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Sample records for dependent dielectric response

  1. Frequency-dependent dielectric response model for polyimide-poly(vinilydenefluoride) multilayered dielectrics

    Science.gov (United States)

    Di Lillo, Luigi; Bergamini, Andrea; Albino Carnelli, Dario; Ermanni, Paolo

    2012-07-01

    A physical model for the frequency-dependent dielectric response of multilayered structures is reported. Two frequency regimes defined by the relative permittivities and volume resistivities of the layers have been analytically identified and experimentally investigated on a structure consisting of polyimide and poly(vinilydenefluoride) layers. The relative permittivity follows an effective medium model at high frequency while showing a dependence on the volume resistivity at low frequency. In this regime, relative permittivities exceeding those expected from effective medium model are recorded. These findings provide insights into inhomogeneous dielectrics behavior for the development of high energy density dielectric films.

  2. Electric field dependent dielectric response of alumina/silicone oil colloids

    Science.gov (United States)

    Magallon, Louis; Tsui, Stephen

    2014-03-01

    We investigate the dielectric response of a mixture of alumina nanopowder and silicone oil. Frequency and electric field dependent measurements of another insulating colloid, i.e., urea-coated Ba0.8Rb0.4TiO(C2O4)2 nanoparticles immersed in silicone oil, revealed universal dielectric response (UDR) characteristics and, with the application of high voltage, a negative capacitance. Alumina in silicone oil represents a simpler system in which to perform similar dielectric investigation. This colloid is sandwiched in a parallel plate capacitor cell, and the complex impedance is measured via lock-in amplifier at various frequencies and applied dc biases. Furthermore, we will compare and discuss the dielectric behaviors of different sized suspended alumina particles.

  3. Thermal analysis and temperature dependent dielectric responses of Co doped anatase TiO{sub 2} nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Alamgir [Department of Physics, Aligarh Muslim University, Aligarh-202002 (India); Centre of Excellence in Materials Science (Nanomaterials), Department of Applied Physics, Z.H. College of Engineering and Technology, Aligarh Muslim University, Aligarh-202002 (India); Khan, Wasi; Ahammed, Nashiruddin; Naqvi, A. H. [Centre of Excellence in Materials Science (Nanomaterials), Department of Applied Physics, Z.H. College of Engineering and Technology, Aligarh Muslim University, Aligarh-202002 (India); Ahmad, Shabbir [Department of Physics, Aligarh Muslim University, Aligarh-202002 (India)

    2015-05-15

    Nanoparticles (NPs) of pure and 5 mol % cobalt doped TiO{sub 2} synthesized through acid modified sol-gel method were characterized to understand their thermal, structural, morphological, and temperature dependent dielectric properties. Thermogravimetric analysis (TGA) has been used for thermal studies and indicates the weight loss in two steps due to the removal of residual organics. X-ray diffraction study was employed to confirm the formation of single anatase phase with tetragonal symmetry for both pure and 5 mol % Co doped TiO{sub 2} NPs. The average crystallite size of both samples was calculated from the Scherrer’s formula and was found in the range from 9-11 nm. TEM micrographs of these NPs reflect their shape and distribution. The dielectric constant (ε′), dielectric loss (tanδ) and ac conductivity (σ{sub ac}) were also studied as a function of temperature at different frequencies. Electrical responses of the synthesized NPs have been analyzed carefully in the framework of relevant models. It is also noticed that the dielectric constant (ε′) of the samples found to decrease with increasing frequency but increases with increasing temperature up to a particular value and then sharply decreases. Temperature variation of dielectric constant exhibits step like escalation and shows relaxation behavior. Study of dielectric properties shows dominant dependence on the grain size as well as Co ion incorporation in TiO{sub 2}.

  4. Temperature dependence of the dielectric constant of acrylic dielectric elastomer

    Energy Technology Data Exchange (ETDEWEB)

    Sheng, Junjie; Chen, Hualing; Li, Bo; Chang, Longfei [Xi' an Jiaotong University, State Key Laboratory for Strength and Vibration of Mechanical Structures, Xi' an (China); Xi' an Jiaotong University, School of Mechanical Engineering, Xi' an (China)

    2013-02-15

    The dielectric constant is an essential electrical parameter to the achievable voltage-induced deformation of the dielectric elastomer. This paper primarily focuses on the temperature dependence of the dielectric constant (within the range of 173 K to 373 K) for the most widely used acrylic dielectric elastomer (VHB 4910). First the dielectric constant was investigated experimentally with the broadband dielectric spectrometer (BDS). Results showed that the dielectric constant first increased with temperature up to a peak value and then dropped to a relative small value. Then by analyzing the fitted curves, the Cole-Cole dispersion equation was found better to characterize the rising process before the peak values than the Debye dispersion equation, while the decrease process afterward can be well described by the simple Debye model. Finally, a mathematical model of dielectric constant of VHB 4910 was obtained from the fitted results which can be used to further probe the electromechanical stability of the dielectric elastomers. (orig.)

  5. ARTICLES: Time-Dependent Stokes Shift from Solvent Dielectric Relaxation

    Science.gov (United States)

    Xu, Jing; Wang, Quan-de; Zhu, Quan; Fu, Ke-xiang; He, Fu-cheng; Li, Xiang-yuan

    2010-06-01

    The Stokes shift response function, which is related to the time dependent solvation energy, is calculated with the dielectric response function and a novel expression of nonequilibrium solvation energy. In the derivation, relationship between the polarization and the dielectric response function is used. With the dipole-in-a-sphere model applied to the system coumarin 343 and water as the solvent, encouraging agreement with the experimental data from Jimenez et al. is obtained [Nature 369, 471 (1994)].

  6. Calculation of Dielectric Response in Molecular Solids for High Capacitance Organic Dielectrics

    Science.gov (United States)

    Heitzer, Henry Matthew

    The dielectric response of a material is critically important in numerous scientific processes spanning the fields of biology, chemistry, materials science, and physics. While important across these fundamental disciplines, it remains difficult to determine theoretically the dielectric environment of a system. With recent advances in nanotechnology, biochemistry, and molecular electronics, it has become necessary to determine the dielectric response in molecular systems that are difficult to measure experimentally, such as nanoscale interfaces, highly disordered biological environments, or molecular materials that are difficult to synthesize. In these scenarios it is highly advantageous to determine the dielectric response through efficient and accurate calculations. A good example of where a theoretical prediction of dielectric response is critical is in the development of high capacitance molecular dielectrics. Molecular dielectrics offer the promise of cheap, flexible, and mass producible electronic devices when used in conjunction with organic semiconducting materials to form Organic Field Effect Transistors (OFETs). To date, molecular dielectrics suffer from poor dielectric properties resulting in low capacitances. A low capacitance dielectric material requires a much larger power source to operate the device in OFETs, leading to modest device performance. Development of better performing dielectric materials has been hindered due to the time it takes to synthesize and fabricate new molecular materials. An accurate and efficient theoretical technique could drastically decrease this time by screening potential dielectric materials and providing design rules for future molecular dielectrics. Here in, the methodology used to calculate dielectric properties of molecular materials is described. The validity of the technique is demonstrated on model systems, capturing the frequency dependence of the dielectric response and achieving quantitative accuracy compared

  7. Terahertz-frequency dielectric response of liquids

    DEFF Research Database (Denmark)

    Jepsen, Peter Uhd; Møller, Uffe; Cooke, David

    -induced dipole moments. In the polar liquid water the fastest relaxational dynamics is found at terahertz frequencies, just below the first intermolecular vibrational and librational modes. In this presentation we will discuss optical terahertz spectroscopic techniques for measurement of the full dielectric......The dielectric response of liquids spans many decades in frequency. The dielectric response of a polar liquid is typically determined by relaxational dynamics of the dipolar moments of the liquid. In contrast, the dielectric response of a nonpolar liquid is determined by much weaker collision...

  8. Terahertz-frequency dielectric response of liquids

    DEFF Research Database (Denmark)

    Jepsen, Peter Uhd; Møller, Uffe; Cooke, David

    -induced dipole moments. In the polar liquid water the fastest relaxational dynamics is found at terahertz frequencies, just below the first intermolecular vibrational and librational modes. In this presentation we will discuss optical terahertz spectroscopic techniques for measurement of the full dielectric......The dielectric response of liquids spans many decades in frequency. The dielectric response of a polar liquid is typically determined by relaxational dynamics of the dipolar moments of the liquid. In contrast, the dielectric response of a nonpolar liquid is determined by much weaker collision...

  9. Mechanisms Responsible for Microwave Properties in High Performance Dielectric Materials

    Science.gov (United States)

    Zhang, Shengke

    Microwave properties of low-loss commercial dielectric materials are optimized by adding transition-metal dopants or alloying agents (i.e. Ni, Co, Mn) to tune the temperature coefficient of resonant frequency (tau f) to zero. This occurs as a result of the temperature dependence of dielectric constant offsetting the thermal expansion. At cryogenic temperatures, the microwave loss in these dielectric materials is dominated by electron paramagnetic resonance (EPR) loss, which results from the spin-excitations of d-shell electron spins in exchange-coupled clusters. We show that the origin of the observed magnetically-induced shifts in the dielectric resonator frequency originates from the same mechanism, as described by the Kramers-Kronig relations. The temperature coefficient of resonator frequency, tauf, is related to three material parameters according to the equation, tau f = - (½ tauepsilon + ½ taumu + alphaL), where tauepsilon, taumu , and alphaL are the temperature coefficient of dielectric constant, magnetic permeability, and lattice constant, respectively. Each of these parameters for dielectric materials of interest are measured experimentally. These results, in combination with density functional simulations, developed a much improved understanding of the fundamental mechanisms responsible for tau f. The same experimental methods have been used to characterize in-situ the physical nature and concentration of performance-degrading point defects in the dielectrics of superconducting planar microwave resonators.

  10. Dielectric Response of Graded Spherical Composites

    Institute of Scientific and Technical Information of China (English)

    LI Zhi; WEI En-Bo; ZHANG Han-De; TIAN Ji-Wei

    2005-01-01

    @@ We investigate the effective dielectric responses of graded spherical composites under an external uniform electric field by taking the dielectric function of spherical inclusion, εi = crkeβr, where r is the inner distance of a point inside the particle from the centre of the spherical particle in the coordination. In the dilute limit, our exact result is used to test the validity of differential effective dipole approximation (DEDA) for estimating the effective response of graded spherical composites and it is shown that the DEDA is in excellent agreement with the exact result.

  11. Effect of Gd3+ doping on structural, optical and frequency-dependent dielectric response properties of pseudo-cubic BaTiO3 nanostructures

    Science.gov (United States)

    Borah, Manjit; Mohanta, Dambarudhar

    2014-06-01

    We report on the structural, optical and dielectric characterization of solid state derived, pseudo-cubic nanoscale barium titanates (BTs) with gadolinium (Gd3+) as substitutional dopant. Referring to X-ray diffractograms, apart from the BT peaks related to perovskite structure, the non-existence of any additional peaks due to byproducts has revealed that Gd3+ has undergone substitutional doping into the BT host lattice. The well-separated BT nanoparticles of typical size ˜10-15 nm were observed through electron microscopy studies. Following a direct, allowed type carrier transition ( n=1/2), a reduction in the optical band gap value (from 3.28 to 3.255 eV) was observed when the Gd-doping level was varied within 0-7 %. Conversely, the Urbach energy followed an increasing trend, from a value of 0.741 to 1.879 eV. Furthermore, the dielectric constant showed a decreasing tendency with doping content and with increasing frequency. However, in the low-frequency region, the loss tangent (tan δ), which is the combined result of orientational polarization and electrical conduction, was found to be quite high in the doped samples as compared to their un-doped counterpart. The frequency-dependent electrical data were also analyzed in the framework of conductivity and impedance formalisms. In particular, the ac conductivity which varies as ˜ ω s approaches ideal Debye behavior ( s→1) for a low Gd level and a higher doping concentration did not show improved dielectric feature of the host. The incorporation of rare-earth (Gd3+) ions into the BT host system could greatly manifest dielectric relaxation and carrier conduction mechanisms, in a given frequency range, and thus can find immense scope in miniaturized nanoelectronic elements including ceramic capacitors and transducers.

  12. Actuation response of polyacrylate dielectric elastomers

    DEFF Research Database (Denmark)

    Kofod, G.; Kornbluh, R.; Pelrine, R.

    2001-01-01

    , though there are discrepancies. Further analysis suggests that these arise mostly from imperfect manufacture of the actuators, though there is a small contribution from an explicitly electrostrictive behavior of the acrylic adhesive. Measurements of the dielectric constant of stretched polymer reveal...... that the dielectric constant drops, when the polymer is strained, indicating the existence of a small electrostrictive effect. Finally, measurements of the electric breakdown field were made. These also show a dependence upon the strain. In the unstrained state the breakdown field is 20 WV/m, which grows to 218MV...

  13. Frequency Dependence of Attenuation Constant of Dielectric Materials

    Directory of Open Access Journals (Sweden)

    A. S. Zadgaonkar

    1975-01-01

    Full Text Available Different dielectric materials have been studied for frequency dependence of attenuation constant. The sensitive cathode ray oscillograph method has been used to evaluate to the dielectric constant and loss factor, and from these attenuation constants have been calculated. The temperature remaining constant, a regular increase has been observed in attenuation constant, at higher frequencies of electro-magnetic propagating wave.

  14. Temperature-dependent dielectric properties of slightly hydrated horn keratin.

    Science.gov (United States)

    Rizvi, Tasneem Zahra; Khan, Muhammad Abdullah

    2008-04-01

    With an aim to reveal the mechanism of protein-water interaction in a predominantly two phase model protein system this study investigates the frequency and temperature dependence of dielectric constant epsilon' and loss factor epsilon'' in cow horn keratin in the frequency range 30 Hz to 3 MHz and temperature range 30-200 degrees C at two levels of hydration. These two levels of hydration were achieved by exposing the sample to air at 50% relative humidity (RH) at ambient temperature and by evacuating the sample for 72 h at 105 degrees C. A low frequency dispersion (LFD) and an intermediate frequency alpha-dispersion were the two main dielectric responses observed in the air-dried sample. The LFD and the high frequency arm of the alpha-dispersion followed the same fractional power law of frequency. Within the framework of percolation cluster model these dispersions, respectively have been attributed to percolation of protons between and within the clusters of hydrogen-bonded water molecules bound to polar or ionizable protein components. The alpha-dispersion peak, which results from intra-cluster charge percolation conformed to Cole-Cole modified Debye equation. Temperature dependence of the dielectric constant in the air-dried sample exhibited peaks at 120 and 155 degrees C which have been identified as temperatures of onset of release of water bound to polar protein components in the amorphous and crystalline regions, respectively. An overall rise in the permittivity was observed above 175 degrees C, which has been identified as the onset of chain melting in the crystalline region of the protein.

  15. Features of dielectric response in PMN-PT ferroelectric ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Guerra, J D S [Grupo de Ferroeletricos e Materiais Multifuncionais, Instituto de Fisica, Universidade Federal de Uberlandia, 38400-902 Uberlandia-MG (Brazil); Araujo, E B; Guarany, C A; Reis, R N; Lima, E C [Grupo Ferroeletricos e Novos Materiais, Departamento de Fisica e Quimica, Universidade Estadual Paulista, 15385-000 Ilha Solteira-SP (Brazil)], E-mail: santos@dfq.feis.unesp.br

    2008-11-21

    In this paper, electrical and structural properties were reported for pyrochlore free (1 - x)[Pb(Mg{sub 1/3}Nb{sub 2/3})O{sub 3}] - xPbTiO{sub 3} (PMN-PT) (with 35 mol% PbTiO{sub 3}) ceramics obtained from fine powders. Dielectric studies were focused on the investigation of the complex dielectric permittivity ({epsilon}' - i{epsilon}'') as a function of frequency and temperature. The effects of the dc applied electric field on dielectric response were also investigated. Results revealed a field dependence dielectric anomaly in the dielectric permittivity curves ({epsilon}(T)) in the low dc electric field region, which in turn prevails in the whole analysed frequency interval. To the best of our knowledge, these properties for the PMN-PT ceramic system have not been reported before as in this work. The results were analysed within the framework of the current models found in the literature.

  16. Effective Dielectric Response of Composites with Graded Material

    Institute of Scientific and Technical Information of China (English)

    YANG Zi-Dong; WEI En-Bo; SONG Jin-Bao

    2004-01-01

    The effective dielectric response of linear composites containing graded material is investigated under an applied electric field Eo. For the cylindrical inclusion with gradient dielectric function, εi(r) = b+cr, randomly embedded in a host with dielectric constant εm, we have obtained the exact solution of local electric potential of the composite media regions, which obeys a linear constitutive relation D= εE, using hypergeometric function. In dilute limit, we have derived the effective dielectric response of the linear composite media. Furthermore, for larger volume fraction, the formulas of effective dielectric response of the graded composite media are given.

  17. The thickness dependence of dielectric permittivity in thin films

    Science.gov (United States)

    Starkov, Ivan A.; Starkov, Alexander S.

    2016-08-01

    It is well known that the physical properties of thin films depend on their thickness. For a description of such dependences, it is proposed to use a classical model taking into account the presence of film interfaces. A dielectric ball near the half-space was chosen to adopt the approach. The dependence of the effective permittivity of the ball on geometrical and physical parameters of the system is analyzed. It is demonstrated that the dielectric constant of a film can be presented as a sum of the constant of a bulk material and the interface term.

  18. Maximizing the dielectric response of molecular thin films via quantum chemical design.

    Science.gov (United States)

    Heitzer, Henry M; Marks, Tobin J; Ratner, Mark A

    2014-12-23

    Developing high-capacitance organic gate dielectrics is critical for advances in electronic circuitry based on unconventional semiconductors. While high-dielectric constant molecular substances are known, the mechanism of dielectric response and the fundamental chemical design principles are not well understood. Using a plane-wave density functional theory formalism, we show that it is possible to map the atomic-scale dielectric profiles of molecule-based materials while capturing important bulk characteristics. For molecular films, this approach reveals how basic materials properties such as surface coverage density, molecular tilt angle, and π-system planarity can dramatically influence dielectric response. Additionally, relatively modest molecular backbone and substituent variations can be employed to substantially enhance film dielectric response. For dense surface coverages and proper molecular alignment, conjugated hydrocarbon chains can achieve dielectric constants of >8.0, more than 3 times that of analogous saturated chains, ∼2.5. However, this conjugation-related dielectric enhancement depends on proper molecular orientation and planarization, with enhancements up to 60% for proper molecular alignment with the applied field and an additional 30% for conformations such as coplanarity in extended π-systems. Conjugation length is not the only determinant of dielectric response, and appended polarizable high-Z substituents can increase molecular film response more than 2-fold, affording estimated capacitances of >9.0 μF/cm2. However, in large π-systems, polar substituent effects are substantially attenuated.

  19. Electromechanical response of silicone dielectric elastomers

    Science.gov (United States)

    Cârlescu, V.; Prisăcaru, G.; Olaru, D.

    2016-08-01

    This paper presents an experimental technique to investigate the electromechanical properties of silicone dielectric elastomers actuated with high DC electric fields. A non-contact measurement technique is used to capture and monitor the thickness strain (contraction) of a circular film placed between two metallic disks electrodes. Two active fillers such as silica (10, 15 and 30 wt%) and barium titanate (5 and 15 wt%) were incorporated in order to increase the actuation performance. Thickness strain was measured at HV stimuli up to 4.5 kV and showed a quadratic dependence against applied electric field indicating that the induced strain is triggered by the Maxwell effect and/or electrostriction phenomenon as reported in literature. The actuation process evidences a rapid contraction upon HV activation and a slowly relaxation when the electrodes are short-circuit due to visco-elastic nature of elastomers. A maximum of 1.22 % thickness strain was obtained at low actuating field intensity (1.5 V/pm) comparable with those reported in literature for similar dielectric elastomer materials.

  20. The flexoelectric effect associated size dependent pyroelectricity in solid dielectrics

    Directory of Open Access Journals (Sweden)

    Gang Bai

    2015-09-01

    Full Text Available A phenomenological thermodynamic theory is used to investigate the effect of strain gradient on the pyroelectric effect in centrosymmetric dielectric solids. Direct pyroelectricity can exist as external mechanical stress is applied to non-pyroelectric dielectrics with shapes such as truncated pyramids, due to elastic strain gradient induced flexoelectric polarization. Effective pyroelectric coefficient was analyzed in truncated pyramids. It is found to be controlled by size, ambient temperature, stress, and aspect ratio and depends mainly on temperature sensitivity of flexoelectric coefficient (TSFC and strain gradient of the truncated pyramids dielectric solids. These results show that the pyroelectric property of Ba0.67Sr0.33TiO3 above Tc similar to PZT and other lead-based ferroelectrics can be obtained. This feature might widely broaden the selection of materials for infrared detectors with preferable properties.

  1. The flexoelectric effect associated size dependent pyroelectricity in solid dielectrics

    Energy Technology Data Exchange (ETDEWEB)

    Bai, Gang, E-mail: baigang@njupt.edu.cn [Jiangsu Provincial Engineering Laboratory for RF Integration and Micropackaging and College of Electronic Science and Engineering, Nanjing University of Posts and Telecommunications, Nanjing 210023 (China); Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093 (China); Liu, Zhiguo [Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093 (China); Xie, Qiyun; Guo, Yanyan; Li, Wei [Jiangsu Provincial Engineering Laboratory for RF Integration and Micropackaging and College of Electronic Science and Engineering, Nanjing University of Posts and Telecommunications, Nanjing 210023 (China); Yan, Xiaobing [College of Electronic and information Engineering, Hebei University, Baoding 071002 (China)

    2015-09-15

    A phenomenological thermodynamic theory is used to investigate the effect of strain gradient on the pyroelectric effect in centrosymmetric dielectric solids. Direct pyroelectricity can exist as external mechanical stress is applied to non-pyroelectric dielectrics with shapes such as truncated pyramids, due to elastic strain gradient induced flexoelectric polarization. Effective pyroelectric coefficient was analyzed in truncated pyramids. It is found to be controlled by size, ambient temperature, stress, and aspect ratio and depends mainly on temperature sensitivity of flexoelectric coefficient (TSFC) and strain gradient of the truncated pyramids dielectric solids. These results show that the pyroelectric property of Ba{sub 0.67}Sr{sub 0.33}TiO{sub 3} above T{sub c} similar to PZT and other lead-based ferroelectrics can be obtained. This feature might widely broaden the selection of materials for infrared detectors with preferable properties.

  2. Dielectric response of double layered perovskite Sr3MnTiO7

    Science.gov (United States)

    Chowki, S.; Sahu, B.; Singh, A. K.; Mohapatra, N.

    2016-05-01

    The results of dielectric and resistivity measurements on the Ruddlesden-Popper (RP) type compound Sr3MnTiO7 (SMTO) is presented here. The dielectric response of the compound was recorded in the temperature range 10-300 K with the probing frequency from 500 Hz-5 MHz. We observe a broad anomaly at ~ 200 K in the temperature dependence of dissipation factor (tanδ) and corresponding change in slope in the dielectric constant ɛr'(T) which may be attributed to a difference in the conduction mechanism below and above 200 K. The overall dielectric dispersion of SMTO resembles to that of the double perovskites Sr2MnTiO6 and La2NiMnO6 which follows the modified Debye relaxation equation. This indicates a relaxor type dielectric behavior of SMTO may be due to the contribution of grain boundary effects.

  3. Dielectric response of capacitor structures based on PZT annealed at different temperatures

    Science.gov (United States)

    Kamenshchikov, Mikhail V.; Solnyshkin, Alexander V.; Pronin, Igor P.

    2016-12-01

    Dielectric response of thin-film capacitor structures of Pt/PZT/Pt deposited by the RF magnetron sputtering method and annealed at temperatures of 540-570 °C was investigated. It was found that dielectric properties of these structures depend on the synthesis temperature. Stability of a polarized state is considered on the basis of the analysis of hysteresis loops and capacitance-voltage (C-V) characteristics. The contribution of the domain mechanism in the dielectric response of the capacitor structure comprising a ferroelectric is discussed. Extreme dependences of electrophysical characteristics of PZT films on their synthesis temperature were observed. Correlation of dielectric properties with microstructure of these films is found out.

  4. Temperature dependent dielectric and electric modulus properties of ZnS nano particles

    Science.gov (United States)

    Ali, Hassan; Falak, Attia; Rafiq, M. A.; Khan, Usman; Karim, Shafqat; Nairan, Adeela; Jing, Tang; Sun, Yue; Sun, Sibai; Qian, Chenjiang; Xu, Xiulai

    2017-03-01

    A comprehensive study of the dielectric and electric modulus properties of Zinc Sulfide (ZnS) semiconductor nanoparticles has been conducted using impedance spectroscopy in the frequency range of 200 Hz to 2 MHz and over the temperature range of 300 K to 400 K. Microscopic analysis confirms the formation of spherical nanoparticles with an average size of ∼20 nm. Maxwell–Wagner–Sillars (MWS) interfacial polarization is responsible for the increase in dielectric permittivity and dielectric loss at lower frequencies. Increase in dielectric permittivity and dielectric loss has been observed with a rise in temperature. The electric modulus complex plane plot reveals the presence of the grain (bulk) effect and non-Debye type relaxation processes in the material. The non-Debye type processes have also been confirmed by the asymmetric relaxation peaks of the imaginary part of the electric modulus. The frequency dependent maximum of the imaginary part of the electric modulus follows the Arrhenius law with an activation energy of 0.13 eV. The modulus analysis also establishes that the hopping mechanism is responsible for electrical conduction in the ZnS nanoparticles.

  5. Condition assessment of transformer insulation using dielectric frequency response analysis by artificial bee colony algorithm

    Directory of Open Access Journals (Sweden)

    Bigdeli Mehdi

    2016-03-01

    Full Text Available Transformers are one of the most important components of the power system. It is important to maintain and assess the condition. Transformer lifetime depends on the life of its insulation and insulation life is also strongly influenced by moisture in the insulation. Due to importance of this issue, in this paper a new method is introduced for determining the moisture content of the transformer insulation system using dielectric response analysis in the frequency domain based on artificial bee colony algorithm. First, the master curve of dielectric response is modeled. Then, using proposed method the master curve and the measured dielectric response curves are compared. By analyzing the results of the comparison, the moisture content of paper insulation, electrical conductivity of the insulating oil and dielectric model dimensions are determined. Finally, the proposed method is applied to several practical samples to demonstrate its capabilities compared with the well-known conventional method.

  6. Generalization of Dielectric-Dependent Hybrid Functionals to Finite Systems

    Science.gov (United States)

    Brawand, Nicholas P.; Vörös, Márton; Govoni, Marco; Galli, Giulia

    2016-10-01

    The accurate prediction of electronic and optical properties of molecules and solids is a persistent challenge for methods based on density functional theory. We propose a generalization of dielectric-dependent hybrid functionals to finite systems where the definition of the mixing fraction of exact and semilocal exchange is physically motivated, nonempirical, and system dependent. The proposed functional yields ionization potentials, and fundamental and optical gaps of many, diverse molecular systems in excellent agreement with experiments, including organic and inorganic molecules and semiconducting nanocrystals. We further demonstrate that this hybrid functional gives the correct alignment between energy levels of the exemplary TTF-TCNQ donor-acceptor system.

  7. Thickness-Dependent Dielectric Constant of Few-Layer In 2 Se 3 Nanoflakes

    KAUST Repository

    Wu, Di

    2015-11-17

    © 2015 American Chemical Society. The dielectric constant or relative permittivity (εr) of a dielectric material, which describes how the net electric field in the medium is reduced with respect to the external field, is a parameter of critical importance for charging and screening in electronic devices. Such a fundamental material property is intimately related to not only the polarizability of individual atoms but also the specific atomic arrangement in the crystal lattice. In this Letter, we present both experimental and theoretical investigations on the dielectric constant of few-layer In2Se3 nanoflakes grown on mica substrates by van der Waals epitaxy. A nondestructive microwave impedance microscope is employed to simultaneously quantify the number of layers and local electrical properties. The measured εr increases monotonically as a function of the thickness and saturates to the bulk value at around 6-8 quintuple layers. The same trend of layer-dependent dielectric constant is also revealed by first-principles calculations. Our results of the dielectric response, being ubiquitously applicable to layered 2D semiconductors, are expected to be significant for this vibrant research field.

  8. Effect of paramagnetic manganese ions doping on frequency and high temperature dependence dielectric response of layered Na1.9Li0.1Ti3O7 ceramics

    Indian Academy of Sciences (India)

    Dharmendra Pal; J L Pandey

    2010-12-01

    The manganese doped layered ceramic samples (Na1.9Li0.1)Ti3O7 : XMn(0.01 ≤ X ≤ 0.1) have been prepared using high temperature solid state reaction. The room temperature electron paramagnetic resonance (EPR) investigations exhibit that at lower percentage of doping the substitution of manganese ions occur as Mn3+ at Ti4+ sites, whereas for higher percentage of doping Mn2+ ions occupy the two different interlayer sodium/lithium sites. In both cases, the charge compensation mechanism should operate to maintain the overall charge neutrality of the lattice. The manganese doped derivatives of layered Na1.9Li0.1Ti3O7 (SLT) ceramics have been investigated through frequency dependence dielectric spectroscopy in this work. The results indicate that the dielectric losses in these ceramics are the collective contribution of electric conduction, dipole orientation and space charge polarization. Smeared peaks in temperature dependence of permittivity plots suggest diffuse nature of high temperature ferroelectric phase transition. The light manganese doping in SLT enhances the dielectric constant. However, manganese doping decreases dielectric loss due to inhibition of domain wall motion, enhances electronhopping conduction, and impedes the interlayer ionic conduction as well. Manganese doping also gives rise to contraction of interlayer space.

  9. Temperature Dependence of the Radio-Frequency Dielectric Properties of Chicken Meat

    Science.gov (United States)

    Dielectric properties of chicken breast meat were measured with an open-ended coaxial-line probe between 200 MHz and 20 GHz at temperature ranging from -20 oC to +25 oC. At a given frequency, the temperature dependence reveals a sharp increase of the dielectric constant and dielectric loss factor a...

  10. Dependence of the dielectric constant of electrolyte solutions on ionic concentration

    CERN Document Server

    Gavish, Nir

    2012-01-01

    We study the dependence of the static dielectric constant of aqueous electrolyte solutions upon the concentration of salt in the solution and temperature. The model takes into account the orientation of the solvent dipoles due to the electric field created by ions, the ionic response to an applied field, and the effect of thermal fluctuations. The analysis suggests that the formation of ion pairs by a small fraction of disassociated ions can have a significant effect on the static dielectric constant. The model predicts the dielectric has the functional dependence $\\varepsilon(c)=\\varepsilon_w-\\beta L(3\\alpha c/\\beta)$ where $L$ is the Langevin function, $c$ is the salt concentration, $\\varepsilon_w$ is the dielectric of the pure water, $\\alpha$ is the total excess polarization of the ions and $\\beta$ is the relative difference between the water dipole moment and the effective dipole moment of ion pairs as weighted by the density of ion pairs and their structural rigidity. The functional form gives an extreme...

  11. Temperature-Dependent Dielectric Properties of Al/Epoxy Nanocomposites

    Science.gov (United States)

    Wang, Zijun; Zhou, Wenying; Sui, Xuezhen; Dong, Lina; Cai, Huiwu; Zuo, Jing; Chen, Qingguo

    2016-06-01

    Broadband dielectric spectroscopy was carried out to study the transition in electrical properties of Al/epoxy nanocomposites over the frequency range of 1-107 Hz and the temperature range of -20°C to 200°C. The dielectric permittivity, dissipation factor, and electrical conductivity of the nanocomposites increased with temperature and showed an abrupt increase around the glass transition temperature ( T g). The results clearly reveal an interesting transition of the electrical properties with increasing temperature: insulator below 70°C, conductor at about 70°C. The behavior of the transition in electrical properties of the nanocomposites was explored at different temperatures. The presence of relaxation peaks in the loss tangent and electric modulus spectra of the nanocomposites confirms that the chain segmental dynamics of the polymer is accompanied by the absorption of energy given to the system. It is suggested that the temperature-dependent transition of the electric properties in the nanocomposite is closely associated with the α-relaxation. The large increase in the dissipation factor and electric conductivity depends on the direct current conduction of thermally activated charge carriers resulting from the epoxy matrix above T g.

  12. Broadening of dielectric response and sum rule conservation

    Energy Technology Data Exchange (ETDEWEB)

    Franta, Daniel, E-mail: franta@physics.muni.cz [Department of Physical Electronics, Faculty of Science, Masaryk University, Kotlářká 2, 611 37 Brno (Czech Republic); CEITEC —Central European Institute of Technology, Masaryk University, Kamenice 5, 625 00 Brno (Czech Republic); Nečas, David; Zajíčková, Lenka [Department of Physical Electronics, Faculty of Science, Masaryk University, Kotlářká 2, 611 37 Brno (Czech Republic); CEITEC —Central European Institute of Technology, Masaryk University, Kamenice 5, 625 00 Brno (Czech Republic); Ohlídal, Ivan [Department of Physical Electronics, Faculty of Science, Masaryk University, Kotlářká 2, 611 37 Brno (Czech Republic)

    2014-11-28

    Different types of broadening of the dielectric response are studied with respect to the preservation of the Thomas–Reiche–Kuhn sum rule. It is found that only the broadening of the dielectric function and transition strength function conserve this sum rule, whereas the broadening of the transition probability function (joint density of states) increases or decreases the sum. The effect of different kinds of broadening is demonstrated for interband and intraband direct electronic transitions using simplified rectangular models. It is shown that the broadening of the dielectric function is more suitable for interband transitions while broadening of the transition strength function is more suitable for intraband transitions. - Highlights: • Preservation of the sum rule by different types of dielectric response broadening • Only broadening of dielectric function and transition strength function preserves it. • Broadening of joint density of states does not preserve the sum rule. • Broadening of dielectric function is better for direct interband transitions. • Broadening of transition strength is better for indirect interband transitions.

  13. Temperature dependence of the dielectric properties of rubber wood

    Science.gov (United States)

    Mohammed Firoz Kabir; Wan M. Daud; Kaida B. Khalid; Haji A.A. Sidek

    2001-01-01

    The effect of temperature on the dielectric properties of rubber wood was investigated in three anisotropic directions—longitudinal, radial, and tangential, and at different measurement frequencies. Low frequency measurements were conducted with a dielectric spectrometer, and high frequencies used microwave applied with open-ended coaxial probe sensors. Dielectric...

  14. Pressure-dependent dielectric properties in a polyurethane elastomer

    Science.gov (United States)

    Hwang, Seung Won; Shin, Jae Sup; Shin, Min Jae; Kim, Chy Hyung

    2017-04-01

    The dielectric responses of polyurethane films were investigated in the pressure range from atmospheric to 20 kpsi and in the frequency range from 0.05 Hz to 4 KHz at -50, 0, 29, 50, and 80 ° C, where T g is close to -15 ° C (α-relaxation) and where the glass temperature of the chain extender is about 80 ° C (I-relaxation). When a higher pressure was applied to the material, a lower dielectric constant (k' ) was obtained owing to the suppression of polarization motions by the external pressure. However, k' increased with rising pressure at temperatures above 50 ° C and at high frequencies due to the predominant thermal effect expanding the film outwards, where a dispersive α-relaxation occurred. Both α- and I-relaxations followed the pressure-frequency superposition principle with a different shifting factor, a( p), where the α-relaxation showed a faster migration of the relaxation time with changing pressure and a( p) values larger than those of I-relaxation. The two relaxations observed at 29 ° C demonstrated linear relations between 1/k' and pressure and between ln a( p) and pressure, regardless of the film thickness.

  15. The dielectric response to the magnetic field of electromagnetic radiation

    Science.gov (United States)

    Mukherjee, Shouvik; Mukhopadhyay, Sourabh; Datta, Prasanta Kumar

    2017-04-01

    Light–matter interaction in transparent dielectrics is revisited, including the magnetic force on bound charges in the Lorentz oscillator model. The parameter ranges of incident radiation and the medium on which the magnetic field of the electromagnetic radiation will have a significant effect are traced using Floquet theory. The analysis reveals that the threshold intensity for a significant response of the magnetic field of the radiation at the second harmonic of the incident radiation can be reduced to {10}12 {{W}}{{cm}}-2 for off resonant and even lower for resonant interaction. This phenomenon has already been observed indirectly in experiments [1, 2]. Induced magnetizing current due to the magnetic force is shown to originate from a modified dielectric response, which may be useful in future magneto-optic devices, solar energy harvesting, and studying the ultrafast dynamics in doped dielectrics.

  16. Nonlinear Dielectric Response of Water Treed XLPE Cable Insulation

    Energy Technology Data Exchange (ETDEWEB)

    Hvidsten, Sverre

    1999-07-01

    Condition assessment of XLPE power cables is becoming increasingly important for the utilities, due to a large number of old cables in service with high probability of failure caused by water tree degradation. The commercial available techniques are generally based upon measurements of the dielectric response, either by time (polarisation/depolarisation current or return voltage) or frequency domain measurements. Recently it has been found that a high number of water trees in XLPE insulated cables causes the dielectric response to increase more than linearly with increasing test voltage. This nonlinear feature of water tree degraded XLPE insulation has been suggested to be of a great importance, both for diagnostic purposes, and for fundamental understanding of the water tree phenomenon itself. The main purpose of this thesis have been to study the nonlinear feature of the dielectric response measured on watertreed XLPE insulation. This has been performed by dielectric response measurements in both time and frequency domain, numerical calculations of losses of simplified water tree models, and fmally water content and water permeation measurements on single water trees. The dielectric response measurements were performed on service aged cable samples and laboratory aged Rogowski type objects. The main reason for performing laboratory ageing was to facilitate diagnostic testing as a function of ageing time of samples containing mainly vented water trees. A new method, based upon inserting NaC1 particles at the interface between the upper semiconductive screen and the insulation, was found to successfully enhance initiation and growth of vented water trees. AC breakdown strength testing show that it is the vented water trees that reduce the breakdown level of both the laboratory aged test objects and service aged cable samples. Vented water treeing was found to cause the dielectric response to become nonlinear at a relatively low voltage level. However, the measured

  17. Response analysis of dielectric elastomer spherical membrane to harmonic voltage and random pressure

    Science.gov (United States)

    Jin, Xiaoling; Wang, Yong; Chen, Michael Z. Q.; Huang, Zhilong

    2017-03-01

    Spherical membranes consisting of dielectric elastomer play important roles in flexible and stretchable devices, such as flexible actuators, sensors and loudspeakers. Executing various functions of devices depends on the dynamical behaviors of dielectric elastomer spherical membranes to external electrical and/or mechanical excitations. This manuscript concentrates on the random aspect of dielectric elastomer spherical membranes, i.e., the random response to combined excitations of harmonic voltage and random pressure. To analytically evaluate the response statistics of the stretch ratio, a specific transformation and stochastic averaging technique are successively adopted to solve the strongly nonlinear equation with respect to the stretch ratio. The stochastic differential equations for the system first integral and the phase difference between harmonic excitation and response are first derived through this transformation. The Fokker-Planck-Kolmogorov equation with respect to the stationary probability density of the system first integral and the phase difference is obtained. The stationary probability densities and the response statistics of the stretch ratio and its rate of change are then subsequently calculated. The phenomenon of stochastic jumps is found and the stochastic jump bifurcates with the variations of the frequency and the amplitude of the harmonic voltage and the intensity of the random pressure. The efficacy and accuracy of the analytical results are verified by comparing with the results from Monte Carlo simulation. Besides, the reliability of the dielectric elastomer spherical membrane is discussed briefly. The obtained results could provide options in implementing and designing dielectric elastomer structures for dynamic applications.

  18. Processing dependent properties of silica xerogels for interlayer dielectric applications

    Science.gov (United States)

    Jain, Anurag

    One of the current and near future research focus in microelectronics is to integrate copper with a new low dielectric constant (K) material. The traditional low K is dense SiO2 (K = 4). Introducing porosity in materials with silica backbone is promising as processing and integration methods are well known. This thesis focuses on studying silica xerogel, also known as nanoporous silica. A new low-K material has to be tested for an array of electrical, mechanical, thermal, and chemical properties before it is deemed successful to replace dense SiO2. These properties of silica xerogels are characterized using various analytical techniques and the effect of processing conditions is studied. The property data is explained by the models and mechanisms relating processing-structure-property behavior. The processing effects on thermal and mechanical properties are studied in great detail and the theories for generic porous low-K materials are developed. The xerogel films are processed at ambient conditions and crack free, thick (0.5--4 mum), highly porous (˜25--90%) films are obtained. Two methods of porosity control were used. One is the traditional single solvent (ethanol) method and another is a binary solvent (mixture of ethanol and ethylene glycol) method. The films underwent aging and silylation procedures to make the backbone stiff and hydrophobic. Sintering of xerogel films eliminates defects and organics and additional condensation reactions make matrix more connected, dense and ordered. Films were characterized for their refractive index, thickness, porosity, pore size and surface roughness. Dielectric constant measurements at 1 MHz show that K varies linearly with porosity. Dielectric loss tangents are low and breakdown strength meets the standards. FTIR and XPS analysis show that films are stable chemically and remain hydrophobic even after boiling in water. Mechanical and thermal properties of porous materials are dependent on the microstructure and various

  19. Dielectric response of polystyrene - BaTiO3 nanocomposites

    Science.gov (United States)

    Korotkova, Tatyana N.; Sysoev, Oleg I.; Belov, Pavel A.; Emelianov, Nikita A.; Velyaev, Yury O.; Mandalawi, Wissam M. Al; Korotkov, Leonid N.

    2016-07-01

    The series of composite materials based on polystyrene and non-ferroelectric BaTiO3 nanoparticles ((1-x)PS-xBT, where the volume concentration x = 0-1.0) was prepared. Their dielectric properties were studied within the temperature range 20-160 °C at the frequency of 100 kHz. It is found that an increase in the barium titanate concentration leads to increase of the both dielectric permittivity (ɛ) and dielectric losses (tgδ). The concentration dependence of ɛ can be described by the modified Kerner model. It was found that the glass transition in polystyrene matrix is diffused and its temperature is increased with concentration x.

  20. Effective dielectric response of graded composite materials containing anisotropic particles

    Institute of Scientific and Technical Information of China (English)

    Sang Zhi-Fang; Li Zhen-Ya

    2005-01-01

    The effective dielectric response of granular composites, in which spheroidal particles with graded shells are randomly distributed in a host matrix, is investigated. General expressions for the effective dielectric constant of the composites and partial resonant condition are obtained in the dilute limit by use of a quasi-static approximation. In particular, spheroidal particles with a power-law gradation profile in the shells are studied in detail. We find that, by adjusting the dielectric gradient profile in the shells, the shape and structure of particles, it is possible to enhance the effective dielectric constant of the composite and to realize partial resonance. Under the partial resonant conditions,the coated spheroidal particles with graded shells within the host matrix can be regarded as equivalent homogeneous spheroids embedded in the same host. The equivalent spheroids have the same dielectric constant as the original cores and semiaxes equal to those of the original shells: i.e., the partial resonant system behaves as if the cores of the particles were enlarged and the shells were absent.

  1. Temperature dependent x-ray diffraction and dielectric studies of multiferroic GaFeO3

    Science.gov (United States)

    Kumar, Rajeev; Mall, Ashish Kumar; Gupta, Rajeev

    2016-05-01

    Polycrystalline GaFeO3 (GFO) samples were synthesized by sol-gel method. The structural and dielectric properties of GaFeO3 ceramic have been investigated by a combination of XRD and permittivity measurement. The X-ray diffraction spectra shows single phase orthorhombically distorted perovskite structure with Pc21n symmetry over a wide range of temperature 300K to 600K, with no evidence of any phase transition. Refined lattice parameters (a, b, c and V) increases with increasing temperature. Temperature dependent dielectric properties were investigated in the frequency range from 100Hz-5MHz. Impedance spectroscopy study on the sample showed that the dielectric constant and ac conductivity with frequency increases on increasing the temperature. Cole-Cole plots suggest that the response from grain is dominant at low temperature whereas grain boundary response overcomes as temperature increases. The relaxation activation energy (calculated from Cole-Cole plots) value is found to be 0.32 eV for the grain boundary. We believe that the oxygen ion vacancies play an important role in conduction processes at higher temperatures.

  2. The effect of vacuum ultraviolet irradiation on the time-dependent dielectric breakdown of organosilicate dielectrics

    Science.gov (United States)

    Pei, D.; Xue, P.; Li, W.; Guo, X.; Lin, Y. H.; Fung, H. S.; Chen, C. C.; Nishi, Y.; Shohet, J. L.

    2016-09-01

    In this work, the effect of vacuum ultraviolet (VUV) exposure on the time-dependent dielectric breakdown (TDDB) properties of porous low-k films was investigated. Synchrotron irradiation was used to simulate the VUV photon irradiation from processing plasmas without any particle flux. The synchrotron flux varies with the wavelength, so the irradiation time was chosen to produce the same fluence at various photon energies. The deterioration of TDDB and generation of negative mobile charge were observed in the film after exposure to the VUV photons with 9 eV or higher energy. These effects were not observed in the films exposed with 7-eV photon energies or less. The creation of paramagnetic defects was observed with the ESR measurement and believed to be the reason for TDDB degradation. Depletion of carbon and breakage and rearrangement of the Si-O-Si structure were observed and believed to be the reason for mobile charge generation and the change in TDDB, chemical, and mechanical properties.

  3. Properties of Atmospheric Pressure Ar Plasma Jet Depending on Treated Dielectric Material

    Science.gov (United States)

    Prysiazhnyi, Vadym; Ricci Castro, Alonso H.; Kostov, Konstantin G.

    2017-02-01

    Atmospheric pressure plasma jet operated in argon was utilized to modify surfaces of glass, acrylic, and PTFE dielectrics. This paper describes the influence of the dielectric substrate on operation and properties of plasma. Two modes of operation (each of those have two patterns) were described. The transition from one mode to another, values of the dissipated power, and spreading of plasma over the dielectric surfaces strongly depended on the substrate material. Additionally, three methods of plasma spreading estimation were presented and discussed.

  4. Effective Dielectric Response of Nonlinear Composites of Coated Metal Inclusions

    Institute of Scientific and Technical Information of China (English)

    CHEN Guo-Qing; WU Ya-Min

    2007-01-01

    The effective dielectric response of the composites in which nondilute coated metal particles are randomly embedded in a linear host is investigated. Two types of coated particles are considered, one is that the core is nonlinear, the other is that the shell is nonlinear. We derive general expressions for the effective linear dielectric function and the effective third-order nonlinear susceptibility, and take one step forward to perform numerical calculations on the coated metal/dielectric composites. Numerical results show that the effective linear and nonlinear dielectric responses can be greatly enhanced near the surface plasmon resonant frequency. Moreover, the resonant peaks are found within a range from 0.46ωp to 0.57ωp for spherical particles and from 0.59ωp to 0.7ωp for cylindrical inclusions. In the frequency region, the resonant peak can achieve the maximum, according to an optimal structural parameter and volume fraction. The resonant frequency exhibits a redshift with the increasing structural parameter k or volume fraction f or dimensionality factor D.

  5. Frequency-dependent dielectric function of semiconductors with application to physisorption

    Science.gov (United States)

    Zheng, Fan; Tao, Jianmin; Rappe, Andrew M.

    2017-01-01

    The dielectric function is one of the most important quantities that describes the electrical and optical properties of solids. Accurate modeling of the frequency-dependent dielectric function has great significance in the study of the long-range van der Waals (vdW) interaction for solids and adsorption. In this work we calculate the frequency-dependent dielectric functions of semiconductors and insulators using the G W method with and without exciton effects, as well as efficient semilocal density functional theory (DFT), and compare these calculations with a model frequency-dependent dielectric function. We find that for semiconductors with moderate band gaps, the model dielectric functions, G W values, and DFT calculations all agree well with each other. However, for insulators with strong exciton effects, the model dielectric functions have a better agreement with accurate G W values than the DFT calculations, particularly in high-frequency region. To understand this, we repeat the DFT calculations with scissors correction, by shifting the DFT Kohn-Sham energy levels to match the experimental band gap. We find that scissors correction only moderately improves the DFT dielectric function in the low-frequency region. Based on the dielectric functions calculated with different methods, we make a comparative study by applying these dielectric functions to calculate the vdW coefficients (C3 and C5) for adsorption of rare-gas atoms on a variety of surfaces. We find that the vdW coefficients obtained with the nearly free electron gas-based model dielectric function agree quite well with those obtained from the G W dielectric function, in particular for adsorption on semiconductors, leading to an overall error of less than 7% for C3 and 5% for C5. This demonstrates the reliability of the model dielectric function for the study of physisorption.

  6. Dependence of crystallizing phase dielectric permittivity on time of glass-ceramics sintering

    Directory of Open Access Journals (Sweden)

    Dmitriyev M. V.

    2010-10-01

    Full Text Available The paper deals with computing technique of effective dielectric permittivity of crystobalite formed in glass-ceramic body by means of measured dielectric permittivity of glass-ceramic composit. Dependence of the calculated parameter from the time of crystallization is found.

  7. Composition-dependent structural, dielectric and ferroelectric responses of lead-free Bi0.5Na0.5TiO3-SrZrO3 ceramics

    Science.gov (United States)

    Maqbool, Adnan; Hussain, Ali; Rahman, Jamil Ur; Malik, Rizwan Ahmed; Song, Tae Kwon; Kim, Myong-Ho; Kim, Won-Jeong

    2016-06-01

    The influence of SrZrO3 (SZ) addition on the crystal structure, piezoelectric and the dielectric properties of lead-free Bi0.5Na0.5TiO3 (BNT-SZ100 x, with x = 0 - 0.10) ceramics was systematically investigated. A significant reduction in the grain size was observed with SZ substitution. The X-ray diffraction analysis of the sintered BNT-SZ ceramics revealed a single perovskite phase with a pseudocubic symmetry; however, electric poling indicated a non-cubic distortion in the poled BNT-SZ ceramics. With increase in the SZ content, the temperature of maximum dielectric constant ( T m ) shifted towards lower temperatures, and the curves became more diffuse. Enhanced piezoelectric constant ( d 33 = 102 pC/N) and polarization response were observed for the BNT-SZ5 ceramics. The results indicated that SZ substitution induced a transition from a ferroelectric to relaxor state with a field-induced strain of 0.24% for BNT-SZ9 corresponding to a normalized strain of 340 pm/V.

  8. Reduced dielectric response in spatially varying electric fields

    DEFF Research Database (Denmark)

    Hansen, Jesper Schmidt

    2015-01-01

    In this paper, the dynamical equation for polarization is derived. From this the dielectric response to a spatially varying electric field is analyzed showing a reduced response due to flux of polarization in the material. This flux is modeled as a diffusive process through linear constitutive...... relations between the flux and the gradient of the polarization. Comparison between the theory and molecular dynamics simulations confirms this effect. The effect is significant for small length scale electric field variations and the inclusion of the flux is thus important in nanoscale modeling...

  9. Optical nonlinear response of a single nonlinear dielectric layer sandwiched between two linear dielectric structures

    Energy Technology Data Exchange (ETDEWEB)

    Lidorikis, E. [Ames Laboratory--USDOE and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011 (United States); Busch, K. [Ames Laboratory--USDOE and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011 (United States)]|[Instituet fuer Theorie der Kondensierten Materie, Universitaet Karlsruhe, D-76128, Karlsruhe (Germany); Li, Q. [Ames Laboratory--USDOE and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011 (United States); Chan, C.T. [Ames Laboratory--USDOE and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011 (United States)]|[Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong (China); Soukoulis, C.M. [Ames Laboratory--USDOE and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011 (United States)

    1997-12-01

    We consider the general problem of electromagnetic wave propagation through a one-dimensional system consisting of a nonlinear medium sandwiched between two linear structures. Special emphasis is given to systems where the latter comprise Bragg reflectors. We obtain an exact expression for the nonlinear response of such dielectric superlattices when the nonlinear impurity is very thin, or in the {delta}-function limit. We find that both the switching-up and switching-down intensities of the bistable response can be made very low, when the frequency of the incident wave matches that of the impurity mode of the structure. Numerical results for a nonlinear layer of finite width display qualitatively similar behavior, thus confirming the usefulness of the simpler {delta}-function model. In addition, an analytical solution for the resonance states of an infinitely extended finite-width superlattice with a finite-width nonlinear impurity is presented. {copyright} {ital 1997} {ital The American Physical Society}

  10. Identification of Structural Relaxation in the Dielectric Response of Water

    Science.gov (United States)

    Hansen, Jesper S.; Kisliuk, Alexander; Sokolov, Alexei P.; Gainaru, Catalin

    2016-06-01

    One century ago pioneering dielectric results obtained for water and n -alcohols triggered the advent of molecular rotation diffusion theory considered by Debye to describe the primary dielectric absorption in these liquids. Comparing dielectric, viscoelastic, and light scattering results, we unambiguously demonstrate that the structural relaxation appears only as a high-frequency shoulder in the dielectric spectra of water. In contrast, the main dielectric peak is related to a supramolecular structure, analogous to the Debye-like peak observed in monoalcohols.

  11. Thermoluminescence and dielectric response of gamma irradiated muscovite mica

    Energy Technology Data Exchange (ETDEWEB)

    Kaur, Sukhnandan, E-mail: sukhnandanphy@gmail.com; Singh, Surinder, E-mail: sukhnandanphy@gmail.com; Singh, Lakhwant, E-mail: sukhnandanphy@gmail.com [Department of Physics, Guru Nanak Dev University, Amritsar-143005 (India); Lochab, S. P. [Inter University Accelerator Centre, New Delhi-110067 (India)

    2014-04-24

    The effect of gamma radiation dose on the thermoluminescence (TL) and dielectric properties of muscovite mica was studied. TL glow curves exhibited a single peak around 141 {sup 0}C and its activation energy was estimated to be about 0.89 eV. Different dielectric parameters like dielectric constant, dielectric loss and ac conductivity have been calculated in both pristine and gamma irradiated samples. These dielectric parameters have been studied as a function of irradiation dose.

  12. Dependence of dielectric properties on BT particle size in EP/BT composites

    Institute of Scientific and Technical Information of China (English)

    YANG Xiaojun; YANG Zhimin; MAO Changhui; DU Jun

    2006-01-01

    The polymer-ceramic composites of epoxy resin (EP) and barium titanate (BT) were prepared.BT powders of different BT particle sizes from 100 nm to 1 μm were used in the preparation.The dielectric properties, such as dielectric constant, dielectric loss and electrical breakdown strength, of the EP/BT composites were studied.The morphology of the composites was characterized by the means of scanning electron microscopy (SEM).The results show that the dielectric constant of the composites is much higher than the epoxy matrix at frequency range from 1 kHz to 10 MHz, and it is also obviously dependent on the size of BT particles.The electrical breakdown strength of the composites decreases with the increase of the BT content.The dependence of electrical breakdown strength on BT particle sizes was also discussed.

  13. Photonic band gap enhancement in frequency-dependent dielectrics.

    Science.gov (United States)

    Toader, Ovidiu; John, Sajeev

    2004-10-01

    We illustrate a general technique for evaluating photonic band structures in periodic d -dimensional microstructures in which the dielectric constant epsilon (omega) exhibits rapid variations with frequency omega . This technique involves the evaluation of generalized electromagnetic dispersion surfaces omega ( k--> ,epsilon) in a (d+1) -dimensional space consisting of the physical d -dimensional space of wave vectors k--> and an additional dimension defined by the continuous, independent, variable epsilon . The physical band structure for the photonic crystal is obtained by evaluating the intersection of the generalized dispersion surfaces with the "cutting surface" defined by the function epsilon (omega) . We apply this method to evaluate the band structure of both two- and three-dimensional (3D) periodic microstructures. We consider metallic photonic crystals with free carriers described by a simple Drude conductivity and verify the occurrence of electromagnetic pass bands below the plasma frequency of the bulk metal. We also evaluate the shift of the photonic band structure caused by free carrier injection into semiconductor-based photonic crystals. We apply our method to two models in which epsilon (omega) describes a resonant radiation-matter interaction. In the first model, we consider the addition of independent, resonant oscillators to a photonic crystal with an otherwise frequency-independent dielectric constant. We demonstrate that for an inhomogeneously broadened distribution of resonators impregnated within an inverse opal structure, the full 3D photonic band gap (PBG) can be considerably enhanced. In the second model, we consider a coupled resonant oscillator mode in a photonic crystal. When this mode is an optical phonon, there can be a synergetic interplay between the polaritonic resonance and the geometrical scattering resonances of the structured dielectric, leading to PBG enhancement. A similar effect may arise when resonant atoms that are

  14. In situ study on low-k interconnect time-dependent-dielectric-breakdown mechanisms

    Energy Technology Data Exchange (ETDEWEB)

    Boon Yeap, Kong, E-mail: KongBoon.Yeap@globalfoundries.com [GLOBALFOUNDRIES, Fab8, 400 Stonebreak Rd. Extension, Malta, New York 12020 (United States); Fraunhofer Institute for Ceramic Technologies and Systems, Maria-Reiche-Str. 2, D-01109 Dresden (Germany); Gall, Martin; Liao, Zhongquan; Sander, Christoph; Muehle, Uwe; Zschech, Ehrenfried [Fraunhofer Institute for Ceramic Technologies and Systems, Maria-Reiche-Str. 2, D-01109 Dresden (Germany); Justison, Patrick [GLOBALFOUNDRIES, Fab8, 400 Stonebreak Rd. Extension, Malta, New York 12020 (United States); Aubel, Oliver; Hauschildt, Meike; Beyer, Armand; Vogel, Norman [GLOBALFOUNDRIES Dresden Module One LLC and Co. KG, Wilschdorfer Landstr. 101, D-01109 Dresden (Germany)

    2014-03-28

    An in situ transmission-electron-microscopy methodology is developed to observe time-dependent dielectric breakdown (TDDB) in an advanced Cu/ultra-low-k interconnect stack. A test structure, namely a “tip-to-tip” structure, was designed to localize the TDDB degradation in small dielectrics regions. A constant voltage is applied at 25 °C to the “tip-to-tip” structure, while structural changes are observed at nanoscale. Cu nanoparticle formation, agglomeration, and migration processes are observed after dielectric breakdown. The Cu nanoparticles are positively charged, since they move in opposite direction to the electron flow. Measurements of ionic current, using the Triangular-Voltage-Stress method, suggest that Cu migration is not possible before dielectric breakdown, unless the Cu/ultra-low-k interconnect stacks are heated to 200 °C and above.

  15. Temperature and Frequency Dependent Empirical Models of Dielectric Properties of Sunflower and Olive Oil

    Directory of Open Access Journals (Sweden)

    J. Vrba

    2013-12-01

    Full Text Available In this article, a known concept and measurement probe geometry for the estimation of the dielectric properties of oils have been adapted. The new probe enables the~measurement in the frequency range of 1 to 3000 MHz. Additionally, the measurement probe has been equipped with a~heat exchanger, which has enabled us to measure the dielectric properties of sunflower and olive oil as well as of two commercial emulsion concentrates. Subsequently, corresponding linear empirical temperature and frequency dependent models of the dielectric properties of the above mentioned oils and concentrates have been created. The dielectric properties measured here as well as the values obtained based on the empirical models created here match the data published in professional literature very well.

  16. Temperature and directional dependences of the infrared dielectric function of free standing silicon nanowire

    Energy Technology Data Exchange (ETDEWEB)

    Kazan, M.; Bruyant, A.; Sedaghat, Z.; Arnaud, L.; Blaize, S.; Royer, P. [Laboratoire de Nanotechnologie et d' Instrumentation Optique, Institut Charles Delaunay, Universite de Technologie de Troyes, CNRS FRE 2848, 12 Rue Marie Curie, 10010 Troyes, Cedex (France)

    2011-03-15

    An approach to calculate the infrared dielectric function of semiconductor nanostructures is presented and applied to silicon (Si) nanowires (NW's). The phonon modes symmetries and frequencies are calculated by means of the elastic continuum medium theory. The modes strengths and damping are calculated from a model for lattice dynamics and perturbation theory. The data are used in anisotropic Lorentz oscillator model to generate the temperature and directional dependences of the infrared dielectric function of free standing Si NW's. Our results showed that in the direction perpendicular to the NW axis, the complex dielectric function is identical to that of bulk Si. However, along the NW axis, the infrared dielectric function is a strong function of the wavelength. (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  17. A study of frequency dependent electrical and dielectric properties of NiO nanoparticles

    Science.gov (United States)

    Usha, V.; Kalyanaraman, S.; Vettumperumal, R.; Thangavel, R.

    2017-01-01

    Nickel oxide nanoparticles were synthesized using low cost sol-gel method. The structure of as prepared NiO nanoparticles has been confirmed from X-ray diffraction (XRD), scanning electron microscope with energy dispersive X-ray (SEM and EDX) spectroscopic analysis. The electrical and dielectric properties were characterized by complex impedance spectroscopy as a function of frequency at different temperatures. To study the dielectric behavior of the nanoparticles different plots like Nyquist plot, modulus plot and Bode plot were used. Also the frequency dependent ac conductivity is analyzed and the activation energy is calculated. The dielectric constant and dielectric loss as a function of frequency at various temperatures are also studied.

  18. Measurement on Spot Size Dependence of Dense WDM Dielectric Multilayer Filters

    Institute of Scientific and Technical Information of China (English)

    Masanobu; Ito; Satoshi; Suda; Fumio; Koyama

    2003-01-01

    We present the spot size dependence of dielectric multilayer filters for use in dense WDM systems. We found large dependences of filter performances on the spot size and the incident angle of input light, which should be important for miniaturizing multi-channel add/drop filters.

  19. Dielectric-dependent Density Functionals for Accurate Electronic Structure Calculations of Molecules and Solids

    Science.gov (United States)

    Skone, Jonathan; Govoni, Marco; Galli, Giulia

    Dielectric-dependent hybrid [DDH] functionals have recently been shown to yield highly accurate energy gaps and dielectric constants for a wide variety of solids, at a computational cost considerably less than standard GW calculations. The fraction of exact exchange included in the definition of DDH functionals depends (self-consistently) on the dielectric constant of the material. In the present talk we introduce a range-separated (RS) version of DDH functionals where short and long-range components are matched using material dependent, non-empirical parameters. Comparing with state of the art GW calculations and experiment, we show that such RS hybrids yield accurate electronic properties of both molecules and solids, including energy gaps, photoelectron spectra and absolute ionization potentials. This work was supported by NSF-CCI Grant Number NSF-CHE-0802907 and DOE-BES.

  20. System identification algorithms for the analysis of dielectric responses from broadband spectroscopies

    Energy Technology Data Exchange (ETDEWEB)

    Hadjiloucas, S; Walker, G C; Bowen, J W [Cybernetics, School of Systems Engineering, The University of Reading, RG6 6AY (United Kingdom); Galvao, R K H, E-mail: s.hadjiloucas@reading.ac.uk [Divisao de Engenharia Eletronica, Instituto Tecnologico de Aeronautica, Sao Jose dos Campos, SP, 12228-900 Brazil (Brazil)

    2011-08-12

    We discuss the modelling of dielectric responses for an electromagnetically excited network of capacitors and resistors using a systems identification framework. Standard models that assume integral order dynamics are augmented to incorporate fractional order dynamics. This enables us to relate more faithfully the modelled responses to those reported in the Dielectrics literature.

  1. Shear and dielectric responses of propylene carbonate, tripropylene glycol, and a mixture of two secondary amides

    DEFF Research Database (Denmark)

    Gainaru, Catalin; Hecksher, Tina; Olsen, Niels Boye

    2012-01-01

    to calculate the dielectric from the mechanical response and vice versa. Using a single parameter for a given system, good agreement between model calculations and experimental data is achieved for the entire relaxation spectra, including secondary relaxations and the Debye-like dielectric peak......Propylene carbonate and a mixture of two secondary amides, N-ethylformamide and Nethylacetamide, are investigated by means of broadband dielectric and mechanical shear spectroscopy. The similarities between the rheological and the dielectric responses of these liquids and of the previously...... in the secondary amides. In addition, the predictions of the shoving model are confirmed for the investigated liquids...

  2. Theoretical study of a screened Hartree–Fock exchange potential using position-dependent atomic dielectric constants

    Energy Technology Data Exchange (ETDEWEB)

    Shimazaki, Tomomi; Nakajima, Takahito [RIKEN, Advanced Institute for Computational Science, 7-1-26 Minatojima-minami-machi, Chuo-ku, Kobe, Hyogo 650-0047 (Japan)

    2015-02-21

    Dielectric-dependent screened Hartree–Fock (HF) exchange potential and Slater-formula have been reported, where the ratio of the HF exchange term mixed into potentials is inversely proportional to the dielectric constant of the target semiconductor. This study introduces a position-dependent dielectric constant method in which the dielectric constant is partitioned between the atoms in a semiconductor. These partitioned values differ depending on the electrostatic environment surrounding the atoms and lead to position-dependent atomic dielectric constants. These atomic dielectric constants provide atomic orbital-based matrix elements for the screened exchange potentials. Energy band structures of several semiconductors and insulators are also presented to validate this approach.

  3. Angular and positional dependence of Purcell effect for layered metal-dielectric structures

    Science.gov (United States)

    Gubaydullin, A. R.; Mazlin, V. A.; Ivanov, K. A.; Kaliteevski, M. A.; Balocco, C.

    2016-04-01

    We study the angular dependence of the spontaneous emission enhancement of a dipole source inserted into a layered metal-dielectric metamaterial. We analyse the dependence of Purcell effect from the position of the dipole in the layered hyperbolic media. We analyse the impact of the complex structure of eigenmodes of the system operating in hyperbolic regime. We have shown that the spontaneous emission rate of the dipole emitter depends on its position, which mainly affect the interaction with Langmuir modes.

  4. The effects of halide anions on the dielectric response of potassium halide solutions in visible, UV and far UV region.

    Science.gov (United States)

    Shagieva, F M; Boinovich, L B

    2013-06-07

    Based on the experimentally measured dispersion of refractive indices, we studied the effects of halide anions on the dielectric response of potassium halide solutions in the visible, UV and far UV regions. It was shown that a specific ion effect according to the Hofmeister series is clearly demonstrated for the visible range of spectra. For the near-, mid-, and far UV ranges of spectra, the specific ion effect essentially depends on solution concentration and temperature. The influence of ions on the behavior of dynamic dielectric permittivity of a solution is discussed on the basis of ion/water and ion/ion electrostatic and electrodynamic interactions and hydration shell structure.

  5. Dielectric Response of Glass-Forming Liquids in the Nonlinear Regime

    Science.gov (United States)

    Samanta, Subarna

    Broadband dielectric spectroscopy is a powerful technique for understanding the dynamics in supercooled liquids. It generates information about the timescale of the orientational motions of molecular dipoles within the liquid. However, dynamics of liquids measured in the non-linear response regime has recently become an area of significant interest, because additional information can be obtained compared with linear response measurements. The first part of this thesis describes nonlinear dielectric relaxation experiments performed on various molecular glass forming-liquids, with an emphasis on the response at high frequencies (excess wing). A significant nonlinear dielectric effect (NDE) was found to persist in these modes, and the magnitude of this NDE traces the temperature dependence of the activation energy. A time resolved measurement technique monitoring the dielectric loss revealed that for the steady state NDE to develop it would take a very large number of high amplitude alternating current (ac) field cycles. High frequency modes were found to be 'slaved' to the average structural relaxation time, contrary to the standard picture of heterogeneity. Nonlinear measurements were also performed on the Johari-Goldstein beta-relaxation process. High ac fields were found to modify the amplitudes of these secondary modes. The nonlinear features of this secondary process are reminiscent of those found for the excess wing regime, suggesting that these two contributions to dynamics have common origins. The second part of this thesis describes the nonlinear effects observed from the application of high direct current (dc) bias fields superposed with a small amplitude sinusoidal ac field. For several molecular glass formers, the application of a dc field was found to slow down the system via reduction in configurational entropy (Adam-Gibbs relation). Time resolved measurements indicated that the rise of the non-linear effect is slower than its decay, as observed in the

  6. Rate dependent constitutive behavior of dielectric elastomers and applications in legged robotics

    Science.gov (United States)

    Oates, William; Miles, Paul; Gao, Wei; Clark, Jonathan; Mashayekhi, Somayeh; Hussaini, M. Yousuff

    2017-04-01

    Dielectric elastomers exhibit novel electromechanical coupling that has been exploited in many adaptive structure applications. Whereas the quasi-static, one-dimensional constitutive behavior can often be accurately quantified by hyperelastic functions and linear dielectric relations, accurate predictions of electromechanical, rate-dependent deformation during multiaxial loading is non-trivial. In this paper, an overview of multiaxial electromechanical membrane finite element modeling is formulated. Viscoelastic constitutive relations are extended to include fractional order. It is shown that fractional order viscoelastic constitutive relations are superior to conventional integer order models. This knowledge is critical for transition to control of legged robotic structures that exhibit advanced mobility.

