WorldWideScience

Sample records for broadband dielectric spectroscopy

  1. Ionomer Dynamics: Insights from Broadband Dielectric Spectroscopy

    Science.gov (United States)

    Runt, James

    2015-03-01

    Ionomers (polymers containing ionic functionality) have been traditionally used as packaging materials and in molding applications, and are now of increasing interest as candidate single ion conductors for energy storage devices, in energy conversion, and for other electroactive materials applications. The focus of this presentation is on the insight that broadband dielectric (impedance) spectroscopy brings to our understanding of ion and polymer dynamics of this family of materials. As an example of our recent work on relatively conductive ionomers, the first portion of the presentation will focus on anion conducting polyphosphazene ionomers, in which polymer bound cations are quaternized with either short alkyl or short ether oxygen chains. The low Tg, amorphous nature, and cation-solvating backbone distinguish polyphosphazenes as promising materials for ion conduction, the iodide variants being of particular interest in solar cells. In the second part of this overview, the first findings on the molecular dynamics of linear precise polyethylene-based ionomers containing 1-methylimidazolium bromide pendants on exactly every 9th, 15th, or 21st carbon atom will be summarized. In order to develop a robust interpretation of the dynamics of these materials, it is imperative to develop a thorough understanding of microphase separation (e.g. ion aggregation), and each of the above studies is complimented by multiangle X-ray scattering experiments. Supported by the NSF Polymers Program and DOE Basic Energy Sciences.

  2. Monitoring Network and Interfacial Healing Processes by Broadband Dielectric Spectroscopy: : A Case Study on Natural Rubber

    NARCIS (Netherlands)

    Hernandez Santana, M.; Grande, A.M.; van der Zwaag, S.; Garcia Espallargas, Santiago J.

    2016-01-01

    Broadband dielectric spectroscopy (BDS) is introduced as a new and powerful technique to monitor network and macroscale damage healing in an elastomer. For the proof of concept, a partially cured sulfur-cured natural rubber (NR) containing reversible disulfides as the healing moiety was employed.

  3. Interest in broadband dielectric spectroscopy to study the electronic transport in materials for lithium batteries

    Energy Technology Data Exchange (ETDEWEB)

    Badot, Jean-Claude, E-mail: jc.badot@chimie-paristech.fr [Institut de Recherche de Chimie Paris, UMR CNRS 8247, Réseau sur le Stockage Electrochimique de l' Energie (RS2E), Chimie Paris Tech, PSL*, 11 rue P. et M. Curie, 75231 Cedex 05 Paris (France); Lestriez, Bernard [Institut des Matériaux Jean Rouxel, UMR CNRS 6502, Université de Nantes, 2 rue de la Houssinière, BP32229, 44322 Nantes (France); Dubrunfaut, Olivier [GeePs | Group of electrical engineering – Paris, UMR CNRS 8507, CentraleSupélec, Univ. Paris-Sud, Université Paris-Saclay, Sorbonne Universités, UPMC Univ Paris 06, 3 & 11 rue Joliot-Curie, Plateau de Moulon, 91192 Gif-sur-Yvette CEDEX, Paris (France)

    2016-11-15

    Highlights: • Broadband dielectric spectroscopy measures the multiscale electronic conductivity from macroscopic to interatomic sizes. • There is an influence of the surface states on the electronic transfer of powdered materials (e.g. thin insulating layer of Li{sub 2}CO{sub 3} on LiNiO{sub 2} and carbon coating on LiFePO{sub 4}). • Electrical relaxations resulting from the interfacial polarizations at the different scales of the carbon black network are evidenced. - Abstract: Broadband dielectric spectroscopy (BDS) is used to measure complex permittivity and conductivity of conducting materials for lithium batteries at frequencies from a few Hz to several GHz with network and impedance analysers. Under the influence of an electric field, there will be charge density fluctuations in the conductor mainly due to electronic transfer. These fluctuations result in dielectric relaxations for frequencies below 100 GHz. The materials are compacted powders in which each element (particles, agglomerates of particles) can have different sizes and morphologies. In the present review, studies are reported on the influence of surface states in LiNiO{sub 2} (ageing and degradation in air) and LiFePO{sub 4} (carbon coating thin layer), and on a composite electrode based on the lithium trivanadate (Li{sub 1.1}V{sub 3}O{sub 8}) active material. The results have shown that the BDS technique is very sensitive to the different scales of materials architectures involved in electronic transport, from interatomic distances to macroscopic sizes.

  4. Molecular dynamics of amorphous pharmaceutical fenofibrate studied by broadband dielectric spectroscopy

    Directory of Open Access Journals (Sweden)

    U. Sailaja

    2016-06-01

    Full Text Available Fenofibrate is mainly used to reduce cholesterol level in patients at risk of cardiovascular disease. Thermal transition study with the help of differential scanning calorimetry (DSC shows that the aforesaid active pharmaceutical ingredient (API is a good glass former. Based on our DSC study, the molecular dynamics of this API has been carried out by broadband dielectric spectroscopy (BDS covering wide temperature and frequency ranges. Dielectric measurements of amorphous fenofibrate were performed after its vitrification by fast cooling from a few degrees above the melting point (Tm=354.11 K to deep glassy state. The sample does not show any crystallization tendency during cooling and reaches the glassy state. The temperature dependence of the structural relaxation has been fitted by single Vogel–Fulcher–Tamman (VFT equation. From VFT fit, glass transition temperature (Tg was estimated as 250.56 K and fragility (m was determined as 94.02. This drug is classified as a fragile glass former. Deviations of experimental data from Kohlrausch–Williams–Watts (KWW fits on high-frequency flank of α-peak indicate the presence of an excess wing in fenofibrate. Based on Ngai׳s coupling model, we identified the excess wing as true Johari–Goldstein (JG process. Below the glass transition temperature one can clearly see a secondary relaxation (γ with an activation energy of 32.67 kJ/mol.

  5. Applying Broadband Dielectric Spectroscopy (BDS) for the Biophysical Characterization of Mammalian Tissues under a Variety of Cellular Stresses.

    Science.gov (United States)

    Souli, Maria P; Klonos, Panagiotis; Fragopoulou, Adamantia F; Mavragani, Ifigeneia V; Pateras, Ioannis S; Kostomitsopoulos, Nikolaos; Margaritis, Lukas H; Zoumpoulis, Pavlos; Kaklamanis, Loukas; Kletsas, Dimitris; Gorgoulis, Vassilis G; Kyritsis, Apostolos; Pissis, Polycarpos; Georgakilas, Alexandros G

    2017-04-15

    The dielectric properties of biological tissues can contribute non-invasively to a better characterization and understanding of the structural properties and physiology of living organisms. The question we asked, is whether these induced changes are effected by an endogenous or exogenous cellular stress, and can they be detected non-invasively in the form of a dielectric response, e.g., an AC conductivity switch in the broadband frequency spectrum. This study constitutes the first methodological approach for the detection of environmental stress-induced damage in mammalian tissues by the means of broadband dielectric spectroscopy (BDS) at the frequencies of 1-10⁶ Hz. Firstly, we used non-ionizing (NIR) and ionizing radiation (IR) as a typical environmental stress. Specifically, rats were exposed to either digital enhanced cordless telecommunication (DECT) radio frequency electromagnetic radiation or to γ-radiation, respectively. The other type of stress, characterized usually by high genomic instability, was the pathophysiological state of human cancer (lung and prostate). Analyzing the results of isothermal dielectric measurements provided information on the tissues' water fraction. In most cases, our methodology proved sufficient in detecting structural changes, especially in the case of IR and malignancy. Useful specific dielectric response patterns are detected and correlated with each type of stress. Our results point towards the development of a dielectric-based methodology for better understanding and, in a relatively invasive way, the biological and structural changes effected by radiation and developing lung or prostate cancer often associated with genomic instability.

  6. Ultra-Broadband Dielectric THz Spectroscopy with Air-Biased-Coherent-Detection

    DEFF Research Database (Denmark)

    D'Angelo, Francesco; Bonn, Mischa; Turchinovich, Dmitry

    2013-01-01

    We present results on ultra-broadband THz-TDS on silicon using air biased coherent detection (ABCD) technique. We find that the positioning of the sample in the spectrometer, leading to the spatial shift of THz focus, is crucial for accurate spectroscopy results....

  7. Broad-band dielectric spectroscopy of Ba 2NaNb 5O 15 single crystal

    Science.gov (United States)

    Buixaderas, E.; Porokhonskyy, V.; Paskhin, A.; Savinov, M.; Petzelt, J.

    2002-12-01

    Barium sodium niobate (BNN) single crystals are studied by IR spectroscopy, time-domain THz transmission spectroscopy, HF coaxial wave-guide technique and LF dielectric spectroscopy to cover the frequency range 10^2 10^{14} Hz in a wide temperature interval. The dielectric response parallel and perpendicular to the polar c-axis is discussed. The ferroelectric transition at T_c=830 K is driven by a relaxational soft mode coupled with another central-mode type relaxation which both gradually disappear on cooling in the ferroelectric phase. Below T_i the parameters of the expected IR active amplitudon were estimated. The low-temperature permittivity increase on cooling for the {ěc E}bot {ěc c} field direction has been explained by an incipient proper ferroelectric-ferroelastic transition driven by an IR and Raman active B2-symmetry soft mode.

  8. Coupling between amino acid and water dynamics by broadband dielectric spectroscopy

    Science.gov (United States)

    Saiz, Luciana; Cerveny, Silvina

    2014-05-01

    The dynamics of proline aqueous solution was investigated for water concentrations from 40 to 60 wt% by dielectric spectroscopy (106 - 109 Hz) in the temperature range from 230 to 300 K, where the solutions remain amorphous. We found two relaxation processes, related with the reorientation of proline and water as previously observed in a higher frequency range at room temperature [1]. We found that both dynamics are strongly coupled, as previously observed in hydrated proteins powders, in spite of the fact that a single amino acid is a molecule much simpler than a protein.

  9. 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.

  10. NATO Advanced Research Workshop on Broadband Dielectric Spectroscopy and its Advanced Technological Applications

    CERN Document Server

    Recent Advances in Broadband Dielectric Spectroscopy

    2013-01-01

    This volume considers experimental and theoretical dielectric studies of the structure and dynamics of complex systems.  Complex systems constitute an almost universal class of materials including associated liquids, polymers, biomolecules, colloids, porous materials, doped ferroelectric crystals, nanomaterials, etc. These systems are characterized by a new "mesoscopic" length scale, intermediate between molecular and macroscopic. The mesoscopic structures of complex systems typically arise from fluctuations or competing interactions and exhibit a rich variety of static and dynamic behaviour. This growing field is interdisciplinary; it complements solid state and statistical physics, and overlaps considerably with chemistry, chemical engineering, materials science, and biology. A common theme in complex systems is that while such materials are disordered on the molecular scale and homogeneous on the macroscopic scale, they usually possess a certain degree of order on an intermediate, or mesoscopic, scale due...

  11. Primary α and secondary β relaxation dynamics of meta-toluidine in the liquid state investigated by broadband dielectric spectroscopy

    Science.gov (United States)

    Švajdlenková, H.; Ruff, A.; Lunkenheimer, P.; Loidl, A.; Bartoš, J.

    2017-08-01

    We report a broadband dielectric spectroscopic (BDS) study on the clustering fragile glass-former meta-toluidine (m-TOL) from 187 K up to 289 K over a wide frequency range of 10-3-109 Hz with focus on the primary α relaxation and the secondary β relaxation above the glass temperature Tg. The broadband dielectric spectra were fitted by using the Havriliak-Negami (HN) and Cole-Cole (CC) models. The β process disappearing at Tβ,disap = 1.12Tg exhibits non-Arrhenius dependence fitted by the Vogel-Fulcher-Tamman-Hesse equation with T0βVFTH in accord with the characteristic differential scanning calorimetry (DSC) limiting temperature of the glassy state. The essential feature of the α process consists in the distinct changes of its spectral shape parameter βHN marked by the characteristic BDS temperatures TB1βHN and TB2βHN. The primary α relaxation times were fitted over the entire temperature and frequency range by several current three-parameter up to six-parameter dynamic models. This analysis reveals that the crossover temperatures of the idealized mode coupling theory model (TcMCT), the extended free volume model (T0EFV), and the two-order parameter (TOP) model (Tmc) are close to TB1βHN, which provides a consistent physical rationalization for the first change of the shape parameter. In addition, the other two characteristic TOP temperatures T0TOP and TA are coinciding with the thermodynamic Kauzmann temperature TK and the second change of the shape parameter at around TB2βHN, respectively. These can be related to the onset of the liquid-like domains in the glassy state or the disappearance of the solid-like domains in the normal liquid state.

  12. Broadband Rotational Spectroscopy

    Science.gov (United States)

    Pate, Brooks

    2014-06-01

    The past decade has seen several major technology advances in electronics operating at microwave frequencies making it possible to develop a new generation of spectrometers for molecular rotational spectroscopy. High-speed digital electronics, both arbitrary waveform generators and digitizers, continue on a Moore's Law-like development cycle that started around 1993 with device bandwidth doubling about every 36 months. These enabling technologies were the key to designing chirped-pulse Fourier transform microwave (CP-FTMW) spectrometers which offer significant sensitivity enhancements for broadband spectrum acquisition in molecular rotational spectroscopy. A special feature of the chirped-pulse spectrometer design is that it is easily implemented at low frequency (below 8 GHz) where Balle-Flygare type spectrometers with Fabry-Perot cavity designs become technologically challenging due to the mirror size requirements. The capabilities of CP-FTMW spectrometers for studies of molecular structure will be illustrated by the collaborative research effort we have been a part of to determine the structures of water clusters - a project which has identified clusters up to the pentadecamer. A second technology trend that impacts molecular rotational spectroscopy is the development of high power, solid state sources in the mm-wave/THz regions. Results from the field of mm-wave chirped-pulse Fourier transform spectroscopy will be described with an emphasis on new problems in chemical dynamics and analytical chemistry that these methods can tackle. The third (and potentially most important) technological trend is the reduction of microwave components to chip level using monolithic microwave integrated circuits (MMIC) - a technology driven by an enormous mass market in communications. Some recent advances in rotational spectrometer designs that incorporate low-cost components will be highlighted. The challenge to the high-resolution spectroscopy community - as posed by Frank De

  13. 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.

  14. Broadband transmission EPR spectroscopy.

    Directory of Open Access Journals (Sweden)

    Wilfred R Hagen

    Full Text Available EPR spectroscopy employs a resonator operating at a single microwave frequency and phase-sensitive detection using modulation of the magnetic field. The X-band spectrometer is the general standard with a frequency in the 9-10 GHz range. Most (biomolecular EPR spectra are determined by a combination of the frequency-dependent electronic Zeeman interaction and a number of frequency-independent interactions, notably, electron spin - nuclear spin interactions and electron spin - electron spin interactions, and unambiguous analysis requires data collection at different frequencies. Extant and long-standing practice is to use a different spectrometer for each frequency. We explore the alternative of replacing the narrow-band source plus single-mode resonator with a continuously tunable microwave source plus a non-resonant coaxial transmission cell in an unmodulated external field. Our source is an arbitrary wave digital signal generator producing an amplitude-modulated sinusoidal microwave in combination with a broadband amplifier for 0.8-2.7 GHz. Theory is developed for coaxial transmission with EPR detection as a function of cell dimensions and materials. We explore examples of a doublet system, a high-spin system, and an integer-spin system. Long, straigth, helical, and helico-toroidal cells are developed and tested with dilute aqueous solutions of spin label hydroxy-tempo. A detection limit of circa 5 µM HO-tempo in water at 800 MHz is obtained for the present setup, and possibilities for future improvement are discussed.

  15. Broadband Transmission EPR Spectroscopy

    Science.gov (United States)

    Hagen, Wilfred R.

    2013-01-01

    EPR spectroscopy employs a resonator operating at a single microwave frequency and phase-sensitive detection using modulation of the magnetic field. The X-band spectrometer is the general standard with a frequency in the 9–10 GHz range. Most (bio)molecular EPR spectra are determined by a combination of the frequency-dependent electronic Zeeman interaction and a number of frequency-independent interactions, notably, electron spin – nuclear spin interactions and electron spin – electron spin interactions, and unambiguous analysis requires data collection at different frequencies. Extant and long-standing practice is to use a different spectrometer for each frequency. We explore the alternative of replacing the narrow-band source plus single-mode resonator with a continuously tunable microwave source plus a non-resonant coaxial transmission cell in an unmodulated external field. Our source is an arbitrary wave digital signal generator producing an amplitude-modulated sinusoidal microwave in combination with a broadband amplifier for 0.8–2.7 GHz. Theory is developed for coaxial transmission with EPR detection as a function of cell dimensions and materials. We explore examples of a doublet system, a high-spin system, and an integer-spin system. Long, straigth, helical, and helico-toroidal cells are developed and tested with dilute aqueous solutions of spin label hydroxy-tempo. A detection limit of circa 5 µM HO-tempo in water at 800 MHz is obtained for the present setup, and possibilities for future improvement are discussed. PMID:23555819

  16. Toward broadband mechanical spectroscopy

    DEFF Research Database (Denmark)

    Hecksher, Tina; Torchinsky, Darius; Klieber, Christoph

    2017-01-01

    Diverse material classes exhibit qualitatively similar behavior when made viscous upon cooling toward the glass transition, suggesting a common theoretical basis. We used seven different measurement methods to determine the mechanical relaxation kinetics of a prototype molecular glass former over...... a temporal range of 13 decades and over a temperature range spanning liquid to glassy states. The data conform to time–temperature superposition for the main (alpha) process and to a scaling relation of schematic mode-coupling theory. The broadband mechanical measurements demonstrated have fundamental...

  17. Dielectric Spectroscopy in Biomaterials: Agrophysics

    Science.gov (United States)

    El Khaled, Dalia; Castellano, Nuria N.; Gázquez, Jose A.; Perea-Moreno, Alberto-Jesus; Manzano-Agugliaro, Francisco

    2016-01-01

    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. PMID:28773438

  18. Broadband highly-efficient dielectric metadevices for polarization control

    CERN Document Server

    Kruk, Sergey; Kravchenko, Ivan; Miroshnichenko, Andrey; Neshev, Dragomir N; Kivshar, Yuri S

    2016-01-01

    Metadevices based on dielectric nanostructured surfaces with both electric and magnetic Mie-type resonances have resulted in the best efficiency to date for functional flat optics with only one disadvantage: narrow operational bandwidth. Here we experimentally demonstrate broadband transparent all-dielectric metasurfaces for highly efficient polarization manipulation. We utilize the generalized Huygens principle with a superposition of the scattering contributions from several electric and magnetic multipolar modes of the constituent meta-atoms to achieve destructive interference in reflection over a large spectral bandwidth. By employing this novel concept, we demonstrate reflectionless (~90% transmission) half-wave plates, quarter-wave plates, and vector beam q-plates that can operate across multiple telecom bands with ~99% polarization conversion efficiency.

  19. Impedance Spectroscopy of Dielectrics and Electronic Conductors

    DEFF Research Database (Denmark)

    Bonanos, Nikolaos; Pissis, Polycarpos; Macdonald, J. Ross

    2013-01-01

    Impedance spectroscopy is used for the characterization of materials, such as electroceramics, solid and liquid electrochemical cells, dielectrics and also fully integrated devices, such as fuel cells. It consists of measuring the electrical impedance - or a closely related property, such as admi......Impedance spectroscopy is used for the characterization of materials, such as electroceramics, solid and liquid electrochemical cells, dielectrics and also fully integrated devices, such as fuel cells. It consists of measuring the electrical impedance - or a closely related property...

  20. Numerical differentiation methods for the logarithmic derivative technique used in dielectric spectroscopy

    Directory of Open Access Journals (Sweden)

    Henrik Haspel

    2010-06-01

    Full Text Available In dielectric relaxation spectroscopy the conduction contribution often hampers the evaluation of dielectric spectra, especially in the low-frequency regime. In order to overcome this the logarithmic derivative technique could be used, where the calculation of the logarithmic derivative of the real part of the complex permittivity function is needed. Since broadband dielectric measurement provides discrete permittivity function, numerical differentiation has to be used. Applicability of the Savitzky-Golay convolution method in the derivative analysis is examined, and a detailed investigation of the influential parameters (frequency, spectrum resolution, peak shape is presented on synthetic dielectric data.

  1. Broadband Asymmetric Light Transmission at Metal/Dielectric Composite Grating.

    Science.gov (United States)

    Zhu, Rui; Wu, Xuannan; Hou, Yidong; Zheng, Gaige; Zhu, Jianhua; Gao, Fuhua

    2018-01-17

    Optical diode-like effect has sparked growing interest in recent years due to its potential applications in integrated photonic systems. In this paper, we propose and numerically demonstrate a new type of easy-processing metal/dielectric cylinder composite grating on semi-sphere substrate, which can achieve high-contrast asymmetric transmission of unpolarized light for the sum of all diffraction modes in the entire visible region, and effectively guide the diffraction light transmitting out the substrate. The asymmetric light transmission (ALT) ratio is larger than 2 dB in the waveband from 380 nm to 780 nm and the maximum ALT ratio can reach to 13 dB at specified wavelengths. The thorough theoretical research reveals that the proposed metal/dielectric pillar composite grating structure, together with the substrate, can effectively excite localized surface plasmonic resonance (LSPR) effect and waveguide mode (WGM), and enlarge the diffraction difference between forward and backward transmission spaces, including both number of diffraction orders and diffraction efficiency, thus resulting in high-contrast broadband ALT phenomenon. In particular, lowering the symmetry of the grating can achieve polarization-dependent ALT. Such a type of easy-processing ALT device with high performance for both polarized and unpolarized light can be regarded as suitable candidates in practical applications.

  2. 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.

  3. Electronic resonances in broadband stimulated Raman spectroscopy

    Science.gov (United States)

    Batignani, G.; Pontecorvo, E.; Giovannetti, G.; Ferrante, C.; Fumero, G.; Scopigno, T.

    2016-01-01

    Spontaneous Raman spectroscopy is a formidable tool to probe molecular vibrations. Under electronic resonance conditions, the cross section can be selectively enhanced enabling structural sensitivity to specific chromophores and reaction centers. The addition of an ultrashort, broadband femtosecond pulse to the excitation field allows for coherent stimulation of diverse molecular vibrations. Within such a scheme, vibrational spectra are engraved onto a highly directional field, and can be heterodyne detected overwhelming fluorescence and other incoherent signals. At variance with spontaneous resonance Raman, however, interpreting the spectral information is not straightforward, due to the manifold of field interactions concurring to the third order nonlinear response. Taking as an example vibrational spectra of heme proteins excited in the Soret band, we introduce a general approach to extract the stimulated Raman excitation profiles from complex spectral lineshapes. Specifically, by a quantum treatment of the matter through density matrix description of the third order nonlinear polarization, we identify the contributions which generate the Raman bands, by taking into account for the cross section of each process.

  4. Hollow plasmonic antennas for broadband SERS spectroscopy

    Directory of Open Access Journals (Sweden)

    Gabriele C. Messina

    2015-02-01

    Full Text Available The chemical environment of cells is an extremely complex and multifaceted system that includes many types of proteins, lipids, nucleic acids and various other components. With the final aim of studying these components in detail, we have developed multiband plasmonic antennas, which are suitable for highly sensitive surface enhanced Raman spectroscopy (SERS and are activated by a wide range of excitation wavelengths. The three-dimensional hollow nanoantennas were produced on an optical resist by a secondary electron lithography approach, generated by fast ion-beam milling on the polymer and then covered with silver in order to obtain plasmonic functionalities. The optical properties of these structures have been studied through finite element analysis simulations that demonstrated the presence of broadband absorption and multiband enhancement due to the unusual geometry of the antennas. The enhancement was confirmed by SERS measurements, which showed a large enhancement of the vibrational features both in the case of resonant excitation and out-of-resonance excitation. Such characteristics indicate that these structures are potential candidates for plasmonic enhancers in multifunctional opto-electronic biosensors.

  5. Ultra-broadband THz time-domain spectroscopy of common polymers using THz air photonics

    DEFF Research Database (Denmark)

    D’Angelo, Francesco; Mics, Zoltán; Bonn, Mischa

    2014-01-01

    index across the entire spectroscopy window, revealing the high potential of these polymers for applications in THz photonics such as ultra-broadband polymer-based dielectric mirrors, waveguides, and fibers. Resonant high-frequency polar vibrational modes are observed and assigned in polymers PA6......Terahertz-range dielectric properties of the common polymers low-density polyethylene (LDPE), cyclic olefin/ethylene copolymer (TOPAS®), polyamide-6 (PA6), and polytetrafluoroethylene (PTFE or Teflon®) are characterized in the ultra-broadband frequency window 2-15 THz, using a THz time......-domain spectrometer employing air-photonics for the generation and detection of single-cycle sub-50 fs THz transients. The time domain measurements provide direct access to both the absorption and refractive index spectra. The polymers LDPE and TOPAS® demonstrate negligible absorption and spectrally-flat refractive...

  6. Graphical programming for broadband pulse NMR spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Belmonte, S.B. [Universidade do Estado (UERJ), Rio de Janeiro, RJ (Brazil). Dept. de Engenharia Eletronica; Oliveira, I.S.; Guimaraes, A.P. [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil)

    1997-12-31

    In a broadband pulsed nuclear magnetic resonance (NMR) spectrometer we often need to sweep the excitation frequency over a wide range, and acquire the spin echo components in quadrature for further spectral analysis. Computer languages such as C or Pascal have been traditionally applied to the development of software control of laboratory equipment, and consequently, the automatization of NMR experiments. However, the use of graphical languages have proved to be a flexible and convenient way for experiment and data acquisition control. In our application we use the graphical language Labview for the automatic control of a broadband pulse NMR spectrometer, dedicated to the study of magnetic metal systems. (author) 2 refs., 2 figs.

  7. Monitoring alcoholic fermentation by microwave dielectric spectroscopy.

    Science.gov (United States)

    Olmi, Roberto; Meriakri, Viacheslav V; Ignesti, Amleto; Priori, Saverio; Riminesi, Cristiano

    2007-01-01

    The dielectric properties of water solutions of ethanol and sugar are investigated in the microwave region with the objective of setting up a method for the quality control of the fermentation process of alcoholic beverages. Alcoholic fermentation is the process by which carbohydrates, in particular sugar, are converted by the yeast into alcohol. During that process several other by-product compounds are produced, including a significant amount of carbon dioxide. The fermentation stage is of fundamental importance in the production of alcoholic beverages because some of the by-products' components have a considerable effect on the flavour, aroma, and other characteristic properties of the beverages. The on-line monitoring of the fermentation process can thus be very useful for controlling the timing and the development of the process in order to correct it earlier if deviations from "normality" occur. Dielectric spectroscopy is shown to be suitable for such a task, being able to discriminate between the initial water-sugar mixture and the final water-alcohol solution and making it possible to detect the production of carbon dioxide during fermentation. A case-study consisting of the monitoring of the primary fermentqtion of beer by dielectric spectroscopy is presented and discussed.

  8. Broadband Dielectric Spectroscopic Characterization of Thermal Stability of Low-k Dielectric Thin Films for Micro- and Nanoelectronic Applications.

    Science.gov (United States)

    Sunday, Christopher E; Montgomery, Karl R; Amoah, Papa K; Obeng, Yaw S

    2017-01-01

    In this paper, we discuss the use of broadband microwaves (MW) to characterize the thermal stability of organic and hybrid silicon-organic thin films meant for insulation applications in micro- and nanoelectronic devices. We take advantage of MW propagation characteristics to extract and examine the relationships between electrical properties and the chemistry of prototypical low-k materials. The impact of thermal anneal at modest temperatures is examined to shed light on the thermal-induced performance and reliability changes within the dielectric films. These changes are then correlated with the chemical changes in the films, and could provide basis for rational selection of organic dielectrics for integrated devices.

  9. All-dielectric resonant cavity-enabled metals with broadband optical transparency

    Science.gov (United States)

    Liu, Zhengqi; Zhang, Houjiao; Liu, Xiaoshan; Pan, Pingping; Liu, Yi; Tang, Li; Liu, Guiqiang

    2017-06-01

    Metal films with broadband optical transparency are desirable in many optoelectronic devices, such as displays, smart windows, light-emitting diodes and infrared detectors. As bare metal is opaque to light, this issue of transparency attracts great scientific interest. In this work, we proposed and demonstrated a feasible and universal approach for achieving broadband optical transparent (BOT) metals by utilizing all-dielectric resonant cavities. Resonant dielectrics provide optical cavity modes and couple strongly with the surface plasmons of the metal film, and therefore produce a broadband near-unity optical transparent window. The relative enhancement factor (EF) of light transmission exceeds 3400% in comparison with that of pure metal film. Moreover, the transparent metal motif can be realized by other common metals including gold (Au), silver (Ag) and copper (Cu). These optical features together with the fully retained electric and mechanical properties of a natural metal suggest that it will have wide applications in optoelectronic devices.

  10. Broadband and chiral binary dielectric meta-holograms.

    Science.gov (United States)

    Khorasaninejad, Mohammadreza; Ambrosio, Antonio; Kanhaiya, Pritpal; Capasso, Federico

    2016-05-01

    Subwavelength structured surfaces, known as meta-surfaces, hold promise for future compact and optically thin devices with versatile functionalities. By revisiting the concept of detour phase, we demonstrate high-efficiency holograms with broadband and chiral imaging functionalities. In our devices, the apertures of binary holograms are replaced by subwavelength structured microgratings. We achieve broadband operation from the visible to the near infrared and efficiency as high as 75% in the 1.0 to 1.4 μm range by compensating for the inherent dispersion of the detour phase with that of the subwavelength structure. In addition, we demonstrate chiral holograms that project different images depending on the handedness of the reference beam by incorporating a geometric phase. Our devices' compactness, lightness, and ability to produce images even at large angles have significant potential for important emerging applications such as wearable optics.

  11. Broadband and chiral binary dielectric meta-holograms

    Science.gov (United States)

    Khorasaninejad, Mohammadreza; Ambrosio, Antonio; Kanhaiya, Pritpal; Capasso, Federico

    2016-01-01

    Subwavelength structured surfaces, known as meta-surfaces, hold promise for future compact and optically thin devices with versatile functionalities. By revisiting the concept of detour phase, we demonstrate high-efficiency holograms with broadband and chiral imaging functionalities. In our devices, the apertures of binary holograms are replaced by subwavelength structured microgratings. We achieve broadband operation from the visible to the near infrared and efficiency as high as 75% in the 1.0 to 1.4 μm range by compensating for the inherent dispersion of the detour phase with that of the subwavelength structure. In addition, we demonstrate chiral holograms that project different images depending on the handedness of the reference beam by incorporating a geometric phase. Our devices’ compactness, lightness, and ability to produce images even at large angles have significant potential for important emerging applications such as wearable optics. PMID:27386518

  12. Broadband infrared vibrational nano-spectroscopy using thermal blackbody radiation.

    Science.gov (United States)

    O'Callahan, Brian T; Lewis, William E; Möbius, Silke; Stanley, Jared C; Muller, Eric A; Raschke, Markus B

    2015-12-14

    Infrared vibrational nano-spectroscopy based on scattering scanning near-field optical microscopy (s-SNOM) provides intrinsic chemical specificity with nanometer spatial resolution. Here we use incoherent infrared radiation from a 1400 K thermal blackbody emitter for broadband infrared (IR) nano-spectroscopy. With optimized interferometric heterodyne signal amplification we achieve few-monolayer sensitivity in phonon polariton spectroscopy and attomolar molecular vibrational spectroscopy. Near-field localization and nanoscale spatial resolution is demonstrated in imaging flakes of hexagonal boron nitride (hBN) and determination of its phonon polariton dispersion relation. The signal-to-noise ratio calculations and analysis for different samples and illumination sources provide a reference for irradiance requirements and the attainable near-field signal levels in s-SNOM in general. The use of a thermal emitter as an IR source thus opens s-SNOM for routine chemical FTIR nano-spectroscopy.

  13. Single-shot spectroscopy of broadband Yb fiber laser

    Science.gov (United States)

    Suzuki, Masayuki; Yoneya, Shin; Kuroda, Hiroto

    2017-02-01

    We have experimentally reported on a real-time single-shot spectroscopy of a broadband Yb-doped fiber (YDF) laser which based on a nonlinear polarization evolution by using a time-stretched dispersive Fourier transformation technique. We have measured an 8000 consecutive single-shot spectra of mode locking and noise-like pulse (NLP), because our developed broadband YDF oscillator can individually operate the mode locking and NLP by controlling a pump LD power and angle of waveplates. A shot-to-shot spectral fluctuation was observed in NLP. For the investigation of pulse formation dynamics, we have measured the spectral evolution in an initial fluctuations of mode locked broadband YDF laser at an intracavity dispersion of 1500 and 6200 fs2 for the first time. In both case, a build-up time between cw and steady-state mode locking was estimated to be 50 us, the dynamics of spectral evolution between cw and mode locking, however, was completely different. A shot-to-shot strong spectral fluctuation, as can be seen in NLP spectra, was observed in the initial timescale of 20 us at the intracavity dispersion of 1500 fs2. These new findings would impact on understanding the birth of the broadband spectral formation in fiber laser oscillator.

  14. Fluorescence Spectroscopy with Metal-Dielectric Waveguides.

    Science.gov (United States)

    Badugu, Ramachandram; Szmacinski, Henryk; Ray, Krishanu; Descrovi, Emiliano; Ricciardi, Serena; Zhang, Douguo; Chen, Junxue; Huo, Yiping; Lakowicz, Joseph R

    2015-07-16

    We describe a hybrid metal-dielectric waveguide structures (MDWs) with numerous potential applications in the biosciences. These structures consist of a thin metal film coated with a dielectric layer. Depending on the thickness of the dielectric layer, the modes can be localized near the metal, within the dielectric, or at the top surface of the dielectric. The optical modes in a metal-dielectric waveguide can have either S (TE) or P (TM) polarization. The dielectric spacer avoids the quenching, which usually occurs for fluorophores within about 5 nm from the metal. Additionally, the resonances display a sharp angular dependence and can exhibit several hundred-fold increases in intensity (E2) at the silica-air interface relative to the incident intensity. Fluorophores placed on top of the silica layer couple efficiently with the metal, resulting in a sharp angular distribution of emission through the metal and down from the bottom of the structure. This coupling occurs over large distances to several hundred nm away from the metal and was found to be consistent with simulations of the reflectivity of the metal-dielectric waveguides. Remarkably, for some silica thicknesses, the emission is almost completely coupled through the structure with little free-space emission away from the metal-dielectric waveguide. The efficiency of fluorophore coupling is related to the quality of the resonant modes sustained by the metal-dielectric waveguide, resulting in coupling of most of the emission through the metal into the underlying glass substrates. Metal-dielectric waveguides also provide a method to resolve the emission from surface-bound fluorophores from the bulk-phase fluorophores. Metal-dielectric waveguides are simple to fabricate for large surface areas, the resonance wavelength can be adjusted by the dielectric thickness, and the silica surface is suitable for coupling to biomolecules. Metal-dielectric waveguides can have numerous applications in diagnostics and high

  15. Broadband Wide Angle Lens Implemented with Dielectric Metamaterials

    Directory of Open Access Journals (Sweden)

    Anthony Starr

    2011-08-01

    Full Text Available The Luneburg lens is a powerful imaging device, exhibiting aberration free focusing for parallel rays incident from any direction. However, its advantages are offset by a focal surface that is spherical and thus difficult to integrate with standard planar detector and emitter arrays. Using the recently developed technique of transformation optics, it is possible to transform the curved focal surface to a flat plane while maintaining the perfect focusing behavior of the Luneburg over a wide field of view. Here we apply these techniques to a lesser-known refractive Luneburg lens and implement the design with a metamaterial composed of a semi-crystalline distribution of holes drilled in a dielectric. In addition, we investigate the aberrations introduced by various approximations made in the implementation of the lens. The resulting design approach has improved mechanical strength with small aberrations and is ideally suited to implementation at infrared and visible wavelengths.

  16. The kinetics of mutarotation in L-fucose as monitored by dielectric and infrared spectroscopy

    Science.gov (United States)

    Kossack, Wilhelm; Kipnusu, Wycliffe Kiprop; Dulski, Mateusz; Adrjanowicz, Karolina; Madejczyk, Olga; Kaminska, Ewa; Mapesa, Emmanuel Urandu; Tress, Martin; Kaminski, Kamil; Kremer, Friedrich

    2014-06-01

    Fourier Transform Infrared Spectroscopy and Broadband Dielectric Spectroscopy are combined to trace kinetics of mutarotation in L-fucose. After quenching molten samples down to temperatures between T = 313 K and 328 K, the concentrations of two anomeric species change according to a simple exponential time dependence, as seen by an increase in absorbance of specific IR-vibrations. In contrast, the dielectric spectra reveal a slowing down of the structural (α-) relaxation process according to a stretched exponential time dependence (stretching exponent of 1.5 ± 0.2). The rates of change in the IR absorption for α- and β-fucopyranose are (at T = 313 K) nearly one decade faster than that of the intermolecular interactions as measured by the shift of the α-relaxation. This reflects the fact that the α-relaxation monitors the equilibration at a mesoscopic length scale, resulting from fluctuations in the anomeric composition.

  17. All electrical propagating spin wave spectroscopy with broadband wavevector capability

    Energy Technology Data Exchange (ETDEWEB)

    Ciubotaru, F., E-mail: Florin.Ciubotaru@imec.be [imec, Kapeldreef 75, B-3001 Leuven (Belgium); KU Leuven, Departement Electrotechniek (ESAT), Kasteelpark Arenberg 10, B-3001 Leuven (Belgium); Devolder, T. [Centre de Nanosciences et de Nanotechnologies, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91405 Orsay (France); Manfrini, M.; Adelmann, C.; Radu, I. P. [imec, Kapeldreef 75, B-3001 Leuven (Belgium)

    2016-07-04

    We developed an all electrical experiment to perform the broadband phase-resolved spectroscopy of propagating spin waves in micrometer sized thin magnetic stripes. The magnetostatic surface spin waves are excited and detected by scaled down to 125 nm wide inductive antennas, which award ultra broadband wavevector capability. The wavevector selection can be done by applying an excitation frequency above the ferromagnetic resonance. Wavevector demultiplexing is done at the spin wave detector thanks to the rotation of the spin wave phase upon propagation. A simple model accounts for the main features of the apparatus transfer functions. Our approach opens an avenue for the all electrical study of wavevector-dependent spin wave properties including dispersion spectra or non-reciprocal propagation.

  18. Dielectric nanostructures for broadband light trapping in organic solar cells

    KAUST Repository

    Raman, Aaswath

    2011-09-15

    Organic bulk heterojunction solar cells are a promising candidate for low-cost next-generation photovoltaic systems. However, carrier extraction limitations necessitate thin active layers that sacrifice absorption for internal quantum efficiency or vice versa. Motivated by recent theoretical developments, we show that dielectric wavelength-scale grating structures can produce significant absorption resonances in a realistic organic cell architecture. We numerically demonstrate that 1D, 2D and multi-level ITO-air gratings lying on top of the organic solar cell stack produce a 8-15% increase in photocurrent for a model organic solar cell where PCDTBT:PC71BM is the organic semiconductor. Specific to this approach, the active layer itself remains untouched yet receives the benefit of light trapping by nanostructuring the top surface below which it lies. The techniques developed here are broadly applicable to organic semiconductors in general, and enable partial decoupling between active layer thickness and photocurrent generation. © 2011 Optical Society of America.

  19. Broadband mid-IR subharmonic OPOs for molecular spectroscopy

    Science.gov (United States)

    Leindecker, Nick; Marandi, Alireza; Vodopyanov, Konstantin L.; Byer, Robert L.

    2012-02-01

    We generate broadband mid-infrared frequency combs via degenerate optical parametric oscillation in a subharmonic OPO. This technique efficiently transfers the desirable properties of shorter wavelength mode-locked sources to the mid- IR. Our OPO resonator is a 3m or 4m ring cavity composed of one pair of concave mirrors with R=50mm and four flat mirrors, all but one of which are gold coated with > 99% reflection. A single dielectric mirror is used to introduce the pump (2.05 micron from IMRA America, 75 MHz, 80 fs, 600mW or 1.55 micron from Menlo Systems C-fiber, 100 MHz, 70 fs, 350 mW or 1.56 micron from Toptica Photonics FemtoFiber Pro, 80 MHz, 85 fs, 380 mW). The dielectric mirror is transmissive for the pump and reflective in a 2.5- 4 micron or 3- 6 micron (for 2 micron pump) range. Broadband parametric gain around the 3.1-micron subharmonic is provided by short (0.2-0.5mm) periodically poled lithium niobate (MgO:PPLN) at Brewster angle. Crystals were cut from Crystal Technology Inc. material having QPM period of 34.8 microns for type 0 (e=e+e) phase matching at t=32 deg. C. With the 2-micron pump, orientation patterned gallium arsenide from BAE systems is used as the non-linear material In both systems, the enormous acceptance bandwidth at degeneracy, typical for OPOs with type 0 (or type I) phase-matching, gives broad bandwidth and makes temperature tuning insignificant. Broadband oscillation is achieved when signal/idler are brought into degenerate resonance by fine-tuning the cavity length with a mirror on a piezo stage. Using an 8% reflective pellicle, we outcouple a frequency comb of more than 1000nm bandwidth, centered around 3.1 microns from the Er/PPLN system. A 1mm or 2.5mm thick ZnSe plate at Brewster angle provides 2nd-order group velocity dispersion compensation, improving the OPO bandwidth. The OPO threshold was measured to be < 30mW. When locked, the OPO outputs 60 mW of average power centered at 3.1 microns. With the Tm/OP-GaAs system we

  20. Gain-assisted broadband ring cavity enhanced spectroscopy

    Science.gov (United States)

    Selim, Mahmoud A.; Adib, George A.; Sabry, Yasser M.; Khalil, Diaa

    2017-02-01

    Incoherent broadband cavity enhanced spectroscopy can significantly increase the effective path length of light-matter interaction to detect weak absorption lines over broad spectral range, for instance to detect gases in confined environments. Broadband cavity enhancement can be based on the decay time or the intensity drop technique. Decay time measurement is based on using tunable laser source that is expensive and suffers from long scan time. Intensity dependent measurement is usually reported based on broadband source using Fabry-Perot cavity, enabling short measurement time but suffers from the alignment tolerance of the cavity and the cavity insertion loss. In this work we overcome these challenges by using an alignment-free ring cavity made of an optical fiber loop and a directional coupler, while having a gain medium pumped below the lasing threshold to improve the finesse and reduce the insertion loss. Acetylene (C2H2) gas absorption is measured around 1535 nm wavelength using a semiconductor optical amplifier (SOA) gain medium. The system is analyzed for different ring resonator forward coupling coefficient and loses, including the 3-cm long gas cell insertion loss and fiber connector losses used in the experimental verification. The experimental results are obtained for a coupler ratio of 90/10 and a fiber length of 4 m. The broadband source is the amplified spontaneous emission of another SOA and the output is measured using a 70pm-resolution optical spectrum analyzer. The absorption depth and the effective interaction length are improved about an order of magnitude compared to the direct absorption of the gas cell. The presented technique provides an engineering method to improve the finesse and, consequently the effective length, while relaxing the technological constraints on the high reflectivity mirrors and free-space cavity alignment.

  1. Dielectric and Raman spectroscopy of TlSe thin films

    Science.gov (United States)

    Ozel, Aysen E.; Deger, Deniz; Celik, Sefa; Yakut, Sahin; Karabak, Binnur; Akyüz, Sevim; Ulutas, Kemal

    2017-12-01

    In this report, the results of Dielectric and Raman spectroscopy of TlSe thin films are presented. The films were deposited in different thicknesses ranging from 290 Å to 3200 Å by thermal evaporation method. The relative permittivity (dielectric constant εr‧) and dielectric loss (εr″) of TlSe thin films were calculated by measuring capacitance (C) and dielectric loss factor (tan δ) in the frequencies ranging between 10-2 Hz-107 Hz and in the temperature ranging between 173 K and 433 K. In the given intervals, both the dielectric constant and the dielectric loss of TlSe thin films decrease with increasing frequency, but increase with increasing temperature. This behavior can be explained as multicomponent polarization in the structure. The ac conductivity obeys the ωs law when s (s dielectric constant of TlSe thin films is determined from Dielectric and Raman spectroscopy measurements. The results obtained by two different methods are in agreement with each other.

  2. Broadband and high efficiency all-dielectric metasurfaces for wavefront steering with easily obtained phase shift

    Science.gov (United States)

    Yang, Hui; Deng, Yan

    2017-12-01

    All-dielectric metasurfaces for wavefront deflecting and optical vortex generating with broadband and high efficiency are demonstrated. The unit cell of the metasurfaces is optimized to function as a half wave-plate with high polarization conversion efficiency (94%) and transmittance (94.5%) at the telecommunication wavelength. Under such a condition, we can get rid of the complicated parameter sweep process for phase shift selecting. Hence, a phase coverage ranges from 0 to 2 π can be easily obtained by introducing the Pancharatnam-Berry phase. Metasurfaces composed of the two pre-designed super cells are demonstrated for optical beam deflecting and vortex beam generating. It is found that the metasurfaces with more phase shift sampling points (small phase shift increment) exhibit better performance. Moreover, optical vortex beams can be generated by the designed metasurfaces within a wavelength range of 200 nm. These results will provide a viable route for designing broadband and high efficiency devices related to phase modulation.

  3. Molecular dynamics of supercooled ionic liquids studied by light scattering and dielectric spectroscopy

    Science.gov (United States)

    Pabst, Florian; Gabriel, Jan; Weigl, Peter; Blochowicz, Thomas

    2017-09-01

    We investigate molecular dynamics of two supercooled room temperature ionic liquids (RTILs) above of their glass transition temperature by means of dynamic light scattering and broadband dielectric spectroscopy from nanoseconds up to ≈105s . We show that a direct comparison of the raw data of these two techniques allows us to identify the reorientation of ions in the dielectric data, giving experimental evidence to a very recently proposed model of Gainaru et al. [1], stating that the conductivity process in ionic liquids takes place through a reorientational step of ions escaping their cage formed by surrounding counterions. Within this approach we can also understand the apparent decoupling of time constants from dielectric spectroscopy and light scattering, often found in ionic liquids, in a very natural way. Furthermore, as a consequence of knowing the reorientational part of the dielectric spectrum, we are able to show that two more processes contribute to these spectra, which are due to electrode polarization effects. The relative position of all three contributions vary among the systems and may overshadow each other, thus complicating the data analysis and favor misinterpretations.

  4. A large coaxial reflection cell for broadband dielectric characterization of coarse-grained materials

    Science.gov (United States)

    Bore, Thierry; Bhuyan, Habibullah; Bittner, Tilman; Murgan, Vignesh; Wagner, Norman; Scheuermann, Alexander

    2018-01-01

    Knowledge of the frequency-dependent electromagnetic properties of coarse-grained materials is imperative for the successful application of high frequency electromagnetic measurement techniques for near and subsurface monitoring. This paper reports the design, calibration and application of a novel one-port large coaxial cell for broadband complex permittivity measurements of civil engineering materials. It was designed to allow the characterization of heterogeneous material with large aggregate dimensions (up to 28 mm) over a frequency range from 1 MHz–860 MHz. In the first step, the system parameters were calibrated using the measured scattering function in a perfectly known dielectric material in an optimization scheme. In the second step, the method was validated with measurements made on standard liquids. Then the performance of the cell was evaluated on a compacted coarse-grained soil. The dielectric spectra were obtained by means of fitting the measured scattering function using a transverse electromagnetic mode propagation model considering the frequency-dependent complex permittivity. Two scenarios were systematically analyzed and compared. The first scenario consisted of a broadband generalized dielectric relaxation model with two Cole–Cole type relaxation processes related to the interaction of the aqueous phase and the solid phase, a constant high frequency contribution as well as an apparent direct current conductivity term. The second scenario relied on a three-phase theoretical mixture equation which was used in a forward approach in order to calibrate the model. Both scenarios provide almost identical results for the broadband effective complex relative permittivity. The combination of both scenarios suggests the simultaneous estimation of water content, density, bulk and pore water conductivity for road base materials for in situ applications.

  5. Structure evolution in amylopectin/ethylene glycol mixtures by H-bond formation and phase separation studied with dielectric relaxation spectroscopy

    NARCIS (Netherlands)

    Vliegenthart, J.F.G.; Smits, A.L.M.; Wübbenhorst, M.; Kruiskamp, P.H.; Soest, J.J.G. van; Turnhout, J. van

    2001-01-01

    The interaction between amylopectin, a starch polysaccharide, and ethylene glycol (EG) was investigated using broad-band dielectric relaxation spectroscopy. Water-free amylopectin (AP) was mixed with 21 wt % ethylene glycol. This resulted in a continuous ethylene glycol phase, as well as a

  6. A Wireless Multi-Sensor Dielectric Impedance Spectroscopy Platform

    Directory of Open Access Journals (Sweden)

    Seyed Alireza Ghaffari

    2015-09-01

    Full Text Available This paper describes the development of a low-cost, miniaturized, multiplexed, and connected platform for dielectric impedance spectroscopy (DIS, designed for in situ measurements and adapted to wireless network architectures. The platform has been tested and used as a DIS sensor node on ZigBee mesh and was able to interface up to three DIS sensors at the same time and relay the information through the network for data analysis and storage. The system is built from low-cost commercial microelectronics components, performs dielectric spectroscopy ranging from 5 kHz to 100 kHz, and benefits from an on-the-fly calibration system that makes sensor calibration easy. The paper describes the microelectronics design, the Nyquist impedance response, the measurement sensitivity and accuracy, and the testing of the platform for in situ dielectric impedance spectroscopy applications pertaining to fertilizer sensing, water quality sensing, and touch sensing.

  7. Characterization of Large Water Clusters by Broadband Rotational Spectroscopy

    Science.gov (United States)

    Perez, Cristobal; Zaleski, Daniel P.; Seifert, Nathan A.; Pate, Brooks H.; Kisiel, Zbigniew; Temelso, Berhane; Shields, George C.; Shipman, Steven T.; Finnerman, Ian

    2013-06-01

    Most theoretical water models match with experimental result reasonably well up to n=10. For clusters larger than the decamer there is no clear consensus in the global minimum geometries, as the low-energy landscape for a given cluster size changes considerably depending on the model applied. However, there is agreement in considering the undecamer regime as one of the richer pure water cluster regimes, with a large number (>50) of isomers within 1 kcal/mol of the global minimum. Using broadband chirped-pulse Fourier transform microwave (CP-FTMW) spectroscopy operating in the 2-8 GHz frequency range, seven low-energy isomers of the water undecamer have been identified in a pulsed molecular beam. The observed water cluster structures have been identified as belonging to four families on basis to their rotational constants according to their different oxygen atom frameworks. These families can be explained by building up the structures from smaller water cluster subunits. Rotational spectra consistent with theoretical predictions for two isomers of (H_{2}O)_{13} and one of (H_{2}O)_{15} have also been identified. Due to the high density of lines observed in the broadband spectrum, the traditional method of pattern recognition using ab-initio calculations was replaced with a new approach combining high-level ab-initio calculations with automatic fitting tools. These autofitting routines were tested on these systems and are also briefly described.

  8. Structural, optical spectroscopy, optical conductivity and dielectric ...

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 39; Issue 7 ... Spectral dependence of optical parameters; real and imaginaryparts of the dielectric function, refractive index, extinction coefficient and absorption coefficient were carried out in the range between 1.4 and 4.96 eV by using the ellipsometry experiments.

  9. Broadband spectroscopy of the electromagnetic properties of aqueous ferrofluids for biomedical applications

    Energy Technology Data Exchange (ETDEWEB)

    Bellizzi, G., E-mail: gbellizz@unina.i [Dipartimento di Ingegneria Biomedica, Elettronica e delle Telecomunicazioni, Universita di Napoli Federico II, via Claudio 21, 80125 Napoli (Italy); Bucci, O.M. [Dipartimento di Ingegneria Biomedica, Elettronica e delle Telecomunicazioni, Universita di Napoli Federico II, via Claudio 21, 80125 Napoli (Italy); Istituto per il Rilevamento Elettromagnetico dell' Ambiente - Consiglio Nazionale delle Ricerche, via Diocleziano 328, I-80124 Napoli (Italy); Capozzoli, A. [Dipartimento di Ingegneria Biomedica, Elettronica e delle Telecomunicazioni, Universita di Napoli Federico II, via Claudio 21, 80125 Napoli (Italy)

    2010-10-15

    This paper presents the results of a broadband spectroscopy study, over the frequency range 1 MHz-2 GHz, of the electromagnetic properties of a ferrofluid consisting of magnetite nanoparticles, with a mean magnetic size of 10 nm, dispersed in water. An innovative measurement approach and apparatus, allowing an accurate determination of the permeability, even in presence of a large permittivity, have been developed to characterize the suspension. The results obtained show a significant magnetic response over the whole analyzed frequency range, with a good agreement with the theoretical models describing the magnetization dynamics of these systems. Moreover, a strong dielectric response has been detected, which is in satisfactory agreement with the models developed to describe the dielectric behavior of charged nanoparticles suspended in aqueous solution. This result implies that measurement techniques able to determine both the permittivity and permeability become mandatory for a reliable determination of the magnetic properties of aqueous ferrofluids. The accuracy of the determined permeability spectrum is estimated to be of the order of few percent, so these results provide a reliable experimental basis to estimate how fruitful the use of magnetic nanoparticles can be in relevant biomedical applications.

  10. Scanning, non-contact, hybrid broadband diffuse optical spectroscopy and diffuse correlation spectroscopy system.

    Science.gov (United States)

    Johansson, Johannes D; Mireles, Miguel; Morales-Dalmau, Jordi; Farzam, Parisa; Martínez-Lozano, Mar; Casanovas, Oriol; Durduran, Turgut

    2016-02-01

    A scanning system for small animal imaging using non-contact, hybrid broadband diffuse optical spectroscopy (ncDOS) and diffuse correlation spectroscopy (ncDCS) is presented. The ncDOS uses a two-dimensional spectrophotometer retrieving broadband (610-900 nm) spectral information from up to fifty-seven source-detector distances between 2 and 5 mm. The ncDCS data is simultaneously acquired from four source-detector pairs. The sample is scanned in two dimensions while tracking variations in height. The system has been validated with liquid phantoms, demonstrated in vivo on a human fingertip during an arm cuff occlusion and on a group of mice with xenoimplanted renal cell carcinoma.

  11. Dielectric Spectroscopy of Nanostructured Polypyrrole-NiO Composites

    Directory of Open Access Journals (Sweden)

    Syeda Seema

    2014-01-01

    Full Text Available Conducting polypyrrole-nickel oxide (polypyrrole-NiO composites were synthesized by in situ deposition technique by placing different weight percentages of NiO powder (10, 20, 30, 40, and 50% during the polymerisation of pyrrole. The polypyrrole-NiO composites were later characterised with Fourier transform infrared spectroscopy (FTIR which confirms the presence of polypyrrole in the composite. AC conductivity was studied in the frequency range from 102 to 107 Hz. From these studies it is found that AC conductivity remains constant at low frequency and increases rapidly at higher frequency, which is the characteristic behavior of disordered materials. The dielectric behavior of these composites was also investigated in the frequency range 102–107 Hz. It is observed from these studies that the dielectric constant and dielectric tangent loss decrease exponentially with frequency. The composites exhibit a low value of dielectric loss at higher frequency.

  12. Subwavelength silicon through-hole arrays as an all-dielectric broadband terahertz gradient index metamaterial

    Energy Technology Data Exchange (ETDEWEB)

    Park, Sang-Gil; Jeong, Ki-Hun, E-mail: kjeong@kaist.ac.kr [Department of Bio and Brain Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 305-701 (Korea, Republic of); KAIST Institute for Optical Science and Technology, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 305-701 (Korea, Republic of); Lee, Kanghee; Han, Daehoon; Ahn, Jaewook [KAIST Institute for Optical Science and Technology, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 305-701 (Korea, Republic of); Department of Physics, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 305-701 (Korea, Republic of)

    2014-09-01

    Structuring at subwavelength scales brings out artificial media with anomalous optical features called metamaterials. All-dielectric metamaterials have high potential for practical applications over the whole electromagnetic spectrum owing to low loss and optical isotropy. Here, we report subwavelength silicon through-hole arrays as an all-dielectric gradient index metamaterial with broadband THz operation. The unit cell consists of a single subwavelength through-hole on highly resistive monocrystalline silicon. Depending on the fill-factor and period, the effective index was linearly modulated at 0.3–1.6 THz. The experimental results also demonstrate silicon gradient refractive index (Si-GRIN) lenses with parabolic index profiles through the spatial modification of a single unit cell along the radial direction. Si-GRIN lenses either focus 0.4–1.6 THz beam to the diffraction-limit or serve as a flat and thin solid immersion lens on the backside of THz photoconductive antenna for highly efficient pulse extraction. This all-dielectric gradient index metamaterial opens up opportunities for integrated THz GRIN optics.

  13. Time domain PD-detection vs. dielectric spectroscopy

    DEFF Research Database (Denmark)

    Holbøll, Joachim T.; Edin, Hans; Gäfvert, Uno

    1997-01-01

    A theoretically developed relationship between partial discharges and the response from a system for dielectric spectroscopy was experimentally confirmed. The losses caused by the discharges were highest at test voltages with low frequencies. At 0.1 Hz, tanδ tip-up at discharge inception was very...

  14. Dielectric spectroscopy for evaluating dry matter content of potato tubers

    DEFF Research Database (Denmark)

    Gunner Brink Nielsen, Glenn; Kjær, Anders; Klösgen, Beate

    2016-01-01

    The present study investigated the application of dielectric spectroscopy as a method for evaluating the dry matter content of potato tubers. Sample specific factors determining the precision of this application were investigated by studying the prediction of the dry material content in agar gel ...

  15. Broadband THz waveguiding and high-precision broadband time-resolved spectroscopy

    DEFF Research Database (Denmark)

    Cooke, David; Iwaszczuk, Krzysztof; Nielsen, Kristian

    2009-01-01

    , have tailored dispersion and may be bent into sharp bends. Due to the confinement of the THz field in the core of the fibers they are ideal for stable guiding of THz light in confined environments, and may serve as a useful basis for a wealth of fiber-based photonic components in the THz range......We demonstrate optical fibers designed for the THz frequency range, fabricated in a low-loss polymer. The polymer fibers display a broadband loss of 0.4 dB/cm over the 0.1-1 THz range, with a minimum loss of 0.1 dB/cm in the region near 500 GHz. The fibers, based on endlessly single-mode design......, particularly in spectroscopic applications where tight confinement of the THz field is required. We further demonstrate a new spectroscopic technique for ultrafast time-resolved THz time-domain spectroscopy which simultaneously acquires both reference and sample data. By using this scheme we show...

  16. A broadband transparent window in a continuous metal film coated with double layer hybrid dielectric gratings

    Science.gov (United States)

    Cai, Anwei; Tan, Jingfeng

    2017-11-01

    In this letter, we propose a highly conductive and transparent structure which consists of two high-low index dielectric gratings placed on two sides of a continuous metal film. A broadband transparent window with over 550 nm wavelength width and 80% transmission is achieved in both visible and near-infrared regions. The excitation of hybrid plasmons cavity resonances in the structure generates multiple transmission peaks. Three different transmission peaks overlap to yield a broad transparent window with proper parameters. In addition, the transmission spectrum can easily be modified by tuning structural parameters. Its excellent performance makes our proposed structure a promising candidate for optoelectronics, such as the highly conductive transparent electrodes, displays and solar cells.

  17. Dual polarized broadband and all dielectric partial cloaking using stacked graded index structures.

    Science.gov (United States)

    Oner, B B; Can, M G; Kurt, H

    2014-08-25

    We propose broadband one-dimensional optical cloaking design based on isotropic and purely dielectric non-absorbent materials. The photonic structures are formed by utilizing graded index (GRIN) concept in stacked form. All simulations are performed by finite-difference time-domain and plane wave basis frequency domain numerical methods. Indications in ray optics are also presented for the cloaking device. The refractive index distribution of the design is also obtained via effective medium theory. The cloaking devices can reroute wavelengths of light in one dimension. The rerouted light is avoided to reach the interior region of the stacked GRIN structure. Unidirectional GRIN cloaking structure demonstrates low-loss and large bandwidth characteristics. It is shown that the structure operates in dual polarization mode. Performed numerical analyses reveal the capability of cloaking devices to hide arbitrary shaped large objects from the incident light.

