamics
Authors: Peng J. , Castonguay T. C. , Coker D. F. , Ziegler L. D.
Published: August 2009

The optical heterodyne detected anisotropic rotational Raman responses of H2 and D2 (22 mol %) in a near critical CO2 (ρ∗=ρ/ρc=0.8, T=308 K) solution are reported. J-specific rotational Raman correlation functions (RCFs) for the S(J) transitions of H2 (J=0,1,2) and D2 (J=0,1,2,3) in this CO2 solution are determined from these measurements. A mixed classical-quantum simulation methodology results in RCFs that are in excellent agreement with the experimentally derived J-specific responses. The observed S(J) coherence decay time scales, J-dependence, rotor mass dependence, and solvent-induced transition frequency shifts are well captured by these simulations. Pure dephasing of these rotational Raman transitions is shown to be close to the homogeneous limit of the standard Kubo line shape analysis and attributable to the rotor center-of-mass translation in an anisotropic solvent cage. Rotor translational motion in the vicinity of a single CO2 appears to dominate this dephasing mechanism. Mixed classical-quantum simulations, incorporating the effects of solution fluctuation driven nonadiabatic coupling of instantaneous adiabatic states, including full J-mixing, are required for the agreement between theory and experiment obtained here. Simulations of the classically excited angular kinetic energy of D2 rotors are used as an estimate of T1 relaxation rates and are found to be negligible compared to the D2 rotational Raman coherence time scale. These results are discussed in the context of previous mixed classical-quantum and rotational friction calculations of the dephasing and energy relaxation contributions to H2 rotational Raman coherence decays. Advantages of time domain acquisition of these rotational Raman responses as compared to spontaneous Raman measurements are illustrated here.
Dissipation in an ultrathin superconducting single-crystal Pb nanobridge
Authors: Wang Jian , Ma Xu-Cun , Qi Yun , Ji Shuai-Hua , Fu Ying-Shuang , Lu Li , Jin Ai-Zi , Gu Chang-Zhi , Xie X. C. , Tian Ming-Liang , Jia Jin-Feng , Xue Qi-Kun
Published: August 2009

The transport property of a superconducting Pb nanobridge, which is carved by focus ion beam technique from an atomically flat single-crystal Pb thin film grown on Si(111) substrate, is investigated. Below the superconducting transition temperature TC, the nanobridge exhibits a series of sharp voltage steps as a function of current. The multiple voltage steps are interpreted as a consequence of spatially localized phase slip centers or hot-spot formation in the bridge. Just below the critical current, the voltages versus current curve shows a power-law behavior in the low temperature region, but Ohmic near the TC. The thermally activated phase slip, quantum phase slip, and imhomogeneity in a one-dimensional superconducting system may contribute to the observed results.
A moving window correlation method to reduce the distortion of scanning probe microscope images
Authors: Chu Wei , Fu Joseph , Dixson Ronald , Orji George , Vorburger Theodore
Published: August 2009

Many scanning probe microscopes such as the scanning tunneling microscope and atomic force microscope use piezoelectric actuators operating in open loop for generating the scans of the surfaces. However, nonlinearities mainly caused by hysteresis and drift of piezoelectric actuators reduce the positioning accuracy and produce distorted images. A moving window correlation method is proposed in this paper to determine and quantify the hysteresis. This method requires both trace and retrace profiles to be recorded. With a window imposed on each of the profiles, correlations are implemented between the data inside two windows to find corresponding pixel pairs on two different profiles but the same physical positions along the fast scanning axis (x). The x-distances between pixel pairs are calculated and then a simple correction scheme is applied to reduce the distortion.
Periodic supply of indium as surfactant for N-polar InN growth by plasma-assisted molecular-beam epitaxy
Authors: Yao Yong-Zhao , Sekiguchi Takashi , Ohgaki Takeshi , Adachi Yutaka , Ohashi Naoki , Okuno Hanako , Takeguchi Masaki
Published: August 2009