  7. Temperature dependence of ratio between dielectric anisotropy and order parameter in fluorinated nematic liquid crystals

    Institute of Scientific and Technical Information of China (English)

    Ma Heng; Sun Rui-Zhi; Li Zhen-Xin; Liu Yu-Fang

    2008-01-01

    Temperature dependence of ratio between dielectric anisotropy and order parameter of fluorinated nematic liquid crystal is investigated by using a semi-empirical molecular orbital package that can accurately calculate an angle between molecular dipole moment and long axis.We optimize the molecular conformations with three semi-empirical Hamiltonians AM1,PM3 and PM5,and then make a comparison between computational results and experimental measurements.It is shown that the results obtained from AM1 method are in good agreement with the measurements.The present study offers an applicable method to predict the dielectric properties of liquid crystal material.

  8. Ac-conductivity and dielectric response of new zinc-phosphate glass/metal composites

    Energy Technology Data Exchange (ETDEWEB)

    Maaroufi, A., E-mail: maaroufi@fsr.ac.ma [University of Mohammed V, Laboratory of Composite Materials, Polymers and Environment, Department of Chemistry, Faculty of Sciences, P.B. 1014, Rabat-Agdal (Morocco); Oabi, O. [University of Mohammed V, Laboratory of Composite Materials, Polymers and Environment, Department of Chemistry, Faculty of Sciences, P.B. 1014, Rabat-Agdal (Morocco); Lucas, B. [XLIM UMR 7252 – Université de Limoges/CNRS, 123 avenue Albert Thomas, 87060 Limoges Cedex (France)

    2016-07-01

    The ac-conductivity and dielectric response of new composites based on zinc-phosphate glass with composition 45 mol%ZnO–55 mol%P{sub 2}O{sub 5}, filled with metallic powder of nickel (ZP/Ni) were investigated by impedance spectroscopy in the frequency range from 100 Hz to 1 MHz at room temperature. A high percolating jump of seven times has been observed in the conductivity behavior from low volume fraction of filler to the higher fractions, indicating an insulator – semiconductor phase transition. The measured conductivity at higher filler volume fraction is about 10{sup −1} S/cm and is frequency independent, while, the obtained conductivity for low filler volume fraction is around 10{sup −8} S/cm and is frequency dependent. Moreover, the elaborated composites are characterized by high dielectric constants in the range of 10{sup 5} for conductive composites at low frequencies (100 Hz). In addition, the distribution of the relaxation processes was also evaluated. The Debye, Cole-Cole, Davidson–Cole and Havriliak–Negami models in electric modulus formalism were used to model the observed relaxation phenomena in ZP/Ni composites. The observed relaxation phenomena are fairly simulated by Davidson–Cole model, and an account of the interpretation of results is given. - Highlights: • Composites of ZnO-P{sub 2}O{sub 5}/metal were investigated by impedance spectroscopy. • Original ac-conductivity behavior was discovered in ZnO-P{sub 2}O{sub 5}/metal composites. • High dielectric constant is measured in ZnO-P{sub 2}O{sub 5}/metal composites. • Dielectric constant as filler function is well interpreted with percolation theory. • Observed relaxation processes are well described using electric modulus formalism.

  9. Temperature-dependent Goos-Hänchen shift on the interface of metal/dielectric composites.

    Science.gov (United States)

    Zhao, Bin; Gao, Lei

    2009-11-23

    The temperature-dependent Goos-Hänchen shift (GHS) for an electromagnetic wave reflected from a metal/dielectric composite material is investigated. With the stationary-phase method, we theoretically show that the effect of the temperature on GHS is significant near the Brewster angle for the dielectric composites and at the grazing angle for the metallic composites. For dielectric composites, the lateral shift can be negative as well as positive. And GHS may become much negative, much positive, and nonmonotonic variation with increasing the temperature under different conditions. Moreover, through the suitable adjustment of the temperature, one may realize the reversal of the GHS. To support the above results, numerical simulations for Gaussian incident beams based on the momentum method and COMSOL Multiphysics software are provided, and reasonable agreement between the theoretical results and numerical simulations is found.

  10. Theory of the temperature dependent dielectric function of semiconductors: from bulk to surfaces. Application to GaAs and Si

    Energy Technology Data Exchange (ETDEWEB)

    Shkrebtii, Anatoli I.; Teatro, Timothy; Henderson, Laura [Faculty of Science, University of Ontario Institute of Technology, Simcoe Street North 2000, L1H 7K4 Oshawa (Canada); Ibrahim, Zahraa A. [Faculty of Science, University of Ontario Institute of Technology, Simcoe Street North 2000, L1H 7K4 Oshawa (Canada); Department of Physics, University of Toronto, M5S 1A7, Toronto (Canada); Richter, Wolfgang [Dipartimento di Fisica, Universita di Roma Tor Vergata, 00133 Rome (Italy); Institut fuer Festkoerperphysik, Technische Universitaet Berlin, 10623 Berlin (Germany); Lee, Martin J.G. [Department of Physics, University of Toronto, M5S 1A7, Toronto (Canada)

    2010-08-15

    A novel, efficient method for calculating the temperature dependencies of the linear dielectric functions of semiconductor systems and its application are presented. The method follows an intuitive and natural path with ab-initio finite temperature molecular dynamics providing the thermally perturbed atomic configurations, which are used as structural inputs for calculating the dielectric function. The effect of lattice dynamics, including quantum zero point vibration, on the electronic bands and dielectric function of crystalline (c-) GaAs and Si as well as hydrogenated amorphous Si (a-Si:H) is discussed. Our theoretical results for bulk c-GaAs and c-Si in the range from 0 to 1000 K are in good overall agreement with highly accurate ellipsometric measurements. The implementation of the method resolves a serious discrepancy in energy and line shape between experiment and the latest optical models, all of which neglect lattice dynamics, and provides information on the indirect gap and indirect optical transitions in c-Si. For a-Si:H, the calculated temperature dependent optical response combined with the vibrational spectroscopy provides detailed insight into electronic, dynamical properties, and stability of this important prototypical amorphous semiconductor material. At semiconductor surfaces, dynamical effects are expected to be even more pronounced due to reduced atom coordination and reconstruction. This is demonstrated for C(111) 2 x 1, an intensively studied but controversial surface of the quantum diamond crystal. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  11. Dependence of Pentacene Crystal Growth on Dielectric Roughness for Fabrication of Flexible Field-Effect Transistors

    Energy Technology Data Exchange (ETDEWEB)

    Yang, H.; Yang, C; Kim, S; Jang, M; Park, C

    2010-01-01

    The dependence of pentacene nanostructures on gate dielectric surfaces were investigated for flexible organic field-effect transistor (OFET) applications. Two bilayer types of polymer/aluminum oxide (Al{sub 2}O{sub 3}) gate dielectrics were fabricated on commercial Al foils laminated onto a polymer back plate. Some Al foils were directly used as gate electrodes, and others were smoothly polished by an electrolytic etching. These Al surfaces were then anodized and coated with poly({alpha}-methyl styrene) (PAMS). For PAMS/Al{sub 2}O{sub 3} dielectrics onto etched Al foils, surface roughness up to 1 nm could be reached, although isolated dimples with a lateral diameter of several micrometers were still present. On PAMS/Al{sub 2}O{sub 3} dielectrics (surface roughness >40 nm) containing mechanical grooves of Al foil, average hole mobility ({mu}FET) of 50 nm thick pentacene-FETs under the low operating voltages (|V| < 6 V) was {approx}0.15 cm{sup 2} V{sup -1} s{sup -1}. In contrast, pentacene-FETs employing the etched Al gates exhibited {mu}FET of 0.39 cm{sup 2} V{sup -1} s{sup -1}, which was comparable to that of reference samples with PAMS/Al{sub 2}O{sub 3} dielectrics onto flat sputtered Al gates. Conducting-probe atomic force microscopy and two-dimensional X-ray diffraction of pentacene films with various thicknesses revealed different out-of-plane and in-plane crystal orderings of pentacene, depending on the surface roughness of the gate dielectrics.

  12. Temperature dependence anomalous dielectric relaxation in Co doped ZnO nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Ansari, Sajid Ali; Nisar, Ambreen; Fatma, Bushara [Centre of Excellence in Materials Science (Nanomaterials), Department of Applied Physics, Z.H. College of Engg. and Tech., Aligarh Muslim University, Aligarh 202 002 (India); Khan, Wasi, E-mail: wasiamu@gmail.com [Centre of Excellence in Materials Science (Nanomaterials), Department of Applied Physics, Z.H. College of Engg. and Tech., Aligarh Muslim University, Aligarh 202 002 (India); Chaman, M. [Centre of Excellence in Materials Science (Nanomaterials), Department of Applied Physics, Z.H. College of Engg. and Tech., Aligarh Muslim University, Aligarh 202 002 (India); Mewat Engg. College (Wakf) Mewat, Haryana (India); Azam, Ameer [Centre of Excellence in Materials Science (Nanomaterials), Department of Applied Physics, Z.H. College of Engg. and Tech., Aligarh Muslim University, Aligarh 202 002 (India); Centre of Nanotechnology, King Abdulaziz University, Jeddah (Saudi Arabia); Naqvi, A.H. [Centre of Excellence in Materials Science (Nanomaterials), Department of Applied Physics, Z.H. College of Engg. and Tech., Aligarh Muslim University, Aligarh 202 002 (India)

    2012-12-15

    Graphical abstract: Display Omitted Highlights: ► We prepared Co doped ZnO by facile gel-combustion method. ► Studied temperature dependent dielectric properties in detail. ► Relaxation time shifts toward the higher temperature as increase in Co content. ► SEM analysis shows formation and agglomeration of nanoparticles. ► Dielectric constants, loss and ac conductivity increases with rise in temperature. ► The dielectric constant, loss and ac conductivity decreases as Co ion increases. -- Abstract: We have reported temperature and frequency dependence of dielectric behavior of nanocrystalline Zn{sub 1−x}Co{sub x}O (x = 0.0, 0.01, 0.05 and 0.1) samples prepared by gel-combustion method. The synthesized samples were examined by X-ray diffraction (XRD), scanning electron microscopy (SEM) and LCR-meter, respectively. The XRD analysis reveals that ZnO has a hexagonal (wurtzite) crystal structure. The morphology and size of the nanoparticles (∼10–25 nm) were observed by SEM for 5% Co doped ZnO sample. In dielectric properties, complex permittivity (ε{sup *} = ε′ − jε″), loss tangent (tan δ) and ac conductivity (σ{sub ac}) in the frequency range 75 kHz to 5 MHz were analyzed with temperature range 150–400 °C. The experimental results indicate that ε′, ε″, tan δ and σ{sub ac} decreases with increase in frequency and temperature. The transition temperature as obtained in dispersion curve of dielectric constant shifts toward higher temperature with increase Co content.

  13. Electronic Structure, Dielectric Response, and Surface Charge Distribution of RGD (1FUV) Peptide

    Science.gov (United States)

    Adhikari, Puja; Wen, Amy M.; French, Roger H.; Parsegian, V. Adrian; Steinmetz, Nicole F.; Podgornik, Rudolf; Ching, Wai-Yim

    2014-07-01

    Long and short range molecular interactions govern molecular recognition and self-assembly of biological macromolecules. Microscopic parameters in the theories of these molecular interactions are either phenomenological or need to be calculated within a microscopic theory. We report a unified methodology for the ab initio quantum mechanical (QM) calculation that yields all the microscopic parameters, namely the partial charges as well as the frequency-dependent dielectric response function, that can then be taken as input for macroscopic theories of electrostatic, polar, and van der Waals-London dispersion intermolecular forces. We apply this methodology to obtain the electronic structure of the cyclic tripeptide RGD-4C (1FUV). This ab initio unified methodology yields the relevant parameters entering the long range interactions of biological macromolecules, providing accurate data for the partial charge distribution and the frequency-dependent dielectric response function of this peptide. These microscopic parameters determine the range and strength of the intricate intermolecular interactions between potential docking sites of the RGD-4C ligand and its integrin receptor.

  14. The low-frequency dielectric response of charged oblate spheroidal particles immersed in an electrolyte

    CERN Document Server

    Hou, Chang-Yu; Sen, Pabitra N

    2016-01-01

    We study the low-frequency polarization response of a surface-charged oblate spheroidal particle immersed in an electrolyte solution. Because the charged spheroid attracts counter-ions which form the electric double layer around the particle, using usual boundary conditions at the interface between the particle and electrolyte can be quite complicated and challenging. Hence, we generalize Fixman's boundary conditions, originally derived for spherical particles, to the case of the charged oblate spheroid. Given two different counter-ion distributions in the thin electric double layer limit, we obtain analytic expressions for the polarization coefficients to the first non-trivial order in frequency. We find that the polarization response normal to the symmetry axis depends on the total amount of charge carried by the oblate spheroid while that parallel to the symmetry axis is suppressed when there is less charge on the edge of the spheroid. We further study the overall dielectric response for a dilute suspensio...

  15. Application of the compensated Arrhenius formalism to explain the dielectric constant dependence of rates for Menschutkin reactions.

    Science.gov (United States)

    Petrowsky, Matt; Glatzhofer, Daniel T; Frech, Roger

    2013-11-21

    The dependence of the reaction rate on solvent dielectric constant is examined for the reaction of trihexylamine with 1-bromohexane in a series of 2-ketones over the temperature range 25-80 °C. The rate constant data are analyzed using the compensated Arrhenius formalism (CAF), where the rate constant assumes an Arrhenius-like equation that also contains a dielectric constant dependence in the exponential prefactor. The CAF activation energies are substantially higher than those obtained using the simple Arrhenius equation. A master curve of the data is observed by plotting the prefactors against the solvent dielectric constant. The master curve shows that the reaction rate has a weak dependence on dielectric constant for values approximately less than 10 and increases more rapidly for dielectric constant values greater than 10.

  16. Tunable Radiation Response in Hybrid Organic-Inorganic Gate Dielectrics for Low-Voltage Graphene Electronics.

    Science.gov (United States)

    Arnold, Heather N; Cress, Cory D; McMorrow, Julian J; Schmucker, Scott W; Sangwan, Vinod K; Jaber-Ansari, Laila; Kumar, Rajan; Puntambekar, Kanan P; Luck, Kyle A; Marks, Tobin J; Hersam, Mark C

    2016-03-01

    Solution-processed semiconductor and dielectric materials are attractive for future lightweight, low-voltage, flexible electronics, but their response to ionizing radiation environments is not well understood. Here, we investigate the radiation response of graphene field-effect transistors employing multilayer, solution-processed zirconia self-assembled nanodielectrics (Zr-SANDs) with ZrOx as a control. Total ionizing dose (TID) testing is carried out in situ using a vacuum ultraviolet source to a total radiant exposure (RE) of 23.1 μJ/cm(2). The data reveal competing charge density accumulation within and between the individual dielectric layers. Additional measurements of a modified Zr-SAND show that varying individual layer thicknesses within the gate dielectric tuned the TID response. This study thus establishes that the radiation response of graphene electronics can be tailored to achieve a desired radiation sensitivity by incorporating hybrid organic-inorganic gate dielectrics.

  17. Universal One-Parametric Dependence of Dielectric Water and Water Steam Permeability on Density-Temperature Ratio

    OpenAIRE

    Yu. V. Mulev; K. M. Arefiev; O. V. Beliayeva; M. Yu. Mulev; T. A/ Zaiats

    2011-01-01

    Available experimental data on dielectric permeability of water and water steam have been analyzed in the paper. The paper presents an universal one-parametric dependence of dielectric water and water steam permeability in single-phase areas and also on boundary curves on density -temperature ratio.

  18. Universal One-Parametric Dependence of Dielectric Water and Water Steam Permeability on Density-Temperature Ratio

    Directory of Open Access Journals (Sweden)

    Yu. V. Mulev

    2011-01-01

    Full Text Available Available experimental data on dielectric permeability of water and water steam have been analyzed in the paper. The paper presents an universal one-parametric dependence of dielectric water and water steam permeability in single-phase areas and also on boundary curves on density -temperature ratio.

  19. Classical density-functional theory of inhomogeneous water including explicit molecular structure and nonlinear dielectric response.

    Science.gov (United States)

    Lischner, Johannes; Arias, T A

    2010-02-11

    We present an accurate free-energy functional for liquid water written in terms of a set of effective potential fields in which fictitious noninteracting water molecules move. The functional contains an exact expression of the entropy of noninteracting molecules and thus provides an ideal starting point for the inclusion of complex intermolecular interactions which depend on the orientation of the interacting molecules. We show how an excess free-energy functional can be constructed to reproduce the following properties of water: the dielectric response; the experimental site-site correlation functions; the surface tension; the bulk modulus of the liquid and the variation of this modulus with pressure; the density of the liquid and the vapor phase; and liquid-vapor coexistence. As a demonstration, we present results for the application of this theory to the behavior of liquid water in a parallel plate capacitor. In particular, we make predictions for the dielectric response of water in the nonlinear regime, finding excellent agreement with known data.

  20. Time Dependent Dielectric Breakdown in Copper Low-k Interconnects: Mechanisms and Reliability Models

    Directory of Open Access Journals (Sweden)

    Terence K.S. Wong

    2012-09-01

    Full Text Available The time dependent dielectric breakdown phenomenon in copper low-k damascene interconnects for ultra large-scale integration is reviewed. The loss of insulation between neighboring interconnects represents an emerging back end-of-the-line reliability issue that is not fully understood. After describing the main dielectric leakage mechanisms in low-k materials (Poole-Frenkel and Schottky emission, the major dielectric reliability models that had appeared in the literature are discussed, namely: the Lloyd model, 1/E model, thermochemical E model, E1/2 models, E2 model and the Haase model. These models can be broadly categorized into those that consider only intrinsic breakdown (Lloyd, 1/E, E and Haase and those that take into account copper migration in low-k materials (E1/2, E2. For each model, the physical assumptions and the proposed breakdown mechanism will be discussed, together with the quantitative relationship predicting the time to breakdown and supporting experimental data. Experimental attempts on validation of dielectric reliability models using data obtained from low field stressing are briefly discussed. The phenomenon of soft breakdown, which often precedes hard breakdown in porous ultra low-k materials, is highlighted for future research.

  1. Size-dependent theories of piezoelectricity: Comparisons and further developments for centrosymmetric dielectrics

    CERN Document Server

    Hadjesfandiari, Ali R

    2014-01-01

    Here the recently developed size-dependent piezoelectricity and the strain gradient theory of flexoelectricity are compared. In the course of this investigation, the strain gradient theory of flexoelectricity is shown to violate fundamental rules of mathematics, continuum mechanics and electromagnetism. The major difficulties are associated with ill-posed boundary conditions, the missing angular (moment) equilibrium equation and the appearance of a non-physical extraneous vectorial electrostatic law. Therefore, the strain gradient flexoelectricity must be classified as an inconsistent theory. The present investigation further reveals that the new size-dependent piezoelectricity is the more consistent theory to describe linear electromechanical coupling in dielectrics. Some new aspects of this theory are presented for isotropic and centrosymmetric cubic dielectric materials, whose coupling effect is described by only one parameter.

  2. Electron radiation effects on time-dependent dielectric breakdown in SiO2 films

    Science.gov (United States)

    Li, S. P.; Maserjian, J.

    1975-01-01

    An experiment testing the effect of ionizing radiation on breakdown characteristics of SiO2 films is presented. Silicon wafers were oxidized and metallized, and a capacitor array was etched into a control sample while the rest were first irradiated with 1 MeV electrons and then etched. Time-dependent dielectric tests were made on all the capacitors, and the average characteristics of 96 capacitors are illustrated graphically. The curves are consistent with the model of holes trapped in the SiO2 film during irradiation leading to a retarding field for positive ion emission and drift toward the interface. It is shown how an externally applied field is reduced by the trapped charge, and that changes in the dielectric breakdown properties of the SiO2 film after irradiation depend on the positive trapped charge near the metal interface.

  3. Oxygen flux and dielectric response study of Mixed Ionic-Electronic Conducting (MIEC) heterogeneous functional materials

    Science.gov (United States)

    Rabbi, Fazle

    Dense mixed ionic-electronic conducting (MIEC) membranes consisting of ionic conductive perovskite-type and/or fluorite-type oxides and high electronic conductive spinel type oxides, at elevated temperature can play a useful role in a number of energy conversion related systems including the solid oxide fuel cell (SOFC), oxygen separation and permeation membranes, partial oxidization membrane reactors for natural gas processing, high temperature electrolysis cells, and others. This study will investigate the impact of different heterogeneous characteristics of dual phase ionic and electronic conductive oxygen separation membranes on their transport mechanisms, in an attempt to develop a foundation for the rational design of such membranes. The dielectric behavior of a material can be an indicator for MIEC performance and can be incorporated into computational models of MIEC membranes in order to optimize the composition, microstructure, and ultimately predict long term membrane performance. The dielectric behavior of the MIECs can also be an indicator of the transport mechanisms and the parameters they are dependent upon. For this study we chose a dual phase MIEC oxygen separation membrane consisting of an ionic conducting phase: gadolinium doped ceria-Ce0.8 Gd0.2O2 (GDC) and an electronic conductive phase: cobalt ferrite-CoFe2O4 (CFO). The membranes were fabricated from mixtures of Nano-powder of each of the phases for different volume percentages, sintered with various temperatures and sintering time to form systematic micro-structural variations, and characterized by structural analysis (XRD), and micro-structural analysis (SEM-EDS). Performance of the membranes was tested for variable partial pressures of oxygen across the membrane at temperatures from 850°C-1060°C using a Gas Chromatography (GC) system. Permeated oxygen did not directly correlate with change in percent mixture. An intermediate mixture 60%GDC-40%CFO had the highest flux compared to the 50%GDC

  4. Interpreting the nonlinear dielectric response of glass-formers in terms of the coupling model

    Energy Technology Data Exchange (ETDEWEB)

    Ngai, K. L. [CNR-IPCF, Largo Bruno Pontecorvo 3, I-56127 Pisa, Italy and Dipartimento di Fisica, Università di Pisa, Largo B. Pontecorvo 3, I-56127 Pisa (Italy)

    2015-03-21

    Nonlinear dielectric measurements at high electric fields of glass-forming glycerol and propylene carbonate initially were carried out to elucidate the dynamic heterogeneous nature of the structural α-relaxation. Recently, the measurements were extended to sufficiently high frequencies to investigate the nonlinear dielectric response of faster processes including the so-called excess wing (EW), appearing as a second power law at high frequencies in the loss spectra of many glass formers without a resolved secondary relaxation. While a strong increase of dielectric constant and loss is found in the nonlinear dielectric response of the α-relaxation, there is a lack of significant change in the EW. A surprise to the experimentalists finding it, this difference in the nonlinear dielectric properties between the EW and the α-relaxation is explained in the framework of the coupling model by identifying the EW investigated with the nearly constant loss (NCL) of caged molecules, originating from the anharmonicity of the intermolecular potential. The NCL is terminated at longer times (lower frequencies) by the onset of the primitive relaxation, which is followed sequentially by relaxation processes involving increasing number of molecules until the terminal Kohlrausch α-relaxation is reached. These intermediate faster relaxations, combined to form the so-called Johari-Goldstein (JG) β-relaxation, are spatially and dynamically heterogeneous, and hence exhibit nonlinear dielectric effects, as found in glycerol and propylene carbonate, where the JG β-relaxation is not resolved and in D-sorbitol where it is resolved. Like the linear susceptibility, χ{sub 1}(f), the frequency dispersion of the third-order dielectric susceptibility, χ{sub 3}(f), was found to depend primarily on the α-relaxation time, and independent of temperature T and pressure P. I show this property of the frequency dispersions of χ{sub 1}(f) and χ{sub 3}(f) is the characteristic of the many

  5. Abnormal Dielectric Response in an Optical Range Based on Electronic Transition in Rare-Earth-Ion-Doped Crystals

    Institute of Scientific and Technical Information of China (English)

    FU Xiao-Jian; XU Yuan-Da; ZHOU Ji

    2012-01-01

    A new scheme to realize an abnormal dielectric response at optical wavelength is developed on the basis of twolevel electronic transition of rare-earth ion doped crystals.Based on the semi-classical theory and the Judd-Ofelt theory,the electric dipole transition under a weak field is analyzed,and a general expression for the frequencydependent dielectric constant is obtained.As an example,the permittivity of (Erx Y1-x)3Al5O12 is calculated numerically in consideration of the transition between 4I15/2and 4F9/2.An optimized dielectric property with a negative real part and low absorption is achieved.This proposes a new mechanism for building extraordinary electromagnetic media at optical frequencies by using a quantum process.%A new scheme to realize an abnormal dielectric response at optical wavelength is developed on the basis of two-level electronic transition of rare-earth ion doped crystals. Based on the semi-classical theory and the Judd-Ofelt theory, the electric dipole transition under a weak Reid is analyzed, and a general expression for the frequency-dependent dielectric constant is obtained. As an example, the permittivity of (ErxY1-x)3A15O12 is calculated numerically in consideration of the transition between 4I15/2 and 4F9/2. An optimized dielectric property with a negative real part and low absorption is achieved. This proposes a new mechanism for building extraordinary electromagnetic media at optical frequencies by using a quantum process.

  6. Broadband dielectric response of AlN ceramic composites

    Directory of Open Access Journals (Sweden)

    Iryna V. Brodnikovska

    2014-03-01

    Full Text Available Aluminium nitride (AlN is considered as a substrate material for microelectronic applications. AlN ceramic composites with different amount of TiO2 (up to 4 vol.% were obtained using hot pressing at different sintering temperature from 1700 to 1900 °C. It was shown that milling of the raw AlN powder has strongly influence on sintering and improves densification. Broadband dielectric spectroscopy was used as a nondestructive method for monitoring of the ceramic microstructures. TiO2 additive affects the key properties of AlN ceramics. Thus, porosity of 0.1 %, dielectric permeability of σ = 9.7 and dielectric loss tangent of tanδ = 1.3·10-3 can be achieved if up to 2 vol.% TiO2 is added.

  7. Voltage-induced pinnacle response in the dynamics of dielectric elastomers

    Science.gov (United States)

    Li, Bo; Zhang, Junshi; Chen, Hualing; Li, Dichen

    2016-05-01

    A dielectric elastomer is capable of large deformation under alternating electromechanical excitation. In this paper, several dynamic properties of a dielectric elastomer are investigated, in particular the effect of strain stiffening. A theoretical model is established that shows that the bias voltage affects the amplitude and the response waveform during vibration, a curve with the shape of a pinnacle. We also describe the underlying physical mechanism by considering the molecular chain length and cross-linking density of the material. A phase portrait is presented that reveals the transitional behavior of the dielectric elastomer as it switches between soft and stiffened vibration states.

  8. Simple Shear Response of a Hyperelastic Dielectric Media Revisited

    Science.gov (United States)

    2014-09-01

    Am. 1989;85(2):599–610. 3. Clayton JD. A non -linear model for elastic dielectric crystals with mobile vacancies. International Journal of Non -Linear...formulation of Maxwellian electrodynamics for continuum mechanics. Continuum Mechanics and Thermodynamics. 2014;26(3):387-401. 13 14. Toupin RA. The elastic

  9. Ac-conductivity and dielectric response of new zinc-phosphate glass/metal composites

    Science.gov (United States)

    Maaroufi, A.; Oabi, O.; Lucas, B.

    2016-07-01

    The ac-conductivity and dielectric response of new composites based on zinc-phosphate glass with composition 45 mol%ZnO-55 mol%P2O5, filled with metallic powder of nickel (ZP/Ni) were investigated by impedance spectroscopy in the frequency range from 100 Hz to 1 MHz at room temperature. A high percolating jump of seven times has been observed in the conductivity behavior from low volume fraction of filler to the higher fractions, indicating an insulator - semiconductor phase transition. The measured conductivity at higher filler volume fraction is about 10-1 S/cm and is frequency independent, while, the obtained conductivity for low filler volume fraction is around 10-8 S/cm and is frequency dependent. Moreover, the elaborated composites are characterized by high dielectric constants in the range of 105 for conductive composites at low frequencies (100 Hz). In addition, the distribution of the relaxation processes was also evaluated. The Debye, Cole-Cole, Davidson-Cole and Havriliak-Negami models in electric modulus formalism were used to model the observed relaxation phenomena in ZP/Ni composites. The observed relaxation phenomena are fairly simulated by Davidson-Cole model, and an account of the interpretation of results is given.

  10. Dielectric response of PLZT ceramics /57/43 across ferroelectric– paraelectric phase transition

    Indian Academy of Sciences (India)

    A K Shukla; V K Agrawal; I M L Das; Janardan Singh; S L Srivastava

    2011-02-01

    The dielectric properties of lead lanthanum zirconate titanate (PLZT) ceramics [Pb(Zr0.57Ti0.43)O3 + at% of La, = 3, 5, 6, 10 and 12] have been measured in the frequency range 1 Hz–1 MHz using the vector impedance spectroscopy (VIS) at different temperatures. All the compositions show both non-dispersive and dispersive dielectric responses in different temperature regions. The non-dispersive region obeys the universal dielectric response. A low frequency (< 1 kHz) relaxation phenomenon with a high value of distribution parameter `ℎ’ (∼0.4 to 0.6) has been observed in all the compositions around the temperature corresponding to themaximum dielectric constant (m). The activation energies as calculated from the relaxation and d.c. conduction processes are comparable. The ferroelectric phase transition is diffuse in nature and broadening of the peak increases with La content.

  11. Temperature dependent dielectric properties and ion transportation in solid polymer electrolyte for lithium ion batteries

    Science.gov (United States)

    Sengwa, R. J.; Dhatarwal, Priyanka; Choudhary, Shobhna

    2016-05-01

    Solid polymer electrolyte (SPE) film consisted of poly(ethylene oxide) (PEO) and poly(methyl methacrylate) (PMMA) blend matrix with lithium tetrafluroborate (LiBF4) as dopant ionic salt and poly(ethylene glycol) (PEG) as plasticizer has been prepared by solution casting method followed by melt pressing. Dielectric properties and ionic conductivity of the SPE film at different temperatures have been determined by dielectric relaxation spectroscopy. It has been observed that the dc ionic conductivity of the SPE film increases with increase of temperature and also the decrease of relaxation time. The temperature dependent relaxation time and ionic conductivity values of the electrolyte are governed by the Arrhenius relation. Correlation observed between dc conductivity and relaxation time confirms that ion transportation occurs with polymer chain segmental dynamics through hopping mechanism. The room temperature ionic conductivity is found to be 4 × 10-6 S cm-1 which suggests the suitability of the SPE film for rechargeable lithium batteries.

  12. Moisture effect on the dielectric response and space charge behaviour of mineral oil impregnated paper insulation

    OpenAIRE

    Hao, Jian; Chen, George; Liao, R

    2011-01-01

    Oil-paper insulation system is widely used in power transformers and cables. Moisture is recognized to the ?enemy number one? for transformer insulation except for temperature [1]. Moisture is not only one of the most important factor which can accelerate the transformer paper insulation aging, but also has great effect on the dielectric properties of oil-paper insulation. In this paper, dielectric response and space charge behaviour of oil-paper insulation sample with three different moistur...

  13. Magnetic Response of Metal-Dielectric Composite at Short Wavelength

    CERN Document Server

    Tang, Jianwei

    2010-01-01

    We propose a new type of split-ring resonator, of which the ring is made of high index dielectric material (e.g. SiC), while metal fills the gap. Such a new magnetic metamaterial is able to operate at short wavelength including the green, blue, violet range and part of ultraviolet range. For ease of fabrication, we also proposed a new type of cut-wire pair structure based on our new type of split-ring resonator.

  14. Thickness dependent electronic structure and morphology of rubrene thin films on metal, semiconductor, and dielectric substrates

    Science.gov (United States)

    Sinha, Sumona; Mukherjee, M.

    2013-08-01

    The evolution of the electronic structure and morphology of rubrene thin films on noble-metal, semiconductor and dielectric substrates have been investigated as a function of thickness of deposited films by using photoelectron spectroscopy and atomic force microscopy. The clean polycrystalline Au and Ag were used as noble-metals, whereas, H passivated and SiO2 coated Si (100) were used as semiconductors and dielectric substrates. Discussion and comparison on interface dipole, energy level alignment, and surface morphology for the four cases are presented. The formation of dipole at metallic interfaces is found to occur due to push back effect. S parameter obtained from the variation of barrier height with the change of work function of the contacting metal indicates moderately weak interaction between rubrene and the metal substrates. The thickness dependent energy level alignment of the physisorbed rubrene films on different substrates is explained by a dielectric model in terms of electrostatic screening of photo-holes or photoemission final state relaxation energy. Films on all the substrates are found to grow following Stranski-Krastnov type growth mode and are more ordered at higher coverage.

  15. The impact of nonlocal response on metallo-dielectric multilayers and optical patch antennas

    CERN Document Server

    Moreau, Antoine; Smith, David R

    2012-01-01

    We analyze the impact of nonlocality on the waveguide modes of metallo-dielectric multilayers and optical patch antennas, the latter formed from metal strips closely spaced above a metallic plane. We model both the nonlocal effects associated with the conduction electrons of the metal, as well as the previously overlooked response of bound electrons. We show that the fundamental mode of a metal-dielectric-metal waveguide, sometimes called the gap-plasmon, is very sensitive to nonlocality when the insulating, dielectric layers are thinner than 5 nm. We suggest that optical patch antennas, which can easily be fabricated with controlled dielectric spacer layers and can be interrogated using far-field scattering, can enable the measurement of nonlocality in metals with good accuracy.

  16. Polarization Dependence of Surface Enhanced Raman Scattering on a Single Dielectric Nanowire

    Directory of Open Access Journals (Sweden)

    Hua Qi

    2012-01-01

    Full Text Available Our measurements of surface enhanced Raman scattering (SERS on Ga2O3 dielectric nanowires (NWs core/silver composites indicate that the SERS enhancement is highly dependent on the polarization direction of the incident laser light. The polarization dependence of the SERS signal with respect to the direction of a single NW was studied by changing the incident light angle. Further investigations demonstrate that the SERS intensity is not only dependent on the direction and wavelength of the incident light, but also on the species of the SERS active molecule. The largest signals were observed on an NW when the incident 514.5 nm light was polarized perpendicular to the length of the NW, while the opposite phenomenon was observed at the wavelength of 785 nm. Our theoretical simulations of the polarization dependence at 514.5 nm and 785 nm are in good agreement with the experimental results.

  17. Effects of sintering on microstructure and dielectric response in YCrO3 nanoceramic

    Indian Academy of Sciences (India)

    J Bahadur; D Sen; S Mazumder; V K Aswal; V Bedekar; R Shukla; A K Tyagi

    2008-11-01

    Effects of sintering on pore morphology and dielectric response have been investigated. Pore structure has been probed by small angle neutron scattering (SANS). It has been observed that the size distribution becomes less polydisperse with a slight modification in the distribution as sintering temperature is increased. Dielectric response in the frequency range 0.02–1000 kHz is significantly altered by modification of pore structure because of sintering. A transition from non-Debye type to near-Debye type response has been observed as the sintering temperature is increased.

  18. The dielectric environment dependent exchange self-energy of the energy structure in graphene

    Energy Technology Data Exchange (ETDEWEB)

    Yang, C.H., E-mail: chyang@nuist.edu.c [Faculty of Maths and Physics, Nanjing University of Information Science and Technology, Nanjing 210044 (China); Xu, W. [Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China)

    2010-10-01

    We theoretically calculate the energy dispersion in the presence of the screened exchange self-energy in extrinsic monolayer graphene. It is found that the exchange self-energy enhances the renormalized Fermi velocity. With decreasing the dielectric constant, the screening effect and the electron correlation effect increase which induces the Fermi velocity increasing. The screened exchange energy has an energy shift at the Dirac points. The self-energy from the valance band carriers gives the main contribution to the effective energy. We also discuss the electron density dependence of the self-energy.

  19. Dielectric response and novel electromagnetic modes in three-dimensional Dirac semimetal films

    Science.gov (United States)

    Kotov, O. V.; Lozovik, Yu. E.

    2016-06-01

    Using the Kubo formalism we have calculated the local dynamic conductivity of a bulk, i.e., three-dimensional (3D), Dirac semimetal (BDS). We obtain that at frequencies lower than Fermi energy the metallic response in a BDS film manifests in the existence of surface-plasmon polaritons, but at higher frequencies the dielectric response is dominated and it occurs that a BDS film behaves as a dielectric waveguide. At this dielectric regime we predict the existence inside a BDS film of novel electromagnetic modes, a 3D analog of the transverse electric waves in graphene. We also find that the dielectric response manifests as the wide-angle passband in the mid-infrared (IR) transmission spectrum of light incident on a BDS film, which can be used for the interferenceless omnidirectional mid-IR filtering. The tuning of the Fermi level of the system allows us to switch between the metallic and the dielectric regimes and to change the frequency range of the predicted modes. This makes BDSs promising materials for photonics and plasmonics.

  20. Molecular motion, dielectric response, and phase transition of charge-transfer crystals: acquired dynamic and dielectric properties of polar molecules in crystals.

    Science.gov (United States)

    Harada, Jun; Ohtani, Masaki; Takahashi, Yukihiro; Inabe, Tamotsu

    2015-04-08

    Molecules in crystals often suffer from severe limitations on their dynamic processes, especially on those involving large structural changes. Crystalline compounds, therefore, usually fail to realize their potential as dielectric materials even when they have large dipole moments. To enable polar molecules to undergo dynamic processes and to provide their crystals with dielectric properties, weakly bound charge-transfer (CT) complex crystals have been exploited as a molecular architecture where the constituent polar molecules have some freedom of dynamic processes, which contribute to the dielectric properties of the crystals. Several CT crystals of polar tetrabromophthalic anhydride (TBPA) molecules were prepared using TBPA as an electron acceptor and aromatic hydrocarbons, such as coronene and perylene, as electron donors. The crystal structures and dielectric properties of the CT crystals as well as the single-component crystal of TBPA were investigated at various temperatures. Molecular reorientation of TBPA molecules did not occur in the single-component crystal, and the crystal did not show a dielectric response due to orientational polarization. We have found that the CT crystal formation provides a simple and versatile method to develop molecular dielectrics, revealing that the molecular dynamics of the TBPA molecules and the dielectric property of their crystals were greatly changed in CT crystals. The TBPA molecules underwent rapid in-plane reorientations in their CT crystals, which exhibited marked dielectric responses arising from the molecular motion. An order-disorder phase transition was observed for one of the CT crystals, which resulted in an abrupt change in the dielectric constant at the transition temperature.

  1. Interplay of magnetic responses in all-dielectric oligomers to realize magnetic Fano resonances

    CERN Document Server

    Hopkins, Ben; Miroshnichenko, Andrey E; Monticone, Francesco; Alù, Andrea; Kivshar, Yuri S

    2016-01-01

    We study the interplay between collective and individual optically-induced magnetic responses in quadrumers made of identical dielectric nanoparticles. Unlike their plasmonic counterparts, all-dielectric nanoparticle clusters are shown to exhibit multiple dimensions of resonant magnetic responses that can be employed for the realization of anomalous scattering signatures. We focus our analysis on symmetric quadrumers made from silicon nanoparticles and verify our theoretical results in proof-of-concept radio frequency experiments demonstrating the existence of a novel type of magnetic Fano resonance in nanophotonics.

  2. Time-dependent current-density-functional theory for the metallic response of solids

    NARCIS (Netherlands)

    Romaniello, P; de Boeij, PL

    2005-01-01

    We extend the formulation of time-dependent current-density-functional theory for the linear response properties of dielectric and semi-metallic solids [Kootstra , J. Chem. Phys. 112, 6517 (2000)] to treat metals as well. To achieve this, the Kohn-Sham response functions have to include both interba

  3. Time-dependent current-density-functional theory for the metallic response of solids

    NARCIS (Netherlands)

    Romaniello, P; de Boeij, PL

    We extend the formulation of time-dependent current-density-functional theory for the linear response properties of dielectric and semi-metallic solids [Kootstra , J. Chem. Phys. 112, 6517 (2000)] to treat metals as well. To achieve this, the Kohn-Sham response functions have to include both

  4. Thickness-dependent piezoelectric behaviour and dielectric properties of lanthanum modified BiFeO3 thin films

    Directory of Open Access Journals (Sweden)

    Glenda Biasotto

    2011-03-01

    Full Text Available Bi0.85La0.15FeO3 (BLFO thin films were deposited on Pt(111/Ti/SiO2 /Si substrates by the soft chemical method. Films with thicknesses ranging from 140 to 280 nm were grown on platinum coated silicon substrates at 500°C for 2 hours. The X-ray diffraction analysis of BLFO films evidenced a hexagonal structure over the entire thickness range investigated. The grain size of the film changes as the number of the layers increases, indicating thickness dependence. It is found that the piezoelectric response is strongly influenced by the film thickness. It is shown that the properties of BiFeO3 thin films, such as lattice parameter, dielectric permittivity, piezoeletric coefficient etc., are functions of misfit strains.

  5. Frequency-dependent response of a pinned charge-density wave

    Science.gov (United States)

    Vinokur, Valerii; Fogler, Michael

    2003-03-01

    Recent theoretical advances in the theory of collective pinning [M. M. Fogler, Phys. Rev. Lett. 88, 186402 (2002)] enable us to go beyond the usual phenomenology in the theory of a finite-frequency response of a pinned charge-density wave (CDW) and to calculate ω and T dependences of the complex dielectric function without additional assumptions. According to our estimates, in typical electrical experiments on CDW, the dominant process is a thermal activation over atypically shallow barriers. It gives rise to a novel T^3/4-dependence of the linear response, in agreement with the experiment. A close analogy with acoustic attenuation in glassy dielectrics is noted.

  6. Direct measurement of the effective infrared dielectric response of a highly doped semiconductor metamaterial

    Science.gov (United States)

    Mohtar, Abeer Al; Kazan, Michel; Taliercio, Thierry; Cerutti, Laurent; Blaize, Sylvain; Bruyant, Aurélien

    2017-03-01

    We have investigated the effective dielectric response of a subwavelength grating made of highly doped semiconductors (HDS) excited in reflection, using numerical simulations and spectroscopic measurement. The studied system can exhibit strong localized surface resonances and has, therefore, a great potential for surface-enhanced infrared absorption (SEIRA) spectroscopy application. It consists of a highly doped InAsSb grating deposited on lattice-matched GaSb. The numerical analysis demonstrated that the resonance frequencies can be inferred from the dielectric function of an equivalent homogeneous slab by accounting for the complex reflectivity of the composite layer. Fourier transform infrared reflectivity (FTIR) measurements, analyzed with the Kramers–Kronig conversion technique, were used to deduce the effective response in reflection of the investigated system. From the knowledge of this phenomenological dielectric function, transversal and longitudinal energy-loss functions were extracted and attributed to transverse and longitudinal resonance modes frequencies.

  7. Sensing Based on Fano-Type Resonance Response of All-Dielectric Metamaterials

    Directory of Open Access Journals (Sweden)

    Elena Semouchkina

    2015-04-01

    Full Text Available A new sensing approach utilizing Mie resonances in metamaterial arrays composed of dielectric resonators is proposed. These arrays were found to exhibit specific, extremely high-Q factor (up to 15,000 resonances at frequencies corresponding to the lower edge of the array second transmission band. The observed resonances possessed with features typical for Fano resonances (FRs, which were initially revealed in atomic processes and recently detected in macro-structures, where they resulted from interference between local resonances and a continuum of background waves. Our studies demonstrate that frequencies and strength of Fano-type resonances in all-dielectric arrays are defined by interaction between local Mie resonances and Fabry-Perot oscillations of Bloch eigenmodes that makes possible controlling the resonance responses by changing array arrangements. The opportunity for obtaining high-Q responses in compact arrays is investigated and promising designs for sensing the dielectric properties of analytes in the ambient are proposed.

  8. Time-dependent dielectric breakdown of MgO magnetic tunnel junctions and novel test method

    Science.gov (United States)

    Kim, Kyungjun; Choi, Chulmin; Oh, Youngtaek; Sukegawa, Hiroaki; Mitani, Seiji; Song, Yunheub

    2017-04-01

    Time-dependent dielectric breakdown (TDDB), which is used to measure reliability, depends on both the thickness of the tunnel barrier and bias voltage. In addition, the heat generated by self-heating in a magnetic tunneling junction (MTJ) affects TDDB. Therefore, we investigated TDDB with the self-heating effect for a MgO tunnel barrier with thicknesses of 1.1 and 1.2 nm by the constant voltage stress (CVS) method. Using the results of this experiment, we predicted a TDDB of 1.0 nm for the tunnel barrier. Also, we suggested the use of not only the CVS method, which is a common way of determining TDDB, but also the constant current stress (CCS) method, which compensates for the disadvantages of the CVS method.

  9. Size-dependent anomalous dielectric behavior in La2O3: SiO2 nano-glass composite system

    Science.gov (United States)

    Kao, T. H.; Mukherjee, S.; Lin, Y. H.; Chou, C. C.; Yang, H. D.

    2012-12-01

    An intriguing anomalous dielectric behavior is observed in nanoparticle (NP) La2O3: SiO2 nano-glass composite system synthesized via sol-gel route at different calcination temperatures. Temperature dependent dielectric properties exhibit a notable dielectric broadening, indicating of diffuse phase transition with high ɛ', quite different from and much higher than pure bulk La2O3 and SiO2. We postulate such dielectric effect in the context of the oxygen vacancies of the rare earth oxide nano-glass composite, where lattice strain related with NPs and their size plays a vital role. Such a material might be treated as a potential candidate to solve the problem of devices miniaturization.

  10. Electrical dependence on the chemical composition of the gate dielectric in indium gallium zinc oxide thin-film transistors

    Science.gov (United States)

    Tari, Alireza; Lee, Czang-Ho; Wong, William S.

    2015-07-01

    Bottom-gate thin-film transistors were fabricated by depositing a 50 nm InGaZnO (IGZO) channel layer at 150 °C on three separate gate dielectric films: (1) thermal SiO2, (2) plasma-enhanced chemical-vapor deposition (PECVD) SiNx, and (3) a PECVD SiOx/SiNx dual-dielectric. X-ray photoelectron and photoluminescence spectroscopy showed the Vo concentration was dependent on the hydrogen concentration of the underlying dielectric film. IGZO films on SiNx (high Vo) and SiO2 (low Vo) had the highest and lowest conductivity, respectively. A PECVD SiOx/SiNx dual-dielectric layer was effective in suppressing hydrogen diffusion from the nitride layer into the IGZO and resulted in higher resistivity films.

  11. Temperature- and Time-Dependent Dielectric Measurements and Modelling on Curing of Polymer Composites

    OpenAIRE

    Prastiyanto, Dhidik

    2016-01-01

    In this work a test set for dielectric measurements at 2.45 GHz during curing of polymer composites is developed. Fast reconstruction of dielectric properties is solved using a neural network algorithm. Modelling of the curing process at 2.45 GHz using both dielectric constant and dielectric loss factor results in a more accurate model compared to low frequency modeling that only uses the loss factor. Effects of various harderners and different amount of filler are investigated.

  12. Green's function surface-integral method for nonlocal response of plasmonic nanowires in arbitrary dielectric environments

    DEFF Research Database (Denmark)

    Yan, Wei; Mortensen, N. Asger; Wubs, Martijn

    2013-01-01

    We develop a nonlocal-response generalization to the Green's function surface-integral method (GSIM), also known as the boundary-element method. This numerically efficient method can accurately describe the linear hydrodynamic nonlocal response of arbitrarily shaped plasmonic nanowires in arbitrary...... dielectric backgrounds. All previous general-purpose methods for nonlocal response are bulk methods. We also expand the possible geometries to which the usual local-response GSIM can be applied, by showing how to regularize singularities that occur in the surface integrals when the nanoparticles touch...... close to and on top of planar dielectric substrates. Especially for the latter geometry, considerable differences in extinction cross sections are found for local as compared to nonlocal response, similar to what is found for plasmonic dimer structures....

  13. Giant piezoelectric response in piezoelectric/dielectric superlattices due to flexoelectric effect

    Science.gov (United States)

    Liu, Chang; Wu, Huaping; Wang, Jie

    2016-11-01

    Flexoelectricity describes the linear response of electrical polarization to a strain gradient, which can be used to enhance the piezoelectric effect of piezoelectric material or realize the piezoelectric effect in nonpiezoelectric materials. Here, we demonstrate from thermodynamics theory that a giant piezoelectric effect exists in piezoelectric/dielectric superlattices due to flexoelectric effect. The apparent piezoelectric coefficient is calculated from the closed-form of analytical expression of the polarization distribution in the piezoelectric/dielectric superlattice subjected to a normal stress, in which the flexoelectric effect is included. It is found that there exists a strong nonlinear coupling between the flexoelectric and piezoelectric effects, which significantly enhances the apparent piezoelectric coefficient in the piezoelectric/dielectric superlattice. For a specific thickness ratio of the piezoelectric and dielectric layers, the enhanced apparent piezoelectric coefficient in the superlattice is ten times larger than that of its pure piezoelectric counterpart. The present work suggests an effective way to obtain giant apparent piezoelectric effect in piezoelectric/dielectric superlattices through flexoelectric effect.

  14. Characterization of Dielectric Responses of Human Cancer Cells in the Terahertz Region

    Science.gov (United States)

    Shiraga, Keiichiro; Ogawa, Yuichi; Suzuki, Tetsuhito; Kondo, Naoshi; Irisawa, Akiyoshi; Imamura, Motoki

    2014-05-01

    Terahertz time-domain attenuated total reflection spectroscopy, in combination with a two-interface model, is used to determine the complex dielectric constants of cultured human cancer cells (DLD-1, HEK293 and HeLa). Picosecond and sub-picosecond water dynamics are dominant in the measured complex dielectric constants of these cells. We demonstrate that dielectric responses below 1.0 THz best characterize the particular water dynamics of cancer cells when compared with extracellular water. Debye-Lorentz fitting revealed that this is due to a significantly attenuated slow relaxation mode and enhanced fast relaxation mode of the water in these cancer cells. These findings could lead to a new procedure to digitally evaluate cellular activities or functions, in terms of intracellular water dynamics, and remove the veil from the mysterious intracellular milieu.

  15. Concentration dependence of molal conductivity and dielectric constant of 1-alcohol electrolytes using the compensated arrhenius formalism.

    Science.gov (United States)

    Fleshman, Allison M; Petrowsky, Matt; Frech, Roger

    2013-05-02

    The molal conductivity of liquid electrolytes with low static dielectric constants (ε(s) Arrhenius formalism (CAF) to the molal conductivity, Λ, of a family of 1-alcohol electrolytes over a broad concentration range. A scaling procedure is applied that results in an energy of activation (E(a)) and an exponential prefactor (Λ0) that are both concentration dependent. It is shown that the increasing molal conductivity in region II results from the combined effect of (1) a decrease in the energy of activation calculated from the CAF, and (2) an inherent concentration dependence in the exponential prefactor that is partly due to the dielectric constant.

  16. Composition dependence of dielectric properties in Se{sub 100-x}Cu{sub x} glassy alloys

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, J.; Shrotriya, D.; Kumar, S., E-mail: dr-santosh-kr@yahoo.com [Department of Physics, Christ Church College, Kanpur-208001 (India)

    2015-06-24

    In this paper we report the composition dependent of dielectric properties in Se{sub 100-x}Cu{sub x} (x = 0, 2, 4 and 6) glassy alloys. The temperature and frequency dependence of the dielectric constants and the dielectric losses in the above glassy systems in the frequency range (1k Hz-5 M Hz) and temperature range (300 K–350 K) have been measured. It has been found that dielectric constant and the dielectric loss both are highly dependent on frequency and temperature and also found to increase with increasing concentration of Cu in pure amorphous Se. The role of Cu, as an impurity in the pure a-Se glassy alloy, is also discussed in terms of electronegativity difference between the elements used in making the aforesaid glassy system. Apart from this, the results have been also correlated in terms of a dipolar model which considers the hopping of charge carriers over a potential barrier between charged defect states.

  17. Impact of electric-field dependent dielectric constants on two-dimensional electron gases in complex oxides

    Energy Technology Data Exchange (ETDEWEB)

    Peelaers, H.; Gordon, L.; Steiauf, D.; Janotti, A.; Van de Walle, C. G. [Materials Department, University of California, Santa Barbara, California 93106-5050 (United States); Krishnaswamy, K. [Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106-9560 (United States); Sarwe, A. [Materials Department, University of California, Santa Barbara, California 93106-5050 (United States); Applied Physics Department, Chalmers Institute of Technology, Gothenburg SE 412-96 (Sweden)

    2015-11-02

    High-density two-dimensional electron gas (2DEG) can be formed at complex oxide interfaces such as SrTiO{sub 3}/GdTiO{sub 3} and SrTiO{sub 3}/LaAlO{sub 3}. The electric field in the vicinity of the interface depends on the dielectric properties of the material as well as on the electron distribution. However, it is known that electric fields can strongly modify the dielectric constant of SrTiO{sub 3} as well as other complex oxides. Solving the electrostatic problem thus requires a self-consistent approach in which the dielectric constant varies according to the local magnitude of the field. We have implemented the field dependence of the dielectric constant in a Schrödinger-Poisson solver in order to study its effect on the electron distribution in a 2DEG. Using the SrTiO{sub 3}/GdTiO{sub 3} interface as an example, we demonstrate that including the field dependence results in the 2DEG being confined closer to the interface compared to assuming a single field-independent value for the dielectric constant. Our conclusions also apply to SrTiO{sub 3}/LaAlO{sub 3} as well as other similar interfaces.

  18. Parametric interactions of acoustic waves in semiconductor quantum plasmas with strain dependent dielectric constants

    Science.gov (United States)

    Yadav, N.; Ghosh, S.; Agrawal, A.

    2017-05-01

    Using quantum hydrodynamic model (QHD) of semiconductor plasma for a one-component we present an analytical investigation on parametric interaction of a laser radiation in an unmagnetised material with a strain-dependent dielectric constant. The nonlinear current density and third order susceptibility are analyzed in different wave number regions in presence and absence of quantum effect. We present the qualitative behavior of threshold pump intensity with respect to wave number in presence and absence of quantum effect. The numeric estimates are made for n-BaTiO3 crystals at 77k duly irradiated by pulsed 10.6μm CO2 laser. It is found that the quantum correction through Fermi temperature and Bohm potential terms modifies the threshold characteristics.

  19. Femtosecond pulse-width dependent trapping and directional ejection dynamics of dielectric nanoparticles

    KAUST Repository

    Chiang, Weiyi

    2013-09-19

    We demonstrate that laser pulse duration, which determines its impulsive peak power, is an effective parameter to control the number of optically trapped dielectric nanoparticles, their ejections along the directions perpendicular to polarization vector, and their migration distances from the trapping site. This ability to controllably confine and eject the nanoparticle is explained by pulse width-dependent optical forces exerted on nanoparticles in the trapping site and ratio between the repulsive and attractive forces. We also show that the directional ejections occur only when the number of nanoparticles confined in the trapping site exceeds a definite threshold. We interpret our data by considering the formation of transient assembly of the optically confined nanoparticles, partial ejection of the assembly, and subsequent filling of the trapping site. The understanding of optical trapping and directional ejections by ultrashort laser pulses paves the way to optically controlled manipulation and sorting of nanoparticles. © 2013 American Chemical Society.

  20. The dielectric calibration of capacitance probes for soil hydrology using an oscillation frequency response model

    Directory of Open Access Journals (Sweden)

    D. A. Robinson

    1998-01-01

    Full Text Available Capacitance probes are a fast, safe and relatively inexpensive means of measuring the relative permittivity of soils, which can then be used to estimate soil water content. Initial experiments with capacitance probes used empirical calibrations between the frequency response of the instrument and soil water content. This has the disadvantage that the calibrations are instrument-dependent. A twofold calibration strategy is described in this paper; the instrument frequency is turned into relative permittivity (dielectric constant which can then be calibrated against soil water content. This approach offers the advantages of making the second calibration, from soil permittivity to soil water content. instrument-independent and allows comparison with other dielectric methods, such as time domain reflectometry. A physically based model, used to calibrate capacitance probes in terms of relative permittivity (εr is presented. The model, which was developed from circuit analysis, predicts, successfully, the frequency response of the instrument in liquids with different relative permittivities, using only measurements in air and water. lt was used successfully to calibrate 10 prototype surface capacitance insertion probes (SCIPS and a depth capacitance probe. The findings demonstrate that the geometric properties of the instrument electrodes were an important parameter in the model, the value of which could be fixed through measurement. The relationship between apparent soil permittivity and volumetric water content has been the subject of much research in the last 30 years. Two lines of investigation have developed, time domain reflectometry (TDR and capacitance. Both methods claim to measure relative permittivity and should therefore be comparable. This paper demonstrates that the IH capacitance probe overestimates relative permittivity as the ionic conductivity of the medium increases. Electrically conducting ionic solutions were used to test the

  1. Structural and frequency dependencies of a.c. and dielectric characterizations of epitaxial InSb-based heterojunctions

    Indian Academy of Sciences (India)

    A ASHERY; A H ZAKI; M HUSSIEN MOURAD; A M AZAB; A A M FARAG

    2016-08-01

    In this work, heterojunction of InSb/InP was grown by liquid phase epitaxy (LPE). Surface morphology and crystalline structure of the heterojunction were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The frequency and temperature dependences of a.c. conductivity and dielectric properties of the heterojunctions were investigated in the ranges of 100 kHz–5 MHz and 298–628 K, respectively. The a.c. conductivity and its frequency exponents were interpreted in terms of correlated barrier hopping model (CBH), as the dominant conduction mechanism for charge carrier transport. The calculated activation energy, from the Arrhenius plot, was found to decrease with increasing frequency. Experimental results of both dielectric constant $\\epsilon_1$ and dielectric loss $\\epsilon_2$ showed a remarkable dependence of both frequency and temperature.

  2. Dielectric response and electric properties of organic semiconducting phthalocyanine thin films

    Institute of Scientific and Technical Information of China (English)

    A.M.Saleh; S.M.Hraibat; R.M-L.Kitaneh; M.M.Abu-Samreh; S.M.Musameh

    2012-01-01

    The dielectric function of some phthalocyanine compounds (ZnPc,H2Pc,CuPc,and FePc) were investigated by analyzing the measured capacitance and loss tangent data.The real part of the dielectric constant,ε1,varies strongly with frequency and temperature.The frequency dependence was expressed as:ε1 =Aωn,where the index,n,assumes negative values (n < 0).In addition,the imaginary part of the dielectric constant,ε2,is also frequency and temperature dependent.Data analysis confirmed that ε2 =Bωm with values of m less than zero.At low frequencies and all temperatures,a strong dependence is observed,while at higher frequencies,a moderate dependence is obvious especially for the Au-electrode sample.Qualitatively,the type of electrode material had little effect on the behavior of the dielectric constant but did affect its value.Analysis of the AC conductivity dependence on frequency at different temperatures indicated that the correlated barrier hopping (CBH) model is the most suitable mechanism for the AC conduction behavior.Maximum barrier height,W,has been estimated for ZnPc with different electrode materials (Au and Al),and had values between 0.10 and 0.9 eV.For both electrode types,the maximum barrier height has strong frequency dependence at high frequency and low temperatures.The relaxation time,τ,for ZnPc and FePc films increases with decreasing frequency.The activation energy was derived from the slopes of τ versus 1/T curves.At low temperatures,an activation energy value of about 0.01 eV and 0.04 eV was estimated for ZnPc and FePc,respectively.The low values of activation energy suggest that the hopping of charge carriers between localized states is the dominant mechanism.

  3. Dielectric analysis of depth dependent curing behavior of dental resin composites.

    Science.gov (United States)

    Steinhaus, Johannes; Moeginger, Bernhard; Grossgarten, Mandy; Rosentritt, Martin; Hausnerova, Berenika

    2014-06-01

    The aim of this study is to investigate depth dependent changes of polymerization process and kinetics of visible light-curing (VLC) dental composites in real-time. The measured quantity - "ion viscosity" determined by dielectric analysis (DEA) - provides the depth dependent reaction rate which is correlated to the light intensity available in the corresponding depths derived from light transmission measurements. The ion viscosity curves of two composites (VOCO Arabesk Top and Grandio) were determined during irradiation of 40s with a light-curing unit (LCU) in specimen depths of 0.5/0.75/1.0/1.25/1.5/1.75 and 2.0mm using a dielectric cure analyzer (NETZSCH DEA 231 with Mini IDEX sensors). The thickness dependent light transmission was measured by irradiation composite specimens of various thicknesses on top of a radiometer setup. The shape of the ion viscosity curves depends strongly on the specimen thickness above the sensor. All curves exhibit a range of linear time dependency of the ion viscosity after a certain initiation time. The determined initiation times, the slopes of the linear part of the curves, and the ion viscosities at the end of the irradiation differ significantly with depth within the specimen. The slopes of the ion viscosity curves as well as the light intensity values decrease with depth and fit to the Lambert-Beer law. The corresponding attenuation coefficients are determined for Arabesk Top OA2 to 1.39mm(-1) and 1.48mm(-1), respectively, and for Grandio OA2 with 1.17 and 1.39mm(-1), respectively. For thicknesses exceeding 1.5mm a change in polymerization behavior is observed as the ion viscosity increases subsequent to the linear range indicating some kind of reaction acceleration. The two VLC composites and different specimen thicknesses discriminate significantly in their ion viscosity evolution allowing for a precise characterization of the curing process even with respect to the polymerization mechanism. Copyright © 2014. Published by

  4. Critical properties and reliability of low-k dielectrics for ULSI interconnect applications: Thickness and temperature dependence

    Science.gov (United States)

    Kim, Hyungkun

    A fundamental understanding and detailed elucidation of the thickness dependent behavior of the key properties of low-k dielectrics IS not only necessary but also essential, and the search for the interfacial behaviors between low-k dielectrics and other layers will be an important task to achieve a thinner layers of low-k dielectrics in current and future devices. Polytetrafluoroethylene (PTFE) has been considered as one of advanced low-k ILD materials for microelectronic interconnect and packaging applications. This study presents the thickness and temperature dependence of main key properties such as structural, mechanical, electrical, dielectric, optical, and thermal properties of on-wafer PTFE low-k polymer thin and ultrathin films, which has the lowest dielectric constant among nonporous low relative permittivity materials. PTFE polycrystalline polymer thin films ranging in thickness of 90 to 1200 nm are investigated by using ellipsometer, optical spectroscopy, nanoindentation, current-voltage (I-V) characteristic method. Both Nanospec/AFT and ellipsometer are used to measure the thickness of films at 16 selected points per sample, and then these values were averaged. In addition, the characterizations of microstructure and morphology has been studied by using small angle X-ray diffraction (SAXRD-Siemens D5000 Diffractometer), fourier transform infrared spectroscopy (MIDAC-PRS 102), and scanning electron microscopy (SEM). Our results show that thermal, dielectric, optical, and mechanical properties such as the solid-liquid transition temperature, coefficient of thermal expansion, dielectric strength, refractive index, Young's modulus, hardness of low-k polycrystalline polymer thin films strongly depend on the film thickness, and this thickness dependence can be related to the microstructure and morphology of the film. These thickness and temperature dependent behaviors can be also well described by the proposed model and a good agreement with experimental and

  5. Temperature and moisture dependence of the dielectric properties of silica sand.

    Science.gov (United States)

    Liu, Chenhui; Zhang, Libo; Peng, Jinhui; Srinivasakannan, Chandrasekar; Liu, Bingguo; Xia, Hongying; Zhou, Junwen; Xu, Lei

    2013-01-01

    The major objective of this work was to investigate the effects of temperature and moisture content on the dielectric properties of silica sand. The dielectric properties of moist silica sand at five temperatures between 20 to 100 degrees C, covering different moisture content levels at a frequency of 2.45 GHz, were measured with an open-ended coaxial probe dielectric measurement system. The wave penetration depth was calculated based on the measured dielectric data. The results show moisture content to be the major influencing factor for the variation of dielectric properties. Dielectric constant, loss factor and loss tangent all increase linearly with increasing moisture content. Three predictive empirical models were developed to relate the dielectric constant, loss factor, loss tangent of silica sand as a linear function of moisture content. An increase in temperature between 20 to 100 degrees C was found to increase the dielectric constant and loss factor. The penetration depth decreased with increase in moisture content and temperature. Variation in penetration depth was found to vary linearly with decrease in moisture content. An predictive empirical model was developed to calculate penetration depth for silica sand. This study offers useful information on dielectric properties of silica sand for developing microwave drying applications in mineral processing towards designing better microwave sensors for measuring silica sand moisture content.

  6. Effect of porosity and pore morphology on the low-frequency dielectric response in sintered ZrO2-8 mol% Y2O3 ceramic compact

    Indian Academy of Sciences (India)

    D Sen; T Mahata; A K Patra; S Mazumder; B P Sharma

    2004-08-01

    Effect of porosity and pore size distribution on the low-frequency dielectric response, in the range 0.01-100 kHz, in sintered ZrO2-8 mol% Y2O3 ceramic compacts have been investigated. Small-angle neutron scattering (SANS) technique has been employed to obtain the pore characteristics like pore size distribution, specific surface area etc. It has been observed that the real and the imaginary parts of the complex dielectric permittivity, for the specimens, depend not only on the porosity but also on the pore size distribution and pore morphology significantly. Unlike normal Debye relaxation process, where the loss tangent vis-à-vis the imaginary part of the dielectric constant shows a pronounced peak, in the present case the same increases at lower frequency region and an anomalous non-Debye type relaxation process manifests.

  7. Terahertz response of dipolar impurities in polar liquids: On anomalous dielectric absorption of protein solutions

    CERN Document Server

    Matyushov, D V

    2009-01-01

    A theory of radiation absorption by dielectric mixtures is presented. The coarse-grained formulation is based on the wavevector-dependent correlation functions of molecular dipoles of the host polar liquid and a density-density structure factor of the positions of the solutes. A nonlinear dependence of the absorption coefficient on the solute concentration is predicted and originates from the mutual polarization of the liquid surrounding the solutes by the collective field of the solute dipoles aligned along the radiation field. The theory is applied to terahertz absorption of hydrated saccharides and proteins. While the theory gives an excellent account of the observations for saccharides without additional assumptions and fitting parameters, experimental absorption coefficient of protein solutions significantly exceeds theoretical calculations within standard dielectric models and shows a peak against the protein concentration. A substantial polarization of protein's hydration shell is required to explain t...

  8. Electric-field-enhanced nutrient consumption in dielectric biomaterials that contain anchorage-dependent cells.

    Science.gov (United States)

    Belfiore, Laurence A; Floren, Michael L; Belfiore, Carol J

    2012-02-01

    This research contribution addresses electric-field stimulation of intra-tissue mass transfer and cell proliferation in viscoelastic biomaterials. The unsteady state reaction-diffusion equation is solved according to the von Kármán-Pohlhausen integral method of boundary layer analysis when nutrient consumption and tissue regeneration occur in response to harmonic electric potential differences across a parallel-plate capacitor in a dielectric-sandwich configuration. The partial differential mass balance with diffusion and electro-kinetic consumption contains the Damköhler (Λ(2)) and Deborah (De) numbers. Zero-field and electric-field-sensitive Damköhler numbers affect nutrient boundary layer growth. Diagonal elements of the 2nd-rank diffusion tensor are enhanced in the presence of weak electric fields, in agreement with the formalism of equilibrium and nonequilibrium thermodynamics. Induced dipole polarization density within viscoelastic biomaterials is calculated via the real and imaginary components of the complex dielectric constant, according to the Debye equation, to quantify electro-kinetic stimulation. Rates of nutrient consumption under zero-field conditions are described by third-order kinetics that include local mass densities of nutrients, oxygen, and attached cells. Thinner nutrient boundary layers are stabilized at shorter dimensionless diffusion times when the zero-field intra-tissue Damköhler number increases above its initial-condition-sensitive critical value [i.e., {Λ(2)(zero-field)}(critical)≥53, see Eq. (23)], such that the biomaterial core is starved of essential ingredients required for successful proliferation. When tissue regeneration occurs above the critical electric-field-sensitive intra-tissue Damköhler number, the electro-kinetic contribution to nutrient consumption cannot be neglected. The critical electric-field-sensitive intra-tissue Damköhler number is proportional to the Deborah number.