  18. Peculiar Bi-ion dynamics in Na.sub.1/2./sub.Bi.sub.1/2./sub.TiO.sub.3./sub. from terahertz and microwave dielectric spectroscopy

    Czech Academy of Sciences Publication Activity Database

    Petzelt, Jan; Nuzhnyy, Dmitry; Bovtun, Viktor; Pasciak, Marek; Kamba, Stanislav; Dittmer, R.; Svirskas, Š.; Banys, J.; Rödel, J.

    2014-01-01

    Roč. 87, 10-11 (2014), s. 953-965 ISSN 0141-1594 R&D Projects: GA ČR GA13-15110S Institutional support: RVO:68378271 Keywords : sodium bismuth titanate * terahertz spectroscopy * broadband dielectric spectroscopy * phase-transition dynamics * Bi-ion dynamics Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.954, year: 2014

  19. Broadband Terahertz Refraction Index Dispersion and Loss of Polymeric Dielectric Substrate and Packaging Materials

    Science.gov (United States)

    Motaharifar, E.; Pierce, R. G.; Islam, R.; Henderson, R.; Hsu, J. W. P.; Lee, Mark

    2018-01-01

    In the effort to push the high-frequency performance of electronic circuits and signal interconnects from millimeter waves to beyond 1 THz, a quantitative knowledge of complex refraction index values and dispersion in potential dielectric substrate, encapsulation, waveguide, and packaging materials becomes critical. Here we present very broadband measurements of the real and imaginary index spectra of four polymeric dielectric materials considered for use in high-frequency electronics: benzocyclobutene (BCB), polyethylene naphthalate (PEN), the photoresist SU-8, and polydimethylsiloxane (PDMS). Reflectance and transmittance spectra from 3 to 75 THz were made using a Fourier transform spectrometer on freestanding material samples. These data were quantitatively analyzed, taking into account multiple partial reflections from front and back surfaces and molecular bond resonances, where applicable, to generate real and imaginary parts of the refraction index as a function of frequency. All materials showed signatures of infrared active organic molecular bond resonances between 10 and 50 THz. Low-loss transmission windows as well as anti-window bands of high dispersion and loss can be readily identified and incorporated into high-frequency design models.

  20. Optimal multisine excitation design for broadband electrical impedance spectroscopy

    Science.gov (United States)

    Sanchez, B.; Vandersteen, G.; Bragos, R.; Schoukens, J.

    2011-11-01

    Electrical impedance spectroscopy (EIS) can be used to characterize biological materials in applications ranging from cell culture to body composition, including tissue and organ state. The emergence of cell therapy and tissue engineering opens up a new and promising field of application. While in most cases classical measurement techniques based on a frequency sweep can be used, EIS based on broadband excitations enables dynamic biological systems to be characterized when the measuring time and injected energy are a constraint. Myocardial regeneration, cell characterization in micro-fluidic systems and dynamic electrical impedance tomography are all examples of such applications. The weakness of such types of fast EIS measuring techniques resides in their intrinsic loss of accuracy. However, since most of the practical applications have no restriction over the excitation used, the input power spectrum can be appropriately designed to maximize the accuracy obtained from the measurements. This paper deals with the problem of designing the optimal multisine excitation for electrical bioimpedance measurements. The optimal multisine is obtained by the minimization of the Cramer-Rao lower bound, or what is the same, by maximizing the accuracy obtained from the measurements. Furthermore, because no analytical solution exists for global optimization involving time and frequency domains jointly, this paper presents the multisine optimization approach partially in both domains and then combines the results. As regards the frequency domain approach, a novel contribution is made for the multisine amplitude power spectrum. In the time domain, multisine is optimized by reducing its crest factor. Moreover, the impact on the information and accuracy of the impedance spectrum obtained from using different multisine amplitude power spectra is discussed, as well as the number of frequencies and frequency distributions. The theory is supported by a set of validation measurements when

  1. Dielectric and electric properties of new chitosan-hydroxyapatite materials for biomedical application: Dielectric spectroscopy and corona treatment.

    Science.gov (United States)

    Petrov, Ivo; Kalinkevich, Oksana; Pogorielov, Maksym; Kalinkevich, Aleksei; Stanislavov, Aleksandr; Sklyar, Anatoly; Danilchenko, Sergei; Yovcheva, Temenuzhka

    2016-10-20

    Chitosan-hydroxyapatite composite materials were synthesized and the possibility to make their surface charged by corona discharge treatment has been evaluated. Dielectric and electric properties of the materials were studied by dielectric spectroscopy, including application of equivalent circuits method and computer simulations. Dielectric spectroscopy shows behavior of the materials quite different from that of both chitosan and HA alone. The obtained dielectric permittivity data are of particular interest in predicting the materials' behavior in electrostimulation after implantation. The ε values observed at physiological temperature in the frequency ranges applied are similar to ε data available for bone tissues. Copyright © 2016 Elsevier Ltd. All rights reserved.

  2. Characterization of Microsolvated Crown Ethers from Broadband Rotational Spectroscopy

    Science.gov (United States)

    Perez, Cristobal; Schnell, Melanie; Blanco, Susana; Lopez, Juan Carlos

    2016-06-01

    Since they were first synthetized, crown ethers have been extensively used in organometallic chemistry due to their unparalleled binding selectivity with alkali metal cations. From a structural point of view, crown ethers are heterocycles containing oxygen and/or other heteroatoms, although the most common ones are formed from ethylene oxide unit. Crown ethers are conventionally seen as being hydrophilic inside and hydrophobic outside when the structures found for the metal cation complexes are considered. However, crown ethers are extremely flexible and in isolation may present a variety of stable conformations so that their structure may be easily adapted in presence of a strong ligand as an alkali metal cation minimize the energy of the resulting complex. Water can be considered a soft ligand which interacts with crown ethers through moderate hydrogen bonds. It is thus interesting to investigate which conformers are selected by water to form complexes, the preferred interaction sites and the possible conformational changes due to the presence of one or more water molecules. Previous studies identified microsolvated crown ethers but in all cases with a chromophore group attached to the structure. Here we present a broadband rotational spectroscopy study of microsolvated crown ethers produced in a pulsed molecular jet expansion. Several 1:1 and 1:2 crown ether:water aggregates are presented for 12-crown-4, 15-crown-5 and 18-crown-6. Unambiguous identification of the structures has been achieved using isotopic substitution within the water unit. The subtle changes induced in the structures of the crown ether monomer upon complexation and the hydrogen-bonding network that hold them together will be also discussed. F. Gámez, B. Martínez-Haya, S. Blanco,J. C. López and J. L. Alonso, Phys. Chem. Chem. Phys. 2014, 14 12912-12918 V. A. Shubert, C.W. Müller and T. Zwier, J. Phys. Chem. A 2009, 113 8067-8079

  3. Liquid 1-propanol studied by neutron scattering, near-infrared, and dielectric spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Sillrén, P.; Matic, A.; Karlsson, M. [Department of Applied Physics, Chalmers University of Technology, SE-412 96 Göteborg (Sweden); Koza, M.; Maccarini, M.; Fouquet, P. [Institut Laue Langevin, 6, rue Jules Horowitz, BP 156, 38042 Grenoble Cedex 9 (France); Götz, M.; Bauer, Th.; Gulich, R.; Lunkenheimer, P.; Loidl, A. [Experimental Physics V, University of Augsburg, 86135 Augsburg (Germany); Mattsson, J. [School of Physics and Astronomy, University of Leeds, Leeds LS2 9JT (United Kingdom); Gainaru, C.; Vynokur, E.; Schildmann, S.; Bauer, S.; Böhmer, R. [Fakultät für Physik, Technische Universität Dortmund, 44221 Dortmund (Germany)

    2014-03-28

    Liquid monohydroxy alcohols exhibit unusual dynamics related to their hydrogen bonding induced structures. The connection between structure and dynamics is studied for liquid 1-propanol using quasi-elastic neutron scattering, combining time-of-flight and neutron spin-echo techniques, with a focus on the dynamics at length scales corresponding to the main peak and the pre-peak of the structure factor. At the main peak, the structural relaxation times are probed. These correspond well to mechanical relaxation times calculated from literature data. At the pre-peak, corresponding to length scales related to H-bonded structures, the relaxation times are almost an order of magnitude longer. According to previous work [C. Gainaru, R. Meier, S. Schildmann, C. Lederle, W. Hiller, E. Rössler, and R. Böhmer, Phys. Rev. Lett. 105, 258303 (2010)] this time scale difference is connected to the average size of H-bonded clusters. The relation between the relaxation times from neutron scattering and those determined from dielectric spectroscopy is discussed on the basis of broad-band permittivity data of 1-propanol. Moreover, in 1-propanol the dielectric relaxation strength as well as the near-infrared absorbance reveal anomalous behavior below ambient temperature. A corresponding feature could not be found in the polyalcohols propylene glycol and glycerol.

  4. Ultrafast broadband Fourier-transform CARS spectroscopy operating at 50,000 spectra/second

    Science.gov (United States)

    Tamamitsu, Miu; Sakaki, Yusuke; Nakamura, Tasuku; Podagatlapalli, G. Krishna; Ideguchi, Takuro; Goda, Keisuke

    2017-02-01

    We present a coherent Raman scattering (CRS) spectroscopy technique achieving a CRS spectral acquisition rate of 50,000 spectra/second over a Raman spectral region of 200 - 1430 cm-1 with a resolution of 4.2 cm-1. This ultrafast, broadband and high-resolution CRS spectroscopic performance is realized by a polygonal Fourier-domain delay line serving as an ultra-rapid optical-path-length scanner in a broadband Fourier-transform coherent anti-Stokes Raman scattering (CARS) spectroscopy platform. We present a theoretical description of the technique and demonstrate continuous, ultrafast, broadband, and high-resolution CARS spectroscopy on a liquid toluene sample using our proof-of-concept setup.

  5. Laboratory Results from Dielectric Spectroscopy of Field Aged XLPE Cables with Respect to Water Trees

    DEFF Research Database (Denmark)

    Pedersen, Kenneth; Sedding, Howard; Fenger, Mark

    2006-01-01

    This paper deals with the application of frequency domain dielectric spectroscopy for the detection of water trees in XLPE cables. During the research, dielectric spectroscopy measurements have been carried out on cable samples with and without water trees while it was attempted to preserve many ...

  6. Completely background free broadband coherent anti-Stokes Raman scattering spectroscopy

    DEFF Research Database (Denmark)

    Liu, Xing; Niu, Hanben; Liu, Wei

    2013-01-01

    For the first time it was proposed a numerical approach to obtain non-NRB time-frequency coherent anti-Stokes Raman scattering (CARS) spectrograms. In order to evaluate the validity of the CARS spectrogram for background free broadband CARS spectroscopy, the authors numerically constructed a CARS...

  7. Leakage radiation spectroscopy of organic/dielectric/metal systems

    DEFF Research Database (Denmark)

    Fiutowski, Jacek; Kawalec, Tomasz; Kostiučenko, Oksana

    2014-01-01

    excitons and surface plasmon polaritons (SPPs) of the metal/dielectric boundary. The presence of the SiO2 layer considerably changes the dispersion curve in comparison to the one of the Ag/p-6P/air system. However, the Ag/SiO2/p-6P/air stack forms a stable structure allowing construction of organic......Leakage radiation spectroscopy of organic para-Hexaphenylene (p-6P) molecules has been performed in the spectral range 420-675 nm which overlaps with the p-6P photoluminescence band. The p-6P was deposited on 40 nm silver (Ag) films on BK7 glass, covered with SiO2 layers. The SiO2 layer thickness...

  8. Evaluation of DNA damage using microwave dielectric absorption spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Hirayama, Makoto; Matuo, Youichrou; Izumi, Yoshinobu [Research Institute of Nuclear Engineering, University of Fukui, Fukui (Japan); Sunagawa, Takeyoshi [Fukui University of Technology, Fukui (Japan)

    2016-12-15

    Evaluation of deoxyribonucleic acid (DNA)-strand break is important to elucidate the biological effect of ionizing radiations. The conventional methods for DNA-strand break evaluation have been achieved by Agarose gel electrophoresis and others using an electrical property of DNAs. Such kinds of DNA-strand break evaluation systems can estimate DNA-strand break, according to a molecular weight of DNAs. However, the conventional method needs pre-treatment of the sample and a relatively long period for analysis. They do not have enough sensitivity to detect the strand break products in the low-dose region. The sample is water, methanol and plasmid DNA solution. The plasmid DNA pUC118 was multiplied by using Escherichia coli JM109 competent cells. The resonance frequency and Q-value were measured by means of microwave dielectric absorption spectroscopy. When a sample is located at a center of the electric field, resonance curve of the frequency that existed as a standing wave is disturbed. As a result, the perturbation effect to perform a resonance with different frequency is adopted. The resonance frequency shifted to higher frequency with an increase in a concentration of methanol as the model of the biological material, and the Q-value decreased. The absorption peak in microwave power spectrum of the double-strand break plasmid DNA shifted from the non-damaged plasmid DNA. Moreover, the sharpness of absorption peak changed resulting in change in Q-value. We confirmed that a resonance frequency shifted to higher frequency with an increase in concentration of the plasmid DNA. We developed a new technique for an evaluation of DNA damage. In this paper, we report the evaluation method of DNA damage using microwave dielectric absorption spectroscopy.

  9. Multi-modality analysis of glucose aqueous solution using photoacoustic and dielectric spectroscopy for non-invasive glucose monitoring

    Science.gov (United States)

    Tajima, Takuro; Tanaka, Yujiro; Nakamura, Masahito; Seyama, Michiko

    2017-03-01

    Quantitative analysis of glucose using conventional optical spectroscopy suffers from a lack of repeatability due to high optical scattering in skin tissue. Here we present a multi-modality analysis of glucose aqueous solution using photoacoustic spectroscopy (PAS) and broadband dielectric spectroscopy (BDS). These techniques involve the direct detection of the acoustic and electromagnetic waves propagating through or reflecting from tissue without their being scattered. They therefore have potential for better tolerance to the variation of scattering. For PAS, to differentiate signals induced by water absorption, we select another laser wavelength (1.38 μm) that exhibits the same absorbance for water at 1.61 μm. Furthermore, one of the two photoacoustic signals is used to normalize the variations of acoustic properties in differential signal. Measured results for glucose solutions (0-2 g/dL) showed that the differential signal has a sensitivity of 1.61%/g·dL-1 and a detection limit of 120 mg/dL. We also tested glucose detection with BDS (500 MHz to 50 GHz) by detecting glucose hydration bonding at around 10-20 GHz. Using a partial least square analysis and first derivation on broadband spectra, we obtained an RMS error 19 mg/dL and a detection limit of 59 mg/dL. Using both the low-scattering ultrasonic and microwave detection techniques, we successfully captured the glucose footprint in the physiological range.

  10. Dynamics of water in strawberry and red onion as studied by dielectric spectroscopy

    Science.gov (United States)

    Jansson, H.; Huldt, C.; Bergman, R.; Swenson, J.

    2005-01-01

    We have investigated the microscopic dynamics of strawberry and red onion by means of broadband dielectric spectroscopy. In contrast to most of the previous experiments on carbohydrate-rich biological materials, which have mainly considered the more global dynamics of the “biological matrix,” we are here focusing on the microscopic dynamics of mainly the associated water. The results for both strawberry and red onion show that the imaginary part of the permittivity contains one conductivity term and a clear dielectric loss peak, which was found to be similar to the strongest relaxation process of water in carbohydrate solutions. The temperature dependence of the relaxation process was analyzed for different water content. The relaxation process slows down, and its temperature dependence becomes more non-Arrhenius, with decreasing water content. The reason for this is most likely that, on average, the water molecules interact more strongly with carbohydrates and other biological materials at low water content, and the dynamical properties of this biological matrix changes substantially with increasing temperature (from an almost rigid matrix where the water is basically unable to perform long-range diffusion due to confinement effects, to a dynamic matrix with no static confinement effects), which also changes (i.e., reduces) the activation energy of the relaxation process with increasing temperature (i.e., causes a non-Arrhenius temperature dependence). This further changes the conductivity from mainly polarization effects at low temperatures, due to hindered ionic motions, to long-range diffusivity at T>250K . Thus, around this temperature ions in the carbohydrate solution no longer get stuck in confined cavities, since the motion of the biological matrix “opens up” the cavities and the ions are then able to perform long-range migration.

  11. Ultra-broadband THz time-domain spectroscopy of energetic materials

    DEFF Research Database (Denmark)

    Kaltenecker, Korbinian J.; Zhou, Binbin; Engelbrecht, Sebastian

    2017-01-01

    Ultra-broadband THz spectroscopy based on photomixing in air plasma allows to exploit an extended frequency range, up to 20 THz and beyond. In this work, we investigate the potential of this technique for chemical recognition of illicit substances like explosives and compare the experimental spec...... spectra with ab-inition DFT simulation results to get deeper insight to the physical nature of the observed spectral features....

  12. Microfluidic platform for assessing pancreatic islet functionality through dielectric spectroscopy

    Science.gov (United States)

    Heileman, K.; Daoud, J.; Hasilo, C.; Gasparrini, M.; Paraskevas, S.; Tabrizian, M.

    2015-01-01

    Human pancreatic islets are seldom assessed for dynamic responses to external stimuli. Thus, the elucidation of human islet functionality would provide insights into the progression of diabetes mellitus, evaluation of preparations for clinical transplantation, as well as for the development of novel therapeutics. The objective of this study was to develop a microfluidic platform for in vitro islet culture, allowing the multi-parametric investigation of islet response to chemical and biochemical stimuli. This was accomplished through the fabrication and implementation of a microfluidic platform that allowed the perifusion of islet culture while integrating real-time monitoring using impedance spectroscopy, through microfabricated, interdigitated electrodes located along the microchamber arrays. Real-time impedance measurements provide important dielectric parameters, such as cell membrane capacitance and cytoplasmic conductivity, representing proliferation, differentiation, viability, and functionality. The perifusion of varying glucose concentrations and monitoring of the resulting impedance of pancreatic islets were performed as proof-of-concept validation of the lab-on-chip platform. This novel technique to elucidate the underlying mechanisms that dictate islet functionality is presented, providing new information regarding islet function that could improve the evaluation of islet preparations for transplantation. In addition, it will lead to a better understanding of fundamental diabetes-related islet dysfunction and the development of therapeutics through evaluation of potential drug effects. PMID:26339324

  13. Ultrafast relaxation dynamics of nitric oxide synthase studied by visible broadband transient absorption spectroscopy

    Science.gov (United States)

    Hung, Chih-Chang; Yabushita, Atsushi; Kobayashi, Takayoshi; Chen, Pei-Feng; Liang, Keng S.

    2017-09-01

    Ultrafast dynamics of endothelial nitric oxide synthase (eNOS) oxygenase domain was studied by transient absorption spectroscopy pumping at Soret band. The broadband visible probe spectrum has visualized the relaxation dynamics from the Soret band to Q-band and charge transfer (CT) band. Supported by two-dimensional correlation spectroscopy, global fitting analysis has successfully concluded the relaxation dynamics from the Soret band to be (1) electronic transition to Q-band (0.16 ps), (2) ligand dissociation and CT (0.94 ps), (3) relaxation of the CT state (4.0 ps), and (4) ligand rebinding (59 ps).

  14. The use of dielectric spectroscopy for the characterization of polymer-induced flocculation of polystyrene particles

    DEFF Research Database (Denmark)

    Christensen, Peter Vittrup; Keiding, Kristian

    2008-01-01

    in dilute suspensions. Thus, techniques usable for flocculation characterization in high-solids suspensions are desirable. This study investigates the use of dielectric spectroscopy to monitor the flocculation of polystyrene particles with a cationic polymer. The frequency-dependent permittivity is modeled...... as a decrease in the magnitude of the dielectric dispersion. The use of dielectric spectroscopy is found to be valuable for assessing flocculation processes in high-solids suspensions, as changes in parameters Such as floc size and charge can be detected....

  15. Broadbanding of circularly polarized patch antenna by waveguided magneto-dielectric metamaterial

    Directory of Open Access Journals (Sweden)

    Xin Mi Yang

    2015-12-01

    Full Text Available Design of bandwidth-enhanced circularly polarized (CP patch antenna using artificial magneto-dielectric substrate was investigated. The artificial magneto-dielectric material adopted here takes the form of waveguided metamaterial (WG-MTM. In particular, the embedded meander line (EML structure was employed as the building element of the WG-MTM. As verified by the retrieved effective medium parameters, the EML-based waveguided magneto-dielectric metamaterial (WG-MDM exhibits two-dimensionally isotropic magneto-dielectric property with respect to TEM wave excitations applied in two orthogonal directions. A CP patch antenna loaded with the EML-based WG-MDM (WG-MDM antenna has been proposed and its design procedure is described in detail. Simulation results show that the impedance and axial ratio bandwidths of the WG-MDM antenna have increased by 125% and 133%, respectively, compared with those obtained with pure dielectric substrate offering the same patch size. The design of the novel WG-MDM antenna was also validated by measurement results, which show good agreement with their simulated counterparts.

  16. Integrated fiber optic incoherent broadband cavity enhanced absorption spectroscopy detector for near-IR absorption measurements of nanoliter samples.

    Science.gov (United States)

    Gomez, Anthony L; Renzi, Ronald F; Fruetel, Julia A; Bambha, Ray P

    2012-05-10

    An integrated fiber-optic sensor is described that uses incoherent broadband cavity enhanced absorption spectroscopy for sensitive detection of aqueous samples in nanoliter volumes. Absorption was measured in a 100 µm gap between the ends of two short segments of multimode graded-index fiber that were integrated into a capillary using a precision machined V-grooved fixture that allowed for passive fiber alignment. The other ends of the fibers were coated with dielectric mirrors to form a 9.5 cm optical resonator. Light from a fiber-coupled superluminescent diode was directly coupled into one end of the cavity, and transmission was measured using a fiber-coupled silicon photodiode. Dilute aqueous solutions of near infrared dye were used to determine the minimum detectable absorption change of 2.4×10(-4) under experimental conditions in which pressure fluctuations limited performance. We also determined that the absolute minimum detectable absorption change would be 1.6×10(-5) for conditions of constant pressure in which absorption measurement is limited by electronic and optical noise. Tolerance requirements for alignment are also presented.

  17. Broad-band time-resolved near infrared spectroscopy in the TJ-II stellarator

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez, M.C.; Pastor, I.; Cal, E. de la; McCarthy, K.J. [Laboratorio Nacional de Fusion, CIEMAT, Madrid (Spain); Diaz, D. [Universidad Autonoma de Madrid, Dept Quimica Fisica Aplicada, Madrid (Spain)

    2014-11-15

    First experimental results on broad-band, time-resolved Near Infrared (NIR;here loosely defined as covering from 750 to 1650 nm) passive spectroscopy using a high sensitivity InGaAs detector are reported for the TJ-II Stellarator. Experimental set-up is described together with its main characteristics, the most remarkable ones being its enhanced NIR response, broadband spectrum acquisition in a single shot, and time-resolved measurements with up to 1.8 kHz spectral rate. Prospects for future work and more extended physics studies in this newly open spectral region in TJ-II are discussed. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  18. Dielectric tube waveguides with absorptive cladding for broadband, low-dispersion and low loss THz guiding

    DEFF Research Database (Denmark)

    Bao, Hualong; Nielsen, Kristian; Bang, Ole

    2015-01-01

    and dielectrics in this frequency range. Here we report on a novel twist on the classical tube waveguide where we deliberately introduce a thick and highly lossy cladding layer. By this we attenuate the field in the cladding and thus prevent interference with the core field. This mechanism breaks the well...

  19. Time domain dielectric spectroscopy of nanosecond pulsed electric field induced changes in dielectric properties of pig whole blood.

    Science.gov (United States)

    Zhuang, Jie; Kolb, Juergen F

    2015-06-01

    The dielectric spectra of fresh pig whole blood in the β-dispersion range after exposure to 300-nanosecond pulsed electric fields (nsPEFs) with amplitude higher than the supra-electroporation threshold for erythrocytes were recorded by time domain reflectometry dielectric spectroscopy. The implications of the dielectric parameters on the dynamics of post-pulse pore development were discussed in light of the Cole-Cole relaxation model. The temporal development of the Cole-Cole parameters indicates that nsPEFs induced significant poration and swelling of erythrocytes within the first 5 min. The results also show that the majority of erythrocytes could not fully recover from supra-electroporation up to 30 min. The findings of this study suggest that time domain dielectric spectroscopy is a promising label-free and real-time physiological measuring technique for nsPEF-blood related biomedical applications, capable of following the conformational and morphological changes of cells. Copyright © 2014 Elsevier B.V. All rights reserved.

  20. Prediction of process cheese instrumental texture and melting characteristics using dielectric spectroscopy and chemometrics.

    Science.gov (United States)

    Amamcharla, J K; Metzger, L E

    2015-09-01

    This study evaluated the potentiality of dielectric spectroscopy as a tool to predict the functional properties of process cheese. Dielectric properties of process cheese were collected over the frequency range 0.2 to 3.2GHz at 25°C. Dielectric spectra of process cheese were collected using a high-temperature, open-ended dielectric probe connected to a vector network analyzer. The present study was conducted using 2 sets of commercial process cheese formulations and a set of specially formulated process cheese. For the all the process cheese samples analyzed, a decrease in dielectric constant and dielectric loss factor was observed as the incident frequency increased. Partial least square regression (PLSR) and multilayer perceptron neural network models were developed using the dielectric spectra of process cheese to predict the hardness (gf), melting point (°C), and modified Schreiber melt diameter (mm) of process cheese. The prediction models were validated using the full cross-validation method. The ratio of prediction error to deviation was greater than 2 for melt diameter and hardness, indicating a good practical utility of the PLSR prediction models. The predictability of multilayer perceptron neural network was less than the PLSR models and could be due to the small number of training samples in the data sets. Dielectric spectroscopy coupled with PLSR could be a useful tool for the nondestructive measurement of functional properties of process cheese. Copyright © 2015 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

  1. Broadband x-ray imaging and spectroscopy of the crab nebula and pulsar with NuSTAR

    DEFF Research Database (Denmark)

    Madsen, Kristin K.; Reynolds, Stephen; Harrison, Fiona

    2015-01-01

    We present broadband (3-78 keV) NuSTAR X-ray imaging and spectroscopy of the Crab nebula and pulsar. We show that while the phase-averaged and spatially integrated nebula + pulsar spectrum is a power law in this energy band, spatially resolved spectroscopy of the nebula finds a break at ~9 ke...

  2. A broadband x-ray imaging spectroscopy with high-angular resolution: the FORCE mission

    Science.gov (United States)

    Mori, Koji; Tsuru, Takeshi Go; Nakazawa, Kazuhiro; Ueda, Yoshihiro; Okajima, Takashi; Murakami, Hiroshi; Awaki, Hisamitsu; Matsumoto, Hironori; Fukazawa, Yasushi; Tsunemi, Hiroshi; Takahashi, Tadayuki; Zhang, William W.

    2016-07-01

    We are proposing FORCE (Focusing On Relativistic universe and Cosmic Evolution) as a future Japan-lead Xray observatory to be launched in the mid 2020s. Hitomi (ASTRO-H) possesses a suite of sensitive instruments enabling the highest energy-resolution spectroscopy in soft X-ray band, a broadband X-ray imaging spectroscopy in soft and hard X-ray bands, and further high energy coverage up to soft gamma-ray band. FORCE is the direct successor to the broadband X-ray imaging spectroscopy aspect of Hitomi (ASTRO-H) with significantly higher angular resolution. The current design of FORCE defines energy band pass of 1-80 keV with angular resolution of black holes" in various mass-scales: "buried supermassive black holes (SMBHs)" (> 104 M⊙) residing in the center of galaxies in a cosmological distance, "intermediate-mass black holes" (102-104 M⊙) acting as the possible seeds from which SMBHs grow, and "orphan stellar-mass black holes" (< 102 M⊙) without companion in our Galaxy. In addition to these missing BHs, hunting for the nature of relativistic particles at various astrophysical shocks is also in our scope, utilizing the broadband X-ray coverage with high angular-resolution. FORCE are going to open a new era in these fields. The satellite is proposed to be launched with the Epsilon vehicle that is a Japanese current solid-fuel rocket. FORCE carries three identical pairs of Super-mirror and wide-band X-ray detector. The focal length is currently planned to be 10 m. The silicon mirror with multi-layer coating is our primary choice to achieve lightweight, good angular optics. The detector is a descendant of hard X-ray imager onboard Hitomi (ASTRO-H) replacing its silicon strip detector with SOI-CMOS silicon pixel detector, allowing an extension of the low energy threshold down to 1 keV or even less.

  3. Accurate optical parameter extraction procedure for broadband near-infrared spectroscopy of brain matter

    Science.gov (United States)

    Sultan, Ebraheem; Najafizadeh, Laleh; Gandjbakhche, Amir H.; Pourrezaei, Kambiz; Daryoush, Afshin

    2013-01-01

    Modeling behavior of broadband (30 to 1000 MHz) frequency modulated near-infrared (NIR) photons through a phantom is the basis for accurate extraction of optical absorption and scattering parameters of biological turbid media. Photon dynamics in a phantom are predicted using both analytical and numerical simulation and are related to the measured insertion loss (IL) and insertion phase (IP) for a given geometry based on phantom optical parameters. Accuracy of the extracted optical parameters using finite element method (FEM) simulation is compared to baseline analytical calculations from the diffusion equation (DE) for homogenous brain phantoms. NIR spectroscopy is performed using custom-designed, broadband, free-space optical transmitter (Tx) and receiver (Rx) modules that are developed for photon migration at wavelengths of 680, 780, and 820 nm. Differential detection between two optical Rx locations separated by 0.3 cm is employed to eliminate systemic artifacts associated with interfaces of the optical Tx and Rx with the phantoms. Optical parameter extraction is achieved for four solid phantom samples using the least-square-error method in MATLAB (for DE) and COMSOL (for FEM) simulation by fitting data to measured results over broadband and narrowband frequency modulation. Confidence in numerical modeling of the photonic behavior using FEM has been established here by comparing the transmission mode's experimental results with the predictions made by DE and FEM for known commercial solid brain phantoms.

  4. Optically tuned dielectric property of barium titanate thin film by THz spectroscopy

    Science.gov (United States)

    Zhou, Siyan; Ji, Jie; Tian, Yue; Ling, Furi; Yu, Wenfeng

    2017-11-01

    The dielectric property of ferroelectric barium titanate (BaTiO3) thin film with optical field was investigated by terahertz time-domain spectroscopy at room temperature. Experimental results showed that dielectric constant of BTO film was increased with the optical pump powers, and tunability of the real part of dielectric constant could be reached to74%. The reason of realizing high modulation depth could be explained as photorefractive and photothermal effects. Furthermore, the variation of refractive index displayed a monotonically increase with the optical powers.

  5. Broadband Microwave Spectroscopy as a Tool to Study Intermolecular Interactions in the Diphenyl Ether - Water System

    Science.gov (United States)

    Fatima, Mariyam; Perez, Cristobal; Schnell, Melanie

    2017-06-01

    Many biological processes, such as chemical recognition and protein folding, are mainly controlled by the interplay of hydrogen bonds and dispersive forces. This interplay also occurs between organic molecules and solvent water molecules. Broadband rotational spectroscopy studies of weakly bound complexes are able to accurately reveal the structures and internal dynamics of molecular clusters isolated in the gas phase. Amongst them, water clusters with organic molecules are of particular interest. In this work, we investigate the interplay between different types of weak intermolecular interactions and how it controls the preferred interaction sites of aromatic ethers, where dispersive interactions may play a significant role. We present our results on diphenyl ether (C_{12}H_{10}O, 1,1'-Oxydibenzene) complexed with up to three molecules of water. Diphenyl ether is a flexible molecule, and it offers two competing binding sites for water: the ether oxygen and the aromatic π system. In order to determine the structure of the diphenyl ether-water complexes, we targeted transitions in the 2-8 GHz range using broadband rotational spectroscopy. We identify two isomers with one water, one with two water, and one with three water molecules. Further analysis from isotopic substitution measurements provided accurate structural information. The preferred interactions, as well as the observed structural changes induced upon complexation, will be presented and discussed.

  6. Broadband spectroscopy of magnetic response in a nano-scale magnetic wire

    Energy Technology Data Exchange (ETDEWEB)

    Yamaguchi, A., E-mail: yamaguti@lasti.u-hyogo.ac.jp [Laboratory of Advanced Science and Technology for Industry, University of Hyogo, Koto, Kamigori, Ako, Hyogo 678-1205 (Japan); Motoi, K.; Miyajima, H. [Department of Physics, Keio University, Hiyoshi, Yokohama, Kanagawa 223-8522 (Japan); Utsumi, Y. [Laboratory of Advanced Science and Technology for Industry, University of Hyogo, Koto, Kamigori, Ako, Hyogo 678-1205 (Japan)

    2014-09-01

    We measure the broadband spectra of magnetic response in a single layered ferromagnetic nano-scale wire in order to investigate the size effect on the ferromagnetic resonance. We found that the resonance frequency difference between 300-nm- and 5-μm-wide wires was varied by about 5 GHz due to the shape anisotropy. Furthermore, we experimentally detected the magnetization precession induced by the thermal fluctuation via the rectification of a radio-frequency (rf) current by incorporating an additional direct current (dc) by using Wheatstone bridge circuit. Our investigation renders that the shape anisotropy is of great importance to control the resonance frequency and to provide thermal stability of the microwave devices. - Highlights: • We describe an experimental investigation of the magnetic response of a single layered ferromagnetic nano-scale wire. • We present the conventional broadband microwave spectroscopy with a vector network analyzer and rectifying spectroscopy obtained with a Wheatstone bridge technique. • The investigation enables us to characterize the size effect on the ferromagnetic response and also to detect the magnetization precession induced by the thermal fluctuations.

  7. Broadband suppression of backscattering at optical frequencies using low permittivity dielectric spheres.

    Science.gov (United States)

    Ismail Abdelrahman, M; Rockstuhl, C; Fernandez-Corbaton, I

    2017-11-07

    The exact suppression of backscattering from rotationally symmetric objects requires dual symmetric materials where ε r = μ r. This prevents their design at many frequency bands, including the optical one, because magnetic materials are not available. Electromagnetically small non-magnetic spheres of large permittivity offer an alternative. They can be tailored to exhibit balanced electric and magnetic dipole polarizabilities a 1 = b 1, which result in approximate zero backscattering. In this case, the effect is inherently narrowband. Here, we put forward a different alternative that allows broadband functionality: Wavelength-sized spheres made from low permittivity materials. The effect occurs in a parameter regime where approximate duality is met for all multipolar order a n  ≈ b n , in a weakly wavelength dependence fashion. In addition, and despite of the low permittivity, the overall scattering response of these spheres is still significant. Scattering patterns are shown to be highly directive across an octave spanning band. The effect is analytically and numerically shown using the Mie coefficients.

  8. Dielectric Spectroscopy of Localized Electrical Charges in Ferrite Thin Film

    Science.gov (United States)

    Abdellatif, M. H.; Azab, A. A.; Moustafa, A. M.

    2018-01-01

    A thin film of Gd-doped Mn-Cr ferrite has been prepared by pulsed laser deposition from a bulk sample of the same ferrite prepared by the conventional double sintering ceramic technique. The charge localization and surface conduction in the ferromagnetic thin film were studied. The relaxation of the dielectric dipoles after exposure to an external alternating-current (AC) electric field was investigated. The effect of charge localization on the real and imaginary parts of the dielectric modulus was studied. The charge localization in the thin film was enhanced and thereby the Maxwell-Wagner-type interfacial polarization. The increase in interfacial polarization is a direct result of the enhanced charge localization. The sample was characterized in terms of its AC and direct-current (DC) electrical conductivity, and thermally stimulated discharge current.

  9. The dielectric spectroscopy of human red blood cells: the differentiation of old from fresh cells.

    Science.gov (United States)

    David, Marcelo; Levy, Evgeniya; Feldman, Yuri; Ben Ishai, Paul; Zelig, Orly; Yedgar, Saul; Barshtein, Gregory

    2017-06-22

    The objective of the study was to gauge the effect of storage lesions on the dielectric response of red blood cells (RBC), in particular those processes linked to deformations of the cellular membrane known as the β-dispersion. The dielectric response of RBC suspensions, exposed to blood-bank cold storage, was studied using time-domain dielectric spectroscopy (TDDS) in the frequency range of 500 kHz up to 1 GHz. The measured dielectric processes are characterized by their dielectric strength (Δε) and relaxation time (τ). Changes in the dielectric properties of the RBC suspensions due to storage-related lesions were evaluated. For a quantitative characterization of RBC lesions, we measured the deformability of fresh and stored RBC as expressed by their elongation ratio (ER), which was achieved under a shear stress of 3.0 Pa. The results show that the storage of RBC induced a statistically significant decrease of dielectric relaxation times. In addition, a sound correlation between the mean values of ER and the relaxation times was observed (Spearman's correlation coefficient ρ  =  0.847). We draw the conclusion that those alterations in the relaxation time are induced by changes in the shape of the RBC that happen during cold-storage. The evolution of the β-dispersion of RBC opens new possibilities in the blood bank inventory management.

  10. Earle K. Plyler Prize for Molecular Spectroscopy & Dynamics Lecture: Broadband Rotational Spectroscopy for Chemical Kinetics, Molecular Structure, and Analytical Chemistry

    Science.gov (United States)

    Pate, Brooks

    2013-03-01

    Advances in high-speed digital electronics have enabled a new generation of molecular rotational spectroscopy techniques that provide instantaneous broadband spectral coverage. These techniques use a chirped excitation pulse to coherently excite the molecular sample over a spectral bandwidth of 10 GHz or larger through rapid passage. The subsequent time-domain emission is recorded using high-speed digitizers (up to 100 Gigasample/s) and the frequency domain spectrum is produced by fast Fourier transformation. The chirped-pulse Fourier transform (CP-FT) method has been implemented in the microwave frequency range (2-40 GHz) for studies of cold samples in pulsed jet sources and in the mm-wave/terahertz (THz) frequency range for studies of samples at room-temperature. The method has opened new applications for molecular rotational spectroscopy in the area of chemical kinetics where dynamic rotational spectroscopy is used to measure the rates of unimolecular isomerization reactions in highly excited molecules prepared by pulsed infrared laser excitation. In these applications, the isomerization rate is obtained from an analysis of the overall line shapes which are modified by chemical exchange leading to coalescence behavior similar to the effect in NMR spectroscopy. The sensitivity of the method and the ability to extend it to low frequency (2-8 GHz) have significantly increased the size range of molecules and molecular clusters for structure determination using isotopic substitution to build up the 3D molecular structures atom-by-atom. Application to the structure of water clusters with up to 15 water molecules will be presented. When coupled with advances in solid-state mm-wave/THz devices, this method provides a direct digital technique for analytical chemistry of room-temperature gases based on molecular rotational spectroscopy. These high-throughput methods can analyze complex sample mixtures with unmatched chemical selectivity and short analysis times. Work

  11. Laser-induced damage of multilayer dielectric for broadband pulse compression grating

    Science.gov (United States)

    Kong, Fanyu; Chen, Shunli; Liu, Shijie; Jin, Yunxia; Guan, Heyuan; Du, Ying; Wei, Chaoyang; He, Hongbo; Yi, Kui

    2012-01-01

    The multilayer dielectrics (MLDs) for broad bandwidth 800nm pulse compression gratings were fabricated with optimized design by electron beam evaporation using three different kinds of materials (Ta2O5/SiO2/HfO2), which had more than 99% reflectance with bandwidth larger than 160nm around the center wavelength of 800 nm and high transmission at the exposure wavelength of 413nm. Laser-induced damage behaviors of the mirrors were investigated. It was found that the laser-induced damage threshold (LIDT) of the samples could reach 1.0J/cm2 and 2.0J/cm2 in the normal beam (57 degrees, TE mode) at pulse duration of 50fs and 120fs, respectively. The depth information of the damage sites at these two cases was explored by atomic force microscope (AFM). The reason of the sample having so high LIDT was also discussed in this paper. The MLDs provide a solid base for the high laser threshold 800nm pulse compression gratings and may open a new way for broad bandwidth 800nm reflectance coatings used in the ultrashort pulse laser system.

  12. Design of tri-level excitation signals for broadband bioimpedance spectroscopy.

    Science.gov (United States)

    Yang, Yuxiang; Wang, Lianhuan; Wang, Peipei; Yang, Xiufang; Zhang, Fu; Wen, He; Teng, Zhaosheng

    2015-09-01

    Bioimpedance spectroscopy (BIS) measurement methods have been evolving from the traditional frequency-sweep approach to the multi-frequency simultaneous measurement technique which can drastically reduce measuring time and will be increasingly attractive for time-varying biological applications. Multi-frequency mixed (MFM) signals with sparsely distributed spectra are desirable for broadband BIS measurement. This paper proposes a synthesis method to design a series of tri-level MFM signals which contain only three values (+1, 0, -1), and has majority energy distributed on its (2(n))th primary harmonics. Tri-level MFM signals have both high energy efficiency and a low crest factor. An impedance measurement experiment excited by an 8th-order tri-level MFM signal on a RC three-element equivalent model has been performed, and the results on 8 primary harmonic frequencies ranging from 8 to 1024 kHz show a high accuracy with the mean amplitude relative error of 0.41% and mean phase absolute error of 0.18°, which has validated the feasibility of the tri-level MFM signals for broadband BIS measurement.

  13. Broadband multi-resonant strong field coherence breaking as a tool for single isomer microwave spectroscopy

    Science.gov (United States)

    Hernandez-Castillo, A. O.; Abeysekera, Chamara; Hays, Brian M.; Zwier, Timothy S.

    2016-09-01

    Using standard hardware available in chirped-pulse Fourier transform microwave (CP-FTMW) spectroscopy, an experimental method is introduced to selectively extract from the microwave spectrum of an otherwise complicated multicomponent mixture a set of transitions due to a single component, thereby speeding spectral assignment. The method operates the broadband chirped-pulse used to excite the sample in the strong-field limit through a combination of high power and control of the sweep rate. A procedure is introduced that leads to selection of three transition frequencies that can be incorporated as a set of resonant sequential single-frequency microwave pulses that follow broadband chirped-pulse excitation, resulting in a reduction in the coherent signal from a set of transitions ascribable to the component of interest. The difference in the CP-FTMW spectrum with and without this set of multi-resonant single-frequency pulses produces a set of transitions that can confidently be assigned to a single component of the mixture, aiding the analysis of its spectrum. The scheme is applied to (i) selectively extract the spectrum of one of five singly 13C-subsituted isotopologues of benzonitrile in natural abundance, (ii) obtain the microwave spectra of the two structural isomers (E)- and (Z)-phenylvinylnitrile, and (iii) obtain conformer-specific microwave spectra of methylbutyrate.

  14. Improving interpretation of geoelectrical signatures arising from biomineralization process in porous media: Low-frequency dielectric spectroscopy measurements on Desulfovibrio vulgaris cell suspensions

    Science.gov (United States)

    Zhang, C.; Prodan, C.; Slater, L. D.; Bot, C.; Ntarlagiannis, D.

    2009-12-01

    Previous geophysical studies have demonstrated the sensitivity of complex conductivity measurements to microbial growth, biofilm formation, and microbial-mineral alternations, indicating that complex conductivity has the potential to serve as non-invasive tool for bioremediation monitoring. However, the inherent dielectric properties of microbes and how they might directly contribute to the geophysical responses observed during microbial-mineral transformations are not well understood. As a first step towards improving the understanding of electrical signals from microbial-mineral transformations in porous media, we studied the low frequency dielectric properties of sulfate-reducing bacteria (Desulfovibrio vulgaris) cell suspensions, a common soil borne microorganism involved in remediation of toxic metals in solution. We utilized a two-electrode dielectric spectroscopy measurement, common in biophysics applications,to acquire high quality dielectric dispersion curves of Desulfovibrio vulgaris cell suspensions over the frequency range 0.1 Hz to 1M Hz. Desulfovibrio vulgaris cell suspensions were placed between two parallel steel electrodes that are enclosed in a cylindrical glass tube, and the complex impedance of sample was measured relative to a known resistor. The measured impedance includes an electrode polarization impedance arising at the interface between electrodes and ionic solutions at low frequencies. This electrode impedance has traditionally precluded the reliable interpretation of two electrode techniques at low frequencies (< 1000 Hz). In order to obtain the true dielectric dispersion curve of sample, we adopt a simple and robust strategy to measure, analyze and remove the polarization impedance. The feasibility of this polarization removal technique was tested on water saturated glass beads. We show that the broadband dielectric response of Desulfovibrio vulgaris can be reliably determined with this approach. The measurements are modeled based on a

  15. Molecular interactions in human nail plate analysed by dielectric spectroscopy.

    Science.gov (United States)

    Marzec, E; Olszewski, J

    2009-02-15

    The influence of diabetes mellitus on dielectric properties of the human fingernail was measured in vitro in the alpha-dispersion region. The frequency dependencies of the permittivity and conductivity for the healthy and the diabetic nail plate revealed three separate relaxations, which were similar for both materials. Significant differences were observed in the values of permittivity at the same frequency between the healthy and the diabetic nails with low water content of about 0% and 3%. Results of this paper suggest that hyperglycemia alters the first-order structure of the nail keratin macromolecule.

  16. Time-resolved broadband cavity-enhanced absorption spectroscopy for chemical kinetics.

    Energy Technology Data Exchange (ETDEWEB)

    Sheps, Leonid; Chandler, David W.

    2013-04-01

    Experimental measurements of elementary reaction rate coefficients and product branching ratios are essential to our understanding of many fundamentally important processes in Combustion Chemistry. However, such measurements are often impossible because of a lack of adequate detection techniques. Some of the largest gaps in our knowledge concern some of the most important radical species, because their short lifetimes and low steady-state concentrations make them particularly difficult to detect. To address this challenge, we propose a novel general detection method for gas-phase chemical kinetics: time-resolved broadband cavity-enhanced absorption spectroscopy (TR-BB-CEAS). This all-optical, non-intrusive, multiplexed method enables sensitive direct probing of transient reaction intermediates in a simple, inexpensive, and robust experimental package.

  17. Broadband coherent anti-Stokes Raman spectroscopy with a modeless dye laser.

    Science.gov (United States)

    Hahn, J W; Park, C W; Park, S N

    1997-09-20

    We develop a modeless dye laser for broadband coherent anti-Stokes Raman spectroscopy (CARS) and investigate the operational characteristics of the modeless laser. The energy efficiency of the modeless laser is 6%, and the beam divergence is 0.65 mrad. We construct a compact movable CARS system with the modeless laser and a graphite tube furnace to assess the accuracy of the CARS temperature. It is found that the difference between the averaged CARS temperature and the radiation temperature measured with an optical pyrometer is <2% at a temperature range from 1000 to 2400 K. We also measure the averaged CARS temperature drift owing to the variation of the spectral distribution of the modeless laser, which is <1.5% during 5 h of operation.

  18. Broadband photon time of flight spectroscopy: advanced spectroscopic analysis for ensuring safety and performance of pharmaceutical tablets

    DEFF Research Database (Denmark)

    Kamran, Faisal; Nielsen, Otto Højager Attermann; Andersson-Engels, Stefan

    2013-01-01

    We report on extended spectroscopic analysis of pharmaceutical tablets performed with broadband photon time-of-flight absorption/scaring spectroscopy. Precise monitoring of absorption and scattering spectra enables cost-efficient monitoring of key safety and performance parameters of the drugs....

  19. Design and Development of Embedded Based System for the Measurement of Dielectric Constant Spectroscopy for Liquids

    Directory of Open Access Journals (Sweden)

    V. V. Ramana C. H.

    2010-09-01

    Full Text Available An embedded based system for the measurement of dielectric constant spectroscopy (for frequencies 1 kHz, 10 kHz, 100 kHz, 1 MHz and 10 MHz for liquids has been designed and developed. It is based on the principle that the change in frequency of an MAX 038 function generator, when the liquid forms the dielectric medium of the dielectric cell, is measured with a microcontroller. Atmel’s AT89LP6440 microcontroller is used in the present study. Further, an LCD module is interfaced with the microcontroller in 4-bit mode, which reduces the hardware complexity. Software is developed in C using Keil’s C-cross compiler. The instrument system covers a wide range of dielectric constants for various liquids at various frequencies and at different temperatures. The system is quite successful in the measurement of dielectric constant in liquids with an accuracy of ± 0.01 %. The dielectric constant is very dependent on the frequency of their measurement. No one-measurement technique is available, however, that will give the frequency range needed to characterize the liquid sample. The paper deals with the hardware and software details.

  20. Dynamics and structure of biopolyelectrolytes in repulsion regime characterized by dielectric spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Tomic, S., E-mail: stomic@ifs.hr [Institut za fiziku, P.O. Box 304, HR-10001 Zagreb (Croatia); Grgicin, D.; Ivek, T.; Vuletic, T. [Institut za fiziku, P.O. Box 304, HR-10001 Zagreb (Croatia); Dolanski Babic, S. [Institut za fiziku, P.O. Box 304, HR-10001 Zagreb (Croatia); Department of Physics and Biophysics, Medical School, University of Zagreb, Zagreb (Croatia); Podgornik, R. [Department of Physics, University of Ljubljana and J. Stefan Institute, Ljubljana (Slovenia)

    2012-06-01

    We overview the study of biopolyelectrolytes by dielectric spectroscopy technique by primarily focusing on the case of repulsive regime of intersegment interactions mediated by univalent counterions. Two observed dielectric relaxations in 100 Hz-100 MHz frequency range due to diffusive motion of counterions are related to polyelectrolyte structural properties: the high frequency mode probes the structural organization of the polyion network in solution, while the low frequency mode is correlated with single polyion conformational properties. Open issues are highlighted and prospects for further research with polyvalent counterions are designated in order to study the crossover from repulsive to attractive regime of intersegment interactions.

  1. Microwave dielectric absorption spectroscopy aiming at novel dosimetry using DNAs

    Energy Technology Data Exchange (ETDEWEB)

    Izumi, Yoshinobu; Hirayama, Makoto; Matuo, Youichirou [Research Institute of Nuclear Engineering, University of Fukui, Fukui (Japan); Sunagawa, Takeyoshi [Fukui University of Technology, Fukui (Japan)

    2017-03-15

    We are developing L-band and S-band microwave dielectric absorption systems aiming novel dosimetry using DNAs, such as plasmid DNA and genomic DNA, and microwave technology. Each system is composed of a cavity resonator, analog signal generator, circulator, power meter, and oscilloscope. Since the cavity resonator is sensitive to temperature change, we have made great efforts to prevent the fluctuation of temperature. We have developed software for controlling and measurement. By using this system, we can measure the resonance frequency, f, and ΔQ (Q is a dimensionless parameter that describes how under-damped an oscillator or resonator is, and characterizes a resonator’s bandwidth relative to its center frequency) within about 3 minutes with high accuracy. This system will be expected to be applicable to DNAs evaluations and to novel dosimetric system.

  2. Dielectric spectroscopy study of water hyacinth collected from different media.

    Science.gov (United States)

    Mahani, Ragab; Atia, Fatma; Al Neklawy, Mohammed M; Fahem, Amin

    2018-02-15

    X-ray fluorescence (XRF) study has been shown that the water hyacinth plant is an effective tool for the removals of heavy metals (As, Ba, Cr, Cu, Ni, Pb, Rb, Sr, Zn and Zr) and metal oxides (SiO2, K2O, CaO, Al2O3, Fe2O3, MgO, Na2O, MnO, P2O5, SO3 and TiO2) from agriculture (media 1) and agriculture wastewaters drainage polluted with municipal wastewater (media 2). As a general description, the heavy metals and metal oxides were found at higher levels in the plant collected from media 1 than those in the plant collected from media 2. Similarly, these pollutants were found at higher levels in the plant roots than those in the plant shoots. The dielectric properties were investigated for the plant samples before (control) and after treating by microwave heating power. They were found at higher values in the control roots than those in the control shoots. Furthermore, the properties were found at relatively higher values in the control roots collected from media 1 (ε'=13 at 103Hz) than those in the control roots collected from media 2 (ε'=9 at 103Hz). The electrical conductivity of the microwave treated samples remarkably increased due to appearance of OH group through which the plant interacts with heavy metals. Accordingly, the pollutants removing ability could be enhanced upon treating the plant by microwave heating power. The plant-pollutant mixture behaves like highly conductive disordered polymers. The conductivity and dielectric properties of all plant samples are dominated by the media and concentration of pollutants. Copyright © 2017 Elsevier B.V. All rights reserved.

  3. Dielectric spectroscopy study of water hyacinth collected from different media

    Science.gov (United States)

    Mahani, Ragab; Atia, Fatma; Al Neklawy, Mohammed M.; Fahem, Amin

    2018-02-01

    X-ray fluorescence (XRF) study has been shown that the water hyacinth plant is an effective tool for the removals of heavy metals (As, Ba, Cr, Cu, Ni, Pb, Rb, Sr, Zn and Zr) and metal oxides (SiO2, K2O, CaO, Al2O3, Fe2O3, MgO, Na2O, MnO, P2O5, SO3 and TiO2) from agriculture (media 1) and agriculture wastewaters drainage polluted with municipal wastewater (media 2). As a general description, the heavy metals and metal oxides were found at higher levels in the plant collected from media 1 than those in the plant collected from media 2. Similarly, these pollutants were found at higher levels in the plant roots than those in the plant shoots. The dielectric properties were investigated for the plant samples before (control) and after treating by microwave heating power. They were found at higher values in the control roots than those in the control shoots. Furthermore, the properties were found at relatively higher values in the control roots collected from media 1 (ε‧ = 13 at 103 Hz) than those in the control roots collected from media 2 (ε‧ = 9 at 103 Hz). The electrical conductivity of the microwave treated samples remarkably increased due to appearance of OH group through which the plant interacts with heavy metals. Accordingly, the pollutants removing ability could be enhanced upon treating the plant by microwave heating power. The plant-pollutant mixture behaves like highly conductive disordered polymers. The conductivity and dielectric properties of all plant samples are dominated by the media and concentration of pollutants.

  4. Dielectric spectroscopy of small molecule pharmaceuticals-effect of sample configuration.

    Science.gov (United States)

    Kothari, Khushboo; Ragoonanan, Vishard; Suryanarayanan, Raj

    2014-10-01

    In dielectric spectroscopy, a technique traditionally used to characterize molecular mobility in polymers, the sample is usually analyzed as a thin film. In recent years, the technique has been extended to characterize both drug substances and drug products and has revealed a correlation between molecular mobility and stability. However, for pharmaceutical systems, analysis of powders is strongly preferred over films. Therefore, the dielectric behavior of several compounds of pharmaceutical interest-nifedipine, indomethacin, itraconazole, and griseofulvin-obtained using powder and film samples were compared. The magnitudes of the intrinsic dielectric properties were affected by the sample configuration with the powder samples consistently yielding lower values. The use of effective medium theories enabled us to account for the effect of air in the powder samples. The relaxation time, a property of immense importance to the pharmaceutical community, was not influenced by the sample configuration. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association.

  5. New terahertz dielectric spectroscopy for the study aqueous solutions

    CERN Document Server

    George, Deepu K; Vinh, N Q

    2015-01-01

    We present a development of a high precision, tunable far-infrared (terahertz) frequency-domain dielectric spectrometer for studying the dynamics of biomolecules in aqueous solutions in the gigahertz-to-terahertz frequency. As a first application we report on the measurement of the absorption and refractive index for liquid water in the frequency range from 5 GHz to 1.12 THz (0.17 to 37.36 cm-1 or 0.268 to 60 mm). The system provides a coherent radiation source with a power up to 20 mW in the gigahertz-to-terahertz region. The power signal-to-noise ratio of our instrument reaches 1015 and the system achieves a spectral resolution of less than 100 Hz. The temperature of samples can be controlled precisely with an error bars of 0.02 oC from above 0 oC to 90 oC. Given these attributes, our spectrometer provides unique capabilities for the accurate measurement of even very strongly absorbing materials such as aqueous solutions.

  6. Nanogap dielectric spectroscopy for aptamer-based protein detection.

    Science.gov (United States)

    Mannoor, Manu Sebastian; James, Teena; Ivanov, Dentcho V; Beadling, Les; Braunlin, William

    2010-02-17

    Among the various label-free methods for monitoring biomolecular interactions, capacitive sensors stand out due to their simple instrumentation and compatibility with multiplex formats. However, electrode polarization due to ion gradient formation and noise from solution conductance limited early dielectric spectroscopic measurements to high frequencies only, which in turn limited their sensitivity to biomolecular interactions, as the applied excitation signals were too fast for the charged macromolecules to respond. To minimize electrode polarization effects, capacitive sensors with 20 nm electrode separation were fabricated using silicon dioxide sacrificial layer techniques. The nanoscale separation of the capacitive electrodes in the sensor results in an enhanced overlapping of electrical double layers, and apparently a more ordered "ice-like" water structure. Such effects in turn reduce low frequency contributions from bulk sample resistance and from electrode polarization, and thus markedly enhance sensitivity toward biomolecular interactions. Using these nanogap capacitive sensors, highly sensitive, label-free aptamer-based detection of protein molecules is achieved. Copyright 2010 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  7. Dielectric Spectroscopy Analysis of Aged EVOH films with Application to Deterioration of Food Packaging Materials

    Science.gov (United States)

    Hoeller, Timothy

    2007-06-01

    Samples of EVOH films from compositions of 29 - 44 mol% ethylene content were exposed to thermal aging with and without light exposure. The results of Dielectric Spectroscopy on select samples showed Cole-Cole plots of skewed dielectric constant indicating multiple distributions of dipole relaxation times. The onset for decreases in dielectric response occurs earlier in samples exposed to elevated temperature under light exposure. Lower permittivity is exhibited in samples of higher ethylene content. Results from heat exposed samples are presented. Colorimetric analysis indicates only a slight film yellowing in one case. Raman spectroscopy on untreated films discerns changes in the C-C-O stretch associated with the alcohol. The effects of aging on microstructure may cause hindrance of molecular motion from moisture desorption. Slight material degradation occurs from film hardening presumably due to crosslinking. An electrical circuit model of the conduction processes associated with the EVOH films is presented. Dielectric analysis shows promise for monitoring material changes related to deterioration. We are also using these methods to understand Fluorescence Imaging which has been recently released for paper and plastic materials analysis. Future work may include refinement of these techniques for identification of changes in material properties correlated to packaging material barrier resistance.

  8. Dielectric properties of isolated adrenal chromaffin cells determined by microfluidic impedance spectroscopy.

    Science.gov (United States)

    Sabuncu, A C; Stacey, M; Craviso, G L; Semenova, N; Vernier, P T; Leblanc, N; Chatterjee, I; Zaklit, J

    2018-02-01

    Knowledge of the dielectric properties of biological cells plays an important role in numerical models aimed at understanding how high intensity ultrashort nanosecond electric pulses affect the plasma membrane and the membranes of intracellular organelles. To this end, using electrical impedance spectroscopy, the dielectric properties of isolated, neuroendocrine adrenal chromaffin cells were obtained. Measured impedance data of the cell suspension, acquired between 1kHz and 20MHz, were fit into a combination of constant phase element and Cole-Cole models from which the effect of electrode polarization was extracted. The dielectric spectrum of each cell suspension was fit into a Maxwell-Wagner mixture model and the Clausius-Mossotti factor was obtained. Lastly, to extract the cellular dielectric parameters, the cell dielectric data were fit into a granular cell model representative of a chromaffin cell, which was based on the inclusion of secretory granules in the cytoplasm. Chromaffin cell parameters determined from this study were the cell and secretory granule membrane specific capacitance (1.22 and 7.10μF/cm2, respectively), the cytoplasmic conductivity, which excludes and includes the effect of intracellular membranous structures (1.14 and 0.49S/m, respectively), and the secretory granule milieu conductivity (0.35S/m). These measurements will be crucial for incorporating into numerical models aimed at understanding the differential poration effect of nanosecond electric pulses on chromaffin cell membranes. Copyright © 2017 Elsevier B.V. All rights reserved.

  9. 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

    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...