We have investigated the self-surfactant effect of In for N-polar InN growth by plasma-assisted molecular-beam epitaxy. We found that InN quality was significantly improved if a thin In coverage (about 1.8 ML) was introduced before InN growth. However, this In coverage was slowly consumed during subsequent InN growth under N-rich condition. Periodically restoring In coverage for thick InN growth was proposed to solve this consumption problem. We suggest that the effect of In surfactant is to terminate the surface N dangling bonds and form an In adlayer, under which an efficient diffusion channel for lateral N adatom transport is created.
Bipolar resistive switching behavior in Ti/MnO2/Pt structure for nonvolatile memory devices
Authors: Yang Min Kyu , Park Jae-Wan , Ko Tae Kuk , Lee Jeon-Kook
Published: August 2009

This study examined the electrical properties of Ti/MnO2/Pt devices with stable and reproducible bipolar resistive switching behavior. The dependency of the memory behavior on the cell area and operating temperature suggest that the conducting mechanism in the low resistance states is due to the locally conducting filaments formed. X-ray photoelectron spectroscopy showed that nonlattice oxygen ions form at the MnO2 surface. The mechanism of resistance switching in the system examined involves the generation and recovery of oxygen vacancies with the nonlattice oxygen ions.
Ultrafast pulse characterization using cross phase modulation in silicon
Authors: Tien En-Kuang , Sang Xing-Zhu , Qing Feng , Song Qi , Boyraz Ozdal
Published: August 2009

Based on the high nonlinearity of the chip-scale silicon waveguide with small dispersion, a compact frequency-resolved optical gating system has been demonstrated using cross phase modulation for ultrafast pulse characterization. The principal component generalized projections algorithm is used to retrieve the amplitude and phase from the spectrogram. Amplitude and phase of a 540 fs pulse have been measured. The measured amplitude result is confirmed by the autocorrelation measurement.
Realization of photoreflectance spectroscopy in very-long wave infrared of up to 20 μm
Authors: Shao Jun , Chen Lu , Lü Xiang , Lu Wei , He Li , Guo Shaoling , Chu Junhao
Published: August 2009

The application of photoreflectance (PR) spectroscopy had been for long time restricted to short-wavelength spectral region and was recently pushed to long wave infrared about 9 μm. In this letter, PR measurement in the very-long wave infrared of up to 20 μm is demonstrated by a step-scan Fourier transform infrared spectrometer-based technique. An arsenic-doped narrow-gap HgCdTe epilayer is measured at 77 K, the resultant infrared PR spectrum is analyzed by line shape function, and donor and acceptor levels are discussed with aid of photoluminescence measurement at nominally identical temperature. The results suggest promising application of PR spectroscopy in the very-long wave infrared spectral region.
Molecular field theory with atomistic modeling for the curvature elasticity of nematic liquid crystals
Authors: Cestari Mirko , Bosco Alessandro , Ferrarini Alberta
Published: August 2009

Liquid crystals oppose a restoring force to distortions of the main alignment axis, the so-called director. For nematics this behavior is characterized by the three elastic moduli associated with the splay (K11), twist (K22), and bend (K33) modes; in addition, two moduli for mixed splay-bend (k13) and saddle-splay (k24) can be defined. The elastic constants are material properties which depend on the mesogen structure, but the relation between molecular features and deformations on a much longer scale has not been fully elucidated. The prediction of elastic properties is a challenge for theoretical and computational methods: atomistic simulations require large samples and must be integrated by statistical thermodynamics models to connect intermolecular correlations and elastic response. Here we present a molecular field theory, wherein expressions for the elastic constants of nematics are derived starting from a simple form of the single molecule orientational distribution function; this is parametrized according to the amount of molecular surface aligned to the nematic director. Such a model allows a detailed account of the chemical structure; moreover the conformational freedom, which is a common feature of mesogens, can be easily included. Given the atomic coordinates, the elastic constants can be calculated without any adjustable parameter at a low computational cost. The example of 4-n-pentyl,4′-cyanobiphenyl (5CB) is used to illustrate the capability of the developed methodology; even for this mesogen, which is usually taken as a prototypal rodlike system, we predict a significant dependence of the elastic moduli on the molecular conformation. We show that good estimates of magnitude and temperature dependence of the elastic constants are obtained, provided that the molecular geometry is correctly taken into account.
Degenerate rhombohedral and orthorhombic states in Ca-substituted Na0.5Bi0.5TiO3
Authors: Ranjan Rajeev , Kothai V. , Garg Rohini , Agrawal Anupriya , Senyshyn Anatoliy , Boysen Hans
Published: August 2009