  9. Temperature dependent dielectric and ferroelectric studies of BiFeO3 thin film

    Science.gov (United States)

    Gaur, Anand P. S.; Barik, Sujit K.; Katiyar, Ram S.

    2013-03-01

    Although BiFeO3 (BFO) has received a lot of interest due to its good multiferroic properties at room temperature, high leakage current limit its usage for practical applications. Recently, it is found that these properties in thin films can be different due to strain effect induced by substrate, preparation conditions and electrode effects, etc. In this context, we have studied the temperature dependence of polarization and dielectric properties of BFO thin film by varying the bottom electrode thickness and using different electrodes. The strain dependent ferroelectric switching behaviors have also been investigated with a traditional ferroelectric tester and switching spectroscopy piezoresponse force microscopy (SS-PFM), respectively. We used pulsed laser deposition to fabricate thin films of BFO using Si (100) substrate and SrTiO3(STO) as buffer layer with different bottom electrodes such as SrRuO3(SRO), LaNiO3(LNO) and Pt/Si. The thickness of STO layer is kept fixed around 70 nm and the thicknesses of BFO and electrode layer were varied from 70 nm to 200nm. The layers were grown under optimized conditions and polycrystalline nature is found from room temperature XRD. A large enhancement of polarization is found while using LNO electrode and also with reducing the thickness of BFO layer. The remnant polarization and cohesivity also shows large increase with increaisng temperature, although leakage current increases significantly. NSF

  10. Modeling of ablation threshold dependence on pulse duration for dielectrics with ultrashort pulsed laser

    Science.gov (United States)

    Sun, Mingying; Zhu, Jianqiang; Lin, Zunqi

    2017-01-01

    We present a numerical model of plasma formation in ultrafast laser ablation on the dielectrics surface. Ablation threshold dependence on pulse duration is predicted with the model and the numerical results for water agrees well with the experimental data for pulse duration from 140 fs to 10 ps. Influences of parameters and approximations of photo- and avalanche-ionization on the ablation threshold prediction are analyzed in detail for various pulse lengths. The calculated ablation threshold is strongly dependent on electron collision time for all the pulse durations. The complete photoionization model is preferred for pulses shorter than 1 ps rather than the multiphoton ionization approximations. The transition time of inverse bremsstrahlung absorption needs to be considered when pulses are shorter than 5 ps and it can also ensure the avalanche ionization (AI) coefficient consistent with that in multiple rate equations (MREs) for pulses shorter than 300 fs. The threshold electron density for AI is only crucial for longer pulses. It is reasonable to ignore the recombination loss for pulses shorter than 100 fs. In addition to thermal transport and hydrodynamics, neglecting the threshold density for AI and recombination could also contribute to the disagreements between the numerical and the experimental results for longer pulses.

  11. Temperature dependence dielectric properties of modified barium titanate-PVB composites

    Science.gov (United States)

    Joshi, N. J.; Rakshit, P. B.; Grewal, G. S.; Shrinet, V.; Pratap, A.

    2013-06-01

    In this work, attempts are made to prepare ceramic polymer-composite followed by characterization of dielectric properties. The Barium Titanate ceramic powders are synthesized using the hydrothermal process. Silane treatment is carried out on Barium Titanate powder to increase its compatibility with polymer, followed with preparation of ceramic-polymer composite. Polyvinyl Butyral (PVB) is used as matrix for preparation of the composites and the concentration of Barium Titanate is increased from 60 to 90 wt%. Dielectric properties such as volume resistivity, dielectric constant, dissipation factor are evaluated. Results indicate that the dielectric constant and dissipation factor vary between 52 to 120 and 0.01 to 0.07; respectively as the relative ratio of polymer and silane modified Barium Titanate is varied. Specifically, at 90 wt% of silane modified Barium Titanate, the highest dielectric constant of 123 along with dissipation factor of 0.07 is obtained.

  12. An experimental study of dielectric dispersion in porous media and its dependence on pore geometry

    Energy Technology Data Exchange (ETDEWEB)

    Haslund, E.

    1996-12-31

    Understanding water saturated composite media are important in the study of oil reservoirs. This doctoral thesis discusses measurements of the frequency dependent permittivity and conductivity of water saturated porous glass specimens. The experiments are designed to investigate the dispersion resulting from the geometrical properties of the pore space. Measurements are presented of the effective complex dielectric constant of water saturated porous glass specimens for frequencies below 13 MHz. The specimens are made from sintered glass spheres, and in some specimens thin plates are mixed in with the spheres. Low-conductivity water is used to saturate the pore space in order to scale the frequency range of the Maxwell-Wagner dispersion into the measurement range. The experiments are compared with two different effective medium approaches. One approach is the Mendelson and Cohen theory with randomly oriented spheroidal grains in addition to spherical grains, the other the Local porosity theory due to Hilfer. Both theories were found to be in good agreement with the experimental observations. 175 refs., 59 figs., 1 table

  13. Microstructure-dependent giant dielectric response in Ba(Fe0 .5 Nb0 .5)O3 ceramics%烧结温度对 Ba(Fe0.5Nb0.5)O3陶瓷微观结构与介电性能的影响

    Institute of Scientific and Technical Information of China (English)

    王卓; 张亮亮; 永飞; 李海娟; 马妍

    2014-01-01

    BFN ceramics were synthesized by a solid-state sintering in a temperature range from 1 300 ℃to 1 400 ℃ ,and the dielectric characteristics were evaluated together with the microstructures .All the diffraction peaks of the XRD pattern can be indexed according to a cubic structure .The average grain size and dielectric constant of BFN ceramics increase with increasing sintered temperature Ts .When Ts rises to 1 400 ℃ ,the dielectric constant increa-ses from 18 868 to 45 167 ,w hile the dielectric loss decreases from 0 .66 to 0 .43 at 1 kHz at room temperature .The complex plane impedance plots concluded that the specimens are elec-trically heterogeneous ,consisting of semiconducting grains and insulating grain boundaries , and can be modeled to an approximation on an equivalent circuit based on two parallel RC el-ements connected in series . Based on the IBLC model ,the enhanced dielectric response should be benefited from the increase of grain size in BFN ceramics .Microstructure evidence had been provided for the extrinsic origins of the enhanced giant dielectric constant .%在1300~1400℃采用固相法制得了致密的Ba(Fe0.5 Nb0.5)O3(BFN )陶瓷,并对其微观结构和介电行为进行研究.XRD分析表明不同烧结温度下都获得了单相立方结构的BFN陶瓷.陶瓷的平均晶粒尺寸和介电常数都会随着烧结温度的升高而增大,且当烧结温度升高到1400℃时,陶瓷的晶粒尺寸急剧增大,介电常数从18868急剧增到45167,介电损耗从0.66降低到0.43.复阻抗分析表明,BFN陶瓷的微观结构是由半导的晶粒和绝缘的晶界构成,可等效为由两个平行RC元件组成的串联电路.根据IB L C巨介电理论模型,介电常数的增加源于平均晶粒尺寸与晶界厚度的比值( tg/tgb )增加,并且晶粒的尺寸增加占主导地位.B F N陶瓷巨介电常数的外部起源与微结构有关.

  14. LDPE/HDPE/Clay Nanocomposites: Effects of Compatibilizer on the Structure and Dielectric Response

    Directory of Open Access Journals (Sweden)

    B. Zazoum

    2013-01-01

    Full Text Available PE/clay nanocomposites were prepared by mixing a commercially available premixed polyethylene/O-MMT masterbatch into a polyethylene blend matrix containing 80 wt% low-density polyethylene and 20 wt% high-density polyethylene with and without anhydride modified polyethylene (PE-MA as the compatibilizer using a corotating twin-screw extruder. In this study, the effect of nanoclay and compatibilizer on the structure and dielectric response of PE/clay nanocomposites has been investigated. The microstructure of PE/clay nanocomposites was characterized using wide-angle X-ray diffraction (WAXD and a scanning electron microscope (SEM. Thermal properties were examined using differential scanning calorimetry (DSC. The dielectric response of neat PE was compared with that of PE/clay nanocomposite with and without the compatibilizer. The XRD and SEM results showed that the PE/O-MMT nanocomposite with the PE-MA compatibilizer was better dispersed. In the nanocomposite materials, two relaxation modes are detected in the dielectric losses. The first relaxation is due to a Maxwell-Wagner-Sillars interfacial polarization, and the second relaxation can be related to dipolar polarization. A relationship between the degree of dispersion and the relaxation rate fmax of Maxwell-Wagner-Sillars was found and discussed.

  15. Surface structures and dielectric response of ultrafine BaTiO{sub 3} particles

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, B.; Peng, J.L.; Bursill, L.A

    1998-09-01

    Characteristic differences are observed for the dielectric response and microstructures of BaTiO{sub 3} nanoscale fine powders prepared using sol gel (SG) and steric acid gel (SAG) methods. The former exhibit a critical size below which there is no paraelectric/ferroelectric phase transition whereas BaTiO{sub 3} prepared via the SAG route remained cubic for all conditions. Atomic resolution images of both varieties showed a high density of interesting surface steps and facets. Computer simulated images of surface structure models showed that the outer (100) surface was typically a BaO layer and that at corners and ledges the steps are typically finished with Ba+2 ions; i.e. the surfaces and steps are Ba-rich. Otherwise the surfaces were typically clean and free of amorphous layers. The relationship between the observed surfaces structures and theoretical models for size effects on the dielectric properties is discussed. (authors) 22 refs., 2 tabs., 8 figs.

  16. Spectral response of dielectric nano-antennas in the far- and near-field regimes

    Science.gov (United States)

    Gutiérrez, Y.; Barreda, Á. I.; González, F.; Moreno, F.

    2016-03-01

    Recent studies show that the spectral behaviour of localized surface plasmon resonances (LPSRs) in metallic nanoparticles suffer from both a redshift and a broadening in the transition from the far- to the near-field regimes. An interpretation of this effect was given in terms of the evanescent and propagating components of the angular spectrum representation of the radiated field. Due to the increasing interest awakened by magnetodielectric materials as a both low-loss material option for nanotechnology applications, and also for their particular scattering properties, here we study the spectral response of a magnetodielectric nanoparticle as a basic element of a dielectric nano-antenna. This study is made by analyzing the changes suffered by the scattered electromagnetic field when propagating from the surface of this dielectric nanostructure to the far-zone in terms of propagating and evanescent plane wave components of the radiated fields.

  17. All-dielectric perforated metamaterials with toroidal dipolar response (Conference Presentation)

    Science.gov (United States)

    Stenishchev, Ivan; Basharin, Alexey A.

    2017-05-01

    We present metamaterials based on dielectric slab with perforated identical cylindrical clusters with perforated holes, which allow to support the toroidal dipolar response due to Mie-resonances in each hole. Note that proposed metamaterial is technologically simple for fabrication in optical frequency range. Metamaterial can be fabricated by several methods. For instance, we may apply the molecular beam epitaxy method for deposition of Si or GaAs layers, which have permittivity close to 16. Next step, nanometer/micrometer holes are perforated by focused ion beam method or laser cutting method. Fundamental difference of proposed metamaterial is technological fabrication process. Classically all- dielectric optical metamaterials consist of nano-spheres or nano-discs, which are complicated for fabrication, while our idea and suggested metamaterials are promising prototype of various optical/THz all-dielectic devices as sensor, nano-antennas elements for nanophotonics.

  18. Designing pH-responsive and dielectric hydrogels from cellulose nanocrystals

    Indian Academy of Sciences (India)

    Xiaoyuan Gao; Kishor Kumar Sadasivuni; Hyun-Chan Kim; Seung-Ki Min; Jaehwan Kim

    2015-06-01

    We report the fabrication and characterization of a pH-responsive hydrogel with improved mechanical and dielectric properties from cellulose nanocrystals. X-ray diffraction and SEM observations were used to analyze the sample morphology. The resulting pH detector exhibits a pronounced change in their swelling index in response to variation in pH. It was used singly and in combination with other nanomaterials to optimize smart material designs. The applications of the developed material are anticipated in chemical, environmental and biological systems.

  19. Enhanced nonlinear optical response of one-dimensional metal-dielectric photonic crystals.

    Science.gov (United States)

    Lepeshkin, Nick N; Schweinsberg, Aaron; Piredda, Giovanni; Bennink, Ryan S; Boyd, Robert W

    2004-09-17

    We describe a new type of artificial nonlinear optical material composed of a one-dimensional metal-dielectric photonic crystal. Because of the resonant nature of multiple Bragg reflections, the transmission within the transmission band can be quite large, even though the transmission through the same total thickness of bulk metal would be very small. This procedure allows light to penetrate into the highly nonlinear metallic layers, leading to a large nonlinear optical response. We present experimental results for a Cu/SiO(2) crystal which displays a strongly enhanced nonlinear optical response (up to 12X) in transmission.

  20. The dependence of electrostatic solvation energy on dielectric constants in Poisson-Boltzmann calculations.

    Science.gov (United States)

    Tjong, Harianto; Zhou, Huang-Xiang

    2006-11-28

    The Poisson-Boltzmann equation gives the electrostatic free energy of a solute molecule (with dielectric constant epsilon(l)) solvated in a continuum solvent (with dielectric constant epsilon(s)). Here a simple formula is presented that accurately predicts the electrostatic free energy for all combinations of epsilon(l) and epsilon(s) from the calculation on a single set of epsilon(l) and epsilon(s) values.

  1. Peculiarities of the dielectric response of the silver-modified-zeolite porous microstructure

    Science.gov (United States)

    Bunyatova, U.; Ozturk Koc, S.; Orbukh, V. I.; Eyvazova, G. M.; Agamaliev, Z. A.; Lebedeva, N. N.; Koçum, İ. C.; Salamov, B. G.; Ozer, M.

    2016-10-01

    The aim of this study was to characterize electrical conductivity and dielectrical properties of the silver-exchanged zeolite - natural clinoptilolite from Western part of Turkey and Azerbaijan in the range of frequencies from 200 Hz to 1 MHz and at room temperature. For a better understanding the effect of concentration and content of silver in the nanoporous zeolite volume on the conductivity, a study of the dielectric properties of an un-modified and silver-modified zeolite plates with different amounts of Ag ions and Ag nanoparticles is performed. Un-modified and three different types of the silver ion-exchanged modified clinoptilolite plates were prepared. It was found, that with increasing silver concentration, resistance of zeolite plate monotonically decreases at the same time a capacitance is increases. It is suggested an explanation of the observed frequency dependence of the capacitance and resistance of zeolite plates on the silver concentrations may be explain on the basis of an electrode-dielectric interface gap model. At the same time, the observed phenomenon can be explained by considering the fact that with increasing content of silver the conductivity increases. These results show that Ag nanoparticles play significant role for performance improvement in plasma electronic devices with zeolite cathode.

  2. Thickness-dependent dielectric breakdown and nanopore creation on sub-10-nm-thick SiN membranes in solution

    Science.gov (United States)

    Yanagi, Itaru; Fujisaki, Koji; Hamamura, Hirotaka; Takeda, Ken-ichi

    2017-01-01

    Recently, dielectric breakdown of solid-state membranes in solution has come to be known as a powerful method for fabricating nanopore sensors. This method has enabled a stable fabrication of nanopores down to sub-2 nm in diameter, which can be used to detect the sizes and structures of small molecules. Until now, the behavior of dielectric breakdown for nanopore creation in SiN membranes with thicknesses of less than 10 nm has not been studied, while the thinner nanopore membranes are preferable for nanopore sensors in terms of spatial resolution. In the present study, the thickness dependence of the dielectric breakdown of sub-10-nm-thick SiN membranes in solution was investigated using gradually increased voltage pulses. The increment in leakage current through the membrane at the breakdown was found to become smaller with a decrease in the thickness of the membrane, which resulted in the creation of smaller nanopores. In addition, the electric field for dielectric breakdown drastically decreased when the thickness of the membrane was less than 5 nm. These breakdown behaviors are quite similar to those observed in gate insulators of metal-oxide-semiconductor devices. Finally, stable ionic-current blockades were observed when single-stranded DNA passed through the nanopores created on the membranes with thicknesses of 3-7 nm.

  3. Electrical dependence on the chemical composition of the gate dielectric in indium gallium zinc oxide thin-film transistors

    Energy Technology Data Exchange (ETDEWEB)

    Tari, Alireza, E-mail: atari@uwaterloo.ca; Lee, Czang-Ho; Wong, William S. [Department of Electrical and Computer Engineering, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1 (Canada)

    2015-07-13

    Bottom-gate thin-film transistors were fabricated by depositing a 50 nm InGaZnO (IGZO) channel layer at 150 °C on three separate gate dielectric films: (1) thermal SiO{sub 2}, (2) plasma-enhanced chemical-vapor deposition (PECVD) SiN{sub x}, and (3) a PECVD SiO{sub x}/SiN{sub x} dual-dielectric. X-ray photoelectron and photoluminescence spectroscopy showed the V{sub o} concentration was dependent on the hydrogen concentration of the underlying dielectric film. IGZO films on SiN{sub x} (high V{sub o}) and SiO{sub 2} (low V{sub o}) had the highest and lowest conductivity, respectively. A PECVD SiO{sub x}/SiN{sub x} dual-dielectric layer was effective in suppressing hydrogen diffusion from the nitride layer into the IGZO and resulted in higher resistivity films.

  4. Quantum Effects in Plasma Dielectric Response: Plasmons and Shielding in Normal Systems and Graphene

    Science.gov (United States)

    Horing, Norman J. M.

    A brief review of quantum plasma theory and phenomenology in solid-state plasmas is presented here, with attention to dynamic and nonlocal features of dielectric response. Focussing on the random-phase approximation, we discuss the RPA screening and dielectric functions in three, two, and one dimensions corresponding to bulk, quantum well, and quantum wire plasmas, respectively, taking care to distinguish quantum effects from classical ones mandated by the correspondence principle. In particular, we exhibit plasmon dispersion, damping, and static shielding in these various dimensionalities. We also review Landau-quantized magnetoplasma phenomenology, with emphasis on de Haas-van Alphen oscillatory features in intermediate strength magnetic fields and the quantum strong field limit in which only the lowest Landau eigenstate is populated. Graphene is an exceptionally device-friendly material, with a massless relativistic Dirac energy spectrum for electrons and holes. We exhibit its RPA dynamic, nonlocal dielectric function in detail, discussing Graphene plasmons and electromagnetic modes in the THz range, self-energy, fast particle energy loss spectroscopy, atom/van der Waals interaction, and static shielding of impurity scatterers limiting dc transport in Graphene.

  5. Temperature-dependent dielectric function of bulk SrTiO3: Urbach tail, band edges, and excitonic effects

    Science.gov (United States)

    Gogoi, Pranjal Kumar; Schmidt, Daniel

    2016-02-01

    We report the temperature-dependent complex dielectric function of pristine bulk SrTiO3 between 4.2 and 300 K within the energy range of 0.6-6.5 eV determined by spectroscopic ellipsometry. Fundamental indirect and direct band-gap energies have been extracted and are discussed with regard to existing state-of-the-art theoretical calculations. Furthermore, the dielectric function around the fundamental direct gap is analyzed by considering excitonic states. The excitonic effects, including the Coulomb enhancement of the continuum, are characterized using an extension of the Elliott's formula considering both the real and imaginary parts of the dielectric function. The Urbach tail below the indirect edge shows an unconventional temperature-dependent behavior correlated to the microstructural changes near the structural phase transition around 105 K from the low-temperature tetragonal phase to the cubic phase. The temperature-dependent characterization reveals that the fundamental indirect edge as well as the Urbach tail are affected conspicuously by the structural phase transition while the fundamental direct edge is not. Moreover, the indirect edge follows Varshni's rule only in the cubic phase and the direct edge exhibits an anomalous linear increase with increasing temperature.

  6. On the dielectric response of complex layered oxides: Mica-type silicates and layered double hydroxides

    Science.gov (United States)

    Mehrotra, Vivek; Giannelis, Emmanuel P.

    1992-08-01

    The dielectric properties of mica-type silicates and layered double hydroxides have been studied in the pristine and various intercalated forms in the frequency range 101-107 Hz. A relaxation peak has been observed for the pristine silicate, whereas the pristine layered double hydroxide exhibits an anomalous low-frequency dispersion. The dielectric response is rationalized in terms of structural ordering and fluctuation of charge carriers as well as models invoking fractal time processes and fractal structure. The response is also related to the structure and mobility of the intercalated water molecules. In both pristine hosts, the predominant conduction mechanism is proton hopping between sites generated by a network of intercalated water molecules. Silicate intercalated with the insulating form of polyaniline exhibits an almost frequency-independent response. In the case of conducting polyaniline intercalated silicate, where polarons are the majority charge carriers, an anomalous low-frequency dispersion is observed and the response is typical of a metal-insulator composite. Finally, impedance measurements have been used to calculate the spatial disorder and/or surface irregularity of the host layers, expressed by the fractal dimension ds. The changes observed in ds upon intercalation of high-charge ions are correlated to the stacking disorder of the host layers.

  7. Temperature dependent dielectric and conductivity studies of polyvinyl alcohol-ZnO nanocomposite films by impedance spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Hemalatha, K. S.; Damle, R.; Rukmani, K., E-mail: rukmani9909@yahoo.co.in [Department of Physics, Bangalore University, Bangalore 560056 (India); Sriprakash, G. [Department of Physics, Maharani' s Science College for Women, Bangalore 560001 (India); Ambika Prasad, M. V. N. [Department of Physics, Gulbarga University, Gulbarga 585106 (India)

    2015-10-21

    Dielectric and conductivity behaviors of nano ZnO doped polyvinyl alcohol (PVA) composites for various concentrations of dopant were investigated using impedance spectroscopy for a wide range of temperatures (303 K–423 K) and frequencies (5 Hz–30 MHZ). The dielectric properties of host polymer matrix have been improved by the addition of nano ZnO and are found to be highly temperature dependent. Anomalous dielectric behavior was observed in the frequency range of 2.5 MHz–5 MHz. Increase in dielectric permittivity and dielectric loss was observed with respect to temperature. The Cole-Cole plot could be modeled by low resistance regions in a high resistance matrix and the lowest resistance was observed for the 10 mol. % films. The imaginary part of the electric modulus showed asymmetric peaks with the relaxation following Debye nature below and non-Debye nature above the peaks. The ac conductivity is found to obey Jonscher's power law, whereas the variation of dc conductivity with temperature was found to follow Arrhenius behavior. Two different activation energy values were obtained from Arrhenius plot indicating that two conduction mechanisms are involved in the composite films. Fitting the ac conductivity data to Jonscher's law indicates that large polaron assisted tunneling is the most likely conduction mechanism in the composites. Maximum conductivity is observed at 423 K for all the samples and it is optimum for 10 mol. % ZnO doped PVA composite film. Significant increase in dc and ac conductivities in these composite films makes them a potential candidate for application in electronic devices.

  8. Temperature dependent dielectric and conductivity studies of polyvinyl alcohol-ZnO nanocomposite films by impedance spectroscopy

    Science.gov (United States)

    Hemalatha, K. S.; Sriprakash, G.; Ambika Prasad, M. V. N.; Damle, R.; Rukmani, K.

    2015-10-01

    Dielectric and conductivity behaviors of nano ZnO doped polyvinyl alcohol (PVA) composites for various concentrations of dopant were investigated using impedance spectroscopy for a wide range of temperatures (303 K-423 K) and frequencies (5 Hz-30 MHZ). The dielectric properties of host polymer matrix have been improved by the addition of nano ZnO and are found to be highly temperature dependent. Anomalous dielectric behavior was observed in the frequency range of 2.5 MHz-5 MHz. Increase in dielectric permittivity and dielectric loss was observed with respect to temperature. The Cole-Cole plot could be modeled by low resistance regions in a high resistance matrix and the lowest resistance was observed for the 10 mol. % films. The imaginary part of the electric modulus showed asymmetric peaks with the relaxation following Debye nature below and non-Debye nature above the peaks. The ac conductivity is found to obey Jonscher's power law, whereas the variation of dc conductivity with temperature was found to follow Arrhenius behavior. Two different activation energy values were obtained from Arrhenius plot indicating that two conduction mechanisms are involved in the composite films. Fitting the ac conductivity data to Jonscher's law indicates that large polaron assisted tunneling is the most likely conduction mechanism in the composites. Maximum conductivity is observed at 423 K for all the samples and it is optimum for 10 mol. % ZnO doped PVA composite film. Significant increase in dc and ac conductivities in these composite films makes them a potential candidate for application in electronic devices.

  9. Joining Chemical Pressure and Epitaxial Strain to Yield Y-doped BiFeO3 Thin Films with High Dielectric Response

    Science.gov (United States)

    Scarisoreanu, N. D.; Craciun, F.; Birjega, R.; Ion, V.; Teodorescu, V. S.; Ghica, C.; Negrea, R.; Dinescu, M.

    2016-05-01

    BiFeO3 is one of the most promising multiferroic materials but undergoes two major drawbacks: low dielectric susceptibility and high dielectric loss. Here we report high in-plane dielectric permittivity (ε’ ∼2500) and low dielectric loss (tan δ chemical pressure and epitaxial strain on the appearance of nanoscale stripe structure which creates conditions for easy reorientation and high dielectric response, and could be of more general relevance for the field of materials science where engineered materials with huge response to external stimuli are a highly priced target.

  10. Quantum beats in the polarization response of a dielectric to intense few-cycle laser pulses

    CERN Document Server

    Korbman, Michael; Yakovlev, Vladislav S

    2012-01-01

    We have investigated the polarization response of a dielectric to intense few-cycle laser pulses with a focus on interband tunnelling. Once charge carriers are created in an initially empty conduction band, they make a significant contribution to the polarization response. In particular, the coherent superposition of conduction- and valence-band states results in quantum beats. We investigate how the quantum-beat part of the polarization response is affected by excitation dynamics and the attosecond-scale motion of charge carriers in an intense laser field. We find that, with the onset of tunnelling and Bloch oscillations, the nonlinear polarization response becomes sensitive to the carrier-envelope phase of a laser pulse.

  11. Functional group dependent dielectric properties of sulfated hydrocolloids extracted from green macroalgal biomass.

    Science.gov (United States)

    Tsubaki, Shuntaro; Hiraoka, Masanori; Hadano, Shingo; Nishimura, Hiroshi; Kashimura, Keiichiro; Mitani, Tomohiko

    2014-07-17

    Dielectric properties of aqueous solutions of sulfated hydrocolloids (ulvan and rhamnan sulfate) extracted from green macroalgal biomass were studied in a frequency range of 100 MHz-10 GHz. Counterion exchange of native hydrocolloids (mixture of Na(+), Mg(2+) and Ca(2+)) to H(+)-form showed significant increase in loss factor due to ionic conduction. On the other hand, desulfations decreased their loss factors. The results suggested that ionic conduction of H(+) has significant contribution to loss factors. Additionally, H(+)-form hydrocolloids showed significant improvement in hydration, which might also affect the dielectric property of the solution by reducing the amount of free water. The viscosity, however, did not show apparent relevance with the dielectric property.

  12. Effects of confinement on the dielectric response of water extends up to mesoscale dimensions

    DEFF Research Database (Denmark)

    De Luca, Sergio; Kannam, Sridhar Kumar; Todd, B.D.

    2016-01-01

    The extent of confinement effects on water is not clear in the literature. While some properties are affected only within a few nanometers from the wall surface, others are affected over long length scales, but the range is not clear. In this work, we have examined the dielectric response...... of confined water under the influence of external electric fields along with the dipolar fluctuations at equilibrium. The confinement induces a strong anisotropic effect which is evident up to 100 nm channel width, and may extend to macroscopic dimensions. The root-mean-square fluctuations of the total...

  13. Contributions to the second order dielectric response of an electron liquid

    Science.gov (United States)

    Bachlechner, Martina E.; Miesenboeck, Helga M.; Macke, Wilhelm

    1988-06-01

    The dielectric response function χ of a uniform electron gas is investigated up to the second order of the Coulomb interaction with different methods. When examining all polarisation diagrams with two interaction lines, it is confirmed that previous work in the Green's function formalism does not contain all second order processes and the importance of the corrections is pointed out. It is further shown, how the evaluation of χ with Green's function can be greatly simplified when taking into account the symmetry of the expressions.

  14. Temperature and frequency dependent dielectric properties of Ni–Mg–Zn–Co ferrites

    Energy Technology Data Exchange (ETDEWEB)

    Patil, S.B., E-mail: sarjeraopatil97@gmail.com [Krantisinh Nana Patil College, Walwa, Sangli 416313, Maharashtra (India); Patil, R.P. [Department of Chemistry, M.H. Shinde Mahavidyalaya, Tisangi 416206, Maharashtra (India); Ghodake, J.S. [Department of Physics, Padmabhushan Dr. Vasantraodada Patil College, Tasgaon, Sangli 416312, Maharashtra (India); Chougule, B.K. [Materials Research Laboratory, Department of Physics, Shivaji University, Kolhapur 416004, Maharashtra (India)

    2014-01-15

    The ferrites having general formula Ni{sub 0.5−x}Mg{sub x−0.01}Zn{sub 0.5−y}Co{sub y+0.01}Fe{sub 2}O{sub 4} (x=0.1, 0.2, 0.3, 0.4 and y=0.1, 0.2, 0.3, 0.4) were prepared by ceramic method. The X-ray diffraction studies of compositions reveal formation of single-phase cubic spinal structure. Dielectric properties such as dielectric constant ε′, dielectric loss tangent (tan δ), and ac resistivity were measured at room temperature as a function of frequency in the range from 1 kHz to 1 MHz. The plots of dielectric constant ε′ vs frequency show a normal dielectric behavior of spinel ferrites. The variation of loss tangent (tan δ) as a function of frequency shows a decreasing trend for all the samples except for the composition with x=0.3 and y=0.1, and y=0.2. The variation of ac resistivity with frequency of all the samples shows a decreasing trend with increase in frequency, a normal behavior of ferrites. All the variations are explained on the basis of Fe{sup 2+}/Fe{sup 3+} ion concentration on octahedral sites as well as the electronic hopping between Fe{sup 2+}↔Fe{sup 3+} ions. - Highlights: • Ni{sub 0.5−x}Mg{sub x−0.01}Zn{sub 0.5−y}Co{sub y+0.01}Fe{sub 2}O{sub 4} were prepared by ceramic method. • Single-phase cubic spinal structure. • Normal dielectric behavior.

  15. Dependence of image flicker on dielectric anisotropy of liquid crystal in a fringe field switching liquid crystal cell

    Science.gov (United States)

    Oh, Seung-Won; Baek, Jong-Min; Kim, Jung-Wook; Yoon, Tae-Hoon

    2016-09-01

    Two types of image flicker, which are caused by the flexoelectric effect of liquid crystals (LCs), are observed when a fringe-field switching (FFS) LC cell is driven by a low frequency electric field. Static image flicker, observed because of the transmittance difference between neighboring frames, has been reported previously. On the other hand, research on dynamic image flicker has been minimal until now. Dynamic image flicker is noticeable because of the brief transmittance drop when the sign of the applied voltage is reversed. We investigated the dependence of the image flicker in an FFS LC cell on dielectric anisotropy of the LCs in terms of both the static and dynamic flicker. Experimental results show that small dielectric anisotropy of the LC can help suppress not only the static but also dynamic flicker for positive LCs. We found that both the static and dynamic flicker in negative LCs is less evident than in positive LCs.

  16. Temperature and frequency dependent dielectric properties of electrically conducting oxidatively synthesized polyazomethines and their structural, optical, and thermal characterizations

    Science.gov (United States)

    Dineshkumar, Sengottuvelu; Muthusamy, Athianna; Chandrasekaran, J.

    2017-01-01

    Three azomethine diol monomers were synthesized by condensing with methanolic solution of aromatic aldehydes with ethylenediamine. These monomers were oxidatively polymerized using NaOCl as an oxidant. The structures of the monomers and polymers were confirmed by various spectroscopic techniques. Spectral results showed that the repeating units are linked by Csbnd C and Csbnd Osbnd C couplings. The polyazomethines have fluorescent property with high stokes shift. Solid state electrical conductivity of polymers both in I2 doped and undoped states, temperature and frequency dependent dielectric measurements were made by two probe method. The electrical conductivities of polyazomethines were compared based on the charge densities on imine nitrogens obtained from Huckel calculation. The conductivity of polymers increases with increase in iodine vapour contact time. Among the synthesized polymers PHNAE has shown high dielectric constant at low applied frequency of 50 Hz at 393 K due the presence of bulky naphthalene unit in polymer chain.

  17. Investigation of temperature dependent dielectric constant of a sputtered TiN thin film by spectroscopic ellipsometry

    Science.gov (United States)

    Tripura Sundari, S.; Ramaseshan, R.; Jose, Feby; Dash, S.; Tyagi, A. K.

    2014-01-01

    The temperature dependence of optical constants of titanium nitride thin film is investigated using Spectroscopic Ellipsometry (SE) between 1.4 and 5 eV in the temperature range of 300 K to 650 K in steps of 50 K. The real and imaginary parts of the dielectric functions ɛ1(E) and ɛ2(E) marginally increase with increase in temperature. A Drude Lorentz dielectric analysis based on free electron and oscillator model are carried out to describe the temperature behavior. With increase in temperature, the unscreened plasma frequency and broadening marginally decreased and increased, respectively. The parameters of the Lorentz oscillator model also showed that the relaxation time decreased with temperature while the oscillator energies increased. This study shows that owing to the marginal change in the refractive index with temperature, titanium nitride can be employed for surface plasmon sensor applications even in environments where rise in temperature is imminent.

  18. The effect of concentration- and temperature-dependent dielectric constant on the activity coefficient of NaCl electrolyte solutions

    Energy Technology Data Exchange (ETDEWEB)

    Valiskó, Mónika; Boda, Dezső, E-mail: boda@almos.vein.hu [Department of Physical Chemistry, University of Pannonia, P.O. Box 158, H-8201 Veszprém (Hungary)

    2014-06-21

    Our implicit-solvent model for the estimation of the excess chemical potential (or, equivalently, the activity coefficient) of electrolytes is based on using a dielectric constant that depends on the thermodynamic state, namely, the temperature and concentration of the electrolyte, ε(c, T). As a consequence, the excess chemical potential is split into two terms corresponding to ion-ion (II) and ion-water (IW) interactions. The II term is obtained from computer simulation using the Primitive Model of electrolytes, while the IW term is estimated from the Born treatment. In our previous work [J. Vincze, M. Valiskó, and D. Boda, “The nonmonotonic concentration dependence of the mean activity coefficient of electrolytes is a result of a balance between solvation and ion-ion correlations,” J. Chem. Phys. 133, 154507 (2010)], we showed that the nonmonotonic concentration dependence of the activity coefficient can be reproduced qualitatively with this II+IW model without using any adjustable parameter. The Pauling radii were used in the calculation of the II term, while experimental solvation free energies were used in the calculation of the IW term. In this work, we analyze the effect of the parameters (dielectric constant, ionic radii, solvation free energy) on the concentration and temperature dependence of the mean activity coefficient of NaCl. We conclude that the II+IW model can explain the experimental behavior using a concentration-dependent dielectric constant and that we do not need the artificial concept of “solvated ionic radius” assumed by earlier studies.

  19. The effect of concentration- and temperature-dependent dielectric constant on the activity coefficient of NaCl electrolyte solutions.

    Science.gov (United States)

    Valiskó, Mónika; Boda, Dezső

    2014-06-21

    Our implicit-solvent model for the estimation of the excess chemical potential (or, equivalently, the activity coefficient) of electrolytes is based on using a dielectric constant that depends on the thermodynamic state, namely, the temperature and concentration of the electrolyte, ε(c, T). As a consequence, the excess chemical potential is split into two terms corresponding to ion-ion (II) and ion-water (IW) interactions. The II term is obtained from computer simulation using the Primitive Model of electrolytes, while the IW term is estimated from the Born treatment. In our previous work [J. Vincze, M. Valiskó, and D. Boda, "The nonmonotonic concentration dependence of the mean activity coefficient of electrolytes is a result of a balance between solvation and ion-ion correlations," J. Chem. Phys. 133, 154507 (2010)], we showed that the nonmonotonic concentration dependence of the activity coefficient can be reproduced qualitatively with this II+IW model without using any adjustable parameter. The Pauling radii were used in the calculation of the II term, while experimental solvation free energies were used in the calculation of the IW term. In this work, we analyze the effect of the parameters (dielectric constant, ionic radii, solvation free energy) on the concentration and temperature dependence of the mean activity coefficient of NaCl. We conclude that the II+IW model can explain the experimental behavior using a concentration-dependent dielectric constant and that we do not need the artificial concept of "solvated ionic radius" assumed by earlier studies.

  20. Structure dependent resistivity and dielectric characteristics of tantalum oxynitride thin films produced by magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Cristea, D., E-mail: daniel.cristea@unitbv.ro [Department of Materials Science, Transilvania University, 500036 Brasov (Romania); Crisan, A. [Department of Materials Science, Transilvania University, 500036 Brasov (Romania); Cretu, N. [Electrical Engineering and Applied Physics Department, Transilvania University, 500036 Brasov (Romania); Borges, J. [Centro de Física, Universidade do Minho, Campus de Gualtar, 4710 - 057 Braga (Portugal); Instituto Pedro Nunes, Laboratório de Ensaios, Desgaste e Materiais, Rua Pedro Nunes, 3030-199 Coimbra (Portugal); SEG-CEMUC, Mechanical Engineering Department, University of Coimbra, 3030-788 Coimbra (Portugal); Lopes, C.; Cunha, L. [Centro de Física, Universidade do Minho, Campus de Gualtar, 4710 - 057 Braga (Portugal); Ion, V.; Dinescu, M. [National Institute for Lasers, Plasma and Radiation Physics, Lasers Department, “Photonic Processing of Advanced Materials” Group, PO Box MG-16, RO 77125 Magurele-Bucharest (Romania); Barradas, N.P. [Centro de Ciências e Tecnologias Nucleares, Instituto Superior Técnico, Universidade de Lisboa, E.N. 10 ao km 139,7, 2695-066 Bobadela LRS (Portugal); Alves, E. [Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, E.N. 10 ao km 139,7, 2695-066 Bobadela LRS (Portugal); Apreutesei, M. [MATEIS Laboratory-INSA de Lyon, 21 Avenue Jean Capelle, 69621 Villeurbanne cedex (France); Université de Lyon, Institut des Nanotechnologies de Lyon INL-UMR5270, CNRS, Ecole Centrale de Lyon, Ecully F-69134 (France); Munteanu, D. [Department of Materials Science, Transilvania University, 500036 Brasov (Romania)

    2015-11-01

    Highlights: • Tantalum oxynitride thin films have been deposited by magnetron sputtering, in various configurations. • The rising of the reactive gases mixture flow has the consequence of a gradual increase in the non-metallic content in the films, which results in a 10 orders of magnitude resistivity domain. • The higher resistivity films exhibit dielectric constants up to 41 and quality factors up to 70. - Abstract: The main purpose of this work is to present and to interpret the change of electrical properties of Ta{sub x}N{sub y}O{sub z} thin films, produced by DC reactive magnetron sputtering. Some parameters were varied during deposition: the flow of the reactive gases mixture (N{sub 2} and O{sub 2}, with a constant concentration ratio of 17:3); the substrate voltage bias (grounded, −50 V or −100 V) and the substrate (glass, (1 0 0) Si or high speed steel). The obtained films exhibit significant differences. The variation of the deposition parameters induces variations of the composition, microstructure and morphology. These differences cause variation of the electrical resistivity essentially correlated with the composition and structural changes. The gradual decrease of the Ta concentration in the films induces amorphization and causes a raise of the resistivity. The dielectric characteristics of some of the high resistance Ta{sub x}N{sub y}O{sub z} films were obtained in the samples with a capacitor-like design (deposited onto high speed steel, with gold pads deposited on the dielectric Ta{sub x}N{sub y}O{sub z} films). Some of these films exhibited dielectric constant values higher than those reported for other tantalum based dielectric films.

  1. Ab-initio optical properties and dielectric response of open-shell spinel zinc ferrite

    Science.gov (United States)

    Ziaei, Vafa; Bredow, Thomas

    2017-02-01

    In the present work, we predict the optical properties and the dielectric response spectrum of the spinel zinc ferrite Zn2Fe4O8, and show in particular the impact of many-body effects on the absorption spectrum, using advanced many-body perturbation approach. The excitonic effects remarkably redistribute the spectral weights causing a red-shift of 1.6 eV of the maximum of the independent particle G 0 W 0 (IP- G 0 W 0) towards the electron-hole affected spectrum. The excitation spectrum of the zinc ferrite exhibits a low lying doubly degenerated bound dark exciton at 1.84 eV with a fully symmetric excited-state density, and a narrow optical gap setting on at 1.93 eV. We further analyse the electronic transitions and exciton density distributions giving insights to the nature of excitations. The dielectric response of Zn2Fe4O8 shows a particular sensitivity to the excitations higher than the electronic band gap, however it abruptly becomes passive to the incoming electro-magnetic wave and propagates to the negative regions at high energy regimes.

  2. Dielectric behavior of Ar{sup +} implanted CR-39 polymer

    Energy Technology Data Exchange (ETDEWEB)

    Shekhawat, Nidhi; Sharma, Annu; Aggarwal, Sanjeev; Deshpande, S. K.; Nair, K. G. M. [Department of Physics, Kurukshetra University Kurukshetra-136119 (India); UGC-DAE Consortium for Scientific Research, Mumbai Centre, BARC, Mumbai 400085 (India); Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India)

    2012-06-05

    The frequency dependent dielectric response of Ar{sup +} implanted CR-39 specimens has been studied. Samples were implanted with 130 keV Ar{sup +} ions to various doses ranging from 5x10{sup 14} to 1x10{sup 16} cm{sup -2}. The frequency response of dielectric constant (e) and dielectric loss has been studied both in the pristine and argon ion implanted samples of CR-39 polymer in the frequency range 10{sup 4} to 10{sup 8} Hz. Structural changes produced in CR-39 specimens due to implantation have been studied using Attenuated total reflectance (ATR) Fourier transform infrared spectroscopic technique. Results of dielectric analysis indicate the lowering in dielectric constant ({epsilon}') and similar behavior of dielectric loss with increase in ion fluence. An attempt has been made to correlate these changes produced in the dielectric properties of implanted specimens with the structural changes produced due to implantation.

  3. Nondestructive approach for measuring temperature-dependent dielectric properties of epoxy resins.

    Science.gov (United States)

    Akhtar, M Jaleel; Feher, Lambert E; Thumm, Manfred

    2008-01-01

    A practical method for measuring the complex relative permittivity of epoxy resins and other viscous liquids over a wide temperature range in S-band is presented. The method involves inserting a hot glass tube, filled with the liquid-under-test (LUT), into a length of WR-340 rectangular waveguide connected between two ports of a Vector Network Analyzer, which measures the reflection and transmission coefficients at 2.45 GHz. The heating arrangement consists of a temperature-controlled glycol bath, where the LUT-filled glass tube is placed. The dielectric properties are determined using an optimization routine, which minimizes the error between the theoretical and measured scattering coefficient data. The theoretical values of the scattering coefficient data are computed with the help of a numerical 3-D electromagnetic field simulator, the CST Microwave Studio. The dielectric properties of the empty glass tube (required by the simulation code) are also measured using the above methodology.

  4. Constrained Molecular Dynamics Modeling of Dielectric Response in Polar Polyethylene Analogs and Poly(vinylidene flouride)

    Science.gov (United States)

    Calame, Jeffrey

    2013-03-01

    A simplified molecular dynamics formalism for polymers, having united atoms with constrained bond lengths and bond angles along the backbone but allowing torsional motion, has been developed to model the dielectric response and ferroelectricity in polymers with permanent dipoles. Analytic relations existing on the backbone geometry and associated dihedral motion allow elimination of many dot and cross product evaluations. Also, constraint error correcting forces, symplectic integration with velocity prediction, random force excitation with damping and a momentum-conserving thermostat, and rapid neighbor list and long range force computation allow efficient computation and time steps as large as 20 fs to enable the study of relatively long time scale dielectric phenomena. Studies are performed on non-polar polyethylene for benchmarking, followed by a model system (polar polyethylene) which retains the molecular structure, dihedral potentials, and non-bonded interactions of polyethylene, except artificial partial charges are placed on the united atoms. The modeling is extended to poly(vinylidene fluoride) by changes to the molecular structure, potentials, and charges. Heterogeneous systems containing crystalline and amorphous arrangements of polymer chains are studied. Work supported by the U.S. Office of Naval Research.

  5. Inducing transparency with large magnetic response and group indices by hybrid dielectric metamaterials.

    Science.gov (United States)

    Chen, Cheng-Kuang; Lai, Yueh-Chun; Yang, Yu-Hang; Chen, Chia-Yun; Yen, Ta-Jen

    2012-03-26

    We present metamaterial-induced transparency (MIT) phenomena with enhanced magnetic fields in hybrid dielectric metamaterials. Using two hybrid structures of identical-dielectric-constant resonators (IDRs) and distinct-dielectric-constant resonators (DDRs), we demonstrate a larger group index (ng~354), better bandwidth-delay product (BDP~0.9) than metallic-type metamaterials. The keys to enable these properties are to excite either the trapped mode or the suppressed mode resonances, which can be managed by controlling the contrast of dielectric constants between the dielectric resonators in the hybrid metamaterials.

  6. Stable dielectric response of low-loss aromatic polythiourea thin films on Pt/SiO2 substrate

    Science.gov (United States)

    Eršte, A.; Fulanović, L.; Čoga, L.; Lin, M.; Thakur, Y.; Zhang, Q. M.; Bobnar, V.

    2016-03-01

    We have investigated dielectric properties of aromatic polythiourea (ArPTU, a polar polymer containing high dipolar moments with very low defect levels) thin films that were developed on Pt/SiO2 substrate. The detected response is compared to the response of commercially available polymers, such as high density polyethylene (HDPE) and polypropylene (PP), which are at present used in foil capacitors. Stable values of the dielectric constant ɛ‧≈5 (being twice higher than in HDPE and PP) over broad temperature and frequency ranges and dielectric losses as low as in commercial systems suggest ArPTU as a promising candidate for future use in a variety of applications.

  7. Propagation of electromagnetic waves in stratified media with nonlinearity in both dielectric and magnetic responses.

    Science.gov (United States)

    Kim, Kihong; Phung, D K; Rotermund, F; Lim, H

    2008-01-21

    We develop a generalized version of the invariant imbedding method, which allows us to solve the electromagnetic wave equations in arbitrarily inhomogeneous stratified media where both the dielectric permittivity and magnetic permeability depend on the strengths of the electric and magnetic fields, in a numerically accurate and efficient manner. We apply our method to a uniform nonlinear slab and find that in the presence of strong external radiation, an initially uniform medium of positive refractive index can spontaneously change into a highly inhomogeneous medium where regions of positive or negative refractive index as well as metallic regions appear. We also study the wave transmission properties of periodic nonlinear media and the influence of nonlinearity on the mode conversion phenomena in inhomogeneous plasmas. We argue that our theory is very useful in the study of the optical properties of a variety of nonlinear media including nonlinear negative index media fabricated using wires and split-ring resonators.

  8. A dielectric response study of the electronic stopping power of liquid water for energetic protons and a new I-value for water.

    Science.gov (United States)

    Emfietzoglou, D; Garcia-Molina, R; Kyriakou, I; Abril, I; Nikjoo, H

    2009-06-07

    The electronic stopping power of liquid water for protons over the 50 keV to 10 MeV energy range is studied using an improved dielectric response model which is in good agreement with the best available experimental data. The mean excitation energy (I) of stopping power theory is calculated to be 77.8 eV. Shell corrections are accounted for in a self-consistent manner through analytic dispersion relations for the momentum dependence of the dielectric function. It is shown that widely used dispersion schemes based on the random-phase approximation (RPA) can result in sizeable errors due to the neglect of damping and local field effects that lead to a momentum broadening and shifting of the energy-loss function. Low-energy Born corrections for the Barkas, Bloch and charge-state effects practically cancel out down to 100 keV proton energies. Differences with ICRU Report 49 stopping power values and earlier calculations are found to be at the approximately 20% level in the region of the stopping maximum. The present work overcomes the limitations of the Bethe formula below 1 MeV and improves the accuracy of previous calculations through a more consistent account of the dielectric response properties of liquid water.

  9. A variational constitutive framework for the nonlinear viscoelastic response of a dielectric elastomer

    KAUST Repository

    Khan, Kamran

    2012-11-10

    We formulate a variational constitutive framework that accounts for nonlinear viscous behavior of electrically sensitive polymers, specifically Dielectric Elastomers (DEs), under large deformation. DEs are highly viscoelastic and their actuation response is greatly affected in dynamic applications. We used the generalized Maxwell model to represent the viscoelastic response of DE allowing the material to relax with multiple mechanisms. The constitutive updates at each load increment are obtained by minimizing an objective function formulated using the free energy and electrostatic energy of the elastomer, in addition to the viscous dissipation potential of the dashpots in each Maxwell branch. The model is then used to predict the electromechanical instability (EMI) of DE. The electro-elastic response of the DE is verified with available analytical solutions in the literature and then the material parameters are calibrated using experimental data. The model is integrated with finite element software to perform a variety of simulations on different types of electrically driven actuators under various electromechanical loadings. The electromechanical response of the DE and the critical conditions at which EMI occurs were found to be greatly affected by the viscoelasticity. Our model predicts that under a dead load EMI can be avoided if the DE operates at a high voltage rate. Subjected to constant, ramp and cyclic voltage, our model qualitatively predicts responses similar to the ones obtained from the analytical solutions and experimental data available in the literature. © 2012 Springer-Verlag Berlin Heidelberg.

  10. Temperature dependences of piezoelectric, elastic and dielectric constants of L-alanine crystal

    Science.gov (United States)

    Tylczyński, Z.; Sterczyńska, A.; Wiesner, M.

    2011-09-01

    Temperature changes in the components of piezoelectric, elastic and dielectric tensors were studied in L-alanine crystals in the range 100-300 K. A jumpwise increase in the c55 component of the elastic stiffness accompanied by maxima in damping of all face-shear modes observed at 199 K in L-alanine crystal were interpreted as a result of changes in the NH3+ vibrations occurring through electron-phonon coupling. All components of the piezoelectric tensor show small anomalies in this temperature range. The components of the electromechanical coupling coefficient determined indicate that L-alanine is a weak piezoelectric.

  11. Dielectrically Loaded Biconical Antennas

    Science.gov (United States)

    Nusseibeh, Fouad Ahmed

    1995-01-01

    Biconical antennas are of great interest to those who deal with broadband applications including the transmission/reception of pulses. In particular, wide-angle conical antennas are an attractive choice in many applications including Electronic Support Measures (ESM) and the measurements of transient surface currents and charge densities on aircraft. Dielectric loading in the interior region of a conical antenna can be used to reduce the size of the antenna especially at low frequencies and/or for structural strength. Therefore, having an analytical solution for the input impedance and the frequency response is very helpful in optimizing the design and understanding the behavior of the antenna. From the quasi-analytical solution for the input impedance and the electric field of a wide-angle conical antenna, it can be seen that the dielectric loading in the antenna region improves the input impedance at low frequencies, but increases the number of resonance points and the magnitude of these peaks. When an inhomogeneous dielectric load is used, the magnitude of the resonance peaks is decreased (depending on the way the load is distributed), improving the input impedance of the antenna significantly. Introducing a dielectric load in the interior region of an electrically short receiving cone makes the antenna behave as an electrically longer antenna. However, this is not true for the case for electrical1y long antennas. For the case of pulse transmission, the dielectric load affects only the amplitude. Of course, if the dielectric fills the whole space, both transmitting and receiving antennas behave as electrically longer antennas.

  12. High-Temperature Dielectric Response and Multiscale Mechanism of SiO2/Si3N4 Nanocomposites

    Institute of Scientific and Technical Information of China (English)

    HOU Zhi-Ling; ZHANG Liang; YUAN Jie; SONG Wei-Li; CAO Mao-Sheng

    2008-01-01

    The high-temperature dielectric properties of SiO2/Si3N4 nanocomposites are investigated theoretically and experimentally. Its permittivities and loss tangents at the temperature ranging from room temperature to 1300℃ at 9.0 GHz are measured by the resonant cavity method. The SiO2/Si3N4 nanocomposites show complex dielectric behaviour at elevated temperature, and a multi-scale model is proposed to describe the dependence of the dielectric properties in the SiO2/Si3N4 on its compositional variations. Such a theory is needed so that the available property measurements could be extrapolated to other operating frequencies and temperatures.

  13. Pulsed EM Field Response of a Thin, High-Contrast, Finely Layered Structure With Dielectric and Conductive Properties

    NARCIS (Netherlands)

    De Hoop, A.T.; Jiang, L.

    2009-01-01

    The response of a thin, high-contrast, finely layered structure with dielectric and conductive properties to an incident, pulsed, electromagnetic field is investigated theoretically. The fine layering causes the standard spatial discretization techniques to solve Maxwell's equations numerically to b

  14. The influence of interfaces and water uptake on the dielectric response of epoxy-cubic boron nitride composites

    NARCIS (Netherlands)

    Tsekmes, I.A.; Morshuis, P.H.F.; Smit, J.J.; Kochetov, R.

    2015-01-01

    In this study, epoxy-cubic boron nitride composites are fabricated, and their dielectric response is investigated. They exhibit the same trend as epoxy composites reinforced with other filler types. Thus, at low filler concentrations, they exhibit a lower relative permittivity than neat epoxy. As

  15. Electrical conductivity, dielectric response and space charge dynamics of an electroactive polymer with and without nanofiller reinforcement

    Science.gov (United States)

    Kochetov, R.; Tsekmes, I. A.; Morshuis, P. H. F.

    2015-07-01

    Electroactive polymers have gained considerable attention over the last 20 years for exhibiting a large displacement in response to electrical stimulation. The promising fields of application include wave energy converters, muscle-like actuators, sensors, robotics, and biomimetics. For an electrical engineer, electroactive polymers can be seen as a dielectric elastomer film or a compliant capacitor with a highly deformable elastomeric medium. If the elastomer is pre-stretched and pre-charged, a reduction of the tensile force lets the elastomer revert to its original form and increases the electrical potential. The light weight of electroactive polymers, low cost, high intrinsic breakdown strength, cyclical way of operation, reliable performance, and high efficiency can be exploited to utilize the elastomeric material as a transducer. The energy storage for a linear dielectric polymer is determined by its relative permittivity and the applied electric field. The latter is limited by the dielectric breakdown strength of the material. Therefore, to generate a high energy density of a flexible capacitor, the film must be used at the voltage level close to the material’s breakdown or inorganic particles with high dielectric permittivity which can be introduced into the polymer matrix. In the present study, silicone-titania elastomer nanocomposites were produced and the influence of nanoparticles on the macroscopic dielectric properties of the neat elastomer including space charge dynamics, complex permittivity, and electrical conductivity, were investigated.

  16. Controlling optical responses through local dielectric resonance in nanometre metallic clusters

    Institute of Scientific and Technical Information of China (English)

    Chen Liang-Liang; Gu Ying; Wang Li-Jin; Gong Qi-Huang

    2007-01-01

    Optical responses in dilute composites are controlled through the local dielectric resonance of metallic clusters. We consider two located metallic clusters close to each other with admittances ε1 and ε2. Through varying the difference admittance ratio η[= (ε2 - ε0)/(ε1 - ε0)], we find that their optical responses are determined by the local resonance.There is a blueshift of absorption peaks with the increase of η. Simultaneously, it is known that the absorption peaks will be redshifted by enlarging the cluster size. By adjusting the nano-metallic cluster geometry, size and admittances,we can control the positions and intensities of absorption peaks effectively. We have also deduced the effective linear optical responses of three-comPonent composites εe = ε0 (1 + ∑nsn=1 [(γn1 + ηγn2 )/(ε0 (s - sn))]), and the sum rule of cross sections: ∑nsn=1 (γn1 + ηγn2) = Nh1 + Nh2, where Nh1and Nh2 are the numbers of ε1 and ε2 bonds along the electric field, respectively. These results may be beneficial to the study of surface plasmon resonances on a nanometre scale.

  17. Temperature-dependent microwave dielectric relaxation studies of hydrogen bonded polar binary mixtures of propan-1-ol and propionaldehyde.

    Science.gov (United States)

    Vishwam, T; Parvateesam, K; Sreeharisastry, S; Murthy, V R K

    2013-10-01

    The molecular interaction between the polar systems of propan-1-ol and propionaldehyde for various mole fractions at different temperatures were studied by determining the frequency dependent complex dielectric permittivity by using the open-ended coaxial probe technique method in the microwave frequency range from 20 MHz to 20 GHz. The geometries are optimized at HF, B3LYP and MP2 with 6-311G and 6-311G+ basis sets. Dipole moments of the binary mixtures are calculated from the dielectric data using Higasi's method and compared with the theoretical results. Conformational analysis of the formation of hydrogen bond between the propan-1-ol and propionaldehyde is supported by the FT-IR and molecular polarizability calculations. The average relaxation times are calculated from their respective Cole-Cole plots. The activation entropy, activation enthalpy and Kirkwood correlation 'g' factor, excess permittivity (ε(E)), excess inverse relaxation time (1/τ)(E), Bruggeman parameter (f(B)) have also been determined for propan-1-ol and propionaldehyde and the results were correlated.

  18. Magnetic response from a composite of metal-dielectric particles in the visible range: T-matrix simulation

    Directory of Open Access Journals (Sweden)

    O. Zhuromskyy

    2011-09-01

    Full Text Available The optical response of a particle composed of a dielectric core surrounded by a densely packed shell of small metal spheres is simulated with the superposition Tmatrix method for realistic material parameters. In order to compute the electric and magnetic particle polarizabilities a single expansion T-matrix is derived from a particle centered T-matrix. Finally the permeability of a medium comprising such particles is found to deviate considerable from unity resulting in a noticeable optical response.

  19. Low-Frequency Dependence of Conductivity and Dielectric Properties of Polyaniline/ZnFe2O4 Nanocomposites

    Institute of Scientific and Technical Information of China (English)

    G. D. Prasanna; H. S. Jayanna; Ashok R Lamani; M. L. Dinesha; C. S. Naveen; G. J. Shankaramurthy

    2011-01-01

    Conducting polyaniline/ZnFe2O4 nanocomposites are synthesized by using a simple and inexpensive one-step in-situ polymerization method in the presence of ZnFe2O4 nanoparticles.The structural,morphological and electrical properties of the samples are characterized by x-ray diffraction,Fourier transform infrared spectra and scanning electron microscopy.These results reveal the formation of polyaniline/ZnFe2O4 nanocomposites.The morphology of these samples is studied by scanning electron microscopy.Further,the ac conductivity (σac) of these composites is investigated in the frequency range of 1 kHz-10 MHz.The presence of polarons and bipolarons are responsible for the frequency dependence of ac conductivity in these nanocomposites.The ac conductivity is found to be constant up to 1 MHz and thereafter it increases steeply.The ac conductivity of 0.695S·cm-1 at room temperature is observed as the maxima for the polyaniline with 40wt% of the ZnFe2O4 nanocomposite.Polymers are known,in general,as a class of heat sensitive,flexible,electrically insulating,amorphous or semicrystalline materials.The electrical properties of polymers can be modified by the addition of inorganic materials.Nanoscale particles as fillers are attractive due to their intriguing properties arising from the nanosize and resulting large surface area.The insertion of nanoscale materials may improve the electrical and dielectric properties of the host polymers.[1]A large number of polymers are now included in the list of conducting polymers,including polyaniline,polypyrrole,polythiophene,polyparaphenylene,polyphenylene sulphide,polyphenylene vinylene,etc.%Conducting polyaniline/ZnFe2O4 nanocomposites are synthesized by using a simple and inexpensive one-step in-situ polymerization method in the presence of ZnFe2OA nanoparticles. The structural, morphological and electrical properties of the samples are characterized by x-ray diffraction, Fourier transform infrared spectra and scanning electron

  20. Microscopic dielectric permittivities of graphene nanoribbons and graphene

    Science.gov (United States)

    Fang, Jingtian; Vandenberghe, William G.; Fischetti, Massimo V.

    2016-07-01

    We derive a microscopic Poisson equation using the density-density response function. This equation is valid for any realistic potential perturbation and permits the study of dielectric response in nanostructures, especially in one-dimensional nanostructures and quantum dots. We apply this equation to simulate a nanoscale parallel-plate capacitor (nanocapacitor) with graphene as dielectric and two nanocapacitors with a graphene nanoribbon (GNR) as dielectric. The density-density response function is calculated using first-order perturbation theory and empirical pseudopotentials. From the microscopic electric field of the graphene nanocapacitor, we calculate the out-of-plane microscopic dielectric constant of graphene and from the electric field of GNR nanocapacitors, we calculate the full microscopic dielectric tensor of several GNRs with different widths. We find that the out-of-plane microscopic dielectric constants of GNRs and graphene do not depend on their energy band gap. We also study the effect of a surrounding dielectric on the dielectric permittivity of graphene and we conclude that the surrounding dielectric barely affects the dielectric permittivity of graphene.

  1. Small- and strong-signal dielectric response in a single-crystal film of partially deuterated betaine phosphite

    Science.gov (United States)

    Balashova, E. V.; Krichevtsov, B. B.; Lemanov, V. V.

    2011-06-01

    Poly- and single-crystal films of betaine phosphite deuterated to ˜20% have been grown by evaporation on NdGaO3 (001) substrates with a preliminarily deposited planar interdigital structure of electrodes. The small-signal dielectric response in the 0.1-100.0-kHz frequency range has revealed a strong anomaly in capacitance upon the transition of the films to the ferroelectric state. Application of a bias field brings about suppression and a slight shift of the dielectric anomaly toward higher temperatures. The strong-signal dielectric response has been studied by the Sawyer-Tower method over the frequency range 0.06-3.00 kHz both in the para- and ferroelectric phases. In contrast to the case of a plane-parallel capacitor, in the planar structure studied, the dielectric hysteresis loops exhibit a very small coercivity at low frequencies, which grows with increasing frequency. This difference should be assigned to different domain structures formed in a planeparallel capacitor and in a planar structure in a saturating field. The growth of hysteresis with increasing frequency in a planar structure is considered to be associated with the domain wall motion.

  2. Theory of tailorable optical response of two-dimensional arrays of plasmonic nanoparticles at dielectric interfaces

    Science.gov (United States)

    Sikdar, Debabrata; Kornyshev, Alexei A.

    2016-01-01

    Two-dimensional arrays of plasmonic nanoparticles at interfaces are promising candidates for novel optical metamaterials. Such systems materialise from ‘top–down’ patterning or ‘bottom–up’ self-assembly of nanoparticles at liquid/liquid or liquid/solid interfaces. Here, we present a comprehensive analysis of an extended effective quasi-static four-layer-stack model for the description of plasmon-resonance-enhanced optical responses of such systems. We investigate in detail the effects of the size of nanoparticles, average interparticle separation, dielectric constants of the media constituting the interface, and the nanoparticle position relative to the interface. Interesting interplays of these different factors are explored first for normally incident light. For off-normal incidence, the strong effects of the polarisation of light are found at large incident angles, which allows to dynamically tune the reflectance spectra. All the predictions of the theory are tested against full-wave simulations, proving this simplistic model to be adequate within the quasi-static limit. The model takes seconds to calculate the system’s optical response and makes it easy to unravel the effect of each system parameter. This helps rapid rationalization of experimental data and understanding of the optical signals from these novel ‘metamaterials’, optimised for light reflection or harvesting. PMID:27652788

  3. Physically responsive field-effect transistors with giant electromechanical coupling induced by nanocomposite gate dielectrics.

    Science.gov (United States)

    Tien, Nguyen Thanh; Trung, Tran Quang; Seoul, Young Gug; Kim, Do Il; Lee, Nae-Eung

    2011-09-27

    Physically responsive field-effect transistors (physi-FETs) that are sensitive to physical stimuli have been studied for decades. The important issue for separating the responses of sensing materials from interference by other subcomponents in a FET transducer under global physical stimuli has not been completely resolved. In addition, challenges remain with regard to the design and employment of smart materials for flexible physi-FETs with a large electro-physical coupling effect. In this article, we propose the direct integration of nanocomposite (NC) gate dielectrics of barium titanate (BT) nanoparticles (NPs) and highly crystalline poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) into flexible organic FETs to achieve a large electro-physical coupling effect. Additionally, a new alternating current biasing method is proposed for precise extraction and quantification of tiny variations in the remnant polarization of NCs caused by mechanical stimuli. An investigation of physi-FETs under static mechanical stimuli revealed the first ever reported giant, positive piezoelectric coefficients of d(33) up to 960 pC/N in the NCs. The large coefficients are presumably due to the significant contributions of the intrinsic positive piezoelectricity of the BT NPs and P(VDF-TrFE) crystallites. © 2011 American Chemical Society

  4. Temperature dependent dielectric function and the E0 critical points of hexagonal GaN from 30 to 690 K

    Directory of Open Access Journals (Sweden)

    Tae Jung Kim

    2014-02-01

    Full Text Available The complex dielectric function ɛ and the E0 excitonic and band-edge critical-point structures of hexagonal GaN are reported for temperatures from 30 to 690 K and energies from 0.74 to 6.42 eV, obtained by rotating-compensator spectroscopic ellipsometry on a 1.9 μm thick GaN film deposited on a c-plane (0001 sapphire substrate by molecular beam epitaxy. Direct inversion and B-splines in a multilayer-structure calculation were used to extract the optical properties of the film from the measured pseudodielectric function ⟨ɛ⟩. At low temperature sharp E0 excitonic and critical-point interband transitions are separately observed. Their temperature dependences were determined by fitting the data to the empirical Varshni relation and the phenomenological expression that contains the Bose-Einstein statistical factor.

  5. Weak ferromagnetism and temperature dependent dielectric properties of Zn{sub 0.9}Ni{sub 0.1}O diluted magnetic semiconductor

    Energy Technology Data Exchange (ETDEWEB)

    Ahmed, Raju [Department of Electrical and Electronic Engineering, Shahjalal University of Science and Technology, Sylhet 3114 (Bangladesh); Department of Applied Physics, Electronics and Communication Engineering, University of Dhaka, Dhaka 1000 (Bangladesh); Moslehuddin, A.S.M.; Mahmood, Zahid Hasan [Department of Applied Physics, Electronics and Communication Engineering, University of Dhaka, Dhaka 1000 (Bangladesh); Hossain, A.K.M. Akther, E-mail: akmhossain@phy.buet.ac.bd [Department of Physics, Bangladesh University of Engineering and Technology, Dhaka 1000 (Bangladesh)

    2015-03-15

    Highlights: • Single phase wurtzite structure was confirmed from XRD analysis. • Weak ferromagnetic behaviour at room temperature. • Pure semiconducting properties confirmed from temperature dependent conductivity. • Smaller dielectric properties at higher frequency. • Possible potential application in high frequency spintronic devices. - Abstract: In this study the room temperature ferromagnetic behaviour and dielectric properties of ZnO based diluted magnetic semiconductor (DMS) have been investigated using nominal chemical composition Zn{sub 0.9}Ni{sub 0.1}O. The X-ray diffraction analysis confirmed formation of single phase hexagonal wurtzite structure. An increase in grain size with increasing sintering temperature was observed from scanning electron microscopy. Field dependent DC magnetization values indicated dominant paramagnetic ordering along with a slight ferromagnetic behaviour at room temperature. Frequency dependent complex initial permeability showed some positive values around 12 at room temperature. In dielectric measurement, an increasing trend of complex permittivity, loss tangent and ac conductivity with increasing temperature were observed. The temperature dependent dispersion curves of dielectric properties revealed clear relaxation at higher temperature. Frequency dependent ac conductivity was found to increase with frequency whereas complex permittivity and loss tangent showed an opposite trend.

  6. Electric and magnetic dipolar response of small dielectric particles: Scattering anisotropy and optical forces

    Directory of Open Access Journals (Sweden)

    R. Gomez-Medina

    2011-09-01

    Full Text Available We predict that real small dielectric particles made of non-magnetic materials present non-conventional scattering properties similar to those previously reported for somewhat hypothetical magnetodielectric particles.

  7. Dielectric response of wurtzite gallium nitride in the terahertz frequency range

    Science.gov (United States)

    Hibberd, M. T.; Frey, V.; Spencer, B. F.; Mitchell, P. W.; Dawson, P.; Kappers, M. J.; Oliver, R. A.; Humphreys, C. J.; Graham, D. M.