  10. Dielectric relaxation processes in ethanol/water mixtures measured with attenuated total reflection terahertz time-domain spectroscopy

    DEFF Research Database (Denmark)

    Møller, Uffe; Yada, Hiriyuki; Arikawa, Takashi

    We use attenuated total reflection terahertz time-domain spectroscopy (THz-ATR) to characterize the dielectric relaxation processes of 10 different ethanol/water mixtures at 25°C with ethanol mole fractions of 0-100%.......We use attenuated total reflection terahertz time-domain spectroscopy (THz-ATR) to characterize the dielectric relaxation processes of 10 different ethanol/water mixtures at 25°C with ethanol mole fractions of 0-100%....

  11. Hybrid dielectric waveguide spectroscopy of individual plasmonic nanoparticles

    Science.gov (United States)

    Cuadra, J.; Verre, R.; Wersäll, M.; Krückel, C.; Torres-Company, V.; Antosiewicz, T. J.; Shegai, T.

    2017-07-01

    Plasmonics is a mature scientific discipline which is now entering the realm of practical applications. Recently, significant attention has been devoted to on-chip hybrid devices where plasmonic nanoantennas are integrated in standard Si3N4 photonic waveguides. Light in these systems is usually coupled at the waveguide apexes by using multiple objectives and/or tapered optical fibers, rendering the analysis of spectroscopic signals a complicated task. Here, we show how by using a grating coupler and a low NA objective, quantitative spectroscopic information similar to standard dark-field spectroscopy can be obtained at the single-nanoparticle level. This technology may be useful for enabling single-nanoparticle studies in non-linear excitation regimes and/or in complex experimental environments, thus enriching the toolbox of nanophotonic methods.

  12. Hybrid dielectric waveguide spectroscopy of individual plasmonic nanoparticles

    Directory of Open Access Journals (Sweden)

    J. Cuadra

    2017-07-01

    Full Text Available Plasmonics is a mature scientific discipline which is now entering the realm of practical applications. Recently, significant attention has been devoted to on-chip hybrid devices where plasmonic nanoantennas are integrated in standard Si3N4 photonic waveguides. Light in these systems is usually coupled at the waveguide apexes by using multiple objectives and/or tapered optical fibers, rendering the analysis of spectroscopic signals a complicated task. Here, we show how by using a grating coupler and a low NA objective, quantitative spectroscopic information similar to standard dark-field spectroscopy can be obtained at the single-nanoparticle level. This technology may be useful for enabling single-nanoparticle studies in non-linear excitation regimes and/or in complex experimental environments, thus enriching the toolbox of nanophotonic methods.

  13. Optical-Fiber-Type Broadband Cavity Ring-Down Spectroscopy Using Wavelength-Tunable Ultrashort Pulsed Light

    Science.gov (United States)

    Hiraoka, Takehiro; Ohta, Takayuki; Ito, Masafumi; Nishizawa, Norihiko; Hori, Masaru

    2013-04-01

    We proposed an optical-fiber-type broadband cavity ring-down spectroscopy system using wavelength-tunable ultrashort pulsed light. The absorbance of glucose in various concentrations in water was derived from the ring-down plots of intensities of the interference waveforms generated using a Mach-Zehnder interferometer with different optical delay path lengths, which were shifted by an automatic optical switching module. The absorption spectrum of glucose was obtained in the wavelength region from 1620 to 1690 nm by varying the wavelength using wavelength-tunable ultrashort pulsed light, which was generated from a femtosecond pulsed laser and polarization-maintaining fiber. The measurement error of concentration was improved using multiple linear regression analysis of absorption spectra. The results demonstrate that the optical-fiber-type cavity ring-down spectroscopy system has the potential to measure broadband absorption spectra with high sensitivity.

  14. Measurements of Iodine Monoxide Levels During the CAST Campaign Using Broadband Cavity Enhanced Absorption Spectroscopy

    Science.gov (United States)

    Harris, N. R. P.; Popoola, O. A.; McLeod, M.; Ouyang, B.; Jones, R. L.

    2014-12-01

    Iodine monoxide (IO) has been regarded as an important radical involved in the ozone destruction in the remote marine boundary layer. Here we presented the first in situ aircraft measurements of IO using broadband cavity enhanced absorption spectroscopy with 1s -sensitivity of ~1.5 ppt Hz-1/2 on the surface level during the Coordinated Airborne Studies in the Tropics (CAST) campaign between January - February 2014. IO was retrieved from analysis of absorption spectrum recorded between 415 nm - 452.5 nm. Instrument baseline corresponding to the "zero" signal of IO was obtained by injection of ~20 ppb of nitric oxide (NO) into the sample air at chosen frequency and period. No clear absorption feature was observable from the spectra by eye with up to 100 seconds averaging, pointing to very low mixing ratios (<~0.5 ppt) of IO over the sampled area. A small positive bias (~0.3 ppt) of IO (against the baseline signal during NO titration) was obtained in the statistical histogram of retrieved IO from average of each straight and level run, but little altitude dependence was noted. In summary, our observation appears to support the existence of IO in the remote marine boundary above the Pacific Ocean at sub ppt levels, but the limited sensitivity precludes us from quantifying spatial gradients more accurately.

  15. Broadband Bioimpedance Spectroscopy Based on a Multifrequency Mixed Excitation and Nuttall Windowed FFT Algorithm

    Directory of Open Access Journals (Sweden)

    Yuxiang Yang

    2014-01-01

    Full Text Available Bioimpedance spectroscopy (BIS has become an important clinical indicator for monitoring the pathological status of biological tissues, and multifrequency simultaneous measurement of BIS may provide more accurate diagnostic information compared with the traditional frequency-sweep measurement technology. This paper proposes a BIS multifrequency simultaneous measurement method based on multifrequency mixed (MFM signal excitation and a Nuttall windowed interpolation FFT algorithm. Firstly, the excitation source adopts the nine-frequency MFM signal f(9,t, which has excellent spectral characteristic and is very suitable for BIS measurement. On this basis, a Nuttall window is adopted to truncate sample data, and an interpolation FFT algorithm based on Nuttall window is built to perform spectral analysis, in which the parameter correction formula is provided based on polynomial approximation. A BIS measurement simulation experiment is performed on an RC three-element equivalent circuit, and results on the 9 primary harmonic frequencies ranging from 3.9 kHz to 1 MHz show a high accuracy with the impedance amplitude relative error |Ez|<0.3%, and the phase absolute error |Ep|<0.1°. This paper validates the feasibility of BIS multifrequency simultaneous measurement method and establishes an algorithm foundation for the development of practical broadband BIS measurement system.

  16. Continuous Vernier filtering of an optical frequency comb for broadband cavity-enhanced molecular spectroscopy

    Science.gov (United States)

    Rutkowski, Lucile; Morville, Jérôme

    2017-01-01

    We have recently introduced the Vernier-based Direct Frequency Comb Cavity-Enhanced Spectroscopy technique which allows us to record broadband spectra at high sensitivity and GHz resolution (Rutkowski and Morville, 2014) [1]. We discuss here the effect of Vernier filtering on the observed lineshapes in the 3 ν + δ band of water vapor and the entire A-band of oxygen around 800 nm in ambient air. We derive expressions for the absorption profiles resulting from the continuous Vernier filtering method, testing them on spectra covering more than 2000 cm-1 around 12,500 cm-1. With 31,300 independent spectral elements acquired at the second time scale, an absorption baseline noise of 2 ×10-8cm-1 is obtained, providing a figure of merit of 1.1×10-10 cm-1/√{ Hz } per spectral element with a cavity finesse of 3000 and a cavity round-trip length around 3.3 m.

  17. Ultra-Broadband Two-Dimensional Electronic Spectroscopy and Pump-Probe Microscopy of Molecular Systems

    Science.gov (United States)

    Spokoyny, Boris M.

    Ultrafast spectroscopy offers an unprecedented view on the dynamic nature of chemical reactions. From charge transfer in semiconductors to folding and isomerization of proteins, these all important processes can now be monitored and in some instances even controlled on real, physical timescales. One of the biggest challenges of ultrafast science is the incredible energetic complexity of most systems. It is not uncommon to encounter macromolecules or materials with absorption spectra spanning significant portions of the visible spectrum. Monitoring a multitude of electronic and vibrational transitions, all dynamically interacting with each other on femtosecond timescales poses a truly daunting experimental task. The first part of this thesis deals with the development of a novel Two-Dimensional Electronic Spectroscopy (2DES) and its associated, advanced detection methodologies. Owing to its ultra-broadband implementation, this technique enables us to monitor femtosecond chemical dynamics that span the energetic landscape of the entire visible spectrum. In order to demonstrate the utility of our method, we apply it to two laser dye molecules, IR-144 and Cresyl Violet. Variation of photophysical properties on a microscopic scale in either man-made or naturally occurring systems can have profound implications on how we understand their macroscopic properties. Recently, inorganic hybrid perovskites have been tapped as the next generation solar energy harvesting materials. Their remarkable properties include low exciton binding energy, low exciton recombination rates and long carrier diffusion lengths. Nevertheless, considerable variability in device properties made with nearly identical preparation methods has puzzled the community. In the second part of this thesis we use non-linear pump probe microscopy to study the heterogeneous nature of femtosecond carrier dynamics in thin film perovskites. We show that the local morphology of the perovskite thin films has a

  18. Sedimentation in Particulate Aqueous Suspensions as studied by means of Dielectric Time Domain Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Pettersen, Bjoernar Hauknes

    1997-12-31

    Many problems in offshore oil production and multiphase transport are related to surface and colloid chemistry. This thesis applies dielectric spectroscopy as an experimental technique to study the behaviour of particle suspensions in polar media. The thesis opens with an introduction to suspensions and time domain dielectric spectroscopy. It then investigates the dielectric properties of silica and alumina dispersed in polar solvents. It is found that theoretical models can be used to calculate the volume fraction disperse phase in the suspension and that the particle sedimentation depends on the wetting of the particles, charge on the particle surface and viscosity of the solvent, and that this dependency can be measured by time domain dielectric spectroscopy. When the surface properties of silica and alumina particles were modified by coating them with a non-ionic polymer and a non-ionic surfactant, then different degrees of packing in the sedimented phase at the bottom of the sedimentation vessel occurred. Chemometrical methods on the synthesis of monodisperse silica particles were used to investigate what factors influence the particle size. It turned out that it is insufficient to consider only main variables when discussing the results of the synthesis. By introducing interaction terms, the author could explain the variation in the size of particles synthesized. The difference in the sedimentation rate of monodisperse silica particles upon variation of volume fraction particles, pH, salinity, amount of silanol groups at the particle surface and temperature was studied. The cross interactions play an important role and a model explaining the variation in sedimentation is introduced. Finally, magnetic particles dispersed in water and in an external magnetic field were used to study the impact on the sedimentation due to the induced flocculation. 209 refs., 90 figs., 9 tabs.

  19. Broadband diffuse optical spectroscopy assessment of hemorrhage- and hemoglobin-based blood substitute resuscitation

    Science.gov (United States)

    Lee, Jangwoen; Kim, Jae G.; Mahon, Sari; Tromberg, Bruce J.; Mukai, David; Kreuter, Kelly; Saltzman, Darin; Patino, Renee; Goldberg, Robert; Brenner, Matthew

    2009-07-01

    Hemoglobin-based oxygen carriers (HBOCs) are solutions of cell-free hemoglobin (Hb) that have been developed for replacement or augmentation of blood transfusion. It is important to monitor in vivo tissue hemoglobin content, total tissue hemoglobin [THb], oxy- and deoxy-hemoglobin concentrations ([OHb], [RHb]), and tissue oxygen saturation (StO2=[OHb]/[THb]×100%) to evaluate effectiveness of HBOC transfusion. We designed and constructed a broadband diffuse optical spectroscopy (DOS) prototype system to measure bulk tissue absorption and scattering spectra between 650 and 1000 nm capable of accurately determining these tissue hemoglobin component concentrations in vivo. Our purpose was to assess the feasibility of using DOS to optically monitor tissue [OHb], [RHb], StO2, and total tissue hemoglobin concentration ([THb]=[OHb]+[RHb]) during HBOC infusion using a rabbit hypovolemic shock model. The DOS prototype probe was placed on the shaved inner thigh muscle of the hind leg to assess concentrations of [OHb], [RHb], [THb], as well as StO2. Hemorrhagic shock was induced in intubated New Zealand white rabbits (N=6) by withdrawing blood via a femoral arterial line to 20% blood loss (10-15 cc/kg). Hemoglobin glutamer-200 (Hb-200) 1:1 volume resuscitation was administered following the hemorrhage. These values were compared against traditional invasive measurements, serum hemoglobin concentration (sHGB), systemic blood pressure, heart rate, and blood gases. DOS revealed increases of [THb], [OHb], and tissue hemoglobin oxygen saturation after Hb-200 infusion, while blood total hemoglobin values continued did not increase; we speculate, due to hyperosmolality induced hemodilution. DOS enables noninvasive in vivo monitoring of tissue hemoglobin and oxygenation parameters during shock and volume expansion with HBOC and potentially enables the assessment of efficacy of resuscitation efforts using artificial blood substitutes.

  20. Broadband Microwave Spectroscopy as a Tool to Study Dispersion Interactions in Camphor-Alcohol Systems

    Science.gov (United States)

    Fatima, Mariyam; Perez, Cristobal; Schnell, Melanie

    2016-06-01

    Many biological processes such as chemical recognition and protein folding are mainly controlled by the interplay between hydrogen bonds and dispersive forces. Broadband rotational spectroscopy studies of weakly bound complexes are able to accurately reveal the structures and internal dynamics of molecular clusters isolated in the gas phase. To investigate the influence of the interplay between different types of weak intermolecular interactions and how it controls the preferred active sites of an amphiphilic molecule, we are using camphor (C10H16O, 1,7,7-trimethylbicyclo[2.2.1]hepta-2-one) with different aliphatic alcohol systems. Camphor is a conformationally rigid bicyclic molecule endowed with considerable steric hindrance and has a single polar group (-C=O). The rotational spectrum of camphor and its structure has been previously reported [1] as well as multiple clusters with water [2]. In order to determine the structure of the camphor-alcohol complexes, we targeted low energy rotational transitions in the 2-8 GHz range under the isolated conditions of a molecular jet in the gas phase. The data obtained suggests that camphor forms one complex with methanol and two with ethanol, with differences in the intermolecular interaction in both complexes. With these results, we aim to study the shift in intermolecular interaction from hydrogen bonding to dispersion with the increase in the size of the aliphatic alcohol. [1] Z. Kisiel, et al., Phys. Chem. Chem. Phys., 5 (2003), 820-826. [2] C. Pérez, et al, J. Phys. Chem. Lett., 7 (2016), 154-160.

  1. Dielectric Spectroscopy Analyses of SrBi4Ti4O15 Films Obtained from Soft Chemical Solution

    OpenAIRE

    Simões, A. Z.; Riccardi, C. S.

    2009-01-01

    SrBi4Ti4O15 (SBTi) thin films were deposited by the polymeric precursor method on Pt bottom electrodes. The obtained films were characterized by X-ray diffraction, scanning electron microscopy, Raman spectroscopy, and dielectric spectroscopy analyses. The capacitance-voltage (C-V) characteristics of perovskite thin film showed normal ferroelectric behavior. The remanent polarization and coercive fields were 5.4 mu C/cm(2) and 85 kV/cm, respectively. Dielectric spectroscopy was employed to exa...

  2. Molecular Relaxations in Supercooled Liquid and Glassy States of Amorphous Quinidine: Dielectric Spectroscopy and Density Functional Theory Approaches.

    Science.gov (United States)

    Schammé, Benjamin; Mignot, Mélanie; Couvrat, Nicolas; Tognetti, Vincent; Joubert, Laurent; Dupray, Valérie; Delbreilh, Laurent; Dargent, Eric; Coquerel, Gérard

    2016-08-04

    In this article, we conduct a comprehensive molecular relaxation study of amorphous Quinidine above and below the glass-transition temperature (Tg) through broadband dielectric relaxation spectroscopy (BDS) experiments and theoretical density functional theory (DFT) calculations, as one major issue with the amorphous state of pharmaceuticals is life expectancy. These techniques enabled us to determine what kind of molecular motions are responsible, or not, for the devitrification of Quinidine. Parameters describing the complex molecular dynamics of amorphous Quinidine, such as Tg, the width of the α relaxation (βKWW), the temperature dependence of α-relaxation times (τα), the fragility index (m), and the apparent activation energy of secondary γ relaxation (Ea-γ), were characterized. Above Tg (> 60 °C), a medium degree of nonexponentiality (βKWW = 0.5) was evidenced. An intermediate value of the fragility index (m = 86) enabled us to consider Quinidine as a glass former of medium fragility. Below Tg (origin coming from the rotation of the CH(OH)C9H14N end group. An excess wing observed in amorphous Quinidine was found to be an unresolved Johari-Goldstein relaxation. These studies were supplemented by sub-Tg experimental evaluations of the life expectancy of amorphous Quinidine by X-ray powder diffraction and differential scanning calorimetry. We show that the difference between Tg and the onset temperature for crystallization, Tc, which is 30 K, is sufficiently large to avoid recrystallization of amorphous Quinidine during 16 months of storage under ambient conditions.

  3. Secondary relaxation in two engineering thermoplastics by neutron scattering and dielectric spectroscopy

    CERN Document Server

    Arrese, S; Alegria, A; Colmenero, J; Frick, B

    2002-01-01

    We present a preliminary investigation of the dynamics of glassy polycarbonate (PC) and polysulfone (PSF) by means of quasielastic neutron scattering and dielectric spectroscopy. Whereas the consideration of pure phenylene ring pi-flips is enough to explain the momentum-transfer (Q) dependence of the inelastic intensity measured for PSF, in the case of PC the Q dependence of both the coherent and the incoherent scattering functions reveal the existence in this polymer of some more complex motion of the phenylene ring. On the other hand, the similarity of the energy landscapes deduced from the different techniques points to a closely related molecular origin for all the relaxation/motions observed. (orig.)

  4. Microcavity-Free Broadband Light Outcoupling Enhancement in Flexible Organic Light-Emitting Diodes with Nanostructured Transparent Metal-Dielectric Composite Electrodes.

    Science.gov (United States)

    Xu, Lu-Hai; Ou, Qing-Dong; Li, Yan-Qing; Zhang, Yi-Bo; Zhao, Xin-Dong; Xiang, Heng-Yang; Chen, Jing-De; Zhou, Lei; Lee, Shuit-Tong; Tang, Jian-Xin

    2016-01-26

    Flexible organic light-emitting diodes (OLEDs) hold great promise for future bendable display and curved lighting applications. One key challenge of high-performance flexible OLEDs is to develop new flexible transparent conductive electrodes with superior mechanical, electrical, and optical properties. Herein, an effective nanostructured metal/dielectric composite electrode on a plastic substrate is reported by combining a quasi-random outcoupling structure for broadband and angle-independent light outcoupling of white emission with an ultrathin metal alloy film for optimum optical transparency, electrical conduction, and mechanical flexibility. The microcavity effect and surface plasmonic loss can be remarkably reduced in white flexible OLEDs, resulting in a substantial increase in the external quantum efficiency and power efficiency to 47.2% and 112.4 lm W(-1).

  5. Monitoring Dielectric Thin-Film Production on Product Wafers Using Infrared Emission Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    NIEMCZYK,THOMAS M.; ZHANG,SONGBIAO; HAALAND,DAVID M.

    2000-12-18

    Monitoring of dielectric thin-film production in the microelectronics industry is generally accomplished by depositing a representative film on a monitor wafer and determining the film properties off line. One of the most important dielectric thin films in the manufacture of integrated circuits is borophosphosilicate glass (BPSG). The critical properties of BPSG thin films are the boron content, phosphorus content and film thickness. We have completed an experimental study that demonstrates that infrared emission spectroscopy coupled with multivariate analysis can be used to simultaneous y determine these properties directly from the spectra of product wafers, thus eliminating the need of producing monitor wafers. In addition, infrared emission data can be used to simultaneously determine the film temperature, which is an important film production parameter. The infrared data required to make these determinations can be collected on a time scale that is much faster than the film deposition time, hence infrared emission is an ideal candidate for an in-situ process monitor for dielectric thin-film production.

  6. Determination of Loops to Bridges Ratio in Triblock Copolymers by Dielectric Relaxation Spectroscopy^#

    Science.gov (United States)

    Karatasos, K.; Anastasiadis, S. H.; Kremer, F.; Watanabe, H.

    1996-03-01

    Dielectric spectroscopy over a broad frequency (10-2 Hz to 10^6 Hz) and temperature (-160 to 300^circC) range has been used to investigate the loops to bridges ratio in ordered triblock copolymers. We have utilized a specifically synthesized poly(styrene-b-1,4-isoprene-styrene) triblock having symmetrically inverted dipoles along the chain backbone of the middle block and the respective diblock precursor. The relaxation process observed for the triblock, with relaxation times identical to the block end-to-end vector relaxation of the diblock, corresponds to relaxation of the loop conformation in the ordered triblock. The weight fraction of loops in the ordered triblock, w_loops, is estimated from comparison of the dielectric loss and/or the dielectric strength of this process in the triblock to that in the diblock. This fraction is being investigated as a function of the sample history. Besides, the very slow relaxation, recently observed in ordered diblocks and attributed to relaxation of the conformal interfaces formed in the ordered state, is also clearly observed for ordered triblocks. # Part of this research was sponsored by NATO's Scientific Affairs Division in the framework of the Science for Stability Programme

  7. The use of dielectric spectroscopy in the investigation of the effect of polymer choice on the flocculation of polystyrene particles

    DEFF Research Database (Denmark)

    Christensen, Peter Vittrup; Hinge, Mogens; Keiding, Kristian

    2009-01-01

    of flocculation processes can only be used on dilute suspensions, new methods applicable at high solid content levels are of interest. This study used dielectric spectroscopy to investigate the mechanisms involved in the flocculation of polystyrene particles with three different cationic polymers. We observed...... that the relaxation time of the dielectric dispersion increased as particle flocculation was initiated. Reduction of particle charge due to polymer addition was found to reduce the magnitude of the dielectric dispersion, whereas the formation of aggregates increased it. This resulted in decreasing magnitude when...

  8. Calculations of band diagrams and low frequency dispersion relations of 2D periodic dielectric scatterers using broadband Green's function with low wavenumber extraction (BBGFL).

    Science.gov (United States)

    Tsang, Leung; Tan, Shurun

    2016-01-25

    The broadband Green's function with low wavenumber extraction (BBGFL) is applied to the calculations of band diagrams of two-dimensional (2D) periodic structures with dielectric scatterers. Periodic Green's functions of both the background and the scatterers are used to formulate the dual surface integral equations by approaching the surface of the scatterer from outside and inside the scatterer. The BBGFL are applied to both periodic Green's functions. By subtracting a low wavenumber component of the periodic Green's functions, the broadband part of the Green's functions converge with a small number of Bloch waves. The method of Moment (MoM) is applied to convert the surface integral equations to a matrix eigenvalue problem. Using the BBGFL, a linear eigenvalue problem is obtained with all the eigenmodes computed simultaneously giving the multiband results at a point in the Brillouin zone Numerical results are illustrated for the honeycomb structure. The results of the band diagrams are in good agreement with the planewave method and the Korringa Kohn Rostoker (KKR) method. By using the lowest band around the Γ point, the low frequency dispersion relations are calculated which also give the effective propagation constants and the effective permittivity in the low frequency limit.

  9. Effects of cations and cholesterol with sphingomyelin membranes investigated by high-resolution broadband sum frequency vibrational spectroscopy

    Science.gov (United States)

    Zhang, Zhen; Feng, Rong-juan; Li, Yi-yi; Liu, Ming-hua; Guo, Yuan

    2017-08-01

    Sphingomyelin(SM) is specifically enriched in the plasma membrane of mammalian cells. Its molecular structure is compose by N-acyl-Derythro-sphingosylphosphorylcholine. The function of the SM related to membrane signaling and protein trafficking are relied on the interactions of the SM, cations, cholesterol and proteins. In this report, the interaction of three different nature SMs, cations and cholesterol at air/aqueous interfaces studied by high-resolution broadband sum frequency vibrational spectroscopy, respectively. Our results shed lights on understanding the relationship between SMs monolayer, cholesterol and Cations.

  10. Dielectric-spectroscopy approach to ferrofluid nanoparticle clustering induced by an external electric field.

    Science.gov (United States)

    Rajnak, Michal; Kurimsky, Juraj; Dolnik, Bystrik; Kopcansky, Peter; Tomasovicova, Natalia; Taculescu-Moaca, Elena Alina; Timko, Milan

    2014-09-01

    An experimental study of magnetic colloidal particles cluster formation induced by an external electric field in a ferrofluid based on transformer oil is presented. Using frequency domain isothermal dielectric spectroscopy, we study the influence of a test cell electrode separation distance on a low-frequency relaxation process. We consider the relaxation process to be associated with an electric double layer polarization taking place on the particle surface. It has been found that the relaxation maximum considerably shifts towards lower frequencies when conducting the measurements in the test cells with greater electrode separation distances. As the electric field intensity was always kept at a constant value, we propose that the particle cluster formation induced by the external ac electric field accounts for that phenomenon. The increase in the relaxation time is in accordance with the Schwarz theory of electric double layer polarization. In addition, we analyze the influence of a static electric field generated by dc bias voltage on a similar shift in the relaxation maximum position. The variation of the dc electric field for the hysteresis measurements purpose provides understanding of the development of the particle clusters and their decay. Following our results, we emphasize the utility of dielectric spectroscopy as a simple, complementary method for detection and study of clusters of colloidal particles induced by external electric field.

  11. Compensating for electrode polarization in dielectric spectroscopy studies of colloidal suspensions: theoretical assessment of existing methods

    Directory of Open Access Journals (Sweden)

    Claire Chassagne

    2016-07-01

    Full Text Available Dielectric spectroscopy can be used to determine the dipole moment of colloidal particles from which important interfacial electrokinetic properties, for instance their zeta potential, can be deduced. Unfortunately, dielectric spectroscopy measurements are hampered by electrode polarization (EP. In this article, we review several procedures to compensate for this effect. First EP in electrolyte solutions is described: the complex conductivity is derived as function of frequency, for two cell geometries (planar and cylindrical with blocking electrodes. The corresponding equivalent circuit for the electrolyte solution is given for each geometry. This equivalent circuit model is extended to suspensions. The complex conductivity of a suspension, in the presence of EP, is then calculated from the impedance measured. Different methods for compensating for EP are critically assessed, with the help of the theoretical findings. Their limit of validity is given in terms of characteristic frequencies. We can identify with one of these frequencies the frequency range within which data uncorrected for EP may be used to assess the dipole moment of colloidal particles. In order to extract this dipole moment from the measured data, two methods are reviewed: one is based on the use of existing models for the complex conductivity of suspensions, the other is the logarithmic derivative method. An extension to multiple relaxations of the logarithmic derivative method is proposed.

  12. Dynamics of asymmetric binary glass formers. I. A dielectric and nuclear magnetic resonance spectroscopy study.

    Science.gov (United States)

    Kahlau, R; Bock, D; Schmidtke, B; Rössler, E A

    2014-01-28

    Dielectric spectroscopy as well as (2)H and (31)P nuclear magnetic resonance spectroscopy (NMR) are applied to probe the component dynamics of the binary glass former tripropyl phosphate (TPP)/polystyrene (PS/PS-d3) in the full concentration (cTPP) range. In addition, depolarized light scattering and differential scanning calorimetry experiments are performed. Two glass transition temperatures are found: Tg 1(cTPP) reflects PS dynamics and shows a monotonic plasticizer effect, while the lower Tg 2(cTPP) exhibits a maximum and is attributed to (faster) TPP dynamics, occurring in a slowly moving or immobilized PS matrix. Dielectric spectroscopy probing solely TPP identifies two different time scales, which are attributed to two sub-ensembles. One of them, again, shows fast TPP dynamics (α2-process), the other (α1-process) displays time constants identical with those of the slow PS matrix. Upon heating the α1-fraction of TPP decreases until above some temperature Tc only a single α2-population exists. Inversely, below Tc a fraction of the TPP molecules is trapped by the PS matrix. At low cTPP the α2-relaxation does not follow frequency-temperature superposition (FTS), instead it is governed by a temperature independent distribution of activation energies leading to correlation times which follow Arrhenius laws, i.e., the α2-relaxation resembles a secondary process. Yet, (31)P NMR demonstrates that it involves isotropic reorientations of TPP molecules within a slowly moving or rigid matrix of PS. At high cTPP the super-Arrhenius temperature dependence of τ2(T), as well as FTS are recovered, known as typical of the glass transition in neat systems.

  13. Insights into the Structural Changes Occurring upon Photoconversion in the Orange Carotenoid Protein from Broadband Two-Dimensional Electronic Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    De Re, Eleonora; Schlau-Cohen, Gabriela S.; Leverenz, Ryan L.; Huxter, Vanessa M.; Oliver, Thomas A. A.; Mathies, Richard A.; Fleming, Graham R.

    2014-05-22

    Carotenoids play an essential role in photoprotection, interacting with other pigments to safely dissipate excess absorbed energy as heat. In cyanobacteria, the short time scale photoprotective mechanisms involve the photoactive orange carotenoid protein (OCP), which binds a single carbonyl carotenoid. Blue-green light induces the photoswitching of OCP from its ground state form (OCPO) to a metastable photoproduct (OCPR). OCPR can bind to the phycobilisome antenna and induce fluorescence quenching. The photoswitching is accompanied by structural and functional changes at the level of the protein and of the bound carotenoid. In this study, we use broadband two-dimensional electronic spectroscopy to look at the differences in excited state dynamics of the carotenoid in the two forms of OCP. Our results provide insight into the origin of the pronounced vibrational lineshape and oscillatory dynamics observed in linear absorption and 2D electronic spectroscopy of OCPO and the large inhomogeneous broadening in OCPR, with consequences for the chemical function of the two forms.

  14. Development of a hybrid broadband NIRS/diffusion correlation spectroscopy system to monitor preterm brain injury (Conference Presentation)

    Science.gov (United States)

    Rajaram, Ajay; St. Lawrence, Keith; Diop, Mamadou

    2017-02-01

    In Canada, 8% of births occur prematurely. Preterm infants weighing less than 1500g are at a high risk of neurodevelopmental impairment: 5-10% develop major disabilities such as cerebral palsy and 40-50% show other cognitive and behavioural deficits. The brain is vulnerable to periods of low cerebral blood flow (CBF) that can impair energy metabolism and cause tissue damage. There is, therefore, a need for an efficient neuromonitoring system to alert the neonatal intensive care team to clinically significant changes in CBF and metabolism, before injury occurs. Optical technologies offer safe, non-invasive, and cost-effective methods for neuromonitoring. Cerebral oxygen saturation (ScO2) can be measured by exploiting the absorption properties of hemoglobin though Near-Infrared Spectroscopy (NIRS), and Diffuse Correlation Spectroscopy (DCS) can monitor CBF by tracking red blood cells. These measures can be combined to describe metabolism, a key indicator of tissue viability. In this study we present the development and testing of a hybrid broadband NIRS/DCS neuromonitor. This system is novel in its ability to simultaneously acquire broadband NIRS and DCS signals, providing a truly real-time measure of metabolism. Narrow bandpass and notch filters have been incorporated to diminish light contamination between the two modalities, preferentially filtering out each source from the opposing detector, allowing for an accurate measure of ScO2, CBF, and metabolism. With a broadband NIRS/DCS system, a real-time measure of CBF and metabolism within the developing brain can aid clinicians in monitoring events that precede brain injury, ultimately leading to better clinical outcomes.

  15. Broadband anti-reflection coating using dielectric Si3N4 nanostructures. Application to amorphous-Si-H solar cells

    Science.gov (United States)

    Elshorbagy, M. H.; Abdel-Hady, Kamal; Kamal, Hala; Alda, Javier

    2017-05-01

    Absorption of amorphous-Si hydrogenated (aSi-H) solar cells can be enhanced by using dielectric nanostructures made of Si3N4 that work like antireflection coatings. The analysis focus on the short-circuit current delivered by the cell under solar irradiance, and it is made taking into account every layer and structure of an aSi-H cell. A customized design of the antireflection coating in the form of nanostructured dielectric layers, produces a short-circuit current enhancement of 15.2% with respect to the reference flat solar cell, and a lower reflectivity of the cell. Three different geometries of linear nanostructures have been analyzed and compared with quite similar results among them. An improvement in performance has been also obtained for realizable geometrical dimensions that could be fabricated while maintaining electric conductivity of the front contact.

  16. Linear and Nonlinear Rheology Combined with Dielectric Spectroscopy of Hybrid Polymer Nanocomposites for Semiconductive Applications

    Directory of Open Access Journals (Sweden)

    Roland Kádár

    2017-01-01

    Full Text Available The linear and nonlinear oscillatory shear, extensional and combined rheology-dielectric spectroscopy of hybrid polymer nanocomposites for semiconductive applications were investigated in this study. The main focus was the influence of processing conditions on percolated poly(ethylene-butyl acrylate (EBA nanocomposite hybrids containing graphite nanoplatelets (GnP and carbon black (CB. The rheological response of the samples was interpreted in terms of dispersion properties, filler distortion from processing, filler percolation, as well as the filler orientation and distribution dynamics inside the matrix. Evidence of the influence of dispersion properties was found in linear viscoelastic dynamic frequency sweeps, while the percolation of the nanocomposites was detected in nonlinearities developed in dynamic strain sweeps. Using extensional rheology, hybrid samples with better dispersion properties lead to a more pronounced strain hardening behavior, while samples with a higher volume percentage of fillers caused a drastic reduction in strain hardening. The rheo-dielectric time-dependent response showed that in the case of nanocomposites containing only GnP, the orientation dynamics leads to non-conductive samples. However, in the case of hybrids, the orientation of the GnP could be offset by the dispersing of the CB to bridge the nanoplatelets. The results were interpreted in the framework of a dual PE-BA model, where the fillers would be concentrated mainly in the BA regions. Furthermore, better dispersed hybrids obtained using mixing screws at the expense of filler distortion via extrusion processing history were emphasized through the rheo-dielectric tests.

  17. Molecular Dynamics Analysis of PVA-AgnP Composites by Dielectric Spectroscopy

    Directory of Open Access Journals (Sweden)

    J. Betzabe González-Campos

    2012-01-01

    Full Text Available The molecular dynamics of PVA/AgnP composites were studied by dielectric spectroscopy (DS in the 20–300°C temperature range. Improper water elimination leads to misinterpretation of thermal relaxations in PVA composites in agreement with the previous report for pristine PVA. The evaporation of water and its plasticizing effect are more evident in pure PVA confirming the existence of strong interaction between OH groups of PVA chains and AgnP. Dry films show a single nonlinear VFT dependence (from 45°C until melting associated to the α-relaxation and, therefore, to the glass transition phenomenon and from dielectric measurements, the Tg of composites vary from 88°C for pristine PVA to 125°C for PVA/AgnP (5 wt%. Below 45°C, dry films exhibit a single Arrhenius behavior showing a 3D hopping conductivity as explained based on the variable range hopping model. PVA/AgnP composites have higher conductivity compared to pristine PVA, and it increases as AgnP weight percent increases. Finally, DMA measurements support the statement that a secondary relaxation was erroneously assigned as the glass transition of PVA and composites in previous reports.

  18. Dual field nonlinear dielectric spectroscopy in a glass forming EPON 828 epoxy resin

    Science.gov (United States)

    Rzoska, Sylwester J.; Drozd-Rzoska, Aleksandra

    2012-01-01

    Results of the dual field nonlinear dielectric spectroscopy (NDS) studies in supercooled glass forming epoxy resin EPON 828 are presented. For the NDS, changes of dielectric permittivity induced by DC (rectangular) or AC (sine-wave) pulses of a strong electric field were probed by a weak radio frequency electric field. A clear stretched exponential (x < 1) decay after switching off the DC pulse and a single exponential decay (x = 1) after switching off the AC pulse were found. The same results are presented for preliminary studies in superpressed low molecular glass former di-isobutyl phthalate. This observation may be considered as an argument for the heterogeneous picture of supercooled glass forming materials. The temperature dependences of the stationary responses related to DC and AC strong electric field excitations are also shown. The sensitivity of the applied set up made it possible to detect NDS outputs even for electric fields Estrong < 10 kV cm-1, qualitatively weaker than in similar ‘nonlinear, dielectric’ experimental studies on glass forming materials carried out so far.

  19. Lattice dynamics and dielectric spectroscopy of BZT and NBT lead-free perovskite relaxors - comparison with lead-based relaxors

    Czech Academy of Sciences Publication Activity Database

    Petzelt, Jan; Nuzhnyy, Dmitry; Bovtun, Viktor; Kempa, Martin; Savinov, Maxim; Kamba, Stanislav; Hlinka, Jiří

    2015-01-01

    Roč. 88, č. 3 (2015), 320-332 ISSN 0141-1594 R&D Projects: GA ČR GA13-15110S Institutional support: RVO:68378271 Keywords : relaxor ferroelectrics * polar phonons * polar nanoregions * dielectric spectroscopy * off-centred ions Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.858, year: 2015

  20. Relaxation and Conductivity in P3HT/PC71BM Blends As Revealed by Dielectric Spectroscopy

    DEFF Research Database (Denmark)

    Cui, Jing; Martinez-Tong, Daniel E.; Sanz, Alejandro

    2016-01-01

    The conduction mechanism and the molecular dynamics on the paradigmatic bulk heterojunction formed by poly(3-hexylthiophene) (P3HT) and phenyl-C-71-butyric acid methyl ester (PC71BM) blends have been characterized by dielectric spectroscopy. The results show that hexyl lateral chains of the polym...

  1. Nonlinear Dielectric Spectroscopy as an Indirect Probe of Metabolic Activity in Thylakoid Membrane

    Directory of Open Access Journals (Sweden)

    John H. Miller

    2011-01-01

    Full Text Available Nonlinear dielectric spectroscopy (NDS is a non-invasive probe of cellular metabolic activity with potential application in the development of whole-cell biosensors. However, the mechanism of NDS interaction with metabolic membrane proteins is poorly understood, partly due to the inherent complexity of single cell organisms. Here we use the light-activated electron transport chain of spinach thylakoid membrane as a model system to study how NDS interacts with metabolic activity. We find protein modification, as opposed to membrane pump activity, to be the dominant source of NDS signal change in this system. Potential mechanisms for such protein modifications include reactive oxygen species generation and light-activated phosphorylation.

  2. Broadband spectroscopy for characterization of tissue-like phantom optical properties

    Science.gov (United States)

    Shahin, Ali; Bachir, Wesam

    2017-12-01

    Optical phantoms are widely used for evaluating the performance of biomedical optical modalities, and hence, absorbing and scattering materials are required for the construction of optical phantoms. Towards that aim, new readily available and inexpensive black Ink (Parker) as a simulating absorber as well as Intralipid 20% as a simulating scatterer are thoroughly investigated. Broadband Transmittance and Diffuse reflectance spectroscopic measurements were performed in the visible range 400 - 700 nm. Optical properties of the phantom materials are determined. Analytical expressions for absorption and scattering coefficient related to the concentrations and wavelength of the Parker ink and Intralipid are also presented and discussed. The results show nonlinear trend in the absorption coefficient of Parker ink over the examined visible spectral range. Furthermore, Intralipid scattering coefficient variation across the mentioned spectral range shows a tissue-like scattering trend. The findings demonstrate the capability of the broadband transmission and diffuse reflectance for characterizing tissue-like phantom materials in the examined spectral range.

  3. The time-dependent emission of molecular iodine from Laminaria Digitata measured with incoherent broadband cavity-enhanced absorption spectroscopy

    Science.gov (United States)

    Dixneuf, S.

    2009-04-01

    The release of molecular iodine (I2) from the oceans into the atmosphere has been recognized to correlate strongly with ozone depletion events and aerosol formation in the Marine Boundary Layer (MBL), which affects in turn global radiative forcing. The detailed mechanisms and dominant sources leading to the observed concentrations of I2 in the marine troposphere are still under intense investigation. In a recent campaign on the Irish west coast at Mace Head Atmospheric Research Station [1], it was found that significant levels of molecular iodine correlated with times of low tide, suggesting that the emission of air-exposed macro-algae may be a prime source of molecular iodine in coastal areas [2]. To further investigate this hypothesis we tried to detect the I2 emission of the brown seaweed Laminaria digitata, one of the most efficient iodine accumulators among living systems, directly by means of highly sensitive incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS) [3]. IBBCEAS combines a good temporal and spatial resolution with high molecule-specific detection limits [4] comparable to that of typical LP-DOAS. IBBCEAS thus complements LP-DOAS in the search for sources of tropospheric trace gases. In this presentation the first direct observation of the time dependence of molecular iodine emission from Laminaria digitata will be shown. Plants were studied under naturally occurring stress for quasi in situ conditions for many hours. Surprisingly, the release of I2 occurs in short, strong bursts with quasi-oscillatory behaviour, bearing similarities to well known "iodine clock reactions". References [1] Saiz-Lopez A. & Plane, J. M. C. Novel iodine chemistry in the marine boundary layer. Geophys. Res. Lett. 31, L04112 (2004) doi:10.1029/2003GL019215. [2] McFiggans, G., Coe, H., Burgess, R., Allan, J., Cubison, M., Alfarra, M. R., Saunders, R., Saiz-Lopez, A., Plane, J. M. C., Wevill, D. J., Carpenter, L. J., Rickard, A. R. & Monks, P. S. Direct

  4. Broadband pump-probe spectroscopy with sub-10-fs resolution for probing ultrafast internal conversion and coherent phonons in carotenoids

    Energy Technology Data Exchange (ETDEWEB)

    Polli, D. [National Laboratory for Ultrafast and Ultraintense Optical Science, CNR-INFM, Dipartimento di Fisica, Politecnico di Milano, P.za L. da Vinci 32, 20133 Milano (Italy); Antognazza, M.R. [Italian Institute of Technology, Dipartimento di Fisica, Politecnico di Milano, P.za L. da Vinci 32, 20133 Milano (Italy); Brida, D.; Lanzani, G. [National Laboratory for Ultrafast and Ultraintense Optical Science, CNR-INFM, Dipartimento di Fisica, Politecnico di Milano, P.za L. da Vinci 32, 20133 Milano (Italy); Cerullo, G. [National Laboratory for Ultrafast and Ultraintense Optical Science, CNR-INFM, Dipartimento di Fisica, Politecnico di Milano, P.za L. da Vinci 32, 20133 Milano (Italy)], E-mail: giulio.cerullo@fisi.polimi.it; De Silvestri, S. [National Laboratory for Ultrafast and Ultraintense Optical Science, CNR-INFM, Dipartimento di Fisica, Politecnico di Milano, P.za L. da Vinci 32, 20133 Milano (Italy)

    2008-06-23

    We use pump-probe spectroscopy with broadband detection to study electronic energy relaxation and coherent vibrational dynamics in carotenoids. A fast optical multichannel analyzer combined with a non-collinear optical parametric amplifier allows simultaneous acquisition of the differential transmission dynamics on the 500-700 nm wavelength range with sub-10-fs temporal resolution. The broad spectral coverage enables on the one hand a detailed study of the ultrafast bright-to-dark state internal conversion process; on the other hand, the tracking of the motion of the vibrational wavepacket launched on the ground state multidimensional potential energy surface. We present results on all-trans {beta}-carotene and on a long-chain polyene in solution. The developed experimental setup enables the straightforward acquisition and analysis of coherent vibrational dynamics, highlighting time-frequency domain features with extreme resolution.

  5. Raman Spectra of High-κ Dielectric Layers Investigated with Micro-Raman Spectroscopy Comparison with Silicon Dioxide

    Directory of Open Access Journals (Sweden)

    P. Borowicz

    2013-01-01

    Full Text Available Three samples with dielectric layers from high-κ dielectrics, hafnium oxide, gadolinium-silicon oxide, and lanthanum-lutetium oxide on silicon substrate were studied by Raman spectroscopy. The results obtained for high-κ dielectrics were compared with spectra recorded for silicon dioxide. Raman spectra suggest the similarity of gadolinium-silicon oxide and lanthanum-lutetium oxide to the bulk nondensified silicon dioxide. The temperature treatment of hafnium oxide shows the evolution of the structure of this material. Raman spectra recorded for as-deposited hafnium oxide are similar to the results obtained for silicon dioxide layer. After thermal treatment especially at higher temperatures (600°C and above, the structure of hafnium oxide becomes similar to the bulk non-densified silicon dioxide.

  6. New Insights into the Dynamics of Zwitterionic Micelles and Their Hydration Waters by Gigahertz-to-Terahertz Dielectric Spectroscopy

    CERN Document Server

    George, Deepu K; Hull, Olivia A; Mishra, Archana; Capelluto, Daniel G S; Mitchell-Koch, Katie R; Vinh, Nguyen Q

    2016-01-01

    Gigahertz-to-terahertz spectroscopy of macromolecules in aqueous environments provides an important approach for identifying their global and transient molecular structures, as well as directly assessing hydrogen-bonding. We report dielectric properties of zwitterionic dodecylphosphocholine (DPC) micelles in aqueous solutions over a wide frequency range, from 50 MHz to 1.12 THz. The dielectric relaxation spectra reveal different polarization mechanisms at the molecular level, reflecting the complexity of DPC micelle-water interactions. We have made a deconvolution of the spectra into different components and combined them with the effective-medium approximation to separate delicate processes of micelles in water. Our measurements demonstrate reorientational motion of the DPC surfactant head groups within the micelles, and two levels of hydration water shells, including tightly- and loosely-bound hydration water layers. From the dielectric strength of bulk water in DPC solutions, we found that the number of wa...

  7. Broadband spectroscopy of magnetic response in a nano-scale magnetic wire

    Science.gov (United States)

    Yamaguchi, A.; Motoi, K.; Miyajima, H.; Utsumi, Y.

    2014-09-01

    We measure the broadband spectra of magnetic response in a single layered ferromagnetic nano-scale wire in order to investigate the size effect on the ferromagnetic resonance. We found that the resonance frequency difference between 300-nm- and 5-μm-wide wires was varied by about 5 GHz due to the shape anisotropy. Furthermore, we experimentally detected the magnetization precession induced by the thermal fluctuation via the rectification of a radio-frequency (rf) current by incorporating an additional direct current (dc) by using Wheatstone bridge circuit. Our investigation renders that the shape anisotropy is of great importance to control the resonance frequency and to provide thermal stability of the microwave devices.

  8. Compact, high-repetition-rate source for broadband sum-frequency generation spectroscopy

    Science.gov (United States)

    Heiner, Zsuzsanna; Petrov, Valentin; Mero, Mark

    2017-06-01

    We present a high-efficiency optical parametric source for broadband vibrational sum-frequency generation (BB-VSFG) for the chemically important mid-infrared spectral range at 2800-3600 cm-1 to study hydrogen bonding interactions affecting the structural organization of biomolecules at water interfaces. The source consists of a supercontinuum-seeded, dual-beam optical parametric amplifier with two broadband infrared output beams and a chirped sum-frequency mixing stage providing narrowband visible pulses with adjustable bandwidth. Utilizing a pulse energy of only 60 μJ from a turn-key, 1.03-μm pump laser operating at a repetition rate of 100 kHz, the source delivers 6-cycle infrared pulses at 1.5 and 3.2 μm with pulse energies of 4.6 and 1.8 μJ, respectively, and narrowband pulses at 0.515 μm with a pulse energy of 5.0 μJ. The 3.2-μm pulses are passively carrier envelope phase stabilized with fluctuations at the 180-mrad level over a 10-s time period. The 1.5-μm beamline can be exploited to deliver pump pulses for time-resolved studies after suitable frequency up-conversion. The high efficiency, stability, and two orders of magnitude higher repetition rate of the source compared to typically employed systems offer great potential for providing a boost in sensitivity in BB-VSFG experiments at a reduced cost.

  9. BROADBAND X-RAY IMAGING AND SPECTROSCOPY OF THE CRAB NEBULA AND PULSAR WITH NuSTAR

    Energy Technology Data Exchange (ETDEWEB)

    Madsen, Kristin K.; Harrison, Fiona; Grefenstette, Brian W. [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125 (United States); Reynolds, Stephen [Physics Department, NC State University, Raleigh, NC 27695 (United States); An, Hongjun [Department of Physics, McGill University, Montreal, Quebec, H3A 2T8 (Canada); Boggs, Steven; Craig, William W.; Zoglauer, Andreas [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States); Christensen, Finn E. [DTU Space, National Space Institute, Technical University of Denmark, Elektronvej 327, DK-2800 Lyngby (Denmark); Fryer, Chris L. [CCS-2, Los Alamos National Laboratory, Livermore, CA 94550 (United States); Hailey, Charles J.; Nynka, Melania [Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States); Markwardt, Craig; Zhang, William [Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Stern, Daniel [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States)

    2015-03-01

    We present broadband (3-78 keV) NuSTAR X-ray imaging and spectroscopy of the Crab nebula and pulsar. We show that while the phase-averaged and spatially integrated nebula + pulsar spectrum is a power law in this energy band, spatially resolved spectroscopy of the nebula finds a break at ∼9 keV in the spectral photon index of the torus structure with a steepening characterized by ΔΓ ∼ 0.25. We also confirm a previously reported steepening in the pulsed spectrum, and quantify it with a broken power law with break energy at ∼12 keV and ΔΓ ∼ 0.27. We present spectral maps of the inner 100'' of the remnant and measure the size of the nebula as a function of energy in seven bands. These results find that the rate of shrinkage with energy of the torus size can be fitted by a power law with an index of γ = 0.094 ± 0.018, consistent with the predictions of Kennel and Coroniti. The change in size is more rapid in the NW direction, coinciding with the counter-jet where we find the index to be a factor of two larger. NuSTAR observed the Crab during the latter part of a γ-ray flare, but found no increase in flux in the 3-78 keV energy band.

  10. Electrochemical impedance spectroscopy for quantitative interface state characterization of planar and nanostructured semiconductor-dielectric interfaces

    Science.gov (United States)

    Meng, Andrew C.; Tang, Kechao; Braun, Michael R.; Zhang, Liangliang; McIntyre, Paul C.

    2017-10-01

    The performance of nanostructured semiconductors is frequently limited by interface defects that trap electronic carriers. In particular, high aspect ratio geometries dramatically increase the difficulty of using typical solid-state electrical measurements (multifrequency capacitance- and conductance-voltage testing) to quantify interface trap densities (D it). We report on electrochemical impedance spectroscopy (EIS) to characterize the energy distribution of interface traps at metal oxide/semiconductor interfaces. This method takes advantage of liquid electrolytes, which provide conformal electrical contacts. Planar Al2O3/p-Si and Al2O3/p-Si0.55Ge0.45 interfaces are used to benchmark the EIS data against results obtained from standard electrical testing methods. We find that the solid state and EIS data agree very well, leading to the extraction of consistent D it energy distributions. Measurements carried out on pyramid-nanostructured p-Si obtained by KOH etching followed by deposition of a 10 nm ALD-Al2O3 demonstrate the application of EIS to trap characterization of a nanostructured dielectric/semiconductor interface. These results show the promise of this methodology to measure interface state densities for a broad range of semiconductor nanostructures such as nanowires, nanofins, and porous structures.

  11. Fed-Batch Production of Bacterial Ghosts Using Dielectric Spectroscopy for Dynamic Process Control

    Directory of Open Access Journals (Sweden)

    Andrea Meitz

    2016-03-01

    Full Text Available The Bacterial Ghost (BG platform technology evolved from a microbiological expression system incorporating the ϕX174 lysis gene E. E-lysis generates empty but structurally intact cell envelopes (BGs from Gram-negative bacteria which have been suggested as candidate vaccines, immunotherapeutic agents or drug delivery vehicles. E-lysis is a highly dynamic and complex biological process that puts exceptional demands towards process understanding and control. The development of a both economic and robust fed-batch production process for BGs required a toolset capable of dealing with rapidly changing concentrations of viable biomass during the E-lysis phase. This challenge was addressed using a transfer function combining dielectric spectroscopy and soft-sensor based biomass estimation for monitoring the rapid decline of viable biomass during the E-lysis phase. The transfer function was implemented to a feed-controller, which followed the permittivity signal closely and was capable of maintaining a constant specific substrate uptake rate during lysis phase. With the described toolset, we were able to increase the yield of BG production processes by a factor of 8–10 when compared to currently used batch procedures reaching lysis efficiencies >98%. This provides elevated potentials for commercial application of the Bacterial Ghost platform technology.

  12. Anisotropic dielectric relaxation of the water confined in nanotubes for terahertz spectroscopy studied by molecular dynamics simulations.

    Science.gov (United States)

    Qi, Wenpeng; Chen, Jige; Yang, Junwei; Lei, Xiaoling; Song, Bo; Fang, Haiping

    2013-07-03

    The dynamics and structure of the hydrogen-bond network in confined water are of importance in understanding biological and chemical processes. Recently, terahertz (THz) time domain spectroscopy was widely applied for studying the kinetics of molecules and the hydrogen-bond network in water. However, the characteristics of the THz spectroscopy varying with respect to the confinement and the mechanism underlying the variation are still unclear. Here, on the basis of molecular dynamics simulations, the relationship between the anisotropic dielectric relaxation and the structure of the water confined in a carbon nanotube (CNT) was investigated. The results show that there are two preferred hydrogen-bond orientations of the confined water in the nanotube: (1) parallel to the CNT axis and (2) perpendicular to the CNT axis, which are clearly different. Moreover, the response of the orientations to the increment of the CNT diameters is opposite, leading to the opposite variations of the dielectric relaxation times along the two directions. The anisotropy in the relaxation time can be presented by the anisotropic dielectric permittivity which is able to be observed through THz spectroscopy. The anormal behaviors above are attributed to the special structure of the water close to the nanotube wall due to the confinement and hydrophobicity of CNT. These studies contribute an important step in understanding the THz experiments of water in nanoscales, and designing a chamber for specific chemical and biological reactions by controlling the diameters and materials of the nanotube.

  13. Frequency-comb-assisted broadband precision spectroscopy with cascaded diode lasers

    DEFF Research Database (Denmark)

    Liu, Junqiu; Brasch, Victor; Pfeiffer, Martin H. P.

    2016-01-01

    Frequency-comb-assisted diode laser spectroscopy, employing both the accuracy of an optical frequency comb and the broad wavelength tuning range of a tunable diode laser, has been widely used in many applications. In this Letter, we present a novel method using cascaded frequency agile diode lasers...

  14. Rapid, broadband spectroscopic temperature measurement of CO2 using VIPA spectroscopy

    CERN Document Server

    Klose, Andrew; Cruz, Flavio C; Maser, Daniel L; Diddams, Scott A

    2016-01-01

    Time-resolved spectroscopic temperature measurements of a sealed carbon dioxide sample cell were realized with an optical frequency comb combined with a two-dimensional dispersive spectrometer. A supercontinuum laser source based on an erbium fiber mode-locked laser was employed to generate coherent light around 2000 nm (5000 cm-1). The laser was passed through a 12-cm long cell containing CO2, and the transmitted light was analyzed in a virtually imaged phased array- (VIPA-) based spectrometer. Broadband spectra spanning more than 100 cm-1 with a spectral resolution of roughly 0.075 cm-1 (2.2 GHz) were acquired with an integration period of 2 ms. The temperature of the CO2 sample was deduced from fitting a modeled spectrum to the line intensities of the experimentally acquired spectrum. Temperature dynamics on the time scale of milliseconds were observed with a temperature resolution of 2.6 K. The spectroscopically-deduced temperatures agreed with temperatures of the sample cell measured with a thermistor. P...

  15. Broadband integrated mid infrared light sources as enabling technology for point of caremid infrared spectroscopy

    Science.gov (United States)

    2017-08-20

    wavelengths is still in its infancy, resulting in mid-IR spectroscopy being currently restricted to academic proof-of- principle experiments only.
 This...journal paper has resulted. I am assuming that the author has just concentrated on finishing this thesis and has not had time to write these papers...I sincerely hope that Xiantao Jiang will find the time to write these papers.” Indeed, we are currently in the process of writing those papers in

  16. High-performance broad-band spectroscopy for breast cancer risk assessment

    Science.gov (United States)

    Pawluczyk, Olga; Blackmore, Kristina; Dick, Samantha; Lilge, Lothar

    2005-09-01

    Medical diagnostics and screening are becoming increasingly demanding applications for spectroscopy. Although for many years the demand was satisfied with traditional spectrometers, analysis of complex biological samples has created a need for instruments capable of detecting small differences between samples. One such application is the measurement of absorbance of broad spectrum illumination by breast tissue, in order to quantify the breast tissue density. Studies have shown that breast cancer risk is closely associated with the measurement of radiographic breast density measurement. Using signal attenuation in transillumination spectroscopy in the 550-1100nm spectral range to measure breast density, has the potential to reduce the frequency of ionizing radiation, or making the test accessible to younger women; lower the cost and make the procedure more comfortable for the patient. In order to determine breast density, small spectral variances over a total attenuation of up to 8 OD have to be detected with the spectrophotometer. For this, a high performance system has been developed. The system uses Volume Phase Holographic (VPH) transmission grating, a 2D detector array for simultaneous registration of the whole spectrum with high signal to noise ratio, dedicated optical system specifically optimized for spectroscopic applications and many other improvements. The signal to noise ratio exceeding 50,000 for a single data acquisition eliminates the need for nitrogen cooled detectors and provides sufficient information to predict breast tissue density. Current studies employing transillumination breast spectroscopy (TIBS) relating to breast cancer risk assessment and monitoring are described.

  17. Broadband Ftmw Spectroscopy of the Urea-Argon and Thiourea-Argon Complexes

    Science.gov (United States)

    Medcraft, Chris; Bittner, Dror M.; Cooper, Graham A.; Mullaney, John C.; Walker, Nick

    2017-06-01

    The rotational spectra complexes of argon-urea, argon-thiourea and water-thiourea have been measured by chirped-pulse Fourier transform microwave spectroscopy from 2-18.5 GHz. The sample was produced via laser vaporisation of a rod containing copper and the organic sample as a stream of argon was passed over the surface and subsequently expanded into the vacuum chamber cooling the sample. Argon was found to bind to π system of the carbonyl bond for both the urea and thiourea complexes.

  18. a New Broadband Cavity Enhanced Frequency Comb Spectroscopy Technique Using GHz Vernier Filtering.

    Science.gov (United States)

    Morville, Jérôme; Rutkowski, Lucile; Dobrev, Georgi; Crozet, Patrick

    2015-06-01

    We present a new approach to Cavity Enhanced - Direct Frequency Comb Spectroscopy where the full emission bandwidth of a Titanium:Sapphire laser is exploited at GHz resolution. The technique is based on a low-resolution Vernier filtering obtained with an appreciable -actively stabilized- mismatch between the cavity Free Spectral Range and the laser repetition rate, using a diffraction grating and a split-photodiode. This particular approach provides an immunity to frequency-amplitude noise conversion, reaching an absorption baseline noise in the 10-9 cm-1 range with a cavity finesse of only 3000. Spectra covering 1800 cm-1 (˜ 55 THz) are acquired in recording times of about 1 second, providing an absorption figure of merit of a few 10-11 cm-1/√{Hz}. Initially tested with ambient air, we report progress in using the Vernier frequency comb method with a discharge source of small radicals. Rutkowski et al, Opt. Lett., 39(23)2014

  19. Broadband terahertz dynamics of propylene glycol monomer and oligomers

    Science.gov (United States)

    Koda, Shota; Mori, Tatsuya; Kojima, Seiji

    2016-12-01

    We investigated the broadband terahertz spectra (0.1-5.0 THz) of glass-forming liquids, propylene glycol (PG), its oligomers poly (propylene glycol)s (PPGs), and poly (propylene glycol) diglycidyl ether (PPG-de) using broadband terahertz time-domain spectroscopy and low-frequency Raman scattering. The numerical value of the dielectric loss at around 1.5 THz, which is the peak position of broad peaks in all samples, decreased as the molecular weight increased. Furthermore, the peak at around 1.5 THz is insensitive to the molecular weight. For PPGs, the side chain effect of the oligomer was observed in the terahertz region. Based on the experimental and calculation results for the PPGs and PPG-de, whose end groups are epoxy groups, the beginnings of the increases in the observed dielectric loss above 3.5 THz of the PPGs are assigned to the OH bending vibration. The higher value of the dielectric loss in the terahertz region for the PPG-de can be the tail of a broad peak located in the MHz region. The difference between the Raman susceptibility and dielectric loss reflects the difference in the observable molecular dynamics between the infrared and Raman spectroscopies.

  20. 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.