Neutron powder diffraction and temperature dependent dielectric studies were carried out on Ca-substituted Na0.5Bi0.5TiO3, i.e., (Na0.5Bi0.5)1−xCaxTiO3. Stabilization of an orthorhombic phase even at a low Ca concentration (0.05<x≤0.10) suggests that Na0.5Bi0.5TiO3 (NBT) is susceptible to orthorhombic distortion. The orthorhombic and rhombohedral phases coexist for x=0.10, suggesting these phases to be nearly degenerate. The orthorhombic distortion favoring tendency of Ca assists in promoting the inherent instability with regard to this structure in pure NBT, which was reported recently.
Facile construction of nanofibrous ZnO photoelectrode for dye-sensitized solar cell applications
Authors: Zhang Wei , Zhu Rui , Liu Xizhe , Liu Bin , Ramakrishna Seeram
Published: August 2009

A facile method to prepare nanofibrous ZnO photoelectrodes with tunable thicknesses by electrospinning is reported. A “self-relaxation layer” is formed spontaneously between ZnO nanofibers and fluorine-doped SnO2 (FTO) substrate, which facilitates the release of interfacial tensile stress during calcination, resulting in good adhesion of ZnO film to FTO substrate. Dye-sensitized solar cells (DSSCs) based on the nanofibrous ZnO photoelectrodes are fabricated and an energy conversion efficiency of 3.02% is achieved under irradiation of AM 1.5 simulated sunlight with a power density of 100 mW cm−2, which shows good promise of electrospun nanofibrous ZnO as the photoelectrode in DSSCs.
Mn
3
O
4
precipitates in laser-ablated manganite films
Authors: Higuchi T. , Yajima T. , Kourkoutis L. Fitting , Hikita Y. , Nakagawa N. , Muller D. A. , Hwang H. Y.
Published: August 2009

Precipitates formed during the growth of manganite thin films by pulsed laser deposition have been an obstacle for fabricating high quality devices incorporating these ferromagnetic metals. In order to analyze the nature of these precipitates, we have investigated their spectroscopic and structural properties by scanning transmission electron microscopy. For LaMnO3 films, crystallites of Mn3O4 are found to segregate out from stoichiometric films to accommodate a net cation off-stoichiometry during growth. By tuning the laser spot conditions, these precipitates can be eliminated.
Magnetoelectric effect at the SrRuO3/BaTiO3 (001) interface: An ab initio study
Authors: Niranjan Manish K. , Burton J. D. , Velev J. P. , Jaswal S. S. , Tsymbal E. Y.
Published: August 2009

Ferromagnet/ferroelectric interface materials have emerged as structures with strong magnetoelectric coupling that may exist due to unconventional physical mechanisms. Here we present a first-principles study of the magnetoelectric effect at the ferromagnet/ferroelectric SrRuO3/BaTiO3 (001) interface. We find that the exchange splitting of the spin-polarized band structure, and therefore the magnetization, at the interface can be altered substantially by reversal of the ferroelectric polarization in the BaTiO3. These magnetoelectric effects originate from the screening of polarization charges at the SrRuO3/BaTiO3 interface and are consistent with the Stoner model for itinerant magnetism.
Split ring resonator sensors for infrared detection of single molecular monolayers
Authors: Cubukcu Ertugrul , Zhang Shuang , Park Yong-Shik , Bartal Guy , Zhang Xiang
Published: August 2009