    2016-12-01

    We report on the characterization of the intrinsic, anisotropic, dielectric properties of wurtzite gallium nitride in the spectral range of 0.5-11 THz, using terahertz time-domain spectroscopy. The ordinary (ε˜⊥) and extraordinary (ε˜∥) components of the complex dielectric function were determined experimentally for a semi-insulating, m-plane gallium nitride single crystal, providing measurements of the refractive indices (n⊥,∥) and absorption coefficients (α⊥,∥) . These material parameters were successfully modeled by considering the contribution of the optical phonon modes, measured using Raman spectroscopy, to the dielectric function, giving values for the relative static dielectric constants of ε0⊥ = 9.22 ± 0.02 and ε0∥ = 10.32 ± 0.03 for wurtzite gallium nitride.

  8. Liquid crystal wavefront corrector with modal response based on spreading of the electric field in a dielectric material

    OpenAIRE

    Loktev, M.; Vdovine, G.V.; Klimov, N.; Kotova, S.

    2007-01-01

    A novel liquid crystal (LC) wavefront corrector with smooth modal influence functions is proposed and realized. The device consists of a thin layer of planar aligned nematic LC sandwiched between a glass plate with a conductive electrode and a plate made of ceramic material with a very high dielectric constant. Control electrodes are positioned on the back side of the ceramic plate, opposite to the LC. The modal character of the response is determined by spreading of the electric field in the...

  9. Distinctive contributions from organic filler and relaxorlike polymer matrix to dielectric response of CuPc-P(VDF-TrFE-CFE) composite.

    Science.gov (United States)

    Bobnar, V; Levstik, A; Huang, C; Zhang, Q M

    2004-01-30

    The dielectric response of copper-phthalocyanine (CuPc) oligomers embedded in a poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) terpolymer matrix was studied. Although admixture of CuPc strongly increases the dielectric constant of the terpolymer at all temperatures, each of the two constituents determines the dielectric dynamics in a different temperature region-the relaxorlike matrix above and CuPc below the terpolymer's freezing temperature. Two relaxations, reflecting the charge carriers' response in CuPc, were detected. Results on ac conductivity reveal that the tunneling of polarons is the dominating charge transport mechanism.

  10. Solvent-Dependent Structure of Iridium Dihydride Complexes: Different Geometries at Low and High Dielectricity of the Medium.

    Science.gov (United States)

    Polukeev, Alexey V; Marcos, Rocío; Ahlquist, Mårten S G; Wendt, Ola F

    2016-03-14

    The hydride iridium pincer complex [(PCyP)IrH2] (PCyP=cis-1,3-bis[(di-tert-butylphosphino)methyl]cyclohexane, 1) reveals remarkably solvent-dependent hydride chemical shifts, isotope chemical shifts, JHD and T1(min), with rHH increasing upon moving to more polar medium. The only known example of such behaviour (complex [(POCOP)IrH2], POCOP=2,6-(tBu2PO)2C6H3) was explained by the coordination of a polar solvent molecule to the iridium (J. Am. Chem. Soc. 2006, 128, 17114). Based on the existence of an agostic bond between α-C-H and iridium in 1 in all solvents, we argue that the coordination of solvent can be rejected. DFT calculations revealed that the structures of 1 and [(POCOP)IrH2] depend on the dielectric permittivity of the medium and these compounds adopt trigonal-bipyramidal geometries in non-polar media and square-pyramidal geometries in polar media.

  11. An amphidynamic inorganic-organic hybrid crystal of bromoplumbate with 1,5-bis(1-methylimidazolium)pentane exhibiting multi-functionality of a dielectric anomaly and temperature-dependent dual band emissions.

    Science.gov (United States)

    Tong, Yuan-Bo; Ren, Li-Te; Duan, Hai-Bao; Liu, Jian-Lan; Ren, Xiao-Ming

    2015-10-28

    Organic-inorganic hybrid crystals, [1,5-bis(1-methylimidazolium)pentane][PbBr3]2 (1), were achieved through the mutual diffusion of a bi-imidazolium based ionic liquid and PbBr2 solution of DMF in a glass tube. The hybrid solid crystallizes in the orthorhombic space group Fdd2 at room temperature; and is composed of one-dimensional [PbBr3]∞ chains where the neighbouring PbBr6 coordination octahedra are linked together via the face-sharing mode and the inorganic chains are surrounded by organic cations. The hybrid solid exhibits a dielectric anomaly around 443 K and dielectric relaxation above 400 K, the dielectric response mechanism was investigated using variable-temperature X-ray single crystal and powder diffraction as well as DSC techniques. Fascinatingly, this hybrid solid shows dual band emissions, moreover, the fluorescence nature of the two emission bands exhibits a distinct response to temperature, leading to a temperature-dependent fluorescence color, this feature has promising application in the emission temperature-sensing field.

  12. Hybrid metal-dielectric ring resonators for homogenizable optical metamaterials with strong magnetic response at short wavelengths down to the ultraviolet range.

    Science.gov (United States)

    Tang, Jianwei; He, Sailing

    2013-10-07

    We derive an analytical LC model from Maxwell's equations for the magnetic resonance of subwavelength ring resonators. Using the LC model, we revisit the scaling of split-ring resonators. Inspired by the LC model, we propose a hybrid metal-dielectric ring resonator mainly composed of high index dielectric material (e.g., TiO₂) with some gaps filled with metal (e.g., Ag). The saturation frequency of magnetic response for the hybrid metal-dielectric ring resonator is much higher (up to the ultraviolet range) than that for split-ring resonators, and can be controlled by the metal fraction in the ring. The hybrid metal-dielectric ring resonator can also overcome the homogenization problem of all-dielectric magnetic resonators, and therefore can form homogenizable magnetic metamaterials at short wavelengths down to the ultraviolet range.

  13. Thickness-dependent dielectric properties of nanoscale Pt/(Pb,Ba)ZrO 3/BaPbO 3 capacitors

    Science.gov (United States)

    Wu, Lin-Jung; Wu, Jenn-Ming

    2007-10-01

    Lead barium zirconate (PBZ) thin films on BaPbO 3(BPO)/Pt/Ti/SiO 2/Si substrates have been prepared by rf-magnetron sputtering at 500 °C. The orientation of PBZ film changes from random to (1 1 1)-prefer oriented when the thickness increases. The grain size increases with increasing PBZ thickness. The dielectric properties are greatly suppressed when the thickness of dielectrics decreases. The dielectric constant and tunability decrease from 536% and 49.1% to 205% and 22.7%, respectively, when the thickness of PBZ decreases from 323 to 62 nm. The origins of the collapsed dielectric behavior are discussed. The variation of dielectric properties with film thickness can be interpreted by (a) antiferroelectric layer at PBZ/BPO interface, (b) dead layer at Pt/PBZ interface, and (c) grain boundary dead layers.

  14. Particle size dependent response of aerosol counters

    Science.gov (United States)

    Ankilov, A.; Baklanov, A.; Colhoun, M.; Enderle, K.-H.; Gras, J.; Julanov, Yu.; Kaller, D.; Lindner, A.; Lushnikov, A. A.; Mavliev, R.; McGovern, F.; O'Connor, T. C.; Podzimek, J.; Preining, O.; Reischl, G. P.; Rudolf, R.; Sem, G. J.; Szymanski, W. W.; Vrtala, A. E.; Wagner, P. E.; Winklmayr, W.; Zagaynov, V.

    During an international workshop at the Institute for Experimental Physics of the University of Vienna, Austria, which was coordinated within the Committee on Nucleation and Atmospheric Aerosols (IAMAS-IUGG), 10 instruments for aerosol number concentration measurement were studied, covering a wide range of methods based on various different measuring principles. In order to investigate the detection limits of the instruments considered with respect to particle size, simultaneous number concentration measurements were performed for monodispersed aerosols with particle sizes ranging from 1.5 to 50 nm diameter and various compositions. The instruments considered show quite different response characteristics, apparently related to the different vapors used in the various counters to enlarge the particles to an optically detectable size. A strong dependence of the 50% cutoff diameter on the particle composition in correlation with the type of vapor used in the specific instrument was found. An enhanced detection efficiency for ultrafine hygroscopic sodium chloride aerosols was observed with water operated systems, an analogous trend was found for n-butanol operated systems with nonhygroscopic silver and tungsten oxide particles.

  15. Interlayer coupling effect on the performance of monolithic three-dimensional inverters and its dependence on the interlayer dielectric thickness

    Science.gov (United States)

    Hattori, Junichi; Fukuda, Koichi; Irisawa, Toshifumi; Ota, Hiroyuki; Maeda, Tatsuro

    2017-04-01

    We study the interlayer coupling in monolithic three-dimensional (3D) inverters and investigate its effect on the performance of 3D inverters using technology computer-aided design simulation. The interlayer coupling in 3D inverters consisting of silicon-on-insulator metal–oxide–semiconductor field-effect transistors (FETs) improves the current driving capability of the top FETs. Owing to this improvement, 3D inverters have a smaller intrinsic delay than the corresponding two-dimensional (2D) inverters although the switching energies of 3D and 2D inverters are comparable to each other. We analyze the relationship of such interlayer coupling effects with the interlayer dielectric (ILD) thickness and find that there exists an appropriate ILD thickness in terms of various aspects of the performance such as speed, energy efficiency, and both. It is also found that decreasing the power supply voltage enhances the interlayer coupling effects. In addition, we reveal that the interlayer coupling in 3D inverters is strongly dependent on the original structure of the constituent FETs.

  16. Characterization of dielectric materials

    Energy Technology Data Exchange (ETDEWEB)

    King, Danny J.; Babinec, Susan; Hagans, Patrick L.; Maxey, Lonnie C.; Payzant, Edward A.; Daniel, Claus; Sabau, Adrian S.; Dinwiddie, Ralph B.; Armstrong, Beth L.; Howe, Jane Y.; Wood, III, David L.; Nembhard, Nicole S.

    2017-06-27

    A system and a method for characterizing a dielectric material are provided. The system and method generally include applying an excitation signal to electrodes on opposing sides of the dielectric material to evaluate a property of the dielectric material. The method can further include measuring the capacitive impedance across the dielectric material, and determining a variation in the capacitive impedance with respect to either or both of a time domain and a frequency domain. The measured property can include pore size and surface imperfections. The method can still further include modifying a processing parameter as the dielectric material is formed in response to the detected variations in the capacitive impedance, which can correspond to a non-uniformity in the dielectric material.

  17. Room-temperature magneto-dielectric response in multiferroic ZnFe2O4/PMN-PT bilayer thin films

    Science.gov (United States)

    Garg, T.; Kulkarni, A. R.; Venkataramani, N.

    2016-08-01

    The magneto-dielectric response in multiferroic ZnFe2O4/PMN-PT bilayer thin films prepared on a glass substrate using RF magnetron sputtering has been investigated in this work. PMN-PT thin films (i.e. PMN-PT/LCMO/Pt/Ti/glass) deposited on glass were used as a substrate for deposition of ZnFe2O4 thin films. ZnFe2O4 thin films were annealed ex situ at different temperatures. Structural, magnetic, ferroelectric, dielectric and magneto-dielectric studies were carried out on these multiferroic bilayer thin films. Structural studies revealed the presence of each layer in its respective single phase. Magnetic and ferroelectric studies revealed the ferromagnetic and ferroelectric behaviors of these bilayers. To quantify the magnetoelectric coupling, the dielectric constant of the bilayer was measured at room temperature as a function of frequency with and without the applied magnetic field. The magneto-dielectric response MD(%) was calculated by finding the relative change in dielectric constant at 1 kHz as a percentage. The observed MD response was correlated with magnetization of the ferrite layer. An MD response of 2.60% was found for a bilayer film annealed at 350 °C. At this particular annealing temperature, the ZnFe2O4 layer also has the highest saturation magnetization of 1900 G.

  18. Frequency and Temperature Dependences of Dielectric Dispersion and Electrical Properties of Polyvinylidene Fluoride/Expanded Graphite Composites

    National Research Council Canada - National Science Library

    Li, Yu Chao; Li, Robert Kwok Yiu; Tjong, Sie Chin

    2010-01-01

    ...) by direct melt blending process. The electrical conductivity and dielectric properties of resulting PVDF/EG composites were investigated in a wide range of frequencies from [superscript]102[/superscript] to [superscript]108[/superscript] Hz...

  19. Measurements of the temperature dependence of radiation induced conductivity in polymeric dielectrics

    Science.gov (United States)

    Gillespie, Jodie

    This study measures Radiation Induced Conductivity (RIC) in five insulating polymeric materials over temperatures ranging from ~110 K to ~350 K: polyimide (PI or Kapton HN(TM) and Kapton E(TM)), polytetraflouroethylene (PTFE or Teflon(TM)), ethylene-tetraflouroethylene (ETFE or Tefzel(TM)), and Low Density Polyethylene (LDPE). RIC occurs when incident ionizing radiation deposits energy and excites electrons into the conduction band of insulators. Conductivity was measured when a voltage was applied across vacuum-baked, thin film polymer samples in a parallel plate geometry. RIC was calculated as the difference in sample conductivity under no incident radiation and under an incident ~4 MeV electron beam at low incident dose rates of 0.01 rad/sec to 10 rad/sec. The steady-state RIC was found to agree well with the standard power law relation, sigmaRIC(D˙) = kRIC(T) D˙Delta(T) between conductivity, sigmaRIC and adsorbed dose rate, D˙. Both the proportionality constant, kRIC, and the power, Delta, were found to be temperature-dependent above ~250 K, with behavior consistent with photoconductivity models developed for localized trap states in disordered semiconductors. Below ~250 K, kRIC and Delta exhibited little change in any of the materials.

  20. Thickness Dependent Structural and Dielectric Properties of Calcium Copper Titanate Thin Films Produced by Spin-Coating Method for Microelectronic Devices

    Science.gov (United States)

    Thiruramanathan, P.; Sankar, S.; Marikani, A.; Madhavan, D.; Sharma, Sanjeev K.

    2017-03-01

    Calcium copper titanate (CaCu3Ti4O12, CCTO) thin films have been deposited on platinized silicon [(111)Pt/Ti/SiO2/Si] substrate through a sol-gel spin coating technique and annealed at 600-900°C with a variation of 100°C per sample for 3 h. The activation energy for crystalline growth, as well as optimal annealing temperature (900°C) of the CCTO crystallites was studied by x-ray diffraction analysis (XRD). Thickness dependent structural, morphological, and optical properties of CCTO thin films were observed. The field emission scanning electron microscopy (FE-SEM) verified that the CCTO thin films are uniform, fully covered, densely packed, and the particle size was found to be increased with film thickness. Meanwhile, quantitative analysis of dielectric properties (interfacial capacitance, dead layers, and bulk dielectric constant) of CCTO thin film with metal-insulator-metal (M-I-M) structures has been investigated systematically using a series capacitor model. Room temperature dielectric properties of all the samples exhibit dispersion at low frequencies, which can be explained based on Maxwell-Wagner two-layer models and Koop's theory. It was found that the 483 nm thick CCTO film represents a high dielectric constant (ɛ r = 3334), low loss (tan δ = 3.54), capacitance (C = 4951 nF), which might satisfy the requirements of embedded capacitor.

  1. Thickness Dependent Structural and Dielectric Properties of Calcium Copper Titanate Thin Films Produced by Spin-Coating Method for Microelectronic Devices

    Science.gov (United States)

    Thiruramanathan, P.; Sankar, S.; Marikani, A.; Madhavan, D.; Sharma, Sanjeev K.

    2017-07-01

    Calcium copper titanate (CaCu3Ti4O12, CCTO) thin films have been deposited on platinized silicon [(111)Pt/Ti/SiO2/Si] substrate through a sol-gel spin coating technique and annealed at 600-900°C with a variation of 100°C per sample for 3 h. The activation energy for crystalline growth, as well as optimal annealing temperature (900°C) of the CCTO crystallites was studied by x-ray diffraction analysis (XRD). Thickness dependent structural, morphological, and optical properties of CCTO thin films were observed. The field emission scanning electron microscopy (FE-SEM) verified that the CCTO thin films are uniform, fully covered, densely packed, and the particle size was found to be increased with film thickness. Meanwhile, quantitative analysis of dielectric properties (interfacial capacitance, dead layers, and bulk dielectric constant) of CCTO thin film with metal-insulator-metal (M-I-M) structures has been investigated systematically using a series capacitor model. Room temperature dielectric properties of all the samples exhibit dispersion at low frequencies, which can be explained based on Maxwell-Wagner two-layer models and Koop's theory. It was found that the 483 nm thick CCTO film represents a high dielectric constant ( ɛ r = 3334), low loss (tan δ = 3.54), capacitance ( C = 4951 nF), which might satisfy the requirements of embedded capacitor.

  2. Stationary Light Waves in Anizotropy and Nonolinear Plane Media, whose Dielectric Tensor's Principal Values Arbitrarily Depend upon Intensity Case of Scattering

    CERN Document Server

    Ochirbat, G

    2000-01-01

    A plane medium, whose dielectric tensor's principal values arbitrarily depend upon intensity, is considered. The problems of the TM and TE waves, within the problem of light scattering, are reduced to quadrature. A question of integrability of the full system of Maxwell equations is discussed. A closed equation has been obtained for an auxiliary variable for a nonlinearity of Kerr type. A scheme for integrating the full system of Maxwell equations by solving the equation over the auxiliary variable is suggested.

  3. Temperature- and frequency-dependent dielectric behaviors of insulator/semiconductor (Al2O3/ZnO) nanolaminates with various ZnO thicknesses

    Science.gov (United States)

    Li, Jin; Bi, Xiaofang

    2016-07-01

    Al2O3/ZnO nanolaminates (NLs) with various ZnO sublayer thicknesses were prepared by atomic layer deposition. The Al2O3 sublayers are characterized as amorphous and the ZnO sublayers have an oriented polycrystalline structure. As the ZnO thickness decreases to a certain value, each NL exhibits a critical temperature at which its dielectric constant starts to rise quickly. Moreover, this temperature increases as the ZnO thickness is decreased further. On the other hand, the permittivity demonstrates a large value of several hundred at a frequency  ⩽1000 Hz, followed by a steplike decrease at a higher frequency. The change in the cut-off frequency with ZnO thickness is characterized by a hook function. It is revealed that the Coulomb confinement effect becomes predominant in the dielectric behaviors of the NLs with very thin ZnO. As the ZnO thickness decreases to about the same as or even smaller than the Bohr radius of ZnO, a great change in the carrier concentration and effective mass of ZnO is induced, which is shown to be responsible for the peculiar dielectric behaviors of Al2O3/ZnO with very thin ZnO. These findings provide insight into the prevailing mechanisms to optimize the dielectric properties of semiconductor/insulator laminates with nanoscale sublayer thickness.

  4. A multi-physical model of actuation response in dielectric gels

    Science.gov (United States)

    Li, Bo; Chang, LongFei; Asaka, Kinji; Chen, Hualing; Li, Dichen

    2016-12-01

    Actuation deformation of a dielectric gel is attributed to: the solvent diffusion, the electrical polarization and material hyperelasticity. A multi-physical model, coupling electrical and mechanical quantities, is established, based on the thermodynamics. A set of constitutive relations is derived as an equation of state for characterization. The model is applied to specific cases as effective validations. Physical and chemical parameters affect the performance of the gel, showing nonlinear deformation and instability. This model offers guidance for engineering application.

  5. Experimental study on the dielectric properties of polyacrylate dielectric elastomer

    Science.gov (United States)

    Qiang, Junhua; Chen, Hualing; Li, Bo

    2012-02-01

    The dielectric constant of elastomeric dielectric material is an essential physical parameter, whose value may affect the electromechanical deformation of a dielectric elastomer actuator. Since the dielectric constant is influenced by several external factors as reported before, and no certain value has been confirmed to our knowledge, in the present paper, on the basis of systematical comparison of recent past literature, we conducted extensive works on the measurement of dielectric properties of VHB films, involving five influencing factors: prestretch (both equal and unequal biaxial), electrical frequency, electrode material, stress relaxation time and temperature. Experimental results directly show that the dielectric response changes according to these factors, based on which we investigate the significance of each factor, especially the interaction of two external conditions on the dielectric constant of deformable dielectric, by presenting a physical picture of the mechanism of polarization.

  6. Microstructural and dielectric susceptibility effects on predictions of dielectric properties

    Energy Technology Data Exchange (ETDEWEB)

    Ferris, K.F.; Exarhos, G.J. [Pacific Northwest National Lab., Richland, WA (United States); Risser, S.M. [Texas A& M Univ., Commerce, TX (United States)

    1997-12-01

    In modeling the dielectric properties of inhomogeneous materials, the treatment of the electric field interactions differentiate the usual modeling formalisms (such as the Maxwell-Garnett and Bruggeman effective medium methods) and their accuracy. In this paper, we show that the performance of effective medium methods is dependent upon a number of variables - defect concentration, alignment, and the dielectric constant of the material itself. Using our previously developed finite element model of an inhomogeneous dielectric, we have developed models for a number of dielectric films of varying dielectric constant and microstructures. Alignment of defects parallel to the applied field and the larger defect aspect ratios increase the overall dielectric constant. The extent of these effects is dependent on the dielectric constant of the bulk component.

  7. Effect of Gadolinium Substitution on Dielectric Properties of Bismuth Ferrite

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Multiferroic Bi1-xGdxFeO3(x=0, 0.05, 0.1, 0.15, 0.2) ceramics were prepared by conventional solid state reaction method. X-ray diffraction was carried out to characterize the crystal structure and to detect any possible impurities existing in these ceramics. Frequency dependence of dielectric properties of Bi1-xGdxFeO3 samples at room temperature was measured in a frequency range from 100 Hz to 1 MHz using an HP4294A precision impedance analyzer. For all the samples studied, the dielectric constant and dielectric loss decreases with increasing frequency in the range between 100 Hz and 1 MHz, as can be expected from a typical orientational dielectric relaxation process. There is no indication of any dips over the whole frequency range studied, which is in direct contrast with that reported previously. It is found that both dielectric constant and dielectric loss are strongly dependent on the Gd3+ content. The effect of introducing Gd3+ is to increase the dielectric constant and to decrease the dielectric loss for slightly doped sample Bi0.95Gd0.05FeO3: the dielectric constant of the sample at 1 kHz reaches 600, six times bigger than that for pure BiFeO3. Complicated dielectric behaviors are observed at higher doping levels. Furthermore, the substitution of rare earth Gd for Bi helps to eliminate the impurity phase in BiFeO3 ceramics. There is strong evidence that both lattice constants a and c of the unit cell become smaller as the Gd3+ content is increased. The dielectric constant and loss and their frequency responses can be varied dramatically by substitution of Gd.

  8. Calculated Optical Properties of Dielectric Shell Coated Gold Nanorods

    Institute of Scientific and Technical Information of China (English)

    CAO Min; WANG Meng; GU Ning

    2009-01-01

    @@ Optical absorption spectra of dielectric shell coated gold nanorods are simulated using the discrete dipole ap-proximation method. The influence of the aspect ratio, shell thickness, dielectric constant of the shell, and surrounding medium on the longitudinal resonance mode is investigated. It is found that the coated dielectric shell does not affect the trend in the dependence of resonance position on the aspect ratio, while it broadens the resonant line width and reduces the sensitivity of plasmon resonance in response to changes of the surrounding medium. Furthermore, the difference of dielectric constants between the shell and surrounding medium plays an important role in determining the resonance position. The screening effect of the dielectric shell tends to be less apparent for a thicker shell thickness.

  9. Temperature dependence of dielectric and electromechanical properties of (K,Na)(Nb,Ta)O3 single crystal and corresponding domain structure evolution.

    Science.gov (United States)

    Zheng, Limei; Wang, Junjun; Huo, Xiaoqing; Wang, Rui; Sang, Shijing; Li, Shiyang; Zheng, Peng; Cao, Wenwu

    2014-07-28

    Domain structures and their evolution with temperature in the [001] C oriented (K,Na)(Nb,Ta)O3 (KNNT) single crystal have been studied before and after poling by polarizing light microscopy. The results indicate that the KNNT crystal is difficult to be completely poled by the room temperature poling process. The domain structure is rather stable in the orthorhombic phase, but exhibits substantial changes near the phase transition temperatures TO-T and TC. Narrower stripe domains are formed during both the orthorhombic-tetragonal and tetragonal-cubic phase transition processes, no intermediate phases were found during the phase transitions. The temperature dependence of the dielectric and piezoelectric properties were measured, and the influence of domain structures on the dielectric and electromechanical properties were quantified.

  10. Exploring electromagnetic response of tellurium dielectric resonator metamaterial at the infrared wavelengths

    Institute of Scientific and Technical Information of China (English)

    宋甲坤; 宋玉志; 李康文; 张祖银; 徐云; 韦欣; 宋国峰

    2015-01-01

    We numerically investigate the electromagnetic properties of tellurium dielectric resonator metamaterial at the infrared wavelengths. The transmission spectra, effective permittivity and permeability of the periodic tellurium metamaterial struc-ture are investigated in detail. The linewidth of the structure in the direction of magnetic field Wx has effects on the position and strength of the electric resonance and magnetic resonance modes. With appropriately optimizing the geometric dimen-sions of the designed structure, the proposed tellurium metamaterial structure can provide electric resonance mode and high order magnetic resonance mode in the same frequency band. This would be helpful to analyze and design low-loss negative refraction index metamaterials at the infrared wavelengths.

  11. Effect of DC Bias on Dielectric Response in Relaxor Ferroelectric Terpolymer Films

    Science.gov (United States)

    Tian, L.; Sun, J.; Wang, J. L.; Li, Y. P.

    2017-06-01

    The permittivity as a function of temperature and dc bias in the poly(vinylindene fluoride-trifluorethylene-chlorofluoroethylene) [P(VDF-TrFE-CFE)] terpolymer was measured and analyzed using both the Vogel-Fulcher and universal Curie-Weiss law. The decreased permittivity with increasing dc bias has been observed. The lower permittivity in dc bias is due to the suppressed diffusion of phase transition rather than the nonlinear dielectric contribution. Furthermore, the suppression of phase diffusion can be explained by the molecular conformation conversion in dc bias.

  12. HfO{sub 2} dielectric thickness dependence of electrical properties in graphene field effect transistors with double conductance minima

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Cheng; Xie, Dan, E-mail: xiedan@mail.tsinghua.edu.cn; Xu, Jian-Long; Sun, Yi-Lin; Dai, Rui-Xuan; Li, Xian [Institute of Microelectronics, Tsinghua National Laboratory for Information Science and Technology (TNList), Tsinghua University, Beijing 100084 (China); Li, Xin-Ming [National Center for Nanoscience and Technology, Zhongguancun, Beijing 100190 (China); Zhu, Hong-Wei [School of Materials Science and Engineering, State Key Laboratory of New Ceramics and Fine Processing, Key Laboratory of Materials Processing Technology of MOE, Tsinghua University, Beijing 100084 (China); Center for Nano and Micro Mechanics, Tsinghua University, Beijing 100084 (China)

    2015-10-14

    We investigate the electrical properties in back-gated graphene field effect transistors (GFETs) with SiO{sub 2} dielectric and different thickness of high-k HfO{sub 2} dielectric. The results show that transform characteristic (I{sub ds}–V{sub gs}) curves of GFETs are uniquely W-shaped with two charge neutrality point (left and right) in both SiO{sub 2} and HfO{sub 2} dielectric (SiO{sub 2}-GFETs and HfO{sub 2}-GFETs). The gate voltage reduces drastically in HfO{sub 2}-GFETs compared with that in SiO{sub 2}-GFETs, and it becomes much smaller with the decline of HfO{sub 2} thickness. The left charge neutrality point in I{sub d}–V{sub g} curves of all HfO{sub 2}-GFETs is negative, compared to the positive ones in SiO{sub 2}-GFETs, which means that there exists n-doping in graphene with HfO{sub 2} as bottom dielectric. We speculate that this n-doping comes from the HfO{sub 2} layer, which brings fixed charged impurities in close proximity to graphene. The carrier mobility is also researched, demonstrating a decreasing trend of hole mobility in HfO{sub 2}-GFETs contrast to that in SiO{sub 2}-GFETs. In a series of HfO{sub 2}-GFETs with different HfO{sub 2} dielectric thickness, the hole mobility shows a tendency of rise when the thickness decreases to 7 nm. The possible reason might be due to the introduced impurities into HfO{sub 2} film from atomic layer deposition process, the concentration of which varies from the thickness of HfO{sub 2} layer.

  13. Core-shell structured polystyrene/BaTiO3 hybrid nanodielectrics prepared by in situ RAFT polymerization: a route to high dielectric constant and low loss materials with weak frequency dependence.

    Science.gov (United States)

    Yang, Ke; Huang, Xingyi; Xie, Liyuan; Wu, Chao; Jiang, Pingkai; Tanaka, Toshikatsu

    2012-11-23

    A novel route to prepare core-shell structured nanocomposites with excellent dielectric performance is reported. This approach involves the grafting of polystyrene (PS) from the surface of BaTiO(3) by an in situ RAFT polymerization. The core-shell structured PS/BaTiO(3) nanocomposites not only show significantly increased dielectric constant and very low dielectric loss, but also have a weak frequency dependence of dielectric properties over a wide range of frequencies. In addition, the dielectric constant of the nanocomposites can also be easily tuned by varying the thickness of the PS shell. Our method is very promising for preparing high-performance nanocomposites used in energy-storage devices.

  14. The 'emergent scaling' phenomenon and the dielectric properties of random resistor-capacitor networks

    CERN Document Server

    Bouamrane, R

    2003-01-01

    An efficient algorithm, based on the Frank-Lobb reduction scheme, for calculating the equivalent dielectric properties of very large random resistor-capacitor (R-C) networks has been developed. It has been used to investigate the network size and composition dependence of dielectric properties and their statistical variability. The dielectric properties of 256 samples of random networks containing: 512, 2048, 8192 and 32 768 components distributed randomly in the ratios 60% R-40% C, 50% R-50% C and 40% R-60% C have been computed. It has been found that these properties exhibit the anomalous power law dependences on frequency known as the 'universal dielectric response' (UDR). Attention is drawn to the contrast between frequency ranges across which percolation determines dielectric response, where considerable variability is found amongst the samples, and those across which power laws define response where very little variability is found between samples. It is concluded that the power law UDRs are emergent pr...

  15. Frequency and temperature dependence of dielectric and electric properties of Ba2-xSm4+2x/3Ti8O24 with structural analysis

    Directory of Open Access Journals (Sweden)

    Narang Sukhleen Bindra

    2015-06-01

    Full Text Available Dielectric ceramics samples of barium titanium oxide doped with samarium, having a complex structural formula of Ba2-xSm4+2x/3Ti8O24 (referred to as BST, were fabricated by a high temperature solid-state reaction technique with varying x (0.0, 0.2, 0.4, 0.6. X-ray diffraction technique was used to check the formation of particular phases. Scanning electron microscope technique was used to study the surface morphology of the samples. The samples were studied in a temperature range of 298 K to 623 K and frequency range of 10 KHz to 1 MHz. The dielectric constant (εr, loss tangent (tan δ, and AC conductivity (σAC were measured on sintered disks of BST samples. The DC resistivity of different compositions was measured at room temperature. Detailed studies of dielectric and electrical properties showed that these properties are strongly dependent on composition, frequency and temperature. The compounds showed stable behavior in lower temperature range (up to 523 K, therefore, they can be used in practical applications in this temperature range.

  16. Simulating the Radio-Frequency Dielectric Response of Relaxor Ferroelectrics: Combination of Coarse-Grained Hamiltonians and Kinetic Monte Carlo Simulations.

    Science.gov (United States)

    Geneste, Grégory; Bellaiche, L; Kiat, Jean-Michel

    2016-06-17

    The radio-frequency dielectric response of the lead-free Ba(Zr_{0.5}Ti_{0.5})O_{3} relaxor ferroelectric is simulated using a coarse-grained Hamiltonian. This concept, taken from real-space renormalization group theories, allows us to depict the collective behavior of correlated local modes gathered in blocks. Free-energy barriers for their thermally activated collective hopping are deduced from this ab initio-based approach, and used as input data for kinetic Monte Carlo simulations. The resulting numerical scheme allows us to simulate the dielectric response for external field frequencies ranging from kHz up to a few tens of MHz for the first time and to demonstrate, e.g., that local (electric or elastic) random fields lead to the dielectric relaxation in the radio-frequency range that has been observed in relaxors.

  17. Simulating the Radio-Frequency Dielectric Response of Relaxor Ferroelectrics: Combination of Coarse-Grained Hamiltonians and Kinetic Monte Carlo Simulations

    Science.gov (United States)

    Geneste, Grégory; Bellaiche, L.; Kiat, Jean-Michel

    2016-06-01

    The radio-frequency dielectric response of the lead-free Ba (Zr0.5Ti0.5)O3 relaxor ferroelectric is simulated using a coarse-grained Hamiltonian. This concept, taken from real-space renormalization group theories, allows us to depict the collective behavior of correlated local modes gathered in blocks. Free-energy barriers for their thermally activated collective hopping are deduced from this ab initio-based approach, and used as input data for kinetic Monte Carlo simulations. The resulting numerical scheme allows us to simulate the dielectric response for external field frequencies ranging from kHz up to a few tens of MHz for the first time and to demonstrate, e.g., that local (electric or elastic) random fields lead to the dielectric relaxation in the radio-frequency range that has been observed in relaxors.

  18. Hemifield dependence of responses to colour in human fusiform gyrus.

    Science.gov (United States)

    Gonzalez, Francisco; Relova, José Luis; Prieto, Angel; Peleteiro, Manuel; Romero, Maria C

    2006-08-01

    To investigate the hemifield dependence of visually evoked responses to colour in the human fusiform gyrus we recorded evoked potentials from subdural electrodes in a patient suffering from occipital epilepsy. The responses in the fusiform gyrus show a strong hemifield dependence and discriminate the onset from the offset of the stimulus. Additionally, we found responses to squares made of random dots, whereas no responses were found to squares with a homogeneous bright surface. Our findings further support the idea that the fusiform gyrus is related to colour and pattern perception. However, the hemifield dependence we found may indicate that further processing is required in order to combine information from both visual hemifields.

  19. Slow dielectric response of Debye-type in water and other hydrogen bonded liquids

    Science.gov (United States)

    Jansson, Helén; Bergman, Rikard; Swenson, Jan

    2010-05-01

    The slow dynamics of some hydrogen bonded glass-forming liquids has been investigated by broadband dielectric spectroscopy. We show that the polyalcohols glycerol, xylitol, and sorbitol, and mixtures of glycerol and water, and in fact, even pure water exhibit a process of Debye character at longer time-scales than the glass transition and viscosity related α-relaxation. Even if it is less pronounced, this process displays many similarities to the well-studied Debye-like process in monoalcohols. It can be observed in both the negative derivative of the real part of the permittivity or in the imaginary part of the permittivity, if the conductivity contribution is reduced. In the present study the conductivity contribution has been suppressed by use of a thin Teflon film placed between the sample and one of the electrodes. The new findings might have important implications for the structure and dynamics of hydrogen bonded liquids in general, and for water in particular.

  20. Dependence of Purcell effect on fluorescence wavelength in dye molecules on metal-dielectric multilayer hyperbolic metamaterials

    Science.gov (United States)

    Tsurumachi, Noriaki; Izawa, Hayato; Tomioka, Ryo; Sakata, Tomohiro; Suzuki, Makoto; Tanaka, Yasuhiro; Shimokawa, Fusao; Nakanishi, Shunsuke

    2016-02-01

    Recently, the enhancement of spontaneous emission, i.e., broadband Purcell effect, has been achieved using hyperbolic metamaterials. Hyperbolic metamaterials, which can be realized using a metal-dielectric multilayer structure, have an extremely large optical anisotropy of permittivity in both the parallel and perpendicular directions to the propagation of light, especially when the signs of permittivities in both directions differ. In this study, we investigated the conditions for realizing the broadband Purcell effect using dye molecules with different fluorescence wavelengths. Our fabricated metal-dielectric multilayer structure exhibited hyperbolic dispersion at wavelengths beyond 500 nm. In the case of coumarin 500 whose fluorescence peak is located at 500 nm, no broadband Purcell effect was observed. However, in the case of pyridine 1 whose fluorescence peak is located at 650 nm, we observed the successfull fluorescence lifetime shortening, i.e., the broadband Purcell effect.

  1. Experimental investigation of streamer affinity for dielectric surfaces

    NARCIS (Netherlands)

    Trienekens, D.J.M.; Nijdam, S.; Akkermans, G.; Plompen, I.; Christen, T.; Ebert, U.

    2015-01-01

    We have experimentally investigated the affinity of streamers for dielectric surfaces using stroboscopic imaging and stereo photography. Affinity of streamers for dielectric surfaces was found to depend on a wide set of parameters, including pressure, voltage, dielectric material and di

  2. Towards all-dielectric metamaterials and nanophotonics

    CERN Document Server

    Krasnok, Alexander; Petrov, Mikhail; Savelev, Roman; Belov, Pavel; Kivshar, Yuri

    2015-01-01

    We review a new, rapidly developing field of all-dielectric nanophotonics which allows to control both magnetic and electric response of structured matter by engineering the Mie resonances in high-index dielectric nanoparticles. We discuss optical properties of such dielectric nanoparticles, methods of their fabrication, and also recent advances in all-dielectric metadevices including couple-resonator dielectric waveguides, nanoantennas, and metasurfaces.

  3. Plant responsiveness to mycorrhizas differs from dependence upon mycorrhizas.

    Science.gov (United States)

    Janos, David P

    2007-03-01

    Soil phosphorus response curves of plants with and without mycorrhizas reflect two different, but complementary, phenomena. The first, plant responsiveness to mycorrhizas, is represented by the difference in growth between plants with and without mycorrhizas at any designated level of phosphorus availability. This is also a measure of mycorrhizal fungus effectiveness. The second, the lowest level of phosphorus availability at which plants can grow without mycorrhizas, is here termed dependence upon mycorrhizas. The latter definition differs from conventional usage which fails to distinguish dependence from responsiveness. Sigmoid curves generated by the three-parameter, logistic equation generally can model the responses of plants to mycorrhizas and phosphorus addition and can be used to assess responsiveness, effectiveness, and dependence. Such curves reveal that plant responsiveness or fungus effectiveness determined at a single level of phosphorus availability may be misleading when used to compare different host species' intrinsic capacities to respond to different mycorrhizal fungus species. Instead, the same relative position should be evaluated among phosphorus response curves for different species combinations. Dependence of a plant species known to benefit from mycorrhizas can be assessed with reference to only the phosphorus response curve of plants without mycorrhizas. Dependence is a constitutive property of plant species that can be used to classify them as facultatively or obligately mycotrophic. Dependence is a plant attribute upon which natural selection can act, but responsiveness and effectiveness cannot be selected directly because they are emergent properties of the interaction between plant and fungus species.

  4. Dielectric response of pure and doped-GaSe crystals studied by an indigenously developed broadband THz-TDS system

    Science.gov (United States)

    Das, Amit C.; Bhattacharya, S.; Mandal, K. C.; Mondal, S.; Jewariya, M.; Ozaki, T.; Bhaktha, S. N. B.; Datta, P. K.

    2016-04-01

    Publisher's Note: This paper, originally published on 12 July 2016, was replaced with a corrected/revised version on 26 July 2016. If you downloaded the original PDF but are unable to access the revision, please contact SPIE Digital Library Customer Service for assistance. We have developed a terahertz time domain spectroscopy system (THz TDS). For THz generation, optical rectification process and for detection, electro-optic sampling processes are used. Identical cut ZnTe crystals are used for both generation and detection of THz radiation.This spectroscopy system can be used for the noninvasive and contactless electrical and optical characterizations of various samples. In this work spectroscopic measurements of pure, Chromium and Indium doped GaSe crystals within 0.4 THz to 3 THz range are taken by the developed set-up to study the dielectric response of the samples.

  5. Liquid crystal wavefront corrector with modal response based on spreading of the electric field in a dielectric material.

    Science.gov (United States)

    Loktev, Mikhail; Vdovin, Gleb; Klimov, Nikolai; Kotova, Svetlana

    2007-03-19

    A novel liquid crystal (LC) wavefront corrector with smooth modal influence functions is proposed and realized. The device consists of a thin layer of planar aligned nematic LC sandwiched between a glass plate with a conductive electrode and a plate made of ceramic material with a very high dielectric constant. Control electrodes are positioned on the back side of the ceramic plate, opposite to the LC. The modal character of the response is determined by spreading of the electric field in the ceramic plate. The device implemented is operating in a reflective (mirror) mode; however, similar principles can be used to build a transmissive device. Low cost and simplicity of control make it a good alternative to continuous face-sheet deformable mirrors.

  6. Tuning of magnetic optical response in a dielectric nanoparticle by ultrafast photo-injection of dense electron-hole plasma

    CERN Document Server

    Makarov, Sergey; Mukhin, Ivan; Mozharov, Alexey; Milichko, Valentin; Krasnok, Alexander; Belov, Pavel

    2015-01-01

    We propose a novel approach for efficient tuning of optical properties of a high refractive index subwavelength nanoparticle with a magnetic Mie-type resonance by means of femtosecond laser irradiation. This concept is based on ultrafast photo-injection of dense (>10^20 cm^-3) electron-hole plasma within such nanoparticle, drastically changing its transient dielectric permittivity. This allows to manipulate by both electric and magnetic nanoparticle responses, resulting in dramatic changes of its scattering diagram and scattering cross section. We experimentally demonstrate 20 % tuning of reflectance of a single silicon nanoparticle by femtosecond laser pulses with wavelength in the vicinity of the magnetic dipole resonance. Such single-particle nanodevice enables to design fast and ultracompact optical switchers and modulators.

  7. Dielectric Properties of Yttria Ceramics at High Temperature

    Institute of Scientific and Technical Information of China (English)

    Jian Chen; Zheng-Ping Gao; Jin-Ming Wang; Da-Hai Zhang

    2007-01-01

    Based on Clausius-Mosotti equation and Debye relaxation theory, the dielectric model of yttria ceramics was developed according to the dielectric loss mechanism. The dielectric properties of yttria ceramics were predicted at high temperature. The temperature dependence and frequency dependence of dielectric constant and dielectric loss were discussed, respectively.As the result, the data calculated by theoretical dielectric model are in agreement with experimental data.

  8. Tunable Dielectric Responses Triggered by Dimensionality Modification in Organic-Inorganic Hybrid Phase Transition Compounds (C5H6N)CdnCl2n+1 (n = 1 and 2).

    Science.gov (United States)

    Sun, Xiao-Fen; Wang, Zhongxia; Li, Peng-Fei; Liao, Wei-Qiang; Ye, Heng-Yun; Zhang, Yi

    2017-03-20

    Two hybrids (C5H6N)CdCl3 (1) and (C5H6N)Cd2Cl5 (2) were synthesized by stoichiometric regulation of reactants. 1 with a one-dimensional chain-like structure shows a step-like dielectric anomaly at around 158 K. 2 with a layered structure undergoes a prominent phase transition in the vicinity of 182 K, accompanying obvious dielectric relaxation behavior in a broad temperature range. Systematic characterization, such as differential scanning calorimetry (DSC), single-crystal X-ray diffraction, and dielectric measurements, has demonstrated that the phase transitions of 1 and 2 are both attributable to the dynamic motion of the organic cation. Significantly, dimensionality modulation triggers the tunable dielectric responses in these two compounds. Thus, regulation of the phase transition temperature and dielectric responses in the various dimensions of the structure is a potentially effective method to construct tunable dielectric phase transition materials.

  9. Comment on "Optical Response of Gas-Phase Atoms at Less than lambda/80 from a Dielectric Surface" published by K. A. Whittaker et al.

    CERN Document Server

    Bloch, Daniel

    2015-01-01

    Comment on "Optical Response of Gas-Phase Atoms at Less than lambda/80 from a Dielectric Surface" published by K. A. Whittaker, J. Keaveney, I. G. Hughes, A. Sargsyan, D. Sarkisyan, C. S. Adams in Phys. Rev. Lett. Lett 112 253201 (2014)

  10. Dielectric relaxation of samarium aluminate

    Energy Technology Data Exchange (ETDEWEB)

    Sakhya, Anup Pradhan; Dutta, Alo; Sinha, T.P. [Bose Institute, Department of Physics, Kolkata (India)

    2014-03-15

    A ceramic SmAlO{sub 3} (SAO) sample is synthesized by the solid-state reaction technique. The Rietveld refinement of the X-ray diffraction pattern has been done to find the crystal symmetry of the sample at room temperature. An impedance spectroscopy study of the sample has been performed in the frequency range from 50 Hz to 1 MHz and in the temperature range from 313 K to 573 K. Dielectric relaxation peaks are observed in the imaginary parts of the spectra. The Cole-Cole model is used to analyze the dielectric relaxation mechanism in SAO. The temperature-dependent relaxation times are found to obey the Arrhenius law having an activation energy of 0.29 eV, which indicates that polaron hopping is responsible for conduction or dielectric relaxation in this material. The complex impedance plane plot of the sample indicates the presence of both grain and grain-boundary effects and is analyzed by an electrical equivalent circuit consisting of a resistance and a constant-phase element. The frequency-dependent conductivity spectra follow a double-power law due to the presence of two plateaus. (orig.)

  11. Response-reinforcer dependency and resistance to change.

    Science.gov (United States)

    Cançado, Carlos R X; Abreu-Rodrigues, Josele; Aló, Raquel Moreira; Hauck, Flávia; Doughty, Adam H

    2017-08-17

    The effects of the response-reinforcer dependency on resistance to change were studied in three experiments with rats. In Experiment 1, lever pressing produced reinforcers at similar rates after variable interreinforcer intervals in each component of a two-component multiple schedule. Across conditions, in the fixed component, all reinforcers were response-dependent; in the alternative component, the percentage of response-dependent reinforcers was 100, 50 (i.e., 50% response-dependent and 50% response-independent) or 10% (i.e., 10% response-dependent and 90% response-independent). Resistance to extinction was greater in the alternative than in the fixed component when the dependency in the former was 10%, but was similar between components when this dependency was 100 or 50%. In Experiment 2, a three-component multiple schedule was used. The dependency was 100% in one component and 10% in the other two. The 10% components differed on how reinforcers were programmed. In one component, as in Experiment 1, a reinforcer had to be collected before the scheduling of other response-dependent or independent reinforcers. In the other component, response-dependent and -independent reinforcers were programmed by superimposing a variable-time schedule on an independent variable-interval schedule. Regardless of the procedure used to program the dependency, resistance to extinction was greater in the 10% components than in the 100% component. These results were replicated in Experiment 3 in which, instead of extinction, VT schedules replaced the baseline schedules in each multiple-schedule component during the test. We argue that the relative change in dependency from Baseline to Test, which is greater when baseline dependencies are high rather than low, could account for the differential resistance to change in the present experiments. The inconsistencies in results across the present and previous experiments suggest that the effects of dependency on resistance to change are

  12. Theoretical study of optical dielectric response of ZnO nanostructure film deposited on silica substrate using Maxwell-Garnett effective medium theory

    Energy Technology Data Exchange (ETDEWEB)

    Bissa, Shivangi; Naruka, Preeti; Bishnoi, Nidhi [Dept. of Physics, Engineering College Bikaner-334004, Rajasthan, India shiwangi-bissa2005@yahoo.co.in (India)

    2016-05-06

    In the present study the dielectric optical response of various nanostructures of ZnO deposited on silica substrate has been studied using Maxwell-Garnett Effective Medium Theory. Using the volume filling factors for different nanostructures of ZnO the effective dielectric constant has been evaluated. The variation of this effective dielectric constant with the frequency of applied signal has been investigated. Moreover, the reflectance of the film, power absorption and variation of refractive index with frequency has been studied. The results obtained show that the quantum confinement effects in ZnO nano-structural films deposited on silica substrate give rise to distinct optical properties making it an ideal choice for high power THz generation.

  13. Exploring electromagnetic response of tellurium dielectric resonator metamaterial at the infrared wavelengths

    Science.gov (United States)

    Song, Jia-Kun; Song, Yu-Zhi; Li, Kang-Wen; Zhang, Zu-Yin; Xu, Yun; Wei, Xin; Song, Guo-Feng

    2015-10-01

    We numerically investigate the electromagnetic properties of tellurium dielectric resonator metamaterial at the infrared wavelengths. The transmission spectra, effective permittivity and permeability of the periodic tellurium metamaterial structure are investigated in detail. The linewidth of the structure in the direction of magnetic field Wx has effects on the position and strength of the electric resonance and magnetic resonance modes. With appropriately optimizing the geometric dimensions of the designed structure, the proposed tellurium metamaterial structure can provide electric resonance mode and high order magnetic resonance mode in the same frequency band. This would be helpful to analyze and design low-loss negative refraction index metamaterials at the infrared wavelengths. Project supported by the National Basic Research Program of China (Grant Nos. 2011CBA00608, 2012CB619203, 2015CB351902, and 2015CB932402), the National Key Research Program of China (Grant No. 2011ZX01015-001), and the National Natural Science Foundation of China (Grant Nos. 61036010, 61177070, 11374295, and U1431231).

  14. Matrix stiffness dependent electro-mechanical response of dipole grafted silicones

    Science.gov (United States)

    Kussmaul, Björn; Risse, Sebastian; Wegener, Michael; Kofod, Guggi; Krüger, Hartmut

    2012-06-01

    The properties of dielectric elastomer actuators can be optimized by modifying the dielectric or mechanical properties of the dielectric elastomer. This paper presents the simultaneous control of both dielectric and mechanical properties, in a silicone elastomer network comprising cross-linker, chains and grafted molecular dipoles. Chains with two different molecular weights were each combined with varying amounts of grafted dipole. Chemical and physical characterization showed that networks with stoichiometric control of cross-linking density and permittivity were obtained, and that longer chain lengths resulted in higher electrical field response due to the reduction in cross-linking density and correspondingly in mechanical stiffness. Both actuation sensitivities were enhanced by 6.3 and 4.6 times for the short and long chain matrix material, respectively.

  15. Frequency-dependent local field factors in dielectric liquids by a polarizable force field and molecular dynamics simulations

    Energy Technology Data Exchange (ETDEWEB)

    Davari, Nazanin; Haghdani, Shokouh; Åstrand, Per-Olof [Department of Chemistry, Norwegian University of Science and Technology (NTNU), Trondheim (Norway)

    2015-12-31

    A force field model for calculating local field factors, i.e. the linear response of the local electric field for example at a nucleus in a molecule with respect to an applied electric field, is discussed. It is based on a combined charge-transfer and point-dipole interaction model for the polarizability, and thereby it includes two physically distinct terms for describing electronic polarization: changes in atomic charges arising from transfer of charge between the atoms and atomic induced dipole moments. A time dependence is included both for the atomic charges and the atomic dipole moments and if they are assumed to oscillate with the same frequency as the applied electric field, a model for frequency-dependent properties are obtained. Furthermore, if a life-time of excited states are included, a model for the complex frequency-dependent polariability is obtained including also information about excited states and the absorption spectrum. We thus present a model for the frequency-dependent local field factors through the first molecular excitation energy. It is combined with molecular dynamics simulations of liquids where a large set of configurations are sampled and for which local field factors are calculated. We are normally not interested in the average of the local field factor but rather in configurations where it is as high as possible. In electrical insulation, we would like to avoid high local field factors to reduce the risk for electrical breakdown, whereas for example in surface-enhanced Raman spectroscopy, high local field factors are desired to give dramatically increased intensities.

  16. Effect of annealing on the temperature-dependent dielectric properties of LaAlO3 at terahertz frequencies

    Directory of Open Access Journals (Sweden)

    Xingquan Zou

    2012-03-01

    Full Text Available We present THz conductivity of LaAlO3 (LAO as a function of temperature and annealing, using terahertz time-domain spectroscopy (THz-TDS. We observed that, after annealing, spectral weight redistribution occurs, such that the real conductivity σ1(ω changed from a featureless and almost frequency-independent spectrum, into one where peaks occur near the phonon frequencies. These phonon frequencies increase with increasing temperature. We attribute the appearance of these absorption peaks to the diffusion and relocation of oxygen vacancies. The dielectric functions of annealed LAO are well fitted with the Drude-Lorentz model.

  17. Structural Response Analysis under Dependent Variables Based on Probability Boxes

    National Research Council Canada - National Science Library

    Xiao, Z; Yang, G

    2015-01-01

      This paper considers structural response analysis when structural uncertainty parameters distribution cannot be specified precisely due to lack of information and there are complex dependencies in the variables...

  18. A Tabulation and Critical Analysis of the Wavelength-Dependent Dielectric Image Coefficient for the Interaction Exerted by a Surface onto a Neighbouring Excited Atom

    CERN Document Server

    Saltiel, S; Ducloy, M; Bloch, Daniel; Ducloy, Martial; Saltiel, Solomon

    2006-01-01

    The near-field interaction of an atom with a dielectric surface is inversely proportional to the cube to the distance to the surface, and its coupling strength depends on a dielectric image coefficient. This coefficient, simply given in a pure electrostatic approach by (eps-1) / (eps+1) with eps the permittivity, is specific to the frequency of each of the various relevant atomic transition : it depends in a complex manner from the bulk material properties, and can exhibit resonances connected to the surface polariton modes. We list here the surface resonances for about a hundred of optical windows whose bulk properties are currently tabulated. The study concentrates on the infrared domain because it is the most relevant for atom-surface interaction. Aside from this tabulation, we discuss simple hints to estimate the position of surface resonances, and how uncertainties in the bulk data for the material dramatically affect the predictions for the image coefficient. We also evaluate the contribution of UV reso...

  19. Dependence of Ozone Generation on Gas Temperature Distribution in AC Atmospheric Pressure Dielectric Barrier Discharge in Oxygen

    Science.gov (United States)

    Takahashi, Go; Akashi, Haruaki

    AC atmospheric pressure multi-filament dielectric barrier discharge in oxygen has been simulated using two dimensional fluid model. In the discharge, three kinds of streamers have been obtained. They are primary streamers, small scale streamers and secondary streamers. The primary streamers are main streamers in the discharge and the small scale streamers are formed after the ceasing of the primary streamers. And the secondary streamers are formed on the trace of the primary streamers. In these streamers, the primary and the small scale streamers are very effective to generate O(3P) oxygen atoms which are precursor of ozone. And the ozone is generated mainly in the vicinity of the dielectrics. In high gas temperature region, ozone generation decreases in general. However, increase of the O(3P) oxygen atom density in high gas temperature region compensates decrease of ozone generation rate coefficient. As a result, amount of ozone generation has not changed. But if the effect of gas temperature was neglected, amount of ozone generation increases 10%.

  20. Optical control of dielectric permittivity in LaAl0.99Zn0.01O3-δ

    Science.gov (United States)

    Nagai, Takayuki; Takahashi, Hidefumi; Okazaki, Ryuji; Tanabe, Kenji; Terasaki, Ichiro; Taniguchi, Hiroki

    2017-04-01

    A photo-dielectric effect (i.e., a change in dielectric permittivity due to photo-irradiation) has been demonstrated in LaAl0.99Zn0.01O3-δ. Photo-irradiation with an incident energy of 3.4 eV was found to enhance the dielectric permittivity in LaAl0.99Zn0.01O3-δ over a wide frequency range from 100 Hz to 1 MHz. The change in dielectric permittivity in the high-frequency region hardly depended on frequency and was not accompanied by an increase in dielectric loss, indicating an intrinsic photo-dielectric effect in LaAl0.99Zn0.01O3-δ that is not due to photo-conduction. The dependence of the photo-dielectric effect on incident energy suggests the existence of deep in-gap states introduced by Zn substitution. The mechanism of the photo-dielectric effect in LaAl0.99Zn0.01O3-δ relates to the dielectric response of the photo-excited electrons trapped in the deep in-gap states, which work as effective polar displacements under an applied electric field. These findings are expected to contribute to the development of photo-capacitors that enable the remote control of the dielectric response via photo-irradiation.

  1. Does responsiveness to arbuscular mycorrhizas depend on plant invasive status?

    Science.gov (United States)

    1. Some posit invasive alien plants are less dependent on mycorrhizal associations than native plants, and thus weak mycorrhizal responsiveness may be a general mechanism of plant invasion. 2. Here, we tested whether mycorrhizal responsiveness varies by plant invasive status while controlling for ph...

  2. Dielectric Metamaterials

    Science.gov (United States)

    2015-05-29

    Final Report  29 May 2015 Dielectric Metamaterials SRI Project P21340 ONR Contract N00014-12-1-0722 Prepared by: Srini Krishnamurthy...2 2. Theory of Metamaterials ....................................................................................................... 2 2.1...accurately assess the impact of various forms of disorder on metamaterials (MMs) (both dielectric and metal inclusions); and (5) identify designs

  3. The role of relativity in the optical response of gold within the time-dependent current-density-functional theory.

    Science.gov (United States)

    Romaniello, P; de Boeij, P L

    2005-04-22

    We included relativistic effects in the formulation of the time-dependent current-density-functional theory for the calculation of linear response properties of metals [P. Romaniello and P. L. de Boeij, Phys. Rev. B (to be published)]. We treat the dominant scalar-relativistic effects using the zeroth-order regular approximation in the ground-state density-functional theory calculations, as well as in the time-dependent response calculations. The results for the dielectric function of gold calculated in the spectral range of 0-10 eV are compared with experimental data reported in literature and recent ellipsometric measurements. As well known, relativistic effects strongly influence the color of gold. We find that the onset of interband transitions is shifted from around 3.5 eV, obtained in a nonrelativistic calculation, to around 1.9 eV when relativity is included. With the inclusion of the scalar-relativistic effects there is an overall improvement of both real and imaginary parts of the dielectric function over the nonrelativistic ones. Nevertheless some important features in the absorption spectrum are not well reproduced, but can be explained in terms of spin-orbit coupling effects. The remaining deviations are attributed to the underestimation of the interband gap (5d-6sp band gap) in the local-density approximation and to the use of the adiabatic local-density approximation in the response calculation.

  4. Phase developments and dielectric responses of barium substituted four-layer CaBi4Ti4O15 Aurivillius

    Indian Academy of Sciences (India)

    Huiling Du; Xiang Shi; Huilu Li

    2011-10-01

    In this paper, mixed Ca–Ba oxide Ca1−BaBi4Ti4O15 (CBBT) ceramics, fabricated by the improved traditional ceramics process were investigated by doping concentrations of Ba ion up to = 0.9 (in steps of 0.1). At room temperature, an orthorhombic crystal system was confirmed using XRD, and their parameter was obtained using the Rietveld method. Dielectric properties and phase transitions were studied and are explained in terms of lattice response of these ceramics. A shift in ferroelectric–paraelectric phase transition (C) to lower temperatures and a corresponding decrease in permittivity peak with increasing concentration of Ba2+ are also observed. The ferroelectric–paraelectric phase transition of CBBT compounds is of normal type in nature, differing from the relaxor characteristic of BBT. The decrease of orthorhombicity in the lattice structure by the larger Ba2+ ion incorporation, indicating an approach of and , results in lower Curie temperature. Appearance of anomalous loss peaks of Ba-rich compounds at 530°C reveals a phase transition development trend from ferroelectric orthorhombic structure to the paraelectric orthorhombic structure. Relationship of polarization with lattice response is discussed.

  5. Principles of dielectric blood coagulometry as a comprehensive coagulation test.

    Science.gov (United States)

    Hayashi, Yoshihito; Brun, Marc-Aurèle; Machida, Kenzo; Nagasawa, Masayuki

    2015-10-06

    Dielectric blood coagulometry (DBCM) is intended to support hemostasis management by providing comprehensive information on blood coagulation from automated, time-dependent measurements of whole blood dielectric spectra. We discuss the relationship between the series of blood coagulation reactions, especially the aggregation and deformation of erythrocytes, and the dielectric response with the help of clot structure electron microscope observations. Dielectric response to the spontaneous coagulation after recalcification presented three distinct phases that correspond to (P1) rouleau formation before the onset of clotting, (P2) erythrocyte aggregation and reconstitution of aggregates accompanying early fibrin formation, and (P3) erythrocyte shape transformation and/or structure changes within aggregates after the stable fibrin network is formed and platelet contraction occurs. Disappearance of the second phase was observed upon addition of tissue factor and ellagic acid for activation of extrinsic and intrinsic pathways, respectively, which is attributable to accelerated thrombin generation. A series of control experiments revealed that the amplitude and/or quickness of dielectric response reflect platelet function, fibrin polymerization, fibrinolysis activity, and heparin activity. Therefore, DBCM sensitively measures blood coagulation via erythrocytes aggregation and shape changes and their impact on the dielectric permittivity, making possible the development of the battery of assays needed for comprehensive coagulation testing.

  6. Role of the magnetic ordering on the dielectric response of M2V2O7 (M = Co and Cu) divanadates

    Science.gov (United States)

    Sánchez-Andújar, M.; Yáñez-Vilar, S.; Mira, J.; Biskup, N.; Rivas, J.; Castro-García, S.; Señarís-Rodríguez, M. A.

    2011-03-01

    We have synthesized two divanadates M2V2O7 (M2+ = Co2+ and Cu2+), that are known to show different and complex magnetic arrangements at low temperatures and have studied their dielectric behavior. We have observed a change in the slope of the dielectric constant at the magnetic transition temperature, result which confirms the existence of magnetodielectric coupling in these two divanadates. The origin of the magnetodielectric coupling seems to be different in the Cu- and Co-compounds, although in both cases it is related to their frustrated magnetic arrangement. In Cu2V2O7, the dielectric anomaly arises from a spin canting due to the antisymmetric exchange which is allowed by structural symmetry. In the Co-divanadate, the structural symmetry does not allow antisymmetric exchange but the compound shows correlation between the behavior of the dielectric constant and inverse magnetization, which points to a dependence of its electrical polarization with the pair correlation function of neighboring magnetic spins.

  7. Dielectric relaxation and localized electron hopping in colossal dielectric (Nb,In)-doped TiO2 rutile nanoceramics.

    Science.gov (United States)

    Tsuji, Kosuke; Han, HyukSu; Guillemet-Fritsch, Sophie; Randall, Clive A

    2017-03-28

    Dielectric spectroscopy was performed on a Nb and In co-doped rutile TiO2 nano-crystalline ceramic (n-NITO) synthesized by a low-temperature spark plasma sintering (SPS) technique. The dielectric properties of the n-NITO were not largely affected by the metal electrode contacts. Huge dielectric relaxation was observed at a very low temperature below 35 K. Both the activation energy and relaxation time suggested that the electronic hopping motion is the underlying mechanism responsible for the colossal dielectric permittivity (CP) and its relaxation, instead of the internal barrier layer effect or a dipolar relaxation. With Havriliak-Negami (H-N) fitting, a relaxation time with a large distribution of dielectric relaxations was revealed. The broad distributed relaxation phenomena indicated that Nb and In were involved, controlling the dielectric relaxation by modifying the polarization mechanism and localized states. The associated distribution function is calculated and presented. The frequency-dependent a.c. conductance is successfully explained by a hopping conduction model of the localized electrons with the distribution function. It is demonstrated that the dielectric relaxation is strongly correlated with the hopping electrons in the localized states. The CP in SPS n-NITO is then ascribed to a hopping polarization.

  8. Frequency and voltage dependence of electric and dielectric properties of Au/TiO2/n-4H-SiC (metal-insulator-semiconductor) type Schottky barrier diodes

    Science.gov (United States)

    Tanrıkulu, E. E.; Yıldız, D. E.; Günen, A.; Altındal, Ş.

    2015-09-01

    The main electrical and dielectric properties of Au/TiO2/n-4H-SiC (MIS) type Schottky barrier diodes (SBDs) have been investigated as functions of frequency and applied bias voltage. We believe that the use of high dielectric interfacial layer between metal and semiconductor can improve the performance of Schottky diodes. From the experimental data, both electrical and dielectric parameters were found as strong function of frequency and applied bias voltage. The Fermi energy level (EF), the concentration of doping donor atoms (P), barrier height (ΦB) and series resistance (Rs) values were obtained from reverse and forward bias C-V characteristics. The changes in EF and ND with frequency are considerably low. Therefore, their values were taken at about constant. The real and imaginary parts of dielectric constant (\\varepsilon \\prime , \\varepsilon \\prime\\prime ), tangent loss (tanδ), ac electrical conductivity (σac), and real and imaginary parts of electric modulus (M‧ and M″) values were also obtained from reverse and forward bias C-V and G/ω-V characteristics. In addition, the voltage dependent profiles of all these electrical and dielectric parameters were drawn for each frequency. These results confirmed that both electrical and dielectric properties of Au/TiO2/n-4H-SiC (MIS) type SBD are quite sensitive to both the frequency and applied bias voltage due to surface polarization, density distribution of interface traps (Dit), and interfacial layer.

  9. Spatial scale dependency of the modelled climatic response to deforestation

    OpenAIRE

    Longobardi, P.; Montenegro, A.; H. Beltrami; M. Eby

    2012-01-01

    Deforestation is associated with increased atmospheric CO2 and alterations to the surface energy and mass balances that can lead to local and global climate changes. Previous modelling studies show that the global surface air temperature (SAT) response to deforestation depends on latitude, with most simulations showing that high latitude deforestation results in cooling, low latitude deforestation causes warming and that the mid latitude response is mixed. T...

  10. Relaxor Behavior and Dielectric Relaxation in Lead-Free Solid Solutions of (1 - x)(Bi0.5Na0.5TiO3)- x(SrNb2O6)

    Science.gov (United States)

    Bajpai, P. K.; Singh, K. N.; Tamrakar, Preeti

    2016-02-01

    Lead-free compositions (1 - x) (Bi0.5Na0.5TiO3)- x(SrNb2O6) (BNT-SN) are synthesized by a simple solid state reaction route. SN diffuse in distorted perovskite BNT for low concentrations of SN ( x ≤ 0.03) and are stabilized in rhombohedral perovskite phase with experimentally observed relative density of the ceramics >92%. A temperature-dependent dielectric response exhibits a broad dielectric peak that shows frequency-dependent shifts towards higher temperatures reflecting typical relaxor behavior. Modified Curie-Weiss law and Lorentz-type empirical relationships are used to fit the dielectric data that exhibit almost complete diffuse phase transition characteristics. In addition, significant dielectric dispersion is observed in a low-frequency regime in both components of the dielectric response and a small dielectric relaxation peak is observed. Cole-Cole plots indicate the poly-dispersive nature of the dielectric relaxation.

  11. Visible-Light Modulation on Lattice Dielectric Responses of a Piezo-Phototronic Soft Material.

    Science.gov (United States)

    Huang, E-Wen; Hsu, Yu-Hsiang; Chuang, Wei-Tsung; Ko, Wen-Ching; Chang, Chung-Kai; Lee, Chih-Kung; Chang, Wen-Chi; Liao, Tzu-Kang; Thong, Hao Cheng

    2015-12-16

    In situ synchrotron X-ray diffraction is used to investigate a three-way piezo-phototronic soft material. This new system is composed of a semi-crystalline poly(vinylidene fluoride-co-trifluoroethylene) piezoelectric polymer and titanium oxide nanoparticles. Under light illumination, photon-induced piezoelectric responses are nearly two times higher at both the lattice-structure and the macroscopic level than under conditions without light illumination. A mechanistic model is proposed.

  12. Evidence for anisotropic dielectric properties of monoclinic hafnia using valence electron energy-loss spectroscopy in high-resolution transmission electron microscopy and ab initio time-dependent density-functional theory

    Energy Technology Data Exchange (ETDEWEB)

    Guedj, C. [University Grenoble Alpes, F-38000 Grenoble (France); CEA, LETI, MINATEC Campus, F-38054 Grenoble (France); Hung, L.; Sottile, F. [LSI, CNRS, CEA, École Polytechnique, F-91128 Palaiseau (France); European Theoretical Spectroscopy Facility (ETSF) (France); Zobelli, A. [LPS, CNRS and University Paris Sud, F-91405 Orsay (France); Blaise, P. [University Grenoble Alpes, F-38000 Grenoble (France); CEA, LETI, MINATEC Campus, F-38054 Grenoble (France); European Theoretical Spectroscopy Facility (ETSF) (France); Olevano, V. [University Grenoble Alpes, F-38000 Grenoble (France); European Theoretical Spectroscopy Facility (ETSF) (France); CNRS, Institut Néel, F-38042 Grenoble (France)

    2014-12-01

    The effect of nanocrystal orientation on the energy loss spectra of monoclinic hafnia (m-HfO{sub 2}) is measured by high resolution transmission electron microscopy (HRTEM) and valence energy loss spectroscopy (VEELS) on high quality samples. For the same momentum-transfer directions, the dielectric properties are also calculated ab initio by time-dependent density-functional theory (TDDFT). Experiments and simulations evidence anisotropy in the dielectric properties of m-HfO{sub 2}, most notably with the direction-dependent oscillator strength of the main bulk plasmon. The anisotropic nature of m-HfO{sub 2} may contribute to the differences among VEELS spectra reported in literature. The good agreement between the complex dielectric permittivity extracted from VEELS with nanometer spatial resolution, TDDFT modeling, and past literature demonstrates that the present HRTEM-VEELS device-oriented methodology is a possible solution to the difficult nanocharacterization challenges given in the International Technology Roadmap for Semiconductors.