  1. Dielectric spectroscopy of isotropic liquids and liquid crystal phases with dispersed graphene oxide

    OpenAIRE

    Shakhawan Al-Zangana; Maria Iliut; Gökçen Boran; Michael Turner; Aravind Vijayaraghavan; Ingo Dierking

    2016-01-01

    Graphene oxide (GO) flakes of different sizes were prepared and dispersed in isotropic and nematic (anisotropic) fluid media. The dielectric relaxation behaviour of GO-dispersions was examined for a wide temperature (25–60 oC) and frequency range (100 Hz–2 MHz). The mixtures containing GO flakes exhibited varying dielectric relaxation processes, depending on the size of the flakes and the elastic properties of the dispersant fluid. Relaxation frequencies of the GO doped isotropic media, such ...

  2. Electrical and Dielectric Properties of Polyaniline and Polyaniline/Montmorillonite Nanocomposite Prepared by Solid Reaction Using Spectroscopy Impedance

    Directory of Open Access Journals (Sweden)

    Imene Bekri-Abbes

    2015-01-01

    Full Text Available The combination of two components with uniform distribution in nanoscale is expected to facilitate wider applications of the material. In this study, polyaniline (PAn and polyaniline/montmorillonite (Mt nanocomposite were prepared by solid reaction using persulfate of ammonium as oxidant. The phase composition and morphology of the nanocomposite were characterized by FTIR, UV-visible spectroscopy, X-ray diffractometer, thermal gravimetric analysis, and scanning electron microscopy. The electrical and dielectric properties were determined using spectroscopy impedance. The analysis of UV-visible and FTIR spectroscopy demonstrated that aniline chloride has been polymerized into PAn in its conducting emeraldine form. Thermogravimetric analysis suggested that PAn chains intercalated in the clay host are more thermally stable than those of free PAn prepared by solid-solid reaction. Electrical measurements were carried out using the complex impedance technique in the frequency range of 10−2 to 104 Hz at different temperatures. The ac conductivity data of different nanocomposites were analyzed as a function of frequency and temperature. It has been found that the incorporation of inorganic clay phase into polyaniline matrix has an effect on the electrical and dielectric properties of the nanomaterial.

  3. Contactless, probeless and non-titrimetric determination of acid-base reactions using broadband acoustic resonance dissolution spectroscopy (BARDS).

    Science.gov (United States)

    Ahmed, M Rizwan; McSweeney, Sean; Krüse, Jacob; Vos, Bastiaan; Fitzpatrick, Dara

    2018-02-12

    pH determination is a routine measurement in scientific laboratories worldwide. Most major advances in pH measurement were made in the 19th and early 20th century. pH measurements are critical for the determination of acid base reactions. This study demonstrates how an acid-base reaction can be monitored without the use of a pH probe, indicator and titres of reagent. The stoichiometric reaction between carbonate and HCl acid yields specific quantities of CO 2 , which causes reproducible changes to the compressibility of the solvent. This in turn slows down the speed of sound in solution which is induced by a magnetic follower gently tapping the inner wall of the vessel. As a consequence the frequencies of the acoustic resonances in the vessel are reduced. This approach is called Broadband Acoustic Resonance Dissolution Spectroscopy (BARDS) which harnesses this phenomenon for many applications. The acid-carbonate experiments have also been validated using H 2 SO 4 acid and using both potassium and sodium counterions for the carbonate. This method can be used to interrogate strong acid-base reactions in a rapid and non-invasive manner using carbonate as the base. The data demonstrate the first example of a reactant also acting as an indicator. The applicability of the method to weak acids has yet to be determined. A novel conclusion from the study is that a person with a well-trained ear is capable of determining the concentration and pH of a strong acid just by listening. This brings pH measurement into the realm of human perception.

  4. Determination of the concentration of alum additive in deep-fried dough sticks using dielectric spectroscopy.

    Science.gov (United States)

    Kang, Wenyu; Lu, Jianfeng; Cheng, Yudong; Jin, Yinzhe

    2015-09-01

    The concentration of alum additive in deep-fried dough sticks (DFDSs) was investigated using a coaxial probe method based on dielectric properties in the 0.3-10-GHz frequency range. The dielectric spectra of aqueous solutions with different concentrations of alum, sodium bicarbonate, and mixtures thereof were used. The correspondence between dielectric loss and alum concentration was thereby revealed. A steady, uniform correspondence was successfully established by introducing ω·ε″(ω), the sum of dielectric loss and conductor loss (i.e., total loss), according to the electrical conductivity of the alum-containing aqueous solutions. Specific, resonant-type dielectric dispersion arising from alum due to atomic polarization was identified around 1 GHz. This was used to discriminate the alum additive in the DFDS from other ingredients. A quantitative relationship between alum and sodium bicarbonate concentrations in the aqueous solutions and the differential dielectric loss Δε″(ω) at 0.425 GHz was also established with a regression coefficient over 0.99. With the intention of eliminating the effects of the chemical reactions with sodium bicarbonate and the physical processes involved in leavening and frying during preparation, the developed technique was successfully applied to detect the alum dosage in a commercial DFDS (0.9942 g/L). The detected value agreed well with that determined using graphite furnace atomic absorption spectrometry (0.9722 g/L). The relative error was 2.2%. The results show that the proposed dielectric differential dispersion and loss technique is a suitable and effective method for determining the alum content in DFDSs. Copyright © 2014. Published by Elsevier B.V.

  5. Determination of the concentration of alum additive in deep-fried dough sticks using dielectric spectroscopy

    Directory of Open Access Journals (Sweden)

    Wenyu Kang

    2015-09-01

    Full Text Available The concentration of alum additive in deep-fried dough sticks (DFDSs was investigated using a coaxial probe method based on dielectric properties in the 0.3–10-GHz frequency range. The dielectric spectra of aqueous solutions with different concentrations of alum, sodium bicarbonate, and mixtures thereof were used. The correspondence between dielectric loss and alum concentration was thereby revealed. A steady, uniform correspondence was successfully established by introducing ω·ε″(ω, the sum of dielectric loss and conductor loss (i.e., total loss, according to the electrical conductivity of the alum-containing aqueous solutions. Specific, resonant-type dielectric dispersion arising from alum due to atomic polarization was identified around 1 GHz. This was used to discriminate the alum additive in the DFDS from other ingredients. A quantitative relationship between alum and sodium bicarbonate concentrations in the aqueous solutions and the differential dielectric loss Δε″(ω at 0.425 GHz was also established with a regression coefficient over 0.99. With the intention of eliminating the effects of the chemical reactions with sodium bicarbonate and the physical processes involved in leavening and frying during preparation, the developed technique was successfully applied to detect the alum dosage in a commercial DFDS (0.9942 g/L. The detected value agreed well with that determined using graphite furnace atomic absorption spectrometry (0.9722 g/L. The relative error was 2.2%. The results show that the proposed dielectric differential dispersion and loss technique is a suitable and effective method for determining the alum content in DFDSs.

  6. Optical, Dielectric Characterization and Impedance Spectroscopy of Ni-Substituted MgTiO3 Thin Films

    Science.gov (United States)

    Gogoi, Pallabi; Srinivas, P.; Sharma, Pramod; Pamu, D.

    2016-02-01

    We report the effects of oxygen mixing percentage (OMP) and annealing temperature on surface morphology, optical, dielectric and electrical properties of (Mg0.95Ni0.05)TiO3 (MNT) thin films deposited onto amorphous SiO2 and platinized silicon (Pt/TiO2/SiO2/Si) substrates by radio frequency (RF) magnetron sputtering. The annealed films exhibited the highest refractive index, 2.05, at 600 nm with an optical bandgap value of 4.33 eV. The metal-insulator-metal (MIM) capacitors of the MNT thin films were fabricated under different OMPs and the dielectric properties were analyzed by using Maxwell-Wagner two-layer theory and Koop's phenomenological theory. MNT films prepared under 50% OMP displayed the highest dielectric constant (11.21) and minimum loss tangent (0.0114) at 1 MHz. The impedance spectroscopy of the films deposited under 50% OMP has been studied. The Nyquist plots of MNT films revealed two semi-circular arcs and is explained on the basis of an equivalent circuit model. The frequency-dependent alternative current (AC) conductivity followed the Jonscher's power law. The activation energies are calculated using the Arrhenius relationship. The hopping frequency of the charged species was calculated, and the correlation between AC and direct current (DC) conduction mechanisms established in accordance with the Barton-Nakajima-Namikawa (BNN) relationship.

  7. Measurements of water molecule density by tunable diode laser absorption spectroscopy in dielectric barrier discharges with gas–water interface

    Science.gov (United States)

    Tachibana, Kunihide; Nakamura, Toshihiro; Kawasaki, Mitsuo; Morita, Tatsuo; Umekawa, Toyofumi; Kawasaki, Masahiro

    2018-01-01

    We measured water molecule (H2O) density by tunable diode-laser absorption spectroscopy (TDLAS) for applications in dielectric barrier discharges (DBDs) with a gas–water interface. First, the effects of water temperature and presence of gas flow were tested using a Petri dish filled with water and a gas injection nozzle. Second, the TDLAS system was applied to the measurements of H2O density in two types of DBDs; one was a normal (non-inverted) type with a dielectric-covered electrode above a water-filled counter electrode and the other was an inverted type with a water-suspending mesh electrode above a dielectric-covered counter electrode. The H2O density in the normal DBD was close to the density estimated from the saturated vapor pressure, whereas the density in the inverted DBD was about half of that in the former type. The difference is attributed to the upward gas flow in the latter type, that pushes the water molecules up towards the gas–water interface.

  8. Application of a broadband blue laser diode to trace NO2 detection using off-beam quartz-enhanced photoacoustic spectroscopy.

    Science.gov (United States)

    Yi, Hongming; Liu, Kun; Chen, Weidong; Tan, Tu; Wang, Lei; Gao, Xiaoming

    2011-02-15

    We applied for the first time, to our knowledge, broadband off-beam quartz-enhanced photoacoustic spectroscopy (BB-OB-QEPAS) to trace NO2 detection using a broadband blue laser diode centered at 450 nm. A detection limit of 18 ppbv (parts in 10(9) by volume) for NO2 in N2 at atmospheric pressure was achieved with an average laser power of 7 mW at a 1 s integration time, which corresponds to a 1 σ normalized noise equivalent absorption coefficient of 4.1×10(-9)  cm(-1) W=Hz(1=2). An Allan variance analysis was performed to investigate the long-term stability of the BB-OB-QEPAS-based NO2 sensor.

  9. Thyroid tissue constituents characterization and application to in vivo studies by broadband (600-1200 nm) diffuse optical spectroscopy

    Science.gov (United States)

    Konugolu Venkata Sekar, Sanathana; Farina, Andrea; dalla Mora, Alberto; Taroni, Paola; Lindner, Claus; Mora, Mireia; Farzam, Parisa; Pagliazzi, Marco; Squarcia, Mattia; Halperin, Irene; Hanzu, Felicia A.; Dehghani, Hamid; Durduran, Turgut; Pifferi, Antonio

    2017-07-01

    We present the first broadband (600-1100 nm) diffuse optical characterization of thyroglobulin and tyrosine, which are thyroid-specific tissue constituents. In-vivo measurements at the thyroid region enabled their quantification for functional and diagnostic applications.

  10. Excitations and relaxation dynamics in multiferroic GeV4S8 studied by terahertz and dielectric spectroscopy

    Science.gov (United States)

    Reschke, S.; Wang, Zhe; Mayr, F.; Ruff, E.; Lunkenheimer, P.; Tsurkan, V.; Loidl, A.

    2017-10-01

    We report on THz time-domain spectroscopy on multiferroic GeV4S8 , which undergoes orbital ordering at a Jahn-Teller transition at 30.5 K and exhibits antiferromagnetic order below 14.6 K. The THz experiments are complemented by dielectric experiments at audio and radio frequencies. We identify a low-lying excitation close to 0.5 THz, which is only weakly temperature dependent and probably corresponds to a molecular excitation within the electronic level scheme of the V4 clusters. In addition, we detect complex temperature-dependent behavior of a low-lying phononic excitation, closely linked to the onset of orbitally driven ferroelectricity. In the high-temperature cubic phase, which is paramagnetic and orbitally disordered, this excitation is of relaxational character becomes an overdamped Lorentzian mode in the orbitally ordered phase below the Jahn-Teller transition, and finally appears as well-defined phonon excitation in the antiferromagnetic state. Abrupt changes in the real and imaginary parts of the complex dielectric permittivity show that orbital ordering appears via a structural phase transition with strong first-order character and that the onset of antiferromagnetic order is accompanied by significant structural changes, which are of first-order character, too. Dielectric spectroscopy documents that at low frequencies, significant dipolar relaxations are present in the orbitally ordered, paramagnetic phase only. In contrast to the closely related GaV4S8 , this relaxation dynamics that most likely mirrors coupled orbital and polar fluctuations does not seem to be related to the dynamic processes detected in the THz regime.

  11. Microwave dielectric relaxation spectroscopy study of propylene glycol/ethanol binary mixtures: Temperature dependence

    Science.gov (United States)

    Vishwam, T.; Shihab, Suriya; Murthy, V. R. K.; Tiong, Ha Sie; Sreehari Sastry, S.

    2017-05-01

    Complex dielectric permittivity measurements of propylene glycol (PG) in ethanol at various mole fractions were measured by using open-ended coaxial probe technique at different temperatures in the frequency range 0.02 propylene glycol and ethanol and their binary system have been evaluated theoretically at gaseous state as well as alcoholic medium by using PCM and IEFPCM solvation models from the Hatree-Fock (HF) and Density Functional Theory (DFT-B3LYP) methods with 6-311G* and 6-311G** basis sets. The obtained results have been interpreted in terms of the short and long range ordering of the dipoles, Kirkwood correlation factor (geff), thermodynamic parameters, mean molecular polarizability (αM) and interaction in the mixture through hydrogen bonding. Dielectric relaxation study of propylene glycol in ethanol medium Determination of excess dielectric and thermodynamic parameters Comparison of experimental dipole moment with theoretical calculations Interpretation of the molecular interactions in the liquid through H-bonding Correlation between the evaluated dielectric parameters and theoretical results

  12. Use of Dielectric Spectroscopy to Estimate the Condition of Cellulose-Based Insulation

    Directory of Open Access Journals (Sweden)

    L.M. Dumitran

    2009-05-01

    Full Text Available Assessment of the power transformersinsulation condition is a permanent concern forcarriers and distributors of electrical energy.Different methods for their monitoring and diagnosiswere developed in recent years. The aim of this workis to present the basis of the dielectric spectroscopymethod and the first results obtained in time-domainand in frequency domain that permit to estimate themoisture content in pressboard. At the end, thepossibility to use this method for off-line and on-linetransformer monitoring is analyzed.

  13. Dielectric spectroscopy of isotropic liquids and liquid crystal phases with dispersed graphene oxide

    Science.gov (United States)

    Al-Zangana, Shakhawan; Iliut, Maria; Boran, Gökçen; Turner, Michael; Vijayaraghavan, Aravind; Dierking, Ingo

    2016-08-01

    Graphene oxide (GO) flakes of different sizes were prepared and dispersed in isotropic and nematic (anisotropic) fluid media. The dielectric relaxation behaviour of GO-dispersions was examined for a wide temperature (25-60 oC) and frequency range (100 Hz-2 MHz). The mixtures containing GO flakes exhibited varying dielectric relaxation processes, depending on the size of the flakes and the elastic properties of the dispersant fluid. Relaxation frequencies of the GO doped isotropic media, such as isopropanol IPA, were observed to be much lower than the GO doped thermotropic nematic medium 5CB. It is anticipated that the slow relaxation frequencies (~10 kHz) could be resulting from the relaxation modes of the GO flakes while the fast relaxation frequencies (~100 kHz) could indicate strongly slowed down molecular modes of the nematogenic molecules, which are anchored to the GO flakes via dispersion interactions. The relaxation frequencies decreased as the size of the GO flakes in the isotropic solvent was increased. Polarizing microscopy showed that GO flakes with a mean diameter of 10 μm, dispersed in water, formed a lyotropic nematic liquid crystal phase. This lyotropic nematic exhibited the slowest dielectric relaxation process, with relaxation frequencies in the order of 2 kHz, as compared to the GO-isotropic suspension and the GO-doped 5CB.

  14. Reactance and resistance: main properties to follow the cell differentiation process in Bacillus thuringiensis by dielectric spectroscopy in real time.

    Science.gov (United States)

    Dinorín-Téllez-Girón, Jabel; Delgado-Macuil, Raúl Jacobo; Larralde Corona, Claudia Patricia; Martínez Montes, Francisco Javier; de la Torre Martínez, Mayra; López-Y-López, Víctor Eric

    2015-07-01

    During growth, Bacillus thuringiensis presents three phases: exponential phase (EP), transition state (TS), and sporulation phase (SP). In order to form a dormant spore and to synthesize delta-endotoxins during SP, bacteria must undergo a cellular differentiation process initiated during the TS. Dielectric spectroscopy is a technique that can be utilized for continuous and in situ monitoring of the cellular state. In order to study on-line cell behavior in B. thuringiensis cultures, we conducted a number of batch cultures under different conditions, by scanning 200 frequencies from 42 Hz to 5 MHz and applying fixed current and voltage of 20 mA and 5 V DC, respectively. The resulting signals included Impedance (Z), Angle phase (Deg), Voltage (V), Current (I), Conductance (G), Reactance (X), and Resistance (R). Individual raw data relating to observed dielectric property profiles were correlated with the different growth phases established using data from cellular growth, cry1Ac gene expression, and free spores obtained with conventional techniques and fermentation parameters. Based on these correlations, frequencies of 0.1, 0.5, and 1.225 MHz were selected for the purpose of measuring dielectric properties in independent batch cultures, at a fixed frequency. X and R manifest more propitious behavior in relation to EP, TS, SP, and spore release, due to particular changes in their signals. Interestingly, these profiles underwent pronounced changes during EP and TS that were not noticed when using conventional methods, but were indicative of the beginning of the B. thuringiensis cell differentiation process.

  15. Dual broadband metamaterial absorber.

    Science.gov (United States)

    Kim, Young Ju; Yoo, Young Joon; Kim, Ki Won; Rhee, Joo Yull; Kim, Yong Hwan; Lee, YoungPak

    2015-02-23

    We propose polarization-independent and dual-broadband metamaterial absorbers at microwave frequencies. This is a periodic meta-atom array consisting of metal-dielectric-multilayer truncated cones. We demonstrate not only one broadband absorption from the fundamental magnetic resonances but additional broadband absorption in high-frequency range using the third-harmonic resonance, by both simulation and experiment. In simulation, the absorption was over 90% in 3.93-6.05 GHz, and 11.64-14.55 GHz. The corresponding experimental absorption bands over 90% were 3.88-6.08 GHz, 9.95-10.46 GHz and 11.86-13.84 GHz, respectively. The origin of absorption bands was elucidated. Furthermore, it is independent of polarization angle owing to the multilayered circular structures. The design is scalable to smaller size for the infrared and the visible ranges.

  16. Application of Atomic Dielectric Resonance Spectroscopy for the screening of blood samples from patients with clinical variant and sporadic CJD.

    Science.gov (United States)

    Fagge, Timothy J; Barclay, G Robin; Stove, G Colin; Stove, Gordon; Robinson, Michael J; Head, Mark W; Ironside, James W; Turner, Marc L

    2007-08-30

    Sub-clinical variant Creutzfeldt-Jakob disease (vCJD) infection and reports of vCJD transmission through blood transfusion emphasise the need for blood screening assays to ensure the safety of blood and transplanted tissues. Most assays aim to detect abnormal prion protein (PrPSc), although achieving required sensitivity is a challenge. We have used innovative Atomic Dielectric Resonance Spectroscopy (ADRS), which determines dielectric properties of materials which are established by reflectivity and penetration of radio/micro waves, to analyse blood samples from patients and controls to identify characteristic ADR signatures unique to blood from vCJD and to sCJD patients. Initial sets of blood samples from vCJD, sCJD, non-CJD neurological diseases and normal healthy adults (blood donors) were screened as training samples to determine group-specific ADR characteristics, and provided a basis for classification of blinded sets of samples. Blood sample groups from vCJD, sCJD, non-CJD neurological diseases and normal healthy adults (blood donors) screened by ADRS were classified with 100% specificity and sensitivity, discriminating these by a co-variance expert analysis system. ADRS appears capable of recognising and discriminating serum samples from vCJD, sCJD, non-CJD neurological diseases, and normal healthy adults, and might be developed to provide a system for primary screening or confirmatory assay complementary to other screening systems.

  17. Application of Atomic Dielectric Resonance Spectroscopy for the screening of blood samples from patients with clinical variant and sporadic CJD

    Directory of Open Access Journals (Sweden)

    Ironside James W

    2007-08-01

    Full Text Available Abstract Background Sub-clinical variant Creutzfeldt-Jakob disease (vCJD infection and reports of vCJD transmission through blood transfusion emphasise the need for blood screening assays to ensure the safety of blood and transplanted tissues. Most assays aim to detect abnormal prion protein (PrPSc, although achieving required sensitivity is a challenge. Methods We have used innovative Atomic Dielectric Resonance Spectroscopy (ADRS, which determines dielectric properties of materials which are established by reflectivity and penetration of radio/micro waves, to analyse blood samples from patients and controls to identify characteristic ADR signatures unique to blood from vCJD and to sCJD patients. Initial sets of blood samples from vCJD, sCJD, non-CJD neurological diseases and normal healthy adults (blood donors were screened as training samples to determine group-specific ADR characteristics, and provided a basis for classification of blinded sets of samples. Results Blood sample groups from vCJD, sCJD, non-CJD neurological diseases and normal healthy adults (blood donors screened by ADRS were classified with 100% specificity and sensitivity, discriminating these by a co-variance expert analysis system. Conclusion ADRS appears capable of recognising and discriminating serum samples from vCJD, sCJD, non-CJD neurological diseases, and normal healthy adults, and might be developed to provide a system for primary screening or confirmatory assay complementary to other screening systems.

  18. The use of dielectric spectroscopy for the characterisation of the precipitation of hydrophobically modified poly(acrylic-acid) with divalent barium ions

    DEFF Research Database (Denmark)

    Christensen, Peter Vittrup; Keiding, Kristian

    2009-01-01

    The use of dielectric spectroscopy as a monitor for coagulation processes was investigated. Hydrophobically modified poly(acrylic-acid) polymers were used as model macromolecules and coagulated with barium ions. The coagulation process was quantified using a photometric dispersion analyser, thereby...

  19. DETERMINING PARAMETERS OF THE DIELECTRIC FUNCTION OF A SUBSTANCE IN AQUEOUS SOLUTION BY SELF-REFERENCED REFLECTION THZ SPECTROSCOPY

    DEFF Research Database (Denmark)

    2008-01-01

    Method and apparatus for determining dielectric function of liquid solutions and thereby concentrations of substances in aqueous solution or the volatile/non-volatile nature of the liquid by self-referenced reflection THz spectroscopy. Having the aqueous solution in any container with a window...... allows irradiating coherent THz radiation with frequencies within the range 0.05 - 2 THz on the front of the window, and recording both a reference signal reflected from the front of the window and a sample signal reflected from the back of the window in contact with the aqueous solution. From...... these signals, the complex index of refraction, (I) or the complex reflection coefficient (II), can be calculated. The calculated components are compared with previously determined components from samples with known concentrations, whereby a concentration of the substance in the mixture can be estimated...

  20. Bismuth germanate as a perspective material for dielectric resonators in EPR spectroscopy

    Science.gov (United States)

    Ivanov, Mikhail Y.; Nadolinny, Vladimir A.; Bagryanskaya, Elena G.; Grishin, Yuriy A.; Fedin, Matvey V.; Veber, Sergey L.

    2016-10-01

    High purity bismuth germanate (Bi4(GeO4)3, BGO) is proposed and implemented as an alternative material for dielectric EPR resonators. A significant improvement of the absolute sensitivity can be readily achieved by substituting the alumina insert (ring) by BGO-made one in commercially available X-band EPR probeheads. Four BGO dielectric inserts of 2, 3, 4 and 5 mm inner diameter (ID) were made for comparison with standard 5 mm inner diameter alumina insert. All inserts were introduced into commercial Bruker EPR resonator ER 4118X-MD-5W1, and their performance was investigated. The Q-values of empty resonators, B1 saturation curves and continuous wave EPR spectra of DPPH (2,2-diphenyl-1-picrylhydrazyl) were measured and analyzed in a temperature range 6-300 K. BGO-made resonators were found superior in several important aspects. The background signals arising from BGO are much weaker compared to those of alumina at B = 0-0.6 T and T = 6-300 K; this is especially useful for measuring weak signals in the half-field region, as well as those near the central field. Moreover, mechanical properties of BGO allow easy fabrication of dielectric bodies having various shapes and sizes; in particular, small BGO resonators (e.g. ID = 2 or 3 mm) strongly enhance sensitivity for small samples due to increase of the filling factor. All these advantages have been also inspected in the pulse mode, proving that higher B1 fields and better filling factors can be achieved, contributing to the overall enhancement of the performance.

  1. Supercooled interfacial water in fine-grained soils probed by dielectric spectroscopy

    Directory of Open Access Journals (Sweden)

    A. Lorek

    2013-12-01

    Full Text Available Water substantially affects nearly all physical, chemical and biological processes on the Earth. Recent Mars observations as well as laboratory investigations suggest that water is a key factor of current physical and chemical processes on the Martian surface, e.g. rheological phenomena. Therefore it is of particular interest to get information about the liquid-like state of water on Martian analogue soils for temperatures below 0 °C. To this end, a parallel plate capacitor has been developed to obtain isothermal dielectric spectra of fine-grained soils in the frequency range from 10 Hz to 1.1 MHz at Martian-like temperatures down to −70 °C. Two Martian analogue soils have been investigated: a Ca-bentonite (specific surface of 237 m2 g−1, up to 9.4% w / w gravimetric water content and JSC Mars 1, a volcanic ash (specific surface of 146 m2 g−1, up to 7.4% w / w. Three soil-specific relaxation processes are observed in the investigated frequency–temperature range: two weak high-frequency processes (bound or hydrated water as well as ice and a strong low-frequency process due to counter-ion relaxation and the Maxwell–Wagner effect. To characterize the dielectric relaxation behaviour, a generalized fractional dielectric relaxation model was applied assuming three active relaxation processes with relaxation time of the ith process modelled with an Eyring equation. The real part of effective complex soil permittivity at 350 kHz was used to determine ice and liquid-like water content by means of the Birchak or CRIM equation. There are evidence that bentonite down to −70 °C has a liquid-like water content of 1.17 monolayers and JSC Mars 1 a liquid-like water content of 1.96 monolayers.

  2. Dielectric spectroscopy as a sensor of membrane headgroup mobility and hydration

    DEFF Research Database (Denmark)

    Klösgen, B; Reichle, C; Kohlsmann, S

    1996-01-01

    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...

  3. 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.)

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

    Science.gov (United States)

    Sheng, Junjie; Chen, Hualing; Li, Bo; Chang, Longfei

    2013-02-01

    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.

  5. Compact and broadband directional coupling and demultiplexing in dielectric-loaded surface plasmon polariton waveguides based on the multimode interference effect

    DEFF Research Database (Denmark)

    Zhu, Zhihong; García Ortíz, César Eduardo; Han, Zhanghua

    2013-01-01

    We theoretically, numerically, and experimentally demonstrate that a directional coupling function can be realized with a wide bandwidth (greater than 200 nm) in dielectric-loaded surface plasmon polariton waveguides based on the multimode interference effect. The functional size of the structure...

  6. Metal-dielectric-CNT nanowires for surface-enhanced Raman spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Bond, Tiziana C.; Altun, Ali; Park, Hyung Gyu

    2017-10-03

    A sensor with a substrate includes nanowires extending vertically from the substrate, a hafnia coating on the nanowires that provides hafnia coated nanowires, and a noble metal coating on the hafnia coated nanowires. The top of the hafnia and noble metal coated nanowires bent onto one another to create a canopy forest structure. There are numerous randomly arranged holes that let through scattered light. The many points of contact, hot spots, amplify signals. The methods include the steps of providing a Raman spectroscopy substrate, introducing nano crystals to the Raman spectroscopy substrate, growing a forest of nanowires from the nano crystals on the Raman spectroscopy substrate, coating the nanowires with hafnia providing hafnia coated nanowires, and coating the hafnia coated nanowires with a noble metal or other metal.

  7. Dielectric relaxation and ultrafast transient absorption spectroscopy of [C6mim]+[Tf2N]−/acetonitrile mixtures.

    Science.gov (United States)

    Lohse, Peter W; Bartels, Nils; Stoppa, Alexander; Buchner, Richard; Lenzer, Thomas; Oum, Kawon

    2012-03-14

    Mixtures of the ionic liquid (IL) [C(6)mim](+)[Tf(2)N](-) and acetonitrile have been investigated by a combination of dielectric relaxation spectroscopy (DRS) and ultrafast transient absorption techniques using the molecular probe 12'-apo-β-carotenoic-12'-acid (12'CA). Steady-state absorption spectra of the 12'CA molecule have also been recorded. The position of the probe's S(0)→ S(2) absorption maximum correlates linearly with the polarizability of the mixture, suggesting that the bulk composition is a good approximation to the local composition. The lifetime τ(1) of the S(1)/ICT state of 12'CA varies rather smoothly with composition between the value for pure acetonitrile (42 ps) and neat [C(6)mim](+)[Tf(2)N](-) (94 ps). At low IL contents there appears to be an influence of discrete ion pairs. Employing static dielectric constants from the DRS experiments, one finds that the lifetime of the probe in the IL mixtures is shorter than that in pure organic solvents with the same polarity parameter. This suggests an increased stabilization of the S(1)/ICT state in IL-containing mixtures, most likely due to IL-specific Coulombic interactions between the cation and the negative end of the probe's dipole. An ultrafast solvation component is observed which is ca. 0.5 ps in pure acetonitrile, and approaches the value for the pure IL (2.0 ps) already around x(IL) = 0.3. This is interpreted in terms of an efficient perturbation of the cooperative solvation response of acetonitrile by the presence of small amounts of IL and possibly also the viscosity increase when adding IL. This view is also supported by the increase of the average longitudinal relaxation time of acetonitrile upon addition of small IL amounts extracted from the DRS experiments.

  8. Characterisation of weak magnetic field effects in an aqueous glutamic acid solution by nonlinear dielectric spectroscopy and voltammetry

    Science.gov (United States)

    Pazur, Alexander

    2004-01-01

    Background Previous reports indicate altered metabolism and enzyme kinetics for various organisms, as well as changes of neuronal functions and behaviour of higher animals, when they were exposed to specific combinations of weak static and alternating low frequency electromagnetic fields. Field strengths and frequencies, as well as properties of involved ions were related by a linear equation, known as the formula of ion cyclotron resonance (ICR, abbreviation mentioned first by Liboff). Under certain conditions already a aqueous solution of the amino acid and neurotransmitter glutamate shows this effect. Methods An aqueous solution of glutamate was exposed to a combination of a static magnetic field of 40 μT and a sinusoidal electromagnetic magnetic field (EMF) with variable frequency (2–7 Hz) and an amplitude of 50 nT. The electric conductivity and dielectric properties of the solution were investigated by voltammetric techniques in combination with non linear dielectric spectroscopy (NLDS), which allow the examination of the dielectric properties of macromolecules and molecular aggregates in water. The experiments target to elucidate the biological relevance of the observed EMF effect on molecular level. Results An ion cyclotron resonance (ICR) effect of glutamate previously reported by the Fesenko laboratory 1998 could be confirmed. Frequency resolution of the sample currents was possible by NLDS techniques. The spectrum peaks when the conditions for ion cyclotron resonance (ICR) of glutamate are matched. Furthermore, the NLDS spectra are different under ICR- and non-ICR conditions: NLDS measurements with rising control voltages from 100–1100 mV show different courses of the intensities of the low order harmonics, which could possibly indicate "intensity windows". Furthermore, the observed magnetic field effects are pH dependent with a narrow optimum around pH 2.85. Conclusions Data will be discussed in the context with recent published models for the

  9. Ultrafast broadband laser spectroscopy reveals energy and charge transfer in novel donor-acceptor triads for photovoltaic applications

    Energy Technology Data Exchange (ETDEWEB)

    Roland, T; Ramirez, G Hernandez; Leonard, J; Mery, S; Haacke, S, E-mail: stefan.haacke@ipcms.u-strasbg.fr [Institut de Physique et Chimie des Materiaux de Strasbourg, Strasbourg University - CNRS UMR 7504, F-67034 Strasbourg (France)

    2011-02-01

    Triggered by the quest for new organic materials and micro-structures for photovoltaic applications, a novel class of donor-acceptor-donor (DAD) triads extended with siloxane chains has been synthesized in our labs. Because of the siloxane chains, the molecules self-organize into a smectic liquid crystal phase, resulting in a stacking of the DAD cores.We report here a preliminary study of the ultrafast dynamics of energy and charge transfer studied by femtosecond broadband transient absorption experiments on isolated triads in chloroform.

  10. Dielectric Properties of Water in Butter and Water-AOT-Heptane Systems Measured using Terahertz Time-Domain Spectroscopy

    DEFF Research Database (Denmark)

    Møller, Uffe; Folkenberg, Jacob Riis; Jepsen, Peter Uhd

    2010-01-01

    We investigate the dielectric properties of water confined in nanometer-sized inverse micelles in mixtures of water, AOT, and heptane. We show that the dielectric properties of the confined water are dependent on the water pool size and different from those of bulk water. We also discuss the diel...... the dielectric properties of different vegetable oils, lard, and butter, and use these properties to deduce the dielectric properties of water in butter, which are shown to deviate significantly from the dielectric properties of bulk water....

  11. Detection of H2S, SO2 and NO2 in CO2 at pressures ranging from 1-40 bar by using broadband absorption spectroscopy in the UV/VIS range

    NARCIS (Netherlands)

    Gersen, Sander; van Essen, Vincent; Visser, Pieter; Ahmad, Mohammad; Mokhov, Anatoli; Sepman, Alexey; Alberts, Ramon; Douma, Arno; Levinsky, Howard

    2014-01-01

    This paper presents a methodology to quantitatively measure H2S, SO2 and NO2 fractions in gaseous CO2 by using broadband absorption spectroscopy at 1 and 40 bar. The mole fractions of binary- and 3-component mixtures of H2S, SO2 and NO2 in CO2 with known fractions ranging from 35-250 ppm are

  12. Impact of patterned anti-reflection coating on the performance of Broadband Blackbody Absorber Based on Dielectric-Thin Metal Film Multilayers

    Science.gov (United States)

    Guo, Shyhauh; Sushkov, Andrei; Drew, Dennis; Phaneuf, Raymond

    2013-03-01

    We present results from measurements on double period structures of alternating dielectric and thin metal layer coated with micro-patterned anti-reflection layer to improve absorption in mid-infrared range. We examine the effect on performance of patterns' period and the correlation with the effective medium theory. We find that the numerical results agree with the measured absorption spectra. We also investigate the limit of pattern feature size to achieve performance suggested by effective medium theory. Laboratory for Physical Sciences, College Park, MD

  13. W/O Emulsions in High Electric Fields as Studied by Means of Time Domain Dielectric Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Foerdedal, Harald

    1995-11-01

    Since oil and brine coexist in the oil reservoirs, the crude oil produced contains free and emulsified water. The type of emulsion formed, water-in-oil or vice versa, generally depends on the amounts of water and oil before mixing. However, the presence of stabilisers, which occur naturally in crude oil, is also of major importance. It is found that dielectric spectroscopy is an appropriate experimental technique for investigating water-in-oil emulsion. When the instrumentation is equipped with an external power supply, information about the coalescence process can be obtained when the critical electric field is approached. Two distinctly different behaviours are observed. In model emulsions stabilised by commercial liquid surfactants a decrease in the static permittivity is observed as the electric field is applied. On the other hand, model emulsions stabilised by indigenous surfactants extracted from crude oils show an increase in the static permittivity as they are exposed to the external electric field. A quantitative parameter is derived for the emulsion stability. The value of the critical electric field is found to be sensitive to changes in the interfacial conditions, and multivariate analysis proves to be suitable for obtaining information about the general trends of variables on the emulsion stability. The stability of emulsions depends on several parameters, such as the amount and properties of the phases, the properties of the stabiliser, etc. Multivariate analysis reveals what variables are most important in characterising the stability/instability of emulsions.

  14. Identification of nanostructural development in epoxy polymer layered silicate nanocomposites from the interpretation of differential scanning calorimetry and dielectric spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Roman, Frida, E-mail: roman@mmt.upc.edu [Laboratori de Termodinamica, Departament de Maquines i Motors Termics, ETSEIAT, Universitat Politecnica de Catalunya, Carrer Colom 11, 08222 Terrassa (Spain); Calventus, Yolanda, E-mail: calventus@mmt.upc.edu [Laboratori de Termodinamica, Departament de Maquines i Motors Termics, ETSEIAT, Universitat Politecnica de Catalunya, Carrer Colom 11, 08222 Terrassa (Spain); Colomer, Pere, E-mail: colomer@mmt.upc.edu [Laboratori de Termodinamica, Departament de Maquines i Motors Termics, ETSEIAT, Universitat Politecnica de Catalunya, Carrer Colom 11, 08222 Terrassa (Spain); Hutchinson, John M., E-mail: hutchinson@mmt.upc.edu [Laboratori de Termodinamica, Departament de Maquines i Motors Termics, ETSEIAT, Universitat Politecnica de Catalunya, Carrer Colom 11, 08222 Terrassa (Spain)

    2012-08-10

    Highlights: Black-Right-Pointing-Pointer Comparison of DSC and DRS in the cure of epoxy nanocomposites. Black-Right-Pointing-Pointer Dependence of exfoliation of nanocomposite on clay content. Black-Right-Pointing-Pointer Anionically initiated homopolymerisation in PLS nanocomposites. - Abstract: The effect of nanoclay on the non-isothermal cure kinetics of polymer layered silicate nanocomposites based upon epoxy resin is studied by calorimetric techniques (DSC and TGA) and by dielectric relaxation spectroscopy (DRS) in non-isothermal cure at constant heating rate. The cure process takes place by homopolymerisation, initiated anionically using 3 wt% dimethylaminopyridine (DMAP), and the influence of the nanoclay content has been analysed. Interesting differences are observed between the nanocomposites with 2 wt% and 5 wt% clay content. At low heating rates, these samples vitrify and then devitrify during the cure. For the sample with 2 wt% clay, the devitrification is accompanied by a thermally initiated homopolymerisation, which can be identified by DRS but not by DSC. The effect of this is to improve the exfoliation of the nanocomposite with 2 wt% clay, as verified by transmission electron microscopy, with a corresponding increase in the glass transition temperature. These observations are interpreted in respect of the nanocomposite preparation method and the cure kinetics.

  15. Dielectric spectroscopy for monitoring human pancreatic islet differentiation within cell-seeded scaffolds in a perfusion bioreactor system.

    Science.gov (United States)

    Daoud, J; Heileman, K; Shapka, S; Rosenberg, L; Tabrizian, M

    2015-09-21

    The long-term in vitro culture and differentiation of human pancreatic islets is still hindered by the inability to emulate a suitable microenvironment mimicking physiological extracellular matrix (ECM) support and nutrient/oxygen perfusion. This is further amplified by the current lack of a non-invasive and rapid monitoring system to readily evaluate cellular processes. In this study, we realized a viable method for non-invasively monitoring isolated human pancreatic islets in vitro. Islets are induced to dedifferentiate into proliferative duct-like structures (DLS) in preparation for potential and subsequent re-differentiation into functional islet-like structures (ILS) in a process reminiscent of islet regeneration strategies. This long-term in vitro process is conducted within a three-dimensional microenvironment involving islets embedded in an optimized ECM gel supported by microfabricated three-dimensional scaffolds. The islet-scaffold is then housed and continuously perfused within chambers of a bioreactor platform. The process in its entirety is monitored through dielectric spectroscopy measurements, yielding an accurate representation of cellular morphology, functionality, and volume fraction. This non-invasive and real-time monitoring tool can be further manipulated to elucidate important information about the optimized cellular microenvironment required for maintaining long-term culture and achieve efficient differentiation for islet regeneration.

  16. Photoconductive, dielectric and percolation properties of anodic TiO2 nanotubes studied by terahertz spectroscopy

    Science.gov (United States)

    Kuchařík, Jiří; Sopha, Hanna; Krbal, Milos; Rychetský, Ivan; Kužel, Petr; Macak, Jan M.; Němec, Hynek

    2018-01-01

    Self-organized layers of anodic TiO2 nanotubes were investigated using time-resolved terahertz spectroscopy in the steady state and upon photoexcitation. The interpretation of the conductivity spectra is based on the response of confined charges calculated by the Monte-Carlo method and on the evaluated distribution of the probing terahertz electric field in the heterogeneous structure. We show that the charge motion perpendicular to the nanotube axis is confined on ~10 nm scale, and that the charge mobility inside these confinement areas is comparable to that observed in a bulk anatase crystal. The electrical connectivity between individual nanotubes assessed from the terahertz spectra qualitatively correlates with the geometry observed in SEM images. The measured transient terahertz transmission spectra feature an apparent resonance; we demonstrate that it is not a signature of a new low-energy excitation but a geometrical effect of Fabry–Pérot interferences in the photoexcited slab.

  17. A Novel Temperature Measurement Approach for a High Pressure Dielectric Barrier Discharge Using Diode Laser Absorption Spectroscopy (Preprint)

    National Research Council Canada - National Science Library

    Leiweke, R. J; Ganguly, B. N

    2006-01-01

    A tunable diode laser absorption spectroscopic technique is used to measure both electronically excited state production efficiency and gas temperature rise in a dielectric barrier discharge in argon...

  18. Broad-band dielectric response of 0.5Ba(Ti.sub.0.8./sub.Zr.sub.0.2./sub.)O-.sub.3./sub.-0.5(Ba.sub.0.7./sub.Ca.sub.0.3./sub.)TiO.sub.3./sub. piezoceramics: soft and central mode behaviour

    Czech Academy of Sciences Publication Activity Database

    Kamba, Stanislav; Simon, Elizabeth; Skoromets, Volodymyr; Bovtun, Viktor; Kempa, Martin; Pokorný, Jan; Savinov, Maxim; Koruza, J.; Malič, B.

    2016-01-01

    Roč. 89, č. 7-8 (2016), s. 785-793 ISSN 0141-1594 R&D Projects: GA MŠk(CZ) LD15014 Institutional support: RVO:68378271 Keywords : Dielectric spectroscopy * lead-free piezoelectrics * soft mode * central mode * phonons * polar nanoregions * infrared * terahertz * Raman spectroscopy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.060, year: 2016

  19. Quantitative Determination of Dielectric Thin-Film Properties Using Infrared Emission Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Franke, J.E.; Haaland, D.M.; Niemczyk, T.M.; Zhang, S.

    1998-10-14

    We have completed an experimental study to investigate the use of infrared emission spectroscopy (IRES) for the quantitative analysis of borophosphosilicate glass (BPSG) thin films on silicon monitor wafers. Experimental parameters investigated included temperatures within the range used in the microelectronics industry to produce these films; hence the potential for using the IRES technique for real-time monitoring of the film deposition process has been evaluated. The film properties that were investigated included boron content, phosphorus content, film thickness, and film temperature. The studies were conducted over two temperature ranges, 125 to 225 *C and 300 to 400 *C. The later temperature range includes realistic processing temperatures for the chemical vapor deposition (CVD) of the BPSG films. Partial least squares (PLS) multivariate calibration methods were applied to spectral and film property calibration data. The cross-validated standard errors of prediction (CVSEP) fi-om the PLS analysis of the IRES spectraof21 calibration samples each measured at 6 temperatures in the 300 to 400 "C range were found to be 0.09 wt. `?40 for B, 0.08 wt. `%0 for P, 3.6 ~m for film thickness, and 1.9 *C for temperature. By lowering the spectral resolution fi-om 4 to 32 cm-l and decreasing the number of spectral scans fi-om 128 to 1, we were able to determine that all the film properties could be measured in less than one second to the precision required for the manufacture and quality control of integrated circuits. Thus, real-time in-situ monitoring of BPSG thin films formed by CVD deposition on Si monitor wafers is possible with the methods reported here.

  20. NIR emission studies and dielectric properties of Er(3+)-doped multicomponent tellurite glasses.

    Science.gov (United States)

    Sajna, M S; Thomas, Sunil; Jayakrishnan, C; Joseph, Cyriac; Biju, P R; Unnikrishnan, N V

    2016-05-15

    Multicomponent tellurite glasses containing altered concentrations of Er2O3 (ranging from 0 to 1 mol%) were prepared by the standard melt quenching technique. Investigations through energy dispersive X-ray spectroscopy (EDS), Raman scattering spectroscopy, Fourier transform infrared (FTIR) spectroscopy, near-infrared (NIR) emission studies and dielectric measurement techniques were done to probe their compositional, structural, spectroscopic and dielectric characteristics. The broad emission together with the high values of the effective linewidth (~63 nm), stimulated emission cross-section (9.67 × 10(-21) cm(2)) and lifetime (2.56 ms) of (4)I13/2 level for 0.5 mol% of Er(3+) makes these glasses attractive for broadband amplifiers. From the measured capacitance and dissipation factor, the relative permittivity, dielectric loss and the conductivity were computed; which furnish the dielectric nature of the multicomponent tellurite glasses that depend on the applied frequency. Assuming the ideal Debye behavior as substantiated by Cole-Cole plot, an examination of the real and imaginary parts of impedance was performed. The power-law and Cole-Cole parameters were resolved for all the glass samples. From the assessment of the emission analysis and dielectric properties of the glass samples, it was obvious that the Er(3+) ion concentration had played a vital role in tuning the optical and dielectric properties and the 0.5 mol% of Er(3+) -doped glass was confirmed as the optimum composition. Copyright © 2016 Elsevier B.V. All rights reserved.

  1. Combined zero-quantum and spin-diffusion mixing for efficient homonuclear correlation spectroscopy under fast MAS: broadband recoupling and detection of long-range correlations.

    Science.gov (United States)

    Lu, Xingyu; Guo, Changmiao; Hou, Guangjin; Polenova, Tatyana

    2015-01-01

    Fast magic angle spinning (MAS) NMR spectroscopy is emerging as an essential analytical and structural biology technique. Large resolution and sensitivity enhancements observed under fast MAS conditions enable structural and dynamics analysis of challenging systems, such as large macromolecular assemblies and isotopically dilute samples, using only a fraction of material required for conventional experiments. Homonuclear dipolar-based correlation spectroscopy constitutes a centerpiece in the MAS NMR methodological toolbox, and is used essentially in every biological and organic system for deriving resonance assignments and distance restraints information necessary for structural analysis. Under fast MAS conditions (rotation frequencies above 35-40 kHz), dipolar-based techniques that yield multi-bond correlations and non-trivial distance information are ineffective and suffer from low polarization transfer efficiency. To overcome this limitation, we have developed a family of experiments, CORD-RFDR. These experiments exploit the advantages of both zero-quantum RFDR and spin-diffusion based CORD methods, and exhibit highly efficient and broadband dipolar recoupling across the entire spectrum, for both short-range and long-range correlations. We have verified the performance of the CORD-RFDR sequences experimentally on a U-(13)C,(15)N-MLF tripeptide and by numerical simulations. We demonstrate applications of 2D CORD-RFDR correlation spectroscopy in dynein light chain LC8 and HIV-1 CA tubular assemblies. In the CORD-RFDR spectra of LC8 acquired at the MAS frequency of 40 kHz, many new intra- and inter-residue correlations are detected, which were not observed with conventional dipolar recoupling sequences. At a moderate MAS frequency of 14 kHz, the CORD-RFDR experiment exhibits excellent performance as well, as demonstrated in the HIV-1 CA tubular assemblies. Taken together, the results indicate that CORD-RFDR experiment is beneficial in a broad range of conditions

  2. Development of a microwave dielectric spectroscopy system for materials characterization using the open-ended coaxial probe technique

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Ruiz, I.; Aviles-Castro, D. [Centro Nacional de Metrologia, Queretaro (Mexico); Jardon-Aguilar, H. [Instituto Politecnico Nacional, Mexico, D. F. (Mexico)

    2001-02-01

    Dielectric spectroscopy is a measurement technique to characterize the interaction between electromagnetic energy and macroscopic samples as a function of frequency. It is based on the measurement of complex permittivity plus conductivity and it has shown to be very useful to provide information about internal structure of matter. It has some advantages over others like optical or chemical analysis: it is very fast, easy to implement, requires little or no preparation of the sample, it can be non-destructive and/or minimally intrusive. In this paper the development of a dielectric spectroscopy system for the microwave frequency range (50 MHz-20 GHz), using an open-ended coaxial probe as sensor, is described. The complete system includes a vector network analyzer, a microwave coaxial cable, the probe, a sample holder and a computer to automate measurements and further data processing. This system has been used to measure some liquid and solid materials such as alcohol, water and Teflon. The real and imaginary parts of permittivity as function of frequency, for several sugarcane alcohol and deionised water mixtures, tequilas and Teflon samples are given. Measurement repeatability and accuracy considerations were taken and it was identified that uncertainty of reference standards and system repeatability are the most important error sources. Also, it was found that open-ended coaxial probe technique is appropriate for measuring not only liquids but also solid materials. Some of the obtained results were compared to those reported in literature and good convergence was observed. [Spanish] La espectroscopia dielectrica es una tecnica moderna de medicion para caracterizar la interaccion entre la energia electromagnetica y muestras macroscopicas como funcion de la frecuencia. Esta tecnica se basa en la medicion de la permitividad compleja y conductividad de los materiales y ha mostrado ser muy util para proporcionar informacion sobre la estructura interna de estos. Tiene

  3. BROADBAND ESO/VISIR-SPITZER INFRARED SPECTROSCOPY OF THE OBSCURED SUPERGIANT X-RAY BINARY IGR J16318-4848

    Energy Technology Data Exchange (ETDEWEB)

    Chaty, S.; Rahoui, F., E-mail: sylvain.chaty@cea.fr, E-mail: frahoui@cfa.harvard.edu [AIM (UMR-E 9005 CEA/DSM-CNRS-Universite Paris Diderot) Irfu/Service d' Astrophysique, Centre de Saclay, FR-91191 Gif-sur-Yvette Cedex (France)

    2012-06-01

    A new class of X-ray binaries has recently been discovered by the high-energy observatory INTEGRAL. It is composed of intrinsically obscured supergiant high-mass X-ray binaries, unveiled by means of multi-wavelength X-ray, optical, near- and mid-infrared observations, in particular, photometric and spectroscopic observations using ESO facilities. However, the fundamental questions about these intriguing sources, namely, their formation, evolution, and the nature of their environment, are still unsolved. Among them, IGR J16318-4848, a compact object orbiting around a supergiant B[e] star, seems to be one of the most extraordinary celestial sources of our Galaxy. We present here new ESO/Very Large Telescope (VLT) VISIR mid-infrared (MIR) spectroscopic observations of this source. First, line diagnostics allow us to confirm the presence of absorbing material (dust and cold gas) enshrouding the whole binary system, and to characterize the nature of this material. Second, by fitting broadband near- to mid-infrared spectral energy distribution, including ESO NTT/SofI, VLT/VISIR, and Spitzer data, with a phenomenological model for sgB[e] stars, we show that the star is surrounded by an irradiated rim heated to a temperature of {approx}3800-5500 K, along with a viscous disk component at an inner temperature of {approx}750 K. VISIR data allow us to exclude the spherical geometry for the dust component. This detailed study will allow us in the future to get better constraints on the formation and evolution of such rare and short-living high-mass X-ray binary systems in our Galaxy.

  4. High dielectric constant and low dielectric loss hybrid nanocomposites fabricated with ferroelectric polymer matrix and BaTiO3 nanofibers modified with perfluoroalkylsilane

    Science.gov (United States)

    Zhang, Xianhong; Ma, Yuhong; Zhao, Changwen; Yang, Wantai

    2014-06-01

    Interfacial interaction and compatibility between the ceramic dielectric and polymer matrix have strong impact on the dielectric permittivity and dielectric loss of their composites. In this work, we presented a simple strategy to fabricate flexible dielectric composite of high dielectric constant BaTiO3 (BT) nanofiber and ferroelectric poly(vinylidene fluoride) (PVDF) matrix. The electrospun BT nanofiber was sintered at about 800 °C to form perovskite crystalline. Fluorosilane 1H,1H,2H,2H-perfluorooctyltrimethoxysilane was used to introduce a short perfluoroalkyl chain to the surface of BT nanofiber by silane coupling. The effects of content of modified BT nanofiber on the dielectric performance of the composites were investigated by broadband dielectric spectroscopy. The results in comparison with pure PVDF showed that the dielectric constant increased about 2 times (from 10 to 22) and dielectric loss tan δ reduced about 50% (from 0.12 to 0.06) when the loading of modified BT nanofiber was up to 20 v%. In the same loading fraction of BT nanofibers (10 v%), the dielectric loss of fluorosilane modified sample (tan δ = 0.08) was lower than that of unmodified one (tan δ = 0.1). In the range of 20-100 °C, the k showed almost no dependence on the temperature. However, the dielectric loss revealed a trend of decreasing at first and increased later with the increasing of temperature, and reached the lowest value (tanδ = 0.01) at about 60 °C.

  5. Semiconductor-to-metallic flipping in a ZnFe{sub 2}O{sub 4}–graphene based smart nano-system: Temperature/microwave magneto-dielectric spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ameer, Shahid, E-mail: shahidameer@scme.nust.edu.pk [School of Chemical and Materials Engineering (SCME), National University of Sciences and Technology (NUST), H-12, Islamabad (Pakistan); Gul, Iftikhar Hussain [School of Chemical and Materials Engineering (SCME), National University of Sciences and Technology (NUST), H-12, Islamabad (Pakistan); Mahmood, Nasir [Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing 100871 (China); Mujahid, Muhammad [School of Chemical and Materials Engineering (SCME), National University of Sciences and Technology (NUST), H-12, Islamabad (Pakistan)

    2015-01-15

    Zn-(FeO{sub 2}){sub 2}–graphene smart nano-composites were synthesized using a novel modified solvothermal synthesis with different percentages of graphene. The structure of the nanocomposite was confirmed through X-ray diffraction, micro-Raman scattering spectroscopy, Ultraviolet–Visible spectroscopy, and Fourier transform infrared spectroscopy. The structural growth and morphological aspects were analyzed using scanning/transmission electron microscopy, revealing marvelous micro-structural features of the assembled nano-system resembling a maple leaf. To determine the composition, energy dispersive spectroscopy and X-ray photoelectron spectroscopy were used. Microwave magneto-dielectric spectroscopy revealed the improved dielectric properties of the nano-composite compared to those of the parent functional nanocrystals. Temperature gradient dielectric spectroscopy was used over the spectral range from 100 Hz to 5 MHz to reveal the phenomenological effect that the nanosystem flips from its usual semiconductor nature to a metallic nature with sensing temperature. Electrical conductivity and dielectric analysis indicated that the dielectric loss and the dielectric permittivity increased at room temperature. This extraordinary switching capability of the functionalized graphene nanosystem opens up a new dimension for engineering advanced and efficient smart composite materials. - Graphical abstract: Display Omitted - Highlights: • Zn-(FeO{sub 2}){sub 2}–graphene smart nano-composites were synthesized using a novel modified solvothermal synthesis. • The synthesized nano-system exhibits marvelous leaf like microstructure. • These nano-composites show improved magneto dielectric response. • This engineered smart nano-system shows phenomenological flipping from semiconductor like nature to metallic behavior.

  6. Ultra-broadband 2D electronic spectroscopy of carotenoid-bacteriochlorophyll interactions in the LH1 complex of a purple bacterium

    Energy Technology Data Exchange (ETDEWEB)

    Maiuri, Margherita [CNR-IFN, Dipartimento di Fisica, Politecnico di Milano, P.zza L. da Vinci 32, Milano 20133 (Italy); Department of Chemistry, Princeton University, Washington Road, Princeton, New Jersey 08544 (United States); Réhault, Julien; Polli, Dario; Cerullo, Giulio, E-mail: giulio.cerullo@polimi.it [CNR-IFN, Dipartimento di Fisica, Politecnico di Milano, P.zza L. da Vinci 32, Milano 20133 (Italy); Carey, Anne-Marie; Hacking, Kirsty; Cogdell, Richard J. [Glasgow Biomedical Research Centre, IBLS, University of Glasgow, 126 Place, Glasgow G12 8TA, Scotland (United Kingdom); Garavelli, Marco [Dipartimento di Chimica “G. Ciamician,” Università di Bologna, Via Selmi 2, IT-40126 Bologna (Italy); CNRS, Institut de Chimie de Lyon, École Normale Supérieure de Lyon, Université de Lyon, 46 Allée d’Italie, F-69364 Lyon Cedex 07 (France); Lüer, Larry [Madrid Institute for Advanced Studies, IMDEA Nanociencia, Madrid (Spain)

    2015-06-07

    We investigate the excitation energy transfer (EET) pathways in the photosynthetic light harvesting 1 (LH1) complex of purple bacterium Rhodospirillum rubrum with ultra-broadband two-dimensional electronic spectroscopy (2DES). We employ a 2DES apparatus in the partially collinear geometry, using a passive birefringent interferometer to generate the phase-locked pump pulse pair. This scheme easily lends itself to two-color operation, by coupling a sub-10 fs visible pulse with a sub-15-fs near-infrared pulse. This unique pulse combination allows us to simultaneously track with extremely high temporal resolution both the dynamics of the photoexcited carotenoid spirilloxanthin (Spx) in the visible range and the EET between the Spx and the B890 bacterio-chlorophyll (BChl), whose Q{sub x} and Q{sub y} transitions peak at 585 and 881 nm, respectively, in the near-infrared. Global analysis of the one-color and two-color 2DES maps unravels different relaxation mechanisms in the LH1 complex: (i) the initial events of the internal conversion process within the Spx, (ii) the parallel EET from the first bright state S{sub 2} of the Spx towards the Q{sub x} state of the B890, and (iii) the internal conversion from Q{sub x} to Q{sub y} within the B890.

  7. Up-regulation of cerebral cytochrome-c-oxidase and hemodynamics by transcranial infrared laser stimulation: A broadband near-infrared spectroscopy study.

    Science.gov (United States)

    Wang, Xinlong; Tian, Fenghua; Reddy, Divya D; Nalawade, Sahil S; Barrett, Douglas W; Gonzalez-Lima, Francisco; Liu, Hanli

    2017-12-01

    Transcranial infrared laser stimulation (TILS) is a noninvasive form of brain photobiomulation. Cytochrome-c-oxidase (CCO), the terminal enzyme in the mitochondrial electron transport chain, is hypothesized to be the primary intracellular photoacceptor. We hypothesized that TILS up-regulates cerebral CCO and causes hemodynamic changes. We delivered 1064-nm laser stimulation to the forehead of healthy participants ( n = 11), while broadband near-infrared spectroscopy was utilized to acquire light reflectance from the TILS-treated cortical region before, during, and after TILS. Placebo experiments were also performed for accurate comparison. Time course of spectroscopic readings were analyzed and fitted to the modified Beer-Lambert law. With respect to the placebo readings, we observed (1) significant increases in cerebral concentrations of oxidized CCO (Δ[CCO]; >0.08 µM; p 0.8 µM; p 0.5 µM; p < 0.01) during and after TILS, and (2) linear interplays between Δ[CCO] versus Δ[HbO] and between Δ[CCO] versus Δ[HbT]. Ratios of Δ[CCO]/Δ[HbO] and Δ[CCO]/Δ[HbT] were introduced as TILS-induced metabolic-hemodynamic coupling indices to quantify the coupling strength between TILS-enhanced cerebral metabolism and blood oxygen supply. This study provides the first demonstration that TILS causes up-regulation of oxidized CCO in the human brain, and contributes important insight into the physiological mechanisms.

  8. Molecular dynamics of a binary mixture of twist-bend nematic liquid crystal dimers studied by dielectric spectroscopy

    Science.gov (United States)

    Robles-Hernández, Beatriz; Sebastián, Nerea; Salud, Josep; Diez-Berart, Sergio; Dunmur, David A.; Luckhurst, Geoffrey R.; López, David O.; de la Fuente, M. Rosario

    2016-06-01

    We report a comprehensive dielectric characterization of a liquid crystalline binary mixture composed of the symmetric mesogenic dimer CB7CB and the nonsymmetric mesogenic dimer FFO9OCB. In addition to the high-temperature nematic phase, such a binary mixture shows a twist-bend nematic phase at room temperature which readily vitrifies on slow cooling. Changes in the conformational distribution of the dimers are reflected in the dielectric permittivity and successfully analyzed by means of an appropriate theoretical model. It is shown that the dielectric spectra of the mixture reflect the different molecular dipole properties of the components, resembling in the present case the characteristic dielectric spectra of nonsymmetric dimers. Comparison of the nematic and twist-bend nematic phases reveals that molecular dynamics are similar despite the difference in the molecular environment.