We report a surface enhanced molecular detection technique with zeptomole sensitivity that relies on resonant coupling of plasmonic modes of split ring resonators and infrared vibrational modes of a self-assembled monolayer of octadecanthiol molecules. Large near-field enhancements at the gap of split ring resonators allow for this resonant coupling when the molecular absorption peaks overlap spectrally with the plasmonic resonance. Electromagnetic simulations support experimental findings.
Periodicity in Al/Ti superconducting single electron transistors
Authors: MacLeod Sarah J. , Kafanov Sergey , Pekola Jukka P.
Published: August 2009

We present experiments on single Cooper-pair transistors made of two different superconducting materials. We chose Ti and Al to create an energy gap profile such that the island has a higher gap than the leads, thereby acting as a barrier to quasiparticle tunneling. Our transport measurements demonstrate that quasiparticle poisoning is suppressed in all our TiAlTi structures (higher gap for the island) with clear 2e periodicity observed, whereas full quasiparticle poisoning is observed in all AlTiAl devices (higher gap for the leads) with e periodicity.
Enhanced superconducting transition temperature in FeSe0.5Te0.5 thin films
Authors: Si Weidong , Lin Zhi-Wei , Jie Qing , Yin Wei-Guo , Zhou Juan , Gu Genda , Johnson P. D. , Li Qiang
Published: August 2009

We report magnetoresistive and structural measurements of superconducting FeSe0.5Te0.5 epitaxial thin films grown by pulsed laser deposition. Enhanced onset superconducting transition temperature (∼17 K) is observed in some of these films. Structural analysis by x-ray diffraction and high resolution transmission electron microscopy reveal that these films generally have significantly shorter out-of-plane lattice constant c than the bulk value, suggesting that the out-of-plane changes have a dominating impact on the superconducting transition in iron-based superconductors. Our data also indicate that the upper critical field Hc2(0) of those films may reach as high as 50 T.
Industry Building as Contested Market Building: Knowledge, Politics, and the Rise of Beijing in China's Virtual Economy
Authors: Zhang Jun
Published: August 2009

Combining insights from the theory of fields to markets and recent geographic literature on regional innovation, I conceptualize regional industry building as a contested process of market building involving initiatives of both economic actors and political actors in intertwined governmental fields and organizational fields. Market building entails the contribution of knowledge brokers capable of bridging the gap between the local industrial community and global leaders. Moreover, it requires the institutionalization of a stable governance structure to enable the rise of productivity-enhancing new entrepreneurship, especially to minimize ‘unproductive’ endeavors of technological entrepreneurs in fighting against powerful incumbents and reactionary institutions. From a policy perspective, regional industry building entails not only policies facilitating the pooling of glocal knowledge brokers at the regional scale, but also institutional reform and political transformation in the national arena, especially in an emerging market economy.
Building Events in Inner-City Gdańsk, Poland: Exploring the Sociospatial Construction of Agency in Built Form
Authors: Bouzarovski Stefan
Published: August 2009

In this paper, I explore the ways in which buildings interact with the social fabric of everyday life. My main argument is that agency in the built environment is practised and performed through a dynamic relation between households and the built fabric, among other actants. The paper is based on an ethnographic study of forty-two inner-city households in the Polish city of Gdańsk, combined with archival research. I investigate the forces that constrain and enable the transformation of residential dwellings over time, with the aid of Jacobs's concept of ‘building events’. I wish to provide a more elaborate theorisation and operationalisation of the building event, while applying it to the interrogation of relations between buildings and households in the given context. The paper explores the different modalities through which buildings have been forced to create new allies and associations—allowing for the interpretive flexibility of their technological frame—in order to keep surviving and functioning in different sociopolitical circumstances.
A repertoire of rhythmic bursting produced by hypoglossal motoneurons in physiological and pathological conditions
Authors: Cifra Alessandra , Nani Francesca , Sharifullina Elina , Nistri Andrea
Published: August 2009

The brainstem
nucleus hypoglossus
contains motoneurons that provide the exclusive motor nerve supply to the tongue. In addition to voluntary tongue movements, tongue muscles rhythmically contract during a wide range of physiological activities, such as respiration, swallowing, chewing and sucking. Hypoglossal motoneurons are destroyed early in amyotrophic lateral sclerosis (ALS), a fatal neurodegenerative disease often associated with a deficit in the transport system of the neurotransmitter glutamate.