  13. Evidence for anisotropic dielectric properties of monoclinic hafnia using valence electron energy-loss spectroscopy in high-resolution transmission electron microscopy and ab initio time-dependent density-functional theory

    Science.gov (United States)

    Guedj, C.; Hung, L.; Zobelli, A.; Blaise, P.; Sottile, F.; Olevano, V.

    2014-12-01

    The effect of nanocrystal orientation on the energy loss spectra of monoclinic hafnia (m-HfO2) is measured by high resolution transmission electron microscopy (HRTEM) and valence energy loss spectroscopy (VEELS) on high quality samples. For the same momentum-transfer directions, the dielectric properties are also calculated ab initio by time-dependent density-functional theory (TDDFT). Experiments and simulations evidence anisotropy in the dielectric properties of m-HfO2, most notably with the direction-dependent oscillator strength of the main bulk plasmon. The anisotropic nature of m-HfO2 may contribute to the differences among VEELS spectra reported in literature. The good agreement between the complex dielectric permittivity extracted from VEELS with nanometer spatial resolution, TDDFT modeling, and past literature demonstrates that the present HRTEM-VEELS device-oriented methodology is a possible solution to the difficult nanocharacterization challenges given in the International Technology Roadmap for Semiconductors.

  14. Stretched exponential relaxation and ac universality in disordered dielectrics

    DEFF Research Database (Denmark)

    Milovanov, Alexander V.; Rypdal, Kristoffer; Juul Rasmussen, Jens

    2007-01-01

    This paper is concerned with the connection between the properties of dielectric relaxation and alternating-current (ac) conduction in disordered dielectrics. The discussion is divided between the classical linear-response theory and a self-consistent dynamical modeling. The key issues are stretc......This paper is concerned with the connection between the properties of dielectric relaxation and alternating-current (ac) conduction in disordered dielectrics. The discussion is divided between the classical linear-response theory and a self-consistent dynamical modeling. The key issues...... are stretched exponential character of dielectric relaxation, power-law power spectral density, and anomalous dependence of ac conduction coefficient on frequency. We propose a self-consistent model of dielectric relaxation in which the relaxations are described by a stretched exponential decay function....... Mathematically, our study refers to the expanding area of fractional calculus and we propose a systematic derivation of the fractional relaxation and fractional diffusion equations from the property of ac universality....

  15. Dielectric screening in semiconductors

    Science.gov (United States)

    Harrison, Walter A.; Klepeis, John E.

    1988-01-01

    Intra-atomic and interatomic Coulomb interactions are incorporated into bond-orbital theory, based upon universal tight-binding parameters, in order to treat the effects of charge redistribution in semiconductor bonds. The dielectric function ɛ(q) is obtained for wave numbers in a [100] direction. The screening of differences in average hybrid energy across a heterojunction is calculated in detail, indicating that the decay length for the potential depends upon the relative values of Madelung and intra-atomic Coulomb terms. The parameters used here predict an imaginary decay length and thus an oscillating potential near the interface. The same theory is applied to point defects by imbedding a cluster in a matrix lattice, taking charges in that lattice to be consistent with continuum theory. Illustrating the theory with a phosphorus impurity in silicon, it is seen that the impurity and its neighboring atoms have charges on the order of only one-tenth of an electronic charge, alternating in sign from neighbor to neighbor as for planar defects. Although there are shifts in the term values on the order of a volt, the difference in these shifts for neighboring atoms is much smaller so that the effect on the bonds is quite small. This behavior is analogous to the response of a dielectric continuum to a point charge: The medium is locally neutral except at the center of the cluster and there are slowly varying potentials e2/ɛr. Because of this slow variation, free-atom term values should ordinarily suffice for the calculation of bond properties and bond lengths at impurities. Corrections are larger for homovalent substitutions such as carbon in silicon.

  16. Linear-response thermal time-dependent density functional theory

    CERN Document Server

    Pribram-Jones, Aurora; Burke, Kieron

    2015-01-01

    The van Leeuwen proof of linear-response time-dependent density functional theory (TDDFT) is generalized to thermal ensembles. This allows generalization to finite temperatures of the Gross-Kohn relation, the exchange-correlation kernel of TDDFT, and fluctuation dissipation theorem for DFT. This produces a natural method for generating new thermal exchange-correlation (XC) approximations.

  17. Dielectric Behavior of Low Microwave Loss Unit Cell for All Dielectric Metamaterial

    Directory of Open Access Journals (Sweden)

    Tianhuan Luo

    2015-01-01

    Full Text Available With a deep study of the metamaterial, its unit cells have been widely extended from metals to dielectrics. The dielectric based unit cells attract much attention because of the advantage of easy preparation, tunability, and higher frequency response, and so forth. Using the conventional solid state method, we prepared a kind of incipient ferroelectrics (calcium titanate, CaTiO3 with higher microwave permittivity and lower loss, which can be successfully used to construct metamaterials. The temperature and frequency dependence of dielectric constant are also measured under different sintering temperatures. The dielectric spectra showed a slight permittivity decrease with the increase of temperature and exhibited a loss of 0.0005, combined with a higher microwave dielectric constant of ~167 and quality factor Q of 2049. Therefore, CaTiO3 is a kind of versatile and potential metamaterial unit cell. The permittivity of CaTiO3 at higher microwave frequency was also examined in the rectangular waveguide and we got the permittivity of 165, creating a new method to test permittivity at higher microwave frequency.

  18. Absorption in dielectric models

    CERN Document Server

    Churchill, R J

    2015-01-01

    We develop a classical microscopic model of a dielectric. The model features nonlinear interaction terms between polarizable dipoles and lattice vibrations. The lattice vibrations are found to act as a pseudo-reservoir, giving broadband absorption of electromagnetic radiation without the addition of damping terms in the dynamics. The effective permittivity is calculated using a perturbative iteration method and is found to have the form associated with real dielectrics. Spatial dispersion is naturally included in the model and we also calculate the wavevector dependence of the permittivity.

  19. Terahertz dielectric response of ferroelectric Ba(x)Sr(1-x)TiO3 thin films.

    Science.gov (United States)

    Kang, Seung Beom; Kwak, Min Hwan; Choi, Muhan; Kim, Sungil; Kim, Taeyong; Cha, Eun Jong; Kang, Kwang Yong

    2011-11-01

    Terahertz time-domain spectroscopy has been used to investigate the dielectric and optical properties of ferroelectric Ba(x)Sr(1-x)TiO(3) thin films for nominal x-values of 0.4, 0.6, and 0.8 in the frequency range of 0.3 to 2.5 THz. The ferroelectric thin films were deposited at approximately 700 nm thickness on [001] MgO substrate by pulsed laser deposition. The measured complex dielectric and optical constants were compared with the Cole-Cole relaxation model. The results show that the Cole-Cole relaxation model fits well with the data throughout the frequency range and the dielectric relaxation behavior of ferroelectric Ba(x)Sr(1-x)TiO(3) thin films varies with the films compositions. Among the compositions of Ba(x)Sr(1-x)TiO(3) films with different Ba/Sr ratios, Ba(0.6)Sr(0.4)TiO(3) has the highest dielectric constants and the shortest dielectric relaxation time.

  20. Exact response functions within the time-dependent Gutzwiller approach

    Science.gov (United States)

    Bünemann, J.; Wasner, S.; Oelsen, E. v.; Seibold, G.

    2015-02-01

    We investigate the applicability of the two existing versions of a time-dependent Gutzwiller approach (TDGA) beyond the frequently used limit of infinite spatial dimensions. To this end, we study the two-particle response functions of a two-site Hubbard model where we can compare the exact results and those derived from the TDGA. It turns out that only the more recently introduced version of the TDGA can be combined with a diagrammatic approach which allows for the evaluation of Gutzwiller wave functions in finite dimensions. For this TDGA method, we derive the time-dependent Lagrangian for general single-band Hubbard models.

  1. Field history dependence of nonlinear dielectric properties of Ba{sub 0.6}Sr{sub 0.4}TiO{sub 3} ceramics under bias electric field: Polarization behavior of polar nano-regions

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Xiaofei [School of Materials Science and Engineering, Wuhan University of Technology, Wuhan 430070 (China); Xu Qing, E-mail: xuqing@whut.edu.c [School of Materials Science and Engineering, Wuhan University of Technology, Wuhan 430070 (China); Liu Hanxing; Chen Wen [School of Materials Science and Engineering, Wuhan University of Technology, Wuhan 430070 (China); Chen Min; Kim, Bok-Hee [Faculty of Advanced Materials Engineering, Chonbuk National University, Jeonju 561-756 (Korea, Republic of)

    2011-04-01

    Nonlinear dielectric properties of Ba{sub 0.6}Sr{sub 0.4}TiO{sub 3} ceramics prepared by citrate method were investigated under bias electric field with respect to field history. X-ray diffraction analysis and temperature dependence of the dielectric constant ({epsilon}{sub r}) confirmed a macroscopically paraelectric state for the specimen at room temperature. A slim polarization versus electric field (P-E) hysteresis loop of the specimen at room temperature indicated the existence of polar nano-regions (PNRs) superimposed on the paraelectric background. The nonlinear dielectric properties in continuous cycles of bias field sweep displayed a strong sensitivity to the field history. This phenomenon was qualitatively explained in terms of an irreversible polarization evolution of the PNRs under the bias fields. A considerable decline of the tunability with the cycle number suggests an appreciable contribution of the PNRs to the dielectric nonlinearity. The polarization and size of the PNRs were determined by fitting the dielectric constants to a multipolarization mechanism model.

  2. Mesa-top quantum dot single photon emitter arrays: Growth, optical characteristics, and the simulated optical response of integrated dielectric nanoantenna-waveguide systems

    Science.gov (United States)

    Zhang, Jiefei; Chattaraj, Swarnabha; Lu, Siyuan; Madhukar, Anupam

    2016-12-01

    Nanophotonic quantum information processing systems require spatially ordered, spectrally uniform single photon sources (SPSs) integrated on-chip with co-designed light manipulating elements providing emission rate enhancement, emitted photon guidance, and lossless propagation. Towards this goal, we consider systems comprising an SPS array with each SPS coupled to a dielectric building block (DBB) based multifunctional light manipulation unit (LMU). For the SPS array, we report triggered single photon emission from GaAs(001)/InGaAs single quantum dots grown selectively on top of nanomesas using the approach of substrate-encoded size-reducing epitaxy (SESRE). Systematic temperature and power dependent photoluminescence (PL), PL excitation, time-resolved PL, and emission statistics studies reveal high spectral uniformity and single photon emission at 8 K with g(2)(0) of 0.19 ± 0.03. The SESRE based SPS arrays, following growth of a planarizing overlayer, are readily integrable with LMUs fabricated subsequently using either the 2D photonic crystal approach or, as theoretically examined here, DBB based LMUs. We report the simulated optical response of SPS embedded in DBB based nanoantenna-waveguide structures as the multifunctional LMU. The multiple functions of emission rate enhancement, guiding, and lossless propagation are derived from the behavior of the same collective Mie resonance (dominantly magnetic) of the interacting DBB based LMU tuned to the SPS targeted emission wavelength of 980 nm. The simulation utilizes an analytical approach that provides physical insight into the obtained numerical results. Together, the combined experimental and modelling demonstrations open a rich approach to implementing co-designed on-chip integrated SPS-LMUs that, in turn, serve as basic elements of integrated nanophotonic information processing systems.

  3. Doping dependent frequency response of MQW infrared photodetector

    Science.gov (United States)

    Billaha, Md. Aref; Das, Mukul K.; Kumar, S.

    2017-04-01

    This work is to study the effect of doping concentration in the active layer on the performance of multiple quantum well (MQW) infrared photodetector based on inter sub-band transitions. A theoretical model for the photocurrent and hence, responsivity of the detector in frequency domain is developed considering the effect of doping dependent absorption and carrier capture at the hetero-interfaces. Transit time and capture time limited bandwidth of the detector is computed from the frequency dependent photocurrent. Results show that, besides the usual effect of capture time, doping concentration in the active layer has an important effect on the bandwidth and responsivity of the device particularly for high value of capture time.

  4. Time dependent density functional calculation of plasmon response in clusters

    Institute of Scientific and Technical Information of China (English)

    Wang Feng(王锋); Zhang Feng-Shou(张丰收); Eric Suraud

    2003-01-01

    We have introduced a theoretical scheme for the efficient description of the optical response of a cluster based on the time-dependent density functional theory. The practical implementation is done by means of the fully fledged timedependent local density approximation scheme, which is solved directly in the time domain without any linearization.As an example we consider the simple Na2 cluster and compute its surface plasmon photoabsorption cross section, which is in good agreement with the experiments.

  5. Depth-Dependent Temporal Response Properties in Core Auditory Cortex

    OpenAIRE

    Christianson, G. Björn; Sahani, Maneesh; Linden, Jennifer F.

    2011-01-01

    The computational role of cortical layers within auditory cortex has proven difficult to establish. One hypothesis is that interlaminar cortical processing might be dedicated to analyzing temporal properties of sounds; if so, then there should be systematic depth-dependent changes in cortical sensitivity to the temporal context in which a stimulus occurs. We recorded neural responses simultaneously across cortical depth in primary auditory cortex and anterior auditory field of CBA/Ca mice, an...

  6. Temperature dependent study of Fin-FET drain current through optimization of controlling gate parameters and dielectric material

    Science.gov (United States)

    Das, Rinku Rani; Maity, Santanu; Muchahary, Deboraj; Bhunia, Chandan Tilak

    2017-03-01

    Various limitations, such as gate leakage through hot carrier tunnelling, parasitic resistance and capacitance, Drain Induced Barrier Lowering (DIBL), subthreshold slope (SS), and threshold voltage roll-off are present due to size reduction. Improvements in transistor speed and performance while, reducing the device dimensions is possible using the concept of Multiple-gate Field Effect phenomenon. Temperature dependency in thin fin transistor has been systematically studied with respect to the dependence on the fin width, fin height, and gate length. In this paper the performance of miniaturized Fin-FET structure is optimized. Also, temperature (300K, 400K and 500K) dependent performances on DIBL, SS and threshold voltage are observed and optimized.

  7. Space-charge-limited leakage current in high dielectric constant and ferroelectric thin films considering the field-dependent permittivity

    Science.gov (United States)

    Sun, J.; Zheng, X. J.; Yin, W.; Tang, M. H.; Li, W.

    2010-12-01

    Distinguishing from the traditional characterization on high-field leakage current density-voltage relationship, the field-dependent permittivity from the polarization derivative is used to solve the space-charge-limited conduction, and the simulated leakage current densities are compared with the previous experimental observations. The influences of the mobility, ferroelectric parameters, and film thickness on the leakage current densities are discussed. The results verify that the high-field quasi-Ohmic region observed experimentally may result from the field-dependent permittivity, and that the leakage current can be influenced by the ferroelectric polarization.

  8. Frequency- dependent cell responses to an electromagnetic stimulus

    Science.gov (United States)

    Taghian, Toloo; Sheikh, Abdul; Narmoneva, Daria; Kogan, Andrei

    2013-03-01

    External electric field (EF) acting on cells in the ionic environment can trigger a variety of mechanical and chemical cell responses that regulate cell functions, such as adhesion, migration and cell signaling; thus manipulation of EF can be used in therapeutic applications. To optimize this process, realistic studies of EF interaction with cells are essential. We have developed a combined theoretical-experimental approach to study cell response to the external EF in the native configuration. The cell is modeled as a membrane-enclosed hemisphere which is cultured on a substrate and is surrounded by electrolyte. Maxwell's equations are solved numerically (ANSYS-HFSS) to obtain 3D EF distribution inside and near the cell subjected to an external EF. Theoretical results indicate that the cell response is frequency dependent, where at low frequency EF is excluded from the cell interior while EF penetration into the cell increases for higher frequencies. In both regimes the spatial distribution and strength of induced EF in membrane varies with frequency. Experimental results are consistent with theoretical predictions and show frequency-dependent cell response, including both membrane-initiated and intracellular pathway activation and growth factor release. The authors acknowledge the financial support from the NSF (DMR-1206784 & DMR-0804199 to AK); the NIH (1R21 DK078814-01A1 to DN) and the University of Cincinnati (Interdisciplinary Faculty Research Support Grant to DN and AK).

  9. Fast response and low power consumption 1×2 thermo-optic switch based on dielectric-loaded surface plasmon polariton waveguides

    Science.gov (United States)

    Qi, Zhipeng; Hu, Guohua; Yun, Binfeng; Zhang, Xiong; Cui, Yiping

    2016-08-01

    In this paper, we present a 1 × 2 thermo-optic (TO) switch based on the integration of the dielectric-loaded surface plasmon polariton (SPP) waveguides with the silicon nanowires. Liquid-curable fluorinated resin (LFR) made of perfluorinated polymer was adopted as the ridge, which has a TO coefficient twice more than that of polymethyl methacrylate, leading to a significant decrease in the power consumption. It was shown that the response time of the dielectric-loaded SPP waveguide could be improved through optimizing the dimensions of the LFR polymer ridge without loss of relative high figure of merit and large confinement factor. Performance characteristics of such a 1 × 2 TO switch operating at a telecom wavelength of 1550 nm was investigated theoretically from the analysis of both heat and optical fields. The results reveal that a switching power as low as 7 mW and an extremely short switching time (with rise time of 3 μs and fall time of 6.7 μs) could be achieved with the proposed dielectric-loaded SPP-based 1 × 2 TO switch. In addition, the crosstalk could be enhanced to at least 40 dB with the applied power of 7 mW at the wavelength of 1550 nm, and it could be retained to be above 20 dB in the wavelength spectrum of 1500-1600 nm during the on/off state.

  10. Liquid crystal wavefront corrector with modal response based on spreading of the electric field in a dielectric material

    NARCIS (Netherlands)

    Loktev, M.; Vdovine, G.V.; Klimov, N.; Kotova, S.

    2007-01-01

    A novel liquid crystal (LC) wavefront corrector with smooth modal influence functions is proposed and realized. The device consists of a thin layer of planar aligned nematic LC sandwiched between a glass plate with a conductive electrode and a plate made of ceramic material with a very high dielectr

  11. Development of a dielectric ceramic based on diatomite-titania part two: dielectric properties characterization

    Directory of Open Access Journals (Sweden)

    Medeiros Jamilson Pinto

    1998-01-01

    Full Text Available Dielectric properties of sintered diatomite-titania ceramics are presented. Specific capacitance, dissipation factor, quality factor and dielectric constant were determined as a function of sintering temperature, titania content and frequency; the temperature coefficient of capacitance was measured as a function of frequency. Besides leakage current, the dependence of the insulation resistance and the dielectric strength on the applied dc voltage were studied. The results show that diatomite-titania compositions can be used as an alternative dielectric.

  12. Terahertz carrier dynamics and dielectric properties of GaN epilayers with different carrier concentrations

    Science.gov (United States)

    Guo, H. C.; Zhang, X. H.; Liu, W.; Yong, A. M.; Tang, S. H.

    2009-09-01

    Using terahertz time-domain spectroscopy, we measured the complex conductivity and dielectric function of n-type GaN with various carrier concentrations on sapphire substrate. The measured complex conductivity, which is due to the free carriers, is well fitted by simple Drude model. The contribution from the lattice vibration to the complex dielectric function increases with the decrease in free carrier concentration. A better fitting of the frequency-dependent complex dielectric response was obtained by considering both of the Drude and the classical damped oscillator model.

  13. Dielectric elastomer memory

    Science.gov (United States)

    O'Brien, Benjamin M.; McKay, Thomas G.; Xie, Sheng Q.; Calius, Emilio P.; Anderson, Iain A.

    2011-04-01

    Life shows us that the distribution of intelligence throughout flexible muscular networks is a highly successful solution to a wide range of challenges, for example: human hearts, octopi, or even starfish. Recreating this success in engineered systems requires soft actuator technologies with embedded sensing and intelligence. Dielectric Elastomer Actuator(s) (DEA) are promising due to their large stresses and strains, as well as quiet flexible multimodal operation. Recently dielectric elastomer devices were presented with built in sensor, driver, and logic capability enabled by a new concept called the Dielectric Elastomer Switch(es) (DES). DES use electrode piezoresistivity to control the charge on DEA and enable the distribution of intelligence throughout a DEA device. In this paper we advance the capabilities of DES further to form volatile memory elements. A set reset flip-flop with inverted reset line was developed based on DES and DEA. With a 3200V supply the flip-flop behaved appropriately and demonstrated the creation of dielectric elastomer memory capable of changing state in response to 1 second long set and reset pulses. This memory opens up applications such as oscillator, de-bounce, timing, and sequential logic circuits; all of which could be distributed throughout biomimetic actuator arrays. Future work will include miniaturisation to improve response speed, implementation into more complex circuits, and investigation of longer lasting and more sensitive switching materials.

  14. Optical studies of multilayer dielectric-metal-dielectric coatings as applied to solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Demichelis, F.; Minetti-Mezzetti, E.; Perotto, V.

    1982-09-01

    A study of antireflection coatings for solar cells which provide maximum transmittance in the range of the spectral response of the cell and maximum reflectance in the IR portion of the spectrum of normally incident radiation is reported. Dielectric-metal-dielectric filters with a relatively low number of dielectric layers are designed as coatings for silicon and GaAs solar cells.

  15. Improvement in temperature dependence and dielectric tunability properties of PbZr0.52Ti0.48O3 thin films using Ba(Mg1/3Ta2/3)O3 buffer layer

    Science.gov (United States)

    Wu, Zhi; Zhou, Jing; Chen, Wen; Shen, Jie; Yang, Huimin; Zhang, Shisai; Liu, Yueli

    2016-12-01

    In this paper, Pb(Zr0.52Ti0.48)O3 (PZT) thin films were prepared via sol-gel method. The effects of Ba(Mg1/3Ta2/3)O3 (BMT) buffer layer on the temperature dependence and dielectric tunability properties of PZT thin films were studied. As the thickness of BMT buffer layer increases, the tan δ and tunability of PZT thin films decrease while tunability still maintains above 10%. This result shows that BMT buffer layer can improve the dielectric tunability properties of PZT thin films. Furthermore, the temperature coefficient of the dielectric constant decreases from 2333.4 to 906.9 ppm/°C with the thickness of BMT buffer layer increasing in the range from 25 to 205 °C, indicating that BMT buffer layer can improve the temperature stability of PZT thin films. Therefore, BMT buffer layer plays a critical role in improving temperature dependence and dielectric tunability properties of PbZr0.52Ti0.48O3 thin films.

  16. Influence of multi-deposition multi-annealing on time-dependent dielectric breakdown characteristics of PMOS with high-/metal gate last process

    Institute of Scientific and Technical Information of China (English)

    王艳蓉; 朱慧珑; 赵超; 陈大鹏; 叶甜春; 杨红; 徐昊; 王晓磊; 罗维春; 祁路伟; 张淑祥; 王文武; 闫江

    2015-01-01

    A multi-deposition multi-annealing technique (MDMA) is introduced into the process of high-k/metal gate MOSFET for the gate last process to effectively reduce the gate leakage and improve the device’s performance. In this paper, we systematically investigate the electrical parameters and the time-dependent dielectric breakdown (TDDB) characteristics of positive channel metal oxide semiconductor (PMOS) under different MDMA process conditions, including the depo-sition/annealing (D&A) cycles, the D&A time, and the total annealing time. The results show that the increases of the number of D&A cycles (from 1 to 2) and D&A time (from 15 s to 30 s) can contribute to the results that the gate leakage current decreases by about one order of magnitude and that the time to fail (TTF) at 63.2% increases by about several times. However, too many D&A cycles (such as 4 cycles) make the equivalent oxide thickness (EOT) increase by about 1 ˚A and the TTF of PMOS worsen. Moreover, different D&A times and numbers of D&A cycles induce different breakdown mechanisms.

  17. Does Customer Loyalty Depend on Corporate Social Responsibility?

    Directory of Open Access Journals (Sweden)

    Stanisavljević Milena

    2017-03-01

    Full Text Available This paper presents the results of a study conducted to examine the dependence of customer loyalty on corporate social responsibility (CSR. CSR is a good opportunity for a company’s differentiation, but only if customers value the company’s efforts in this field. Loyalty is a primary goal of each company, but it is influenced by numerous factors. The goal of this paper was to examine if CSR influences customer loyalty as one possible factor. Based on the presented results, management recommendations are provided concerning business strategy, mission, and vision formulation, so companies can fulfill customers’ interests and gain their loyalty.

  18. Time- and space-dependent electric response of Ovonic devices

    Science.gov (United States)

    Jacoboni, C.; Piccinini, E.; Brunetti, R.; Rudan, M.

    2017-06-01

    A time- and space-dependent 1D model including the self-consistent solution of the Poisson equation is presented to study the electric response of nanometer Ovonic samples. The model accounts for the main features of the relevant microscopic processes occurring inside the material, and is easily incorporated in commercial device-simulation tools. Numerical results are presented and discussed for Ovonic samples of different lengths and material parameters, and successfully compared to recent optimized experimental results for AgInTeSb. The analysis indicates a very short intrinsic response time of Ovonic devices, of the order of tens of ps and a minimum device length of the order of 5-10 nm, in order to guarantee the device functionality. Tests on the sensitivity of the model on some physical parameters have also been carried out.

  19. Intrinsic microwave dielectric loss of lanthanum aluminate.

    Science.gov (United States)

    Shimada, Takeshi; Ichikawa, Koji; Minemura, Tetsuro; Yamauchi, Hiroki; Utsumi, Wataru; Ishii, Yoshinobu; Breeze, Jonathan; Alford, Neil McN

    2010-10-01

    The intrinsic dielectric properties of LaAlO₃ were investigated to understand the microwave properties of several materials containing LaAlO₃. In this study, LaAlO₃ single crystals were prepared by the Czochralski method. The temperature dependence of the dielectric properties and neutron inelastic scattering of the single crystals were measured. From these data, the intrinsic dielectric properties were evaluated and it was found that the dielectric loss of the LaAlO₃ includes two types of dielectric loss. One is a phonon absorption-related loss and the other is a component of the loss arising from Debye- type orientation polarization. The latter affects the room temperature dielectric loss in materials containing LaAlO₃. The present study suggests that avoiding this polarization loss is an important goal in decreasing the total dielectric loss.

  20. Hydration dependence of myoglobin dynamics studied with elastic neutron scattering, differential scanning calorimetry and broadband dielectric spectroscopy.

    Science.gov (United States)

    Fomina, Margarita; Schirò, Giorgio; Cupane, Antonio

    2014-01-01

    In this work we present a thorough investigation of the hydration dependence of myoglobin dynamics. The study is performed on D2O-hydrated protein powders in the hydration range 0Differential Scanning Calorimetry is used to obtain a thermodynamic description of the system. The effect of increasing hydration is to speed up the relaxations of the myoglobin+hydration water system and, thermodynamically, to decrease the glass transition temperature; these effects tend to saturate at h values greater than ~0.3. Moreover, the calorimetric scans put in evidence the occurrence of an endothermic peak whose onset temperature is located at ~230K independent of hydration. From the point of view of the protein equilibrium fluctuations, while the amplitude of anharmonic mean square displacements is found to increase with hydration, their onset temperature (i.e. the onset temperature of the well known "protein dynamical transition") is hydration independent. On the basis of the above results, the relevance of protein+hydration water relaxations and of the thermodynamic state of hydration water to the onset of the protein dynamical transition is discussed. Copyright © 2013 Elsevier B.V. All rights reserved.

  1. Interfaces: nanometric dielectrics

    Energy Technology Data Exchange (ETDEWEB)

    Lewis, T J [School of Informatics, University of Wales Bangor, Dean Street, Bangor, Gwynedd, LL70 9PX (United Kingdom)

    2005-01-21

    The incorporation of nanometric size particles in a matrix to form dielectric composites shows promise of materials (nanodielectrics) with new and improved properties. It is argued that the properties of the interfaces between the particles and the matrix, which will themselves be of nanometric dimensions, will have an increasingly dominant role in determining dielectric performance as the particle size decreases. The forces that determine the electrical and dielectric properties of interfaces are considered, with emphasis on the way in which they might influence composite behaviour. A number of examples are given in which interfaces at the nanometric level exercise both passive and active control over dielectric, optical and conductive properties. Electromechanical properties are also considered, and it is shown that interfaces have important electrostrictive and piezoelectric characteristics. It is demonstrated that the process of poling, namely subjecting macroscopic composite materials to electrical stress and raised temperatures to create piezoelectric materials, can be explained in terms of optimizing the collective response of the nanometric interfaces involved. If the electrical and electromechanical features are coupled to the long-established electrochemical properties, interfaces represent highly versatile active elements with considerable potential in nanotechnology.

  2. Interfaces: nanometric dielectrics

    Science.gov (United States)

    Lewis, T. J.

    2005-01-01

    The incorporation of nanometric size particles in a matrix to form dielectric composites shows promise of materials (nanodielectrics) with new and improved properties. It is argued that the properties of the interfaces between the particles and the matrix, which will themselves be of nanometric dimensions, will have an increasingly dominant role in determining dielectric performance as the particle size decreases. The forces that determine the electrical and dielectric properties of interfaces are considered, with emphasis on the way in which they might influence composite behaviour. A number of examples are given in which interfaces at the nanometric level exercise both passive and active control over dielectric, optical and conductive properties. Electromechanical properties are also considered, and it is shown that interfaces have important electrostrictive and piezoelectric characteristics. It is demonstrated that the process of poling, namely subjecting macroscopic composite materials to electrical stress and raised temperatures to create piezoelectric materials, can be explained in terms of optimizing the collective response of the nanometric interfaces involved. If the electrical and electromechanical features are coupled to the long-established electrochemical properties, interfaces represent highly versatile active elements with considerable potential in nanotechnology.

  3. Response mode-dependent differences in neurofunctional networks during response inhibition: an EEG-beamforming study.

    Science.gov (United States)

    Dippel, Gabriel; Chmielewski, Witold; Mückschel, Moritz; Beste, Christian

    2016-11-01

    Response inhibition processes are one of the most important executive control functions and have been subject to intense research in cognitive neuroscience. However, knowledge on the neurophysiology and functional neuroanatomy on response inhibition is biased because studies usually employ experimental paradigms (e.g., sustained attention to response task, SART) in which behavior is susceptible to impulsive errors. Here, we investigate whether there are differences in neurophysiological mechanisms and networks depending on the response mode that predominates behavior in a response inhibition task. We do so comparing a SART with a traditionally formatted task paradigm. We use EEG-beamforming in two tasks inducing opposite response modes during action selection. We focus on theta frequency modulations, since these are implicated in cognitive control processes. The results show that a response mode that is susceptible to impulsive errors (response mode used in the SART) is associated with stronger theta band activity in the left temporo-parietal junction. The results suggest that the response modes applied during response inhibition differ in the encoding of surprise signals, or related processes of attentional sampling. Response modes during response inhibition seem to differ in processes necessary to update task representations relevant to behavioral control.

  4. Spatial scale dependency of the modelled climatic response to deforestation

    Directory of Open Access Journals (Sweden)

    P. Longobardi

    2012-10-01

    Full Text Available Deforestation is associated with increased atmospheric CO2 and alterations to the surface energy and mass balances that can lead to local and global climate changes. Previous modelling studies show that the global surface air temperature (SAT response to deforestation depends on latitude, with most simulations showing that high latitude deforestation results in cooling, low latitude deforestation causes warming and that the mid latitude response is mixed. These earlier conclusions are based on simulated large scale land cover change, with complete removal of trees from whole latitude bands. Using a global climate model we determine effects of removing fractions of 5% to 100% of forested areas in the high, mid and low latitudes. All high latitude deforestation scenarios reduce mean global SAT, the opposite occurring for low latitude deforestation, although a decrease in SAT is registered over low latitude deforested areas. Mid latitude SAT response is mixed. For all simulations deforested areas tend to become drier and have lower surface air temperature, although soil temperatures increase over deforested mid and low latitude grid cells. For high latitude deforestation fractions of 45% and above, larger net primary productivity, in conjunction with colder and drier conditions after deforestation, cause an increase in soil carbon large enough to generate a previously not reported net drawdown of CO2 from the atmosphere. Our results support previous indications of the importance of changes in cloud cover in the modelled temperature response to deforestation at low latitudes. They also show the complex interaction between soil carbon dynamics and climate and the role this plays on the climatic response to land cover change.

  5. Dielectric Metamaterial Reflector

    Science.gov (United States)

    2017-02-14

    induced plasma coupled to a fluidized bed reactor have been utilized at SRI for 20+ years. As such, it would seem that Si particles may be easier to... etching process limits this process to cm2 areas. There have been several studies and demonstrations of the optical properties of dilute as well...magnetic optical response in a dielectric nanoparticle by ultrafast photoexcitation of dense electron–hole plasma . Nano letters, 15(9), pp.6187-6192. 34

  6. Impedance response and dielectric relaxation in co-precipitation derived ferrite (Ni,Zn)Fe{sub 2}O{sub 4} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Chen, D. G.; Tang, X. G.; Liu, Q. X.; Jiang, Y. P.; Ma, C. B.; Li, R. [School of Physics and Optoelectric Engineering, Guangdong University of Technology, Guangzhou Higher Education Mega Center, Guangzhou 510006 (China)

    2013-06-07

    Dielectric spectra and magnetization hysteresis loops were used to investigate the grain size effect with temperature on the electrical and magnetic response of co-precipitation derived spinel (Ni{sub 0.5}Zn{sub 0.5})Fe{sub 2}O{sub 4} (NZFO) ceramics. Remarkable dielectric relaxation phenomena of non-Debye type have been observed in each NZFO ceramics as confirmed by two kinds of Cole-Cole plots of the 1100 Degree-Sign C sintered samples, mainly due to the electron-hopping mechanism between n-type and p-type carriers and interfacial ion effect when applied an increase of temperature. The high and low response of grain and grain-boundary regions were determined by modeling the impedance experimental results on two equivalent RC circuits taking into account grain deep trap states. By employing the modified Arrhenius equation, activation energy values of different sintering temperatures were calculated and analyzed in combination with oxygen vacancy. In addition, the magnetization of various sintering temperature samples is dominated by cation distribution and surface effect in different particle ranges.

  7. Context and strain-dependent behavioral response to stress

    Directory of Open Access Journals (Sweden)

    Baum Amber E

    2008-06-01

    Full Text Available Abstract Background This study posed the question whether strain differences in stress-reactivity lead to differential behavioral responses in two different tests of anxiety. Strain differences in anxiety-measures are known, but strain differences in the behavioral responses to acute prior stress are not well characterized. Methods We studied male Fisher 344 (F344 and Wistar Kyoto (WKY rats basally and immediately after one hour restraint stress. To distinguish between the effects of novelty and prior stress, we also investigated behavior after repeated exposure to the test chamber. Two behavioral tests were explored; the elevated plus maze (EPM and the open field (OFT, both of which are thought to measure activity, exploration and anxiety-like behaviors. Additionally, rearing, a voluntary behavior, and grooming, a relatively automatic, stress-responsive stereotyped behavior were measured in both tests. Results Prior exposure to the test environment increased anxiety-related measures regardless of prior stress, reflecting context-dependent learning process in both tests and strains. Activity decreased in response to repeated testing in both tests and both strains, but prior stress decreased activity only in the OFT which was reversed by repeated testing. Prior stress decreased anxiety-related measures in the EPM, only in F344s, while in the OFT, stress led to increased freezing mainly in WKYs. Conclusion Data suggest that differences in stressfulness of these tests predict the behavior of the two strains of animals according to their stress-reactivity and coping style, but that repeated testing can overcome some of these differences.

  8. Dielectric Spectroscopy in Biomaterials: Agrophysics

    Directory of Open Access Journals (Sweden)

    Dalia El Khaled

    2016-04-01

    Full Text Available Being dependent on temperature and frequency, dielectric properties are related to various types of food. Predicting multiple physical characteristics of agri-food products has been the main objective of non-destructive assessment possibilities executed in many studies on horticultural products and food materials. This review manipulates the basic fundamentals of dielectric properties with their concepts and principles. The different factors affecting the behavior of dielectric properties have been dissected, and applications executed on different products seeking the characterization of a diversity of chemical and physical properties are all pointed out and referenced with their conclusions. Throughout the review, a detailed description of the various adopted measurement techniques and the mostly popular equipment are presented. This compiled review serves in coming out with an updated reference for the dielectric properties of spectroscopy that are applied in the agrophysics field.

  9. Decoherence in Josephson Qubits from Dielectric Loss

    OpenAIRE

    Martinis, John M.; Cooper, K. B.; McDermott, R.; Steffen, Matthias; Ansmann, Markus; Osborn, K; Cicak, K.; Oh, S.; Pappas, D. P.; Simmonds, R. W.; Yu, Clare C

    2005-01-01

    Dielectric loss from two-level states is shown to be a dominant decoherence source in superconducting quantum bits. Depending on the qubit design, dielectric loss from insulating materials or the tunnel junction can lead to short coherence times. We show that a variety of microwave and qubit measurements are well modeled by loss from resonant absorption of two-level defects. Our results demonstrate that this loss can be significantly reduced by using better dielectrics and fabricating junctio...

  10. Relativistic Spin-Isospin Dependent Response Function of Nucleus

    Institute of Scientific and Technical Information of China (English)

    LIU Liang-Gang; CHEN Wei; AI Bao-Quan; ZHENG Xiao-Ping; Masahiro Nakano

    2000-01-01

    A full relativistic formalism is employed to derive the relativistic particle-hole and delta-hole excitation polariza tion insertion of pion propagator in nuclear matter. The spin-isospin-dependent response function of nucleus at high energy-momentum transfer is calculated with the nuclear matter approximation. The short range correlation effect, two-nucleon absorption and nucleus form factor effects are included in the calculation. The position and width of the resonance peak of the spin-isospin mode are reproduced and found to be coincident with experiment data. The position of the peak and its width is sensitive to Landau-Migdal parameter g' which is about 0.6.

  11. Size-dependent antimicrobial response of zinc oxide nanoparticles.

    Science.gov (United States)

    Palanikumar, Loganathan; Ramasamy, Sinna Nadar; Balachandran, Chandrasekaran

    2014-06-01

    Antibacterial and antifungal activities of zinc oxide nanoparticles (ZnO NPs) were investigated against infectious microorganisms. ZnO NPs were prepared by wet chemical precipitation method varying the pH values. Particle size and morphology of the as-prepared ZnO powders were characterised by X-ray diffraction, Fourier transform infrared spectroscopy and transmission electron microscope. The zone of inhibition by NPs ranged from 0 to 17 mm. The lowest minimum inhibitory concentration value of NPs is 25 µg.ml(-1) against Staphylococcus epidermidis. These studies demonstrate that ZnO NPs have wide range of antimicrobial activities towards various microorganisms. The results obtained in the authors' study indicate that the inhibitory efficacy of ZnO NPs is significantly dependent on its chosen concentration and size. Significant inhibition in antibacterial response was observed for S. epidermidis when compared with control antibiotic.

  12. Dielectric response of MgO-added Ba{sub 0.6}Sr{sub 0.4}TiO{sub 3} ceramics under bias electric field: Examination of contributing mechanisms

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Xiaofei [School of Materials Science and Engineering, Wuhan University of Technology, Wuhan 430070 (China); School of Mathematics and Physics, Hubei Ploytechnic University, Huangshi, 435003 (China); Xu Qing, E-mail: xuqing@whut.edu.cn [School of Materials Science and Engineering, Wuhan University of Technology, Wuhan 430070 (China); Zhan Di; Liu Hanxing; Chen Wen; Huang Duanping [School of Materials Science and Engineering, Wuhan University of Technology, Wuhan 430070 (China)

    2013-02-01

    The structure and dielectric properties of (1-x)wt% Ba{sub 0.6}Sr{sub 0.4}TiO{sub 3}-xwt% MgO (x=0.5-60) ceramics were studied. The specimens with x{<=}1 had a single-phase perovskite structure and those with higher MgO contents presented a biphasic structure comprising Ba{sub 0.6}Sr{sub 0.4}TiO{sub 3} and MgO phases. The temperature dependence of the dielectric properties showed a frequency-dispersion behavior. The dielectric constants of the ceramics under bias electric field displayed an obvious deviation from the behavior as predicted by the phenomenological Johnson model. These dielectric phenomena were explained in relation to Mg{sup 2+} doping and polar nano-regions (PNRs) in Ba{sub 0.6}Sr{sub 0.4}TiO{sub 3} phase. Fitting the dielectric constants to a multipolarization mechanism model resolved intrinsic and extrinsic contributions to the dielectric non-linearity of the ceramics. Characteristic parameters of the contributions were determined from the fitting. Increasing MgO content led to a monotonous enhancement of the anharmonic coefficient ({alpha}). The polarization of PNRs tended to decrease with the increase of MgO content while the size of PNRs was insensitive to MgO content.

  13. Frequency and voltage dependence dielectric properties, ac electrical conductivity and electric modulus profiles in Al/Co{sub 3}O{sub 4}-PVA/p-Si structures

    Energy Technology Data Exchange (ETDEWEB)

    Bilkan, Çiğdem, E-mail: cigdembilkan@gmail.com [Department of Physics, Faculty of Sciences, The University of Çankırı Karatekin, 18100 Çankırı (Turkey); Azizian-Kalandaragh, Yashar [Department of Physics, Faculty of Science, The University of Mohaghegh Ardabili, Ardabil (Iran, Islamic Republic of); Altındal, Şemsettin [Department of Physics, Faculty of Sciences, The University of Gazi, 06500 Ankara (Turkey); Shokrani-Havigh, Roya [Department of Physics, Faculty of Science, The University of Mohaghegh Ardabili, Ardabil (Iran, Islamic Republic of)

    2016-11-01

    In this research a simple microwave-assisted method have been used for preparation of cobalt oxide nanostructures. The as-prepared sample has been investigated by UV–vis spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM). On the other hand, frequency and voltage dependence of both the real and imaginary parts of dielectric constants (ε′, ε″) and electric modulus (M′ and M″), loss tangent (tanδ), and ac electrical conductivity (σ{sub ac}) values of Al/Co{sub 3}O{sub 4}-PVA/p-Si structures were obtained in the wide range of frequency and voltage using capacitance (C) and conductance (G/ω) data at room temperature. The values of ε′, ε″ and tanδ were found to decrease with increasing frequency almost for each applied bias voltage, but the changes in these parameters become more effective in the depletion region at low frequencies due to the charges at surface states and their relaxation time and polarization effect. While the value of σ is almost constant at low frequency, increases almost as exponentially at high frequency which are corresponding to σ{sub dc} and σ{sub ac}, respectively. The M′ and M″ have low values at low frequencies region and then an increase with frequency due to short-range mobility of charge carriers. While the value of M′ increase with increasing frequency, the value of M″ shows two peak and the peaks positions shifts to higher frequency with increasing applied voltage due to the decrease of the polarization and N{sub ss} effects with increasing frequency.

  14. The electric field distribution in the brain during TTFields therapy and its dependence on tissue dielectric properties and anatomy: a computational study

    Science.gov (United States)

    Wenger, Cornelia; Salvador, Ricardo; Basser, Peter J.; Miranda, Pedro C.

    2015-09-01

    Tumor treating fields (TTFields) are a non-invasive, anti-mitotic and approved treatment for recurrent glioblastoma multiforme (GBM) patients. In vitro studies have shown that inhibition of cell division in glioma is achieved when the applied alternating electric field has a frequency in the range of 200 kHz and an amplitude of 1-3 V cm-1. Our aim is to calculate the electric field distribution in the brain during TTFields therapy and to investigate the dependence of these predictions on the heterogeneous, anisotropic dielectric properties used in the computational model. A realistic head model was developed by segmenting MR images and by incorporating anisotropic conductivity values for the brain tissues. The finite element method (FEM) was used to solve for the electric potential within a volume mesh that consisted of the head tissues, a virtual lesion with an active tumour shell surrounding a necrotic core, and the transducer arrays. The induced electric field distribution is highly non-uniform. Average field strength values are slightly higher in the tumour when incorporating anisotropy, by about 10% or less. A sensitivity analysis with respect to the conductivity and permittivity of head tissues shows a variation in field strength of less than 42% in brain parenchyma and in the tumour, for values within the ranges reported in the literature. Comparing results to a previously developed head model suggests significant inter-subject variability. This modelling study predicts that during treatment with TTFields the electric field in the tumour exceeds 1 V cm-1, independent of modelling assumptions. In the future, computational models may be useful to optimize delivery of TTFields.

  15. Frequency and voltage dependence dielectric properties, ac electrical conductivity and electric modulus profiles in Al/Co3O4-PVA/p-Si structures

    Science.gov (United States)

    Bilkan, Çiğdem; Azizian-Kalandaragh, Yashar; Altındal, Şemsettin; Shokrani-Havigh, Roya

    2016-11-01

    In this research a simple microwave-assisted method have been used for preparation of cobalt oxide nanostructures. The as-prepared sample has been investigated by UV-vis spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM). On the other hand, frequency and voltage dependence of both the real and imaginary parts of dielectric constants (ε‧, ε″) and electric modulus (M‧ and M″), loss tangent (tanδ), and ac electrical conductivity (σac) values of Al/Co3O4-PVA/p-Si structures were obtained in the wide range of frequency and voltage using capacitance (C) and conductance (G/ω) data at room temperature. The values of ε‧, ε″ and tanδ were found to decrease with increasing frequency almost for each applied bias voltage, but the changes in these parameters become more effective in the depletion region at low frequencies due to the charges at surface states and their relaxation time and polarization effect. While the value of σ is almost constant at low frequency, increases almost as exponentially at high frequency which are corresponding to σdc and σac, respectively. The M‧ and M″ have low values at low frequencies region and then an increase with frequency due to short-range mobility of charge carriers. While the value of M‧ increase with increasing frequency, the value of M″ shows two peak and the peaks positions shifts to higher frequency with increasing applied voltage due to the decrease of the polarization and Nss effects with increasing frequency.

  16. Ionic Structure at Dielectric Interfaces

    Science.gov (United States)

    Jing, Yufei

    The behavior of ions in liquids confined between macromolecules determines the outcome of many nanoscale assembly processes in synthetic and biological materials such as colloidal dispersions, emulsions, hydrogels, DNA, cell membranes, and proteins. Theoretically, the macromolecule-liquid boundary is often modeled as a dielectric interface and an important quantity of interest is the ionic structure in a liquid confined between two such interfaces. The knowledge gleaned from the study of ionic structure in such models can be useful in several industrial applications, such as biosensors, lithium-ion batteries double-layer supercapacitors for energy storage and seawater desalination. Electrostatics plays a critical role in the development of such functional materials. Many of the functions of these materials, result from charge and composition heterogeneities. There are great challenges in solving electrostatics problems in heterogeneous media with arbitrary shapes because electrostatic interactions remains unknown but depend on the particular density of charge distributions. Charged molecules in heterogeneous media affect the media's dielectric response and hence the interaction between the charges is unknown since it depends on the media and on the geometrical properties of the interfaces. To determine the properties of heterogeneous systems including crucial effects neglected in classical mean field models such as the hard core of the ions, the dielectric mismatch and interfaces with arbitrary shapes. The effect of hard core interactions accounts properly for short range interactions and the effect of local dielectric heterogeneities in the presence of ions and/or charged molecules for long-range interactions are both analyzed via an energy variational principle that enables to update charges and the medium's response in the same simulation time step. In particular, we compute the ionic structure in a model system of electrolyte confined by two planar dielectric

  17. Behavioral responses of wolves to roads: scale-dependent ambivalence

    Science.gov (United States)

    Nelson, Lindsey; Wabakken, Petter; Sand, Håkan; Liberg, Olof

    2014-01-01

    Throughout their recent recovery in several industrialized countries, large carnivores have had to cope with a changed landscape dominated by human infrastructure. Population growth depends on the ability of individuals to adapt to these changes by making use of new habitat features and at the same time to avoid increased risks of mortality associated with human infrastructure. We analyzed the summer movements of 19 GPS-collared resident wolves (Canis lupus L.) from 14 territories in Scandinavia in relation to roads. We used resource and step selection functions, including >12000 field-checked GPS-positions and 315 kill sites. Wolves displayed ambivalent responses to roads depending on the spatial scale, road type, time of day, behavioral state, and reproductive status. At the site scale (approximately 0.1 km2), they selected for roads when traveling, nearly doubling their travel speed. Breeding wolves moved the fastest. At the patch scale (10 km2), house density rather than road density was a significant negative predictor of wolf patch selection. At the home range scale (approximately 1000 km2), breeding wolves increased gravel road use with increasing road availability, although at a lower rate than expected. Wolves have adapted to use roads for ease of travel, but at the same time developed a cryptic behavior to avoid human encounters. This behavioral plasticity may have been important in allowing the successful recovery of wolf populations in industrialized countries. However, we emphasize the role of roads as a potential cause of increased human-caused mortality. PMID:25419085

  18. Reward-related neural responses are dependent on the beneficiary.

    Science.gov (United States)

    Braams, Barbara R; Güroğlu, Berna; de Water, Erik; Meuwese, Rosa; Koolschijn, P Cédric; Peper, Jiska S; Crone, Eveline A

    2014-07-01

    Prior studies have suggested that positive social interactions are experienced as rewarding. Yet, it is not well understood how social relationships influence neural responses to other persons' gains. In this study, we investigated neural responses during a gambling task in which healthy participants (N = 31; 18 females) could win or lose money for themselves, their best friend or a disliked other (antagonist). At the moment of receiving outcome, person-related activity was observed in the dorsal medial prefrontal cortex (dmPFC), precuneus and temporal parietal junction (TPJ), showing higher activity for friends and antagonists than for self, and this activity was independent of outcome. The only region showing an interaction between the person-participants played for and outcome was the ventral striatum. Specifically, the striatum was more active following gains than losses for self and friends, whereas for the antagonist this pattern was reversed. Together, these results show that, in a context with social and reward information, social aspects are processed in brain regions associated with social cognition (mPFC, TPJ), and reward aspects are processed in primary reward areas (striatum). Furthermore, there is an interaction of social and reward information in the striatum, such that reward-related activity was dependent on social relationship.

  19. Efficient evaluation of dielectric response functions and calculations of ground and excited state properties beyond local Density Functional approaches

    Science.gov (United States)

    Lu, Deyu; Li, Yan; Rocca, Dario; Viet Nguyen, H.; Gygi, Francois; Galli, Giulia

    2010-03-01

    A recently developed technique to diagonalize iteratively dielectric matrices [1], is used to carry out efficient, ab-initio calculations of dispersion interactions, and excited state properties of nanostructures. In particular, we present results for the binding energies of weakly bonded molecular crystals [2], obtained at the EXX/RPA level of theory, and for absorption spectra of semiconducting clusters, obtained by an iterative solution of the Bethe-Salpeter equations [3]. We show that the ability to obtain the eigenmodes of dielectric matrices from Density Functional perturbation theory, without computing single particle excited states, greatly improves the efficiency of both EXX/RPA and many body perturbation theory [3,4] calculations and opens the way to large scale computations. [1] H. Wilson, F. Gygi and G. Galli, Phys. Rev. B , 78, 113303, 2008; and H. Wilson, D. Lu, F. Gygi and G. Galli, Phys. Rev. B, 79, 245106, 2009. [2] D. Lu, Y. Li, D. Rocca and G. Galli, Phys. Rev. Lett, 102, 206411, 2009; and Y. Li, D. Lu, V. Nguyen and G. Galli, J. Phys. Chem. C (submitted) [3] D. Rocca, D. Lu and G. Galli, submitted. [4] D. Lu, F. Gygi and G. Galli, Phys. Rev. Lett. 100, 147601, 2008. Work was funded by DOE/Scidac DE-FC02-06ER25794 and DOE/BES DE-FG02-06ER46262.

  20. Broadband local dielectric spectroscopy

    Science.gov (United States)

    Labardi, M.; Lucchesi, M.; Prevosto, D.; Capaccioli, S.

    2016-05-01

    A route to extend the measurement bandwidth of local dielectric spectroscopy up to the MHz range has been devised. The method is based on a slow amplitude modulation at a frequency Ω of the excitation field oscillating at a frequency ω and the coherent detection of the modulated average electric force or force gradient at Ω. The cantilever mechanical response does not affect the measurement if Ω is well below its resonant frequency; therefore, limitations on the excitation field frequency are strongly reduced. Demonstration on a thin poly(vinyl acetate) film is provided, showing its structural relaxation spectrum on the local scale up to 45 °C higher than glass temperature, and nanoscale resolution dielectric relaxation imaging near conductive nanowires embedded in the polymer matrix was obtained up to 5 MHz frequency, with no physical reason to hinder further bandwidth extension.

  1. Giant dielectric response and low dielectric loss in Al{sub 2}O{sub 3} grafted CaCu{sub 3}Ti{sub 4}O{sub 12} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Rajabtabar-Darvishi, A. [School of Chemical Engineering and Technology, Harbin Institute of Technology, Harbin 150001 (China); Center for Surface and Nanoanalytics (ZONA), Johannes Kepler University, Altenberger Straße 69, 4040 Linz (Austria); Bayati, R., E-mail: reza.bayati@intel.com, E-mail: mbayati@ncsu.edu, E-mail: wdfei@hit.edu.cn [Intel Corporation, IMO-RA, RA2, Hillsboro, Oregon 97124 (United States); Sheikhnejad-Bishe, O. [School of Chemical Engineering and Technology, Harbin Institute of Technology, Harbin 150001 (China); Wang, L. D.; Li, W. L.; Sheng, J.; Fei, W. D., E-mail: reza.bayati@intel.com, E-mail: mbayati@ncsu.edu, E-mail: wdfei@hit.edu.cn [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China)

    2015-03-07

    This study sheds light on the effect of alumina on dielectric constant and dielectric loss of novel CaCu{sub 3}Ti{sub 4}O{sub 12} composite ceramics. Alumina, at several concentrations, was deposited on the surface of CaCu{sub 3}Ti{sub 4}O{sub 12} particles via sol-gel technique. The dielectric constant significantly increased for all frequencies and the dielectric loss substantially decreased for low and intermediate frequencies. These observations were attributed to the change in characteristics of grains and grain boundaries. It was found that the insulating properties of the grain boundaries are improved following the addition of Al{sub 2}O{sub 3}. The relative density of CaCu{sub 3}Ti{sub 4}O{sub 12}/Al{sub 2}O{sub 3} composite ceramics decreased compared to the pure CaCu{sub 3}Ti{sub 4}O{sub 12} and the grain size was greatly changed with the alumina content affecting the dielectric properties. With the addition of alumina into CaCu{sub 3}Ti{sub 4}O{sub 12}, tighter interfaces formed. The 6%- and 10%-alumina ceramics showed the minimum dielectric loss and the maximum dielectric constant, respectively. Both the dielectric constant and loss tangent decreased in the 20%-alumina ceramic due to the formation of CuO secondary phase. It was revealed that Al serves as an electron acceptor decreasing the electron concentration, if Al{sup 3+} ions substitute for Ti{sup 4+} ions, and as an electron donor increasing the electron concentration, if Al{sup 3+} ions substitute for Ca{sup 2+} ions. We established a processing-microstructure-properties paradigm which opens new avenues for novel applications of CaCu{sub 3}Ti{sub 4}O{sub 12}/Al{sub 2}O{sub 3} composite ceramics.

  2. Effects of Ni{sup 3+} substitution on structural and temperature dependent dielectrical properties of NdFeO{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Kaur, Pawanpreet, E-mail: merry2286@gmail.com; Pandit, Rabia, E-mail: merry2286@gmail.com; Sharma, K. K., E-mail: merry2286@gmail.com [Department of Physics, National Institute of Technology Hamirpur-177005, Himachal Pradesh (India); Kumar, Ravi [Beant College of Engineering and Technology Gurdaspur-143521, Punjab (India)

    2014-04-24

    The polycrystalline samples of NdFe{sub 1−x}Ni{sub x}O{sub 3} (x=0.0, 0.2) were prepared by solid state reaction route, the single phase of powdered samples were ensured by Rietveld refinement of their X-ray diffraction (XRD) data. We have also studied the variation of dielectric constant (ε′), tangent loss (tan δ) and AC conductivity (σ{sub ac}) as a function of frequency and temperature for both the compositions. It is noticed that both the increase in temperature and Ni{sup 3+} ion substitution results in enhancement of dielectric constant, tangent loss and AC conductivity.

  3. Response of the capacitance and dielectric loss of the SrRuO3/SrTiO3/SrRuO3 film heterostructures to variations in temperature and electric field

    Science.gov (United States)

    Boikov, Yu. A.; Danilov, V. A.

    2016-10-01

    Three-layer epitaxial heterostructures with a 750-nm-thick intermediate strontium titanate layer between two strontium ruthenate conductive thin-film electrodes have been grown by laser deposition. Photolithography and ion etching have been used to form film parallel-plate capacitors based on the grown heterostructures. The capacitance ( C) and dielectric loss tangent (tanδ) of the parallel-plate capacitors have been measured in the temperature range T = 4.2-300 K at an applied bias voltage of up to ±2.5 V and without it. At T > 100 K, the temperature dependence of the dielectric permittivity (ɛ) of the SrTiO3 intermediate layer is well approximated by the Curie-Weiss law taking into account the capacitance induced by the penetration of an electric field into the oxide electrodes. At T ≈ 20 K, the dielectric permittivity ɛ of the SrTiO3 intermediate layer decreases by approximately 20% in an electric field of 25 kV/cm. The dielectric loss tangent of the film capacitor heterostructures decreases monotonically with a decrease in the temperature in the range from 300 to 80 K and almost does not depend on the electric field strength. However, in the range from 80 to 4.2 K, the dielectric loss tangent increases nonmonotonically (abruptly) with a decrease in the temperature and decreases significantly in an applied electric field.

  4. The Theory of SERS on Dielectrics and Semiconductors

    CERN Document Server

    Polubotko, V P Chelibanov A M

    2016-01-01

    It is demonstrated that the reason of SERS on dielectric and semiconductor substrates is the enhancement of the electric field in the regions of the tops of the surface roughness with very small radius, or a very large curvature. The enhancement depends on the dielectric constant of the substrate and is stronger for a larger dielectric constant. It is indicated that the enhancement on dielectrics and semiconductors is stronger than on metals with the same modulus of the dielectric constant. The result obtained is confirmed by experimental data on the enhancement coefficients obtained for various semiconductor and dielectric substrates.

  5. Aging of Dielectric Properties below Tg

    DEFF Research Database (Denmark)

    Olsen, Niels Boye; Dyre, Jeppe; Christensen, Tage Emil

    The dielectric loss at 1Hz in TPP is studied during a temperature step from one equilibrium state to another. In the applied cryostate the temperature can be equilibrated on a timescale of 1 second. The aging time dependence of the dielectric loss is studied below Tg applying temperature steps...

  6. Electrical conductivity and dielectric studies of MnO2 doped V2O5

    Science.gov (United States)

    Tan, Foo Khoon; Hassan, Jumiah; Wahab, Zaidan Abd.; Azis, Raba'ah Syahidah

    The investigation on electrical conductivity and dielectric properties of mixed oxide of manganese (Mn) and vanadium (V) was carried out to study the mixed oxides response to different frequencies and different measuring temperatures. The frequency and temperature dependence of AC conductivity, dielectric constant and dielectric loss factor of mixed oxides were studied in the frequency range of 40 Hz-1 MHz and a temperature range of 30-250 °C. Since the mixed oxides are multi phase materials, hence the properties of the pure oxides are also presented in this study to discuss the multi phase behaviour of the mixed oxides. The XRD pattern shows the Mn-V oxide is multiphase and quantitative phase analysis was performed to determine the relative phases. The overall results indicate that with increasing temperature, the AC conductivity, dielectric constant, dielectric loss factor and loss tangent of the Mn-V mixed oxide increases. However, it shows an overlap in the dielectric constant at 225 °C and 250 °C due to the V2O5 phase in the mixed oxide. From the AC activation energy, the mixed oxides underwent conduction mechanism transition from band to hopping in the investigated frequency range. The MnV2O6 has relatively good resistivity, therefore the mixed oxide sintered at 550 °C with the highest composition of MnV2O6 gives the highest dielectric constant of 9845 at 1 kHz, and at 250 °C.

  7. Dielectric relaxation dependent memory elements in pentacene/[6,6]-phenyl-C61-butyric acid methyl ester bi-layer field effect transistors

    Energy Technology Data Exchange (ETDEWEB)

    Park, Byoungnam

    2015-03-02

    We fabricate a pentacene/[6,6]-phenyl-C{sub 61}-butyric acid methyl ester (PCBM) bi-layer field effect transistor (FET) featuring large hysteresis that can be used as memory elements. Intentional introduction of excess electron traps in a PCBM layer by exposure to air caused large hysteresis in the FET. The memory window, characterized by the threshold voltage difference, increased upon exposure to air and this is attributed to an increase in the number of electron trapping centers and (or) an increase in the dielectric relaxation time in the underlying PCBM layer. Decrease in the electron conduction in the PCBM close to the SiO{sub 2} gate dielectric upon exposure to air is consistent with the increase in the dielectric relaxation time, ensuring that the presence of large hysteresis in the FET originates from electron trapping at the PCBM not at the pentacene. - Highlights: • Charge trapping-induced memory effect was clarified using transistors. • The memory window can be enhanced by controlling charge trapping mechanism. • Memory transistors can be optimized by controlling dielectric relaxation time.

  8. Frequency Dependent Electrical and Dielectric Properties of Au/P3HT:PCBM:F4-TCNQ/n-Si Schottky Barrier Diode

    Science.gov (United States)

    Taşçıoğlu, İ.; Tüzün Özmen, Ö.; Şağban, H. M.; Yağlıoğlu, E.; Altındal, Ş.

    2017-04-01

    In this study, poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester: 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (P3HT:PCBM:F4-TCNQ) organic film was deposited on n-type silicon (n-Si) substrate by spin coating method. The electrical and dielectric analysis of Au/P3HT:PCBM:F4-TCNQ/n-Si Schottky barrier diode was conducted by means of capacitance-voltage ( C- V) and conductance-voltage ( G/ ω- V) measurements in the frequency range of 10 kHz-2 MHz. The C- V- f plots exhibit fairly large frequency dispersion due to excess capacitance caused by the presence of interface states ( N ss). The values of N ss located in semiconductor bandgap at the organic film/semiconductor interface were calculated by Hill-Coleman method. Experimental results show that dielectric constant ( ɛ') and dielectric loss ( ɛ″) decrease with increasing frequency, whereas loss tangent (tan δ) remains nearly the same. The decrease in ɛ' and ɛ″ was interpreted by the theory of dielectric relaxation due to interfacial polarization. It is also observed that ac electrical conductivity ( σ ac) and electric modulus ( M' and M″) increase with increasing frequency.

  9. Magnitude-dependent response of osteoblasts regulated by compressive stress

    Science.gov (United States)

    Shen, Xiao-qing; Geng, Yuan-ming; Liu, Ping; Huang, Xiang-yu; Li, Shu-yi; Liu, Chun-dong; Zhou, Zheng; Xu, Ping-ping

    2017-01-01

    The present study aimed to investigate the role of magnitude in adaptive response of osteoblasts exposed to compressive stress. Murine primary osteoblasts and MC3T3-E1 cells were exposed to compressive stress (0, 1, 2, 3, 4, and 5 g/cm2) in 3D culture. Cell viability was evaluated, and expression levels of Runx2, Alp, Ocn, Rankl, and Opg were examined. ALP activity in osteoblasts and TRAP activity in RAW264.7 cells co-cultured with MC3T3-E1 cells were assayed. Results showed that compressive stress within 5.0 g/cm2 did not influence cell viability. Both osteoblastic and osteoblast-regulated osteoclastic differentiation were enhanced at 2 g/cm2. An increase in stress above 2 g/cm2 did not enhance osteoblastic differentiation further but significantly inhibited osteoblast-regualted osteoclastic differentiation. This study suggested that compressive stress regulates osteoblastic and osteoclastic differentiation through osteoblasts in a magnitude-dependent manner. PMID:28317941

  10. Brain response to prosodic boundary cues depends on boundary position

    Directory of Open Access Journals (Sweden)

    Julia eHolzgrefe

    2013-07-01

    Full Text Available Prosodic information is crucial for spoken language comprehension and especially for syntactic parsing, because prosodic cues guide the hearer’s syntactic analysis. The time course and mechanisms of this interplay of prosody and syntax are not yet well understood. In particular, there is an ongoing debate whether local prosodic cues are taken into account automatically or whether they are processed in relation to the global prosodic context in which they appear. The present study explores whether the perception of a prosodic boundary is affected by its position within an utterance. In an event-related potential (ERP study we tested if the brain response evoked by the prosodic boundary differs when the boundary occurs early in a list of three names connected by conjunctions (i.e., after the first name as compared to later in the utterance (i.e., after the second name. A closure positive shift (CPS — marking the processing of a prosodic phrase boundary — was elicited only for stimuli with a late boundary, but not for stimuli with an early boundary. This result is further evidence for an immediate integration of prosodic information into the parsing of an utterance. In addition, it shows that the processing of prosodic boundary cues depends on the previously processed information from the preceding prosodic context.

  11. Dielectric metasurfaces

    Science.gov (United States)

    Valentine, Jason

    While plasmonics metasurfaces have seen much development over the past several years, they still face throughput limitations due to ohmic losses. On the other hand, dielectric resonators and associated metasurfaces can eliminate the issue of ohmic loss while still providing the freedom to engineer the optical properties of the composite. In this talk, I will present our recent efforts to harness this freedom using metasurfaces formed from silicon and fabricated using CMOS-compatible techniques. Operating in the telecommunications band, I will discuss how we have used this platform to realize a number of novel functionalities including wavefront control, near-perfect reflection, and high quality factor resonances. In many cases the optical performance of these silicon-based metasurfaces can surpass their plasmonic counterparts. Furthermore, for some cases the surfaces are more amenable to large-area fabrication techniques.

  12. Copper response regulator1-dependent and -independent responses of the Chlamydomonas reinhardtii transcriptome to dark anoxia.

    Science.gov (United States)

    Hemschemeier, Anja; Casero, David; Liu, Bensheng; Benning, Christoph; Pellegrini, Matteo; Happe, Thomas; Merchant, Sabeeha S

    2013-09-01

    Anaerobiosis is a stress condition for aerobic organisms and requires extensive acclimation responses. We used RNA-Seq for a whole-genome view of the acclimation of Chlamydomonas reinhardtii to anoxic conditions imposed simultaneously with transfer to the dark. Nearly 1.4 × 10(3) genes were affected by hypoxia. Comparing transcript profiles from early (hypoxic) with those from late (anoxic) time points indicated that cells activate oxidative energy generation pathways before employing fermentation. Probable substrates include amino acids and fatty acids (FAs). Lipid profiling of the C. reinhardtii cells revealed that they degraded FAs but also accumulated triacylglycerols (TAGs). In contrast with N-deprived cells, the TAGs in hypoxic cells were enriched in desaturated FAs, suggesting a distinct pathway for TAG accumulation. To distinguish transcriptional responses dependent on copper response regulator1 (CRR1), which is also involved in hypoxic gene regulation, we compared the transcriptomes of crr1 mutants and complemented strains. In crr1 mutants, ~40 genes were aberrantly regulated, reaffirming the importance of CRR1 for the hypoxic response, but indicating also the contribution of additional signaling strategies to account for the remaining differentially regulated transcripts. Based on transcript patterns and previous results, we conclude that nitric oxide-dependent signaling cascades operate in anoxic C. reinhardtii cells.