  9. Dynamics of asymmetric non-polymeric binary glass formers-A nuclear magnetic resonance and dielectric spectroscopy study.

    Science.gov (United States)

    Pötzschner, B; Mohamed, F; Lichtinger, A; Bock, D; Rössler, E A

    2015-10-21

    We study a dynamically asymmetric binary glass former with the low-Tg component m-tri-cresyl phosphate (m-TCP: Tg = 206 K) and a spirobichroman derivative as a non-polymeric high-Tg component (Tg = 382 K) by means of (1)H nuclear magnetic resonance (NMR), (31)P NMR, and dielectric spectroscopy which allow component-selectively probing the dynamics. The entire concentration range is covered, and two main relaxation processes with two Tg are identified, Tg 1 and Tg 2. The slower one is attributed to the high-Tg component (α1-process), and the faster one is related to the m-TCP molecules (α2-process). Yet, there are indications that a small fraction of m-TCP is associated also with the α1-process. While the α1-relaxation only weakly broadens upon adding m-TCP, the α2-relaxation becomes extremely stretched leading to quasi-logarithmic correlation functions at low m-TCP concentrations-as probed by (31)P NMR stimulated echo experiments. Frequency-temperature superposition does not apply for the α2-process and it reflects an isotropic, liquid-like motion which is observed even below Tg 1, i.e., in the matrix of the arrested high-Tg molecules. As proven by 2D (31)P NMR, the corresponding dynamic heterogeneities are of transient nature, i.e., exchange occurs within the distribution G(lnτα 2). At Tg 1 a crossover is found for the temperature dependence of (mean) τα 2(T) from non-Arrhenius above to Arrhenius below Tg 1 which is attributed to intrinsic confinement effects. This "fragile-to-strong" transition also leads to a re-decrease of Tg 2(cm - TCP) at low concentration cm - TCP, i.e., a maximum is observed in Tg 2(cm - TCP) while Tg 1(cm - TCP) displays the well-known plasticizer effect. Although only non-polymeric components are involved, we re-discover essentially all features previously reported for polymer-plasticizer systems.

  10. THE CHANDRA MULTI-WAVELENGTH PROJECT: OPTICAL SPECTROSCOPY AND THE BROADBAND SPECTRAL ENERGY DISTRIBUTIONS OF X-RAY-SELECTED AGNs

    Energy Technology Data Exchange (ETDEWEB)

    Trichas, Markos; Green, Paul J.; Aldcroft, Tom; Kim, Dong-Woo; Mossman, Amy [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Silverman, John D. [Institute for the Physics and Mathematics of the Universe (IPMU), University of Tokyo, Kashiwanoha 5-1-5, Kashiwa-shi, Chiba 277-8568 (Japan); Barkhouse, Wayne [Department of Physics and Astrophysics, University of North Dakota, Grand Forks, ND 58202 (United States); Cameron, Robert A. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Constantin, Anca [Department of Physics and Astronomy, James Madison University, PHCH, Harrisonburg, VA 22807 (United States); Ellison, Sara L. [Department of Physics and Astronomy, University of Victoria, Victoria, BC V8P 1A1 (Canada); Foltz, Craig [Division of Astronomical Sciences, National Science Foundation, 4201 Wilson Blvd., Arlington, VA 22230 (United States); Haggard, Daryl [Center for Interdisciplinary Exploration and Research in Astrophysics, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208 (United States); Jannuzi, Buell T. [NOAO, Kitt Peak National Observatory, Tucson, AZ 85726 (United States); Marshall, Herman L. [Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139 (United States); Perez, Laura M. [Department of Astronomy, California Institute of Technology, 1200 East California Blvd, Pasadena, CA 91125 (United States); Romero-Colmenero, Encarni [South African Astronomical Observatory, P.O. Box 9, Observatory, 7935 (South Africa); Ruiz, Angel [Osservatorio Astronomico di Brera-INAF, Milan (Italy); Smith, Malcolm G., E-mail: mtrichas@cfa.harvard.edu [Cerro Tololo Interamerican Observatory, La Serena (Chile); and others

    2012-06-01

    From optical spectroscopy of X-ray sources observed as part of the Chandra Multi-wavelength Project (ChaMP), we present redshifts and classifications for a total of 1569 Chandra sources from our targeted spectroscopic follow-up using the FLWO/1.5 m, SAAO/1.9 m, WIYN 3.5 m, CTIO/4 m, KPNO/4 m, Magellan/6.5 m, MMT/6.5 m, and Gemini/8 m telescopes, and from archival Sloan Digital Sky Survey (SDSS) spectroscopy. We classify the optical counterparts as 50% broad-line active galactic nuclei (AGNs), 16% emission line galaxies, 14% absorption line galaxies, and 20% stars. We detect QSOs out to z {approx} 5.5 and galaxies out to z {approx} 3. We have compiled extensive photometry, including X-ray (ChaMP), ultraviolet (GALEX), optical (SDSS and ChaMP-NOAO/MOSAIC follow-up), near-infrared (UKIDSS, Two Micron All Sky Survey, and ChaMP-CTIO/ISPI follow-up), mid-infrared (WISE), and radio (FIRST and NVSS) bands. Together with our spectroscopic information, this enables us to derive detailed spectral energy distributions (SEDs) for our extragalactic sources. We fit a variety of template SEDs to determine bolometric luminosities, and to constrain AGNs and starburst components where both are present. While {approx}58% of X-ray Seyferts (10{sup 42} erg s{sup -1} < L{sub 2-10keV} <10{sup 44} erg s{sup -1}) require a starburst event (>5% starburst contribution to bolometric luminosity) to fit observed photometry only 26% of the X-ray QSO (L{sub 2-10keV} >10{sup 44} erg s{sup -1}) population appear to have some kind of star formation contribution. This is significantly lower than for the Seyferts, especially if we take into account torus contamination at z > 1 where the majority of our X-ray QSOs lie. In addition, we observe a rapid drop of the percentage of starburst contribution as X-ray luminosity increases. This is consistent with the quenching of star formation by powerful QSOs, as predicted by the merger model, or with a time lag between the peak of star formation and QSO

  11. Broadband radiometer

    Science.gov (United States)

    Cannon, T.W.

    1994-07-26

    A broadband radiometer is disclosed including (a) an optical integrating sphere having generally spherical integrating chamber and an entry port for receiving light (e.g., having visible and ultraviolet fractions), (b) a first optical radiation detector for receiving light from the sphere and producing an electrical output signal corresponding to broadband radiation, (c) a second optical radiation detector for receiving light from the sphere and producing an electrical output signal corresponding to a predetermined wavelength fraction of the broadband radiation, and (d) an output for producing an electrical signal which is proportional to the difference between the two electrical output signals. The radiometer is very useful, for example, in measuring the absolute amount of ultraviolet light present in a given light sample. 8 figs.

  12. 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.

  13. Dielectric properties of pure and Nb-doped SrTiO{sub 3} surfaces: a reflection electron energy loss spectroscopy study

    Energy Technology Data Exchange (ETDEWEB)

    Fouquet-Parry, V; Guittet, M J; Gautier-Soyer, M [Service de Physique et Chimie des Surfaces et des Interfaces, DSM/DRECAM/SPCSI, CEA Saclay, 91191 Gif sur Yvette Cedex (France); Paumier, F [Laboratoire de Matallurgie Physique - UMR 6630 CNRS -SP2MI, Universita de Poitiers, BP 30179 - 86962 Chasseneuil - Futuroscope Cedex (France)], E-mail: mgautiersoyer@cea.fr

    2008-01-15

    Reflection Electron Energy Loss Spectroscopy (REELS) is a valuable tool to characterize the electronic structure of insulating surfaces and nanometric films. The REELS inelastic single scattering cross section obtained after removing multiple losses is related to the complex dielectric function in the surface layers. Moreover the probing depth can be varied by changing the primary energy of electrons. One can expect in essence to obtain non-destructive REELS depth profiles, where the evolution of the REELS spectrum translates to the in-depth evolution of the dielectric constant. We present a REELS study of pure and Nb-doped SrTiO{sub 3} single crystals, with primary energies ranging from 200 eV to 1500 eV so as to vary the probing depth between 0.7 and 3 nm. The resulting variations in the shape of the spectra are qualitatively interpreted by considering the energy loss functions corresponding to a double interface SrTiO{sub 3}/carbon monolayer/vacuum, on the basis of the experimental dielectric function derived from TEELS measurements on strontium titanate and amorphous carbon.

  14. Towards Solvation of a Chiral Alpha-Hydroxy Ester: Broadband Chirp and Narrow Band Cavity Fouirier Transform Microwave Spectroscopy of Methyl Lactate-Water Clusters

    Science.gov (United States)

    Thomas, Javix; Sukhorukov, Oleksandr; Jaeger, Wolfgang; Xu, Yunjie

    2013-06-01

    Methyl lactate (ML), a chiral alpha-hydroxy ester, has attracted much attention as a prototype system in studies of chirality transfer,[1] solvation effects on chiroptical signatures,[2] and chirality recognition.[3] It has multiple functional groups which can serve both as a hydrogen donor and acceptor. By applying rotational spectroscopy and high level ab initio calculations, we examine the delicate competition between inter- and intramolecular hydrogen-bonding in the ML-water clusters. Broadband rotational spectra obtained with a chirp Fourier transform microwave (FTMW) spectrometer, reveal that the insertion conformations are the most favourable ones in the binary and ternary solvated complexes. In the insertion conformations, the water molecule(s) inserts itself (themselves) into the existing intramolecular hydrogen-bonded ring formed between the alcoholic hydroxyl group and the oxygen of the carbonyl group of ML. The final frequency measurements have been carried out using a cavity based FTMW instrument where internal rotation splittings due to the ester methyl group have also been detected. A number of insertion conformers with subtle structural differences for both the binary and ternary complexes have been identified theoretically. The interconversion dynamics of these conformers and the identification of the most favorable conformers will be discussed. 1. C. Merten, Y. Xu, Angew. Chem. Int. Ed., 2013, 52, 2073 -2076. 2. M. Losada, Y. Xu, Phys. Chem. Chem. Phys., 2007, 9, 3127-3135; Y. Liu, G. Yang, M. Losada, Y. Xu, J. Chem. Phys., 2010, 132, 234513/1-11. 3. A. Zehnacker, M. Suhm, Angew. Chem. Int. Ed. 2008, 47, 6970 - 6992.

  15. Trans-cranial infrared laser stimulation induces hemodynamic and metabolic response measured by broadband near infrared spectroscopy in vivo on human forehead (Conference Presentation)

    Science.gov (United States)

    Wang, Xinlong; Nalawade, Sahil Sunil; Reddy, Divya Dhandapani; Tian, Fenghua; Gonzalez-Lima, F.; Liu, Hanli

    2017-02-01

    Transcranial infrared laser stimulation (TILS) uses infrared light (lasers or LEDs) for nondestructive and non-thermal photobiomodulation on the human brain. Although TILS has shown its beneficial effects to a variety of neurological and psychological conditions, its physiological mechanism remains unknown. Cytochrome-c-oxidase (CCO), the last enzyme in the electron transportation chain, is proposed to be the primary photoacceptor of this infrared laser. In this study, we wish to validate this proposed mechanism. We applied 8 minutes in vivo TILS on the right forehead of 11 human participants with a 1064-nm laser. Broad-band near infrared spectroscopy (bb-NIRS) from 740-900nm was also employed near the TILS site to monitor hemodynamic and metabolic responses during the stimulation and 5-minute recovery period. For rigorous comparison, we also performed similar 8-min bb-NIR measurements under placebo conditions. A multi-linear regression analysis based on the modified Beer-Lambert law was performed to estimate concentration changes of oxy-hemoglobin (Δ[HbO]), deoxy-hemoglobin (Δ[Hb]), and cytochrome-c-oxidase (Δ[CCO]). We found that TILS induced significant increases of [CCO], [HbO] and a decrease of [Hb] with dose-dependent manner as compared with placebo treatments. Furthermore, strong linear relationships or interplays between [CCO] versus [HbO] and [CCO] versus [Hb] induced by TILS were observed in vivo for the first time. These relationships have clearly revealed close coupling/relationship between the hemodynamic oxygen supply and blood volume versus up-regulation of CCO induced by photobiomodulation. Our results demonstrate the tremendous potential of bb-NIRS as a non-invasive in vivo means to study photobiomodulation mechanisms and perform treatment evaluations of TILS.

  16. Dielectric properties and electrical conductivity of flat micronic graphite/polyurethane composites

    Science.gov (United States)

    Plyushch, Artyom; Macutkevic, Jan; Kuzhir, Polina P.; Banys, Juras; Fierro, Vanessa; Celzard, Alain

    2016-03-01

    Results of broadband dielectric spectroscopy of flat micronic graphite (FMG)/polyurethane (PU) resin composites are presented in a wide temperature range (25-450 K). The electrical percolation threshold was found to lie between 1 and 2 vol. % of FMG. Above the percolation threshold, the composites demonstrated a huge hysteresis of properties on heating and cooling from room temperature up to 450 K, along with extremely high values of dielectric permittivity and electrical conductivity. Annealing proved to be a very simple but powerful tool for significantly improving the electrical properties of FMG-based composites. In order to explain this effect, the distributions of relaxation times were calculated by the complex impedance formalism. Below room temperature, both dielectric permittivity and electrical conductivity exhibited a very low temperature dependence, mainly caused by the different thermal properties of FMG and pure PU matrix.

  17. Analysis of the Phase Transitions in BNT-BT Lead-Free Ceramics Around Morphotropic Phase Boundary by Mechanical and Dielectric Spectroscopies

    Directory of Open Access Journals (Sweden)

    Silva P.S.

    2016-03-01

    Full Text Available In this work, the syntheses and characterization by mechanical and dielectric spectroscopies of (1-x Bi0.5Na0.5TiO3-xBaTiO3 (BNT-100xBT, with x = 0.05, 0.06 and 0.07, lead-free piezoelectric ceramics is reported. Ceramic samples of BNT-BT have been prepared by mixed-oxide method and then conventionally sintered. X-ray diffraction patterns of sintered samples, indicated for BNT-7BT the presence of tetragonal (P4mm complex perovskite structure, whereas for BNT-5BT and BNT-6BT the samples exhibit a mixture of tetragonal (P4mm and rhombohedral (R3c crystalline phases, which reveal the presence of a morphotropic phase boundary (MPB in the BNT-BT system. Measurements of internal friction, Q-1, and the storage modulus, E’, as a function of temperature at various frequencies were carried out in a Dynamic Mechanical Analyzer (DMA, in the temperature range from 0ºC to 600ºC. Dielectric profiles are recorded in the frequency range from 1kHz to 100kHz and the temperature range from room temperature to 475ºC. Mechanical loss spectra obtained for investigated compositions of BNT-BT samples showed different frequency-independent anomalies. Two main anomalies for BNT-5BT and BNT-6BT, observed around 100ºC and 430ºC were associated with the ferroelectric-antiferroelectric and antiferroelectricparaelectric phase transitions, respectively. The results obtained from mechanical loss measurements were supported by dielectric relaxation spectra. For BNT-7BT, outside the MPB, four different frequency-independent processes were observed.

  18. Thermally tunable water-substrate broadband metamaterial absorbers

    Science.gov (United States)

    Pang, Yongqiang; Wang, Jiafu; Cheng, Qiang; Xia, Song; Zhou, Xiao Yang; Xu, Zhuo; Cui, Tie Jun; Qu, Shaobo

    2017-03-01

    The naturally occurring water has frequency dispersive permittivity at microwave frequencies and thus is a promising constituent material for broadband absorbers. Here, we develop water as the dielectric spacer in the substrate of metal-backed metamaterial (MM) absorbers. The designed substrate is a hybrid of water and a low-permittivity dielectric material. Such a design allows tight packaging of water and easy fabrication of the absorber. We obtain broadband absorption at temperatures of interest by designing the hybrid substrate and MM inclusions. Additionally, the absorption performance of the water-substrate MM absorbers could be tunable according to the environment temperature. We experimentally demonstrate the broadband and thermally tunable absorption performance. We expect that water could replace dielectric layers in other structural MM absorbers to achieve the broadband and thermally tunable absorption performance.

  19. Mechanical, dielectric, and physicochemical properties of impregnating resin based on unsaturated polyesterimides

    Science.gov (United States)

    Fetouhi, Louiza; Petitgas, Benoit; Dantras, Eric; Martinez-Vega, Juan

    2017-10-01

    This work aims to characterize the dielectric and the mechanical properties of a resin based on an unsaturated polyesterimide diluted in methacrylate reactive diluents used in the impregnation of rotating machines. The broadband dielectric spectrometry and the dynamic mechanical analysis were used to quantify the changes in dielectric and mechanical properties of the network PEI resin, as a function of temperature and frequency. The network characterizations highlight the presence of two main relaxations, α and α', confirmed by the differential scanning calorimetry analysis, showing the complexity of the chemical composition of this resin. The dielectric spectroscopy shows a significant increase in the dielectric values due to an increase of the material conductivity, while the mechanical spectroscopy shows an important decrease of the polymer rigidity and viscosity expressed by an important decrease in the storage modulus. The PEI resin shows a high reactivity when it is submitted in successive heating ramps, which involves in a post-cross-linking reaction. Contribution to the topical issue "Electrical Engineering Symposium (SGE 2016)", edited by Adel Razek

  20. Broadband electromagnetic dipole scattering by coupled multiple nanospheres

    Science.gov (United States)

    Jing, Xufeng; Ye, Qiufeng; Hong, Zhi; Zhu, Dongshuo; Shi, Guohua

    2017-11-01

    With the development of nanotechnology, the ability to manipulate light at the nanoscale is critical to future optical functional devices. The use of high refractive index dielectric single silicon nanoparticle can achieve electromagnetic dipole resonant properties. Compared with single nanosphere, the use of dimer and trimer introduces an additional dimension (gap size) for improving the performance of dielectric optical devices through the coupling between closely connected silicon nanospheres. When changing the gap size between the nanospheres, the interaction between the particles can be from weak to strong. Compared with single nanospheres, dimerized or trimeric nanospheres exhibit more pronounced broadband scattering properties. In addition, by introducing more complex interaction, the trimericed silicon nanospheres exhibit a more significant increase in bandwidth than expected. In addition, the presence of the substrate will also contribute to the increase in the bandwidth of the nanospheres. The broadband response in dielectric nanostructures can be effectively applied to broadband applications such as dielectric nanoantennas or solar cells.

  1. Leakage radiation spectroscopy of organic/dielectric/metal systems: influence of SiO2 on exciton-surface plasmon polariton interaction

    DEFF Research Database (Denmark)

    Fiutowski, Jacek; Kawalec, Tomasz; Kostiučenko, Oksana

    excitons and surface plasmon polaritons (SPPs) of the metal/dielectric boundary. The presence of the SiO2 layer considerably changes the dispersion curve in comparison to the one of the Ag/p-6P/air system. However, the Ag/SiO2/p-6P/air stack forms a stable structure allowing construction of organic......Leakage radiation spectroscopy of organic para-Hexaphenylene (p-6P) molecules has been performed in the spectral range 420-675 nm which overlaps with the p-6P photoluminescence band. The p-6P was deposited on 40 nm silver (Ag) films on BK7 glass, covered with SiO2 layers. The SiO2 layer thickness...

  2. Metal-insulator phase transition in a VO2 thin film observed with terahertz spectroscopy

    DEFF Research Database (Denmark)

    Jepsen, Peter Uhd; Fischer, Bernd M.; Thoman, Andreas

    2006-01-01

    We investigate the dielectric properties of a thin VO2 film in the terahertz frequency range in the vicinity of the semiconductor-metal phase transition. Phase-sensitive broadband spectroscopy in the frequency region below the phonon bands of VO2 gives insight into the conductive properties...... of the film during the phase transition. We compare our experimental data with models proposed for the evolution of the phase transition. The experimental data show that the phase transition occurs via the gradual growth of metallic domains in the film, and that the dielectric properties of the film...

  3. Towards rapid nanoscale chemical analysis using tip-enhanced Raman spectroscopy with Ag-coated dielectric tips.

    Science.gov (United States)

    Yeo, Boon-Siang; Schmid, Thomas; Zhang, Weihua; Zenobi, Renato

    2007-04-01

    The influence of dielectric substrates on the Raman scattering activities of Ag overlayers has been investigated. Materials with low refractive indices, such as SiO(2), SiO(x) and AlF(3), were found to provide suitable supporting platforms for Ag films to give strong surface-enhanced Raman scattering for dye molecules when illuminated at 488 nm. This finding was then extended to tip-enhanced Raman scattering (TERS). Huge enhancements of 70-80x, corresponding to net enhancements of >10(4), were observed for brilliant cresyl blue test analyte when Ag-coated tips made from or precoated with low refractive index materials were applied. The yield of fabricated tips that significantly enhance the Raman signals was found to be close to 100%. These findings provide crucial steps towards the use of TERS as a robust technique for rapid chemical imaging with nanometer spatial resolution. Figure Silver-coated dielectric tips for tip-enhanced Raman scattering (TERS) are capable of more than 10,000-fold enhancement.

  4. Dielectric study on mixtures of ionic liquids.

    Science.gov (United States)

    Thoms, E; Sippel, P; Reuter, D; Weiß, M; Loidl, A; Krohns, S

    2017-08-07

    Ionic liquids are promising candidates for electrolytes in energy-storage systems. We demonstrate that mixing two ionic liquids allows to precisely tune their physical properties, like the dc conductivity. Moreover, these mixtures enable the gradual modification of the fragility parameter, which is believed to be a measure of the complexity of the energy landscape in supercooled liquids. The physical origin of this index is still under debate; therefore, mixing ionic liquids can provide further insights. From the chemical point of view, tuning ionic liquids via mixing is an easy and thus an economic way. For this study, we performed detailed investigations by broadband dielectric spectroscopy and differential scanning calorimetry on two mixing series of ionic liquids. One series combines an imidazole based with a pyridine based ionic liquid and the other two different anions in an imidazole based ionic liquid. The analysis of the glass-transition temperatures and the thorough evaluations of the measured dielectric permittivity and conductivity spectra reveal that the dynamics in mixtures of ionic liquids are well defined by the fractions of their parent compounds.

  5. On the cooperative nature of the β-process in neat and binary glasses: a dielectric and nuclear magnetic resonance spectroscopy study.

    Science.gov (United States)

    Bock, D; Kahlau, R; Micko, B; Pötzschner, B; Schneider, G J; Rössler, E A

    2013-08-14

    By means of dielectric as well as (2)H and (31)P nuclear magnetic resonance spectroscopy (NMR) the component dynamics of the binary glass tripropyl phosphate (TPP)/polystyrene (PS/PS-d3) is selectively investigated for concentrations distributed over the full range. We study the secondary (β-) relaxation below T(g), which is found in all investigated samples containing TPP, but not in neat polystyrene. The dielectric spectrum of the β-process is described by an asymmetric distribution of activation energies, essentially not changing in the entire concentration regime; its most probable value is E/k ≅ 24 T(g). Persistence of the β-process is confirmed by (31)P NMR Hahn-echo and spin-lattice relaxation experiments on TPP, which identify the nature of the β-process as being highly spatially hindered as found for other (neat) glasses studied previously, or re-investigated within this work. The corresponding (2)H NMR experiments on PS-d3 confirm the absence of a β-process in neat PS-d3, but reveal a clear signature of a β-process in the mixture, i.e., polystyrene monomers perform essentially the same type of secondary relaxation as the TPP molecules. Yet, there are indications that some fractions of PS-d3 as well as TPP molecules become immobilized in the mixture in contrast to the case of neat glasses. We conclude that in a binary glass the β-process introduced by one component induces a highly similar motion in the second component, and this may be taken as an indication of its cooperative nature.

  6. Structural characterization, vibrational spectroscopy accomplished with DFT calculation, thermal and dielectric behaviors in a new organic-inorganic tertrapropylammonium aquapentachlorostannate dihydrate compound

    Energy Technology Data Exchange (ETDEWEB)

    Hajlaoui, Sondes, E-mail: hajlaouisondes@yahoo.fr [Unité de recherche de la matière condensée, Faculté des Sciences de Sfax, Université de Sfax, BP 1171, 3000, Sfax (Tunisia); Chaabane, Iskandar [Unité de recherche de la matière condensée, Faculté des Sciences de Sfax, Université de Sfax, BP 1171, 3000, Sfax (Tunisia); Lhoste, Jérôme; Bulou, Alain [LUNAM Université, Université du Maine, CNRS UMR 6283, Institut des Molécules et Matériaux du Mans (IMMM), Avenue Olivier Messiaen, 72085, Le Mans, Cedex 9 (France); Guidara, Kamel [Unité de recherche de la matière condensée, Faculté des Sciences de Sfax, Université de Sfax, BP 1171, 3000, Sfax (Tunisia)

    2016-09-15

    In this work a novel compound tertrapropylammonium aquapentachlorostannate dihydrate was synthesized and characterized by; single crystal X-ray diffraction, vibrational spectroscopy, differential scanning calorimetric and dielectric measurement. The crystal structure refinement at room temperature reveled that this later belongs to the monoclinic compound with P121/c1 space group with the following unit cell parameters a = 8.2699(3) Å, b = 12.4665(4) Å, c = 22.3341(7) Å and β = 92.94(0)°. The crystal arrangement can be described by stacked organic-inorganic layers in the c direction with two independent water molecules placed between each two layers. The detailed interpretations of the vibrational properties of the studied compound were performed using density functional theory (DFT) with the B3LYP/LanL2DZ basis set, and has enabled us to make the detailed assignments by comparative study of the experimental and calculated Raman and IR spectra. The differential scanning calorimetry (DSC) measurement disclosed two anomalies in the temperature range 356–376 (T{sub 1}) K and at 393 K (T{sub 2}) characterized by the dehydration of the sample and probably a reconstruction of a new structure after T{sub 2} transition. The temperature dependences of dielectric permittivity show a relaxation process around T{sub 2} anomaly indicating the occurrence of the disorder at high temperature. The dependence of the exponent m(T) on temperature, extracted from the straight lines of log(ε″) with log (ω), suggests that the correlated barrier hopping is the appropriate model for the conduction mechanism. - Highlights: • The single-crystal X-ray diffraction has been performed. • The assignments of the vibration modes based on DFT were reported and discussed. • Differential scanning calorimetric reveals the presence of two endothermic peaks. • The electric permittivity was studied using the impedance measurements. • The CBH is the appropriate model for the conduction

  7. Broadband Polarizers Based on Graphene Metasurfaces

    CERN Document Server

    Guo, Tianjing

    2016-01-01

    We present terahertz (THz) metasurfaces based on aligned rectangular graphene patches placed on top of a dielectric layer to convert the transmitted linearly polarized waves to circular or elliptical polarized radiation. Our results lead to the design of an ultrathin broadband THz quarter-wave plate. In addition, ultrathin metasurfaces based on arrays of L-shaped graphene periodic patches are demonstrated to achieve broadband cross-polarization transformation in reflection and transmission. The proposed metasurface designs have tunable responses and are envisioned to become the building blocks of several integrated THz systems.

  8. Lattice dynamics and dielectric spectroscopy of BZT and NBT lead-free perovskite relaxors - comparison with lead-based relaxors

    Science.gov (United States)

    Petzelt, Jan; Nuzhnyy, Dmitry; Bovtun, Viktor; Kempa, Martin; Savinov, Maxim; Kamba, Stanislav; Hlinka, Jiri

    2015-03-01

    Appearance of the polar nanoregions (PNR) and their manifestation in the dielectric spectra is discussed for lead-free Ba(ZrxTi1-x)O3 (BZT-x) and (Na1/2Bi1/2)TiO3 (NBT) ceramics. Phonon softening is not as pronounced as in the lead-based relaxors, but the relaxation contribution is dominating in all cases, caused by the dynamics of the off-centred ions (Ti4+, Bi3+, Pb2+). In the lead-based relaxors, where there is no relation between the quenched chemical clusters at the B-sites and PNR, which concern the A-site Pb-ion correlations, the relaxation dynamics follows the Vogel-Fulcher behaviour with a clear freezing. However, in BZT and NBT, the PNR are smaller, since they are localised within the small quenched chemical clusters of BaTiO3 and BiTiO3, respectively. Their dynamics is Arrhenius-like, which indicates hopping of the off-centred Ti4+ and Bi3+ ions, respectively, without their complete freezing. BZT can be classified as a dipolar glass and NBT as a nanoscopic ferroelectric with peculiar Bi-ion dynamics.

  9. Bioinspired irregularly chirped broadband reflecting multilayers

    Science.gov (United States)

    Chiadini, Francesco; Fiumara, Vincenzo; Scaglione, Antonio

    2017-08-01

    Dielectric multilayers consisting of alternating layers of two different materials with thicknesses irregularly decreasing with depth in the structure are included in the cuticle of some beetles whose shell exhibits broadband reflection in the optical wavelength range. Emulating these structures, we propose and numerically analyze irregularly chirped dielectric multilayers. Analysis was performed using a dedicated genetic algorithm (GA) that searches for the multilayer configurations maximizing the reflection for normal incidence over a large wavelength range. We found that the GA leads to the irregularly chirped reflectors that significantly outperform the regularly chirped ones proposed and analyzed in the literature.

  10. Dielectric Properties and Characterisation of Titanium Dioxide Obtained by Different Chemistry Methods

    Directory of Open Access Journals (Sweden)

    Aleksandra Wypych

    2014-01-01

    Full Text Available We made comparison of titanium dioxide powders obtained from three syntheses including sol-gel and precipitation methods as well as using layered (tetramethylammonium titanate as a source of TiO2. The obtained precursors were subjected to step annealing at elevated temperatures to transform into rutile form. The transformation was determined by Raman measurements in each case. The resulting products were characterised using Raman spectroscopy and dynamic light scattering. The main goal of the studies performed was to compare the temperature of the transformation in three titania precursors obtained by different methods of soft chemistry routes and to evaluate dielectric properties of rutile products by means of broadband dielectric spectroscopy. Different factors affecting the electrical properties of calcinated products were discussed. It was found that sol-gel synthesis provided rutile form after annealing at 850°C with the smallest particles size about 20 nm, the highest value of dielectric permittivity equal to 63.7, and loss tangent equal to 0.051 at MHz frequencies. The other powders transformed to rutile at higher temperature, that is, 900°C, exhibit lower value of dielectric permittivity and had a higher value of particles size. The correlation between the anatase-rutile transformation temperature and the size of annealed particles was proposed.

  11. Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Hellman, Hal

    1968-01-01

    This booklet discusses spectroscopy, the study of absorption of radiation by matter, including X-ray, gamma-ray, microwave, mass spectroscopy, as well as others. Spectroscopy has produced more fundamental information to the study of the detailed structure of matter than any other tools.

  12. Insight into the dielectric response of transformer oil-based nanofluids

    Directory of Open Access Journals (Sweden)

    Ming Dong

    2017-02-01

    Full Text Available The oil-based nanofluids with greater dielectric strength have attracted much attention as a crucial insulating materials in high-voltage oil-immersed power equipment. In fact, the different microstructures of the transformer oil-based nanofluids (TNFs would result in different dielectric properties. In this work, the broadband dielectric spectroscopy measurement was used to establish the linkage between the electric double layer (EDL and dielectric response properties of TNFs which was performed at 298K temperature and with frequency range from 10-2Hz∼106Hz. The modified Havriliak-Negami (HN model function was used to analyze the measured results. The results demonstrate that both the real and imaginary parts of dielectric spectra of two kinds of oil are composed of the conductivity and polarization process. Compared with pure oil, two polarization process could be observed for the TNFs, explained by the EDL structure reasonably. The introduction of the EDL structure provides an idea to account for the insulating strength improvement of TNFs for the first time.

  13. Insight into the dielectric response of transformer oil-based nanofluids

    Science.gov (United States)

    Dong, Ming; Dai, Jianzhuo; Li, Yang; Xie, Jiacheng; Ren, Ming; Dang, Zhimin

    2017-02-01

    The oil-based nanofluids with greater dielectric strength have attracted much attention as a crucial insulating materials in high-voltage oil-immersed power equipment. In fact, the different microstructures of the transformer oil-based nanofluids (TNFs) would result in different dielectric properties. In this work, the broadband dielectric spectroscopy measurement was used to establish the linkage between the electric double layer (EDL) and dielectric response properties of TNFs which was performed at 298K temperature and with frequency range from 10-2Hz˜106Hz. The modified Havriliak-Negami (HN) model function was used to analyze the measured results. The results demonstrate that both the real and imaginary parts of dielectric spectra of two kinds of oil are composed of the conductivity and polarization process. Compared with pure oil, two polarization process could be observed for the TNFs, explained by the EDL structure reasonably. The introduction of the EDL structure provides an idea to account for the insulating strength improvement of TNFs for the first time.

  14. 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.

  15. Dielectric response of the human tooth dentine

    Science.gov (United States)

    Leskovec, J.; Filipič, C.; Levstik, A.

    2005-07-01

    Dielectric properties of tooth dentine can be well described by the model which was developed for the dielectric response to hydrating porous cement paste. It is shown that the normalized dielectric constant and the normalized specific conductivity are proportional to the model parameters ɛ and σv, indicating the deposition of AgCl in the dentine tubules during the duration of the precipitation. The fractal dimension of the tooth dentine was determined by dielectric spectroscopy.

  16. Dielectric response of the human tooth dentine

    Energy Technology Data Exchange (ETDEWEB)

    Leskovec, J. [Dental Clinic, Faculty of Medicine, University of Ljubljana, Hrvatski trg 6, 1104 Ljubljana (Slovenia); Filipic, C. [Jozef Stefan Institute, P.O. Box 3000, 1001 Ljubljana (Slovenia); Levstik, A. [Jozef Stefan Institute, P.O. Box 3000, 1001 Ljubljana (Slovenia)]. E-mail: adrijan.levstik@ijs.si

    2005-07-15

    Dielectric properties of tooth dentine can be well described by the model which was developed for the dielectric response to hydrating porous cement paste. It is shown that the normalized dielectric constant and the normalized specific conductivity are proportional to the model parameters -bar {sub v0} and {sigma}{sub v}, indicating the deposition of AgCl in the dentine tubules during the duration of the precipitation. The fractal dimension of the tooth dentine was determined by dielectric spectroscopy.

  17. Dynamic behaviour of a ferro-electric liquid crystal by means of nuclear magnetic resonance and dielectric spectroscopy

    Science.gov (United States)

    Domenici, Valentina; Marini, Alberto; Menicagli, Rita; Veracini, Carlo Alberto; Bubnov, Aleksej M.; Glogarova, Milada

    2007-05-01

    The field of ferroelectric liquid crystals (FLCs) is one of the most fascinating aspects of the Science of Materials for their interesting electro-optic applications. Among different chemical and physical properties those related to the molecular dynamics are very stimulating due to the relationship between molecular motions and macroscopic response to external fields, such as electric and magnetic ones. In this work, the molecular dynamics of a ferroelectric smectogen, namely the (S)-2-methylbutyl-[4'-(4"-heptyloxyphenyl)-benzoyl-4-oxy-(S)-2-((S)-2')-benzoyl)-propionyl)]-propionate (ZLL 7/*) has been investigated by means of 2H NMR and dielectric relaxation techniques. The first method allows us to get information on the molecular motions in the fast motion regime, in particular the diffusion reorientational motions of the whole molecule, as well as of the internal motions affecting the phenyl and biphenyl fragments. The second technique, which covers the slow motion regime, has been used to detect collective motions and fluctuation modes. This study allows us to have a complete idea of molecular motions in the different smectic phases formed by the ZLL 7/* mesogens, in particular the paraelectric smectic A (SmA), the ferroelectric smectic C* (SmC*), the antiferroelectric smectic C* A (SmC* A) and the re-entrant ferroelectric smectic C* (SmC* r) phases. This last phase has been investigated for the first time in this work, from the point of view of the dynamic behaviour. All results will be discussed in the framework of the molecular dynamics of ferroelectric liquid crystals, reported in the literature so far.

  18. Spectroscopy

    CERN Document Server

    Walker, S

    1976-01-01

    The three volumes of Spectroscopy constitute the one comprehensive text available on the principles, practice and applications of spectroscopy. By giving full accounts of those spectroscopic techniques only recently introduced into student courses - such as Mössbauer spectroscopy and photoelectron spectroscopy - in addition to those techniques long recognised as being essential in chemistry teaching - sucha as e.s.r. and infrared spectroscopy - the book caters for the complete requirements of undergraduate students and at the same time provides a sound introduction to special topics for graduate students.

  19. Non-polymeric asymmetric binary glass-formers. I. Main relaxations studied by dielectric, 2H NMR, and 31P NMR spectroscopy

    Science.gov (United States)

    Pötzschner, B.; Mohamed, F.; Bächer, C.; Wagner, E.; Lichtinger, A.; Minikejew, R.; Kreger, K.; Schmidt, H.-W.; Rössler, E. A.

    2017-04-01

    In Paper I of this series of two papers we study the main relaxations of a binary glass former made of the low-Tg component tripropyl phosphate (TPP, Tg = 134 K) and of a specially synthesized (deuterated) spirobichroman derivative (SBC, Tg = 356 K) as the non-polymeric high-Tg component for the full concentration range. A large Tg contrast of the neat components is put into effect. Dielectric spectroscopy and different techniques of 2H nuclear magnetic resonance (NMR) as well as of 31P NMR spectroscopy allow to selectively probe the dynamics of the components. For all concentrations, two well separated liquid-like processes are identified. The faster α2-process associated with the low-Tg component TPP shows pronounced dynamic heterogeneities reflected by quasi-logarithmic correlation functions at low TPP concentrations. The slower α1-process involves the reorientation of the high-Tg component SBC. Its correlation function is Kohlrausch-like as in neat glass formers. The corresponding time constants and consequently their glass transition temperatures Tg1 and Tg2 differ more the lower the TPP concentration is. Plasticizer and anti-plasticizer effect, respectively, is observed. At low temperatures a situation arises that the TPP molecules isotropically reorient in an arrested SBC matrix (Tg2 < T < Tg1). At T < Tg2 the liquid-like reorientation of TPP gets arrested too. We find indications that a fraction of the TPP molecule takes part in the slower α1-process of the high-Tg component. All the features known from polymer-plasticizer systems are rediscovered in this non-polymeric highly asymmetric binary mixture. In Paper II [B. Pötzschner et al., J. Chem. Phys. 146, 164504 (2017)] we study the secondary (β-) relaxations of the mixtures.

  20. Super-Eddington accretion on to the neutron star NGC 7793 P13: Broad-band X-ray spectroscopy and ultraluminous X-ray sources

    Science.gov (United States)

    Walton, D. J.; Fürst, F.; Harrison, F. A.; Stern, D.; Bachetti, M.; Barret, D.; Brightman, M.; Fabian, A. C.; Middleton, M. J.; Ptak, A.; Tao, L.

    2018-02-01

    We present a detailed, broad-band X-ray spectral analysis of the ultraluminous X-ray source (ULX) pulsar NGC 7793 P13, a known super-Eddington source, utilizing data from the XMM-Newton, NuSTAR and Chandra observatories. The broad-band XMM-Newton+NuSTAR spectrum of P13 is qualitatively similar to the rest of the ULX sample with broad-band coverage, suggesting that additional ULXs in the known population may host neutron star accretors. Through time-averaged, phase-resolved and multi-epoch studies, we find that two non-pulsed thermal blackbody components with temperatures ∼0.5 and 1.5 keV are required to fit the data below 10 keV, in addition to a third continuum component which extends to higher energies and is associated with the pulsed emission from the accretion column. The characteristic radii of the thermal components appear to be comparable, and are too large to be associated with the neutron star itself, so the need for two components likely indicates the accretion flow outside the magnetosphere is complex. We suggest a scenario in which the thick inner disc expected for super-Eddington accretion begins to form, but is terminated by the neutron star's magnetic field soon after its onset, implying a limit of B ≲ 6 × 1012 G for the dipolar component of the central neutron star's magnetic field. Evidence of similar termination of the disc in other sources may offer a further means of identifying additional neutron star ULXs. Finally, we examine the spectrum exhibited by P13 during one of its unusual 'off' states. These data require both a hard power-law component, suggesting residual accretion on to the neutron star, and emission from a thermal plasma, which we argue is likely associated with the P13 system.

  1. Refractory plasmonics with titanium nitride: broadband metamaterial absorber.

    Science.gov (United States)

    Li, Wei; Guler, Urcan; Kinsey, Nathaniel; Naik, Gururaj V; Boltasseva, Alexandra; Guan, Jianguo; Shalaev, Vladimir M; Kildishev, Alexander V

    2014-12-17

    A high-temperature stable broadband plasmonic absorber is designed, fabricated, and optically characterized. A broadband absorber with an average high absorption of 95% and a total thickness of 240 nm is fabricated, using a refractory plasmonic material, titanium nitride. This absorber integrates both the plasmonic resonances and the dielectric-like loss. It opens a path for the interesting applications such as solar thermophotovoltaics and optical circuits. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Adoption of Broadband Services

    DEFF Research Database (Denmark)

    Falch, Morten

    2008-01-01

    Broadband is seen as a key infrastructure for developing the information society. For this reason many Governments are actively engaged in stimulating investments in broadband infrastructures and use of broadband services. This chapter compares a wide range of broadband strategies in the most...... successful markets for broadband. This is done through analysis of national policies in three European countries-Denmark, Sweden, and Germany-and the U.S., Japan, and South Korea. We concluded that successful implementation of broadband depends on the kind of policy measures to be taken at the national level...

  3. Non-polymeric asymmetric binary glass-formers. II. Secondary relaxation studied by dielectric, 2H NMR, and 31P NMR spectroscopy

    Science.gov (United States)

    Pötzschner, B.; Mohamed, F.; Bächer, C.; Wagner, E.; Lichtinger, A.; Bock, D.; Kreger, K.; Schmidt, H.-W.; Rössler, E. A.

    2017-04-01

    We investigate the secondary (β-) relaxations of an asymmetric binary glass former consisting of a spirobichroman derivative (SBC; Tg = 356 K) as the high-Tg component and the low-Tg component tripropyl phosphate (TPP; Tg = 134 K). The main relaxations are studied in Paper I [B. Pötzschner et al., J. Chem. Phys. 146, 164503 (2017)]. A high Tg contrast of ΔTg = 222 K is put into effect in a non-polymeric system. Component-selective studies are carried out by combining results from dielectric spectroscopy (DS) for mass concentrations cTPP ≥ 60% and those from different methods of 2H and 31P NMR spectroscopy. In the case of NMR, the full concentration range (10% ≤ cTPP ≤ 100%) is covered. The neat components exhibit a β-relaxation (β1 (SBC) and β2 (TPP)). The latter is rediscovered by DS in the mixtures for all concentrations with unchanged time constants. NMR spectroscopy identifies the β-relaxations as being alike to those in neat glasses. A spatially highly restricted motion with angular displacement below ±10° encompassing all molecules is involved. In the low temperature range, where TPP shows the typical 31P NMR echo spectra of the β2-process, very similar spectral features are observed for the (deuterated) SBC component by 2H NMR, in addition to its "own" β1-process observed at high temperatures. Apparently, the small TPP molecules enslave the large SBC molecules to perform a common hindered reorientation. The temperature dependence of the spin-lattice relaxation time of both components is the same and reveals an angular displacement of the SBC molecules somewhat smaller than that of TPP, though the time constants τβ2 are the same. Furthermore, T1(T) of TPP in the temperature region of the β2-process is absolutely the same as in the mixture TPP/polystyrene investigated previously. It appears that the manifestations of the β-process introduced by one component are essentially independent of the second component. Finally, at cTPP ≤ 20% one

  4. Fruit and Vegetable Quality Assessment via Dielectric Sensing.

    Science.gov (United States)

    El Khaled, Dalia; Novas, Nuria; Gazquez, Jose A; Garcia, Rosa M; Manzano-Agugliaro, Francisco

    2015-06-29

    The demand for improved food quality has been accompanied by a technological boost. This fact enhances the possibility of improving the quality of horticultural products, leading towards healthier consumption of fruits and vegetables. A better electrical characterization of the dielectric properties of fruits and vegetables is required for this purpose. Moreover, a focused study of dielectric spectroscopy and advanced dielectric sensing is a highly interesting topic. This review explains the dielectric property basics and classifies the dielectric spectroscopy measurement techniques. It comprehensively and chronologically covers the dielectric experiments explored for fruits and vegetables, along with their appropriate sensing instrumentation, analytical modelling methods and conclusions. An in-depth definition of dielectric spectroscopy and its usefulness in the electric characterization of food materials is presented, along with the various sensor techniques used for dielectric measurements. The collective data are tabulated in a summary of the dielectric findings in horticultural field investigations, which will facilitate more advanced and focused explorations in the future.

  5. Dielectric siphons.

    Science.gov (United States)

    Jones, T. B.; Perry, M. P.; Melcher, J. R.

    1971-01-01

    The normally weak polarization force density, exerted on insulating dielectric liquids by a nonuniform electric field, is enhanced if high pressures are used. The nonuniform electric field acts as an elastic ?wall' to contain and guide the dielectric fluid. A general theory for these electrohydrodynamic (EHD) conduits has been developed. An illustrative example of the EHD conduits is the dielectric siphon consisting of two U-shaped electrodes held adjacent to each other by insulating nylon screws.

  6. Spectroscopy

    DEFF Research Database (Denmark)

    Berg, Rolf W.

    This introductory booklet covers the basics of molecular spectroscopy, infrared and Raman methods, instrumental considerations, symmetry analysis of molecules, group theory and selection rules, as well as assignments of fundamental vibrational modes in molecules.......This introductory booklet covers the basics of molecular spectroscopy, infrared and Raman methods, instrumental considerations, symmetry analysis of molecules, group theory and selection rules, as well as assignments of fundamental vibrational modes in molecules....

  7. Flat dielectric grating reflectors with focusing abilities

    Science.gov (United States)

    Fattal, David; Li, Jingjing; Peng, Zhen; Fiorentino, Marco; Beausoleil, Raymond G.

    2010-07-01

    Sub-wavelength dielectric gratings have emerged recently as a promising alternative to distributed Bragg reflection dielectric stacks for broadband, high-reflectivity filtering applications. Such a grating structure composed of a single dielectric layer with the appropriate patterning can sometimes perform as well as 30 or 40 dielectric distributed Bragg reflection layers, while providing new functionalities such as polarization control and near-field amplification. In this Letter, we introduce an interesting property of grating mirrors that cannot be realized by their distributed Bragg reflection counterpart: we show that a non-periodic patterning of the grating surface can give full control over the phase front of reflected light while maintaining a high reflectivity. This new feature of dielectric gratings allows the creation of miniature planar focusing elements that could have a substantial impact on a number of applications that depend on low-cost, compact optical components, from laser cavities to CD/DVD read/write heads.

  8. 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

  9. Improving dielectric properties of BaTiO3/poly(vinylidene fluoride) composites by employing core-shell structured BaTiO3@Poly(methylmethacrylate) and BaTiO3@Poly(trifluoroethyl methacrylate) nanoparticles

    Science.gov (United States)

    Zhang, Xianhong; Zhao, Sidi; Wang, Fang; Ma, Yuhong; Wang, Li; Chen, Dong; Zhao, Changwen; Yang, Wantai

    2017-05-01

    Polymer based dielectric composites were fabricated through incorporation of core-shell structured BaTiO3 (BT) nanoparticles into PVDF matrix by means of solution blending. Core-shell structured BT nanoparticles with different shell composition and shell thickness were prepared by grafting methacrylate monomer (MMA or TFEMA) onto the surface of BT nanoparticles via surface initiated atom transfer radical polymerization (SI-ATRP). The content of the grafted polymer and the micro-morphology of the core-shell structured BT nanoparticles were investigated by thermo gravimetric analyses (TGA) and transmission electron microscopy (TEM), respectively. The dielectric properties were measured by broadband dielectric spectroscopy. The results showed that high dielectric constant and low dielectric loss are successfully realized in the polymer based composites. Moreover, the type of the grafted polymer and its content had different effect on the dielectric constant. In detail, the attenuation of dielectric constant was 16.6% for BT@PMMA1/PVDF and 10.7% for BT@PMMA2/PVDF composite in the range of 10 Hz to 100 kHz, in which the grafted content of PMMA was 5.5% and 8.0%, respectively. However, the attenuation of dielectric constant was 5.5% for BT@PTFEMA1/PVDF and 4.0% for BT@PTFEMA2/PVDF composite, in which the grafted content of PTFEMA was 1.5% and 2.0%, respectively. These attractive features of BT@PTFEMA/PVDF composites suggested that dielectric ceramic fillers modified with fluorinated polymer can be used to prepare high performance composites, especially those with low dielectric loss and high dielectric constant.

  10. Electronically Switchable Broadband Metamaterial Absorber.

    Science.gov (United States)

    Lee, Dongju; Jeong, Heijun; Lim, Sungjoon

    2017-07-07

    In this study, the novel electronically switchable broadband metamaterial absorber, using a PIN diode, is proposed. The unit cell of the absorber was designed with a Jerusalem-cross resonator and an additive ring structure, based on the FR-4 dielectric substrate. Chip resistors and PIN diodes were used to provide both a broadband characteristic and a switching capability. To satisfy the polarization insensitivity, the unit cell was designed as a symmetrical structure, including the DC bias network, electronic devices, and conductor patterns. The performance of the proposed absorber was verified using full-wave simulation and measurements. When the PIN diode was in the ON state, the proposed absorber had a 90% absorption bandwidth from 8.45-9.3 GHz. Moreover, when the PIN diode was in the OFF state, the 90% absorption bandwidth was 9.2-10.45 GHz. Therefore, the absorption band was successfully switched between the low-frequency band and the high-frequency band as the PIN diode was switched between the ON and OFF states. Furthermore, the unit cell of the proposed absorber was designed as a symmetrical structure, and its performance showed insensitivity with respect to the polarization angle.

  11. Dielectric study on hierarchical water structures restricted in cement and wood materials

    Science.gov (United States)

    Abe, Fumiya; Nishi, Akihiro; Saito, Hironobu; Asano, Megumi; Watanabe, Seiei; Kita, Rio; Shinyashiki, Naoki; Yagihara, Shin; Fukuzaki, Minoru; Sudo, Seiichi; Suzuki, Youki

    2017-04-01

    Dielectric relaxation processes for mortar observed by broadband dielectric spectroscopy were analyzed in the drying and hydration processes for an aging sample in the frequency region from 1 MHz up to 2 MHz. At least two processes for structured water in the kHz frequency region and another mHz relaxation process affected by ionic behaviors were observed. Comparison of the relaxation parameters obtained for the drying and hydration processes suggests an existence of hierarchical water structures in the exchange of water molecules, which are originally exchanged from free water observed at around 20 GHz. The water molecules reflected in the lower frequency process of the two kHz relaxation processes are more restricted and take more homogeneous structures than the higher kHz relaxation process. These structured water usually hidden in large ionic behaviors for wood samples was observed by electrodes covered by a thin Teflon film, and hierarchical water structures were also suggested for wood samples. Dielectric spectroscopy technique is an effective tool to analyze the new concept of hierarchical water structures in complex materials.

  12. Double-corrugated metamaterial surfaces for broadband microwave absorption

    Science.gov (United States)

    Pang, Yongqiang; Cheng, Haifeng; Zhou, Yongjiang; Wang, Jun

    2013-02-01

    Double-corrugated metamaterial surfaces are proposed to achieve broadband absorbers in the microwave region. The principal corrugation having a long period is made of hypo-corrugated metal structures filled with a dielectric medium. It is shown that the incident electromagnetic wave with a certain frequency can be strongly absorbed by the corrugation region where the height is about λ/4, with λ being the corresponding wavelength in the dielectric. Assembling various heights of corrugations together to form a graded corrugation surface can excite many distinct absorption modes and their overlapping with each other results in a broadband absorption. We experimentally demonstrate a broadband metamaterial absorber with more than 80% absorbance in the frequency range of 7.22-18.0 GHz which agrees well with the numerical simulation.

  13. Enhanced dielectric loss induced by the doping of SiC in thick defective graphitic shells of Ni@C nanocapsules with ash-free coal as carbon source for broadband microwave absorption

    Science.gov (United States)

    Li, Zhenxing; Ding, Xiaoli; Li, Fan; Liu, Xianguo; Zhang, Shihong; Long, Hongming

    2017-11-01

    The rapid development of microelectronic devices means increasing attention is being paid to the exploration of high-performance microwave absorption materials. Enhanced dielectric loss is an effective way of improving microwave absorption performance. Here, we report that Ni@C nanocapsules with ash-free carbon as a carbon source, functionalized by the doping of SiC in a thick defective graphitic shell, demonstrate enhanced dielectric losses at the gigahertz level, and energy transfer from permeability to permittivity at 14.24 GHz. Compared with Ni@C nanocapsules, which have ethanol as a carbon source, the same absorption band and absorption intensity can be obtained with a thinner absorber in the present Ni@C nanocapsules, and the frequency corresponding to maximum reflection loss exhibits a red shift for the same absorbing thickness. At 5.12 GHz, the maximum reflection loss value of the present Ni@C nanocapsules can reach  -49.99 dB for a planar absorber with a thickness of 5.1 mm. Experimental results coupled with theoretical simulations reveal the electromagnetic losses of the present Ni@C nanocapsules originating from the core-shell interfacial polarization and dipole polarization of the doping of SiC in the defective graphitic shell.

  14. Glass transition-related changes in molecular mobility below glass transition temperature of freeze-dried formulations, as measured by dielectric spectroscopy and solid state nuclear magnetic resonance.

    Science.gov (United States)

    Yoshioka, Sumie; Aso, Yukio

    2005-02-01

    The purpose of this study was to explore why changes in the molecular mobility associated with glass transition, the timescale of which is on the order of 100 s, can be detected by measuring the nuclear magnetic resonance relaxation times that reflect molecular motions on the order of 10 kHz and 1 MHz. The molecular motions in freeze-dried dextran 40k, dextran 1k, isomaltotriose (IMT), and alpha-glucose comprising a common unit but with different glass transition temperatures, were investigated by dielectric spectroscopy (DES) in the frequency range of 0.01 Hz to 100 kHz and in the temperature range of -20 degrees to 200 degrees C, in order to compare with the molecular motions reflected in nuclear magnetic resonance relaxation times. The alpha-relaxation process for freeze-dried alpha-glucose was visualized by DES, whereas those for freeze-dried dextran 40k, dextran 1k, and IMT were too slow to be visualized by DES. The latter freeze-dried cakes exhibited quasi-dc polarization because of proton-hopping-like motion rather than alpha-relaxation process. The correlation time (tau(c)) for the backbone carbon of dextran 40k and IMT, calculated from the measured value of spin-lattice relaxation time in the rotating frame, was found to be close to the relaxation time of proton-hopping-like motion determined by DES (tau(DES)) at temperatures around glass transition temperature. The timescales of molecular motions reflected in the tau(c) and tau(DES) were significantly smaller than that of motions leading to molecular rearrangement (molecular rearrangement motions), which correspond to alpha-relaxation. However, the shapes of temperature dependence for the tau(c) and tau(DES) were similar to that of the calorimetrically determined relaxation time of molecular rearrangement motions. Results suggest that the molecular motions reflected in the tau(c) and tau(DES) are linked to molecular rearrangement motions, such that enhancement of molecular rearrangement motions enhances

  15. Resonant coupling in the Van der Waals interaction between an excited alkali atom and a dielectric surface: an experimental study via stepwise selective reflection spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Failache, H.; Saltiel, S.; Fichet, M.; Bloch, D.; Ducloy, M. [Paris-13 Univ., Lab. de Physique des Lasers, UMR 7538 du CNRS, 93 - Villetaneuse (France)

    2003-05-01

    We present a detailed experimental study of the evaluation of the van der Waals (vW) atom-surface interaction for high-lying excited states of alkali-metal atoms (Cs and Rb), notably R-hen they couple resonantly with a surface-polariton mode of the neighbouring dielectric surface. This report extends our initial observation [Phys. Rev. Lett. 83, 5467 (1999)) of a vW repulsion between Cs(6D{sub 3/2}) and a sapphire surface. The experiment is based upon FM selective reflection spectroscopy, on a transition reaching a high-lying state from a resonance level, that has been thermally pumped by an initial one-photon step. Along with a strong vW repulsion fitted with a blue line-shift, -160 {+-} 25 kHz {mu}m{sup 3} for Cs(6D{sub 3/2}) in front of a sapphire surface (with a perpendicular c-axis), we demonstrate a weaker vW repulsion (-32{+-}5 kHz {mu}m{sup 3}) for Cs(6D{sub 3/2}) in front of a YAG surface, as due to a similar resonant coupling at 12 {mu}m between a virtual atomic emission (6D{sub 3/2}-7P{sub 1/2}) and the surface polariton modes. A resonant behaviour of Rb(6D{sub 5/2}) in front of a sapphire surface exists also because of analogous decay channels in the 12 {mu}m range. Finally. one demonstrates that fused silica. nonresonant for a virtual transition in the 12 {mu}m range and hence weakly attracting for Cs(6D{sub 3/2}), exhibits a resonant behaviour for Cs(9S{sub 1/2}) as due to its surface polariton resonance in the 8-9 {mu}m range. The limiting factors that affect both the accuracy of the theoretical prediction, and that of the fitting method applied to the experimental data. are discussed in the conclusion. (authors)

  16. An ultra-broadband multilayered graphene absorber

    KAUST Repository

    Amin, Muhammad

    2013-01-01

    An ultra-broadband multilayered graphene absorber operating at terahertz (THz) frequencies is proposed. The absorber design makes use of three mechanisms: (i) The graphene layers are asymmetrically patterned to support higher order surface plasmon modes that destructively interfere with the dipolar mode and generate electromagnetically induced absorption. (ii) The patterned graphene layers biased at different gate voltages backedup with dielectric substrates are stacked on top of each other. The resulting absorber is polarization dependent but has an ultra-broadband of operation. (iii) Graphene\\'s damping factor is increased by lowering its electron mobility to 1000cm 2=Vs. Indeed, numerical experiments demonstrate that with only three layers, bandwidth of 90% absorption can be extended upto 7THz, which is drastically larger than only few THz of bandwidth that can be achieved with existing metallic/graphene absorbers. © 2013 Optical Society of America.

  17. Dielectric spectroscopy of SiO2, ZnO - nanoparticle loaded epoxy resin in the frequency range of 20 Hz to 2 MHz

    Science.gov (United States)

    Thakor, Sanketsinh; Rana, V. A.; Vankar, H. P.

    2017-05-01

    In present work, Bisphenol A-(epichlorhydrin); epoxy resin with hardener N(3-dimethylaminopropyl)-1,3-propylenediamine were used to determine the dielectric properties. Sample of the neat epoxy resin and nanoparticle loaded epoxy resin in the form of disc were prepared of different weight fraction. SiO2 and ZnO nanoparticles were taken as filler in the epoxy resin. Complex permittivity of the prepared samples was measured in the frequency range of 20 Hz to 2 MHz using precision LCR meter at room temperature. The charismatic change in dielectric behavior based on type and concentration of nanoparticle are discussed in detail.

  18. Ultra-broadband microwave metamaterial absorber

    Science.gov (United States)

    Ding, Fei; Cui, Yanxia; Ge, Xiaochen; Jin, Yi; He, Sailing

    2012-03-01

    A microwave ultra-broadband polarization-independent metamaterial absorber is demonstrated. It is composed of a periodic array of metal-dielectric multilayered quadrangular frustum pyramids. These pyramids possess resonant absorption modes at multi-frequencies, of which the overlapping leads to the total absorption of the incident wave over an ultra-wide spectral band. The experimental absorption at normal incidence is above 90% in the frequency range of 7.8-14.7 GHz, and the absorption is kept large when the incident angle is smaller than 60°. The experimental results agree well with the numerical simulation.

  19. Correlating the Integral Sensing Properties of Zeolites with Molecular Processes by Combining Broadband Impedance and DRIFT Spectroscopy--A New Approach for Bridging the Scales.