The present study shows how periodic electrical discharges of motoneurons are mainly produced by a neuronal network that drives them into bursting mode via glutamatergic excitatory synapses. Burst activity is, however, modulated by the intrinsic properties of motoneurons that collectively synchronize their discharges via gap junctions to create ‘group bursters’. When glial uptake of glutamate is blocked, a distinct form of pathological bursting spontaneously emerges and leads to motoneuron death. Conversely, H
2
O
2
-induced oxidative stress strongly increases motoneuron excitability without eliciting bursting. Riluzole (the only drug currently licensed for the treatment of ALS) suppresses bursting of hypoglossal motoneurons caused by blockage of glutamate uptake and limits motoneuron death. These findings highlight how different patterns of electrical oscillations of brainstem motoneurons underpin not only certain physiological activities, but also motoneuron death induced by glutamate transporter impairment.
Pontine respiratory activity involved in inspiratory/expiratory phase transition
Authors: Mörschel Michael , Dutschmann Mathias
Published: August 2009

Control of the timing of the inspiratory/expiratory (IE) phase transition is a hallmark of respiratory pattern formation. In principle, sensory feedback from pulmonary stretch receptors (Breuer–Hering reflex, BHR) is seen as the major controller for the IE phase transition, while pontine-based control of IE phase transition by both the pontine Kölliker–Fuse nucleus (KF) and parabrachial complex is seen as a secondary or backup mechanism. However, previous studies have shown that the BHR can habituatein vivo. Thus, habituation reduces sensory feedback, so the role of the pons, and specifically the KF, for IE phase transition may increase dramatically.

Pontine-mediated control of the IE phase transition is not completely understood. In the present review, we discuss existing models for ponto-medullary interaction that may be involved in the control of inspiratory duration and IE transition. We also present intracellular recordings of pontine respiratory units derived from anin situintra-arterially perfused brainstem preparation of rats. With the absence of lung inflation, this preparation generates a normal respiratory pattern and many of the recorded pontine units demonstrated phasic respiratory-related activity. The analysis of changes in membrane potentials of pontine respiratory neurons has allowed us to propose a number of pontine-medullary interactions not considered before. The involvement of these putative interactions in pontine-mediated control of IE phase transitions is discussed.
Central and peripheral chemoreceptors evoke distinct responses in simultaneously recorded neurons of the raphé-pontomedullary respiratory network
Authors: Nuding Sarah C. , Segers Lauren S. , Shannon Roger , O'Connor Russell , Morris Kendall F. , Lindsey Bruce G.
Published: August 2009

The brainstem network for generating and modulating the respiratory motor pattern includes neurons of the medullary ventrolateral respiratory column (VRC), dorsolateral pons (PRG) and raphé nuclei. Midline raphé neurons are proposed to be elements of a distributed brainstem system of central chemoreceptors, as well as modulators of central chemoreceptors at other sites, including the retrotrapezoid nucleus. Stimulation of the raphé system or peripheral chemoreceptors can induce a long-term facilitation of phrenic nerve activity; central chemoreceptor stimulation does not. The network mechanisms through which each class of chemoreceptor differentially influences breathing are poorly understood. Microelectrode arrays were used to monitor sets of spike trains from 114 PRG, 198 VRC and 166 midline neurons in six decerebrate vagotomized cats; 356 were recorded during sequential stimulation of both receptor classes via brief CO
2
-saturated saline injections in vertebral (central) and carotid arteries (peripheral). Seventy neurons responded to both stimuli. More neurons were responsive only to peripheral challenges than those responsive only to central chemoreceptor stimulation (PRG, 20 : 4; VRC, 41 : 10; midline, 25 : 13). Of 16 474 pairs of neurons evaluated for short-time scale correlations, similar percentages of reference neurons in each brain region had correlation features indicative of a specific interaction with at least one target neuron: PRG (59.6%), VRC (51.0%) and raphé nuclei (45.8%). The results suggest a brainstem network architecture with connectivity that shapes the respiratory motor pattern via overlapping circuits that modulate central and peripheral chemoreceptor-mediated influences on breathing.
Noeud vital for breathing in the brainstem: gasping—yes, eupnoea—doubtful
Authors: St John Walter M.
Published: August 2009