  13. All-dielectric metamaterials.

    Science.gov (United States)

    Jahani, Saman; Jacob, Zubin

    2016-01-01

    The ideal material for nanophotonic applications will have a large refractive index at optical frequencies, respond to both the electric and magnetic fields of light, support large optical chirality and anisotropy, confine and guide light at the nanoscale, and be able to modify the phase and amplitude of incoming radiation in a fraction of a wavelength. Artificial electromagnetic media, or metamaterials, based on metallic or polar dielectric nanostructures can provide many of these properties by coupling light to free electrons (plasmons) or phonons (phonon polaritons), respectively, but at the inevitable cost of significant energy dissipation and reduced device efficiency. Recently, however, there has been a shift in the approach to nanophotonics. Low-loss electromagnetic responses covering all four quadrants of possible permittivities and permeabilities have been achieved using completely transparent and high-refractive-index dielectric building blocks. Moreover, an emerging class of all-dielectric metamaterials consisting of anisotropic crystals has been shown to support large refractive index contrast between orthogonal polarizations of light. These advances have revived the exciting prospect of integrating exotic electromagnetic effects in practical photonic devices, to achieve, for example, ultrathin and efficient optical elements, and realize the long-standing goal of subdiffraction confinement and guiding of light without metals. In this Review, we present a broad outline of the whole range of electromagnetic effects observed using all-dielectric metamaterials: high-refractive-index nanoresonators, metasurfaces, zero-index metamaterials and anisotropic metamaterials. Finally, we discuss current challenges and future goals for the field at the intersection with quantum, thermal and silicon photonics, as well as biomimetic metasurfaces.

  14. All-dielectric metamaterials

    Science.gov (United States)

    Jahani, Saman; Jacob, Zubin

    2016-01-01

    The ideal material for nanophotonic applications will have a large refractive index at optical frequencies, respond to both the electric and magnetic fields of light, support large optical chirality and anisotropy, confine and guide light at the nanoscale, and be able to modify the phase and amplitude of incoming radiation in a fraction of a wavelength. Artificial electromagnetic media, or metamaterials, based on metallic or polar dielectric nanostructures can provide many of these properties by coupling light to free electrons (plasmons) or phonons (phonon polaritons), respectively, but at the inevitable cost of significant energy dissipation and reduced device efficiency. Recently, however, there has been a shift in the approach to nanophotonics. Low-loss electromagnetic responses covering all four quadrants of possible permittivities and permeabilities have been achieved using completely transparent and high-refractive-index dielectric building blocks. Moreover, an emerging class of all-dielectric metamaterials consisting of anisotropic crystals has been shown to support large refractive index contrast between orthogonal polarizations of light. These advances have revived the exciting prospect of integrating exotic electromagnetic effects in practical photonic devices, to achieve, for example, ultrathin and efficient optical elements, and realize the long-standing goal of subdiffraction confinement and guiding of light without metals. In this Review, we present a broad outline of the whole range of electromagnetic effects observed using all-dielectric metamaterials: high-refractive-index nanoresonators, metasurfaces, zero-index metamaterials and anisotropic metamaterials. Finally, we discuss current challenges and future goals for the field at the intersection with quantum, thermal and silicon photonics, as well as biomimetic metasurfaces.

  15. Attosecond clocking of scattering dynamics in dielectrics

    Science.gov (United States)

    Kling, Matthias

    2016-05-01

    In the past few years electronic-device scaling has progressed rapidly and miniaturization has reached physical gate lengths below 100 nm, heralding the age of nanoelectronics. Besides the effort in size scaling of integrated circuits, tremendous progress has recently been made in increasing the switching speed where strong-field-based ``dielectric-electronics'' may push it towards the petahertz frontier. In this contest, the investigation of the electronic collisional dynamics occurring in a dielectric material is of primary importance to fully understand the transport properties of such future devices. Here, we demonstrate attosecond chronoscopy of electron collisions in SiO2. In our experiment, a stream of isolated aerodynamically focused SiO2 nanoparticles of 50 nm diameter was delivered into the laser interaction region. Photoemission is initiated by an isolated 250 as pulse at 35 eV and the electron dynamics is traced by attosecond streaking using a delayed few-cycle laser pulse at 700 nm. Electrons were detected by a kilohertz, single-shot velocity-map imaging spectrometer, permitting to separate frames containing nanoparticle signals from frames containing the response of the reference gas only. We find that the nanoparticle photoemission exhibits a positive temporal shift with respect to the reference. In order to understand the physical origin of the shift we performed semi-classical Monte-Carlo trajectory simulations taking into account the near-field distributions in- and outside the nanoparticles as obtained from Mie theory. The simulations indicate a pronounced dependence of the streaking time shift near the highest measured electron energies on the inelastic scattering time, while elastic scattering only shows a small influence on the streaking time shift for typical dielectric materials. We envision our approach to provide direct time-domain access to inelastic scattering for a wide range of dielectrics.

  16. Grain size and Fe{sup 2+} concentration-dependent magnetic, dielectric, and magnetodielectric properties of Y{sub 3}Fe{sub 5}O{sub 12} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Huarui [National Laboratory of Solid State Microstructures and Physics School, Nanjing University, Nanjing, 210093 (China); College of Physics and Electronic Engineering, Xinxiang University, Xinxiang, 453003 (China); Huang, Fengzhen; Lu, Xiaomei; Zhu, Jinsong [National Laboratory of Solid State Microstructures and Physics School, Nanjing University, Nanjing, 210093 (China); Collaborative Innovation Center of Advanced Microstructures, Nanjing, 210093 (China); Lu, Xueliang; Xu, Tingting; Ti, Ruixia; Jin, Yaming [National Laboratory of Solid State Microstructures and Physics School, Nanjing University, Nanjing, 210093 (China)

    2016-01-15

    Y{sub 3}Fe{sub 5}O{sub 12} ceramics are prepared by the solid state reaction method. Grain size and Fe{sup 2+} concentration-dependent magnetic, dielectric, and magnetodielectric properties are investigated systematically. It is found that grain size and Fe{sup 2+} concentration increase with increasing sintering temperature, which thus results in increased saturation magnetization while decreased coercive field and remanent magnetization. Three sets of dielectric relaxation are observed in temperature range from 10 to 500 K, which are considered to be originated from quantum tunneling effect of electrons, electron hopping between Fe{sup 2+} and Fe{sup 3+}, and the migration of oxygen vacancies, respectively. Cole-Cole fitting results of relaxation II indicate that a correlation exists among the hopping electrons, and the correlation is strengthened as Fe{sup 2+} concentration increases, which in turn results in easier hopping process and decreased activation energy. More interesting, YIG ceramics sintered at 1350 C show both considerable magnetic and dielectric properties at room temperature, opening a new window for the application of YIG as a possible multi-susceptible single-phase material. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  17. Dielectric properties of piezoelectric 3–0 composites of lithium ferrite/barium titanate

    Indian Academy of Sciences (India)

    P Sarah; S V Suryanarayana

    2003-12-01

    Piezoelectric 3–0 composite ceramics are prepared from a mixture of barium titanate and lithium ferrite phase constituents. Dielectric properties of composites are affected by a number of parameters that include electrical properties, size, shape and amount of constituent phases. The frequency dependent measurements can provide additional insight into mechanisms controlling electrical response. Frequency dependence of dielectric constant plots of lithium ferrite/barium titanate composites will be given and the relevance of trends seen in them will be discussed. Connectivity in composites developed is studied.

  18. Growth-stage dependent crop yield response to ozone exposure.

    Science.gov (United States)

    Younglove, T; McCool, P M; Musselman, R C; Kahl, M E

    1994-01-01

    Data from four crop yield-loss field trials were examined to determine if analysis using an imposed phenological weighting function based on seasonal growth stage would provide a more accurate indication of impact of ozone exposure. Alfalfa (Medicago sativa L. cv. Moapa 69), dry bean (Phaseolus vulgaris L. cv. California Dark Red kidney), fresh market and processing tomato (Lycopersicon esculentum Mill. cv. 6718 VF and VF-145-B7879, respectively) were grown at 9-11 ambient field plots within southern California comprising an ambient gradient of ozone. The growing season for each crop was artificially divided into 'quarters' composed of equal numbers of whole days and roughly corresponding to specific growth stages. Ozone exposure was calculated for each of these 'quarters' and regressed against final crop yield using 163 different exposure statistics. Weighting functions were developed using reciprocal residual mean square (1/RMS) or percentage of the best 100 exposure statistics of the 163 tested (TOP100) for each of the quarters. The third quarter of the alfalfa season was clearly most responsive to ozone as measured by both of the weighting functions. Third quarter ozone was also weighted highest by both weighting functions for dry bean. Fresh market and processing tomato were each influenced the greatest by second quartero zone as demonstrated by both weighting functions. The occurrence of ozone during physiologically important events (flowering and initial fruit set in second quarter for tomato; pod development in third quarter for dry bean) appeared to influence the yield of these crops the greatest. Growth-stage-dependent phenological weighting of pollutant exposure may result in more effective predictions of levels of ozone exposure resulting in yield reductions.

  19. B6-responsive disorders: a model of vitamin dependency.

    Science.gov (United States)

    Clayton, Peter T

    2006-01-01

    Pyridoxal phosphate is the cofactor for over 100 enzyme-catalysed reactions in the body, including many involved in the synthesis or catabolism of neurotransmitters. Inadequate levels of pyridoxal phosphate in the brain cause neurological dysfunction, particularly epilepsy. There are several different mechanisms that lead to an increased requirement for pyridoxine and/or pyridoxal phosphate. These include: (i) inborn errors affecting the pathways of B(6) vitamer metabolism; (ii) inborn errors that lead to accumulation of small molecules that react with pyridoxal phosphate and inactivate it; (iii) drugs that react with pyridoxal phosphate; (iv) coeliac disease, which is thought to lead to malabsorption of B(6) vitamers; (v) renal dialysis, which leads to increased losses of B(6) vitamers from the circulation; (vi) drugs that affect the metabolism of B(6) vitamers; and (vii) inborn errors affecting specific pyridoxal phosphate-dependent enzymes. The last show a very variable degree of pyridoxine responsiveness, from 90% in X-linked sideroblastic anaemia (delta-aminolevulinate synthase deficiency) through 50% in homocystinuria (cystathionine beta-synthase deficiency) to 5% in ornithinaemia with gyrate atrophy (ornithine delta-aminotransferase deficiency). The possible role of pyridoxal phosphate as a chaperone during folding of nascent enzymes is discussed. High-dose pyridoxine or pyridoxal phosphate may have deleterious side-effects (particularly peripheral neuropathy with pyridoxine) and this must be considered in treatment regimes. None the less, in some patients, particularly infants with intractable epilepsy, treatment with pyridoxine or pyridoxal phosphate can be life-saving, and in other infants with inborn errors of metabolism B(6) treatment can be extremely beneficial.

  20. Dielectric studies of wheat in powder form at microwave frequencies.

    Science.gov (United States)

    Sharma, Kavita; Jain, Ritu; Bhargava, Nidhi; Sharma, Ritu; Sharma, K S

    2010-10-01

    Dielectric constant and loss factor of Raj-4120 variety of Indian wheat were determined in powder form (grain size 125 to 150 micron) at room temperature. Microwaves at three different frequencies were employed in C-band, X-band and Ku-band respectively for investigating frequency dependence of dielectric parameters of the sample. Bulk dielectric values of the sample were determined by employing the dielectric mixture relations, such as, half power mixture equation, Landau and Lifshitz, Looyenga equation etc.

  1. Modeling of dielectric viscoelastomers with application to electromechanical instabilities

    Science.gov (United States)

    Wang, Shuolun; Decker, Martina; Henann, David L.; Chester, Shawn A.

    2016-10-01

    Soft dielectrics are electrically-insulating elastomeric materials, which are capable of large deformation and electrical polarization, and are used as smart transducers for converting between mechanical and electrical energy. While much theoretical and computational modeling effort has gone into describing the ideal, time-independent behavior of these materials, viscoelasticity is a crucial component of the observed mechanical response and hence has a significant effect on electromechanical actuation. In this paper, we report on a constitutive theory and numerical modeling capability for dielectric viscoelastomers, able to describe electromechanical coupling, large-deformations, large-stretch chain-locking, and a time-dependent mechanical response. Our approach is calibrated to the widely-used soft dielectric VHB 4910, and the finite-element implementation of the model is used to study the role of viscoelasticity in instabilities in soft dielectrics, namely (1) the pull-in instability, (2) electrocreasing, (3) electrocavitation, and (4) wrinkling of a pretensioned three-dimensional diaphragm actuator. Our results show that viscoelastic effects delay the onset of instability under monotonic electrical loading and can even suppress instabilities under cyclic loading. Furthermore, quantitative agreement is obtained between experimentally measured and numerically simulated instability thresholds. Our finite-element implementation will be useful as a modeling platform for further study of electromechanical instabilities and for harnessing them in design and is provided as online supplemental material to aid other researchers in the field.

  2. Leakage current conduction, hole injection, and time-dependent dielectric breakdown of n-4H-SiC MOS capacitors during positive bias temperature stress

    Science.gov (United States)

    Samanta, Piyas; Mandal, Krishna C.

    2017-01-01

    The conduction mechanism(s) of gate leakage current JG through thermally grown silicon dioxide (SiO2) films on the silicon (Si) face of n-type 4H-silicon carbide (4H-SiC) has been studied in detail under positive gate bias. It was observed that at an oxide field above 5 MV/cm, the leakage current measured up to 303 °C can be explained by Fowler-Nordheim (FN) tunneling of electrons from the accumulated n-4H-SiC and Poole-Frenkel (PF) emission of trapped electrons from the localized neutral traps located at ≈2.5 eV below the SiO2 conduction band. However, the PF emission current IPF dominates the FN electron tunneling current IFN at oxide electric fields Eox between 5 and 10 MV/cm and in the temperature ranging from 31 to 303 °C. In addition, we have presented a comprehensive analysis of injection of holes and their subsequent trapping into as-grown oxide traps eventually leading to time-dependent dielectric breakdown during electron injection under positive bias temperature stress (PBTS) in n-4H-SiC metal-oxide-silicon carbide structures. Holes were generated in the heavily doped n-type polycrystalline silicon (n+-polySi) gate (anode) as well as in the oxide bulk via band-to-band ionization by the hot-electrons depending on their energy and SiO2 film thickness at Eox between 6 and 10 MV/cm (prior to the intrinsic oxide breakdown field). Transport of hot electrons emitted via both FN and PF mechanisms was taken into account. On the premise of the hole-induced oxide breakdown model, the time- and charge-to-breakdown ( tBD and QBD ) of 8.5 to 47 nm-thick SiO2 films on n-4H-SiC were estimated at a wide range of temperatures. tBD follows the Arrhenius law with activation energies varying inversely with initial applied constant field Eox supporting the reciprocal field ( 1 /E ) model of breakdown irrespective of SiO2 film thicknesses. We obtained an excellent margin (6.66 to 6.33 MV/cm at 31 °C and 5.11 to 4.55 MV/cm at 303 °C) of normal operating field for a 10

  3. Colossal breakdown electric field and dielectric response of Al-doped CaCu{sub 3}Ti{sub 4}O{sub 12} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Jia, Ran [State Key Laboratory of Electrical Insulation and Power Equipment, Xi’an Jiaotong University, Xi’an 710049 (China); Zhao, Xuetong [State Key Laboratory of Electrical Insulation and Power Equipment, Xi’an Jiaotong University, Xi’an 710049 (China); State Key Laboratory of Power Transmission Equipment and System Security and New Technology, Chongqing University, Chongqing 400044 (China); Li, Jianying, E-mail: lijy@mail.xjtu.edu.cn [State Key Laboratory of Electrical Insulation and Power Equipment, Xi’an Jiaotong University, Xi’an 710049 (China); Tang, Xian [State Key Laboratory of Electrical Insulation and Power Equipment, Xi’an Jiaotong University, Xi’an 710049 (China)

    2014-07-01

    Highlights: • An extremely enhanced breakdown electric field of ∼21 kV/cm was achieved. • A new secondary phase of CuAl{sub 2}O{sub 4} in CaCu{sub 3}Ti{sub 4}O{sub 12} was found. • The grain boundary resistance was increased from 0.37 MΩ to 13.55 MΩ at 393 K. • The activation energy of grain boundary was elevated from 0.63 to 0.81 eV. • Dimensional effect of CaCu{sub 3}Ti{sub 4}O{sub 12} was found. - Abstract: A greatly enhanced breakdown electric field of ∼21 kV/cm was achieved by liquid-phase doping of Al{sub 2}O{sub 3} in CaCu{sub 3}Ti{sub 4}O{sub 12} (CCTO) ceramics. It was found that the dielectric loss of CCTO ceramics was composed of two dielectric relaxation peaks and dc conduction. Impedance analysis showed that the grain boundary resistance was increased from 0.37 MΩ to 13.55 MΩ and the corresponding activation energy of grain boundary was elevated from 0.63 eV to 0.81 eV. The frequency dependence of the conductivity was interpreted with the Jonscher's law, which indicated that the contribution of dc-like conduction at low frequency was effectively suppressed by Al{sub 2}O{sub 3} doping. In addition, dimensional effect of the CCTO ceramics was found and an inflection (or critical) point behavior can be observed for pure and Al-doped samples, which referred to the variation of the breakdown electric field with the thickness of the samples.

  4. Dielectric properties of uncooked chicken breast muscles from ten to one thousand eight hundred megahertz.

    Science.gov (United States)

    Zhuang, H; Nelson, S O; Trabelsi, S; Savage, E M

    2007-11-01

    The dielectric properties, consisting of the dielectric constant (epsilon') and loss factor (epsilon''), were measured with an open-ended coaxial-line probe and impedance analyzer for uncooked broiler breast muscle pectoralis major and pectoralis minor, deboned at 2- and 24-h postmortem, over the frequency range from 10 to 1,800 MHz at temperatures ranging from 5 to 85 degrees C. The dielectric property profiles of chicken breast muscle are dependent upon the radio-wave and microwave frequencies and temperature. Increasing frequency from 10 to 1,800 MHz results in decreasing values of the dielectric constant and loss factor regardless of temperature in this range, chicken breast muscle type, or deboning time. However, the response to temperature varies with the frequency, muscle type, and deboning time. There are no differences in the dielectric constant and loss factor values at frequencies of 26 or 1,800 MHz between samples deboned at 2- and at 24-h postmortem. However, the muscle type significantly affects the average values of the dielectric constant and loss factor, with pectoralis minor having significantly higher average values. Both the deboning time and muscle type significantly affect the average values of the loss tangent (tan delta = dielectric loss factor/dielectric constant) at 26 and 1,800 MHz, with pectoralis minor having higher values than pectoralis major and 2-h samples having higher values than 24-h samples. Our quality measurements also show there are significant differences in chicken meat quality characteristics, including color, pH, drip loss, water holding capacity, and texture (Warner-Bratzler shear force value) between the different muscle types and between different deboning times in the same test. These results suggest that there is a probable potential for using dielectric property measurements to assess the quality of chicken meat.

  5. Temperature dependence of dielectric function and optical transitions in TlInSe{sub 2} and TlGaTe{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Shim, YongGu, E-mail: shim@pe.osakafu-u.ac.j [Department of Physics and Electronics, Graduate School of Engineering, Osaka Prefecture University, Gakuen-cho 1-1, Sakai, Osaka 599-8531 (Japan); Aoh, Hitoshi; Sakamoto, Junichi [Department of Physics and Electronics, Graduate School of Engineering, Osaka Prefecture University, Gakuen-cho 1-1, Sakai, Osaka 599-8531 (Japan); Wakita, Kazuki [Department of Electronics and Computer Engineering, Chiba Institute of Technology, 2-17-1, Tsudanuma, Narashino, Chiba 275-0016 (Japan); Mamedov, Nazim [Department of Ellipsometry, Institute of Physics, National Academy of Sciences of Azerbaijan, H. Javid ave. 33, Baku AZ-1143 (Azerbaijan)

    2011-02-28

    The principal components of the dielectric function of TlInSe{sub 2} and TlGaTe{sub 2} crystals with quasi-one-dimensional chain structure have been studied over the photon energies 1.5-5.0eV in the temperature range 140-400 K, with due regard to the reported phase transitions. For TlGaTe{sub 2}, the absolute values of the dielectric function experience a sudden temperature-induced change at 290 K in nearly all the accessed photon energy range. The energy and other parameters of the critical points for inter-band optical transitions related to the obtained dielectric function have then been retrieved for both TlInSe{sub 2} and TlGaTe{sub 2}. An abrupt change in the energy of the critical point, positioned at 2.93 eV at room temperature and formed by optical transitions induced by the light polarized along the chains, has then been disclosed for TlGaTe{sub 2} at 290 K.

  6. Electrical Conduction and Dielectric Breakdown Characteristics of Alkyl Ester Dielectric Fluids obtained from Palm Kernel Oil

    OpenAIRE

    Abdelmalik, A. A.; Fothergill, J; Dodd, S. J.

    2012-01-01

    Naturally occurring palm kernel oil (PKO) and its ester derivatives are being considered as sustainable alternatives to synthetic oils for use as dielectric fluids. This paper reports on their dielectric properties, which have been studied and compared to BS148 mineral oil. The low frequency complex dielectric response of the PKO and its derivatives are related to ionic conduction and electrode polarization phenomena. The purified PKO has an electrical conductivity of 3.04 ?? 10-12 Sm-1 at 30...

  7. Dielectric relaxation of gamma irradiated muscovite mica

    Energy Technology Data Exchange (ETDEWEB)

    Kaur, Navjeet [Department of Physics, Guru Nanak Dev University, Amritsar, Punjab 143005 (India); Singh, Mohan, E-mail: mohansinghphysics@gmail.com [Department of Physics, Guru Nanak Dev University, Amritsar, Punjab 143005 (India); Singh, Lakhwant [Department of Physics, Guru Nanak Dev University, Amritsar, Punjab 143005 (India); Awasthi, A.M. [Thermodynamics Laboratory, UGC-DAE Consortium for Scientific Research, Indore 452001 (India); Lochab, S.P. [Inter-University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067 (India)

    2015-03-15

    Highlights: • The present article reports the effect of gamma irradiation on the dielectric relaxation characteristics of muscovite mica. • Dielectric and electrical relaxations have been analyzed in the framework of dielectric permittivity, electric modulus and Cole–Cole formalisms. • The frequency dependent electrical conductivity has been rationalized using Johnsher’s universal power law. • The experimentally measured electric modulus and conductivity data have been fitted using Havriliak–Negami dielectric relaxation function. - Abstract: In the present research, the dielectric relaxation of gamma irradiated muscovite mica was studied in the frequency range of 0.1 Hz–10 MHz and temperature range of 653–853 K, using the dielectric permittivity, electric modulus and conductivity formalisms. The dielectric constants (ϵ′ and ϵ′′) are found to be high for gamma irradiated muscovite mica as compared to the pristine sample. The frequency dependence of the imaginary part of complex electric modulus (M′′) and dc conductivity data conforms Arrhenius law with single value of activation energy for pristine sample and two values of activation energy for gamma irradiated mica sample. The experimentally assessed electric modulus and conductivity information have been interpreted by the Havriliak–Negami dielectric relaxation explanation. Using the Cole–Cole framework, an analysis of real and imaginary characters of the electric modulus for pristine and gamma irradiated sample was executed which reflects the non-Debye relaxation mechanism.

  8. Polycarbonate based three-phase nanocomposite dielectrics

    Science.gov (United States)

    Sain, P. K.; Goyal, R. K.; Prasad, Y. V. S. S.; Bhargava, A. K.

    2016-08-01

    Three-phase polycarbonate (PC) matrix nanocomposites are prepared using the solution method. One of the nanocomposite fillers is dielectric and the other is conducting. Lead zirconate titanate (PZT) is used as the dielectric filler. The conducting fillers, nano-Cu and multi-walled carbon nanotubes (MWCNTs), are used to make two different nanocomposites, MWCNT-PZT-PC and Cu-PZT-PC. The prepared nanocomposites are characterized using density measurement, x-ray diffractometry, scanning electron microscopy, energy dispersive x-ray spectroscopy, and differential scanning calorimetry. Percolation is absent in both three-phase nanocomposites within the study’s concentration window of conducting fillers. The dielectric properties of the nanocomposites are evaluated using a precision impedance analyser. The dielectric constant of the Cu-PZT-PC nanocomposite increases to 14 (a dissipation factor of 0.17), whereas in the case of the MWCNT-PZT-PC nanocomposite it increases to 8.5 (a dissipation factor of 0.002). The melting point of both nanocomposites decreases with respect to the control PC. The frequency (1 kHz to 1 MHz) and temperature (room temperature to 200 °C) dependence of the dielectric constant and dissipation factor are examined. For the Cu-PZT-PC nanocomposites, the dielectric constant decreases with increasing frequency, whereas in the case of the MWCNT-PZT-PC nanocomposites the dielectric constant is almost constant. The dielectric constant and dissipation factor exhibit a slight temperature dependence.

  9. Phosphate-dependent root system architecture responses to salt stress

    KAUST Repository

    Kawa, Dorota

    2016-05-20

    Nutrient availability and salinity of the soil affect growth and development of plant roots. Here, we describe how phosphate availability affects root system architecture (RSA) of Arabidopsis and how phosphate levels modulate responses of the root to salt stress. Phosphate (Pi) starvation reduced main root length and increased the number of lateral roots of Arabidopsis Col-0 seedlings. In combination with salt, low Pi dampened the inhibiting effect of mild salt stress (75mM) on all measured RSA components. At higher NaCl concentrations, the Pi deprivation response prevailed over the salt stress only for lateral root elongation. The Pi deprivation response of lateral roots appeared to be oppositely affected by abscisic acid (ABA) signaling compared to the salt stress response. Natural variation in the response to the combination treatment of salt and Pi starvation within 330 Arabidopsis accessions could be grouped into four response patterns. When exposed to double stress, in general lateral roots prioritized responses to salt, while the effect on main root traits was additive. Interestingly, these patterns were not identical for all accessions studied and multiple strategies to integrate the signals from Pi deprivation and salinity were identified. By Genome Wide Association Mapping (GWAS) 13 genomic loci were identified as putative factors integrating responses to salt stress and Pi starvation. From our experiments, we conclude that Pi starvation interferes with salt responses mainly at the level of lateral roots and that large natural variation exists in the available genetic repertoire of accessions to handle the combination of stresses.

  10. Does sensitivity in binary choice tasks depend on response modality?

    NARCIS (Netherlands)

    Szumska, Izabela; Lubbe, van der Rob H.J.; Grzeczkowski, Lukasz; Herzog, Michael H.

    2016-01-01

    In most models of vision, a stimulus is processed in a series of dedicated visual areas, leading to categorization of this stimulus, and possible decision, which subsequently may be mapped onto a motor-response. In these models, stimulus processing is thought to be independent of the response modali

  11. Emergence of ratio-dependent and predator-dependent functional responses for pollination mutualism and seed parasitism

    Science.gov (United States)

    DeAngelis, Donald L.; Holland, J. Nathaniel

    2006-01-01

    Prey (N) dependence [g(N)], predator (P) dependence [g(P) or g(N,P)], and ratio dependence [f(P/N)] are often seen as contrasting forms of the predator's functional response describing predator consumption rates on prey resources in predator–prey and parasitoid–host interactions. Analogously, prey-, predator-, and ratio-dependent functional responses are apparently alternative functional responses for other types of consumer–resource interactions. These include, for example, the fraction of flowers pollinated or seeds parasitized in pollination (pre-dispersal) seed-parasitism mutualisms, such as those between fig wasps and fig trees or yucca moths and yucca plants. Here we examine the appropriate functional responses for how the fraction of flowers pollinated and seeds parasitized vary with the density of pollinators (predator dependence) or the ratio of pollinator and flower densities (ratio dependence). We show that both types of functional responses can emerge from minor, but biologically important variations on a single model. An individual-based model was first used to describe plant–pollinator interactions. Conditional upon on whether the number of flowers visited by the pollinator was limited by factors other than search time (e.g., by the number of eggs it had to lay, if it was also a seed parasite), and on whether the pollinator could directly find flowers on a plant, or had to search, the simulation results lead to either a predator-dependent or a ratio-dependent functional response. An analytic model was then used to show mathematically how these two cases can arise.

  12. Generalisation of new sequence knowledge depends on response modality.

    Directory of Open Access Journals (Sweden)

    Clive R Rosenthal

    Full Text Available New visuomotor skills can guide behaviour in novel situations. Prior studies indicate that learning a visuospatial sequence via responses based on manual key presses leads to effector- and response-independent knowledge. Little is known, however, about the extent to which new sequence knowledge can generalise, and, thereby guide behaviour, outside of the manual response modality. Here, we examined whether learning a visuospatial sequence either via manual (key presses, without eye movements, oculomotor (obligatory eye movements, or perceptual (covert reorienting of visuospatial attention responses supported generalisation to direct and indirect tests administered either in the same (baseline conditions or a novel response modality (transfer conditions with respect to initial study. Direct tests measured the use of conscious knowledge about the studied sequence, whereas the indirect tests did not ostensibly draw on the study phase and measured response priming. Oculomotor learning supported the use of conscious knowledge on the manual direct tests, whereas manual learning supported generalisation to the oculomotor direct tests but did not support the conscious use of knowledge. Sequence knowledge acquired via perceptual responses did not generalise onto any of the manual tests. Manual, oculomotor, and perceptual sequence learning all supported generalisation in the baseline conditions. Notably, the manual baseline condition and the manual to oculomotor transfer condition differed in the magnitude of general skill acquired during the study phase; however, general skill did not predict performance on the post-study tests. The results demonstrated that generalisation was only affected by the responses used to initially code the visuospatial sequence when new knowledge was applied to a novel response modality. We interpret these results in terms of response-effect distinctiveness, the availability of integrated effector- and motor-plan based

  13. Does sensitivity in binary choice tasks depend on response modality?

    Science.gov (United States)

    Szumska, Izabela; van der Lubbe, Rob H J; Grzeczkowski, Lukasz; Herzog, Michael H

    2016-07-01

    In most models of vision, a stimulus is processed in a series of dedicated visual areas, leading to categorization of this stimulus, and possible decision, which subsequently may be mapped onto a motor-response. In these models, stimulus processing is thought to be independent of the response modality. However, in theories of event coding, common coding, and sensorimotor contingency, stimuli may be very specifically mapped onto certain motor-responses. Here, we compared performance in a shape localization task and used three different response modalities: manual, saccadic, and verbal. Meta-contrast masking was employed at various inter-stimulus intervals (ISI) to manipulate target visibility. Although we found major differences in reaction times for the three response modalities, accuracy remained at the same level for each response modality (and all ISIs). Our results support the view that stimulus-response (S-R) associations exist only for specific instances, such as reflexes or skills, but not for arbitrary S-R pairings.

  14. Materials Fundamentals of Gate Dielectrics

    CERN Document Server

    Demkov, Alexander A

    2006-01-01

    This book presents materials fundamentals of novel gate dielectrics that are being introduced into semiconductor manufacturing to ensure the continuous scalling of the CMOS devices. This is a very fast evolving field of research so we choose to focus on the basic understanding of the structure, thermodunamics, and electronic properties of these materials that determine their performance in device applications. Most of these materials are transition metal oxides. Ironically, the d-orbitals responsible for the high dielectric constant cause sever integration difficulties thus intrinsically limiting high-k dielectrics. Though new in the electronics industry many of these materials are wel known in the field of ceramics, and we describe this unique connection. The complexity of the structure-property relations in TM oxides makes the use of the state of the art first-principles calculations necessary. Several chapters give a detailed description of the modern theory of polarization, and heterojunction band discont...

  15. Multi-component induction logging response in large dielectric formation%大介电常数地层中多分量感应测井响应研究

    Institute of Scientific and Technical Information of China (English)

    洪德成; 杨善德

    2011-01-01

    研究大介电常数对多分量感应测井的影响,并通过不同磁场分量的组合量来同时提取地层电阻率和介电常数以及地层纵向边界信息,实现地层参数的重构,直观识别烃源岩地层.%Wireline induction logs operating at a frequency of some tens of kHz are used to detect the resistivity of hydrocarbon reservoir.The dielectric constant of typical formation is usually smaller than that of pure water and its effect is negligible for induction log.However some peculiar rocks including organic matter named source rock have large dielectric permittivities caused by polarization,which can lead the traditional induction logging to have an nusual log response.Multi-component induction logging is new log method and has been developed in nearly ten years,which can provide more information about formation than traditional axial instrument and has large potential applications.In this paper,we study the effect of large dielectric constant on multi-component induction logging response and extract the information about resistivity and dielectric permittivity through the different combinations,there by realizing the formation parameters reconstruction and intuitive recognition for the hydrocarbon source rock.

  16. Dependence of CdTe response of bias history

    Energy Technology Data Exchange (ETDEWEB)

    Sites, J.R.; Sasala, R.A.; Eisgruber, I.L. [Colorado State Univ., Boulder, CO (United States)

    1995-11-01

    Several time-dependent effect have been observed in CdTe cells and modules in recent years. Some appear to be related to degradation at the back contact, some to changes in temperature at the thin-film junction, and some to the bias history of the cell or module. Back-contact difficulties only occur in some cases, and the other two effects are reversible. Nevertheless, confusion in data interpretation can arise when these effects are not characterized. This confusion can be particularly acute when more than one time-dependent effect occurs during the same measurement cycle. The purpose of this presentation is to help categorize time-dependent effects in CdTe and other thin-film cells to elucidate those related to bias history, and to note differences between cell and module analysis.

  17. Frequency and temperature dependence of dielectric and electric properties of Ba2-xSm4+2x/3Ti8O24 with structural analysis

    OpenAIRE

    Narang Sukhleen Bindra; Kaur Dalveer; Pubby Kunal

    2015-01-01

    Dielectric ceramics samples of barium titanium oxide doped with samarium, having a complex structural formula of Ba2-xSm4+2x/3Ti8O24 (referred to as BST), were fabricated by a high temperature solid-state reaction technique with varying x (0.0, 0.2, 0.4, 0.6). X-ray diffraction technique was used to check the formation of particular phases. Scanning electron microscope technique was used to study the surface morphology of the samples. The samples were studied in a temperature range of 298 K t...

  18. Activated human neutrophil response to perfluorocarbon nanobubbles: oxygen-dependent and -independent cytotoxic responses.

    Science.gov (United States)

    Hwang, Tsong-Long; Fang, Chia-Lang; Al-Suwayeh, Saleh A; Yang, Li-Jia; Fang, Jia-You

    2011-06-10

    Nanobubbles, a type of nanoparticles with acoustically active properties, are being utilized as diagnostic and therapeutic nanoparticles to better understand, detect, and treat human diseases. The objective of this work was to prepare different nanobubble formulations and investigate their physicochemical characteristics and toxic responses to N-formyl-methionyl-leucyl-phenylalanine (fMLP)-activated human neutrophils. The nanobubbles were prepared using perfluoropentane and coconut oil as the respective core and shell, with soybean phosphatidylcholine (SPC) and/or cationic surfactants as the interfacial layers. The cytotoxic effect of the nanobubbles on neutrophils was determined by extracellular O₂(.)⁻ release, intracellular reactive oxygen species (ROS), lactate dehydrogenase (LDH), and elastase release. Particle sizes of the nanobubbles with different percentages of perfluorocarbon, oil, and surfactants in ranged 186-432 nm. The nanobubbles were demonstrated to inhibit the generation of superoxide and intracellular ROS. The cytotoxicity of nanobubbles may be mainly associated with membrane damage, as indicated by the high LDH leakage. Systems with Forestall (FE), a cationic surfactant, or higher SPC contents exhibited the greatest LDH release by 3-fold compared to the control. The further addition of an oil component reduced the cytotoxicity induced by the nanobubbles. Exposure to most of the nanobubble formulations upregulated elastase release by activated neutrophils. Contrary to this result, stearylamine (SA)-containing systems slightly but significantly suppressed elastase release. FE and SA in a free form caused stronger responses by neutrophils than when they were incorporated into nanobubbles. In summary, exposure to nanobubbles resulted in a formulation-dependent toxicity toward human neutrophils that was associated with both oxygen-dependent and -independent pathways. Clinicians should therefore exercise caution when using nanobubbles in patients

  19. Phosphate-dependent root system architecture responses to salt stress

    NARCIS (Netherlands)

    Kawa, D.; Julkowska, M.M.; Montero Sommerfeld, H.; ter Horst, A.; Haring, M.A.; Testerink, C.

    2016-01-01

    Nutrient availability and salinity of the soil affect growth and development of plant roots. Here, we describe how phosphate availability affects root system architecture (RSA) of Arabidopsis and how phosphate levels modulate responses of the root to salt stress. Phosphate (Pi) starvation reduced ma

  20. DOSE-DEPENDENT ALLERGIC ASTHMA RESPONSES TO PENICILLIUM CHRYSOGENUM

    Science.gov (United States)

    ABSTRACT Indoor mold has been associated with development of allergic asthma. Penicillium chrysogenum, a common indoor mold, is known to have several allergens and its viable conidia can induce allergic responses in a mouse model of allergic penicilliosis. The hypothesis o...

  1. Dielectric nanoparticles for the enhancement of OLED light extraction efficiency

    Science.gov (United States)

    Mann, Vidhi; Rastogi, Vipul

    2017-03-01

    This work reports the use of dielectric nanoparticles placed at glass substrate in the improvement of light extraction efficiency of organic light emitting diode (OLED). The nanoparticles will act as scattering medium for the light trapped in the waveguiding modes of the device. The scattering efficiency of dielectric nanoparticles has been calculated by Mie Theory. The finite difference time domain (FDTD) analysis and simulation estimate the effect of dielectric nanoparticles on the light extraction efficiency of OLED. The efficiency depends upon the diameter, interparticle separation and refractive index of dielectric nanoparticles. It is shown that the dielectric nanoparticles layer can enhance the light extraction efficiency by a factor of 1.7.

  2. Moisture Content Analysis of Oil-paper Insulation for Large Power Transformers Using Dielectric Response Methods%大型电力变压器油纸绝缘含水量的介质响应诊断技术

    Institute of Scientific and Technical Information of China (English)

    许渊; 刘有为; 王文焕; 弓艳朋; 邓彦国; 陈小军

    2012-01-01

    介质响应技术是检测油纸绝缘含水量的一种无损诊断技术,该技术通过油纸绝缘的介质响应曲线判断其含水量.为推动该技术的发展和实际应用,以电介质理论为基础,对大型油纸绝缘电力变压器的介质响应特性开展了大量研究.结果表明,大型电力变压器介质响应曲线受频率、温度、含水量的影响具有较强的规律.提出了大型电力变压器油纸绝缘含水量的定性分析方法,并通过建立不同含水量、不同温度油浸纸板的复介电常数数据库及设备的X-Y模型,实现了大型电力变压器油纸绝缘含水量的定量计算,计算结果与实际基本相符.%The dielectric response technology is a nondestructive technology of moisture content diagnosis for oil-paper insulation by dielectric response curve. To promote the development and application for the dielectric response technology, the dielectric response characteristics of the actual large oil-paper insulation power transformer were studied on the basis of dielectric theory, and the test results show a strong regularity that frequency, temperature, and moisture content effect on the dielectric response curve of large power transformer. The qualitative analysis method of moisture content in oil-paper insulation for the large power transformer was proposed. The quantitative analysis method of moisture content in oil-paper insulation of the large power transformer was developed based on the equipment X-Y model and the complex permittivity database of oil impregnated pressboard under various moisture contents and temperatures, and the calculated values agree with the experimental data approximately.

  3. Hantaan virus triggers TLR4-dependent innate immune responses.

    Science.gov (United States)

    Yu, Hai-Tao; Jiang, Hong; Zhang, Ye; Nan, Xue-Ping; Li, Yu; Wang, Wei; Jiang, Wei; Yang, Dong-Qiang; Su, Wen-Jing; Wang, Jiu-Ping; Wang, Ping-Zhong; Bai, Xue-Fan

    2012-10-01

    The innate immune response induced by Hantavirus is responsible for endothelial cell dysfunction and viral pathogenicity. Recent studies demonstrate that TLR4 expression is upregulated and mediates the secretion of several cytokines in Hantaan virus (HTNV)-infected endothelial cells. To examine viral interactions with host endothelial cells and characterize the innate antiviral responses associated with Toll-like receptors, we selected TLR4 as the target molecule to investigate anti-hantavirus immunity. TLR4 mRNA-silenced EVC-304 (EVC-304 TLR4-) cells and EVC-304 cells were used to investigate signaling molecules downstream of TLR4. The expression of the adaptor protein TRIF was higher in HTNV-infected EVC-304 cells than in EVC-304 TLR4- cells. However, there was no apparent difference in the expression of MyD88 in either cell line. The transcription factors for NF-κB and IRF-3 were translocated from the cytoplasm into the nucleus in HTNV-infected EVC-304 cells, but not in HTNV-infected EVC-304 TLR4- cells. Our results demonstrate that TLR4 may play an important role in the antiviral immunity of the host against HTNV infection through an MyD88-independent signaling pathway.

  4. Murine Anorectic Response to Deoxynivalenol (Vomitoxin Is Sex-Dependent

    Directory of Open Access Journals (Sweden)

    Erica S. Clark

    2015-07-01

    Full Text Available Deoxynivalenol (DON, vomitoxin, a common trichothecene mycotoxin found in cereal foods, dysregulates immune function and maintenance of energy balance. The purpose of this study was to determine if sex differences are similarly evident in DON’s anorectic responses in mice. A bioassay for feed refusal, previously developed by our lab, was used to compare acute i.p. exposures of 1 and 5 mg/kg bw DON in C57BL6 mice. Greater anorectic responses were seen in male than female mice. Male mice had higher organ and plasma concentrations of DON upon acute exposure than their female counterparts. A significant increase in IL-6 plasma levels was also observed in males while cholecystokinin response was higher in females. When effects of sex on food intake and body weight changes were compared after subchronic dietary exposure to 1, 2.5, and 10 ppm DON, males were found again to be more sensitive. Demonstration of male predilection to DON-induced changes in food intake and weight gain might an important consideration in future risk assessment of DON and other trichothecenes.

  5. The cardiovascular response to passive movement is joint dependent.

    Science.gov (United States)

    Burns, Keith J; Pollock, Brandon S; McDaniel, John

    2016-03-01

    The cardiovascular responses to passive limb movement (PLM) at the knee are well established, however, responses to PLM at other joints involving smaller muscle volume are unknown. To compare the cardiovascular responses to passive movement at other joints, 10 participants underwent a PLM protocol in which the wrist, elbow, ankle, and knee joints were passively extended and flexed at 1 Hz for 1 min. Heart rate (HR), mean arterial blood pressure (MAP), and arterial blood flow to that limb segment (BF) were measured and vascular conductance (VC) was calculated for a 30-sec baseline period and for 3-sec intervals throughout PLM protocols. PLM of the knee and elbow resulted in significant increases in BF and VC from baseline values with peak values 180% (P PLM of the elbow resulted in significant increases in BF and VC from baseline values with peak values 109% and 115% (P PLM to assess vascular function or as a rehabilitation modality to maintain vascular health may be most appropriate for the muscles that span the elbow and knee.

  6. New trends in Brunner's relation: dielectric levels

    Science.gov (United States)

    Trouiller, Yorick; Didiergeorges, Anne; Fanget, Gilles L.; Laviron, Cyrille; Comboure, Corinne; Quere, Yves

    1999-07-01

    The goal of this paper is to understand the optical phenomena at dielectric levels. The purpose is also to quantify the impact of dielectric and resist thickness variations on the CD range with and without Bottom Anti Reflective COating (BARC). First we will show how all dielectric levels can be reduced to the stack metal/oxide/BARC/resist, and what are the contributions to resists and dielectric thickness range for each levels. Then a simple model will be developed to understand CD variation in this tack: by extending the Perot/Fabry model to the dielectric levels, developed by Brunner for the gate level, we can obtain a simple relation between the CD variation and all parameters. Experimentally CD variation for Damascene line level on 0.18micrometers technology has been measured depending on oxide thickness and resist thickness and can confirm this model. UV5 resist, AR2 BARC from Shipley and Top ARC from JSR have been used for these experiments. The main conclusions are: (1) Depending on your dielectric deposition and CMP processes, if resist thickness is controlled, a standard BARC process used for the gate is adapted to remove oxide thickness variation influence providing the optimized resist thickness is used. (2) If both resist thickness and dielectric thickness are uncontrolled, a more absorbent BARC is required.

  7. Dielectrics in electric fields

    CERN Document Server

    Raju, Gorur G

    2003-01-01

    Discover nontraditional applications of dielectric studies in this exceptionally crafted field reference or text for seniors and graduate students in power engineering tracks. This text contains more than 800 display equations and discusses polarization phenomena in dielectrics, the complex dielectric constant in an alternating electric field, dielectric relaxation and interfacial polarization, the measurement of absorption and desorption currents in time domains, and high field conduction phenomena. Dielectrics in Electric Fields is an interdisciplinary reference and text for professionals and students in electrical and electronics, chemical, biochemical, and environmental engineering; physical, surface, and colloid chemistry; materials science; and chemical physics.

  8. Study of optical and dielectric properties of annealed ZnO nanoparticles in the terahertz regime

    Institute of Scientific and Technical Information of China (English)

    WANG Ming-wei; Boon Kuan Woo; TIAN Zhen; HAN Jia-guang; CHEN Wei; ZHANG Wei-li

    2009-01-01

    The frequency-dependent optical and dielectric properties of annealed ZnO nanoparticles in the range of 0.1 to 0.9 THz are studied by using terahertz time-domain spectroscopy (THz-TDS). The refractive index, power absorption and complex dielectric constants are obtained and the experimental results are well fit with a simple effective medium theory in conjunc-tion with a pseudo-harmonic model. This study reveals that annealed ZnO nanoparticles exhibit the similar phonon response characteristics to the single ZnO crystal and other ZnO nanostructures, such as tetrapods and nanowires.

  9. Dielectric Response and Broadband Microwave Absorption Properties of Three-Layer Graded ZnO Nanowhisker/Polyester Composites

    Institute of Scientific and Technical Information of China (English)

    ZHOU Yan; SHI Xiao-Ling; YUAN Jie; FANG Xiao-Yong; CAO Mao-Sheng

    2007-01-01

    We design and prepare three-layer graded ZnO nanowhisker/polyester composites. The dispersion configuration of ZnO nanowhiskers in the polyester is investigated, and their microwave reflectivity curves are also measured. Experimental results have shown that the graded dispersion with ZnO nanowhiskers contributes to broadband microwave absorption. In other words, the absorption band depends on the graded dispersion configuration of ZnO nanowhiskers in polyester matrix.

  10. Microwave dielectric properties of nanostructured nickel ferrite

    Indian Academy of Sciences (India)

    John Jacob; M Abdul Khadar; Anil Lonappan; K T Mathew

    2008-11-01

    Nickel ferrite is one of the important ferrites used in microwave devices. In the present work, we have synthesized nanoparticles of nickel ferrite using chemical precipitation technique. The crystal structure and grain size of the particles are studied using XRD. The microwave dielectric properties of nanostructured nickel ferrite samples of three different average grain sizes and those of two sintered samples were studied. The parameters like dielectric constant, dielectric loss and heating coefficient of the nanoparticles samples are studied in the frequency range from 2.4 to 4 GHz. The values of these parameters are compared with those of sintered pellets of the same samples. All these parameters show size dependent variations.

  11. Responses of arthropod populations to warming depend on latitude

    DEFF Research Database (Denmark)

    Youngsteadt, Elsa; Ernst, Andrew F.; Dunn, Robert Roberdeau

    2017-01-01

    Biological effects of climate change are expected to vary geographically, with a strong signature of latitude. For ectothermic animals, there is systematic latitudinal variation in the relationship between climate and thermal performance curves, which describe the relationship between temperature...... and an organism's fitness. Here we ask whether these documented latitudinal patterns can be generalized to predict arthropod responses to warming across mid and high temperate latitudes, for taxa whose thermal physiology has not been measured. To address this question, we used a novel natural experiment...

  12. Lattices of dielectric resonators

    CERN Document Server

    Trubin, Alexander

    2016-01-01

    This book provides the analytical theory of complex systems composed of a large number of high-Q dielectric resonators. Spherical and cylindrical dielectric resonators with inferior and also whispering gallery oscillations allocated in various lattices are considered. A new approach to S-matrix parameter calculations based on perturbation theory of Maxwell equations, developed for a number of high-Q dielectric bodies, is introduced. All physical relationships are obtained in analytical form and are suitable for further computations. Essential attention is given to a new unified formalism of the description of scattering processes. The general scattering task for coupled eigen oscillations of the whole system of dielectric resonators is described. The equations for the  expansion coefficients are explained in an applicable way. The temporal Green functions for the dielectric resonator are presented. The scattering process of short pulses in dielectric filter structures, dielectric antennas  and lattices of d...

  13. The simulation of temperature dependence of responsivity and response time for 6H-SiC UV photodetector

    Institute of Scientific and Technical Information of China (English)

    Zhang Yi-Men; Zhou Yong-Hua; Zhang Yu-Ming

    2007-01-01

    In this paper the temperature dependence of responsivity and response time for 6H-SiC ultraviolet (UV) photodetector is simulated based on numerical model in the range from 300 K to 900 K. The simulation results show that the responsivity and the response time of device are less sensitive to temperature and this kind of UV photodetector has excellent temperature stability. Also the effects of device structure and bias voltage on the responsivity and the response time are presented. The thicker the drift region is, the higher the responsivity and the longer the response time are. So the thickness of drift region has to be carefully designed to make trade-off between responsivity and response time.

  14. Parametrized dielectric functions of amorphous GeSn alloys

    Science.gov (United States)

    D'Costa, Vijay Richard; Wang, Wei; Schmidt, Daniel; Yeo, Yee-Chia

    2015-09-01

    We obtained the complex dielectric function of amorphous Ge1-xSnx (0 ≤ x ≤ 0.07) alloys using spectroscopic ellipsometry from 0.4 to 4.5 eV. Amorphous GeSn films were formed by room-temperature implantation of phosphorus into crystalline GeSn alloys grown by molecular beam epitaxy. The optical response of amorphous GeSn alloys is similar to amorphous Ge and can be parametrized using a Kramers-Kronig consistent Cody-Lorentz dispersion model. The parametric model was extended to account for the dielectric functions of amorphous Ge0.75Sn0.25 and Ge0.50Sn0.50 alloys from literature. The compositional dependence of band gap energy Eg and parameters associated with the Lorentzian oscillator have been determined. The behavior of these parameters with varying x can be understood in terms of the alloying effect of Sn on Ge.

  15. Exactly Solvable Dielectrics and the Abraham-Minkowskii Controversy

    CERN Document Server

    Chafin, Clifford

    2014-01-01

    We present an exactly solvable model of a classical dielectric medium that gives an unambiguous local decomposition of field and charge motion and their contribution to the conserved quantities. This is done with special care to the forces that exist at surfaces, coatings and the ends of packets. The result is a mathematically simpler and more intuitive understand- ing of causality in media than the Brillouin and Sommerfeld theories and an understanding of the Kramers-Kronig relations in terms of dynamics and conservation laws. The Abraham-Minkowskii paradox is clarified from this point of view and the export of such notions to realistic media and metamaterials are discussed. This model can be extended to manifestly maintain these features as general nonlinear and time and space dependent changes in medium response are introduced and provides a universal description for all dielectrics.

  16. Low frequency dielectric spectroscopy of bitumen binders as an indicator of adhesion potential to quartz aggregates using Portland cement

    OpenAIRE

    Lyne, Åsa Laurell; Taylor, Nathaniel; Jaeverberg, Nadja; Edin, Hans; Birgisson, Björn

    2015-01-01

    The purpose of this investigation was to interpret the bitumen-aggregate adhesion based on the dielectric spectroscopic response of individual material components utilizing their dielectric constants, refractive indices and average tangent of the dielectric loss angle (average loss tangent). Dielectric spectroscopy of bitumen binders at room temperature was performed in the frequency range of 0.01–1000 Hz. Dielectric spectroscopy is an experimental method for characterizing the dielectric per...

  17. The effect of surface plasmon resonance on optical response in dielectric (core)–metal (shell) nanoparticles

    Indian Academy of Sciences (India)

    S Farjami Shayesteh; Matin Saie

    2015-12-01

    In this work, we present the effect of refractive index of an embedding medium, core and shell having various sizes of metallic nanoshells on the surface plasmon resonance (SPR) properties in the spherical dielectric–metal core–shell nanoparticles based on the quasistatic approaches and Mie theory. For the metallic nanoshell with dimensions comparable to the wavelength of light, the quasistatic approximation shows good agreement with the Mie theory results. However, for large nanoparticles the quasistatic approximation is not appropriate and Mie theory illustrates SPR due to dipole and quadrupole in extinction cross-section. The typical cross-section calculations show two peaks that related to inner and outer surfaces. The dimensional dependence of optical constant in the Drude model leads to a decrease in plasma absorption in metal core–shell. By increasing the shell radius and therefore increasing the metal content the SPR at the outer surface shifts to higher energy and the weaker peak (at inner surface) shifts to lower energy. Also, depending on the metal shell materials SPR occurs in different energy regions and therefore can be tuned the SP frequency at higher energy by changing the shell materials. In addition, SPR frequency is sensitive to variation in refractive index of the environment of core-shell.

  18. Composite Dielectric Materials for Electrical Switching

    Energy Technology Data Exchange (ETDEWEB)

    Modine, F.A.

    1999-04-25

    Composites that consist of a dielectric host containing a particulate conductor as a second phase are of interest for electrical switching applications. Such composites are "smart" materials that can function as either voltage or current limiters, and the difference in fimction depends largely upon whether the dielectric is filled to below or above the percolation threshold. It also is possible to combine current and voltage limiting in a single composite to make a "super-smart" material.

  19. Scenario dependency of the transient climate response to cumulative emissions

    Science.gov (United States)

    Turner, Katherine; Williams, Ric; Oschlies, Andreas

    2017-04-01

    The transient climate response to emissions (TCRE), in relating surface temperature changes to cumulative carbon emissions, provides a means of estimating carbon budgets from global warming benchmarks. Current Earth System Model results indicate that the TCRE is linear and scenario-independent. We explore the sensitivity of the TCRE to scenario and model parameter uncertainties using 8 configurations of the UVic Earth System Model of Intermediate Complexity, forced by 2 twenty-first-century emissions scenarios (RCP 4.5 and 8.5). We find that the TCRE is higher under RCP 4.5 than 8.5 by 0.3-0.8 K/1000 Pg C and shows opposing nonlinear tendencies in these scenarios: an increase of 0.15-0.5 K/1000 Pg C over RCP 4.5 and a decrease of 0-0.7 K/1000 Pg C over RCP 8.5. These differences are robust across model configurations with perturbed land and ocean parametrizations and are the result of the decreased efficiency of heat transport into the deep ocean under decelerating emissions.

  20. Dissecting ion-specific dielectric spectra of sodium-halide solutions into solvation water and ionic contributions

    Energy Technology Data Exchange (ETDEWEB)

    Rinne, Klaus F.; Netz, Roland R. [Fachbereich Physik, Freie Universität Berlin, 14195 Berlin (Germany); Gekle, Stephan [Physikalisches Institut, Universität Bayreuth, 95440 Bayreuth (Germany)

    2014-12-07

    Using extensive equilibrium molecular dynamics simulations we determine the dielectric spectra of aqueous solutions of NaF, NaCl, NaBr, and NaI. The ion-specific and concentration-dependent shifts of the static dielectric constants and the dielectric relaxation times match experimental results very well, which serves as a validation of the classical and non-polarizable ionic force fields used. The purely ionic contribution to the dielectric response is negligible, but determines the conductivity of the salt solutions. The ion-water cross correlation contribution is negative and reduces the total dielectric response by about 5%-10% for 1 M solutions. The dominating water dielectric response is decomposed into different water solvation shells and ion-pair configurations, by this the spectral blue shift and the dielectric decrement of salt solutions with increasing salt concentration is demonstrated to be primarily caused by first-solvation shell water. With rising salt concentration the simulated spectra show more pronounced deviations from a single-Debye form and can be well described by a Cole-Cole fit, in quantitative agreement with experiments. Our spectral decomposition into ionic and different water solvation shell contributions does not render the individual contributions more Debye-like, this suggests the non-Debye-like character of the dielectric spectra of salt solutions not to be due to the superposition of different elementary relaxation processes with different relaxation times. Rather, the non-Debye-like character is likely to be an inherent spectral signature of solvation water around ions.

  1. Dissecting ion-specific dielectric spectra of sodium-halide solutions into solvation water and ionic contributions

    Science.gov (United States)

    Rinne, Klaus F.; Gekle, Stephan; Netz, Roland R.

    2014-12-01

    Using extensive equilibrium molecular dynamics simulations we determine the dielectric spectra of aqueous solutions of NaF, NaCl, NaBr, and NaI. The ion-specific and concentration-dependent shifts of the static dielectric constants and the dielectric relaxation times match experimental results very well, which serves as a validation of the classical and non-polarizable ionic force fields used. The purely ionic contribution to the dielectric response is negligible, but determines the conductivity of the salt solutions. The ion-water cross correlation contribution is negative and reduces the total dielectric response by about 5%-10% for 1 M solutions. The dominating water dielectric response is decomposed into different water solvation shells and ion-pair configurations, by this the spectral blue shift and the dielectric decrement of salt solutions with increasing salt concentration is demonstrated to be primarily caused by first-solvation shell water. With rising salt concentration the simulated spectra show more pronounced deviations from a single-Debye form and can be well described by a Cole-Cole fit, in quantitative agreement with experiments. Our spectral decomposition into ionic and different water solvation shell contributions does not render the individual contributions more Debye-like, this suggests the non-Debye-like character of the dielectric spectra of salt solutions not to be due to the superposition of different elementary relaxation processes with different relaxation times. Rather, the non-Debye-like character is likely to be an inherent spectral signature of solvation water around ions.

  2. The 'emergent scaling' phenomenon and the dielectric properties of random resistor-capacitor networks

    Energy Technology Data Exchange (ETDEWEB)

    Bouamrane, R [LEPM, Departement de Physique, USTO-MB, BP 1505 El M' Naouer, Oran 31000 (Algeria); Almond, D P [Department of Engineering and Applied Science, University of Bath, Bath BA2 7AY (United Kingdom)

    2003-06-25

    An efficient algorithm, based on the Frank-Lobb reduction scheme, for calculating the equivalent dielectric properties of very large random resistor-capacitor (R-C) networks has been developed. It has been used to investigate the network size and composition dependence of dielectric properties and their statistical variability. The dielectric properties of 256 samples of random networks containing: 512, 2048, 8192 and 32 768 components distributed randomly in the ratios 60% R-40% C, 50% R-50% C and 40% R-60% C have been computed. It has been found that these properties exhibit the anomalous power law dependences on frequency known as the 'universal dielectric response' (UDR). Attention is drawn to the contrast between frequency ranges across which percolation determines dielectric response, where considerable variability is found amongst the samples, and those across which power laws define response where very little variability is found between samples. It is concluded that the power law UDRs are emergent properties of large random R-C networks.

  3. Frequency-dependent capacitance-voltage and conductance-voltage characteristics of low-dielectric-constant SiOC(-H) thin films deposited by using plasma-enhanced chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Chang Young; Lee, Heang Seuk; Woo, Jong Kwan; Choi, Chi Kyu; Lee, Kwang Man; Hyun, Myung Taek [Jeju National University, Jeju (Korea, Republic of); Navamathavan, Rangaswamy [Chonbuk National University, Chonju (Korea, Republic of)

    2010-12-15

    We report on the electrical characteristics of the metal-insulator-semiconductor (MIS) structure of low-dielectric-constant SiOC(-H) films. SiOC(-H) thin films were deposited on p-Si(100) substrates by using a plasma-enhanced chemical vapor deposition (PECVD) system. The frequency dependence of the capacitance-voltage (C-V) and the conductance-voltage (G/{omega}-V) characteristics of the A1/SiOC(-H)/p-Si(100)/Al MIS structures was analyzed. C-V and G/{omega}-V measurements were carried out over a frequency range of 1 kHz to 5 MHz. Based on our analysis, the C-V and the G/{omega}-V characteristics confirmed that the surface states and the series resistance were important parameters that strongly influenced the electrical properties of the A1/SiOC(-H)/p-Si(100)/Al MIS structures.

  4. Nonstationary photonic jet from dielectric microsphere

    CERN Document Server

    Geints, Yu; Zemlyanov, A

    2014-01-01

    A photonic jet commonly denotes the specific spatially localized region in the near-field forward scattering of a light wave at a dielectric micron-sized particle. We present the detailed calculations of the transient response of an airborne silica microsphere illuminated by a femtosecond laser pulse. The spatial area constituting the photonic jet is theoretically investigated and the temporal dynamics of jet dimensions as well as of jet peak intensity is analyzed. The role of morphology-dependent resonances in jet formation is highlighted. The evolution scenario of a nonstationary photonic jet generally consists of the non-resonant and resonant temporal phases. In every phase, the photonic jet can change its spatial form and intensity.

  5. Dielectric breakdown of cell membranes.

    Science.gov (United States)

    Zimmermann, U; Pilwat, G; Riemann, F

    1974-11-01

    With human and bovine red blood cells and Escherichia coli B, dielectric breakdown of cell membranes could be demonstrated using a Coulter Counter (AEG-Telefunken, Ulm, West Germany) with a hydrodynamic focusing orifice. In making measurements of the size distributions of red blood cells and bacteria versus increasing electric field strength and plotting the pulse heights versus the electric field strength, a sharp bend in the otherwise linear curve is observed due to the dielectric breakdown of the membranes. Solution of Laplace's equation for the electric field generated yields a value of about 1.6 V for the membrane potential at which dielectric breakdown occurs with modal volumes of red blood cells and bacteria. The same value is also calculated for red blood cells by applying the capacitor spring model of Crowley (1973. Biophys. J. 13:711). The corresponding electric field strength generated in the membrane at breakdown is of the order of 4 . 10(6) V/cm and, therefore, comparable with the breakdown voltages for bilayers of most oils. The critical detector voltage for breakdown depends on the volume of the cells. The volume-dependence predicted by Laplace theory with the assumption that the potential generated across the membrane is independent of volume, could be verified experimentally. Due to dielectric breakdown the red blood cells lose hemoglobin completely. This phenomenon was used to study dielectric breakdown of red blood cells in a homogeneous electric field between two flat platinum electrodes. The electric field was applied by discharging a high voltage storage capacitor via a spark gap. The calculated value of the membrane potential generated to produce dielectric breakdown in the homogeneous field is of the same order as found by means of the Coulter Counter. This indicates that mechanical rupture of the red blood cells by the hydrodynamic forces in the orifice of the Coulter Counter could also be excluded as a hemolysing mechanism. The detector

  6. Metal clusters and nanoparticles in dielectric matrices: Formation and optical properties

    Science.gov (United States)

    Gladskikh, I. A.; Vartanyan, T. A.

    2016-12-01

    The optical properties of thin dielectric films with metal inclusions and their dependence on thermal and laser annealing are studied experimentally. Metal clusters (Ag, Au, and Cu) in dielectric materials (Al2O3 and SiO2) are obtained by simultaneous vacuum deposition of metal and dielectric on the surface of a corresponding dielectric substrate (sapphire and quartz). It is shown that, depending on the deposited dielectric material, on the weight ratio of deposited metal and dielectric, and on the subsequent thermal treatment, one can obtain different metal structures, from clusters with a small number of atoms to complex dendritic plasmonic structures.

  7. Large magneto (thermo) dielectric effect in multiferroic orthorhombic LuMnO3

    Science.gov (United States)

    Wang, L. J.; Chai, Y. S.; Feng, S. M.; Zhu, J. L.; Manivannan, N.; Jin, C. Q.; Gong, Z. Z.; Wang, X. H.; Li, L. T.

    2012-06-01

    We have investigated the relation between ferroelectric and magnetic orders of orthorhombic (o-) LuMnO3 ceramics. The increase of dielectric constant ɛ exceeds 82% near incommensurate to commensurate E-type antiferromagnetic (AFM) spin ordering transition temperature TL, reflecting a large magneto (thermo) dielectric response. Meanwhile, distinct anomalies and thermal hysteresis behavior are observed near this temperature in both temperature dependence of ɛ and specific heat Cp, indicating a strong coupling between FE and magnetic orders in o-LuMnO3. Comparing to o-HoMnO3, TmMnO3, and YbMnO3 with similar E-type AFM ground state, o-LuMnO3 has the largest magneto (thermo) dielectric effect

  8. Dielectric constant of graphene-on-polarized substrate: A tight-binding model study

    Indian Academy of Sciences (India)

    SIVABRATA SAHU; S K S PARASHAR; G C ROUT

    2017-07-01

    We report here a microscopic tight-binding theoretical study of the dynamic dielectric response of graphene-on-polarizable substrate with impurity. The Hamiltonian consists of first, second and third nearest neighbour electron hopping interactions besides doping and substrate-induced effects on graphene. We have introduced electron–electron correlation effect at A and B sublattices of graphene which is considered within Hartree–Fock mean-field approximation. The electron occupancies at both sublattices are calculated and solvedself-consistently and numerically for both up- and down-spin orientations. The polarization function appearing in the dielectric function is a two-particle Green’s function which is calculated by using Zubarev’s Green’s function technique. The temperature and optical frequency-dependent dielectric function is evaluated and compared with experimental data by varying Coulomb correlation energy, substrate-induced gap and impurity concentrations.

  9. Investigation on the dielectric response of NdMnO3/LSAT thin films: Effect of 200 MeV Ag+15 ion irradiation

    Science.gov (United States)

    Udeshi, Malay; Vyas, Brinda; Trivedi, Priyanka; Katba, Savan; Ravalia, Ashish; Solanki, P. S.; Shah, N. A.; Asokan, K.; Ojha, S.; Kuberkar, D. G.

    2015-12-01

    We report the results of the modifications in structural and dielectric behaviour of pulsed laser deposited NdMnO3 manganite thin films grown on (1 0 0) single crystalline (LaAlO3)0.3 (Sr2AlTaO6)0.7 substrate irradiated with the 200 MeV Ag+15 ion irradiation having different fluences, ∼5 × 1010, ∼5 × 1011, ∼5 × 1012 ions/cm2. Structural strain was quantified using analysis of X-ray Diffraction data while Rutherford Backscattering measurements were performed on pristine NdMnO3 film to confirm the elemental composition, thickness and oxygen content. Dielectric measurements performed on all the irradiated films show that, the dielectric constant decreases with increase in ion fluence which has been correlated with the irradiation induced increase in strain at the film-substrate interface. The dielectric relaxation behaviour of pristine and irradiated NdMnO3 films have been understood by fitting the dielectric data using the Cole-Cole plots.

  10. Resonant dielectric metamaterials

    Science.gov (United States)

    Loui, Hung; Carroll, James; Clem, Paul G; Sinclair, Michael B

    2014-12-02

    A resonant dielectric metamaterial comprises a first and a second set of dielectric scattering particles (e.g., spheres) having different permittivities arranged in a cubic array. The array can be an ordered or randomized array of particles. The resonant dielectric metamaterials are low-loss 3D isotropic materials with negative permittivity and permeability. Such isotropic double negative materials offer polarization and direction independent electromagnetic wave propagation.

  11. Frequency sweep rate dependence on the dielectrophoretic response of polystyrene beads and red blood cells

    Science.gov (United States)

    Adams, T. N. G.; Leonard, K. M.; Minerick, A. R.

    2013-01-01

    Alternating current (AC) dielectrophoresis (DEP) experiments for biological particles in microdevices are typically done at a fixed frequency. Reconstructing the DEP response curve from static frequency experiments is laborious, but essential to ascertain differences in dielectric properties of biological particles. Our lab explored the concept of sweeping the frequency as a function of time to rapidly determine the DEP response curve from fewer experiments. For the purpose of determining an ideal sweep rate, homogeneous 6.08 μm polystyrene (PS) beads were used as a model system. Translatability of the sweep rate approach to ∼7 μm red blood cells (RBC) was then verified. An Au/Ti quadrapole electrode microfluidic device was used to separately subject particles and cells to 10Vpp AC electric fields at frequencies ranging from 0.010 to 2.0 MHz over sweep rates from 0.00080 to 0.17 MHz/s. PS beads exhibited negative DEP assembly over the frequencies explored due to Maxwell-Wagner interfacial polarizations. Results demonstrate that frequency sweep rates must be slower than particle polarization timescales to achieve reliable incremental polarizations; sweep rates near 0.00080 MHz/s yielded DEP behaviors very consistent with static frequency DEP responses for both PS beads and RBCs. PMID:24396548

  12. Origin of colossal dielectric response of CaCu3Ti4O12 studied by using CaTiO3/CaCu3Ti4O12/CaTiO3 multilayer thin films

    Science.gov (United States)

    Mitsugi, Masakazu; Asanuma, Shutaro; Uesu, Yoshiaki; Fukunaga, Mamoru; Kobayashi, Wataru; Terasaki, Ichiro

    2007-06-01

    To elucidate the origin of the colossal dielectric response (CDR) of CaCu3Ti4O12 (CCTO), multilayer thin films of CCTO interposed in insulating CaTiO3 (CTO) were synthesized using a pulsed laser deposition technique. The capacitance C of CTO/CCTO/CTO films with different layer thicknesses is measured. After removing the capacitance of CTO by extrapolating C to zero CTO thickness, the real part of dielectric constant of CCTO is estimated to be 329-435, which is much smaller than the reported value for CCTO thin films. This fact indicates that the CDR of CCTO is extrinsic and originates from an internal barrier layer capacitor.