    Science.gov (United States)

    Chen, Peirong; Schönebaum, Simon; Simons, Thomas; Rauch, Dieter; Dietrich, Markus; Moos, Ralf; Simon, Ulrich

    2015-11-13

    Zeolites have been found to be promising sensor materials for a variety of gas molecules such as NH₃, NOx, hydrocarbons, etc. The sensing effect results from the interaction of the adsorbed gas molecules with mobile cations, which are non-covalently bound to the zeolite lattice. The mobility of the cations can be accessed by electrical low-frequency (LF; mHz to MHz) and high-frequency (HF; GHz) impedance measurements. Recent developments allow in situ monitoring of catalytic reactions on proton-conducting zeolites used as catalysts. The combination of such in situ impedance measurements with diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), which was applied to monitor the selective catalytic reduction of nitrogen oxides (DeNOx-SCR), not only improves our understanding of the sensing properties of zeolite catalysts from integral electric signal to molecular processes, but also bridges the length scales being studied, from centimeters to nanometers. In this work, recent developments of zeolite-based, impedimetric sensors for automotive exhaust gases, in particular NH₃, are summarized. The electrical response to NH₃ obtained from LF impedance measurements will be compared with that from HF impedance measurements, and correlated with the infrared spectroscopic characteristics obtained from the DRIFTS studies of molecules involved in the catalytic conversion. The future perspectives, which arise from the combination of these methods, will be discussed.

  20. Preparation and Preliminary Dielectric Characterization of Structured C60-Thiol-Ene Polymer Nanocomposites Assembled Using the Thiol-Ene Click Reaction

    Directory of Open Access Journals (Sweden)

    Hanaa M. Ahmed

    2015-11-01

    Full Text Available Fullerene-containing materials have the ability to store and release electrical energy. Therefore, fullerenes may ultimately find use in high-voltage equipment devices or as super capacitors for high electric energy storage due to this ease of manipulating their excellent dielectric properties and their high volume resistivity. A series of structured fullerene (C60 polymer nanocomposites were assembled using the thiol-ene click reaction, between alkyl thiols and allyl functionalized C60 derivatives. The resulting high-density C60-urethane-thiol-ene (C60-Thiol-Ene networks possessed excellent mechanical properties. These novel networks were characterized using standard techniques, including infrared spectroscopy (FTIR, differential scanning calorimetry (DSC, dynamic mechanical analysis (DMA, and thermal gravimetric analysis (TGA. The dielectric spectra for the prepared samples were determined over a broad frequency range at room temperature using a broadband dielectric spectrometer and a semiconductor characterization system. The changes in thermo-mechanical and electrical properties of these novel fullerene-thiol-ene composite films were measured as a function of the C60 content, and samples characterized by high dielectric permittivity and low dielectric loss were produced. In this process, variations in chemical composition of the networks were correlated to performance characteristics.

  1. Identifying Broadband Rotational Spectra with Neural Networks

    Science.gov (United States)

    Zaleski, Daniel P.; Prozument, Kirill

    2017-06-01

    A typical broadband rotational spectrum may contain several thousand observable transitions, spanning many species. Identifying the individual spectra, particularly when the dynamic range reaches 1,000:1 or even 10,000:1, can be challenging. One approach is to apply automated fitting routines. In this approach, combinations of 3 transitions can be created to form a "triple", which allows fitting of the A, B, and C rotational constants in a Watson-type Hamiltonian. On a standard desktop computer, with a target molecule of interest, a typical AUTOFIT routine takes 2-12 hours depending on the spectral density. A new approach is to utilize machine learning to train a computer to recognize the patterns (frequency spacing and relative intensities) inherit in rotational spectra and to identify the individual spectra in a raw broadband rotational spectrum. Here, recurrent neural networks have been trained to identify different types of rotational spectra and classify them accordingly. Furthermore, early results in applying convolutional neural networks for spectral object recognition in broadband rotational spectra appear promising. Perez et al. "Broadband Fourier transform rotational spectroscopy for structure determination: The water heptamer." Chem. Phys. Lett., 2013, 571, 1-15. Seifert et al. "AUTOFIT, an Automated Fitting Tool for Broadband Rotational Spectra, and Applications to 1-Hexanal." J. Mol. Spectrosc., 2015, 312, 13-21. Bishop. "Neural networks for pattern recognition." Oxford university press, 1995.

  2. Preliminary study on broadband antireflection coatings for large aperture telescopes

    Science.gov (United States)

    Wang, Ye-Ru; Li, Xin-Nan; Wang, Jin-Feng; Tian, Jie

    2017-12-01

    A broadband anti-reflective (AR) coating design for astronomical large-aperture telescopes is proposed. We give simulations of two-, three- and four-layer silica sol-gel on fused silica and finally get the optimal optical constants. As a comparison, we discuss the traditional dielectric material that has been applied to broadband AR coatings. To better guide the following experiment, we also conduct error analysis and feasibility analysis, combining with the technological characteristics of sol-gel. The analytical method is suitable for other wavebands and substrates. It is also instructive for large area AR coatings in the field of solar cells.

  3. Broadband high reflectivity in subwavelength-grating slab waveguides.

    Science.gov (United States)

    Tian, Hao; Cui, Xuan; Du, Yan; Tan, Peng; Shi, Guang; Zhou, Zhongxiang

    2015-10-19

    We computationally study a subwavelength dielectric grating structure, show that slab waveguide modes can be used to obtain broadband high reflectivity, and analyze how slab waveguide modes influence reflection. A structure showing interference between Fabry-Perot modes, slab waveguide modes, and waveguide array modes is designed with ultra-broadband high reflectivity. Owing to the coupling of guided modes, the region with reflectivity R > 0.99 has an ultra-high bandwidth (Δf / ̅f > 30%). The incident-angle region with R > 0.99 extends over a range greater than 40°. Moreover, an asymmetric waveguide structure with a semiconductor substrate is studied.

  4. Broadband Electromagnetic Technology

    Science.gov (United States)

    2011-06-23

    The objectives of this project are to continue the enhancements to the combined Broadband Electromagnetic and Full Encirclement Unit (BEM-FEU) technologies and to evaluate the systems capability in the laboratory and the field. The BEM instrument ...

  5. Dielectric behaviour and functionality of polymer matrix – ceramic BaTiO3 composites

    Directory of Open Access Journals (Sweden)

    2008-10-01

    Full Text Available Dielectric properties of polymer matrix – ceramic BaTiO3 composites were examined by means of Broadband Dielectric Spectroscopy (BDS in the frequency range of 10–1–107 Hz and over the temperature range of 30–160°C, varying the content of ferroelectric particles. Experimental results provide evidence that the recorded relaxation phenomena include contributions from both the polymeric matrix and the presence of the reinforcing phase. Obtained results are analysed via the electric modulus formalism. Polymer matrix exhibits two distinct relaxation processes attributed, with ascending relaxation rate, to glass/rubber transition, and local motions of polar side groups. Interfacial polarization or Maxwell-Wagner-Sillars process is present in the low frequency range and at high temperatures. Finally, in the vicinity of the characteristic Curie temperature (TC an abrupt variation of the real part of dielectric permittivity with temperature is recorded. This peak is probably related to the ferroelectric to paraelectric phase transition of the employed ceramic inclusions.

  6. Development of New Dielectric NDE Techniques for Spaceflight Materials

    Science.gov (United States)

    Nurge, Mark A. (Compiler)

    2014-01-01

    Dielectric Spectroscopy is a relatively new technique for non-destructively measuring material properties. The goal for this project is to extend the use of state-of-the-art dielectric spectroscopy systems to measure the spectra of spaceflight materials and develop non-destructive evaluation (NDE) sensors based on dielectric material properties. This work may lead to a new class of material density, moisture, temperature, and defect sensors providing structural integrity and health measurements for future spacecraft and launch structures.

  7. High-Resolution Broadband Spectral Interferometry

    Energy Technology Data Exchange (ETDEWEB)

    Erskine, D J; Edelstein, J

    2002-08-09

    We demonstrate solar spectra from a novel interferometric method for compact broadband high-resolution spectroscopy. The spectral interferometer (SI) is a hybrid instrument that uses a spectrometer to externally disperse the output of a fixed-delay interferometer. It also has been called an externally dispersed interferometer (EDI). The interferometer can be used with linear spectrometers for imaging spectroscopy or with echelle spectrometers for very broad-band coverage. EDI's heterodyning technique enhances the spectrometer's response to high spectral-density features, increasing the effective resolution by factors of several while retaining its bandwidth. The method is extremely robust to instrumental insults such as focal spot size or displacement. The EDI uses no moving parts, such as purely interferometric FTS spectrometers, and can cover a much wider simultaneous bandpass than other internally dispersed interferometers (e.g. HHS or SHS).

  8. Broadband Radiometric LED Measurements.

    Science.gov (United States)

    Eppeldauer, G P; Cooksey, C C; Yoon, H W; Hanssen, L M; Podobedov, V B; Vest, R E; Arp, U; Miller, C C

    2016-01-01

    At present, broadband radiometric measurements of LEDs with uniform and low-uncertainty results are not available. Currently, either complicated and expensive spectral radiometric measurements or broadband photometric LED measurements are used. The broadband photometric measurements are based on the CIE standardized V(λ) function, which cannot be used in the UV range and leads to large errors when blue or red LEDs are measured in its wings, where the realization is always poor. Reference irradiance meters with spectrally constant response and high-intensity LED irradiance sources were developed here to implement the previously suggested broadband radiometric LED measurement procedure [1, 2]. Using a detector with spectrally constant response, the broadband radiometric quantities of any LEDs or LED groups can be simply measured with low uncertainty without using any source standard. The spectral flatness of filtered-Si detectors and low-noise pyroelectric radiometers are compared. Examples are given for integrated irradiance measurement of UV and blue LED sources using the here introduced reference (standard) pyroelectric irradiance meters. For validation, the broadband measured integrated irradiance of several LED-365 sources were compared with the spectrally determined integrated irradiance derived from an FEL spectral irradiance lamp-standard. Integrated responsivity transfer from the reference irradiance meter to transfer standard and field UV irradiance meters is discussed.

  9. Broadband Radiometric LED Measurements

    Science.gov (United States)

    Eppeldauer, G. P.; Cooksey, C. C.; Yoon, H. W.; Hanssen, L. M.; Podobedov, V. B.; Vest, R. E.; Arp, U.; Miller, C. C.

    2017-01-01

    At present, broadband radiometric measurements of LEDs with uniform and low-uncertainty results are not available. Currently, either complicated and expensive spectral radiometric measurements or broadband photometric LED measurements are used. The broadband photometric measurements are based on the CIE standardized V(λ) function, which cannot be used in the UV range and leads to large errors when blue or red LEDs are measured in its wings, where the realization is always poor. Reference irradiance meters with spectrally constant response and high-intensity LED irradiance sources were developed here to implement the previously suggested broadband radiometric LED measurement procedure [1, 2]. Using a detector with spectrally constant response, the broadband radiometric quantities of any LEDs or LED groups can be simply measured with low uncertainty without using any source standard. The spectral flatness of filtered-Si detectors and low-noise pyroelectric radiometers are compared. Examples are given for integrated irradiance measurement of UV and blue LED sources using the here introduced reference (standard) pyroelectric irradiance meters. For validation, the broadband measured integrated irradiance of several LED-365 sources were compared with the spectrally determined integrated irradiance derived from an FEL spectral irradiance lamp-standard. Integrated responsivity transfer from the reference irradiance meter to transfer standard and field UV irradiance meters is discussed. PMID:28649167

  10. The design of broadband radar absorbing surfaces

    Science.gov (United States)

    Suk, Go H.

    1990-09-01

    There has been a growing and widespread interest in radar absorbing material technology. As the name implies, radar absorbing materials or RAM's are coatings whose electric and magnetic properties have been selected to allow the absorption of microwave energy at discrete or broadband frequencies. In military applications low radar cross section (RCS) of a vehicle may be required in order to escape detection while a covert mission is being carried on. These requirements have led to the very low observable or stealth technology that reduces the probability of detection of an aircraft. The design of radar absorbing materials is limited by constraints on the allowable volume and weight of the surface coating, and it is difficult to design a broadband radar absorbing structure in limited volume. This thesis investigates the use of lossy dielectric materials of high dielectric permittivity in multilayer composites for the production of low radar cross section (RCS). The analysis is done by computing the plane wave reflection coefficient at the exterior surface of the composite coating by means of a computer program which selects layer parameters which determine low reflection coefficients for electromagnetic radiation under constraint of limited layer thickness as well as maximum frequency bandwidth.

  11. Broadband luminescence in liquid-solid transition

    CERN Document Server

    Achilov, M F; Trunilina, O V

    2002-01-01

    Broadband luminescence (BBL) intensity behavior in liquid-solid transition in polyethyleneglycol-600 has been established. Oscillation of BBL intensity observed in liquid-polycrystal transition are not found to observed in liquid-amorphous solid transition. It is shown that application of the theory of electron state tails to interpretation of BBL spectral properties in liquids demands restriction. BBL spectroscopy may be applied for optimization of preparation of polymers with determined properties. (author)

  12. Accurate determination of dielectric permittivity of polymers from 75  GHz to 1.6  THz using both S-parameters and transmission spectroscopy.

    Science.gov (United States)

    Chang, Tianying; Zhang, Xiansheng; Zhang, Xiaoxuan; Cui, Hong-Liang

    2017-04-20

    Interactions of terahertz (THz) electromagnetic radiation with polymer materials have been studied recently with increasing depth and breadth, for purposes of both using polymers in fabricating THz optical components such as lenses, waveplates, waveguides, and sample holders/containers, and employing THz spectral imaging as a new tool for nondestructive testing of polymer composite structures. Either endeavor cannot even begin without a quantitative knowledge of the complex dielectric permittivity, i.e., the propagation and attenuation properties of such polymers in the requisite wave band. In this paper, a number of non-polar and non-magnetic polymers, such as polytetrafluoroethylene, polypropylene, high-density polyethylene, and polymethyl methacrylate, are studied for the purpose of determining their complex dielectric permittivity, including its real part and imaginary parts, in the wide frequency band from millimeter wave to THz wave (75 GHz-1.6 THz), in two ways. The first is a free space method based on a vector network analyzer covering the frequency region from 75 to 500 GHz, and the second is the THz time-domain spectroscopy (THz-TDS), effective for the region of 100 GHz-1.6 THz. The results are consistent with existing data (with discrepancies less than 1% in most cases for both the index of refraction and the absorption coefficient), and where they overlap in frequency coverage, the two methods yield identical results to within measurement error.

  13. Influence of ionic liquids on the dielectric relaxation behavior of CNT based elastomer nanocomposites

    Directory of Open Access Journals (Sweden)

    A. Das

    2012-11-01

    Full Text Available The influence of an imidazolium type ionic liquid (IL on the relaxation behavior of carbon-nanotube (CNT based polychloroprene nanocomposites prepared by melt mixing has been investigated by broadband dielectric spectroscopy. It is demonstrated that the presence of the ionic liquid modifies the relaxation behavior of the pure rubber matrix and leads to a significant increase of the conductivity for the CNT/rubber composites. For the unfilled rubber, a distinct glass transition of the IL is observed for high concentrations demonstrating that the IL forms a separate phase. The increased conductivity of the CNT-filled rubber composites is related to a physical coupling between CNTs and rubber matrix mediated by IL leading to a better dispersion of the CNTs.

  14. Broadband electromagnetic analysis of compacted kaolin

    Science.gov (United States)

    Bore, Thierry; Wagner, Norman; Cai, Caifang; Scheuermann, Alexander

    2017-01-01

    The mechanical compaction of soil influences not only the mechanical strength and compressibility but also the hydraulic behavior in terms of hydraulic conductivity and soil suction. At the same time, electric and dielectric parameters are increasingly used to characterize soil and to relate them with mechanic and hydraulic parameters. In the presented study electromagnetic soil properties and suction were measured under defined conditions of standardized compaction tests. The impact of external mechanical stress conditions of nearly pure kaolinite was analyzed on soil suction and broadband electromagnetic soil properties. An experimental procedure was developed and validated to simultaneously determine mechanical, hydraulic and broadband (1 MHz-3 GHz) electromagnetic properties of the porous material. The frequency dependent electromagnetic properties were modeled with a classical mixture equation (advanced Lichtenecker and Rother model, ALRM) and a hydraulic-mechanical-electromagnetic coupling approach was introduced considering water saturation, soil structure (bulk density, porosity), soil suction (pore size distribution, water sorption) as well as electrical conductivity of the aqueous pore solution. Moreover, the relaxation behavior was analyzed with a generalized fractional relaxation model concerning a high-frequency water process and two interface processes extended with an apparent direct current conductivity contribution. The different modeling approaches provide a satisfactory agreement with experimental data for the real part. These results show the potential of broadband electromagnetic approaches for quantitative estimation of the hydraulic state of the soil during densification.

  15. Simplex-TSDC spectroscopy: An efficient tool to measure the relaxation time of the isothermal transient depolarization current in organic dielectrics

    Energy Technology Data Exchange (ETDEWEB)

    Benchenane-Mehor, Halima, E-mail: halima_mehor_2000@yahoo.fr [Laboratoire CaSiCCE, Département de Génie Electrique, ENSET-Oran, B.P. 1523, El M’Naouer, 31000 Oran (Algeria); Laboratoire de Microphysique et de Nanophysique (LaMiN), Département de Physique-Chimie, ENSET-Oran, B.P. 1523 EL M’Naouer, 31000 Oran (Algeria); Soufi, Manil M.; Saiter, Jean-Marc; Benzohra, Mohamed [Laboratoire LECAP-AMME, EA 4528, Université de Rouen, Faculté des Sciences, Avenue de l' Université BP 12, 76801 Saint Etienne du Rouvray (France)

    2013-03-01

    The temporal technique analysis by a simplex optimization method of isothermal transient depolarization current measurements (Simplex-TSDC) is presented for the study of the glass transition domain of different polymers. The advantage of the present method compared to the classical TSDC is that it gives direct results comparable to the experiment and allows a good estimate of the relaxation time close to the glass transition temperature in dielectric thin films. The present method also allows a direct determination of two relaxation times corresponding to a fast and a slow dynamics; and then confirms the heterogeneous character of the molecular relaxation dynamics.

  16. Chemical recognition with broadband THz spectroscopy

    DEFF Research Database (Denmark)

    Fischer, Bernd M.; Helm, Hanspeter; Jepsen, Peter Uhd

    2004-01-01

    contains unique fingerprints of a very large number of crystalline materials, including explosives, illicit drugs as well as most other chemicals in powder form. Since many packaging materials are transparent to THz radiation this fundamental property of crystalline compounds allows remote (contact...... interest in this field has also been growing, spurred by the potential of tHz tools in quality control and the biotechnology sector. We will review some contrast mechanisms, which form the basis for real-world applications of THz technology, in particular in the fields of applied chemistry...... and biotechnology. Whereas narrow bandwidth THz technology may become important for e.g. real-time imaging at larger standoff distances, we will concentrate on broad bandwidth THz technologies for spectroscopic identification of various substances. It has recently been established that the 0.1-5 THz spectral range...

  17. Direct UV-written broadband directional broadband planar waveguide couplers

    DEFF Research Database (Denmark)

    Olivero, Massimo; Svalgaard, Mikael

    2005-01-01

    We report the fabrication of broadband directional couplers by direct UV-writing. The fabrication process is shown to be beneficial, robust and flexible. The components are compact and show superior performance in terms of loss and broadband operation....

  18. Broadband infrared metamaterial absorber with visible transparency using ITO as ground plane.

    Science.gov (United States)

    Dayal, Govind; Ramakrishna, S Anantha

    2014-06-16

    Metamaterials that have broadband absorption at MIR frequencies, and yet, are transmitive at visible frequencies are fabricated using a semi-conducting Indium Tin Oxide (ITO) film as ground plane. The metamaterial absorber consists of an array of uniform aluminum disks separated by a Zinc Sulphide (ZnS) dielectric spacer layer from the ITO ground plane. The metamaterial was fabricated by a simple, cost-effective vapor deposition through a shadow mask. Compared with the usual metal/dielectric/metal tri-layer absorbers, the metal/dielectric/ITO absorber shows a peak absorbance of 98% and >70% over the mid-infrared regime from 4 to 7 μm. The broadband nature arises due to smaller dispersion in the dielectric permittivity of ITO compared to that of plasmonic metals at mid-infrared frequencies.

  19. Dielectric Characteristics of Microstructural Changes and Property Evolution in Engineered Materials

    Science.gov (United States)

    Clifford, Jallisa Janet

    Heterogeneous materials are increasingly used in a wide range of applications such as aerospace, civil infrastructure, fuel cells and many others. The ability to take properties from two or more materials to create a material with properties engineered to needs is always very attractive. Hence heterogeneous materials are evolving into more complex formulations in multiple disciplines. Design of microstructure at multiple scales control the global functional properties of these materials and their structures. However, local microstructural changes do not directly cause a proportional change to the global properties (such as strength and stiffness). Instead, local changes follow an evolution process including significant interactions. Therefore, in order to understand property evolution of engineered materials, microstructural changes need to be effectively captured. Characterizing these changes and representing them by material variables will enable us to further improve our material level understanding. In this work, we will demonstrate how microstructural features of heterogeneous materials can be described quantitatively using broadband dielectric spectroscopy (BbDS). The frequency dependent dielectric properties can capture the change in material microstructure and represent these changes in terms of material variables, such as complex permittivity. These changes in terms of material properties can then be linked to a number of different conditions, such as increasing damage due to impact or fatigue. Two different broadband dielectric spectroscopy scanning modes are presented: bulk measurements and continuous scanning to measure dielectric property change as a function of position across the specimen. In this study, we will focus on ceramic materials and fiber reinforced polymer matrix composites as test bed material systems. In the first part of the thesis, we will present how different micro-structural design of porous ceramic materials can be captured

  20. X-ray diffraction, dielectric, and Raman spectroscopy studies of BaSrTiO{sub 3}-NaNbO{sub 3} ceramic

    Energy Technology Data Exchange (ETDEWEB)

    Abdessalem, L. Ben; Aydi, S.; Aydi, A.; Maalej, A.; Khemakhem, H. [Universite de Sfax, Laboratoire des Materiaux Multifonctionnels et Applications (LaMMA), Faculte des Sciences de Sfax (FSS), Sfax (Tunisia); Sassi, Z. [Laboratoire de Genie Electrique et Ferroelectricite (LGEF) de L' INSA de Lyon, Villeurbanne (France)

    2017-05-15

    Ba{sub 0.837}Sr{sub 0.093}Na{sub 0.07}Ti{sub 0.93}Nb{sub 0.07}O{sub 3} (BSNTN) ceramic was synthesized by the solid-state reaction at 1350 C for 3 h. The crystal structure, investigated by X-ray diffraction at room temperature, revealed a single-phase perovskite crystallizing with tetragonal P4mm group space. Dielectric properties were investigated as a function of applied frequency. The ferroelectric behavior has been confirmed by hysteresis investigation. The evolution of the Raman spectra was used to study the variations of the basic phase transition of BaTiO{sub 3}, at room temperature. It shows the introduction of a disorder in this composition, thus favoring a ferroelectric relaxor behavior. (orig.)

  1. Broadband non-unity magnetic permeability in planar hyperbolic metamaterials

    Science.gov (United States)

    Papadakis, Georgia Theano; Fleischman, Dagny; Davoyan, Artur R.; Thyagarajan, Krishnan; Atwater, Harry A.

    Metal/dielectric heterostructures with extreme anisotropy and topologically nontrivial dispersion are of fundamental and applied interest due to unique optical and opto-electronic properties. Here we demonstrate that, surprisingly, such systems exhibit a broadband non-unity magnetic response. Typically the electromagnetic properties of such metal-dielectric stacks are deduced from effective medium theories for unbounded, i.e., infinite in size periodic arrangements (c.f., Maxwell-Garnett approximation). In this talk, we show that this description is incomplete for metamaterials with finite number of layers. We demonstrate that a few-layer metal-dielectric metamaterial exhibits a non-unity magnetic permeability across the whole visible spectrum. The response can be diamagnetic or paramagnetic depending on the type of the terminating layers: metallic or dielectric, with non-resonant magnetic permeability that can be engineered to attain values as low as -2 or as high as 2. We have developed a theoretical model that explains the underlying mechanism. We further experimentally validate non-unity effective permeability in the optical range of frequencies. Ag/SiO2 and Ge-based metamaterials fabricated with electron beam evaporation are characterized by ellipsometric measurements and also phase and amplitude of transmittance/reflectance. These results open pathways for creating broadband subwavelength magnetic structures in the visible regime.

  2. Raman spectroscopy, dielectric properties and phase transitions of Ag{sub 0.96}Li{sub 0.04}NbO{sub 3} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Niewiadomski, Adrian, E-mail: aniewiadomski@us.edu.pl [A. Chelkowski Institute of Physics, University of Silesia, Uniwersytecka 4, 40-007 Katowice (Poland); Kania, Antoni [A. Chelkowski Institute of Physics, University of Silesia, Uniwersytecka 4, 40-007 Katowice (Poland); Kugel, Godefroy E. [LMPOS, University of Metz and Supelec Metz, 2 rue E. Belin, Metz 57070 (France); Hafid, Mustapha [LPGC Dept. of Physics BP 133, Faculty of Science, Ibn Tofail University, 14000 Kenitra (Morocco); Sitko, Dorota [Institute of Physics, Pedagogical University, ul. Podchorazych 2, PL 30-084 Krakow (Poland)

    2015-05-15

    Highlights: • First Raman scattering studies of Ag{sub 0.96}Li{sub 0.04}NbO{sub 3}, allowed us to correlate temperature evolution of relaxational frequency γ{sub R}(T) with the Nb-ion dynamics and showed its changes at freezing temperature and ferrielectric transition. - Abstract: Silver lithium niobates Ag{sub 1−x}Li{sub x}NbO{sub 3} are promising lead free piezoelectrics. Good quality Ag{sub 0.96}Li{sub 0.04}NbO{sub 3} ceramics were obtained. Dielectric and DSC studies showed that, in comparison to AgNbO{sub 3,} temperatures of phase transitions slightly decrease. Dielectric studies pointed to enhancement of polar properties. Remnant polarisations achieves value of 0.6 μC/cm{sup 2}. Maximum of ϵ(T) dependences related to the relaxor-like ferroelectric/ferrielectric M{sub 1}–M{sub 2} transition becomes higher and more frequency dependent. Analysis of Raman spectra showed that two modes at 50 and 194 cm{sup −1} exhibit significant softening. Low frequency part of the Raman spectra which involve central peak and soft mode were analysed using two models. CP was assumed as relaxational vibration and described by Debye function. The slope of temperature dependences of relaxational frequency γ{sub R}(T) changes at approximately 470 and 330 K, indicating that slowing down process of relaxational vibrations changes in the vicinity of partial freezing of Nb-ion dynamics T{sub f} and further freezing at ferroelectric/ferrielectric phase transition.

  3. Ac conductivity and dielectric properties of CuFe{sub 1-x}Cr{sub x}O{sub 2} : Mg delafossite

    Energy Technology Data Exchange (ETDEWEB)

    Lalanne, M; Demont, P; Barnabe, A, E-mail: demont@cict.fr [Institut Carnot CIRIMAT, Universite de Toulouse UPS, 118 Route de Narbonne, 31062, Toulouse cedex 9 France (France)

    2011-05-11

    The electrical and dielectric properties of CuFe{sub 1-x}Cr{sub x}O{sub 2} (0 {<=} x {<=} 1) powders, doped with 3% of Mg and prepared by solid-state reaction, were studied by broadband dielectric spectroscopy in the temperature range from -100 to 150 {sup 0}C. The frequency-dependent electrical and dielectric data have been discussed in the framework of a power law conductivity and complex impedance and dielectric modulus. At room temperature, the ac conductivity behaviour is characteristic of the charge transport in CuFe{sub 1-x}Cr{sub x}O{sub 2} powders. The substitution of Fe{sup 3+} by Cr{sup 3+} results in an increase in dc conductivity and a decrease in the Cu{sup +}-Cu{sup +} distance. Dc conductivity, characteristic onset frequency and Havriliak-Negami characteristics relaxation times are thermally activated above -40 deg. C for x = 0.835. The associated activation energies obtained from dc and ac conductivity and from impedance and modulus losses are similar and show that CuFe{sub 1-x}Cr{sub x}O{sub 2} delafossite powders satisfy the BNN relation. Dc and ac conductivities have the same transport mechanism, namely thermally activated nearest neighbour hopping and tunnelling hopping above and below -40 {sup 0}C, respectively.

  4. Broadband graphene-based metamaterial absorbers

    Science.gov (United States)

    Liu, Chang; Qi, Limei; Zhang, Xu

    2018-01-01

    In this paper, a new type of broadband tunable metamaterial absorber is proposed. The structure consists of a single-layer ring graphene and a metal ground plane separated by a dielectric spacer. The graphene rings are connected each other to be easily tuned by the voltage. In addition, this absorber is polarization-independent at normal incidence due to the symmetric pattern of the unit cell. Results reveal the bandwidth of 90% absorption reaches to 2.25 THz for a single-ring structure. The bandwidth of 90% absorption increases to 3.2 THz by combining two similar rings with different sizes in one unit cell. The physical mechanism of the single-ring and dual-ring absorbers are given based on the impedance matching theory.

  5. Broadband graphene-based metamaterial absorbers

    Directory of Open Access Journals (Sweden)

    Chang Liu

    2018-01-01

    Full Text Available In this paper, a new type of broadband tunable metamaterial absorber is proposed. The structure consists of a single-layer ring graphene and a metal ground plane separated by a dielectric spacer. The graphene rings are connected each other to be easily tuned by the voltage. In addition, this absorber is polarization-independent at normal incidence due to the symmetric pattern of the unit cell. Results reveal the bandwidth of 90% absorption reaches to 2.25 THz for a single-ring structure. The bandwidth of 90% absorption increases to 3.2 THz by combining two similar rings with different sizes in one unit cell. The physical mechanism of the single-ring and dual-ring absorbers are given based on the impedance matching theory.

  6. Optical and X-ray emission spectroscopy of high-power laser-induced dielectric breakdown in molecular gases and their mixtures.

    Science.gov (United States)

    Babankova, Dagmar; Civis, Svatopluk; Juha, Libor; Bittner, Michal; Cihelka, Jaroslav; Pfeifer, Miroslav; Skala, Jirí; Bartnik, Andrzej; Fiedorowicz, Henryk; Mikolajczyk, Janusz; Ryć, Leszek; Sedivcova, Tereza

    2006-11-09

    Large-scale plasma was created in molecular gases (CO, CO2, N2, H2O) and their mixtures by high-power laser-induced dielectric breakdown (LIDB). Compositions of the mixtures used are those suggested for the early earth's atmosphere of neutral and/or mildly reducing character. Time-integrated optical spectra emitted from the laser spark have been measured and analyzed. The spectra of the plasma generated in the CO-containing mixtures are dominated by emission of both C2 and CN radicals. A vibrational temperature of approximately 10(4) K was determined according to an intensity distribution in a vibronic structure of the CN (B2Sigma(+)u-X2Sigma(+)g) violet band. For comparison, the NH3-CH4-H2-H2O mixture has been irradiated as a model of the strongly reducing version of the early earth's atmosphere. In this mixture, excited CN seems to be significantly less abundant than C2. The LIDB experiments were in the molecular gases carried out not only in the static cell but also using a large, double stream pulse jet (gas puff target) placed in the vacuum interaction chamber. The obtained soft X-ray emission spectra indicate the presence of highly charged atomic ions in the hot core of high-power laser sparks.

  7. Broadband Radio Service (BRS) and Educational Broadband Service (EBS) Transmitters

    Data.gov (United States)

    Department of Homeland Security — The Broadband Radio Service (BRS), formerly known as the Multipoint Distribution Service (MDS)/Multichannel Multipoint Distribution Service (MMDS), is a commercial...

  8. Broadband terahertz fiber directional coupler

    DEFF Research Database (Denmark)

    Nielsen, Kristian; Rasmussen, Henrik K.; Jepsen, Peter Uhd

    2010-01-01

    We present the design of a short broadband fiber directional coupler for terahertz (THz) radiation and demonstrate a 3 dB coupler with a bandwidth of 0:6 THz centered at 1:4 THz. The broadband coupling is achieved by mechanically downdoping the cores of a dual-core photonic crystal fiber by micro......We present the design of a short broadband fiber directional coupler for terahertz (THz) radiation and demonstrate a 3 dB coupler with a bandwidth of 0:6 THz centered at 1:4 THz. The broadband coupling is achieved by mechanically downdoping the cores of a dual-core photonic crystal fiber...

  9. BPL (Broadband Power Line)

    OpenAIRE

    Peralta, Arturo

    2010-01-01

    El mundo actual requiere cada vez más el estar conectados con la sociedad de la Información y el Conocimiento, esto demanda que en los hogares, lugares de turismo, trabajos, universidades, etcétera, se cuente con una conexión a Internet de Alta Velocidad, que además sea segura y confiable. En este documento se presenta las características más importantes de la tecnología BPL (Broadband Power Line) o PLC (Power Line Comunication), la cual permite brindar el servicio de Internet ...

  10. Broadband frequency conversion

    DEFF Research Database (Denmark)

    Sanders, Nicolai; Jensen, Ole Bjarlin; Tidemand-Lichtenberg, Peter

    We present a simple, passive and static setup for broadband frequency conversion. By using simple optical components like lenses, mirrors and gratings, we obtain the spectral angular dispersion to match the second harmonic generation phasematching angles in a nonlinear BiBO crystal. We are able...... to frequency double a single-frequency diode laser, tunable in the 1020-1090 nm range, with almost equal efficiency for all wavelengths. In the experimental setup, the width of the phasematch was increased with a factor of 50. The method can easily be extended to other wavelength ranges and nonlinear crystals...

  11. Improving dielectric properties of BaTiO{sub 3}/poly(vinylidene fluoride) composites by employing core-shell structured BaTiO{sub 3}@Poly(methylmethacrylate) and BaTiO{sub 3}@Poly(trifluoroethyl methacrylate) nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xianhong; Zhao, Sidi; Wang, Fang [Key Laboratory of Carbon Fiber and Functional Polymers, Ministry of Education, Beijing University of Chemical Technology, Beijing 100029 (China); Ma, Yuhong, E-mail: mayh@mail.buct.edu.cn [Key Laboratory of Carbon Fiber and Functional Polymers, Ministry of Education, Beijing University of Chemical Technology, Beijing 100029 (China); Beijing Engineering Research Center of Syntheses and Applications of Waterborne Polymers, Beijing University of Chemical Technology, 100029 (China); Wang, Li; Chen, Dong; Zhao, Changwen [Key Laboratory of Carbon Fiber and Functional Polymers, Ministry of Education, Beijing University of Chemical Technology, Beijing 100029 (China); Beijing Engineering Research Center of Syntheses and Applications of Waterborne Polymers, Beijing University of Chemical Technology, 100029 (China); Yang, Wantai, E-mail: yangwt@mail.buct.edu.cn [Key Laboratory of Carbon Fiber and Functional Polymers, Ministry of Education, Beijing University of Chemical Technology, Beijing 100029 (China); Beijing Engineering Research Center of Syntheses and Applications of Waterborne Polymers, Beijing University of Chemical Technology, 100029 (China)

    2017-05-01

    Highlights: • Core-shell structured BT@PMMA and BT@PTFEMA nanoparticles were synthesized. • The dispersity of BT nanoparticles in PVDF matrix was improved significantly. • Dielectric properties both of BT@PMMA/PVDF and BT@PTFEMA/PVDF composites were improved. • The frequency dependence of dielectric constant attenuation of BT@PTFEMA/PVDF composites was smaller than that of BT@PMMA/PVDF composites. - Abstract: Polymer based dielectric composites were fabricated through incorporation of core-shell structured BaTiO{sub 3} (BT) nanoparticles into PVDF matrix by means of solution blending. Core-shell structured BT nanoparticles with different shell composition and shell thickness were prepared by grafting methacrylate monomer (MMA or TFEMA) onto the surface of BT nanoparticles via surface initiated atom transfer radical polymerization (SI-ATRP). The content of the grafted polymer and the micro-morphology of the core-shell structured BT nanoparticles were investigated by thermo gravimetric analyses (TGA) and transmission electron microscopy (TEM), respectively. The dielectric properties were measured by broadband dielectric spectroscopy. The results showed that high dielectric constant and low dielectric loss are successfully realized in the polymer based composites. Moreover, the type of the grafted polymer and its content had different effect on the dielectric constant. In detail, the attenuation of dielectric constant was 16.6% for BT@PMMA1/PVDF and 10.7% for BT@PMMA2/PVDF composite in the range of 10 Hz to 100 kHz, in which the grafted content of PMMA was 5.5% and 8.0%, respectively. However, the attenuation of dielectric constant was 5.5% for BT@PTFEMA1/PVDF and 4.0% for BT@PTFEMA2/PVDF composite, in which the grafted content of PTFEMA was 1.5% and 2.0%, respectively. These attractive features of BT@PTFEMA/PVDF composites suggested that dielectric ceramic fillers modified with fluorinated polymer can be used to prepare high performance composites, especially

  12. Graphene induced tunable and polarization-insensitive broadband metamaterial absorber

    Science.gov (United States)

    Zhang, Yuping; Li, Yue; Cao, Yanyan; Liu, Yuanzhong; Zhang, Huiyun

    2017-01-01

    We design a tunable and broadband metamaterial absorber in the mid-infrared region based on graphene. The unit cell of the proposed metamaterial absorber consists of circular gold patches, which coupled with a graphene layer, and are separated by a dielectric spacer from the gold film on the bottom. The absorption bandwidth is effectively extended by patterning multi-circular gold patches of different dimension elements with appropriate geometrical parameters in a co-plane. The metamaterial absorber achieves its frequency tunable characteristics via changing the applied voltage or chemical doping to manipulate graphene's Fermi energy. We analyzed the surface current distributions and the distributions of the z-component electric field for understanding the absorption mechanism. Moreover, the design principle here could be regarded as a template to extend bandwidth by introducing more circular patches into each unit cell. Our design has potential applications in various fields of stealth technology, photovoltaic devices, sensors, and broadband communication.

  13. imide, crystal structure, thermal and dielectric studies

    Indian Academy of Sciences (India)

    IR and Raman spectroscopies and its crystal structure is confirmed by single crystal X-ray diffraction method. The X-ray studies on ... Di-cationic ionic liquids; crystal structure; dielectric; thermal properties. 1. Introduction. The chemistry of ionic ... exposed in various emerging areas as solvents of high tem- perature organic ...

  14. Unusual dielectric response in cobalt doped reduced graphene oxide

    Energy Technology Data Exchange (ETDEWEB)

    Akhtar, Abu Jahid; Gupta, Abhisek; Kumar Shaw, Bikash; Saha, Shyamal K., E-mail: cnssks@iacs.res.in [Department of Materials Science, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032 (India)

    2013-12-09

    Intensive research on cobalt doped reduced graphene oxide (Co-RGO) to investigate the modification in graphene magnetism and spin polarization due to presence of transition metal atom has been carried out, however, its dielectric spectroscopy, particularly, how capacitance changes with impurity levels in graphene is relatively unexplored. In the present work, dielectric spectroscopy along with magneto-dielectric effect are investigated in Co-RGO. Contrary to other materials, here permittivity increases abruptly with frequency in the low frequency region and continues to increase till 10{sup 7} Hz. This unusual behavior is explained on the basis of trap induced capacitance created due to impurity levels.

  15. 75 FR 29516 - Broadband Researchers' Data Workshop

    Science.gov (United States)

    2010-05-26

    ... Administration Broadband Researchers' Data Workshop AGENCY: National Telecommunications and Information... demonstrated in the agency's October 30, 2009, Broadband Data Transparency Public Workshop.\\2\\ \\2\\ See http...

  16. Dielectric characterisation of soil

    NARCIS (Netherlands)

    Hilhorst, M.A.

    1998-01-01

    The potential of dielectric measuring techniques for soil characterisation has not been fully explored. This is attributed to the complex and incomplete theory on dielectrics, as well as to the lack of sensors suited for practical applications.

    The theory on dielectric properties of soils is

  17. Broadband metamaterial absorber based on coupling resistive frequency selective surface.

    Science.gov (United States)

    Sun, LiangKui; Cheng, HaiFeng; Zhou, YongJiang; Wang, Jun

    2012-02-13

    We report the design, fabrication, and measurement of a broadband metamaterial absorber, which consists of lossy frequency selective surface (FSS) and a metallic ground plane separated by a dielectric layer. The compact single unit cell of the FSS contains crisscross and fractal square patch which couple with each other. Both qualitative analysis by equivalent circuit and accurate numeric calculation show that the coupling between the crisscross and the fractal square patch can enhance the bandwidth with the reflectivity below -10dB in the frequency range of 2-18GHz by producing a third absorption null. In the end, the designed absorber was realized by experiment.

  18. 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.

  19. Broadband unidirectional ultrasound propagation

    Energy Technology Data Exchange (ETDEWEB)

    Sinha, Dipen N.; Pantea, Cristian

    2017-12-12

    A passive, linear arrangement of a sonic crystal-based apparatus and method including a 1D sonic crystal, a nonlinear medium, and an acoustic low-pass filter, for permitting unidirectional broadband ultrasound propagation as a collimated beam for underwater, air or other fluid communication, are described. The signal to be transmitted is first used to modulate a high-frequency ultrasonic carrier wave which is directed into the sonic crystal side of the apparatus. The apparatus processes the modulated signal, whereby the original low-frequency signal exits the apparatus as a collimated beam on the side of the apparatus opposite the sonic crystal. The sonic crystal provides a bandpass acoustic filter through which the modulated high-frequency ultrasonic signal passes, and the nonlinear medium demodulates the modulated signal and recovers the low-frequency sound beam. The low-pass filter removes remaining high-frequency components, and contributes to the unidirectional property of the apparatus.

  20. How does static stretching decrease the dielectric constant of VHB 4910 elastomer?

    Science.gov (United States)

    Vu-Cong, T.; Nguyen-Thi, N.; Jean-Mistral, C.; Sylvestre, A.

    2014-03-01

    Subject to a voltage, dielectric elastomers deform by the effect of Maxwell stress which is depended directly on the dielectric constant of the material. The combination of large strain, soft elastic response and good dielectric properties has established VHB 4910 elastomer as the most used material for dielectric elastomer actuators. However, the effect of stretch on the dielectric constant for this elastomer is much debated topic while controversy results are demonstrated in the literature. The dielectric constant of this material is studied and demonstrated that it decreases slightly or hugely among the stretch but any pertinent response and any physic explications are validated by the scientific community. In this paper, we presented a detail study about dielectric behavior of VHB 4910 elastomer versus a broadband of stretch and temperature. We found that the dielectric constant of this material depends strongly on the stretch following a polynomial law. Among all the explanations of stretch dependence of the dielectric constant of VHB 4910 in the literature: the crystallization, the change of glass transition temperature, the decrease of dipole orientation, the electrostriction effect under stress; and based on our experimental result, we conclude that the decrease of dipole orientation seems the main reason to the drop of dielectric constant of VHB 4910 elastomer versus the stretch. We proposed also an accurate model describing the dielectric constant of this material for a large range of stretch and temperature.

  1. 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...

  2. Dielectric silicone elastomers with mixed ceramic nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Stiubianu, George, E-mail: george.stiubianu@icmpp.ro [“Petru Poni” Institute of Macromolecular Chemistry, Aleea Gr. Ghica Voda 41A, Iasi 700487 (Romania); Bele, Adrian; Cazacu, Maria; Racles, Carmen; Vlad, Stelian [“Petru Poni” Institute of Macromolecular Chemistry, Aleea Gr. Ghica Voda 41A, Iasi 700487 (Romania); Ignat, Mircea [National R& D Institute for Electrical Engineering ICPE-CA Bucharest, Splaiul Unirii 313, District 3, Bucharest 030138 (Romania)

    2015-11-15

    Highlights: • Composite ceramics nanoparticles (MCN) with zirconium dioxide and lead zirconate. • Dielectric elastomer films wDith PDMS matrix and MCN as dielectric filler. • Hydrophobic character—water resistant and good flexibility specific to siloxanes. • Increased value of dielectric constant with the content of MCN in dielectric films. • Increased energy output from uniaxial deformation of the dielectric elastomer films. - Abstract: A ceramic material consisting in a zirconium dioxide-lead zirconate mixture has been obtained by precipitation method, its composition being proved by wide angle X-ray powder diffraction and energy-dispersive X-ray spectroscopy. The average diameter of the ceramic particles ranged between 50 and 100 nm, as revealed by transmission electron microscopy images. These were surface treated and used as filler for a high molecular mass polydimethylsiloxane-α,ω-diol (Mn = 450,000) prepared in laboratory, the resulted composites being further processed as films and crosslinked. A condensation procedure, unusual for polydimethylsiloxane having such high molecular mass, with a trifunctional silane was approached for the crosslinking. The effect of filler content on electrical and mechanical properties of the resulted materials was studied and it was found that the dielectric permittivity of nanocomposites increased in line with the concentration of ceramic nanoparticles.

  3. Photonic crystals with broadband, wide-angle, and polarization-insensitive transparency.

    Science.gov (United States)

    Yao, Zhongqi; Luo, Jie; Lai, Yun

    2016-11-01

    Photonic crystals (PhCs) are well-known band gap materials that can block the propagation of electromagnetic waves within certain frequency regimes. Here, we demonstrate that PhCs can also exhibit the contrary property: broadband, wide-angle, and polarization-insensitive transparency beyond normal dielectric solids. Such high transparency attributes to robust impedance matching between a large group of eigen-states in PhCs and propagating waves in free space. As a demonstration, a transparent wall for broadband microwaves is designed for enhancing the transmittance of WiFi and 4G signals.

  4. Broadband Advanced Spectral System Project

    Data.gov (United States)

    National Aeronautics and Space Administration — NovaSol proposes to develop an advanced hyperspectral imaging system for earth science missions named BRASS (Broadband Advanced Spectral System). BRASS combines...

  5. Does broadband internet affect fertility?

    OpenAIRE

    Billari, Francesco C.; Giuntella, Osea; Stella, Luca

    2017-01-01

    The spread of high-speed Internet epitomizes the digital revolution, affecting several aspects of our life. Using German panel data, we test whether the availability of broadband Internet influences fertility choices in a low-fertility setting, which is well-known for the difficulty to combine work and family life. We exploit a strategy devised by Falck et al. (2014) to obtain causal estimates of the impact of broadband on fertility. We find positive effects of highspeed Internet availability...

  6. Broadband accelerator control network

    Energy Technology Data Exchange (ETDEWEB)

    Skelly, J.; Clifford, T.; Frankel, R.

    1983-01-01

    A broadband data communications network has been implemented at BNL for control of the Alternating Gradient Synchrotron (AG) proton accelerator, using commercial CATV hardware, dual coaxial cables as the communications medium, and spanning 2.0 km. A 4 MHz bandwidth Digital Control channel using CSMA-CA protocol is provided for digital data transmission, with 8 access nodes available over the length of the RELWAY. Each node consists of an rf modem and a microprocessor-based store-and-forward message handler which interfaces the RELWAY to a branch line implemented in GPIB. A gateway to the RELWAY control channel for the (preexisting) AGS Computerized Accelerator Operating system has been constructed using an LSI-11/23 microprocessor as a device in a GPIB branch line. A multilayer communications protocol has been defined for the Digital Control Channel, based on the ISO Open Systems Interconnect layered model, and a RELWAY Device Language defined as the required universal language for device control on this channel.

  7. ATST visible broadband imager

    Science.gov (United States)

    McBride, William R.; Wöger, Friedrich; Hegwer, Steve L.; Ferayorni, Andrew; Gregory, B. Scott

    2012-09-01

    The Advanced Technology Solar Telescope (ATST) is a 4 meter class telescope for observation of the solar atmosphere currently in the construction phase. The Visible Broadband Imager (VBI) is a diffraction limited imaging instrument planned to be the first-light instrument in the ATST instrumentation suite. The VBI is composed of two branches, the "VBI blue" and the "VBI red", and uses state-of-the-art narrow bandwidth interference filters and two custom designed high speed filter wheels to take bursts of images that will be re-constructed using a Graphics Processing Unit (GPU) optimized near-real-time speckle image reconstruction engine. At first light, the VBI instrument will produce diffraction-limited movies of solar activity at eight discrete wavelengths with a field of view of 2 arc minutes square. In this contribution, the VBI design team will discuss the capabilities of the VBI and describe the design of the instrument, highlighting the unique challenges faced in the development of this unique instrument.

  8. 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.

  9. 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.

  10. Inductive dielectric analyzer

    Science.gov (United States)

    Agranovich, Daniel; Polygalov, Eugene; Popov, Ivan; Ben Ishai, Paul; Feldman, Yuri

    2017-03-01

    One of the approaches to bypass the problem of electrode polarization in dielectric measurements is the free electrode method. The advantage of this technique is that, the probing electric field in the material is not supplied by contact electrodes, but rather by electromagnetic induction. We have designed an inductive dielectric analyzer based on a sensor comprising two concentric toroidal coils. In this work, we present an analytic derivation of the relationship between the impedance measured by the sensor and the complex dielectric permittivity of the sample. The obtained relationship was successfully employed to measure the dielectric permittivity and conductivity of various alcohols and aqueous salt solutions.

  11. Method of making dielectric capacitors with increased dielectric breakdown strength

    Science.gov (United States)

    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.

  12. Structural, optical spectroscopy, optical conductivity and dielectric ...

    Indian Academy of Sciences (India)

    may be mainly associated with the structural disorder pro- duced by mixture of cubic double and hexagonal pervoskite phases, impurities, defects, grain boundaries and dangling bond states in BTFW ceramic. In the context of the determination of the energy that characterizes our sample, we also investigated the photon.

  13. Metallic dielectric photonic crystals and methods of fabrication

    Energy Technology Data Exchange (ETDEWEB)

    Chou, Jeffrey Brian; Kim, Sang-Gook

    2017-12-05

    A metallic-dielectric photonic crystal is formed with a periodic structure defining a plurality of resonant cavities to selectively absorb incident radiation. A metal layer is deposited on the inner surfaces of the resonant cavities and a dielectric material fills inside the resonant cavities. This photonic crystal can be used to selectively absorb broadband solar radiation and then reemit absorbed radiation in a wavelength band that matches the absorption band of a photovoltaic cell. The photonic crystal can be fabricated by patterning a sacrificial layer with a plurality of holes, into which is deposited a supporting material. Removing the rest of the sacrificial layer creates a supporting structure, on which a layer of metal is deposited to define resonant cavities. A dielectric material then fills the cavities to form the photonic crystal.

  14. Dielectric prisms would improve performance of quasi-optical microwave components

    Science.gov (United States)

    Carson, J. W.

    1967-01-01

    Properties of the Brewster angle and internal reflection in a dielectric prism are proposed as the basis of a new type of element for use in oversize waveguide in quasi-optical microwave components. Waveguide loss is reduced and precision broadband attenuators, phase shifters, and directional couplers can be constructed on the basis of the properties.

  15. A Broadband Bessel Beam Launcher Using Metamaterial Lens.

    Science.gov (United States)

    Qi, Mei Qing; Tang, Wen Xuan; Cui, Tie Jun

    2015-06-30

    An approach of generating broadband Bessel beams is presented. The broadband Bessel beams are produced by a gradient index (GRIN) metamaterial lens illuminated by broadband waveguide antenna. The metamaterial lens is constructed with multi-layered structure and each layer is composed of GRIN metamaterials. The metamaterials are designed as dielectric plates printed with metallic patterns in the center region and drilled by air holes near the edge, which operate in wide band. The metamaterial lens serves as a convertor which transforms the spherical beams emitted from feed into conical beams. The conical beams form quasi-Bessel beams in the near-field region. The aperture diameter of the GRIN lens is much larger than the operating wavelength to guarantee the transformation. In principle, this kind of metamaterial lens can produce Bessel beams at arbitrary distance by designing the refractive-index distribution. To verify the approach, we have designed, fabricated and tested a metamaterial lens. Full-wave simulation and experiment results have proved that the generated Bessel beams can be maintained in distance larger than 1 meter within a ranging from 12 GHz to 18 GHz.

  16. Broadband polarization-insensitive absorber based on gradient structure metamaterial

    Science.gov (United States)

    Yang, Guo-Hui; Liu, Xiao-Xin; Lv, Yue-Long; Fu, Jia-Hui; Wu, Qun; Gu, Xuemai

    2014-05-01

    Metamaterial absorber (MA) is a hot spot in the research on electromagnetic absorbers. In this paper, a metamaterial based broadband polarization-insensitive absorber is proposed. The absorber is fabricated with FR-4 dielectric substrate foiled with copper. The top layer of the unit cell of the MA is composed of resistors mounted crosswire and gradient split ring resonator (SRR) with a square metal patch (SMP) in it. The overall structure is symmetrical, which makes the MA polarization-insensitive. The gradient SRRs and SMPs resonate at adjacent frequencies resulting in broadband property. The absorption rates of the MA for TE and TM wave are calculated through the simulated S-parameters. The bandwidth is 9.9 GHz, where the absorption rate maintains 60% up to 98.28% in both cases and the relative bandwidth is 57.13%. Both broadband and polarization-insensitivity properties are achieved, which demonstrate promising application prospect of the proposed MA in shielding and stealth technology.

  17. Broadband Absorber for the Microwave Region Using Ball-Milled Graphite Gratings

    Science.gov (United States)

    Chen, Xiqiao; Zhang, Zilong; Wang, Zilin; Wang, Shuai; Heng, Liuyang; Zou, Yanhong

    2017-10-01

    A broadband absorber for the microwave region based on a dielectric structure with ball-milled graphite gratings has been proposed. In this absorber, electromagnetic waves in the frequency range of 5.4 to 18 GHz are absorbed efficiently with more than 90% absorptivity. The ball-milled graphite with high a imaginary part of its permittivity used in this work can exhibit dielectric loss to some extent, while there is almost no magnetic loss owing to its low permeability. By comparing the electric field of a single absorbing layer and our grating structure, we found that a λ/4 resonance mode with a narrowband property is excited in the single-layer structure, while the cavity-mode resonance and the edge diffraction effects are the main reasons for the broadband absorption of our designed grating structure. This result provides a guideline for microwave-absorbing materials to greatly extend their bandwidth using a simple structure.

  18. Existence conditions for bulk large-wavevector waves in metal-dielectric and graphene-dielectric multilayer hyperbolic metamaterials

    DEFF Research Database (Denmark)

    Zhukovsky, Sergei; Andryieuski, Andrei; Lavrinenko, Andrei

    2014-01-01

    -dielectric and recently introduced graphene-dielectric stacks. We confirm that short-range surface plasmons in thin metal layers can give rise to hyperbolic metamaterial properties and demonstrate that long-range surface plasmons cannot. We also show that graphene-dielectric multilayers tend to support high-k waves...... and explore the range of parameters, where this is possible, confirming the prospects of using graphene for materials with hyperbolic dispersion. The suggested formalism is applicable to a large variety of structures, such as continuous or structured microwave, terahertz (THz) and optical metamaterials......We theoretically investigate general existence conditions for broadband bulk large-wavevector (high-k) propagating waves (such as volume plasmon polaritons in hyperbolic metamaterials) in arbitrary subwavelength periodic multilayers structures. Treating the elementary excitation in the unit cell...

  19. Driving demand for broadband networks and services

    CERN Document Server

    Katz, Raul L

    2014-01-01

    This book examines the reasons why various groups around the world choose not to adopt broadband services and evaluates strategies to stimulate the demand that will lead to increased broadband use. It introduces readers to the benefits of higher adoption rates while examining the progress that developed and emerging countries have made in stimulating broadband demand. By relying on concepts such as a supply and demand gap, broadband price elasticity, and demand promotion, this book explains differences between the fixed and mobile broadband demand gap, introducing the notions of substitution and complementarity between both platforms. Building on these concepts, ‘Driving Demand for Broadband Networks and Services’ offers a set of best practices and recommendations aimed at promoting broadband demand.  The broadband demand gap is defined as individuals and households that could buy a broadband subscription because they live in areas served by telecommunications carriers but do not do so because of either ...

  20. PREFACE: Dielectrics 2009: Measurement Analysis and Applications

    Science.gov (United States)

    Vaughan, Alun; Williams, Graham

    2009-07-01

    The conference Dielectrics 2009: Measurements, Analysis and Applications represents a significant milestone in the evolution of dielectrics research in the UK. It is reasonable to state that the academic study of dielectrics has led to many fundamental advances and that dielectric materials underpin the modern world in devices ranging from field effect transistors, which operate at extremely high fields, albeit low voltages, to the high voltage plants that provide the energy that powers our economy. The origins of the Dielectrics Group of the Institute of Physics (IOP), which organized this conference, can be traced directly back to the early 1960s, when Professor Mansel Davies was conducting research into the dielectric relaxation behaviour of polar liquids and solids at The Edward Davies Chemical Laboratories of the University College of Wales, Aberystwyth. He was already well-known internationally for his studies of molecular structure and bonding of small molecules, using infra-red-spectroscopy, and of the physical properties of hydrogen-bonded liquids and solids, using thermodynamic methods. Dielectric spectroscopy was a fairly new area for him and he realized that opportunities for scientists in the UK to gather together and discuss their research in this developing area of physical chemistry/chemical physics were very limited. He conceived the idea of forming a Dielectrics Discussion Group (DDG), which would act as a meeting point and provide a platform for dielectrics research in the UK and beyond and, as a result, a two-day Meeting was convened in the spring of 1968 at Gregynog Hall of the University of Wales, near Newtown, Montgomeryshire. It was organized by Mansel Davies, Alun Price and Graham Williams, all physical chemists from the UCW, Aberystwyth. Fifty scientists attended, being a mix of physical chemists, theoretical chemists, physicists, electrical engineers, polymer and materials scientists, all from the UK, except Dr Brendan Scaife of Trinity

  1. Optics of dielectric microstructures

    DEFF Research Database (Denmark)

    Søndergaard, Thomas

    2002-01-01

    From the work carried out within the ph.d. project two topics have been selected for this thesis, namely emission of radiation by sources in dielectric microstructures, and planar photonic crystal waveguides. The work done within the first topic, emission of radiation by sources in dielectric mic...

  2. 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.

  3. Broadband angle- and permittivity-insensitive nondispersive optical activity based on chiral metamaterials

    CERN Document Server

    Song, Kun; Su, Zhaoxian; Ding, Changlin; Liu, Yahong; Luo, Chunrong; Zhao, Xiaopeng; Bhattarai, Khagendra; Zhou, Jiangfeng

    2016-01-01

    Because of the strong inherent resonances, the giant optical activity obtained via chiral metamaterials generally suffers from high dispersion, which has been a big stumbling block to broadband applications. In this paper, we propose a type of chiral metamaterial consisting of interconnected metal helix structures with four-fold symmetry, which exhibits nonresonant Drude-like response and can therefore avoid the highly dispersive optical activity resulting from resonances. It shows that the well-designed chiral metamaterial can achieve nondispersive and pure optical activity with high transmittance in a broadband frequency range. And the optical activity of multi-layer chiral metamaterials is proportional to the layer numbers of single-layer chiral metamaterial. Most remarkably, the broadband behaviors of nondispersive optical activity and high transmission are insensitive to the incident angles of electromagnetic waves and permittivity of dielectric substrate, thereby enabling more flexibility in polarizatio...

  4. Section 1Tunable broadband terahertz absorbers based on multiple layers of graphene ribbons.

    Science.gov (United States)

    Chen, Dingbo; Yang, Junbo; Zhang, Jingjing; Huang, Jie; Zhang, Zhaojian

    2017-11-20

    A novel metamaterial structure consisting of multiple graphene/dielectric layers and metallic substrate is proposed to achieve the broadband absorption response at terahertz (THz) frequencies. Utilizing the phase modulation effect generated by graphene ribbons, the bright-dark field is formed to suppress the reflection based on interference theory in a wide period. By irregularly stacking four graphene ribbons of varying widths on four dielectric layers with unequal thickness in a period, we merge successive absorption peaks into a broadband absorption spectrum successfully. The absorption decreases with fluctuations as the incident angle increases. The position of the absorption spectrum can be dynamically tuned by a small change in the Fermi level of graphene instead of re-optimizing and re-fabricating the device. In addition, the bandwidth of the absorber can be further improved by means of increasing the graphene/dielectric layers. The structure proposed in this paper has potential applications in tunable terahertz photonic devices such as dynamic broadband filters, modulators and sensors.