For the past 200 years, various regions of the brainstem have been proposed as a ‘noeud vital’ for breathing—a critical region which, when destroyed, results in an irreversible cessation of breathing and death. Complicating this search for a noeud vital is the extensive network of neurons that comprises the brainstem respiratory control system of pons and medulla. Does a cessation of breathing following ablation of any region reflect the removal of a critical set of neurons whose activity generates the respiratory rhythm or does it reflect the interruption of one component of the neuronal circuit, such that this circuit cannot function, at least temporarily? An additional complication is that in contemporary neuroscience, a number ofin vitropreparations have been introduced for the study of the generation of the respiratory rhythms. However, how are the rhythms that these preparations generate related to normal breathing? Are these rhythms similar to those of gasping, which is recruited when normal, eupnoeic breathing fails, or are these rhythms unique to thein vitropreparation and not related to any breathing patternin vivo?
Breathing withPhox2b
Authors: Dubreuil Véronique , Barhanin Jacques , Goridis Christo , Brunet Jean-François
Published: August 2009

In the last few years, elucidation of the architecture of breathing control centres has reached the cellular level. This has been facilitated by increasing knowledge of the molecular signatures of various classes of hindbrain neurons. Here, we review the advances achieved by studying the homeodomain factorPhox2b, a transcriptional determinant of neuronal identity in the central and peripheral nervous systems. Evidence from human genetics, neurophysiology and mouse reverse genetics converges to implicate a small population ofPhox2b-dependent neurons, located in the retrotrapezoid nucleus, in the detection of CO2, which is a paramount source of the ‘drive to breathe’. Moreover, the same and other studies suggest that an overlapping or identical neuronal population, the parafacial respiratory group, might contribute to the respiratory rhythm at least in some circumstances, such as for the initiation of breathing following birth. Together with the previously establishedPhox2bdependency of other respiratory neurons (which we review briefly here), our new data highlight a key role of this transcription factor in setting up the circuits for breathing automaticity.
Qualitative Evaluation of the Project P.A.T.H.S.: Findings Based on Focus Groups with Student Participants
Authors: Shek Daniel T. L. , Ng Catalina S. M.
Published: August 2009

This paper reports a qualitative evaluation study conducted to explore the perceptions of students who joined the Tier 1 Program of the Project P.A.T.H.S. A total of 92 students were randomly selected to participate in 10 focus groups, which provided qualitative data for the study. With specific focus on how the informants described the program, the descriptors used were primarily positive; the metaphors named by the informants that could stand for the program were basically positive. Program participants also perceived the program to be beneficial in different psychosocial domains. The present study lends further support to the effectiveness of the Tier 1 Program of the Project P.A.T.H.S. in promoting holistic development in Chinese adolescents.
Rapidly Shifting Concepts Regarding Androgens and Prostate Cancer
Authors: Morgentaler Abraham
Published: August 2009