  13. Dielectric behaviour of erbium substituted Mn–Zn ferrites

    Indian Academy of Sciences (India)

    D Ravinder; K Vijaya Kumar

    2001-10-01

    Dielectric properties such as dielectric constant (') and dielectric loss tangent (tan ⋹ ) of mixed Mn–Zn–Er ferrites having the compositional formula Mn0.58Zn0.37Fe2.05–ErO4 (where = 0.2, 0.4, 0.6, 0.8 and 1.0) were measured at room temperature in the frequency range 1–13 MHz using a HP 4192A impedance analyser. Plots of dielectric constant (') vs frequency show a normal dielectric behaviour of spinel ferrites. The frequency dependence of dielectric loss tangent (tan ) was found to be abnormal, giving a peak at certain frequency for all mixed Mn–Zn–Er ferrites. A qualitative explanation is given for the composition and frequency dependence of the dielectric constant and dielectric loss tangent. Plots of dielectric constant vs temperature have shown a transition near the Curie temperature for all the samples of Mn–Zn–Er ferrites. However, Mn0.58Zn0.37Er1.0Fe1.05O4 does not show a transition. On the basis of these results an explanation for the dielectric mechanism in Mn–Zn–Er ferrites is suggested.

  14. Dielectric Studies on Fe3O4 Nanodoped p-n-Alkyloxybenzoic Acids

    Directory of Open Access Journals (Sweden)

    S. Sreehari Sastry

    2014-01-01

    Full Text Available The stability of phase transition temperatures and textural changes for thermotropic pure and nanodoped p-n-alkyloxybenzoic acid mesogens were aimed to study at considerable time periods. Frequency and temperature dependent dielectric constant and dielectric loss for the pure and nanodoped liquid crystals were carried out. Significant anomalies in dielectric studies were observed near phase transitions when dielectric constant and dielectric loss had been measured as a function of temperature and frequency. Changes in dielectric constant and loss were observed and there were no apparent changes at high frequencies instead maintaining constant values. The variations in conductivity, activation energy, and relaxation times had also been studied in the nematic and smectic phases. The temperature dependent dielectric constant stability (temperature coefficient of dielectric constant τε had shown shift in the observed frequency range of thermotropic liquid crystals corresponding to the change in the dielectric constant values.

  15. Method of making dielectric capacitors with increased dielectric breakdown strength

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Beihai; Balachandran, Uthamalingam; Liu, Shanshan

    2017-05-09

    The invention is directed to a process for making a dielectric ceramic film capacitor and the ceramic dielectric laminated capacitor formed therefrom, the dielectric ceramic film capacitors having increased dielectric breakdown strength. The invention increases breakdown strength by embedding a conductive oxide layer between electrode layers within the dielectric layer of the capacitors. The conductive oxide layer redistributes and dissipates charge, thus mitigating charge concentration and micro fractures formed within the dielectric by electric fields.

  16. Influence of Ni{sup 2+} substitution on the structural, dielectric and magnetic properties of Cu–Cd ferrite nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Hashim, Mohd., E-mail: md.hashim09@gmail.com [Department of Applied Physics, Aligarh Muslim University, Aligarh 202 002 (India); Alimuddin [Department of Applied Physics, Aligarh Muslim University, Aligarh 202 002 (India); Shirsath, Sagar E. [Spin Device Technology Centre, Department of Information Engineering, Shinshu University, Nagano 380-8553 (Japan); Kotnala, R.K. [National Physical Laboratory (CSIR), Dr. K.S. Krishnan Road, New Delhi 110 012 (India); Meena, Sher Singh [Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Kumar, Shalendra [Department of Physics, Pohang University of Science and Technology, Pohang 790 784 (Korea, Republic of); Roy, Aashis [Department of Materials Science, Gulbarga University, Gulbarga 585106, Karnataka (India); Jotania, R.B. [Department of Physics, University School of Sciences, Gujarat University, Ahmedabad 380 009 (India); Bhatt, Pramod [Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Kumar, Ravi [Centre for Material Science Engineering, National Institute of Technology, Hamirpur, HP 171 005 (India)

    2013-10-05

    Highlights: •XRD and IR measurements reveal the formation of Cu–Cd–FeO in spinel phase. •The dielectric response shows decreasing trend while resistivity increases with enhancing the doping ion content. •Temperature dependent magnetization study shows that the magnetization and Curie temperature increases with increase in Ni{sup 2+} substitution. -- Abstract: Nanoparticles with compositions of Cu{sub 0.4−0.5x}Cd{sub 0.2}Ni{sub 0.4+x}Fe{sub 2−0.5x}O{sub 4} (0.0 ⩽ x ⩽ 0.5) were successfully synthesized by a citrate–nitrate sol–gel auto combustion route. The combusted powder was calcinated at four hours in a furnace and then slowly cooled to room temperature. The analysis methods of FTIR, XRD, FESEM, VSM and dielectric measurements were used to characterize prepared magnetic particles. The effect of Ni{sup 2+} substitution on structural, magnetic and dielectric properties of Cu–Cd ferrite nanoparticles was studied. The comprehensive studies on compositional and frequency dependent dielectric properties were carried out by means of AC conductivity (σ{sub ac}), imaginary dielectric constant (ε′′), loss tangent (tan δ), impedance and dielectric modulus (real and imaginary) measurements in frequency range of 50 Hz–5 MHz at room temperature. The structural properties investigated by using X-ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy. X-ray diffraction pattern and FTIR results revealed that synthesized samples are in single phase. It is observed that the dielectric constant (ε′′) and dielectric loss (tan δ) value decreases with increase in Ni{sup 2+} concentration (x). At low frequency the Maxwell type interfacial polarization was observed. Magnetization measurement shows that the Curie temperature of the samples increases with Ni{sup 2+} concentration, which is explained by a change in the A–O–B super exchange interaction.

  17. Overcoming the concentration-dependence of responsive probes for magnetic resonance imaging

    Science.gov (United States)

    Ekanger, Levi A.

    2015-01-01

    In magnetic resonance imaging, contrast agents are molecules that increase the contrast-to-noise ratio of non-invasively acquired images. The information gained from magnetic resonance imaging can be increased using responsive contrast agents that undergo chemical changes, and consequently changes to contrast enhancement, for example in response to specific biomarkers that are indicative of diseases. A major limitation with modern responsive contrast agents is concentration-dependence that requires the concentration of contrast agent to be known: an extremely challenging task in vivo. Here, we review advances in several strategies aimed at overcoming the concentration-dependent nature of responsive contrast agents. PMID:25579206

  18. Disorder driven structural and dielectric properties of silicon substituted strontium titanate

    Science.gov (United States)

    Dugu, Sita; Pavunny, Shojan P.; Sharma, Yogesh; Scott, James F.; Katiyar, Ram S.

    2015-07-01

    A systematic study on structural, microstructural, optical, dielectric, and electrical properties of phase-pure silicon-modified SrTiO3 polycrystalline electroceramics synthesized using high energy solid state reaction techniques is presented. The asymmetry and splitting in the x-ray diffractometer spectra and the observation of first order transverse optical TO2 and longitudinal optical LO4 modes in Raman spectra (nominally forbidden) revealed the distortion in the cubic lattice as a result of breaking of inversion symmetry due to doping. A bandgap Eg of 3.27 eV was determined for the sample by diffuse reflectance spectroscopy. A high dielectric constant of ˜400 and very low dielectric loss of ˜0.03 were obtained at 100 kHz near ambient conditions. The temperature dependence of the dielectric data displayed features of high temperature relaxor ferroelectric behavior as evidence of existence of polar nano-regions. The ac conductivity as a function of frequency showed features typical of universal dynamic response and obeyed a power law σ a c = σ d c + A ω n . The temperature dependent dc conductivity followed an Arrhenius relation with activation energy of 123 meV in the 200-500 K temperature range. The linear dielectric response of Pt/SrSi0.03Ti0.97O3/Pt dielectric capacitors was well characterized. The measured leakage current was exceptionally low, 13 nA/cm2 at 8.7 kV/cm, revealing an interface blocked bulk conduction mechanism.

  19. Pneumococcal conjugate vaccines overcome splenic dependency of antibody response to pneumococcal polysaccharides

    NARCIS (Netherlands)

    Breukels, MA; Zandvoort, A; van den Dobbelsteen, GPJM; van den Muijsenberg, A; Lodewijk, ME; Beurret, M; Klok, PA; Timens, W; Rijkers, GT

    2001-01-01

    Protection against infectious with Streptococcus pneumoniae depends on the presence of antibodies against capsular polysaccharides that facilitate phagocytosis. Asplenic patients are at increased risk for pneumococcal infections, since both phagocytosis and the initiation of the antibody response to

  20. Phase-dependent modulation of percutaneously elicited multisegmental muscle responses after spinal cord injury

    OpenAIRE

    Dy, Christine J.; Gerasimenko, Yury P.; Edgerton, V Reggie; Dyhre-Poulsen, Poul; Courtine, Grégoire; Harkema, Susan J.

    2010-01-01

    Phase-dependent modulation of monosynaptic reflexes has been reported for several muscles of the lower limb of uninjured rats and humans. To assess whether this step-phase-dependent modulation can be mediated at the level of the human spinal cord, we compared the modulation of responses evoked simultaneously in multiple motor pools in clinically complete spinal cord injury (SCI) compared with noninjured (NI) individuals. We induced multisegmental responses of the soleus, medial gastrocnemius,...

  1. Infrared and THz spectroscopy of nanostructured dielectrics

    Directory of Open Access Journals (Sweden)

    Jan Petzelt

    2009-09-01

    Full Text Available Results achieved using the infrared/THz spectroscopy of various inhomogeneous dielectrics in the Department of Dielectrics, Institute of Physics, Prague, during the last decade are briefly reviewed. The discussion concerns high-permittivity ceramics with inevitable low-permittivity dead layers along the grain boundaries, relaxor ferroelectrics with highly anisotropic polar nano-regions, classical matrix-type composites, core-shell composites, filled nanoporous glasses, polycrystalline and epitaxial thin films, heterostructures and superlattices on dielectric substrates. The analysis using models based on the effective medium approach is discussed. The importance of depolarizing field and of the percolation of components on the effective ac dielectric response and the excitations contributing to it are emphasized.

  2. Clonal progression during the T cell-dependent B cell antibody response depends on the immunoglobulin DH gene segment repertoire.

    Directory of Open Access Journals (Sweden)

    Ahmad eTrad

    2014-08-01

    Full Text Available The diversity of the third complementarity determining region of the Ig H chain is constrained by natural selection of immunoglobulin diversity (DH sequence. To test the functional significance of this constraint in the context of thymus-dependent (TD immune responses, we immunized BALB/c mice with WT or altered DH sequence with 2-phenyloxazolone-coupled chicken serum albumin (phOx-CSA. We chose this antigen because studies of the humoral immune response to the hapten phOx were instrumental in the development of the current theoretical framework on which our understanding of the forces driving TD responses is based. To allow direct comparison, we used the classic approach of generating monoclonal Ab (mAb from various stages of the immune response to phOx to assess the effect of changing the sequence of the DH on clonal expansion, class switching and affinity maturation, which are hallmarks of TD responses. Compared to WT, TD-induced humoral IgM as well as IgG antibody production in the D-altered D-DFS and D-iD strains were significantly reduced. An increased prevalence of IgM producing hybridomas from late primary, secondary, and tertiary memory responses suggested either impaired class switch recombination (CSR or impaired clonal expansion of class switched B cells with phOx reactivity. Neither of the D-altered strains demonstrated the restriction in the VH/VL repertoire, the elimination of VH1 family-encoded antibodies, the focusing of the distribution of CDR-H3 lengths, or the selection for the normally dominant Ox1 clonotype which all are hallmarks of the anti-phOx response in WT mice. These changes in clonal selection and expansion as well as class switch recombination indicate that the genetic constitution of the DH locus, which has been selected by evolution, can strongly influence the functional outcome of a TD humoral response.

  3. Molecular dynamics simulations of the dielectric properties of fructose aqueous solutions

    Science.gov (United States)

    Sonoda, Milton T.; Elola, M. Dolores; Skaf, Munir S.

    2016-10-01

    The static dielectric permittivity and dielectric relaxation properties of fructose aqueous solutions of different concentrations ranging from 1.0 to 4.0 mol l-1 are investigated by means of molecular dynamics simulations. The contributions from intra- and interspecies molecular correlations were computed individually for both the static and frequency-dependent dielectric properties, and the results were compared with the available experimental data. Simulation results in the time- and frequency-domains were analyzed and indicate that the presence of fructose has little effect on the position of the fast, high-frequency (>500 cm-1) components of the dielectric response spectrum. The low-frequency (concentration. Our analysis indicates that fructose-fructose and fructose-water interactions strongly affect the rotational-diffusion regime of molecular motions in the solutions. Increasing fructose concentration not only enhances sugar-sugar and sugar-water low frequency contributions to the dielectric loss spectrum but also slows down the reorientational dynamics of water molecules. These results are consistent with previous computer simulations carried out for other disaccharide aqueous solutions.

  4. Dielectric properties of Ga{sub 2}O{sub 3}-doped barium iron niobate ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Sanjoom, Kachaporn [Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai, 50200 (Thailand); Thailand Center of Excellence in Physics, Commission on Higher Education, 328 Sri Ayutthaya Road, Bangkok, 10400 (Thailand); Pengpat, Kamonpan; Eitssayeam, Sukum; Tunkasiri, Tawee [Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai, 50200 (Thailand); Materials Science Research Center, Faculty of Science, Chiang Mai University, Chiang Mai, 50200 (Thailand); Rujijanagul, Gobwute [Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai, 50200 (Thailand); Materials Science Research Center, Faculty of Science, Chiang Mai University, Chiang Mai, 50200 (Thailand); Thailand Center of Excellence in Physics, Commission on Higher Education, 328 Sri Ayutthaya Road, Bangkok, 10400 (Thailand)

    2014-08-15

    Ga-doped BaFe{sub 0.5}Nb{sub 0.5}O{sub 3} (Ba(Fe{sub 1-x}Ga{sub x}){sub 0.5}Nb{sub 0.5}O{sub 3}) ceramics were fabricated and their properties were investigated. All ceramics showed perovskite structure with cubic symmetry and the solubility of Ga in BFN ceramics had a limit at x = 0.2. Examination of the dielectric spectra indicated that all ceramic samples presented high dielectric constants that were frequency dependent. The x = 0.2 ceramic showed a very high dielectric constant (ε{sub r} > 240 000 at 1 kHz) while the x = 0.4 sample exhibited high thermal stability of dielectric constant with low loss tangent from room temperature (RT) to 100 C with ε{sub r} > 28 000 (at 1 kHz) when compared to other samples. By using a complex impedance analysis technique, bulk grain, grain boundary, and electrode response were found to affect the dielectric behavior that could be related to the Maxwell-Wagner polarization mechanism. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  5. Dielectric and Ferroelectric Properties of Complex Perovskite Ceramics Under Compressive Stress

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Dielectric and ferroelectric properties of complex perovskite PZT-PZN ceramic system were investigated under the influence of the compressive stress. The results showed that the dielectric properties, i.e. dielectric constant ( εr ) and dielectric loss ( tan δ), and the ferroelectric characteristics, i.e. the area of the ferroelectric hysteresis loops, the saturation polarization ( P(sat) ), and the remnant polarization (Pr) changed significantly with increasing compressive stress. These changes depended strongly on the ceramic compositions. The experimental results on the dielectric properties could be explained by both intrinsic and extrinsic domain-related mechanisms involving domain wall motions, as well as the de-aging phenomenon. The stress-induced domain wall motion suppression and non-180° ferroelectric domain switching processes were responsible for the changes observed in the ferroelectric parameters. In addition,a significant decrease in those parameters after a cycle of stress was observed and attributed to the stress induced decrease in switchable part of spontaneous polarization. This study clearly show that the applied stress had significant influence on the electrical properties of complex perovskite ceramics.

  6. Evaluating Radiometric Measurements Using a Fixed 45 Degrees Responsivity and Zenith Angle Dependent Responsivities (Poster)

    Energy Technology Data Exchange (ETDEWEB)

    Dooraghi, M.; Habte, A.; Reda, I.; Sengupta, M.; Gotseff, P.; Andreas, A.; Anderberg, M.

    2014-03-01

    This poster seeks to demonstrate the importance and application of an existing but unused approach that ultimately reduces the uncertainty of radiometric measurements. Current radiometric data is based on a single responsivity value that introduces significant uncertainty to the data, however, through using responsivity as a function of solar zenith angle, the uncertainty could be decreased by 50%.

  7. Evaluating Radiometric Measurements Using a Fixed 45 Degrees Responsivity and Zenith Angle Dependent Responsivities (Poster)

    Energy Technology Data Exchange (ETDEWEB)

    Dooraghi, M.; Habte, A.; Reda, I.; Sengupta, M.; Gotseff, P.; Andreas, A.; Anderberg, M.

    2014-03-01

    This poster seeks to demonstrate the importance and application of an existing but unused approach that ultimately reduces the uncertainty of radiometric measurements. Current radiometric data is based on a single responsivity value that introduces significant uncertainty to the data, however, through using responsivity as a function of solar zenith angle, the uncertainty could be decreased by 50%.

  8. Contemporary dielectric materials

    CERN Document Server

    Saravanan, R

    2016-01-01

    This book deals with experimental results of the physical characterization of several important, dielectric materials of great current interest. The experimental tools used for the analysis of these materials include X-ray diffraction, dielectric measurements, magnetic measurements using a vibrating sample magnetometer, optical measurements using a UV-Visible spectrometer etc.

  9. Dielectric material for dosimeters

    Energy Technology Data Exchange (ETDEWEB)

    Moran, P.R.; Podgorsak, E.; Fullerton, G.D.; Fuller, G.E.

    1976-01-27

    A RITAD dosimeter is described having a dielectric material such as sapphire wherein the efficiency as measured by mean drift distance and trapping efficiency is increased by making use of a dielectric material in which the total active impurity does not exceed 50 ppm and in which any one active impurity does not exceed 10 ppm.

  10. Light in complex dielectrics

    NARCIS (Netherlands)

    Schuurmans, F.J.P.

    1999-01-01

    In this thesis the properties of light in complex dielectrics are described, with the two general topics of "modification of spontaneous emission" and "Anderson localization of light". The first part focuses on the spontaneous emission rate of an excited atom in a dielectric host with variable refra

  11. On Casimir Forces for Media with Arbitrary Dielectric Properties

    CERN Document Server

    Mochán, W L; Esquivel-Sirvent, R

    2002-01-01

    We derive an expression for the Casimir force between slabs with arbitrary dielectric properties characterized by their reflection coefficients. The formalism presented here is applicable to media with a local or a non-local dielectric response, an infinite or a finite width, inhomogeneous dissipative, etc. Our results reduce to the Lifshitz formula for the force between semi-infinite dielectric slabs by replacing the reflection coefficients by the Fresnel amplitudes.

  12. Resistance to Change and Frequency of Response-Dependent Stimuli Uncorrelated with Reinforcement

    Science.gov (United States)

    Podlesnik, Christopher A.; Jimenez-Gomez, Corina; Ward, Ryan D.; Shahan, Timothy A.

    2009-01-01

    Stimuli uncorrelated with reinforcement have been shown to enhance response rates and resistance to disruption; however, the effects of different rates of stimulus presentations have not been assessed. In two experiments, we assessed the effects of adding different rates of response-dependent brief stimuli uncorrelated with primary reinforcement…

  13. TRPM8-Dependent Dynamic Response in a Mathematical Model of Cold Thermoreceptor

    Science.gov (United States)

    Olivares, Erick; Salgado, Simón; Maidana, Jean Paul; Herrera, Gaspar; Campos, Matías; Madrid, Rodolfo; Orio, Patricio

    2015-01-01

    Cold-sensitive nerve terminals (CSNTs) encode steady temperatures with regular, rhythmic temperature-dependent firing patterns that range from irregular tonic firing to regular bursting (static response). During abrupt temperature changes, CSNTs show a dynamic response, transiently increasing their firing frequency as temperature decreases and silencing when the temperature increases (dynamic response). To date, mathematical models that simulate the static response are based on two depolarizing/repolarizing pairs of membrane ionic conductance (slow and fast kinetics). However, these models fail to reproduce the dynamic response of CSNTs to rapid changes in temperature and notoriously they lack a specific cold-activated conductance such as the TRPM8 channel. We developed a model that includes TRPM8 as a temperature-dependent conductance with a calcium-dependent desensitization. We show by computer simulations that it appropriately reproduces the dynamic response of CSNTs from mouse cornea, while preserving their static response behavior. In this model, the TRPM8 conductance is essential to display a dynamic response. In agreement with experimental results, TRPM8 is also needed for the ongoing activity in the absence of stimulus (i.e. neutral skin temperature). Free parameters of the model were adjusted by an evolutionary optimization algorithm, allowing us to find different solutions. We present a family of possible parameters that reproduce the behavior of CSNTs under different temperature protocols. The detection of temperature gradients is associated to a homeostatic mechanism supported by the calcium-dependent desensitization. PMID:26426259

  14. TRPM8-Dependent Dynamic Response in a Mathematical Model of Cold Thermoreceptor.

    Directory of Open Access Journals (Sweden)

    Erick Olivares

    Full Text Available Cold-sensitive nerve terminals (CSNTs encode steady temperatures with regular, rhythmic temperature-dependent firing patterns that range from irregular tonic firing to regular bursting (static response. During abrupt temperature changes, CSNTs show a dynamic response, transiently increasing their firing frequency as temperature decreases and silencing when the temperature increases (dynamic response. To date, mathematical models that simulate the static response are based on two depolarizing/repolarizing pairs of membrane ionic conductance (slow and fast kinetics. However, these models fail to reproduce the dynamic response of CSNTs to rapid changes in temperature and notoriously they lack a specific cold-activated conductance such as the TRPM8 channel. We developed a model that includes TRPM8 as a temperature-dependent conductance with a calcium-dependent desensitization. We show by computer simulations that it appropriately reproduces the dynamic response of CSNTs from mouse cornea, while preserving their static response behavior. In this model, the TRPM8 conductance is essential to display a dynamic response. In agreement with experimental results, TRPM8 is also needed for the ongoing activity in the absence of stimulus (i.e. neutral skin temperature. Free parameters of the model were adjusted by an evolutionary optimization algorithm, allowing us to find different solutions. We present a family of possible parameters that reproduce the behavior of CSNTs under different temperature protocols. The detection of temperature gradients is associated to a homeostatic mechanism supported by the calcium-dependent desensitization.

  15. TRPM8-Dependent Dynamic Response in a Mathematical Model of Cold Thermoreceptor.

    Science.gov (United States)

    Olivares, Erick; Salgado, Simón; Maidana, Jean Paul; Herrera, Gaspar; Campos, Matías; Madrid, Rodolfo; Orio, Patricio

    2015-01-01

    Cold-sensitive nerve terminals (CSNTs) encode steady temperatures with regular, rhythmic temperature-dependent firing patterns that range from irregular tonic firing to regular bursting (static response). During abrupt temperature changes, CSNTs show a dynamic response, transiently increasing their firing frequency as temperature decreases and silencing when the temperature increases (dynamic response). To date, mathematical models that simulate the static response are based on two depolarizing/repolarizing pairs of membrane ionic conductance (slow and fast kinetics). However, these models fail to reproduce the dynamic response of CSNTs to rapid changes in temperature and notoriously they lack a specific cold-activated conductance such as the TRPM8 channel. We developed a model that includes TRPM8 as a temperature-dependent conductance with a calcium-dependent desensitization. We show by computer simulations that it appropriately reproduces the dynamic response of CSNTs from mouse cornea, while preserving their static response behavior. In this model, the TRPM8 conductance is essential to display a dynamic response. In agreement with experimental results, TRPM8 is also needed for the ongoing activity in the absence of stimulus (i.e. neutral skin temperature). Free parameters of the model were adjusted by an evolutionary optimization algorithm, allowing us to find different solutions. We present a family of possible parameters that reproduce the behavior of CSNTs under different temperature protocols. The detection of temperature gradients is associated to a homeostatic mechanism supported by the calcium-dependent desensitization.

  16. Dose-dependent pheromone responses of mountain pine beetle in stands of lodgepole pine

    Science.gov (United States)

    Daniel R. Miller; B. Staffan Lindgren; John H. Borden

    2005-01-01

    We conducted seven behavioral choice tests with Lindgren multiple-funnel traps in stands of mature lodgepole pine in British Columbia, from 1988 to 1994, to determine the dosedependent responses of the mountain pine beetle, Dendroctonus ponderosae Hopkins, to its pheromones. Amultifunctional dose-dependent response was exhibited by D. ...

  17. Hepcidin Response to Iron Therapy in Patients with Non-Dialysis Dependent CKD

    NARCIS (Netherlands)

    Gaillard, Carlo A.; Bock, Andreas H.; Carrera, Fernando; Eckardt, Kai-Uwe; Van Wyck, David B.; Bansal, Sukhvinder S.; Cronin, Maureen; Meier, Yvonne; Larroque, Sylvain; Roger, Simon D.; Macdougall, Iain C.

    2016-01-01

    Hepcidin is the key regulator of iron homeostasis but data are limited regarding its temporal response to iron therapy, and response to intravenous versus oral iron. In the 56-week, open-label, multicenter, prospective, randomized FIND-CKD study, 626 anemic patients with non-dialysis dependent

  18. AN EXTRACT OF PENICILLIUM CHRYSOGENUM INDUCES DOSE-DEPENDENT ALLERGIC ASTHMA RESPONSES IN MICE

    Science.gov (United States)

    Rationale: Penicillium chrysogenum, a common indoor mold, is known to have several allergens and can induce allergic responses in a mouse model of allergic penicilliosis. Our hypothesis is that soluble components of P. chrysogenum (PCE) can dose-dependently induce responses typ...

  19. Significantly elevated dielectric permittivity of Si-based semiconductor/polymer 2-2 composites induced by high polarity polymers

    Science.gov (United States)

    Feng, Yefeng; Gong, Honghong; Xie, Yunchuan; Wei, Xiaoyong; Zhang, Zhicheng

    2016-02-01

    To disclose the essential influence of polymer polarity on dielectric properties of polymer composites filled with semiconductive fillers, a series of Si-based semiconductor/polymer 2-2 composites in a series model was fabricated. The dielectric permittivity of composites is highly dependant on the polarity of polymer layers as well as the electron mobility in Si-based semiconductive sheets. The huge dielectric permittivity achieved in Si-based semiconductive sheets after being coated with high polarity polymer layers is inferred to originate from the strong induction of high polarity polymers. The increased mobility of the electrons in Si-based semiconductive sheets coated by high polarity polymer layers should be responsible for the significantly enhanced dielectric properties of composites. This could be facilely achieved by either increasing the polarity of polymer layers or reducing the percolative electric field of Si-based semiconductive sheets. The most promising 2-2 dielectric composite was found to be made of α-SiC with strong electron mobility and poly(vinyl alcohol) (PVA) with high polarity, and its highest permittivity was obtained as 372 at 100 Hz although the permittivity of α-SiC and PVA is 3-5 and 15, respectively. This work may help in the fabrication of high dielectric constant (high-k) composites by tailoring the induction effect of high polarity polymers to semiconductors.

  20. Time-Dependant Responses of High-Definition Induction Log and Case Studies

    Directory of Open Access Journals (Sweden)

    Jianhua Zhang

    2014-01-01

    Full Text Available The process of drilling mud filtrate invading into a reservoir is time dependant. It causes dynamic invasion profiles of formation parameters such as water saturation, salinity, and formation resistivity. Thus, the responses of a high-definition induction log (HDIL tool are time dependent. The logging time should be considered as an important parameter during logging interpretation for the purposes of determining true formation resistivity, estimating initial water saturation, and evaluating a reservoir. The time-dependent HDIL responses are helpful for log analysts to understand the invasion process physically. Field examples were illustrated for the application of present method.

  1. Dose dependency and individual variability of the lipopolysaccharide-induced bovine acute phase protein response

    DEFF Research Database (Denmark)

    Jacobsen, S.; Andersen, P.H.; Tølbøll, T.

    2004-01-01

    In order to investigate the dose dependency and the individual variability of the lipopolysaccharide (LPS)-induced acute phase protein response in cattle, 8 nonlactating, nonpregnant Danish Holstein cows were challenged 3 times each by intravenous injection of increasing doses (10, 100, and 1000 ng...... for several days after each LPS injection, and their increase or decrease was significantly related to LPS dose. In addition to dose dependency, the response was also dependent on the individual, as APP concentrations differed significantly among cows. To compare APP production in 2 consecutive challenges...

  2. Aeroelastic response of an aircraft wing with mounted engine subjected to time-dependent thrust

    Science.gov (United States)

    Mazidi, A.; Kalantari, H.; Fazelzadeh, S. A.

    2013-05-01

    In this paper, the aeroelastic response of a wing containing an engine subjected to different types of time-dependent thrust excitations is presented. In order to precisely consider the spanwise and chordwise locations of the engine and the time-dependent follower force in governing equations, derived through Lagrange's method, the generalized function theory is used. Unsteady aerodynamic lift and moment in the time domain are considered in terms of Wagner's function. Numerical simulations of the aeroelastic response to different types of time-dependent thrust excitation and comparisons with the previously published results are supplied. Effects of the engine mass and location and also the type of time-dependent thrust on the wing aeroelastic response are studied and pertinent conclusions are outlined.

  3. Dielectric relaxation in AgI doped silver selenomolybdate glasses

    Science.gov (United States)

    Palui, A.; Shaw, A.; Ghosh, A.

    2016-05-01

    We report the study of dielectric properties of some silver ion conducting silver selenomolybdate mixed network former glasses in a wide frequency and temperature range. The experimental data have been analyzed in the framework of complex dielectric permittivity. The dielectric permittivity data have been well interpreted using the Cole-Cole function. The temperature dependence of relaxation time obtained from real part of dielectric permittivity data shows an Arrhenius behavior. The activation energy shows a decreasing trend with the increase of doping content. Values of stretched exponential parameter are observed to be independent of temperature and composition.

  4. System for calibrating the energy-dependent response of an elliptical Bragg-crystal spectrometer.

    Science.gov (United States)

    Marrs, R E; Brown, G V; Emig, J A; Heeter, R F

    2014-11-01

    A multipurpose spectrometer (MSPEC) with elliptical crystals is in routine use to obtain x-ray spectra from laser produced plasmas in the energy range 1.0-9.0 keV. Knowledge of the energy-dependent response of the spectrometer is required for an accurate comparison of the intensities of x-ray lines of different energy. The energy-dependent response of the MSPEC has now been derived from the spectrometer geometry and calibration information on the response of its components, including two different types of detectors. Measurements of the spectrometer response with a laboratory x-ray source are used to test the calculated response and provide information on crystal reflectivity and uniformity.

  5. Prediction and set-dependent scaling of early postural responses in cerebellar patients.

    Science.gov (United States)

    Timmann, D; Horak, F B

    1997-02-01

    We reported previously that patients with cerebellar deficits were unable to scale the magnitude of their early automatic postural responses to the predicted amplitudes of surface translations based on central set from prior experience. The present study investigated whether this deficit in set-dependent amplitude scaling was based predominantly on the cerebellar patient's disability (i) to predict perturbation amplitudes on the basis of prior experience, (ii) to scale the gain or magnitude of upcoming postural responses or (iii) to habituate postural responses. The increase in size of the early postural response when a larger than actual platform amplitude was expected and decrease when a smaller one was expected was defined as a measure of set-dependent amplitude prediction. The suppression of the postural response when the same platform velocity was repeated was used as a measure of habituation. The correlation between the size of early postural responses and platform amplitudes when presented serially, but not randomly, tested the ability to scale the gain of postural responses based on prior experience. Results show that although cerebellar patients could predict perturbation amplitudes based on prior experience, they could not use this prediction to modify precisely the gain of responses. The ability to habituate the magnitude of postural responses was not affected by cerebellar lesions. Thus, the cerebellum might not be critical for predicting upcoming events or for habituating to repeated postural stimuli, although it is important for accurate tuning of response gain based on prediction.

  6. All-dielectric nanophotonics: fundamentals, fabrication, and applications

    CERN Document Server

    Krasnok, Alexander; Baranov, Denis; Belov, Pavel

    2016-01-01

    In this Article, we review a novel, rapidly developing field of modern light science named all-dielectric nanophotonics. This branch of nanophotonics is based on the properties of high-index dielectric nanoparticles which allow for controlling both magnetic and electric responses of a nanostructured matter. Here, we discuss optical properties of high-index dielectric nanoparticles, methods of their fabrication, and recent advances in practical applications, including the quantum source emission engineering, Fano resonances in all-dielectric nanoclusters, surface enhanced spectroscopy and sensing, coupled-resonator optical waveguides, metamaterials and metasurfaces, and nonlinear nanophotonics.

  7. Principal response curves: analysis of time-dependent multivariate responses of biological community to stress

    NARCIS (Netherlands)

    Brink, van den P.J.; Braak, ter C.J.F.

    1999-01-01

    In this paper a novel multivariate method is proposed for the analysis of community response data from designed experiments repeatedly sampled in time. The long-term effects of the insecticide chlorpyrifos on the invertebrate community and the dissolved oxygen (DO)–pH–alkalinity–conductivity syndrom

  8. Dielectric Behavior of Low Microwave Loss Unit Cell for All Dielectric Metamaterial

    OpenAIRE

    Tianhuan Luo; Bo Li; Qian Zhao; Ji Zhou

    2015-01-01

    With a deep study of the metamaterial, its unit cells have been widely extended from metals to dielectrics. The dielectric based unit cells attract much attention because of the advantage of easy preparation, tunability, and higher frequency response, and so forth. Using the conventional solid state method, we prepared a kind of incipient ferroelectrics (calcium titanate, CaTiO3) with higher microwave permittivity and lower loss, which can be successfully used to construct metamaterials. The ...

  9. Dielectric properties of conductive ionomers

    Science.gov (United States)

    Klein, Robert James

    Ion and polymer dynamics of ion-containing polymers were investigated, with the majority of results obtained from application of a physical model of electrode polarization (EP) to dielectric spectroscopy data. The physical model of MacDonald, further developed by Coelho, was extended for application to tan delta (the ratio of dielectric loss to dielectric constant) as a function of frequency. The validity of this approach was confirmed by plotting the characteristic EP time as a function of thickness and comparing the actual and predicted unrelaxed dielectric constant for a poly(ethylene oxide) (PEO)-based ionomer neutralized by lithium, sodium, and cesium. Results were obtained for ion mobility and mobile ion concentration for a neat PEO-based ionomer, two (methoxyethoxy-ethoxy phosphazene) (MEEP) -based ionomers, two MEEP-based salt-doped polymers, sulfonated polystyrene (SPS) neutralized by sodium with a high sulfonation fraction, and SPS neutralized by zinc with a low sulfonation fraction. Additionally, the conductivity parameters of six plasticized forms of a neat PEO-based ionomer were characterized, but the method apparently failed to correctly evaluate bulk ionic behavior. In all cases except the SPS ionomers ion mobility follows a Vogel-Fulcher-Tammann (VFT) temperature dependence. In all cases, mobile ion concentration follows an Arrhenius temperature dependence. Fitting parameters from these two relationships yielded direct information about the state of ionic diffusion and ion pairing in each system. Combination of these two functionalities predicts a relationship for conductivity that is significantly different than the VFT relation typically used in the literature to fit conductivity. The most outstanding result was the extremely small fraction of ions found to be mobile. For ionomers it can be concluded that the primary reason for low conductivities arises from the low fraction of mobile ions. The local and segmental dynamics of the neat and

  10. Investigation of Dielectric Response Characteristics of Transformer Oil-Paper Insulation Dielectric Spectroscopy of Acceleratedly Thermal Aging%变压器油纸绝缘的介电响应特性研究一加速热老化的介电谱

    Institute of Scientific and Technical Information of China (English)

    魏建林; 王世强; 彭华东; 董明; 张冠军; 冯玉昌; 于峥

    2012-01-01

    为了研究变压器油纸绝缘老化的介电响应特征量,本文对油纸绝缘试品进行了加速热老化,并在老化的不同阶段开展了相同试验温度下的极化、去极化电流(PDC)和频域谱(FDS)试验。在PDC试验数据的基础上,引入时域介电谱理论,提取其峰值和峰值时间常数作为老化特征量,研究了该特征量与绝缘老化的关系。结果表明,绝缘老化使PDC试验的极化及去极化电流曲线均明显上移,FDS试验的复电容实部和虚部曲线在低频段均向右上平移,时域介电谱曲线则向左上方平移,这是由于老化弓I起水分、有机酸等含量的增加以及对纤维素结构的破坏,提高了油纸绝缘间夹层介质界面极化的强度和响应速度而造成的。在本文的试验条件下,油纸绝缘的时域介电谱对其老化反应灵敏,可定量反映油纸绝缘老化程度的变化情况,其峰值和峰值时间常数可考虑用作表征油纸绝缘老化程度的特征量。%For achieving the characteristic parameters ot dielectric response pnenomena o~ transformer oil-paper insulation aging, the oil-impregnated pressboard samples were acceleratedly thermally aged. The dielectric response tests, including polarization and depolarization current (PDC) and frequency domain spectroscopy (FDS), were performed on the samples with different aging degree at the same temperature. The time-domain dielectric spectroscopy theory was introduced to investigate the aging characteristic parameters of dielectric response based on the PDC data. The results reveal that, with sample aging, its polarization and depolarization currents shift upwards to higher value, the real and imaginary capacitance and dissipation factor shift upwards and rightwards at lower frequencies, and the time-domain dielectric spectroscopy shifts upwards and leftwards. It is considered that aging process induces the increment of water and organic

  11. Preisach modeling of temperature-dependent ferroelectric response of piezoceramics at sub-switching regime

    Science.gov (United States)

    Ochoa, Diego Alejandro; García, Jose Eduardo

    2016-04-01

    The Preisach model is a classical method for describing nonlinear behavior in hysteretic systems. According to this model, a hysteretic system contains a collection of simple bistable units which are characterized by an internal field and a coercive field. This set of bistable units exhibits a statistical distribution that depends on these fields as parameters. Thus, nonlinear response depends on the specific distribution function associated with the material. This model is satisfactorily used in this work to describe the temperature-dependent ferroelectric response in PZT- and KNN-based piezoceramics. A distribution function expanded in Maclaurin series considering only the first terms in the internal field and the coercive field is proposed. Changes in coefficient relations of a single distribution function allow us to explain the complex temperature dependence of hard piezoceramic behavior. A similar analysis based on the same form of the distribution function shows that the KNL-NTS properties soften around its orthorhombic to tetragonal phase transition.

  12. Dielectric materials for electrical engineering

    CERN Document Server

    Martinez-Vega, Juan

    2013-01-01

    Part 1 is particularly concerned with physical properties, electrical ageing and modeling with topics such as the physics of charged dielectric materials, conduction mechanisms, dielectric relaxation, space charge, electric ageing and life end models and dielectric experimental characterization. Part 2 concerns some applications specific to dielectric materials: insulating oils for transformers, electrorheological fluids, electrolytic capacitors, ionic membranes, photovoltaic conversion, dielectric thermal control coatings for geostationary satellites, plastics recycling and piezoelectric poly

  13. Temperature dependence of the Al2O3:C response in medical luminescence dosimetry

    DEFF Research Database (Denmark)

    Edmund, Jens Morgenthaler; Andersen, Claus Erik

    2007-01-01

    is not varied. The RL response only depends on the irradiation temperature. We recommend that calibration should be carried out at the same irradiation temperature at which the measurement is performed (i.e. at body temperature for in vivo measurements). The overall change in the integrated OSL and RL signals...... and detection wavelengths. The reported temperature dependence seems to be a general property of Al2O3:C. (C) 2006 Elsevier Ltd. All rights reserved....

  14. Polypyrrole Composite Nanoparticles with Morphology-Dependent Photothermal Effect and Immunological Responses.

    Science.gov (United States)

    Tian, Ye; Zhang, Jianping; Tang, Shiwei; Zhou, Lei; Yang, Wuli

    2016-02-10

    Polypyrrole composite nanoparticles with controlled shape are synthesized, which exhibit a morphology-dependent photothermal effect: the raspberry-like composite nanoparticles have a much better photothermal effect than the spherical ones, and the immune responses to the nanocomposites are also dependent on their morphology. The outstanding performance of the nanocomposites promises their potential application in photothermal therapy and immunotherapy of cancer. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Epidemiology of pyridoxine dependent and pyridoxine responsive seizures in the UK

    OpenAIRE

    1999-01-01

    OBJECTIVE—To study the epidemiology of pyridoxine dependent seizures and other forms of pyridoxine responsive seizures.
DESIGN—Monthly notifications to the British Paediatric Surveillance Unit over two years. Questionnaire follow up.
SETTING—UK and the Republic of Ireland.
PATIENTS—Children aged 15 years or younger whose seizures respond to pyridoxine.
INTERVENTIONS—None.
MAIN OUTCOME MEASURES—Numbers of children with definite, probable, and possible pyridoxine depende...

  16. Increased oxidative stress in AOA3 cells disturbs ATM-dependent DNA damage responses.

    Science.gov (United States)

    Kobayashi, Junya; Saito, Yuichiro; Okui, Michiyo; Miwa, Noriko; Komatsu, Kenshi

    2015-04-01

    Ataxia telangiectasia (AT) is caused by a mutation in the ataxia-telangiectasia-mutated (ATM) gene; the condition is associated with hyper-radiosensitivity, abnormal cell-cycle checkpoints, and genomic instability. AT patients also show cerebellar ataxia, possibly due to reactive oxygen species (ROS) sensitivity in neural cells. The ATM protein is a key regulator of the DNA damage response. Recently, several AT-like disorders have been reported. The genes responsible for them are predicted to encode proteins that interact with ATM in the DNA-damage response. Ataxia with oculomotor apraxia types 1-3 (AOA1, 2, and 3) result in a neurodegenerative and cellular phenotype similar to AT; however, the basis of this phenotypic similarity is unclear. Here, we show that the cells of AOA3 patients display aberrant ATM-dependent phosphorylation and apoptosis following γ-irradiation. The ATM-dependent response to H2O2 treatment was abrogated in AOA3 cells. Furthermore, AOA3 cells had reduced ATM activity. Our results suggest that the attenuated ATM-related response is caused by an increase in endogenous ROS in AOA3 cells. Pretreatment of cells with pyocyanin, which induces endogenous ROS production, abolished the ATM-dependent response. Moreover, AOA3 cells had decreased homologous recombination (HR) activity, and pyocyanin pretreatment reduced HR activity in HeLa cells. These results indicate that excess endogenous ROS represses the ATM-dependent cellular response and HR repair in AOA3 cells. Since the ATM-dependent cell-cycle checkpoint is an important block to carcinogenesis, such inactivation of ATM may lead to tumorigenesis as well as neurodegeneration.

  17. Hot plasma dielectric tensor

    NARCIS (Netherlands)

    Westerhof, E.

    1996-01-01

    The hot plasma dielectric tensor is discussed in its various approximations. Collisionless cyclotron resonant damping and ion/electron Bernstein waves are discussed to exemplify the significance of a kinetic description of plasma waves.

  18. Sex differences in cocaine-dependent individuals’ response to disulfiram treatment

    Science.gov (United States)

    Nich, Charla; McCance-Katz, Elinore F.; Petrakis, Ismene L.; Cubells, Joseph F.; Rounsaville, Bruce J.; Carroll, Kathleen M.

    2013-01-01

    The objective of this study is to evaluate differential response to disulfiram treatment of cocaine dependence by sex. Sex by treatment interactions from two pooled randomized clinical trials involving 191 cocaine-dependent subjects (36% female) were evaluated. Primary outcomes were days of abstinence and percentage of drug-free urine specimens. Significant sex by treatment interactions were found, where men treated with disulfiram had better outcomes than those who were not. Women had an intermediate outcome regardless of whether they received disulfiram. Sex differences in response to disulfiram treatment have important clinical and theoretical implications. Reasons for this apparent sex-based response are not clear, but possible mechanisms worthy of greater study include differences in alcohol use by sex as well as differences in dopamine-mediated responses to cocaine and disulfiram. PMID:15236812

  19. Empirically indistinguishable multidimensional IRT and locally dependent unidimensional item response models.

    Science.gov (United States)

    Ip, Edward Haksing

    2010-05-01

    Multidimensionality is a core concept in the measurement and analysis of psychological data. In personality assessment, for example, constructs are mostly theoretically defined as unidimensional, yet responses collected from the real world are almost always determined by multiple factors. Significant research efforts have concentrated on the use of simulated studies to evaluate the robustness of unidimensional item response models when applied to multidimensional data with a dominant dimension. In contrast, in the present paper, I report the result from a theoretical investigation that a multidimensional item response model is empirically indistinguishable from a locally dependent unidimensional model, of which the single dimension represents the actual construct of interest. A practical implication of this result is that multidimensional response data do not automatically require the use of multidimensional models. Circumstances under which the alternative approach of locally dependent unidimensional models may be useful are discussed.

  20. Topological dependence of mechanical responses of solidification microstructures in aluminum brazed joints

    Institute of Scientific and Technical Information of China (English)

    GAO Feng(高峰); QIAN Yi-yu(钱乙余); D.P.Sekulic; MA Xin(马鑫); F.Yoshida

    2003-01-01

    The main objective is to provide an evidence of spatial dependence of mechanical responses of a heterogeneous aluminum brazed joint re-solidified clad,and to confirm a sufficient sensitivity of a nano-indentation--load curve method for identifying the dependence.Topological features of a network of solidification microstructures(αphase and eutectic),formed during quench in a brazing process of aluminum alloy,influence significantly dynamic mechanical responses of resulting heterogeneous material.Nano/micro indentation depth vs load characteristics of differing phases suggest a spatially sensitive mechanical response of a re-solidified fillet in the joint zone.Hence,a spatial distribution,pattern formations and other morphological characteristics of microstructures have a direct impact on an ultimate joint integrity.Topology-induced variations of indentation-load curves was presented.A hypothesis involving microstructures'spatial distribution vs mechanical response was formulated.

  1. Phase-dependent modulation of percutaneously elicited multisegmental muscle responses after spinal cord injury.

    Science.gov (United States)

    Dy, Christine J; Gerasimenko, Yury P; Edgerton, V Reggie; Dyhre-Poulsen, Poul; Courtine, Grégoire; Harkema, Susan J

    2010-05-01

    Phase-dependent modulation of monosynaptic reflexes has been reported for several muscles of the lower limb of uninjured rats and humans. To assess whether this step-phase-dependent modulation can be mediated at the level of the human spinal cord, we compared the modulation of responses evoked simultaneously in multiple motor pools in clinically complete spinal cord injury (SCI) compared with noninjured (NI) individuals. We induced multisegmental responses of the soleus, medial gastrocnemius, tibialis anterior, medial hamstring, and vastus lateralis muscles in response to percutaneous spinal cord stimulation over the Th11-Th12 vertebrae during standing and stepping on a treadmill. Individuals with SCI stepped on a treadmill with partial body-weight support and manual assistance of leg movements. The NI group demonstrated phase-dependent modulation of evoked potentials in all recorded muscles with the modulation of the response amplitude corresponding with changes in EMG amplitude in the same muscle. The SCI group demonstrated more variation in the pattern of modulation across the step cycle and same individuals in the SCI group could display responses with a magnitude as great as that of modulation observed in the NI group. The relationship between modulation and EMG activity during the step cycle varied from noncorrelated to highly correlated patterns. These findings demonstrate that the human lumbosacral spinal cord can phase-dependently modulate motor neuron excitability in the absence of functional supraspinal influence, although with much less consistency than that in NI individuals.

  2. Reactive oxygen species-dependent wound responses in animals and plants.

    Science.gov (United States)

    Suzuki, Nobuhiro; Mittler, Ron

    2012-12-15

    Animals and plants evolved sophisticated mechanisms that regulate their responses to mechanical injury. Wound response in animals mainly promotes wound healing processes, nerve cell regeneration, and immune system responses at the vicinity of the wound site. In contrast, wound response in plants is primarily directed at sealing the wound site via deposition of various compounds and generating systemic signals that activate multiple defense mechanisms in remote tissues. Despite these differences between animals and plants, recent studies have shown that reactive oxygen species (ROS) play very common signaling and coordination roles in the wound responses of both systems. This review provides an update on recent findings related to ROS-regulated coordination of intercellular communications and signal transduction during wound response in plants and animals. In particular, differences and similarities in H2O2-dependent long-distance signaling between zebrafish and Arabidopsis thaliana are discussed. Published by Elsevier Inc.

  3. Regulation of Toll-like receptors-dependent inflammatory response 

    Directory of Open Access Journals (Sweden)

    Ewa Kowalczyk

    2013-03-01

    Full Text Available Toll-like receptors (TLRs are a pivotal part of our innate immune response. They recognize a wide variety of pathogens and instigate an immune response, thus facilitating the removal of the disease-causing agent. Due to the intense nature of this response its strict control is of keyimportance, as a prolonged inflammatory signal leads to carcinogenesis and autoimmune disorders. The signaling cascade initiated by the activated TLR is complex and consists of multiple stages. It involves a variety of adaptor proteins, protein kinases and effector transcription factors. The number of stages in this process enables many possible checkpoints and ways of regulation. Signal modulation involves differentiated expression of TLRs, splicing variants of their adaptorproteins, enzymes modifying proteins engaged in the cascade and many more. This review focuses on endogenous factors responsible for controlling the TLR-dependent inflammatory response as well as on pharmacological therapies designed for regulating the innate immune response.  

  4. A variational formulation of electrostatics in a medium with spatially varying dielectric permittivity.

    Science.gov (United States)

    Jadhao, Vikram; Solis, Francisco J; Olvera de la Cruz, Monica

    2013-02-07

    In biological and synthetic materials, many important processes involve charges that are present in a medium with spatially varying dielectric permittivity. To accurately understand the role of electrostatic interactions in such systems, it is important to take into account the spatial dependence of the permittivity of the medium. However, due to the ensuing theoretical and computational challenges, this inhomogeneous dielectric response of the medium is often ignored or excessively simplified. We develop a variational formulation of electrostatics to accurately investigate systems that exhibit this inhomogeneous dielectric response. Our formulation is based on a true energy functional of the polarization charge density. The defining characteristic of a true energy functional is that at its minimum it evaluates to the actual value of the energy; this is a feature not found in many commonly used electrostatic functionals. We explore in detail the charged systems that exhibit sharp discontinuous change in dielectric permittivity, and we show that for this case our functional reduces to a functional of only the surface polarization charge density. We apply this reduced functional to study model problems for which analytical solutions are well known. We demonstrate, in addition, that the functional has many properties that make it ideal for use in molecular dynamics simulations.

  5. Mayor Erythropoietic Response after Deferasirox Treatment in a Transfusion-Dependent Anemic Patient with Primary Myelofibrosis

    Science.gov (United States)

    Lisette, Del Corso; Enrico, Balleari; Eleonora, Arboscello; Riccardo, Ghio; Manlio, Mencoboni; Omar, Racchi

    2013-01-01

    Primary myelofibrosis (PMF) is a myeloproliferative neoplasm frequently complicated by transfusion dependent anemia. Both anemia and transfusion-dependence are associated with a poor outcome, at least in part because of toxic effects of iron overload (IOL). Iron-chelating therapy (ICT) is increasingly used in order to prevent IOL in this setting. Here, we describe the case of a 73-year-old man affected by PMF and severe transfusion-dependent anemia who experienced a dramatic erythroid response after being treated with deferasirox to prevent IOL. PMID:24307957

  6. Mayor erythropoietic response after deferasirox treatment in a transfusion-dependent anemic patient with primary myelofibrosis.

    Science.gov (United States)

    Lisette, Del Corso; Enrico, Balleari; Eleonora, Arboscello; Riccardo, Ghio; Manlio, Mencoboni; Omar, Racchi

    2013-01-01

    Primary myelofibrosis (PMF) is a myeloproliferative neoplasm frequently complicated by transfusion dependent anemia. Both anemia and transfusion-dependence are associated with a poor outcome, at least in part because of toxic effects of iron overload (IOL). Iron-chelating therapy (ICT) is increasingly used in order to prevent IOL in this setting. Here, we describe the case of a 73-year-old man affected by PMF and severe transfusion-dependent anemia who experienced a dramatic erythroid response after being treated with deferasirox to prevent IOL.

  7. Mayor Erythropoietic Response after Deferasirox Treatment in a Transfusion-Dependent Anemic Patient with Primary Myelofibrosis

    Directory of Open Access Journals (Sweden)

    Del Corso Lisette

    2013-01-01

    Full Text Available Primary myelofibrosis (PMF is a myeloproliferative neoplasm frequently complicated by transfusion dependent anemia. Both anemia and transfusion-dependence are associated with a poor outcome, at least in part because of toxic effects of iron overload (IOL. Iron-chelating therapy (ICT is increasingly used in order to prevent IOL in this setting. Here, we describe the case of a 73-year-old man affected by PMF and severe transfusion-dependent anemia who experienced a dramatic erythroid response after being treated with deferasirox to prevent IOL.

  8. Nonlinear electroelastic deformations of dielectric elastomer composites: II - Non-Gaussian elastic dielectrics

    Science.gov (United States)

    Lefèvre, Victor; Lopez-Pamies, Oscar

    2017-02-01

    This paper presents an analytical framework to construct approximate homogenization solutions for the macroscopic elastic dielectric response - under finite deformations and finite electric fields - of dielectric elastomer composites with two-phase isotropic particulate microstructures. The central idea consists in employing the homogenization solution derived in Part I of this work for ideal elastic dielectric composites within the context of a nonlinear comparison medium method - this is derived as an extension of the comparison medium method of Lopez-Pamies et al. (2013) in nonlinear elastostatics to the coupled realm of nonlinear electroelastostatics - to generate in turn a corresponding solution for composite materials with non-ideal elastic dielectric constituents. Complementary to this analytical framework, a hybrid finite-element formulation to construct homogenization solutions numerically (in three dimensions) is also presented. The proposed analytical framework is utilized to work out a general approximate homogenization solution for non-Gaussian dielectric elastomers filled with nonlinear elastic dielectric particles that may exhibit polarization saturation. The solution applies to arbitrary (non-percolative) isotropic distributions of filler particles. By construction, it is exact in the limit of small deformations and moderate electric fields. For finite deformations and finite electric fields, its accuracy is demonstrated by means of direct comparisons with finite-element solutions. Aimed at gaining physical insight into the extreme enhancement in electrostriction properties displayed by emerging dielectric elastomer composites, various cases wherein the filler particles are of poly- and mono-disperse sizes and exhibit different types of elastic dielectric behavior are discussed in detail. Contrary to an initial conjecture in the literature, it is found (inter alia) that the isotropic addition of a small volume fraction of stiff (semi

  9. Study on influences of TiN capping layer on time-dependent dielectric breakdown characteristic of ultra-thin EOT high-k metal gate NMOSFET with kMC TDDB simulations

    Science.gov (United States)

    Xu, Hao; Yang, Hong; Luo, Wei-Chun; Xu, Ye-Feng; Wang, Yan-Rong; Tang, Bo; Wang, Wen-Wu; Qi, Lu-Wei; Li, Jun-Feng; Yan, Jiang; Zhu, Hui-Long; Zhao, Chao; Chen, Da-Peng; Ye, Tian-Chun

    2016-08-01

    The thickness effect of the TiN capping layer on the time dependent dielectric breakdown (TDDB) characteristic of ultra-thin EOT high-k metal gate NMOSFET is investigated in this paper. Based on experimental results, it is found that the device with a thicker TiN layer has a more promising reliability characteristic than that with a thinner TiN layer. From the charge pumping measurement and secondary ion mass spectroscopy (SIMS) analysis, it is indicated that the sample with the thicker TiN layer introduces more Cl passivation at the IL/Si interface and exhibits a lower interface trap density. In addition, the influences of interface and bulk trap density ratio N it/N ot are studied by TDDB simulations through combining percolation theory and the kinetic Monte Carlo (kMC) method. The lifetime reduction and Weibull slope lowering are explained by interface trap effects for TiN capping layers with different thicknesses. Project supported by the National High Technology Research and Development Program of China (Grant No. SS2015AA010601), the National Natural Science Foundation of China (Grant Nos. 61176091 and 61306129), and the Opening Project of Key Laboratory of Microelectronics Devices & Integrated Technology, Institute of MicroElectronics of Chinese Academy of Sciences.

  10. Dielectric spectroscopy in agrophysics

    Science.gov (United States)

    Skierucha, W.; Wilczek, A.; Szypłowska, A.

    2012-04-01

    The paper presents scientific foundation and some examples of agrophysical applications of dielectric spectroscopy techniques. The aim of agrophysics is to apply physical methods and techniques for studies of materials and processes which occur in agriculture. Dielectric spectroscopy, which describes the dielectric properties of a sample as a function of frequency, may be successfully used for examinations of properties of various materials. Possible test materials may include agrophysical objects such as soil, fruit, vegetables, intermediate and final products of the food industry, grain, oils, etc. Dielectric spectroscopy techniques enable non-destructive and non-invasive measurements of the agricultural materials, therefore providing tools for rapid evaluation of their water content and quality. There is a limited number of research in the field of dielectric spectroscopy of agricultural objects, which is caused by the relatively high cost of the respective measurement equipment. With the fast development of modern technology, especially in high frequency applications, dielectric spectroscopy has great potential of expansion in agrophysics, both in cognitive and utilitarian aspects.

  11. Field quantization in inhomogeneous absorptive dielectrics

    NARCIS (Netherlands)

    Suttorp, L.G.; Wubs, Martijn

    2004-01-01

    The quantization of the electromagnetic field in a three-dimensional inhomogeneous dielectric medium with losses is carried out in the framework of a damped-polariton model with an arbitrary spatial dependence of its parameters. The equations of motion for the canonical variables are solved explicit

  12. Spontaneous emission from active dielectric microstructures

    DEFF Research Database (Denmark)

    Søndergaard, Thomas; Tromborg, Bjarne

    2001-01-01

    and engineered due to the dependence of the emission rate on the location and polarisation of the emitters in the structure. This paper addresses the methods of quantum electrodynamics of dielectric media which enable calculation of the local rate of spontaneous emission in active microstructures....

  13. Effect on the grain size of single-mode microwave sintered NiCuZn ferrite and zinc titanate dielectric resonator ceramics.

    Science.gov (United States)

    Sirugudu, Roopas Kiran; Vemuri, Rama Krishna Murthy; Venkatachalam, Subramanian; Gopalakrishnan, Anisha; Budaraju, Srinivasa Murty

    2011-01-01

    Microwave sintering of materials significantly depends on dielectric, magnetic and conductive Losses. Samples with high dielectric and magnetic loss such as ferrites could be sintered easily. But low dielectric loss material such as dielectric resonators (paraelectrics) finds difficulty in generation of heat during microwave interaction. Microwave sintering of materials of these two classes helps in understanding the variation in dielectric and magnetic characteristics with respect to the change in grain size. High-energy ball milled Ni0.6Cu0.2Zn0.2Fe1.98O4-delta and ZnTiO3 are sintered in conventional and microwave methods and characterized for respective dielectric and magnetic characteristics. The grain size variation with higher copper content is also observed with conventional and microwave sintering. The grain size in microwave sintered Ni0.6Cu0.2Zn0.2Fe1.98O4-delta is found to be much small and uniform in comparison with conventional sintered sample. However, the grain size of microwave sintered sample is almost equal to that of conventional sintered sample of Ni0.3Cu0.5Zn0.2Fe1.98O4-delta. In contrast to these high dielectric and magnetic loss ferrites, the paraelectric materials are observed to sinter in presence of microwaves. Although microwave sintered zinc titanate sample showed finer and uniform grains with respect to conventional samples, the dielectric characteristics of microwave sintered sample are found to be less than that of conventional sample. Low dielectric constant is attributed to the low density. Smaller grain size is found to be responsible for low quality factor and the presence of small percentage of TiO2 is observed to achieve the temperature stable resonant frequency.

  14. Pyroelectric and dielectric properties of ferroelectric films with interposed dielectric buffer layers

    Science.gov (United States)

    Espinal, Y.; Kesim, M. T.; Misirlioglu, I. B.; Trolier-McKinstry, S.; Mantese, J. V.; Alpay, S. P.

    2014-12-01

    The dielectric and pyroelectric properties of c-domain ferroelectric films with linear dielectric buffer layers were investigated theoretically. Computations were carried out for multilayers consisting of PbZr0.2Ti0.8O3 with Al2O3, SiO2, Si3N4, HfO2, and TiO2 buffers on metalized Si. It is shown that the dielectric and pyroelectric properties of such multilayers can be increased by the presence of the buffer compared to ferroelectric monolayers. Calculations for PbZr0.2Ti0.8O3 films with 1% Al2O3 interposed between electrodes on Si show that the dielectric and pyroelectric coefficients are 310 and 0.070 μC cm-2 °C-1, respectively. Both values are higher than the intrinsic response of PbZr0.2Ti0.8O3 monolayer on Si.

  15. All-dielectric left-handed metamaterial based on dielectric resonator: design, simulation and experiment

    Institute of Scientific and Technical Information of China (English)

    Yang Yi-Ming; Wang Jia-Fu; Xia Song; Bai Peng; Li Zhe; Wang Jun; Xu Zhuo; Qu Shao-Bo

    2011-01-01

    Dipoles with Lorentz-type resonant electromagnetic responses can realise negative effective parameters in their negative resonant region. The electric dipole and magnetic dipole can realise, respectively, negative permittivity and negative permeability, so both the field distribution forms of electric and magnetic dipoles are fundamentals in designing left-handed metamaterial. Based on this principle, this paper studies the field distribution in high-permittivity dielectric materials. The field distributions at different resonant modes are analysed based on the dielectric resonator theory. The origination and influence factors of the electric and magnetic dipoles are confirmed. Numerical simulations indicate that by combining dielectric cubes with different sizes, the electric resonance frequency and magnetic resonance frequency can be superposed. Finally, experiments are carried out to verify the feasibility of all-dielectric left-handed metamaterial composed by this means.

  16. PREFACE: Dielectrics 2009: Measurement Analysis and Applications

    Science.gov (United States)

    Vaughan, Alun; Williams, Graham

    2009-07-01

    2001 the Annual Meetings focused on numerous topics, including relaxation and conduction processes in liquids, solids, liquid crystals, synthetic polymers and biopolymers, piezoelectric materials, electrets and ferroelectrets, interfacial phenomena, high field conduction and breakdown phenomena in solids, liquids and gases and, importantly, the remarkable developments in dielectric instrumentation during this period. These activities reflected the need, and willingness, to move dielectrics researches with the times. As examples of the variety and diversity of these meetings we may refer briefly to the 1981, 1989 and 1996 Meetings. The 1981 Oxford Meeting on High Field Phenomena in Dielectrics included strong themes on fundamental and practical effects of high E-fields on the dielectric and conduction behaviour of liquids and solids, electrical treeing and dielectric breakdown, non-linear dielectric effects, electrets, thin-film devices and electro-rheology. The late 1980's had seen large initiatives in the UK and globally in the general area of Molecular Electronics so, in timely fashion, this was the subject of the 1989 Meeting in Bangor. The 1996 Smart Dielectrics Meeting at Canterbury reported subsequent advances in designer materials having electro-responsive and electro-optical properties. The programme concerned electro- and photo-active materials, mainly organic, in the form of polar dielectrics, polyelectrolytes, organic semi- and photo-conductors, photo-refractive polymer films, organic ferroelectric films, liquid crystalline polymer films, piezo- and pyro-electric polymer films, electroluminescent polymers, electro-rheological fluids and non-linear optical polymer films as described by leading international scientists. The physico-chemical functions of the materials were demonstrated and interpreted in terms of fundamental molecular properties. An Archive, containing full details of all the Meetings of the DDG and the Dielectrics Society, has been placed on

  17. Temperature and relative humidity dependence of radiochromic film dosimeter response to gamma electron radiation

    DEFF Research Database (Denmark)

    McLaughlin, W.L.; Puhl, J.M.; Miller, A.

    1995-01-01

    on some earlier studies, their response functions have been reported to be dependent on the temperature and relative humidity during irradiation. The present study investigates differences in response over practical ranges of temperature, relative humidity, dose, and for different recent batches of films...... of both types. It is observed that for each new batch of film to be used for radiation processing, the effects of such parameters on response to both gamma rays and electrons should be investigated. It is also suggested that the films should be packaged under controlled atmospheric conditions (relative...

  18. Predator-dependent functional response in wolves: from food limitation to surplus killing.

    Science.gov (United States)

    Zimmermann, Barbara; Sand, Håkan; Wabakken, Petter; Liberg, Olof; Andreassen, Harry Peter

    2015-01-01

    The functional response of a predator describes the change in per capita kill rate to changes in prey density. This response can be influenced by predator densities, giving a predator-dependent functional response. In social carnivores which defend a territory, kill rates also depend on the individual energetic requirements of group members and their contribution to the kill rate. This study aims to provide empirical data for the functional response of wolves Canis lupus to the highly managed moose Alces alces population in Scandinavia. We explored prey and predator dependence, and how the functional response relates to the energetic requirements of wolf packs. Winter kill rates of GPS-collared wolves and densities of cervids were estimated for a total of 22 study periods in 15 wolf territories. The adult wolves were identified as the individuals responsible for providing kills to the wolf pack, while pups could be described as inept hunters. The predator-dependent, asymptotic functional response models (i.e. Hassell-Varley type II and Crowley-Martin) performed best among a set of 23 competing linear, asymptotic and sigmoid models. Small wolf packs acquired >3 times as much moose biomass as required to sustain their field metabolic rate (FMR), even at relatively low moose abundances. Large packs (6-9 wolves) acquired less biomass than required in territories with low moose abundance. We suggest the surplus killing by small packs is a result of an optimal foraging strategy to consume only the most nutritious parts of easy accessible prey while avoiding the risk of being detected by humans. Food limitation may have a stabilizing effect on pack size in wolves, as supported by the observed negative relationship between body weight of pups and pack size. © 2014 The Authors. Journal of Animal Ecology published by John Wiley & Sons Ltd on behalf of British Ecological Society.

  19. Interaction of a point charge with the surface of a uniaxial dielectric

    CERN Document Server

    Ribič, Primož Rebernik

    2013-01-01

    We analyze the force on a point charge moving at relativistic speeds parallel to the surface of a uniaxial dielectric. Two cases are examined: a lossless dielectric with no dispersion and a dielectric with a plasma type response. The treatment focuses on the peculiarities of the strength and direction of the interaction force as compared to the isotropic case. We show that a plasma type dielectric can, under specific conditions, repel the point charge.

  20. A Microsomal Proteomics View of H2O2- and ABA-Dependent Responses

    KAUST Repository

    Alquraishi, May Majed

    2017-08-21

    The plant hormone abscisic acid (ABA) modulates a number of plant developmental processes and responses to stress. In planta, ABA has been shown to induce reactive oxygen species (ROS) production through the action of plasma membrane-associated nicotinamide adenine dinucleotide phosphate (NADPH)-oxidases. Although quantitative proteomics studies have been performed to identify ABA- or hydrogen peroxide (H₂O₂)-dependent proteins, little is known about the ABA- and H₂O₂-dependent microsomal proteome changes. Here, we examined the effect of 50 µM of either H₂O₂ or ABA on the Arabidopsis microsomal proteome using tandem mass spectrometry and identified 86 specifically H₂O₂-dependent, and 52 specifically ABA-dependent proteins that are differentially expressed. We observed differential accumulation of proteins involved in the tricarboxylic acid (TCA) cycle notably in response to H₂O₂. Of these, aconitase 3 responded to both H₂O₂ and ABA. Additionally, over 30 proteins linked to RNA biology responded significantly to both treatments. Gene ontology categories such as \\'response to stress\\' and \\'transport\\' were enriched, suggesting that H₂O₂ or ABA directly and/or indirectly cause complex and partly overlapping cellular responses. Data are available via ProteomeXchange with identifier PXD006513.