  5. Comprehensive techniques to determine broadband physically-consistent material characteristics using transmission lines

    Science.gov (United States)

    Zhou, Zhen

    Dispersion, attenuation, and crosstalk are several major challenges that both a high-speed digital and a microwave serial link must overcome to achieve their desirable performance. These phenomena are directly related to the frequency dependency of the dielectric property of the material used in package and interconnect. The dielectric property of a material is commonly measured by its manufacturer in a particular direction at a few discrete frequencies using resonator and waveguide methodology. Since the dielectric property may vary during manufacturing processing, the measurements taken by the manufacturer might be not adequate. Moreover, the dielectric property of a material in a bandwidth that covers at least the second harmonics of the fundamental operational frequency is required to accurately predict the link performance. One of the efforts in this research is to investigate the methodology of realizing broadband characteristics of the dielectric property of a material in its "as packaged" configuration using various transmission line topologies, such as microstrip line and Co-Planar Waveguide (CPW). Transitions from CPW to other transmission line topologies are mandatory if CPW probes are used to achieve broadband and repeatable measurements. Since microstrip line is one of the transmission line topologies involved in this research, a research effort is dedicated to develop a broadband CPW-to-microstrip line transition. An effort is also expended to creating casual material models that can be used in electromagnetic simulators to appropriately model the link based on the polarization mechanism of the materials. In addition to focusing on the measurement method in frequency domain, Short Pulse Propagation (SPP), a time domain method, is investigated as well. A virtual test bench is created to investigate the correlation between impedance variations in stripline structures due to fabricated tolerance and the attenuation predicted by SPP.

  6. Observations involving broadband impedance modelling

    Energy Technology Data Exchange (ETDEWEB)

    Berg, J.S. [Stanford Linear Accelerator Center, Menlo Park, CA (United States)

    1996-08-01

    Results for single- and multi-bunch instabilities can be significantly affected by the precise model that is used for the broadband impedance. This paper discusses three aspects of broadband impedance modelling. The first is an observation of the effect that a seemingly minor change in an impedance model has on the single-bunch mode coupling threshold. The second is a successful attempt to construct a model for the high-frequency tails of an r.f. cavity. The last is a discussion of requirements for the mathematical form of an impedance which follow from the general properties of impedances. (author)

  7. Coaxial Sensors For Broad-Band Complex Permittivity Measurements of Petroleum Fluids

    Energy Technology Data Exchange (ETDEWEB)

    Folgeroe, K.

    1996-12-31

    This doctoral thesis verifies that dielectric spectroscopy and microwave permittivity measurements can be used to characterize petroleum liquids. It concentrates on developing sensors for three potential industrial applications: quality characterization of crude oil and petroleum fractions, monitoring of gas-hydrate formation in water-in-oil emulsions, and determination of water-content in thin liquid layers. The development of a permittivity measurement system for crude oil and petroleum fractions is described. As black oils have low dielectric constant and loss, the system must be very sensitive in order to measure the dielectric spectra and to distinguish oils of different permittivity. Such a system was achieved by combining impedance and scattering parameter measurements with appropriate permittivity calculation methods. The frequency range from 10 kHz to 6 GHz was found convenient for observing the main dispersion of the oils. All the oils had dielectric constants between 2.1 and 2.9 and dielectric loss below 0.01. The oils studied were samples of the feedstock for the cracker and coke processes at a petroleum refinery. This verifies that dielectric spectroscopy is a potential technique for on-line quality monitoring of the feedstock at petroleum refineries. Gas hydrates may cause major problems like clogging of pipelines. Dielectric spectroscopy is proposed as a means of monitoring the formation of gas hydrates in emulsions. It is found that open-ended coaxial probes fulfill the sensitivity requirements for such sensors. 312 refs., 87 figs., 20 tabs.

  8. 75 FR 27984 - Broadband Technology Opportunities Program

    Science.gov (United States)

    2010-05-19

    ... interoperability framework for use across the United States. The FCC's National Broadband Plan recognized that... Research, Projects, at http://www.pscr.gov/projects/broadband/700mhz/700mhz.php . Pursuant to the eligible...

  9. XRD, XPS, SEM/EDX and broadband impedance spectroscopy study of pyrophosphate (LiFeP2O7 and Li0.9Fe0.9Ti0.1P2O7) ceramics

    Science.gov (United States)

    Venckutė, V.; Miškinis, J.; Kazlauskienė, V.; Šalkus, T.; Dindune, A.; Kanepe, Z.; Ronis, J.; Maneikis, A.; Lelis, M.; Kežionis, A.; Orliukas, A. F.

    2014-05-01

    LiFeP2O7 and Li0.9Fe0.9Ti0.1P2O7 were synthesised by solid-state reaction and ceramics were sintered. The structure of compounds was studied in the temperature range 300-700 K by X-ray diffraction. Ceramics' surfaces were investigated by scanning electron microscope. Binding energies of Fe 2p, P 2p and O 1s core levels at ceramics' surfaces have been determined by X-ray photoelectron spectroscopy and different valence states of Fe and P were detected. Elemental compositions of the compounds were studied by energy dispersive X-ray spectrometer. Impedance spectroscopy was performed in the frequency range 10 Hz-3 GHz and in the temperature interval 400-700 K. The changes of the activation energy of ionic conductivity at 528 and 550 K for LiFeP2O7 and Li0.9Fe0.9Ti0.1P2O7, respectively, were found. The phenomena can be related to disordering in the unit cells of the compounds.

  10. Thermal Experimental Analysis for Dielectric Characterization of High Density Polyethylene Nanocomposites

    Directory of Open Access Journals (Sweden)

    Ahmed Thabet Mohamed

    2016-01-01

    Full Text Available The importance of nanoparticles in controlling physical properties of polymeric nanocomposite materials leads us to study effects of these nanoparticles on electric and dielectric properties of polymers in industry In this research, the dielectric behaviour of High-Density Polyethylene (HDPE nanocomposites materials that filled with nanoparticles of clay or fumed silica has been investigated at various frequencies (10 Hz-1 kHz and temperatures (20-60°C. Dielectric spectroscopy has been used to characterize ionic conduction, then, the effects of nanoparticles concentration on the dielectric losses and capacitive charge of the new nanocomposites can be stated. Capacitive charge and loss tangent in high density polyethylene nanocomposites are measured by dielectric spectroscopy. Different dielectric behaviour has been observed depending on type and concentration of nanoparticles under variant thermal conditions.

  11. Broadband Synthetic Ground Motion Records

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — The dataset contains broadband synthetic ground motion records for three events: 1) 1994 M6.7 Northridge, CA, 2) 1989 M7.0 Loma Prieta, CA, and 3) 1999 M7.5 Izmit,...

  12. Dielectric and Bioimpedance Research Studies: A Scientometric Approach Using the Scopus Database

    Directory of Open Access Journals (Sweden)

    Dalia El Khaled

    2018-01-01

    Full Text Available This work describes the worldwide applications of dielectric and bioimpedance measurements techniques in various fields. Dielectric and bioimpedance spectroscopy are major non-destructive measurement systems with great potential in the technology field. All results produced by the Scopus database were used as the core of the study in hand, with different items from journals, papers and conference proceedings being taken into account. The results of this analysis show that the interest in electrical properties has risen in the last years due to the advanced technological measurements offered on the scientific level. Results show that bioimpedance studies are considerably more recent compared to dielectric studies, and are more directed towards medical purposes while dielectric spectroscopy focuses on physical aspects, and is used mostly in engineering and material science. It can be stated that bioimpendance and dielectric spectroscopy are being increasingly applied and that they have the capacity to deepen and enhance research investigation.

  13. Cast dielectric composite linear accelerator

    Science.gov (United States)

    Sanders, David M [Livermore, CA; Sampayan, Stephen [Manteca, CA; Slenes, Kirk [Albuquerque, NM; Stoller, H M [Albuquerque, NM

    2009-11-10

    A linear accelerator having cast dielectric composite layers integrally formed with conductor electrodes in a solventless fabrication process, with the cast dielectric composite preferably having a nanoparticle filler in an organic polymer such as a thermosetting resin. By incorporating this cast dielectric composite the dielectric constant of critical insulating layers of the transmission lines of the accelerator are increased while simultaneously maintaining high dielectric strengths for the accelerator.

  14. 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

  15. Methods and apparatus for vertical coupling from dielectric waveguides

    Science.gov (United States)

    Yaacobi, Ami; Cordova, Brad Gilbert

    2014-06-17

    A frequency-chirped nano-antenna provides efficient sub-wavelength vertical emission from a dielectric waveguide. In one example, this nano-antenna includes a set of plasmonic dipoles on the opposite side of a SiYV.sub.4 waveguide from a ground plane. The resulting structure, which is less than half a wavelength long, emits a broadband beam (e.g., >300 nm) that can be coupled into an optical fiber. In some embodiments, a diffractive optical element with unevenly shaped regions of high- and low-index dielectric material collimates the broadband beam for higher coupling efficiency. In some cases, a negative lens element between the nano-antenna and the diffractive optical element accelerates the emitted beam's divergence (and improves coupling efficiency), allowing for more compact packaging. Like the diffractive optical element, the negative lens element includes unevenly shaped regions of high- and low-index dielectric material that can be designed to compensate for aberrations in the beam emitted by the nano-antenna.

  16. Broadband laser polarization control with aligned carbon nanotubes

    CERN Document Server

    Yang, He; Lia, Diao; Chen, Ya; Mattila, Marco; Tian, Ying; Yong, Zhenzhong; Yang, Changxi; Tittonen, Ilkka; Ren, Zhaoyu; Bai, Jingtao; Li, Qingwen; Kauppinen, Esko I; Lipsanen, Harri; Sun, Zhipei

    2015-01-01

    We introduce a simple approach to fabricate aligned carbon nanotube (ACNT) device for broadband polarization control in fiber laser systems. The ACNT device was fabricated by pulling from as-fabricated vertically-aligned carbon nanotube arrays. Their anisotropic property is confirmed with optical and scanning electron microscopy, and with polarized Raman and absorption spectroscopy. The device was then integrated into fiber laser systems (at two technologically important wavelengths of 1 and 1.5 um) for polarization control. We obtained a linearly-polarized light output with the maximum extinction ratio of ~12 dB. The output polarization direction could be fully controlled by the ACNT alignment direction in both lasers. To the best of our knowledge, this is the first time that ACNT device is applied to polarization control in laser systems. Our results exhibit that the ACNT device is a simple, low-cost, and broadband polarizer to control laser polarization dynamics, for various photonic applications (such as ...

  17. Center for Dielectric Studies,

    Science.gov (United States)

    1984-05-01

    desired dielectric formulation into thin sheets, then laminating and firing the shoots to form a monolithic structure with the noble metal probes internal...of the pyre-signaL of she disordered PST ceramicas under DC bias.The dmini e of miroaemem La reliaxr ferrol.,crIcs La che tperacure region lower chin...increase the dielectric constant. ....... .. Itoci Many of today’s multilayer ceramic capacitors employ costly precious metal internal electrodes. In some

  18. Plasmonic and Dielectric Metasurfaces: Design, Fabrication and Applications

    Directory of Open Access Journals (Sweden)

    Jian Wang

    2016-09-01

    Full Text Available Two-dimensional metasurfaces are widely focused on for their ability for flexible light manipulation (phase, amplitude, polarization over sub-wavelength propagation distances. Most of the metasurfaces can be divided into two categories by the material type of unit structure, i.e., plasmonic metasurfaces and dielectric metasurfaces. For plasmonic metasurfaces, they are made on the basis of metallic meta-atoms whose optical responses are driven by the plasmon resonances supported by metallic particles. For dielectric metasurfaces, the unit structure is constructed with high refractive index dielectric resonators, such as silicon, germanium or tellurium, which can support electric and magnetic dipole responses based on Mie resonances. The responses of plasmonic and dielectric metasurfaces are all relevant to the characteristics of unit structure, such as dimensions and materials. One can manipulate the electromagnetic field of light wave scattered by the metasurfaces through designing the dimension parameters of each unit structure in the metasurfaces. In this review article, we give a brief overview of our recent progress in plasmonic and dielectric metasurface-assisted nanophotonic devices and their design, fabrication and applications, including the metasurface-based broadband and the selective generation of orbital angular momentum (OAM carrying vector beams, N-fold OAM multicasting using a V-shaped antenna array, a metasurface on conventional optical fiber facet for linearly-polarized mode (LP11 generation, graphene split-ring metasurface-assisted terahertz coherent perfect absorption, OAM beam generation using a nanophotonic dielectric metasurface array, as well as Bessel beam generation and OAM multicasting using a dielectric metasurface array. It is believed that metasurface-based nanophotonic devices are one of the devices with the most potential applied in various fields, such as beam steering, spatial light modulator, nanoscale

  19. Techniques in Broadband Interferometry

    Energy Technology Data Exchange (ETDEWEB)

    Erskine, D J

    2004-01-04

    This is a compilation of my patents issued from 1997 to 2002, generally describing interferometer techniques that modify the coherence properties of broad-bandwidth light and other waves, with applications to Doppler velocimetry, range finding, imaging and spectroscopy. Patents are tedious to read in their original form. In an effort to improve their readability I have embedded the Figures throughout the manuscript, put the Figure captions underneath the Figures, and added section headings. Otherwise I have resisted the temptation to modify the words, though I found many places which could use healthy editing. There may be minor differences with the official versions issued by the US Patent and Trademark Office, particularly in the claims sections. In my shock physics work I measured the velocities of targets impacted by flyer plates by illuminating them with laser light and analyzing the reflected light with an interferometer. Small wavelength changes caused by the target motion (Doppler effect) were converted into fringe shifts by the interferometer. Lasers having long coherence lengths were required for the illumination. While lasers are certainly bright sources, and their collimated beams are convenient to work with, they are expensive. Particularly if one needs to illuminate a wide surface area, then large amounts of power are needed. Orders of magnitude more power per dollar can be obtained from a simple flashlamp, or for that matter, a 50 cent light bulb. Yet these inexpensive sources cannot practically be used for Doppler velocimetry because their coherence length is extremely short, i.e. their bandwidth is much too wide. Hence the motivation for patents 1 & 2 is a method (White Light Velocimetry) for allowing use of these powerful but incoherent lamps for interferometry. The coherence of the illumination is modified by passing it through a preparatory interferometer.

  20. Ac conductivity and dielectric study of LiNiPO 4 synthesized by solid ...

    Indian Academy of Sciences (India)

    Administrator

    characterized by X-ray powder diffraction, infrared, Raman analysis spectroscopy and electrical impedance spectroscopy. The compound crystallizes in the ... paper, we analyse IR and Raman spectroscopies, the dielectric properties and the .... The impedance components were fitted to an equiva- lent circuit realized by two ...

  1. Metamaterial-based perfect absorber: polarization insensitivity and broadband

    Science.gov (United States)

    Hien Nguyen, Thi; Bui, Son Tung; Nguyen, Trong Tuan; Nguyen, Thanh Tung; Lee, YoungPak; Nguyen, Manh An; Vu, Dinh Lam

    2014-06-01

    We report the design and simulation of a microwave metamaterials-based perfect absorber using a simple and highly symmetric structure. The basic structure consists of three functional layers: the middle is a dielectric, the back is a metallic plane and the front is a ring of metal. The influence of structural parameters on the absorbance and absorption frequency were investigated. The results show an exceptional absorption performance of near unity around 16 GHz. In addition, the absorption is insensitive to the polarization of the incident beam due to the highly symmetric structure. Finally, four and nine rings with different sizes are arranged appropriately in a unit cell in order to construct a broadband absorber. A polarization-insensitive absorbance of above 90% is achieved over a bandwidth of 15%.

  2. A reflective-backing-free metamaterial absorber with broadband response

    Science.gov (United States)

    Xu, Cuilian; Qu, Shaobo; Wang, Jiafu; Yan, Mingbao; Pang, Yongqiang; Wang, Wenjie; Ma, Hua

    In this paper, we propose a polarization-independent and broadband perfect infrared (IR) metamaterial absorber (MA) without reflective backing. The proposed absorber is a periodic meta-atom array consisting of metal-dielectric-multilayer truncated cones which can absorb 80% EM wave from 50.70 to 81.87THz, while transmit 80% EM wave from 0 to 37.71THz. With the decreasing of frequency, the transmissivity increases, which is close to 100% from 0 to 5THz. We can broaden the absorption bandwidth of the MA by cascading multi-layers truncated cones. Furthermore, the proposed IR MA promises to be one desirable stealth material for radar-IR compatibility.

  3. Surface Modification of Textured Dielectrics and Their Wetting Behavior

    Science.gov (United States)

    Kumar, Vijay; Dhillon, Ajaypal Singh; Sharma, Niti Nipun

    2017-02-01

    Controlling the wettability on dielectric materials is a classical topic in surface engineering. Surface texturing and deposition of self-assembled monolayers (SAMs) are major approaches to achieve lower or higher water contact angle ( θ c) and thereby making surface less or more wettable (more hydrophobic). Dielectric surfaces wetting has been engineered by surface modification and has been shown to achieve θ c to a maximum of 120° ± 5°. Further improvement in θ c to an extent greater than 150° ± 5° is desired to render the surface superhydrophobic. We report in this work an achievement of θ c > 150° ± 5° by combining the plasma-treated surface and octadecyltrichlorosilane (OTS) SAMs deposition on dielectrics, and this had been shown on dielectric ranging from low- k to high- k values. The improvement in wetting behavior and quality of dielectric surface with monolayer on plasma-treated surfaces are (is) investigated and characterized using atomic-force microscope (AFM), scanning electron microscope (SEM), contact angle goniometer, and Raman spectroscopy and x-ray photoelectron spectroscopy (XPS) and are compared with untreated dielectric surface with OTS monolayers.

  4. The apparent effect of sample surface damage on the dielectric parameters of GaAs

    Energy Technology Data Exchange (ETDEWEB)

    Engelbrecht, J.A.A. [Physics Department, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031 (South Africa)], E-mail: Japie.Engelbrecht@nmmu.ac.za; Hashe, N.G. [Physics Department, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031 (South Africa); Hillie, K.T. [CSIR-NML Laboratory, P.O. Box 395, Pretoria 0001 (South Africa); Claassens, C.H. [Physics Department, University of the Free State, Bloemfontein 9300 (South Africa)

    2007-12-15

    The dielectric and optical parameters determined by infrared reflectance spectroscopy and computer simulation of a set of GaAs substrates of various surface topologies are reported. The influence of surface damage on the parameters is noted.

  5. Measurements of Dielectric Properties of Mars Analog Soils with Variable Temperature and Moisture Content

    Science.gov (United States)

    Cereti, A.; Mellon, M. T.; Sizemore, H. G.; Phillips, R. J.

    2009-03-01

    We performed impedance spectroscopy of various martian analog soils, with varying temperature and moisture content, to investigate how the complex dielectric permittivity depends on these factors, as this parameter can strongly affect radar signals propagation.

  6. Linearization of broadband microwave amplifier

    Directory of Open Access Journals (Sweden)

    Đorić Aleksandra

    2014-01-01

    Full Text Available The linearization of broadband power amplifier for application in the frequency range 0.9-1.3 GHz is considered in this paper. The amplifier is designed for LDMOSFET characterized by the maximum output power 4W designing the broadband lumped element matching circuits and matching circuits in topologies that combines LC elements and transmission lines. The linearization of the amplifier is carried out by the second harmonics of the fundamental signals injected at the input and output of the amplifier transistor. The effects of linearization are considered for the case of two sinusoidal signals separated in frequency by different intervals up to 80 MHz ranging input power levels to saturation. [Projekat Ministarstva nauke Republike Srbije, br. TR-32052

  7. Dielectric properties of (Bi0.9La0.1)(2)NiMnO6 thin films : Determining the intrinsic electric and magnetoelectric response

    NARCIS (Netherlands)

    Langenberg, E.; Fina, I.; Ventura, J.; Noheda, Beatriz; Varela, M.; Fontcuberta, J.

    2012-01-01

    We have used temperature-dependent impedance spectroscopy to study the dielectric response of thin films of ferromagnetic and ferroelectric (Bi0.9La0.1)(2)NiMnO6 oxide. This technique has allowed us to disentangle its intrinsic dielectric response and extract the dielectric permittivity of similar

  8. Making robust electrowetting processes: dielectric breakdown and satellite droplets

    Science.gov (United States)

    Randall, Greg; Blue, Brent

    2011-03-01

    For over ten years, charge-related wetting phenomena such as electrowetting or dielectrophoresis have been used to manipulate individual liquid droplets on grids of patterned electrodes. Many proof-of-principle droplet actuations have been shown, however some physics-based problems are complicating this technology's move to industry. These problems include: breakdown of a device's dielectric coating at field strengths lower than anticipated and generation of satellite droplets from the primary droplet's surface. We use atomic layer deposition (ALD) to fabricate high-quality dielectric layers required for robust droplet electrowetting and generate operating plots for several dielectric materials. Using scanning electron microscopy and X-ray spectroscopy, we study damage and ionic penetration into the device's dielectric layer. Using video and current measurements, we examine the physics of satellite droplet generation. We apply these findings to engineer a microfluidic process to mass produce inertial fusion energy targets.

  9. Refining the phase diagram of Pb{sub 1−x}La{sub x}(Zr{sub 0.9}Ti{sub 0.1}){sub 1−x/4}O{sub 3} ceramics by structural, dielectric, and anelastic spectroscopy investigations

    Energy Technology Data Exchange (ETDEWEB)

    Craciun, F., E-mail: Floriana.Craciun@isc.cnr.it; Cordero, F. [CNR-ISC, Istituto dei Sistemi Complessi, Area della Ricerca di Roma-Tor Vergata, Via del Fosso del Cavaliere 100, Roma I-00133 (Italy); Ciuchi, I. V. [CNR-ISTEC, Istituto di Scienza e Tecnologia dei Materiali Ceramici, Via Granarolo 64, Faenza I-48018 (Italy); Dielectrics, Ferroelectrics and Multiferroics Group, Faculty of Physics, Univ. “A. I. Cuza,” Bv. Carol I, n. 11, Iasi 700506 (Romania); Mitoseriu, L. [Dielectrics, Ferroelectrics and Multiferroics Group, Faculty of Physics, Univ. “A. I. Cuza,” Bv. Carol I, n. 11, Iasi 700506 (Romania); Galassi, C. [CNR-ISTEC, Istituto di Scienza e Tecnologia dei Materiali Ceramici, Via Granarolo 64, Faenza I-48018 (Italy)

    2015-05-14

    We present the results of dielectric and anelastic spectroscopy measurements, together with X-ray diffraction investigations, which allow us to establish more precisely the phase diagram of Pb{sub 1−x}La{sub x}(Zr{sub 0.9}Ti{sub 0.1}){sub 1−x/4}O{sub 3} (PLZT x/90/10) in the compositional range around the AFE/FE phase boundary (0 < x < 0.04). From structural analysis and polarization-electric field measurements, we have found that the ground state of PLZT samples with x < 0.025 is rhombohedral R3c, while samples with x > 0.032 are antiferroelectric with orthorhombic Pbam structure. In-between, for compositions with 0.025 ≤ x ≤ 0.032, a coexistence of the AFE/FE phases is evidenced. The use of complementary dielectric and anelastic techniques allows to follow the phase transitions shifts throughout all the interesting composition range and to construct the temperature-composition phase diagram. The tilt instability line, separating the R3c and R3m low and high temperature phases, has been evidenced. Moreover, the new transition, associated with the onset of disordered tilting preceding the long range order of the R3c phase, previously found in Zr-rich Pb(Zr,Ti)O{sub 3}, is confirmed in rhombohedral PLZT x/90/10 compositions.

  10. Terahertz polarization converter based on all-dielectric high birefringence metamaterial with elliptical air holes

    KAUST Repository

    Zi, Jianchen

    2018-02-15

    Metamaterials have been widely applied in the polarization conversion of terahertz (THz) waves. However, common plasmonic metamaterials usually work as reflective devices and have low transmissions. All-dielectric metamaterials can overcome these shortcomings. An all-dielectric metamaterial based on silicon with elliptical air holes is reported to achieve high artificial birefringence at THz frequencies. Simulations show that with appropriate structural parameters the birefringence of the dielectric metamaterial can remain flat and is above 0.7 within a broad band. Moreover, the metamaterial can be designed as a broadband quarter wave plate. A sample metamaterial was fabricated and tested to prove the validity of the simulations, and the sample could work as a quarter wave plate at 1.76 THz. The all-dielectric metamaterial that we proposed is of great significance for high performance THz polarization converters.

  11. Broadband light-emitting diode

    Science.gov (United States)

    Fritz, Ian J.; Klem, John F.; Hafich, Michael J.

    1998-01-01

    A broadband light-emitting diode. The broadband light-emitting diode (LED) comprises a plurality of III-V compound semiconductor layers grown on a semiconductor substrate, with the semiconductor layers including a pair of cladding layers sandwiched about a strained-quantum-well active region having a plurality of different energy bandgaps for generating light in a wavelength range of about 1.3-2 .mu.m. In one embodiment of the present invention, the active region may comprise a first-grown quantum-well layer and a last-grown quantum-well layer that are oppositely strained; whereas in another embodiment of the invention, the active region is formed from a short-period superlattice structure (i.e. a pseudo alloy) comprising alternating thin layers of InGaAs and InGaAlAs. The use a short-period superlattice structure for the active region allows different layers within the active region to be simply and accurately grown by repetitively opening and closing one or more shutters in an MBE growth apparatus to repetitively switch between different growth states therein. The broadband LED may be formed as either a surface-emitting LED or as an edge-emitting LED for use in applications such as chemical sensing, fiber optic gyroscopes, wavelength-division-multiplexed (WDM) fiber-optic data links, and WDM fiber-optic sensor networks for automobiles and aircraft.

  12. 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.

  13. Ultra-broadband microwave metamaterial absorber based on resistive sheets

    Science.gov (United States)

    Kim, Y. J.; Yoo, Y. J.; Hwang, J. S.; Lee, Y. P.

    2017-01-01

    We investigate a broadband perfect absorber for microwave frequencies, with a wide incident angle, using resistive sheets, based on both simulation and experiment. The absorber uses periodically-arranged meta-atoms, consisting of snake-shape metallic patterns and metal planes separated by three resistive sheet layers between four dielectric layers. We demonstrate the mechanism of the broadband by impedance matching with free space, and the distribution of surface currents at specific frequencies. In simulation, the absorption was over 96% in 1.4-6.0 GHz. The corresponding experimental absorption band over 96% was 1.4-4.0 GHz, however, the absorption was lower than 96% in the 4.0-6.0 GHz range because of the rather irregular thickness of the resistive sheets. Furthermore, it works for wide incident angles and is relatively independent of polarization. The design is scalable to smaller sizes in the THz range. The results of this study show potential for real applications in prevention of microwave frequency exposure, with devices such as cell phones, monitors, and microwave equipment.

  14. Dendritic-metasurface-based flexible broadband microwave absorbers

    Science.gov (United States)

    Wang, Mei; Weng, Bin; Zhao, Jing; Zhao, Xiaopeng

    2017-06-01

    Based on the dendritic metasurface model, a type of flexible and lightweight microwave absorber (MA) comprising resistance film array with dendritic slot (RFADS), dielectric material, and metal plate is proposed. A broadband absorptivity of >80% is obtained both from simulation and experiment at frequency ranges of 3.0-9.2 and 3.2-9.00 GHz, respectively. And the thickness of MA is 5 mm, which is only 0.05λ _{low}, or 0.15λ _ {high}, where the λ _{low} and the λ _{high} are the beginning and the end of the working frequency. By combining this metasurface-based MA with the dendritic-resistance-film-based microwave metasurface absorber (MMA), we designed a broadband MMA. The simulations and experiments showed that this kind of MMA can absorb the radiation effectively at a wide frequency range 4.5-17.5 GHz. And the thickness of this combined MMA is 4 mm. All the structures showed their insensitivity to the incident angle (0°-40°) and the polarization of the incident wave because of their structural symmetry. In addition, the small thickness, low apparent density, and flexibility made those structures possess the advantages of being applied in microwave stealth and radar cross-section (RCS) reduction.

  15. 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.

  16. Photonic nanojet properties of dielectric microcylinders

    Science.gov (United States)

    Darafsheh, Arash; Bollinger, Douglas

    2017-02-01

    In recent years, it has been demonstrated that micron-scale dielectric spheres and cylinders can form an intense sharply focused photon beam, termed a photonic nanojet. The photonic nanojet effect can be used in a broad range of biomedical and photonics applications, including super-resolution microscopy, optical endoscopy, spectroscopy, and nanolithography. In this work, by means of finite-difference time-domain (FDTD) numerical simulation, we studied the nanojet properties of dielectric microcylinders over a wide range of diameters (4λ-20λ) and refractive indices (1.5-2.0), where λ is the wavelength of light. We studied how the nanojet beam size, intensity, and focal distance vary as a function of size and refractive index of the microcylinders, and refractive index contrast between the microcylinders and the background medium surrounding them.

  17. An omnidirectional retroreflector based on the transmutation of dielectric singularities.

    Science.gov (United States)

    Ma, Yun Gui; Ong, C K; Tyc, Tomás; Leonhardt, Ulf

    2009-08-01

    Transformation optics is a concept used in some metamaterials to guide light on a predetermined path. In this approach, the materials implement coordinate transformations on electromagnetic waves to create the illusion that the waves are propagating through a virtual space. Transforming space by appropriately designed materials makes devices possible that have been deemed impossible. In particular, transformation optics has led to the demonstration of invisibility cloaking for microwaves, surface plasmons and infrared light. Here, on the basis of transformation optics, we implement a microwave device that would normally require a dielectric singularity, an infinity in the refractive index. To fabricate such a device, we transmute a dielectric singularity in virtual space into a mere topological defect in a real metamaterial. In particular, we demonstrate an omnidirectional retroreflector, a device for faithfully reflecting images and for creating high visibility from all directions. Our method is robust, potentially broadband and could also be applied to visible light using similar techniques.

  18. An omnidirectional retroreflector based on the transmutation of dielectric singularities

    Science.gov (United States)

    Ma, Yun Gui; Ong, C. K.; Tyc, Tomáš; Leonhardt, Ulf

    2009-08-01

    Transformation optics is a concept used in some metamaterials to guide light on a predetermined path. In this approach, the materials implement coordinate transformations on electromagnetic waves to create the illusion that the waves are propagating through a virtual space. Transforming space by appropriately designed materials makes devices possible that have been deemed impossible. In particular, transformation optics has led to the demonstration of invisibility cloaking for microwaves, surface plasmons and infrared light. Here, on the basis of transformation optics, we implement a microwave device that would normally require a dielectric singularity, an infinity in the refractive index. To fabricate such a device, we transmute a dielectric singularity in virtual space into a mere topological defect in a real metamaterial. In particular, we demonstrate an omnidirectional retroreflector, a device for faithfully reflecting images and for creating high visibility from all directions. Our method is robust, potentially broadband and could also be applied to visible light using similar techniques.

  19. Dielectric and structural relaxation in water and some monohydric alcohols

    Science.gov (United States)

    Kaatze, Udo

    2017-07-01

    Relaxation times of the principal (Debye-type) relaxation terms in the dielectric spectra of water and normal alcohols have been evaluated in order to eliminate the effect of multi-molecular cross-correlations and to thus yield reorientation times of the molecular electric dipole moments. The reorientation times have been compared to relaxation times from ultraviolet and X-ray Brillouin spectra as well as from broadband ultrasonic spectra, which are considered as the structure relaxation times characterizing the density fluctuations of the liquid hydrogen bond networks. With some alcohols, shear impedance spectra indicate the network fluctuations to be tightly associated with shear viscosity relaxation. Within the limits of uncertainty, the molecular dipole moment reorientation times and the structure relaxation times feature close correlations. This finding suggests a coupling between translational and orientational molecular motions, and it is discussed in the light of the wait-and-switch model of dielectric relaxation.

  20. Thickness and dielectric constant determination of thin dielectric layers

    NARCIS (Netherlands)

    de Bruijn, H.E.; de Bruijn, Helene E.; Minor, Marcel; Kooyman, R.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

  1. Super Dielectric Materials

    Science.gov (United States)

    Fromille, Samuel; Phillips, Jonathan

    2014-01-01

    Evidence is provided here that a class of materials with dielectric constants greater than 105 at low frequency (dielectric materials (SDM), can be generated readily from common, inexpensive materials. Specifically it is demonstrated that high surface area alumina powders, loaded to the incipient wetness point with a solution of boric acid dissolved in water, have dielectric constants, near 0 Hz, greater than 4 × 108 in all cases, a remarkable increase over the best dielectric constants previously measured for energy storage capabilities, ca. 1 × 104. It is postulated that any porous, electrically insulating material (e.g., high surface area powders of silica, titania, etc.), filled with a liquid containing a high concentration of ionic species will potentially be an SDM. Capacitors created with the first generated SDM dielectrics (alumina with boric acid solution), herein called New Paradigm Super (NPS) capacitors display typical electrostatic capacitive behavior, such as increasing capacitance with decreasing thickness, and can be cycled, but are limited to a maximum effective operating voltage of about 0.8 V. A simple theory is presented: Water containing relatively high concentrations of dissolved ions saturates all, or virtually all, the pores (average diameter 500 Å) of the alumina. In an applied field the positive ionic species migrate to the cathode end, and the negative ions to the anode end of each drop. This creates giant dipoles with high charge, hence leading to high dielectric constant behavior. At about 0.8 V, water begins to break down, creating enough ionic species to “short” the individual water droplets. Potentially NPS capacitor stacks can surpass “supercapacitors” in volumetric energy density. PMID:28788298

  2. Dielectric properties and structural dynamics of melt compounded ...

    Indian Academy of Sciences (India)

    dispersed OMMT nano-platelets in PEO matrix governs the PEO segmental dynamics. A.C. conductivity of these nanocomposites increases by two orders of magnitude in the experimental frequency range. Keywords. PEO–OMMT nanocomposites; dielectric relaxation; electrical conductivity; impedance spectroscopy. 1.

  3. Dielectric properties of CdS nanoparticles synthesized by soft ...

    Indian Academy of Sciences (India)

    The frequency-dependent electrical data are analysed in the framework of conductivity and modulus formalisms. The frequency-dependent conductivity spectra obey the power law. Keywords. Cadmium sulphide; chemical synthesis; impedance spectroscopy; dielectric properties. PACS Nos 61.46.Df; 61.46.Hk; 81.07.Wx. 1.

  4. Analysis of the Proposed Ghana Broadband Strategy

    DEFF Research Database (Denmark)

    Williams, Idongesit; Botwe, Yvonne

    This project studied the Ghana Broadband Strategy with the aim of evaluating the recommendations in the strategy side by side the broadband development in Ghana. The researchers conducted interviews both officially and unofficially with ICT stakeholders, made observations, studied Government...... intervention policies recommended in the Ghana broadband policy is used to evaluate the broadband market to find out whether the strategy consolidates with the Strengths and opportunities of the market and whether it corrects the anomalies that necessitate the weaknesses and threats to the market....... The strategy did address some threats and weaknesses of the broadband market. It also consolidated on some strengths and opportunities of the broadband market. The researchers also discovered that a market can actually grow without a policy. But a market will grow faster if a well implemented policy is guiding...

  5. s-SNOM based microscopy and spectroscopy for nanoscale material characterization

    Science.gov (United States)

    Eisele, Max

    Scattering-type Scanning Near-field Optical Microscopy (s-SNOM) is a scanning probe approach to optical microscopy and spectroscopy bypassing the ubiquitous diffraction limit of light to achieve a spatial resolution below 10 nanometer. s-SNOM employs the strong confinement of light at the apex of a sharp metallic AFM tip to create a nanoscale optical hot-spot. Analyzing the scattered light from the tip enables the extraction of the optical properties (dielectric function) of the sample directly below the tip and yields nanoscale resolved images simultaneous to topography. In addition to near-field microscopy the technology has been advanced to enable Fourier-transform spectroscopy (nano-FTIR) on the nanoscale using broadband radiation from the far-infrared to the visible spectral range. This presentation will summarize the latest achievements in the in the field of near-field microscopy and spectroscopy on polymers, biomaterials and 2D materials. In addition, the combination of near-field microscopy with ultrafast pump-probe experiments will be discussed opening a complete new approach solid-state physics where intriguing phenomena like surface plasmons polaritons or carrier relaxation dynamics can be observed with a combined <200fs temporal and <20nm spatial resolution.

  6. Principles of broadband switching and networking

    CERN Document Server

    Liew, Soung C

    2010-01-01

    An authoritative introduction to the roles of switching and transmission in broadband integrated services networks Principles of Broadband Switching and Networking explains the design and analysis of switch architectures suitable for broadband integrated services networks, emphasizing packet-switched interconnection networks with distributed routing algorithms. The text examines the mathematical properties of these networks, rather than specific implementation technologies. Although the pedagogical explanations in this book are in the context of switches, many of the fundamenta

  7. Dielectric properties of fly ash

    Indian Academy of Sciences (India)

    Unknown

    Abstract. This paper reports the dielectric properties of fly ash. The dielectric measurements were performed as a function of frequency and temperature. The sample of fly ash shows almost similar behaviour in the frequency and temperature range studied. The large value of dielectric constant in the typical frequency range.

  8. Broadband Traffic Forecasting in the Transport Network

    Directory of Open Access Journals (Sweden)

    Valentina Radojičić

    2012-07-01

    Full Text Available This paper proposes a modification of traffic forecast model generated by residential and small business (SOHO, Small Office Home Office users. The model includes forecasted values of different relevant factors and competition on broadband market. It allows forecasting the number of users for various broadband technologies and interaction impact of long-standing technologies as well as the impact of the new technology entrant on the market. All the necessary parameters are evaluated for the Serbian broadband market. The long-term forecasted results of broadband traffic are given. The analyses and evaluations performed are important inputs for the transport network resources planning.

  9. Electrical and dielectric behaviour of Na0.5La0.25Sm0.25Cu3Ti4O12 ceramics investigated by impedance and modulus spectroscopy

    Directory of Open Access Journals (Sweden)

    A.K. Thomas

    2017-03-01

    Full Text Available Polycrystalline samples of Na0.5La0.25Sm0.25Cu3Ti4O12 ceramics were prepared by solid state sintering. Its crystallographic structure, electrical properties and dielectric behaviour are investigated over wide ranges of temperature (30–325 °C and frequency (42 Hz–1 MHz. Rietveld refinement of the powder diffraction data has confirmed a cubic, single phase structure with space group Im3. This ceramic material exhibits colossal value of dielectric constant with very low values of loss factor, over wide frequency ranges and thus highlights the quality of the sample to be used for the fabrication of capacitive devices. Impedance spectroscopic studies have revealed that the compound is electrically heterogeneous. The scaling behaviour of Z″ suggests a temperature independent distribution of relaxation time. The mismatch in the peak frequencies of Z″/Zmax″ and M″/Mmax″ suggest that the relaxation mechanism is dominated by short range movement of charge carriers.

  10. Effects of dielectric charging on the output voltage of a capacitive accelerometer

    Science.gov (United States)

    Qu, Hao; Yu, Huijun; Zhou, Wu; Peng, Bei; Peng, Peng; He, Xiaoping

    2016-11-01

    Output voltage drifting observed in one typical capacitive microelectromechanical system (MEMS) accelerometer is discussed in this paper. Dielectric charging effect is located as one of the major determinants of this phenomenon through a combination of experimental and theoretical studies. A theoretical model for the electromechanical effects of the dielectric surface charges within the electrode gap is established to analyze the dielectric charge effect on the output voltage. Observations of output voltage drift against time are fitted to this model in order to estimate the possible dielectric layer thickness. Meanwhile, Auger electron spectroscopy is carried out to analyze the electrode surface material composition and confirms a mixture layer of dielectric SiO2 and Si with a thickness about 5 nm, which is very close to the model estimation. In addition, observation of time-varing output drift in the variable bias voltage experiment indicates the movement of dielectric charge can be controlled by the applied electric field.

  11. Molds for cable dielectrics

    Science.gov (United States)

    Roose, L.D.

    1996-12-10

    Molds for use in making end moldings for high-voltage cables are described wherein the dielectric insulator of a cable is heated and molded to conform to a desired shape. As a consequence, high quality substantially bubble-free cable connectors suitable for mating to premanufactured fittings are made. 5 figs.

  12. Dielectric Waveguide lasers

    NARCIS (Netherlands)

    Pollnau, Markus; Orlovic, V.A.; Pachenko, V.; Scherbakov, I.A.

    2007-01-01

    Our recent results on planar and channel waveguide fabrication and lasers in the dielectric oxide materials Ti:sapphire and rare-earth-ion-doped potassium yttrium double tungstate (KYW) are reviewed. We have employed waveguide fabrication methods such as liquid phase epitaxy and reactive ion etching

  13. Achieving universal access to broadband

    DEFF Research Database (Denmark)

    Falch, Morten; Henten, Anders

    2009-01-01

    The paper discusses appropriate policy measures for achieving universal access to broadband services in Europe. Access can be delivered by means of many different technology solutions described in the paper. This means a greater degree of competition and affects the kind of policy measures...... to be applied. The paper concludes that other policy measure than the classical universal service obligation are in play, and discusses various policy measures taking the Lisbon process as a point of departure. Available policy measures listed in the paper include, universal service obligation, harmonization...

  14. POTS to broadband ... cable modems.

    Science.gov (United States)

    Kabachinski, Jeff

    2003-01-01

    There have been 3 columns talking about broadband communications and now at the very end when it's time to compare using a telco or cableco, I'm asking does it really matter? So what if I can actually get the whole 30 Mbps with a cable network when the website I'm connecting to is running on an ISDN line at 128 Kbps? Broadband offers a lot more bandwidth than the connections many Internet servers have today. Except for the biggest websites, many servers connect to the Internet with a switched 56-Kbps, ISDN, or fractional T1 line. Even with the big websites, my home network only runs a 10 Mbps Ethernet connection to my cable modem. Maybe it doesn't matter that the cable lines are shared or that I can only get 8 Mbps from an ADSL line. Maybe the ISP that I use has a T1 line connection to the Internet so my new ADSL modem has a fatter pipe than my provider! (See table 1). It all makes me wonder what's in store for us in the future. PC technology has increased exponentially in the last 10 years with super fast processor speeds, hard disks of hundreds of gigabytes, and amazing video and audio. Internet connection speeds have failed to keep the same pace. Instead of hundreds of times better or faster--modem speeds are barely 10 times faster. Broadband connections offer some additional speed but still not comparable growth as broadband connections are still in their infancy. Rather than trying to make use of existing communication paths, maybe we need a massive infrastructure makeover of something new. How about national wireless access points so we can connect anywhere, anytime? To use the latest and fastest wireless technology you will simply need to buy another $9.95 WLAN card or download the latest super slick WLAN compression/encryption software. Perhaps it is time for a massive infra-restructuring. Consider the past massive infrastructure efforts. The telcos needed to put in their wiring infrastructure starting in the 1870s before telephones were useful to the

  15. Achieving Universal Access to Broadband

    Directory of Open Access Journals (Sweden)

    Morten FALCH

    2009-01-01

    Full Text Available The paper discusses appropriate policy measures for achieving universal access to broadband services in Europe. Access can be delivered by means of many different technology solutions described in the paper. This means a greater degree of competition and affects the kind of policy measures to be applied. The paper concludes that other policy measure than the classical universal service obligation are in play, and discusses various policy measures taking the Lisbon process as a point of departure. Available policy measures listed in the paper include, universal service obligation, harmonization, demand stimulation, public support for extending the infrastructure, public private partnerships (PPP, and others.

  16. Understanding broadband over power line

    CERN Document Server

    Held, Gilbert

    2006-01-01

    Understanding Broadband over Power Line explores all aspects of the emerging technology that enables electric utilities to provide support for high-speed data communications via their power infrastructure. This book examines the two methods used to connect consumers and businesses to the Internet through the utility infrastructure: the existing electrical wiring of a home or office; and a wireless local area network (WLAN) access point.Written in a practical style that can be understood by network engineers and non-technologists alike, this volume offers tutorials on electric utility infrastru

  17. Electrical breakdown phenomena of dielectric elastomers

    DEFF Research Database (Denmark)

    Yu, Liyun; Mateiu, Ramona Valentina; Skov, Anne Ladegaard

    years. However, optimization with respect to the dielectric permittivity solely may lead to other problematic phenomena such as premature electrical breakdown. In this work, we focus on the chloro propyl functionalized silicone elastomers prepared in Madsen et al[2] and we investigate the electrical...... breakdown patterns of two similar chloro propyl functionalized silicone elastomers which break down electrically in a rather different way as well as we compare them to a silicone based reference. Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Spectroscopy (EDS) are used to evaluate...... the elastomers after electrical breakdown....

  18. From surface to volume plasmons in hyperbolic metamaterials: General existence conditions for bulk high-k waves in metal-dielectric and graphene-dielectric multilayers

    DEFF Research Database (Denmark)

    Zhukovsky, Sergei; Andryieuski, Andrei; Sipe, John E.

    2014-01-01

    -dielectric and recently introduced graphene-dielectric stacks. We confirm that short-range surface plasmons in thin metal layers can give rise to hyperbolic metamaterial properties and demonstrate that long-range surface plasmons cannot. We also show that graphene-dielectric multilayers tend to support high- k waves...... and explore the range of parameteres for which this is possible, confirming the prospects of using graphene for materials with hyperbolic dispersion. The approach is applicable to a large variety of structures, such as continuous or structured microwave, terahertz, and optical metamaterials.......We theoretically investigate general existence conditions for broadband bulk large-wave-vector (high- k ) propagating waves (such as volume plasmon polaritons in hyperbolic metamaterials) in subwavelength periodic multilayer structures. Describing the elementary excitation in the unit cell...

  19. Broadband Wireline Provider Service Summary; BBRI_wirelineSum12

    Data.gov (United States)

    University of Rhode Island Geospatial Extension Program — This dataset represents the availability of broadband Internet access in Rhode Island via all wireline technologies assessed by Broadband Rhode Island. Broadband...

  20. Broadband absorber with periodically sinusoidally-patterned graphene layer in terahertz range.

    Science.gov (United States)

    Ye, Longfang; Chen, Yao; Cai, Guoxiong; Liu, Na; Zhu, Jinfeng; Song, Zhengyong; Liu, Qing Huo

    2017-05-15

    We demonstrate that a broadband terahertz absorber with near-unity absorption can be realized using a net-shaped periodically sinusoidally-patterned graphene sheet, placed on a dielectric spacer supported on a metallic reflecting plate. Because of the gradient width modulation of the unit graphene sheet, continuous plasmon resonances can be excited, and therefore broadband terahertz absorption can be achieved. The results show that the absorber's normalized bandwidth of 90% terahertz absorbance is over 65% under normal incidence for both TE and TM polarizations when the graphene chemical potential is set as 0.7 eV. And the broadband absorption is insensitive to the incident angles and the polarizations. The peak absorbance remains more than 70% over a wide range of the incident angles up to 60° for both polarizations. Furthermore, this absorber also has the advantage of flexible tunability via electrostatic doping of graphene sheet, which peak absorbance can be continuously tuned from 14% to 100% by controlling the chemical potential from 0 eV to 0.8 eV. The design scheme is scalable to develop various graphene-based tunable broadband absorbers at other terahertz, infrared, and visible frequencies, which may have promising applications in sensing, detecting, and optoelectronic devices.

  1. Nanometrology using localized surface plasmon resonance spectroscopy

    DEFF Research Database (Denmark)

    Jeppesen, Claus; Lindstedt, Daniel N.; Laurberg, Asger V.

    2013-01-01

    A novel optical characterization technique called localized surface plasmon resonance (LSPR) spectroscopy is presented. LSPR spectroscopy exploits light excited surface plasmons, which are collective coherent electron oscillations at a metal/dielectric interface. The LSPR can be observed in a tra...

  2. Dielectric response of epoxy-amine compositions during isothermal curing

    Science.gov (United States)

    Rodin, D. L.; Stefanovich, S. Yu.; Yablokova, M. Yu.

    2017-04-01

    The change in electric conductivity and dielectric permittivity during the curing of epoxy-amine compositions in a mixture with the thermoplastic Ultem 1000 polyetherimide at 180°C is studied by means of dielectric spectroscopy. TGDDM epoxy resin and DADPS, MDEA, and MIPA amine curing agents are used as the epoxy-amine composition. The times of the gel and glass transition are determined from the time and frequency dependences of the dielectric response of the investigated mixtures. At a certain step of curing of epoxy-amine compositions, the separation of a new phase enriched with the thermoplastic is detected. This separation is accompanied by charge accumulation along the phase boundary and its interaction with the external electric field. In the dielectric spectrum, this effect of phase separation appears as an individual relaxation process with characteristic parameters of dielectric relaxation. It is found that at the final step of isothermal curing, there is a glass transition of the polymer, leading to a sharp drop in the reaction rate and stabilization of the dielectric response with respect to time. The detected steps of the reaction and the corresponding changes in the structure and rheology of the investigated polymer systems are characterized and confirmed by methods of viscometry and optical microscopy.

  3. 78 FR 32165 - Broadband Over Power Lines

    Science.gov (United States)

    2013-05-29

    ... providing for Access BPL technology--which has potential applications for broadband and Smart Grid uses... strike an appropriate balance between the dual objectives of providing for Access BPL technology--which has potential applications for broadband and Smart Grid uses--while protecting incumbent radio...

  4. Broadband Helps Bridge the Achievement Gap

    Science.gov (United States)

    Simmons, Jamal

    2013-01-01

    In education, technology is giving new meaning to the phrase "equal opportunity." Teachers and students in schools across America--urban, rural, wealthy, and impoverished--are gaining access to online learning and all of its benefits through broadband technology. What is broadband? According to the Federal Communications Commission (FCC), it is…

  5. Antenna with Dielectric Having Geometric Patterns

    Science.gov (United States)

    Dudley, Kenneth L. (Inventor); Elliott, Holly A. (Inventor); Cravey, Robin L. (Inventor); Connell, John W. (Inventor); Ghose, Sayata (Inventor); Watson, Kent A. (Inventor); Smith, Jr., Joseph G. (Inventor)

    2013-01-01

    An antenna includes a ground plane, a dielectric disposed on the ground plane, and an electrically-conductive radiator disposed on the dielectric. The dielectric includes at least one layer of a first dielectric material and a second dielectric material that collectively define a dielectric geometric pattern, which may comprise a fractal geometry. The radiator defines a radiator geometric pattern, and the dielectric geometric pattern is geometrically identical, or substantially geometrically identical, to the radiator geometric pattern.

  6. High-Resolution Broadband Spectroscopy Using an Externally Dispersed Interferometer

    Science.gov (United States)

    Erskine, David J.; Edelstein, Jerry; Feuerstein, W. Michael; Welsh, Barry

    2003-08-01

    An externally dispersed interferometer (EDI) is a series combination of a fixed delay interferometer and an external grating spectrograph. We describe how the EDI can boost the effective resolving power of an echelle or linear grating spectrograph by a factor of 2-3 or more over the spectrograph's full bandwidth. The interferometer produces spectral fringes over the entire spectrograph's bandwidth. The fringes heterodyne with spectral features to provide a low spatial frequency moiré pattern. The heterodyning is numerically reversed to recover highly detailed spectral information unattainable by the spectrograph alone. We demonstrate resolution boosting for stellar and solar measurements of two-dimensional echelle and linear grating spectra. An effective spectral resolution of ~100,000 has been obtained from the ~50,000 resolution Lick Observatory two-dimensional echelle spectrograph, and that of ~50,000 from an ~20,000 resolution linear grating spectrograph.

  7. Fifth International Conference on Dielectric and Realted Phenomena

    National Research Council Canada - National Science Library

    1998-01-01

    ...: relaxation theory, characterized of dielectric responses, molecular dynamics, "smart" dielectric, polymer-ceramic structures, nonlinear optical materials, space charges in dielectric, dielectric...

  8. Customer Churn Prediction for Broadband Internet Services

    Science.gov (United States)

    Huang, B. Q.; Kechadi, M.-T.; Buckley, B.

    Although churn prediction has been an area of research in the voice branch of telecommunications services, more focused studies on the huge growth area of Broadband Internet services are limited. Therefore, this paper presents a new set of features for broadband Internet customer churn prediction, based on Henley segments, the broadband usage, dial types, the spend of dial-up, line-information, bill and payment information, account information. Then the four prediction techniques (Logistic Regressions, Decision Trees, Multilayer Perceptron Neural Networks and Support Vector Machines) are applied in customer churn, based on the new features. Finally, the evaluation of new features and a comparative analysis of the predictors are made for broadband customer churn prediction. The experimental results show that the new features with these four modelling techniques are efficient for customer churn prediction in the broadband service field.

  9. Broadband and wide-angle nonreciprocity with a non-Hermitian metamaterial

    Science.gov (United States)

    Barton, David R.; Alaeian, Hadiseh; Lawrence, Mark; Dionne, Jennifer

    2018-01-01

    We theoretically demonstrate a non-Hermitian metamaterial exhibiting broadband and wide-angle nonreciprocity. The metamaterial consists of planar metal-dielectric layers with a parity-time (PT ) symmetric distribution of loss and gain. With increasing loss and gain, the band structure and band gap are strongly modified; further, the PT potential leads to distinct internal field distributions when illuminated from different sides. Including nonlinearities arising from natural loss and gain saturation leads to nonreciprocal transmission in the visible over a 50-nm wavelength and ±60∘ angular range.

  10. Broadband non-polarizing terahertz beam splitters with variable split ratio

    KAUST Repository

    Wei, Minggui

    2017-08-15

    Seeking effective terahertz functional devices has always aroused extensive attention. Of particular interest is the terahertz beam splitter. Here, we have proposed, designed, manufactured, and tested a broadband non-polarizing terahertz beam splitter with a variable split ratio based on an all-dielectric metasurface. The metasurface was created by patterning a dielectric surface of the N-step phase gradient and etching to a few hundred micrometers. The conversion efficiency as high as 81% under the normal incidence at 0.7 THz was achieved. Meanwhile, such a splitter works well over a broad frequency range. The split ratio of the proposed design can be continuously tuned by simply shifting the metasurface, and the angle of emergences can also be easily adjusted by choosing the step of phase gradients. The proposed design is non-polarizing, and its performance is kept under different polarizations.

  11. DIELECTRIC WALL ACCELERATOR TECHNOLOGY

    Energy Technology Data Exchange (ETDEWEB)

    Sampayan, S; Caporaso, G; Chen, Y; Harris, J; Hawkins, S; Holmes, C; Nelson, S; Poole, B; Rhodes, M; Sanders, D; Sullivan, J; Wang, L; Watson, J

    2007-10-18

    The dielectric wall accelerator (DWA) is a compact pulsed power device where the pulse forming lines, switching, and vacuum wall are integrated into a single compact geometry. For this effort, we initiated a extensive compact pulsed power development program and have pursued the study of switching (gas, oil, laser induced surface flashover and photoconductive), dielectrics (ceramics and nanoparticle composites), pulse forming line topologies (asymmetric and symmetric Blumleins and zero integral pulse forming lines), and multilayered vacuum insulator (HGI) technology. Finally, we fabricated an accelerator cell for test on ETAII (a 5.5 MeV, 2 kA, 70 ns pulsewidth electron beam accelerator). We review our past results and report on the progress of accelerator cell testing.

  12. A Comparison of Exact Versus Perturbed Pole Locations of Dielectric Objects in Dielectric Medium

    National Research Council Canada - National Science Library

    Worthy, Mark

    1997-01-01

    The dielectric properties of soils and plastic targets are given. The approach for finding exact pole locations from a dielectric infinite slab, a dielectric sphere, and a dielectric infinite cylinder is presented (and applied...

  13. A Review: Origins of the Dielectric Properties of Proteins and Potential Development as Bio-Sensors

    Directory of Open Access Journals (Sweden)

    Fabien Bibi

    2016-08-01

    Full Text Available Polymers can be classified as synthetic polymers and natural polymers, and are often characterized by their most typical functions namely their high mechanical resistivity, electrical conductivity and dielectric properties. This bibliography report consists in: (i Defining the origins of the dielectric properties of natural polymers by reviewing proteins. Despite their complex molecular chains, proteins present several points of interest, particularly, their charge content conferring their electrical and dielectric properties; (ii Identifying factors influencing the dielectric properties of protein films. The effects of vapors and gases such as water vapor, oxygen, carbon dioxide, ammonia and ethanol on the dielectric properties are put forward; (iii Finally, potential development of protein films as bio-sensors coated on electronic devices for detection of environmental changes particularly humidity or carbon dioxide content in relation with dielectric properties variations are discussed. As the study of the dielectric properties implies imposing an electric field to the material, it was necessary to evaluate the impact of frequency on the polymers and subsequently on their structure. Characterization techniques, on the one hand dielectric spectroscopy devoted for the determination of the glass transition temperature among others, and on the other hand other techniques such as infra-red spectroscopy for structure characterization as a function of moisture content for instance are also introduced.

  14. The dielectric breakdown limit of silicone dielectric elastomer actuators

    Science.gov (United States)

    Gatti, Davide; Haus, Henry; Matysek, Marc; Frohnapfel, Bettina; Tropea, Cameron; Schlaak, Helmut F.

    2014-02-01

    Soft silicone elastomers are used in a generation of dielectric elastomer actuators (DEAs) with improved actuation speed and durability compared to the commonly used, highly viscoelastic polyacrylate 3M VHB™ films. The maximum voltage-induced stretch of DEAs is ultimately limited by their dielectric breakdown field strength. We measure the dependence of dielectric breakdown field strength on thickness and stretch for a silicone elastomer, when voltage-induced deformation is prevented. The experimental results are combined with an analytic model of equi-biaxial actuation to show that accounting for variable dielectric field strength results in different values of optimal pre-stretch and thickness that maximize the DEA actuation.

  15. Incipient ferroelectric to a possible ferroelectric transition in Te4+ doped calcium copper titanate (CaCu3Ti4O12 ceramics at low temperature as evidenced by Raman and dielectric spectroscopy

    Directory of Open Access Journals (Sweden)

    Nabadyuti Barman

    2017-03-01

    Full Text Available Partial replacement of Ti4+ by Te4+ ions in calcium copper titanate lattice improved its dielectric behaviour mostly due to cubic-to-tetragonal structural transformation and associated distortion in TiO6 octahedra. The relative permittivity values (23–30 x 103 of Te4+ doped ceramics is more than thrice that of un-doped ceramics (8 x 103 at 1 kHz. A decreasing trend in relative permittivity with increasing temperature (50–300 K is observed for all the samples. Barrett’s formula, as a signature of incipient ferroelectricity, is invoked to rationalize the relative permittivity variation as a function of temperature. A systematic investigation supported by temperature dependent Raman studies reveal a possible ferroelectric transition in Te4+ doped ceramic samples below 120 K. The possible ferroelectric transition is attributed to the interactions between quasi-local vibrations associated with the micro-clusters comprising TiO6 and TeO6 structural units and indirect dipole-dipole interactions of off-center B–cations (Ti4+ and Te4+ in double perovskite lattice.

  16. 47 CFR 27.1305 - Shared wireless broadband network.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 2 2010-10-01 2010-10-01 false Shared wireless broadband network. 27.1305... broadband network. The Shared Wireless Broadband Network developed by the 700 MHz Public/Private Partnership must be designed to meet requirements associated with a nationwide, public safety broadband network. At...

  17. 47 CFR 90.1405 - Shared wireless broadband network.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false Shared wireless broadband network. 90.1405... broadband network. The Shared Wireless Broadband Network developed by the 700 MHz Public/Private Partnership must be designed to meet requirements associated with a nationwide, public safety broadband network. At...

  18. Helicity multiplexed broadband metasurface holograms

    Science.gov (United States)

    Wen, Dandan; Yue, Fuyong; Li, Guixin; Zheng, Guoxing; Chan, Kinlong; Chen, Shumei; Chen, Ming; Li, King Fai; Wong, Polis Wing Han; Cheah, Kok Wai; Yue Bun Pun, Edwin; Zhang, Shuang; Chen, Xianzhong

    2015-09-01

    Metasurfaces are engineered interfaces that contain a thin layer of plasmonic or dielectric nanostructures capable of manipulating light in a desirable manner. Advances in metasurfaces have led to various practical applications ranging from lensing to holography. Metasurface holograms that can be switched by the polarization state of incident light have been demonstrated for achieving polarization multiplexed functionalities. However, practical application of these devices has been limited by their capability for achieving high efficiency and high image quality. Here we experimentally demonstrate a helicity multiplexed metasurface hologram with high efficiency and good image fidelity over a broad range of frequencies. The metasurface hologram features the combination of two sets of hologram patterns operating with opposite incident helicities. Two symmetrically distributed off-axis images are interchangeable by controlling the helicity of the input light. The demonstrated helicity multiplexed metasurface hologram with its high performance opens avenues for future applications with functionality switchable optical devices.