There has been a recent dramatic shift in our understanding of the relationship between androgens and prostate cancer (PCa). Whereas for several decades it had been assumed that higher serum testosterone (T) concentrations would lead to ever-greater PCa growth, current literature indicates that PCa growth is unaffected by changes in serum T throughout most of the naturally occurring range. A Saturation Model has been proposed to explain how prostate tissue can be exquisitely sensitive to changes in serum T at the very low end of the concentration range, but appears indifferent to such changes above the near-castrate range. This has special applicability to T-deficient men, since this means that T therapy may not be nearly as risky as once assumed. Indeed, one of the more interesting changes over the last several years has been the growing acceptance of the use of T therapy in men with a prior history of PCa, with early data indicating minimal risk of cancer recurrence or progression. Provocative new evidence suggests that it is not high serum T that is problematic for PCa, butlowserum T that is associated with worrisome cancer features and outcomes, such as high Gleason score, advanced stage of presentation, and increased risk of biochemical recurrence after surgery. It will be interesting to see what changes will occur in this rapidly changing field over the next several years.
A regulator from Chlamydia trachomatis modulates the activity of RNA polymerase through direct interaction with the β subunit and the primary σ subunit
Authors: Rao Xiancai , Deighan Padraig , Hua Ziyu , Hu Xiaomei , Wang Jin , Luo Miao , Wang Jie , Liang Yanmei , Zhong Guangming , Hochschild Ann , Shen Li
Published: August 2009

The obligate intracellular human pathogen Chlamydia trachomatis undergoes a complex developmental program involving transition between two forms: the infectious elementary body (EB), and the rapidly dividing reticulate body (RB). However, the regulators controlling this development have not been identified. To uncover potential regulators of transcription in C. trachomatis, we screened a C. trachomatis genomic library for sequences encoding proteins that interact with RNA polymerase (RNAP). We report the identification of one such protein, CT663, which interacts with the β and σ subunits of RNAP. Specifically, we show that CT663 interacts with the flap domain of the β subunit (β-flap) and conserved region 4 of the primary σ subunit (σ66 in C. trachomatis). We find that CT663 inhibits σ66-dependent (but not σ28-dependent) transcription in vitro, and we present evidence that CT663 exerts this effect as a component of the RNAP holoenzyme. The analysis of C. trachomatis-infected cells reveals that CT663 begins to accumulate at the commencement of the RB-to-EB transition. Our findings suggest that CT663 functions as a negative regulator of σ66-dependent transcription, facilitating a global change in gene expression. The strategy used here is generally applicable in cases where genetic tools are unavailable.
The pathophysiology of mitochondrial disease as modeled in the mouse
Authors: Wallace Douglas C. , Fan WeiWei
Published: August 2009

It is now clear that mitochondrial defects are associated with a plethora of clinical phenotypes in man and mouse. This is the result of the mitochondria's central role in energy production, reactive oxygen species (ROS) biology, and apoptosis, and because the mitochondrial genome consists of roughly 1500 genes distributed across the maternal mitochondrial DNA (mtDNA) and the Mendelian nuclear DNA (nDNA). While numerous pathogenic mutations in both mtDNA and nDNA mitochondrial genes have been identified in the past 21 years, the causal role of mitochondrial dysfunction in the common metabolic and degenerative diseases, cancer, and aging is still debated. However, the development of mice harboring mitochondrial gene mutations is permitting demonstration of the direct cause-and-effect relationship between mitochondrial dysfunction and disease. Mutations in nDNA-encoded mitochondrial genes involved in energy metabolism, antioxidant defenses, apoptosis via the mitochondrial permeability transition pore (mtPTP), mitochondrial fusion, and mtDNA biogenesis have already demonstrated the phenotypic importance of mitochondrial defects. These studies are being expanded by the recent development of procedures for introducing mtDNA mutations into the mouse. These studies are providing direct proof that mtDNA mutations are sufficient by themselves to generate major clinical phenotypes. As more different mtDNA types and mtDNA gene mutations are introduced into various mouse nDNA backgrounds, the potential functional role of mtDNA variation in permitting humans and mammals to adapt to different environments and in determining their predisposition to a wide array of diseases should be definitively demonstrated.