  1. SEX, SELF-ESTEEM, DEPENDENCY AND EXTRADYADIC SEXUAL EXPERIENCE AS RELATED TO JEALOUSY RESPONSES

    NARCIS (Netherlands)

    BUUNK, BP

    1995-01-01

    A study of a heterogeneous sample of 250 mostly married individuals examined the impact of sex, self-esteem, emotional dependency and extradyadic sexual experience upon betrayal-anger, disappointment and self-doubt as responses to extradyadic sexual behavior of the partner. Women scored higher in se

  2. Actin-dependence of the chloroplast cold positioning response in the liverwort Marchantia polymorpha L.

    Directory of Open Access Journals (Sweden)

    Shun Kimura

    2016-09-01

    Full Text Available The subcellular positioning of chloroplasts can be changed by alterations in the environment such as light and temperature. For example, in leaf mesophyll cells, chloroplasts localize along anticlinal cell walls under high-intensity light, and along periclinal cell walls under low-intensity light. These types of positioning responses are involved in photosynthetic optimization. In light-mediated chloroplast positioning responses, chloroplasts move to the appropriate positions in an actin-dependent manner, although some exceptions also depend on microtubule. Even under low-intensity light, at low temperature (e.g., 5°C, chloroplasts localize along anticlinal cell walls; this phenomenon is termed chloroplast cold positioning. In this study, we analyzed whether chloroplast cold positioning is dependent on actin filaments and/or microtubules in the liverwort Marchantia polymorpha L. When liverwort cells were treated with drugs for the de-polymerization of actin filaments, chloroplast cold positioning was completely inhibited. In contrast, chloroplast cold positioning was not affected by treatment with a drug for the de-polymerization of microtubules. These observations indicate the actin-dependence of chloroplast cold positioning in M. polymorpha. Actin filaments during the chloroplast cold positioning response were visualized by using fluorescent probes based on fluorescent proteins in living liverwort cells, and thus, their behavior during the chloroplast cold positioning response was documented.

  3. SEX, SELF-ESTEEM, DEPENDENCY AND EXTRADYADIC SEXUAL EXPERIENCE AS RELATED TO JEALOUSY RESPONSES

    NARCIS (Netherlands)

    BUUNK, BP

    1995-01-01

    A study of a heterogeneous sample of 250 mostly married individuals examined the impact of sex, self-esteem, emotional dependency and extradyadic sexual experience upon betrayal-anger, disappointment and self-doubt as responses to extradyadic sexual behavior of the partner. Women scored higher in se

  4. Anti-TNF treatment blocks the induction of T cell-dependent humoral responses

    NARCIS (Netherlands)

    M. Salinas; L. de Rycke (Leen); B.H. Barendregt (Barbara); J.E. Paramarta (Jacqueline); H. Hreggvidstdottir (Hulda); T. Cantaert (Tineke); M. van der Burg (Mirjam); P.P. Tak (Paul); D. Baeten (Dominique)

    2013-01-01

    textabstractObjective: Experimental and human data suggest that tumour necrosis factor (TNF) blockade may affect B cell responses, in particular the induction of T cell-dependent (TD) humoral immunity. This study aimed to assess this hypothesis directly in patients with arthritis by analysing

  5. Structure of doped polyaniline - dielectric spectroscopy measurements

    OpenAIRE

    Diaz Calleja, R.; Matveeva, E.

    1993-01-01

    The role of doping reagents (residual water and acid anions) in determining the electric properties of a chemically synthesized polyaniline (PANI) was studied using a dielectric spectroscopy method. Dependencies of dielectric losses and susceptibility of PANI as the functions of temperature (-100 ÷ +100°C) and electric field frequency (0.3 ÷ 30000 Hz) were examined at it was shown that water acts as a doping impurity similar to acid anions. The model is proposed to explain the role of water i...

  6. Structure of doped polyaniline - dielectric spectroscopy measurements

    Energy Technology Data Exchange (ETDEWEB)

    Diaz Calleja, R. (Polytechnical Univ. of Valencia, Valencia (Spain)); Matveeva, E.S. (Polytechnical Univ. of Valencia, Valencia (Spain))

    1993-11-01

    The role of doping reagents (residual water and acid anions) in determining the electric properties of a chemically synthesized polyaniline (PANI) was studied using a dielectric spectroscopy method. Dependencies of dielectric losses and susceptibility of PANI as the functions of temperature (-100 / + 100 C) and electric field frequency (0.3 / 30000 Hz) were examined at it was shown that water acts as a doping impurity similar to acid anions. The model is proposed to explain the role of water in terms of adsorption of H[sub 2]O molecules at nitrogen cites of PANI chain and their dissociation. (orig.).

  7. Preparation of high dielectric constant thin films of CaCu3Ti4O12 by sol–gel

    Indian Academy of Sciences (India)

    Deepam Maurya; Devendra P Singh; D C Agrawal; Y N Mohapatra

    2008-02-01

    Preparation of sol–gel derived CaCu3Ti4O12 (CCTO) thin films using two different sols and their characterization including their dielectric response are reported. The properties of CCTO films depend heavily on solvents used to prepare the sols. Dielectric constant as high as ∼900 at 100 kHz could be obtained when acetic acid was used to prepare the sol; in contrast, use of hexanoic acid in the sol yielded films with a much lower dielectric constant. The variation in grain and grain boundary conductivities with temperature has been measured. Activation energies of 0.08 eV and 0.68 eV have been found for grain and grain boundary conduction, respectively.

  8. Effects of Gate Stack Structural and Process Defectivity on High-k Dielectric Dependence of NBTI Reliability in 32 nm Technology Node PMOSFETs

    Directory of Open Access Journals (Sweden)

    H. Hussin

    2014-01-01

    Full Text Available We present a simulation study on negative bias temperature instability (NBTI induced hole trapping in E′ center defects, which leads to depassivation of interface trap precursor in different geometrical structures of high-k PMOSFET gate stacks using the two-stage NBTI model. The resulting degradation is characterized based on the time evolution of the interface and hole trap densities, as well as the resulting threshold voltage shift. By varying the physical thicknesses of the interface silicon dioxide (SiO2 and hafnium oxide (HfO2 layers, we investigate how the variation in thickness affects hole trapping/detrapping at different stress temperatures. The results suggest that the degradations are highly dependent on the physical gate stack parameters for a given stress voltage and temperature. The degradation is more pronounced by 5% when the thicknesses of HfO2 are increased but is reduced by 11% when the SiO2 interface layer thickness is increased during lower stress voltage. However, at higher stress voltage, greater degradation is observed for a thicker SiO2 interface layer. In addition, the existence of different stress temperatures at which the degradation behavior differs implies that the hole trapping/detrapping event is thermally activated.

  9. Simulation of temperature dependent dielectric breakdown in n+-polySi/SiO2/n-6H-SiC structures during Poole-Frenkel stress at positive gate bias

    Science.gov (United States)

    Samanta, Piyas; Mandal, Krishna C.

    2016-08-01

    We present for the first time a thorough investigation of trapped-hole induced gate oxide deterioration and simulation results of time-dependent dielectric breakdown (TDDB) of thin (7-25 nm) silicon dioxide (SiO2) films thermally grown on (0 0 0 1) silicon (Si) face of n-type 6H-silicon carbide (n-6H-SiC). Gate oxide reliability was studied during both constant voltage and current stress with positive bias on the degenerately doped n-type poly-crystalline silicon (n+-polySi) gate at a wide range of temperatures between 27 and 225 °C. The gate leakage current was identified as the Poole-Frenkel (PF) emission of electrons trapped at an energy 0.92 eV below the SiO2 conduction band. Holes were generated in the n+-polySi anode material as well as in the oxide bulk via band-to-band ionization depending on the film thickness tox and the energy of the hot-electrons (emitted via PF mechanism) during their transport through oxide films at oxide electric fields Eox ranging from 5 to 10 MV/cm. Our simulated time-to-breakdown (tBD) results are in excellent agreement with those obtained from time consuming TDDB measurements. It is observed that irrespective of stress temperatures, the tBD values estimated in the field range between 5 and 9 MV/cm better fit to reciprocal field (1/E) model for the thickness range studied here. Furthermore, for a 10 year projected device lifetime, a good reliability margin of safe operating field from 8.5 to 7.5 MV/cm for 7 nm and 8.1 to 6.9 MV/cm for 25 nm thick SiO2 was observed between 27 and 225 °C.

  10. Rate dependent response and failure of a ductile epoxy and carbon fiber reinforced epoxy composite

    Energy Technology Data Exchange (ETDEWEB)

    Brown, Eric N [Los Alamos National Laboratory; Rae, Philip J [Los Alamos National Laboratory; Dattelbaum, Dana M [Los Alamos National Laboratory; Stahl, David B [Los Alamos National Laboratory

    2010-01-01

    An extensive characterization suite has been performed on the response and failure of a ductile epoxy 55A and uniaxial carbon fiber reinforced epoxy composite of IM7 fibers in 55A resin from the quasistatic to shock regime. The quasistatic and intermediate strain rate response, including elastic modulus, yield and failure have are characterized by quasistatic, SHPB, and DMA measurements as a function of fiber orientation and temperature. The high strain rate shock effect of fiber orientation in the composite and response of the pure resin are presented for plate impact experiments. It has previously been shown that at lower impact velocities the shock velocity is strongly dependent on fiber orientation but at higher impact velocity the in-plane and through thickness Hugoniots converge. The current results are compared with previous studies of the shock response of carbon fiber composites with more conventional brittle epoxy matrices. The spall response of the composite is measured and compared with quasistatic fracture toughness measurements.

  11. p18(Hamlet) mediates different p53-dependent responses to DNA-damage inducing agents.

    Science.gov (United States)

    Lafarga, Vanesa; Cuadrado, Ana; Nebreda, Angel R

    2007-10-01

    Cells organize appropriate responses to environmental cues by activating specific signaling networks. Two proteins that play key roles in coordinating stress responses are the kinase p38alpha (MAPK14) and the transcription factor p53 (TP53). Depending on the nature and the extent of the stress-induced damage, cells may respond by arresting the cell cycle or by undergoing cell death, and these responses are usually associated with the phosphorylation of particular substrates by p38alpha as well as the activation of specific target genes by p53. We recently characterized a new p38alpha substrate, named p18(Hamlet) (ZNHIT1), which mediates p53-dependent responses to different genotoxic stresses. Thus, cisplatin or UV light induce stabilization of the p18(Hamlet) protein, which then enhances the ability of p53 to bind to and activate the promoters of pro-apoptotic genes such as NOXA and PUMA leading to apoptosis induction. In a similar way, we report here that p18(Hamlet) can also mediate the cell cycle arrest induced in response to gamma-irradiation, by participating in the p53-dependent upregulation of the cell cycle inhibitor p21(Cip1) (CDKN1A).

  12. Dependence of climate forcing and response on the altitude of black carbon aerosols

    Science.gov (United States)

    Ban-Weiss, George A.; Cao, Long; Bala, G.; Caldeira, Ken

    2012-03-01

    Black carbon aerosols absorb solar radiation and decrease planetary albedo, and thus can contribute to climate warming. In this paper, the dependence of equilibrium climate response on the altitude of black carbon is explored using an atmospheric general circulation model coupled to a mixed layer ocean model. The simulations model aerosol direct and semi-direct effects, but not indirect effects. Aerosol concentrations are prescribed and not interactive. It is shown that climate response of black carbon is highly dependent on the altitude of the aerosol. As the altitude of black carbon increases, surface temperatures decrease; black carbon near the surface causes surface warming, whereas black carbon near the tropopause and in the stratosphere causes surface cooling. This cooling occurs despite increasing planetary absorption of sunlight (i.e. decreasing planetary albedo). We find that the trend in surface air temperature response versus the altitude of black carbon is consistent with our calculations of radiative forcing after the troposphere, stratosphere, and land surface have undergone rapid adjustment, calculated as "regressed" radiative forcing. The variation in climate response from black carbon at different altitudes occurs largely from different fast climate responses; temperature dependent feedbacks are not statistically distinguishable. Impacts of black carbon at various altitudes on the hydrological cycle are also discussed; black carbon in the lowest atmospheric layer increases precipitation despite reductions in solar radiation reaching the surface, whereas black carbon at higher altitudes decreases precipitation.

  13. A single dielectric nanolaser

    Science.gov (United States)

    Huang, Tsung-Yu; Yen, Ta-Jen

    2016-09-01

    To conquer Ohmic losses from metal and enhance pump absorption efficiency of a nanolaser based on surface plasmon polariton, we theoretically calculate the first magnetic and electric scattering coefficient of a dielectric sphere under a plane wave excitation with a dielectric constant of around 12. From this calculation, we could retrieve both negative effective permittivity and permeability of the sphere simultaneously at frequencies around 153 THz in the aids of Lewin's theory and the power distribution clearly demonstrate the expected negative Goos-Hänchen effect, which usually occurred in a negative refractive waveguide, thus creating two energy vortices to trap incident energy and then promoting the pump absorption efficiency. Meanwhile, a magnetic lasing mode at 167.3 THz is demonstrated and reveals a magnetic dipole resonance mode and a circulating energy flow within the dielectric sphere, providing a possible stopped light feedback mechanism to enable the all-dielectric nanolaser. More importantly, the corresponding mode volume is reduced to 0.01λ3 and a gain threshold of 5.1×103 is obtained. To validate our design of all-dielectric nanolaser, we employ finite-difference-time-domain simulation software to examine the behavior of the nanolaser. From simulation, we could obtain a pinned-down population inversion of 0.001 and a lasing peak at around 166.5 THz, which is very consistent with the prediction of Mie theory. Finally, according to Mie theory, we can regard the all-dielectric nanolaser as the excitation of material polariton and thus could make an analogue between lasing modes of the dielectric and metallic nanoparticles.

  14. Broadband Dielectric Spectroscopy on Human Blood

    CERN Document Server

    Wolf, M; Lunkenheimer, P; Loidl, A

    2011-01-01

    Dielectric spectra of human blood reveal a rich variety of dynamic processes. Achieving a better characterization and understanding of these processes not only is of academic interest but also of high relevance for medical applications as, e.g., the determination of absorption rates of electromagnetic radiation by the human body. The dielectric properties of human blood are studied using broadband dielectric spectroscopy, systematically investigating the dependence on temperature and hematocrit value. By covering a frequency range from 1 Hz to 40 GHz, information on all the typical dispersion regions of biological matter is obtained. We find no evidence for a low-frequency relaxation (alpha-relaxation) caused, e.g., by counterion diffusion effects as reported for some types of biological matter. The analysis of a strong Maxwell-Wagner relaxation arising from the polarization of the cell membranes in the 1-100 MHz region (beta-relaxation) allows for the test of model predictions and the determination of variou...

  15. Predicting invasive species impacts: a community module functional response approach reveals context dependencies.

    Science.gov (United States)

    Paterson, Rachel A; Dick, Jaimie T A; Pritchard, Daniel W; Ennis, Marilyn; Hatcher, Melanie J; Dunn, Alison M

    2015-03-01

    Predatory functional responses play integral roles in predator-prey dynamics, and their assessment promises greater understanding and prediction of the predatory impacts of invasive species. Other interspecific interactions, however, such as parasitism and higher-order predation, have the potential to modify predator-prey interactions and thus the predictive capability of the comparative functional response approach. We used a four-species community module (higher-order predator; focal native or invasive predators; parasites of focal predators; native prey) to compare the predatory functional responses of native Gammarus duebeni celticus and invasive Gammarus pulex amphipods towards three invertebrate prey species (Asellus aquaticus, Simulium spp., Baetis rhodani), thus, quantifying the context dependencies of parasitism and a higher-order fish predator on these functional responses. Our functional response experiments demonstrated that the invasive amphipod had a higher predatory impact (lower handling time) on two of three prey species, which reflects patterns of impact observed in the field. The community module also revealed that parasitism had context-dependent influences, for one prey species, with the potential to further reduce the predatory impact of the invasive amphipod or increase the predatory impact of the native amphipod in the presence of a higher-order fish predator. Partial consumption of prey was similar for both predators and occurred increasingly in the order A. aquaticus, Simulium spp. and B. rhodani. This was associated with increasing prey densities, but showed no context dependencies with parasitism or higher-order fish predator. This study supports the applicability of comparative functional responses as a tool to predict and assess invasive species impacts incorporating multiple context dependencies. © 2014 The Authors. Journal of Animal Ecology © 2014 British Ecological Society.

  16. Dielectric spectroscopy as a sensor of membrane headgroup mobility and hydration

    DEFF Research Database (Denmark)

    Klösgen, B; Reichle, C; Kohlsmann, S

    1996-01-01

    probe technique makes it possible to sweep the measuring frequency between 1 and 1000 MHz in the temperature range 286-323 K. The response yields both the dispersion (epsilon') and the absorption part (epsilon") of the complex dielectric permittivity, which are attributed to the rotational diffusions...... of the zwitterionic phosphatidylcholine headgroup and the hydration water, respectively. Although the contributions of the headgroup and the hydration dipole moments to the dielectric relaxation are found to be situated close together, we succeeded in separating them. In the language of the Debye description, we...... propose to assign the lower frequency portion of the signal response to the relaxation contributed by the headgroups. The respective relaxation frequency is a discrete value in the range of 15-100 MHz and it shows normal temperature dependence. The contribution of the hydration water molecules exhibits...

  17. Investigation of dielectric properties of different cake formulations during microwave and infrared-microwave combination baking.

    Science.gov (United States)

    Sakiyan, Ozge; Sumnu, Gulum; Sahin, Serpil; Meda, Venkatesh

    2007-05-01

    Dielectric properties can be used to understand the behavior of food materials during microwave processing. Dielectric properties influence the level of interaction between food and high frequency electromagnetic energy. Dielectric properties are, therefore, important in the design of foods intended for microwave preparation. In this study, it was aimed to determine the variation of dielectric properties of different cake formulations during baking in microwave and infrared-microwave combination oven. In addition, the effects of formulation and temperature on dielectric properties of cake batter were examined. Dielectric constant and loss factor of cake samples were shown to be dependent on formulation, baking time, and temperature. The increase in baking time and temperature decreased dielectric constant and loss factor of all formulations. Fat content was shown to increase dielectric constant and loss factor of cakes.

  18. The dielectric function of condensed systems

    CERN Document Server

    Keldysh, LV; Kirzhnitz, DA

    1989-01-01

    Much progress has been made in the understanding of the general properties of the dielectric function and in the calculation of this quantity for many classes of media. This volume gathers together the considerable information available and presents a detailed overview of the present status of the theory of electromagnetic response functions, whilst simultaneously covering a wide range of problems in its application to condensed matter physics.The following subjects are covered:- the dielectric function of the homogeneous electron gas, of crystalline systems, and of inh

  19. Low dielectric constant Parylene-F-like films for intermetal dielectric applications

    Science.gov (United States)

    Hanyaloglu, Bengi; Aydinli, Atilla; Oye, Michael; Aydi, Eray S.

    1999-01-01

    We report on the dielectric properties and thermal stability of thin polymer films that are suitable candidates for replacing silicon dioxide as the intermetal dielectric material in integrated circuits. Parylene-F-like films, (-CF2-C6H4-CF2-)n, were produced by plasma deposition from a mixture of Ar and 1,4-bis(trifluoromethyl)benzene (CF3-C6H4-CF3) discharges and characterized using infrared absorption spectroscopy, spectroscopic ellipsometry, and capacitance measurements. The dielectric constant and the magnitude of the electronic and ionic contributions to the dielectric constant were determined through capacitance measurements and Kramers-Kronig analysis of the infrared absorption data. The film's dielectric constant ranges between 2 and 2.6 depending on the deposition conditions and the largest contribution to the dielectric constant is electronic. The films deposited at 300 °C are stable above 400 °C and further optimization could push this limit to as high as 500 °C.

  20. Pyridoxine-dependent epilepsy initially responsive to phenobarbital Epilepsia por dependência de piridoxina inicialmente responsiva ao fenobarbital

    Directory of Open Access Journals (Sweden)

    Jaime Lin

    2007-12-01

    Full Text Available Pyridoxine-dependent epilepsy is a rare autossomal recessive disorder characterized by recurrent seizures that are not controlled by anticonvulsant medications but remits after administration of pyridoxine. We report on a 30 day-old girl who presented with seizures during the first day of life, initially responsive to anticonvulsant therapy, which remitted within two weeks. Seizures were characterized as multifocal myoclonic jerks of upper and lower limbs associated with buccal-lingual oral movements and eyelid blinking. Laboratory and neuroimaging studies were normal. Electroencephalographic record demonstrated a abnormal background activity with high-voltage epileptic discharges and a burst-suppression pattern. The seizures ceased after oral administration of pyridoxine, but recurred after withdrawal, confirming the diagnosis.A epilepsia por dependência de piridoxina é uma doença autossômica recessiva rara caracterizada por crises recorrentes refratárias a tratamento medicamentoso, mas que remitem após a administração de piridoxina. Relatamos o caso de menina de 30 dias de vida que iniciou crises convulsivas desde o primeiro dia de vida, inicialmente responsivas a tratamento com drogas anticonvulsivantes, mas que reiniciaram após a segunda semana de vida. As crises eram caracterizadas por movimentos clônicos erráticos de membros superiores e inferiores associados a movimentos oromandibulares e piscamentos. Exames laboratoriais e de neuroimagem foram normais. O exame eletrencefalográfico evidenciou atividade de base desorganizada com descargas epilépticas de alta voltagem associadas a um padrão de surto-supressão. As crises cessaram após a administração de piridoxina e recorreram após a sua retirada, confirmando o diagnóstico.

  1. Bronchodilator response of advanced lung function parameters depending on COPD severity

    Science.gov (United States)

    Jarenbäck, Linnea; Eriksson, Göran; Peterson, Stefan; Ankerst, Jaro; Bjermer, Leif; Tufvesson, Ellen

    2016-01-01

    Background COPD is defined as partly irreversible airflow obstruction. The response pattern of bronchodilators has not been followed in advanced lung function parameters. Purpose The aim of this study was to investigate bronchodilator response pattern in advanced lung function parameters in a continuous fashion along forced expiratory volume in 1 second (FEV1) percent predicted (%p) in COPD patients and controls. Patients and methods Eighty-one smokers/ex-smokers (41 controls and 40 COPD) performed spirometry, body plethysmography, impulse oscillometry and single-breath helium dilution carbon monoxide diffusion at baseline, after salbutamol inhalation and then after an additional inhalation of ipratropium. Results Most pulmonary function parameters showed a linear increase in response to decreased FEV1%p. The subjects were divided into groups of FEV1%p 65, and the findings from continuous analysis were verified. The exceptions to this linear response were inspiratory capacity (IC), forced vital capacity (FVC), FEV1/FVC and expiratory resistance (Rex), which showed a segmented response relationship to FEV1%p. IC and FVC, with break points (BP) of 57 and 58 FEV1%p respectively, showed no response above, but an incresed slope below the BP. In addition, in patients with FEV1%p 65, response of FEV1%p did not correlate to response of volume parameters. Conclusion Response of several advanced lung function parameters differs depending on patients’ baseline FEV1%p, and specifically response of volume parameters is most pronounced in COPD patients with FEV1%p <65. Volume and resistance responses do not follow the flow response measured with FEV1 and may thus be used as a complement to FEV1 reversibility to identify flow, volume and resistance responders. PMID:27932874

  2. Abnormal dielectric behaviors in Mn-doped CaCu{sub 3}Ti{sub 4}O{sub 12} ceramics and their response mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Yuan-Hua, E-mail: linyh@tsinghua.edu.cn [State Key Laboratory of New Ceramics and Fine Processing, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Deng, Wei [State Key Laboratory of New Ceramics and Fine Processing, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Xu, Wei [Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); Liu, Yong [State Key Laboratory of New Ceramics and Fine Processing, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Chen, Dongliang; Zhang, Xiaoli [Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); Nan, Ce-Wen [State Key Laboratory of New Ceramics and Fine Processing, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China)

    2012-12-01

    Highlights: Black-Right-Pointing-Pointer Mn-doping affects the electric behaviors remarkably in CCTO ceramics. Black-Right-Pointing-Pointer The activation energy of grain and grain boundary disappears with increasing the Mn doping concentration. Black-Right-Pointing-Pointer The XANES spectra reveal that valence states of Ti, Mn and Cu in the grain and grain boundary changes greatly. - Abstract: Mn-doped CaCu{sub 3}Ti{sub 4}O{sub 12} (CCTO) polycrystalline ceramics have been prepared by the conventional solid state sintering. Our results indicate that 10% Mn doping can decrease the dielectric permittivity in CaCu{sub 3}Ti{sub 4}O{sub 12} by about 2 orders of magnitude (from 10{sup 4} to 10{sup 2}). The grain and grain boundary activation energies show an obvious increase from 0.054 eV to 0.256 eV, and decrease from 0.724 eV to 0.258 eV with increasing the Mn doping concentration, respectively, which may be caused by the variation of Cu and Ti valence states in the CCTO samples evidenced by the X-ray absorption spectra. The similar grain and grain boundary activation energies result in invalidation of the internal boundary layer capacitance effect for the 10% Mn-doped CCTO sample, and thus result in the dramatic decrease of dielectric permittivity.

  3. Dielectric elastomer actuators for facial expression

    Science.gov (United States)

    Wang, Yuzhe; Zhu, Jian

    2016-04-01

    Dielectric elastomer actuators have the advantage of mimicking the salient feature of life: movements in response to stimuli. In this paper we explore application of dielectric elastomer actuators to artificial muscles. These artificial muscles can mimic natural masseter to control jaw movements, which are key components in facial expressions especially during talking and singing activities. This paper investigates optimal design of the dielectric elastomer actuator. It is found that the actuator with embedded plastic fibers can avert electromechanical instability and can greatly improve its actuation. Two actuators are then installed in a robotic skull to drive jaw movements, mimicking the masseters in a human jaw. Experiments show that the maximum vertical displacement of the robotic jaw, driven by artificial muscles, is comparable to that of the natural human jaw during speech activities. Theoretical simulations are conducted to analyze the performance of the actuator, which is quantitatively consistent with the experimental observations.

  4. Multimode directionality in all-dielectric metasurfaces

    CERN Document Server

    Yang, Yuanqing; Kostinski, Sarah V; Odit, Mikhail; Kapitanova, Polina; Qiu, Min; Kivshar, Yuri

    2016-01-01

    All-dielectric resonant nanophotonics has emerged recently as a new direction of research aiming at the manipulation of strong optically-induced electric and magnetic Mie resonances in dielectric nanoparticles with high refractive index, for a design of metadevices with reduced dissipative losses and large resonant enhancement of both electric and magnetic fields. Usually, the geometry of dielectric nanoparticles is considered to be close to either sphere or rod, so the exact Mie solutions of the scattering problem are applied. Here we study nanoparticles with a large aspect ratio (such as nanobars) and describe a novel type of hybrid Mie-Fabry-Perot modes responsible for the existence of multiple magnetic dipole resonances. The multiple magnetic dipoles originate from a combination of a magnetic dipolar mode and a number of standing waves of an elongated anisotropic nanobar. We reveal that these novel hybrid modes can interfere constructively with the induced electric dipoles and thereby lead to multimode un...

  5. Extended-release naltrexone modulates brain response to drug cues in abstinent heroin-dependent patients.

    Science.gov (United States)

    Langleben, Daniel D; Ruparel, Kosha; Elman, Igor; Loughead, James W; Busch, Elliot L; Cornish, James; Lynch, Kevin G; Nuwayser, Elie S; Childress, Anna R; O'Brien, Charles P

    2014-03-01

    Drug cues play an important role in relapse to drug use. Naltrexone is an opioid antagonist that is used to prevent relapse in opioid dependence. Central opioidergic pathways may be implicated in the heightened drug cue-reactivity, but the effects of the opioid receptors' blockade on the brain responses to drug cues in opioid dependence are unknown. To pursue this question, we studied 17 abstinent i.v. heroin users with brain functional magnetic resonance imaging (fMRI) during exposure to visual heroin-related cues and matched neutral images before and 10-14 days after an injection of extended-release naltrexone (XRNTX). Whole brain analysis of variance of fMRI data showed main effect of XRNTX in the medial frontal gyrus, precentral gyrus, cuneus, precuneus, caudate and the amygdala. fMRI response was decreased in the amygdala, cuneus, caudate and the precentral gyrus and increased in the medial frontal gyrus and the precuneus. Higher plasma levels of naltrexone's major metabolite, 6-beta-naltrexol, were associated with larger reduction in the fMRI response to drug cues after XRNTX in the precentral, caudate and amygdala clusters. The present data suggest that XRNTX pharmacotherapy of opioid-dependent patients may, respectively, decrease and potentiate prefrontal and limbic cortical responses to drug cues and that this effect might be related to the XRNTX metabolism. Our findings call for further evaluation of the brain fMRI response to drug-related cues and of the 6-beta-naltrexol levels as potential biomarkers of XRNTX therapeutic effects in patients with opioid dependence.

  6. The effect of ionic species on pH dependent response of silica coated optical fibers

    Science.gov (United States)

    Elwood, Jacqueline; Ohodnicki, Paul R.

    2016-05-01

    Optical fiber pH sensors functionalized with a gold nanoparticle (AuNP)/porous silica film were developed. The transmission of light through the fiber is affected by the change in the refractive index of the porous silica-based nanocomposite coated film as ionic species are concentrated into the coating film when the silica surface becomes negatively charged with increasing pH. To investigate the dependence of the response on the ionic species in solution, we report the optical response of Au/silica film coated fibers in a variety of salt solutions. The response is indeed sensitive to different ionic species in solution. The details of the response are likely also sensitive to the microstructure of the porous silica-based sensing layer.

  7. Thickness and dielectric constant determination of thin dielectric layers

    NARCIS (Netherlands)

    Bruijn, de Helene E.; Minor, Marcel; Kooyman, Rob P.H.; Greve, Jan

    1993-01-01

    We derive a method for the determination of the dielectric constant and thickness of a thin dielectric layer, deposited on top of a thick dielectric layer which is in turn present on a metal film. Reflection of p- and s-polarized light from the metal layer yields minima for certain angles of inciden

  8. Controlling birefringence in dielectrics

    Science.gov (United States)

    Danner, Aaron J.; Tyc, Tomáš; Leonhardt, Ulf

    2011-06-01

    Birefringence, from the very essence of the word itself, refers to the splitting of light rays into two parts. In natural birefringent materials, this splitting is a beautiful phenomenon, resulting in the perception of a double image. In optical metamaterials, birefringence is often an unwanted side effect of forcing a device designed through transformation optics to operate in dielectrics. One polarization is usually implemented in dielectrics, and the other is sacrificed. Here we show, with techniques beyond transformation optics, that this need not be the case, that both polarizations can be controlled to perform useful tasks in dielectrics, and that rays, at all incident angles, can even follow different trajectories through a device and emerge together as if the birefringence did not exist at all. A number of examples are shown, including a combination Maxwell fisheye/Luneburg lens that performs a useful task and is achievable with current fabrication materials.

  9. Dielectric assist accelerating structure

    Science.gov (United States)

    Satoh, D.; Yoshida, M.; Hayashizaki, N.

    2016-01-01

    A higher-order TM02 n mode accelerating structure is proposed based on a novel concept of dielectric loaded rf cavities. This accelerating structure consists of ultralow-loss dielectric cylinders and disks with irises which are periodically arranged in a metallic enclosure. Unlike conventional dielectric loaded accelerating structures, most of the rf power is stored in the vacuum space near the beam axis, leading to a significant reduction of the wall loss, much lower than that of conventional normal-conducting linac structures. This allows us to realize an extremely high quality factor and a very high shunt impedance at room temperature. A simulation of a 5 cell prototype design with an existing alumina ceramic indicates an unloaded quality factor of the accelerating mode over 120 000 and a shunt impedance exceeding 650 M Ω /m at room temperature.

  10. Influence of conductivity and dielectric constant of water-dioxane mixtures on the electrical response of SiNW-based FETs.

    Science.gov (United States)

    Mescher, Marleen; Brinkman, Aldo G M; Bosma, Duco; Klootwijk, Johan H; Sudhölter, Ernst J R; de Smet, Louis C P M

    2014-01-01

    In this study, we report on the electrical response of top-down, p-type silicon nanowire field-effect transistors exposed to water and mixtures of water and dioxane. First, the capacitive coupling of the back gate and the liquid gate via an Ag/AgCl electrode were compared in water. It was found that for liquid gating smaller potentials are needed to obtain similar responses of the nanowire compared to back gating. In the case of back gating, the applied potential couples through the buried oxide layer, indicating that the associated capacitance dominates all other capacitances involved during this mode of operation. Next, the devices were exposed to mixtures of water and dioxane to study the effect of these mixtures on the device characteristics, including the threshold voltage (V(T)). The V(T) dependency on the mixture composition was found to be related to the decreased dissociation of the surface silanol groups and the conductivity of the mixture used. This latter was confirmed by experiments with constant conductivity and varying water-dioxane mixtures.

  11. Influence of Conductivity and Dielectric Constant of Water–Dioxane Mixtures on the Electrical Response of SiNW-Based FETs

    Directory of Open Access Journals (Sweden)

    Marleen Mescher

    2014-01-01

    Full Text Available In this study, we report on the electrical response of top-down, p-type silicon nanowire field-effect transistors exposed to water and mixtures of water and dioxane. First, the capacitive coupling of the back gate and the liquid gate via an Ag/AgCl electrode were compared in water. It was found that for liquid gating smaller potentials are needed to obtain similar responses of the nanowire compared to back gating. In the case of back gating, the applied potential couples through the buried oxide layer, indicating that the associated capacitance dominates all other capacitances involved during this mode of operation. Next, the devices were exposed to mixtures of water and dioxane to study the effect of these mixtures on the device characteristics, including the threshold voltage (VT. The VT dependency on the mixture composition was found to be related to the decreased dissociation of the surface silanol groups and the conductivity of the mixture used. This latter was confirmed by experiments with constant conductivity and varying water–dioxane mixtures.

  12. Expression profiling the temperature-dependent amphibian response to infection by Batrachochytrium dendrobatidis.

    Directory of Open Access Journals (Sweden)

    Laia Ribas

    Full Text Available Amphibians are experiencing a panzootic of unprecedented proportions caused by the emergence of Batrachochytrium dendrobatidis (Bd. However, all species are not equally at risk of infection, and risk is further modified by environmental variables, specifically temperature. In order to understand how, and when, hosts mount a response to Bd we analysed infection dynamics and patterns of gene expression in the model amphibian species Silurana (Xenopus tropicalis. Mathematical modelling of infection dynamics demonstrate the existence of a temperature-dependent protective response that is largely independent of the intrinsic growth-rate of Bd. Using temporal expression-profiling by microarrays and qRT-PCR, we characterise this response in the main amphibian lymphoid tissue, the spleen. We demonstrate that clearance of Bd at the host-optimal temperature is not clearly associated with an adaptive immune response, but rather is correlated with the induction of components of host innate immunity including the expression of genes that are associated with the production of the antimicrobial skin peptide preprocareulein (PPCP as well as inflammatory responses. We find that adaptive immunity appears to be lacking at host-optimal temperatures. This suggests that either Bd does not stimulate, or suppresses, adaptive immunity, or that trade-offs exist between innate and adaptive limbs of the amphibian immune system. At cold temperatures, S. tropicalis loses the ability to mount a PPCP-based innate response, and instead manifests a more pronounced inflammatory reaction that is characterised by the production of proteases and higher pathogen burdens. This study demonstrates the temperature-dependency of the amphibian response to infection by Bd and indicates the influence that changing climates may exert on the ectothermic host response to pathogens.

  13. Near-field for electrodynamics at sub-wavelength scales: generalizing to an arbitrary number of dielectrics.

    Science.gov (United States)

    Li, Shaohong; Gao, Yi; Neuhauser, Daniel

    2012-06-21

    We extend the recently developed near-field (NF) method to include an arbitrary number of dielectrics. NF assumes that the dipoles and fields respond instantaneously to the density, without retardation. The central task in NF is the solution of the Poisson equation for every time step, which is here done by a conjugate gradient method which handles any dielectric distribution. The optical response of any metal-dielectric system can now be studied very efficiently in the near field region. The improved NF method is first applied to simple benchmark systems: a gold nanoparticle in vacuum and embedded in silica. The surface plasmons in these systems and their dependence on the dielectrics are reproduced in the new NF approach. As a further application, we study a silver nanoparticle-based structure for the optical detection of a "lipid" (i.e., dielectric) layer in water, where the layer is wrapping around part of the metallic nanostructure. We show the ~0.1-0.15 eV shift in the spectrum due to the presence of the layer, for both spherical and non-spherical (sphere+rod) systems with various polarizations.

  14. Molecular dynamics of the supercooled pharmaceutical agent posaconazole studied via differential scanning calorimetry and dielectric and mechanical spectroscopies.

    Science.gov (United States)

    Adrjanowicz, K; Kaminski, K; Wlodarczyk, P; Grzybowska, K; Tarnacka, M; Zakowiecki, D; Garbacz, G; Paluch, M; Jurga, S

    2013-10-07

    This paper presents comprehensive studies on the molecular dynamics of a pharmaceutically important substance, posaconazole. In order to characterize relaxation dynamics in the supercooled liquid and glassy states, dielectric and mechanical spectroscopies were applied. Dielectric data have indicated multiple relaxation processes that appear above and below the glass transition temperature Tg (τα=100 s) of posaconazole. From the curvature of the dielectric log10(τα) versus inverse of temperature dependence, we determine so-called "fragility", being a very popular parameter for classifying the structural dynamics of supercooled liquids and polymers. From the calculations, we get m=150, which means that is one of the most fragile glass-forming liquids. In this paper, the relaxation dynamics of supercooled posaconazole extracted from the dielectric response function was also confronted with shear-mechanical relaxation. Finally, we have also presented a direct comparison of the fragility and the number of dynamically correlated molecules Nc determined from dynamic calorimetry curves and dielectric and mechanical spectroscopies, showing a clear deviation in the picture of glass-transition dynamics generated by calorimetric and spectroscopic techniques.

  15. Low field, non-destructive investigation of the effect of moisture on the reliability of low-k dielectrics via dielectric relaxation

    Science.gov (United States)

    Laibowitz, Robert; Raja, Archana; Liniger, Eric; Shaw, Thomas

    2015-03-01

    Assessing the reliability of low dielectric constant (problem for the scalability of integrated circuits to reduced dimensions. The decrease in capacitance ensures lower power consumption and shorter RC delays. The materials are typically nanoporous and are composed of Si, C, O and H. We present a non-destructive, low field investigation of the effect of moisture on Back End of Line integrated circuit capacitors as used in industry. The low-k dielectric layers are around 40nm thick with a k=2.5. Through the measurement of dielectric losses as a function of temperature and applied frequency, we assign two relaxation modes of water in the pores of the dielectric, having thermal activation energies of 0.30 and 0.56eV. Study of dielectric loss as a function of humidification yields a direct correlation to the time dependent dielectric breakdown, wherein increased water incursion into the low k dielectric reduces the lifetime of the device.

  16. The Phosphorylation-Dependent Regulation of Mitochondrial Proteins in Stress Responses

    Directory of Open Access Journals (Sweden)

    Yusuke Kanamaru

    2012-01-01

    Full Text Available To maintain cellular homeostasis, cells are equipped with precise systems that trigger the appropriate stress responses. Mitochondria not only provide cellular energy but also integrate stress response signaling pathways, including those regulating cell death. Several lines of evidence suggest that the mitochondrial proteins that function in this process, such as Bcl-2 family proteins in apoptosis and phosphoglycerate mutase family member 5 (PGAM5 in necroptosis, are regulated by several kinases. It has also been suggested that the phosphorylation-dependent regulation of mitochondrial fission machinery, dynamin-related protein 1 (Drp1, facilitates appropriate cellular stress responses. However, mitochondria themselves are also damaged by various stresses. To avoid the deleterious effects exerted by damaged mitochondria, cells remove these mitochondria in a selective autophagic degradation process called mitophagy. Interestingly, several kinases, such as PTEN-induced putative kinase 1 (PINK1 in mammals and stress-responsive mitogen-activated protein (MAP kinases in yeast, have recently been shown to be involved in mitophagy. In this paper, we focus on the phosphorylation-dependent regulation of mitochondrial proteins and discuss the roles of this regulation in the mitochondrial and cellular stress responses.

  17. Analysis of the frequency-dependent response to wave forcing in the extratropics

    Directory of Open Access Journals (Sweden)

    A. J. Haklander

    2006-01-01

    Full Text Available A quasigeostrophic model for the frequency-dependent response of the zonal-mean flow to planetary-wave forcing at Northern Hemisphere (NH midlatitudes is applied to 4-D-Var ECMWF analysis data for six extended winter seasons. The theoretical response is a non-linear function of the frequency of the forcing, the thermal damping time α−1, and a scaling parameter µ which includes the aspect ratio of the meridional to the vertical length scale of the response. Regression of the calculated response from the analyses onto the theoretical response yields height-dependent estimates for both α−1 and µ. The thermal damping time estimated from this dynamical model is about 2 days in the troposphere, 7–10 days in the stratosphere, and 2–4 days in the lower mesosphere. For the stratosphere and lower mesosphere, the estimates lie within the range of existing radiative damping time estimates, but for the troposphere they are significantly smaller.

  18. Nonlinearity and Strain-Rate Dependence in the Deformation Response of Polymer Matrix Composites Modeled

    Science.gov (United States)

    Goldberg, Robert K.

    2000-01-01

    There has been no accurate procedure for modeling the high-speed impact of composite materials, but such an analytical capability will be required in designing reliable lightweight engine-containment systems. The majority of the models in use assume a linear elastic material response that does not vary with strain rate. However, for containment systems, polymer matrix composites incorporating ductile polymers are likely to be used. For such a material, the deformation response is likely to be nonlinear and to vary with strain rate. An analytical model has been developed at the NASA Glenn Research Center at Lewis Field that incorporates both of these features. A set of constitutive equations that was originally developed to analyze the viscoplastic deformation of metals (Ramaswamy-Stouffer equations) was modified to simulate the nonlinear, rate-dependent deformation of polymers. Specifically, the effects of hydrostatic stresses on the inelastic response, which can be significant in polymers, were accounted for by a modification of the definition of the effective stress. The constitutive equations were then incorporated into a composite micromechanics model based on the mechanics of materials theory. This theory predicts the deformation response of a composite material from the properties and behavior of the individual constituents. In this manner, the nonlinear, rate-dependent deformation response of a polymer matrix composite can be predicted.

  19. Resistance to change and frequency of response-dependent stimuli uncorrelated with reinforcement.

    Science.gov (United States)

    Podlesnik, Christopher A; Jimenez-Gomez, Corina; Ward, Ryan D; Shahan, Timothy A

    2009-09-01

    Stimuli uncorrelated with reinforcement have been shown to enhance response rates and resistance to disruption; however, the effects of different rates of stimulus presentations have not been assessed. In two experiments, we assessed the effects of adding different rates of response-dependent brief stimuli uncorrelated with primary reinforcement on relative response rates and resistance to change. In both experiments, pigeons responded on variable-interval 60-s schedules of food reinforcement in two components of a multiple schedule, and brief response-dependent keylight-color changes were added to one or both components. Although relative response rates were not systematically affected in either experiment, relative resistance to presession feeding and extinction were. In Experiment 1, adding stimuli on a variable-interval schedule to one component of a multiple schedule either at a low rate (1 per min) for one group or at a high rate (4 per min) for another group similarly increased resistance to disruption in the components with added stimuli. When high and low rates of stimuli were presented across components (i.e., within subjects) in Experiment 2, however, relative resistance to disruption was greater in the component presenting stimuli at a lower rate. These results suggest that stimuli uncorrelated with food reinforcement do not strengthen responding in the same way as primary reinforcers.

  20. Nonlinear dielectric properties of planar structures based on ferroelectric betaine phosphite films

    Science.gov (United States)

    Balashova, E. V.; Krichevtsov, B. B.; Svinarev, F. B.; Yurko, E. I.

    2014-02-01

    Ferroelectric films of partly deuterated betaine phosphite are grown on NdGaO3(001) substrates with an interdigitated system of electrodes on their surfaces by evaporation at room temperature. These films have a high capacitance in the ferroelectric phase transition range. The dielectric nonlinearity of the grown structures is studied in small-signal and strong-signal response modes and in the intermediate region between these two modes by measuring the capacitance in a dc bias field, dielectric hysteresis loops, and the Fourier spectra of an output signal in the Sawyer-Tower circuit. In the phase transition range, the capacitance control ratio at a bias voltage U bias = 40 V is K ≅ 7. The dielectric nonlinearity of the structures in the paraelectric phase is described by the Landau theory of second-order phase transitions. The additional contribution to the nonlinearity in the ferroelectric phase is related to the motion of domain walls and manifests itself when the input signal amplitude is higher than U st ˜ 0.7-1.0 V. The relaxation times of domain walls are determined from an analysis of the frequency dependences of the dielectric hysteresis.

  1. Dielectric behavior, conduction and EPR active centres in BiVO4 nanoparticles

    Science.gov (United States)

    Venkatesan, Rajalingam; Velumani, Subramaniam; Tabellout, Mohamed; Errien, Nicolas; Kassiba, Abdelhadi

    2013-12-01

    Bismuth vanadate (BiVO4) nanomaterials were synthesized by mechano-chemical ball milling method and complementary investigations were devoted to their structures, nanoparticle morphologies and electronic active centres. The dielectric and conductivity behaviour were analysed systematically in wide temperature and frequency ranges to correlate such physical responses with the peculiarities of the samples. Large interfacial polarisations favoured by high specific surfaces of nanoparticles account for a drastic enhancement of the dielectric function in the quasi-static regime. Exhaustive analyses of the dielectric experiments were achieved and account for the main features of dielectric functions and their related relaxation mechanisms. The electrical conductivity is thermally activated with energies in the range 0.1-0.6 eV depending on the sample features. DC conductivity up to 10-3 S/cm was obtained in well crystallized nanoparticles. Vanadium ions reduction was revealed by EPR spectroscopy with higher concentrations of the active centres (V4+) in more agglomerated and amorphous nanopowders. The EPR spectral parameters of V4+ were determined and correlated with the local environments of reduced vanadium ions and the characteristics of their electronic configurations. An insight is also made on the role of active electronic centres (V4+) on the conduction mechanism in nanostructured BiVO4.

  2. Effect of swift heavy ion irradiation on dielectrics properties of polymer composite films

    Energy Technology Data Exchange (ETDEWEB)

    Singh, N.L. [Physics Department, M.S. University of Baroda, Vadodara 390002 (India)]. E-mail: singhnl_msu@yahoo.com; Qureshi, Anjum [Physics Department, M.S. University of Baroda, Vadodara 390002 (India)]. E-mail: anjumqur@gmail.com; Singh, F. [Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067 (India); Avasthi, D.K. [Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067 (India)

    2007-02-25

    Ferric oxalate was used as organometallics fillers in polyvinyl chloride (PVC) to form polymer matrix composite films at different concentration of filler. These films were irradiated with 80 MeV O{sup 6+} ions at the fluences of 1 x 10{sup 11} and 1 x 10{sup 12} ions/cm{sup 2}. The radiation induced modifications in dielectric properties, microhardness, surface morphology and surface roughness of polymer composite films have been investigated at different concentration (i.e. 5%, 10% and 15%) of filler. It was observed that hardness and electrical conductivity of the films increase with the concentration of the dispersed ferric oxalate and also with the fluence. From the analysis of frequency, f, dependence of dielectric constant, {epsilon}, it has been found that the dielectric response in both pristine and irradiated samples obey the Universal law given by {epsilon} {proportional_to} f {sup n-1}. The dielectric constant/loss is observed to change significantly due to the irradiation. This suggests that ion beam irradiation promotes (i) the metal to polymer bonding and (ii) convert the polymeric structure into hydrogen depleted carbon network. Thus irradiation makes the polymer harder and more conductive. Atomic force microscopy (AFM) shows that average roughness (R {sub a}) of the irradiated films is lower than that of unirradiated films. Surface morphology of irradiated polymer composite films is observed to change. Scanning electron microscopy (SEM) results show that partial agglomeration of fillers in the polymer matrix.

  3. The hyperaemic response to passive leg movement is dependent on nitric oxide

    DEFF Research Database (Denmark)

    Mortensen, Stefan Peter; Askew, Christopher D; Walker, Meegan;

    2012-01-01

    interstitial space. Inhibition of NO synthesis lowered the vasodilatory response to passive leg movement by ~90%. The increase in leg blood flow was lower in elderly subjects compared to young subjects and leg blood flow did not increase when passive leg movement was performed by elderly with peripheral artery...... disease. The results suggest that the hyperaemia induced by passive leg movement is NO dependent. The hyperaemic response to passive leg movement and to ACh was also assessed in elderly subjects and patients with peripheral artery disease....

  4. Calcium-dependent behavioural responses to acute copper exposure in Oncorhynchus mykiss

    DEFF Research Database (Denmark)

    Poulsen, S.B.; Svendsen, Jon Christian; Aarestrup, Kim;

    2014-01-01

    Using rainbow trout Oncorhynchus mykiss, the present study demonstrated that: (1) calcium (Ca) increased the range of copper (Cu) concentrations that O. mykiss avoided; (2) Ca conserved the maintenance of pre-exposure swimming activity during inescapable acute (10 min) Cu exposure. Data showed...... their spontaneous swimming speed, whereas no response was observed in O. mykiss acclimated and tested at high Ca concentration. Collectively, the data support the conclusion that in O. mykiss the behavioural responses to acute Cu exposure are Ca-dependent....

  5. Magnetic effects on dielectric and polarization behavior of multiferroic heterostructures

    Science.gov (United States)

    Dussan, Sandra; Kumar, Ashok; Scott, J. F.; Katiyar, Ram S.

    2010-02-01

    PbZr0.52Ti0.48O3/La0.67Sr0.33MnO3(PZT/LSMO) bilayer with surface roughness ˜1.8 nm thin films have been grown by pulsed laser deposition on LaAlO3(LAO) substrates. High remnant polarization (30-54 μC/cm2), dielectric constant (400-1700), and well saturated magnetization were observed depending upon the deposition temperature of the ferromagnetic layer and applied frequencies. Giant frequency-dependent change in dielectric constant and loss were observed above the ferromagnetic-paramagnetic temperature. The frequency dependent dielectric anomalies are attributed to the change in metallic and magnetic nature of LSMO and also the interfacial effect across the bilayer; an enhanced magnetoelectric interaction may be due to the Parish-Littlewood mechanism of inhomogeneity near the metal-dielectric interface.

  6. Optics of dielectric microstructures

    DEFF Research Database (Denmark)

    Søndergaard, Thomas

    2002-01-01

    microstructures, will be presented in the part I of this thesis consisting of the chapters 2-5. An introductions is given in chapter 2. In part I three methods are presented for calculating spontaneous and classical emission from sources in dielectric microstructures. The first method presented in chapter 3...... near fields and far fields generated by a dipole emitter in finite-sized dielectric disks. A collection of results obtained within the second topic, planar photonic crystal waveguides, are presented in part II of this thesis consisting of the chapters 6-10. Chapter 6 contains a further introduction...

  7. Thermally switchable dielectrics

    Science.gov (United States)

    Dirk, Shawn M.; Johnson, Ross S.

    2013-04-30

    Precursor polymers to conjugated polymers, such as poly(phenylene vinylene), poly(poly(thiophene vinylene), poly(aniline vinylene), and poly(pyrrole vinylene), can be used as thermally switchable capacitor dielectrics that fail at a specific temperature due to the non-conjugated precursor polymer irreversibly switching from an insulator to the conjugated polymer, which serves as a bleed resistor. The precursor polymer is a good dielectric until it reaches a specific temperature determined by the stability of the leaving groups. Conjugation of the polymer backbone at high temperature effectively disables the capacitor, providing a `built-in` safety mechanism for electronic devices.

  8. On the subsystem formulation of linear-response time-dependent DFT.

    Science.gov (United States)

    Pavanello, Michele

    2013-05-28

    A new and thorough derivation of linear-response subsystem time-dependent density functional theory (TD-DFT) is presented and analyzed in detail. Two equivalent derivations are presented and naturally yield self-consistent subsystem TD-DFT equations. One reduces to the subsystem TD-DFT formalism of Neugebauer [J. Chem. Phys. 126, 134116 (2007)]. The other yields Dyson type equations involving three types of subsystem response functions: coupled, uncoupled, and Kohn-Sham. The Dyson type equations for subsystem TD-DFT are derived here for the first time. The response function formalism reveals previously hidden qualities and complications of subsystem TD-DFT compared with the regular TD-DFT of the supersystem. For example, analysis of the pole structure of the subsystem response functions shows that each function contains information about the electronic spectrum of the entire supersystem. In addition, comparison of the subsystem and supersystem response functions shows that, while the correlated response is subsystem additive, the Kohn-Sham response is not. Comparison with the non-subjective partition DFT theory shows that this non-additivity is largely an artifact introduced by the subjective nature of the density partitioning in subsystem DFT.

  9. Responses of Escherichia coli bacteria to two opposing chemoattractant gradients depend on the chemoreceptor ratio.

    Science.gov (United States)

    Kalinin, Yevgeniy; Neumann, Silke; Sourjik, Victor; Wu, Mingming

    2010-04-01

    Escherichia coli chemotaxis has long served as a simple model of environmental signal processing, and bacterial responses to single chemical gradients are relatively well understood. Less is known about the chemotactic behavior of E. coli in multiple chemical gradients. In their native environment, cells are often exposed to multiple chemical stimuli. Using a recently developed microfluidic chemotaxis device, we exposed E. coli cells to two opposing but equally potent gradients of major attractants, methyl-aspartate and serine. The responses of E. coli cells demonstrated that chemotactic decisions depended on the ratio of the respective receptor number of Tar/Tsr. In addition, the ratio of Tar to Tsr was found to vary with cells' growth conditions, whereby it depended on the culture density but not on the growth duration. These results provide biological insights into the decision-making processes of chemotactic bacteria that are subjected to multiple chemical stimuli and demonstrate the importance of the cellular microenvironment in determining phenotypic behavior.

  10. Delay-Dependent Response in Weakly Electric Fish under Closed-Loop Pulse Stimulation.

    Science.gov (United States)

    Forlim, Caroline Garcia; Pinto, Reynaldo Daniel; Varona, Pablo; Rodríguez, Francisco B

    2015-01-01

    In this paper, we apply a real time activity-dependent protocol to study how freely swimming weakly electric fish produce and process the timing of their own electric signals. Specifically, we address this study in the elephant fish, Gnathonemus petersii, an animal that uses weak discharges to locate obstacles or food while navigating, as well as for electro-communication with conspecifics. To investigate how the inter pulse intervals vary in response to external stimuli, we compare the response to a simple closed-loop stimulation protocol and the signals generated without electrical stimulation. The activity-dependent stimulation protocol explores different stimulus delivery delays relative to the fish's own electric discharges. We show that there is a critical time delay in this closed-loop interaction, as the largest changes in inter pulse intervals occur when the stimulation delay is below 100 ms. We also discuss the implications of these findings in the context of information processing in weakly electric fish.

  11. The horizontal angular vestibulo-ocular reflex: a nonlinear mechanism for context-dependent responses.

    Science.gov (United States)

    Ranjbaran, Mina; Galiana, Henrietta L

    2013-11-01

    Studies of the vestibulo-ocular reflex (VOR) have revealed that this type of involuntary eye movement is influenced by viewing distance. This paper presents a bilateral model for the horizontal angular VOR in the dark based on realistic physiological mechanisms. It is shown that by assigning proper nonlinear neural computations at the premotor level, the model is capable of replicating target-distance-dependent VOR responses that are in agreement with geometrical requirements. Central premotor responses in the model are also shown to be consistent with experimental observations. Moreover, the model performance after simulated unilateral canal plugging also reproduces experimental observations, an emerging property. Such local nonlinear computations could similarly generate context-dependent behaviors in other more complex motor systems.

  12. The Influence of Dielectric Decrement on Electrokinetics.

    Science.gov (United States)

    Zhao, Hui; Zhai, Shengjie

    2013-06-01

    We treat the dielectric decrement induced by excess ion polarization as a source of ion specificity and explore its impact on electrokinetics. We employ a modified Poisson-Nernst-Planck (PNP) equations accounting for the dielectric decrement. The dielectric decrement is determined by the excess ion polarization parameter α and when α = 0 the standard PNP model is recovered. Our model shows that ions saturate at large zeta potentials (ζ). Because of ion saturation, a condensed counterion layer forms adjacent to the charged surface, introducing a new length scale, the thickness of the condensed layer (lc ). For the electro-osmotic mobility, the dielectric decrement weakens the electro-osmotic flow owing to the decrease of the dielectric permittivity. At large ζ, when α ≠ 0, the electro-osmotic mobility is found to be proportional to ζ/2, in contrast to ζ predicted by the standard PNP model. This is attributed to ion saturation at large ζ. In terms of the electrophoretic mobility Me , we carry out both an asymptotic analysis in the thin-double-layer limit and solve the full modified PNP model to compute Me . Our analysis reveals that the impact of the dielectric decrement is intriguing. At small and moderate ζ, the dielectric decrement decreases Me with an increasing α. At large ζ, it is well known that the surface conduction becomes significant and plays an important role in determining Me . It is observed that the dielectric decrement effectively reduces the surface conduction. Hence in stark contrast, Me increases as α increases. Our predictions of the contrast dependence of the mobility on α at different zeta potentials qualitatively agree with experimental results on the dependence of the mobility among ions and provide a possible explanation for such ion specificity. Finally, the comparisons between the thin-double-layer asymptotic analysis and the full simulations of the modified PNP model suggest that at large ζ the validity of the thin

  13. Dielectric Behavior of Biomaterials at Different Frequencies on Room Temperature

    Science.gov (United States)

    Shrivastava, B. D.; Barde, Ravindra; Mishra, A.; Phadke, S.

    2014-09-01

    Propagation of electromagnetic (EM) waves in radiofrequency (RF) and microwave systems is described mathematically by Maxwell's equations with corresponding boundary conditions. Dielectric properties of lossless and lossy materials influence EM field distribution. For a better understanding of the physical processes associated with various RF and microwave devices, it is necessary to know the dielectric properties of media that interact with EM waves. For telecommunication and radar devices, variations of complex dielectric permittivity (referring to the dielectric property) over a wide frequency range are important. For RF and microwave applicators intended for thermal treatments of different materials at ISM (industrial, scientific, medical) frequencies, one needs to study temperature and moisture content dependencies of the Permittivity of the treated materials. Many techniques have been developed for the measurement of materials. In the present paper authors used Bones and scales of Fish taken from Narmada River (Rajghat Dist. Barwani) as biomaterials. Dielectric properties of Biomaterials with the frequency range from 1Hz to 10 MHz at room temperature with low water content were measured by in-situ performance dielectric kit. Analysis has been done by Alpha high performance impedance analyzer and LCR meters. The experimental work were carried out in Inter University Consortium UGC-DAE, CSR center Indore MP. Measured value indicates the dielectric constant (ɛ') dielectric loss (ɛ") decreases with increasing frequency while conductivity (σ) increases with frequency increased.

  14. Waveguide sensor with metamaterial structure for determination of dielectric properties

    Science.gov (United States)

    Steigmann, R.; Savin, A.; Isteníková, K.; Faktorová, D.; Fabo, P.

    2017-08-01

    Microwave sensor (MWS) compared with classical sensor, offers many advantage such as rapid and nondestructive measurement. At microwave (MW) frequencies, dielectric properties of materials depend on frequency, moisture content, bulk density and temperature. MW waveguide sensors can measure properties of materials based on MW interaction with matter, and provide information about dielectric properties of investigated dielectric material, characterized with complex permittivity. The paper presents a new approach for determination of the dielectric properties of dielectric material by embedding a metamaterial (MM) structure over the aperture of waveguide sensor in order to increase the sensing properties of classical waveguide sensor. The optimal design of MM structure for waveguide sensor tuning in MW X-band is obtained. In this new approach the MM function in two ways: like a tool for increasing the sensibility of classical waveguide sensor and the tool sensitive to the dielectric properties of investigated material through the adjusted resonance frequency of designed MM units. The numerical simulation of 2D MM structure properties and experimental results for dielectric properties of dielectric materials are carried out.

  15. Interclonal proteomic responses to predator exposure in Daphnia magna may depend on predator composition of habitats.

    Science.gov (United States)

    Otte, Kathrin A; Schrank, Isabella; Fröhlich, Thomas; Arnold, Georg J; Laforsch, Christian

    2015-08-01

    Phenotypic plasticity, the ability of one genotype to express different phenotypes in response to changing environmental conditions, is one of the most common phenomena characterizing the living world and is not only relevant for the ecology but also for the evolution of species. Daphnia, the water flea, is a textbook example for predator-induced phenotypic plastic defences; however, the analysis of molecular mechanisms underlying these inducible defences is still in its early stages. We exposed Daphnia magna to chemical cues of the predator Triops cancriformis to identify key processes underlying plastic defensive trait formation. To get a more comprehensive idea of this phenomenon, we studied four genotypes with five biological replicates each, originating from habitats characterized by different predator composition, ranging from predator-free habitats to habitats containing T. cancriformis. We analysed the morphologies as well as proteomes of predator-exposed and control animals. Three genotypes showed morphological changes when the predator was present. Using a high-throughput proteomics approach, we found 294 proteins which were significantly altered in their abundance after predator exposure in a general or genotype-dependent manner. Proteins connected to genotype-dependent responses were related to the cuticle, protein synthesis and calcium binding, whereas the yolk protein vitellogenin increased in abundance in all genotypes, indicating their involvement in a more general response. Furthermore, genotype-dependent responses at the proteome level were most distinct for the only genotype that shares its habitat with Triops. Altogether, our study provides new insights concerning genotype-dependent and general molecular processes involved in predator-induced phenotypic plasticity in D. magna. © 2015 John Wiley & Sons Ltd.

  16. Global stability for delay-dependent HTLV-I model with CTL immune response

    Science.gov (United States)

    Wang, Yan; Liu, Jun

    2016-06-01

    We present a delay-dependent HTLV-I model with CTL immune response. The basic reproduction number is obtained for the existence of positive steady state. By constructing suitable Lyapunov functions, when the basic reproduction number is less than one, the infection-free steady state is globally asymptotically stable; when the basic reproduction number is greater than one, the infected steady state is globally asymptotically stable.

  17. Differential pathway dependency discovery associated with drug response across cancer cell lines. | Office of Cancer Genomics

    Science.gov (United States)

    The effort to personalize treatment plans for cancer patients involves the identification of drug treatments that can effectively target the disease while minimizing the likelihood of adverse reactions. In this study, the gene-expression profile of 810 cancer cell lines and their response data to 368 small molecules from the Cancer Therapeutics Research Portal (CTRP) are analyzed to identify pathways with significant rewiring between genes, or differential gene dependency, between sensitive and non-sensitive cell lines.

  18. Linear-response time-dependent density-functional theory with pairing fields.

    Science.gov (United States)

    Peng, Degao; van Aggelen, Helen; Yang, Yang; Yang, Weitao

    2014-05-14

    Recent development in particle-particle random phase approximation (pp-RPA) broadens the perspective on ground state correlation energies [H. van Aggelen, Y. Yang, and W. Yang, Phys. Rev. A 88, 030501 (2013), Y. Yang, H. van Aggelen, S. N. Steinmann, D. Peng, and W. Yang, J. Chem. Phys. 139, 174110 (2013); D. Peng, S. N. Steinmann, H. van Aggelen, and W. Yang, J. Chem. Phys. 139, 104112 (2013)] and N ± 2 excitation energies [Y. Yang, H. van Aggelen, and W. Yang, J. Chem. Phys. 139, 224105 (2013)]. So far Hartree-Fock and approximated density-functional orbitals have been utilized to evaluate the pp-RPA equation. In this paper, to further explore the fundamentals and the potential use of pairing matrix dependent functionals, we present the linear-response time-dependent density-functional theory with pairing fields with both adiabatic and frequency-dependent kernels. This theory is related to the density-functional theory and time-dependent density-functional theory for superconductors, but is applied to normal non-superconducting systems for our purpose. Due to the lack of the proof of the one-to-one mapping between the pairing matrix and the pairing field for time-dependent systems, the linear-response theory is established based on the representability assumption of the pairing matrix. The linear response theory justifies the use of approximated density-functionals in the pp-RPA equation. This work sets the fundamentals for future density-functional development to enhance the description of ground state correlation energies and N ± 2 excitation energies.

  19. Neural mechanisms of interstimulus interval-dependent responses in the primary auditory cortex of awake cats

    Directory of Open Access Journals (Sweden)

    Qin Ling

    2009-02-01

    Full Text Available Abstract Background Primary auditory cortex (AI neurons show qualitatively distinct response features to successive acoustic signals depending on the inter-stimulus intervals (ISI. Such ISI-dependent AI responses are believed to underlie, at least partially, categorical perception of click trains (elemental vs. fused quality and stop consonant-vowel syllables (eg.,/da/-/ta/continuum. Methods Single unit recordings were conducted on 116 AI neurons in awake cats. Rectangular clicks were presented either alone (single click paradigm or in a train fashion with variable ISI (2–480 ms (click-train paradigm. Response features of AI neurons were quantified as a function of ISI: one measure was related to the degree of stimulus locking (temporal modulation transfer function [tMTF] and another measure was based on firing rate (rate modulation transfer function [rMTF]. An additional modeling study was performed to gain insight into neurophysiological bases of the observed responses. Results In the click-train paradigm, the majority of the AI neurons ("synchronization type"; n = 72 showed stimulus-locking responses at long ISIs. The shorter cutoff ISI for stimulus-locking responses was on average ~30 ms and was level tolerant in accordance with the perceptual boundary of click trains and of consonant-vowel syllables. The shape of tMTF of those neurons was either band-pass or low-pass. The single click paradigm revealed, at maximum, four response periods in the following order: 1st excitation, 1st suppression, 2nd excitation then 2nd suppression. The 1st excitation and 1st suppression was found exclusively in the synchronization type, implying that the temporal interplay between excitation and suppression underlies stimulus-locking responses. Among these neurons, those showing the 2nd suppression had band-pass tMTF whereas those with low-pass tMTF never showed the 2nd suppression, implying that tMTF shape is mediated through the 2nd suppression. The

  20. Global patterns in lake ecosystem responses to warming based on the temperature dependence of metabolism.

    Science.gov (United States)

    Kraemer, Benjamin M; Chandra, Sudeep; Dell, Anthony I; Dix, Margaret; Kuusisto, Esko; Livingstone, David M; Schladow, S Geoffrey; Silow, Eugene; Sitoki, Lewis M; Tamatamah, Rashid; McIntyre, Peter B

    2017-05-01

    Climate warming is expected to have large effects on ecosystems in part due to the temperature dependence of metabolism. The responses of metabolic rates to climate warming may be greatest in the tropics and at low elevations because mean temperatures are warmer there and metabolic rates respond exponentially to temperature (with exponents >1). However, if warming rates are sufficiently fast in higher latitude/elevation lakes, metabolic rate responses to warming may still be greater there even though metabolic rates respond exponentially to temperature. Thus, a wide range of global patterns in the magnitude of metabolic rate responses to warming could emerge depending on global patterns of temperature and warming rates. Here we use the Boltzmann-Arrhenius equation, published estimates of activation energy, and time series of temperature from 271 lakes to estimate long-term (1970-2010) changes in 64 metabolic processes in lakes. The estimated responses of metabolic processes to warming were usually greatest in tropical/low-elevation lakes even though surface temperatures in higher latitude/elevation lakes are warming faster. However, when the thermal sensitivity of a metabolic process is especially weak, higher latitude/elevation lakes had larger responses to warming in parallel with warming rates. Our results show that the sensitivity of a given response to temperature (as described by its activation energy) provides a simple heuristic for predicting whether tropical/low-elevation lakes will have larger or smaller metabolic responses to warming than higher latitude/elevation lakes. Overall, we conclude that the direct metabolic consequences of lake warming are likely to be felt most strongly at low latitudes and low elevations where metabolism-linked ecosystem services may be most affected. © 2016 John Wiley & Sons Ltd.