  19. Helicity multiplexed broadband metasurface holograms.

    Science.gov (United States)

    Wen, Dandan; Yue, Fuyong; Li, Guixin; Zheng, Guoxing; Chan, Kinlong; Chen, Shumei; Chen, Ming; Li, King Fai; Wong, Polis Wing Han; Cheah, Kok Wai; Pun, Edwin Yue Bun; Zhang, Shuang; Chen, Xianzhong

    2015-09-10

    Metasurfaces are engineered interfaces that contain a thin layer of plasmonic or dielectric nanostructures capable of manipulating light in a desirable manner. Advances in metasurfaces have led to various practical applications ranging from lensing to holography. Metasurface holograms that can be switched by the polarization state of incident light have been demonstrated for achieving polarization multiplexed functionalities. However, practical application of these devices has been limited by their capability for achieving high efficiency and high image quality. Here we experimentally demonstrate a helicity multiplexed metasurface hologram with high efficiency and good image fidelity over a broad range of frequencies. The metasurface hologram features the combination of two sets of hologram patterns operating with opposite incident helicities. Two symmetrically distributed off-axis images are interchangeable by controlling the helicity of the input light. The demonstrated helicity multiplexed metasurface hologram with its high performance opens avenues for future applications with functionality switchable optical devices.

  20. Effect of Logarithmic and Linear Frequency Scales on Parametric Modelling of Tissue Dielectric Data.

    Science.gov (United States)

    Salahuddin, Saqib; Porter, Emily; Meaney, Paul M; O'Halloran, Martin

    2017-02-01

    The dielectric properties of biological tissues have been studied widely over the past half-century. These properties are used in a vast array of applications, from determining the safety of wireless telecommunication devices to the design and optimisation of medical devices. The frequency-dependent dielectric properties are represented in closed-form parametric models, such as the Cole-Cole model, for use in numerical simulations which examine the interaction of electromagnetic (EM) fields with the human body. In general, the accuracy of EM simulations depends upon the accuracy of the tissue dielectric models. Typically, dielectric properties are measured using a linear frequency scale; however, use of the logarithmic scale has been suggested historically to be more biologically descriptive. Thus, the aim of this paper is to quantitatively compare the Cole-Cole fitting of broadband tissue dielectric measurements collected with both linear and logarithmic frequency scales. In this way, we can determine if appropriate choice of scale can minimise the fit error and thus reduce the overall error in simulations. Using a well-established fundamental statistical framework, the results of the fitting for both scales are quantified. It is found that commonly used performance metrics, such as the average fractional error, are unable to examine the effect of frequency scale on the fitting results due to the averaging effect that obscures large localised errors. This work demonstrates that the broadband fit for these tissues is quantitatively improved when the given data is measured with a logarithmic frequency scale rather than a linear scale, underscoring the importance of frequency scale selection in accurate wideband dielectric modelling of human tissues.

  1. Very high dielectric strength for dielectric elastomer actuators in liquid dielectric immersion

    Science.gov (United States)

    La, Thanh-Giang; Lau, Gih-Keong

    2013-05-01

    This letter reported that a dielectric elastomer actuator (3M VHB), which is immersed in a liquid dielectric bath, is enhanced tremendously in dielectric strength up to 800 MV/m, as compared to 450 MV/m for the actuator operated in air. The bath consists of silicone oil (Dow Corning Fluid 200 50cSt), which is 6.5 times more thermally conductive than air, and it is found able to maintain the actuator at a stable temperature. As a result, the oil-immersed dielectric elastomer actuator is prevented from local thermal runaway, which causes loss of electrical insulation, and consequently avoids the damage by electromechanical instability.

  2. Dielectric materials and electrostatics

    CERN Document Server

    Gallot-Lavalle, Olivier

    2013-01-01

    An introduction to the physics of electrical insulation, this book presents the physical foundations of this discipline and the resulting applications. It is structured in two parts. The first part presents a mathematical and intuitive approach to dielectrics; various concepts, including polarization, induction, forces and losses are discussed. The second part provides readers with the keys to understanding the physics of solid, liquid and gas insulation. It comprises a phenomenological description of discharges in gas and its resulting applications. Finally, the main electrical properties

  3. Analyzing Broadband Divide in the Farming Sector

    DEFF Research Database (Denmark)

    Jensen, Michael; Gutierrez Lopez, Jose Manuel; Pedersen, Jens Myrup

    2013-01-01

    , upstream and downstream connection. The main constraint is that farms are naturally located in rural areas where the required access broadband data rates are not available. This paper studies the broadband divide in relation to the Danish agricultural sector. Results show how there is an important......Agriculture industry has been evolving for centuries. Currently, the technological development of Internet oriented farming tools allows to increase the productivity and efficiency of this sector. Many of the already available tools and applications require high bandwidth in both directions...... difference between the broadband availability for farms and the rest of the households/buildings the country. This divide may be slowing down the potential technological development of the farming industry, in order to keep their competitiveness in the market. Therefore, broadband development in rural areas...

  4. 75 FR 3820 - Broadband Initiatives Program

    Science.gov (United States)

    2010-01-22

    ... the RUS, under the Recovery Act. Broadband means providing two-way data transmission with advertised... no cost (including no costs for installation, activation, or other hidden fees) and to providing to...

  5. 75 FR 14131 - Broadband Technology Opportunities Program

    Science.gov (United States)

    2010-03-24

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF COMMERCE... Program AGENCY: National Telecommunications and Information Administration, U.S. Department of Commerce... for the electronic submission of CCI projects under the Broadband Technology Opportunities Program...

  6. Nanophotonic Design for Broadband Light Management

    Energy Technology Data Exchange (ETDEWEB)

    Kosten, Emily; Callahan, Dennis; Horowitz, Kelsey; Pala, Ragip; Atwater, Harry

    2014-10-13

    We describe nanophotonic design approaches for broadband light management including i) crossed-trapezoidal Si structures ii) Si photonic crystal superlattices, and iii) tapered and inhomogeneous diameter III-V/Si nanowire arrays.

  7. Broadband networks, smart grids and climate change

    CERN Document Server

    Noam, Eli M; Kranz, Johann J

    2015-01-01

    Noted scholars and professionals from the energy and telecommunications businesses explain in this volume how the convergence of broadband services and responsive 'smart' energy grids could help to mitigate climate change and boost corporation profits.

  8. Realizing the potential of dielectric elastomer generators

    Science.gov (United States)

    McKay, Thomas; O'Brien, Benjamin; Calius, Emilio; Anderson, Iain

    2011-04-01

    The global demand for renewable energy is growing, and ocean waves and wind are renewable energy sources that can provide large amounts of power. A class of variable capacitor power generators called Dielectric Elastomer Generators (DEG), show considerable promise for harvesting this energy because they can be directly coupled to large broadband motions without gearing while maintaining a high energy density, have few moving parts, and are highly flexible. At the system level DEG cannot currently realize their full potential for flexibility, simplicity and low mass because they require rigid and bulky external circuitry. This is because a typical generation cycle requires high voltage charge to be supplied or drained from the DEG as it is mechanically deformed. Recently we presented the double Integrated Self-Priming Circuit (ISPC) generator that minimized external circuitry. This was done by using the inherent capacitance of DEG to store excess energy. The DEG were electrically configured to form a pair of charge pumps. When the DEG were cyclically deformed, the charge pumps produced energy and converted it to a higher charge form. In this paper we present the single ISPC generator that contains just one charge pump. The ability of the new generator to increase its voltage through the accumulation of generated energy did not compare favourably with that of the double ISPC generator. However the single ISPC generator can operate in a wider range of operating conditions and the mass of its external circuitry is 50% that of the double ISPC generator.

  9. Characterization of dielectric properties of nanocellulose from wood and algae for electrical insulator applications.

    Science.gov (United States)

    Le Bras, David; Strømme, Maria; Mihranyan, Albert

    2015-05-07

    Cellulose is one of the oldest electrically insulating materials used in oil-filled high-power transformers and cables. However, reports on the dielectric properties of nanocellulose for electrical insulator applications are scarce. The aim of this study was to characterize the dielectric properties of two nanocellulose types from wood, viz., nanofibrillated cellulose (NFC), and algae, viz., Cladophora cellulose, for electrical insulator applications. The cellulose materials were characterized with X-ray diffraction, nitrogen gas and moisture sorption isotherms, helium pycnometry, mechanical testing, and dielectric spectroscopy at various relative humidities. The algae nanocellulose sample was more crystalline and had a lower moisture sorption capacity at low and moderate relative humidities, compared to NFC. On the other hand, it was much more porous, which resulted in lower strength and higher dielectric loss than for NFC. It is concluded that the solid-state properties of nanocellulose may have a substantial impact on the dielectric properties of electrical insulator applications.

  10. Terahertz dielectric properties of multiwalled carbon nanotube/polyethylene composites

    Science.gov (United States)

    Dorozhkin, K. V.; Dunaevsky, G. E.; Sarkisov, S. Yu; Suslyaev, V. I.; Tolbanov, O. P.; Zhuravlev, V. A.; Sarkisov, Yu S.; Kuznetsov, V. L.; Moseenkov, S. I.; Semikolenova, N. V.; Zakharov, V. A.; Atuchin, V. V.

    2017-10-01

    The terahertz dielectric properties of multiwalled carbon nanotube/polyethylene (MWCNT/PE) composites prepared in different ways and with various contents of carbon nanotubes have been measured by terahertz time-domain spectroscopy. The experimental dielectric susceptibilities were modeled within effective medium approximation. The MWCNTs with average diameter of 9 nm produced by ethylene decomposition over FeCo catalyst were used in the experiments. Two types of composites were prepared by various mechanical mixing of MWCNT and polyethylene powders. The other two types of composites were fabricated employing ethylene polymerization on the MWCNTs before mechanical mixing with polyethylene powder. The samples with MWCNT concentration of 0.1, 0.5, 1 and 4 wt. % were prepared for each composite type. The measured dielectric susceptibilities were higher for composites made of nanotubes with preliminary polymerization of ethylene as compared to the composites produced by just mechanical mixing at equal concentrations of MWCNTs. It was also found that the dielectric susceptibilities of the MWCNT/PE composites can be satisfactory described within Maxwell–Garnett effective medium approximation at sufficient levels (>0.5–1 wt. %) of MWCNT contents. The obtained results confirm the possibility to produce MWCNT/PE composite materials with desired dielectric properties in terahertz range.

  11. Broadband direct RF digitization receivers

    CERN Document Server

    Jamin, Olivier

    2014-01-01

    This book discusses the trade-offs involved in designing direct RF digitization receivers for the radio frequency and digital signal processing domains.  A system-level framework is developed, quantifying the relevant impairments of the signal processing chain, through a comprehensive system-level analysis.  Special focus is given to noise analysis (thermal noise, quantization noise, saturation noise, signal-dependent noise), broadband non-linear distortion analysis, including the impact of the sampling strategy (low-pass, band-pass), analysis of time-interleaved ADC channel mismatches, sampling clock purity and digital channel selection. The system-level framework described is applied to the design of a cable multi-channel RF direct digitization receiver. An optimum RF signal conditioning, and some algorithms (automatic gain control loop, RF front-end amplitude equalization control loop) are used to relax the requirements of a 2.7GHz 11-bit ADC. A two-chip implementation is presented, using BiCMOS and 65nm...

  12. Ultra-broadband photonic internet

    Science.gov (United States)

    Romaniuk, Ryszard S.

    2011-06-01

    In this paper, there is presented a review of our today's understanding of the ultimately broadband photonic Internet. A simple calculation is presented showing the estimate of the throughput of the core photonic network branches. Optoelectronic components, circuits, systems and signals, together with analogous electronic entities and common software layers, are building blocks of the contemporary Internet. Participation of photonics in development of the physical layer in the future Internet will probably increase. The photonics leads now to a better usage of the available bandwidth (increase of the spectral efficiency measured in Bit/s/Hz), increase in the transmission rate (from Gbps, via Tbps up to probably Pbps), increase in the transmission distance without signal regeneration (in distortion compensated active optical cables), increase in energy/power efficiency measured in W/Gbps, etc. Photonics may lead, in the future, to fully transparent optical networks and, thus, to essential increase in bandwidth and network reliability. It is expected that photonics (with biochemistry, electronics and mechatronics) may build psychological and physiological interface for humans to the future global network. The following optical signal multiplexing methods were considered, which are possible without O/E/O conversion: TDM-OTDM, FDM-CO-OFDM, OCDM-OCDMA, WDM-DWDM.

  13. Image potential in lossy dielectrics

    Science.gov (United States)

    Lenac, Z.

    2017-11-01

    The interaction of a point charge with surrounding media ( the image potential) is analyzed using the quantum-mechanical description of dielectrics that consistently takes losses in media into account. We have derived a real dielectric function (without an imaginary part) appropriate for lossy dielectrics which, compared to the lossless one, significantly changes the image potential in the standard (first-order) calculations. However, when one adds to the Hamiltonian all higher-order terms caused by the losses, one finds that the image potential remains the same, as if there were no losses in media. Our calculations are approximative when analyzing complicated systems with various lossy dielectrics, but in some simple and essential cases ( e.g., a dielectric plate) we are able to give the exact proof.

  14. Self assembled monolayers of octadecyltrichlorosilane for dielectric materials

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Vijay, E-mail: cirivijaypilani@gmail.com [Centre for Nanoscience and Engineering, Indian Institute of Science-Bangalore (India); Mechanical Engineering Department, Birla Institute of Technology and Science-Pilani (India); Puri, Paridhi; Nain, Shivani [Mechanical Engineering Department, Birla Institute of Technology and Science-Pilani (India); Bhat, K. N. [Centre for Nanoscience and Engineering, Indian Institute of Science-Bangalore (India); Sharma, N. N. [Mechanical Engineering Department, Birla Institute of Technology and Science-Pilani (India); School of Automobile, Mechanical & Mechatronics, Manipal University-Jaipur (India)

    2016-04-13

    Treatment of surfaces to change the interaction of fluids with them is a critical step in constructing useful microfluidics devices, especially those used in biological applications. Selective modification of inorganic materials such as Si, SiO{sub 2} and Si{sub 3}N{sub 4} is of great interest in research and technology. We evaluated the chemical formation of OTS self-assembled monolayers on silicon substrates with different dielectric materials. Our investigations were focused on surface modification of formerly used common dielectric materials SiO{sub 2}, Si{sub 3}N{sub 4} and a-poly. The improvement of wetting behaviour and quality of monolayer films were characterized using Atomic force microscope, Scanning electron microscope, Contact angle goniometer, Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) monolayer deposited oxide surface.

  15. Broadband infrared absorption enhancement by electroless-deposited silver nanoparticles

    Directory of Open Access Journals (Sweden)

    Gritti Claudia

    2016-07-01

    Full Text Available Decorating semiconductor surfaces with plasmonic nanoparticles (NPs is considered a viable solution for enhancing the absorptive properties of photovoltaic and photodetecting devices. We propose to deposit silver NPs on top of a semiconductor wafer by a cheap and fast electroless plating technique. Optical characterization confirms that the random array of electroless-deposited NPs improves absorption by up to 20% in a broadband of near-infrared frequencies from the bandgap edge to 2000 nm. Due to the small filling fraction of particles, the reflection in the visible range is practically unchanged, which points to the possible applications of such deposition method for harvesting photons in nanophotonics and photovoltaics. The broadband absorption is a consequence of the resonant behavior of particles with different shapes and sizes, which strongly localize the incident light at the interface of a high-index semiconductor substrate. Our hypothesis is substantiated by examining the plasmonic response of the electroless-deposited NPs using both electron energy loss spectroscopy and numerical calculations.

  16. Fabrication of Broad Band Mid-Infrared Absorber based on Periodic Dielectric-Thin Metal Film Multilayer Structures

    Science.gov (United States)

    Guo, Shy-Hauh; Sushkov, Andrei B.; Corrigan, Timothy; Park, Dong; Drew, H. Dennis; Kolb, Paul; Herman, Warren; Phaneuf, Raymond

    2012-02-01

    We present results from measurements on periodic multilayer structure of alternating dielectric and thin metal layers to achieve a broadband absorber of mid-infrared radiation. We examine the effect on performance of a back-reflective metallic bottom layer, surface roughness at interfaces, the metal conductance, the thickness of dielectric layers, and a patterned anti-reflective layer. We determine optimum structure parameters for absorption of a 500 K-black body spectrum, and find that the numerical results agree well with the measured absorption spectra. We also investigate the possibility of fabricating a patterned anti-reflective layer to further increase the absorption.

  17. Effect of water on Debye peak in mono-hydroxy liquid: A high frequency dielectric study

    Science.gov (United States)

    Singh, Lokendra P.

    2017-07-01

    High frequency dielectric spectroscopy has been used to investigate the dielectric behavior of the pure as well as the aqueous solutions of 2-ethyl-1-hexanol at 270 and 300 K. It was found that the strength of Debye peak decreases systematically with increasing concentration of water. This behavior has been explained on the basis of the fact that alcohol favors more reduced structure in presence of water. This result is consistent with the simulation work as well as low frequency dielectric results on alcohol-water system.

  18. Reinforced poly(propylene oxide)- a very soft and extensible dielectric electroactive polymer

    DEFF Research Database (Denmark)

    Goswami, Kaustav; Galantini, F.; Mazurek, Piotr Stanislaw

    2013-01-01

    Poly(propylene oxide) (PPO), a novel soft elastomeric material, and its composites were investigated as a new dielectric electroactive polymer (EAP). The PPO networks were obtained from thiol-ene chemistry by photochemical crosslinking of ,!-diallyl PPO with a tetra-functional thiol. The elastomer...... of the otherwise mechanically weak pure PPO network. Dielectric spectroscopy revealed high relative dielectric permittivity of PPO at 103 Hz of 5.6. The relative permittivity was decreased slightly upon addition of fillers, but remained higher than the commonly used acrylic EAP material VHB4910...

  19. Automatically acquired broadband plasmonic-metamaterial black absorber during the metallic film-formation.

    Science.gov (United States)

    Liu, Zhengqi; Liu, Xiaoshan; Huang, Shan; Pan, Pingping; Chen, Jing; Liu, Guiqiang; Gu, Gang

    2015-03-04

    Broadband electromagnetic wave absorbers are highly desirable in numerous applications such as solar-energy harvesting, thermo-photovoltaics, and photon detection. The aim to efficiently achieve ultrathin broadband absorbers with high-yield and low-cost fabrication process has long been pursued. Here, we theoretically propose and experimentally demonstrate a unique broadband plasmonic-metamaterial absorber by utilizing a sub-10 nm meta-surface film structure to replace the precisely designed metamaterial crystal in the common metal-dielectric-metal absorbers. The unique ultrathin meta-surface can be automatically obtained during the metal film formation process. Spectral bandwidth with absorbance above 80% is up to 396 nm, where the full absorption width at half-maximum is about 92%. The average value of absorbance across the whole spectral range of 370-880 nm reaches 83%. These super absorption properties can be attributed to the particle plasmon resonances and plasmon near-field coupling by the automatically formed metallic nanoparticles as well as the plasmon polaritons of the metal film with the induced plasmonic magnetic resonances occurring between the top meta-surface and the bottom metal mirror. This method is quite simple, cost-effective for large-area fabrication, and compatible with current industrial methods for microelectro-mechanical systems, which makes it an outstanding candidate for advanced high-efficiency absorber materials.

  20. Broadband polarization-independent perfect absorber using a phase-change metamaterial at visible frequencies.

    Science.gov (United States)

    Cao, Tun; Wei, Chen-wei; Simpson, Robert E; Zhang, Lei; Cryan, Martin J

    2014-02-04

    We report a broadband polarization-independent perfect absorber with wide-angle near unity absorbance in the visible regime. Our structure is composed of an array of thin Au squares separated from a continuous Au film by a phase change material (Ge2Sb2Te5) layer. It shows that the near perfect absorbance is flat and broad over a wide-angle incidence up to 80° for either transverse electric or magnetic polarization due to a high imaginary part of the dielectric permittivity of Ge2Sb2Te5. The electric field, magnetic field and current distributions in the absorber are investigated to explain the physical origin of the absorbance. Moreover, we carried out numerical simulations to investigate the temporal variation of temperature in the Ge2Sb2Te5 layer and to show that the temperature of amorphous Ge2Sb2Te5 can be raised from room temperature to > 433 K (amorphous-to-crystalline phase transition temperature) in just 0.37 ns with a low light intensity of 95 nW/μm(2), owing to the enhanced broadband light absorbance through strong plasmonic resonances in the absorber. The proposed phase-change metamaterial provides a simple way to realize a broadband perfect absorber in the visible and near-infrared (NIR) regions and is important for a number of applications including thermally controlled photonic devices, solar energy conversion and optical data storage.

  1. Broadband in schools: towards a definition and model of broadband for South African schools

    CSIR Research Space (South Africa)

    Ford, Merryl

    2017-05-01

    Full Text Available South Africa is about to provide broadband internet connectivity to all schools in the country via the implementation of the national broadband policy. The challenge is to ensure a balance between the schools’ demand-side usage and supply...

  2. Broadband degenerate OPO for mid-infrared frequency comb generation.

    Science.gov (United States)

    Leindecker, Nick; Marandi, Alireza; Byer, Robert L; Vodopyanov, Konstantin L

    2011-03-28

    We present a new technique suitable for generating broadband phase- and frequency-locked frequency combs in the mid-infrared. Our source is based on a degenerate optical parametric oscillator (OPO) which rigorously both down-converts and augments the spectrum of a pump frequency comb provided by a commercial mode-locked near-IR laser. Low intracavity dispersion, combined with extensive cross-mixing of comb components, results in extremely broad instantaneous mid-IR bandwidths. We achieve an output power of 60 mW and 20 dB bandwidth extending from 2500 to 3800 nm. Among other applications, such a source is well-suited for coherent Fourier-transform spectroscopy in the absorption-rich mid-IR 'molecular fingerprint' region.

  3. Broadband quantitative NQR for authentication of vitamins and dietary supplements

    Science.gov (United States)

    Chen, Cheng; Zhang, Fengchao; Bhunia, Swarup; Mandal, Soumyajit

    2017-05-01

    We describe hardware, pulse sequences, and algorithms for nuclear quadrupole resonance (NQR) spectroscopy of medicines and dietary supplements. Medicine and food safety is a pressing problem that has drawn more and more attention. NQR is an ideal technique for authenticating these substances because it is a non-invasive method for chemical identification. We have recently developed a broadband NQR front-end that can excite and detect 14N NQR signals over a wide frequency range; its operating frequency can be rapidly set by software, while sensitivity is comparable to conventional narrowband front-ends over the entire range. This front-end improves the accuracy of authentication by enabling multiple-frequency experiments. We have also developed calibration and signal processing techniques to convert measured NQR signal amplitudes into nuclear spin densities, thus enabling its use as a quantitative technique. Experimental results from several samples are used to illustrate the proposed methods.

  4. A broadband ultrathin metamaterial absorber using tilted parallel strips

    Science.gov (United States)

    Ahmadi, Farzad; Ida, Nathan

    2017-02-01

    A polarization insensitive metamaterial absorber is proposed consisting of a dielectric layer sandwiched between two tilted parallel metallic strips and a ground plane. First, a new analytical model is introduced to predict the resonance frequency for square, rectangular and wire geometries which shows less relative errors in comparison with previously proposed models. Then, ultra wide bandwidth absorption covering the entire x-band and Ku-band restricting a 10-dB absorption bandwidth is achieved with a relative material thickness λ0/10 and a relative FWHM absorption bandwidth of 90% for normal incidence angle. The model also shows good absorption coefficients for oblique incident angles for both s- and p-polarizations. Three different resonance modes are observed, which led to such broadband absorption. Each resonance mode is investigated to determine its dependence on the scatterers and unit cell dimensions, which can help one to design a multiple band absorber. The electromagnetic field distributions of the scatterers are studied to explain the absorber mechanism. The results are compared to previous works showing remarkable improvement.

  5. On the dielectric behaviour of collagen-algal sulfated polysaccharide blends: effect of glutaraldehyde crosslinking.

    Science.gov (United States)

    Figueiró, S D; Macêdo, A A M; Melo, M R S; Freitas, A L P; Moreira, R A; de Oliveira, R S; Góes, J C; Sombra, A S B

    2006-03-20

    In this paper, impedance measurements in the frequency range from 10(-2) to 10(6) Hz are presented for collagen and algal sulfated polysaccharide crosslinked films. We are considering the development of new biomaterials which have potential applications in coating of cardiovascular prostheses, support for cellular growth and in systems for controlled drug delivery. The effect of crosslink sulfated polysaccharide on the physical chemical properties of collagen was studied using FT-infrared spectroscopy, differential scanning calorimetry (DSC), dielectric spectroscopy. The resulting films crosslinked with glutaraldehyde (GA) in concentrations of 0.001% and 0.05% when analysed by DSC, showed that the GA treatment not only left the thermal stability of the collagen unaffected, but it also decreased the thermal transition energy. Dielectric spectroscopy shows that the effect of the crosslink on the blend film was associated to the decrease and stabilization of the dielectric permittivity at low frequencies and decreased its conductivity.

  6. Broadband Measurement of Aerosol Extinction in the Visible Range

    Science.gov (United States)

    He, Quanfu; Bluvshtein, Nir; Segev, Lior; Flores, Michel; Rudich, Yinon; Washenfelder, Rebecca; Brown, Steven

    2017-04-01

    Atmospheric aerosols influence the Earth's radiative budget directly by scattering and absorbing incoming solar radiation. Aerosol direct forcing remains one of the largest uncertainties in quantifying the role that aerosols play in the Earth's radiative budget. The optical properties of aerosols vary as a function of wavelength, but few measurements reported the wavelength dependence of aerosol extinction cross section and complex refractive indices, particularly in the blue and visible spectral range. There is also currently a large gap in our knowledge of how the optical properties evolve as a function of atmospheric aging in the visible spectrum. In this study, we constructed a new and novel laboratory instrument to measure aerosol extinction as a function of wavelength, using cavity enhanced spectroscopy with a white light source. This broadband cavity enhanced spectroscopy (BBCES) covers the 395-700 nm spectral region using a broadband light source and a grating spectrometer with charge-coupled device detector (CCD). We evaluated this BBCES by measuring extinction cross section for aerosols that are pure scattering, slightly absorbing and strongly absorbing atomized from standard materials. We also retrieved the refractive indices from the measured extinction cross sections. Secondary organic aerosols from biogenic and anthropogenic precursors were "aged" to differential time scales (1 to 10 days) in an Oxidation Flow Reactor (OFR) under the combined influence of OH, O3 and UV light. The new BBCES was used to online measure the extinction cross sections of the SOA. This talk will provide a comprehensive understanding of aerosol optical properties alerting during aging process in the 395 - 700 nm spectrum.

  7. Tunable dielectric properties of ferrite-dielectric based metamaterial.

    Directory of Open Access Journals (Sweden)

    K Bi

    Full Text Available A ferrite-dielectric metamaterial composed of dielectric and ferrite cuboids has been investigated by experiments and simulations. By interacting with the electromagnetic wave, the Mie resonance can take place in the dielectric cuboids and the ferromagnetic precession will appear in the ferrite cuboids. The magnetic field distributions show the electric Mie resonance of the dielectric cuboids can be influenced by the ferromagnetic precession of ferrite cuboids when a certain magnetic field is applied. The effective permittivity of the metamaterial can be tuned by modifying the applied magnetic field. A good agreement between experimental and simulated results is demonstrated, which confirms that these metamaterials can be used for tunable microwave devices.

  8. Dielectric Properties of PE/Clay Nanocomposites

    Directory of Open Access Journals (Sweden)

    E. David

    2013-01-01

    Full Text Available Polyethylene/nanoclay specimens containing from 0 to 5% nanoclays were prepared from a commercially available premixed PE/nanoclay masterbatch containing 50% wt of nanoclay. The masterbatch was diluted to the desired concentration by adding PE along with various amounts of compatibilizer in order to achieve the best possible dispersion of the nanoclay platelets. The dielectric response of the compounded samples was investigated using a combination of time and frequency-domain spectroscopy in order to cover a wide frequency window. Both techniques were in good agreement when the time-domain data was transformed into frequency-domain data. Despite their low concentration, the addition of the dispersed nanoclays led to a significant alteration of the material dielectric response in the form of the appearance of various interfacial relaxation processes and an increase of charge carrier transport within the insulation material. Moreover, an onset of nonlinear charge transport process was observed at moderate fields for specimens containing a relatively low level of nanoclays. The high-field breakdown strength was shown to have been improved by the incorporation of the nanoparticles, particularly when the exfoliation was enhanced by the use of a maleic anhydride grafted polyethylene compatibilizer.

  9. Spectral characterization of dielectric materials using terahertz measurement systems

    Science.gov (United States)

    Seligman, Jeffrey M.

    The performance of modern high frequency components and electronic systems are often limited by the properties of the materials from which they are made. Over the past decade, there has been an increased emphasis on the development of new, high performance dielectrics for use in high frequency systems. The development of these materials requires novel broadband characterization, instrumentation, and extraction techniques, from which models can be formulated. For this project several types of dielectric sheets were characterized at terahertz (THz) frequencies using quasi-optical (free-space) techniques. These measurement systems included a Fourier Transform Spectrometer (FTS, scalar), a Time Domain Spectrometer (TDS, vector), a Scalar Network Analyzer (SNA), and a THz Vector Network Analyzer (VNA). Using these instruments the THz spectral characteristics of dielectric samples were obtained. Polarization based anisotropy was observed in many of the materials measured using vector systems. The TDS was the most informative and flexible instrument for dielectric characterization at THz frequencies. To our knowledge, this is the first such comprehensive study to be performed. Anisotropy effects within materials that do not come into play at microwave frequencies (e.g. ~10 GHz) were found, in many cases, to increase measured losses at THz frequencies by up to an order of magnitude. The frequency dependent properties obtained during the course of this study included loss tangent, permittivity (index of refraction), and dielectric constant. The results were largely consistent between all the different systems and correlated closely to manufacturer specifications over a wide frequency range (325 GHz-1.5 THz). Anisotropic behavior was observed for some of the materials. Non-destructive evaluation and testing (NDE/NDT) techniques were used throughout. A precision test fixture was developed to accomplish these measurements. Time delay, insertion loss, and S-parameters were

  10. Broadband mid-infrared and THz chemical detection with quantum cascade laser multi-heterodyne spectrometers (Conference Presentation)

    Science.gov (United States)

    Westberg, Jonas; Sterczewski, Lukasz A.; Patrick, Link; Wysocki, Gerard

    2017-05-01

    Majority of chemical species of interest in security and safety applications (e.g. explosives) have complex molecular structures that produce unresolved rotational-vibrational spectroscopic signatures in the mid-infrared. This requires spectroscopic techniques that can provide broadband coverage in the mid-IR region to target broadband absorbers and high resolution to address small molecules that exhibit well-resolved spectral lines. On the other hand, many broadband mid-IR absorbers exhibit well-resolved rotational components in the THz spectral region. Thus, development of spectroscopic sensing technologies that can address both spectral regions is of great importance. Here we demonstrate recent progress towards broadband high-resolution spectroscopic sensing applications with Fabry-Perot quantum cascade lasers (QCLs) and frequency combs using multi-heterodyne spectroscopy (MHS) techniques. In this paper, we will present spectroscopic sensing of large and small molecules in the mid-IR region using QCLs operating at 8.5µm. An example high-resolution, broadband MHS of ammonia (small molecule) and isobutane (broadband absorber) at atmospheric pressure in the 1165-1190 cm^-1 range will be discussed. We have developed a balanced MHS system for mitigation of the laser intensity fluctuations. Absorption spectroscopy as well as dispersion spectroscopy with minimum fractional absorption down to 10^-4/Hz1/2 and fast spectral acquisition capabilities down to 10 µs/spectrum range will be demonstrated. In order to mitigate the shortcomings of the limited chemical selectivity in the mid-IR, THz QCL based spectrometer is currently under development to provide spectral de-congestion and thus significantly improve chemical identification. Preliminary characterization of the performance of THZ QCL combs for the THz QCL-MHS will be presented.

  11. Dielectric properties of BaTiO{sub 3}-CoFe{sub 2}O{sub 4} nanocomposite thin films

    Energy Technology Data Exchange (ETDEWEB)

    Fina, I.; Dix, N. [Institut de Ciencia de Materials de Barcelona-CSIC, Campus de la UAB, Bellaterra E-08193, Barcelona (Spain); Laukhin, V. [Institut de Ciencia de Materials de Barcelona-CSIC, Campus de la UAB, Bellaterra E-08193, Barcelona (Spain); Institut Catala de Recerca i Estudis Avancats (ICREA), Barcelona (Spain); Fabrega, L. [Institut de Ciencia de Materials de Barcelona-CSIC, Campus de la UAB, Bellaterra E-08193, Barcelona (Spain)], E-mail: lourdes@icmab.es; Sanchez, F.; Fontcuberta, J. [Institut de Ciencia de Materials de Barcelona-CSIC, Campus de la UAB, Bellaterra E-08193, Barcelona (Spain)

    2009-06-15

    We report on the dielectric characterization of CoFe{sub 2}O{sub 4}-BaTiO{sub 3} nanocomposites grown by rf sputtering. Dielectric properties have been analyzed for samples grown at different deposition temperatures and with different thicknesses. Impedance spectroscopy data has been analyzed by fitting to an equivalent circuit and different contributions have been identified. Correlations between dielectric properties and deposition temperature and thickness have been established.

  12. EPR UNIFORM FIELD SIGNAL ENHANCEMENT BY DIELECTRIC TUBES IN CAVITIES.

    Science.gov (United States)

    Hyde, James S; Mett, Richard R

    2017-12-01

    The dielectric tube resonator (DTR) for EPR spectroscopy is introduced. It is defined as a metallic cylindrical TE011 microwave cavity that contains a dielectric tube centered on the axis of the cylinder. Contour plots of dimensions of the metallic cylinder to achieve resonance at 9.5 GHz are shown for quartz, sapphire, and rutile tubes as a function of wall thickness and average radius. These contour plots were developed using analytical equations and confirmed by finite element modeling. They can be used in two ways: design of the metallic cylinder for use at 9.5 GHz that incorporates a readily available tube such as a sapphire tube intended for NMR, or design of a custom procured tube for optimized performance for specific sample-size constraints. The charts extend to the limiting condition where the dielectric fills the tube. However, the structure at this limit is not a dielectric resonator due to the metal wall and does not radiate. In addition, the uniform field (UF) DTR is introduced. Development of the UF resonator starting with a dielectric tube resonator is shown. The diameter of the tube remains constant along the cavity axis, and the diameter of the cylindrical metallic enclosure increases at the ends of the cavity to satisfy the uniform field condition. This structure has advantages over the previously developed UF TE011 resonators: higher resonator efficiency parameter Λ, convenient overall size when using sapphire tubes, and higher quality data for small samples. The DTR and UF DTR structures fill the gap between free space and dielectric resonator limits in a continuous manner.

  13. Policy factors affecting broadband development in Poland

    DEFF Research Database (Denmark)

    Henten, Anders; Windekilde, Iwona Maria

    2014-01-01

    Poland joined the EU in 2004 and still has one of the Europe’s least developed information societies. Broadband penetration in Poland is still amongst the lowest in the EU and significantly below the EU average. Considering the present state of information technology, the key challenge for Poland...... will gradually change the previous balance of power. The specific problem of the Polish market is its very poor infrastructure development and the lack of competitors on the fixed market. This translates into limited access to services for end users particularly in the rural areas. A much lower level...... and discuss broadband access development in Poland and the policy factors influencing this development as well as to examine national strategies used to stimulate service and infrastructure competition in Poland. There are, indeed, many other factors affecting broadband development such as the income level...

  14. Service Differentiation in Residential Broadband Networks

    DEFF Research Database (Denmark)

    Sigurdsson, Halldór Matthias

    2004-01-01

    As broadband gains widespread adoption with residential users, revenue generating voice- and video-services have not yet taken off. This slow uptake is often attributed to lack of Quality of Service management in residential broadband networks. To resolve this and induce service variety, network...... access providers are implementing service differentiation in their networks where voice and video gets prioritised before data. This paper discusses the role of network access providers in multipurpose packet based networks and the available migration strategies for supporting multimedia services...... in digital subscriber line (DSL) based residential broadband networks. Four possible implementation scenarios and their technical characteristics and effects are described. To conclude, the paper discusses how network access providers can be induced to open their networks for third party service providers....

  15. Is European Broadband Ready for Smart Grid?

    DEFF Research Database (Denmark)

    Balachandran, Kartheepan; Pedersen, Jens Myrup

    2014-01-01

    In this short paper we compare the communication requirements for three Smart Grid scenarios with the availability of broadband and mobile communication networks in Europe. We show that only in the most demanding case - where data is collected and transmitted every second - a standard GSM/GPRS co....../GPRS connection is not enough. Whereas in the less demanding scenarios it is almost all of the European households that can be covered by a standard broadband technology for use with Smart Grid.......In this short paper we compare the communication requirements for three Smart Grid scenarios with the availability of broadband and mobile communication networks in Europe. We show that only in the most demanding case - where data is collected and transmitted every second - a standard GSM...

  16. Omnidirectional, polarization-independent, ultra-broadband metamaterial perfect absorber using field-penetration and reflected-wave-cancellation.

    Science.gov (United States)

    Zhong, Yan Kai; Lai, Yi-Chun; Tu, Ming-Hsiang; Chen, Bo-Ruei; Fu, Sze Ming; Yu, Peichen; Lin, Albert

    2016-05-16

    In this work, we present the result of nickel (Ni)-based metamaterial perfect absorbers (MPA) with ultra-broadband close-to-one absorbance. The experimental broadband characteristic is significantly improved over the past effort on metamaterial perfect absorbers. An in-depth physical picture and quantitative analysis is presented to reveal the physical origin of its ultrabroadband nature. The key constituent is the cancellation of the reflected wave using ultra-thin, moderate-extinction metallic films. The ultra-thin metal thickness can reduce the reflection as the optical field penetrates through the metallic films. This leads to minimal reflection at each ultra-thin metal layer, and light is penetrating into the Ni/SiO2 stacking. More intuitively, when the layer thickness is much smaller than the photon wavelength, the layer is essentially invisible to the photons. This results in absorption in the metal thin-film through penetration while there is minimal reflection by the metal film. More importantly, the experimental evidence for omni-directionality and polarization-insensitivity are established for the proposed design. Detailed measurement is conducted. Due to the ultrathin metal layers and the satisfactory tolerance in dielectric thickness, the broadband absorption has minimal degradation at oblique incidence. Such a wide angle, polarization-insensitive, ultra-broadband MPA can be very promising in the future, and the optical physics using sub-skin-depth metal film can also facilitate miniaturized high-performance nano-photonic devices.

  17. Ion implanted dielectric elastomer circuits

    OpenAIRE

    O’Brien, Benjamin M.; Rosset, Samuel; Anderson, Iain A.; Shea, Herbert R.

    2013-01-01

    Starfish and octopuses control their infinite degree of- freedom arms with panache—capabilities typical of nature where the distribution of reflex-like intelligence throughout soft muscular networks greatly outperforms anything hard, heavy, and man-made. Dielectric elastomer actuators show great promise for soft artificial muscle networks. One way to make them smart is with piezo-resistive Dielectric Elastomer Switches (DES) that can be combined with artificial muscles to create arbitrary dig...

  18. Interconnect Between a Waveguide and a Dielectric Waveguide Comprising an Impedance Matched Dielectric Lens

    Science.gov (United States)

    Decrossas, Emmanuel (Inventor); Chattopadhyay, Goutam (Inventor); Chahat, Nacer (Inventor); Tang, Adrian J. (Inventor)

    2016-01-01

    A lens for interconnecting a metallic waveguide with a dielectric waveguide is provided. The lens may be coupled a metallic waveguide and a dielectric waveguide, and minimize a signal loss between the metallic waveguide and the dielectric waveguide.

  19. Design of metamaterial surfaces with broadband absorbance.

    Science.gov (United States)

    Wu, Chihhui; Shvets, Gennady

    2012-02-01

    A simple design paradigm for making broadband ultrathin plasmonic absorbers is introduced. The absorber's unit cell is composed of subunits of various sizes, resulting in nearly 100% absorbance at multiple adjacent frequencies and high absorbance over a broad frequency range. A simple theoretical model for designing broadband absorbers is presented. It uses a single-resonance model to describe the optical response of each subunit and employs the series circuit model to predict the overall response. Validity of the circuit model relies on short propagation lengths of the surface plasmons.

  20. Temperature-independent broadband silicon modulator

    Science.gov (United States)

    Yi, H. X.; Li, T. T.; Zhang, J. L.; Wang, X. J.; Zhou, Z.

    2015-04-01

    We demonstrate a 20 Gb/s temperature-independent silicon modulator based on symmetrical Mach-Zehnder Interferometer. The MMI coupler was used as splitter/combiner in symmetrical MZI for balanced propagation. The ±15 °C temperature-independent eye diagrams were measured at 10 Gb/s with over 15 dB extinction ratio. Based on over 30 nm flat optical bandwidth, the broadband modulation was demonstrated from 1530 nm to 1560 nm. The temperature-independent broadband silicon modulator is adaptable to interconnection and communication systems in practice.

  1. Participation in the broadband society in Denmark

    DEFF Research Database (Denmark)

    Falch, Morten; Henten, Anders; Skouby, Knud Erik

    2009-01-01

    The purpose of the paper is to provide an empirical overview of broadband developments in Denmark. The overview includes sections on coverage and penetration, connection speeds, retail prices, competition, interconnection prices, and residential access to Internet. The documentation shows...... that Denmark is doing well in most international comparisons, but retail prices are still relatively high and connection speeds are lower than the best performing countries. In terms of households, approximately three quarters have broadband access. Denmark - and a number of other countries as well - has thus...

  2. Polarization insensitive, broadband terahertz metamaterial absorber.

    Science.gov (United States)

    Grant, James; Ma, Yong; Saha, Shimul; Khalid, Ata; Cumming, David R S

    2011-09-01

    We present the simulation, implementation, and measurement of a polarization insensitive broadband resonant terahertz metamaterial absorber. By stacking metal-insulator layers with differing structural dimensions, three closely positioned resonant peaks are merged into one broadband absorption spectrum. Greater than 60% absorption is obtained across a frequency range of 1.86 THz where the central resonance frequency is 5 THz. The FWHM of the device is 48%, which is two and half times greater than the FWHM of a single layer structure. Such metamaterials are promising candidates as absorbing elements for bolometric terahertz imaging.

  3. Techno-Economics of Residential Broadband Deployment

    DEFF Research Database (Denmark)

    Sigurdsson, Halldor Matthias

    2007-01-01

    og kombinerer en solid teknisk viden om telenet og tjenester med økonomisk teori og teori for regulering af telekommunikation. På grundlag heraf opstilles en tekno-økonomisk omkostningsmodel, der simulerer kapitaludgifter og ydelser. Som et særligt element i modellen benyttes spilteori til......-Economics of Residential Broadband Deployment. It investigates the current market situation of broadband services, where the electricity companies challenge the incumbent telecom operators by extensive deployment of optical fibres to the end users. Very often the old telecom operators have a well-developed infrastructure...

  4. VT Wireless Broadband Availability by Census Block - 06-2013

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201306 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 6/30/2013. This...

  5. VT Detailed Broadband Availability by Census Block - 06-2010

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201006 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 6/30/2010. This...

  6. VT Total Broadband Availability by Census Block - 12-2010

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201012 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 12/31/2010. This...

  7. VT Cable Broadband Availability by Census Block - 06-2011

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201106 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 6/30/2011. This...

  8. VT Detailed Broadband Availability by Census Block - 12-2010

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201012 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 12/31/2010. This...

  9. VT Wireline Broadband Availability by Census Block - 06-2013

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201306 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 6/30/2013. This...

  10. VT Detailed Broadband Availability by Census Block - 06-2013

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201306 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 6/30/2013. This...

  11. VT DSL Broadband Availability by Census Block - 12-2011

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201112 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 12/31/2011. This...

  12. VT Wireline Broadband Availability by Census Block - 12-2012

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201212 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 12/31/2012. This...

  13. VT Cable Broadband Availability by Census Block - 06-2010

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201006 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 6/30/2010. This...

  14. VT DSL Broadband Availability by Census Block - 12-2012

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201212 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 12/31/2012. This...

  15. VT Total Broadband Availability by Census Block - 06-2013

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201306 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 6/30/2013. This...

  16. VT Wireline Broadband Availability by Census Block - 06-2010

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201006 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 6/30/2010. This...

  17. VT Public Locations of Broadband Data - 12-2012

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201212 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 12/31/2012. This...

  18. VT DSL Broadband Availability by Census Block - 06-2010

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201006 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 6/30/2010. This...

  19. VT Cable Broadband Availability by Census Block - 12-2012

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201212 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 12/31/2012. This...

  20. VT Detailed Broadband Availability by Census Block -12-2012

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201212 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 12/31/2012. This...

  1. VT DSL Broadband Availability by Census Block - 06-2011

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201106 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 6/30/2011. This...

  2. VT Public Locations of Broadband Data - 12-2011

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201112 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 12/31/2011. This...

  3. VT Public Locations of Broadband Data - 06-2013

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201306 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 6/30/2013. This...

  4. VT Wireless Broadband Availability by Census Block - 06-2011

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201106 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 6/30/2011. This...

  5. VT Wireline Broadband Availability by Census Block - 12-2010

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201012 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 12/31/2010. This...

  6. VT Wireline Broadband Availability by Census Block - 12-2011

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201112 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 12/31/2011. This...

  7. VT Total Broadband Availability by Census Block - 06-2011

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201106 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 6/30/2011. This...

  8. VT Detailed Broadband Availability by Census Block -12-2011

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201112 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 12/31/2011. This...

  9. VT Total Broadband Availability by Census Block - 12-2012

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201212 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 12/31/2012. This...

  10. VT Wireline Broadband Availability by Census Block - 06-2011

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201106 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 6/30/2011. This...

  11. VT Wireless Broadband Availability by Census Block - 12-2011

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201112 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 12/31/2011. This...

  12. VT Total Broadband Availability by Census Block - 06-2010

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201006 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 6/30/2010. This...

  13. VT Total Broadband Availability by Census Block - 12-2011

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201112 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 12/31/2011. This...

  14. VT Wireless Broadband Availability by Census Block - 06-2010

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201006 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 6/30/2010. This...

  15. VT Detailed Broadband Availability by Census Block - 06-2011

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201106 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 6/30/2011. This...

  16. VT Public Locations of Broadband Data - 06-2011

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201106 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 6/30/2011. This...

  17. VT Public Locations of Broadband Data - 06-2010

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201006 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 6/30/2010. This...

  18. VT Cable Broadband Availability by Census Block - 12-2010

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201012 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 12/31/2010. This...

  19. VT DSL Broadband Availability by Census Block - 12-2010

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201012 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 12/31/2010. This...

  20. VT Cable Broadband Availability by Census Block - 12-2011

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201112 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 12/31/2011. This...

  1. VT Wireless Broadband Availability by Census Block - 12-2012

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201212 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 12/31/2012. This...

  2. VT Wireless Broadband Availability by Census Block - 12-2010

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201012 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 12/31/2010. This...

  3. VT DSL Broadband Availability by Census Block - 06-2013

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201306 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 6/30/2013. This...

  4. VT Cable Broadband Availability by Census Block - 06-2013

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201306 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 6/30/2013. This...

  5. VT Public Locations of Broadband Data - 12-2010

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) The VTBB201012 VT Broadband Availability Dataset represents wireline and wireless 'broadband service' availability in VT as of 12/31/2010. This...

  6. Dielectric optical invisibility cloaks

    Science.gov (United States)

    Blair, J.; Tamma, V. A.; Park, W.; Summers, C. J.

    2010-08-01

    Recently, metamaterial cloaks for the microwave frequency range have been designed using transformative optics design techniques and experimentally demonstrated. The design of these structures requires extreme values of permittivity and permeability within the device, which has been accomplished by the use of resonating metal elements. However, these elements severely limit the operating frequency range of the cloak due to their non-ideal dispersion properties at optical frequencies. In this paper we present designs to implement a simpler demonstration of cloaking, the carpet cloak, in which a curved reflective surface is compressed into a flat reflective surface, effectively shielding objects behind the curve from view with respect to the incoming radiation source. This approach eliminates the need for metallic resonant elements. These structures can now be fabricated using only high index dielectric materials by the use of electron beam lithography and standard cleanroom technologies. The design method, simulation analysis, device fabrication, and near field optical microscopy (NSOM) characterization results are presented for devices designed to operate in the 1400-1600nm wavelength range. Improvements to device performance by the deposition/infiltration of linear, and potentially non-linear optical materials, were investigated.

  7. Migration factors among broadband services: Panel data analysis

    OpenAIRE

    Shinohar, Sobee; Akematsu, Yuji; Tsuji, Masatsugu

    2012-01-01

    Providing nationwide deployment of broadband services has become an important national agenda. The U.S. announced a National Broadband Plan and EU a Digital Agenda for Europe, both of which aim at providing access to 100 Mbps broadband services by 2020 to substantial numbers of households. The purpose of this paper is to analyze the migration factors among broadband services, namely CATV (BB), DSL and FTTx, in OECD 30 countries. In so doing, we focus especially on migration from CATV (BB) and...

  8. Broadband Grounded Vertical Antennas for 30-180 MHZ (VHF)

    Science.gov (United States)

    2013-10-18

    antennas are well known for their broadband gain (monocone, bicone ) but are never combined with a monopole. An eccentric combination of broadband...DATES COVERED 00-00-2014 to 00-00-2014 4. TITLE AND SUBTITLE Broadband Grounded Vertical Antennas For 30-180 MZH (VHF) 5a. CONTRACT NUMBER 5b...18 Attorney Docket No. 102536 1 of 17 BROADBAND GROUNDED VERTICAL ANTENNAS FOR 30-180 MHZ (VHF) STATEMENT OF GOVERNMENT INTEREST

  9. A flexible experimental setup for femtosecond time-resolved broad-band ellipsometry and magneto-optics

    Energy Technology Data Exchange (ETDEWEB)

    Boschini, F.; Hedayat, H.; Piovera, C.; Dallera, C. [Dipartimento di Fisica, Politecnico di Milano, p.zza Leonardo da Vinci 32, 20133 Milano (Italy); Gupta, A. [Department of Chemistry, University of Alabama, Tuscaloosa, Alabama 35487 (United States); Carpene, E., E-mail: ettore.carpene@polimi.it [CNR-IFN, Dipartimento di Fisica, Politecnico di Milano, p.zza Leonardo da Vinci 32, 20133 Milano (Italy)

    2015-01-15

    A versatile experimental setup for femtosecond time-resolved ellipsometry and magneto-optical Kerr effect measurements in the visible light range is described. The apparatus is based on the pump-probe technique and combines a broad-band probing beam with an intense near-infrared pump. According to Fresnel scattering matrix formalism, the analysis of the reflected beam at different polarization states of the incident probe light allows one to determine the diagonal and the off-diagonal elements of the dielectric tensor in the investigated sample. Moreover, the pump-probe method permits to study the dynamics of the dielectric response after a short and intense optical excitation. The performance of the experimental apparatus is tested on CrO{sub 2} single crystals as a benchmark.

  10. Broadband: An Insight and Its Benefits | Devardhi | Science ...

    African Journals Online (AJOL)

    It is viewed by some as a double-edged sword: networking could promote economic development, yet electronic commerce also has the potential to displace local businesses. The paper focuses on defining broadband, identifying and assessing the benefits of broadband technologies. Although broadband technologies are ...

  11. 75 FR 36071 - Framework for Broadband Internet Service

    Science.gov (United States)

    2010-06-24

    ... COMMISSION Framework for Broadband Internet Service AGENCY: Federal Communications Commission. ACTION: Notice..., broadband Internet service. Recent developments--including a decision of the United States Court of Appeals... broadband Internet service. DATES: Comments must be submitted by July 15, 2010, and reply comments must be...

  12. Modelling and control of broadband traffic using multiplicative ...

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    Modelling of broadband network traffic has emerged as an active area in the last decade. This has been primarily ... that broadband network traffic exhibits statistical self-similarity triggered off an immense volume of ...... with CAC control techniques and adaptive prediction of delay for bandwidth management in broadband ...

  13. Characterization, Microstructure, and Dielectric properties of cubic pyrochlore structural ceramics

    KAUST Repository

    Li, Yangyang

    2013-05-01

    The (BMN) bulk materials were sintered at 1050°C, 1100°C, 1150°C, 1200°C by the conventional ceramic process, and their microstructure and dielectric properties were investigated by Scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, Transmission electron microscopy (TEM) (including the X-ray energy dispersive spectrometry EDS and high resolution transmission electron microscopy HRTEM) and dielectric impedance analyzer. We systematically investigated the structure, dielectric properties and voltage tunable property of the ceramics prepared at different sintering temperatures. The XRD patterns demonstrated that the synthesized BMN solid solutions had cubic phase pyrochlore-type structure when sintered at 1050°C or higher, and the lattice parameter (a) of the unit cell in BMN solid solution was calculated to be about 10.56Å. The vibrational peaks observed in the Raman spectra of BMN solid solutions also confirmed the cubic phase pyrochlore-type structure of the synthesized BMN. According to the Scanning Electron Microscope (SEM) images, the grain size increased with increasing sintering temperature. Additionally, it was shown that the densities of the BMN ceramic tablets vary with sintering temperature. The calculated theoretical density for the BMN ceramic tablets sintered at different temperatures is about 6.7521 . The density of the respective measured tablets is usually amounting more than 91% and 5 approaching a maximum value of 96.5% for sintering temperature of 1150°C. The microstructure was investigated by using Scanning Transmission Electron Microscope (STEM), X-ray diffraction (XRD). Combined with the results obtained from the STEM and XRD, the impact of sintering temperature on the macroscopic and microscopic structure was discussed. The relative dielectric constant ( ) and dielectric loss ( ) of the BMN solid solutions were measured to be 161-200 and (at room temperature and 100Hz-1MHz), respectively. The BMN solid

  14. Properties and Applications of Silicon Oxynitride Gate Dielectrics.

    Science.gov (United States)

    Krisch, K. S.

    1996-03-01

    Reducing the size of silicon CMOS transistors enables higher speed, lower-power, denser and cheaper circuits, but introduces many challenges in process technology. As the gate oxide thickness is reduced, and as electric fields in the MOSFET increase, there are increased concerns about hot-carrier damage and oxide breakdown. Additionally, thinner SiO2 layers cannot effectively block diffusion of dopants and impurities. Silicon oxynitride dielectrics minimize these difficulties, making them attractive as gate dielectrics for future CMOS processes. Silicon oxynitrides are thermally grown on Si, in N_2O at temperatures ranging from 800-1100^circC, to thicknesses of 3-10 nm. The resulting material is primarily SiO_2, with 10^14-10^15 cm-2 nitrogen atoms incorporated (as measured by nuclear reaction analysis), equivalent to less than a monolayer of pure Si_3N_4. Secondary ion mass spectroscopy profiles indicate that this nitrogen is mainly near the crystalline silicon/dielectric interface, as a result of two competing reactions:(E.C. Carr, K.A. Ellis and R.A. Buhrman, Appl. Phys. Lett., v. 66, n. 12, p. 1492, (1995).) first, a nitrogen-oxygen species diffuses through the film and reacts at the Si interface, growing a silicon oxynitride layer. As the reaction proceeds and the grown layer is pushed up from the interface, a competing reaction removes the nitrogen from the dielectric ``bulk'', leaving behind SiO_2. This small amount of nitrogen incorporated at the dielectric interface has a dramatic effect on electrical reliability. Nitrogen-containing gate dielectrics inhibit generation of electrical defects and charge traps that degrade device performance, and they can more than double the time until breakdown. Such improvements are attributed to reduction of strain at the interface, which allows stronger bonds and fewer defect precursors. Oxynitrides also have the advantage of acting as a diffusion barrier. In MOS structures, boron dopant atoms originating in the

  15. 77 FR 36903 - Accelerating Broadband Infrastructure Deployment

    Science.gov (United States)

    2012-06-20

    ... and wireless broadband infrastructure. The Federal Government controls nearly 30 percent of all land... their respective agencies, in consultation with the Director of the Office of Science and Technology... of all application and other requirements; ensuring consistent interpretation and application of all...

  16. Catalyzing Broadband Internet in Africa | IDRC - International ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    This project aims to inform policies that help marginalized groups in Africa, such as women and the poor, to take advantage of the social and economic opportunities of broadband Internet. Internet access is critical for social and economic development in developing countries. According to a 2009 World Bank study, a 10% ...

  17. Broadband Minimum Variance Beamforming for Ultrasound Imaging

    DEFF Research Database (Denmark)

    Holfort, Iben Kraglund; Gran, Fredrik; Jensen, Jørgen Arendt

    2009-01-01

    A minimum variance (MV) approach for near-field beamforming of broadband data is proposed. The approach is implemented in the frequency domain, and it provides a set of adapted, complex apodization weights for each frequency subband. The performance of the proposed MV beamformer is tested on simu...

  18. Broadband Satellite Technologies and Markets Assessed

    Science.gov (United States)

    Wallett, Thomas M.

    1999-01-01

    The current usage of broadband (data rate greater than 64 kilobits per second (kbs)) for multimedia network computer applications is increasing, and the need for network communications technologies and systems to support this use is also growing. Satellite technology will likely be an important part of the National Information Infrastructure (NII) and the Global Information Infrastructure (GII) in the next decade. Several candidate communications technologies that may be used to carry a portion of the increased data traffic have been reviewed, and estimates of the future demand for satellite capacity have been made. A study was conducted by the NASA Lewis Research Center to assess the satellite addressable markets for broadband applications. This study effort included four specific milestones: (1) assess the changing nature of broadband applications and their usage, (2) assess broadband satellite and terrestrial technologies, (3) estimate the size of the global satellite addressable market from 2000 to 2010, and (4) identify how the impact of future technology developments could increase the utility of satellite-based transport to serve this market.

  19. 75 FR 10455 - Broadband Initiatives Program

    Science.gov (United States)

    2010-03-08

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF AGRICULTURE Rural Utilities Service RIN 0572-ZA01 Broadband Initiatives Program AGENCY: Rural Utilities Service... fraud, waste and abuse, contact [email protected] for BIP. You may obtain additional...

  20. Dielectric properties of nickel doped bismuth lithium borate glasses

    Energy Technology Data Exchange (ETDEWEB)

    Dalal, Seema, E-mail: seemadal2014@gmail.com [Department of Physics, Baba Mast Nath University, Asthal Bohr, Rohtak-124001 (India); Department of Physics, Deenbandhu Chhotu Ram University of Science and Technology, Murthal-131039 (India); Dahiya, Sunita [Department of Physics, Baba Mast Nath University, Asthal Bohr, Rohtak-124001 (India); Ashima,; Khasa, S. [Department of Physics, Deenbandhu Chhotu Ram University of Science and Technology, Murthal-131039 (India)

    2016-05-23

    Glasses with composition xBi{sub 2}O{sub 3}•(30-x)Li{sub 2}O•70B{sub 2}O{sub 3} (x = 0, 2, 5, 7 and 10 mol% with codes BLBN1-5 respectively) containing 2 mol% of NiO were prepared via melt-quenching technique and dielectric properties are discussed. The dielectric properties have been studied using impedance spectroscopy. The frequency dependent conductivity investigations for prepared compositions have been carried out using impedance spectroscopy over a frequency range of 1 KHz to 5 MHz and in the temperature range of 300 K-523 K. The complex impedance data have been analyzed by using both the conductivity and the electric modulus formalisms. Standard dielectric behavior is observed in prepared samples. The ac conductivity variations satisfy the Arrhenius relation. The study of the equivalent circuit analysis up to a temperature of 473 K shows a significant change in the equivalent circuit with change in temperature and composition.